WO2004063780A1

WO2004063780A1 - Broad-band-cholesteric liquid-crystal film and process for producing the same, circularly polarizing plate, linearly polarizing element, illuminator, and liquid-crystal display

Info

Publication number: WO2004063780A1
Application number: PCT/JP2004/000068
Authority: WO
Inventors: Miki Shiraogawa; Takahiro Fukuoka; Naoki Takahashi; Kazutaka Hara
Original assignee: Nitto Denko Corporation
Priority date: 2003-01-10
Filing date: 2004-01-08
Publication date: 2004-07-29
Also published as: TW200419197A

Abstract

A broad-band-cholesteric liquid-crystal film which is obtained by applying a liquid-crystal mixture comprising a polymerizable mesogenic compound (a), a polymerizable chiral reagent (b), and a photopolymerization initiator (c) to an alignment substrate and polymerizing the coating with ultraviolet in an inert gas atmosphere, and which has a reflection band width of 200 nm or more. The broad-band-cholesteric liquid-crystal film has a broad reflection band and satisfactory durability.

Description

Broadband cholesteric liquid crystal film and manufacturing method thereof, circular polarizer, linear polarizer, lighting device, and liquid crystal display device

The present invention relates to a broadband cholesteric liquid crystal film and a method for producing the same. The broadband cholesteric liquid crystal film of the present invention is used as a circularly polarizing plate (reflective polarizer).

It is for. Further, the present invention provides a linear polarizer, a lighting device, and a liquid using the circularly polarizing plate.

One

The present invention relates to a crystal display device. Background art

Generally, a liquid crystal display has a structure in which liquid crystal is injected between glass plates on which transparent electrodes are formed, and polarizers are arranged before and after the glass plates. A polarizer used for such a liquid crystal display is manufactured by adsorbing iodine, a dichroic dye, or the like on a polyvinyl alcohol film, and stretching the same in a certain direction. The polarizer itself manufactured as described above absorbs light oscillating in one direction, and passes only light oscillating in the other direction to produce linearly polarized light. As a result, the efficiency of the polarizer cannot theoretically exceed 50%, which is the biggest factor in reducing the efficiency of liquid crystal displays. Also, due to the absorbed light, if the output of the light source is increased to a certain degree or more, the liquid crystal display device may destroy the polarizer due to heat generated by the heat conversion of the absorbed light, or may have a negative effect on the liquid crystal layer inside the cell. This causes adverse effects such as deterioration of display quality.

Cholesteric liquid crystals having a function of separating circularly polarized light have a selective reflection characteristic of reflecting only circularly polarized light whose wavelength is the helical pitch of the liquid crystal, in which the direction of rotation of the liquid crystal helix coincides with the direction of circular polarization. By using this selective reflection characteristic, only specific circularly polarized light of natural light in a certain wavelength band is transmitted and separated, and the remainder is reflected and reused, whereby a highly efficient polarizing film can be manufactured. At this time, the transmitted circularly polarized light is converted into linearly polarized light by passing through a 义 / 4 wavelength plate, and the direction of the linearly polarized light is transmitted to the liquid crystal display. A liquid crystal display device with high transmittance can be obtained by adjusting the transmission direction of the absorption polarizer used. That is, when a cholesteric liquid crystal film is used as a linear polarizer in combination with a λ / 4 wavelength plate, there is theoretically no loss of light, so a conventional absorption polarizer that absorbs 50% of light was used alone. Compared to the case, theoretically, the brightness can be improved twice.

However, the selective reflection characteristic of the cholesteric liquid crystal is limited only to a specific wavelength band, and it has been difficult to cover the entire visible light range. The selective reflection wavelength range of the cholesteric liquid crystal is 80,

Δλ = 2 Α-(n e— n 0) / (n e + no)

n o: Refractive index of cholesteric liquid crystal molecules for normal light

n e: refractive index of cholesteric liquid crystal molecules for extraordinary light

λ: center wavelength of selective reflection

It depends on the molecular structure of the cholesteric liquid crystal itself. According to the above equation, the width of the selective reflection wavelength region △ λ can be increased by increasing One-n0, but ne-η0 is usually 0.3 or less. If this value is increased, other functions (alignment characteristics, liquid crystal temperature, etc.) of the liquid crystal become insufficient and practical use was difficult. Therefore, in practice, the selective reflection wavelength region width Δλ was at most about 15 O nm. Most of the practically usable cholesteric liquid crystals were only about 30 to 100 nm. Also, the selective reflection center wavelength is

λ = (ne + no) P / 2

P: Spiral pitch length required for one turn of cholesteric liquid crystal

If the pitch is constant, it depends on the average refractive index of the liquid crystal molecules and the pitch length. Therefore, in order to cover the entire visible light region, a plurality of layers having different selective reflection center wavelengths are laminated, or the pitch length is continuously changed in the thickness direction to form the existence distribution of the selective reflection center wavelength itself. Was.

For example, there is a method of continuously changing the pitch length in the thickness direction (for example, see Japanese Patent Application Laid-Open No. Hei 6-218814, Japanese Patent No. 3272668, Japanese Patent Application Laid-Open No. 11-248943). )). In this method, when the cholesteric liquid crystal composition is cured by UV exposure, the difference between the exposure speed and the exposure speed on the exposure surface side and the polymerization speed is different. By adding, the composition ratio change of the liquid crystal compositions having different reaction rates is provided in the thickness direction.

The point of this method is to take a large difference in exposure intensity between the exposure surface side and the emission surface side. Therefore, in many cases of the above-mentioned prior art examples, a technique of mixing an ultraviolet absorber into a liquid crystal composition to generate absorption in a thickness direction and amplify a difference in exposure amount due to an optical path length is employed. Was.

However, in the cholesteric liquid crystal film obtained by additional testing of the above-mentioned prior art, during an endurance test (heating test or humidification test), an ultraviolet absorber precipitates on the cholesteric liquid crystal film surface or the bonding interface with other layers. Was observed. This is considered to be due to the low molecular weight of the UV absorber, which migrated through the film during the long-term durability test and aggregated. For general industrial material applications, this level of surface precipitation was not recognized as an abnormal appearance, and even if it was deposited on the interface, it was not a problem that led to interface separation. However, cholesteric liquid crystal films used in liquid crystal display devices are located on the optical path of strong transmitted light, and when such precipitates are generated, the deposited particles are directly visible, and the light utilization efficiency due to depolarization of the precipitates is reduced. Optical problems such as a decrease in the light scattering distribution of the light source due to the haze at which the precipitates are generated or reduced are caused.

If the cholesteric liquid crystal film is used in a room temperature environment, it is unlikely that this type of precipitate will occur. However, when used in a liquid crystal display device, deposition of an ultraviolet absorber is inevitable if the radiation from the light source of the backlight is strongly exposed for a long period of time. Such precipitates are difficult to be visually recognized if they are uniformly deposited on the surface, and are not easily recognized as defects.However, the radiation heat from the light source has a large fluctuation with respect to the liquid crystal display device surface, and the radiation heat is wide. In some cases, the amount of precipitation increased only in a large part of the area, and the area was visually recognized as in-plane unevenness. In addition, the display luminance required for liquid crystal display devices in recent years has exceeded 200 candela, and the light source side is exposed to a light irradiation intensity of about 10,000 ndera. Due to this irradiation intensity, the light source side of the liquid crystal display device is continuously heated to about 40 to 60 ° C depending on the ambient temperature. For this reason, precipitation of the UV absorber was observed not only in the heating reliability test but also in the continuous lighting test mounted on the liquid crystal display device. For example, an ultraviolet polymer obtained from a cholesteric liquid crystal composition to which an ultraviolet absorber is combined is used at 80 ° C. X 500 Time, 60 ° C, 90% RHX

In addition, powder deposition on the surface was observed. Disclosure of the invention

An object of the present invention is to provide a broadband cholesteric liquid crystal film having a broadband reflection band and a method for producing the same. Another object of the present invention is to provide a broadband cholesteric liquid crystal film having a broadband reflection band and excellent durability, and a method for producing the same.

Another object of the present invention is to provide a circularly polarizing plate using the broadband cholesteric liquid crystal film, and further to provide a linear polarizer, a lighting device, and a liquid crystal display using the circularly polarizing plate.

The present inventors have conducted intensive studies to solve the above problems, and as a result, have found that the above object can be achieved by the following broadband cholesteric liquid crystal film and a method for producing the same, and have completed the present invention.

That is, the present invention provides a method for applying a liquid crystal mixture containing a polymerizable mesogen compound (a), a polymerizable chiral agent (b) and a photopolymerization initiator (c) on an alignment substrate, and under an inert gas atmosphere, The present invention relates to a cholesteric liquid crystal film obtained by ultraviolet polymerization, which has a reflection bandwidth of 20 O nm or more.

The broadband cholesteric liquid crystal film of the present invention is obtained by subjecting a polymerizable liquid crystal mixture to UV polymerization, and the reflection bandwidth of the selective reflection wavelength is as wide as 200 nm or more, which is an unprecedented broadband. Has a reflection bandwidth of The reflection bandwidth is preferably at least 300 nm, more preferably at least 400 nm. Further, it is preferable that the reflection bandwidth is not less than 200 nm in a visible light region, particularly in a wavelength region of 400 to 800 nm. '

The reflection bandwidth was measured by measuring the reflection spectrum of a broadband cholesteric liquid crystal film with a spectrophotometer (MCPD-200, instantaneous multi-photometry system, manufactured by Otsuka Electronics Co., Ltd.). Reflection band.

The broadband cholesteric liquid crystal film is a cholesteric liquid crystal film. It is preferable that the switch length is changed so as to continuously narrow from the ultraviolet radiation side. In the broadband cholesteric liquid crystal film, it is preferable that the polymerizable mesogen compound (a) has one polymerizable functional group and the polymerizable chiral agent (b) has two or more polymerizable functional groups.

As disclosed in Broer et al., Nature, 378, pp. 467 (1995), a mesogenic compound having chirality is diffused to obtain a broadband cholesteric liquid crystal film having a continuous pitch change. Has been. On the other hand, in the present invention, by diffusing a mesogen compound having one polymerizable functional group, a broadband cholesteric liquid crystal that continuously changes in pitch is obtained, so that the order of change in chiral bitch is reversed. That is, in the present invention, it is possible to obtain a broadband cholesteric liquid crystal film having a pitch change such that the pitch length continuously narrows from the ultraviolet irradiation side. Further, the pitch length is preferably changed so that the difference between the ultraviolet radiation side and the opposite side is at least 100 nm. The pitch length was read from a cross-sectional TEM image of the broadband cholesteric liquid crystal film. The obtained cholesteric liquid crystal film has a grunge yang structure in which the pitch length is continuously reduced from one side. On the long pitch length side, it is preferable to have a spiral structure having a pitch length showing reflection in the infrared region continuously or discontinuously or a layer in which the spiral is substantially eliminated. In the above-mentioned broadband cholesteric liquid crystal film, the layer in which the spiral structure having a long pitch length or the spiral is almost eliminated is a retardation layer having a retardation value of 50 to 450 nm optically with respect to incident light from the front. Is preferred. Thus, it has a Grand Jean structure and can be used as a cholesteric liquid crystal.

It has a portion exhibiting selective reflection in the visible region (380 to 780 nm), and has a layer having a pitch completely different from that of the portion exhibiting selective reflection on the long pitch length side. This layer is a retardation layer as an optical property, and its retardation value is controllable between 50 and 45 O nm. For example, when the retardation value is 100 to 16 O nm, light in the visible light region passing through the cholesteric liquid crystal film shows linearly polarized light. On the other hand, when the phase difference value is between 200 and 400 nm, it can be converted into a state of circularly polarized light that rotates in the opposite direction to the state of circularly polarized light transmitted through the cholesteric liquid crystal. This Thus, the polarization state of transmitted light can be freely controlled by the retardation value of the retardation layer of the broadband cholesteric liquid crystal film. Therefore, it is easy to use it as a polarizing plate according to the mode of the liquid crystal display to be used.

The liquid crystal mixture forming the broadband cholesteric liquid crystal film may not contain an ultraviolet absorber.

The broadband cholesteric liquid crystal film of the present invention can have a broadband reflection bandwidth without using an ultraviolet absorber. Therefore, it is possible to suppress an increase in haze, a decrease in the transmittance of polarized light, and visual observation of precipitated particles due to the use of an ultraviolet absorber, and the durability under a heated and humidified environment is good, and the reliability is excellent. .

In the broad band cholesteric liquid crystal film, the molar absorption coefficient of the polymerizable mesogen compound (a) ^{is, 50~5 00 dm 3 mo 1 ^} cm '1 ® 36 5 nm Dearuko and are preferred. Those having the molar extinction coefficient have an ultraviolet absorbing ability. Molar absorption light coefficient is more preferably ^{100~2 5 0 dm 3 mo 1- i} cm- '@ 3 6 5 nm. Molar extinction coefficient of ^{^{5 0 dm 3 mo l "1}} cm- 1 ® 3 6 5 nm less than sufficient Polymerization speed difference is hardly wideband I spoon without stick. Meanwhile, 500 dm ³ mo 1 one ¹ cm- If it is larger than 365 nm, the polymerization may not completely proceed and the curing may not be completed.The molar extinction coefficient is obtained by measuring the spectrophotometric spectrum of each material and obtaining the absorbance at 365 nm. It is a measured value.

As the polymerizable mesogen compound (a), the following general formula (1):

(However, represents a hydrogen atom or a methyl group. N represents an integer of 1 to 5.). Further, the present invention provides a method for applying a liquid crystal mixture containing a polymerizable mesogen compound (a), a polymerizable chiral agent (b) and a photopolymerization initiator (c) on an alignment substrate, and then applying the mixture under an inert gas atmosphere. And a method for producing a broadband cholesteric liquid crystal film by UV polymerization. The broadband cholesteric liquid crystal film of the present invention can be manufactured by controlling the temperature, ultraviolet light irradiation, and irradiation time of ultraviolet light irradiation of the liquid crystal mixture applied on an alignment substrate in an inert gas atmosphere.

The present invention also relates to a circularly polarizing plate using the broadband cholesteric liquid crystal film.

The present invention also relates to a linear polarizer obtained by laminating a quarter-wave plate on the circularly polarizing plate. In the linear polarizer, it is preferable that the cholesteric liquid crystal film, which is a circularly polarizing plate, is laminated on the 長 / 4 plate so that the pitch length is continuously narrowed. And a linear polarizer obtained by bonding an absorption polarizer with its transmission axis direction aligned.

The four plates used for the linear polarizer have the in-plane principal refractive index nx, ny, and the principal refractive index in the thickness direction nz, where Nz is defined by the following formula: (nx—nz) / (nx_ny) It is preferable that the coefficient satisfies 0.5 to 12.5.

In addition, the present invention relates to a lighting device, characterized in that the circular polarizer or the linear polarizer is provided on the front side of a surface light source having a reflective layer on the back side.

Furthermore, the present invention relates to a liquid crystal display device having a liquid crystal cell on a light emission side of the lighting device.

As the linear polarizer, the illuminating device, and the liquid crystal display device, those in which all or a part of each forming layer is in close contact with an adhesive layer can be used.

The broadband cholesteric liquid crystal film of the present invention is used as a circularly polarizing plate, and a linear polarizer can be obtained by combining a λ / 4 plate. Furthermore, the reliability of the liquid crystal display device can be improved by combining an absorbing polarizer and the like. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a conceptual diagram of a polarizing plate used in evaluations of Examples 1 to 3 and Comparative Examples 1 to 3. 1: polarizing plate, 2: / 4 plate, 3: cholesteric liquid crystal film (circular polarizing plate), 4 adhesive layers.

FIG. 2 is a reflection spectrum of the cholesteric liquid crystal film produced in Example 1.

FIG. 3 is a reflection spectrum of the cholesteric liquid crystal film produced in Example 2.

FIG. 4 shows the reflection spectrum of the cholesteric liquid crystal film produced in Example 3.

FIG. 5 shows the reflection spectrum of the cholesteric liquid crystal film produced in Comparative Example 1.

FIG. 6 shows the reflection spectrum of the cholesteric liquid crystal film produced in Comparative Example.

FIG. 7 is a reflection spectrum of the cholesteric liquid crystal film produced in Comparative Example 3. BEST MODE FOR CARRYING OUT THE INVENTION

The cholesteric liquid crystal film of the present invention is obtained by applying a liquid crystal mixture containing a polymerizable mesogen compound), a polymerizable chiral agent (b) and a photopolymerization initiator (c) on an alignment substrate, and then, under an inert gas atmosphere. It is obtained by ultraviolet polymerization. As the polymerizable mesogen compound (a), a compound having at least one polymerizable functional group and having a mesogen group comprising a cyclic unit or the like is preferably used. Examples of the polymerizable functional group include an acryloyl group, a methacryloyl group, an epoxy group, and a vinyl ether group. Of these, an acryloyl group and a methacryloyl group are preferable. As described above, the polymerizable mesogen compound (a) preferably has a molar extinction coefficient of 50 to 500 dm ³ mo 1 cm ^-1 ® 365 nm. As described above, the polymerizable mesogen compound (a) having such a molar extinction coefficient includes the following general formula (1):

(However, represents a hydrogen atom or a methyl group. Η represents an integer of 1 to 5.).

Specific examples of the polymerizable mesogen compound (a) include, for example, the following compounds.

Examples of the polymerizable chiral agent (b) include LC756 manufactured by BASF.

The amount of the polymerizable chiral agent (b) is 1 to 20 parts by weight based on 100 parts by weight of the polymerizable mesogen compound) and the polymerizable chiral agent (b) in total. ^ Is preferred and 3 to 7 parts by weight is more preferred. The helical torsional force (HTP) is controlled by the ratio of the polymerizable mesogen compound (a) and the polymerizable chiral agent (b). Before the percentage Within the above range, the reflection band can be selected so that the reflection spectrum of the obtained cholesteric liquid crystal film can cover the entire visible range.

Various photopolymerization initiators (C) can be used without particular limitation. For example, irgacure 184, irgacure 907, irgacure 369, and irgacure 651 manufactured by Ciba Specialty Chemicals Co., Ltd. may be mentioned. The amount of the photopolymerization initiator to be combined is preferably from 0.01 to 100 parts by weight per 100 parts by weight of the total of the polymerizable mesogen compound (a) and the polymerizable chiral agent (b). , 0.05 to 5 weight is more preferred.

Further, in the present invention, a liquid crystal mixture containing a polymerizable mesogen compound (a), a polymerizable chiral agent (b) and a photopolymerization initiator (c) can be used as a solution in a solvent. Although the solvent used is not particularly limited, methyl ethyl ketone, cyclohexanone, cyclopentanone and the like are preferable. The concentration of the solution is usually about 3 to 50% by weight.

The production of the cholesteric liquid crystal film of the present invention is carried out by applying the liquid crystal mixture on an alignment substrate, and then performing ultraviolet polymerization under an inert gas atmosphere. As the alignment base material, a conventionally known one can be used. For example, a thin film made of polyimide or polyvinyl alcohol is formed on a substrate, and the thin film is rubbed with rayon cloth or the like. A light directing film or a stretched film irradiated with ultraviolet rays is used. In addition, it can be oriented by magnetic field, electric field orientation, and shear stress operation.

The substrate may be a film made of a plastic such as polyethylene terephthalate, triacetyl cell mouth, norbornene resin, polyvinyl alcohol, polyimide, polyarylate, polycarbonate, polysulfone / polyethersulfone, a glass plate, quartz. Sheets are used.

The liquid crystal mixture is transferred to an inert gas atmosphere after being applied to the alignment substrate. When the liquid crystal mixture is a solution, the solution is applied to an alignment substrate, dried, and then transferred to an inert gas atmosphere. The drying temperature for volatilizing the solvent may be any temperature as long as it is higher than the boiling point of the solvent. Usually, the solvent species in the range of about 80 to 160 The temperature may be set according to the type.

The coating thickness of the liquid crystal mixture (the coating thickness after drying the solvent in the case of a solution) is preferably 5 to 20 m 1 ^, more preferably about 7 to 12 μm. If the coating thickness is thinner than 5 m, it may not be possible to form a helical pitch sufficient to cover the reflection bandwidth of 100 nm or more.If the coating thickness is thicker than 20 m, the alignment regulating force does not act sufficiently. Poor alignment may occur.

The inert gas is not particularly limited as long as it does not affect the ultraviolet polymerization of the liquid crystal mixture. Examples of such inert gas include nitrogen, argon, helium, neon, xenon, and krypton. Of these, nitrogen is the most versatile and preferred. ·

The ultraviolet irradiation may be performed from either the alignment substrate side or the applied liquid crystal mixture side.

The polymerization temperature when irradiating ultraviolet rays is generally 140 ° C. or less. Specifically, the temperature is preferably about 60 to 140 ° C, and more preferably 80 ° to 120 ° C. Heating has the effect of accelerating the diffusion rate of the monomer component. If the temperature is lower than 60 ° C, the diffusion rate of the polymerizable mesogen compound (a) is very slow, and it takes a very long time to broaden the band.

Ultraviolet illuminance is preferably ^{0. l~20mW / cm 2, l~10mW /} cm 2 is more preferable. If the UV illuminance exceeds 2 OmW / cm ² , the polymerization reaction rate is higher than the diffusion rate, and it is not preferable because the band broadens better. The irradiation time is as short as 5 minutes or less, preferably 3 minutes or less, and most preferably 1 minute or less.

The cholesteric liquid crystal film thus obtained is used without being separated from the substrate, and may be used while being separated from the substrate.

The broadband cholesteric liquid crystal film of the present invention is used as a circularly polarizing plate. A linear polarizer can be obtained by laminating a λ / 4 plate on a circularly polarizing plate. It is preferable that the cholesteric liquid crystal film, which is a circularly polarizing plate, is laminated on the 連続 / 4 plate so that the pitch length is continuously narrowed.

In the iZ4 plate, the in-plane main refractive index is nx and ny, and the main refractive index in the thickness direction is nz. In this case, it is preferable that the Nz coefficient defined by the formula: (nx-nz) / (nx-ny) satisfies 0.5 to -2.5.

For the 4th plate, stretch films made of suitable polymers such as polycarbonate, norbornene resin, polyvinyl alcohol, polystyrene, polymethyl methacrylate, polypropylene and other polyolefins, polyarylates, and polyamides. Examples include a birefringent film obtained by treatment, an alignment film made of a liquid crystal material such as a liquid crystal polymer, and an alignment layer of a liquid crystal material supported by a film. The thickness of the quarter-wave plate is usually preferably 0.5 to 20 and particularly preferably 1 to L 0 m.

In a wide wavelength range such as a visible light region; a retarder functioning as a quarter-wave plate is, for example, for light-color light having a wavelength of 550 nm; a retarder functioning as an IZ four-wave plate and other positions It can be obtained by a method in which a phase difference layer exhibiting phase difference characteristics, for example, a phase difference layer functioning as a λ / 2 wavelength plate is superposed. Therefore, the retardation plate disposed between the polarizing plate and the brightness enhancement film may be composed of one or two or more retardation layers. It is used with the transmission axis direction aligned.

The polarizer is not particularly limited, and various types can be used. Examples of polarizers include hydrophilic polymer films such as polyvinyl alcohol-based films, partially formalized polyvinyl alcohol-based films, and ethylene-vinyl acetate copolymer-based partially saponified films. Examples thereof include a uniaxially stretched film obtained by adsorbing a dichroic substance such as a dichroic dye, a dehydrated product of polyvinyl alcohol, a dehydrochlorinated product of polychlorinated vinyl, and a polyene-based oriented film. Among these, a polarizer made of a polybutyl alcohol-based film and a dichroic substance such as iodine is preferable. The thickness of these polarizers is not particularly limited, but is generally about 5 to 80 m.

A polarizer which is obtained by dyeing a polyvinyl alcohol-based film with iodine and uniaxially stretching is dyed, for example, by immersing polyvinyl alcohol in an aqueous solution of iodine.

It can be manufactured by stretching to 3 to 7 times the original length. If necessary, it can be immersed in an aqueous solution of boric acid or potassium iodide. Further dyeing if necessary Before the color, the polyvinyl alcohol-based film may be immersed in water and washed. Rinse the polyvinyl alcohol-based film with water to remove dirt on the surface of the polyvinyl alcohol-based film and the anti-blocking agent, and swell the polyvinyl alcohol-based film to create unevenness such as uneven dyeing. It also has the effect of preventing Stretching may be performed after dyeing with iodine, or may be performed while dyeing, or may be dyed with iodine after stretching. Stretching can be performed in an aqueous solution of boric acid or potassium iodide or in a water bath.

The polarizer is usually provided with a transparent protective film on one or both sides and used as a polarizing plate. It is preferable that the transparent protective film is excellent in transparency, mechanical strength, heat stability, moisture shielding property, isotropy and the like. Examples of the transparent protective film include polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, and cellulosic polymers such as diacetyl cellulose and triacetyl cellulose.

—, A film made of a transparent polymer such as an acrylic polymer such as a polycarbonate-based polymer or polymethyl methacrylate. Also, styrene-based polymers such as polystyrene, acrylonitrile-styrene copolymer, polyethylene, polypropylene, polyolefins having a cyclic or norbornene structure, olefin-based polymers such as ethylene-propylene copolymer, and salt-based butyl-based polymers Also, a film made of a transparent polymer such as an amide polymer such as nylon or an aromatic polyamide may be used. Furthermore, imid-based polymers, sulfone-based polymers, polyethersulfone-based polymers, and polyethers; 3-terketone-based polymers, polyphenylene sulfide-based polymers, butyl alcohol-based polymers, vinylidene chloride-based polymers, and vinyl butyral-based polymers And films made of transparent polymers such as arylate polymers, polyoxymethylene polymers, epoxy polymers and blends of the above polymers. In particular, those having low optical birefringence are preferably used. From the viewpoint of the protective film of the polarizing plate, triacetyl cellulose, polycarbonate, atheryl polymer, cycloolefin resin, polyolefin having a norpolenene structure, and the like are preferable.

Further, a polymer film described in Japanese Patent Application Laid-Open Publication No. 2001-3434929 (WO01Z37007), for example, (A) side chain substituted and / or unsubstituted De group And (B) a thermoplastic resin having a substituted and / or unsubstituted phenyl and a nitrile group in a side chain. A specific example is a film of a resin composition containing an alternating copolymer of isobutylene and N-methylmaleimide and an acrylonitrile / styrene copolymer. As the film, a film made of a mixed extruded product of a resin composition or the like can be used. A transparent protective film that can be particularly preferably used in view of polarization characteristics and durability is a triacetyl cellulose film whose surface has been treated with an adhesive or the like. The thickness of the transparent protective film can be determined as appropriate, but is generally from 10 to 500 m in consideration of workability such as ^^ ゃ handling and thinness. In particular, the power is preferably 20 to 300 μm, and more preferably 30 to 200 m.

Further, it is preferable that the transparent protective film has as little coloring as possible. Therefore, Rt h = [(nx + ny) / 2 -nz] · d (where nx and ny are the main refractive index in the film plane, nz is the refractive index in the film thickness direction, and d is the film thickness. A protective film having a retardation value in the film thickness direction represented by the formula (1) of from 190 nm to 1075 nm is preferably used. By using such a retardation value (Rth) in the thickness direction of 190 nm to 1075 nm, coloring (optical coloring) of the polarizing plate due to the protective film can be almost eliminated. . The thickness direction retardation value (Rth) is more preferably from 180 nm to 1060 nm, particularly preferably from 170 nm to 1445 nm.

As the transparent protective film, a transparent protective film made of the same polymer material on the front and back sides may be used, or a transparent protective film made of a different polymer material or the like may be used.

The surface of the transparent protective film on which the polarizer is not adhered may be subjected to a hard coat layer / reflection P blocking treatment, a treatment for preventing sticking, and a treatment for diffusion or anti-glare.

The hard coat treatment is performed for the purpose of preventing scratches on the surface of the polarizing plate. For example, a cured film having an excellent hardness and a sliding property by a suitable ultraviolet-curable resin such as an acrylic resin or a silicone resin is used as a transparent protective film. It can be formed by a method of adding to the surface of the substrate. Anti-reflection treatment is to prevent reflection of external light on the polarizing plate surface This can be achieved by forming an anti-reflection film or the like according to the related art. The anti-stating treatment is performed to prevent adhesion to the adjacent layer. The anti-glare treatment is performed to prevent external light from being reflected on the surface of the polarizing plate and hindering the visibility of light transmitted through the polarizing plate. It is formed by giving a fine uneven structure to the surface of the transparent protective film by an appropriate method such as a sandblast method or an embossing method with a rough surface or a compounding method of transparent fine particles. can do. Examples of the fine particles to be included in the formation of the surface fine irregularities include silica, alumina, titania, zirconia, tin oxide, indium oxide, oxidized power, and oxidized antimony having an average particle size of 0.5 to 50 m. Transparent fine particles such as inorganic fine particles which may be conductive, such as inorganic fine particles, and organic fine particles formed of a crosslinked or uncrosslinked polymer or the like are used. When forming the fine surface unevenness structure, the amount of the fine particles used is generally 2 to 50 weight parts per 100 parts by weight of the transparent resin forming the fine surface unevenness structure; 25 parts by weight are preferred. The anti-glare layer may also serve as a diffusion layer (such as a viewing angle expanding function) for dispersing the light transmitted through the polarizing plate and expanding the viewing angle and the like.

The anti-reflection layer, anti-stating layer, diffusion layer, anti-glare layer and the like can be provided on the transparent protective film itself, or can be separately provided as an optical layer separately from the transparent protective layer.

The lamination of the linear polarizers and the lamination of the type 光学 optical layers can also be performed by a method of sequentially laminating them sequentially in the process of manufacturing a liquid crystal display device or the like. It has an advantage that it is excellent in stability and assembling work and can improve a manufacturing process of a liquid crystal display device and the like. Appropriate bonding means such as an adhesive layer can be used for lamination.

l In self-adhesion, their optical axes can be set at an appropriate arrangement angle according to the target retardation characteristics and the like.

The above-mentioned linear polarizer may be provided with an adhesive layer for bonding to another member such as a liquid crystal cell. The pressure-sensitive adhesive that forms the pressure-sensitive adhesive layer is not particularly limited, but includes, for example, an acryl polymer, a silicone polymer, a polyester, a polyurethane, a polyamide, a polyether, a fluorine-based or rubber-based polymer as a base polymer. Can be appropriately selected and used. In particular, an acrylic adhesive having excellent optical transparency, exhibiting appropriate wettability, cohesiveness and adhesive adhesive properties and having excellent weather resistance and heat resistance can be preferably used.

In addition to the above, the foaming phenomenon due to moisture absorption is prevented, the phenomena are prevented from falling, the light property is reduced due to the difference in thermal expansion, etc., and the liquid crystal cell is prevented from warping. In view of the above, an adhesive layer having a low moisture absorption rate and excellent heat resistance is preferred. .

The adhesive layer is made of, for example, natural or synthetic resins, particularly, tackifier resins, fillers, pigments, coloring agents, and antioxidants made of glass fibers, glass beads, metal powders, and other inorganic powders. The adhesive may contain an additive to be added to the pressure-sensitive adhesive layer. Further, it may be a pressure-sensitive adhesive layer containing fine particles and exhibiting light diffusibility.

The attachment of the adhesive layer can be performed by an appropriate method. For example, about 10 to 40% by weight of a pressure-sensitive adhesive prepared by dissolving or dispersing a base polymer or a composition thereof in a solvent consisting of an appropriate solvent alone or a mixture such as toluene or ethyl acetate. A solution is prepared, and the solution is directly attached on the polarizer by an appropriate developing method such as a casting method or a coating method, or an adhesive layer is formed on a separator according to the above, and the solution is formed on an optical element. Transfer method to the public. The adhesive layer may be provided as a superimposed layer of different compositions or types of layers. The thickness of the pressure-sensitive adhesive layer can be appropriately determined depending on the purpose of use and adhesive strength, etc., and is generally 1 to 500 m, preferably 5 to 200 m, and particularly preferably 10 to 100 m. preferable.

A separator is temporarily attached to the exposed surface of the adhesive layer for the purpose of preventing contamination and the like until practical use, and is covered. This can prevent the adhesive layer from coming into contact with the adhesive layer in a normal handling state. Except for the above thickness conditions, a suitable thin leaf such as a plastic film, rubber sheet, paper, cloth, nonwoven fabric, net, foamed sheet or metal foil, or a laminate thereof is required as the separator. Depending on the type, an appropriate material according to the prior art, such as a material coated with an appropriate release agent such as a silicone-based, long-chain alkyl-based, fluorine-based, or molybdenum sulfide, may be used.

Each layer such as an adhesive layer may include, for example, a salicylic acid ester compound, a benzophenol compound, a benzotriazole compound, a cyanoacrylate compound, or the like. Alternatively, a material having an ultraviolet absorbing ability by a method such as a method of treating with an ultraviolet absorbent such as a nickel complex salt compound may be used.

The linear polarizer of the present invention can be preferably used for forming various devices such as a liquid crystal display device. The formation of the liquid crystal display device can be performed according to a conventional method. That is, a liquid crystal display device is generally formed by appropriately assembling components such as a liquid crystal cell, an optical element, and an illumination system as necessary and incorporating a drive circuit. There is no particular limitation except for using, and it can be in accordance with the prior art. Any type of liquid crystal cell, such as a TN type, STN type, or 7C type, can be used.A liquid crystal display device in which the linear polarizer is disposed on one or both sides of the liquid crystal cell, or a backlight for an illumination system Alternatively, an appropriate liquid crystal display device such as one using a reflection plate can be formed. In that case, the linear polarizer according to the present invention can be installed on one side or both sides of the liquid crystal cell. When linear polarizers are provided on both sides, they may be the same or different. Further, when forming a liquid crystal display device, for example, one layer of appropriate parts such as a diffusion plate, an anti-glare layer, an anti-reflection film, a protection plate, a prism array, a lens array sheet, a light diffusion plate, and a backlight is provided at an appropriate position. Alternatively, two or more layers can be arranged. Example

Hereinafter, the present invention will be described with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

In each example, the following compounds were used as the polymerizable mesogen compound (a).

Molar extinction ^{coefficient, 2 2 0 dm 3 mo 1} cm- 1 ® 3 6 5 nm and which was also a heavy polymerizable chiral agent (b), was used from BASF LC 7 5 6. Example 1

96 parts by weight of the polymerizable mesogen compound (a) shown above, 4 parts by weight of the above-mentioned polymerizable chiral agent (b), and 5 parts by weight of Irgacure 184 (Cibas Specialty Chemicals) as a photopolymerization initiator (c) A cyclopentanone solution (30 wt% solids content) of a mixture consisting of was prepared. The solution was cast on a stretched polyethylene terephthalate substrate and dried at 100 ° C. for 2 minutes to remove the solvent. Subsequently, while heating at 110 ° C. in a nitrogen atmosphere, the substrate was irradiated with ultraviolet light at 3 mW / cm ² for 5 minutes to obtain a target cholesteric liquid crystal film.

Figure 2 shows the reflection spectrum of the obtained cholesteric liquid crystal film (circular polarizer). — The circularly polarizing plate had good circularly polarized light separation characteristics (reflection band) in the range of 450 to 890 nm. The total thickness of the cholesteric liquid crystal layer (film) was about 9 m. The pitch length of the obtained cholesteric liquid crystal layer is 0.54 m near the UV-irradiated surface (one layer below the UV-irradiated surface) and 0.1 mm near the opposite surface (1 mm below the opposite surface). 7 m.

The pitch of the obtained circularly polarizing plate is continuous compared to the wide viewing angle / 4 plate (Νζ coefficient = —1.2) obtained by biaxially stretching a polycarbonate resin film (thickness: 80〃πι). The shells were forked by acrylic adhesive (thickness: 25 urn) so that they became narrower. Further, a broadband polarizing plate was obtained by laminating an absorption polarizing plate SEG14425DU manufactured by Nitto Denko with an adhesive.

Example 2,

96 parts by weight of the polymerizable mesogen compound (a) shown above, 4 parts by weight of the above-mentioned polymerizable chiral agent (b), and Irgacure 907 as a photopolymerization initiator (c) (manufactured by Ciba Specialty Chemicals) 0 A cyclopentanone solution (30% by weight solids content) of a mixture consisting of .5 parts by weight was prepared. The solution was cast on a stretched polyethylene terephthalate substrate and dried at 100 ° C. for 2 minutes to remove the solvent. Next, while heating at 120 ° C. in a nitrogen atmosphere, ultraviolet irradiation was performed from the substrate side at 3 mW / cm ² for 5 minutes to obtain a target cholesteric liquid crystal film.

Figure 3 shows the reflection spectrum of the obtained cholesteric liquid crystal film (circular polarizer). The obtained circularly polarizing plate has good circularly polarized light separating characteristics in the range of 501 to 970 nm. Had. The total thickness of the cholesteric liquid crystal layer (film) was about 9 m. The pitch length of the obtained cholesteric liquid crystal layer is 0.57 m near the ultraviolet radiation surface (1 μm below the ultraviolet irradiation surface) and 0.3 μm near the opposite surface (1 μm below the opposite surface). 1 m.

A wide viewing angle obtained by biaxially stretching a polycarbonate resin film (80 m thick); in contrast to a 1/4 plate (Nz coefficient = -1.2), the obtained circularly polarizing plate has a continuous pitch length. It was attached with an ataryl-based adhesive (5 m. Thick) so that it would be narrower. Further, an absorption type polarizing plate TEG 1465 DU manufactured by Nitto Denko was laminated on this with an adhesive material to obtain a broadband polarizing plate.

Example 3

96 parts by weight of the above polymerizable mesogen compound (a), the above polymerizable chiral agent

(b) 4 parts by weight of a photopolymerization initiator and (c) irgacure 369 (Cibas chartical chemicals ± ズ) 0.0 0.05 part by weight of a mixture of cyclopentanone (30% by weight solid content) Was prepared. The solution was cast on a stretched polyethylene terephthalate substrate and dried at 100 for 2 minutes to remove the solvent. Next, while heating at 120 ° C. in a nitrogen atmosphere, the substrate was irradiated with ultraviolet light at 1 lmW / cm ² for 5 minutes to obtain a target cholesteric liquid crystal film.

Fig. 4 shows the reflection spectrum of the obtained cholesteric liquid crystal film (circular polarizer). The obtained circularly polarizing plate had good circularly polarized light separation characteristics in the range of 520 to 920 nm. The total thickness of the cholesteric liquid crystal layer and (film) was about 9 m. The pitch length of the obtained cholesteric liquid crystal layer is 0.56 m near the UV-irradiated surface (1 m below the UV-irradiated surface) and 0.31 m near the opposite surface (1 m below the opposite surface). m.

The obtained circularly polarizing plate is laminated on a 义 / 4 plate (Nitto Denko NRF film An = 140 nm, Nz coefficient = —1.2), in such a direction that the pitch length is continuously narrowed. A 1/2 plate (NRZ film made by Nitto Denko, n = 270 nm, Nz {¾ = .0.5, viewing angle characteristic compensation type) was placed at 17.5 degrees with respect to the axis angle. Acrylic adhesive (25 m thick) was used for each lamination. In this case, the transmission polarization axis is 10 degrees with respect to the axis of the L / 4 plate. Photon SEG 14 25 DU was bonded in the same manner to obtain a broadband polarizing plate.

Comparative Example 1

96 parts by weight of the above polymerizable mesogen compound (a), 4 parts by weight of the above polymerizable chiral agent (b), and 5 parts by weight of Irgacure 184 (manufactured by Ciba Specialty Chemicals) as a photopolymerization initiator (c) A cyclopentanone solution (30% by weight solids content) of a mixture consisting of was prepared. The above solution was cast on a stretched polyethylene terephthalate base material, and the solvent was removed by drying at 10 (TC for 2 minutes. Then, while heating at 80 ° C under a nitrogen atmosphere, 5 ° C was applied from the base material side. Irradiation with OmW / cm ² was performed for 5 minutes to obtain a target cholesteric liquid crystal film.

Figure 5 shows the reflection spectrum of the obtained cholesteric liquid crystal film (circular polarizer). The obtained circularly polarizing plate had good circularly polarized light separating characteristics in the range of 710 to 880 nm. The total thickness of the cholesteric liquid crystal layer (film) was about 9 m. The pitch length of the obtained cholesteric liquid crystal layer is 0.52 m near the UV-irradiated surface (1 μm below the UV-irradiated surface) and 0.52 m near the opposite surface (1 m below the opposite surface). ym.

Wide viewing angle obtained by biaxially stretching a polycarbonate resin film (thickness 80 ιη); 円 4 plate (Νζ coefficient = -1.2), the obtained circularly polarizing plate has a continuously narrower pitch length. The shells were forked by acrylic adhesive (25 m thick) in such a direction. Further, a polarizing plate was obtained by laminating an absorption polarizing plate SEG1425DU manufactured by Nitto Denko with an adhesive. ,

Comparative Example 2

96 parts by weight of the polymerizable mesogen compound (a) shown above, 4 parts by weight of the above-mentioned polymerizable power agent (b), and 5 parts by weight as a photopolymerization initiator (c) Irgacure 184 (manufactured by Ciba Specialty Chemicals) A cyclopentanone solution (30% by weight solids content) of a mixture consisting of two parts was prepared. The solution was cast on a stretched polyethylene terephthalate substrate and dried at 100 ° C. for 2 minutes to remove the solvent. Next, while heating at 40 ° C. under a nitrogen atmosphere, the substrate was irradiated with ultraviolet light at 3 mW / cm ² for 5 minutes to obtain a target cholesteric liquid crystal film.

Figure 6 shows the reflection spectrum of the obtained cholesteric liquid crystal film (circular polarizer). Show. The obtained circularly polarizing plate had good circularly polarized light separation characteristics in the range of 720 to 870 nm. The total thickness of the cholesteric liquid crystal layer (film) was about 9 / m. The pitch length of the obtained cholesteric liquid crystal layer was 0.52 m near the UV-irradiated surface (1 μm below the UV-irradiated surface) and 0.52 m near the opposite surface (1 m below the opposite surface). Um.

In contrast to the wide viewing angle 1/4 plate (Nz coefficient = -1.2) obtained by biaxially stretching a polycarbonate resin film (80 m thick), the pitch of the obtained circularly polarizing plate is continuously narrowed. The shells were forked by acrylic adhesive (thickness: 25 urn). Furthermore, a polarizing plate was obtained by laminating an absorption polarizing plate SEG14425DU manufactured by Nitto Denko with an adhesive.

Comparative Example 3

96 parts by weight of the polymerizable mesogen compound (a) shown above, the polymerizable chiral agent

(b) 4 parts by weight, photopolymerization initiator (c) 5 parts by weight of irgacure 184 (manufactured by Ciba-Salty Chemicals) and Tinuvin 400 (manufactured by CHI-SPECIALI CHEMICALS, an ultraviolet absorber) 1 part by weight of the mixture

(30 wt% solids content) was prepared. The above solution is drawn

It was cast on a rate substrate and dried at 100 ° C. for 2 minutes to remove the solvent. Then

While heating at 80 ° C. under a nitrogen atmosphere, the substrate was irradiated with ultraviolet rays at 5 OmW / cm ² for 5 minutes to obtain a target cholesteric liquid crystal film.

Figure 7 shows the reflection spectrum of the obtained cholesteric liquid crystal film (circular polarizer). The obtained circularly polarizing plate had good circularly polarized light separation characteristics in the range of 710 to 860 nm. The total thickness of the cholesteric liquid crystal layer (film) was about 9 m

. The pitch length of the obtained cholesteric liquid crystal layer is 0.5〃1 m near the UV-irradiated surface (1 μm below the UV-irradiated surface) and 0.5 mm near the opposite surface (1 m below the opposite surface). 1〃m.

The pitch of the obtained circularly polarizing plate is continuously narrowed compared to the wide viewing angle 义 4 plate (Nz coefficient = 1.2) obtained by biaxially stretching a polycarbonate resin film (80 m thick). The shells were forked by acrylic adhesive (thickness: 25 ^ m) in such a way as to achieve the desired orientation. In addition, Nitto Denko's absorption type polarizer SEG 1 4 2 5 DU is used as an adhesive. To obtain a polarizing plate.

The following evaluations were performed on the (wideband) polarizing plates obtained in Examples and Comparative Examples. Table 1 shows the results.

(Brightness improvement rate)

(Broadband) The brightness when the polarizing plate was mounted on a 15-inch TFT liquid crystal display device was measured by BM7 manufactured by TOPCON. The magnification of the increased luminance was calculated as compared to the luminance without the broadband cholesteric liquid crystal film.

(Viewing angle characteristics: color change)

The viewing angle characteristics were evaluated based on the following criteria by deriving Δχγ with a viewing angle measuring device EZ-CONTRAST manufactured by EL DIM.

Δχγ = ((χ. — _{X l} "+ (y. One) ² ) °" ⁵

Front chromaticity (x., Y.), 60 ° chromaticity (X !, y :)

i: Color tone change Xy at a viewing angle of 60 ° is 0.04 or less.

Poor: color change Δ X y is 0.04 or more in the field of view angle of 60 ^0.

Belief)

After the broadband polarizing plate or polarizing plate was put in an environment of 80 ° C. and 60 T: 90% RH for 500 hours, the presence or absence of a powdery substance precipitated on the surface was visually determined. In the case where a powdery substance is present, there is a problem as an optical application.

Table i

Industrial applicability

The broadband cholesteric liquid crystal film of the present invention is useful as a circularly polarizing plate (reflection type polarizer). Circularly polarizing plates can be used for linear polarizers, lighting devices, liquid crystal display devices, and the like.

Claims

The scope of the claims

1. A liquid crystal mixture containing a polymerizable mesogen compound (a), a polymerizable chiral agent (b) and a photopolymerization initiator (c) is applied on an alignment substrate, and subjected to ultraviolet polymerization under an inert gas atmosphere. A cholesteric liquid crystal film obtained by the above method, having a reflection bandwidth of 200 nm or more.

2. The broadband cholesteric liquid crystal film according to claim 1, wherein the pitch length of the cholesteric liquid crystal film changes so as to continuously narrow from the ultraviolet radiation side.

3. The polymerizable mesogen compound (a) has one polymerizable functional group, and the polymerizable chiral agent (b) has two or more polymerizable functional groups. Is a broadband cholesteric liquid crystal film according to item 2.

4. The broadband cholesteric liquid crystal film according to any one of claims 1 to 3, wherein the liquid crystal mixture does not contain an ultraviolet absorber.

5. The polymerizable mesogen conjugate has a molar extinction coefficient of 50 to 500 dm ³ mo 1 to ¹ cm — '@ 365 nm, wherein the molar extinction coefficient is 50 to 500 dm ³ mo 1 to ¹ cm —' @ 365 nm. The broadband cholesteric liquid crystal film according to any of the above.

6. The polymerizable mesogen compound (a) has the following general formula (1):

(Wherein represents a hydrogen atom or a methyl group; n represents an integer of 1 to 5). A compound according to any one of claims 1 to 5, wherein The broadband cholesteric liquid crystal film according to any of the above-mentioned items.

7. A liquid crystal mixture containing a polymerizable mesogen compound (a), a polymerizable chiral agent (b), and a photopolymerization initiator (c) is applied on an alignment substrate, and then in an inert gas atmosphere. The method for producing a broadband cholesteric liquid crystal film according to any one of claims 1 to 6, wherein ultraviolet polymerization is performed.

8. A circularly polarizing plate using the broadband cholesteric liquid crystal film according to any one of claims 1 to 6. .

9. A linear light beam obtained by laminating a λ / 4 plate on the circularly polarizing plate according to claim 8.

10. The linear polarizer according to claim 9, which is obtained by laminating a cholesteric liquid crystal film, which is a circularly polarizing plate, on a λ / 4 plate so that the pitch length is continuously narrowed.

1 1. A linear polarizer obtained by attaching an absorption polarizer to the transmission axis of the linear polarizer according to claim 9 or 10 so that the transmission axis direction thereof is aligned.

1 2. Assuming that the in-plane principal refractive index is nx and ny and the principal refractive index in the thickness direction is nz, the s / 4 plate is defined by the formula: (n xn z) / (nx-ny) The linear polarizer according to any one of claims 9 to 11, wherein the Nz coefficient satisfies 0.5-2.5.

1 3. A circular polarizer according to claim 8 or a linear polarizer according to any one of claims 9 to 11 on the front side of a surface light source having a reflective layer on the back side. Lighting device characterized by the following.

14. A liquid crystal display device comprising a liquid crystal cell on the light emission side of the lighting device according to claim 13. ,