WO2015105366A1

WO2015105366A1 - Display apparatus

Info

Publication number: WO2015105366A1
Application number: PCT/KR2015/000218
Authority: WO
Inventors: Hye Jin Kim; Won Yong Lee
Original assignee: Samsung Electronics Co., Ltd.
Priority date: 2014-01-09
Filing date: 2015-01-09
Publication date: 2015-07-16
Also published as: KR20150083282A

Abstract

Disclosed herein is a display apparatus including a polarizer to polarize incident light, a first electrode through which polarized light passes, a liquid crystal layer to change a polarization direction of light passing through the first electrode, a second electrode to reflect light having changed polarization direction and patterned to at least one group, and a controller to control reflectance of light of the second electrode by controlling voltage applied to the first electrode and the second electrode patterned to at least one group.

Description

DISPLAY APPARATUS

Embodiments of the present invention relate to display apparatuses capable of controlling reflectance.

Display apparatuses are devices to display visible images in accordance with control signals. In recent years, a variety of flat panel display devices have been developed with reduced weight and volume in comparison to a cathode ray tube (CRT) display. These flat panel display devices have excellent characteristics including compact size, a large image display area, high degree of flatness, and excellent image quality.

In general, a display apparatus includes a liquid crystal layer that changes optical properties of incident light in accordance with a voltage applied thereto, and displays a visual image by changing properties of the incident light by controlling the voltage applied to the liquid crystal layer.

In addition, display apparatuses have been used in various application fields with the development of related technology. For example, display apparatuses have been applied to windows capable of adjusting light transmittance.

Therefore, it is an aspect of the present invention to provide a display apparatus capable of controlling reflectance.

Additional aspects of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

In accordance with one aspect of the present invention, a display apparatus includes a polarizer to polarize incident light, a first electrode through which polarized light passes, a liquid crystal layer to change a polarization direction of light passing through the first electrode, a second electrode to reflect light having changed polarization direction and patterned to at least one group, and a controller to control reflectance of light of the second electrode by controlling voltage applied to the first electrode and the second electrode patterned to at least one group.

The second electrode may be a wire grid polarizer. The wire grid polarizer may include a plurality of metallic grids, and a base unit on which the plurality of metallic grids are disposed. The plurality of metallic grids may be patterned to a plurality of groups.

Light incident on one group to which a voltage is applied among the plurality of groups may pass through the second electrode, and light incident on another group to which a voltage is not applied may be reflected by the second electrode.

In accordance with another aspect of the present invention, a display apparatus includes a first display panel including a first polarizer to polarize incident light, a first electrode to transmit the polarized light, a first liquid crystal layer to change a polarization direction of the light passing through the first electrode, and a second electrode to reflect the light, the polarization direction of which is changed, and patterned to at least one group, a second display panel disposed adjacent to the second electrode and displaying an image by using an inner light source, and a controller to control reflectance of the second electrode by applying a voltage to the first liquid crystal layer and control the second display panel to display the image.

The second electrode may be a wire grid polarizer. The wire grid polarizer may include a plurality of metallic grids, and a base unit on which the plurality of metallic grids are disposed.

The first display panel and the second display panel may be insulated from each other by the base unit.

The second display panel may include a third electrode disposed on the opposite surface of the base unit, a fourth electrode disposed to be spaced apart from the third electrode, and a second liquid crystal layer disposed between the third electrode and the fourth electrode and changing a polarization direction of incident light.

The display apparatus may further include a color layer disposed between the base unit and the third electrode and transmitting light having a selected wavelength.

The second electrode may be patterned to a plurality of groups. Light incident on one group to which a voltage is applied among the plurality of groups may pass through the second electrode, and light incident on another group to which a voltage is not applied may be reflected by the second electrode.

The second display panel may further include a second polarizer disposed between the fourth electrode and a light source and polarizing light emitted from the light source. Light, the polarization direction of which is changed by the second liquid crystal layer, among light polarized by the second polarizer may be reflected by the wire grid polarizer.

As is apparent from the above description, manufacturing costs of the display apparatus may be reduced, and a manufacturing process thereof may be simplified. In addition, a physical thickness of the display apparatus may be reduced.

FIG. 1 is a perspective view illustrating an appearance of a display apparatus according to an embodiment of the present invention;

FIG. 2 is a perspective view for describing a reflection mode of the display apparatus;

FIG. 3 is a perspective view for describing a transmission mode of the display apparatus;

FIG. 4 is a control block diagram for describing the display apparatus in detail;

FIG. 5 is a schematic exploded perspective view illustrating the display apparatus;

FIG. 6 is a perspective view schematically illustrating a wire grid polarizer;

FIG. 7 is a diagram for describing a reflection mode of the display apparatus;

FIG. 8 is a diagram for describing a transmission mode of the display apparatus;

FIGS. 9A and 9B are diagrams for describing a combination mode of the display apparatus;

FIG. 10 is a control block diagram for describing a display apparatus according to another embodiment of the present invention in detail;

FIG. 11 is a schematic cross-sectional view illustrating the display apparatus of FIG. 10;

FIG. 12 is a schematic view illustrating a second display panel of FIG. 10; and.

FIG. 13 is a diagram for describing a transmission mode of the display apparatus of FIG. 10.

Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout.

FIG. 1 is a perspective view illustrating an appearance of a display apparatus 1 according to an embodiment of the present invention. FIG. 2 is a perspective view for describing a reflection mode of the display apparatus 1. FIG. 3 is a perspective view for describing a transmission mode of the display apparatus 1.

Referring to FIG. 1, a display apparatus 1 includes a display panel 10, and further includes a front case 20F and a rear case 20R to define an appearance of the display apparatus 1 and support and protect the display panel 10.

In addition, the display apparatus 1 may control reflectance of externally incident light. For example, the display apparatus 1 may have a reflection mode to reflect external light at high reflectance and a transmission mode to absorb the external light at low reflectance. In the reflection mode, the display apparatus 1 reflects light incident on the front surface of the display apparatus 1 functioning as a mirror as illustrated in FIG. 2. For example, the reflection mode may be a state in which the display panel 10 is turned off.

Meanwhile, in the transmission mode, the display apparatus 1 outputs light incident from the inside of the display apparatus 1 or from the backside toward the front surface of the display apparatus 1 as illustrated in FIG. 3. For example, the transmission mode may be a state in which the display panel 10 is turned on. Hereinafter, a configuration of the display apparatus 1 will be described in detail, and operation of the display apparatus 1 in each mode will be described in detail.

FIG. 4 is a control block diagram for describing the display apparatus 1 in detail. The display apparatus 1 may include an input unit 30 to receive a control instruction from a user, a display panel 10 to control reflectance, a drive unit 40 to drive the display panel 10, and a controller 50 to control the overall operation of the display apparatus 1.

The input unit 30 receives an instruction to control the display apparatus 1 from the user. Particularly, the input unit 30 may receive an instruction to select a mode of the display apparatus 1 from the user. In this case, the input unit 30 may be mounted at one side of the front case 20F as illustrated in FIG. 1, without being limited thereto. For example, the input unit 30 may be a controller connected to the display apparatus 1 via only a wired or wireless communication network.

The display panel 10 may control reflectance of externally incident light. To this end, the display panel 10 may linearly polarize the externally incident light and change a polarization direction of the linearly polarized light.

The drive unit 40 may control a voltage applied to each electrode of the display panel 10 such that the display panel 10 displays image information in response to the instruction from the controller 50. More particularly, the drive unit 40 is electrically connected to at least one electrode of the display panel 10 to apply a voltage to the electrode of the display panel 10. An electric field generated by the voltage is applied thereto changes an arrangement of the first liquid crystal layer 130, thereby controlling reflectance of the display panel 10.

The controller 50 controls the overall operation of each component of the display apparatus 1 such that reflectance of externally incident light is controlled. For example, the controller 50 may control the display panel 10 to operate in the reflection mode or the transmission mode. In this regard, the controller 50 may include one or more processors. Here, the processor may be implemented by using an array of a plurality of logic gates or a combination of a universal microprocessor and a memory storing a program executable in the microprocessor. Furthermore, it will be understood by those of ordinary skill in the art that the processor may be implemented by another form of hardware.

Hereinafter, the display panel 10 will be described in detail with reference to FIGS. 4 to 9. Display panels are classified into passive matrix (PM) display panels and active matrix (AM) display panels according to a driving method. The PM display panel applies voltages to a row electrode and a column electrode to drive liquid crystals at junctions thereof. The AM display panel controls each pixel by using a thin film transistor (TFT). Hereinafter, a PM display panel will be described as the display panel 10, for descriptive convenience. However, AM display panels may also be applied thereto.

FIG. 5 is a schematic exploded perspective view illustrating the display apparatus 1. Referring to FIG. 5, the display panel 10 may be disposed between the front case 20F and the rear case 20R. The display panel 10 may include a first polarizer 110 to linearly polarize incident light, a first substrate 120, a wire grid polarizer 140 to selectively reflect incident light, and a first liquid crystal layer 130 interposed between the first substrate 120 and the wire grid polarizer 140.

The first substrate 120 may be formed of a transparent material to allow transmission of incident light. For example, the first substrate 120 may be formed of glass or plastic and may be flexible.

The first polarizer 110 selectively absorbs or transmits light according to a direction of incident light, thereby linearly polarizing the incident light. That is, light parallel to a polarization axis of the first polarizer 110 passes through the first polarizer 110, and light perpendicular to the polarization axis of the first polarizer 110 is absorbed by the first polarizer 110.

In this case, the first polarizer 110 may be a polarizing plate or a reflective polarizing thin film to prevent light loss by the polarizing plate, such as a dual brightness enhancement film (DBEF).

The wire grid polarizer 140 selectively reflects or transmits incident light according to the direction of the incident light. Hereinafter, the wire grid polarizer 140 will be described in detail with reference to FIG. 6.

FIG. 6 is a perspective view schematically illustrating the wire grid polarizer 140. Referring to FIG. 6, the wire grid polarizer 140 includes a base unit 141 and a metal unit 143 formed on the base unit 141. In this regard, the base unit 141 may be a substrate on which the metal unit 143 is disposed and may be formed of a light transmittable material. For example, the base unit 141 may be a film formed of poly ethylene terephthalate (PET) or triacetyl cellulose (TAC).

The metal unit 143 may include a plurality of metallic grids 142. That is, the metallic grids 142 having a predetermined height h and a predetermined width w are arranged to be spaced apart from each other at a constant interval, thereby constituting the metal unit 143.

Here, color of light reflected by the wire grid polarizer 140 may vary according to the interval between the metallic grids 142. That is, when the interval between the metallic grids 142 is 1/2 or less of a wavelength of the incident light, the wire grid polarizer 140 only transmits or reflects the incident light. Thus, the metallic grids 142 according to an embodiment of the present invention are aligned to be spaced apart from each other by an interval less than 380 nm, which is the lowest wavelength of visible light, so as to transmit or reflect the incident light without diffracting the light.

The metallic grids 142 may be fabricated by a thin film processing method using a conductive material such as aluminum (Al), copper (Cu), gold (Au), silver (Ag), chromium (Cr), tungsten (W), nickel (Ni), titanium (Ti), tantalum (Ta), molybdenum (Mo), neodymium (Nd), a carbonaceous conductive material, such as carbon nanotube and graphene, or any alloy thereof. In addition, the surfaces of the metallic grids 142 may be coated with a material capable of improving electrical conductivity of the metallic grids 142.

When light is incident on the wire grid polarizer 140 having the structure as described above, incident light parallel to the length direction d of the metallic grids 142 passes through the wire grid polarizer 140, and incident light perpendicular to the length direction d of the metallic grids 142 is reflected by the metallic grids 142. Here, the metallic grids 142 may be arranged parallel to the polarization axis of the first polarizer 110. Thus, light linearly polarized by the first polarizer 110 may also pass through the wire grid polarizer 140, and light linearly polarized by the wire grid polarizer 140 may also pass through the first polarizer 110.

The first liquid crystal layer 130 is disposed between the first substrate 120 and the wire grid polarizer 150. In this regard, liquid crystals are matter in a state having properties between those of liquid and those of solid crystals, and the arrangement of the liquid crystals may be adjusted by applying a voltage thereto. The first liquid crystal layer 130 may have liquid crystals arranged in a twisted nematic (TN) mode, in-plane switching (IPS) mode, vertical alignment (VA) mode, or patterned vertical alignment (PVA) mode, without being limited thereto.

Light incident on the first liquid crystal layer 130 is polarized by the liquid crystals by a predetermined angle. When an electric field is formed by a voltage applied to the first liquid crystal layer 130, the liquid crystals in the first liquid crystal layer 130 are re-arranged by the electric field, and accordingly the polarization angle of light incident on the first crystal layer 130 may be changed. Meanwhile, when a voltage is not applied to the first liquid crystal layer 130, light incident on the first liquid crystal layer 130 is polarized by 90 degrees by the liquid crystals. As such, in order to generate an electric field in the first liquid crystal layer 130, the first liquid crystal layer 130 may be provided with a plurality of electrodes.

A first electrode 131 may be disposed between the first liquid crystal layer 130 and the first substrate 120 to generate an electric field in the first liquid crystal layer 130. For example, the first electrode 131 may be deposited on the surface of the first substrate 120 in contact with the first liquid crystal layer 130 and may form an electric field in the first liquid crystal layer 130 together with the wire grid polarizer 140.

In addition, the first electrode 131 may be a transparent electrode in order to increase light transmittance of the display panel 10. For example, the first electrode 131 may be formed of a transparent conductive material such as indium tin oxide (ITO), indium zinc oxide (IZO), and aluminum doped zinc oxide (ZAO).

In addition, the first electrode 131 may be patterned to allow the display panel 10 to have a pixel structure. The surface of the first electrode 131 may be processed such that liquid crystal molecules adjacent to the surface are aligned in a preferred direction.

Meanwhile, the wire grid polarizer 140 may be used as a second electrode. As described above, the wire grid polarizer 140 includes a plurality of metallic grids 142, and the metallic grids 142 are formed of a conductive metal. Thus, an electric field may be formed in the first liquid crystal layer 130 by using the wire grid polarizer 140 and the first electrode 131 based on electrical conductivity of the metallic grids 142.

In order to generate the electric field, the metallic grids 142 of the wire grid polarizer 140 and the first electrode 131 may be electrically connected to the drive unit 40. Thus, a voltage is applied to the first electrode 131 and the wire grid polarizer 140 by the drive unit 40, and an electric field may be generated by the applied voltage.

As such, a manufacturing process of the display panel 10 may be simplified, and manufacturing costs thereof may be reduced by using the metallic grids 142 of the wire grid polarizer 140 as an electrode. In addition, a physical thickness of the display panel 10 may be reduced.

In this case, the metallic grids 142 of the wire grid polarizer 140 are patterned to a plurality of groups or patterned to micro units such that the display panel 10 has a pixel structure. The wire grid polarizer 140 may be processed such that liquid crystal molecules adjacent to each surface are aligned in a preferred direction.

Hereinafter, operation of the display panel 10 in each mode of the display apparatus 1 will be described in detail with reference to FIGS. 7 and 8.

FIG. 7 is a diagram for describing a reflection mode of the display apparatus 1.

In the reflection mode, light incident on the front surface of the display panel 10 is reflected by the wire grid polarizer 140 and emitted through the front surface. Here, the reflection mode may be a state in which power is not applied to the first electrode 131 and the wire grid polarizer 140, i.e., a state in which the display panel 10 is turned off.

In the reflection mode, light incident on the front surface of the display panel 10 partially passes through the first polarizer 110 and is partially reflected by the first polarizer 110, thereby being linearly polarized. That is, light parallel to the polarization axis of the first polarizer 110 passes through the first polarizer 110, and light perpendicular to the polarization axis of the first polarizer 110 is absorbed by the first polarizer 110.

Light linearly polarized by the first polarizer 110 as described above passes through the first substrate 120 and the first electrode 131 to be incident on the first liquid crystal layer 130. Light incident on the first liquid crystal layer 130 is polarized by 90 degrees due to characteristics of liquid crystals.

Light output from the first liquid crystal layer 130 is incident on the wire grid polarizer 140. In this regard, the metallic grids 142 of the wire grid polarizer 140 are arranged parallel to the polarization axis of the first polarizer 110. Thus, since light polarized by 90 degrees by the first liquid crystal layer 130 is incident on the metallic grids 142 perpendicularly to the metallic grids 142, the light is reflected by the wire grid polarizer 140.

The light reflected by the wire grid polarizer 140 is incident on the first liquid crystal layer 130 again, polarized by 90 degrees by the first liquid crystal layer 130, and passes through the first electrode 131, the first substrate 120, and the first polarizer 110, thereby being output through the front surface of the display panel 10.

Meanwhile, light incident on the rear surface of the display panel 10 is absorbed by the display panel 10 or reflected thereby. Particularly, light parallel to the arrangement of the metallic grinds 142 of the wire grid polarizer 140 passes through the wire grid polarizer 140 and incident on the first liquid crystal layer 130. Meanwhile, light perpendicular to the arrangement of the metallic grinds 142 of the wire grid polarizer 140 is reflected by the wire grid polarizer 140 to be output through the rear surface of the display panel 10.

Here, light incident on the first liquid crystal layer 130 is polarized by 90 degrees by the liquid crystals, passes through the first electrode 131 and the first substrate 120 to be incident on the first polarizer 110. Since the light incident on the first polarizer 110 is perpendicular to the polarization of the first polarizer 110, the light is absorbed by the first polarizer 110 and is not output through the front surface of the display panel 10.

Thus, in the reflection mode where the display panel 10 is turned off, light incident on the front surface of the display panel 10 is reflected by the wire grid polarizer 140. Accordingly, the display panel 10 may function as a mirror in the reflection mode as illustrated in FIG.2.

FIG. 8 is a diagram for describing a transmission mode of the display apparatus 1.

In the transmission mode, light incident on the rear surface of the display panel 10 is output through the front surface of the display panel 10. In the transmission mode, a voltage is applied to the first electrode 131 and the metallic grids 142 of the wire grid polarizer 140 of the display panel 10. As such, when a voltage is applied to the first electrode 131 and the metallic grids 142, the liquid crystals are re-arranged such that light incident on the first liquid crystal layer 130 passes through the liquid crystal layer 130.

Particularly, light incident on the front surface of the display panel 10 partially passes through the first polarizer 110 and is partially reflected by the first polarizer 110, thereby being linearly polarized. That is, light parallel to the polarization axis of the first polarizer 110 passes through the first polarizer 110, and light perpendicular to the polarization axis of the first polarizer 110 is absorbed by the first polarizer 110.

Light passing through the first polarizer 110 passes through the first substrate 120 and the first electrode 131 to be incident on the first liquid crystal layer 130. In this regard, the first liquid crystal layer 130 is re-arranged by an electric field generated by a voltage applied to the first electrode 131 and the metallic grids 142. Thus, light incident on the first liquid crystal layer 130 is not polarized and passes through the first liquid crystal layer 130.

Light passing through the first liquid crystal layer 130 reaches the wire grid polarizer 140. In this regard, the metallic grids 142 of the wire grid polarizer 140 are arranged parallel to the polarization axis of the first polarizer 110. Thus, light passing through the first liquid crystal layer 130 is incident in parallel on the metallic grids 142, thereby passing through the wire grid polarizer 140.

That is, in the transmission mode, light incident on the front surface of the display panel 10 is not reflected, but passes through the rear surface of the display panel 10. In this regard, the display panel 10 may further include a polarizer at a rear surface to absorb light passing through the wire grid polarizer 140.

Meanwhile, light incident on the rear surface of the display panel 10 is absorbed by the display panel 10 or reflected thereby. Particularly, light parallel to the arrangement of the metallic grinds 142 of the wire grid polarizer 140 passes through the wire grid polarizer 140 and incident on the first liquid crystal layer 130. Meanwhile, light perpendicular to the arrangement of the metallic grids 142 of the wire grid polarizer 140 is reflected by the wire grid polarizer 140 to be output through the rear surface of the display panel 10.

In this regard, light passing through the wire grid polarizer 140 sequentially passes through the first liquid crystal layer 130, the first electrode 131, the first substrate 120, and the first polarizer 110, thereby being output through the front surface.

As described above, when a voltage is applied to the display panel 10, only the light incident on the rear surface is output through the front surface of the display panel 10. In this regard, light applied to the rear surface of the display panel 10 may be natural light.

Meanwhile, the display apparatus 1 may simultaneously have the transmission mode and the reflection mode. Hereinafter, the display apparatus 1 having a combination mode of the transmission mode and the reflection mode will be described in detail with reference to FIGS. 9A and 9B.

FIGS. 9A and 9B are diagrams for describing a combination mode of the display apparatus 1.

The display apparatus 1 may simultaneously display the reflection mode and the transmission mode as illustrated in FIG. 9A. Here, a reflection mode region functions as a mirror, and a transmission mode region outputs light incident on the rear surface of the display panel 10, as described above.

In order to simultaneously have the reflection mode and the transmission mode, a voltage needs to be applied to only the transmission mode region. Thus, as illustrated in FIG. 9B, the metallic grids 142 of the wire grid polarizer 140 may be patterned to a plurality of groups. The patterned metallic grids 142 may respectively be connected to the drive unit 40.

Meanwhile, patterning of the metallic grids 142 of the wire grid polarizer 140 is not limited thereto. For example, the metallic grids 142 of the wire grid polarizer 140 may be patterned in to micro units such that the display panel 10 has a pixel structure. The drive unit 40 may control voltage application to the micro-patterned first electrode 131 and metallic grids 142.

Meanwhile, a display apparatus 1 according to another embodiment of the present invention may further include a display panel 10 to display information in the transmission mode. That is, while the display apparatus 1 according to an embodiment of the present invention outputs light incident on the rear surface of the transmission mode, the display apparatus according to another embodiment of the present invention may further include a display to display an image in the transmission mode. Hereinafter, the same components are designated by like numerals and their description is omitted.

FIG. 10 is a control block diagram for describing a display apparatus 1 according to another embodiment of the present invention in detail. FIG. 11 is a schematic cross-sectional view illustrating the display apparatus 1 of FIG. 10.

The display panel of the display apparatus 1 according to another embodiment of the present invention includes an input unit 30 to receive a control instruction from a user, a first display panel 10 to display a screen according to a selected mode, a second display panel 20 to display image information in a transmission mode, a drive unit 40 to drive the first display panel 10 and the second display panel 20, and a controller 50 to control the overall operation of the display apparatus 1.

The first display panel 10 may have the same structure as that of the display panel descried above, and may operate in the same mode as described above in accordance with controlling by the controller 50.

The drive unit 40 may be connected to an electrode of the first display panel 10 and an electrode of the second display panel 20 to drive the first display panel 10 and the second display panel 20. That is, the drive unit 40 may also apply a voltage to the electrodes in accordance with controlling by the controller 50.

The controller 50 may control the first display panel 10 and the second display panel 20. Particularly, the controller 50 may control the first display panel 10 to select the mode of the display apparatus 1 and control the second display panel 20 to display an image.

FIG. 12 is a schematic view illustrating a second display panel of FIG. 10. The second display panel 20 may be disposed to be adjacent to the wire grid polarizer 140 as illustrated in FIG. 11 and may include an inner light source differently from the first display panel 10. Hereinafter, a thin film transistor (TFT) light emitting diode (LED) display panel is described as an example of the second display panel 2. However, the embodiments of the present invention are not limited thereto, and any display panels capable of displaying image information in accordance with controlling by the controller 50, such as a liquid crystal display (LCD) panel, a light emitting diode (LED) display panel, or an organic light emitting diode (OLED) display panel, may also be applied thereto.

As illustrated in FIG. 12, the second display panel 20 may include a second polarizer 270, a third substrate 260, a second liquid crystal layer 240, a color layer 230 to determine color of each pixel, a pixel layer 250 to control arrangement of the second liquid crystal layer 240, and a light source unit 280 to generate light.

The third substrate 260 may be disposed to be adjacent to the light source unit 280, and may be formed of a transparent material to allow transmission of incident light.

In addition, the first display panel 10 and the second display panel 20 may be electrically insulated from each other by a base of the wire grid polarizer 140.

The second liquid crystal layer 240 may be disposed between a third electrode 241 and a fourth electrode 242. In this case, the second liquid crystal layer 240 may be re-arranged by an electric field generated by a voltage applied to the third electrode 241 and the fourth electrode 242, and a polarization angle of light passing through the second liquid crystal layer 240 may vary according to the arrangement of liquid crystals of the second liquid crystal layer 240.

The pixel layer 250 includes a TFT structure, and may control the arrangement of the liquid crystals of the second liquid crystal layer 240 with the first electrode and the second electrode. Here, the pixel may include a plurality of sub-pixels, and the sub-pixels may constitute a pixel, which is a unit to display image information.

Particularly, the pixel layer 250 includes a gate electrode 251, a gate insulating layer 252, a drain electrode 254, a source electrode 255, and a passivation layer 256 which constitute a TFT.

The gate electrode 251 is disposed on the third substrate 260 to turn on or off a gate in accordance with a control signal from a gate line. In this regard, the gate electrode 251 may be formed of a single metal or an alloy of at least two metals.

The gate insulating layer 252 may cover the gate electrode 251. Here, the gate insulating layer 252 may include an insulating material such as silicon oxide (SiOx), silicon nitride (SiNx), or silicon oxynitride (SiON).

A semiconductor layer 253 is disposed on the gate insulating layer 252. In this regard, the semiconductor layer 253 may be formed of a semiconductor material such as amorphous silicon, and the drain electrode 254 and the source electrode 255 may be disposed on the semiconductor layer 253.

The drain electrode 254 and the source electrode 255 may be spaced apart from each other, and the drain electrode 254 and the source electrode 255 may have a single-layered or multi-layered structure.

The color layer 230 may include an overcoating layer 231, a black matrix 232, and a color filter 233. Here, the overcoating layer 231 that protects the black matrix 232 and the color filter 233 may be formed of an acrylic epoxy. The black matrix 232 partitions the sub-pixels, and the color filter 233 realizes a color image by selectively transmitting incident light having a predetermined wavelength.

The fourth electrode 242 is disposed in a pixel region partitioned by gate lines and generates a potential difference from the third electrode 241 in response to a control signal from the gate lines. As such, the arrangement of the liquid crystals of the second liquid crystal layer 240 may be controlled by the potential difference between the third electrode 241 and the fourth electrode 242.

The light source unit 280 that is a device emitting light includes a light source 281 disposed at one side of the second display panel 20 to emit light toward a light guide plate 282, and the light guide plate 282 to guide light emitted from the light source 281 to proceed toward the front surface of the second display panel 20. Here, the light source 281 may be a cold cathode fluorescent lamp (CCFL) or a light emitting diode (LED). In addition, the light source unit 280 may be replaced or switched with a direct type light source.

The second polarizer 270 selectively absorbs or transmits light according to direction of incident light, thereby linearly polarizing light emitted from the light source 281. In this regard, the polarization axis of the first polarizer 110 may be parallel to that of the second polarizer 270.

As described above, the arrangement of the metallic grinds 142 of the wire grid polarizer 140 is identical to the polarization axis of the first polarizer 110, and the polarization axes of the first polarizer 110 and the second polarizer 210 are the same. Thus, the wire grid polarizer 140 transmits only light that is not polarized by the second liquid crystal layer 240.

Hereinafter, operation of the display apparatus 2 of FIG. 10 in each mode will be described in detail with reference to FIG. 13. FIG. 13 is a diagram for describing a transmission mode of the display apparatus 2 of FIG. 10.

In a reflection mode, the first display panel 10 reflects light incident on the front surface of the display apparatus 2 as described above. In this case, the second display panel 20 may be in a state of being turned off. That is, a voltage is not applied to the second liquid crystal layer 240 and the light source 281 is turned off.

In a transmission mode, light may be emitted from the light source 281 of the second display panel 20, and the controller 50 may control the arrangement of the liquid crystal layer to display image information. That is, the display apparatus 2 may display an image by controlling the arrangement of the second liquid crystal layer 240 on a pixel basis in accordance with image information.

As illustrated in FIG. 13, light emitted from the light source 281 proceeds toward the second pixel layer 250 by the light guide plate 282. Here, while light parallel to the polarization axis of the second polarizer 270 passes through the second polarizer 270, light perpendicular to the polarization axis of the second polarizer 270 is absorbed by the second polarizer 270. Accordingly, a linearly polarized light is incident on the pixel layer 250. The linearly polarized light passes through the pixel layer 250 and is incident on the second liquid crystal layer 240.

In this regard, the liquid crystals of the second liquid crystal layer 240 may be controlled on a sub-pixel basis. Particularly, one portion of the second liquid crystal layer 240 corresponding to sub-pixels emitting light is re-arranged to transmit the light, and another portion thereof corresponding to sub-pixels not emitting light polarizes light by 90 degrees and outputs the polarized light.

The light output from the liquid crystal layer is incident on the color layer 230, and light having a wavelength selected by the color layer 230 passes through the color layer 230 and is incident on the first display panel 10.

In this regard, among light incident on the first display panel 10, light passing through the color layer 230 is selectively transmitted by the wire grid polarizer 140 as illustrated in FIG. 8.

Particularly, the polarization axis of the second polarizer 270 is the same as the arrangement of the metallic grids 142 of the wire grid polarizer 140. Thus, light passing through the second liquid crystal layer 240 passes through the wire grid polarizer 140, and sequentially passes through the first liquid crystal layer 130, the first electrode, the first substrate, and the first polarizer 110, thereby being output through the front surface of the display apparatus 2.

Meanwhile, light polarized by 90 degrees by the second liquid crystal layer 240 is reflected by the wire grid polarizer 140 and thus is not output through the front surface of the display apparatus 2.

Although a few embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.

Claims

A display apparatus comprising:

a polarizer to polarize incident light;

a first electrode through which polarized light passes;

a liquid crystal layer to change a polarization direction of light passing through the first electrode;

a second electrode to reflect light having changed polarization direction and patterned to at least one group; and

a controller to control reflectance of light of the second electrode by controlling voltage applied to the first electrode and the second electrode patterned to at least one group.
The display apparatus according to claim 1, wherein the second electrode is a wire grid polarizer.
The display apparatus according to claim 2, wherein the wire grid polarizer comprises:

a plurality of metallic grids; and

a base unit on which the plurality of metallic grids are disposed.
The display apparatus according to claim 3, wherein the plurality of metallic grids are patterned to a plurality of groups.
The display apparatus according to claim 4, wherein light incident on one group to which a voltage is applied among the plurality of groups passes through the second electrode, and light incident on another group to which a voltage is not applied is reflected by the second electrode.
A display apparatus comprising:

a first display panel comprising a first polarizer to polarize incident light, a first electrode to transmit the polarized light, a first liquid crystal layer to change a polarization direction of the light passing through the first electrode, and a second electrode to reflect the light, the polarization direction of which is changed, and patterned to at least one group;

a second display panel disposed adjacent to the second electrode and displaying an image by using an inner light source; and

a controller to control reflectance of the second electrode by applying a voltage to the first liquid crystal layer and control the second display panel to display the image.
The display apparatus according to claim 6, wherein the second electrode is a wire grid polarizer.
The display apparatus according to claim 7, wherein the wire grid polarizer comprises:

a plurality of metallic grids; and

a base unit on which the plurality of metallic grids are disposed.
The display apparatus according to claim 8, wherein the first display panel and the second display panel are insulated from each other by the base unit.
The display apparatus according to claim 8, wherein the second display panel comprises:

a third electrode disposed on the opposite surface of the base unit;

a fourth electrode disposed to be spaced apart from the third electrode; and

a second liquid crystal layer disposed between the third electrode and the fourth electrode and changing a polarization direction of incident light.
The display apparatus according to claim 10, further comprising a color layer disposed between the base unit and the third electrode and transmitting light having a selected wavelength.
The display apparatus according to claim 7, wherein the second electrode is patterned to a plurality of groups.
The display apparatus according to claim 12, wherein light incident on one group to which a voltage is applied among the plurality of groups passes through the second electrode, and light incident on another group to which a voltage is not applied is reflected by the second electrode.
The display apparatus according to claim 10, wherein the second display panel further comprises a second polarizer disposed between the fourth electrode and a light source and polarizing light emitted from the light source.
The display apparatus according to claim 14, wherein light, the polarization direction of which is changed by the second liquid crystal layer, among light polarized by the second polarizer is reflected by the wire grid polarizer.