US20050016855A1

US20050016855A1 - Method for manufacturing a light guide plate mold

Info

Publication number: US20050016855A1
Application number: US10/898,076
Authority: US
Inventors: Ga-Lane Chen; Tai-Cherng Yu
Original assignee: Individual
Current assignee: Hon Hai Precision Industry Co Ltd
Priority date: 2003-07-23
Filing date: 2004-07-23
Publication date: 2005-01-27
Also published as: TW200504471A; TWI258060B

Abstract

A method for manufacturing a light guide plate mold includes the steps of: forming a photo-resist film (210) on a substrate (200); disposing a gray level mask (220) having a predetermined pattern over the substrate, illuminating the photo-resist film through the gray level mask by illuminating rays; developing the photo-resist film to form a photo-resist pattern (211) on the substrate; etching simultaneously the substrate and the photo-resist pattern to form a stamper (201); coating a metal-plating layer (230) over the stamper; electroforming the stamper coated with the metal-plating layer to form a master stamper (240); and stripping the metal-plating layer from the master stamper to attain the light guide plate mold. The method is highly precise and simple.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to methods for manufacturing light guide plate molds, and particularly to a method of manufacturing a light guide plate mold using photolithography technology.
2. The Prior Art
In a liquid crystal display, a backlight module is always used to provide a planar light source for illuminating the liquid crystal display. In general, the backlight module includes a light source and a light guide plate, the light source being located adjacent to one side of the light guide plate. The light guide plate transfers light beams emitted from the light source to planar light beams, and directs them to a liquid crystal panel of the liquid crystal display.
A plurality of printing-dots is distributed on a bottom surface of the light guide plate for improving the uniformity of the backlight module. The printing-dots scatter and reflect the light beams emitted from the light source to uniform planar light beams. The shape, the density and the size of the printing-dots are configured according to requirements of different applications. For example, the printing-dots can have square, circular, or diamond-shaped profiles.
Brightness is another important factor for the backlight module. A conventional method for increasing the brightness of the backlight module is by providing two prism sheets. The two prism sheets are made of transparent material. One surface of each prism sheet includes a plurality of parallel V-shaped grooves, for collimating the planar light beams. The V-shaped grooves of the two prism sheets are disposed orthogonally to each other. The two prism sheets can efficiently improve the brightness of the backlight module. However, the cost of the backlight module is high due to the two expensive prism sheets, and the assembly is complex.
FIG. 8 shows a conventional surface light source module. The surface light source module 100 includes a light tube 110, a light tube shield 111, a light guide plate 120, a reflective sheet 150, a prism sheet 130, and a diffuser 140. The reflective sheet 150 is disposed below the light guide plate 120. The prism sheet 130 and the diffuser 140 are stacked on the light guide plate 120 in that order. A plurality of printing-dots 121 is distributed on the bottom surface of the light guide plate 120, for increasing the uniformity of light beams output from the surface light source module. The printing-dots 121 can have square, elliptic, rectangular or semi-circular profiles. A plurality of V-shaped grooves 122 provided on a top surface can collimate light beams instead of one prism sheet. The surface light source module 100 just needs one prism sheet 130 in order to obtain the same effect as two prism sheets. Therefore, the cost of the surface light source module 100 is reduced, and it is easily assembled.
A conventional method for manufacturing the V-shaped grooves is by way of mechanical machining technology. The mechanical machining technology includes the steps of: forming a stamper having V-shaped grooves machined by a precision cutting tool; electro-forming the stamper to form a light guide plate mold having reverse V-shaped grooves according to that of the stamper; forming a light guide plate having V-shaped grooves by the injection molding technology or hot embossing technology. However, the machining precision is low due to inherent mechanical error and wearing out of the cutting tool.
A manufacturing method of a light guide plate mold is described in China Pat. Pub. No. 1,372,161A. The manufacturing method can form a plurality of micro structures on a surface of the light guide plate mold, the micro structures being arcuate protrusions or concavities. In order to form a plurality of V-shaped grooves, the whole process needs to be repeated several times. Therefore, the process of forming V-shape grooves is unduly complicated, and the precision of the V-shaped grooves is low due to compounding of inherent error with each repeat of the process.
An improved manufacturing method for a light guide plate mold that overcomes the above-mentioned disadvantages is desired.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a manufacturing method for a light guide plate mold which is highly precise and simple.
In order to achieve the object set forth, a method for manufacturing a light guide plate mold in accordance with the present invention, comprises steps of: forming a photo-resist film on a substrate; disposing a gray level mask having a predetermined pattern over the substrate, illuminating the photo-resist film through the gray level mask by illuminating rays; developing the photo-resist film to form a photo-resist pattern on the substrate; etching simultaneously the substrate and the photo-resist pattern to form a stamper; coating a metal-plating layer over the stamper; electroforming the stamper coated with the metal-plating layer to form a master stamper; and stripping the metal-plating layer from the master stamper to attain the light guide plate mold. The light guide plate mold has high precision, and the manufacturing method is simple.
Other objects, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a step of coating a photo-resist layer on a substrate in a method for manufacturing a light guide plate mold according to the present invention;
FIG. 2 shows a step of exposing the photo-resist layer using a gray level mask in the method for manufacturing the light guide plate mold;
FIG. 3 shows a developing step in the method for manufacturing the light guide plate mold;
FIG. 4 shows an etching step for forming a stamper in the method for manufacturing the light guide plate mold;
FIG. 5 shows a step of coating a metal-plating layer onto a surface of the stamper in the method for manufacturing the light guide plate mold;
FIG. 6 shows an electroforming step of forming a master stamper in the method for manufacturing the light guide plate mold;
FIG. 7 is a schematic view of the master stamper; and
FIG. 8 is a schematic view of a conventional surface light source module.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 to 7 are views illustrating stages in a method for manufacturing a light guide plate mold according to the present invention. The manufacturing method includes the following steps:

- (1) forming a photo-resist film 210 on a substrate 200, as shown in FIG. 1;
- (2) disposing a gray level mask 220 having a predetermined pattern over the substrate 200, illuminating the photo-resist film 210 through the gray level mask 220, as illustrated in FIG. 2;
- (3) developing the photo-resist film 210 to form a photo-resist pattern 211 on the substrate 200, as shown in FIG. 3;
- (4) etching simultaneously the substrate 200 and the photo-resist pattern 211 to form a stamper 201 with a plurality of V-shaped grooves 202, as illustrated in FIG. 4;
- (5) coating a metal-plating layer 230 over the stamper 201, as shown in FIG. 5;
- (6) electroforming the stamper 201 coated with the metal-plating layer 230 to form a master stamper 240, as illustrated in FIG. 6; and
- (7) stripping the metal-plating layer 230 from the master stamper 240 to attain a light guide plate mold, as shown in FIG. 7.

In FIG. 1, the photo-resist film 210 coating on the substrate 200 comprises positive or negative photo-resist material. The process for forming the photo-resist film 210 may be a spin-coating process, a dip-coating process, a roll-coating process, a spray-coating process, an extrusion slot-coating process, etc. Furthermore, before coating the photo-resist film 210, a thin film layer (not shown) is formed on the substrate 200 to improve the smoothness of the substrate 200.
In FIG. 2, the gray level mask 220 is made of a high-energy beam sensitive glass. The gray level mask 220 suitable for photolithography is constructed of a transparent glass substrate which supports plural levels of materials having different optical transmissivities. The mask is fabricated with the aid of a photoresist structure which is etched in specific regions by photolithographic masking to enable selective etching of exposed regions of the level of materials of differing optical transmissivities. The high-energy beam sensitive glass is a composite crystal of silver-alkali-halide. For example, by exposing the substrate 200 having the photo-resist film 210 to yellow light, ultraviolet light, or ion beams, different depth levels can be made on the substrate 200 by using the gray-level mask 220.
In FIG. 3, the process for developing the photo-resist film 210 can be a soaking process, a spraying process, etc. The remained photo-resist pattern 211 is a plurality of V-shaped grooves which is the same pattern as the pattern of the grey-level mask 220.
The substrate 200 and the photo-resist pattern 211 are etched simultaneously with dry etching techniques to define the stamper 201 with a plurality of V-shaped grooves 202. Plasma gases are usually used as a driving gas because they have a high excitation energy. The plasma dry etching technology has the advantage of anisotropic etching for most etching materials.
In FIG. 5, the process for coating the metal-plating layer 230 on the stamper 201 may be a sputtering process, an evaporating process, or a spraying process. Various metals can be used as the material of the metal-plating layer 230. However, nickel (Ni) is most preferred in view of the desired uniformity and mechanical properties of the metal-plating layer 230.
In FIGS. 5 and 6, after the electroforming step and the stripping step, V-shaped grooves are transferred from the stamper 201 to the light guide plate mold.
However, the method for manufacturing a light guide plate mold can be not only used to form a light guide plate mold with V-shaped grooves. Other patterns also can be defined according to the particular configured pattern of the gray level mask 220 and the etching process.
Further, it is to be understood that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed._

Claims

1. A method for manufacturing a light guide plate mold, comprising the steps of:

forming a photo-resist film on a substrate;

disposing a gray level mask having a predetermined pattern over the substrate, and illuminating the photo-resist film through the gray level mask;

developing the photo-resist film to form a photo-resist pattern on the substrate;

etching simultaneously the substrate and the photo-resist pattern to form a stamper;

coating a metal-plating layer over the stamper; and

electroforming the stamper coated with the metal-plating layer to form a master stamper; and

stripping the metal-plating layer from the master stamper to attain the light guide plate mold.

2. The method according to claim 1, wherein the photo-resist pattern formed by the developing step comprises a plurality of V-shaped grooves.

3. The method according to claim 1, wherein the illumination is by yellow rays.

4. The method according to claim 1, wherein the illumination is by ultraviolet rays.

5. The method according to claim 1, wherein the stamper formed by the etching step has a plurality of V-shaped grooves thereon.

6. The method according to claim 1, wherein the step of etching comprises dry-etching.

7. The method according to claim 6, wherein the dry-etching is plasma dry-etching.

8. The method according to claim 1, further comprising the step of forming a thin film layer before forming the photo-resist film on the substrate.

9. The method according to claim 1, wherein the photo-resist film is formed by a spin-coating process.

10. The method according to claim 1, wherein the photo-resist film is formed by a dip-coating process.

11. The method according to claim 1, wherein the photo-resist film is formed by a roll-coating process.

12. The method according to claim 1, wherein the photo-resist film is formed by a spray-coating process.

13. The method according to claim 1, wherein the photo-resist film is formed by an extrusion slot-coating process.

14. The method according to claim 1, wherein the photo-resist film comprises positive photo-resist material.

15. The method according to claim 1, wherein the photo-resist film comprises negative photo-resist material.

16. A method for manufacturing a light guide plate mold, comprising the steps of:

forming a photo-resist film on a substrate;

etching the substrate to form a stamper having a first set of densely arranged V-shaped slots in an upper face thereof;

coating a metal-plating layer over the stamper; and

stripping the metal-plating layer from the master stamper to attain the light guide plate mold; wherein

said master stamper defines a second set of densely arranged V-shaped slots in an upper face thereof corresponding to the first set of densely arranged V-shaped slots.