JP2002169006A - Method for manufacturing light diffusing layer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain uniform brightness in the whole display region even in a large-sizes reflection type liquid crystal display device. SOLUTION: Slopes 31A which are the higher in regions having the lower reflectance are formed on the surface of a substrate sucking chuck 30 which sucks a transparent substrate 1, and the transparent substrate 1 is placed along the slopes 31A. The photosensitive resin layer on the surface of the transparent substrate 1 is exposed through a pattern forming mask 33 disposed above the transparent substrate 1 and parallel to the substrate sucking chuck 30 so as to form a light diffusing layer 9 having inhomogeneous diffusion characteristics by a photolithographic method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a light diffusion layer in a liquid crystal display device having a light diffusion layer such as a reflection type or a transflective type, and more particularly, to a light diffusion layer having a good light diffusion property. And a method for producing the same.

[0002]

2. Description of the Related Art Generally, a reflective liquid crystal display element in which a liquid crystal display can be viewed only by external light without using a backlight, or a half-tone display in which a liquid crystal display can be viewed by external light without using a backlight continuously. The transflective liquid crystal display element has a smaller power consumption when using the backlight than a transmissive liquid crystal display element that continuously uses a backlight, and is therefore often used particularly for a portable liquid crystal display.

In such a reflective or transflective liquid crystal display element, it is necessary to incorporate a reflective layer for reflecting external light and visually recognizing a liquid crystal display inside the liquid crystal display panel. Here, assuming that the reflection surface of the reflection layer incorporated inside is a mirror surface, when the light source is a point light source, the display image cannot be recognized in a direction other than the regular reflection direction, character blur occurs, or the reflectance is low. Or lower. Therefore, it is necessary to provide a part of the liquid crystal display panel with a light diffusion function.

As an example of a configuration having such a light diffusion function, there is a liquid crystal display device having an inner surface diffusion type light diffusion layer laminated on a substrate. That is, in a reflective or transflective liquid crystal display device, a light diffusion layer having an uneven surface is provided inside the liquid crystal display device to prevent blurring of characters and to improve the reflectance. There is a method of forming a reflection diffusion layer. As a method for manufacturing the light diffusion layer, there is a method of forming a photosensitive resin such as an acrylic resin to a predetermined size and melting it by heat, and a method of forming irregularities by frost-etching glass. Further, there is a method in which the unevenness is formed by controlling the energy distribution using a collimation angle (CA) of an exposure light source or a diffraction phenomenon of light passing through a pattern forming mask.

First, a specific example of a reflection type liquid crystal display device having such a light diffusion layer will be described with reference to FIG. In FIG. 4, the steps of forming individual liquid crystal display elements from a mother substrate for forming a plurality of liquid crystal display elements will be described in the order of steps.

In FIG. 4, in order to form a light diffusion layer 9 on the inner surface 1A of the glass mother substrate 1, a photosensitive resin is applied to the inner surface 1A of the mother substrate 1 and preliminarily dried (prebaked). A photosensitive resin layer is formed on the inner surface 1A of the substrate 1.

The light diffusion layer 9 is formed by partially removing the photosensitive resin layer by a photolithography method to form fine irregularities on the photosensitive resin layer. After forming into the size, it is deformed to the optimal waveform by heat treatment, or by using a photosensitive resin, the photolithography method controls the light diffraction and collimation angle (CA) at the time of exposure or the optimal wave shape by controlling the development conditions. Is formed.

Thus, the inner surface 1 of the mother substrate 1
After forming the light diffusion layer 9 on A, an aluminum film is deposited on the light diffusion layer 9 to form the reflection diffusion layer 12.

Next, after an insulating film 13 is applied to the mother substrate 1, a transparent electrode 14 made of ITO is provided, and a display electrode, a connection electrode, and a terminal electrode are formed on a single striped column electrode. Patterning is performed on the same number of column electrode groups and row electrodes as the number of liquid crystal display elements, striped connection electrodes and terminal electrodes, and polyimide is laminated except for terminal portions and inter-substrate conductive connection portions. The alignment film 15 is formed by performing an alignment process, and the column electrode substrate 16 is completed.

Next, a color filter 18 is disposed on the inner surface 17B of the glass mother substrate 17, a transparent electrode 14 made of ITO is provided, and a display electrode and a connection electrode are formed on one striped row electrode. A row electrode group in the form of a stripe is formed, polyimide is laminated except for the conductive connection between the substrates, and an alignment process is similarly performed by rubbing to form an alignment film 15, thereby completing the row electrode substrate 20.

The row electrode substrates 20 are sprayed with in-plane spacers 21, while the column electrode substrates 16 are
In the sealing material 22, conductive beads obtained by plating two layers of gold / nickel on resin beads and a conductive filler are mixed to form a conductive connecting material between substrates.

Next, after the electrode surfaces of the substrates 16 and 20 are opposed to each other and the substrates 16 and 20 are press-bonded, the liquid crystal display elements are arranged in a line with each injection hole opened. A plurality of reflective liquid crystal display elements 10 can be formed by cutting into a plurality of stick-shaped substrates, injecting liquid crystal in this state, applying pressure, and sealing the injection holes with a UV curing resin.

[0013]

The light diffusing property of the light diffusing layer in the above-described conventional reflective liquid crystal display element 10 or the conventional transflective liquid crystal display element whose description is omitted is within the plane of the light diffusing layer. It was uniform.

Therefore, in a liquid crystal display such as a cellular phone, light is irradiated from above, and there is a problem that the upper part of the liquid crystal display is bright but the lower part is dark.

In a large-sized liquid crystal display for a personal computer or the like, the central portion of the liquid crystal display is viewed from directly above, but the left and right or upper and lower portions of the liquid crystal display are viewed from a slightly oblique direction. Although the central part of the display is bright, the left and right parts or the upper and lower parts of the liquid crystal display appear dark.

This problem will be described with reference to FIGS.

FIG. 5 shows a reflection type liquid crystal display element 10 in which the diffusion characteristics of a reflection film (not shown) in the reflection type liquid crystal display element 10 are uniform over the whole area under a light source 23 having a certain degree of directivity. It shows the state when viewed. Then, in this state, as shown by the curve in FIG.
At point a close to the regular reflection angle (glare angle), the liquid crystal image looks bright, whereas C at a point far from the glare angle of the light source.
At that point, the liquid crystal image will appear dark. In particular,
If the vertical dimension of the reflective liquid crystal display element 10 is large, the brightness will differ considerably at point a and point c, giving an unpleasant appearance. Therefore, if the diffusivity is gradually increased from the point a toward the point c, the difference in brightness in the entire display area is reduced, and the appearance of display is improved.

In view of the foregoing, it is an object of the present invention to provide a method of manufacturing a light diffusion layer capable of obtaining uniform brightness over the entire display area even in a reflective liquid crystal display element having a large size. And

[0019]

In order to achieve the above-mentioned object, a feature of a method for manufacturing a light diffusion layer according to the present invention according to the present invention is that a photolithography method for controlling light diffraction and collimation angle during exposure is performed. This is based on the premise that an inclined surface having a higher height is formed on a surface of the substrate suction chuck that adsorbs the transparent substrate, as the reflectance is smaller, and the transparent substrate is disposed along the inclined surface, and the transparent substrate is disposed. The point is that the photosensitive resin layer on the surface of the transparent substrate is exposed through a pattern forming mask arranged in parallel with the substrate suction chuck above the substrate to form a light diffusion layer having non-uniform diffusion characteristics by a photolithographic method. . And, by adopting such a configuration, a difference occurs in the proximity gap between the pattern forming mask and the transparent substrate at the time of exposure, so that the light passes through the hole of the pattern forming mask at the time of exposure and reaches the photosensitive resin layer. Since the unevenness of the light diffusion layer can be changed by making a difference in the light energy to be applied, the reflectivity can be made substantially uniform, and a liquid crystal display element having a small difference in brightness over the entire display area. Can be.

[0020]

FIG. 1 shows a structure for carrying out a method of manufacturing a light diffusing layer according to the present invention, wherein an acrylic film is provided on an upper surface 30A which is a flat surface of a substrate suction chuck 30. FIG. An inclined surface forming plate 31 having an upper surface 31A serving as a surface as an inclined surface by processing a resin or the like is bonded. The substrate suction chuck 30 and the inclined surface forming plate 31 are formed with a large number of suction holes (not shown) for sucking a substrate (not shown).

As described above, the substrate suction chuck 3
An inclined surface may be directly formed on the upper surface 30A of the substrate suction chuck 30 without adhering the inclined surface forming plate 31 on the upper surface 0, or a film such as an acrylic resin or a metal plate may be used as the inclined surface forming plate 31. May be used. Therefore, it is described that an inclined surface is formed on the surface of the substrate suction chuck 30 as an expression including all of these.

FIG. 2 is a schematic perspective view showing a specific example of the inclined surface forming plate 31 bonded to the substrate suction chuck 30 of FIG. 1. The substrate attracting chuck 30 and the inclined surface forming plate 31 of FIG. It is formed in such a size as to adsorb a large mother substrate (not shown) for forming a plurality of liquid crystal display elements.

The upper surface 31A of the inclined surface forming plate 31 on which the mother substrate 1 (FIG. 1) is attracted and mounted is provided with a plurality of planar rectangular individual regions 32 which are finally divided into individual substrates. Is formed on the upper surface of each individual region 32. The inclined surface 31A having the same gradient in the same direction in each individual region 32 is formed. The inclined surface 31A is used for sequentially changing the unevenness of the light diffusion layer surface in one direction when the light diffusion layer is formed on the mother substrate 1 adsorbed and mounted on the inclined surface forming plate 31. It is.

That is, although the cross-sectional shape along the line AA 'in FIG. 2 is shown by a broken line, four individual regions 32 are formed along the line AA'. The inclined surface forming plate 31 in the direction of the line AA '
The length of each of the four individual regions 3 having a length of 55 mm is 280 mm, for example.
2 are spaced from each other by 10 mm. As described above, each individual region 32 has a length in each individual region 32 in order to sequentially change the unevenness of the surface of the light diffusion layer when forming the light diffusion layer on the mother substrate 1 along one direction. The gradient is set to rise by 20 μm between the dimensions of 55 mm. In addition, a pair of adjacent individual regions 32, 32
Between the individual regions 32, there is formed an inclined surface 31B in the opposite direction, which is lowered by the amount raised in each individual region 32.

Next, the operation of the embodiment of the present invention having the above-described configuration will be described. In the present embodiment, a light diffusion layer is formed by a photolithography method, but only steps which are the gist of the present invention will be described.

The present invention uses a light diffraction phenomenon to obtain a light-irradiated portion larger than the aperture of the opening formed in the pattern forming mask 33, so that the light-irradiated portion larger than the aperture of the opening is obtained. By making use of the fact that the light energy is lower than the light energy of the light irradiation part where the light energy does not increase, an inclined part is formed in the photosensitive resin which is exposed to light.

Then, as shown in FIG. 1, the mother substrate 1 is placed on the inclined surface forming plate 31 adhered to the substrate suction chuck 30 and sucked. Then, this mother board 1
Is made of flexible plastic or thin glass, and therefore bends along the inclined surfaces 31A and 31B on the upper surface of the inclined surface forming plate 31.

Then, a photosensitive resin is applied to the inner surface 1A of the mother substrate 1 facing upward to form a photosensitive resin layer (not shown), and a photosensitive resin layer (not shown) is formed above the mother substrate 1 in parallel with the substrate suction chuck 30. The pattern forming mask 33 is arranged so that light is emitted from above the pattern forming mask 33.

Then, the photosensitive resin layer is partially exposed to light transmitted through a large number of openings (not shown) of the pattern forming mask 33. When the photosensitive resin layer reaches the final step of the photolithography method, the photosensitive resin layer is exposed. The light diffusion layer in which many fine irregularities are formed in the layer is formed.

Incidentally, the mother substrate 1 adsorbed on the inclined surface forming plate 31 is attached to the inclined surface 31 of the inclined surface forming plate 31.
A and 31B are bent along the proximity mask (PG), which is the distance between the pattern forming mask 33 and the mother substrate 1, in the configuration of the inclined surface forming plate 31 shown in FIG. There is a variation of 20 μm. The change amount of the PG is preferably from 10 to 50 μm, and particularly preferably from 10 to 30 μm. If the amount of change in PG is too small or too large, the brightness in the display area of the liquid crystal display element cannot be made uniform.

When the PG becomes large, the diffraction width becomes large, so that the light energy becomes smaller than that of the part where the PG is small, and the light irradiation part becomes wider, so that unevenness having a smooth inclination can be formed. . Therefore, regardless of whether the photosensitive resin is a positive type or a negative type, P
Since the light energy applied to the photosensitive resin is larger at a portion where G is smaller than at a portion where G is large, a concavo-convex state changes in the final light diffusion layer along the direction in which PG changes.

Therefore, by changing the PG, the unevenness of the light diffusion layer can be changed, so that the reflectance in the light diffusion layer can be made substantially uniform, and the difference in brightness over the entire display area can be obtained. And a liquid crystal display element with a small number of components

That is, as shown in FIG. 3, among the points a, b and c having different reflectivities described with reference to FIG. 6, the light diffusivity at points b and c having a lower reflectivity than point a is improved. Exposure is performed by changing PG to increase the reflectivity at point b to point b 'and increase the reflectivity at point c to point c', thereby forming a light diffusion layer having substantially uniform light diffusivity. Can be formed.

[0034]

EXAMPLE A Nissan Chemical Industries RN-901 photosensitive resin was applied to a glass substrate having a thickness of 0.4 mm by a spinner to a thickness of about 3 μm.
In a firing furnace at 90 ° C. × 1
After prebaking for 0 minutes, a predetermined pattern was exposed by an exposing machine located above the substrate suction chuck. At this time, the surface shape of the inclined surface forming plate 31 on the substrate suction chuck has a step of max 20 as shown in the graph of FIG.
μm, and this step is formed for each individual region 32 described above.

The suction of the substrate is performed by using a 1 mmφ hole drilled on the entire surface of the substrate suction chuck 30 and the inclined surface forming plate 31.
Was performed under a negative pressure in the adsorption hole. Further, a slight pitch shift occurs when the substrate is sucked, and this pitch shift was corrected by a pattern forming mask.

After exposure, a phenomenon was carried out at 25 ° C. for 5 minutes with a 2.38% tetramethylammonium hydroxide (TMAH) solution, and baked at 350 ° C. for 1 hour.

After sintering, aluminum is formed on the light diffusion layer of the substrate with a splatter so as to have a thickness of about 0.25 μm, and after forming an RGB color filter, an acrylic resin is applied at 3 μm for smoothing. did. Table 1 shows the measurement results of the reflection characteristics after the formation of the reflection film. Table 1 is a comparison between the conventional example and this embodiment.
The reflection characteristics are obtained by using MINOLTA CS-A5 for ref, and measuring the reflectance at an incident angle of 30 degrees by BM-7.

[0038]

[Table 1]

As a result, the reflectivity difference between the point a and the point c was 10 times or more in the prior art, but by the improvement of this embodiment, the reflectivity was reduced to about 2.5 times at the points a and c '. It can be seen that is improved.

If a light diffusing layer having a high diffusivity is formed uniformly, point a = 350%, point b = 336%, point c = 256%, and the difference in reflectance is small. The image itself is reduced, resulting in a dark display as a whole.

Note that the present invention is not limited to the above-described embodiment, and various modifications can be made as necessary.

[0042]

As described above, according to the present invention, it is possible to form a light diffusion layer capable of obtaining uniform brightness over the entire display area even in a reflective liquid crystal display element having a large size.

That is, an inclined surface having a higher height is formed on the surface of the substrate suction chuck for adsorbing the transparent substrate, the lower the reflectance, the higher the height of the inclined surface, and the transparent substrate is arranged along the inclined surface. The photosensitive resin layer on the surface of the transparent substrate is exposed to light through a patterning mask arranged in parallel with the substrate suction chuck to form a light diffusion layer having non-uniform diffusion characteristics by a photolithographic method. Due to the difference in the proximity gap between the pattern forming mask and the transparent substrate, the amount of light that reaches the photosensitive resin layer through the holes in the pattern forming mask during exposure is changed to change the uneven shape of the light diffusion layer. The liquid crystal display element can be provided with a substantially uniform reflectance and a small difference in brightness over the entire display area.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a configuration for carrying out a method for manufacturing a light diffusion layer according to the present invention.

FIG. 2 is a perspective view of the inclined surface forming plate of FIG. 1 and a graph showing a specific example of the inclined surface.

FIG. 3 is a graph showing an improved state of light diffusion performance in the embodiment of FIG. 1;

FIG. 4 is a longitudinal sectional view showing a general reflection type liquid crystal display device having an inner surface diffusion layer.

FIG. 5 is an explanatory diagram showing a state in which a reflective liquid crystal display element is viewed by a directional light source.

FIG. 6 is a graph showing light diffusion performance of a conventional light diffusion layer.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 mother substrate 9 light diffusion layer 10 reflective liquid crystal display element 14 transparent electrode 15 alignment film 16 column electrode substrate 18 color filter 20 row electrode substrate 21 in-plane spacer 22 sealing material 23 light source 30 substrate suction chuck 31 inclined surface forming plate 31A inclined Surface 32 Individual area 33 Pattern forming mask

Claims (1)

[Claims] 1. A method for manufacturing a light diffusion layer, wherein a photosensitive resin layer formed on a surface of a transparent substrate is formed on the light diffusion layer by a photolithographic method, wherein the surface of the substrate suction chuck for sucking the transparent substrate has a small reflectance. An inclined surface whose height is increased as the position is formed, the transparent substrate is disposed along the inclined surface, and the surface of the transparent substrate is disposed above the transparent substrate via a pattern forming mask disposed in parallel with the substrate suction chuck. A method for producing a light diffusion layer, wherein the photosensitive resin layer is exposed.