JP2002139606A - Method for manufacturing light diffusing layer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an inner diffusion layer in which most of recessed grooves are asymmetric. SOLUTION: A control means 10 for the transmittance of light is disposed in the exitation light side of a condenser lens 6 in a batch type proximity gap exposure device 1, so that the energy distribution of the light passing through the aperture of a photomask 7 and irradiating a photosensitive resin 9 is made to deviate.

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 diffusing layer provided in a reflective or transflective liquid crystal display device, and more particularly, to a method of deviating from the regular reflection angle of external light on the device surface. However, the present invention relates to a technique for manufacturing an internal light diffusion layer having a brightness peak.

[0002]

2. Description of the Related Art In a reflection type (semi-transmission type) liquid crystal display element of an inner surface diffusion type, a light diffusion / reflection layer is formed on the inner surface of the cell, so that a bright display can be made by effectively utilizing external light. Is obtained. In many cases, the inner surface diffusion layer is formed by a photolithography method using a collimation angle of an exposure machine and light diffraction.

However, when the external light source is a line light source such as a fluorescent lamp or a point light source such as a light bulb, if the angle of the liquid crystal display element is turned to a position where the display looks bright, the light source is reflected on the display surface, and the liquid crystal display Is difficult to see.

Therefore, conventionally, an anti-glare treatment or an anti-reflector treatment is applied to the element surface as an anti-reflection treatment, or a film for changing the angle of incident light is attached.

Another method is to shift the reflection peak of the inner surface diffusion layer from the regular reflection angle of external light on the element surface to make the liquid crystal display easier to see. It is also practiced to provide an inclined surface having a predetermined gradient from the upper end to the lower end of the portion, and then form irregularities on the inclined surface.

[0006]

However, when the above-described treatment is performed on the element surface, not only the cost is increased but also the liquid crystal display itself becomes dark or the contrast is lowered. Occurs.

In the method of forming irregularities on the inclined surface by the inner surface diffusion layer, not only the step of forming the inclined surface once, but also forming the irregularity again increases the number of steps and obtains an effective inclination angle. In this case, a considerable gap difference occurs in one pixel, and in the STN display, there is a possibility that display gaps or domains may occur due to the gap difference.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and an object of the present invention is to provide an anti-reflection treatment on the element surface or to provide a diffusion layer on the inner surface of the element with no inclined surface. It is an object of the present invention to provide a method for manufacturing a light diffusion layer which makes it easy to view a liquid crystal display by shifting an angle at which a liquid crystal display by an inner surface diffusion layer looks brightest from a regular reflection angle of external light on an element surface.

[0009]

In order to achieve the above object, the present invention relates to a method in which a photosensitive resin applied on a glass substrate for a reflective or semi-transmissive liquid crystal display element is packaged through a photomask. After exposing with a proximity proximity exposure device, developing and forming a light diffusion layer having fine irregularities on the glass substrate, adjusting the light transmittance on the exit light side of the condenser lens of the exposure device Means for providing a bias in the energy distribution of light applied to the photosensitive resin through the opening of the photomask. According to this, most of the concave grooves included in the uneven surface are provided. Has an asymmetric shape with respect to the normal line of the display element surface.

As described above, in order to impart a bias to the energy distribution of light, the collimation angle of the exposure machine is set to θ _CA (゜), and the proximity gap between the photomask and the photosensitive resin surface is set to PG (μm), and the width of the opening of the photomask is W (μm), and it is preferable that an expression of 2 × PG × tan (θ _CA × 1/2) ≦ W be established between them. Is done.

In the present invention, the light transmittance adjusting means includes a light transmittance adjusting film or a light transmittance adjusting film for changing the transmittance of the photosensitive resin in a photosensitive wavelength range from one end of the condenser lens to the other end facing the same. It is possible to use a punching plate whose aperture ratio changes from one end of the optical lens to the other end.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, referring to FIG. 1, the structure of a collective proximity gap exposure machine used in the present invention will be schematically described.

The exposure apparatus 1 includes a light source 2 composed of, for example, a high-pressure mercury lamp disposed at the focal point of a parabolic mirror 3, a collimator lens 4 composed of a concave mirror, and a plane mirror for guiding light from the light source 2 to the collimator lens 4. Light (ultraviolet light) is applied from a collimator lens 4 to a photosensitive resin 9 applied on a glass substrate 8 via a photomask 7. The glass substrate 8 is used as a back side substrate of a reflective or transflective liquid crystal display device.

As the condenser lens 6, a fly array lens or an integrated rod lens which mixes and emits incident light from various directions is used. Although the light emitted from the condenser lens 6 has a certain degree of directionality, the light exits the collimator lens 4 with a certain width.

That is, since light enters the collimator lens 4 from any part of the entire surface of the aperture of the condenser lens 6, when viewed from the glass substrate 8 side, the condenser lens 6 has an apparent size of the light source. Become. The apparent size of the light source is a collimation angle abbreviated as CA.
The collimation angle θ _CA is determined by the aperture of the condenser lens 6 and the optical path length, and θ _CA = 2 × tan ⁻¹ ｛(aperture of the condenser lens × １ ／)
/ Optical path length｝

According to the present invention, the light transmittance adjusting means 10 is provided on the outgoing light side of the condenser lens 6. The light transmittance adjusting means 10 has a function of gradually changing the transmittance of the photosensitive resin 9 in the photosensitive wavelength range from one end of the condenser lens 6 to the other end thereof, and in this embodiment, the light transmittance adjusting film Is used.

This light transmittance adjusting film is made of, for example, ND
It can be obtained by laminating filters called "neutral density filters (trade name)" and adjusting the light transmittance. Instead of the light transmittance adjusting film, it is also possible to use a punching plate whose aperture ratio changes from one end of the condenser lens 6 to the opposite end.

Next, the optical path from the condenser lens (rod lens in this embodiment) 6 to the photomask 7 via the collimator lens 4 will be described with reference to the schematic plan view of FIG. In FIG. 2, light emitted from the upper end of the rod lens 6 is represented by U, and light emitted from the lower end of the rod lens 6 is represented by L.

The light emitted from the rod lens 6 strikes the collimator lens 4 and reaches the photomask 7, passes through the opening thereof, and reaches the exposed surface of the photosensitive resin 9. The collimator lens 4 is designed so that the light emitted from the rod lens 6 becomes parallel light as much as possible.

However, since the diameter of the rod lens 6 is finite, light emitted from the center of the rod lens 6 travels as parallel light perpendicular to the exposure surface.
Light U emitted from the upper and lower ends of the rod lens 6,
L has a certain angle with respect to the exposure surface, that is, the collimation angle described above.

Therefore, when the light from the rod lens 6 passes through the opening 71 of the photomask 7 and irradiates the exposed surface of the photosensitive resin 9, The light U emitted from the upper end of the lens 6 is incident on the exposed surface of the photosensitive resin 9 from an oblique left direction,
The light L emitted from the lower end of the rod lens 6 enters the exposed surface of the photosensitive resin 9 from an oblique right direction.

Here, the transmittance of the light transmittance adjusting film 10 extends from the lower end to the upper end of the rod lens 6.
Exposure surface of photosensitive resin 9 when changing to 6 levels of 1, 3, 5, 10, 50, and 100% (per pit)
FIG. 4 illustrates the energy distribution of light with respect to.

As can be seen from FIG. 4, since the transmittance at the left end of the pit is 1%, the exposure amount is extremely small.
The amount of exposure gradually increases in accordance with the transmittance as it goes to the right end side, and at the right end, the amount of exposure becomes almost 100%.
Therefore, the energy distribution of light is not a normal distribution,
The distribution shows that the peak is shifted to the right.

When the exposed photosensitive resin 9 is developed and baked, pits (concave grooves) 91 are obtained which are asymmetrical as shown in FIG. 5, so that the liquid crystal display by the inner surface diffusion layer looks brightest. The angle can be shifted from the regular reflection angle of external light on the element surface.

The above-mentioned left and right asymmetric pits 91 are obtained.
Has the collimation angle θ _CA(゜), photo
Proximity between the mask 7 and the exposed surface of the photosensitive resin 9
The gap is PG (μm) and the opening 7 of the photomask 7 is
1 is W (μm), and 2 × PG × tan (θ_CA× 1/2) ≦ W The mask is designed and exposure conditions are set so as to satisfy the following expression.
It is preferable to specify According to this equation, for example, P
G = 300 μm, θ_CA= 4.0 °, opening
The width of 71 is W ≦ about 21 μm.

[0026]

[Example] Hitachi DECO's batch exposure machine LE-405
The light wavelengths of 365 nm, 405 nm and 420 nm are set to 0 to 1 on the exit light side of the integrated rod lens of No. 0.
A light transmittance adjusting film having a transmittance characteristic of gradually transmitting the light to 00% was installed. In this exposure machine, 2.5 μm of positive photosensitive resin PC-403 manufactured by Nippon Synthetic Rubber Co., Ltd.
The substrate coated to a thickness of m was exposed, developed and fired to form an inner surface uneven layer.

On this uneven surface, a thickness of about 1
After forming a 00 nm aluminum reflective film, the reflection characteristics were measured. At the time of measurement, an optical oil was applied to the reflection surface and sandwiched between glasses of the same thickness. FIG. 6 shows the reflection characteristics of the inner surface uneven layer according to this embodiment at an incident light of 30 °. Also,
As a comparative example, FIG. 7 shows the reflection characteristics of the inner surface uneven layer formed without using the light transmittance adjusting film at an incident light of 30 °.

In the comparative example of FIG. 7, the reflectance is maximum at a glare angle of 30 ° with respect to the incident light, and the reflectance at 10 ° is about 25% of the maximum, but in the case of the present embodiment shown in FIG. ,
The reflectance at 10 ° was almost equal to the glare angle.

[0029]

As described above, according to the present invention,
Light transmittance adjusting means is provided on the outgoing light side of the condensing lens of the collective proximity gap exposure machine, so that the energy distribution of light irradiated to the photosensitive resin through the opening of the photomask is biased. Thereby, the inner surface diffusion layer in which most of the concave grooves are asymmetrical in the left-right direction is obtained.

Therefore, the angle at which the liquid crystal display by the inner surface diffusion layer can be viewed brightest can be adjusted without external reflection treatment on the element surface or providing the inner surface diffusion layer with an inclined surface or the like. The liquid crystal display can be easily viewed by shifting from the regular reflection angle.

[Brief description of the drawings]

FIG. 1 is a front view schematically showing an entire configuration of a collective proximity gap exposure apparatus used in the present invention.

FIG. 2 is a schematic plan view for explaining an optical path from a condenser lens of the exposure machine to a photomask.

FIG. 3 is an enlarged view of a portion surrounded by a circle in FIG. 2;

FIG. 4 is an explanatory view illustrating an energy distribution of light on an exposed surface of a photosensitive resin.

FIG. 5 is a sectional view showing an example of a pit shape included in an inner surface diffusion layer formed according to the present invention.

FIG. 6 is a graph showing reflection characteristics of the example of the present invention.

FIG. 7 is a graph showing reflection characteristics of a comparative example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Exposure machine 2 Light source 3 Parabolic mirror 4 Collimator lens 5 Plane mirror 6 Condensing lens 7 Photomask 71 Opening 8 Glass substrate 9 Photosensitive resin 10 Light transmittance adjusting means

Claims (4)

[Claims] A photosensitive resin coated on a glass substrate for a reflective or semi-transmissive liquid crystal display element is exposed through a photomask by a collective proximity gap exposure device, and then developed. In the method of manufacturing a light diffusion layer for forming a light diffusion layer having a fine uneven surface on the glass substrate, a light transmittance adjusting means is provided on an outgoing light side of a condenser lens of the exposure machine, and an opening of the photomask is provided. A method for producing a light diffusion layer, wherein the energy distribution of light applied to the photosensitive resin through a portion is biased. 2. A collimation angle of the exposure machine is θ _CA (゜), a proximity gap between the photomask and the photosensitive resin surface is PG (μm), and a width of an opening of the photomask is W. The method for producing a light diffusion layer according to claim 1, wherein the following expression is satisfied: (μm) 2 × PG × tan (θ _CA × 1/2) ≦ W 3. A light transmittance adjusting film for changing the transmittance of the photosensitive resin in a photosensitive wavelength range from one end of the condenser lens to the other end facing the light collecting lens as the light transmittance adjusting means. 3. The method for producing a light diffusion layer according to item 2. 4. The method for manufacturing a light diffusing layer according to claim 1, wherein a punching plate whose aperture ratio changes from one end of the condenser lens to the other end is used as the light transmittance adjusting means.