JP2003139927A - Reflection plate, liquid crystal display device using the same and photo mask - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress variation of diffuse reflectance in a mother glass substrate surface. SOLUTION: The shapes in a substrate surface are made respectively different so as to suppress the variation of diffuse reflectance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflective liquid crystal display device, a transflective liquid crystal display device, and a reflector.

[0002]

2. Description of the Related Art A reflection type liquid crystal display device for displaying by utilizing external light is for controlling display by controlling the amount of light reflected by a reflector, and for displaying without a backlight, it is consumed. It is characterized by low power consumption and high visibility even under strong external light such as direct sunlight, and is often used in portable devices.

Further, a semi-transmissive liquid crystal display device capable of displaying by both reflected light by external light and transmitted light by a backlight has high visibility due to reflective display under strong external light such as direct sunlight. Can be secured, the backlight can be turned off to display when the ambient environment is relatively bright, and power consumption can be suppressed, and the backlight can be turned on to display when the ambient environment is dark. It has the feature of being capable of being used, and is often used in portable devices like the reflective liquid crystal display device.

In both the reflection type display device and the semi-transmissive liquid crystal display device as described above, display is performed by using external light, and therefore a reflection plate for reflecting the external light is required. In order to secure sufficient display brightness with such a reflector,
It is necessary to diffuse the incident light with a reflector. There are two methods for diffusing the incident light: (1) forming a fine uneven shape on the surface of the reflecting plate, and (2) providing a diffusing film for diffusing the light on the display viewing side of the liquid crystal display device. There is a method. Among these, in the former case, since the reflection characteristics of the reflection plate are determined by the uneven shape of the surface of the reflection plate, the uneven shape formed on the surface is an extremely important factor that determines the characteristics of the liquid crystal display device.

A reflector having such an uneven surface is disclosed in, for example, Japanese Patent No. 2756206.

FIG. 5 is a diagram showing the structure of the reflector disclosed in Japanese Patent No. 2756206, FIG. 5 (a) is a plan view, and FIG. 5 (b) is a line I--I in FIG. 5 (a). FIG. As shown in FIGS. 5A and 5B, in the reflection plate 14 of this example, a plurality of convex portions 16 are formed on a flat substrate 15 so as to be separated from each other. A leveling layer 18 for smoothing unevenness between the surfaces of the convex portions 16 and the surface of the substrate 17 exposed between the convex portions 16 is formed on the convex portions 16 and on the substrate 17 exposed between the convex portions 16. A reflective film 19 is formed on the leveling layer 18. By forming the leveling layer 18 in this manner, the surface of the reflective film 19 has a smoother uneven shape, and the proportion of the flat portion can be reduced. Thereby, it becomes possible to secure a good light scattering property in which a sharp peak does not appear in the regular reflection direction, and it is possible to realize sufficient brightness in the display device.

[0007]

However, in the actual mass production process, the reflector is manufactured on the mother glass substrate having a size of about 300 mm × 300 mm or more based on the above conventional technique. At this time, the shape of the reflector differs depending on the position on the mother glass substrate, and the diffuse reflectance SCE that greatly affects the display performance varies. As a result, we found a problem that the SCE margin becomes small.

On the mother glass, 1) apply a resist,
In each of the four steps of prebaking, 2) exposing the pattern using a mask with an exposure device, 3) developing the resist with the pattern exposed, 4) melting the resist by annealing, each mother glass surface There is a factor that causes variations in reflection characteristics depending on internal positions.

In the step 1), as a result of variations in the mother glass surface when applying and pre-baking the resist, the amount of film loss during development differs between the central portion and the end surface in the surface. This is because the heat energy supplied during prebaking varies within the glass surface, and as a result, the amount of heat loss is small and the amount of heat energy is small in the part where the amount of heat energy is large, that is, in the part where the temperature is high. In a small portion, that is, a portion where the temperature is low, the amount of film reduction is large. As a result, the shape of the convex portion after development becomes large in a portion where the pre-baking temperature is high in the glass surface and becomes small in a portion where the pre-baking temperature is low. By melting these shapes, the end face portion has more flat portions than the central portion, and the diffuse reflectance SCE decreases. As a result, the diffuse reflectance SCE, which determines the reflection characteristics, varies greatly within the surface of the glass substrate.

Also in the developing step 3), the developing time varies in-plane depending on the position of the developing solution ejecting portion. Therefore, the shape of the convex portion is small near the developing solution ejecting portion. The shape of the convex portion increases as the distance from the discharge portion increases. The film thickness becomes thin in the vicinity of the developer discharge portion, and the flat portion increases as the melt property deteriorates. The diffuse reflectance in the vicinity of the discharge portion is lower than that in the distance from the discharge portion. As a result, the diffuse reflectance SCE varies within the surface of the glass substrate. The present invention has been made to solve the above problems, and an object of the present invention is to provide a reflective liquid crystal display device, a transflective liquid crystal display device, and a reflector that can be manufactured with a higher yield. .

[0011]

A reflector according to the present invention is a reflector having an uneven shape formed on a mother glass substrate, wherein the uneven shape on the mother glass substrate surface is different. I am trying.

According to this structure, the high temperature portion on the mother glass substrate during prebaking has a smaller number of flat ends even if the film thickness is thin by making the shape of the convex portion smaller than that of the low temperature portion. With a reflector that can obtain a shape and is formed by forming a reflective layer through exposure and development and other processes, it is possible to suppress variations in SCE within the mother glass substrate.

The photomask according to the present invention is a photomask for forming an uneven shape on a mother glass substrate, wherein the pattern for forming the uneven shape is different in the plane on the mother glass substrate. I am trying.

According to such a structure, as compared with the photomask in which the same pattern is formed on the substrate surface, the convex pattern is made smaller in the portion where the temperature during pre-baking is higher and larger in the portion where the temperature is lower, so that the shape due to the temperature difference is formed. It is possible to suppress variations in diffuse reflectance SCE due to changes.

The photomask according to the present invention is a photomask in which a pattern for patterning a reflective film between irregularities among the reflective film formed on the mother glass substrate is formed. It is characterized in that the intervals or areas of the patterns are different in the upper surface.

According to this structure, the width between the patterns is narrow in the portion where the pre-baking temperature is low, and the width between the patterns is large in the portion where the raw pre-baking temperature is high. It is possible to suppress variations in the area of the film and variations in the diffuse reflectance SCE.

The liquid crystal display device according to the present invention is a liquid crystal display device using a reflection plate formed on a mother glass substrate, and is characterized in that the diameters of the spacers in the substrate surface are different.

With such a structure, the diameter of the spacer is increased in a portion where the prebaking temperature is low and the film thickness of the unevenness is thin, and the diameter of the spacer is reduced in a portion where the unevenness shape is high and the prebaking temperature is high. It is possible to suppress variations in cell thickness within the cell.

The liquid crystal display device according to the present invention is a liquid crystal display device using a reflection plate formed on a mother glass substrate, and is characterized in that the dispersion density of the spacers within the substrate surface is different.

With this structure, it is possible to obtain the same effect as controlling the diameter of the spacer, and it is possible to suppress variations in cell thickness within the mother glass surface (claim 10).

The liquid crystal display device according to the present invention is a liquid crystal display device using a reflection plate formed on a mother glass substrate, and is characterized in that the column spacers are arranged at different positions in the substrate surface. .

According to this structure, the column spacers are arranged in the thick portion of the uneven shape and the thin film portion, and the column spacers are arranged in the thin portion of the uneven shape of the thick film portion. It is possible to suppress the variation in cell thickness within the mother glass surface.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 schematically shows a reflector and a mother glass substrate according to the present invention. The reflector used in a normal reflective liquid crystal display device is 3
On a mother glass substrate 1 of 00 mm x 300 mm or more,
It is manufactured in the form of multiplex using photolithography. When the mother glass substrate 1 is heated, a phenomenon occurs in which the substrate is warped due to the temperature difference between the substrate heating surface and the opposite side. Therefore, the chip 2 moves away from the substrate heating surface, which lowers the temperature on the mother glass substrate. On the other hand, in the chip 3 in the central portion of the substrate, the distance from the substrate heating surface is small, so that the temperature of the chip 3 on the mother glass substrate becomes high. As a result, a large temperature difference occurs between the chip 2 and the chip 3 on the mother glass substrate surface.

A positive resist PC403 (manufactured by JSR Corporation) is applied on the mother glass substrate 1 by a spin coater so as to have a film thickness of 2.5 μm and prebaked to 9 μm.
It was carried out at 0 ° C. for 120 seconds. Then, as shown in FIG. 2, exposure is performed through a photomask 6 in which circular light-shielding patterns 5 having a diameter of 15 μm are randomly arranged for each portion 4 corresponding to each pixel, and 0.4% TMAH (tetramethylammonium hydride) is used. Static development was carried out for 120 seconds with a developing solution containing. Next, it was melt-flowed on a hot plate at 180 ° C. for 120 seconds. Furthermore, after this, 220 ℃, 12
After main curing in an oven for 0 minutes, Al was formed as a reflective film by sputtering. After that, when the diffuse reflectance SCE was measured, the central portion of the chip 3 was 39.8%.
However, with the partial chip 2 near the end face, 34.9%
That was 5% lower. When the shape after development was measured,
The diameter of the pattern is 14um at the center and 1 at the end face.
The thickness of the chip 3 at the central portion having a high temperature was 2.1 μm, while the thickness of the chip 2 at the end portion having a low temperature was 1.8 μm.
It was as thin as m and 0.3 um. If the film thickness is thin, the amount of deformation of the resist due to melt flow is small, and the flat portion is increased, so that the diffuse reflectance is lowered. As a result, the diffuse reflectance SCE varied between the central portion and the end face portion.

In order to rectify this, a mask having a pattern in which the entire tip 3 of the chip 3 has a diameter of 12 μm is reduced is used to fabricate a reflector through the same steps.

When the shape of the reflector is compared between the tip 2 at the end face and the tip 3 at the center, the tip 2 has a diameter of 1
0.5um, film thickness 1.9um, diameter of chip 3 is 14.0
um, film thickness 2.1 um. When the diffuse reflectance of each part was measured, it was 38.
8%, and 39.6% for the chip 3 in the central portion, which is smaller than when using a mask having the same pattern on the entire surface.

When a reflection type liquid crystal display device was constructed using the reflection plate according to the present invention, the diffuse reflectance SCE was 21.5% in the central portion and 20.8% in the end face portion. On the other hand, in a liquid crystal display device using a semi-transmissive reflective plate in which Al is patterned with the same mask on the entire surface, the central portion is 2
The end face portion was 19.0% compared to 1.4%.

In the present embodiment, the convex portion is described, but the concave portion can be similarly implemented by making the end face portion and the central portion have different patterns. Also,
In this embodiment, the reflector having a single resin layer is described. However, a reflector having a method in which a convex portion or a concave portion is formed in the first resin layer and then the second resin layer is leveled Can be similarly implemented. Further, in the present embodiment, the diffuse reflectances at the end face and the central portion are compared, but the same can be done at other portions where the temperature variation during prebaking is large. Further, in the present embodiment, the pre-baking process is focused on, but other processes such as the melt baking process for determining the shape of the resin can be similarly performed by changing the pattern according to the temperature distribution on the substrate. Further, although the present invention describes the whole-exposure-type photomask, for example, a reduction-exposure-type reticle can also obtain similar effects by using a plurality of reticles having different patterns at the central portion and the end face portion. it can.

(Second Embodiment) FIG. 3 shows a photomask according to the present invention. A reflector plate was manufactured based on the same steps as those described in the first embodiment. At this time, the distance between the flat portions between the convex portions was narrow in the central portion of the substrate and wide in the end face portion. With respect to the mother glass substrate on which this reflection plate was formed, the reflection film on the flat portion of the convex portion of the reflection plate was patterned in order to obtain a semi-transmissive reflection plate. At this time, a positive resist OFPR5000 (manufactured by Tokyo Ohka Kogyo Co., Ltd.) was applied by spin coating so as to have a film thickness of 2.0 μm. After application, prebaking was performed at 90 ° C. for 90 seconds. Next, the photomask 1 shown in FIG.
3 is used for exposure. In the photomask 13, a circular light-shielding pattern 8 having a diameter of 12 um is randomly arranged in a portion 7 having a central portion corresponding to a pixel, and a pixel 10 at an end face portion.
So that the inside becomes a circular light-shielding pattern 11 with a diameter of 15 um,
It consists of a circular pattern reduced in position. At this time, among the portions for patterning the reflection film between the convex portions, a certain interval is 6 μm in the central portion 9, and the end face portion 12
Was designed to be 4.5 um. This mask 13
Using, the resist was exposed and developed, and Al, which is a reflective film, was patterned. Furthermore, when a transparent electrode film ITO was formed on the upper surface of Al and the scattering reflectance SCE thereof was measured, it was 21.4% in the central portion and 20.
It became 5%. On the other hand, after patterning the resist with a photomask on which the pixel pattern 7 is entirely arranged,
When the diffuse reflectance SCE was measured for the reflection plate with Al removed and the ITO film formed, it was 21.3 at the center.
% And 18.2% at the end face.

If the distance between the flat portions between the convex portions becomes large, the coating film thickness of the resist becomes thin and the film thickness on the convex portions becomes apparently thin, and the resist pattern remains much smaller than the light shielding pattern. It will be. In order to make the shape of the reflective film after patterning uniform in the central portion and the end surface portion, by making the interval of the flat portion different between the central portion and the end surface portion of the photomask used for patterning the reflective film, It is possible to suppress variations in diffuse reflectance due to the shape of the convex portion. Even with the semi-transmissive reflection plate after the removal of Al, uniform diffuse reflectance could be obtained in the plane of the mother glass substrate.

When a liquid crystal display device was constructed using the semi-transmissive reflector according to the present invention, the diffuse reflectance SCE was 8.56% in the central portion and 8.2% in the end face portion. On the other hand, in the liquid crystal display device using the semi-transmissive reflection plate in which Al was patterned with the same mask all over, the central portion was 8.52% and the end face portion was 7.28%.

In this embodiment, the convex portion is described, but the concave portion can be similarly formed by changing the photomask pattern for patterning the reflective layer at the end face portion and the central portion. Further, in the present embodiment, the reflection plate in which the resin layer is manufactured by one layer has been described, but after the convex portion or the concave portion is formed by the first resin layer,
The same can be applied to the reflection plate of the type in which the leveling is performed with the second resin layer.

Further, in the present embodiment, the shapes of the convex portions on the end face and the central portion are compared, but the same can be applied to other portions where the intervals between the convex portions are different.
Further, although the present invention describes the whole-exposure-type photomask, for example, a reduction-exposure-type reticle can also obtain similar effects by using a plurality of reticles having different patterns at the central portion and the end face portion. it can.

(Third Embodiment) A reflector is manufactured by the same steps as in the first embodiment. When a reflective liquid crystal display device is constructed using this reflector, the height of the convex shape is 2.1 μm and the end face is 1.8 μm at the center, so that the center and the end face each have an average height. Diameter is 2.9um and 3.2um
Sprinkled with spacers. When the diffuse reflectance of this liquid crystal display device was measured, it was 21.0% at the central portion and 20.5% at the end face portions. On the other hand, when only the spacers having an average diameter of 3.2 um were scattered using the reflector manufactured through the same process, 19.5% was formed in the central portion and 2 was formed in the end face portion.
The variation within the mother glass substrate surface was as large as 0.8%.

It is known that the reflectance decreases with respect to the optimum cell thickness as shown in FIG. In the reflective liquid crystal display device, the cell thickness is determined by the height of the uneven shape of the reflection plate. Therefore, when the height of the convex shape varies within the mother glass substrate surface, it is necessary to correct it by the spacer.

In the present invention, the variation of the cell thickness due to the variation in the surface of the uneven shape is corrected by the diameter of the spacer to suppress the variation of the diffuse reflectance within the surface.

In the present invention, the diffuse reflectance is suppressed by scattering the spacers having different average diameters. However, the same can be done by correcting the cell thickness by changing the scattering density. . Further, even if a column spacer or the like is used instead of the scatter type spacer, it can be similarly carried out by appropriately setting the height, diameter, and formation density. Further, when the pillar spacer is used, the cell thickness can be corrected by changing the arrangement position within the mother glass substrate surface. That is, in the central portion where the shape of the convex portion is high, the column spacer is arranged in a place where the film thickness in the pixel is large,
If the column spacers are arranged at locations where the film thickness is small in the pixel at the end face portion where the film thickness is thin, the variation in the cell thickness can be similarly corrected.

[0039]

EFFECT OF THE INVENTION With the above structure, a reflector having a small variation in diffuse reflectance in the plane of the mother glass substrate, and
It was possible to provide a liquid crystal display device using a photomask and a reflector for manufacturing the same.

[Brief description of drawings]

FIG. 1 is a diagram showing an outline of a reflector and a mother glass substrate.

FIG. 2 is a diagram showing a photomask.

FIG. 3 is a diagram showing a photomask.

FIG. 4 is a diagram showing a correlation between cell thickness and reflectance.

FIG. 5 is a diagram showing a conventional example.

[Explanation of symbols]

1 mother glass substrate 2 chips (substrate end face) 3 chips (center of substrate) Portion corresponding to 4 pixels 5 circular shading pattern 6 Photo mask Portion corresponding to 7 pixels 8 circular shading pattern 9 Distance between convex parts (center part) 10 circular shading pattern 11 circular shading pattern 12 Distance between convex parts (end face part) 13 Photomask 14 Reflector 15 substrates 16 convex 17 board 18 Leveling layer 19 Reflective film

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G03F 1/08 G03F 1/08 D G09F 9/30 310 G09F 9/30 310 9/35 9/35 F term (Reference) 2H042 BA03 BA15 BA20 DA12 DC08 DE00 2H089 LA20 NA09 QA12 TA02 TA17 2H091 FA14Y GA08 KA10 LA12 LA16 2H095 BA12 BB02 BB36 BC09 5C094 AA03 BA43 EB04 FA04

Claims (11)

[Claims] 1. A reflector having an uneven shape made of a photosensitive resin formed on a mother glass substrate, wherein the mother glass substrate surface is provided to make the diffuse reflectance of the reflector uniform within the substrate surface. A reflector characterized by having different uneven shapes inside. 2. The reflector according to claim 1, wherein the different shape is a height, a diameter, or a volume of the convex portion or the concave portion. 3. A photomask for forming an uneven shape on a mother glass substrate, wherein the pattern for forming the uneven shape is different in a plane on the mother glass substrate. 4. A photomask having a pattern for patterning a reflection film between irregularities among reflection films formed on a mother glass substrate, wherein the pattern is formed within a plane on the mother glass substrate. Photomasks characterized by different intervals or areas. 5. A reflection type liquid crystal display device, comprising the reflection plate according to claim 1 or 2. 6. A semi-transmissive liquid crystal display device comprising the reflection plate according to claim 1 or 2. 7. A reflective liquid crystal display device manufactured by using the photomask according to claim 3. 8. A semi-transmissive liquid crystal display device manufactured using the photomask according to claim 4. 9. A liquid crystal display device using a reflection plate formed on a mother glass substrate, wherein the diameters of the spacers in the substrate surface are different. 10. A liquid crystal display device using a reflection plate formed on a mother glass substrate, wherein the dispersion densities of spacers in the substrate surface are different. 11. A liquid crystal display device using a reflection plate formed on a mother glass substrate, wherein the column spacers are arranged at different positions in the substrate surface.