JPH10282324A - Reflection type color filter and method of manufacturing the same - Google Patents

Abstract

[PROBLEMS] To provide a reflective color filter having excellent display characteristics using an ultraviolet curable cholesteric liquid crystal or a chiral nematic liquid crystal, and a method of manufacturing the same. A light-absorbing layer is provided on a substrate, a concave portion is provided from the surface of the light-absorbing layer to the inside thereof, and a wavelength and polarization selective reflection layer made of an ultraviolet-curable cholesteric liquid crystal or an ultraviolet-curable chiral nematic liquid crystal is provided in the concave portion. It is characterized by being provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflection type color filter used in a reflection type color liquid crystal display device and a method of manufacturing the same.

[0002]

2. Description of the Related Art A reflection type liquid crystal display device is thinner and lighter than a transmission type liquid crystal display device using a conventional backlight.
It is an excellent and promising technology in terms of low power consumption. However, if a color filter is inserted for color display as in the case of the transmissive type, the reflectance decreases due to the light absorption of the color material, and the brightness of the display device becomes insufficient.

As a countermeasure, a method of improving the brightness by lowering the color material density of the color filter has been studied. However, in this method, the color purity of the color filter is reduced and the color reproducibility of the liquid crystal display device is reduced. Resulting in.

Therefore, as a method of improving brightness without lowering color reproducibility, a reflection type color filter using a wavelength selective reflection characteristic of a cholesteric liquid crystal without using a coloring material such as a pigment or a dye is used. Methods of forming have been proposed. Above all, a UV curable cholesteric liquid crystal or a chiral nematic liquid crystal capable of changing the selective reflection wavelength depending on the temperature and fixing the selective reflection wavelength by exposing to ultraviolet light at a desired temperature can be used in a single layer. It is possible to form a reflection color pattern, and studies are being made as a material for forming a reflection type color filter. (SID @ 94 Choleste
ric Reflecters withColor
Pattern)

A UV-curable cholesteric liquid crystal or a chiral nematic liquid crystal can obtain a high reflectance by aligning the orientation direction of each molecule, and can control the temperature to change the twist pitch of the liquid crystal molecules to increase the selective reflection wavelength. Because it is a material that can be controlled, it is important to control these characteristics in order to form a reflective color filter.

As a method proposed at present, first, an ultraviolet-curable cholesteric liquid crystal or a chiral nematic liquid crystal is sandwiched between two glass substrates on each of which an alignment film such as polyimide is formed in order to align the alignment directions. While applying pressure, the whole is uniformly oriented. Subsequently, while being heated to a temperature at which a necessary wavelength is reflected, ultraviolet exposure is performed through a photomask having a necessary pattern, and the pitch of the liquid crystal in only the exposed portion is fixed to obtain a reflective layer pattern. This process is repeated to form a plurality of reflective color filters.

In this method, since the liquid crystal layer itself is a reflective layer, there is no need to provide a separate reflective layer.
Conversely, a light absorbing layer is required to remove light transmitted through the liquid crystal layer (reflected light other than the selective reflection wavelength. This light absorbing layer is usually provided below the alignment film.

The problem in this step is that, first, since the film is sandwiched between glass substrates and developed by applying pressure, the film is exposed through the glass substrate during ultraviolet exposure. Even when a photomask having a predetermined pattern is used, a gap between the mask and the liquid crystal layer is generated due to the thickness of the glass substrate, and a resolution cannot be obtained.

A second problem is that during exposure to ultraviolet light, so-called exposure fog occurs due to irregular reflection in the liquid crystal layer. That is, although the liquid crystal molecules are uniformly aligned using the alignment film, they are not completely oriented in the same direction, but are oriented in a random direction to some extent. As a result, the ultraviolet light is scattered in a random direction, a portion other than the predetermined pattern portion is also exposed, and the liquid crystal pitch is fixed, so that the next color cannot be patterned.

[0010]

SUMMARY OF THE INVENTION The present invention has been made to solve these problems, and an object of the present invention is to use a cholesteric liquid crystal or a chiral nematic liquid crystal which is curable by ultraviolet light to obtain a display characteristic. And a method of manufacturing the same.

[0011]

According to the present invention, in order to solve the above problems, a light absorbing layer is provided on a substrate, a concave portion is provided from the surface to the inside of the light absorbing layer, and a wavelength and polarization selective reflection layer is provided in the concave portion. And a reflection type color filter characterized by comprising: In particular, the present invention provides a reflection type color filter, wherein the wavelength and polarization selective reflection layer is an ultraviolet curable cholesteric liquid crystal or an ultraviolet curable chiral nematic liquid crystal.

In addition, as a method for producing the same, 1) a photosensitive black resin composition is coated on a substrate, and 2) light is exposed using a photomask having a desired pattern to reduce the unexposed portion of the light absorbing layer to a required depth. A concave portion is provided in the light absorbing layer by development and removal. 3) An ultraviolet curable cholesteric liquid crystal or an ultraviolet curable chiral nematic liquid crystal is filled in the concave portion of the light absorbing layer while applying an orientation while applying pressure. 4) A substrate is required. To a desired temperature while controlling the reflection wavelength of the ultraviolet-curable cholesteric liquid crystal or the ultraviolet-curable chiral nematic liquid crystal using a photomask having a desired pattern to cure the necessary portions, and 5) 3) and 4) A) a method of manufacturing a reflective color filter, wherein the method comprises repeating the number of colors requiring the step (d).

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the drawings. First, the light absorption layer 2 is formed on the substrate 1. At this time, the material of the substrate can be arbitrarily selected as long as it is a material used for a liquid crystal display device. Usually, a glass substrate is used.

Light absorbing layer 2 provided on this glass substrate
Is formed of a black resin composition having the following composition. That is, it is a photosensitive black resin composition obtained by diluting a black pigment, a binder, a photosensitive resin, and a photosensitive agent with a diluting solvent, and a black resist used for forming a black matrix of a transmission type color filter can be used. .

A black resist is uniformly applied on a substrate by spin coating, roll coating, or the like, and dried using a clean oven, a hot plate, or the like. At this time, the film thickness to be applied needs to be set to be larger than the film thickness of the selective reflection layer formed in the subsequent steps, and is usually applied at 10 to 20 μm.

Next, after exposure to ultraviolet light using a predetermined photomask 3, development is performed using a predetermined developing solution. At this time, in the present invention, the light absorption layer is not completely developed by controlling the development time, and the development is stopped when a residual film that does not impair the function as the light absorption layer is left.

Here, the light absorbing layer becomes a layer 2 'having a concave portion (rib shape) of a predetermined shape. The depth of the concave portion is the depth of the selective reflection layer formed in the next step, that is, 8 to 18
About μm is appropriate.

Subsequently, a predetermined amount of an ultraviolet-curable cholesteric liquid crystal or a chiral nematic liquid crystal is dropped onto the light absorbing layer while heating the substrate provided with the light absorbing layer. An embedded and selective reflection layer 5 is formed. At this time, a sufficiently flexible material such as urethane rubber or silicon rubber is used as a material of the squeegee so as not to damage the light absorbing layer.
Here, by applying with a squeegee, the ultraviolet curable cholesteric liquid crystal or chiral nematic liquid crystal is given a share in the processing direction of the squeegee, and the alignment direction of the liquid crystal molecules is uniform, so that good reflection characteristics can be obtained.

In order to further uniform the orientation,
It is also possible to form an alignment film on the light absorbing layer in advance before applying the UV-curable cholesteric liquid crystal or chiral nematic liquid crystal, and rub it in accordance with the processing direction of the squeegee to provide the alignment layer.

By performing the above steps, the shape of the reflection type color filter according to the present invention is formed as shown in FIG. Subsequently, a step of giving the selective reflection layer a selective reflection characteristic of a desired wavelength is performed. First, the substrate on which the light absorbing layer and the selective reflection layer are formed is heated to a desired temperature. The temperature at this time is determined by the characteristics of the ultraviolet curable cholesteric liquid crystal or chiral nematic liquid crystal used and the required reflection wavelength.

Next, while maintaining this temperature, ultraviolet exposure is performed using a photomask conforming to the shape of the selective reflection layer. In the portion exposed to ultraviolet light, the pitch of the liquid crystal is fixed by a polymerization reaction caused by the radical generated by the initiator, and the reflection wavelength does not change even if the temperature is changed thereafter. Since the polymerization reaction has not occurred in the unexposed portion, it is possible to change the selective reflection wavelength by changing the temperature.

Further, in the present invention, since the selective reflection layer is surrounded by the rib formed of the same material as the light absorbing layer, the ultraviolet light scattered in the exposed portion is absorbed by the rib, and the ultraviolet light radiated to the portions other than the pattern. There is no scattering of light and no so-called fogging occurs.

Subsequently, the reflection type color filter is formed by repeating the number of colors requiring the above steps.

[0024]

EXAMPLE A 300 mm × 300 mm non-alkali glass substrate having a thickness of 1.1 mm (Corning Co., Ltd .: “# 705”)
9 ") on a black resist (Fujihunt Co., Ltd .:" CK
7000 ") was spin coated at 300 rpm and dried in a clean oven at 70 ° C. for 20 minutes. This process was further repeated three times to obtain a black resist film having a thickness of 12 μm. This black resist film is formed with a line width of 20 μm.
UV exposure was performed at 300 mJ using a super high pressure mercury lamp through a photomask having a pitch of 100 μm. Subsequently, it was immersed in a developing solution (manufactured by Fuji Hunt: "CD") for 10 minutes and rinsed with pure water spray. At this time, the unexposed portions of the black resist film were developed by 10 μm to form a rib-shaped light absorbing layer.

This substrate is placed on a hot plate for 100
While heating to ° C, a stripe (WA
CKER: “TC3947L” (5 g) was dropped, and the mixture was applied while applying pressure using a urethane rubber squeegee. This was buried in the rib shape of the light absorbing layer, forming the selective reflection layer. Then, 95
° C to a peak reflection wavelength of 465 nm,
Only pixels desired to be displayed in blue in the selective reflection layer were exposed to ultraviolet light at 900 mJ via a photomask. Next, the substrate temperature was set to 70 ° C., and the selective reflection layer except that the pitch was fixed by exposing in the previous step was set to reflect 545 nm, and only the green display pixels were similarly exposed. Further, when the substrate temperature is 45
After 620 nm was reflected at a temperature of ℃, the same exposure was performed to form a red display pixel. At this time, the reflection characteristics of each pixel were good. Each pixel had no problem such as color mixing at a pitch of 100 μm.

[0026]

Since the present invention has the above-described configuration, the following effects can be obtained. That is, the light absorbing layer is developed to a predetermined thickness to form a concave portion (rib shape), and the concave portion is formed by embedding an ultraviolet curable cholesteric liquid crystal or a chiral nematic liquid crystal. Can be prevented from scattering to unexposed portions, and a pattern with good resolving power can be obtained. In addition, uniform alignment is realized by inserting a UV-curable cholesteric liquid crystal or chiral nematic liquid crystal into the rib shape of the light absorbing layer using a doctor, and a reflective color filter having high reflectance is manufactured by a simple method. Becomes possible.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a cross-sectional structure of an example of a reflection type color filter of the present invention.

FIG. 2 is an explanatory view showing steps of a method for manufacturing a reflection type color filter of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Substrate 2, 2 '... Light absorption layer 3 ... Photomask 4
… Doctor 5… Selective reflection layer

Claims (3)

[Claims] 1. A reflection type color filter comprising: a light absorbing layer provided on a substrate; a concave portion provided from the surface to the inside of the light absorbing layer; and a wavelength and polarization selective reflection layer provided in the concave portion. 2. The reflection type color filter according to claim 1, wherein said wavelength and polarization selective reflection layer is made of an ultraviolet curable cholesteric liquid crystal or an ultraviolet curable chiral nematic liquid crystal. 3. A photosensitive black resin composition is coated on a substrate, 2) exposed using a photomask having a desired pattern, and an unexposed portion of the light absorbing layer is developed and removed to a required depth. A concave portion is provided in the light absorbing layer; 3) an ultraviolet curable cholesteric liquid crystal or an ultraviolet curable chiral nematic liquid crystal is filled in the concave portion of the light absorbing layer while applying pressure while applying pressure; and 4) the substrate is heated to a required temperature. Then, while controlling the reflection wavelength of the ultraviolet-curable cholesteric liquid crystal or the ultraviolet-curable chiral nematic liquid crystal, exposure is performed using a photomask having a desired pattern to cure necessary portions, and the steps 5) and 3) and 4) are performed. A method for manufacturing a reflection type color filter, wherein a required number of colors are repeated.