JP2008134511A - Color filter with protrusion for liquid crystal alignment control - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a color filter with protrusions for liquid crystal alignment control having a sufficient height even if one pixel size of the color filter is a micropattern and a substrate surface is uneven. <P>SOLUTION: The protrusions 5, 6 for liquid crystal alignment control comprise a cured product of a photosensitive resin composition containing an alkali-soluble resin, a photopolymerizable monomer, a photopolymerization initiator and inorganic fine particles. The inorganic fine particles are contained in a range of 5-50 wt.% of the cured product. The inorganic fine particles have a primary particle diameter of ≤100 nm. The inorganic fine particles are silica. The cured product has a relative dielectric constant of <5 and a dielectric loss tangent of ≤0.014. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a color filter for a liquid crystal display device that forms an image by applying an electric charge to a liquid crystal material held between substrates. More specifically, the present invention relates to a multi-domain vertical alignment method (Multi-domain Vertical Alignment method, The present invention relates to a color filter having a liquid crystal alignment control projection used in the following (abbreviated as MVA system).

  In recent years, liquid crystal display devices are used in various fields. Fields used range from mobile phones and digital cameras with a relatively small area to televisions and monitors with a large area.

  Among them, the MVA type liquid crystal display device has the characteristics that the contrast ratio is high and the viewing angle is very wide as compared with a general twisted nematic type (TN type) liquid crystal display device. This is optimal when high-quality image display is required, for example, when displaying television images, and the technology is widely used.

On the other hand, in recent years, the following characteristics are required in a liquid crystal display device having a relatively small screen.
(1) High contrast, wide viewing angle, response speed (2) High resolution (3) Transflective display This is the start of one-segment broadcasting, so that TV can be viewed on a mobile phone, and the panel characteristics are also high contrast. This is because a wide viewing angle and response speed are required. In order to satisfy this requirement, the MVA method has been proposed.

  On the other hand, in order to increase the display information on a small screen, an increase in the number of pixels such as from QVGA to VGA is required. For mobile use, a transflective type that has both transmission and reflection functions is adopted for easy viewing even outdoors. Among them, a structure in which a step is provided by a resin layer on a color filter substrate has been proposed (Patent Document 1).

Due to the characteristics required above, the color filter is required to have a very complex structure of transflective type using the MVA method. In the MVA method, a protrusion for controlling the orientation is required from the driving principle.
Here, the protrusion can be formed on a small pixel area, and is required to be formed with high dimensional accuracy at a time even on a stepped substrate.

Until now, positive photosensitive materials have been widely used for the formation of protrusions. However, the conventional positive type photosensitive material has the following problems.
(1) The heat flow property at the time of baking is high, and projections having a small area cannot be formed.
(2) In order to form a pattern such as a projection used for a color filter, a photomask used for a positive type photosensitive material in which an exposed portion is dissolved has an area that is almost an opening. For this reason, a minute amount of the same defective pattern is formed when the photomask is attached with minute scratches and foreign matters, and problems such as a decrease in the yield during formation tend to occur.

For the above reasons, a negative photosensitive resin composition has been proposed (Patent Document 2). However, in the conventional negative photosensitive resin composition, in the case of a complex substrate having a height difference of 1 μm or more on the upper surface of the substrate immediately before the formation of the protrusion, the upper portion of the step is sufficient. A projection for controlling the alignment of liquid crystal with a high height could not be formed.
JP 2001-141922 A JP 2003-330011 A

  The present invention has been made to solve the above-described problems, and the problem is that the pixel size of the color filter is a very small pattern and is sufficiently high even if there is a step on the substrate. Another object of the present invention is to provide a color filter having a liquid crystal alignment control protrusion.

  The present invention is a color filter having a liquid crystal alignment control protrusion, wherein the liquid crystal alignment control protrusion includes an alkali-soluble resin, a photopolymerizable monomer, a photopolymerization initiator, and inorganic fine particles. It is a color filter which has the protrusion for liquid crystal orientation control characterized by consisting of the hardened | cured material of a conductive resin composition.

  In the color filter having the liquid crystal alignment control protrusion according to the invention, the inorganic fine particles are contained in the range of 5% by weight to 50% by weight of the cured product. A color filter having a control protrusion.

  The present invention also provides a color filter having a liquid crystal alignment control protrusion according to the invention, wherein the inorganic fine particles have a primary particle size of 100 nm or less. is there.

  Further, the present invention provides the liquid crystal alignment control protrusion according to claim 1, 2 or 3, wherein the inorganic fine particles are silica in the color filter having the liquid crystal alignment control protrusion according to the invention. A color filter having

  According to the present invention, in the color filter having the liquid crystal alignment control protrusion according to the invention, the relative permittivity of the cured product in a frequency range of 10 to 50 Hz is less than 5, wherein the liquid crystal alignment control protrusion is characterized in that A color filter having an object.

  In the color filter having the liquid crystal alignment control protrusion according to the invention, the dielectric loss tangent of the cured product in a frequency range of 10 to 50 Hz is 0.014 or less. A color filter having protrusions.

  According to the present invention, it is possible to obtain a color filter having a liquid crystal alignment control protrusion having a sufficiently high height even if the pixel size of the color filter is a minute pattern and there is a step in the film thickness on the substrate. Furthermore, it is possible to provide a color filter with few identical defects in the protrusion forming step. Furthermore, in the case of a liquid crystal display device, it is possible to provide a color filter having excellent display characteristics that does not cause display burn-in, unevenness, or malfunction.

Embodiments according to the present invention will be described below.
First, FIG. 1 shows a schematic diagram of a cross section of a color filter having a liquid crystal alignment control protrusion according to the present invention.
As shown in FIG. 1, first, a light shielding film (black matrix) 2 is formed on a transparent substrate 1. Thereafter, R (red), G (green), and B (blue) color filter pixels are formed. At this time, the chromaticity of the color filter needs to be adjusted because the chromaticity required for the transmission part and the reflection part is different.
As a method for adjusting the chromaticity, there are methods such as forming a pattern separately, reducing the thickness of the reflective portion, and making a thin hole by making a hole in the pixel of the reflective portion. Although FIG. 1 shows a type in which a hole is provided in the reflecting portion, the present invention is not particularly limited to this method.

Next, in order to control the cell gap between the transmissive portion 7 and the reflective portion 8, a step is formed by the resin layer 3 on the reflective portion of the color filter.
The film thickness of the resin layer is adjusted so that the phase difference at the time of cell passage between the transmitting portion that transmits the light of the backlight and the reflecting portion that receives and reflects external light is made uniform.
Subsequently, the transparent electrode 4 is formed on the outermost surface. An electrode substrate with a level difference is produced by the steps so far. Further, the liquid crystal alignment control protrusions 5 and 6 of the present invention are formed on the transmission part and the reflection part at a time to form the color filter of the present invention.

  In the present invention, at least an alkali-soluble resin, a photopolymerizable monomer, and a photopolymerization initiator are used as components to form a predetermined size with high dimensional accuracy. In addition, in order to form protrusions on the stepped substrate, inorganic fine particles are added to the above composition to improve the thixotropy and increase the height of the protrusions on the reflective part during coating. . From the above, at least alkali-soluble resin, photopolymerization initiator, photopolymerizable monomer, and inorganic fine particles are the main components.

  Here, the alkali-soluble resin refers to a resin in which an unexposed portion can be dissolved and removed by an alkaline developer during development after exposure. Specifically, an acrylic transparent resin composed of an acrylic monomer such as alkyl acrylate, cyclic acrylate, cyclic methacrylate, hydroxyethylethyl acrylate, hydroxyethyl methacrylate and the like and a radical polymerizable monomer having an ethylenically unsaturated group, a fluorene skeleton Epoxy acrylate transparent resin having a functional group or a polyfunctional epoxy resin in which a radical polymerizable monomer having an ethylenically unsaturated group is added can be used. However, it is not limited to the above resin.

  The polymerizable monomer is a monomer that is polymerized by exposure. Specifically, a group of polyfunctional acrylates, that is, pentaerythritol tri (meth) acrylate, pentaerythritol hexa (meth) acrylate, trimethylolpropane tri ( (Meth) acrylate, ethylene oxide modified trimethylolpropane tri (meth) acrylate, propylene oxide modified trimethylolpropane tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, tricyclodecanyl (meth) acrylate, dipentaerythritol hexa Examples include hexa (meth) acrylate and melamine (meth) acrylate, which are caprolactone adducts of (meth) acrylate.

Examples of the photopolymerization initiator in the invention include 4-phenoxydichloroacetophenone, 4-t-butyl-dichloroacetophenone, diethoxyacetophenone, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropane- Acetophenone-based photopolymerization initiators such as 1-one, 1-hydroxycyclohexyl phenyl ketone, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one, benzoin, benzoin methyl ether, benzoin Benzoin photopolymerization initiators such as ethyl ether, benzoin isopropyl ether, benzyldimethyl ketal, benzophenone, benzoylbenzoic acid, methyl benzoylbenzoate, 4-phenylbenzophenone, hydroxybenzophenone, acrylic Benzophenone-based photopolymerization initiators such as benzophenone and 4-benzoyl-4′-methyldiphenyl sulfide, thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, etc. Thioxanthone photopolymerization initiator, 2,4,6-trichloro-s-triazine, 2-phenyl-4,6-bis (trichloromethyl) -s-triazine, 2- (p-methoxyphenyl) -4,6 -Bis (trichloromethyl) -s-triazine, 2- (p-tolyl) -4,6-bis (trichloromethyl) -s-triazine, 2-piperonyl-4,6-bis (trichloromethyl) -s- Triazine, 2,4-bis (trichloromethyl) -6-styryl s-triazine, 2- (naphtho- -Yl) -4,6-bis (trichloromethyl) -s-triazine, 2- (4-methoxy-naphth-1-yl) -4,6-bis (trichloromethyl) -s-triazine, 2,4- Triazine photopolymerization initiators such as trichloromethyl- (piperonyl) -6-triazine and 2,4-trichloromethyl (4′-methoxystyryl) -6-triazine, carbazole photopolymerization initiators, imidazole photopolymerization initiators Etc. The said photoinitiator is used individually by 1 type or in mixture of 2 or more types.

  Further, the inorganic fine particles used in the present invention are 5% by weight to 50% by weight and preferably 10% by weight to 30% by weight in the solid content composition. This is because if the height is less than 4% by weight, the height of the protrusions on the substrate becomes thin when the height of the protrusions on the transmission part is made appropriate, and does not contribute to the alignment of the liquid crystal. In addition, even if the amount is higher than 50% by weight, the height of the protrusions on the upper part of the substrate is almost the same as the height when added within the limited range. This is because rattling is seen.

  The inorganic fine particles used at this time have a primary particle size of 100 nm or less. This is because when the thickness is 100 nm or more, roughness of the projection surface and taper backlash at the time of pattern formation can be seen. As the kind of inorganic fine particles, titanium oxide, zinc oxide, aluminum oxide, silica and the like can be used, but are not particularly limited thereto. Of these, silica is particularly desirable because the height of the protrusions on the reflective portion is likely to increase.

  The photosensitive resin composition preferably contains a solvent in order to facilitate application on the substrate. Examples of the solvent include cyclohexanone, ethyl cellosolve acetate, butyl cellosolve acetate, 1-methoxy-2-propyl acetate, diethylene glycol dimethyl ether, ethylbenzene, ethylene glycol diethyl ether, xylene, ethyl cellosolve, methyl-n amyl ketone, propylene glycol monomethyl ether, propylene Examples include glycol monomethyl ether acetate, toluene, methyl ethyl ketone, ethyl acetate, methanol, ethanol, isopropyl alcohol, butanol, isobutyl ketone, and petroleum solvents. These are used alone or in combination.

  To the photosensitive resin composition, additives such as a chain transfer agent, a surfactant, and a silane coupling agent may be added for the purpose of improving coatability, sensitivity, and adhesion.

  The photosensitive resin composition can be produced by mixing the components and dispersing them using various dispersing devices such as a shaker, a desper, a sand mill, and an attritor.

The relative dielectric constant of the protrusion is less than 5. When the relative dielectric constant was high, a phenomenon called burn-in was observed when the liquid crystal was driven. This is a phenomenon in which when a pattern with a certain shape is displayed for a long time, the previous pattern remains even if a uniform display is attempted after that.
This is considered to be caused by the fact that the response characteristic of the transmittance with respect to the applied voltage for liquid crystal driving, that is, the VT characteristic deviates from the original characteristic. This shift in VT characteristics is considered to be caused by a phenomenon called residual DC in which an electric field remains in a portion where a signal is input. Therefore, it is necessary to suppress the relative dielectric constant of the protrusion to less than 5 which is about the same as or lower than the relative dielectric constant of the liquid crystal.

  Similarly, in order to suppress residual DC, it is necessary to align the characteristics of the dielectric in the liquid crystal cell. At this time, the dielectric loss tangent of the protrusion needs to be 0.014 or less, preferably 0.010 or less, more preferably 0.008 or less in the frequency range of 10 to 50 Hz from the material of the alignment film.

Hereinafter, examples of the present invention will be described.
<Example 1>
[Formation of colored layer (color filter pixel) and transparent conductive film (transparent electrode)]
A glass substrate was used as the transparent substrate, and a light shielding film (black matrix) was formed on the glass substrate. Next, a colored layer of a transmissive part and a colored layer of a reflective part made of R (red), G (green), and B (blue) were formed on a glass substrate by a known pigment dispersion method. The film thickness of the transmissive portion colored layer was 2.0 μm ± 0.2 μm for all of R, G, and B. The colored layer of the reflective part has the same hue as the colored layer of the transmissive part, and the total hue of the pixels in the reflective part is reduced by making a hole. Next, a resin layer was formed on the reflective portion colored layer for cell gap adjustment. The film thickness was 2 μm. Next, an ITO film (indium synoxide) was formed on the front surface by sputtering.

[Preparation of photosensitive resin composition of protrusion for controlling liquid crystal alignment]
-Preparation of alkali-soluble resin composition In a five-necked reaction vessel with an internal volume of 1 liter, 263.1 g of bisphenol full orange hydroxyethyl ether, 72.4 g of biphenyltetracarboxylic dianhydride, 10.5 g of phthalic anhydride, tetraethylammonium 0.6 g of promide and 346 g of propylene glycol monomethyl ether acetate were charged and reacted at 115 to 120 ° C. for 20 hours to obtain an alkali-soluble resin composition.

-Preparation of photosensitive resin composition for protrusions for controlling liquid crystal alignment The alkali-soluble resin obtained above was adjusted at the ratio shown below to obtain a photosensitive resin composition.
A: 10% by weight of alkali-soluble resin
B: Photopolymerizable monomer (manufactured by Toagosei Co., Ltd.) 10% by weight
C: Photopolymerization initiator (BASF, trade name “TPO”) 1% by weight
D: Inorganic fine particles (manufactured by Sanyo Kasei Co., Ltd., trade name “Nanostar”) 4% by weight
E: 75% by weight of organic solvent (propylene glycol monomethyl ether acetate)
A to E were sufficiently mixed as described above to prepare a photosensitive resin composition.

[Preparation of liquid crystal alignment control protrusions]
Using the photosensitive resin composition obtained above, a liquid crystal alignment control protrusion was prepared. The photosensitive resin composition was spin-coated on the ITO surface of the color filter thus obtained at 1000 rpm to obtain a film thickness of 2.4 μm for the transmission part and 1.5 μm for the reflection part. Thereafter, prebaking was performed at 115 ° C. for 100 seconds on a hot plate.

The obtained substrate was aligned with high accuracy through a circular pattern mask having a diameter of 10 μm, exposed to 100 mJ / cm ^{2 from the} coated surface side, and then developed. The developer was used with the composition shown below.
・ 1.5% by weight sodium carbonate
・ Sodium bicarbonate 0.5% by weight
・ Anionic surfactant (Kao / Berylex NBL) 8.0% by weight
・ Water 90% by weight
Then, after the development, washing with water and drying were performed for 60 seconds. Finally, baking was performed at 230 ° C. for 45 minutes, and liquid crystal split alignment control protrusions were produced at the transmission part and the reflection part of the color filter.

  The liquid crystal split alignment control projection formed at this time had a transmissive part height of 1.5 μm and a reflective part height of 1.0 μm. Further, the patterned diameter at this time was 10 μm for the transmissive part and 9 μm for the reflective part.

<Example 2>
About Example 2, it carried out similarly to Example 1 until formation of a colored layer and a transparent conductive film.
Moreover, the photosensitive resin composition was prepared with the composition shown below. The alkali-soluble resin was the same as that used in Example 1.
A: 10% by weight of alkali-soluble resin
B: Photopolymerizable monomer (manufactured by Toagosei Co., Ltd.) 10% by weight
C: Photopolymerization initiator (BASF, trade name “TPO” 1% by weight
D: Inorganic fine particles (trade name “Nanostar”, manufactured by Sanyo Chemical Co., Ltd.) 2.5% by weight
E: 76.5% by weight of organic solvent (propylene glycol monomethyl ether acetate)
A to E were sufficiently mixed as described above to prepare a photosensitive resin composition.
Thereafter, pattern formation was performed by the same production method as in Example 1.

  The liquid crystal split alignment control projection formed at this time had a transmissive part height of 1.5 μm and a reflective part height of 1.0 μm. Further, the patterned diameter at this time was 10 μm for the transmissive part and 9 μm for the reflective part.

<Example 3>
About Example 3, it carried out similarly to Example 1 until formation of a colored layer and a transparent conductive film.
Moreover, the photosensitive resin composition was prepared with the composition shown below. The alkali-soluble resin was the same as that used in Example 1.
A: Alkali-soluble resin 10% by weight
B: Photopolymerizable monomer (manufactured by Toagosei Co., Ltd.) 10% by weight
C: Photopolymerization initiator (BASF, trade name “TPO” 1% by weight
D: Inorganic fine particles (manufactured by Sanyo Kasei Co., Ltd., trade name “Nanostar”) 9% by weight
E: 76.5% by weight of organic solvent (propylene glycol monomethyl ether acetate)
A to E were sufficiently mixed as described above to prepare a photosensitive resin composition.
Thereafter, pattern formation was performed by the same production method as in Example 1.

  The liquid crystal split alignment control protrusions formed at this time had a transmission part height of 1.5 μm and a reflection part height of 1.1 μm. In addition, the diameters patterned at this time were a transmission part of 11 μm and a reflection part of 10 μm.

<Comparative Example 1>
About Comparative example 1, it carried out similarly to Example 1 until formation of a colored layer and a transparent conductive film.
Moreover, the photosensitive resin composition was prepared with the composition shown below. The alkali-soluble resin was the same as that used in Example 1.
A: 10% by weight of alkali-soluble resin
B: Photopolymerizable monomer (manufactured by Toagosei Co., Ltd.) 10% by weight
C: Photopolymerization initiator (BASF, trade name “TPO” 1% by weight
D: 79% by weight of organic solvent (propylene glycol monomethyl ether acetate)
A to E were sufficiently mixed as described above to prepare a photosensitive resin composition.
Thereafter, pattern formation was performed by the same production method as in Example 1.

  The liquid crystal split alignment control projection formed at this time had a transmissive part height of 1.5 μm and a reflective part height of 0.3 μm. Further, the patterned diameter at this time was 10 μm for the transmissive part and 9 μm for the reflective part.

<Comparative example 2>
About Comparative Example 2, it carried out similarly to Example 1 until formation of a colored layer and a transparent conductive film.
The photosensitive resin composition was formed by patterning using a positive resist LC-100 (Rohm and Haas).
Thereafter, pattern formation was performed by the same production method as in Example 1.

  The liquid crystal split alignment control projection formed at this time had a transmissive part height of 1.5 μm and a reflective part height of 1.0 μm. Further, the patterned diameter at this time was a transmissive portion of 15 μm and a reflective portion of 12 μm.

<Comparative Example 3>
About Comparative example 3, it carried out similarly to Example 1 until formation of a colored layer and a transparent conductive film.
In addition, the photosensitive resin composition was prepared with the composition shown below. The alkali-soluble resin was the same as that used in Example 1.
A: 10% by weight of alkali-soluble resin
B: Photopolymerizable monomer (manufactured by Toagosei Co., Ltd.) 10% by weight
C: Photopolymerization initiator (BASF, trade name “TPO” 1% by weight
D: Inorganic fine particles (manufactured by Sanyo Kasei Co., Ltd., trade name “Nanostar”) 1% by weight
E: 78% by weight of organic solvent (propylene glycol monomethyl ether acetate)
A to E were sufficiently mixed as described above to prepare a photosensitive resin composition.
Thereafter, pattern formation was performed by the same production method as in Example 1.

  The liquid crystal split alignment control projection formed at this time had a transmissive part height of 1.5 μm and a reflective part height of 0.6 μm. Further, the patterned diameter at this time was 10 μm for the transmissive part and 9 μm for the reflective part.

<Comparative Example 4>
About Comparative example 4, it carried out similarly to Example 1 until formation of a colored layer and a transparent conductive film.
In addition, the photosensitive resin composition was prepared with the composition shown below. The alkali-soluble resin was the same as that used in Example 1.
A: 10% by weight of alkali-soluble resin
B: Photopolymerizable monomer (manufactured by Toagosei Co., Ltd.) 10% by weight
C: Photopolymerization initiator (BASF, trade name “TPO” 1% by weight
D: Inorganic fine particles (manufactured by Sanyo Kasei Co., Ltd., trade name “Nanostar”) 30% by weight
E: 75% by weight of organic solvent (propylene glycol monomethyl ether acetate)
A to E were sufficiently mixed as described above to prepare a photosensitive resin composition.
Thereafter, pattern formation was performed by the same production method as in Example 1.

  At this time, the liquid crystal split alignment control projection had a poor shape and could not maintain the shape.

[Evaluation of Examples and Comparative Examples]
In the evaluation of Examples and Comparative Examples, image sticking and image display were confirmed using the substrates prepared in Examples and Comparative Examples in the state of liquid crystal display devices.
In addition, as a characteristic of the protrusion itself at this time, a relative dielectric constant and a dielectric loss tangent were measured. The results are shown in Table 1.

Sectional drawing of an example of the color filter by this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Transparent substrate 2 ... Black matrix 3 ... Resin layer 4 ... Transparent electrode 5 ... Projection 6 for liquid crystal orientation control of a color filter transmission part ... Liquid crystal of a color filter reflection part Projection 7 for orientation control ... Color filter transmitting portion 8 ... Color filter reflecting portion 9 ... One pixel of color filter

Claims (6)

  A color filter having a liquid crystal alignment control protrusion, wherein the liquid crystal alignment control protrusion includes an alkali-soluble resin, a photopolymerizable monomer, a photopolymerization initiator, and inorganic fine particles. A color filter having a protrusion for controlling liquid crystal alignment, comprising a cured product of   The color filter having a protrusion for controlling liquid crystal alignment according to claim 1, wherein the inorganic fine particles are contained in a range of 5 wt% to 50 wt% of the cured product.   The color filter having a projection for controlling liquid crystal alignment according to claim 1 or 2, wherein the inorganic fine particles have a primary particle size of 100 nm or less.   4. The color filter having a liquid crystal alignment control protrusion according to claim 1, wherein the inorganic fine particles are silica.   5. The color filter having a projection for controlling liquid crystal alignment according to claim 1, wherein the cured product has a relative dielectric constant of less than 5 in a frequency range of 10 to 50 Hz.   6. The color filter having protrusions for controlling liquid crystal alignment according to claim 1, wherein a dielectric loss tangent of the cured product in a frequency range of 10 to 50 Hz is 0.014 or less.

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