JP2001154011A - Color filter and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a red paste for a color filter of a reflection-type liquid crystal display device, capable of providing a red filter which can realize both of high transmittance and color purity by effectively using the ambient light. SOLUTION: Color filter for a reflection-type liquid crystal display device consists of red pixels containing a coloring agent, having a threshold wavelength for transmittance at >=550 nm and <=575 nm and >=20% average transmittance in the range from 430 nm to 470 nm when the average transmittance from 480 nm to 530 nm is 10%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color filter and a liquid crystal display using the same, particularly to a reflection type liquid crystal display and a transflective type liquid crystal display.

[0002]

2. Description of the Related Art At present, liquid crystal display devices utilize characteristics such as light weight, thinness, and low power consumption, and are used for notebook PCs, portable information terminals,
It is used for various purposes such as desktop monitors and digital cameras. In a liquid crystal display device using a backlight, it is required to increase the use efficiency of backlight light in order to reduce power consumption, and a high transmittance of a color filter is required. Although the transmittance of color filters has been improving year by year, it has become impossible to expect a significant decrease in power consumption due to the improvement in transmittance. Recently, a reflective liquid crystal display device that does not require a backlight source that consumes a large amount of power is being developed, and it is possible to greatly reduce power consumption by about 1/7 compared to a transmissive liquid crystal display device. (Nikkei Microdevices Separate Volume Flat Panel Display 1998, P.12
6). A color filter for a reflective liquid crystal display device cannot reproduce bright and vivid colors simply by reducing the pixel thickness of the color filter for a transmissive liquid crystal display device. As an example of a color filter that reproduces bright and vivid red, a chromaticity range of a red pixel for a reflection type liquid crystal display device is described in JP-A-10-339871. However, they did not mention specific pigment combinations. As a combination of pigments for obtaining a red pixel for a reflection type liquid crystal display device, JP-A-11-1005
No. 29 discloses that a combination of a quinacridone pigment CI Pigment Violet 19 and an orange pigment CI Pigment Orange 71 exhibits particularly good color characteristics. However, it was not sufficient to satisfy the brightness required for a color filter for a reflection type liquid crystal display device.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks of the prior art, and it is an object of the present invention to improve the color characteristics of a red pixel of a color filter for a reflective or transflective liquid crystal display device. It is in.

[0004]

The present inventors have conducted intensive studies in order to solve the problems of the prior art. As a result, the following color filter having red pixels and a liquid crystal display device have been used to form particularly bright and vivid red pixels. I found something that could be achieved. That is, (1) from 480 nm to 530
a red pixel containing a colorant having an average transmittance from 430 nm to 470 nm of 20% or more when the average transmittance at 10 nm is 10% and a threshold wavelength of the transmittance of 550 nm or more and 575 nm or less. A color filter for a reflection type liquid crystal display device, wherein (2) the colorant described in (1) is CI Pigment Red 209 (PR20).
9) a color filter for a reflective liquid crystal display device, which is at least one selected from CI Pigment Red 242 (PR242) and CI Pigment Orange 38 (PO38); (1) The color filter for a reflective liquid crystal display device, wherein the resin component contained in the red pixel of (1) or (2) is a polyimide resin. (4) The color filter according to any one of (1) to (3) above. A reflective liquid crystal display device using a color filter.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The threshold wavelength here is 480n
The wavelength at which the transmittance is 50% when the colorant concentration and the film thickness are adjusted so that the average transmittance from m to 530 nm is 10%. The average transmittance is the average value of the transmittance in the corresponding range when the transmittance is measured at intervals of 5 nm.

The color filter of the present invention is composed of at least three color pixels of red, green and blue, and is used in combination with a reflective liquid crystal display device or a transflective liquid crystal display device. The color filter of the present invention is not limited to a driving method and a display method of a liquid crystal display device, and is applied to various liquid crystal display devices such as an active matrix type, a passive matrix type, a TN mode, a STN mode, an ECB mode, and an OCB mode. You. Further, the present invention can be applied to a reflective liquid crystal display device or a transflective liquid crystal display device without being limited by the configuration of the liquid crystal display device, for example, the number of polarizing plates, the positions of scatterers, and the like.

The formation of the color filter is not limited to the transparent substrate side such as glass or polymer film, but can be performed also on the driving element side substrate. The pattern shape of the color filter includes a stripe shape and an island shape, but is not particularly limited. Further, if necessary, a columnar fixed spacer may be arranged on the color filter.

The method of forming the pixel includes, but is not particularly limited to, a photolithography method, a printing method, an electrodeposition method and the like. In consideration of the pattern formability and the like, it is more preferable to use the photolithography method. There is no particular limitation on the resin that is a component of the pixel, and, regardless of photosensitivity or non-photosensitivity, various resins such as acrylic resin, alkyd resin, melamine resin, polyvinyl alcohol, phenol resin, polyamide, polyamide imide, and polyimide. Can be used. In particular, a resin dissolved in an alkaline aqueous solution is desirable because the equipment can be simplified in the developing or etching step. Among resins that dissolve in an aqueous alkali solution, a resin having a carboxyl group is preferably used, and specifically, an acrylic resin and a polyimide are preferable in terms of solvent resistance. In the case of polyimide, polyimide precursors are particularly preferred because they function as a pigment dispersant. Further, from the viewpoint of heat resistance of the color filter, it is preferable to use polyimide. As the coloring material used in the present invention, general coloring agents can be used regardless of organic pigments, inorganic pigments, and dyes.

Next, the components of the present invention will be described.

In the present invention, in order to obtain a bright red pixel for a reflection type liquid crystal display device, it is necessary to use a pixel having a wavelength of 480 nm to 53 nm.
430 nm when the average transmittance at 0 nm is 10%
It is important to use a colorant having an average transmittance of from 20% to 470 nm and a threshold wavelength of the transmittance of from 550 nm to 575 nm, provided that the colorant used satisfies this property. There is no particular limitation. Examples of pigments satisfying the above properties include Pigment Red PR
209, Pigment Red PR242, and Pigment Orange PO38. Pigment Red PR209,
Pigment Red PR242, Pigment Orange PO
38 has an average transmittance of 10 from 480 nm to 530 nm.
Table 1 shows the average transmittance and the threshold wavelength from 430 nm to 470 nm when the ratio is%.

[0011]

[Table 1]

In order to display bright and vivid red,
Pigment Red PR209, Pigment Red PR2
42 and Pigment Orange PO38 may be mixed with each other, or a red pigment, a violet pigment, an orange pigment, and a yellow pigment may be mixed as a toning pigment. As a pigment used for mixing, a pigment having a quinacridone skeleton is preferable. Pigment Violet PV19, Pigment Red PR
122, Pigment Red PR202, Pigment Red PR206, Pigment Red PR207, Pigment Red PR209 and the like. When Pigment Red PR209 is combined with an orange (yellow) pigment (Pigment A) for toning, the weight ratio of PR209 to Pigment A is PR20.
9 / Pigment A = 60/40 to 99/1, and more preferably PR209 / Pigment A = 70/30 to 98/2. When a pigment having a quinacridone skeleton (Pigment B) is combined with Pigment Red PR242, the weight ratio of Pigment B to PR242 is changed to Pigment B / PR.
242 = 20/80 to 95/5, preferably
The pigment B / PR242 is more preferably 30/70 to 90/10. When a pigment having a quinacridone skeleton (Pigment B) is combined with Pigment Orange PO38, the weight ratio of Pigment B to PO38 is as follows: Pigment B / PO38 =
30/70 to 99/1, and pigment B /
More preferably, PO38 = 35/65 to 98/2. When combining Pigment Red PR209 with Pigment Orange PR242, PR209 and PR
Weight ratio of 242 is PR209 / PR242 = 50/5
0 to 99/1, preferably PR209 / PR
More preferably, 242 = 60/40 to 98/2. When Pigment Red PR209 and Pigment Orange PO38 are combined, PR209 and PO38
Is PR209 / PO38 = 65 / 35-99.
/ 1, PR209 / PO38 = 7
More preferably, it is 0/30 to 98/2.

If necessary, the pigment may be subjected to a surface treatment such as a rosin treatment, an acid group treatment, a basic treatment and a pigment derivative treatment.

An example of the method for producing a color filter of the present invention will be described.

At least a polyimide precursor, an organic pigment,
After a color paste made of a solvent is applied on a transparent substrate, a polyimide precursor colored film is formed by air drying, heat drying, vacuum drying, or the like. In the case of heating and drying, it is preferable to use an oven, a hot plate, or the like, and perform the heating at 50 to 180 ° C. for 1 minute to 3 hours. Next, a pattern is formed on the thus obtained polyimide precursor colored film by ordinary wet etching. First, apply a positive photoresist on the polyimide precursor colored film,
Form a photoresist coating. Subsequently, a mask is placed on the photoresist film, and ultraviolet light is irradiated using an exposure device. After the exposure, the photoresist coating and the polyimide precursor colored coating are simultaneously etched with an alkaline developer for a positive photoresist. After the etching, the unnecessary photoresist film is removed.

The polyimide precursor colored film is thereafter converted into a polyimide colored film by heat treatment. The heat treatment is usually performed at 150 to 450 ° C., preferably at 18 ° C. in air, in a nitrogen atmosphere, or in vacuum.
It is performed continuously or stepwise at a temperature of 0 to 350 ° C. for 0.5 to 5 hours.

When the above steps are performed for three color pastes such as red, green, and blue and, if necessary, black color paste, a color filter for a liquid crystal display device can be manufactured.

Next, a liquid crystal display device produced using the color filter will be described. A transparent protective film is formed on the color filter as needed, and a transparent electrode such as an ITO film is formed thereon. Next, this color filter substrate and a reflective electrode substrate on which a reflective electrode such as a metal vapor-deposited film is formed, and a liquid crystal alignment film that has been subjected to a rubbing process for liquid crystal alignment provided on those substrates, and The substrates are bonded to each other via a spacer for maintaining a cell gap. In addition, on the reflective electrode substrate, in addition to the reflective electrode, a projection for light diffusion, a thin film transistor (TFT) element, a thin film diode (TFD) element, a scanning line, a signal line, and the like are provided. A TFD liquid crystal display device can be created.
Next, after injecting liquid crystal from an injection port provided in the seal portion, the injection port is sealed. Next, a module is completed by mounting an IC driver and the like.

[0019]

[Example] <Measurement method> Transmittance, color coordinates: Otsuka Electronics Co., Ltd.
Manufactured by MCPD-2000 microspectrophotometer.

Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited thereto.

Examples 1 to 5 A. Synthesis of polyamic acid 9,4 g of 4,4'-diaminodiphenyl ether and 6.2 g of bis (3-aminopropyl) tetramethyldisiloxane were charged together with 525 g of γ-butyrolactone and 220 g of N-methyl-2-pyrrolidone. 4,
4'-biphenyltetracarboxylic dianhydride 144.
After 1 g was added and reacted at 70 ° C. for 3 hours, 3.0 g of phthalic anhydride was added and further reacted at 70 ° C. for 2 hours to obtain a 25% by weight polyamic acid solution (PAA-1).

B. Synthesis of polymer dispersant 4,4′-diaminobenzanilide 161.3 g, 3,
176.7 g of 3'-diaminodiphenyl sulfone and 18.6 g of bis (3-aminopropyl) tetramethyldisiloxane were converted into 2667 g of γ-butyrolactone, N-
Charged with 527 g of methyl-2-pyrrolidone, 3,
3 ', 4,4'-biphenyltetracarboxylic dianhydride
After adding 439.1 g and reacting at 70 ° C. for 3 hours,
2.2 g of phthalic anhydride was added, and the mixture was further reacted at 70 ° C. for 2 hours. A 20% by weight polyamic acid solution (PD-
1) was obtained.

C. Preparation of Dispersion Pigment Red PR209, 3.38g (75wt
%), Pigment Red PR242, 1.12 g (25
wt%), 22.5 g of a polymer dispersant (PD-1) and 42.8 g of γ-butyrolactone, 3-methoxy-
20.2 g of 3-methyl-1-butanol was charged together with 90 g of glass beads, and 7 g of the mixture was prepared using a homogenizer.
After dispersion at 000 rpm for 5 hours, the glass beads were filtered,
Removed. The pigments PR209 and PR242 are thus obtained.
(RJD-1) was obtained. Similarly, the pigments PR209, PR242, PO
38, PO71, PV19 5% dispersion (R
JD-2 to RJD-5) were obtained. Where RJD-1 to RJD
JD-5 indicates the number of the dispersion used in Examples 1 to 5.

D. Preparation of Color Paste A solution prepared by diluting 8.0 g of the polymer solution (PAA-1) with 42.0 g of γ-butyrolactone in 50.0 g of the dispersion liquid (RJD-1 to RJD-5) is added and mixed. 1 to RJP-5). Where RJ
P-1 to RJP-5 indicate the numbers of the color pastes used in Examples 1 to 5.

E. Preparation and Evaluation of Colored Coating Film Color paste (RJP-1 to RJP-1) with a spinner so that the chromaticity (x, y) of the finish when passing a C light source on a glass substrate is (0.390, 0.295). RJP-
5) is applied, dried at 120 ° C. for 20 minutes, and a positive photoresist (OFPR-800 manufactured by Tokyo Ohka Co., Ltd.) is formed thereon.
And dried at 90 ° C. for 10 minutes. Using a UV exposure machine PLA-501F manufactured by Canon Inc., exposure was performed at 60 mJ / cm2 (ultraviolet intensity of 365 nm) through a chrome photomask. After the exposure, the film was immersed in a developing solution composed of a 2.25% aqueous solution of tetramethylammonium hydroxide, and the development of the photoresist and the edging of the polyimide precursor colored coating film were simultaneously performed. The unnecessary photoresist layer after the etching was removed with acetone.
Further, the colored coating film of the polyimide precursor was heat-treated at 240 ° C. for 30 minutes to convert to polyimide. On the pixel film thus obtained, an ITO film was sputtered to a thickness of 0.1 μm.

Table 2 shows the chromaticity of the thus-obtained colored coating film with a C light source.

[0027]

[Table 2]

Comparative Examples 1-2 Pigment Violet PV19, 3.38 g (75 w
t%) and 1.12 g of Pigment Orange PO71 (2
5 wt%) and 63.5 g of γ-butyrolactone, 3
-Methoxy-3-methyl-1-butanol 21.1 g
Was mixed with 90 g of glass beads, and dispersed at 7000 rpm for 5 hours using a homogenizer, and then the glass beads were filtered and removed. The pigments PV19 and P
A 6% dispersion of O71 was obtained. Similarly, a dispersion 5 composed of the pigments PR122 and PO71 in the proportions shown in Table 3
% Solutions (RHD-1, RHD-2) were obtained. Where RH
D-1 and RHD-2 indicate the numbers of the dispersions used in Comparative Examples 1 and 2.

To 60.0 g of the above dispersion, 25.0 g of the polymer solution (PAA-1) was added with γ-butyrolactone 2
The solution diluted with 2.5 g was added and mixed to obtain a color paste (RHP-1, RHP-2). Where RHP-
1, RHP-2 indicates the number of the color paste used in Comparative Examples 1 and 2.

Colored coating films were prepared in the same manner as in Examples 1 to 5. Table 3 shows the chromaticity of the colored coating film with the C light source.

[0031]

[Table 3]

Comparison when the pigment (PO71) used for mixing is the same and the quinacridone pigment is changed (Example 3: PR209, Comparative Example 1: PV19, Comparative Example 2: PR
122), the comparative example has a luminance of 50 or less, while the example has a luminance of 50 or more, indicating that the red pixel obtained by the present invention is brighter. That is, among pigments having a quinacridone skeleton, Pigment Red PR2
09 was found to be preferable as a pigment used for a color filter for a reflection type liquid crystal display device. Comparison when the quinacridone pigment (PV19) is the same and the mixing pigment is changed (Example 4: PR242, Example 5: PO3
8, Comparative Example 1: PO71), while the Comparative Example has a luminance of 50 or less, the Example has a luminance of 50 or more, and it can be seen that the red pixel obtained by the present invention is brighter.
That is, among the pigments used for mixing, Pigment Red P
It was found that R242 and Pigment Orange PO38 were preferable as pigments used for a color filter for a reflection type liquid crystal display device. 430 nm to 470 nm when the average transmittance at 480 nm to 530 nm is 10%.
PR20 having an average transmittance of not less than 20% and a threshold wavelength of the transmittance of not less than 550 nm and not more than 575 nm
9, when PR242 and PO38 were combined with each other (Examples 1 and 2), a particularly bright red color could be obtained. The liquid crystal display devices using the color filters manufactured in Examples 1 to 5 exhibited brighter display characteristics than the liquid crystal display devices using the color filters of Comparative Examples 1 and 2.

That is, the red pixel for the reflective liquid crystal display device of the present invention can display bright red with the same color purity and higher luminous transmittance than the conventional red pixel.

Embodiment 6 Preparation of Photosensitive Acrylic Color Paste 5.0 g of the pigment in the ratio used in Example 1 was weighed and dispersed in 25 g of 3-methyl-3-methoxybutanol using zirconia beads, and commercially available methacrylic acid was added. 15.0 g of methyl / methacrylic acid copolymer resin powder,
2. a photosensitive resin solution (solid content concentration: 20% by weight) in which 15.0 g of pentaerythritol tetramethacrylate as a polyfunctional monomer and 150 g of cyclopentanone are added to 7.5 g of "Irgacure" 369 as a photopolymerization initiator;
5 g was added to prepare a color paste for a color filter (RJP-6).

G. Preparation and evaluation of colored coating film
A color paste (RJP-6) is applied with a spinner so that the finished chromaticity (x, y) when passing through a wavelength type backlight becomes (0.390, 0.295),
Thereafter, a heat treatment was performed at 80 ° C. for 15 minutes to obtain a color paste coating film. Further, a predetermined area is exposed through a negative mask, and “Emulgen” A-60 is added as a nonionic surfactant to a 0.2% diethylaminoethanol aqueous solution.
(HLB 12.8, polyoxyethylene derivative)) (manufactured by Kao Corporation) was developed by immersing in an alkali developing solution containing 0.1% of the total amount of the developing solution while oscillating for 90 seconds. By washing with water, a patterned substrate was obtained. The acrylic resin was cured by holding the obtained patterned substrate in a hot air oven at 200 ° C. for 30 minutes to obtain a colored pattern. On the pixel film thus obtained, an ITO film was sputtered to a thickness of 0.1 μm.

Table 2 shows the chromaticity of the colored coating film thus obtained with a C light source. The color characteristics of the colored coating film produced in Example 6 were equivalent to those of Example 1.

Comparative Example 3 Table 3 shows the chromaticity of the colored coating film produced by the same method as in Example 6 using the C light source at the same pigment composition ratio as in Comparative Example 1. The color characteristics of the colored coating film produced in Comparative Example 3 were equivalent to those of Comparative Example 1. Further, the liquid crystal display device using the color filter manufactured in Example 6 showed brighter display characteristics than the liquid crystal display device using the color filter of Comparative Example 3.

From the comparison between Example 6 and Comparative Example 3, as in the case of the polyimide resin, the photosensitive acrylic resin
It can be said that the red pixel of the present invention has a higher luminous transmittance with the same color purity as the conventional red pixel and can provide a bright display.

[0039]

Since the present invention is constructed as described above, it is possible to obtain a red paste for a color filter for a reflection type liquid crystal display device, which can provide a red filter which achieves both high transmission and color purity by effectively utilizing ambient light. Can be.

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Claims (4)

[Claims] When the average transmittance from 480 nm to 530 nm is 10%, the average transmittance from 430 nm to 470 nm is 20% or more, and the threshold wavelength of the transmittance is 5%.
A color filter for a reflective liquid crystal display device, comprising a red pixel containing a colorant having a size of 50 nm or more and 575 nm or less. 2. The colorant is CI Pigment Red 209.
(PR209), CI Pigment Red 242 (PR
242) or CI Pigment Orange 38 (PO3
2. The color filter according to claim 1, wherein the color filter is at least one selected from the group consisting of 8). 3. A color filter for a reflective liquid crystal display device according to claim 1, wherein the resin component contained in the red pixel is a polyimide resin. 4. A reflection type liquid crystal display device using the color filter according to claim 1.