JPH0915651A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device with which the improvement in contrast being one of display performances, is made possible by sufficiently prohibiting the so-called non-modulated light from other regions exclusive of pixel electrodes. SOLUTION: This liquid crystal display device includes a layer 8 of electrodes and optical modulation materials to be held between a first substrate 1 having pixel electrodes 4 connected via nonlinear elements TFTs to the respective intersected points of matrix wirings constituted of plural row electrodes and plural column electrodes 5 and a second substrates 2. The device particularly has an insulatable light shielding film 11 for prohibiting the transmission of the non-moldulated light and an orientation control film which is arranged on this insulatable light shielding film 11 and controls the orientation of the layer of the electrodes and optical modulation materials on the first substrate.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a display device,
In particular, the present invention relates to a liquid crystal display device having a so-called active matrix type electrode structure in which a non-linear element represented by a thin film transistor is provided at an intersection of a matrix wiring and operating an electro-optical modulation material such as a liquid crystal.

[0002]

2. Description of the Related Art Conventionally, a thin film transistor (hereinafter abbreviated as TFT) made of polysilicon, amorphous silicon, tellurium, or a metal / insulating film / metal diode having a sandwich structure of a metal thin film made of aluminum oxide has been used. An active matrix type liquid crystal display device using a non-linear element is disclosed and widely known, for example, in Japanese Patent Laid-Open Nos. 56-25714 and 56-25777.

[0003] With respect to this type of display device, for example, a case in which a TFT is used, a conventional technique will be described.

That is, FIG. 4 (a) is commonly used to explain wiring lines of an active matrix type liquid crystal display device using TFTs. TFT at each intersection of matrix wiring
And one of the source electrode and the drain electrode is connected to the pixel electrode.

FIG. 4 (b) is a sectional view taken along line BB of FIG.
The cross section taken along ′ is shown in consideration of the counter substrate, and a liquid crystal 8 is used between the substrate 1 and the counter substrate 2 as electro-optical modulation light, and light irradiation is performed from either of the substrates. In this case, the transmission type is used. At this time, a red (R), green (G), and blue (B) color filter 6 is provided on the counter substrate 2 side in order to display the display device in color. In the figure, reference numeral 3 denotes a polarizing plate, and reference numeral 5 denotes a signal line electrode. And when operating as a transmission type,
The pixel electrode 4 uses a transparent conductive film. Strictly speaking, the liquid crystal operation is limited to only the region of the counter electrode 7.

That is, the liquid crystal 8 on the substrate except for the pixel electrode region does not operate at all. On the substrate 1 provided with the matrix wiring, wiring electrodes for signal lines, wiring electrodes for scanning lines, and TFTs are provided in addition to the pixel electrode regions, and these are electrically connected to each other by the multilayer wiring or wiring arrangement. Insulated. Therefore, for example, even when an opaque material such as a metal thin film is used as the electrode material, a space between wirings is often present, and the liquid crystal 8 does not operate in this area, so-called unmodulated light is transmitted. The unmodulated light means that there is always leakage light for the display device, and increases the background, that is, significantly lowers the contrast.

As a method of reducing the non-modulated light, for example, the rubbing direction of the alignment control film is set to be a right angle, and
There is a method in which the polarizing plates are arranged in parallel so that light is not transmitted when no voltage is applied to the liquid crystal 8.

In this case, since only the pixel electrode region is light-modulated by the signal voltage, in principle, non-modulated light cannot exist. However, when the manufacturing process of the display device is taken into consideration, the polarization directions of the two polarizing plates 3 need to be adjusted to be exactly parallel, and the background due to the leaked light is determined only by this alignment accuracy. Even if the deviation angle is within 1 ° as a practical alignment accuracy, it is very difficult to manage this during mass production.

On the other hand, when the polarizers are arranged at right angles, the angle shift merely causes a slight decrease in the transmittance, has little effect on the contrast, and can be said to be high in mass productivity. At this time, only the liquid crystal corresponding to the pixel electrode region to which the signal voltage has been applied gives a light modulation effect, and the aforementioned unmodulated light determines the contrast. A conventional method for solving this problem is to provide a light shielding screen with a thin metal film on the counter substrate side.

That is, as shown in FIG. 4 (c), only the R,
This is a method in which the G and B color filters 6 are arranged and all the remaining regions are covered with a light shielding screen 9 made of a metal thin film. This certainly achieves its initial purpose, but this method also has the following disadvantages.

First, both the matrix wiring substrate 1 and the counter substrate 2 provided with the light shielding screen 9 must be fixed in an accurate positional relationship. In such a liquid crystal display device, the pixel pitch is often designed to be several hundred microns. For example, when the pixel pitch is set to 200 microns, the alignment accuracy is about several microns in order to obtain a predetermined aperture ratio.

Also, the light from the light source is hardly a perfect parallel ray, and the aperture ratio is further reduced in consideration of the non-modulated light component of the light obliquely incident on the substrate. For example, the above 2
In the case of the 00 micron pitch, 10 μm in the signal scanning line electrode, and in consideration of the area of the TFT portion, the effective pixel electrode size is approximately 50 to 60% in terms of the aperture ratio. When the precision and the margin of the oblique incident light are taken into account, the aperture ratio is reduced to about 40 to 50%. This decrease in the aperture ratio directly leads to a decrease in the image quality of the display device.

[0013]

As seen in the above-mentioned prior art, the problem of non-modulated light, which is one of the causes of the deterioration of the image quality of the liquid crystal display device, is caused by the polarization direction of the polarizing plate 3, the liquid crystal operating state, the opposite substrate, and the like. Although various measures such as the light-shielding screen 9 in 1 have been made, they have their respective disadvantages, and the disadvantages directly lead to a decrease in yield during mass production.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a display device which eliminates non-modulated light and which can be easily manufactured to provide a high yield.

[0015]

According to a first aspect of the present invention, there is provided a pixel electrode connected via a non-linear element to each intersection of a matrix wiring composed of a plurality of row electrodes and a plurality of column electrodes. A liquid crystal display device comprising a first substrate, a second substrate facing the first substrate, and a liquid crystal layer sandwiched between the first substrate and the second substrate, On the first substrate, an insulating light-shielding film made of an organic resin that blocks transmission of unmodulated light, and an alignment control film that is disposed on the insulating light-shielding film and controls the alignment of the liquid crystal layer are provided. And a liquid crystal display device.

According to a second aspect of the present invention, in the liquid crystal display device according to the first aspect, the insulating light-shielding film is formed by spinner coating.

According to a third aspect of the present invention, the insulating light-shielding film is characterized in that a coloring dye is contained in an organic resin and the average optical density in the visible region is set to 1.0 or more. The liquid crystal display device according to claim 1.

The invention described in claim 4 is the liquid crystal display device according to claim 1, wherein the insulating light-shielding film has a thickness of 2.0 μm or less.

As the material of the insulating light-shielding film in the present invention, there is an organic resin cured at a temperature of 400 ° C. or less, and a material containing a dye as one of its components is suitable. Here, curing means that in the case of a polyimide-based resin, a polyamic acid as a precursor thereof is heat-treated to form a polyimide, and in the case of other organic resins, a heat-shielding film is formed from an organic resin solution and then heat-treated. To remove residual solvent.

Although the light-shielding effect depends on the spectrum of the light source used, it is generally desirable that the optical transmittance spectrum has an average optical density of 1.0 or more in the visible region, and from the viewpoint of leakage current between wirings and the like. The electrical resistivity is desirably 10 ohm-cm or more. In particular, as the organic resin, polyimide, polyamide imide, polyester imide, polyamide, polyester amide,
And a polymer comprising at least one of polyether sulfone is preferable.

Since such an insulating light-shielding film is provided directly on the substrate having the matrix wiring, that is, directly on the pixel electrode portion, the problems of the angle alignment accuracy and the aperture ratio of the polarizing plate as pointed out in the conventional example are excluded. In addition, since it is a high-resistance material unlike a metal material, problems such as electrical short-circuit and interlayer short-circuit can be solved.

Further, with respect to the light-shielding effect, in the case of a metal material, an optical density of 4 or more can be easily obtained. In the case of a polymer material, its transmission spectrum cannot be constant over all wavelength ranges. If the average optical density is at least 1.0 in the visible region, the purpose of blocking unmodulated light can be sufficiently achieved.

Further, from the viewpoint of the manufacturing process, a light-shielding film can be easily formed on an already completed matrix wiring substrate by using existing photolithography technology, and the alignment accuracy is simply determined by the accuracy of the photolithography used. It is easy to determine and to keep the accuracy within, for example, 3 μm even in mass production.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will now be described in detail with reference to the drawings.

FIGS. 1A and 1B show an embodiment of a display device according to the present invention. If the same parts as those in the conventional example are denoted by the same reference numerals, a TFT as a non-linear element is used.
In a transmission type TN mode in which a liquid crystal which is an electric / light modulating material is sandwiched between a first substrate on which a matrix wiring is formed and a second substrate on which a color filter and a counter electrode are formed. This is an example applied to a color liquid crystal display device used.

That is, 1 and 2 in FIG.
, And a transparent plate made of glass or the like, and a deflection plate is provided on the outer surface of each of the substrates 1 and 2.

Further, the substrate 1 is also called a matrix substrate. On the inner surface of the transparent substrate 1, a scanning line connected to a gate electrode of a TFT and a pixel electrode 4 connected to a drain electrode or a source electrode are provided. Is formed.

According to the present invention, the insulating light-shielding film 11 is provided to prevent light transmitted through other portions of the substrate 1 except for the pixel electrode 4 region, that is, regions such as matrix wirings and TFTs. A liquid crystal alignment control film (not shown) made of, for example, polyimide, polyamide, polyvinyl alcohol, or the like is formed on the light shielding film 11 by rubbing, and is in contact with the liquid crystal 8.

On the other hand, on the inner surface of the substrate 2, R, G, B color filters 6 are formed at positions corresponding to the respective pixel electrodes 4. On the color filters 6, for example, an indium tin oxide film or the like is formed. A counter electrode 7 made of a transparent conductive film and a rubbed liquid crystal alignment control film (not shown) is formed thereon, and is in contact with the liquid crystal 8.

Next, as a specific embodiment, a case where a polymer containing a black dye is used as the material of the insulating light-shielding film 11 will be described.

The polymer serving as the base material is required to have excellent electrical insulation and heat resistance and good compatibility with the dye, and specific examples thereof include polyimide, polyamideimide, polyesterimide, polyamide, Polyesteramide, polysulfone, polyethersulfone,
Polyarylate, polyether ketone, polyacetal, polycarbonate, nylon, polybutylene terephthalate, (modified) polyphenylene oxide, polyphenylene sulfide, epoxy resin, unsaturated polyester resin, bismaleimide resin, and the like. Used in a mixture of two or more.

As the black dye, any dye can be used as long as it absorbs light in the visible region, that is, at least in the wavelength range of 400 to 800 nm, and specific examples thereof include products manufactured by Sumitomo Chemical Co., Ltd. Name Amil Black F-8
BL, Sumilite Black Gconc, Direct Deep Black XA, Sumifix Black B, Amil Black F-GL, Sumicaron Black S-BF, Spirit Black No. 920, Japananol First Black Dconc, Sumicolor Black PR-3F-3
65, Sumicolor Black PR-8T-364, Sumicolor Black PR-8T-363, Oil Black No
1. Mitsui PS Black EX-58 and Mitsui PS Black EX-174 manufactured by Mitsui Toatsu Chemicals, Inc .; Oleosol First Black B manufactured by Taoka Chemical Co., Ltd.
LN and the like.

The method also includes a method in which two or more coloring dyes such as a red dye, a blue dye, a green dye, and a yellow dye are blended, and the resulting mixture is blackened.

The amount of the black dye used in the present invention ranges from 1 to 200 parts by weight, preferably from 5 to 150 parts by weight, per 100 parts by weight of the polymer. When the amount of the black dye used is less than 1 part by weight, the light absorbing effect is poor.
If it exceeds 200 parts by weight, it becomes difficult to form a coating film.

In the present invention, an infrared absorbing agent can be used for the purpose of improving the effect of the light absorbing ability. The infrared absorber used at this time is 700 to 1
There is no particular limitation as long as it absorbs light in a wavelength region of 500 nm. Specific examples include PA1001, PA1005, and PA1 manufactured by Mitsui Toatsu Chemicals, Inc.
HR and HR series such as HR102 and HR105-R manufactured by Hodogaya Chemical Industry Co., Ltd. The amount of these infrared absorbers used is
0.1 to 50 parts by weight based on 100 parts by weight of the polymer,
Preferably it is in the range of 0.5 to 40 parts by weight.

Next, a more specific example will be described in detail.

Concrete Example 1 Preparation and Performance of Black Polymer Pyromellitic dianhydride was added to a reaction flask (internal volume: 500 ml) equipped with a stir bar, thermometer and dropping funnel.
Of 0,86 g, 3,3 ', 4,4'-benzophenonetetracarboxylic dianhydride and 19.40 g of N, N-dimethylacetamide were added. A solution obtained by dissolving 17.538 g of 1,4-bis (4-aminophenoxy) benzene in 130 g of N, N-dimethylacetamide was gradually dropped by a dropping funnel. After completion of the dropwise addition, the mixture was stirred at 0 to 10 ° C for 4 hours to obtain a polyamic acid solution. To the polyamic acid solution thus obtained, 4.2 g of a black dye (trade name: No. 920 of Spirit Black, manufactured by Sumitomo Chemical Co., Ltd.) and an infrared absorber (PA10, manufactured by Mitsui Toatsu Chemicals, Inc.)
06) 35 g of N, N-dimethylacetamide was added to 1.0 g.
Was added and mixed well to obtain a black polyamic acid solution. This solution was applied to a quartz glass wafer by spinner at a rotation speed of 2000 rpn. Then 10
It was dried and cured at 0 ° C. for 20 minutes, 150 ° C. for 20 minutes, and 250 ° C. for 1 hour to form a 1.8 μm-thick black polyimide film. The light transmittance of the black polyimide film obtained by measuring the light transmittance of the black polyimide film thus obtained was satisfactory as shown in FIG.

Concrete Example 2 Manufacturing Method and Performance of Display Device By a conventional method, a scanning line electrode, a signal line electrode, a TFT using hydrogenated amorphous silicon as a semiconductor material, a pixel electrode, etc. are formed on a glass transparent substrate. Black polyamic acid solution 2
Spinner coating at 000 rpm, then dried and cured at 100 ° C. for 30 minutes and 150 ° C. for 1 hour to give a film thickness of 2.0
A μm black polyimide film was formed. Next, using a known photolithography technique, a desired pattern including an opening in a pixel electrode portion was obtained. Here, a hydrazine / ethlenediamine (weight ratio: 5: 5) solution was used for etching the black polyimide. Subsequently, after performing drying with nitrogen gas, the polyamic acid was completely cured by performing a heat treatment at 200 ° C. for 1.5 hours. An alignment control film is provided on the surface of the substrate thus prepared in accordance with a conventional method, rubbed, and a liquid crystal display device is formed by pairing with a counter electrode substrate provided with a color filter, a transparent counter electrode, an alignment control film, and the like in advance. Produced. FIG. 3 shows the measurement results of the transmittance characteristics with respect to the signal voltage of the display device thus obtained.

As apparent from FIG. 3, the contrast ratio was about 10 in the case of the conventional method, but the contrast ratio was greatly improved to 50 by the effect of the light shielding film 11 in the present invention. Was done.

[0040]

As described above in detail, in the display device of the present invention, since the insulating light-shielding film that blocks the transmission of unmodulated light is arranged on the substrate on which the pixel electrode is formed, the pixel electrode is not formed. It has a function of sufficiently blocking so-called non-modulated light from other regions except the region, and greatly contributes to improvement of the contrast ratio which is one of the display performances.

In addition, since the insulating light-shielding film material is used, it is not necessary to structurally consider an electric short circuit, a leak, and the like, and it can be easily applied to all liquid crystal display devices using existing active matrix wirings. I can do it.

In particular, when a black polymer having extremely large light absorption is employed, a light-weight, thin, and inexpensive liquid crystal display device can be provided which can be manufactured by an easy process.

[Brief description of the drawings]

FIG. 1 relates to a liquid crystal display device according to an embodiment of the present invention, FIG. 1 (a) is a plan view thereof, and FIG. 1 (b) is taken along line AA ′ in FIG. 1 (a). It is sectional drawing cut | disconnected and seen in the arrow direction.

FIG. 2 is a characteristic curve diagram showing a transmittance spectrum of a black polymer in the liquid crystal display device according to one embodiment of the present invention.

FIG. 3 is a characteristic curve diagram showing transmittance-signal voltage characteristics in a liquid crystal display device according to an embodiment of the present invention, as compared with a conventional example.

FIG. 4 relates to a conventional liquid crystal display device.
(A) is a plan view thereof, and (b) of FIG.
Sectional view of one example cut along the line B 'and viewed in the direction of the arrow, and FIG. 3C shows another section cut along the line BB' of FIG. FIG.

[Explanation of symbols]

 1, 2 ... Substrate 3 ... Deflection plate 4 ... Pixel electrode 5 ... Signal line 6 ... Color filter 7 ... Counter electrode 8 ... Liquid crystal 11 ... Light-shielding film

Claims (4)

[Claims] 1. A first substrate having a pixel electrode connected to each intersection of a matrix wiring composed of a plurality of row electrodes and a plurality of column electrodes via a non-linear element, and facing the first substrate. A liquid crystal display device including a second substrate and a liquid crystal layer sandwiched between the first substrate and the second substrate, wherein the non-modulated light is blocked on the first substrate. A liquid crystal display device, comprising: an insulating light-shielding film made of an organic resin, and an alignment control film disposed on the insulating light-shielding film to control the alignment of the liquid crystal layer. 2. The liquid crystal display device according to claim 1, wherein the insulating light-shielding film is formed by spinner coating. 3. The liquid crystal display according to claim 1, wherein the insulating light-shielding film contains a coloring dye in an organic resin and has an average optical density in the visible region of 1.0 or more. apparatus. 4. The insulating light-shielding film has a thickness of 2.0 μm.
The liquid crystal display device according to claim 1, wherein: