JPS6364023A - Display device - Google Patents

Abstract

PURPOSE:To contrive to improve a contrast ratio by covering areas other than picture element electrodes, which are formed on the first substrate, with an insulating light shielding film. CONSTITUTION:Polarizing plates 3 are provided on outside faces of transparent substrates 1 and 2 which hold a liquid crystal 8 between themselves and consist of a glass or the like. Scanning lines connected to gate electrodes of thin film transistors TRs, signal lines 5 connected to drain or source electrodes, picture element electrodes 4 connected to drain or source electrodes, etc., are formed on the inside face of the substrate 1. An insulating light shielding film 11 is provided on parts other than areas of electrodes 4 of this substrate 1 for the purpose of intercepting the transmitted light which passes areas of a matrix wiring, thin film TRs, etc., and a liquid crystal orientation control film consisting of a polyimide or the like is formed on the film 11 and is brought into contact with the liquid crystal. Meanwhile, R, G, and B color filters 6 are formed in positions corresponding to electrodes 4 on the inside face of the substrate 2, and a transparent conductive film and a counter electrode 7 are formed on filters 6 in order and are brought into contact with the liquid crystal.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a display device, and in particular to a so-called active matrix type electrode in which a nonlinear element represented by a thin film transistor is provided at each intersection of matrix wiring. The present invention relates to a display device having a structure and operating an electrical/light modulating substance such as a liquid crystal.

(Prior Art) Conventionally, ms transistors (hereinafter abbreviated as TPT) made of polysilicon, amorphous silicon, tellurium, etc., or metal/insulator/metal with a sandwich structure made of metal thin films such as aluminum oxide have been used. Active matrix liquid crystal display devices using nonlinear elements such as diodes are disclosed in, for example, Japanese Patent Laid-Open No. 56-25714 and Japanese Patent Laid-Open No. 56-25.
It is widely known as disclosed in Japanese Patent No. 777 and the like.

Regarding this type of display device, a conventional technique will be described with respect to a case where TPT is used, for example.

That is, FIG. 4(a) is commonly used to explain the wiring of an active matrix type liquid crystal display device using TPT, but it is a diagram of matrix wiring consisting of a group of signal lines and a group of scanning lines. A TPT is provided at each intersection, and one of its source electrode or drain electrode is connected to the pixel electrode.

Further, FIG. 4(b) shows a cross section taken along line BB' in FIG. 4(a), taking into account the opposing substrate.
A case is shown in which a liquid crystal 8 is used as an electrical/light modulating material between the substrate 2 and the counter substrate 2, and light is irradiated from either side of the substrate, so that the device is used as a so-called transmission type. At this time, in order to display color in this display device, red (R), green (G), and blue (B) color filters 6 are provided on the opposing substrate 2 side. In addition, 3 in the figure is a polarizing plate, 5 is a signal line electrode,
7 indicates a counter electrode. When operating as a transmissive type, a transparent conductive film is used for the pixel electrode 4, and strictly speaking, liquid crystal operation is limited only to the region between the pixel electrode 4 and the counter electrode 7.

In other words, 1g of pixels on this board! The liquid crystal 8 in the area other than the area does not operate at all. On the substrate 1 provided with matrix wiring, wiring electrodes for signal lines, wiring electrodes for scanning lines, and TPT are provided in addition to the pixel electrode area, and these are electrically interconnected by multilayer structure wiring or wiring arrangement. Insulated. Therefore, for example, 1g of metal is used as the electrode material! Even if an opaque material such as
So-called non-modulated light, which does not work, is transmitted. This unmodulated light means that there is always leakage light for the display device, which increases the background and thus significantly reduces the contrast.

As a method to reduce this non-modulated light, for example, orientation control@
One method is to make the rubbing direction of the film perpendicular and the two polarizing plates sandwiching the substrate parallel, so that no light is transmitted when no voltage is applied to the liquid crystal 8.

In this case, since only the pixel electrode region is optically modulated by the signal voltage, unmodulated light is theoretically impossible. However, when considering the manufacturing process of the display device, it is necessary to precisely align the polarization directions of the two polarizing plates 3 in parallel, and the background caused by leaked light is determined only by this alignment accuracy. Even if the deviation angle is within 1 degree as a practical alignment accuracy, it is extremely difficult to manage this during mass production.

On the other hand, when the polarizing plates are arranged at right angles, the angular deviation merely causes a slight decrease in transmittance and has little effect on contrast, which can be said to be highly productive. At this time, only the liquid crystal corresponding to the pixel M8i region to which the signal voltage is applied gives a light modulation effect, and the above-mentioned non-modulated light determines the contrast. A conventional method to solve this problem is to provide a light-shielding screen made of a metal thin film on the opposing substrate side.

That is, as shown in 4K(C), for example, RlG, B color filters 6 are arranged only in the area corresponding to the pixel electrode 4 on the counter substrate 2, and all the remaining 11!1 are made of metal sg.
This is a method of covering with a light-shielding screen 9 consisting of i. Although this certainly achieves the initial objective, this method also has disadvantages as described below.

First, both the matrix wiring board 1 and the counter board 2 provided with the light-shielding screen 9 must be fixed in an accurate positional relationship.

Such liquid crystal display devices are often designed with a pixel pitch of several hundred microns. For example, when the pitch is 200 microns, the alignment accuracy is on the order of several microns in order to obtain a predetermined aperture ratio.

In addition, the light from the light source is not completely parallel, and if we also take into account the non-modulated light component of the light obliquely incident on the substrate,
Furthermore, the aperture ratio becomes smaller. For example, in the case of the above-mentioned pitch of 200 microns, if the width of the signal scanning line electrode is 10 microns and the area of the TFT section is also taken into account, the effective pixel electrode size expressed as an aperture ratio is about 50 to 60%. If accuracy and margin for obliquely incident light are incorporated into this, the aperture ratio decreases to about 40 to 50%. This decrease in aperture ratio directly causes a decrease in the image quality of the display device.

What can be easily inferred from these is that the light-shielding screen 9
This is an attempt to provide this on the matrix wiring board 1 side. This method is effective and realizable in principle, and has the following two
The street can be considered. In other words, there is a method in which an insulating film is provided between the matrix wiring including TPT and the substrate, and an insulating film is provided above the matrix wiring! 110 (FIG. 4(d)). However, from the viewpoint of device manufacturing, in either method, the intersection of matrix wiring has a five-layer structure of signal electrodes, scanning electrodes, and light shielding screen 9 via an interlayer insulating film, and for example, the number of scanning electrodes is 240. When the number of electrodes and signal electrodes is 480, the number of intersections is 115°200, and any one of them
There is a strict condition that interlayer short circuits must not occur at any point. Moreover, as the display device becomes larger in area, the probability of occurrence of interlayer short circuits due to pinholes, dust, clumps, etc. in the interlayer insulating film increases, which causes a decrease in yield during mass production.

<Problems to be Solved by the Invention> As can be seen in the above-mentioned conventional example, the problem of unmodulated light, which is one of the causes of deterioration of image quality in liquid crystal display devices, is caused by the liquid crystal operating state depending on the polarization direction of the polarizing plate 3, Various efforts have been made, such as a light-shielding screen 9 on the substrate 1 and a light-shielding screen 9 on the matrix substrate 1f11, but each has its disadvantages, and these disadvantages directly lead to a decrease in yield during mass production. .

SUMMARY OF THE INVENTION An object of the present invention is to provide a display device that eliminates non-modulated light, simplifies the manufacturing process, and provides a high yield.

[Structure of the Invention (Means for Solving the Problems)] This invention provides a method of connecting a non-linear element to each intersection of a matrix wiring composed of a plurality of row electrodes which are scanning lines and a plurality of column electrodes which are signal lines. In a display device in which a layer of an electrical/light modulating substance is sandwiched between a first substrate (matrix substrate) having pixel electrodes connected to each other and a second substrate (counter substrate) having a counter electrode formed thereon. , is a display device in which an area other than a pixel electrode formed on the first substrate is covered with an insulating light-shielding film to eliminate transmission of non-modulated light.

Suitable materials for the insulating light-shielding film include organic resins that are cured at a temperature of 400° C. or lower, and that contain dyes as one of their components. In the case of polyimide-based resins, curing means that polyamic acid, which is a precursor thereof, is heat-treated to produce polyimide; in the case of other organic resins, heat treatment is performed after forming a light-shielding film from a resin solution. means to remove residual solvent.

The light shielding effect depends on the spectrum of the light source used, but it is generally desirable that the average optical density in the visible range in the light transmittance spectrum is 1.0 or more. Resistivity is iQ o
hm-cm or more is desirable. In particular, as the organic resin, a polymer consisting of at least one of polyimide, polyamideimide, polyesterimide, polyamide, polyesteramide, and polyethersulfone is preferred.

<Function> According to the present invention, since the insulating light-shielding film is provided directly on the substrate having matrix wiring, that is, on the pixel electrode portion, the problems of angle alignment accuracy and aperture ratio of the polarizing plate as pointed out in the conventional example are avoided. Moreover, since it is a high-resistance material unlike metal materials, problems such as electrical short circuits and interlayer short circuits can be solved.

Furthermore, regarding the light shielding effect, an optical density of 4 or more can be easily obtained with metal materials, but with polymer materials, the transmission spectrum cannot be a constant value over the entire wavelength range. If the average optical density is 1.0 or more in at least the visible range, the purpose of blocking unmodulated light can be sufficiently achieved.

In addition, from the viewpoint of the manufacturing process, a light-shielding film can be easily formed on an already completed matrix wiring board using existing photolithography techniques, and the alignment accuracy is simple due to the accuracy of the photolithography used. Even during mass production, it is easy to maintain the accuracy within 3 μm, for example.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIGS. 1(a) and 1(b) show an embodiment of a display device according to the present invention, and the same parts as in the conventional example are denoted by the same reference numerals.Matrix wiring using TPT as a nonlinear element A color liquid crystal used in a transmission type TN mode, in which a liquid crystal, which is an electric/luminous substance, is sandwiched between a first substrate formed with a color filter and a second substrate formed with a color filter and a counter electrode. This is an example applied to a display device.

That is, 1 and 2 in FIG. 1(b) are transparent substrates made of glass or the like that sandwich the liquid crystal 8, and a polarizing plate 3 is provided on the outer surface of each substrate 1.2. .

Furthermore, the substrate 1 is also called a matrix substrate,
On the inner surface of this transparent substrate 1, a scanning line connected to the gate electrode of the TPT, a signal line 5 connected to the drain electrode or source electrode, a pixel electrode 4 connected to the drain electrode or source electrode, etc. are formed. There is.

In order to block the transmitted light from passing through areas other than the pixel electrode 4 area on the substrate 1, that is, areas such as matrix wiring and TPT, the present invention uses an insulating light shielding film 1.
1 is provided, and on this light shielding film 11, for example, polyimide,
A liquid crystal alignment control film (not shown) made of polyamide, polyvinyl alcohol, or the like is formed by a rubbing process and is in contact with the liquid crystal 8 .

On the other hand, R, G, and B color filters 6 are formed on the inner surface of the substrate 2 at positions corresponding to each pixel electrode 4, and a transparent conductive film made of, for example, an indium tin oxide film is formed on the color filter 6. Further, a counter electrode 7 made of a liquid crystal alignment υ control 1 (not shown) which has been subjected to a rubbing process is formed thereon and is in contact with the liquid crystal 8 .

Now, as a particularly specific example, the insulating light shielding 11
A case where a polymer containing a black dye is used as material 1 will be explained.

The polymer used as the base material is required to have excellent electrical insulation and heat resistance, and good compatibility with dyes. Specific examples include polyimide, polyamideimide,
Polyesterimide, polyamide, polyesteramide, polysulfone, polyethersulfone, polyarylate, polyetheretherketone, polyacetal, polycarbonate, nylon, polybutylene terephthalate, (modified) polyphenylene oxide, polyphenylene sulfide, epoxy resin, unsaturated polyester resin, bis Examples include maleimide resins, and these polymers may be used alone or in a mixed system of two or more.

In addition, as a black dye, in the visible range, that is, at least 400
Any material may be used as long as it absorbs light in the wavelength range of ~800 nm. Specific examples include Amil Black F-88L, Sumilite Black GOOnC, and Direct Deep Black XA manufactured by Sumitomo Chemical Co., Ltd. .

Sumifix Black B1 Amyl Black F-GL1
Sumikaron Black 5-BF, Spirit Black No.
920, Japanol Fast Black oconc,
Sumicolor Black PR-3F-365, Sumicolor Black PR-8T-364, Sumicolor Blank PR-
8T-363, Oil Black N01, Mitsui Toatsu Chemical (
Examples include Mitsui PS Black B1, Mitsui PS Black EX-58, Mitsui PS Black EX-174, produced by Deme Kagaku Co., Ltd., and Oleosol Fast Black BLN, produced by Deme Kagaku Co., Ltd.

It also includes a method in which two or more types of coloring dyes such as red dye, blue dye, green dye, yellow dye, etc. are blended to form a black color.

The amount of black dye used in this invention is the polymer ioo
1 to 200 parts by weight, preferably 5 to 150 parts by weight
Parts by weight range. If the amount of black dye used is less than 1 part by weight, the light absorption effect will be poor, while if it exceeds 200 parts by weight, it will be difficult to form a coating film.

Further, in this invention, it is also possible to use an infrared absorber for the purpose of improving the effect of light absorption ability. The infrared absorber used at this time is not particularly limited as long as it absorbs light in the wavelength range of 700 to 1500 nm, and a specific example is the product name P manufactured by Mitsui Toatsu Chemical Co., Ltd.
PA series such as A100I, PA10o5, PA1006!
, I-X, trade name HR10 manufactured by Hodogaya Chemical Industry Co., Ltd.
2. HR series such as HR105-R can be mentioned. The amount of these infrared absorbers used is as follows:
0.1 to 50 parts by weight, preferably 0.00 parts by weight.
It is in the range of 5 to 40 parts by weight.

Next, a specific example will be given and a more detailed explanation will be given.

Specific example 1: Preparation and performance of black polymer A reaction flask equipped with a stirring bar, a thermometer, and a dropping funnel (inner volume: 50
Pyromellitic dianhydride 13.086G, 3
．． 19.34C1 of 3',4,4'-benzophenonetetracarboxylic dianhydride and 150g of N,N-dimethylacetamide were added, and while stirring thoroughly and maintaining the temperature at 0°C, 1,4-bis (4-aminophexy)benzene 17.5380 to N,N-dimethylacetamide 1
A solution of 30 g was gradually added dropwise using a dropping funnel.

After the dropwise addition was completed, stirring was performed 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 black dye (trade name Spirit Black N0920, manufactured by Sumitomo Chemical Co., Ltd.) and 1 infrared absorber (trade name PA1006, manufactured by Mitsui Toatsu Chemical Co., Ltd.), A solution of OQ dissolved in N5N-dimethylacetamide at 35° was added and thoroughly mixed to obtain a black polyamic acid solution. This solution was applied to a quartz glass wafer at a rotation speed of 200 rpm.
It was applied with a spinner. Then at 100°C for 20 minutes,
It was dried and cured at 150° C. for 20 minutes and at 250° C. for 1 hour to form a black polyimide film with a thickness of 1.8 μm.

The light transmittance of the black polyimide film thus obtained was measured and was found to be satisfactory as shown in FIG.

Specific example 2: Display device manufacturing method and performance TPT using scanning line electrodes, signal line electrodes, and hydrogenated amorphous silicon as a semiconductor material by a conventional method.

A black polyamic acid solution was applied with a spinner at 200 rpm onto a transparent glass substrate on which pixel electrodes etc. were formed.
Next, it was dried and cured at 100° C. for 30 minutes and at 150° C. for 1 hour to form a black polyimide film with a thickness of 2.0 μm.

Next, a desired pattern including an opening in the pixel electrode portion was obtained using a well-known photolithography technique. Here, a hydrazine/ethylendiamine (weight ratio 5:5) solution was used for etching the black polyimide.

After drying with nitrogen gas, the polyamic acid was completely cured by heat treatment at 200° C. for 1.5 hours. An alignment control film is provided on the surface of the substrate prepared in this manner according to a conventional method, and a rubbing treatment is performed to prepare a color filter, a transparent counter electrode, and an alignment control film.
A liquid crystal display device was manufactured by pairing the substrate with a counter electrode substrate provided with Ilm and the like. FIG. 3 shows the measurement results of the transmittance characteristics with respect to the signal voltage of the display device thus obtained.

As is clear from FIG. 3, the contrast ratio was about 10 when using the conventional method, but due to the effect of the light shielding WA11 in the present invention, the contrast ratio was significantly improved to 50.

[Effects of the Invention] As detailed above, the display device of the present invention has a function of sufficiently blocking so-called non-modulated light from other areas except the pixel electrode, and contrast, which is one of display performance, is improved. This greatly contributes to improving the ratio.

Further, by using an insulating light-shielding film material, there is no need to consider electrical short circuits, leakage, etc. structurally, and it can be easily applied to all display devices using existing active matrix wiring.

In particular, when a black polymer with extremely high light absorption is used, it is possible to manufacture the display device through an easy process, and to provide a lightweight, thin, and inexpensive display device.

[Brief explanation of drawings]

FIGS. 1(a) and 1(b) show a display device according to an embodiment of the present invention, in which FIG. 1(a) is a plan view and FIG. 1(b) is an A-A in FIG.
Figure 2 is a characteristic curve diagram showing the transmittance spectrum of the black polymer in the display device of the present invention, and Figure 3 is a cross-sectional view taken along the line and viewed in the direction of the arrow. Characteristic curve diagrams showing signal voltage characteristics in comparison with conventional examples; FIGS. 4(a), (b), (C), and (d) show conventional display devices; (a) is a plan view; ), (C
) and (d) are cross-sectional views taken along line B-8' in (a) and viewed in the direction of the arrow. 1.2...Substrate, 3...Light leaking plate, 4...Pixel electrode, 5...Signal line, 6...Color filter, 7...
Counter electrode, 8...liquid crystal, 11...light shielding film. Applicant's representative Patent attorney Tonaga Suzue Takehiko (nm) Figure 2 A, Senyu 1 Ward, Pressure, (■) Figure 3

Claims (5)

[Claims] (1) A first substrate having a pixel electrode connected via a nonlinear element to each intersection of a matrix wiring composed of a plurality of row electrodes and a plurality of column electrodes, and a second substrate having a counter electrode formed thereon. 1. A display device comprising a layer of an electrical/light modulating material sandwiched between layers, characterized in that a region other than the pixel electrode is covered with an insulating light-shielding film. (2) The insulating light-shielding film is a thin layer of organic resin cured at a temperature of 400° C. or less, and contains a dye as a part of its components. display device. (3) The display device according to claim 1, wherein the insulating light-shielding film has an average optical density in the visible range of 1.0 or more in a light transmittance spectrum. (4) The electrical resistivity of the above insulating light shielding film is 10ohm・
2. The display device according to claim 1, wherein the display device has a width of cm or more. (5) The display according to claim 2, wherein the insulating light-shielding film is a polymer made of at least one of polyimide, polyamideimide, polyesterimide, polyamide, polyesteramide, and polyethersulfone. Device.