JPH04181216A - Production of liquid crystal display element substrate - Google Patents

Abstract

PURPOSE:To eliminate the unequalness of a coated film and the failure of a substrate, etc., by having a smooth and flat layer formed by a heating and spraying method using an org. high polymer having the molecular structure to allow easy free rotation. CONSTITUTION:Colored films 2 are formed in the form of stripes having 90mum width and about 2.0mum film thickness as color filters on the glass substrate. The surface undulations of the films 2 are kept at 1.0mum max. step. A xylene soln. of polymethyl methacrylate having 2,000 average mol. wt. and 1,500 to 2,500mol.wt. distribution is sprayed thereon by a heating and spraying device 6 which sprays the soln. not by using an air pressure for discharging but by pressing the soln. to the material and by heating a spray nozzle 7 to 60 deg.C. The substrate is thereafter rested at room temp. and is then heated to obtain 4mum film thickness. The surface undulations of this time are 0.07mum max. step and decrease considerably from 2.0mum thickness and 1.0mum max. step of the initial film 2. The film is thus smoothed and flattened. The film deposition and photolithographic characteristic are improved in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a liquid crystal display element that is a display device, a method for manufacturing the same, a liquid crystal display element substrate used in the liquid crystal display element, and a method for manufacturing the same.

2. Description of the Related Art Substrates used in liquid crystal display devices require smoothness and flatness, and if these characteristics are lacking, the gap between the two substrates in the liquid crystal display device becomes uneven and the display quality deteriorates. This effect is particularly noticeable in STN type liquid crystals. Here, smoothness is the performance related to roughness consisting of fine irregularities,
This is commonly referred to as smoothness. Furthermore, flatness refers to the performance related to the undulations of the substrate, and is generally referred to as flatness. If the substrate surface has undulations, disconnection or short-circuiting of the transparent conductive film is likely to occur when a thin transparent conductive film is formed thereon. In addition, the light transmittance of color filter substrates is impaired due to the light diffusion phenomenon caused by the undulations of the surface.
The function of the color filter may also deteriorate. Although several attempts have been made to smooth and planarize the substrate, a method in which a coating film layer is provided on a color filter will be described as an example of a conventional method.

FIG. 4 shows a cross-sectional view of a substrate on which a transparent coating layer is formed on a color filter. In Fig. 4, the color filter colored film 2 is formed on a glass substrate 1 with a thickness of several μm, and on top of this is a coating film of varnish made of modified silicone, Evokin, acrylic resin, etc. with a thickness of several μm. Layer 4 was formed.

Problems to be Solved by the Invention However, in the case of liquid crystal display element substrates, the above-mentioned method of coating a general resin to form a smoothing and flattening layer produces extremely fine pock-like undulations on the surface of the coating layer. High smoothness and flatness could not be obtained due to the occurrence of unevenness and unevenness of the color filter surface and the color filter colored film itself, making it difficult to obtain a product that could be used particularly for STN type liquid crystals. According to the press molding method, which transfers the surface condition by pressing a smoothed and flattened press plate onto the coating film, smoothness and flatness can be obtained, but it is a contact method.
Transfer of surface defects such as the pressing plate, adhesion of dirt, and damage to the substrate during pressing and peeling were likely to occur. In addition, it was necessary to use consumables such as a press plate and a special press molding device.

In view of the above problems, the present invention provides smoothness and smoothness with a simple manufacturing method.
The purpose is to easily and inexpensively provide a substrate that has high flatness and can be used for liquid crystal display elements.

Means to Solve the Problem After spraying an organic polymer resin with a molecular structure that allows for easy free rotation while heating, the molecules are freed by applying heat treatment by heating above the liquid flow temperature of the organic polymer. The purpose is to promote rotation and obtain a substrate with good smoothness and flatness.

When a solvent or the like is added to an organic polymer resin to lower its viscosity and the resin is coated or heated, smoothing progresses due to flow, and this is used industrially as leveling. However, commonly used methods rely on solvents etc. to reduce the viscosity.
The molecular weight of the organic polymer used is as large as several hundreds of thousands, and its distribution is large, resulting in insufficient fluidity.

As a result, the degree of smoothness and flatness was insufficient to achieve the level required for STN type liquid crystals, etc., and steps in the base remained and extremely fine undulations occurred on the surface.

Further, the chemical resistance and solvent resistance of the coating film were sometimes insufficient.

If an organic polymer resin has molecules that can freely rotate in its molecular structure, it will actively flow due to the energy given to it (
Literature: Polymer Materials Handbook, published in 1970, edited by the Society of Polymer Science, published by Corona Publishing, p. 1076).
In addition, it is made of a material that has a small molecular weight distribution so that free rotation of the molecular chain, which is the minimum active segment, becomes active, and after heating and spraying, the substrate is heat-treated.

By spraying while heating, the organic polymer resin becomes fine particles and has a low viscosity, and since heating increases the energy when adhering to the substrate, the adhesion to the substrate is high, and the smoothness and flatness when adhering is low. Then, during heat treatment, when heat energy is applied above the liquid flow temperature of this resin, the free rotation of the molecules becomes active and the viscosity of the resin itself is extremely reduced, resulting in a fluid state and high smoothness. Flatness can be obtained, and it can be expressed uniformly over a wide area.

In this way, an organic polymer resin layer with a molecular structure that can easily rotate freely is formed on a substrate by a heated spraying method, and then a series of steps applying thermal energy is applied to improve smoothness and smoothness.
A substrate with good flatness can be obtained.

Example An embodiment of the present invention will be described below with reference to the drawings.

First, the color filter substrate shown in Fig. 2(a) is prepared by marking red (R) and green (G
), blue (B) ink was printed to form a colored film 2 (2R, 2G, 2B) with a width of 90 μm as a color filter.
The surface undulations (difference in height of R, G, and B) of the zero-colored film 2 formed in stripes with a film thickness of 2.0 μm were 1.0 μm at the maximum step. Here, a xylene solution (45% concentration) of polymethyl methacrylate with an average molecular weight of 2,000 and a molecular weight distribution of 1,500 to 2,500 is heated and atomized by pressure on the material rather than air pressure during ejection, as shown in Figure 3. In the apparatus 6, the heated airless spray nozzle 7 was heated to 60'C for spraying, and after being left at room temperature, the substrate was heated to 200C to obtain a film thickness of 4 μm (FIG. 1).

The surface undulation at this time is 0.07 μm at the maximum step,
The original thickness of the colored M2 is 2.0 μm and the maximum height difference of 1.0 μm, which is the height difference between R, G, and B, has been significantly reduced to achieve the purpose of smoothing and flattening. Even at another measurement point 100 mm apart, the maximum step difference was 0.07 μm, which was uniform over a wide area. In addition, the average molecular weight 5
000 (distribution about 3,000 to 10,000) and 30,000 polymethyl methacrylate were used to confirm the same, but the maximum step difference was 0.6 μm and 0.7 μm, making it smooth.

No flattening was obtained. In this way, the molecular weight is small (,
We confirmed the smoothing and flattening effects obtained by heated spraying of an organic polymer resin whose fluidity is increased by the applied energy, that is, a molecular structure that allows molecules to easily rotate freely, and by subsequent heat treatment.

In addition, since the ratio of resin to solvent was high, the coating layer had high density, and the chemical resistance and solvent resistance were at a practical level.

In this example, polymethyl methacrylate was used, but similar effects were confirmed with other organic polymer resins such as polymethyl methacrylate and polystyrene. In addition to reducing the molecular weight to obtain active free rotation, -C
It is also possible to select a resin having a structure such as -C- that has many bonds that can easily rotate freely. In addition to airless spraying, other spraying methods can also be used by heating the material during discharge, such as air spray, which uses pneumatic pressure, and Hell-2, which uses a bowl-shaped rotating body to rotate at high speed and spray using centrifugal force. .

Effects of the Invention By depositing an organic polymer resin having a molecular structure that allows free rotation on a substrate by heating and spraying, the original undulations of the substrate can be smoothed and flattened.

Furthermore, since the surface of the substrate is smooth and non-contact during flattening, transfer of surface defects such as pressure plates that occur when forming using the contact method, adhesion of dirt, unevenness of the coating film that is likely to occur during pressing and peeling, and damage to the substrate. etc. can be resolved. In addition, there is no need to use consumables such as pressure plates, so smoothing is easy and inexpensive.

A flat substrate is obtained. In addition, a thin film of transparent conductor tM is placed on the substrate.
When forming a transparent conductive IT film, the smoothness and flatness of the substrate surface are high, so film deposition and photolithography properties are improved, and the occurrence of disconnections and short circuits in the transparent conductive IT film is reduced. In addition, the color filter surface has high smoothness and there is no light diffusion phenomenon, so that the color filter function can be highly exhibited.

Furthermore, when assembled as a liquid crystal display element, the gear knobs between the substrates become uniform, resulting in a high display quality.

The method of the present invention has a particularly excellent effect on smoothing and flattening the surface of a color filter, but in addition, by similarly treating the surface of general glass, it can be used as an inexpensive substitute for polished glass. It can be applied to a wide range of substrates that require smoothness and flatness, such as providing a glass substrate with a smooth surface.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a color filter substrate on which a smoothing and flattening layer is formed according to an embodiment of the present invention, and FIG. A cross-sectional view of a color filter substrate before forming a flattening layer,
FIG. 2(b) is a cross-sectional view of a color filter substrate according to an embodiment of the present invention, after an organic polymer is deposited by heating spraying and before a smoothing and flattening layer is formed by heat treatment. 4 is a conceptual diagram showing how organic polymer resin is deposited and formed by a heated spraying device in an embodiment of the present invention, and FIG. 4 is a sectional view of a color filter substrate on which a coating film layer is formed, according to a conventional example. 1...Glass substrate, 2...Colored film (2
R: red, 2G: green, 2B: blue), 3...
Smoothing, flattening layer, 4... Coating film layer, 5...
... Color filter substrate, 6 ... Heating spray device, 7 ... Heating airless spray nozzle, 8 ...
...Organic polymer resin layer.

Claims (1)

[Scope of Claims] (1) A method for producing a liquid crystal display element substrate having a smooth and flat layer formed by depositing an organic polymer having a molecular structure that allows free rotation by a heated spraying method. (2) A liquid crystal display element substrate having a structure obtained by the manufacturing method according to claim (1). (3) A method for manufacturing a liquid crystal display element, comprising the method for manufacturing a liquid crystal display element substrate according to claim (1), which comprises a color filter for the liquid crystal display element. (4) A liquid crystal display element comprising the liquid crystal display element substrate according to claim (2), which is provided with a color filter for liquid crystal display element.