JPS60120325A - Oriented liquid crystal film and its production - Google Patents

Abstract

PURPOSE:To decrease the change in quantity of transmission of light in a specific frequency band by forming an oriented liquid crystal film of plasma polymn. of the gas or vapor of an org. compd. having a nitrogen atom in a molecule. CONSTITUTION:While the inside 20 of a bell-jar 13 is evacuated by a vacuum pump 17, N-vinyl-2-pyrolidone is introduced from a cylinder 18 into the inside 20 of the bell-jar. The pressure of the inside 20 of the bell-jar is maintained under 0.1-1.0Torr and high frequency electric discharge of 13.56MHz is generated between an upper electrode 11 and a lower electrode 12 by a high-frequency power source 14. When 50W of electric power is applied in this stage, the plasma state of the gas of the N-vinyl-2-pyrolidone is generated in the inside 20 of the bell-jar and is maintained so that the N-vinyl-2-pyrolidone polymer film is deposited on a glass base plate 1 and a transparent electrode 4. The uniform and defectless oriented film having 0.03mu film thickness is formed after 10min.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a liquid crystal alignment film for parallel alignment of a liquid crystal display panel used in a liquid crystal display device.

A field-effect liquid crystal display device that uses a conventional structure and a nematic liquid crystal having positive dielectric anisotropy, and combines the arrangement of molecules of the liquid crystal film on each surface of opposing electrodes to be perpendicular to each other. This is called a twisted nematic type (hereinafter referred to as TN type) liquid crystal cell. In recent years, there has been a demand for more sophisticated and more complex information display (3), and to meet this demand, the above-mentioned T1 (type liquid crystal cell) IJ Lux display has been implemented. There is. In order to display such a matrix,
A large number of divided band-shaped transparent electrodes are respectively provided on two glass substrates, and the electrode groups on each glass substrate are configured to face each other so that the directions of the electrode groups are orthogonal to each other, and each portion where the opposing electrodes intersect. By selectively applying voltage to these electrode groups, complex matrix display is possible on a liquid crystal display panel.

In addition, in order to perform the above-mentioned matrix display, it is necessary that the change in the amount of light transmitted through the liquid crystal display panel has a threshold characteristic that is steep with respect to the applied voltage. The contrast of the panel depends on the degree. In addition, in liquid crystal display panels for matrix display, in order to eliminate the so-called crosstalk phenomenon between each picture element, the Kameko averaging method is adopted, which applies a constant voltage evenly to non-selected picture elements. Showa GO-12032
5(2). This is a driving method that utilizes the property that the amount of light transmitted through the LCD panel is determined depending on the effective value of the applied AC voltage, and therefore the amount of light transmitted through the LCD panel responds to the effective value of the applied voltage. It has to be something. That is, it is required that the amount of light transmission remains stable and does not change with respect to frequency changes within a certain range.

As shown in FIG. 1, a liquid crystal display panel usually has two glass substrates 1 and 1° above which are each provided with a plurality of band-shaped transparent lightnings tII.
114 and 4'' are provided, liquid crystal alignment films 3 and 31 are respectively formed thereon, and both are formed into strip-shaped transparent types!
4 and 4" are arranged facing each other with a certain gap maintained so as to cross at right angles, the surroundings are sealed with +h material 9 to withstand the weight, and a liquid crystal 6 is placed in the above gap.
After the glass substrate 1 and the glass substrate 1 are sealed, polarizing plates 7 and 71 are attached to the back surfaces of the glass substrate 1 and the ζ month 1, respectively, resulting in a structure 7Ae.

Liquid crystal alignment films 3 and 3I in such a liquid crystal display panel
The role of IJI is to align the long axis direction of the liquid crystal molecules in a certain direction with a small inclination (hereinafter referred to as tilt (5) angle) with respect to the surface of the glass substrate 1 and 1° when no voltage is applied. In particular, conventionally for this purpose SiO@3 and 31 are obliquely deposited on glass substrates 1 and 11 containing transparent electrodes 4 and 4°, or polyimide coatings 3 and 31 are deposited on glass substrates 1 and 11 containing transparent electrodes 4 and 4°.
After coating, the surface of the coating film has been rubbed in a certain direction with a cotton cloth or the like (hereinafter referred to as "rubbing").

However, in the case of the SiO obliquely deposited film, it is difficult to form a uniform tilt angle over the entire surface of the film, and the steep threshold characteristics described above cannot be obtained, so a liquid crystal display panel with sufficient cost resistance cannot be obtained. There wasn't.

On the other hand, in the case of a polyimide film, even if the same effective voltage is applied, when the frequency changes, the amount of light transmitted changes accordingly.
It did not have the performance to respond to the effective value described above, and sufficient contrast could not be obtained during matrix address driving using the electronic averaging method.

Purpose of the Invention The purpose of the present invention is to solve the above-mentioned drawbacks of the conventional liquid crystal aligning film, and to create a liquid crystal display panel with good contrast and little change in light transmission in the frequency band C from 3QHz to 2KH2. It is an object of the present invention to provide a liquid crystal alignment film necessary for this purpose, and a method for producing the same.

Structure of the Invention The present invention provides a liquid crystal alignment film provided to cover a glass substrate provided with a transparent electrode, wherein the liquid crystal alignment film is formed by plasma polymerization of a gas or vapor of an organic compound having nitrogen atoms in its molecules. The liquid crystal alignment film for parallel alignment is a formed film.

Further, the present invention involves exposing a glass substrate on which a transparent electrode has been previously provided to a glow discharge generated in a vacuum containing a gas or vapor of an organic compound having nitrogen atoms in its molecules.1. A film is formed by plasma polymerizing the above-mentioned organic compound under glow discharge so as to cover the entire surface of the glass substrate provided with the transparent electrode except for one end of the transparent electrode for external extraction, and then the surface of the above-mentioned film is A method of manufacturing a liquid crystal alignment film for parallel alignment, which comprises rubbing in a certain direction.

Examples of the above-mentioned organic compounds having a nitrogen atom in the molecule that can be used in the present invention include N-vinyl-2-pyrrolidone, diethylaminoethyl methacrylate, achloronitrile,
There are benzyldimethylamine and vinylpyridine, each of which may be used alone or any mixture thereof may be used.

In manufacturing the liquid crystal alignment film according to the present invention, the above-mentioned organic compound having a nitrogen atom in its molecule (hereinafter referred to as a nitrogen-containing compound) is introduced into a glow discharge device in a gas or vapor state.

The nitrogen-containing compound may be brought into a gas or vapor state by heating, if necessary, or by vaporization or vaporization using an inert gas such as argon or helium as a carrier gas.

As the glow discharge device, any conventionally used device can be used.
Glow discharge is performed using a Hz power source. The discharge time may normally be 1 to 30 minutes.

Under the above conditions, a plasma polymerized film of a nitrogen-containing compound is formed on a glass substrate-L provided with a transparent electrode. The film thickness is usually 0.01 to 1μ, preferably 0.01 to 0.1μ.

According to the present invention, a polymer film of a nitrogen-containing compound is formed on the entire surface of a glass substrate provided with a transparent electrode as described above except for a part of the electrode for drawing out the electrode, and then a desired tilt angle is formed. For example, transparent electrode 4,
Rub in the 4' length direction and in the 450 angle direction.

In this way, a liquid crystal alignment film, which is the object of the present invention, is produced.

Description of examples An embodiment of the present invention will be described below with reference to FIG.

FIG. 2 is an explanatory diagram showing a method of manufacturing a liquid crystal alignment film according to the present invention by glow discharge. In FIG. - Vinyl-2-pyrrolidone is introduced into the Pelger interior 20 from the cylinder 18 (9) via the introduction tube 19.

The inside of the Pelger 20 is maintained at a pressure of 0.1 to 1.0 Torr with N-vinyl-2-pyrrolidone gas. At this time, the band-shaped transparent electrode 4 (
A glass substrate 1 with transparent electrodes (three in the figure) is placed, and
is placed so as to face the upper electrode 11. The gas inflow amount of the N-vinyl-2-pyrrolidone was adjusted to the pressure inside the Pelger 20 of 0.1 to 1. A high frequency discharge of 13.56 MHz is generated between the upper electrode 11 and the lower electrode 12 by the high frequency power source 14 while adjusting to maintain the OTorr.

If the power at this time is 50W, the Pelger internal 20
A gaseous plasma state of N-vinyl-2-pyrrolidone is generated and maintained, and the glass substrate 1 and the transparent electrode 4 are
An N-vinyl-2-pyrrolidone polymer film is deposited on top.

After 10 minutes, a very uniform and defect-free alignment film with a film thickness of 0.03 mm is formed.

Note that when coating with a conventional polyimide film, cleaning of the glass substrate was essential, but in case (10) of the present invention, such cleaning is not necessarily necessary, and there is no problem in immediately forming a liquid crystal alignment film. It turned out that.

As described above, according to the present invention, the liquid crystal alignment film formed on the entire surface of the glass substrate provided with the transparent electrode except for one end of the electrode for external extraction is made of cotton, polyester,
Using a cloth such as polyamide, a fixed direction, that is, a transparent electrode 4
．． Rub in the length direction of 41 and in the angle direction of 45'. This rubbing occurs when the liquid crystal molecules do not apply an electric field to −f
This is for arranging them in the same direction, that is, parallel to the rubbing direction, with a tilt angle of fl.

In manufacturing a TN type liquid crystal display panel using the glass substrate 1 provided with the transparent electrode 4 on which the liquid crystal alignment film manufactured as described above is formed, as shown in FIG. Two sets of glass substrates 1 and 11 having liquid crystal alignment films 3 and 3° are placed facing each other while maintaining a certain width (11) so that the rubbing directions of the respective alignment films 3 and 3' are orthogonal to each other. After combining and sealing with a sealing material 9, a well-known nematic liquid crystal 6 having positive dielectric anisotropy is sealed in the gap. After that, a linear polarizing plate 7 is pasted on the back surface of each glass substrate 1 (no transparent electrode is provided (11!l)) so that its polarization axis is parallel to the rubbing direction of the alignment film 3, and on the other hand, the back surface of the substrate 1° A linear polarizing plate of 7° is pasted on the substrate so that its polarization axis is parallel to the rubbing direction of the alignment film 3'.A positive display TN type liquid crystal display panel is thus completed.

Note that the plasma-polymerized liquid crystal alignment film 3 according to the present invention
The contact angle between 3' and the liquid crystal 6 is preferably 150 or less. If it exceeds 156, unevenness tends to occur in the orientation and the surface condition deteriorates, which is not preferable.

FIG. 3 shows the optical properties of a liquid crystal display panel made using the liquid crystal alignment film according to the present invention, particularly the steepness of the threshold value of the amount of light transmitted with respect to the applied voltage.

Further, FIG. 4 shows the change in the amount of light transmission with respect to the change in frequency. According to the present invention, nitrogen-containing compounds, namely 18 Kaisho GO-1
20325(4) A liquid crystal display panel made using a liquid crystal alignment film made from N-vinyl-2-pyrrolidone, diethylaminoethyl methacrylate, acrylonitrile, benzyldimethylamine or vinylpyridine is shown in FIGS.
The characteristics within the shaded area are shown. On the other hand, a liquid crystal display panel of the same configuration using a conventional SiO obliquely vapor-deposited film as an alignment film exhibited the characteristics shown by the curve B in FIGS. 3 and 4. In addition, in a liquid crystal display panel of the same configuration using commercially available polyimide as an alignment film, the results shown in Figures 3 and 4 are
The characteristic shown by the curve O is shown in the figure.

As is clear from Figures 3 and 4, when the liquid crystal alignment film according to the present invention is used, the threshold characteristic of the amount of light transmitted relative to the applied voltage is steeper than when the conventional alignment film is used. , and it can be seen that the amount of light transmission has a stable so-called effective value response with respect to frequency changes.

Effects of the Invention As described above, the liquid crystal alignment film according to the present invention (13) does not require complicated processes such as substrate cleaning and drying, unlike conventional polyimide alignment films, and is suitable for liquid crystal alignment films such as SiO vapor deposited films. The liquid crystal alignment film is very transparent and free from alignment unevenness, and has the advantage that it can be produced by a simple method. In addition, the liquid crystal display panel using the liquid crystal alignment film according to the present invention has no liquid crystal alignment unevenness, and has excellent optical properties such as steep threshold characteristics and effective response, so it has excellent performance as a matrix display panel. has.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of the structure of a liquid crystal display panel, Fig. 2 is an explanation N showing a method of manufacturing a liquid crystal alignment film by glow discharge, and Figs. 3 and 4 are optical characteristics of the liquid crystal display panel. This is a graph showing. 1.1' is a glass substrate, 3, 3' is an alignment film, 4°4' is a transparent electrode, 6 is a liquid crystal, 7, 7' is a polarizing plate, 11 is an upper electrode, 12 is a lower electrode, 13 is a bell jar ( 14) -114 is a high frequency power supply, 18 is a nitrogen-containing compound cylinder,
19 is the introduction pipe, 17 is the vacuum pump, and 2° is inside the Pelger. Patent applicant Matsushita Electric Industrial Co., Ltd. 1021) 31♂ IC, 71

Claims (1)

[Scope of Claims] 1. A liquid crystal alignment film provided to cover a glass substrate provided with a transparent electrode, wherein the liquid crystal alignment film is formed by plasma of a gas or vapor of an organic compound having nitrogen atoms in its molecules. A liquid crystal alignment film for parallel alignment, characterized in that it is a film formed by polymerization. 2. The organic compound having a nitrogen atom in the molecule is N-vinyl-2-pyrrolidone, diethylaminoethyl methacrylate, acrylonitrile, benzyldimethylamine,
The liquid crystal aligning film according to claim 1, which is one type or a mixture of two or more types of vinylpyridine. 3. A glass substrate provided with a transparent electrode in advance is exposed to a glow discharge generated in a vacuum containing a gas or vapor of an organic compound having nitrogen atoms in its molecules to cover the entire surface of the glass substrate provided with the transparent electrode. A method for producing a liquid crystal alignment film for parallel alignment, characterized in that a film is formed by plasma polymerizing the above organic compound under glow discharge, and then the surface of the film is rubbed in a certain direction. 4. The organic compound having a nitrogen atom in the molecule is N-vinyl-2-pyrrolidone, diethylaminoethyl methacrylate, acrylonitrile, benzyldimethylamine,
The manufacturing method according to claim 3, wherein the manufacturing method is one type or a mixture of two or more types of vinylpyridine.