JPH03123318A - Production of liquid crystal display device - Google Patents

Abstract

PURPOSE:To obtain an oriented film which has uniform thickness and has no contamination, and also, in which static electricity, etc., are not accumulated by forming an oriented film consisting of a uniform accumulated film on a substrate, radiating accelerated particles to this oriented film surface from the specific direction and executing orientation processing. CONSTITUTION:While holding the surface pressure by applying a pressure by a partition plate 2 to an LB film 8 dripped down onto ion exchange water 7 in a water tank 1, a substrate 3 is drawn up vertically to the water surface and the LB film is allowed to adhere, and by repeating the operation, an accumulated film is formed on the substrate. A substrate 18 obtained by forming very thinly and uniformly a polyimide oriented film on this substrate is attached to a fixing device 17 in a bell jar 16, gas which is led in by a plasma generating device 12 is brought to plasma state, and by impressing a voltage to an acceleration electrode 13, accelerated particles are radiated to the substrate 18 from the oblique direction. In such a way, with respect to the oriented film formed on the substrate, the orientation processing is executed by a method of non- contact without contaminating the surface of the oriented film.

Description

[Detailed description of the invention] (b) Industrial application fields The present invention relates to a method for manufacturing a liquid crystal display device.

More details relate to its improvement.

(B) Conventional technology Conventionally, as a method for forming an alignment film for unidirectional horizontal alignment of liquid crystal molecules, there is a spinner method in which an alignment film is formed on a substrate using centrifugal force, and a spinner method in which a substrate is placed in an alignment film solution. A dipping method in which an alignment film is formed by dipping the substrate, and an offset printing method in which an alignment film solution is transferred onto a substrate using a printing machine to form an alignment film are known.

In addition, alignment treatment methods for alignment films include a rubbing method in which a substrate on which a silicon oxide or polyimide alignment film is formed is polished in one direction using a brushed or flocked cloth, and a vacuum evaporation method in which silicon oxide is diagonally applied to the substrate. A commonly used method is an oblique evaporation method in which the film is grown in a specific direction.

Furthermore, in addition to the above, L a using a polymer compound
ngmuir-B lodget (L B ) l
! Alignment methods are known, such as forming an alignment film by pulling up LB and rubbing the formed alignment film, and applying a magnetic field to the alignment film formed by pulling LB.

(c) Problems to be Solved by the Invention However, it is difficult to reduce the thickness of the alignment film to 500 Å or less using the spinner method, dipping method, or offset printing method, which are the alignment film forming methods described above. Furthermore, the thicker the film, the greater the insulation, which causes a voltage drop, and the voltage applied to the liquid crystal becomes smaller.

In addition, it is difficult to make the film thickness uniform with the alignment film forming method described above. If the film thickness is non-uniform in this way, a voltage difference will occur within the same substrate when an electric field is applied, causing display unevenness.

On the other hand, in the above-mentioned alignment treatment of the alignment film, in the case of a large-area, high-definition substrate, unevenness in the rubbing pressure is likely to occur due to unevenness on the substrate, especially for substrates on which a nonlinear element array is formed using an active matrix method. At the top, due to the thickness of the gate electrode, source electrode, nonlinear element, etc., a step is created with respect to the substrate plane, and the rubbing strength is weakened in the shadow of the step. Furthermore, uneven rubbing pressure occurs due to differences in the thickness of the substrates. These pressure irregularities adversely affect display as alignment irregularities of liquid crystal molecules. Furthermore, since the rubbing method comes into contact with the fabric, the fibers of the fabric and impurities contained in the fabric adhere to the alignment film, which changes the properties, making cleaning after the alignment process essential and requiring a large amount of cleaning solvent. Become. Furthermore, TF'T, MI
In a liquid crystal display element having a nonlinear element array such as M, static electricity is generated due to friction during rubbing, and the semiconductor switching element may be destroyed.

On the other hand, the oblique evaporation method has problems in that the growth direction of the deposited silicon oxide crystals spreads out in a fan shape, and flakes are generated, resulting in uneven orientation.

Furthermore, with the method of depositing multiple monomolecular layers of a polymer compound (L Bll) on a substrate and aligning the liquid crystal molecules parallel to the direction in which the substrate is pulled up, sufficient alignment regulating force cannot be obtained, and pre-tilt It is not possible to obtain a corner.In the method of rubbing an alignment film made of a cumulative film of LB films,
Since the LB film is extremely thin and has weak adhesion to the substrate, the film may be destroyed by contact with fibers during rubbing.

Furthermore, even with a method of applying a magnetic field to an alignment film formed from the cumulative film of the LB films, sufficient alignment force cannot be obtained for a liquid crystal display device.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a method for manufacturing a liquid crystal display device that can form an alignment film that has a uniform thickness, is free from contamination, and does not accumulate static electricity.

(d) Means for Solving the Problems Thus, according to the present invention, a pair of substrates on which alignment films for aligning liquid crystals in a predetermined direction are formed are arranged with their alignment film-formed surfaces facing each other, and between them, liquid crystals are In the manufacturing method of a liquid crystal display device configured to sandwich a substrate and to apply a predetermined voltage between the substrates, the alignment film is a cumulative film formed by laminating one or more monomolecular layers of a polymer compound on the substrates. is formed, and this cumulative film is polymerized as necessary, and then at least a portion of the resulting cumulative film is irradiated with accelerated particles from a specific direction on the surface of the polymerized film to undergo orientation treatment. A method for manufacturing a liquid crystal display device is provided.

In the method of this invention, substrates commonly used in the field can be used as they are, and transparent glass substrates are preferred. The above board has i! corresponding to a predetermined display pattern. A pole is formed.

In the method of this invention, an alignment film is formed on the substrate. The alignment film is a single molecule FfJ (hereinafter L) of a polymer compound.
It is composed of a cumulative film of B film).

The above-mentioned polymer compound may be any compound that produces an LB film and is commonly used in the field; for example, it can be obtained from polyamic acid and a long-chain alkylamine compound having hydrophobicity. Polyamic acid derivatives are preferred.

The above-mentioned cumulative IN film is obtained by depositing the above-mentioned LB film in several layers. The above-mentioned LB film can be formed using an LB film forming apparatus known in the art. With the above device, LBW
When forming A, film forming conditions are selected based on the relationship between the area of the film developed on the water surface and the surface pressure. For example, the surface pressure is preferably in the range of 4 to 35 m+1/m. That is, if it is smaller than 4zN/m, gaps will occur between molecules, and if it is larger than 35xN/m, there is a risk that the membrane will be destroyed, which is not preferable. When the film is used as a liquid crystal aligning film, the film is formed by lifting the substrate perpendicularly to the water surface within the range of the liquid film. In this way, an LB film is obtained on the substrate, and by repeating such lifting operations several times and depositing, a predetermined cumulative film is obtained. However, in the formation of a cumulative film, 1
It is necessary to dry the LB film of the second layer after formation.

In the method of the present invention, the alignment film made of the cumulative film obtained above is subjected to polymerization, if necessary.

That is, when the cumulative film obtained above is partially obtained from the precursor before polymerization, it is necessary to complete the polymerization. For example, when the monomolecular layer has a polyamic acid derivative as a constituent unit, it is necessary to polymerize it to form an imide.

In the method of this invention, the cumulative film obtained above includes:
At least a portion of its surface is irradiated with accelerated particles. This irradiation is done from a specific direction. The specific direction is preferably an oblique direction parallel to the pulling direction during film formation from the viewpoint of alignment uniformity. Specifically, reference is made to the description of Examples described later. The accelerated particles may be charged particles or electrically neutral particles. Examples of charged particles include ions. Equipment known in the art is used to irradiate the particles. When using ions as the accelerated particles in the present invention, an ion beam irradiation device can be used. Further, in the case where the cumulative film is an insulating film such as polyimide in the above ion irradiation, charging occurs due to ion irradiation, so it is a preferred embodiment of the present invention to electrically neutralize this. For this specific example as well, reference is made to the description of the embodiment described later.

(E) Function According to the present invention, an alignment film consisting of a thin and uniform cumulative film is formed on the substrate.

By a non-contact method of irradiating the alignment film with accelerated particles from a specific direction, the alignment process can be performed without contaminating the surface of the alignment film.

The present invention will be described in detail below with reference to Examples, but the present invention is not limited thereby.

(f) Example Sunever 11, a commercially available polyamic acid for liquid crystal alignment
fsnol/(2) per repeating unit of polyamic acid using a mixed solvent of N-methylpyrrolidone and benzene (1:l)
dilute to N,N-dimethyl-n at the same concentration and in the same solvent
- A hexadecylamine solution is added in an amount twice equivalent to the repeating unit of polyamic acid to prepare a polyamic acid alkylamine salt solution.

Using this solution, LBI [
An LB film of a polyamic acid alkylamine salt solution was formed on a substrate using formation. In the same figure, l is a water tank, 2 is a partition plate, 3 is a substrate, 4 is a pulling machine, 5 is a Vilhelmi plate, 6 is a membrane pressure gauge, 7 is ion exchange water, 8
is an LB film, and 9 is an LB film attached on the substrate.

LBI8 of polyamic acid alkylamine salt solution is 20
Drop onto ion-exchanged water kept at ℃ and spread it.
Pressure was applied through a partition [2 provided therein, and at this time, the correlation between the area (A) of the L membrane 8 developed on the surface of the ion-exchanged water 7 and the surface pressure (π) was investigated. The results are shown in FIG. From the figure, it was found that a good π-A curve was obtained and a liquid film was obtained when the surface pressure was in the range of 4 to 20×N/a. In addition, the area occupied per repeating unit of the polymer was 1.1 nm''. Furthermore, the surface pressure was 351!I/
If it exceeds I11, the membrane will be destroyed and the surface pressure will be 4zN/la.
It was found that if the size is smaller, gaps are created between molecules, which is not a favorable condition for film formation. In addition, when used as a liquid crystal alignment film, in the π-A curve in Fig. 2,
In a solid film in the range of 20 to 35 ffiN/s, the molecules in the LB simulated film are in a densely packed state, and when the substrate is pulled up, alignment parallel to the pulling direction is difficult to occur, and the alignment regulating force of the liquid crystal molecules becomes small. Therefore, as the conditions for forming LBII, it is preferable to form it within the range of a liquid film, and in this case, the LB film was obtained by pulling the substrate perpendicular to the water surface while maintaining a surface pressure of 15 iN/*. This was repeated 5 times to form a cumulative film of 5 layers on the substrate (however, after forming the LB film for the first time, leave it for 30 minutes after forming the film to increase the adhesion between the substrate and the LB film. (This step was not performed from the second time onwards.)

The substrate is a transparent glass substrate with I as a display electrode.
Partially formed TO (indium-tin oxide) was used. Also, the pulling speed of the substrate is 1oaIl/wi
It was set as n. Note that even when the pulling speed was increased to 10 cm/win, there was no significant change in the thickness or orientation of the formed film. However, at a pulling speed of 5a+m/min or less, the orientation regulating force during pulling becomes very weak.

Next, the substrate on which the cumulative film was formed was immersed in a mixed solution of acetic anhydride-pyridine-benzene (1:l:3) at 20°C for 12 hours to desorb the long-chain alkyl groups and complete imidization. Thereafter, the imidization accelerator was removed by allowing the mixture to stand under a vacuum of IX 10-'Torr for 12 hours. The thickness of the polyimide thus obtained was extremely thin and uniform.

Next, the substrate on which the polyimide alignment film was formed in the above process was irradiated with accelerated particles from an oblique direction using an ion beam irradiation device having the structure shown in FIG. In the figure, 11 is an AC power supply, 12 is a plasma generator, 13 is an acceleration electrode, 14 is an extraction electrode, 15 is a ground electrode, 16 is a Pelger, 17 is a substrate fixing device, 18 is a substrate, 19 is a mask, and 2o is a neutralizing filament, 2 [
22 is a gas cylinder for introduction, 23 is a cock, and 24 is a vacuum pump.

The substrate 18 was attached to the substrate fixing device 17 and fixed at an appropriate angle with respect to the irradiation direction of the accelerated particles. 1 to 2XIO-' inside the Pelger 16 using the vacuum pump 24
After reaching a vacuum level of Torr, a gas such as argon, krypton, xenon, oxygen, etc. is introduced into the Pel jar 16 through the gas flow rate control device 21, and 1 to IOX 10-
'Turr the gas introduced by the plasma generator 12 into a plasma state with a pressure of 100~500V
A certain voltage was applied to the accelerating electrode 13, and the generated ions were given interlocking energy and irradiated onto the alignment film. At this time L
B: When forming a film, irradiation from an oblique direction parallel to the substrate pulling direction and irradiation from an oblique direction perpendicular to the direction in which the substrate is lifted are better. The results were shown. In addition, insulating films such as polyimide are charged due to ion irradiation, so
Ions were neutralized by emitting thermoelectrons from the neutralizing filament 20.

Using the substrate thus formed, a TN cell with a cell thickness of 5 μl as shown in FIG. 4 was fabricated.

In the figure, 31 and 32 are glass substrates, 33 and 34 are transparent electrodes, 35 and 36 are alignment films, and 37 and 3 are glass substrates.
8 is a sealing resin, 39 and 40 are spacers, and 41 is a liquid crystal.

The characteristics of the liquid crystal cell obtained above are shown in Table 1 below. Here, argon was used as the introduced gas, the irradiation angle and irradiation time were used as the irradiation condition parameters, and the evaluation items were orientation uniformity, pretilt angle, voltage holding rate, and memory voltage when DC voltage was applied. Orientation uniformity was defined by the area where uniform horizontal orientation was obtained (in the same table, ◎ indicates completely uniform orientation, hereinafter O1Δ indicates a decrease in the oriented area, and × indicates no orientation). ).

The pretilt angle must be at least 0.5 layers, and if it is too small, the liquid crystal molecules will not rise in one direction when a voltage is applied, resulting in disclination.

The voltage holding rate is related to the display contrast during time-division driving, and the larger the value, the greater the contrast obtained.
A value of about 95% provides sufficient practical contrast.

In addition, the memory voltage when a DC voltage is applied is mainly an indicator of the display quality of an active matrix liquid crystal display element having a nonlinear element array, and it is a measure of the flickering phenomenon when a voltage with an asymmetrical waveform is applied to liquid crystal molecules. It indicates the ease of occurrence, and the smaller the value, the higher the display quality.

Further, this value has a correlation with the thickness of the alignment film, and the thinner the film, the smaller the value. Here, the applied voltage for erasing flicker after applying a DC voltage of ±3V3GHz rectangular wave medium 2 for 30 minutes was specified. This value is obtained by forming an alignment film on polyimide using a spinner method, dipping method, offset printing method, etc., and then aligning it using a rubbing method.
The voltage is 0.7 to 0.8V, and it is about 2V when silicon oxide is rubbed, and it is about 2V when silicon oxide is obliquely deposited.

As shown in Table 1 above, a polyamic acid alkylamine salt solution Bll was deposited on the substrate of the above example and imidized to form a polyimide film, and further accelerated particles were added to the polyimide film. 40 to the normal direction of the board
By using an alignment method that horizontally aligns liquid crystal molecules in one direction by irradiating in the range of ~80°, it is possible to obtain a liquid crystal element with extremely high display quality in both simple matrix type and active matrix type. I can do it.

Furthermore, when the liquid crystal molecule alignment method of the present invention was applied to an active matrix type liquid crystal display device having TPT,
No change in TPT properties before or after irradiation, no breakage or short circuit of the pass line, and no uneven orientation due to steps were observed.

(G) Effects of the Invention According to the present invention, an alignment film can be formed that has a uniform thickness, is free from contamination, and does not accumulate static electricity, etc., without being affected by the thickness of the substrate or the unevenness of the surface, so that the alignment of liquid crystal molecules can be improved. A stable liquid crystal display device can be obtained. In either case of a simple matrix type or an active matrix type, a liquid crystal display device with extremely high display quality can be obtained.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the configuration of an LB film forming apparatus used for forming an alignment film in an example of the method of the present invention, and FIG. 2 shows the area and surface pressure of the film developed on the water surface in the apparatus of FIG. A graph showing the relationship, FIG. 3 is an explanatory diagram of the configuration of an ion beam irradiation device used in forming an alignment film in an example of the method of the present invention, and FIG. 4 is an illustration of an example of a liquid crystal cell obtained by the method of the present invention. It is a configuration explanatory diagram. l...water tank, 2...partition plate, 3.18...substrate, 4...
...Lifting machine, 5...Willhelmi plate, 6...Membrane pressure gauge, 8.9...
・LB film, xi... AC power supply, 12... Plasma generator, 13... Accelerating electrode, 17... Substrate fixing device, 19... ... Mask, 20 ... Neutralizing filament, 21 ...
・Gas flow control device, 24... Vacuum pump, 31.32...
Glass substrate, 33.34...Transparent electrode, 3
5.36...Alignment film, 37.38...
Sealing resin 41...Liquid crystal. 39.40...Spacer, 1st figure drawing structure (H outside nm) 4th Sengaki figure 4 2 0

Claims (1)

[Claims] 1. A pair of substrates on which an alignment film for aligning liquid crystal in a predetermined direction is arranged with the faces on which the alignment film is formed facing each other, and the liquid crystal is sandwiched between the substrates. In the method of manufacturing a liquid crystal display device configured to be able to apply a voltage of Production of a liquid crystal display device, characterized in that the liquid crystal display device is formed by polymerizing according to the method, and then performing alignment treatment by irradiating at least a part of the resulting cumulative film with accelerated particles from a specific direction on the surface of the polymerized film. Method.