JP5142357B2 - Method for producing liquid crystal alignment film - Google Patents

Description

  The present invention relates to a method of applying an alignment film for aligning a liquid crystal material on a flexible resin substrate drawn from a roll or performing an alignment treatment, a flexible resin substrate obtained by the above-described manufacturing method, and this flexible resin substrate. The present invention relates to an optical film and a liquid crystal display element obtained by using a flexible resin substrate.

  The conventional method of manufacturing a liquid crystal display element is a method using a glass substrate, and a large liquid crystal display element or a small-sized liquid crystal display element is manufactured and used for a liquid crystal television, a monitor for a personal computer, a mobile phone, and the like. Yes. A liquid crystal display element using a glass substrate has drawbacks such as glass being damaged or heavy when dropped, and cracking during production resulting in poor mass productivity. For this reason, a liquid crystal display element using a resin substrate that is less likely to be damaged than a glass substrate and that is lightweight (hereinafter referred to as a liquid crystal display element using a resin substrate) has been produced. Liquid crystal display elements using a resin substrate are mass-produced by STN (Super Twisted Nematic) with passive matrix drive, but it is difficult to enlarge the screen compared to active matrix drive and the contrast is inferior compared to active matrix. There was a drawback that it was difficult to refine. Therefore, in recent years, active matrix drive liquid crystal display elements using a resin substrate have been actively developed.

As the resin substrate coating process and orientation process, a single wafer or batch process and a continuous process using a roll-shaped substrate are conceivable.
Patent Document 1 discloses a liquid crystal display element characterized in that an alignment film is subjected to processing such as printing and rubbing treatment in a state where a resin substrate is attached to a support substrate using an adhesive, and then the resin substrate is peeled off. A manufacturing method is disclosed.
In such a single wafer / batch processing process, it is easy to ensure the accuracy of the orientation processing, but the processing time per unit area becomes long, so that the productivity is inferior. For this reason, it is not suitable for mass production.

On the other hand, Patent Document 2 discloses a method for manufacturing a liquid crystal optical element, in which a polyimide resin is applied on a roll-shaped flexible resin substrate with a micro-gravure coater and then continuously rubbed. Has been.
Such a continuous processing process is highly productive, but the accuracy of the width and the film position in the height direction, etc. deteriorates, so the quality after processing deteriorates due to film position misalignment during processing, etc. May get worse.
JP 2001-125082 A JP-A-1-253712

  Accordingly, an object of the present invention is to apply an alignment film and an alignment treatment to both the substrate pulled out from the roll and the single-wafer substrate, which do not have the above-mentioned drawbacks, or have only a small extent. An object of the present invention is to provide a method for producing a high-quality liquid crystal alignment film with a high yield using a flexible resin substrate drawn out from a roll.

As a result of diligent studies to solve the above-mentioned problems, both the case where a thin film is applied on a flexible resin substrate drawn from a roll and the case where an alignment treatment is performed by rubbing are equivalent to conventional single wafers in a processing stage. Positioning and fixing of the flexible resin substrate by a film pressing mechanism that adsorbs the processing surface of the flexible resin substrate to the processing stage and sandwiches the flexible resin substrate at a position that does not interfere with the apparatus during processing so that processing is performed. It was carried out, by the method for producing a liquid crystal alignment film which is characterized in that the coating and orientation processing by the processing stage is movable, and investigated that the problems can be solved.

  According to the method of the present invention, a high-quality liquid crystal alignment film can be produced from a flexible resin substrate with a high yield.

  Hereinafter, a method for applying an alignment film to a flexible resin substrate and an alignment processing method in an optimal embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a conventional method in the case where an alignment film is applied to a flexible resin substrate drawn from a roll and an alignment process is performed. In this method, the resin substrate can be processed continuously, but the film cannot be fixed by a method such as adsorbing the film to the processing stage, so the film position in the width / height direction is likely to shift during processing. , The quality after processing becomes worse. Moreover, it is not possible to process a single substrate using such equipment.

Figure 2 is a diagram showing a method of manufacturing a flexible resin substrate. As shown in FIG. 2, in the present invention, the processing surface of a flexible resin substrate is fixed to a processing stage by suction, and the processing is performed by moving the processing stage. have. Since the substrate is adsorbed on the stage, there is no shift in the width / height direction during processing, and the quality after processing is high.

Further, as shown in FIG. 3, it is also desirable to install a movable temporary baking apparatus that can perform temporary baking after applying the alignment film on the unwinding side or the winding side of the processing stage.
By providing the temporary baking apparatus, a uniform coated film can be formed by moving the surface on which the alignment film is applied to the temporary baking apparatus and performing temporary baking immediately.

  As shown in FIG. 4, it is also desirable to provide an accumulator mechanism that absorbs the transport length of the substrate accompanying the stage movement during processing. In particular, the stage movement during rubbing is fast, so the operation speed such as unwinding from the roll and rotation of the take-up part cannot catch up with the stage movement speed, and excessive stress is applied to the substrate, which may cause tearing and distortion. is there. By providing the accumulating mechanism, the transport length of the substrate is absorbed by the accumulating mechanism, and no excessive stress is applied to the substrate.

  As shown in FIGS. 4 and 5, the accumulator mechanism can be provided on only one of the unwinding side and the winding side, or can be provided on both the unwinding side and the winding side.

FIG. 6 is a view illustrating a method of manufacturing a flexible resin substrate according to an embodiment of the present invention. As shown in FIG. 6, by providing a film pressing mechanism for sandwiching a flexible resin substrate in the processing stage and using it together with suction, the possibility of substrate displacement can be further reduced and the yield can be improved.

  As the flexible resin substrate that can be used in the present invention, in principle, all flexible resin substrates known to those skilled in the art for this purpose can be used. Preferably, for example, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, triacetyl cellulose, polyamide, polyimide, polymethyl methacrylate, polycycloolefin, cycloolefin copolymer, crosslinked epoxy resin, crosslinked acrylic resin, crosslinked silicone resin , Substrates made of unsaturated polyester, polysulfone, polyethersulfone, polycarbonate, polyarylate, and the like, but are not limited thereto. If the thickness of the flexible resin substrate is too thin, resistance to stress is weakened, so that tearing, wrinkling, and distortion are likely to occur, and if it is too thick, problems such as bending due to difficulty in deformation are likely to occur. Therefore, the thickness range is preferably 50 to 3,000 μm, and particularly preferably 100 to 1,000 μm.

As the alignment film that can be used in the present invention, for example, an organic film of a polymer material such as polyimide, polyamic acid, polyamide, or polyvinyl alcohol can be used. The film thickness is preferably 50 to 5,000 mm, more preferably 100 to 3,000 mm.
In addition, the flexible resin substrate with an alignment film manufactured according to the present invention can be used as an optical film such as an optical retardation film or an optical compensation film by forming a liquid crystal material on the alignment film.
The liquid crystal material that can be used for the optical film can be selected from all known liquid crystal materials, but is preferably a polymerizable liquid crystal compound, a side chain type or main chain type linear or cross-linked liquid crystal polymer, or liquid crystal. An oligomer or a mixture of these materials.

Example 1 (Reference Example)
(Preparation of flexible resin substrate with liquid crystal alignment film)
An ITO film is formed as a transparent electrode on a flexible resin substrate having a thickness of 200 μm, a width of 300 mm, and a length of 20 m based on polyethersulfone (glass transition temperature 223 ° C.), and the substrate is washed with pure water The liquid crystal aligning agent is applied using a flexographic printing apparatus of the type illustrated in FIG. 3 (the provisional baking apparatus is installed on the winding side of the processing stage unlike the illustrated one). The coated surface was dried at 80 ° C. for 1 minute using a hot plate as a temporary baking apparatus. Then, it dried in 180 degreeC oven for 20 minutes, and formed the coating film with a dry average film thickness of 600 上 on the surface in which the ITO film | membrane was formed. Using the rubbing apparatus illustrated in FIG. 6 having a rubbing roll on which a cloth made of rayon is wound, this coating film has a roll rotation speed of 400 rpm, a stage moving speed of 30 mm / sec, and a hair foot pushing length of 0. After being rubbed at 4 mm and washed with water, it was dried in an oven at 120 ° C. for 10 minutes. When the coating state of the alignment film was visually confirmed, a uniform alignment film was formed.

(Production of liquid crystal display element)
Two flexible resin substrates with an alignment film are cut out from a roll at a length of 300 mm, and an epoxy resin adhesive containing aluminum oxide spheres with a diameter of 6 μm is applied to the outer edge of the alignment film forming surface of one substrate. did. A spherical spacer having a diameter of 6 μm was dispersed on the other substrate to obtain a lower substrate. In order to form a twisted nematic (TN) type liquid crystal cell, the upper substrate and the lower substrate were overlapped and bonded so as to face each other at an angle of 90 ° (FIG. 7), and the adhesive was cured. Next, after filling a nematic liquid crystal (MLC-6221, manufactured by Merck & Co., Inc.) from the liquid crystal injection port, the liquid crystal injection port was sealed with an acrylic photo-curing adhesive. A liquid crystal display element was produced by laminating polarizing plates so as to be crossed Nicols up and down.

(Evaluation of liquid crystal display elements)
A voltage was applied at 3 V (rectangular wave 60 Hz) at 23 ° C., and it was confirmed whether display unevenness was observed in the cell. As the display state, uniform black display was obtained, and good cell quality could be confirmed.

Comparative Example 1
A flexible resin substrate with an alignment film was produced in the same manner as in Example 1 except that the alignment film was applied using the micro-gravure coater illustrated in FIG. When the coating state of the alignment film was confirmed by visual observation, film unevenness was observed and the coating state was uneven. A liquid crystal display device was produced in the same manner as in Example 1, and the display state of the cell was confirmed. The black display state was uneven and the cell quality was poor.

Comparative Example 2
A liquid crystal display element was prepared and the display state of the cell was confirmed in the same manner as in Example 1 except that the rubbing process was performed using the rubbing apparatus illustrated in FIG. The black display state was uneven and the cell quality was poor.

The schematic diagram of the apparatus for the conventional method of performing alignment film coating and orientation processing with respect to a roll-shaped flexible resin substrate. Schematic diagram of the basic structure of the line USo place the alignment film coating and the alignment treatment for the flexible resin substrate. Schematic diagram of the alignment film coating and orientation processing apparatus provided with a row cormorants variable-acting calcination apparatus for flexible resin substrate. Schematic diagram of the alignment film coating and orientation processing apparatus having a accumulation mechanism to a row cormorants winding side against the flexible resin substrate. Schematic diagram of the alignment film coating and orientation processing apparatus having a accumulator mechanism to both the row cormorants unwinding side and the winding side against the flexible resin substrate. It is a schematic diagram of the apparatus provided with the film pressing mechanism for the method of this invention which performs alignment film coating and alignment processing with respect to a flexible resin substrate. FIG. 3 is an explanatory diagram showing an overlapping direction of an upper substrate and a lower substrate in the liquid crystal display element of Example 1.

Claims (4)

In both when performing the alignment process and by rubbing when applying the alignment agent on a flexible resin substrate drawn from the roll, the device at the time of processing as well as adsorbing the treated surface of the flexible resin substrate in the processing stage interference The liquid crystal alignment film is characterized in that the flexible resin substrate is positioned and fixed by a film pressing mechanism that sandwiches the flexible resin substrate at a position where there is no gap, and the coating and alignment processing is performed by moving the processing stage. Production method.   The method for producing a liquid crystal alignment film according to claim 1, wherein a movable temporary baking device is further provided on the unwinding side or the winding side of the processing stage to temporarily fire the alignment agent-coated substrate.   The method for producing a liquid crystal alignment film according to claim 1, further comprising an accumulator mechanism to absorb the transport length of the substrate accompanying the stage movement during processing. Method of manufacturing a liquid crystal alignment film according thickness of the flexible resin substrate to any one of claims 1 to 3 which is a 50~3,000μm to process.

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