JP5616919B2 - Rubbing treatment method and optical film manufacturing method - Google Patents

Description

  The present invention relates to a rubbing treatment method and an optical film manufacturing method, and more particularly to a rubbing treatment method and an optical film manufacturing method used when manufacturing an optical compensation film or the like of a liquid crystal display device.

  In recent years, development of liquid crystal display devices has been promoted, and liquid crystal display devices have become widespread all over the world. Various optical films are used in liquid crystal display devices. Among them, there are films that are given orientation by rubbing treatment, such as alignment films and optical compensation films, and play an important role. I'm in charge.

  A viewing angle improving film, which is one of the films imparted with orientation, generally has an alignment film forming material on the surface of a transparent flexible belt-like support (hereinafter also referred to as “web”). After coating and drying to form an alignment film forming resin layer, the surface is rubbed to form an alignment film. And it manufactures by apply | coating and drying a liquid crystalline coating liquid on alignment film, forming a liquid-crystal layer, and making it harden | cure after that.

  The rubbing treatment is a typical method for aligning liquid crystal molecules. A rubbing roller in which an alignment film forming material is formed on a web surface and a rubbing cloth is wound around the surface of the alignment film forming material. This is done by rotating and rubbing.

  As such a rubbing treatment method, Patent Document 1 includes a ground fabric composed of warp and weft and a pile yarn woven into the fabric, and the pile yarn is made of resin on the surface of the filament. A rubbing treatment method using a rubbing cloth material coated with a coating material is disclosed.

  Thereby, even if the film becomes long, there is little variation in optical characteristics, and an optical compensation film with less bright spot generation frequency can be manufactured.

JP 2010-204173 A

  However, the rubbing treatment method described in Patent Document 1 still has a problem that dust generation is not small.

  In view of such circumstances, the present invention intends to provide a rubbing treatment method and an optical film manufacturing method capable of rubbing with good orientation and reducing dust generation.

  The problems of the present invention can be solved by the following inventions.

That is, the rubbing treatment method of the present invention is a rubbing treatment method for imparting orientation to the alignment film forming material, comprising a step of rubbing the surface of the alignment film forming material with a cloth material, The pile yarn is a fiber having a sea-island structure. The pile yarn is a fiber having a sea-island structure, and the sea part is EVA (ethylene vinyl acetate). The main feature is that the island is formed of a resin selected from PET (polyethylene terephthalate), PBT (polybutylene terephthalate), and nylon .

  Thereby, since the pile yarn has a sea-island structure, it is possible to perform a rubbing process with good orientation and reduced dust generation.

  Further, in the rubbing treatment method of the present invention, in the cross section perpendicular to the longitudinal direction of the pile yarn, the proportion of the area of the sea portion is 50% to 67%, and the proportion of the area of the island portion is 50% to 33%. It is a key feature.

  Thereby, the rubbing process with good orientation and reduced dust generation is possible.

  Furthermore, the rubbing treatment method of the present invention is mainly characterized in that the sea island structure of the pile yarn is a structure having three or more island portions.

  Thereby, the rubbing process with good orientation and reduced dust generation is possible.

In addition, the rubbing treatment method of the present invention is mainly characterized in that the tensile elastic modulus of the pile yarn is 0.1 × 10 ^{11 to} 2.0 × 10 ¹¹ Pa.

  Thereby, the rubbing process with good orientation and reduced dust generation is possible.

  Furthermore, the method for producing an optical film of the present invention includes a step of forming an alignment film forming material on a support, and a rubbing treatment method on the surface of the alignment film forming material formed on the support. And a rubbing process.

  Thereby, it is possible to produce an optical film with good orientation and reduced dust generation.

  Dust generation can be reduced.

It is explanatory drawing which shows the manufacturing line of an optical film. It is a partial expansion perspective view of the cloth material 1 for rubbing. It is explanatory drawing explaining the internal structure of a pile yarn. It is explanatory drawing which shows the installation place of a particle counter.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings. Here, in the drawing, portions indicated by the same symbols are similar elements having similar functions. In addition, in the present specification, when a numerical range is expressed using “˜”, upper and lower numerical values indicated by “˜” are also included in the numerical range.

<Method for producing optical film>
An embodiment of a method for producing an optical film according to the present invention will be described with reference to the drawings. FIG. 1 is an explanatory view showing an optical film production line.

  An optical film manufacturing method according to the present invention mainly includes a step of forming an alignment film forming material on a web as a support, and a step of rubbing the surface of the alignment film forming material formed on the web. Configured.

  Describing in detail with reference to FIG. 1, a web 16 that is a transparent support is fed from a feeder 66. The web 16 is guided by a guide roller 68 and passes through a dust remover 15A to remove dust attached to the surface of the web 16. As the dust remover 15A, various known types can be adopted. For example, a configuration in which compressed air (nitrogen gas) subjected to electrostatic dust removal is sprayed on the surface of the web 16 to remove dust adhering to the surface of the web 16 can be employed.

  A bar coating device 11A is provided downstream of the dust remover 15A in the web running direction (hereinafter simply referred to as downstream), and a coating liquid containing an alignment film forming material is applied to the web 16. The coating device is not limited to a bar coating device, but various coating devices such as a gravure coater, roll coater (transfer roll coater, reverse roll coater, etc.), die coater, extrusion coater, fountain coater, curtain coater, dip coater, spray coater. Or a slide hopper etc. are employable.

  A drying zone 76 </ b> A and a heating zone 78 </ b> A are sequentially provided downstream of the bar coating apparatus 11 </ b> A, and an alignment film forming material layer is formed on the web 16.

  After coating and drying the coating solution, the web 16 is guided by the guide roller 68 and sent to the rubbing processing device 70. The rubbing roller 72A (72B) is provided to perform a rubbing process on the alignment film forming material layer. A dust remover 71A (71B) is provided upstream of the rubbing roller 72A (72B) to remove dust adhering to the surface of the web 16.

  The rubbing apparatus 70A (70B) is an apparatus for performing a rubbing process on the polymer layer. In this example, the rubbing apparatus 70A (70B) has a two-stage roller configuration with rubbing rollers 72A and 72B. Note that a one-stage roller configuration may be employed as the rubbing processing device 70.

  The rubbing treatment device 70A (70B) is a device that rotationally drives a rubbing roller 72A (72B) in which a rubbing cloth material, which will be described later, is wound on the outer peripheral surface, and the rotational speed is controlled to, for example, about 1000 rpm. can do. The shape of the rubbing roller 72A (72B) is, for example, a roller having an outer diameter of 150 mm and a length slightly longer than the width of the web 16 even when the rubbing angle is applied. The rubbing treatment device 70A (70B) is rotatable in a horizontal plane with respect to the traveling direction of the web 16 so that the rubbing treatment device 70A (70B) can be adjusted to an arbitrary rubbing angle.

  Above the rubbing roller 72A (72B), a roller stage 84A (84B) is provided, and backup rollers 86A (86B) and 88A (88B) are rotatable on the lower surface of the roller stage 84A (84B) via a spring. Attached to. The backup rollers 86A (86B) and 88A (88B) are provided with a mechanism for detecting the tension of the web 16 so that the tension during rubbing can be managed.

  Further, the backup rollers 86A (86B) and 88A (88B) can be adjusted up and down, and the wrap angle of the web 16 to the rubbing roller 72A (72B) can be adjusted by moving the rollers up and down.

  With the above configuration, the alignment film forming material on the surface (lower surface) of the web 16 is pressed by the rubbing roller 72A (72B) pressed from the lower side while the web 16 is pressed from above by the backup rollers 86A (86B) and 88A (88B). The surface of the layer is rubbed to form an alignment film imparted with orientation.

  A dust remover 15 </ b> B is provided downstream of the rubbing treatment device 70, and dust attached to the surface of the web 16 can be removed.

  A bar coating device 11B is provided downstream of the dust remover 15B, and a coating liquid containing a disconematic liquid crystal is applied to the web 16. As the coating device 11B, various coating devices can be used in the same manner as when the coating liquid containing the alignment film forming material is applied to the web 16.

  A drying zone 76B and a heating zone 78B are sequentially provided downstream of the bar coating device 11B, and a liquid crystal layer is formed on the web 16. Further, an ultraviolet lamp 80 is provided downstream of this, and the liquid crystal is cross-linked by ultraviolet irradiation to form a desired polymer. Then, the protective film 88A, which is inspected by the inspection device 84 and delivered from the laminating machine 88, is laminated on the web 16, and the web 16 on which the polymer is formed is taken up by the winder 82 provided downstream thereof.

  In the present embodiment, the entire optical film production line 10, particularly the bar coating apparatuses 11 </ b> A and 11 </ b> B, may be installed in a clean atmosphere such as a clean room. At that time, the cleanliness is preferably class 1000 or less, more preferably class 100 or less, and still more preferably class 10 or less.

<Rubbing cloth material>
Next, the rubbing cloth material 1 which is a characteristic part of the present invention will be described. FIG. 2 is a partially enlarged perspective view of the rubbing cloth material 1.

(1) Outline of rubbing cloth material This rubbing cloth material 1 is obtained by weaving pile yarns 4 on a base cloth 5 in which warp yarns 2 of a ground fabric structure and weft yarns 3 of a ground fabric texture are woven in a lattice shape. It is formed. Among these, a material in which pile yarns 4 are woven into three wefts 3 like a rubbing fabric material 1 shown in FIG. 2 (A) is called a W structure, and a rubbing fabric material 1 shown in FIG. 2 (B). As described above, the pile yarn 4 woven into one weft 3 is referred to as a V structure. The W structure and the V structure differ only in how the pile yarns 4 are woven, and the same materials can be used.

  Examples of the base fabric 5 include polyamides such as nylon 6-6 (registered trademark), polyesters such as polyethylene terephthalate, polyolefins such as polyethylene, polyvinyl alcohol, polyvinylidene chloride, polyvinyl chloride, polyacrylonitrile, Synthetic fibers such as acrylics such as acrylamide and methacrylamide, poly (vinylidene cyanide), polyfluoroethylene and polyurethane, natural fibers such as silk, cotton, wool, cellulose and cellulose ester, and regenerated fibers (rayon, acetate, etc.) ) Or a combination of two or more selected from among the above.

  Of these fiber materials, preferably, polyamides such as nylon 6 and nylon 6-6 (registered trademark), acrylics such as polyacrylonitrile, acrylamide and methacrylamide, polyesters such as polyethylene terephthalate, and celluloses as recycled fibers And cellulose ester-based rayon and acetate.

  The warp yarn 2 and the weft yarn 3 of the base fabric 5 are preferably used in a state where, for example, 70 pieces of 1.4 denier fibers are combined to form a filament of about 100 denier (long continuous fiber). As such warp yarns 2 and weft yarns 3, for example, cupra rayon (Bemberg) filaments manufactured by Asahi Kasei Corporation can be preferably used.

(2) About pile yarn Next, the pile yarn which is the most characteristic part of this invention is demonstrated with reference to drawings. FIG. 3 is an explanatory diagram for explaining the internal structure of the pile yarn.

  As shown in FIG. 3, the pile yarn 4 of the rubbing cloth material has a sea-island structure in the fiber cross section, and PET (polyethylene terephthalate), PBT (polyethylene) is formed in the sea part 100 formed of EVA (ethylene vinyl acetate). There is an island 110 formed of butylene terephthalate) or nylon. The island part 110 exists continuously in the longitudinal direction of the pile yarn 4.

  The sea-island structure here refers to a structure having at least two island portions, but the number of island portions is preferably three or more, more preferably seven or more, and most preferably fifteen or more. The reason is as follows. That is, the pile yarn is likely to be crimped due to the difference in thermal expansion coefficient between the island part and the sea part. However, by arranging the island parts evenly in three cross sections, the tensile stress due to the difference in the thermal expansion coefficient is piled up. This is because it can be prevented from occurring in a part of the yarn and causing shrinkage.

  If there is only one island, placing the island in the middle of the cross section cancels the tensile stress due to the difference in the coefficient of thermal expansion, but the island is completely in the middle along the entire length of the pile yarn. It is difficult to arrange, and a slight deviation from the middle causes the pile yarn to shrink.

  However, when there are three or more islands, even if the position of the islands fluctuates slightly in the longitudinal direction, random fluctuations between different islands cancel the tensile stress due to the difference in thermal expansion coefficient. The pile yarn can be prevented from shrinking.

  This effect is more conspicuous as the number of islands increases. According to the study of the present inventor, the number of islands is preferably 3 or more, more preferably 7 or more, and most preferably 15 or more. It has been found.

  By rubbing with a cloth material for rubbing provided with the pile yarn 4 having such a sea-island structure, a rubbing treatment can be performed with less dust generation and good orientation.

<Evaluation>
Next, rubbing treatment was performed using various kinds of rubbing cloth materials, and the orientation, dust generation, and printing of the alignment film were evaluated. The rubbing fabric used for the evaluation is different only in the pile yarn, and the ground fabric structure is common.

Below, it shows about the pile yarn used for evaluation.
Comparative Example 1: A core-sheath structure having a PET core at the center and an EVA sheath around the center is provided, and the area ratio in the fiber cross section (cross section perpendicular to the longitudinal direction) is EVA: PET = 50: 50. What will be.
Comparative Example 2: A core-sheath structure having a PET core at the center and an EVA sheath around it, and the area ratio in the fiber cross section (cross section perpendicular to the longitudinal direction) is EVA: PET = 67: 33 What will be.
Comparative Example 3: Consists of PET alone.
Comparative Example 4: Consists of EVA alone.
Comparative Example 5: Consists of rayon alone.
Example 1: A sea-island structure having an EVA sea part and a PET island part, and the area ratio in the fiber cross section (cross section perpendicular to the longitudinal direction) is EVA: PET = 50: 50.
Example 2: A sea-island structure having an EVA sea part and a PET island part, and the area ratio in the fiber cross section (cross section perpendicular to the longitudinal direction) is EVA: PET = 67: 33.
Example 3: A sea island structure having an EVA sea part and a PBT island part is provided, and the area ratio in the fiber cross section (cross section perpendicular to the longitudinal direction) is EVA: PBT = 50: 50.
Example 4: A sea island structure having an EVA sea part and a nylon island part is provided, and the area ratio in the fiber cross section (cross section perpendicular to the longitudinal direction) is EVA: nylon = 50: 50.

<Evaluation method of unevenness on pile yarn surface>
An electron microscope manufactured by JEOL Ltd. was used to evaluate the unevenness of the pile yarn surface. In this apparatus, the magnification was set to 2000 times, and the unevenness was evaluated by focusing on the surface of each pile yarn.

<Evaluation method of pile yarn shrinkage>
An electron microscope manufactured by JEOL Ltd. was used to evaluate the unevenness of the pile yarn surface. In this apparatus, the magnification was set to 100 times, and the shrinkage was evaluated by focusing on the entire pile yarn.

<< Evaluation method of orientation by quenching degree >>
For the evaluation of the orientation based on the extinction degree, a quenching degree measuring apparatus manufactured by Otsuka Electronics Co., Ltd. was used. In this apparatus, the measurement wavelength was 550 nm, and the transmittance of the Paranicol polarizing plate was 100%. Then, the orientation of two discotic liquid crystals arranged in crossed Nicols was evaluated.

  As for dust generation, as shown in FIG. 4, rubbing is performed by rubbing the side of the web 16 on which the alignment film forming material is formed while rotating the rubbing cloth 1 wound around the roller 120 in the direction of the arrow. The particle counter HANDHELD3016 manufactured by Lighthouse is installed at the upstream measurement location A and downstream measurement location B of the web 16 at that time, and the particle size of 0.3 μm or more is obtained. The number of suspended particles was measured and indicated as a relative ratio when the number in Comparative Example 1 was 100. FIG. 4 is an explanatory diagram showing the installation location of the particle counter.

The printing is a value obtained by evaluating the number of bright spot defects of the transparent film after the rubbing process based on the bright spot occurrence frequency of a surface inspection apparatus using a CCD camera. The ratio is shown.

The table below summarizes the evaluation conditions and the evaluation results.
<Table 1>

Here, the standard of each evaluation result is as follows.
・ Pile yarn surface irregularities: Excellent (no irregularities), impossible (irregularities)
・ Pile yarn shrinkage: Excellent (no shrinkage), impossible (shrinkage)
・ Orientation: Excellent (the orientation of the alignment film at the end is almost the same as that at the start of the rubbing process, and is acceptable) Yes (but the orientation of the alignment film at the end is slightly worse than at the start of the rubbing process) , Pass line), not possible (the alignment of the alignment film at the end is worse than at the beginning of the rubbing treatment, and the alignment uniformity in the rubbing treatment cannot be maintained for a long time, and is rejected)
・ Dust generation: Excellent (0-50), possible (51-250), impossible (251 or more)
・ Printing: Excellent (0 to 0.50), Acceptable (0.51 to 2.50), Impossible (2.51 to)
・ Comprehensive evaluation: Excellent (all evaluated excellent), acceptable (no one is impossible, one is included), impossible (one is included)
As the evaluation results indicate, all the Examples 1 to 4 having the sea-island structure have an excellent overall evaluation. From this, it was clarified that the pile yarn has a sea-island structure, the orientation of the orientation film is good, the dust generation is small, and the printing can be rubbed well.

  It has also been found that the sea-island structure is preferably such that the sea is formed of EVA and the island is formed of a resin selected from PET, PBT, and nylon. Furthermore, in the cross section perpendicular to the longitudinal direction of the pile yarn, it was also found that the ratio of the area of the sea part is 50% to 67%, and the ratio of the area of the island part is preferably 50% to 33%. .

Further, in the pile yarn having the sea-island structure as described above, one having a tensile elastic modulus of 0.1 × 10 ^{11 to} 2.0 × 10 ¹¹ Pa is preferable from the viewpoints of orientation of the alignment film, dust generation, printing, and the like. The inventor found that there was.

  In the present invention, when the pile yarn of the rubbing cloth material has a sea-island structure, the mechanism that can impart good orientation to the alignment film forming material is presumed to be as follows. That is, the pile yarn according to the present invention has less unevenness on the surface of the pile yarn compared to natural fibers such as rayon and cotton, and the entire pile yarn compared to the yarn of EVA coated structure (core-sheath structure with EVA as a sheath). Since there is little crimp (shrinkage), rubbing debris generated during the rubbing process is difficult to accumulate in the pile yarn, and it seems that the surface-like body suitable for the rubbing process can be maintained for a long time.

DESCRIPTION OF SYMBOLS 1 ... Rubbing cloth material, 2 ... Warp, 3 ... Weft, 4 ... Pile yarn, 5 ... Base fabric, 10 ... Production line, 11A ... Bar coating device, 11B ... Bar coating device, 15A ... Dust remover, 15B ... Dust removal Machine 16 ... web 66 ... feeding machine 68 ... guide roller 70 ... rubbing device 70A ... rubbing device 71A ... dust remover 72A ... rubbing roller 76A ... drying zone 76B ... drying zone 78A ... Heating zone, 78B ... Heating zone, 80 ... UV lamp, 82 ... Winder, 84 ... Inspection device, 84A ... Roller stage, 86A ... Backup roller, 88 ... Laminating machine, 88A ... Protective film, 100 ... Sea part, 110 ... Island, 120 ... roller, A ... measurement location, B ... measurement location

Claims (5)

A rubbing treatment method for imparting orientation to an alignment film forming material,
A step of rubbing the surface of the alignment film forming material with a cloth material;
The cloth material is composed of a ground fabric composed of warps and wefts, and a pile yarn woven into the ground fabric,
Wherein the pile yarn, Ri fibers der having a sea-island structure,
The pile yarn is Ama is formed by EVA (ethylene vinyl acetate), the island portion is PET (polyethylene terephthalate), PBT (polybutylene terephthalate), rubbing how formed of a resin selected from nylon. 2. The rubbing treatment according to claim 1 , wherein in the cross section perpendicular to the longitudinal direction of the pile yarn, the ratio of the area of the sea portion is 50% to 67%, and the ratio of the area of the island portion is 50% to 33%. Method. The rubbing treatment method according to claim 1 or 2 , wherein the sea island structure of the pile yarn is a structure having three or more island portions. The pile yarn tensile ^{modulus, 0.1 × 10 11 ~2.0 × 10} 11 Pa rubbing processing method according to any one of claims 1 to 3 is. Forming an alignment film forming material on a support;
Performing a rubbing treatment on the surface of the alignment film forming material formed on the support by the rubbing treatment method according to any one of claims 1 to 4 ,
The manufacturing method of the optical film provided with.

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