JP6647875B2 - Optical film manufacturing method - Google Patents

Description

  The present invention relates to an optical film including a laminated structure in which at least a first film and a second film are bonded via an adhesive layer or a pressure-sensitive adhesive layer formed of a cured product layer of the adhesive composition or the pressure-sensitive adhesive composition. It relates to a manufacturing method.

  Liquid crystal display devices are rapidly developing in markets such as watches, mobile phones, PDAs, notebook computers, monitors for personal computers, DVD players, and TVs. The liquid crystal display device visualizes a polarization state by switching of liquid crystal, and a polarizer is used from the display principle. In particular, for applications such as TVs, higher brightness, higher contrast, and wider viewing angles are required, and even higher polarizing films are required to have higher transmittance, higher degree of polarization, higher color reproducibility, and the like.

  As a polarizer, for example, an iodine-based polarizer having a structure in which iodine is adsorbed on polyvinyl alcohol (hereinafter, also simply referred to as “PVA”) and stretched because it has a high transmittance and a high degree of polarization is most commonly used. It is used. Generally, a polarizing film in which a transparent protective film is bonded to both surfaces of a polarizer with a so-called water-based adhesive obtained by dissolving a polyvinyl alcohol-based material in water has been used. However, in recent years, the use of an active energy ray-curable resin composition that does not contain water or an organic solvent is becoming the mainstream because it has advantages such as the drying step can be omitted and the dimensional change is small. is there.

  When using an active energy ray-curable resin composition to produce an optical film by laminating a plurality of films, for example, apply the adhesive composition only to the lamination surface of the transparent protective film, such a lamination surface Generally, an optical film having a laminated structure is manufactured by attaching a polarizer or the like from the side. However, in the conventional manufacturing method, foreign substances such as dust and dirt are attached to the surface of the polarizer and the transparent protective film before applying the adhesive composition and the like, or the adhesive composition contains fine foreign substances. In this case, foreign matters remain in the adhesive layer, and as a result, appearance defects may occur.

Patent Document 1 below discloses an optical film comprising a step of applying a thin layer of an optical functional layer having a wet application amount of 10 mL / m ² or less on a transparent support or an undercoat layer formed on the transparent support. In the production method, there is described a method for producing an optical film including a step of removing foreign substances having a height of 10 μm or more from a transparent support or an undercoat layer before applying an optical functional layer.

  Patent Literature 2 below discloses a method for producing a polarizing film by subjecting a polyvinyl alcohol-based resin film having a thickness of 1 to 60 μm to a dyeing treatment, a crosslinking treatment, and a washing treatment in this order, and after the washing treatment, A method for efficiently producing a polarizing film having a good appearance by applying a tension of 200 to 1500 N / m to a film while alternately blowing air on both surfaces of the film to drain the film.

JP 2008-180905 A JP 2014-109740 A

  However, as a result of the study by the present inventor, the technique described in Patent Document 1 attempts to crush and remove foreign matter by calendering or the like in a state where foreign matter is already present on a transparent support or the like. Therefore, the accuracy of removing the foreign matter is not high, and the minute foreign matter remains after the removing step. For this reason, the technique described in Patent Document 1 is difficult to apply to a method for manufacturing a thin optical film in which the thickness is small and appearance defects are problematic even when minute foreign matter is present. Was the actual situation.

  Further, in the manufacturing method described in Patent Document 2, foreign matter once removed from the film surface due to being blown off by air is re-attached, and thus the foreign matter removal accuracy may be poor.

  In recent years, there has been a growing demand for prevention of appearance defects of optical films, and in order to meet this demand, further improvement in process has been required.

  The present invention has been accomplished in view of the above circumstances, and has as its object to manufacture an optical film in which appearance defects due to foreign matter and / or air bubbles are prevented even when the optical film is thin. It is to provide a method.

  The present inventors have conducted intensive studies in order to solve the above-mentioned problems, and as a result, when manufacturing an optical film including a laminated structure in which at least two films are laminated, a specific coating method is adopted, and two laminated films are laminated. It has been found that by applying a liquid material to the opposite side of each bonding surface of the film, foreign substances such as dust and dust which may cause a defect in appearance can be removed. Further, effectively, in the subsequent step of applying the adhesive composition (or the adhesive composition), by applying the adhesive composition or the adhesive composition to the bonding surface of at least one of the films. It has been found that the removal of foreign matter and / or air bubbles and the formation of the adhesive composition layer or the pressure-sensitive adhesive composition layer can be performed at one time. The present invention has been obtained as a result of such ingenuity and has the following configuration.

That is, the present invention provides an optical film including a laminated structure in which at least a first film and a second film are bonded via an adhesive layer or a pressure-sensitive adhesive layer composed of a cured product layer of the adhesive composition or the pressure-sensitive adhesive composition. Before bonding the first film and the second film, the first film, the side opposite to the bonding surface with the second film, and the second film of the second film The foreign matter is removed by applying a liquid material having a viscosity of 1 to 10000 cP on at least one surface of the side opposite to the surface to be bonded with the 1 film using a gravure roll coating method using a gravure roll. A method for producing an optical film, comprising a first coating step.

  In the present invention, before laminating the first film and the second film, the first film, the side opposite to the laminating surface with the second film, and the second film, the laminating surface with the first film. A liquid material having a viscosity of 1 to 10,000 cP is applied to at least one of the opposite side surfaces (first application step). Then, the liquid material is applied using a gravure roll coating method while removing foreign matter. As a result, foreign matter such as dust and dirt present on the opposite sides of the bonding surfaces of the two films to be bonded is scraped off. As a result, in the method for manufacturing an optical film according to the present invention having the first coating step, even when the optical film is thin, it is possible to manufacture an optical film in which appearance defects caused by foreign matter are prevented. it can.

  In the above manufacturing method, a second method for removing foreign matter and / or air bubbles by applying the adhesive composition or the pressure-sensitive adhesive composition to a bonding surface of at least one film using a post-metering coating method. It is preferable to have a coating step. According to such a configuration, using a post-metering coating method, while scraping foreign substances such as dust and dirt present on at least one of the bonding surfaces of the two films to be bonded, and using the adhesive composition or the pressure-sensitive adhesive composition The adhesive composition or the pressure-sensitive adhesive composition is applied while also scraping off the gel-like substance or aggregate derived from the substance from the bonding surface. As a result, it is possible to manufacture an optical film in which appearance defects caused by foreign matter are further prevented.

  By the way, when an optical film having a laminated structure is manufactured by laminating two films, an adhesive composition or a pressure-sensitive adhesive composition is applied to one of the two films, and the other is applied thereto. (Hereinafter, also referred to as “single-side coating method”). In the single-side coating method, the adhesive (or pressure-sensitive adhesive) -coated surface of one film is in direct contact with the bonding surface of the other film (with no adhesive composition (or pressure-sensitive adhesive composition)). Laminated. In this case, since the viscous adhesive composition (or pressure-sensitive adhesive composition) comes into direct contact with the bonding surface of the other film, air bubbles are likely to bite during bonding. On the other hand, in the method according to the present invention, particularly when the adhesive composition (or the adhesive composition) is applied to both the bonding surface of the first film and the bonding surface of the second film, the adhesive of the first film The bonding surface of the (or pressure-sensitive adhesive) is attached while being in contact with the surface of the second film where the adhesive (or pressure-sensitive adhesive) is coated. That is, since the adhesive compositions (or pressure-sensitive adhesive compositions) having viscosity are attached to each other while being overlapped with each other, air bubbles are less likely to be caught at the time of bonding, and the air bubbles are easily released. Therefore, in the method according to the present invention, especially when the adhesive composition (or the adhesive composition) is applied to both the bonding surface of the first film and the bonding surface of the second film, compared with the single-side coating method. Also, since it is excellent also in terms of bubble removal effect, it is possible to produce an optical film in which occurrence of appearance defects caused by bubbles is prevented.

  In the present invention, the “post-metering coating method” means a method in which an external force is applied to a liquid film to remove an excess liquid and obtain a predetermined coating film thickness. In the method for producing an optical film according to the present invention, when an external force is applied to the liquid film composed of the adhesive composition or the pressure-sensitive adhesive composition, foreign substances such as dust and dust present on the bonding surface are scraped off. . Specific examples of the post-metering coating method include a gravure roll coating method, a forward roll coating method, an air knife coating method, a rod / bar coating method, and the like. Preferably, a gravure roll coating method using a gravure roll is used. In the present invention, “removing foreign matter and / or air bubbles” means removing at least one or both of the foreign matter and air bubbles.

  In the above production method, the liquid material preferably contains at least 50% by weight of water. If the liquid applied to remove the foreign matter remains in the second application step of applying the adhesive composition (or the adhesive composition), poor adhesion (or poor adhesion) may occur. Therefore, after the first coating step, the liquid material needs to be promptly removed in a drying step or the like. It is preferable that the liquid material contains at least 50% by weight or more of water because the drying step after application of the liquid material can be simplified.

  In the above production method, the liquid material preferably further contains an alcohol. According to such a configuration, the wettability (leveling property) of the liquid material itself on the film can be increased, and the evaporation rate of the liquid material can be increased. Therefore, the efficiency of drying and removing the liquid material can be further increased, and the productivity is improved, which is preferable.

  In the above manufacturing method, the post-metering coating method is a method in which the adhesive composition or the pressure-sensitive adhesive composition is circulated and applied, and the adhesive composition or the adhesive composition or the second film is applied from the first film and / or the second film. It is preferable to have a foreign matter removing function of removing foreign matter mixed in the pressure-sensitive adhesive composition from the adhesive composition or the pressure-sensitive adhesive composition. In the post-metering coating method, a coating solution composed of an adhesive composition or a pressure-sensitive adhesive composition is applied to the bonding surface of the first film and / or the second film. Alternatively, when foreign matter is removed from the bonding surface of the second film, the possibility that foreign matter is present on the bonding surfaces of the first film and the second film after application is increased. However, the coating method used has a foreign matter removing function of removing foreign matter mixed into the adhesive composition or the pressure-sensitive adhesive composition from the first film and / or the second film by coating from the adhesive composition or the pressure-sensitive adhesive composition. When it is provided, the amount of foreign matter in the coating liquid can be significantly reduced. Thereby, the possibility that a foreign substance exists on the bonding surface of the first film and the second film after application can be significantly reduced.

  In the above manufacturing method, it is preferable that a rotation direction of the gravure roll is opposite to a traveling direction of the first film and the second film. In this case, foreign substances such as dust and dirt present on the bonding surface of the first film and the bonding surface of the second film, as well as gels and aggregates derived from the adhesive composition or the adhesive composition are scraped off. The effect is effectively enhanced, and the appearance defects of the finally obtained optical film can be more effectively prevented.

Various patterns can be formed on the surface of the gravure roll, and for example, a honeycomb mesh pattern, a trapezoid pattern, a lattice pattern, a pyramid pattern, or a diagonal pattern can be formed. In order to effectively prevent appearance defects from occurring in the optical film finally obtained, the pattern formed on the surface of the gravure roll is preferably a honeycomb mesh pattern. If the honeycomb mesh pattern, in order to improve the surface accuracy of the coated surface after the adhesive composition or adhesive composition coating, it is preferable that the cell volume is ^{1~5cm 3 / m 2, 2~3cm 3} / m It is preferably ² . Similarly, in order to increase the surface accuracy of the coated surface after the application of the adhesive composition or the pressure-sensitive adhesive composition, the number of cell lines per one inch of the roll is preferably 200 to 3000 lines / inch. In addition, it is preferable that a rotation speed ratio of the gravure roll to a traveling speed of the first film and the second film is 100% to 300%.

  By the way, as the thickness of the adhesive layer (or the pressure-sensitive adhesive layer) and further the total thickness of the optical film are thicker, foreign substances are less likely to be visually recognized, and appearance defects are less likely to be regarded as problems. On the other hand, as the thickness of the adhesive layer (or the pressure-sensitive adhesive layer) is thinner, and further, as the total thickness of the optical film is thinner, the foreign matter is more easily recognized, and as a result, the appearance defect becomes a problem. Often. However, in the method for producing an optical film according to the present invention, an optical film having an extremely low generation rate of foreign substances in an adhesive layer (or a pressure-sensitive adhesive layer) can be produced. The manufacturing method according to the present invention is particularly useful when a method for manufacturing a particularly large polarizing film, specifically, when the first film is a polarizer and the second film is a transparent protective film.

  In the production method according to the present invention, even when a thin polarizing film is produced, as in the case where the thickness of the polarizer is 10 μm or less, the presence of foreign matter or foreign matter in the adhesive layer (or pressure-sensitive adhesive layer) This is preferable because a thin polarizing film in which appearance defects caused by bubbles are prevented can be produced.

  By the way, when the optical film is a polarizing film, while the polarizer as the first film is in contact with the roll, it is sequentially transported to the polarizer manufacturing step, and subsequently to the first and second steps. A polyvinyl alcohol (PVA) layer, which is a raw material of a polarizer, is appropriately immersed and treated in a boric acid bath, a potassium iodide bath, or the like, to produce a polarizer. The PVA layer conveyed from each bath removes excess water by using a pinch roll or a bar coater, etc., but in some cases, boric acid or potassium iodide, which is a component in the bath, is deposited and polarized light is removed. They may remain on the surface of the polarizer, and these may cause surface scratches on the polarizer. Note that a thin polarizer having a thickness of 10 μm or less is generally manufactured in a state of being laminated with a base film such as polyethylene terephthalate (PET) (a state in which a laminate of a polarizer having a thickness of 10 μm or less and a base film is formed). However, as a result of intensive studies, the present inventors, particularly by removing boric acid and potassium iodide attached to the side of the base film of the laminate, to prevent the occurrence of surface scratches on the polarizer surface, It has been found that appearance defects can be effectively suppressed. Therefore, in the production method according to the present invention, the first film is a laminate in which the polarizer is laminated on a base film, and the liquid crystal is formed on the side of the base film with the polarizer side as a bonding surface. Preferably, an object is applied. According to such a configuration, by using the side surface of the polarizer as a bonding surface and applying a liquid material having a viscosity of 1 to 10000 cP on the side surface of the base film using a gravure roll coating method, the boss existing on this surface is applied. Foreign substances such as dust and dirt can be further removed while effectively removing acids and potassium iodide. As a result, even when a high pressing force such as a nip roll is applied to the polarizer in the bonding step of the transparent protective film and the polarizer, the occurrence of surface scratches on the polarizer is prevented and appearance defects are prevented. It can be effectively prevented.

  The present invention also relates to an optical film manufactured by any one of the manufacturing methods described above, and further to an image display device using the optical film described above.

  In the method for manufacturing an optical film according to the present invention, foreign matter existing on the opposite side of the bonding surface of each of the two films to be bonded can be efficiently removed, so that appearance defects caused by the foreign matter can be prevented. Can be manufactured. Therefore, the manufacturing method of the optical film according to the present invention is particularly problematic in appearance defects caused by foreign matter, an optical film having a thin adhesive layer, and further an optical film having a small total thickness, especially a thin polarizing film. This is particularly effective as a manufacturing method.

It is an example of the schematic diagram of the manufacturing method of the optical film which concerns on this invention. FIG. 1 is an example of a schematic view of a gravure roll coating method which is a post-metering coating method used in the present invention.

  Hereinafter, a method for producing an optical film according to the present invention will be described with reference to the drawings.

  The method for producing an optical film according to the present invention is characterized in that before laminating the first film and the second film, the first film has a side opposite to the laminating surface with the second film, and the first film has a first film. A liquid material having a viscosity of 1 to 10000 cP is applied to at least one surface of the opposite side of the bonding surface with the above using a gravure roll coating method.

  FIG. 1 shows an example of a schematic diagram of a method for manufacturing an optical film according to the present invention. In the present embodiment, not only the first coating step X but also the second coating step Y is performed as a gravure as a post-metering coating method. The example which applied the adhesive composition to both the bonding surface of the 1st film and the bonding surface of the 2nd film using the gravure roll coating system using a roll is shown.

  In the first coating step X, the liquid material applied to the opposite side of the bonding surface of the first film 1 using the gravure roll coating method 10A removes foreign substances present on the bonding surfaces of the two films to be bonded. For efficient removal, a material having a viscosity of 1 to 10,000 cP is used. In particular, as the liquid substance, it is preferable to use a substance containing water as a main component, specifically, at least 50% by weight or more of water, more preferably a substance containing 60% by weight or more, It is more preferable to use one containing 70% by weight or more.

  In order to increase the wettability (leveling property) of the liquid itself on the film and the evaporation rate of the liquid, it is preferable that the liquid further contains alcohol, and the liquid is mixed with 50 to 100% by weight of water. , 0 to 50% by weight of an alcohol, and particularly preferably 50 to 70% by weight of water and 30 to 50% by weight of an alcohol.

  In the present embodiment, the first film 1 is a laminate in which the polarizer 11 is laminated on the base film 12, and the liquid material is applied to the side of the base film 12 with the side of the polarizer 11 as a bonding surface. Is shown. In the present embodiment, the liquid material is not applied to the second film (transparent protective film) 2 on the side opposite to the surface to be bonded to the polarizer 11, but in the present invention, the liquid material is also applied to this surface. May be coated.

  In the embodiment shown in FIG. 1, a laminate in which a polarizer 11 is laminated on a base film 12 as a first film 1 is used, and a boric acid bath or a potassium iodide bath (in FIG. , For convenience, only one bath 20 is shown) and the like, and then the first film 1 is transported to the first coating step X. In the first coating step X, the base film 12 is designed to be located on the gravure roll side provided in the gravure roll coating system 10A, and the polarizer 11 is designed to be located on the opposite side to the gravure roll provided in the gravure roll coating system 10A. I have. In the first coating step X, the first film 1 is being conveyed rightward in FIG. 1, while the gravure roll is rotating counterclockwise. That is, the rotation direction of the gravure roll and the traveling direction of the first film are opposite to each other. In this case, while effectively removing boric acid, potassium iodide, and the like existing on the surface of the base film 12 of the first film 1 (the polarizer 11 + the base film 12), foreign substances such as dust and dirt are further removed. can do. As a result, generation of surface scratches on the first film 1, particularly on the polarizer 11, is prevented. Further, foreign matter such as dust and dirt present on the side of the base film 12 of the first film 1, The effect of scraping off gels and aggregates derived from the composition is effectively increased, and the appearance defects of the finally obtained optical film can be more effectively prevented.

  After the first coating step X and before reaching the second coating step Y, a drying step for drying and removing the liquid material may be provided as necessary. In the drying step, a drying method known to those skilled in the art can be used.

  After passing through the first coating step X, the adhesive composition 3 is applied to the first film 1 on the side of the polarizer 11 using the gravure roll coating method on the first film 1 transported to the second step Y. At this point, the gravure roll provided in the gravure coating method 10B rotates clockwise while being conveyed rightward in FIG. That is, the rotation direction of the gravure roll and the traveling direction of the first film 1 are opposite to each other. Similarly, in the relationship between the second film 2 and the gravure roll provided in the gravure coating method 10B, the rotation direction of the gravure roll and the traveling direction of the second film 2 are opposite. In this case, the effect of scraping foreign substances such as dust and dirt present on the bonding surface of the first film 1 and the bonding surface of the second film 2, as well as the effect of scraping gels and aggregates derived from the adhesive composition is effective. And the appearance defects of the finally obtained optical film can be more effectively prevented.

  In this embodiment, the example in which the adhesive composition 3 is applied to both the bonding surfaces of the first film 1 and the second film 2 is shown, but only the bonding surface of one of the films is bonded. An agent composition may be applied.

  In order to more effectively prevent appearance defects of the finally obtained optical film, the rotation speed of the gravure roll with respect to the traveling speed of the first film 1 and the second film 2 is preferably 100 to 300%. Preferably, it is 150 to 250%.

  FIG. 2 shows an example of a schematic view of a gravure roll coating method which is a post-metering coating method used in the present invention. In particular, the adhesive composition 3 is applied to the first film 1 using the gravure coating method 10B. It shows the situation. As shown in FIG. 2, when foreign matter is removed while pressing the gravure roll 4 against the first film 1, foreign matter such as dust and dirt present on the bonding surface of the first film 1, and furthermore, the foreign matter derived from the adhesive composition Gels and aggregates can be more effectively removed.

As shown in FIG. 2, the gravure coating method 10B includes at least a gravure roll 4. On the surface of the gravure roll, an uneven pattern such as a honeycomb mesh pattern, a trapezoid pattern, a lattice pattern, a pyramid pattern, or a diagonal pattern is formed. In order to increase the surface accuracy of the coated surface after the application of the adhesive composition or the pressure-sensitive adhesive composition, a honeycomb mesh pattern is preferably formed, and the cell volume is preferably 1 to 5 cm ³ / m ^2. , 2 to ³ cm ³ / m ² . Similarly, in order to increase the surface accuracy of the coated surface after the application of the adhesive composition or the pressure-sensitive adhesive composition, the number of cell lines per one inch of the roll is preferably 200 to 3000 lines / inch. The concavo-convex pattern of the gravure roll 4 has a function of applying the adhesive composition 3 to the bonding surface of the first film 1 while scraping up the adhesive composition (coating solution) 3. In the present invention, in order to prevent foreign substances from being mixed into the adhesive composition 3, a closed system in which the adhesive coating liquid is not exposed to the outside air is preferable.

  In the example shown in FIG. 2, at the time of coating, foreign substances present on the bonding surface of the first film 1, and further, gels and aggregates derived from the adhesive composition 3 are scraped off by the gravure roll 4, and the adhesive It may be moved into the container 5 containing the composition 3 and applied again to the bonding surface of the first film by the gravure roll 4. Therefore, especially when the post-metering coating method is a method in which the adhesive composition or the adhesive composition is circulated and applied, the gravure roll 4 scrapes the adhesive composition 3 as the application step of the adhesive composition 3 becomes longer. There is a concern that the amount of accumulated foreign matter and the like will increase. However, the gravure coating method 10B removes foreign substances mixed into the adhesive composition or the pressure-sensitive adhesive composition from the first film 1 and / or the second film 2 by coating, from the adhesive composition or the pressure-sensitive adhesive composition. In the case where the adhesive composition 3 is provided, the amount of foreign substances and the like present in the adhesive composition 3 to be applied is always kept from a very small amount to zero. Therefore, finally, the generation amount of foreign substances and the like on the bonding surface of the first film 1 can be extremely reduced. In the present invention, the foreign matter removing function includes a filter, a distillation apparatus, a centrifuge, and the like. When a filter is used as the foreign matter removing function, a filter 7 can be arranged, for example, on the downstream side of the pump function 8 as shown in FIG. Further, the filter 7 can be arranged on the upstream side of the pump function 8, and the number thereof is not limited. The mesh size of the filter 7 can be appropriately changed depending on the material of the first film 1 and the second film, the blending design of the adhesive composition 3, and the like, but is preferably 10 μm or less, more preferably 5 μm or less. The adhesive composition 3 may be circulated using a tank 6 or the like as shown in FIG. 2, or the adhesive composition 3 applied by the gravure roll 4 may be discarded.

  In the present invention, the same gravure coating method 10A as the gravure coating method 10B used in the first coating step X for coating the liquid material can be employed.

  After the adhesive composition 3 is applied to the bonding surface of the first film 1 and / or the bonding surface of the second film 2 in the second coating step by the coating method of the post-metering coating method shown in FIG. For example, the first film 1 and the second film 2 are bonded to each other with an adhesive composition (adhesive layer) using a nip roll 9.

  When the optical film is manufactured in a continuous line, the line speed of the first film and / or the second film depends on the curing time of the adhesive composition (or the pressure-sensitive adhesive composition), but is preferably 1 to 500 m / min. Preferably it is 5-300 m / min, more preferably 10-100 m / min. If the line speed is too low, the productivity is poor, or the first film and / or the second film is damaged too much, and an optical film that can withstand a durability test or the like cannot be produced. If the line speed is too high, the curing of the adhesive composition may be insufficient, and the desired adhesiveness may not be obtained.

  Next, an optical film manufactured by the manufacturing method according to the present invention will be described below. Such an optical film includes a laminated structure in which at least a first film and a second film are bonded via an adhesive layer or a pressure-sensitive adhesive layer formed of a cured product layer of the adhesive composition or the pressure-sensitive adhesive composition.

<Adhesive layer or pressure-sensitive adhesive layer>
The adhesive layer or the pressure-sensitive adhesive layer is not particularly limited as long as it is optically transparent, and various types of water-based, solvent-based, hot-melt, and radical-curable types are used. When producing a transparent conductive laminate or a polarizing film as the optical film, a transparent curable adhesive layer is suitable.

<Transparent curable adhesive layer>
For forming the transparent curable adhesive layer, for example, a radical curable adhesive is suitably used as the adhesive composition. Examples of the radical curing type adhesive include an active energy ray curing type adhesive such as an electron beam curing type and an ultraviolet ray curing type. In particular, an active energy ray-curable adhesive which can be cured in a short time is preferable, and an ultraviolet-curable adhesive which can be cured with a low energy is more preferable.

  Ultraviolet curing adhesives can be broadly classified into radical polymerization curing adhesives and cationic polymerization adhesives. In addition, a radical polymerization-curable adhesive can be used as a thermosetting adhesive.

  Examples of the curable component of the radical polymerization-curable adhesive include a compound having a (meth) acryloyl group and a compound having a vinyl group. Any of these curable components may be monofunctional or bifunctional or more. These curable components can be used alone or in combination of two or more. As these curable components, for example, compounds having a (meth) acryloyl group are suitable.

  Specific examples of the compound having a (meth) acryloyl group include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, 2-methyl-2-nitro Propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, s-butyl (meth) acrylate, t-butyl (meth) acrylate, n-pentyl (meth) acrylate, t-pentyl (meth) Acrylate, 3-pentyl (meth) acrylate, 2,2-dimethylbutyl (meth) acrylate, n-hexyl (meth) acrylate, cetyl (meth) acrylate, n-octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate , 4-methyl-2- Ropirupenchiru (meth) acrylate, n- octadecyl (meth) (meth) acrylic acid (1-20 carbon atoms) such as acrylates alkyl esters.

  Examples of the compound having a (meth) acryloyl group include, for example, cycloalkyl (meth) acrylate (eg, cyclohexyl (meth) acrylate, cyclopentyl (meth) acrylate), aralkyl (meth) acrylate (eg, benzyl (meth) Acrylate), polycyclic (meth) acrylate (for example, 2-isobornyl (meth) acrylate, 2-norbornylmethyl (meth) acrylate, 5-norbornen-2-yl-methyl (meth) acrylate, 3-methyl -2-norbornylmethyl (meth) acrylate, etc.), hydroxyl group-containing (meth) acrylates (eg, hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2,3-dihydroxypropylmethyl Butyl (meth) methacrylate, etc.), alkoxy or phenoxy group-containing (meth) acrylates (2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, 2-methoxymethoxyethyl (meth) acrylate, 3-methoxybutyl (meth) acrylate, ethyl carbitol (meth) acrylate, phenoxyethyl (meth) acrylate, etc., epoxy group-containing (meth) acrylates (e.g., glycidyl (meth) acrylate, etc.), halogen-containing ( (Meth) acrylic acid esters (for example, 2,2,2-trifluoroethyl (meth) acrylate, 2,2,2-trifluoroethylethyl (meth) acrylate, tetrafluoropropyl (meth) acrylate, hexafluoropro Le (meth) acrylate, octafluoropentyl (meth) acrylate, heptadecafluorodecyl (meth) acrylate), alkylaminoalkyl (meth) acrylates (e.g., dimethylaminoethyl (meth) acrylate, etc.) and the like.

  Examples of the compound having a (meth) acryloyl group other than the above include amide group-containing monomers such as hydroxyethylacrylamide, N-methylolacrylamide, N-methoxymethylacrylamide, N-ethoxymethylacrylamide, and (meth) acrylamide. Can be Further, a nitrogen-containing monomer such as acryloyl morpholine may be used.

  Further, as the curable component of the radical polymerization-curable adhesive, a compound having a plurality of polymerizable double bonds such as a (meth) acryloyl group and a vinyl group can be exemplified. It can also be mixed with the adhesive component. Examples of the curable component to be the crosslinking component include tripropylene glycol diacrylate, 1,9-nonanediol diacrylate, tricyclodecane dimethanol diacrylate, cyclic trimethylolpropane formal acrylate, dioxane glycol diacrylate, and EO. Modified diglycerin tetraacrylate, Aronix M-220 (Toagosei Co., Ltd.), light acrylate 1,9ND-A (Kyoeisha Chemical Co., Ltd.), light acrylate DGE-4A (Kyoeisha Chemical Co., Ltd.), light acrylate DCP-A (Kyoeisha Co., Ltd.) Chemical Co., Ltd.), SR-531 (Sartomer), CD-536 (Sartomer) and the like. If necessary, various epoxy (meth) acrylates, urethane (meth) acrylates, polyester (meth) acrylates, and various (meth) acrylate monomers can be used.

  The radical polymerization-curable adhesive contains the curable component. In addition to the component, a radical polymerization initiator is added according to the type of curing. When the adhesive is used in an electron beam-curable type, it is not particularly necessary to include a radical polymerization initiator in the adhesive. Agent is used. The amount of the radical polymerization initiator to be used is generally about 0.1 to 10 parts by weight, preferably 0.5 to 3 parts by weight, per 100 parts by weight of the curable component. If necessary, a photosensitizer that increases the curing speed and sensitivity with an electron beam represented by a carbonyl compound or the like can be added to the radical polymerization-curable adhesive. The amount of the photosensitizer to be used is generally about 0.001 to 10 parts by weight, preferably 0.01 to 3 parts by weight, per 100 parts by weight of the curable component.

  Examples of the curable component of the cationic polymerization curable adhesive include a compound having an epoxy group or an oxetanyl group. The compound having an epoxy group is not particularly limited as long as it has at least two epoxy groups in a molecule, and various curable epoxy compounds generally known can be used. Preferred epoxy compounds include compounds having at least two epoxy groups and at least one aromatic ring in the molecule, and compounds having at least two epoxy groups in the molecule, at least one of which has an alicyclic ring. A compound formed between two adjacent carbon atoms constituting the compound is exemplified.

  For forming the transparent curable adhesive layer, examples of aqueous curable adhesives include, for example, vinyl polymer, gelatin, vinyl latex, polyurethane, isocyanate, polyester, and epoxy. . The adhesive layer made of such an aqueous adhesive can be formed as a coating and drying layer of an aqueous solution, but when preparing the aqueous solution, a catalyst such as a crosslinking agent and other additives and an acid may be used, if necessary. Can be blended.

  As the water-based adhesive, an adhesive containing a vinyl polymer is preferably used, and as the vinyl polymer, a polyvinyl alcohol-based resin is preferable. As the polyvinyl alcohol-based resin, an adhesive containing a polyvinyl alcohol-based resin having an acetoacetyl group is more preferable from the viewpoint of improving durability. As the crosslinking agent that can be blended with the polyvinyl alcohol-based resin, a compound having at least two functional groups reactive with the polyvinyl alcohol-based resin can be preferably used. For example, boric acid and borax, carboxylic acid compounds, alkyl diamines; isocyanates; epoxies; monoaldehydes; dialdehydes; amino-formaldehyde resins; and salts of divalent metals or trivalent metals and oxides thereof. Is mentioned.

  The adhesive forming the curable adhesive layer may contain an additive as needed, if necessary. Examples of additives include silane coupling agents, coupling agents such as titanium coupling agents, adhesion promoters represented by ethylene oxide, additives for improving wettability with transparent films, acryloxy-based compounds and hydrocarbon-based compounds. (Natural and synthetic resins), additives that improve mechanical strength and processability, ultraviolet absorbers, anti-aging agents, dyes, processing aids, ion trapping agents, antioxidants, tackifiers, Fillers (other than metal compound fillers), plasticizers, leveling agents, foam inhibitors, stabilizers such as antistatic cracks, heat stabilizers, hydrolysis stabilizers, and the like are included.

  Further, it is preferable that the thickness of the transparent curable adhesive layer is 0.01 to 10 μm. More preferably, it is 0.1 to 5 μm, further preferably 0.3 to 4 μm. In addition, since the height of the appearance defect caused by foreign matter or bubbles between the respective film layers is generally several μm (about 2 to 5 μm), if the thickness of the adhesive layer is 2 μm or less, the problem of the appearance defect becomes large. Become. However, the method for producing an optical film according to the present invention is particularly useful as a method for producing an optical film in which the thickness of the adhesive layer is 2 μm or less, since appearance defects can be prevented.

  The pressure-sensitive adhesive layer is formed from a pressure-sensitive adhesive. As the pressure-sensitive adhesive, various pressure-sensitive adhesives can be used, for example, a rubber-based pressure-sensitive adhesive, an acrylic-based pressure-sensitive adhesive, a silicone-based pressure-sensitive adhesive, a urethane-based pressure-sensitive adhesive, a vinylalkyl ether-based pressure-sensitive adhesive, a polyvinylpyrrolidone-based pressure-sensitive adhesive, An acrylamide-based pressure-sensitive adhesive, a cellulose-based pressure-sensitive adhesive and the like can be mentioned. An adhesive base polymer is selected according to the type of the adhesive. Among the above-mentioned pressure-sensitive adhesives, acrylic pressure-sensitive adhesives are preferably used because they are excellent in optical transparency, show appropriate wettability, cohesiveness and adhesive pressure-sensitive adhesive properties, and are excellent in weather resistance and heat resistance. You.

  The radical polymerization-curable adhesive can be used in an electron beam-curable or ultraviolet-curable mode.

  In the electron beam curing type, any appropriate condition can be adopted as the irradiation condition of the electron beam as long as the radical polymerization curing type adhesive composition can be cured. For example, the electron beam irradiation preferably has an acceleration voltage of 5 kV to 300 kV, and more preferably 10 kV to 250 kV. If the accelerating voltage is less than 5 kV, the electron beam may not reach the adhesive and curing may be insufficient. If the accelerating voltage exceeds 300 kV, the penetrating power through the sample is too strong, and the transparent protective film and the polarizer are damaged. May be given. The irradiation dose is 5 to 100 kGy, more preferably 10 to 75 kGy. If the irradiation dose is less than 5 kGy, the adhesive will be insufficiently cured, and if it exceeds 100 kGy, the transparent protective film and the polarizer will be damaged, resulting in a decrease in mechanical strength and yellowing, and obtaining predetermined optical characteristics. Can not.

  The electron beam irradiation is usually performed in an inert gas, but may be performed in the atmosphere or under a condition in which oxygen is slightly introduced, if necessary. Depending on the material of the transparent protective film, by appropriately introducing oxygen, it is possible to prevent oxygen from being applied to the transparent protective film surface to which the electron beam first strikes, thereby preventing damage to the transparent protective film and preventing the adhesive from being applied only to the adhesive. An electron beam can be efficiently irradiated.

  On the other hand, in the case of using a transparent protective film provided with an ultraviolet absorbing ability in the ultraviolet curing type, the light having a wavelength shorter than 380 nm is absorbed by the active energy ray-curable adhesive composition because it absorbs light having a wavelength shorter than about 380 nm. Since it does not reach, it does not contribute to the polymerization reaction. Further, light having a wavelength shorter than 380 nm absorbed by the transparent protective film is converted into heat, and the transparent protective film itself generates heat, which causes defects such as curling and wrinkling of the polarizing film. Therefore, when employing the ultraviolet curing type in the present invention, it is preferable to use a device that does not emit light having a wavelength shorter than 380 nm as the ultraviolet generator, and more specifically, the integrated illuminance and wavelength in the wavelength range of 380 to 440 nm. The ratio to the integrated illuminance in the range of 250 to 370 nm is preferably from 100: 0 to 100: 50, and more preferably from 100: 0 to 100: 40. As the ultraviolet rays satisfying such a relationship of the integrated illuminance, a gallium-filled metal halide lamp and an LED light source emitting light in a wavelength range of 380 to 440 nm are preferable. Alternatively, use a low-pressure mercury lamp, medium-pressure mercury lamp, high-pressure mercury lamp, ultra-high-pressure mercury lamp, incandescent lamp, xenon lamp, halogen lamp, carbon arc lamp, metal halide lamp, fluorescent lamp, tungsten lamp, gallium lamp, excimer laser or sunlight as a light source, The light having a wavelength shorter than 380 nm can be cut off using a bandpass filter.

  The first film and / or the second film can be used without particular limitation as long as they are transparent optical films. As described above, as the thickness of the adhesive layer (or the pressure-sensitive adhesive layer) and further the total thickness of the optical film are larger, foreign substances are less likely to be visually recognized, and appearance defects are less likely to be regarded as problems. On the other hand, as the thickness of the adhesive layer (or the pressure-sensitive adhesive layer) is thinner, and further, as the total thickness of the optical film is thinner, the foreign matter is more easily recognized, and as a result, the appearance defect becomes a problem. Often. However, in the method for producing an optical film according to the present invention, an optical film having an extremely low generation rate of foreign substances in an adhesive layer (or a pressure-sensitive adhesive layer) can be produced. The manufacturing method according to the present invention is particularly useful when a method for manufacturing a particularly large polarizing film, specifically, when the first film is a transparent protective film and the second film is a polarizer. In the production method according to the present invention, even when a thin polarizing film is produced, as in the case where the thickness of the polarizer is 10 μm or less, the presence of foreign matter or foreign matter in the adhesive layer (or pressure-sensitive adhesive layer) This is preferable because a thin polarizing film in which appearance defects caused by bubbles are prevented can be produced.

  The first film and / or the second film may be subjected to a surface modification treatment before applying the active energy ray-curable adhesive composition. Specific treatments include corona treatment, plasma treatment, and saponification treatment.

  In the method for producing an optical film according to the present invention, the first film and the second film are preferably bonded to each other via an adhesive layer formed by a cured product layer of the radical polymerization-curable adhesive composition. However, an easy adhesion layer can be provided between the first film and the second film. The easy-adhesion layer can be formed of, for example, various resins having a polyester skeleton, polyether skeleton, polycarbonate skeleton, polyurethane skeleton, silicone, polyamide skeleton, polyimide skeleton, polyvinyl alcohol skeleton, and the like. These polymer resins can be used alone or in combination of two or more. Further, other additives may be added for forming the easy-adhesion layer. Specifically, stabilizers such as tackifiers, ultraviolet absorbers, antioxidants, and heat stabilizers may be used.

  The easy-adhesion layer is formed by applying and drying a material for forming an easy-adhesion layer on a film by a known technique. The material for forming the easily adhesive layer is usually prepared as a solution diluted to an appropriate concentration in consideration of the thickness after drying, the smoothness of application, and the like. The thickness of the easy-adhesion layer after drying is preferably 0.01 to 5 μm, more preferably 0.02 to 2 μm, and still more preferably 0.05 to 1 μm. In addition, although a plurality of easy-adhesion layers can be provided, it is preferable that the total thickness of the easy-adhesion layers be in the above range also in this case.

  Hereinafter, a polarizing film will be described as an example of the optical film. For example, in FIG. 1, the polarizing film including the laminated structure in which the first film and the second film are bonded is a first film 1 which is a laminate of the polarizer 11 and the base film 12, and a transparent protective film. It can be manufactured by laminating a certain second film 1 via an adhesive layer composed of a cured product layer of the adhesive composition.

  In the manufacturing method according to the present invention, since an optical film in which the generation of foreign matter in the adhesive layer can be effectively prevented can be manufactured, the appearance defect caused by the foreign matter can be a serious problem, particularly, an optical film having a small thickness. Suitable for manufacturing. Therefore, the thickness of the first film and the second film (in the present embodiment, the first film is a laminate of a polarizer and a base film, and the second film is a transparent protective film) is preferably 60 μm or less, More preferably, it is 40 μm or less. If the total thickness of the polarizing film is 100 μm or less, the thickness is so thin that appearance defects caused by foreign matters in the adhesive layer often become a problem. However, in the production method according to the present invention, since it is possible to effectively produce an optical film in which the generation of foreign matter in the adhesive layer is prevented, especially when producing a thin polarizing film having a total thickness of 100 μm or less, Is suitable for producing a thin polarizing film having a total thickness of 50 μm or less. In the present invention, when a thin polarizing film is manufactured, particularly when a thin polarizing film including a thin polarizer having a thickness of 10 μm or less is manufactured, appearance defects can be effectively prevented.

  The polarizer is not particularly limited, and various types can be used. Examples of the polarizer include, for example, a hydrophilic polymer film such as a polyvinyl alcohol-based film, a partially formalized polyvinyl alcohol-based film, an ethylene-vinyl acetate copolymer-based partially saponified film, and two colors such as iodine and a dichroic dye. And uniaxially stretched by adsorbing a hydrophilic material, or a polyene-based oriented film such as a dehydrated product of polyvinyl alcohol or a dehydrochlorinated product of polyvinyl chloride. Among these, a polarizer composed of a polyvinyl alcohol-based film and a dichroic substance such as iodine is preferable. The thickness of these polarizers is not particularly limited, but is generally about 80 μm or less.

  A polarizer obtained by dyeing a polyvinyl alcohol-based film with iodine and uniaxially stretching can be produced by, for example, dyeing polyvinyl alcohol by immersing it in an aqueous solution of iodine and stretching the film to 3 to 7 times its original length. If necessary, it can be immersed in an aqueous solution of boric acid or potassium iodide. Further, if necessary, the polyvinyl alcohol-based film may be immersed in water and washed with water before dyeing. By washing the polyvinyl alcohol-based film with water, dirt on the surface of the polyvinyl alcohol-based film and an anti-blocking agent can be washed, and by swelling the polyvinyl alcohol-based film, the effect of preventing unevenness such as uneven dyeing can be obtained. is there. Stretching may be performed after dyeing with iodine, may be performed while dyeing, or may be dyed with iodine after stretching. Stretching can be performed in an aqueous solution of boric acid or potassium iodide or in a water bath.

  As the polarizer, a thin polarizer having a thickness of 10 μm or less can be used. From the viewpoint of thinning, the thickness is preferably 1 to 7 μm. Such a thin polarizer preferably has a small thickness unevenness, is excellent in visibility, is small in dimensional change, is excellent in durability, and furthermore, is preferably thin in thickness as a polarizing film.

  Typical examples of the thin polarizer include Japanese Patent Application Laid-Open Nos. 51-069644 and 2000-338329, WO2010 / 100917, pamphlet of PCT / JP2010 / 001460, and Japanese Patent Application No. 2010-001460. The thin polarizers described in Japanese Patent Application No. 269002 and Japanese Patent Application No. 2010-263892 can be exemplified. These thin polarizers can be obtained by a manufacturing method including a step of stretching a polyvinyl alcohol-based resin (hereinafter, also referred to as a PVA-based resin) layer and a resin base material for stretching in a laminated state, and a step of dyeing. According to this manufacturing method, even if the PVA-based resin layer is thin, it can be stretched without any trouble such as breakage due to stretching because it is supported by the stretching resin base material.

  Among the thin polarizers, WO2010 / 100917, PCT / PCT, which can be stretched at a high magnification to improve the polarization performance among the production methods including a stretching step and a dyeing step in the state of a laminate. JP 2010/001460, or those obtained by a production method including a step of stretching in an aqueous boric acid solution as described in Japanese Patent Application No. 2010-269002 or Japanese Patent Application No. 2010-263892 are preferable, and particularly preferable. What is obtained by the manufacturing method including the process of auxiliary | assistant air stretching before extending | stretching in a boric acid aqueous solution as described in Japanese Patent Application No. 2010-269002 or Japanese Patent Application No. 2010-263692 is preferable.

  The thin high-performance polarizer described in the specification of PCT / JP2010 / 001460 is a thin type having a thickness of 7 μm or less made of a PVA-based resin in which a dichroic substance is oriented and formed integrally with a resin substrate. It is a high-performance polarizer having optical characteristics such that a single transmittance is 42.0% or more and a degree of polarization is 99.95% or more.

  The thin high-performance polarizer described above generates a PVA-based resin layer by coating and drying a PVA-based resin on a resin base material having a thickness of at least 20 μm, and stains the generated PVA-based resin layer with a dichroic dye solution. The PVA-based resin layer is adsorbed with a dichroic substance, and the PVA-based resin layer adsorbed with the dichroic substance is combined with the resin base material in a boric acid aqueous solution to obtain a total stretch ratio of the original length. It can be manufactured by stretching so as to be 5 times or more of the following.

  Also, a method of manufacturing a laminated film including a thin high-performance polarizer having a dichroic substance oriented, comprising a resin base material having a thickness of at least 20 μm and a PVA-based resin on one surface of the resin base material A step of producing a laminate film including a PVA-based resin layer formed by applying and drying an aqueous solution, and the laminate including a resin base material and a PVA-based resin layer formed on one surface of the resin base material A step of adsorbing the dichroic substance to the PVA-based resin layer contained in the laminate film by immersing the film in a dyeing solution containing the dichroic substance; and a step of adsorbing the dichroic substance to the PVA-based resin. Stretching the laminate film including the layer in a boric acid aqueous solution so that the total stretching ratio is at least 5 times the original length; and forming a PVA-based resin layer adsorbed with a dichroic substance on a resin substrate. Stretch together with As a result, a thickness of 7 μm or less, a single transmittance of 42.0% or more, and a degree of polarization of 99.95% or more, comprising a PVA-based resin layer in which a dichroic substance is oriented on one surface of the resin substrate. By including the step of manufacturing a laminated film in which a thin high-performance polarizer having the above optical characteristics is formed, the thin high-performance polarizer can be manufactured.

The above-mentioned Japanese Patent Application No. 2010-269002 and Japanese Patent Application No. 2010-263892 are thin polarizers which are continuous web polarizers made of a PVA-based resin in which dichroic substances are oriented, and are made of an amorphous ester. A laminate having a thickness of 10 μm or less obtained by stretching a laminate containing a PVA-based resin layer formed on a thermoplastic resin base material in a two-stage stretching step including an aerial auxiliary stretching and a boric acid in water stretching. It is. When such a thin polarizer has a single transmittance T and a polarization degree P, P> − (100.929T-42.4-1) × 100 (where T <42.3), and P ≧ 99. 0.9 (however, T ≧ 42.3).

  More specifically, the thin polarizer is formed by stretching a PVA-based resin layer formed on an amorphous ester-based thermoplastic resin substrate of a continuous web in the air at a high temperature in the air. A step of producing a product, and a step of producing a colored intermediate comprising a PVA-based resin layer in which a dichroic substance (preferably iodine or a mixture of iodine and an organic dye) is oriented by adsorbing the dichroic substance on the stretched intermediate product A thin polarizer comprising a step of producing a polarizer and a step of producing a polarizer having a thickness of 10 μm or less composed of a PVA-based resin layer in which a dichroic substance is oriented by stretching in a boric acid aqueous solution with respect to a colored intermediate product. It can be manufactured by a manufacturing method.

In this manufacturing method, the total stretching ratio of the PVA-based resin layer formed on the amorphous ester-based thermoplastic resin base material by the high-temperature stretching in air and the stretching in boric acid in water is set to be 5 times or more. desirable. The temperature of the aqueous solution of boric acid for drawing in boric acid in water can be 60 ° C. or higher. Before stretching the colored intermediate product in an aqueous boric acid solution, it is desirable to perform an insolubilization treatment on the colored intermediate product. In this case, the colored intermediate product is added to an aqueous boric acid solution having a liquid temperature not exceeding 40 ° C. Is desirably carried out by immersion. The amorphous ester-based thermoplastic resin base material is an amorphous polyethylene containing copolymerized polyethylene terephthalate obtained by copolymerizing isophthalic acid, copolymerized polyethylene terephthalate obtained by copolymerizing cyclohexanedimethanol, or another copolymerized polyethylene terephthalate. It can be terephthalate and is preferably made of a transparent resin, and its thickness can be at least seven times the thickness of the PVA-based resin layer to be formed. The stretching ratio of the high-temperature aerial stretching is preferably 3.5 times or less, and the stretching temperature of the high-temperature aerial stretching is preferably equal to or higher than the glass transition temperature of the PVA-based resin, specifically, in the range of 95 ° C to 150 ° C. When performing high-temperature stretching in the air by free-end uniaxial stretching, the total stretching ratio of the PVA-based resin layer formed on the amorphous ester-based thermoplastic resin substrate is preferably 5 times or more and 7.5 times or less. . Further, when performing high-temperature stretching in the air by fixed-end uniaxial stretching, the total stretching ratio of the PVA-based resin layer formed on the amorphous ester-based thermoplastic resin base material is 5 times or more and 8.5 times or less. Is preferred.
More specifically, a thin polarizer can be manufactured by the following method.

  A continuous web substrate of isophthalic acid copolymerized polyethylene terephthalate (amorphous PET) obtained by copolymerizing isophthalic acid at 6 mol% is prepared. The glass transition temperature of amorphous PET is 75 ° C. A laminate composed of a continuous web amorphous PET substrate and a polyvinyl alcohol (PVA) layer is prepared as follows. Incidentally, the glass transition temperature of PVA is 80 ° C.

  An amorphous PET substrate having a thickness of 200 μm and a 4 to 5% aqueous PVA solution prepared by dissolving PVA powder having a degree of polymerization of 1000 or more and a degree of saponification of 99% or more in water are prepared. Next, a PVA aqueous solution is applied to an amorphous PET substrate having a thickness of 200 μm, and dried at a temperature of 50 to 60 ° C. to obtain a laminate in which a 7 μm thick PVA layer is formed on the amorphous PET substrate. .

  The laminate including the 7 μm-thick PVA layer is manufactured through the following steps including a two-stage stretching step of an aerial auxiliary stretching and a boric acid aqueous stretching to produce a 3 μm-thick thin high-performance polarizer. In the first-stage auxiliary aerial stretching step, the laminate including the 7 μm-thick PVA layer is stretched together with the amorphous PET substrate to produce a stretched laminate including the 5 μm-thick PVA layer. Specifically, this stretched laminate is subjected to a stretching device provided in an oven set to a stretching temperature environment of 130 ° C., with a laminate including a 7 μm-thick PVA layer, so that the stretching ratio becomes 1.8 times. At the free end uniaxially. By this stretching treatment, the PVA layer included in the stretched laminate is changed into a 5 μm-thick PVA layer in which PVA molecules are oriented.

  Next, by a dyeing process, a colored laminate in which iodine is adsorbed on a 5 μm-thick PVA layer in which PVA molecules are oriented is generated. Specifically, this colored laminate is prepared by adding the stretched laminate to a dye solution containing iodine and potassium iodide at a liquid temperature of 30 ° C., and transmitting the single transmittance of the PVA layer constituting the high-performance polarizer finally produced. The iodine is adsorbed on the PVA layer contained in the stretched laminate by immersing it for an arbitrary time so that the ratio becomes 40 to 44%. In this step, the dyeing solution is adjusted to have a concentration of iodine within a range of 0.12 to 0.30% by weight and a concentration of potassium iodide within a range of 0.7 to 2.1% by weight using water as a solvent. The ratio between the concentrations of iodine and potassium iodide is 1: 7. Incidentally, potassium iodide is required to dissolve iodine in water. More specifically, the stretched laminate is immersed in a dyeing solution having an iodine concentration of 0.30% by weight and a potassium iodide concentration of 2.1% by weight for 60 seconds, so that a 5 μm-thick PVA layer in which PVA molecules are oriented is provided with iodine. To produce a colored laminate to which is adsorbed.

  Further, the colored laminate is further stretched integrally with the amorphous PET substrate by the second stage of boric acid in water stretching step to produce an optical film laminate including a PVA layer constituting a high-performance polarizer having a thickness of 3 μm. I do. Specifically, this optical film laminate is subjected to a stretching device provided in a processing device set in a boric acid aqueous solution having a liquid temperature range of 60 to 85 ° C. containing boric acid and potassium iodide, and the colored laminate is stretched. The film is uniaxially stretched at the free end so that the magnification becomes 3.3 times. More specifically, the liquid temperature of the boric acid aqueous solution is 65 ° C. It also has a boric acid content of 4 parts by weight for 100 parts by weight of water and a potassium iodide content of 5 parts by weight for 100 parts by weight of water. In this step, the colored laminate having the adjusted iodine adsorption amount is first immersed in a boric acid aqueous solution for 5 to 10 seconds. Thereafter, the colored laminate is passed as it is between a plurality of sets of rolls having different peripheral speeds, which are stretching apparatuses provided in a processing apparatus, and freely stretched to have a stretching ratio of 3.3 times in 30 to 90 seconds. Stretch uniaxially. By this stretching treatment, the PVA layer contained in the colored laminate is changed into a 3 μm-thick PVA layer in which adsorbed iodine is unidirectionally oriented as a polyiodide ion complex in one direction. This PVA layer constitutes a high-performance polarizer of the optical film laminate.

  Although not an essential step for the production of the optical film laminate, the washing step removed the optical film laminate from the boric acid aqueous solution and attached it to the surface of the 3 μm thick PVA layer formed on the amorphous PET substrate. Preferably, boric acid is washed with an aqueous solution of potassium iodide. Thereafter, the washed optical film laminate is dried by a drying process using hot air at 60 ° C. The washing step is a step for eliminating appearance defects such as boric acid precipitation.

  Similarly, it is not an essential step for the production of an optical film laminate, but an adhesive is applied to the surface of a 3 μm thick PVA layer formed on an amorphous PET substrate by a bonding and / or transfer step. Then, after laminating an 80 μm-thick triacetyl cellulose film, the amorphous PET substrate is peeled off, and the 3 μm-thick PVA layer can be transferred to the 80 μm-thick triacetyl cellulose film.

[Other steps]
The above method for producing a thin polarizer may include other steps in addition to the above steps. Other steps include, for example, an insolubilization step, a cross-linking step, a drying (adjustment of moisture content) step, and the like. Other steps can be performed at any appropriate timing. The insolubilization step is typically performed by immersing the PVA-based resin layer in an aqueous boric acid solution. By performing the insolubilization treatment, water resistance can be imparted to the PVA-based resin layer. The concentration of the boric acid aqueous solution is preferably 1 part by weight to 4 parts by weight based on 100 parts by weight of water. The liquid temperature of the insolubilizing bath (boric acid aqueous solution) is preferably from 20C to 50C. Preferably, the insolubilization step is performed after the production of the laminate and before the dyeing step or the underwater stretching step. The cross-linking step is typically performed by immersing the PVA-based resin layer in a boric acid aqueous solution. By performing the cross-linking treatment, water resistance can be imparted to the PVA-based resin layer. The concentration of the boric acid aqueous solution is preferably 1 part by weight to 4 parts by weight based on 100 parts by weight of water. When a crosslinking step is performed after the above-mentioned dyeing step, it is preferable to further mix iodide. By blending iodide, elution of iodine adsorbed on the PVA-based resin layer can be suppressed. The amount of iodide is preferably 1 to 5 parts by weight based on 100 parts by weight of water. Specific examples of iodide are as described above. The liquid temperature of the crosslinking bath (boric acid aqueous solution) is preferably from 20C to 50C. Preferably, the cross-linking step is performed before the second boric acid aqueous stretching step. In a preferred embodiment, the dyeing step, the crosslinking step, and the second drawing step in boric acid in water are performed in this order.

  As a material for forming the transparent protective film provided on one or both surfaces of the polarizer, a material having excellent transparency, mechanical strength, heat stability, moisture barrier properties, isotropy, and the like is preferable. For example, polyester polymers such as polyethylene terephthalate and polyethylene naphthalate; cellulose polymers such as diacetyl cellulose and triacetyl cellulose; acrylic polymers such as polymethyl methacrylate; styrene such as polystyrene and acrylonitrile-styrene copolymer (AS resin) Polymers, polycarbonate polymers, and the like. In addition, polyethylene, polypropylene, polyolefin having a cyclo- or norbornene structure, polyolefin polymers such as ethylene-propylene copolymer, vinyl chloride polymers, amide polymers such as nylon and aromatic polyamide, imide polymers, and sulfone polymers , Polyether sulfone polymer, polyether ether ketone polymer, polyphenylene sulfide polymer, vinyl alcohol polymer, vinylidene chloride polymer, vinyl butyral polymer, arylate polymer, polyoxymethylene polymer, epoxy polymer, or the above Blends of polymers and the like are also mentioned as examples of the polymer forming the transparent protective film. The transparent protective film may contain one or more optional appropriate additives. Examples of the additives include an ultraviolet absorber, an antioxidant, a lubricant, a plasticizer, a release agent, a coloring inhibitor, a flame retardant, a nucleating agent, an antistatic agent, a pigment, and a coloring agent. The content of the thermoplastic resin in the transparent protective film is preferably 50 to 100% by weight, more preferably 50 to 99% by weight, further preferably 60 to 98% by weight, and particularly preferably 70 to 97% by weight. . When the content of the thermoplastic resin in the transparent protective film is 50% by weight or less, the high transparency inherent to the thermoplastic resin may not be sufficiently exhibited.

  Examples of the transparent protective film include polymer films described in JP-A-2001-343529 (WO 01/37007), for example, (A) a thermoplastic resin having a substituted and / or unsubstituted imide group in a side chain; B) A resin composition containing a thermoplastic resin having a substituted and / or unsubstituted phenyl and a nitrile group in a side chain. A specific example is a film of a resin composition containing an alternating copolymer of isobutylene and N-methylmaleimide and an acrylonitrile-styrene copolymer. As the film, a film composed of a mixed extruded product of a resin composition or the like can be used. These films have a small retardation and a small photoelastic coefficient, so that problems such as unevenness due to distortion of the polarizing film can be eliminated, and the moisture permeability is small, so that they are excellent in humidification durability.

  Although the thickness of the transparent protective film can be determined as appropriate, it is generally about 1 to 500 μm from the viewpoint of workability such as strength and handleability and thin layer property. In particular, 20 to 80 μm is preferable, and 30 to 60 μm is more preferable.

  When a transparent protective film is provided on both sides of the polarizer, a transparent protective film made of the same polymer material may be used on the front and back sides, or a transparent protective film made of a different polymer material may be used.

  A functional layer such as a hard coat layer, an anti-reflection layer, an anti-sticking layer, a diffusion layer or an anti-glare layer can be provided on the surface of the transparent protective film on which the polarizer is not adhered. The functional layers such as the hard coat layer, the antireflection layer, the antisticking layer, the diffusion layer and the antiglare layer can be provided on the transparent protective film itself, or separately provided separately from the transparent protective film. You can also.

  The polarizing film of the present invention can be used as an optical film laminated with another optical layer in practical use. The optical layer is not particularly limited. For example, it is used for forming a liquid crystal display device such as a reflection plate, a semi-transmission plate, a retardation plate (including a wavelength plate such as や or や), a viewing angle compensation film, and the like. One or more optical layers that may be used may be used. In particular, a reflective polarizing film or a transflective polarizing film in which a polarizing plate or a transflective reflecting plate is further laminated on the polarizing film of the present invention, an elliptically polarizing film or a circularly polarized light in which a retardation plate is further laminated on a polarizing film A wide viewing angle polarizing film in which a viewing angle compensation film is further laminated on a film or a polarizing film, or a polarizing film in which a brightness enhancement film is further laminated on a polarizing film is preferable.

  An optical film obtained by laminating the above-mentioned optical layer on a polarizing film can also be formed by a method of sequentially laminating the optical film in a manufacturing process of a liquid crystal display device or the like. It is excellent in stability, assembling work, and the like, and has an advantage that a manufacturing process of a liquid crystal display device or the like can be improved. For the lamination, an appropriate adhesive means such as a pressure-sensitive adhesive layer can be used. In bonding the above-mentioned polarizing film and other optical films, their optical axes can be arranged at an appropriate angle depending on the intended retardation characteristics and the like.

  The above-mentioned polarizing film or an optical film in which at least one polarizing film is laminated can be provided with an adhesive layer for bonding to another member such as a liquid crystal cell. The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is not particularly limited. For example, an acrylic polymer, a silicone-based polymer, a polyester, a polyurethane, a polyamide, a polyether, and a polymer having a fluorine-based or rubber-based polymer as a base polymer may be appropriately used. Can be selected and used. In particular, an acrylic adhesive having excellent optical transparency, exhibiting appropriate wettability, cohesiveness and adhesive adhesive properties, and having excellent weather resistance and heat resistance can be preferably used.

  The pressure-sensitive adhesive layer may be provided on one side or both sides of a polarizing film or an optical film as a superimposed layer of different compositions or types. When provided on both surfaces, the pressure-sensitive adhesive layers may have different compositions, types, and thicknesses on the front and back of the polarizing film or the optical film. The thickness of the pressure-sensitive adhesive layer can be appropriately determined depending on the purpose of use, adhesive strength, and the like, and is generally 1 to 500 μm, preferably 1 to 200 μm, and particularly preferably 1 to 100 μm.

  A separator is temporarily attached to the exposed surface of the pressure-sensitive adhesive layer for the purpose of preventing contamination and the like until it is practically used, and is covered. Accordingly, it is possible to prevent the pressure-sensitive adhesive layer from coming into contact with the adhesive layer in a usual handling state. Except for the above thickness conditions, for example, a suitable thin sheet such as a plastic film, a rubber sheet, paper, cloth, nonwoven fabric, a net, a foamed sheet or a metal foil, or a laminate thereof may be used as a separator, if necessary, using a silicone-based or long-sheet. Appropriate conventional ones, such as those coated with an appropriate release agent such as a chain alkyl type, fluorine type or molybdenum sulfide, may be used.

  The polarizing film or optical film of the present invention can be preferably used for forming various devices such as a liquid crystal display device. The formation of the liquid crystal display device can be performed according to a conventional method. That is, a liquid crystal display device is generally formed by appropriately assembling components such as a liquid crystal cell and a polarizing film or an optical film and, if necessary, an illumination system and incorporating a drive circuit. There is no particular limitation except that a polarizing film or an optical film according to the present invention is used, and conventional methods can be followed. As for the liquid crystal cell, any type such as TN type, STN type and π type can be used.

  An appropriate liquid crystal display device such as a liquid crystal display device in which a polarizing film or an optical film is disposed on one or both sides of a liquid crystal cell, or a lighting system using a backlight or a reflector can be formed. In that case, the polarizing film or the optical film according to the present invention can be installed on one side or both sides of the liquid crystal cell. When a polarizing film or an optical film is provided on both sides, they may be the same or different. Further, in forming the liquid crystal display device, for example, appropriate components such as a diffusion plate, an anti-glare layer, an anti-reflection film, a protection plate, a prism array, a lens array sheet, a light diffusion plate, and a backlight are placed at an appropriate position in one layer or Two or more layers can be arranged.

  Hereinafter, examples of the present invention will be described, but embodiments of the present invention are not limited thereto. "Parts by weight" in the composition means the number of parts when the total amount of the composition is 100 parts by weight.

(1) Adjustment of adhesive composition <Adjustment of active energy ray-curable adhesive composition>
HEAA (hydroxyethyl acrylamide) [produced by Kojin Co., Ltd.] 38.5 parts by weight, Aronix M-220 (tripropylene glycol diacrylate) [produced by Toagosei Co., Ltd.] 20.0 parts by weight, ACMO (acryloylmorpholine) [Kojinsha Co., Ltd.] 38.5 parts by weight, KAYACURE DETX-S (diethylthioxanthone) [manufactured by Nippon Kayaku Co., Ltd.] 1.5 parts by weight, IRGACURE907 (2-methyl-1- (4-methylthiophenyl) -2-morpholinopropane- 1-one) [manufactured by BASF] 1.5 parts by weight were mixed and stirred at 50 ° C. for 1 hour to obtain an active energy ray-curable adhesive.

(2) Production of Thin Polarizer In order to produce a thin polarizer, first, a laminate in which a 24 μm-thick PVA layer was formed on an amorphous PET base film was stretched and laminated by aerial auxiliary stretching at a stretching temperature of 130 ° C. Then, the stretched laminate is dyed to produce a colored laminate, and the colored laminate is stretched in water in boric acid at a stretching temperature of 65 ° C. so that the stretched laminate becomes amorphous so that the total stretch ratio becomes 5.94 times. An optical film laminate including a 10 μm thick PVA layer that was integrally stretched with a conductive PET substrate was produced. By such two-stage stretching, the PVA molecules of the PVA layer formed on the amorphous PET base film are highly oriented, and the iodine adsorbed by the dyeing is oriented in one direction as a polyiodide ion complex. An optical film laminate (first film (total thickness: 40 μm)) including a PVA layer having a thickness of 5 μm and constituting the thin polarizer thus obtained was able to be produced.

  As the second film, a transparent protective film (40 μm in thickness) made of a (meth) acrylic resin having a lactone ring structure was used.

Example 1
In the lines shown in FIGS. 1 and 2, a gravure roll coating system 10A including a gravure roll 4 (both MCD coater (manufactured by Fuji Machinery Co., Ltd.) (cell shape: honeycomb mesh pattern, number of gravure roll cell lines: 1000 / inch, A liquid material is applied to the side of the PET base film 12 of the first film 1, which is a laminate of the polarizer 11 and the PET base film 12, using a rotation speed ratio of 140%). Foreign matter, air bubbles, etc. existing on the side surface of the film 12 were removed, and then the adhesive composition 3 was applied to the side surface of the polarizer 11 of the first film and the bonding surface of the second film using a gravure roll coating method 10B. The adhesive composition 3 was applied to remove the foreign matter and air bubbles to produce a polarizing film. Was applied to the first film and the second film so that 1 [mu] m. The gravure roll coating method 10A and 10B, were used with the foreign matter removing function shown in FIG. 2 (foreign matter removing method using a filter).

<Active energy rays>
After passing through the line shown in FIG. 1, ultraviolet (gallium-filled metal halide lamp) irradiating apparatus is used as an active energy ray: Fusion UV Systems, Inc. Light HAMMER10 bulb: V valve Peak illuminance: 1600 mW / cm ² , integrated irradiation amount The adhesive composition 3 was cured using 1000 / mJ / cm ² (wavelength 380 to 440 nm) to produce an optical film. In addition, the illuminance of ultraviolet rays was measured using a Sola-Check system manufactured by Solatell.

Examples 2 to 5, Comparative Examples 1 to 3
An optical film was manufactured in the same manner as in Example 1, except that the type of the film for performing the first coating step, the type of the coating method, the viscosity of the liquid material, and the composition were changed to those shown in Table 1. In the bar coater coating method and the air knife coating method, commercially available coating devices were used.

<Counting method for appearance defects due to foreign matter in adhesive layer> The number of appearance defects (from foreign matter and (laminated) bubbles) in the adhesive layer of the polarizing film was determined by visual inspection and reflection inspection using an automatic inspection device. The number of appearance defects (number / m ² ) was counted. Table 1 shows the results.

<In-plane surface water contact angle>
The in-plane surface water contact angle was measured at 10 equally spaced points in the film width direction (total width 1500 mm) using DM-701 manufactured by Kyowa Interface Science Co., Ltd. The smaller the number of appearance defects present on the measurement surface, the smaller the variation in water contact angle. Table 1 shows the results.

<In-plane surface scratches>
By visual inspection and reflection inspection using an automatic inspection device, the number of film surface scratches (lines / m ² ) caused by foreign matter was counted. Table 1 shows the results.

<In-plane film crack>
By a visual inspection and a reflection inspection using an automatic inspection device, the presence or absence of an in-plane film crack caused by a foreign substance was observed. Table 1 shows the results.

Claims (8)

A method for producing a polarizing film including a laminated structure in which at least a first film and a second film are bonded via an adhesive layer or a pressure-sensitive adhesive layer formed of a cured product layer of the adhesive composition or the pressure-sensitive adhesive composition. hand,
The first film is a laminate in which a polarizer having a thickness of 10 μm or less is laminated on a base film, and the second film is a transparent protective film,
Before bonding the first film and the second film, the side surface of the polarizer is used as a bonding surface, and the viscosity is 1 to 10000 cP using a gravure roll coating method using a gravure roll on the side surface of the base film. 1. A method for producing a polarizing film, comprising a first application step of applying a liquid material to remove foreign matter. A second coating step of removing foreign matter and / or air bubbles by applying the adhesive composition or the pressure-sensitive adhesive composition to a bonding surface of at least one film using a post-metering coating method. Item 4. The method for producing a polarizing film according to Item 1. The method for producing a polarizing film according to claim 1 or 2, wherein the liquid material contains at least 50% by weight or more of water. The method for producing a polarizing film according to any one of claims 1 to 3, wherein the liquid material further contains an alcohol. The post-metering coating method is a method in which the adhesive composition or the adhesive composition is circulated and applied, and the adhesive composition or the adhesive composition is applied from the first film and / or the second film by application. The method for producing a polarizing film according to claim 2 , further comprising a foreign matter removing function of removing foreign matter mixed into the adhesive composition or the pressure-sensitive adhesive composition. The method for manufacturing a polarizing film according to any one of claims 1 to 5, wherein a rotation direction of the gravure roll is opposite to a traveling direction of the first film and the second film. The method for producing a polarizing film according to any one of claims 1 to 6, wherein the pattern formed on the surface of the gravure roll is a honeycomb mesh pattern. The method for producing a polarizing film according to any one of claims 1 to 7, wherein a rotation speed ratio of the gravure roll to a traveling speed of the first film and the second film is 100 to 300%.

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