JP5446933B2 - Manufacturing method of polarizing plate - Google Patents

Description

  The present invention relates to a method for producing a polarizing plate in which a polypropylene resin film is bonded to one side of a polarizing film made of a polyvinyl alcohol resin, and a stretched transparent resin film is bonded to the other side of the polarizing film. is there.

  The polarizing plate is useful as a constituent member of a liquid crystal display device, and the demand for the polarizing plate is rapidly increasing with the spread of the liquid crystal display device. With the application of a liquid crystal display device to a large-sized television or the like, the polarizing plate is also required to be thinner and cheaper while maintaining or improving its performance.

  Traditionally, a polarizing plate has a structure in which a transparent protective film is bonded to at least one side, usually both sides, of a polarizing film made of a polyvinyl alcohol resin on which a dichroic dye is adsorbed and oriented. Conventionally, a film of a cellulose acetate resin typified by triacetyl cellulose has been used as a protective film for a polarizing plate, and its thickness is usually about 40 to 120 μm. For bonding such a cellulose acetate resin film to a polarizing film, an adhesive composed of an aqueous solution of a polyvinyl alcohol resin is often used. However, when a polarizing film made of polyvinyl alcohol resin is laminated with a protective film made of cellulose acetate resin via an adhesive made of an aqueous solution of polyvinyl alcohol resin, the polarizing plate is used for a long time under wet heat conditions. Further, there are problems that the polarization performance is deteriorated and the protective film is peeled off from the polarizing film.

  Therefore, there is an attempt to configure at least one of the protective films bonded to both surfaces of the polarizing film with a resin other than the cellulose acetate resin. For example, in Japanese Patent Laid-Open No. 8-43812 (Patent Document 1), in a polarizing plate in which a protective film is laminated on both surfaces of a polarizing film, at least one of the protective films is a thermoplastic having a retardation film function. It is described that it is composed of a norbornene resin. Japanese Patent Laid-Open No. 2002-174729 (Patent Document 2) includes an amorphous polyolefin resin on one surface of a polarizing film made of a polyvinyl alcohol resin on which iodine or a dichroic dye is adsorbed and oriented. A polarizing plate is described in which a protective film is bonded and a protective film made of a resin different from an amorphous polyolefin-based resin, such as a cellulose acetate-based resin, is bonded to the other surface of the polarizing film.

  Amorphous polyolefin resins, including norbornene resins, are also called cycloolefin resins, and give a suitable retardation value by stretching uniaxially or biaxially. Suitable for phase difference compensation. Therefore, a polarizing plate in which a cycloolefin-based resin film stretched on one side of a polarizing film is bonded, and a protective film made of a cellulose acetate-based resin such as triacetyl cellulose is bonded on the other side of the polarizing film, By bonding to the liquid crystal cell on the stretched film side, the film has an optical compensation function.

  However, when the protective film arranged on the side far from the liquid crystal cell is made of cellulose acetate resin, the thickness is required to be at least about 40 μm as described above. There was a problem in handling that the cellulose acetate resin film was torn and broken in the manufacturing process of the plate. Moreover, since the cellulose acetate resin is formed by a solvent casting method, there is a limit to the cost reduction.

  In order to reduce the thickness of the polarizing plate, JP 2009-109995 A (Patent Document 3) has a norbornene resin film laminated on one side of the polarizing film and stretched on the other side of the polarizing film. It is described that a laminated polyethylene terephthalate film is used as a polarizing plate. Since the polyethylene terephthalate film can be obtained at low cost, this polarizing plate is excellent in terms of cost. This polarizing plate is applied to a liquid crystal display device so that the polyethylene terephthalate film side is far from the liquid crystal cell. However, the polyethylene terephthalate film does not exhibit sufficient strength unless stretched, and a very large retardation is caused by stretching. The value is expressed. For this reason, even when this polyethylene terephthalate film is disposed on the side far from the liquid crystal cell, it may be colored during white display.

  On the other hand, JP 2007-334295 A (Patent Document 4) describes a polarizing plate in which a protective film is bonded to both surfaces of a polarizing film and at least one of the protective films is made of a polypropylene resin. Yes. Since a polypropylene resin film is also available at a low cost, a polarizing plate using a polypropylene resin as a protective film is advantageous in terms of cost.

  Further, studies have been made to use a non-aqueous adhesive instead of the aqueous solution of the polyvinyl alcohol resin that has been traditionally used for joining the polarizing film and the protective film. For example, in Japanese Patent Application Laid-Open No. 2004-245925 (Patent Document 5) and Japanese Patent Application Laid-Open No. 2008-257199 (Patent Document 6), an adhesive mainly composed of a specific epoxy compound is used and irradiated with active energy rays. A technique for curing an adhesive and bonding a polarizing film and a protective film has been proposed.

JP-A-8-43812 JP 2002-174729 A JP 2009-109995 A JP 2007-334295 A JP 2004-245925 A JP 2008-257199 A

  The present inventors bonded a polypropylene resin film to one side of the polarizing film via an adhesive and bonded to the other side of the polarizing film for the purpose of further reducing the price and thickness of the polarizing plate. The structure which bonds the stretched transparent resin film which has a function of retardation film through the agent was examined. In this configuration, a pressure-sensitive adhesive layer is provided outside the stretched transparent resin film, and is bonded to the liquid crystal cell via the pressure-sensitive adhesive layer. And in this case, the polypropylene-based resin film side is concave, the stretched transparent resin film side or the pressure-sensitive adhesive layer side provided thereon is convex, showing a so-called positive curl, but on the opposite side of the polypropylene-based resin film The curl amount (the height at which the corners or sides of the film float from the surface when placed on a flat surface with the convex surface down, the same applies below) is probably because the transparent resin film to be placed is stretched It has become clear that it will grow.

  If the curl amount becomes extremely large in this way, defects such as air bubbles being caught in the end portion are likely to occur when bonding to a liquid crystal cell, and this is not the case when a durability test is performed in a harsh environment. The curling is further promoted, and the end of the polarizing plate may be peeled off from the liquid crystal cell. Such entrapment of bubbles and a decrease in durability deteriorate the reliability of the liquid crystal display device.

  On the other hand, when a curl showing a so-called reverse curl occurs, the side of the polypropylene-based resin film becomes convex and the side of the stretched transparent resin film or the pressure-sensitive adhesive layer provided thereon becomes concave. In addition, problems such as entrapment of bubbles in the central portion are likely to occur, which also reduces the reliability of the liquid crystal display device.

  Therefore, as a result of further research to reduce the curl amount while holding the positive curl, when a polypropylene resin film is bonded to one side of the polarizing film and a transparent resin film stretched to the other side is bonded. By setting a difference between the tension per unit cross-sectional area of the polypropylene resin film and the tension per unit cross-section of the stretched transparent resin film, and adjusting the difference, the polypropylene resin at the time of bonding The internal stress present in the film and the stretched transparent resin film is changed, and the stress that will remain on the polypropylene resin film side and the stretched transparent resin film side after bonding is controlled to maintain the positive curl. However, the present inventors have found that the curl amount can be adjusted and have completed the present invention.

  Therefore, an object of the present invention is to provide a polarizing plate in which a polypropylene resin film is bonded to one side of a polarizing film and a transparent resin film stretched to the other side, and is industrially advantageous without causing reverse curl and large positive curl. It is to provide a method of manufacturing.

  In the present invention, a polypropylene resin film is bonded to one side of a polarizing film made of a polyvinyl alcohol resin on which a dichroic dye is adsorbed and oriented, and an adhesive is attached to the other side of the polarizing film. The transparent resin film extended | stretched through the agent is bonded and the method of manufacturing a polarizing plate is provided. This method basically includes the following steps (A) to (C).

(A) The polarizing film, the polypropylene-based resin film, and the stretched transparent resin film are respectively arranged in a certain direction via a pinch roll, and the polarizing film is the polypropylene-based resin film and the stretched transparent resin film; Raw material film transport process for transporting so as to be sandwiched between
(B) The polypropylene resin film is bonded to one side of the polarizing film, and the stretched transparent resin film is bonded to the other side of the polarizing film via a curable adhesive, and the polypropylene type With the first bonding roll that contacts the outside of the resin film and rotates in the transport direction, and the second bonding roll that contacts the outside of the stretched transparent resin film and rotates in the transport direction, A bonding step of performing the bonding while sandwiching a laminate of polypropylene resin film / polarizing film / stretched transparent resin film, and (C) after the bonding step (B), the adhesive is cured, A curing step of bonding the polypropylene resin film, the polarizing film, the stretched transparent resin film, and the polarizing film.

  In this method, the laminating step (B) includes a pre-bonding tension per unit cross-sectional area of the stretched transparent resin film with respect to a pre-bonding tension per unit cross-sectional area of the polypropylene resin film. The ratio is 1.34 or more and 1.90 or less.

  Moreover, in this method, the ratio of the pre-bonding tension per unit cross-sectional area of the polarizing film to the pre-bonding tension per unit cross-sectional area of the polypropylene-based resin film is 3 in the bonding step (B). It is preferable to carry out so that it may become 0.23 or more and 4.58 or less.

  A polypropylene-type resin film can be used for a raw material film conveyance process (A) in the state by which the protective film was laminated | stacked on the opposite side to the surface bonded by a polarizing film. In this case, the polypropylene-based resin film is subjected to the protective film bonding step for bonding the protective film, and then subjected to the raw material film transporting step (A). It is preferable that the laminate of the resin film and the protect film exhibit a so-called positive curl that is slightly convex on the polypropylene resin film side. For this purpose, the ratio of the pre-bonding tension per unit cross-sectional area of the protective film to the pre-bonding tension per unit cross-sectional area of the polypropylene resin film is 5 or more and 35 or less. It is preferable to be performed.

  The stretched transparent resin film bonded to the opposite side of the polarizing film from the polypropylene resin film can be uniaxially stretched or biaxially stretched. It is preferably used for optical compensation of a liquid crystal cell.

  Moreover, what is necessary is just to apply | coat an adhesive agent to the bonding surface of a polypropylene resin film, the bonding surface of the extended transparent resin film, or both surfaces of a polarizing film in the arbitrary steps before a bonding process (B). In particular, in the course of the raw material film conveying step (A), an adhesive is applied to the bonding surface of the polypropylene resin film to the polarizing film, and the adhesive is applied to the bonding surface of the stretched transparent resin film to the polarizing film. It is preferable to provide an adhesive coating process for coating the film.

  The adhesive used in this method contains a cationic polymerization initiator together with an epoxy compound, is composed of a composition that is cured by cationic polymerization by irradiation of active energy rays, and the curing step (C) is performed by irradiation of active energy rays. Is preferred.

  According to the present invention, a structure in which a polypropylene resin film is bonded to one side of a polarizing film and a transparent resin film stretched to the other side is bonded, and can be thinned and is inexpensive in terms of material. In addition, a polarizing plate with a reduced curl amount can be advantageously produced. Specifically, the polarizing plate produced by this method is formed by forming a pressure-sensitive adhesive layer on the stretched transparent resin film side, providing a release film for temporarily protecting the pressure-sensitive adhesive layer, and bonding the liquid crystal cell. When the chip is cut into a shape to be formed, the curled amount can be reduced to 5 mm or less while the pressure-sensitive adhesive layer side can be formed into a positive curl with the release film peeled off. Therefore, a liquid crystal panel or a liquid crystal display device obtained by bonding this polarizing plate to a liquid crystal cell can be reduced in price and / or thinned, and has no problems such as entrapment of bubbles. Even when a durability test is performed under the above, defects such as peeling do not occur and the reliability is excellent.

It is sectional drawing which shows typically the example of arrangement | positioning of the apparatus for enforcing the method of this invention. It is a perspective view which shows typically the measuring method of curl amount.

  Hereinafter, embodiments of the present invention will be described in detail. With reference to FIG. 1, in this invention, the polypropylene resin film 2 is bonded to the single side | surface of the polarizing film 1 which consists of polyvinyl alcohol-type resin in which the dichroic pigment | dye is adsorbing-oriented through an adhesive agent, and polarized light. The transparent resin film 3 stretched through an adhesive is bonded to the other surface of the film 1 to produce the polarizing plate 5. And the manufacturing method of the polarizing plate which concerns on this invention is equipped with a raw material film conveyance process (A), a bonding process (B), and a hardening process (C) in this order as stated above.

  In the raw film transporting step (A), the polarizing film 1 is transported in a certain direction via the pinch rolls 21 and 22, and the polypropylene resin film 2 is supplied to the one surface via the pinch rolls 23 and 24. The stretched transparent resin film 3 is supplied to the other surface via pinch rolls 25 and 26. Each of the peach rolls 21 to 26 is rotated in the conveying direction of the film with which the peach rolls 21 and 26 are in contact with each other, and the curved arrow in the figure indicates the rotation direction.

  The polypropylene resin film 2 can be used for the raw film transporting step (A) in a state where a protective film is laminated on the side opposite to the surface to be bonded to the polarizing film 1. In this case, the polypropylene resin film 2 is subjected to a raw film transporting step (A) after undergoing a protective film laminating step for laminating the protective film. Further, in the course of the raw material film conveying step (A), an adhesive is applied to the surface of the polypropylene resin film 2 to be bonded to the polarizing film 1 by the adhesive application device 12, and another adhesive application device 13. Thereby, the adhesive agent coating process which apply | coats an adhesive agent to the surface bonded to the polarizing film 1 of the stretched transparent resin film 3 can be provided.

  The bonding step (B) is a first bonding roll 15 that contacts the outside of the polypropylene resin film 2 and a second bonding roll 16 that contacts the outside of the stretched transparent resin film 3. It is carried out while sandwiching a laminate of the resin film 2 / polarizing film 1 / stretched transparent resin film 3. The 1st bonding roll 15 and the 2nd bonding roll 16 are rotating in the conveyance direction of the film which each contacts, and the curve arrow in a figure has shown the rotation direction.

  In the curing step (C), energy for curing the adhesive is supplied from the curing device 18 to the laminate obtained in the pasting step (B), and between the polarizing film 1 and the polypropylene resin film 2. And a step for curing the adhesive between the polarizing film 1 and the stretched transparent resin film 3.

  First, about each process of these raw material film conveyance processes (A) (a protection film bonding process and an adhesive application process are included), a bonding process (B), and a hardening process (C), referring FIG. The explanation will proceed in order.

[Raw material film transport process (A)]
In the raw material film transporting step (A), a polypropylene-based resin film that is manufactured by the method described later and is usually fed out from the feeding device in a roll shape, centering on the polarizing film 1 that is sent through the pinch rolls 21 and 22. 2 is supplied to one side thereof via the pinch rolls 23, 24, and the stretched transparent resin film 3 which is also usually delivered in a roll form from the feeding device is provided on the other side via the pinch rolls 25, 26. Supplied. The conveyance speed of each film 2 and 3 may be set to a value suitable for the production apparatus, and is not particularly limited, but is usually adjusted to the conveyance speed of the polarizing film 1 manufactured and conveyed in the previous step. Speed. As long as it is not restricted by the kind and quality of a polarizing plate, the one where the conveyance speed is larger is preferable from a viewpoint of productivity, for example, can be set to about 1-30 m / min.

  The direction in which each film is conveyed may be such that the polarizing film 1 is sandwiched between the polypropylene resin film 2 and the stretched transparent resin film 3 at the end of the conveying step. In the intermediate stage, for example, there is a portion in which the polypropylene resin film 2 and / or the stretched transparent resin film 3 is conveyed in a direction perpendicular to the conveyance direction of the polarizing film 1 as shown in the drawing. Alternatively, there may be a portion in which the polypropylene resin film 2 and / or the stretched transparent resin film 3 is conveyed in parallel to the conveyance direction of the polarizing film 1. Further, when there is a restriction on the arrangement of the manufacturing apparatus, the polypropylene-based resin film 2 and / or the stretched transparent resin film 3 is once fed out in the direction opposite to the conveying direction of the polarizing film 1 and then an appropriate roll. The polarizing film 1 may be changed in direction so as to be directed to one side of the polarizing film 1, or may be conveyed at an appropriate angle including a vertical direction from the transverse direction in which the polarizing film 1 is conveyed, and then the polarizing film 1 by an appropriate roll. The direction may be changed so as to be directed to one side of 1 and conveyed.

[Protect film pasting process]
Although illustration is abbreviate | omitted, the polypropylene resin film 2 can use for a raw material film conveyance process (A) in the state by which the protective film was laminated | stacked on the opposite side to the surface bonded to the polarizing film 1. FIG. Since a polypropylene resin film has a relatively low rigidity, it is effective to stack and supply such a protective film in order to increase the reliability of conveyance and bonding. In this case, the polypropylene resin film 2 is subjected to a raw film transporting step (A) after undergoing a protective film laminating step for laminating the protective film. The polypropylene resin film having the protective film attached thereto may be hereinafter referred to as “protective film attached polypropylene resin film”.

  This protective film-attached polypropylene resin film preferably has a curl amount that is a positive curl that is slightly convex on the polypropylene resin film side and that is 10 mm or less. When the curl amount of the protective film-attached polypropylene resin film is within this range, the curl amount of the obtained polarizing plate can be adjusted to a more preferable range.

  The curl amount of the protective film-attached polypropylene resin film is measured as follows. That is, as shown in FIG. 2, the sample film (here, a protective film-attached polypropylene resin film) 31 is cut into a size of 30 cm × 30 cm along the film flow direction (MD). When the sample film 31 is curled, the reference surface 35 (for example, the convex surface is directed downward, and when the curl is not generated, either surface is directed downward. Place on a horizontal table) and let stand for 1 hour in an environment of temperature 22 ° C. and relative humidity 60%. In this figure, the surface when it is assumed that the sample film has no curl is displayed as a virtual surface 33 represented by a square ABCD. If no curl is observed for the first time, the curl amount is measured by the following method as it is if the bottom is convex after standing for 1 hour in an environment of temperature 22 ° C. and relative humidity 60%. If the top is convex after standing for a period of time, the front and back of the film are reversed and the curl amount is measured by the method described below. On the other hand, if the curl is not observed in the first place after standing for 1 hour, the front and back of the film are reversed. If no curl is observed even when the film is reversed, the curl amount is judged to be zero and the front and back are reversed. If curl is observed in this state, the amount of curl is measured in the state by the following method. When curl is observed, the amount of curl is measured with the convex surface facing downward as shown in FIG.

  In FIG. 2, one corner A in the virtual plane 33 is at the position A1 in the curled sample film 31, and the other corners B, C, and D are B1, C1, and D1 in the curled sample film 31, respectively. It is displayed as if it was in position. That is, in this figure, the four corners A1, B1, C1, and D1 of the sample film 31 are all floating, but one, two, or three of the four corners of the sample film are raised. There may be no. Of course, if there is no curl at all, the four corners A1, B1, C1, and D1 all coincide with the quadrangle ABCD of the virtual surface 33.

  In this state, the height H from the reference surface 35 is measured for each of the four corners A1, B1, C1, and D1 of the sample film 31, and the minimum value and the maximum value thereof are used as the curl amount. Here, as described above, a case where the polypropylene resin film side of the protective resin-attached polypropylene resin film is convex is called a normal curl, and conversely, a case where the polypropylene resin film side is concave is reversed. Call it curl.

  A laminating machine such as a roll type laminator can be used for laminating the polypropylene resin film and the protective film. The protective film bonding step is performed so that the ratio of the pre-bonding tension per unit cross-sectional area of the protective film to the pre-bonding tension per unit cross-sectional area of the polypropylene resin film is 5 or more and 35 or less. It is preferable. Thus, it is preferable to make the pre-bonding tension on the protect film side larger than the pre-bonding tension on the polypropylene resin film side in order to cause the positive curl as described above.

The term “tension before bonding per unit cross-sectional area” as used herein refers to the tension (unit is, for example, “N”) applied to the film actually measured, the cross-sectional area of the film, that is, the width and thickness of the film. (Unit is, for example, “mm ² ”) and a value (unit is, for example, “N / mm ² ”). Then, the relationship of the pre-bonding tension stipulates above protective film lamination step, the polypropylene-based resin film before lamination tension per unit cross-sectional area according to the T _PP1, bonding per unit cross-sectional area according to the protective film When the pretension is T _PF , this means that the following formula (1) is satisfied.
5 ≦ T _PF / T _PP1 ≦ 35 (1)

  Although the method to adjust each tension | tensile_strength before bonding is not specifically limited, For example, the method of adjusting the torque concerning the film roll or the pinch roll which is drawn | fed out with the bonding roll of the film with which the bonding apparatus was equipped, A method of generating a tension by making a slight difference between the peripheral speed and the peripheral speed of the fed film roll or pinch roll can be adopted.

[Adhesive application process]
Bonding of the polarizing film 1 and the polypropylene resin film 2, and the polarizing film 1 and the stretched transparent resin film 3 are performed via an adhesive. The adhesive is at an arbitrary stage in the raw film transporting step (A), and includes at least one of the bonding surfaces of the polarizing film 1 and the polypropylene resin film 2 and the transparent resin film 3 stretched with the polarizing film 1. It can apply | coat to at least one of the bonding surfaces. For example, an adhesive can be applied to both surfaces of the polarizing film 1, and the polypropylene resin film 2 and the stretched transparent resin film 3 are bonded to both surfaces of the polarizing film 1 by bonding rolls 15 and 16, respectively. Immediately before, the adhesive can be applied to each of the bonding surfaces of the two films by a method of spraying the adhesive on each bonding surface. However, from the viewpoint of operability, it is preferable to apply an adhesive to the surfaces of the polypropylene resin film 2 and the stretched transparent resin film 3 that are bonded to the polarizing film 1. That is, in the raw film transporting step (A), there is a portion where the polypropylene resin film 2 and the stretched transparent resin film 3 are transported so as to sandwich the polarizing film 1 in preparation for the subsequent bonding step (B). Since it exists, it is preferable to apply an adhesive at that portion.

  Then, Preferably, an adhesive agent coating process is provided in the middle of a raw material film conveyance process (A). In this adhesive application step, the adhesive is applied to the surfaces of the polypropylene resin film 2 and the stretched transparent resin film 3 that are bonded to the polarizing film 1. In FIG. 1, an adhesive is applied to the surface of the polypropylene resin film 2 to be bonded to the polarizing film 1 by the adhesive application device 12, and the transparent resin film 3 stretched by another adhesive application device 13. The example comprised so that an adhesive agent might be apply | coated to the surface bonded by the polarizing film 1 of this is shown.

  The polypropylene resin film 2 and the stretched transparent resin film 3 are subjected to surface activation treatment such as corona treatment, plasma treatment, ultraviolet irradiation treatment, or electron beam irradiation treatment before the adhesive is applied. Also good. In addition, each film may be subjected to washing and drying treatment as necessary, or may be subjected to application of an easy adhesion treatment agent, a surface modifier, etc. and subsequent drying treatment.

  The structure and application method of the adhesive application devices 12 and 13 are not particularly limited, and an apparatus and method that can uniformly apply a required amount of adhesive may be adopted. For example, various coating methods such as a doctor blade, a wire bar, a die coater, a comma coater, and a gravure coater can be adopted.

[Bonding process (B)]
In the raw material film conveying step (A), the polypropylene resin film 2 and the stretched transparent resin film 3 supplied from both sides so as to sandwich the polarizing film 1 are the polypropylene resin film in the subsequent bonding step (B). 2 is bonded by the first bonding roll 15 that contacts the outside of 2 and the second bonding roll 16 that contacts the outside of the stretched transparent resin film 3.

In this bonding step (B), the ratio of the pre-bonding tension per unit cross-sectional area of the stretched transparent resin film 3 to the pre-bonding tension per unit cross-sectional area of the polypropylene resin film 2 is 1. It is performed so that it becomes 34 or more and 1.90 or less. Here the relationship before lamination tension defining a polypropylene-based resin film 2 before lamination tension per unit cross-sectional area according to the T _PP2, before bonding per unit cross-sectional area according to the stretched transparent resin film 3 tension the when the T _SF, which means that satisfies the following equation (2).
1.34 ≦ T _SF / T _PP2 ≦ 1.90 (2)

  Although the method to adjust the tension before bonding of each film is not particularly limited, for example, the first and second bonding rolls 15 and 16 and film rolls that are respectively installed on the upstream side of the film and feed out the respective films. Or the method of adjusting the torque concerning the pinch roll installed after that, the peripheral speed of the 1st and 2nd bonding rolls 15 and 16, and the peripheral speed of the above rolls installed on the upstream side of the film, respectively It is possible to adopt a method of generating a tension with a slight difference.

  By applying a difference in the tension per unit cross-sectional area of the polypropylene resin film 2 and the stretched transparent resin film 3 so that the ratio of both is in the range specified above, the applied shrinkage stress However, the stretched transparent resin film 3 is conveyed to the next curing step (C) in a state in which a tensile stress stronger than that of the polypropylene resin film 2 is applied, and the adhesive is cured. After the curing, the polarizing plate is distorted and curls with each stress release. The pre-bonding tension per unit cross-sectional area of the stretched transparent resin film 3 is larger than the pre-bonding tension per unit cross-sectional area of the polypropylene resin film 2, and the ratio between the two is within the above range. By setting so as to be, the curl amount of the obtained polarizing plate is appropriately controlled.

In the bonding step (B), the ratio of the pre-bonding tension per unit cross-sectional area of the polarizing film 1 to the pre-bonding tension per unit cross-sectional area of the polypropylene resin film 2 is 3.23. It is preferable to be performed so as to be 4.55 or less. This makes it easier to control curl generated in the polarizing plate. Here the relationship before lamination tension defining includes the pre-bonding tension per unit cross-sectional area according to the polypropylene resin film 2 T _PP2, the pre-bonding tension per unit cross-sectional area according to the polarization film 1 T _PL Means that the following expression (3) is satisfied.
3.23 ≦ T _PL / T _PP2 ≦ 4.58 (3)

  Surface materials constituting the bonding rolls 15 and 16 are metals such as stainless steel, copper alloy, and chrome-plated products; rubbers such as polyurethane, polyfluoroethylene, and silicone; chromium oxide, silicon oxide And ceramics obtained by thermal spraying of zirconium oxide or aluminum oxide. Especially, the 1st bonding roll 15 which contacts the outer side of the polypropylene resin film 2 shall be a rubber roll, and the 2nd bonding roll 16 which contacts the outer side of the stretched transparent resin film 3 shall be a metal roll. preferable. That is, an elastic rubber roll is applied to the surface of the polypropylene-based resin film 2 that is relatively thin and has a low rigidity, and a metal film is generally disposed on the side of the stretched transparent resin film 3 having a relatively higher rigidity than the polypropylene-based resin film. By applying the roll, the tension applied to both can be effectively and uniformly applied to the film.

[Curing step (C)]
Bonded in the order of propylene resin film 2 / adhesive (not shown) / polarizing film 1 / adhesive (not shown) / stretched transparent resin film 3 conveyed from the bonding step (B). The laminated body is cured in the curing step (C), and the propylene-based resin film 2 and the stretched transparent resin film 3 are bonded to the polarizing film 1 to form the polarizing plate 5. In FIG. 1, the laminated body bonded by the bonding rolls 15 and 16 is sent into the hardening apparatus 18, and a hardening process is given there. The curing treatment can be performed by irradiation with active energy rays, heating, or drying depending on the type of adhesive.

  As will be described later, in the present invention, it is preferable to use an adhesive composition that cures upon irradiation with active energy rays, particularly one containing an epoxy compound and a cationic polymerization initiator, as the adhesive. In this case, the curing step (C) is performed by irradiation with active energy rays. The active energy rays used for curing the adhesive may be, for example, X-rays having a wavelength of 1 pm to 10 nm, ultraviolet rays having a wavelength of 10 to 400 nm, visible rays having a wavelength of 400 to 800 nm, and the like. Among these, ultraviolet rays are preferably used from the viewpoints of ease of handling, ease of preparation of the curable adhesive composition and its stability, and its curing performance. As an ultraviolet light source, for example, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a chemical lamp, a black light lamp, a microwave excitation mercury lamp, a metal halide lamp or the like having a light emission distribution at a wavelength of 400 nm or less may be used. it can.

The irradiation intensity of ultraviolet rays is determined by the type of adhesive and the irradiation time and is not particularly limited. For example, the irradiation intensity in the wavelength region effective for activation of the initiator is 0.1 to 300 mW / cm ^2. It is preferable to set so that it becomes, and it is more preferable to set so that it may become 1-200 mW / cm < ² >. If the light irradiation intensity to the curable adhesive composition is less than 0.1 mW / cm ² , the curing reaction time becomes long, and it becomes difficult to cure unless the irradiation time is lengthened, which is disadvantageous in terms of productivity. . On the other hand, when the light irradiation intensity exceeds 300 mW / cm ² , yellowing of the curable adhesive composition or deterioration of the polarizing film occurs due to heat radiated from the lamp and heat generated during polymerization of the curable adhesive composition. Sometimes.

The ultraviolet irradiation time is also determined by the type of adhesive and the irradiation intensity, and is not particularly limited. For example, the integrated light amount represented by the product of the irradiation intensity and the irradiation time is 10 to 5,000 mJ / cm ^2. Is preferably set so as to be 50 to 1,000 mJ / cm ² . When the cumulative amount of light to the curable adhesive composition is less than 10 mJ / cm ² , active species derived from the initiator are not sufficiently generated, and the resulting adhesive layer tends to be insufficiently cured. On the other hand, if the integrated light quantity exceeds 5,000 mJ / cm ² , the irradiation time becomes very long, which is disadvantageous in terms of productivity.

  When the curing step (C) is performed by irradiation with active energy rays, the thickness of the cured adhesive layer is usually 1 μm or more and 50 μm or less, but the viewpoint of thinning the polarizing plate while maintaining an appropriate adhesive force Therefore, it is preferably 20 μm or less, more preferably 10 μm or less.

  Next, each member thru | or material used in the manufacturing method of the polarizing film of this invention is demonstrated.

[Polarized film]
The polarizing film 1 usually has a step of uniaxially stretching a polyvinyl alcohol-based resin film, a step of adsorbing a dichroic dye by dyeing the polyvinyl alcohol-based resin film with a dichroic dye, and a dichroic dye adsorbed. The polyvinyl alcohol resin film is manufactured through a step of treating with a boric acid aqueous solution and a step of washing with water after the treatment with the boric acid aqueous solution.

  The polyvinyl alcohol-based resin can be produced by saponifying a polyvinyl acetate-based resin. The polyvinyl acetate resin may be a copolymer of vinyl acetate and another monomer copolymerizable therewith, in addition to polyvinyl acetate which is a homopolymer of vinyl acetate. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

  The saponification degree of the polyvinyl alcohol resin is usually about 85 to 100 mol%, preferably 98 mol% or more. The polyvinyl alcohol resin may be modified, for example, polyvinyl formal or polyvinyl acetal modified with aldehydes can be used. The degree of polymerization of the polyvinyl alcohol resin is usually about 1,000 to 10,000, preferably about 1,500 to 5,000.

  What formed such a polyvinyl alcohol-type resin into a film is used as a raw film of a polarizing film. The method for forming a polyvinyl alcohol-based resin is not particularly limited, and can be formed by a known method. The film thickness of the polyvinyl alcohol resin raw film is, for example, about 10 to 150 μm, preferably about 10 to 100 μm.

  Uniaxial stretching of the polyvinyl alcohol-based resin film can be performed before dyeing with the dichroic dye, simultaneously with dyeing, or after dyeing. When uniaxial stretching is performed after dyeing, the uniaxial stretching may be performed before boric acid treatment or during boric acid treatment. Of course, uniaxial stretching can also be performed in a plurality of stages shown here. For uniaxial stretching, a method of stretching uniaxially between rolls having different peripheral speeds, a method of stretching uniaxially using a hot roll, or the like can be adopted. Uniaxial stretching may be performed by dry stretching in which stretching is performed in the air, or may be performed by wet stretching in which a polyvinyl alcohol-based resin film is stretched using a solvent such as water. The draw ratio is usually about 3 to 8 times.

  The polyvinyl alcohol resin film can be dyed with a dichroic dye by, for example, a method of immersing the polyvinyl alcohol resin film in an aqueous solution containing the dichroic dye. Specifically, iodine or a dichroic organic dye is used as the dichroic dye. In addition, it is preferable to perform the process which a polyvinyl alcohol-type resin film swells by immersing in water before a dyeing process.

  When iodine is used as the dichroic dye, a method of dyeing a polyvinyl alcohol-based resin film in an aqueous solution containing iodine and potassium iodide is usually employed. The content of iodine in this aqueous solution is usually about 0.01 to 1 part by weight per 100 parts by weight of water, and the content of potassium iodide is usually about 0.5 to 20 parts by weight per 100 parts by weight of water. It is. The temperature of the aqueous solution used for dyeing is usually about 20 to 40 ° C. Moreover, the immersion time (dyeing time) in this aqueous solution is usually about 20 to 1,800 seconds.

On the other hand, when a dichroic organic dye is used as the dichroic dye, a method of immersing and dyeing a polyvinyl alcohol-based resin film in an aqueous solution containing a water-soluble dichroic organic dye is usually employed. The content of the dichroic organic dye in this aqueous solution is usually about 1 × 10 ⁻⁴ to 10 parts by weight, preferably 1 × 10 ⁻³ to 1 part by weight per 100 parts by weight of water. This aqueous dye solution may contain an inorganic salt such as sodium sulfate as a dyeing assistant. The temperature of the aqueous dichroic organic dye solution used for dyeing is usually about 20 to 80 ° C. Moreover, the immersion time (dyeing time) in this aqueous solution is usually about 10 to 1,800 seconds.

  The boric acid treatment after dyeing with the dichroic dye can be performed by a method of immersing the dyed polyvinyl alcohol resin film in a boric acid-containing aqueous solution. The boric acid content in the boric acid-containing aqueous solution is usually about 2 to 15 parts by weight, preferably 5 to 12 parts by weight per 100 parts by weight of water. When iodine is used as the dichroic dye, the boric acid-containing aqueous solution preferably contains potassium iodide. The content of potassium iodide in the boric acid-containing aqueous solution is usually about 0.1 to 15 parts by weight, preferably 5 to 12 parts by weight per 100 parts by weight of water. The immersion time in the boric acid-containing aqueous solution is usually about 60 to 1,200 seconds, preferably 150 to 600 seconds, and more preferably 200 to 400 seconds. The temperature of the boric acid-containing aqueous solution is usually 50 ° C. or higher, preferably 50 to 85 ° C., more preferably 60 to 80 ° C.

  The polyvinyl alcohol resin film after the boric acid treatment is usually washed with water. The water washing treatment can be performed, for example, by a method of immersing a boric acid-treated polyvinyl alcohol resin film in water. The temperature of water in the water washing treatment is usually about 5 to 40 ° C. The immersion time is usually about 1 to 120 seconds.

  After washing with water, a drying process is performed to obtain a polarizing film. The drying process can be performed using a hot air dryer or a far infrared heater. The temperature of a drying process is about 30-100 degreeC normally, Preferably it is 50-80 degreeC. The drying time is usually about 60 to 600 seconds, preferably 120 to 600 seconds. By the drying treatment, the moisture content in the polarizing film is reduced to a practical level. The moisture content is usually about 5 to 20% by weight, preferably 8 to 15% by weight. When the moisture content is less than 5% by weight, the polarizing film loses its flexibility, and may be damaged or broken after drying. On the other hand, if the moisture content exceeds 20% by weight, the thermal stability tends to be insufficient.

  As described above, a polarizing film having a dichroic dye adsorbed and oriented on a polyvinyl alcohol-based resin film can be produced. The resulting polarizing film can have a thickness of, for example, about 5 to 40 μm.

  In the present invention, a polarizing film starting from flowing a raw film of a polyvinyl alcohol resin into a production line is continuously produced, and the resulting polarizing film is used as it is for the raw material film conveying step (A) described above. Is preferred. Thereby, it is possible to continuously produce a polarizing plate starting from a raw film of polyvinyl alcohol resin.

[Polypropylene resin film]
The polypropylene resin constituting the polypropylene resin film 2 can be composed of a propylene homopolymer and a small amount of a comonomer mainly composed of propylene and copolymerizable therewith, for example, 1% by weight to 20% by weight. Further, it may be constituted by copolymerizing at a ratio of preferably 10% by weight or less. Those excellent in transparency, durability, moldability and the like required as a protective film for a polarizing plate are suitably used.

  In the copolymer mainly composed of propylene, the comonomer copolymerizable with propylene can be, for example, ethylene or α-olefin. The α-olefin has 4 or more carbon atoms, and usually about 4 to 10 carbon atoms is sufficient. Examples of the α-olefin having 4 to 10 carbon atoms include linear α-olefins such as 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, and 1-decene; -Branched α-olefins such as methyl-1-butene, 3-methyl-1-pentene, and 4-methyl-1-pentene; and vinylcyclohexane. The copolymer may be a random copolymer or a block copolymer as long as it has properties required for the protective film of the polarizing plate described above.

  The polypropylene resin has a content of xylene-soluble component at 20 ° C. (hereinafter sometimes referred to as “CXS component” as an abbreviation of cold xylene-soluble component) of 1% by weight or less. Further, it is more preferably 0.8% by weight or less, and particularly preferably 0.5% by weight or less. When the CXS component content in the polypropylene resin film exceeds 1% by weight, when the polarizing plate bonded as a protective film is exposed to a high temperature environment, the protective film made of the polypropylene resin is whitened. The transmittance of the polarizing plate may be reduced.

  Here, the CXS component content can be measured as follows. First, after 5 g of polypropylene resin is completely dissolved in 500 ml of boiling xylene, the temperature is lowered to 20 ° C. and held for 4 hours. Next, the liquid is separated into a precipitate and a filtrate, and the solvent is distilled off from the filtrate and dried at 70 ° C. under reduced pressure to obtain a dried residue. The value expressed by the ratio of the weight of the residue to the weight of the polypropylene resin first dissolved is the CXS component content.

  The polypropylene resin can contain a known additive as long as it does not adversely affect the polarizing plate. Examples of the additive include an antioxidant, an ultraviolet absorber, an antistatic agent, a lubricant, a nucleating agent, an antifogging agent, and an antiblocking agent.

  As the polypropylene resin, a commercially available product can be easily obtained. Examples of commercial products are "Prime Polypro" sold by Prime Polymer Co., Ltd., "Novatech" and "Wintech" sold by Nippon Polypro Corporation, and Sumitomo Chemical Co., Ltd. There are “Sumitomo Noblen” sold, and “Sun Aroma” sold by Sun Aroma Co., Ltd.

  As a method for forming a film by forming a polypropylene resin film, a melt extrusion film forming method is usually employed. In the melt extrusion film forming method, a thermoplastic resin is put into an extruder and melted, and a film-like molten resin is extruded from a T-die and taken on a cooling roll as it is to be cooled and solidified. Can be obtained.

  Here, the thickness of the film can be determined by appropriately controlling the lip interval of the T die. The thickness of the polypropylene resin film is preferably about 5 to 200 μm, more preferably 120 μm or less. When the thickness is less than 5 μm, the handling property of the film is deteriorated, and problems such as pasting and cutting may be caused. On the other hand, if the thickness exceeds 200 μm, the transparency of the film tends to be impaired. In addition, the polypropylene resin film can usually be formed thinner than 100 μm, and the thickness is more preferably 60 μm or less from the viewpoint of contributing to the thinning of the polarizing plate.

  As for the polypropylene resin film, a commercially available product can be easily obtained. Examples of commercially available products are “FILMAX CPP film” sold by FILMAX, “Santox” sold by Sun Tox Co., Ltd. "Tosero", "Toyobo Pyrene Film" sold by Toyobo Co., Ltd., "Trephan" sold by Toray Film Processing Co., Ltd., "Nihon Polyace" sold by Nippon Polyace Corporation, Futamura Chemical There is "Dazai FC" sold by the corporation.

  The polypropylene resin film 2 can be produced as having the transparency, smoothness and homogeneity required for a protective film for a polarizing plate. For example, the haze value measured according to JIS K 7105 is preferably 10% or less, and more preferably 7% or less.

[Protect film laminated to polypropylene resin film]
When the protective film is applied to the raw material film transporting step (A) as a protective film-attached polypropylene-based resin film in which a protective film is laminated on the side opposite to the surface to be bonded to the polarizing film 1 of the polypropylene-based resin film 2, as the protective film Usually, an adhesive / peelable resin layer or an adhesive resin layer is formed on a transparent resin film to give weak adhesiveness. For example, examples of the transparent resin film include extruded films of thermoplastic resins such as polyethylene terephthalate, polyethylene naphtholate, polyethylene, and polypropylene, co-extruded films combining them, and films obtained by stretching them uniaxially or biaxially. It is done. Adhesive / peelable resin layers include acrylic adhesives, natural rubber adhesives, styrene-butadiene copolymer resin adhesives, polyisobutylene adhesives, vinyl ether resin adhesives, silicone resin adhesives, etc. Can be mentioned. Examples of the adhesive resin layer include ethylene-vinyl acetate copolymer resin.

  Among them, an acrylic pressure-sensitive adhesive having excellent transparency and homogeneity as a transparent resin film, using an inexpensive polyethylene terephthalate or polyethylene uniaxial or biaxially stretched film as an adhesive / peelable resin layer. Those using are preferred.

  The thickness of the protective film is preferably 15 to 75 μm. If this thickness is less than 15 μm, the handleability may be inferior or the surface protection performance originally required may be reduced. On the other hand, if the thickness exceeds 75 μm, the rigidity is too strong, and the handleability may be inferior or the peel strength may be increased.

  The tensile elastic modulus of the protective film is preferably 1,000 MPa or more, more preferably 3000 MPa or more in the longitudinal direction (MD). When this tensile elasticity modulus is too small, it may be inferior in handleability, or may not be able to withstand the tension when being bonded to a polypropylene resin film.

  The surface of the protective film may be subjected to antifouling treatment, antireflection treatment, hard coat treatment, antistatic treatment and the like. Further, the adhesive layer of the protective film may contain an antistatic agent or the like in order not to induce static electricity at the time of peeling.

  A commercially available product can be easily obtained as a protective film having a suitable tackiness on one side. Examples of commercially available products are “Mastak” sold by Fujimori Kogyo Co., Ltd., “Sanitect” sold by Sanei Kaken Co., Ltd., and “Nitto Denko Co., Ltd.” E-mask "and" Tretec "sold by Toray Film Processing Co., Ltd.

[Stretched transparent resin film]
The stretched transparent resin film 3 bonded to the opposite side of the surface of the polarizing film 1 to which the polypropylene resin film 2 is bonded is excellent in transparency and can express an appropriate retardation value by stretching. What is necessary is just to comprise. Examples of such resins include polycarbonate resins, polyvinyl alcohol resins, polystyrene resins, (meth) acrylate resins, polyolefin resins including cyclic polyolefin resins and polypropylene resins, polyarylate resins, polyimide resins, Examples thereof include polyamide-based resins. A stretched transparent resin film 3 can be obtained by stretching a film made of such a resin by an appropriate method such as uniaxial or biaxial.

  The stretched transparent resin film 3 is provided with an appropriate retardation by stretching. The film provided with the retardation may be a wave plate such as a quarter wave plate or a half wave plate, or a viewing angle compensation film. The thickness of the retardation film is usually about 20 to 200 μm, preferably 20 to 120 μm.

When a viewing angle compensation film is used as the retardation film, it is necessary to consider the mode employed in the liquid crystal cell. For example, vertical alignment: If (Vertical Alignment VA) mode liquid crystal cell, as a viewing angle compensation film, a polymer film having a positive intrinsic birefringence is uniaxially stretched, the refractive index ellipsoid n _x> n _y ≒ positive a plate having a relationship of n _z, transverse stretching and sequential biaxial stretching is performed, biaxial film having a relation of _{n x> n y> n z} , or relationship of n _x ≒ n _y> n _z A negative C plate can be used. Here, n _x plane slow axis (x-axis) of the film refractive index in the direction of, n _y in-plane fast axis (y-axis: Axis perpendicular in slow axis in-plane) direction of the refractive index, N _z is the refractive index in the thickness (z-axis) direction.

  In particular, a biaxially stretched biaxial film is preferably used. When a biaxial viewing angle compensation film is used, the Nz coefficient, which is a measure of the biaxiality, is defined by the following equation (4), and the in-plane retardation when the film thickness is d: The value Ro and the thickness direction retardation value Rth are defined by the following equations (5) and (6), respectively.

_{Nz = (n x -n z)} / (n x -n y) (4)
_{Ro = (n x -n y)} × d (5)
Rth = _{[(n x + n y) /} 2-n z ] × d (6)

  From the above equations (4) to (6), the relationship between the Nz coefficient, the in-plane retardation value Ro and the thickness direction retardation value Rth can be expressed by the following equation (7).

    Nz = Rth / Ro + 0.5 (7)

  When a viewing angle compensation film is used as the stretched transparent resin film 3, the in-plane retardation value Ro is preferably in the range of 30 to 300 nm, particularly 50 to 260 nm. The Nz coefficient is preferably in the range of 1.1-7, particularly in the range of 1.4-5. From these ranges, the value of the optical characteristic may be appropriately selected according to the viewing angle characteristic required for the applied liquid crystal display device.

  When the stretched transparent resin film 3 is a retardation film, when the polarizing film and the retardation film are bonded, the angle formed by the absorption axis of the polarizing film and the slow axis of the retardation film is determined by What is necessary is just to select suitably according to a use. For example, when the retardation film is a viewing angle compensation film, the angle formed by the absorption axis of the polarizing film and the slow axis of the viewing angle compensation film is substantially 0 ° or 90 °.

[adhesive]
An adhesive is used for bonding the polarizing film 1 and the polypropylene resin film 2 and for bonding the polarizing film 1 and the stretched transparent resin film 3. This adhesive is cured by irradiation with active energy rays, heating, drying, and the like, and can bond the polarizing film 1 and the polypropylene resin film 2 and the polarizing film 1 and the stretched transparent resin film 3 with a strength sufficient for practical use. Anything is acceptable. For example, a cationically polymerizable photocurable adhesive composition comprising a cationically polymerizable compound such as a glycidyl ether epoxy compound, an alicyclic epoxy compound, and an oxetane compound and a cationic photopolymerization initiator; acrylic Radical polymerizable photocurable adhesive composition comprising a radical polymerizable compound such as a compound and a radical photopolymerization initiator; thermal polymerization is initiated with the cationic polymerizable or radical polymerizable compound shown above A thermosetting adhesive composition comprising an agent, that is, a thermal cation generator or a thermal radical generator; a water-soluble or hydrophilic crosslinkable epoxy compound or urethane compound, if necessary, such as a polyvinyl alcohol resin. And an aqueous adhesive composition comprising an aqueous solution or an aqueous dispersion containing a water-soluble resin having a reactive group.

  Of these, a cationically polymerizable photocurable adhesive composition containing an epoxy compound and a photocationic polymerization initiator is preferred. The adhesive composition is more preferably usable without a solvent. That is, an active energy obtained by selecting a photocationically curable epoxy compound that is solvent-free and has an appropriate fluidity and gives an appropriate curing adhesive strength, and blending a cationic polymerization initiator suitable for it. The linear curable adhesive composition can omit the drying equipment in the curing step, and generally adheres the polypropylene resin film 2 which is difficult to adhere in other photocuring and thermosetting systems to the polarizing film 1 with a good adhesive force. . In addition, by irradiating with an appropriate active energy dose, the curing rate can be accelerated and the production rate can be improved.

  Examples of epoxy compounds used in such adhesive compositions include glycidyl etherified products of aromatic compounds or chain compounds having hydroxyl groups, glycidyl aminated products of compounds having amino groups, and C—C double bonds. Epoxy product of chain compound having alicyclic epoxy compound in which glycidyloxy group or epoxyethyl group is bonded directly to saturated carbon ring or via alkylene, or epoxy group is directly bonded to saturated carbon ring and so on. These epoxy compounds may be used alone or in combination with a plurality of different types. Of these, alicyclic epoxy compounds are preferably used because of their excellent cationic polymerizability.

  A glycidyl etherified product of an aromatic compound or a chain compound having a hydroxyl group can be obtained, for example, by a method of addition condensation of epichlorohydrin to a hydroxyl group of the aromatic compound or chain compound under basic conditions. Examples thereof include bisphenol type epoxy resins, polyaromatic ring type epoxy resins, alkylene glycol type epoxy resins and the like.

  Examples of bisphenol type epoxy resins include glycidyl etherified products of bisphenol A and oligomers thereof, glycidyl etherified products of bisphenol F and oligomers thereof, 3,3 ′, 5,5′-tetramethyl-4,4′-biphenol. Examples thereof include glycidyl etherified products and oligomers thereof.

  Examples of polyaromatic epoxy resins include glycidyl etherified products of phenol novolac resins, glycidyl etherified products of cresol novolac resins, glycidyl etherified products of phenol aralkyl resins, glycidyl etherified products of naphthol aralkyl resins, and glycidyl ethers of phenol dicyclopentadiene resins. And the like. Further, glycidyl etherified products of trisphenols and oligomers thereof also belong to the polyaromatic epoxy resin.

  Examples of the alkylene glycol type epoxy resin include glycidyl etherification product of ethylene glycol, glycidyl etherification product of diethylene glycol, glycidyl etherification product of 1,4-butanediol, glycidyl etherification product of 1,6-hexanediol, and the like.

  A glycidyl aminated product of a compound having an amino group can be obtained by a method in which epichlorohydrin is addition-condensed to the amino group of the compound under basic conditions. The compound having an amino group may have a hydroxyl group at the same time. For example, glycidyl amination product of 1,3-phenylenediamine and oligomer thereof, glycidyl amination product and oligomer of 1,4-phenylenediamine, glycidyl amination and glycidyl etherification product of 3-aminophenol and oligomer thereof And glycidyl amination and glycidyl etherification product of 4-aminophenol and oligomers thereof.

  An epoxidized product of a chain compound having a C—C double bond can be obtained by a method of epoxidizing a C—C double bond of the chain compound under a basic condition using a peroxide. . Examples of the chain compound having a C—C double bond include butadiene, polybutadiene, isoprene, pentadiene, hexadiene and the like. Terpenes having a double bond can also be used as a raw material for epoxidation, and examples of acyclic monoterpenes include linalool. Examples of peroxides used for epoxidation include hydrogen peroxide, peracetic acid, tert-butyl hydroperoxide, and the like.

  An alicyclic epoxy compound in which a glycidyloxy group or an epoxyethyl group is bonded to a saturated carbocycle directly or via an alkylene is an aromatic ring of an aromatic compound having a hydroxyl group, typically a bisphenol. Examples thereof include a glycidyl etherified product of a hydrogenated cyclic polyhydroxy compound obtained by hydrogenation, a glycidyl etherified product of a saturated cyclic compound having a hydroxyl group, and an epoxidized product of a saturated cyclic compound having a vinyl group.

  The epoxy compound as described above can be easily obtained as a commercial product. Examples of commercially available products are "Epicoat" sold by Japan Epoxy Resin Co., Ltd., "Epicron" sold by DIC Corporation, and "Epototo" sold by Toto Kasei Corporation. "Adeka Resin" sold by ADEKA Co., Ltd., "Denacol" sold by Nagase ChemteX Corporation, "Dow Epoxy" sold by Dow Chemical Company, and sold by Nissan Chemical Industries, Ltd. There is "tepic".

  On the other hand, an alicyclic epoxy compound in which an epoxy group is directly bonded to a saturated carbocyclic ring, for example, peroxidizes a CC double bond of a non-aromatic cyclic compound having a C—C double bond in the ring. Can be obtained by a method of epoxidizing the product under basic conditions. As a non-aromatic cyclic compound having a C—C double bond in the ring, for example, a compound having a cyclopentene ring, a compound having a cyclohexene ring, a cyclopentene ring or a cyclohexene ring added with at least two additional carbon atoms And a polycyclic compound forming the ring. This non-aromatic cyclic compound having a C—C double bond in the ring may have another C—C double bond outside the ring. Examples of non-aromatic cyclic compounds having a C—C double bond in the ring include cyclohexene, 4-vinylcyclohexene, limonene and α-pinene, which are monocyclic monoterpenes.

  An alicyclic epoxy compound in which an epoxy group is directly bonded to a saturated carbocyclic ring has an alicyclic structure having an epoxy group directly bonded to the ring as described above in the molecule through an appropriate linking group. It may be a compound in which at least two are formed. Examples of the linking group herein include groups having an ester bond, an ether bond, an alkylene bond, and the like.

Examples of alicyclic epoxy compounds in which an epoxy group is directly bonded to a saturated carbocycle include the following.
3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate,
1,2-epoxy-4-vinylcyclohexane,
1,2-epoxy-4-epoxyethylcyclohexane,
1,2-epoxy-1-methyl-4- (1-methylepoxyethyl) cyclohexane,
3,4-epoxycyclohexylmethyl (meth) acrylate,
An adduct of 2,2-bis (hydroxymethyl) -1-butanol and 4-epoxyethyl-1,2-epoxycyclohexane,
Ethylene bis (3,4-epoxycyclohexanecarboxylate),
Oxydiethylene bis (3,4-epoxycyclohexanecarboxylate),
1,4-cyclohexanedimethyl bis (3,4-epoxycyclohexanecarboxylate),
3- (3,4-epoxycyclohexylmethoxycarbonyl) propyl 3,4-epoxycyclohexanecarboxylate and the like.

  Commercially available alicyclic epoxy compounds in which an epoxy group is directly bonded to a saturated carbocyclic ring as described above can also be easily obtained. Examples of commercially available products include “Celoxide” and “Cyclomer” sold by Daicel Chemical Industries, Ltd. and “Syracure” sold by Dow Chemical Company, respectively.

  The curable adhesive composition containing the epoxy compound may further contain an active energy ray-curable compound other than the epoxy compound. Examples of the active energy ray-curable compound other than the epoxy compound include an oxetane compound and an acrylic compound. Especially, since a cure rate can be improved in cationic polymerization, it is preferable to use an oxetane compound together.

The oxetane compound is a compound having a 4-membered ring ether in the molecule, and examples thereof include the following.
1,4-bis [(3-ethyloxetane-3-yl) methoxymethyl] benzene,
3-ethyl-3- (2-ethylhexyloxymethyl) oxetane,
Bis (3-ethyl-3-oxetanylmethyl) ether,
3-ethyl-3- (phenoxymethyl) oxetane,
3-ethyl-3- (cyclohexyloxymethyl) oxetane,
Phenol novolac oxetane,
1,3-bis [(3-ethyloxetane-3-yl) methoxy] benzene and the like.

  As for oxetane compounds, commercially available products can be easily obtained. Examples of commercially available products include “Aron Oxetane” sold by Toagosei Co., Ltd. and “ETERNACOLL” sold by Ube Industries, Ltd.

  As the curable compound including the epoxy compound and the oxetane compound, it is preferable to use a curable compound which is not diluted with an organic solvent or the like in order to make the curable adhesive composition obtained by blending these compounds solvent-free. In addition, a small amount of components including a cationic photopolymerization initiator and a sensitizer constituting the adhesive composition to be described later are also a powder of the compound alone from which the organic solvent has been removed and dried rather than those dissolved in the organic solvent. It is preferable to use a body or a liquid.

  The cationic photopolymerization initiator is one that generates an active energy ray, for example, a cationic species upon irradiation with ultraviolet rays, and can provide the adhesive strength and the curing rate required for the adhesive composition in which it is blended. Good. Examples include aromatic diazonium salts; onium salts such as aromatic iodonium salts and aromatic sulfonium salts; iron-allene complexes. These photocationic polymerization initiators may be used alone or in combination with a plurality of different types.

Examples of the aromatic diazonium salt include the following compounds.
Benzenediazonium hexafluoroantimonate,
Benzenediazonium hexafluorophosphate,
Benzenediazonium hexafluoroborate, etc.

Examples of the aromatic iodonium salt include the following compounds.
Diphenyliodonium tetrakis (pentafluorophenyl) borate,
Diphenyliodonium hexafluorophosphate,
Diphenyliodonium hexafluoroantimonate,
Bis (4-nonylphenyl) iodonium hexafluorophosphate and the like.

Examples of the aromatic sulfonium salt include the following compounds.
Triphenylsulfonium hexafluorophosphate,
Triphenylsulfonium hexafluoroantimonate,
Triphenylsulfonium tetrakis (pentafluorophenyl) borate,
Diphenyl (4-phenylthiophenyl) sulfonium hexafluoroantimonate,
4,4'-bis (diphenylsulfonio) diphenyl sulfide bishexafluorophosphate,
4,4′-bis [di (β-hydroxyethoxyphenyl) sulfonio] diphenyl sulfide bishexafluoroantimonate,
4,4′-bis [di (β-hydroxyethoxyphenyl) sulfonio] diphenyl sulfide bishexafluorophosphate,
7- [di (p-toluyl) sulfonio] -2-isopropylthioxanthone hexafluoroantimonate,
7- [di (p-toluyl) sulfonio] -2-isopropylthioxanthone tetrakis (pentafluorophenyl) borate,
4-phenylcarbonyl-4'-diphenylsulfoniodiphenyl sulfide hexafluorophosphate,
4- (p-tert-butylphenylcarbonyl) -4'-diphenylsulfoniodiphenyl sulfide hexafluoroantimonate,
4- (p-tert-butylphenylcarbonyl) -4'-di (p-toluyl) sulfonio-diphenyl sulfide tetrakis (pentafluorophenyl) borate and the like.

Examples of the iron-allene complex include the following compounds.
Xylene-cyclopentadienyl iron (II) hexafluoroantimonate,
Cumene-cyclopentadienyl iron (II) hexafluorophosphate,
Xylene-cyclopentadienyl iron (II) tris (trifluoromethylsulfonyl) methanide.

  Among these photocationic polymerization initiators, the aromatic sulfonium salt has an ultraviolet absorption property even in a wavelength region of 300 nm or more, and therefore provides an adhesive layer having excellent curability and good mechanical strength and adhesive strength. Therefore, it is preferably used.

  A commercial product can also be easily obtained as the cationic photopolymerization initiator. Examples of commercially available products are “Kayarad” sold by Nippon Kayaku Co., Ltd., “Syracure” sold by Union Carbide, and photoacid generators sold by San Apro Corporation. Agent "CPI", photoacid generators "TAZ", "BBI" and "DTS" sold by Midori Chemical Co., Ltd., "Adekaoptomer" sold by ADEKA Corporation, sold by Rhodia There is “RHODORSIL”.

  The compounding quantity of a photocationic polymerization initiator is 0.5-20 weight part normally with respect to 100 weight part of total amounts of a photocurable adhesive composition, Preferably it is 1-15 weight part. If the amount is less than 0.5 parts by weight, curing may be insufficient and the mechanical strength and adhesive strength of the adhesive layer may be reduced. On the other hand, when the amount exceeds 20 parts by weight, the ionic substance in the adhesive layer increases, so that the hygroscopicity of the adhesive layer increases, and the durability performance of the obtained polarizing plate may be lowered.

  The photocurable adhesive composition can contain a photosensitizer as necessary. By using a photosensitizer, the reactivity is improved, and the mechanical strength and adhesive strength of the adhesive layer can be further improved. Examples of the photosensitizer include carbonyl compounds, organic sulfur compounds, persulfides, redox compounds, azo compounds, diazo compounds, halogen compounds, and photoreducible dyes.

  Examples of carbonyl compounds that can be photosensitizers include benzoin derivatives such as benzoin methyl ether, benzoin isopropyl ether, and α, α-dimethoxy-α-phenylacetophenone; anthracene such as 9,10-dibutoxyanthracene Compounds; benzophenones and derivatives thereof such as benzophenone, 2,4-dichlorobenzophenone, methyl o-benzoylbenzoate, 4,4'-bis (dimethylamino) benzophenone, and 4,4'-bis (diethylamino) benzophenone; 2 Anthraquinone derivatives such as chloroanthraquinone and 2-methylanthraquinone; acridone derivatives such as N-methylacridone and N-butylacridone; acetophenone derivatives such as α, α-diethoxyacetophenone There are conductors; xanthone derivatives; fluorenone derivatives and the like. Examples of organic sulfur compounds that can be used as photosensitizers include 2-chlorothioxanthone and thioxanthone derivatives such as 2-isopropylthioxanthone. In addition, benzyl compounds and uranyl compounds can also be used as photosensitizers. These photosensitizers may be used alone or in combination with a plurality of different types.

  When mix | blending a photosensitizer, it is preferable to make the compounding quantity into the range of 0.1-20 weight part with respect to 100 weight part of total amounts of a photocurable adhesive composition.

  Various additives can be blended in the photocurable adhesive composition as long as the effect is not impaired. Examples of the additive include an ion trap agent, an antioxidant, a chain transfer agent, a tackifier, a thermoplastic resin, a filler, a flow regulator, a plasticizer, and an antifoaming agent.

  The photocurable adhesive composition only needs to have a viscosity that can be applied to the film by an appropriate method, but the viscosity at 25 ° C. is preferably in the range of 10 to 30,000 mPa · sec. More preferably, it is in the range of 50 to 6,000 mPa · sec. If the viscosity is less than 10 mPa · sec, the apparatus that can be applied is limited, and even if it can be applied, it tends to be difficult to obtain a uniform coating film without unevenness. On the other hand, when the viscosity exceeds 30,000 mPa · sec, it becomes difficult to flow, and the apparatus that can be applied similarly is limited, and it is difficult to obtain a uniform coating film without unevenness. The viscosity here is a value measured at 60 rpm after the composition is adjusted to 25 ° C. using a B-type viscometer.

[Adhesive layer]
The polarizing plate produced by the present invention can be formed as a polarizing plate with an adhesive layer by forming an adhesive layer on the stretched transparent resin film 3 side. It will be bonded to a liquid crystal cell through this adhesive layer. Examples of the pressure-sensitive adhesive forming the pressure-sensitive adhesive layer include those having an acrylic polymer, a silicone-based polymer, polyester, polyurethane, polyether or the like as a base polymer. Among them, acrylic pressure-sensitive adhesives based on acrylic polymers are excellent in optical transparency, maintain appropriate wettability and cohesive strength, and have excellent weather resistance and heat resistance. It is preferably used because peeling problems such as floating and peeling hardly occur under the conditions.

  In the acrylic base polymer constituting the acrylic pressure-sensitive adhesive, an acrylic acid alkyl ester having an ester group having an alkyl group having 20 or less carbon atoms such as a methyl group, an ethyl group, a butyl group, or a 2-ethylhexyl group; An acrylic copolymer with a functional group-containing (meth) acrylic monomer such as (meth) acrylic acid or 2-hydroxyethyl (meth) acrylate is preferably used. The pressure-sensitive adhesive layer containing such an acrylic copolymer can be compared without causing any adhesive residue on the glass substrate when it has to be peeled off after being bonded to a liquid crystal cell. Can be easily peeled off. The acrylic copolymer used for the pressure-sensitive adhesive preferably has a glass transition temperature of 25 ° C. or lower, more preferably 0 ° C. or lower. The acrylic copolymer usually has a weight average molecular weight of 100,000 or more.

  As a pressure-sensitive adhesive forming the pressure-sensitive adhesive layer, a diffusion pressure-sensitive adhesive in which a light diffusing agent is dispersed can be used. The light diffusing agent is for imparting light diffusibility to the pressure-sensitive adhesive layer, and may be fine particles having a refractive index different from that of the base polymer constituting the pressure-sensitive adhesive layer. Fine particles made of (polymer) can be used. Since the base polymer constituting the pressure-sensitive adhesive layer including the acrylic base polymer as described above often has a refractive index of about 1.4, the light diffusing agent has a refractive index of about 1-2. May be selected as appropriate. The difference in refractive index between the base polymer constituting the pressure-sensitive adhesive layer and the light diffusing agent is usually 0.01 or more, and from the viewpoint of maintaining the brightness and visibility of the liquid crystal display device, 0.01 to 0.5 or less. It is preferable that The fine particles used as the light diffusing agent are preferably spherical, and those close to monodispersion. For example, fine particles having an average particle diameter in the range of about 2 to 6 μm are preferably used.

  Examples of the fine particles made of an inorganic compound include aluminum oxide (refractive index 1.76) and silicon oxide (refractive index 1.45). Examples of the fine particles comprising an organic compound (polymer) include melamine resin beads (refractive index 1.57), polymethyl methacrylate beads (refractive index 1.49), and methyl methacrylate / styrene copolymer resin beads (refractive index). 1.550), polycarbonate beads (refractive index 1.55), polyethylene beads (refractive index 1.53), polystyrene beads (refractive index 1.6), polyvinyl chloride beads (refractive index 1.46). ) And silicone resin beads (refractive index 1.46).

  The amount of the light diffusing agent is appropriately determined in consideration of the haze value required for the pressure-sensitive adhesive layer in which it is dispersed and the brightness of the liquid crystal display device to which it is applied. The amount is about 3 to 30 parts by weight with respect to 100 parts by weight of the base polymer constituting the layer.

  The haze value of the pressure-sensitive adhesive layer in which the light diffusing agent is dispersed is 20 from the viewpoint of ensuring the brightness of the liquid crystal display device to which the polarizing plate with the pressure-sensitive adhesive layer is applied and making the display image less likely to bleed or blur. It is preferable to make it into the range of -80%. Here, the haze value is a value defined by (diffuse transmittance / total light transmittance) × 100 (%), and is measured according to JIS K 7105.

  Each component constituting the transparent adhesive or diffusion adhesive is dissolved in an appropriate solvent such as ethyl acetate to form an adhesive composition. However, components that are not soluble in a solvent such as a light diffusing agent are dispersed. This pressure-sensitive adhesive composition can be applied on a suitable substrate and dried to form a pressure-sensitive adhesive layer.

  Formation of the pressure-sensitive adhesive layer on the stretched transparent resin film 3 constituting the polarizing plate 5 is, for example, using a release film as the substrate and forming the pressure-sensitive adhesive layer by applying the pressure-sensitive adhesive composition thereto. Then, the pressure-sensitive adhesive layer is applied to the surface of the stretched transparent resin film 3, and the pressure-sensitive adhesive composition is directly applied to the surface of the stretched transparent resin film 3 constituting the polarizing plate 5. The method can be carried out by forming a pressure-sensitive adhesive layer and attaching a release film to the pressure-sensitive adhesive surface.

  After the pressure-sensitive adhesive layer is formed on the release film, another release film can be bonded to the pressure-sensitive adhesive layer to form a double-sided release film type pressure-sensitive adhesive sheet that is not supported by the optical film. Such a double-sided release film-type pressure-sensitive adhesive sheet is used for bonding to the stretched transparent resin film 3 by peeling the release film on one side at a necessary time.

  Examples of products that are commercially available as double-sided release film type adhesive sheets are "LUCIACS" sold by Nitto Denko Co., Ltd., "Non-Carrier" sold by Lintec Corporation, "Optical substrate-less double-sided adhesive tape MHM-F25" sold by Niei Kogyo Co., Ltd., "Optical adhesive sheet FS800" sold by Toyo Ink Co., Ltd., "Optical sold by Soken Chemical Co., Ltd." Double-sided tape SK "etc.

  For example, the pressure-sensitive adhesive layer is aged for about 3 to 20 days at a temperature of 23 ° C. and a relative humidity of 65%, and after the reaction of the crosslinking agent has sufficiently progressed, the pressure-sensitive adhesive layer is used for bonding to a liquid crystal cell.

  The thickness of the pressure-sensitive adhesive layer is appropriately determined according to the adhesive force and the like, but is usually about 1 to 40 μm. In order to obtain a thin polarizing plate without impairing properties such as workability and durability, the thickness of the pressure-sensitive adhesive layer is preferably about 3 to 25 μm. In addition, by setting the thickness of the pressure-sensitive adhesive layer within this range, it is possible to maintain brightness when the liquid crystal display device is viewed from the front or from an oblique direction, and to prevent bleeding and blurring of the display image. .

  The polarizing plate produced by the method of the present invention is provided with the pressure-sensitive adhesive layer described above, and the pressure-sensitive adhesive layer-attached polarizing plate obtained by temporarily protecting the pressure-sensitive adhesive layer with a release film is bonded to a liquid crystal cell. In a state where the product is chip-cut into a product shape, or in a state where the release film is peeled therefrom, a positive curl having a convex adhesive layer side can be obtained. Moreover, when sticking to a liquid crystal cell, it is preferable that the curl amount shall be 5 mm or less from a viewpoint of preventing malfunctions, such as biting a bubble into a center part or an edge part.

  The amount of curl here can be measured by a method according to the explanation made earlier with reference to FIG. In the explanation when measuring the curl amount of the polypropylene resin film with the protective film, the sample film was cut into a size of 30 cm × 30 cm. However, in the polarizing plate with an adhesive layer, it was bonded to the liquid crystal cell. In the state of cutting to the size of the product to be observed, the curl is observed to determine the curl amount. Also, when the release film is peeled off and the pressure-sensitive adhesive layer is exposed, if the pressure-sensitive adhesive layer is faced down, it will adhere to the reference surface as it is. Is placed on the reference surface facing up, and is allowed to stand for 1 hour in an environment of a temperature of 22 ° C. and a relative humidity of 60%. Thereafter, the curl amount may be measured according to the method described above. A case where the pressure-sensitive adhesive layer side is convex is called normal curl, and a case where the pressure-sensitive adhesive layer side is concave is called reverse curl.

  In addition, a pressure-sensitive adhesive layer and a release film are provided in this order on the stretched transparent resin film 3 side of the polarizing plate having a layer structure of polypropylene-based resin film 2 / polarizing film 1 / stretched transparent resin film 3; In forming the protective film on the resin film 2 side, the curling change behavior of the polarizing plate before and after providing the release film, the pressure-sensitive adhesive layer, and the protective film is also evaluated. As a result, the curling amount of the polarizing film before forming the release film, the pressure-sensitive adhesive layer, and the protective film correlates with the curling amount of the polarizing plate on which each of these layers is formed or the peeling film is peeled off from the polarizing film. Make sure that there is.

  As described above, a polarizing plate in which a pressure-sensitive adhesive layer and a release film are provided in this order on the stretched transparent resin film 3 side, and a protective film is provided on the polypropylene resin film 2 side is a product to be bonded to a liquid crystal cell. It is preferable that the curl amount be 5 mm or less with a positive curl having a convex surface on the pressure-sensitive adhesive layer side in a state where the chip is cut into a shape or the peeled film is peeled therefrom. In order to satisfy this, the amount of polarizing plate curl before forming the pressure-sensitive adhesive layer, the release film, and the protective film is measured on the side of forming the pressure-sensitive adhesive layer when measured with a sample size of 30 cm × 30 cm ( The curl amount at any of the four corners (vertex portions) of the sample may be controlled to be within a range of 15 to 50 mm in a positive curl state where the stretched transparent resin film 3 side is convex.

[Other layers that can be provided on the polarizing plate]
In the polarizing plate obtained by the present invention, a surface treatment layer such as a hard coat layer, an antireflection layer, and an antiglare layer may be formed on the surface of the polypropylene resin film 2. In this case, it is general that the surface-treated layer is formed on the surface of the polypropylene resin film 2 and then provided to the raw material film transporting step (A) and further to the bonding step (B). Is. Also, a brightness-enhancing film is bonded to the polypropylene resin film 2 side, or a polymer film having a negative intrinsic birefringence is uniaxially or biaxially formed by transverse stretching or sequential stretching on the stretched transparent resin film 3 side. A laminated retardation film can also be bonded.

[Liquid Crystal Display]
The polarizing plate obtained by this invention can be bonded to a liquid crystal cell through an adhesive layer, and can be set as a liquid crystal panel. When manufacturing a liquid crystal panel, the amount of curl of the polarizing plate is small, and therefore, when the liquid crystal panel is bonded to the liquid crystal cell, it is difficult to cause problems such as entrapment of bubbles in the end portion. Here, the liquid crystal cells constituting the liquid crystal panel are TN (Twisted Nematic), STN (Super Twisted Nematic), VA (Vertical Alignment), IPS (In-Plane Switching), OCB (Optically Compensated Bend), etc. in this field. It can be of various known modes. The liquid crystal panel to which the polarizing plate is bonded becomes a liquid crystal display device by further incorporating a drive circuit, a backlight unit, and the like. This liquid crystal display device can be thinned at low cost and has excellent reliability by using the polarizing plate produced according to the present invention.

  EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated further more concretely, this invention is not limited by these examples. In the following examples, the part representing the amount used is based on weight unless otherwise specified. The physical property values in each example were measured by the following methods.

[Measurement of curl amount of film]
The amount of curl was measured for each of the protective film-attached polypropylene-based resin film and the polarizing plate with the convex surface of the film facing down by the method according to the explanation made earlier with reference to FIG. . In the case of the protective film-attached polypropylene resin film, the case where the polypropylene resin film side is convex is defined as a positive curl, and in the polarizing plate, the case where the stretched transparent resin film 3 side is convex is defined as a positive curl.

[Measurement of tensile modulus of film]
The tensile modulus of the film is a method specified in JIS K 7161 “Plastics-Test Method for Tensile Properties Part 1: General Rules”, using an autograph (model “AG-1”, manufactured by Shimadzu Corporation). The measurement was performed at a temperature of 22 ° C. and a relative humidity of 53%.

[Example 1]
(A) Preparation of adhesive composition The following components were mixed to prepare an ultraviolet curable adhesive composition.

3,4-epoxycyclohexylmethyl
3,4-epoxycyclohexanecarboxylate 40 parts Diglycidyl ether of bisphenol A 60 parts Diphenyl (4-phenylthiophenyl) sulfonium
Hexafluoroantimonate (photo cationic polymerization initiator) 4 parts

(B) Bonding of protective film to polypropylene film A polypropylene film having a thickness of 50 μm was obtained from a homopolymer of propylene by a melt extrusion film forming method. The CXS component content of this polypropylene was 0.2%. Separately, a biaxially stretched polyethylene terephthalate film having a thickness of 38 μm provided with a weakly adhesive acrylic adhesive layer on one side was prepared and used as a protective film. This polyethylene terephthalate film had a tensile modulus in the longitudinal direction (MD) of 3,500 MPa.

  Supply to roll type laminator for film bonding so that the ratio of the pre-bonding tension per unit cross-sectional area of the protective film to the pre-bonding tension per unit cross-sectional area of the polypropylene film is 19, The protective film adhesive layer was laminated so as to overlap the polypropylene film. A sample of 30 cm × 30 cm was cut out from the obtained protective film-laminated polypropylene film, and the curl amount was measured by the above method. As a result, the polypropylene film side was a positive curl, and the minimum value among the four corners was 0. The maximum value was 4 mm.

(C) Preparation of polarizing plate On one side of a polarizing film in which iodine is adsorbed and oriented on polyvinyl alcohol, on the other side of the polarizing film, the polypropylene film side of the protective film-attached polypropylene film prepared in (b) above, Biaxially stretched film of cycloolefin resin obtained from Nippon Zeon Co., Ltd. and having a thickness of 60 μm, “Zeonor film” (trade name, in-plane retardation value Ro = 63 nm, thickness direction retardation value Rth = 225 nm ) Were respectively bonded to prepare a polarizing plate. In pasting, the UV curable adhesive composition prepared in the above (a) is applied to each of the surfaces of the protective film pasted polypropylene film and the cycloolefin-based resin film to the polarizer, and each coating is performed. After the surface was superimposed on both surfaces of the polarizing film, the two films were integrated by passing between two bonding rolls 15 and 16. Here, a rubber roll whose surface is made of rubber was used for the first bonding roll 15, and a metal roll whose surface was chrome plated was used for the second bonding roll 16. The ratio of the pre-bonding tension per unit cross-sectional area of the cycloolefin-based resin stretched film 3 to the pre-bonding tension per unit cross-sectional area of the polypropylene resin film 2 is 1.42, and the polypropylene The ratio of the pre-bonding tension per unit cross-sectional area of the polarizing film 1 to the pre-bonding tension per unit cross-sectional area of the film 2 was 3.43.

After bonding, using an ultraviolet irradiation device using a metal halide lamp as a light source, the adhesive is cured by irradiating with ultraviolet rays from the cycloolefin resin film side so that the integrated light quantity at a wavelength of 320 to 400 nm is 200 mJ / cm ² , The obtained polarizing plate was wound up on a roll.

(D) Curling Evaluation of Polarizing Plate A 30 cm × 30 cm sample was cut out from the polarizing plate obtained in (c) above, and the amount of curling was measured by the above method with the protective film removed therefrom. The curl was a convex curl on the olefin resin film side, and the four corners were 45.5 mm.

[Example 2]
In Example 1 (c), the ratio of the pre-bonding tension per unit cross-sectional area of the cycloolefin-based resin stretched film 3 to the pre-bonding tension per unit cross-sectional area of the polypropylene film 2 is 1.90. In addition, the ratio of the pre-bonding tension per unit cross-sectional area of the polarizing film 1 to the pre-bonding tension per unit cross-sectional area of the polypropylene film 2 is 4.58, and the other examples. In the same manner as in Example 1, a polarizing plate was produced. A sample of 30 cm × 30 cm was cut out from the obtained polarizing plate, and when the amount of curling was measured by the above method in a state where the protective film was peeled from the sample, it was a positive curl in which the cycloolefin resin film side was convex, All four corners were 15.5 mm.

[Comparative Example 1]
In (c) of Example 1, the ratio of the pre-bonding tension per unit cross-sectional area of the cycloolefin-based resin stretched film 3 to the pre-bonding tension per unit cross-sectional area of the polypropylene film 2 is 1.15. In addition, the ratio of the pre-bonding tension per unit cross-sectional area of the polarizing film 1 to the pre-bonding tension per unit cross-sectional area of the polypropylene film 2 is 2.27. In the same manner as in Example 1, a polarizing plate was produced. A 30 cm × 30 cm sample was cut out from the obtained polarizing plate, and when the amount of curling was measured by the above method in a state where the protective film was peeled therefrom, it was a positive curl in which the cycloolefin resin film side was convex. However, the maximum reached 87mm.

1 …… Polarizing film,
2 ... Polypropylene resin film,
3 ... stretched transparent resin film,
5 ... Polarizing plate,
12, 13 ... adhesive application device,
15 …… First bonding roll,
16 …… Second bonding roll,
18 …… Curing device,
21-26 Peach roll,
31 ... curled film,
33 …… A virtual surface on the reference surface when it is assumed that the film is not curled,
35 …… Reference plane,
A, B, C, D ... Corners on the virtual plane,
A1, B1, C1, D1 ... curled film corners,
H: Curling amount (height from the reference surface to the corner of the film).

Claims (6)

A polypropylene resin film is bonded to one side of a polarizing film made of a polyvinyl alcohol-based resin on which a dichroic dye is adsorbed and oriented via an adhesive, and the other side of the polarizing film is bonded via an adhesive. A method for producing a polarizing plate by laminating a stretched cycloolefin-based resin film,
The polarizing film has a thickness of 5 to 40 μm,
The polypropylene resin film has a thickness of 60 μm or less,
The stretched cycloolefin resin film has a thickness of 20 to 120 μm,
The polarizing film, the polypropylene-based resin film, and the stretched cycloolefin-based resin film are respectively arranged in a fixed direction via pinch rolls, and the polarizing film is the polypropylene-based resin film and the stretched cycloolefin-based resin film. A raw material film transporting process for transporting so as to be sandwiched between,
The polypropylene resin film is bonded to one side of the polarizing film, and the stretched cycloolefin resin film is bonded to the other side of the polarizing film via a curable adhesive, and the polypropylene resin With the 1st bonding roll which contacts the outer side of a film and rotates in the conveyance direction, and the 2nd bonding roll which contacts the outer side of the said stretched cycloolefin type resin film and rotates in the conveyance direction A bonding step of performing the bonding while sandwiching a laminate of a polypropylene resin film / polarizing film / stretched cycloolefin resin film;
Curing the adhesive after the bonding step, and a curing step of bonding the polypropylene resin film and the polarizing film and the stretched cycloolefin resin film and the polarizing film;
In the bonding step, the ratio of the pre-bonding tension per unit cross-sectional area of the stretched cycloolefin-based resin film to the pre-bonding tension per unit cross-sectional area of the polypropylene-based resin film is 1.34. The ratio of the pre-bonding tension per unit cross-sectional area of the polarizing film to the pre-bonding tension per unit cross-sectional area of the polypropylene-based resin film is 3.23 or more so as to be 1.90 or less. The manufacturing method of a polarizing plate characterized by performing so that it may become 4.58 or less .   The method according to claim 1, wherein the polypropylene resin film has a protective film laminated on the side opposite to the surface to be bonded to the polarizing film. The polypropylene-based resin film is subjected to a protective film bonding step for bonding the protective film, and then provided to the raw material film conveying step. The protective film bonding step is a unit cross-sectional area of the propylene-based resin film. The method of Claim 2 performed so that ratio of the pre-bonding tension concerning the said protection film with respect to the pre-bonding tension | tensile_strength may be 5 or more and 35 or less. The cycloolefin-based resin film stretched A method according to any one of claims 1 to 3, which is biaxially oriented. In the course of the raw material film conveying step, the adhesive is applied to the bonding surface of the polypropylene resin film to the polarizing film, and the bonding is performed to the bonding surface of the stretched cycloolefin resin film to the polarizing film. The method according to any one of claims 1 to 4 , further comprising an adhesive application step of applying an agent. The adhesive contains an epoxy compound and a cationic polymerization initiator, method according to any one of claims 1 to 5, wherein the curing step carried out by irradiation of active energy rays.