JP2012215821A - Method for manufacturing polarizing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a polarizing plate which hardly causes an excessive reverse curl and has excellent optical characteristics or lamination strength.SOLUTION: There is provided a method for manufacturing a polarizing plate by laminating an acrylic resin film 25 on one surface of a polarizing film 21 and laminating a transparent resin film 23 on the other surface of the polarizing film 21, the method comprising: (A) a conveying step for conveying a raw material film so that the polarizing film 21 is sandwiched by the acrylic resin film 25 and the transparent resin film 23; (B) a laminating step for performing lamination while sandwiching a film laminate by a first laminating roll 15 which rotates in contact with the outside of the acrylic resin film 25 and a second laminating roll 16 which rotates in contact with the outside of the transparent resin film 23; and (C) a curing step for curing an adhesive. The laminating step (B) laminates the polarizing film 21 in a state of applying tension to both films so that the contraction stress in a conveyance direction on the side of the acrylic resin film 25 is larger than the contraction stress in the conveyance direction on the side of the transparent resin film 23.

Description

  The present invention relates to a method for producing a polarizing plate, and particularly relates to a method for producing a polarizing plate in which an acrylic resin film is bonded to one side of a polarizing film and a transparent resin film is bonded to the other side.

  The polarizing plate is used 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.

  In general, 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-based resin in which a dichroic dye is adsorbed and oriented. As the protective film for the polarizing plate, a film of cellulose acetate resin typified by triacetyl cellulose is often used, and the thickness is usually about 40 to 120 μm. For bonding such a cellulose acetate resin film to a polarizing film, an adhesive made of an aqueous solution of a polyvinyl alcohol resin is often used. However, a polarizing plate in which a protective film is laminated on a polarizing film through a water-soluble adhesive has a problem that the polarizing performance is deteriorated or the protective film is peeled off from the polarizing film when used for a long time under wet heat conditions. was there.

  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. As such a resin, a technique using an acrylic resin which is a relatively inexpensive resin material is known. For example, a protective film (see Patent Document 1) using a (meth) acrylic resin containing a lactone ring is known. Furthermore, a protective film (see Patent Document 2) is also developed in which an acrylic resin is uniaxially or biaxially stretched within a stretch ratio of 50 to 200%. By using such a stretched acrylic resin, an optical film having excellent mechanical strength and heat shrinkability can be obtained.

  A polarizing plate obtained by laminating a long protective film on a long polarizing film can be produced by a roll-to-roll bonding method using a bonding roll. The roll-to-roll laminating method is a method of laminating a long protective film on a long polarizing film via an adhesive, and in this state, narrowing the pressure with two laminating rolls to paste the polarizing film and the protective film. It is a method to match. In this bonding method, an adhesive that cures with an active energy ray or the like is often used as the adhesive. Such a curable adhesive is preferable because the curing speed is high and it is difficult to adversely affect the film due to moisture.

JP 2009-122663 A JP 2008-216586 A

  For the purpose of further reducing the thickness and thickness of the polarizing plate, the present inventors have applied a polarizing plate having an acrylic resin film on one side of the polarizing film and a transparent resin film on the other side. The method of manufacturing by the combined method was examined. As a result, when roll-to-roll bonding is performed under normal conditions, the acrylic resin film side becomes convex due to the difference in shrinkage stress between the acrylic resin film and the transparent resin film, and the transparent resin film side and its surface It was found that there is a tendency to show so-called reverse curl, in which the pressure-sensitive adhesive layer side provided in is concave.

  When the polarizing plate is bonded to the liquid crystal cell, an adhesive layer is provided on the outside of the transparent resin film, and is bonded to the liquid crystal cell via the adhesive layer. At this time, the reverse-curled polarizing plate has a concave shape on the side of the pressure-sensitive adhesive layer, so there is no problem if it is slightly reverse-curled. However, when the curl amount is excessively large, the pressure-sensitive adhesive is used when bonding to the liquid crystal cell. Air bubbles are easily caught in the center of the layer. For this reason, it becomes easy to produce inconveniences, such as a deterioration of the optical characteristic due to a bubble, and the fall of bonding strength.

  On the contrary, a so-called positive curl state in which the pressure-sensitive adhesive layer side is convex can be considered. This positive curled polarizing plate has a convex central portion of the pressure-sensitive adhesive layer, so that the central portion of the pressure-sensitive adhesive layer can be pressed against the liquid crystal cell and adhered while allowing air to escape to the surroundings. Curling is preferable because it facilitates the bonding of the polarizing plate to the liquid crystal cell. However, if the positive curl becomes excessively large, this time, the force to curl the polarizing plate is large, so that the adhesion peels off from the end of the polarizing plate adhered to the surface of the liquid crystal cell, and the polarizing plate is removed from the liquid crystal cell. The inconvenience of easy peeling is likely to occur.

  An object of the present invention is to provide a method for producing a polarizing plate that is less prone to excessive reverse curling and has good optical properties and bonding strength.

  According to the method for producing a polarizing film of the present invention, the above-mentioned problem is that an acrylic 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 via an adhesive. A polarizing plate is produced by laminating a transparent resin film on the other surface of the polarizing film with an adhesive, and (A) the polarizing film, the acrylic resin film, and the transparent resin. A raw material film transporting step of transporting the film in a certain direction and sandwiching the polarizing film between the acrylic resin film and the transparent resin film; and (B) the acrylic resin film on one side of the polarizing film. The transparent resin film is bonded to the other surface of the polarizing film via a curable adhesive, and the acrylic resin film is bonded. A first bonding roll that contacts the outside of the rum and rotates in the conveying direction, and a second bonding roll that contacts the outside of the transparent resin film and rotates in the conveying direction, and the acrylic resin. A bonding step of performing the bonding while sandwiching a laminate of the film / the polarizing film / the transparent resin film; and (C) after bonding, the adhesive is cured to bond the acrylic resin film and the polarizing film. And a curing step for adhering the transparent resin film and the polarizing film, and the bonding step (B) is more preferably performed on the acrylic resin film side than the shrinkage stress in the transport direction on the transparent resin film side. The polarizing film in a state where tension is applied to the transparent resin film and the acrylic resin film so that the shrinkage stress in the transport direction is larger. It is solved by laminating.

  In this case, the said bonding process (B) is the peripheral speed of the 2nd bonding roll which contacts the outer side of the said transparent resin film with respect to the peripheral speed of the 1st bonding roll which contacts the outer side of the said acrylic resin film. Is preferably 1.0105 or more and 1.0141 or less.

  Alternatively, in the bonding step (B), the ratio of the pre-bonding tension per unit cross-sectional area of the acrylic resin film to the pre-bonding tension per unit cross-sectional area of the transparent resin film is 1 or more. Preferably it is done.

  In this case, it is preferable to further include a protective film bonding step of bonding a protective film to a surface of the acrylic resin film opposite to the surface bonded to the polarizing film.

  The transparent resin film is preferably a film that has not been stretched, or a film that has been uniaxially or biaxially stretched.

  Furthermore, the said adhesive agent is apply | coated to the bonding surface to the said polarizing film of the said acrylic resin film in the middle of the said raw material film conveyance process (A), and the bonding surface to the said polarizing film of the said transparent resin film It is preferable to further include an adhesive application step of applying the adhesive to the substrate.

  Moreover, it is preferable that the said adhesive agent contains active energy ray hardening resin, and the said hardening process (C) is performed by hardening the said active energy ray hardening resin by irradiation of an active energy ray.

  According to the method for producing a polarizing plate of the present invention, an inexpensive and thin polarizing plate can be produced by using an acrylic resin. In addition, it is bonded to the polarizing film with tension applied to both films so that the shrinkage stress in the transport direction on the acrylic resin film side is greater than the shrinkage stress in the transport direction on the transparent resin film side. ing. For this reason, a stronger shrinkage stress acts on the acrylic resin film side than on the transparent resin film side, and a force to warp the acrylic resin film side works. In this way, by giving a difference in the shrinkage stress between the two films, the excessive reverse curl in which the convex shape on the acrylic resin film side increases due to the difference in the shrinkage stress between the two films is corrected, and the reverse The curl amount can be reduced, and further, a slight positive curl can be obtained. Thereby, it becomes possible to provide a polarizing plate that suppresses excessive reverse curling and has excellent optical properties and bonding strength.

It is the cross-sectional schematic diagram which showed the process of bonding an acrylic resin film and a transparent resin film to a polarizing film. It is the perspective view which showed the state by which the polarizing plate carried out normal curl and reverse curl. It is the perspective view which showed typically the measuring method of the curl amount. It is a cross-sectional schematic diagram of a polarizing plate. It is the graph which showed the result of the Example and the comparative example.

  Hereinafter, some embodiments of the present invention will be described with reference to the drawings. In addition, this invention is not limited by the member, arrangement | positioning, etc. which are demonstrated below, These members etc. can be suitably changed in accordance with the meaning of this invention.

  Hereinafter, the manufacturing method of a polarizing plate is demonstrated in detail. FIG. 1 is a schematic cross-sectional view illustrating a process of bonding an acrylic resin film and a transparent resin film to a polarizing film. As shown in this figure, the polarizing plate 20 bonds an acrylic resin film 25 via an adhesive to one surface of a polarizing film 21 made of a polyvinyl alcohol-based resin in which a dichroic dye is adsorbed and oriented. Moreover, the transparent resin film 23 is bonded to the other surface of the polarizing film 21 through an adhesive. The manufacturing method of the polarizing plate 20 of this invention is equipped with a raw material film conveyance process (A), a bonding process (B), and a hardening process (C). Furthermore, in this embodiment, the protect film bonding process (D) is performed.

  In the raw film transporting step (A), the polarizing film 21 is transported in a certain direction, the acrylic resin film 25 is supplied to one surface, and the transparent resin film 23 is supplied to the other surface. In the middle of the raw material film transporting step (A), the adhesive application device 12 applies an adhesive to the bonding surface of the acrylic resin film 25 and the polarizing film 21, and the other adhesive application device 13 uses a transparent resin. An adhesive is applied to the bonding surface of the film 23 and the polarizing film 21.

  The bonding step (B) is a first bonding roll 15 that contacts the outside of the acrylic resin film 25 and a second bonding roll 16 that contacts the outside of the transparent resin film 23, and the acrylic resin film. 25 / polarizing film 21 / transparent resin film 23 is sandwiched between layers. 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 polarized light is polarized between the polarizing film 21 and the acrylic resin film 25. In this process, the adhesive between the film 21 and the transparent resin film 23 is cured. Hereinafter, the description of each of these steps will be made in order.

[Raw material film transport process (A)]
In the raw film transporting step (A), the long polarizing film 21 is fed out from the polarizing film 21 wound in a roll shape. A long acrylic resin film 25 fed out from an acrylic resin film 25 wound in the same roll shape is supplied to one surface of the polarizing film 21 sent at a predetermined speed. On the other hand, the other side of the polarizing film 21 is supplied with a long transparent resin film 23 that is fed out from the transparent resin film 23 that is also wound into a roll.

  The conveyance speed of each film may be set to a value suitable for the production apparatus, and is not particularly limited. Usually, the film is produced at the previous step and is conveyed in accordance with the conveyance speed of the polarizing film 21 to be conveyed. Is done. Unless the type and quality of the polarizing plate 20 are restricted, the takt time is increased, so that a higher conveying speed is preferable from the viewpoint of productivity. Specifically, the conveyance speed can be set to about 1 to 30 m / min, for example.

  The direction in which each film is transported is not particularly limited as long as the polarizing film 21 is sandwiched between the acrylic resin film 25 and the transparent resin film 23 at the end of the transport process. In the middle of the process, for example, there may be a portion where the acrylic resin film 25 and the transparent resin film 23 are transported in a direction perpendicular to the transport direction of the polarizing film 21 as shown in FIG. There may be a part to be conveyed. In addition, when there is a restriction on the arrangement of the manufacturing apparatus, the acrylic resin film 25 and the transparent resin film 23 are once drawn out in the direction opposite to the conveying direction of the polarizing film 21, and then the polarizing film 21 by an appropriate roll. The direction may be changed so as to be directed to one side. Furthermore, after the polarizing film 21 is fed out at an appropriate angle including the vertical direction from the transverse direction in which the polarizing film 21 is conveyed, the direction may be changed so as to be directed to one side of the polarizing film 21 by an appropriate roll.

[Protect film pasting step (D)]
Although illustration is omitted, the acrylic resin film 25 can be subjected to the raw film transporting step (A) in a state where the protective film is laminated on the side opposite to the surface to be bonded to the polarizing film 21. The protect film has a role of protecting the surface of the acrylic resin film 25 and increasing the reliability of conveyance and bonding. In addition, since the protective film has high rigidity and so-called “strain”, the protective film is bonded to the acrylic resin film 25 or the polarizing plate 20 provided with the protective film, so that the film is shaped and curled. . In this case, the acrylic resin film 25 is subjected to a raw film transporting step (A) after undergoing a protective film laminating step for laminating the protective film. In addition, this protect film bonding process (D) is not an essential process in this invention, but an arbitrary process.

  A laminating machine such as a roll type laminator can be used for laminating the acrylic resin film 25 and the protect film. In this protection film bonding step (D), the tension before bonding of the acrylic resin film 25 and the tension before bonding of the protection film may be the same or different.

  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 between the polarizing film 21 and the acrylic resin film 25 and bonding between the polarizing film 21 and the transparent resin film 23 are performed via an adhesive. An adhesive is a bonding surface of the polarizing film 21 and the transparent resin film 23 on at least one of the bonding surfaces of the polarizing film 21 and the acrylic resin film 25 at an arbitrary stage in the raw film transporting step (A). It can apply | coat to at least one of each. In the figure, the adhesive is applied to the bonding surface of the acrylic resin film 25 using the adhesive application device 12, and the adhesive is applied to the bonding surface of the transparent resin film 23 using the adhesive application device 13. The surface to which the adhesive is applied is not limited to this. For example, an adhesive may be applied to the bonding surface of the polarizing film 21 instead of the acrylic resin film 25 or the transparent resin film 23, or all of the acrylic resin film 25, the transparent resin film 23, and the polarizing film 21 are bonded. An adhesive may be applied to the mating surface.

  However, from the viewpoint of operability, it is preferable to apply an adhesive to the surfaces of the acrylic resin film 25 and the transparent resin film 23 that are bonded to the polarizing film 21. That is, in the raw film transporting step (A), there is a portion that is transported so as to sandwich the polarizing film 21 between the acrylic resin film 25 and the transparent resin film 23 in preparation for the subsequent bonding step (B). Therefore, it is preferable to apply an adhesive at that portion.

  Then, Preferably, an adhesive agent coating process is performed in the middle of a raw material film conveyance process (A). The adhesive is applied to the surfaces of the acrylic resin film 25 and the transparent resin film 23 that are bonded to the polarizing film 21 in this adhesive application step.

  The adhesive surface between the acrylic resin film 25 and the transparent resin film 23 is subjected to surface activation treatment such as corona treatment, plasma treatment, ultraviolet irradiation treatment, or electron beam irradiation treatment before the adhesive is applied. May be. 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 apply a required amount of adhesive uniformly 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 film transporting step (A), the acrylic resin film 25 and the transparent resin film 23 supplied from both sides so as to sandwich the polarizing film 21 are supplied to the subsequent bonding step (B). In this bonding step (B), these films are formed by the first bonding roll 15 that contacts the outside of the acrylic resin film 25 and the second bonding roll 16 that contacts the outside of the transparent resin film 23. Bonded.

  Here, when the normal bonding conditions, that is, the peripheral speed of the first bonding roll 15 and the peripheral speed of the second bonding roll 16 are the same, the obtained polarizing plate 20 is the acrylic resin film 25. The side is convex, the transparent resin film 23 side is concave, and excessive reverse curling tends to occur. Therefore, in the present invention, in the bonding step (B), the shrinkage stress on the acrylic resin film 25 side is larger than the shrinkage stress on the acrylic resin film 25 side than the shrinkage stress on the transparent resin film 23 side. The polarizing film 21 is bonded in a state where tension is applied.

As described above, there are various methods for applying tension to the films 23 and 25. For example, the following two embodiments can be given.
(B-1) Ratio of the peripheral speed of the 2nd bonding roll 16 which contacts the outer side of the transparent resin film 23 with respect to the peripheral speed of the 1st bonding roll 15 which contacts the outer side of the acrylic resin film 25 is 1. 0105 or more and 1.0414 or less.
(B-2) The ratio of the pre-bonding tension per unit cross-sectional area of the acrylic resin film 25 to the pre-bonding tension per unit cross-sectional area of the transparent resin film 23 is 1 or more.
Hereinafter, the embodiments (B-1) and (B-2) will be described in order.

(B-1) 1st Embodiment In this embodiment, in the bonding process (B), the ratio of the circumferential speed of the 2nd bonding roll 16 with respect to the circumferential speed of the 1st bonding roll 15 is 1.0105. As mentioned above, it bonds so that it may become 1.0141 or less. The relationship between the peripheral speed, the peripheral speed of the first lamination roll 15 R _1, the peripheral speed of the second lamination roll 16 as R _2, means that fulfill the following equation (1).
1.0105 ≦ R ₂ / R ₁ ≦ 1.0141 (1)

  Depending on the ratio of the peripheral speeds, the acrylic resin film 25 is fed out along the transport direction with a large force, and the transparent resin film 23 is fed out along the transport direction with a smaller force. For this reason, the acrylic resin film 25 is in a more tensioned state than the transparent resin film 23. As a result, the acrylic resin film 25 is conveyed to the next curing step (C) in a state in which the acrylic resin film 25 is relatively contracted and the transparent resin film 23 is relatively tensile stressed. Is cured. As a result, the polarizing plate 20 becomes almost flat due to the difference in shrinkage stress between the acrylic resin film 25 and the transparent resin film 23.

  When the ratio of the peripheral speed of the second laminating roll 16 to the peripheral speed of the first laminating roll 15 is small, it tends to be a reverse curl as shown in FIG. 2A, and conversely, the ratio of the peripheral speed is large. The positive curl as shown in FIG.

  When the ratio of the circumferential speed of the second laminating roll 16 to the circumferential speed of the first laminating roll 15 is less than 1.0105, the curl amount of the reverse curl becomes too large and the laminating to the liquid crystal cell 40 is performed. It becomes easy to bite bubbles. As the ratio of the peripheral speeds increases, the curl amount of the reverse curl decreases and becomes nearly flat. When the ratio exceeds a certain value, the transparent resin film 23 side becomes a convex forward curl. If the curl amount is small and a slight amount of positive curl, the pressure-sensitive adhesive layer becomes convex, so that when the polarizing plate 20 is bonded to the liquid crystal cell 40, bubbles and the like are less likely to enter. However, if the ratio of the peripheral speed of the second bonding roll 16 to the peripheral speed of the first bonding roll 15 exceeds 1.0141, the curl amount of the positive curl becomes too large, and the liquid crystal cell 40 has The inconvenience that the polarizing plate 20 is easily peeled off from the liquid crystal cell 40 after bonding is likely to occur.

When the positive curl is positive (+) and the reverse curl is negative (−), the curl amount is preferably in the range of about −80 to +80 mm. As shown in the examples described later, the curl amount is within the range. The ratio of the peripheral speeds is 1.0105 or more and 1.0141 or less. Thus, by setting the circumferential speed R2 of the _second laminating roll 16 slightly higher than the circumferential speed R1 of the _first laminating roll 15, and setting the ratio of both in the above range, The reverse curl and normal curl of the obtained polarizing plate 20 do not become excessive, and the curl amount is appropriately controlled.

  The curl amount of the polarizing plate 20 is measured as follows. First, the polarizing plate 20 is cut into an appropriate size along the flow direction (MD) of the roll-shaped polarizing plate 20. The size is cut into an arbitrary size such as 250 mm × 300 mm or 400 mm × 700 mm. When indicating the curl amount, it is necessary to specify the measured size. Then, as shown in FIG. 3, when the curling has occurred in the polarizing plate 20, the convex side faces downward, and when no curling has occurred, either side faces down. And placed on a reference surface (for example, on a horizontal table) and allowed to stand for 1 hour in an environment of a temperature of 22 ° C. and a relative humidity of 60%. In this figure, the surface when it is assumed that the polarizing plate 20 has no curl is displayed as a virtual surface (surface indicated by a dotted line in the drawing) represented by a quadrilateral 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 polarizing plate 20 are reversed, and the curl amount is measured by the following method. 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 polarizing plate 20 are reversed. If the curl is not observed even in the reversed state, the curl amount is determined to be zero. If curl is observed in the inverted state, the amount of curl is measured in the state by the following method. When curl is observed, the curl amount is measured with the convex side facing down as shown in the figure.

  FIG. 3A shows a reversely curled polarizing plate 20 having a concave on the transparent resin film 23 side and a convex on the acrylic resin film 25 side. In the reversely curled polarizing plate 20, the acrylic resin film 25 side is placed on the reference surface with the side facing down. In the reversely curled polarizing plate 20, one corner A on the virtual plane is at the position A1, and the other corners B, C, and D are at the positions B1, C1, and D1, respectively. That is, in this figure, the four corners A1, B1, C1, and D1 of the polarizing plate 20 are all floating, but one, two, or three of the four corners of the polarizing plate 20 are displayed. Sometimes it does not rise. Of course, if there is no curl at all, the four corners A1, B1, C1, and D1 all coincide with the quadrilateral ABCD of the virtual surface. In this state, the height H from the reference surface is measured for each of the four corners A1, B1, C1, and D1 of the polarizing plate 20, and the maximum value thereof is taken as the curl amount.

  On the other hand, FIG. 3B shows a positively curled polarizing plate 20 that is convex on the transparent resin film 23 side and concave on the acrylic resin film 25 side. The positively curled polarizing plate 20 is placed on the reference surface with the transparent resin film 23 side down. Similarly to the reverse curl, the height H from the reference plane is measured for each of the four corners A1, B1, C1, and D1 of the polarizing plate 20, and the maximum value thereof is used as the curl amount.

  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 oxidation. And ceramics obtained by thermal spraying one or more of zirconium and aluminum oxide. Especially, it is preferable that the 1st bonding roll 15 is made into a rubber roll and the 2nd bonding roll 16 is made into a metal roll. That is, a rubber roll having elasticity on the surface is applied to the acrylic resin film 25 that is relatively thin and has a low rigidity, and a metal roll is generally applied to the transparent resin film 23 side having a relatively higher rigidity than the acrylic resin film 25. Thus, the stress caused by the difference between the peripheral speeds of both can be effectively and uniformly applied to the film.

(B-2) 2nd Embodiment In this embodiment, ratio of the pre-bonding tension per unit cross-sectional area of the acrylic resin film 25 with respect to the pre-bonding tension per unit cross-sectional area of the transparent resin film 23 is 1. Bonding is performed so that it becomes the above. That is, the acrylic resin film 25 is bonded in a state where a larger tension is applied than the transparent resin film 23, thereby generating a larger shrinkage stress in the acrylic resin film 25 and suppressing excessive reverse curl. is doing. Here, the tension before bonding can be imparted by pulling the film before bonding in a direction along the film conveyance direction. Specifically, for example, a winding roll (not shown) that winds the polarizing plate 20 in a roll shape has a higher winding force than a feeding roll (not shown) that feeds the roll-shaped acrylic resin film 25. In addition, there is a method of giving a difference between the rotation speeds of both rolls.

Here, the pre-bonding tension per unit cross-sectional area means the pre-bonding tension applied to the film per unit cross-sectional area in the width direction of the film. Specifically, in the following formula (2) Can be represented.
Pre-bonding tension per unit cross-sectional area (N / mm ² ) = film pre-bonding tension (N) / cross-sectional area in the film width direction (mm ² ) (2)
For example, when the pre-bonding tension of the film is 1000 N and the cross-sectional area in the film width direction is 2000 mm ² , the pre-bonding tension per unit cross-sectional area is 0.50 (N / mm ² ).

In this embodiment, the ratio of the tension before bonding per unit cross-sectional area is adjusted so as to satisfy the following formula (3).
Ratio of pre-bonding tension per unit cross-sectional area = pre-bonding tension per unit cross-sectional area of acrylic resin film 25 / tension before bonding per unit cross-sectional area of transparent resin film ≧ 1 (3)

  The ratio of the tension before bonding is preferably 1 or more. When the ratio of the tension before bonding is less than 1, excessive reverse curl is likely to occur where the acrylic resin film 25 side has a large convex shape. The upper limit of the ratio of tension before bonding is not particularly limited, but is preferably 2 or less. This is because if the ratio of the tension before bonding exceeds 2, this tends to cause excessive positive curl.

  In addition, although the circumferential speed ratio of 1st Embodiment (B-1) and the tension ratio before bonding of 2nd Embodiment (B-2) have an effect which suppresses reverse curl only by any one, By satisfying both the circumferential speed ratio and the tension ratio before bonding, a higher effect can be obtained. That is, per unit cross-sectional area of the transparent resin film 23 while the peripheral speed ratio of the second bonding roll 16 to the peripheral speed ratio of the first bonding roll 15 is 1.0105 or more and 1.0414 or less. The ratio of the tension before bonding per unit cross-sectional area of the acrylic resin film 25 to the tension before bonding is set to 1 or more. Thereby, it becomes possible to produce a larger shrinkage stress in the acrylic resin film 25 than in the transparent resin film 23, and to suppress excessive reverse curl more reliably.

[Curing step (C)]
Laminated body bonded in the order of acrylic resin film 25 / adhesive (not shown) / polarizing film 21 / adhesive (not shown) / transparent resin film 23 conveyed from the bonding step (B). In the curing step (C), the adhesive is cured, and the acrylic resin film 25 and the transparent resin film 23 are bonded to the polarizing film 21 to form the polarizing plate 20. In the figure, the laminated body bonded by the bonding rolls 15 and 16 is sent to the curing device 18 where the curing process is performed. The curing treatment can be performed by irradiation with active energy rays, heating, drying, or the like depending on the type of adhesive.

  As the adhesive, it is preferable to use an active energy ray-curable adhesive that is cured by irradiation with active energy rays. 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 a wavelength region effective for activation of the initiator is 0.1 to 300 mW / cm ^2. It is preferable to set it, and it is more preferable to set it to be 1 to 200 mW / cm ² . When 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 21 is caused by heat radiated from the lamp or heat generated during polymerization of the curable adhesive composition. May occur.

The irradiation time of ultraviolet rays 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. It is preferable to set, and it is more preferable to set so that it may become 50-1,000 mJ / cm < ² >. When the integrated light quantity to the curable adhesive composition is less than 10 mJ / cm ² , it is difficult to generate active species derived from the initiator, and the resulting adhesive layer is likely 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 tends to be 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 from the viewpoint of thinning the polarizing plate 20 while maintaining an appropriate adhesive force. 20 μm or less, more preferably 10 μm or less.

  The embodiment of the method for manufacturing the polarizing plate 20 has been described above. In addition, in embodiment mentioned above, during performing the raw material film conveyance process (A), the protective film bonding process (D) which bonds a protective film to the acrylic resin film 25 is performed, and a bonding process is carried out after that. (B) and the curing step (C) are performed. However, as a timing which performs a protect film bonding process (D), it is not limited during the raw material film conveyance process (A) mentioned above. For example, after the raw material film transporting step (A), the bonding step (B), and the curing step (C) are performed to produce a laminate of the acrylic resin film 25 / polarizing film 21 / transparent resin film 23, the protective film A protective film may be bonded to the surface of the acrylic resin film 25 by performing a bonding step (D).

(Polarizing plate 20)
Next, the polarizing plate 20 will be described. As shown in FIG. 4, the polarizing plate 20 has a layer structure in which an acrylic resin film 25, a polarizing film 21, and a transparent resin film 23 are laminated in this order. Hereinafter, each layer constituting the polarizing plate 20 will be described.

(1) Polarizing film 21
The polarizing film 21 is a member having a function of converting natural light into linearly polarized light. As the polarizing film 21, a film obtained by adsorbing and orienting a dichroic dye on a uniaxially stretched polyvinyl alcohol resin film can be used. As the polyvinyl alcohol resin, a saponified polyvinyl acetate resin can be used. As the polyvinyl acetate resin, in addition to polyvinyl acetate which is a homopolymer of vinyl acetate, polyvinyl acetate and Examples thereof include copolymers with other copolymerizable monomers. 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-based resin may be modified, and for example, polyvinyl formal or polyvinyl acetal modified with aldehydes can also 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.

  A film obtained by forming such a polyvinyl alcohol resin is used as a raw film of the polarizing film 21. The method for forming a polyvinyl alcohol-based resin is not particularly limited, and can be formed by a known method. Although the thickness of a polyvinyl alcohol-type raw film is not specifically limited, For example, it is about 5-150 micrometers.

  The polarizing film 21 usually has a step of uniaxially stretching such a polyvinyl alcohol resin film, a step of adsorbing a dichroic dye by dyeing the polyvinyl alcohol resin film with a dichroic dye, and a dichroic dye It is manufactured through a step of treating the adsorbed polyvinyl alcohol-based resin film with a boric acid aqueous solution and a step of washing with water after the treatment with the boric acid aqueous solution.

  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, this uniaxial stretching may be performed before boric acid treatment or during boric acid treatment. Moreover, uniaxial stretching can also be performed in several steps. 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. Further, the uniaxial stretching may be dry stretching in which stretching is performed in the air, or may be wet stretching in which stretching is performed in a state where a polyvinyl alcohol-based resin film is swollen 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 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 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 dye is usually employed. The content of the dichroic dye in this aqueous solution is usually about 1 × 10 ⁻⁴ to 10 parts by weight, preferably about 1 × 10 ⁻³ to 1 part by weight per 100 parts by weight of water. This aqueous solution may contain an inorganic salt such as sodium sulfate as a dyeing assistant. The temperature of the aqueous dichroic 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 a dichroic dye can be performed by immersing the dyed polyvinyl alcohol-based 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 about 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 about 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 about 150 to 600 seconds, and more preferably about 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 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., and the immersion time is usually about 1 to 120 seconds.

  After washing with water, a drying process is performed to obtain the polarizing film 21. 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.

  In this way, the polyvinyl alcohol-based resin film is subjected to uniaxial stretching, dyeing with a dichroic dye, and boric acid treatment, and the polarizing film 21 is obtained. The thickness of the polarizing film 21 can be about 2-40 micrometers, for example.

  The polarizing film 21 thus obtained is preferably used as it is for the raw film transporting step (A). Thereby, it can produce continuously from the raw film of a polyvinyl alcohol-type resin until the polarizing plate 20 is manufactured.

(2) Acrylic resin film 25
The acrylic resin film 25 is a member having a function of preventing or reinforcing the surface of the polarizing film 21 and is made of an acrylic resin. Here, acrylic resin means (meth) acrylic resin and is a concept including both acrylic resin and methacrylic resin. Hereinafter, the acrylic resin will be described.

(2-1) Acrylic Resin The acrylic resin is a (meth) acrylic resin as described above, and means a polymer of acrylic acid ester or methacrylic acid ester. As the polymer of the methacrylic acid ester, for example, a polymer composed mainly of an alkyl methacrylate is preferable. The monomer composition of the alkyl methacrylate is preferably 70% by weight or more, more preferably 80% by weight or more, and still more preferably 90% by weight or more, based on the total 100% by weight of all monomers. And alkyl methacrylate is 99% by weight or less. The acrylic resin may be a homopolymer of alkyl methacrylate, or a copolymer of 50% by weight or more of alkyl methacrylate and 50% by weight or less of a monomer other than alkyl methacrylate. Also good. As the alkyl methacrylate, those having 1 to 4 carbon atoms of the alkyl group are usually used, and among them, methyl methacrylate is preferably used.

  The monomer other than alkyl methacrylate may be a monofunctional monomer having one polymerizable carbon-carbon double bond in the molecule, or two or more polymerizable carbons in the molecule. -A polyfunctional monomer having a carbon double bond may be used. In particular, monofunctional monomers are preferably used. Examples thereof include alkyl acrylates such as methyl acrylate and ethyl acrylate, styrene monomers such as styrene and alkyl styrene, acrylonitrile and methacrylonitrile. Such unsaturated nitriles. When using alkyl acrylate as a copolymerization component, the carbon number is 1-8 normally.

  The acrylic resin preferably does not have a glutarimide derivative, a glutaric anhydride derivative, a lactone ring structure, or the like. These acrylic resins may not have sufficient mechanical strength and heat-and-moisture resistance as the acrylic resin film 25 in some cases.

(2-2) Rubber elastic particles In order to improve flexibility and improve handling properties, rubber elastic particles may be blended with the acrylic resin. The rubber elastic particles are particles containing a rubber elastic body, and may be particles composed only of a rubber elastic body, or may be particles having a multilayer structure having a rubber elastic body layer. Examples of rubber elastic bodies include olefin-based elastic polymers, diene-based elastic polymers, styrene-diene-based elastic copolymers, and acrylic-based elastic polymers. Among these, an acrylic elastic polymer is preferably used from the viewpoint of the surface hardness, light resistance, and transparency of the acrylic resin film 25.

  The acrylic elastic polymer is preferably a polymer mainly composed of alkyl acrylate, and may be a homopolymer of alkyl acrylate, or may be a single polymer other than alkyl acrylate of 50% by weight or more and alkyl acrylate. A copolymer with 50% by weight or less of the monomer may be used. As the alkyl acrylate, those having 4 to 8 carbon atoms in the alkyl group are usually used. Examples of monomers other than alkyl acrylate include alkyl methacrylates such as methyl methacrylate and ethyl methacrylate, styrene monomers such as styrene and alkyl styrene, acrylonitrile and methacrylonitrile. Monofunctional monomers such as unsaturated nitriles, alkenyl esters of unsaturated carboxylic acids such as allyl (meth) acrylate and methallyl (meth) acrylate, dialkenyl esters of dibasic acids such as diallyl maleate, And polyfunctional monomers such as unsaturated carboxylic acid diesters of glycols such as alkylene glycol di (meth) acrylate.

  The rubber elastic particle containing the acrylic elastic polymer is preferably a multi-layered particle having an acrylic elastic polymer layer, and a polymer mainly composed of alkyl methacrylate outside the acrylic elastic polymer. It may be a two-layer structure having the above-mentioned layer, or a three-layer structure having a polymer layer mainly composed of alkyl methacrylate inside the acrylic elastic polymer. In addition, the example of the monomer composition of the polymer mainly composed of alkyl methacrylate constituting the layer formed on the outside or inside of the acrylic elastic polymer is the alkyl methacrylate mentioned above as an example of the acrylic resin. It is the same as that of the example of the monomer composition of the polymer which has mainly. Such acrylic rubber elastic particles having a multilayer structure can be produced, for example, by the method described in Japanese Patent Publication No. 55-27576.

  As the rubber elastic particles, those having a number average particle diameter of 10 to 300 nm of rubber elastic bodies contained therein are used. Thereby, when the acrylic resin film 25 is laminated | stacked on the polarizing film 21 using an adhesive agent, the acrylic resin film 25 can be made hard to peel from an adhesive bond layer. The number average particle diameter of the rubber elastic body is preferably 50 nm or more and 250 nm or less.

  In the case of rubber elastic particles in which the outermost layer is a polymer mainly composed of methyl methacrylate and the acrylic elastic polymer is encapsulated therein, the rubber elastic particles are mixed with the base acrylic resin. Since the outermost layer of the resin is mixed with the base acrylic resin, the rubber elastic particles are excluded from the outermost layer when the acrylic elastic polymer is dyed with ruthenium oxide in the cross section and observed with an electron microscope. It is observed as particles in a wet state. Specifically, in the case of using rubber elastic particles having a two-layer structure in which the inner layer is an acrylic elastic polymer and the outer layer is a polymer mainly composed of methyl methacrylate, the inner layer is an acrylic elastic polymer. The portion is dyed and observed as particles having a single layer structure. Further, the rubber elastic particles having a three-layer structure in which the innermost layer is a polymer mainly composed of methyl methacrylate, the intermediate layer is an acrylic elastic polymer, and the outermost layer is a polymer mainly composed of methyl methacrylate. When is used, the center part of the innermost layer particle is not dyed, and only the acrylic elastic polymer part of the intermediate layer is dyed and observed as a two-layered particle.

  In the present specification, the number average particle diameter of the rubber elastic particles is, as described above, when the rubber elastic particles are mixed with the base resin and the cross section is dyed with ruthenium oxide, and is dyed in a substantially circular shape. It is the number average value of the diameters of the parts observed in FIG.

  In the acrylic resin composition forming the acrylic resin film 25, 25 to 45% by weight of rubber elastic body particles having a number average particle diameter of 10 to 300 nm is blended in a transparent acrylic resin.

  The acrylic resin composition is produced, for example, by obtaining rubber elastic particles and then polymerizing a monomer as a raw material of the acrylic resin in the presence thereof to produce a base acrylic resin. Alternatively, after obtaining rubber elastic particles and an acrylic resin, they may be produced by mixing them by melt kneading or the like.

  As necessary, the acrylic resin composition includes a colorant such as a pigment or a dye, a fluorescent brightener, a dispersant, a heat stabilizer, a light stabilizer, an infrared absorber, an ultraviolet absorber, an antistatic agent, You may contain compounding agents, such as antioxidant, a lubricant, and a solvent.

  The ultraviolet absorber is added to improve durability by absorbing ultraviolet rays of 400 nm or less. As the ultraviolet absorber, known ones such as a benzophenone ultraviolet absorber, a benzotriazole ultraviolet absorber, and an acrylonitrile ultraviolet absorber can be used. Among them, 2,2'-methylenebis (4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol), 2- (2'-hydroxy-3 ' -Tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2,4-di-tert-butyl-6- (5-chlorobenzotriazol-2-yl) phenol, 2,2'-dihydroxy- 4,4′-dimethoxybenzophenone, 2,2 ′, 4,4′-tetrahydroxybenzophenone and the like are preferably used. Among these, 2,2′-methylenebis (4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol) is particularly preferable.

  The concentration of the ultraviolet absorber can be selected in such a range that the transmittance of the acrylic resin film 25 having a wavelength of 370 nm or less is preferably 10% or less, more preferably 5% or less, and further preferably 2% or less. Examples of the method of containing the ultraviolet absorber include a method of previously blending the ultraviolet absorber into the acrylic resin; a method of supplying it directly at the time of melt extrusion molding, and any method may be employed.

  Infrared absorbers include nitroso compounds, metal complexes thereof, cyanine compounds, squarylium compounds, thiol nickel complex compounds, phthalocyanine compounds, naphthalocyanine compounds, triallylmethane compounds, imonium compounds, diimonium compounds, Infrared absorption of naphthoquinone compounds, anthraquinone compounds, amino compounds, aminium salt compounds, carbon black, indium tin oxide, antimony tin oxide, oxides of metals belonging to Group 4A, 5A or 6A, carbides, borides, etc. An agent etc. can be mentioned. These infrared absorbers are preferably selected so as to be able to absorb the entire infrared ray (light having a wavelength in the range of about 800 nm to 1100 nm), and two or more types may be used in combination. The amount of the infrared absorber can be appropriately adjusted so that, for example, the light transmittance at a wavelength of 800 nm or more of the acrylic resin film 25 is 10% or less.

  The glass transition temperature Tg of the acrylic resin composition is preferably in the range of 80 to 120 ° C. Furthermore, the acrylic resin composition preferably has a high surface hardness when formed into a film, specifically, a pencil hardness (with a load of 500 g, conforming to JIS K5600-5-4) of B or higher. .

  In addition, the acrylic resin composition preferably has a flexural modulus (JIS K7171) of 1500 MPa or less from the viewpoint of flexibility of the acrylic resin film 25. The flexural modulus is more preferably 1300 MPa or less, and still more preferably 1200 MPa or less. This flexural modulus varies depending on the type and amount of acrylic resin and rubber elastic particles in the acrylic resin composition. For example, as the content of rubber elastic particles increases, the flexural modulus generally decreases. . In addition, the use of a copolymer of an alkyl methacrylate and an alkyl acrylate as an acrylic resin generally has a lower flexural modulus than using an alkyl methacrylate homopolymer.

  In addition, the elastic elastic polymer particles having the two-layer structure are generally used as the elastic rubber particles, rather than the acrylic elastic polymer particles having the two-layer structure. In general, the flexural modulus is smaller when the acrylic elastic polymer particles having a layer structure are used. Further, in the rubber elastic body particles, as the average particle diameter of the rubber elastic body is smaller or the amount of the rubber elastic body is larger, the bending elastic modulus is generally smaller. Therefore, it is preferable to adjust the kind and amount of the acrylic resin and the rubber elastic body particles within the predetermined range so that the flexural modulus is 1500 MPa or less.

  In the case where the acrylic resin film 25 has a multilayer structure, the layer that can exist other than the layer of the acrylic resin composition is not particularly limited in its composition. For example, an acrylic resin that does not contain rubber elastic particles or a composition thereof Or a layer made of an acrylic resin composition in which the content of the rubber elastic particles and the average particle diameter of the rubber elastic bodies in the rubber elastic particles are outside the above-mentioned regulations. Good.

  Typically, it has a two-layer or three-layer structure, and may be a two-layer structure including, for example, an acrylic resin composition layer / an acrylic resin not containing rubber elastic particles or a layer of the composition. Further, it may have a three-layer structure comprising an acrylic resin composition layer / an acrylic resin not containing rubber elastic particles or a layer of the composition / an acrylic resin composition layer. The acrylic resin film 25 having a multilayer structure may have a surface of the acrylic resin composition layer as a bonding surface with the polarizing film 21.

  Moreover, when making the acrylic resin film 25 into a multilayer structure, you may mutually differ content of rubber elastic-body particle | grains or each layer of the said compounding agent. For example, a layer containing an ultraviolet absorber and / or an infrared absorber and a layer not containing an ultraviolet absorber and / or an infrared absorber may be laminated with this layer interposed therebetween. Further, the content of the ultraviolet absorber in the layer of the acrylic resin composition may be higher than the content of the ultraviolet absorber in the layer of the acrylic resin not containing rubber elastic particles or the composition thereof. Well, specifically, the former is preferably 0.5 to 10% by weight, more preferably 1 to 5% by weight, and the latter is preferably 0 to 1% by weight, more preferably 0 to 0.5% by weight. As a result, ultraviolet rays can be efficiently blocked without deteriorating the color tone of the polarizing plate 20, and a decrease in the degree of polarization during long-term use can be prevented.

  The acrylic resin film 25 may be non-oriented or unstretched or may be stretched. When the stretching process is not performed, the thickness of the polarizing plate 20 is likely to increase because the thickness is increased. On the other hand, the handling property of the acrylic resin film 25 is improved because the thickness is increased. Such an acrylic resin film 25 can be obtained from an unstretched film (raw film) obtained by forming an acrylic resin composition. On the other hand, when stretched, the phase difference is easily developed, but stretching has the advantage that the thickness of the acrylic resin film 25 is reduced and the rigidity is improved. The stretched film can be produced by stretching an unstretched film by an arbitrary method.

  The acrylic resin can be formed into an unstretched film by any method. This unstretched film is preferably transparent and substantially free of in-plane retardation. Examples of the film forming method include an extrusion method in which a molten resin is extruded to form a film, and a solvent cast method in which a solvent dissolved in an organic solvent is cast on a flat plate and then the solvent is removed to form a film. Etc. can be adopted.

  As a specific example of the extrusion molding method, for example, there is a method of forming a film in a state where an acrylic resin composition is sandwiched between two metal rolls. In this case, the metal roll is preferably a mirror roll. Thereby, the unstretched film excellent in surface smoothness can be obtained. In addition, when obtaining the thing of a multilayer structure as the acrylic resin film 25, what is necessary is just to film-form an acrylic resin composition after multilayer extrusion with another acrylic resin composition. The thickness of the unstretched film thus obtained is preferably 5 to 200 μm, more preferably 10 μm to 85 μm.

  An unstretched film made of an acrylic resin can be stretched by a known method such as uniaxial stretching or biaxial stretching. Examples of the stretching method include a tenter method using a tenter stretching machine. Biaxial stretching may be simultaneous biaxial stretching in which stretching is performed simultaneously in two stretching directions, or sequential biaxial stretching in which stretching is performed in a predetermined direction and then stretching in another direction.

  Next, the haze value of the acrylic resin film 25 will be described. The haze value is the ratio of the diffuse light transmittance to the total light transmittance when the film is irradiated with visible light. It is recognized that the smaller the haze value is, the better the film is. Moreover, an internal haze value shows the value which deducted the haze value (external haze value) resulting from the surface shape of a film from the haze value of a film.

  As described above, the haze value of the acrylic resin film 25 has an internal haze value of 1.0% or less, more preferably 0.5% or less, and an external haze value of 5% or less. When the internal haze value exceeds 1.0% and the external haze value exceeds 5%, the light transmitted through the film is scattered, and the display characteristics may be deteriorated when the liquid crystal display device 1 is bonded.

  In addition, by performing a surface treatment on the acrylic resin film 25, it is possible to impart a function that the acrylic resin film 25 alone did not have. For example, the acrylic resin film 25 can be subjected to a hard coat treatment from the viewpoint of preventing surface scratches in the assembly process of the liquid crystal module. In addition, surface treatment such as antistatic treatment can be performed. However, when the acrylic resin film 25 is used as a protective film for the polarizing film and the polarizing plate 20 is formed, the antistatic function can be imparted by subjecting the acrylic resin film 25 to a surface treatment, It can also be applied to other parts of the polarizing plate 20 in which the substrate film is incorporated, such as an adhesive layer. Other examples of surface treatment on the acrylic resin film 25 include antireflection treatment and antifouling treatment. Furthermore, an antiglare treatment can be performed from the viewpoints of improving visibility, preventing reflection of external light, and reducing moire due to interference between the prism sheet and the color filter.

(3) Transparent resin film 23
The transparent resin film 23 is preferably made of a resin having excellent transparency. Examples of such resins include polycarbonate resins, polyvinyl alcohol resins, polystyrene resins, (meth) acrylate resins, olefin resins including cyclic olefin resins and polypropylene resins, polyarylate resins, and polyimide resins. Examples thereof include resins, polyamide resins, and cellulose resins. The transparent resin film 23 is preferably an unstretched film that has not been stretched, or a stretched film that has been uniaxially or biaxially stretched.

  When the transparent resin film 23 is a stretched film, an appropriate phase difference is imparted 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 10 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 40. For example, vertical alignment: If (Vertical Alignment VA) mode liquid crystal cell 40, 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 ≒ _{n z,} transverse stretching and sequential biaxial stretching is _performed, biaxial having a relation of _{n x>} n _y> n _z film, or _{n x} ≒ _n y> _{n z} A negative C plate with a relationship 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, _Nz is the refractive index in the thickness (z-axis) direction.

As the transparent resin film 23, in particular, a biaxially stretched biaxial film is preferably used. When a biaxial viewing angle compensation film is used, the _Nz coefficient that is a measure of the biaxiality is defined by the following equation (4), and further, the in-plane position when the film thickness is d. The phase difference value _Ro and the thickness direction retardation value _Rth are defined by the following equations (5) and (6), respectively.
_{N z = (n x -n z} ) / (n x -n y) (4)
_{R o = (n x -n y} ) × d (5)
_Rth = [( _nx + _ny ) / 2- _nz ] * d (6)

Further, from the equation (4) to (6), and N _z coefficient, the relationship between the retardation value R _th retardation value R _o and the thickness direction in the plane, is expressed by the following equation (7) it can.
N _z = R _th / R _o +0.5 (7)

When using a viewing angle compensation film as the transparent resin film 23, the retardation value _{R o} in the plane is in the range of 30 to 300 nm, especially preferably in the range of 50～260Nm. The _{N z} coefficient is in the range of 1.1 to 7, especially preferably in the range of 1.4 to 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 transparent resin film 23 is a retardation film, when the polarizing film 21 and the retardation film are bonded, the angle formed by the absorption axis of the polarizing film 21 and the slow axis of the retardation film is used for the purpose. It may be appropriately selected depending on the situation. For example, when the retardation film is a viewing angle compensation film, the angle formed by the absorption axis of the polarizing film 21 and the slow axis of the viewing angle compensation film is substantially 0 ° or 90 °.

  On the other hand, in the case where the transparent resin film 23 is an unstretched film, the retardation hardly appears and functions as a protective film for the polarizing film 21. The transparent resin film 23 as an unstretched film can be suitably used for the liquid crystal cell 40 in an IPS (In Plane Switching) mode among the modes employed in the liquid crystal cell 40, for example.

(4) Adhesive (not shown)
An adhesive is used for bonding the polarizing film 21 and the acrylic resin film 25 or bonding the polarizing film 21 and the transparent resin film 23. This adhesive can be cured by irradiation with active energy rays, heating, drying, etc., and can bond the polarizing film 21 and the acrylic resin film 25, and the polarizing film 21 and the transparent resin film 23 with a strength sufficient for practical use. Good. Specifically, the following adhesive compositions are mentioned, 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 photocationic polymerization initiator;
A radical polymerizable photocurable adhesive composition comprising a radical polymerizable compound such as an acrylic compound and a radical photopolymerization initiator;
A thermosetting adhesive composition comprising the above-described cationic polymerizable or radical polymerizable compound and a thermal polymerization initiator, ie, a thermal cation generator or a thermal radical generator;
An aqueous adhesive composition comprising an aqueous solution or an aqueous dispersion in which a water-soluble or hydrophilic crosslinkable epoxy compound or urethane compound is blended with a water-soluble resin having a reactive group such as a polyvinyl alcohol resin as necessary.

  Epoxy compounds can be easily obtained as commercial products. Examples of commercially available products are "Epicoat" sold by Japan Epoxy Resin Co., Ltd., "Epicron" sold by DIC Corporation, and Toto Kasei Co., Ltd. "Epototo", "Adeka Resin" sold by ADEKA Corporation, "Denacol" sold by Nagase ChemteX Corporation, "Dow Epoxy" sold by Dow Chemical Company, Nissan Chemical Industries, Ltd. ) Etc. are sold by “Tepic”.

  Commercially available alicyclic epoxy compounds in which an epoxy group is directly bonded to a saturated carbocyclic ring 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.

  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.

  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.

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

  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. When the amount is less than 0.5 parts by weight, curing becomes insufficient, and the mechanical strength and adhesive strength of the adhesive layer may be lowered. 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 20 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 Body; and the like fluorenone derivatives; xanthone derivatives. 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 that the compounding quantity shall be 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, and 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. When the viscosity is less than 10 mPa · sec, the apparatus that can be applied is limited, and even if the application can be performed, 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, the number of devices that can be applied in the same way is limited, and a uniform coating without unevenness tends to be difficult to obtain. The viscosity referred to here is a value measured at 60 rpm after the temperature of the composition is adjusted to 25 ° C. using a B-type viscometer.

(5) Adhesive layer (not shown)
The pressure-sensitive adhesive layer is a layer having adhesiveness and is used for bonding the polarizing plate 20 to the liquid crystal cell 40. 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 are also excellent in weather resistance and heat resistance. It is preferably used because it does not easily cause separation problems such as floating and peeling even under 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 does not cause adhesive residue or the like on the glass substrate when it is necessary to peel off after having been bonded to the liquid crystal cell 40, It can be peeled relatively easily. 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. The light diffusing agent may be fine particles having a refractive index different from that of the base polymer constituting the pressure-sensitive adhesive layer, and fine particles made of an inorganic compound or fine particles made of an organic compound (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 ensuring the brightness and visibility of the applied liquid crystal display device 1, it is 0.01 or more. It is preferable that it is 0.5 or less. The fine particles used as the light diffusing agent are preferably spherical and those close to monodisperse, and fine particles having an average particle diameter 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 composed of an organic compound (polymer) include melamine resin beads (refractive index 1.57), polymethyl methacrylate beads (refractive index 1.49), methyl methacrylate / styrene copolymer resin beads ( (Refractive index 1.50 to 1.59), 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), silicone resin beads (refractive index 1.46), and the like.

  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, the brightness of the liquid crystal display device 1 to which it is applied, etc. The amount is about 3 to 30 parts by weight with respect to 100 parts by weight of the base polymer constituting the agent layer.

  The haze value measured according to JIS K 7361 of the pressure-sensitive adhesive layer in which the light diffusing agent is dispersed is from the viewpoint of ensuring the brightness of the liquid crystal display device 1 to be applied and making the display image less likely to bleed or blur. A range of 20 to 80% is preferable.

  Each component (base polymer, light diffusing agent, crosslinking agent, etc.) constituting the transparent pressure-sensitive adhesive or diffusion pressure-sensitive adhesive is dissolved in a suitable solvent such as ethyl acetate to form a pressure-sensitive adhesive composition. However, components that are not soluble in a solvent such as a light diffusing agent are dispersed. A pressure-sensitive adhesive layer can be formed by applying this pressure-sensitive adhesive composition on a transparent resin film 23 or a release film (not shown) and drying it.

  The pressure-sensitive adhesive layer preferably has antistatic properties in order to eliminate static electricity charged on the polarizing plate 20. The polarizing plate 20 may be charged with static electricity when the release film laminated on the pressure-sensitive adhesive layer is peeled off and bonded to the liquid crystal cell 40. At this time, if the pressure-sensitive adhesive layer has antistatic properties, the static electricity is quickly eliminated, and the display circuit of the liquid crystal cell 40 is prevented from being broken and the liquid crystal molecules from being disturbed in alignment. .

  Examples of the method for imparting antistatic properties to the pressure-sensitive adhesive layer include a method in which the pressure-sensitive adhesive composition contains metal fine particles, metal oxide fine particles, or fine particles coated with a metal; an electrolyte salt and an organopolysiloxane; And a method of incorporating an organic salt-based antistatic agent. The required antistatic holding time is at least about 6 months from the viewpoint of production, distribution, and storage period of a general polarizing plate.

  The pressure-sensitive adhesive layer may pass active energy rays in order to cure the adhesive layer. Therefore, it is preferable to have a high transmittance in the corresponding spectral region of the active energy ray. In addition, it is preferable that various characteristics as an adhesive do not change by irradiation of an active energy ray.

  For example, the pressure-sensitive adhesive layer is aged for about 3 to 20 days in an environment of a temperature of 23 ° C. and a relative humidity of 65%, and after sufficiently proceeding with the reaction of the cross-linking agent, it is used for bonding to the liquid crystal cell 40. .

  Although the thickness of an adhesive layer is suitably determined according to the adhesive force etc., it is about 1-40 micrometers normally. In order to obtain a thin polarizing plate 20 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, when the pressure-sensitive adhesive layer in which the light diffusing agent is dispersed is used, by keeping the thickness of the pressure-sensitive adhesive layer within this range, the brightness when the liquid crystal display device 1 is viewed from the front or obliquely is maintained. Thus, it is possible to prevent the display image from blurring or blurring.

(6) Protect film (not shown)
A protective film can be laminated on the surface of the acrylic resin film 25 opposite to the surface bonded to the polarizing film 21. The protect film is a peelable film and is a member for protecting the surface of the acrylic resin film 25 from damage, abrasion and the like. The protective film is composed of a base film made of a transparent resin, and a pressure-sensitive adhesive layer having weak adhesion laminated on the surface of the base film. The protective film is bonded to the acrylic resin film 25 until the polarizing plate 20 is used, and is peeled off from the acrylic resin film 25 when used.

  The protective film can be easily obtained as a commercial product. Examples of commercially available products include “Mastack” sold by Fujimori Kogyo Co., Ltd., “Sanitect” sold by Sanei Kaken Co., Ltd., and “Emask” sold by Nitto Denko Co., Ltd. And “Tretec” sold by Toray Film Processing Co., Ltd.

(6-1) Base film The base film is not particularly limited as long as it is made of a transparent resin. Examples of such transparent resins include acrylic resins typified by polymethyl methacrylate, olefin resins typified by polypropylene and polyethylene, and polyester resins typified by polybutylene terephthalate and polyethylene terephthalate. Can be mentioned. In particular, polyethylene terephthalate is preferable because it is excellent in transparency and homogeneity, and has a strong and inexpensive cocoon.

  Further, the base film may be blended with a nucleating agent in order to increase rigidity and strengthen the stiffness. A nucleating agent is a substance that becomes a crystal nucleus in a polymer molecule, and has the effect of increasing the crystallinity of the polymer and increasing the elastic modulus of the base film by being blended with the base film. As the nucleating agent, either an inorganic nucleating agent or an organic nucleating agent can be used. Examples of the inorganic nucleating agent include talc, clay, calcium carbonate and the like. Examples of organic nucleating agents include metal salts such as aromatic carboxylic acid metal salts and aromatic phosphoric acid metal salts, high density polyethylene, poly-3-methylbutene-1, polycyclopentene, and polyvinylcyclohexane. And high molecular compounds. Among these, organic nucleating agents are preferable, and the above metal salts and high density polyethylene are more preferable. Moreover, 0.01 to 3 weight% is preferable and, as for content of the nucleating agent in a base film, 0.05 to 1.5 weight% is more preferable. Only one type of nucleating agent may be used, or a plurality of types may be used in combination.

  The thickness of the base film is preferably 15 to 75 μm. If this thickness is less than 15 μm, the handleability may be inferior or the originally required surface protection performance 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 modulus of the base film is preferably 1,000 MPa or more, more preferably 3,000 MPa or more in the longitudinal direction (MD). If this tensile elastic modulus is too small, the handleability may be inferior, or the tension at the time of bonding to the acrylic resin film 25 may not be able to be endured. The surface of the base film may be subjected to antifouling treatment, antireflection treatment, hard coat treatment, antistatic treatment and the like.

(6-2) Pressure-sensitive adhesive layer As the pressure-sensitive adhesive layer, a known re-peeling pressure-sensitive adhesive such as an acrylic pressure-sensitive adhesive can be used. Among these, an acrylic resin having a high elastic modulus and hardness is preferable from the viewpoint of the strength of the protective film. From the standpoint of strength, the pressure-sensitive adhesive layer should be thicker. The pressure-sensitive adhesive layer may contain an antistatic agent or the like in order not to generate static electricity at the time of peeling.

  The acrylic adhesive is based on one or more acrylic esters such as butyl acrylate, ethyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, and a polar monomer is copolymerized therewith. The thing comprised with a polymer is mentioned. Examples of polar monomers include (meth) acrylic acid, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, (meth) acrylamide, N, N-dimethylaminoethyl (meth) acrylate, and glycidyl. Mention may be made of monomers having a carboxyl group, a hydroxyl group, an amino group, an epoxy group and the like, such as (meth) acrylate. In addition, crosslinking agents, such as a polyisocyanate compound, an epoxy compound, and an aziridine compound, may be mix | blended with the adhesive.

  EXAMPLES Hereinafter, although an Example is given 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]
Acrylic resin film to which a protective film is attached, a polarizing plate, and a polarizing plate with an adhesive layer (a state with a peeling film and a peeling film) in a method according to the explanation made previously with reference to FIG. The amount of curl was measured with the convex side of the film facing down. When the acrylic resin film side is convex, the curl is normal and when it is concave, the curl is reverse.

[Measurement of tensile modulus of film]
The tensile modulus of the film is a method defined 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 under the conditions of a temperature of 22 ° C. and a relative humidity of 53%.

[Example 1]
(A) Production of acrylic resin film (acrylic resin and acrylic elastic polymer particles)
A copolymer having a weight ratio of methyl methacrylate / methyl acrylate of 96/4 was used as an acrylic resin. The innermost layer is a hard polymer polymerized with methyl methacrylate using a small amount of allyl methacrylate, and the intermediate layer is polymerized with butyl acrylate as the main component, and further using styrene and a small amount of allyl methacrylate. Soft elastic body, the outermost layer is a three-layered elastic particle made of a hard polymer obtained by polymerizing methyl methacrylate with a small amount of ethyl acrylate, up to an elastic body that is an intermediate layer Acrylic elastic polymer particles having an average particle size of 240 nm were used.

(Preparation of acrylic resin film)
While melting and kneading a pellet in which the above acrylic resin and the above acrylic elastic polymer particles are blended in a weight ratio of the former / the latter = 70/30 with a twin screw extruder, did. This pellet is put into a 65 mmφ single screw extruder, extruded through a T die having a set temperature of 275 ° C., and two polishings having mirror surfaces whose temperatures are set to 45 ° C. on both sides of the extruded film-like molten resin. Acrylic resin film was prepared by sandwiching between rolls and cooling.

(B) Bonding of protective film to acrylic resin film A biaxially stretched polyethylene terephthalate film having a thickness of 60 μm and having a weak adhesive acrylic pressure-sensitive adhesive layer provided 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. The acrylic resin film and the protective film were bonded with a roll type laminator so that the adhesive layer of the protective film overlapped with the acrylic resin film. At this time, 250 mm × 300 mm was cut out from the protective film-attached acrylic resin film, and the curl was measured. The curl value at this time was a minimum value of 7.0 mm, a maximum value of 31.0 mm, and was a positive curl.

(C) Preparation of polarizing plate The acrylic resin film side of the protective resin-laminated acrylic resin film prepared in (b) above is attached to one side of a polarizing film in which iodine is adsorbed and oriented on polyvinyl alcohol. On the surface is a biaxially stretched film of a cyclic olefin resin obtained from Nippon Zeon Co., Ltd., having a thickness of 50 μm, “Zeonor film” (in-plane retardation value R _o = 55 nm, thickness direction retardation value R _th = 124 nm) were bonded to each other to prepare a polarizing plate.

In pasting, an ultraviolet curable adhesive composition is applied to each of the protective film pasting acrylic resin film and the cyclic olefin resin film to the polarizing film, and the respective coating surfaces are applied to the polarizing film. After being stacked on both sides, the two bonding rolls 15 and 16 were passed through and integrated. Here, a rubber roll whose surface is made of rubber was used as the first bonding roll 15, and a metal roll whose surface was chrome plated was used as the second bonding roll 16. Moreover, ratio ( ₂₎ of peripheral speed R2 of the _2nd bonding roll 16 arrange | positioned at the cyclic olefin resin film side with respect to peripheral speed R1 of the _1st bonding roll 15 arrange | positioned at the acrylic resin film side ( (Ratio of peripheral speed) R ₂ / R ₁ was set to 1.0113.

Moreover, in pasting, the tension | tensile_strength before pasting is provided to the direction along the conveyance direction (longitudinal direction of a film) to each of the said protective film adhesion acrylic resin film and cyclic olefin resin film, and it is polarized in this state. Bonded to film. The pre-bonding tension was generated by the difference in rotational speed between the feed roll for feeding out each film and the take-up roll for winding up the laminated polarizing plate. The tension before bonding was measured using a tension pickup installed before the bonding roll. Furthermore, the respective cross-sectional areas of the acrylic resin film and the cyclic olefin-based resin film were calculated, and the pre-bonding tension per unit cross-sectional area was calculated by dividing the pre-bonding tension obtained above by the cross-sectional area. . When the pre-bonding tension per unit cross-sectional area of the acrylic resin film is T ₁ and the pre-bonding tension per unit cross-sectional area of the cyclic olefin resin film is T ₂ , per unit cross-sectional area of the cyclic olefin resin film unit cross before lamination ratio of the tension _{T 1} of the per area (before lamination tension _ratio) T 1 / _{T 2} of the acrylic resin film before lamination for the tension _{T 2} of the it was 0.94.

After bonding, using an ultraviolet irradiation device with a metal halide lamp as a light source, the adhesive is cured by irradiating with ultraviolet rays from the cyclic olefin 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 400 mm × 700 mm sample was cut out from the polarizing plate obtained in (c) and allowed to stand at 25 ° C. for 1 hour. Then, when the amount of curl was measured by the above method with the protective film peeled off, the curl amount was reverse curl where the cyclic olefin resin film side was concave, and the maximum value was -39.0 mm. The results are shown in Table 1.

[Example 2]
A polarizing plate was produced in the same manner as in Example 1 except that the peripheral speed ratio R ₂ / R ₁ was 1.0107 in Example 1 (c). When the curl amount of the obtained polarizing plate was measured by the same method as (d), it was a reverse curl in which the cyclic olefin resin film side was concave, and the maximum value was -79.0 mm. The results are shown in Table 1.

[Example 3]
In Example 1 (c), a polarizing plate was produced in the same manner as in Example 1 except that the ratio of the tension before bonding per unit cross-sectional area was 1.1. When the curl amount of the obtained polarizing plate was measured by the same method as (d), it was a reverse curl in which the cyclic olefin resin film side was concave, and the maximum value was −4.0 mm. The results are shown in Table 1.

[Comparative Example 1]
A polarizing plate was produced in the same manner as in Example 1 except that the peripheral speed ratio R ₂ / R ₁ was 1.0098 in (c) of Example 1. When the curl amount of the obtained polarizing plate was measured by the same method as (d), it was a reverse curl in which the cyclic olefin resin film side was concave, and the maximum value was −107.0 mm. The results are shown in Table 1.

(E) Extrapolation of data FIG. 5 is a graph plotting the results obtained in Examples 1 and 2 and Comparative Example 1 that were experimented with the same ratio of tension before bonding. A minus (−) curl amount indicates a reverse curl, and a plus (+) indicates a normal curl. As shown in this figure, it was found that there is a correlation between the circumferential speed ratio R ₂ / R ₁ and the curl amount, and the relationship between the two is a linear (linear function) relationship. When the horizontal axis x is the peripheral speed ratio and the vertical axis y is the curl amount, the regression line is expressed by the following equation (8). Further, the correlation coefficient R ^{2 at} this time was 0.9539.
y = 44211x-44754 (8)

Therefore, the regression line was extrapolated to obtain a range in which the curl amount was −80 to +80 mm. As a result, it was found that the peripheral speed ratio R ₂ / R ₁ was in the range of 1.0105 or more and 1.0141 or less. That is, if the peripheral speed ratio is within this range, it is considered that the curl amount is not excessive and is within an appropriate range.

  Moreover, when Example 1 and Example 3 which experimented with ratio (1.0113) of the same peripheral speed are compared, the ratio of Example 3 whose ratio of the tension before bonding per unit cross-sectional area is 1.10 is the same ratio. It can be seen that the curl amount is significantly smaller than that in Example 1 in which is 0.94, and excessive reverse curl is suppressed. Therefore, the tension ratio before bonding per unit cross-sectional area is preferably 1.0 or more, and more preferably 1.1 or more as in Example 3.

DESCRIPTION OF SYMBOLS 12 Adhesive coating device, 13 Adhesive coating device, 15 1st bonding roll, 16 2nd bonding roll, 18 Curing device, 20 Polarizing plate, 21 Polarizing film, 23 Transparent resin film, 25 Acrylic resin film , 40 liquid crystal cell

Claims (7)

An acrylic 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 via an adhesive. A method for producing a polarizing plate by laminating a transparent resin film,
(A) A raw material film transporting step of transporting the polarizing film, the acrylic resin film, and the transparent resin film in a certain direction and sandwiching the polarizing film between the acrylic resin film and the transparent resin film, ,
(B) The acrylic resin film is bonded to one surface of the polarizing film, the transparent resin film is bonded to the other surface of the polarizing film via a curable adhesive, and the acrylic resin film A first bonding roll that contacts the outside and rotates in the transport direction, and a second bonding roll that contacts the outside of the transparent resin film and rotates in the transport direction, the acrylic resin film / A bonding step of performing the bonding while sandwiching a laminate of the polarizing film / the transparent resin film;
(C) After bonding, the adhesive is cured, and the curing step of bonding the acrylic resin film, the polarizing film, the transparent resin film, and the polarizing film,
In the bonding step (B), the transparent resin film and the transparent resin film so that the contraction stress in the transport direction on the acrylic resin film side is larger than the contraction stress in the transport direction on the transparent resin film side. A method for producing a polarizing plate, wherein the polarizing film is bonded to the acrylic resin film in a state where tension is applied.   In the bonding step (B), the ratio of the peripheral speed of the second bonding roll contacting the outside of the transparent resin film to the peripheral speed of the first bonding roll contacting the outside of the acrylic resin film is The method for producing a polarizing plate according to claim 1, wherein the method is performed so as to be 1.0105 or more and 1.0141 or less.   The bonding step (B) is performed such that the ratio of the pre-bonding tension per unit cross-sectional area of the acrylic resin film to the pre-bonding tension per unit cross-sectional area of the transparent resin film is 1 or more. The manufacturing method of the polarizing plate of Claim 1 or 2 characterized by these.   The polarized light according to any one of claims 1 to 3, further comprising a protective film bonding step of bonding a protective film to a surface of the acrylic resin film opposite to a surface bonded to the polarizing film. A manufacturing method of a board.   The said transparent resin film is a manufacturing method of the polarizing plate in any one of Claims 1-4 which is a film which is not extended | stretched, or is a film uniaxially or biaxially stretched.   In the course of the raw film transporting step (A), the adhesive is applied to the bonding surface of the acrylic resin film to the polarizing film, and the adhesive is bonded to the bonding surface of the transparent resin film to the polarizing film. The manufacturing method of the polarizing plate in any one of Claims 1-5 further equipped with the adhesive agent application | coating process which apply | coats an agent.   The adhesive comprises an active energy ray curable resin, and the curing step (C) is performed by curing the active energy ray curable resin by irradiation with an active energy ray. The manufacturing method of the polarizing plate of description.

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