JP2013019996A - Manufacturing method of polarization plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a polarization plate capable of improving adhesion between a polarization film and a cycloolefin resin film.SOLUTION: The polarization plate is a film laminate including polarization film of a polyvinyl alcohol resin laminated with an acetic acid cellulose resin film on one surface and a cycloolefin resin film on the other surface being interposed by an adhesive layer. The manufacturing method of the polarization plate includes a step to press the film laminate by passing through between a pair of sticking rolls which are disposed facing each other with a center-to-center distance of L (μm). Defining the maximum value of the center-to-center distance of the sticking rolls at which a triacetyl cellulose film of 40 μm in thickness, which is sandwiched between the pair of the sticking rolls, maintains the position without moving when a tensile force of 100 N/m is applied thereto in a direction perpendicular to an axis direction of the sticking rolls as reference center-to-center distance L(μm), the center-to-center distance L satisfies a formula :L-L≤600.

Description

  The present invention relates to a method for producing a polarizing plate in which a cellulose acetate resin film is laminated on one surface of a polarizing film made of a polyvinyl alcohol resin, and a cycloolefin resin film is laminated on the other surface.

  A polarizing plate widely used in an image display device such as a liquid crystal display device is usually triacetyl cellulose via an adhesive layer on one or both sides of a polarizing film made of a polyvinyl alcohol resin to which a dichroic dye is adsorbed and oriented. It is the structure which laminated | stacked the transparent protective film which consists of a cellulose acetate type resin represented by (TAC). As one transparent protective film, a retardation film made of, for example, a cycloolefin resin and having a predetermined retardation characteristic may be laminated (for example, Patent Document 1).

  Since the cycloolefin resin film has lower adhesion to the polarizing film made of polyvinyl alcohol resin than the cellulose acetate resin film, impact is applied to the polarizing plate in the polishing process for the end face decoration of the polarizing plate. In the process of reworking the polarizing plate from the liquid crystal cell (the step of peeling the polarizing plate together with the adhesive when there is some inconvenience after bonding the polarizing plate to the liquid crystal cell using the adhesive) There has been a problem that peeling easily occurs between the film and the cycloolefin-based resin film, and attempts have been made to improve the adhesion.

  For example, Patent Document 1 describes performing a corona discharge treatment with a predetermined output intensity on a bonding surface of a cycloolefin-based resin film. Patent Document 2 relates to bonding of a cellulose ester film, but describes that a plasma treatment is performed on a bonding surface with a polarizer. Patent Document 3 discloses that adhesion between a polarizing film and a cycloolefin-based resin film can be improved by using an adhesive having a specific composition different from that used for a cellulose acetate-based resin film. Have been described.

JP 2007-279621 A JP 2010-256909 A JP-A-2005-208456

  The corona discharge treatment and plasma treatment described in Patent Literature 1 and Patent Literature 2 described above may not exhibit an effect of improving adhesion unless adhesion is performed within a certain time after the treatment, and strict manufacturing management is required. . Further, the effect of improving the adhesion is not always sufficient, and there is room for improvement. Even in the bonding of the cycloolefin resin film using the adhesive having the specific composition described in Patent Document 3, there was room for further improvement regarding the adhesive.

  An object of the present invention is a polarizing plate in which a cellulose acetate-based resin film is laminated on one surface of a polarizing film made of a polyvinyl alcohol-based resin and a cycloolefin-based resin film is laminated on the other surface, and the polarizing film and the cycloolefin An object of the present invention is to provide a method for producing a polarizing plate having improved adhesion with a resin film.

  The polarizing plate is formed by laminating a cellulose acetate-based resin film on one surface of a polarizing film and the cycloolefin-based resin film on the other surface via an adhesive layer. It is manufactured through a step of sandwiching pressure between the combined rolls (nip rolls). The inventor diligently studied to solve the above problems, and the completely activated factor of the film bonding surface and the composition of the adhesive, that is, the distance between the bonding rolls in the pressing step, A bonding roll that serves as a reference based on the fact that it closely affects the adhesion between the polarizing film and the cycloolefin-based resin film, and the distance between specific bonding rolls (the distance between the roll centers). It discovered that the polarizing plate excellent in adhesiveness was obtained by enlarging the distance between the bonding rolls in a pinching process so that a predetermined relationship might be satisfy | filled between distances.

That is, the present invention continuously feeds a polarizing film made of a polyvinyl alcohol-based resin, supplies a cellulose acetate-based resin film and a cycloolefin-based resin film, and the cellulose acetate-based one surface of the polarizing film. The resin film is overlapped with the cycloolefin-based resin film on the other surface via an adhesive layer, and the film laminate is paired with a pair of opposingly arranged with a center-to-center distance L [μm]. And a step of pressing between the pair of bonding rolls, and 100 N / m in a direction perpendicular to the axial direction of the bonding rolls with respect to the 40 μm thick triacetyl cellulose film sandwiched between the pair of bonding rolls. The position of the triacetyl cellulose film does not move even when the tension of When the maximum value of the center distance between the bonding rolls maintaining the center is the reference center distance L ₀ [μm], the center distance L is expressed by the following formula (1):
L ₀ −L ≦ 600 (1)
The manufacturing method of the polarizing plate which satisfy | fills is provided. The center distance L is preferably the following formula (2):
500 ≦ L ₀ −L (2)
Meet.

  The thicknesses of the polarizing film, the cellulose acetate-based resin film, and the cycloolefin-based resin film are preferably 5 to 40 μm, 10 to 50 μm, and 10 to 50 μm, respectively.

  The pair of bonding rolls are preferably elastic rolls having a hardness of 70 to 80 on a JIS Shore C scale. The adhesive layer is made of, for example, an aqueous adhesive.

  According to the present invention, the adhesiveness between the polarizing film and the cycloolefin-based resin film can be improved without performing corona discharge treatment or plasma treatment. Peeling of the polarizing film and the cycloolefin-based resin film in the process of reworking the polarizing plate can be prevented.

It is a schematic side view which shows an example of the manufacturing method of the polarizing plate of this invention, and a manufacturing apparatus used suitably for it. It is a schematic sectional drawing explaining the distance L between centers of a pair of bonding roll. It is a schematic cross-sectional view illustrating a reference center distance L ₀ of the pair of lamination rolls. It is the schematic explaining a peelability evaluation test.

  In the present invention, a cellulose acetate resin film is disposed on one surface of a polarizing film made of a polyvinyl alcohol resin continuously conveyed via an adhesive layer, and an adhesive layer is disposed on the other surface. It is related with the method of manufacturing a polarizing plate through the process of arrange | positioning a cycloolefin type resin film through this, and pinching by making this film laminated body pass between a pair of bonding rolls opposingly arranged.

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

  As the polyvinyl alcohol resin, a saponified polyvinyl acetate resin can be used. Examples of the polyvinyl acetate resin include, in addition to polyvinyl acetate, which is a homopolymer of vinyl acetate, copolymers with other monomers copolymerizable with vinyl acetate. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

  The saponification degree of the polyvinyl alcohol resin is usually about 85 to 100 mol%, preferably 98 mol% or more. This polyvinyl alcohol-based resin may be modified, and for example, polyvinyl formal and 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, and preferably about 1,500 to 5,000.

  What formed such a polyvinyl alcohol-type resin into a film is used as a raw film of a polarizing film. A polyvinyl alcohol-type resin can be formed into a film by a well-known method. The thickness of the raw film is, for example, about 10 to 150 μm.

  Uniaxial stretching of the polyvinyl alcohol-based resin film can be performed before, simultaneously with, or after dyeing the dichroic dye. When uniaxial stretching is performed after dyeing, this uniaxial stretching may be performed before boric acid treatment or during boric acid treatment. Moreover, you may uniaxially stretch in these several steps.

  In uniaxial stretching, it may be uniaxially stretched between rolls having different peripheral speeds, or may be uniaxially stretched using a hot roll. The uniaxial stretching may be dry stretching in which stretching is performed in the atmosphere, 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.

  As a method of dyeing the polyvinyl alcohol resin film with the dichroic dye, for example, a method of immersing the polyvinyl alcohol resin film in an aqueous solution containing the dichroic dye is employed. Specifically, iodine or a dichroic dye is used as the dichroic dye. In addition, it is preferable that the polyvinyl alcohol-type resin film performs the immersion process to water before a dyeing process.

  When iodine is used as the dichroic dye, a method of dyeing a polyvinyl alcohol resin film by dipping it 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. The content of potassium iodide is usually about 0.5 to 20 parts by weight per 100 parts by weight of water. 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 the aqueous solution is usually about 1 × 10 ⁻⁴ to 10 parts by weight per 100 parts by weight of water, and preferably about 1 × 10 ⁻³ to 1 part by weight. 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 is usually performed by immersing the dyed polyvinyl alcohol-based resin film in a boric acid-containing aqueous solution.

  The amount of boric acid in the boric acid-containing aqueous solution is usually about 2 to 15 parts by weight per 100 parts by weight of water, and preferably 5 to 12 parts by weight. When iodine is used as the dichroic dye, the boric acid-containing aqueous solution preferably contains potassium iodide. The amount of potassium iodide in the boric acid-containing aqueous solution is usually about 0.1 to 15 parts by weight and 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, and 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 is 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. The immersion time is usually about 1 to 120 seconds.

  After washing with water, a drying process is performed to obtain a polarizing film. The drying treatment can be performed using a hot air dryer or a far infrared heater. The temperature of the drying treatment is usually about 30 to 100 ° C, preferably 50 to 80 ° C. The drying time is usually about 60 to 600 seconds, and preferably 120 to 600 seconds.

  The moisture content of the polarizing film after the drying treatment is usually 5 to 20% by weight, and preferably 8 to 15% by weight. When the moisture content is less than 5% by weight, the flexibility of the polarizing film is lost and the film may be damaged or broken. If the moisture content exceeds 20% by weight, the thermal stability of the polarizing film may be inferior. The thickness of the polarizing film obtained by adsorbing and orienting the polyvinyl alcohol-based resin film dichroic dye in this manner is usually about 5 to 40 μm, preferably 5 to 30 μm.

[Cellulose acetate resin film]
The cellulose acetate-based resin constituting the cellulose acetate-based resin film is a cellulose portion or a complete acetate ester, and examples thereof include triacetyl cellulose, diacetyl cellulose, cellulose acetate propionate, and the like.

  Examples of the cellulose acetate-based resin film include appropriate commercial products such as “Fujitac TD80”, “Fujitac TD80UF”, “Fujitac TD80UZ” (manufactured by FUJIFILM Corporation), “KC8UX2M”, “KC4UY” (above, Konica). Minolta Opto Co., Ltd.) can be preferably used. In addition, a cellulose acetate-based resin film imparted with retardation characteristics such as “WV BZ 438” (manufactured by Fuji Film Co., Ltd.), “KC4FR-1” (manufactured by Konica Minolta Opto Co., Ltd.) or the like can also be used.

  The thickness of the cellulose acetate-based resin film is preferably 10 to 50 μm and more preferably 20 to 50 μm from the viewpoints of strength, handleability, thinning of the polarizing plate, and the like.

  Cellulose acetate-based resin film is saponified for the purpose of further improving the adhesion with the polarizing film prior to bonding with the polarizing film, particularly when bonding to the polarizing film using an aqueous adhesive. You may give it. As the saponification treatment, a method of immersing in an alkaline aqueous solution such as sodium hydroxide or potassium hydroxide can be employed.

  On the surface of the cellulose acetate-based resin film (or cycloolefin-based resin film, which will be described later) opposite to the polarizing film, an antiglare layer, a light diffusion layer, an antireflection layer, a low reflection layer, a hard coat, if necessary. Functional layers such as a layer, an antistatic layer, and an antifouling layer can be provided.

[Cycloolefin resin film]
The cycloolefin-based resin constituting the cycloolefin-based resin film is a heat mainly containing structural units derived from alicyclic olefins such as norbornene and substituted products thereof (hereinafter collectively referred to as norbornene-based monomers). It is a plastic resin. Norbornene is a compound in which one carbon-carbon bond of norbornane is a double bond, and according to IUPAC nomenclature, it is named bicyclo [2,2,1] hept-2-ene. is there. Examples of substituted norbornene include 3-substituted, 4-substituted, 4,5-disubstituted, etc., with the norbornene double bond position being 1,2-position. Cyclopentadiene, dimethanooctahydronaphthalene, and the like can also be used as monomers constituting the cycloolefin resin.

  The cycloolefin-based resin may or may not have a norbornane ring in its structural unit. Examples of the norbornene-based monomer that forms a cycloolefin-based resin having no norbornane ring in the structural unit include, for example, those that become a 5-membered ring by ring opening, typically norbornene, dicyclopentadiene, 1- or 4- Examples thereof include methyl norbornene and 4-phenyl norbornene. When the cycloolefin resin is a copolymer, the arrangement state of the molecules is not particularly limited, and may be a random copolymer, a block copolymer, or a graft copolymer. It may be a polymer.

  More specific examples of cycloolefin resins include, for example, ring-opening polymers of norbornene monomers, ring-opening copolymers of norbornene monomers and other monomers, addition of maleic acid and cyclopentadiene, etc. Examples of the polymer-modified product, a polymer or copolymer obtained by hydrogenation of these, an addition polymer of a norbornene monomer, an addition copolymer of a norbornene monomer and another monomer, and the like. Examples of other monomers in the case of a copolymer include α-olefins, cycloalkenes, and non-conjugated dienes. The cycloolefin-based resin may be a copolymer using one or more of norbornene-based monomers and other alicyclic olefins.

  Among the specific examples, as the cycloolefin resin, a resin obtained by hydrogenating a ring-opening polymer using a norbornene monomer is preferably used. Such a cycloolefin-based resin can be subjected to a stretching treatment to obtain a retardation film, and in addition to stretching, a shrinkable film having a predetermined shrinkage rate is pasted to perform a heat shrinking treatment, A retardation film having high uniformity and a large retardation value can also be obtained. Examples of the stretching treatment include longitudinal uniaxial stretching, tenter transverse uniaxial stretching, simultaneous biaxial stretching, and sequential biaxial stretching. In addition to appropriately adjusting the draw ratio and draw speed, the desired retardation characteristics can be obtained by appropriately selecting various temperatures such as preheating temperature, drawing temperature, heat setting temperature, cooling temperature, and pattern during drawing. Can do.

  Commercially available products of cycloolefin resins using norbornene monomers include “Zeonex” and “Zeonor” sold by Nippon Zeon Co., Ltd., “Arton” sold by JSR Corporation, and the like. Commercially available products of these cycloolefin-based resin films and stretched films thereof are also available, for example, “Zeonor Film” and JSR Co., Ltd., both of which are sold by Nippon Zeon Co., Ltd. There are “Arton Film” sold and “Essina” sold by Sekisui Chemical Co., Ltd.

  The thickness of the cycloolefin-based resin film is preferably 10 to 50 μm and more preferably 20 to 35 μm from the viewpoints of strength, handleability, thinning of the polarizing plate, and the like.

  Prior to bonding with the polarizing film, the bonding surface of the cycloolefin resin film with the polarizing film is subjected to corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, and flame (flame) treatment for the purpose of further improving adhesion. Further, surface treatment such as saponification treatment may be performed. Among these, corona discharge treatment and plasma treatment that can be performed relatively easily are preferable.

[Adhesive layer]
As an adhesive used for laminating a polarizing film with a cellulose acetate-based resin film and a cycloolefin-based resin film, an aqueous adhesive (adhesive using water as a solvent), an organic solvent-based adhesive, a hot-melt adhesive, A solventless type adhesive agent etc. are mentioned. Examples of water-based adhesives include polyvinyl alcohol-based resin aqueous solutions, water-based two-component urethane emulsion adhesives, and organic solvent-based adhesives such as two-component urethane-based adhesives and solventless adhesives. Liquid urethane adhesives and epoxy adhesives can be mentioned. Of these, aqueous adhesives, especially polyvinyl alcohol resin aqueous solutions are preferably used.

  In an adhesive comprising an aqueous polyvinyl alcohol resin solution, the polyvinyl alcohol resin includes a vinyl alcohol homopolymer obtained by saponifying polyvinyl acetate, which is a homopolymer of vinyl acetate, as well as vinyl acetate and this. Examples include vinyl alcohol copolymers obtained by saponifying a copolymer with other polymerizable monomers, and modified polyvinyl alcohol polymers obtained by partially modifying their hydroxyl groups. To this adhesive, a polyvalent aldehyde, a water-soluble epoxy compound, a melamine compound, a zirconia compound, a zinc compound, a glyoxylate and the like may be added as a crosslinking agent. When an aqueous adhesive is used, the thickness of the adhesive layer obtained therefrom is usually 1 μm or less.

  As the adhesive, a curable adhesive that is cured by irradiation with active energy rays or heating can also be used. Examples of the curable adhesive include those containing a curable resin such as an epoxy resin, an acrylic resin, an okitacene resin, a urethane resin, and a polyvinyl alcohol resin, and a radical polymerization initiator and / or a cationic polymerization initiator. Among these, an adhesive containing an epoxy resin that is cured by irradiation with active energy rays or heating and a cationic polymerization initiator is preferably used. The curable adhesive can be solventless. When a curable adhesive is used, the thickness of the adhesive layer obtained therefrom is usually about 0.5 to 5 μm.

  When using a curable adhesive, after pasting the film using a pasting roll, drying is performed as necessary, and the curable adhesive is cured by irradiating with active energy rays or heating. . The light source of the active energy ray is not particularly limited, but an active energy ray having a light emission distribution at a wavelength of 400 nm or less is preferable. Specifically, the low-pressure mercury lamp, the medium-pressure mercury lamp, the high-pressure mercury lamp, the ultrahigh-pressure mercury lamp, the chemical lamp, and the black light lamp A microwave excited mercury lamp, a metal halide lamp, or the like is preferably used.

  Although the adhesive for laminating the cellulose acetate-based resin film and the adhesive for laminating the cycloolefin-based resin film may be different, it is preferable to use the same adhesive from the viewpoint of productivity. .

[Production method of polarizing plate]
Next, the manufacturing method of the polarizing plate of this invention is demonstrated in detail, referring drawings. FIG. 1 is a schematic side view showing an example of a method for producing a polarizing plate of the present invention and a production apparatus suitably used for the method. The straight arrows in the figure mean the film transport direction (flow direction), and the curved arrows mean the roll rotation direction.

  First, while supplying the cellulose acetate type-resin film 2 from one side with respect to the elongate polarizing film 1 conveyed continuously, the cycloolefin type-resin film 3 is supplied from the other side. On one surface of the polarizing film 1, the cellulose acetate-based resin film 2, and the cycloolefin-based resin film 3, a conveyance guide roll 24 is appropriately provided. On one side of the cellulose acetate-based resin film 2 and the cycloolefin-based resin film 3 (the surface to be bonded to the polarizing film 1), the first coating device 10 and the first coating device 10 are arranged before being superimposed on the polarizing film surface. The adhesive is applied using the second coating device 12 to form an adhesive layer. Examples of the adhesive coating method include various conventionally known methods such as a doctor blade method, a wire bar coating method, a die coating method, a comma coating method, a gravure coating method, a knife coating method, a dip coating method, a casting method, and a spraying method. The coating method can be adopted.

  The polarizing film 1 and the film laminate obtained by laminating the cellulose acetate-based resin film 2 and the cycloolefin-based resin film 3 on the polarizing film 1 are wound up as the polarizing plate 4, for example, 300 to 500 N / m, preferably 300. It is conveyed with a tension of ˜400 N / m.

  Next, the cellulose acetate-based resin film 2 is superimposed on one surface of the polarizing film 1 and the cycloolefin-based resin film 3 is superimposed on the other surface via the adhesive layer. And a pair of laminating rolls (nip rolls) 20 and 21 arranged opposite to each other are passed through (i.e., sandwiched between the laminating rolls 20 and 21 to press the film laminate in the thickness direction). As shown in FIG. 2, the center-to-center distance between the pair of bonding rolls 20 and 21 at the time of the pinching is L [μm]. The center-to-center distance means the distance between the rotation axis centers of cylindrical (or columnar) laminating rolls. The timing at which the cellulose acetate-based resin film 2 and the cycloolefin-based resin film 3 are superimposed on the polarizing film 1 and the timing at which the pressure is sandwiched between the pair of bonding rolls 20 and 21 are usually the same or substantially the same, and the timing is different. Even if it exists, the one where the difference of both timing is shorter is preferable.

  As the bonding rolls 20 and 21, elastic rolls such as rubber rolls and sponge rubber rolls and metal rolls can be used, and among these, rubber rolls are preferably used. The rubber roll can be made of NBR or the like, and its hardness is preferably 60 to 90, more preferably 70 to 80 on the JIS Shore C scale measured by the test method of JIS K 6301. One may be an elastic roll such as a rubber roll, and the other may be a metal roll. The roll diameter of the bonding rolls 20 and 21 is usually 100 to 300 mm, preferably 200 to 250 mm.

Here, the center distance L [μm] is related to the reference center distance L ₀ [μm] by the following formula (1):
L ₀ −L ≦ 600 (1)
It is set to satisfy. As shown in FIG. 3, the reference center-to-center distance L ₀ is a direction perpendicular to the axial direction of the bonding roll with respect to the 40 μm thick triacetyl cellulose film 50 sandwiched between the bonding rolls 20 and 21 ( That is, even when a tension of 100 N / m is applied in the same direction as the transport direction of the film laminate, the distance between the centers of the bonding rolls 20 and 21 that maintains the position without moving the triacetyl cellulose film 50. The maximum value [μm].

The above formula (1) means that the center-to-center distance L when sandwiching the film laminate is (L ₀ -600) [μm] or more. Thus, the adhesiveness of the polarizing film 1 and the cycloolefin-type resin film 3 in the polarizing plate 4 obtained can be improved by setting the center distance L comparatively large. However, from the viewpoint of preventing air bubbles from being mixed into the film interface and curling of the polarizing plate 4, it is preferable to satisfy L ₀ > L. For the same reason, (L ₀ -L) is preferably 300 μm or more, and more preferably Is 400 μm or more, more preferably 500 μm or more.

  As for the thickness of the film laminate composed of cellulose acetate-based resin film 2 / adhesive layer / polarizing film 1 / adhesive layer / cycloolefin-based resin film 3 sandwiched between bonding rolls 20 and 21, each film is generally used. Although it may be the same thickness as the total thickness that can be taken in, if it is too large, it is difficult to pass the bonding rolls 20 and 21, or even if the above formula (1) is satisfied The effect of improving the properties may not be sufficiently obtained. On the other hand, if the thickness is too small, the pinching pressure becomes insufficient, and air bubbles are mixed into the film interface or the polarizing plate 4 is likely to be curled. Therefore, the thickness of the film laminate is preferably 25 to 140 μm, and more preferably 60 to 110 μm. In order to obtain a thickness within such a range, the thickness of each film is appropriately selected from the range described above.

  A drying process is performed after the clamping process by the bonding rolls 20 and 21. However, when a solventless adhesive is used, the drying process can be omitted. For example, as shown in FIG. 1, the drying treatment can be performed by transporting the film laminate after the compaction to the drying furnace 18 and retaining the film laminate for a certain period of time in the furnace. The set temperature in the drying furnace 18 is, for example, 40 to 100 ° C, and preferably 60 to 90 ° C. The residence time of the film laminate in the drying furnace 18 is, for example, 20 to 1200 seconds, preferably 100 seconds or more, and more preferably 200 seconds or more. When a curable adhesive is used, the curable adhesive is cured by irradiation with active energy rays or heating.

  The polarizing plate 4 obtained as described above is wound around the winding roll 30 via, for example, the pre-winding nip rolls 22 and 23. The rolled polarizing plate 4 may be cured at a temperature of room temperature or higher. The curing temperature is usually 30 to 50 ° C, preferably 35 to 45 ° C. When the curing temperature is 50 ° C. or higher, so-called “roll tightening” is likely to occur in the roll winding state. The relative humidity during curing is usually about 0 to 70% RH. The curing time is usually 1 day to 10 days, preferably 2 days to 7 days.

  EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated further more concretely, this invention is not limited by these examples.

<Example 1>
(1) Production of polarizing film A polyvinyl alcohol film having a thickness of 75 μm made of polyvinyl alcohol having an average degree of polymerization of about 2400 and a saponification degree of 99.9 mol% or more is uniaxially stretched about 5 times in a dry process, and is in a tension state. The sample was immersed in pure water at 60 ° C. for 1 minute, and then immersed in an aqueous solution having a weight ratio of iodine / potassium iodide / water of 0.05 / 5/100 at 28 ° C. for 60 seconds. Thereafter, it was immersed in an aqueous solution having a weight ratio of potassium iodide / boric acid / water of 10.5 / 7.5 / 100 at 72 ° C. for 300 seconds. Subsequently, the film was washed with pure water at 10 ° C. for 5 seconds, and then dried at 40 ° C. for 75 seconds and then at 70 ° C. for 30 seconds in a state of being held at a tension of 400 N. Obtained.

(2) Preparation of water-based adhesive In 100 parts by weight of water, 4 parts by weight of acetoacetyl group-modified polyvinyl alcohol [“Gosefimer Z-200” manufactured by Nippon Synthetic Chemical Industry Co., Ltd.], sodium glyoxylate [Nippon Synthesis] 4 parts by weight of Chemical Industry Co., Ltd. “SPM-01”] was dissolved to prepare an aqueous adhesive A. Further, 2 parts by weight of the same acetoacetyl group-modified polyvinyl alcohol and 2 parts by weight of sodium glyoxylate as described above were dissolved in 100 parts by weight of water to prepare an aqueous adhesive B.

(3) Measurement of reference center distance L ₀ An apparatus similar to the polarizing plate manufacturing apparatus shown in FIG. 1 was prepared. The laminating rolls 20 and 21 are cylindrical rubber rolls having a diameter of 243 mm and a length of 1300 mm, and using a spring-type hardness tester (“TYPE A DURMETER GSD-719S” manufactured by TECLOCK) in accordance with JIS K 6301. The measured hardness of the bonding rolls 20 and 21 is about 72 on the JIS Shore C scale.

A 40 μm thick triacetyl cellulose (TAC) film is sandwiched between the laminating rolls 20 and 21, and this is pulled with a tension of 100 N / m. Even when pulled with the tension, the TAC film does not move and maintains its position. The maximum value of the center-to-center distance of the bonding rolls 20 and 21 when the bonding rolls 20 and 21 were brought close to each other was measured, and this was defined as the reference center-to-center distance L ₀ . The reference center distance L ₀ was about 240 mm.

(4) Production of Polarizing Plate Thickness made of triacetyl cellulose, which is continuously conveyed with a long polarizing film 1 under a tension of 344 N / m and subjected to saponification treatment from one side. A 40 μm cellulose acetate-based resin film 2 [“KC4UY” manufactured by Konica Minolta Opto Co., Ltd.] was supplied, and a corona discharge treatment was applied from the other side to a 32 μm-thick cycloolefin resin film 3 [Nippon Zeon Corporation ZEONOR FILM ZD12-141158-A1330] sold by As the first coating device 10, a Mohno pump manufactured by Hyojin Equipment Co., Ltd. is used, and the water-based adhesive A is applied to one side of the cellulose acetate-based resin film 2, and the second coating device 12 is the same as the above. , The aqueous adhesive B is applied to one side of the cycloolefin-based resin film 3, the cellulose acetate-based resin film 2 is applied to one surface of the polarizing film 1, and the cycloolefin-based resin film 3 is applied to the other surface, respectively. The film laminate was sandwiched between the bonding rolls 20 and 21 which were overlapped and disposed opposite each other with a center-to-center distance L [μm] through an adhesive layer. In this example, (L ₀ -L) was 580 μm.

  The film laminate after the clamping was transported to a drying furnace 18 set at 75 ° C. to dry (film laminate residence time 228 seconds) to obtain a polarizing plate.

<Example 2>
As the bonding rolls 20 and 21, a rubber roll having a hardness of about 80 on a JIS Shore C scale was used, and a polarizing plate was produced in the same manner as in Example 1 except that (L ₀ -L) was 600 μm.

<Comparative Example 1>
As the bonding rolls 20 and 21, a rubber roll having a hardness of about 80 on the JIS Shore C scale was used, and a polarizing plate was produced in the same manner as in Example 1 except that (L ₀ -L) was set to 700 μm.

The following evaluation test was performed about the obtained polarizing plate.
(A) Adhesive strength (adhesive strength) evaluation test The polarizing plate was cut into a size of 100 mm x 25 mm so that the absorption axis of the polarizing film was parallel to the long side, and used as an evaluation sample. The sample for evaluation was bonded to a glass plate on the retardation film side via an acrylic pressure-sensitive adhesive, and then subjected to a pressure treatment for 20 minutes in an autoclave at a temperature of 50 ° C. and a pressure of 5 MPa. It was left for one day in an atmosphere of 60 ° C. and a relative humidity of 60%. Then, a cutter blade is inserted from the corner of the sample for evaluation into the interface between the polarizing film and the retardation film of the evaluation sample bonded to the glass plate, and in the 90 ° direction at the interface between the polarizing film and the retardation film. A test for peeling at a peeling speed of 200 mm / min was conducted. The peel strength (adhesion strength) [N / 25 mm] at this time was measured using “Autograph ASG-100D” manufactured by Shimadzu Corporation. The results are shown in Table 1.

(B) Peelability evaluation test The polarizing plate was cut into a size of 500 mm x 400 mm so that the absorption axis of the polarizing film was parallel to the long side, and used as an evaluation sample 60. As shown in FIG. 4, the evaluation sample 60 is placed on a movable stage 70 of a “plane wear tester PA-2A” manufactured by Daiei Kagaku Seiki Seisakusho through an acrylic adhesive on the retardation film side. The short side of the evaluation sample 60 is tilted about 45 ° counterclockwise with respect to the surface 80 with which the heavy stone 90 (mass 464 g) fixed by the support is in contact, and the corner of the evaluation sample 60 is a heavy stone during the test. It pasted so that it might touch 90. Next, the movable stage 70 was reciprocated 10 times at a speed of 80 rpm, and an impact was applied to the corner of the sample 60 for evaluation. Thereafter, a cellophane tape made of Nichiban was attached to the corner and pulled in the upward direction (perpendicular direction of the sample surface for evaluation) to confirm the presence or absence of peeling at the interface between the polarizing film and the retardation film. The above test is performed with an evaluation number N = 10, and the following formula:
Peeling ratio = (number of peelings) / 10
Based on the above, the peel rate was calculated. The results are shown in Table 1.

  DESCRIPTION OF SYMBOLS 1 Polarizing film, 2 Cellulose acetate type resin film, 3 Cycloolefin type resin film, 4 Polarizing plate, 10 1st coating apparatus, 12 2nd coating apparatus, 18 Drying furnace, 20, 21 Pasting roll, 22 , 23 Pre-winding nip roll, 24 guide roll, 30 winding roll, 50 triacetyl cellulose film, 60 sample for evaluation, 70 movable stage, 80 surface in contact with the heavy stone on the movable stage, 90 weight stone.

Claims (5)

While continuously conveying a polarizing film made of a polyvinyl alcohol-based resin, supplying a cellulose acetate-based resin film and a cycloolefin-based resin film;
The cellulose acetate-based resin film is laminated on one surface of the polarizing film, and the cycloolefin-based resin film is laminated on the other surface via an adhesive layer. And a step of clamping by passing between a pair of bonding rolls arranged opposite to each other,
With
The triacetyl cellulose film moves even when a tension of 100 N / m is applied to the 40 μm thick triacetyl cellulose film sandwiched between the pair of bonding rolls in a direction orthogonal to the axial direction of the bonding roll. When the maximum value of the center distance between the bonding rolls that maintains the position without the reference is the reference center distance L ₀ [μm], the center distance L is represented by the following formula (1):
L ₀ −L ≦ 600 (1)
The manufacturing method of the polarizing plate which satisfy | fills. The center distance L is the following formula (2):
500 ≦ L ₀ −L (2)
The manufacturing method of the polarizing plate of Claim 1 which satisfy | fills.   3. The polarized light according to claim 1, wherein the polarizing film has a thickness of 5 to 40 μm, the cellulose acetate-based resin film has a thickness of 10 to 50 μm, and the cycloolefin-based resin film has a thickness of 10 to 50 μm. A manufacturing method of a board.   The method for producing a polarizing plate according to any one of claims 1 to 3, wherein the pair of bonding rolls are elastic rolls having a hardness of 70 to 80 on a JIS Shore C scale.   The method for producing a polarizing plate according to claim 1, wherein the adhesive layer is made of a water-based adhesive.

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