Method for manufacturing polarizing plate protective film

Abstract

The present invention addresses the problem of providing a production method for a polarizing plate protection film that contains a cycloolefin polymer having improved adhesion to a polyvinyl alcohol film.　This production method for a polarizing plate protection film is characterized by comprising at least: a rolled source film production step including a step for forming a web through flow-casting of a dope on a support at a transport speed V1, a step for performing the first stage of stretching on the web having a web width immediately after the flow-casting, and a step for rolling up a film formed by drying the web; and a processing step including a step for transporting the rolled-up film at a transport speed V2 satisfying V1<V2 and performing the second stage of stretching thereon. In the step for performing the second stage of stretching on the rolled-up film, the stretching is performed such that the amount of a residual solvent immediately before the second stage of stretching with respect to the rolled-up width falls within the range of 0.1-0.5 mass%.

Description

[Technical Field]

[0001] The present invention relates to a method for producing a polarizing plate protective film, and more particularly to a method for producing a polarizing plate protective film containing a cycloolefin polymer having improved adhesion to a polyvinyl alcohol film. [Background technology]

[0002] As a polarizing plate protective film used in a polarizing plate of a liquid crystal display, a cellulose ester polymer such as triacetyl cellulose is suitable because of its small birefringence and is therefore often used.

[0003] A polarizing plate generally consists of a film (hereinafter also referred to as a "polarizing film," "polarizer film," or "polarizer film") made of a polyvinyl alcohol-based film or the like that has iodine or a dye adsorbed and oriented thereon, and transparent polymer (resin) film layers laminated on both sides of the film. Conventionally, a protective film of triacetyl cellulose has been widely used as this transparent polymer film layer, but in recent years, various methods for improving it have been proposed to meet the demand for higher levels of performance from various viewpoints. For example, Patent Document 1 discloses a technique for controlling the angle unevenness in the slow axis direction of a cellulose ester-based protective film during the production of the polarizing plate protective film.

[0004] On the other hand, since cycloolefin-based polymers are superior to cellulose ester-based polymers in transparency, optical properties, durability, etc., there has been an increasing demand year by year for the use of polarizing plate protective films using such cycloolefin-based polymers in display devices such as liquid crystal display devices. However, like protective films made of cellulose ester polymers, protective films made of cycloolefin polymers still have some shortcomings in terms of the high performance required, and when the improvement technology described in Patent Document 1 was applied, a new problem was discovered: there was room for improvement in the adhesion between the polarizing film and the polarizing plate protective film. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-311240 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in consideration of the above problems and circumstances, and the problem to be solved is to provide a method for producing a polarizing plate protective film containing a cycloolefin-based polymer that has improved adhesion to a polyvinyl alcohol-based polarizing film. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, the present inventors have investigated the causes of the above-mentioned problems, and as a result, have found that when producing a polarizing plate protective film, the condition of the film surface can be improved and the above-mentioned problems can be solved by controlling the relative relationship between the film conveying speed in the raw film production process and the processing process, and the amount of residual solvent in the film during stretching within a certain range, and have arrived at the present invention. That is, the above-mentioned problems of the present invention are solved by the following means.

[0008] 1. A method for producing a polarizing plate protective film containing a cycloolefin polymer, comprising: We have a raw film manufacturing process and a processing process. the raw film manufacturing process comprises at least a step of casting a dope onto a support at a conveying speed V1 to form a web, a step of stretching the web in a first stage to the web width immediately after casting, and a step of drying the web to form a film and winding it up; the processing step includes a step of conveying the wound film at a conveying speed V2 that satisfies the following formula (1) and performing a second-stage stretching, Formula (1):V1 <V2 Furthermore, in the second-stage stretching step, the wound film is stretched so that the amount of residual solvent immediately before the second-stage stretching is in the range of 0.1 to 0.5% by mass relative to the winding width.

[0009] 2. The method for producing a polarizing plate protective film described in item 1, wherein the amount of residual solvent immediately before the first stage of stretching is in the range of 1 to 15% by mass, and the stretching ratio is in the range of 1.1 to 2.0 times.

[0010] 3. The method for producing a polarizing plate protective film according to item 1 or 2, wherein the stretching ratio in the second stretching step is within the range of 1.1 to 2.0 times. [Effects of the Invention]

[0011] According to the above-mentioned means of the present invention, it is possible to provide a method for producing a polarizing plate protective film containing a cycloolefin polymer having improved adhesiveness to a polyvinyl alcohol film. The mechanism by which the effects of the present invention are manifested or the mechanism of action is not clear, but is speculated as follows.

[0012] In the present invention, when producing a polarizing plate protective film, the condition of the film surface can be improved by controlling the relative relationship between the film transport speed in the raw film production process and the processing process, and the amount of residual solvent in the film during stretching within a certain range. In other words, it is thought that first, in the raw film manufacturing process, the first stage of stretching is performed when there is a considerable amount of solvent remaining in the film (web), which prevents the orientation of the polymer constituent molecules in the film, such as the polymer molecular chains, from being biased toward the surface and forming a high-density layer, thereby making the physicochemical state of the surface suitable for improving adhesion.

[0013] Furthermore, by controlling the relative relationship between the film conveying speeds in the raw film manufacturing process and the processing process so as to satisfy the above formula (1), it is possible to diffuse the residual solvent during the second stretching stage and suppress the formation of a high-density layer due to heat treatment. It is also thought that by adjusting the amount of residual solvent to a certain level or less, it is possible to prevent excessive penetration of the adhesive into the film and prevent a deterioration in the strength of the film.

[0014] In addition, by controlling the conveying speed and the amount of residual solvent in the second stretching stage, it is possible to produce a stretched film without deteriorating the adhesiveness. The reason for this is thought to be that when the film is further stretched in the second stretching stage with a residual solvent content of 0.1 to 0.5 mass%, if formula (1) is satisfied, the residual solvent diffuses during the stretching process, thereby suppressing the formation of a high-density layer due to heat treatment. On the other hand, if formula (1) is not satisfied, i.e., if the film conveying speed V2 is slower than V1, the internal solvent will evaporate before the film enters the stretching process, and the surface layer will become densified by the heat treatment in the additional stretching process. [Brief explanation of the drawings]

[0015] [Figure 1] Flowchart showing the flow of the manufacturing process of the present invention [Figure 2] Schematic diagram of a device for manufacturing polarizing plate protective film DETAILED DESCRIPTION OF THE INVENTION

[0016] The method for producing a polarizing plate protective film of the present invention is a method for producing a polarizing plate protective film containing a cycloolefin-based polymer, and includes a raw film production step and a processing step, wherein the raw film production step includes at least a step of casting a dope onto a support at a conveying speed V1 to form a web, a step of stretching the web in a first stage to the web width immediately after casting, and a step of drying the web to form a film and winding it up, and the processing step includes a step of transporting the wound film at a conveying speed V2 that satisfies the following formula (1) and stretching it in a second stage: Formula (1):V1 <V2 Furthermore, in the second-stage stretching step, the wound film is stretched so that the amount of residual solvent immediately before the second-stage stretching is in the range of 0.1 to 0.5 mass % relative to the winding width. This feature is a technical feature common to or corresponding to each of the following embodiments (configurations).

[0017] In an embodiment of the present invention, it is preferred that the amount of residual solvent immediately before the first-stage stretching is in the range of 1 to 15% by mass and that the stretching ratio is in the range of 1.1 to 2.0, from the viewpoints of improving the adhesiveness of the film and suppressing deterioration of the film strength.

[0018] Furthermore, it is more preferable from the viewpoint of achieving the desired effect that the stretching ratio in the second-stage stretching step is within the range of 1.1 to 2.0 times.

[0019] The present invention, its components, and embodiments for carrying out the present invention will be described in detail below. In this application, the symbol "to" is used to mean that the numerical values ​​before and after it are included as lower and upper limits.

[0020] [Method of manufacturing polarizing plate protective film] The method for producing a polarizing plate protective film of the present invention is a method for producing a polarizing plate protective film containing a cycloolefin-based polymer, and includes a raw film production step and a processing step, wherein the raw film production step includes at least a step of casting a dope onto a support at a conveying speed V1 to form a web, a step of stretching the web in a first stage to the web width immediately after casting, and a step of drying the web to form a film and winding it up, and the processing step includes a step of transporting the wound film at a conveying speed V2 that satisfies the following formula (1) and stretching it in a second stage: Formula (1):V1 <V2 Furthermore, in the second-stage stretching step, the wound film is stretched so that the amount of residual solvent immediately before the second-stage stretching is in the range of 0.1 to 0.5 mass % relative to the winding width. The steps of the manufacturing method using the solution casting film-forming method will be described below with reference to FIGS.

[0021] FIG. 1 is a flow chart showing the flow of the manufacturing process of the present invention, and FIG. 2 is a schematic diagram of an apparatus for manufacturing a polarizing plate protective film.

[0022] 1. Raw film manufacturing process The raw film of the present invention is a film produced by a solution casting film-forming method, and the raw film production process comprises at least a step of casting a dope onto a support at a conveying speed V1 to form a web, a step of stretching the web in the first stage to the web width immediately after casting, and a step of drying the web to form a film and winding it up.

[0023] (1.1) A step of casting the dope onto a support at a conveying speed V1 to form a web The process of forming a web by casting the dope onto the support at a transport speed V1 includes at least a dope preparation step (S1), a casting step (S2), and a peeling step (S3).

[0024] (1.1.1) Dope preparation (stirring preparation) step (S1) In the dope preparation (stirring and preparation) step (S1), at least a resin and a solvent are stirred in a stirring tank 1a of a stirring device 1 to prepare a dope to be cast onto a support 3 (endless belt).

[0025] Hereinafter, as one embodiment of the present invention, a dope preparation process will be described using a case where a cycloolefin polymer (hereinafter also referred to as "COP"), which is a thermoplastic resin, is used as an example.

[0026] This step is a step of dissolving a cycloolefin polymer (COP) and, if necessary, other compounds in a solvent mainly consisting of a good solvent for the COP in a dissolution vessel while stirring the COP, to form a dope, or a step of mixing, if necessary, a solution of other compounds with the COP solution to form a dope, which is a main solution.

[0027] (Concentration of cycloolefin polymer) The concentration of the cycloolefin polymer (COP) in the dope is preferably high because the drying load after casting on the support can be reduced. However, if the COP concentration is too high, the load during filtration increases and accuracy deteriorates. The concentration that satisfies both of these requirements is preferably in the range of 10 to 35% by mass, and more preferably in the range of 15 to 30% by mass.

[0028] (Solvent used in dope) The solvents used in the dope may be used alone or in combination of two or more kinds. However, it is preferable to use a mixture of a good solvent and a poor solvent for the cycloolefin polymer (COP) in terms of production efficiency, and it is preferable to use a larger amount of the good solvent in terms of solubility of the COP.

[0029] The preferred range of the mixing ratio of the good solvent to the poor solvent is 70 to 98 mass % of the good solvent and 2 to 30 mass % of the poor solvent. In this specification, a "good solvent" or a "poor solvent" is defined as a solvent that dissolves the cycloolefin polymer (COP) used alone, and a poor solvent is defined as a solvent that swells or does not dissolve the COP alone. Therefore, whether a solvent is a good solvent or a poor solvent may depend on the type and number of substituents on the COP.

[0030] The good solvent used in the present invention is not particularly limited, but examples thereof include organic halogen compounds such as methylene chloride, dioxolanes, acetone, methyl acetate, and methyl acetoacetate. Particularly preferred are methylene chloride and methyl acetate.

[0031] The poor solvent used in the present invention is not particularly limited, but for example, methanol, ethanol, n-butanol, cyclohexane, cyclohexanone, etc. are preferably used. The dope preferably contains 0.01 to 2.00 mass % of water.

[0032] The solvent used to dissolve the cycloolefin polymer (COP) is recovered and reused after being removed from the film by drying in the polarizing plate protective film production process.

[0033] The recovered solvent may contain trace amounts of additives added to the COP, such as plasticizers, ultraviolet absorbers, polymers, and monomer components. However, even if these additives are contained, the recovered solvent can be preferably reused, and if necessary, it can be purified and reused.

[0034] As the method for dissolving COP when preparing the dope described above, a general method can be used. Specifically, preferred are methods carried out at normal pressure, at or below the boiling point of the main solvent, and methods carried out under pressure at or above the boiling point of the main solvent. Combining heating and pressure allows heating above the boiling point at normal pressure.

[0035] In addition, a method of stirring and dissolving while heating at a temperature equal to or higher than the boiling point of the solvent at normal pressure but within a range in which the solvent does not boil under pressure is also preferred, as this prevents the formation of lumpy undissolved matter called gel or lumps.

[0036] Also preferably used is a method in which a cycloolefin polymer (COP) is mixed with a poor solvent to wet or swell it, and then a good solvent is added to dissolve it.

[0037] The pressure may be applied by injecting an inert gas such as nitrogen gas or by increasing the vapor pressure of the solvent by heating. Heating is preferably performed from the outside, and for example, a jacket type is preferred because it is easy to control the temperature.

[0038] The heating temperature after adding the solvent is preferably higher from the viewpoint of the solubility of the cycloolefin polymer (COP). However, if the heating temperature is too high, the required pressure increases, resulting in poor productivity.

[0039] The heating temperature is preferably within a range of 30 to 120°C, more preferably within a range of 60 to 110°C, and even more preferably within a range of 70 to 105°C. The pressure is also adjusted so that the solvent does not boil at the set temperature.

[0040] Alternatively, a cooling dissolution method is also preferably used, by which the cycloolefin polymer (COP) can be dissolved in a solvent such as methyl acetate.

[0041] (filtration) Next, it is preferable to filter the cycloolefin polymer (COP) solution (dope during or after dissolution) using a suitable filter material such as filter paper.

[0042] It is preferable that the filter has a low absolute filtration accuracy in order to remove insoluble matters, but if the absolute filtration accuracy is too low, there is a problem that the filter is easily clogged. Therefore, a filter medium with an absolute filtration accuracy of 0.008 mm or less is preferred, a filter medium with an absolute filtration accuracy in the range of 0.001 to 0.008 mm is more preferred, and a filter medium with an absolute filtration accuracy in the range of 0.003 to 0.006 mm is even more preferred.

[0043] There are no particular restrictions on the material of the filter medium, and ordinary filter medium can be used, but filter medium made of plastic such as polypropylene or Teflon (registered trademark), or filter medium made of metal such as stainless steel is preferred as it does not cause fiber shedding.

[0044] It is preferable to remove or reduce impurities, particularly bright spot foreign matter, contained in the raw material cycloolefin polymer (COP) by filtration.

[0045] Bright spot foreign matter is a point (foreign matter) that is visible as light leaking from the opposite side when two polarizing plates are placed in a cross-Nicol state, a film or the like is placed between them, and light is shone from one polarizing plate side and observed from the other polarizing plate side. The number of bright spots is 200 / cm and is 0.01 mm or more in diameter. 2 It is preferable that: More preferably 100 / cm 2 More preferably, 50 cells / cm or less. 2 More preferably, 10 particles / cm or less. 2 The following is the result. It is also preferable to have fewer bright spots of 0.01 mm or less.

[0046] The dope can be filtered by a conventional method. However, a method of filtering the dope while heating the solvent at a temperature above the boiling point of the solvent at normal pressure and within a range where the solvent does not boil under pressure is preferred because the increase in the difference in filtration pressure (referred to as differential pressure) before and after filtration is small.

[0047] The temperature is preferably in the range of 30 to 120°C, more preferably in the range of 45 to 70°C, and even more preferably in the range of 45 to 55°C.

[0048] A small filtration pressure is preferred. Specifically, it is preferably 1.6 MPa or less, more preferably 1.2 MPa or less, and even more preferably 1.0 MPa or less.

[0049] (1.1.2) Casting process (S2) In the casting step (S2), the web 5 formed by the dope cast onto the support 3 at a conveying speed V1 is heated on the support 3, and the solvent is evaporated until the web 5 can be peeled from the support 3 by a peeling roller 4. The amount of the remaining solvent immediately before the first stage of stretching is controlled by evaporating the solvent.

[0050] The evaporation is preferably carried out in an atmosphere within a range of 5 to 75°C. There are several ways to evaporate the solvent, including blowing hot air onto the top surface of the web and / or transferring heat from the back surface of the support 3 using a liquid, and transferring heat from the front and back using radiant heat. However, the method of transferring heat from the front and back using radiant heat is preferred as it has good drying efficiency. A combination of these methods is also preferably used.

[0051] The casting width is preferably 1.3 m or more from the viewpoint of productivity. More preferably, it is in the range of 1.3 to 4.0 m. If the casting width does not exceed 4.0 m, no streaks will appear during the manufacturing process and the film will be more stable during the subsequent transport process. From the viewpoint of transportability and productivity, a range of 1.3 to 3.0 m is more preferable.

[0052] The support 3 in the casting step (S2) preferably has a mirror-finished surface, and the support 3 is preferably a stainless steel belt or a cast drum with a plated surface.

[0053] The surface temperature of the support 3 in the casting step (S2) is in the range of -50°C to the boiling point of the solvent, and a higher temperature is preferred because it increases the drying speed of the web.

[0054] The support temperature is preferably in the range of 0 to 55°C, more preferably in the range of 22 to 50°C.

[0055] There are no particular limitations on the method for controlling the temperature of the support 3, but examples include a method of blowing hot or cold air onto the support, or a method of bringing hot water into contact with the back side of the support. The use of warm water is preferable because heat is transferred more efficiently and the time required for the temperature of the support to become constant is shorter. When using hot air, the temperature may be higher than the desired temperature.

[0056] In the casting step (S2), the dope prepared in the dope preparation step (S1) is sent to the casting die 2 through a conduit via a pressure-type metering gear pump or the like, and the dope is cast from the casting die 2 onto a casting position on a support 3 made of a rotating stainless steel endless belt that is transported endlessly.

[0057] Here, the part of the casting die slit from which the dope comes out is called a lip. A casting die is preferred in which the slit shape of the lip can be adjusted and the film thickness can be easily made uniform. Casting dies include coat hanger dies and T-dies, and any of these is preferably used. In the present invention, the term "web" refers to the dope film cast from the lip portion. In order to increase the film-forming speed of the raw film, two or more of the above-mentioned casting dies may be provided on the support, and the dope may be divided and layered. Alternatively, it is also preferable to obtain a raw film having a laminated structure by a co-casting method in which a plurality of dopes are simultaneously cast.

[0058] The slit can be narrowed by manually turning and pushing the heat bolt to make the film thinner, or opened to make it thicker. A common method is to apply voltage to a heat bolt to press it in place using heat, but these methods are usually used in combination. It is also possible to use a push-pull system. However, the pitch of the bolts may not be narrow due to the mechanism of the casting die. In the case of a highly viscous dope (including a molten dope), the pressure load on the lip when the dope is discharged from the casting die is large, and the pressure suddenly decreases after the discharge, which causes the film thickness to increase (balance effect), resulting in a variation in the film thickness across the width. Therefore, it is necessary to design the casting die so that the lip of the casting die is not subjected to excessive load due to the internal structure of the casting die.

[0059] In the casting step (S2), the dope cast at a conveying speed V1 is dried on the support 3 to form a web 5. In this case, the inclination of the casting die 2, i.e., the direction of the dope discharged from the casting die 2 to the support 3, may be set appropriately so that the angle with respect to the normal to the surface of the support 3 (the surface onto which the dope is cast) falls within the range of 0 to 90°.

[0060] The support 3 is made of, for example, a stainless steel belt, and is held by a pair of rollers 3a and 3b and a plurality of rollers positioned between them. In this case, the surface of the support is preferably a mirror surface.

[0061] One or both of the rollers 3a and 3b are provided with a drive device that applies tension to the support 3, so that the support 3 is used in a tensioned state. The support 3 may be a drum.

[0062] (1.1.3) Peeling process (S3) In this process, in the casting process (S2), the solvent is evaporated until the web 5 has a film strength on the support 3 that allows it to be peeled off, and after drying and solidifying or cooling and solidifying, the web is peeled off from the support 3 before the raw film makes one revolution around the support 3. That is, this step is a step in which the web from which the solvent has evaporated on the support 3 is peeled off at the peeling position. At this time, from the viewpoints of surface quality, moisture permeability, and releasability, it is preferable to peel the raw film from the support within a range of 30 to 600 seconds. The position where the web is peeled from the support is called the peeling point, and the roll that assists the peeling is called the peeling roller. In the peeling step (S3), the web is peeled off by a peeling roller 4 while maintaining its self-supporting property. The temperature at the peeling position on the support is preferably within the range of -50 to 40°C, more preferably within the range of 10 to 40°C, and most preferably within the range of 15 to 30°C.

[0063] (Residual solvent amount) The amount of remaining solvent immediately before the first stage of stretching is adjusted appropriately depending on the strength of the drying conditions, the length of the support 3, and the like. Although it depends on the thickness of the web, if the amount of residual solvent at the peeling point is too high, the web may become too soft and difficult to peel, which may impair flatness and make it more susceptible to horizontal steps, wrinkles, and vertical streaks due to peeling tension. Conversely, if the amount of residual solvent is too small, part of the web may peel off during the process. In order for the web to have good flatness, the amount of residual solvent is preferably within the range of 1 to 50% by mass, from the viewpoint of balancing economic speed and quality. From the viewpoint of achieving the effects of the present invention, the content is preferably within the range of 1 to 15% by mass.

[0064] One method to increase the film production speed (to increase the film production speed by peeling while the residual solvent content is still as high as possible) is the gel casting method, which allows peeling even when the residual solvent content is high. The methods include adding a poor solvent for the cycloolefin polymer (COP) to the dope, gelling the web after casting the dope, and cooling the support to gel the web and peeling it off in a state where it contains a large amount of residual solvent. There is also a method of adding a metal salt to the dope. As described above, by gelling the web on the support and strengthening the film, peeling can be accelerated and the film production rate can be increased.

[0065] The amount of residual solvent is defined by the following formula: Residual solvent amount (mass%) = {(MN) / N} × 100 Here, M is the mass of a sample taken at any time during or after the production of the web or polarizing plate protective film, and N is the mass of M after heating at 115° C. for 1 hour.

[0066] (Method for measuring residual solvent amount) The amount of residual solvent can be measured by headspace gas chromatography. In headspace gas chromatography, a sample is sealed in a container, heated, and when the container is filled with volatile components, the gas in the container is quickly injected into a gas chromatograph, where mass spectrometry is performed to identify the compounds and quantify the volatile components. The headspace method allows the observation of all peaks of volatile components using a gas chromatograph, and also allows for highly accurate quantification of volatile substances and monomers by using an analytical method that utilizes electromagnetic interactions.

[0067] (peel tension) The peel tension when peeling the support and the web is preferably 300 N / m or less. A more preferable range is 196 to 245 N / m, but if wrinkles are likely to occur during peeling, peeling is preferably performed with a tension of 190 N / m or less.

[0068] (1.2) A step of first-stage stretching of the web to the web width immediately after casting This step is the first-stage stretching step (S4), and is carried out by stretching the web after peeling it from the support in the machine direction (hereinafter also referred to as "MD direction"). In this case, the web shrinks in the transverse direction (hereinafter also referred to as "TD direction"), which is perpendicular to the MD direction within the web plane. The stretching may be carried out depending on the required optical properties, and it is preferable to stretch in at least one direction, but it may also be stretched in two mutually perpendicular directions (for example, biaxial stretching in the width direction (TD direction) of the film-like material and the conveying direction (MD direction) perpendicular to it). The stretching ratio is defined as (size of the film in the stretching direction after stretching) / (size of the film in the stretching direction before stretching). When biaxial stretching is performed, the stretching ratio is preferably set within the range of 1.1 to 2.0 times in each of the TD and MD directions.

[0069] (Residual solvent amount) In the present invention, the residual solvent amount immediately before the first-stage stretching is the same as the residual solvent amount at the peeling point in the peeling step (S3) described above. In an embodiment of the present invention, it is preferred that the amount of residual solvent immediately before the first-stage stretching is in the range of 1 to 15% by mass and that the stretching ratio is in the range of 1.1 to 2.0, from the viewpoints of improving the adhesiveness of the film and suppressing deterioration of the film strength.

[0070] The first-stage stretching step (S4) promotes entanglement between polymer molecules (matrix molecules) in the web thickness direction, so that even when the polarizing plate protective film is bonded to the polarizer layer via an adhesive during polarizing plate production, the adhesive can easily penetrate into the polarizing plate protective film through the entangled parts (crosslinked parts) between the matrix molecules. As a result, the polarizing plate protective film can be firmly fixed to the polarizer layer (also called a "polarizing film," "polarizer film," or "polarizer film") via an adhesive, thereby improving the peel strength of the polarizing plate protective film relative to the polarizer layer. That is, the adhesion between the polarizing plate protective film and the polarizer layer is improved, and the function of suppressing deterioration of the film strength can be ensured.

[0071] In the first-stage stretching step (S4), the web is shrunk in the width direction. Methods for shrinking the web include, for example, (1) subjecting the web to high-temperature treatment without holding the width of the web to increase the density of the web, (2) applying tension to the web in the conveying direction (MD) to shrink the web in the width direction (TD), and (3) rapidly reducing the amount of residual solvent in the web.

[0072] (1.3) A process of drying the web and winding up the film formed. This process comprises a drying step (S5), a first cutting step (S6), and a first winding step (S7). The dope transport speed V1 in the dope preparation step (S1) and the winding speed in the first winding step (S7) are the same. In the above, "the conveying speed and the winding speed are the same" strictly speaking means that they are the same within a range of ±10%.

[0073] (1.3.1) Drying process (S5) The drying step (S5) is a step in which the web is heated on a support to evaporate the solvent, and the formed film is wound up.

[0074] In the drying device 7 in FIG. 2, the web is transported by a plurality of transport rollers arranged in a staggered pattern when viewed from the side, and the web is dried during this transport.

[0075] The drying method in the drying device 7 is not particularly limited, and the web is generally dried using hot air, infrared rays, a heated roller, microwaves, etc., but from the standpoint of simplicity, a method of drying the web with hot air is preferred. A combination of these methods is also preferred. The drying step (S5) may be carried out as needed.

[0076] If the web is thin, it dries quickly, but if it dries too quickly, the flatness of the finished film is likely to be impaired. When drying at high temperatures, the amount of residual solvent must be taken into consideration, but failure due to foaming of the solvent can be prevented by ensuring that the amount of residual solvent is not too large. The drying is generally carried out within the range of 30 to 250°C. It is particularly preferable to dry within the range of 35 to 200°C, and it is preferable to increase the drying temperature stepwise.

[0077] The temperature of the support may be the same throughout or may vary depending on the position.

[0078] In the web drying process, the roller drying method (a method in which the web is dried by passing it alternately through multiple rollers arranged above and below) or the tenter method, in which the web is dried while being transported, is generally used.

[0079] When a tenter stretching apparatus is used, it is preferable to use an apparatus that can independently control the gripping length (the distance from the start of gripping to the end of gripping) of the web on the left and right sides by the left and right gripping means of the tenter stretching apparatus in the stretching step described below.

[0080] (1.3.2) First cutting process (S6) In the first cutting step (S6), a cutting unit 8 consisting of a slitter cuts both widthwise ends of the film F that has been stretched in the first-stage stretching step (S4) and has been through the drying step (S5). In the film F, the portions remaining after cutting both ends constitute product portions that will become film products. On the other hand, the portion cut from the film F may be recovered and reused as part of the raw material for producing a polarizing plate protective film.

[0081] (1.3.3) First winding process (S7) In the first winding step (S7), the film F is wound by the winding device 9 at a conveying speed V1 (winding speed V1), completing the raw film manufacturing process. The initial tension when winding the film F in the winding step is preferably in the range of 20 to 300 N / m.

[0082] 2. Processing process The processing step is a step in which the wound film is unwound from the roll (S8), then conveyed at a conveying speed V2 that satisfies the following formula (1), and subjected to a second-stage stretching, and is composed of at least the unwound step (S8), the second-stage stretching step (S9), the second cutting step (S10), and the second winding step (S11). Formula (1)V1 <V2

[0083] (Residual solvent amount) In the production method of the present invention, the amount of residual solvent immediately before the second stage of stretching is in the range of 0.1 to 0.5% by mass.

[0084] (2.1) Second-stage stretching process (S9) The second stretching step (S9) may be a step of stretching the film only in the MD direction within the film plane, or a step of stretching only in the TD direction, or a step of stretching in both the MD and TD directions, or a step of stretching in an oblique direction. There is no limitation on the stretching direction, but from the viewpoint of obtaining a wide film, it is preferable to include a step including stretching at least in the width direction. Such stretching can be carried out using a stretching device 10.

[0085] In order to ensure a high retardation, a wide width, and to promote penetration of adhesive when adhering to a polarizing film, it is preferable to stretch the film at a high ratio in the second stretching step. However, if the stretching ratio is too high, crazes may occur in the film due to the stretching stress, or the entanglement between matrix molecules that maintain the strength of the film may be dissociated, resulting in weakening of the film.

[0086] Therefore, from the viewpoint of realizing the effects of the present invention, it is more preferable that the stretching ratio in the second stretching step is within the range of 1.1 to 2.0 times.

[0087] In addition, when stretching is performed multiple times, such as stretching after the peeling step and stretching in the second stretching step, as in the present invention, it is preferable that the stretching at the highest magnification, which has the highest risk of dissociating the matrix molecules, is performed in the final stretch among the multiple stretchings. Therefore, in the present invention, it is preferable that the stretching is carried out at the highest ratio in the second stretching step. In this case, the entanglement of the matrix molecules can be strengthened before the maximum stretching ratio, so that even when the film is stretched to the maximum stretching ratio, dissociation of the entanglement of the matrix molecules can be suppressed, thereby suppressing cohesive failure.

[0088] In the second stretching step (S9), the film F is stretched by a stretching device . The stretching method used here is preferably a method in which a difference in peripheral speed between rollers is used to stretch in the conveyance direction (longitudinal direction of the film; film-forming direction; casting direction; MD direction), or a tenter method in which both side edges of the film are fixed with clips or the like and stretched in the width direction (direction perpendicular to the film plane; TD direction), in order to improve the performance, productivity, flatness, and dimensional stability of the film.

[0089] In the case of the so-called tenter method, it is preferable to drive the clip portion by a linear drive system, since this allows smooth stretching and reduces the risk of breakage.

[0090] The width holding or transverse stretching in the film-forming process is preferably carried out by a tenter stretching device, which may be a pin tenter or a clip tenter. In addition to stretching, drying may also be carried out in the stretching device 10.

[0091] (2.2) Second cutting process (S10) In the second cutting step (S10), a cutting unit 11 made of a slitter cuts both widthwise ends of the film F stretched in the second-stage stretching step (S9). In the film F, the portions remaining after cutting both ends constitute product portions that will become film products. On the other hand, the portion cut from the film F may be recovered and reused as part of the raw material for film production.

[0092] (2.3) Second winding process (S11) In the second winding step (S11), the film F is wound by the winding device 12 at a transport speed V2. In this case, the thickness of the film is preferably in the range of 5 to 100 μm, more preferably in the range of 5 to 80 μm, and even more preferably in the range of 5 to 40 μm. The initial tension when winding the film F in the second winding step (S11) is preferably in the range of 20 to 300 N / m.

[0093] (Winding method) The film F can be wound using a commonly used winder, and various tension control methods such as the constant torque method, constant tension method, taper tension method, and program tension control method with constant internal stress can be used appropriately.

[0094] Before winding, the ends are slit and cut to the width of the product, and both ends of the film may be subjected to a surface modification treatment to prevent sticking or scratches during winding.

[0095] 3. Polymer type The polymer (resin) used in the manufacturing method of the polarizing plate protective film of the present invention is a cycloolefin-based polymer (also referred to as a "cycloolefin-based resin"), which is superior to other thermoplastic polymers (resins) in that it is easier to control the stretchability and crystallinity, and adhesives can easily penetrate into it, ensuring better adhesion to the polarizing film. The polarizing plate protective film may be subjected to a surface modification treatment after production.

[0096] (cycloolefin polymer) The cycloolefin polymer contained in the polarizing plate protective film is preferably a polymer of a cycloolefin monomer or a copolymer of a cycloolefin monomer and another copolymerizable monomer.

[0097] The cycloolefin monomer is preferably a cycloolefin monomer having a norbornene skeleton, and more preferably a cycloolefin monomer having a structure represented by the following general formula (A-1) or (A-2).

[0098] [ka]

[0099] In general formula (A-1), R 1 ~R 4 each independently represents a hydrogen atom, a hydrocarbon group having 1 to 30 carbon atoms, or a polar group, and p represents an integer of 0 to 2. 1 ~R 4 Not all of these represent hydrogen atoms at the same time, and R 1 and R 2 does not simultaneously represent a hydrogen atom, and R 3 and R 4 does not simultaneously represent a hydrogen atom.

[0100] In general formula (A-1), R 1 ~R 4 The hydrocarbon group having 1 to 30 carbon atoms represented by the formula (I) is preferably a hydrocarbon group having 1 to 10 carbon atoms, and more preferably a hydrocarbon group having 1 to 5 carbon atoms. The hydrocarbon group having 1 to 30 carbon atoms may further have a linking group containing, for example, a halogen atom, an oxygen atom, a nitrogen atom, a sulfur atom, or a silicon atom. Examples of such linking groups include divalent polar groups such as a carbonyl group, an imino group, an ether bond, a silyl ether bond, and a thioether bond. Examples of the hydrocarbon group having 1 to 30 carbon atoms include a methyl group, an ethyl group, a propyl group, and a butyl group.

[0101] In general formula (A-1), R 1 ~R 4 Examples of the polar group represented by the formula include a carboxy group, a hydroxy group, an alkoxy group, an alkoxycarbonyl group, an aryloxycarbonyl group, an amino group, an amido group, and a cyano group. Among these, a carboxy group, a hydroxy group, an alkoxycarbonyl group, and an aryloxycarbonyl group are preferred, and from the viewpoint of ensuring solubility during solution casting, an alkoxycarbonyl group and an aryloxycarbonyl group are more preferred.

[0102] In formula (A-1), p is preferably 1 or 2 from the viewpoint of improving the heat resistance of the polarizing plate protective film. When p is 1 or 2, the resulting polymer becomes bulky and the glass transition temperature tends to be improved.

[0103] [ka]

[0104] In general formula (A-2), R 5 represents a hydrogen atom, a hydrocarbon group having 1 to 5 carbon atoms, or an alkylsilyl group having an alkyl group having 1 to 5 carbon atoms. 6 represents a carboxy group, a hydroxy group, an alkoxycarbonyl group, an aryloxycarbonyl group, an amino group, an amido group, a cyano group, or a halogen atom (a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom). p represents an integer of 0 to 2.

[0105] R in general formula (A-2) 5 preferably represents a hydrocarbon group having 1 to 5 carbon atoms, and more preferably represents a hydrocarbon group having 1 to 3 carbon atoms.

[0106] R in general formula (A-2) 6preferably represents a carboxy group, a hydroxy group, an alkoxycarbonyl group or an aryloxycarbonyl group, and more preferably an alkoxycarbonyl group or an aryloxycarbonyl group from the viewpoint of ensuring solubility during solution casting.

[0107] In formula (A-2), p preferably represents 1 or 2 from the viewpoint of improving the heat resistance of the polarizing plate protective film. When p is 1 or 2, the resulting polymer becomes bulky and the glass transition temperature tends to be improved.

[0108] A cycloolefin monomer having a structure represented by general formula (A-2) is preferred from the viewpoint of improving solubility in organic solvents. In general, by breaking the symmetry of an organic compound, the crystallinity decreases, and the solubility in organic solvents improves. R in general formula (A-2) 5 and R 6 is substituted on only one ring-constituting carbon atom on one side of the axis of symmetry of the molecule, so the molecule has low symmetry. In other words, cycloolefin monomers having a structure represented by general formula (A-2) have high solubility and are therefore suitable for producing polarizing plate protective films by a solution casting method.

[0109] The content of the cycloolefin monomer having the structure represented by general formula (A-2) in the polymer of cycloolefin monomers can be, for example, 70 mol% or more, preferably 80 mol% or more, and more preferably 100 mol% relative to the total of all cycloolefin monomers constituting the cycloolefin-based polymer. When the cycloolefin monomer having the structure represented by general formula (A-2) is contained in a certain amount or more, the orientation of the polymer increases, and the phase difference (retardation) value tends to increase.

[0110] Specific examples of cycloolefin monomers having a structure represented by general formula (A-1) are shown below as exemplary compounds 1 to 14, and specific examples of cycloolefin monomers having a structure represented by general formula (A-2) are shown below as exemplary compounds 15 to 34.

[0111] [ka]

[0112] Examples of the copolymerizable monomer copolymerizable with the cycloolefin monomer include a copolymerizable monomer capable of ring-opening copolymerization with the cycloolefin monomer, and a copolymerizable monomer capable of addition copolymerization with the cycloolefin monomer.

[0113] Examples of copolymerizable monomers capable of ring-opening copolymerization include cycloolefins such as cyclobutene, cyclopentene, cycloheptene, cyclooctene, and dicyclopentadiene.

[0114] Examples of copolymerizable monomers capable of addition copolymerization include unsaturated double bond-containing compounds, vinyl-based cyclic hydrocarbon monomers, and (meth)acrylates.

[0115] Examples of the unsaturated double bond-containing compound include olefinic compounds having 2 to 12 carbon atoms (preferably 2 to 8 carbon atoms), and examples thereof include ethylene, propylene, and butene.

[0116] Examples of the vinyl-based cyclic hydrocarbon monomer include vinylcyclopentene-based monomers such as 4-vinylcyclopentene and 2-methyl-4-isopropenylcyclopentene.

[0117] Examples of the (meth)acrylate include alkyl (meth)acrylates having 1 to 20 carbon atoms, such as methyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and cyclohexyl (meth)acrylate.

[0118] The content of the cycloolefin monomer in the copolymer of a cycloolefin monomer and a copolymerizable monomer can be, for example, within the range of 20 to 80 mol %, preferably within the range of 30 to 70 mol %, relative to the sum of all monomers constituting the copolymer.

[0119] As described above, the cycloolefin polymer is a polymer obtained by polymerizing or copolymerizing a cycloolefin monomer having a norbornene skeleton, preferably a cycloolefin monomer having a structure represented by general formula (A-1) or (A-2), and examples thereof include the following polymers (1) to (7).

[0120] (1) Ring-opening polymer of cycloolefin monomer (2) Ring-opening copolymers of cycloolefin monomers and copolymerizable monomers capable of ring-opening copolymerization with the cycloolefin monomers. (3) Hydrogenated ring-opening (co)polymer of (1) or (2) above (4) A (co)polymer obtained by cyclizing the ring-opening (co)polymer of (1) or (2) above by the Friedel-Crafts reaction and then adding hydrogen. (5) Saturated copolymer of cycloolefin monomer and unsaturated double bond-containing compound (6) Addition copolymers of cycloolefin monomers with vinyl cyclic hydrocarbon monomers and their hydrogenated products (7) Alternating copolymer of cycloolefin monomer and (meth)acrylate

[0121] The polymers (1) to (7) above can all be obtained by known methods, for example, the methods described in JP-A Nos. 2008-107534 and 2005-227606.

[0122] For example, the catalyst and solvent used in the ring-opening copolymerization (2) above may be those described in paragraphs 0019 to 0024 of JP-A No. 2008-107534. As the catalyst used for the hydrogenated products (3) and (6) above, for example, those described in paragraphs 0025 to 0028 of JP-A No. 2008-107534 can be used. The acidic compound used in the Friedel-Crafts reaction (4) above can be, for example, the one described in paragraph 0029 of JP-A No. 2008-107534. As the catalyst used in the addition polymerization of the above (5) to (7), for example, those described in paragraphs 0058 to 0063 of JP-A No. 2005-227606 can be used. The alternating copolymerization reaction (7) above can be carried out by, for example, the method described in paragraphs 0071 and 0072 of JP-A No. 2005-227606.

[0123] Among these, the polymers (1) to (3) and (5) are preferred, and the polymers (3) and (5) are more preferred.

[0124] That is, the cycloolefin-based polymer preferably contains at least one of a structural unit represented by the following general formula (B-1) and a structural unit represented by the following general formula (B-2), from the viewpoint of increasing the glass transition temperature and light transmittance of the resulting cycloolefin-based polymer, and more preferably contains only a structural unit represented by the general formula (B-2), or contains both a structural unit represented by the general formula (B-1) and a structural unit represented by the general formula (B-2).

[0125] The structural unit represented by general formula (B-1) is a structural unit derived from the cycloolefin monomer represented by the above-mentioned general formula (A-1), and the structural unit represented by general formula (B-2) is a structural unit derived from the cycloolefin monomer represented by the above-mentioned general formula (A-2).

[0126] [ka]

[0127] In the general formula (B-1), X represents -CH=CH- or -CH2CH2-. 1 ~R 4 and p are R in general formula (A-1), 1 ~R 4 and p.

[0128] [ka]

[0129] In the general formula (B-2), X represents -CH=CH- or -CH2CH2-. 5 ~R 6and p are R in general formula (A-2), 5 ~R 6 and p.

[0130] The cycloolefin polymer according to the present invention may be a commercially available product. Examples of commercially available cycloolefin polymers include Arton G (for example, G7810), Arton F, Arton R (for example, R4500, R4900, and R5000), and Arton RX, all manufactured by JSR Corporation.

[0131] The intrinsic viscosity [η]inh of cycloolefin polymers is 0.2 to 5 cm when measured at 30°C. 3 / g, and 0.3 to 3 cm 3 / g, and more preferably in the range of 0.4 to 1.5 cm 3 It is more preferable that the content is in the range of / g.

[0132] The number average molecular weight (Mn) of the cycloolefin polymer is preferably within a range of 8,000 to 100,000, more preferably within a range of 10,000 to 80,000, and even more preferably within a range of 12,000 to 50,000.

[0133] The weight average molecular weight (Mw) of the cycloolefin polymer is preferably within a range of 20,000 to 300,000, more preferably within a range of 30,000 to 250,000, and even more preferably within a range of 40,000 to 200,000.

[0134] The number average molecular weight and weight average molecular weight of the cycloolefin polymer can be measured by gel permeation chromatography (GPC) in terms of polystyrene.

[0135] (Gel Permeation Chromatography) Solvent: methylene chloride Column: Shodex K806, K805, K803G (three columns connected together, manufactured by Showa Denko K.K.) Column temperature: 25℃ Sample concentration: 0.1% by mass Detector: RI Model 504 (GL Sciences) Pump: L6000 (Hitachi, Ltd.) Flow rate: 1.0ml / min Calibration curve: A calibration curve was used using 13 samples of standard polystyrene STK standard polystyrene (manufactured by Tosoh Corporation) in the range of Mw=500 to 2,800,000. It is preferable to use the 13 samples at approximately equal intervals.

[0136] When the intrinsic viscosity [η]inh, number average molecular weight and weight average molecular weight are within the above ranges, the cycloolefin polymer has good heat resistance, water resistance, chemical resistance, mechanical properties and moldability into a film.

[0137] The glass transition temperature (Tg) of the cycloolefin polymer is usually 110°C or higher, preferably in the range of 110 to 350°C, more preferably in the range of 120 to 250°C, and even more preferably in the range of 120 to 220°C.

[0138] When the glass transition temperature (Tg) is 110°C or higher, deformation under high temperature conditions is easily suppressed. On the other hand, if the glass transition temperature (Tg) is 350°C or lower, molding processing becomes easy and deterioration of the polymer (resin) due to heat during molding processing is also easily suppressed.

[0139] The content of the cycloolefin polymer is preferably 70% by mass or more, and more preferably 80% by mass or more, based on the film.

[0140] 4. Polarizing plate The polarizing plate of the present invention has a polarizer layer, the polarizing plate protective film of the present invention, and an adhesive layer containing a water-based adhesive or an ultraviolet-curable adhesive disposed therebetween.

[0141] (4.1) Polarizer Layer The polarizer layer according to the present invention is a layer made of at least a polarizing film (also called a "polarizer film" or a "polarizer film"). Here, the term "polarizer" refers to an element that transmits only light polarized in a certain direction. The polarizing film according to the present invention is a polyvinyl alcohol-based polarizing film. Polyvinyl alcohol polarizing films include those dyed with iodine and those dyed with a dichroic dye.

[0142] The polyvinyl alcohol-based polarizing film may be a polyvinyl alcohol-based film that has been uniaxially stretched and then dyed with iodine or a dichroic dye (preferably a film that has been further subjected to a durability treatment with a boron compound); or a polyvinyl alcohol-based film that has been dyed with iodine or a dichroic dye and then uniaxially stretched (preferably a film that has been further subjected to a durability treatment with a boron compound). The absorption axis of the polarizer layer is usually parallel to the direction of maximum stretch.

[0143] For example, ethylene-modified polyvinyl alcohol having an ethylene unit content of 1 to 4 mol %, a polymerization degree of 2000 to 4000, and a saponification degree of 99.0 to 99.99 mol %, as described in JP-A Nos. 2003-248123 and 2003-342322, etc., is used.

[0144] The thickness of the polarizer layer is preferably 5 to 30 μm, and more preferably 5 to 20 μm in order to make the polarizing plate thinner.

[0145] (4.2) Polarizing plate protective film The polarizing plate protective film produced by the method for producing a polarizing plate protective film of the present invention is disposed on at least one surface of the polarizer layer (at least the surface facing the liquid crystal cell). The surface of the polarizing plate protective film on which the polarizer layer is to be laminated has been subjected to an activation treatment as described below.

[0146] When the polarizing plate protective film produced by the polarizing plate protective film producing method of the present invention is placed on only one side of the polarizer layer, an optical film such as a retardation film can be placed on the other side of the polarizer layer. Other examples of optical films include commercially available cellulose ester films (e.g., Konica Minolta TAC KC8UX, KC5UX, KC4UX, KC8UCR3, KC4SR, KC4BR, KC4CR, KC4DR, KC4FR, KC4KR, KC8UY, KC6UY, KC4UY, KC4UE, KC8UE, KC8UY-HA, KC2UA, KC4UA , KC6UA, KC8UA, KC2UAH, KC4UAH, KC6UAH, all manufactured by Konica Minolta, Inc.; Fujitac T40UZ, Fujitac T60UZ, Fujitac T80UZ, Fujitac TD80UL, Fujitac TD60UL, Fujitac TD40UL, Fujitac R02, Fujitac R06, all manufactured by Fujifilm Corporation.

[0147] The thickness of the other optical film may be, for example, 5 to 100 μm, and preferably 40 to 80 μm.

[0148] (4.3) Adhesive layer The adhesive layer is formed by drying a water-based adhesive or an ultraviolet-curable adhesive, which will be described later, disposed between the optical film (or another optical film) and the polarizer layer.

[0149] The thickness of the adhesive layer may be, for example, about 0.01 to 10 μm, and preferably about 0.03 to 5 μm.

[0150] (4.4) Polarizing Plate Manufacturing Method The method for manufacturing a polarizing plate according to the present invention comprises the steps of: 1) subjecting the surface of a polarizing plate protective film to an activation treatment; 2) laminating a polarizer layer (polarizing film) onto the activated surface of the polarizing plate protective film via a water-based adhesive or an ultraviolet-curable adhesive; and 3) drying the resulting laminate.

[0151] Regarding process 1) The surface of the polarizing plate protective film (the surface to be bonded to the polarizer layer) is subjected to an activation treatment. This makes it easier to obtain adhesion to the polarizer layer. Specifically, the activation treatment hydrophilizes the siloxane bonds, ether bonds, tertiary carbon atoms, etc. in the side chains of specific graft polymers contained in the polarizing plate protective film, thereby increasing their affinity with water-based adhesives and facilitating their interaction, thereby facilitating adhesion between the polarizing plate protective film and the polarizer layer.

[0152] Examples of the activation treatment include corona treatment, plasma treatment and saponification treatment, preferably corona treatment and plasma treatment, more preferably corona treatment.

[0153] The activation treatment conditions may be such that the siloxane bond, ether bond, tertiary carbon atom, etc. contained in the side chain of the specific graft polymer can be sufficiently activated. When the activation treatment is a corona treatment, the irradiation dose is 100 to 1000 (W·min / m 2 ), and 150 to 900 (W·min / m 2 ) is more preferable.

[0154] Regarding step 2) Next, a polarizer layer is laminated on the activated surface of the optical film via a water-based adhesive or an ultraviolet-curable adhesive.

[0155] (water-based adhesive) Examples of water-based adhesives include vinyl-based, gelatin-based, vinyl-latex-based, polyurethane-based, isocyanate-based, polyester-based, and epoxy-based adhesives. Among these, from the viewpoint of easily obtaining adhesion to the polyvinyl alcohol-based polarizing film, which is the polarizer layer, an aqueous adhesive containing a vinyl-based polymer is preferred, and an aqueous adhesive containing a polyvinyl alcohol-based polymer (such as a fully saponified polyvinyl alcohol aqueous solution) is more preferred. The water-based adhesive containing a polyvinyl alcohol-based polymer may further contain a water-soluble crosslinking agent such as boric acid, borax, glutaraldehyde, melamine, or oxalic acid.

[0156] (UV-curing adhesive) The ultraviolet-curable adhesive may be a photo-radical polymerizable composition or a photo-cationic polymerizable composition. Among these, photocationically polymerizable compositions are preferred.

[0157] The photocationically polymerizable composition contains an epoxy compound and a photocationic polymerization initiator.

[0158] An epoxy compound is a compound having one or more, preferably two or more, epoxy groups in the molecule. Examples of epoxy compounds include hydrogenated epoxy compounds (glycidyl ethers of polyols having alicyclic rings) obtained by reacting alicyclic polyols with epichlorohydrin; aliphatic epoxy compounds such as polyglycidyl ethers of aliphatic polyhydric alcohols or their alkylene oxide adducts; and alicyclic epoxy compounds having one or more epoxy groups bonded to an alicyclic ring in the molecule. The epoxy compounds may be used alone or in combination of two or more.

[0159] The photocationic polymerization initiator may be, for example, an aromatic diazonium salt; an onium salt such as an aromatic iodonium salt or an aromatic sulfonium salt; or an iron-arene complex.

[0160] The cationic photopolymerization initiator may further contain additives such as a cationic polymerization accelerator such as oxetane or polyol, a photosensitizer, and a solvent, as required.

[0161] The thickness of the adhesive layer is not particularly limited, but may be, for example, 0.01 to 10 μm, and preferably about 0.01 to 5 μm.

[0162] Regarding step 3) The resulting laminate is then dried to obtain a polarizing plate.

[0163] Drying can be carried out by heating. The drying temperature may be any temperature at which the water-based adhesive or the ultraviolet-curable adhesive is sufficiently dried, and may be, for example, 60 to 100°C.

[0164] 5. Other additives In the method for producing a polarizing plate protective film of the present invention, the following may be contained as other additives in addition to the cycloolefin polymer (COP).

[0165] (5.1) Plasticizers The polarizing plate protective film preferably contains at least one type of plasticizer for the purpose of imparting processability to the polarizing plate protective film, for example. The plasticizers are preferably used alone or in combination.

[0166] Among plasticizers, it is preferable to include at least one plasticizer selected from the group consisting of sugar esters, polyesters, and styrene-based compounds, from the viewpoint of achieving both effective control of moisture permeability and high compatibility with base polymers (resins) such as cellulose esters.

[0167] The plasticizer preferably has a molecular weight of 15,000 or less, more preferably 10,000 or less, from the viewpoint of achieving both improved wet heat resistance and compatibility with the base polymer (resin) such as cellulose ester.

[0168] When the compound having a molecular weight of 10,000 or less is a polymer, it preferably has a weight average molecular weight (Mw) of 10,000 or less. The weight average molecular weight (Mw) is preferably in the range of 100 to 10,000, and more preferably in the range of 400 to 8,000.

[0169] In particular, to obtain the effects of the present invention, it is preferable to contain the compound having a molecular weight of 1500 or less in an amount within the range of 6 to 40 parts by mass, and more preferably within the range of 10 to 20 parts by mass, per 100 parts by mass of the base polymer (resin). By containing the component within the above range, it is possible to effectively control the moisture permeability and also to ensure compatibility with the base resin, which is preferable.

[0170] (sugar esters) The polarizing plate protective film may contain a sugar ester compound for the purpose of preventing hydrolysis. Specifically, the sugar ester compound may be a sugar ester having 1 to 12 of at least one kind of pyranose structure or furanose structure, in which all or some of the OH groups in the structure have been esterified.

[0171] (polyester) The polarizing plate protective film may contain polyester.

[0172] The polyester is not particularly limited, but examples thereof include a polymer (polyester polyol) having a terminal hydroxy group that can be obtained by a condensation reaction between a dicarboxylic acid or an ester-forming derivative thereof and a glycol, and a polymer (terminal-capped polyester) in which the terminal hydroxy group of the polyester polyol is capped with a monocarboxylic acid. The ester-forming derivatives referred to here include esters of dicarboxylic acids, dicarboxylic acid chlorides, and dicarboxylic acid anhydrides.

[0173] (styrene compounds) In addition to or instead of the sugar ester and polyester, a styrene-based compound may be used in the polarizing plate protective film in order to improve the water resistance of the polarizing plate protective film.

[0174] The styrene-based compound may be a homopolymer of a styrene-based monomer, or a copolymer of a styrene-based monomer and another copolymerizable monomer. The content of structural units derived from styrene monomers in the styrene compound is preferably within a range of 30 to 100 mol %, more preferably within a range of 50 to 100 mol %, so that the molecular structure has a certain level of bulkiness.

[0175] Examples of styrene-based monomers include styrene; alkyl-substituted styrenes such as α-methylstyrene, β-methylstyrene, and p-methylstyrene; halogen-substituted styrenes such as 4-chlorostyrene and 4-bromostyrene; hydroxystyrenes such as p-hydroxystyrene, α-methyl-p-hydroxystyrene, 2-methyl-4-hydroxystyrene, and 3,4-dihydroxystyrene; vinylbenzyl alcohols; alkoxy-substituted styrenes such as p-methoxystyrene, p-tert-butoxystyrene, and m-tert-butoxystyrene; 3-vinylbenzoic acid, 4-vinylbenzoic acid, and the like. vinylbenzoates such as benzoic acid; 4-vinylbenzyl acetate; 4-acetoxystyrene; amidostyrenes such as 2-butylamidostyrene, 4-methylamidostyrene, and p-sulfonamidostyrene; aminostyrenes such as 3-aminostyrene, 4-aminostyrene, 2-isopropenylaniline, and vinylbenzyldimethylamine; nitrostyrenes such as 3-nitrostyrene and 4-nitrostyrene; cyanostyrenes such as 3-cyanostyrene and 4-cyanostyrene; vinylphenylacetonitrile; arylstyrenes such as phenylstyrene, and indenes. The styrene-based monomer may be one type or a combination of two or more types.

[0176] (5.2) Optional components The polarizing plate protective film may contain other optional components such as antioxidants, colorants, ultraviolet absorbers, matting agents, acrylic particles, hydrogen-bonding solvents, and ionic surfactants. These components can be added in an amount of 0.01 to 20 parts by mass per 100 parts by mass of the base polymer (resin).

[0177] (antioxidant) The polarizing plate protective film can use any commonly known antioxidant. In particular, lactone-based, sulfur-based, phenol-based, double bond-based, hindered amine-based, and phosphorus-based compounds can be preferably used.

[0178] These antioxidants and the like are added in an amount of 0.05 to 20% by mass, preferably 0.1 to 1% by mass, based on the polymer (resin) that is the main raw material of the polarizing plate protective film. A synergistic effect can be obtained by using several different compounds in combination with these antioxidants rather than using only one type. For example, it is preferable to use lactone-based, phosphorus-based, phenol-based and double bond-based compounds in combination.

[0179] (coloring agent) The polarizing plate protective film preferably contains a colorant for adjusting the color tone, within a range that does not impair the effects of the present invention.

[0180] The colorant means a dye or pigment, and in the present invention refers to a dye or pigment that has the effect of making the color tone of the liquid crystal screen blue, adjusting the yellow index, or reducing haze.

[0181] As the colorant, various dyes and pigments can be used, but anthraquinone dyes, azo dyes, phthalocyanine pigments, etc. are effective.

[0182] (ultraviolet absorber) The polarizing plate protective film may be used on the viewing side or backlight side of the polarizing plate, and may therefore contain an ultraviolet absorber for the purpose of imparting an ultraviolet absorbing function.

[0183] The ultraviolet absorber is not particularly limited, but examples thereof include ultraviolet absorbers such as benzotriazole-based, 2-hydroxybenzophenone-based, and salicylic acid phenyl ester-based ultraviolet absorbers. Examples include triazoles such as 2-(5-methyl-2-hydroxyphenyl)benzotriazole, 2-[2-hydroxy-3,5-bis(α,α-dimethylbenzyl)phenyl]-2H-benzotriazole, and 2-(3,5-di-t-butyl-2-hydroxyphenyl)benzotriazole, and benzophenones such as 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, and 2,2′-dihydroxy-4-methoxybenzophenone. The above ultraviolet absorbents may be used singly or in combination of two or more.

[0184] The amount of ultraviolet absorber used varies depending on the type of ultraviolet absorber, conditions of use, etc., but is generally added in the range of 0.05 to 10 mass % and preferably 0.1 to 5 mass % relative to the base polymer (resin).

[0185] (fine particles) The polarizing plate protective film preferably contains fine particles that impart slip properties to the polarizing plate protective film. In particular, the addition of fine particles is effective from the viewpoint of improving the surface slipperiness of the polarizing plate protective film according to the present invention, improving the slipperiness during winding, and preventing the occurrence of scratches and blocking.

[0186] The fine particles may be either inorganic or organic as long as they do not impair the transparency of the resulting polarizing plate protective film and are heat resistant when melted, but inorganic fine particles are more preferred. These fine particles can be used alone or in combination of two or more kinds.

[0187] By using particles with different particle sizes and shapes (for example, needle-like and spherical), it is possible to achieve both high transparency and lubricity.

[0188] Among the compounds constituting the fine particles, silicon dioxide is particularly preferably used because it has a refractive index close to that of the cycloolefin polymer, acrylic polymer, and cellulose ester polymer and therefore has excellent transparency (haze).

[0189] Specific examples of silicon dioxide that can be preferably used include commercially available products with trade names such as Aerosil (registered trademark) 200V, Aerosil (registered trademark) R972V, Aerosil (registered trademark) R972, R974, R812, 200, 300, R202, OX50, TT600, and NAX50 (all manufactured by Nippon Aerosil Co., Ltd.), Seahoster (registered trademark) KEP-10, Seahoster (registered trademark) KEP-30, and Seahoster (registered trademark) KEP-50 (all manufactured by Nippon Shokubai Co., Ltd.), Silohorbic (registered trademark) 100 (manufactured by Fuji Silysia Co., Ltd.), Nipsil (registered trademark) E220A (manufactured by Nippon Silica Kogyo Co., Ltd.), and Admafine (registered trademark) SO (manufactured by Admatechs Co., Ltd.).

[0190] The shape of the particles is not particularly limited and may be irregular, acicular, flat, spherical, etc., but spherical particles are particularly preferred since the resulting polarizing plate protective film has good transparency.

[0191] If the particle size is close to the wavelength of visible light, the light will be scattered and transparency will be reduced, so the particle size is preferably smaller than the wavelength of visible light, and more preferably 1 / 2 or less of the wavelength of visible light.

[0192] If the particle size is too small, the lubricity may not be improved, so it is particularly preferable that the particle size is within the range of 80 to 180 nm. The particle size means the size of the aggregate when the particle is an aggregate of primary particles. When the particle is not spherical, the particle diameter means the diameter of a circle equivalent to the projected area of ​​the particle.

[0193] The fine particles are preferably added in an amount within a range of 0.05 to 10% by mass, and more preferably within a range of 0.1 to 5% by mass, relative to the base polymer (resin).

[0194] 6. Uses of polarizing plate protective film The polarizing plate protective film produced by the manufacturing method of the present invention can also be used as a retardation film, and is suitably used as a polarizing plate protective film, etc., and can be used in various optical measuring devices and display devices such as liquid crystal display devices and organic electroluminescence display devices.

[0195] 7.Other (7.1) Water contact angle (wettability) In the present invention, from the viewpoint of adhesion between the polyvinyl alcohol film (polarizing film) and the polarizing plate protective film containing a cycloolefin polymer, the water contact angle of the film is preferably within the range of 75 to 85° under the following measurement conditions.

[0196] (Water contact angle measurement) In the present invention, the water contact angle was measured 1 minute after dropping 1 μL of pure water onto the sample using a contact angle meter (manufactured by Kyowa Interface Science Co., Ltd., product name: DropMaster DM100) in an atmosphere of 23°C and 55% relative humidity after leaving the sample for 24 hours. The measurement was carried out five times, and the average value of the measurements was taken as the water contact angle.

[0197] (7.2) Surface layer density of film In the present invention, the surface layer density of the film is 1.9 to 2.0 g / cm 3 is preferable from the viewpoint of adhesiveness of the film. In the present invention, the "surface layer density" refers to the average density per unit volume in the region from the surface to a depth of 100 nm (0.1 μm) in the thickness direction. The average density can be calculated using X-ray reflectometry (XRR) as described in paragraphs

[0011] to

[0018] of Japanese Patent No. 4921612. X-rays are totally reflected when they are incident on the film at a very shallow angle. When the angle of incident X-rays exceeds the critical angle for total reflection, the X-rays penetrate the film and split into transmitted and reflected waves at the film surface and interface, with the reflected waves interfering with each other. The density of the film can be determined by analyzing the critical angle of total reflection, and the average density can be determined by averaging each of these values.

[0198] (Method for measuring average density using X-ray reflectometry (XRR)) The average density in the region from the surface to 100 nm (0.1 μm) in the thickness direction was calculated by measuring the X-ray reflectivity under the measurement conditions shown below to determine the critical angle of total reflection θc, and calculating the density ρ from this value.Furthermore, the distribution (density distribution) of this density ρ in the thickness direction in the region from the surface to 100 nm (0.1 μm) in the thickness direction was determined, and the average value of this density distribution was calculated as the average density. The measurement device and measurement conditions are as follows.

[0199] Measurement equipment: "SmartLab" horizontal sample X-ray diffraction equipment for thin film evaluation, manufactured by Rigaku Corporation Measurement conditions: X-ray source; Cu-Kα1 (wavelength: 1.54059Å) Optical system; parallel beam optical system Entrance slit system: Ge(220)2 crystal, height limiting slit 5mm, entrance slit 0.05mm Receiving side slit system: Receiving slit 0.10mm, Soller slit 5° Detector; Scintillation counter Tube voltage / current: 45kV / 200mA Scanning axis; 2θ / θ Scanning mode: continuous scan Scanning range: 0.1-3.0°. Scanning speed: 1deg. / min. Sampling interval: 0.002° / step

[0200] (7.3) Breaking stress The breaking stress is an index that indicates the force that occurs when a film is continuously pulled in a certain direction and breaks. By increasing the breaking stress in the longitudinal direction, it is possible to suppress breakage and deformation during film transport and processing.

[0201] In the present invention, the amount of residual solvent immediately before the second-stage stretching must be within the range of 0.1 to 0.5% by mass. From the viewpoint of suppressing the formation of a high-density layer on the film surface, the greater the amount of residual solvent, the better. However, if the film is stretched when the amount of residual solvent is greater than 0.5% by mass, the amount of adhesive that penetrates into the finished film will be excessive, weakening the strength of the film.

[0202] In the production method of the present invention, the film is conveyed at a conveying speed V2 that satisfies the following formula (1), and the amount of residual solvent immediately before the second-stage stretching is set to the range of 0.1 to 0.5 mass %, thereby increasing the stress at break. Formula (1):V1 <V2 In the present invention, the stress at break is preferably in the range of 2.1 to 2.7 GPa, and more preferably 2.4 to 2.7 GPa from the viewpoint of film strength.

[0203] (Method for measuring stress at break) Specifically, the stress at break of the polarizing plate protective film of the present invention is measured by cutting the polarizing plate protective film into a strip of 70 mm long (TD: width direction) x 10 mm long (MD: length direction), and then performing a tensile test using a Tensilon tensile tester (manufactured by Orientec Co., Ltd., RTC-1225A) in an atmosphere of room temperature 23°C and relative humidity 55%, with an initial tensile chuck distance of 50 mm and a tensile speed of 50 mm / min, and the stress is determined from the load-strain curve obtained.

[0204] The measurement is carried out five times for each sample, and the evaluation is based on the average value. In this case, by setting the longitudinal breaking stress of the polarizing plate protective film to 2.1 GPa or more, breakage and deformation can be suppressed even when force is applied to the film in the longitudinal direction, making it easier to suppress a decrease in yield due to breakage and deformation of the film and a decrease in the optical properties and quality of the obtained film. [Example]

[0205] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these. In the examples, the terms "parts" and "%" are used, but unless otherwise specified, they represent "parts by mass" or "% by mass."

[0206] <Preparation of Polarizing Plate Protective Film> (Preparation of Polarizing Plate Protective Film No. 1) The polarizing plate protective film was formed by a solution casting method.

[0207] [Raw film manufacturing process] (Dope preparation step (S1)) <Synthesis of cyclic polyolefin polymer P-1> 100 parts by mass of purified toluene and 100 parts by mass of norbornenecarboxylic acid methyl ester were placed in a stirrer. Next, 25 mmol % (based on the monomer mass) of ethylhexanoate-Ni dissolved in toluene, 0.225 mmol % (based on the monomer mass) of tri(pentafluorophenyl)boron, and 0.25 mmol % (based on the monomer mass) of triethylaluminum dissolved in toluene were added to the stirring device. The reaction was carried out at room temperature with stirring for 18 hours. After the reaction was completed, the reaction mixture was poured into excess ethanol to precipitate a polymer. The precipitate was purified, and the resulting polymer (P-1) was dried in a vacuum oven at 65° C. for 24 hours.

[0208] Preparation of Dope D-1 The following composition 1 was charged into a mixing tank and stirred to dissolve each component, and then filtered through a filter paper having an average pore size of 34 μm and a sintered metal filter having an average pore size of 10 μm to prepare a dope.

[0209] (Composition 1) Cyclic polyolefin polymer (P-1) 150 parts by mass Dichloromethane 380 parts by mass Methanol 70 parts by mass

[0210] Next, the following composition 2 containing the cyclic polyolefin solution (dope) prepared by the above method was charged into a disperser to prepare a fine particle dispersion (M-1) as an additive.

[0211] (Composition 2) Fine particles (Aerosil R812: manufactured by Nippon Aerosil Co., Ltd., primary average particle size: 7 nm, apparent specific gravity 50 g / L) 4 parts by mass Dichloromethane 76 parts by mass Methanol 10 parts by mass Cyclic polyolefin solution (Dope D-1) 10 parts by mass

[0212] 100 parts by mass of the cyclic polyolefin solution and 0.75 parts by mass of the fine particle dispersion were mixed to prepare a film-forming dope (polymer (resin) composition cycloolefin polymer: COP).

[0213] (Casting process (S2)) The dope (polymer (resin) composition cycloolefin polymer: COP) prepared in the dope preparation step (S1) was sent to a casting die through a conduit via a pressure-type metering gear pump, and the dope was cast from the casting die onto a casting position on a support consisting of an endless, rotating, stainless steel belt in a film-forming line at a width of 1,800 mm. The dope was heated on the support until it became self-supporting, and dried by evaporating the solvent until the web could be peeled off from the support with a peel roller, thereby forming a web. At this time, the dope transport speed V1 was 40 [m / min].

[0214] (Peeling step (S3)) After forming a web in the casting step (S2), the web was peeled from the support by a peeling roller while maintaining its self-supporting property.

[0215] (Step (S4) of first-stage stretching of the web to the web width immediately after casting) The web was treated at a high temperature without being held in the width direction to increase the density of the web, and the first stage of stretching was performed while the web was shrinking in the width direction. At this time, the amount of residual solvent measured immediately before the first stage of stretching was 12% by mass. The stretching ratio was 1.50.

[0216] (Drying process (S5)) The web was then heated on the support to evaporate the solvent.

[0217] (1st cutting process (S6)) Both ends of the stretched web in the width direction were cut.

[0218] (1st winding process (S7)) The film was wound around a core by a winding device while being transported at a transport speed V1 (40 m / min). The initial tension was 50 N, the taper was 70%, and the corners were 25%.

[0219] [Processing process] (Second-stage stretching process (S9)) Thereafter, the wound film was subjected to a step (S8) of unwinding from the roll, and then to a second-stage stretching while being conveyed in a stretching device at a conveying speed V2 (65 [m / min]). At this time, the amount of residual solvent measured immediately before the second stage of stretching was 0.30% by mass. The stretching ratio was 1.50.

[0220] (Second cutting process (S10)) Similar to the first cutting step, both ends of the stretched film in the width direction were cut.

[0221] (Second winding process (S11)) The above film was wound up. The initial tension was 50 N, the taper was 70%, and the corners were 25%.

[0222] Polarizing plate protective film No. 1 was produced by the above steps. The polarizing plate protective film produced by the above steps had a thickness of 40 μm.

[0223] Furthermore, the water contact angle, surface layer density and stress at break of the produced polarizing plate protective film No. 1 were measured and each value was evaluated.

[0224] (Preparation of Polarizing Plate Protective Films No. 2 to 15) Polarizing plate protective films Nos. 2 to 15 were produced in the same manner as polarizing plate protective film No. 1, except that the first-stage stretching conditions in the raw film production process, i.e., the dope conveying speed V1, the residual solvent amount just before the first-stage stretching, and the stretching ratio, and the second-stage stretching conditions, i.e., the film conveying speed V2, the residual solvent amount just before the second-stage stretching, and the stretching ratio, were changed as shown in Table I. Furthermore, the water contact angle, film surface layer density and stress at break were measured for the produced polarizing plate protective films Nos. 2 to 15, and each value was evaluated.

[0225] [Water contact angle] (Measurement method) The water contact angle was measured 1 minute after the sample was left to stand in an atmosphere at a temperature of 23°C and a relative humidity of 55% for 24 hours and then 1 μL of pure water was dropped onto the sample using a contact angle meter (manufactured by Kyowa Interface Science Co., Ltd., product name: DropMaster DM100) in an atmosphere at a temperature of 23°C and a relative humidity of 55%. The measurement was carried out five times, and the average value of the measurements was taken as the water contact angle. The methods for measuring the surface layer density and breaking stress of the film are as described above, and therefore will not be repeated here. The measured values ​​and their evaluations are shown in Table I. The above evaluation criteria are as follows:

[0226] (Evaluation criteria) ○: Water contact angle is within the range of 75 to 85° △: Water contact angle is greater than 85° and less than 88° ×: Water contact angle is greater than 88° and less than 90° It should be noted that values ​​outside the above range (values ​​less than 75° or greater than 90°) were not calculated as measured values ​​and therefore were excluded from the above evaluation range.

[0227] [Film surface layer density] (Measurement method) The method for measuring the surface layer density of the film has been described above, so a detailed description will be omitted.

[0228] (Evaluation criteria) ◯: Surface layer density is 1.8 to 2.0 g / cm 3 Within the range △: Surface layer density is 2.0 g / cm 3 Larger than 2.1g / cm 3 below ×: Surface layer density is 2.1 g / cm 3 Greater than In addition, values ​​outside the above range (1.8 g / cm 3 Values ​​less than 1000 kJ / cm2 were not calculated as measurements and are therefore excluded from the scope of the above evaluation.

[0229] [Stress at break] (Measurement method) The method for measuring the breaking stress of the film is as described above, and therefore will not be described here.

[0230] (Evaluation criteria) ○: Breaking stress is within the range of 2.4 to 2.7 GPa △: Breaking stress is 2.1 GPa or more and less than 2.4 GPa ×: Breaking stress is less than 2.1 Values ​​outside the above range (values ​​greater than 2.7 GPa) were not calculated as measured values ​​and therefore were excluded from the above evaluation range.

[0231] [Table 1]

[0232] [Adhesiveness] (Evaluation method) Furthermore, polarizing plates were produced using the obtained polarizing plate protective films Nos. 1 to 15 by the following method, and the adhesion to the polarizer layer of each was evaluated.

[0233] (Adhesion between polarizer layer and polarizing plate protective film) (1) Preparation of polarizer layer (polarizing film) A polyvinyl alcohol film with a thickness of 70 μm was swollen in water at 35°C. The above film was immersed for 60 seconds in an aqueous solution consisting of 0.075 g of iodine, 5 g of potassium iodide and 100 g of water, and further immersed in an aqueous solution at 45° C. consisting of 3 g of potassium iodide, 7.5 g of boric acid and 100 g of water. The above film was uniaxially stretched at a stretching temperature of 55° C. and a stretching ratio of 5 times. This uniaxially stretched film was washed with water and then dried to obtain a polarizer layer (polarizing film: polyvinyl alcohol-iodine based polarizer layer) having a thickness of 20 μm.

[0234] (2) Preparation of adhesive (Preparation of Water-Based Adhesive) Aqueous adhesive A was prepared by dissolving 4 parts by mass of acetoacetyl group-modified polyvinyl alcohol ("GOHSEFIRMER Z-200" manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) and 4 parts by mass of sodium glyoxylate ("SPM-01" manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) in 100 parts by mass of water.

[0235] (Preparation of UV-curable adhesive) The following components were mixed and then degassed to prepare an ultraviolet-curable adhesive. The triarylsulfonium hexafluorophosphate was blended as a 50% propylene carbonate solution, and the solid content of the triarylsulfonium hexafluorophosphate is shown below.

[0236] (component) 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate 45.0 parts by mass Epolead GT-301 (alicyclic epoxy resin manufactured by Daicel Corporation) 40.0 parts by mass 1,4-butanediol diglycidyl ether 15.0 parts by mass Triarylsulfonium hexafluorophosphate 2.3 parts by mass 9,10-dibutoxyanthracene 0.1 parts by mass 1,4-diethoxynaphthalene 2.0 parts by mass

[0237] (3) Preparation of polarizing plates The optical films Nos. 1 to 12 prepared above were prepared, and their surfaces were subjected to a corona discharge treatment. The conditions for the corona discharge treatment were a corona output intensity of 2.0 kW and a line speed of 18 m / min. Next, when a water-based adhesive was used as the adhesive, the water-based adhesive was applied to the corona discharge treated surface of the film with a bar coater to form an adhesive layer with a film thickness of about 3 μm. When an ultraviolet-curable adhesive was used as the adhesive, the adhesive layer was formed by coating with a bar coater so that the film thickness after curing by ultraviolet irradiation would be about 3 μm.

[0238] The polyvinyl alcohol-iodine polarizer layer was attached to the adhesive layer obtained by the above-mentioned operation. Similarly, optical films Nos. 1 to 12 were attached to the other surface of the polarizer layer to prepare polarizing plates.

[0239] Next, when a UV-curable adhesive was used as the adhesive, a UV irradiation device with a belt conveyor (using a D bulb manufactured by Fusion UV Systems) was used to irradiate the laminate from both sides of the laminate with an integrated light dose of 750 mJ / cm. 2 The ultraviolet curing adhesive layer was cured by irradiating it with ultraviolet light so that the ultraviolet curing adhesive layer was cured.

[0240] The resulting laminates were each dried in an oven at 90° C. for 10 minutes to obtain polarizing plates having a laminate structure of polarizing plate protective films.

[0241] (4) Evaluation of adhesiveness Using the polarizing plate obtained by the above procedure, the peel strength (adhesion) when peeled at the interface between the polarizing plate protective film and the polarizer layer was measured by a 90° peel test (in accordance with JIS Z0237:2009) under an environment of 23°C and 55% RH using a 90° peel test jig (P90-200N) manufactured by Imada Co., Ltd.

[0242] The evaluation was carried out according to the following evaluation criteria, and a score of △ or higher was judged to be good. The evaluation results are shown in Table I.

[0243] (Evaluation criteria) ○: Peel strength is 2.0 (N / 25 mm) or more △: Peel strength is within the range of 1.0 to 2.0 (N / 25 mm) ×: Peel strength is less than 1.0 (N / 25 mm)

[0244] As is clear from Table I, the Examples are generally superior to the Comparative Examples. [Industrial Applicability]

[0245] The present invention provides a method for producing a polarizing plate protective film containing a cycloolefin polymer having improved adhesiveness to a polyvinyl alcohol film. [Explanation of symbols]

[0246] 1, 1a Stirring device (stirring tank) 2 Casting die 3 Support (endless belt, drum) 3a, 3b rolls 4 Peeling roller 5. Web 6 Stretching device 7 Drying equipment 8 Cut section 9 Winding device 10 Stretching device 11 Cut section 12 Winding device F film

Claims

1. A method for producing a polarizing plate protective film containing a cycloolefin-based polymer, comprising: We have a raw film manufacturing process and a processing process. The raw film manufacturing process includes at least conveying the dope at a conveying speed V １ a step of casting the web onto a support at a temperature of 1000°C to form a web, a step of stretching the web in a first stage to the web width immediately after casting, and a step of drying the web to form a film and winding it up, The processing step is performed by conveying the wound film at a conveying speed V ２ and performing a second-stage stretching step, Formula (1): V １ <V ２ Furthermore, in the second-stage stretching step, the wound film is stretched so that the amount of residual solvent immediately before the second-stage stretching is in the range of 0.1 to 0.5% by mass relative to the winding width.

1. A method for producing a polarizing plate protective film, comprising:

2. The amount of residual solvent immediately before the first-stage stretching is in the range of 1 to 15% by mass, and the stretching ratio is in the range of 1.1 to 2.0 times. The method for producing a polarizing plate protective film according to claim 1 .

3. The stretching ratio in the second stretching step is within the range of 1.1 to 2.0 times.

3. The method for producing a polarizing plate protective film according to claim 1 or 2.

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