JP6619986B2 - Method for producing stretched film and method for producing polarizing film - Google Patents

Description

  The present invention relates to a method for producing a stretched film made of a polyvinyl alcohol resin and a method for producing a polarizing film.

  A polarizing plate is widely used in an image display device typified by a liquid crystal display device. As a polarizing plate, the thing of the structure which bonded the protective film to the single side | surface or both surfaces of the polarizing film obtained by performing a extending | stretching process and the dyeing | staining process by a dichroic dye with respect to a polyvinyl alcohol-type resin film is common.

  The stretching of the polyvinyl alcohol-based resin film that is performed in the production of the polarizing film is generally longitudinal stretching. Longitudinal stretching means stretching in the “machine flow direction” (that is, the film length direction) of the film, and this direction is also referred to as MD in this specification. The direction orthogonal to MD, that is, the film width direction is also referred to as TD in this specification.

  According to the longitudinal stretching, it is relatively easy to stably produce a polarizing film excellent in optical performance (polarization performance and the like). However, in order to sufficiently improve the optical performance, it is necessary to make the polyvinyl alcohol-based resin film neck-in greatly in the width direction by longitudinal stretching, and typically a neck-in rate of 50% or more is required. Therefore, the method for producing a polarizing film by longitudinal stretching has an essential problem that it is difficult to produce a wide polarizing film. If an extremely wide polyvinyl alcohol-based resin film is used, it is possible to obtain a relatively wide polarizing film. However, it is difficult to extremely widen the film original in terms of manufacturing equipment.

  On the other hand, attempts to produce a polarizing film using transverse stretching (stretching to TD) have also been proposed. Examples thereof include Japanese Patent No. 4701555 (Patent Document 1) and Japanese Patent No. 5362059 (Patent Document 2). No. 4,971066 (Patent Document 3) and the like.

Japanese Patent No. 4701555 Japanese Patent No. 5362059 Japanese Patent No. 4971066

  An object of the present invention is to provide a method for producing a stretched film made of a polyvinyl alcohol-based resin that can realize a high stretch ratio in the TD (film width direction) and is excellent in the axial orientation of TD. Another object of the present invention is to provide a method for producing a polarizing film using the stretched film, wherein the TD is a slow axis (absorption axis) direction and exhibits a good optical performance. It is in.

  This invention provides the manufacturing method of the stretched film shown below, a stretched film, and the manufacturing method of a polarizing film.

[1] A stretching step of stretching a polyvinyl alcohol-based resin film to obtain a stretched film having a TD stretch ratio of A _f [times] and an MD shrinkage ratio of B _f [times],
The stretching step includes
In comparison with the same TD stretch ratio, the stretching to TD and the shrinking to MD are simultaneously performed so that the MD shrinkage ratio is larger than the MD shrinkage ratio when the polyvinyl alcohol-based resin film is stretched freely at the free end. 1 stretching process,
A second stretching step for simultaneously stretching to TD and shrinking to MD so that the MD shrinkage ratio is reduced by 0.17 or more;
The manufacturing method of a stretched film which contains these in this order.

  [2] The production method according to [1], wherein a TD stretch ratio of the polyvinyl alcohol-based resin film at the start of the second stretch treatment step is 4.3 times or more.

[3] By performing the second stretching step, the TD stretching ratio of the polyvinyl alcohol-based resin film is made to reach A _f [times], and the MD shrinkage ratio is made to reach B _f [times]. [1] or [2 ] The manufacturing method of description.

[4] The polyvinyl alcohol-based resin film is an unstretched film,
The manufacturing method according to any one of [1] to [3], wherein the first stretching treatment step is first performed in the stretching step.

[5] The production method according to any one of [1] to [4], wherein the MD shrinkage ratio _{Bf of the} stretched film is 0.2 to 0.8 times.

[6] The production method according to any one of [1] to [5], wherein the TD stretch ratio A _{f of the} stretched film is 5 times or more.

  [7] In any one of [1] to [6], the stretched film laminated on the base film is obtained by stretching a laminated film having the polyvinyl alcohol-based resin film on the base film. Manufacturing method.

  [8] The production method according to any one of [1] to [7], wherein the stretched film has a thickness of 30 μm or less.

[9] A stretched film having a length of 100 m or more comprising a polyvinyl alcohol-based resin,
When the refractive indices n _x in the film width direction of the film plane at a wavelength of 590 nm, the refractive index in the direction of perpendicular to the film width direction in the film plane and n _y, the following formula:
Birefringence ΔP = n _x -n _y
The stretched film whose birefringence (DELTA) P represented by these is 0.031 or more.

[10] A step of obtaining a stretched film by the production method according to any one of [1] to [8];
Dyeing the stretched film with a dichroic dye;
The manufacturing method of a polarizing film containing.

  According to the present invention, a stretched film having a high TD stretch ratio and high axial orientation can be produced. Moreover, according to this invention, the polarizing film which makes TD the slow axis (absorption axis) direction, and shows favorable optical performance can be manufactured.

It is a flowchart which shows a preferable example of the manufacturing method of the stretched film which concerns on this invention. It is a schematic sectional drawing which shows an example of the laminated constitution of the laminated | multilayer film obtained at a PVA-type resin film formation process. It is a schematic sectional drawing which shows an example of the layer structure of the extending | stretching laminated | multilayer film obtained at an extending | stretching process. It is a graph which shows the example of the extending | stretching pattern of the extending process which concerns on this invention. It is a top view which shows typically an example of the internal structure of a tenter type | mold extending | stretching apparatus. It is a flowchart which shows a preferable example of the manufacturing method of the polarizing film and polarizing plate which concern on this invention. It is a schematic sectional drawing which shows an example of the laminated constitution of the light-polarizing laminated film obtained at a dyeing process. It is a schematic sectional drawing which shows an example of the laminated constitution of the polarizing laminated film with a protective film obtained by a 1st bonding process. It is a schematic sectional drawing which shows an example of the layer structure of the polarizing plate with a single-sided protective film obtained by a peeling process. It is a schematic sectional drawing which shows an example of the laminated constitution of the polarizing plate with a double-sided protective film obtained by a 2nd bonding process. It is a graph which shows the extending | stretching pattern of the extending process in an Example and a comparative example.

<Method for producing stretched film>
The stretched film according to the present invention is a film obtained by carrying out a stretching step of stretching a polyvinyl alcohol-based resin film (hereinafter, the polyvinyl alcohol-based resin is also referred to as “PVA-based resin”). The stretched film according to the present invention may be a film that exists in a state of being supported by the base film (in a state of being laminated on the base film), or by itself without being supported by the base film. An existing film may be used. In the former case, a stretched film supported by the base film is obtained by subjecting a laminated film including a base film and a PVA-based resin film (PVA-based resin layer) formed thereon to the stretching step. (First embodiment). In the latter case, a single stretched film is obtained by subjecting a single PVA resin film to the stretching step (second embodiment).

Below, 1st Embodiment which manufactures the stretched film supported by the base film is mainly demonstrated. With reference to FIG. 1, the manufacturing method of the stretched film which concerns on 1st Embodiment is the following process:
PVA-based resin film forming step S10 for forming a PVA-based resin film by applying a coating solution containing a PVA-based resin on at least one surface of the base film film and then drying the laminate. Stretching step S20 for stretching a film to obtain a stretched laminated film including a base film and a stretched film
May be included in this order.

  Hereinafter, each step will be described. In addition, in PVA-type resin film formation process S10, although you may form a PVA-type resin film on both surfaces of a base film, the case where it forms mainly on one side is demonstrated below.

(1) PVA-based resin film forming step S10
With reference to FIG. 2, this step is a step in which a laminated film 100 is obtained by forming the PVA resin film 6 on at least one surface of the base film 30. The PVA-based resin layer 6 can be formed by applying a coating solution containing a PVA-based resin to one or both sides of the base film 30 and drying the coating layer. The method of forming the PVA resin film 6 by such coating is advantageous in that it is easy to obtain a thin PVA resin film 6, and thus a thin polarizing film.

  The base film 30 can be composed of a thermoplastic resin, and among them, it is preferably composed of a thermoplastic resin that is excellent in transparency, mechanical strength, thermal stability, stretchability, and the like. Specific examples of such thermoplastic resins include, for example, polyolefin resins such as chain polyolefin resins and cyclic polyolefin resins (norbornene resins, etc.); polyester resins; (meth) acrylic resins; cellulose triacetate, Cellulose ester resins such as cellulose diacetate; Polycarbonate resins; Polyvinyl alcohol resins; Polyvinyl acetate resins; Polyarylate resins; Polystyrene resins; Polyethersulfone resins; Polysulfone resins; Polyamide resins; System resins; and mixtures and copolymers thereof.

  The base film 30 may have a single-layer structure made of one resin layer made of one kind or two or more kinds of thermoplastic resins, or a plurality of resin layers made of one kind or two or more kinds of thermoplastic resins. A laminated multilayer structure may be used. The base film 30 is preferably made of a resin that can be stretched at a stretching temperature suitable for stretching the PVA-based resin film in the stretching step S20 described later.

  The base film 30 can contain an additive. Specific examples of the additive include an ultraviolet absorber, an antioxidant, a lubricant, a plasticizer, a release agent, an anti-coloring agent, a flame retardant, a nucleating agent, an antistatic agent, a pigment, and a coloring agent.

  The thickness of the base film 30 is usually 1 to 500 μm, preferably 1 to 300 μm, more preferably 5 to 200 μm, and still more preferably 5 to 150 μm from the viewpoints of strength and handleability.

  It is preferable that the coating liquid applied to the base film 30 is an aqueous solution of a PVA resin containing a PVA resin and water. This aqueous solution may contain additives such as a solvent other than water, a plasticizer, and a surfactant as necessary. Examples of the solvent other than water include water-compatible organic solvents such as methanol, ethanol, propanol, and alcohols typified by polyhydric alcohols (such as glycerin).

  As the PVA resin, a saponified polyvinyl acetate resin can be used. Examples of the polyvinyl acetate-based resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and (meth) acrylamides having an ammonium group. In the present specification, “(meth) acryl” means at least one selected from the group consisting of acryl and methacryl. The same applies to “(meth) acryloyl” and the like.

  The saponification degree of the PVA-based resin can be in the range of 80.0 to 100.0 mol%, but is preferably in the range of 90.0 to 99.5 mol%, more preferably 94.0. It is in the range of 99.0 mol%. When the saponification degree is less than 80.0 mol%, the water resistance of the polarizing film obtained from the stretched film tends to decrease. When a PVA resin having a saponification degree exceeding 99.5 mol% is used, the dyeing speed in the dyeing process in the method for producing a polarizing film, which will be described later, is slowed down, and productivity is lowered and polarized light having sufficient polarizing performance It may be difficult to obtain a film.

The degree of saponification is expressed as a unit ratio (mol%) of the ratio of acetic acid groups (acetoxy groups: —OCOCH ₃ ) contained in polyvinyl acetate resin, which is a raw material for PVA resins, to hydroxyl groups by the saponification step. The following formula:
Saponification degree (mol%) = 100 × (number of hydroxyl groups) ÷ (number of hydroxyl groups + number of acetate groups)
Defined by The saponification degree can be determined according to JIS K 6726 (1994). The higher the degree of saponification, the higher the proportion of hydroxyl groups, and thus the lower the proportion of acetate groups that inhibit crystallization.

  The PVA resin may be a modified polyvinyl alcohol partially modified. For example, PVA resins may be modified with olefins such as ethylene and propylene; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid; alkyl esters of unsaturated carboxylic acids, (meth) acrylamide, and the like. The proportion of modification is preferably less than 30 mol%, and more preferably less than 10%. When modification exceeding 30 mol% is performed, the dichroic dye is hardly adsorbed to the stretched film, and a polarizing film having sufficient polarization performance tends to be hardly obtained.

  The average degree of polymerization of the PVA-based resin is preferably 100 to 10,000, more preferably 1500 to 8000, and further preferably 2000 to 5000. The average degree of polymerization of the PVA resin can also be determined according to JIS K 6726 (1994).

  The coating liquid is applied to the base film 30 by a wire bar coating method; a roll coating method such as reverse coating or gravure coating; a die coating method; a comma coating method; a lip coating method; a spin coating method; The method can be appropriately selected from a method such as a fountain coating method, a dipping method, and a spray method. The coating layer may be formed only on one surface of the base film 30 or may be formed on both surfaces.

  The drying temperature and drying time of the coating layer are set according to the type of solvent contained in the coating solution. A drying temperature is 50-200 degreeC, for example, Preferably it is 60-150 degreeC. When the solvent contains water, the drying temperature is preferably 80 ° C. or higher.

  The thickness of the PVA-based resin film 6 in the laminated film 100 is preferably 3 to 100 μm, more preferably 5 to 50 μm, and further preferably 5 to 30 μm. In the case of the PVA-based resin film 6 having a thickness within this range, the dichroic dye has good dyeability and excellent polarization performance through a stretching step S20 and a dyeing step, which will be described later, and is sufficiently thin (for example, a thickness of 10 μm). The following polarizing film can be obtained.

  Prior to the application of the coating liquid, in order to improve the adhesion between the base film 30 and the PVA resin film 6, at least the surface of the base film 30 on which the coating layer is formed is subjected to corona treatment, Plasma treatment, flame (flame) treatment, or the like may be performed. For the same reason, a coating layer may be formed on the base film 30 via a primer layer or the like.

  The primer layer can be formed by applying a primer layer forming coating solution to the surface of the substrate film 30 and then drying it. This coating liquid contains a component that exhibits a certain degree of strong adhesion to both the base film 30 and the PVA-based resin film 6, and usually contains a resin component that imparts such adhesion and a solvent. As the resin component, a thermoplastic resin excellent in transparency, thermal stability, stretchability and the like is preferably used, and examples thereof include (meth) acrylic resins and polyvinyl alcohol resins. Among these, polyvinyl alcohol resins that give good adhesion are preferably used. More preferably, it is a polyvinyl alcohol resin. As the solvent, a general organic solvent or an aqueous solvent capable of dissolving the resin component is usually used, but it is preferable to form the primer layer from a coating solution containing water as a solvent.

  In order to increase the strength of the primer layer, a crosslinking agent may be added to the primer layer forming coating solution. Specific examples of the crosslinking agent include epoxy-based, isocyanate-based, dialdehyde-based, metal-based (for example, metal salts, metal oxides, metal hydroxides, organometallic compounds), and polymer-based crosslinking agents. When a polyvinyl alcohol-based resin is used as the resin component forming the primer layer, a polyamide epoxy resin, a methylolated melamine resin, a dialdehyde-based crosslinking agent, a metal chelate compound-based crosslinking agent, or the like is preferably used.

  The thickness of the primer layer is preferably about 0.05 to 1 μm, more preferably 0.1 to 0.4 μm. When it becomes thinner than 0.05 μm, the effect of improving the adhesion between the base film 30 and the PVA resin film 6 is small.

  The method for applying the primer layer forming coating solution to the substrate film 30 may be the same as the coating solution for forming the PVA resin film. The drying temperature of the coating layer made of the primer layer forming coating solution is, for example, 50 to 200 ° C, and preferably 60 to 150 ° C. When the solvent contains water, the drying temperature is preferably 80 ° C. or higher.

(2) Stretching step S20
With reference to FIG. 3, this process extends | stretches the laminated | multilayer film 100 containing the base film 30 and the PVA-type resin film 6, and is the extending | stretching lamination | stacking containing the stretched film 7 which consists of the extended base film 31 and PVA-type resin. In this step, the film 200 is obtained.

The stretching step S20 includes the following steps:
In the comparison with the same TD stretch ratio, the first stretch that simultaneously performs stretching to TD and shrinking to MD so that the MD shrinkage ratio is larger than the MD shrinkage ratio when the PVA-based resin film is horizontally stretched at the free end. Process Step S20-1 and Second Stretching Process Step S20-2 for simultaneously stretching to TD and shrinking to MD so that the MD shrinkage ratio is reduced by 0.17 or more.
Are included in this order.

  According to the stretching process method including the first stretching process step S20-1 and the second stretching process step S20-2 in this order, a stretched film made of a polyvinyl alcohol resin having a high TD stretch ratio and excellent TD axial orientation. 7 can be manufactured stably. The polarizing film manufactured using the stretched film 7 as a raw material film is a polarizing film having TD as the slow axis (absorption axis) direction, and can exhibit good optical performance (polarization performance, etc.).

FIG. 4 is a graph showing an example of a stretching pattern in the stretching step S20 according to the present invention, and shows two types of stretching patterns X and Y as specific examples. The horizontal axis of the graph represents the TD draw ratio A (TD draw ratio, unit: times). When the TD stretch ratio A of the PVA-based resin film 6 used in the stretching step S20 is 1, the TD stretch ratio A can take a value exceeding 1 in the stretching step S20. The TD stretch ratio A is expressed by the following formula:
TD stretch ratio A [times] = (TD length of stretched PVA-based resin film 6) / (TD length of PVA-based resin film 6 used in the stretching step)
It is represented by “TD length” is synonymous with the width of the PVA-based resin film 6. The “stretched PVA-based resin film 6” does not necessarily indicate only the PVA-based resin film 6 (that is, the stretched film 7) at the end of the stretching step S20, but a stretched PVA-based resin in the middle of the stretching step S20. The film 6 is also indicated.

The vertical axis of the graph shown in FIG. 4 is the MD contraction magnification B (MD contraction magnification, unit: times). When the MD shrinkage ratio B of the PVA-based resin film 6 used in the stretching step S20 is 1, the MD shrinkage ratio B can take a value of less than 1 in the stretching step S20. MD shrinkage ratio B is expressed by the following formula:
MD shrinkage ratio B [times] = (MD length of contracted PVA-based resin film 6) / (MD length of PVA-based resin film 6 subjected to the stretching step)
It is represented by “MD length” is synonymous with the length of the PVA-based resin film 6. The “shrinked PVA-based resin film 6” does not necessarily indicate only the PVA-based resin film 6 at the end of the stretching step S20 (that is, the stretched film 7), but the contracted PVA-based resin film 6 in the middle of the stretching step S20. Also points to.

  As illustrated by the stretching patterns X and Y in FIG. 4, in the present invention, the stretching step S20 includes a first stretching process step S20-1 and a second stretching process step S20-2 in this order. As is apparent from the fact that the graph line has an inclination, the stretching process performed in the first stretching process step S20-1 and the second stretching process step S20-2 is stretching to TD (lateral stretching). And simultaneous shrinking to MD (longitudinal shrinkage). In the stretch pattern X, a third stretch treatment step for performing only transverse stretch is interposed between the first stretch treatment step S20-1 and the second stretch treatment step S20-2. Like the extending | stretching pattern X, 1st extending | stretching process process S20-1 and 2nd extending | stretching process process S20-2 may be discontinuous. In the stretching pattern Y, such a third stretching process is not performed, and the second stretching process S20-2 is performed following the first stretching process S20-1.

  In the first stretching step S20-1, in the comparison at the same TD stretching ratio A, simultaneous biaxial stretching is performed so that the MD shrinkage ratio B is larger than the MD shrinkage ratio when the PVA resin film is laterally stretched at the free end. Process. It is preferable that 1st extending | stretching process process S20-1 satisfies the said conditions over all the processes. “When the PVA-based resin film is stretched freely at the free end” means the stretch pattern Z in FIG. 4, and is a stretch pattern when performing transverse stretching (TD stretching) while freely shrinking to MD. This reference stretch pattern Z can be actually measured using the same film as the PVA-based resin film 6 (the laminated film 100 when supported by the base film) that is actually used in the stretching step S20. .

  By performing the first stretching step S20-1 that satisfies the above conditions prior to the second stretching step S20-2, it becomes possible to achieve a high stretch ratio to TD without problems such as film breakage, Moreover, it becomes easy to obtain the stretched film 7 excellent in the axial orientation to TD. Moreover, it can suppress that external appearance defects, such as a wrinkle, arise in the stretched film 7 obtained by carrying out moderate vertical shrinkage with horizontal stretching in the initial stage of extending | stretching process S20 so that the said conditions may be satisfied.

  The TD stretch ratio A at the end of the first stretching step S20-1 is preferably greater than the elastic region of the PVA-based resin film 6 (the laminated film 100 when supported by the base film). Is 1.5 to 4.8 times, more preferably 1.8 to 4.5 times. In addition, the MD shrinkage ratio B at the end of the first stretching step S20-1 causes most shrinkage in this region in the case of free-end lateral stretching, but causes MD shrinkage to some extent in the second stretching step S20-2. Therefore, it is preferably 0.6 to 0.97 times, and more preferably 0.65 to 0.85 times.

  On the other hand, the second stretching step S20-2 is a step in which simultaneous biaxial stretching is performed while causing MD shrinkage to some extent, specifically, simultaneous biaxial so that the MD shrinkage ratio B decreases by 0.17 or more. This is a step of performing a stretching treatment. The amount of decrease in the MD shrinkage ratio B here is the difference between the MD shrinkage ratio [times] at the start of the second stretching step S20-2 and the MD shrinkage ratio [B] at the end of the process. The amount of decrease in the MD shrinkage ratio B in the second stretching step S20-2 is preferably 0.2 or more, and more preferably 0.25 or more.

  By carrying out the second stretching treatment step S20-2 that satisfies the above conditions after the first stretching treatment step S20-1, it becomes possible to achieve a high stretch ratio to TD without any defects such as film breakage. It becomes easy to obtain the stretched film 7 excellent in the axial orientation to TD. If the amount of decrease in the MD shrinkage ratio B in the second stretching step S20-2 is too large, the resulting stretched film 7 is likely to have poor appearance such as wrinkles. Therefore, the amount of decrease in the MD shrinkage ratio B is preferably It is 0.45 or less, more preferably 0.4 or less, and still more preferably 0.35 or less.

  The TD stretch ratio A at the start of the second stretching step S20-2 is desirably performed in a region exceeding the lower yield point of the PVA-based resin film 6 (laminate film 100 when supported by the base film). Therefore, it is preferably 4.0 times or more, more preferably 4.3 times or more. The TD stretch ratio A at the start of the second stretching step S20-2 is usually less than 5 times. Further, the MD shrinkage ratio B at the start of the second stretching treatment step S20-2 is preferably 0.6 to 0.97 times, more preferably 0. 65 to 0.85 times.

  In the first stretching process step S20-1 and the second stretching process step S20-2, TD stretching and MD shrinkage are usually performed at a constant rate from the start to the end of the process (MD shrinkage ratio change amount). / TD stretch ratio change ratio is constant), but may be accompanied by slight speed fluctuations. As described above, the first stretching step S20-1 and the second stretching step S20-2 may be continuous. In this case, the TD stretching ratio A at the end of the first stretching step S20-1 and The MD shrinkage ratio B is the same as the TD stretch ratio A and the MD shrinkage ratio B at the start of the second stretching step S20-2, respectively. In addition, when the ratio of MD shrinkage ratio change amount / TD stretch ratio change amount is consistently constant from the start to the end of the stretching step S20, the first stretching step S20-1 or the second stretching step S20- 2 is considered to be included, and the condition that the first stretching process step S20-1 and the second stretching process step S20-2 are included in this order is not satisfied.

  As described above, the third (and fourth, fifth,...) Stretching process is interposed between the first stretching process S20-1 and the second stretching process S20-2. May be. In this case, the third stretching treatment step may be simultaneous biaxial stretching treatment or other stretching treatment such as transverse stretching and longitudinal shrinkage, but at least the amount of change in MD shrinkage ratio / The ratio of the TD stretch ratio change amount is different from that in the first stretching process step S20-1 and the second stretching process step S20-2.

  The stretching step S20 may include other stretching treatment steps such as transverse stretching and longitudinal shrinkage before the first stretching treatment step S20-1. However, from the viewpoint of sufficiently causing MD shrinkage during TD stretching and improving the orientation of the stretched film 7, it is preferable to first perform the first stretching step S20-1 in the stretching step S20. In this case, the film provided for the first stretching step S20-1 is an unstretched PVA-based resin film 6 (a laminated film 100 when supported by a base film).

The stretching step S20 may include other stretching processing steps such as lateral stretching and longitudinal shrinkage after the second stretching processing step S20-2. However, since the stress of transverse stretching increases after exceeding the lower yield point, it is preferable to perform the second stretching step S20-2 last in the stretching step S20. In this case, the PVA-based resin film 6 is simultaneously biaxially stretched until the TD stretch ratio A and the MD shrinkage ratio B reach desired values (A _f and B _f below) by performing the second stretching step S20-2. Thus, a stretched film 7 having a final TD stretch ratio _Af and a final MD shrinkage ratio _Bf is obtained.

The final TD stretch ratio _Af in the stretched film 7 obtained by a series of stretching processes in the stretching step S20 is preferably 5 times or more, and more preferably 5.3 times or more. According to the stretching method according to the present invention, a TD stretch ratio _Af of 5 times or more can be achieved without causing problems such as film breakage and wrinkle generation. The final TD stretch ratio _Af is usually 10 times or less, preferably 7 times or less. Although TD stretching exceeding 10 times depends on the thickness of the stretched film, it tends to be accompanied by film breakage.

The final MD shrinkage ratio B _f in the stretched film 7 is preferably 0.2 to 0.8 times, and more preferably 0.35 to 0.7 times. When the MD shrinkage ratio _Bf is within this range, a high stretch ratio to TD becomes easy, and the axial orientation to TD becomes good.

Known for simultaneous biaxial stretching that simultaneously performs stretching to TD (lateral stretching) and shrinking to MD (longitudinal shrinkage) performed in the first stretching process S20-1 and the second stretching process S20-2. Tenter type stretching apparatus can be used. FIG. 5 is a plan view schematically showing an example of the internal configuration of the tenter type stretching apparatus. As shown in FIG. 5, the tenter type stretching apparatus grips and stretches both ends in the width direction of a traveling film (PVA resin film 6) with a plurality of clips 50 arranged in the traveling direction (machine flow direction). In the zone, the film is stretched in the width direction by widening the clip interval in the width direction while the clip 50 is running with the film, and the film is contracted in the running direction by narrowing the clip interval in the running direction. More specifically, it can be subjected to TD stretching by increasing the width of the clip spacing D ₂ immediately after exiting from the stretching zone than the width direction of the clip spacing D ₁ of the a stretching zone before. Further, MD contraction can be performed by making the clip interval G ₂ in the running direction immediately after coming out of the drawing zone smaller than the clip interval G ₁ in the running direction before the drawing zone. By adjusting these clip intervals, the stretching pattern of the simultaneous biaxial stretching process can be controlled.

  The stretching temperature in the stretching step S20 including the simultaneous biaxial stretching treatment step is such that when the PVA resin film 6 supported by the substrate film 30, that is, the laminated film 100 is subjected to the stretching step S20, the PVA resin film 6 and the substrate. It is set to a temperature higher than the temperature at which the entire film 30 can be stretched, and is preferably in the range of −30 ° C. to + 30 ° C. of the phase transition temperature (melting point or glass transition temperature) of the base film 30, more preferably. Is in the range of −30 ° C. to + 5 ° C., more preferably in the range of −25 ° C. to + 0 ° C. When the base film 30 consists of a plurality of resin layers, the phase transition temperature means the highest phase transition temperature among the phase transition temperatures exhibited by the plurality of resin layers.

  When the stretching temperature is lower than the phase transition temperature of −30 ° C., it is difficult to achieve stretching at a high magnification of 5 times or more, or the fluidity of the base film 30 is too low and the stretching process tends to be difficult. When the stretching temperature exceeds + 30 ° C. of the phase transition temperature, the fluidity of the base film 30 is too large and stretching tends to be difficult. When the laminated film 100 is subjected to the stretching step S20, it is easier to achieve a high stretching ratio of 5 times or more, so the stretching temperature is within the above range, and more preferably 120 ° C. or more. The stretching temperature is usually 230 ° C. or lower.

  As a heating method of the film in the stretching process, a zone heating method (for example, a method in which hot air is blown and heated in a stretching zone such as a heating furnace adjusted to a predetermined temperature); a heater heating method (infrared heater, halogen heater, There is a method in which panel heaters are installed above and below the film and heated by radiant heat).

  Prior to the stretching step S20, a preheat treatment step for preheating the film to be subjected to the stretching step S20 may be provided. As the preheating method, the same method as the heating method in the stretching process can be used. The preheating temperature is preferably in the range of −50 ° C. to ± 0 ° C. of the stretching temperature, and more preferably in the range of −40 ° C. to −10 ° C. of the stretching temperature.

  Moreover, you may provide a heat setting process process after the extending | stretching process in extending process S20. The heat setting process is a process in which heat treatment is performed at a temperature equal to or higher than the crystallization temperature of PVA while maintaining a tension state in a state where the end of the stretched film 7 is held by a clip. Crystallization of the stretched film 7 is promoted by this heat setting treatment. The temperature of the heat setting treatment is preferably in the range of −0 ° C. to −80 ° C. of the stretching temperature, and more preferably in the range of −0 ° C. to −50 ° C. of the stretching temperature.

  The thickness of the stretched film 7 obtained through the stretching step S20 can be, for example, 30 μm or less, and further 20 μm or less, but is preferably 15 μm or less, more preferably from the viewpoint of thinning the polarizing film and thus the polarizing plate. It is 10 μm or less, more preferably 7 μm or less. The thickness of the stretched film 7 is usually 2 μm or more.

  As described above, the method for producing the stretched film 7 supported by the base film 31 from the PVA-based resin film 6 supported by the base film 30 (first embodiment) is taken as an example, and the stretched film according to the present invention. However, the PVA-based resin film, which is present alone without being supported by the base film 30, is subjected to a predetermined stretching process in the same manner as described above, so that the film is broken or wrinkled. A stretched film 7 having a high TD stretch ratio and high axial orientation can be obtained without causing problems such as occurrence (second embodiment). When the PVA-based resin film 6 present alone is subjected to the stretching step S20, the stretching temperature in the stretching step S20 including the simultaneous biaxial stretching process step is preferably 150 ° C. or higher. The stretching temperature is usually 230 ° C. or lower. Also in the second embodiment, a pre-heat treatment process and / or a heat setting process can be provided.

  The PVA-based resin film forming step S10 (when using a base film) and the stretching step S20 include a long base film 30 (when using a base film) and a long PVA-based resin film 6 (base film). Can be carried out continuously while being conveyed continuously. In this case, the obtained stretched film 7 is also long, and is usually taken up by a winding device to form a roll of the stretched film 7. Or you may use for a polarizing film formation process (dyeing process), without winding up the elongate stretched film 7 manufactured continuously. The length of the stretched film which is a long product is usually 100 m or more, and preferably 1000 m or more. The length of the stretched film is usually 10000 m or less.

Since the stretched film 7 according to the present invention is obtained through the stretching step S20, the stretched film 7 has high uniaxial orientation in TD. When the refractive indices n _x in the film width direction of the film plane at a wavelength of 590 nm, a refractive index in a direction perpendicular to the film width direction in the film plane and n _y, stretched film 7 according to the present invention, the following formula:
Birefringence ΔP = n _x -n _y
The birefringence ΔP represented by can be 0.031 or more, further 0.032 or more, and is usually 0.04 or less. When the stretched film 7 is obtained as supported by the base film 31, the birefringence ΔP of the stretched film 7 is measured using the single stretched film 7 obtained by peeling off the base film 31 as a measurement sample. Is done.

<Production method of polarizing film and polarizing plate>
The manufacturing method of the polarizing film which concerns on this invention manufactures a polarizing film by using the stretched film obtained by the manufacturing method of the stretched film which concerns on the said invention as a raw material film. According to this manufacturing method, it is possible to obtain a polarizing film having TD as the slow axis (absorption axis) direction and showing good optical performance.

  The stretched film as the raw material film may be the stretched film 7 supported by the base film 31 (that is, the stretched laminated film 200), or may be a single stretched film 7 not supported by the base film 30. .

Taking a method for producing a polarizing film supported by a base film from the stretched laminated film 200 as an example, this production method will be described with reference to FIG.
Dyeing process S30 which obtains a polarizing laminated film by dyeing the stretched film of a stretched laminated film with a dichroic dye, and forming a polarizing film (polarizer layer)
It can be a method including. The polarizing laminated film is a laminated film having a base film and a polarizing film laminated thereon (that is, a polarizing film supported by the base film).

Referring to FIG. 6, the polarizing laminated film is subjected to the following steps:
1st bonding process S40 which bonds a 1st protective film on the polarizing film of a light-polarizing laminated film, and obtains a light-polarizing laminated film with a protective film.
If it uses, a polarizing laminated film with a protective film can be obtained.

Referring to FIG. 6, a polarizing laminated film with a protective film is subjected to the following steps:
Peeling step S50 to obtain a polarizing plate with a single-sided protective film by peeling off and removing the base film from the polarizing laminated film with protective film
If it uses, it can obtain the polarizing plate with a single-sided protective film, and also this is the following process:
2nd bonding process S60 which bonds a 2nd protective film to the polarizing film surface of a polarizing plate with a single-sided protective film.
If it uses, a polarizing plate with a double-sided protective film can be obtained.

  In addition, in this specification, the film laminated body which contains a polarizing film and does not contain a base film is called "polarizing plate."

(1) Dyeing step S30
Referring to FIG. 7, this step is a step in which the stretched film 7 of the stretched laminated film 200 is dyed with a dichroic dye and adsorbed and oriented to obtain a polarizing film (polarizer layer) 5. Through this step, the polarizing laminated film 300 in which the polarizing film 5 is laminated on one side or both sides of the base film 31 is obtained.

  Specific examples of the dichroic dye include iodine and dichroic organic dyes. Specific examples of the dichroic organic dye include, for example, Red BR, Red LR, Red R, Pink LB, Rubin BL, Bordeaux GS, Sky Blue LG, Lemon Yellow, Blue BR, Blue 2R, Navy RY, Green LG, Violet LB, Violet B, Black H, Black B, Black GSP, Yellow 3G, Yellow R, Orange LR, Orange 3R, Scarlet GL, Scarlet KGL, Congo Red, Brilliant Violet BK, Splat Blue G, Splat Blue GL, Splat Orange GL , Direct Sky Blue, Direct First Orange S, First Black. A dichroic dye may be used individually by 1 type, and may use 2 or more types together.

  The dyeing step S30 can be usually performed by immersing the stretched laminated film 200 in a liquid (dye bath) containing a dichroic dye. As the dyeing bath, a solution in which the above dichroic dye is dissolved in a solvent can be used. As a solvent for the dyeing solution, water is generally used, but an organic solvent compatible with water may be further added. The concentration of the dichroic dye in the dyeing bath is preferably 0.01 to 10% by weight, and more preferably 0.02 to 7% by weight.

  When iodine is used as the dichroic dye, it is preferable to further add an iodide to the dyeing bath containing iodine because the dyeing efficiency can be improved. Examples of iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. Is mentioned. The iodide concentration in the dyeing bath is preferably 0.01 to 20% by weight. Of the iodides, it is preferable to add potassium iodide. When potassium iodide is added, the ratio of iodine to potassium iodide is, by weight, preferably 1: 5 to 1: 100, more preferably 1: 6 to 1:80. The temperature of the dyeing bath is preferably 10 to 60 ° C, more preferably 20 to 40 ° C.

  The dyeing step S30 may include a crosslinking treatment step that is performed subsequent to the dyeing treatment. The crosslinking treatment can be performed by immersing the stretched film dyed in a liquid (crosslinking bath) containing a crosslinking agent. Examples of the crosslinking agent include boron compounds such as boric acid and borax, glyoxal, and glutaraldehyde. Only 1 type may be used for a crosslinking agent and it may use 2 or more types together. As the crosslinking bath, a solution in which a crosslinking agent is dissolved in a solvent can be used. As the solvent, water can be used, but an organic solvent compatible with water may be further included. The concentration of the crosslinking agent in the crosslinking bath is preferably 1 to 20% by weight, more preferably 6 to 15% by weight.

  The crosslinking bath can further comprise iodide. By adding iodide, the polarization characteristics in the plane of the polarizing film 5 can be made more uniform. Specific examples of iodide are the same as described above. The concentration of iodide in the crosslinking bath is preferably 0.05 to 15% by weight, more preferably 0.4 to 8% by weight. The temperature of the crosslinking bath is preferably 10 to 90 ° C.

  The crosslinking treatment can be performed simultaneously with the dyeing treatment by blending a crosslinking agent in the dyeing bath. Moreover, you may perform the process immersed in a crosslinking bath 2 or more times using 2 or more types of crosslinking baths from which a composition differs.

  It is preferable to perform a washing | cleaning process and a drying process after dyeing process S30. The washing process usually includes a water washing process. The water washing treatment can be performed by immersing the film after the dyeing treatment or after the crosslinking treatment in pure water such as ion exchange water or distilled water. The water washing temperature is usually 3 to 50 ° C, preferably 4 to 20 ° C. The washing step may be a combination of a water washing step and a washing step with an iodide solution. As a drying process performed after the washing process, any appropriate method such as natural drying, blow drying, and heat drying can be adopted. For example, in the case of heat drying, the drying temperature is usually 20 to 95 ° C.

  The thickness of the polarizing film 5 included in the polarizing laminated film 300 can be, for example, 30 μm or less, and further 20 μm or less. From the viewpoint of thinning the polarizing plate, it is preferably 15 μm or less, more preferably 10 μm or less, Preferably it is 7 micrometers or less. The thickness of the polarizing film 5 is usually 2 μm or more.

(2) 1st bonding process S40
Referring to FIG. 8, this step is a first step through the first adhesive layer 15 on the polarizing film 5 of the polarizing laminated film 300, that is, on the surface opposite to the base film 31 side of the polarizing film 5. In this step, the protective laminated film 400 with protective film is obtained by laminating the protective film 10.

  In addition, when the polarizing laminated film 300 has the polarizing film 5 on both surfaces of the base film 31, the 1st protective film 10 is normally bonded on the polarizing film 5 of both surfaces, respectively. In this case, these first protective films 10 may be the same type of protective film or different types of protective films.

  The adhesive forming the first adhesive layer 15 is an active energy ray-curable adhesive (preferably containing a curable compound that is cured by irradiation with active energy rays such as ultraviolet rays, visible light, electron beams, and X-rays). UV curable adhesives) and water based adhesives in which adhesive components such as polyvinyl alcohol resins are dissolved or dispersed in water.

  As the active energy ray-curable adhesive, an active energy ray-curable adhesive composition containing a cationic polymerizable curable compound and / or a radical polymerizable curable compound is preferably used because it exhibits good adhesiveness. be able to. The active energy ray curable adhesive may further include a cationic polymerization initiator and / or a radical polymerization initiator for initiating a curing reaction of the curable compound.

  Examples of the cationic polymerizable curable compound include epoxy compounds (compounds having one or more epoxy groups in the molecule) and oxetane compounds (one or two or more oxetane rings in the molecule). Or a combination thereof. Examples of the radical polymerizable curable compound include (meth) acrylic compounds (compounds having one or more (meth) acryloyloxy groups in the molecule) and radical polymerizable double bonds. Other vinyl compounds or combinations thereof can be mentioned. A cationic polymerizable curable compound and a radical polymerizable curable compound may be used in combination.

  The active energy ray curable adhesive may be a cationic polymerization accelerator, an ion trap agent, an antioxidant, a chain transfer agent, a tackifier, a thermoplastic resin, a filler, a flow modifier, a plasticizer, Additives such as foaming agents, antistatic agents, leveling agents and solvents can be contained.

  When bonding the 1st protective film 10 using an active energy ray hardening adhesive, the 1st protective film 10 is put on the polarizing film 5 through the active energy ray hardening adhesive used as the 1st adhesive bond layer 15. After the lamination, the adhesive layer is cured by irradiating active energy rays such as ultraviolet rays, visible light, electron beams, and X-rays. Among them, ultraviolet rays are preferable, and as a light source in this case, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a chemical lamp, a black light lamp, a microwave excitation mercury lamp, a metal halide lamp, or the like can be used. In the case of using an aqueous adhesive, the first protective film 10 may be laminated on the polarizing film 5 via the aqueous adhesive and then dried by heating.

  In bonding the first protective film 10 to the polarizing film 5, the first protective film 10 and / or the bonding surface of the polarizing film 5 is subjected to plasma treatment, corona in order to improve adhesiveness with the polarizing film 5. Surface treatment (easy adhesion treatment) such as treatment, ultraviolet irradiation treatment, flame (flame) treatment, and saponification treatment can be performed, and among them, plasma treatment, corona treatment or saponification treatment is preferable.

  The first protective film 10 is a light-transmitting (preferably optically transparent) thermoplastic resin such as a chain polyolefin resin (polypropylene resin or the like) or a cyclic polyolefin resin (norbornene resin or the like). A polyolefin resin such as cellulose triacetate, cellulose ester resin such as cellulose diacetate, polyester resin, polycarbonate resin, (meth) acrylic resin, polystyrene resin, or a mixture or copolymer thereof. Can be a film.

  The first protective film 10 can also be a protective film having an optical function such as a retardation film and a brightness enhancement film. For example, a retardation film provided with an arbitrary retardation value by stretching a film made of the thermoplastic resin (uniaxial stretching or biaxial stretching) or by forming a liquid crystal layer or the like on the film. It can be.

  Examples of the chain polyolefin-based resin include a homopolymer of a chain olefin such as a polyethylene resin and a polypropylene resin, and a copolymer composed of two or more chain olefins.

  Cyclic polyolefin resin is a general term for resins that are polymerized using a cyclic olefin as a polymerization unit. Specific examples of cyclic polyolefin resins include ring-opening (co) polymers of cyclic olefins, addition polymers of cyclic olefins, copolymers of cyclic olefins and chain olefins such as ethylene and propylene (typically Are random copolymers), graft polymers obtained by modifying them with unsaturated carboxylic acids or derivatives thereof, and hydrides thereof. Among these, norbornene resins using norbornene monomers such as norbornene and polycyclic norbornene monomers as cyclic olefins are preferably used.

  The cellulose ester resin is an ester of cellulose and a fatty acid. Specific examples of the cellulose ester resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. Moreover, these copolymers and those in which a part of the hydroxyl group is modified with other substituents can also be used. Among these, cellulose triacetate (triacetyl cellulose: TAC) is particularly preferable.

  The polyester-based resin is a resin having an ester bond other than the cellulose ester-based resin, and generally includes a polycondensate of a polyvalent carboxylic acid or a derivative thereof and a polyhydric alcohol. As the polyvalent carboxylic acid or a derivative thereof, a dicarboxylic acid or a derivative thereof can be used, and examples thereof include terephthalic acid, isophthalic acid, dimethyl terephthalate, and dimethyl naphthalenedicarboxylate. A diol can be used as the polyhydric alcohol, and examples thereof include ethylene glycol, propanediol, butanediol, neopentyl glycol, and cyclohexanedimethanol.

  Specific examples of the polyester resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polycyclohexanedimethyl terephthalate, and polycyclohexanedimethyl naphthalate.

  The polycarbonate resin is composed of a polymer in which monomer units are bonded via a carbonate group. The polycarbonate-based resin may be a resin called a modified polycarbonate having a modified polymer skeleton, a copolymer polycarbonate, or the like.

The (meth) acrylic resin is a resin containing a compound having a (meth) acryloyl group as a main constituent monomer. Specific examples of (meth) acrylic resins include, for example, poly (meth) acrylic acid esters such as polymethyl methacrylate; methyl methacrylate- (meth) acrylic acid copolymer; methyl methacrylate- (meth) acrylic acid Ester copolymer; methyl methacrylate-acrylic ester- (meth) acrylic acid copolymer; (meth) methyl acrylate-styrene copolymer (MS resin etc.); methyl methacrylate and alicyclic hydrocarbon group And a copolymer (for example, methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate- (meth) acrylate norbornyl copolymer). Preferably, a polymer based on a poly (meth) acrylic acid C _1-6 alkyl ester such as poly (meth) acrylic acid methyl is used, and more preferably methyl methacrylate is the main component (50-100). % Methyl methacrylate resin is used.

  In addition, the description about each thermoplastic resin shown above is applicable also to the thermoplastic resin which comprises the base film 30. FIG.

  A surface treatment layer (coating layer) such as a hard coat layer, an antiglare layer, an antireflection layer, an antistatic layer, and an antifouling layer is formed on the surface of the first protective film 10 opposite to the polarizing film 5. You can also. The first protective film 10 contains one or more additives such as a lubricant, a plasticizer, a dispersant, a heat stabilizer, an ultraviolet absorber, an infrared absorber, an antistatic agent, and an antioxidant. Can do.

  The thickness of the first protective film 10 is preferably 90 μm or less, more preferably 50 μm or less, and still more preferably 30 μm or less, from the viewpoint of thinning the polarizing plate. The thickness of the 1st protective film 10 is 5 micrometers or more normally from a viewpoint of intensity | strength and a handleability.

(3) Peeling step S50
With reference to FIG. 9, this process is a process of peeling and removing the base film 31 from the polarizing laminated film 400 with a protective film, and obtaining the polarizing plate 1 with a single-side protective film. When the polarizing laminated film 300 has the polarizing film 5 on both surfaces of the base film 31 and the first protective film 10 is bonded to both of the polarizing films 5, one polarizing film is obtained by the peeling step S50. The polarizing plate 1 with a single-sided protective film is obtained from the conductive laminated film 300.

  The method for peeling and removing the base film 31 is not particularly limited, and can be peeled by the same method as the peeling step of a separator (peeling film) performed with a normal pressure-sensitive adhesive polarizing plate. The base film 31 may be peeled off as it is after the first bonding step S40, or is wound into a roll once after the first bonding step S40 and peeled off while being unwound in the subsequent steps. Also good.

(4) 2nd bonding process S60
With reference to FIG. 10, this process is further performed on the polarizing film 5 of the polarizing plate 1 with a single-side protective film, that is, on the surface opposite to the first protective film 10 bonded in the first bonding process S40. 2 It is the process of bonding the 2nd protective film 20 through the adhesive bond layer 25, and obtaining the polarizing plate 2 with a double-sided protective film. The bonding of the second protective film 20 via the second adhesive layer 25 can be performed in the same manner as the bonding of the first protective film 10. About the structure and material of the 2nd protective film 20 and the 2nd adhesive bond layer 25, the description about the 1st protective film 10 and the 1st adhesive bond layer 15 is quoted, respectively.

  As mentioned above, although the polarizing film (polarizing laminated film, polarizing laminated film with a protective film) using the stretched film (stretched laminated film) supported by the base material film and the method for producing the polarizing plate were described, Even when a single stretched film not supported by the material film is used, a polarizing film can be produced in the same manner by performing a dyeing treatment. Moreover, the polarizing plate with a single-sided protective film or the polarizing plate with a double-sided protective film can be manufactured by sticking a protective film on the single side | surface or both surfaces of this polarizing film similarly through an adhesive bond layer.

  A polarizing plate is put on the polarizing film 5 in the polarizing plate 1 with a single-sided protective film shown in FIG. 9 or on the first protective film 10 or the second protective film 20 in the polarizing plate 2 with a double-sided protective film shown in FIG. You may laminate | stack the adhesive layer for bonding to the member (for example, liquid crystal cell in the case of applying to a liquid crystal display device). The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is usually based on a (meth) acrylic resin, styrene resin, silicone resin or the like, and a crosslinking agent such as an isocyanate compound, an epoxy compound, or an aziridine compound is added thereto. It consists of an adhesive composition. Furthermore, it can also be set as the adhesive layer which contains microparticles | fine-particles and shows light-scattering property. The thickness of an adhesive layer is 1-40 micrometers normally, Preferably it is 3-25 micrometers.

  The polarizing plate 1 with a single-sided protective film and the polarizing plate 2 with a double-sided protective film can further include other optical layers laminated on the first and / or second protective films 10 and 20 and the polarizing film 5. As another optical layer, a reflective polarizing film that transmits a certain kind of polarized light and reflects polarized light that exhibits the opposite properties; a film with an antiglare function having a concavo-convex shape on the surface; a film with a surface antireflection function A reflective film having a reflective function on the surface; a transflective film having both a reflective function and a transmissive function; and a viewing angle compensation film.

  By using a stretched film uniaxially oriented in TD, a polarizing film and a polarizing plate having TD as the absorption axis direction can be provided. If such a polarizing plate is used as one of a pair of polarizing plates constituting a liquid crystal panel, the pair of polarizing plates can be directly bonded to the liquid crystal cell without shifting the MD by 90 °. That is, roll-to-panel bonding of the pair of polarizing plates to the liquid crystal cell so that the MDs thereof are parallel is possible, and the absorption axes of the pair of polarizing plates are orthogonal to each other. . Moreover, according to the elongate polarizing plate which makes TD the absorption-axis direction, when bonding with a brightness enhancement film (reflection type polarizing plate), roll-to-roll bonding is attained.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated further more concretely, this invention is not limited by these examples. In the following examples, the birefringence ΔP of the stretched film, the film breakability during the stretching process, the appearance quality of the stretched film, the visibility corrected single transmittance Ty and the visibility corrected polarization degree Py of the polarizing film are measured by the following measuring methods. According to the evaluation method.

[A] Measurement of birefringence ΔP of stretched film Using a stretched film obtained by peeling and removing the base film from the stretched laminated film as a sample, using a phase difference measuring device “KOBRA-WR” manufactured by Oji Scientific Instruments Co., Ltd. The birefringence ΔP at a wavelength of 590 nm based on the above formula was measured. The results are shown in Table 1.

[B] Evaluation of film breakability during stretching step According to the following evaluation criteria, the film breakability during stretching of the laminated film was evaluated. The results are shown in Table 1.

A: No film breakage,
B: The number of film breaks per 10 m of the laminated film is one.
C: The number of film breaks per 10 m of the laminated film is 2 times or more.

[C] Evaluation of Appearance Quality of Stretched Film The stretched film of the obtained stretched laminated film was visually observed, and the appearance quality was evaluated according to the following evaluation criteria. The results are shown in Table 1.

A: No wrinkling,
B: Slight wrinkles are observed,
C: Many wrinkles are recognized.

[D] Measurement of visibility corrected single transmittance Ty and visibility corrected polarization degree Py of polarizing film Using a polarizing laminated film as a sample, an absorptiometer (“V7100” manufactured by JASCO Corporation) was used for viewing. The sensitivity correction single transmittance Ty and the visibility correction polarization degree Py were measured. In the measurement, a polarizing laminated film sample was set so that incident light was irradiated on the polarizing film side. The results are shown in Table 1.

<Example 1>
(1) Primer layer forming step PVA powder (“Z-200” manufactured by Nippon Synthetic Chemical Industry Co., Ltd., average polymerization degree 1100, saponification degree 99.5 mol%) is dissolved in hot water at 95 ° C. to obtain a concentration. A 3 wt% PVA aqueous solution was prepared. The resulting aqueous solution was mixed with a crosslinking agent (“Smile Resin 650” manufactured by Taoka Chemical Industry Co., Ltd.) at a ratio of 5 parts by weight with respect to 6 parts by weight of PVA powder to prepare a primer layer forming coating solution. Obtained.

  Next, an unstretched polypropylene (PP) film (melting point: 163 ° C.) having a thickness of 90 μm is prepared as a base film, and after corona treatment is performed on one side thereof, a small-diameter gravure coater is used on the corona treatment surface. The primer layer-forming coating solution was applied and dried at 80 ° C. for 10 minutes to form a primer layer having a thickness of 0.2 μm.

(2) Production of laminated film (PVA resin film forming step)
Polyvinyl alcohol powder (“PVA124” manufactured by Kuraray Co., Ltd., average polymerization degree 2400, saponification degree 98.0 to 99.0 mol%) was dissolved in hot water at 95 ° C., and a polyvinyl alcohol aqueous solution having a concentration of 8% by weight. Was prepared and used as a PVA-based resin film-forming coating solution. By applying the PVA-based resin film-forming coating solution on the surface of the primer layer of the base film having the primer layer prepared in (1) above using a die coater, and then drying at 70 ° C. for 4 minutes, A PVA resin film was formed on the primer layer to obtain a long laminated film. The thickness of the PVA resin film (PVA resin layer) was 9 μm.

(3) Production of stretched film (stretching process)
While continuously unwinding the long laminated film produced in (2) above, stretching to TD (lateral stretching) and shrinking to MD (longitudinal shrinkage) are performed according to the stretching pattern shown in FIG. The stretching process including the first stretching process step and the second stretching process step, which are simultaneous biaxial stretching processes performed simultaneously with each other, was continuously performed using a tenter-type stretching device to obtain a long stretched laminated film. . The stretching process was performed at 160 ° C. (the same applies to the following comparative examples). The drawing pattern was controlled by adjusting the clip interval. The final TD stretch ratio A _f and a final MD shrinkage ratio B _f in stretched laminated film is 5.5-fold, respectively, were 0.5 times (the same applies to the following comparative examples.). The stretched film (PVA resin layer) in the stretched laminated film had a thickness of about 3 μm. The film was not broken in the stretching process, and a stretched laminated film having a length of more than 100 m could be obtained.

(4) Production of polarizing laminated film (dyeing process)
The stretched laminated film produced in the above (3) contains a dyeing aqueous solution at 30 ° C. containing iodine and potassium iodide (0.4 parts by weight of iodine and 5.0 parts by weight of potassium iodide per 100 parts by weight of water). ), The PVA film was dyed for about 70 seconds, and then the excess dyeing aqueous solution was washed away with 10 ° C. pure water.

  Next, it is immersed in a first crosslinked aqueous solution at 78 ° C. containing boric acid (containing 10.4 parts by weight boric acid per 100 parts by weight of water) for 120 seconds, and then a 70 ° C. aqueous solution containing boric acid and potassium iodide is added. 2 Crosslinking treatment was performed by immersing in a cross-linking aqueous solution (containing 5.0 parts by weight of boric acid and 12.0 parts by weight of potassium iodide per 100 parts by weight of water) for 60 seconds. Thereafter, the film was immersed in pure water at 10 ° C. for about 10 seconds, and finally dried at 80 ° C. for 300 seconds to obtain a polarizing laminated film including a polarizing film. The Ty and Py of the polarizing film were 41.5% and> 99.99%, respectively.

<Example 2>
A stretched laminated film was obtained in the same manner as in Example 1 except that the stretched pattern in the stretching step was as shown in FIG. The thickness of the stretched film (PVA resin layer) in the stretched laminated film was about 3 μm. Moreover, the polarizing laminated film containing a polarizing film was obtained like Example 1 except having used the obtained stretched laminated film. At this time, the Ty of the polarizing film was adjusted to 41.5% by adjusting the immersion time in the dyeing aqueous solution. The Py of the polarizing film was> 99.99%.

<Comparative Examples 1-4>
A stretched laminated film was obtained in the same manner as in Example 1 except that the stretched pattern in the stretching step was as shown in FIG. The thickness of the stretched film (PVA resin layer) in the stretched laminated film was about 3 μm. Moreover, the polarizing laminated film containing a polarizing film was obtained like Example 1 except having used the obtained stretched laminated film. At this time, the Ty of the polarizing film was adjusted to 41.5% by adjusting the immersion time in the dyeing aqueous solution (however, in Comparative Example 4, Ty and Py were not measured). In Comparative Example 3, the film was not broken in the stretching step, and a stretched laminated film having a length of more than 100 m could be obtained, but in Comparative Examples 1, 2, and 4, the film was broken and the obtained stretched laminated film was obtained. The length of each was about 10 m, less than 10 m, and less than 10 m.

  DESCRIPTION OF SYMBOLS 1 Polarizing plate with single-sided protective film, 2 Polarizing plate with double-sided protective film, 5 Polarizing film (polarizer layer), 6 PVA-based resin film (PVA-based resin layer), 7 Stretched film, 10 First protective film, 15 First Adhesive layer, 20 Second protective film, 25 Second adhesive layer, 30 Base film, 31 Stretched base film, 50 clips, 100 Laminated film, 200 Stretched laminated film, 300 Polarized laminated film, 400 Protection Polarizing laminated film with film.

Claims (9)

A stretching step of obtaining a stretched film having a TD stretch ratio of A _f [times] and an MD shrinkage ratio of B _f [times] by stretching the polyvinyl alcohol-based resin film;
The stretching step includes
In comparison with the same TD stretch ratio, the stretching to TD and the shrinking to MD are simultaneously performed so that the MD shrinkage ratio is larger than the MD shrinkage ratio when the polyvinyl alcohol-based resin film is horizontally stretched at the free end. 1 stretching process,
A second stretching step for simultaneously stretching to TD and shrinking to MD so that the MD shrinkage ratio is reduced by 0.17 or more;
Look at including in this order,
A method for producing a stretched film, wherein a TD stretch ratio of the polyvinyl alcohol-based resin film at the start of the second stretch treatment step is 4.0 times or more .   The manufacturing method of Claim 1 whose TD draw ratio of the said polyvinyl alcohol-type resin film at the time of the start of a said 2nd extending | stretching process process is 4.3 times or more. 3. The production according to claim 1, wherein by performing the second stretching treatment step, the TD stretching ratio of the polyvinyl alcohol-based resin film reaches A _f [times] and the MD shrinkage ratio reaches B _f [times]. Method. The polyvinyl alcohol-based resin film is an unstretched film,
The manufacturing method of any one of Claims 1-3 which perform a said 1st extending | stretching process process first in the said extending process. The manufacturing method according to any one of claims 1 to 4, wherein the MD shrinkage ratio _{Bf of the} stretched film is 0.2 to 0.8 times. The manufacturing method of any one of Claims 1-5 whose said TD draw ratio _Af of the said stretched film is 5 times or more.   The manufacturing method of any one of Claims 1-6 which obtains the said stretched film laminated | stacked on the said base film by extending | stretching the laminated film which has the said polyvinyl alcohol-type resin film on a base film. .   The manufacturing method of any one of Claims 1-7 whose thickness of the said stretched film is 30 micrometers or less. A step of obtaining a stretched film by the production method according to any one of claims 1 to 8,
Dyeing the stretched film with a dichroic dye;
The manufacturing method of a polarizing film containing.