JP2016151632A - Production method of polyvinyl alcohol resin film and production method of polarizing film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method of a polyvinyl alcohol resin film that can exhibit high polarization performance when the film is formed into a polarizing film, and a production method of a polarizing film by using the polyvinyl alcohol resin film.SOLUTION: The production method of a polyvinyl alcohol resin film includes a drying step of removing water from an aqueous solution that comprises a polyvinyl alcohol resin and has a water content of over 30 wt.%, in which a removal rate of water in the drying step when the water content is 30 wt.% is 0.01 to 1.8 wt.%/sec. The production method of a polarizing film is carried out by using the polyvinyl alcohol resin film obtained by the above production method.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing a polyvinyl alcohol-based resin film and a method for producing a polarizing film.

  The polarizing plate is widely used in image display devices such as liquid crystal display devices. 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 formed by dye | staining with the dichroic dye to the stretched polyvinyl alcohol-type resin film is common. A polyvinyl alcohol-based resin film used as a raw material for a polarizing film can be produced by drying and removing water from a film-like aqueous solution containing a polyvinyl alcohol-based resin [for example, Japanese Patent Application Laid-Open No. 2014-059564 (Patent Document). 1), Japanese Patent No. 5390053 (Patent Document 2)].

JP 2014-059564 A Patent No. 5390053

  A polyvinyl alcohol-based resin film for a polarizing film is required to exhibit high polarizing performance when formed into a polarizing film by stretching and dyeing. Although it is possible to increase the polarizing performance of the polarizing film by increasing the draw ratio and neck-in ratio when stretching the polyvinyl alcohol-based resin film, in this method, 1) the film is likely to break. ) The heat shrinkage rate of the obtained polarizing film is increased, and the heat resistance of the polarizing plate is lowered. 3) The width efficiency (ratio of the width of the obtained polarizing film to the width of the polyvinyl alcohol-based resin film) is lowered. There is a problem.

  An object of the present invention is to provide a method for producing a polyvinyl alcohol-based resin film that can exhibit high polarization performance when used as a polarizing film, and a method for producing a polarizing film using the polyvinyl alcohol-based resin film. .

  This invention provides the manufacturing method of the polyvinyl alcohol-type resin film shown below, and the manufacturing method of a polarizing film.

[1] A drying step for removing water from an aqueous solution containing a polyvinyl alcohol-based resin and having a water content exceeding 30% by weight,
The manufacturing method of the polyvinyl-alcohol-type resin film whose removal rate of water when a moisture content is 30 weight% in the said drying process is 0.01-1.8 weight% / sec.

[2] A drying step for removing water from an aqueous solution containing a polyvinyl alcohol-based resin and having a water content exceeding 30% by weight,
The manufacturing method of the polyvinyl-alcohol-type resin film whose average removal rate of the water in the said drying process is 0.01-1.8 weight% / second in the moisture content of 30-10 weight%.

  [3] The production method according to [1] or [2], further including a step of forming a coating layer of the aqueous solution on the base film before the drying step.

[4] A step of obtaining a polyvinyl alcohol-based resin film by the production method according to any one of [1] to [3];
Stretching the polyvinyl alcohol resin film to obtain a stretched film;
Obtaining a polarizing film from the stretched film;
The manufacturing method of a polarizing film containing.

  [5] The manufacturing method according to [4], wherein the polarizing film has a thickness of 10 μm or less.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the polyvinyl-alcohol-type resin film which can show high polarizing performance when it is set as a polarizing film, and the manufacturing method of the polarizing film using the said polyvinyl-alcohol-type resin film can be provided. .

It is a flowchart which shows a preferable example of the manufacturing method of the polyvinyl alcohol-type resin film which concerns on this invention. It is a schematic sectional drawing which shows an example of the layer structure of the coating film obtained at a coating process. It is a schematic sectional drawing which shows an example of the laminated constitution of the laminated | multilayer film obtained at a drying process. 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 stretched film obtained at a extending process. 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 the graph which plotted the relationship between the removal rate V (30) in a drying process in each Example and a comparative example, and the visibility correction | amendment polarization degree Py of the obtained polarizing plate with a single-sided protective film. It is the graph which plotted the relationship between the average removal speed Vave (30-10) in the drying process in each Example and the comparative example, and the visibility correction | amendment polarization degree Py of the obtained polarizing plate with a single-sided protective film. It is the graph which plotted the relationship between the visibility correction single-piece | unit transmittance | permeability Ty of the polarizing plate with a single-sided protective film obtained by each Example and the comparative example, and the visibility correction | amendment polarization degree Py.

<Method for producing polyvinyl alcohol-based resin film>
The method for producing a polyvinyl alcohol-based resin film according to the present invention (hereinafter, the polyvinyl alcohol-based resin is also referred to as “PVA-based resin”) removes water from an aqueous solution containing the PVA-based resin, and removes the PVA-based resin from the aqueous solution. A drying step for obtaining a PVA-based resin film by forming a layer (film) to be contained is included.

FIG. 1 is a flowchart showing a preferred example of a method for producing a PVA-based resin film according to the present invention. It is preferable that the manufacturing method of the PVA-type resin film which concerns on this invention includes the process of making the said aqueous solution into a film | membrane before the said drying process, and this process typically includes the said aqueous solution on a base film. It can be a step of forming a coating layer by coating. In this case, as shown in FIG. 1, the method for producing the PVA resin film according to the present invention includes the following steps:
(1) Coating process S10 which forms the coating layer by coating the aqueous solution on the substrate film,
(2) Drying step S20 to remove water from the coating layer (film-like aqueous solution) to obtain a PVA resin film,
Are included in this order.

  Hereinafter, each step will be described. In addition, although a PVA-type resin film (it is also called "PVA-type resin layer") may be formed in both surfaces of a base film by forming a coating layer in both surfaces of a base film in coating process S10, Below, the case where it forms mainly on one side is demonstrated.

(1) Coating process S10
With reference to FIG. 2, this step is a step of obtaining a coating film 100 by applying an aqueous solution containing a PVA-based resin to at least one surface of the base film 30 to form a coating layer 6. is there. The method of forming the coating layer 6 by coating on the base film 30 and forming a PVA-based resin film (PVA-based resin layer) from this coating layer 6 is a thin PVA-based resin film, and thus a thin-film polarization. This is advantageous in that it is easy to obtain a 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 composed of a resin that can be stretched at a stretching temperature suitable for stretching the PVA-based resin film (PVA-based resin layer) in the stretching step in the polarizing film manufacturing method 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.

  The aqueous solution (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 solvents other than water include water-compatible organic solvents such as methanol, ethanol, propanol, and alcohols typified by polyhydric alcohols (preferably 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.

  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 degree of saponification is less than 80.0 mol%, the water resistance of the polarizing film obtained from the PVA-based resin 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 the polarized light has a sufficient polarizing performance as well as productivity. 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 the modification exceeding 30 mol% is performed, it becomes difficult to adsorb the dichroic dye, and it tends to be difficult to obtain a polarizing film having sufficient polarization performance. 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 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).

  As will be described in detail later, the water content of the aqueous solution containing the PVA resin is more than 30% by weight.

  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 6 may be formed only on one surface of the base film 30 or may be formed on both surfaces.

  Prior to the application of the coating liquid, in order to improve the adhesion between the base film 30 and the PVA resin film, at least the surface of the base film 30 on which the coating layer 6 is formed is subjected to corona treatment, Plasma treatment, flame (flame) treatment, or the like may be performed. For the same reason, the coating layer 6 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 resin film, 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 resin is used as the resin component for forming the primer layer, a polyamide epoxy resin, a methylolated melamine resin, a dialdehyde crosslinking agent, a metal chelate compound 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 is small.

  The method of applying the primer layer forming coating solution to the base film 30 can be the same as the aqueous solution for the PVA-based 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) Drying step S20
With reference to FIG. 3, this process removes water from the coating layer 6 with which the moisture content with which the coating film 100 is provided exceeds 30 weight%, and is set as the PVA-type resin film (PVA-type resin layer) 7, and is a laminated film. This is a process of obtaining 200. Although drying (removal of water) of the coating layer 6 can be performed by heating the coating film 100, drying by reduced pressure or the like may be used in combination. Examples of the method for heating the coating film 100 include a method in which the coating film 100 is brought into contact (embracing) with a heated roll (heat roll), a method in which hot air is blown over the coating film 100, or a combination thereof. be able to. The drying temperature in drying process S20 is in the range of 50-200 degreeC, for example, Preferably it exists in the range of 60-150 degreeC.

  In this step (drying step S20), the coating layer 6 having a moisture content exceeding 30% by weight (hereinafter, the moisture content of the coating layer 6 immediately before the drying step S20 is also referred to as “initial moisture content W1”). The PVA resin film 7 is obtained by removing water from the substrate and drying until reaching a desired moisture content (hereinafter also referred to as “final moisture content W2”). At this time, the removal rate of water when the moisture content is 30% by weight (meaning a decrease in the moisture content (% by weight) per unit time, the unit is% by weight) or the moisture content is 30% by weight. It is important to appropriately adjust the average water removal rate in the vicinity of% (that is, between 30 to 10% by weight of water content). Within the range of ˜1.8% by weight / second. Below, the water removal rate when the moisture content of the coating layer 6 becomes 30% by weight is also referred to as “removal rate V (30)”, and the moisture content of the coating layer 6 is 30 to 10% by weight. The average water removal rate in the range is also referred to as “average removal rate Vave (30-10)”. By adjusting the drying conditions so that the removal rate V (30) and / or the average removal rate Vave (30-10) are within the above range, a PVA-based resin film 7 that exhibits high polarization performance when used as a polarizing film. Can be obtained.

  Although this invention is not limited at all, the reason why high polarization performance can be exhibited by adjusting the removal rate V (30) and / or the average removal rate Vave (30-10) within the predetermined range. Is estimated as follows.

  That is, high polarization performance is manifested when crystal nuclei of the PVA resin begin to form when the water content is 30% by weight or in the vicinity thereof (between 30 and 10% by weight), and the coating layer 6 The water removal rate V (30) and / or the average removal rate Vave (30-10) when the water content is 30% by weight and / or the water content in the vicinity thereof is within the above range, and drying is performed slowly. This is considered to be because a sufficient number of crystal nuclei are generated. Then, by generating a large number of crystal nuclei in this way, the density of crystallites is increased, and a denser crystal structure can be formed. As a result, a large amount of dichroic dye-PVA resin complex having a high stability and orientation is formed in the vicinity of a dense crystallite when dyeing with a dichroic dye such as iodine. Since it becomes easy, it is thought that polarization performance improves.

  On the other hand, in a region where the water content exceeds 30% by weight, the PVA resin is uniformly dissolved in water, and the molecular chain of the PVA resin is uniformly present (solution) is stable. It is believed that there is. Actually, in the region where the moisture content exceeds 30% by weight, the formation of stable crystal nuclei having a critical size or more hardly occurs. When the water content is reduced to about 30% by weight, crystal nucleation of a stable critical size or more is performed. This is because it is more stable to form and crystallize a crystal nucleus. It is done.

  Thus, crystal nuclei of the PVA-based resin begin to occur when the water content is reduced to about 30% by weight, and generation of crystal nuclei also occurs in the vicinity thereof, that is, in a region with a water content of 30 to 10% by weight. In the region where the water content is less than 10% by weight, the formation of stable crystal nuclei having a critical size or more is unlikely to occur. This is considered to be because water as a good solvent is very little and the mobility of the molecular chain of the PVA resin is excessively lowered.

  The present invention is not a region where the water content is more than 30% by weight and less than 10% by weight, in which the generation of crystal nuclei does not occur or hardly occurs, and at the time when the water content is 30% by weight at which the generation of crystal nuclei actually occurs and / or Paying attention to the region with a water content of 30 to 10% by weight, adjusting the water removal rate V (30) and / or the average removal rate Vave (30-10) at that time and / or region within the predetermined range. Is one feature.

  In this step (drying step S20), the removal rate V (30) at a moisture content of 30% by weight within a range of 0.01 to 1.8% by weight / second starts to form crystal nuclei of the PVA resin. And / or the average removal rate Vave (30-10) at a water content of 30 to 10% by weight where the generation of crystal nuclei is similarly generated is 0.01 to 1.8. You may make it adjust in the range of weight% / second. However, since a sufficiently large number of crystal nuclei can be generated over the entire water content range where the generation of crystal nuclei occurs, it is preferable to adjust at least the average removal rate Vave (30-10) within the above range. It is more preferable to adjust both (30) and the average removal rate Vave (30-10) within the above range.

  As a method of reducing the removal rate V (30) and / or the average removal rate Vave (30-10) to the upper limit of the above range, if the drying is performed using a hot roll, the surface temperature of the hot roll is lowered. In the case of drying using hot air, a method of reducing the temperature and / or wind speed of hot air can be mentioned. Moreover, you may make it raise the humidity of the environment which implements drying. From the viewpoint of productivity, in the region where the moisture content greatly exceeds 30% by weight, it is preferable to increase the removal rate of water as much as possible by strengthening drying. However, the moisture content is 30% by weight for the operation of the drying equipment. Since it is difficult to reduce the removal rate abruptly at the moment when the water content reaches, the removal rate V (30) and / or lowering the removal rate to some extent before reaching the moisture content of 30% by weight. Or it is easy to adjust average removal speed Vave (30-10) in the said range.

  In addition, when drying from the initial moisture content W1 to the final moisture content W2, the temperature of the coating film 100 gradually increases when drying is performed under a constant drying condition from beginning to end, and the water removal rate increases significantly during the drying. Tend to. Therefore, in order to set the removal rate V (30) and / or the average removal rate Vave (30-10) within the above range, the drying conditions are not constant throughout the drying step S20, but are dried from the middle. It is preferable to relax the conditions.

  The upper limit of the removal rate V (30) and the average removal rate Vave (30-10) is preferably 1.65% by weight / second or less from the viewpoint of further increasing the density of crystal nuclei of the PVA resin. More preferably, it is 5 wt% / second or less. The lower limit of the removal rate V (30) and the average removal rate Vave (30-10) is 0.01% by weight / second or more because if the removal rate of water is too slow, the density of crystal nuclei increases. This is because the dyeing efficiency in the dyeing step in the method for producing a polarizing film described later is lowered. From this viewpoint, and from the viewpoint of the productivity of the PVA-based resin film 7, the lower limit value is preferably 0.15% by weight / second or more, more preferably 0.5% by weight / second or more.

Next, the measurement method of the removal rate V (30) and the average removal rate Vave (30-10) will be described. These plot the moisture content of the coating layer 6 against the elapsed time from the start of the drying step S20. It can be calculated from the resulting moisture content decrease curve (fitting curve). If the measurement data (measurement points) of the moisture content is sufficiently dense, the slope [removal speed V (30)] can be accurately obtained from the differential value at the time when the moisture content is 30% by weight. However, it is difficult to acquire continuous measurement data in actual measurement, and it is often impossible to acquire sufficiently dense measurement data. Therefore, in this case, the removal rate V (30) is obtained as an average value of measurement data in a predetermined range including a time point when the moisture content is 30% by weight. Specifically, in this case, the removal rate V (30) is expressed by the following formula [a]:
Removal rate V (30) = 4 [wt%] / (time required for the water content to change from 32 wt% to 28 wt% [sec]) [a]
In accordance with the above fitting curve, the water content decrease amount between 32% and 28% by weight (that is, 4 [% by weight]) is changed from 32% by weight to 28% by weight. It is obtained as a value divided by the required time [seconds].

  In obtaining the fitting curve, the moisture content measurement data is obtained at intervals of about 2% by weight in order to accurately calculate the removal rate.

The average removal speed Vave (30-10) is also obtained in the same manner as the above formula [a]. That is, the average removal rate Vave (30-10) is expressed by the following formula [b]:
Average removal rate Vave (30-10) = 20 [% by weight] / (time required for the water content to change from 30% by weight to 10% by weight [seconds]] [b]
In accordance with the above-mentioned fitting curve, the water content decrease amount (that is, 20 [wt%]) between 30 wt% and 10 wt% is determined when the moisture content is changed from 30 wt% to 10 wt%. It is obtained as a value divided by the required time [seconds].

  The moisture content of the coating layer 6 is "IR moisture content meter: IRMA series" sold by CHINO Co., Ltd., "Fiber type infrared moisture meter: IM series" sold by Fuji Work Ltd., etc. It is measured using an IR moisture content meter. The IR moisture content meter obtains the moisture content from the intensity of infrared absorption derived from water. Therefore, in order to calculate the moisture content (moisture content) from the intensity, it is necessary to create a calibration curve that defines these correspondences.

The moisture content of the film necessary for preparing the calibration curve is measured by the dry weight method. The dry weight method is to measure the weight [initial weight] of the PVA-based resin film (coating layer) for a film sample in the course of drying having a predetermined size, and then perform a drying process at 105 ° C. for 2 hours. Then, the weight [post-treatment weight] of the PVA-based resin film (coating layer) was measured again, and the following formula [c]:
Water content = {(initial weight−weight after treatment) / initial weight} × 100 [c]
Is a method of measuring the moisture content based on

  The calibration curve prepares a plurality of film samples having different moisture contents, measures the moisture content according to the above formula [c] for these samples, and uses the IR moisture content meter to determine the intensity of infrared absorption derived from water. It is obtained by measuring and plotting the correspondence between the obtained water content and the intensity of infrared absorption. The moisture content range of the film sample for preparing the calibration curve is preferably equal to or more than the moisture content range of the coating layer 6 to be actually measured. This is because, if a calibration curve is created in a range that is too narrow with respect to the measurement target range, there will be a problem that the actual moisture content will not be met depending on the approximation method to be swept out. The calibration curve is usually approximated by a linear expression, but a quadratic expression or the like may be used if necessary.

The following points should be noted when creating a calibration curve.
1) When a coating layer of a film sample for preparing a calibration curve contains volatile components other than water (such as alcohol), the water content obtained by the above formula [c] is the weight due to volatilization of the volatile components. It includes the decrease. Therefore, in this case, in order to obtain an accurate moisture content based on the above equation [c], it is necessary to perform correction for subtracting the weight reduction. Preferably, a film sample for preparing a calibration curve does not contain or hardly contains volatile components other than water.

  2) A film sample for preparing a calibration curve may have a film configuration similar to the coating film 100 in which a PVA-based resin film (coating layer) in the course of drying is formed on a base film, In this case, you may measure a moisture content with the base film. However, in this case, in order to obtain an accurate moisture content of the coating layer based on the above formula [c], it is necessary to perform correction for subtracting the weight of the base film from the initial weight and the weight after treatment.

  In addition, when using what has a film structure similar to the coating film 100 as a film sample, when calculating | requiring the intensity | strength of the infrared absorption derived from water using an IR moisture content meter, the water | moisture content which a base film may contain Infrared absorption that the base film may have and infrared absorption overlapping with the infrared absorption region derived from water is usually negligible. This is because the base film is usually made of a hydrophobic resin such as a cyclic polyolefin resin, a chain polyolefin resin, or a polyethylene terephthalate resin, and its water content is negligibly small. . In addition, the absorption band other than water is an inherent absorption band of the resin, and is usually constant in the drying process, and can be ignored.

  3) Since the IR moisture content meter determines the moisture content from the intensity of infrared absorption derived from water, for example, when the thickness of the PVA-based resin film to be produced is changed, the moisture content per unit volume is Even if it is the same, the intensity of infrared absorption changes by the thickness. Therefore, when changing the thickness of the PVA resin film to be manufactured, it is necessary to create a calibration curve each time. Further, when the base film has scattering, absorption, etc. in the infrared absorption region derived from water, the intensity of infrared absorption changes depending on the thickness of the base film. Therefore, it is necessary to create a calibration curve every time the thickness of the base film is changed.

  The initial moisture content W1 of the coating layer 6 (the moisture content of the coating layer 6 immediately before the drying step S20) is set to a value exceeding 30% by weight. When the initial water content W1 exceeds 30% by weight, the aqueous solution containing the PVA-based resin becomes a uniform solution, and it is possible to prevent unintended crystallization from occurring before the drying step S20. Further, the initial moisture content W1 is preferably 32% by weight or more and more preferably more than 32% by weight so that the removal rate V (30) can be obtained based on the above formula [a]. On the other hand, from the viewpoint of handleability when applying an aqueous solution containing a PVA resin, the initial moisture content W1 is preferably 40% by weight or more, and more preferably 50% by weight or more.

  The final water content W2 (water content at the end of the drying step S20) of the coating layer 6 may be 28% by weight or less so that the removal rate V (30) can be obtained based on the above formula [a]. Preferably, it is less than 28% by weight. Further, the final moisture content W2 is more preferably 10% by weight or less, and preferably less than 10% by weight so that the average removal rate Vave (30-10) can be obtained based on the above formula [b]. Particularly preferred. On the other hand, from the viewpoint of the stability and strength of the PVA-based resin film (PVA-based resin layer) 7 obtained through the drying step S20, the initial moisture content W2 is preferably 20% by weight or less, and is preferably 10% by weight or less. More preferably, it is more preferably 6% by weight or less.

  The thickness of the PVA resin film (PVA resin layer) 7 in the laminated film 200 is preferably 3 to 30 μm, more preferably 5 to 20 μm. If it is the PVA-type resin film 7 which has the thickness in this range, the dyeing | staining property of a dichroic pigment | dye is favorable, it is excellent in polarizing performance, and a sufficiently thin (for example, thickness of 10 micrometers or less) polarizing film can be obtained.

<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 PVA-type resin obtained by the manufacturing method of the PVA-type resin film which concerns on the said invention as a raw material film. According to this manufacturing method, a polarizing film with high polarization performance can be obtained.

  The PVA-based resin film as the raw material film may be the PVA-based resin film 7 (that is, the laminated film 200) supported by the base film 30, or a single PVA-based resin film 7 that is not supported by the base film 30. It may be.

Taking a method of manufacturing a polarizing film supported by a base film from a laminated film 200 as an example, this manufacturing method will be described with reference to FIG.
(1) Stretching step S30 for stretching a laminated film to obtain a stretched film,
(2) Dyeing process S40 which obtains a polarizing laminated film by dyeing a PVA system resin film (PVA system resin layer) of a stretched 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. 4, the polarizing laminated film is subjected to the following steps:
(3) 1st bonding process S50 which pastes a 1st protective film on the polarizing film of a polarizing laminated film, and obtains a polarizing laminated film with a protective film,
If it uses, a polarizing laminated film with a protective film can be obtained.

Referring to FIG. 4, the polarizing laminated film with a protective film is subjected to the following steps:
(4) Peeling step S60 to peel and remove the base film from the polarizing laminated film with protective film to obtain a polarizing plate with a single-side protective film,
If it uses, it can obtain the polarizing plate with a single-sided protective film, and also this is the following process:
(5) 2nd bonding process S70 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) Stretching step S30
With reference to FIG. 5, this process extends | stretches the laminated | multilayer film 200 which consists of the base film 30 and the PVA-type resin film 7, and the stretched film 300 which consists of the extended base film 30 'and the PVA-type resin film 7'. It is the process of obtaining. The stretching process is usually uniaxial stretching. The laminated film 200 may be one in which the PVA-based resin film 7 is laminated on both surfaces of the base film 30.

  The draw ratio of the laminated film 200 can be appropriately selected according to the desired polarization characteristics, but is preferably more than 5 times and not more than 17 times, more preferably more than 5 times the original length of the laminated film 200. 8 times or less. If the draw ratio is 5 times or less, the PVA resin film 7 ′ is not sufficiently oriented, and the polarization degree of the polarizing film may not be sufficiently high. On the other hand, when the draw ratio exceeds 17 times, the film is likely to be broken during stretching, and the thickness of the stretched film 300 becomes unnecessarily thin, and the workability and handleability in subsequent processes may be reduced.

  The stretching process is not limited to stretching in one stage, and can be performed in multiple stages. In this case, all the multistage stretching processes may be performed continuously before the dyeing process S40, or the second and subsequent stretching processes may be performed simultaneously with the dyeing process and / or the crosslinking process in the dyeing process S40. Good. Thus, when performing a extending | stretching process in multistage, it is preferable to perform an extending | stretching process so that it may become a draw ratio exceeding 5 times combining all the stages of an extending | stretching process.

  The stretching treatment may be longitudinal stretching that extends in the film longitudinal direction (film transport direction), and may be lateral stretching or oblique stretching that extends in the film width direction. Examples of the longitudinal stretching method include inter-roll stretching using a roll, compression stretching, stretching using a chuck (clip), and the like, and examples of the lateral stretching method include a tenter method. As the stretching treatment, either a wet stretching method or a dry stretching method can be adopted. However, it is preferable to use the dry stretching method because the stretching temperature can be selected from a wide range.

  The stretching temperature is set to be equal to or higher than the temperature at which the PVA-based resin film 7 and the entire base film 30 can be stretched, and preferably − of the phase transition temperature (melting point or glass transition temperature) of the base film 30. It is in the range of 30 ° C to + 30 ° C, more preferably in the range of -30 ° C to + 5 ° C, and still 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.

  If the stretching temperature is lower than the phase transition temperature of −30 ° C., high-strength stretching exceeding 5 times is difficult to achieve, or the fluidity of the base film 30 is too low and the stretching treatment 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. Since it is easier to achieve a high draw ratio of more than 5 times, the drawing temperature is within the above range, and more preferably 120 ° C. or higher.

  As a heating method of the laminated film 200 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); And a method of heating the roll itself; a heater heating method (a method in which infrared heaters, halogen heaters, panel heaters and the like are installed above and below the laminated film 200 and heated by radiant heat) and the like. In the inter-roll stretching method, the zone heating method is preferable from the viewpoint of the uniformity of the stretching temperature.

  The stretching temperature means the atmospheric temperature in the zone (for example, in the heating furnace) in the case of the zone heating method, and also means the atmospheric temperature in the furnace in the case of heating in the furnace even in the heater heating method. Moreover, in the case of the method of heating roll itself, the surface temperature of a roll is meant.

  Prior to the stretching step S30, a preheat treatment step for preheating the laminated film 200 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 S30. The heat setting process is a process in which heat treatment is performed at a temperature equal to or higher than the crystallization temperature while maintaining the tensioned state with the end of the stretched film 300 held by a clip. Crystallization of the PVA resin 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.

(2) Dyeing step S40
Referring to FIG. 6, this step is a step of forming polarizing film (polarizer layer) 5 by dyeing PVA resin film 7 ′ of stretched film 300 with a dichroic dye and adsorbing and orienting it. Through this step, a polarizing laminated film 400 in which the polarizing film 5 is laminated on one side or both sides of the base film 30 ′ 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 S40 can be usually performed by immersing the stretched film 300 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 S40 can be performed before the stretching step S30, or these steps can be performed simultaneously, but the dichroic dye adsorbed on the PVA resin film can be favorably oriented. It is preferable to carry out the dyeing step S40 after subjecting the laminated film 200 to at least some degree of stretching treatment.

  The dyeing step S40 can include a cross-linking treatment step 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 0.5 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 S40. 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 400 can be, for example, 30 μm or less, and further 20 μm or less. However, from the viewpoint of thinning the polarizing plate, the thickness is preferably 10 μm or less, more preferably 7 μm or less. It is. By setting the thickness of the polarizing film 5 to 10 μm or less, a thin polarizing laminated film 400 can be configured. The thickness of the polarizing film 5 is usually 2 μm or more.

(3) 1st bonding process S50
With reference to FIG. 7, this step is performed on the polarizing film 5 of the polarizing laminated film 400, that is, on the surface opposite to the base film 30 ′ side of the polarizing film 5 through the first adhesive layer 15. 1 is a process of obtaining a polarizing laminated film 500 with a protective film by laminating 1 protective film 10.

  In addition, when the polarizing laminated film 400 has the polarizing film 5 on both surfaces of the base film 30 ′, the first protective film 10 is usually bonded to the polarizing films 5 on both surfaces. 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 an epoxy compound (a compound having one or more epoxy groups in the molecule) and an oxetane compound (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.

(4) Peeling step S60
With reference to FIG. 8, this process is a process of peeling off and removing base film 30 'from the polarizing laminated film 500 with a protective film, and obtaining the polarizing plate 1 with a single-sided protective film. When the polarizing laminated film 400 has the polarizing film 5 on both surfaces of the base film 30 ′ and the first protective film 10 is bonded to both the polarizing films 5, one sheet is obtained by the peeling step S 60. Two polarizing plates 1 with a single-sided protective film are obtained from the polarizing laminated film 400.

  The method for peeling and removing the base film 30 ′ is not particularly limited, and can be peeled by the same method as the separator (peeling film) peeling step performed with a normal pressure-sensitive adhesive polarizing plate. Substrate film 30 'may peel immediately after 1st bonding process S50 as it is, and after 1st bonding process S50, it will wind up in roll shape once, and will peel off, unwinding in the subsequent process. May be.

(5) 2nd bonding process S70
With reference to FIG. 9, this process is further performed on the polarizing film 5 of the polarizing plate 1 with a single-sided protective film, that is, on the surface opposite to the first protective film 10 bonded in the first bonding process S50. 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 described above, although a polarizing film (polarizing laminated film, polarizing laminated film with protective film) using a PVA resin film (laminated film) supported by a base film has been described, and further a method for producing a polarizing plate, Even when a single PVA-based resin film that is not supported by the base film is used, a polarizing film can be produced in the same manner by performing a stretching treatment and 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. 1 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.

  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. The measurement method of the water removal rate V (30) and the average removal rate Vave (30-10) in the drying process of each example and comparative example basically follows the above description, but specifically, as follows. It was.

[Measurement of removal rate V (30) and average removal rate Vave (30-10)]
The removal rate V (30) and the average removal rate Vave (30-10) are obtained from a moisture content decrease curve (fitting curve) obtained by plotting the moisture content of the coating layer against the elapsed time from the start of the drying process. , Respectively, according to the above formulas [a] and [b]. Acquisition of moisture content measurement data was performed at intervals of 2% by weight. For measurement of the moisture content of the coating layer, an IR moisture meter (infrared multi-component meter) “IRMA-5162S” manufactured by CHINO Co., Ltd. was used.

  For the calibration curve, ten film samples with different moisture contents were prepared, and the moisture content of these samples was measured according to the above formula [c] (dry weight method), and the IR moisture meter “IRMA-5162S” was measured. It was obtained by measuring the intensity of infrared absorption derived from water, plotting the correspondence between the obtained water content and the intensity of infrared absorption, and approximating with a linear expression. The acquisition range of the calibration curve was a moisture content range of 40 to 3% by weight. As the film sample, a coating film having a coating layer formed by coating an aqueous solution containing polyvinyl alcohol (PVA) on the same substrate film as that used in each example and comparative example was used. This aqueous solution contains only water as a volatile component.

In measuring the water content according to the above formula [c] (dry weight method), the following (1), (2) and (3) are measured in order for each of the 10 film samples, and the following formula [c ']:
Water content = {[measured value of (1) −measured value of (2)] / [measured value of (1) −measured value of (3)]} × 100 [c ′]
The water content was determined according to the dry weight method. The following formula [c ′] and the above formula [c] are synonymous.

(1) Measure the weight of the coated film as a film sample (before drying),
(2) Measure the weight of the coated film after drying at 105 ° C. for 2 hours,
(3) The coating layer is peeled and removed, and the weight of the remaining base film is measured.

  In addition, the final moisture content W2 (the moisture content of the coating layer (PVA film) at the end of the drying step) in each of the examples and comparative examples is the value measured by the IR moisture content meter “IRMA-5162S”. It is calculated by substituting into the linear equation of the line.

<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 (coating process, drying process)
PVA 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 PVA aqueous solution having a concentration of 7.5% by weight. Was prepared. The primer layer surface of the base film having the primer layer prepared in (1) was coated with the PVA aqueous solution having a concentration of 7.5% by weight using a die coater to form a coating layer having a thickness of 130 μm (coating) Construction process).

  Thereafter, the coating layer was dried by blowing hot air at 70 ° C. (drying step). At this time, while monitoring the moisture content during drying with the IR moisture meter “IRMA-5162S” (as described above, measurement data was acquired at intervals of 2 wt% moisture content), the wind speed of the hot air was changed. Thus, the removal rate V (30) was controlled to be 1.30% by weight / second. Thereafter, drying was continued while adjusting the wind speed of the hot air so that the average removal speed Vave (30-10) was 1.35 wt% / second, and when the final moisture content W2 reached 4.86 wt%. The drying process was terminated to obtain a laminated film composed of base film / primer layer / PVA film (PVA layer). The thickness of the PVA film was 9.2 μm.

(3) Production of stretched film (stretching process)
The laminated film produced in the above (2) was subjected to 5.3 times free end uniaxial stretching at 160 ° C. using a floating longitudinal uniaxial stretching apparatus to obtain a stretched film. The thickness of the PVA film after stretching was 5.1 μm.

(4) Production of polarizing laminated film (dyeing process)
The stretched film prepared in (3) above is dyed at 30 ° C. containing iodine and potassium iodide (0.6 parts by weight of iodine and 10.0 parts by weight of potassium iodide per 100 parts by weight of water). Then, after the PVA film was dyed for about 180 seconds, excess dyeing aqueous solution was washed away with pure water at 10 ° C.

  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 immediately after that, moisture adhered to the surface was removed using an air blower to obtain a polarizing laminated film including a polarizing film.

(5) Production of polarizing plate with single-sided protective film (bonding process, peeling process)
On the polarizing film of the polarizing laminated film produced in the above (4), a protective film [triacetylcellulose] is passed through an adhesive layer made of an ultraviolet curable adhesive (“KR-75T” manufactured by ADEKA Corporation). A transparent protective film (“KC-2UAW” manufactured by Konica Minolta Opto Co., Ltd.) made of (TAC) was bonded. Next, the adhesive layer was cured by irradiating ultraviolet rays using a high-pressure mercury lamp to obtain a polarizing laminated film with a protective film (first bonding step). Then, the base film was peeled and removed from the obtained polarizing laminated film with a protective film to obtain a polarizing plate with a single-side protective film (peeling step).

(6) Measurement of polarization degree About the obtained polarizing plate with a single-sided protective film, using an absorptiometer ("V7100" manufactured by JASCO Corporation), the visibility corrected single transmittance Ty and the visibility corrected polarization degree Py was measured. In the measurement, a polarizing plate sample with a single-sided protective film was set so that incident light was irradiated on the polarizing film side. Table 1 shows the measurement results of Ty and Py. The polarization performance was good.

<Examples 2 to 12>
A single-sided protective film in the same manner as in Example 1 except that the removal speed V (30) and the average removal speed Vave (30-10) in the drying process were adjusted as shown in Table 1 by adjusting the wind speed of the hot air. An attached polarizing plate was produced. Table 1 shows the measurement results of Ty and Py. The polarization performance was good.

<Example 13>
A drying step was performed in the same manner as in Example 1 to obtain a laminated film having a final water content W2 of 4.86% by weight of the PVA film. The laminated film was allowed to stand for several hours in an environment of 25 ° C. and 55% RH, and then further dried while blowing hot air at 80 ° C. until the water content reached 1.05% by weight. Thereafter, in the same manner as in Example 1, a stretching process, a dyeing process, a bonding process, and a peeling process were performed to obtain a polarizing plate with a single-side protective film.

  Table 1 shows the measurement results of Ty and Py. Even if additional drying was performed, the polarization performance was the same as in Example 1 and remained good. Control of the removal rate V (30) and / or the average removal rate Vave (30-10) is important for improving the polarization performance, and additional drying after the drying step and the resulting decrease in moisture content are It was confirmed that the performance was not affected.

<Comparative Examples 1-2>
A single-sided protective film in the same manner as in Example 1 except that the removal speed V (30) and the average removal speed Vave (30-10) in the drying process were adjusted as shown in Table 1 by adjusting the wind speed of the hot air. An attached polarizing plate was produced. Table 1 shows the measurement results of Ty and Py. The polarization performance was inferior to that of Example 1.

<Comparative Example 3>
A drying process was performed in the same manner as in Comparative Example 2 to obtain a laminated film having a final water content W2 of 4.05% by weight of the PVA film. The laminated film was allowed to stand for several hours in an environment of 25 ° C. and 55% RH, and then further dried while blowing hot air at 80 ° C. until the water content reached 1.05% by weight. Thereafter, in the same manner as in Comparative Example 2, a stretching step, a dyeing step, a pasting step, and a peeling step were performed to obtain a polarizing plate with a single-side protective film.

  Table 1 shows the measurement results of Ty and Py. Even if additional drying was performed, the polarization performance was not different from that of Comparative Example 2. Control of the removal rate V (30) and / or the average removal rate Vave (30-10) is important for improving the polarization performance, and additional drying after the drying step and the resulting decrease in moisture content are It was confirmed that the performance was not affected.

<Comparative example 4>
After performing a drying process and then additional drying in the same manner as in Comparative Example 3 to obtain a laminated film having a water content of 1.05% by weight of the PVA film, the laminated film was subjected to an environment of 25 ° C. and 70% RH. The moisture absorption process (re-humidification process) which raises the moisture content of a PVA film to 5.05 weight% was performed. Thereafter, in the same manner as in Comparative Example 3, a stretching step, a dyeing step, a pasting step, and a peeling step were performed to obtain a polarizing plate with a single-side protective film.

  Table 1 shows the measurement results of Ty and Py. Even when additional drying and moisture absorption treatment (rehumidification treatment) were performed, the polarization performance was not different from that of Comparative Example 2. Control of the removal rate V (30) and / or the average removal rate Vave (30-10) is important for improving the polarization performance, and additional drying and moisture absorption (humidity adjustment) after the drying step is completed. It was confirmed that it does not affect

  In Table 1, when additional processing was performed after the drying process, the processing content was described in the “addition processing” column. In the column of “final moisture content W2” in Table 1, the moisture content of the PVA film at the end of the drying process is shown. When additional processing is performed, the additional processing is performed in the “additional processing” column. The moisture content after the test is shown in parentheses.

  Moreover, the graph which plotted the relationship between the removal rate V (30) in the drying process and the visibility correction polarization degree Py of the obtained polarizing plate with a single-sided protective film in each Example and Comparative Example is shown in FIG. FIG. 11 is a graph plotting the relationship between the average removal speed Vave (30-10) and the visibility correction polarization degree Py of the obtained polarizing plate with a single-sided protective film. FIG. 12 is a graph plotting the relationship between the visibility-corrected single transmittance Ty and the visibility-corrected polarization degree Py of the polarizing plate with a single-side protective film obtained in each example and comparative example.

  1 polarizing plate with single-sided protective film, 2 polarizing plate with double-sided protective film, 5 polarizing film, 6 coating layer, 7 PVA-based resin film (PVA-based resin layer), 7 'stretched PVA-based resin film (PVA-based resin) Layer), 10 first protective film, 15 first adhesive layer, 20 second protective film, 25 second adhesive layer, 30 base film, 30 ′ stretched base film, 100 coating film, 200 laminates Film, 300 stretched film, 400 polarizing laminated film, 500 polarizing laminated film with protective film.

Claims (5)

Including a drying step for removing water from an aqueous solution containing a polyvinyl alcohol-based resin and having a water content of more than 30% by weight;
The manufacturing method of the polyvinyl-alcohol-type resin film whose removal rate of water when a moisture content is 30 weight% in the said drying process is 0.01-1.8 weight% / sec. Including a drying step for removing water from an aqueous solution containing a polyvinyl alcohol-based resin and having a water content of more than 30% by weight;
The manufacturing method of the polyvinyl-alcohol-type resin film whose average removal rate of the water in the said drying process is 0.01-1.8 weight% / second in the moisture content of 30-10 weight%.   The manufacturing method of Claim 1 or 2 which further includes the process of forming the coating layer of the said aqueous solution on a base film before the said drying process. The process of obtaining a polyvinyl alcohol-type resin film with the manufacturing method of any one of Claims 1-3,
Stretching the polyvinyl alcohol resin film to obtain a stretched film;
Obtaining a polarizing film from the stretched film;
The manufacturing method of a polarizing film containing.   The manufacturing method of Claim 4 whose thickness of the said polarizing film is 10 micrometers or less.