KR20210074200A - Polarizing plate and method for manufacturing same - Google Patents

Abstract

An object of the present invention is to provide a polarizing plate, which does not change color even in a high temperature (105 DEG C) and long-term (600 hours or more) endurance test. The present invention provides the polarizing plate, which has a single color b value of 2.7 or more and an absorbance of 4.5 or less at a wavelength of 700 nm.

Description

Polarizing plate and its manufacturing method

The present invention relates to a polarizing plate and a method for manufacturing the same.

Patent Documents 1 and 2 propose a polarizing film having a small color change even after heating at 120°C for 100 hours.

Patent Document 3 discloses a polarizing film that provides a polarizing plate having excellent durability against a heat cycle test and has an orthogonal color to be neutral gray.

Patent Document 4 proposes an optical laminate excellent in the yellowing inhibitory effect even when exposed to a high-temperature environment.

Patent Document 1: Japanese Patent Laid-Open No. 2004-226707 Patent Document 2: Japanese Patent Laid-Open No. 2007-304626 Patent Document 3: Japanese Patent Application Laid-Open No. 2013-148806 Patent Document 4: Japanese Patent Laid-Open No. 2018-025765

In the polarizing plate of patent documents 1-4, discoloration may arise in the durability test in high temperature (for example, 105 degreeC) which is more severe conditions, and a long time (for example, 600 hours or more).

An object of the present invention is to provide a polarizing plate that does not cause discoloration even in a durability test at high temperature (105° C.) and for a long time (600 hours or more).

This invention provides the following polarizing plate and its manufacturing method.

[1] A polarizing plate having a single color b-value of 2.7 or more and an absorbance of 4.5 or less at a wavelength of 700 nm.

[2] The polarizing plate according to [1], comprising a polarizer and a first thermoplastic resin film bonded to one side thereof via an adhesive.

[3] The polarizing plate according to [2], further comprising a second thermoplastic resin film bonded via an adhesive on a side opposite to the first thermoplastic resin film side of the polarizer.

[4] The polarizing plate according to [2] or [3], wherein the adhesive is a water-based adhesive.

[5] The polarizing plate according to any one of [1] to [4], wherein the content of the zinc element in the polarizing plate is 150 ppm or more.

[6] An in-vehicle display device comprising the polarizing plate according to any one of [1] to [5].

[7] A method for producing the polarizing plate according to [2], comprising:

The polarizer includes a polyvinyl alcohol-based resin film,

A method for manufacturing a polarizing plate comprising a washing step of washing the polyvinyl alcohol-based resin film with a washing solution, and not washing with a washing solution having a temperature exceeding 22°C.

[8] The method for producing a polarizing plate according to [7], further comprising a drying step of drying the polyvinyl alcohol-based resin film at a temperature of 96°C or higher.

[9] The method for producing a polarizing plate according to [7] or [8], further comprising a bonding step of bonding the first thermoplastic resin film to one side of the polarizer through an adhesive, and drying the adhesive at a temperature of 85°C or higher .

ADVANTAGE OF THE INVENTION According to this invention, the polarizing plate which does not produce discoloration even in the durability test at high temperature (105 degreeC) and a long time (600 hours or more) can be provided.

1 is a schematic cross-sectional view of a polarizing plate according to an embodiment of the present invention.
2 is a schematic cross-sectional view of a polarizing plate according to an embodiment of the present invention.
It is a cross-sectional schematic diagram which shows the arrangement example of the apparatus used for a polarizer manufacturing process.

EMBODIMENT OF THE INVENTION Hereinafter, although embodiment of this invention is described, referring drawings, this invention is not limited to the following embodiment. In all the drawings below, the scales are appropriately adjusted for easy understanding of each component, and the scale of each component shown in the drawings does not necessarily coincide with the scale of the actual component.

<Polarizer>

A polarizing plate according to an aspect of the present invention has a single color b value of 2.7 or more and an absorbance at a wavelength of 700 nm of 4.5 or less. The polarizing plate, when the single color b value is 2.7 or more, by making the absorbance at a wavelength of 700 nm 4.5 or less, a durability test at a high temperature (105° C.) and a long time (600 hours or more) (hereinafter also referred to as an endurance test for short) ) also tends to be difficult to cause discoloration. In this specification, the endurance test refers to an endurance test performed according to the method described in the column of Examples to be described later. That no discoloration occurs means that yellowing is not visually recognized when the polarizing plate is observed according to the method described in the column of Examples to be described later. As for the polarizing plate of this invention, in an endurance test, Preferably it is up to 1000 hours, More preferably, discoloration does not arise until 1400 hours.

Generally, the higher the absorbance at a wavelength of 700 nm of the polarizing plate, the less likely to be discoloration, and the lower the single color b value of the polarizing plate, the less likely to be yellowing. In the durability test, the polyiodine complex I ₅ ^{− in} the polarizer is disintegrated and polyvinyl alcohol in the polarizer is polyenized by heating, and a decrease in absorbance at a wavelength of 700 nm and an increase in the color b value tend to occur. have. Therefore, in order to suppress discoloration in the durability test of a polarizing plate, the one where the absorbance at the wavelength of 700 nm of a polarizing plate is high, and the one where the single color|color b value is low was considered advantageous. However, unexpectedly, by the present inventors, in a more severe endurance test at high temperature (105 ° C.) and for a long time (600 hours or more), the single color b value of the polarizing plate is 2.7 or more, and the absorbance at a wavelength of 700 nm is 4.5 or less. It was discovered that discoloration can be suppressed by this. A polarizing plate having a single hue b value of 2.7 or more and an absorbance at a wavelength of 700 nm of 4.5 or less is a novel thing not disclosed in any of Patent Documents 1-4.

The single hue b value of a polarizing plate becomes like this. Preferably it is 2.9 or more, More preferably, it is 3.1 or more, More preferably, it is 3.3 or more, Especially preferably, it is 3.5 or more. The single hue b value of a polarizing plate is 4.1 or less normally, for example, 3.9 or less may be sufficient.

The single color b value of the polarizing plate is the b value in the Lab color system in the single polarizing plate. The b value is calculated by the following formula from the tristimulus values X, Y and Z specified in JIS Z 8722:2009 "Measuring method of color - reflected and transmitted object color".

b value = 7.0(Y-0.847Z)/Y ^1/2

The single color b value of a polarizing plate can be measured according to the measuring method demonstrated in the column of the Example mentioned later.

The absorbance in the wavelength of 700 nm of a polarizing plate becomes like this. Preferably it is 4.4 or less, More preferably, it is 4.3 or less. The absorbance at a wavelength of 700 nm of the polarizing plate is usually 3.9 or more, for example, 4.1 or more, or 4.2 or more.

The absorbance at a wavelength of 700 nm of the polarizing plate can be measured using a light absorption spectrometer such as an ultraviolet and visible spectrophotometer, and is calculated from the following formula.

Absorbance at wavelength 700 nm = -log[{TD transmittance (%) at wavelength 700 nm}/100]

The incident light is measured using polarized light parallel to the absorption axis direction of the polarizer. In this formula, TD transmittance|permeability is the transmittance|permeability when the direction of the polarization|polarized-light emitted from a Glen Thompson prism and the transmission axis of a polarizer are made orthogonal.

The absorbance at a wavelength of 700 nm of the polarizing plate can be measured according to the measurement method described in the section of Examples to be described later.

The single color b value within the above range and the absorbance at a wavelength of 700 nm can be determined by adjusting the temperature of the washing liquid in the washing process in the polarizer manufacturing process described later, adjusting the drying temperature in the drying process, and bonding the polarizer and the thermoplastic resin film. It can be obtained by controlling the temperature for drying the adhesive for

The polarizing plate may contain a zinc element. When the polarizing plate contains a zinc element, the zinc element is preferably contained in at least either one of the polarizer and the adhesive. When a polarizing plate contains a zinc element, 150 ppm or more may be sufficient as content of the zinc element in a polarizing plate, for example. When content of the zinc element in a polarizing plate is 150 ppm or more, it exists in the tendency which becomes easy to suppress discoloration in an endurance test. From a viewpoint of suppressing discoloration, content of the zinc element in a polarizing plate becomes like this. Preferably it is 200 ppm or more, More preferably, it is 250 ppm or more. On the other hand, content of the zinc element in a polarizing plate is 1000 ppm or less normally. The content of the zinc element is measured in accordance with the measurement method described in the section of Examples to be described later. Content of the zinc element in a polarizing plate can be made into the said range by adjusting the zinc concentration in a polarizer and/or an adhesive agent, for example.

1 shows a polarizing plate 10 according to an embodiment of the present invention. As shown in FIG. 1 , the polarizing plate 10 may include a polarizer 12 and a first thermoplastic resin film 11 bonded to one side thereof via an adhesive. As shown in FIG. 2 , the polarizing plate 10 may further include a second thermoplastic resin film 13 bonded through an adhesive on the opposite side to the first thermoplastic resin film 11 side of the polarizer 12 . . Hereinafter, a 1st thermoplastic resin film and a 2nd thermoplastic resin film may be generically called a thermoplastic resin film. A polarizing plate can further be equipped with the adhesive layer mentioned later, an optical function layer, and a protection film on the opposite side to the polarizer side of a thermoplastic resin film.

A polarizing plate can be used for an image display apparatus. The image display device may be any, such as a liquid crystal display device and an organic EL display device, but is preferably a liquid crystal display device. A liquid crystal display device is equipped with the liquid crystal panel provided with the liquid crystal cell as an image display element, and a backlight. In constructing a liquid crystal display device, a polarizing plate may be used for the polarizing plate arrange|positioned at the visual recognition side, may be used for the polarizing plate arrange|positioned at the backlight side, and may be used for both the polarizing plate of the visual recognition side and the backlight side.

When a polarizing plate is equipped with a 1st thermoplastic resin film and a 2nd thermoplastic resin film, a polarizing plate can be bonded to an image display apparatus so that a 1st thermoplastic resin film may become the outer side of an image display apparatus. When the polarizing plate includes a first thermoplastic resin film and a second thermoplastic resin film, the polarizing plate includes a light-transmitting member disposed on the first thermoplastic resin film side of the polarizing plate, and a display device disposed on the second thermoplastic resin film side of the polarizing plate. It is suitable for the vehicle-mounted display apparatus provided in this order. The translucent member may be a glass plate, a translucent resin film, or the like.

[Polarizer]

The polarizer is an absorption type polarizer having a property of absorbing linearly polarized light having an oscillation plane parallel to the absorption axis and transmitting linearly polarized light having an oscillation plane perpendicular to the absorption axis (parallel to the transmission axis). The polarizer may be, for example, a polarizer in which a dichroic dye such as iodine is adsorbed and oriented to a uniaxially stretched polyvinyl alcohol-based resin film.

The thickness of a polarizer is 65 micrometers or less normally, Preferably it is 50 micrometers or less, More preferably, it is 35 micrometers or less, More preferably, it is 30 micrometers or less. The thickness of a polarizer is 2 micrometers or more normally, Preferably it is 5 micrometers or more, More preferably, it is 10 micrometers or more, More preferably, it is 15 micrometers or more. The thickness of the polarizer can be controlled, for example, by selection of a polyvinyl alcohol-based resin film, adjustment of draw ratio, and the like.

An example of a polarizer manufacturing process is demonstrated with reference to FIG. The polyvinyl alcohol-based resin film 110, which is a raw film unwound from the feeding roll 111, is then guided to a swelling tank 113 using water as a swelling bath, where it is immersed in a swelling bath (water) for swelling treatment. is carried out (swelling process). The swollen film is guided to a dyeing tank 115 using an aqueous solution containing iodine as a dyeing bath, where it is dyed and iodine is adsorbed (dyeing step). Thereafter, it is guided to a crosslinking tank 117 using an aqueous solution containing boric acid as a treatment bath, and the polyvinyl alcohol-based resin to which iodine has been adsorbed is crosslinked with boric acid to fix iodine (crosslinking step). Next, the film is washed with the washing tank 119 (washing process) and dried in the drying furnace 123 (drying process) to obtain the polarizer 130 . The polarizer 130 is wound around the winding roll 127 . The polyvinyl alcohol-based resin film is uniaxially stretched in any one or more steps of the polarizer manufacturing process, more specifically, in any one or more steps from the swelling process to the crosslinking process.

Each treatment process can be performed continuously by conveying the polyvinyl alcohol-type resin film which is a raw film continuously along the film conveyance path|route of a polarizer manufacturing apparatus. The film conveyance path is equipped with the facilities (processing tank, a furnace, etc.) for implementing the said various processing process in these implementation order.

A film conveyance path|route can be constructed by arrange|positioning a guide roll, a nip roll, etc. at appropriate positions other than the said installation. For example, a guide roll can be arrange|positioned before and after each processing tank, or in a processing tank, and can perform introduction and immersion of the film with respect to a processing tank by this, and take-out from a processing tank. More specifically, a film can be immersed in each processing tank by providing two or more guide rolls in each processing tank, and conveying a film along these guide rolls.

As polyvinyl alcohol-type resin which comprises a polyvinyl alcohol-type resin film, what saponified polyvinyl acetate-type resin is mentioned, for example. As polyvinyl acetate-type resin, the copolymer of vinyl acetate and other monomer copolymerizable to this other than polyvinyl acetate which is a homopolymer of vinyl acetate is illustrated. Examples of the other monomer copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and (meth)acrylamides having an ammonium group. The degree of saponification of the polyvinyl alcohol-based resin is usually about 85 mol% or more, preferably about 90 mol% or more, and more preferably about 99 mol% or more. In this specification, "(meth)acryl" means at least one selected from acryl and methacryl. It is the same also about "(meth)acryloyl."

The polyvinyl alcohol-based resin may be modified, for example, polyvinyl formal, polyvinyl acetal, polyvinyl butyral, etc. modified with aldehydes may also be used.

The average degree of polymerization of polyvinyl alcohol-type resin becomes like this. Preferably it is 100 or more and 10000 or less, More preferably, they are 1500 or more and 8000 or less, More preferably, they are 2000 or more and 5000 or less. The average degree of polymerization of polyvinyl alcohol-type resin can be calculated|required based on JISK6726 (1994). When the average degree of polymerization is within the above range, polarization performance and film processability tend to be excellent.

The thickness of the polyvinyl alcohol-based resin film, which is a raw film, may be, for example, 10 µm or more and 150 µm or less, preferably 15 µm or more and 100 µm or less, and more preferably 20 µm or more and 80 µm or less. The length of the polyvinyl alcohol-type resin film which is a raw film in the width direction may be 600 mm or more and 5000 mm or less, for example.

The polyvinyl alcohol-based resin film, which is a raw film, can be prepared, for example, as a roll (wound product) of a long unstretched or stretched polyvinyl alcohol-based resin film. In this case, a polarizer is also obtained as an elongate object.

(1) swelling process

The swelling treatment in this step is a treatment performed as needed for the purpose of removing foreign substances from the polyvinyl alcohol-based resin film, which is a raw film, removing a plasticizer, imparting dichromaticity, plasticizing the film, etc., specifically, water It may be a process of immersing the polyvinyl alcohol-based resin film 110 in a swelling tank containing a treatment liquid containing. The said film may be immersed in one swelling tank, and may be immersed in two or more swelling tanks sequentially. Before a swelling process, at the time of a swelling process, or before a swelling process and at the time of a swelling process, you may perform a uniaxial stretching process with respect to a film.

The treatment liquid accommodated in the swelling tank may be water (eg, pure water) or an aqueous solution to which a water-soluble organic solvent such as alcohol is added. As described above, the treatment liquid accommodated in the swelling tank may contain a zinc salt.

The temperature of the processing liquid accommodated in the swelling tank at the time of immersing a film is 10 degrees C or more and 70 degrees C or less normally, Preferably it is 15 degrees C or more and 50 degrees C or less, The immersion time of a film is 10 seconds or more and 600 seconds or less normally, Preferably Usually 20 seconds or more and 300 seconds or less.

(2) Dyeing process

The dyeing treatment in this step is a treatment performed for the purpose of adsorbing and orienting the dichroic dye to the polyvinyl alcohol-based resin film, specifically, polyvinyl alcohol in a dyeing tank containing a treatment liquid containing the dichroic dye. It may be a treatment in which the system resin film is immersed. The said film may be immersed in one dyeing tank, and may be immersed sequentially in two or more dyeing tanks. In order to improve the dyeability of a dichroic dye, the uniaxial stretching process to a certain extent may be given to the film used for a dyeing process at least. Instead of the uniaxial stretching treatment before the dyeing treatment, or in addition to the uniaxial stretching treatment before the dyeing treatment, a uniaxial stretching treatment may be performed at the time of the dyeing treatment.

The dichroic dye may be iodine or a dichroic organic dye. Specific examples of the dichroic organic dye include 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, Supra Blue G, Supra Blue GL, Super Orange GL, Direct Includes Sky Blue, Direct First Orange S, and First Black. A dichroic dye may be used individually by 1 type, and may use 2 or more types together.

When using an iodine as a dichroic dye, the aqueous solution containing an iodine and potassium iodide can be used for the processing liquid accommodated in a dyeing tank. Instead of potassium iodide, other iodides, such as zinc iodide, may be used, and potassium iodide and another iodide may be used together. In addition, compounds other than iodide, for example, boric acid, zinc chloride, cobalt chloride, etc. may coexist. When adding boric acid, it is distinguished from the crosslinking process mentioned later at the point containing an iodine. Content of the iodine in the said aqueous solution is 0.01 mass part or more and 1 mass part or less per 100 mass parts of water normally. In addition, content of iodides, such as potassium iodide, is 0.5 mass part or more and 20 mass parts or less per 100 mass parts of water normally.

The temperature of the processing liquid accommodated in the dyeing tank at the time of immersing a film is 10 degreeC or more and 45 degrees C or less normally, Preferably it is 10 degreeC or more and 40 degrees C or less, More preferably, it is 20 degreeC or more and 35 degrees C or less, and immersion of a film The time may be, for example, 20 seconds or more and 600 seconds or less, and preferably 20 seconds or more and 300 seconds or less.

When using a dichroic organic dye as a dichroic dye, the aqueous solution containing a dichroic organic dye can be used for the processing liquid accommodated in a dyeing tank. Content of the dichroic organic dye in the said aqueous solution is 1x10 ^-4 mass part or more and 10 mass parts or less per 100 mass parts of water, Preferably they are 1x10 ^-3 mass part or more and 1 mass part or less. The dyeing tank may be made to coexist with a dyeing aid etc., For example, inorganic salts, such as sodium sulfate, surfactant, etc. may be made to contain. A dichroic organic dye may be used individually by 1 type, and may use 2 or more types together. The temperature of the treatment liquid accommodated in the dyeing tank at the time of immersing the film is, for example, 20°C or more and 80°C or less, preferably 25°C or more and 50°C or less, and the immersion time of the film is usually 30 seconds or more and 600 seconds or less, preferably It is usually 60 seconds or more and 300 seconds or less.

(3) crosslinking process

The crosslinking treatment of treating the polyvinyl alcohol-based resin film with a crosslinking agent after the dyeing step is a treatment performed for the purpose of water resistance or color adjustment by crosslinking, specifically, a dyeing step in a treatment solution accommodated in a crosslinking tank containing a crosslinking agent It may be a treatment for immersing the later film. The said film may be immersed in one crosslinking tank, and may be immersed in two or more crosslinking tanks sequentially. You may perform a uniaxial stretching process at the time of a crosslinking process.

As a crosslinking agent, a boric acid, a glyoxal, glutaraldehyde, etc. are mentioned, A boric acid is used preferably. Two or more types of crosslinking agents can also be used together. Content of the boric acid in the process liquid accommodated in a crosslinking tank is 0.1 mass part or more and 15 mass parts or less per 100 mass parts of water normally, Preferably they are 1 mass part or more and 10 mass parts or less. When a dichroic dye is an iodine, it is preferable that the processing liquid accommodated in a crosslinking tank contains iodide in addition to boric acid. Content of the iodide in the process liquid accommodated in a crosslinking tank is 0.1 mass part or more and 15 mass parts or less per 100 mass parts of water normally, Preferably they are 5 mass parts or more and 12 mass parts or less. Potassium iodide, zinc iodide, etc. are mentioned as an iodide. Further, a compound other than iodide, such as zinc chloride, cobalt chloride, zirconium chloride, sodium thiosulfate, potassium sulfite, sodium sulfate and the like, may coexist in the crosslinking tank.

The temperature of the treatment liquid accommodated in the crosslinking tank at the time of immersing the film may be, for example, 30°C or more and 85°C or less, preferably 30°C or more and 60°C or less, and the immersion time of the film is, for example, 2 seconds or more and 600 seconds or less. It may be continuous, and preferably 2 seconds or more and 300 seconds or less.

In a crosslinking process, two or more sets of crosslinking tanks may be sufficient. In this case, the composition and temperature of the processing liquid accommodated in each crosslinking tank may be same or different. The processing liquid accommodated in the crosslinking tank may have the density|concentration and temperature of a crosslinking agent, iodide, etc. according to the objective of immersing a polyvinyl alcohol-type resin film. You may perform the bridge|crosslinking process for the waterproofing by bridge|crosslinking, and the bridge|crosslinking process for hue adjustment (complementary color), respectively in a plurality of steps (for example, a plurality of sets).

In general, when both crosslinking treatment for water resistance by crosslinking and crosslinking treatment for color adjustment (complementary color) are performed, a ton (complementary color tint) subjected to crosslinking treatment for color adjustment (complementary color) is disposed at the rear end do. The temperature of the processing liquid accommodated in the complementary color tone is, for example, 10 degreeC or more and 55 degrees C or less, Preferably it is 20 degreeC or more and 50 degrees C or less. Content of the crosslinking agent in the processing liquid accommodated in the complementary color tone is, for example, 1 mass part or more and 5 mass parts or less per 100 mass parts of water. The content of iodide in the treatment liquid accommodated in the complementary color tone is, for example, 3 parts by mass or more and 30 parts by mass or less per 100 parts by mass of water.

As mentioned above, in manufacturing a polarizer, a polyvinyl alcohol-type resin film is uniaxially stretched in any 1 or 2 or more steps from a swelling process to a crosslinking process (stretching process). From the viewpoint of improving the dyeability of the dichroic dye, the film provided for the dyeing process is preferably a film subjected to at least some degree of uniaxial stretching treatment, or instead of the uniaxial stretching treatment before the dyeing treatment, or in the uniaxial stretching treatment before the dyeing treatment In addition, it is preferable to perform a uniaxial stretching process at the time of a dyeing|staining process.

Any of the dry extending|stretching which extends|stretches in the air, and wet extending|stretching which extend|stretches in a tank may be sufficient as a uniaxial stretching process, and these both may be performed. The uniaxial stretching treatment may be inter-roll stretching in which longitudinal uniaxial stretching is performed by applying a circumferential speed difference between two nip rolls, hot roll stretching, tenter stretching, etc., but preferably includes inter-roll stretching. The draw ratio on the basis of a raw film (in the case of performing an extending|stretching process in 2 or more steps, these cumulative draw ratios) is about 3 times or more and 8 times or less. In order to provide favorable polarization characteristics, a draw ratio becomes like this. Preferably it is 4 times or more, More preferably, it is set to 5 times or more.

(4) cleaning process

The washing treatment in this step is a treatment carried out as needed for the purpose of removing a drug such as an excess crosslinking agent or a dichroic dye adhering to the polyvinyl alcohol-based resin film, and is a crosslinking step using a washing solution containing water. It is a process of washing|cleaning the polyvinyl alcohol-type resin film later. Specifically, it may be a treatment in which the polyvinyl alcohol-based resin film after the crosslinking process is immersed in the treatment liquid (washing liquid) accommodated in the cleaning tank. The said film may be immersed in one washing tank, and may be immersed in two or more washing tanks sequentially. Alternatively, the washing treatment may be a treatment of spraying a washing liquid as a shower onto the polyvinyl alcohol-based resin film after the crosslinking step, or a combination of the immersion treatment and the spraying treatment.

The washing liquid may be water (eg, pure water) or an aqueous solution to which a water-soluble organic solvent such as alcohol is added.

In the washing step, the temperature of the washing solution for washing the polyvinyl alcohol-based resin film after the crosslinking step may be, for example, 2°C or more and 40°C or less, from the viewpoint of obtaining a single color b value within the above-mentioned range and absorbance at a wavelength of 700 nm Preferably, washing is not performed with a washing liquid having a temperature exceeding 22°C.

When the polyvinyl alcohol-based resin film after the crosslinking step is immersed in a washing tank, the temperature of the washing liquid in the washing tank is preferably 2°C or more and 22°C or less, more preferably 2°C or more and 10°C or less. The time to be immersed in the washing tank may be, for example, 10 seconds or more and 100 seconds or less, and preferably 20 seconds or more and 80 seconds or less.

When the cleaning liquid is sprayed as a shower on the polyvinyl alcohol-based resin film after the crosslinking step, the temperature of the cleaning liquid may be the same or different at the central portion and both ends in the width direction of the polyvinyl alcohol-based resin film, but may be a single color From the viewpoint of the b value and the absorbance at a wavelength of 700 nm, the temperature is preferably different, and more preferably the temperature at the central portion is lower than the temperature at both ends. The temperature of the washing liquid is preferably 2°C or more and 10°C or less at the central portion and 10°C or more and 22°C or less at both ends, more preferably 3°C in the central portion, from the viewpoint of the single color b value and the absorbance at a wavelength of 700 nm. 7°C or higher and 15°C or higher and 22°C or lower at both ends.

(5) drying process

A drying process is a zone for drying the polyvinyl alcohol-type resin film after a washing|cleaning process. A drying process can be performed by introduce|transducing the said film into a drying process, conveying the polyvinyl alcohol-type resin film after a washing|cleaning process continuously, Thereby, a polarizer is obtained.

A drying process is performed using the drying means (heating means) of a film. An example where the drying means is suitable is a drying furnace. As for a drying furnace, Preferably, the temperature in a furnace is controllable. The drying furnace is, for example, a hot-air oven capable of raising the furnace temperature by supplying hot air or the like. Further, the drying treatment by the drying means may be a treatment in which the polyvinyl alcohol-based resin film after the washing step is brought into close contact with one or two or more heating elements having a convex curved surface, or a treatment in which the film is heated using a heater.

Examples of the heating element include a roll (eg, a guide roll also serving as a heating roll) having a heat source (eg, a heat source such as hot water or an infrared heater) inside and capable of increasing the surface temperature. As said heater, an infrared heater, a halogen heater, a panel heat, etc. are mentioned.

In the drying step, the temperature of the drying treatment (for example, the furnace temperature of the drying furnace, the surface temperature of the hot roll, etc.) may be, for example, 30° C. or higher, from the viewpoint of obtaining a single color b value and an absorbance at a wavelength of 700 nm within the above-mentioned range Preferably it is 96 degreeC or more. The temperature of a drying process is 100 degrees C or less normally. Although drying time in particular is not restrict|limited, For example, 30 second or more and 900 second or less may be sufficient, Preferably it is 30 second or more and 60 second or less.

One step may be sufficient as a drying process, and it may be divided into multiple steps, Preferably it is divided into 2 or more steps and 4 steps or less. When the drying process is divided into multiple stages, it is preferable that the drying temperature of at least one stage is 96° C. or higher from the standpoint of the single color b value and the absorbance at a wavelength of 700 nm. When the drying process is divided into multiple stages, it is preferable to set the temperature of the drying process so that the temperature of the subsequent stage becomes higher than that of the first stage. When the drying step is divided into multiple steps, the drying time in each step may be, for example, 10 seconds or more and 300 seconds or less, and preferably 10 seconds or more and 20 seconds or less.

A polarizer manufacturing process WHEREIN: At least 1 of the process liquid which processes with respect to a polyvinyl alcohol-type resin film may contain the zinc salt. As a processing tank which accommodates a processing liquid, a swelling tank, a dyeing tank, a crosslinking tank, a washing tank, a complementary color tank, etc. are mentioned, for example. The treatment tank for accommodating the treatment liquid containing the zinc salt is preferably a treatment tank located after the dyeing tank and before the washing tank, more preferably at least one selected from a crosslinking tank and a complementary color tank, and still more preferably having two or more crosslinking tanks. In this case, at least one selected from the last crosslinking tone and the complementary color tone. By immersing a polyvinyl alcohol-type resin film in the processing liquid containing a zinc salt, a zinc element can be made to contain the polarizer obtained. The content of the zinc element in the polarizer is the zinc element in the range described above by adjusting the concentration of the zinc salt in the treatment liquid, the time for immersing the polyvinyl alcohol-based resin film in the treatment liquid containing the zinc salt, the temperature of the treatment liquid, and the like. It can be made with the content of

Examples of the zinc salt contained in the treatment liquid include zinc halide such as zinc chloride and zinc iodide, zinc sulfate, zinc acetate, zinc nitrate, and the like. Among them, zinc nitrate is preferable because the change in tension is small. A zinc salt can be added to a process liquid as a zinc salt solution.

The concentration of the zinc salt in the treatment liquid may be different for each treatment tank, but for example, 1 part by mass or more and 10 parts by mass or less, preferably 2 parts by mass or more and 7 parts by mass or less with respect to 100 parts by mass of the treatment liquid accommodated in the treatment tank. .

Through the above process, the polarizer which carried out adsorption-oriented orientation of the dichroic dye to the polyvinyl alcohol-type resin film uniaxially stretched can be obtained.

The obtained polarizer can be conveyed to the next polarizing plate preparation process (process of bonding a thermoplastic resin film to one or both sides of a polarizer) as it is, for example.

[Thermoplastic resin film]

Examples of the thermoplastic resin film include polyolefin-based resins such as chain polyolefin-based resins (polypropylene-based resins, etc.) and cyclic polyolefin-based resins (norbornene-based resins, etc.); Cellulose ester-based resins such as triacetyl cellulose or diacetyl cellulose; polyester-based resins such as polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate; polycarbonate-based resin; (meth)acrylic resins such as polymethyl methacrylate-based resins; Alternatively, it may be a resin film having light-transmitting properties made of a mixture or copolymer thereof. The thermoplastic resin film may have a single-layer structure composed of one resin layer composed of one or two or more types of thermoplastic resins, or a multilayer structure in which a plurality of resin layers composed of one type or two or more types of thermoplastic resins are laminated. The first thermoplastic resin film and the second thermoplastic resin film may be the same or different types of thermoplastic resin films.

Examples of the chain polyolefin resin include homopolymers of chain olefins such as polyethylene resin and polypropylene resin, and copolymers composed of two or more kinds of chain olefins.

The cyclic polyolefin-based resin is a generic term for a resin containing, as a polymerization unit, a cyclic olefin having norbornene, tetracyclododecene (alias: dimethanooctahydronaphthalene) or a derivative thereof as a representative example. Examples of the cyclic polyolefin resin include a ring-opened (co)polymer of cyclic olefin and a hydrogenated product thereof, an addition polymer of cyclic olefin, a copolymer of a cyclic olefin and a chain olefin such as ethylene or propylene, or an aromatic compound having a vinyl group , and a modified (co)polymer obtained by modifying these with an unsaturated carboxylic acid or a derivative thereof.

Among them, norbornene-based resins using norbornene-based monomers such as norbornene and polycyclic norbornene-based monomers are preferably used as cyclic olefins.

Cellulose ester-type resin may be resin by which at least one part of the hydroxyl group in a cellulose was acetic acid esterified, and the mixed ester by which the acetic acid esterification was carried out partly, and the other acid esterification part is esterified. The cellulose ester-based resin is preferably an acetyl cellulose-based resin.

Examples of the acetyl cellulose-based resin include triacetyl cellulose, diacetyl cellulose, cellulose acetate propionate, and cellulose acetate butyrate.

Polyester resin is resin other than the said cellulose ester resin which has an ester bond, and what consists of polycondensate of polyhydric carboxylic acid or its derivative(s), and polyhydric alcohol is common.

Examples of the polyester-based resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polycyclohexanedimethyl terephthalate, and polycyclohexanedimethyl naphthalate. Phthalate etc. are mentioned.

Among them, polyethylene terephthalate is preferably used from the viewpoints of mechanical properties, solvent resistance, scratch resistance, cost, and the like. Polyethylene terephthalate means resin in which 80 mol% or more of a repeating unit is comprised by ethylene terephthalate, and may contain the structural unit derived from another copolymerization component.

As another copolymerization component, a dicarboxylic acid component and a diol component are mentioned.

As the dicarboxylic acid component, isophthalic acid, 4,4'-dicarboxydiphenyl, 4,4'-dicarboxybenzophenone, bis(4-carboxyphenyl)ethane, adipic acid, sebacic acid, 5-sodium A sulfoisophthalic acid, 1, 4- dicarboxy cyclohexane, etc. are mentioned.

Examples of the diol component include propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexanediol, an ethylene oxide adduct of bisphenol A, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol.

A dicarboxylic acid component and a diol component can also be used in combination of 2 or more types, respectively as needed.

Moreover, it is also possible to use together hydroxycarboxylic acids, such as p-hydroxybenzoic acid, p-hydroxyethoxybenzoic acid, and (beta)-hydroxyethoxybenzoic acid, with the said dicarboxylic acid component and a diol component.

As the other copolymerization component, a small amount of a dicarboxylic acid component and/or a diol component having an amide bond, a urethane bond, an ether bond, a carbonate bond, or the like may be used.

Polycarbonate-type resin is polyester formed from carbonic acid, glycol, or bisphenol. Especially, aromatic polycarbonate which has diphenyl alkane in a molecular chain is used preferably from a viewpoint of heat resistance, weather resistance, and acid resistance.

Examples of the polycarbonate include 2,2-bis(4-hydroxyphenyl)propane (alias bisphenol A), 2,2-bis(4-hydroxyphenyl)butane, 1,1-bis(4-hydroxyphenyl) and polycarbonates derived from bisphenols such as cyclohexane, 1,1-bis(4-hydroxyphenyl)isobutane, and 1,1-bis(4-hydroxyphenyl)ethane.

A (meth)acrylic-type resin is a polymer containing the structural unit derived from a (meth)acrylic-type monomer, and methacrylic acid ester and an acrylic acid ester are mentioned as a (meth)acrylic-type monomer.

Examples of methacrylic acid esters include methyl methacrylate, ethyl methacrylate, n-, i- or t-butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, methacrylic acid 2 -Ethylhexyl, 2-hydroxyethyl methacrylate, etc. are mentioned.

Examples of the acrylic acid ester include ethyl acrylate, n-, i- or t-butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate, and 2-hydroxyethyl acrylate.

The thermoplastic resin film is preferably a cellulose ester-based resin film or a cyclic polyolefin-based resin film.

The thermoplastic resin film may contain an additive as needed. Examples of the additive include lubricants, antiblocking agents, heat stabilizers, antioxidants, ultraviolet absorbers, antistatic agents, light resistance agents, impact resistance improving agents, surfactants, and the like.

Examples of the ultraviolet absorber include a salicylic acid ester-based compound, a benzophenone-based compound, a benzotriazole-based compound, a cyanoacrylate-based compound, and a nickel complex salt-based compound.

Either one or both of a 1st thermoplastic resin film and a 2nd thermoplastic resin film may be a protective film which has optical functions like retardation film and a brightness improvement film. For example, by stretching (uniaxial stretching or biaxial stretching, etc.) a transparent resin film made of the above material, or forming a liquid crystal layer or the like on the film, a retardation film to which an arbitrary retardation value is provided can be obtained.

A surface treatment layer (coating layer) such as a hard coat layer, an anti-glare layer, an antireflection layer, an antistatic layer, and an antifouling layer may be formed on the surface on the opposite side to the polarizer side in the thermoplastic resin film.

The thickness of the thermoplastic resin film is preferably thin from the viewpoint of reducing the thickness of the polarizing plate, but if it is too thin, the strength is lowered and the workability tends to be poor. Therefore, preferably 5 µm or more and 150 µm or less, more preferably 5 µm or more It is 100 micrometers or less, More preferably, it is 10 micrometers or more and 60 micrometers or less.

[glue]

An adhesive may be used to bond the polarizer and the thermosetting resin film. The adhesive should just express adhesive force with respect to a polarizer and a thermovirtual resin film, For example, the water-based adhesive agent which melt|dissolved or disperse|distributed the adhesive agent component in water, and the curable adhesive agent containing an active energy ray-curable compound are mentioned. When the adhesive agent considers that the surface of a polarizing film is hydrophilic, the water-based adhesive agent which melt|dissolved or disperse|distributed the adhesive agent component in water is preferable. A water-based adhesive is preferable also from a viewpoint that the thickness of the adhesive agent after hardening can be made thin. The adhesive component used as the main component of the water-based adhesive includes a polyvinyl alcohol-based resin, a urethane resin, and the like.

When using a polyvinyl alcohol-type resin as a main component of a water-based adhesive agent, the polyvinyl alcohol-type resin is obtained by saponifying polyvinyl acetate-type resin. Examples of the polyvinyl acetate-based resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and a copolymer of vinyl acetate and another monomer copolymerizable therewith. Examples of the other monomer copolymerized with vinyl acetate include unsaturated carboxylic acids, unsaturated sulfonic acids, olefins, vinyl ethers, and acrylamides having an ammonium group. The polyvinyl alcohol-based resin used for the adhesive preferably has an appropriate degree of polymerization. For example, when an aqueous solution having a concentration of 4% by mass is used, the viscosity is within the range of 4 mPa·sec or more and 50 mPa·sec or less, and further 6 mPa It is more preferable to exist in the range of sec or more and 30 mPa·sec or less.

Although the degree of saponification of the polyvinyl alcohol-based resin used for the adhesive is not particularly limited, in general, it is preferably 80 mol% or more, and more preferably 90 mol% or more. When the degree of saponification of the polyvinyl alcohol-based resin used for the adhesive is low, the water resistance of the adhesive tends to be insufficient.

As the adhesive, a modified polyvinyl alcohol-based resin is preferably used. Suitable modified polyvinyl alcohol-based resins include acetoacetyl group-modified polyvinyl alcohol-based resins, anion-modified polyvinyl alcohol-based resins, cation-modified polyvinyl alcohol-based resins, and the like. When such a modified polyvinyl alcohol-based resin is used, the effect of improving the water resistance of the adhesive is easily obtained.

The acetoacetyl group-modified polyvinyl alcohol-based resin has an acetoacetyl group (CH ₃ COCH ₂ CO-) in addition to the hydroxyl group constituting the polyvinyl alcohol skeleton, and may have other groups such as an acetyl group. This acetoacetyl group typically exists in a state in which a hydrogen atom of a hydroxyl group constituting polyvinyl alcohol is substituted. The acetoacetyl group-modified polyvinyl alcohol-based resin may be prepared by, for example, reacting polyvinyl alcohol with diketene. Since the acetoacetyl group-modified polyvinyl alcohol-based resin has an acetoacetyl group, which is a highly reactive functional group, it is preferable for improving the durability of the adhesive.

The content of the acetoacetyl group in the acetoacetyl group-modified polyvinyl alcohol-based resin is not particularly limited as long as it is 0.1 mol% or more. The content of acetoacetyl groups as used herein is a value expressed by the mole fraction of acetoacetyl groups with respect to the total amount of hydroxyl groups, acetoacetyl groups and other ester groups (acetyl groups, etc.) in the polyvinyl alcohol-based resin, expressed in %, It is sometimes referred to as “degree of acetylation”. When the degree of acetoacetylation in the polyvinyl alcohol-based resin is less than 0.1 mol%, the effect of improving the water resistance of the adhesive is not necessarily sufficient. The degree of acetoacetylation in the polyvinyl alcohol-based resin is preferably about 0.1 to 40 mol%, more preferably 1 to 20 mol%, and particularly preferably 2 to 7 mol%. When the degree of acetoacetylation exceeds 40 mol%, the effect of improving water resistance becomes small.

The anion-modified polyvinyl alcohol-based resin contains, in addition to the hydroxyl group constituting the polyvinyl alcohol skeleton, an anionic group, typically a carboxyl group (-COOH) or a salt thereof, and may contain other groups such as an acetyl group. good. The anion-modified polyvinyl alcohol-based resin can be produced by, for example, copolymerizing an unsaturated monomer having an anionic group (typically a carboxyl group) with vinyl acetate, followed by saponification. On the other hand, the cation-modified polyvinyl alcohol-based resin contains, in addition to the hydroxyl group constituting the polyvinyl alcohol skeleton, a cationic group, typically a tertiary amino group or a quaternary ammonium group, and has other groups such as an acetyl group. good to be The cation-modified polyvinyl alcohol-based resin can be produced by, for example, copolymerizing an unsaturated monomer having a cationic group (typically a tertiary amino group or a quaternary ammonium group) with vinyl acetate, followed by saponification.

The adhesive may contain two or more types of the modified polyvinyl alcohol-based resin described above, and an unmodified polyvinyl alcohol-based resin (specifically, a complete or partially saponified product of polyvinyl acetate) and the aforementioned modified polyvinyl alcohol-based resin. All polyvinyl alcohol-based resins may be included.

The polyvinyl alcohol-based resin constituting the adhesive can be appropriately selected from commercially available products. Specifically, for example, "PVA-117H" sold by Kuraray Co., Ltd., which is polyvinyl alcohol having a high degree of saponification, and "Gosenol NH-20" sold by Nippon Synthetic Chemical Co., Ltd. , acetoacetyl group-modified polyvinyl alcohol, “Gosepaima Z” series sold by Nippon Synthetic Chemical Industry Co., Ltd., and “KL-318” anion-modified polyvinyl alcohol sold by Kuraray Co., Ltd. and “KM-118”, “Kosenal T-330” sold by Nippon Synthetic Chemical Industry Co., Ltd., “CM-318” sold by Kuraray, which is cation-modified polyvinyl alcohol, "Gose Paima K-210" sold by Nippon Synthetic Chemical Industry Co., Ltd. is mentioned.

The concentration of the polyvinyl alcohol-based resin in the adhesive is not particularly limited, but since it is used in the form of an aqueous solution, the polyvinyl alcohol-based resin is in the range of 1 to 20 parts by mass relative to 100 parts by mass of water. Among them, it is more preferable to be in the range of 1 mass part or more and 15 mass parts or less, further 1 mass part or more and 10 mass parts or less, and especially 2 mass parts or more and 10 mass parts or less. When the concentration of the polyvinyl alcohol-based resin in the aqueous solution is too small, the adhesiveness tends to be lowered. On the other hand, when the concentration is too large, the optical properties of the resulting polarizing plate tend to be easily lowered. The water used for this adhesive may be pure water, ultrapure water, tap water, etc., and is not particularly limited, but pure water or ultrapure water is preferable from the viewpoint of maintaining the uniformity and transparency of the adhesive to be formed. Also, alcohol such as methanol or ethanol may be added to the aqueous adhesive solution.

A water-based adhesive containing a polyvinyl alcohol-based resin as a main component may contain a crosslinking agent. The crosslinking agent may be a compound having a functional group having reactivity with respect to the polyvinyl alcohol-based resin, and those conventionally used in polyvinyl alcohol-based adhesives may be used without any particular limitation. Examples of compounds that can serve as crosslinking agents include isocyanate compounds having at least two isocyanate groups (-NCO) in the molecule; Epoxy compound which has at least 2 epoxy groups (crosslinked -O-) in a molecule|numerator; mono- or di-aldehydes; organic titanium compounds; inorganic salts of divalent or trivalent metals such as magnesium, calcium, iron, nickel, zinc and aluminum; metal salts of glyoxylic acid; methylolmelamine and the like.

As a specific example of the isocyanate compound used as a crosslinking agent, tolylene diisocyanate, hydrogenated tolylene diisocyanate, the adduct body of trimethylol propane and tolylene diisocyanate, diphenylmethane diisocyanate, triphenylmethane triisocyanate, isophorone diisocyanate, these of ketoxime block products or phenol block products, and the like.

Specific examples of the epoxy compound used as the crosslinking agent include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, di- or tri-glycidyl ether of glycerin, and 1,6-hexanediol diglycidyl ether. Water-soluble polyamide epoxy obtained by reacting epichlorohydrin with trimethylolpropane triglycidyl ether, diglycidyl aniline, diglycidylamine, polyamide polyamine, which is a reaction product of polyalkylene polyamine and dicarboxylic acid resin etc. are mentioned.

Specific examples of monoaldehydes serving as crosslinking agents include formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, and the like. Specific examples of dialdehydes include glyoxal, malondialdehyde, succindialdehyde, and glue. Thaldialdehyde, maleindialdehyde, phthaldialdehyde, etc. are mentioned.

As for the organotitanium compound used as a crosslinking agent, various things are sold by Matsumoto Fine Chemicals. From the homepage (Internet <URL: http://www.m-chem.co.jp/products/products1.html>, searched on November 18, 2010) about the organic titanium compound of Matsumoto Fine Chemical Co., Ltd. , The water-soluble organic titanium compound suitably used in the present invention is given in the order of its canonization formula, the chemical name of Matsumoto Fine Chemical Co., Ltd., and the trade name of Matsumoto Fine Chemical Co., Ltd., as follows.

[(CH ₃ ) ₂ CHO] ₂ Ti[OCH ₂ CH ₂ N(CH ₂ CH ₂ OH) ₂ ] ₂ : Chemical name “Titandiisopropoxybis(triethanolaminate)” by Matsumoto Fine Chemicals Co., Ltd. ”, the brand name of Matsumoto Fine Chemicals Co., Ltd. “Orgatics TC-400”,

(HO) ₂ Ti[OCH(CH ₃ )COO-] ₂ (NH4 ₄ ⁺ ) ₂ : Chemical name “Titan Lactate Ammonium Salt” spoken by Matsumoto Fine Chemicals Co., Ltd., brand name of Matsumoto Fine Chemicals Co., Ltd. “Orgatics TC-300”,

(HO) ₂ Ti[OCH(CH ₃ )COOH] ₂ : Chemical name “Titan Lactate” by Matsumoto Fine Chemicals Co., Ltd., trade name “Orgatics TC-310” by Matsumoto Fine Chemicals Co., Ltd. “Orgatics TC-315”.

The metal salt of glyoxylic acid is preferably an alkali metal salt or an alkaline earth metal salt, and examples thereof include sodium glyoxylate, potassium glyoxylate, magnesium glyoxylate, calcium glyoxylate, and the like.

Among these crosslinking agents, epoxy compounds including the above-mentioned water-soluble polyamide epoxy resin, aldehydes, methylolmelamine, alkali metals or alkaline earth metal salts of glyoxylic acid, etc. are preferably used.

The crosslinking agent is preferably dissolved in water together with the polyvinyl alcohol-based resin to form an adhesive. However, as described below, since the amount of the crosslinking agent in the aqueous solution may be small, any crosslinking agent having a solubility of, for example, at least about 0.1 mass% in water can be used as the crosslinking agent. Of course, a compound having solubility in water to such a degree that it is generally called water-soluble is suitable as the crosslinking agent used in the present invention.

The mixing amount of the crosslinking agent is appropriately designed according to the type of polyvinyl alcohol-based resin, etc., but is usually 5 parts by mass or more and 60 parts by mass or less, preferably 10 parts by mass or more and 50 parts by mass with respect to 100 parts by mass of the polyvinyl alcohol-based resin. less than wealth When a crosslinking agent is mix|blended in this range, favorable adhesiveness will be obtained. As described above, in order to improve the durability of the adhesive, an acetoacetyl group-modified polyvinyl alcohol-based resin is preferably used, but even in this case, 5 to 60 parts by mass of a crosslinking agent per 100 parts by mass of the polyvinyl alcohol-based resin It is preferable to mix|blend in the ratio of 10 mass parts or more and 50 mass parts or less. When the blending amount of the crosslinking agent is excessively large, the reaction of the crosslinking agent proceeds in a short time, and the adhesive tends to gel at an early stage. As a result, the pot life becomes extremely short, making industrial use difficult.

The water-based adhesive having a polyvinyl alcohol-based resin as a main component may preferably contain a zinc salt from the viewpoint of suppressing discoloration apart from the crosslinking agent. Examples of the zinc salt include zinc halides such as zinc chloride and zinc iodide, zinc sulfate, zinc acetate, and zinc nitrate. Among them, zinc nitrate is preferable. A zinc salt can be added to the water-based adhesive agent which has a polyvinyl alcohol-type resin as a main component as a zinc salt solution.

When the water-based adhesive having a polyvinyl alcohol-based resin as a main component contains a zinc salt, the content of the zinc salt is, for example, 0.01 parts by mass or more and 10 parts by mass or less, based on 100 parts by mass of water, from a viewpoint of ensuring durability of the adhesive. Preferably it is 0.1 mass part or more and 5 mass parts or less, More preferably, it is 0.5 mass part or more and 2.5 mass parts or less.

The adhesive may contain, for example, a conventionally known appropriate additive such as a silane coupling agent, a plasticizer, an antistatic agent, and fine particles within a range that does not impair the effects of the present invention.

When a urethane resin is used as the main component of the water-based adhesive, as an example of a suitable adhesive, a mixture of a polyester-based ionomer-type urethane resin and a compound having a glycidyloxy group is exemplified. The polyester-based ionomer type urethane resin referred to herein is a urethane resin having a polyester skeleton, and a small amount of an ionic component (hydrophilic component) is introduced therein. Since such an ionomer type urethane resin is emulsified in water directly without using an emulsifier and becomes an emulsion, it is used suitably for a water-based adhesive agent. The use of a polyester-based ionomer type urethane resin for an adhesive for a polarizing film and a protective film is disclosed and known in, for example, Japanese Patent Laid-Open Nos. 2005-070140, 4432487, and 2005-208456. has been

As an active energy ray-curable adhesive agent, an ultraviolet curable adhesive agent etc. are mentioned, for example.

The ultraviolet curing adhesive may be a mixture of a radically polymerizable (meth)acrylic compound and a photoradical polymerization initiator, a mixture of a cationically polymerizable epoxy compound and a photocationic polymerization initiator, or the like. Moreover, a cationically polymerizable epoxy compound and a radically polymerizable (meth)acrylic-type compound can be used together, and a photocationic polymerization initiator and a photoradical polymerization initiator can also be used together as an initiator.

When bonding a thermoplastic resin film to both sides of a polarizer, the same type or different types may be sufficient as an adhesive agent. For example, when bonding a thermoplastic resin film to both sides of a polarizer, one side may be bonded using a water-based adhesive agent, and the other side may be bonded using an active energy ray-curable adhesive agent.

The thickness of the adhesive in the polarizing plate may be, for example, 0.001 µm or more and 10 µm or less, preferably 0.01 µm or more and 5 µm or less from the viewpoint of adhesion and thinning, more preferably 0.01 µm or more and 3 µm or less, still more preferably It is 0.02 micrometer or more and 2 micrometers or less.

[Adhesive layer]

A polarizing plate may have an adhesive layer in any one outermost surface of the 1st thermoplastic resin film side and the 2nd thermoplastic resin film side for bonding with a translucent member and an image display element. The pressure-sensitive adhesive layer can be composed of a pressure-sensitive adhesive composition mainly containing a polymer such as a (meth)acrylic resin, a rubber-based polymer, a urethane-based resin, an ester-based resin, a silicone-based resin, or a polyvinyl ether-based resin. Especially, the adhesive composition which uses the (meth)acrylic-type resin excellent in transparency, weather resistance, heat resistance, etc. as a base polymer is suitable. An active energy ray hardening type or a thermosetting type may be sufficient as an adhesive composition.

As the (meth)acrylic resin (base polymer) used in the pressure-sensitive adhesive composition, for example, (meth) butyl acrylate, (meth) ethyl acrylate, (meth) acrylate isooctyl, (meth) acrylate 2-ethylhexyl (meth) The polymer or copolymer which uses 1 type(s) or 2 or more types of acrylic acid ester as a monomer is used suitably. It is preferable to copolymerize a polar monomer with a base polymer. As the polar monomer, (meth)acrylic acid, (meth)acrylic acid 2-hydroxypropyl, (meth)acrylic acid hydroxyethyl, (meth)acrylamide, N,N-dimethylaminoethyl (meth)acrylate, glycidyl The monomer which has carboxyl groups, such as (meth)acrylate, a hydroxyl group, an amide group, an amino group, an epoxy group, etc. are mentioned.

Although the adhesive composition may contain only the said base polymer, normally, it further contains a crosslinking agent. Examples of the crosslinking agent include: divalent or higher metal ions that form carboxylate metal salts between carboxyl groups; a polyamine compound which forms an amide bond between a carboxyl group; a polyepoxy compound or polyol which forms an ester bond between a carboxyl group; The polyisocyanate compound which forms an amide bond between a carboxyl group is illustrated. Especially, a polyisocyanate compound is preferable.

The pressure-sensitive adhesive layer is formed by dissolving or dispersing the pressure-sensitive adhesive composition in an organic solvent such as toluene or ethyl acetate to prepare a pressure-sensitive adhesive solution, and coating this directly on the target surface of the laminate to form the pressure-sensitive adhesive layer, or a release-treated separator It can perform by the method etc. which form an adhesive layer on a film in sheet form, and transfer it to the target surface of a polarizing plate.

Although the thickness of the pressure-sensitive adhesive layer is determined depending on the adhesive strength thereof, for example, it may be in the range of 1 µm or more and 50 µm or less, preferably 2 µm or more and 40 µm or less, more preferably 3 µm or more and 30 µm or less, still more preferably 3 micrometer or more and 25 micrometers or less.

The polarizing plate may include the separate film. The separator film may be a film made of a polyethylene-based resin such as polyethylene, a polypropylene-based resin such as polypropylene, or a polyester-based resin such as polyethylene terephthalate. Especially, the stretched film of polyethylene terephthalate is preferable.

The pressure-sensitive adhesive layer may include optional components, glass fibers, glass beads, resin beads, fillers made of metal powder or other inorganic powders; pigment; coloring agent; antioxidants; UV absorbers; Antistatic agents and the like may be included.

[Optical functional layer]

The optical function layer may be an optical functional film other than a polarizer for providing a desired optical function. A suitable example of the optically functional film is a retardation film. Examples of the retardation film include a film imparting a retardation of λ/2 (λ/2 wave plate), a film imparting a retardation of λ/4 (λ/4 wave plate), and a positive C plate. The optical functional film may contain the orientation layer and the base material, and may have each two or more of a liquid crystal layer, an orientation layer, and a base material.

Although the thermoplastic resin film may also serve as retardation film, retardation film can be laminated|stacked separately from these films.

As retardation film, the birefringent film comprised from the stretched film of the thermoplastic resin which has translucency; a film in which a discotic liquid crystal or a nematic liquid crystal is aligned; Those in which the said liquid crystal layer was formed on the base film, etc. are mentioned.

A base film is a film which consists of a thermoplastic resin normally, and an example of a thermoplastic resin is cellulose ester-type resin, such as a triacetyl cellulose.

Examples of other optically functional films (optical members) that may be included in the polarizing plate are a light collecting plate, a brightness enhancing film, a reflective layer (reflective film), a transflective layer (semitransmissive reflective film), a light diffusing layer (light diffusing film), and the like. These are generally formed when the polarizing plate is disposed on the back side (backlight side) of the liquid crystal cell.

[Protection Film]

The polarizing plate may include a protection film for protecting the surface (typically, the surface of the thermoplastic resin film of the polarizing plate). After a polarizing plate is bonded to an image display element or another optical member, for example, a protection film peels and removes for every adhesive layer which it has.

The protection film is composed of, for example, a base film and an adhesive layer laminated thereon. Regarding the pressure-sensitive adhesive layer, the above description is cited. The resin constituting the base film may be, for example, a polyethylene-based resin such as polyethylene, a polypropylene-based resin such as polypropylene, a polyester-based resin such as polyethylene terephthalate or polyethylene naphthalate, or a thermoplastic resin such as a polycarbonate-based resin. have. Preferably, it is polyester-type resin, such as a polyethylene terephthalate.

Although it does not specifically limit as thickness of a protection film, It is preferable to set it as the range of 20 micrometers or more and 200 micrometers or less. When the thickness of a base film is 20 micrometers or more, there exists a tendency for intensity|strength to become easy to be provided to a polarizing plate.

<Method for producing a polarizing plate>

The manufacturing method of the polarizing plate which concerns on another aspect of this invention is a manufacturing method of a polarizing plate provided with the 1st thermoplastic resin film joined to the polarizer and the 1st through the adhesive agent. The manufacturing method of a polarizing plate may include the above-mentioned polarizer manufacturing process. The manufacturing method of the polarizing plate is a washing process of preferably washing the polyvinyl alcohol-based resin film with water from the viewpoint of obtaining a single color b value and absorbance at a wavelength of 700 nm within the above-mentioned range, with a washing solution having a temperature exceeding 22 ° C. includes at least one of a washing process without washing and a drying process of drying the polyvinyl alcohol-based resin film at a temperature of 96° C. or higher.

The manufacturing method of the polarizer may further include a bonding step of bonding the first thermoplastic resin film to one side of the polarizer through an adhesive, and drying the adhesive at a temperature of 85° C. or higher. In the bonding step, an adhesive is applied to either or both of the bonding surfaces of the polarizer and the first thermoplastic resin film, and the other bonding surface is laminated thereto, for example, by pressing from the top and bottom using a bonding roll or the like to bond. can Various coating methods, such as a doctor blade, a wire bar, a die coater, a comma coater, a gravure coater, can be used for coating of an adhesive agent, for example. Moreover, the method of casting an adhesive agent in between may be sufficient, supplying a polarizer and a 1st thermoplastic resin film continuously so that both bonding surfaces may become inside.

After bonding a polarizer and a 1st thermoplastic resin film, an adhesive agent can be dried by heat-processing with respect to the laminated body containing a polarizer, an adhesive agent, and a 1st thermoplastic resin film. Since the evaporation, curing, and crosslinking of the solvent proceed at different temperatures, it is preferable to heat treatment continuously or in multiple steps to gradually increase the temperature. The temperature of the heat treatment preferably includes treatment at 85° C. or higher from the viewpoint of obtaining a single color b value within the above range and absorbance at a wavelength of 700 nm. The upper limit of the temperature of the heat treatment for drying the adhesive is usually 100°C or less, and preferably 90°C or less. The solvent contained in the adhesive agent can be removed by heat processing. Moreover, when an adhesive agent is a curable adhesive agent, hardening and a crosslinking reaction can advance by the said heat processing.

When using an active energy ray-curable adhesive agent as an adhesive agent, the adhesive agent can be hardened by irradiating an active energy ray after bonding. Although the light source of the active energy ray is not particularly limited, an active energy ray (ultraviolet ray) having a light emission distribution at a wavelength of 400 nm or less is preferable, and specifically, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultra high pressure mercury lamp, a chemical lamp, a black light A lamp, a microwave excited mercury lamp, a metal halide lamp, etc. are used preferably.

In order to improve the adhesion between the polarizer and the thermoplastic resin film, prior to bonding the polarizer and the thermoplastic resin film, corona treatment, flame treatment, plasma treatment, ultraviolet irradiation treatment, primer application to the bonding surface of the polarizer and/or the thermoplastic resin film You may perform surface treatment, such as a treatment and a saponification process.

When a polarizing plate is equipped with a 2nd thermoplastic resin film, bonding of a polarizer and a 2nd thermoplastic resin film can be carried out similarly to bonding of a polarizer and a 1st thermoplastic resin film, and can be performed. Bonding of a polarizer and a 2nd thermoplastic resin film may be performed before or after bonding of a polarizer and a 1st thermoplastic resin film, and may be performed simultaneously with bonding of a polarizer and a 1st thermoplastic resin film.

<Use of Polarizer>

A polarizing plate can be used for mobile device uses, such as a television, a personal computer, a mobile phone, and a tablet terminal. Moreover, since discoloration is suppressed even after a high temperature (105 degreeC) and long-time (600 hours or more) durability test of a polarizing plate, it is suitable for the vehicle-mounted use which is easy to be exposed under more severe temperature conditions. As an in-vehicle application, the image display apparatus etc. used for a car navigation device, a speedometer, the touch panel for air conditioners, a back monitor, a rear monitor, etc. are mentioned, for example.

[Example]

Hereinafter, the present invention will be described in more detail by way of Examples. "%" and "part" in the examples are mass% and parts by mass, unless otherwise specified.

[Production Example 1: Preparation of water-based adhesive (1)]

Acetoacetyl group-modified polyvinyl alcohol [trade name “Gosepaima Z-200”, manufactured by Nippon Synthetic Chemical Co., Ltd., viscosity of 4% aqueous solution = 12.4 mPa sec, degree of saponification = 99.1 mol%] was dissolved in pure water, , an aqueous solution having a concentration of 10% was prepared. The obtained aqueous solution of acetoacetyl group-modified polyvinyl alcohol and sodium glyoxylate used as a crosslinking agent were mixed so that the solid content mass ratio of aqueous solution: sodium glyoxylate was 1:0.1. Further, zinc nitrate and pure water were added so that 1.5 parts of zinc nitrate and 2.5 parts of acetoacetyl group-modified polyvinyl alcohol were contained with respect to 100 parts of water to prepare an aqueous adhesive composition (1).

<Example 1>

A long polyvinyl alcohol (PVA) raw film with a width of 3390 mm and a thickness of 60 μm (trade name "M6000" manufactured by Kurare Co., Ltd., saponification degree of 99.9 mol% or more) is continuously conveyed while unwinding from the roll, It was immersed in the formed swelling bath for 45 seconds for a residence time (swelling process). Thereafter, the film taken out from the swelling bath was immersed in a dyeing bath at 30°C containing iodine having an iodine in potassium iodide/water of 1.5/100 (mass ratio) for a residence time of 120 seconds (dyeing step). Next, the film taken out from the dyeing bath was immersed in a first crosslinking bath at 30°C where potassium iodide/boric acid/water was 0.5/0.6/100 (mass ratio) for a residence time of 70 seconds, and then potassium iodide/boric acid/water It was immersed in this 15/4.9/100 (mass ratio) 60 degreeC 2nd crosslinking bath for 50 second residence time (crosslinking process). Thereafter, the film was immersed in a washing bath made of pure water at 7° C. for a residence time of 40 seconds. Moreover, it wash|cleaned by showering the temperature of 5.3 degreeC and the temperature of both ends with the water temperature of 22 degreeC for the temperature of the center part (washing process). The obtained PVA was continuously dried (drying) under the drying conditions of the following three steps of temperature and time (1st step: 75°C 15 seconds, 2nd step: 85°C 15 seconds, 3rd step: 96°C 15 seconds) fair). In the dyeing process and the crosslinking process, longitudinal uniaxial stretching was performed by extending|stretching between rolls in a bath. The total draw ratio on the basis of the raw film was 5.8 times. The thickness of the obtained polarizer was 25 micrometers.

With respect to the polarizer thus obtained, a thermoplastic resin film (trade name "KC4CT1W", manufactured by Konica Minolta Co., Ltd.) made of tricetyl cellulose as a protective film was bonded through an aqueous adhesive composition (1) at a bonding temperature of 70° C., and then, The water-based adhesive was continuously dried under the drying conditions of the following three steps of temperature and time (1st step: 60° C. 25 seconds, 2nd step: 85° C. 25 seconds, 3rd step: 90° C. 25 seconds) (bonding process) ). The water-based adhesive was applied to one side of the thermoplastic resin film at a thickness of 200 nm. It was 280 ppm when zinc content was measured about the obtained polarizing plate. Table 1 shows the measurement results of the single color b value and the absorbance at a wavelength of 700 nm and the durability test results.

<Comparative Example 1>

A polarizing plate of Comparative Example 1 was produced in the same manner as in Example 1, except that the water temperature of the shower on both ends was 24° C. in the washing process of Example 1, and the temperature of the third step in the drying process was 93° C. did. It was 280 ppm when the zinc content was measured about the obtained polarizing plate. Table 1 shows the measurement results of the single color b value and the absorbance at a wavelength of 700 nm and the durability test results.

[endurance test]

The obtained polarizing plate was cut and the sample for durability tests (dimension: 12 cm x 30 cm) was produced. This durability test sample was autoclaved for 1 hour (temperature of 50 degreeC, pressure of 5 kg/cm<2> (490.3 kPa)], Then, it was left to stand in the environment of temperature 23 degreeC and 55% of relative humidity for 24 hours. The heating test was done in the heating environment of the temperature of 105 degreeC, and the change of the color before and behind a heating was confirmed visually. The time required for the color to change was measured.

[Measurement of single color b-value and absorbance at a wavelength of 700 nm]

The single color b value of the polarizing plate before the durability test and the absorbance at a wavelength of 700 nm were measured using a spectrophotometer ("V-7100" manufactured by Nippon Spectroscopy Co., Ltd.).

[Measurement of zinc content]

The measurement of the zinc content in a polarizing plate was performed as follows.

Nitric acid was added to the precisely weighed polarizing plate, and a solution obtained by acid decomposition with a microwave sample preprocessor (ETHOS D) manufactured by Milestone General was used as the measurement solution. The zinc concentration quantified the zinc concentration of a measurement liquid with the Agilent Technology ICP emission spectroscopy apparatus (5110 ICP-OES), and computed it as the zinc mass with respect to the polarizing plate mass.

10 polarizing plate, 11: first thermoplastic resin film, 12: polarizer, 13: second thermoplastic resin film, 110: polyvinyl alcohol-based resin raw film, 111: feeding roll, 113: swelling tank, 115: dyeing tank, 117: crosslinking tank, 119: washing tank, 123: drying furnace, 127: winding roll, 130: polarizer.

Claims (9)

A polarizing plate having a single color b-value of 2.7 or more and an absorbance of 4.5 or less at a wavelength of 700 nm. The polarizing plate according to claim 1, comprising a polarizer and a first thermoplastic resin film bonded to one side thereof via an adhesive. The polarizing plate according to claim 2, further comprising a second thermoplastic resin film bonded through an adhesive on a side opposite to the first thermoplastic resin film side of the polarizer. The polarizing plate according to claim 2 or 3, wherein the adhesive is a water-based adhesive. The polarizing plate according to any one of claims 1 to 4, wherein the content of the zinc element in the polarizing plate is 150 ppm or more. The vehicle-mounted display device provided with the polarizing plate in any one of Claims 1-5. As a manufacturing method of the polarizing plate of Claim 2,
The polarizer includes a polyvinyl alcohol-based resin film,
A method for manufacturing a polarizing plate, comprising a washing step of washing the polyvinyl alcohol-based resin film with a washing solution, and not washing with a washing solution having a temperature exceeding 22°C. The method of claim 7 , further comprising a drying step of drying the polyvinyl alcohol-based resin film at a temperature of 96° C. or higher. The method for manufacturing a polarizing plate according to claim 7 or 8, further comprising a bonding step of bonding the first thermoplastic resin film to one side of the polarizer through an adhesive, and drying the adhesive at a temperature of 85°C or higher.

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