JP2018041113A - Polarizer, polarizing film and method for manufacturing polarizer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a polarizer that can be made thin and reduces unevenness in the distribution of thickness.SOLUTION: One aspect of the method for manufacturing a polarizer according to the present invention is a method for manufacturing a polarizer having a dichroic dye aligned in a polyvinyl alcohol resin. The polarizer has a thickness of 10 μm or less. The method includes: a resin layer formation step of forming a resin layer using a polyvinyl alcohol resin as a formation material on a substrate; a stretching step of stretching the resin layer with the substrate; and a dyeing step of allowing the resin layer to adsorb a dichroic dye. The resin layer formation step includes: a step of applying a coating liquid for the resin layer comprising the polyvinyl alcohol resin on the substrate; and a step of drying the applied coating liquid for the resin layer. The duration of the step of drying the applied coating liquid for the resin layer is 180 seconds or shorter.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a polarizer, a polarizing film, and a method for producing a polarizer.

  A polarizer obtained by adsorbing a dichroic substance on a hydrophilic polymer layer made of a polyvinyl alcohol (PVA: Poly Vinyl Alcohol) resin is known (for example, Patent Document 1). A polarizing film using such a polarizer is used in a liquid crystal display device such as a personal computer, a TV, a monitor, a mobile phone, and a PDA (Personal Digital Assistant). In recent years, with the improvement in performance and thinning of liquid crystal display devices, there has been a demand for thinning the polarizers of polarizing films used in liquid crystal display devices.

JP 2009-0986653 A

  In order to produce a relatively thin polarizer, for example, as described in Patent Document 1, after applying an aqueous solution containing a hydrophilic polymer to the base material layer, the hydrophilic polymer is contained. The aqueous solution to be dried is dried to form a laminate in which the hydrophilic polymer layer is laminated on the base material layer. And a stretching process and a dyeing | staining process are performed with respect to this laminated body, and a polarizer is manufactured. However, when a polarizer is manufactured using such a method, there is a problem that unevenness of the thickness distribution of the polarizer in the transmission axis direction (width direction) becomes large. In recent years, backlights have been increasing in brightness for the purpose of improving visibility, and uneven thickness distribution of the polarizer is more easily visible than in the past.

  In view of the above problems, an embodiment of the present invention has an object of providing a polarizer that is thin and has a small unevenness in thickness distribution, and a polarizing film including such a polarizer. Another object of one embodiment of the present invention is to provide a method for manufacturing a polarizer that can be thinned and can reduce unevenness in thickness distribution.

  One aspect of the polarizer of the present invention is a polarizer in which a dichroic dye is oriented in a polyvinyl alcohol resin, and the thickness of the polarizer is 10 μm or less, and the transmission axis direction of the polarizer The maximum amplitude of the thickness distribution is 0.4 μm or less.

  In the transmission axis direction of the polarizer, the periodic intensity of the thickness distribution may be 0.13 μm or less.

  One aspect of the polarizer of the present invention is a polarizer in which a dichroic dye is oriented in a polyvinyl alcohol resin, and the thickness of the polarizer is 10 μm or less, and the transmission axis direction of the polarizer The periodic strength of the thickness distribution is 0.13 μm or less.

  The maximum amplitude of the phase difference distribution of the polyvinyl alcohol resin in the transmission axis direction of the polarizer may be 10 nm or less.

  One aspect of the polarizer of the present invention is a polarizer in which a dichroic dye is oriented in a polyvinyl alcohol resin, and the thickness of the polarizer is 10 μm or less, and the transmission axis direction of the polarizer The maximum amplitude of the phase difference distribution of the polyvinyl alcohol resin is 10 nm or less.

  The periodic intensity of the phase difference distribution of the polyvinyl alcohol resin in the transmission axis direction of the polarizer may be 2 nm or less.

  One aspect of the polarizer of the present invention is a polarizer in which a dichroic dye is oriented in a polyvinyl alcohol resin, and the thickness of the polarizer is 10 μm or less, and the transmission axis direction of the polarizer The period intensity of the phase difference distribution of the polyvinyl alcohol resin is 2 nm or less.

  One aspect of the polarizing film of the present invention is characterized by comprising the above polarizer and a protective film provided on at least one surface of the polarizer.

  One embodiment of the method for producing a polarizer of the present invention is a method for producing a polarizer in which a dichroic dye is aligned in a polyvinyl alcohol-based resin, and the thickness of the polarizer is 10 μm or less. A resin layer forming step for forming a resin layer using a polyvinyl alcohol-based resin as a forming material on the material, a stretching step for stretching the resin layer together with the base material, and a dye for adsorbing the dichroic dye on the resin layer The resin layer forming step includes a step of applying a resin layer coating solution containing a polyvinyl alcohol resin on the substrate, and a step of drying the applied resin layer coating solution. The length of the step of drying the resin layer coating solution is 180 seconds or less.

  Prior to the resin layer forming step, the method further includes a primer layer forming step of forming a primer layer on the substrate, and the primer layer forming step is a step of applying a primer layer coating liquid on the substrate. And a step of drying the applied primer layer coating solution.

  According to one aspect of the present invention, there are provided a polarizer that is thin and has a small variation in thickness distribution in the transmission axis direction, and a polarizing film that includes such a polarizer. Moreover, according to one aspect of the present invention, there is provided a method for manufacturing a polarizer that can be thinned and can reduce unevenness.

It is sectional drawing which shows the polarizing film of this embodiment. It is a flowchart which shows the procedure of the manufacturing method of the polarizing film of this embodiment. It is a schematic diagram which shows a part of procedure of the manufacturing method of the polarizing film of this embodiment. It is sectional drawing which shows a part of procedure of the manufacturing method of the polarizing film of this embodiment. It is sectional drawing which shows a part of procedure of the manufacturing method of the polarizing film of this embodiment. It is sectional drawing which shows a part of procedure of the manufacturing method of the polarizing film of this embodiment. It is sectional drawing which shows a part of procedure of the manufacturing method of the polarizing film of this embodiment. It is sectional drawing which shows a part of procedure of the manufacturing method of the polarizing film of this embodiment. It is sectional drawing which shows the laminated body of a verification example. It is a graph which shows the thickness of the resin layer with respect to the width direction position. It is a graph which shows the thickness of the polarizer with respect to the width direction position. It is a graph which shows the periodic intensity | strength of the thickness distribution of a polarizer with respect to the nonuniformity period of the thickness distribution of a polarizer. It is a graph which shows the phase difference of the polyvinyl alcohol-type resin in a polarizer with respect to the width direction position. It is a graph which shows the periodic intensity | strength of phase difference distribution of the polyvinyl alcohol-type resin in a polarizer with respect to the nonuniformity period of the thickness distribution of a polarizer.

  Hereinafter, the polarizing film which concerns on embodiment of this invention is demonstrated, referring drawings. The scope of the present invention is not limited to the following embodiments, and can be arbitrarily changed within the scope of the technical idea of the present invention. In the following drawings, the scale and number of each structure may be different from the scale and number of the actual structure in order to make each configuration easy to understand.

  FIG. 1 is a cross-sectional view showing a polarizing film 1 of the present embodiment. As shown in FIG. 1, the polarizing film 1 includes a polarizer 10, a protective film 11, and an adhesive layer 12. The polarizer 10, the adhesive layer 12, and the protective film 11 are laminated in this order. Although illustration is omitted, the polarizing film 1 of the present embodiment has a long belt shape. For example, the polarizing film 1 is wound around a core material and stored as a roll.

  In the following description, the direction in which the layers in the polarizing film 1 are laminated may be simply referred to as “lamination direction”, and the longitudinal direction orthogonal to the lamination direction in the polarizing film 1 is simply referred to as “longitudinal direction”. The width direction orthogonal to both the laminating direction and the longitudinal direction in the polarizing film 1 may be simply referred to as “width direction”.

  In the drawings, a three-dimensional orthogonal coordinate system (XYZ coordinate system) is shown as appropriate. In the three-dimensional orthogonal coordinate system, the Z-axis direction is a direction parallel to the stacking direction, the Y-axis direction is a direction parallel to the width direction, and the X-axis direction is a direction parallel to the longitudinal direction. In the stacking direction, the positive side in the Z-axis direction may be referred to as “upper side”, and the negative side in the Z-axis direction may be referred to as “lower side”. The upper side and the lower side are simply names used to describe the relative positional relationship of each part, and the orientation of each part at the time of manufacturing the polarizing film, the actual attitude of the polarizing film, the usage mode of the polarizing film, etc. Not limited.

  The polarizer 10 is a layer in which a dichroic dye is oriented in a polyvinyl alcohol-based resin. In the present embodiment, the absorption axis of the polarizer 10 is, for example, parallel to the longitudinal direction (X-axis direction), and the transmission axis of the polarizer 10 is, for example, parallel to the width direction (Y-axis direction).

  Examples of the polyvinyl alcohol-based resin that is a material for forming the polarizer 10 include polyvinyl alcohol resins, polyvinyl alcohol resin derivatives, and modified products of polyvinyl alcohol resin derivatives. Examples of the polyvinyl alcohol resin derivative include polyvinyl formal, polyvinyl acetal, polyvinyl butyral, and the like. Examples of the modified polyvinyl alcohol resin derivative include the above-described polyvinyl alcohol resin derivatives such as olefins such as ethylene and propylene; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid; alkyl esters of unsaturated carboxylic acids; or Those modified with acrylamide or the like can be mentioned.

  The average degree of polymerization of the polyvinyl alcohol resin is preferably 100 or more and 10,000 or less, more preferably 1000 or more and 10,000 or less, further preferably 1500 or more and 8000 or less, and further preferably 2000 or more and 5000 or less. When the average degree of polymerization of the polyvinyl alcohol-based resin is less than 100, it is difficult to obtain suitable optical characteristics. When the average degree of polymerization is larger than 10,000, the solubility in water becomes low, and the resin layer coating solution described later This is because it becomes difficult to manufacture 33. In this specification, the average degree of polymerization of the polyvinyl alcohol-based resin is determined by, for example, a method defined by JIS K 6727 (1994).

  The polyvinyl alcohol-based resin that is a material for forming the polarizer 10 is preferably saponified. The saponification degree of the polyvinyl alcohol-based resin is preferably 80.0 mol% or more and 100.0 mol% or less, more preferably 90.0 mol% or more and 99.5% mol or less, 93.0 mol% or more, More preferably, it is 99.5 mol% or less. By setting the saponification degree of the polyvinyl alcohol-based resin to 80 mol% or more, suitable optical characteristics can be easily obtained.

The degree of saponification of the polyvinyl alcohol-based resin is expressed in mol% of the ratio of the acetate group contained in the polyvinyl acetate-based resin, which is a raw material of the polyvinyl alcohol-based resin, to the hydroxyl group by the saponification step. , Defined by (Equation 1) below.
(Formula 1) Degree of saponification (mol%) = (number of hydroxyl groups) ÷ (number of hydroxyl groups + number of acetate groups) × 100
In this specification, the saponification degree of polyvinyl alcohol-type resin is calculated | required by the method defined by JISK6727 (1994), for example.

  The polarizer 10 may contain additives such as a plasticizer and a surfactant. As a plasticizer, the condensate of a polyol and a polyol is mentioned, for example. Examples of polyols and polyol condensates include glycerin, diglycerin, triglycerin, ethylene glycol, propylene glycol, and polyethylene glycol. The content of the plasticizer in the polarizer 10 is not particularly limited, but is preferably 20% by mass or less, for example.

  The thickness T1 of the polarizer 10 is 10 μm or less, preferably 5 μm or less. In the width direction (transmission axis direction, Y-axis direction) of the polarizer 10, the maximum amplitude of the thickness distribution of the polarizer 10 is 0.4 μm or less, preferably 0.2 μm or less, more preferably 0.1 μm. It is as follows. Considering the resolution of the measuring device, the maximum amplitude of the thickness distribution of the polarizer 10 is usually 0.01 μm or more. The maximum amplitude of the thickness distribution is a difference between the maximum value and the minimum value of the thickness T1 of the polarizer 10. In the present specification, the thickness T1 of the polarizer 10 is measured using, for example, a white interference type non-contact film thickness meter (for example, model number: F20 manufactured by Filmmetrics). As a result, precise measurement is possible without touching the object to be measured (polarizer 10), and even if the object to be measured is a partial layer of the laminate, the film thickness of the object can be reduced without peeling off each layer. Can be measured.

  In the width direction of the polarizer 10 (transmission axis direction, Y-axis direction), the periodic intensity of the thickness distribution of the polarizer 10 is preferably 0.13 μm or less, more preferably 0.05 μm or less, and even more preferably. 0.04 μm or less. Further, the periodic intensity of the thickness distribution of the polarizer 10 is usually 0.0025 μm or more. In this specification, the periodic intensity of the thickness distribution of the polarizer 10 is obtained as follows, for example.

  The thickness distribution of the polarizer 10 in the width direction is subjected to Fast Fourier Transform (FFT). For example, a Boolean-Tukey type FFT algorithm is used as the fast Fourier transform algorithm. The fast Fourier transform using the Boolean-Tukey type FFT algorithm can be performed, for example, by executing “ATPVBAEN.XLAM! Fourier” which is an add-in of spreadsheet software “Excel (registered trademark) 2010” manufactured by Microsoft Corporation. . By executing this add-in on the measured raw point data of the thickness T1 of the polarizer 10, the thickness distribution of the polarizer 10 in the width direction can be subjected to fast Fourier transform.

  In general, the fast Fourier transform converts a time waveform function into a frequency distribution function. In the case of the present embodiment, the waveform function f (L) representing the thickness distribution of the polarizer 10 at the width direction position L (Y-axis direction position) is subjected to fast Fourier transform to thereby distribute the frequency ω of the thickness distribution of the polarizer 10. A function f (ω) is obtained. The sampling period is 1 / ω.

In this specification, the periodic intensity of the thickness distribution of the polarizer 10 is represented by | f (ω _N ) | / (N / 2). | F (ω _N ) | is the absolute value of the distribution function obtained by fast Fourier transform of the waveform function f (L _N ) corresponding to the Nth sample point. L _N is the position L in the width direction of the Nth sample point. The physical quantity of the periodic intensity of the thickness distribution of the polarizer 10 is equal to the physical quantity of the thickness distribution of the polarizer 10. Note that the maximum number of sample points is a power value of 2 that is not more than the number of prime points A of the obtained film thickness distribution and is closest to A.

A power spectrum can be obtained with the period intensity of the thickness distribution of the polarizer 10 obtained as described above as the vertical axis and the period of the sample points as the horizontal axis. The period of the sample point is L _N / N.

  In addition, in this specification, that the periodic intensity is equal to or less than a predetermined value includes that the periodic intensity in a region where the period is 10 mm or more and 70 mm or less is equal to or less than a predetermined value. That is, that the periodic intensity of the thickness distribution of the polarizer 10 is 0.05 μm or less includes that the periodic intensity of the thickness distribution of the polarizer 10 in a region where the period is 10 mm or more and 70 mm or less is 0.05 μm or less. . In other words, the periodic intensity of the thickness distribution of the polarizer 10 being 0.05 μm or less means that the maximum value of the periodic intensity of the thickness distribution of the polarizer 10 is 0.05 μm or less in a region where the period is 10 mm or more and 70 mm or less. Including.

  Moreover, in this specification, the thickness of a certain film (layer) is a dimension of the lamination direction (Z-axis direction) of a certain film (layer), and includes the average thickness of a certain film (layer). That is, the thickness of the polarizer includes the average thickness of the polarizer.

  In the width direction (transmission axis direction, Y axis direction) of the polarizer 10, the maximum amplitude of the phase difference distribution of the polyvinyl alcohol-based resin is preferably 10 nm or less, more preferably 5.7 nm or less, and still more preferably. It is 5.3 nm or less. Moreover, the maximum amplitude of the retardation distribution of the polyvinyl alcohol resin is usually 0.3 nm or more. The maximum amplitude of the phase difference distribution is the maximum value of the phase difference Rpva of the polyvinyl alcohol resin in a region where the period is 10 mm or more and 20 mm or less.

The phase difference Rpva of the polyvinyl alcohol resin can be obtained from the phase difference R (λ) of the polarizer 10 in a wavelength region where there is no absorption band of the dichroic dye. In the present specification, the retardation Rpva of the polyvinyl alcohol-based resin refers to a retardation at a wavelength of 1000 nm. Specifically, the phase difference R (λ) of the polarizer 10 is measured for each of a plurality of wavelengths λ of 850 nm or longer, and the measured wavelength λ and the measured phase difference R (λ) are plotted. To fit the selmeier formula (formula 2) by the least square method. Here, E and F in (Expression 2) are fitting parameters and are coefficients determined by the least square method.
(Formula 2) R (λ) = E + F / (λ ² −600 ² )
E in (Formula 2) corresponds to the retardation Rpva of the polyvinyl alcohol resin. Note that F / (λ ² -600 ² ) corresponds to the phase difference of the dichroic dye. In this specification, the measurement of the phase difference R (λ) of the polarizer 10 is performed using, for example, a phase difference measuring apparatus (manufactured by Oji Scientific Instruments, model: KOBRA-WPR / IR).

  In the width direction of the polarizer 10 (transmission axis direction, Y-axis direction), the periodic intensity of the phase difference distribution of the polyvinyl alcohol-based resin is preferably 2 nm or less, more preferably 0.9 nm or less, and still more preferably. 0.8 nm or less. Moreover, the periodic intensity | strength of the phase difference distribution of polyvinyl alcohol-type resin is 0.075 nm or more normally. The periodic intensity of the phase difference distribution of the polyvinyl alcohol resin is the maximum amplitude in the region where the period is 10 mm or more and 20 mm or less in the wave number spectrum obtained by subjecting the phase difference distribution of the polyvinyl alcohol resin in the width direction to the fast Fourier transform. Is the value of The calculation method of the periodic intensity of the phase difference distribution is the same as the periodic intensity of the thickness distribution of the polarizer 10 described above.

  Examples of the dichroic dye oriented in the polyvinyl alcohol resin include iodine and organic dyes.

  The protective film 11 is provided on the upper surface 10 a of the polarizer 10. More specifically, in the present embodiment, the protective film 11 is bonded to the upper surface 10 a of the polarizer 10 through the adhesive layer 12. The protective film 11 may be a simple protective film having no optical function, or may be a protective film having both optical functions such as a retardation film and a brightness enhancement film.

  The material for forming the protective film 11 is not particularly limited. For example, a cyclic polyolefin resin film; a cellulose acetate resin film made of a resin such as triacetyl cellulose or diacetyl cellulose; polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, or the like. Polyester resin film made of the above resin; polycarbonate resin film; acrylic resin film; and polypropylene resin film.

  The cyclic polyolefin resin film may be uniaxially stretched or biaxially stretched. By stretching, an arbitrary retardation can be imparted to the cyclic polyolefin resin film.

  The cyclic polyolefin resin film generally has poor surface activity. Therefore, when the protective film 11 is a cyclic polyolefin-based resin film, a plasma treatment, corona treatment, ultraviolet irradiation treatment, flame (flame) treatment, saponification treatment, etc. are applied to the lower surface of the protective film 11 that is bonded to the polarizer 10. It is preferable to perform the surface treatment. In particular, plasma treatment and corona treatment that can be performed relatively easily are suitable.

  When the protective film 11 is a cellulose acetate resin film, a liquid crystal layer or the like may be formed on the surface of the protective film 11 in order to improve viewing angle characteristics. Further, the protective film 11 may be obtained by stretching a cellulose acetate-based resin film in order to impart a phase difference. When the protective film 11 is a cellulose acetate-based resin film, the lower surface of the protective film 11 is usually subjected to saponification treatment in order to enhance the adhesiveness with the polarizing film 1. As the saponification treatment, a method of immersing in an aqueous alkali solution such as sodium hydroxide and potassium hydroxide can be employed.

  Optical layers such as a hard coat layer, an antiglare layer, and an antireflection layer can be formed on the surface of the protective film 11. The method for forming these optical layers on the surface of the protective film 11 is not particularly limited, and a known method can be used.

  The thickness T2 of the protective film 11 is preferably as thin as possible from the demand for thinning, is preferably 90 μm or less, and more preferably 50 μm or less. If the thickness T2 of the protective film 11 is too thin, the strength of the protective film 11 is reduced and the processability is poor. Therefore, the thickness T2 of the protective film 11 is preferably 5 μm or more.

  In this embodiment, although the protective film 11 is provided only on the upper surface 10a of the polarizer 10, it is not restricted to this. The protective film 11 should just be provided in the at least one surface of the polarizer 10, and may be provided in both the upper surface 10a of the polarizer 10, and the lower surface 10b.

  The adhesive layer 12 is laminated on the upper surface 10 a of the polarizer 10. The adhesive layer 12 is a layer that adheres the polarizer 10 and the protective film 11 to each other. As a material for forming the adhesive layer 12, for example, an aqueous adhesive, an ultraviolet curable adhesive, an electron beam curable adhesive, and the like are preferable, and an aqueous adhesive is more preferable. Examples of the water-based adhesive include an aqueous solution of a polyvinyl alcohol resin, an aqueous solution in which a general crosslinking agent is mixed with an aqueous solution of a polyvinyl alcohol resin, and a urethane emulsion adhesive. Further, the forming material of the adhesive layer 12 can contain a metal compound filler.

  Next, the manufacturing method of the polarizing film 1 of this embodiment is demonstrated. FIG. 2 is a flowchart showing the procedure of the method for manufacturing the polarizing film 1 of the present embodiment. FIG. 3 is a schematic diagram showing a part of the procedure of the method for manufacturing the polarizing film 1. 4 to 8 are cross-sectional views illustrating a part of the procedure of the method for manufacturing the polarizing film 1. FIG. 4 is a cross-sectional view at a position P1 shown in FIG. FIG. 5 is a cross-sectional view at the position P2 shown in FIG. FIG. 6 is a cross-sectional view at a position P3 shown in FIG. FIG. 7 is a cross-sectional view at the position P4 shown in FIG. In FIGS. 5 to 8, the uneven shape due to thermal shrinkage of the base film 20 described later and the uneven shape of each layer accompanying the thermal shrinkage of the base film 20 are schematically highlighted.

  The manufacturing method of the polarizing film 1 of this embodiment includes resin layer formation process S2, extending process S3, dyeing process S4, bonding process S5, and peeling process S6, as shown in FIG. As shown in FIG. 2, the primer layer forming step S1 may be included before the resin layer forming step S2. As shown in FIG. 3, in this embodiment, the polarizing film 1 is manufactured, conveying the roll-shaped base film (base material) 20 to a longitudinal direction with a nip roll and a conveyance roll. Note that FIG. 3 shows a mode in which each step is performed continuously, but the film may be wound once on a roll each time the step is completed.

  The material of the base film 20 is not particularly limited as long as it can be stretched together with the resin layer 34 described later in the stretching step S3. The material of the base film 20 is, for example, a thermoplastic resin. The thermoplastic resin used as the material for the base film 20 is preferably excellent in transparency, mechanical strength, thermal stability, stretchability, and the like.

  Specifically, examples of the thermoplastic resin used as the material of the base film 20 include polyolefin resins such as chain polyolefin resins and cyclic polyolefin resins (norbornene resins and the like); polyester resins such as polyethylene terephthalate and the like. ; (Meth) acrylic resins; cellulose ester resins such as cellulose triacetate and cellulose diacetate; polycarbonate resins; polyvinyl alcohol resins; polyvinyl acetate resins; polyarylate resins; polystyrene resins; A polysulfone resin; a polyamide resin; a polyimide resin; and a mixture or copolymer of these resins.

  The base film 20 is comprised from 1 type, or 2 or more types of thermoplastic resins among the thermoplastic resins mentioned above. The base film 20 may have a single layer structure or a multilayer structure.

  The thickness of the base film 20 is not particularly limited, but is preferably 1 μm or more and 500 μm or less, more preferably 1 μm or more and 300 μm or less, further preferably 5 μm or more and 200 μm or less, and more preferably 5 μm or more from the viewpoints of strength and handleability. 150 μm or less is even more preferable. The dimension of the base film 20 in the width direction (Y-axis direction) is, for example, 500 mm or more.

  The tensile elastic modulus in the longitudinal direction of the base film 20 is, for example, 140 MPa or more at 80 ° C. 150 MPa or more is preferable at 80 degreeC, and, as for the tensile elasticity modulus in the longitudinal direction of the base film 20, 155 MPa or more is more preferable. By using such a base film, the thermal shrinkage of the base film 20 in the first drying step S1b and the second drying step S2b described later can be suppressed. In this specification, the tensile elastic modulus in the longitudinal direction of the base film 20 is measured by, for example, Autograph (registered trademark) (manufactured by Shimadzu Corporation, model number: AG-IS). Specifically, it is measured according to JIS K7163.

  The primer layer forming step S1 is a step of forming the primer layer 32 (see FIG. 5) on the base film 20. The primer layer 32 is a layer provided to improve the adhesion between the base film 20 and a resin layer 34 described later. As shown in FIG. 2, the primer layer forming step S1 includes a first application step S1a and a first drying step S1b. As shown in FIG. 3, in the first coating step S <b> 1 a, the primer layer coating liquid 31 is applied to the upper surface 20 a of the base film 20 by the first coating device 41.

  The primer layer coating solution 31 is, for example, a resin solution obtained by dissolving resin powder in a solvent. The resin contained in the primer layer coating liquid 31 is a resin containing a component capable of improving the above-described adhesion, and is a thermoplastic resin excellent in transparency, thermal stability, stretchability, and the like. preferable. Examples of the resin contained in the primer layer coating liquid 31 include (meth) acrylic resins and polyvinyl alcohol resins. In particular, the resin contained in the primer layer coating liquid 31 is preferably a polyvinyl alcohol resin. This is because the adhesive force between the base film 20 and a resin layer 34 to be described later can be obtained satisfactorily.

  The polyvinyl alcohol resin used as the resin contained in the primer layer coating liquid 31 can be selected in the same manner as the polyvinyl alcohol resin of the polarizer 10 described above. The resin contained in the primer layer coating solution 31 may be the same as or different from the polyvinyl alcohol resin of the polarizer 10.

  Examples of the solvent for the primer layer coating solution 31 include an organic solvent and an aqueous solvent that can dissolve the above-described resin. Examples of the organic solvent include aromatic hydrocarbons such as benzene, toluene, and xylene; ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; esters such as ethyl acetate and isobutyl acetate; methylene chloride, trichloroethylene, chloroform, and the like. Chlorinated hydrocarbons; and alcohols such as ethanol, 1-propanol, 2-propanol, and 1-butanol. As a solvent of the primer layer coating solution 31, for example, water is preferable. This is because the base film 20 is hardly dissolved regardless of the material of the base film 20, and the influence on the environment can be reduced. The concentration of the resin in the primer layer coating solution 31 is preferably about 1% by mass or more and 25% by mass or less.

  The method for applying the primer layer coating solution 31 using the first coating device 41 is not particularly limited as long as the primer layer coating solution 31 can be applied to the upper surface 20 a of the base film 20. As a coating method of the primer layer coating liquid 31 using the first coating device 41, for example, a wire bar coating method, a roll coating method such as reverse coating, gravure coating, a die coating method, a comma coating method, a lip coating method, Examples thereof include a screen coating method, a fountain coating method, a dipping method, and a spray method. As the 1st coating device 41, the coating device according to each coating method can be selected suitably.

  As shown in FIG. 4, the first coating step S <b> 1 a forms a primer layer coating liquid 31 on the upper surface 20 a of the base film 20.

  As shown in FIG. 3, the first drying step S <b> 1 b is a step of drying the primer layer coating liquid 31 applied on the base film 20 using the first drying furnace 51. In the first drying furnace 51, for example, heat is applied to the primer layer coating liquid 31 by hot air blown or the like, and the primer layer coating liquid 31 is dried and cured. The 1st drying furnace 51 will not be specifically limited if the coating liquid 31 for primer layers can be dried. The drying temperature in the 1st drying furnace 51 is 50 degreeC or more and 200 degrees C or less, for example, and 60 degreeC or more and 150 degrees C or less are preferable. The drying temperature in the 1st drying furnace 51 can be suitably set according to the kind of solvent contained in the coating liquid 31 for primer layers. When the solvent of the primer layer coating liquid 31 contains water, the drying temperature of the first drying furnace 51 is preferably 80 ° C. or higher.

  The drying time in the first drying furnace 51, that is, the length of the first drying step S1b is, for example, 30 seconds or more and 20 minutes or less. The length of the first drying step S1b is a length of time from when the primer layer coating liquid 31 is applied to when the primer layer coating liquid 31 is dried and the primer layer 32 is formed.

  By the first drying step S1b, as shown in FIG. 5, the primer layer 32 is formed on the base film 20 by drying and curing the primer layer coating liquid 31.

  Here, in 1st drying process S1b, heat is applied also to the base film 20 with the coating liquid 31 for primer layers. Since the material of the base film 20 is a thermoplastic resin, the base film 20 is thermally contracted in the width direction (Y-axis direction) when heated. Thereby, the base film 20 becomes a wave shape, and the upper surface 20a and the lower surface 20b of the base film 20 become uneven | corrugated shape. The concavo-convex shape of the upper surface 20a of the base film 20 and the concavo-convex shape of the lower surface 20b of the base film 20 are provided so that the concave portions and the convex portions are staggered along the width direction. That is, in the width direction, a convex portion of the lower surface 20b is formed at a position where the concave portion of the upper surface 20a is formed, and a concave portion of the lower surface 20b is formed at a position where the convex portion of the upper surface 20a is formed. Has been.

  Since the primer layer 32 is formed on the upper surface 20a of the base film 20, the primer layer 32 is formed in a wave shape along the uneven shape of the upper surface 20a. The thickness of the primer layer 32 is, for example, preferably 0.05 μm or more and 1 μm or less, and more preferably 0.1 μm or more and 0.4 μm or less. When the thickness of the primer layer 32 is smaller than 0.05 μm, the adhesive force between the base film 20 and a resin layer 34 described later is reduced, and when it is larger than 1 μm, the thickness of the produced polarizing film 1 is likely to be increased. Sometimes.

  The resin layer forming step S2 is a step of forming a resin layer 34 (see FIG. 7) using a polyvinyl alcohol-based resin as a forming material on the base film 20. As shown in FIG. 2, the resin layer forming step S2 includes a second coating step S2a and a second drying step S2b.

  The second application step S2a is a step of applying a resin layer coating liquid 33 containing a polyvinyl alcohol-based resin on the base film 20. As shown in FIG. 3, in the second coating step S <b> 2 a, the resin layer coating liquid 33 is applied to the upper surface 20 a of the base film 20 via the primer layer 32 by the second coating device 42.

  The resin layer coating solution 33 is, for example, a polyvinyl alcohol resin solution obtained by dissolving a polyvinyl alcohol resin powder in a solvent. The polyvinyl alcohol-based resin is as described above in the description of the material for forming the polarizer 10. The solvent is, for example, water. The concentration of the polyvinyl alcohol resin in the resin layer coating liquid 33 is preferably 5% by mass or more, more preferably 5% by mass or more and 15% by mass or less, and further preferably 5% by mass or more and 10% by mass or less. When the concentration of the polyvinyl alcohol-based resin in the resin layer coating solution 33 is less than 5% by mass, the ratio of the liquid component in the resin layer coating solution 33 is increased, so that the drying efficiency is improved in the second drying step S2b. May decrease. When the concentration of the polyvinyl alcohol resin in the resin layer coating liquid 33 is 15% by mass or more, the viscosity of the resin layer coating liquid 33 becomes too high, and the resin layer coating liquid 33 is applied. It may be difficult.

  The viscosity of the resin layer coating liquid 33 is within a range in which it is easy to apply on the base film 20 and the thickness of the resin layer coating liquid 33 formed on the base film 20 is less likely to be uneven. If there is, it will not be specifically limited. The viscosity of the resin layer coating solution 33 is, for example, preferably 0.5 Pa · s or more and 10 Pa · s or less, and 0.8 Pa · s or more and 7 Pa · s or less when applied on the base film 20. More preferably, it is 1 Pa · s or more and 5 Pa · s or less. When the viscosity of the resin layer coating liquid 33 is less than 0.5 Pa · s, the applied resin layer coating liquid 33 may flow to reduce the thickness accuracy of the resin layer 34. Further, when the viscosity of the resin layer coating liquid 33 is greater than 10 Pa · s, the resin formed by limiting the filter that can be used in the second coating device 42 that applies the resin layer coating liquid 33. The quality of the layer 34 may be degraded.

  In addition, the viscosity of the coating liquid 33 for resin layers should just be in the said numerical range, when apply | coating on the base film 20. FIG. Therefore, for example, in a tank (not shown) for storing the resin layer coating solution 33 connected to the second coating device 42, the viscosity of the resin layer coating solution 33 may be outside the above numerical range. . In this case, for example, the viscosity of the resin layer coating liquid 33 can be within the above numerical range by heating or cooling the resin layer coating liquid 33.

  The resin layer coating liquid 33 may contain additives such as a plasticizer and a surfactant. The kind of plasticizer is as described above. The compounding amount of the additive in the resin layer coating liquid 33 is preferably 20% by mass or less with respect to the amount of the polyvinyl alcohol resin.

  The method for applying the resin layer coating solution 33 using the second coating device 42 is not particularly limited as long as the resin layer coating solution 33 can be applied onto the base film 20. Examples of the method for applying the resin layer coating solution 33 using the second coating device 42 include the same method as the method for applying the primer layer coating solution 31 described above. The coating method of the resin layer coating liquid 33 using the second coating apparatus 42 may be the same as or different from the coating method of the primer layer coating liquid 31 using the first coating apparatus 41. Also good. As the 2nd coating device 42, the coating device according to each coating method can be selected suitably.

  By the second coating step S2a, a layer of the resin layer coating liquid 33 is formed on the upper surface 20a of the base film 20 via the primer layer 32, as shown in FIG. The layer of the resin layer coating solution 33 is formed in a wave shape along the upper surface 20 a of the base film 20. The layer thickness of the resin layer coating solution 33 is, for example, 50 μm or more and 200 μm or less, and preferably 150 μm or less.

  The second drying step S <b> 2 b is a step of drying the resin layer coating liquid 33 applied on the base film 20. In 2nd drying process S2b, as shown in FIG. 3, using the 2nd drying furnace 52, the coating liquid 33 for resin layers apply | coated on the base film 20 is dried. In the second drying furnace 52, for example, heat is applied to the layer of the resin layer coating solution 33 by hot air blown or the like, and the resin layer coating solution 33 is dried and cured. The 2nd drying furnace 52 will not be specifically limited if the coating liquid 33 for resin layers can be dried. The drying temperature in the second drying furnace 52 is, for example, 50 ° C. or higher and 200 ° C. or lower, and preferably 60 ° C. or higher and 150 ° C. or lower. The drying temperature in the 2nd drying furnace 52 can be suitably set according to the kind of solvent contained in the coating liquid 33 for resin layers. When the solvent of the resin layer coating liquid 33 contains water, the drying temperature of the second drying furnace 52 is preferably 80 ° C. or higher.

  The drying time in the second drying furnace 52, that is, the length of the second drying step S2b is, for example, 180 seconds or shorter, preferably 150 seconds or shorter, and more preferably 140 seconds or shorter. Although details will be described later, by setting the length of the second drying step S2b in this way, the unevenness of the thickness distribution of the polarizer 10 can be reduced. The length of the second drying step S2b is the length of time from when the resin layer coating solution 33 is applied to when the resin layer coating solution 33 is dried and the resin layer 34 is formed. That is, for example, even when the time from when the resin layer coating liquid 33 is applied until the resin layer 34 comes out of the second drying furnace 52 is longer than 150 seconds, the resin layer coating liquid The time from application of 33 to formation of the resin layer 34 may be 180 seconds or less.

  The method of setting the length of the second drying step S2b to 180 seconds or less is not particularly limited as long as the resin layer coating liquid 33 can be dried and the resin layer 34 can be formed in 180 seconds or less. For example, the output (for example, air volume) of the second drying furnace 52 may be increased, the thickness of the resin layer coating solution 33 may be decreased, or the solvent of the resin layer coating solution 33 may be reduced. It is good also as a substance which is easy to volatilize, such as alcohol. For example, the drying rate of the resin layer coating solution 33 is preferably 1.6% by mass / second or more, and more preferably 2.0% by mass / second or more. In addition, the speed at which the base film 20 on which the resin layer coating solution 33 is applied may be appropriately adjusted according to the length of the second drying step S2b.

  In addition, the drying speed in this specification is, for example, a drying speed in a relatively early stage after the drying of the resin layer coating liquid 33 is started. Specifically, the drying rate in the present specification is, for example, the drying rate until the solvent contained in the resin layer coating liquid 33 is reduced from 30% by mass to 10% by mass.

  By the second drying step S2b, a resin layer 34 is formed on the base film 20, preferably on the primer layer 32, as shown in FIG. Thereby, the laminated | multilayer film 70 with which the base film 20, the primer layer 32, and the resin layer 34 were laminated | stacked is formed. The upper surface 34a of the resin layer 34 has an uneven shape. The uneven shape of the upper surface 34a of the resin layer 34 is flattened compared to the uneven shape of the upper surface 33a of the layer 33 of the resin layer coating liquid 33 shown in FIG. Immediately after the resin layer coating solution 33 is applied and before the resin layer coating solution 33 is dried to become the resin layer 34, the resin layer coating solution 33 flows and the upper surface 33a is flat. This is because The thickness T4 of the resin layer 34 is, for example, 3 μm or more and 20 μm or less, preferably 5 μm or more and 20 μm or less in that the drying time can be shortened.

  The stretching step S <b> 3 is a step of stretching the resin layer 34 together with the base film 20. In the stretching step S3, as shown in FIG. 3, the laminated film 70 is uniaxially stretched in the longitudinal direction using a stretching device 60. Thereby, the resin layer 34 is extended. The thickness T4 of the resin layer 34 is reduced by being stretched. When the thickness T4 of the resin layer 34 is larger than 10 μm before the stretching step S3, the thickness T4 of the resin layer 34 becomes 10 μm or less by the stretching step S3.

  The draw ratio of the resin layer 34 can be appropriately selected according to the desired polarization characteristics of the polarizer 10. The draw ratio of the resin layer 34 is larger than 5 times, preferably 17 times or less, more preferably larger than 5 times and 8 times or less with respect to the longitudinal dimension of the resin layer 34 before stretching. When the draw ratio of the resin layer 34 is 5 times or less, the orientation of the resin layer 34 is insufficient and the degree of polarization of the manufactured polarizer 10 may not be sufficiently increased. Moreover, when the draw ratio of the resin layer 34 is larger than 17 times, the laminated film 70 is easily broken or the thickness of the laminated film 70 becomes too small, and the workability and the handleability in the subsequent process are lowered. Sometimes.

  The stretching device 60 is not particularly limited as long as the resin layer 34 can be stretched to a predetermined stretching ratio. The stretching method of the laminated film 70 using the stretching device 60 may be inter-roll stretching in which stretching is performed with a peripheral speed difference of the transport rolls, or tenter stretching. In addition, the stretching process may be performed in multiple stages. In this case, all of the stretching processes in multiple stages may be performed before the dyeing process S4, or part or all of the stretching processes in the second and subsequent stages may be performed during the dyeing process S4.

  The stretching temperature at which the laminated film 70 (resin layer 34) is stretched using the stretching device 60 is set to a temperature at which the base film 20 and the resin layer 34 are fluid enough to stretch. The stretching temperature is, for example, preferably in the range of −30 ° C. to + 30 ° C., more preferably in the range of −30 ° C. to + 5 ° C., of the phase transition temperature (melting point or glass transition temperature) of the base film 20 − A range of 25 ° C. or higher and ± 0 ° C. or lower is more preferable. When the stretching temperature is lower than −30 ° C. of the phase transition temperature of the base film 20, the fluidity of the base film 20 is too small and it may be difficult to stretch the base film 20 and the resin layer 34. Moreover, when extending | stretching temperature is larger than +30 degreeC of the phase transition temperature of the base film 20, the fluidity | liquidity of the base film 20 is too large, and the base film 20 and the resin layer 34 may be difficult to extend | stretch. When the base film 20 is a multilayer, the phase transition temperature of the base film 20 means the highest temperature among the phase transition temperatures of a plurality of layers.

  The dyeing step S4 is a step of causing the resin layer 34 to adsorb the dichroic dye. In the dyeing step S4, as shown in FIG. 3, the entire laminated film 70 is immersed in a dyeing solution 80 containing a dichroic dye. The dyeing solution 80 is a solution in which a dichroic dye is dissolved in a solvent. The solvent of the dyeing solution 80 is water, for example. In addition to water, an organic solvent compatible with water may be added to the solvent of the dyeing solution 80. The concentration of the dichroic dye in the dyeing solution 80 is preferably 0.01% by mass or more and 10% by mass or less, more preferably 0.02% by mass or more and 7% by mass or less, and 0.025% by mass or more and 5% by mass. % Or less is more preferable.

  When iodine is used as the dichroic dye, it is preferable to further add iodide to the dyeing solution 80 containing iodine. This is because the dyeing efficiency can be improved. Examples of the 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. Etc. The concentration of iodide in the dyeing solution 80 is preferably 0.01% by mass or more and 20% by mass or less.

  Of the iodides, it is preferable to add potassium iodide. In the case of adding potassium iodide, the ratio of the mass of potassium iodide to the mass of iodine is preferably 5 or more and 100 or less, more preferably 6 or more and 80 or less, and further preferably 7 or more and 70 or less.

  The immersion time of the laminated film 70 in the dyeing solution 80 is not particularly limited, but is preferably 15 seconds or longer and 15 minutes or shorter, and more preferably 1 minute or longer and 3 minutes or shorter. The temperature of the dyeing solution 80 is preferably 10 ° C. or higher and 60 ° C. or lower, and more preferably 20 ° C. or higher and 40 ° C. or lower.

  By performing the above-described dyeing treatment, the oriented dichroic dye is adsorbed to the resin layer 34, and the polarizer laminated on the base film 20 via the primer layer 32 as shown in FIG. 10 is obtained. Thereby, the polarizing laminated film 71 by which the base film 20, the primer layer 32, and the polarizer 10 were laminated | stacked is obtained.

  In addition, dyeing process S4 may include the bridge | crosslinking process process implemented following the dyeing | staining process mentioned above. In the crosslinking treatment step, the entire dyed laminated film 70 is immersed in a crosslinking solution containing a crosslinking agent. Examples of the crosslinking agent include boron compounds such as boric acid and borax; glyoxal; and glutaraldehyde. One type of cross-linking agent may be used, or two or more types may be used in combination.

  As the crosslinking solution, a solution in which a crosslinking agent is dissolved in a solvent can be used. The solvent of the crosslinking solution is, for example, water. In addition to water, an organic solvent compatible with water may be added to the solvent of the crosslinking solution. The concentration of the crosslinking agent in the crosslinking solution is, for example, preferably 1% by mass or more and 20% by mass or less, and more preferably 6% by mass or more and 15% by mass or less.

  Iodide may be added to the crosslinking solution. By adding iodide, the in-plane polarization characteristics of the resin layer 34 can be made more uniform. Examples of the iodide added to the crosslinking solution include the same iodide as the iodide added to the dyeing solution 80 described above. The iodide added to the crosslinking solution and the iodide added to the dyeing solution 80 may be the same or different. The concentration of iodide in the crosslinking solution is preferably 0.05% by mass or more and 15% by mass or less, and more preferably 0.5% by mass or more and 8% by mass or less.

  The immersion time of the laminated film 70 in the crosslinking solution is preferably 15 seconds or longer and 20 minutes or shorter, and more preferably 30 seconds or longer and 15 minutes or shorter. The temperature of the crosslinking solution is preferably 10 ° C or higher and 80 ° C or lower.

  In addition, you may perform a crosslinking process simultaneously with a dyeing | staining process by mix | blending a crosslinking agent in the dyeing | staining solution 80. FIG. Moreover, you may perform the process immersed in a crosslinking solution 2 or more times using 2 or more types of crosslinking solutions from which a composition differs.

  Bonding process S5 is a process of bonding the protective film 11 on the polarizer 10. An adhesive layer 12 is formed on the upper surface 10 a of the polarizer 10, and the protective film 11 is bonded to the upper surface 10 a of the polarizer 10 through the adhesive layer 12. The formation method of the contact bonding layer 12 is not specifically limited, For example, the method similar to the method of forming each layer in primer layer formation process S1, resin layer formation process S2, etc. is employable.

  The bonding method of the protective film 11 is not specifically limited. For example, the protective film 11 wound in a roll shape is unwound and passed between two rollers sandwiching the protective film 11 and the polarizing laminated film 71 with the protective film 11 placed on the adhesive layer 12. Thus, the protective film 11 can be bonded.

  Peeling process S6 is a process of peeling and removing the base film 20 from the polarizing laminated film 71 to which the protective film 11 is bonded. The method of peeling and removing the base film 20 is not particularly limited, and for example, the same method as the peeling step of the separator (peeling film) performed with a polarizing plate with an adhesive can be employed. The base film 20 may be peeled off immediately after the bonding step S5, or after the bonding step S5, the polarizing laminated film 71 on which the protective film 11 is bonded is wound into a roll shape. And may be peeled off while unwinding in the subsequent process.

  The polarizing film 1 of this embodiment shown in FIG. 1 is manufactured by peeling and removing the base film 20 by peeling process S6. A polarizing plate is obtained by cutting the polarizing film 1 into a predetermined size.

  According to the present embodiment, it is possible to obtain the polarizer 10 which is thin and has a small unevenness in thickness distribution in the transmission axis direction. Details will be described below.

  When manufacturing a thin polarizer having a thickness of 10 μm or less, as described above, a resin layer coating solution containing a polyvinyl alcohol-based resin is applied on the base film, and the resin layer coating solution is dried. A resin layer is formed. And the manufacturing method (henceforth a thin polarizer manufacturing method) which extends | stretches a resin layer with a base film is employ | adopted. When this method is used, there is a problem that unevenness of the manufactured polarizer is large. The reason is considered to be as follows.

  When the thin polarizer manufacturing method is employed, the base film needs to be a material that can be stretched together with the resin layer, and thus heat shrinks easily when heat is applied. Therefore, for example, when heat is applied to the base film in the first drying step S1b of the primer layer forming step S1 described above, the base film is thermally contracted, and like the base film 20 shown in FIG. Concave and convex shapes are formed on the upper and lower surfaces. In this state, when the layer of the resin layer coating liquid is formed on the base film, the top surface of the resin layer coating liquid also has an uneven shape along the shape of the top surface of the base film.

  Since the resin layer coating solution has fluidity, the upper surface of the resin layer coating solution is gradually flattened until the resin layer coating solution is dried and a resin layer is formed. It will be done. Here, for example, when the length of the second drying step S2b is sufficiently long, the resin layer coating liquid 33 applied in the second coating step S2a is dried until the resin layer 34 is formed. The upper surface 33a of the layer coating solution 33 is completely flattened. Thereby, the upper surface of the resin layer 34 becomes a flat surface 35 as shown by a two-dot chain line in FIG.

  In this case, the thickness T3a, which is the distance in the stacking direction between the uppermost point 34c of the concave portion on the upper side of the lower surface of the resin layer and the flat surface 35, and the lower convex portion of the lower surface of the resin layer The difference between the lowermost point 34d and the thickness T3b, which is the distance in the stacking direction, between the flat surface 35 increases. The thickness T3b is larger than the thickness T3a. Therefore, in the past, in the case of using the thin polarizer manufacturing method, it is considered that the uneven thickness distribution of the resin layer becomes large, and as a result, the uneven thickness distribution of the polarizer becomes large.

  For example, in the case of manufacturing a polarizer having a relatively large thickness, it is not necessary to adopt the above-described thin manufacturing method, and since the base film is not used, the shape of the heat-shrinkable base film is a resin layer. The above problem does not occur.

  In addition, the amount of hot air blown to the resin layer coating liquid in the second drying furnace 52 tends to be non-uniform in the width direction, and the base film tends to vibrate during transport in the second drying step S2b. For example, the coating liquid for the resin layer may flow to increase the unevenness of the thickness distribution of the resin layer, resulting in a problem that the unevenness of the thickness distribution of the polarizer increases.

  For example, in the case of manufacturing a polarizer having a relatively large thickness, it is not necessary to employ the above-described thin manufacturing method, and thus it is not necessary to form a resin layer on the substrate film to be transported. There is no problem.

  The knowledge regarding the cause of unevenness in the thin polarizer manufacturing method described above is a knowledge newly obtained by the present inventors.

  On the other hand, according to the present embodiment, the length of the second drying step S2b is preferably 150 seconds or less. Therefore, the length of the second drying step S2b is relatively small, and the layer of the resin layer coating solution 33 is dried before the upper surface 33a of the resin layer coating solution 33 is flattened to become the flat surface 35. Thus, the resin layer 34 is obtained. Thereby, although the upper surface 34a of the resin layer 34 is flattened more than the upper surface 33a of the resin layer coating liquid 33, it still has an uneven shape. Therefore, there is a difference between the thickness T4a that is the distance between the uppermost point 34c and the upper surface 34a on the lower surface 34b of the resin layer 34 and the thickness T4b that is the distance between the lowermost point 34d and the upper surface 34a on the lower surface 34b of the resin layer 34. Get smaller. That is, the thickness T4 of the resin layer 34 becomes nearly uniform in the width direction, and unevenness in the thickness distribution of the resin layer 34 is reduced. Therefore, unevenness in the thickness distribution of the polarizer 10 can be reduced.

  The thickness T4a is the distance between the uppermost point 34c of the lower surface 34b and the uppermost point 34e of the upper surface 34a that is convex upward. The thickness T4b is a distance between the lowest point 34d of the lower surface 34b and the lowest point 34f of the upper surface 34a that is recessed downward.

  In addition, since the length of the second drying step S2b is relatively small, the time during which the hot air is blown to the resin layer coating liquid 33 in the second drying furnace 52 is shortened, and the resin layer coating liquid 33 is reduced. The time during which the base film 20 is transported from the application to the drying until it becomes the resin layer 34 is shortened. Therefore, the flow of the resin layer coating liquid 33 due to the hot air blown in the second drying furnace 52 and the vibration of the base film 20 is suppressed, and the thickness distribution unevenness of the resin layer 34 is reduced. Therefore, unevenness in the thickness distribution of the polarizer 10 can be reduced.

  As described above, according to this embodiment, in order to obtain a thin polarizer having a thickness of 10 μm or less, the polarizer 10 having a small thickness distribution unevenness can be obtained even when the thin polarizer manufacturing method is employed. Can do. Specifically, the polarizer 10 having a thickness T1 of 10 μm or less and a maximum thickness distribution amplitude of 0.4 μm or less can be obtained. A polarizer 10 having a thickness T1 of 10 μm or less and a periodic intensity of thickness distribution of 0.13 μm or less can be obtained. A polarizer 10 having a thickness T1 of 10 μm or less and a maximum amplitude of the retardation distribution of the polyvinyl alcohol resin of 10 nm or less can be obtained. A polarizer 10 having a thickness T1 of 10 μm or less and a periodic intensity of retardation distribution of the polyvinyl alcohol resin of 2 nm or less can be obtained.

  The polarizer 10 having these characteristics can be obtained by adopting the manufacturing method of the present embodiment described above based on new knowledge regarding the cause of the uneven thickness distribution of the polarizer in the thin polarizer manufacturing method. This is a new polarizer. In other words, when manufacturing a thin polarizer having a thickness of 10 μm or less, it is necessary to employ a thin polarizer manufacturing method, but conventionally there is no knowledge about the cause of the uneven thickness distribution described above. The manufacturing method of the polarizer of the embodiment was not adopted. Therefore, conventionally, the polarizer 10 of this embodiment cannot be realized.

  In addition, in the thin polarizer manufacturing method, the cause of uneven thickness distribution of the polarizer is that the shape of the heat-shrinkable base film is transferred to the resin layer coating solution, and the resin layer coating solution is flattened. It is thought that it is the biggest to do. Therefore, as in this embodiment, the primer film forming step S1 including the first drying step S1b is provided before the resin layer forming step S2, so that the base film is thermally contracted, and the polarizer Unevenness in the thickness distribution tends to be particularly large. Therefore, the effect of reducing the uneven thickness distribution of the polarizer 10 described above is particularly high when the primer layer forming step S1 is provided. The same applies to a case in which, in addition to the primer layer forming step S1, a step in which heat is applied to the base film 20 is included before the resin layer forming step S2.

  In the present embodiment, the following method may be employed.

  In the above description, the unevenness of the thickness distribution of the polarizer 10 is reduced by the method of adjusting the length of the second drying step S2b. However, the present invention is not limited to this. Based on one of the new findings regarding the cause of the uneven thickness distribution described above, the resin 33 before the upper surface 33a of the resin layer coating liquid 33 applied on the base film 20 is completely flattened. If the layer coating liquid 33 can be dried to form the resin layer 34, the polarizer 10 having a small thickness distribution unevenness can be obtained. Therefore, for example, the viscosity of the resin layer coating liquid 33 is made relatively large so that the upper surface 33a of the resin layer coating liquid 33 is flattened or the resin layer coating liquid 33 is coated. The thickness of the resulting resin layer 34 may be reduced by adjusting the amount. In this case, it is easy to form the resin layer 34 by drying the resin layer coating liquid 33 before the upper surface 33a of the resin layer coating liquid 33 is completely flattened. Accordingly, it is possible to manufacture the polarizer 10 having a small thickness distribution unevenness. Moreover, it is also preferable to combine the above-described methods in that it is easy to manufacture the polarizer 10 having a small thickness distribution unevenness.

  Moreover, you may provide the process of giving a corona treatment to the upper surface 20a of the base film 20 with which the primer layer coating liquid 31 is applied before the primer layer forming process S1.

  Moreover, when using a plasticizer for formation of the resin layer 34 in resin layer formation process S2, you may perform the process which removes a plasticizer before dyeing process S4. The removal of the plasticizer is performed by, for example, immersing the laminated film 70 in water at room temperature or higher and about 50 ° C. or less, and causing the laminated film 70 to swell water, thereby eluting the plasticizer from the laminated film 70.

  Further, when a crosslinking treatment is provided in the dyeing step S4, after the crosslinking treatment, the polarizing laminated film 71 is immersed in water such as pure water, ion exchange water, distilled water, tap water, and washed with water. You may perform the process which flushes a boric acid etc. The cleaning liquid may contain iodide. And you may perform the process which dries the polarizing laminated film 71 after that. As the drying treatment, a known method such as natural drying, heat drying, air drying, or reduced pressure drying can be employed.

  Further, the dyeing step S4 may be performed before the stretching step S3, or the dyeing step S4 and the stretching step S3 may be performed simultaneously. Moreover, primer layer formation process S1 does not need to be provided.

  Each method and each configuration described above can be combined with each other within a consistent range.

  In the thin polarizer manufacturing method, the flattening of the coating liquid for the resin layer with respect to the heat-shrinkable shape of the base film was verified among the causes of the uneven thickness distribution of the polarizer. FIG. 9 is a cross-sectional view showing a verification laminate 2 manufactured as a verification example. In FIG. 9, the same reference numerals are given to the same configurations as those in the above-described embodiment.

  The verification laminate 2 includes a base film 20, a primer layer 32, and resin layers 134a and 134b. The resin layer 134 a is formed on the upper surface 20 a of the base film 20 via the primer layer 32. The resin layer 134 b is formed on the lower surface 20 b of the base film 20 via the primer layer 32. The upper surface of the resin layer 134a and the lower surface of the resin layer 134b are flat surfaces.

  In this verification example, the material of the base film 20 was polypropylene. In this verification example, the average thickness of the primer layer 32 was 0.2 μm. Moreover, in 1st drying process S1b, the drying temperature was 90 degreeC and the conveyance speed of the base film 20 was 20 m / min. In this verification example, the solvent of the resin layer coating solution was water. The density | concentration of the polyvinyl alcohol-type resin in the coating liquid for resin layers was 8 mass%. In 2nd application | coating process S2a, the average thickness of the layer of the coating liquid for resin layers at the time of apply | coating was 140 micrometers.

  The resin layers 134a and 134b are formed so that the length of the second drying step S2b is such that the upper surface of the resin layer coating liquid applied in the second application step S2a is completely flattened. The thickness T5a of 134a and the thickness T5b of the resin layer 134b were measured for each width direction (Y-axis direction). The results are shown in FIG.

  FIG. 10 is a graph showing the thickness T5 of the resin layers 134a and 134b with respect to the position in the width direction (Y-axis direction). In FIG. 10, the vertical axis indicates the thickness T5 of the resin layers 134a and 134b, and the horizontal axis indicates the width direction position of the resin layers 134a and 134b. In FIG. 10, the thickness T5a of the resin layer 134a and the thickness T5b of the resin layer 134b are shown.

  From FIG. 10, it was confirmed that the thickness T5a of the resin layer 134a and the thickness T5b of the resin layer 134b were alternately increased and decreased. That is, the thickness T5b of the resin layer 134b decreases at the position in the width direction where the thickness T5a of the resin layer 134a increases, and the thickness T5b of the resin layer 134b increases at the position of the width direction where the thickness T5a of the resin layer 134a decreases. It was confirmed that

  The result shown in FIG. 10 is a result confirming that unevenness in the thickness distribution of the polarizer occurs due to the flattening of the resin layer coating solution. As shown in FIG. 9, when the base film 20 is thermally contracted to form an uneven shape on the surface, the uneven shape of the upper surface 20 a of the base film 20 and the uneven shape of the lower surface 20 b of the base film 20 are The concave portions and the convex portions are staggered along the width direction (Y-axis direction). Therefore, when the resin layer is formed on both surfaces of the base film 20, the concave and convex portions are alternately arranged along the width direction in the concave and convex shape on the lower surface of the resin layer 134a and the concave and convex shape on the upper surface of the resin layer 134b. become. Accordingly, the thickness T5b of the resin layer 134b is minimized at the position in the width direction where the thickness T5a of the resin layer 134a is maximum, and the thickness T5b of the resin layer 134b is determined at the position in the width direction where the thickness T5a of the resin layer 134a is minimized. Maximum. As a result, the thickness T5a of the resin layer 134a and the thickness T5b of the resin layer 134b are considered to change as shown in FIG. 10 according to the position in the width direction.

  From the above, it has been confirmed that at least one of the causes of the uneven thickness distribution of the polarizer is that the resin layer coating solution formed on the thermally contracted base film 20 is flattened. It was.

  Next, the polarizing film of Examples 1-3 was manufactured using the manufacturing method of the polarizing film 1 of embodiment mentioned above, and the comparison with the polarizing film of a comparative example was performed.

  In Example 1, the base film was produced as follows. First, 1% by mass of a nucleating agent composed of high-density polyethylene is blended with homopolypropylene (a “Sumitomo Noblen (registered trademark) FLX80E4” manufactured by Sumitomo Chemical Co., Ltd., melting point: 163 ° C.), which is a homopolymer of propylene. A polypropylene containing a nucleating agent was prepared. From this polypropylene and a propylene / ethylene random copolymer “Sumitomo Nobrene (registered trademark) W151” containing about 5% by mass of ethylene units, a long polypropylene-based laminated film is formed by coextrusion molding using a multilayer extrusion molding machine. This was used as a base film. The polypropylene-based laminated film has a three-layer structure in which the resin layer made of polypropylene containing the nucleating agent described above is disposed on both sides of the resin layer made of “Sumitomo Nobrene (registered trademark) W151”. The average thickness of the base film of Example 1 was 100 μm. The ratio of the thickness of each layer in the base film was nucleating agent-containing polypropylene: Sumitomo Nobrene (registered trademark) W151: nucleating agent-containing polypropylene = 3: 4: 3. The tensile elastic modulus in the longitudinal direction of the base film was 210 MPa.

  In Example 1, the primer layer coating solution was prepared as follows. Polyvinyl alcohol powder (“Z-200” manufactured by Nippon Synthetic Chemical Industry Co., Ltd., average molecular weight 1100, average saponification degree 99.5 mol%) is dissolved in 95 ° C. hot water, and a polyvinyl alcohol aqueous solution having a concentration of 3% by mass did. A crosslinking agent (“SUMIREZ RESIN (registered trademark) 650” manufactured by Sumitomo Chemical Co., Ltd.) was mixed with 1 part by mass of 2 parts by mass of polyvinyl alcohol in the obtained aqueous solution to prepare a primer layer coating solution.

  In Example 1, the resin layer coating solution was prepared as follows. Polyvinyl alcohol powder (“PVA124” manufactured by Kuraray Co., Ltd., average polymerization degree 2400, average saponification degree 98.0 mol% or more, 99.0 mol% or less) was dissolved in 95 ° C. hot water, and the concentration was 8 mass%. It was set as the polyvinyl alcohol aqueous solution and this was made into the coating liquid for resin layers.

  For the primer layer described above using a microgravure coater (first coating device) on the corona-treated surface while continuously conveying the substrate film obtained as described above on one side. The coating solution was applied continuously. The applied primer layer coating solution was dried at 60 ° C. for 3 minutes in the first drying apparatus to form a primer layer having an average thickness of 0.2 μm.

  While continuously transporting the base film on which the primer layer was formed, the above-described resin layer coating solution was continuously applied onto the primer layer using a lip coater (second coating device). The applied resin layer coating solution was dried at 90 ° C. for 130 seconds using a second drying device to form a resin layer on the primer layer. At this time, the drying rate of the resin layer coating solution was 2.1% by mass / second. In the formed resin layer, drying unevenness and the like were not confirmed, and no defects were recognized. The average thickness of the polarizer was 3.6 μm.

  The laminated film in which the primer layer and the resin layer were formed on the base film was uniaxially stretched in the longitudinal direction (film transport direction) using an air-to-roll stretcher while continuously transporting. The stretching temperature was 150 ° C. The draw ratio was 5.3 times.

  The stretched laminated film was immersed in a dyeing solution at 30 ° C. containing iodine and potassium iodide so that the residence time was about 150 seconds, and the resin layer made of polyvinyl alcohol resin was dyed. Next, excess dyeing solution was washed away with pure water at 10 ° C. Subsequently, a crosslinking treatment was performed by dipping in a crosslinking solution at 76 ° C. containing boric acid and potassium iodide so that the residence time was 600 seconds. Thereafter, the film was washed with pure water at 10 ° C. for 4 seconds and dried at 80 ° C. for 300 seconds to obtain a polarizing laminated film in which the base film, the primer layer, and the polarizer were laminated.

  While continuously transporting the polarizing laminated film obtained above, the adhesive solution was applied onto the polarizer to form an adhesive layer. A triacetylcellulose (TAC) film (“KC4UY” manufactured by Konica Minolta Opto Co., Ltd., thickness 40 μm) having a saponification treatment applied to the bonding surface was bonded to a polarizer via an adhesive layer.

  The adhesive solution was prepared as follows. Polyvinyl alcohol powder (“KL-318” manufactured by Kuraray Co., Ltd., average polymerization degree 1800) was dissolved in hot water at 95 ° C. to obtain a polyvinyl alcohol aqueous solution having a concentration of 3% by mass. The resulting aqueous solution was mixed with a crosslinking agent (“SUMIREZ RESIN (registered trademark) 650” manufactured by Sumitomo Chemical Co., Ltd.) at a ratio of 1 part by mass with respect to 2 parts by mass of polyvinyl alcohol to obtain an adhesive solution.

  The base film was peeled and removed from the polarizing laminate film on which the TAC film (protective film) was bonded to obtain the polarizing film of Example 1.

  In Example 2, the resin layer coating solution applied on the base film through the primer layer is dried at 90 ° C. for 150 seconds using the second drying device, whereby the resin layer is formed on the primer layer. Formed. At this time, the drying rate of the resin layer coating solution was 1.9% by mass / second. In the formed resin layer, drying unevenness and the like were not confirmed, and no defects were recognized. The average thickness of the polarizer was 4.0 μm. The other points of Example 2 were the same as Example 1.

  In Example 3, the resin layer coating liquid applied on the base film through the primer layer was dried at 90 ° C. for 170 seconds using the second drying device, whereby the resin layer was formed on the primer layer. Formed. At this time, the drying rate of the resin layer coating solution was 1.7% by mass / second. In the formed resin layer, drying unevenness and the like were not confirmed, and no defects were recognized. The average thickness of the polarizer was 4.5 μm. The other points of Example 3 were the same as Example 1.

  In the comparative example, the resin layer coating liquid applied on the base film through the primer layer is dried at 90 ° C. for 188 seconds using the second drying device, whereby the resin layer is formed on the primer layer. Formed. At this time, the drying rate of the resin layer coating solution was 1.5% by mass / second. In the formed resin layer, drying unevenness and the like were not confirmed, and no defects were recognized. The average thickness of the polarizer was 5.0 μm. The other points of the comparative example were the same as in Example 1.

  Each of the polarizing films of Examples 1 to 3 and the polarizing film of the comparative example was cut out 100 mm in the longitudinal direction (absorption axis direction) to obtain a polarizing plate. About each polarizing plate, the thickness of a polarizer and the phase difference for every wavelength were measured for every position of the width direction. The thickness of the polarizer was measured by changing the measurement position in the width direction (transmission axis direction) at intervals of 5 mm in the approximately 200 mm width portion at the center in the width direction of the polarizer. The measurement position was changed by moving the measuring instrument with an automatic stage.

  From the thickness distribution of the polarizer, the periodic intensity of the thickness distribution was calculated using fast Fourier transform. The phase difference of the polyvinyl alcohol resin was calculated for each position in the width direction from the phase difference for each wavelength of the polarizer. From the phase difference distribution of the polyvinyl alcohol resin, the periodic intensity of the phase difference distribution of the polyvinyl alcohol resin was calculated using fast Fourier transform. Further, after each polarizing plate was placed in an environment of 105 ° C. for 30 minutes, the unevenness of the polarizing plate was visually observed as other polarizing plates and crossed Nicols on the backlight. The results are shown in Tables 1 and 2 and FIGS.

  In Table 1, about Examples 1-3 and a comparative example, the length (second) of a 2nd drying process, the maximum amplitude (micrometer) of thickness distribution, and the maximum value of the periodic intensity of thickness distribution are shown. Yes. In Table 2, for Examples 1 to 3 and Comparative Example, the length of the second drying step (seconds), the maximum amplitude of the phase difference distribution (nm), and the maximum value of the periodic intensity of the phase difference distribution, Show. Moreover, in Table 1 and Table 2, the external appearance evaluation of the nonuniformity is shown about Examples 1-3 and the comparative example. In the appearance evaluation of the unevenness, “◯” indicates that the unevenness is hardly visually recognized, and “X” indicates that the stripe-shaped unevenness that is strong and easily visible is visually recognized.

  FIG. 11 is a graph showing the thickness of the polarizer with respect to the position in the width direction. In FIG. 11, the vertical axis indicates the thickness (μm) of the polarizer, and the horizontal axis indicates the width direction position (mm) of the polarizer.

  FIG. 12 is a graph showing the periodic intensity of the thickness distribution of the polarizer with respect to the uneven period of the thickness distribution of the polarizer. The vertical axis represents the periodic intensity of the thickness distribution of the polarizer, and the horizontal axis represents the uneven period (mm) of the thickness distribution of the polarizer.

  FIG. 13 is a graph showing the retardation Rpva of the polyvinyl alcohol resin in the polarizer with respect to the position in the width direction. In FIG. 13, the vertical axis represents the retardation Rpva (nm) of the polyvinyl alcohol resin, and the horizontal axis represents the width direction position (mm) of the polarizer.

  FIG. 14 is a graph showing the period intensity of the phase difference distribution of the polyvinyl alcohol resin in the polarizer with respect to the uneven period of the thickness distribution of the polarizer. The vertical axis represents the periodic intensity of the phase difference distribution of the polyvinyl alcohol resin, and the horizontal axis represents the uneven period (mm) of the thickness distribution of the polarizer.

  11 to 14 collectively show the results of Examples 1 and 2 and the comparative example.

  From FIG. 11, in the comparative example, the thickness of the polarizer varies relatively depending on the position in the width direction, whereas in Examples 1 and 2, the thickness of the polarizer is relatively uniform regardless of the position in the width direction. It was confirmed that. Thereby, it was confirmed that the thickness distribution unevenness of Examples 1 and 2 was small with respect to the thickness distribution unevenness of the comparative example. Moreover, from Table 1, it was confirmed that the maximum amplitude of the thickness distribution of Examples 1 to 3 was 0.4 μm or less, while the maximum amplitude of the thickness distribution of the comparative example was 0.67 μm. As described above, it was confirmed that by controlling the length of the second drying step, unevenness in the thickness distribution of the polarizer can be reduced, and the maximum amplitude of the thickness distribution of the polarizer can be reduced to 0.4 μm or less.

  Further, the maximum amplitude of the thickness distribution in Example 2 is smaller than the maximum amplitude of the thickness distribution in Example 3, and the maximum amplitude of the thickness distribution in Example 1 is smaller than the maximum amplitude of the thickness distribution in Example 2. Therefore, it was confirmed that the smaller the length of the second drying step, the smaller the maximum amplitude of the thickness distribution of the polarizer, and the smaller the unevenness of the thickness distribution of the polarizer.

  From FIG. 12, in the comparative example, the thickness intensity of the thickness distribution is large in the range where the unevenness period is about 12 mm or more and 17 mm or less, whereas in Examples 1 and 2, the thickness distribution is independent of the unevenness period. It was confirmed that the period intensities of these were almost the same. This shows that in the comparative example, the thickness varies relatively greatly along the width direction with a period of about 12 mm or more and 17 mm or less, and shows that the uneven thickness distribution of the polarizer is large. Yes. On the other hand, Examples 1 and 2 show that the thickness does not fluctuate greatly at a specific period, and the uneven thickness distribution of the polarizer is small. Further, from Table 1, the maximum value of the periodic intensity of the thickness distribution of the comparative example is 0.15 μm, whereas the maximum value of the periodic intensity of the thickness distribution of Examples 1 to 3 is 0.13 μm or less. It was confirmed that there was. As described above, it was confirmed that by controlling the length of the second drying step, unevenness in the thickness distribution of the polarizer can be reduced, and the periodic intensity of the thickness distribution of the polarizer can be reduced to 0.13 μm or less.

  Further, the maximum value of the periodic intensity of the thickness distribution in Example 2 is smaller than the maximum value of the periodic intensity of the thickness distribution in Example 3, and the maximum value of the periodic intensity of the thickness distribution in Example 1 is in Example 2. Since it is smaller than the maximum value of the periodic intensity of the thickness distribution, it can be confirmed that as the length of the second drying step is reduced, the periodic intensity of the thickness distribution of the polarizer can be reduced and the unevenness of the thickness distribution of the polarizer can be reduced. It was.

  From FIG. 13, in the comparative example, the phase difference Rpva varies relatively depending on the position in the width direction, whereas in Examples 1 and 2, the phase difference Rpva is relatively uniform regardless of the position in the width direction. I was able to confirm. Thereby, it was confirmed that the unevenness of the phase difference Rpva in Examples 1 and 2 was small compared to the unevenness of the phase difference Rpva in the comparative example. Since the unevenness of the phase difference Rpva is caused by the unevenness of the thickness distribution of the polarizer, the unevenness of the thickness distribution of the polarizers of Examples 1 and 2 is smaller than the unevenness of the thickness distribution of the polarizer of the comparative example. I was able to confirm. Also, from Table 2, it was confirmed that the maximum amplitude of the phase difference distribution of the comparative example was 18 nm, whereas the maximum amplitude of the phase difference distribution of Examples 1 to 3 was 10 nm or less. From the above, it was confirmed that by controlling the length of the second drying step, unevenness in the thickness distribution of the polarizer can be reduced, and the maximum amplitude of the phase difference distribution of the polyvinyl alcohol resin in the polarizer can be reduced to 10 nm or less. .

  Further, the maximum amplitude of the phase difference distribution in the second embodiment is smaller than the maximum amplitude of the phase difference distribution in the third embodiment, and the maximum amplitude of the phase difference distribution in the first embodiment is the maximum amplitude of the phase difference distribution in the second embodiment. Therefore, it was confirmed that the smaller the length of the second drying step, the smaller the maximum amplitude of the retardation distribution of the polarizer and the less the unevenness of the thickness distribution of the polarizer.

  From FIG. 14, in the comparative example, the period intensity of the phase difference distribution is large in the range where the unevenness period is about 12 mm or more and 17 mm or less, whereas in Examples 1 and 2, it is not dependent on the unevenness period. It was confirmed that the periodic intensity of the phase difference distribution was almost the same. This indicates that in the comparative example, the phase difference Rpva fluctuates relatively greatly along the width direction with a period of about 12 mm or more and 17 mm or less, and the uneven thickness distribution of the polarizer is large. Is shown. On the other hand, in the first and second embodiments, the phase difference Rpva does not fluctuate greatly in a specific cycle, indicating that the uneven thickness distribution of the polarizer is small. Moreover, from Table 2, the maximum value of the periodic intensity of the phase difference distribution of the comparative example is 4.8 nm, whereas the maximum value of the periodic intensity of the phase difference distributions of Examples 1 to 3 is 2 nm or less. I was able to confirm. From this, it was confirmed that by controlling the length of the second drying step, unevenness in the thickness distribution of the polarizer can be reduced, and the periodic intensity of the retardation distribution of the polyvinyl alcohol resin in the polarizer can be reduced to 2 nm or less. .

  Further, the maximum value of the periodic intensity of the phase difference distribution in Example 2 is smaller than the maximum value of the periodic intensity of the phase difference distribution in Example 3, and the maximum value of the periodic intensity of the phase difference distribution in Example 1 is implemented. Since it is smaller than the maximum value of the periodic intensity of the phase difference distribution in Example 2, the periodic intensity of the phase difference distribution of the polarizer can be reduced as the length of the second drying step is reduced, and unevenness of the thickness distribution of the polarizer is reduced. It was confirmed that can be reduced.

  From Tables 1 and 2, it was confirmed that, in the comparative example, strong and easy-to-view streak-like unevenness was visually recognized, whereas in Examples 1 to 3, the unevenness was hardly visually recognized. Thereby, it was confirmed that the unevenness of the thickness distribution of the polarizer can be reduced by controlling the length of the second drying step.

  From the above results, according to Examples 1 to 3, it was confirmed that a thin polarizer and a small thickness distribution unevenness were obtained.

  DESCRIPTION OF SYMBOLS 1 ... Polarizing film, 10 ... Polarizer, 11 ... Protective film, 20 ... Base film (base material), 31 ... Primer layer coating liquid, 32 ... Primer layer, 33 ... Resin layer coating liquid, 34 ... Resin layer, S1 ... primer layer forming step, S2 ... resin layer forming step, S3 ... stretching step, S4 ... dyeing step

Claims (2)

A method for producing a polarizer in which a dichroic dye is oriented in a polyvinyl alcohol-based resin,
The polarizer has a thickness of 10 μm or less,
A resin layer forming step of forming a resin layer having a polyvinyl alcohol-based resin as a forming material on a substrate;
A stretching step of stretching the resin layer together with the substrate;
A dyeing step of adsorbing the dichroic dye on the resin layer;
Including
The resin layer forming step includes
Applying a resin layer coating solution containing a polyvinyl alcohol-based resin on the substrate;
Drying the applied resin layer coating solution;
Including
The length of the process of drying the said resin layer coating liquid is 180 second or less, The manufacturing method of the polarizer characterized by the above-mentioned. Prior to the resin layer forming step, further comprising a primer layer forming step of forming a primer layer on the substrate,
The primer layer forming step includes
Applying a primer layer coating solution on the substrate;
Drying the applied primer layer coating solution; and
The manufacturing method of the polarizer of Claim 1 containing this.

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