TW201802168A - Polarizer, polarizing film and method of producing polarizer - Google Patents

Abstract

The present invention provides a thin polarizer having small unevenness in thickness distribution, and a polarizing film having such polarizer. One aspect of the polarizer of the present invention is characterized by the fact that dichroic dye is oriented in polyvinyl alcohol resin of the polarizer; wherein, the thickness of the polarizer is 10 [mu]m or less; and in the transmission axis direction of the polarizer, the maximum amplitude of the thickness distribution is 0.4 [mu]m or less.

Description

Polarizer, polarizing film, and manufacturing method of polarizer

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

A polarizer obtained by adsorbing a dichroic substance to a hydrophilic polymer layer containing a polyvinyl alcohol (PVA; PolyVinyl Alcohol) resin as a forming material 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 television (TV), a monitor, a mobile phone, and a personal digital assistant (PDA). In recent years, with the increase in the performance and thickness of the liquid crystal display device, the polarizer used for the polarizing film of the liquid crystal display device is also required to be thinner.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2009-098653

In order to make relatively thin polarizers, such as patents In the description of the first embodiment, after the aqueous solution containing the hydrophilic polymer is applied to the base material layer, the aqueous solution containing the hydrophilic polymer is dried to form a laminate in which the hydrophilic polymer layer is laminated on the base material layer. Then, the laminate was subjected to elongation treatment and dyeing treatment to produce a polarizer. However, when the polarizer is produced by such a method, there is a problem that the unevenness of the thickness distribution of the polarizer in the direction of the transmission axis (width direction) becomes large. In addition, in recent years, as the brightness of the backlight is improved for the purpose of improving the visibility, it is easier to recognize that the thickness distribution of the polarizer is not uniform.

In view of the above problems, it is one of the objects of the present invention to provide a polarizer having a small thickness and a small unevenness in thickness distribution, and a polarizing film having such a polarizer. Further, one aspect of the present invention is to provide a method for producing a polarizer which can be made thinner and which can reduce unevenness in thickness distribution.

In one aspect of the polarizer of the present invention, the polarizer is a dichroic dye which is oriented in a polyvinyl alcohol-based resin, wherein the polarizer has a thickness of 10 μm or less and is in a thickness direction of the polarizer. The maximum amplitude of the distribution is 0.4 μm or less.

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

In one aspect of the polarizer of the present invention, the polarizer is a dichroic dye which is oriented in a polyvinyl alcohol-based resin, wherein the polarizer has a thickness of 10 μm or less and is in a thickness direction of the polarizer. The periodic intensity of the distribution is 0.13 μm or less.

In the transmission axis direction of the polarizer, the maximum amplitude of the phase difference distribution of the polyvinyl alcohol-based resin may be 10 nm or less.

In one aspect of the polarizer of the present invention, the polarizer of the polyvinyl alcohol-based resin is a dichroic dye, wherein the polarizer has a thickness of 10 μm or less, and is in the direction of the transmission axis of the polarizer. The maximum amplitude of the phase difference distribution of the polyvinyl alcohol-based resin is 10 nm or less.

In the transmission axis direction of the polarizer, the periodic strength distribution of the polyvinyl alcohol-based resin may have a periodic intensity of 2 nm or less.

In one aspect of the polarizer of the present invention, the polarizer of the polyvinyl alcohol-based resin is a dichroic dye, wherein the polarizer has a thickness of 10 μm or less, and is in the direction of the transmission axis of the polarizer. The periodic strength distribution of the polyvinyl alcohol-based resin has a periodic intensity of 2 nm or less.

In one aspect of the polarizing film of the present invention, the polarizing film and the protective film provided on at least one surface of the polarizer are provided.

In one aspect of the method for producing a polarizer of the present invention, a method for producing a polarizer in which a dichroic dye is aligned to a polyvinyl alcohol-based resin, wherein the polarizer has a thickness of 10 μm or less, and the production method includes: a resin layer forming step of forming a resin layer using a polyvinyl alcohol-based resin as a forming material on the substrate; an extending step of extending the resin layer together with the substrate; and dyeing the dichroic dye to the resin layer In the step of forming the resin layer, the step of applying a coating liquid for a resin layer containing a polyvinyl alcohol-based resin to the substrate, and The step of drying the coating liquid layer for coating the resin layer, wherein the step of drying the coating liquid for a resin layer has a length of 180 seconds or less.

Before the foregoing resin layer forming step, further comprising an undercoat layer forming step of forming a primer layer on the foregoing substrate, wherein the foregoing undercoat layer forming step may include applying a primer layer on the foregoing substrate A step of using a coating liquid and a method of producing a step of drying the coating liquid for coating the undercoat layer.

According to an aspect of the present invention, it is possible to provide a polarizer having a small thickness and a small thickness distribution in the axial direction, and a polarizing film having such a polarizer. Moreover, according to an aspect of the present invention, it is possible to provide a method of manufacturing a polarizer which can be made thinner and which can reduce unevenness.

1‧‧‧ polarizing film

10‧‧‧ polarizer

10a‧‧‧above

10b‧‧‧ below

11‧‧‧Protective film

12‧‧‧Next layer

2‧‧‧Verification layer for verification

20‧‧‧Substrate film (substrate)

20a‧‧‧above

20b‧‧‧ below

31‧‧‧ Coating solution for undercoating

32‧‧‧Undercoat

33‧‧‧ Coating liquid for resin layer

33a‧‧‧above

34, 134a, 134b‧‧‧ resin layer

34a‧‧‧above

34b‧‧‧ below

34c‧‧‧ the top

34d‧‧‧ lowest point

34e‧‧‧ the top

34f‧‧‧ lowest point

35‧‧‧flat surface

41‧‧‧First coating device

42‧‧‧Second coating device

51‧‧‧First drying oven

52‧‧‧Second drying oven

60‧‧‧Extension

70‧‧‧ laminated film

71‧‧‧Polarized laminated film

80‧‧‧Staining solution

S1‧‧‧ undercoat layer formation step

S1a‧‧‧First coating step

S1b‧‧‧First drying step

S2‧‧‧ resin layer forming step

S2a‧‧‧second coating step

S2b‧‧‧Second drying step

S3‧‧‧Extension step

S4‧‧‧ staining step

Fig. 1 is a cross-sectional view showing a polarizing film of the present embodiment.

Fig. 2 is a flow chart showing the procedure of the method for producing a polarizing film of the present embodiment.

Fig. 3 is a schematic view showing a part of the procedure of the method for producing a polarizing film of the present embodiment.

Fig. 4 is a cross-sectional view showing a part of the procedure of the method for producing a polarizing film of the present embodiment.

Fig. 5 is a cross-sectional view showing a part of the procedure of the method for producing a polarizing film of the present embodiment.

Fig. 6 is a view showing the order of the method for producing the polarizing film of the present embodiment. A section of the section.

Fig. 7 is a cross-sectional view showing a part of the procedure of the method for producing a polarizing film of the present embodiment.

Fig. 8 is a cross-sectional view showing a part of the procedure of the method for producing a polarizing film of the present embodiment.

Fig. 9 is a cross-sectional view showing a laminate of the verification example.

Fig. 10 is a graph showing the thickness of the resin layer versus the position in the width direction.

Fig. 11 is a graph showing the thickness of the polarizer versus the position in the width direction.

Fig. 12 is a graph showing the period of the thickness distribution of the polarizer and the uneven period of the thickness distribution of the polarizer.

Fig. 13 is a graph showing the phase difference versus the position in the width direction of the polyvinyl alcohol-based resin in the polarizer.

Fig. 14 is a graph showing the period of the phase difference distribution of the polyvinyl alcohol-based resin in the polarizer and the uneven period of the thickness distribution of the polarizer.

Hereinafter, the polarizing film of the embodiment of the present invention will be described in detail with reference to the drawings.

Further, the scope of the present invention is not limited to the following embodiments, and may be arbitrarily changed within the scope of the technical idea of the present invention. In addition, in the following drawings, in order to make it easy to understand each structure, the scale, the number, and the like of each structure may be different from the scale and number of actual structures.

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 is provided with a polarizer 10 and a protective film 11 And then layer 12. The polarizer 10, the adhesive layer 12, and the protective film 11 are laminated in this order. Although the drawings are omitted, the polarizing film 1 of the present embodiment has a long strip shape. The polarizing film 1 is, for example, wound up on a core material, and stored in the form of a roll.

In the following description, the direction in which the layers of the polarizing film 1 are stacked is simply referred to as the "layering direction", and the length direction orthogonal to the layering direction of the polarizing film 1 is simply referred to as "longitudinal direction". In the case where the width direction of the polarizing film 1 orthogonal to both the lamination direction and the longitudinal direction is simply referred to as "width direction".

Moreover, in the drawings, a suitable three-dimensional orthogonal coordinate system (XYZ coordinate system) is shown. In the three-dimensional orthogonal coordinate system, the Z-axis direction is a direction parallel to the lamination 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. Further, in the lamination 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 merely names used to explain the relative positional relationship of the respective portions, and do not limit the posture of each portion at the time of production of the polarizing film, the actual posture of the polarizing film, and the use pattern of the polarizing film.

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

The polyvinyl alcohol-based resin which is a material for forming the polarizer 10 may, for example, be a polyvinyl alcohol resin, a polyvinyl alcohol resin derivative or a modified product of a polyvinyl alcohol resin derivative. Polyvinyl alcohol resin The organism may, for example, be polyvinyl formal, polyvinyl acetal or polyvinyl butyral. Examples of the modified polyvinyl alcohol resin derivative include an olefin such as ethylene or propylene; an unsaturated carboxylic acid such as acrylic acid, methacrylic acid or crotonic acid; and an unsaturated carboxylic acid. An alkyl ester; or a acrylamide or the like modified.

The average degree of polymerization of the polyvinyl alcohol-based resin is preferably 100 or more and 10,000 or less, more preferably 1,000 or more and 10,000 or less, still more preferably 1,500 or more and 8,000 or less, and still more preferably 2,000 or more and 5,000 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, and when it is more than 10,000, the solubility in water is lowered, and it becomes difficult to produce the coating liquid 33 for a resin layer to be described later. In the present specification, the average degree of polymerization of the polyvinyl alcohol-based resin can be determined, for example, by a method specified in JIS K 6727 (1994).

The polyvinyl alcohol-based resin which is a material for forming the polarizer 10 is preferably a saponified one. The degree of saponification 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, and still more preferably 93.0 mol% or more and 99.5 mol% or less. When the degree of saponification of the polyvinyl alcohol-based resin is 80 mol% or more, appropriate optical characteristics are easily obtained.

In addition, the degree of saponification of the polyvinyl alcohol-based resin means that the proportion of the acetic acid group contained in the polyvinyl acetate-based resin which is a raw material of the polyvinyl alcohol-based resin is converted into a hydroxyl group by a saponification step in terms of mol%. The presenter is defined by the following (Formula 1).

(Formula 1) Degree of saponification (% by mole) = (number of hydroxyl groups) ÷ (number of hydroxyl groups + B The number of acid groups) × 100 In the present specification, the degree of saponification of the polyvinyl alcohol-based resin can be determined, for example, by a method specified in JIS K 6727 (1994).

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

The thickness T1 of the polarizer 10 is 10 μm or less, and preferably 5 μm or less. In the width direction (transmission axis direction and 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 or less. The maximum amplitude of the thickness distribution of the polarizer 10 is usually 0.01 μm or more in consideration of the analysis ability of the measuring device. The maximum amplitude of the thickness distribution refers to the 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, for example, using a white interference type non-contact type film thickness meter (for example, model: F20 manufactured by Filmetrics Co., Ltd.). Thereby, it is possible to perform precise measurement without contacting the object to be measured (polarizing sheet 10), and even if the object to be measured is a layer of a part of the laminated body, the thickness of the object can be measured without peeling off the respective layers.

In the width direction (transmission axis direction and Y-axis direction) of the polarizer 10, 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, still more preferably 0.04 μm or less. Moreover, the periodic intensity of the thickness distribution of the polarizer 10 is usually 0.0025 μm or more. In the present specification, the periodic intensity of the thickness distribution of the polarizer 10 is obtained, for example, by the following method.

The thickness of the polarizer 10 in the width direction is distributed and subjected to Fast Fourier Transform (FFT). Fast Fourier transform algorithm, for example using the Cooley-Tukey type FFT algorithm. The fast Fourier transform using the Cooley-Tukey type FFT algorithm can be performed, for example, by implementing the gain set "ATPVBAEN.XLAM! Fourier" of the Microsoft Excel spreadsheet software "Excel (registered trademark) 2010". The gain set is applied to the raw fraction data of the thickness T1 of the measured polarizer 10, and the thickness distribution of the polarizer 10 in the width direction can be subjected to fast Fourier transform.

In general, fast Fourier transform converts the time's waveform function into a frequency distribution function. In the case of the present embodiment, the waveform function f(L) indicating the thickness distribution of the polarizer 10 in the width direction position L (the Y-axis direction position) is obtained by the fast propagation of the blade, and the thickness distribution of the polarizer 10 is obtained. The distribution function f(ω) of the frequency ω. Furthermore, the sampling period is 1/ω.

In the present specification, the periodic intensity of the thickness distribution of the polarizer 10 is represented by |f(ω _N )|/(N/2). |f(ω _N )| is an absolute value of a distribution function obtained by performing fast Fourier transform on the waveform function f(L _N ) corresponding to the Nth sampling point. L _N is the width direction position L of the Nth sampling 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. Furthermore, the maximum number of sampling points is below the original fraction A of the obtained film thickness distribution and is the index value of 2 closest to A.

The period intensity of the thickness distribution of the polarizer 10 obtained as described above is the vertical axis, and the period of the sampling point is plotted on the horizontal axis to obtain a power spectrum. The period of the sampling point is L _N /N.

In the present specification, the periodic intensity is equal to or less than a predetermined value, and means that the period intensity in a region including a period of 10 mm or more and 70 mm or less is not more than a predetermined value. In other words, the periodic intensity of the thickness distribution of the polarizer 10 is 0.05 μm or less, and the periodic intensity of the thickness distribution of the polarizer 10 in the region including the period of 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 is 0.05 μm or less, and the maximum value of the periodic intensity of the thickness distribution of the polarizer 10 is 0.05 μm or less in a region having a period of 10 mm or more and 70 mm or less.

Further, in the present specification, the thickness of a certain film (layer) means the size of the film (layer) in the lamination direction (Z-axis direction), and also the average thickness of the film (layer). That is, the thickness of the polarizer also includes the average thickness of the polarizer.

In the width direction (transmission axis direction and 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, still more preferably 5.3 nm or less. . Further, the maximum amplitude of the phase difference distribution of the polyvinyl alcohol-based resin is usually 0.3 nm or more. The maximum amplitude of the phase difference distribution refers to the maximum value of the phase difference Rpva of the polyvinyl alcohol-based resin in the region of the period of 10 mm or more and 20 mm or less.

The phase difference Rpva of the polyvinyl alcohol-based resin can be obtained from the phase difference R (λ) of the polarizer 10 in the wavelength region of the absorption band of the dichroic dye. In the present specification, the phase difference Rpva of the polyvinyl alcohol-based resin means a phase difference at a wavelength of 1000 nm. Specifically, the phase difference R (λ) of the polarizer 10 is measured one by one for the complex wavelength λ of 850 nm or more, and the measured wavelength λ and the measured phase difference R (λ) are plotted as follows. The Sellmeier formula (Formula 2) is fitting in a least squares method. Here, E and F in (Formula 2) are fitting parameters, and are coefficients determined by the least squares method.

(Formula 2) R(λ)=E+F/(λ ² -600 ² )

E in (Formula 2) corresponds to the phase difference Rpva of the polyvinyl alcohol-based resin. Further, F/(λ ^{2 -} 600 ² ) corresponds to a phase difference of the dichroic dye. In the present specification, the phase difference R (λ) of the polarizer 10 is measured by, for example, a phase difference measuring device (manufactured by Oji Scientific Instruments Co., Ltd., model: KOBRA-WPR/IR).

In the width direction (transmission axis direction, Y-axis direction) of the polarizing plate 10, 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, still more preferably 0.8 nm or less. . Further, the periodic strength of the phase difference distribution of the polyvinyl alcohol-based resin is usually 0.075 nm or more. The periodic intensity of the phase difference distribution of the polyvinyl alcohol-based resin refers to a wavenumber spectrum obtained by applying a phase difference distribution of a polyvinyl alcohol-based resin in the width direction by a fast Fourier transform, and a period of 10 mm or more and 20 mm or less. The value of the maximum amplitude. The calculation method of the periodic intensity of the phase difference distribution is the period of the thickness distribution of the polarizer 10 described above. The same strength.

Examples of the dichroic dye to be used in the polyvinyl alcohol-based resin include iodine and an organic dye.

The protective film 11 is provided on the upper surface 10a of the polarizer 10. More specifically, in the present embodiment, the protective film 11 is attached to the upper surface 10a of the polarizer 10 via 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 an optical function such as a retardation film and a brightness enhancement film.

The material for forming the protective film 11 is not particularly limited, and examples thereof include a cyclic polyolefin resin film; a cellulose acetate resin film composed of a resin such as triethyl fluorenyl cellulose or diethyl hydrazine cellulose; a polyester resin film composed of a resin such as polyethylene terephthalate, polyethylene naphthalate or polybutylene terephthalate; a polycarbonate resin film; an acrylic resin film; A propylene resin film or the like.

The cyclic polyolefin-based resin film may be a one-axis stretcher or a biaxially stretched one, and may have an arbitrary phase difference imparted to the cyclic polyolefin-based resin film by stretching.

The cyclic polyolefin resin film generally has poor surface activity. Therefore, in the case where the protective film 11 is a cyclic polyolefin-based resin film, it is preferable to perform plasma treatment, corona treatment, ultraviolet irradiation treatment, flame on the lower surface of the protective film 11 to be next to the polarizing film 10. ) Surface treatment such as treatment and saponification. In particular, it is suitable for plasma treatment and corona treatment which are relatively easy to implement.

The protective film 11 is a cellulose acetate resin film. In the case of the surface of the protective film 11, a liquid crystal layer or the like may be formed in order to improve the viewing angle characteristics. Further, the protective film 11 may be an extension of the cellulose acetate-based resin film in order to impart a phase difference. When the protective film 11 is a cellulose acetate-based resin film, in order to improve the adhesion to the polarizing film 1, the lower surface of the protective film 11 is usually subjected to a saponification treatment. As the saponification treatment, a method of immersing in an aqueous solution of a base such as sodium hydroxide or potassium hydroxide can be employed.

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

The thickness T2 of the protective film 11 is preferably as thin as possible, and is preferably as small as 90 μm or less, more preferably 50 μm or less. When the thickness T2 of the protective film 11 is too thin, the strength of the protective film 11 is lowered, and the workability is poor. Therefore, the thickness T2 of the protective film 11 is preferably 5 μm or more.

In the present embodiment, the protective film 11 may be provided only on the upper surface 10a of the polarizer 10, but is not limited thereto. The protective film 11 may be provided on at least one surface of the polarizer 10, or may be provided on both the upper surface 10a and the lower surface 10b of the polarizer 10.

Next, the layer 12 is laminated on the upper surface 10a of the polarizer 10. Next, the layer 12 is a layer in which the polarizer 10 and the protective film 11 are adhered to each other. As a material for forming the adhesive layer 12, for example, a water-based adhesive, an ultraviolet-curable adhesive, an electron beam-curable adhesive, or the like is preferable, and a water-based adhesive is more preferable. The water-based adhesive may, for example, be an aqueous solution of a polyvinyl alcohol-based resin or a solution of an aqueous solution of a polyvinyl alcohol-based resin. An aqueous solution of a crosslinking agent, an amine ester emulsion adhesive, and the like. Further, the material for forming the adhesive 12 may contain a metal compound filler.

Next, a method of manufacturing the polarizing film 1 of the present embodiment will be described. Fig. 2 is a flow chart showing the procedure of the method of manufacturing the polarizing film 1 of the present embodiment. Fig. 3 is a schematic view showing a part of the procedure of the method of manufacturing the polarizing film 1. 4 to 8 are cross-sectional views showing a part of the procedure of the method of manufacturing the polarizing film 1. Fig. 4 is a cross-sectional view showing the position of P1 shown in Fig. 3. Fig. 5 is a cross-sectional view showing the position of P2 shown in Fig. 3. Fig. 6 is a cross-sectional view showing the position of P3 shown in Fig. 3. Fig. 7 is a cross-sectional view showing the position of P4 shown in Fig. 3. In addition, in the fifth to eighth drawings, the uneven shape of the unevenness due to the heat shrinkage of the base film 20 described later and the unevenness of the respective layers accompanying the heat shrinkage of the base film 20 are schematically emphasized.

The method for producing the polarizing film 1 of the present embodiment includes a resin layer forming step S2, an extending step S3, a dyeing step S4, a bonding step S5, and a peeling step S6 as shown in Fig. 2 . As shown in Fig. 2, before the resin layer forming step S2, the undercoat layer forming step S1 may be included. As shown in Fig. 3, in the present embodiment, the roll-shaped base film (base material) 20 is conveyed in the longitudinal direction by the nip roller and the conveying roller, and the polarizing film 1 is produced. Further, although Fig. 3 shows a pattern in which each step is continuously performed, the film may be temporarily wound into a roll at the end of each step.

The material of the base film 20 is not particularly limited as long as it can be extended together with the resin layer 34 to be described later in the extending step S3. The material of the base film 20 is, for example, a thermoplastic resin. Used as the substrate film 20 The thermoplastic resin of the material is preferably excellent in transparency, mechanical strength, thermal stability, and elongation.

Specifically, the thermoplastic resin to be used as the material of the base film 20 may, for example, be a polyolefin resin such as a chain polyolefin resin or a cyclic polyolefin resin (such as a decene-based resin); Polyester resin such as ethylene phthalate; (meth)acrylic resin; cellulose ester resin such as cellulose triacetate or cellulose diacetate; polycarbonate resin; polyvinyl alcohol Resin; polyvinyl acetate resin; polyarylate resin; polystyrene resin; polyether oxime resin; polyfluorene resin; polyamine resin; polyimine resin; Mixtures, copolymers, and the like.

The base film 20 may be composed of one or two or more thermoplastic resins of the above thermoplastic resins. 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, and is preferably 1 μm or more and 500 μm or less, more preferably 1 μm or more and 300 μm or less, and still more preferably 5 μm or more and 200 μm or less, and more preferably from the viewpoint of strength and workability. 5 μm or more and 150 μm or less. 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. The tensile elastic modulus in the longitudinal direction of the base film 20 is preferably 150 MPa or more at 80 ° C, more preferably 155 MPa or more. By using such a base film, heat 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 manual In the longitudinal direction, the tensile modulus of the base film 20 is measured by, for example, AUTOGRAPH (registered trademark) (manufactured by Shimadzu Corporation, model: AG-IS). Specifically, it is measured in accordance with JIS K7163.

The undercoat layer forming step S1 is a step of forming the undercoat layer 32 (refer to Fig. 5) on the substrate film 20. The undercoat layer 32 is a layer provided to increase the adhesion between the base film 20 and the resin layer 34 to be described later. The undercoat layer forming step S1, as shown in Fig. 2, includes a first coating step S1a and a first drying step S1b. As shown in FIG. 3, in the first coating step S1a, the coating liquid 31 for the undercoat layer is applied onto the upper surface 20a of the base film 20 by the first coating device 41.

The coating liquid 31 for an undercoat layer is, for example, a resin solution obtained by dissolving a powder of a resin in a solvent. The resin contained in the coating liquid 31 for the undercoat layer is a resin containing a component capable of improving the above-mentioned adhesive strength, and is preferably a thermoplastic resin excellent in transparency, thermal stability, and elongation. The resin contained in the coating liquid 31 for the undercoat layer may, for example, be a (meth)acrylic resin or a polyvinyl alcohol-based resin. In particular, the resin contained in the coating liquid 31 for the undercoat layer is preferably a polyvinyl alcohol-based resin. This is because the adhesion of the base film 20 to the resin layer 34 to be described later can be obtained.

The polyvinyl alcohol-based resin used as the resin contained in the coating liquid 31 for the undercoat layer can be selected in the same manner as the polyvinyl alcohol-based resin of the polarizing plate 10 described above. The resin contained in the coating liquid 31 for the undercoat layer may be the same as or different from the polyvinyl alcohol-based resin of the polarizing plate 10.

The solvent of the coating liquid 31 for the undercoat layer may, for example, be an organic solvent or an aqueous solvent which can dissolve the above resin. As an organic solvent Examples thereof 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; and dichloro Chlorinated hydrocarbons such as methane, trichloroethylene, and chloroform; and alcohols such as ethanol, 1-propanol, 2-propanol, and 1-butanol. The solvent of the coating liquid 31 for the undercoat layer is preferably water, for example. This is because the base film 20 is less likely to be dissolved regardless of the material of the base film 20, and the influence on the environment can be made small. The concentration of the resin in the coating liquid 31 for the undercoat layer is preferably from 1% by mass to 25% by mass.

The coating method of the undercoat layer coating liquid 31 of the first coating device 41 is not particularly limited as long as the coating liquid 31 for the undercoat layer can be applied to the upper surface 20a of the base film 20. The coating method of the coating liquid 31 for undercoat layer of the first coating device 41 is, for example, a roll coating method such as a bar coating method, a reverse coating method, or a gravure coating method, a die coating method, or the like. Comma coating, lip coating, screen coating, fountain coating, dip coating, spray coating, and the like. As the first coating device 41, a coating device corresponding to each coating method can be appropriately selected.

By the first coating step S1a, as shown in Fig. 4, a layer of the undercoat layer coating liquid 31 is formed on the upper surface 20a of the base film 20.

The first drying step S1b is a step of drying the undercoat layer coating liquid 31 applied to the base film 20 by using the first drying furnace 51 as shown in Fig. 3 . In the first drying furnace 51, heat is applied to the coating liquid for primer layer 31 by hot air blowing, for example, and the coating liquid for primer layer 31 is dried and cured. The first drying furnace 51 as long as the coating liquid for the undercoat layer can be dried 31, that is, there is no special limit. The drying temperature of the first drying furnace 51 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 of the first drying furnace 51 can be appropriately set depending on the type of the solvent contained in the coating liquid 31 for the undercoat layer. When the solvent of the coating liquid 31 for undercoat layer contains water, the drying temperature of the first drying furnace 51 is preferably 80 ° C or higher.

The drying time of 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 the length from the application of the undercoat layer coating liquid 31 to the drying undercoat layer coating liquid 31 to form the undercoat layer 32.

By the first drying step S1b, as shown in Fig. 5, the coating liquid 31 for the undercoat layer is dried on the base film 20 to form a hardened undercoat layer 32.

Here, in the first drying step S1b, heat is applied to the base film 20 together with the coating liquid 31 for the undercoat layer. Since the material of the base film 20 is a thermoplastic resin, the base film 20 is thermally shrunk in the width direction (Y-axis direction) by application of heat. Therefore, the base film 20 is wavy, and the upper surface 20a and the lower surface 20b of the base film 20 are formed into a concavo-convex shape. The uneven shape of the upper surface 20a of the base film 20 and the uneven shape of the lower surface 20b of the base film 20 are provided so that the concave portion and the convex portion are different from each other in 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 is formed on the upper surface 20a, and a concave portion of the lower surface 20b is formed at a position where the convex portion is formed on the upper surface 20a.

Since the undercoat layer 32 is formed on the upper surface 20a of the base film 20, it is formed in a wave shape along the uneven shape of the upper surface 20a. Undercoat layer 32 The thickness is 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 undercoat layer 32 is less than 0.05 μm, the adhesion between the base film 20 and the resin layer 34 to be described later becomes small, and when it is larger than 1 μm, the thickness of the polarized film 1 to be produced tends to be large.

In the resin layer forming step S2, a step of forming a resin layer 34 (refer to Fig. 7) using a polyvinyl alcohol-based resin as a forming material is formed 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 coating step S2a is a step of applying a coating liquid 33 for a resin layer containing a polyvinyl alcohol-based resin onto the base film 20. As shown in FIG. 3, in the second coating step S2a, the coating liquid 33 for the resin layer is applied to the upper surface 20a of the base film 20 via the undercoat layer 32 in the second coating step 42. .

The coating liquid 33 for a resin layer is, for example, a polyvinyl alcohol-based resin solution obtained by dissolving a powder of a polyvinyl alcohol-based resin in a solvent. The polyvinyl alcohol-based resin is as described in the description of the material for forming the polarizer 10 described above. The solvent is, for example, water. The concentration of the polyvinyl alcohol-based resin in the coating liquid 33 for a resin layer is preferably 5% by mass or more, more preferably 5% by mass or more and 15% by mass or less, and still more preferably 5% by mass or more and 10% by mass or less. When the concentration of the polyvinyl alcohol-based resin in the coating liquid 33 for a resin layer is less than 5% by mass, the ratio of the liquid component in the coating liquid 33 for the resin layer increases, so in the second drying step S2b Sometimes the efficiency of drying will decrease. In addition, when the concentration of the polyvinyl alcohol-based resin in the coating liquid 33 for a resin layer is 15% by mass or more, the coating liquid for the resin layer 33 The viscosity becomes too large, and it may become difficult to apply the coating liquid 33 for the resin layer.

The viscosity of the coating liquid 33 for the resin layer is not likely to be uneven in the thickness of the layer of the coating liquid 33 for the resin layer formed on the base film 20 and is easily applied to the base film 20, that is, Special restrictions. When the viscosity of the coating liquid 33 for a resin layer is applied to the base film 20, for example, it is preferably 0.5 Pa ‧ or more and 10 Pa ‧ s or less, and more preferably 0.8 Pa ‧ s or more and 7 Pa ‧ s or less. It is more desirable to be 1 Pa‧s or more and 5 Pa‧s or less.

When the viscosity of the coating liquid 33 for a resin layer is less than 0.5 Pa s, the applied coating liquid 33 for a resin layer flows, and the thickness precision of the resin layer 34 may fall. In the case where the viscosity of the coating liquid 33 for the resin layer is more than 10 Pa s, the filter which can be used in the second coating device 42 for applying the coating liquid for the resin layer 33 is limited, and the like may be formed. The quality of the resin layer 34 is lowered.

Further, the viscosity of the coating liquid 33 for a resin layer may be within the above numerical range when applied to the base film 20. Therefore, for example, in the groove (not shown) of the coating liquid 33 for storing the resin layer of the second coating device 42, the viscosity of the coating liquid 33 for the resin layer may be outside the above numerical range. In this case, for example, the viscosity of the coating liquid 33 for a resin layer can be set to the above numerical range by heating or cooling the coating liquid 33 for a resin layer.

The coating liquid 33 for a resin layer may contain an additive such as a plasticizer or a surfactant. The type of plasticizer is as described above. The amount of the additive to be added to the coating liquid 33 for the resin layer is preferably 20% by mass or less based on the amount of the polyvinyl alcohol-based resin.

The coating method of the coating liquid 33 for a resin layer using the second coating device 42 is not particularly limited as long as the coating liquid 33 for a resin layer can be applied onto the base film 20. The method of applying the coating liquid 33 for a resin layer using the second coating device 42 is the same as the method of applying the coating liquid 31 for the undercoat layer. The coating method of the coating liquid 33 for a resin layer using the second coating device 42 may be the same as or different from the coating method of the coating liquid 31 for the undercoat layer using the first coating device 41. The second coating device 42 can appropriately select a coating device corresponding to each coating method.

By the second coating step S2a, as shown in Fig. 6, a layer of the coating liquid 33 for a resin layer is formed on the upper surface 20a of the base film 20 via the undercoat layer 32. The layer of the coating liquid 33 for a resin layer is formed in a wave shape along the upper surface 20a of the base film 20. The thickness of the layer of the coating liquid 33 for a resin layer is, for example, 50 μm or more and 200 μm or less, and more preferably 150 μm or less.

The second drying step S2b is a step of drying the coating liquid 33 for the resin layer applied on the base film 20. In the second drying step S2b, as shown in Fig. 3, the resin layer coating liquid 33 applied to the base film 20 is dried using the second drying furnace 52. In the second drying furnace 52, heat is applied to the layer of the coating liquid 33 for the resin layer by hot air blowing, for example, and the coating liquid 33 for the resin layer is dried and cured. The second drying furnace 52 is not particularly limited as long as the coating liquid 33 for the resin layer can be dried. The drying temperature of 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 of the second drying furnace 52 can be appropriately set depending on the type of the solvent contained in the coating liquid 33 for the resin layer. When the solvent of the coating liquid 33 for a resin layer contains water, the second drying furnace 52 The drying temperature is preferably 80 ° C or more.

The drying time of 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, more preferably 140 seconds or shorter. As will be described later in detail, by setting the length of the second drying step S2b in this manner, unevenness in the thickness distribution of the polarizer 10 can be reduced. The length of the second drying step S2b is the length from the application of the coating liquid layer coating liquid 33 to the drying resin layer coating liquid 33 to form the resin layer 34. In other words, for example, even after the application of the coating liquid for coating the resin layer 33 until the time when the resin layer 34 comes out of the second drying furnace 52 is greater than 150 seconds, the coating liquid for coating the resin layer 33 is applied. The time until the resin layer 34 is formed may be 180 seconds or less.

The method of making the length of the second drying step S2b to 180 seconds or less is not particularly limited as long as the resin layer 34 can be formed by drying the coating liquid 33 for a resin layer for 180 seconds or less. For example, the output of the second drying furnace 52 (for example, the amount of air) may be increased, or the thickness of the layer of the coating liquid 33 for the resin layer may be reduced, and the solvent of the coating liquid 33 for the resin layer may be, for example, an alcohol. Such as volatile substances. For example, the drying rate of the coating liquid 33 for a resin layer is preferably 1.6% by mass/sec or more, and more preferably 2.0% by mass or more. Further, the transport speed of the base film 20 coated with the coating liquid 33 for a resin layer can be appropriately adjusted in accordance with the length of the second drying step S2b.

In the drying speed in the present specification, for example, after the drying of the coating liquid 33 for the resin layer is started, the drying speed at the initial stage is compared. Specifically, the drying rate in the present specification is, for example, reduced from 30% by mass to 10% by mass of the solvent contained in the coating liquid 33 for a resin layer. The drying speed between stops.

By the second drying step S2b, as shown in Fig. 7, a resin layer 34 is formed on the base film 20, preferably on the undercoat layer 32. Thereby, the laminated film 70 in which the base film 20, the undercoat layer 32, and the resin layer 34 are laminated 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 than the uneven shape of the upper surface 33a of the layer of the coating liquid 33 for a resin layer shown in Fig. 6 . This is because the coating liquid 33 for the resin layer flows and the upper surface 33a is flattened until the resin layer 34 is formed until the coating liquid 33 for the resin layer is dried. The thickness T4 of the resin layer 34 is, for example, 3 μm or more and 20 μm or less, and preferably 5 μm or more and 20 μm or less, in order to shorten the drying time.

The extending step S3 is a step of extending the resin layer 34 together with the substrate film 20. In the extending step S3, as shown in Fig. 3, the laminate film 70 is stretched in one direction in the longitudinal direction by using the stretching device 60. Thereby, the resin layer 34 is stretched. The thickness T4 of the resin layer 34 is small due to the elongation. When the thickness T4 of the resin layer 34 is larger than 10 μm before the extending step S3, the thickness T4 of the resin layer 34 becomes 10 μm or less by the extending step S3.

The stretching ratio of the resin layer 34 can be appropriately selected depending on the desired polarization characteristics of the polarizer 10. The stretching ratio of the resin layer 34 is preferably more than 5 times and 17 times or less with respect to the dimension in the longitudinal direction of the resin layer 34 before stretching, and more preferably more than 5 times and 8 times or less. In the case where the stretching ratio of the resin layer 34 is 5 times or less, the resin layer The alignment of 34 is insufficient, and the degree of polarization of the polarizer 10 to be produced cannot be sufficiently increased. In addition, when the stretching ratio of the resin layer 34 is more than 17 times, the laminated film 70 may be easily broken, or the thickness of the laminated film 70 may become too small, and the workability and workability of the subsequent step may be lowered.

The stretching device 60 is not particularly limited as long as the resin layer 34 can be extended to a predetermined stretching ratio. The method of extending the laminated film 70 using the stretching device 60 may be extended between the rollers for extending the circumferential speed difference of the conveying roller, or may be extended by a tenter. Moreover, the stretching process can be carried out in multiple stages. In this case, all of the multi-stage stretching treatment may be performed before the dyeing step S4, or part or all of the stretching treatment after the second stage may be performed in the dyeing step S4.

The elongation temperature when the build-up film 70 (resin layer 34) is extended by the stretching device 60 is set to a temperature higher than the temperature at which the base film 20 and the resin layer 34 are likely to extend. The stretching temperature is preferably in the range of -30 ° C or more and + 30 ° C or less in the phase transition temperature (melting point or glass transition temperature) of the base film 20, and more preferably in the range of -30 ° C or more and + 5 ° C or less. A range of -25 ° C or more and ± 0 ° C or less is more desirable. When the extension temperature is less than the phase transition temperature of the base film 20 by -30 ° C, the fluidity of the base film 20 is too small, and it may be difficult to extend the base film 20 and the resin layer 34. Further, when the stretching temperature is higher than the phase transition temperature of the base film 20 by +30 ° C, the fluidity of the base film 20 is too large, and it may be difficult to extend the base film 20 and the resin layer 34. In the case where the base film 20 is a plurality of layers, the phase transition temperature of the base film 20 means the highest temperature among the phase transition temperatures of the plurality of layers.

Dyeing step S4, the dichroic dye is adsorbed to the resin The steps of layer 34. In the dyeing step S4, as shown in Fig. 3, the entire laminated film 70 is immersed in the dyeing solution 80 containing the dichroic dye. The dyeing solution 80 is a solution obtained by dissolving a dichroic dye in a solvent. The solvent of the dyeing solution 80 is, for example, water. In the solvent of the dyeing solution 80, in addition to water, an organic solvent compatible with water may be added. 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 more preferably 0.025% by mass or more and 5% by mass or less. .

In the case where the dichroic dye is iodine, it is preferred to add an iodide to the dye 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, cesium iodide, calcium iodide, tin iodide, titanium iodide, and the like. . The concentration of the iodide in the dyeing solution 80 is preferably 0.01% by mass or more and 20% by mass or less.

Among the iodides, potassium iodide is preferably added. When potassium iodide is added, 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 more preferably 7 or more and 70 or less.

The immersion time of the laminated film 70 to the dyeing solution 80 is not particularly limited, and 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 dyeing treatment, the aligned dichroic dye is adsorbed to the resin layer 34, as shown in Fig. 8, and the base film 20 is obtained. The polarizer 10 is laminated on the primer layer 32. Thereby, the polarizing laminated film 71 in which the base film 20, the undercoat layer 32, and the polarizer 10 are laminated is obtained.

Further, the dyeing step S4 may include a crosslinking treatment step performed in response to the dyeing treatment. In the cross-linking 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. The crosslinking agent may be used alone or in combination of two or more.

As the crosslinking solution, a solution obtained by dissolving a crosslinking agent 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 preferably, for example, 1% by mass or more and 20% by mass or less, more preferably 6% by mass or more and 15% by mass or less.

Iodide may also be added to the crosslinking solution. The in-plane polarization characteristics of the resin layer 34 can be made more uniform by the addition of iodide. The iodide added to the crosslinking solution may, for example, be 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 the iodide in the crosslinking solution is preferably 0.05% by mass or more and 15% by mass or less, more preferably 0.5% by mass or more and 8% by mass or less.

The immersion time of the laminated film 70 to 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 more and 80 ° C or less.

Further, the crosslinking treatment can be carried out simultaneously with the dyeing treatment by blending a crosslinking agent in the dyeing solution 80. Further, two or more kinds of crosslinking solutions having different compositions may be used, and two or more times of immersion in the crosslinking solution may be performed.

The bonding step S5 is a step of bonding the protective film 11 to the polarizer 10. The adhesive layer 12 is formed on the upper surface 10a of the polarizer 10, and the protective film 11 is bonded to the upper surface 10a of the polarizer 10 via the adhesive layer 12. The method of forming the layer 12 is not particularly limited, and for example, the same method as the method of forming each layer in the undercoat layer forming step S1 and the resin layer forming step S2 can be employed.

The bonding method of the protective film 11 is not particularly limited. For example, the protective film 11 wound in a roll shape can be taken up, and the two rollers that sandwich the protective film 11 and the polarizing laminated film 71 can be placed in a state where the protective film 11 is placed on the adhesive layer 11. The protective film 11 is attached to each other.

The peeling step S6 is a step of peeling off the base film 20 from the polarizing laminated film 71 to which the protective film 11 is bonded. The method of peeling off the base film 20 is not particularly limited, and for example, the same method as the peeling step of a separator (release film) by a polarizing plate with a pressure-sensitive adhesive can be employed. The base film 20 can be directly peeled off immediately after the bonding step S5, and the polarizing laminated film 71 to which the protective film 11 is bonded can be temporarily wound into a roll shape after the bonding step S5, and thereafter The step is taken out while peeling off.

The base film 20 is peeled off by the peeling step S6, and the polarizing film 1 of this embodiment shown in FIG. 1 is produced. Cut the polarizing film 1 For a given size, a polarizing plate is obtained.

According to this embodiment, it is possible to obtain a polarizing plate 10 which is thin and has a small unevenness in thickness distribution in the axial direction. The details will be described below.

In the case of producing a thin polarizer having a thickness of 10 μm or less, as described above, a coating liquid for a resin layer containing a polyvinyl alcohol-based resin is applied onto a base film, and the coating liquid for a resin layer is dried to form a resin layer. Then, a production method in which the resin layer is extended together with the base film (hereinafter referred to as a method of producing a thin polarizer) is employed. In the case of using this method, there is a problem that the unevenness of the manufactured polarizer is large. The reason is considered to be as follows.

In the case of a manufacturing method using a thin polarizer, since the base film must be a material that can be extended together with the resin layer, heat shrinkage is easily caused by application of heat. Therefore, for example, in the first drying step S1b of the undercoat layer forming step S1 or the like, when heat is applied to the base film, the base film is thermally shrunk, and the base film 20 shown in Fig. 5 has unevenness on the upper and lower surfaces. shape. In this state, when the layer of the coating liquid for a resin layer is formed on the base film, the upper surface of the layer of the coating liquid for the resin layer also has an uneven shape along the shape of the upper surface of the base film.

Since the coating liquid for a resin layer has fluidity, the upper surface of the coating liquid for a resin layer is gradually flattened from the coating liquid for drying the resin layer to the resin layer. Here, for example, when the length of the second drying step S2b is sufficiently large, the resin layer coating liquid 33 applied in the second coating step S2a is dried to form the resin layer 34, and the resin layer is coated. The upper surface 33a of the liquid 33 is completely flattened. Therefore, the upper side of the resin layer 34 The surface becomes a flat surface 35 as shown by the two-dot chain line in Fig. 7.

In this case, the thickness T3a of the distance in the lamination direction between the most apex 34c and the flat surface 35 of the portion which becomes concave on the upper side in the lower surface of the resin layer, and the lowest portion of the lower portion of the resin layer which becomes convex on the lower side. The difference in thickness T3b of the distance between the point 34d and the flat surface 35 in the lamination direction becomes large. The thickness T3b is larger than the thickness T3a. Therefore, in the case of the production method using a thin polarizer, the unevenness of the thickness distribution of the resin layer is increased, and as a result, the unevenness of the thickness distribution of the polarizer becomes large.

Further, for example, in the case of producing a polarizer having a relatively large thickness, since the above-described thin manufacturing method is not required, the substrate film is not used, and the shape of the heat-shrinkable substrate film is not transferred to the resin layer, and the above does not occur. problem.

In addition, it is considered that the air volume of the hot air blown by the coating liquid for the resin layer in the second drying furnace 52 is likely to be uneven in the width direction, and it is easy to vibrate when the base film is conveyed in the second drying step S2b. Therefore, the coating liquid for the resin layer flows, and the unevenness of the thickness distribution of the resin layer becomes large, and as a result, the unevenness of the thickness distribution of the polarizer becomes large.

Further, for example, in the case of producing a polarizer having a relatively large thickness, since the above-described thin manufacturing method is not required, it is not necessary to form a resin layer on the transferred base film, and the above problem does not occur.

The knowledge about the cause of the unevenness in the manufacturing method of the thin polarizer described above is the knowledge newly discovered by the present inventors.

In contrast, according to this embodiment, the second drying step The length of the step S2b is preferably 150 seconds or less. Therefore, the length of the second drying step S2b is small, and before the flat surface 35 of the resin layer coating liquid 33 is flattened to become the flat surface 35, the layer of the resin layer coating liquid 33 is dried to become the resin layer 34. Thereby, although the upper surface 34a of the resin layer 34 is flatter than the upper surface 33a of the coating liquid 33 for resin layers, it has the uneven shape. Therefore, the difference between the thickness T4a of the distance between the most apex 34c and the upper surface 34a of the lower surface 34b of the resin layer 34 and the thickness T4b of the distance between the lowest point 34d of the lower surface 34b of the resin layer 34 and the upper surface 34a becomes small. That is, in the width direction, the thickness T4 of the resin layer 34 becomes nearly uniform, and the unevenness of the thickness distribution of the resin layer 34 becomes small. Therefore, the unevenness of the thickness distribution of the polarizer 10 can be made small.

Further, the thickness T4a is the distance between the most apex 34c of the lower surface 34b and the most apex 34e of the portion of the upper surface 34a which becomes convex on the upper side. The thickness T4b is the distance between the lowest point 34d of the lower surface 34b and the lowest point 34f of the portion of the upper surface 34a which becomes concave on the lower side.

Further, the length of the second drying step S2b is small, and the time for blowing the hot air to the coating liquid 33 for the resin layer in the second drying furnace 52 is shortened, and after the coating liquid 33 for the resin layer is applied, The time during which the base film 20 is dried until the resin layer 34 is dried is shortened. Therefore, the flow of the coating liquid 33 for the resin layer due to the hot air blown in the second drying furnace 52 and the vibration of the base film 20 is suppressed, and the unevenness in the thickness distribution of the resin layer 34 is small. Therefore, the unevenness of the thickness distribution of the polarizer 10 can be made small.

Therefore, according to the present embodiment, even in the case of obtaining a thin polarizer having a thickness of 10 μm or less, the manufacture of a thin polarizer is employed. In the case of the method, the polarizing plate 10 having a small unevenness in thickness distribution can still be obtained. Specifically, the polarizer 10 having a thickness T1 of 10 μm or less and a maximum amplitude of the thickness distribution of 0.4 μm or less can be obtained. The polarizer 10 having a thickness T1 of 10 μm or less and a periodic intensity of a thickness distribution of 0.13 μm or less can be obtained. The polarizer 10 having a thickness T1 of 10 μm or less and a maximum phase difference of the phase difference distribution of the polyvinyl alcohol-based resin of 10 nm or less can be obtained. The polarizer 10 having a thickness T1 of 10 μm or less and a periodic difference distribution of a polyvinyl alcohol-based resin having a periodic intensity of 2 nm or less can be obtained.

The polarizer 10 having such characteristics is based on a new knowledge about the cause of the unevenness in the thickness distribution of the polarizer in the manufacturing method of the thin polarizer, and is obtained by the above-described manufacturing method of the present embodiment. New polarizer. In other words, in the case of producing a thin polarizer having a thickness of 10 μm or less, it is necessary to use a method of manufacturing a thin polarizer. However, conventionally, there is no knowledge of the reason why the unevenness of the thickness distribution is increased, and the polarized light of the present embodiment is not used. The manufacturing method of the sheet. Therefore, the polarizer 10 of this embodiment cannot be realized in the past.

Further, in the method for producing a thin polarizer, the cause of the unevenness in the thickness distribution of the polarizer is considered to be mainly because the shape of the substrate film which is thermally contracted is transferred to the coating liquid for the resin layer, and the resin layer is used. The coating liquid is flattened. Therefore, as in the present embodiment, by providing the undercoat layer forming step S1 including the first drying step S1b before the resin layer forming step S2, the substrate film is thermally shrunk, and the unevenness of the thickness distribution of the polarizer is particularly easy. Become bigger. Therefore, the effect of reducing the unevenness in the thickness distribution of the polarizer 10 can be achieved in the case where the undercoat layer forming step S1 is provided. high. Further, in addition to the undercoat layer forming step S1, the same applies to the step of applying heat to the base film 20 before the resin layer forming step S2.

Furthermore, in the present embodiment, the following method can also be employed.

In the above description, the unevenness of the thickness distribution of the polarizer 10 is reduced by adjusting the length of the second drying step S2b, but the invention is not limited thereto. If one of the new knowledge about the cause of the unevenness in the thickness distribution is large, the resin layer can be dried before the upper surface 33a of the coating liquid 33 for the resin layer applied on the base film 20 is completely flattened. When the resin layer 34 is formed by the coating liquid 33, the polarizing plate 10 having a small unevenness in thickness distribution can be obtained. Therefore, for example, the viscosity of the coating liquid 33 for a resin layer may be relatively large, and the flattening speed of the upper surface 33a of the coating liquid 33 for a resin layer may be slow, or the coating amount of the coating liquid 33 for a resin layer may be adjusted. The thickness of the obtained resin layer 34 becomes small. In this case, before the upper surface 33a of the coating liquid 33 for a resin layer is completely flattened, the resin layer 34 is easily formed by drying the coating liquid 33 for the resin layer. Therefore, it is possible to manufacture the polarizing plate 10 having a small unevenness in thickness distribution. Further, in combination with the above-described method, it is preferable to easily manufacture the polarizing plate 10 having a small unevenness in thickness distribution.

Further, before the undercoat layer forming step S1, a step of performing a corona treatment on the upper surface 20a of the base film 20 on which the undercoat layer coating liquid 31 is to be applied may be provided.

Further, in the case where a plasticizer is used in the formation of the resin layer 34 in the resin layer forming step S2, the treatment for removing the plasticizer may be performed before the dyeing step S4. Removal of the plasticizer, for example, the laminated film 70 The plastic film is melted from the build-up film 70 by immersing it in water of about 50 ° C or less at room temperature or higher to swell the water.

In the case where the crosslinking treatment is provided in the dyeing step S4, after the crosslinking treatment, the polarizing laminated film 71 can be immersed in water such as pure water, ion-exchanged water, distilled water or tap water, washed with water, and rinsed off. Treatment of boric acid or the like. The cleaning solution may also contain iodide. Then, after this, the process of drying the polarizing laminated film 71 can also be performed. For the drying treatment, a conventional method such as natural drying, heat drying, air drying, and vacuum drying may be employed.

Further, the dyeing step S4 may be performed before the extending step S3, or the dyeing step S4 may be performed simultaneously with the extending step S3. Further, the undercoat layer forming step S1 may not be provided.

Furthermore, each of the above methods and configurations can be combined with each other within a range not contradictory.

[Examples]

In the method of producing a thin polarizer, the flatness of the coating liquid for a resin layer having a heat-shrinkable shape of the base film is verified for the reason that the unevenness of the thickness distribution of the polarizer is increased. Fig. 9 is a cross-sectional view showing the laminated body 2 for verification manufactured as a verification example. In the ninth embodiment, the same components as those in the above embodiment are denoted by the same reference numerals.

The laminated body 2 for verification includes a base film 20, an undercoat layer 32, and resin layers 134a and 134b. The resin layer 134a is formed on the upper surface 20a of the base film 20 via the undercoat layer 32. The resin layer 134b is separated by a primer layer 32 is formed on the lower surface 20b of the base film 20. The upper surface of the resin layer 134a and the lower surface of the resin layer 134b are flat surfaces.

In the present verification example, the material of the base film 20 was made of polypropylene. In the present verification example, the average thickness of the undercoat layer 32 was set to 0.2 μm. Further, in the first drying step S1b, the drying temperature was set to 90 ° C, and the conveying speed of the base film 20 was set to 20 m/min. In the present verification example, the solvent of the coating liquid for a resin layer was set to water. The concentration of the polyvinyl alcohol-based resin in the coating liquid for a resin layer was set to 8 mass%. In the second coating step S2a, the average thickness of the layer of the coating liquid for a resin layer at the time of coating was set to 140 μm.

The length of the second drying step S2b is taken as the length of the upper surface of the layer of the coating liquid for coating the resin layer applied in the second coating step S2a, and the resin layer 134a, 134b is formed, and the thickness T5a of the resin layer 134a is formed. The thickness T5b of the resin layer 134b was measured one by one in the width direction (Y-axis direction).

The results are shown in Figure 10.

Fig. 10 is a graph showing the positions of the thicknesses T5 of the resin layers 134a and 134b 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 position in the width direction 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 respectively shown.

It can be confirmed from Fig. 10 that the thickness T5a of the resin layer 134a and the thickness T5b of the resin layer 134b are different from each other. In other words, in the width direction position where the thickness T5a of the resin layer 134a is increased, the thickness T5b of the resin layer 134b becomes smaller, and the thickness T5a of the resin layer 134a becomes smaller. In the width direction position, the thickness T5b of the resin layer 134b becomes large.

The results shown in Fig. 10 support the unevenness in the thickness distribution of the polarizer due to the flattening of the coating liquid for the resin layer. As shown in FIG. 9, when the base film 20 is thermally shrunk and the uneven shape is formed on the surface, the uneven shape of the upper surface 20a of the base film 20 and the uneven shape of the lower surface 20b of the base film 20 are along the width direction. (Y-axis direction), the concave portion and the convex portion become different from each other. Therefore, when the resin layer is formed on both surfaces of the base film 20, the uneven shape of the lower surface of the resin layer 134a and the uneven shape of the upper surface of the resin layer 134b are different from each other in the width direction. Therefore, the thickness T5b of the resin layer 134b becomes the smallest in the width direction position where the thickness T5a of the resin layer 134a becomes the largest, and the thickness T5b of the resin layer 134b becomes the largest in the width direction position where the thickness T5a of the resin layer 134a becomes the smallest. As a result, it is considered that the thickness T5a of the resin layer 134a and the thickness T5b of the resin layer 134b correspond to the position in the width direction and exhibit the change shown in FIG.

As a result, at least one of the causes of the unevenness in the thickness distribution of the polarizer is that the coating liquid for the resin layer formed on the heat-shrinkable base film 20 is flattened.

Then, the polarizing films of Examples 1 to 3 were produced by the method for producing the polarizing film 1 of the above-described embodiment, and compared with the polarizing film of the comparative example.

In Example 1, the base film was produced in the following manner. First, the homopolymer polypropylene which is a homopolymer of propylene (Sumitomo NOBLEN (registered trademark) FLX80E4, manufactured by Sumitomo Chemical Co., Ltd.), melting point In 163 ° C), 1% by mass of a nucleating agent composed of high-density polyethylene was prepared to prepare a nucleating agent-containing polypropylene. From the polypropylene, and a random copolymer of propylene/ethylene containing about 5% by mass of ethylene unit, Sumitomo NOBLEN (registered trademark) W151, a strip was produced by co-extrusion molding using a multilayer extrusion molding machine. A polypropylene laminated film is used as a base film. The polypropylene-based laminated film is a three-layer structure in which a resin layer composed of the nucleating agent-containing polypropylene is disposed on both sides of a resin layer composed of "Sumitomo NOBLEN (registered trademark) W151". The average thickness of the base film of Example 1 was set to 100 μm. The thickness ratio of each layer in the base film was set to a nucleating agent-containing polypropylene: Sumitomo NOBLEN (registered trademark) W151: nucleating agent-containing polypropylene = 3:4:3. The tensile modulus of the base film in the longitudinal direction was 210 MPa.

In Example 1, the coating liquid for the undercoat layer was produced in the following manner. Polyvinyl alcohol powder ("Z-200" manufactured by Nippon Synthetic Chemical Co., Ltd., average molecular weight 1100, average saponification degree: 99.5 mol%) was dissolved in hot water at 95 ° C to prepare a polyvinyl alcohol having a concentration of 3 mass%. Aqueous solution. In the obtained aqueous solution, 1 part by mass of a crosslinking agent ("SUMIREZ RESIN (registered trademark) 650" manufactured by Sumitomo Chemical Co., Ltd.) was mixed with 2 parts by mass of the polyvinyl alcohol to prepare a coating liquid for an undercoat layer.

In Example 1, the coating liquid for a resin layer was produced in the following manner. Polyvinyl alcohol powder ("PVA124" manufactured by Kuraray Co., Ltd., average polymerization degree 2400, average saponification degree: 98.0 mol% or more and 99.0 mol% or less) was dissolved in hot water at 95 ° C to prepare a polycondensate having a concentration of 8 mass%. A vinyl alcohol aqueous solution was used as a coating liquid for a resin layer.

Continuously transferring the substrate film obtained as described above, the same At the time of the corona treatment, the coating liquid for the undercoat layer was continuously applied to the surface subjected to the corona treatment using a micro gravure coater (first coating device). The coating layer for the applied undercoat layer was dried in a first drying apparatus at 60 ° C for 3 minutes to form an undercoat layer having an average thickness of 0.2 μm.

The substrate film on which the undercoat layer was formed was continuously transferred, and the coating liquid for a resin layer described above was continuously applied to the undercoat layer using a lip coater (second coating device). The coating layer for the applied resin layer was dried at 90 ° C for 130 seconds by using a coating liquid for coating the resin layer, and a resin layer was formed on the undercoat layer. At this time, the drying speed of the coating liquid for the resin layer was 2.1. Mass % / sec. No defects were observed in the formed resin layer, and no defects were recognized. The average thickness of the polarizer was 3.6 μm.

The laminated film in which the undercoat layer and the resin layer are formed on the substrate film is continuously transferred, and the free end is axially extended in the longitudinal direction (film transfer direction) by using the inter-roller air extension device. The extension temperature was set to 150 °C. The stretching ratio was set to 5.3 times.

The laminated film which has been extended is immersed in the dyeing solution of 30 degreeC containing iodine and potassium iodide, and the dyeing process of the resin layer which consists of polyvinyl- Then, the excess dye solution was washed away by pure water at 10 °C. Then, the crosslinking solution containing boric acid and potassium iodide at 76 ° C was immersed in a residence time of 600 seconds to carry out a crosslinking treatment. 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 a base film, an undercoat layer and a polarizer were laminated.

Continuously transferring the polarizing laminated film obtained above, the same The adhesive solution was applied to the polarizer to form an adhesive layer. A triacetyl cellulose (TAC) film ("KC4UY" manufactured by Konica Minolta Optical Co., Ltd., thickness: 40 μm) which was subjected to saponification treatment on the bonding surface was bonded to the polarizer via an adhesive layer.

The subsequent 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 prepare a polyvinyl alcohol aqueous solution having a concentration of 3 mass%. In the obtained aqueous solution, a cross-linking agent ("SUMIREZ RESIN (registered trademark) 650" manufactured by Sumitomo Chemical Co., Ltd.) was mixed as a binder in an amount of 1 part by mass based on 2 parts by mass of the polyvinyl alcohol. Solution.

The polarizing film of Example 1 was obtained by peeling off the base film from the polarizing laminated film to which the TAC film (protective film) was bonded.

In the second embodiment, the coating liquid for a resin layer applied to the base film via the undercoat layer was dried at 90 ° C for 150 seconds using a second drying device, thereby forming a resin on the undercoat layer. Floor. At this time, the drying rate of the coating liquid for a resin layer was 1.9% by mass/second.

No defects were observed in the formed resin layer, and no defects were recognized. The average thickness of the polarizer was 4.0 μm. The other points of the second embodiment are the same as those of the first embodiment.

In the third embodiment, the coating liquid for a resin layer applied to the base film via the undercoat layer was dried at 90 ° C for 170 seconds using a second drying device, thereby forming a resin on the undercoat layer. Floor. At this time, the drying rate of the coating liquid for a resin layer was 1.7% by mass/second.

No unidentified drying unevenness was observed in the formed resin layer. To the defect. The average thickness of the polarizer was 4.5 μm. The other points of the third embodiment are the same as those of the first embodiment.

In the comparative example, the coating liquid for a resin layer applied to the base film via the undercoat layer was dried at 90 ° C for 188 seconds using a second drying device, thereby forming a resin layer on the undercoat layer. . At this time, the drying speed of the coating liquid for a resin layer was 1.5 mass% / sec. No defects were observed in the formed resin layer, and no defects were recognized. The average thickness of the polarizer was 5.0 μm. The other points of the comparative example are the same as those of the first embodiment.

The polarizing film of Examples 1 to 3 and the polarizing film of the comparative example were cut out in the longitudinal direction (absorption axis direction) by 100 mm, respectively, and used as a polarizing plate. With respect to each polarizing plate, the thickness of the polarizer and the phase difference of each wavelength were measured at each width direction position. The thickness of the polarizer was measured by a width of about 200 mm in the center in the width direction of the polarizer, and the measurement position was changed at intervals of 5 mm in the width direction (transmission axis direction). The measurement position is changed by moving the measuring device by the automatic table.

From the thickness distribution of the polarizer, the periodic intensity of the thickness distribution was calculated using a fast Fourier transform. The phase difference of the polyvinyl alcohol-based resin at each position in the width direction was calculated from the phase difference of each wavelength of the polarizer. From the phase difference distribution of the polyvinyl alcohol-based resin, the periodic intensity of the phase difference distribution of the polyvinyl alcohol-based resin was calculated using fast Fourier transform. Further, each of the polarizing plates was allowed to stand in an environment of 105 ° C for 30 minutes, and then crossed with other polarizing plates on the backlight to form a cross-polarization (Cross Nicol), and the unevenness of the polarizing plates was visually observed. The results are shown in Table 1, Table 2, and Figures 11 to 14.

In Table 1, the lengths (seconds) of the second drying step, the maximum amplitude (μm) of the thickness distribution, and the maximum value of the period intensity of the thickness distribution are shown in Examples 1 to 3 and Comparative Examples. In Table 2, regarding Examples 1 to 3 and Comparative Examples, the length (second) of the second drying step and the phase difference are shown. The maximum amplitude (nm) of the cloth and the maximum value of the periodic intensity of the phase difference distribution. Further, in Tables 1 and 2, the examples 1 to 3 and the comparative examples show uneven appearance evaluation. In the uneven appearance evaluation, "○" indicates that unevenness was hardly recognized, and "X" indicates that unevenness in stripes which was strong and easily recognized was recognized.

Fig. 11 is a graph showing the thickness of the polarizer versus the position in the width direction. In Fig. 11, the vertical axis represents the thickness (μm) of the polarizer, and the horizontal axis represents the width direction position (mm) of the polarizer.

Fig. 12 is a graph showing the period of the thickness distribution of the polarizer and 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 phase difference Rpva of the polyvinyl alcohol-based resin in the polarizer versus the position in the width direction. In Fig. 13, the vertical axis represents the phase difference Rpva (nm) of the polyvinyl alcohol-based resin, and the horizontal axis represents the position (mm) in the width direction of the polarizer.

Fig. 14 is a graph showing the period of the phase difference distribution of the polyvinyl alcohol-based resin in the polarizer and 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-based resin, and the horizontal axis represents the uneven period (mm) of the thickness distribution of the polarizer.

In Figures 11 to 14, the respective plots show the results for Examples 1, 2 and Comparative Examples.

From Fig. 11, it can be confirmed that in the comparative example, the thickness of the polarizer fluctuates greatly with the position in the width direction, and In Examples 1 and 2, the thickness of the polarizer was relatively uniform irrespective of the position in the width direction. Thereby, it was confirmed that the unevenness of the thickness distribution of Examples 1 and 2 was small as compared with the unevenness of the thickness distribution of the comparative example. Further, from Table 1, it was confirmed that the maximum amplitude of the thickness distribution compared to the comparative example was 0.67 μm, and the maximum amplitude of the thickness distribution of Examples 1 to 3 was 0.4 μm or less. From the above, it was confirmed that by controlling the length of the second drying step, the unevenness of the thickness distribution of the polarizer can be made small, and the maximum amplitude of the thickness distribution of the polarizer can be made 0.4 μm or less.

Further, the maximum amplitude of the thickness distribution from Example 2 was smaller than the maximum amplitude of the thickness distribution of Example 3, and the maximum amplitude of the thickness distribution of Example 1 was smaller than the maximum amplitude of the thickness distribution of Example 2, and it was confirmed that the second drying was performed. The smaller the length of the step, the smaller the maximum amplitude of the thickness distribution of the polarizer can be, and the unevenness of the thickness distribution of the polarizer can be made smaller.

From the 12th example, it can be confirmed that in the comparative example, the period intensity of the thickness distribution is increased in the range of the uneven period of 12 mm or more and 17 mm or less, and in the first and second embodiments, regardless of the uneven period The period intensity of the thickness distribution is almost the same. In the comparative example, the thickness varies greatly in the period of 12 mm or more and 17 mm or less along the width direction, and the unevenness of the thickness distribution of the polarizer is large. On the other hand, in the first and second embodiments, the thickness did not largely vary in a specific cycle, and the unevenness in the thickness distribution of the display polarizer was small. Further, from Table 1, it was confirmed that the maximum value of the period intensity of the thickness distribution compared to the comparative example was 0.15 μm, and the maximum value of the period intensity of the thickness distributions of Examples 1 to 3 was 0.13 μm or less. It can be confirmed from the above that by controlling the second drying The length of the step makes it possible to reduce the unevenness of the thickness distribution of the polarizer, and the period intensity of the thickness distribution of the polarizer can be made 0.13 μm or less.

Moreover, the maximum value of the period intensity of the thickness distribution from Example 2 is smaller than the maximum value of the period intensity of the thickness distribution of Example 3, and the maximum value of the period intensity of the thickness distribution of Example 1 is smaller than that of the thickness distribution of Example 2. The maximum value of the cycle intensity was confirmed to be such that the smaller the length of the second drying step, the smaller the periodic intensity of the thickness distribution of the polarizer, and the smaller the unevenness of the thickness distribution of the polarizer.

As can be seen from Fig. 13, in the comparative example, the phase difference Rpva fluctuates greatly with the position in the width direction. In contrast, in the first and second embodiments, the phase difference Rpva is relatively uniform regardless of the position in the width direction. Thereby, it is confirmed that the unevenness of the phase difference Rpva of the first and second embodiments is small compared to the unevenness of the phase difference Rpva of the comparative example. The unevenness of the phase difference Rpva is caused by the unevenness of the thickness distribution of the polarizer, so that the thickness distribution of the polarizer of the first and second embodiments can be confirmed as compared with the unevenness of the thickness distribution of the polarizer of the comparative example. Not evenly small. Further, from Table 2, it was confirmed that the maximum amplitude of the phase difference distribution compared to the comparative example was 18 nm, and 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, the unevenness of the thickness distribution of the polarizer can be made small, and the maximum amplitude of the phase difference distribution of the polyvinyl alcohol-based resin in the polarizer can be 10 nm or less.

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

From the 14th example, it can be confirmed that in the comparative example, the period intensity of the phase difference distribution in the range of the uneven period of 12 mm or more and 17 mm or less is large, and in the first and second embodiments, regardless of the uneven period, The period strength of the phase difference distribution is almost the same. In the comparative example, the phase difference Rpva fluctuates greatly in a period of from about 12 mm to about 17 mm in the width direction, and the unevenness in the thickness distribution of the polarizer is large. On the other hand, in the first and second embodiments, the phase difference Rpva does not largely vary in a specific cycle, and the unevenness in the thickness distribution of the display polarizer is small. Further, from Table 2, it was confirmed that the maximum value of the periodic intensity of the phase difference distribution compared to the comparative example was 4.8 nm, and the maximum value of the periodic intensity of the phase difference distribution of Examples 1 to 3 was 2 nm or less. From this, it was confirmed that the unevenness of the thickness distribution of the polarizing film and the light sheet can be reduced by controlling the length of the second drying step, and the periodic intensity distribution of the phase difference distribution of the polyvinyl alcohol-based resin in the polarizing plate can be made 2 nm or less. .

Further, the maximum value of the periodic intensity of the phase difference distribution from the second embodiment is smaller than the maximum value of the periodic intensity of the phase difference distribution of the third embodiment, and the maximum value of the periodic intensity of the phase difference distribution of the first embodiment is smaller than that of the second embodiment. The maximum value of the periodic intensity of the phase difference distribution is such that the smaller the length of the second drying step, the smaller the periodic intensity of the phase difference distribution of the polarizer, and the smaller the unevenness of the thickness distribution of the polarizer. .

From Table 1 and Table 2, it can be confirmed that in the comparative example, it is identifiable In contrast to the strong and easily recognizable stripe-like unevenness, in Examples 1 to 3, almost no unevenness was recognized. From this, it was confirmed that the unevenness in the thickness distribution of the polarizer can be made small by controlling the length of the second drying step.

From the above results, it was confirmed that according to Examples 1 to 3, a polarizer having a small thickness and a small unevenness in thickness distribution can be obtained.

1‧‧‧ polarizing film

10‧‧‧ polarizer

10a‧‧‧above

10b‧‧‧ below

11‧‧‧Protective film

12‧‧‧Next layer

Claims (10)

A polarizer for aligning a dichroic dye into a polyvinyl alcohol-based resin, wherein the polarizer has a thickness of 10 μm or less; and the maximum amplitude of the thickness distribution in the transmission axis direction of the polarizer is 0.4 μm or less. The polarizer according to claim 1, wherein the periodic intensity of the thickness distribution in the direction of the transmission axis of the polarizer is 0.13 μm or less. A polarizer for aligning a dichroic dye into a polyvinyl alcohol-based resin, wherein the polarizer has a thickness of 10 μm or less; and the periodic intensity of the thickness distribution in the transmission axis direction of the polarizer is 0.13 μm or less. The polarizer according to any one of the first to third aspect, wherein the polyvinyl alcohol-based resin has a maximum amplitude of a phase difference distribution of 10 nm or less in the transmission axis direction of the polarizer. A polarizer for aligning a dichroic dye into a polyvinyl alcohol-based resin, wherein the polarizer has a thickness of 10 μm or less; and the polyvinyl alcohol-based resin is in a direction of a transmission axis of the polarizer; The maximum amplitude of the phase difference distribution is 10 nm or less. The polarizer according to any one of claims 1 to 5, wherein the polyethylene is in the direction of the transmission axis of the polarizer The periodic strength of the phase difference distribution of the alcohol resin is 2 nm or less. A polarizer for aligning a dichroic dye into a polyvinyl alcohol-based resin, wherein the polarizer has a thickness of 10 μm or less; and the polyvinyl alcohol-based resin is in a direction of a transmission axis of the polarizer; The periodic intensity of the phase difference distribution is 2 nm or less. A polarizing film comprising: the polarizer according to any one of claims 1 to 7; and a protective film provided on at least one surface of the polarizer. A method for producing a polarizer comprising a method of producing a polarizer of a dichroic dye in a polyvinyl alcohol-based resin; wherein the polarizer has a thickness of 10 μm or less; and the manufacturing method comprises: forming on a substrate a resin layer forming step of a resin layer using a polyvinyl alcohol-based resin as a forming material; an extending step of extending the resin layer together with the base material; and a dyeing step of adsorbing the dichroic dye to the resin layer; The resin layer forming step includes a step of applying a coating liquid for a resin layer containing a polyvinyl alcohol-based resin onto the substrate, and a step of drying the applied coating liquid for the resin layer; Length of the step of drying the coating liquid for the resin layer It is less than 180 seconds. The method for producing a polarizer according to claim 9, wherein before the step of forming the resin layer, the method further comprises an undercoat layer forming step of forming an undercoat layer on the substrate; wherein the undercoat layer The forming step includes a step of applying a coating liquid for an undercoat layer on the substrate, and a step of drying the applied coating liquid for the undercoat layer.