JP2019152853A - Polarizing plate and method for manufacturing polarizing plate - Google Patents

Abstract

To make it difficult to visually recognize irregularities occurring on a surface on a visual recognition side of the polarizing plate to improve the appearance of the polarizing plate, even when the polarizing plate includes a phase difference film.SOLUTION: A polarizing plate has a polarizer and a phase difference film laminated with an adhesive layer therebetween, wherein when the one-dimensional power spectrum for the frequency f(μm) of surface irregularities is H(f), a surface of the phase difference film on the opposite side of the polarizer satisfies the following formula (1), and the phase difference film is a film laminated on an image display device side. (1) H(425)/H(212)≤10.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a polarizing plate and a method for producing a polarizing plate.

  Liquid crystal display devices and organic electroluminescence (EL) display devices are used in various display devices by taking advantage of features such as low power consumption, operation at low voltage, light weight and thinness. A liquid crystal panel constituting a liquid crystal display device has a configuration in which a pair of linearly polarizing plates are laminated on both surfaces of a liquid crystal cell. As the linear polarizing plate, one having a configuration in which a polarizer and a protective film are laminated with an adhesive is usually used. The organic EL display device has a circularly polarizing plate disposed on the viewing side of the organic EL display element. As a circularly-polarizing plate, the thing of the structure which laminated | stacked the polarizer and retardation film through the adhesive bond layer is used normally.

  With the development of linearly polarizing plates and circularly polarizing plates (hereinafter collectively referred to as polarizing plates) to mobile devices, it is increasingly required to reduce the thickness of polarizers, protective films, and the like that constitute the polarizing plates. When the thickness of the polarizer, the protective film, or the like is reduced, the adhesive contracts when the adhesive is cured or dried, so that the surface of the protective film may be uneven. Such unevenness, when the polarizing plate is laminated on an image display element, that is, a liquid crystal cell or an organic EL display element, leads to a problem in appearance such as poor surface uniformity and lack of high-class feeling especially on the viewing side surface. .

  Patent Document 1 discloses a polarizing plate in which a protective film is laminated on the viewing side surface of a polarizer via an adhesive layer. The polarizing plate described in Patent Document 1 reduces the shrinkage force of the adhesive by making the thickness of the adhesive layer relatively thin with respect to the total thickness of the polarizer and the protective film. By doing so, the unevenness generated on the viewing side surface of the protective film can be reduced, but the room for improvement is still large.

  Moreover, when a polarizing plate has a retardation film, since the unevenness is emphasized and visually recognized more than the physical surface unevenness, the appearance defect is easily recognized.

JP-A-2015-114538

  An object of the present invention is to make it difficult to visually recognize the unevenness generated on the viewing-side surface of the polarizing plate even when the polarizing plate includes a retardation film, and to improve the appearance of the polarizing plate.

[1] A polarizer and a retardation film are laminated via an adhesive layer,
When the one-dimensional power spectrum with respect to the period f (μm) of the surface irregularities is H ² (f), the surface opposite to the polarizer in the retardation film satisfies the following formula (1):
The retardation film is a polarizing plate that is laminated on the image display element side.
H ² (425) / H ² (212) ≦ 10 (1)

[2] The retardation film includes a liquid crystal layer having a thickness of 0.5 to 5.0 μm and a base film having a thickness of 10 to 50 μm, and an in-plane retardation value at a wavelength of 590 nm is 100 to 150 nm. 1].

[3] The polarizing plate according to [1] or [2], wherein the adhesive layer is a cured layer of an active energy ray-curable adhesive.

[4] A step of pasting process paper on the retardation film to obtain a laminated film;
Peeling the process paper from the laminated film to obtain a retardation film;
Bonding a polarizer on a retardation film via an adhesive to obtain a polarizing plate,
Manufacture of a polarizing plate in which the bonding surface with the retardation film in the process paper satisfies the following formula (2) when the one-dimensional power spectrum for the period f (μm) of the surface unevenness is H ² (f). Method.
H ² (425) / H ² (212) ≦ 10 (2)

  According to the present invention, even when the polarizing plate is provided with a retardation film, it is difficult to visually recognize the unevenness generated on the viewing side surface of the polarizing plate, and the appearance of the polarizing plate can be improved.

It is sectional drawing which shows an example of the polarizing plate of this invention. It is sectional drawing which shows an example of the polarizing plate of this invention.

  The polarizing plate of the present invention and the method for producing the polarizing plate will be described with reference to the drawings as appropriate.

  In one embodiment, the polarizing plate of the present invention comprises the member shown in FIG. In the polarizing plate 100 shown in FIG. 1, the polarizer 2 and the retardation film 20 are laminated via an adhesive layer 10. In FIG. 1, the retardation film 20 includes a base film 3 and a liquid crystal layer 5.

  The polarizing plate of the present invention may further contain a protective film, an adhesive layer and the like. In one embodiment, the polarizing plate of the present invention comprises the member shown in FIG. In the polarizing plate 101 shown in FIG. 2, a retardation film 20 is laminated on one surface of the polarizer 2 via an adhesive layer 10, and the protective film 4 is disposed on the other surface of the polarizer 2 via an adhesive layer 11. Are laminated, and the pressure-sensitive adhesive layer 6 is laminated on the retardation film 20. The pressure-sensitive adhesive layer 6 may be, for example, a pressure-sensitive adhesive layer for bonding to an image display element such as a liquid crystal cell.

In the polarizing plate of the present invention, when the one-dimensional power spectrum with respect to the period f (μm) of the surface irregularities is H ² (f), the surface opposite to the polarizer in the retardation film is represented by the following formula (1) Is satisfied. The left side of the following formula (1) is preferably 6 or less, and more preferably 4 or less. The lower limit is not particularly limited, but can be 2 or more.
H ² (425) / H ² (212) ≦ 10 (1)
H ² (425) represents a one-dimensional power spectrum at a period of 425 μm, H ² (212) represents a one-dimensional power spectrum at a period of 212 μm, and can be measured by the method described in the examples described later. .

  When the surface unevenness of the retardation film satisfies the above formula (1), it is difficult to visually recognize the unevenness generated on the viewing side surface of the polarizing plate. The viewing side surface of the polarizing plate is, for example, the surface of the polarizer 2 in the polarizing plate 100 shown in FIG. 1, and the surface of the protective film 4 in the polarizing plate 101 shown in FIG. That is, when the surface shape of the retardation film arranged on the side closer to the image display element with respect to the polarizer satisfies the formula (1), the unevenness on the surface of the polarizing plate far from the image display element is visually recognized. It becomes hard and the appearance can be improved.

  It is estimated as follows how the above formula (1) contributes to making it difficult to visually recognize the irregularities on the surface on the viewing side, but the present invention is not limited at all. The one-dimensional power spectrum having a period of 212 μm or a period of 425 μm on the surface irregularities represents the size of the undulation around the surface period of 200 μm or the period of 400 μm on the retardation film, respectively. As will be described later, in the manufacturing process of the retardation film, process paper may be bonded to prevent scratches or to prevent blocking between the retardation films. As a result, the surface shape of the process paper may be transferred to the retardation film. It became clear that the ease of transfer of the surface shape depends on the period of the surface shape. Specifically, the inventors have clarified that a surface shape having a period of about 400 μm is easily transferred and a surface shape having a period of 300 μm or less is difficult to transfer. That is, simply reducing the physical unevenness on the surface of the retardation film by simply setting the arithmetic average waviness Wa to a predetermined value or less is insufficient to make it difficult to visually recognize the unevenness on the surface on the viewing side. It is considered that the unevenness on the surface on the viewing side can be made difficult to visually recognize by setting the size of the undulation in the vicinity of the cycle of 400 μm to the undulation of the cycle of 200 μm.

The surface of the retardation film opposite to the polarizer satisfies the above formula (1). The arithmetic average roughness Ra (JIS B 0601-2001) of this surface is usually 0 nm or more, preferably 10 nm or more, usually 1000 nm or less, preferably 500 nm or less, and Kurtosis Pku (JIS B 0601-2001) is usually 0 or more. It is preferably 1.0 or more, usually 10 or less, preferably 5 or less, and the skewness Psk (JIS B 0601-2001) is usually −5 to +5, preferably −1 to +1.

  Hereinafter, each member which comprises the polarizing plate of this invention is demonstrated.

(Polarizer)
The polarizer used in the present invention is usually a step of uniaxially stretching a polyvinyl alcohol resin film, a step of adsorbing a dichroic dye by dyeing the polyvinyl alcohol resin film with a dichroic dye, a dichroic dye It is manufactured through a step of treating the polyvinyl alcohol-based resin film adsorbed with boric acid aqueous solution and a step of washing with water after the treatment with boric acid aqueous solution.

  As the polyvinyl alcohol resin, a saponified polyvinyl acetate resin can be used. Examples of the polyvinyl acetate resin include, in addition to polyvinyl acetate, which is a homopolymer of vinyl acetate, copolymers with other monomers copolymerizable with vinyl acetate. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

  The saponification degree of the polyvinyl alcohol resin is usually about 85 to 100 mol%, preferably 98 mol% or more. This polyvinyl alcohol-based resin may be modified, and for example, polyvinyl formal and polyvinyl acetal modified with aldehydes can also be used. Moreover, the polymerization degree of polyvinyl alcohol-type resin is about 1,000-10,000 normally, and about 1,500-5,000 are preferable.

What formed the polyvinyl alcohol-type resin into a film is used as a raw film of a polarizer. The method for forming a polyvinyl alcohol-based resin can be formed by a known method. The film thickness of the polyvinyl alcohol-based raw film is preferably about 5 to 35 μm, more preferably 5 to 20 μm, considering that the thickness of the obtained polarizer is 15 μm or less. When the film thickness of the original film is 35 μm or more, it is necessary to increase the draw ratio when producing the polarizer, and the dimensional shrinkage of the obtained polarizer tends to increase.
On the other hand, when the film thickness of the raw film is 5 μm or less, the handling property at the time of stretching is lowered, and there is a tendency that problems such as cutting are likely to occur during production.

  Uniaxial stretching of the polyvinyl alcohol-based resin film can be performed before dyeing of the dichroic dye, simultaneously with dyeing, or after dyeing. When uniaxial stretching is performed after dyeing, this uniaxial stretching may be performed before boric acid treatment or during boric acid treatment. Moreover, you may uniaxially stretch in these several steps.

  In uniaxial stretching, it may be uniaxially stretched between rolls having different peripheral speeds, or may be uniaxially stretched using a hot roll. Further, the uniaxial stretching may be dry stretching in which stretching is performed in the air, or may be wet stretching in which stretching is performed in a state where a solvent is used and the polyvinyl alcohol-based resin film is swollen. The draw ratio is usually about 3 to 8 times.

  As a method of dyeing the polyvinyl alcohol resin film with the dichroic dye, for example, a method of immersing the polyvinyl alcohol resin film in an aqueous solution containing the dichroic dye is employed. Specifically, iodine or a dichroic dye is used as the dichroic dye. In addition, it is preferable that the polyvinyl alcohol-type resin film performs the immersion process to water before a dyeing process.

When iodine is used as the dichroic dye, a method of dyeing a polyvinyl alcohol-based resin film in an aqueous solution containing iodine and potassium iodide is usually employed. The content of iodine in this aqueous solution is usually about 0.01 to 1 part by weight per 100 parts by weight of water. The content of potassium iodide is usually about 0.5 to 20 parts by weight per 100 parts by weight of water. The temperature of the aqueous solution used for dyeing is usually about 20 to 40 ° C.
Moreover, the immersion time (dyeing time) in this aqueous solution is usually about 20 to 1800 seconds.

On the other hand, when a dichroic dye is used as the dichroic dye, a method of immersing and dyeing a polyvinyl alcohol-based resin film in an aqueous solution containing a water-soluble dichroic dye is usually employed. The content of the dichroic dye in this aqueous solution is usually about 1 × 10 ⁻⁴ to 10 parts by weight and preferably about 1 × 10 ⁻³ to 1 part by weight per 100 parts by weight of water. This aqueous solution may contain an inorganic salt such as sodium sulfate as a dyeing assistant. The temperature of the aqueous dichroic dye solution used for dyeing is usually about 20 to 80 ° C. Moreover, the immersion time (dyeing time) in this aqueous solution is usually about 10 to 1,800 seconds.

  The boric acid treatment after dyeing with a dichroic dye can usually be performed by immersing the dyed polyvinyl alcohol-based resin film in a boric acid-containing aqueous solution.

  The amount of boric acid in the boric acid-containing aqueous solution is usually about 2 to 15 parts by weight and preferably 5 to 12 parts by weight per 100 parts by weight of water. When iodine is used as the dichroic dye, the boric acid-containing aqueous solution preferably contains potassium iodide. The amount of potassium iodide in the boric acid-containing aqueous solution is usually about 0.1 to 15 parts by weight and preferably about 5 to 12 parts by weight per 100 parts by weight of water. The immersion time in the boric acid-containing aqueous solution is usually about 60 to 1,200 seconds, preferably about 150 to 600 seconds, and more preferably about 200 to 400 seconds. The temperature of the boric acid-containing aqueous solution is usually 50 ° C or higher, preferably 50 to 85 ° C, and more preferably 60 to 80 ° C.

  The polyvinyl alcohol resin film after the boric acid treatment is usually washed with water. The water washing treatment can be performed, for example, by immersing a boric acid-treated polyvinyl alcohol resin film in water. The temperature of water in the water washing treatment is usually about 5 to 40 ° C. Further, the immersion time is usually about 1 to 120 seconds.

  After washing with water, a drying process is performed to obtain a polarizer. The drying process can be performed using a hot air dryer or a far infrared heater. The temperature of the drying treatment is usually about 30 to 100 ° C, and preferably 50 to 80 ° C. The time for the drying treatment is usually about 60 to 600 seconds, and preferably 120 to 600 seconds.

By the drying process, the moisture content of the polarizer is reduced to a practical level. The water content is usually 5 to 20% by weight, preferably 8 to 15% by weight. When the moisture content is less than 5% by weight, the flexibility of the polarizer is lost, and the polarizer may be damaged or broken after drying.
On the other hand, if the moisture content exceeds 20% by weight, the thermal stability of the polarizer may be inferior.

  Further, the stretching, dyeing, boric acid treatment, water washing step, and drying step of the polyvinyl alcohol resin film in the production process of the polarizer may be performed in accordance with, for example, the method described in JP2012-159778A. . In the method described in this document, a polyvinyl alcohol resin layer to be a polarizer is formed by coating a polyvinyl alcohol resin on a base film.

  The effect of the present invention is significant when the thickness of the polarizer is thinner (when there is no stiffness). For example, the thickness of the polarizer may be 15 μm or less, or 10 μm or less. From the viewpoint of improving the optical characteristics, the thickness of the polarizer is, for example, 3 μm or more.

(Protective film)
The protective film is composed of a resin film and can be composed of a transparent resin film. In particular, it is preferable to use a material that is excellent in transparency, mechanical strength, thermal stability, moisture shielding properties, and the like. In this specification, the transparent resin film means a resin film having a single transmittance of 80% or more in the visible light region.

The resin for forming the protective film is not particularly limited. For example, methyl methacrylate resin, polyolefin resin, cyclic olefin resin, polyvinyl chloride resin, cellulose resin, styrene resin, acrylonitrile.・ Butadiene / styrene resins, acrylonitrile / styrene resins, polyvinyl acetate resins, polyvinylidene chloride resins, polyamide resins, polyacetal resins, polycarbonate resins, modified polyphenylene ether resins, polybutylene terephthalate resins, Examples thereof include films made of polyethylene terephthalate resin, polysulfone resin, polyethersulfone resin, polyarylate resin, polyamideimide resin, polyimide resin, and the like.
These resin films are a film formed from a raw material resin, a uniaxially stretched film obtained by transverse stretching after film formation, a biaxially stretched film obtained by longitudinally stretching after film formation and then transversely stretching, etc. be able to.

  These resins can be used alone or in combination of two or more. These resins can also be used after any appropriate polymer modification. Examples of the polymer modification include copolymerization, crosslinking, molecular terminal modification, stereoregularity control, and reaction between different polymers. Modifications such as mixing including the case involving the.

  Among these, as the material for the protective film, it is preferable to use a methyl methacrylate resin, a polyethylene terephthalate resin, a polyolefin resin, or a cellulose resin. The polyolefin resin here includes a chain polyolefin resin and a cyclic polyolefin resin.

  The film used as the protective film can be easily obtained as a commercial product, and if it is a methyl methacrylate-based resin film, the trade name is Sumipex (manufactured by Sumitomo Chemical Co., Ltd.), Acrylite (registered trademark), Acriprene (registered trademark) (Mitsubishi Rayon Co., Ltd.), Delagras (registered trademark) (Asahi Kasei Co., Ltd.), Paragrass (registered trademark), Comogras (registered trademark) (manufactured by Kuraray Co., Ltd.), Registered trademark) (manufactured by Nippon Shokubai Co., Ltd.). If it is a polyolefin-type resin film, ZEONOR (registered trademark) (Nippon Zeon Co., Ltd.), Arton (registered trademark) (JSR Co., Ltd.), etc. are mentioned by a brand name, respectively. If it is a polyethylene terephthalate-type resin film, a Novaclear (trademark) (made by Mitsubishi Chemical Corporation), a Teijin A-PET sheet (made by Teijin Chemicals Ltd.), etc. will be mentioned, respectively. For polypropylene resin films, FILMAX CPP film (manufactured by FILMAX), Santox (registered trademark) (manufactured by Sun Tox Co., Ltd.), Tosero (registered trademark) (manufactured by Tosero Co., Ltd.), Toyobo Pyrene Film (Registered trademark) (manufactured by Toyobo Co., Ltd.), Treffan (registered trademark) (manufactured by Toray Film Processing Co., Ltd.), Nihon Polyace (manufactured by Nippon Polyace Co., Ltd.), and Dazai (registered trademark) FC (Futamura Chemical Co., Ltd.) Manufactured). In the case of cellulose-based resin films, Fujitac (registered trademark) TD (manufactured by Fuji Film Co., Ltd.), KC2UA and Konica Minolta TAC film KC (manufactured by Konica Minolta Co., Ltd.) and the like can be mentioned.

  Moreover, a protective film can also contain an additive as needed. Examples of the additive include a lubricant, an antiblocking agent, a heat stabilizer, an antioxidant, an antistatic agent, a light resistance agent, and an impact resistance improver.

  The effect of this invention is remarkable when the thickness of a protective film is thinner (when there is no stiffness), for example, the thickness of a protective film may be 1-50 micrometers and may be 10-40 micrometers. And may be 10 to 35 μm.

  Prior to bonding with the polarizer, the protective film may be subjected to saponification treatment, corona treatment, plasma treatment or the like. The protective film can further be provided with functional layers such as a conductive layer, a hard coat layer, an antiglare layer and a low reflection layer.

(Retardation film)
The retardation film can be formed from, for example, a resin exemplified as the material of the protective film, and among them, a cyclic olefin resin and a styrene resin are preferable. The retardation film may be formed from a single layer or may be formed from a plurality of layers. Examples of the retardation film having a plurality of layers include a resin film (base film) exemplified as the material of the protective film, and a liquid crystal layer obtained by polymerizing a liquid crystal compound, and a plurality (for example, two layers) of liquid crystal layers. May be included. The layer having a phase difference can be a resin film and / or a liquid crystal layer.

  When the in-plane retardation value at the wavelength λ (nm) is Re (λ) and the retardation value in the thickness direction is Rth (λ), in one embodiment, the in-plane retardation value Re (590) of the retardation film. ) Can be set to 100 to 150 nm, for example, and the thickness direction retardation value Rth (590) can be set to −200 to +200 nm, for example.

  The in-plane retardation value Re and the thickness direction retardation value Rth are the refractive index in the in-plane slow axis direction nx and the refractive index in the in-plane fast axis direction (direction orthogonal to the in-plane slow axis direction) ny. When the refractive index in the thickness direction is nz and the thickness of the retardation film is d, it is defined by the following formulas (3) and (4).

Re = (nx−ny) × d (3)
Rth = [{(nx + ny) / 2} -nz] × d (4)

The liquid crystal layer included in the retardation layer can be a λ / 4 plate, a λ / 2 plate, or a positive C layer.
When the retardation layer includes a plurality of liquid crystal layers, a combination of a quarter wavelength plate and a half wavelength plate, or a combination of a quarter wavelength plate and a positive C plate is preferable. The λ / 4 plate is a layer whose in-plane retardation value Re (550) at a wavelength of 550 nm satisfies the relationship of 100 nm ≦ Re (550) ≦ 200 nm. The λ / 4 plate may exhibit reverse wavelength dispersion satisfying Re (450) <Re (550) <Re (650). The λ / 2 plate is a layer in which Re (550) satisfies 210 nm ≦ Re (550) ≦ 300 nm. The positive C layer satisfies the relationship of nz> nx ≧ ny (the difference between the magnitude of nx and the magnitude of ny is within ± 1%, for example), and the thickness direction retardation at the wavelength λ [nm]. It is preferable that the value Rth (λ) satisfies the relationship of −300 nm ≦ Rth (550) ≦ −20 nm.

  In the case where the retardation layer includes a liquid crystal layer, it is easy to perceive a defect in appearance as compared with the case where the retardation layer is constituted only by a resin film. This is because the liquid crystal layer is thinner than the resin film, so that the change in retardation per unit thickness is large.

The liquid crystal layer included in the retardation layer is a layer including a layer obtained by polymerizing and curing a liquid crystal compound. The type of the liquid crystal compound is not particularly limited, but can be classified into a rod-shaped type (bar-shaped liquid crystal compound) and a disk-shaped type (disk-shaped liquid crystal compound, discotic liquid crystal compound) depending on the shape. Furthermore, there are a low molecular type and a high molecular type, respectively. Polymer generally means a polymer having a degree of polymerization of 100 or more (Polymer Physics / Phase Transition Dynamics, Masao Doi, 2 pages, Iwanami Shoten, 1992). In the present embodiment, any liquid crystal compound can be used.
Further, two or more kinds of rod-like liquid crystal compounds, two or more kinds of disk-like liquid crystal compounds, or a mixture of a rod-like liquid crystal compound and a disk-like liquid crystal compound may be used.

  As the rod-like liquid crystal compound, for example, the one described in claim 1 of JP-T-11-53019 or paragraphs [0026] to [0098] of JP-A-2005-289980 is preferably used. Can do. As the discotic liquid crystal compound, for example, those described in paragraphs [0020] to [0067] of JP-A-2007-108732 or paragraphs [0013] to [0108] of JP-A-2010-244038 are suitable. Can be used.

  The liquid crystal layer is more preferably formed using a liquid crystal compound having a polymerizable group (rod-like liquid crystal compound or discotic liquid crystal compound). Thereby, the temperature change and humidity change of an optical characteristic can be made small.

  The liquid crystal compound may be a mixture of two or more. In that case, it is preferable that at least one has two or more polymerizable groups. That is, the liquid crystal layer is preferably a layer formed by fixing a rod-like liquid crystal compound having a polymerizable group or a discotic liquid crystal compound having a polymerizable group by polymerization. In this case, it is no longer necessary to exhibit liquid crystallinity after forming a layer.

  The kind of the polymerizable group contained in the rod-like liquid crystal compound or the disk-like liquid crystal compound is not particularly limited. For example, a functional group capable of an addition polymerization reaction such as a polymerizable ethylenically unsaturated group or a ring polymerizable group. Is preferred. More specifically, for example, (meth) acryloyl group, vinyl group, styryl group, allyl group and the like can be mentioned. Among these, a (meth) acryloyl group is preferable. The (meth) acryloyl group is a concept including both a methacryloyl group and an acryloyl group.

  The method for forming the liquid crystal layer is not particularly limited, and may be a known method. For example, an optically anisotropic layer forming composition containing a liquid crystal compound having a polymerizable group (hereinafter simply referred to as “composition”) is applied to a resin film (base film) to form a coating film, A retardation layer can be produced by subjecting the obtained coating film to curing treatment (ultraviolet irradiation (light irradiation treatment) or heat treatment). The manufactured retardation layer can be transferred onto, for example, a polarizer, a protective film, or another resin film (base film).

  The composition can be applied by a known method such as a wire bar coating method, an extrusion coating method, a direct gravure coating method, a reverse gravure coating method, and a die coating method.

  The composition may contain components other than the above-described liquid crystal compounds. For example, the composition may contain a polymerization initiator. As the polymerization initiator to be used, for example, a thermal polymerization initiator or a photopolymerization initiator is selected according to the type of the polymerization reaction. Examples of the photopolymerization initiator include α-carbonyl compounds, acyloin ethers, α-hydrocarbon-substituted aromatic acyloin compounds, polynuclear quinone compounds, combinations of triarylimidazole dimers and p-aminophenyl ketones. The amount of the polymerization initiator used is preferably 0.01 to 20% by mass and more preferably 0.5 to 5% by mass with respect to the total solid content of the composition.

  In addition, the composition may contain a polymerizable monomer from the viewpoint of the uniformity of the coating film and the strength of the film. Examples of the polymerizable monomer include radically polymerizable or cationically polymerizable compounds. Among these, a polyfunctional radically polymerizable monomer is preferable.

  In addition, as a polymerizable monomer, a thing copolymerizable with the liquid crystal compound containing the polymeric group mentioned above is preferable. Specific examples of the polymerizable monomer include those described in paragraphs [0018] to [0020] in JP-A-2002-296423. It is preferable that the usage-amount of a polymerizable monomer is 1-50 mass% with respect to the total mass of a liquid crystal compound, and it is more preferable that it is 2-30 mass%.

  The composition may contain a surfactant from the viewpoint of the uniformity of the coating film and the strength of the film. Examples of the surfactant include conventionally known compounds. Of these, fluorine compounds are particularly preferred.

The composition may contain a solvent, and an organic solvent is preferably used. Examples of the organic solvent include amides (eg, N, N-dimethylformamide), sulfoxides (eg, dimethyl sulfoxide), heterocyclic compounds (eg, pyridine), hydrocarbons (eg, benzene, hexane), alkyl halides (eg, , Chloroform, dichloromethane), esters (eg, methyl acetate, ethyl acetate, butyl acetate), ketones (eg, acetone, methyl ethyl ketone), ethers (eg, tetrahydrofuran, 1,2-dimethoxyethane).
Of these, alkyl halides and ketones are preferred. Two or more organic solvents may be used in combination.

  The composition includes a vertical alignment accelerator such as a polarizer interface side vertical alignment agent and an air interface side vertical alignment agent, and a horizontal alignment accelerator such as a polarizer interface side horizontal alignment agent and an air interface side horizontal alignment agent. Such various orientation agents may be included. Furthermore, in addition to the above components, the composition may contain an adhesion improving agent, a plasticizer, a polymer, and the like.

  The liquid crystal layer may include an alignment film having a function of defining the alignment direction of the liquid crystal compound. The alignment film generally contains a polymer as a main component. The polymer material for alignment film is described in many documents, and many commercially available products can be obtained.

  The alignment film is usually subjected to a known alignment process. For example, a rubbing treatment, a photo-alignment treatment for applying polarized light, and the like can be mentioned. From the viewpoint of arithmetic average waviness of the alignment film, the photo-alignment treatment is preferable.

  The effect of the present invention is remarkable when the thickness of the retardation film is thinner (when there is no stiffness), and the thickness of the retardation film may be, for example, 60 μm or less, or 40 μm or less. . The thickness of the retardation film is usually 5 μm or more. When the retardation film includes a base film and a liquid crystal layer, the thickness of the base film is preferably 10 to 50 μm, more preferably 10 to 30 μm, and the thickness of the liquid crystal layer is 0.00. It is preferable that it is 5-5.0 micrometers.

  In addition, the elastic modulus of the retardation film may be 5000 MPa or less, or 3000 MPa or less, and is usually 2000 MPa or more at 23 ° C. The elastic modulus can be measured according to JIS K 7161. When the elastic modulus is anisotropic in the MD direction and the TD direction, in this specification, the elastic modulus can be an average of both.

  Even if the retardation film has a thickness and an elastic modulus in such a range, according to the present invention, it is difficult to visually recognize the unevenness on the surface on the viewing side by satisfying the expression (1).

  Further, from the viewpoint of improving the appearance of the polarizing plate, the surface on the side opposite to the polarizer side in the retardation film preferably has an arithmetic average waviness Wa of 50 nm or less, and preferably 40 nm or less. More preferably, it is more preferably 30 nm or less. The arithmetic average waviness Wa on the surface opposite to the polarizer side in the retardation film is usually 10 nm or more.

(Adhesive layer)
As the adhesive forming the adhesive layer, an active energy ray-curable adhesive or a water-based adhesive can be used. That is, the adhesive layer is a cured layer of the adhesive.

  As described above, one of the factors that cause unevenness on the surface of the polarizing plate is curing shrinkage when the adhesive is cured or dried. The shrinkage force (per unit time) in the case of using an active energy ray-curable adhesive that cures the adhesive in a short time by light irradiation is generally determined by drying the solvent (for example, water) by heating and thereafter. It is larger than a water-based adhesive that adheres over a relatively long time by curing as required. Therefore, in the present invention, it can be particularly suitably applied when the adhesive layer for laminating the retardation film is formed from an active energy ray-curable adhesive, and the resulting unevenness suppressing effect is high.

  When the protective film and the retardation film are respectively disposed on both sides of the polarizer like the polarizing plate 101 shown in FIG. 2, the adhesive for laminating the protective film and the adhesive for laminating the retardation film are: They may be the same as or different from each other. For the same reason as described above, the adhesive for laminating the protective film and the adhesive for forming the adhesive layer are preferably active energy ray-curable adhesives.

  An active energy ray-curable adhesive refers to an adhesive that cures when irradiated with an active energy ray such as an electron beam or an ultraviolet ray. For example, an adhesive containing a polymerizable compound and a photopolymerization initiator, a photoreactive resin. And those containing a binder resin and a photoreactive cross-linking agent. Examples of the polymerizable compound include a photocurable epoxy compound; a photocurable vinyl compound such as a photocurable acrylic compound; and a photocurable urethane compound. Examples of the photopolymerization initiator include a cationic photopolymerization initiator (for example, when using a photocurable epoxy compound) and a photoradical polymerization initiator (for example, when using a photocurable acrylic compound). .

  Examples of the water-based adhesive include an adhesive made of a polyvinyl alcohol-based resin aqueous solution and a water-based two-component urethane emulsion adhesive. Among these, a water-based adhesive composed of a polyvinyl alcohol-based resin aqueous solution is preferably used.

  Polyvinyl alcohol resins include vinyl alcohol homopolymers obtained by saponifying polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith. A polyvinyl alcohol copolymer obtained by saponifying a polymer or a modified polyvinyl alcohol polymer obtained by partially modifying the hydroxyl group thereof can be used. The water-based adhesive can include additives such as polyvalent aldehydes, water-soluble epoxy compounds, melamine compounds, zirconia compounds, and zinc compounds.

  The thickness of the adhesive layer is, for example, 5 μm or less, preferably 2 μm or less, preferably 1 μm or less, from the viewpoint of reducing shrinkage when the adhesive is cured or drying and further reducing the unevenness of the polarizing plate. It may be. Further, from the viewpoint of developing sufficient adhesive force, the thickness of the adhesive layer is usually 0.01 μm or more.

  The adhesive may contain an additive. Examples of the additive include an ion trap agent, an antioxidant, a chain transfer agent, a sensitizer, a tackifier, a thermoplastic resin, a filler, a flow regulator, a plasticizer, and an antifoaming agent.

(Adhesive layer)
An adhesive layer can be laminated on the surface of the polarizing plate. A polarizing plate can be bonded to an image display element such as a liquid crystal cell via the pressure-sensitive adhesive layer. In FIG. 2, the pressure-sensitive adhesive layer 6 corresponds to this. The thickness of the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive is preferably 5 to 25 μm. More preferably, it is 10-25 micrometers.

  Examples of the pressure-sensitive adhesive forming the pressure-sensitive adhesive layer include acrylic polymers, silicone polymers, polyesters, polyurethanes, polyamides, polyvinyl ethers, vinyl acetate / vinyl chloride copolymers, modified polyolefins, epoxy-based, fluorine-based, natural rubber, What uses rubber-type polymers, such as a synthetic rubber, as a base polymer can be selected suitably, and can be used. As the pressure-sensitive adhesive, those having excellent optical transparency, moderate wettability, cohesiveness and adhesive pressure-sensitive adhesive properties, and excellent weather resistance and heat resistance are particularly preferable.

  Various other additives may be blended in the adhesive. Examples of the additive include a silane coupling agent and an antistatic agent.

  Hereinafter, the manufacturing method of the polarizing plate of this invention is demonstrated. The polarizing plate of the present invention can be produced, for example, by a method including the following steps.

Step (1): A step of obtaining a retardation film by forming an alignment film on a base film and then applying a liquid crystal compound on the alignment film and polymerizing it to form a liquid crystal layer.
Process (2): The process of bonding a process paper on retardation film and obtaining a laminated film.
Step (3): A step of peeling the process paper from the laminated film to obtain a retardation film.
Process (4): The process of bonding a polarizer (or polarizer with a protective film) on a retardation film through an adhesive, and obtaining a polarizing plate.

(Process (1))
Step (1) is a step of producing a retardation film. When a base film and a liquid crystal layer are included as a retardation film, an alignment film for aligning a liquid crystal compound is first formed on the base film as described above. Examples of the alignment film include an alignment film containing an alignment polymer, a photo-alignment film, a groove alignment film that forms an uneven pattern and a plurality of grooves on the surface, and the like, and can be formed by a conventionally known method.

  Next, a composition containing a liquid crystal compound is applied onto the alignment film, and if necessary, the solvent is dried, and then the liquid crystal compound is polymerized. Polymerization of the liquid crystal compound can be performed by a known method of polymerizing a compound having a polymerizable functional group. Specific examples include thermal polymerization and photopolymerization, and photopolymerization is preferred from the viewpoint of ease of polymerization. Photopolymerization can be carried out by irradiating the liquid crystal compound with active energy rays such as ultraviolet rays. The active energy ray may be irradiated from the base film side, from the liquid crystal compound side, or from both the base film side and the liquid crystal compound side.

(Process (2))
Step (2) is a step of obtaining a laminated film by laminating process papers on a retardation film. By laminating process paper on the retardation film, it is easy to handle and store the retardation film, prevent blocking of the retardation films, and dust adheres to the retardation film. It can be prevented from becoming a defect. From such a viewpoint, the process paper is preferably laminated on the liquid crystal layer in the retardation film.

  The process paper in the process (2) may be formed from a single layer or a plurality of layers. Although the pressure-sensitive adhesive layer may be included or the pressure-sensitive adhesive layer may not be provided, a process paper having a self-adhesive layer is preferable in that defects such as adhesive residue can be reduced. Examples of the material for forming the process paper include the same resin as the material for forming the protective film, and among them, a polyolefin-based resin and a polyethylene terephthalate-based resin are preferable.

  As process paper, what can be obtained as a commercial item can be used. As an example of a commercial product having a base film of polyethylene terephthalate resin, “Cosmo Shine (registered trademark) A4100” manufactured by Toyobo Co., Ltd. may be mentioned. Examples of commercially available products having a base film of polyethylene resin include “Force Field (registered trademark) 1035” manufactured by Tredegar Film Products Corporation and “Tretech (registered trademark)” manufactured by Toray Film Processing Co., Ltd.

In order to achieve the surface shape satisfying the above formula (1), the surface shape of the process paper used in the step (2) is particularly important. When the one-dimensional power spectrum for the period f (μm) is H ² (f), it is preferable to satisfy the following formula (2). The power spectrum can be measured by the method described in Examples described later. The lower limit of H ² (425) / H ² (212) is not particularly limited, but can be 2 or more.
H ² (425) / H ² (212) ≦ 10 (2)

The arithmetic mean roughness Ra (JIS B 0601-2001) of the surface of the process paper is usually 0 nm or more, preferably 10 nm or more, usually 500 nm or less, preferably 200 nm or less, and Kurtosis Pku (JIS B 0601-2001) is usually 0. Above, preferably 1.0 or more, usually 10 or less, preferably 5 or less, and the skewness Psk (JIS B 0601-2001) is usually −5 to +5, preferably −1 to +1.

  By laminating the process paper having such a surface shape on the retardation film, a desired surface shape satisfying the formula (1) can be transferred to the retardation film, and the appearance on the viewing side surface of the polarizing plate is good. Can be.

  When the above-mentioned commercially available film is used as the process paper, the surface shape may differ depending on the grade or lot. Therefore, a film satisfying the formula (2) is appropriately selected and used. Moreover, what is necessary is just to let the surface which satisfy | fills Formula (2) be the surface where a retardation film is laminated | stacked, when the surface shape differs by the one surface and the other surface of process paper.

  Further, from the viewpoint of improving the appearance of the polarizing plate, the surface on which the retardation film in the process paper is laminated preferably has an arithmetic mean waviness Wa of 200 nm or less, more preferably 150 nm or less. 100 nm or less. The arithmetic average waviness Wa of the surface of the process paper on which the retardation film is laminated is usually 50 nm or more.

(Process (3))
Step (3) is a step of peeling the process paper from the laminated film to obtain a retardation film. The peeling method is not particularly limited, and for example, the process paper or the retardation film may be peeled while being held on a roll. Moreover, you may wind up the process paper which peeled.

(Process (4))
A process (4) is a process of bonding a polarizer (or polarizer with a protective film) on a retardation film via an adhesive to obtain a polarizing plate. The adhesive may be applied to the retardation film, may be applied to the polarizer, or may be applied to both the retardation film and the polarizer.
When the retardation film includes a liquid crystal layer and a resin film, the surface to be bonded to the polarizer may be the surface of the resin film or the surface of the liquid crystal layer. When a water-based adhesive is used as the adhesive, the retardation film and the polarizer can be bonded by drying. When an active energy ray-curable adhesive is used as the adhesive, the retardation film and the polarizer can be bonded by irradiating active energy rays such as ultraviolet rays.

  When using an aqueous adhesive, drying can be performed by, for example, introducing the film after pasting into a drying furnace. The drying temperature (temperature of the drying furnace) is preferably 30 to 90 ° C. When the temperature is lower than 30 ° C., the retardation film or the protective film tends to be peeled off from the polarizer. On the other hand, when the drying temperature exceeds 90 ° C., the polarizing performance of the polarizer may be deteriorated by heat. The drying time can be about 10 to 1000 seconds.

  After the drying step, a curing step of curing at room temperature or slightly higher temperature, for example, at a temperature of about 20 to 45 ° C. for about 12 to 600 hours may be provided. The curing temperature is generally set lower than the drying temperature.

  The active energy ray may be irradiated from the retardation film side, may be irradiated from the polarizer side, or may be irradiated from both the retardation film side and the polarizer side.

The irradiation intensity of the active energy ray to the active energy ray curable adhesive is appropriately determined depending on the composition of the active energy ray curable adhesive, but the irradiation intensity in the wavelength region effective for the activation of the polymerization initiator is 0. It is preferably set to be 1 to 6000 mW / cm ² . When the irradiation intensity is 0.1 mW / cm ² or more, the reaction time does not become too long, and when it is 6000 mW / cm ² or less, the heat radiated from the radiation source and the active energy ray curable adhesive are cured. There is little risk of yellowing of the active energy ray-curable adhesive or deterioration of the polarizer due to heat generation.

The light irradiation time for the active energy ray-curable adhesive is also appropriately determined depending on the composition of the active energy ray-curable adhesive, but the integrated light amount expressed as the product of the irradiation intensity and the irradiation time is 10 to 10,000 mJ. It is preferably set to be / cm ² . When the integrated light quantity is 10 mJ / cm ² or more, a sufficient amount of active species derived from the polymerization initiator can be generated to advance the curing reaction more reliably, and when it is 10000 mJ / cm ² or less, the irradiation time is long. It does not become too much, and good productivity can be maintained.

  When laminating a polarizer on a retardation film, the surface of the retardation film is subjected to plasma treatment, corona treatment, ultraviolet irradiation treatment, flame (flame) treatment, saponification in order to improve adhesion to the polarizer. Surface treatment such as treatment (easy adhesion treatment) can be performed. For example, when the retardation film contains a cyclic polyolefin resin, it is preferable to perform plasma treatment or corona treatment. In addition, when the retardation film is made of a cellulose ester resin, it is preferable to perform a saponification treatment. Examples of the saponification treatment include a method of immersing in an alkaline aqueous solution such as sodium hydroxide or potassium hydroxide.

  In the step (4), a polarizer with a protective film can be bonded to a retardation film to obtain a polarizing plate. A protective film may be laminated on the polarizer in advance through an adhesive to produce a polarizer with a protective film, and then the polarizer in the polarizer with a protective film and the retardation film may be bonded together. . Examples of the method for bonding the protective film and the polarizer include the same method as the method for bonding the retardation film and the polarizer. Moreover, a protective film, a polarizer, and a phase difference film can be bonded together to obtain a polarizing plate.

  In the above example, the process paper was peeled off and then the retardation film and the polarizer were bonded. Of course, after the retardation film and the polarizer were bonded, the process paper was peeled off. Also good. That is, the order of the step (3) and the step (4) is arbitrary.

  Although a polarizing plate can be manufactured as described above, an adhesive layer may be further formed on the retardation film. This pressure-sensitive adhesive layer may be a pressure-sensitive adhesive layer for laminating on an image display element such as a liquid crystal cell. The pressure-sensitive adhesive layer may be formed by directly applying a pressure-sensitive adhesive on the retardation film, or by previously applying a pressure-sensitive adhesive on the base film to form a pressure-sensitive adhesive layer. You may form by transferring on a phase difference film.

  When a long polarizing plate is produced continuously, it may be cut into a predetermined shape (for example, a rectangle) to obtain a single plate of the polarizing plate.

  An image display device can be obtained by laminating the polarizing plate of the present invention on an image display element. Examples of the image display element include a liquid crystal cell and an organic EL display element.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not prescribed | regulated by these examples. In the examples, “%” and “part” representing the content or amount used are based on weight unless otherwise specified. The evaluation methods used in the examples are as follows.

(1) Thickness:
Measurement was performed using a digital micrometer MH-15M manufactured by Nikon Corporation.

(2) In-plane retardation Re and thickness direction retardation Rth:
It measured with the light of wavelength 590nm in 23 degreeC using the phase difference meter based on a parallel Nicol rotation method, and KOBRA-WPR by Oji Scientific Instruments.

(3) One-dimensional power spectrum with respect to the period f (μm) of the retardation film surface and the process paper surface: H ² (f)
Surface irregularities were scanned using PLμ NEOX (Sensofa Japan), which is a confocal interference microscope. The obtained unevenness data was analyzed, and H ² (212) and H ² (425) at a period of 212 μm and a period of 425 μm were calculated.

(4) Arithmetic mean swell: Wa
Arithmetic mean waviness Wa was measured using VS1000 (manufactured by Hitachi High-Tech Science Co., Ltd.) which is a scanning white interference microscope. The measurement range was X = 4000 μm or more, Y = 2000 μm or more, and the cutoff value was 100 μm.

(5) Appearance evaluation of polarizing plate An adhesive layer was laminated | stacked on the phase difference film of a polarizing plate, and the polarizing plate was bonded to the glass plate through the adhesive layer. A fluorescent lamp was projected on the polarizing plate, and the appearance was evaluated by observing the reflected image. The case where the outline of the fluorescent lamp was clearly observed without distortion was determined to be good, and the case where the outline of the fluorescent lamp was distorted and could not be clearly observed was determined to be defective.

(6) The surface roughness Ra, the kurtosis Pku, and the skewness Psk were determined according to JIS B 0601-2001 from the data of the unevenness obtained by measuring the one-dimensional power spectrum.

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

  An unstretched polypropylene (PP) film (melting point: 163 ° C.) having a thickness of 90 μm is prepared as a base film, subjected to corona treatment on one side, and then the primer layer is formed on the corona-treated surface using a small-diameter gravure coater. The primer coating liquid was applied and dried at 80 ° C. for 10 minutes to form a primer layer having a thickness of 0.2 μm.

(2) Production of laminated film (resin layer forming step)
Polyvinyl alcohol powder (“PVA124” manufactured by Kuraray Co., Ltd., average polymerization degree 2400, saponification degree 98.0 to 99.0 mol%) was dissolved in 95 ° C. hot water, and an aqueous polyvinyl alcohol solution having a concentration of 8% by weight was dissolved. This was prepared and used as a coating liquid for forming a polyvinyl alcohol-based resin layer.

  By applying the polyvinyl alcohol-based resin layer forming coating solution to the primer layer surface of the base film having the primer layer prepared in (1) above using a lip coater, and then drying at 80 ° C. for 20 minutes. A polyvinyl alcohol-based resin layer was formed on the primer layer to obtain a laminated film composed of base film / primer layer / polyvinyl alcohol-based resin layer.

(3) Production of stretched film (stretching process)
The laminated film produced in (2) above was subjected to 5.8-fold free end uniaxial stretching at 160 ° C. using a floating longitudinal uniaxial stretching apparatus to obtain a stretched film. The thickness of the stretched polyvinyl alcohol resin layer was 6.1 μm.

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

A first crosslinking aqueous solution containing 78 ° C containing boric acid (containing 9.5 parts by weight of boric acid per 100 parts by weight of water) for 120 seconds, and then a second crosslinking at 70 ° C containing boric acid and potassium iodide. Aqueous solution (9.5 parts by weight of boric acid and 4 parts by weight of potassium iodide per 100 parts by weight of water)
) For 60 seconds to carry out a crosslinking treatment. Thereafter, the film was washed with pure water at 10 ° C. for 10 seconds, and finally dried at 40 ° C. for 300 seconds to obtain a polarizing laminated film comprising a base film / primer layer / polarizer.

(Protective film)
A film having a hard coat layer formed on one surface of a cyclic olefin-based resin film (Zeonor Film (registered trademark), manufactured by Nippon Zeon Co., Ltd.) was prepared. The thickness was 50 μm.

(Process paper)
The following process papers were prepared. All of them are process papers containing a polyethylene resin and having a self-adhesive layer as a surface layer.
Process paper A: “Force Field 1035” manufactured by Toledegaer
Process paper B: “Tretec (registered trademark) 7332K” manufactured by Toray Film Processing Co., Ltd.
Process paper C: “Toretec (registered trademark) N711” manufactured by Toray Film Processing Co., Ltd.
Process paper D: "Pearl" manufactured by Toledegaer

The arithmetic average waviness Wa on one surface of the process paper A was 130 nm, H ² (425) was 160, and H ² (212) was 54. H ² (425) / H ² (212) of this surface was 3.0. Note that the surface of the process paper A was smooth to the naked eye.
The arithmetic average waviness Wa on one surface of the process paper B was 140 nm, H ² (425) was 2700, and H ² (212) was 41. The H ² (425) / H ² (212) of this surface was 66. The surface of the process paper B was smooth with the naked eye.
H ² (425) on one surface of the process paper C is 2.71 × 10 ⁻⁵ , H ² (212) is 2.69 × 10 ⁻⁵ , the surface roughness Ra is 190 nm, and Kurtosis Pku Was 2.51 and the skewness Psk was -0.002. H ² (425) / H ² (212) of this surface is 1.01. The surface of the process paper C was smooth to the naked eye.
H ² (425) on one surface of the process paper D is 2.87 × 10 ⁻⁶ , H ² (212) is 1.24 × 10 ⁻⁶ , the surface roughness Ra is 98 nm, and kurtosis Pku was 2.47, and the skewness Psk was -0.114. The H ² (425) / H ² (212) of this surface is 2.31. The surface of the process paper C was smooth to the naked eye.

[Table 1]
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
Process paper surface shape
───────────── H ² (425) / H ² (212)
H ² (425) H ² (212)
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
Process paper A 160 54 3.0
Process paper B 2700 41 66
Process paper C 2.71 × 10 ⁻⁵ 2.69 × 10 ⁻⁵ 1.01
Process paper D 2.87 × 10 ⁻⁶ 1.24 × 10 ⁻⁶ 2.31
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

(Retardation film)
A cyclic olefin resin film manufactured by Nippon Zeon Co., Ltd. was prepared. The thickness was 20 μm. One side of this film was corona treated. The composition for vertical alignment films was applied to the surface subjected to the corona treatment so that the film thickness became 1 μm. The coating film was heat-treated at 100 ° C. for 120 seconds to form an alignment film. As the composition for the vertical alignment film, Sun Chemical SE610 manufactured by Nissan Chemical Industries, Ltd. was used.

A composition containing the prepared photopolymerizable nematic liquid crystal compound (manufactured by Merck & Co., RMM28B) was applied on the alignment film formed above. The composition contains propylene glycol monomethyl ether acetate (PGMEA) as a solvent and Irgacure (Irg-907) as a photopolymerization initiator. The composition of this composition is as follows.
Photopolymerizable nematic liquid crystal compound [RMM28B]: 20 parts by weight Photopolymerization initiator [Irgacure (Irg-907)]: 5 parts by weight Solvent [propylene glycol monomethyl ether acetate]: 80 parts by weight

  The coated layer after coating was dried at a temperature of 90 ° C. for 120 seconds. Thereafter, the liquid crystal compound was polymerized by ultraviolet (UV) irradiation to form a liquid crystal retardation layer having a thickness of 1 μm cured (the total thickness of the liquid crystal retardation layer was 2 μm). Thus, the retardation film which consists of a base film and a liquid crystal retardation layer was obtained. The elastic modulus of the retardation film was 1900 MPa and 2300 MPa in the MD direction and the TD direction at 23 ° C., respectively.

Subsequently, the prepared process paper A to process paper D are bonded onto the liquid crystal layer so that the surface having the surface shape shown in Table 1 (the one surface) becomes the bonding surface with the liquid crystal layer. Then, a retardation film with process paper A, a retardation film with process paper B, a retardation film with process paper C, and a retardation film with process paper D were obtained.
This retardation film can function as a λ / 4 wavelength plate in the visible light wavelength region, and also exhibits a retardation in the thickness direction.

(UV curable adhesive)
An ultraviolet curable adhesive having the following composition was prepared.
3 ′, 4′-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate (trade name “CEL2021P”, manufactured by Daicel Corporation): 70 parts by weight,
Neopentyl glycol diglycidyl ether [trade name “EX-211”, manufactured by Nagase ChemteX Corporation]: 20 parts by weight,
2-ethylhexyl glycidyl ether [trade name “EX-121”, manufactured by Nagase ChemteX Corporation]: 10 parts by weight,
Photocationic polymerization initiator [trade name “CPI-100P”, manufactured by San Apro Co., Ltd.]: 2.25 parts by weight

[Reference Example 1]
When the process paper A was peeled from the retardation film with the process paper A obtained above and the surface shape of the retardation film on the peeled surface (liquid crystal layer surface) was measured, H ² (425) was 7.70. × 10 ⁻⁵ and H ² (212) was 7.51 × 10 ⁻⁵ . The H ² (425) / H ² (212) of this surface is 1.03. In addition, this peeling surface (liquid crystal layer surface) was smooth with the naked eye.

[Example 1]
A polarizing plate was produced as follows.
The protective film was subjected to corona treatment. The UV curable adhesive was applied to the corona-treated surface using a small-diameter gravure coater. Using a bonding roll, a protective film was bonded onto the polarizer of the polarizing laminated film via an ultraviolet curable adhesive. The ultraviolet curable adhesive was cured by ultraviolet irradiation to form an adhesive layer, and a laminated film composed of a protective film / adhesive layer / polarizer / primer layer / substrate film was obtained. The thickness of the adhesive layer was 0.8 μm.

  The base film was peeled off from the obtained laminated film. The base film was easily peeled off to obtain a polarizing plate with a single-sided protective film comprising the first protective film / adhesive layer / polarizer / primer layer.

  The corona treatment was performed on the cyclic olefin resin film in the retardation film with the process paper A. The UV curable adhesive was applied to the corona-treated surface using a small-diameter gravure coater. A retardation film with process paper was bonded onto the primer layer of the polarizing plate with a single-sided protective film through a UV curable adhesive using a bonding roll. The ultraviolet curable adhesive was cured by ultraviolet irradiation to form an adhesive layer. The thickness of the adhesive layer was 0.8 μm.

The process paper A was peeled off to obtain a polarizing plate comprising a first protective film / first adhesive layer / polarizer / primer layer / adhesive layer / retardation film. The power spectrum ratio H ² (425) / H ² (212) on the surface of the liquid crystal layer that appeared after peeling off the process paper A was measured, and the appearance of the polarizing plate was evaluated.
The arithmetic average waviness Wa on the surface of the retardation film opposite to the polarizer was 50 nm or less. In addition, this peeling surface (liquid crystal layer surface) was smooth with the naked eye.

[Comparative Example 1]
A polarizing plate was produced in the same manner as in Example 1 except that the retardation film with process paper A was changed to a retardation film with process paper B. The power spectrum ratio H ² (425) / H ² (212) on the surface of the liquid crystal layer that appeared after peeling off the process paper B was measured, and the appearance of the polarizing plate was evaluated. The arithmetic average waviness Wa on the surface of the retardation film opposite to the polarizer was 50 nm or less. In addition, this peeling surface (liquid crystal layer surface) was smooth with the naked eye.

The results are shown in Table 2.

[Table 2]
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
Surface shape of retardation film
────────────────────── Appearance of polarizing plate
H ² (425) H ² (212) H ² (425) / H ² (212)
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
Example 1 43 4.6 9.3 Good
Comparative Example 1 130 6.4 20 Defect
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

[Reference Example 2]
When the process paper C was peeled from the retardation film with the process paper C obtained above and the surface shape of the retardation film on the peeled surface was measured, H ² (425) was 6.09 × 10 ⁻⁴ . H ² (212) was 1.08 × 10 ⁻³ , the surface roughness Ra was 344 nm, the kurtosis Pku was 1.84, and the skewness Psk was +0.209. The H ² (425) / H ² (212) of this surface is 0.56. In addition, this peeling surface (liquid crystal layer surface) was smooth with the naked eye.

[Example 2]
The polarizing plate produced in the same manner as in Example 1 except that the phase difference film with the process paper A is changed to the phase difference film with the process paper C, and the surface of the liquid crystal layer that appears when the process paper C is peeled off. The power spectrum ratio H ² (425) / H ² (212) is 10 or less, and the appearance is good.

[Reference Example 3]
When the process paper D was peeled from the retardation film with the process paper D obtained above and the surface shape of the retardation film on the peeled surface (liquid crystal layer surface) that appeared was measured, H ² (425) was 3.60. × 10 ⁻⁶ , H ² (212) is 9.48 × 10 ⁻⁶ , surface roughness Ra is 212 nm, kurtosis Pku is 3.051, and skewness Psk is −0.010. It was. The H ² (425) / H ² (212) of this surface is 0.38. In addition, this peeling surface (liquid crystal layer surface) was smooth with the naked eye.

[Example 3]
The polarizing plate produced in the same manner as in Example 1 except that the phase difference film with the process paper A is changed to the phase difference film with the process paper D, and the surface of the liquid crystal layer that appears when the process paper D is peeled off. The power spectrum ratio H ² (425) / H ² (212) is 10 or less, and the appearance is good.

  According to the present invention, even when the polarizing plate includes a retardation film, it is difficult to visually recognize the unevenness generated on the viewing side surface of the polarizing plate, and the appearance of the polarizing plate can be improved.

2 Polarizer 3 Base film 4 Protective film 5 Liquid crystal layer 6 Adhesive layer 10, 11 Adhesive layer 20 Retardation film 100, 101 Polarizing plate

Claims (4)

A polarizer and a retardation film are laminated via an adhesive layer,
When the one-dimensional power spectrum with respect to the period f (μm) of the surface irregularities is H ² (f), the surface opposite to the polarizer in the retardation film satisfies the following formula (1):
The retardation film is a polarizing plate that is laminated on the image display element side.
H ² (425) / H ² (212) ≦ 10 (1) The retardation film includes a liquid crystal layer having a thickness of 0.5 to 5.0 μm and a base film having a thickness of 10 to 50 μm, and an in-plane retardation value at a wavelength of 590 nm is 100 to 150 nm. The polarizing plate as described. The polarizing plate according to claim 1, wherein the adhesive layer is a cured layer of an active energy ray-curable adhesive. On the retardation film, the process paper is pasted to obtain a laminated film;
Peeling the process paper from the laminated film to obtain a retardation film;
Bonding a polarizer on a retardation film via an adhesive to obtain a polarizing plate,
Manufacture of a polarizing plate in which the bonding surface with the retardation film in the process paper satisfies the following formula (2) when the one-dimensional power spectrum for the period f (μm) of the surface unevenness is H ² (f). Method.
H ² (425) / H ² (212) ≦ 10 (2)

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