KR20230098898A - Polarizing plate and polarizing plate with retardation layer - Google Patents

Abstract

The present invention provides a polarizing plate excellent in adhesion and curve followability despite being very thin. The polarizing plate in the present invention includes a polarizer and a protective layer disposed on both sides of the polarizer, the protective layer includes an epoxy resin having an aromatic skeleton and a diol skeleton, and the glass transition temperature of the epoxy resin is 40 ℃ or less, and the elongation at the time of the stab test is 1.40 mm or more.

Description

Polarizing plate and polarizing plate with retardation layer

The present invention relates to a polarizing plate and a polarizing plate with a retardation layer.

BACKGROUND OF THE INVENTION In image display devices (eg, liquid crystal display devices and organic EL display devices), a polarizing plate is disposed on at least one side of a display cell in many cases due to its image formation method. In recent years, thinning and flexibility of image display devices are progressing, and along with this, thinning of polarizing plates is also strongly desired. However, when a conventional thin polarizing plate is applied to a flexible image display device, there is a problem in that the adhesion of the polarizing plate is lowered and the followability of the polarizing plate to a curved surface is lowered.

Japanese Unexamined Patent Publication No. 2015-210474

The present invention has been made in order to solve the above conventional problems, and its main object is to provide a polarizing plate excellent in adhesion and excellent in conformability to a curved surface in spite of being very thin.

The polarizing plate of the present invention includes a polarizer and a protective layer disposed on both sides of the polarizer, and the protective layer includes an epoxy resin having an aromatic skeleton and a diol skeleton, and has a glass transition temperature of 40 ° C. or less, The amount of elongation at the time of the stabbing test of the polarizing plate is 1.40 mm or more.

In one embodiment, the polarizer is composed of a polyvinyl alcohol-based resin film containing a dichroic substance, and an orientation function is 0.30 or less.

In one embodiment, the said protective layer is comprised from the solidified material of the photocationic polymerization hardened|cured material of the said epoxy resin or the coating film of the said organic solvent solution of the said epoxy resin.

In one embodiment, the total thickness of the polarizer is 20 μm or less.

In one embodiment, the puncture strength of the polarizing plate is 300 g or more.

In one embodiment, the glass transition temperature of the protective layer is 0°C or higher.

In another situation of this invention, the polarizing plate with a retardation layer is provided. This polarizing plate with a retardation layer includes a retardation layer, the polarizer, and the protective layer.

According to the present invention, the protective layer disposed on both sides of the polarizer includes an epoxy resin having an aromatic skeleton and a diol skeleton, and has a glass transition temperature of 40 ° C. or less, so that, despite being very thin, adhesion is excellent, In addition, a polarizing plate having excellent curve followability can be obtained.

1 is a schematic cross-sectional view of a polarizing plate according to one embodiment of the present invention.

A. Outline of polarizer

1 is a schematic cross-sectional view of a polarizing plate according to one embodiment of the present invention. The polarizing plate 100 of the illustrated example includes a polarizer 10 and protective layers 20 and 30 disposed on both sides of the polarizer 10 . When applied to an image display device, the polarizing plate 100 may be disposed on the viewing side of the display cell, or may be disposed on the side opposite to the viewing side (rear side). The polarizing plate may be long or sheeted. When a polarizing plate is long, it can be wound preferably in roll shape.

Typically, a polarizing plate includes an adhesive layer as an outermost layer on one side, and bonding to a display cell is possible. If necessary, a surface protection film and/or a carrier film may be temporarily attached to the polarizing plate in a peelable manner to reinforce and/or support the polarizing plate. When a polarizing plate contains an adhesive layer, while a separator is temporarily attached to the surface of the adhesive layer so that exfoliation is possible, and while protecting an adhesive layer until actual use, roll-ization of a polarizing plate is enabled.

In an embodiment of the present invention, the protective layer contains an epoxy resin having an aromatic skeleton and a diol skeleton, and its glass transition temperature is 40°C or less. If it is such a structure, the polarizing plate excellent in adhesiveness and curve followability can be realized.

The protective layer is preferably composed of a photo-cationic cured product of an epoxy resin having an aromatic skeleton and a diol skeleton, or a solidified product of a coating film of an organic solvent solution of the epoxy resin. With such a configuration, the protective layer can be made very thin (for example, 10 μm or less). In addition, the protective layer can be directly formed on the polarizer (ie, without an adhesive layer or pressure-sensitive adhesive layer interposed therebetween). According to the embodiment of the present invention, since the protective layer is very thin as described above, and the adhesive layer or the pressure-sensitive adhesive layer can be omitted, the total thickness of the polarizing plate can be made very thin. Moreover, the adhesiveness of a polarizer and a protective layer is also excellent. The total thickness of the polarizing plate is preferably 20 μm or less, more preferably 15 μm or less, still more preferably 12 μm or less. The total thickness of the polarizing plate may be, for example, 4 μm or more.

The polarizing plate has an elongation of 1.40 mm or more, preferably 1.60 mm or more, in a stab test. When the elongation amount of the polarizing plate in the stab test is within such a range, a polarizing plate excellent in adhesion and conformability to a curved surface can be obtained.

In the embodiment of the present invention, the puncture strength of the polarizing plate is preferably 300 g or more, more preferably 340 g or more. If the puncture strength of the polarizing plate is within this range, a polarizing plate excellent in adhesion and conformability to a curved surface can be obtained.

In an embodiment of the present invention, the thickness of the polarizing plate may be very thin as described above. Therefore, it can be suitably applied to a flexible image display device. More preferably, the image display device has a curved shape (actually, a curved display screen) and/or is bendable or bendable. As a specific example of an image display device, a liquid crystal display device and an electroluminescence (EL) display device (eg, an organic EL display device and an inorganic EL display device) are exemplified. Of course, the above description does not prevent the polarizing plate of the present invention from being applied to a typical image display device.

Hereinafter, a polarizer and a protective layer are demonstrated in detail.

B. Polarizer

As the polarizer, any suitable polarizer can be employed. A polarizer is comprised by the PVA system resin film containing a dichroism substance typically. The resin film forming the polarizer may be, for example, a single-layer resin film or a laminate of two or more layers.

Specific examples of polarizers composed of a single-layer resin film include polyvinyl alcohol (PVA)-based films, partially formalized PVA-based films, hydrophilic polymer films such as ethylene-vinyl acetate copolymer-based partially saponified films, iodine, dichroic dyes, etc. Polyene-based oriented films, such as what was dyed and stretched with a dichroic substance, PVA dehydrated, and polyvinyl chloride dehydrochlorinated, etc. are mentioned. Preferably, a polarizer obtained by dyeing a PVA-based film with iodine and uniaxially stretching is used because of its excellent optical properties.

The dyeing with iodine is performed, for example, by immersing the PVA-based film in an aqueous solution of iodine. The draw ratio of the said uniaxial stretching is preferably 3 to 7 times. Stretching may be performed after dyeing treatment or may be performed while dyeing. Moreover, you may dye after extending|stretching. Swelling treatment, crosslinking treatment, washing treatment, drying treatment, etc. are applied to the PVA-based film as necessary. For example, by immersing and washing the PVA-based film in water before dyeing, stains on the surface of the PVA-based film and anti-blocking agent can be washed away, as well as swelling of the PVA-based film to prevent staining and the like.

The polarizer may be typically manufactured using a laminate of two or more layers. As a specific example of the light polarizer obtained using a laminated body, the polarizer obtained using the laminated body of the resin base material and the PVA system resin layer apply|coated to the said resin base material is mentioned. A polarizer obtained by using a laminate of a resin substrate and a PVA-based resin layer coated and formed on the resin substrate, for example, by applying a PVA-based resin solution to the resin substrate, drying it, and forming a PVA-based resin layer on the resin substrate, Obtaining a laminated body of a substrate and a PVA-based resin layer; It can be produced by: stretching and dyeing the layered product to make the PVA-based resin layer a polarizer. In this embodiment, preferably, a polyvinyl alcohol-based resin layer containing a halide and a polyvinyl alcohol-based resin is formed on one side of the resin substrate. Stretching typically involves immersing the layered product in an aqueous solution of boric acid and extending the laminate. Further, the stretching preferably further includes air stretching the laminate at a high temperature (eg, 95° C. or higher) before stretching in a boric acid aqueous solution. The total draw ratio of the laminate is preferably 5.0 times or more, more preferably 5.5 times or more with respect to the original length of the laminate. Hereinafter, the embodiment of the present invention in which a polarizer is obtained in this way is referred to as Embodiment A. The details of the manufacturing method of such a polarizer are described, for example in Unexamined-Japanese-Patent No. 2012-73580 (patent No. 5414738) and patent No. 6470455. As for the publication, the entire description thereof is incorporated herein by reference.

In one embodiment of the present invention, the total draw ratio of the laminate is preferably 3.0 to 4.5 times the original length of the laminate, and is significantly smaller than usual. Even at such a total magnification of stretching, a polarizer having acceptable optical characteristics can be obtained by a combination of halide addition and drying shrinkage treatment. Further, in the embodiment of the present invention, the draw ratio of air assisted stretching is preferably greater than the draw ratio of stretching in boric acid water. More specifically, the ratio of the draw ratio of the air-assisted stretching to the draw ratio of the underwater stretching (underwater stretching/air-assisted stretching) is preferably 0.4 to 0.9, more preferably 0.5 to 0.8. By setting it as such a structure, even if the total magnification of extending|stretching is small, the polarizer which has acceptable optical characteristics can be obtained. In addition, the laminate is preferably subjected to a drying shrinkage treatment to shrink by 2% or more in the width direction by heating while conveying in the longitudinal direction. In one embodiment, the manufacturing method of a light polarizer includes giving a laminated body an air assisted stretching process, a dyeing process, an underwater stretching process, and a drying shrinkage process in this order. By introducing auxiliary stretching, even when the PVA-based resin is applied on a thermoplastic resin, it becomes possible to increase the crystallinity of the PVA-based resin and achieve high optical properties. In addition, by simultaneously increasing the orientation of the PVA-based resin in advance, problems such as deterioration in orientation and dissolution of the PVA-based resin when immersed in water in a subsequent dyeing step or stretching step can be prevented, and high optical properties are achieved. It is possible. Further, in the case where the PVA-based resin layer is immersed in a liquid, the disorder of the orientation of the polyvinyl alcohol molecules and the decrease in orientation can be suppressed compared to the case where the PVA-based resin layer does not contain a halide. For this reason, the optical characteristics of the polarizer obtained through the processing process performed by immersing a layered product in liquid, such as a dyeing process and an underwater extension process, can be improved. In addition, optical properties can be improved by shrinking the laminate in the width direction by drying shrinkage treatment. The obtained laminate of the resin substrate/polarizer may be used as it is (ie, the resin substrate may be used as a protective layer for the polarizer), the resin substrate is peeled from the laminate of the resin substrate/polarizer, and the peel surface is applied to the purpose. Any suitable protective layer according to the above may be laminated and used. Hereinafter, embodiment of this invention which does in this way and obtains a polarizer is called embodiment B.

The thickness of the polarizer is preferably 1 μm to 12 μm, more preferably 2 μm to 10 μm, still more preferably 3 μm to 8 μm. By making the thickness of a polarizer extremely thin in this way, it can contribute to thinning of a polarizing plate. In addition, heat shrinkage can be made very small.

The polarizer preferably exhibits absorption dichroism at any wavelength of 380 nm to 780 nm. The single transmittance of the light polarizer obtained in the above embodiment A is preferably 42.0% to 46.0%, and more preferably 44.5% to 46.0%. The degree of polarization of the polarizer is preferably 97.0% or more, more preferably 99.0% or more, still more preferably 99.9% or more. The single transmittance of the light polarizer obtained in the above embodiment B is preferably 40.0% or more, more preferably 41.0% or more. The upper limit of single transmittance may be, for example, 49.0%. The single transmittance of the polarizer is, for example, 40.0% to 45.0% in Embodiment B. The polarization degree of the polarizer obtained in the above embodiment B is preferably 99.0% or more, more preferably 99.4% or more. The upper limit of the degree of polarization may be, for example, 99.999%. The degree of polarization of the polarizer is, for example, 99.0% to 99.9% in Embodiment B.

The orientation function (f) of the PVA-based resin constituting the polarizer obtained in the embodiment B is preferably 0.30 or less, more preferably 0.25 or less, still more preferably 0.20 or less, and particularly preferably 0.15 or less. am. The lower limit of the orientation function may be, for example, 0.05. When the orientation function is too small, acceptable unit transmittance and/or polarization degree may not be obtained in some cases.

The orientation function f can be obtained by attenuated total reflection (ATR) measurement using, for example, a Fourier transform infrared spectrophotometer (FT-IR) and polarized light as measurement light. Specifically, germanium is used for the crystallizer that adheres the polarizer, the incident angle of the measurement light is 45 ° incident, and the incident polarized infrared light (measurement light) is a polarized light that vibrates parallel to the surface of the germanium crystal that adheres the sample ( s polarization), and the measurement was performed in a state in which the stretching direction of the polarizer was arranged parallel and perpendicular to the polarization direction of the measurement light, and the absorbance spectrum obtained at 2941 cm ^-1 was used to calculate according to the following formula do. Here, the intensity I is a value of 2941 cm ^{-1 /} 3330 cm -1 with 3330 cm ^-1 as the reference peak. In addition, when f = 1, it is perfectly aligned, and when f = 0, it is random. The peak at 2941 cm ^-1 is considered to be absorption due to vibration of the PVA main chain (-CH ₂ -) in the polarizer.

f=(3<cos ² θ>-1)/2

=(1-D)/[c(2D+1)]

=-2×(1-D)/(2D+1)

step,

c=(3cos ² β-1)/2, and in the case of oscillation of 2941 cm ⁻¹ , β=90°.

θ: angle of the molecular chain with respect to the stretching direction

β: angle of the transition dipole moment with respect to the molecular chain axis

D=(I _⊥ )/(I _// ) (in this case, D increases as the PVA molecules are oriented)

I _⊥ : Absorption intensity when the polarization direction of the measurement light and the stretching direction of the polarizer are perpendicular to each other

I _// : Absorption intensity when the polarization direction of the measurement light and the stretching direction of the polarizer are parallel

In the polarizer obtained in the above embodiment B, the PVA-based resin constituting the PVA-based resin film (substantially the polarizer) preferably contains an acetoacetyl-modified PVA-based resin. With such a structure, a polarizer having a desired piercing strength can be obtained. The blending amount of the acetoacetyl-modified PVA-based resin is preferably from 5% by weight to 20% by weight, more preferably from 8% by weight to 12% by weight, based on 100% by weight of the entire PVA-based resin.

C. protective layer

The protective layer contains an epoxy resin having an aromatic skeleton and a diol skeleton.

C-1. epoxy resin

The protective layer is preferably composed of a photo-cationic polymerization cured product of an epoxy resin having an aromatic skeleton and a diol skeleton, or a solidified product of a coating film of an organic solvent solution of the epoxy resin. When the protective layer contains an epoxy resin having an aromatic skeleton and a diol skeleton, a polarizing plate having excellent adhesion and excellent curve followability can be obtained despite being very thin. The protective layer is more preferably a photocationic polymerization cured product of an epoxy resin having an aromatic skeleton and a diol skeleton. Hereinafter, the constituent components of the protective layer will be described in detail, followed by the characteristics of the protective layer.

Examples of the aromatic skeleton in the epoxy resin include bisphenol A-type skeleton, bisphenol F-type skeleton, and biphenyl skeleton. More specifically, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, biphenyl type epoxy resin, naphthalene ring-containing epoxy resin, epoxy resin having a dicyclopentadiene skeleton, phenol novolac type resin , cresol novolak-type epoxy resins, triphenylmethane-type epoxy resins, aliphatic epoxy resins, copolymer epoxy resins of aliphatic epoxy resins and aromatic epoxy resins, and the like, among which bisphenol A type epoxy resins and bisphenol F type Epoxy resins, bisphenol S-type epoxy resins, biphenyl-type epoxy resins, and naphthalene ring-containing epoxy resins are preferred, more preferably bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, naphthalene ring-containing epoxy resins, and biphenyl-type epoxies. resin is used.

The diol skeleton preferably includes an aliphatic skeleton having 2 to 6 carbon atoms. More specifically, 1,4-butanediol, 1,6-hexanediol, 1,4-naphthalenediol, 1,6-naphthalenediol and the like are exemplified, and among these, 1,4-butanediol and 1,6-hexanediol This is preferably used.

The epoxy resin has a glass transition temperature (Tg) of 40°C or less, preferably 35°C or less. As a result, the Tg of the protective layer is 40°C or less, preferably 35°C or less. The lower limit of the glass transition temperature (Tg) of the epoxy resin is preferably 0°C. When the glass transition temperature (Tg) of the epoxy resin is within this range, a polarizing plate having excellent adhesion and excellent curve followability can be obtained. On the other hand, if the glass transition temperature (Tg) of the epoxy resin is less than 0°C, the epoxy resin may be sticky.

In the embodiment of the present invention, an epoxy resin and another resin may be used in combination. That is, a blend or copolymer of an epoxy resin and another resin may be used for molding the protective layer. Examples of other resins include styrene-based resins, polyethylene, polypropylene, polyamide, polyphenylene sulfide, polyether ether ketone, polyester, polysulfone, polyphenylene oxide, polyacetal, polyimide, and polyetherimide. A thermoplastic resin is mentioned. The type and compounding amount of the resin used in combination can be appropriately set depending on the purpose and properties desired for the obtained film.

When an epoxy resin and another resin are used together, the content of the epoxy resin relative to the total of the epoxy resin and the other resin is preferably 50% by weight to 100% by weight, more preferably 60% by weight to 100% by weight, still more preferably It is preferably 70% by weight to 100% by weight, particularly preferably 80% by weight to 100% by weight. When content is less than 50 weight%, there exists a possibility that sufficient adhesiveness of the heat resistance of a protective layer and a polarizer may not be obtained.

C-2. curing agent

Epoxy resins can be cured by being used with any suitable curing agent. As the curing agent, any suitable curing agent capable of curing an epoxy resin can be used. In one embodiment, the curing agent includes a photo cationic polymerization initiator. By including a photocationic polymerization initiator, a protective layer that is a cationic polymerization cured product can be formed. As the photocationic polymerization initiator, any suitable compound capable of curing an epoxy resin having an aromatic skeleton and a diol skeleton by irradiation with light such as ultraviolet rays can be used. Photocationic polymerization initiators may be used alone or in combination of two or more.

As a photocationic polymerization initiator, for example, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium hexafluorophosphate, p-(phenylthio)phenyldiphenylsulfonium hexafluoroantimonate, p-(phenyl Thio) phenyldiphenylsulfonium hexafluorophosphate, 4-chlorophenyldiphenylsulfonium hexafluorophosphate, 4-chlorophenyldiphenylsulfonium hexafluoroantimonate, bis[4-(diphenylsulfonio )phenyl]sulfidebishexafluorophosphate, bis[4-(diphenylsulfonio)]phenyl]sulfidebishexafluoroantimonate, (2,4-cyclopentadien-1-yl)[(1- methylethyl)benzene]-Fe-hexafluorophosphate, diphenyliodonium hexafluoroantimonate, and the like. Preferably, a triphenylsulfonium salt-based hexafluoroantimonate-type photocationic polymerization initiator and a diphenyliodonium salt-based hexafluoroantimonate-type photocationic polymerization initiator are used.

As a photocationic polymerization initiator, you may use a commercial item. As commercially available products, triphenylsulfonium salt-based hexafluoroantimonate type SP-170 (manufactured by Adeka), CPI-101A (manufactured by Sun-Apro), WPAG-1056 (manufactured by Wako Pure Chemical Industries, Ltd.), and WPI-116 (manufactured by Wako Pure Chemical Industries, Ltd.) of a diphenyliodonium salt-based hexafluoroantimonate type.

The content of the photocationic polymerization initiator is preferably from 0.1 part by weight to 3 parts by weight, more preferably from 0.25 part by weight to 2 parts by weight, based on 100 parts by weight of the epoxy resin. When the content of the photocationic polymerization initiator is less than 0.1 part by weight, it may not be sufficiently cured even when irradiated with light (ultraviolet rays).

C-3. Composition and characteristics of the protective layer

As described above, the protective layer contains an epoxy resin having an aromatic skeleton and a diol skeleton. Further, the protective layer is preferably composed of a photo-cationic polymerization cured product of an epoxy resin having an aromatic skeleton and a diol skeleton, or a solidified product of a coating film of an organic solvent solution of the epoxy resin. If it is such a hardened|cured material or solidified material, compared with an extrusion molded film, thickness can be made remarkably thin. The thickness of the protective layer is preferably 10 μm or less, more preferably 7 μm or less, still more preferably 5 μm or less, and particularly preferably 3 μm or less. The thickness of the protective layer may be, for example, 1 μm or more. The protective layer, which is a cured product of an epoxy resin having an aromatic skeleton and a diol skeleton, has excellent adhesion to a polarizer. Therefore, even if it is the thickness as mentioned above, it can protect a polarizer to the same degree as the protective layer using the conventional film.

The protective layer (cured product of an epoxy resin having an aromatic skeleton and a diol skeleton) may contain any appropriate additive depending on the purpose. Specific examples of additives include ultraviolet absorbers; leveling agent; Antioxidants, such as a hindered phenol type, a phosphorus type, and a sulfur type; stabilizers such as light stabilizers, weathering stabilizers, and heat stabilizers; reinforcing materials such as glass fibers and carbon fibers; near-infrared absorbers; flame retardants such as tris(dibromopropyl) phosphate, triallyl phosphate, and antimony oxide; antistatic agents such as anionic, cationic, and nonionic surfactants; colorants such as inorganic pigments, organic pigments and dyes; organic or inorganic fillers; resin modifier; organic or inorganic fillers; plasticizer; lubricant; antistatic agent; A flame retardant etc. are mentioned. Additives are usually added to the solution at the time of forming the protective layer. The type, number, combination, addition amount, etc. of additives can be appropriately set according to the purpose.

D. Polarizing plate with retardation layer

The polarizing plate described in the above item C may be provided as a laminate of other optical films and/or optical members. In one embodiment, the polarizing plate may be provided as a laminate with retardation film (polarizing plate with retardation layer). Therefore, the present invention includes a polarizing plate with a retardation layer including the above polarizing plate. A polarizing plate with a retardation layer according to an embodiment of the present invention includes the polarizing plate and the retardation layer. The optical characteristics (eg, refractive index characteristics, in-plane retardation (Re), thickness direction retardation (Rth), wavelength dispersion characteristics), number, combination, arrangement order, etc. of the retardation layer may be appropriately set according to the purpose.

[Example]

Hereinafter, the present invention will be specifically described by examples, but the present invention is not limited by these examples. The measurement method of each characteristic is as follows. In addition, unless otherwise specified, 'part' and '%' in Examples are based on weight.

(1) stab test

With respect to the polarizing plate or polarizer obtained in Examples or Comparative Examples, placed in a compression tester equipped with a needle (manufactured by Katotech, product name 'NDG5', needle penetration measurement specification), in a room temperature (23 ° C ± 3 ° C) environment, Stabbed with a load of 5 kg. Elongation (mm) and strength (g) when the polarizing plate or polarizer broke were calculated.

(2) thickness

For the polarizing plate or polarizer obtained in Examples or Comparative Examples, the thickness was measured using a dial gauge (manufactured by PEACOCK, product name 'DG-205', dial gauge stand (product name 'pds-2')).

(3) Glass transition temperature (Tg)

After cutting the protective layer obtained in Example or Comparative Example into a strip shape, using a viscoelastic spectrometer (manufactured by SII Nanotechnology, product name 'DMS6100'), the temperature range is -80 ° C to 150 ° C, and the heating rate is 2 ° C. /min, and the measurement was performed under the conditions of a frequency of 1 Hz.

(4) Adhesion

From the polarizing plates obtained in Examples and Comparative Examples, test pieces (50 mm × 50 mm) having two sides facing each other in a direction orthogonal to the direction of the absorption axis of the polarizer and in the direction of the absorption axis were cut out. An adhesive was applied to the surface of the test piece on the polarizer side, and it was affixed to a glass plate. Next, incisions were made on the surface on the side of the protective layer (solidified product of the coating film) with a cutter knife so as to form a lattice of 10 × 10, and an adhesive tape (manufactured by Sekisui Chemical Industry Co., Ltd.) was affixed to the surface. After that, the adhesive tape was peeled off, and the number of peeled cells in a grid of 100 was evaluated.

Yang (良): The number of squares is 50 or more

Poor: Number of slots less than 50

(5) Curve conformability

A jig assuming the corner of a smartphone was made of acrylic resin, and the polarizing plate obtained in Examples and Comparative Examples was followed by a curved part and pulled by hand, and whether wrinkles or cracks entered the polarizer was visually evaluated.

Quantity: No wrinkles, cracks or cracks could be identified

Defect: Wrinkles, cracks, or cracks were observed.

<Example 1>

1. Production of polarizer/resin substrate laminate

As the resin substrate, an amorphous isophthalic copolymerized polyethylene terephthalate film (thickness: 100 μm) having a long, water absorption of 0.75% and a Tg of about 75° C. was used. Corona treatment was performed on one side of the resin substrate.

Potassium iodide 13 Part by weight was added to prepare a PVA aqueous solution (coating liquid).

A PVA-based resin layer having a thickness of 13 μm was formed by applying the PVA aqueous solution to the corona-treated surface of the resin substrate and drying at 60° C. to prepare a laminate.

The obtained layered product was uniaxially stretched at the free end by 2.4 times in the machine direction (longitudinal direction) between rolls having different circumferential speeds in a 130°C oven (air assisted stretching treatment).

Next, the laminate was immersed in an insolubilization bath (boric acid aqueous solution obtained by blending 4 parts by weight of boric acid with respect to 100 parts by weight of water) at a liquid temperature of 40°C for 30 seconds (insolubilization treatment).

Subsequently, in a dyeing bath (100 parts by weight of water, an iodine aqueous solution obtained by blending iodine and potassium iodide at a weight ratio of 1:7 with respect to 100 parts by weight of water) at a liquid temperature of 30 ° C., the polarizer finally obtained has a single transmittance (Ts) of 41.5%± It was immersed for 60 seconds while adjusting the concentration so as to be 0.1% (dyeing treatment).

Then, it was immersed in a crosslinking bath (boric acid aqueous solution obtained by blending 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with respect to 100 parts by weight of water) at a liquid temperature of 40°C for 30 seconds (crosslinking treatment).

Thereafter, the laminate was immersed in an aqueous boric acid solution (boric acid concentration: 4.0% by weight, potassium iodide: 5% by weight) at a liquid temperature of 70°C, while the total draw ratio was 5.5 in the machine direction (longitudinal direction) between rolls having different circumferential speeds. Uniaxial stretching was performed so as to double (underwater stretching treatment).

Thereafter, the laminate was immersed in a washing bath (an aqueous solution obtained by blending 4 parts by weight of potassium iodide with respect to 100 parts by weight of water) at a liquid temperature of 20°C (washing treatment).

Thereafter, while drying in an oven maintained at 90°C, it was brought into contact with a heating roll made of SUS whose surface temperature was maintained at 75°C for about 2 seconds (dry shrinkage treatment). The shrinkage rate in the width direction of the layered product by the drying shrinkage treatment was 5.2%.

In this way, a polarizer having a thickness of 5 μm was formed on the resin substrate, and a laminate of the polarizer/resin substrate was produced. Hereinafter, the said polarizer is called polarizer A.

2. Preparation of protective layer forming composition

30 parts of an epoxy resin having an aromatic skeleton and a diol skeleton ("YX7105" manufactured by Mitsubishi Chemical Corporation) was dissolved in 67.6 parts of methyl ethyl ketone to obtain an epoxy resin solution. To the obtained epoxy resin solution, 2.4 parts of photocationic polymerization initiator (trade name: CPI (registered trademark) -100P, manufactured by San-Apro Corporation) was added to obtain a protective layer forming composition.

3. Fabrication of polarizer

The protective layer forming composition obtained in 2. was applied to the polarizer surface of the polarizing plate obtained above using a wire bar, and the coated film was dried at 60°C for 3 minutes. Then, by using a high-pressure mercury lamp, the accumulated light amount is 600 mJ/cm2. A protective layer was formed by irradiation with ultraviolet rays. The thickness of the protective layer was 2 μm to 3 μm, and the glass transition temperature (Tg) was 31°C. Hereinafter, the said protective layer is called protective layer A.

In this way, a laminate having a configuration of protective layer A/polarizer A/resin substrate was obtained. Moreover, the resin base material of the said laminated body was peeled, and the protective layer A was formed in the surface on the opposite side to the protective layer of the polarizer by the same method. In this way, a polarizing plate having a configuration of protective layer A/polarizer A/protective layer A was obtained. The elongation of the polarizing plate was 1.44 mm, the strength was 344 g, and the thickness was 11 μm. The obtained polarizing plate was used for evaluation of the above (4) and (5). The results are shown in Table 1.

<Example 2>

1. Production of polarizer/resin substrate laminate

As the thermoplastic resin base material, an amorphous isophthalic copolymerized polyethylene terephthalate film (thickness: 100 μm) was used, which was long and had a water absorption of 0.75% and a Tg of about 75°C. Corona treatment (treatment conditions: 55 W·min/m 2 ) was performed on one side of the resin substrate.

100 parts by weight of a PVA-based resin obtained by mixing polyvinyl alcohol (degree of polymerization 4200, degree of saponification 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Nippon Kosei Chemical Industry Co., Ltd., trade name: 'Gose Primer Z410') at a ratio of 9:1, potassium iodide By adding 13 parts by weight, a PVA aqueous solution (coating liquid) was prepared.

A PVA-based resin layer having a thickness of 13 μm was formed by applying the PVA aqueous solution to the corona-treated surface of the resin substrate and drying at 60° C., thereby producing a laminate.

The obtained layered product was uniaxially stretched at the free end by 2.4 times in the machine direction (longitudinal direction) between rolls having different circumferential speeds in a 130°C oven (air assisted stretching treatment).

Next, the laminate was immersed in an insolubilization bath (boric acid aqueous solution obtained by blending 4 parts by weight of boric acid with respect to 100 parts by weight of water) at a liquid temperature of 40°C for 30 seconds (insolubilization treatment).

Subsequently, in a dyeing bath (100 parts by weight of water, an iodine aqueous solution obtained by blending iodine and potassium iodide at a weight ratio of 1:7) with a liquid temperature of 30°C, the finally obtained polarizer single transmittance (Ts) is 41.6%. It was immersed for 60 seconds while adjusting the concentration as much as possible (dyeing treatment).

Then, it was immersed in a crosslinking bath (boric acid aqueous solution obtained by blending 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with respect to 100 parts by weight of water) at a liquid temperature of 40°C for 30 seconds (crosslinking treatment).

Thereafter, the laminate was immersed in an aqueous boric acid solution (boric acid concentration: 4.0% by weight, potassium iodide: 5.0% by weight) at a liquid temperature of 62°C, while the total ratio of stretching in the machine direction (longitudinal direction) between rolls having different circumferential speeds was Uniaxial stretching was performed so as to be 3.0 times (underwater stretching treatment: the stretching ratio in the underwater stretching treatment is 1.25 times).

Thereafter, the laminate was immersed in a washing bath (an aqueous solution obtained by blending 4 parts by weight of potassium iodide with respect to 100 parts by weight of water) at a liquid temperature of 20°C (washing treatment).

Thereafter, while drying in an oven maintained at 90°C, it was brought into contact with a heating roll made of SUS whose surface temperature was maintained at 75°C for about 2 seconds (dry shrinkage treatment). The shrinkage rate in the width direction of the layered product by the drying shrinkage treatment was 2%. In this way, a polarizer having a thickness of 6.0 μm was formed on the resin substrate. Hereinafter, the said polarizer is called polarizer B. The orientation function of the obtained polarizer was 0.15.

Except having prepared the polarizer by the said method, it carried out similarly to Example 1, and obtained the polarizing plate which has the structure of protective layer A/polarizer B/protective layer A. The polarizing plate had an elongation of 1.66 mm, a strength of 415 g, and a thickness of 12 μm. The obtained polarizing plate was used for evaluation of the above (4) and (5). The results are shown in Table 1.

(Comparative Example 1)

1. Preparation of protective layer forming composition

15 parts of an epoxy resin having a biphenyl skeleton (manufactured by Mitsubishi Chemical Corporation, trade name: jER (registered trademark) YX4000) was dissolved in 83.8 parts of methyl ethyl ketone to obtain an epoxy resin solution. To the obtained epoxy resin solution, 1.2 parts of photocationic polymerization initiator (trade name: CPI (registered trademark) -100P, manufactured by San-Apro Corporation) was added to obtain a protective layer forming composition. Hereinafter, the protective layer formed from the protective layer forming composition is referred to as protective layer B. The glass transition temperature (Tg) of the protective layer B was 106°C. Except having prepared the protective layer forming composition by the said method, it carried out similarly to Example 1, and obtained the polarizing plate which has the structure of protective layer B / polarizer A / protective layer B. The polarizing plate had an elongation of 1.17 mm, a strength of 256 g, and a thickness of 11 μm. The obtained polarizing plate was used for evaluation of the above (4) and (5). The results are shown in Table 1.

(Comparative Example 2)

Except having obtained polarizer B by the method similar to Example 2, it carried out similarly to Comparative Example 1, and obtained the polarizing plate which has the structure of protective layer B/polarizer B/protective layer B. The elongation of the polarizing plate was 1.26 mm, the strength was 337 g, and the thickness was 12 μm. The obtained polarizing plate was used for evaluation of the above (4) and (5). The results are shown in Table 1.

(Comparative Example 3)

Except having provided the protective layer A only on one side of the polarizer A, it carried out similarly to Example 1, and obtained the polarizing plate which has the structure of protective layer A/polarizer A. The elongation rate of the polarizing plate was 1.35 mm when the puncture test was performed from the protective layer side, and was 1.00 mm or less when the puncture test was performed from the polarizer side. The strength of the polarizing plate was 285 g when the puncture test was performed from the protective layer side, and 100 g or less when the puncture test was performed from the polarizer side. In addition, the thickness of the said polarizing plate was 8 micrometers. The obtained polarizing plate was used for evaluation of the above (4) and (5). The results are shown in Table 1.

(Comparative Example 4)

Polarizer A was produced by the method similar to Example 1, and the protective layer was not provided. The elongation rate of the polarizer was 1.00 mm or less, the strength was 100 g or less, and the thickness was 5 μm. The obtained polarizer was used for evaluation of the above (4) and (5). The results are shown in Table 1.

(Comparative Example 5)

Polarizer B was produced by the method similar to Example 2, and the protective layer was not provided. The elongation rate of the polarizer was 1.38 mm, the strength was 267 g, and the thickness was 6 μm. The obtained polarizer was used for evaluation of the above (4) and (5). The results are shown in Table 1.

(Comparative Example 6)

Except for using an acrylic film (thickness of 20 μm, glass transition temperature (Tg) of 123 ° C., hereinafter referred to as protective layer C) for the protective layer, in the same manner as in Example 1, the configuration of protective layer C / polarizer A / protective layer C A polarizing plate having The elongation of the polarizing plate was 1.00 mm or less, the strength was 500 g or more, and the thickness was 45 μm. The obtained polarizing plate was used for evaluation of the above (4) and (5). The results are shown in Table 1.

(Comparative Example 7)

A polarizing plate having a configuration of protective layer C/polarizer A was obtained in the same manner as in Comparative Example 6 except that the protective layer C was formed only on one side of the polarizer A. The elongation of the polarizing plate was 1.00 mm or less, the strength was 500 g or more, and the thickness was 25 μm. The obtained polarizing plate was used for evaluation of the above (4) and (5). The results are shown in Table 1.

[Table 1]

(1) in Comparative Example 3 shows the result when the pierce test was performed from the protective layer side, and (2) shows the result when the pierce test was performed from the polarizer side.

<evaluation>

As apparent from Table 1, it can be seen that the polarizing plates having the constitutions of Examples 1 and 2 are excellent in adhesion and excellent in conformability to curved surfaces.

The polarizing plate of the present invention is suitably used for an image display device. Examples of the image display device include portable devices such as a personal digital assistant (PDA), a smartphone, a mobile phone, a watch, a digital camera, and a portable game machine; OA devices such as PC monitors, notebooks, and copiers; household electrical appliances such as video cameras, TVs, and microwave ovens; in-vehicle devices such as bag monitors, monitors for car navigation systems, and car audios; display devices such as digital signage and information monitors for commercial stores; security devices such as monitoring monitors; Nursing care/medical devices such as monitors for nursing care and medical monitors are exemplified.

10: polarizer
20: protective layer
30: protective layer
100: polarizer

Claims (7)

A polarizer and a protective layer disposed on both sides of the polarizer,
The protective layer includes an epoxy resin having an aromatic skeleton and a diol skeleton, and has a glass transition temperature of 40° C. or less,
Elongation at the time of the stab test is 1.40 mm or more,
polarizer. According to claim 1,
The polarizing plate in which the said polarizer is comprised from the polyvinyl alcohol-type resin film containing a dichroic substance, and an orientation function is 0.30 or less. According to claim 1 or 2,
The polarizing plate in which the said protective layer is comprised from the photocationic polymerization hardened|cured material of the said epoxy resin, or the solidified material of the coating film of the organic solvent solution of the said epoxy resin. According to any one of claims 1 to 3,
A polarizing plate having a total thickness of 20 µm or less. According to any one of claims 1 to 4,
A polarizing plate having a puncture strength of 300 g or more. According to any one of claims 1 to 5,
The glass transition temperature of the protective layer is 0 ℃ or more, the polarizing plate. A polarizing plate with a retardation layer comprising a retardation layer, the polarizer according to any one of claims 1 to 6, and a protective layer.

Images