TW202313344A - Retardation layer-equipped polarizing plate and image display device using same - Google Patents

Abstract

Provided is a retardation layer-equipped polarizing plate having both hardness and durability against deformation. A retardation layer-equipped polarizing plate according to an embodiment of the present invention has a protection layer, a polarizing film, and a retardation layer in this order, the surface hardness on the protection layer side thereof is 2B or more in pencil hardness, and the thickness of a stacked portion from the protection layer to the retardation layer is 32 [mu]m or less.

Description

Polarizing plate with retardation layer and image display device using same

The present invention relates to a polarizing plate with retardation layer and an image display device using it.

Image display devices represented by liquid crystal display devices and electroluminescent (EL) display devices (such as organic EL display devices and inorganic EL display devices) are rapidly spreading. Typically, a polarizing plate and a phase difference plate are used in an image display device. In terms of practicability, a polarizing plate with a retardation layer integrated with a polarizing plate and a retardation plate is widely used (for example, Patent Document 1).

In recent years, the possibilities of bending, bending, folding, and winding of image display devices have been studied using flexible substrates (such as resin substrates), and polarizing plates with retardation layers that can cope with these possibilities have been sought. . On the other hand, from the viewpoint of preventing damage to an image display device, it is required to increase the hardness of a polarizing plate with a retardation layer. [Prior Art Literature] [Patent Document]

Patent Document 1: Japanese Patent No. 3325560

[Problem to be solved by the invention]

The present invention was made in view of the above circumstances, and its main purpose is to provide a polarizing plate with a retardation layer having both hardness and durability against deformation. [Technical means to solve the problem]

A polarizing plate with a retardation layer according to an embodiment of the present invention has a protective layer, a polarizing film, and a retardation layer in this order, and the surface hardness on the side of the protective layer is 2B or more in pencil hardness, from the protective layer to the retardation layer. The thickness of the laminated part up to the first layer is 32 μm or less. In one embodiment, the protective layer includes a substrate having an indentation elastic recovery rate of 67% or less. In one embodiment, the base material accounts for 65% or more of the thickness from the center of the laminated portion to the surface of the protective layer. In one embodiment, the protective layer includes a portion having an indentation hardness of 0.35 GPa or higher. In one embodiment, the protective layer has a thickness of not less than 12 μm and not more than 20 μm. In one embodiment, the protective layer includes a hard coat layer with a thickness of 5 μm or less. In one embodiment, the retardation layer is an alignment solidified layer of a liquid crystal compound. In one embodiment, the protective layer includes a substrate whose moisture permeability is less than 200 g/m ² ·24 h at 40° C. and 92% RH (Relative Humidity, relative humidity). According to another aspect of the present invention, an image display device is provided. The image display device has the above-mentioned polarizing plate with a retardation layer. [Effect of Invention]

According to the embodiments of the present invention, the polarizing plate with a retardation layer can have both hardness and durability against deformation.

Embodiments of the present invention will be described below, but the present invention is not limited to these embodiments. In addition, in order to clarify the description, the drawings may schematically show the width, thickness, shape, etc. of each part in comparison with the embodiment, but these are just examples and do not limit the interpretation of the present invention.

(Definition of terms and symbols) Definitions of terms and symbols in this manual are as follows. (1) Refractive index (nx, ny, nz) "nx" is the refractive index in the direction of the maximum refractive index in the plane (ie, the direction of the slow axis), "ny" is the refractive index in the direction perpendicular to the slow axis in the plane (ie, the direction of the slow axis), "nz ” is the refractive index in the thickness direction. (2) In-plane retardation (Re) "Re(λ)" is the in-plane retardation measured by light with a wavelength of λ nm at 23°C. For example, "Re(550)" is the in-plane retardation measured by light with a wavelength of 550 nm at 23°C. Re(λ) is obtained by the formula: Re(λ)=(nx-ny)×d when the thickness of the layer (film) is d (nm). (3) Phase difference in thickness direction (Rth) "Rth(λ)" is the retardation in the thickness direction measured by light with a wavelength of λ nm at 23°C. For example, "Rth(550)" is the retardation in the thickness direction measured with light with a wavelength of 550 nm at 23°C. Rth(λ) is obtained by the formula: Rth(λ)=(nx−nz)×d when the thickness of the layer (film) is d (nm). (4) Nz coefficient The Nz coefficient is obtained by Nz=Rth/Re. (5) angle In this specification, when referring to an angle, the angle includes both the clockwise direction and the counterclockwise direction with respect to the reference direction. Thus, for example, "45°" means ±45°.

FIG. 1 is a schematic cross-sectional view showing a schematic configuration of a polarizing plate with a retardation layer according to an embodiment of the present invention. The polarizing plate 100 with a retardation layer has a polarizing plate 10 including a polarizing film 11 and a protective layer 12 disposed on one side of the polarizing film 11 , and a retardation layer 20 . Specifically, the polarizing plate with retardation layer 100 has a protective layer 12 , a polarizing film 11 and a retardation layer 20 in sequence. The retardation layer 20 can function as a protective layer of the polarizing film 11 . According to such a structure, the thickness of the polarizing plate with a retardation layer mentioned later can be satisfactorily achieved. The polarizing plate 100 with a retardation layer is typically arranged so that the polarizing plate 10 is closer to the viewing side than the retardation layer 20 in the image display device. In one embodiment, the protective layer 12 is located on the outermost surface of the image display device.

In the illustrated example, the retardation layer 20 has a laminated structure including a first retardation layer 21 and a second retardation layer 22, but unlike the illustrated example, the retardation layer 20 may have a laminated structure of more than three layers, and also Can be set to single layer.

Each member constituting the retardation layer polarizing plate can be laminated via any appropriate adhesive layer (not shown). Specific examples of the adhesive layer include an adhesive layer and an adhesive layer. For example, the protective layer 12 is bonded to the polarizing film 11 via an adhesive layer (preferably using an active energy ray curing adhesive). For example, the retardation layer 20 is bonded to the polarizing film 11 via an adhesive layer (preferably using an active energy ray curing adhesive). As shown in the figure, when the phase difference layer 20 has a laminated structure of two or more layers, the phase difference layers are bonded together via an adhesive layer (preferably using an active energy ray curing type adhesive), for example. The thickness of the adhesive layer is preferably at least 0.4 μm, more preferably 0.4 μm to 3.0 μm, and still more preferably 0.6 μm to 1.5 μm.

Although not shown, an adhesive layer may be provided on the side of the retardation layer 20 where the polarizing film 11 is not disposed. Through the adhesive layer, for example, the polarizing plate with retardation layer 100 can be attached to an image display panel included in an image display device. And, practically, a peeling film (separator) is bonded to the surface of the adhesive layer. The release film can be temporarily adhered before the polarizing plate with retardation layer is put into use. By using a release film, for example, the adhesive layer can be protected and a roll of a polarizing plate can be formed.

The polarizing plate with retardation layer can be in the shape of a strip or a single sheet. Here, "elongated" refers to an elongated shape that is sufficiently long relative to the width, for example, refers to an elongated shape that is 10 times or more, preferably 20 times or more, relative to the width. The elongated retardation layer polarizing plate can be wound into a roll.

The surface hardness of the protective layer 12 (polarizing plate 10 ) side of the polarizing plate with retardation layer is 2B or higher in pencil hardness, preferably B or higher. On the other hand, the surface hardness of the protective layer 12 side is, for example, 4H or less in pencil hardness.

The thickness of the layered part from the protective layer 12 to the retardation layer 20 (sometimes simply referred to as "the thickness of the polarizing plate with a retardation layer") is 32 μm or less, preferably 31 μm or less. According to such a thickness, the surface hardness as described above can be satisfied, and durability against deformation (such as flex resistance) can be achieved remarkably. Specifically, expansion and contraction due to deformation (such as bending) can be reduced, and damage (such as interface damage) can be suppressed. In addition, it also contributes to the thinning of the image display device, for example, it is also possible to mount components (batteries, etc.) to cope with the enlargement of the screen. On the other hand, the thickness of the polarizing plate with a retardation layer is, for example, 25 μm or more.

The thickness of the above-mentioned polarizing plate with retardation layer also includes the thickness of the above-mentioned adhesive layer. Specifically, it also includes an adhesive layer that can be arranged between the protective layer and the polarizing film, an adhesive layer that can be arranged between the polarizing film and the retardation layer, and an adhesive layer that can be arranged between the phase difference layer when the retardation layer has a laminated structure. The thickness of the bonding layer between different layers. Furthermore, the thickness of the polarizing plate with a retardation layer does not include the adhesive layer for making the polarizing plate with a retardation layer in close contact with an external substrate such as a panel or glass.

A. Polarizer The above-mentioned polarizing plate includes a polarizing film and a protective layer. Typically, a polarizing plate can be obtained by laminating a polarizing film and a protective layer through a subsequent lamination layer.

A-1. Polarizing film The aforementioned polarizing film is typically a resin film containing a dichroic substance (for example, iodine). Examples of the resin film include hydrophilic polymer films such as polyvinyl alcohol (PVA)-based films, partially formalized PVA-based films, and ethylene-vinyl acetate copolymer-based partially saponified films.

The thickness of the polarizing film is preferably not more than 12 μm, more preferably not more than 10 μm, and still more preferably not more than 8 μm. On the other hand, the thickness of the polarizing film is preferably 1 μm or more.

The polarizing film preferably exhibits absorption dichroism at any wavelength of 380 nm to 780 nm. The single transmittance of the polarizing film is, for example, 41.5% to 48.0%, preferably 42.0% to 46.0%. The degree of polarization of the polarizing film is, for example, 90.0% or higher, preferably 99.0% or higher, and more preferably 99.9% or higher.

The polarizing film can be produced by any appropriate method. Specifically, the polarizing film can be made of a single-layer resin film, or a laminate of two or more layers.

A method of producing a polarizing film from the above-mentioned single-layer resin film typically includes dyeing the resin film with a dichroic substance such as iodine or a dichroic dye, and stretching. As the resin film, for example, hydrophilic polymer films such as polyvinyl alcohol (PVA)-based films, partially formalized PVA-based films, and ethylene-vinyl acetate copolymer-based partially saponified films can be used. This method may further include insolubilization treatment, swelling treatment, crosslinking treatment and the like. Since this manufacturing method is well known and commonly used in the industry, detailed description is omitted.

The polarizing film obtained by using the said laminated body can be produced using the laminated body of a resin base material, a resin film, or a resin layer (typically, a PVA-type resin layer), for example. Specifically, it can be produced in the following manner: apply a PVA-based resin solution to a resin substrate, dry it to form a PVA-based resin layer on the resin substrate, and obtain a laminate of the resin substrate and the PVA-based resin layer ; Stretch and dye the laminate to make the PVA-based resin layer a polarizing film. In this embodiment, it is preferable to form a PVA-based resin layer including a halide and a PVA-based resin on one side of the resin substrate. Extending typically includes immersing and extending the laminate in an aqueous solution of boric acid. Furthermore, stretching may further include stretching the laminate in air at a high temperature (for example, 95° C. or higher) before stretching in an aqueous solution of boric acid, if necessary. In addition, in the present embodiment, it is preferable that the laminated body is subjected to a dry shrinkage treatment in which the laminate is shrunk by 2% or more in the width direction by heating while conveying in the longitudinal direction. Typically, the manufacturing method of this embodiment includes sequentially performing aerial assisted stretching, dyeing, underwater stretching, and drying shrinkage on the laminate. By introducing auxiliary stretching, even when PVA is coated on a thermoplastic resin, the crystallinity of PVA can be improved, and high optical characteristics can be achieved. In addition, by improving the alignment of PVA in advance at the same time, when it is immersed in water in the subsequent dyeing step or stretching step, problems such as reduction or dissolution of the alignment of PVA can be prevented, and higher optical properties can be achieved. Furthermore, when the PVA-based resin layer is immersed in the liquid, compared with the case where the PVA-based resin layer does not contain halides, the disorder of the alignment of the PVA molecules and the decrease in alignment can be suppressed, and a higher level can be achieved. optical properties. Furthermore, by shrinking the laminate in the width direction by drying shrinkage treatment, higher optical characteristics can be achieved. A polarizing plate can be obtained by peeling off the peeled surface of the resin substrate or the area opposite to the peeled surface from the obtained resin substrate/polarizing film laminate. The details of the manufacturing method of such a polarizing film are described in Japanese Patent Application Laid-Open No. 2012-73580 and Japanese Patent No. 6470455, for example. The entire contents of these publications are incorporated herein by reference.

A-2. Protective layer FIG. 2 is a cross-sectional view showing an example of the structure of the protective layer of the polarizing plate with retardation layer shown in FIG. 1 . The protective layer 12 has a base material (film) 12a and a hard coat (HC) layer 12b formed on the base material 12a. By providing the hard coat layer 12b, the above-mentioned surface hardness on the side of the protective layer can be satisfactorily achieved. The above-mentioned polarizing plate with a retardation layer is typically arranged on the viewing side of the image display device, and the hard coat layer 12b is arranged on the viewing side of the substrate 12a. The hard coat layer 12b can function as other functional layers such as an antireflection layer, an antisticking layer, and an antiglare layer, for example.

The thickness of the protective layer is preferably not more than 20 μm, more preferably not more than 18 μm. On the other hand, the thickness of the protective layer is preferably at least 12 μm, more preferably at least 14 μm.

The moisture permeability of the protective layer at 40°C and 92%RH is preferably less than 200 g/m ² ·24 h, may be less than 150 g/m ² ·24 h, may be less than 100 g/m ² ·24 h , or less than 50 g/m ² ·24 h. By using such a protective layer, generation|occurrence|production of discoloration of a polarizing film, specifically, generation|occurrence|production of discoloration of a polarizing film at the edge part of the polarizing plate with a retardation layer can be suppressed. On the other hand, the moisture permeability at 40° C. and 92% RH of the protective layer is, for example, 1 g/m ² ·24 h or more.

The indentation elastic recovery rate of the substrate is preferably less than 67%, more preferably less than 65%, and may be less than 60%. By using such a base material, durability against deformation (such as flex resistance) can be improved. Specifically, stress due to deformation (such as bending) can be dispersed, thereby suppressing the occurrence of damage (such as interface damage). Moreover, the adhesiveness with a hard-coat layer can also be made excellent. On the other hand, the indentation elastic recovery rate of the substrate is, for example, 35% or more.

The thickness of the aforementioned base material is, for example, 10 μm to 16 μm, preferably 11 μm to 15 μm, more preferably 12 μm to 14 μm.

In the thickness from the center of the layered part (polarizing plate with retardation layer) to the surface of the protective layer from the above protective layer to the retardation layer, the proportion of the base material is preferably 65% or more, more preferably 75%. above. On the other hand, in the thickness from the center of the laminated portion (polarizing plate with retardation layer) to the surface of the protective layer, the proportion of the base material is preferably 90% or less.

Fig. 3 is a diagram illustrating the ratio of the center of the laminated part (polarizing plate with a retardation layer) to the base material. Also, hatching is omitted in FIG. 3 . The laminated part (polarizing plate with retardation layer) 102 has a protective layer 12 including a hard coat layer 12b and a substrate 12a, an adhesive layer 52, a polarizing film 11, an adhesive layer 54, a first retardation layer 21, Adhesive agent layer 56 and second retardation layer 22 . As mentioned above, in the thickness direction, in the distance d from the center 103 of the laminated part 102 to the surface 13 of the protective layer 12, the ratio of the thickness t of the base material 12a is preferably 65% or more, more preferably 75%. %above. In one embodiment, the above ratio is controlled by adjusting the thickness of the hard coat layer.

As a base material, any appropriate film which can be used as a protective layer of a polarizing film can be comprised. Specific examples of the material used as the main component of such a film include: cellulose-based resins such as triacetyl cellulose (TAC); polyester-based, polyvinyl alcohol-based, polycarbonate-based, polyamide-based Transparent resins such as cycloolefins, polyimides, polyethersulfones, polyethenes, polystyrenes, polynorthylenes, polyolefins, (meth)acrylics, and acetates. As a material constituting the base material, it is preferable to use at least one selected from polycarbonate-based resins and cycloolefin-based resins.

The indentation hardness of the hard coat layer is preferably at least 0.35 GPa, more preferably at least 0.4 GPa, and still more preferably at least 0.45 GPa. On the other hand, the indentation hardness of the hard coat layer is, for example, 0.70 GPa or less. The indentation elastic recovery rate of the hard coating is preferably above 70%, more preferably above 75%. On the other hand, the indentation elastic recovery rate of the hard coat layer is, for example, 95% or less.

The thickness of the hard coat layer is preferably at most 5 μm, more preferably at most 4 μm, and still more preferably at most 3 μm. By providing such a hard coat layer, the surface hardness as described above can be satisfied, and durability against deformation (for example, flex resistance) can be achieved. On the other hand, the thickness of the hard coat layer is, for example, 1 μm or more.

Typically, a hard-coat layer is formed by applying a hard-coat-forming material to the said base material, and hardening a coating layer. The hard coat layer forming material typically contains a curable compound as a layer forming component. The curing mechanism of the curable compound may, for example, be a thermosetting type or a photocuring type. As a curable compound, a monomer, an oligomer, and a prepolymer are mentioned, for example. As the curable compound, it is preferable to use a polyfunctional monomer or oligomer. Examples of polyfunctional monomers or oligomers include monomers or oligomers having two or more (meth)acryl groups, urethane (meth)acrylate, or urethane Oligomers of ester (meth)acrylates, epoxy-based monomers or oligomers, silicone-based monomers or oligomers.

The aforementioned hard coat layer forming material may contain any appropriate additives. Examples of additives include polymerization initiators, leveling agents, antiblocking agents, dispersion stabilizers, thixotropic agents, antioxidants, ultraviolet absorbers, defoamers, thickeners, dispersants, and surfactants. , catalyst, filler, lubricant, antistatic agent, etc. The type, combination, content, etc. of additives can be appropriately set according to the purpose and required characteristics.

When the curable compound is a thermosetting type, the heating temperature is, for example, 60°C to 140°C, preferably 60°C to 100°C. When the curable compound is a photocurable type, the curing treatment is typically performed by ultraviolet irradiation. The cumulative light quantity of ultraviolet irradiation is, for example, 100 mJ/cm ² to 300 mJ/cm ² . Combinations of UV radiation and heating are also possible. In this case, typically, ultraviolet irradiation is performed after heating a coating film. The heating temperature is as described above for the thermosetting curable compound.

B. Retardation layer The thickness of the retardation layer also depends on its composition (single layer or laminated structure), but it is preferably 10 μm or less, more preferably 8 μm or less, further preferably 7 μm or less. On the other hand, the thickness of the retardation layer is, for example, 0.5 μm or more. In addition, when the retardation layer has a laminated structure, the "thickness of the retardation layer" means the total thickness of each retardation layer. Specifically, the "thickness of the retardation layer" does not include the thickness of the adhesive layer.

As the retardation layer, an alignment-cured layer (liquid crystal alignment-cured layer) using a liquid crystal compound is preferable. By using a liquid crystal compound, for example, the difference between nx and ny of the obtained retardation layer can be significantly increased compared with non-liquid crystal materials, so the difference between the retardation layer used to obtain the required in-plane retardation can be significantly reduced. thickness. Therefore, remarkable thinning of the polarizing plate with retardation layer can be realized. In this specification, "alignment solidified layer" refers to a layer in which liquid crystal compounds are aligned along a specific direction within the layer, and the alignment state is fixed. In addition, the "alignment hardened layer" is a concept including the alignment hardened layer obtained by hardening the liquid crystal monomer as described below. In the retardation layer, typically, the rod-shaped liquid crystal compound is aligned in a state in which the rod-like liquid crystal compound is aligned along the slow axis direction of the retardation layer (horizontal alignment).

The above-mentioned liquid crystal alignment solidified layer can be formed by the following methods: performing an alignment treatment on the surface of a specific substrate, coating the surface with a coating liquid containing a liquid crystal compound, and aligning the liquid crystal compound in a direction corresponding to the above-mentioned alignment treatment, and fix the alignment state. As the alignment treatment, any appropriate alignment treatment can be employed. Specifically, mechanical alignment treatment, physical alignment treatment, and chemical alignment treatment may, for example, be mentioned. Specific examples of mechanical alignment treatment include rubbing treatment and stretching treatment. Specific examples of physical alignment processing include magnetic field alignment processing and electric field alignment processing. Specific examples of chemical alignment treatment include oblique vapor deposition and photo-alignment treatment. The treatment conditions of various alignment treatments can be any appropriate conditions depending on the purpose.

The alignment of the liquid crystal compound is performed by performing a treatment at a temperature at which a liquid crystal phase is exhibited according to the type of the liquid crystal compound. By performing such temperature treatment, the liquid crystal compound is in a liquid crystal state, and the liquid crystal compound is aligned according to the direction of the alignment treatment on the surface of the substrate.

In one embodiment, the alignment state is fixed by cooling the liquid crystal compound aligned in the above manner. When the liquid crystal compound is a polymerizable monomer or a crosslinkable monomer, the alignment state is fixed by subjecting the liquid crystal compound aligned as described above to a polymerization treatment or a crosslinking treatment.

Specific examples of liquid crystal compounds and details of a method for forming an alignment solidified layer are described in Japanese Patent Application Laid-Open No. 2006-163343. The description of this publication is incorporated in this specification as a reference.

As described above, the retardation layer may be a single layer, or may have a laminated structure of two or more layers.

Unlike the example shown in the figure, when the retardation layer is a single layer, the retardation layer can function as a λ/4 plate. Specifically, the Re(550) of the retardation layer is preferably from 100 nm to 180 nm, more preferably from 110 nm to 170 nm, and still more preferably from 110 nm to 160 nm. The thickness of the retardation layer can be adjusted to obtain the required in-plane retardation of the λ/4 plate. When the retardation layer is the liquid crystal alignment solidified layer described above, its thickness is, for example, 1.0 μm to 2.5 μm. In this embodiment, the angle formed by the retardation axis of the retardation layer and the absorption axis of the polarizing film is preferably 40°-50°, more preferably 42°-48°, further preferably 44°-46° . Furthermore, the retardation layer preferably exhibits inverse wavelength dispersion characteristics in which the retardation value increases according to the wavelength of the measurement light.

As shown in the figure, when the retardation layer 20 has a laminated structure, the retardation layer 20 has, for example, a first retardation layer (H layer) 21 and a second retardation layer (Q layer) arranged in sequence from the polarizing plate 10 side. Layer) 22 is a laminated structure of two layers. The H layer typically functions as a λ/2 plate, and the Q layer typically functions as a λ/4 plate. Specifically, the Re(550) of the H layer is preferably 200 nm to 300 nm, more preferably 220 nm to 290 nm, and further preferably 230 nm to 280 nm; the Re(550) of the Q layer is preferably 100 nm nm to 180 nm, more preferably 110 nm to 170 nm, further preferably 110 nm to 150 nm. The thickness of the H layer can be adjusted to obtain the desired in-plane retardation of the λ/2 plate. When the H layer is the above liquid crystal alignment solidified layer, its thickness is, for example, 2.0 μm to 4.0 μm. The thickness of the Q layer can be adjusted to obtain the required in-plane retardation of the λ/4 plate. When the Q layer is the aforementioned liquid crystal alignment and solidification layer, its thickness is, for example, 0.5 μm to 2.5 μm. In this embodiment, the angle formed by the retardation axis of the H layer and the absorption axis of the polarizing film is preferably 10°-20°, more preferably 12°-18°, further preferably 12°-16°; The angle formed by the retardation axis of the Q layer and the absorption axis of the polarizing film is preferably 70°-80°, more preferably 72°-78°, further preferably 72°-76°. In the case where the retardation layer 20 has a laminated structure, each layer (for example, the H layer and the Q layer) can show the inverse wavelength dispersion characteristic in which the retardation value increases according to the wavelength of the measurement light, and can show that the retardation value increases according to the wavelength of the measurement light. The positive wavelength dispersion characteristic that decreases with the wavelength can also show the smooth wavelength dispersion characteristic that the phase difference value hardly changes due to the wavelength of the measurement light.

The retardation layer (at least one layer in the case of having a laminated structure) typically exhibits a relationship of nx>ny=nz in refractive index characteristics. Furthermore, "ny=nz" includes not only the case where ny and nz are completely equal, but also the case where they are substantially equal. Therefore, within the range that does not impair the effect of the present invention, ny>nz or ny<nz may exist. The Nz coefficient of the retardation layer is preferably from 0.9 to 1.5, more preferably from 0.9 to 1.3.

As mentioned above, the phase difference layer is preferably a liquid crystal alignment solidified layer. As said liquid crystal compound, the liquid crystal compound (nematic liquid crystal) whose liquid crystal phase is a nematic phase is mentioned, for example. As such a liquid crystal compound, for example, a liquid crystal polymer or a liquid crystal monomer can be used. The expression mechanism of the liquid crystallinity of the liquid crystal compound can be lyotropic or thermotropic. The liquid crystal polymer and the liquid crystal monomer may be used alone or in combination.

When the liquid crystal compound is a liquid crystal monomer, the liquid crystal monomer is preferably a polymerizable monomer and a crosslinkable monomer. The reason for this is that the alignment state of the liquid crystal monomer can be fixed by polymerizing or crosslinking (ie, hardening) the liquid crystal monomer. After aligning the liquid crystal monomers, for example, if the liquid crystal monomers are polymerized or cross-linked, the above alignment state can be fixed. Here, a polymer is formed by polymerization, and a three-dimensional network structure is formed by crosslinking, but these are non-liquid crystalline. Therefore, the formed retardation layer does not change into a liquid crystal phase, a glass phase, or a crystal phase due to temperature changes peculiar to liquid crystal compounds, for example. As a result, the retardation layer becomes a retardation layer extremely excellent in stability not affected by temperature changes.

The temperature range in which a liquid crystal monomer exhibits liquid crystallinity differs depending on its type. Specifically, the temperature range is preferably from 40°C to 120°C, more preferably from 50°C to 100°C, most preferably from 60°C to 90°C.

Any appropriate liquid crystal monomer can be used as the above-mentioned liquid crystal monomer. For example, polymerizable mesogen compounds described in Japanese Patent Application Laid-Open No. 2002-533742 (WO00/37585), EP358208 (US5211877), EP66137 (US4388453), WO93/22397, EP0261712, DE19504224, DE4408171, and GB2280445 can be used. wait. Specific examples of such polymerizable mesogen compounds include LC242 (brand name) from BASF, E7 (brand name) from Merck, and LC-Sillicon-CC3767 (brand name) from Wacker-Chem. As the liquid crystal monomer, a nematic liquid crystal monomer is preferred.

C. Production of polarizing plate with retardation layer The polarizing plate with a retardation layer according to the embodiment of the present invention can be obtained by laminating the polarizing plate and the retardation layer. The lamination of the polarizing plate and the retardation layer is carried out, for example, while transporting them in a roll (by a so-called roll-to-roll method). Lamination is typically performed by transferring the liquid crystal alignment solidified layer formed on the substrate. As shown in the figure, when the retardation layer has a laminated structure, the retardation layers can be sequentially laminated (transferred) to the polarizing plate, or the laminated volume layer (transfer) in which the retardation layers are laminated in advance. printed) to the polarizer.

D. Image display device The above-mentioned polarizing plate with a phase difference layer can be applied to an image display device. Therefore, an image display device according to an embodiment of the present invention includes the above-mentioned polarizing plate with a retardation layer. [Example]

Hereinafter, the present invention will be specifically described with examples, but the present invention is not limited to these examples. In addition, the thickness and moisture permeability are the values measured by the following measurement methods. In addition, "parts" and "%" in Examples and Comparative Examples are based on weight unless otherwise specified. 1. Thickness The thickness of 10 μm or less was measured using a scanning electron microscope (manufactured by JEOL Ltd., product name "JSM-7100F"). The thickness exceeding 10 μm was measured using a digital micrometer (manufactured by Anritsu Co., Ltd., product name "KC-351C"). 2. Moisture permeability The moisture permeability was determined by the cup method (JIS Z 0208).

[Example 1] (Production of Polarizing Plate) As the thermoplastic resin substrate, a long amorphous isophthalic acid copolymerized polyethylene terephthalate film (thickness: 100 μm) with a Tg of about 75°C was used, and one side of the resin substrate was Implement corona treatment. It is obtained by mixing polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mole%) and acetoacetyl modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOHSEFIMER") in a weight ratio of 9:1 13 parts by weight of potassium iodide was added to 100 parts by weight of the PVA-based resin, and the resultant was dissolved in water to prepare an aqueous PVA solution (coating solution). The above-mentioned PVA aqueous solution was applied to the corona-treated surface of the resin substrate and dried at 60°C to form a PVA-based resin layer with a thickness of 13 μm to produce a laminate. The obtained laminate was uniaxially stretched to 2.4 times in the longitudinal direction (length direction) in an oven at 130° C. (in-air assisted stretching treatment). Next, the laminated body was immersed for 30 seconds in an insolubilization bath (an aqueous solution of boric acid prepared by mixing 4 parts by weight of boric acid with respect to 100 parts by weight of water) at a liquid temperature of 40° C. (insolubilization treatment). Then, adjust the concentration and immerse for 60 seconds in a dyeing bath at a liquid temperature of 30°C (an iodine aqueous solution prepared by mixing iodine and potassium iodide at a weight ratio of 1:7 with respect to 100 parts by weight of water), so that the finally obtained The single transmittance (Ts) of the polarizing film reaches the required value (dyeing treatment). Then, it was immersed for 30 seconds in a crosslinking bath (a boric acid aqueous solution prepared by mixing 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with respect to 100 parts by weight of water) of a liquid temperature of 40°C for 30 seconds (crosslinking treatment). Afterwards, the laminated body was dipped in a boric acid aqueous solution (boric acid concentration: 4% by weight, potassium iodide concentration: 5% by weight) at a liquid temperature of 70°C on one side, and stretched in the longitudinal direction (longitudinal direction) between rolls with different circumferential speeds. Uniaxial stretching (stretching in water) is carried out in a way up to 5.5 times. Thereafter, the laminate was immersed in a cleaning bath (an aqueous solution prepared by mixing 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 about 90° C., it was brought into contact with a heating roll made of SUS (Steel Use Stainless) whose surface temperature was kept at about 75° C. (drying shrinkage treatment). In this way, a polarizing film with a thickness of 5.4 μm was formed on the resin substrate to obtain a laminate having a composition of resin substrate/polarizing film.

A polycarbonate-based film formed with a hard coat (HC) layer was attached as a protective layer to the polarizing film side of the obtained laminate via an ultraviolet curable adhesive (thickness after curing: 1.5 μm). Thereafter, the resin substrate was peeled off from the polarizing film to obtain a polarizing plate having a composition of HC layer/polycarbonate film/adhesive layer/polarizing film. Furthermore, the polycarbonate-based film (water vapor transmission rate at 40°C and 92%RH: 170 g/m ² ·24 h) on which the HC layer was formed was obtained by mixing the following hard coat layer forming materials A Coated on the polycarbonate film (thickness 13 μm) shown below, heated at 60°C for 1 minute, and irradiated the heated coating layer with ultraviolet rays with a cumulative light intensity of 250 mJ/cm ² using a high-pressure mercury lamp. The coated layer was hardened to form a HC layer with a thickness of 2 μm.

(Production of polycarbonate film) With respect to 81.98 parts by mass of isosorbide, 47.19 parts by mass of tricyclodecane dimethanol, 175.1 parts by mass of diphenyl carbonate, and 0.979 parts by mass of an aqueous solution of 0.2 mass % cesium carbonate as a catalyst were put into the reaction container, Under a nitrogen atmosphere, as a step of the first stage of the reaction, the temperature of the heating tank was heated to 150° C., and the raw materials were dissolved while stirring as necessary (about 15 minutes). Then, while changing the pressure from normal pressure to 13.3 kPa, and raising the temperature of the heating tank to 190° C. within 1 hour, the generated phenol was extracted out of the reaction vessel. After maintaining the entire reaction vessel at 190°C for 15 minutes, as the second step, the pressure inside the reaction vessel was changed to 6.67 kPa, the temperature of the heating tank was raised to 230°C within 15 minutes, and the produced phenol Pump out to the outside of the reaction vessel. Due to the increased stirring torque of the stirrer, the temperature was raised to 250° C. within 8 minutes. In order to further remove the generated phenol, the pressure in the reaction vessel was kept below 0.200 kPa. After the specified stirring torque is reached, the reaction is terminated, and the resulting reactant is extruded into water to obtain polycarbonate copolymer particles. For the obtained pellets, a single-screw extruder (manufactured by Isuzu Kakoki Co., Ltd., screw diameter 25 mm, cylinder set temperature: 220° C.), T-die (width 200 mm, set temperature: 220° C.), Cool roll (setting temperature: 120~130°C) and film forming device of coiler to obtain polycarbonate film.

(Preparation of Hard Coat Forming Material A) 80 parts of urethane acrylate resin (manufactured by Mitsubishi Chemical, "UT-7314"), 20 parts of urethane acrylate resin (manufactured by DIC, "ELS888"), leveling agent (Kyoei Mixed 0.1 parts of "LE-303", manufactured by Shaka Chemical Co., Ltd., and 3 parts of photopolymerization initiator (manufactured by IGM Resins Italia S.r.l., "OMNIRAD907"), the cyclopentanone was used so that the solid content concentration was 30%. and methyl isobutyl ketone were diluted to prepare a hard coat layer forming material A.

(Preparation of retardation layer) 10 g of a polymerizable liquid crystal displaying a nematic liquid crystal phase (manufactured by BASF Corporation: trade name "Paliocolor LC242", represented by the following formula) and a photopolymerization initiator for the polymerizable liquid crystal compound (BASF Manufactured by the company: trade name "Irgacure 907") 3 g was dissolved in 40 g of toluene to prepare a liquid crystal composition (coating liquid). [chemical 1]

The alignment treatment was performed by rubbing the surface of a polyethylene terephthalate (PET) film (38 μm in thickness) with a rubbing cloth. The direction of the alignment treatment is set to a direction that is 15° relative to the direction of the absorption axis of the polarizing film when viewed from the viewing side when it is attached to the polarizing plate. The above-mentioned liquid crystal coating solution was coated on the alignment-treated surface by a bar coater, and heated and dried at 90° C. for 2 minutes, thereby aligning the liquid crystal compound. The liquid crystal layer thus formed was irradiated with light of 1 mJ/cm ² using a metal halide lamp to harden the liquid crystal layer, thereby forming a liquid crystal alignment solidified layer A (layer H) on the PET film. The thickness of the liquid crystal alignment solidified layer A is 2.5 μm, and the in-plane retardation Re(550) is 270 nm. Furthermore, the liquid crystal alignment solidified layer A exhibits a refractive index characteristic of nx>ny=nz.

Except for changing the coating thickness and setting the alignment treatment direction to a direction of 75° relative to the direction of the absorption axis of the polarizing film as viewed from the viewing side, a liquid crystal alignment solidified layer B was formed on the PET film in the same manner as above ( Q layer). The thickness of the liquid crystal alignment solidified layer B is 1.5 μm, and the in-plane retardation Re(550) is 140 nm. Furthermore, the liquid crystal alignment solidified layer B exhibits a refractive index characteristic of nx>ny=nz.

(Production of polarizing plate with retardation layer) The obtained liquid crystal alignment solidified layer A (H layer) and liquid crystal alignment solidified layer B (Q layer) were sequentially transferred to the polarizing film side of the obtained polarizing plate. At this time, the angle formed by the absorption axis of the polarizing film and the slow axis of the alignment cured layer A is 15°, and the angle formed by the absorption axis of the polarizing film and the slow axis of the alignment cured layer B is 75°. Perform transfer (lamination). Each transfer was carried out with an ultraviolet curable adhesive (thickness after curing: 1 μm) while the roll was conveyed. In this way, a polarizing plate with a retardation layer was obtained.

[Example 2] A polarizing plate with a retardation layer was obtained in the same manner as in Example 1 except that the thickness of the HC layer was set to 5 μm.

[Example 3] A polarizing plate with a retardation layer was obtained in the same manner as in Example 1 except that the COP film on which the HC layer was formed was used as the protective layer. Furthermore, the COP film with the HC layer formed was obtained by coating the hard coat forming material B shown below on a cycloolefin-based unstretched film (manufactured by Nippon Zeon Co., Ltd., thickness 13 μm, 40°C and moisture permeability at 92%RH of 35 g/m ² 24 h) and heated at 60°C for 1 minute, using a high-pressure mercury lamp to irradiate the heated coating layer with ultraviolet rays with a cumulative light intensity of 250 mJ/cm ² to make the coating The cloth layer is hardened to form an HC layer with a thickness of 2 μm.

(Preparation of Hard Coat Forming Material B) 60 parts of urethane acrylate resin (manufactured by DIC Corporation, "ELS888"), 40 parts of urethane acrylate resin (manufactured by DIC Corporation, "RS28-605"), leveling agent (manufactured by DIC Corporation, , "GRANDIC PC4100") 0.03 parts, and 3.9 parts of a photopolymerization initiator (manufactured by IGM Resins Italia S.r.l., "OMNIRAD184") were mixed, and diluted with ethyl acetate so that the solid content concentration was 25%, to prepare hard Coating forming material B.

[Comparative Example 1] Except using an acrylic film having a lactone ring structure (thickness: 20 μm, moisture permeability at 40°C and 92%RH: 150 g/m ² ·24 h) as the protective layer, the same procedure as in Example 1 A polarizing plate with a retardation layer is obtained by this method.

[Comparative example 2] A polarizing plate with a retardation layer was obtained in the same manner as in Example 1 except that the thickness of the HC layer was set to 7 μm.

[Comparative Example 3] A polarizing plate with a retardation layer was obtained in the same manner as in Example 1 except that an acrylic film formed with an HC layer was used as a protective layer. Furthermore, the acrylic film with the HC layer formed was obtained by applying the hard coat forming material C shown below to the above-mentioned acrylic film having a lactone ring structure and heating at 60° C. for 1 minute, using A high-pressure mercury lamp irradiates ultraviolet rays with a cumulative light intensity of 250 mJ/cm ² to the heated coating layer to harden the coating layer and form an HC layer with a thickness of 5 μm.

(Preparation of Hard Coat Forming Material C) 100 parts of urethane acrylate resin (manufactured by DIC Corporation, "UNIDIC 17-806"), 0.01 part of a leveling agent (manufactured by DIC Corporation, product name "GRANDIC PC4100"), and a photopolymerization initiator (IGM Made by Resin Italia S.r.l., "OMNIRAD907") was mixed in 3 parts, diluted with ethyl acetate and propylene glycol monomethyl ether so that the solid content concentration was 36%, and a hard coat layer forming material C was prepared.

[Comparative Example 4] In addition to changing the COP film to a cycloolefin-based unstretched film (manufactured by Zeon Corporation, thickness 25 μm, moisture permeability at 40°C and 92%RH: 20 g/m ² ·24 h), the In the same manner as in Example 3, a polarizing plate with a retardation layer was obtained.

[Reference example 1] A polarizing plate with a retardation layer was obtained in the same manner as in Example 1 except that the polarizing plate shown below was used as the polarizing plate.

(Production of Polarizing Plate) For a long roll of polyvinyl alcohol (PVA)-based resin film (manufactured by Kuraray Corporation, product name "PE3000") with a thickness of 30 μm, one side is extended 5.9 times in the longitudinal direction by a roll stretcher. Uniaxial stretching, swelling, dyeing, cross-linking, and washing are performed sequentially on one side, and finally drying is performed to produce a polarizing film with a thickness of 12 μm. The above-mentioned swelling treatment is performed with pure water at 20°C on the one hand, and extended to 2.2 times on the other hand. Next, the dyeing treatment was carried out in an aqueous solution at 30°C whose iodine concentration was adjusted so that the monomer transmittance of the obtained polarizing film was 45.0%, and the weight ratio of iodine to potassium iodide was 1:7, while extending to 1.4 times. Next, the cross-linking treatment adopts two-stage cross-linking treatment, and the first-stage cross-linking treatment is performed in an aqueous solution of boric acid and potassium iodide dissolved at 40° C., while extending to 1.2 times. In the aqueous solution of the first-stage crosslinking treatment, the content of boric acid was set to 5.0% by weight, and the content of potassium iodide was set to 3.0% by weight. The cross-linking treatment in the second stage is carried out in an aqueous solution of boric acid and potassium iodide dissolved at 65°C on the one hand, and on the other hand, it is extended to 1.6 times. In the aqueous solution of the second-stage crosslinking treatment, the content of boric acid was set to 4.3% by weight, and the content of potassium iodide was set to 5.0% by weight. Next, washing treatment was carried out in a potassium iodide aqueous solution at 20°C. The potassium iodide content in the aqueous solution of the cleaning treatment was set to 2.6% by weight. Finally, a polarizing film was obtained by drying at 70° C. for 5 minutes.

A TAC film with a hard coat (HC) layer and a TAC film with a thickness of 20 μm were attached to both sides of the obtained polarizing film through a polyvinyl alcohol-based adhesive to obtain a HC layer/TAC film/adhesive Polarizing plate composed of layer/polarizing film/adhesive layer/TAC film. Furthermore, the TAC film (water vapor transmission rate at 40°C and 92%RH: 800 g/m ² ·24 h) formed with the HC layer was obtained by coating the above hard coat layer forming material C on the TAC film (thickness: 25 μm) and heated at 60°C for 1 minute, and then irradiate the heated coating layer with ultraviolet rays with a cumulative light intensity of 250 mJ/ ^cm2 using a high-pressure mercury lamp to harden the coating layer and form a HC layer with a thickness of 7 μm .

The following evaluations were performed on Examples and Comparative Examples. The evaluation results are summarized in Table 1. ＜Evaluation＞ 1. Indentation hardness, indentation elastic recovery rate The hardness of the protective layer (the outermost layer) and the elastic recovery rate of the protective layer (HC layer and film) were measured by nanoindentation test. Specifically, the obtained polarizing plate with a retardation layer was cut into dimensions of 20 mm in length (absorption axis direction of the polarizing film, MD direction) and 20 mm in width (TD direction) using a cutting machine to obtain test pieces. Cut the cut surface of the obtained test piece with a microtome, place it in an environment of 23° C. and 55% RH for 3 hours (with humidity control), and then measure it with a nanoindenter. The "Triboindenter" manufactured by Hysitron Inc. was used in the measurement with the nanoindenter, and Berkovich (triangular cone) was used for indentation. Under the conditions of indentation speed of 20 nm/s and indentation depth of 100 nm, as follows As shown in Figure 4, indent from the cutting surface and measure the load-displacement curve, and calculate the indentation hardness and indentation elastic recovery rate. 2. Surface hardness According to the pencil hardness test of JIS K5600-5-4, the pencil hardness of the protective layer side of the obtained polarizing plate with a retardation layer was measured under the condition of a load of 500 g. 3. Flex resistance Evaluated by the MIT test. The MIT test was performed in accordance with JIS P 8115. Specifically, the obtained polarizing plate with a retardation layer was cut into a size of 15 cm in length and 15 mm in width so that the absorption axis direction of the polarizing film became the longitudinal direction using a cutting machine to obtain test pieces. Install the test piece (load: 200 gf, fixture R: 0.38 mm) on the MIT bending fatigue tester (manufactured by TESTER SANGYO Co., Ltd., BE-202 type), and bend at a bending speed of 175 times/min. Repeated bending under the condition of an angle of 135°, and calculate the number of bending times when the tested sample breaks, so as to evaluate the flex resistance. 4. Adhesiveness Evaluation was performed by checkerboard peel test. The checkerboard peel test was performed in accordance with JIS K-5400. Specifically, on the surface of the protective layer side of the obtained polarizing plate with a retardation layer, cuts of substrates (films) up to 11 x 11 lines were cut at intervals of 1 mm using a cutting guide and a cutting knife. Line, after forming 100 checkerboard grids, press the adhesive tape (manufactured by Miqibang Co., Ltd.) on it, and peel it off instantly at an angle of 90°, and calculate the number of checkerboard grids after the HC layer is peeled off (pcs/100 ), to evaluate the tightness.

[Table 1] Example 1 Example 2 Example 3 Comparative example 1 Comparative example 2 Comparative example 3 Comparative example 4 Reference example 1 Thickness of polarizing plate with retardation layer/μm 28 31 28 32 33 37 39 71 Thickness of HC layer/μm 2 5 2 - 7 5 2 7 Film thickness/μm 13 13 13 20 13 20 25 25(20) The ratio of the film from the center to the surface of the protective layer/% 86 68 86 100 58 74 90 80 Indentation elastic recovery rate/% HC layer 90 90 77 - 90 80 77 80 membrane 56 56 65 72 56 72 65 58 Indentation hardness of the outermost layer/GPa 0.46 0.46 0.50 0.11 0.46 0.36 0.50 0.36 Surface hardness 2B HB HB 6B HB h 2B 2H Flex resistance/time >8000 >6000 >6000 >6000 <1000 <1000 <300 <100 Tightness/piece 0 0 0 - 0 100 0 100

The polarizing plate with retardation layer of the embodiment has both hardness and durability. In Comparative Examples 2-4, in the MIT test, failure occurred at the interface between the HC layer and the film until the number of times of bending reached 1000. In Comparative Example 3, peeling occurred at the interface between the HC layer and the film in the checkerboard peeling test. [Industrial availability]

The polarizing plate with a retardation layer according to the embodiment of the present invention is used in an image display device, and is particularly suitably used in a curved, flexible, foldable, or rollable image display device. As an image display device, representatively, a liquid crystal display device, an organic EL display device, and an inorganic EL display device may, for example, be mentioned.

10: polarizer 11: Polarizing film 12: Protective layer 12a: Substrate (film) 12b: Hard coating 13: surface 20: Retardation layer 21: The first retardation layer 22: The second retardation layer 52: Adhesive layer 54: Adhesive layer 56: Adhesive layer 100: Polarizing plate with retardation layer 102: layered part 103: center d: distance MD: longitudinal direction (absorption axis direction of polarizing film) t: thickness TD: Landscape

FIG. 1 is a schematic cross-sectional view showing a schematic configuration of a polarizing plate with a retardation layer according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing an example of the structure of the protective layer of the polarizing plate with retardation layer shown in FIG. 1 . Fig. 3 is a diagram for explaining the ratio of the center of the laminated part to the base material. Fig. 4 is a diagram for explaining indentation directions in a nanoindentation test.

10: polarizer

11: Polarizing film

12: Protective layer

20: Retardation layer

21: The first retardation layer

22: The second retardation layer

100: Polarizing plate with retardation layer

Claims (9)

A polarizing plate with a retardation layer, which has a protective layer, a polarizing film, and a retardation layer in sequence, The surface hardness on the side of the above-mentioned protective layer is 2B or more in terms of pencil hardness, The thickness of the layered portion from the protective layer to the retardation layer is 32 μm or less. A polarizing plate with a retardation layer as claimed in claim 1, wherein the protective layer includes a base material with an indentation elastic recovery rate of 67% or less. The polarizing plate with retardation layer according to claim 2, wherein the ratio of the above-mentioned base material to the thickness from the center of the above-mentioned layered part to the surface of the above-mentioned protective layer is 65% or more. The polarizing plate with a retardation layer according to any one of claims 1 to 3, wherein the protective layer includes a portion having an indentation hardness of 0.35 GPa or more. The polarizing plate with a retardation layer according to any one of claims 1 to 4, wherein the thickness of the protective layer is more than 12 μm and less than 20 μm. The polarizing plate with a retardation layer according to any one of claims 1 to 5, wherein the protective layer includes a hard coat layer with a thickness of 5 μm or less. The polarizing plate with a retardation layer according to any one of claims 1 to 6, wherein the retardation layer is an alignment solidified layer of a liquid crystal compound. The polarizing plate with a retardation layer according to any one of claims 1 to 7, wherein the above-mentioned protective layer comprises a substrate whose moisture permeability at 40°C and 92%RH is less than 200 g/m ² ·24 h. An image display device having a polarizing plate with a retardation layer according to any one of Claims 1 to 8.

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