KR20240034769A - Polarizer with phase contrast layer and image display device using the same - Google Patents

Abstract

The present invention provides a polarizing plate with a retardation layer that has both hardness and durability against deformation. The polarizing plate with a retardation layer according to an embodiment of the present invention includes a protective layer, a polarizing film, and a retardation layer in this order, the surface hardness of the protective layer side is 2B or more in pencil hardness, and the retardation layer is separated from the protective layer. The thickness of the laminated portion up to is 32㎛ or less.

Description

Polarizer with phase contrast layer and image display device using the same

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

Image display devices represented by liquid crystal displays and electroluminescence (EL) display devices (eg, organic EL display devices and inorganic EL display devices) are rapidly becoming popular. Polarizing plates and retardation plates are typically used in image display devices. In practical terms, a polarizing plate with a retardation layer that integrates a polarizing plate and a retardation plate is widely used (for example, patent document 1).

In recent years, the possibility of curvature, bending, folding, and winding of an image display device using a flexible substrate (e.g., a resin substrate) has been studied, and a polarizing plate with a retardation layer capable of responding thereto has been sought. On the other hand, from the viewpoint of preventing damage to the image display device, there is a demand for improvement in the hardness of the polarizing plate with a retardation layer.

Japanese Patent Publication No. 3325560

The present invention has been made in consideration of the above, and its main purpose is to provide a polarizing plate with a retardation layer that has both hardness and durability against deformation.

The polarizing plate with a retardation layer according to an embodiment of the present invention includes a protective layer, a polarizing film, and a retardation layer in this order, the surface hardness of the protective layer side is 2B or more in pencil hardness, and the retardation layer is separated from the protective layer. The thickness of the laminated portion up to is 32㎛ or less.

In one embodiment, the protective layer includes a substrate having an indentation elastic recovery of 67% or less.

In one embodiment, the proportion of the base material in the thickness from the center of the laminated portion to the surface of the protective layer is 65% or more.

In one embodiment, the protective layer includes a portion having an indentation hardness of 0.35 GPa or more.

In one embodiment, the thickness of the protective layer is greater than or equal to 12 μm and less than 20 μm.

In one embodiment, the protective layer includes a hard coat layer having a thickness of 5 μm or less.

In one embodiment, the retardation layer is an alignment solidification layer of a liquid crystal compound.

In one embodiment, the protective layer includes a substrate having a moisture permeability of less than 200 g/m ² ·24h at 40° C. and 92%RH.

According to another aspect of the present invention, an image display device is provided. This image display device includes the above polarizing plate with a retardation layer.

According to an embodiment of the present invention, in a polarizing plate with a retardation layer, both hardness and durability against deformation can be achieved.

1 is a schematic cross-sectional view showing the schematic configuration of a polarizing plate with a retardation layer according to one 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 a retardation layer shown in FIG. 1.
Figure 3 is a diagram for explaining the ratio occupied by the center of the laminated portion and the base material.
Figure 4 is a diagram for explaining the indentation direction in the nanoindenter test.

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these embodiments. In addition, in order to make the explanation clearer, the drawings may schematically show the width, thickness, shape, etc. of each part compared to the embodiment, but are only examples and do not limit the interpretation of the present invention.

(Definition of terms and symbols)

The definitions of terms and symbols in this specification are as follows.

(1) Refractive index (nx, ny, nz)

'nx' is the refractive index in the direction where the in-plane refractive index is maximum (i.e., slow axis direction), 'ny' is the refractive index in the direction orthogonal to the slow axis in the plane (i.e., fast axis direction), and 'nz' is It is the refractive index in the thickness direction.

(2) In-plane phase difference (Re)

'Re(λ)' is the in-plane phase difference measured with light with a wavelength of λ nm at 23°C. For example, 'Re(550)' is the in-plane phase difference measured with light with a wavelength of 550 nm at 23°C. Re(λ) can be obtained by the formula: Re(λ)=(nx-ny)×d, when the thickness of the layer (film) is d (nm).

(3) Phase difference in the thickness direction (Rth)

'Rth(λ)' is the phase difference in the thickness direction measured with light with a wavelength of λ nm at 23°C. For example, 'Rth(550)' is the phase difference in the thickness direction measured with light with a wavelength of 550 nm at 23°C. Rth(λ) can be 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 can be obtained by Nz=Rth/Re.

(5) angle

When an angle is mentioned herein, the angle includes both clockwise and counterclockwise directions with respect to the reference direction. Therefore, for example, '45°' means ±45°.

1 is a schematic cross-sectional view showing the schematic configuration of a polarizing plate with a retardation layer according to one embodiment of the present invention. The polarizing plate 100 with a retardation layer includes 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 100 with a retardation layer includes a protective layer 12, a polarizing film 11, and a retardation layer 20 in this order. The retardation layer 20 can function as a protective layer of the polarizing film 11. According to this configuration, the thickness of the polarizing plate with a retardation layer described later can be achieved satisfactorily. The polarizing plate 100 with a retardation layer is typically arranged so that the polarizing plate 10 is on the viewing side rather than the retardation layer 20 in an 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 phase difference layer 20 includes a laminated structure including the first phase difference layer 21 and the second phase difference layer 22. However, unlike the illustrated example, the phase difference layer 20 has 3 It may contain a laminated structure of more than one layer, or may be a single layer.

Each member constituting the polarizing plate with a retardation layer can be laminated through any suitable 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 through an adhesive layer (preferably using an active energy ray-curable adhesive). For example, the retardation layer 20 is bonded to the polarizing film 11 through an adhesive layer (preferably using an active energy ray-curable adhesive). As shown, when the retardation layer 20 includes a laminated structure of two or more layers, the retardation layers are bonded together, for example, through an adhesive layer (preferably using an active energy ray-curable adhesive). The thickness of the adhesive layer is preferably 0.4 μm or more, 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. By this adhesive layer, for example, the polarizing plate 100 with a retardation layer can be attached to an image display panel included in an image display device. And, in practical terms, a release film (separator) is bonded to the surface of this adhesive layer. The release film can be temporarily affixed until the polarizer with a retardation layer is ready for use. By using a release film, for example, while protecting the adhesive layer, roll formation of a polarizing plate becomes possible.

The polarizing plate with a retardation layer may have a long shape or a single leaf shape. Here, 'elongated shape' refers to an elongated shape whose length is sufficiently long relative to the width, for example, an elongated shape whose length is 10 times or more, preferably 20 times or more, compared to the width. A long polarizing plate with a retardation layer can be wound into a roll.

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

The thickness of the laminated portion 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, and is preferably 31 μm or less. According to this thickness, durability against deformation (eg, bending resistance) can be significantly achieved while satisfying the above surface hardness. Specifically, the expansion and contraction caused by deformation (eg, bending) can be reduced and the occurrence of breakage (eg, interface breakage) can be suppressed. In addition, it contributes to thinning of the image display device and, for example, makes it possible to mount members (batteries, etc.) to cope with the enlargement of the screen. Meanwhile, the thickness of the polarizing plate with a retardation layer is, for example, 25 μm or more.

The thickness of the polarizing plate with a retardation layer also includes the thickness of the adhesive layer. Specifically, the thickness of the adhesive layer that may be disposed between the protective layer and the polarizing film, the adhesive layer that may be disposed between the polarizing film and the retardation layer, and the adhesive layer that may be disposed between the retardation layers when the retardation layer includes a laminated structure. Included. Additionally, the thickness of the polarizing plate with a retardation layer does not include an adhesive layer for adhering the polarizing plate with a retardation layer to an external adherend such as a panel or glass.

A. Polarizer

The 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 with an adhesive layer interposed therebetween.

A-1. polarizer

The polarizing film is typically a resin film containing a dichroic material (eg, 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 12 μm or less, more preferably 10 μm or less, and still more preferably 8 μm or less. Meanwhile, the thickness of the polarizing film is preferably 1 μm or more.

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

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

The method of producing a polarizing film from the above-described single-layer resin film typically includes subjecting the resin film to dyeing treatment and stretching treatment with a dichroic substance such as iodine or a dichroic dye. 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 are used. The method may further include insolubilization treatment, swelling treatment, crosslinking treatment, etc. Since this manufacturing method is well known in the art, detailed description is omitted.

A polarizing film obtained using the above laminate can be produced, for example, using a laminate of a resin substrate and a resin film or resin layer (typically a PVA-based resin layer). Specifically, applying a PVA-based resin solution to a resin substrate, drying it to form a PVA-based resin layer on the resin substrate, and obtaining a laminate of the resin substrate and the PVA-based resin layer; It can be produced by stretching and dyeing the laminate and using the PVA-based resin layer as a polarizing film. In this embodiment, a PVA-based resin layer containing a halide and a PVA-based resin is preferably formed on one side of the resin substrate. Stretching typically includes stretching the laminate by immersing it in an aqueous solution of boric acid. Additionally, stretching, if necessary, may further include air stretching the laminate at a high temperature (for example, 95°C or higher) before stretching in an aqueous boric acid solution. Additionally, in this embodiment, the laminate is preferably subjected to dry shrinkage treatment to shrink it by 2% or more in the width direction by heating it while conveying it in the longitudinal direction. Typically, the manufacturing method of this embodiment includes performing aerial auxiliary stretching treatment, dyeing treatment, underwater stretching treatment, and dry shrink treatment on the laminate in this order. By introducing auxiliary stretching, even in the case of applying PVA on a thermoplastic resin, it becomes possible to increase the crystallinity of PVA and achieve high optical properties. In addition, by increasing the orientation of PVA in advance, problems such as a decrease in the orientation of the PVA or dissolution can be prevented when it is immersed in water in the subsequent dyeing process or stretching process, and high optical properties can be achieved. . In addition, when the PVA-based resin layer is immersed in a liquid, compared to the case where the PVA-based resin layer does not contain a halide, disturbance of the orientation of PVA molecules and a decrease in orientation can be suppressed, and high optical properties can be achieved. It can be achieved. Additionally, high optical properties can be achieved by shrinking the laminate in the width direction through dry shrinkage treatment. A polarizing plate can be obtained by laminating a protective layer on the peeling surface where the resin substrate is peeled from the obtained resin substrate/polarizing film laminate, or on the surface opposite to the peeling surface. Details of the manufacturing method of such a polarizing film are described in, for example, Japanese Patent Application Laid-Open No. 2012-73580 and Japanese Patent Application Publication No. 6470455. The entire description of these publications is 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 a retardation layer shown in FIG. 1. The protective layer 12 includes a substrate (film) 12a and a hard coat (HC) layer 12b formed on the substrate 12a. By providing the hard coat layer 12b, good surface hardness on the protective layer side can be achieved. The polarizing plate with a retardation layer is typically placed on the viewing side of the image display device, and the hard coat layer 12b is placed on the viewing side of the base material 12a. The hard coat layer 12b may function as another functional layer, such as an anti-reflection layer, an anti-sticking layer, or an anti-glare layer.

The thickness of the protective layer is preferably less than 20 μm, and more preferably 18 μm or less. On the other hand, the thickness of the protective layer is preferably 12 μm or more, and more preferably 14 μm or more.

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

The indentation elastic recovery rate of the base material is preferably 67% or less, more preferably 65% or less, and may be 60% or less. By using such a substrate, durability against deformation (eg, bending resistance) can be improved. Specifically, the stress generated by deformation (eg, bending) can be dispersed and the occurrence of fracture (eg, interface breakdown) can be suppressed. Additionally, adhesion to the hard coat layer may be excellent. Meanwhile, the indentation elastic recovery rate of the base material is, for example, 35% or more.

The thickness of the substrate is, for example, 10 μm to 16 μm, preferably 11 μm to 15 μm, and more preferably 12 μm to 14 μm.

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

Figure 3 is a diagram for explaining the ratio occupied by the center of the laminated portion (polarizing plate with retardation layer) and the base material. Additionally, in Figure 3, hatching is omitted. The laminated portion (polarizing plate with retardation layer) 102 includes a protective layer 12 including a hard coat layer 12b and a base material 12a, an adhesive layer 52, a polarizing film 11, and an adhesive layer 54. , a first phase difference layer 21, an adhesive layer 56, and a second phase difference layer 22 in this order. As described above, the ratio of the thickness t of the substrate 12a to the distance d from the center 103 of the laminated portion 102 to the surface 13 of the protective layer 12 in the thickness direction. It is preferable that it is 65% or more, and more preferably, it is 75% or more. In one embodiment, the ratio is controlled by adjusting the thickness of the hard coat layer.

As a base material, it can be comprised of any suitable film that can be used as a protective layer of a polarizing film. Specific examples of materials that become the main components of such films include cellulose-based resins such as triacetylcellulose (TAC), polyester-based, polyvinyl alcohol-based, polycarbonate-based, polyamide-based, polyimide-based, and polyethersulfone-based. , polysulfone-based, polystyrene-based, cycloolefin-based resins such as polynorbornene, polyolefin-based, (meth)acrylic-based, and acetate-based transparent resins. Preferably, at least one selected from polycarbonate-based resin and cycloolefin-based resin is used as the material constituting the base material.

The indentation hardness of the hard coat layer is preferably 0.35 GPa or more, more preferably 0.4 GPa or more, and still more preferably 0.45 GPa or more. 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 coat layer is preferably 70% or more, and more preferably 75% or more. 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 5 μm or less, more preferably 4 μm or less, and even more preferably 3 μm or less. By providing such a hard coat layer, durability against deformation (for example, bending resistance) can be achieved while satisfying the above surface hardness. On the other hand, the thickness of the hard coat layer is, for example, 1 μm or more.

The hard coat layer is typically formed by applying a hard coat layer forming material to the substrate and curing the applied layer. The hard coat layer forming material typically contains a curable compound as a layer forming component. Examples of the curing mechanism of the curable compound include thermosetting type and photocuring type. Examples of curable compounds include monomers, oligomers, and prepolymers. Preferably, a polyfunctional monomer or oligomer is used as the curable compound. Examples of polyfunctional monomers or oligomers include monomers or oligomers containing two or more (meth)acryloyl groups, urethane (meth)acrylate or oligomers of urethane (meth)acrylate, epoxy-based monomers or oligomers, silicone-based monomers, or Oligomers may be mentioned.

The hard coat layer forming material may contain any appropriate additives. Examples of additives include polymerization initiators, leveling agents, anti-blocking agents, dispersion stabilizers, thixotropic agents, antioxidants, ultraviolet absorbers, anti-foaming agents, thickeners, dispersants, surfactants, catalysts, fillers, lubricants, antistatic agents, etc. The type, combination, content, etc. of additives can be appropriately set depending on the purpose or desired characteristics.

When the curable compound is a thermosetting type, the heating temperature is, for example, 60°C to 140°C, and is preferably 60°C to 100°C. When the curable compound is a photocurable type, the curing treatment is typically performed by ultraviolet irradiation. The accumulated light amount of ultraviolet irradiation is, for example, 100 mJ/cm ² to 300 mJ/cm ² . Ultraviolet irradiation and heating may be combined. In this case, typically, ultraviolet ray irradiation is performed after heating the coating film. The heating temperature is as described above for the thermosetting type curable compound.

B. Phase contrast layer

The thickness of the retardation layer depends on its structure (whether it has a single layer or a laminated structure), but is preferably 10 μm or less, more preferably 8 μm or less, and even more preferably 7 μm or less. Meanwhile, the thickness of the retardation layer is, for example, 0.5 μm or more. Additionally, when the retardation layer has a laminated structure, 'thickness of the retardation layer' means the sum of the thicknesses of each retardation layer. Specifically, the ‘thickness of the phase contrast layer’ does not include the thickness of the adhesive layer.

As the retardation layer, an alignment-fixed layer of a liquid crystal compound (liquid-crystal alignment-fixed layer) is preferably used. By using a liquid crystal compound, for example, the difference between nx and ny of the resulting retardation layer can be significantly increased compared to a non-liquid crystal material, so the thickness of the retardation layer for obtaining the desired in-plane retardation can be significantly reduced. Therefore, it is possible to realize significant thinning of the polarizing plate with a retardation layer. In this specification, the term 'alignment-fixed layer' refers to a layer in which a liquid crystal compound is oriented in a predetermined direction within the layer, and its orientation state is fixed. In addition, the 'alignment solidification layer' is a concept that includes an alignment hardening layer obtained by curing a liquid crystal monomer, as will be described later. In the phase contrast layer, typically, rod-shaped liquid crystal compounds are oriented in a line in the slow axis direction of the phase contrast layer (homogeneous orientation).

The liquid crystal alignment solidification layer applies an orientation treatment to the surface of a predetermined substrate, applies a coating liquid containing a liquid crystal compound to the surface, orients the liquid crystal compound in a direction corresponding to the orientation treatment, and maintains the orientation state. It can be formed by fixing . As the orientation treatment, any appropriate orientation treatment may be employed. Specifically, mechanical alignment treatment, physical alignment treatment, and chemical alignment treatment can be mentioned. Specific examples of mechanical orientation treatment include rubbing treatment and stretching treatment. Specific examples of physical alignment treatment include magnetic field alignment treatment and electric field alignment treatment. Specific examples of chemical alignment treatment include oblique vapor deposition and photo-alignment treatment. The treatment conditions for various orientation treatments may be any appropriate conditions depending on the purpose.

The liquid crystal compound is aligned by treating it at a temperature that exhibits a liquid crystal phase depending on the type of the liquid crystal compound. By performing such temperature treatment, the liquid crystal compound assumes a liquid crystal state, and the liquid crystal compound is aligned according to the orientation treatment direction of the substrate surface.

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

Specific examples of the liquid crystal compound and details of the method for forming the alignment solidification layer are described in Japanese Patent Application Laid-Open No. 2006-163343. The description in this publication is incorporated herein by 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, 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 100 nm to 180 nm, more preferably 110 nm to 170 nm, and still more preferably 110 nm to 160 nm. The thickness of the retardation layer can be adjusted to obtain the desired in-plane retardation of the λ/4 plate. When the retardation layer is the above-mentioned liquid crystal alignment solidification layer, its thickness is, for example, 1.0 μm to 2.5 μm. In this embodiment, the angle formed by the slow axis of the retardation layer and the absorption axis of the polarizing film is preferably 40° to 50°, more preferably 42° to 48°, and even more preferably 44° to 46°. am. Additionally, the phase difference layer preferably exhibits inverse dispersion wavelength characteristics in which the phase difference value increases depending on the wavelength of the measurement light.

As shown, when the retardation layer 20 has a laminated structure, the retardation layer 20 includes, for example, a first retardation layer (H layer) 21 and a second retardation layer in order from the polarizer 10 side. (Q layer) has a two-layer stacked structure in which 22 is disposed. The H layer can typically function as a λ/2 plate, and the Q layer can typically function as a λ/4 plate. Specifically, Re(550) of the H layer is preferably 200 nm to 300 nm, more preferably 220 nm to 290 nm, and still more preferably 230 nm to 280 nm; Re(550) of the Q layer is preferably 100 nm to 180 nm, more preferably 110 nm to 170 nm, and still more 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-mentioned liquid crystal alignment solidification 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 desired in-plane retardation of the λ/4 plate. When the Q layer is the above-mentioned liquid crystal alignment solidification layer, its thickness is, for example, 0.5 μm to 2.5 μm. In this embodiment, the angle formed by the slow axis of the H layer and the absorption axis of the polarizing film is preferably 10° to 20°, more preferably 12° to 18°, and even more preferably 12° to 16°. ego; The angle formed between the slow axis of the Q layer and the absorption axis of the polarizing film is preferably 70° to 80°, more preferably 72° to 78°, and still more preferably 72° to 76°. When the phase difference layer 20 includes a laminated structure, each layer (e.g., H layer and Q layer) may exhibit inverse dispersion wavelength characteristics in which the phase difference value increases depending on the wavelength of the measurement light, and the phase difference value may be that of the measurement light. It may exhibit positive wavelength dispersion characteristics that become smaller depending on the wavelength, or it may exhibit flat wavelength dispersion characteristics in which the phase difference value hardly changes depending on the wavelength of the measurement light.

The refractive index characteristic of the retardation layer (at least one layer when it has a laminated structure) typically shows the relationship nx>ny=nz. Additionally, 'ny=nz' includes not only the case where ny and nz are completely the same, but also the case where they are substantially the same. Therefore, there may be cases where ny > nz or ny < nz within a range that does not impair the effect of the present invention. The Nz coefficient of the phase difference layer is preferably 0.9 to 1.5, and more preferably 0.9 to 1.3.

As mentioned above, the retardation layer is preferably a liquid crystal alignment solidification layer. Examples of the liquid crystal compound include a liquid crystal compound (nematic liquid crystal) whose liquid crystal phase is a nematic phase. As such a liquid crystal compound, for example, liquid crystal polymer or liquid crystal monomer can be used. The mechanism for expressing liquid crystallinity of the liquid crystal compound may be lyotropic or thermotropic. The liquid crystal polymer and liquid crystal monomer may be used individually or in combination.

When the liquid crystal compound is a liquid crystal monomer, the liquid crystal monomer is preferably a polymerizable monomer or a crosslinkable monomer. This is because the alignment state of the liquid crystal monomer can be fixed by polymerizing or crosslinking (i.e., curing) the liquid crystal monomer. After aligning the liquid crystal monomers, for example, by polymerizing or crosslinking the liquid crystal monomers, the alignment state can be fixed accordingly. Here, polymers are formed by polymerization and a three-dimensional network structure is formed by crosslinking, but these are non-liquid crystalline. Therefore, the formed retardation layer is unlikely to transition into a liquid crystal phase, a glass phase, or a crystal phase due to temperature changes characteristic of liquid crystalline compounds, for example. As a result, the phase difference layer becomes a phase difference layer that is unaffected by temperature changes and has extremely excellent stability.

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

As the liquid crystal monomer, any suitable liquid crystal monomer may be employed. For example, polymerization described in Japanese Patent Application Publication 2002-533742 (WO00/37585), EP358208 (US5211877), EP66137 (US4388453), WO93/22397, EP0261712, DE19504224, DE4408171, and GB2280445. Mesogenic compounds, etc. can be used. Specific examples of such polymerizable mesogenic compounds include, for example, BASF's trade name LC242, Merck's trade name E7, and Wacker-Chem's trade name LC-Sillicon-CC3767. As the liquid crystal monomer, a nematic liquid crystal monomer is preferable.

C. Fabrication of polarizer with phase contrast layer

The polarizing plate with a retardation layer according to an embodiment of the present invention can be obtained by laminating the polarizing plate and the retardation layer. Lamination of the polarizing plate and the retardation layer is performed, for example, while conveying them on a roll (so-called roll-to-roll). Lamination is typically performed by transferring the liquid crystal alignment solidification layer formed on the base material. As shown, when the retardation layer has a laminated structure, each retardation layer may be sequentially laminated (transferred) on the polarizing plate, or a laminate in which the retardation layers are previously laminated may be laminated (transferred) on the polarizing plate. .

D. Image display device

The polarizing plate with a retardation layer can be applied to an image display device. Therefore, the image display device according to the embodiment of the present invention includes the polarizing plate with the retardation layer.

[Example]

Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to these examples. In addition, the thickness and moisture permeability are values measured by the following measurement method. Additionally, unless otherwise specified, 'part' and '%' in Examples and Comparative Examples are based on weight.

1. Thickness

The thickness of 10 μm or less was measured using a scanning electron microscope (manufactured by Nippon Electronics, product name ‘JSM-7100F’). Thickness exceeding 10㎛ was measured using a digital micrometer (manufactured by Anritsu, product name 'KC-351C').

2. Water vapor permeability

The moisture permeability was determined by the cup method (JIS Z 0208).

[Example 1]

(Production of polarizer)

An amorphous isophthalic copolymerized polyethylene terephthalate film (thickness: 100 µm), which is long and has a Tg of approximately 75°C, was used as a thermoplastic resin substrate, and corona treatment was performed on one side of the resin substrate.

100 parts by weight of PVA-based resin mixed with polyvinyl alcohol (degree of polymerization 4200, degree of saponification 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Nippon Synthetic Chemicals, brand name 'Gosephimer') at a weight ratio of 9:1, was iodinated. 13 parts by weight of potassium was dissolved in water to prepare an aqueous PVA solution (coating solution).

The 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, thereby producing a laminate.

The obtained laminate was uniaxially stretched 2.4 times in the longitudinal direction (longitudinal direction) in an oven at 130°C (air auxiliary stretching treatment).

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

Next, in a dyeing bath (iodine aqueous solution obtained by mixing 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 single transmittance (Ts) of the finally obtained polarizing film is set to the desired value. It was immersed for 60 seconds while adjusting the concentration to achieve this (dyeing treatment).

Next, it was immersed in a crosslinking bath (a boric acid aqueous solution obtained 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) 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% by weight, potassium iodide concentration: 5% by weight) at a liquid temperature of 70°C, and the total stretch ratio was stretched in the longitudinal direction (longitudinal direction) between rolls with different circumferential speeds. Uniaxial stretching was performed to make this 5.5 times larger (underwater stretching treatment).

Thereafter, the laminate was immersed in a washing bath (aqueous solution obtained 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).

Afterwards, it was dried in an oven maintained at about 90°C and brought into contact with a heating roll made of SUS whose surface temperature was maintained at about 75°C (dry shrink treatment).

In this way, a polarizing film with a thickness of 5.4 μm was formed on the resin substrate, and a laminate having a resin substrate/polarizing film configuration was obtained.

A polycarbonate-based film with a hard coat (HC) layer was bonded to the polarizing film side of the obtained laminate through an ultraviolet curing adhesive (thickness after curing: 1.5 μm) as a protective layer. After that, the resin substrate was peeled from the polarizing film to obtain a polarizing plate having the structure of HC layer/polycarbonate-based film/adhesive layer/polarizing film.

In addition, the polycarbonate-based film on which the HC layer was formed (water vapor transmission rate of 170 g/m ² ·24h at 40°C and 92%RH) formed a hard coat layer shown below on the polycarbonate-based film (thickness 13 μm) shown below. Material A was applied, heated at 60°C for 1 minute, and the applied layer after heating was irradiated with ultraviolet rays with an accumulated light amount of 250 mJ/cm ² using a high-pressure mercury lamp to cure the applied layer to form an HC layer with a thickness of 2 μm.

(Production of polycarbonate-based 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% by mass of cesium carbonate as a catalyst were placed in a reaction vessel, and the reaction was carried out under a nitrogen atmosphere. As a first stage process, the heating bath temperature was heated to 150°C, and the raw materials were dissolved while stirring as necessary (about 15 minutes).

Next, the pressure was set to 13.3 kPa from normal pressure, and the temperature of the heating tank was raised to 190°C in 1 hour, while the generated phenol was taken out of the reaction vessel.

After maintaining the entire reaction vessel at 190°C for 15 minutes, as a second stage process, the pressure inside the reaction vessel is set to 6.67 kPa, the temperature of the heating tank is raised to 230°C in 15 minutes, and the generated phenol is released to the outside of the reaction vessel. I took it out. As the stirring torque of the stirrer increased, the temperature was raised to 250°C in 8 minutes, and the pressure in the reaction vessel was brought to 0.200 kPa or less in order to remove the generated phenol. After reaching a predetermined stirring torque, the reaction was terminated, and the resulting reactant was extruded into water to obtain polycarbonate copolymer pellets.

The obtained pellets were extruded through a single-screw extruder (manufactured by Isuzu Chemical Co., Ltd., screw diameter 25 mm, cylinder set temperature: 220°C), T die (width 200 mm, set temperature: 220°C), cooling roll (set temperature: 120 to 130°C), and A polycarbonate-based film was obtained using a film forming apparatus equipped with a winder.

(Preparation of hard coat layer forming material A)

80 parts of urethane acrylate resin (manufactured by Mitsubishi Chemical Company, 'UT-7314'), 20 parts of urethane acrylate resin (manufactured by DIC Company, 'ELS888'), leveling agent (manufactured by Kyoeisha Chemical Company, 'LE-303') Mix 0.1 part and 3 parts of photopolymerization initiator ('OMNIRAD907', manufactured by IGM Resins Italia S. r. l.), dilute with cyclopentanone and methyl isobutyl ketone so that the solid content concentration is 30%, and prepare hard coat layer forming material A. It was prepared.

(Production of phase contrast layer)

10 g of a polymerizable liquid crystal exhibiting a nematic liquid crystalline phase (manufactured by BASF, brand name 'Paliocolor LC242', shown in the formula below), and a photopolymerization initiator for the polymerizable liquid crystal compound (manufactured by BASF, brand name 'Irr') 3 g of Gacure 907') was dissolved in 40 g of toluene to prepare a liquid crystal composition (coating solution).

[Formula 1]

The surface of a polyethylene terephthalate (PET) film (thickness 38 μm) was rubbed using a rubbing cloth to perform orientation treatment. The direction of the orientation treatment was set to be 15° when viewed from the viewing side with respect to the direction of the absorption axis of the polarizing film when bonding to the polarizing plate. The liquid crystal coating liquid was applied to this alignment treated surface using a bar coater, and the liquid crystal compound was aligned by heating and drying at 90°C for 2 minutes. The liquid crystal layer formed in this way was irradiated with light at 1 mJ/cm ² using a metal halide lamp to cure the liquid crystal layer, thereby forming a liquid crystal alignment solidification layer A (H layer) on the PET film. The thickness of the liquid crystal alignment solidification layer A was 2.5 μm, and the in-plane retardation Re(550) was 270 nm. In addition, the liquid crystal alignment solidification layer A showed a refractive index characteristic of nx>ny=nz.

Liquid crystal alignment-fixed layer B (Q layer) was formed on the PET film in the same manner as above, except that the coating thickness was changed and the orientation treatment direction was 75° when viewed from the viewer's side with respect to the direction of the absorption axis of the polarizing film. formed. The thickness of the liquid crystal alignment solidification layer B was 1.5 μm, and the in-plane retardation Re(550) was 140 nm. In addition, the liquid crystal alignment solidification layer B showed a refractive index characteristic of nx>ny=nz.

(Production of polarizer with phase contrast layer)

The obtained liquid crystal orientation fixed layer A (H layer) and liquid crystal orientation fixed layer B (Q layer) were transferred to the polarizing film side of the obtained polarizing plate in this order. At this time, transfer (lamination) was performed so that the angle between the absorption axis of the polarizing film and the slow axis of the alignment-fixed layer A was 15°, and the angle between the absorption axis of the polarizing film and the slow axis of the orientation-fixed layer B was 75°. Each transfer was performed through an ultraviolet curing adhesive (thickness after curing: 1 μm) while roll conveying. 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 5 μm.

[Example 3]

A polarizing plate with a retardation layer was obtained in the same manner as in Example 1 except that a COP film on which an HC layer was formed as a protective layer was used.

In addition, the COP film on which the HC layer was formed was a cycloolefin-based unstretched film (manufactured by Nippon Zeon Co., Ltd., thickness 13 ㎛, moisture permeability 35 g/m ² 24h at 40°C and 92%RH) and a hard coat layer shown below. Forming material B was applied, heated at 60°C for 1 minute, and the applied layer after heating was irradiated with ultraviolet rays with an accumulated light amount of 250 mJ/cm ² using a high-pressure mercury lamp to cure the applied layer to form an HC layer with a thickness of 2 μm.

(Preparation of hard coat layer forming material B)

60 parts of urethane acrylate resin ('ELS888', manufactured by DIC), 40 parts of urethane acrylate resin ('RS28-605', manufactured by DIC), 0.03 parts of leveling agent ('GRANDIC PC4100', manufactured by DIC), and 3.9 parts of a photopolymerization initiator ('OMNIRAD184' manufactured by IGM Resins Italia S. r.l.) was mixed and diluted with ethyl acetate to a solid content concentration of 25% to prepare hard coat layer forming material B.

[Comparative Example 1]

A polarizing plate with a retardation layer was obtained in the same manner as in Example 1, except that an acrylic film with a lactone ring structure (thickness of 20 μm, moisture permeability of 150 g/m ² ·24 h at 40°C and 92%RH) was used as a protective layer.

[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 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 with an HC layer was used as the protective layer.

In addition, the acrylic film with the HC layer formed is an acrylic film having the lactone ring structure, which is coated with the hard coat layer forming material C shown below, heated at 60° C. for 1 minute, and the applied layer after heating is integrated with a high-pressure mercury lamp. It was obtained by curing the applied layer by irradiating ultraviolet rays with an amount of 250 mJ/cm ² to form an HC layer with a thickness of 5 μm.

(Preparation of hard coat layer forming material C)

100 parts of urethane acrylate resin (manufactured by DIC, 'Unidic 17-806'), 0.01 part of leveling agent (manufactured by DIC, product name 'GRANDIC PC4100'), 0.01 part of light polymerization initiator (manufactured by IGM Resin Italia S. r. l., 'OMNIRAD907') ') 3 parts were mixed and diluted with ethyl acetate and propylene glycol monomethyl ether so that the solid content concentration was 36% to prepare hard coat layer forming material C.

[Comparative Example 4]

Retardation layer was attached in the same manner as in Example 3 except that the COP film was changed to a cycloolefin-based unstretched film (manufactured by Nippon Zeon Co., Ltd., thickness 25㎛, moisture permeability at 40°C and 92%RH: 20g/m ² ·24h). Got a polarizer.

[Reference Example 1]

As a polarizing plate, 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.

(Production of polarizer)

A long roll of a 30㎛ thick polyvinyl alcohol (PVA)-based resin film (manufactured by Kuraray, product name 'PE3000') is uniaxially stretched in the longitudinal direction to a length of 5.9 times by a roll stretching machine, and simultaneously swelled. After dyeing, crosslinking, and washing were performed in this order, a drying treatment was performed at the end to produce a polarizing film with a thickness of 12 μm.

The swelling treatment was performed with pure water at 20°C and stretched 2.2 times. Next, the dyeing treatment was carried out in an aqueous solution at 30°C with a weight ratio of iodine and potassium iodide of 1:7, with the iodine concentration adjusted so that the resulting polarizing film had a single transmittance of 45.0%, and was stretched 1.4 times. Next, a two-step crosslinking treatment was adopted for the crosslinking treatment, and the first crosslinking treatment was stretched 1.2 times while being treated in an aqueous solution of boric acid and potassium iodide at 40°C. The boric acid content of the aqueous solution in the first stage crosslinking treatment was 5.0% by weight, and the potassium iodide content was 3.0% by weight. In the second stage of crosslinking treatment, the material was stretched 1.6 times while being treated in an aqueous solution of boric acid and potassium iodide at 65°C. The boric acid content of the aqueous solution in the second stage crosslinking treatment was 4.3% by weight, and the potassium iodide content was 5.0% by weight. Next, the washing treatment was performed with an aqueous potassium iodide solution at 20°C. The potassium iodide content of the aqueous solution for washing treatment was 2.6% by weight. Finally, a polarizing film was obtained by drying at 70°C for 5 minutes.

On both sides of the obtained polarizing film, a TAC film with a hard coat (HC) layer formed thereon and a TAC film with a thickness of 20 μm are bonded through a polyvinyl alcohol-based adhesive, respectively, and HC layer/TAC film/adhesive layer/polarizing film/adhesive A polarizer with a composition of layer/TAC film was obtained.

In addition, the TAC film with the HC layer (water vapor transmission rate at 40°C and 92%RH: 800 g/m ² ·24h) was obtained by applying the hard coat layer forming material C to the TAC film (thickness 25 μm) at 60°C. It was obtained by heating for a minute and curing the applied layer by irradiating ultraviolet rays with an accumulated light amount of 250 mJ/cm ² using a high-pressure mercury lamp to form an HC layer with a thickness of 7 μm.

For Examples and Comparative Examples, the following evaluation was performed. The evaluation results are summarized in Table 1.

<Evaluation>

1. Indentation hardness, indentation elasticity recovery rate

The hardness of the protective layer (outermost layer) and the elastic recovery rate of the protective layer (HC layer and film) were measured by the nanoindenter test. Specifically, the obtained polarizing plate with a retardation layer was cut to a size of 20 mm vertically (absorption axis direction of the polarizing film, MD direction) and 20 mm horizontally (TD direction) with a cutter to obtain a test piece. The cut surface of the obtained test piece was cut using a microtome, placed in an environment of 23°C and 55%RH for 3 hours (humidity controlled), and then measured using a nanoindenter. For measurement using a nanoindenter, a 'Triboindenter' manufactured by Hysitron Inc. is used, and a Berkovich (triangular pyramid) is used as the indenter. Under the conditions of an indentation speed of 20 nm/sec and an indentation depth of 100 nm, the indenter is measured from the cut surface as shown in Figure 4. After indentation, the load-displacement curve was measured, and indentation hardness and indentation elastic recovery rate were calculated.

2. Surface hardness

In accordance with 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. Flexibility

Evaluated by MIT test. The MIT test was conducted in accordance with JIS P 8115. Specifically, the obtained polarizing plate with a retardation layer was cut to a size of 15 cm in length and 15 mm in width with a cutter so that the absorption axis direction of the polarizing film was in the longitudinal direction to obtain a test piece. The test piece was mounted on an MIT bending fatigue tester (Type BE-202, manufactured by Tester Industry Co., Ltd.) (load: 200 gf, clamp R: 0.38 mm), and repeatedly bent under the conditions of a bending speed of 175 times/min and a bending angle of 135°. , bending resistance was evaluated by calculating the number of bending times when the measurement sample broke.

4. Adhesion

Evaluated by cross cut peel test. The cross cut peeling test was conducted in accordance with JIS K-5400. Specifically, on the surface of the obtained polarizing plate with a retardation layer on the protective layer side, cutting lines reaching 11 × 11 substrates (films) at 1 mm intervals are made using a cutter guide and a cutter knife to form 100 cross cuts. After that, an adhesive tape (manufactured by Nichiban Co., Ltd.) was pressed, peeled off instantly at an angle of 90°, and adhesion was evaluated by determining the number of cross cuts (pieces/100) from which the HC layer peeled.

[Table 1]

The polarizing plate with a retardation layer of the example had both hardness and durability. In Comparative Example 2-4, in the MIT test, failure occurred at the interface between the HC layer and the film before the number of bending reached 1000 times. In Comparative Example 3, peeling occurred at the interface between the HC layer and the film in the crosscut peeling test.

The polarizing plate with a retardation layer according to an embodiment of the present invention is used in an image display device, and in particular, can be suitably used in an image display device that is curved or can be bent, folded, or rolled. Representative image display devices include liquid crystal display devices, organic EL display devices, and inorganic EL display devices.

10: Polarizer
11: Polarizing film
12: protective layer
20: Phase contrast layer
21: first phase contrast layer
22: second phase contrast layer
100: Polarizer with phase contrast layer

Claims (9)

It includes a protective layer, a polarizing film, and a retardation layer in this order,
The surface hardness of the protective layer side is 2B or more in pencil hardness,
The thickness of the laminated portion from the protective layer to the retardation layer is 32 μm or less,
Polarizer with phase contrast layer. According to paragraph 1,
A polarizing plate with a retardation layer, wherein the protective layer includes a substrate having an indentation elastic recovery rate of 67% or less. According to paragraph 2,
A polarizing plate with a retardation layer, wherein the ratio of the base material to the thickness from the center of the laminated portion to the surface of the protective layer is 65% or more. According to any one of claims 1 to 3,
A polarizing plate with a retardation layer, wherein the protective layer includes a portion having an indentation hardness of 0.35 GPa or more. According to any one of claims 1 to 4,
A polarizing plate with a retardation layer, wherein the thickness of the protective layer is 12 ㎛ or more and less than 20 ㎛. According to any one of claims 1 to 5,
A polarizing plate with a retardation layer, wherein the protective layer includes a hard coat layer with a thickness of 5 μm or less. According to any one of claims 1 to 6,
A polarizing plate with a retardation layer, wherein the retardation layer is an alignment-fixed layer of a liquid crystal compound. According to any one of claims 1 to 7,
The protective layer is a polarizing plate with a retardation layer including a substrate having a moisture permeability of less than 200 g/m ² ·24h at 40°C and 92%RH. An image display device comprising the polarizing plate with a retardation layer according to any one of claims 1 to 8.

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