TWI855147B - Circular polarizing plate, laminate for flexible image display device containing the circular polarizing plate, and image dispaly device having the circular polarizing plate - Google Patents

Abstract

An object of the present invention is to provide a circular polarizing plate in which generation of crack in a liquid crystal cured retardation layer is suppressed and non-uniform hue in the plane of the circular polarizing plate is suppressed even after a thermal shock test is performed.

As a solution, the circular polarizing plate of the present invention includes: a linear polarizing plate having a polarizer and a polarizer protective layer having a thickness of 30 μm or less provided on at least one surface of the polarizer, and a liquid crystal cured retardation layer laminated on the linear polarizing plate via an adhesive layer, wherein after a thermal shock test is performed in a state in which an inorganic glass plate is bond to the liquid crystal cured retardation layer side of the circularly polarizing plate, the amount of displacement in the phase-advancing axis direction between the liquid crystal cured retardation layer and the polarizer at a peripheral portion as compared with that before the thermal impact test is 190 μm or less, provided that in the thermal impact test, an operation of cooling to -40℃ for 30 minutes and heating to 85℃ for 30 minutes is taken as 1 cycle, and the test is repeated for 300 cycles.

Description

Circular polarizing plate, multilayer body for flexible image display device including the circular polarizing plate, and image display device having the circular polarizing plate

The present invention relates to a circular polarizing plate, and also to an image display device including the circular polarizing plate and a multilayer body for a flexible image display device.

Patent document 1 proposes an optical laminate in which a linear polarizing plate having a protective polarizer film and an optically anisotropic layer are bonded together via an adhesive layer.

[Prior Art Literature] [Patent Literature]

[Patent document 1] Japanese Patent Publication No. 2019-7002

A linear polarizing plate with a polarizer protective layer having a thickness of less than 30μm and a circular polarizing plate with a liquid crystal hardened phase difference layer, when the liquid crystal hardened phase difference layer side of the circular polarizing plate is bonded to an inorganic glass plate, will produce cracks in the liquid crystal hardened phase difference layer or uneven color in the surface of the circular polarizing plate if a hot and cold shock test (hereinafter referred to as "hot and cold shock test") is performed. The hot and cold shock test is to cool to -40℃ for 30 minutes, then heat to 85℃ for 30 minutes as one cycle, and repeat the test 300 times.

The purpose of the present invention is to provide a circular polarizing plate that suppresses the occurrence of cracks in the liquid crystal curing phase difference layer and suppresses hue non-uniformity within the surface of the circular polarizing plate even after the above-mentioned hot and cold shock test.

The present invention provides the following aspects [1] to [7].

[1] A circular polarizing plate having:

A linear polarizing plate having a polarizer and a polarizer protective layer with a thickness of 30 μm or less disposed on at least one side of the polarizer; and

The liquid crystal hardened phase difference layer is laminated on the aforementioned linear polarizing plate via a bonding agent layer; wherein,

The aforementioned liquid crystal cured phase difference layer has a layer containing a cured material of a polymerizable liquid crystal compound;

After the hot and cold shock test was conducted with the liquid crystal hardened phase difference layer side of the circular polarizing plate attached to the inorganic glass plate, the displacement of the liquid crystal hardened phase difference layer at the periphery and the polarizer in the fast axis direction compared to before the hot and cold shock test was less than 190μm, wherein the hot and cold shock test was performed with cooling to -40℃ for 30 minutes and then heating to 85℃ for 30 minutes as one cycle, and the test was repeated 300 times.

[2] A circular polarizing plate having:

A linear polarizing plate having a polarizer and a polarizer protective layer with a thickness of 30 μm or less disposed on at least one side of the polarizer; and

The liquid crystal hardened phase difference layer is laminated on the aforementioned linear polarizing plate via a bonding agent layer; wherein,

In a state where the liquid crystal hardened phase difference layer side of the circularly polarizing plate is bonded to an inorganic glass plate, in a thermal shock test, the change in the reflected color difference (△ ₁ a * b * ) between the peripheral portion and the central portion after the thermal shock test relative to the reflected color difference (△ ₀ ^{a * b *} ) between the peripheral portion and ^the central portion before the thermal shock test is less than 0.65, wherein the thermal shock test is performed with one cycle of cooling to -40°C for 30 minutes and then heating to 85°C for 30 minutes, and the test is repeated 300 times.

[3] A circular polarizing plate comprising: a linear polarizing plate having a polarizer and a polarizer protective layer having a thickness of 30 μm or less and disposed on at least one side of the polarizer; and a liquid crystal curing phase difference layer laminated on the linear polarizing plate via an adhesive layer; wherein the storage elastic modulus of the adhesive layer is greater than 46,000 Pa.

[4] A circular polarizer as described in any one of [1] to [3], wherein in the linear polarizer, the polarizer protective layer is disposed on both sides of the polarizer.

[5] The circularly polarizing plate as described in any one of [1] to [4] further comprises a bonding layer on the outermost surface on the liquid crystal hardened phase difference layer side.

[6] A multilayer body for a flexible image display device, comprising a circular polarizer, a front panel and/or a touch sensor as described in any one of [1] to [5].

[7] An image display device comprising a circular polarizer as described in any one of [1] to [5].

According to the present invention, a circular polarizing plate can be provided, which can suppress the occurrence of cracks in the liquid crystal hardening phase difference layer and suppress the uneven color in the surface of the circular polarizing plate even after a hot and cold shock test.

10: Linear polarizing plate

11: Polarizer

12,13: Polarizer protective layer

20: Next is the agent layer

30,40,70: Liquid crystal hardening phase difference layer (phase difference layer)

41: 1st liquid crystal hardening phase difference layer (1st phase difference layer)

42: Second liquid crystal hardening phase difference layer (second phase difference layer)

50: Lamination layer

60: Linear polarizing plate

80:Front panel

81:Shading pattern

90: Touch sensor

100,200: Circular polarizing plate

300: Multilayer for flexible image display device

FIG1 is a schematic cross-sectional view of a circular polarizing plate according to one embodiment of the present invention.

FIG2 is a schematic cross-sectional view of a circular polarizing plate according to one embodiment of the present invention.

FIG3 is a schematic cross-sectional view of a multilayer body used in a flexible image display device according to one embodiment of the present invention.

Figure 4 shows the displacement of the fast axis and the measurement point of the reflected hue.

Figure 5 is an optical microscope photograph showing the deviation of the long side after the thermal shock test.

The following describes the implementation of the present invention with reference to the drawings, but the present invention is not limited to the following implementation. In order to facilitate the understanding of each component, all the following drawings are appropriately adjusted in scale, and the proportion of each component shown in the drawings is not necessarily the same as the proportion of the actual component.

〈Circular polarizing plate〉

FIG1 is a schematic cross-sectional view of a circular polarizing plate of one embodiment of the present invention. The circular polarizing plate 100 shown in FIG1 has a linear polarizing plate 10 and a liquid crystal curing phase difference layer (hereinafter also referred to as a phase difference layer) 30 laminated on the linear polarizing plate 10 via a bonding agent layer 20. The linear polarizing plate 10 has a polarizer 11 and a polarizer protective layer 12.

The phase difference layer 30 may be a layer including a layer providing a λ/4 phase difference, for example, it may be composed of only a layer providing a λ/4 phase difference, or it may be a layer obtained by laminating a combination of a layer providing a λ/4 phase difference and a layer providing a λ/2 phase difference and/or a positive C layer. As a laminate obtained by combining liquid crystal curing phase difference layers (hereinafter also referred to as a phase difference layer laminate), for example, a laminate of a layer providing a λ/4 phase difference and a layer providing a λ/2 phase difference, a laminate of a layer providing a λ/4 phase difference and a positive C layer, etc. By laminating the phase difference layer 30 including a layer that imparts a λ/4 phase difference on the linear polarizing plate 10, it can function as a circular polarizing plate.

The phase difference layer 30 can be laminated on the linear polarizer 10 in such a way that the slow axis of the layer imparting the λ/4 phase difference and the absorption axis of the polarizer 11 form a predetermined angle. For example, the angle between the slow axis of the layer imparting the λ/4 phase difference of the phase difference layer 30 and the absorption axis of the polarizer 11 can be 45°±10°.

In this specification, the so-called "layer that provides a λ/4 phase difference" refers to a phase difference layer that converts linear polarization of a specific wavelength into circular polarization (or converts circular polarization into linear polarization).

In this specification, the so-called "layer that provides a λ/2 phase difference" refers to a phase difference layer that converts the polarization direction of linear polarization of a specific wavelength into 90°.

In this specification, the so-called "positive C layer" refers to a layer that satisfies the relationship Nz>Nx≧ _Ny when the refractive index in the slow axis direction in the plane is _Nx , the refractive index in the fast axis direction in the plane is _Ny , and the refractive index in the thickness direction is _Nz . The difference between _{the value of Nx and} the _{value of Ny is} preferably within 0.5% of the value of _Ny , and more preferably within 0.3%. If it is within 0.5%, it can be regarded as _Nx = _Ny in essence.

In recent years, in order to reduce the thickness of circular polarizing plates, there are cases where a polarizing film protective layer with a thickness of less than 30μm is used in linear polarizing plates. When a circular polarizing plate composed of a linear polarizing plate including such a thin polarizing film protective layer and a liquid crystal curing phase difference layer is subjected to a hot and cold shock test, it is known that cracks may occur in the liquid crystal curing phase difference layer, or the color phase may be uneven within the surface of the circular polarizing plate. This is a new issue arising from the strong demand for thinner circular polarizing plates in recent years.

The inventors of the present invention have found that in hot and cold test environments, the stress caused by the expansion or contraction of the polarizer, which causes the deformation of the liquid crystal hardening phase difference layer, will act, thereby causing cracks in the liquid crystal hardening phase difference layer. In addition, the uneven hue within the circular polarizer surface is known to be caused by the expansion or contraction of the above-mentioned polarizer, which causes the change of the reflected hue of the peripheral part.

As a result of further research, it was found that when the displacement in the fast axis direction between the liquid crystal cured phase difference layer and the polarizer at the periphery of the circular polarizing plate after the hot and cold shock test (hereinafter referred to as "displacement in the fast axis direction") is less than 190μm, the phase difference layer can be suppressed from cracking even when the hot and cold test is performed, and the color unevenness in the circular polarizing plate surface can be suppressed. The so-called fast axis direction refers to the direction parallel to the fast axis direction of the phase difference layer 30 that imparts the λ/4 phase difference.

From the perspective of suppressing cracking of the liquid crystal hardening phase difference layer and suppressing hue non-uniformity in the circular polarizing plate surface, the displacement amount in the fast axis direction of the circular polarizing plate 100 is preferably 150 μm or less, more preferably 100 μm or less, more preferably 80 μm or less, particularly preferably 50 μm or less, and particularly preferably 20 μm or less. On the other hand, the displacement amount in the fast axis direction is usually 0 μm or more, for example, greater than 0 μm or 1 μm or more. The displacement amount in the fast axis direction can be measured according to the measurement method described in the column of the embodiment described later.

Furthermore, the inventors have found that, when the change in the reflected chromatic aberration (△ ₁ a ^* b ^* ) between the peripheral portion and the central portion after the above-mentioned hot and cold shock test relative to the reflected chromatic aberration (△ ₀ a ^* b ^* ) between the peripheral portion and the central portion before the above-mentioned hot and cold shock test (hereinafter referred to as "the change in reflected chromatic aberration") is 0.65 or less, cracking of the phase difference layer can be suppressed even after the above-mentioned hot and cold test, and hue non-uniformity within the surface of the circularly polarizing plate can be suppressed.

From the perspective of suppressing cracks in the liquid crystal hardening phase difference layer and suppressing hue non-uniformity in the circular polarizer surface, the change in the reflected hue difference of the circular polarizer 100 is preferably less than 0.5, and more preferably less than 0.45. The change in the reflected hue difference is usually greater than 0, for example greater than 0, or greater than 0.1. The change in the reflected hue difference can be measured according to the measurement method described in the column of the embodiment described later.

Furthermore, the inventors of the present invention have found that, in the circular polarizing plate constructed as described above, by controlling the storage elastic modulus of the adhesive layer between the linear polarizing plate and the liquid crystal curing phase difference layer, a circular polarizing plate can be obtained in which the displacement between the polarizing plate and the liquid crystal curing phase difference layer after the hot and cold shock test and the generation of cracks accompanying the phase difference and the change of the reflected hue are suppressed. That is, in the circular polarizing plate constructed as described above, by controlling the storage elastic modulus of the adhesive layer connected to the liquid crystal curing phase difference layer to be above 46000Pa, the idea of suppressing the stress applied to the liquid crystal curing phase difference layer is obtained, and the present invention is completed.

The circular polarizing plate 100 preferably has a storage elastic modulus of the bonding agent layer 20 of 50,000 Pa or more, and more preferably 100,000 Pa or more, from the viewpoint of suppressing cracking of the liquid crystal hardening phase difference layer and suppressing hue non-uniformity within the surface of the circular polarizing plate. The storage elastic modulus of the bonding agent layer 20 may be, for example, less than 5,000 MPa. The storage elastic modulus of the bonding agent layer 20 may be measured according to the measurement method described in the column of the embodiment described later.

As a method of setting the storage elastic modulus of the adhesive layer 20 to 46000 Pa or more, for example, a method of selecting the type of adhesive used in the adhesive layer 20, etc.

From the perspective of suppressing cracking of the liquid crystal hardening phase difference layer and suppressing hue non-uniformity within the circular polarizing plate surface, the circular polarizing plate 100 ideally satisfies at least two of the following (1) to (3), and more ideally satisfies all of (1) to (3).

(1) After the hot and cold shock test was performed with the liquid crystal hardened phase difference layer of the polarizing plate attached to the inorganic glass plate, the displacement of the peripheral liquid crystal hardened phase difference layer and the polarizing plate in the fast axis direction compared to before the hot and cold shock test was less than 190μm, wherein the hot and cold shock test was performed with cooling to -40℃ for 30 minutes and then heating to 85℃ for 30 minutes as one cycle, and the test was repeated 300 times;

(2) In a state where the liquid crystal hardened phase difference layer side of the polarizing plate is bonded to an inorganic glass plate, in a thermal shock test, the change in the reflected color difference (△ 1 a ^* b ^* ) between the peripheral portion and the central portion after the thermal shock test relative to the reflected color difference (△ ₀ a ^* b ^* ) before the thermal shock test is less than 0.65, wherein the thermal shock test is performed by cooling to -40°C for 30 minutes and then heating to 85°C for 30 minutes as one cycle, and the test is repeated 300 times;

(3) The storage elastic modulus of the adhesive layer is above 46000Pa.

The shape of the circular polarizing plate 100 when viewed from above may be, for example, a rectangular shape, preferably a rectangular shape having long sides and short sides, and more preferably a rectangular shape. In the case where the shape of the circular polarizing plate 100 when viewed from above is a rectangle, the length of the long side may be, for example, from 10 mm to 1400 mm, preferably from 50 mm to 600 mm, more preferably from 50 mm to 300 mm, and more preferably from 100 mm to 200 mm. The length of the short side may be, for example, from 5 mm to 800 mm, preferably from 10 mm to 500 mm, more preferably from 20 mm to 300 mm, and more preferably from 30 mm to 100 mm. In each layer constituting the circular polarizing plate 100, the corners may be rounded, and the ends may be notched or opened. In this specification, the term "top view" refers to observation from the thickness direction of the layer.

The upper limit of the thickness of the circular polarizing plate 100 may be, for example, 200 μm or less, preferably 180 μm or less, more preferably 150 μm or less, more preferably 120 μm or less, and particularly preferably 100 μm or less. The lower limit of the thickness of the circular polarizing plate 100 may be, for example, 10 μm or more, preferably 20 μm or more, more preferably 45 μm or more, and more preferably 60 μm or more.

FIG2 is a cross-sectional schematic diagram of another embodiment of the circular polarizing plate of the present invention. The circular polarizing plate 200 shown in FIG2 has a linear polarizing plate 10 and a liquid crystal curing phase difference layer 40 (hereinafter also referred to as the phase difference layer 40) laminated on the linear polarizing plate 10 via a bonding agent layer 20. The linear polarizing plate 10 has a polarizer protective layer 13, a polarizer 11, and a polarizer protective layer 12. The phase difference layer 40 is a phase difference layer laminated body having a first phase difference layer 41 and a second phase difference layer 42 laminated thereon. The circular polarizing plate 200 has a bonding layer 50 bonded to the side of the phase difference layer 40.

〈Linear polarizing plate〉

The linear polarizer 10 has a polarizer 11 and a polarizer protective layer 12 disposed on at least one side of the polarizer 11. In FIG1 , in the linear polarizer 10, the polarizer protective layer 12 is disposed only on one side of the polarizer 11, and the polarizer protective layer 12 is disposed on the side of the polarizer 11 opposite to the phase difference layer 30. However, the polarizer protective layer may also be disposed on the phase difference layer 30 side of the polarizer 11. As shown in FIG2 , the polarizer protective layer 12 and the polarizer protective layer 13 may be disposed on both sides of the polarizer 11. In FIG2 , the polarizer protective layer 12 and the polarizer protective layer 13 may be the same type of thermoplastic resin film, or may be different types of thermoplastic resin films. The linear polarizing plate 10 may further include a substrate, an alignment film, and a protective layer as described below.

The polarizer protective layer is used to protect the polarizer, especially the surface of the polarizer. The polarizer protective layer is only separated by an adhesive layer or directly configured on one side or both sides of the polarizer.

The thickness of the linear polarizer 10 is, for example, greater than 2 μm and less than 100 μm, and preferably greater than 10 μm and less than 60 μm.

〈Polarizing film〉

As the polarizer 11, for example, a stretched film or stretched layer adsorbed with a pigment having absorption anisotropy, or a film coated with a pigment having absorption anisotropy and hardened. As the pigment having absorption anisotropy, for example, a dichroic pigment is used. As the dichroic pigment, iodine and dichroic organic dyes are specifically used. The dichroic organic dyes include dichroic direct dyes containing diazo compounds such as C.I.DIRECT RED39, and dichroic direct dyes containing triazo, tetrakisazo and other compounds.

As a film coated with a dye having absorption anisotropy and then cured, for example, a layer obtained by coating a composition containing a dichroic dye having liquid crystal properties or a composition containing a dichroic dye and polymerizable liquid crystal and then curing it, a film containing a cured product of a polymerizable liquid crystal compound, etc.

(1) A polarizer having a stretched film or stretched layer adsorbed with a pigment having absorption anisotropy

First, a polarizer having a stretched film adsorbed with a dye having absorption anisotropy (hereinafter also referred to as "stretched film") is described. A stretched film adsorbed with a dye having absorption anisotropy can usually be manufactured by the following steps: a step of uniaxially stretching a polyvinyl alcohol resin film; a step of dyeing the polyvinyl alcohol resin film with a dichroic dye so that it adsorbs the dichroic dye; a step of treating the polyvinyl alcohol resin film adsorbed with the dichroic dye with a boric acid aqueous solution; and a step of washing the film with water after the treatment with the boric acid aqueous solution. The polarizer protective layer 12 described later is bonded to one or both sides of the polarizer, and can be used as a linear polarizer 10. The thickness of the polarizer is preferably not less than 2μm and not more than 40μm.

Polyvinyl alcohol resins can be obtained by saponifying polyvinyl acetate resins. As polyvinyl acetate resins, in addition to polyvinyl acetate which is a homopolymer of vinyl acetate, copolymers of vinyl acetate and other monomers copolymerizable with the vinyl acetate can be used. Other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, or (meth)acrylamides having an ammonium group.

The saponification degree of polyvinyl alcohol resin is usually 85 to 100 mol%, preferably 98 mol% or more. Polyvinyl alcohol resin can be modified, for example, polyvinyl formal and polyvinyl acetaldehyde modified by aldehydes can be used. The polymerization degree of polyvinyl alcohol resin is usually 1000 to 10000, preferably 1500 to 5000.

The polyvinyl alcohol resin can be used as a raw material film for a polarizer. The method for making a polyvinyl alcohol resin film is not particularly limited, and the film can be made by a known method. The film thickness of the polyvinyl alcohol raw material film can be, for example, about 10 to 150 μm.

The uniaxial stretching of the polyvinyl alcohol resin film can be performed before, at the same time as, or after dyeing with a dichroic dye. When the uniaxial stretching is performed after dyeing, the uniaxial stretching can be performed before or during the boric acid treatment. Furthermore, the uniaxial stretching can be performed in these multiple stages. During the uniaxial stretching, the uniaxial stretching can be performed between rollers with different rotation speeds, or using a hot roller. Furthermore, the uniaxial stretching can be dry stretching performed in the atmosphere, or wet stretching performed using a solvent while the polyvinyl alcohol resin film is swollen. The stretching ratio is usually about 3 to 8 times.

The polyvinyl alcohol resin film can be dyed with a dichroic dye, for example, by immersing the polyvinyl alcohol resin film in an aqueous solution containing a dichroic dye. As the dichroic dye, iodine or a dichroic organic dye is specifically used. The dichroic organic dye includes a dichroic direct dye containing a diazo compound such as C.I.DIRECT RED39, and a dichroic direct dye containing a triazo, tetrakisazo, and other compounds. It is ideal to immerse the polyvinyl alcohol resin film in water before dyeing.

When iodine is used as a dichroic pigment, a method is usually adopted in which a polyvinyl alcohol resin film is immersed in an aqueous solution containing iodine and potassium iodide. The iodine content of the aqueous solution is usually about 0.01 to 1 mass part per 100 mass parts of water. In addition, the potassium iodide content is usually about 0.5 to 20 mass parts per 100 mass parts of water. The temperature of the aqueous solution used for dyeing is usually about 20 to 40°C. And the immersion time in the aqueous solution (dyeing time) is usually about 20 to 1,800 seconds.

On the other hand, when using dichroic organic dyes as dichroic pigments, a method is usually adopted in which a polyvinyl alcohol-based resin film is immersed in an aqueous solution containing a water-soluble dichroic dye. The content of the dichroic organic dye in the aqueous solution is usually about 1× ^10-4 to 10 parts by mass, preferably 1× ^10-3 to 1 part by mass, and more preferably 1× ^10-3 to 1× ^10-2 parts by mass per 100 parts by mass of water. The aqueous solution may also contain an inorganic salt such as sodium sulfate as a dyeing auxiliary. The temperature of the dichroic dye aqueous solution used for dyeing is usually about 20 to 80°C. Moreover, the immersion time (dyeing time) in the aqueous solution is usually 10 to 1,800 seconds.

The boric acid treatment after dyeing with a dichroic dye can be performed by immersing the dyed polyvinyl alcohol-based resin film in an aqueous boric acid solution. The content of boric acid in the aqueous boric acid solution is generally about 2 to 15 parts by mass, preferably 5 to 12 parts by mass, per 100 parts by mass of water. In the case of using iodine as the dichroic dye, the aqueous boric acid solution preferably contains potassium iodide, and the content of potassium iodide in this case is generally about 0.1 to 15 parts by mass, preferably 5 to 12 parts by mass, per 100 parts by mass of water. The immersion time in the aqueous boric acid solution is generally about 60 to 1,200 seconds, preferably 150 to 600 seconds, and more preferably 200 to 400 seconds. The temperature of boric acid treatment is usually above 50°C, preferably 50 to 85°C, and more preferably 60 to 80°C.

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

After washing, drying is performed to obtain a polarizer. Drying treatment can be performed using, for example, a hot air dryer or a far infrared heater. The temperature of the drying treatment is usually about 30 to 100°C, and preferably 50 to 80°C. The drying treatment time is usually about 60 to 600 seconds, and preferably 120 to 600 seconds. Through the drying treatment, the moisture content of the polarizer is reduced to a practical level. The moisture content is usually 5 to 20% by mass, and preferably 8 to 15% by mass. When the moisture content is lower than 5% by mass, the polarizer loses its flexibility, and the polarizer is damaged or cracked after drying. Moreover, when the moisture content is higher than 20% by mass, the thermal stability of the polarizing film tends to deteriorate.

As described above, the thickness of the polarizer obtained by uniaxially stretching the polyvinyl alcohol resin film, dyeing it with a dichroic pigment, treating it with boric acid, washing it with water and drying it is ideally 5 to 40 μm.

Next, a polarizer having a stretched layer adsorbed with a dye having absorption anisotropy (hereinafter also referred to as a "stretched layer") is described. The stretched layer adsorbed with a dye having absorption anisotropy can be generally manufactured by the following steps: a step of applying a coating liquid containing the above-mentioned polyvinyl alcohol-based resin on a substrate; a step of uniaxially stretching the obtained laminated film; a step of dyeing the polyvinyl alcohol-based resin layer of the uniaxially stretched laminated film with a dichroic dye to make it adsorb the dichroic dye to make a polarizer; a step of treating the film adsorbed with the dichroic dye with an aqueous boric acid solution; and a step of washing with water after the treatment with an aqueous boric acid solution.

As an example of a substrate film, the example of the polarizer protective layer 12 described later can be applied. The substrate film can be peeled off from the polarizer, and the substrate film can be used as the polarizer protective layer 12. The thickness of the substrate film can be, for example, 5 μm to 200 μm. When the substrate is assembled in a circular polarizer, the thickness of the substrate is preferably 30 μm or less.

(2) Polarizer coated with a film that has anisotropically absorbing pigment and hardened

A polarizer having a film coated with a dye having anisotropic absorption and cured is described. The film coated with a dye having anisotropic absorption and cured is, for example, a film obtained by coating a composition containing a dichroic dye having liquid crystal properties or a composition containing a dichroic dye and a liquid crystal compound on a substrate and curing it. The film can be used as a linear polarizer 10 after peeling off the substrate or used as a linear polarizer 10 together with the substrate, and can also be used as a linear polarizer 10 with a polarizer protective layer on only one side or on both sides.

As an example of a substrate, the following polarizer protective layer 12 can be used. The substrate can be peeled off from the polarizer, and the substrate film can also be used as the polarizer protective layer 12. The thickness of the substrate can be, for example, 5 μm or more and 200 μm or less. In the case where the substrate is assembled on a circular polarizer, the thickness of the substrate is preferably 30 μm or less. The substrate can have a hard coating layer, an anti-reflection layer, or an anti-static layer on at least one side. The substrate can also form a hard coating layer, an anti-reflection layer, an anti-static layer, etc. only on the surface of the side where the polarizer is not formed. The substrate can also form a hard coating layer, an anti-reflection layer, an anti-static layer, etc. only on the surface of the side where the polarizer is formed.

The film hardened by applying anisotropically absorbing pigments is ideally thin, but if it is too thin, the strength will decrease and the processability tends to deteriorate. The thickness of the film is usually less than 20μm, preferably less than 5μm, and more preferably more than 0.5μm and less than 3μm.

As a film hardened by applying a dye having absorption anisotropy, specifically, it is described in Japanese Patent Publication No. 2013-37353 and Japanese Patent Publication No. 2013-33249.

(Alignment film)

The alignment film can be arranged between the above-mentioned substrate and a layer of a cured product containing a composition of a dichroic pigment with liquid crystal properties or a composition containing a dichroic pigment and a liquid crystal compound. The alignment film has an alignment control force that allows the liquid crystal layer formed thereon to align the liquid crystal in the desired direction. As an alignment film, for example, an alignment polymer layer formed by an alignment polymer, a photoalignment polymer layer formed by a photoalignment polymer, and a groove alignment film having a concave-convex shape or a plurality of grooves (grooves) on the surface of the layer. The thickness of the alignment film can be, for example, more than 10nm and less than 500nm, and preferably more than 10nm and less than 200nm.

The composition of the alignment polymer dissolved in the solvent is applied to the substrate and the solvent is removed, and a friction treatment is performed as needed to form an alignment polymer layer. In this case, in the alignment polymer layer formed by the alignment polymer, the alignment control force can be arbitrarily adjusted by the surface state of the alignment polymer and the friction conditions.

The photo-aligned polymer layer can be formed by applying a composition containing a polymer or monomer having a photoreactive group and a solvent to a base layer and irradiating it with polarized light. In this case, the alignment control force in the photo-aligned polymer layer can be arbitrarily adjusted by, for example, the polarized light irradiation conditions for the aligning polymer.

The groove alignment film can be formed by the following methods, for example: a method of forming a concave-convex pattern by exposing and developing the surface of a photosensitive polyimide film through an exposure mask having a slit in a pattern shape; a method of forming an uncured layer of an active energy ray-curable resin on a plate-shaped master having grooves on the surface, and transferring the layer to a substrate for curing; a method of forming an uncured layer of an active energy ray-curable resin on a substrate, pressing a roll-shaped master having concave-convex patterns into the layer, and then curing the layer, etc.

〈Polarizer protective layer〉

The polarizer protective layer is a layer used to protect the polarizer 11, especially the surface of the polarizer 11. As the polarizer protective layer, for example, a thermoplastic resin film as a material of the polarizer protective layer 12 described later is exemplified. As the polarizer protective layer, for example, a coating type polarizer protective layer is used. The coating type polarizer protective layer may be, for example, a layer obtained by coating and curing a coating composition such as a composition used for the hard coating layer described later, a cation-curable composition such as an epoxy resin, a radical-curable composition such as a (meth)acrylate, etc. The coating type polarizer protective layer can also be the following layer: using an aqueous solution of polyvinyl alcohol resin as a coating composition, coating it on the surface of the polarizer, and forming a layer by drying. The coating composition may include plasticizers, ultraviolet absorbers, infrared absorbers, colorants such as pigments and dyes, fluorescent whitening agents, dispersants, heat stabilizers, light stabilizers, antistatic agents, antioxidants, lubricants, etc. as needed.

When the polarizer protective layer is a coated polarizer protective layer, its thickness can be, for example, less than 30 μm, preferably less than 25 μm, more preferably less than 20 μm, more preferably less than 15 μm, and particularly more preferably less than 10 μm. The thickness of the protective layer is, for example, greater than 0.1 μm.

(Thermoplastic resin film)

Thermoplastic resin films can be used as polarizer protective layers 12 and 13, and can be assembled on the linear polarizer 10 in the form of being attached to one or both sides of the polarizer 11. The thermoplastic resin film can be, for example, a light-transmitting (ideally optically transparent) thermoplastic resin film, such as: polyolefin resins such as chain polyolefin resins (polyethylene resins, polypropylene resins, polymethylpentene resins, etc.), cyclic polyolefin resins (norbornene resins, etc.); cellulose resins such as triacetyl cellulose; polyester resins such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate; polybutylene terephthalate; Carbonate resins; ethylene-vinyl acetate resins; polystyrene resins; polyamide resins; polyetherimide resins; (meth)acrylic resins such as poly(methyl)acrylate resins; polyimide resins; polyethersulfone resins; polysulfone resins; polyvinyl chloride resins; polyvinylidene chloride resins; polyvinyl alcohol resins; polyvinyl acetal resins; polyetherketone resins; polyetheretherketone resins; polyethersulfone resins; polyamideimide resins, etc. Thermoplastic resins may be used alone or in combination of two or more. Among them, from the perspective of strength and light transmittance, triacetyl cellulose resin films, cyclic polyolefin resin films, and (meth) acrylic resin films are more ideal.

Thermoplastic resin film can function not only as a film for protecting polarizers, but also as a phase difference film. On the surface of the thermoplastic resin film opposite to the polarizer, a surface treatment layer (coating layer) such as a hard coating layer, an anti-reflection layer, or an anti-static layer can be formed.

By providing a hard coating layer on a thermoplastic resin film, a resin film with improved hardness and scratch resistance can be obtained. The hard coating layer can be formed by a hardened material of a hard coating layer forming composition containing an active energy ray-curing resin. Examples of UV-curing resins include acrylic resins, silicone resins, polyester resins, urethane resins, amide resins, and epoxy resins. In order to increase strength, the hard coating layer may contain additives. There are no particular restrictions on additives, such as inorganic microparticles, organic microparticles, or a mixture thereof.

When the polarizer protective layer is a thermoplastic resin film, its thickness is 30μm or less. From the perspective of thinning, it is preferably 25μm or less, more preferably 20μm or less, and usually 1μm or more, preferably 5μm or more, and more preferably 15μm or more. Thermoplastic resin films may or may not have a phase difference.

As the adhesive used for bonding the polarizer 11 to the thermoplastic resin film, for example, an active energy ray-hardening adhesive such as an ultraviolet-hardening adhesive, an aqueous solution of a polyvinyl alcohol-based resin or an aqueous solution containing a crosslinking agent, and a water-based adhesive such as an urethane-based emulsified adhesive. When bonding the thermoplastic resin film to both sides of the polarizer 11, the adhesives forming the two adhesive layers may be of the same type or different types. For example, when bonding the thermoplastic resin film to both sides, a water-based adhesive may be used for bonding on one side and an active energy ray-hardening adhesive may be used for bonding on the other side. The UV curable adhesive may be a mixture of a free radical polymerizable (meth) acrylic compound and a photo radical polymerization initiator, a mixture of a cation polymerizable epoxy compound and a photo cationic polymerization initiator, etc. Moreover, a cation polymerizable epoxy compound and a free radical polymerizable (meth) acrylic compound may be used together, and a photo cationic polymerization initiator and a photo radical polymerization initiator may be used together as initiators.

When using an active energy ray-curable adhesive, after lamination, the adhesive is cured by irradiating the active energy ray. The light source of the active energy ray is not particularly limited, but preferably, it is an active energy ray (ultraviolet ray) having a luminescence distribution below a wavelength of 400nm. Specifically, it is more preferable to use a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a chemical lamp, a black light lamp, a microwave-excited mercury lamp, a metal halide lamp, etc.

In order to improve the adhesion between the polarizer 11 and the thermoplastic resin film, before laminating the polarizer 11 and the thermoplastic resin film, the laminating surface of the polarizer 11 and/or the thermoplastic resin film may be subjected to surface treatments such as corona treatment, flame treatment, plasma treatment, ultraviolet irradiation treatment, primer coating treatment, and saponification treatment.

〈Liquid crystal hardening phase difference layer〉

The phase difference layer 30 is composed of a layer of a cured product containing a polymerizable liquid crystal compound. The phase difference layer 30 is preferably a layer of a cured product containing a polymer obtained by polymerizing the polymerizable liquid crystal compound in an aligned state. The phase difference layer 30 may have an alignment layer and/or a substrate described below, or may have two or more layers of a liquid crystal cured phase difference layer, an alignment layer and/or a substrate. In the case where the phase difference layer 30 has a substrate, the substrate is usually removed when the phase difference layer 30 is attached to a linear polarizer.

A polymerizable liquid crystal compound is a compound that has a polymerizable group and can be in a liquid crystal state. The polymerizable groups of the polymerizable liquid crystal compound react with each other to polymerize the polymerizable liquid crystal compound, and the polymerizable liquid crystal compound hardens.

(Base material)

The layer containing the cured product of the polymerizable liquid crystal compound can be formed, for example, on the alignment layer provided on the substrate. The aforementioned substrate can be a substrate having the function of supporting the alignment layer and formed in a strip shape. The substrate can function as a releasable support body to support the phase difference layer and the alignment layer for transfer. Furthermore, it is more desirable that the surface has a degree of adhesion that can be peeled off. The substrate may be, for example, a film made of the following resins: a light-transmitting (ideally optically transparent) thermoplastic resin, such as a polyolefin resin such as a chain polyolefin resin (such as a polypropylene resin) or a cyclic polyolefin resin (such as a norbornene resin); a cellulose resin such as triacetyl cellulose or diacetyl cellulose; a polyester resin such as polyethylene terephthalate or polybutylene terephthalate; a polycarbonate resin; or a methyl acrylate resin. (Meth) acrylic resins of methyl acrylate resins; polystyrene resins; polyvinyl chloride resins; acrylonitrile/butadiene/styrene resins; acrylonitrile/styrene resins; polyvinyl acetate resins; polyvinylidene chloride resins; polyamide resins; polyacetal resins; modified polyphenylene ether resins; polysulfide resins; polyethersulfone resins; polyarylate resins; polyamide imide resins; polyimide resins; maleimide resins, etc.

Furthermore, the substrate can be subjected to various anti-sticking treatments. Examples of anti-sticking treatments include easy-to-attach treatment, treatments such as mixing fillers, embossing treatments (rolling treatments), etc. By subjecting the substrate to such anti-sticking treatments, adhesion of the substrates to each other, i.e., so-called adhesion, can be effectively prevented when the substrate is rolled up, which tends to improve productivity.

(Orientation layer)

The layer containing the cured polymerizable liquid crystal compound can be formed on the substrate via the alignment layer. That is, the substrate and the alignment layer are sequentially stacked, and the layer containing the cured polymerizable liquid crystal compound is stacked on the alignment layer.

Furthermore, the alignment layer is not limited to a vertical alignment layer, and can be an alignment layer that aligns the molecular axes of the polymerizable liquid crystal compound horizontally, or an alignment layer that aligns the molecular axes of the polymerizable liquid crystal compound obliquely. As an alignment layer, it is ideal to have solvent resistance that will not be dissolved by the coating of the composition containing the polymerizable liquid crystal compound described later, and to have heat resistance in heat treatment for solvent removal and alignment of the liquid crystal compound. As an alignment layer, for example, an alignment layer containing an alignment polymer, a photoalignment film, and a groove alignment layer having a concave-convex pattern or a plurality of grooves formed on the surface. The thickness of the alignment layer is usually in the range of 10 nm to 10000 nm.

Furthermore, the alignment layer can have the function of supporting the liquid crystal layer and function as a releasable support. It can support the liquid crystal layer for transfer, and its surface can have a degree of adhesion that allows it to be peeled off.

As the resin used for the alignment layer, a resin obtained by polymerizing a polymerizable compound can be used. The polymerizable compound is a compound having a polymerizable group, and is usually a non-liquid crystal polymerizable non-liquid crystal compound that does not become a liquid crystal state. The polymerizable groups of the polymerizable compound react with each other to polymerize the polymerizable compound to form a resin. As such a resin, in the formation stage of the liquid crystal layer, an alignment layer is used to align the polymerizable liquid crystal compound. If it is not included in the liquid crystal layer, as long as the material of the known alignment layer is used, there is no particular limitation, and a cured product obtained by curing a conventionally known monofunctional or polyfunctional (meth)acrylate monomer under a polymerization initiator can be used. Specifically, as (meth)acrylate monomers, for example, 2-ethylhexyl acrylate, cyclohexyl acrylate, diethylene glycol mono-2-ethylhexyl ether acrylate, diethylene glycol monophenyl ether acrylate, tetraethylene glycol monophenyl ether acrylate, trihydroxymethylpropane triacrylate, lauryl acrylate, lauryl methacrylate, isoborneol acrylate, isoborneol methacrylate, 2-phenoxyethyl acrylate, tetrahydrofuranyl methyl acrylate, 2-hydroxypropyl acrylate, benzyl acrylate, tetrahydrofuranyl methyl methacrylate, 2-hydroxyethyl methacrylate, benzyl methacrylate, cyclohexyl methacrylate, methacrylic acid, urethane methacrylate, etc. Furthermore, the resin may be one of the above or a mixture of two or more.

After the phase difference layer 30 is formed, the alignment layer can be peeled off together with the substrate before or after the step of laminating with the linear polarizer 30.

Furthermore, in order to improve the releasability from the substrate and to impart strength to the liquid crystal layer, the liquid crystal layer may include an alignment layer. When the liquid crystal layer includes an alignment layer, a cured product obtained by curing a monofunctional or bifunctional (meth)acrylate monomer, an imide monomer, or a vinyl ether monomer is preferably used as the resin used for the alignment layer.

As a monofunctional (meth)acrylate monomer, for example, (meth)acrylate alkyl esters with carbon numbers of 4 to 16, (meth)acrylate β-carboxyl alkyl esters with carbon numbers of 4 to 14, (meth)acrylate alkyl phenyl esters with carbon numbers of 2 to 14, methoxy polyethylene glycol (meth)acrylate, phenoxy polyethylene glycol (meth)acrylate, and isoborneol (meth)acrylate, etc.

As a bifunctional (meth)acrylate monomer, for example: 1,3-butanediol di(meth)acrylate: 1,3-butanediol (meth)acrylate; 1,6-hexanediol di(meth)acrylate; ethylene glycol di(meth)acrylate; diethylene glycol di(meth)acrylate; neopentyl glycol di(meth)acrylate; triethylene glycol di(meth)acrylate; tetraethylene glycol di(meth)acrylate; polyethylene glycol diacrylate; bis(acryloyloxyethyl) ether of bisphenol A; ethoxylated bisphenol A di(meth)acrylate; propoxylated neopentyl glycol di(meth)acrylate; ethoxylated neopentyl glycol di(meth)acrylate and 3-methylpentanediol di(meth)acrylate, etc.

Moreover, the imide resin obtained by curing the imide monomer includes polyamide, polyimide, etc. Furthermore, the imide resin may be one of the above or a mixture of two or more.

Furthermore, the resin forming the alignment layer may contain monomers other than monofunctional or difunctional (meth)acrylate monomers, imide monomers, and vinyl ether monomers, and the content ratio of monofunctional or difunctional (meth)acrylate monomers, imide monomers, and vinyl ether monomers in all monomers may be 50% by mass or more, preferably 55% by mass or more, and more preferably 60% by mass or more.

In the case where the alignment layer is included in the phase difference layer 30, the thickness of the alignment layer is usually in the range of 10nm to 10000nm. In the case where the alignment of the phase difference layer 30 is in-plane alignment relative to the film surface, the thickness of the alignment layer is preferably 10nm to 1000nm. In the case where the alignment of the phase difference layer 30 is vertical alignment relative to the film surface, the thickness of the alignment layer is preferably 100nm to 10000nm. When the thickness of the phase difference layer 30 is within the above range, the substrate can be given improved releasability and appropriate film strength.

(Polymerizable liquid crystal compound)

There are no special restrictions on the types of polymerizable liquid crystal compounds. Based on their shapes, they can be classified into rod-shaped (rod-shaped liquid crystal compounds) and disc-shaped (disc-shaped liquid crystal compounds, disc-shaped liquid crystal compounds). Furthermore, there are low-molecular-weight and high-molecular-weight types. Furthermore, the so-called polymer generally refers to a polymer with a degree of polymerization of 100 or more (Polymer Physics/Phase Change Kinetics, written by Masao Doi, page 2, Iwanami Shoten, 1992).

Any polymerizable liquid crystal compound can also be used in this embodiment. Furthermore, two or more rod-shaped liquid crystal compounds, two or more disc-shaped liquid crystal compounds, or a mixture of rod-shaped liquid crystal compounds and disc-shaped liquid crystal compounds can be used.

Furthermore, as a rod-shaped liquid crystal compound, for example, the compound described in claim 1 of Japanese Patent Publication No. 11-513019 can be suitably used. As a disc-shaped liquid crystal compound, for example, the compound described in paragraphs [0020] to [0067] of Japanese Patent Publication No. 2007-108732 or paragraphs [0013] to [0108] of Japanese Patent Publication No. 2010-244038 can be suitably used.

Two or more polymerizable liquid crystal compounds may be used together. In this case, at least one of them has two or more polymerizable groups in the molecule. That is, it is more ideal that the layer of the polymerizable liquid crystal compound hardened is a layer fixed by polymerization of the liquid crystal compound having a polymerizable group. In this case, it is no longer necessary to show liquid crystal properties after forming the layer.

The polymerizable liquid crystal compound has a polymerizable group that can undergo polymerization reaction. As the polymerizable group, functional groups that can undergo addition polymerization reaction, such as polymerizable ethylenic unsaturated groups and cyclic polymerizable groups, are more ideal. More specifically, as the polymerizable group, for example, (meth)acryl, vinyl, styrene, allyl, etc. are examples. Among them, (meth)acryl is more ideal. Furthermore, the so-called (meth)acryl refers to the concept of including methacryl and acryl.

The liquid crystal properties of polymerizable liquid crystal compounds can be thermotropic liquid crystals or lyotropic liquid crystals. When thermotropic liquid crystals are classified by their degree of alignment, they can be nematic liquid crystals or lamellar liquid crystals.

The layer of the cured material containing the polymerizable liquid crystal compound can be formed by applying a composition containing the polymerizable liquid crystal compound (hereinafter also referred to as a phase difference layer forming composition) on, for example, an alignment layer, and irradiating the composition with active energy rays, as described later. The phase difference layer forming composition may contain components other than the above-mentioned polymerizable liquid crystal compound. For example, it is more desirable for the phase difference layer forming composition to contain a polymerization initiator. The polymerization initiator used is selected, for example, from a thermal polymerization initiator or a photopolymerization initiator, depending on the type of polymerization reaction. For example, as a photopolymerization initiator, a combination of α-carbonyl compounds, acyloin ethers, α-alkyl substituted aromatic acyloin compounds, polynuclear quinone compounds, triaromatic imidazole dimers, and para-aminophenyl ketones can be used. The amount of the polymerization initiator used is preferably 0.01 mass % to 20 mass % relative to the total solids in the aforementioned coating liquid, and more preferably 0.5 mass % to 5 mass %. Furthermore, the so-called "hardened material" refers to the state in which the formed layer will not deform or flow when alone and can exist independently.

Furthermore, from the perspective of uniformity of the coating film and strength of the film, the phase difference layer forming composition may also contain a polymerizable monomer. As a polymerizable monomer, for example, a free radical polymerizable or cationic polymerizable compound. Among them, a polyfunctional free radical polymerizable monomer is more desirable.

Furthermore, as a polymerizable monomer, it is more ideal to be copolymerizable with the above-mentioned polymerizable liquid crystal compound. The amount of the polymerizable monomer used is preferably 1% by mass to 50% by mass, and more preferably 2% by mass to 30% by mass, relative to the total mass of the polymerizable liquid crystal compound.

Furthermore, from the perspective of uniformity of the coating film and strength of the film, the phase difference layer forming composition may also contain a surfactant. As the surfactant, for example, conventionally known compounds are used. Among them, fluorine compounds are particularly preferred.

Furthermore, the phase difference layer forming composition may also contain a solvent, and an organic solvent is preferably used. Examples of organic solvents include amides (e.g., N,N-dimethylformamide), sulfones (e.g., dimethylsulfone), heterocyclic compounds (e.g., pyridine), hydrocarbons (e.g., benzene, hexane), halides (e.g., chloroform, dichloromethane), esters (e.g., methyl acetate, ethyl acetate, butyl acetate), ketones (e.g., acetone, methyl ethyl ketone), and ethers (e.g., tetrahydrofuran, 1,2-dimethoxyethane). Among them, halides and ketones are more ideal. Furthermore, two or more organic solvents may be used in combination.

Moreover, the phase difference layer forming composition may include vertical alignment promoters such as vertical alignment agents on the interface side of the polarizer and vertical alignment agents on the interface side of the air, and various alignment promoters such as horizontal alignment agents on the interface side of the polarizer and horizontal alignment agents on the interface side of the air. Furthermore, in addition to the above-mentioned components, the phase difference layer forming composition may also include adhesive modifiers, plasticizers, polymers, etc.

The above-mentioned active energy rays include ultraviolet rays, visible light, electron rays, and X-rays, and ultraviolet rays are more preferred. As the light source of the above-mentioned active energy rays, for example, low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, xenon lamps, halogen lamps, carbon arc lamps, tungsten lamps, gallium lamps, excimer lasers, LED light sources emitting in the wavelength range of 380 to 440nm, chemical lamps, black light lamps, microwave-excited mercury lamps, metal halide lamps, etc.

The irradiation intensity of ultraviolet light is usually 100 mW/ ^cm2 to 3,000 mW/ ^cm2 in the case of ultraviolet B wave (wavelength range of 280 nm to 310 nm). The irradiation intensity of ultraviolet light is preferably an intensity in the wavelength range effective for the activation of cationic polymerization initiators or radical polymerization initiators. The irradiation time of ultraviolet light is usually 0.1 second to 10 minutes, preferably 0.1 second to 5 minutes, more preferably 0.1 second to 3 minutes, and even more preferably 0.1 second to 1 minute.

The ultraviolet rays may be irradiated once or in multiple times. Although it depends on the polymerization initiator used, the accumulated light amount at a wavelength of 365nm is preferably 700mJ/ ^cm2 or more, more preferably 1,100mJ/ ^cm2 or more, and more preferably 1,300mJ/ ^cm2 or more. The above accumulated light amount is beneficial to increase the polymerization rate of the polymerizable liquid crystal compound constituting the liquid crystal layer and improve the heat resistance. The accumulated light amount at a wavelength of 365nm is preferably 2,000mJ/cm2 or ^less , and more preferably 1,800mJ/cm2 or ^less . The above accumulated light amount may cause coloring of the liquid crystal layer.

In this embodiment, the thickness of the phase difference layer 30 is preferably 0.5 μm or more. Moreover, the thickness of the phase difference layer 30 is preferably 10 μm or less, and more preferably 5 μm or less. Furthermore, the upper limit and lower limit values mentioned above can be combined arbitrarily, and when the thickness of the phase difference layer 30 is above the aforementioned lower limit, sufficient durability can be obtained. When the thickness of the phase difference layer 30 is below the aforementioned upper limit, it can contribute to the thinning of the circular polarizing plate 100. The thickness of the phase difference layer 30 can be adjusted so that the layer with a λ/4 phase difference, the layer with a λ/2 phase difference, or the positive C layer can obtain the desired in-plane phase difference value and the phase difference value in the thickness direction.

The phase difference layer 30 may include a plurality of liquid crystal curing phase difference layers having different phase difference characteristics which are respectively laminated. Each liquid crystal curing phase difference layer may be laminated using an adhesive, or a composition including a polymerizable liquid crystal compound may be coated on the surface of the already formed liquid crystal layer to cure it.

(Phase difference layered structure)

The phase difference layer 40 included in the circular polarizing plate 200 shown in FIG2 is a phase difference layer stack including a first liquid crystal hardened phase difference layer 41 (hereinafter also referred to as the first phase difference layer 41) and a second liquid crystal hardened phase difference layer 42 (hereinafter also referred to as the second phase difference layer 42). The first phase difference layer 41 and the second phase difference layer 42 can be a layer providing a λ/2 phase difference, a layer providing a λ/4 phase difference, or a positive C layer. In the phase difference layer 40, it is preferable that either the first phase difference layer 41 or the second phase difference layer 42 functions as a layer that imparts a λ/4 phase difference, while the other functions as a layer that imparts a λ/2 phase difference, or either the first phase difference layer 41 or the second phase difference layer 42 functions as a layer that imparts a λ/4 phase difference, while the other functions as a positive C layer. Therefore, the thickness of the first phase difference layer 41 and the second phase difference layer 42 and the materials constituting them can be adjusted so that the layer that imparts a λ/4 phase difference, the layer that imparts a λ/2 phase difference, or the positive C layer obtains the desired in-plane phase difference value and the phase difference value in the thickness direction.

In the case where the first phase difference layer 41 functions as a layer that imparts a λ/2 phase difference, and the second phase difference layer 42 functions as a layer that imparts a λ/4 phase difference, the thickness of the first phase difference layer 41 is, for example, 1 μm to 10 μm, and the thickness of the second phase difference layer 42 is, for example, 1 μm to 10 μm. In the case where the first phase difference layer 41 functions as a layer that imparts a λ/2 phase difference, and the second phase difference layer 42 functions as a positive C layer, the thickness of the first phase difference layer 41 is, for example, 1 μm to 10 μm, and the thickness of the second phase difference layer 42 is, for example, 1 μm to 10 μm.

The transparent substrate, alignment layer and liquid crystal compound used in the formation of the first phase difference layer 41 and the second phase difference layer 42 can be the same as those exemplified in the above phase difference layer 30. The composition of the first phase difference layer 41 and the second phase difference layer 42 can be the same or different.

The first phase difference layer 41 and the second phase difference layer 42 can be laminated in the order of transparent substrate, alignment layer and phase difference layer, respectively, similarly to the description of the above phase difference layer 3. The transparent substrate and alignment layer can be peeled off and assembled to the circular polarizing plate. The transparent substrate is usually peeled off and removed when the phase difference layer laminate is assembled to the circular polarizing plate.

The first phase difference layer 41 and the second phase difference layer 42 can usually be bonded together via an adhesive. The adhesive is applied to the bonding surface of either the first phase difference layer 41 or the second phase difference layer 42 or the bonding surfaces of both.

As adhesives, there are water-based adhesives and active energy ray-hardening adhesives. As water-based adhesives, there are adhesives in which polyvinyl alcohol resin is dissolved or dispersed in water. As active energy ray-hardening adhesives, there are adhesives containing hardening compounds that are hardened by irradiation with active energy rays such as ultraviolet rays, visible light, and electron beams. The storage elastic modulus, which is an indicator of the hardness of the active energy ray-hardening adhesive after hardening, is higher than the storage elastic modulus of the water-based adhesive in most cases. As adhesives, active energy ray-hardening adhesives are preferably used.

As an active energy ray-curable adhesive, it is ideal to include one or both of a cationic polymerizable curable compound and a free radical polymerizable curable compound in order to exhibit good adhesion. The active energy ray-curable adhesive may further include one or both of a cationic polymerization initiator and a free radical polymerization initiator for causing the curing reaction of the curable compound.

As a cationically polymerizable curable compound, for example, an epoxy compound (a compound having one or more epoxy groups in the molecule), an oxycyclobutane compound (a compound having one or more oxycyclobutane rings in the molecule), or a combination thereof.

As free radical polymerizable curable compounds, for example, (meth)acrylic compounds (compounds having one or more (meth)acryloyloxy groups in the molecule), other vinyl compounds having free radical polymerizable double bonds, and combinations thereof.

Active energy ray-curable adhesives may contain additives such as cationic polymerization accelerators, ion scavengers, antioxidants, chain transfer agents, adhesion promoters, thermoplastic resins, fillers, flow regulators, plasticizers, defoamers, antistatic agents, leveling agents, solvents, etc. as needed.

In the case of using an adhesive to bond the first phase difference layer 41 and the second phase difference layer 42 in the phase difference layer laminate, the adhesive is first applied to the bonding surface of one or both of the first phase difference layer 41 and the second phase difference layer 42.

As a method for applying the adhesive to the above-mentioned joint surface, a common coating technology such as a slit coater, a notch wheel coater, a reverse roller coater, a gravure coater, a rod coater, a wire rod coater, a scraper coater, an air scraper coater, etc. may be used.

When using a water-based adhesive, there is no particular restriction on the drying method, and a hot air dryer or an infrared dryer may be used for drying.

On the other hand, when an active energy ray-curable adhesive is used, active energy rays such as ultraviolet rays, visible light, electron rays, and X-rays are irradiated to cure the active energy ray-curable adhesive. Ultraviolet rays are preferably used as active energy rays, and low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, chemical lamps, black light lamps, microwave-excited mercury lamps, metal halide lamps, etc. can be used as light sources in this case.

The thickness of the adhesive for bonding the first phase difference layer 41 and the second phase difference layer 42 is preferably 10 μm or less, and more preferably 5 μm or less. When the thickness of the adhesive is below the upper limit, it is not easy for the first phase difference layer 41 and the second phase difference layer 42 to float or peel off.

〈Next layer〉

The adhesive layer 20 for bonding the linear polarizing plate 10 and the liquid crystal curing phase difference layer 30 or 40 can usually be an adhesive layer formed by a pressure-sensitive adhesive (hereinafter also referred to as an adhesive). The storage elastic modulus of the adhesive layer is preferably 46000Pa or more, more preferably 50000Pa or more, and more preferably 100000Pa or more. The storage elastic modulus of the adhesive layer is usually 50MPa or less. The storage elastic modulus of the adhesive layer can be measured according to the measurement method described in the column of the embodiment described later.

The adhesive layer may be composed of an adhesive composition with (meth) acrylic, rubber, urethane, silicone, or polyvinyl ether resin as the main component. Among them, from the perspective of transparency, weather resistance, heat resistance, and storage elastic modulus, an adhesive composition with (meth) acrylic resin as the base polymer is more desirable. The adhesive composition may be active energy ray curing type or heat curing type.

As the (meth)acrylic resin (base polymer) used as the adhesive composition, it is suitable to use a polymer or copolymer with one or more of (meth)acrylates such as butyl (meth)acrylate, ethyl (meth)acrylate, isooctyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate as monomers. The base polymer is preferably copolymerized with a polar monomer. As polar monomers, monomers having carboxyl, hydroxyl, amide, amino, epoxy, etc. such as (meth)acrylic acid, 2-hydroxypropyl (meth)acrylate, hydroxyethyl (meth)acrylate, (meth)acrylamide, N,N-dimethylaminoethyl (meth)acrylate, and glycidyl (meth)acrylate are used.

The adhesive composition may only contain the above-mentioned base polymer, and usually further contains a crosslinking agent. As the crosslinking agent, for example, a metal ion with a valence of more than two and forming a carboxylic acid metal salt with a carboxyl group; a polyamine compound and forming an amide bond with a carboxyl group; a polyepoxide compound or a polyol and forming an ester bond with a carboxyl group; a polyisocyanate compound and forming an amide bond with a carboxyl group. Among them, a polyisocyanate compound is more ideal.

The adhesive layer can be formed, for example, by dissolving or dispersing the adhesive composition in an organic solvent such as toluene or ethyl acetate to prepare an adhesive liquid, and applying the adhesive liquid directly to the target surface of the laminate to form the adhesive layer; or by first forming a sheet-like adhesive layer on a release-treated separator and transferring it to the target surface of the circular polarizer.

The circular polarizing plate may include the above-mentioned separator. The separator may be a film made of polyethylene resins such as polyethylene, polypropylene resins such as polypropylene, and polyester resins such as polyethylene terephthalate. Among them, the stretched film of polyethylene terephthalate is more ideal.

The adhesive layer may contain any ingredients, such as glass fibers, glass beads, resin particles, fillers composed of metal powder or other inorganic powders, pigments, colorants, antioxidants, ultraviolet absorbers, antistatic agents, etc.

As antistatic agents, such as ionic compounds, conductive microparticles, and conductive polymers, it is ideal to use ionic compounds.

The cationic components that make up ionic compounds can be inorganic cations or organic cations.

Examples of organic cations include pyridinium cations, imidazolium cations, ammonium cations, cobalt cations, phosphonium cations, piperidinium cations, and pyrrolidinium cations, and examples of inorganic cations include lithium ions and potassium ions.

On the other hand, the anionic component constituting the ionic compound may be an inorganic anion or an organic anion, and an anionic component containing fluorine atoms is preferred because it can impart good antistatic function to the ionic compound. Examples of anionic components containing fluorine atoms include hexafluorophosphate anions [(PF ₆ ^- )], bis(trifluoromethanesulfonyl)imide anions [(CF ₃ SO ₂ ) ₂ N ^- ], and bis(fluorosulfonyl)imide anions [(FSO ₂ ) ₂ N ^- ].

The thickness of the adhesive layer is determined by its adhesive strength, for example, in the range of 1μm to 50μm, preferably 2μm to 45μm, more preferably 3μm to 40μm, and even more preferably 5μm to 35μm.

(Other layers)

The circular polarizing plate may further have, for example, a bonding layer, a touch sensing panel, an image display element, etc. As an image display element, for example, an organic electroluminescent (EL) display element, a liquid crystal display element, etc.

(bonding layer)

As shown in FIG2 , the circular polarizing plate 200 may be provided with a bonding layer 50 on the outermost surface of the liquid crystal curing phase difference layer side. The bonding layer 50 may be a layer for bonding a touch sensing panel, an image display element, etc. to the circular polarizing plate 200. The bonding layer 50 is usually composed of an adhesive. As the adhesive constituting the bonding layer 50, conventionally known adhesives may be used without particular limitation, and adhesives having a base polymer such as an acrylic polymer, a urethane polymer, a polysilicone polymer, a polyvinyl ether polymer, etc. may be used. Moreover, it may be an active energy ray curing adhesive or a thermosetting adhesive, etc.

The storage elastic modulus of the laminating layer 50 is preferably 10000Pa or more, and more preferably 20000Pa or more. The storage elastic modulus of the laminating layer 50 is usually below 50MPa.

〈Application of circular polarizing plate〉

Circular polarizing plates can be used in image display devices. There are no particular restrictions on image display devices, such as organic electroluminescence (organic EL) display devices, inorganic electroluminescence (inorganic EL) display devices, liquid crystal display devices, touch panel display devices, electroluminescence display devices, etc.

〈Multilayer body for flexible image display device〉

The image display device may be a flexible image display device. The flexible image display device is composed of a flexible image display device laminate and an organic EL display panel, and the flexible image display device laminate is arranged on the identification side of the organic EL display panel to form a bendable device. The flexible image display device laminate may include the circular polarizing plate of the present invention, the front panel and/or the touch sensor, and the lamination order thereof is arbitrary. It is more ideal to laminate the front panel (window), the circular polarizing plate of the present invention, the touch sensor, or the front panel, the touch sensor, and the circular polarizing plate of the present invention in order from the identification side. When there is a circular polarizing plate on the recognition side of the touch sensor, the pattern of the touch sensor becomes difficult to be recognized, and the recognition of the displayed image becomes better, which is more ideal. Each component can be laminated using adhesives, adhesives, etc. In addition, a light-shielding pattern can be formed on at least one side of the front panel, circular polarizing plate, and touch sensor.

[Front panel]

A front panel can be arranged on the identification side of the linear polarizer. The front panel can be laminated on the polarizer via a bonding layer. The bonding layer may be, for example, the aforementioned adhesive layer or bonding layer.

As the front panel, for example, a hard coating layer is included on at least one side of glass or resin film. As glass, for example, high-transmittance glass or tempered glass can be used. In particular, when using thin transparent surface materials, chemically tempered glass is ideal. The thickness of the glass can be, for example, more than 100μm and less than 5mm.

The front panel, which includes a hard coating layer on at least one side of the resin film, is not as hard as existing glass and can have flexible properties. The thickness of the hard coating layer is not particularly limited and can be, for example, more than 5μm and less than 100μm.

The resin film may be a film formed of a cycloolefin derivative having a monomer unit containing a cycloolefin such as norbornene or a polycyclic norbornene monomer, cellulose (diethylcellulose, triacetylcellulose, acetylcellulose butyrate, isobutylcellulose, propylcellulose, butyrylcellulose, acetylacetylcellulose), ethylene-vinyl acetate copolymer, polycycloolefin, polyester, polystyrene, polyacrylamide, or the like. Amine, polyetherimide, polyacrylic acid, polyimide, polyamide-imide, polyether sulfone, polysulfone, polyethylene, polypropylene, polymethylpentene, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyvinyl ketone, polyether ketone, polyether ether ketone, polyether sulfone, polymethyl methacrylate, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyurethane, Epoxy resin and other polymers. The resin film can be unstretched, uniaxially stretched or biaxially stretched. These polymers can be used alone or in combination of two or more. As the resin film, polyamide-imide film or polyimide film with good transparency and heat resistance, uniaxial or biaxially stretched polyester film, cycloolefin derivative film with good transparency and heat resistance and adaptable to large-scale film, polymethyl methacrylate film, triacetyl cellulose and isobutyl cellulose film without transparency and optical anisotropy are more preferred. The thickness of the resin film is 5μm to 200μm, preferably 20μm to 100μm.

[Shading pattern]

The shading pattern (frame) can be formed on the display element side of the front panel. The shading pattern can hide the wiring of the display device without being recognized by the user. The color and material of the shading pattern are not particularly limited, and can be formed with resin materials of various colors such as black, white, and gold. In one embodiment, the thickness of the shading pattern can be greater than 2μm and less than 50μm, preferably greater than 4μm and less than 30μm, and more preferably greater than 6μm and less than 15μm. In addition, in order to suppress the mixing of bubbles caused by the step difference between the shading pattern and the display part and the recognition of the boundary part, the shading pattern can be given a shape.

[Touch sensor]

Touch sensors are used as input means. As touch sensors, various types such as resistive film method, surface elastic wave method, infrared method, electromagnetic induction method, electrostatic capacitance method, etc. have been proposed, and any method may be used. Among them, the electrostatic capacitance method is more ideal. The electrostatic capacitance touch sensor is divided into an active area and an inactive area located at the contour of the aforementioned active area. The active area is an area corresponding to the area (display part) of the display panel that displays the screen, and senses the user's touch, and the inactive area is an area corresponding to the area (non-display part) of the display device that does not display the screen. The touch sensor may include: a flexible substrate; a sensing pattern formed in the active area of the substrate; and sensing lines formed in the inactive area of the substrate and connected to an external driving circuit via the sensing pattern and the pad. As the flexible substrate, the same material as the transparent substrate of the window can be used. From the perspective of suppressing cracks that may occur in the touch sensor, the toughness of the substrate of the touch sensor is preferably 2,000MPa% or more. More preferably, the toughness is 2,000MPa% to 30,000MPa%. Here, toughness is defined as the lower area of the curve before the fracture point is reached in the stress (MPa)-strain (%) curve obtained by tensile testing of polymer materials.

The layer structure of the multilayer body for flexible image display device is described with reference to FIG3. The multilayer body 300 for flexible image display device shown in FIG3 has a liquid crystal curing phase difference layer 70 and a linear polarizing plate 60 laminated on one side thereof. The multilayer body 300 for flexible image display device further has a front panel 80 located on the recognition side of the linear polarizing plate 60, and a touch sensor 90 located on the opposite side of the liquid crystal curing phase difference layer 70 from the linear polarizing plate 60. The front panel 80 has a light shielding pattern 81 on the surface on the linear polarizing plate 60 side.

〈Manufacturing method of circular polarizing plate〉

The circular polarizing plate can be manufactured by a method including the following steps: a step of laminating a linear polarizing plate and a liquid crystal curing phase difference layer via an adhesive layer. In the case of laminating the layers to each other via an adhesive layer, it is desirable to perform a surface activation treatment such as a corona treatment on one or both laminating surfaces in order to improve adhesion.

In the case where the polarizer is a stretched film or stretched layer adsorbed with a dye having absorption anisotropy, the manufacturing method of the polarizer can be as described in the description of the stretched film or stretched layer adsorbed with a dye having absorption anisotropy.

In the case where the polarizer is a film coated with a dye having anisotropic absorption and cured, the polarizer can be formed on a substrate via an alignment film. The polarizer can be formed by coating a polarizer forming composition including a dichroic dye and a polymerizable liquid crystal compound and curing it. In addition to the above-mentioned dichroic dye and polymerizable liquid crystal compound, the polarizer forming composition further includes a polymerization initiator, a leveling agent, and a solvent. It is more ideal to further include a photosensitizer, a polymerization inhibitor, a leveling agent, etc.

By coating a phase difference layer forming composition containing a polymerizable liquid crystal compound on a substrate and an alignment film (if an alignment film exists), and polymerizing the polymerizable liquid crystal compound, a liquid crystal curable phase difference layer can be manufactured. The phase difference layer forming composition further includes a solvent, a polymerization initiator, and may further include a photosensitizer, a polymerization inhibitor, a leveling agent, etc. The substrate and the alignment film can be assembled on the liquid crystal curable phase difference layer, or peeled off from the liquid crystal curable phase difference layer without being a constituent element of the circular polarizer.

The coating, drying and polymerization of the composition for forming the polarizer and the composition for forming the phase difference layer can be carried out by conventionally known coating methods, drying methods and polymerization methods.

For example, as a coating method for the polarizer forming composition and the phase difference layer forming composition, wire bar coating, extrusion coating, direct gravure coating, reverse gravure coating, and slit coating can be used.

The polymerization method of the polymerizable liquid crystal compound can be selected according to the type of the polymerizable group of the polymerizable liquid crystal compound. If the aforementioned polymerizable group is a photopolymerizable group, it can be polymerized by photopolymerization. If the aforementioned polymerizable group is a thermally polymerizable group, it can be polymerized by thermal polymerization. The method for manufacturing the liquid crystal hardened phase difference layer of this embodiment is preferably photopolymerization. Since the photopolymerization method does not necessarily require heating the transparent substrate to a high temperature, a transparent substrate with low heat resistance can be used. The photopolymerization method can be performed by irradiating a film formed by a polarizer forming composition or a phase difference layer forming composition containing a polymerizable liquid crystal compound with visible light or ultraviolet light. From the point of easy handling, ultraviolet light is more ideal.

The adhesive layer can be prepared as an adhesive sheet. The adhesive sheet can be prepared by dissolving or dispersing an adhesive composition in an organic solvent such as toluene or ethyl acetate to prepare an adhesive liquid, applying the adhesive liquid to a release film to form a sheet-like layer composed of an adhesive, and further bonding different release films to the adhesive layer. Each layer can be bonded by bonding an adhesive sheet with a release film peeled off on one side to one layer, then peeling off the release film on the other side and bonding another layer.

As a method for applying the adhesive liquid on the release film, a common coating technology such as a slit coater, a notch wheel coater, a reverse roller coater, a gravure coater, a rod coater, a wire rod coater, a scraper coater, an air scraper coater, etc. can be used.

The release film is preferably composed of a plastic film and a release layer. The plastic film may be a polyester film such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, or a polyolefin film such as a polypropylene film. The release layer may be formed by, for example, a release layer forming composition. The main component (resin) constituting the release layer forming composition is not particularly limited, and may include, for example, silicone resins, alkyd resins, acrylic resins, and long-chain alkyl resins.

The thickness of the adhesive layer can be adjusted according to the coating conditions of each adhesive liquid. In order to reduce the thickness of the adhesive layer, it is effective to reduce the coating thickness.

The circular polarizing plate can be manufactured by cutting a predetermined size from a long strip of film formed by laminating a linear polarizing plate and a liquid crystal curing phase difference layer via an adhesive layer. In addition, the circular polarizing plate can also be manufactured by laminating a linear polarizing plate cut to a predetermined size and a liquid crystal curing phase difference layer via an adhesive layer.

[Implementation example]

The present invention is described in more detail below through examples.

〈Hot and cold shock test〉

The circular polarizing plates obtained in the embodiments and comparative examples, with a long side dimension (the dimension of the side parallel to the slow axis direction of the first liquid crystal curing phase difference layer) of 130 mm and a short side dimension (the dimension of the side parallel to the fast axis direction of the first liquid crystal curing phase difference layer) of 70 mm, were subjected to a hot and cold shock test to obtain the absolute value of the change in the dimensional difference and the absolute value of the change in the reflected chromatic aberration.

The hot and cold shock test is to place the circular polarizing plate with the adhesive layer on the side of the liquid crystal hardened phase difference layer attached to the inorganic glass in a heat shock test tank. After cooling to -40℃ and keeping it at -40℃ for 30 minutes, heating to 85℃ and keeping it at 85℃ for 30 minutes is one cycle. Repeat the hot and cold test 300 times.

After the hot and cold shock test, the circular polarizer is observed through an optical microscope to confirm whether cracks occur.

[Method for measuring the displacement in the fast axis direction]

At the center of both long sides of the circularly polarizing plate before the thermal shock test, an optical microscope is used to measure the deviations D1 and D2 of the end positions of the polarizing plate relative to the end positions of the phase difference layer [Figure 4]. The deviations D1 and D2 are added together to obtain the total deviation in the fast axis direction before the thermal shock test. After 300 cycles of measurement, the temperature of the circularly polarizing plate is cooled from 85°C to room temperature. The deviation is based on the end position of the phase difference layer, with the inner side of the circularly polarizing plate being positive and the outer side of the circularly polarizing plate being negative. Then, after the thermal shock test is performed on the circularly polarizing plate, the total deviation in the fast axis direction after the thermal shock test is obtained in the same way. Then, the displacement in the fast axis direction is calculated according to the following formula. In addition, the fast axis direction is the fast axis direction of the first liquid crystal curing phase difference layer.

Displacement in the fast axis direction (μm) = |[Total deviation in the fast axis direction before the thermal shock test (μm)]-[Total deviation in the fast axis direction after the thermal shock test (μm)]|

[Method for measuring the variation of reflection color difference]

mm)測定反射色相(a^*、b^*)。從相對於周緣部4處(1)至(4)的反射色相的平均值(a₀ ^*、b₀ ^*)之中央部(5)的反射色相(a₀ ^*’、b₀ ^*’)，根據下述式，求出冷熱衝擊測試前的周緣部與中央部的反射色相差(△₀a^*b^*)。 The surface of the circular polarizing plate opposite to the linear polarizing plate shown in FIG4 was bonded to an aluminum plate (reflecting plate) via an adhesive layer, and the four peripheral portions (1) to (4) and the central portion (5) were measured using a spectrophotometer (CM2600d manufactured by Konica Minolta, measuring diameter: 3

The reflection hue (a ^* , b ^* ) was measured at 400 mm. The reflection hue ( _a0 ^*' , _b0 * ^' ) of the central part (5) was compared with the average value (a0 ^* , b0 ^* ) of the reflection hue of the peripheral part 4 ( ₁ ) to (4), and the reflection hue difference (△ _0a ^* b _* ⁾ between the peripheral part and the central part before the thermal shock test was calculated according to the following formula.

Reflection hue difference (△ ₀ a ^* b ^* ) = {[a ₀ ^* -a ₀ ^*' ] ² + [b ₀ ^* -b ₀ ^*' ] ² } ^1/2

Then, after the thermal shock test was performed on the circularly polarizing plate, the difference in reflected hue (△ ₁ a ^* b ^* ) between the peripheral portion and the central portion after the thermal shock test was calculated from the reflected hue (a ₁ *', b ₁ ^*' ) of the central portion (5) relative to the average value (a 1 ^* , b ₁ ^* ) of the reflected hue at the peripheral portion 4 ₍₁ ⁾ to (4) in the same manner as described above, according to the following formula.

Reflection color difference (△ ₁ a ^* b ^* ) = {[a ₁ ^* -a ₁ ^*' ] ² + [b ₁ ^* -b ₁ ^*' ] ² } ^1/2

From the difference in reflected hue before and after the hot and cold shock test, the absolute value of the change in reflected hue is calculated using the following formula.

Change in reflection color difference = | reflection color difference (△ ₁ a ^* b ^* ) - reflection color difference (△ ₀ a ^* b ^* )|

〈Measurement method of storage elastic modulus〉

The storage elastic modulus of the coating is then measured by the following method.

The adhesive layer used in the embodiment and the comparative example was stacked in multiple sheets to a thickness of 0.2 mm. A cylinder with a diameter of 8 mm was punched out from the obtained adhesive layer and used as a sample for measuring the storage elastic modulus. According to JIS K7244-6, the above sample was measured for storage elastic modulus (Pa) by a torsional shear method under the following conditions using a viscoelasticity measuring device (manufactured by Physica, MCR300).

[Measurement conditions]

Normal force FN: 1N

Deformation γ: 1%

Frequency: 1Hz

Temperature: 25℃

〈Linear polarizing plate〉

[Production of polarizer]

A polyvinyl alcohol film [Kuraray Co., Ltd.'s trade name "VF-PE # 3000"] with an average degree of polymerization of 2400, a saponification degree of 99.9 mol% and a thickness of 30μm was immersed in pure water at 37°C, and then immersed in an aqueous solution of iodine/potassium iodide/water with a weight ratio of 0.04/1.5/100 at 30°C. Then, it was immersed in an aqueous solution of potassium iodide/boric acid/water with a weight ratio of 12/3.6/100 at 56.5°C. Then, after washing with pure water at 10°C and drying at 85°C, a polarizer with a thickness of about 12μm with iodine adsorption and alignment on polyvinyl alcohol was produced. The stretching was performed during the iodine dyeing and boric acid treatment steps. The total stretching ratio was 4.8 times.

[1st protective film]

A 30μm thick norbornene resin film is used. One side of the film is surface treated, and the other side becomes the bonding surface with the polarizer.

[Second protective film]

A triacetylcellulose resin membrane with a thickness of 20μm was used.

[Production of linear polarizing plate]

The polarizer is laminated with the first protective film and the second protective film in sequence via a water-based adhesive to produce a polarizing plate. As the water-based adhesive, 3 parts of carboxyl-modified polyvinyl alcohol (trade name "KL-318" manufactured by Kuraray Co., Ltd.) is dissolved in 100 parts of water, and 1.5 parts of a polyamide epoxy additive of a water-soluble epoxy resin (trade name "SUMIREZ RESIN (registered trademark) 650 (30)" obtained from TAOKA CHEMICAL CO., LTD., a 30% solids concentration aqueous solution) is added to the aqueous solution.

〈Liquid crystal hardening phase difference layer〉

[1st liquid crystal hardening phase difference layer]

As the first liquid crystal cured phase difference layer, a layer for imparting a λ/4 phase difference consisting of a layer formed by curing a nematic liquid crystal compound, an alignment film, and a transparent substrate is prepared. The total thickness of the layer formed by curing a nematic liquid crystal compound and the alignment layer is 2μm. The layer formed by curing a nematic liquid crystal compound is formed by applying a phase difference layer forming composition containing a nematic liquid crystal compound on an alignment film formed on a transparent substrate and curing it.

[Second liquid crystal hardening phase difference layer]

A polyethylene terephthalate substrate with a thickness of 38 μm was used as a transparent substrate, and a vertical alignment layer composition was coated on one side thereof to a film thickness of 3 μm, and irradiated with ultraviolet light at 20 mJ/cm ² to prepare an alignment layer. Furthermore, as the vertical alignment layer composition, a mixture of 2-phenoxyethyl acrylate, tetrahydrofuran methyl acrylate, dipentaerythritol triacrylate and bis(2-vinyloxyethyl) ether was used, which was mixed in a ratio of 1:1:4:5, and 4% of LUCIRIN (registered trademark) TPO was added as a polymerization initiator.

Then, a phase difference layer forming composition containing photopolymerizable nematic liquid crystal (RMM28B manufactured by Merck) is applied on the formed alignment layer by a slit coater. Here, in the liquid crystal composition, a mixed solvent of methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK) and cyclohexanone (CHN) with a boiling point of 155°C in a mass ratio (MEK: MIBK: CHN) of 35:30:35 is used as a solvent. Then, the solid matter is adjusted to 1 to 1.5 g of the prepared phase difference layer forming composition, and applied on the alignment layer in an amount of 4 to 5 g (wet).

After applying the phase difference layer forming composition on the alignment layer, the drying temperature is set to 75°C and the drying time is set to 120 seconds for drying treatment. Then, the liquid crystal compound is polymerized by ultraviolet (UV) irradiation to obtain a positive C layer consisting of a layer formed by curing the photopolymerizable nematic liquid crystal compound, an alignment layer, and a transparent substrate. The total thickness of the layer formed by curing the photopolymerizable nematic liquid crystal compound and the alignment layer is 4μm.

[Preparation of phase difference laminate]

The first liquid crystal curable phase difference layer and the second liquid crystal curable phase difference layer are bonded together by using a UV curable adhesive so that the surfaces of the respective liquid crystal curable phase difference layers (the surfaces opposite to the transparent substrate) become bonding surfaces. Then, the UV curable adhesive is cured by irradiating with UV rays. The thickness of the UV curable adhesive after curing is 2 μm. In this way, a phase difference layer laminate consisting of two layers of liquid crystal curable phase difference layers, namely the first liquid crystal curable phase difference layer and the second liquid crystal curable phase difference layer, is prepared.

〈Next layer〉

[Adhesive layer 1]

A commercially available adhesive sheet was used in which a 5μm thick acrylic adhesive layer was laminated on the release-treated surface of a 38μm thick polyethylene terephthalate substrate (release film) subjected to release treatment. The storage elastic modulus of the adhesive layer after removing the release film from the adhesive sheet was 125,000 Pa at 25°C.

[Adhesive layer 2]

A commercially available adhesive sheet was used in which a 17μm thick acrylic adhesive layer was laminated on the release-treated surface of a 38μm thick polyethylene terephthalate substrate (release film) subjected to release treatment. The storage elastic modulus of the adhesive layer after removing the release film from the adhesive sheet was 45200 Pa at 25°C.

[Adhesive layer 3]

A commercially available adhesive sheet was used in which a 25μm thick acrylic adhesive layer was laminated on the release-treated surface of a 38μm thick polyethylene terephthalate substrate (release film) subjected to release treatment. The storage elastic modulus of the adhesive layer after removing the release film from the adhesive sheet was 25500 Pa at 25°C.

[Adhesive layer 4]

A commercially available adhesive sheet was used in which a 20μm thick acrylic adhesive layer was laminated on the release-treated surface of a 38μm thick polyethylene terephthalate substrate (release film) subjected to release treatment. The storage elastic modulus of the adhesive layer after removing the release film from the adhesive sheet was 125,000 Pa at 25°C.

<Implementation Example 1>

The adhesive layer 1 is transferred to the second protective film (triacetyl cellulose resin film) side of the polarizing plate. The separation film layered on the adhesive layer 1 is peeled off, and then the transparent substrate layered on the peeled surface of the phase difference layer stack composed of the two layers of liquid crystal hardening phase difference layer on the first liquid crystal hardening phase difference layer side is peeled off. The transparent substrate on the opposite side of the liquid crystal hardening phase difference layer layered on the polarizing plate is peeled off. The adhesive layer 4 is layered on the exposed surface after peeling off the transparent substrate. In this way, a circular polarizing plate of Example 1 is prepared, which is sequentially composed of a first protective film, a polarizer, a second protective film, an adhesive layer 1, a first liquid crystal curing phase difference layer (a layer imparting a λ/4 phase difference), an adhesive layer, a second liquid crystal curing phase difference layer (a positive type C layer), and an adhesive layer 4.

The obtained circular polarizing plate with adhesive layer was cut into a size of 130 mm × 70 mm, and the adhesive layer 4 was attached to the inorganic glass plate to perform a hot and cold shock test. The total deviation in the fast axis direction before the hot and cold shock test was zero. The results are shown in Table 1. In addition, Figure 5 shows an optical microscope photograph of the deviation of the polarizer and the phase difference layer on the long side after the hot and cold shock test.

<Implementation Example 2>

In Example 1, except that the adhesive layer is replaced by the adhesive layer 34, the circular polarizing plate of Example 2 is manufactured in the same manner as Example 1 and subjected to a hot and cold shock test. The results are shown in Table 1.

〈Comparison Example 1〉

In Example 1, except that the adhesive layer 1 was replaced by the adhesive layer 2, the circular polarizing plate of Comparative Example 1 was prepared in the same manner as in Example 1 and subjected to a hot and cold shock test. The occurrence of a turtle crack with a length of more than 50 mm was confirmed in the slow axis direction. The results are shown in Table 1.

[Table 1]

Claims (11)

A circular polarizing plate, comprising: a linear polarizing plate, comprising a polarizing plate, and a polarizing plate protective layer with a thickness of 30 μm or less provided on at least one side of the polarizing plate; and a liquid crystal curing phase difference layer, which is laminated on the linear polarizing plate via an adhesive layer; wherein the liquid crystal curing phase difference layer is a phase difference layer laminated body in which a first liquid crystal curing phase difference layer and a second liquid crystal curing phase difference layer are laminated; and either the first liquid crystal curing phase difference layer or the second liquid crystal curing phase difference layer functions as a layer for imparting a λ/4 phase difference. function, and the other functions as a positive C layer; when the liquid crystal hardened phase difference layer side of the circular polarizing plate is bonded to the inorganic glass plate, after the hot and cold shock test, the displacement of the liquid crystal hardened phase difference layer at the periphery and the polarizer in the fast axis direction compared with that before the hot and cold shock test is less than 190μm, wherein the hot and cold shock test is performed with cooling to -40℃ for 30 minutes, then heating to 85℃ for 30 minutes as one cycle, and the test is repeated 300 times. A circular polarizing plate, comprising: a linear polarizing plate, comprising a polarizing plate, and a polarizing plate protective layer with a thickness of 30 μm or less provided on at least one side of the polarizing plate; and a liquid crystal curing phase difference layer, which is laminated on the linear polarizing plate via an adhesive layer; wherein the liquid crystal curing phase difference layer is a phase difference layer laminated body in which a first liquid crystal curing phase difference layer and a second liquid crystal curing phase difference layer are laminated; either the first liquid crystal curing phase difference layer or the second liquid crystal curing phase difference layer functions as a layer imparting a λ/4 phase difference, and the other functions as a positive C layer; In a state where the liquid crystal hardened phase difference layer side of the circularly polarizing plate is bonded to an inorganic glass plate, in a thermal shock test, the change in the reflected color difference (△ ₁ a * b * ) between the peripheral portion and the central portion after the thermal shock test relative to the reflected color difference (△ ₀ ^{a * b *} ) between the peripheral portion and ^the central portion before the thermal shock test is less than 0.65, wherein the thermal shock test is performed with one cycle of cooling to -40°C for 30 minutes and then heating to 85°C for 30 minutes, and the test is repeated 300 times. A circular polarizing plate, comprising: a linear polarizing plate having a polarizer and a polarizer protective layer with a thickness of 30 μm or less provided on at least one side of the polarizer; and a liquid crystal curing phase difference layer, which is laminated on the linear polarizing plate via an adhesive layer; wherein the liquid crystal curing phase difference layer is a phase difference layer laminated body having a first liquid crystal curing phase difference layer and a second liquid crystal curing phase difference layer laminated; either the first liquid crystal curing phase difference layer or the second liquid crystal curing phase difference layer functions as a layer imparting a λ/4 phase difference, while the other functions as a positive C layer; the storage elastic modulus of the adhesive layer is 46000 Pa or more. A circular polarizing plate as described in any one of claims 1 to 3, wherein the aforementioned polarizer, the aforementioned polarizer protective layer and the aforementioned adhesive layer are sequentially layered. The circularly polarizing plate as described in claim 1 or 2, wherein the storage elastic modulus of the adhesive layer is greater than 46000 Pa. A circular polarizer as described in any one of claims 1 to 3, wherein in the linear polarizer, the polarizer protective layer is disposed on both sides of the polarizer. The circular polarizing plate as described in claim 6, wherein the polarizer protective layer is a first protective film and a second protective film bonded to both sides of the polarizer, the first protective film is a norbornene resin film, and the second protective film is a triacetyl cellulose resin film. The circular polarizing plate as described in claim 7, wherein the polarizer, the second protective film and the adhesive layer are laminated in the order of polarizer/second protective film/adhesive layer. The circular polarizing plate as described in any one of claims 1 to 3 further has a bonding layer on the outermost surface on the side of the aforementioned liquid crystal hardened phase difference layer. A multilayer body for a flexible image display device, comprising a circular polarizer, a front panel and/or a touch sensor as described in any one of claims 1 to 9. An image display device having a circular polarizer as described in any one of claims 1 to 9.

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