KR20210005108A - Polarizer - Google Patents

Abstract

The present invention provides a polarizing plate having at least one curved portion. This polarizing plate is a polarizing plate having a polarizer having a first surface and a second surface, and a first substrate disposed on the first surface of the polarizer, the thickness of the polarizer is 15 μm or less, and the first substrate is It is a thermoplastic resin substrate, and the polarizing plate has at least one curved portion.

Description

Polarizer

The present invention relates to a polarizing plate.

The polarizing plate is an optical element having a specific orientation structure. For example, Patent Document 1 discloses a polarizing film in which iodine or a dichroic dye is adsorbed to a polymer film typified by a film containing polyvinyl alcohol (PVA) or a derivative thereof, and the film is uniaxially stretched and oriented.

Patent Document 1: Japanese Patent Laid-Open No. 2007-047498

The polarizing plate may be heat-molded depending on the application. For example, when a polarizing plate is bonded to a lens having a curved surface such as sunglasses, the polarizing plate is heat-molded while bonding along the lens to give the polarizing plate a shape according to the curved surface. However, when heat-molding a polarizing plate, the following problems may arise.

The thickness of a polarizer of a conventional polarizing plate using a stretched PVA is 20 µm to 30 µm, and when such a polarizing plate is heat-molded, the shrinking force of the stretched PVA is large, and there is a case where it heats and shrinks in the stretching direction, or it is torn along the stretching direction. have. In order to suppress such a phenomenon, in a polarizing plate using stretched PVA, a polarizing plate must be bonded to a substrate such as a resin, or the periphery of the polarizing plate must be fixed with a curable resin.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a thin-film polarizing plate by suppressing shrinkage due to thermoforming.

The present invention includes the following aspects.

[1] A polarizing plate having a polarizer having a first side and a second side, and a first substrate disposed on the first side of the polarizer, wherein the polarizer has a thickness of 15 μm or less, and the first substrate is thermoplastic It is a resin substrate, and the polarizing plate has at least one curved portion.

[2] The polarizing plate according to [1], wherein the curvature radius of the curved portion is 30 mm to 150 mm.

[3] The polarizing plate according to [1] or [2], wherein the first substrate contains at least one of an acrylic resin and a cyclic olefin resin.

[4] [1] to [3] wherein the polarizer includes a polarizing layer, the polarizing layer includes a cured product of a liquid crystal compound and a dichroic dye, and the dichroic dye is dispersed and oriented in the polarizing layer. ] The polarizing plate according to any one of.

[5] The polarizing plate according to any one of [1] to [4], wherein the first substrate has a thickness of 40 µm to 120 µm.

[6] The polarizing plate according to any one of [1] to [5], further comprising a second substrate on the second surface of the polarizer.

[7] The polarizing plate according to [6], wherein the second substrate contains at least one selected from acrylic resin, cyclic olefin resin, and triacetylcellulose resin.

[8] The polarizing plate according to any one of [1] to [7], wherein the polarizing plate is used by bonding to the display surface of a display device having a curved surface on the display surface, and wherein the curved portion matches the curved surface.

According to the present invention, shrinkage due to thermoforming is suppressed, and a thin-film polarizing plate can be provided.

1 is a schematic cross-sectional view of a polarizing plate in an embodiment of the present invention.
2 is a schematic cross-sectional view of a polarizing plate according to an embodiment of the present invention.
3 is a schematic cross-sectional view of a circular polarizing plate in an embodiment of the present invention.
4 is a schematic cross-sectional view of a circular polarizing plate in an embodiment of the present invention.

The polarizing plate in this embodiment is a polarizing plate having a polarizer having a first surface and a second surface, and a first substrate disposed on the first surface of the polarizer, and the thickness of the polarizer is 15 μm or less, The first substrate is a thermosetting resin substrate, and the polarizing plate has at least one curved portion.

Hereinafter, as an aspect of the present invention, a case where the polarizing layer contains a cured product of a liquid crystal compound and a case where PVA is included will be described, respectively.

<First embodiment>

1 is a schematic cross-sectional view of a polarizing plate 1 according to the present embodiment. The polarizing plate 1 includes a polarizer 11 and a first base material 12. The polarizer 11 has a first surface 31 and a second surface 32. The first substrate 12 is located on the first surface 31. The polarizer 11 includes the polarizing layer 21 and the alignment layer 22. The polarizing layer 21 contains a cured product 101 of a liquid crystal compound and a dichroic dye 102. The dichroic dye 102 is dispersed in the cured product 101 of the liquid crystal compound. The orientation layer 22 exhibits an orientation regulating force. By disposing the liquid crystal compound before curing on the alignment layer 22, the liquid crystal compound before curing is aligned in one direction. Thereafter, by curing the liquid crystal compound, a cured product 101 of the liquid crystal compound aligned in one direction is obtained. Since the dichroic dye 102 is dispersed in the liquid crystal compound before curing and is disposed on the alignment layer 22, depending on the orientation of the cured product 101 of the liquid crystal compound, the dichroic dye 102 is also a liquid crystal compound. It is oriented in the orientation direction of the cured product 101.

The polarizing plate 1 has at least one curved portion 13. The shape of the curved portion 13 depends on the shape of the object to which the polarizing plate 1 is bonded. In the present embodiment, the curved portion 13 may be a curved portion having a plurality of radii of curvature. The radius of curvature in this embodiment is defined on the surface closest to the virtual center of the curved portion 13. For example, the radius of curvature in the polarizing plate 1 of FIG. 1 is defined as the radius of curvature of the second surface 32. The radius of curvature is a value obtained from the arc length, chord length, and flesh height of the curved portion 13 using the following equation.

Arc length (L) = radius (r) * center angle ( θ ) (1)

Chord length(d)=2*r*sin( θ /2) (2)

Flesh height(h)=r*{1-cos( θ /2)} (3)

The radius of curvature of the curved portion 13 may be, for example, 30 mm to 150 mm. In addition, the polarizing plate 1 may have two or more curved portions 13. The shape of the curved portion 13 is not particularly limited, and for example, a curved portion having a small radius of curvature that could not be followed by a polarizing plate containing stretched PVA may be used.

In addition, in a polarizing plate in which a stretched PVA having a thickness of 20 µm to 30 µm is used as a polarizing layer, it may be thermally contracted in the stretching direction of the stretched PVA during heat molding or may be torn along the stretching direction of the stretched PVA. In order to suppress this phenomenon, it is necessary to hold the polarizing plate by the second substrate for maintaining the shape.

In the case of using the polarizer of the polarizing plate 1 in which the cured product 101 of the liquid crystal compound and the dichroic dye 102 are aligned, stretching is not necessary. Therefore, compared with a conventional polarizing plate containing stretched PVA having a thickness of 20 µm to 30 µm, shrinkage due to heat is small. From this, when heat-molding a polarizing plate using a conventional stretched PVA having a thickness of 20 µm to 30 µm, the second base material used for shape retention can be thinned or omitted. The polarizing plate 1 can be bonded to an object having a more complex shape, and contributes to the improvement of the design of the object.

When a polarizer of the polarizing plate 1 in which the cured product 101 of a liquid crystal compound and the dichroic dye 102 are aligned is used, the bending strength does not become uneven depending on the bending direction at the time of heat molding. Therefore, it is possible to join an object having a more complicated shape, thereby contributing to the improvement of the design of the object.

The thickness of the polarizing plate 1 is 25 µm to 200 µm, preferably 50 µm to 180 µm, and more preferably 60 µm to 170 µm. By setting the thickness of the polarizing plate 1 to 60 µm to 170 µm, the conformability to the shape of the object to which the polarizing plate 1 is bonded becomes good. The thickness of the polarizing plate 1 in this embodiment is defined as a value obtained by measuring an arbitrary five points in the polarizing plate 1 with a contact-type film thickness meter and calculating the average thereof.

The thickness of the polarizer 11 is 1 µm or more and 15 µm or less, preferably 1 µm or more and 10 µm or less, more preferably 1 µm or more and 5 µm or less, and still more preferably 1 µm or more and 3 µm or less. The thickness of the polarizer 11 in this embodiment is determined by measuring the arbitrary five points of the polarizer 11 with a contact type film thickness meter, an interference film thickness meter, a laser microscope or a stylus type film thickness meter, and calculating the average value. I can.

Since the polarizing plate 1 of the present embodiment has the cured product 101 of the liquid crystal compound and the polarizing layer 21 in which the dichroic dye 102 is aligned, the polarization characteristic is obtained even when the polarizing plate 1 is heated. Difficult to change The retention of the polarization characteristics of the polarizing plate 1 before and after heating is, for example, 90% to 100%, and preferably 95% to 100%. In this embodiment, the retention rate of the polarization characteristic of the polarizing plate 1 before and after heating can be calculated as the absorbance retention rate (%) in the orientation direction (also referred to as the absorption axis direction) of the dichroic dye 102.

Specifically, it is defined as follows. First, the absorbance (A1) of the polarizing plate 1 in the direction of the absorption axis at 23°C is measured [A1 (23°C)]. Using a spectrophotometer (UV-3150 manufactured by Shimadzu Corporation) and a folder with a polarizing plate (1) attached to it, A1 (23) in a wavelength range of 380 to 680 nm in 2 nm steps according to the double beam method. °C) is measured. Further, in order to remove the contribution of the light loss due to the surface reflection of the polarizing plate 1, after setting a measurement sample, the measurement is performed after performing zero point correction at 800 nm without light absorption. Thereafter, it was put in an oven at 85° C. for 500 hours, and after extraction, the absorbance was measured again according to the above method. The absorbance retention rate (%) is calculated according to the following formula (I).

Absorbance retention rate (%) = A1(85℃)/A1(23℃)×100 (I)

In the formula, A1 (85°C) is the absorbance in the direction of the absorption axis after holding the polarizing plate in an oven at 85°C for 500 hours, and A1 (23°C) is the absorbance in the direction of the absorption axis as measured at 23°C before the heat resistance test. Represents.

In the polarizing plate 1, since the polarizer is as thin as 15 µm or less, the shrinkage due to heating is small as compared with a polarizing plate including a stretched PVA having a thickness of 20 µm to 30 µm as a polarizer. Further, when the cured product 101 of the liquid crystal compound and the polarizing layer 21 in which the dichroic dye 102 is aligned are employed, the shrinkage due to heating is smaller. Therefore, there is little variation in the polarization characteristic even after heat molding and also at a plurality of arbitrary points on the curved portion 13.

2 is a schematic cross-sectional view of a polarizing plate according to an embodiment of the present invention. As for the polarizing plate 1', as shown in FIG. 2, the 2nd base material 14 is located on the 2nd surface 32 of the polarizer 11. The polarizer 11 can be protected by the second base material 14. Specifically, when the polarizer 11 is directly touched by hand, a scratch or the like may occur, and the polarization characteristics may deteriorate only in that part. The second substrate 14 can prevent such a decrease in polarization characteristics.

Hereinafter, each element included in the polarizing plate 1 will be described in detail.

1. Polarizer

The polarizer according to the present embodiment has a dichroic dye and a polarizing layer in which a cured product of a liquid crystal compound is aligned. This polarizing layer can be formed using a composition containing a dichroic dye (hereinafter, referred to as "a composition for forming a polarizer" in some cases). In this embodiment, the liquid crystal compound may also serve as a dichroic dye, that is, the liquid crystal compound may exhibit dichroism. As a liquid crystal compound exhibiting dichroism, a compound described in WO2011/024891 and Japanese Patent Laid-Open No. 2018-120229 is illustrated, for example.

1-1. Dichroic pigment

As the dichroic dye, one having absorption in the wavelength range of 380 nm to 800 nm can be used, and it is preferable to use an organic dye. As a dichroic dye, an azo compound is mentioned, for example.

As the azo compound, a dichroic dye (1) having an absorption maximum in a range of 380 nm to 550 nm in wavelength is exemplified. As the dichroic dye (1), for example, a compound represented by the following formula (1) (hereinafter, referred to as "compound (1)" in some cases) can be mentioned. The geometric isomer of the azobenzene moiety of the compound (1) is preferably trans.

Y in formula (1) is a group represented by the following formula (Y1) or formula (Y2), and is preferably a group represented by formula (Y1).

In formulas (Y1) and (Y2), the straight line at both ends represents a bonding hand, the bonding hand on the left is bonded to a phenylene group having an azo group, and the bonding hand on the right is phenylene having R ² It is combined with the tile. L is an oxygen atom or -NR-, and R is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. Examples of this alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group and a t-butyl group. Among these, L is preferably an oxygen atom or -NH-, and more preferably an oxygen atom.

R ¹ is a group represented by the following formula (R ¹ -1), formula (R ¹ -2) or formula (R ¹ -3), preferably formula (R ¹ -2) and formula (R ^1- It is a group represented by 3). * In the formula represents a bond hand.

It is preferable that it is an integer of 0-10, and, as for ma in the group represented by Formula (R ¹ -2) each independently, it is more preferable that it is an integer of 0-5. Although the two ma may be the same or different, respectively, it is preferable if they are the same.

R ² is a formula (R ² -1), a formula (R ² -2), a formula (R ² -3), a formula (R ² -4), a formula (R ² -5), or a formula (R ² -6 ) And is preferably a group represented by a formula (R ² -2), a formula (R ² -5) or a formula (R ² -6), and a group represented by a formula (R ² -6) More preferable.

When R ² is a group represented by formula (R ² -1), formula (R ² -2), formula (R ² -3), formula (R ² -5) or formula (R ² -6), Mb to be included is preferably an integer of 0 to 10, and more preferably an integer of 0 to 5.

Examples of the compound (1) include compounds represented by the following formulas (1-1) to (1-8).

Among them, compounds represented by formula (1-1), formula (1-2), formula (1-3), formula (1-5), formula (1-7), and formula (1-8) are preferred. And, a compound represented by formula (1-1), formula (1-2), formula (1-3), and formula (1-7) is more preferable.

Here, the manufacturing method of compound (1) is demonstrated. Compound (1) is, for example, a compound represented by formula (1X) [compound (1X)] and a compound represented by formula (1Y) [compound (1Y)], which can be prepared by a reaction represented by the following scheme. have.

In the above scheme, R ¹ , R ² and Y have the same meaning as above, and Re ¹ and Re ² are groups that react with each other to become a group represented by Y. Examples of the combination of Re ¹ and Re ² include a combination of a carboxyl group and a hydroxyl group, a combination of a carboxy group and an amino group (such amino groups may be substituted with R), a combination of a carbonyl halide group and a hydroxyl group, a carbonyl halide group and an amino group ( A combination of such an amino group may be substituted with R), a combination of a carbonyloxyalkyl group and a hydroxyl group, a combination of a carbonyloxyalkyl group and an amino group (such an amino group may be substituted with R). In addition, here, the compound having R ¹ (1X) and the compound having R ² (1Y) are described, but a compound protected by R ¹ with an appropriate protecting group or a compound protected with R ² with an appropriate protecting group are reacted with each other, Thereafter, compound (1) can also be produced by performing an appropriate deprotection reaction.

As the reaction conditions for reacting the compound (1X) and the compound (1Y), appropriate known conditions can be appropriately selected depending on the kind of the compound (1X) and compound (1Y) to be used.

For example, when Re ¹ is a carboxyl group, Re ² is a hydroxyl group, and Y is -C(=O)-O-, the reaction conditions include, for example, condensation conditions in the presence of an esterification condensing agent in a solvent. have. As a solvent, a solvent in which compound (1X) and compound (1Y) are soluble together, such as chloroform, can be mentioned. Examples of the esterified condensing agent include diisopropylcarbodiimide (IPC). Here, it is further preferable to use a base such as dimethylaminopyridine (DMAP) in combination. The reaction temperature is selected depending on the type of compound (1X) and compound (1Y), but includes, for example, a range of -15 to 70°C, preferably 0 to 40°C. The reaction time is, for example, in the range of 15 minutes to 48 hours.

The reaction time is determined by appropriately sampling the reaction mixture in the middle of the reaction, and the degree of disappearance of the compound (1X) and the compound (1Y) by a known analytical means such as liquid chromatography or gas chromatography, and the compound (1). It can be determined by checking the degree of generation of.

From the reaction mixture after the reaction, compound (1) can be extracted according to known methods such as recrystallization, reprecipitation, extraction, and various chromatography, or by combining operations thereof.

As the azo compound, a dichroic dye 2 having an absorption maximum in the range of 550 nm to 700 nm in wavelength can be used.

The dichroic dye (2) is a dichroic dye (2-1) having an absorption maximum in a range of 550 nm to 600 nm and/or a dichroic dye (2) having an absorption maximum in a range of 600 nm to 700 nm. -2) may be included. If the dichroic dye (2-1) has an absorption maximum in the range of 570 nm to 600 nm, and the dichroic dye (2-2) has an absorption maximum in the range of 600 nm to 680 nm, More preferable.

As the dichroic dye (2), a compound represented by the following formula (2) (hereinafter, referred to as "compound (2)" in some cases) is exemplified. The geometric isomer of the azobenzene moiety of compound (2) is preferably trans. In formula (2), n is 1 or 2.

Ar ¹ and Ar ³ are each independently a group represented by a formula (AR-1), a formula (AR-2), a formula (AR-3), or a formula (AR-4). * Represents a bond hand.

Ar ² is a group represented by a formula (AR2-1), a formula (AR2-2), or a formula (AR2-3).

A ¹ and A ² are each independently a group represented by any one of formulas (A-1) to (A-9). In formulas (A-2), (A-3), (A-5) and (A-6), mc is an integer of 0 to 10, and when there are two mcs in the same group, these two mc is the same or different from each other.

Compound (2) usable as a dichroic dye (2-1) is determined by combining Ar ¹ , Ar ² and Ar ³ so that compound (2) has an absorption maximum in the range of 550 nm to 600 nm in wavelength. . Similarly, by combining Ar ¹ , Ar ² and Ar ³ so that the compound (2) has absorption in the wavelength range of 600 nm to 700 nm, the compound (2) that can be used as the dichroic dye (2-2) is determined. All.

When compound (2) is specifically shown, the compound represented respectively by Formula (2-11)-Formula (2-37) is mentioned, for example.

In the specific examples of the compound (2), as the dichroic dye (2-1), formula (2-12), formula (2-13), formula (2-18), formula (2-20), formula (2-21), equation (2-22), equation (2-23), equation (2-24), equation (2-26), equation (2-27), equation (2-28), equation ( 2-29), those represented by formulas (2-30) and (2-37), respectively, and as dichroic dyes (2-2), formulas (2-31), (2-32), Those represented by Equations (2-33), (2-34), (2-35), and (2-36) are applicable. In addition, although each represented by formula (2-11), formula (2-15) and formula (2-16) is not a dye exhibiting absorption at a wavelength of 550 nm to 700 nm, it can be used in combination with other dichroic dyes. .

Among the specific examples of compound (2), as a dichroic dye (2), formula (2-15), formula (2-16), formula (2-18), formula (2-20), and formula (2-21 ), equation (2-22), equation (2-23), equation (2-27), equation (2-29), equation (2-31), equation (2-32), equation (2-33) , It is preferably represented by formula (2-34), formula (2-35), and formula (2-37), respectively.

The dichroic dye 2 is produced, for example, by a known method described in Japanese Unexamined Patent Publication No. 58-38756, Japanese Unexamined Patent Publication No. 63-301850, or the like.

The aforementioned dichroic dyes may be used singly or in combination of two or more.

When the composition for forming a polarizer contains two or more dichroic dyes, each content of the dichroic dye is expressed in terms of 100 parts by mass of the polymerizable liquid crystal compound described later, and 3 parts by mass or less is preferable, and 0.1 mass More preferably more than 2.5 parts by mass and less than or equal to 2.5 parts by mass, and still more preferably not less than 1 part by mass and not more than 1.5 parts by mass. When each content of the dichroic dye is within the above range, since the dichroic dye in the composition for forming a polarizer exhibits sufficient solubility in a solvent, when a polarizer is manufactured using the composition for forming a polarizer, the occurrence of defects occurs. Easy to get no polarizer. Thereby, even a thin film has high light absorption selection performance, and it becomes easier to manufacture a polarizing plate excellent in heat resistance. The total amount of the dichroic dye contained in the composition for forming a polarizer is expressed as a content based on 100 parts by mass of the polymerizable liquid crystal compound described later, and is preferably 9 parts by mass or less, more preferably 0.1 parts by mass or more and 7.5 parts by mass or less. , 1 part by mass or more and 4.5 parts by mass or less are more preferable.

1-2. Liquid crystal compound

The polarizer 11 according to the present embodiment has a polarizing layer 21 including a cured product 101 of a liquid crystal compound and a dichroic dye 102. That is, the said composition for polarizer formation contains a liquid crystal compound together with a dichroic dye.

As a liquid crystal compound in this embodiment, a polymerizable liquid crystal compound is mentioned. The polymerizable liquid crystal compound is a liquid crystal compound that can be polymerized while being aligned, and has a polymerizable group in a molecule. The composition for forming a polarizer containing a polymerizable liquid crystal compound forms a cured film by polymerizing in a state in which the polymerizable liquid crystal compound is aligned. The cured film, that is, the cured product 101 of the liquid crystal compound need not exhibit liquid crystallinity. The polymerizable group is particularly preferably a radical polymerizable group. The radical polymerizable group means a group involved in a radical polymerization reaction.

A polymerizable liquid crystal compound is a liquid crystal phase of a nematic phase (hereinafter, referred to as a ``nematic liquid crystal phase'' in some cases), but a liquid crystal phase of a smectic phase (hereinafter, referred to as a ``smectic liquid crystal phase'' in some cases) ) May be represented, or both a nematic liquid crystal phase and a smectic liquid crystal phase may be represented, but a polymerizable smectic liquid crystal compound showing at least a smectic liquid crystal phase is preferable. In the composition for forming a polarizer containing a polymerizable smectic liquid crystal compound, coloring is suppressed by interaction with a dichroic dye, and a polarizer having more excellent polarization performance is obtained.

As the smectic liquid crystal phase exhibited by the polymerizable smectic liquid crystal compound, a higher order smectic liquid crystal phase is more preferable. The high-order Smectic liquid crystal phase here refers to Smectic B phase, Smectic D phase, Smectic E phase, Smectic F phase, Smectic G phase, Smectic H phase, Smectic I phase, Smectic J phase, Smectic They are the Smectic K phase and the Smectic L phase, and among them, the Smectic B phase, the Smectic F phase, and the Smectic I phase are more preferable.

If the Smectic liquid crystal phase represented by the polymerizable liquid crystal compound is these high-order Smectic liquid crystal phases, a polarizer having a higher degree of alignment order can be produced. Further, in the polarizer produced by using the polymerizable liquid crystal compound which is a high-order smectic liquid crystal phase with high alignment order, Bragg peaks derived from higher order structures such as a hexatic phase or a crystal phase are obtained in X-ray diffraction measurement. This Bragg peak is a peak derived from a plane periodic structure of molecular orientation. According to the composition for forming a polarizer according to the present embodiment, a polarizer having a periodic interval of 3.0 to 5.0 Å can be obtained.

Whether or not the polymerizable liquid crystal compound shows a nematic liquid crystal phase or a smectic liquid crystal phase can be confirmed as follows, for example. A suitable substrate is prepared, and a composition for forming a polarizer is applied to the substrate to form a coating film. After that, the solvent contained in the coating film is removed by heat treatment or reduced pressure treatment under conditions in which the polymerizable liquid crystal compound is not polymerized. Subsequently, the coating film formed on the substrate is heated to an isotropic temperature, and the liquid crystal phase expressed by gradually cooling is inspected by observation of a texture with a polarizing microscope. In this test, for example, a polymerizable liquid crystal compound showing a nematic liquid crystal phase by cooling, and further cooling a smectic liquid crystal phase is particularly preferred. In the nematic liquid crystal phase and the smectic liquid crystal phase, the fact that the polymerizable liquid crystal compound and the dichroic dye are not phase-separated can be confirmed by, for example, surface observation with various microscopes or scattering degree measurement with a haze meter.

Examples of the polymerizable liquid crystal compound include a compound represented by formula (4) (hereinafter, referred to as “compound (4)” in some cases).

U ¹ -V ¹ -W ¹ -X ¹ -Y ¹ -X ² -Y ² -X ³ -W ² -V ² -U ² (4)

In formula (4), X ¹ , X ² and X ³ each independently represent a 1,4-phenylene group which may have a substituent or a cyclohexane-1,4-diyl group which may have a substituent. At least one of X ¹ , X ² and X ³ is preferably a cyclohexane-1,4-diyl group which may have a substituent, and X ¹ or X ³ is a cyclohexane-1,4-diyl group which may have a substituent. It is particularly preferred that it is a diyl group. -CH ₂ -constituting the cyclohexane-1,4-diyl group which may have a substituent may be substituted with -O-, -S-, or -NR-. R is a C1-C6 alkyl group or a phenyl group.

The cyclohexane-1,4-diyl group which may have a substituent is preferably a trans-cyclohexane-1,4-diyl group which may have a substituent, and the trans-cyclohexane-1,4-diyl group which does not have a substituent It is more preferable that it is a diyl group. In formula (4), at least ^{two of} X ¹ , X ² and X ³ may be 1,4-phenylene groups which may have a substituent and are preferably 1,4-phenylene groups which do not have a substituent.

As a substituent optionally having a 1,4-phenylene group which may have a substituent or a cyclohexane-1,4-diyl group which may have a substituent, for example, an alkyl group having 1 to 4 carbon atoms such as a methyl group, an ethyl group and a butyl group, No group and a halogen atom.

In formula (4), Y ¹ and Y ² are each independently -CH ₂ CH ₂ -, -CH ₂ O-, -COO-, -OCOO-, single bond, -N=N-, -CR ^a =CR ^b -, -C≡C- or -CR ^a =N-. R ^a and R ^b each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. Y ¹ is preferably -CH ₂ CH ₂ -, -COO- or a single bond, and Y ² is preferably -CH ₂ CH ₂ -, -COO- or -CH ₂ O-.

In formula (4), U ¹ is a hydrogen atom or a polymerizable group, and preferably a polymerizable group. U ² is a polymerizable group. Together, U ¹ and U ² are preferably a polymerizable group, and more preferably a photopolymerizable group. The photopolymerizable group refers to a group capable of participating in a polymerization reaction by an active radical generated from a photopolymerization initiator described later, an acid or the like. The polymerizable liquid crystal compound having a photopolymerizable group is advantageous in that it can be polymerized under lower temperature conditions.

The polymerizable groups of U ¹ and U ² may be different from each other, but are preferably of the same kind. Examples of the polymerizable group include vinyl group, vinyloxy group, 1-chlorovinyl group, isopropenyl group, 4-vinylphenyl group, acryloyloxy group, methacryloyloxy group, oxiranyl group and oxetanyl group. . Among them, as the polymerizable group, an acryloyloxy group, a methacryloyloxy group, a vinyloxy group, an oxiranyl group and an oxetanyl group are preferable, and an acryloyloxy group is more preferable.

In formula (4), V ¹ and V ² each independently represent an alkanediyl group having 1 to 20 carbon atoms which may have a substituent, and -CH ₂ -constituting this alkanediyl group is -O-, It may be substituted with -S- or -NH-. Examples of the alkanediyl group having 1 to 20 carbon atoms include methylene group, ethylene group, propane-1,3-diyl group, butane-1,3-diyl group, butane-1,4-diyl group, pentane-1,5 -Diyl group, hexane-1,6-diyl group, heptane-1,7-diyl group, octane-1,8-diyl group, decane-1,10-diyl group, tetradecane-1,14-diyl group and Icosane-1,20-diyl group is mentioned. V ¹ and V ² are preferably an alkanediyl group having ² to 12 carbon atoms, and more preferably an alkanediyl group having 6 to 12 carbon atoms. Examples of the substituents that the alkanediyl group having 1 to 20 carbon atoms have optionally include a cyano group and a halogen atom. It is preferable that this alkanediyl group is unsubstituted, and it is more preferable that it is unsubstituted and linear.

In formula (4), W ¹ and W ² each independently represent a single bond, -O-, -S-, -COO-, or -OCOO-, and preferably a single bond or -O-.

Examples of the compound (4) include compounds represented by formulas (4-1) to (4-43). When a specific example of compound (4) has a cyclohexane-1,4-diyl group, it is preferable that the cyclohexane-1,4-diyl group is a trans chain.

The polymerizable liquid crystal compound can be used alone or in a mixture of two or more for forming a polarizer. When two or more kinds of polymerizable liquid crystal compounds are mixed, it is preferable that at least one kind is compound (4). As a mixing ratio in the case of mixing two kinds of polymerizable liquid crystal compounds, usually, a polymerizable liquid crystal compound other than compound (4): compound (4) is 1:99 to 50:50, preferably 5:95 to 50 :50, More preferably, it is 10:90-50:50.

Among compound (4), formula (4-5), formula (4-6), formula (4-7), formula (4-8), formula (4-9), formula (4-10), formula ( 4-11), equation (4-12), equation (4-13), equation (4-14), equation (4-15), equation (4-22), equation (4-24), equation (4 Compounds represented by -25), formula (4-26), formula (4-27), formula (4-28), and formula (4-29) are preferred. These compounds can be polymerized under a temperature condition that is easily lower than the crystal phase transition temperature by interaction with other polymerizable liquid crystal compounds, that is, while sufficiently maintaining the liquid crystal state of the higher order smectic phase. Specifically, these compounds can be polymerized under a temperature condition of 70° C. or less, preferably 60° C. or less, while sufficiently maintaining the liquid crystal state of a high-order smectic phase.

The content ratio of the polymerizable liquid crystal compound in the composition for polarizer formation is preferably 50% by mass to 99.9% by mass, and more preferably 80% by mass to 99.9% by mass with respect to the solid content of the composition for polarizer formation. When the content ratio of the polymerizable liquid crystal compound is within the above range, the orientation of the polymerizable liquid crystal compound tends to increase. The solid content refers to the total amount of components excluding volatile components such as a solvent from the composition for forming a polarizer.

Polymerizable liquid crystal compounds are, for example, Lub et al. It is produced by a known method described in Recl. Trav. Chim. Pays-Bas, 115, 321-328 (1996), Japanese Patent No. 4719156, and the like.

1-3. solvent

It is preferable that the composition for polarizer formation contains a solvent. As the solvent, a solvent capable of completely dissolving a dichroic dye and a polymerizable liquid crystal compound is preferable. Moreover, it is preferable that it is a solvent inert to the polymerization reaction of the polymerizable liquid crystal compound contained in the composition for polarizer formation.

Examples of the solvent include alcohol solvents such as methanol, ethanol, ethylene glycol, isopropyl alcohol, propylene glycol, ethylene glycol methyl ether, ethylene glycol butyl ether and propylene glycol monomethyl ether; Ester solvents such as ethyl acetate, butyl acetate, ethylene glycol methyl ether acetate, γ-butyrolactone, propylene glycol methyl ether acetate, and ethyl lactate; Ketone solvents such as acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, 2-heptanone and methyl isobutyl ketone; Aliphatic hydrocarbon solvents such as pentane, hexane and heptane; Aromatic hydrocarbon solvents such as toluene and xylene; Nitrile solvents such as acetonitrile; Ether solvents such as tetrahydrofuran and dimethoxyethane; And chlorine-containing solvents such as chloroform and chlorobenzene. These solvents may be used alone or in combination of two or more.

The content of the solvent is preferably 50% by mass to 98% by mass with respect to the total amount of the composition for forming a polarizer. In other words, the solid content in the composition for forming a polarizer is preferably 2% by mass to 50% by mass. When the solid content is 2% by mass or more, it becomes easy to obtain a thin polarizing plate that is one of the objects of the present embodiment. In addition, when the solid content is 50% by mass or less, the viscosity of the composition for forming a polarizer decreases, so that the thickness of the polarizer becomes substantially uniform, so that it is difficult to cause variation in the polarizer. The solid content can be determined in consideration of the thickness of the polarizer.

1-4. additive

The composition for forming a polarizer according to the present embodiment may optionally contain an additive. As an additive, a polymerization initiator, a photosensitizer, a polymerization inhibitor, and a leveling agent are mentioned, for example.

1-4-1. Polymerization initiator

It is preferable that the composition for polarizer formation contains a polymerization initiator. The polymerization initiator is a compound capable of initiating a polymerization reaction of a polymerizable liquid crystal compound. As a polymerization initiator, a photoinitiator is preferable because a polymerization reaction can be started under low temperature conditions. Specifically, a compound that generates an active radical or an acid by the action of light is used as a photopolymerization initiator. Among the photopolymerization initiators, it is more preferable to generate active radicals by the action of light.

Examples of the polymerization initiator include benzoin compounds, benzophenone compounds, alkylphenone compounds, acylphosphine oxide compounds, triazine compounds, iodonium salts and sulfonium salts.

As a benzoin compound, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and benzoin isobutyl ether are mentioned, for example.

As a benzophenone compound, for example, benzophenone, o-benzoyl methylbenzoate, 4-phenylbenzophenone, 4-benzoyl-4'-methyldiphenylsulfide, 3,3',4,4'-tetra(tert-butylper Oxycarbonyl)benzophenone and 2,4,6-trimethylbenzophenone.

Examples of the alkylphenone compound include diethoxyacetophenone, 2-methyl-2-morpholino-1-(4-methylthiophenyl)propan-1-one, and 2-benzyl-2-dimethylamino-1-(4 -Morpholinophenyl)butan-1-one, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1,2-diphenyl-2,2-dimethoxyethan1-one, 2- Hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]propan-1-one, 1-hydroxycyclohexylphenylketone and 2-hydroxy-2-methyl-1-[4 Oligomers of -(1-methylvinyl)phenyl]propan-1-one.

Examples of the acylphosphine oxide compound include 2,4,6-trimethylbenzoyldiphenylphosphine oxide and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide.

As a triazine compound, for example, 2,4-bis(trichloromethyl)-6-(4-methoxyphenyl)-1,3,5-triazine, 2,4-bis(trichloromethyl)-6- (4-methoxynaphthyl)-1,3,5-triazine, 2,4-bis(trichloromethyl)-6-(4-methoxystyryl)-1,3,5-triazine, 2 ,4-bis(trichloromethyl)-6-[2-(5-methylfuran-2-yl)ethenyl]-1,3,5-triazine, 2,4-bis(trichloromethyl)-6 -[2-(furan-2-yl)ethenyl]-1,3,5-triazine, 2,4-bis(trichloromethyl)-6-[2-(4-diethylamino-2-methylphenyl ) Ethenyl]-1,3,5-triazine and 2,4-bis(trichloromethyl)-6-[2-(3,4-dimethoxyphenyl)ethenyl]-1,3,5-tri Ajin is mentioned.

As the polymerization initiator, a commercially available one can also be used. As a commercially available polymerization initiator, for example, "Irgacure 907", "Igacure 184", "Igacure 651", "Igacure 819", "Igacure 250", "Igacure 369" [BASF Japan ( week)]; "Seikuol BZ", "Seikuol Z", "Seikuol BEE" [Seiko Chemical Co., Ltd.]; "Kayacure BP100" [Nihon Kayaku Co., Ltd.]; "UVI-6992" (manufactured by Dow Chemical); "Adeka Optomer SP-152", "Adeka Optomer SP-170" [ADEKA Co., Ltd.]; "TAZ-A", "TAZ-PP" (DKSH Japan company); And "TAZ-104" [Sanwa Chemical Co., Ltd.].

When the composition for forming a polarizer contains a polymerization initiator, the content can be appropriately adjusted depending on the type and amount of the polymerizable liquid crystal compound contained in the composition for forming a polarizer, but usually 100 masses in total of the polymerizable liquid crystal compound The content of the polymerization initiator with respect to parts is 0.1 to 30 parts by mass, preferably 0.5 to 10 parts by mass, and more preferably 0.5 to 8 parts by mass. When the content of the polymerizable initiator is within this range, polymerization can be performed without disturbing the orientation of the polymerizable liquid crystal compound, which is preferable.

1-4-2. Photosensitizer

When the composition for forming a polarizer contains a photopolymerization initiator, it may further contain a photosensitizer. Examples of the photosensitizer include xanthone compounds such as xanthone and thioxanthone (eg, 2,4-diethyloxanthone, 2-isopropyl thioxanthone, etc.); Anthracene compounds such as anthracene and an alkoxy group-containing anthracene (eg, dibutoxyanthracene, etc.); Phenothiazine and rubrene.

When the composition for forming a polarizer contains a photoinitiator and a photosensitizer, the polymerization reaction of the polymerizable liquid crystal compound contained in the composition for forming a polarizer is further promoted. The content of the photosensitizer can be appropriately adjusted depending on the type and amount of the photopolymerization initiator and the polymerizable liquid crystal compound to be used in combination, but usually 0.1 to 30 parts by mass based on 100 parts by mass of the content of the polymerizable liquid crystal compound And preferably 0.5 to 10 parts by mass, more preferably 0.5 to 8 parts by mass.

1-4-3. Polymerization inhibitor

The composition for forming a polarizer may contain a polymerization inhibitor in order to stably advance the polymerization reaction of the polymerizable liquid crystal compound. The degree of progression of the polymerization reaction of the polymerizable liquid crystal compound can be controlled by the polymerization inhibitor.

Examples of the polymerization inhibitor include hydroquinone, alkoxy group-containing hydroquinone, alkoxy group-containing catechol (eg, butylcatechol, etc.), pyrogallol, 2,2,6,6-tetramethyl-1-piperidinyloxy radical, etc. Radical supplements of; Thiophenols; β-naphthylamines and β-naphthols are mentioned.

When the composition for forming a polarizer contains a polymerization inhibitor, its content is appropriately adjusted depending on the kind and amount of the polymerizable liquid crystal compound to be used, and the content of the photosensitizer, but usually, the content of the polymerizable liquid crystal compound is 100 masses. With respect to parts, it is 0.1 to 30 parts by mass, preferably 0.5 to 10 parts by mass, and more preferably 0.5 to 8 parts by mass.

When the content of the polymerization inhibitor is within the above range, polymerization can be performed without disturbing the orientation of the polymerizable liquid crystal compound contained in the composition for forming a polarizer, which is preferable.

1-4-4. Leveling agent

It is preferable that the composition for polarizer formation contains a leveling agent. The leveling agent has a function of making the coating film obtained by applying the composition for forming a polarizer by adjusting the fluidity of the composition for forming a polarizer and making the coating film more flat, and examples thereof include surfactants. Examples of the leveling agent include a leveling agent containing a polyacrylate compound as a main component and a leveling agent containing a fluorine atom-containing compound as a main component.

As a leveling agent containing a polyacrylate compound as a main component, for example, "BYK-350", "BYK-352", "BYK-353", "BYK-354", "BYK-355", "BYK-358N", "BYK-361N", "BYK-380", "BYK-381" and "BYK-392" [BYK Chemie Corporation] are mentioned.

As a leveling agent containing a fluorine atom-containing compound as a main component, for example, Megapak "R-08", "R-30", "R-90", "F-410", "F-411", "F-443" ", "F-445", "F-470", "F-471", "F-477", "F-479", "F-482" and "F-483" [DIC Corporation]; Surflons "S-381", "S-382", "S-383", "S-393", "SC-101", "SC-105", "KH-40" and "SA-100" [ AGC Semichemical Co., Ltd.]; "E1830", "E5844" [Daikin High School Co., Ltd.]; Ftop "EF301", "EF303", "EF351" and "EF352" (Mitsubishima Teral Denshi Kasei Co., Ltd.) are mentioned.

When the composition for forming a polarizer contains a leveling agent, the content is usually 0.3 parts by mass or more and 5 parts by mass or less, and preferably 0.5 parts by mass or more and 3 parts by mass based on 100 parts by mass of the content of the polymerizable liquid crystal compound. Below. When the content of the leveling agent is within the above range, it is easy to horizontally align the polymerizable liquid crystal compound, and the obtained polarizer tends to become smoother. When the content of the leveling agent with respect to the polymerizable liquid crystal compound exceeds the above range, there is a tendency that variations tend to occur in the obtained polarizer. Moreover, the composition for polarizer formation may contain two or more types of leveling agents.

2. The first description and the second description

As the first substrate 12 and the second substrate 14, a thermoplastic resin substrate can be used. The first substrate 12 and the second substrate 14 are preferably transparent thermoplastic resin substrates. The transparent thermoplastic resin substrate is a thermoplastic resin substrate having a degree of transparency capable of transmitting light, particularly visible light. Transparency refers to a characteristic in which the transmittance of light having a wavelength of 380 nm to 780 nm is 80% or more. The first substrate and the second substrate may be formed of the same thermoplastic resin, or may be formed of different thermoplastic resins.

Specifically, examples of the first substrate 12 and the second substrate 14 include polyolefins such as polyethylene, polypropylene, and norbornene-based polymer; Cyclic olefin resin; Polyvinyl alcohol; Polyethylene terephthalate; Acrylic resins such as polymethacrylic acid ester and polyacrylic acid ester; Polyethylene naphthalate; Polycarbonate; Polysulfone; Polyethersulfone; Polyether ketone; Polyphenylene sulfide and polyphenylene oxide. Among them, from the viewpoint of being readily available on the market or having excellent transparency, preferably, it is a cyclic olefin resin, polyethylene terephthalate, or acrylic resin, and particularly preferably, a cyclic olefin resin or polymethacryl. It is an acid ester. In the manufacturing process of the polarizing plate 1, the first substrate 12 and the second substrate 14 can be easily handled without causing breakage or other damage when transporting or storing the first substrate. (12) and the second substrate 14 may be adhered to a supporting substrate or the like.

If either of the first substrate 12 and the second substrate 14 is a thermoplastic resin substrate, the other may not be a thermoplastic resin substrate. When either of the first substrate 12 and the second substrate 14 is a thermoplastic resin substrate, the curved formability of the polarizing plate 1 is maintained. For example, as the first substrate, a substrate containing a cellulose ester resin such as triacetyl cellulose, diacetyl cellulose and cellulose acetate propionate may be used. As an example, a substrate containing triacetyl cellulose can be used as the first substrate, and a substrate containing an acrylic resin can be used as the second substrate.

When imparting a retardation property to the first substrate 12, a plastic substrate containing a cellulose ester or a cyclic olefin resin is preferable from the viewpoint of being easy to control the retardation value.

As for the cellulose ester, at least part of the hydroxyl groups contained in cellulose is acetic acid esterified. A cellulose ester film containing such a cellulose ester can be easily obtained from the market. As a commercially available triacetylcellulose film, for example, "Fuji Tag Film" [Fuji Shashin Film Co., Ltd.]; "KC8UX2M", "KC8UY", and "KC4UY" (Konica Minolta Opto Co., Ltd.) are mentioned. Such a commercially available triacetylcellulose film can be used as the first substrate 12 as it is or after imparting retardation as necessary. Further, the surface of the prepared first substrate 12 can be used as the first substrate 12 after surface treatment such as antiglare treatment, hard coat treatment, antistatic treatment or antireflection treatment is performed.

The cyclic olefin resin is composed of, for example, a polymer or copolymer of a cyclic olefin such as norbornene or a polycyclic norbornene monomer. The cyclic olefin-based resin may partially contain a ring-opening portion, or a cyclic olefin-based resin including a ring-opening portion may be hydrogenated. The cyclic olefin-based resin may be a copolymer of, for example, a cyclic olefin and a chain olefin or a vinylated aromatic compound (such as styrene), in terms of not significantly impairing transparency or not significantly increase hygroscopicity. In addition, the cyclic olefin resin may have a polar group introduced into its molecule.

When the cyclic olefin resin is a copolymer of a cyclic olefin and an aromatic compound having a chain olefin or a vinyl group, examples of the chain olefin include ethylene and propylene, and examples of the vinylated aromatic compound include styrene, α-methylstyrene. And alkyl substituted styrene. In such a copolymer, the content ratio of the structural unit derived from the cyclic olefin is in the range of 50 mol% or less, such as about 15 mol% to 50 mol%, based on the total structural units of the cyclic olefin resin. When the cyclic olefin resin is a ternary copolymer obtained from a cyclic olefin, a chain olefin, and a vinylated aromatic compound, for example, the content ratio of the structural unit derived from the chain olefin is 5 with respect to the total structural units of the cyclic olefin resin. It is about 5 mol% to 80 mol%, and the content ratio of the structural unit derived from a vinylated aromatic compound is about 5 mol%-80 mol%. The cyclic olefin resin of such a ternary copolymer has the advantage of being able to relatively reduce the amount of expensive cyclic olefin used when producing this cyclic olefin resin.

Cyclic olefin resin can be easily obtained from the market. Examples of commercially available cyclic olefin resins include "Topas" (Ticona (Germany)); "Aton" [JSR Corporation]; "ZEONOR" and "ZEONEX" (Nippon Xeon Corporation); "Apel" (manufactured by Mitsui Chemical Co., Ltd.) is mentioned. Such a cyclic olefin resin can be formed into a film (cyclic olefin resin film) by producing a film by a known film production means such as a solvent casting method or a melt extrusion method. In addition, a cyclic olefin resin film already commercially available in the form of a film can also be used. Examples of such commercially available cyclic olefin-based resin films include "Esshina" and "SCA40" (Sekisui Chemical Co., Ltd.); "Zeonore Film" [Optes Co., Ltd.]; And "Aton Film" [JSR Corporation].

The thickness of the first substrate 12 and the second substrate 14 is preferably thinner in terms of weight that can be handled practically and sufficient transparency can be secured, but if it is too thin, the strength is increased. There is a tendency to decrease and workability is inferior. The appropriate thickness of each of the first substrate 12 and the second substrate 14 is, for example, about 20 µm to 200 µm, and preferably about 20 µm to 160 µm. When the polarizing plate 1 of this embodiment is used as a circular polarizing plate to be described later, or in particular, when used as a polarizing plate for mobile devices, the thickness of the transparent substrate is preferably about 20 µm to 80 µm, and 20 µm to It may be 50 µm.

3. Alignment layer

It is preferable that the orientation layer 22 is formed on the 1st base material 12 or the 2nd base material 14. In this case, the composition for forming a polarizer is applied on the alignment layer 22. For this reason, it is preferable that the orientation layer 22 has a solvent resistance such that it does not dissolve by application of the composition for forming a polarizer. Moreover, it is preferable to have heat resistance in heat treatment for removal of a solvent or alignment of a liquid crystal. The alignment layer 22 can be formed of an alignment polymer.

As the orientation polymer, for example, polyamide, gelatin, polyimide, polyamic acid, polyvinyl alcohol, alkyl-modified polyvinyl alcohol, polyacrylamide, polyoxazole, polyethyleneimine, polystyrene, polyvinylpyrrolidone, polyacrylic acid, and Polyacrylic acid ester is mentioned. Among these, polyvinyl alcohol is preferable. These oriented polymers may be used alone or in combination of two or more.

The oriented polymer is an oriented polymer composition (a solution containing the oriented polymer) dissolved in a solvent, and is applied on the first base 12 or the second base 14 to prepare the first base 12 or the second base 14. ) On the alignment layer 22 may be formed. Examples of the solvent include water; Alcohol solvents such as methanol, ethanol, ethylene glycol, isopropyl alcohol, propylene glycol, methyl cellosolve, butyl cellosolve, and propylene glycol monomethyl ether; Ester solvents such as ethyl acetate, butyl acetate, ethylene glycol methyl ether acetate, γ-butyrolactone, propylene glycol methyl ether acetate, and ethyl lactate; Ketone solvents such as acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, methyl amyl ketone and methyl isobutyl ketone; Aliphatic hydrocarbon solvents such as pentane, hexane and heptane; Aromatic hydrocarbon solvents such as toluene and xylene, nitrile solvents such as acetonitrile; Ether solvents such as tetrahydrofuran and dimethoxyethane; And chlorine-substituted hydrocarbon solvents such as chloroform and chlorobenzene. These solvents may be used alone or in combination of multiple types.

As the alignment polymer composition, a commercially available alignment film material may be used as it is. Examples of commercially available alignment film materials include Sunever (registered trademark, manufactured by Nissan Chemical Industry Co., Ltd.) and optomer (registered trademark, manufactured by JSR Corporation), for example.

The alignment layer 22 may be a photo-alignment layer. With the photo-alignment layer, a composition containing a polymer or monomer having a photoreactive group and a solvent (hereinafter, referred to as a composition for forming a photo-alignment layer) is applied to the first substrate 12, and polarized light (preferably In other words, it refers to an alignment layer to which an alignment regulating force is imparted by irradiation with polarized UV). The photoreactive group refers to a group in which liquid crystal aligning ability is generated by irradiating light. Specifically, the photoreactive group generates a photoreaction that is the origin of the liquid crystal alignment ability, such as an orientation organic or isomerization reaction, dimerization reaction, photocrosslinking reaction, or photodecomposition reaction of molecules generated by irradiation with light. The photoreactive group which causes a dimerization reaction or a photocrosslinking reaction is excellent in orientation and is preferable in terms of maintaining a smectic liquid crystal state at the time of forming a polarizer. As the photoreactive group, it is preferable to have an unsaturated bond, particularly a double bond, and a carbon-carbon double bond (C=C bond), a carbon-nitrogen double bond (C=N bond), a nitrogen-nitrogen double bond (N=N Bond) and a group having at least one selected from the group consisting of a carbon-oxygen double bond (C=O bond).

Examples of the photoreactive group having a C=C bond include a vinyl group, a polyene group, a stilbene group, a stilbazole group, a stilbazolium group, a chalcone group and a cinnamoyl group. Examples of the photoreactive group having a C=N bond include groups having structures such as an aromatic cipro base and an aromatic hydrazone. Examples of the photoreactive group having an N=N bond include an azobenzene group, an azonaphthalene group, an aromatic heterocyclic azo group, a bisazo group, and a formazane group, and a group having azoxybenzene as a basic structure. Examples of the photoreactive group having a C=O bond include a benzophenone group, a coumarin group, an anthraquinone group and a maleimide group. These groups may have a substituent such as an alkyl group, an alkoxy group, an aryl group, an allyloxy group, a cyano group, an alkoxycarbonyl group, a hydroxyl group, a sulfonic acid group, or a halogenated alkyl group. Among them, a photoreactive group capable of causing a light dimerization reaction is preferable, and a cinnamoyl group and a chalcone group have a relatively small amount of polarization irradiation required for photo-alignment, and it is easy to obtain a photo-alignment layer excellent in thermal stability and stability over time Because it is desirable. Further, as a polymer having a photoreactive group, it is more preferable to have a cinnamoyl group in which the terminal portion of the side chain of the polymer has a cinnamic acid structure.

As the solvent for the composition for forming a photo-alignment layer, it is preferable to dissolve a polymer and a monomer having a photoreactive group, and for example, the solvent used in the above-described alignment polymer composition can be mentioned.

The concentration of the polymer or monomer having a photoreactive group in the composition for forming a photo-alignment layer can be appropriately adjusted according to the type of the polymer or monomer having a photoreactive group or the thickness of the photo-alignment layer to be manufactured, but expressed in solid content concentration. Therefore, it is preferable to set it as at least 0.2 mass %, and the range of 0.3 mass%-10 mass% is more preferable. The composition for forming a photo-alignment layer may contain a polymer material such as polyvinyl alcohol or polyimide, and a photosensitizer, within a range in which the characteristics of the alignment layer 22 are not significantly impaired.

The thickness of the alignment layer 22 is 10 nm or more and 10000 nm or less, and preferably 10 nm or more and 1000 nm or less. The thickness of the alignment layer 22 in this embodiment can be determined by measuring five arbitrary points of the alignment layer 22 with an interference film thickness meter, and calculating the average value.

In the polarizer 11 according to the present embodiment, the absorbance (A1) in the absorption axis direction at a wavelength of 380 nm to 760 nm is 0.3 or more and 1.5 or less, preferably 0.3 or more and 1.0 or less, and more preferably 0.33 or more and 0.9 or less. And more preferably 0.36 or more and 0.85 or less. The absorbance (A2) in the direction of the transmission axis is 0.001 or more and 0.15 or less, preferably 0.001 or more and 0.10 or less, more preferably 0.002 or more and 0.05 or less, and still more preferably 0.005 or more and 0.040 or less.

The absorbance is to control the thickness of the polarizer 11 by adjusting the type of the dichroic dye 102 contained in the polarizer 11, the amount of the dichroic dye 102, and the solid content concentration or coating amount of the composition for forming a polarizer. It can be adjusted appropriately by the thing or the like.

4. Manufacturing method of polarizing plate

A method of manufacturing the polarizing plate 1 using the composition for forming a polarizer will be described. In this method, the polarizing plate 1 is formed by applying the composition for forming a polarizer to the first substrate 12, preferably to the first substrate 12 which is a transparent thermoplastic resin substrate. In addition, in the present embodiment, an example in which the cured product 101 of the liquid crystal compound is a polymerizable liquid crystal compound will be described.

As a method of forming the alignment layer 22 on the first substrate 12, for example, a method of applying a composition for forming an alignment layer or a commercially available alignment film material on the first substrate 12 and heating it may be mentioned. The thickness of the coating film of the composition for forming an alignment layer is determined in consideration of the thickness of the alignment layer 22 to be obtained.

In order to impart an orientation regulating force to the orientation layer 22, it is preferable to perform rubbing as necessary (rubbing method). The cured product 101 of the liquid crystal compound can be aligned in a desired direction by imparting an alignment regulating force.

As a method of imparting an orientation regulating force according to the rubbing method, for example, a rubbing cloth is wound, a rotating rubbing roll is prepared, and a coating film for forming an alignment layer is formed on the first substrate 12. The method of bringing the coating film for forming an alignment layer into contact with the rotating rubbing roll by carrying the sieve on the stage and conveying it toward the rotating rubbing roll is mentioned.

As a method of applying the composition for forming an alignment layer or the composition for forming a photo-alignment layer on the first substrate 12, a spin coating method, an extrusion method, a gravure coating method, a die coating method, a bar coating method, and A known method such as a coating method such as an applicator method or a printing method such as a flexo method is employed. In addition, when the polarizer is manufactured by a continuous manufacturing method of a Roll to Roll format, a printing method such as a gravure coating method, a die coating method, or a flexo method is usually employed as the coating method.

In addition, when performing rubbing or polarization irradiation, if masking is performed, a plurality of regions (patterns) having different orientation directions may be formed.

On the first substrate 12 or the alignment layer 22 formed on the first substrate 12, a composition for forming a polarizer is applied to obtain a coating film. As a method of applying the composition for forming a polarizer, the same method as exemplified as a method of applying the composition for forming an alignment layer or the composition for forming a photo-alignment layer to a substrate may be mentioned.

Next, a dry film is formed by drying and removing the solvent contained in the composition for forming a polarizer under conditions not to polymerize the liquid crystal compound contained in the coating film. As a drying method, a natural drying method, a ventilation drying method, a heat drying method, and a vacuum drying method are mentioned, for example.

As a preferred embodiment, after the liquid crystal state of the liquid crystal compound contained in the dry film is set to a nematic liquid crystal, the nematic liquid crystal phase is transferred to the smectic liquid crystal phase. In order to form the Smectic liquid crystal phase via the nematic liquid crystal phase as described above, for example, the liquid crystal compound contained in the dry film is heated to a temperature above the temperature exhibiting the nematic liquid crystal phase, and then the liquid crystal compound is A method of cooling down to a temperature indicating a temperature is adopted.

When the liquid crystal compound in the dry film is made into a smectic liquid crystal phase or the polymerizable liquid crystal compound is made into a smectic liquid crystal phase via a nematic liquid crystal phase, the liquid crystal state is controlled by measuring the phase transition temperature of the polymerizable liquid crystal compound The condition (heating condition) can be obtained.

Next, the polymerization step of the liquid crystal compound will be described. Herein, a photopolymerization initiator is contained in the composition for forming a polarizer, and the liquid crystal state of the liquid crystal compound in the dried film is Smectic liquid crystal phase, and then the liquid crystal compound is photopolymerized while maintaining the liquid crystal state of the Smectic liquid crystal phase. It will be described in detail.

In photopolymerization, as the light irradiated to the dry film, as appropriate depending on the kind of the photopolymerization initiator contained in the dry film or the kind of the liquid crystal compound (particularly, the kind of polymerizable group of the liquid crystal compound) and the amount thereof, visible light or magnetic It can be performed with light selected from the group consisting of external light and laser light, or with active electron beams. Among these, ultraviolet light is preferred because it is easy to control the progress of the polymerization reaction, or because one widely used in the art can be used as an apparatus related to photopolymerization. Therefore, it is preferable to select the kind of liquid crystal compound or photoinitiator contained in the composition for polarizer formation so that photopolymerization can be performed by ultraviolet light.

In addition, at the time of polymerization, the polymerization temperature can also be controlled by cooling the dried film by an appropriate cooling means together with irradiation with ultraviolet light. By employing such a cooling means, if polymerization of the liquid crystal compound can be performed at a lower temperature, even if a substrate having relatively low heat resistance is used as the first substrate 12, the polarizer 11 can be appropriately formed. There is also an advantage. In addition, the patterned polarizer 11 can also be obtained by performing masking or development during photopolymerization.

By performing the photopolymerization as described above, the liquid crystal compound is polymerized while maintaining a nematic liquid crystal phase or a smectic liquid crystal phase, preferably a high-order smectic liquid crystal phase as already illustrated, and the polarizer 11 is formed. do. The polarizer 11 obtained by polymerizing the liquid crystal compound while maintaining the smectic liquid crystal phase has the advantage of having higher polarization performance compared to the polarizer obtained by polymerizing a polymerizable liquid crystal compound and the like while maintaining the liquid crystal state of the nematic liquid crystal phase. have. In addition, there is an advantage in that the strength is excellent compared to that of coating only a lyotropic dichroic dye.

The thickness of the polarizing layer 21 is preferably 1 µm or more and less than 15 µm, more preferably 1 µm or more and 10 µm or less, even more preferably 1 µm or more and 5 µm or less, and 1 µm or more and 3 µm or less. It is particularly preferred. Therefore, the thickness of the coating film for forming a polarizer is determined in consideration of the thickness of the obtained polarizing layer 21. As for the thickness of the polarizing layer 21 in the present embodiment, five arbitrary points of the polarizing layer 21 are measured with a contact type film thickness meter, an interference film thickness meter, a laser microscope or a stylus type film thickness meter, and the average value is calculated. It can be obtained by doing.

In addition, in addition to the method of forming the polarizer 11 on the first substrate 12 as described above, after forming the polarizer 11 on the other substrate by the above-described method, the polarizer 11 is attached to the first substrate ( A polarizing plate can also be manufactured by a method of transferring and bonding to 12).

In the above example, an example of forming the alignment layer 22 and the polarizing layer 21 on the first substrate 12 has been described, but on the second substrate 14, the alignment layer 22 and the polarizing layer ( 21) may be formed. In this case, by laminating the first substrate 12 on the polarizing layer 21 through an adhesive layer or an adhesive layer, the second substrate 14, the alignment layer 22, the polarizing layer 21 and the first substrate A polarizing plate having a is obtained.

It is preferable that the formed polarizer 11 obtains a Bragg peak in X-ray diffraction measurement. As a polarizer from which the Bragg peak is obtained, for example, a polarizer exhibiting a diffraction peak derived from a hexatic phase or a crystal phase may be mentioned.

When commercially manufacturing a polarizer, a method capable of continuously forming a polarizer is required. This continuous manufacturing method is in accordance with the Roll to Roll type, and in some cases, it is referred to as "this manufacturing method". In addition, in this manufacturing method, the case where the 1st base material 12 is transparent is mainly demonstrated. When the first substrate 12 is transparent, what is finally obtained is the polarizing plate 1 having the transparent first substrate 12 and the polarizer 11.

This manufacturing method includes, for example, the following steps. A first roll in which the first substrate 12 is wound around a first core is prepared. The first base material 12 is continuously delivered from the first roll. On this first substrate 12, an alignment layer 22 is continuously formed. On this alignment layer 22, a composition for forming a polarizer is continuously applied. By drying the applied composition for forming a polarizer under conditions in which the liquid crystal compound does not polymerize, a dry film is continuously formed on the alignment layer 22. The liquid crystal compound contained in this dried film is made into a nematic liquid crystal phase, preferably a smectic liquid crystal phase. After that, by polymerizing a liquid crystal compound while holding this Smectic liquid crystal phase, the polarizing layer 21 is continuously obtained, and the polarizer 11 is used. The polarizer 11 obtained continuously is wound up around a 2nd winding core, and a 2nd roll is obtained.

As for the polarizing plate 1 obtained by this manufacturing method, the shape is a film-shaped and a long-shaped polarizing film. When this polarizing plate 1 is used for lenses such as sunglasses, which will be described later, it is cut and used according to the dimensions of lenses such as sunglasses.

As for the polarizing plate 1, the form of the laminated body of the 1st base material 12/orientation layer 22/polarization layer 21 is mentioned. In addition, the polarizing plate 1 may have a form in which layers or films other than the first substrate 12 / alignment layer 22 / polarizing layer 21 are further stacked. As these layers and films, a retardation film may be further provided in the polarizing plate 1, or an antireflection layer or a brightness improving film may be further provided.

For example, the polarizing plate 1 of the present embodiment becomes a circular polarizing plate 2 by further providing a quarter wave plate. 3 is a schematic cross-sectional view of a circular polarizing plate in an embodiment of the present invention. The circular polarizing plate 2 is different from the first substrate 12 on which the alignment layer 22 is disposed on one surface, the polarizing layer 21 provided on the alignment layer 22, and the first substrate 12 It includes a retardation film 15, which is a 1/4 wavelength plate disposed on the side of the side. Moreover, the retardation film 15 may be located on the second surface 32 of the polarizer 11. In this case, as shown in FIG. 4, the circular polarizing plate 2'takes a form arranged in the order of the first substrate 12, the alignment layer 22, the polarizing layer 21, and the retardation film 15. May be.

When producing a circular polarizing plate, the first substrate 12 or the polarizer 11 and the retardation film 15 may be bonded to each other through an adhesive layer formed of an adhesive using an appropriate adhesive.

By using the first substrate 12 to which the retardation property has been previously imparted, the first substrate 12 itself may have a function as a retardation layer. By using the first substrate 12 itself as a retardation film, a circular polarizing plate or an elliptically polarizing plate in the form of the first substrate 12/alignment layer 22/polarization layer 21 may be used. It is preferable that the quarter-wave plate used when manufacturing the circular polarizing plate as described above has a characteristic that the in-plane retardation value for visible light decreases as the wavelength decreases.

Using a 1/2 wavelength plate as the retardation film 15, a linear polarizing plate roll as set by shifting the angle of the slow axis and the absorption axis of the polarizer 11 was prepared, and the surface on which the polarizer 11 was formed It is also possible to form a broadband circular polarizing plate by further forming a quarter wave plate on the opposite side.

The birefringence index for light having a wavelength of 450 nm, the birefringence index for light having a wavelength of 550 nm, and the birefringence index for light having a wavelength of 650 nm of the 1/4 wavelength plate used as the retardation film 15 are represented by the following formula (II): And it is preferable to have reverse wavelength dispersion that satisfies the relationship represented by (III). In the formula, Δn(λ) represents the birefringence index for light having a wavelength of λ nm.

Δn(450)/Δn(550)≤1.00 (II)

1.00≤Δn(650)/Δn(550) (III)

A retardation film exhibiting such reverse wavelength dispersion characteristics can be produced according to the method described in Japanese Patent No. 553666.

As a method of forming a curved portion by heating the polarizing plate 1 of the present embodiment, insert molding, injection molding, pressure hole molding, vacuum molding, and mold press may be mentioned.

Since the polarizing plate 1 in this embodiment has small heat shrinkage and is thin, it can have a curved part with a small radius of curvature.

As an aspect of the present invention, it is preferable that the first base material 12 is an acrylic resin film or a cyclic olefin resin film. When these thermoplastic resin substrates are used, the polarizing plate 1 having a curved portion having a small radius of curvature can be realized because it is easy to process at a low temperature and has good thermoformability.

As an aspect of the present invention, the liquid crystal compound is preferably a compound represented by formula (4-6) shown below or a compound represented by formula (4-7).

As an aspect of the present invention, the dichroic dye 102 is selected from the group consisting of a compound represented by formula (2-15), a compound formula represented by formula (2-18) and formula (2-37). It is preferable to include at least one of. The compound represented by formula (2-15) has a maximum absorption wavelength at 380 nm. The compound represented by formula (2-18) has a maximum absorption wavelength at 490 nm. The compound represented by formula (2-37) has a maximum absorption wavelength at 590 nm. When these dichroic dyes are used, a polarizing plate having high polarization characteristics can be realized. It is more preferable that the dichroic dye 102 contains a compound represented by a formula (2-15), a compound formula represented by a formula (2-18) and a formula (2-37).

As an aspect of the present invention, the polarizing plate 1 includes an acrylic resin film as the first thermoplastic resin substrate [the first substrate 12], and a compound represented by formula (4-6) as a liquid crystal compound and a formula A compound represented by formula (2-15), a compound represented by formula (2-18), and a compound represented by formula (2-37) as a dichroic dye (102) containing a compound represented by (4-7) It is preferable to include a compound that becomes. In such a polarizing plate 1, since a thinner polarizing plate can be realized without the need to provide a second base material, a polarizing plate having a curved portion having a small radius of curvature can be realized.

As an aspect of the present invention, the polarizing plate 1 has a thickness of the first thermoplastic resin substrate [the first substrate 12] of 20 µm to 200 µm, the thickness of the polarizing layer 21 is 1 µm to 5 µm, It is preferable that the thickness of the alignment layer 22 is 10 nm to 1000 nm. In such a polarizing plate 1, since a thinner polarizing plate can be realized, a polarizing plate having a curved portion having a small radius of curvature can be realized.

<Second Embodiment>

The polarizing plate according to the second embodiment of the present invention differs from the first embodiment in that the polarizer has a polarizing layer in which iodine or a dichroic dye is oriented in a PVA film. In addition, since the polarizing layer does not contain a liquid crystal compound, the polarizer in this embodiment does not need to have an alignment layer. That is, the polarizer of this embodiment may have only a polarizing layer. About the structure other than the polarizer of this embodiment, it is the same as 1st Embodiment.

As a specific example of the polarizing layer of this embodiment, the polarizing layer which adsorbs iodine to the PVA film, the polarizing layer which adsorbs and aligns a dichroic dye to the PVA film, and at least the surface and the inside of the modified PVA film containing a cationic group in a molecule|numerator. The polarizing layer etc. which have a dichroic dye are mentioned in one. In addition, as the dichroic dye, the aforementioned dichroic dye can be used.

When the thickness of the polarizer having a polarizing layer in which iodine or dichroic dye is oriented in the PVA film is 15 µm or less, the shape change can be made small even when it is placed in a high-temperature environment after curved surface molding.

In the case of a polarizing layer in which iodine is oriented in a PVA film, the moisture content of the PVA film is usually 5 to 20% by weight, and 8 to 15% by weight is preferable. If the moisture content is less than 5% by weight, the flexibility of the polarizing layer is lost, and the polarizing layer may be damaged or broken after drying. In addition, when the moisture content exceeds 20% by weight, the thermal stability of the polarizing layer may be inferior.

As the substrate laminated with the polarizer in the present embodiment, the first substrate and the second substrate described in the first embodiment can be used. Since the polarizer in this embodiment has a thickness of 15 µm or less, the shape change is small even when it is placed in a high-temperature environment after performing curved surface molding.

In the polarizing plate of this embodiment, as in the first embodiment, only the first substrate may be laminated on the polarizer. Like the first embodiment, the polarizing plate may include a polarizer, a first substrate positioned on the first surface of the polarizer, and a second substrate positioned on the second surface of the polarizer.

The method of manufacturing such a polarizing layer is not particularly limited, and for example, a method of adsorbing iodine ions to a PVA film after drawing a PVA film, a method of drawing a PVA film after dyeing with a dichroic dye, and drawing a PVA film Known methods, such as a method of dyeing with a dichroic dye, a method of printing and then stretching a dichroic dye on a PVA film, and a method of printing a dichroic dye after stretching a PVA film, may be mentioned. In order to make the thickness of the polarizing layer 15 µm or less, it is preferable to use a PVA film having a thickness of 30 µm or less before stretching.

For example, iodine is dissolved in a potassium iodide solution to prepare high-order iodine ions, and the iodine ions are adsorbed on a PVA film to be stretched, and then immersed in a 1 to 4% by weight aqueous boric acid solution at a bath temperature of 30 to 40°C and a polarizing layer The method of manufacturing is mentioned. Alternatively, the PVA film is treated with boric acid in the same manner, stretched about 3 to 7 times in the uniaxial direction, and immersed in an aqueous solution of 0.05 to 5% by weight of a dichroic dye at a bath temperature of 30 to 40°C to adsorb the dye, and then 80 to 100°C. And a method of drying and heat setting to prepare a polarizing layer.

In addition, also in the case of the polarizer of this embodiment, it can be used as a circular polarizing plate by further providing a 1/4 wave plate.

As a method of forming a curved portion by heating the polarizing plate having a polarizer of the present embodiment, insert molding, injection molding, pressure molding, vacuum molding, mold press, and the like can be mentioned in the same manner as the above-described method.

Since the polarizing plate in this embodiment has a polarizer having a thickness of 15 µm or less, heat shrinkage is smaller than that of a conventional polarizing plate including a 20 µm to 30 µm stretched PVA as a polarizer. In addition, the polarizing plate in this embodiment can have a curved part with a small radius of curvature.

<Use of polarizing plate>

The polarizing plate or circular polarizing plate in this embodiment can be used for various articles having a curved portion, but can be used, for example, for a lens for sunglasses, a lens for goggles for a three-dimensional image display device, or the like. The polarizing plate or circular polarizing plate in this embodiment contributes to the improvement of design, because the polarizing plate or the circular polarizing plate can be bonded on a curved surface having a small radius of curvature.

The polarizing plate in this embodiment can be used for various display devices having a curved surface on the display surface. A display device is a device having a display element and includes a light emitting element or a light emitting device as a light emitting source. As a display device, for example, a liquid crystal display device, an organic electroluminescence (EL) display device, an inorganic electroluminescence (EL) display device, an electron emission display device (e.g., a field emission display device (FED), a surface field emission display device) Device (SED)], electronic paper (display device using electronic ink or electrophoretic element), plasma display device, projection type display device (eg grating light valve (GLV) display device, display device having digital micro mirror device (DMD)) ], piezoelectric ceramic displays, and the like.

As a liquid crystal display device, a transmissive liquid crystal display device, a transflective liquid crystal display device, and a reflective liquid crystal display device are mentioned, for example. These display devices may be a display device that displays a two-dimensional image or a three-dimensional display device that displays a three-dimensional image.

The polarizing plate of this embodiment can be particularly effectively used for a display device of an organic EL display device or an inorganic EL display device. Since the polarizing plate or circular polarizing plate in this embodiment can bond a polarizing plate or a circular polarizing plate on a curved surface having a small radius of curvature, even when having a curved portion at an end or a corner of the display device, a polarizing plate or The circular polarizing plate can be bonded, contributing to the improvement of design.

As electronic papers, those represented by molecules such as optical anisotropy and orientation of dye molecules, those represented by particles such as electrophoresis, particle movement, particle rotation, and phase change, those displayed when one end of the film moves, and molecules What is displayed by the color/phase change of, is displayed by light absorption of molecules, and is displayed by self-luminescence by combining electrons and holes.

More specifically, microcapsule type electrophoresis, horizontal movement type electrophoresis, vertical movement type electrophoresis, spherical twist ball, magnetic twist ball, circumferential twist ball method, charged toner, electromagnetic fluid, magnetophoresis type, magnetic thermal type, electrophoresis Electrowetting, light scattering (transparency/cloudiness change), cholesteric liquid crystal/photoconductive layer, cholesteric liquid crystal, bistable nematic liquid crystal, ferroelectric liquid crystal, dichroic dye/liquid crystal dispersion type, movable film, leuco dye Discoloration, photochromic, electrochromic, electrodeposition, flexible organic EL, and the like. Electronic papers may be used not only for personal use of texts and images, but also for advertisement display (signage). According to the polarizing plate or circular polarizing plate of this embodiment, the thickness of the electronic paper can be reduced.

As a three-dimensional display device, a method of alternately arranging different retardation films, such as a micropole method, has been proposed (Japanese Patent Laid-Open No. 2002-185983). However, using the polarizing plate of this embodiment, printing, inkjet, and photo Since patterning is easy by lithography or the like, the manufacturing process of the display device can be shortened, and a retardation film is unnecessary.

The polarizing plate and the circular polarizing plate in this embodiment can be particularly used for a display device having a curved portion having a small radius of curvature. Specifically, the polarizing plate can be bonded to a smartphone having a curved portion at the end or corner of the screen. Moreover, the polarizing plate and circular polarizing plate of this embodiment can be used for a head mounted display for VR (virtual reality).

Example

Hereinafter, the present invention will be described in more detail using examples, but the present invention is not limited by the examples.

[Evaluation of curved formability]

The curved surface shaping of the polarizing plate was performed as follows. A polarizing plate was sandwiched between two metal plates having a diameter of 10 cm in the center. Using a heat gun, the polarizing plate was heated to 100°C to 140°C. A curved surface was formed by pressing the glass of a cylinder having an arbitrary radius of curvature on the heated polarizing plate. The radius of curvature of the polarizing plate was calculated from the diameter of the curved portion and the height of the flesh.

The evaluation of the curved surface formability was performed visually, and when a curved surface was formed and a problem such as a crack did not occur in the base material or the polarizer, it was judged that the curved surface formability was good, and if not, it was evaluated as defective.

[Measurement of the thickness of the polarizer]

Five arbitrary points of the polarizer were measured using a contact-type film thickness meter (digital micrometer MH-15M; manufactured by Nikon Corporation), and the thickness of the polarizer was calculated by calculating the average value.

[Evaluation of shape change under high temperature environment]

The polarizing plate having a curved surface according to the above method was put in an oven at 60°C or 80°C for 24 hours. Then, the shape change was evaluated using a normal. When dimensions such as a radius of curvature or height were maintained in a state before being put into the oven, it was judged as good, and if not, it was judged as defective.

[Example 1]

[Preparation of a composition for forming a polarizer]

The following polymerizable liquid crystal compound, dichroic dye, polymerization initiator, leveling material, and solvent were mixed in the following proportions. The obtained mixture was stirred at 80°C for 1 hour to obtain a composition for forming a polarizer. In addition, the dichroic dye was synthesized in the same manner as the compound described in Japanese Patent Laid-Open No. 2013-101328.

(Polymerizable liquid crystal compound)

As the polymerizable liquid crystal compound, 75 parts by mass of the compound represented by formula (4-6) and 25 parts by mass of the compound represented by formula (4-7) were used.

(Two-color pigment)

As a dichroic dye, 2.6 parts by mass of a compound represented by formula (2-15) (having a maximum absorption wavelength at 380 nm), and a compound represented by formula (2-18) (having a maximum absorption wavelength at 490 nm) Was used so that 2.6 parts by mass and 2.2 parts by mass of the compound (having a maximum absorption wavelength at 590 nm) represented by the formula (2-37) were used.

(Other ingredients)

As a polymerization initiator, 2-dimethylamino-2-benzyl-1-(4-morpholinophenyl)butan-1-one (Igacure 369; manufactured by Chiba Specialty Chemicals) was used so as to be 6 parts by mass.

As a leveling agent, a polyacrylate compound (BYK-361N; manufactured by BYK-Chemie) was used so as to be 1.2 parts by mass.

As a solvent, o-xylene was used so as to contain 250 parts by mass.

[Polarizing plate manufacturing method]

A roll of the second substrate, triacetyl cellulose (TAC) film (manufactured by Konica Minolta, KC4UY-TAC, thickness 40 μm) was continuously unwound at a speed of 10 m/min, and the optical alignment layer was performed by a slot die coater. The composition for formation was discharged to form a first coating film. Further, the solvent was removed by conveying it in a ventilation drying furnace set at 120°C for 2 minutes to form a first dry film.

Thereafter, the polarized UV light polarized in the direction of 0° with respect to the film transport direction is irradiated to the first dried film to have an intensity of 50 mJ/cm 2 (based on 313 nm), thereby imparting an orientation regulating force to the substrate having a photo-alignment layer. The film was produced. On the surface of the photo-alignment layer, a composition for forming a polarizer was applied by a slot die coater to form a second coating film. Further, the solvent was removed by conveying in a ventilation drying furnace set at 120° C. for 2 minutes to form a second dry film.

Thereafter, UV light was irradiated at 50 mJ/cm 2 (365 nm basis) to polymerize and cure the polymerizable liquid crystal compound to form a polarizer. Thereafter, an acrylic resin film (S001G, manufactured by Sumitomo Chemical Co., Ltd.), which is a first base material, is bonded to a polarizer through an ultraviolet-curable adhesive, and is continuously wound in a roll shape, thereby having an absorption axis in the 0° direction. The roll was produced.

Various evaluations were performed using what was cut out from the thus-produced long polarizing film roll into a 10 cm square size as a polarizing plate. The thickness of the alignment layer of the prepared polarizing plate was 100 nm, and the thickness of the polarizing layer was 2 μm. The thickness of the alignment layer and the polarizing layer was determined by measuring five arbitrary points of each layer with an interference film thickness meter, a laser microscope or a stylus film thickness meter, and calculating the average value. Table 1 shows the evaluation results of the evaluation of the curved formability of the polarizing plate and the shape change in a high temperature environment.

(Examples 2 to 5, Comparative Example 1)

The polarizing plates of Examples 2 to 5 and Comparative Example 1 were produced in the same procedure as in Example 1 except that the first and second substrates and curved surface molding were changed to be shown in Table 1. In addition, in Examples 4 and 5 and Comparative Example 1, the second substrate was not provided on the polarizing plate. In addition, COP in Table 1 represents a cyclic olefin resin film (manufactured by Nippon Zeon Corporation).

(Example 6)

The polarizing plate of Example 6 was produced as follows. On the acrylic resin (manufactured by Kaneka, Inc.) as the first substrate, a polarizer (manufactured by Sumitomo Chemical Co., Ltd.) in which stretched PVA was dyed with iodine was bonded. The TAC film was bonded to the other side of the polarizer through an adhesive. The water content of this polarizer was 10% by weight.

(Examples 7 to 10, Comparative Example 2)

The polarizing plates of Examples 7 to 10 and Comparative Example 2 were produced in the same procedure as in Example 6 except that the first and second substrates were changed as shown in Table 1. In addition, in Examples 9 and 10 and Comparative Example 2, the second substrate was not provided on the polarizing plate.

The polarizing plates of Examples 1 to 5 were excellent in curved formability, and no change in shape was observed even in an environment of 60°C and 80°C. The polarizing plates of Examples 6 to 10 were excellent in curved formability, and no change in shape was observed in an environment of 60°C. However, a shape change occurred in an environment of 80°C. It is considered that the cause of this is that the stretched PVA contracted in the stretching direction at 80°C. In addition, in Comparative Examples 1 and 2 in which a triacetylcellulose film was used as the first substrate and the second substrate was not provided, the curved formability was poor. Therefore, it was not possible to evaluate the shape change under a high temperature environment.

The polarizing plate of the present invention has suppressed shrinkage due to thermoforming, and can be bonded to an object having a curved portion having a small radius of curvature.

1, 1'... Polarizer, 2, 2'... Circular polarizer, 11... Polarizer, 12... First substrate, 13... Curve, 14... 2nd base material, 15... Retardation film, 101... Cured product of liquid crystal compound, 102... Dichroic pigment, 21... Polarizing layer, 22... Orientation layer

Claims (8)

A polarizing plate having a polarizer having a first side and a second side and a first substrate disposed on the first side of the polarizer,
The thickness of the polarizer is 15 μm or less,
The first substrate is a thermoplastic resin substrate,
The polarizing plate is to have at least one curved portion. The polarizing plate according to claim 1, wherein a radius of curvature of the curved portion is 30 mm to 150 mm. The polarizing plate according to claim 1 or 2, wherein the first substrate contains at least one of an acrylic resin and a cyclic olefin resin. The method according to any one of claims 1 to 3, wherein the polarizer comprises a polarizing layer,
The polarizing layer includes a cured product of a liquid crystal compound and a dichroic dye,
A polarizing plate in which the dichroic dye is dispersed and oriented in the polarizing layer. The polarizing plate according to any one of claims 1 to 4, wherein the first substrate has a thickness of 40 µm to 120 µm. The polarizing plate according to any one of claims 1 to 5, further comprising a second substrate on the second surface of the polarizer. The polarizing plate of claim 6, wherein the second substrate comprises at least one selected from acrylic resins, cyclic olefin resins, and triacetylcellulose resins. The polarizing plate according to any one of claims 1 to 7, wherein the polarizing plate is used by bonding to the display surface of a display device having a curved surface on the display surface, and the curved portion coincides with the curved surface.

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