KR102735933B1 - Polarizing film, circular polarizing plate and method of producing the same - Google Patents

Abstract

The present invention aims to provide a polarizing film that is easy to thin and has excellent neutral color properties, a polarizer including the polarizing film, and a method for manufacturing the same.
Provided are a polarizing film comprising a polymer formed of a polymerizable liquid crystal compound, at least one dichroic dye (1) having an absorption peak in a wavelength range of 380 to 550 nm and at least two dichroic dyes (2) having absorption peaks in a wavelength range of 550 to 700 nm when dispersed in the polymer and measuring light absorption, a polarizer comprising the polarizing film, and a method for producing these. It is preferable that the dichroic dye (2) include a dichroic dye having absorption in a wavelength range of 550 to 600 nm and a dichroic dye having absorption in a wavelength range of 600 to 700 nm.

Description

Polarizing film, circular polarizing plate and method of producing the same {POLARIZING FILM, CIRCULAR POLARIZING PLATE AND METHOD OF PRODUCING THE SAME}

The present invention relates to a polarizing film, a circular polarizing plate, and a method for manufacturing the same.

Polarizers used in liquid crystal displays have both high transmittance and polarization, so films (polarizing films) made of polyvinyl alcohol (iodine-dyed PVA) dyed with a dichroic dye such as iodine and stretched are commonly used. For example, Patent Document 1 describes a polarizing film made of iodine-dyed PVA.

Patent Document 1: Japanese Patent Publication No. 7-142170

However, polarizing films made of iodine-dyed PVA tend to have a yellowish tint, and thus have the problem that the so-called neutral color properties are inferior. In addition, polarizing films made of iodine-dyed PVA are difficult to thin, and thus have limitations in application to recent display devices requiring thinner films. Therefore, the object of the present invention is to provide a polarizing film that is easy to thin and has excellent neutral color properties, a polarizer including the polarizing film, and a method for manufacturing the polarizing film.

The present invention includes the following inventions.

[1] A polarizing film comprising a polymer formed of a polymerizable liquid crystal compound, and at least one dichroic dye (1) having an absorption peak in a wavelength range of 380 to 550 nm, and at least two dichroic dyes (2) having absorption peaks in a wavelength range of 550 to 700 nm when the dye is dispersed in the polymer and light absorption is measured.

[2] A polarizing film described in [1] having an absorption peak in the range of wavelengths 400 to 550 nm when the above-mentioned dichroic dye (1) is dispersed in a polymer formed of a polymerizable liquid crystal compound and light absorption is measured.

[3] When the light absorption is measured by dispersing the polymer, at least two types of dichroic dyes (2) having absorption peaks in the range of wavelengths 550 to 700 nm are present.

When the light absorption is measured by dispersing it in the above polymer,

A dichroic dye (2-1) having an absorption peak in the wavelength range of 550–600 nm,

A polarizing film according to [1] or [2], comprising a dichroic dye (2-2) having an absorption peak in the range of 600 to 700 nm in wavelength.

[4] A polarizing film according to any one of [1] to [3], wherein the polymerizable liquid crystal compound exhibits a smectic liquid crystal phase.

[5] A polarizing film described in any one of [1] to [4], which obtains a Bragg peak in X-ray diffraction measurement.

[6] A polarizing film described in any one of [1] to [5], wherein the color coordinates a* and b* values in the L*a*b* colorimetric system satisfy the relationships of the following equations (1F) and (2F).

-3≤color a*≤3 (1F)

-3≤color b*≤3 (2F)

[7] A polarizing film according to any one of [1] to [6], wherein the dichroic dye (1) and the dichroic dye (2) are azo compounds.

[8] A polarizing film according to any one of [1] to [7], wherein the dichroic dye (2) is composed of a compound represented by formula (2).

[In equation (2), n is 1 or 2.

Ar ¹ and Ar ³ are each independently a group represented by any one of the formulae (AR-1) to (AR-4).

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

A ₁ and A ₂ are each independently a group represented by any one of formulae (A-1) to (A-9), and * represents a bond number.

(mc is an integer from 0 to 10, and if there are two mc in the same base, these two mc are the same or different.)]

[9] A polarizing film according to any one of [1] to [8], wherein the dichroic dye (1) is composed of a compound represented by formula (1).

[In formula (1), Y is a group represented by formula (Y1) or formula (Y2).

(In the formula, L is an oxygen atom or -NR-, and R is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.)

R ¹ is a group represented by any of the formulas (R ¹ -1) to (R ¹ -3).

(In the formula, ma is an integer from 0 to 10, and if there are two ma in the same group, these two ma are the same or different. * indicates a combination number.)

R ² is a group represented by any of the formulas (R ² -1) to (R ² -6).

(In the formula, mb is an integer from 0 to 10.)]

[10] A polarizer formed by forming a polarizing film as described in any one of [1] to [9] on a transparent substrate.

[11] [10] A method for manufacturing a polarizer,

A process for preparing a laminate having an alignment film on a transparent substrate,

A process for applying a composition containing one type of dichroic dye (1) having an absorption peak in the range of wavelengths 380 to 550 nm, two types of dichroic dyes (2) having absorption peaks in the range of wavelengths 550 to 700 nm, and a solvent, when measuring light absorption by dispersing a polymerizable liquid crystal compound and a polymer formed of the polymerizable liquid crystal compound on the alignment film of the laminate,

A manufacturing method having a process of polymerizing the polymerizable liquid crystal compound included in the above composition.

[12] A manufacturing method described in [11], wherein the transparent substrate is a plastic substrate and the alignment film is a photoalignment film.

[13] A liquid crystal display device having a polarizing film as described in any one of [1] to [9].

[14] A circular polarizing plate having a polarizing film and a λ/4 layer as described in any of [1] to [9] and satisfying the requirements of (A1) and (A2) below.

(A1) The angle formed by the absorption axis of the polarizing film and the ground axis of the λ/4 layer shall be approximately 45°;

(A2) The value of the frontal retardation of the λ/4 layer measured under light of wavelength 550 nm shall be in the range of 100 to 150 nm.

[15] An organic EL display device having a circular polarizing plate and an organic EL element as described in [14].

According to the present invention, a polarizing film that is easy to thin and has excellent neutral color properties, and a polarizer including the polarizing film can be provided.

Figure 1 is a schematic diagram of a method for continuously manufacturing a polarizer (this polarizer) including a polarizing film of the present invention.
Figure 2 is a schematic diagram showing the relationship between the alignment direction D2 of the photo-alignment film and the return direction D1 of the film.
Figure 3 is a schematic diagram showing the cross-sectional configuration of a liquid crystal display device using the polarizing film of the present invention.
Figure 4 is a schematic diagram showing the layer order of the polarizer used in the liquid crystal display device of Figure 3.
Figure 5 is a schematic diagram showing the layer order of the polarizer used in the liquid crystal display device of Figure 3.
Figure 6 is a schematic diagram showing the cross-sectional configuration of an EL display device using a polarizing film of the present invention.
Figure 7 is a schematic diagram showing a cross-sectional configuration of an embodiment of the polarizer including the polarizing film of the present invention.
Figure 8 is a schematic diagram showing an example of a method for continuously manufacturing a circular polarizing plate (the present circular polarizing plate) including a polarizing film of the present invention.
Fig. 9 is a schematic diagram showing the layer order of the circular polarizing plate used in the EL display device of Fig. 6.
Figure 10 is a schematic diagram showing the cross-sectional configuration of an EL display device using a polarizing film of the present invention.
Figure 11 is a schematic diagram showing the configuration of a projection-type liquid crystal display device using the polarizing film of the present invention.

The polarizing film of the present invention (hereinafter, referred to as “the polarizing film” as the case may be) is characterized by comprising a polymer formed of a polymerizable liquid crystal compound and three or more specific dichroic dyes. The polarizing film of the present invention is preferably formed of a composition (hereinafter, referred to as “the composition for forming a polarizing film” as the case may be) comprising a polymerizable liquid crystal compound and the three or more specific dichroic dyes. First, the composition for forming a polarizing film will be described.

1. Composition for forming a polarizing film

The polarizing film-forming composition of the present invention comprises a polymerizable liquid crystal compound and three or more specific dichroic dyes as described above, and preferably further comprises a solvent. The polarizing film formed by this polarizing film-forming composition is easy to be thinned. First, each of the components included in the polarizing film-forming composition will be described.

1-1. Dichromatic pigment

The dichroic dye included in the composition for forming a polarizing film includes at least one dichroic dye (1) having an absorption maximum in a wavelength range of 380 to 550 nm when the dichroic dye is dispersed in a polymer formed of a polymerizable liquid crystal compound and light absorption is measured, and at least two dichroic dyes (2) having absorption maximums in a wavelength range of 550 to 700 nm in the same measurement.

1-1-1. Dichromatic pigment (1)

When the dichroic dye (1) is dispersed in a polymer formed of a polymerizable liquid crystal compound and the light absorption is measured, the dichroic dye has an absorption maximum in the range of wavelengths 380 to 550 nm. Meanwhile, this measurement can be carried out by preparing a composition for maximum absorption measurement in which the dichroic dye of the polarizing film-forming composition in the present invention is replaced with a dichroic dye whose absorption maximum is to be measured, forming a film for maximum absorption measurement by the same method as the method for forming the polarizing film using the polarizing film-forming composition described later, and measuring the light absorption of this film for maximum absorption measurement. The specific method for the absorption maximum measurement is the same as the method described in the Examples of the present application.

As a dichroic dye (1), an azo compound can be exemplified. Preferably, a compound represented by the above formula (1) (hereinafter, sometimes referred to as “compound (1)”) can be exemplified.

The geometrical isomorphism of the azobenzene moiety of compound (1) is preferably trans.

In formula (1), Y is a group represented by the above formula (Y1) or formula (Y2), and is preferably a group represented by formula (Y1). In formulas (Y1) and (Y2), the straight lines at both ends represent bond numbers, and the bond number on the left is bonded to a phenylene group having an azo group, and the bond number on the right is bonded to a phenylene group having R ² . 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 the 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 them, L is preferably an oxygen atom or -NH-, and is more preferably an oxygen atom.

R ¹ is a group represented by the above formula (R ¹ -1), formula (R ¹ -2) or formula (R ¹ -3), and is preferably a group represented by formula (R ¹ -2) and formula (R ¹ -3). In the group represented by formula (R ¹ -2), the two ma may be the same or different, but are preferably the same. It is more preferable that ma be an integer from 0 to 5.

R ² is a group represented by formula (R ² -1), formula (R ² -2), formula (R ² -3), formula (R ² -4), formula (R ² -5), or formula (R ² -6), and it is more preferable if it is a group represented by formula (R ² -2), formula (R ² -5), or formula (R ² -6), and it is even more preferable if it is a group represented by formula (R ² -6). 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 contained in the group is preferably an integer from 0 to 10, and it is still more preferable if it is an integer from 0 to 5.

As preferred compounds (1), compounds represented by the following formulae (1-1) to (1-8) can be mentioned.

Among them, compounds represented by formulas (1-1), (1-2), (1-3), (1-5), (1-7), and (1-8) are preferable, and compounds represented by formulas (1-1), (1-2), (1-3), and (1-7) are particularly preferable.

When the light absorption of the dichroic dye (1) is obtained by the above measurement, it has an absorption maximum in the range of a wavelength of 380 to 550 nm. It is preferable that it has an absorption maximum in the range of a wavelength of 400 to 550 nm, it is more preferable that it has an absorption maximum in the range of a wavelength of 400 to 520 nm, it is still more preferable that it has an absorption maximum in the range of a wavelength of 430 to 520 nm, and it is particularly preferable that it has an absorption maximum in the range of a wavelength of 440 to 510 nm. As long as it has an absorption maximum in the above range, a plurality of compounds (1) can be used as the dichroic dye (1).

Here, a method for producing compound (1) is described. Compound (1) can be produced, for example, by a reaction represented by the following diagram, with a compound represented by formula (1X) [compound (1X)] and a compound represented by formula (1Y) [compound (1Y)].

In the above schematic diagram, R ¹ , R ² and Y have the same meanings as above, and Re ¹ and Re ² are groups which react with each other to form a group represented by Y. Examples of combinations of Re ¹ and Re ² include a combination of a carboxyl group and a hydroxyl group, a combination of a carboxyl group and an amino group (these amino groups may be substituted by R), a combination of a carbonyl halide group and a hydroxyl group, a combination of a carbonyl halide group and an amino group (these amino groups may be substituted by R), a combination of a carbonyloxyalkyl group and a hydroxyl group, and a combination of a carbonyloxyalkyl group and an amino group (these amino groups may be substituted by R). In addition, although the compound (1X) having R ¹ and the compound (1Y) having R ² are described here, compound (1) can also be prepared by reacting a compound in which R ¹ is protected with a suitable protecting group or a compound in which R ² is protected with a suitable protecting group, and then performing an appropriate deprotection reaction.

When reacting compound (1X) and compound (1Y), the reaction conditions can be appropriately selected as optimal known conditions depending on the types of compound (1X) and compound (1Y) used.

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

The reaction time can also be determined by appropriately sampling the reaction mixture during the reaction and checking the extent of disappearance of compound (1X) and compound (1Y) or the extent of production of compound (1) by a known analytical means such as liquid chromatography or gas chromatography.

Compound (1) can be extracted from the reaction mixture after the reaction by known methods such as recrystallization, reprecipitation, extraction, and various chromatography, or by a combination of these operations.

1-1-2. Dichromatic pigment (2)

When the above measurement is performed, the dichroic dye (2) has an absorption maximum in the range of wavelengths 550 to 700 nm. The method for measuring the absorption maximum is the same as that for the dichroic dye (1).

The dichroic dye (2) is included in two or more types in the composition for forming a polarizing film, and among them, it is more preferable to include a dichroic dye (2-1) having an absorption maximum in a wavelength range of 550 to 600 nm and a dichroic dye (2-2) having an absorption maximum in a wavelength range of 600 to 700 nm. Here, it is more preferable if the dichroic dye (2-1) has an absorption maximum in a wavelength range of 570 to 600 nm, and it is even more preferable if the dichroic dye (2-2) has an absorption maximum in a wavelength range of 600 to 680 nm.

As a dichroic dye (2), an azo compound can be exemplified. The dichroic dye (2) is preferably a compound represented by the above formula (2) (hereinafter, referred to as “compound (2)” as the case may be).

The geometrical isomorphism of the azobenzene moiety of compound (2) is preferably trans.

In the combination of each group of compound (2), a compound (2) that can be used as a dichroic dye (2-1) is determined by combining Ar ¹ , Ar ² and Ar ³ so that the compound (2) has an absorption maximum in the range of a wavelength of 550 to 600 nm in the measurement. As a specific dichroic dye (2-1), a compound (2) represented by each combination of groups in Table 1 can be mentioned. Compound (2-1) representing each combination of groups in Table 1 represents the case where n in formula (2) is 1. Meanwhile, in Table 1, a group represented by formula (AR-1), for example, is expressed as "(AR-1)", etc.

Next, in the combination of each group of compound (2), a compound (2) that can be used as a dichroic dye (2-2) is determined by combining Ar ¹ , Ar ² and Ar ³ so that the compound (2) has absorption in the range of a wavelength of 600 to 700 nm in the measurement. As a specific dichroic dye (2-2), a compound (2) shown in Table 2 by the combination of each group can be mentioned. Compound (2-2) showing the combination of each group in Table 2 shows the case where n in formula (2) is 1. Meanwhile, the notation of groups in Table 2 is the same as in Table 1.

Here, if compound (2) is specifically represented, compounds represented by formulas (2-11) to (2-39) can be mentioned.

Among the specific examples of compounds (2) given here, the dichroic dye (2-1) is represented by formulas (2-12), (2-13), (2-18), (2-20), (2-21), (2-22), (2-23), (2-24), (2-26), (2-27), (2-28), (2-29), and (2-30), respectively, and the dichroic dye (2-2) is represented by formulas (2-31), (2-32), (2-33), (2-34), (2-35), and (2-36), respectively. Meanwhile, the pigments represented by formulas (2-11), (2-15), and (2-16) respectively are not pigments that exhibit absorption at a wavelength of 550 to 700 nm, but can be used in combination with the pigment of formula (1) as a supplement.

Among the specific examples of compound (2), as the dichroic dye (2) included in the composition for forming a polarizing film, those represented by formula (2-15), formula (2-16), formula (2-18), formula (2-20), formula (2-21), formula (2-22), formula (2-23), formula (2-27), formula (2-29), formula (2-31), formula (2-32), formula (2-33), formula (2-34), and formula (2-35) are more preferable. Among these, when the dichroic dye (2) is represented by a combination of two or more types selected from the specific examples of compound (2), depending on the mixing ratio, it is as shown in Table 3, for example. In this Table 3, for example, the compound (2) represented by formula (2-11) is represented as "(2-11)".

The content of the dichroic dye (1) in the composition for forming a polarizing film is expressed as the content relative to 100 parts by mass of the polymerizable liquid crystal compound described later, and is preferably 50 parts by mass or less, more preferably 0.1 parts by mass or more and 10 parts by mass or less, and still more preferably 0.1 parts by mass or more and 5 parts by mass or less.

The content of the dichroic dye (2) in the composition for forming a polarizing film is expressed as the content relative to 100 parts by mass of the polymerizable liquid crystal compound described later, and is preferably 10 parts by mass or less, more preferably 0.1 parts by mass or more and 5 parts by mass or less, and still more preferably 0.1 parts by mass or more and 3 parts by mass or less.

In addition, the total content of the dichroic dye (1) and the dichroic dye (2) in the composition for forming a polarizing film is expressed as the content relative to 100 parts by mass of the polymerizable liquid crystal compound described later, and is preferably 30 parts by mass or less, more preferably 0.1 part by mass or more and 20 parts by mass or less, and still more preferably 1 part by mass or more and 15 parts by mass or less.

When the content of each dichroic dye is within the above range, since the dichroic dye in the polarizing film-forming composition exhibits sufficient solubility in the solvent, when the polarizing film is manufactured using the polarizing film-forming composition, a polarizing film without occurrence of defects can be obtained. Meanwhile, as described above, the polarizing film-forming composition may contain at least one dichroic dye (1) and at least two dichroic dyes (2), but the polarizing film-forming composition may contain at least two dichroic dyes (1) or at least three dichroic dyes (2). When it contains at least two dichroic dyes (1), the content of the dichroic dye (1) is the total amount of the two or more dichroic dyes (1), and when it contains at least three dichroic dyes (2), the content of the dichroic dye (2) is the total amount of the three or more dichroic dyes (2).

The dichroic dye (2) is produced by a known method described in, for example, Japanese Patent Application Laid-Open No. 58-38756, Japanese Patent Application Laid-Open No. 63-301850, and Japanese Patent Application Laid-Open No. 58-104984.

Next, the components other than the dichroic dye in the composition for forming a polarizing film are described.

1-2. Polymerizable liquid crystal compound

The polymerizable liquid crystal compound is a liquid crystal compound that can be polymerized while aligned, and has a polymerizable group in the molecule. The polarizing film-forming composition containing the polymerizable liquid crystal compound forms the polarizing film by polymerizing the polymerizable liquid crystal compound while aligned. The polymerizable group is particularly preferably a radical polymerizable group. The radical polymerizable group means a group involved in a radical polymerization reaction.

The polymerizable liquid crystal compound included in the polarizing film-forming composition of the present invention may be one exhibiting a nematic liquid crystal phase (hereinafter, sometimes referred to as a "nematic liquid crystal phase"), a smectic liquid crystal phase (hereinafter, sometimes referred to as a "smectic liquid crystal phase"), or may exhibit both a nematic liquid crystal phase and a smectic liquid crystal phase, but it is preferably a polymerizable smectic liquid crystal compound exhibiting at least a smectic liquid crystal phase. The polarizing film-forming composition containing a polymerizable smectic liquid crystal compound can obtain the present polarizing film having excellent neutral color properties and superior polarization performance due to the interaction between the dichroic dye (1) and the dichroic dye (2).

Among the smectic liquid crystal phases exhibited by the polymerizable smectic liquid crystal compound, higher-order smectic liquid crystal phases are more preferable. The higher-order smectic liquid crystal phases referred to here are 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 K phase and Smectic L phase, and among them, Smectic B phase, Smectic F phase and Smectic I phase are more preferable.

If the smectic liquid crystal phase exhibited by the polymerizable liquid crystal compound is a higher-order smectic liquid crystal phase, a polarizing film having a higher degree of orientational order can be produced. In addition, the polarizing film produced with the higher-order smectic liquid crystal phase having a high degree of orientational order in this way obtains a Bragg peak derived from a higher-order structure such as a hexatic phase or a crystal phase in X-ray diffraction measurement. The Bragg peak is a peak derived from a plane periodic structure of molecular orientation, and according to the composition for forming a polarizing film of the present invention, a polarizing film having a periodic interval of 3.0 to 5.0 Å can be obtained.

Whether the polymerizable liquid crystal compound included in the composition for forming a polarizing film exhibits a nematic liquid crystal phase or a smectic liquid crystal phase can be confirmed, for example, as follows. An appropriate substrate is prepared, and the composition for forming a polarizing film is applied to the substrate to form a coating film, and then heat treatment or depressurization treatment is performed under conditions in which the polymerizable liquid crystal compound does not polymerize, thereby removing the solvent contained in the coating film. Next, the coating film formed on the substrate is heated to an isotropic temperature, and the liquid crystal phase developed by gradually cooling is examined by texture observation using a polarizing microscope, X-ray diffraction measurement, or differential scanning calorimetry. In this examination, a polymerizable liquid crystal compound which exhibits a nematic liquid crystal phase by cooling, and a smectic liquid crystal phase by further cooling is particularly preferable. In the nematic liquid crystal phase and the smectic liquid crystal phase, it can be confirmed, for example, by surface observation using various microscopes or scattering measurement using a haze meter, that the polymerizable liquid crystal compound and the dichroic dye are not phase separated.

Hereinafter, specific examples of preferred polymerizable liquid crystal compounds used in a composition for forming a polarizing film are given.

As a preferable polymerizable liquid crystal composition, for example, a compound represented by formula (4) (hereinafter, sometimes referred to as “compound (4)”) can be mentioned.

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 independently represent a good 1,4-phenylene group even if they have a substituent or a good cyclohexane-1,4-diyl group even if they have a substituent. However, at least one of X ¹ , X ² and X ³ is a good 1,4-phenylene group even if it has a substituent. -CH ₂ - constituting the good cyclohexane-1,4-diyl group even if it has a substituent may be substituted with -O-, -S- or -NR-. R is an alkyl group having 1 to 6 carbon atoms or a phenyl group.

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

U ¹ represents a hydrogen atom or a polymerizable group.

U ² represents a polymerization group.

W ¹ and W ² independently represent a single bond, -O-, -S-, -COO-, or -OCOO-.

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 the alkanediyl group may be substituted with -O-, -S- or -NH-.]

In compound (4), it is preferable that at least two of X ¹ , X ² and X ³ are 1,4-phenylene groups having a substituent.

Even if it has a substituent, a good 1,4-phenylene group is preferably unsubstituted. Even if it has a substituent, a good cyclohexane-1,4-diyl group is preferably a good trans-cyclohexane-1,4-diyl group even if it has a substituent, and even if it has a substituent, a good trans-cyclohexane-1,4-diyl group is more preferably unsubstituted.

As a substituent that may optionally be present in a good 1,4-phenylene group having a substituent or a good cyclohexane-1,4-diyl group having a substituent, examples thereof include alkyl groups having 1 to 4 carbon atoms, such as a methyl group, an ethyl group, and a butyl group; a cyano group; a halogen atom, and the like.

It is preferable that Y ¹ of compound (4) is -CH ₂ CH ₂ -, -COO- or a single bond, and it is preferable that Y ² is -CH ₂ CH ₂ - or -CH ₂ O-.

U ² is a polymerizable group. U ¹ is a hydrogen atom or a polymerizable group, and is preferably a polymerizable group. It is preferable that U ¹ and U ² are both polymerizable groups, and it is more preferable that they are both photopolymerizable groups. A photopolymerizable group refers to a group that can participate in a polymerization reaction by an active radical or acid generated from a photopolymerization initiator described later. A polymerizable liquid crystal compound having a photopolymerizable group is advantageous in that it can polymerize under lower temperature conditions.

In compound (4), the polymerizable groups of U ¹ and U ² may be different, but are preferably the same type of group. Examples of the polymerizable group include a vinyl group, a vinyloxy group, a 1-chlorovinyl group, an isopropenyl group, a 4-vinylphenyl group, an acryloyloxy group, a methacryloyloxy group, an oxiranyl group, and an oxetanyl group. Among them, 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.

As alkanediyl groups having 1 to 20 carbon atoms, which may have substituents represented by V ¹ and V ^{2 ,} examples thereof include a methylene group, an ethylene group, a propane-1,3-diyl group, a butane-1,3-diyl group, a butane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,6-diyl group, a heptane-1,7-diyl group, an octane-1,8-diyl group, a decane-1,10-diyl group, a tetradecane-1,14-diyl group, and aicosane-1,20-diyl group. V ¹ and V ² are preferably alkanediyl groups having 2 to 12 carbon atoms, and more preferably, they are alkanediyl groups having 6 to 12 carbon atoms.

As a substituent that may be optionally included in an alkanediyl group having 1 to 20 carbon atoms, even if it has a substituent, examples thereof include a cyano group and a halogen atom. It is preferable that the alkanediyl group is unsubstituted, and it is more preferable that the unsubstituted alkanediyl group is also a straight-chain alkanediyl group.

W ¹ and W ² are independently preferably a single bond or -O-.

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

Polymerizable liquid crystal compounds can be used alone or in combination of two or more in a composition for forming a polarizing film. In addition, when two or more are mixed, it is preferable that at least one is a compound (4). When two polymerizable liquid crystal compounds are mixed, the mixing ratio is usually 1:99 to 50:50, preferably 5:95 to 50:50, and more preferably 10:90 to 50:50.

Among the exemplified compounds (4), compounds represented by formulas (4-5), (4-6), (4-7), (4-8), (4-9), (4-10), (4-11), (4-12), (4-13), (4-14), (4-15), (4-22), (4-24), (4-25), (4-26), (4-27), (4-28), and (4-29) are preferable. These compounds can be easily polymerized under temperature conditions below the crystal phase transition temperature, i.e., while sufficiently maintaining the liquid crystal state of the higher-order smectic phase, by interaction with other polymerizable liquid crystal compounds. Specifically, these compounds can be polymerized under temperature conditions of 70°C or lower, preferably 60°C or lower, while sufficiently maintaining the liquid crystal state of the higher-order smectic phase.

The content ratio of the polymerizable liquid crystal compound in the polarizing film-forming composition is preferably 50 to 99.9 mass%, more preferably 80 to 99.9 mass%, based on the solid content of the polarizing film-forming composition. 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, which is preferable. Here, the solid content refers to the total amount of components excluding volatile components such as solvents in the polarizing film-forming composition.

Polymerizable liquid crystal compounds are prepared by known methods, such as those described in Lub et al. Recl. Trav. Chim. Pays-Bas, 115, 321-328 (1996) or Japanese Patent No. 4719156.

1-3. Solvent

It is preferable that the composition for forming a polarizing film contains a solvent. As the solvent, a solvent capable of completely dissolving the polymerizable liquid crystal compound and the dichroic dye is preferable. In addition, it is preferable that the solvent is inactive to the polymerization reaction of the polymerizable liquid crystal compound contained in the composition for forming a polarizing film.

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 or 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.

The content of the solvent is preferably 50 to 98 mass% with respect to the total amount of the polarizing film-forming composition. In other words, the solid content in the polarizing film-forming composition is preferably 2 to 50 mass%. If the solid content is 2 mass% or more, it is preferable because it tends to be easy to obtain a thin polarizing film, which is one of the purposes of the present invention. In addition, if the solid content is 50 mass% or less, the viscosity of the polarizing film-forming composition decreases, so that the thickness of the polarizing film becomes approximately uniform, and thus it tends to be difficult for unevenness to occur in the polarizing film, which is preferable. In addition, the solid content can be determined in consideration of the thickness of the polarizing film.

1-4. Other additives

The composition for forming a polarizing film in the present invention optionally contains additives other than a dichroic dye, a polymerizable liquid crystal compound, and a solvent.

1-4-1. Preparation of polymerization reaction

It is preferable that the composition for forming a polarizing film contains a polymerization initiator. The polymerization initiator is a compound capable of initiating a polymerization reaction of a polymerizable liquid crystal compound. As the polymerization initiator, a photopolymerization initiator is preferable in that it can initiate a polymerization reaction under low-temperature conditions. Specifically, a compound that generates an active radical or an acid by the action of light is used as the photopolymerization initiator. Among the photopolymerization initiators, those that generate an active radical by the action of light are more preferable.

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

Examples of benzoin compounds include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and benzoin isobutyl ether.

Examples of benzophenone compounds include benzophenone, o-benzoyl methyl benzoate, 4-phenylbenzophenone, 4-benzoyl-4'-methyldiphenyl sulfide, 3,3',4,4'-tetra(tert-butylperoxycarbonyl)benzophenone, and 2,4,6-trimethylbenzophenone.

Examples of alkylphenone compounds include diethoxyacetophenone, 2-methyl-2-morpholino-1-(4-methylthiophenyl)propan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butan-1-one, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1,2-diphenyl-2,2-dimethoxyethane-1-one, 2-hydroxy-2-methyl-1-〔4-(2-hydroxyethoxy)phenyl〕propan-1-one, 1-hydroxycyclohexylphenyl ketone, and oligomers of 2-hydroxy-2-methyl-1-〔4-(1-methylvinyl)phenyl〕propan-1-one.

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

Examples of triazine compounds include 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 Examples include 2,4-bis(trichloromethyl)-6-〔2-(3,4-dimethoxyphenyl)ethenyl〕-1,3,5-triazine.

A commercially available polymerization initiator can also be used. Commercially available polymerization initiators include "Irgacure 907", "Irgacure 184", "Irgacure 651", "Irgacure 819", "Irgacure 250", "Irgacure 369" (Chiba Japan Co., Ltd.); "Seikul BZ", "Seikul Z", "Seikul BEE" (Seiko Chemical Co., Ltd.); "Kayacure BP100" (Nippon Kayaku Co., Ltd.); "Kayacure UVI-6992" (Dow); "Adeka Optoma SP-152", "Adeka Optoma SP-170" (ADEKA Co., Ltd.); "TAZ-A", "TAZ-PP" (Nippon Shiverhegna Co., Ltd.); and “TAZ-104” (Sanwa Chemical Co., Ltd.).

When the composition for forming a polarizing film contains a polymerization initiator, the content thereof can be appropriately adjusted depending on the type and amount of the polymerizable liquid crystal compound contained in the composition for forming a polarizing film. Usually, the content of the polymerization initiator relative to the total of 100 parts by mass of the polymerizable liquid crystal compound 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 initiator is within the above range, polymerization can be performed without disturbing the orientation of the polymerizable liquid crystal compound, which is preferable.

1-4-2. Photosensitizer

When the polarizing film-forming composition contains a photopolymerization initiator, the polarizing film-forming composition may contain a photosensitizer. As the photosensitizer, examples thereof include xanthone compounds such as xanthone and thioxanthone (e.g., 2,4-diethylthioxanthone, 2-isopropylthioxanthone, etc.); anthracene compounds such as anthracene and anthracene containing an alkoxy group (e.g., dibutoxyanthracene, etc.); phenothiazine, and rubrene.

When the composition for forming a polarizing film contains a photopolymerization initiator and a photosensitizer, the polymerization reaction of the polymerizable liquid crystal compound contained in the composition for forming a polarizing film 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 used together, and is usually 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, per 100 parts by mass of the content of the polymerizable liquid crystal compound.

1-4-3. Polymerization inhibitor

The composition for forming a polarizing film may contain a polymerization inhibitor in order to stably proceed with the polymerization reaction of the polymerizable liquid crystal compound. The progress of the polymerization reaction of the polymerizable liquid crystal compound can be controlled by the polymerization inhibitor.

Examples of polymerization inhibitors include hydroquinone, alkoxy group-containing hydroquinone, alkoxy group-containing catechol (e.g., butylcatechol), pyrogallol, radical supplements such as 2,2,6,6-tetramethyl-1-piperidinyloxy radical; thiophenols; β-naphthylamines and β-naphthols.

When a polymerization inhibitor is included in a composition for forming a polarizing film, its content is appropriately adjusted depending on the type and amount of the polymerizable liquid crystal compound used, the content of the photosensitizer, etc., and is usually 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, per 100 parts by mass of the polymerizable liquid crystal compound.

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

1-4-4. Leveling agent

It is preferable that the polarizing film-forming composition contain a leveling agent. A leveling agent is a substance that has the function of adjusting the fluidity of the polarizing film-forming composition and making the coating film obtained by applying the polarizing film-forming composition flatter, and examples thereof include surfactants. Preferred leveling agents 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.

Leveling agents containing polyacrylate compounds as their main components include "BYK-350", "BYK-352", "BYK-353", "BYK-354", "BYK-355", "BYK-358N", "BYK-361N", "BYK-380", "BYK-381", and "BYK-392" [BYK Chemie].

Leveling agents containing fluorine atoms as their main components include “Megapark 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 Co., Ltd.]; “Suplon S-381”, “S-382”, “S-383”, “S-393”, “SC-101”, “SC-105”, “KH-40” and “SA-100” [AGC Seimi Chemical Co., Ltd.]; Examples thereof include "E1830", "E5844" [Daikin Fine Chemicals Co., Ltd.]; "F-Top EF301", "EF303", "EF351" and "EF352" [Mitsubishi Materials Alden Shiga Sei Co., Ltd.].

When a leveling agent is contained in a composition for forming a polarizing film, the content thereof 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 or less, per 100 parts by mass of the polymerizable liquid crystal compound. 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 polarizing film tends to be smoother, which is preferable. When the content of the leveling agent with respect to the polymerizable liquid crystal compound exceeds the above range, the obtained polarizing film tends to be prone to unevenness. Meanwhile, the polarizing film-forming composition may contain two or more types of leveling agents.

2. Method for forming this polarizing film

Next, a method for forming the polarizing film using the polarizing film-forming composition is described. In this method, the polarizing film is formed by applying the polarizing film-forming composition to a substrate, preferably a transparent substrate.

2-1. Transparent material

A transparent substrate is a substrate that has transparency enough to transmit light, particularly visible light. The transparency above refers to a property in which the transmittance for light with a wavelength of 380 to 780 nm is 80% or more. Specifically, examples of the transparent substrate include glass substrates and plastic substrates, and preferably a plastic substrate. Examples of the plastic constituting the plastic substrate include polyolefins such as polyethylene, polypropylene, and norbornene polymers; cyclic olefin resins; polyvinyl alcohol; polyethylene terephthalate; polymethacrylic acid esters; polyacrylic acid esters; cellulose esters such as triacetyl cellulose, diacetyl cellulose, and cellulose acetate propionate; polyethylene naphthalate; polycarbonate; polysulfone; polyether sulfone; polyether ketone; polyphenylene sulfide, and polyphenylene oxide. Among them, in terms of being easily available on the market or having excellent transparency, cellulose esters, cyclic olefin resins, polyethylene terephthalate, or polymethacrylic acid esters are particularly preferable. When manufacturing the polarizing film using such a transparent substrate, it is possible to adhere a support substrate, etc. to the transparent substrate because the transparent substrate can be easily handled without causing damage such as tearing when transporting or storing it. In addition, as described later, when manufacturing a circular polarizing plate using the polarizing film, there are cases where phase difference is imparted to a plastic substrate. In such a case, phase difference may be imparted to the plastic substrate by stretching treatment, etc.

When imparting phase difference to a plastic substrate, a plastic substrate made of a cellulose ester or a cyclic olefin resin is preferable because the phase difference value is easy to control.

Cellulose ester is a cellulose in which at least a portion of the hydroxyl groups are esterified with acetic acid. Cellulose ester films made of such cellulose esters are readily available on the market. Commercially available triacetyl cellulose films include, for example, "Fujitech Film" (Fuji Shashin Film Co., Ltd.); "KC8UX2M", "KC8UY", and "KC4UY" (Konica Minolta Opto Co., Ltd.). These commercially available triacetyl cellulose films can be used as transparent substrates as they are or after imparting phase difference thereto as needed. In addition, the surface of the prepared transparent substrate can be treated with an antiglare treatment, a hard coat treatment, an antistatic treatment, or an antireflection treatment, and then used as a transparent substrate.

In order to impart phase difference to a plastic substrate, a method such as stretching the plastic substrate as described above is used. Any plastic substrate made of a thermoplastic resin can be stretched, but a plastic substrate made of a cyclic olefin resin is more preferable in that it is easy to control phase difference. The cyclic olefin resin is composed of a polymer or copolymer of a cyclic olefin such as, for example, norbornene or a polycyclic norbornene monomer, and the cyclic olefin resin may partially include a ring-opening portion. Furthermore, a cyclic olefin resin including a ring-opening portion may also be hydrogenated. Furthermore, the cyclic olefin resin may also be a copolymer of a cyclic olefin and a chain olefin or a vinylated aromatic compound (such as styrene) in that it does not significantly impair transparency or significantly increase hygroscopicity. Furthermore, the cyclic olefin resin may also 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, the chain olefin is preferably ethylene or propylene, and the vinylated aromatic compound is preferably styrene, α-methylstyrene, and alkyl-substituted styrene. In such a copolymer, the content of structural units derived from the cyclic olefin is 50 mol% or less, for example, in a range of about 15 to 50 mol%, with respect to 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, the content of structural units derived from the chain olefin is preferably 5 to 80 mol%, with respect to the total structural units of the cyclic olefin resin, and the content of structural units derived from the vinylated aromatic compound is preferably 5 to 80 mol%. The cyclic olefin resin of this ternary copolymer has the advantage of being able to use a relatively small amount of expensive cyclic olefin when producing the cyclic olefin resin.

Cyclic olefin resins are readily available on the market. Commercially available cyclic olefin resins include "Topas" [Ticona (Germany)]; "Aton" [JSR Co., Ltd.]; "ZEONOR" and "ZEONEX" [Nippon Zeon Co., Ltd.]; and "APEL" [manufactured by Mitsui Chemical Co., Ltd.]. These cyclic olefin resins can be formed into films (cyclic olefin resin films) by known film forming means, such as a solvent casting method or a melt extrusion method. In addition, cyclic olefin resin films that are already commercially available in the form of films can also be used. Commercially available cyclic olefin resin films include, for example, "ESINA" and "SCA40" [Sekisui Chemical Industry Co., Ltd.]; Examples include "ZeoNor Film" [Office Co., Ltd.]; "Aton Film" [JSR Co., Ltd.].

Next, a method for imparting phase difference to a plastic substrate will be described. The plastic substrate can be imparted phase difference by a known stretching method. For example, a roll (roller) in which a plastic substrate is wound on a roll is prepared, the plastic substrate is continuously unwound from this roll, and the unwound plastic substrate is returned to a heating furnace. The set temperature of the heating furnace is in the range of about the glass transition temperature (℃) to [glass transition temperature + 100] (℃) of the plastic substrate, preferably in the range of about the glass transition temperature (℃) to [glass transition temperature + 50] (℃). In the heating furnace, when stretching in the direction of travel of the plastic substrate or in a direction orthogonal to the direction of travel, the return direction or tension is adjusted to incline at an arbitrary angle and uniaxial or biaxial thermal stretching is performed. The stretching ratio is usually in the range of about 1.1 to 6 times, and preferably in the range of about 1.1 to 3.5 times. In addition, as a method for stretching in an oblique direction, any known stretching method can be adopted without particular limitation as long as the orientation axis can be continuously tilted at a desired angle. Such stretching methods include, for example, methods described in Japanese Patent Application Laid-Open No. 50-83482 and Japanese Patent Application Laid-Open No. 2-113920.

The thickness of the transparent substrate is preferably thin in terms of the weight that allows practical handling and the ability to secure sufficient transparency, but if it is too thin, the strength tends to decrease and the processability tends to be poor. An appropriate thickness of the glass substrate is, for example, about 100 to 3000 ㎛, preferably about 100 to 1000 ㎛. An appropriate thickness of the plastic substrate is, for example, about 5 to 300 ㎛, preferably about 20 to 200 ㎛. When the present polarizing film is used as a circularly polarizing plate described below, particularly when it is used as a circularly polarizing plate for mobile devices, the thickness of the transparent substrate is preferably about 20 to 100 ㎛. On the other hand, when imparting phase difference to the film by stretching, the thickness after stretching is determined by the thickness before stretching or the stretching ratio.

2-2. Alignment film

It is preferable that the substrate used for manufacturing the polarizing film has an alignment film formed thereon. In that case, the polarizing film-forming composition is applied onto the alignment film. Therefore, it is preferable that the alignment film has solvent resistance that is not dissolved by application of the polarizing film-forming composition, etc. In addition, it is preferable that it has heat resistance in the heat treatment for removing the solvent or for aligning the liquid crystal. Such an alignment film can be formed by an alignment polymer.

As the above-mentioned orientation polymer, examples thereof include polyamides or gelatins having an amide bond in the molecule, polyimides having an imide bond in the molecule, and polymers such as polyamic acid, polyvinyl alcohol, alkyl-modified polyvinyl alcohol, polyacrylamide, polyoxazole, polyethyleneimine, polystyrene, polyvinylpyrrolidone, polyacrylic acid, or polyacrylic acid esters which are hydrolyzed products thereof. Among these, polyvinyl alcohol is preferable. These orientation polymers forming the orientation film may be used alone, or two or more types may be mixed and used.

The above-mentioned orienting polymer can form an orientation film on a substrate by applying it as an orienting polymer composition (a solution containing the orienting polymer) dissolved in a solvent onto the substrate. The solvent may 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, and nitrile solvents such as acetonitrile; Examples thereof include ether solvents such as tetrahydrofuran and dimethoxyethane; chlorine-substituted hydrocarbon solvents such as chloroform and chlorobenzene; and the like. These organic solvents may be used alone or in combination of two or more types.

In addition, it is also possible to use a commercially available alignment film material as it is as an orientation polymer composition for forming an alignment film. Examples of commercially available alignment film materials include San-Eba (registered trademark, manufactured by Nissan Chemical Industries, Ltd.) or Optoma (registered trademark, manufactured by JSR Corporation).

As a method for forming an alignment film on a substrate, for example, a method of applying the alignment polymer composition or a commercially available alignment film material on a substrate and annealing the same may be exemplified. The thickness of the alignment film thus obtained is usually in the range of 10 nm to 10,000 nm, and preferably in the range of 10 nm to 1,000 nm.

In order to provide orientation control force to the above-mentioned alignment film, it is preferable to perform rubbing (rubbing method) as needed. By providing orientation control force, the polymerizable liquid crystal compound can be oriented in a desired direction.

As a method of imparting orientation control force by a rubbing method, an example of which is a method in which a rubbing cloth is wound around a rotating rubbing roll, a laminated body on which a coating film for forming an orientation film is formed on a substrate is placed on a stage, and returned toward the rotating rubbing roll, thereby bringing the coating film for forming an orientation film into contact with the rotating rubbing roll.

In addition, a so-called photo-alignment film can also be used. A photo-alignment film refers to an alignment film that provides alignment control power by applying a composition containing a polymer or monomer having a photo-reactive group and a solvent (hereinafter, sometimes referred to as a "photo-alignment layer forming composition") to a substrate and irradiating polarized light (preferably, polarized UV). A photo-reactive group refers to a group that generates liquid crystal alignment ability by irradiating light (light irradiation). Specifically, it is one that causes a photoreaction that becomes the origin of liquid crystal alignment ability, such as alignment induction or isomerization reaction, dimerization reaction, photocrosslinking reaction, or photodecomposition reaction of molecules caused by irradiating light. Among the above-mentioned photo-reactive groups, those that cause a dimerization reaction or photocrosslinking reaction are preferable because they have excellent alignment properties and maintain a smectic liquid crystal state when forming a polarizing film. As a photoreactive group capable of causing a reaction as described above, a group having an unsaturated bond, particularly a double bond, is preferable, and a group having at least one selected from the group consisting of 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 carbon-oxygen double bond (C=O bond) is particularly preferable.

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 Schiff 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 formazan group, and those 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, and a halogenated alkyl group.

Among them, a photoreactive group capable of inducing a photodimerization reaction is preferable, and a cinnamoyl group and a chalcone group are preferable because they require a relatively small amount of polarized light irradiation required for photoalignment and make it easy to obtain a photoalignment film having excellent thermal stability and stability over time. In other words, among polymers having a photoreactive group, those having a cinnamoyl group in which the terminal portion of the polymer side chain has a cinnamic acid structure are particularly preferable.

As a solvent for the composition for forming a photoalignment layer, it is preferable to use one that dissolves a polymer and monomer having a photoreactive group, and examples of the solvent include the solvent used in the above-described orientation polymer composition.

The concentration of the polymer or monomer having a photoreactive group in the composition for forming a photoalignment layer can be appropriately adjusted depending on the type of the polymer or monomer having the photoreactive group or the thickness of the photoalignment film to be manufactured. In terms of solid content concentration, it is preferably at least 0.2 mass%, and particularly preferably in the range of 0.3 to 10 mass%. In addition, the composition for forming a photoalignment layer may contain a polymer material such as polyvinyl alcohol or polyimide, or a photosensitizer, as long as the properties of the photoalignment film are not significantly impaired.

As a method for applying the orientational polymer composition or the composition for forming the photo-alignment layer onto a substrate, a known method such as a spin coating method, an extrusion method, a gravure coating method, a die coating method, a bar coating method, and an applicator method, or a printing method such as a flexography method, may be employed. Meanwhile, when the polarizing film is manufactured by a continuous manufacturing method in the Roll-to-Roll format described below, a gravure coating method, a die coating method, or a printing method such as a flexography method is usually employed as the coating method.

Meanwhile, when masking is performed while conducting rubbing or polarization investigation, multiple areas (patterns) with different orientation directions can be formed.

2-3. Manufacturing method of this polarizing film

A polarizing film-forming composition is applied onto the substrate or an alignment film formed on the substrate to obtain a coating film. As a method for applying the polarizing film-forming composition, for example, the same method as that exemplified as a method for applying an alignment polymer or a composition for forming a photoreactive layer to the substrate can be exemplified.

Next, a dry film is formed by drying and removing the solvent under conditions in which the polymerizable liquid crystal compound included in the coating film does not polymerize. Examples of drying methods include a natural drying method, a ventilation drying method, a heat drying method, and a reduced pressure drying method.

Next, in a preferred form, the liquid crystal state of the polymerizable liquid crystal composition included in the above-described dry film is first changed to a nematic liquid crystal phase, and then the nematic liquid crystal phase is transferred to a smectic liquid crystal phase.

In order to form a smectic liquid crystal phase via a nematic liquid crystal phase, a method is employed in which, for example, the polymerizable liquid crystal compound included in the dry film is heated to a temperature higher than the temperature at which the polymerizable liquid crystal compound exhibits the nematic liquid crystal phase, and then the polymerizable liquid crystal compound is cooled to a temperature at which the polymerizable liquid crystal compound exhibits the smectic liquid crystal phase.

When the polymerizable liquid crystal compound in the above-mentioned dry film is converted into a smectic liquid crystal phase or the polymerizable liquid crystal compound is converted into a smectic liquid crystal phase via a nematic liquid crystal phase, the conditions (heating conditions) for controlling the liquid crystal state can be determined by measuring the phase transition temperature of the polymerizable liquid crystal compound used. The conditions for measuring such phase transition temperature are described in the examples of the present application.

Next, the polymerization process of the polymerizable liquid crystal compound is described. Here, a method of including a photopolymerization initiator in a composition for forming a polarizing film to change the liquid crystal state of the polymerizable liquid crystal compound in the dried film to a smectic liquid crystal phase, and then photopolymerizing the polymerizable liquid crystal compound while maintaining the liquid crystal state of the smectic liquid crystal phase is described in detail.

In photopolymerization, the light irradiated onto the dry film may be light appropriately selected from the group consisting of visible light, ultraviolet light, and laser light, or an active electron beam, depending on the type of the photopolymerization initiator contained in the dry film or the type of the polymerizable liquid crystal compound (in particular, the type of the polymerizable group possessed by the polymerizable liquid crystal compound) and the amount thereof. Among these, ultraviolet light is preferable because it is easy to control the progress of the polymerization reaction and because a device widely used in the relevant field as a device related to photopolymerization can be used. Therefore, it is preferable to select the type of the polymerizable liquid crystal compound or the photopolymerization initiator contained in the composition for forming a polarizing film so that photopolymerization can be performed by ultraviolet light. In addition, when polymerizing, the polymerization temperature can be controlled by cooling the dry film by an appropriate cooling means together with the ultraviolet light irradiation. By employing such a cooling means, if polymerization of a polymerizable liquid crystal compound can be carried out at a lower temperature, there is also an advantage in that the polarizing film can be formed appropriately even if a relatively low heat resistance material is used in the above-described substrate. On the other hand, during photopolymerization, a patterned polarizing film can also be obtained by masking or developing.

By performing the photopolymerization as described above, the polymerizable liquid crystal compound is polymerized while maintaining a nematic liquid crystal phase, a smectic liquid crystal phase, and preferably a higher-order smectic liquid crystal phase as exemplified above, thereby forming the polarizing film. The polarizing film obtained by polymerizing the polymerizable liquid crystal compound while maintaining the smectic liquid crystal phase has an advantage of high polarization performance compared to a conventional host-guest type polarizing film, that is, a polarizing film obtained by polymerizing a polymerizable liquid crystal compound or the like while maintaining a liquid crystal state of a nematic liquid crystal phase. In addition, it has an advantage of superior strength compared to a film in which only a lyotropic dichroic dye is applied.

The thickness of the polarizing film thus formed is preferably in the range of 0.5 ㎛ to 10 ㎛, more preferably 1 ㎛ to 5 ㎛. Therefore, the thickness of the coating film for forming the polarizing film is determined in consideration of the thickness of the polarizing film obtained. Meanwhile, the thickness of the polarizing film is obtained by measurement using an interference thickness meter, a laser microscope, or a stylus thickness meter.

In addition, the polarizing film formed in this manner is particularly preferable if it obtains a Bragg peak in X-ray diffraction measurement as described above. As the polarizing film that obtains such a Bragg peak, for example, the polarizing film that exhibits a diffraction peak derived from a hexagonal phase or a crystal phase can be exemplified.

In addition, the polarizing film manufactured in this manner has excellent neutral color properties. Here, a polarizing film having excellent neutral color properties means a polarizing film whose color coordinates a* value and b* value in the L*a*b* (Lab) color system satisfy the relationships of the following equations (1F) and (2F). In addition, these color coordinates a* value and b* value are obtained by, for example, the measurement method described in the examples of the present application.

-3≤color a*≤3 (1F)

-3≤color b*≤3 (2F)

The color coordinates a* and b* values mentioned here are also called "chromaticity a*" and "chromaticity b*", respectively. The closer the a* and b* are to 0 (zero), the more the polarizing film is judged to exhibit a neutral color. A display device equipped with such a polarizing film can obtain a good white display without coloration.

In addition, in the color of the polarizing film, when two polarizing films are overlapped so that their absorption axes are orthogonal to each other, and the color at that time is obtained by the above formula and "orthogonal a*" and "orthogonal b*" are calculated, it is more preferable if each of these orthogonal a* and orthogonal b* satisfies the relationships of the following formulas (1F') and (2F'). These orthogonal a* and orthogonal b* are indicators indicating whether the color of the black display in a display device having a polarizing film is neutral. The closer both the orthogonal a* and the orthogonal b* are to 0 (zero), the more a good black display without coloration can be obtained.

-3≤orthogonal a*≤3 (1F')

-3≤orthogonal b*≤3 (2F')

3. Continuous manufacturing method of this polarizing film

Above, the outline of the manufacturing method of the polarizing film has been explained, but when manufacturing the polarizing film commercially, a method capable of continuously manufacturing the polarizing film is required. This continuous manufacturing method is in the Roll-to-Roll format and is sometimes referred to as the "present manufacturing method." Meanwhile, the manufacturing method will be explained mainly based on the case where the substrate is a transparent substrate. When the substrate is a transparent substrate, the final product is a polarizer having a transparent substrate and the present polarizing film (hereinafter, sometimes referred to as the "present polarizer").

The present manufacturing method comprises, for example,

A process for preparing a first roll in which a transparent substrate is wound around a first core,

A process for continuously sending out the transparent material from the first roll,

A process for continuously forming an alignment film on the above transparent substrate,

A process of continuously applying a composition for forming a polarizing film on the above-mentioned alignment layer,

A process for continuously forming a dry film on the alignment film by drying the applied polarizing film forming composition under conditions in which the polymerizable liquid crystal compound does not polymerize,

A process of forming a polymerizable liquid crystal compound included in the above dry film into a nematic liquid crystal phase, preferably a smectic liquid crystal phase, and then polymerizing the polymerizable liquid crystal compound while maintaining the smectic liquid crystal phase, thereby continuously obtaining a polarizing film and making it into a polarizer;

The process of obtaining a second roll by winding the continuously obtained polarizer onto a second core is provided. Here, the manufacturing method is described with reference to Fig. 1, particularly with respect to the case where a photo-alignment film is used as the alignment film.

The first roll (210) in which the transparent substrate is wound around the first core (210A) can be easily obtained, for example, from the market. As transparent substrates that can be obtained from the market in the form of such a roll, among the transparent substrates already exemplified, films made of cellulose ester, cyclic olefin resin, polyethylene terephthalate, polycarbonate or polymethacrylic acid ester can be exemplified. In addition, when using the polarizing film as a circular polarizing plate, transparent substrates to which phase difference is provided in advance can also be easily obtained from the market, for example, phase difference films made of cellulose ester or cyclic olefin resin can be exemplified.

Next, the transparent material is released from the first roll (210). The method of releasing the transparent material is performed by installing a suitable rotating means on the core (210A) of the first roll (210) and rotating the first roll (210) by the rotating means. In addition, a suitable auxiliary roll (300) may be installed in the direction in which the transparent material is returned from the first roll (210), and the transparent material may be released by the rotating means of the auxiliary roll (300). In addition, a method may be used in which the first core (210A) and the auxiliary roll (300) are both provided with rotating means, thereby releasing the transparent material while applying an appropriate tension to the transparent material.

When the transparent substrate released from the first roll (210) passes through the coating device (211A), a composition for forming a photo-alignment layer is applied onto the surface thereof by the coating device (211A). In order to continuously apply the composition for forming a photo-alignment layer in this manner, a printing method such as a gravure coating method, a die coating method, or a flexographic method is performed by the coating device (211A) as described above.

The transparent substrate that has passed through the coating device (211A) is returned to a drying furnace (212A), and is heated by the drying furnace (212A) to continuously form a first dry film on the transparent substrate. As the drying furnace (212A), a hot air drying furnace, etc., is used. The set temperature of the drying furnace (212A) is determined according to the type of solvent included in the composition for forming the photoalignment layer coated by the coating device (211A), etc. In addition, the drying furnace (212A) may be divided into a plurality of zones, and the set temperature may be different for each of the divided zones, or a plurality of drying furnaces may be arranged in series, and the set temperature may be different for each drying furnace.

By passing through the heater (212A), the first dry film formed continuously is then irradiated with polarized UV to the surface on the side of the first dry film or the surface on the side of the transparent substrate by a polarized UV irradiation device (213A), so that the first dry film forms a (photo)alignment film. At that time, the angle formed by the return direction D1 of the transparent substrate and the alignment direction D2 of the formed photoalignment film may intersect. Fig. 2 is a schematic diagram showing the relationship between the alignment direction D2 of the formed photoalignment film and the return direction D1 of the transparent substrate after polarized UV irradiation. That is, Fig. 2 shows that when the surface of the first laminate after passing through the polarized UV irradiation device (213A) is viewed with respect to the return direction D1 of the transparent substrate and the alignment direction D2 of the photoalignment film, the angle formed by them is approximately 45°.

In this way, the transparent substrate (first laminate) on which the photo-alignment film is continuously formed passes through a coating device (211B), whereby a polarizing film-forming composition is applied onto the photo-alignment film, and then passes through a drying furnace (212B). By passing through the drying furnace (212B), the polymerizable liquid crystal compound included in the polarizing film-forming composition forms a nematic liquid crystal phase, preferably a smectic liquid crystal phase, thereby forming a second dry film.

The transparent substrate that has passed through the drying oven (212B) is returned to the light irradiation device (213B) while the polymerizable liquid crystal compound in the second drying film maintains the liquid crystal state of a nematic liquid crystal phase, preferably a smectic liquid crystal phase, by sufficiently removing the solvent contained in the polarizing film forming composition. By light irradiation by the light irradiation device (213B), the polymerizable liquid crystal compound is photopolymerized while maintaining the liquid crystal state, and the polarizing film is continuously formed on the alignment film, thereby obtaining the polarizer.

The polarizing film formed in this manner is wound on a second core (220A) in the form of a laminate including a transparent substrate and an alignment film, thereby obtaining the form of a second roll (220). When the formed polarizing film is wound to obtain a second roll, co-winding using an appropriate spacer may be performed.

In this way, as the transparent substrate passes through the first roll/application device (211A)/drying furnace (212A)/polarizing UV irradiation device (213A)/application device (211B)/drying furnace (212B)/light irradiation device (213B) in that order, the polarizing film is continuously formed on the photo-alignment film on the transparent substrate, thereby manufacturing the polarizer.

In addition, although the manufacturing method illustrated in Fig. 1 shows a method of continuously manufacturing from a transparent substrate to the polarizing film, for example, by passing the transparent substrate through the first roll/coating device (211A)/drying furnace (212A)/polarizing UV irradiation device (213A) in that order, the first laminate formed continuously is wound around a core to manufacture the first laminate in the form of a roll, the first laminate is unwound from the roll, and the unwound first laminate is passed through the coating device (211B)/drying furnace (212B)/light irradiation device (213B) in that order, thereby manufacturing the polarizer.

The polarizer obtained by the present manufacturing method is a film-like and elongated shape. When this polarizing film is used in a liquid crystal display device, etc., which will be described later, it is cut to a desired size according to the scale of the liquid crystal display device, etc., and then used.

Above, the configuration and manufacturing method of this polarizer have been described focusing on the case in which it is in the form of a laminate of transparent substrate/photoalignment film/main polarizing film. However, this polarizing film can also be obtained as a single layer by peeling off the photoalignment film or transparent substrate from this polarizer. Furthermore, this polarizer may have a form in which a layer or film other than the transparent substrate/photoalignment film/main polarizing film is laminated. As these layers and films, as described above, this polarizing film may further include a retardation film, and may further include an antireflection layer or a brightness enhancing film.

In addition, by making the transparent substrate itself a phase difference film, it is also possible to make a circular polarizing plate or an ellipsoidal polarizing plate in the form of a phase difference film/optical alignment film/main polarizing film. For example, when using a uniaxially stretched quarter-wave plate as a phase difference film, it is possible to manufacture a circular polarizing plate Roll-to-Roll by setting the irradiation direction of polarizing UV to be approximately 45° to the return direction of the transparent substrate. It is preferable that the quarter-wave plate used when manufacturing a circular polarizing plate in this way have a characteristic that the in-plane phase difference value for visible light decreases as the wavelength becomes shorter.

In addition, it is also possible to manufacture a linear polarizing plate roll by using a 1/2 wavelength plate as a phase difference film and setting the angle between its ground axis and the absorption axis of the polarizing film to be different, and then forming a 1/4 wavelength plate on the opposite side to the side where the polarizing film is formed, thereby making a broadband circular polarizing plate.

4. Use of this polarizing film

The polarizing film can be used in various display devices. 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. Examples of the display device include a liquid crystal display, an organic electroluminescence (EL) display, an inorganic electroluminescence (EL) display, an electron emission display (e.g., a field emission display (FED) or a surface field emission display (SED)), an electronic paper (a display device using electronic ink or an electrophoretic element), a plasma display, a projection display device (e.g., a grating light valve (GLV) display device or a display device having a digital micromirror device (DMD)), and a piezoelectric ceramic display. The liquid crystal display device includes any of a transmissive liquid crystal display, a semi-transmissive liquid crystal display, a reflective liquid crystal display, a direct-view liquid crystal display, and a projection liquid crystal display. These display devices may be a display device that displays a two-dimensional image, or a stereoscopic display device that displays a three-dimensional image.

This polarizing film can be effectively used, particularly, in a display device such as an organic electroluminescence (EL) display device or an inorganic electroluminescence (EL) display device.

Figure 3 is a schematic diagram showing the cross-sectional configuration of a liquid crystal display device (hereinafter, sometimes referred to as “the liquid crystal display device”) (10) using the polarizing film. The liquid crystal layer (17) is sandwiched between two substrates (14a) and (14b).

FIG. 6 and FIG. 10 are schematic diagrams showing the cross-sectional configuration of an EL display device using the present polarizing film (hereinafter, referred to as “present EL display device” as the case may be).

Figure 11 is a schematic diagram showing the configuration of a projection-type liquid crystal display device using this polarizing film.

First, the liquid crystal display device (10) shown in Fig. 3 will be described.

A color filter (15) is arranged on the liquid crystal layer (17) side of the substrate (14a). The color filter (15) is arranged at a position facing the pixel electrode (22) with the liquid crystal layer (17) interposed therebetween, and a black matrix (20) is arranged at a position facing the boundary between the pixel electrodes. A transparent electrode (16) is arranged on the liquid crystal layer (17) side so as to cover the color filter (15) and the black matrix (20). Meanwhile, an overcoat layer (not shown) may be provided between the color filter (15) and the transparent electrode (16).

On the liquid crystal layer (17) side of the substrate (14b), thin film transistors (21) and pixel electrodes (22) are regularly arranged. The pixel electrodes (22) are arranged at a position facing the color filter (15) with the liquid crystal layer (17) interposed therebetween. An interlayer insulating film (18) having a connection hole (not shown) is arranged between the thin film transistors (21) and the pixel electrodes (22).

As the substrate (14a) and the substrate (14b), a glass substrate and a plastic substrate are used. The glass substrate or the plastic substrate may be made of the same material as that exemplified as the transparent substrate used in manufacturing the polarizing film. In addition, the transparent substrate (1) of the polarizing film may also serve as the substrate (14a) and the substrate (14b). When a process of heating to a high temperature is required when manufacturing a color filter (15) or a thin film transistor (21) formed on the substrate, a glass substrate or a quartz substrate is preferable.

The thin film transistor can be selected to be optimal depending on the material of the substrate (14b). Examples of the thin film transistor (21) include a high-temperature polysilicon transistor formed on a quartz substrate, a low-temperature polysilicon transistor formed on a glass substrate, and an amorphous silicon transistor formed on a glass substrate or a plastic substrate. In order to further miniaturize the liquid crystal display device, the driver IC may be formed on the substrate (14b).

A liquid crystal layer (17) is arranged between the transparent electrode (16) and the pixel electrode (22). A spacer (23) is arranged on the liquid crystal layer (17) to maintain a constant distance between the substrate (14a) and the substrate (14b). Meanwhile, although a columnar spacer is illustrated in FIG. 3, the spacer is not limited to a columnar shape, and its shape may be arbitrary as long as it can maintain a constant distance between the substrate (14a) and the substrate (14b).

Each member is laminated in the following order: a substrate (14a), a color filter (15) and a black matrix (20), a transparent electrode (16), a liquid crystal layer (17), a pixel electrode (22), an interlayer insulating film (18) and a thin film transistor (21), and a substrate (14b).

Among the substrates (14a) and (14b) with the liquid crystal layer (17) interposed therebetween, polarizers (12a and 12b) are installed on the outer side of the substrate (14b), and this polarizer is used in at least one of them.

In addition, it is preferable if phase difference layers (e.g., 1/4 wavelength plates or optical compensation films) (13a and 13b) are laminated. By arranging this polarizing film on the polarizer (12b) among the polarizers (12a and 12b), the function of converting incident light into linearly polarized light can be imparted to the liquid crystal display device (10). Meanwhile, the phase difference films (13a and 13b) may not be arranged depending on the structure of the liquid crystal display device or the type of liquid crystal compound included in the liquid crystal layer (17), and when the transparent substrate is a phase difference film and a circular polarizing plate including this polarizing film is used, the phase difference film can be used as the phase difference layer, and therefore the phase difference layer (13a and/or 13b) of Fig. 3 can be omitted. It is also acceptable to further install a polarizing film on the light-emitting side (outer side) of the polarizer.

In addition, it is acceptable to have an anti-reflection film placed on the outside of this polarizer (or on the outside if a polarizing film is additionally installed on the polarizing film) to prevent reflection of external light.

As described above, the polarizer (12a or 12b) of the liquid crystal display device (10) of Fig. 3 can be used. By installing the polarizer in the polarizer (12a and/or 12b), there is an effect that the thinning of the liquid crystal display device (10) can be achieved.

When this polarizer is used for polarizer (12a or 12b), the stacking order is not particularly limited. This is explained with reference to the enlarged views of parts A and B surrounded by dotted lines in Fig. 3.

Fig. 4 is an enlarged schematic cross-sectional view of part A of Fig. 3. Fig. 4 (A1) shows that when the polarizer (100) is used as a polarizer (12a), the polarizing film (3), the optical alignment film (2), and the transparent substrate (1) are installed so as to be arranged in the above order from the phase difference layer (13a) side. In addition, Fig. 4 (A2) shows that the transparent substrate (1), the optical alignment film (2), and the polarizing film (3) are installed so as to be arranged in the above order from the phase difference layer (13a) side.

Fig. 5 is an enlarged schematic diagram of part B of Fig. 3. Fig. 5 (B1) shows that when this polarizer (100) is used as a polarizer (12b), the transparent substrate (1), the optical alignment film (2), and the polarizing film (3) are installed in this order from the phase difference film (13b) side. Fig. 5 (B2) shows that when this polarizer (100) is used as a polarizer (12b), the polarizing film (3), the optical alignment film (2), and the transparent substrate (1) are installed in this order from the phase difference film (13b) side.

A backlight unit (19) which is a light source is arranged on the outside of the polarizer (12b). The backlight unit (19) includes a light source, a light guide, a reflector, a diffusion sheet, and a viewing angle adjustment sheet. Examples of the light source include electroluminescence, a cold cathode tube, a hot cathode tube, a light-emitting diode (LED), a laser light source, and a mercury lamp. In addition, the type of the polarizing film can be selected according to the characteristics of the light source.

When the liquid crystal display device (10) is a transmissive liquid crystal display device, white light generated from a light source in the backlight unit (19) is incident on a light guide, its path is changed by a reflector, and is diffused by a diffusion sheet. After the diffused light is adjusted to have a desired directivity by a viewing angle adjustment sheet, it is incident on a polarizer (12b) from the backlight unit (19).

Among the unpolarized incident light, only one linearly polarized light transmits through the polarizer (12b) of the liquid crystal panel. The linearly polarized light is converted into circularly polarized light or elliptically polarized light by the phase difference layer (13b), and sequentially transmits through the substrate (14b), pixel electrode (22), etc., and reaches the liquid crystal layer (17).

Here, depending on the presence or absence of a potential difference between the pixel electrode (22) and the opposing transparent electrode (16), the alignment state of the liquid crystal molecules included in the liquid crystal layer (17) changes, thereby controlling the brightness of light emitted from the liquid crystal display device (10). When the liquid crystal layer (17) is in an alignment state that converts polarization and transmits it, the polarization transmits through the liquid crystal layer (17) and the transparent electrode (16), and light of a certain wavelength range transmits through the color filter (15) and reaches the polarizer (12a), and the liquid crystal display device displays the color determined by the color filter most brightly.

On the other hand, when the liquid crystal layer (17) is in an alignment state that directly transmits polarized light, light transmitted through the liquid crystal layer (17), the transparent electrode (16), and the color filter (15) is absorbed by the polarizer (12a). As a result, the pixel displays black. In an alignment state intermediate between these two states, the luminance of light emitted from the liquid crystal display device (10) also becomes intermediate between the two, so the pixel displays an intermediate color.

If the liquid crystal display device (10) is a semi-transmissive liquid crystal display device, it is preferable to use a 1/4 wavelength plate (circular polarizing plate) further laminated on the polarizing film side of the polarizer. At this time, the pixel electrode (22) has a transmissive portion formed of a transparent material and a reflective portion formed of a material that reflects light, and an image is displayed in the transmissive portion in the same manner as in the aforementioned transmissive liquid crystal display device. On the other hand, in the reflective portion, external light is incident on the liquid crystal display device, and circularly polarized light transmitted through the polarizing film by the action of the 1/4 wavelength plate further provided in the polarizing film passes through the liquid crystal layer (17), is reflected by the pixel electrode (22), and is used for display.

Next, the EL display device (30) using the polarizing film will be described with reference to FIG. 6. When the polarizing film is used in the EL display device, it is preferable to use the polarizing film as a circular polarizing plate (hereinafter, referred to as “circular polarizing plate” as the case may be). There are two embodiments of the circular polarizing plate. Therefore, before describing the configuration of the EL display device (30), etc., two embodiments of the circular polarizing plate will be described with reference to FIG. 7.

Fig. 7(A) is a schematic diagram showing a first embodiment of the present circular polarizing plate (110). The first embodiment is the present circular polarizing plate (110) in which a phase difference layer (phase difference film) (4) is further formed on the polarizing film (3) of the present polarizer (100). Fig. 7(B) is a schematic diagram showing a second embodiment of the present circular polarizing plate (110). The second embodiment is the present circular polarizing plate (110) in which the transparent substrate (1) (phase difference film (4)) to which phase difference properties are previously imparted is used when manufacturing the present polarizer, so that the transparent substrate (1) itself functions as the phase difference layer (4).

As the present circular polarizing plate including the present polarizing film, the second embodiment of the present circular polarizing plate described above is preferable because the configuration is simple, and in this case, it is preferable to use a 1/4 wavelength plate as the transparent substrate, and further, it is preferable to use a 1/4 wavelength plate as the transparent substrate and satisfy the following requirements (A1) and (A2).

(A1) The angle formed by the absorption axis of the polarizing film and the ground axis of the 1/4 wavelength plate shall be approximately 45°;

(A2) The value of the front retardation of the above 1/4 wavelength plate measured under light of wavelength 550 nm shall be in the range of 100 to 150 nm.

Here, the manufacturing method of the present circular polarizing plate (110) is explained. As already explained, the second embodiment of the present circular polarizing plate (110) can be manufactured by using a transparent substrate (1) to which phase difference properties have been previously provided, i.e., a phase difference film, as the transparent substrate (1) in the present manufacturing method for manufacturing the present polarizing film (100). The first embodiment of the present circular polarizing plate (110) is formed by bonding a phase difference film onto the present polarizing film (3) manufactured by the present manufacturing method B to form a phase difference layer (4). Meanwhile, in the case where the polarizing film (100) is manufactured in the form of a second roll (220) by the manufacturing method B of the present invention, the polarizing film (100) may be unrolled from the second roll (220), cut to a predetermined dimension, and then a phase difference film may be bonded to the cut polarizing film (100). However, by preparing a third roll in which the phase difference film is wound around a core, the circular polarizing plate (110) having a film-like shape and a long shape can also be continuously manufactured.

A method for continuously manufacturing the first embodiment of the present polarizing plate (110) is described with reference to Fig. 8. This manufacturing method is,

A process of continuously releasing the polarizer (100) from the second roll (220) and simultaneously releasing the phase difference film from the third roll (230) on which the phase difference film is wound,

A process of forming a circular polarizing plate (110) by continuously bonding a polarizing film formed on a polarizer (100) released from the second roll (220) and the phase difference film released from the third roll;

The process is comprised of winding the formed circular polarizing plate (110) onto a fourth core (240A) to obtain a fourth roll (240).

Above, the manufacturing method of the first embodiment of the present circular polarizing plate (110) has been described, but when bonding the present polarizing film (3) and the phase difference film in the polarizer (100), an appropriate adhesive may be used to bond the present polarizing film (3) and the phase difference film through an adhesive layer formed with the adhesive.

Next, the EL display device equipped with the circular polarizing plate (110) will be described again with reference to Fig. 6.

The present EL display device (30) is formed by laminating an organic functional layer (36) and a cathode electrode (37) as a light-emitting source on a substrate (33) on which a pixel electrode (35) is formed. A circularly polarizing plate (31) is arranged on the opposite side to the organic functional layer (36) with the substrate (33) interposed therebetween, and the present circularly polarizing plate (110) is used as this circularly polarizing plate (31). By applying a positive voltage to the pixel electrode (35) and a negative voltage to the cathode electrode (37), and applying a direct current between the pixel electrode (35) and the cathode electrode (37), the organic functional layer (36) emits light. The organic functional layer (36) as a light-emitting source is composed of an electron transport layer, a light-emitting layer, a hole transport layer, etc. Light emitted from the organic functional layer (36) passes through the pixel electrode (35), the interlayer insulating film (34), the substrate (33), and the circular polarizing plate (31) (this circular polarizing plate (110)). Although the present invention is described with respect to an organic EL display device having an organic functional layer (36), it may also be applied to an inorganic EL display device having an inorganic functional layer.

In order to manufacture this EL display device (30), first, a thin film transistor (40) is formed in a desired shape on a substrate (33). Then, an interlayer insulating film (34) is formed, and then a pixel electrode (35) is formed using a sputtering method and patterned. Thereafter, an organic functional layer (36) is laminated.

Next, a circular polarizing plate (31) (this circular polarizing plate (110)) is installed on the surface opposite to the surface on which the thin film transistor (40) of the substrate (33) is installed.

When the present circular polarizing plate (110) is used as a circular polarizing plate (31), the stacking order is explained with reference to the enlarged view of the portion C surrounded by the dotted line in Fig. 6. When the present circular polarizing plate (110) is used as a circular polarizing plate (31), the phase difference layer (4) in the present circular polarizing plate (110) is arranged on the substrate (33) side. Fig. 9 (C1) is an enlarged view of the first embodiment of the present circular polarizing plate (110) used as a circular polarizing plate (31), and Fig. 9 (C2) is an enlarged view of the second embodiment of the present circular polarizing plate (110) used as a circular polarizing plate (31).

Next, the components other than the polarizing film (31) (circular polarizing plate (110)) of the EL display device (30) will be described.

As the substrate (33), examples thereof include a sapphire glass substrate, a quartz glass substrate, a soda glass substrate, and a ceramic substrate such as alumina; a metal substrate such as copper; and a plastic substrate. Although not shown, a thermally conductive film may be formed on the substrate (33). Examples of the thermally conductive film include a diamond thin film (DLC, etc.). When the pixel electrode (35) is reflective, light is emitted in the opposite direction to the substrate (33). Therefore, not only a transparent material but also an opaque material such as stainless steel can be used. The substrate may be formed as a single substrate, or may be formed as a laminated substrate by bonding a plurality of substrates with an adhesive. In addition, these substrates are not limited to a plate-shaped one, and may also be a film.

As the thin film transistor (40), a polycrystalline silicon transistor, etc. may be used, for example. The thin film transistor (40) is installed at the end of the pixel electrode (35) and has a size of about 10 to 30 ㎛. Meanwhile, the size of the pixel electrode (35) is about 20 ㎛×20 ㎛ to 300 ㎛×300 ㎛.

A wiring electrode of a thin film transistor (40) is installed on the substrate (33). The wiring electrode has low resistance and has the function of electrically connecting to the pixel electrode (35) to suppress the resistance value to a low level. Generally, the wiring electrode is used containing one or more of Al, Al, and a transition metal (excluding Ti), Ti, or titanium nitride (TiN).

An interlayer insulating film (34) is formed between the thin film transistor (40) and the pixel electrode (35). The interlayer insulating film (34) may be any insulating material, such as a film formed by sputtering or vacuum deposition of an inorganic material such as silicon oxide or silicon nitride such as SiO ₂ , a silicon oxide layer formed by SOG (spin-on glass), a coating of a resin material such as photoresist, polyimide, and acrylic resin, etc.

A rib (41) is formed on the interlayer insulating film (34). The rib (41) is arranged on the periphery of the pixel electrode (35) (between adjacent pixels). Examples of the material for the rib (41) include acrylic resin and polyimide resin. The thickness of the rib (41) is preferably 1.0 ㎛ or more and 3.5 ㎛ or less, and more preferably 1.5 ㎛ or more and 2.5 ㎛ or less.

Next, an EL element composed of a pixel electrode (35) which is a transparent electrode, an organic functional layer (36) which is a light-emitting source, and a cathode electrode (37) will be described. The organic functional layer (36) each has at least one hole transport layer and one light-emitting layer, and for example, has an electron injection transport layer, a light-emitting layer, a hole transport layer, and a hole injection layer in sequence.

As the pixel electrode (35), examples thereof include ITO (tin-doped indium oxide), IZO (zinc-doped indium oxide), IGZO, ZnO, SnO ₂ , and In ₂ O ₃ , but ITO or IZO is particularly preferable. The thickness of the pixel electrode (35) should be a certain thickness or more that can sufficiently perform hole injection, and is preferably set to about 10 to 500 nm.

The pixel electrode (35) can be formed by a deposition method (preferably a sputtering method). The sputtering gas is not particularly limited, and an inert gas such as Ar, He, Ne, Kr, and Xe, or a mixed gas thereof can be used.

As the constituent material of the cathode electrode (37), metal elements such as K, Li, Na, Mg, La, Ce, Ca, Sr, Ba, Al, Ag, In, Sn, Zn, and Zr may be used, but in order to improve the operational stability of the electrode, it is preferable to use an alloy system of two or three components selected from the exemplified metal elements. As the alloy system, for example, Ag·Mg (Ag: 1∼20 at%), Al·Li (Li: 0.3∼14 at%), In·Mg (Mg: 50∼80 at%), and Al·Ca (Ca: 5∼20 at%) are preferable.

The cathode electrode (37) is formed by a deposition method, a sputtering method, or the like. The thickness of the cathode electrode (37) is preferably 0.1 nm or more, and preferably 1 to 500 nm.

The hole injection layer has a function of facilitating the injection of holes from the pixel electrode (35), and the hole transport layer has a function of transporting holes and a function of hindering electrons, and is also called a charge injection layer or charge transport layer.

The thickness of the light-emitting layer, the combined thickness of the hole injection layer and the hole transport layer, and the thickness of the electron injection transport layer are not particularly limited and vary depending on the formation method, but are preferably set to about 5 to 100 nm. Various organic compounds can be used for the hole injection layer or the hole transport layer. The vacuum deposition method can be used to form the hole injection transport layer, the light-emitting layer, and the electron injection transport layer because it can form a homogeneous thin film.

As the organic functional layer (36) which is a light-emitting source, one that utilizes light emission (fluorescence) from singlet excitons, one that utilizes light emission (phosphorescence) from triplet excitons, one that includes light emission (fluorescence) from singlet excitons and light emission (phosphorescence) from triplet excitons, one formed of an organic substance, one that includes both light emission (fluorescence) from an organic substance and light emission (phosphorescence) from a triplet exciton, one formed of an organic substance, one that includes a polymer material, a low-molecular material, one that includes a polymer material and a low-molecular material, etc. can be used. However, the present invention is not limited thereto, and an organic functional layer (36) that utilizes various materials known for use in EL elements can be used in the EL display device (30).

A desiccant (38) is placed in the space between the cathode electrode (37) and the sealing lid (39). This is because the organic functional layer (36) is weak to humidity. The desiccant (38) absorbs moisture to prevent deterioration of the organic functional layer (36).

Fig. 10 is a schematic diagram showing a cross-sectional configuration of another embodiment of the EL display device (30). This EL display device (30) has a sealing structure using a thin film sealing film (42), and can obtain light emitted from the opposite surface of the array substrate.

As the thin film sealing film (42), it is preferable to use a DLC film in which DLC (diamond-like carbon) is deposited on the film of the electrolytic capacitor. The DLC film has the characteristic of being very poor in moisture permeability and has high moisture-proofing performance. In addition, the DLC film may be formed by directly depositing it on the surface of the cathode electrode (37). In addition, the thin film sealing film (42) may be formed by laminating a resin film and a metal film in multiple layers.

In this manner, a novel polarizing film (the polarizing film) according to the present invention and a novel display device (the liquid crystal display device and the EL display device) comprising the polarizing film are provided.

Finally, a projection-type liquid crystal display device using this polarizing film is described.

Figure 11 is a schematic diagram illustrating a projection-type liquid crystal display device using this polarizing film.

This polarizing film is used as a polarizer (142) and/or polarizer (143) of this projection-type liquid crystal display device.

A light beam bundle emitted from a light source (e.g., a high-pressure mercury lamp) (111), which is a light source, first passes through a first lens array (112), a second lens array (113), a polarization conversion element (114), and a superposition lens (115), thereby achieving uniformity of brightness and polarization in the cross section of the anti-light beam bundle.

Specifically, a light beam bundle emitted from a light source (111) is divided into a plurality of micro light beam bundles by a first lens array (112) in which micro lenses (112a) are formed in a matrix shape. The second lens array (113) and the overlapping lens (115) are provided so that each of the divided light beam bundles irradiates the entire three liquid crystal panels (140R, 140G, 140B) that are the illumination targets, and therefore, the entire incident surface of each liquid crystal panel has almost uniform illuminance.

The polarization conversion element (114) is composed of a polarization beam splitter array and is placed between the second lens array (113) and the overlapping lens (115). Accordingly, it converts random polarization from a light source into polarization having a predetermined polarization direction, thereby reducing light loss in the incident-side polarizer described later, and improving the brightness of the screen.

As described above, the light, which is uniform in brightness and polarized, passes through a reflective mirror (122) and is sequentially separated into red channel, green channel, and blue channel by dichroic mirrors (121, 123, 132) for separating into the three primary colors of RGB, and is then incident on the liquid crystal panels (140R, 140G, 140B), respectively.

In the liquid crystal panel (140R, 140G, 140B), a polarizer (142) is placed on the incident side, and a polarizer (143) is placed on the emission side. The polarizing film can be used for the polarizer (142) and the polarizer (143).

Polarizers (142) and polarizers (143) arranged in each RGB optical path are arranged so that their respective absorption axes are orthogonal. Each liquid crystal panel (140R, 140G, 140B) arranged in each optical path has the function of converting the polarization state controlled for each pixel by an image signal into light quantity.

This polarizing film (100) is useful as a polarizing film with excellent durability in optical paths such as the blue channel, green channel, and red channel by selecting the type of dichroic dye appropriate for the corresponding channel.

An optical image created by transmitting incident light with different transmittance for each pixel according to the image data of the liquid crystal panel (140R, 140G, 140B) is synthesized by a cross dichroic prism (150) and enlarged and projected onto a screen (180) by a projection lens (170).

Electronic paper may be indicated by molecules such as optical anisotropy and dye molecule orientation, by particles such as electrophoresis, particle movement, particle rotation, and phase change, by movement of one end of the film, by molecular color development/phase change, by molecular light absorption, and by spontaneous luminescence caused by the combination of electrons and holes. More specifically, microcapsule type electrophoresis, horizontal movement type electrophoresis, vertical movement type electrophoresis, spherical twist ball, magnetic twist ball, cylindrical twist ball method, charged toner, electro-dispersive fluid, magnetic electrophoresis type, magnetic thermal type, electrowetting, light scattering (transparency/turbidity 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-induced phosphorescence, photochromic, electrochromic, electrodeposition, flexible organic EL, etc. Electronic paper may be used not only for personal use of text or images, but also for advertising signage, etc. According to the present polarizing film, the thickness of the electronic paper can be made thin.

As a stereoscopic display device, a method of arranging different phase difference films alternately, such as a micropole method, has been proposed (Japanese Patent Application Laid-Open No. 2002-185983). However, if this polarizing film is used, patterning is easy by printing, inkjet, photolithography, etc., so the manufacturing process of the display device can be shortened, and the phase difference film becomes unnecessary.

Example

Hereinafter, the present invention will be described in more detail by examples. In the examples, “%” and “part” are mass% and mass part, respectively, unless otherwise specified.

In this example, the following dichroic dye (1) was used.

Preparation of compound (1-1) (compound represented by (1-1) below)

Compound (1-1) was synthesized according to the following scheme.

5.00 g of a compound represented by formula (1B) [compound (1B)], 4.63 g of ethyl 4-hydroxybenzoate, 0.23 g of dimethylaminopyridine (DMAP), and 25 g of chloroform were mixed and stirred at 5°C for 10 minutes in a light-shielding, nitrogen atmosphere. 2.58 g of diisopropylcarbodiimide (IPC) was added dropwise to the obtained mixture over 5 minutes, and the mixture was stirred for further 4 hours. 75 g of methanol was added to the obtained reaction solution, crystallized, and the crystals were collected by filtration. The crystals were further washed with the same amount of methanol and then vacuum-dried to obtain 6.78 g of compound (1-1). The yield was 87% based on compound (1B).

¹ H-NMR (CDCl ₃ ) of compound (1-1): δ (ppm) 1.41 (t, 3H), 3.12 (s, 6H), 4.40 (m, 2H), 6.76 (m, 2H), 7.33 ( m, 2H), 7.93(dd, 4H), 8.15(m, 2H), 8.30(m, 2H).

Preparation of compound (1-7) (compound represented by (1-7) below)

Compound (1-7) was synthesized by the following scheme.

Compound (1B) (5.00 g), 4-butyloxyphenol (4.63 g), DMAP (0.23 g) and chloroform (25 g) were mixed and stirred at 5°C for 10 minutes under a light-shielding, nitrogen atmosphere. To the obtained mixture, 2.58 g of IPC was added dropwise over 5 minutes and stirred for 4 more hours. 75 g of methanol was added to the obtained reaction solution and crystals were filtered off. The crystals were dissolved in 50 g of dimethylacetamide, and the insoluble matter was filtered off through Celite. The filtrate was recovered and crystallized with water. The obtained crystals were further dissolved in 50 g of tetrahydrofuran, and the insoluble matter was removed by filtration, heptane was added to crystallize, and the mixture was vacuum-dried to obtain 4.66 g of compound (1-7). The yield was 60% based on compound (1B).

¹ H-NMR (CDCl ₃ ) of compound (1-7): δ (ppm) 0.99 (t, 3H), 1.45 (m, 2H), 1.78 (m, 2H), 3.12 (s, 6H), 3.98 ( t, 2H), 6.77(m, 2H), 6.93(m, 2H), 7.15(m, 2H), 7.92(dd, 4H), 8.29(dd, 2H).

In this example, the following polymerizable liquid crystal compound was used.

Compound (4-6) (compound represented by the following formula (4-6))

Compounds (4-6) were synthesized according to the method described in Lub et al. Recl. Trav. Chim. Pays-Bas, 115, 321-328 (1996).

〔Measurement of phase transition temperature〕

The phase transition temperature of compound (4-6) was confirmed by obtaining the phase transition temperature of a film composed of compound (4-6). The operation is as follows.

A film made of compound (4-6) was formed on a glass substrate on which an alignment film was formed, and the phase transition temperature was confirmed by observing the texture using a polarizing microscope (BX-51, manufactured by Olympus) while heating. The film made of compound (4-6) transitioned into a nematic phase at 112°C, into a smectic A phase at 110°C, and into a smectic B phase at 94°C when the temperature was raised to 120°C and then lowered.

Compound (4-8) (compound represented by the following formula (4-8))

Compound (4-8) was synthesized with reference to the synthetic method of compound (4-6) described above.

〔Measurement of phase transition temperature〕

The phase transition temperature of compound (4-8) was confirmed in the same manner as the phase transition temperature of compound (4-6). When the temperature of compound (4-8) was increased to 140°C and then decreased, it transitioned to a nematic phase at 131°C, to a smectic A phase at 80°C, and to a smectic B phase at 68°C.

Compound (4-22) (compound represented by the following formula (4-22))

Compound (4-22) was synthesized with reference to the synthetic method described in Japanese Patent No. 4719156.

〔Measurement of phase transition temperature〕

The phase transition temperature of compound (4-22) was confirmed in the same manner as the phase transition temperature of compound (4-6). When the temperature of compound (4-22) was increased to 140°C and then decreased, it transitioned to a nematic phase at 106°C, to a smectic A phase at 103°C, and to a smectic B phase at 86°C.

Compound (4-25) (compound represented by the following formula (4-25))

Compound (4-25) was synthesized with reference to the synthetic method described in Japanese Patent No. 4719156.

〔Measurement of phase transition temperature〕

The phase transition temperature of compound (4-25) was confirmed in the same manner as the phase transition temperature of compound (4-6). When the temperature of compound (4-25) was increased to 140°C and then decreased, it transitioned to a nematic phase at 119°C, to a smectic A phase at 100°C, and to a smectic B phase at 77°C.

Example 1 [Preparation of composition (A) for forming a polarizing film]

By mixing the following components and stirring at 80°C for 1 hour, a composition (A) for forming a polarizing film was obtained. In addition, the "compound (1-7)" of the dichroic dye used herein means a compound represented by the above formula (1-7), and compounds used as other dichroic dyes also follow the formula number. The same applies hereinafter.

Polymerizable liquid crystal compound; Compound (4-6) 75 parts

Compound (4-8) 25 parts

Dichromatic pigment; Compound (1-7) 3.0 parts

Compound (2-17) Part 2.5

Compound (2-29) 1.5 parts

Compound (2-32) Part 2.0

Polymerization initiator; 2-dimethylamino-2-benzyl-1-(4-morpholinophenyl)butan-1-one (Irgacure 369; manufactured by Ciba Specialty Chemicals Co., Ltd.) 6 parts

Leveling agent; 1.2 parts polyacrylate compound (BYK-361N; manufactured by BYK-Chemie)

Solvent; 250 parts toluene

1. X-ray diffraction measurement

A 2 mass% aqueous solution (orientation layer forming composition) of polyvinyl alcohol (polyvinyl alcohol 1000 completely saponified type, manufactured by Wako Pure Chemical Industries, Ltd.) was applied onto a glass substrate by a spin coating method, dried, and a film having a thickness of 100 nm was formed. Next, a rubbing treatment was performed on the surface of the obtained film to form an orientation layer. The rubbing treatment was performed using a semi-automatic rubbing device (trade name: LQ-008 type, manufactured by Joyo Kogaku Co., Ltd.) with a cloth (trade name: YA-20-RW, manufactured by Yoshikawa Kako Co., Ltd.) under the conditions of a pressing amount of 0.15 mm, a rotational speed of 500 rpm, and 16.7 mm/s. In this way, a polarizing film-forming composition (A) was applied onto the alignment film manufactured by the spin coating method, heated and dried on a 120°C hot plate for 1 minute, and then quickly cooled to room temperature to form a dry film on the alignment layer. Next, a UV irradiation device (SPOT CURE SP-7; manufactured by Ushio Denki Co., Ltd.) was used to irradiate the dry film with ultraviolet rays at an exposure dose of 2000 mJ/cm2 (based on 365 nm), thereby polymerizing the polymerizable liquid crystal compound contained in the dry film while maintaining the liquid crystal state of the polymerizable liquid crystal composition, thereby forming a polarizing film with the dry film. The thickness of the polarizing film at this time, as measured by a laser microscope (OLS3000 manufactured by Olympus Co., Ltd.), was 1.7 μm. For the above polarizing film, similar X-ray diffraction measurement was performed using an X-ray diffraction apparatus X'Pert PRO MPD (manufactured by Spectris Co., Ltd.), and as a result, a sharp diffraction peak (Bragg peak) with a peak full width at half maximum (FWHM) of approximately 0.17° was obtained at around 2θ = 20.2°. In addition, the same result was obtained even when the incident light was from the rubbing vertical direction. The order period (d) obtained from the peak position was approximately 4.4 Å, and it was confirmed that a structure reflecting a higher-order smectic phase was formed.

2. Fabrication of a photo-alignment film on a transparent film

A triacetyl cellulose film (KC8UX2M, manufactured by Konica Minolta Co., Ltd.) as a transparent substrate was used, and a solution of a photo-alignment polymer represented by the following formula (3) dissolved in toluene at a concentration of 5% was applied by the bar coat method, and dried at 120°C to obtain a dry film. This dry film was irradiated with polarized UV to obtain a photo-alignment film. The polarized UV treatment was performed using a UV irradiation device (SPOT CURE SP-7; manufactured by Ushio Denki Co., Ltd.) under the condition that the intensity measured at a wavelength of 365 nm was 100 mJ.

3. Fabrication of polarizing film

As described above, a polarizing film-forming composition (A) was applied onto a film having an alignment film obtained by the above-described method by the bar coat method (#5 17 mm/s), dried by heating in a drying oven at 120°C for 1 minute, and then cooled to room temperature. Next, by irradiating the layer formed with the polarizing film-forming composition with ultraviolet rays having an exposure dose of 2000 mJ/cm2 (based on 365 nm) using a UV irradiation device (SPOT CURE SP-7; manufactured by Ushio Denki Co., Ltd.), the polymerizable liquid crystal compound contained in the dry film was polymerized while maintaining the liquid crystal state of the polymerizable liquid crystal composition, thereby forming a polarizing film with the dry film. The film thickness of the polarizing film at this time was measured by a laser microscope (OLS3000 manufactured by Olympus Co., Ltd.), and was 1.6 μm. What was thus obtained was a polarizer including a polarizing film and a transparent substrate.

4. Measurement of polarization, transmittance, and color

To verify the usefulness of the polarizer, the visibility-corrected polarization, the visibility-corrected transmittance, the chromaticity a* value, the chromaticity b* value, the orthogonal a*, and the orthogonal b* were measured as follows.

The transmittance (T ¹ ) in the transmission axis direction and the transmittance (T ² ) in the absorption axis direction in the wavelength range of 380 nm to 780 nm were measured by the double beam method using a spectrophotometer (UV-3150 manufactured by Shimadzu Corporation) equipped with a folder having a polarizer. The folder had a mesh installed on the reference side that cuts the amount of light by 50%. Using the following equations (Equation 1) and (Equation 2), the single-body transmittance and polarization degree at each wavelength were calculated, and further, visibility correction was performed using a 2-degree field of view (C illuminant) of JIS Z 8701, to calculate the visibility-corrected single-body transmittance (Ty) and the visibility-corrected polarization degree (Py). Furthermore, from the single-body transmittance measured in the same manner, the chromaticities a* and b* in the L*a*b* (CIE) colorimetric system were calculated using the chromaticity function of the C illuminant. In addition, from the similarly measured orthogonal transmittance, the chromaticity function of the C illuminant was used to calculate the orthogonal a* and orthogonal b* in the L*a*b* (CIE) colorimetric system. The closer the values of chromaticity a*, chromaticity b*, orthogonal a*, and orthogonal b* are to 0, the more neutral the color is. These results are shown in Table 4.

Single body transmittance (%) = (T1+T2)/2 (Formula 1)

Polarization (%) = (T1-T2)/(T1+T2) × 100 (Formula 2)

Example 2

1. Production of polarizing film

A polarizing film was produced in the same manner as in Example 1, except that the wire width and coating speed of the bar coater were changed (#7 15 mm/s). The film thickness of the polarizing film at this time was measured using a laser microscope (OLS3000 manufactured by Olympus Co., Ltd.) and was 1.8 ㎛.

2. Measurement of polarization, transmittance, and color

The results of measuring the sensitivity-corrected single-body transmittance (Ty) and the sensitivity-corrected polarization (Py) and the chromaticity a*, chromaticity b*, orthogonal a*, and orthogonal b* of the manufactured polarizing film using the same method as in Example 1 are shown in Table 4.

Example 3 [Preparation of composition (B) for forming a polarizing film]

A composition (B) for forming a polarizing film was obtained by mixing the following components and stirring at 80°C for 1 hour.

Polymerizable liquid crystal compound; Compound (4-22) 75 parts

Compound (4-25) 25 parts

Dichromatic pigment; Compound (1-1) 3.0 parts

Compound (2-15) 2.5 parts

Compound (2-20) Part 1.2

Compound (2-33) 2.5 parts

Polymerization initiator; 2-dimethylamino-2-benzyl-1-(4-morpholinophenyl)butan-1-one (Irgacure 369; manufactured by Ciba Specialty Chemicals Co., Ltd.) 6 parts

Leveling agent; 1.2 parts polyacrylate compound (BYK-361N; manufactured by BYK-Chemie)

Solvent; 250 parts toluene

1. Production of polarizing film

A polarizing film was produced in the same manner as in Example 1, except that the polarizing film-forming composition (A) was changed to the polarizing film-forming composition (B) and the wire width of the bar of the bar coater and the coating speed were also changed (#5 25 mm/s). The film thickness of the polarizing film at this time was measured using a laser microscope (OLS3000 manufactured by Olympus Co., Ltd.), and was 1.7 ㎛.

2. Measurement of polarization, transmittance, and color

The results of measuring the sensitivity-corrected single-body transmittance (Ty) and the sensitivity-corrected polarization (Py) and the chromaticity a*, chromaticity b*, orthogonal a*, and orthogonal b* of the manufactured polarizing film using the same method as in Example 1 are shown in Table 4.

Example 4

1. Production of polarizing film

A polarizing film was produced in the same manner as in Example 3, except that the wire width and coating speed of the bar coater were changed (#7 20 mm/s). The film thickness of the polarizing film at this time was measured using a laser microscope (OLS3000 manufactured by Olympus Co., Ltd.) and was found to be 2.0 ㎛.

2. Measurement of polarization, transmittance, and color

The results of measuring the sensitivity-corrected single-body transmittance (Ty) and the sensitivity-corrected polarization (Py) and the chromaticity a*, chromaticity b*, orthogonal a*, and orthogonal b* of the manufactured polarizing film using the same method as in Example 1 are shown in Table 4.

Example 5

1. Production of black polarizing film

A polarizing film was produced in the same manner as in Example 3, except that the wire width and coating speed of the bar coater were changed (#5 50 mm/s). The film thickness of the polarizing film at this time was measured using a laser microscope (OLS3000 manufactured by Olympus Co., Ltd.) and was 2.2 ㎛.

2. Measurement of polarization, transmittance, and color

The results of measuring the sensitivity-corrected single-body transmittance (Ty) and the sensitivity-corrected polarization (Py) and the chromaticity a*, chromaticity b*, orthogonal a*, and orthogonal b* of the manufactured polarizing film using the same method as in Example 1 are shown in Table 4.

Example 6 [Preparation of composition (C) for forming a polarizing film]

A composition (C) for forming a polarizing film was obtained by mixing the following components and stirring at 80°C for 1 hour.

Polymerizable liquid crystal compound; Compound (4-6) 75 parts

Compound (4-8) 25 parts

Dichromatic pigment; Compound (1-1) 3.6 parts

Compound (2-15) 3.0

Compound (2-18) 1.5 parts

Compound (2-27) Part 2.0

Compound (2-32) 1.5 parts

Polymerization initiator; 2-dimethylamino-2-benzyl-1-(4-morpholinophenyl)butan-1-one (Irgacure 369; manufactured by Ciba Specialty Chemicals Co., Ltd.) 6 parts

Leveling agent; 1.2 parts polyacrylate compound (BYK-361N; manufactured by BYK-Chemie)

Solvent; 250 parts toluene

1. Production of polarizing film

A polarizing film was produced in the same manner as in Example 1, except that the polarizing film-forming composition (A) was changed to the polarizing film-forming composition (C) and the wire width and coating speed of the bar coater were also changed (#7 20 mm/s). The film thickness of the polarizing film at this time was measured using a laser microscope (OLS3000 manufactured by Olympus Co., Ltd.), and was 2.0 ㎛.

2. Measurement of polarization, transmittance, and color

The results of measuring the sensitivity-corrected single-body transmittance (Ty) and the sensitivity-corrected polarization (Py) and the chromaticity a*, chromaticity b*, orthogonal a*, and orthogonal b* of the manufactured polarizing film using the same method as in Example 1 are shown in Table 4.

Example 7

1. Production of black polarizing film

A polarizing film was produced in the same manner as in Example 6, except that the wire width and coating speed of the bar coater were changed (#5 50 mm/s). The film thickness of the polarizing film at this time was measured using a laser microscope (OLS3000 manufactured by Olympus Co., Ltd.) and was 2.2 ㎛.

2. Measurement of polarization, transmittance, and color

The results of measuring the sensitivity-corrected single-body transmittance (Ty) and the sensitivity-corrected polarization (Py) and the chromaticity a*, chromaticity b*, orthogonal a*, and orthogonal b* of the manufactured polarizing film using the same method as in Example 1 are shown in Table 4.

Comparative Example 1

1. Fabrication of iodine-PVA polarizing plate

A polyvinyl alcohol film having an average degree of polymerization of about 2,400, a degree of saponification of 99.9 mol% or more, and a thickness of 75 ㎛ was uniaxially stretched about 5 times in a dry manner and, while maintaining the tension, immersed in pure water at 60°C for 1 minute, then immersed in an aqueous solution having a mass ratio of iodine/potassium iodide/water of 0.1/5/100 at 28°C for 60 seconds. Thereafter, it was immersed in an aqueous solution having a mass ratio of potassium iodide/boric acid/water of 810.5/7.5/100 at 72°C for 300 seconds. Subsequently, it was washed in pure water at 10°C for 5 seconds and dried at 80°C for 3 minutes, to obtain a polarizer in which iodine was adsorbed and aligned on a polyvinyl alcohol resin film.

2. Measurement of polarization, transmittance, and color

The results of measuring the sensitivity-corrected single-body transmittance (Ty) and the sensitivity-corrected polarization (Py) and the chromaticity a*, chromaticity b*, orthogonal a*, and orthogonal b* of the manufactured polarizer using the same method as in Example 1 are shown in Table 4.

As can be seen from Table 4, the polarizing films of Examples 1 to 7 were all thinner than the conventional iodine-PVA polarizer. In addition, the polarizing films of Examples 1 to 7 all exhibited neutral color properties.

Example 8

1. Production of a photo-alignment film on a phase difference film

Instead of a triacetyl cellulose film (KC8UX2M, manufactured by Konica Minolta Co., Ltd.) as a transparent substrate, a retardation film (uniaxially oriented film WRF-S (modified polycarbonate-based resin), retardation value 137.5 nm, thickness 50 µm, manufactured by Teijin Kasei Co., Ltd.) was used, and a solution of the photo-alignment polymer represented by the above formula (3) dissolved 5% in cyclopentanone was applied by the bar coat method, and dried at 120°C to obtain a dry film. This dry film was irradiated with polarized UV to obtain a photo-alignment film. The polarized UV treatment was performed using a UV irradiation device (SPOT CURE SP-7; manufactured by Ushio Denki Co., Ltd.) under the condition that the intensity measured at a wavelength of 365 nm was 100 mJ. In addition, at this time, the irradiation direction of the polarized UV was 45° with respect to the ground axis of the retardation film.

2. Manufacturing of a circular polarizing plate

A composition (C) for forming a polarizing film was applied onto the photoalignment film of the phase difference film having the manufactured photoalignment film by the bar coat method (#7 20 mm/s), dried by heating in a drying oven at 120°C for 1 minute, and then cooled to room temperature. Next, by irradiating the layer formed with the composition for forming a polarizing film with ultraviolet rays at an exposure dose of 2000 mJ/cm2 (based on 365 nm) using a UV irradiation device (SPOT CURE SP-7; manufactured by Ushio Denki Co., Ltd.), the polymerizable liquid crystal compound contained in the dry film was polymerized while maintaining the liquid crystal state of the polymerizable liquid crystal composition, thereby forming a polarizing film with the dry film, thereby manufacturing a circular polarizing plate. The film thickness of the polarizing film at this time was measured by a laser microscope (OLS3000 manufactured by Olympus Co., Ltd.), and was 2.0 μm.

3. Confirmation of anti-reflection performance

The phase difference film side of the obtained circular polarizing plate and the aluminum metal plate were bonded using an adhesive, and the metallic luster observed in the single aluminum metal plate disappeared, and a uniform black display was obtained. Thus, it can be seen that the circular polarizing plate manufactured using this polarizing film has excellent antireflection properties.

The present polarizing film is very useful in manufacturing liquid crystal displays, (organic) EL displays and projection type liquid crystal displays.

1: Transparent substrate 2: Photo-alignment film
3: Main polarizing film 4: Phase difference layer
100: Main polarizer 210: 1st roll
210A: Core 220: Second Roll
220A: Core 230: Third Roll
230A: Core 240: 4th Roll
240A: Core 211A, 211B: Applicator
212A, 212B: Drying furnace 213A: Polarizing UV irradiation device
213B: Light irradiation device 300: Auxiliary roll
10: Liquid crystal display device 11: Surface protection layer
12a, 12b: Polarizer 13a, 13b: Phase difference layer
14a, 14b: substrate 15: color filter
16: Transparent electrode 17: Liquid crystal layer
18: Interlayer insulation film 19: Backlight unit
20: Black Matrix 21: Thin Film Transistor
22: Pixel electrode 23: Spacer
30: EL display device 31: Circular polarizing plate
32: Phase difference film 33: Substrate
34: Interlayer insulating film 35: Pixel electrode
36: Organic functional layer 37: Cathode electrode
38: Desiccant 39: Sealing lid
40: Thin film transistor 41: Rib
42: Thin film sealing film 44: EL display device
111: Light source 112: First lens array
112a: Lens 113: Second lens array
114: Polarization conversion element 115: Superposition lens
121, 123, 132: Dichroic mirror 122: Reflective mirror
140R, 140G, 140B: Liquid crystal panel 142, 143: Polarizer
150: Cross dichroic prism 170: Projection lens
180: Screen

Claims (15)

A polarizing film comprising a polymer formed of a polymerizable liquid crystal compound, and at least one dichroic dye (1) having an absorption maximum in a wavelength range of 380 to 550 nm and at least two dichroic dyes (2) having absorption maximums in a wavelength range of 550 to 700 nm when the dye is dispersed in the polymer and light absorption is measured,
In X-ray diffraction measurements, Bragg peaks are obtained,
A polarizing film having a structure represented by the following formula, wherein at least two types of dichroic dyes (2) having absorption maxima in the range of wavelengths 550 to 700 nm are present:

[In the formula, * indicates a combining number] In the first paragraph, a polarizing film having an absorption maximum in the range of wavelengths 400 to 550 nm when the dichroic dye (1) is dispersed in a polymer formed of a polymerizable liquid crystal compound and light absorption is measured. A polarizing film in claim 1, wherein the polymerizable liquid crystal compound is a compound exhibiting a smectic liquid crystal phase. delete A polarizing film according to any one of claims 1 to 3, wherein the color coordinates a* value and b* value in the L*a*b* colorimetric system satisfy the relationships of the following formulas (1F) and (2F).
-3≤color a*≤3 (1F)
-3≤color b*≤3 (2F) A polarizing film according to any one of claims 1 to 3, wherein the dichroic dye (1) and the dichroic dye (2) are azo compounds. A polarizer formed by forming a polarizing film according to any one of claims 1 to 3 on a transparent substrate. A liquid crystal display device having a polarizing film according to any one of claims 1 to 3. A circular polarizing plate having a polarizing film and a λ/4 layer as described in any one of claims 1 to 3, and satisfying the requirements of (A1) and (A2) below:
(A1) The angle formed by the absorption axis of the polarizing film and the ground axis of the λ/4 layer shall be 45°;
(A2) The value of frontal retardation of the λ/4 layer measured under light having a wavelength of 550 nm shall be in the range of 100 to 150 nm. An organic EL display device having a circular polarizing plate and an organic EL element as described in Article 9. delete delete delete delete delete