JP2018159879A - Circularly polarizing film and method for producing the same - Google Patents

Abstract

A thin circularly polarizing film using a liquid crystal compound is provided.
A liquid crystal cured layer formed of a cured material containing a liquid crystal compound and having optical anisotropy, and a grid polarization having a plurality of grid lines formed on the surface of the liquid crystal cured layer and provided in parallel to each other. And a circularly polarizing film.
[Selection] Figure 1

Description

  The present invention relates to a circularly polarizing film and a method for producing the same.

  Grid polarizers are known as optical members that exhibit reflective polarization characteristics. This is an optical member having a grid structure in which a large number of grid lines made of metal are arranged in parallel at a predetermined period. When a grid structure in which the period of the grid is shorter than the wavelength of incident light is formed, the polarization component parallel to the grid structure is reflected and the perpendicular polarization component is transmitted to function as a polarizer that creates a single polarization.

  Patent Document 1 discloses a method of forming such a grid polarizer as a grid polarizing layer on the surface of a resin film. Patent Document 2 discloses that a grid polarizing layer is formed on a substrate such as a glass plate and a liquid crystal fixing layer is formed on the grid polarizing layer.

JP-A-2005-195824 JP 2010-243769 A

  When it is going to manufacture a circularly-polarizing film using a grid polarizing layer, combining a grid polarizing layer with the member which has optical anisotropy is considered. Then, this inventor tried using the stretched film which has optical anisotropy as a resin film in the structure described in patent document 1. FIG. However, since the orientation of stretched films is generally easily relaxed at high temperatures, the optical anisotropy tends to be impaired in a high temperature environment, and the heat resistance of the circularly polarizing film is poor.

  In addition, the inventor tried to use a liquid crystal fixing layer having optical anisotropy in the configuration described in Patent Document 1. In a layer obtained by polymerizing a liquid crystal compound, it is difficult for alignment relaxation to occur even in a high temperature environment, so that high heat resistance is achieved. However, in order to develop optical anisotropy in the liquid crystal fixed layer, it is required to align liquid crystal molecules in the liquid crystal fixed layer. For this reason, an alignment layer is formed between the grid polarizing layer and the liquid crystal fixing layer, which is thicker by the alignment layer, making it difficult to reduce the thickness of the circularly polarizing film.

  The present invention has been made in view of the above problems, and an object thereof is to provide a thin circularly polarizing film using a liquid crystal compound and a method for producing the same.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have formed a cured product of a material containing a liquid crystal compound, formed on the surface of the liquid crystal cured layer having optical anisotropy and the liquid crystal cured layer, and The inventors have found that a circularly polarizing film including a grid polarizing layer having a plurality of grid lines provided in parallel can be reduced in thickness, thereby completing the present invention.
That is, the present invention includes the following.

[1] A liquid crystal cured layer formed of a cured product of a material containing a liquid crystal compound and having optical anisotropy;
A circularly polarizing film comprising a grid polarizing layer formed on the surface of the liquid crystal cured layer and having a plurality of grid lines provided in parallel to each other.
[2] The circularly polarizing film according to [1], wherein the liquid crystal cured layer has reverse wavelength dispersion characteristics, and the liquid crystal cured layer has an in-plane retardation of λ / 4.
[3] The circularly polarizing film according to [1] or [2], wherein the liquid crystal compound includes a main chain mesogen and a side chain mesogen bonded to the main chain mesogen in the molecule.
[4] The circularly polarizing film according to [3], wherein the side chain mesogen has a benzothiazole ring.
[5] The circularly polarizing film has a long shape,
The direction of the slow axis of the liquid crystal cured layer is parallel or perpendicular to the longitudinal direction of the circularly polarizing film, and the extending direction of the grid lines is 40 ° with respect to the longitudinal direction of the circularly polarizing film. The circularly polarizing film according to any one of [1] to [4], which forms an angle of ˜50 °.
[6] The circularly polarizing film has a long shape,
The direction of the slow axis of the liquid crystal cured layer forms an angle of 40 ° to 50 ° with respect to the longitudinal direction of the circularly polarizing film, and the extending direction of the grid lines is in the longitudinal direction of the circularly polarizing film. The circularly polarizing film according to any one of [1] to [4], which is parallel to the film.
[7] The circularly polarizing film according to any one of [1] to [6], wherein the circularly polarizing film further includes a protective layer on the grid polarizing layer.
[8] The method for producing a circularly polarizing film according to any one of [1] to [7],
Forming a layer of a material containing a liquid crystal compound;
A step of polymerizing the liquid crystal compound to obtain a semi-cured layer;
Forming a recess in the surface of the semi-cured layer;
Forming a grid line in the recess, and a method for producing a circularly polarizing film.
[9] The method for producing a circularly polarizing film according to [8], wherein the recess is formed by a nanoimprint method.
[10] The circularly polarized light according to [9], wherein the nanoimprint method includes transferring the shape of the peripheral surface to the surface of the semi-cured layer using an embossing roll having a peripheral surface corresponding to the concave portion. A method for producing a film.
[11] The method for producing a circularly polarizing film according to any one of [8] to [10], further including a step of further curing the semi-cured layer in which the concave portion is formed.

  ADVANTAGE OF THE INVENTION According to this invention, the thin circularly-polarizing film using a liquid crystal compound and its manufacturing method can be provided.

FIG. 1 is a perspective view schematically showing a state in which a circularly polarizing film as an example of the present invention is cut along a plane perpendicular to the extending direction of grid lines. FIG. 2 is a perspective view schematically showing a state in which a circularly polarizing film as an example of the present invention is cut along a plane perpendicular to the extending direction of the grid lines.

  Hereinafter, the present invention will be described in detail with reference to examples and embodiments, but the present invention is not limited to the examples and embodiments shown below, and the claims of the present invention and the equivalent scope thereof Any change can be made without departing from the scope of the invention.

  In the following description, unless otherwise specified, the in-plane retardation Re of a certain layer indicates a value represented by Re = (nx−ny) × d. Here, nx represents a refractive index in a direction perpendicular to the thickness direction of the layer (in-plane direction) and giving the maximum refractive index, and ny is the in-plane direction of the layer, and nx Represents the refractive index in the direction orthogonal to the direction of, and d represents the thickness of the layer. The measurement wavelength of in-plane retardation is 590 nm unless otherwise specified.

In the following description, unless otherwise specified, “reverse wavelength dispersion characteristic” means that in-plane retardations Re ₄₅₀ and Re _{650 at} wavelengths of 450 nm and 650 nm satisfy the relationship of Re ₄₅₀ <Re ₆₅₀ .

  In the following description, the slow axis of a certain layer represents the slow axis in the in-plane direction of the layer unless otherwise specified.

  In the following description, unless otherwise specified, the directions of the elements are “parallel”, “vertical”, and “orthogonal” include errors within a range that does not impair the effects of the present invention, for example, within ± 5 °. You may go out.

  In the following description, unless otherwise specified, the term “circularly polarized light” includes not only circularly polarized light in a narrow sense but also elliptically polarized light.

  In the following description, a material having a positive intrinsic birefringence means a material in which the refractive index in the stretching direction is larger than the refractive index in the direction perpendicular thereto unless otherwise specified. In addition, a material having a negative intrinsic birefringence means a material in which the refractive index in the stretching direction is smaller than the refractive index in the direction perpendicular thereto unless otherwise specified. The intrinsic birefringence value of the material can be calculated from the dielectric constant distribution.

[1. Outline of circularly polarizing film]
1 and 2 are perspective views schematically showing a state in which the circularly polarizing film 100 as an example of the present invention is cut along a plane perpendicular to the extending direction of the grid lines 121. FIG.
As shown in FIGS. 1 and 2, the circularly polarizing film 100 includes a liquid crystal cured layer 110 having optical anisotropy and a grid polarizing layer having a plurality of grid lines 121 formed on the surface 110U of the liquid crystal cured layer 110. 120. The plurality of grid lines 121 are provided in parallel to each other with an interval therebetween. Moreover, the grid line 121 is normally formed in direct contact with the surface 110U of the liquid crystal cured layer 110, and no other layer is interposed between the grid line 121 and the liquid crystal cured layer 110.

  As shown in FIG. 1, the surface 110U of the liquid crystal cured layer 110 may be a flat surface without a concave portion and a convex portion. Further, the surface 110U of the liquid crystal cured layer 110 may be provided with a recess 111 corresponding to the grid line 121 as shown in FIG. When the concave portion 111 is formed on the surface 110 </ b> U of the liquid crystal cured layer 110, the grid line 121 is usually formed in the concave portion 111.

  In the circularly polarizing film 100 as described above, out of the light incident on the grid polarizing layer 120, linearly polarized light perpendicular to the extending direction of the grid lines 121 passes through the grid polarizing layer 120, and the linearly polarized light is cured by liquid crystal. By passing through the layer 110, it becomes circularly polarized and exits the circularly polarizing film 100.

  Since this circularly polarizing film 100 includes a liquid crystal cured layer in which optical anisotropy is not easily damaged under a high temperature environment, the circularly polarizing film 100 has excellent heat resistance, and can function as a circular polarizer even in a high temperature environment. Moreover, since this circularly polarizing film 100 does not have another layer between the liquid crystal cured layer 110 and the grid polarizing layer 120, the thickness can be reduced. Further, since there is no other layer between the liquid crystal cured layer 110 and the grid polarizing layer 120, usually, a high polarization transmittance and polarization efficiency can be obtained.

  Since the circularly polarizing film 100 can be continuously manufactured, it is preferable to have a long shape. Here, the “long shape” of the film means a shape having a length of usually 5 times or more, preferably 10 times or more, and specifically a roll. A shape having such a length that it is wound into a shape and stored or transported. There is no restriction | limiting in particular in the upper limit of the length of the film which has a long shape, For example, it can be 100,000 times or less with respect to a width | variety.

  The circularly polarizing film 100 may further include an arbitrary layer in combination with the liquid crystal cured layer 110 and the grid polarizing layer 120. For example, the circularly polarizing film 100 preferably further includes a protective layer (not shown) on the grid polarizing layer 120.

[2. Liquid crystal cured layer]
The liquid crystal cured layer is a layer formed of a cured product of a material containing a liquid crystal compound. In the following description, the material containing a liquid crystal compound may be referred to as a “liquid crystal composition”. However, the term “liquid crystal composition” includes not only a material containing two or more kinds of components but also a material containing only one kind of liquid crystal compound.

  A liquid crystal compound is a compound that can exhibit a liquid crystal phase when blended and aligned in a liquid crystal composition. As such a liquid crystal compound, a polymerizable liquid crystal compound is usually used. Here, the polymerizable liquid crystal compound is a liquid crystal compound that is polymerized in a liquid crystal composition in a state of exhibiting a liquid crystal phase, and can be a polymer while maintaining molecular orientation in the liquid crystal phase.

  Examples of the polymerizable liquid crystal compound include compounds such as a liquid crystal compound having a polymerizable group, a compound capable of forming a side chain type liquid crystal polymer, and a discotic liquid crystal compound. Among them, light such as visible light, ultraviolet light, and infrared light is used. A photopolymerizable compound that can be polymerized by irradiating is preferred. Examples of the liquid crystal compound having a polymerizable group include JP-A-11-513360, JP-A-2002-030042, JP-A-2004-204190, JP-A-2005-263789, and JP-A-2007-119415. Examples thereof include rod-like liquid crystal compounds having a polymerizable group described in JP-A No. 2007-186430. Moreover, as a side chain type liquid crystal polymer compound, the side chain type liquid crystal polymer compound etc. which are described in Unexamined-Japanese-Patent No. 2003-177242 etc. are mentioned, for example. Further, examples of preferable liquid crystal compounds include “LC242” manufactured by BASF and the like. Specific examples of the discotic liquid crystal compound are disclosed in JP-A-8-50206, literature (C. Destrade et al., Mol. Crysr. Liq. Cryst., Vol. 71, page 111 (1981); , Quarterly Review, No. 22, Liquid Crystal Chemistry, Chapter 5, Chapter 10, Section 2 (1994); J. Lehn et al., J. Chem. Soc., Chem. Commun., Page 1794 (1985) ); J. Zhang et al., J. Am. Chem. Soc., Vol. 116, page 2655 (1994)). A liquid crystal compound may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  Especially, as a liquid crystal compound, a reverse wavelength dispersion liquid crystal compound is preferable. Here, the reverse wavelength dispersive liquid crystal compound refers to a liquid crystal compound exhibiting reverse wavelength dispersion characteristics when homogeneously oriented. Here, the liquid crystal compound is homogeneously aligned means that a layer containing the liquid crystal compound is formed, and the major axis direction of the mesogen of the molecule of the liquid crystal compound in the layer is set in one direction parallel to the plane of the layer. It means that it is oriented. When the liquid crystal compound contains a plurality of types of mesogens having different alignment directions, the direction in which the longest type of mesogens is aligned is the alignment direction. Whether or not the liquid crystal compound is homogeneously aligned and the alignment direction are determined by measuring the slow axis direction using a phase difference meter represented by AxoScan (manufactured by Axometrics) and the incident angle in the slow axis direction. It can be confirmed by measuring the retardation distribution for each. A liquid crystal cured layer having reverse wavelength dispersion characteristics can be easily obtained by using a reverse wavelength dispersive liquid crystal compound as a part or all of the liquid crystal compounds contained in the liquid crystal composition.

  For example, a compound containing a main chain mesogen and a side chain mesogen bonded to the main chain mesogen in the molecule of the reverse wavelength dispersive liquid crystal compound is preferably used as the liquid crystal compound. More preferably, it is used. In the reverse wavelength dispersive liquid crystal compound containing a main chain mesogen and a side chain mesogen, the side chain mesogen can be aligned in a direction different from the main chain mesogen in a state where the reverse wavelength dispersive liquid crystal compound is aligned. In such a case, birefringence appears as the difference between the refractive index corresponding to the main chain mesogen and the refractive index corresponding to the side chain mesogen, and as a result, when the reverse wavelength dispersive liquid crystal compound is homogeneously oriented, Inverse chromatic dispersion characteristics can be shown.

  Examples of the reverse wavelength dispersible liquid crystal compound having polymerizability include compounds represented by the following formula (I). In the following description, the compound represented by the formula (I) may be referred to as “compound (I)” as appropriate.

Compound (I) is usually a group represented by the following formula: —Y ⁵ —A ⁴ —Y ³ — (A ² —Y ¹ ) _m —A ¹ — (Y ² —A ³ ) _m —Y ⁴ —. It includes two mesogenic skeletons of a main chain mesogen 1a composed of A ⁵ -Y ^6- and a side chain mesogen 1b composed of a group> A ¹ -C (Q ¹ ) = NN (A ^x ) A ^y . The main chain mesogen 1a and the side chain mesogen 1b cross each other. Although the main chain mesogen 1a and the side chain mesogen 1b can be combined into one mesogen, in the present invention, they are divided into two mesogens.

  The refractive index in the major axis direction of the main chain mesogen 1a is n1, and the refractive index in the major axis direction of the side chain mesogen 1b is n2. At this time, the absolute value and the wavelength dispersion of the refractive index n1 usually depend on the molecular structure of the main chain mesogen 1a. Further, the absolute value and wavelength dispersion of the refractive index n2 usually depend on the molecular structure of the side chain mesogen 1b. Here, in the liquid crystal phase, the reverse wavelength dispersive liquid crystal compound normally performs a rotational motion with the major axis direction of the main chain mesogen 1a as the rotation axis, and the refractive indexes n1 and n2 here are the refraction as a rotating body. Represents the rate.

  Due to the molecular structure of the main chain mesogen 1a and the side chain mesogen 1b, the absolute value of the refractive index n1 is larger than the absolute value of the refractive index n2. Furthermore, the refractive indexes n1 and n2 usually show forward wavelength dispersion. Here, the forward wavelength dispersive refractive index represents a refractive index in which the absolute value of the refractive index decreases as the measurement wavelength increases. Since the refractive index n1 of the main chain mesogen 1a has a small forward wavelength dispersion, the refractive index measured at a long wavelength is not significantly smaller than the refractive index measured at a short wavelength. On the other hand, since the refractive index n2 of the side chain mesogen 1b has a large forward wavelength dispersion, the refractive index measured at the long wavelength is significantly smaller than the refractive index measured at the short wavelength. Therefore, when the measurement wavelength is short, the difference Δn between the refractive index n1 and the refractive index n2 is small, and when the measurement wavelength is long, the difference Δn between the refractive index n1 and the refractive index n2 is large. Thus, derived from main chain mesogen 1a and side chain mesogen 1b, compound (I) can exhibit reverse wavelength dispersion characteristics when homogeneously oriented.

In the formula (I), Y ^{1 to} Y ⁸ are each independently a chemical single bond, —O—, —S—, —O—C (═O) —, —C (═O) —. O—, —O—C (═O) —O—, —NR ¹ —C (═O) —, —C (═O) —NR ¹ —, —O—C (═O) —NR ¹ —, —NR ¹ —C (═O) —O—, —NR ¹ —C (═O) —NR ¹ —, —O—NR ¹ —, or —NR ¹ —O— is represented. Here, R ¹ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.

In the formula (I), G ¹ and G ² each independently represent a divalent aliphatic group having 1 to 20 carbon atoms, which may have a substituent. The aliphatic group includes one or more —O—, —S—, —O—C (═O) —, —C (═O) —O—, —O—C per one aliphatic group. Even if (═O) —O—, —NR ² —C (═O) —, —C (═O) —NR ² —, —NR ² —, or —C (═O) — are present. Good. However, the case where two or more of -O- or -S- are adjacent to each other is excluded. Here, R < ² > represents a hydrogen atom or a C1-C6 alkyl group.

In the formula (I), Z ¹ and Z ² each independently represent an alkenyl group having 2 to 10 carbon atoms which may be substituted with a halogen atom.

In the formula (I), A ^x represents an organic group having 2 to 30 carbon atoms having at least one aromatic ring selected from the group consisting of an aromatic hydrocarbon ring and an aromatic heterocyclic ring. “Aromatic ring” means a cyclic structure having a broad sense of aromaticity according to the Huckle rule, that is, a cyclic conjugated structure having (4n + 2) π electrons, and sulfur, oxygen, typified by thiophene, furan, benzothiazole, etc. It means a cyclic structure in which a lone electron pair of a hetero atom such as nitrogen is involved in the π-electron system and exhibits aromaticity.

  Examples of the aromatic hydrocarbon ring include a benzene ring, a naphthalene ring, and an anthracene ring. Examples of the aromatic heterocyclic ring include monocyclic aromatic heterocyclic rings such as a pyrrole ring, a furan ring, a thiophene ring, a pyridine ring, a pyridazine ring, a pyrimidine ring, a pyrazine ring, a pyrazole ring, an imidazole ring, an oxazole ring, and a thiazole ring; Benzothiazole ring, benzoxazole ring, quinoline ring, phthalazine ring, benzimidazole ring, benzopyrazole ring, benzofuran ring, benzothiophene ring, thiazolopyridine ring, oxazolopyridine ring, thiazolopyrazine ring, oxazolopyrazine ring, thia And a condensed aromatic heterocycle such as a zolopyridazine ring, an oxazolopyridazine ring, a thiazolopyrimidine ring, and an oxazolopyrimidine ring.

In the formula (I), A ^y is a hydrogen atom, an optionally substituted alkyl group having 1 to 20 carbon atoms, an optionally substituted alkenyl group having 2 to 20 carbon atoms, a cycloalkyl group having from 3 to 12 carbon atoms which may have a substituent, which may have a substituent group an alkynyl group having a carbon number of ^{2~20, -C (= O) -R} 3, -SO 2 An organic group having 2 to 30 carbon atoms having at least one aromatic ring selected from the group consisting of —R ⁴ , —C (═S) NH—R ⁹ , or an aromatic hydrocarbon ring and an aromatic heterocyclic ring; Represent. Here, R ³ has an optionally substituted alkyl group having 1 to 20 carbon atoms, an optionally substituted alkenyl group having 2 to 20 carbon atoms, and a substituent. Or a C3-C12 cycloalkyl group or a C5-C12 aromatic hydrocarbon ring group. R ⁴ represents an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, a phenyl group, or a 4-methylphenyl group. R ⁹ is an optionally substituted alkyl group having 1 to 20 carbon atoms, an optionally substituted alkenyl group having 2 to 20 carbon atoms, and an optionally substituted carbon. The C3-C12 cycloalkyl group or the C5-C20 aromatic group which may have a substituent is represented. The aromatic ring which said ^Ax and ^Ay have may have a substituent. A ^x and A ^y may be combined to form a ring.

In the formula (I), A ¹ represents a trivalent aromatic group which may have a substituent.
In the formula (I), A ² and A ³ each independently represent a C 3-30 divalent alicyclic hydrocarbon group which may have a substituent.
In the formula (I), A ⁴ and A ⁵ each independently represent a C 6-30 divalent aromatic group which may have a substituent.
In the formula (I), Q ¹ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms which may have a substituent.
In the formula (I), each m independently represents 0 or 1.

  Examples of the compound (I) include compounds described in International Publication No. 2014/0669515, International Publication No. 2015/064581, and the like.

  Among the liquid crystal compounds described above, those that contain a benzothiazole ring in the molecule of the liquid crystal compound are preferable from the viewpoint of remarkably exhibiting the desired effect of the present invention, and in particular, the side chain mesogen has a benzothiazole ring. Those are preferred. Here, the benzothiazole ring indicates a ring structure having a structure represented by the following formula (II).

  Moreover, a liquid crystal compound may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  The amount of the liquid crystal compound in the liquid crystal composition can be arbitrarily set within a range in which a desired liquid crystal cured layer can be obtained, preferably 1% by weight or more, more preferably 5% by weight or more, particularly preferably 10% by weight or more, Further, it is preferably 100% by weight or less, more preferably 80% by weight or less, and particularly preferably 60% by weight or less.

  The liquid crystal composition may contain an arbitrary component in combination with the liquid crystal compound. Optional components include, for example, polymerization initiators, surfactants, solvents, metals, metal complexes, dyes, pigments, fluorescent materials, phosphorescent materials, leveling agents, thixotropic agents, gelling agents, polysaccharides, ultraviolet absorbers, Examples include infrared absorbers, antioxidants, ion exchange resins, and metal oxides such as titanium oxide. Reference may be made to WO 2015/064581 for optional ingredients.

  The liquid crystal cured layer is a layer formed of a cured product of a liquid crystal composition containing the liquid crystal compound, and usually includes cured liquid crystal molecules obtained from the liquid crystal compound. Here, the “cured liquid crystal molecule” means a molecule of the compound when the compound capable of exhibiting the liquid crystal phase is turned into a solid while exhibiting the liquid crystal phase. The cured liquid crystal molecule contained in the liquid crystal cured layer is usually a polymer obtained by polymerizing a liquid crystal compound. Therefore, the liquid crystal cured layer usually includes a polymer obtained by polymerizing a liquid crystal compound, and is a resin layer that can include any component as necessary. Such a liquid crystal cured layer can have optical anisotropy corresponding to the orientation state of the cured liquid crystal molecules.

  The liquid crystal cured layer preferably has an in-plane retardation of λ / 4 from the viewpoint of realizing the function as a circularly polarizing film. Specifically, the in-plane retardation of the liquid crystal cured layer at a measurement wavelength of 590 nm is preferably 108 nm to 168 nm, more preferably 128 nm to 148 nm, and particularly preferably 133 nm to 143 nm.

The liquid crystal cured layer preferably has reverse wavelength dispersion characteristics. Accordingly, in the liquid crystal cured layer, the in-plane retardations Re ₄₅₀ , Re ₅₅₀ and Re _{650 at} wavelengths of 450 nm, 550 nm and 650 nm preferably satisfy the relationship of Re ₄₅₀ <Re ₆₅₀ , and Re ₄₅₀ <Re ₅₅₀ <Re _650. It is more preferable to satisfy the relationship. Further, Re ₄₅₀ / Re ₅₅₀ ≦ 0.95 is preferable, and Re ₆₅₀ / Re ₅₅₀ ≧ 1.05 is preferable. Accordingly, the liquid crystal cured layer can convert linearly polarized light into circularly polarized light in a wider wavelength range. Therefore, it is possible to realize a broadband circularly polarizing film. A liquid crystal cured layer having reverse wavelength dispersion characteristics as described above can be obtained, for example, by using a reverse wavelength dispersive liquid crystal compound as the liquid crystal compound.

  The direction of the slow axis of the liquid crystal cured layer may be parallel or perpendicular to the longitudinal direction of the circularly polarizing film, or may be in an oblique direction that is neither parallel nor perpendicular. However, in order to convert linearly polarized light transmitted through the grid polarizing layer into circularly polarized light by the liquid crystal cured layer, the direction of the slow axis of the liquid crystal cured layer is 40 with respect to the extending direction of the grid lines of the grid polarizing layer. It is preferable to make an angle of 50 ° to 50 °.

  In particular, when the direction of the slow axis of the liquid crystal cured layer is oblique to the longitudinal direction of the circularly polarizing film, the angle formed by the direction of the slow axis of the liquid crystal cured layer with respect to the longitudinal direction of the circularly polarizing film is 40 ° to 50 °, more preferably 42 ° to 48 °, and still more preferably 44 ° to 46 °. By setting the direction of the slow axis of the liquid crystal cured layer as described above, it becomes easy to adjust the angle between the slow axis of the liquid crystal cured layer and the transmission axis of the grid polarizing layer. Can be done.

  Concave portions may be formed on the surface of the liquid crystal cured layer corresponding to the grid lines. Since the grid line is formed in a linear shape, the concave portion is usually formed in a groove shape extending in the same direction as the extending direction of the grid line. The width and pitch of the grooves can usually be the same as the width and pitch of the grid lines. Further, the depth of the groove may be the same as or larger than the thickness of the grid line. Specifically, the depth of the groove can be 50 nm to 800 nm.

  The liquid crystal cured layer preferably has a high total light transmittance from the viewpoint of use as an optical member. The specific total light transmittance of the liquid crystal cured layer is preferably 85% to 100%, more preferably 87% to 100%, and particularly preferably 90% to 100%. The total light transmittance can be measured within a wavelength range of 400 nm to 700 nm using a commercially available spectrophotometer.

  The liquid crystal cured layer preferably has a small haze. The haze of the liquid crystal cured layer is preferably 1% or less, more preferably 0.8% or less, and particularly preferably 0.5% or less. The haze can be measured using a turbidimeter based on JIS K7361-1997.

  The thickness of the liquid crystal cured layer can be appropriately adjusted so that the properties such as retardation can be adjusted within a desired range, and is preferably 0.5 μm or more, more preferably 1.0 μm or more, preferably 10 μm or less, more preferably 7 μm. Hereinafter, it is particularly preferably 5 μm or less.

[3. Grid polarizing layer]
The grid polarizing layer is a layer provided as a set of a plurality of grid lines. The material of the grid line is preferably a material having an absolute value of the difference between the real part n and the imaginary part κ of the complex refractive index N (N = n−iκ) of 1.0 or more. Here, the complex refractive index N is a theoretical relational expression of electromagnetic waves, and is expressed by N = n−iκ using the refractive index n of the real part and the extinction coefficient κ of the imaginary part. It is known that light travels faster in a medium with a refractive index n than in a vacuum, and light intensity attenuates in a medium with a large extinction coefficient κ.

  Examples of the material that satisfies the requirements for the complex refractive index N include metals; inorganic semiconductors such as silicon and germanium; conductive polymers such as polyacetylene, polypyrrole, polythiophene, and poly-p-phenylene; and the conductive polymers described above. , Organic conductive materials doped with a dopant such as iodine, boron trifluoride, arsenic pentafluoride, perchloric acid, and the like. Moreover, the said material may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios. For example, an organic-inorganic composite conductive material obtained by drying a mixed liquid containing the conductive polymer or the organic conductive material and conductive metal particles such as gold and silver may be used.

  Among the above materials, metal is preferable from the viewpoint of productivity and durability of the grid polarizing layer. In order to efficiently separate and split light in the visible range, the real part n of the complex refractive index at a temperature of 25 ° C. and a wavelength of 550 nm is 4.0 or less, the imaginary part κ is 3.0 or more, and the absolute value of the difference | n-κ | is preferably 1.0 or more. Examples of the material that satisfies such requirements include silver, aluminum, chromium, indium, iridium, magnesium, palladium, platinum, rhodium, ruthenium, antimony, and tin. Among them, the real part n is particularly preferably 2.0 or less, the imaginary part κ is 4.5 or more, and the absolute value | n−κ | of the difference is 3.0 or more. Examples of the material satisfying such requirements include aluminum, indium, magnesium, rhodium, and tin. In addition to the above, a material in which the real part n of the complex refractive index at a temperature of 25 ° C. and a wavelength of 550 nm is 3.0 or more and the imaginary part κ is 2.0 or less is preferable, and the real part n is 4.0 or more. A material having an imaginary part κ in the range of 1.0 or less is more preferable. An example of a material that satisfies such requirements is silicon.

  JP, 2007-057971, A can refer to the details concerning the material of a grid line.

The extending direction of the grid lines is preferably set according to the slow axis direction of the liquid crystal cured layer.
For example, when the direction of the slow axis of the liquid crystal cured layer is parallel or perpendicular to the longitudinal direction of the circularly polarizing film, the extending direction of the grid lines is oblique to the longitudinal direction of the circularly polarizing film. It is preferable that it exists in. Specifically, the angle formed by the extending direction of the grid lines with respect to the longitudinal direction of the circularly polarizing film is preferably 40 ° to 50 °, more preferably 42 ° to 48 °, and still more preferably 44 ° to 46 °. is there.
For example, when the direction of the slow axis of the liquid crystal cured layer forms an angle of 40 ° to 50 ° with respect to the longitudinal direction of the circularly polarizing film, the extending direction of the grid lines is the longitudinal direction of the circularly polarizing film. It is preferable that it is parallel to.
By setting the extending direction of the grid lines as described above, the polarized light transmitted through the grid polarizing layer can be efficiently converted into circularly polarized light by the liquid crystal cured layer. In particular, when the extending direction of the grid lines is parallel to the longitudinal direction of the circularly polarizing film, continuous grid lines can be easily formed.

  The dimension of each grid line can be arbitrarily set as long as the grid polarizing layer can function as a polarizer. The pitch of the grid lines (symbol P in FIGS. 1 and 2) is preferably set to be equal to or less than ½ of the wavelength of light that causes the grid polarizing layer to function as a polarizer. Further, the narrower the grid line width (reference numeral W in FIGS. 1 and 2), the smaller the absorption of the polarization component in the transmission direction, which is preferable. In the grid polarizing layer used for visible light, the pitch P is preferably 10 nm to 1000 nm, more preferably 50 nm to 200 nm. The width W is preferably 25 nm to 600 nm, and the thickness T is preferably 10 nm to 800 nm.

  Moreover, when a liquid-crystal hardened layer has a recessed part, a grid line is normally provided in the said recessed part (refer FIG. 2). In this case, since the grid line is accommodated in the concave portion, it is possible to suppress the wear, damage and breakage of the grid line. Therefore, durability can be improved.

[4. Any layer]
The circularly polarizing film may further include an arbitrary layer in combination with the liquid crystal cured layer and the grid polarizing layer described above. For example, a protective layer that is formed on the grid polarizing layer and protects the grid polarizing layer may be included as the outermost layer.

  Examples of protective layers include cellulose esters such as cellulose acetate, cellulose acetate butyrate, and cellulose propionate; polycarbonate; polyolefin; polystyrene; polyester; urethane polymer; acrylic polymer; organic materials such as silicon nitride, aluminum nitride, and oxidation. It can be formed by inorganic materials such as silicon; organic-inorganic composite materials such as organoalkoxysilane and inorganic fine particle-dispersed acrylic.

  In addition, the circularly polarizing film may include, as an optional layer, for example, a hard coat layer such as a mat layer that improves the slipperiness of the film, an impact-resistant polymethacrylate resin layer, an antifouling layer, and the like.

[5. Major advantages of circularly polarizing films]
Since the circularly polarizing film described above includes the grid polarizing layer so as to be in direct contact with the surface of the thin liquid crystal cured layer, the thickness can be reduced. In particular, when the liquid crystal cured layer has a recess, and grid lines are provided in the recess, the grid lines usually fit in the recess and do not protrude from the surface of the liquid crystal cured layer. Therefore, since the grid line is provided in the concave portion, an increase in thickness due to the protrusion of the grid line can be suppressed, so that the circularly polarizing film can be effectively thinned as a whole. The specific thickness of the circularly polarizing film is preferably 15 μm or less, more preferably 10 μm or less, and particularly preferably 7 μm or less. Although the minimum of thickness is arbitrary, Usually, it is 0.5 micrometer or more.

  In addition, the circularly polarizing film described above does not require components other than the liquid crystal cured layer and the grid polarizing layer, and since the liquid crystal cured layer is thin, high total light transmittance can be achieved. The total light transmittance of the circularly polarizing film is preferably 30% to 50%, more preferably 40% to 50%, and particularly preferably 45% to 50%.

  Furthermore, the liquid crystal cured layer included in the above-described circularly polarizing film is generally less susceptible to orientation relaxation than a stretched film in a high temperature environment. For this reason, the function as a circular polarizer is hardly impaired even in a high temperature environment, and the heat resistance is excellent.

[6. Method for producing circularly polarizing film]
The circularly polarizing film can be manufactured by a manufacturing method including a step of preparing a liquid crystal cured layer and a step of forming a grid polarizing layer on the surface of the liquid crystal cured layer. The specific manufacturing method is arbitrary. For example, when the grid polarizing layer is formed on the surface of the liquid crystal cured layer as shown in FIG. 1, photolithography is performed as described in Patent Documents 1 and 2. You may employ | adopt the manufacturing method including the process of forming and using a grid polarizing layer.

  However, from the viewpoint of forming a grid polarizing layer at a low cost without using a reagent such as a photoresist, from the viewpoint of increasing the production efficiency by reducing the number of steps required to manufacture a circular polarizing film, and particularly thin the circular polarizing film. In view of this, as shown in FIG. 2, it is preferable to form a circularly polarizing film by forming a grid polarizing layer on a liquid crystal cured layer having concave portions on the surface.

Specifically, the circularly polarizing film is
Forming a layer of a liquid crystal composition as a material containing a liquid crystal compound;
A step of polymerizing a liquid crystal compound in a liquid crystal composition layer to obtain a semi-cured layer;
Forming a recess on the surface of the semi-cured layer;
Forming grid lines in the recesses;
It is preferable to manufacture by the manufacturing method containing this. Hereinafter, this manufacturing method will be described.

  The liquid crystal composition layer can be formed, for example, by coating the liquid crystal composition on a substrate. As the substrate, it is preferable to use a long substrate. When using a long base material, it is possible to apply | coat a liquid-crystal composition continuously on the base material conveyed continuously. Therefore, by using a long base material, the liquid crystal cured layer can be continuously produced, so that productivity can be improved.

  As the substrate, a substrate film is usually used. The material of the base film is not particularly limited, and various resins can be used. Examples of the resin include resins containing various polymers. Examples of the polymer include an alicyclic structure-containing polymer, polyethylene terephthalate, cellulose ester, polyvinyl alcohol, polyimide, UV transparent acrylic, polycarbonate, polysulfone, polyethersulfone, epoxy polymer, polystyrene, and combinations thereof. . Among these, an alicyclic structure-containing polymer or polyethylene terephthalate is preferable from the viewpoints of transparency, low hygroscopicity, dimensional stability, and lightness.

  Moreover, as a base material, what has an orientation control force can be used. The alignment regulating force of the substrate refers to the property of the substrate that can align the liquid crystal compound in the liquid crystal composition coated on the substrate. The orientation regulating force can be imparted by applying a treatment for imparting the orientation regulating force to a member such as a film as a material of the base material. Examples of such treatment include stretching treatment and rubbing treatment. In a preferred embodiment, the substrate is a stretched film. By stretching, the molecular director is oriented substantially uniformly over the entire thickness direction of the substrate, and a good orientation regulating force according to the stretching direction is obtained.

The stretch direction of the stretched film can be appropriately set according to the orientation direction of the liquid crystal compound in the layer of the liquid crystal composition. Therefore, the stretching may be only oblique stretching (stretching in a direction not parallel to both the longitudinal direction and the width direction of the base material), or only lateral stretching (stretching in the width direction of the base material), and longitudinal stretching ( Only stretching in the longitudinal direction of the base material) may be used. Further, these stretching may be performed in combination. In particular, when the direction of the slow axis of the liquid crystal cured layer forms an angle of 40 ° to 50 ° with respect to the longitudinal direction of the circularly polarizing film, it is preferable to adopt oblique stretching. The draw ratio can be appropriately set within the range in which the orientation regulating force is generated on the substrate surface. When a resin having a positive intrinsic birefringence as a base material is used as a material, normally, molecules are oriented in the stretching direction and a slow axis is developed in the stretching direction. Stretching can be performed using a known stretching machine such as a tenter stretching machine.
As a base material mentioned above, the base material of international publication 2015/064581 can be used, for example.

  After preparing the base material, the liquid crystal composition is applied onto the base material to obtain a layer of the liquid crystal composition. Examples of coating methods include curtain coating, extrusion coating, roll coating, spin coating, dip coating, bar coating, spray coating, slide coating, print coating, gravure coating, and die coating. Method, gap coating method, and dipping method. The thickness of the layer of the liquid crystal composition to be applied can be appropriately set according to a desired thickness required for the liquid crystal cured layer.

  After obtaining the liquid crystal composition layer, the liquid crystal compound contained in the liquid crystal composition layer is usually aligned. Although alignment of a liquid crystal compound may be achieved immediately by application of a liquid crystal composition, it may be achieved by performing alignment treatment such as a heating treatment after application, if necessary. The conditions for the alignment treatment can be appropriately set according to the properties of the liquid crystal composition to be used. For example, the alignment treatment can be performed at a temperature of 50 ° C. to 160 ° C. for 30 seconds to 5 minutes. Thereby, the liquid crystal compound contained in the layer of the liquid crystal composition is aligned in the alignment direction according to the alignment regulating force of the substrate. For example, when a stretched film is used as the substrate, the liquid crystal compound contained in the layer of the liquid crystal composition is aligned in parallel to the stretching direction of the stretched film.

  Furthermore, you may perform the process of drying the layer of a liquid-crystal composition as needed during the alignment of a liquid crystal compound or after alignment. Such drying can be achieved by a drying method such as natural drying, heat drying, reduced pressure drying, and reduced pressure heat drying. By such drying, the solvent can be removed from the liquid crystal composition layer.

  Thereafter, a step of polymerizing the liquid crystal compound in the liquid crystal composition layer to obtain a semi-cured layer is performed. Here, the semi-cured layer refers to a layer obtained by polymerizing the liquid crystal compound contained in the liquid crystal composition, and the polymerization conversion rate of the liquid crystal compound is not 100%. This semi-cured layer is usually in a state in which no trace of fingerprints remains and does not exhibit tackiness even when pressed lightly with a fingertip. Since such a semi-cured layer is softer than a layer having a polymerization conversion rate of 100%, it is easy to impart a surface shape. Therefore, it is easy to form a recess using a mold in this semi-cured layer.

  The polymerization of the liquid crystal compound may be performed by heating, but it is preferably performed by irradiating the layer of the liquid crystal composition with active energy rays. As the active energy ray, any energy ray capable of curing the liquid crystal composition can be used, but ionizing radiation is preferable, and ultraviolet rays are particularly preferable.

At this time, the amount of active energy rays applied to the liquid crystal composition layer is usually adjusted to a predetermined range. Specifically, the amount of active energy rays to be irradiated can be appropriately adjusted within a range of usually 400 mJ / cm ² or less.

  The irradiation with the active energy ray may be performed in the air, or a part or all of the process may be performed in an atmosphere in which the oxygen concentration is controlled (for example, in a nitrogen atmosphere).

  After obtaining the semi-cured layer, a step of forming a recess on the surface of the semi-cured layer is performed. Since the shape of the recess is set to a shape corresponding to the grid line, it is usually a groove shape. The formation of the recess may be performed by, for example, a cutting method, but is preferably performed by a nanoimprint method. In the nanoimprint method, a mold having a shape corresponding to the recess is prepared, and the mold is pressed against the surface of the semi-cured layer to form the recess on the surface of the semi-cured layer.

  As the mold, various molds such as a flat mold and a roll mold can be used. Especially, since continuous manufacture using a roll-to-roll method is possible, it is preferable to use an embossing roll. The embossing roll is a roll having a peripheral surface having a shape corresponding to the recess to be formed. Such an embossing roll can be manufactured, for example, in the same manner as the transfer roll manufacturing method described in JP-A-2007-057971. By pressing the circumferential surface of the embossing roll against the surface of the semi-cured layer at an appropriate temperature, the shape of the circumferential surface of the embossing roll is transferred to the surface of the semi-cured layer to form a recess.

  Conditions for pressing the mold against the semi-cured layer can be arbitrarily set as long as a desired recess can be formed. In a preferred range, the pressure for pressing the mold against the semi-cured layer is preferably 0.05 MPa or more, more preferably 0.1 MPa or more, particularly preferably 0.2 MPa or more, preferably 80 MPa or less, more preferably 50 MPa or less, particularly preferably 20 MPa or less. When the pressure is equal to or higher than the lower limit value, the shape of the mold can be effectively transferred, and when the pressure is equal to or lower than the upper limit value, the breakage of the semi-cured layer can be suppressed.

  The temperature when pressing the mold against the semi-cured layer is preferably 40 ° C. or higher, more preferably 50 ° C. or higher, particularly preferably 60 ° C. or higher, preferably 300 ° C. or lower, more preferably 200 ° C. or lower, Especially preferably, it is 180 degrees C or less. When the temperature is equal to or higher than the lower limit value of the above range, the mold shape can be effectively transferred to the semi-cured layer having a sufficiently stable orientation state at room temperature, and is equal to or lower than the upper limit value. Thereby, decomposition | disassembly and deterioration of a semi-hardened layer can be suppressed.

  Furthermore, although the time for pressing the mold against the semi-cured layer varies depending on the kind of the semi-cured layer, the form of the substrate, the material of the mold, etc., it cannot be generally stated, but is preferably 0.01 seconds or more, more preferably 0. .05 seconds or longer, particularly preferably 0.1 seconds or longer, preferably 120 seconds or shorter, more preferably 60 seconds or shorter, particularly preferably 30 seconds or shorter. When the pressing time is equal to or longer than the lower limit value, the shape of the mold can be effectively transferred, and when the pressing time is equal to or shorter than the upper limit value, productivity can be increased.

  Thus, in the formation method using the nanoimprint method described above, the concave portions can be continuously formed on the surface of the liquid crystal cured layer. Since this nanoimprint method does not generate scraps unlike the cutting method, it is possible to suppress the occurrence of optical defects and contamination of the manufacturing apparatus due to adhesion of the scraps.

  By the way, in a circularly-polarizing film, you may use the said semi-hardened layer as a liquid-crystal hardened layer from a viewpoint which can form a recessed part easily with the said formation method. However, from the viewpoint of obtaining a liquid crystal cured layer having excellent mechanical strength, the method for producing a circularly polarizing film includes a step of further curing the semi-cured layer in which the recesses are formed after forming the recesses in the semi-cured layer. Is preferred. Thereby, the polymerization of the liquid crystal compound further proceeds in the semi-cured layer, the hardness of the semi-cured layer is increased, and a cured resin layer having excellent mechanical strength is obtained. This step may be performed before removing the mold from the semi-cured layer, may be performed simultaneously with removing the mold from the semi-cured layer, or may be performed after removing the mold from the semi-cured layer.

Further curing of the semi-cured layer can usually be performed by further proceeding the polymerization reaction of the liquid crystal compound contained in the semi-cured layer. The polymerization may be performed by heating, but is preferably performed by irradiation with active energy rays. The amount of active energy rays to be irradiated can be, for example, more than 400 mJ / cm ² and 10,000 mJ / cm ² or less.

  As described above, a liquid crystal cured layer is obtained as a semi-cured layer having a concave portion formed on the surface or a layer obtained by further curing the semi-cured layer. After obtaining the liquid crystal cured layer in this way, a step of forming grid lines in the recesses on the surface of the liquid crystal cured layer is performed.

  The grid lines may be formed by, for example, a vacuum film forming process such as a vacuum deposition method, a sputtering method, or an ion plating method. The grid lines may be formed by a wet process such as a coating method such as a micro gravure method, a screen coating method, a dip coating method, or a plating method such as an electroless plating method or an electrolytic plating method. As a specific example, after forming the metal layer by vapor-depositing a metal such as aluminum on the entire surface of the liquid crystal cured layer, the metal layer formed in a portion other than the recess is polished by a grinder. It may be removed by a removal process to form a grid line made of metal in the recess.

  However, from the viewpoint of easily forming the grid line, it is preferable to form the grid line by a method including a coating method. When grid lines are formed by such a method, a step of preparing a liquid composition containing the material of the grid lines, a step of applying the liquid composition to the surface of the liquid crystal cured layer, and an excess liquid composition Removing from the surface of the liquid crystal cured layer.

  As the liquid composition, one containing a grid line material and a solvent is usually used. As the solvent, a solvent capable of dissolving or dispersing the grid line material can be used. The solvent is preferably a solvent that does not dissolve the liquid crystal cured layer. Such a solvent may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios. A preferable example of the solvent is water.

  In the liquid composition, the grid line material is usually dispersed as particles. For example, when the material of the grid line is a metal, the metal is usually dispersed as nano-level particles. Preferable examples of the liquid composition as described above include metal ink containing metal as a grid line material, such as silver ink.

  After preparing the liquid composition, the liquid composition is applied to the surface of the liquid crystal cured layer. The coated liquid composition enters a recess formed on the surface of the liquid crystal cured layer and fills the recess.

  Usually, the coated liquid composition adheres to portions other than the recesses on the surface of the liquid crystal cured layer. Therefore, after the application of the liquid composition, a step of removing the excess liquid composition other than that filled in the recesses is performed. The excess liquid composition can be removed, for example, by scraping off the excess liquid composition using a scraping member such as a doctor blade.

  Thereby, a liquid composition remains only in the recessed part of the surface of a liquid-crystal hardened layer. Therefore, if necessary, grid lines can be formed in the recesses by performing a step of removing the solvent from the liquid composition remaining in the recesses. The removal of the solvent is usually performed by a drying process such as a heat treatment. However, if the solvent is removed without performing any special treatment, the drying treatment may not be performed.

  By the above manufacturing method, a circularly polarizing film including a liquid crystal cured layer having a recess formed on the surface and a grid polarizing layer having grid lines formed in the recess is obtained. In this manufacturing method, grid lines are formed by using concave portions on the surface of the liquid crystal cured layer. The formation of the recess can be continuously performed by a simple process of heating and pressing. Therefore, according to the said manufacturing method, since a grid line can be formed continuously and easily, a circularly-polarizing film can be manufactured easily.

The method for producing a circularly polarizing film may further include an optional step in combination with the above-described steps.
For example, the method for producing a circularly polarizing film may include a step of peeling the substrate from the liquid crystal cured layer. Thereby, it is possible to make a circularly-polarizing film thin.
For example, the manufacturing method of a circularly-polarizing film may include the process of forming a protective layer for the corrosion suppression and shape maintenance of a grid polarizing layer. The protective layer can be formed, for example, by the method described in JP-A-2007-057971.

  Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples, and can be implemented with any modifications without departing from the scope of the claims of the present invention and the equivalents thereof. In the following description, “%” and “part” representing amounts are based on weight unless otherwise specified. Further, the operations described below were performed in a normal temperature and pressure atmosphere unless otherwise specified.

[Example 1]
Polymerizable liquid crystal compound represented by the following formula (A) (refractive index anisotropy Δn = 0.07, phase transition temperature from liquid crystal phase to isotropic phase is 200 ° C. or higher, phase transition from crystal phase to liquid crystal phase 1 part at a temperature of 102 ° C., 0.035 part of a photopolymerization initiator (“Irgacure 379” manufactured by BASF), 0.0013 part of a surfactant (“s242” manufactured by AGC Sey Chemical Co.), and cyclohexane as a solvent A liquid crystal composition was obtained by mixing 1.5 parts of pentanone.

As a base film, a polyethylene terephthalate film (thickness: 100 μm) having a long shape with one side subjected to easy adhesion treatment was prepared. The following operation was performed while conveying this base film in the longitudinal direction of the base film.
A rubbing treatment was performed on the surface of the base film that was not subjected to the easy adhesion treatment. Next, the liquid crystal composition was applied to the surface subjected to the rubbing treatment. Thereby, the layer of the uncured liquid crystal composition was formed on one side of the base film.

  Then, it dried on 80 degreeC and 1 minute conditions, and removed the solvent from the layer of the liquid-crystal composition. Further, during this drying, the liquid crystal compound in the layer was aligned in the longitudinal direction of the base film.

Next, the liquid crystal composition layer was irradiated with ultraviolet rays having an illuminance of 100 mW / cm ² and an integrated light amount of 100 mJ / cm ² to polymerize the liquid crystal compound, thereby obtaining a semi-cured layer. The in-plane retardation of this semi-cured layer was 142 nm as measured with a phase meter (“AXOSCAN” manufactured by Axometrics) at a wavelength of 590 nm. The semi-cured layer has reverse wavelength dispersion characteristics. Specifically, the in-plane retardation satisfies Re ₄₅₀ / Re ₅₅₀ ≦ 0.95 and Re ₆₅₀ / Re ₅₅₀ ≧ 1.05. It was.

  In order to form a recess for a wire grid pattern, an embossing roll having a peripheral surface on which an embossed uneven structure (diffraction grating pattern) having a pitch of 290 nm, a width of 200 nm, and a depth of 200 nm was formed was prepared. In addition, the said uneven structure was set so that the recessed part extended in the direction inclined 45 degrees with respect to the liquid crystal aligning direction (longitudinal direction of a base film) of a semi-hardened layer could be formed in the surface of a semi-hardened layer. The embossing roll was set to 100 ° C., and the semi-cured layer was pressed at a pressure of 5 MPa for 1 second while moving the semi-cured layer at a speed of 10 m / min to form a recess in the semi-cured layer.

After forming a recess on the surface of the semi-cured layer, the semi-cured layer was irradiated with ultraviolet rays having an illuminance of 1000 mW / cm ² and an integrated light amount of 2000 mJ / cm ^{2 in} a nitrogen atmosphere. Polymerization of the polymerizable liquid crystal compound further proceeded by irradiation with ultraviolet rays, and a nematic resin layer (thickness 5 μm) as a liquid crystal cured layer was formed on one side of the base film. A plurality of linear recesses extending in parallel to each other were formed on the surface of the nematic resin layer opposite to the base film. Further, these recesses had a pitch of 290 nm, a width of 200 nm, and a depth of 200 nm. Thereby, the multilayer film provided with the base film and the nematic resin layer by which the recessed part was formed in the surface was obtained.

A liquid composition containing 15% by weight of silver nanoparticles, 80% by weight of water as a solvent, and 5% by weight of a binder was prepared. The particle diameter of the silver nanoparticles was 10 nm. The liquid composition was applied to the surface of the nematic resin layer of the multilayer film. Thereafter, the excess liquid composition other than that filled in the concave portions of the nematic resin layer was scraped off with a reverse roll coater. After the liquid composition was dried, a silver baking treatment was performed at 100 ° C. for 5 minutes to form grid lines made of silver wires only in the recesses, and a grid polarizing layer was provided. In the grid polarizing layer, the pitch of the grid lines was 290 nm, the width was 200 nm, and the thickness was 200 nm.
This obtained the circularly-polarizing film provided with a base film, a nematic resin layer, and a grid polarizing layer. The degree of circular polarization of this circularly polarizing film was 90% or more when measured at a wavelength of 590 nm using an elliptical polarization measuring device (“KOBRA-WPR” manufactured by Oji Scientific Instruments).

DESCRIPTION OF SYMBOLS 100 Circularly-polarizing film 110 Liquid crystal cured layer 110U Surface of liquid crystal cured layer 111 Recessed part 120 Grid polarizing layer 121 Grid line

Claims (11)

A liquid crystal cured layer formed of a cured material containing a liquid crystal compound and having optical anisotropy;
A circularly polarizing film comprising a grid polarizing layer formed on the surface of the liquid crystal cured layer and having a plurality of grid lines provided in parallel to each other. The circularly polarizing film according to claim 1, wherein the liquid crystal cured layer has reverse wavelength dispersion characteristics, and the liquid crystal cured layer has an in-plane retardation of λ / 4.   The circularly polarizing film according to claim 1 or 2, wherein the liquid crystal compound includes a main chain mesogen and a side chain mesogen bonded to the main chain mesogen in a molecule.   The circularly polarizing film according to claim 3, wherein the side chain mesogen has a benzothiazole ring. The circularly polarizing film has a long shape,
The direction of the slow axis of the liquid crystal cured layer is parallel or perpendicular to the longitudinal direction of the circularly polarizing film, and the extending direction of the grid lines is 40 ° with respect to the longitudinal direction of the circularly polarizing film. The circularly-polarizing film according to any one of claims 1 to 4, which forms an angle of -50 °. The circularly polarizing film has a long shape,
The direction of the slow axis of the liquid crystal cured layer forms an angle of 40 ° to 50 ° with respect to the longitudinal direction of the circularly polarizing film, and the extending direction of the grid lines is in the longitudinal direction of the circularly polarizing film. The circularly-polarizing film as described in any one of Claims 1-4 which is parallel with respect to.   The circularly polarizing film according to any one of claims 1 to 6, wherein the circularly polarizing film further has a protective layer on the grid polarizing layer. A method for producing a circularly polarizing film according to any one of claims 1 to 7,
Forming a layer of a material containing a liquid crystal compound;
A step of polymerizing the liquid crystal compound to obtain a semi-cured layer;
Forming a recess in the surface of the semi-cured layer;
Forming a grid line in the recess, and a method for producing a circularly polarizing film.   The method for producing a circularly polarizing film according to claim 8, wherein the recess is formed by a nanoimprint method.   The manufacturing method of the circularly-polarizing film according to claim 9, wherein the nanoimprint method includes transferring the shape of the peripheral surface to the surface of the semi-cured layer using an embossing roll having a peripheral surface corresponding to the concave portion. Method.   The manufacturing method of the circularly-polarizing film as described in any one of Claims 8-10 including the process of further hardening the said semi-hardened layer in which the said recessed part was formed.

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