Method for producing liquid crystal layer

Abstract

The present invention addresses the problem of providing a method for producing a liquid crystal layer which is thick and has a liquid crystal alignment pattern having few defects. The method for producing a liquid crystal layer comprises: a step 1 for forming a composition layer that contains a liquid crystal compound having a polymerizable group and a chiral agent having a variable helical twisting power, wherein the composition layer has a liquid crystal alignment pattern in which the direction of an optical axis arising from the liquid crystal compound varies while continuously rotating along at least one in-plane direction, and in a cross section including one direction and the thickness direction of the composition layer, as observed by an atomic force microscope, a bright region and a dark region resulting from the optical axis of the liquid crystal compound are inclined with respect to a main surface of the composition layer; a step 2 for varying the helical twisting power of the chiral agent so that the bright region and the dark region resulting from the optical axis of the liquid crystal compound in the cross section of the composition layer, as observed by an atomic force microscope, approach a direction perpendicular to the main surface of the composition layer; and a step 3 for curing the composition layer so as to form a liquid crystal layer.

Description

Method for manufacturing a liquid crystal layer

[0001] The present invention relates to a method for manufacturing a liquid crystal layer.

[0002] Optical elements that control the direction of light are used in many optical devices or systems. For example, the backlight of a liquid crystal display device; AR (Augmented Reality) glasses, VR (Virtual Reality) glasses, and MR (Mixed Reality) glasses such as head-mounted displays (HMDs (Head Mounted Display)) that display virtual images and various information and other images superimposed on the actual scene being viewed; head-up displays (HUDs (Head Up Display)); projectors; beam steering; and sensors for detecting objects and measuring the distance to objects, etc. Optical elements that control the direction of light are used in various optical devices.

[0003] As such an optical element that controls the direction of light, a liquid crystal optical element having a liquid crystal layer formed using a liquid crystal composition containing a liquid crystal compound and exhibiting optical anisotropy has been proposed. Patent Document 1 describes an optical element including a plurality of laminated birefringence sub-layers configured to change the propagation direction of light passing through the inside according to the Bragg condition. Each of the laminated birefringence sub-layers has a local optical axis that changes along the respective interface between adjacent ones of the laminated birefringence sub-layers so as to define each grating period.

[0004] Japanese Patent Translation of PCT International Publication No. 2017-522601

[0005] Patent Document 1 discloses a liquid crystal layer having a liquid crystal alignment pattern derived from a liquid crystal compound (a liquid crystal alignment pattern in which the direction of the optical axis derived from the liquid crystal compound changes while continuously rotating along at least one direction in the plane). However, recently, there has been a demand for a method for manufacturing a liquid crystal layer having a large thickness and few defects.

[0006] In view of the above circumstances, an object of the present invention is to provide a method for manufacturing a liquid crystal layer having a liquid crystal alignment pattern with a large thickness and few defects.

[0007] The inventors of this invention have diligently studied the problems of the prior art and have found that the above problems can be solved by the following configuration.

[0008] [1] A method for manufacturing a liquid crystal layer, comprising: step 1 forming a composition layer comprising a liquid crystal compound having polymerizable groups and a chiral agent whose helical induced force can be changed, wherein the composition layer has a liquid crystal orientation pattern in which the orientation of the optical axis derived from the liquid crystal compound changes while continuously rotating along at least one direction in the plane, and in a cross-section of the composition layer including the one direction and the thickness direction as observed by an atomic force microscope, the bright and dark areas derived from the optical axis of the liquid crystal compound are inclined with respect to the main surface of the composition layer; step 2 changing the helical induced force of the chiral agent to bring the bright and dark areas derived from the optical axis of the liquid crystal compound in the cross-section of the composition layer as observed by an atomic force microscope closer to a direction perpendicular to the main surface of the composition layer; and step 3 curing the composition layer to form a liquid crystal layer. [2] Thickness T of the liquid crystal layer Ｌ The method for manufacturing a liquid crystal layer according to [1], wherein the length Λ over which the orientation of the optical axis derived from the liquid crystal compound in the liquid crystal alignment pattern rotates 180° along the above one direction satisfies the following formula (1). Ｌ / Λ ≥ 1 / 2 (1) [3] A method for manufacturing a liquid crystal layer according to [1] or [2], wherein in the composition layer formed by step 1, the angle between the bright and dark parts originating from the optical axis of the liquid crystal compound and the main surface of the composition layer is less than 85°. [4] A method for manufacturing a liquid crystal layer according to [1] or [2], wherein in the composition layer formed by step 1, the angle between the bright and dark parts originating from the optical axis of the liquid crystal compound and the main surface of the composition layer is 30° or less. [5] A method for manufacturing a liquid crystal layer according to any one of [1] to [4], wherein the chiral agent is a compound whose helical induced force changes by any one of light irradiation, heat treatment, or acid treatment. [6] A method for manufacturing a liquid crystal layer according to any one of [1] to [5], wherein in step 2, the composition layer is irradiated with light in an atmosphere with an oxygen concentration of 1 volume% or more to change the helical induced force of the chiral agent. [7] A method for manufacturing a liquid crystal layer according to any one of [1] to [6], wherein the viscosity of the composition layer at the temperature at which step 2 is performed is 10 Pa·s or more. [8] A method for manufacturing a liquid crystal layer according to any one of [1] to [7], wherein in the cross-section of the composition layer formed by step 2, the angle between the bright and dark areas originating from the optical axis of the liquid crystal compound and the main surface of the composition layer is 50 to 90°.

[0009] According to the present invention, it is possible to provide a method for manufacturing a liquid crystal layer having a thick liquid crystal alignment pattern with few defects.

[0010] This is a plan view conceptually showing an example of a liquid crystal alignment pattern of a composition layer. This is a plan view conceptually showing another example of a liquid crystal alignment pattern of a composition layer. This is a cross-sectional view of a composition layer for explaining step 1 of the manufacturing method of the present invention. This is a diagram conceptually showing an example of an exposure apparatus for forming an alignment pattern. This is a cross-sectional view of a composition layer for explaining step 2 of the manufacturing method of the present invention. This is a conceptual diagram for explaining the function of a liquid crystal alignment pattern. This is a conceptual diagram for explaining the function of a liquid crystal alignment pattern.

[0011] The present invention will now be described in detail with reference to the embodiments shown in the accompanying drawings. The following descriptions of the constituent elements may be based on representative embodiments of the present invention, but the present invention is not limited to such embodiments. In each drawing, the scale of the components has been appropriately changed from the actual scale to facilitate viewing and explanation.

[0012] In this specification, numerical ranges expressed using "~" mean a range that includes the numbers before and after "~" as the lower and upper limits. In this specification, each component may be made using one substance alone or using two or more substances in combination. Here, when two or more substances are used in combination for each component, the content of that component refers to the total content of the substances used in combination, unless otherwise specified.

[0013] In this specification, the refractive indices nx, ny, and nz are measured using an Abbe refractometer (NAR-4T, manufactured by Atago Corporation) with a sodium lamp (λ = 589 nm) as the light source. Wavelength dependence can be measured using a multi-wavelength Abbe refractometer DR-M2 (manufactured by Atago Corporation) in combination with an interference filter. Values ​​from the Polymer Handbook (JOHN WILEY & SONS, INC.) and catalogs of various optical films can also be used. Examples of average refractive index values ​​for major optical films are given below: cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), and polystyrene (1.59).

[0014] In this specification, "light" means active light or radiation, including, for example, the emission spectrum of a mercury lamp, far ultraviolet light represented by an excimer laser, extreme ultraviolet light (EUV light), X-rays, ultraviolet light, and electron beams (EB). Of these, ultraviolet light is preferred. In this specification, "visible light" means light between 380 and 780 nm. In this specification, unless otherwise specified, the measurement wavelength is 550 nm.

[0015] In this specification, “identical” includes the generally accepted margin of error in the art. Furthermore, in this specification, “all,” “all,” and “entire surface” include not only 100% but also the generally accepted margin of error in the art, such as 99% or more, 95% or more, or 90% or more. Regarding angles, “orthogonal” or “perpendicular” means within the range of 90° ± 5°, and “parallel” means within the range of 0° ± 5°. Similarly, unless otherwise specified, angles mean that the difference from the exact angle is within 5 degrees. Also, “equal” of multiple angles means that the difference between multiple angles is within 5 degrees. The difference between the above angles is preferably within 4 degrees, and more preferably within 3 degrees.

[0016] [Method for Manufacturing a Liquid Crystal Layer] The method for manufacturing a liquid crystal layer of the present invention (hereinafter also referred to as "this manufacturing method") comprises the following steps 1 to 3. Step 1: A step to form a composition layer comprising a liquid crystal compound having polymerizable groups and a chiral agent whose helical induced force can be changed, having a liquid crystal orientation pattern in which the orientation of the optical axis derived from the liquid crystal compound changes while continuously rotating along at least one direction in the plane, and in a cross-section of the composition layer including the above-mentioned one direction and thickness direction as observed by an atomic force microscope, the bright and dark areas derived from the optical axis of the liquid crystal compound are inclined with respect to the main surface of the composition layer. Step 2: A step to change the helical induced force of the chiral agent and bring the bright and dark areas derived from the optical axis of the liquid crystal compound in the cross-section of the composition layer as observed by an atomic force microscope closer to a direction perpendicular to the main surface of the composition layer. Step 3: A step to cure the composition layer to form a liquid crystal layer.

[0017] Conventionally, liquid crystal layers having a liquid crystal alignment pattern in which the orientation of the optical axis derived from the liquid crystal compound changes while continuously rotating along at least one direction in the plane are manufactured by applying a composition containing the liquid crystal compound to the surface of an alignment film to form a composition layer, and then performing a curing treatment to harden the composition layer. However, in this manufacturing method, it is known that if the thickness of the composition layer is made too thick, orientation disorder in the liquid crystal alignment pattern is likely to occur on the surface opposite to the alignment film side. Therefore, in order to manufacture an optical element having a liquid crystal layer with the optically required thickness and few defects, a series of processes including the formation and hardening of the composition layer are often repeated multiple times, and there has been a need to improve production efficiency.

[0018] To address such problems, the inventors have found that by forming a composition layer in which the bright and dark areas originating from the optical axis of the liquid crystal compound are inclined with respect to the main surface, then changing the helical induced force of the chiral agent in the formed composition layer so that the bright and dark areas approach a direction perpendicular to the main surface, and then curing the composition layer, it is possible to suppress the orientation disorder of the liquid crystal alignment pattern on the surface opposite to the alignment film side, even when the thickness of the layer is increased. The details of this reason are not yet clear, but the inventors speculate that it is due to the following reasons. First, in a composition layer in which the bright and dark areas originating from the optical axis of the liquid crystal compound are inclined with respect to the main surface, the liquid crystal compound is twisted and oriented along a helical axis extending in the thickness direction. The inventors speculate that within the composition layer in which the liquid crystal compound constituting the liquid crystal alignment pattern is twisted and oriented, the liquid crystal compound is further inclined with respect to the main surface, and on a certain surface within the composition layer, the orientation of the optical axis of the liquid crystal compound is aligned, and the energy becomes stable. When the liquid crystal compound is matured in this state, the orientation of the liquid crystal compound stabilizes. Subsequently, even if the helical induced force of the chiral agent is changed, and the light and dark areas become closer to being perpendicular to the main surface (i.e., the torsional orientation in the thickness direction of the liquid crystal compound becomes looser), the orientation of the liquid crystal compound is maintained, and as a result, a liquid crystal layer with suppressed orientation disorder is produced. The procedures for each step of this manufacturing method are described in detail below.

[0019] <Step 1> Step 1 is a step of forming a composition layer containing a liquid crystal compound having polymerizable groups and a chiral agent whose helical induced force can be altered. The composition layer formed by Step 1 has a liquid crystal orientation pattern in which the orientation of the optical axis derived from the liquid crystal compound changes while continuously rotating along at least one direction in the plane, and in a predetermined cross-section observed by an atomic force microscope, the bright and dark areas derived from the optical axis of the liquid crystal compound are inclined with respect to the main surface of the composition layer. Below, the materials and composition layer used in this step will be described in detail, followed by a detailed description of the procedure.

[0020] (Chiral Agent) The composition layer contains a chiral agent whose helical induced force may change. The helical induced force (HTP) of the chiral agent is a factor indicating the helical orientation ability, represented by the following formula (X). Formula (X) HTP = 1 / (Helical pitch length (unit: μm) × Concentration of chiral agent relative to the liquid crystal compound (mass%)) [μm －１ The length of the helical pitch refers to the thickness of the composition layer from 0° to 360° in the thickness direction of the liquid crystal compound. The length of the helical pitch can be measured by the method described on page 196 of the Liquid Crystal Handbook (published by Maruzen Co., Ltd.).

[0021] Chiral agents have the function of inducing a helical structure in liquid crystal compounds. Since the direction of twisting or helical pitch induced differs depending on the compound, the chiral agent should be selected according to the purpose. There are no particular restrictions on the chiral agent, and known compounds (for example, described in Liquid Crystal Device Handbook, Chapter 3, Section 4-3, Chiral Agents for TN (twisted nematic) and STN (Super Twisted Nematic), page 199, edited by the 142nd Committee of the Japan Society for the Promotion of Science, 1989), isosorbide, and isomannide derivatives can be used. Chiral agents may have polymerizable groups. Furthermore, chiral agents may be liquid crystal compounds.

[0022] Examples of chiral agents whose helical induced force can change include compounds whose helical induced force changes in response to external stimuli such as light irradiation, heat treatment, and acid treatment.

[0023] The chiral agent may be one in which the helical-inducing force increases or decreases due to the external stimulus described above. In this specification, "increase and decrease in helical-inducing force" refers to the increase or decrease when the initial (before light irradiation) helical direction of the chiral agent is considered "positive". Therefore, even if the helical-inducing force continues to decrease due to light irradiation and exceeds 0, resulting in a "negative" helical direction (i.e., inducing a helix in the opposite direction to the initial (before light irradiation) helical direction), it still falls under the category of "a chiral agent in which the helical-inducing force decreases".

[0024] As the chiral agent, a photosensitive chiral agent (hereinafter also referred to as "chiral agent A") whose helical induced force can be changed by light irradiation is preferred. Chiral agent A often contains an asymmetric carbon atom, but axially asymmetric compounds or planar asymmetric compounds that do not contain an asymmetric carbon atom can also be used. Examples of axially asymmetric compounds or planar asymmetric compounds include binaphthyl, helicene, paracyclophane, and their derivatives.

[0025] Chiral agent A is a so-called photoreactive chiral agent. A photoreactive chiral agent is a compound that has a chiral moiety and a photoreactive moiety that undergoes a structural change upon light irradiation, and for example, it greatly changes the torsional force of a liquid crystal compound depending on the amount of irradiation. Examples of photoreactive moieties that undergo a structural change upon light irradiation include photochromic compounds (Kingo Uchida, Masahiro Irie, Chemical Industry, vol. 64, 640p, 1999; Kingo Uchida, Masahiro Irie, Fine Chemical, vol. 28(9), 15p, 1999). Furthermore, the above structural change refers to decomposition, addition reaction, isomerization, racemization, [2+2] photocyclization, and dimerization reaction that occur upon light irradiation of the photoreactive moiety, and the above structural change may be irreversible. Furthermore, an example of a chiral moiety is the asymmetric carbon described in Hiroyuki Nodaira, Chemical Review, No. 22 Liquid Crystal Chemistry, 73p: 1994.

[0026] Examples of chiral agent A include the photoreactive chiral agent described in paragraphs 0044 to 0047 of Japanese Patent Publication No. 2001-159709, the optically active compound described in paragraphs 0019 to 0043 of Japanese Patent Publication No. 2002-179669, the optically active compound described in paragraphs 0020 to 0044 of Japanese Patent Publication No. 2002-179633, the optically active compound described in paragraphs 0016 to 0040 of Japanese Patent Publication No. 2002-179670, the optically active compound described in paragraphs 0017 to 0050 of Japanese Patent Publication No. 2002-179668, and the optically active compound described in paragraphs 0018 to 000 of Japanese Patent Publication No. 2002-180051. Optically active compounds described in 44, optically active isosorbide derivatives described in paragraphs 0016 to 0055 of Japanese Patent Publication No. 2002-338575, photoreactive optically active compounds described in paragraphs 0023 to 0032 of Japanese Patent Publication No. 2002-080478, photoreactive caral agents described in paragraphs 0019 to 0029 of Japanese Patent Publication No. 2002-080851, optically active compounds described in paragraphs 0022 to 0049 of Japanese Patent Publication No. 2002-179681, optically active compounds described in paragraphs 0015 to 0044 of Japanese Patent Publication No. 2002-302487, Japanese Patent Publication No. 2002-338668 Optically active polyesters described in paragraphs 0015 to 0050 of Japanese Patent Publication No. 2003-055315, binaphthol derivatives described in paragraphs 0019 to 0041 of Japanese Patent Publication No. 2003-073381, optically active fulgid compounds described in paragraphs 0008 to 0043 of Japanese Patent Publication No. 2003-306490, optically active isosorbide derivatives described in paragraphs 0015 to 0057 of Japanese Patent Publication No. 2003-306491, optically active isosorbide derivatives described in paragraphs 0015 to 0041 of Japanese Patent Publication No. 2003-313187 Examples include isosorbide derivatives, optically active isomannide derivatives described in paragraphs 0015 to 0057 of Japanese Patent Publication No. 2003-313188, optically active isosorbide derivatives described in paragraphs 0015 to 0049 of Japanese Patent Publication No. 2003-313189, optically active polyesters / amides described in paragraphs 0015 to 0052 of Japanese Patent Publication No. 2003-313292, optically active compounds described in paragraphs 0012 to 0053 of WO2018 / 194157, and optically active compounds described in paragraphs 0020 to 0049 of Japanese Patent Publication No. 2002-179682.

[0027] Among the chiral agents A, compounds having at least a photoisomerization site are preferred, and it is more preferable that the photoisomerization site has a photoisomerizable double bond. As the photoisomerization site having the photoisomerizable double bond, the cinnamoyl site, chalcone site, azobenzene site, or stilbene site are preferred in that photoisomerization occurs easily and the difference in helical induced force before and after light irradiation is large, and the cinnamoyl site, chalcone site, or stilbene site is even more preferred in that it absorbs less visible light. The photoisomerization site corresponds to the photoreaction site that undergoes structural changes upon light irradiation as described above.

[0028] Furthermore, it is preferable that chiral agent A has a trans-type photoisomerizable double bond, which has a high initial (before light irradiation) helical induced force and exhibits superior change in helical induced force due to light irradiation. Alternatively, it is preferable that chiral agent A has a cis-type photoisomerizable double bond, which has a low initial (before light irradiation) helical induced force and exhibits superior change in helical induced force due to light irradiation.

[0029] Chiral agent A preferably has a substructure selected from a binaphthyl substructure, an isosorbide substructure (a substructure derived from isosorbide), and an isomannide substructure (a substructure derived from isomannide). The binaphthyl substructure, isosorbide substructure, and isomannide substructure refer to the following structures, respectively. In the binaphthyl substructure, the parts where the solid and dashed lines are parallel represent single or double bonds. In the structures shown below, * indicates a bond position.

[0030]

[0031] Chiral agent A may have a polymerizable group. The type of polymerizable group is not particularly limited, but a functional group capable of addition polymerization is preferred, a polymerizable ethylenically unsaturated group or a cyclic polymerizable group is more preferred, and a (meth)acryloyl group, vinyl group, styryl group, or allyl group is even more preferred.

[0032] As chiral agent A, the compound represented by formula (C) is preferred. Formula (C) R-L-R R independently represents a group having at least one moiety selected from the group consisting of a cinnamoyl moiety, a chalcone moiety, an azobenzene moiety, and a stilbene moiety. L represents a divalent linking group formed by removing two hydrogen atoms from the structure represented by formula (D) (a divalent linking group formed by removing two hydrogen atoms from the binaphthyl substructure), a divalent linking group represented by formula (E) (a divalent linking group consisting of the isosorbide substructure), or a divalent linking group represented by formula (F) (a divalent linking group consisting of the isomannide substructure). In formulas (E) and (F), * represents the bond position.

[0033]

[0034] The composition layer preferably contains chiral agent A. The chiral agent A contained in the composition layer may be a single type or two or more types. The composition layer may contain at least one type of chiral agent A and at least one type of chiral agent whose helical induction force does not change upon light irradiation (hereinafter also simply referred to as "chiral agent B"). Chiral agent B may be liquid crystalline or non-liquid crystalline. Chiral agent B often contains an asymmetric carbon atom, but may also be an axially asymmetric compound or a planar asymmetric compound that does not contain an asymmetric carbon atom. Chiral agent B may have polymerizable groups. Examples of polymerizable groups include those that chiral agent A may have. Known chiral agents can be used as chiral agent B. It is preferable that chiral agent B is a chiral agent that induces a helix in the opposite direction to that of chiral agent A described above. That is, for example, if the helix induced by chiral agent A is right-handed, the helix induced by chiral agent B will be left-handed.

[0035] The molar extinction coefficient of chiral agent A is not particularly limited, but the molar extinction coefficient at the wavelength of light irradiated in step 2 described later (for example, 365 nm) is preferably 100 to 100,000 L / (mol·cm) and preferably 500 to 50,000 L / (mol·cm).

[0036] The respective contents of chiral agent A and chiral agent B in the composition layer can be appropriately set according to the characteristics of the liquid crystal layer to be formed (e.g., retardation and wavelength dispersion). Since the torsion angle of the liquid crystal compound in the liquid crystal layer depends greatly on the type and concentration of chiral agent A and chiral agent B, the desired torsion angle can be obtained by adjusting these.

[0037] The chiral agent may be used alone or in combination of two or more. The content of the chiral agent in the composition layer (total content if two or more chiral agents are included) is not particularly limited, but it is preferably 30% by mass or less, and more preferably 15% by mass or less, relative to the total mass of the liquid crystal compound, in order to facilitate uniform orientation of the liquid crystal compound. The lower limit is not particularly limited, but it is preferably 1% by mass or more, and more preferably 5% by mass or more.

[0038] Furthermore, the content of chiral agents that can alter the helical induced force in the composition layer (total content if two or more chiral agents that can alter the helical induced force are included) is not particularly limited, but is preferably 20% by mass or less, and more preferably 10% by mass or less, relative to the total mass of the liquid crystal compound. The lower limit is not particularly limited, but is preferably 1% by mass or more, and more preferably 5% by mass or more.

[0039] (Liquid Crystal Compound) The composition layer formed by step 1 contains a liquid crystal compound having polymerizable groups. The type of liquid crystal compound is not particularly limited. Generally, liquid crystal compounds can be classified into rod-shaped type (rod-shaped liquid crystal compounds) and disc-shaped type (discotic liquid crystal compounds) based on their shape. Furthermore, liquid crystal compounds can be classified into low-molecular-weight type and high-molecular-weight type. High-molecular-weight compounds generally refer to those with a degree of polymerization of 100 or more (Polymer Physics and Phase Transition Dynamics, by Masao Doi, p. 2, Iwanami Shoten, 1992). In the present invention, any liquid crystal compound can be used, but it is preferable to use a rod-shaped liquid crystal compound or a discotic liquid crystal compound, and it is more preferable to use a rod-shaped liquid crystal compound. Two or more rod-shaped liquid crystal compounds, two or more discotic liquid crystal compounds, or a mixture of a rod-shaped liquid crystal compound and a discotic liquid crystal compound may be used. As the rod-shaped liquid crystal compound, for example, those described in claim 1 of Japanese Patent Publication No. 11-513019 or paragraphs 0026 to 0098 of Japanese Patent Application Publication No. 2005-289980 can be preferably used. As the discotic liquid crystal compound, for example, those described in paragraphs 0020 to 0067 of Japanese Patent Application Publication No. 2007-108732 or paragraphs 0013 to 0108 of Japanese Patent Application Publication No. 2010-244038 can be preferably used.

[0040] The type of polymerizable group in the liquid crystal compound is not particularly limited, but functional groups capable of addition polymerization are preferred, polymerizable ethylenically unsaturated groups or cyclic polymerizable groups are more preferred, and (meth)acryloyl groups, vinyl groups, styryl groups, or allyl groups are even more preferred.

[0041] Furthermore, the liquid crystal layer produced by the present invention is a layer formed by fixing a liquid crystal compound having polymerizable groups (a rod-shaped liquid crystal compound or a discotic liquid crystal compound having polymerizable groups) by polymerization or the like, and once it is formed as a layer, it no longer needs to exhibit liquid crystal properties.

[0042] The content of the liquid crystal compound in the composition layer is not particularly limited, but it is preferably 60% by mass or more, and more preferably 70% by mass or more, relative to the total mass of the composition layer, as this makes it easier to control the orientation state of the liquid crystal compound. There is no particular upper limit, but it is preferably 99% by mass or less, and more preferably 97% by mass or less.

[0043] (Other Components) The composition layer may contain other components besides the chiral agent and liquid crystal compound mentioned above. For example, the composition layer may contain a polymerization initiator. When the composition layer contains a polymerization initiator, polymerization of the liquid crystal compound having polymerizable groups proceeds more efficiently. Known polymerization initiators can be used as polymerization initiators, including photopolymerization initiators and thermal polymerization initiators, which can be selected depending on the curing treatment method in step 3. For example, when the composition layer is cured by light irradiation in step 3, the composition layer preferably contains a polymerization initiator that is sensitive to the light irradiated in step 3. The content of the polymerization initiator in the composition layer is not particularly limited, but is preferably 0.01 to 20% by mass and more preferably 0.5 to 10% by mass relative to the total mass of the composition layer.

[0044] The composition layer may contain polymerizable monomers different from the liquid crystal compound having polymerizable groups. Examples of polymerizable monomers include radical polymerizable compounds and cationic polymerizable compounds, with polyfunctional radical polymerizable monomers being preferred. Examples of polymerizable monomers include those described in paragraphs 0018 to 0020 of Japanese Patent Application Publication No. 2002-296423. The content of polymerizable monomers in the composition layer is not particularly limited, but is preferably 1 to 50% by mass, and more preferably 5 to 30% by mass, relative to the total mass of the liquid crystal compound.

[0045] The composition layer may contain a surfactant. Examples of surfactants include conventionally known compounds, but fluorine-based compounds are preferred. Specifically, examples include the compounds described in paragraphs 0028 to 0056 of Japanese Patent Application Publication No. 2001-330725 and the compounds described in paragraphs 0069 to 0126 of Japanese Patent Application No. 2003-295212.

[0046] The composition layer may contain a polymer. Examples of polymers include cellulose esters. Examples of cellulose esters include those described in paragraph 0178 of Japanese Patent Application Publication No. 2000-155216. The polymer content in the composition layer is not particularly limited, but is preferably 0.1 to 10% by mass, and more preferably 0.1 to 8% by mass, relative to the total mass of the liquid crystal compound.

[0047] In addition to the above, the composition layer may also contain additives (orientation control agents) that promote horizontal or vertical orientation in order to bring the liquid crystal compound into a horizontal or vertical orientation state.

[0048] The composition layer may contain a leveling agent. The leveling agent is not particularly limited, but a fluorine-based leveling agent or a silicon-based leveling agent is preferred, and a fluorine-based leveling agent is more preferred. The fluorine-based leveling agent is a leveling agent having a fluorine atom, and it is preferable that it has a fluoroaliphatic group. The silicon-based leveling agent is a leveling agent having a silicon atom, and it is preferable that it contains multiple dialkylsilyloxy units as repeating units.

[0049] The content of the leveling agent in the composition layer is not particularly limited, but in order to obtain a liquid crystal layer that is less prone to peeling within the layer, it is preferably 0.010 to 5.000% by mass, and more preferably 0.020 to 2.000% by mass, relative to the total mass of the composition layer.

[0050] (Liquid Crystal Alignment Pattern) The liquid crystal alignment pattern of the composition layer will be described in detail below with reference to the drawings. Figure 1 is a conceptual plan view showing an example of the liquid crystal alignment pattern of the composition layer formed by this manufacturing method. As shown in Figure 1, the composition layer 12 has a liquid crystal alignment pattern in which the orientation of the optical axis 40A derived from the liquid crystal compound 40 changes while continuously rotating along at least one direction in the plane of the composition layer 12. The optical axis 40A derived from the liquid crystal compound 40 is the axis in the liquid crystal compound 40 where the refractive index is highest, the so-called slow axis. For example, if the liquid crystal compound 40 is a rod-shaped liquid crystal compound, the optical axis 40A is along the long axis of the rod shape. In the following description, the optical axis 40A derived from the liquid crystal compound 40 will also be referred to as "optical axis 40A of the liquid crystal compound 40" or "optical axis 40A".

[0051] A plan view is a diagram of the composition layer viewed from the thickness direction (i.e., the stacking direction of each layer (film)). Also, in Figure 1, in order to clearly show the composition layer, only the surface liquid crystal compound 40 is shown.

[0052] As shown in Figure 1, on the surface, the liquid crystal compound 40 constituting the composition layer has a liquid crystal orientation pattern in which the orientation of the optical axis 40A changes while continuously rotating along a predetermined one direction indicated by arrow D (hereinafter referred to as the array axis D) within the plane of the composition layer. In the illustrated example, the liquid crystal compound 40 has a liquid crystal orientation pattern in which the optical axis 40A changes while continuously rotating clockwise along the direction of the array axis D. The liquid crystal compound 40 constituting the composition layer is arranged two-dimensionally along the array axis D and in a direction perpendicular to this one direction (the direction of the array axis D). In the following description, the direction perpendicular to the direction of the array axis D will be conveniently referred to as the Y direction. That is, the arrow Y direction is the direction perpendicular to the one direction in which the orientation of the optical axis 40A of the liquid crystal compound 40 changes while continuously rotating within the plane of the composition layer.

[0053] The statement that the orientation of the optical axis 40A of the liquid crystal compound 40 changes while continuously rotating in the direction of the array axis D (a predetermined one direction) means that, specifically, the angle between the optical axis 40A of the liquid crystal compounds 40 arranged along the direction of the array axis D and the direction of the array axis D differs depending on the position in the direction of the array axis D, and that the angle between the optical axis 40A and the direction of the array axis D changes sequentially from θ to θ+180° or θ-180° along the direction of the array axis D. The difference in angle between the optical axes 40A of liquid crystal compounds 40 adjacent to each other in the direction of the array axis D is preferably 45° or less, more preferably 15° or less, and even more preferably a smaller angle.

[0054] Furthermore, in the present invention, the rotation direction of the optical axis 40A of the liquid crystal compound in the direction of the array axis D is such that the liquid crystal compound 40 (optical axis 40A) rotates in a direction that reduces the angle between the optical axes 40A of adjacent liquid crystal compounds 40 in the direction of the array axis D. Therefore, in the composition layer shown in Figure 1, the optical axis 40A of the liquid crystal compound 40 rotates clockwise along the direction of the arrow on the array axis D.

[0055] On the other hand, in the liquid crystal compound 40 that forms the composition layer, the orientation of the optical axis 40A is the same in the Y direction which is perpendicular to the array axis D direction, that is, in the Y direction which is perpendicular to the direction in which the optical axis 40A rotates continuously. In other words, in the liquid crystal compound 40 that forms the composition layer, the angle between the optical axis 40A of the liquid crystal compound 40 and the array axis D direction is the same in the Y direction.

[0056] In the composition layer, the liquid crystal compounds arranged in the Y direction have an equal angle between their optical axis 40A and the arrangement axis D direction (one direction in which the orientation of the optical axis of the liquid crystal compound 40 rotates). The region in which these liquid crystal compounds 40, which have an equal angle between their optical axis 40A and the arrangement axis D direction, are arranged in the Y direction is defined as region R. In this case, it is preferable that the in-plane retardation (Re) value in each region R is half a wavelength, i.e., λ / 2. These in-plane retardations are calculated by the product of the refractive index difference Δn due to the refractive index anisotropy of region R and the thickness of the composition layer. Here, the refractive index difference due to the refractive index anisotropy of region R in the composition layer is defined as the refractive index difference between the refractive index in the direction of the slow axis within the plane of region R and the refractive index in the direction perpendicular to the direction of the slow axis. In other words, the refractive index difference Δn due to the refractive index anisotropy of region R is equal to the difference between the refractive index of the liquid crystal compound 40 in the direction of the optical axis 40A and the refractive index of the liquid crystal compound 40 in the direction perpendicular to the optical axis 40A within the plane of region R. That is, the refractive index difference Δn is equal to the refractive index difference of the liquid crystal compound 40.

[0057] In the composition layer, in the liquid crystal alignment pattern of such liquid crystal compound 40, the length (distance) of a 180° rotation of the optical axis 40A of the liquid crystal compound 40 in the direction of the array axis D, where the optical axis 40A rotates continuously and changes within the plane, is defined as the length of one period Λ in the liquid crystal alignment pattern. That is, the distance between the centers of two liquid crystal compounds 40 with the same angle to the direction of the array axis D, in the direction of the array axis D, is defined as the length of one period Λ. Specifically, as shown in Figure 1, the distance between the centers of two liquid crystal compounds 40 whose direction of the array axis D coincides with the direction of the optical axis 40A, is defined as the length of one period Λ. In the following explanation, this length of one period Λ will also be referred to as "period Λ". The liquid crystal alignment pattern of the composition layer repeats this period Λ in one direction, i.e., the direction of the optical axis 40A rotates continuously and changes.

[0058] As described later, a composition layer 12 having a liquid crystal alignment pattern in which the orientation of the optical axis 40A derived from the liquid crystal compound 40 changes while continuously rotating along at least one direction in the plane is formed, for example, by forming a composition layer having a liquid crystal compound on the surface of an alignment film that is oriented in a predetermined pattern.

[0059] In the example shown in FIG. 1, the liquid crystal alignment pattern of the composition layer has the alignment axis D existing along one direction in the plane, and the optical axis 40A of the liquid crystal compound 40 continuously rotates in one direction along the alignment axis D direction. However, the liquid crystal alignment pattern is not limited to this, and various configurations can be used as long as the optical axis 40A of the liquid crystal compound 40 continuously rotates along at least one direction.

[0060] For example, the composition layer may have a configuration having a radial liquid crystal alignment pattern. FIG. 2 is a plan view conceptually showing another example of the liquid crystal alignment pattern possessed by the composition layer. In the composition layer 12c shown in FIG. 2, the direction of the optical axis of the liquid crystal compound 40 changes while continuously rotating along a number of directions from the center of the composition layer 12c to the outside, for example, the directions indicated by the arrows A １ shown by, the arrow A ２ shown by, the arrow A ３ shown by... That is, the arrow A １ , A ２ and A ３ are the alignment axes.

[0061] Further, as shown in FIG. 2, the optical axis of the liquid crystal compound 40 changes while rotating in the same direction from the center of the composition layer 12c to the outside. The mode shown in FIG. 2 is a counterclockwise alignment. The rotation direction of the optical axis that rotates and changes along each of the arrows A １ , A ２ and A ３ in FIG. 2 is counterclockwise as it goes from the center to the outside.

[0062] (Inclination of the light part and the dark part) The composition layer is characterized in that in a cross section including one direction (the alignment axis D direction shown in FIG. 1) and the thickness direction in which the optical axis 40A of the composition layer observed by an atomic force microscope (AFM) continuously rotates and changes, the light part and the dark part derived from the optical axis of the liquid crystal compound are inclined with respect to the main surface of the composition layer.

[0063] Using Figure 3, a cross-section of a composition layer including a unidirectional direction in which the optical axis derived from the liquid crystal compound changes while continuously rotating, and a thickness direction, will be described. Figure 3 is a conceptual cross-sectional view showing an example of a composition layer for explaining step 2. In the following description, the image obtained by observing the cross-section of the composition layer including the direction of the array axis D and the thickness direction, that is, the cross-section obtained by cutting the composition layer along the unidirectional direction in which the optical axis changes while continuously rotating and the thickness direction, using AFM, will also simply be referred to as a "cross-sectional image". The composition layer 12 shown in Figure 3 has the same configuration as the composition layer 12 shown in Figure 1, except that the liquid crystal compound 40 is torsionally oriented along a helical axis extending along the thickness direction indicated by arrow Z in the figure. That is, when the composition layer 12 shown in Figure 3 is observed from the thickness direction, the orientation of the optical axis 40A changes while continuously rotating along the array axis D within the plane of the composition layer 12, similar to the example shown in Figure 1. Also, in Figure 3, arrow T Ｃ The thickness T of the composition Ｃ This indicates.

[0064] Furthermore, as shown in Figure 3, in the cross-sectional image of the composition layer 12 formed in step 1, including the direction of the array axis D and the thickness direction, bright areas 42 and dark areas 44 that are inclined with respect to the main surfaces 12a and 12b of the composition layer 12 can be observed. The striped pattern consisting of the bright areas 42 and dark areas 44 originates from a torsional structure in which the liquid crystal compound 40 is twisted and oriented along a helical axis extending along the thickness direction. The inventors considered that in the composition layer 12 before step 2, in which bright areas 42 and dark areas 44 that are inclined with respect to the main surfaces 12a and 12b are observed in the cross-sectional image including the direction of the array axis D and the thickness direction, the orientation of the liquid crystal compound is stabilized by the liquid crystal compound 40 being further inclined and oriented with respect to the main surfaces 12a and 12b.

[0065] In this specification, "the bright and dark areas originating from the optical axis of the liquid crystal compound are inclined with respect to the main surface of layer 14" means that, in the cross-sectional image of the composition layer observed by AFM, the center O1 of line segment L1, which is the intersection line of one main surface 12a and the bright area 42, and the center O2 of line segment L2, which is the intersection line of the other main surface 12b and the bright area 42, are derived, and the angle θ (hereinafter also referred to as "bright line inclination angle θ") between the straight line L connecting these centers O1 and O2 and the main surface 12a (or 12b) of the composition layer is within the range of 0° or more and less than 85°.

[0066] The bright fringe inclination angle θ in the cross-sectional image of the composition layer after step 1 and before step 2 is preferably 60° or less in terms of superior orientation, more preferably 30° or less, and even more preferably 20° or less in terms of fewer defects in the liquid crystal alignment pattern. Furthermore, a bright fringe inclination angle θ greater than 5° is preferable.

[0067] With respect to the torsional orientation along the helical axis extending in the thickness direction of the liquid crystal compound 40, the total rotation angle from the liquid crystal compound 40 present on one main surface side of the composition layer 12 to the liquid crystal compound 40 present on the other main surface side can be selected according to the thickness Tc of the composition layer 12 and the bright line inclination angle θ, but it is preferably 360° or less.

[0068] Thus, one method for creating a composition layer in which the bright and dark areas in the cross-sectional image are inclined with respect to the main surface, or in other words, a configuration in which the liquid crystal compound is torsionally oriented, is to form the composition layer using a composition containing a chiral agent.

[0069] As described above, this manufacturing method involves a step 1 to form a composition layer having a liquid crystal alignment pattern in which the orientation of the optical axis derived from the liquid crystal compound changes while continuously rotating along at least one direction in the plane, and in a cross-section of the composition layer including the above-mentioned one direction and thickness direction, the bright and dark areas derived from the optical axis of the liquid crystal compound are inclined with respect to the main surface of the composition layer; then, a step 2 to bring the bright and dark areas closer to a direction perpendicular to the main surface of the composition layer; and a step 3 to cure the composition layer. As a result, even when forming a liquid crystal layer with a thickness greater than conventional methods, the orientation of the formed liquid crystal compound is stabilized, resulting in a liquid crystal layer with fewer defects and a liquid crystal alignment pattern with suppressed orientation disorder.

[0070] In this manufacturing method, the thickness T of the composition layer formed in step 1 is determined. Ｃ The ratio T of the liquid crystal alignment pattern to one period Λ Ｃ / Λ represents the thickness T of the liquid crystal layer, which will be described later. Ｌ The ratio T of the liquid crystal alignment pattern to one period Λ Ｌ It is preferable that the range is the same as the preferred range of / Λ.

[0071] The thickness of the composition layer and the liquid crystal layer can be measured from a cross-sectional image obtained by observing the cross-section, which is obtained by cutting along the thickness direction with a microtome, using an AFM (atomic force microscope).

[0072] The procedure for step 1, which involves forming the above-mentioned composition layer, will be described in detail below.

[0073] (Procedure for Step 1) Step 1 involves forming a composition layer containing the above-mentioned components, but the procedure is not particularly limited. For example, one method involves coating a composition containing the above-mentioned chiral agent and liquid crystal compound having polymerizable groups, and subjecting it to heat treatment and drying treatment as necessary (hereinafter also simply referred to as the "coating method"), and another method involves forming a separate composition layer and transferring it to a substrate. From the viewpoint of productivity, the coating method is preferred. The composition layer can be manufactured, for example, by coating a composition containing a liquid crystal compound having polymerizable groups and a chiral agent onto the surface of an alignment film for aligning the liquid crystal compound to a predetermined liquid crystal alignment pattern, thereby forming a liquid crystal phase oriented to a liquid crystal alignment pattern in which the orientation of the optical axis derived from the liquid crystal compound changes while continuously rotating along at least one direction in the plane, and then curing it.

[0074] -Substrate- In step 1, it is preferable to form a composition layer on the surface of the substrate. Various sheet-like, film-like, or plate-like materials can be used as the substrate, as long as they can support the composition layer. The substrate preferably has a transmittance of 50% or more for diffracted light, more preferably 70% or more, and even more preferably 85% or more.

[0075] There are no restrictions on the thickness of the substrate; the thickness should be appropriately set to support the composition layer, depending on the application of the liquid crystal layer to be manufactured and the substrate forming material. The substrate thickness is preferably 1 to 1000 μm, more preferably 3 to 250 μm, and even more preferably 5 to 150 μm.

[0076] The substrate may be single-layer or multi-layer. Examples of single-layer substrates include those made of glass, triacetylcellulose (TAC), polyethylene terephthalate (PET), polycarbonate, polyvinyl chloride, acrylic, and polyolefin. Examples of multi-layer substrates include those that include one of the aforementioned single-layer substrates as the substrate, with other layers provided on the surface of this substrate.

[0077] - Alignment film - Preferably, an alignment film is formed on the surface of the substrate to orient the liquid crystal compound into a predetermined liquid crystal alignment pattern. As described above, the composition layer formed in step 1 has a liquid crystal alignment pattern in which the orientation of the optical axis 40A (see Figure 1) derived from the liquid crystal compound 40 changes while continuously rotating along one direction in the plane. Therefore, the alignment film is formed so that the composition layer can form this liquid crystal alignment pattern. In the following description, "the orientation of the optical axis 40A rotates" will also simply be referred to as "the optical axis 40A rotates".

[0078] Various known orientation films are available. Examples include rubbing films made of organic compounds such as polymers, obliquely deposited films of inorganic compounds, films having microgrooves, and films formed by accumulating Langmuir-Blodgett (LB) films of organic compounds such as ω-tricosanoic acid, dioctadecylmethylammonium chloride, and methyl stearylate using the Langmuir-Blodgett method.

[0079] The aligning film formed by rubbing can be created by rubbing the surface of the polymer layer several times in a certain direction with paper or cloth. Preferred materials for the aligning film include polyimide, polyvinyl alcohol, polymers having polymerizable groups as described in Japanese Patent Publication No. 9-152509, materials used for forming the aligning film 32 as described in Japanese Patent Publication No. 2005-97377, Japanese Patent Publication No. 2005-99228, and Japanese Patent Publication No. 2005-128503.

[0080] The alignment film is preferably a so-called photo-alignment film, which is formed by irradiating a photo-alignable material with polarized or unpolarized light. In other words, a photo-alignment film formed by coating a photo-alignment material onto a substrate is preferably used as the alignment film. Irradiation with polarized light can be performed perpendicular or oblique to the photo-alignment film, and irradiation with unpolarized light can be performed obliquely to the photo-alignment film.

[0081] Examples of photo-alignment materials used in the alignment film applicable to the present invention include those described in Japanese Patent Publication No. 2006-285197, Japanese Patent Publication No. 2007-76839, Japanese Patent Publication No. 2007-138138, Japanese Patent Publication No. 2007-94071, Japanese Patent Publication No. 2007-121721, Japanese Patent Publication No. 2007-140465, Japanese Patent Publication No. 2007-156439, and Japanese Patent Publication No. 2007 - Azo compounds described in Japanese Patent Publication No. 133184, Japanese Patent Publication No. 2009-109831, Japanese Patent Publication No. 3883848 and Japanese Patent Publication No. 4151746, aromatic ester compounds described in Japanese Patent Publication No. 2002-229039, maleimides having photo-orienting units described in Japanese Patent Publication No. 2002-265541 and Japanese Patent Publication No. 2002-317013 and Alternatively, alkenyl-substituted nadiimide compounds, photocrosslinkable silane derivatives described in Japanese Patent No. 4205195 and Japanese Patent No. 4205198, photocrosslinkable polyimides, photocrosslinkable polyamides and photocrosslinkable polyesters described in Japanese Patent Publication No. 2003-520878, Japanese Patent Publication No. 2004-529220 and Japanese Patent No. 4162850, and photodimerizable compounds described in Japanese Patent Publication No. 9-118717, Japanese Patent Publication No. 10-506420, Japanese Patent Publication No. 2003-505561, International Publication No. 2010 / 150748, Japanese Patent Publication No. 2013-177561 and Japanese Patent Publication No. 2014-12823, particularly cinnamate compounds, chalcone compounds and coumarin compounds, are exemplified as preferred examples. Among these, azo compounds, photocrosslinkable polyimides, photocrosslinkable polyamides, photocrosslinkable polyesters, cinnamate compounds, and chalcone compounds are particularly suitable for use.

[0082] There are no restrictions on the thickness of the orientation film; the thickness should be appropriately set to obtain the necessary orientation function depending on the material used to form the orientation film. The thickness of the orientation film is preferably 0.01 to 5 μm, and more preferably 0.05 to 2 μm.

[0083] There are no limitations on the method for forming the alignment film, and various known methods depending on the material used to form the alignment film can be used. As an example, one method involves coating the alignment film onto the surface of a substrate, drying it, and then exposing the alignment film with laser light to form an alignment pattern.

[0084] Figure 4 conceptually shows an example of an exposure apparatus for exposing an alignment film to form an alignment pattern. The exposure apparatus 60 shown in Figure 4 comprises a light source 64 equipped with a laser 62, a λ / 2 plate 65 that changes the polarization direction of the laser light M emitted by the laser 62, a beam splitter 68 that separates the laser light M emitted by the laser 62 into two rays MA and MB, mirrors 70A and 70B positioned on the optical paths of the two separated rays MA and MB, respectively, and λ / 4 plates 72A and 72B. The light source 64 emits linearly polarized light P0. The λ / 4 plate 72A converts the linearly polarized light P0 (ray MA) into right-circularly polarized light P R λ / 4 plate 72B converts linearly polarized light P0 (light ray MB) to left-circularly polarized light P L Convert them to the following:

[0085] A substrate 30 having an alignment film 32 before the alignment pattern is formed is placed in the exposure section, and two light rays MA and MB are intersected and interfered with on the alignment film 32, and the resulting interfered light is irradiated onto the alignment film 32 for exposure. Due to this interference, the polarization state of the light irradiated onto the alignment film 32 changes periodically in an interference fringe pattern. As a result, an alignment film having an alignment pattern in which the alignment state changes periodically (hereinafter also referred to as a patterned alignment film) is obtained. In the exposure apparatus 60, the period of the alignment pattern can be adjusted by changing the intersection angle α of the two light rays MA and MB. That is, in the exposure apparatus 60, by adjusting the intersection angle α, the length of one period in which the optical axis 40A rotates 180° in one direction in an alignment pattern in which the optical axis 40A derived from the liquid crystal compound 40 rotates continuously along one direction can be adjusted. By forming a composition layer on an alignment film 32 having an alignment pattern in which such an alignment state changes periodically, a composition layer can be formed having a liquid crystal alignment pattern in which the optical axis 40A derived from the liquid crystal compound 40 rotates continuously along one direction. Furthermore, the direction of rotation of the optical axis 40A can be reversed by rotating the optical axes of the λ / 4 plates 72A and 72B by 90°, respectively.

[0086] As described above, the pattern alignment film has an orientation pattern that aligns liquid crystal compounds such that the orientation of the optical axis of the liquid crystal compounds in the composition layer formed on the pattern alignment film changes while continuously rotating along at least one direction in the plane. If the orientation axis of the pattern alignment film is the axis along the direction in which the liquid crystal compounds are oriented, then the pattern alignment film can be said to have an orientation pattern in which the orientation axis changes while continuously rotating along at least one direction in the plane. The orientation axis of the pattern alignment film can be detected by measuring absorption anisotropy. For example, when linearly polarized light is irradiated onto the pattern alignment film while rotating, and the amount of light transmitted through the pattern alignment film is measured, the direction in which the amount of light is maximum or minimum is observed to gradually change along one direction in the plane.

[0087] In this manufacturing method, the alignment film is provided as a preferred embodiment and is not an essential component. For example, by forming an alignment pattern on the substrate by a method such as rubbing the substrate or processing the substrate with laser light, the composition layer can be configured to have a liquid crystal alignment pattern in which the orientation of the optical axis 40A derived from the liquid crystal compound 40 changes while continuously rotating along at least one direction in the plane. In other words, in the present invention, the substrate may be used as the alignment film.

[0088] Furthermore, in this manufacturing method, the alignment layer may be a liquid crystal-containing layer having a liquid crystal alignment pattern in which the orientation of the optical axis derived from the liquid crystal compound changes while continuously rotating along at least one direction in the plane. The liquid crystal alignment pattern of this liquid crystal-containing layer acts as an alignment layer on the composition layer formed thereon, and the liquid crystal compound contained in the composition layer is properly aligned. The liquid crystal compound contained in the liquid crystal compound layer used as the alignment layer may be the same as or different from the liquid crystal compound contained in the composition layer formed in step 1. In addition, the liquid crystal compound layer may contain a chiral agent, and the chiral agent contained in the liquid crystal compound layer may be the same as or different from the chiral agent contained in the composition layer formed in step 1.

[0089] -Formation of the Composition Layer- The method for forming a composition layer on the surface of the substrate and the alignment film by a coating method will be described in more detail below. The composition used to form the composition layer (hereinafter also referred to as "Composition A") includes the chiral agent, the liquid crystal compound having polymerizable groups, and other components used as needed (for example, polymerization initiators, polymerizable monomers, surfactants, polymers, and leveling agents). It is preferable that the content of each component in Composition A is adjusted to match the content of each component in the composition layer described above.

[0090] The coating method is not particularly limited and includes, for example, wire bar coating, extrusion coating, direct gravure coating, reverse gravure coating, and die coating. If necessary, a drying process may be performed on the coating film applied to the substrate after coating composition A. This drying process removes the solvent from the coating film. The thickness of the coating film is not particularly limited, and T is the thickness of the composition layer, which is the coating film after drying. ｃ It is preferable that the thickness be adjusted as appropriate so that it becomes the preferred thickness described later.

[0091] - Heat Treatment - In step 1, it is preferable to heat treat the coating film containing the chiral agent and the liquid crystal compound having polymerizable groups. By heat treating, a liquid crystal orientation pattern is formed in the in-plane direction in which the liquid crystal compound changes while continuously rotating along at least one direction within the plane. In the thickness direction, in response to the helical induced force of the chiral agent, the liquid crystal compound becomes twisted and oriented along a helical structure extending in the thickness direction, resulting in a cross-sectional image in which the light and dark areas are inclined with respect to the main plane.

[0092] The optimal conditions for the heat treatment are selected according to the liquid crystal compound and chiral agent used. In particular, the heating temperature is often 10 to 250°C, more often 40 to 150°C, and even more often 50 to 130°C. The heating time is often 0.1 to 60 minutes, more often 0.2 to 5 minutes.

[0093] The orientation of the liquid crystal compound in the composition layer obtained by step 1, particularly the orientation of the liquid crystal compound in the thickness direction, changes depending on the helical induced force of the chiral agent contained in composition A. Preferred embodiments of the chiral agent contained in composition A will be described in detail in step 2.

[0094] <Step 2> Step 2 is a step in which the helical induced force of the chiral agent contained in the composition layer obtained in Step 1 is changed, and the bright and dark areas originating from the liquid crystal compound in the cross-sectional image observed by AFM are brought closer to a direction perpendicular to the main surface of the composition layer.

[0095] Using Figure 5, a cross-section of the composition layer, including the direction of the alignment axis D and the thickness direction, after carrying out step 2 will be explained. Figure 5 is a conceptual cross-sectional view showing an example of a composition layer for explaining step 2, and conceptually shows a cross-sectional image of the composition layer after carrying out step 2. Step 2 changes the helical induced force of the chiral agent contained in the composition layer, and as a result of the change in the orientation state of the liquid crystal compound due to the changed helical induced force, the bright areas 42 and dark areas 44 in the cross-sectional image approach directions perpendicular to the main surfaces 14a and 14b, and a composition layer 14 is obtained in which the bright areas 42 and dark areas 44 are substantially perpendicular to the main surfaces 14a and 14b, as shown in Figure 5. In this specification, "substantially perpendicular" means in the range of 90° ± 5°. That is, with respect to step 2, "the bright areas and dark areas originating from the optical axis of the liquid crystal compound are substantially perpendicular to the main surface of the composition layer" means that the angle between the bright areas and dark areas and the main surface of the composition layer is 85 to 95°.

[0096] Here, step 2 will be explained using the example of a case where the composition layer formed in step 1 contains a chiral agent A whose helical induced force can be changed by light irradiation treatment, and also contains a chiral agent B1 that induces a helix in the opposite direction to that of chiral agent A by the heat treatment in step 1. As shown in Figure 3, in the composition layer 12 formed in step 1, the liquid crystal compound 40 is twisted and oriented along a helical axis extending in the thickness direction due to the helical induced force of chiral agent B1, and the light areas 42 and dark areas 44 are inclined with respect to the main surfaces 12a and 12b. When light irradiation treatment is performed on such a composition layer 12 as step 2, the helical induced force of chiral agent A changes. Along with the change in the helical induced force of chiral agent A, the orientation state of the liquid crystal compound changes according to the weighted average helical induced forces of chiral agent A and chiral agent B1. As a result, the liquid crystal compound does not twist or align along the helical axis extending in the thickness direction, and the composition layer 14 becomes such that the bright areas 42 and dark areas 44 observed in the cross-sectional image are closer to the direction perpendicular to the main surfaces 14a and 14b of the composition layer 14.

[0097] Here, the weighted average helical induced force of chiral agents is the sum of the values ​​obtained by dividing the product of the helical induced force of each chiral agent contained in the composition layer and the concentration (mass%) of each chiral agent in the composition layer by the total concentration (mass%) of the chiral agents in the composition layer, when two or more chiral agents are contained in the composition layer. For example, when two types of chiral agents (chiral agent X and chiral agent Y) are used in combination, it is expressed by the following formula (Y). Formula (Y) Weighted average helical induced force (μm －１ ) = (Helical induced force of chiral agent X (μm) －１ ) × Concentration of chiral agent X in the composition layer (mass%) + helical induced force of chiral agent Y (μm) －１ ) × Concentration of chiral agent Y in the composition layer (mass%) / (Concentration of chiral agent X in the composition layer (mass%) + Concentration of chiral agent Y in the composition layer (mass%)) However, in the above formula (Y), if the helical direction of the chiral agent is right-handed, its helical induced force shall be a positive value. Also, if the helical direction of the chiral agent is left-handed, its helical induced force shall be a negative value. That is, for example, if the helical induced force is 10 μm －１ In the case of the chiral agent, if the helical direction of the helix induced by the above chiral agent is right-handed, the helical induction force is 10 μm－１ This is expressed as follows. On the other hand, if the helical direction of the helix induced by the above chiral agent is left-handed, the helical induction force is -10 μm －１ It is expressed as follows.

[0098] For example, in the above example, if chiral agent A and chiral agent B1 are present in the composition layer 12 at the same concentration, and the helical direction induced by chiral agent A and the helical direction induced by chiral agent B1 are in opposite directions, then by performing a light irradiation treatment until the absolute value of the helical induced force of chiral agent A becomes equal to the absolute value of the helical induced force of chiral agent B1, a composition layer 14 is obtained in which the bright areas 42 and dark areas 44 observed in the cross-sectional image are substantially perpendicular to the main surfaces 14a and 14b.

[0099] In step 2, the treatment to change the helical induced force of the chiral agent is selected according to the type of chiral agent contained in the composition layer whose helical induced force can be changed. Examples of such treatments include light irradiation, heat treatment, and acid treatment, with light irradiation being preferred. That is, in step 2, it is preferable to perform light irradiation on the composition layer containing chiral agent A whose helical induced force can be changed by light irradiation, thereby changing the helical induced force of chiral agent A.

[0100] The light used for irradiation can be any light that the chiral agent A is sensitive to. In other words, the light used for irradiation is not particularly limited as long as it is an active light or radiation that changes the helical induced force of the chiral agent A. Examples include the emission line spectrum of a mercury lamp, far ultraviolet light represented by an excimer laser, extreme ultraviolet light, X-rays, ultraviolet light, and electron beams. Of these, ultraviolet light is preferred.

[0101] The irradiation intensity of the above light irradiation treatment is not particularly limited and can be appropriately determined based on the helical induced force of chiral agent A. The amount of light irradiation is not particularly limited, but 300 mJ / cm is preferred for easier formation of the predetermined composition layer. ２ The following is preferable: 200 mJ / cm ２ The following is more preferable. As a lower limit, 10 mJ / cm is preferable in terms of how easily the predetermined composition layer is formed. ２ The above is preferable, and 30 mJ / cm ２The above is more preferable. Furthermore, the light irradiation treatment is preferably carried out at 15 to 70°C (preferably 15 to 50°C).

[0102] In the above example, a composition layer was shown containing chiral agent A and chiral agent B1, which induces a helix in the opposite direction to that of chiral agent A by the heat treatment in step 1. However, the chiral agents included in the composition layer are not limited to the above example. For example, two or more chiral agents A with different wavelengths of light that change the helical induction force may be used. In step 1, light of a wavelength that changes the helical induction force of at least one of the chiral agents A may be irradiated, and in step 2, light of a wavelength that changes the helical induction force of the remaining chiral agent A may be irradiated. Alternatively, a chiral agent A with a high initial helical induction force and a decrease in helical induction force due to light irradiation may be used alone. In the composition layer formed in step 1, the liquid crystal compound may be twisted and oriented, and the helical induction force may be reduced by the light irradiation treatment in step 2, bringing the bright and dark areas closer to a direction perpendicular to the main surface. Alternatively, the chiral agent A and a chiral agent whose helical induced force can be changed by heat treatment may be used, and in step 1, light of a wavelength that changes the helical induced force of the chiral agent A is irradiated, and in step 2, heat treatment is performed.

[0103] Furthermore, when using two or more chiral agents, the concentration and helical induced force of the chiral agents in the composition layer are not particularly limited, as long as the weighted average helical induced force of the chiral agents is adjusted in step 2 so that the light and dark areas approach a direction perpendicular to the main surface. They may be the same or different for each chiral agent. From the above viewpoint, the absolute value of the weighted average helical induced force of the chiral agents in the composition layer after carrying out step 2 is 0.0 to 1.9 μm. －１ Preferably, 0.0 to 1.5 μm －１ More preferably, 0.0 to 1.0 μm －１ More preferably, 0.0 to 0.5 μm －１ This is particularly preferable, and zero is most preferable.

[0104] Furthermore, the absolute value of the difference in the weighted average helical induced force of the chiral agent contained in the composition layer before and after step 2 is not particularly limited, but is 0.05 μm. －１ The above is preferable, with a range of 0.05 to 10.0 μm.－１ More preferably, 0.1 to 10.0 μm －１ That is even more preferable.

[0105] In this manufacturing method, as a chiral agent used and a treatment to change the helical induced force of the chiral agent in step 2, as in the example described above, a chiral agent A whose helical induced force changes with light irradiation and a chiral agent B1 which induces a helix in the opposite direction to that of chiral agent A with heat treatment is used, and in step 1, only the helical induced force of chiral agent B1 is exerted by heat treatment to form a composition layer in which the light and dark areas are inclined with respect to the main surface, and in step 2, the helical induced force of chiral agent A is exerted by light irradiation treatment is particularly preferred.

[0106] Furthermore, the process of changing the helical induced force of the chiral agent in step 2 is preferably carried out under conditions that hinder the polymerization of the polymerizable liquid crystal compound contained in the composition layer. As an example of the above, a method is used in which the composition layer is irradiated with light in an atmosphere with an oxygen concentration of 1 volume% or more to change the helical induced force of the chiral agent A. When the oxygen concentration is high, the polymerization of the liquid crystal compound is inhibited by oxygen, thus suppressing the progression of polymerization by light irradiation. In terms of further suppressing the progression of polymerization of the liquid crystal compound, an oxygen concentration of 2 volume% or more is preferred, and 5 volume% or more is more preferred. There is no particular upper limit, but 100 volume% is an example.

[0107] Another example of a method to hinder the polymerization of liquid crystal compounds is to use a combination of chiral agent A and a photopolymerization initiator, each having different optimal wavelength ranges, and to irradiate the compound with light of different wavelengths in steps 2 and 3.

[0108] The viscosity of the composition layer to be processed in step 2 is, for example, 2 Pa·s or more, preferably 10 Pa·s or more, and more preferably 30 Pa·s or more, in that it reduces defects in the liquid crystal alignment pattern. There is no particular upper limit to the viscosity of the composition layer, but it is more preferable to be 200 Pa·s or less in that it shortens the time required for alignment. The viscosity of the composition layer is the viscosity of the composition layer at the temperature at which step 2 is performed, that is, the temperature at which the process to change the helical induced force of the chiral agent contained in the composition layer obtained in step 1 is performed. The method for measuring the viscosity of the composition layer will be described in detail in the examples below. The viscosity of the composition layer can be adjusted by the type and content of components such as liquid crystal compounds and chiral agents contained in the composition layer.

[0109] In step 2, the composition layer may be subjected to heat treatment. Heat treatment makes the orientation state of the liquid crystal compound more susceptible to change due to the change in the helical induced force of the chiral agent A. The heat treatment may be performed during or after the treatment that changes the helical induced force of the chiral agent (such as light irradiation). The optimal conditions for the heat treatment are selected according to the liquid crystal compound used. The heating temperature is often 30 to 250°C, and more often 35 to 150°C. When heat treatment is performed after the treatment that changes the helical induced force of the chiral agent, the heating time is often 0.01 to 60 minutes, and more often 0.03 to 5 minutes.

[0110] The angle of light fringe inclination θ in the cross-sectional image of the composition layer after step 2 should be closer to 90° than the angle of light fringe inclination θ before step 2. The angle of light fringe inclination θ in the cross-sectional image of the composition layer after step 2 is preferably 50 to 90°, more preferably 80 to 90°, and even more preferably 85 to 90°.

[0111] <Step 3> Step 3 is a process in which, after Step 2, a curing treatment is applied to the composition layer to fix the orientation state of the liquid crystal compound and form a liquid crystal layer.

[0112] The curing method is not particularly limited and is appropriately selected depending on the type of polymerization initiator contained in the composition layer. Examples of curing methods include photocuring and thermocuring, of which photocuring is preferred, and ultraviolet irradiation is more preferred. For ultraviolet irradiation, a light source such as an ultraviolet lamp is used. The amount of light (e.g., ultraviolet) irradiated is not particularly limited, but is 100 to 800 mJ / cm². ２ A certain degree is preferable. The atmosphere during light irradiation is not particularly limited; light irradiation may be carried out in air or in an inert atmosphere. In particular, it is preferable that light irradiation be carried out at an oxygen concentration of less than 1 volume percent.

[0113] When photocuring is performed as the curing treatment, the temperature conditions during photocuring are not particularly limited and should be such that the orientation state of the liquid crystal compound after step 2 is maintained. If heat treatment is performed in step 2, it is preferable that the temperature of the heat treatment and the temperature of the photocuring treatment are the same, or that the temperature of the photocuring treatment is lower than the temperature of the heat treatment.

[0114] In the liquid crystal layer obtained by curing treatment, the orientation state of the liquid crystal compound is fixed. While the most typical and preferred embodiment of "fixed" is a state in which the orientation of the liquid crystal compound is maintained, it is not limited to this. Specifically, when the orientation state of the liquid crystal compound is fixed, it is more preferable that the layer is non-fluid at temperatures typically between 0 and 50°C, and under more severe conditions between -30 and 70°C, and that the fixed orientation state can be stably maintained without being altered by external fields or forces. It is not necessary for the liquid crystal compound in the liquid crystal layer to exhibit liquid crystalline properties. Known methods can be used to determine the orientation state of the liquid crystal compound. For example, one method involves observing a cross-section of the liquid crystal layer with a polarizing microscope to determine the orientation state of the liquid crystal compound.

[0115] The liquid crystal layer manufactured by the above method has a liquid crystal alignment pattern, and when circularly polarized light is incident on the liquid crystal layer, the light is refracted and the direction of the circular polarization is changed. This effect is conceptually shown in Figures 6 and 7. Figures 6 and 7 are conceptual diagrams to explain the effect of the liquid crystal alignment pattern. It is assumed that the liquid crystal layer has a product of the refractive index difference of the liquid crystal compound and the thickness of the liquid crystal layer of λ / 2. As shown in Figure 6, the refractive index difference of the liquid crystal compound 40 of the liquid crystal layer 16 and the thickness T of the liquid crystal layer 16. Ｌ When the product of the two values ​​is λ / 2, the incident light L, which is left-circularly polarized, enters the liquid crystal layer 16. １ When incident light L １ By passing through the liquid crystal layer 16, a phase difference of 180° is given, and the transmitted light L ２ This is converted to right-circular polarization. Also, since the liquid crystal alignment pattern formed in the liquid crystal layer 16 is a periodic pattern in the direction of the array axis D, the transmitted light L ２ is the incident light L １ It travels in a direction different from the direction of propagation. In this way, the incident light L is left-circularly polarized. １ This refers to transmitted light L, which is right-circularly polarized and tilted at a certain angle in the direction of the array axis D relative to the direction of incidence. ２ It is converted to the transmitted light L shown in the example in Figure 6. ２ The light is diffracted so that it propagates downwards and to the right.

[0116] On the other hand, as shown in Figure 7, the refractive index difference of the liquid crystal compound 40 in the liquid crystal layer 16 and the thickness T of the liquid crystal layer 16 Ｌ When the product of the two values ​​is λ / 2, right-circularly polarized incident light L enters the liquid crystal layer 16. ４ When incident light L ４ By passing through the liquid crystal layer 16, a phase difference of 180° is given, resulting in the transmission of left-circularly polarized light L. ５ It is converted to [this]. Also, since the liquid crystal alignment pattern formed on the liquid crystal layer 16 is a periodic pattern in the direction of the array axis D, the transmitted light L ５ is the incident light L ４ It travels in a direction different from the direction of travel. In this case, transmitted light L ５ is transmitted light L ２ It travels in a different direction, that is, in the opposite direction to the direction of the arrow on the array axis D relative to the direction of incidence. In this way, the incident light L ４This is transmitted light L, which is left-circularly polarized and tilted at a certain angle in the direction opposite to the array axis D relative to the incident direction. ５ It is converted to the transmitted light L shown in the example in Figure 7. ５ The light is diffracted so that it propagates downwards and to the left.

[0117] The liquid crystal layer 16 transmits light L depending on the length of one period Λ of the formed liquid crystal alignment pattern. ２ and L ５ The angle of refraction can be adjusted. Specifically, the shorter the period Λ of the liquid crystal alignment pattern in the liquid crystal layer 16, the stronger the interference between light passing through adjacent liquid crystal compounds 40, so the transmitted light L ２ and L ５ It can significantly refract light.

[0118] Furthermore, by reversing the direction of rotation of the optical axis of the liquid crystal compound 40, which rotates along the array axis D, the direction of refraction of transmitted light can be reversed. That is, in the examples shown in Figures 6 and 7, the direction of rotation of the optical axis toward the array axis D is clockwise, but by changing this direction of rotation to counterclockwise, the direction of refraction of transmitted light can be reversed. Specifically, in Figures 6 and 7, when the direction of rotation of the optical axis toward the array axis D is counterclockwise, left-circularly polarized light incident on the liquid crystal layer from the top in the figure is converted to right-circularly polarized light upon passing through the liquid crystal layer and is diffracted to propagate in the lower left direction in the figure. Also, right-circularly polarized light incident on the liquid crystal layer from the top in the figure is converted to left-circularly polarized light upon passing through the liquid crystal layer and is diffracted to propagate in the lower right direction in the figure.

[0119] The bright line inclination angle θ in the cross-sectional image of the liquid crystal layer produced by this manufacturing method is preferably 50 to 90°, more preferably 80 to 90°, and even more preferably 85 to 90°.

[0120] The thickness T of the liquid crystal layer manufactured by this manufacturing method. Ｌ Preferably, the length Λ over which the orientation of the optical axis originating from the liquid crystal compound in the liquid crystal alignment pattern rotates 180° along one direction satisfies the following equation (1). Ｌ / Λ ≥ 1 / 2 (1) Thickness T of the liquid crystal layer ＬThe ratio T of the liquid crystal alignment pattern to one period Λ Ｌ The reason is that by satisfying equation (1), it is not necessary to repeatedly perform a series of processes including the formation and curing of the composition layer, or at least the number of repetitions can be reduced, thereby improving the production efficiency of the optical element. From the above viewpoint, ratio T Ｌ The ratio T is preferably 1 / 2 or greater, and more preferably 1 or greater. Ｌ There is no particular upper limit to / Λ; for example, it may be 5 or less, or 3 or less.

[0121] The liquid crystal layer preferably exhibits inverse wavelength dispersion. That is, it is preferable that the in-plane retardation Re(450) measured at a wavelength of 450 nm of the liquid crystal layer, the in-plane retardation Re(550) measured at a wavelength of 550 nm of the liquid crystal layer, and the in-plane retardation Re(650) measured at a wavelength of 650 nm of the liquid crystal layer satisfy the relationship Re(450) ≤ Re(550) ≤ Re(650).

[0122] The optical properties of the liquid crystal layer are not particularly limited, but it is preferable that it functions as a λ / 4 plate. A λ / 4 plate is a plate that has the function of converting linearly polarized light of a certain wavelength to circularly polarized light (or circularly polarized light to linearly polarized light), and refers to a plate (liquid crystal layer) in which the in-plane retardation Re(λ) at a specific wavelength λnm satisfies Re(λ) = λ / 4. This equation only needs to be achieved at any wavelength in the visible light range (for example, 550 nm), but it is preferable that the in-plane retardation Re(550) at a wavelength of 550 nm satisfies the relationship 110 nm ≤ Re(550) ≤ 180 nm.

[0123] [Applications] The liquid crystal layer produced by this manufacturing method can be used as an optical element. An example of an embodiment of the optical element is an optical element comprising a substrate, a polarizing film, and this liquid crystal layer in that order. The substrate and polarizing film have already been described. The optical element does not need to have at least one of the substrate and the polarizing film. In particular, the optical element is preferably a λ / 4 plate.

[0124] The liquid crystal layer produced by this manufacturing method can be combined with various components. For example, the liquid crystal layer may be combined with other optically anisotropic layers. That is, a laminate may be made that includes a substrate, the liquid crystal layer produced by the above manufacturing method, and other optically anisotropic layers. The laminate does not need to include a substrate. The other optically anisotropic layers are not particularly limited and include, for example, A plates (positive A plates and negative A plates) and C plates (positive C plates and negative C plates). Among these, C plates are preferred because they are easy to apply to various applications described later (for example, circular polarizers). The range of the absolute value of the retardation in the thickness direction of the C plate at a wavelength of 550 nm is not particularly limited, but 5 to 300 nm is preferred, and 10 to 200 nm is more preferred.

[0125] In this specification, A plates and C plates are defined as follows: There are two types of A plates: positive A plates and negative A plates. When the refractive index in the slow axis direction within the film plane (the direction in which the refractive index is maximum within the plane) is nx, the refractive index in the direction perpendicular to the slow axis within the plane is ny, and the refractive index in the thickness direction is nz, a positive A plate satisfies the relationship in equation (A1), and a negative A plate satisfies the relationship in equation (A2). Note that a positive A plate shows a positive value for Rth, and a negative A plate shows a negative value for Rth. Equation (A1) nx > ny ≈ nz Equation (A2) ny < nx ≈ nz Note that the above "≈" includes not only cases where the two are completely identical, but also cases where the two are substantially identical. "Substantially identical" means, for example, that when (ny - nz) × d (where d is the film thickness) is -10 to 10 nm, preferably -5 to 5 nm, it is included in "ny ≈ nz", and when (nx - nz) × d is -10 to 10 nm, preferably -5 to 5 nm, it is included in "nx ≈ nz". There are two types of C plates: positive C plates and negative C plates. A positive C plate satisfies the relationship in equation (C1), and a negative C plate satisfies the relationship in equation (C2). Note that a positive C plate shows a negative Rth value, and a negative C plate shows a positive Rth value. Equation (C1) nz > nx ≈ ny Equation (C2) nz < nx ≈ ny Note that the above "≈" includes not only cases where the two are completely identical, but also cases where the two are substantially identical. "Substantially identical" means, for example, that when (nx - ny) × d (where d is the thickness of the film) is 0 to 10 nm, preferably 0 to 5 nm, then "nx ≈ ny" is included.

[0126] The method for manufacturing the above-mentioned laminate is not particularly limited and known methods can be used. For example, one method is to laminate the liquid crystal layer obtained by this manufacturing method with another optically anisotropic layer (e.g., a C-plate) to obtain a laminate. As for the lamination method, another optically anisotropic layer prepared separately may be bonded onto the liquid crystal layer obtained by this manufacturing method, or a composition for forming another optically anisotropic layer may be applied onto the liquid crystal layer obtained by this manufacturing method to form another optically anisotropic layer.

[0127] Furthermore, the liquid crystal layer obtained by this manufacturing method may be combined with a polarizer. That is, a polarized liquid crystal layer may be made having a substrate, a liquid crystal layer manufactured by this manufacturing method, and a polarizer in that order. The polarized liquid crystal layer may have a liquid crystal layer, a substrate, and a polarizer in that order. Also, the polarized liquid crystal layer does not have to include a substrate.

[0128] A polarizer can be any material that has the function of converting natural light into a specific linearly polarized light, for example, an absorptive polarizer. There are no particular restrictions on the type of polarizer, and commonly used polarizers can be used, for example, iodine-based polarizers, dye-based polarizers using dichroic dyes, and polyene-based polarizers. Iodine-based polarizers and dye-based polarizers are generally made by adsorbing iodine or a dichroic dye onto polyvinyl alcohol and then stretching it. A protective film may be placed on one or both sides of the polarizer.

[0129] The method for manufacturing the polarized liquid crystal layer described above is not particularly limited and known methods can be used. For example, one method is to obtain a polarized liquid crystal layer by stacking the liquid crystal layer obtained by this manufacturing method with a polarizer.

[0130] The liquid crystal layer can be applied to various applications. For example, the liquid crystal layer can be suitably applied to a circular polarizer, and the liquid crystal layer with a polarizer can also be used as a circular polarizer. A circular polarizer having the above configuration can be suitably used for anti-reflection applications in image display devices such as liquid crystal displays (LCDs), plasma display panels (PDPs), electroluminescent displays (ELDs), and cathode ray tube displays (CRTs), and can improve the contrast ratio of the displayed light. For example, one embodiment is in which a circular polarizer is used on the light extraction surface side of an organic EL display device. In this case, ambient light is linearly polarized by the polarizing film, and then becomes circularly polarized after passing through the liquid crystal layer. When this is reflected by the metal electrode, the circular polarization state is reversed, and when it passes through the liquid crystal layer again, it becomes linearly polarized tilted 90° from the incident state, and reaches the polarizing film and is absorbed. As a result, the influence of ambient light can be suppressed.

[0131] In particular, the polarizer-equipped liquid crystal layer or polarizer-equipped laminate described above is preferably applied to an organic EL display device. That is, the polarizer-equipped liquid crystal layer or polarizer-equipped laminate is preferably placed on the organic EL panel of the organic EL display device and applied for anti-reflective purposes. An organic EL panel is a component in which a light-emitting layer or multiple organic compound thin films including a light-emitting layer are formed between a pair of electrodes, an anode and a cathode. In addition to the light-emitting layer, it may also have a hole injection layer, a hole transport layer, an electron injection layer, an electron transport layer, and a protective layer, and each of these layers may have other functions. Various materials can be used to form each layer.

[0132] The features of the present invention will be further described below with reference to examples and comparative examples. The materials, amounts used, proportions, processing content, and processing procedures shown in the following examples can be modified as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the specific examples shown below.

[0133] [Measurement Method] The physical properties of the composition layer and liquid crystal layer formed in each example were measured by the following method.

[0134] <Thickness> After embedding the sample containing the composition layer or liquid crystal layer prepared in each example with UV adhesive, the sample was cut using an ultramicrotome (Leica, UC7 model) to form a cross-section including the thickness direction. The cross-section was observed with an atomic force microscope (AFM) (Brker "SPM Dimension Icon") to obtain a cross-sectional image. The thickness of the composition layer or liquid crystal layer was measured from the obtained cross-sectional image.

[0135] <Angle of Bright Lines> Similar to the thickness measurement method described above, a sample embedded in UV adhesive was cut to form a cross-section that includes one direction (arrangement axis D direction) within the plane where the thickness direction and the orientation of the optical axis derived from the liquid crystal compound change while continuously rotating, and a cross-sectional image was obtained. The angle between the straight line connecting the center position of the bright area on one main plane and the center position of the bright area on the other main plane of the obtained cross-sectional image and the main plane of the composition layer was measured and defined as the angle of bright lines (°).

[0136] <Viscosity of the Composition Layer> The composition used to form the composition layer was placed in a petri dish, and the petri dish containing the composition was heated in a 120°C oven for 20 minutes to volatilize and remove the solvent from the composition, drying it out and obtaining a composition sample for viscosity measurement. Using a rheometer (Anton Paar, "MCR302"), viscosity measurement tests were performed under the following conditions, and the viscosity of the composition sample at each temperature when the temperature was lowered from 100°C to 25°C was measured. Of the obtained measurement results, the viscosity of the composition sample measured at the same temperature as when step 2 was performed was taken as the viscosity of the composition layer at the temperature when step 2 was performed. (Measurement conditions) Plate: DPP12, Gap: 0.6 mm, Strain: 0.1%, Angular frequency: 10 rad / s, Temperature conditions: Heating from 25°C to 100°C at 3°C / min, then cooling from 100°C to 25°C at 3°C / min.

[0137] [Example 1] <Formation of alignment film P-1> A glass substrate was prepared as a support. The following alignment film forming coating solution was applied to this support by spin coating. The support on which the alignment film forming coating solution was applied was dried on a 60°C hot plate for 60 seconds to form an alignment film.

[0138] Coating solution for forming alignment film ---------------------------------------------------------------- Photo-alignment material A 4.00 parts by mass Water 48.00 parts by mass Butoxyethanol 24.00 parts by mass Propylene glycol monomethyl ether 24.00 parts by mass ----------------------------------------------------------------

[0139] - Photo-alignment material A -

[0140] An orientation film P-1 having an orientation pattern was formed by exposing the orientation film using the exposure apparatus shown in Figure 4. The exposure apparatus used emitted laser light with a wavelength of 355 nm. The exposure dose due to interference was 1000 mJ / cm². ２ That's what I decided.

[0141] <Formation of Alignment Film P-2> Composition A-1 was prepared as a liquid crystal composition for forming alignment film P-2. Composition A-1 was also used for forming liquid crystal layer X-1. Chiral agent K-1 is chiral agent A whose helical induced force can be changed by light irradiation, and chiral agent K-2 is chiral agent B. Composition A-1 -------------------------------------------------- Liquid crystal compound L-1 60.00 parts by mass Liquid crystal compound L-2 40.00 parts by mass Leveling agent T-1 0.40 parts by mass Photopolymerization initiator P-1 2.75 parts by mass Chiral agent K-1 9.00 parts by mass Chiral agent K-2 1.90 parts by mass Methyl ethyl ketone 323.00 parts by mass Cyclopentanone 323.00 parts by mass --------------------------------------------------

[0142] Liquid crystal compound L-1

[0143] Liquid crystal compound L-2

[0144] Leveling agent T-1

[0145] Photopolymerization initiator P-1

[0146] Chiral agent K-1

[0147] Chiral agent K-2

[0148] Composition A-1 was applied to the surface of the orientation film P-1 to form a coating, and the formed coating was heated at 80°C for 60 seconds using a hot plate. Subsequently, under a nitrogen atmosphere and at a temperature of 80°C, ultraviolet light with a wavelength of 365 nm was applied using a high-pressure mercury lamp at an irradiance of 10 mW / cm². ２ , irradiation amount 200mJ / cm ２ By irradiating the coating film under these conditions, the orientation of the liquid crystal compound was fixed, forming an orientation film P-2 with a thickness of 0.2 μm.

[0149] <Formation of Liquid Crystal Layer X-1> (Step 1) Composition A-1 was applied to the surface of the alignment film P-2 to form a coating film, and the formed coating film was heated at 80°C for 60 seconds using a hot plate to form composition layer Y-1. The surface of composition layer Y-1 was observed with a polarizing microscope and it was confirmed that a liquid crystal alignment pattern was formed in which the orientation of the optical axis derived from the liquid crystal compound changed while continuously rotating along the alignment axis D direction, which is one direction within the plane. The period Λ, which is the length of 180° rotation of the optical axis orientation along the alignment axis D direction, was 1.0 μm. A cross-section of composition layer Y-1 including the alignment axis D direction and the thickness direction was observed according to the above method, and the bright fringe inclination angle was measured from the observed image. As a result, as shown in Figure 3, a stripe-like pattern in which the bright and dark areas are inclined with respect to the main surface was observed in the above cross-sectional image of composition layer Y-1, and the bright fringe inclination angle θ was 11°. The thickness T of composition layer Y-1 was also measured according to the above method. Ｃ It was 0.7 μm.

[0150] (Step 2) After Step 1, the composition layer Y-1 is exposed to ultraviolet light with a wavelength of 365 nm at a temperature of 40°C using a high-pressure mercury lamp in an atmosphere containing oxygen (oxygen concentration: approximately 20 vol%), with an irradiance of 5 mW / cm².２ , irradiation amount 100mJ / cm ２ The coating film was irradiated under the specified conditions. Following the method described above, a cross-section of composition layer Y-1 after step 2, including the alignment axis D direction and the thickness direction, was observed, and the light fringe inclination angle was measured from the observed image. As a result, as shown in Figure 5, a stripe-like pattern was observed in the cross-section of composition layer Y-1, with light and dark areas substantially perpendicular to the main surface, and the light fringe inclination angle was 90° with respect to the main surface. Furthermore, as measured according to the method described above, the viscosity of composition layer Y-1 at the temperature at which step 2 was performed was 58 Pa·s.

[0151] (Step 3) After Step 2, under a nitrogen atmosphere and at a temperature of 60°C, an LED lamp is used to emit ultraviolet light with a wavelength of 365 nm at an irradiance of 10 mW / cm². ２ , irradiation amount 200mJ / cm ２ By irradiating the composition layer Y-1 under the specified conditions, the orientation of the liquid crystal compound was fixed, forming a liquid crystal layer X-1, and a sample S-1 of an optical element having a support, alignment film P-1, alignment film P-2, and liquid crystal layer X-1 was prepared. The surface of the liquid crystal layer X-1 was observed using a polarizing microscope and it was confirmed that a liquid crystal alignment pattern (1 period Λ: 1.0 μm) similar to that of the composition layer Y-1 was formed. Furthermore, the measurement results showed that the bright fringe tilt angle of the liquid crystal layer X-1 was 90°, the same as the bright fringe tilt angle of the composition layer Y-1 after step 2. The thickness T of the liquid crystal layer X-1 was also measured according to the above method. Ｌ It was 0.7 μm.

[0152] [Example 2] Sample S-2 of the optical element was prepared in the same manner as in Example 1, except that in step 1 of Example 1, composition A-2 was used, which was prepared by changing the amount of chiral agent K-1 added to composition A-1 to 0.9 parts by mass and the amount of chiral agent K-2 added to composition A-1 to 0.7 parts by mass.

[0153] [Example 3] An optical element sample S-3 was prepared in the same manner as in Example 1, except that in step 1 of Example 1, composition A-3 was used instead of composition A-1.

[0154] Composition A-3 -------------------------------------------------- Liquid crystal compound L-3 80.00 parts by mass Liquid crystal compound L-4 10.00 parts by mass Liquid crystal compound L-5 10.00 parts by mass Leveling agent T-1 0.40 parts by mass Photopolymerization initiator P-1 2.75 parts by mass Chiral agent K-1 9.00 parts by mass Chiral agent K-2 1.90 parts by mass Methyl ethyl ketone 323.00 parts by mass Cyclopentanone 323.00 parts by mass --------------------------------------------------

[0155] Liquid crystal compound L-3

[0156] Liquid crystal compound L-4

[0157] Liquid crystal compound L-5

[0158] [Example 4] Sample S-4 of the optical element was prepared in the same manner as in Example 1, except that the temperature during ultraviolet irradiation was changed to 80°C in step 1 of Example 1.

[0159] [Example 5] An optical element sample S-5 was prepared in the same manner as in Example 1, except that the amount of composition A-1 applied in step 1 of Example 1 was changed so that the thickness Tc of the composition layer formed was 0.35 μm.

[0160] [Example 6] Sample S-6 of the optical element was prepared in the same manner as in Example 1, except that in step 1 of Example 1, composition A-6 was used, which was prepared by changing the amount of chiral agent K-2 added to composition A-1 to 1.0 part by mass.

[0161] [Comparative Example 1] A sample of optical element S-C1 was prepared in the same manner as in Example 1, except that composition A-4 was used instead of composition A-1 in step 1 of Example 1, and step 2 was not performed. In Comparative Example 1, the surface of the composition layer after step 1 was observed with a polarizing microscope. As a result, a liquid crystal alignment pattern was formed in which the orientation of the optical axis derived from the liquid crystal compound changed while continuously rotating along one direction in the plane, and it was confirmed that the period Λ, which is the length of a 180° rotation of the optical axis orientation along the array axis D direction, was 1.0 μm. Furthermore, as a result of observing a cross-section of the composition layer after step 1, including the array axis D direction and the thickness direction, a stripe-like pattern was observed in the above cross-section of composition layer Y-1, in which the bright and dark areas were approximately perpendicular to the main surface, and the bright line inclination angle was 90° with respect to the main surface. That is, it was confirmed that the bright and dark areas derived from the optical axis of the liquid crystal compound were not inclined with respect to the main surface of the composition layer.

[0162] Composition A-4 -------------------------------------------------- Liquid crystal compound L-1 60.00 parts by mass Liquid crystal compound L-2 40.00 parts by mass Leveling agent T-1 0.40 parts by mass Photopolymerization initiator P-1 2.75 parts by mass Methyl ethyl ketone 323.00 parts by mass Cyclopentanone 323.00 parts by mass --------------------------------------------------

[0163] [Evaluation] For each example of optical element, the liquid crystal alignment pattern on the surface of the liquid crystal layer was observed using a polarizing microscope to confirm the alignment state of the liquid crystal compound, and the number of defects caused by the disorder of the liquid crystal compound's alignment was measured. Based on the number of defects per surface of the liquid crystal layer, the alignment defects of each liquid crystal layer were evaluated according to the following evaluation criteria. <<Orientation Defect Evaluation Criteria>> "S": Number of defects is 1 / cm ２ Below, "A": Number of defects is 1 / cm ２ Super 10 pieces / cm ２ Less than "B": Number of defects is 10 / cm ２Above

[0164] In the following table, the bright line tilt angle of the composition layer, the viscosity of the composition layer at the temperature at which Step 2 is carried out, one period Λ and the thickness T of the liquid crystal alignment pattern of the liquid crystal layer, which are measured by the above measurement method, are shown respectively. In the table, the column of "Step 1" of "Bright line tilt angle [°]" indicates the bright line tilt angle obtained from the observation image of the cross section of the composition layer after carrying out Step 1 according to the above method, and the column of "Step 2" of the same indicates the bright line tilt angle obtained from the observation image of the cross section of the composition layer after carrying out Step 2 according to the above method. The column of "Viscosity [Pa·s]" indicates the viscosity of each composition layer at the temperature at which Step 2 is carried out, which is measured according to the above method. For Comparative Example 1, the measurement result of the viscosity at 40°C of the composition sample obtained using Composition A-4 according to the above method is shown. Ｌ Further, the evaluation results of the alignment defects are shown respectively. In the table, the column of "Step 1" of "Bright line tilt angle [°]" indicates the bright line tilt angle obtained from the observation image of the cross section of the composition layer after carrying out Step 1 according to the above method, and the column of "Step 2" of the same indicates the bright line tilt angle obtained from the observation image of the cross section of the composition layer after carrying out Step 2 according to the above method. The column of "Viscosity [Pa·s]" indicates the viscosity of each composition layer at the temperature at which Step 2 is carried out, which is measured according to the above method. For Comparative Example 1, the measurement result of the viscosity at 40°C of the composition sample obtained using Composition A-4 according to the above method is shown.

[0165]

[0166] As shown in Table 1 above, it was confirmed that the liquid crystal layer formed by the production method of the present invention having Steps 1 to 3 is a liquid crystal layer having a greater thickness and fewer defects as compared with the liquid crystal layer formed by the production method of Comparative Example 1 in which Steps 1 to 3 are not carried out.

[0167] 12, 12c, 14 Composition layer 12a, 12b, 14a, 14b Main surface 16 Liquid crystal layer 30 Substrate 32 Alignment film 40 Liquid crystal compound 40A Optical axis 42 Light part 44 Dark part 60, 80 Exposure apparatus 62, 82 Laser 64, 84 Light source 65 λ / 2 plate 68 Beam splitter 70A, 70B, 90A, 90B Mirror 72A, 72B, 96 λ / 4 plate 86, 94 Polarizing beam splitter 92 Lens D, A １ , A ２ , A ３ Array axis Λ One period L Straight line La, Lb Line segment L １ , L ２ Incident light L ４ , L ５ Emergent light M Laser light MA, MB Light ray O1, O2 Center P ０ Linear polarization P Ｒ Right circular polarization P ＬLeft circular polarization α crossing angle

Claims

1. A method for manufacturing a liquid crystal layer, comprising: step 1 forming a composition layer comprising a liquid crystal compound having polymerizable groups and a chiral agent whose helical induced force can be changed, wherein the composition layer has a liquid crystal orientation pattern in which the orientation of the optical axis derived from the liquid crystal compound changes while continuously rotating along at least one direction in the plane, and in a cross-section of the composition layer including the one direction and the thickness direction as observed by an atomic force microscope, the bright and dark areas derived from the optical axis of the liquid crystal compound are inclined with respect to the main surface of the composition layer; step 2 changing the helical induced force of the chiral agent to bring the bright and dark areas derived from the optical axis of the liquid crystal compound in the cross-section of the composition layer as observed by an atomic force microscope closer to a direction perpendicular to the main surface of the composition layer; and step 3 curing the composition layer to form a liquid crystal layer.

2. Thickness T of the liquid crystal layer Ｌ The method for manufacturing a liquid crystal layer according to claim 1, wherein the length Λ at which the orientation of the optical axis originating from the liquid crystal compound in the liquid crystal alignment pattern rotates 180° along the one direction satisfies the following formula (1). Ｌ / Λ ≧ 1 / 2 (1) 3. The method for manufacturing a liquid crystal layer according to claim 1 or 2, wherein in the composition layer formed by step 1, the angle between the bright and dark areas originating from the optical axis of the liquid crystal compound and the main surface of the composition layer is less than 85°.

4. The method for manufacturing a liquid crystal layer according to claim 1 or 2, wherein in the composition layer formed by step 1, the angle between the bright and dark areas originating from the optical axis of the liquid crystal compound and the main surface of the composition layer is 30° or less.

5. The method for producing a liquid crystal layer according to claim 1 or 2, wherein the chiral agent is a compound whose helical induced force changes by any of light irradiation, heat treatment, or acid treatment.

6. The method for manufacturing a liquid crystal layer according to claim 1 or 2, wherein in step 2, the composition layer is irradiated with light in an atmosphere with an oxygen concentration of 1 volume percent or more to change the helical induced force of the chiral agent.

7. The method for manufacturing a liquid crystal layer according to claim 1 or 2, wherein the viscosity of the composition layer at the temperature at which step 2 is performed is 10 Pa·s or more.

8. The method for manufacturing a liquid crystal layer according to claim 1 or 2, wherein in the cross-section of the composition layer formed by step 2, the angle between the bright and dark areas originating from the optical axis of the liquid crystal compound and the main surface of the composition layer is 50 to 90°.

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