Liquid crystal layer

Abstract

The present invention addresses the problem of providing a liquid crystal layer having a liquid crystal alignment pattern that is thick and has fewer defects. A liquid crystal layer according to the present invention contains a liquid crystal compound and a chiral agent, and is a single layer having a liquid crystal alignment pattern in which the orientation of an optical axis derived from the liquid crystal compound changes while continuously rotating along at least one in-plane direction, wherein in a cross section including one direction and a thickness direction of the liquid crystal layer observed by an atomic force microscope, an angle θ which a bright part and a dark part derived from the optical axis of the liquid crystal compound form with a main surface of the liquid crystal layer is 50-90°; and the thickness TL of the liquid crystal layer and a length Λ by which the orientation of the optical axis derived from the liquid crystal compound in the liquid crystal alignment pattern rotates 180° along the one direction satisfy formula (1) (TL / Λ ≥ 1 / 2).

Description

Liquid crystal layer

[0001] This invention relates to a liquid crystal layer.

[0002] Optical elements that control the direction of light are used in many optical devices and systems. For example, they are used in the backlights of liquid crystal displays; head-mounted displays (HMDs) such as AR (Augmented Reality) glasses, VR (Virtual Reality) glasses, and MR (Mixed Reality) glasses that overlay images such as virtual images and various information onto the actual view; head-up displays (HUDs); projectors; beam steering; and sensors for detecting objects and measuring distances to objects. Optical elements that control the direction of light are used in a variety of optical devices.

[0003] As an optical element that controls the direction of light in this way, a liquid crystal optical element has been proposed that is formed using a liquid crystal composition containing a liquid crystal compound and has a liquid crystal layer exhibiting optical anisotropy. Patent Document 1 describes an optical element comprising a plurality of stacked birefringent sublayers configured to change the direction of propagation of light passing through the interior according to the Bragg condition, wherein each stacked birefringent sublayer has a local optical axis that changes along the respective interface between adjacent stacked birefringent sublayers so as to define its respective lattice period.

[0004] Special table 2017-522601 publication

[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 orientation 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 liquid crystal layer that is thick and has few defects.

[0006] In view of the above circumstances, the present invention aims to provide a liquid crystal layer having a thick liquid crystal alignment pattern with 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 liquid crystal layer comprising a liquid crystal compound and a chiral agent, wherein the liquid crystal layer has a liquid crystal orientation pattern in which the orientation of the optical axis originating from the liquid crystal compound changes while continuously rotating along at least one direction in the plane, and in a cross-section of the liquid crystal layer including the one direction and the thickness direction as observed by an atomic force microscope, the angle θ between the bright and dark areas originating from the optical axis of the liquid crystal compound and the main surface of the liquid crystal layer is 50 to 90°, and the thickness T of the liquid crystal layer Ｌ A liquid crystal layer that satisfies the following equation (1) and is a single layer, wherein the length Λ at which the orientation of the optical axis originating from the liquid crystal compound in the above liquid crystal alignment pattern rotates 180° along the above one direction is satisfied. Ｌ / Λ ≥ 1 / 2 (1) [2] The liquid crystal layer according to [1], further comprising a leveling agent. [3] The liquid crystal layer according to [2], wherein the leveling agent is at least one selected from the group consisting of silicone-based leveling agents and fluoroalkyl-based leveling agents. [4] The liquid crystal layer according to [2] or [3], satisfying requirement A described later. [5] The liquid crystal layer according to any one of [1] to [4], wherein the chiral agent comprises a first chiral agent having a right-handed helical inductive force and a second chiral agent having a left-handed helical inductive force. [6] Thickness T of the liquid crystal layer Ｌ A liquid crystal layer according to any one of [1] to [5], wherein the angle θ and the content Q of the chiral agent in the liquid crystal layer satisfy the following formula (2) or formula (3): θ / (T Ｌ / Q)<-133 (2) 133<θ / (T Ｌ / Q) (3) [7] A liquid crystal layer according to any one of [1] to [6], wherein the content Q of the chiral agent in the liquid crystal layer is 1% by mass or more with respect to the total mass of the liquid crystal layer. [8] A liquid crystal layer according to any one of [1] to [7], wherein the content Q of the chiral agent in the liquid crystal layer is 5% by mass or more with respect to the total mass of the liquid crystal layer.

[0009] According to the present invention, it is possible to provide 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 the liquid crystal alignment pattern of the liquid crystal layer of the present invention. This is a conceptual diagram for explaining the function of the liquid crystal alignment pattern. This is a conceptual diagram for explaining the function of the liquid crystal alignment pattern. This is a plan view conceptually showing another example of the liquid crystal alignment pattern of the liquid crystal layer of the present invention. This is a cross-sectional view conceptually showing an example of the configuration of the liquid crystal layer of the present invention. This is a schematic diagram for explaining the depth-direction profile of the secondary ion intensity derived from the leveling agent detected by analyzing the depth-direction components of the liquid crystal layer by time-of-flight secondary ion mass spectrometry (TOF-SIMS). This is a cross-sectional view of a composition layer for explaining the manufacturing method of the liquid crystal layer. This is a diagram conceptually showing an example of an exposure apparatus for forming an 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] [Liquid Crystal Layer] The liquid crystal layer of the present invention (hereinafter also referred to as "this liquid crystal layer") is a liquid crystal layer comprising a liquid crystal compound and a chiral agent, 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 predetermined cross-section of the liquid crystal layer observed by an atomic force microscope, the angle θ between the bright and dark areas derived from the optical axis of the liquid crystal compound and the main surface of the liquid crystal layer is 50 to 90°, and the thickness of the liquid crystal layer T Ｌ 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 is given by equation (1) (T Ｌ The condition Λ ≥ 1 / 2 is satisfied, and it is a single layer.

[0017] The liquid crystal 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 liquid crystal layer. As shown in Figure 1, the liquid crystal 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 liquid crystal 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".

[0018] A plan view is a diagram of the liquid crystal 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 structure of the liquid crystal layer, only the surface liquid crystal compound 40 is shown.

[0019] As shown in Figure 1, on the surface, the liquid crystal compound 40 constituting the liquid crystal 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 liquid crystal 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 liquid crystal 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 explanation, 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 liquid crystal layer.

[0020] 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.

[0021] 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 liquid crystal 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.

[0022] On the other hand, in the liquid crystal compound 40 that forms the liquid crystal layer, the orientation of the optical axis 40A is the same in the Y direction which is perpendicular to the arrangement 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 liquid crystal layer, the angle between the optical axis 40A of the liquid crystal compound 40 and the arrangement axis D direction is equal in the Y direction.

[0023] In the liquid crystal 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 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 liquid crystal layer. Here, the refractive index difference due to the refractive index anisotropy of region R in the liquid crystal 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.

[0024] In the liquid crystal layer, in such a liquid crystal alignment pattern of the liquid crystal compound 40, in the direction of the alignment axis D in which the optical axis 40A continuously rotates and changes in the plane, the length (distance) by which the optical axis 40A of the liquid crystal compound 40 rotates 180° is defined as the length Λ of one period in the liquid crystal alignment pattern. That is, the distance between the centers in the direction of the alignment axis D of two liquid crystal compounds 40 having equal angles with respect to the direction of the alignment axis D is defined as the length Λ of one period. Specifically, as shown in FIG. 1, the distance between the centers in the direction of the alignment axis D of two liquid crystal compounds 40 in which the direction of the alignment axis D and the direction of the optical axis 40A coincide is defined as the length Λ of one period. In the following description, this length Λ of one period is also referred to as "one period Λ". The liquid crystal alignment pattern of the liquid crystal layer repeats this one period Λ in one direction in which the alignment axis D direction, that is, the direction of the optical axis 40A continuously rotates and changes.

[0025] When circularly polarized light is incident on a liquid crystal layer having such a liquid crystal alignment pattern, the light is refracted and the direction of the circularly polarized light is converted. This action is conceptually shown in FIGS. 2 and 3. FIGS. 2 and 3 are conceptual diagrams for explaining the action of the liquid crystal alignment pattern. It is assumed that the value of the product of the refractive index difference of the liquid crystal compound and the thickness of the liquid crystal layer in the liquid crystal layer is λ / 2. As shown in FIG. 2, when incident light L which is left circularly polarized light is incident on the liquid crystal layer when the value of the product of the refractive index difference of the liquid crystal compound and the thickness of the liquid crystal layer in the liquid crystal layer is λ / 2 １ is incident, the incident light L １ is given a phase difference of 180° by passing through the liquid crystal layer, and the transmitted light L ２ is converted into right circularly polarized light. Further, since the liquid crystal alignment pattern formed on the liquid crystal layer is a periodic pattern in the direction of the alignment axis D, the transmitted light L ２ travels in a direction different from the traveling direction of the incident light L １ . Thus, the incident light L which is left circularly polarized light １ is converted into transmitted light L which is right circularly polarized light and is inclined by a certain angle in the direction of the alignment axis D with respect to the incident direction ２ . In the example shown in FIG. 2, the transmitted light L ２ is diffracted so as to travel in the lower right direction.

[0026] On the other hand, as shown in Figure 3, when the product of the refractive index difference of the liquid crystal compounds in the liquid crystal layer and the thickness of the liquid crystal layer is λ / 2, right-circularly polarized incident light L enters the liquid crystal layer. ４ When incident light L ４ By passing through the liquid crystal layer, a phase difference of 180° is given, resulting in left-circularly polarized transmitted light L ５ It is converted to [this]. Also, the liquid crystal alignment pattern formed in the liquid crystal layer is a periodic pattern in the direction of the array axis D, so 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 ４ This 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 3. ５ The light is diffracted so that it propagates downwards and to the left.

[0027] As mentioned above, the liquid crystal layer 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, 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.

[0028] Furthermore, by reversing the rotation direction of the optical axis 40A 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 2 and 3, the rotation direction of the optical axis 40A toward the array axis D is clockwise, but by changing this rotation direction to counterclockwise, the direction of refraction of transmitted light can be reversed. Specifically, in Figures 2 and 3, when the rotation direction of the optical axis 40A 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.

[0029] As described later, a liquid crystal 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 the liquid crystal compound 40 on the surface of an alignment film that is oriented in a predetermined pattern.

[0030] In the example shown in Figure 1, the liquid crystal alignment pattern of the liquid crystal layer is shown in which the alignment axis D is aligned along one direction in the plane, and the optical axis 40A of the liquid crystal compound 40 rotates continuously in one direction along the direction of the alignment axis D. 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 rotates continuously along at least one direction.

[0031] For example, the liquid crystal layer may have a configuration in which the liquid crystal alignment pattern is arranged radially. In the liquid crystal layer 12c shown in Figure 4, the orientation of the optical axis of the liquid crystal compound 40 is in multiple directions, such as arrow A, which points outward from the center of the liquid crystal layer 12c. １ The direction indicated by arrow A ２ The direction indicated by arrow A ３ It changes while continuously rotating along the direction indicated by arrow A. １ A ２ and A ３ This is the array axis.

[0032] Furthermore, as shown in Figure 4, the optical axis of the liquid crystal compound 40 changes while rotating in the same direction from the center outward from the center of the liquid crystal layer 12c. The configuration shown in Figure 4 is a counterclockwise orientation. Arrow A in Figure 4 １ A ２ and A ３ The direction of rotation of the optical axis, which changes along each arrow, is counterclockwise as you move from the center outwards.

[0033] <Angle θ between the bright and dark areas and the main surface> This liquid crystal layer is characterized in that, in a cross-section including one direction (the direction of the array axis D shown in Figure 1) and the thickness direction in which the optical axis 40A of the liquid crystal layer observed by an atomic force microscope (AFM) changes while continuously rotating, the angle θ (hereinafter also simply referred to as "angle θ") between the bright and dark areas originating from the optical axis of the liquid crystal compound and the main surface of the liquid crystal layer is 50 to 90°.

[0034] Using Figure 5, we will explain a cross-section of a liquid crystal layer that includes the alignment axis D direction and the thickness direction. Figure 5 is a conceptual cross-sectional view showing an example of the structure of a liquid crystal layer. In the following explanation, a cross-section that includes the alignment axis D direction and the thickness direction of the liquid crystal layer, that is, a cross-section obtained by cutting the liquid crystal layer along one direction in which the optical axis changes while continuously rotating and along the thickness direction, and an image obtained by observing this cross-section using an AFM, will also simply be referred to as a "cross-sectional image".

[0035] As shown in Figure 5, a cross-sectional image of the liquid crystal layer 12 including the direction of the array axis D and the thickness direction shows a striped pattern consisting of bright areas 42 and dark areas 44 perpendicular to the main surfaces 12a and 12b of the liquid crystal layer 12. Also, in Figure 5, arrow T Ｌ The thickness T of the composition Ｌ This is shown. Furthermore, when the liquid crystal layer 12 shown in Figure 5 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 liquid crystal layer 12, similar to the example shown in Figure 1.

[0036] In this specification, "angle θ between the bright and dark areas derived from the optical axis of the liquid crystal compound and the main surface of the liquid crystal layer" means the angle between the straight line L connecting the centers O1 and O2 of the line segment La, which is the intersection line of one main surface 12a and the bright area 42, and the main surface 12a (or 12b) of the liquid crystal layer, obtained from a cross-sectional image of the liquid crystal layer observed by AFM, and the main surface 12a (or 12b) of the liquid crystal layer. That is, this liquid crystal layer is characterized in that the angle θ obtained from the cross-sectional image of the liquid crystal layer by the above method is 50 to 90°.

[0037] The angle θ between the bright and dark areas and the main surface of the liquid crystal layer is preferably 80 to 90°, and more preferably 85 to 90°.

[0038] <Thickness T of the liquid crystal layer relative to one period Λ> Ｌ Ratio > This liquid crystal layer has a thickness T Ｌ 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 one direction is characterized by satisfying the following equation (1). Ｌ / Λ ≥ 1 / 2 (1) Thickness T of the liquid crystal layer Ｌ The ratio T of the liquid crystal alignment pattern to one period Λ Ｌ When / Λ satisfies equation (1), it is not necessary to form multiple single liquid crystal layers, or at least the number of single liquid crystal layers can be reduced, when manufacturing an optical element that has the optically required thickness and few defects in the liquid crystal alignment pattern.

[0039] From the above perspective, 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.

[0040] The thickness of the liquid crystal layer and the composition layer described later can be measured from the 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). The method for measuring the thickness of each layer will be described in detail in the examples below.

[0041] This liquid crystal layer is a single layer. In this specification, "single-layer liquid crystal layer" means a liquid crystal layer formed by a series of steps, in which a film is formed using a composition containing a liquid crystal compound, and then the liquid crystal compound contained in the film is immobilized, without repeating the series of steps. The fact that the liquid crystal layer is a single layer can be confirmed, for example, by observing a cross-section including the thickness direction of the liquid crystal layer. Furthermore, if the liquid crystal layer contains a leveling agent, the fact that the liquid crystal layer is a single layer can be confirmed by the method described later.

[0042] <Ingredients> The following describes the ingredients contained in this liquid crystal layer.

[0043] (Liquid Crystal Compound) This liquid crystal layer contains a liquid crystal compound. 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 rod-shaped liquid crystal compounds and discotic liquid crystal compounds 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.

[0044] In the liquid crystal layer, the orientation state of the liquid crystal compound may be fixed. The most typical and preferred embodiment of the "fixed" state is one in which the orientation of the liquid crystal compound is maintained, but 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. 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.

[0045] This liquid crystal layer may be 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. The type of polymerizable group that the liquid crystal compound has is not particularly limited, but functional groups that can undergo 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. Furthermore, the liquid crystal compound after this liquid crystal layer is formed does not need to exhibit liquid crystallinity anymore.

[0046] The content of the liquid crystal compound in the liquid crystal 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 liquid crystal 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.

[0047] (Chiral Agent) This liquid crystal layer contains a chiral agent. The chiral agent is a compound that has the function of inducing a helical structure in the liquid crystal compound. Since the direction of the helical twisting and the helical twisting power (HTP) induced by the chiral agent differ depending on the compound, it should be selected according to the purpose. The helical twisting power (HTP) of the chiral agent is a factor that indicates the helical orientation ability, expressed 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 liquid crystal layer from 0° to 360° in the thickness direction. The length of the helical pitch can be measured using the method described on page 196 of the Liquid Crystal Handbook (published by Maruzen Co., Ltd.).

[0048] 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 often 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. When a thick liquid crystal layer is manufactured by this manufacturing method, orientation disorder in the liquid crystal alignment pattern tends to occur on the surface opposite to the alignment film side. In contrast, the present inventors, after diligent research, have found that a liquid crystal layer having the above configuration suppresses orientation disorder in the liquid crystal alignment pattern and reduces defects, even when the thickness of a single liquid crystal layer is increased, thus achieving the excellent effect of completing the present invention. The details of the reason for the above excellent effect are not clear, but it is presumed that it is related to the fact that the liquid crystal layer contains a chiral agent, yet the angle between the bright and dark areas observed in a predetermined cross-section of the liquid crystal layer and the main surface is X1 to X2°, that is, the liquid crystal compound is not torsionally oriented in the thickness direction.

[0049] There are no particular restrictions on the chiral agent, and known compounds (for example, described in the 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. The chiral agent may have polymerizable groups. The chiral agent may also be a liquid crystal compound.

[0050] The chiral agent contained in the liquid crystal layer may be a single type or two or more types. Preferably, the liquid crystal layer contains a combination of chiral agents whose induced helical directions (chirality) are opposite to each other. In other words, preferably, the liquid crystal layer contains a first chiral agent having a right-handed helical inductive force and a second chiral agent having a left-handed helical inductive force. The first chiral agent and the second chiral agent may each be a single type or two or more types.

[0051] The chiral agent may be a chiral agent whose helical induced force can be altered. Examples of chiral agents whose helical induced force can be altered include compounds whose helical induced force changes in response to external stimuli such as light irradiation, heat treatment, and acid treatment.

[0052] 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".

[0053] 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.

[0054] 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.

[0055] 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. The optically active compounds described in 44, the optically active isosorbide derivatives described in paragraphs 0016 to 0055 of Japanese Patent Publication No. 2002-338575, the photoreactive optically active compounds described in paragraphs 0023 to 0032 of Japanese Patent Publication No. 2002-080478, the photoreactive chiral agents described in paragraphs 0019 to 0029 of Japanese Patent Publication No. 2002-080851, the optically active compounds described in paragraphs 0022 to 0049 of Japanese Patent Publication No. 2002-179681, the optically active compounds described in paragraphs 0015 to 0044 of Japanese Patent Publication No. 2002-302487, and Japanese Patent Publication No. 2002-338668 Optically active polyesters described in paragraphs 0015 to 0050 of the report, binaphthol derivatives described in paragraphs 0019 to 0041 of JP 2003-055315, optically active fulgid compounds described in paragraphs 0008 to 0043 of JP 2003-073381, optically active isosorbide derivatives described in paragraphs 0015 to 0057 of JP 2003-306490, optically active isosorbide derivatives described in paragraphs 0015 to 0041 of JP 2003-306491, optically active Examples include optically active 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 Japanese Patent Publication No. WO2018 / 194157, and optically active compounds described in paragraphs 0020 to 0049 of Japanese Patent Publication No. 2002-179682.

[0056] 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.

[0057] 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.

[0058] 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.

[0059]

[0060] Chiral agent A may have a polymerizable group. The type of polymerizable group 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.

[0061] 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.

[0062]

[0063] The chiral agent A contained in the liquid crystal layer may be a single type or two or more types. The liquid crystal layer may contain at least one type of chiral agent A and at least one type of chiral agent whose helical-inducing 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, it is preferable that at least one of chiral agent A and chiral agent B is a first chiral agent and the other is a second chiral agent.

[0064] 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).

[0065] The respective contents of the first and second chiral agents in the liquid crystal layer can be appropriately set according to the characteristics of the liquid crystal layer (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 the first and second chiral agents, the torsion structure of the liquid crystal compound can be adjusted by adjusting these, thereby obtaining a desired angle θ.

[0066] Furthermore, when using two or more chiral agents, the concentration and helical induced force of the chiral agents in the liquid crystal layer are not particularly limited, as long as the weighted average helical induced force of the chiral agents is adjusted so that a liquid crystal layer with the above-mentioned angle θ is formed within the above-mentioned range. 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 liquid crystal layer 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.

[0067] The content Q of the chiral agent in the liquid crystal layer is not particularly limited, but it is preferably 5% by mass or more, and more preferably 10% by mass or more, relative to the total mass of the liquid crystal layer, in that it reduces defects in the liquid crystal alignment pattern. The upper limit is not particularly limited, but it is preferably 30% by mass or less, and more preferably 20% by mass or less, relative to the total mass of the liquid crystal compound. Furthermore, the content of the chiral agent A 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 it is preferably 1% by mass or more, and more preferably 5% by mass or more, relative to the total mass of the liquid crystal compound.

[0068] In this liquid crystal layer, the number of defects in the liquid crystal alignment pattern is reduced, and the thickness of the liquid crystal layer T Ｌ Preferably, the following equation (2) satisfies the following conditions: |θ / (T)|, the angle θ (°) between the bright and dark areas in the cross-sectional image and the main surface of the liquid crystal layer, and the chiral agent content Q (mass%) relative to the total mass of the liquid crystal layer. Ｌ / Q) | > 133 (2)

[0069] That is, the thickness T of the liquid crystal layer Ｌ (Unit: μm), angle θ (unit: °), and chiral agent content Q (unit: mass%) are given by θ / (T Ｌ / Q) < -133, or θ / (T Ｌ It is preferable that the condition (Q) > 133 is satisfied. It is more preferable that the value calculated from the left side of the above formula (2) is 500 or more. There is no particular upper limit to the value calculated from the left side of the above formula (2), and it may be, for example, 2000 or less.

[0070] (Leveling agent) The liquid crystal layer may contain a leveling agent, and it is preferable that it contains a leveling agent. The leveling agent is an additive that has the function of adjusting the fluidity of the composition containing the liquid crystal compound and making the composition layer containing this composition flatter. Examples of leveling agents include silicone-based leveling agents, polyacrylate-based leveling agents, and fluorine-based leveling agents.

[0071] Fluorine-based leveling agents are leveling agents having a fluorine atom, with fluoroalkyl-based leveling agents having a fluoroalkyl group being preferred, and perfluoroalkyl-based leveling agents having a perfluoroalkyl group being more preferred. Silicone-based leveling agents are leveling agents having an alkylsilyloxy group, with leveling agents containing multiple dialkylsilyloxy units as repeating units being preferred.

[0072] As the leveling agent, a silicone-based leveling agent or a fluorine-based leveling agent is preferred, and a silicone-based leveling agent or a fluoroalkyl-based leveling agent is more preferred. The content of the leveling agent in the liquid crystal layer is not particularly limited, but in order to obtain a liquid crystal layer that is less prone to delamination within the layer, 0.010 to 5.000% by mass and 0.020 to 2.000% by mass are preferred based on the total mass of the liquid crystal layer.

[0073] If the liquid crystal layer contains a leveling agent, it is preferable that the liquid crystal layer satisfies the following requirement A. (Requirement A) Analyze the components of the liquid crystal layer in the depth direction by time-of-flight secondary ion mass spectrometry while irradiating an ion beam from one main surface of the liquid crystal layer toward the other main surface, and obtain a profile of the secondary ion intensity derived from the leveling agent in the depth direction. Of the secondary ion intensity derived from the leveling agent on one main surface of the liquid crystal layer and the secondary ion intensity derived from the leveling agent on the other main surface of the liquid crystal layer, the larger secondary ion intensity derived from the leveling agent is defined as the first intensity, and the secondary ion intensity that is 1 / 1000 of the first intensity is defined as the second intensity. When the depth position closest to one main surface among the depth positions showing the second intensity in the profile is defined as the first position, and the depth position closest to the other main surface among the depth positions showing the second intensity in the profile is defined as the second position, no secondary ion intensity derived from the leveling agent greater than 1 / 500 of the first intensity is observed at any depth in the region between the first and second positions. Requirement A will be described in detail below with reference to the drawings. Please note that the following diagrams are presented with different scales and other characteristics from the actual data to facilitate understanding of the invention.

[0074] Figure 6 shows an example of a profile obtained by analyzing the depth-direction components in each layer using TOF-SIMS while ion sputtering from one main surface of a liquid crystal layer toward the other main surface. In this specification, the depth direction refers to the direction toward the other main surface of the liquid crystal layer, with one main surface as the reference. In the depth-direction profile shown in Figure 6, the horizontal axis (the axis extending horizontally in the paper direction in Figure 6) represents the depth with respect to one main surface of the liquid crystal layer, and the vertical axis (the axis extending vertically in the paper direction in Figure 6) represents the secondary ion intensity derived from the leveling agent. For more details on the TOF-SIMS method, please refer to "Selected Techniques for Main Surface Analysis: Secondary Ion Mass Spectrometry" edited by the Japan Main Surface Science Society, published by Maruzen Co., Ltd. (1999).

[0075] The profiles in Figure 6 correspond to the results of analyzing the depth-direction components in each layer using TOF-SIMS while ion sputtering from one main surface 12a to the other main surface 12b of the liquid crystal layer 12 shown in Figure 5. In Figure 6, the position of 0 on the horizontal axis corresponds to the main surface 12a of the liquid crystal layer 12, and the position of E on the horizontal axis corresponds to the main surface 12b of the liquid crystal layer 12. In other words, the range from 0 to E on the horizontal axis corresponds from one main surface to the other main surface of the liquid crystal layer 12.

[0076] Furthermore, when analyzing the components in the depth direction of a liquid crystal layer using TOF-SIMS while irradiating with an ion beam, a series of operations are repeated in which the component analysis is performed in the main surface depth region of 1-2 nm, and then the depth direction is further advanced from 1 nm to several hundred nm, and the component analysis is performed in the next main surface depth region of 1-2 nm.

[0077] The depth profile shown in Figure 6 represents the results of the secondary ion intensity derived from the leveling agent. In this specification, the "secondary ion intensity derived from the leveling agent" obtained from the depth profile detected by analyzing the components in the depth direction of the liquid crystal layer using TOF-SIMS refers to the intensity of fragment ions derived from the leveling agent.

[0078] As shown in Figure 6, when analyzing the components in the depth direction of the liquid crystal layer using TOF-SIMS while irradiating with an ion beam from one main surface of the liquid crystal layer toward the other main surface, a high secondary ion intensity originating from the leveling agent is initially observed. As the ion beam is further irradiated toward the depth direction, this intensity gradually decreases. Furthermore, as the irradiation moves toward the other main surface, the secondary ion intensity originating from the leveling agent remains low, and as the irradiation approaches the other main surface, its intensity begins to increase. Since the leveling agent tends to be unevenly distributed on the air interface side and the substrate interface side (especially the air interface side), the secondary ion intensity originating from the leveling agent tends to be high near both the one main surface and the other main surface, as described above.

[0079] Next, a baseline is drawn in the profile obtained above to determine the reference for secondary ion intensity. Specifically, as shown in Figure 6, a baseline BL is drawn as a thick dashed line, and this position is defined as the point where the secondary ion intensity is 0. To draw the baseline, first, starting from one main surface of the liquid crystal layer toward the other main surface, a reference position SP1 is set at a depth equivalent to 1 / 10 of the total thickness of the liquid crystal layer, and a reference position SP2 is set at a depth equivalent to 9 / 10 of the total thickness of the liquid crystal layer. Then, the average value of the secondary ion intensity derived from the leveling agent located between reference position SP1 and reference position SP2 is calculated, and the baseline is drawn using this average value. In other words, the average value of the secondary ion intensity derived from the leveling agent in the region between reference position SP1 and reference position SP2 is calculated, a straight line representing this average value is drawn along the horizontal axis, and this straight line is used as the baseline.

[0080] Next, in the profile obtained above, the secondary ion intensity derived from the leveling agent on one main surface of the liquid crystal layer and the secondary ion intensity derived from the leveling agent on the other main surface of the liquid crystal layer are defined as the first intensity, which is greater. In Figure 6, the secondary ion intensity derived from the leveling agent on one main surface of the liquid crystal layer (the secondary ion intensity derived from the leveling agent at depth position 0 in Figure 6) is greater than the secondary ion intensity derived from the leveling agent on the other main surface of the liquid crystal layer (the secondary ion intensity derived from the leveling agent at depth position E in Figure 6). Therefore, the secondary ion intensity derived from the leveling agent on one main surface of the liquid crystal layer is defined as the first intensity S1. As shown in Figure 6, the first intensity S1 refers to the intensity relative to the baseline BL described above. In other words, the baseline BL is set to a secondary ion intensity of 0, and the first intensity S1 is calculated. Next, the secondary ion intensity that is 1 / 1000 of the first intensity S1 is defined as the second intensity S2.

[0081] For the secondary ion intensity derived from the leveling agent on one main surface of the liquid crystal layer, the maximum value of the secondary ion intensity derived from the leveling agent in a region of 10 nm along the depth direction from the one main surface is adopted. Similarly, for the secondary ion intensity derived from the leveling agent on the other main surface of the liquid crystal layer, the maximum value of the secondary ion intensity derived from the leveling agent in a region of 10 nm from the other main surface toward the one main surface is adopted.

[0082] Next, in the profile shown in Figure 6, the depth position closest to one main surface among the depth positions showing the second intensity S2 is defined as the first position P1, and the depth position closest to the other main surface among the depth positions showing the second intensity S2 is defined as the second position P2.

[0083] Next, the secondary ion intensity derived from the leveling agent is observed at the depth position in the region between the first position P1 and the second position P2. In the liquid crystal layer, no secondary ion intensity derived from the leveling agent greater than 1 / 500 of the first intensity S1 is observed at any depth in the region between the first position P1 and the second position P2. More specifically, in Figure 6, the intensity that is 1 / 500 of the first intensity S1 is shown as the third intensity S3, and it is observed that the secondary ion intensity derived from the leveling agent at any depth position in the region between the first position P1 and the second position P2 is not greater than or equal to the third intensity S3. A liquid crystal layer that satisfies the above requirement A is a single layer. Furthermore, delamination within the liquid crystal layer is suppressed in a liquid crystal layer that satisfies the above requirement A. Note that if the secondary ion intensity derived from the leveling agent at any depth position in the region between the first position P1 and the second position P2 is greater than or equal to the third intensity S3, delamination is more likely to occur near that depth position where the third intensity S3 is greater.

[0084] The distribution of the leveling agent that satisfies requirement A can be achieved, for example, by the procedure for manufacturing a liquid crystal layer described later. More specifically, a liquid crystal layer that satisfies requirement A can be manufactured by using a composition containing a liquid crystal compound having polymerizable groups, a chiral agent that changes the helical induced force, and a leveling agent, and carrying out a liquid crystal layer manufacturing method having steps 1 to 3 described later. In the manufacturing method described later, this can be achieved by performing a series of steps in one step: forming a composition layer using the above composition, and then immobilizing the liquid crystal compound contained in the composition layer. In the composition layer and liquid crystal layer formed in such a procedure, the leveling agent tends to be unevenly distributed on the air interface side or the substrate side to which the composition is applied, and as a result, the leveling agent contained in the liquid crystal layer has the distribution state described above.

[0085] The liquid crystal layer may contain materials other than those described above. Examples of other materials include other components that may be included in composition A for forming the liquid crystal layer, as described later. Details of these other components will be described later.

[0086] 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).

[0087] 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.

[0088] [Method for Manufacturing a Liquid Crystal Layer] An example of a method for manufacturing this liquid crystal layer is a manufacturing method having the following steps 1 to 3 (hereinafter also referred to as "Manufacturing Method A"). 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 parts 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 so that the angle θ between the bright and dark parts derived from the optical axis of the liquid crystal compound and the main surface of the composition layer in a cross-section of the composition layer as observed by an atomic force microscope is within the range of 50 to 90°. Step 3: A step to cure the composition layer to form a liquid crystal layer.

[0089] The following details the steps of each process in manufacturing method A. Note that the manufacturing method for this liquid crystal layer is not limited to manufacturing method A.

[0090] <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. Furthermore, 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.

[0091] The composition layer formed by step 1 will be described in more detail with reference to Figure 7. Figure 7 is a conceptual cross-sectional view showing an example of a composition layer formed by step 1 in order to explain manufacturing method A. Figure 7 shows a cross-sectional image obtained by observing a cross section of the composition layer 14 including the arrangement axis D direction and the thickness direction using AFM.

[0092] The composition layer 14 shown in Figure 7 has the same configuration as the liquid crystal layer 12 shown in Figure 5, except that the liquid crystal compound 40 is torsionally oriented along a helical axis extending in the thickness direction indicated by arrow Z in the figure. That is, when the composition layer 14 shown in Figure 7 is viewed from the thickness direction, the orientation of the optical axis 40A changes continuously while rotating along the array axis D within the plane of the composition layer 14, similar to the example shown in Figure 1. Also, in Figure 7, arrow T Ｃ The thickness T of the composition Ｃ This indicates.

[0093] As shown in Figure 7, in the cross-sectional image of the composition layer 14 including the direction of the arrangement axis D and the thickness direction, bright areas 42 and dark areas 44 that are inclined with respect to the main surfaces 14a and 14b of the composition layer 14 can be observed. Such striped patterns consisting of bright areas 42 and dark areas 44 originate from a torsional structure in which the liquid crystal compound 40 is twisted and oriented along a helical axis extending in the thickness direction. As an example, in the cross-sectional image shown in Figure 7, the dark areas 44 are inclined toward the upper right.

[0094] In the composition layer, "the bright and dark areas originating from the optical axis of the liquid crystal compound are inclined with respect to the main surface of the composition layer" means that, in the cross-sectional image of the composition layer observed by AFM, the center O1 of line segment La, which is the intersection line of one main surface 14a and the bright area 42, and the center O2 of line segment Lb, which is the intersection line of the other main surface 14b and the bright area 42, are derived, and the angle θ between the straight line L connecting these centers O1 and O2 and the main surface 14a (or 14b) of the composition layer is within the range of 0° or more and less than 85°. The angle θ in the cross-sectional image of the composition layer 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, the bright line inclination angle θ is preferably greater than 5°.

[0095] 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 14 to the liquid crystal compound 40 present on the other main surface side is equal to the thickness T of the composition layer 14. ＣThe angle can be selected according to the angle θ, but 360° or less is preferred. As a method for forming a composition layer in which the bright and dark areas in the cross-sectional image are inclined with respect to the main surface, in other words, in which the liquid crystal compound is twisted in the thickness direction, one example is to form the composition layer using a composition containing a chiral agent.

[0096] The procedure in Step 1 is not particularly limited as long as the above-mentioned composition layer can be formed. Examples include a method of applying the 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 a method of separately forming the composition layer and transferring it to the substrate. From the viewpoint of productivity, the coating method is preferred. Below, Step 1 will be described in more detail using a method of forming the composition layer on the surface of the alignment film formed on the substrate by the coating method as an example.

[0097] The composition used to form the composition layer (hereinafter also referred to as "Composition A") includes components contained in the liquid crystal layer or their precursors. Composition A includes, for example, the chiral agent, liquid crystal compound (preferably a liquid crystal compound having polymerizable groups), leveling agent, and other components used as needed (e.g., polymerization initiator, polymerizable monomer, surfactant, polymer, and orientation control agent).

[0098] (Other components) For example, composition A may contain a polymerization initiator. When composition A 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, composition A is preferably a polymerization initiator that is sensitive to the light irradiated in step 3. The content of the polymerization initiator in composition A 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 solids content of composition A. "Total solids content" means the total content of the components contained in the composition layer after formation, out of the components contained in composition A. The total solids content of composition A often does not contain solvents that are removed by the drying treatment.

[0099] Composition A may contain polymerizable monomers other than 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 Composition A 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.

[0100] Composition A 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.

[0101] Composition A 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 Composition A 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.

[0102] In addition to the above, composition A 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. Preferably, the content of each component in composition A is adjusted to match the content of each component in the liquid crystal layer described above.

[0103] -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.

[0104] 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.

[0105] 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.

[0106] - Alignment film - Preferably, an alignment film is formed on the surface of the substrate to align the liquid crystal compound to a predetermined liquid crystal alignment pattern. The alignment film is formed such that the composition layer formed in step 1 can form 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. In the following description, "the orientation of the optical axis 40A rotates" will also simply be referred to as "the optical axis 40A rotates".

[0107] 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.

[0108] 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.

[0109] 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.

[0110] Examples of photo-alignment materials used in the alignment film applicable to manufacturing method A 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. 20 Azo compounds described in Japanese Patent Publication No. 07-133184, Japanese Patent Publication No. 2009-109831, Japanese Patent No. 3883848 and Japanese Patent 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 Preferred examples include 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. Among these, azo compounds, photocrosslinkable polyimides, photocrosslinkable polyamides, photocrosslinkable polyesters, cinnamate compounds, and chalcone compounds are particularly suitable for use.

[0111] 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.

[0112] 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.

[0113] Figure 8 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 8 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 The λ / 4 plate 72B converts linearly polarized light P0 (light ray MB) to left-circularly polarized light P L Convert them to the following:

[0114] 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.

[0115] 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.

[0116] In the manufacturing method of this liquid crystal layer, 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 manufacturing method of this liquid crystal layer, the substrate may be used as the alignment film.

[0117] Furthermore, in manufacturing method A, the alignment film 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 film 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 film 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.

[0118] -Coating Process- 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. By performing the drying process, the solvent can be removed from the coating film. The thickness of the coating film is not particularly limited and is limited to the thickness T of the liquid crystal layer. Ｌ It is preferable to adjust the thickness as needed to achieve the desired thickness.

[0119] - 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.

[0120] 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.

[0121] Furthermore, the thickness T of the composition layer formed by step 1. Ｃ The ratio T of the liquid crystal alignment pattern to one period Λ Ｃ / Λ is 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.

[0122] The orientation state of the liquid crystal compound in the composition layer obtained by step 1, particularly the orientation state of the liquid crystal compound in the thickness direction, changes depending on the helical induced force of the chiral agent contained in composition A.

[0123] <Step 2> Step 2 is a process to change the helical induced force of the chiral agent contained in the composition layer obtained in Step 1, so that the bright and dark areas originating from the liquid crystal compound are substantially perpendicular to the main surface of the composition layer in the cross-sectional image observed by AFM. As a result of Step 2, the helical induced force of the chiral agent contained in the composition layer is changed, and the orientation state of the liquid crystal compound is changed by the changed helical induced force. As a result, a composition layer is obtained in which bright and dark areas substantially perpendicular to the main surface of the composition layer are observed, similar to the cross-sectional image of the liquid crystal layer shown in Figure 5.

[0124] 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 B (hereinafter also referred to as "chiral agent B1") which induces a helix in the opposite direction to that of chiral agent A by the heat treatment in step 1. As shown in Figure 7, in the composition layer 14 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 surface. When light irradiation treatment is performed on such a composition layer 14 as step 2, the helical induced force of chiral agent A changes. As the helical induced force of chiral agent A changes, the orientation state of the liquid crystal compound changes in accordance with the weighted average helical induced forces of chiral agent A and chiral agent B1. As shown in Figure 5, the liquid crystal compound does not twist in the thickness direction, and bright areas 42 and dark areas 44 that are substantially perpendicular to the main surface of the liquid crystal layer 12 are observed.

[0125] 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 the first and second chiral agents described above are used in combination, it is expressed by the following formula (Y). Formula (Y) Weighted average helical induced force (μm －１ ) = (Helical-inducing force of the first chiral agent (μm) －１ ) × Concentration of the first chiral agent in the composition layer (mass%) + Helical induced force of the second chiral agent (μm) －１) × Concentration of the second chiral agent in the composition layer (mass%) / (Concentration of the first chiral agent in the composition layer (mass%) + Concentration of the second chiral agent 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.

[0126] For example, in the above example, if chiral agent A and chiral agent B1 are present in the composition layer 14 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 light irradiation 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 surface of the composition layer 14.

[0127] 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.

[0128] The light used for irradiation can be any light that is sensitive to chiral agent A. 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 chiral agent A. Examples include the emission 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.

[0129] 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 ２ The above is more preferable. Furthermore, the light irradiation treatment is preferably carried out at 15 to 70°C (preferably 15 to 50°C).

[0130] In the above example, composition A was shown to include chiral agent A and chiral agent B1 which can induce a helix in the opposite direction to that of chiral agent A by heat treatment. However, the chiral agents included in composition A are not limited to the above example. For example, chiral agents A with different wavelengths of light that change the helical induction force may be used, and 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, chiral agent A with a high initial helical induction force and a decrease in helical induction force by light irradiation may be used alone, and 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, so that the light and dark areas are substantially 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.

[0131] When using two or more chiral agents, the concentration and helical induced force of the chiral agents in composition A 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 are substantially perpendicular to the main surface. They may be the same or different for each chiral agent. The absolute value of the weighted average helical induced force of the chiral agents contained in the composition layer after step 2 is the same as the absolute value of the weighted average helical induced force of the chiral agents contained in the liquid crystal layer.

[0132] 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.

[0133] As for the chiral agent used in manufacturing method A and the process for changing 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 so that the light and dark areas are substantially perpendicular to the main surface is particularly preferred.

[0134] 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.

[0135] Another example of making it difficult for the polymerization of liquid crystal compounds to proceed is to use a combination of chiral agent A and a photopolymerization initiator such that each has a different optimal wavelength range of light, and to irradiate with light of different wavelengths in steps 2 and 3. The wavelength of light irradiated in step 2 to change the helical induced force of the chiral agent and the wavelength of light irradiated in step 3 as a curing treatment may be the same or different.

[0136] When the composition layer contains chiral agent A and photopolymerization initiator, the absorption maximum wavelength λa of the photopolymerization initiator and the absorption maximum wavelength λc of chiral agent A may be the same. However, in order to make polymerization of the liquid crystal compound less likely to proceed in step 2, it is preferable that the difference between λa and λc be 20 nm or more, and more preferably 50 nm or more. The upper limit of the difference between λa and λc is not particularly limited, but may be 100 nm or less.

[0137] 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.

[0138] <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.

[0139] 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.

[0140] 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.

[0141] [Applications of the Liquid Crystal Layer] This liquid crystal layer 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. This liquid crystal layer is a single layer, yet it has a thick liquid crystal alignment pattern with few defects. Therefore, when manufacturing an optical element that has the optically required thickness and few defects in the liquid crystal alignment pattern, it is not necessary to form multiple single liquid crystal layers, or at least the number of single liquid crystal layers can be reduced, thus improving the production efficiency of the optical element.

[0142] This liquid crystal layer can be combined with various components. For example, this liquid crystal layer may be combined with other optical anisotropic layers. That is, a laminate may be made that includes a substrate, this liquid crystal layer, and other optical anisotropic layers. The laminate does not need to include a substrate. The other optical 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 is preferably 5 to 300 nm, and more preferably 10 to 200 nm.

[0143] 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 that, for example, when (nx - ny) × d (where d is the thickness of the film) is 0 to 10 nm, preferably 0 to 5 nm, it is included in "nx ≈ ny".

[0144] The method for manufacturing the above-mentioned laminate is not particularly limited and known methods can be cited. For example, one method is to obtain a laminate by laminating the liquid crystal layer with another optically anisotropic layer (e.g., a C-plate). As for the lamination method, another optically anisotropic layer prepared separately may be bonded onto the liquid crystal layer, or a composition for forming another optically anisotropic layer may be applied onto the liquid crystal layer to form another optically anisotropic layer.

[0145] Furthermore, this liquid crystal layer may be combined with a polarizer. That is, a liquid crystal layer with a polarizer may be fabricated having the substrate, this liquid crystal layer, and a polarizer in that order. The liquid crystal layer with a polarizer may have the liquid crystal layer, substrate, and polarizer in that order. Also, the liquid crystal layer with a polarizer may not include a substrate.

[0146] 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.

[0147] The method for manufacturing the above-mentioned liquid crystal layer with a polarizer is not particularly limited and known methods can be used. For example, one method is to obtain a liquid crystal layer with a polarizer by stacking the liquid crystal layer and a polarizer.

[0148] 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.

[0149] 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.

[0150] 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.

[0151] [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.

[0152] 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 ----------------------------------------------------------------

[0153] - Photo-alignment material A -

[0154] An orientation film P-1 having an orientation pattern was formed by exposing the orientation film using the exposure apparatus shown in Figure 8. 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.

[0155] <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 --------------------------------------------------

[0156] Liquid crystal compound L-1

[0157] Liquid crystal compound L-2

[0158] Leveling agent T-1

[0159] Photopolymerization initiator P-1

[0160] Chiral agent K-1

[0161] Chiral agent K-2

[0162] 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.

[0163] <Formation of liquid crystal layer X-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 (corresponding to step 1). Thickness T of the formed liquid crystal layer X-1 Ｌ The amount of composition A-1 applied was adjusted so that the thickness was 0.7 μm. Then, composition layer Y-1 was exposed to ultraviolet light with a wavelength of 365 nm at a temperature of 40°C using a high-pressure mercury lamp in an oxygen-containing atmosphere (oxygen concentration: approximately 20 vol%) at an irradiance of 5 mW / cm². ２ , irradiation amount 100mJ / cm ２ The coating was irradiated under these conditions (corresponding to step 2). Subsequently, under a nitrogen atmosphere and at a temperature of 60°C, ultraviolet light with a wavelength of 365 nm was irradiated using an LED lamp at an irradiance of 10 mW / cm². ２ , irradiation amount 200mJ / cm ２ By irradiating the composition layer Y-1 under these conditions, the orientation of the liquid crystal compound was fixed, and the liquid crystal layer X-1 was formed (corresponding to step 3). As a result, a sample S-1 of an optical element having a support, an alignment film P-1, an alignment film P-2, and a liquid crystal layer X-1 was fabricated.

[0164] [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 instead of composition A-1.

[0165] Composition A-2 -------------------------------------------------- Liquid crystal compound L-3 100.00 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 1.36 parts by mass Chiral agent K-2 0.45 parts by mass Methyl ethyl ketone 323.00 parts by mass Cyclopentanone 323.00 parts by mass --------------------------------------------------

[0166] Liquid crystal compound L-3

[0167] [Comparative Example 1] In Step 1 of Example 1, the following Composition A-3 was used instead of Composition A-1, and the sample S-C1 of the optical element was produced in the same manner as in Example 1, except that the coating amount of Composition A-3 was adjusted so that the thickness T of the formed liquid crystal layer became 0.35 μm. Ｌ A sample S-C1 of the optical element was produced in the same manner as in Example 1, except that the coating amount of Composition A-3 was adjusted so that the thickness T of the formed liquid crystal layer became 0.35 μm.

[0168] Composition A-3 -------------------------------------------------------------------------------- Liquid crystal compound L-1 80.00 parts by mass Liquid crystal compound L-4 20.00 parts by mass Levelling agent T-1 0.40 parts by mass Photoinitiator P-1 2.75 parts by mass Chiral agent K-1 1.20 parts by mass Methyl ethyl ketone 580.00 parts by mass Cyclopentanone 580.00 parts by mass --------------------------------------------------------------------------------

[0169] Liquid crystal compound L-4

[0170] [Comparative Example 2] In Step 1 of Example 1, the following Composition A-4 was used instead of Composition A-1, and the sample S-C2 of the optical element was produced in the same manner as in Example 1.

[0171] Composition A-4 -------------------------------------------------------------------------------- Liquid crystal compound L-1 80.00 parts by mass Liquid crystal compound L-4 20.00 parts by mass Levelling agent T-1 0.40 parts by mass Photoinitiator P-1 2.75 parts by mass Chiral agent K-1 1.20 parts by mass Methyl ethyl ketone 323.00 parts by mass Cyclopentanone 323.00 parts by mass --------------------------------------------------------------------------------

[0172] [Measurement] The physical properties of the liquid crystal layer formed in each example were measured using the following method.

[0173] <Period 1 Λ> The surface of each liquid crystal layer was observed using a polarizing microscope, and it was confirmed that a liquid crystal orientation pattern was formed in which the orientation of the optical axis derived from the liquid crystal compound continuously rotates along the alignment axis D, which is one direction within the plane. In each liquid crystal layer formed in each example, the period Λ, which is the length of a 180° rotation of the optical axis orientation along the alignment axis D, was 1.0 μm.

[0174] <Thickness T of the liquid crystal layer> Ｌ > After embedding the liquid crystal layer samples prepared in each example with UV adhesive, the samples were cut using an ultramicrotome (Leica, UC7 model) to form cross-sections including the thickness direction. These cross-sections were observed with an atomic force microscope (AFM) (Brker "SPM Dimension Icon") to obtain cross-sectional images. From the obtained cross-sectional images, the thickness T of the liquid crystal layer was determined. Ｌ The thickness T of the liquid crystal layer in Example 1, Example 2, and Comparative Example 2 was measured. Ｌ In both cases, the thickness T of the liquid crystal layer in Comparative Example 1 was 0.7 μm. Ｌ It was 0.35 μm.

[0175] <Angle θ> Similar to the thickness measurement method described above, a sample embedded in UV adhesive was cut to form a cross-section including the alignment axis D direction and the thickness direction, and a cross-sectional image was obtained. In the obtained cross-sectional image, the angle θ (°) between the main surface and a straight line L connecting the centers of the bright areas on one main surface and the centers of the bright areas on the other main surface was measured. As a result of the above measurement, a stripe-like pattern as shown in Figure 5 was observed in the cross-section of the liquid crystal layer formed in Example 1 and the liquid crystal layer formed in Example 2, and the angle θ between the bright and dark areas and the main surface was 90°. In addition, a stripe-like pattern in which the bright and dark areas were inclined relative to the main surface was observed in the cross-section of the liquid crystal layer formed in Comparative Example 1, and the angle θ between the bright and dark areas and the main surface was 58°. On the other hand, in the liquid crystal layer formed in Comparative Example 2, the orientation of the liquid crystal compound was disordered, and no stripe-like pattern consisting of bright and dark areas was observed in the cross-section, so the angle θ could not be measured.

[0176] <Distribution of leveling agent> As described above, from one surface to the other surface of the liquid crystal layer formed in each example, Ar ＋ ion beam was irradiated from a cluster gun, and while cutting the liquid crystal layer in the depth direction, the components in the depth direction of the liquid crystal layer were analyzed using a time-of-flight secondary ion mass spectrometer (TOF-SIMS) ("SIMS5" manufactured by IONTOF). The depth-direction profile of the secondary ion intensity derived from the leveling agent obtained for each liquid crystal layer was a profile as shown in FIG. 6, and at any depth in the region between the first position and the second position in the liquid crystal layer, no secondary ion intensity derived from the leveling agent of 1 / 500 or more of the first intensity was observed. Thereby, it was confirmed that each liquid crystal layer was a single layer.

[0177] [Evaluation] For each optical element of each example, the liquid crystal alignment pattern on the surface (main surface) of the liquid crystal layer was observed using a polarizing microscope, the alignment state of the liquid crystal compound was confirmed, and the number of defects caused by the alignment disorder of the liquid crystal compound was measured. Based on the following evaluation criteria, the alignment defects of each liquid crystal layer were evaluated from the number of defects per surface area of the liquid crystal layer. For the liquid crystal layer formed in Comparative Example 2, the disorder of the alignment of the liquid crystal compound was large, and the above evaluation could not be performed. ≪Alignment defect evaluation criteria≫ "S": The number of defects is 1 defect / cm ２ or less "A": The number of defects is 1 defect / cm ２ to more than 10 defects / cm ２ "B": The number of defects is 10 defects / cm ２ or more

[0178] In the following table, the types and contents of the liquid crystal compound and the chiral agent used for forming each liquid crystal layer, the one-period Λ of the liquid crystal alignment pattern of the liquid crystal layer, the thickness T Ｌ of the liquid crystal layer, the ratio T Ｌ of T to Λ for one period Λ Ｌ of the liquid crystal layer, the angle θ, the value calculated from formula (2), and the evaluation result of the alignment are shown respectively.

[0179]

[0180] ​​As shown in Table 1 above, the angle θ between the light and dark areas and the main surface is 90°, and the thickness T of the liquid crystal layer relative to one period Λ in the liquid crystal alignment pattern is 90°. Ｌ ratio T Ｌ The liquid crystal layers of Examples 1 and 2, where / Λ is 1 / 2 or greater, were confirmed to be thicker and have fewer alignment defects compared to the liquid crystal layers of Comparative Examples 1 and 2.

[0181] Furthermore, a comparison of Examples 1 and 2 confirmed that when the chiral agent content is 5% by mass or more relative to the total mass of the liquid crystal layer, the orientation defects are reduced, resulting in a liquid crystal layer with superior orientation.

[0182] 12, 12c Liquid crystal layer 12a, 12b, 14a, 14b Main surface 14 Composition layer 30 Substrate 32 Alignment film 40 Liquid crystal compound 40A Optical axis 42 Bright area 44 Dark area 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 1 period L Straight line La, Lb Line segment L １ , L ２ Incident light L ４ , L ５ Emitted light M Laser light MA, MB Ray O1, O2 Center P ０ Linear polarized light P Ｒ Right-circular polarization P Ｌ Left circular polarization α crossing angle

Claims

1. A liquid crystal layer comprising a liquid crystal compound and a chiral agent, wherein the liquid crystal layer has a liquid crystal orientation pattern in which the orientation of the optical axis originating from the liquid crystal compound changes while continuously rotating along at least one direction in the plane, and in a cross-section of the liquid crystal layer including the one direction and the thickness direction as observed by an atomic force microscope, the angle θ between the bright and dark areas originating from the optical axis of the liquid crystal compound and the main surface of the liquid crystal layer is 50 to 90°, and the thickness T of the liquid crystal layer Ｌ 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 the one direction satisfies the following equation (1), T Ｌ / Λ ≥ 1 / 2 (1) A single-layer liquid crystal layer.

2. The liquid crystal layer according to claim 1, further comprising a leveling agent.

3. The liquid crystal layer according to claim 2, wherein the leveling agent is at least one selected from the group consisting of silicone-based leveling agents and fluoroalkyl-based leveling agents.

4. A liquid crystal layer according to claim 2, satisfying the following requirement A: (Requirement A) Analyzing the components of the liquid crystal layer in the depth direction by time-of-flight secondary ion mass spectrometry while irradiating the liquid crystal layer from one main surface toward the other main surface with an ion beam, obtaining a profile of the secondary ion intensity derived from the leveling agent in the depth direction, and setting the larger secondary ion intensity derived from the leveling agent at the one main surface of the liquid crystal layer and the secondary ion intensity derived from the leveling agent at the other main surface of the liquid crystal layer as the first intensity, setting the secondary ion intensity that is 1 / 1000 of the first intensity as the second intensity, setting the depth position closest to the one main surface among the depth positions showing the second intensity in the profile as the first position, and setting the depth position closest to the other main surface among the depth positions showing the second intensity in the profile as the second position, in which case no secondary ion intensity derived from the leveling agent greater than 1 / 500 of the first intensity is observed at any depth in the region between the first position and the second position.

5. The liquid crystal layer according to any one of claims 1 to 4, wherein the chiral agent comprises a first chiral agent having a right-handed helical inductive force and a second chiral agent having a left-handed helical inductive force.

6. Thickness T of the liquid crystal layer Ｌ A liquid crystal layer according to any one of claims 1 to 4, wherein the (μm), the angle θ (°), and the content Q (mass%) of the chiral agent relative to the total mass of the liquid crystal layer satisfy the following formula (2): |θ / (T Ｌ / Q) | > 133 (2) 7. The liquid crystal layer according to any one of claims 1 to 4, wherein the content Q of the chiral agent in the liquid crystal layer is 1% by mass or more with respect to the total mass of the liquid crystal layer.

8. The liquid crystal layer according to any one of claims 1 to 4, wherein the content Q of the chiral agent in the liquid crystal layer is 5% by mass or more with respect to the total mass of the liquid crystal layer.

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