JP7012603B2 - Manufacturing method of optical element and optical element - Google Patents

Description

The present invention relates to a method for manufacturing an optical element and an optical element.

In a liquid crystal layer formed by using a composition containing a liquid crystal compound, a liquid crystal lens (liquid crystal diffraction lens) that diffracts and transmits incident light in a desired direction by controlling the direction of an optical axis derived from the liquid crystal compound. Is obtained.
As an example, a liquid crystal alignment pattern is exemplified in which the liquid crystal compound is oriented so that the orientation of the optical axis derived from the liquid crystal compound changes while continuously rotating toward a predetermined direction in the plane of the liquid crystal layer. .. According to this liquid crystal alignment pattern, light can be diffracted in a direction in which the direction of the optical axis changes while continuously rotating depending on the swirling direction of the circularly polarized light incident on the liquid crystal layer.

For example, in Patent Document 1, two transparent substrates having an optically transparent electrode film and an alignment film are held with a certain gap, and a liquid crystal compound (liquid crystal) is sealed in the gap of the transparent substrate. Further, a Frenelzone plate having a polarization separation function, in which one or both surfaces of an alignment film are subjected to an alignment treatment, is described.
Specifically, Patent Document 1 describes a one-dimensional Frenelzone plate in which the surface of an alignment film is oriented so that the orientation of the liquid crystal compound is symmetrically distributed in one direction. There is. In other words, in Patent Document 1, the direction of the optical axis derived from the liquid crystal compound changes while continuously rotating in one direction, and at a certain position toward one direction, the direction of the optical axis rotates. A one-dimensional Frenel zone plate that has been oriented so that the direction is reversed is described.

Further, Patent Document 1 also describes a two-dimensional Frenel zone plate in which the surface of the alignment film is subjected to an orientation treatment so that the orientation orientation of the liquid crystal compound is distributed point-symmetrically. In other words, Patent Document 1 describes a two-dimensional Fresnel zone plate in which the orientation of the optical axis derived from the liquid crystal compound is oriented so as to rotate continuously radially from the center. .. In this two-dimensional Fresnel zone plate, the direction of rotation of the optical axis derived from the liquid crystal compound on a straight line passing through the center point of radiation is reversed at the center.

The Fresnel zone plate described in Patent Document 1 acts as a convex lens or a concave lens depending on the turning direction of the incident circularly polarized light.
For example, the Fresnel zone plate described in Patent Document 1 acts as a convex lens to collect light when left circular polarization is incident, and acts as a concave lens when right circular polarization is incident. , Diffuse light.

Further, Patent Document 2 has a pattern alignment film whose surface is patterned so that the orientation direction continuously rotates in one direction, and a cholesteric liquid crystal phase is fixed on the surface of the pattern alignment film. A reflective structure forming a cholesteric liquid crystal layer is described.
In this reflective structure, due to the action of the pattern alignment film, the cholesteric liquid crystal layer changes the direction of the optical axis derived from the liquid crystal compound while continuously rotating in one direction in the plane. Have.
As a result, in the reflection structure of Patent Document 2, the reflection direction of the incident light (incident circular polarization) changes in one direction in which the optical axis continuously rotates with respect to the specular reflection. For example, when light is incident on the reflection structure of Patent Document 2 from the normal direction (direction light orthogonal to the surface of the cholesteric liquid crystal layer), the reflected light is not mirror reflection (retroreflection) but an optical axis. Is reflected at an angle in one direction that rotates continuously.

The reflection direction of this light differs depending on the rotation direction of the optical axis in the cholesteric liquid crystal layer in one direction in which the optical axis rotates continuously.
For example, in the reflection structure of Patent Document 2, the direction of rotation of the optical axis toward the x direction when light (circular polarization) is incident from the normal direction, with one direction in which the optical axis rotates continuously as the x direction. When is clockwise, the light is tilted and reflected in the x direction. On the contrary, when the rotation direction of the optical axis toward the x direction is counterclockwise, the light is inclined and reflected in the direction opposite to the x direction.
Therefore, in the reflection structure of Patent Document 2, a reflection structure that condenses or diffusely reflects light is obtained by reversing the rotation direction of the optical axis in one direction in which the optical axis rotates continuously. Be done.

Japanese Unexamined Patent Publication No. 2005-274847 International Publication No. 2016/194961

As described in Patent Document 1 and Patent Document 2, according to the liquid crystal layer in which the orientation of the optical axis derived from the liquid crystal compound is controlled, a liquid crystal lens, a reflective structure, etc. that diffract the incident light in a desired direction, etc. Optical element is obtained.

However, in order to form an alignment film that orients the liquid crystal compound in this way, it is necessary to control the orientation in a minute region with high definition.
To deal with this, in the formation of the alignment film in the manufacture of liquid crystal lenses, for example, a nanorubbing method using an atomic force microscope (AFM) nanoprobe, or microneedles such as a diamond needle and a sapphire needle are used. It is necessary to perform orientation processing by a micro-rubbing method, writing by ND: YAG laser writing, or the like.
Therefore, in the manufacture of a liquid crystal lens, it takes a lot of time and effort to form an alignment film, and a large-scale device is required.

An object of the present invention is to solve such a problem of the prior art, and it is manufactured by a method for manufacturing an optical element capable of manufacturing an optical element such as a liquid crystal lens by a simple method, and a method for manufacturing the optical element. It is an object of the present invention to provide an optical element such as a lens which can be made.

In order to solve this problem, the present invention has the following configurations.
[1] One surface of the substrate is subjected to an orientation treatment for orienting the liquid crystal compound so that the optical axis derived from the liquid crystal compound is in one direction.
An alignment film composition containing a liquid crystal compound and a chiral agent whose spiral-inducing force changes by irradiation with light is applied to the surface of the alignment-treated substrate to form a coating film.
A part of the coating film of the alignment film composition is irradiated with light exposed to the chiral agent.
The coating film of the alignment film composition irradiated with light is cured to form an alignment film, and the alignment film is formed.
A method for manufacturing an optical element, which comprises applying a composition containing a liquid crystal compound to the surface of an alignment film and curing it to form a liquid crystal layer.
[2] The method for manufacturing an optical element according to [1], wherein the light irradiating the coating film of the alignment film composition is spot light.
[3] The method for manufacturing an optical element according to [2], wherein the spot shape of the spot light is circular or elliptical.
[4] The method for manufacturing an optical element according to [1], wherein the light irradiating the coating film of the alignment film composition is linear light.
[5] The method for manufacturing an optical element according to any one of [1] to [4], wherein the liquid crystal layer is a cholesteric liquid crystal layer in which a cholesteric liquid crystal phase is fixed.
[6] It has an alignment film formed by using a liquid crystal compound and a chiral agent whose spiral-inducing force changes by irradiation with light, and a liquid crystal layer laminated on the alignment film.
In the alignment film, the optical axis derived from the liquid crystal compound is oriented in one direction on the first surface, which is one surface, and the optical axis derived from the liquid crystal compound is oriented on the second surface, which is the other surface. It has a liquid crystal orientation pattern that changes while continuously rotating in at least one direction, and in the middle, the direction of rotation of the direction of the optical axis derived from the liquid crystal compound is reversed.
The liquid crystal layer is laminated on the second surface of the alignment film, and the liquid crystal compound is oriented on the surface of the alignment film on the second surface side according to the liquid crystal alignment pattern on the second surface of the alignment film. An optical element characterized by this.
[7] The optical element according to [6], wherein the liquid crystal layer is a cholesteric liquid crystal layer in which the cholesteric liquid crystal phase is fixed.
[8] The liquid crystal alignment pattern on the second surface of the alignment film has a plurality of directions in which the direction of the optical axis derived from the liquid crystal compound changes while continuously rotating, and the optical axis derived from the liquid crystal compound. The direction of rotation of the optical axis derived from the liquid crystal compound is reversed at one point where a plurality of directions intersect at one point and the directions of the above intersect while continuously rotating. , The optical element according to [6] or [7], which is a liquid crystal alignment pattern.
[9] The liquid crystal alignment pattern on the second surface of the alignment film is a liquid crystal alignment pattern having only one direction in which the direction of the optical axis derived from the liquid crystal compound changes while continuously rotating. [6] Or the optical element according to [7].

According to the present invention, an optical element such as a liquid crystal lens can be obtained by a simple method.

It is a figure which shows an example of the optical element of this invention conceptually. It is a figure which conceptually shows the alignment film of the optical element shown in FIG. It is a figure which conceptually shows the lower surface of the alignment film of the optical element shown in FIG. It is a figure which conceptually shows the upper surface of the alignment film of the optical element shown in FIG. It is a figure which conceptually shows the vicinity of the interface between the alignment film of an optical element shown in FIG. 1 and a liquid crystal layer. It is a figure which conceptually shows the lower surface of the liquid crystal layer of the optical element shown in FIG. It is a conceptual diagram for demonstrating the operation of the liquid crystal layer of the optical element shown in FIG. It is a conceptual diagram for demonstrating the operation of the liquid crystal layer of the optical element shown in FIG. It is a conceptual diagram for demonstrating the operation of the optical element shown in FIG. It is a figure which conceptually shows another example of the optical element of this invention. It is a figure which conceptually shows the upper surface of the alignment film of the optical element shown in FIG. FIG. 10 is a diagram conceptually showing the vicinity of the interface between the alignment film of the optical element shown in FIG. 10 and the liquid crystal layer. FIG. 10 is a diagram conceptually showing the lower surface of the liquid crystal layer of the optical element shown in FIG. It is a conceptual diagram for demonstrating the operation of the liquid crystal layer of the optical element shown in FIG. It is a conceptual diagram for demonstrating the operation of the liquid crystal layer of the optical element shown in FIG. It is a conceptual diagram for demonstrating the operation of the optical element shown in FIG. It is a conceptual diagram for demonstrating an example of the manufacturing method of the optical element shown in FIG. It is a figure which conceptually shows another example of the optical element of this invention. It is a figure which conceptually shows the lower surface of the alignment film of the optical element shown in FIG. It is a figure which conceptually shows the upper surface of the alignment film of the optical element shown in FIG. It is a figure which conceptually shows the lower surface of the liquid crystal layer of the optical element shown in FIG. It is a conceptual diagram for demonstrating an example of the manufacturing method of the optical element shown in FIG. It is a conceptual diagram of the mask used in the Example of this invention. It is a conceptual diagram of the mask used in the Example of this invention.

Hereinafter, the method for manufacturing an optical element and the optical element of the present invention will be described in detail with reference to preferred embodiments shown in the accompanying drawings.

The numerical range represented by using "-" in the present specification means a range including the numerical values before and after "-" as the lower limit value and the upper limit value.
As used herein, "(meth) acrylate" is used to mean "either or both of acrylate and methacrylate".

FIG. 1 conceptually shows an example of the optical element of the present invention.
The optical element 10 shown in FIG. 1 has a substrate 12, an alignment film 14, and a liquid crystal layer 16.

In the optical element 10 of the present invention, the alignment film 14 is formed by using a liquid crystal compound and a chiral agent whose spiral-inducing force changes by irradiation with light.
Further, the alignment film 14 is oriented on the surface 14a on the substrate 12 side so that the direction of the optical axis derived from the liquid crystal compound is one direction, that is, the direction of the arrow X in the figure (horizontal direction in the figure). is doing. Further, in the alignment film 14, on the surface 14b on the liquid crystal layer 16 side, the direction of the optical axis derived from the liquid crystal compound changes while continuously rotating in at least one direction in the plane, that is, in the direction of arrow X. Moreover, it has a liquid crystal orientation pattern in which the rotation direction of the direction of the optical axis derived from the liquid crystal compound is reversed on the way (see FIGS. 2 to 4).
The optical axis derived from the liquid crystal compound is the axis having the highest refractive index in the liquid crystal compound, and for example, in the case of a rod-shaped liquid crystal compound, the long axis corresponds.
In the optical element 10, the surface 14a on the substrate 12 side of the alignment film 14 corresponds to the first surface in the present invention, and the surface 14b on the liquid crystal layer 16 side of the alignment film 14 corresponds to the second surface in the present invention. ..

In the following description, the upper part in FIG. 1, that is, the liquid crystal layer 16 side is also referred to as "upper", and the lower part in the figure, that is, the substrate 12 side is also referred to as "lower". Accordingly, the surface 14a on the substrate 12 side of the alignment film 14 is also referred to as "lower surface 14a", and the surface 14b on the liquid crystal layer 16 side of the alignment film 14 is also referred to as "upper surface 14b".
Further, in the following description, the optical axis derived from the liquid crystal compound is also simply referred to as "optical axis of the liquid crystal compound" or "optical axis".
Further, in the following description, the rotation of the direction of the optical axis is also simply referred to as "the rotation of the optical axis". In addition, in the following description, the change of the optical axis while continuously rotating in one direction is also simply referred to as "the optical axis rotates in one direction".
Further, in the following description, the "arrow X direction" is also simply referred to as "X direction".

In the optical element 10 of the present invention, on the lower surface of the liquid crystal layer 16 (the surface on the alignment film 14 side), the liquid crystal compound is oriented according to the liquid crystal alignment pattern on the upper surface 14b of the alignment film 14.
That is, on the lower surface of the liquid crystal layer 16 of the optical element 10, the liquid crystal is such that the optical axis of the liquid crystal compound rotates in the X direction and the rotation direction of the optical axis is reversed in the middle. It has a liquid crystal alignment pattern in which the compound is oriented.

Such an optical element 10 of the present invention can be manufactured by the method for manufacturing an optical element of the present invention, which will be described later.

The substrate 12 supports the alignment film 14 and the liquid crystal layer 16.
The substrate 12 is not limited, and various sheet-like materials (films, plate-like materials) can be used as long as the alignment film 14 and the liquid crystal layer 16 can be supported.
As an example, a substrate 12 made of glass and a film made of a resin such as triacetyl cellulose (TAC), polyethylene terephthalate (PET), polycarbonate, polyvinyl chloride, acrylic and polyolefin is exemplified.

The substrate 12 may be transparent (light transmissive) or opaque.
However, when the optical element of the present invention is used for a purpose of transmitting light like a lens while holding the substrate 12, the substrate 12 is preferably transparent. Specifically, when the substrate 12 is transparent, the substrate 12 preferably has a total light transmittance of 50% or more in accordance with JIS (Japanese Industrial Standards) K 7631-1 (1996). It is more preferably 70% or more, and further preferably 85% or more.

In the optical element 10 of the illustrated example, the surface of the substrate 12 is subjected to orientation treatment. This alignment process is an alignment process for aligning the liquid crystal compound on the lower surface 14a of the alignment film 14 so that the optical axes coincide with the X direction. For example, the surface of the substrate 12 is oriented by rubbing in the X direction.
That is, in the optical element 10, the substrate 12 also has an action as an alignment film for orienting the liquid crystal compound on the lower surface 14a of the alignment film 14.
There are no restrictions on the method of aligning the surface of the substrate 12, and various known methods such as an alignment treatment by rubbing and a method of providing an alignment film such as a photoalignment film and an oblique vapor deposition film of an inorganic compound are available. It is available.

The optical element of the present invention does not have to have the substrate 12.
That is, the optical element of the present invention may be formed by forming the liquid crystal layer 16 by manufacturing the optical element of the present invention, which will be described later, and then peeling off the substrate 12, or after peeling off the substrate 12, the glass plate or the like may be used. It may be attached to the support of the above, or as shown in Examples described later, the substrate 12 may be peeled off after being attached to another support.

An alignment film 14 is provided on one surface of the substrate 12.
The optical element of the present invention is not limited to a configuration in which the alignment film 14 and the liquid crystal layer 16 are provided only on one surface of the substrate 12, unlike the optical element 10 in the illustrated example. That is, the optical element of the present invention may have a configuration in which both surfaces of the substrate 12 are subjected to the alignment treatment as described above, and further have an alignment film 14 and a liquid crystal layer 16 described later.

The alignment film 14 is a film for orienting the liquid crystal compound of the liquid crystal layer 16 described later.
FIG. 2 conceptually shows the alignment film 14. Note that FIG. 2 is a view of the alignment film 14 viewed from the same direction as that of FIG. 1, that is, a view of the optical element 10 viewed in the plane direction of the substrate 12.
Further, FIG. 3 conceptually shows the lower surface 14a (surface on the substrate 12 side) of the alignment film 14, and FIG. 4 conceptually shows the upper surface 14b (surface on the liquid crystal layer 16 side) of the alignment film 14. That is, FIG. 3 is a view of the alignment film 14 viewed from below of FIGS. 1 and 2, and FIG. 4 is a view of the alignment film 14 viewed from above of FIGS. 1 and 2, that is, a flat surface. It is a figure.

As described above, the alignment film 14 is formed by using a liquid crystal compound and a chiral agent whose spiral-inducing force is changed by irradiation with light. In the following description, the spiral-induced force is also referred to as HTP. HTP is an abbreviation for "Helical Twisting Power".
On the lower surface 14a of the alignment film 14, the liquid crystal compound 20 is oriented so that the optical axis coincides with the X direction. In the illustrated example, the liquid crystal compound 20 is, for example, a rod-shaped liquid crystal compound, and the longitudinal direction of the liquid crystal compound 20 and the direction of the optical axis coincide with each other. The same applies to the liquid crystal compounds of the optical elements shown in FIGS. 10 and 18.
On the other hand, on the upper surface 14b of the alignment film 14, the optical axis of the liquid crystal compound 20 is rotating in the plane toward the X direction in the drawing, and the rotation direction of the optical axis is reversed in the middle of the X direction. Has a liquid crystal orientation pattern. In the illustrated example, the liquid crystal compound 20 on the upper surface 14b has its optical axis rotated counterclockwise from the state where the optical axis coincides with the X direction toward the X direction, and the rotation direction changes when the optical axis rotates 180 °. It has a liquid crystal orientation pattern that reverses and rotates 180 ° clockwise toward the downstream.
The fact that the optical axis of the liquid crystal compound 20 is rotated in the X direction (one direction) means that the angle formed by the optical axis of the liquid crystal compound 20 arranged along the X direction and the X direction is specifically. , It depends on the position in the X direction, and means that the angle formed by the optic axis and the X direction changes sequentially from θ to θ + 180 ° or θ-180 ° toward the X direction.
In addition, "the optical axis of the liquid crystal compound is rotating in one direction" specifically means that "the direction of the optical axis derived from the liquid crystal compound changes while continuously rotating in one direction." It is as described above that it indicates that it is doing.

In the optical element of the present invention, the alignment pattern of the liquid crystal compound 20 on the upper surface 14b of the alignment film 14 is not limited to this configuration, and various alignment patterns can be used.
For example, the optical axis rotates by a predetermined angle toward the X direction, then the rotation direction of the optical axis is reversed, and the optical axis rotates by a predetermined angle toward the X direction. It may be a pattern. That is, in the illustrated example, the optical axis rotates 180 ° counterclockwise toward the X direction, and then the rotation direction of the optical axis is reversed so that the optical axis rotates 180 ° clockwise. , The liquid crystal orientation pattern may be repeated in the X direction.
As will be described later, the rotation angle of the optical axis of the liquid crystal compound 20 is not limited to 180 ° and may be less than 180 °, for example 90 °, or more than 180 °, for example 360 °.

Further, the direction of the optical axis of the liquid crystal compound 20 on the lower surface 14a of the alignment film 14 is not limited to the direction in which the direction of the optical axis changes in the X direction, that is, the upper surface 14b, as shown in the illustrated example. For example, in the illustrated example, the directions of the optical axes of the liquid crystal compound 20 on the lower surface 14a of the alignment film 14 may all coincide with the directions orthogonal to the X direction (the Y direction described later).

The alignment film 14 is formed by using a chiral agent and a liquid crystal compound. Therefore, the liquid crystal compound 20 contained in the alignment film 14 is twisted and oriented along a spiral axis extending along the thickness direction by the action of the chiral agent. As shown in FIG. 2, in the alignment film 14, the twisting direction of the spiral axis of the liquid crystal compound 20 is, as an example, a right-handed twist.
As described above, on the lower surface 14a of the alignment film 14, the direction of the optical axis of the liquid crystal compound 20 coincides with the X direction. On the other hand, on the upper surface 12b of the alignment film 14, the optical axis of the liquid crystal compound 20 is continuously rotated in the X direction. Further, the chiral agent changes HTP by irradiation with light.
That is, in the alignment film 14, the twist angle of the liquid crystal compound 20 gradually changes toward the X direction.

As shown in FIGS. 3 and 4, in the alignment film 14, the liquid crystal compounds 20 are two-dimensionally arranged in the (arrow) X direction and the arrow Y direction orthogonal to the X direction. Therefore, in FIGS. 1 and 2, the arrow Y direction is orthogonal to the paper surface. In the following description, the "arrow Y direction" is also simply referred to as the "Y direction".
Further, as shown in FIGS. 3 and 4, the liquid crystal compounds 20 arranged in the Y direction, that is, each row in the X direction, have the same optical axis direction. That is, in the alignment film 14, the liquid crystal compounds 20 arranged in the Y direction have the same twist angle in the twist orientation along the spiral axis extending along the thickness direction. Therefore, the alignment film 14 has a different twist angle of the liquid crystal compound 20 only in the X direction, and the optical axis rotates on the upper surface 14b.

Specifically, assuming that each row of the liquid crystal compound 20 in the X direction is an x1 row, an x2 row, ..., X13 rows toward the X direction, the liquid crystal compound 20 of the alignment film 14 has a lower surface in the x1 row. In 14a, the optical axis is twisted and oriented by 180 ° along a spiral axis extending along the thickness direction from the state where the optical axis coincides with the X direction, and on the upper surface 14b, the optical axis coincides with the X direction (liquid crystal compound 20). The twist angle is 180 °).
In the x2 row, the liquid crystal compound 20 is twisted and oriented by 150 ° along a spiral axis extending along the thickness direction from the state where the optical axis coincides with the X direction on the lower surface 14a, and the optical axis is oriented in the X direction on the upper surface 14b. It is tilted by 30 ° with respect to the liquid crystal compound 20 (the twist angle of the liquid crystal compound 20 is 150 °).
In the x3 row, the liquid crystal compound 20 is twisted and oriented by 120 ° along a spiral axis extending along the thickness direction from the state where the optical axis coincides with the X direction on the lower surface 14a, and the optical axis is oriented in the X direction on the upper surface 14b. It is tilted by 60 ° with respect to the liquid crystal compound 20 (the twist angle of the liquid crystal compound 20 is 120 °).
In the x4 row, the liquid crystal compound 20 is twisted and oriented by 90 ° along a spiral axis extending along the thickness direction from the state where the optical axis coincides with the X direction on the lower surface 14a, and the optical axis is oriented in the X direction on the upper surface 14b. It is tilted 90 ° with respect to the liquid crystal compound 20 (the twist angle of the liquid crystal compound 20 is 90 °).
In the x5 row, the liquid crystal compound 20 is twisted and oriented by 60 ° along a spiral axis extending along the thickness direction from the state where the optical axis coincides with the X direction on the lower surface 14a, and the optical axis is oriented in the X direction on the upper surface 14b. It is tilted 120 ° with respect to the liquid crystal compound 20 (the twist angle of the liquid crystal compound 20 is 60 °).
In the x6 row, the liquid crystal compound 20 is twisted and oriented by 30 ° along a spiral axis extending along the thickness direction from the state where the optical axis coincides with the X direction on the lower surface 14a, and the optical axis is oriented in the X direction on the upper surface. It is tilted by 150 ° (the twist angle of the liquid crystal compound 20 is 30 °).
In the x7 row, the liquid crystal compound 20 is not twist-oriented, and the optical axis of the liquid crystal compound 20 is aligned with the X direction even on the upper surface 14b while the optical axis is aligned with the X direction on the lower surface 14a side (the liquid crystal compound 20). The twist angle is 0 °).
In the x8 row, as in the x6 row, the liquid crystal compound 20 is twisted and oriented by 30 ° along the spiral axis extending along the thickness direction from the state where the optical axis coincides with the X direction on the lower surface 14a, and on the upper surface 14b. The optical axis is tilted by 150 ° with respect to the X direction (the twist angle of the liquid crystal compound 20 is 30 °).
In the x9 row, as in the x5 row, the liquid crystal compound 20 is twisted and oriented by 60 ° along the spiral axis extending along the thickness direction from the state where the optical axis coincides with the X direction on the lower surface 14a, and on the upper surface 14b. The optical axis is tilted by 120 ° with respect to the X direction (the twist angle of the liquid crystal compound 20 is 60 °).
In the x10 row, as in the x4 row, the liquid crystal compound 20 is twisted and oriented by 90 ° along the spiral axis extending along the thickness direction from the state where the optical axis coincides with the X direction on the lower surface 14a, and on the upper surface 14b. The optical axis is tilted 90 ° with respect to the X direction (the twist angle of the liquid crystal compound 20 is 90 °).
In the x11 row, as in the x3 row, the liquid crystal compound 20 is twisted and oriented by 120 ° along the spiral axis extending along the thickness direction from the state where the optical axis coincides with the X direction on the lower surface 14a, and on the upper surface 14b. The optical axis is tilted by 60 ° with respect to the X direction (the twist angle of the liquid crystal compound 20 is 120 °).
In the x12 row, as in the x2 row, the liquid crystal compound 20 is twisted and oriented by 160 ° along the spiral axis extending along the thickness direction from the state where the optical axis coincides with the X direction on the lower surface 14a, and on the upper surface 14b. The optical axis is tilted by 30 ° with respect to the X direction (the twist angle of the liquid crystal compound 20 is 160 °).
In the x13 row, as in the x1 row, the liquid crystal compound 20 is twisted and oriented by 180 ° along the spiral axis extending along the thickness direction from the state where the optical axis coincides with the X direction on the lower surface 14a, and is twisted and oriented on the upper surface 14b. The optical axis coincides with the X direction (the twist angle of the liquid crystal compound 20 is 180 °).

In the present invention, the twist angle of the twist-oriented liquid crystal compound 20 is from the lower surface 14a to the upper surface 14b of the liquid crystal compound 20 twist-oriented along the spiral axis extending along the thickness direction in the alignment film 14. It is the twist angle to reach.

That is, in the liquid crystal compound 20 of the alignment film 14, the twist angle gradually decreases from the maximum of 180 ° to the minimum of 0 ° between the x1 row and the x7 row in the X direction, and the x7 row. Between the x13 rows, the twist angle gradually increases from the minimum of 0 ° to the maximum of 180 °.
Therefore, the rotation direction of the optical axis of the liquid crystal compound 20 on the upper surface 14b of the alignment film 14 is counterclockwise in the x1 row to the x7 row toward the X direction, and the rotation direction is reversed in the x7 row, and the rotation direction is reversed in the x7 row to the x7 row. In the x13 row, it is clockwise in the X direction.

In the optical element 10 of the present invention, the twist angle of the liquid crystal compound 20 in the alignment film 14 is not limited to 0 to 180 ° in the illustrated example, and any twist angle can be used.
The maximum twist angle and the minimum twist angle of the liquid crystal compound 20 in the alignment film 14 are the type of the chiral agent in the alignment film 14, the amount of the chiral agent added to the alignment film 14, and the alignment film composition in the production method of the present invention described later. It can be adjusted by the size of the light (spot size, line width) irradiating the coating film of the above, the amount of the same light, and the like.

Further, on the upper surface 14b of the alignment film 14, the rotation angle of the optical axis until the rotation direction of the optical axis of the liquid crystal compound 20 is reversed is not limited to 180 ° in the illustrated example, and any rotation angle can be used. be.
The rotation angle of the optical axis on the upper surface 14b of the alignment film 14 in which the rotation direction of the optical axis of the liquid crystal compound 20 is reversed is determined by the type of the chiral agent in the alignment film 14, the amount of the chiral agent added to the alignment film 14, and the amount described later. It can be adjusted by the magnitude of light irradiating the coating film of the alignment film composition in the production method of the present invention, the interval of the same light, the amount of the same light, and the like.

The thickness of the alignment film 14 is also not particularly limited, and a spiral extending along the thickness direction depending on the type of the liquid crystal compound forming the alignment film 14, the components added to the alignment film 14 such as a chiral agent, and the like. The thickness of the liquid crystal compound 20 twist-oriented along the axis may be appropriately set so as to realize the desired maximum twist angle.
The thickness of the alignment film 14 is preferably 0.1 to 10 μm, more preferably 0.1 to 5 μm, and even more preferably 0.1 to 1 μm.

As an example, the alignment film 14 is in a state in which the polymerizable liquid crystal compound is twist-oriented along a spiral axis extending along the thickness direction, and then polymerized and cured by ultraviolet irradiation, heating, etc., and has no fluidity. The layer is formed, and at the same time, it is changed to a state in which the orientation form is not changed by an external field or an external force.
In the present invention, the optical axis of the liquid crystal compound 20 may rotate in the X direction (one direction) only on the upper surface 14b. Therefore, when the alignment film 14 is completed, the liquid crystal compound 20 does not have to exhibit liquid crystallinity. For example, the polymerizable liquid crystal compound may lose its liquid crystal property by increasing its molecular weight by a curing reaction.

Examples of the material used for forming the alignment film 14 include a liquid crystal composition for forming the alignment film 14, which contains a liquid crystal compound and a chiral agent, that is, the alignment film composition in the production method of the present invention. The liquid crystal compound is preferably a polymerizable liquid crystal compound.
Further, the chiral agent added to the alignment film composition is a chiral agent whose HTP changes by irradiation with light, as described above.

－－Polymerizable liquid crystal compound －－
The polymerizable liquid crystal compound may be a rod-shaped liquid crystal compound or a disk-shaped liquid crystal compound, but is preferably a rod-shaped liquid crystal compound as shown in the illustrated example.
Examples of the rod-shaped polymerizable liquid crystal compound forming the alignment film 14 include a rod-shaped nematic liquid crystal compound. Examples of the rod-shaped nematic liquid crystal compound include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, and alkoxy-substituted phenylpyrimidines. , Phenyldioxans, trans, alkenylcyclohexylbenzonitriles and the like are preferably used. Not only low molecular weight liquid crystal compounds but also high molecular weight liquid crystal compounds can be used.

The polymerizable liquid crystal compound is obtained by introducing a polymerizable group into the liquid crystal compound. Examples of the polymerizable group include an unsaturated polymerizable group, an epoxy group, and an aziridinyl group, and an unsaturated polymerizable group is preferable, and an ethylenically unsaturated polymerizable group is more preferable. The polymerizable group can be introduced into the molecule of the liquid crystal compound by various methods. The number of polymerizable groups contained in the polymerizable liquid crystal compound is preferably 1 to 6, more preferably 1 to 3.
Examples of polymerizable liquid crystal compounds include Makromol. Chem. , 190, 2255 (1989), Advanced Materials 5, 107 (1993), US Pat. No. 4,683,327, US Pat. No. 5,622,648, US Pat. No. 5,770,107, International Publication No. 95/22586, International Publication No. 95/24455, International Publication No. 97/00600, International Publication No. 98/23580, International Publication No. 98/52905, Japanese Patent Application Laid-Open No. 1-272551, Japanese Patent Application Laid-Open No. 6-16616 The compounds described in Japanese Patent Application Laid-Open No. 7-110469, Japanese Patent Application Laid-Open No. 11-8801, Japanese Patent Application Laid-Open No. 2001-328973, and the like are included. Two or more kinds of polymerizable liquid crystal compounds may be used in combination. When two or more kinds of polymerizable liquid crystal compounds are used in combination, the orientation temperature can be lowered.

As the other polymerizable liquid crystal compound, a cyclic organopolysiloxane compound having a cholesteric phase as disclosed in Japanese Patent Application Laid-Open No. 57-165480 can be used. Further, as the polymer liquid crystal compound, a polymer having a mesogen group exhibiting liquidity introduced at the main chain, a side chain, or both the main chain and the side chain, and a polymer cholesteric liquid crystal having a cholesteryl group introduced into the side chain. , A liquid crystal polymer as disclosed in JP-A-9-133810, a liquid crystal polymer as disclosed in JP-A-11-293252, and the like can be used.

The amount of the polymerizable liquid crystal compound added to the alignment film composition is preferably 75 to 99.9% by mass, preferably 80 to 99.9% by mass, based on the solid content mass (mass excluding the solvent) of the alignment film composition. It is more preferably to 99% by mass, and even more preferably 85 to 90% by mass.

--Surfactant ---
The alignment film composition used when forming the alignment film 14 may contain a surfactant.
The surfactant is preferably a compound that can function as an orientation control agent (horizontal alignment agent), which contributes to the effect of stably or rapidly orienting the liquid crystal compound in a planar manner.
Examples of the surfactant include a silicone-based surfactant and a fluorine-based surfactant, and a fluorine-based surfactant is preferably exemplified.

Specific examples of the surfactant include the compounds described in paragraphs [2002] to [0090] of JP-A-2014-119605, and the compounds described in paragraphs [0031]-[0034] of JP-A-2012-203237. , The compounds exemplified in paragraphs [0092] and [093] of JP-A-2005-99248, paragraphs [0076] to [0078] and paragraphs [0087] to [985] of JP-A-2002-129162. Examples thereof include the compounds exemplified in the above, and the fluorine (meth) acrylate-based polymers described in paragraphs [0018] to [0043] of JP-A-2007-272185.
As the surfactant, one type may be used alone, or two or more types may be used in combination.
As the fluorine-based surfactant, the compounds described in paragraphs [2002] to [0090] of JP-A-2014-119605 are preferable.

The amount of the surfactant added to the alignment film composition is preferably 0.01 to 10% by mass, more preferably 0.01 to 5% by mass, and 0.02 to 1% by mass with respect to the total mass of the liquid crystal compound. % Is more preferable.

--Chiral agent (optically active compound) ---
The chiral agent (chiral agent) has a function of inducing a helical structure of the liquid crystal compound 20 in the alignment film 14. In the present invention, a chiral agent whose HTP (spiral-inducing force) is changed by irradiation with light is used.
By using a chiral agent whose HTP changes by irradiation with light, as will be described later, a chiral agent is applied to a part of the coating film of the alignment film composition, such as light irradiation of the coating film of the alignment film composition through a mask. By irradiating the light that is exposed to the light, the HTP of the chiral auxiliary can be continuously changed from the center of the irradiated light toward the outside. Thereby, the twist angle of the liquid crystal compound 20 can be changed in the plane of the alignment film 14, for example, in the X direction, and as described above, the optical axis of the liquid crystal compound 20 is in the X direction on the upper surface 14b of the alignment film 14. It is possible to form a liquid crystal alignment pattern in which the rotation direction of the optical axis is reversed in the middle of the X direction.
The chiral agent whose HTP changes by light irradiation may be a chiral agent whose HTP decreases by light irradiation or a chiral agent whose HTP increases by light irradiation. As the chiral agent whose HTP changes, a chiral agent whose HTP is lowered by light irradiation is generally used.

As the chiral agent, a known compound can be used as long as the HTP is changed by irradiation with light.
The chiral agent has a different twisting direction and / or spiral pitch of the spiral induced by the compound. Therefore, the chiral agent used in the alignment film composition depends on the spiral pitch of the target liquid crystal compound 20, the twist angle of the target liquid crystal compound 20, the main use of the optical element 10 (condensing or light diffusion, etc.), and the like. , It may be selected as appropriate. The same applies to the liquid crystal composition described later in this respect.
Examples of chiral agents include liquid crystal device handbooks, Chapter 3, 4-3, TN (twisted nematic), STN (Super Twisted Nematic) chiral agents, p. 199, edited by the 142nd Committee of the Japan Society for the Promotion of Science, 1989. The described chiral agents, isosorbides, isomannide derivatives and the like can be used.

The chiral agent generally contains an asymmetric carbon atom, but an axial asymmetric compound or a plane asymmetric compound containing no asymmetric carbon atom can also be used as the chiral agent. Examples of axial or asymmetric compounds include binaphthyl, helicene, paracyclophane, and derivatives thereof. The chiral agent may have a polymerizable group. When both the chiral agent and the liquid crystal compound have a polymerizable group, the repeating unit derived from the polymerizable liquid crystal compound and the repeating unit derived from the chiral agent are derived by the polymerization reaction between the polymerizable chiral agent and the polymerizable liquid crystal compound. Polymers with repeating units can be formed. In this aspect, the polymerizable group of the polymerizable chiral agent is preferably a group of the same type as the polymerizable group of the polymerizable liquid crystal compound. Therefore, the polymerizable group of the chiral agent is preferably an unsaturated polymerizable group, an epoxy group or an aziridinyl group, more preferably an unsaturated polymerizable group, and preferably an ethylenically unsaturated polymerizable group. More preferred.
Moreover, the chiral agent may be a liquid crystal compound.

The chiral agent may have a photoisomerizing group. When the chiral agent has a photoisomerizing group, the HTP of the chiral agent can be changed by irradiation with light, which is preferable.
As the photoisomerizing group, an isomerization site of a compound exhibiting photochromic properties, an azo group, an azoxy group, or a cinnamoyl group is preferable. Specific compounds include JP-A-2002-80478, JP-A-2002-80851, JP-A-2002-179668, JP-A-2002-179669, JP-A-2002-179670, and JP-A-2002. Compounds described in JP-A-179681, JP-A-2002-179682, JP-A-2002-338575, JP-A-2002-338668, JP-A-2003-313189, JP-A-2003-313292, and the like. Can be used.

The content of the chiral agent in the alignment film composition may be appropriately set to an amount capable of realizing the maximum twist angle of the liquid crystal compound 20 to be twist-oriented, depending on the type of the chiral agent and the like.
The content of the chiral agent is preferably 0.1 to 30% by mass, more preferably 0.1 to 15% by mass, based on the molar content of the liquid crystal compound.

－－Initiator of polymerization －－
When the alignment film composition contains a polymerizable compound, it preferably contains a polymerization initiator. In the embodiment in which the polymerization reaction is allowed to proceed by irradiation with ultraviolet rays, the polymerization initiator used is preferably a photopolymerization initiator capable of initiating the polymerization reaction by irradiation with ultraviolet rays.
Examples of photopolymerization initiators include α-carbonyl compounds (described in US Pat. No. 2,376,661 and US Pat. No. 2,376,670), acidoin ethers (described in US Pat. No. 2,448,828), and α-hydrogen. Substituent aromatic acidoine compound (described in US Pat. No. 2,725,512), polynuclear quinone compound (described in US Pat. No. 3,46127, US Pat. No. 2,951,758), triarylimidazole dimer and p-aminophenyl ketone. Combinations (described in US Pat. No. 3,549,67), acridin and phenazine compounds (Japanese Patent Laid-Open No. 60-105667, described in US Pat. No. 4,239,850), and oxadiazole compounds (US Pat. No. 4,212,970). Description) and the like.
The content of the photopolymerization initiator in the alignment film composition is preferably 0.1 to 20% by mass, more preferably 0.5 to 12% by mass, based on the content of the liquid crystal compound.

－－Crosslinking agent －－
The alignment film composition may optionally contain a cross-linking agent in order to improve the film strength and durability after curing. As the cross-linking agent, those that are cured by ultraviolet rays, heat, moisture and the like can be preferably used.
The cross-linking agent is not particularly limited and may be appropriately selected depending on the intended purpose. For example, a polyfunctional acrylate compound such as trimethylolpropane tri (meth) acrylate and pentaerythritol tri (meth) acrylate; glycidyl (meth) acrylate. And epoxy compounds such as ethylene glycol diglycidyl ether; aziridine compounds such as 2,2-bishydroxymethylbutanol-tris [3- (1-aziridinyl) propionate] and 4,4-bis (ethyleneiminocarbonylamino) diphenylmethane; hexa Isocyanate compounds such as methylenediisocyanate and biuret-type isocyanate; polyoxazoline compounds having an oxazoline group in the side chain; and alkoxysilane compounds such as vinyltrimethoxysilane and N- (2-aminoethyl) 3-aminopropyltrimethoxysilane; And so on. Further, a known catalyst can be used depending on the reactivity of the cross-linking agent, and the productivity can be improved in addition to the improvement of the film strength and the durability. These may be used alone or in combination of two or more.
The content of the cross-linking agent is preferably 1 to 20% by mass, more preferably 3 to 10% by mass, based on the solid content mass of the alignment film composition. When the content of the cross-linking agent is within the above range, the effect of improving the cross-linking density can be easily obtained, and the stability of the alignment film 14 is further improved.

--Other additives ---
If necessary, a polymerization inhibitor, an antioxidant, an ultraviolet absorber, a light stabilizer, a coloring material, metal oxide fine particles, etc. are added to the alignment film composition so as not to deteriorate the optical performance and the like. It can be added in a range.

The alignment film composition is preferably used as a liquid (paint) when forming the alignment film 14.
The alignment film composition may contain a solvent. The solvent is not limited and may be appropriately selected depending on the intended purpose, but an organic solvent is preferable.
The organic solvent is not limited and may be appropriately selected depending on the intended purpose. For example, ketones, alkyl halides, amides, sulfoxides, heterocyclic compounds, hydrocarbons, esters, and ethers. And so on. These may be used alone or in combination of two or more. Among these, ketones are preferable in consideration of the burden on the environment.

The optical element 10 has a liquid crystal layer 16 on the alignment film 14 (upper surface 14b).
FIG. 5 conceptually shows the vicinity of the interface between the alignment film 14 and the liquid crystal layer 16.
In the optical element 10 of the present invention, on the lower surface (the surface on the alignment film 14 side) of the liquid crystal layer 16, the liquid crystal compound 24 is oriented by the liquid crystal compound 20 on the upper surface 14b of the alignment film 14, and the upper surface 14b of the alignment film 14 is oriented. It has a liquid crystal alignment pattern similar to the liquid crystal alignment pattern in. That is, the liquid crystal layer 16 of the optical element 10 has a liquid crystal alignment pattern on the lower surface, in which the optical axis of the liquid crystal compound 24 rotates in the X direction and the rotation direction is reversed in the middle.
In the liquid crystal layer 16 of the illustrated example, the liquid crystal compound 24 is in a normal orientation state in which the liquid crystal compound 24 is not twist-oriented in the thickness direction. Therefore, the liquid crystal compound 24 of the liquid crystal layer 16 is the alignment film 14 over the entire area in the thickness direction. It is oriented with the same liquid crystal alignment pattern as the upper surface 14b of.

In the optical element 10 of the present invention, the liquid crystal layer 16 is formed by using a composition (liquid crystal composition) containing a liquid crystal compound as an example.
The liquid crystal layer 16 preferably has a product of the thickness of the liquid crystal layer 16 and Δn (difference in refractive index) at a wavelength of 550 nm of the liquid crystal compound in the liquid crystal composition used for forming the liquid crystal layer 16 at 200 to 350 nm. In one case, that is, when the product of the thickness of the liquid crystal layer 16 and the Δn of the liquid crystal compound is about λ / 2, the two linearly polarized components contained in the light incident on the liquid crystal layer 16 which are orthogonal to each other have a half wavelength, that is, 180. It has a function to give a phase difference of °.

FIG. 6 conceptually shows the lower surface of the liquid crystal layer 16.
Note that FIG. 6 shows the orientation state of the liquid crystal compound 24 on the lower surface of the liquid crystal layer 16, but as shown in FIG. 5, the liquid crystal layer 16 is formed from the liquid crystal compound 24 on the lower surface in the thickness direction. As described above, the liquid crystal compounds 24 having the same orientation have a stacked structure.

The liquid crystal layer 16 has a liquid crystal orientation pattern that changes while continuously rotating in the plane toward the direction X of the optical axis of the liquid crystal compound 24.
On the other hand, the liquid crystal compound 24 forming the liquid crystal layer 16 has the same optical axis orientation as the upper surface 14b of the alignment film 14 in the Y direction orthogonal to the X direction, that is, in the Y direction orthogonal to one direction in which the optical axis rotates. Equal liquid crystal compounds 24 are arranged at equal intervals. In other words, in the liquid crystal layer 16, the angles formed by the direction of the optical axis and the X direction are equal between the liquid crystal compounds 24 arranged in the Y direction.

The region where the liquid crystal compounds 24 having the same angle formed by the optical axis and the X direction are arranged in the Y direction is defined as the region R.
In this case, the value of the in-plane retardation (Re) at a wavelength of 550 nm in each region R is preferably a half wavelength, that is, λ / 2. Here, λ / 2 means that the in-plane retardation is 200 to 350 nm. These in-plane retardations are calculated by the product of the refractive index difference Δn at a wavelength of 550 nm due to the refractive index anisotropy of the region R and the thickness of the liquid crystal layer 16. Here, the difference in the refractive index due to the refractive index anisotropy of the region R in the liquid crystal layer 16 is the refractive index in the direction of the slow axis in the plane of the region R and the refraction in the direction orthogonal to the direction of the slow axis. It is the difference in refractive index defined by the difference from the rate. That is, the refractive index difference Δn due to the refractive index anisotropy of the region R is the refractive index of the liquid crystal compound 24 in the direction of the optical axis and the refractive index of the liquid crystal compound 24 in the plane of the region R in the direction perpendicular to the optical axis. Is equal to the difference with. That is, the refractive index difference Δn is equal to the refractive index difference of the liquid crystal compound.

When circularly polarized light is incident on such a liquid crystal layer 16, the light is refracted and the direction of circularly polarized light is changed.
Refer to the liquid crystal layer 16A, in which the optical axis of the liquid crystal compound 24 rotates toward the X direction, but the rotation direction of the optical axis does not reverse in the middle of the X direction, which is conceptually shown in FIGS. 7 and 8. And explain.
In the liquid crystal layer 16A, it is assumed that the value of the product of the difference in the refractive index of the liquid crystal compound 24 and the thickness of the liquid crystal layer 16A is λ / 2. Here, λ / 2 means that the above value is 200 to 350 nm.
Further, in FIGS. 7 and 8, in order to simplify the drawing and clarify the action, the liquid crystal layer 16A shows only the liquid crystal compound 24 (liquid crystal compound molecule) on the surface on the alignment film 14 side. However, the liquid crystal layer 16A also has a structure in which the liquid crystal compounds 24 oriented in the same direction are laminated in the thickness direction, similarly to the liquid crystal layer 16 shown in FIG.

As shown in FIG. 7, when the value of the product of the difference in the refractive index of the liquid crystal compound of the liquid crystal layer 16A and the thickness of the liquid crystal layer 16A is λ / 2, the incident light L ₁ which is left circularly polarized light is generated in the liquid crystal layer 16A. When incident, the incident light L ₁ is given a phase difference of 180 ° by passing through the liquid crystal layer 16A, and the transmitted light L ₂ is converted into right circular polarization.
Further, when the incident light L ₁ passes through the liquid crystal layer 16A, its absolute phase changes according to the direction of the optical axis of each liquid crystal compound 24. At this time, since the direction of the optical axis changes while rotating toward the X direction, the amount of change in the absolute phase of the incident light L ₁ differs depending on the direction of the optical axis. Further, since the liquid crystal alignment pattern formed on the liquid crystal layer 16A is a pattern that is periodic in the X direction, the incident light L1 that has passed through the liquid crystal layer 16A has the _respective optical axes as shown in FIG. A periodic absolute phase Q1 is given in the X direction corresponding to the orientation. As a result, the equiphase plane E1 inclined in the direction opposite to the X direction is formed.
Therefore, the transmitted light L ₂ is refracted so as to be inclined in a direction perpendicular to the equiphase plane E 1, and travels in a direction different from the traveling direction of the incident light L ₁ . In this way, the left circularly polarized incident light L ₁ is converted into the right circularly polarized transmitted light L ₂ tilted by a certain angle in the X direction with respect to the incident direction.

On the other hand, as conceptually shown in FIG. 8, when the value of the product of the difference in the refractive index of the liquid crystal compound of the liquid crystal layer 16A and the thickness of the liquid crystal layer 16A is λ / 2, the incident light of right circular polarization is applied to the liquid crystal layer 16A. When L ₄ is incident, the incident light L ₄ passes through the liquid crystal layer 16A, is given a phase difference of 180 °, and is converted into left circularly polarized transmitted light L ₅ .
Further, when the incident light L ₄ passes through the liquid crystal layer 16A, its absolute phase changes according to the direction of the optical axis of each liquid crystal compound 24. At this time, since the direction of the optical axis changes while rotating along the X direction, the amount of change in the absolute phase of the incident light L ₄ differs depending on the direction of the optical axis. Further, since the liquid crystal alignment pattern formed on the liquid crystal layer 16A is a periodic pattern in the X direction, the incident light L ₄ passing through the liquid crystal layer 16A has the orientation of each optical axis as shown in FIG. A periodic absolute phase Q2 is given in the X direction corresponding to.
Here, since the incident light L ₄ is right-handed circularly polarized light, the absolute phase Q2 periodic in the X direction corresponding to the direction of the optical axis is opposite to the incident light L1 which is left _- handed circularly polarized light. As a result, in the incident light L ₄ , an equiphase plane E 2 inclined in the X direction is formed, which is opposite to the incident light L ₁ .
Therefore, the incident light L ₄ is refracted so as to be inclined in a direction perpendicular to the equiphase plane E2, and travels in a direction different from the traveling direction of the incident light L ₄ . In this way, the incident light L ₄ is converted into the transmitted light L ₅ of left circularly polarized light tilted by a certain angle in the direction opposite to the X direction with respect to the incident direction.

The direction of the absolute phase and the inclination direction of the equiphase plane become opposite when the rotation direction of the liquid crystal compound 24 toward the X direction (one direction) is reversed. That is, the refraction direction of the circularly polarized light incident on the liquid crystal layer 16 becomes the opposite direction when the rotation direction of the liquid crystal compound 24 toward the X direction is reversed.
In the example shown in FIGS. 7 and 8, the rotation direction of the optical axis in the liquid crystal layer 16A toward the X direction is clockwise.
Therefore, when the rotation direction of the optical axis toward the X direction is counterclockwise and the incident light L ₁ which is left circularly polarized light is incident on the liquid crystal layer 16A as shown in FIG. 7, the incident light L ₁ is in the X direction. It is refracted in the opposite direction to the incident light L ₁ and is emitted at an angle opposite to the X direction. That is, in this case, the transmitted light is emitted in the same direction as the transmitted light L ₅ in FIG.
Further, when the rotation direction of the optical axis toward the X direction is counterclockwise and the incident light L ₄ having right circular polarization is incident on the liquid crystal layer 16A as shown in FIG. 8, the incident light L ₄ is directed to the X direction. The transmitted light is tilted in the X direction with respect to the incident light L ₄ and is emitted. That is, in this case, the transmitted light is emitted in the same direction as the transmitted light L ₂ in FIG. 7.

As described above, on the upper surface 14b of the alignment film 14 of the optical element 10, the optical axis of the liquid crystal compound 20 rotates counterclockwise in the region of x1 to x7 and in the region of x7 to x13 in the X direction. , Rotate clockwise. Further, the liquid crystal alignment pattern in the plane of the liquid crystal layer 16 is the same as that of the upper surface 14b of the alignment film 14.
Therefore, for example, when the incident light L ₁ of right-handed circular polarization is incident on the optical element 10 (liquid crystal layer 16), it is incident in the region corresponding to x1 to x7 of the upper surface 14b of the alignment film 14 in the liquid crystal layer 16. The light is refracted in the X direction, the region corresponding to x7 to x13 is refracted in the direction opposite to the X direction, and the transmitted light is focused as conceptually shown in FIG.
Further, when the incident light L ₂ of left circular polarization is incident on the optical element 10, the incident light is refracted in the direction opposite to the X direction in the region corresponding to x1 to x7 on the upper surface 14b of the alignment film 14. The region corresponding to x7 to x13 is refracted in the X direction, and the transmitted light spreads.

As shown in FIG. 6, in the liquid crystal layer 16 of the optical element 10, the optical axis of the liquid crystal compound 24 does not rotate in the Y direction but faces a certain direction. Therefore, even if circularly polarized light is incident on the optical element 10 (liquid crystal layer 16), the light is not refracted in the Y direction. That is, the optical element 10 does not have so-called lens power in the Y direction.
Therefore, the optical element 10 acts like a cylindrical lens having a ridgeline in the Y direction.

The refraction of light by the liquid crystal layer 16 can be adjusted by the length in which the optical axis of the liquid crystal compound 24 rotates 180 ° in the X direction in the plane, that is, the period Λ shown in FIG. In other words, the period Λ is the distance between the centers of two liquid crystal compounds adjacent to the X direction and having the same angle with respect to the X direction.
Specifically, the shorter the period Λ is, the stronger the light that has passed through the liquid crystal compounds 24 adjacent to each other interferes with each other, so that the transmitted light can be greatly refracted.
The period Λ of the liquid crystal layer 16 irradiates the coating film of the alignment film composition in the type of chiral agent added to the alignment film 14, the amount of the chiral agent added to the alignment film 14, and the production method of the present invention described later. It can be adjusted by the size of the light, the interval of the same light, the amount of the same light, and the like.

In the liquid crystal layer 16, the value of the in-plane retardation of the plurality of regions R is preferably half wavelength, but the in-plane retardation Re (550) of the plurality of regions R of the liquid crystal layer 16 with respect to the incident light having a wavelength of 550 nm. = Δn ₅₅₀ × d is preferably within the range defined by the following equation (1). Here, Δn ₅₅₀ is the refractive index difference due to the refractive index anisotropy of the region R when the wavelength of the incident light is 550 nm, and d is the thickness of the liquid crystal layer 16.
200 nm ≤ Δn ₅₅₀ × d ≤ 350 nm ... (1)
That is, if the in-plane retardation Re (550) = Δn ₅₅₀ × d of the plurality of regions R of the liquid crystal layer 16 satisfies the equation (1), a sufficient amount of circularly polarized light components of the light incident on the liquid crystal layer 16 can be obtained. , Can be converted to circular polarization traveling in the direction tilted in the X direction or the direction opposite to the X direction. The in-plane retardation Re (550) = Δn ₅₅₀ × d is more preferably 225 nm ≦ Δn ₅₅₀ × d ≦ 340 nm, and even more preferably 250 nm ≦ Δn ₅₅₀ × d ≦ 330 nm.
Although the above equation (1) is a range for incident light having a wavelength of 550 nm, the in-plane retardation Re (λ) = Δn _λ × d of the plurality of regions R of the liquid crystal layer 16 with respect to the incident light having a wavelength of λ nm is It is preferably within the range specified in the following formula (1-2), and can be appropriately set.
0.7λnm ≤ Δn _λ × d ≤ 1.3λnm ... (1-2)

Further, the in-plane retardation values of the plurality of regions R in the liquid crystal layer 16 can be used outside the range of the above formula (1). Specifically, by setting Δn ₅₅₀ × d <200 nm or 350 nm <Δn ₅₅₀ × d, the light traveling in the same direction as the traveling direction of the incident light and the light traveling in a direction different from the traveling direction of the incident light. It can be divided into light. When Δn ₅₅₀ × d approaches 0 nm or 550 nm, the component of light traveling in the same direction as the traveling direction of the incident light increases, and the component of light traveling in a direction different from the traveling direction of the incident light decreases.

Further, the in-plane retardation Re (450) = Δn ₄₅₀ × d of the region R of the liquid crystal layer 16 with respect to the incident light having a wavelength of 450 nm and the in-plane of each region R of the liquid crystal layer 16 with respect to the incident light having a wavelength of 550 nm. The retardation Re (550) = Δn ₅₅₀ × d preferably satisfies the following formula (2). Here, Δn ₄₅₀ is the difference in refractive index due to the refractive index anisotropy of the region R when the wavelength of the incident light is 450 nm.
(Δn ₄₅₀ × d) / (Δn ₅₅₀ × d) <1.0 ... (2)
The formula (2) represents that the liquid crystal compound 24 contained in the liquid crystal layer 16 has reverse dispersibility. That is, when the equation (2) is satisfied, the liquid crystal layer 16 can cope with incident light having a wide band wavelength.

The liquid crystal layer 16 can be formed, for example, by curing a liquid crystal composition containing the liquid crystal compound 24. In the illustrated example, the liquid crystal compound 24 is a rod-shaped liquid crystal compound, but as the liquid crystal compound, a disk-shaped liquid crystal compound can also be used.
A liquid crystal layer 16 made of a cured layer of the liquid crystal composition can be obtained by forming the alignment film 14 on the substrate 12, applying the liquid crystal composition on the alignment film 14, and curing the liquid crystal composition. Although it is the liquid crystal layer 16 that functions as a so-called λ / 2 plate, the present invention includes an embodiment in which a laminate that integrally includes a substrate 12 and an alignment film 14 functions as a λ / 2 plate.
Further, the liquid crystal composition for forming the liquid crystal layer 16 contains a rod-shaped liquid crystal compound or a disk-shaped liquid crystal compound, and further contains other components such as a leveling agent, an orientation control agent, a polymerization initiator and an orientation aid. You may be doing it.

Further, it is desirable that the liquid crystal layer 16 has a wide band with respect to the wavelength of the incident light, and it is preferable that the liquid crystal layer 16 is formed by using a liquid crystal material having a birefringence of reverse dispersion. It is also preferable that the liquid crystal layer 16 has a substantially wide band with respect to the wavelength of the incident light by imparting a twist component to the liquid crystal composition and by laminating different retardation layers. For example, in the liquid crystal layer 16, a method of realizing a wide-band patterned λ / 2 plate by laminating two layers of liquid crystals having different twisting directions is shown in Japanese Patent Application Laid-Open No. 2014-089476 and the like. It can be preferably used in the invention.

-Bar-shaped liquid crystal compound-
As the rod-shaped liquid crystal compound, various rod-shaped polymerizable liquid crystal compounds exemplified in the above-mentioned alignment film 14 can be used.
-Disc-shaped liquid crystal compound-
As the disk-shaped liquid crystal compound, for example, those described in JP-A-2007-108732 and JP-A-2010-244033 can be preferably used.
When a disk-shaped liquid crystal compound is used for the liquid crystal layer 16, the liquid crystal compound 24 rises in the thickness direction in the liquid crystal layer 16, and the optical axis derived from the liquid crystal compound is an axis perpendicular to the disk surface. It is defined as the so-called phase advance axis.

The optical elements shown in FIGS. 1 to 9 are optical elements such as so-called lenses (liquid crystal lenses) that refract and transmit incident light to collect or diffuse the transmitted light, but the optical element of the present invention. Is not limited to this.
That is, the optical element may be a reflecting element that reflects incident light, that is, an optical element such as a reflecting mirror.
FIG. 10 shows an example thereof. Since the optical element 30 shown in FIG. 10 uses a large number of the same members as the above-mentioned optical element 10, the same members are designated by the same reference numerals, and the following description mainly describes different parts.

The optical element 30 has a substrate 12, an alignment film 32 formed on one surface of the substrate 12, and a liquid crystal layer 34 formed on the alignment film 32.
The substrate 12 is the same as the substrate of the optical element 10.

The alignment film 32 is basically the same as the alignment film 14 of the optical element 10 described above.
However, in the alignment film 32, the twisting direction of the spiral axis along the thickness direction of the liquid crystal compound 20 is opposite to that of the alignment film 14 of the optical element 10, and the spiral axis is left-twisted. Therefore, the alignment film 32 contains, as a chiral agent, a chiral agent that induces a left-handed twist that twists the liquid crystal compound 20 in a turning direction opposite to that of the alignment film 14 of the optical element 10.
Therefore, in the alignment film 32, the lower surface 32a has the same direction of the optical axis of the liquid crystal compound 20 in the X direction as in the alignment film 14.
On the other hand, on the upper surface 32b, the optical axis of the liquid crystal compound 20 rotates in the X direction as in the alignment film 14, but as conceptually shown in FIG. 11, the optical axis in the X direction The rotation direction is clockwise at x1 to x7, reverses the rotation direction at x7, and counterclockwise at x7 to x13. That is, the rotation direction of the optical axis in the upper surface 32b toward the X direction is opposite to that of the upper surface 14b of the alignment film 14 of the optical element 10.

In the optical element 30, the liquid crystal layer 34 provided on the alignment film 32 is a cholesteric liquid crystal layer in which the cholesteric liquid crystal phase is fixed. That is, the liquid crystal layer 34 is a layer made of a liquid crystal compound (liquid crystal material) having a cholesteric structure.
In the following description, the liquid crystal layer 34 is also referred to as a cholesteric liquid crystal layer 34.

As is well known, the cholesteric liquid crystal phase has a spiral structure in which the liquid crystal compound 36 is spirally swirled and stacked, and the liquid crystal compound 36 is spirally rotated once (360 ° rotation) and stacked. As one spiral pitch, the liquid crystal compound 36 that swirls in a spiral shape has a structure in which a plurality of pitches are laminated (see FIG. 12).

The cholesteric liquid crystal phase is known to exhibit selective reflectivity at specific wavelengths. The center wavelength of selective reflection (selective reflection center wavelength) λ depends on the pitch P (= period of the spiral) of the spiral structure in the cholesteric liquid crystal phase, and follows the relationship between the average refractive index n and λ = n × P of the cholesteric liquid crystal phase. .. Therefore, the selective reflection center wavelength can be adjusted by adjusting the pitch of this spiral structure. Since the pitch of the cholesteric liquid crystal phase depends on the type of chiral agent used together with the liquid crystal compound or the concentration thereof added when forming the cholesteric liquid crystal layer 34, a desired pitch can be obtained by adjusting these.
For pitch adjustment, see Fujifilm Research Report No. 50 (2005) p. There is a detailed description in 60-63. For the measurement method of spiral sense and pitch, use the method described in "Introduction to Liquid Crystal Chemistry Experiment", ed. Can be done.

The reflected light of the cholesteric liquid crystal phase is circularly polarized light, and selectively reflects either right-handed circularly polarized light or left-handed circularly polarized light.
Therefore, the optical element 30 having the cholesteric liquid crystal layer 34 selectively reflects only the right circular polarization or the left circular polarization in a predetermined wavelength band, and the other light is transmitted.
Whether the reflected light of the cholesteric liquid crystal layer 34 is right-handed circularly polarized light or left-handed circularly polarized light depends on the twisting direction (sense) of the spiral of the cholesteric liquid crystal phase. The selective reflection of circularly polarized light by the cholesteric liquid crystal phase reflects the right circularly polarized light when the twisting direction of the spiral of the cholesteric liquid crystal phase is right, and reflects the left circularly polarized light when the twisting direction of the spiral is left.
The twisting direction of the spiral of the cholesteric liquid crystal phase can be adjusted by the type of the liquid crystal compound forming the cholesteric liquid crystal layer 34 and / or the type of the chiral auxiliary added.

As an example, the cholesteric liquid crystal layer 34 of the optical element 30 is a layer in which a right-handed cholesteric liquid crystal phase is fixed, as shown in FIG.
Therefore, the cholesteric liquid crystal layer 34 selectively reflects the right circular polarization in a predetermined wavelength band, and the other light is transmitted.

Further, the full width at half maximum Δλ (nm) of the selective reflection band (circular polarization reflection band) indicating selective reflection depends on Δn of the cholesteric liquid crystal phase and the pitch P of the spiral, and follows the relationship of Δλ = Δn × P. Therefore, the width of the selective reflection band can be controlled by adjusting Δn. Δn can be adjusted by the type of the liquid crystal compound forming the cholesteric liquid crystal layer 34, the mixing ratio thereof, and the temperature at the time of fixing the orientation.

Such a cholesteric liquid crystal layer 34 can be basically formed by using the same liquid crystal composition as the liquid crystal composition (alignment film composition) for forming the above-mentioned alignment film 14. However, the chiral agent is not limited to the one whose HTP changes by irradiation with light, and all known chiral agents can be used.
Further, the thickness of the cholesteric liquid crystal layer 34 is appropriately set to a thickness that can secure the pitch number of the spirals of the liquid crystal compound 36 that can obtain the reflectance required for the optical element 30 according to the liquid crystal compound 36 and the like. do it.

FIG. 13 conceptually shows the lower surface of the cholesteric liquid crystal layer 34 of the optical element 30, that is, the surface of the alignment film 32 on the upper surface 32b side.
In addition, in FIG. 13, in order to clearly show the structure of the cholesteric liquid crystal layer 34, the liquid crystal compound 36 shows only the liquid crystal compound 36 on the upper surface 32b side of the alignment film 32. However, the cholesteric liquid crystal layer 34 has a spiral structure in which the liquid crystal compound 36 spirally swirls and is stacked from the liquid crystal compound 36 on the surface of the alignment film 32 in the thickness direction, as shown in FIG. It has as described above.

As shown in FIG. 13, on the lower surface of the cholesteric liquid crystal layer 34 (the surface of the alignment film 32 on the upper surface 32b side), the liquid crystal compound 36 is in the X direction and the Y direction according to the liquid crystal compound 20 on the upper surface 32b of the alignment film 32. It is in a state of being arranged two-dimensionally.
On the lower surface of the cholesteric liquid crystal layer 34, the liquid crystal compound 36 is oriented according to the liquid crystal alignment pattern of the liquid crystal compound 20 on the upper surface 32b of the alignment film 32.
Therefore, in the cholesteric liquid crystal layer 34, the optical axis of the liquid crystal compound 36 rotates in the X direction, similarly to the upper surface 32b of the alignment film 32. That is, the rotation direction of the optical axis of the liquid crystal compound 36 in the plane of the cholesteric liquid crystal layer 34 is clockwise in the region corresponding to x1 to x7 of the alignment film 32 toward the X direction, and the rotation direction is reversed at x7. Then, in the region corresponding to x7 to x13 of the alignment film 32, it is counterclockwise.
On the other hand, the liquid crystal compound 36 forming the cholesteric liquid crystal layer 34 has the same optical axis orientation in the Y direction orthogonal to the X direction, that is, in the Y direction orthogonal to one direction in which the optical axis continuously rotates. In other words, the liquid crystal compound 36 forming the cholesteric liquid crystal layer 34 has the same angle formed by the optical axis of the liquid crystal compound 36 and the X direction in the Y direction.

The cholesteric liquid crystal layer in which the cholesteric liquid crystal phase is fixed usually mirror-reflects the incident light (circularly polarized light).
On the other hand, in the plane, the cholesteric liquid crystal layer 34 having a liquid crystal alignment pattern in which the optical axis changes while continuously rotating along the X direction (a predetermined one direction) causes the incident light to be incident light. It reflects in the direction having an angle in the X direction or the direction opposite to the X direction.
Hereinafter, the action of the cholesteric liquid crystal layer in which the optical axis of the liquid crystal compound 36 rotates in the X direction (one direction) will be described with reference to the conceptual diagrams of FIGS. 14 and 15. FIG. 14 shows an example in which the optical axis of the liquid crystal compound 36 rotates clockwise toward the X direction, and FIG. 15 shows an example in which the optical axis of the liquid crystal compound rotates counterclockwise toward the X direction. In 34A, the rotation direction of the optical axis toward the X direction is constant in both cases.

In the example shown below, the case where the cholesteric liquid crystal layer reflects the right circular polarization is taken as an example, but even when the cholesteric liquid crystal layer reflects the left circular polarization, the direction of the absolute phase and the inclination direction of the equiphase plane, And, the same effect occurs except that the light reflection direction is reversed.

As described above, the cholesteric liquid crystal layer is a cholesteric liquid crystal layer that selectively reflects right circular polarization in a predetermined wavelength band. Therefore, when light is incident on the cholesteric liquid crystal layer 34A, the cholesteric liquid crystal layer 34A reflects only the right circularly polarized light in a predetermined wavelength band and transmits the other light. In the following description, the "predetermined wavelength band" will be omitted.

In the example shown in FIG. 14, the incident light Lr of right circular polarization incident on the cholesteric liquid crystal layer 34A changes its absolute phase according to the direction of the optical axis of each liquid crystal compound 36 when reflected by the cholesteric liquid crystal layer 34A. do.
Here, in the cholesteric liquid crystal layer 34A, the optical axis of the liquid crystal compound 36 is rotated clockwise toward the X direction (one direction). Therefore, the amount of change in the absolute phase of the incident light Lr of the incident right circularly polarized light differs depending on the direction of the optical axis.
As a result, as shown in FIG. 14, the incident light Lr of the right circularly polarized light incident on the cholesteric liquid crystal layer 34A is given a periodic absolute phase Q1 in the X direction corresponding to the direction of each optical axis.
Further, the orientation of the optical axis of the liquid crystal compound 36 with respect to the X direction is uniform in the arrangement of the liquid crystal compound 36 in the Y direction orthogonal to the X direction.
As a result, in the cholesteric liquid crystal layer 34A, an equiphase plane E1 inclined in the direction opposite to the X direction with respect to the incident light Lr of right circular polarization is formed.
Therefore, the incident light Lr of right circular polarization is reflected so as to be reflected in the normal direction of the equiphase plane E1, and the incident light Lr of right circular polarization is reflected in the mirror surface reflection direction according to the incident direction of the incident light Lr. Then, it is reflected in the direction inclined in the X direction (reflected light Lr1).

On the other hand, the rotation of the optical axis of the liquid crystal compound 36 is not clockwise as in the cholesteric liquid crystal layer 34A shown in FIG. 14, but counterclockwise in the X direction as in the cholesteric liquid crystal layer 34B shown in FIG. In the case of, the absolute phase Q2 periodic in the X direction corresponding to the direction of the optical axis is opposite to the case where the optical axis is clockwise as shown in FIG.
As a result, when the rotation of the optical axis of the liquid crystal compound 36 is counterclockwise, it is inclined in the opposite direction to the case where the rotation of the optical axis is clockwise, and the equiphase is inclined in the X direction with respect to the XY plane. Since the surface E2 is formed, the incident light Lr of the right circularly polarized light incident on the cholesteric liquid crystal layer 34B in which the rotation of the optical axis of the liquid crystal compound 36 is counterclockwise is reflected in the normal direction of the equiphase surface E2. The incident light Lr of right circular polarization is reflected in a direction inclined in the direction opposite to the X direction with respect to the mirror surface reflection direction corresponding to the incident direction of the incident light Lr (reflected light Lr2).

As described above, on the upper surface 32b of the alignment film 32 of the optical element 30, the optical axis of the liquid crystal compound 20 rotates clockwise in the region of x1 to x7 in the X direction, and in the region of x7 to x13. Rotate counterclockwise. The liquid crystal alignment pattern on the lower surface of the cholesteric liquid crystal layer 34 is the same as that on the upper surface 32b of the alignment film 32.
Therefore, as described above, in the region corresponding to x1 to x7 in the alignment film 32 of the cholesteric liquid crystal layer 34, the optical axis of the liquid crystal compound 36 rotates clockwise in the X direction, and the alignment film of the cholesteric liquid crystal layer 34. In the region corresponding to x7 to x13 in 32, the optical axis of the liquid crystal compound 36 rotates counterclockwise toward the X direction.
Therefore, when the incident light Lr of right circular polarization is incident on the optical element 30 (cholesteric liquid crystal layer 34), the reflected light is reflected in the region corresponding to x1 to x7 of the upper surface 32b of the alignment film 32 in the cholesteric liquid crystal layer 34. Is reflected at an angle of X direction with respect to the incident light, and in the region corresponding to x7 to x13, the reflected light is inclined at an angle opposite to the X direction with respect to the incident light, and the reflected light is shown in the figure. As conceptually shown in 16, the light is focused.
As shown in FIG. 13, in the cholesteric liquid crystal layer 34 of the optical element 30, the optical axis of the liquid crystal compound 36 does not rotate in the Y direction, but faces a certain direction. Therefore, even if circularly polarized light is incident on the optical element 30 (liquid crystal layer 34), the light is reflected without being tilted in the Y direction.

The light reflection angle by the cholesteric liquid crystal layer 34 is also the length that the optical axis of the liquid crystal compound 24 rotates 180 ° in the X direction in the plane, that is, the period Λ shown in FIG. 13, as in the liquid crystal layer 16 of the optical element described above. Can be adjusted by. In other words, the period Λ is the distance between the centers of two liquid crystal compounds 36 adjacent to the X direction and having the same angle with respect to the X direction.
Specifically, the shorter the period Λ, the larger the angle of the reflected light with respect to the incident light. The period Λ in the cholesteric liquid crystal layer 34 can be adjusted in the same manner as above.

In the optical element 30 of the present invention having such a cholesteric liquid crystal layer, the chiral agent used for the alignment film 32 is changed to reverse the twisting direction (left twist) of the spiral axis along the thickness direction of the alignment film 30. Then, by reversing the rotation direction of the optical axis of the liquid crystal compound 36 toward the X direction on the upper surface 32b (that is, the lower surface of the cholesteric liquid crystal layer 34) of the alignment film 32, the right circular polarization of the specific band is changed to the X direction and An optical element that reflects in the direction opposite to the X direction and diffuses can be obtained.
Further, the above description is an example in which the cholesteric liquid crystal layer reflects the right circular polarization, but the optical element of the present invention can also be used when the cholesteric liquid crystal layer reflects the left circular polarization. When the cholesteric liquid crystal layer reflects the left circular polarization, the liquid crystal compound that goes in one direction on the upper surface of the alignment film (that is, the lower surface of the cholesteric liquid crystal layer) regardless of whether the light is condensed or diffused. It is necessary to reverse the direction of rotation of the optical axis of the above to the case of reflecting the right-handed circular polarization described above.
The above points are the same even when the cholesteric liquid crystal layer is used in the optical element having the radial liquid crystal orientation pattern shown in FIG. 18, which will be described later.

Such an optical element of the present invention can be manufactured by the method for manufacturing an optical element of the present invention. Hereinafter, a method for manufacturing the optical element 10 according to the manufacturing method of the present invention will be described.
The following manufacturing method may be performed by a batch-type process using a cut sheet-shaped substrate 12, or may be performed by using a long substrate 12 while transporting the substrate 12 in the longitudinal direction. So-called roll-to-roll may be performed.

When manufacturing the optical element 10, first, the surface of the substrate 12 is subjected to an orientation treatment so that the liquid crystal compound 20 (liquid crystal compound 36) is oriented in a state where the optical axis is oriented in one direction.
As described above, there is no limitation on the method of orientation processing of the substrate 12. Therefore, the alignment treatment includes a rubbing treatment on the surface of the substrate 12, an orientation treatment in which a photoalignment film is formed on the surface of the substrate 12 and irradiated with linearly polarized light, and a method of providing an alignment film such as an oblique vapor deposition film of an inorganic compound. Etc., it may be performed by a known method.

Next, an alignment film composition containing the above-mentioned liquid crystal compound and a chiral agent whose HTP is changed by light irradiation is applied to the surface of the substrate 12 that has been subjected to the alignment treatment, and dried to obtain a coating film of the alignment film composition. Form. As described above, since the surface of the substrate 12 is oriented so that the optical axis of the liquid crystal compound 20 faces in one direction, the liquid crystal compound 20 is placed on the surface of the substrate 12, that is, the lower surface 14a of the alignment film 14. As shown in FIG. 3, the optical axis, that is, the longitudinal direction is aligned with one direction (X direction in the illustrated example).
As a method for applying the alignment film composition, various known methods such as bar coating, gravure coating, and spray coating can be used. Further, the thickness of the coating film of the alignment film composition may be appropriately set to the thickness of the coating film (coating thickness) of the target thickness according to the composition of the alignment film composition and the like.

After forming a coating film of the alignment film composition on the surface of the substrate 12 that has been subjected to the alignment treatment, a part of the alignment film composition is irradiated with light exposed to the chiral agent, and the chiral agent in the alignment film composition is irradiated. HTP is changed.
In this example, as conceptually shown in FIG. 17, a mask 40 having a long slit 40a is used with the orientation processing direction of the substrate 12 as the X direction, and the longitudinal direction of the slit 40a is orthogonal to the X direction. The coating film 14A of the alignment film composition is irradiated with linear light transmitted through the slit 40a in a state corresponding to the direction, that is, the Y direction (exposure of the coating film 14A).
The mask 40 shown in FIG. 17 has only one slit 40a, but as shown in Examples described later, by using a mask having a plurality of slits, a lens array having a plurality of lenses and the like can be obtained. Can be made.
The linear light (that is, the slit 40a) irradiating the coating film of the alignment film composition irradiates the coating film 14A with a long linear light exceeding the coating film 14A of the alignment film composition in the longitudinal direction. It is preferable to do so. That is, in the present invention, the linear light preferably indicates a long light exceeding the region of the coating film 14A of the alignment film composition. Further, it is preferable that the length of the linear light (in the lateral direction) is uniform over the entire length in the longitudinal direction.

As will be described later, when manufacturing an optical element such as the optical element 10 in which the optical axis of the liquid crystal compound 20 rotates in only one direction on the upper surface 14b of the alignment film 14, the slit 40a, that is, linear light is used. The direction orthogonal to the longitudinal direction of the optical axis is the direction in which the optical axis rotates (the direction in which the direction of the optical axis changes while rotating), that is, the X direction.
In this setting in the X direction, the direction of the alignment treatment previously applied to the substrate 12, that is, the direction of the optical axis of the liquid crystal compound 20 on the lower surface 14a of the alignment film 14, is irrelevant. For example, even if the orientation direction of the substrate 12 is the Y direction orthogonal to the X direction, the direction of the optical axis of the liquid crystal compound on the upper surface 14b of the alignment film 14 differs only by 90 °, and other than that, the alignment film is similarly the same. An optical element in which the optical axis of the liquid crystal compound 20 on the upper surface 14b of 14 rotates in only one direction in the X direction can be manufactured.

The width (length in the lateral direction) of the slit 40a is not limited, and the type and / or the amount of the chiral agent added to the alignment film composition, the size of the optical element 10, the amount of light to be irradiated, and the like. The alignment film 14 is desired, such that the rotation of the optical axis of the liquid crystal compound 20 in the X direction on the upper surface 14b of the alignment film 14 has a desired rotation angle (0 to 180 ° in FIGS. 2 and 4). The width of the state may be set as appropriate.

The slit 40a may have a concentration distribution, if necessary. For example, the slit may have a concentration distribution such that the concentration gradually increases from the center in the width direction to the outside.

The light to be irradiated may be ultraviolet light, visible light, or infrared light. That is, the light emitted through the mask 40 is appropriately selected from the light exposed by the chiral agent, that is, the light capable of changing the HTP of the chiral agent, depending on the chiral agent contained in the alignment film composition. do it.
There is no limit to the amount of irradiation light. For example, if the chiral agent has a chiral agent whose HTP is lowered by irradiation with light, the amount of light that can be set to the minimum target value for the chiral agent's HTP may be appropriately set.
When irradiating the light through the mask 40, the atmosphere may be a predetermined atmosphere such as an oxygen atmosphere and a nitrogen atmosphere, if necessary.

After irradiating the coating film 14A of the alignment film composition 10a with light (mask exposure) via the mask 40, the liquid crystal compound 20 is brought into a state of a liquid crystal phase twisted and oriented along the spiral axis by heating or the like. ..
At this time, the chiral agent whose HTP is changed by exposure is continuously diffused in the width direction of the slit 40a, that is, in the X direction and in the direction opposite to the X direction due to the action of heat or the like. Further, the exposure through the mask 40 also affects the region where the light passing through the slit 40a is not irradiated.
As a result, in the exposure of the coating film 14A through the slit 40a, the exposure amount is the largest in the center of the slit 40a in the X direction (width direction), and the exposure amount is gradually increased in the X direction and in the direction opposite to the X direction. It will be in a lowered state.

Therefore, for example, when the HTP of the chiral agent contained in the alignment film composition is lowered by exposure, in the coating film 14A of the alignment film composition, the center of the slit 40a in the X direction has the lowest chiral agent HTP, and X The HTP of the chiral auxiliary gradually increases in the direction opposite to the direction and the X direction.
Therefore, the twist angle of the liquid crystal compound 20 along the thickness direction in the coating film 14A is the smallest at the center of the slit 40a in the X direction, and gradually increases in the X direction and the direction opposite to the X direction. That is, the twist angle of the liquid crystal compound 20 in the coating film 14A is the largest on the upstream side in the X direction (180 ° of x1 in the illustrated example), gradually decreases from the upstream side in the X direction toward the center, and gradually decreases in the X direction. It becomes the smallest in the center (0 ° of x7 in the illustrated example), gradually increases from the center in the X direction toward the downstream side, and becomes the largest again in the downstream side in the X direction (180 of x13 in the illustrated example). °).

Here, the twisting direction (sense) of the spiral of the liquid crystal compound 20 along the thickness direction by the chiral agent is the same over the entire area of the coating film 14A. Further, as described above, the substrate 12 is oriented in the X direction, and the liquid crystal compound of the coating film 14A has the optical axis oriented in the X direction on the lower surface (the surface on the substrate 12 side). ..
Therefore, the twist angle of the liquid crystal compound 20 due to the chiral agent gradually decreases from the upstream side in the X direction toward the center, becomes the minimum in the center, and then gradually decreases from the center to the downstream side in the X direction. By increasing the size, the liquid crystal compound 20 is formed on the upper surface (the surface opposite to the substrate 12) of the coating film 14A of the alignment film composition, that is, the upper surface 14b of the alignment film 14, toward the X direction, for example, as shown in FIG. The optical axis of the optical axis rotates counterclockwise, and at the center (x7), the relationship between the magnitude of the twist angle toward the X direction is reversed. , The optical axis rotates clockwise, and a liquid crystal orientation pattern can be formed.

After the liquid crystal compound 20 is twisted and oriented into a liquid crystal phase, the coating film 14A of the alignment film composition is cured by light irradiation and / or heating to prepare the alignment film 14.
The curing of the alignment film composition 10a is preferably light irradiation, and above all, curing by ultraviolet irradiation is preferable. When the alignment film composition 10a is cured, the atmosphere may be a predetermined atmosphere such as an oxygen atmosphere and a nitrogen atmosphere, if necessary.

In the example shown in FIG. 4, the maximum twist angle of the liquid crystal compound due to the chiral agent is 180 °, the minimum twist angle is 0 °, and the optical axis of the liquid crystal compound 20 until the rotation direction is reversed on the upper surface 14b of the alignment film 14. The angle of rotation of the liquid crystal display is 180 °, that is, the liquid crystal alignment pattern in which the optical axis rotates half a turn × 2 on the upper surface 14b of the alignment film 14, but the present invention is not limited to this as described above.
For example, the maximum twist angle of the liquid crystal compound 20 due to the chiral agent is set to 720 °, and the rotation direction is reversed on the upper surface 14b of the alignment film 14 by irradiating linear light with an exposure amount that makes the HTP of the chiral agent 0. The rotation angle of the optical axis of the liquid crystal compound 20 until the liquid crystal compound 20 is 720 °, that is, the optical axis is rotated 720 ° counterclockwise on the upper surface 14b toward the X direction, then the rotation direction is reversed, and then the rotation direction is reversed. An alignment film 14 having a liquid crystal alignment pattern is obtained in which the optical axis is rotated 720 ° clockwise.

After the alignment film 14 is formed in this way, the liquid crystal composition for forming the liquid crystal layer 16 containing the liquid crystal compound 24 such as the rod-shaped liquid crystal compound as described above is applied and dried, and then the liquid crystal compound is heated or the like. Let 24 be the state of the liquid crystal phase.
At this time, the liquid crystal compound 24 in the coating film of the liquid crystal composition is oriented by the liquid crystal compound 20 on the upper surface 14b of the alignment film 14. That is, in the liquid crystal compound 24 in the coating film of the liquid crystal composition, the optical axis rotates in the X direction, which is the same as the liquid crystal alignment pattern of the liquid crystal compound 20 on the upper surface 14b of the alignment film 14, and the liquid crystal compound 24 is in the middle. Is oriented in a liquid crystal alignment pattern in which the direction of rotation is reversed.
After that, depending on the composition of the liquid crystal composition, the coating film of the liquid crystal composition is effective by irradiation with light and / or heating to form the liquid crystal layer 16.
As a result, the substrate 12, the alignment film 14, and the liquid crystal layer 16 are provided, and in the plane of the liquid crystal layer 16, the optical axis of the liquid crystal compound 24 rotates in the X direction, and the rotation direction is in the middle. It is possible to manufacture an optical element 10 having a liquid crystal alignment pattern in which the light is reversed and condensing or diffusing transmitted light according to the swirling direction of the incident circularly polarized light.

Alternatively, the alignment film 32 is similarly formed by using the alignment film composition containing the chiral agent in which the spiral rotation direction of the liquid crystal compound is opposite to that of the alignment film 14. Next, using the liquid crystal composition containing the liquid crystal compound 36 and the chiral agent described above, the cholesteric liquid crystal layer 34 is similarly formed on the alignment film 32.
As a result, the substrate 12, the alignment film 32, and the cholesteric liquid crystal layer 34 are provided, and in the cholesteric liquid crystal layer 34, the optical axis of the liquid crystal compound 36 rotates in the X direction, and the rotation direction is changed in the middle. It is possible to manufacture an optical element 30 having a liquid crystal orientation pattern that reverses and condensing right-handed or left-handed circularly polarized light in a specific wavelength band.

As described in Patent Document 1, the liquid crystal layer in which the optical axis of the liquid crystal compound rotates in at least one direction and the rotation direction of the optical axis is reversed in the middle causes the circularly polarized light to rotate in the swirling direction due to diffraction. Accordingly, liquid crystal lenses are known that can collect or diffuse light.
In order to manufacture such a liquid crystal lens, it is necessary to form an alignment film for orienting the liquid crystal compound in order to form a liquid crystal alignment pattern in which the optical axis rotates in a predetermined direction in the liquid crystal layer. However, in order to form such an alignment film, a nano-rubbing method using an AFM nanoprobe, a micro-rubbing method using a microneedle such as a diamond needle, an orientation treatment by writing by ND: YAG laser writing, or the like is performed in a minute region. It is necessary to control the orientation with high definition. As a result, it takes a lot of time and effort to form the alignment film, and a large-scale device is required.

On the other hand, according to the production method of the present invention, an alignment film composition containing a liquid crystal compound and a chiral agent whose HTP is changed by light irradiation is used to form a coating film of the alignment film composition, and then the coating is applied. By irradiating a part of the film with the linear light described above or the spot light described later using a mask or the like to form an alignment film, the optical axis of the liquid crystal compound rotates in at least one direction. In addition, it is possible to form an alignment film whose orientation is controlled with high definition in a minute region corresponding to the liquid crystal layer in which the rotation direction of the optical axis is reversed on the way.
Therefore, according to the manufacturing method of the present invention, an optical element such as a liquid crystal lens capable of condensing or diffusing light according to the swirling direction of circularly polarized light by diffraction is manufactured by a general device and a simple manufacturing method. can.

FIG. 18 conceptually shows another example of the optical element of the present invention.
The optical element 50 shown in FIG. 18 has the same configuration as the above-mentioned optical element 10 and the like except that the shape is disk-shaped and the orientation of the liquid crystal compound in the alignment film and the liquid crystal layer is different. The members are designated by the same reference numerals, and the following description mainly describes different parts.

The optical element 50 shown in FIG. 18 has a substrate 12, an alignment film 52, and a liquid crystal layer 34.
The substrate 12 is the same as the substrate 12 such as the optical element 10 described above, and is oriented in one direction.

An alignment film 52 is formed on the substrate 12.
Like the alignment film 14 of the optical element 10, the alignment film 52 is also formed by using the liquid crystal compound 20 and a chiral agent whose HTP changes by irradiation with light, and is formed by the liquid crystal compound 20 and irradiation with light. It is formed using an alignment film composition containing a chiral agent that changes HTP. Therefore, also in the alignment film 52, the liquid crystal compound 20 is twisted and oriented along the spiral axis along the thickness direction.

Here, on the lower surface 52a (the surface on the substrate 12 side) of the alignment film 52, the liquid crystal compound 20 is oriented so that the optical axis faces in one direction according to the alignment treatment applied to the substrate 12. In the illustrated example, as conceptually shown in FIG. 19, the liquid crystal compound is oriented on the lower surface 52a of the alignment film 52 so that the optical axis faces in the vertical direction in the figure.

On the other hand, the upper surface 52b of the alignment film 52 has a liquid crystal alignment pattern in which the direction of the optical axis of the liquid crystal compound 20 changes not only in one direction but also in a plurality of directions while continuously rotating. ..
Specifically, on the upper surface 52b of the alignment film 52, as conceptually shown in FIG. 20, the optical axis of the liquid crystal compound 20 rotates radially (clockwise or counterclockwise) from a certain center. It has a liquid crystal orientation pattern. Therefore, in this liquid crystal alignment pattern, focusing on the straight line passing through the center point of radiation, the optic axis rotates in one direction that coincides with the straight line, and the direction of rotation of the optic axis is reversed at the center point of radiation. do.
In other words, on the upper surface 52b of the alignment film 52, a plurality of straight lines intersect at a certain point, the optical axis of the liquid crystal compound 20 rotates in the direction of the arrow corresponding to each straight line, and the optical axis at the intersection. It has a liquid crystal orientation pattern in which the direction of rotation of the optic axis is reversed. In other words, the liquid crystal alignment pattern on the upper surface 52b of the alignment film 52 has one direction in which the direction of the optical axis of the liquid crystal compound 20 changes while continuously rotating, in a concentric circle from the inside to the outside. It is a liquid crystal alignment pattern in which the rotation direction of the optical axis is reversed at the center of concentric circles in one direction on a straight line passing through the center of the liquid crystal display.
In the following description, the liquid crystal alignment pattern as shown in FIG. 20 is also referred to as a “radial liquid crystal alignment pattern” for convenience.

Although FIGS. 19 and 20 show only six directions in which the optical axis of the liquid crystal compound 20 rotates in the plane of the alignment film 52, the same applies to each of the six directions. There are many directions in which the optical axis rotates.

For example, when looking in the direction of arrow X1 passing through the center point of radiation (the intersection of straight lines (arrows)) on the upper surface 52b of the alignment film 52, the optical axis of the liquid crystal compound 20 is from the upstream side of the center in the direction of arrow X1. To the center, it rotates counterclockwise in the direction of arrow X1, reverses the direction of rotation at the center, and rotates clockwise from the center toward the downstream in the direction of arrow X1.
Similarly, in another arrow X2 direction passing through the center, the optical axis of the liquid crystal compound 20 rotates counterclockwise from the upstream end in the arrow X1 direction toward the center in the arrow X1 direction, and at the center. It reverses the direction of rotation and rotates clockwise from the center toward the downstream in the direction of arrow X1.
That is, the upper surface 52b of the alignment film 52 of the optical element 50 shown in FIG. 18 having a radial liquid crystal alignment pattern is the liquid crystal oriented in the X direction arranged in the Y direction on the upper surface 14b of the alignment film 14 shown in FIG. Each row of the compound 20 is provided at an angle and has a liquid crystal alignment pattern as if they intersected at x7 where the rotation direction of the optical axis is reversed.

A liquid crystal layer 54 is formed on the alignment film 52.
In the optical element 50 of the illustrated example, the liquid crystal layer 54 is the same as the liquid crystal layer 16 of the above-mentioned optical element 10 except that the orientation of the liquid crystal compound 24 is different, and a liquid crystal composition containing the liquid crystal compound 24 is used. It is a liquid crystal layer to be formed.
Like the optical element 10, the liquid crystal compound 24 of the liquid crystal layer 54 of the optical element 50 is also oriented by the liquid crystal compound 20 on the upper surface 52b of the alignment film 52. Therefore, the liquid crystal compound in the liquid crystal layer 54 also has an in-plane radial liquid crystal alignment pattern, as conceptually shown in FIG. 21, like the liquid crystal compound 20 on the upper surface 52b of the alignment film 52.
That is, when viewed in the direction of a certain arrow X1 passing through the center point of radiation in the liquid crystal layer 54, the optical axis of the liquid crystal compound 24 is in the plane from the upstream side in the direction of the arrow X1 as in the upper surface of the alignment film 52. It rotates counterclockwise toward the center in the direction of arrow X1, reverses the direction of rotation at the center, and rotates clockwise from the center toward the downstream side in the direction of arrow X1.

As described above, the liquid crystal layer having a liquid crystal orientation pattern in which the optical axis rotates in one direction in the plane refracts and transmits the incident light according to the swirling direction of the incident circularly polarized light. Further, in the liquid crystal layer having this liquid crystal alignment pattern, the refraction direction of the transmitted light becomes the opposite direction when the rotation direction of the optical axis in one direction is reversed.
Further, as described above, in the alignment film 52 of the optical element 50 shown in FIG. 18, the upper surface 52b is arranged in the Y direction on the surface of the liquid crystal layer 16 on the alignment film 14 side shown in FIG. 6, in the X direction. Each row of the liquid crystal compound 24 of the above has a liquid crystal orientation pattern as if they intersect at x7 in which the rotation direction of the optical axis is reversed, and the liquid crystal compound 24 in the liquid crystal layer 54 also has the same liquid crystal orientation pattern.
Therefore, when circularly polarized light is incident on the optical element 50, the optical element 50 acts like a convex lens according to the swirling direction of the circularly polarized light, and the incident and transmitted light passes through the center (the intersection of the arrows). The light is focused toward the vertical line of the optical element 50, or acts like a concave lens, and the incident and transmitted light is radially diffused outward.

In the optical element of the present invention, the optical element having such a liquid crystal orientation pattern is not only an optical element that refracts transmitted light as shown in the illustrated example, but also an optical element that refracts transmitted light as shown in FIG. It can also be used for an optical element that reflects incident light and collects it.
That is, similarly to the optical element 30, the twisting direction of the spiral of the liquid crystal compound 20 in the alignment film is reversed, that is, the rotation direction of the optical axis of the liquid crystal compound 20 on the upper surface of the alignment film is set to the alignment film of the optical element 50. Is in the opposite direction.
On it, a liquid crystal composition containing a chiral agent in addition to the liquid crystal compound is used to form a cholesteric liquid crystal layer in which the liquid crystal compound 36 is twisted and oriented along a spiral axis in the thickness direction as shown in FIG. This gives an optical element that reflects the incident right-handed or left-handed circularly polarized light in a specific wavelength band so as to be focused or diffused.

The optical element 50 having such an alignment film 52 whose upper surface 52b is a radial liquid crystal alignment pattern can be basically manufactured in the same manner as the above-mentioned optical element 10 (optical element 30).
That is, after the substrate 12 is oriented so that the optical axis of the liquid crystal compound 20 is oriented in one direction, the alignment film composition is applied to the alignment-treated surface of the substrate 12 and cured to obtain the alignment film composition. To form a coating film.
Next, a part of the coating film is irradiated with light exposed to the chiral agent.

Here, in the above-mentioned optical element 10, the coating film is irradiated with linear light by using the mask 40 having the slit 40a.
As a result, a difference in the amount of exposure occurs in the width direction of the linear light, and the HTP of the chiral auxiliary changes in the X direction (one direction) that coincides with the width direction of the linear light. The twist angle of the liquid crystal compound 20 changes. As a result, on the upper surface 14b of the alignment film 14, the optical axis of the liquid crystal compound 20 rotates counterclockwise from the upstream to the center in the X direction, the rotation direction of the optical axis is reversed at the center, and the X direction is from the center. The optic axis rotates clockwise toward the downstream of the liquid crystal, forming a liquid crystal orientation pattern.

On the other hand, when forming a radial liquid crystal alignment pattern in which the optical axis of the liquid crystal compound rotates in a plurality of directions intersecting at one point, the coating film of the alignment film composition is not formed with linear light. A part of the spot light (light contained in the coating film) is irradiated.
The spot shape of the spot light is not limited, and any various spot shapes such as a polygon such as a circle, an ellipse, a triangle, a quadrangle and a hexagon, a star shape, and an amorphous shape can be used. .. Among them, the circular shape and the elliptical shape are preferably used, and among them, the circular shape is particularly preferably used.

FIG. 22 shows a case where the coating film of the alignment film composition is irradiated with spot light having a circular spot shape.
As conceptually shown in FIG. 22, when the coating film 52A of the alignment film composition is irradiated with the circular spot light S, the spot light S has the same effect as the linear light passing through the slit 40a described above. Radially from the center of the light, the exposure gradually decreases,
Therefore, as in the above example, for example, when the HTP of the chiral agent contained in the alignment film composition is lowered by exposure, the coating film 52A of the alignment film composition is radially outside from the center of the spot light S. In the direction, the HTP of the chiral agent gradually increases.
Therefore, the twist angle of the liquid crystal compound 20 along the spiral axis in the thickness direction of the coating film 52A is the smallest at the center of the spot light S and gradually increases outward in a radial direction. That is, the twist angle of the liquid crystal compound 20 in the coating film 52A is the largest in the outward end of the two radial lines riding on a straight line, and the outward end toward the center of the spot light S. Gradually, it becomes smaller, becomes smaller at the center of the spot light S, gradually becomes larger toward the other outward end, and becomes larger again at the other outer end.

Similar to the above example, the twisting direction (sense) of the liquid crystal compound 20 by the chiral agent is the same over the entire area of the coating film 52A. Further, as described above, the substrate 12 is oriented so that the optical axis of the liquid crystal compound faces in one direction, and the liquid crystal compound of the coating film 52A has an optical axis on the lower surface (the surface on the substrate 12 side). The orientation matches the vertical direction in the figure.
Therefore, in the two radial lines riding on a straight line, the twist angle of the liquid crystal compound 20 on the spiral axis in the thickness direction gradually decreases from one outside toward the center of the spot light S, and the spot light S becomes smaller. It becomes the smallest in the center and gradually increases toward the outside of the other. As a result, on the upper surface (the surface opposite to the substrate 12) of the coating film 52A of the alignment film composition, that is, the upper surface 52b of the alignment film 52, for example, two radial lines on a straight line corresponding to the direction of the arrow X1 in FIG. In the line, as shown in FIG. 20, the optical axis of the liquid crystal compound 20 rotates counterclockwise from the upstream side in the X direction toward the center of the spot light S, and in the center of the spot light S, in the X direction. Since the relationship between the magnitude of the twist angle is reversed, the rotation direction of the optical axis is reversed here, and the optical axis rotates clockwise from the center of the spot light S toward the downstream side in the X direction. It becomes.

As described above, such a change in the exposure amount, that is, a change in the HTP of the chiral agent, that is, a change in the twist angle of the liquid crystal compound 20, occurs radially from the center of the spot light S.
Therefore, by irradiating the coating film 54A of the alignment film composition with the spot light S, as shown in FIG. 20, a plurality of straight lines in which the optical axes rotate in one direction radially intersect at one point and are on each straight line. It is possible to form a radial liquid crystal alignment pattern in which the optical axis of the liquid crystal compound 20 rotates in one direction, that is, in the direction of the arrow along each straight line, and the rotation direction of the optical axis is reversed at the intersection.

In irradiating the coating film 54A of the alignment film composition with spot light, for example, a mask having a plurality of circular openings is used to irradiate the coating film 54A of the alignment film composition with a plurality of spot lights. This makes it possible to manufacture a lens array or the like having a plurality of lenses.

All of the above-mentioned optical elements have only a substrate, an alignment film, and a liquid crystal layer, but the optical element of the present invention is not limited to these, and other than these members, if necessary, It may have various members.
As an example, the optical element of the present invention may further have a λ / 4 plate. As described above, all of the optical elements of the present invention transmit or reflect circularly polarized light. Therefore, by having the λ / 4 plate on the emission side of the light, the emitted light can be converted and linearly polarized light can be emitted. Further, by having the λ / 4 plate on the incident side of the light, the linear polarization of the incident light can be converted into the circular polarization on which the optical element of the present invention acts.

Although the method for manufacturing the optical element of the present invention and the optical element have been described in detail above, the present invention is not limited to the above-mentioned example, and various improvements and changes are made without departing from the gist of the present invention. Of course, it is also good.

Hereinafter, the features of the present invention will be described in more detail with reference to examples. The materials, reagents, usage amounts, substance amounts, ratios, treatment contents, treatment procedures, etc. shown in the following examples can be appropriately changed as long as they do not deviate from the gist of the present invention. Therefore, the scope of the present invention should not be construed as limiting by the specific examples shown below.

[Example 1]
(Preparation of alignment film composition)
Each component shown below was mixed to prepare an alignment film composition.
-Liquid crystal compound 1 (structure below): 1 g
Chiral agent 1 (structure below): 73.5 mg
-Horizontal alignment agent 1 (structure below): 0.4 mg
-Horizontal alignment agent 2 (structure below): 0.15 mg
-Photoradical initiator 1 (structure below): 20 mg
-Pentaerythritol tetraacrylate (A-TMMT (Tetramethylol Methane Tetaacrylate) manufactured by Shin Nakamura Chemical Industry Co., Ltd.): 10 mg
-Methyl ethyl ketone (MEK): 1.09 g
-Cyclohexanone: 0.16 g

Photoradical initiator 1 (IRGACURE907 manufactured by BASF (the structure below))

(Formation of alignment film)
As a substrate, a PET film having a thickness of 100 μm (Cosmo Shine A4100 manufactured by Toyobo Co., Ltd.) was prepared.
One side of the support was rubbed with rayon cloth. The conditions for the rubbing treatment were pressure: 0.1 kgf (0.98N), rotation speed: 1000 rpm, transport speed: 10 m / min, number of times: 1 reciprocation.

A coating film was formed by applying the alignment film composition to the rubbing-treated surface of the PET film at room temperature using a wire bar and then drying it. The thickness of the coating film after drying (dry film) was adjusted to 1 μm.

As conceptually shown in FIG. 23, a mask 58 in which circular openings having a diameter of 500 μm were formed in 3 × 5 (15 in total) at intervals of 10 mm was prepared on a black light-shielding plate.
The formed coating film of the alignment film composition was irradiated with ultraviolet rays via a mask 58 at room temperature in an oxygen atmosphere (mask exposure).
The time of irradiation with ultraviolet rays was adjusted so that the exposure amount in the light transmitting portion was 33 mJ / cm ² . As the light source for ultraviolet irradiation, "2UV transilluminator LM-26 type" manufactured by Funakoshi Co., Ltd. was used at a wavelength of 365 nm.

Next, the substrate irradiated with ultraviolet rays was allowed to stand on a hot plate at 90 ° C. for 1 minute to heat-treat the coating film to obtain a liquid crystal phase.
Then, the heat-treated coating film was irradiated with ultraviolet rays at 500 mJ / cm ² at 80 ° C. under a nitrogen atmosphere (oxygen concentration of 500 ppm or less) to cure the coating film of the alignment film composition. An alignment film was formed on the surface. As the light source of ultraviolet rays, "EXECURE3000-W" manufactured by HOYA CANDEO OPTRONICS was used.

With respect to the formed alignment film, the direction (orientation direction) of the optical axis of the liquid crystal compound on the lower surface and the upper surface is observed under a polarizing microscope by applying a GH type dichroic liquid crystal (ZLI-1842, manufactured by Merck Group) to each surface. Confirmed by doing.
As a result, on the lower surface (substrate side) of the alignment film, the direction of the optical axis of the liquid crystal compound coincided with the rubbing direction of the substrate, as shown in FIG. On the other hand, on the upper surface of the alignment film, as shown in FIG. 20, the optical axis of the liquid crystal compound is rotated clockwise from the center of the opening at 15 points corresponding to the opening of the mask 58, and therefore the opening. The optical axis of the liquid crystal compound was rotated in one direction on a plurality of straight lines passing through the center of the aperture, and the rotation direction of the optical axis was reversed at the center of the aperture. ..

(Preparation of Liquid Crystal Composition 1)
The liquid crystal composition 1 was prepared by mixing the components shown below.
・ Liquid crystal compound 1: 1 g
・ Horizontal alignment agent 1: 0.4 mg
-Horizontal alignment agent 2: 0.15 mg
-Photoradical initiator 1: 20 mg
-Pentaerythritol tetraacrylate (A-TMMT (Tetramethylol Methane Tetaacrylate) manufactured by Shin Nakamura Chemical Industry Co., Ltd.): 10 mg
-Methyl ethyl ketone (MEK): 1.09 g
-Cyclohexanone: 0.16 g

(Formation of liquid crystal layer (liquid crystal lens array 1))
The prepared liquid crystal composition 1 was applied onto the formed alignment film at room temperature using a wire bar, and then dried to form a coating film. The coating film was adjusted so that the thickness of the coating film (dry film) after drying was 2 μm.
Then, the coating film was heat-treated by allowing it to stand on a hot plate at 90 ° C. for 1 minute to obtain a liquid crystal phase.
Then, the heat-treated coating film is irradiated with ultraviolet rays at 500 mJ / cm ² at 80 ° C. under a nitrogen atmosphere (oxygen concentration of 500 ppm or less) to cure the coating film of the liquid crystal composition 1 to cure the liquid crystal layer. Formed.
As a result, a liquid crystal lens array 1 having 15 liquid crystal lenses was produced.

(Preparation of laminated body)
OCA tape (MHM-UVC15, manufactured by Niei Kako Co., Ltd.) was attached onto the flat glass.
The produced liquid crystal lens array 1 was attached onto the OCA tape so that the liquid crystal lens array 1 side (liquid crystal layer side) was on the OCA tape side. The laminate and the OCA tape were attached using a roller.
Then, the substrate was peeled off to prepare a laminate of the liquid crystal lens array 1 and the glass plate.

When the prepared laminate was confirmed in a cross-nicol state using a polarizing microscope, the surface of the liquid crystal lens array 1 on the glass plate side corresponds to the liquid crystal alignment pattern on the upper surface of the alignment film, as shown in FIG. The liquid crystal alignment pattern in which the optical axis of the liquid crystal compound rotates clockwise from one point, that is, the optical axis of the liquid crystal compound rotates in one direction on a straight line passing through one point of the center point of radiation. In addition, it had a total of 15 liquid crystal orientation patterns of 3 × 5 in which the rotation direction of the optical axis was reversed at the center point of radiation.
Further, the center points of radiation in the liquid crystal alignment pattern all coincided with the center of the circular opening of the mask 58 exposed in the formation of the alignment film.

The laminated body of the prepared liquid crystal lens array 1 and the glass plate was irradiated with right-handed circularly polarized light and left-handed circularly polarized light via a circularly polarizing plate.
As a result, when irradiated with right circular polarization, the light is focused on the perpendicular line of the liquid crystal lens array passing through the center of the liquid crystal lens (liquid crystal alignment pattern), and when irradiated with left circular polarization, the liquid crystal lens The light was diffused outward from the center.

[Example 2]
As shown in FIG. 24, a mask 60 was prepared in which five rows of linear (rectangular) openings having a width of 500 μm and a length of 50 mm were formed at intervals of 10 mm on a black light-shielding plate.
In Example 1, the line is the same as in Example 1 except that the mask 58 used for mask exposure of the coating film of the alignment film composition at the time of forming the alignment film is changed to the mask 60 shown in FIG. 24. A liquid crystal lens array 2 having five shaped liquid crystal lenses was produced, and a laminate of the liquid crystal lens array 2 and a glass plate was further produced.

After forming the alignment film, the formed alignment film was confirmed in the same manner as in Example 1.
As a result, on the lower surface (substrate side) of the alignment film, the direction of the optical axis of the liquid crystal compound coincided with the rubbing direction of the substrate, as shown in FIG. On the other hand, on the upper surface, in the region corresponding to the opening of the mask 60, as shown in FIG. 4, the optical axis of the liquid crystal compound is rotated in the width direction (direction orthogonal to the longitudinal direction) of the opening of the mask 60. Moreover, it had five orientation patterns in which the rotation direction of the optical axis was reversed at the center of the opening of the mask 60 in the width direction.

Further, when the prepared laminate was confirmed in the same manner as in Example 1, the optical axis of the liquid crystal compound rotated in one direction on the surface of the liquid crystal lens array 2 on the glass plate side, as shown in FIG. It also had five liquid crystal alignment patterns in which the rotation direction was reversed in the middle of one direction.
Further, the rotation direction of the optical axis coincided with the width direction of the opening of the mask, and the position where the rotation direction of the optical axis was reversed was the center in the width direction of the opening of the mask.

In the same manner as in Example 1, the laminated body of the produced liquid crystal lens array 2 and the glass plate was irradiated with right-handed circularly polarized light and left-handed circularly polarized light via a circularly polarizing plate.
As a result, when irradiated with right circular polarization, the light is focused toward the perpendicular line of the liquid crystal lens array passing through the center in the width direction of the liquid crystal lens (liquid crystal alignment pattern), and when irradiated with left circular polarization, the light is condensed. , The light was diffused outward from the center in the width direction of the liquid crystal lens. It should be noted that each liquid crystal lens did not refract light in the longitudinal direction (it did not have lens power).

[Example 3]
(Preparation of Liquid Crystal Composition 2)
The liquid crystal composition 2 was prepared by mixing the components shown below.
・ Liquid crystal compound 1: 1 g
・ Chiral auxiliary 2 (structure below) 55 mg
・ Horizontal alignment agent 1: 0.4 mg
-Horizontal alignment agent 2: 0.15 mg
-Photoradical initiator 1: 20 mg
-Pentaerythritol tetraacrylate (A-TMMT (Tetramethylol Methane Tetaacrylate) manufactured by Shin Nakamura Chemical Industry Co., Ltd.): 10 mg
-Methyl ethyl ketone (MEK): 1.09 g
-Cyclohexanone: 0.16 g

Chiral auxiliary 2

(Manufacturing of liquid crystal layer (liquid crystal lens array 3) and laminate)
In Example 2, the liquid crystal lens array 3 is formed in the same manner as in Example 2 except that the liquid crystal composition 1 used for forming the liquid crystal layer is changed to the liquid crystal composition 2 and the dry film thickness is 5 μm. Further, a laminated body of the liquid crystal lens array 3 and the glass plate was produced.
The liquid crystal lens array 3 is a reflective liquid crystal lens array having five reflective lenses (reflecting mirrors).

When the produced laminate was confirmed in the same manner as in Example 1, the optical axis of the liquid crystal compound was rotated in one direction on the surface of the liquid crystal lens array 3 on the glass plate side, as shown in FIG. Moreover, it has five liquid crystal orientation patterns in which the rotation direction is reversed in the middle of one direction.
Further, the rotation direction of the optical axis coincided with the width direction of the opening of the mask, and the position where the rotation direction of the optical axis was reversed was the center in the width direction of the opening of the mask.

Further, in the same manner as in Example 1, the laminated body of the produced liquid crystal lens array 3 and the glass plate was irradiated with right circular polarization via a circular polarizing plate.
As a result, the reflected light was focused toward the perpendicular line of the liquid crystal lens array passing through the center in the width direction of the liquid crystal lens (liquid crystal alignment pattern). In addition, each liquid crystal lens did not refract light in the longitudinal direction.

[Comparative Example 1]
In Example 1, the irradiation of ultraviolet rays using the mask 58 was not performed at the time of forming the alignment film.
Except for this, an alignment film was formed, a liquid crystal layer was formed, and a laminate of the liquid crystal layer and the glass plate was prepared in the same manner as in Example 1.
When the alignment film was formed, the alignment film was confirmed in the same manner as in Example 1. As a result, on the lower surface (substrate side) of the alignment film, the direction of the optical axis of the liquid crystal compound coincided with the rubbing direction of the substrate, as shown in FIG. On the other hand, on the upper surface, the directions of the optical axes of the liquid crystal compound were aligned in one direction on the entire surface.
Further, when the prepared laminate was confirmed in the same manner as in Example 1, the direction of the optical axis of the liquid crystal compound was the direction of the optical axis of the liquid crystal compound on the upper surface of the alignment film on the surface of the liquid crystal layer on the glass plate side. It was aligned in the same direction.

In the same manner as in Example 1, the laminated body of the produced liquid crystal layer and the glass plate was irradiated with right-handed circularly polarized light and left-handed circularly polarized light via a circularly polarizing plate.
As a result, the laminated body did not exhibit any action as a lens in both right-handed circularly polarized light and left-handed circularly polarized light.
From the above results, the effect of the present invention is clear.

It can be suitably used for manufacturing lenses and reflectors for condensing or diffusing light.

10, 30, 50 Optical element 12 Substrate 14, 32, 52 Alignment film 14A, 52A Coating film 14a, 32a, 52a Lower surface 14b, 32b, 52b Upper surface 16, 16A, 54 Liquid crystal layer 20, 24, 36 Liquid crystal compound 34, 34A , 34B Cholesteric liquid crystal layer 40, 58, 60 Mask 40a Slit L ₁ , L ₄ , Lr Incident light L ₂ , L ₅ Transmitted light Lr1, Lr2 Reflected light Q1, Q2 Absolute phase E1, E2 Equal phase surface S Spot light

Claims (9)

One surface of the substrate is subjected to an orientation treatment for orienting the liquid crystal compound so that the optical axis derived from the liquid crystal compound is in one direction.
An alignment film composition containing a liquid crystal compound and a chiral agent whose spiral-inducing force changes by irradiation with light is applied to the surface of the substrate subjected to the alignment treatment to form a coating film.
A part of the coating film of the alignment film composition is irradiated with light exposed to the chiral agent.
The coating film of the alignment film composition irradiated with the light is cured to form an alignment film, and the alignment film is formed.
A method for manufacturing an optical element, which comprises applying a composition containing a liquid crystal compound to the surface of the alignment film and curing it to form a liquid crystal layer. The method for manufacturing an optical element according to claim 1, wherein the light irradiating the coating film of the alignment film composition is spot light. The method for manufacturing an optical element according to claim 2, wherein the spot shape of the spot light is circular or elliptical. The method for manufacturing an optical element according to claim 1, wherein the light irradiating the coating film of the alignment film composition is linear light. The method for manufacturing an optical element according to any one of claims 1 to 4, wherein the liquid crystal layer is a cholesteric liquid crystal layer in which a cholesteric liquid crystal phase is fixed. An alignment film formed by using a liquid crystal compound and a chiral agent whose spiral-inducing force is changed by irradiation with light, and a liquid crystal layer formed by using a composition containing a liquid crystal compound laminated on the alignment film. Have and
In the alignment film, the optical axis derived from the liquid crystal compound is oriented in one direction on the first surface, which is one surface, and the optical axis derived from the liquid crystal compound is oriented on the second surface, which is the other surface. Has a liquid crystal alignment pattern in which the orientation of the liquid crystal changes while continuously rotating toward at least one direction, and the direction of rotation of the direction of the optical axis derived from the liquid crystal compound is reversed on the way.
The liquid crystal layer is laminated on the second surface of the alignment film, and the liquid crystal compound derived from the composition is formed on the surface of the alignment film on the second surface side of the alignment film. An optical element characterized in that it is oriented according to the liquid crystal alignment pattern on the second surface. The optical element according to claim 6, wherein the liquid crystal layer is a cholesteric liquid crystal layer in which a cholesteric liquid crystal phase is fixed. The liquid crystal alignment pattern on the second surface of the alignment film is
It has a plurality of directions in which the direction of the optical axis derived from the liquid crystal compound changes while continuously rotating, and
The plurality of directions, in which the direction of the optical axis derived from the liquid crystal compound changes while continuously rotating, intersect at one point, and further.
The optical element according to claim 6 or 7, which is a liquid crystal orientation pattern in which the rotation direction of the direction of the optical axis derived from the liquid crystal compound is reversed at the one point where the plurality of directions intersect. The liquid crystal alignment pattern on the second surface of the alignment film is
The optical element according to claim 6 or 7, which is a liquid crystal orientation pattern having only one direction in which the direction of the optical axis derived from the liquid crystal compound changes while continuously rotating.

Images