WO2023149211A1

WO2023149211A1 - Onboard lighting device, automobile, and diffraction element

Info

Publication number: WO2023149211A1
Application number: PCT/JP2023/001370
Authority: WO
Inventors: 昭裕安西; 之人齊藤
Original assignee: 富士フイルム株式会社
Priority date: 2022-02-02
Filing date: 2023-01-18
Publication date: 2023-08-10

Abstract

The present invention addresses the problem of providing: an onboard lighting device that uses excitation light from a solid light source such as a semiconductor light-emitting element to excite a phosphor region and can efficiently guide the excitation light and fluorescence from the phosphor region to an optical system for use; an automobile that comprises the onboard lighting device; and a diffraction element. According to the present invention, an onboard lighting device that distributes light into the space outside an automobile comprises a light source, a member that diffuses light emitted by the light source, and a diffraction element at which the pitch of a periodic structure gradually changes from the center toward the outside.

Description

Automotive lighting equipment, automobiles and diffraction elements

The present invention relates to an in-vehicle lighting device using a diffraction element suitable for miniaturization and weight reduction, an automobile equipped with this in-vehicle lighting device, and a diffraction element used in this in-vehicle lighting device.

Light source devices and lighting devices that use semiconductor light-emitting elements such as LEDs (Light Emitting Diodes) and semiconductor lasers as excitation sources to excite phosphors and use them as light sources have been put to practical use. For example, Patent Literature 1 proposes a light source device and a lighting device that use laser light to excite a phosphor to provide a high-intensity light source.

JP-A-2005-191483

However, in the conventional method, in the light source device and the lighting device that excite the phosphor with the semiconductor light emitting element, the plate-like phosphor diffuses the light and cannot be efficiently introduced into the optical system for use. There was a problem.
Furthermore, in recent years, attempts have been made to project characters and symbols onto roads and walls using the light emitted outside the vehicle. Therefore, an efficient optical system is required.
In addition, the light emitted outside the vehicle often has multiple outlets for low beams, high beams, turn lamps, parking lights, etc. In addition, in-vehicle lighting systems with functions such as adaptive headlights are difficult to adapt to road curves. In addition, it is necessary to drive the direction in which the lamp is emitted, and there is a demand for simplification of the internal structure of the lighting device and reduction in the weight of driving parts.

An object of the present invention is to provide an in-vehicle lighting device that utilizes a diffraction element that is suitable for miniaturization and weight reduction.

As a result of intensive studies in view of the above problems, the present inventor found that it is possible to reduce the size and weight by using a diffraction element in order to efficiently introduce the diffused light spread by the phosphor or the diffuser plate. Further, the present inventors have found that, in the case of having a plurality of outlets to the outside of the vehicle, it is possible to reduce the size of the illumination device by using a driving device including a diffraction element, and have completed the present invention.

That is, the problems of the present invention have been solved by the following means.
[1] An in-vehicle lighting device, comprising a light source, a diffusion member that diffuses the light emitted from the light source, and the diffusion member that diffracts the diffused light, and the pitch of the periodic structure gradually changes outward from the center. 1. An on-vehicle lighting device for distributing light to an exterior space of a motor vehicle, comprising a first diffractive element.
[2] The first diffraction element is a liquid crystal diffraction element formed using a composition containing a liquid crystal compound, wherein the direction of the optic axis derived from the liquid crystal compound rotates continuously along at least one in-plane direction. The vehicle-mounted lighting device according to [1], comprising an optically anisotropic layer having a liquid crystal alignment pattern that changes as it moves.
[3] The vehicle lighting device according to [1] or [2], which has an oxygen blocking layer adjacent to the first diffraction element.
[4] an exit port and an optical waveguide for distributing light to the exterior space of the automobile;
an optical deflection element that deflects the light emitted by the light source toward the first diffraction element or the optical waveguide;
The on-vehicle use according to any one of [1] to [3], further comprising a second diffraction element arranged on the light exit side of the light deflection element and having a periodic structure pitch that gradually changes outward from the center. lighting device.
[5] The second diffraction element is a liquid crystal diffraction element formed using a composition containing a liquid crystal compound, wherein the direction of the optic axis derived from the liquid crystal compound rotates continuously along at least one in-plane direction. The vehicle-mounted lighting device according to [4], comprising an optically anisotropic layer having a liquid crystal alignment pattern that changes as it moves.
[6] The vehicle lighting device according to [4] or [5], which has an oxygen blocking layer adjacent to the second diffraction element.
[7] The vehicle-mounted lighting device according to any one of [4] to [6], wherein the light deflection element is a MEMS light deflection element.
[8] The vehicle-mounted lighting device according to any one of [1] to [7], which has a λ/4 plate.
[9] An automobile equipped with the in-vehicle lighting device according to any one of [1] to [8].
[10] A diffraction element used in the vehicle-mounted lighting device according to any one of [1] to [8].

According to the present invention, it is possible to provide an in-vehicle lighting device that uses a diffraction element that is suitable for miniaturization and weight reduction.

FIG. 1 is a schematic diagram showing an example of the vehicle-mounted lighting device of the present invention. FIG. 2 is a schematic diagram schematically showing another example of the vehicle-mounted lighting device of the present invention. FIG. 3 is a schematic diagram schematically showing another example of the vehicle-mounted lighting device of the present invention. FIG. 4 is a conceptual diagram of a liquid crystal diffraction element. FIG. 5 is a schematic plan view of an optically anisotropic layer. FIG. 6 is a conceptual diagram for explaining the action of the optically anisotropic layer. FIG. 7 is a conceptual diagram for explaining the action of the optically anisotropic layer. FIG. 8 is a conceptual diagram for explaining the action of the optically anisotropic layer. FIG. 9 is a schematic plan view of another example of an optically anisotropic layer. FIG. 10 is a conceptual diagram of an exposure apparatus that exposes an alignment film. FIG. 11 is a conceptual diagram of another example of an exposure apparatus that exposes an alignment film. FIG. 12 is a conceptual diagram of another example of an optically anisotropic layer. FIG. 13 is a conceptual diagram of another example of an optically anisotropic layer. FIG. 14 is a conceptual diagram for explaining the action of the optically anisotropic layer.

Hereinafter, a vehicle-mounted lighting device of the present invention will be described with reference to the drawings.
In addition, in each drawing, the scale of the constituent elements is appropriately changed from the actual scale in order to facilitate visual recognition.

In this specification, a numerical range represented by "to" means a range including the numerical values before and after "to" as lower and upper limits.
In addition, "perpendicular" and "parallel" with respect to angles mean a strict angle range of ±10°.

In this specification, Re(λ) represents the in-plane retardation at wavelength λ. Unless otherwise specified, the wavelength λ is 550 nm.
In the present specification, Re(λ) is a value measured at wavelength λ with AxoScan (manufactured by Axometrics). By entering the average refractive index ((nx+ny+nz)/3) and film thickness (d (μm)) in AxoScan,
Slow axis direction (°)
Re(λ)=R0(λ)
is calculated.
Note that R0(λ), which is displayed as a numerical value calculated by AxoScan, means Re(λ).

(In-vehicle lighting device)
A configuration of an in-vehicle lighting device according to an embodiment of the present invention will be described with reference to conceptual diagrams of FIGS. 1 to 3. FIG.

The vehicle-mounted lighting device shown in FIG. It is composed of a wavelength conversion member 105 for conversion and a first liquid crystal diffraction element 106 for condensing and collimating (parallelizing) the diffused light and projecting it out of the vehicle.

The vehicle-mounted lighting device shown in FIG. 1 has three laser light sources 101 .
In the illustrated example, the laser light emitted from the laser light source 101 positioned at the upper side of the figure and the laser light emitted from the laser light source 101 positioned at the lower side of the figure are reflected by the mirror 102 toward the optical axis of the lens 103. A laser beam emitted from a laser light source 101 located in the center travels along the optical axis of the lens 103 and directly enters the lens 103 .
The three laser beams incident on the lens 103 are condensed by the lens 103 , reflected along a predetermined optical path by the mirror 104 , and incident on the wavelength conversion member 105 .

The wavelength conversion member 105 is a diffusion member in the present invention, and converts the laser light emitted from the laser light source 101 into white light.
As an example, the laser light source 101 emits blue light. Also, the wavelength conversion member 105 uses a phosphor that converts incident blue light into red light and green light. In this case, white light is emitted from wavelength conversion member 105 by red light and green light converted from blue light by the phosphor of wavelength conversion member 105 and blue light transmitted without being converted by the phosphor. be.

In this example using the wavelength conversion member 105 , the laser light source 101 may emit light having a wavelength that allows the wavelength conversion member 105 to generate white light according to the wavelength conversion member 105 . Regarding this point, the example shown in FIG. 3, which will be described later, is the same.
Therefore, the laser light emitted by the laser light source 101 may be any one that can generate white light according to the wavelength conversion member 105, and may be visible light, near infrared rays, far infrared rays, or longer wavelengths than far infrared rays. It may be an electromagnetic wave.

The white light incident on and converted by the wavelength converting member 105 using phosphor becomes diffused light diffused by the phosphor.
The white light emitted from the wavelength conversion member 105 is reflected toward a predetermined optical path by the first liquid crystal diffraction element 106, is condensed, and is projected as, for example, a headlight of an automobile. Light is distributed to the exterior space of the automobile.

In the present invention, the first diffraction element is a reflective diffraction element in which the pitch of the periodic structure of the diffraction element gradually changes from the center toward the outside.
The first liquid crystal diffraction element 106 is a liquid crystal diffraction element formed using a composition containing a liquid crystal compound, and the orientation of the optic axis derived from the liquid crystal compound rotates continuously along at least one in-plane direction. It comprises an optically anisotropic layer having a liquid crystal alignment pattern that changes as it moves.
As will be described later, in the liquid crystal alignment pattern of the optically anisotropic layer, the first liquid crystal diffraction element 106 has a length of 180° along one direction of the optical axis, which is one period (one pitch) of the periodic structure of the diffraction element. ).

The diffraction angle of light by the diffraction element is determined by the wavelength of light incident on the diffraction element and one period of the periodic structure (periodic structure pitch). Specifically, the shorter one period and the longer the wavelength of light, the larger the diffraction angle. For example, when light enters from the normal direction of the diffraction element, the shorter the period, the larger the angle of the reflected light with respect to the normal direction.
The normal direction is a direction orthogonal to the surfaces of various members such as sheet-like objects (plate-like objects, films, layers).
Therefore, if one cycle of the first liquid crystal diffraction element 106 is configured so that the center of the direction in which the rotation axis derived from the liquid crystal compound rotates is large and gradually decreases toward the outside, the light incident on the first liquid crystal diffraction element 106 The emitted light is reflected and collected.
The wavelength of light incident on the first liquid crystal diffraction element 106 is white light, that is, visible light. Therefore, if one period is in the range of 0.2 to 10 μm, a sufficient effect of condensing light can be obtained. The wavelength range of visible light is, for example, 380 to 780 nm.

As an optical system for reflecting the diffused light that has passed through the wavelength conversion member 105 in a predetermined direction and condensing it into projected light, a combination of a concave mirror and a projection lens is used to direct the diffused light in a desired direction. A method of concentrating and collimating the light by reflecting the light is conceivable.
However, it is difficult to produce the free curved surface of the concave mirror with high precision so as to reflect and condense the light so as to obtain the desired projected light. Moreover, when using such a concave mirror and a projection lens, the optical system also becomes large.
On the other hand, in the vehicle-mounted lighting device of the present invention, instead of the optical system having the concave mirror and the projection lens, one period of the diffraction element gradually changes from the center of the periodic structure toward the outside. The white light diffused by the wavelength conversion member 105 (diffusion member) can be reflected by the first liquid crystal diffraction element 106 (first diffraction element), which is a diffraction element, and can be focused and collimated. The first liquid crystal diffraction element 106 uses, for example, a cholesteric liquid crystal layer, and can diffract and reflect diffused light with a flat plate to condense light, so that a small optical system can be assembled.
As a result, according to the present invention, it is possible to realize a compact and lightweight in-vehicle lighting device.
The first liquid crystal diffraction element 106 will be detailed later.

FIG. 2 shows another example of the vehicle-mounted lighting device of the present invention. The in-vehicle lighting device shown in FIG. 2 is a system for projecting (projecting) characters and images on roads and walls outside the vehicle.
In the vehicle-mounted lighting device shown in FIG. 2, the same reference numerals as those in the vehicle-mounted lighting device shown in FIG. 1 basically indicate the same members. This also applies to FIG. 3, which will be described later.
The in-vehicle lighting device shown in FIG. 2 is similar to the in-vehicle lighting device shown in FIG. have. In this example, the intermediate screen 108 is the diffusing member in the present invention.

1, also in the vehicle-mounted lighting apparatus shown in FIG. 2, the three laser beams emitted by the laser light source 101 are condensed by the lens 103 and enter the drawing mirror 104a of the drawing element. .
In this example, it is not necessary to convert the laser light emitted by the laser light source 101 into white light. Therefore, the laser light emitted by the laser light source 101 may be monochromatic light such as red light, blue light and green light, or white light. Therefore, in this example, a light source such as an LED, which will be described later, can also be suitably used.

As an example of the drawing element, a MEMS optical deflection element is used. By two-dimensionally swinging the drawing mirror 104a by the driving device 107a, the incident laser beam is deflected in the orthogonal x and y directions. Scan to
As an example, the drawing element swings the drawing mirror 104a in the x-direction by the driving device 107a to scan the laser light while changing the angle in the y-direction. The drawing elements thereby form scanning lines elongated in the x direction and arranged in the y direction.
The in-vehicle illumination device shown in FIG. 2 modulates the laser light source 101 in accordance with the image to be drawn in synchronization with the scanning of the laser beam, that is, turns on/off the laser light source 101 to draw. Therefore, in the example shown in FIG. 2, it can be said that the laser light source 101 (its driving means) also constitutes a part of the drawing element.

The laser light scanned by the drawing mirror 104a enters the intermediate screen 108 and scans the intermediate screen 108 to form scanning lines.
As the laser light enters and scans the intermediate screen 108 , the laser light is diffused by the intermediate screen 108 and images such as characters and patterns are realized on the intermediate screen 108 .
The image formed into a real image by the intermediate screen 108 enters the first liquid crystal diffraction element 106, is reflected, condensed and collimated, and is projected onto the road, wall, etc. projected as an image.
In this example as well, by using the first liquid crystal diffraction element 106 that can diffract and reflect diffused light with a flat plate and converge the light, it is possible to realize a compact and lightweight in-vehicle lighting device.

FIG. 3 shows another example of the vehicle-mounted lighting device of the present invention. The in-vehicle lighting device shown in FIG. 3 is an example having a plurality of output ports (projection ports) for projecting illumination to the outside, such as a high beam output port and a low beam output port.
In addition to the constituent members of the vehicle-mounted lighting device shown in FIG. 3, the vehicle-mounted lighting device shown in FIG. It has a second liquid crystal diffraction element 110 which is an element, and a second exit port composed of a lens 111 , an optical waveguide 112 , a concave mirror 113 and a projection lens 114 . Note that this in-vehicle lighting device does not have the mirror 104 .
In this example, the first liquid crystal diffraction element 106 (first diffraction element) constitutes the first exit, and the first liquid crystal diffraction element 106 of the first exit and the lens 111 of the second exit Correspondingly, it has two wavelength conversion members 105 .

In the vehicle-mounted lighting apparatus shown in FIG. 3 as well as the vehicle-mounted lighting apparatus shown in FIG.
In the in-vehicle lighting device shown in FIG. 3, a laser light source 101 emits linearly polarized laser light. The λ/4 plate 109 converts the linearly polarized laser light into circularly polarized light in a predetermined rotating direction.
As will be described later, the second liquid crystal diffraction element 110 refracts (diffracts) the transmitted light in a direction of diffusing or condensing, depending on the direction of rotation of the incident circularly polarized light. The λ/4 plate 109 converts the incident linearly polarized laser light into circularly polarized light in the direction in which the second liquid crystal diffraction element 110 diffuses.
Therefore, when the laser light source 101 emits circularly polarized laser light, the λ/4 plate 109 is unnecessary.

Also, when a cholesteric liquid crystal layer is used as a reflective diffraction element, the above-described first liquid crystal diffraction element 106 selectively diffracts and reflects circularly polarized light in a predetermined turning direction.
Therefore, for the same reason, the vehicle-mounted lighting device shown in FIG. Alternatively, the first liquid crystal diffraction element 106 may have a λ/4 plate on the light incident side of the cholesteric liquid crystal layer.

The laser light converted into circularly polarized light by the λ/4 plate 109 is incident on the deflection mirror 104b of the MEMS optical deflection element. Since this MEMS deflection element does not perform drawing, the scanning direction of the laser light may be one direction.
The MEMS optical deflection element has a deflection mirror 104b and a driver 107b. The MEMS optical deflection element deflects the incident circularly polarized laser light by swinging the deflection mirror 104b by the driving device 107b, and directs the laser light to the first liquid crystal diffraction element 106 side (first exit side) and the , and the lens 111 side (second exit side).

The circularly polarized laser light distributed by the MEMS optical deflection element enters the second liquid crystal diffraction element 110 .
As described above, the second liquid crystal diffraction element 110 refracts the transmitted light in the direction of diffusing or condensing according to the direction of rotation of the incident circularly polarized light. , the light is converted into circularly polarized light in the direction in which the second liquid crystal diffraction element 110 diffuses.
Therefore, the laser light incident on the second liquid crystal diffraction element 110 is emitted from the second liquid crystal diffraction element 110 after the deflection angle of the MEMS optical deflection element is widened.
The second liquid crystal diffraction element 110 will be detailed later.

The laser light deflected to the first exit side and diffracted by the second liquid crystal diffraction element 110 is converted into white light by the wavelength conversion member 105 on the first exit side as in the example shown in FIG. 1 The light is reflected, condensed and collimated by the liquid crystal diffraction element 106 and projected outside the vehicle as a headlight of the vehicle, for example.

On the other hand, the laser light deflected to the second exit side and diffracted by the second liquid crystal diffraction element 110 is converted into white light by the wavelength conversion member 105 on the second exit side, condensed by the lens 111, and It enters the entrance of the optical waveguide 112 .
The laser light that has entered the optical waveguide 112 propagates through the optical waveguide 112 , is emitted from the exit port of the optical waveguide 112 , and enters the concave mirror 113 .
The laser light incident on the concave mirror 113 is reflected and condensed by the concave mirror 113, then condensed and collimated by the projection lens 114, and similarly projected outside the vehicle as a headlight of an automobile.

In the in-vehicle lighting device shown in FIG. 3 as well, a compact and lightweight in-vehicle lighting device can be realized by using the first liquid crystal diffraction element 106 that can diffract and reflect diffused light and condense light with a flat plate.
In this example, instead of the concave mirror 113 and the projection lens 114, the first liquid crystal diffraction element 106 may also be used on the second exit side. This makes it possible to more preferably reduce the size and weight of the vehicle-mounted lighting device.

In the in-vehicle lighting device shown in FIG. 3, by switching the deflection toward the first exit port side and the deflection toward the second exit port side by the MEMS optical deflection element according to the exit port to be used, for example, a low beam You may switch a projected light like switching with a high beam. The switching at this time may be automatically performed by a MEMS optical deflection element according to the detection result by providing a sensor to detect the presence or absence of an oncoming vehicle.
Alternatively, the deflection to the first exit port side and the deflection to the second exit port side by the MEMS optical deflection element are continuously performed at high speed, and two types of projection are performed, such as simultaneous lighting of the low beam and the high beam. You may make it project light simultaneously. Also in this aspect, as described above, switching between simultaneous lighting and low beam may be automatically performed by the MEMS optical deflection element according to the detection result of the presence or absence of an oncoming vehicle by the sensor.

In the vehicle-mounted lighting device shown in FIG. 3, the second liquid crystal diffraction element 110 is not required if the deflection mirror 104b has a sufficient swing angle in the MEMS optical deflection element having the deflection mirror 104b and the driving device 107b. .
However, in order to guide the light to a plurality of spaced-apart exit ports, the distance between the MEMS optical deflection element and the first liquid crystal diffraction element 106 and/or the optical waveguide 112 must be increased, resulting in a large illuminating device. Also, in order to increase the swing angle of the deflection mirror 104b, it is necessary to increase the size of the MEMS optical deflection element.
On the other hand, in the vehicle-mounted lighting device shown in FIG. 3, the deflection angle of the laser light after passing through the second liquid crystal diffraction element 110 is can be increased. As a result, the distance between the MEMS optical deflection element and the first liquid crystal diffraction element 106 and/or the optical waveguide 112 can be reduced, making it possible to reduce the size of the illumination device.

In FIG. 3, the lens 111 is arranged in front of the optical waveguide in order to collect the light diffused by the wavelength conversion member 105 into the optical waveguide, but a diffraction element may be used to collect the light.
Since the light diffuses after passing through the optical waveguide 112, it is condensed and collimated using a concave mirror 113 and a projection lens 114 and projected outside the vehicle. The means for condensing and collimating this diffused light may be the first liquid crystal diffraction element 106, in which case the optical system can be made more compact.

Furthermore, in the vehicle-mounted lighting device shown in FIG. 3, a driving device may be provided to adjust the projection direction of the projection light according to the situation.
Such adjustment of the projection direction is conceivable, for example, by directing the projection direction of the low beam to the traveling direction of the automobile according to the steering direction and steering angle by the steering wheel.
Here, in the in-vehicle lighting device of the present invention shown in FIG. 3, for example, when the first emission port side is a low beam, only by changing the angle of the plate-like first liquid crystal diffraction element 106, such You can change the projection direction. Therefore, according to the in-vehicle lighting device of the present invention, it is possible to change the projection direction of projection light with a small, simple, and lightweight driving device.
The angle of the first liquid crystal diffraction element 106 may be changed by using a known plate-like angle changing polarizing means.
In this regard, the vehicle-mounted lighting device of the present invention shown in FIGS. 1 and 2 is similar.

The automobile of the present invention is an automobile (vehicle) equipped with such an in-vehicle lighting device of the present invention.
Also, the diffraction element of the present invention is a diffraction element used in such a vehicle-mounted lighting device of the present invention.

Each member constituting the vehicle-mounted lighting device described above will be described below.
(light source)
In the vehicle-mounted lighting device shown in FIGS. 1 to 3, the light source is a laser light source 101. FIG.
The laser light source 101 is not limited, and various known laser light sources such as a semiconductor laser (LD (Laser Diode)) can be used.

In addition, in the vehicle-mounted lighting device of the invention, the light source is not limited to the laser light source 101, and may be an LED, a halogen lamp, a xenon lamp, a light-emitting diode, an organic light-emitting diode (OLED (Organic Light Emitting Diode) is included), or the like. A variety of known light sources are available. As described above, these light sources can be suitably used in an in-vehicle lighting device that projects the image shown in FIG.
As for the light source, compared to a light source such as an LED, the laser light source in the illustrated example can have a longer irradiation distance, can provide brighter illumination, has high energy efficiency, and can be easily miniaturized. It is preferably used.

(mirror)
Mirror 102 is a known mirror for reflecting light to change the optical path.
In addition, in the vehicle-mounted lighting device of the present invention, the optical path changing means is not limited to mirrors, and various known optical path changing members used in various optical devices can be used.

(lens)
Lens 103 and lens 111 are known condenser lenses. In the present invention, the condensing element is not limited to lenses, and all known optical elements capable of condensing light (light beams) can be used.

(Wavelength conversion member)
As described above, the wavelength conversion member 105 converts laser light into white light, and for example, one that converts incident light using a phosphor is preferably used. Here, the phosphor diffuses and emits incident light and wavelength-converted light. That is, in the examples shown in FIGS. 1 and 3, the wavelength converting member 105 is the diffusing member of the present invention.
As an example, the wavelength conversion member 105 (phosphor) converts incident blue laser light into red light and green light as described above, unconverted blue light (blue laser light), and converted blue light (blue laser light). Together with red and green light, white light is produced.

The phosphor used for the wavelength conversion member 105 is not limited, and various known phosphors can be used as long as they can generate white light according to incident light.
Examples include quantum dot phosphors such as CdSe/ZnS, InP/ZnS, perovskite materials CsPbX ₃ (X=Cl, Br, I), and combinations thereof.

(diffraction element)
[Liquid crystal diffraction element]
FIG. 4A conceptually shows the first liquid crystal diffraction element 106, and FIG. 4B conceptually shows the second liquid crystal diffraction element 110. As shown in FIG. 4A and 4B are both side views of the first liquid crystal diffraction element 106 and the second liquid crystal diffraction element 110. FIG.
A liquid crystal diffraction element is formed using a composition containing a liquid crystal compound.
Both the first liquid crystal diffraction element 106 and the second liquid crystal diffraction element 110 are sheet-shaped.
The first liquid crystal diffraction element 106 has a support 12, an alignment film 13, and a cholesteric liquid crystal layer 14a as an optically anisotropic layer. The first liquid crystal diffraction element 106 is a reflective liquid crystal diffraction element using the cholesteric liquid crystal layer 14a, and as described above, collects and collimates incident light, and reflects and projects it in a predetermined direction.
On the other hand, the second liquid crystal diffraction element 110 has a support 12, an alignment film 13, and an optically anisotropic layer 14b. The second liquid crystal diffraction element 110 is a transmissive liquid crystal diffraction element using the optically anisotropic layer 14b. By doing so, the deflection angle is widened.
4A and 4B, the sheet surface direction of the first liquid crystal diffraction element 106 and the second liquid crystal diffraction element 110 is defined as the xy direction, and the thickness direction is defined as the z direction. . 4(A) and 4(B), the horizontal direction in the drawing is the direction in which the optic axis derived from the liquid crystal compound rotates in one direction, that is, the direction of axis A (direction along axis A), which will be described later. and this direction is the x-direction. Therefore, the y-direction is a direction orthogonal to the planes of FIGS. 4(A) and 4(B).

In the vehicle-mounted lighting device of the present invention, the first liquid crystal diffraction element 106 and the second liquid crystal diffraction element 110 are flat. However, the first liquid crystal diffraction element 106 and the second liquid crystal diffraction element 110 are not limited to flat plates, and may be curved.

<Oxygen blocking layer>
The vehicle-mounted lighting device of the present invention may have an oxygen blocking layer adjacent to the first liquid crystal diffraction element 106 (first diffraction element) and/or the second liquid crystal diffraction element 110 (second diffraction element). good.
The oxygen blocking layer is an oxygen blocking film having an oxygen blocking function. In the present specification, the oxygen blocking function is not limited to a state in which oxygen is not permeated at all, but also includes a state in which oxygen is slightly permeable depending on the intended performance.
When the laser light source continuously irradiates the liquid crystal diffraction element with a laser beam, the liquid crystal diffraction element reaches a high temperature, which promotes the decomposition of the liquid crystal compound and may deteriorate over time. Therefore, by providing an oxygen blocking layer (gas barrier layer) adjacent to the cholesteric liquid crystal layer 14a of the first liquid crystal diffraction element 106 and/or the optically anisotropic layer 14b of the second liquid crystal diffraction element 110, the liquid crystal diffraction element high temperature resistance can be improved.
In the first liquid crystal diffraction element 106, the oxygen blocking layer may be provided adjacent to the cholesteric liquid crystal layer 14a, but may be provided so as to sandwich both surfaces of the first liquid crystal diffraction element 106, if necessary. In the second liquid crystal diffraction element 110, the oxygen blocking layer may be provided adjacent to the optically anisotropic layer 14b, but if necessary, it may be provided so as to sandwich both surfaces of the second liquid crystal diffraction element 110. may

There are no restrictions on the oxygen-blocking layer, and various types of oxygen-blocking layers (gas barrier layers) used in various products and members can be used.
Specific examples of the oxygen blocking layer include polyvinyl alcohol, modified polyvinyl alcohol, polyethylene vinyl alcohol, polyvinyl ether, polyvinylpyrrolidone, polyacrylamide, polyacrylic acid, cellulose ether, polyamide, polyimide, styrene/maleic acid copolymer, gelatin, Layers containing organic compounds such as vinylidene chloride and cellulose nanofibers are included. Among them, polyacrylic acid, polyvinyl alcohol, modified polyvinyl alcohol, and the like are preferable.

The oxygen-blocking layer may further contain a light resistance improver together with the organic compound from the viewpoint of further improving light resistance.
When the oxygen-blocking layer contains a light resistance improver, the content of the light resistance improver is preferably 0.1 to 5.0% by mass, preferably 0.3%, based on the total weight of the oxygen-blocking barrier layer. ~3.0% by mass is more preferred.

The thickness of the oxygen barrier layer is preferably 0.1-10 μm, more preferably 0.5-5.5 μm.
The refractive index of the oxygen blocking layer at a wavelength of 550 nm is preferably 1.40 to 1.60, more preferably 1.45 to 1.55.
Here, the refractive index of the protective layer at a wavelength of 550 nm can be measured by the same method as for the average refractive index of the light absorption anisotropic film.

In the first liquid crystal diffraction element 106 and the second liquid crystal diffraction element 110, the support 12 and the alignment film 13 are basically the same except for the alignment pattern of the alignment film, for example.
<Support>
Various sheet-like materials (films, plate-like materials) can be used as the support 12 as long as they can support the alignment film and the optically anisotropic layer.
The support 12 is preferably a transparent support, and examples thereof include polyacrylic resin films such as polymethyl methacrylate, cellulose resin films such as cellulose triacetate, and cycloolefin polymer films. Examples of the cycloolefin polymer film include JSR's trade name "ARTON" and Nippon Zeon's trade name "Zeonor". Note that the support of the first liquid crystal diffraction element 106 does not necessarily have to be transparent.
The support 12 may be a flexible film or a non-flexible substrate such as a glass substrate.

<Alignment film>
In the first liquid crystal diffraction element 106 and the second liquid crystal diffraction element 110 , the orientation film 13 is formed on the surface of the support 12 . The alignment film 13 is an alignment film for aligning the liquid crystal compound 20 in a predetermined liquid crystal alignment pattern when forming the cholesteric liquid crystal layer 14a and the optically anisotropic layer 14b.

As will be described later, in the first liquid crystal diffraction element 106 and the second liquid crystal diffraction element 110, the cholesteric liquid crystal layer 14a and the optically anisotropic layer 14b have an optical axis 22 (see FIG. 9) derived from the liquid crystal compound 20. It has a liquid crystal orientation pattern that changes while continuously rotating along at least one in-plane direction.
4A and 4B exemplify a rod-like liquid crystal compound as the liquid crystal compound 20. As shown in FIG. Therefore, in the illustrated example, the orientation of the optical axis 22 coincides with the longitudinal direction of the liquid crystal compound 20 .
Therefore, the alignment films 13 of the first liquid crystal diffraction element 106 and the second liquid crystal diffraction element 110 are formed so that the cholesteric liquid crystal layer 14a and the optically anisotropic layer 14b can form this liquid crystal alignment pattern.

In the cholesteric liquid crystal layer 14a of the first liquid crystal diffraction element 106 and the optically anisotropic layer 14b of the second liquid crystal diffraction element 110, the direction of the optical axis 22 in the liquid crystal alignment pattern changes while rotating continuously. In addition, the length by which the direction of the optical axis 22 is rotated by 180° is defined as one period Λ (rotational period Λ (rotational period pitch)). The one direction in which the direction of the optical axis 22 changes while rotating continuously is the direction along the axis A, which will be described later.
In the in-vehicle lighting device of the present invention, the cholesteric liquid crystal layer 14a of the first liquid crystal diffraction element 106 and the optically anisotropic layer 14b of the second liquid crystal diffraction element 110 are continuously rotated while the direction of the optical axis 22 rotates continuously. One period Λ is gradually shortened outward from the center of the changing one direction. Further, the rotation direction of the optical axis 22 of the liquid crystal compound 20 in one direction is reversed at the center of the axis A direction toward the axis A direction (arrow x direction). As described above, one direction in which the direction of the optical axis 22 changes while rotating continuously is the direction along the axis A, which will be described later.
Therefore, the alignment films 13 of the first liquid crystal diffraction element 106 and the second liquid crystal diffraction element 110 are formed so that the cholesteric liquid crystal layer 14a and the optically anisotropic layer 14b can form this liquid crystal alignment pattern.

Various known materials can be used for the alignment film 13 .
Examples of the alignment film 13 include a rubbing treatment film made of an organic compound such as a polymer, an oblique vapor deposition film of an inorganic compound, a film having microgrooves, ω-tricosanoic acid, dioctadecylmethylammonium chloride, and methyl stearate. A film obtained by accumulating LB (Langmuir-Blodgett) films of an organic compound by the Langmuir-Blodgett method.
As the alignment film 13, one formed by rubbing the surface of a polymer layer is exemplified. The rubbing treatment is performed by rubbing the surface of the polymer layer with paper or cloth several times in one direction. The types of polymers used for the alignment film include polyimide, polyvinyl alcohol, polymers having a polymerizable group described in JP-A-9-152509, JP-A-2005-97377, JP-A-2005-99228, and , and the orthogonal alignment films described in JP-A-2005-128503 and the like can be preferably used.
The term “orthogonal alignment film” as used in the present invention means an alignment film in which the major axes of the molecules of the polymerizable rod-like liquid crystal compound of the present invention are oriented substantially perpendicular to the rubbing direction of the orthogonal alignment film. The thickness of the alignment film does not need to be large as long as it can provide the alignment function, and is preferably 0.01 to 5 μm, more preferably 0.05 to 2 μm.

As the alignment film 13, a so-called photo-alignment film obtained by irradiating a photo-alignment material with polarized or non-polarized light to form an alignment film can also be used. That is, a light-distribution material may be applied on the support 12 to form a light-alignment film.
Irradiation with polarized light can be performed in a direction perpendicular to or oblique to the photo-alignment film, and irradiation with non-polarized light can be performed in a direction oblique to the photo-alignment film.

Examples of the photo-alignment material used in the photo-alignment film that can be used in the present invention include, for example, JP-A-2006-285197, JP-A-2007-76839, JP-A-2007-138138, and JP-A-2007-94071. Publications, JP 2007-121721, JP 2007-140465, JP 2007-156439, JP 2007-133184, JP 2009-109831, JP 3883848 and JP 4151746 Azo compounds described in No., aromatic ester compounds described in JP-A-2002-229039, maleimide having a photo-orientation unit described in JP-A-2002-265541 and JP-A-2002-317013 and / or Alkenyl-substituted nadimide compounds, photocrosslinkable silane derivatives described in Japanese Patent Nos. 4205195 and 4205198, Japanese Patent Publication No. 2003-520878, Japanese Patent Publication No. 2004-529220 and light described in Japanese Patent No. 4162850 Crosslinkable polyimide, polyamide or ester, and JP-A-9-118717, JP-A-10-506420, JP-A-2003-505561, WO 2010/150748, JP-A-2013-177561 and photodimerizable compounds described in JP-A-2014-12823, particularly cinnamate compounds, chalcone compounds and coumarin compounds. Particularly preferred are azo compounds, photocrosslinkable polyimides, polyamides, esters, cinnamate compounds and chalcone compounds.
In the present invention, it is preferable to use a photo-alignment film.

FIG. 10 shows a schematic diagram of an alignment film exposure apparatus that applies a photo-alignment material onto a support 12 and dries it, and then exposes the alignment film to form an alignment pattern.
This exposure apparatus 50 forms an orientation pattern (liquid crystal orientation pattern) in which the optical axis 22 derived from the liquid crystal compound 20 continuously changes while rotating in one direction, as conceptually shown in FIG. is.
The exposure device 50 includes a light source 54 having a laser 52, a beam splitter 56 for splitting the laser light 70 from the laser 52 into two, and mirrors arranged on the optical paths of the two split

light beams

72A and 72B. 58A and 58B and λ/4

plates

60A and 60B.
Although not shown, the light source 64 has, for example, a polarizing plate and emits linearly polarized light P0. The λ/ ₄ _plates 60A and 60B have optical axes _{perpendicular} to each other. Convert to polarization P _L .

The support 12 having the alignment film 13 before the alignment pattern is formed is placed in the exposure area, and the two

light beams

72A and 72B are crossed and interfered on the alignment film 13, and the interference light is directed to the alignment film 13. Illuminate and expose.
Due to the interference at this time, the polarization state of the light with which the alignment film 13 is irradiated periodically changes in the form of interference fringes. As a result, an alignment pattern in which the alignment state changes periodically is obtained.
By changing the crossing angle β of the two

light beams

72A and 72B in the exposure device 50, the period of the alignment pattern can be changed. That is, in the exposure device 50, by adjusting the crossing angle β, in the orientation pattern in which the optical axis 22 derived from the liquid crystal compound 20 rotates continuously along one direction, , the length of one cycle in which the optical axis 22 is rotated by 180° (rotational cycle Λ) can be adjusted.
By forming a cholesteric liquid crystal layer 14a or an optically anisotropic layer 14b, which will be described later, on the alignment film 13 having such an alignment pattern in which the alignment state changes periodically, a liquid crystal alignment pattern corresponding to this cycle is provided. Alternatively, a cholesteric liquid crystal layer 14a or an optically anisotropic layer 14b can be formed.

Further, by rotating the optical axes of the λ/4 plate 60A and the λ/4 plate 60B by 90°, the rotation direction of the optical axis 22 can be reversed. Therefore, one half of the alignment film 13 is masked and exposed, then the exposed area is masked, and the optical axes of the λ/4

plates

60A and 60B are rotated by 90° for exposure. can reverse the rotation direction of the optical axis 22 at the center in one direction in which the optical axis 22 of the liquid crystal compound 20 rotates.
Furthermore, by adjusting the crossing angle β of the

light beams

72A and 72B and masking the unnecessary regions for exposure, the length of one cycle (one cycle Λ ) can be gradually shortened outward from the center in one direction in which the optical axis 22 rotates.

For the exposure of the alignment film 13, an exposure device 80 conceptually shown in FIG. 11 is also preferably used. An exposure device 80 shown in FIG. 11 is an exposure device used for forming a concentric alignment pattern (liquid crystal alignment pattern) as conceptually shown in FIG.
The exposure device 80 includes a light source 84 having a laser 82, a polarizing beam splitter 86 that splits the laser beam M from the laser 82 into S-polarized light MS and P-polarized light MP, and a mirror 90A arranged in the optical path of the P-polarized light MP. and a mirror 90B arranged in the optical path of the S-polarized MS, a lens 92 (convex lens) arranged in the optical path of the S-polarized MS, a polarizing beam splitter 94, and a λ/4 plate 96.

The P-polarized light MP split by the polarizing beam splitter 86 is reflected by the mirror 90A and enters the polarizing beam splitter 94 . On the other hand, the S-polarized light MS split by the polarizing beam splitter 86 is reflected by the mirror 90B, condensed by the lens 92, and enters the polarizing beam splitter 94. FIG.
The P-polarized MP and S-polarized light MS are combined by a polarizing beam splitter 94 into right-handed circularly polarized light and left-handed circularly polarized light according to the polarization direction by a λ/4 plate 96, and are applied to the alignment film 13 on the support 12. incident on.
Here, due to the interference between the right-handed circularly polarized light and the left-handed circularly polarized light, the polarization state of the light with which the alignment film 13 is irradiated changes periodically in the form of interference fringes. Since the crossing angle of the left-handed circularly polarized light and the right-handed circularly polarized light changes from the inside to the outside of the concentric circle, an exposure pattern is obtained in which the pitch changes from the inside to the outside. As a result, a concentric alignment pattern in which the alignment state changes periodically is obtained in the alignment film 13 .

In this exposure apparatus 80, the length of one cycle (one cycle Λ) in which the optical axis 22 of the liquid crystal compound 20 rotates continuously by 180° along one direction is the refractive power of the lens 92, the focal length of the lens 92, Also, it can be controlled by changing the distance between the lens 92 and the alignment film 13 or the like. Note that the refractive power of the lens 92 is the F number of the lens 92 .
Also, by adjusting the refractive power of the lens 92, the length of one cycle in which the optical axis 22 rotates 180° can be changed in one direction in which the optical axis 22 rotates continuously. Specifically, it is possible to change the length of one cycle in which the optical axis 22 rotates by 180° depending on the degree of convergence of the light transmitted through the lens 92 that interferes with the parallel light. More specifically, when the refractive power of the lens 92 is weakened, the light becomes closer to parallel light. growing. Conversely, when the refractive power of the lens 92 is strengthened, the length of one cycle in which the optical axis 22 rotates by 180° becomes suddenly shorter from the inside to the outside, and the F-number becomes smaller.

In this way, in one direction in which the optical axis 22 rotates continuously, one period Λ in which the optical axis 22 rotates by 180° is changed. A continuously rotating variable configuration is also available.
For example, by gradually shortening one cycle in which the optical axis 22 rotates 180° in the direction of the arrow x, an optical element that transmits light so as to converge can be obtained. Further, by reversing the direction in which the optical axis 22 is rotated by 180° in the liquid crystal orientation pattern, an optical element that transmits light so as to diffuse only in the arrow x direction can be obtained. By reversing the rotating direction of the incident circularly polarized light, it is possible to obtain an optical element that transmits light so that the light is diffused only in the x direction indicated by the arrow.
Furthermore, depending on the application of the optical element, for example, when it is desired to provide a light amount distribution in the transmitted light, instead of gradually changing one period in which the optical axis 22 rotates 180° in the direction of the arrow x, , it is also possible to use a configuration in which the optical axis 22 is partially rotated by 180° and has regions with different one periods. For example, as a method of partially changing one cycle in which the optical axis 22 rotates 180°, a method of patterning the photo-alignment film by scanning exposure while arbitrarily changing the polarization direction of the focused laser beam is used. be able to.

In addition, in the first liquid crystal diffraction element 106 and the second liquid crystal diffraction element 110, the alignment film 13 is provided as a preferred embodiment, and is not an essential component.
For example, by forming an alignment pattern on the support 12 by a method of rubbing the support 12, a method of processing the support 12 with a laser beam, or the like, the cholesteric liquid crystal layer 14a and the optically anisotropic layer 14b are A configuration having a liquid crystal orientation pattern in which the orientation of the optical axis 22 derived from the liquid crystal compound 20 changes while continuously rotating along at least one in-plane direction is also possible.
Further, the first liquid crystal diffraction element 106 and the second liquid crystal diffraction element 110 may be composed of an alignment film and an optically anisotropic layer from which the support 12 is peeled off. Alternatively, the optically anisotropic layer from which the support 12 and the alignment film 13 are peeled off may be adhered to another support.
That is, the first liquid crystal diffraction element 106 and the second liquid crystal diffraction element 110 that constitute the vehicle-mounted lighting device of the present invention may have various layer structures as long as they include an optically anisotropic layer (cholesteric liquid crystal layer). It is possible.

<Cholesteric liquid crystal layer>
As described above, in the first liquid crystal diffraction element 106, the surface of the alignment film 13 is provided with the cholesteric liquid crystal layer 14a as an optically anisotropic layer.
The cholesteric liquid crystal layer 14a is a layer having a fixed cholesteric liquid crystal phase. In other words, the cholesteric liquid crystal layer is a layer in which liquid crystal compounds are fixed in a cholesteric alignment state.
In the in-vehicle lighting device of the present invention, the cholesteric liquid crystal layer that constitutes the first liquid crystal diffraction element 106 has an optical axis 22 derived from the liquid crystal compound 20 that continuously rotates along at least one in-plane direction. A cholesteric liquid crystal layer with varying liquid crystal alignment patterns. In FIG. 4A, since the liquid crystal compound 20 is a rod-like liquid crystal compound, the optical axis 22 coincides with the longitudinal direction of the liquid crystal compound 20 as described above.

As conceptually shown in FIG. 4A, the cholesteric liquid crystal layer 14a is a helical liquid crystal layer in which liquid crystal compounds 20 are helically rotated and stacked in the same manner as a cholesteric liquid crystal layer in which a normal cholesteric liquid crystal phase is fixed. A structure in which the liquid crystal compound 20 is stacked with one spiral rotation (360° rotation) is defined as one spiral pitch, and the spirally rotating liquid crystal compound 20 has a structure in which multiple pitches are stacked. .

As is well known, a cholesteric liquid crystal layer in which a cholesteric liquid crystal phase is fixed has wavelength-selective reflectivity. As will be described in detail later, the selective reflection wavelength range of the cholesteric liquid crystal layer depends on the length in the thickness direction of the helical 1-pitch described above. The length of one spiral pitch in the thickness direction is the pitch P shown in FIG. 4(A).
In addition, the cholesteric liquid crystal layer selectively reflects right-handed circularly polarized light or left-handed circularly polarized light according to the spiral turning direction of the liquid crystal compound 20 .
The cholesteric liquid crystal layer transmits light other than the circularly polarized light in the selective reflection wavelength range, which is selectively reflected in the rotating direction.

Therefore, when the cholesteric liquid crystal layer 14a is made to have wavelength selectivity and is configured to diffract only light of a predetermined wavelength, the helical pitch P of the cholesteric liquid crystal layer is adjusted to selectively reflect the cholesteric liquid crystal layer. The wavelength range may be appropriately set.
Here, as described above, the first liquid crystal diffraction element 106 reflects the white light converted by the wavelength conversion member 105 . Therefore, the first liquid crystal diffraction element 106 has three layers: a cholesteric liquid crystal layer that selectively reflects red light, a cholesteric liquid crystal layer that selectively reflects green light, and a cholesteric liquid crystal layer that selectively reflects blue light. It is preferred to have a layer of cholesteric liquid crystal layers.
Additionally, as described above, the cholesteric liquid crystal layer selectively reflects either right-handed circularly polarized light or left-handed circularly polarized light. Correspondingly, the first liquid crystal diffraction element 106 may have a cholesteric liquid crystal layer that selectively reflects right-handed circularly polarized light and a cholesteric liquid crystal layer that selectively reflects left-handed circularly polarized light for each color. good.

<<Cholesteric liquid crystal phase>>
Cholesteric liquid crystal phases are known to exhibit selective reflectivity at specific wavelengths.
In a general cholesteric liquid crystal phase, the selective reflection central wavelength λ (selective reflection central wavelength λ) depends on the helical pitch P in the cholesteric liquid crystal phase, and the average refractive index n of the cholesteric liquid crystal phase and λ = n × P Follow relationship. Therefore, by adjusting this helical pitch, the selective reflection central wavelength can be adjusted.
The central wavelength of selective reflection of the cholesteric liquid crystal phase becomes longer as the pitch P becomes longer.
As described above, the pitch P of the spiral is one pitch of the spiral structure of the cholesteric liquid crystal phase (the period of the spiral). The pitch P of the helix is, in other words, the number of turns of the helix, that is, the length in the direction of the helix axis at which the director of the liquid crystal compound constituting the cholesteric liquid crystal phase rotates 360°. The director of the liquid crystal compound is, for example, the long axis direction in the case of a rod-like liquid crystal compound.

The helical pitch of the cholesteric liquid crystal phase depends on the type of chiral agent used together with the liquid crystal compound and the addition concentration of the chiral agent when forming the cholesteric liquid crystal layer. Therefore, a desired helical pitch can be obtained by adjusting these.
As for the adjustment of the pitch, refer to Fuji Film Research Report No. 50 (2005) p. 60-63 for a detailed description. As for the method for measuring the sense and pitch of the helix, the method described in "Introduction to Liquid Crystal Chemistry Experiments" edited by the Japan Liquid Crystal Society, published by Sigma Publishing, 2007, page 46, and "Liquid Crystal Handbook" Liquid Crystal Handbook Editing Committee, Maruzen, page 196 is used. be able to.

A cholesteric liquid crystal phase exhibits selective reflectivity for either left or right circularly polarized light at a specific wavelength. Whether the reflected light is right-handed circularly polarized light or left-handed circularly polarized light depends on the twist direction (sense) of the cholesteric liquid crystal phase. The selective reflection of circularly polarized light by the cholesteric liquid crystal phase reflects right-handed circularly polarized light when the helical twist direction of the cholesteric liquid crystal layer is rightward, and reflects left-handed circularly polarized light when the helical twist direction is leftward.
The direction of rotation of the cholesteric liquid crystal phase can be adjusted by the type of liquid crystal compound forming the cholesteric liquid crystal layer and/or the type of chiral agent added.

Further, the half width Δλ (nm) of the selective reflection wavelength region (circularly polarized light reflection wavelength region) indicating selective reflection depends on Δn of the cholesteric liquid crystal phase and the spiral pitch P, and follows the relationship Δλ=Δn×P. Therefore, the width of the selective reflection wavelength band (selective reflection wavelength band) can be controlled by adjusting Δn. Δn can be adjusted by the type and mixing ratio of the liquid crystal compounds forming the cholesteric liquid crystal layer, and the temperature during orientation fixation.
The half width of the reflected wavelength range is adjusted, for example, according to the spectral distribution of the white light emitted by the wavelength conversion member 105, and may be, for example, 10 to 500 nm, preferably 20 to 300 nm, more preferably 30 to 150 nm. be.

<<Method for Forming Cholesteric Liquid Crystal Layer>>
The cholesteric liquid crystal layer can be formed by fixing a cholesteric liquid crystal phase in layers.
The structure in which the cholesteric liquid crystal phase is fixed may be any structure as long as the alignment of the liquid crystal compound in the cholesteric liquid crystal phase is maintained. Preferably, the structure is polymerized and cured by UV irradiation, heating, or the like to form a layer having no fluidity, and at the same time, the structure is changed to a state in which the orientation is not changed by an external field or external force.
In the structure in which the cholesteric liquid crystal phase is fixed, it is sufficient if the optical properties of the cholesteric liquid crystal phase are maintained, and the liquid crystal compound 20 does not have to exhibit liquid crystallinity in the cholesteric liquid crystal layer. For example, the polymerizable liquid crystal compound may be polymerized by a curing reaction and lose liquid crystallinity.

Materials used for forming a cholesteric liquid crystal layer in which a cholesteric liquid crystal phase is fixed include a liquid crystal composition containing a rod-like or disk-like liquid crystal compound. The liquid crystal compound is preferably a polymerizable liquid crystal compound.
As the liquid crystal compound, various rod-like liquid crystal compounds and discotic liquid crystal compounds exemplified in the later-described optically anisotropic layer 14b can be used.
Moreover, the liquid crystal composition used for forming the cholesteric liquid crystal layer may further contain a surfactant and a chiral agent.

--Surfactant--
The liquid crystal composition used for forming the cholesteric liquid crystal layer may contain a surfactant. The surfactant is preferably a compound that can stably or quickly function as an alignment control agent that contributes to the alignment of the cholesteric liquid crystal phase. Examples of surfactants include silicone-based surfactants and fluorine-based surfactants, with fluorine-based surfactants being preferred examples.

Specific examples of the surfactant include compounds described in paragraphs [0082] to [0090] of JP-A-2014-119605, and compounds described in paragraphs [0031] to [0034] of JP-A-2012-203237. , compounds exemplified in paragraphs [0092] and [0093] of JP-A-2005-99248, paragraphs [0076] to [0078] and paragraphs [0082] to [0085] of JP-A-2002-129162 compounds exemplified therein, and fluorine (meth)acrylate polymers described in paragraphs [0018] to [0043] of JP-A-2007-272185.
In addition, surfactant may be used individually by 1 type, and may use 2 or more types together.
As the fluorosurfactant, compounds described in paragraphs [0082] to [0090] of JP-A-2014-119605 are preferable.

The amount of the surfactant added in the liquid crystal 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 preferred.

--Chiral agent (optically active compound)--
A chiral agent (chiral agent) has a function of inducing a helical structure of a cholesteric liquid crystal phase. The chiral agent may be selected depending on the purpose, since the helical twist direction or helical pitch induced by the compound differs.
The chiral agent is not particularly limited, and known compounds (for example, liquid crystal device handbook, Chapter 3, Section 4-3, chiral agent for TN (twisted nematic), STN (Super Twisted Nematic), page 199, Japan Society for the Promotion of Science 142nd Committee, 1989), isosorbide, isomannide derivatives and the like can be used.
Chiral agents generally contain an asymmetric carbon atom, but axially chiral compounds or planar chiral compounds that do not contain an asymmetric carbon atom can also be used as chiral agents. Examples of axially or planarly chiral 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, a repeating unit derived from the polymerizable liquid crystal compound and a repeating unit derived from the chiral agent are formed by the polymerization reaction of the polymerizable chiral agent and the polymerizable liquid crystal compound. A polymer having repeating units can be formed. In this aspect, the polymerizable group possessed by the polymerizable chiral agent is preferably the same type of group as the polymerizable group possessed by the polymerizable liquid crystal compound. Therefore, the polymerizable group of the chiral agent is also preferably an unsaturated polymerizable group, an epoxy group or an aziridinyl group, more preferably an unsaturated polymerizable group, and an ethylenically unsaturated polymerizable group. More preferred.
Also, the chiral agent may be a liquid crystal compound.

When the chiral agent has a photoisomerizable group, it is preferable because it is possible to form a desired reflection wavelength pattern corresponding to the emission wavelength by photomask irradiation with actinic rays or the like after coating and orientation. The photoisomerizable group is preferably an isomerization site of a compound exhibiting photochromic properties, an azo group, an azoxy group, or a cinnamoyl group. Specific compounds include JP-A-2002-080478, JP-A-2002-080851, JP-A-2002-179668, JP-A-2002-179669, JP-A-2002-179670, JP-A-2002- 179681, JP-A-2002-179682, JP-A-2002-338575, JP-A-2002-338668, JP-A-2003-313189, and compounds described in JP-A-2003-313292, etc. can be used.

The content of the chiral agent in the liquid crystal composition is preferably 0.01 to 200 mol%, more preferably 1 to 30 mol%, relative to the content molar amount of the liquid crystal compound.

--Polymerization initiator--
When the liquid crystal composition contains a polymerizable compound, it preferably contains a polymerization initiator. In the embodiment in which the polymerization reaction is advanced by ultraviolet irradiation, the polymerization initiator used is preferably a photopolymerization initiator capable of initiating the polymerization reaction by ultraviolet irradiation.
Examples of photoinitiators include α-carbonyl compounds (described in US Pat. Nos. 2,367,661 and 2,367,670), acyloin ethers (described in US Pat. No. 2,448,828), α-hydrocarbons substituted aromatic acyloin compounds (described in US Pat. No. 2,722,512), polynuclear quinone compounds (described in US Pat. Nos. 3,046,127 and 2,951,758), triarylimidazole dimers and p-aminophenyl ketone Combinations (described in US Pat. No. 3,549,367), acridine and phenazine compounds (described in JP-A-60-105667, US Pat. No. 4,239,850), and oxadiazole compounds (described in US Pat. No. 4,212,970) described) and the like.
The content of the photopolymerization initiator in the liquid crystal 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 liquid crystal composition may optionally contain a cross-linking agent in order to improve film strength and durability after curing. As the cross-linking agent, one that is cured by ultraviolet rays, heat, humidity, and the like can be preferably used.
The cross-linking agent is not particularly limited and can be appropriately selected depending on the intended purpose. For example, polyfunctional acrylate compounds such as trimethylolpropane tri(meth)acrylate and pentaerythritol tri(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 methylene diisocyanate and biuret-type isocyanate; polyoxazoline compounds having oxazoline groups in side chains; and alkoxysilane compounds such as vinyltrimethoxysilane and N-(2-aminoethyl)3-aminopropyltrimethoxysilane. is mentioned. In addition, a known catalyst can be used depending on the reactivity of the cross-linking agent, and productivity can be improved in addition to improving film strength and durability. These may be used individually by 1 type, and may use 2 or more types together.
The content of the cross-linking agent is preferably 3 to 20% by mass, more preferably 5 to 15% by mass, based on the solid mass of the liquid crystal composition. When the content of the cross-linking agent is within the above range, the effect of improving the cross-linking density is likely to be obtained, and the stability of the cholesteric liquid crystal phase is further improved.

--Other Additives--
If necessary, the liquid crystal composition may further contain polymerization inhibitors, antioxidants, ultraviolet absorbers, light stabilizers, colorants, metal oxide fine particles, etc., within a range that does not reduce the optical performance. can be added at

The liquid crystal composition is preferably used as a liquid when forming the cholesteric liquid crystal layer.
The liquid crystal composition may contain a solvent. The solvent is not limited and can be appropriately selected depending on the purpose, but organic solvents are preferred.
The organic solvent is not limited and can be appropriately selected depending on the purpose. Examples include ketones, alkyl halides, amides, sulfoxides, heterocyclic compounds, hydrocarbons, esters and ethers. etc. These may be used individually by 1 type, and may use 2 or more types together. Among these, ketones are preferable in consideration of the load on the environment.

When forming the cholesteric liquid crystal layer, a liquid crystal composition is applied to the surface on which the cholesteric liquid crystal layer is to be formed, the liquid crystal compound is aligned in a cholesteric liquid crystal phase state, and then the liquid crystal compound is cured to form a cholesteric liquid crystal layer. is preferred.
That is, when a cholesteric liquid crystal layer is formed on the alignment film 13, a liquid crystal composition is applied to the alignment film 13 to align the liquid crystal compound in a cholesteric liquid crystal phase, and then the liquid crystal compound is cured to form a cholesteric liquid crystal phase. It is preferable to form a cholesteric liquid crystal layer in which the liquid crystal phase is fixed.
The liquid crystal composition can be applied by printing methods such as inkjet and scroll printing, and known methods such as spin coating, bar coating and spray coating, which can uniformly apply the liquid to the sheet.

The applied liquid crystal composition is dried and/or heated as necessary, and then cured to form a cholesteric liquid crystal layer. In this drying and/or heating step, the liquid crystal compound in the liquid crystal composition may be oriented in the cholesteric liquid crystal phase. When heating is performed, the heating temperature is preferably 200° C. or lower, more preferably 130° C. or lower.

The aligned liquid crystal compound is further polymerized as necessary. Polymerization may be either thermal polymerization or photopolymerization by light irradiation, but photopolymerization is preferred. It is preferable to use ultraviolet rays for light irradiation. The irradiation energy is preferably 20 mJ/cm ² to 50 J/cm ² , more preferably 50 to 1500 mJ/cm ² . In order to accelerate the photopolymerization reaction, light irradiation may be performed under heating conditions or under a nitrogen atmosphere. The wavelength of the ultraviolet rays to be irradiated is preferably 250 to 430 nm.
The thickness of the cholesteric liquid crystal layer is not limited, and the required light reflectance is determined according to the application of the cholesteric liquid crystal layer, the light reflectance required for the cholesteric liquid crystal layer, and the material used to form the cholesteric liquid crystal layer. The thickness at which is obtained can be set as appropriate.

<<Liquid crystal alignment pattern of cholesteric liquid crystal layer>>
As described above, the cholesteric liquid crystal layer has a liquid crystal orientation in which the direction of the optical axis 22 derived from the liquid crystal compound 20 forming the cholesteric liquid crystal phase changes while continuously rotating in one direction within the plane of the cholesteric liquid crystal layer. have a pattern.
The optical axis 22 derived from the liquid crystal compound 20 is an axis with the highest refractive index in the liquid crystal compound 20, a so-called slow axis. As described above, when the liquid crystal compound 20 is a rod-like liquid crystal compound, the optical axis 22 extends along the longitudinal direction (major axis direction) of the rod shape. In the following description, the optic axis 22 derived from the liquid crystal compound 20 is also referred to as "the optic axis 22 of the liquid crystal compound 20" or "the optic axis 22".

FIG. 5 conceptually shows an example of the liquid crystal alignment pattern of the cholesteric liquid crystal layer 14a. This figure is a plan view of the cholesteric liquid crystal layer 14a.
The plan view is a view of the cholesteric liquid crystal layer (optically anisotropic layer) in FIG. 4(A) viewed from above, that is, a view of the cholesteric liquid crystal layer 14a viewed from the thickness direction. The thickness direction of the cholesteric liquid crystal layer 14a coincides with the stacking direction of each layer (film).
5 shows only the liquid crystal compound 20 on the surface of the alignment film 13 in order to clearly show the structure of the cholesteric liquid crystal layer 14a. However, in reality, as shown in FIG. 4A, the liquid crystal compound 20 is spirally oriented and laminated with several pitches.
As will be described later, this liquid crystal alignment pattern can also be suitably used in the optically anisotropic layer 14b of the second liquid crystal diffraction element 110. FIG.

As shown in FIG. 5, on the surface of the alignment film 13, the liquid crystal compounds 20 forming the cholesteric liquid crystal layer 14a are aligned in the plane of the cholesteric liquid crystal layer according to the alignment pattern formed on the alignment film 13 below. It has a liquid crystal alignment pattern in which the direction of the optical axis 22 changes while rotating continuously along a predetermined direction indicated by A.
The liquid crystal compound 20 constituting the cholesteric liquid crystal layer 14a of the illustrated example is arranged two-dimensionally in one direction (axis A direction) in which the direction of the optical axis 22 rotates continuously and in a direction orthogonal to this one direction. is in a state of
In the following description, the y direction is the direction orthogonal to one direction in which the orientation of the optic axis 22 of the liquid crystal compound 20 changes while continuously rotating in the plane of the cholesteric liquid crystal layer. Therefore, in FIG. 4(A) and FIG. 4(B) described later, the y direction is a direction perpendicular to the plane of the paper.

Further, the rotation direction of the optical axis of the liquid crystal compound 20 is reversed at the center of the cholesteric liquid crystal layer 14a (first liquid crystal diffraction element) in the direction of the axis A.
For example, the optic axis 22 of the liquid crystal compound 20 rotates clockwise from the left end of the drawing toward the right side of the drawing, that is, toward the axis A, reverses the rotation direction at the center of the axis A direction, and rotates in the direction of the axis A. It rotates counterclockwise from the center toward the right in the figure. That is, in this example, the optic axis 22 of the liquid crystal compound 20 rotates counterclockwise from the center of the axis A direction to the left in the figure and from the center of the axis A direction to the right in the figure.

That the direction of the optic axis 22 of the liquid crystal compound 20 changes while continuously rotating in the direction of the axis A (the direction of the arrow x, a predetermined direction) specifically means that the liquid crystal compound 20 is arranged along the direction of the axis A. The angle formed between the optical axis 22 of the liquid crystal compound 20 and the axis A differs depending on the position along the axis A direction. °, or up to θ-180°.
The angle difference between the optical axes 22 of the liquid crystal compounds 20 adjacent to each other in the direction of the axis A is preferably 45° or less, more preferably 15° or less, and even more preferably a smaller angle. .

On the other hand, the liquid crystal compound 20 forming the cholesteric liquid crystal layer 14a has an optical axis 22 directions are equal.
In other words, the liquid crystal compound 20 forming the cholesteric liquid crystal layer 14a has an equal angle between the optic axis 22 of the liquid crystal compound 20 and the axis A direction in the y direction.

As described above, in the cholesteric liquid crystal layer 14a, in the liquid crystal alignment pattern of the liquid crystal compound 20, the optical axis of the liquid crystal compound 20 is aligned in the direction of the axis A along which the optical axis 22 continuously rotates and changes in the plane. The length (distance) by which 22 is rotated by 180° is defined as one period Λ (length of one period Λ) in the liquid crystal alignment pattern.
That is, the distance between the centers in the direction of the axis A of two liquid crystal compounds 20 having the same angle with respect to the direction of the axis A is defined as one period Λ. Specifically, as shown in FIGS. 4A and 5, the distance between the centers of the two liquid crystal compounds 20 in the direction of the axis A and the direction of the optical axis 22 is equal to one cycle. Let Λ In the first liquid crystal diffraction element 106, this one period Λ is the pitch of the periodic structure in the diffraction element.
The liquid crystal orientation pattern of the cholesteric liquid crystal layer 14a repeats this one period Λ in the direction of the axis A (and the direction opposite to the direction of the axis A), that is, in one direction in which the direction of the optical axis 22 rotates continuously and changes.

In addition, in the cholesteric liquid crystal layer 14a, one period Λ of the cholesteric liquid crystal layer 14a in one direction of rotation of the optical axis 22 is gradually shortened from the center of the axis A direction toward both outer directions of the axis A direction.
That is, one period Λ of the cholesteric liquid crystal layer 14a gradually shortens from the center in the direction of the axis A toward the left and right in the drawing.
note that. One period Λ may be shortened continuously or stepwise from the center toward the outside. Furthermore, the change (decrease) of one period Λ may be linear, non-linear, or have linear and non-linear regions.

A cholesteric liquid crystal layer in which a cholesteric liquid crystal phase is fixed normally mirror-reflects incident light (circularly polarized light).
On the other hand, the cholesteric liquid crystal layer 14a reflects the incident light by tilting it in the direction opposite to the direction of the axis A with respect to the specular reflection. The cholesteric liquid crystal layer 14a has a liquid crystal alignment pattern that changes while the optic axis 22 continuously rotates counterclockwise along the direction of the axis A (predetermined one direction) in the plane.
Description will be made below with reference to FIG.

As an example, assume that the cholesteric liquid crystal layer 14a is a cholesteric liquid crystal layer that selectively reflects right-handed circularly polarized red light R _R . Therefore, when light is incident on the cholesteric liquid crystal layer 14a, the cholesteric liquid crystal layer 14a reflects only the right circularly polarized red light _RR and transmits the other light.

The right circularly polarized red light R _R incident on the cholesteric liquid crystal layer 14 a changes its absolute phase according to the orientation of the optical axis 22 of each liquid crystal compound 20 when reflected by the cholesteric liquid crystal layer.
Here, in the cholesteric liquid crystal layer 14a, the optical axis 22 of the liquid crystal compound 20 changes while rotating along the axis A direction (one direction). Therefore, the amount of change in the absolute phase of the right circularly polarized light _RR of the incident red light differs depending on the direction of the optical axis 22 .
Furthermore, the liquid crystal alignment pattern formed in the cholesteric liquid crystal layer 14a is a periodic pattern in the axis A direction. Therefore, as conceptually shown in FIG. 14, the right-handed circularly polarized red light R _R incident on the cholesteric liquid crystal layer 14 a has a periodic absolute phase Q in the direction of the axis A corresponding to the direction of each optical axis 22 . is given.
The orientation of the optical axis 22 of the liquid crystal compound 20 with respect to the direction of the axis A (the direction of the arrow x) is uniform in the alignment of the liquid crystal compound 20 in the y direction orthogonal to the direction of the axis A.
As a result, in the cholesteric liquid crystal layer 14a, an equiphase plane E inclined in the direction of the axis A with respect to the XY plane is formed with respect to the right-handed circularly polarized red light R _R .
Therefore, the right-handed circularly polarized red light R _R is reflected in the normal direction of the equiphase plane E, and the reflected right-handed circularly polarized light R _R is directed to the XY plane (principal plane of the cholesteric liquid crystal layer). The light is reflected in a direction inclined opposite to the direction of the axis A.

Therefore, by appropriately setting the direction of the axis A, which is one direction in which the optical axis 22 rotates counterclockwise, the reflection direction of the right-handed circularly polarized light _RR of red light can be adjusted.
That is, if the direction of the axis A is reversed, the direction of reflection of the right-handed circularly polarized light R _R of red light is also reversed from that in FIG.

In addition, by reversing the rotation direction of the optical axis 22 of the liquid crystal compound 20 toward the direction of the axis A (the direction of the arrow x), the reflection direction of the right-handed circularly polarized light R _R of red light can be reversed.
That is, in FIGS. 4A and 14, the rotation direction of the optical axis 22 in the direction of the axis A is clockwise, and the right circularly polarized light _RR of the red light is tilted in the direction of the axis A and reflected. Here, by setting the rotation direction of the optical axis 22 in the direction of the axis A to be counterclockwise, the right-handed circularly polarized light _RR of the red light is tilted in the opposite direction to the direction of the axis A and reflected.
As described above, the optical axis 22 of the cholesteric liquid crystal layer 14a rotates counterclockwise from the center of the axis A toward the left side in the drawing and the right side in the drawing. In other words, over the entire area along the axis A, the optical axis 22 rotates clockwise from the right end of the drawing toward the center, the direction of rotation is reversed at the center, and the direction of rotation is reversed from the center toward the left end of the drawing. , the optical axis 22 rotates counterclockwise.
Therefore, the right-handed circularly polarized light incident on the cholesteric liquid crystal layer 14a is diffracted and reflected rightward on the left side of the drawing in the direction of the axis A, and is diffracted and reflected leftward on the right side of the drawing.

Furthermore, in the cholesteric liquid crystal layer having the same liquid crystal alignment pattern, the reflection direction is reversed depending on the spiraling direction of the liquid crystal compound 20, that is, the rotating direction of the reflected circularly polarized light.
The cholesteric liquid crystal layer 14a shown in FIG. 14 is a liquid crystal orientation pattern in which the helical turning direction is right-handed and selectively reflects right-handed circularly polarized light, and the optical axis 22 rotates clockwise along the arrow x direction. , the right-handed circularly polarized light is tilted in the direction of the axis A and reflected.
Therefore, a cholesteric liquid crystal layer having a liquid crystal orientation pattern in which the direction of spiral rotation is left-handed, selectively reflects left-handed circularly polarized light, and the optical axis 22 rotates counterclockwise along the direction of the axis A, The left circularly polarized light is tilted in the direction of the axis A and reflected.

In the cholesteric liquid crystal layer having the liquid crystal alignment pattern, the shorter the period Λ, the larger the diffraction angle of the reflected light with respect to the specular reflection of the incident light. That is, the shorter the period Λ, the more the reflected light can be reflected with a greater inclination with respect to the specular reflection of the incident light.
For example, when light is incident from the normal direction of the cholesteric liquid crystal layer, the shorter the period Λ, the larger the angle formed by the reflected light with respect to the normal direction.
As described above, in the cholesteric liquid crystal layer 14a, one period .LAMBDA. Therefore, in the cholesteric liquid crystal layer 14a, the diffraction angle of light due to reflection increases in the direction of the axis A and in the opposite direction.

In addition, as described above, in the cholesteric liquid crystal layer having the liquid crystal alignment pattern, the longer the wavelength of the reflected light, the more the reflected light is reflected with a greater inclination with respect to the specular reflection of the incident light. For example, when light is incident from the normal direction of the cholesteric liquid crystal layer, the longer the wavelength of the light, the larger the angle formed by the reflected light with respect to the normal direction.
Considering the above points, as described above, when the first liquid crystal diffraction element 106 has a plurality of cholesteric liquid crystal layers with different selective reflection center wavelengths, each cholesteric liquid crystal layer has a wavelength of light to be selectively reflected. It is preferable that the permutation of wavelengths and the permutation of one period Λ match.
For example, as described above, the first liquid crystal diffraction element 106 has a cholesteric liquid crystal layer that selectively reflects red light, a cholesteric liquid crystal layer that selectively reflects green light, and a cholesteric liquid crystal layer that selectively reflects blue light. In the case of having three layers of cholesteric liquid crystal layers, one period Λ of the cholesteric liquid crystal layer selectively reflecting red light is made the longest, and one period Λ of the cholesteric liquid crystal layer selectively reflecting blue light is set to the longest. is the shortest.

As described above, a cholesteric liquid crystal layer having a liquid crystal alignment pattern has wavelength-selective reflectivity and reflects light of a selected wavelength while diffracting it.
Here, the optical axis 22 of the cholesteric liquid crystal layer 14a rotates counterclockwise from the center of the axis A direction toward the right side in the drawing and toward the left side in the drawing. As a result, the right-handed circularly polarized light incident on the cholesteric liquid crystal layer 14a is diffracted and reflected rightward on the left side of the drawing in the direction of the axis A, and diffracted and reflected leftward on the right side of the drawing.
In addition, one period Λ of the cholesteric liquid crystal layer 14a is gradually shortened in the direction of the axis A and in the opposite direction. Therefore, in the cholesteric liquid crystal layer 14a, the diffraction angle of light due to reflection gradually increases from the center in the direction of the axis A toward the outside.
Therefore, the right-handed circularly polarized light of the red light incident on the cholesteric liquid crystal layer 14a (liquid crystal diffraction element) is reflected so as to be condensed toward the direction of the arrow x, that is, the center of one direction in which the optical axis 22 rotates.

Therefore, by using the reflective liquid crystal diffraction element having the cholesteric liquid crystal layer 14a as the reflector of the light deflection element, the incident light (light beam) is deflected and condensed toward the center in the direction of the arrow x. It can be reflected and emitted.

The optic axis 22 of the liquid crystal compound 20 in the liquid crystal alignment pattern of the cholesteric liquid crystal layer shown in FIG. 5 rotates continuously only along the axis A direction.
However, the present invention is not limited to this, and various configurations are available as long as the optic axis 22 of the liquid crystal compound 20 rotates continuously along at least one direction in the cholesteric liquid crystal layer. .

A preferred example is a liquid crystal orientation pattern in which the direction of the optical axis 22 derived from the liquid crystal compound 20 changes while continuously rotating in one direction, as conceptually shown in the plan view of FIG. 9 described above. , radially from the inside (center) to the outside.
That is, the liquid crystal alignment pattern of the cholesteric liquid crystal layer 14a shown in FIG. pattern.
As will be described later, as in FIG. 5, the optically anisotropic layer 14b of the second liquid crystal diffraction element 110 can also be used for the liquid crystal alignment pattern shown in FIG.

9 also shows only the liquid crystal compound 20 on the surface of the alignment film, as in FIG. 5. However, as in the example shown in FIG. As described above, 20 has a helical structure in which it is spirally turned and stacked.

In the cholesteric liquid crystal layer 14a shown in FIG. 9, the orientation of the optic axis of the liquid crystal compound 20 is oriented in a number of directions outward from the center of the cholesteric liquid crystal layer 14a, for example, the direction indicated by the above-described axis _A1 and the axis _A2 . The direction, the direction indicated by the axis _A3 , the direction indicated by the axis _A4 .
Therefore, in the cholesteric liquid crystal layer 14a, the rotation direction of the optical axis of the liquid crystal compound 20 is the same in all directions (one direction). In the illustrated example, the directions of rotation of the optic axis of the liquid crystal compound 20 in all the directions indicated by the axis _A1 , the direction indicated by the axis _A2 , the direction indicated by the axis _A3 , and the direction indicated by the axis _A4 are: counterclockwise.
That is, when the axis A ₁ and the axis A ₄ are regarded as one straight line, the rotation direction of the optical axis 22 of the liquid crystal compound 20 is reversed at the center of the cholesteric liquid crystal layer 14a on this straight line. As an example, it is assumed that the straight line formed by the axes _A1 and _A4 is directed to the right in the drawing (direction of the axis _A1 ). In this case, the optic axis of the liquid crystal compound 20 first rotates clockwise from the outer direction of the cholesteric liquid crystal layer 14a toward the center, reverses the direction of rotation at the center of the cholesteric liquid crystal layer 14a, and then rotates clockwise. It rotates counterclockwise outward from the center of the cholesteric liquid crystal layer 14a.
In the direction of each arrow, one period Λ of the liquid crystal alignment pattern gradually becomes shorter from the inside (center) toward the outside. That is, one period Λ of the liquid crystal alignment pattern gradually becomes shorter in the direction of the arrow.

In the illustrated cholesteric liquid crystal layer 14a, the optic axis 22 of the liquid crystal compound 20 rotates counterclockwise in the direction of each arrow. Tilt in the opposite direction and reflect.
The direction of reflection of circularly polarized light is reversed by reversing the direction of rotation of the optical axis 22 in the direction of the arrow. For example, in the illustrated example, by rotating the optical axis 22 of the liquid crystal compound 20 in the direction of each arrow clockwise, right-handed circularly polarized light is tilted in the direction of the arrow and reflected.
Furthermore, the direction of reflection of circularly polarized light is reversed by reversing the direction of rotation of the circularly polarized light. For example, in the illustrated example, if the helical rotation direction of the cholesterically aligned liquid crystal compound is reversed to form a cholesteric liquid crystal layer that selectively reflects left-handed circularly polarized light, the cholesteric liquid crystal layer reflects left-handed circularly polarized light as follows: Tilt in the direction of the arrow to reflect.

Therefore, the cholesteric liquid crystal layer 14a having a concentric liquid crystal alignment pattern as shown in FIG. And depending on the direction of the reflected circularly polarized light, the incident light can be reflected as divergent or convergent light.
That is, by making the liquid crystal alignment pattern of the cholesteric liquid crystal layer concentric, the reflective liquid crystal diffraction element selectively reflects circularly polarized light and rotates the optical axis 22 of the liquid crystal compound 20 in one direction. Accordingly, it functions as a concave mirror or a convex mirror.

Furthermore, in the illustrated example, as a preferred embodiment, one cycle Λ in which the optic axis rotates 180° in the liquid crystal alignment pattern is set in the direction of each arrow, that is, one direction in which the optic axis rotates continuously from the center of the cholesteric liquid crystal layer. progressively shorten in the outward direction of the
As described above, in a cholesteric liquid crystal layer having a liquid crystal orientation pattern in which the optic axis rotates in one direction, the diffraction angle of reflected light, that is, the reflection angle of reflected light with respect to specular reflection, is one period Λ in the liquid crystal orientation pattern. The shorter the , the larger. Therefore, by gradually shortening one period Λ in the liquid crystal alignment pattern from the center of the cholesteric liquid crystal layer toward the outer direction in which the optical axis rotates continuously, the light can be more focused and the concave mirror can improve performance as

That is, the cholesteric liquid crystal having a concentric liquid crystal orientation pattern in the first liquid crystal diffraction element 106 that reflects the white light converted and diffused by the wavelength conversion member 105 in a predetermined direction and condenses and collimates the light. By using the reflective liquid crystal diffraction element having the layer 14a, incident light (light beam) can be condensed in the entire circumferential direction, and the light can be reflected and emitted.
In addition, by appropriately setting the length of one cycle in one direction in which the optical axis 22 (liquid crystal compound 20) rotates outward from the center, the state of convergence and collimation of the projected light can be obtained as desired. state can be adjusted.
A reflective first liquid crystal diffraction element 106 having a cholesteric liquid crystal layer 14a having a concentric liquid crystal orientation pattern is used as the first diffraction element of the vehicle-mounted lighting device of the present invention to project desired projection light outside the vehicle. it becomes possible to

<Optically anisotropic layer>
As shown in FIG. 4B, in the second liquid crystal diffraction element 110, the alignment film 13 has an optically anisotropic layer 14b, which is a cured layer of a liquid crystal composition containing a liquid crystal compound 20, on the surface thereof.
In the optically anisotropic layer 14b, the optical axis 22 (slow axis) of the liquid crystal compound 20 is a liquid crystal pattern arranged along at least one direction in the plane of the optically anisotropic layer, and the liquid crystal compound 20 has a liquid crystal alignment pattern in which the orientation of the optic axis 22 of is changed in rotation in one direction.

The second liquid crystal diffraction element 110 has a retardation R (=Δn·d1) of 0.36λ to 0.64λ in the thickness direction (z direction in the drawing) of the optically anisotropic layer 14b with respect to light of wavelength λ. . The retardation R is preferably 0.4λ to 0.6λ, more preferably 0.45λ to 0.55λ, particularly preferably 0.5λ. Δn is the birefringence of the optically anisotropic layer 14b, and d1 is the thickness. For example, when light of 940 nm is assumed as incident light, the retardation R with respect to light of 940 nm may be in the range of 338 to 602 nm, preferably 470 nm.
Since the optically anisotropic layer 14b has such a retardation R, the optically anisotropic layer 14b functions as a general λ/2 plate, i.e., 180° (=π=λ/ 2) It expresses the function of giving a phase difference.

The second liquid crystal diffraction element 110 functions as a transmissive diffraction grating. The principle of functioning as a diffraction grating will be described with reference to FIGS. 5 and 6. FIG.
As described above, FIG. 5 is a schematic plan view showing the liquid crystal alignment pattern of the optically anisotropic layer 14b, that is, the view of FIG. 4 viewed from above.

As shown in FIGS. 4 and 5, in the optically anisotropic layer 14b, the liquid crystal compound 20 is fixed in a liquid crystal alignment pattern in which the optical axis 22 is continuously rotated in one direction. In the illustrated example, the optical axis 22 rotates continuously in the direction of the axis A (the direction along the axis A) in FIG. 5, which coincides with the direction of the arrow x. That is, the liquid crystal compound 20 is oriented such that the angle between the in-plane component of the long axis (axis of extraordinary light: director) of the liquid crystal compound 20 defined as the optical axis 22 and the axis A rotates. .
As shown in FIG. 5, in the optically anisotropic layer 14b, the directions of the optic axes 22 of the liquid crystal compounds 20 are aligned in the direction perpendicular to the direction of the axis A, that is, in the direction of the arrow y. ing. The optically anisotropic layer 14b functions as a general λ/2 plate as described above for each region where the y-direction optical axis 22 of the liquid crystal compound 20 is aligned.

In the liquid crystal alignment pattern in which the direction of the optical axis 22 is changed by rotation, the angle formed by the optical axis 22 of the liquid crystal compound 20 arranged along the axis A and the axis A varies depending on the position in the direction of the axis A. The pattern is oriented and fixed such that the angle between the optical axis 22 and the axis A along the axis A gradually changes from φ to φ+180° or φ−180°.
In the optically anisotropic layer 14b shown in FIG. 6 below, the optical axis 22 of the liquid crystal compound 20 is parallel to the surface of the optically anisotropic layer 14b, and the direction of the optical axis 22 is constant. Local regions (unit regions), that is, regions in which the liquid crystal compounds 20 are arranged in the direction of the arrow y are arranged in the direction x perpendicular to the direction of the arrow y, and between a plurality of local regions arranged in the direction of the arrow x , the orientation of the optical axis 22 is oriented such that it rotates continuously in one direction (the direction along the axis A) is referred to as a horizontal rotational orientation.

It should be noted that, as shown in FIGS. 5 and 6, the continuous change in rotation means that areas with a constant angle such as 30° increments rotate from 0° to 180° (=0°) adjacent to each other. good too. Alternatively, the angular change of the optical axis 22 toward the direction of the axis A may be a rotating object that rotates at non-uniform angular intervals instead of constant angular intervals. In the present invention, if the average value of the direction of the optical axis 22 of the unit area changes linearly at a constant rate, it means that the direction changes gradually. However, the change in the inclination of the optical axis between unit areas adjacent to each other in the direction of the axis A and having different inclinations of the optical axis 22 is preferably 45° or less. It is preferable that the change in inclination between adjacent unit areas is smaller.

As before, in the optically anisotropic layer 14b, the optic axis 22 (liquid crystal compound 20) rotates 180° in the direction of the axis A, that is, the optic axis 22 and the axis A A distance in which the formed angle changes from φ to φ+180° (returning to the original), that is, a period in which the optical axis 22 rotates by 180° is defined as one period Λ (rotational period Λ). This one period Λ is preferably 0.5 to 5 μm.
As described above, the shorter the period Λ and the longer the wavelength of the incident light, the larger the diffraction angle by the optically anisotropic layer 14b, that is, the second liquid crystal diffraction element 110. FIG. That is, when light is incident from the normal direction, the shorter the period Λ and the longer the wavelength of the incident light, the greater the angle of the transmitted light with respect to the normal direction.
Therefore, one period Λ may be determined according to the wavelength of light incident on the second liquid crystal diffraction element 110 and the desired output angle.

The second liquid crystal diffraction element 110 provides a phase difference of λ/2 with respect to incident light due to the configuration of the optically anisotropic layer 14b described above, and is incident at an incident angle of 0°, that is, normal incidence (normal direction ) is emitted at an exit angle θ ₂ .
That is, as shown in FIG. 6, when light L ₁ of right-handed circularly polarized light P _R is incident on the optically anisotropic layer 14b from the normal direction, left-handed circularly polarized light P _L is polarized in the direction forming an angle θ ₂ with the normal direction. of light L ₂ is emitted. In the following description, the right-handed circularly polarized light P _R light L ₁ incident on the optically anisotropic layer 14b is also referred to as "incident light L ₁ ". Furthermore, in the following description, the left-handed circularly polarized light P _L emitted from the optically anisotropic layer L ₂ is also referred to as “outgoing light L ₂ ”.
When light of a predetermined wavelength is incident on the second liquid crystal diffraction element 110, the smaller the one period Λ in the optically anisotropic layer 14b, the larger the diffraction angle, that is, the output angle of the output light _L2 . The output angle of the output light _L2 is the angle formed by the normal direction of the optically anisotropic layer 14b and the output light _L2 .

In addition, since the second liquid crystal diffraction element 110 diffracts right-handed circularly polarized light and left-handed circularly polarized light in different directions, the diffraction direction of the emitted light L ₂ from the second liquid crystal diffraction element 110 is different from that incident on the second liquid crystal diffraction element 110. The state of circularly polarized light is controlled and incident. That is, as shown in the figure, when the incident light is linearly polarized light, the λ/4 plate 109 is inserted to convert the light into either left or right circularly polarized light before the light is incident. It can only be

FIG. 6 is a diagram schematically showing the principle that the incident light L ₁ vertically incident on the optically anisotropic layer 14b is emitted at a predetermined emission angle θ ₂ . The action of the optically anisotropic layer 14b will be described below with reference to FIG.

First, the case of using right-handed circularly polarized light P _R of wavelength λ as the incident light L ₁ will be described.
The incident light L ₁ , which is right-handed circularly polarized light P _R , is given a phase difference of λ/2 by passing through the optically anisotropic layer 14 b and converted into left-handed circularly polarized light P _L .
In addition, in the optically anisotropic layer 14b, the absolute phase of the incident light L1 changes depending on the optic axis 22 of the liquid crystal compound 20 in each in-plane unit region (local region). Here, in the optically anisotropic layer 14b, the direction of the optic axis 22 of the liquid crystal compound 20 is changed by rotating toward the direction of the axis A (which coincides with the direction of the arrow x in this example). The amount of change in absolute phase varies depending on the direction of the optical axis 22 of the liquid crystal compound 20 on the x-coordinate (position in the x-direction) of the plane (xy plane) of the optically anisotropic layer 14b on which the light is incident. In the area indicated by the dashed line in FIG. 6, it is schematically shown how the amount of change in the absolute phase differs depending on the x-coordinate.
As shown in FIG. 6, due to the absolute phase shift when passing through the optically anisotropic layer 14b, an equiphase plane 24 of absolute phase having an angle with respect to the plane of the optically anisotropic layer is formed. As a result, the incident light _L1 incident from the normal direction is given a bending force in the direction perpendicular to the equiphase plane 24, and the traveling direction of the incident light _L1 is changed. That is, the incident light L ₁ which is right-handed circularly polarized light PR becomes left-handed circularly polarized light P _L after passing through the optically anisotropic layer 14b, and travels in a direction forming a predetermined angle θ ₂ with the normal direction. It is emitted from the optically anisotropic layer 14b as incident light _L2 .

As described above, in the second liquid crystal diffraction element 110, the incident light L ₁ incident along the normal direction perpendicular to the surface of the second liquid crystal diffraction element 110 is projected in a direction different from the normal direction. It is emitted as outgoing light _L2 .

By changing one period Λ of the direction of the optical axis in the liquid crystal alignment pattern in the optically anisotropic layer 14b, the inclination of the output angle can be changed. The smaller the period Λ, the greater the bending force that can be applied to the incident light, and the greater the inclination.

Thus, it is possible to change the wavefront of incident light by changing the amount of change in the absolute phase by the liquid crystal alignment pattern in the optically anisotropic layer 14b.

When the second liquid crystal diffraction element 110 has a uniform liquid crystal orientation pattern of one period Λ in only one direction, the conversion of the incident light L ₁ to the output light L ₂ based on the above principle is as follows. It can be explained as transmission diffraction.
The optically anisotropic layer 14b functions as _a transmission diffraction grating for the incident light _L1 _. Transmission diffracted as _L2 . In this case, the following formula (1), which is a general light diffraction formula, is satisfied.
n ₂ sin θ ₂ −n ₁ sin θ ₁ =mλ/p Equation (1)
where _n1 is the refractive index of medium 1 on the incident surface side of the diffraction grating, _θ1 is the incident angle, _n2 is the refractive index of medium 2 on the output surface side of the diffraction grating, and _θ2 is the diffraction angle (output angle). , λ is the wavelength, p is the rotation period, and m is the order of diffraction. In this example, the diffraction grating is the optically anisotropic layer 14b.
Here, m=1 is set so that the maximum diffraction efficiency is obtained. Also, here, since the incident angle θ ₁ =0°, equation (1) is
n ₂ sin θ ₂ =λ/p Formula (2)
becomes.

FIG. 7 is a diagram schematically showing the diffraction phenomenon represented by Equation (2).
An optically anisotropic layer 14b is arranged as a diffraction grating between the medium _n1 and the medium _n2 .
Light L ₁ incident on the optically anisotropic layer _14b in the normal direction from the side of the medium 1 having a refractive index n 1 is diffracted by the diffraction action of the optically anisotropic layer 14b to form a medium ₂ having a refractive index n 2 . emitted to the side. At this time, the output light _L2 emitted at the output angle _θ2 can be rephrased as the transmitted diffraction light _L2 at the diffraction angle _θ2 .

In this way, the optically anisotropic layer 14b in which the liquid crystal compound 20 is horizontally rotated and fixed functions as a transmissive liquid crystal diffraction grating.

The wavelength λ of the light that causes the diffraction action by the second liquid crystal diffraction element 110 (optically anisotropic layer 14b) may range from ultraviolet to visible light, infrared, or even electromagnetic wave level.
For the same period Λ, the larger the wavelength of the incident light, the larger the diffraction angle, and the smaller the wavelength of the incident light, the smaller the diffraction angle.
As will be described later, as the liquid crystal compound 20, a rod-like liquid crystal compound and a discotic liquid crystal compound can be used. When the wavelength λ is 380 nm, the discotic liquid crystal compound can provide higher diffraction efficiency than the rod-like liquid crystal compound in the range of 0.5<p<1 for one period Λ (μm). Further, when the wavelength λ is 1100 nm, the discotic liquid crystal compound can obtain higher diffraction efficiency than the rod-like liquid crystal compound in the range of 2<p<5 for one period Λ (μm).

As shown in FIG. 7, when incident light L ₁ of right-handed circularly polarized light P _R is incident along the normal to the surface of the second liquid crystal diffraction element 110, left- _handed circularly polarized An emitted light L ₂ of P _L is emitted.
On the other hand, when left-handed circularly polarized light is incident on the second liquid crystal diffraction element 110, the incident light is converted into right-handed circularly polarized light by the optically anisotropic layer 14b, and the bending force in the direction opposite to that in FIG. is received and the direction of travel is changed.

As shown in FIG. 8, when randomly polarized (non-polarized) incident light L ₄₁ is incident on the second liquid crystal diffraction element 110 (optically anisotropic layer 14b), out of the incident light L ₄₁ , right-handed circularly polarized light P _R is converted into left-handed circularly polarized light P _L in the optically anisotropic layer 14b as described above. It is transmitted through the layer and emitted as the first transmitted diffraction light _L42 .
On the other hand, the left-handed circularly polarized light P _L component of the incident light L ₄₁ is converted into right-handed circularly polarized light P _R by the optically anisotropic layer 14b, and converted from right-handed circularly polarized light to left-handed circularly polarized light. It receives a bending force in the opposite direction to the light, passes through the optically anisotropic layer 14b with its traveling direction changed, and passes through the opposite surface of the second liquid crystal diffraction element 110 as the second transmitted diffraction light _L43 . emitted. The traveling directions of the first transmitted diffraction light L ₄₂ and the second transmitted diffraction light L ₄₃ are substantially symmetrical with respect to the normal line.

In the above description, an example in which the incident light is perpendicularly incident on the optically anisotropic layer is shown, but the effect of transmission diffraction can also be obtained when the incident light is oblique.
In the case of oblique incidence, the rotation period may be designed so as to obtain the desired diffraction angle θ ₂ so as to satisfy the above formula (1) taking into consideration the incident angle θ ₁ .

As described above, the in-vehicle lighting device of the present invention refracts (diffracts) the polarized light by the second liquid crystal diffraction element 110 (optically anisotropic layer 14b). This allows the light to be deflected by a deflection angle much larger than the maximum deflection angle of the MEMS light deflection element (deflecting mirror 104b) in the case.

The refraction (diffraction angle) of light by the optically anisotropic layer 14b increases as one period of 180° rotation of the optical axis 22 of the liquid crystal compound 20, that is, one period Λ is shorter.

Furthermore, when the direction of polarization (direction of rotation) of incident circularly polarized light is the same, the direction of refraction of light by the optically anisotropic layer 14b is reversed depending on the direction of rotation of the optical axis 22 of the liquid crystal compound 20 .
That is, when the incident light L ₁ is right-handed circularly polarized light P _R , the rotation direction of the optical axis 22 is the direction of the axis A (arrow x direction), the outgoing light L ₂ is refracted in the direction of axis A, for example.
On the other hand, when the incident light L ₁ is right-handed circularly polarized light P _R and the direction of rotation of the optical axis 22 is counterclockwise toward the direction of the axis A as viewed from the exit surface side, The emitted light L ₂ is refracted in a direction opposite to the direction of the opposite axis A (see emitted light L ₄₃ in FIG. 8).

Accordingly, in the in-vehicle lighting device of the present invention shown in FIG. 3, the optically anisotropic layer 14b has one period Λ of the liquid crystal orientation pattern in the direction of the axis A, which is formed by the MEMS light deflection element (deflection mirror 104b). gradually shorten from the center of the deflection (deflection azimuth) by . That is, the amount of light refracted by the optically anisotropic layer 14b increases toward the outside in the deflection direction.
In addition, in the vehicle-mounted lighting device of the present invention shown in FIG. At the center of deflection by the deflection element, the reversal occurs. For example, in the illustrated example, the direction of rotation of the optical axis 22 toward the direction of axis A is counterclockwise from the upstream side in the direction of axis A to the center of the deflection direction, and the direction of rotation of the optical axis 22 is counterclockwise. , the direction of rotation of the optical axis 22 is reversed, and the direction of rotation of the optical axis 22 toward the direction of the axis A is clockwise from the center of deflection toward the downstream in the direction of the axis A.
In the vehicle-mounted lighting device of the present invention shown in FIG. 3, the optically anisotropic layer 14b of the second liquid crystal diffraction element 110 has such a configuration, so that the light is directed from the center in the direction of the axis A to both sides (upstream side and toward the downstream side), and the diffraction angle of the light is gradually increased from the center toward both sides in the direction of the axis A so that it is far larger than the maximum deflection angle of the MEMS optical deflection element. It allows the deflection of light with a large deflection angle.
The direction of rotation of the optical axis 22 is usually reversed in the direction of the axis A (direction of arrow x) in the optically anisotropic layer 14b, that is, the center of one direction in which the optical axis 22 rotates. That is, in the vehicle-mounted lighting device, the center of deflection of the MEMS light deflection element and the center of the optically anisotropic layer 14b in the direction of the axis A are usually aligned.

In addition, in the present invention, one period Λ may be continuously shortened from the deflection center toward the outside, or may be shortened stepwise.

<Formation of optically anisotropic layer>
The optically anisotropic layer 14b is formed of, for example, a liquid crystal composition containing a liquid crystal compound.
A liquid crystal composition containing a liquid crystal compound for forming the optically anisotropic layer 14b contains other components such as a leveling agent, an alignment control agent, a polymerization initiator and an alignment aid, in addition to the liquid crystal compound. may An optically anisotropic layer in which a predetermined liquid crystal alignment pattern is fixed, comprising a cured layer of a liquid crystal composition formed by forming an alignment film on a support and coating and curing a liquid crystal composition on the alignment film. can be obtained.
Next, each constituent component of the liquid crystal composition of the present invention will be described in detail.

The optically anisotropic layer 14b is a cured layer of a liquid crystal composition containing a rod-like liquid crystal compound or a discotic liquid crystal compound, and the optical axis of the rod-like liquid crystal compound or the discotic liquid crystal compound is oriented as described above. It has a liquid crystal alignment pattern.
An optically anisotropic layer comprising a cured layer of the liquid crystal composition can be obtained by forming an alignment film on the support 12 and coating and curing the liquid crystal composition on the alignment film. It is the optically anisotropic layer 14b that functions as a so-called λ/2 plate. include.
Further, the liquid crystal composition for forming the optically anisotropic layer contains a rod-like liquid crystal compound or a discotic liquid crystal compound, and other components such as a leveling agent, an alignment control agent, a polymerization initiator and an alignment aid. may contain.

Moreover, the optically anisotropic layer preferably has a wide band with respect to the wavelength of the incident light, and is preferably composed of a liquid crystal material having a reverse dispersion of birefringence.
Furthermore, it is also preferable to make the optically anisotropic layer substantially broadband with respect to the wavelength of incident light by imparting a twist component to the liquid crystal composition or by laminating different retardation layers. For example, Japanese Unexamined Patent Application Publication No. 2014-089476 discloses a method of realizing a broadband patterned λ/2 plate by laminating two layers of liquid crystal having different twist directions in an optically anisotropic layer. , can be preferably used in the present invention.

- Rod-shaped liquid crystal compound -
Rod-shaped liquid crystal compounds include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines, Phenyldioxanes, tolanes and alkenylcyclohexylbenzonitriles are preferably used. Not only low-molecular-weight liquid crystalline molecules as described above, but also high-molecular-weight liquid crystalline molecules can be used.

It is more preferable to fix the alignment of the rod-shaped liquid crystal compound by polymerization. As the polymerizable rod-shaped liquid crystal compound, Makromol. Chem. , 190, 2255 (1989), Advanced Materials 5, 107 (1993), US Pat. 95/24455, 97/00600, 98/23580, 98/52905, JP-A-1-272551, JP-A-6-16616, JP-A-7-110469, JP-A-11-80081 No. 2001-64627, etc. can be used. Furthermore, as the rod-like liquid crystal compound, for example, those described in JP-A-11-513019 and JP-A-2007-279688 can also be preferably used.

- Discotic Liquid Crystal Compounds -
As the discotic liquid crystal compound, for example, those described in JP-A-2007-108732 and JP-A-2010-244038 can be preferably used.
When the discotic liquid crystal compound is used for the optically anisotropic layer, the liquid crystal compound 20 rises in the thickness direction in the optically anisotropic layer, and the optical axis 22 derived from the liquid crystal compound is aligned with the disc surface. is defined as the axis perpendicular to , the so-called fast axis.
As described above, these rod-like liquid crystal compounds and discotic liquid crystal compounds can also be used in the cholesteric liquid crystal layer 14a of the first liquid crystal diffraction element 106 described above.

The optically anisotropic layer 14b can be formed by coating the alignment film 13 with a liquid crystal composition in multiple layers.
Multi-layer coating means that the liquid crystal composition is applied on the alignment film, heated, cooled, and then UV-cured to prepare the first liquid crystal fixing layer, and the second and subsequent layers are used to fix the liquid crystal. It refers to repeating the process of repeatedly applying a coating to the curable layer, heating in the same manner, and performing UV curing after cooling. By forming the optically anisotropic layer 14b by applying multiple layers as described above, even when the total thickness of the optically anisotropic layer 14b is increased, the orientation direction of the orientation film 13 can be adjusted to the direction of the optically anisotropic layer 14b. can be reflected from the bottom surface to the top surface.

As the optically anisotropic layer 14b in the second liquid crystal diffraction element 110, the concentric liquid crystal orientation pattern shown in FIG. 9, which is exemplified by the cholesteric liquid crystal layer described above, can also be used.
The liquid crystal alignment pattern in the optically anisotropic layer 14b shown in FIG. 9 is different from the liquid crystal alignment pattern in the optically anisotropic layer 14b described above. As described above, in the optically anisotropic layer 14b of FIG. 9, the direction of the optical axis 22 gradually rotates along multiple directions from the center to the outside, for example, along the axes A ₁ , A ₂ , A ₃ . It has a varying liquid crystal alignment pattern.
That is, as described above, the liquid crystal alignment pattern of the optically anisotropic layer 14b shown in FIG. 9 is a liquid crystal alignment pattern in which the optical axis 22 rotates radially. In other words, the liquid crystal alignment pattern of the optically anisotropic layer 14b shown in FIG. 9 is a concentric circular pattern in which one direction in which the direction of the optical axis changes while continuously rotating is formed concentrically from the inside to the outside. is.
Due to the optically anisotropic layer 14b having the liquid crystal alignment pattern shown in FIG. 9, the absolute phase of the incident light is changed by different amounts between the local regions where the orientation of the optical axis 22 is different. In the case of having a liquid crystal orientation pattern in which the optical axis changes radially in rotation as shown in FIG. 9, incident light can be transmitted as divergent light or condensed light. That is, the liquid crystal alignment pattern in the optically anisotropic layer 14b can realize a function as a concave lens or a convex lens.

In the in-vehicle lighting device of the present invention shown in FIG. 3, when an optically anisotropic layer having a concentric liquid crystal orientation pattern shown in FIG. 9 is used as the optically anisotropic layer 14b of the second liquid crystal diffraction element 110, , a second liquid crystal diffraction element 110 acting as a concave lens is used. At this time, by aligning the center of the concave lens with the center of the laser beam, that is, the optical axis of the lens 103, the deflection angle can be most efficiently widened with respect to the maximum deflection angle of the MEMS optical deflection element.
The smaller the size of the divided regions of the second liquid crystal diffraction element 110, the smoother the change. For example, it may be about 10 to several hundred μm.

In the above example, the liquid crystal compound 20 of the optically anisotropic layer 14b constituting the second liquid crystal diffraction element 110 faces one direction in the thickness direction, but the present invention is not limited to this.
In the vehicle-mounted lighting device of the present invention, the optically anisotropic layers constituting the second liquid crystal diffraction element 110 are the first optically anisotropic layer 215 and the second optically anisotropic layer of the liquid crystal diffraction element 220 shown in FIG. Like 216, it may have the liquid crystal compound 20 twisted along the helical axis extending along the thickness direction. In the following description, the twisted orientation along the helical axis extending along the thickness direction is also simply referred to as "twisted orientation".
The first optically anisotropic layer 215 and the second optically anisotropic layer 216 in which the liquid crystal compound 20 is twisted are obtained by observing the cross section of the liquid crystal diffraction element 220 with a scanning electron microscope (SEM). In the SEM image, as shown in FIG. 12, bright and dark lines originating from the twisted alignment of the liquid crystal compound 20 are perpendicular to the normal to the interface between the first optically anisotropic layer 215 and the second optically anisotropic layer 216. It is a tilted optically anisotropic layer.
As described above, in the liquid crystal alignment pattern, if one cycle (one cycle Λ) in which the optic axis of the liquid crystal compound rotates by 180° gradually becomes shorter in the direction in which the optic axis 22 rotates, The inclination angles of the bright and dark lines with respect to the normals of the first optically anisotropic layer 215 and the second optically anisotropic layer 216 gradually decrease in the direction in which the optical axis 22 rotates. That is, in this case, the angle of inclination of the bright and dark lines rises with respect to the main surface of the optically anisotropic layer. Furthermore, in this case, the pattern of bright and dark lines of the first optically anisotropic layer 215 and the second optically anisotropic layer 216 has a shorter period in the direction in which the optical axis 22 rotates.
Thus, according to the optically anisotropic layer having the twisted liquid crystal compound 20, the diffraction efficiency of light can be improved even in high-angle diffraction. As a result, compared with the optically anisotropic layer in which the liquid crystal compound is not twisted and aligned as shown in FIG.

In the liquid crystal diffraction element 220 , the first optically anisotropic layer 215 and the second optically anisotropic layer 216 have different twist directions in the twisted orientation of the liquid crystal compound 20 . That is, in the first optically anisotropic layer 215, the liquid crystal compound 20 is twisted clockwise toward the traveling direction of light. On the other hand, in the second optically anisotropic layer 216, the liquid crystal compound 20 is twisted counterclockwise in the light traveling direction.
Therefore, the first optically anisotropic layer 215 and the second optically anisotropic layer 216 have different directions of inclination of bright and dark lines derived from the twisted orientation in cross-sectional SEM images.

In such a first optically anisotropic layer 215, for example, when incident light is right-handed circularly polarized light, diffraction efficiency is improved for light traveling toward the left side (outside) in the figure indicated by the solid line. Great effect is obtained. However, when the incident light is right-handed circularly polarized light, the first optically anisotropic layer 215 improves the diffraction efficiency of the light traveling toward the right side (center side) in the drawing indicated by the dashed line. effect is small.
On the other hand, in the second optically anisotropic layer 216, when the incident light is right-handed circularly polarized light, the diffraction efficiency is improved for the light traveling toward the left side (outside) in the figure indicated by the solid line. effect is small. However, when the incident light is right-handed circularly polarized light, the second optically anisotropic layer 216 has a large effect of improving the diffraction efficiency for the light traveling toward the right side (center side) in the drawing indicated by the dashed line.
This effect is reversed when the incident light is left circularly polarized.

In the liquid crystal diffraction element 220, only the light traveling toward the left side (outside) in the figure indicated by the solid line is incident on the area shown in FIG. 12 where the center of deflection is on the right side in the figure. Therefore, the first optically anisotropic layer 215 acts strongly on this light (right-handed circularly polarized light), that is, in the area on the left side of the drawing, improving the diffraction efficiency and increasing the amount of emitted light. .
On the other hand, with respect to the area shown in FIG. 12, in the area on the right side of the center, only the light that travels toward the right side in the drawing indicated by the dashed line is incident. Therefore, the second optically anisotropic layer 216 acts strongly on this light (right-handed circularly polarized light) to improve diffraction efficiency and increase the amount of emitted light.
In addition, since the angle of incidence of incident light on the optically anisotropic layer is small in the region at the center of the polarized light, both the first optically anisotropic layer 215 and the second optically anisotropic layer 216 contribute to improving the diffraction efficiency. contribute.
As a result, according to the liquid crystal diffraction element 220 having the first optically anisotropic layer 215 and the second optically anisotropic layer 216 in which the twist directions of the twist alignment of the liquid crystal compound 20 are different from each other, in the entire range of light deflection directions, An effect of improving the diffraction efficiency can be obtained, and a large amount of light can be emitted over the entire deflection angle range.

In the optically anisotropic layer in which the liquid crystal compound 20 is twisted, the twist angle of the liquid crystal compound is not limited. The twist angle of the liquid crystal compound may be appropriately set according to the deflection angle of the optical deflection element, the desired diffraction efficiency, and the like.
In the optically anisotropic layer in which the liquid crystal compound 20 is twisted, the twist angle of the liquid crystal compound 20 is preferably 10 to 200°, more preferably 20 to 190°, even more preferably 40 to 170°.
The twist angle (twist angle in the thickness direction) of the twisted liquid crystal compound 20 means that the twisted liquid crystal compound 20 is twisted along the helical axis extending along the thickness direction in the optically anisotropic layer. This is the twist angle from the lower surface to the upper surface.

In this way, the liquid crystal diffraction element having the first optically anisotropic layer 215 and the second optically anisotropic layer 216 in which the liquid crystal compound 20 is helically twisted has the following characteristics, like the liquid crystal diffraction element 224 shown in FIG. Between the first optically anisotropic layer 215 and the second optically anisotropic layer 216, there may be a third optically anisotropic layer 219 in which the liquid crystal compound 20 is not twisted.
The third optically anisotropic layer 219 in which the liquid crystal compound is not twisted orientated is a non-inclined optically anisotropic layer in which the bright and dark lines extend along the normal direction.
By having such a third optically anisotropic layer 219 between the first optically anisotropic layer 215 and the second optically anisotropic layer 216, diffraction by the third optically anisotropic layer 219 is synergistic. , the light can be deflected over a wider deflection angle.

(drawing element)
As described above, the in-vehicle lighting device of the present invention shown in FIG. 2 has drawing elements for projecting images such as characters and patterns.
In the in-vehicle lighting device shown in FIG. 2, as described above, the drawing element is a MEMS optical deflection element having the drawing mirror 104a and the driving device 107a. It is a drawing element by optical scanning.
In the in-vehicle illumination device of the present invention, the drawing element is not limited to the drawing element by optical scanning using such an optical scanning element, and various known elements can be used. An example is DLP (Digital Light Processing) using a DMD (Digital (Micro) mirror Device).
In addition, as a drawing element by optical scanning, a drawing element using a galvanometer mirror or a polygon mirror as a light deflection element, and a drawing element using a combination of a galvanometer mirror and a polygon mirror as a light deflection element are also used. It is possible.
In the case of projecting a color image in the in-vehicle lighting device of the present invention, for example, drawing elements that display a red image, a green image, and a blue image are used, and the images are synthesized by a known method to produce a color image. should be projected.

(middle screen)
As described above, in the in-vehicle lighting device shown in FIG. 2, the image formed by the drawing element is rendered into a real image by the intermediate screen 108 .
The intermediate screen 108 is not limited, and various known intermediate screens used in projectors and the like, such as diffusion plates and microlens arrays, can be used.

(λ/4 plate)
As described above, in the in-vehicle lighting device of the present invention shown in FIG. 3, the linearly polarized laser light emitted by the laser light source 101 and condensed by the lens 103 is converted into circularly polarized light by the λ/4 plate 109. ing. The vehicle-mounted lighting device shown in FIG. 3 thereby enables the second liquid crystal diffraction element 110 to suitably diffract the laser light.
The λ/4 plate 109 is a known λ/4 plate (1/4 wavelength plate, 1/4 retardation plate) that converts linearly polarized light into circularly polarized light.
As the λ/4 plate 109, known ones can be used without limitation. Therefore, the λ/4 plate 109 may be derived from polymer or liquid crystal.
As described above, the λ/4 plate 109 may not be provided when the light emitted from the laser light source 101 is circularly polarized light.

(Optical deflection element)
In the in-vehicle lighting device of the present invention shown in FIG. 3, the circularly polarized laser light converted by the λ/4 plate 109 is deflected by the MEMS optical deflection element having the deflecting mirror 104b and the driving device 107b to obtain the above-mentioned circularly polarized light. is incident on the second liquid crystal diffraction element 110 that diffracts .

In this optical deflection element, the deflection mirror 104b of the MEMS optical deflection element preferably does not depolarize. Specifically, it is a metal mirror or the like that exhibits a mirror surface. In the case of a metal mirror, the direction of rotation (sense) of the circularly polarized light is reversed when the circularly polarized light is reflected. It is preferable that the circularly polarized light with the opposite direction of rotation is incident on the MEMS light polarizing element.
When the incident angle with respect to the mirror surface of the deflection mirror 104b of the MEMS optical deflection element is large, the polarization state of light changes due to the difference in reflectance and phase between P-polarized light (P-wave) and S-polarized light (S-wave). Change.
Correspondingly, the polarization state may be adjusted in advance so that the polarized light after reflection by the mirror becomes the desired circularly polarized light. As the adjustment of the polarization state, for example, a method of making the light elliptically polarized is exemplified. Further, a retardation plate for phase adjustment may be arranged so that the light becomes desired circularly polarized light after being reflected by the mirror of the MEMS light deflection element 132 .
Furthermore, a circular polarization mirror, such as a circular polarization mirror having a cholesteric liquid crystal layer, may be used as the deflection mirror 104b of the MEMS optical deflection element. In the case of a circularly polarizing mirror having a cholesteric liquid crystal layer, the circularly polarized light is kept in the rotating direction during reflection. , are preferably incident on the MEMS light polarizing element.

The light circularly polarized by the λ/4 plate 109 is deflected by the MEMS optical deflection element. The direction of light deflection by the MEMS optical deflection element 132 is made to coincide with the direction of the axis A (the direction of the arrow x), as in the case of the optical deflection element 100 described above.
In FIG. 3, the driving device 107b may be a known device that corresponds to the configuration of the MEMS optical deflection element 132 and the like.

In the vehicle-mounted lighting device of the present invention, the MEMS optical deflection element is not limited, and the MEMS optical deflection element described in JP-A-2012-208352 and the MEMS optical deflection element described in JP-A-2014-134642. , and known MEMS optical deflection elements such as the MEMS optical deflection element described in Japanese Patent Application Laid-Open No. 2015-22064, which deflect light (deflect and scan) by swinging a mirror using a piezoelectric actuator or the like. Devices (MEMS (optical) scanners), MEMS optical deflectors, MEMS mirrors and DMDs are all available.

In addition, in the vehicle-mounted lighting device of the present invention, the light deflection element is not limited to the MEMS light deflection element, and various known light deflection elements such as a galvanometer mirror, a polygon mirror, and a resonant scanner can be used. is.
Among them, the MEMS optical deflection element is preferably used as the optical deflection element because it has a small mechanical movable portion.

As described above, in the in-vehicle lighting device shown in FIG. 3 , of the laser light deflected by the MEMS light deflection element, the laser light that is deflected toward the first exit port enters the wavelength conversion member 105 to produce a white light. The light is converted into light, reflected in a predetermined direction by the first liquid crystal diffraction element 106 (first diffraction element), condensed and collimated, and projected outside the vehicle.
On the other hand, the laser light deflected toward the second exit port enters the wavelength conversion member 105, is converted into white light, is condensed by the lens 111, is incident on the optical waveguide 112, is propagated, is emitted, and enters the concave mirror. After being reflected and condensed by 113, it is condensed and collimated by projection lens 114 and projected outside the vehicle.

(Optical waveguide)
In the vehicle-mounted lighting device of the present invention, the optical waveguide 112 is not limited, and various known optical waveguides such as optical fibers can be used.
(concave mirror)
In the vehicle-mounted lighting device of the present invention, the concave mirror 113 is also not limited, and various known concave mirrors can be used.
The concave mirror may be a spherical mirror, a parabolic mirror, or a free-form mirror.
(projection lens)
In the in-vehicle illumination device of the present invention, the projection lens 114 is not limited, and various known projection lenses used in automobiles, such as projection lenses used for automobile headlights, can be used. be.

In the above-described in-vehicle lighting device of the present invention, the diffraction element is preferably a liquid crystal in which the direction of the optical axis derived from the liquid crystal compound changes while continuously rotating along at least one direction in the plane. Although the first liquid crystal diffraction element 106 and the second liquid crystal diffraction element 110 having an optically anisotropic layer (cholesteric liquid crystal layer) with an orientation pattern are used, the present invention is not limited to this.
That is, the optical deflection element of the present invention can be any known diffraction element as long as the periodic structure pitch changes gradually so that the diffraction angle increases outward from the center of deflection by the optical deflection element. , all available.

As a preferred example, a method using a photonic crystal without using a liquid crystal material can also be used based on the same principle as the liquid crystal diffraction element described above.
For example, as in the method described in Japanese Patent Application Laid-Open No. 2017-111277, a transparent substrate formed of an inorganic material and a concave-convex pattern forming portion formed of a plurality of ridges formed of Si or the like are fixed. Structural birefringence is generated by drawing a plurality of lines at intervals, and by changing the azimuth angle within the plane, a diffraction effect similar to that of the liquid crystal orientation pattern described above can be obtained.

As another suitable diffraction element, a holographic diffraction element is exemplified in which a pattern shape is exposed on a photosensitive material or the like by holography, and light is diffracted according to the difference in the refractive index of the exposed portion.
For example, the hologram diffraction element has a periodic pattern that gradually changes from the center of deflection by the light deflection element toward both ends so that the diffraction angle increases outward from the center of deflection of the light deflection element. It is sufficient that it has a refractive index distribution.
The hologram diffraction element is not limited as long as it satisfies the above-mentioned limitations. ) are all available.

As another suitable diffraction element, a surface relief diffraction element that diffracts light by fine unevenness formed on the surface can also be used.
In the surface relief diffraction element, for example, the grating period (relief pattern) of the unevenness is increased from the center of deflection by the light deflection element toward both ends so that the diffraction angle increases from the center of deflection of the light deflection element toward both ends. It should be changed gradually toward
The surface relief diffraction element is also not limited as long as it satisfies the above-mentioned limitations. , all available.
When a hologram diffraction element or a surface relief diffraction element is used as the diffraction element, the light incident on the diffraction element need not be circularly polarized light. Therefore, in this case, the λ/4 plate 109 is unnecessary.

As is clear from the above description, the vehicle-mounted lighting device of the present invention has a simple structure, can be driven simply, and is suitable for miniaturization and weight reduction, and utilizes a diffraction element. can be done.

The features of the present invention will be described more specifically below with reference to examples. The materials, reagents, amounts used, amounts of substances, ratios, treatment details, treatment procedures, etc. shown in the following examples can be changed as appropriate without departing from the gist of the present invention. Therefore, the scope of the present invention should not be construed to be limited by the specific examples shown below.

[Example 1]
<Fabrication of Optical Deflection Element Including Liquid Crystal Diffractive Element>
A liquid crystal optical phase modulation element described in JP-A-2003-295153 was used as the deflection element.
That is, a nematic liquid crystal layer is provided between a transparent substrate having a plurality of individual ITO electrodes made of a transparent conductor arranged in parallel stripes and a transparent substrate having a common ITO electrode made of a transparent conductor, and each individual electrode is provided with a nematic liquid crystal layer. By applying a predetermined voltage, the nematic liquid crystal layer was configured to cause a modulation of the refractive index.
As a result, it was confirmed that the blue laser light incident from the front is bent in a direction perpendicular to the direction of the parallel stripes. The deflection angle was about ±3°. The blue laser emits linearly polarized light with a wavelength of 450 nm, and the azimuth of the polarization axis is the extraordinary azimuth of the liquid crystal.
A method of manufacturing a liquid crystal diffraction element is shown below.

<Production of liquid crystal diffraction element>
(Support and saponification treatment of the support)
As a support, a commercially available triacetyl cellulose film (Z-TAC manufactured by Fuji Film Co., Ltd.) was prepared.
The support was passed through a dielectric heating roll at a temperature of 60°C to raise the surface temperature of the support to 40°C.
After that, on one side of the support, an alkaline solution shown below was coated using a bar coater at a coating amount of 14 mL (liter)/m ² , the support was heated to 110° C., and a steam type far infrared heater ( (manufactured by Noritake Co., Ltd.) for 10 seconds.
Subsequently, using the same bar coater, 3 mL/m ² of pure water was applied to the alkaline solution coated surface of the support. Then, after repeating water washing with a fountain coater and draining with an air knife three times, the support was dried by transporting it through a drying zone at 70° C. for 10 seconds to saponify the surface of the support with an alkali.

Alkaline solution ――――――――――――――――――――――――――――――
Potassium hydroxide 4.70 parts by mass Water 15.80 parts by mass Isopropanol 63.70 parts by mass Surfactant SF-1: C ₁₄ H ₂₉ O(CH ₂ CH ₂ O) ₂ OH 1.0 parts by mass Propylene glycol 14. 8 parts by mass――――――――――――――――――――――――――――――――

(Formation of undercoat layer)
The alkali-saponified surface of the support was continuously coated with the following undercoat layer-forming coating solution using a #8 wire bar. The support with the coating film formed thereon was dried with hot air at 60° C. for 60 seconds and then with hot air at 100° C. for 120 seconds to form an undercoat layer.

Coating liquid for forming undercoat layer ――――――――――――――――――――――――――――――――
The following modified polyvinyl alcohol 2.40 parts by mass Isopropyl alcohol 1.60 parts by mass Methanol 36.00 parts by mass Water 60.00 parts by mass ――――――――――

(Formation of alignment film)
On the support having the undercoat layer formed thereon, the following coating solution for forming an alignment layer was continuously applied with a #2 wire bar. The support on which the coating film of the alignment film-forming coating liquid was formed was dried on a hot plate at 60° C. for 60 seconds to form an alignment film.

Alignment film forming coating solution――――――――――――――――――――――――――――――――
Photo-alignment material A 1.00 parts by mass Water 16.00 parts by mass Butoxy ethanol 42.00 parts by mass Propylene glycol monomethyl ether 42.00 parts by mass ―――――――――――――――――― ――――――――――――――

Photo-alignment material A

(Exposure of alignment film)
The alignment film was exposed using the exposure apparatus shown in FIG. 11 to form an alignment film P-1 having an alignment pattern.
In the exposure apparatus, a laser that emits laser light with a wavelength (405 nm) was used. The amount of exposure by interference light was set to 100 mJ/cm ² .
By adjusting the refractive power of the lens (convex lens), when the optically anisotropic layer is subsequently formed, the rotational period of the rotation of the optic axis of the liquid crystal compound in the optically anisotropic layer from the center toward the outside is Gradually shortened.

(Formation of optically anisotropic layer)
Composition A-1 below was prepared as a liquid crystal composition for forming an optically anisotropic layer.
Composition A-1
――――――――――――――――――――――――――――――――
Liquid crystal compound L-1 100.00 parts by mass polymerization initiator (manufactured by BASF, Irgacure (registered trademark) 907)
3.00 parts by mass Photosensitizer (manufactured by Nippon Kayaku Co., Ltd., KAYACURE DETX-S)
1.00 parts by mass Leveling agent T-1 0.08 parts by mass Methyl ethyl ketone 313.00 parts by mass―――――――――――――――――――――――――――――― ―――

Liquid crystal compound L-1
Leveling agent T-1

The optically anisotropic layer was formed by preparing composition A-1 and coating it in multiple layers on alignment film P-1. Multi-layer coating means that the first layer composition A-1 is first applied on the alignment film, heated, cooled, and then UV-cured to prepare a liquid crystal fixing layer, and the second and subsequent layers are liquid crystal fixed. It refers to repeating the process of coating in multiple layers, heating and cooling in the same way, and then UV curing. By forming by multilayer coating, even when the total thickness of the liquid crystal layer is increased, the alignment direction of the alignment film is reflected from the bottom surface to the top surface of the liquid crystal layer.

First, for the first layer, the composition A-1 was applied onto the alignment film P-1, and the coating film was heated to 70°C on a hot plate and then cooled to 25°C. Thereafter, the orientation of the liquid crystal compound was fixed by irradiating the coating film with ultraviolet rays having a wavelength of 365 nm at an irradiation dose of 100 mJ/cm ² using a high-pressure mercury lamp in a nitrogen atmosphere. At this time, the film thickness of the first liquid crystal layer was 0.2 μm.

The second and subsequent layers were overcoated on this liquid crystal layer, heated under the same conditions as above, cooled, and then UV-cured to prepare a liquid crystal fixing layer. In this manner, repeated coating is repeated until the total thickness reaches a desired thickness to form an optically anisotropic layer. A device was produced.
The optically anisotropic layer finally has a liquid crystal Δn450×thickness (Re(450)) of 470 nm, and has a concentric periodic liquid crystal alignment pattern as shown in FIG. , in one direction in which the optic axis rotates, the rotation period of the optic axis of the liquid crystal compound in the optically anisotropic layer is gradually shortened from the center toward the outside, and the rotation direction of the optic axis at the center was confirmed by a polarizing microscope.
In the liquid crystal alignment pattern of this optically anisotropic layer, the rotation period (one period) in which the optical axis of the liquid crystal compound rotates by 180° has a very large rotation period at the center (the reciprocal of the rotation period is 0). The rotation period at a distance of 2.5 mm from the center is 5.1 μm, the rotation period at a distance of 5.0 mm from the center is 2.5 μm, and the rotation period gradually decreases outward from the center. It was a liquid crystal alignment pattern.

<Fabrication of λ/4 plate>
A λ/4 plate (circularly polarizing plate) was prepared in order to convert linearly polarized light after passing through the liquid crystal optical phase modulation element into circularly polarized light and enter the liquid crystal diffraction element.
First, a support having an undercoat layer formed thereon was prepared in the same manner as described above.

(Formation of alignment film P-10)
The following coating liquid for forming alignment layer P-10 was continuously coated on the support with the undercoat layer formed thereon using a #2.4 wire bar. The support on which the coating film of the coating solution for forming alignment film P-10 was formed was dried on a hot plate at 80° C. for 5 minutes to form alignment film P-10.

Coating liquid for forming alignment film P-10 ――――――――――――――――――――――――――――――――
Photo-alignment material Polymer A2 4.35 parts by mass Low-molecular compound B2 0.80 parts by mass Crosslinking agent C1 2.20 parts by mass Compound D1 0.48 parts by mass Compound D2 1.15 parts by mass Butyl acetate 100.00 parts by mass ――――――――――――――――――――――――――――――――

<<Synthesis of Polymer A2>>
100 parts by weight of 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 500 parts by weight of methyl isobutyl ketone, and 10 parts by weight of triethylamine were added to a reaction vessel equipped with a stirrer, thermometer, dropping funnel and reflux condenser. were charged and mixed at room temperature. Then, 100 parts by mass of deionized water was added dropwise from the dropping funnel over 30 minutes, and the mixture was reacted at 80° C. for 6 hours while being mixed under reflux. After completion of the reaction, the organic phase was taken out and washed with a 0.2% by mass aqueous ammonium nitrate solution until the water after washing became neutral, and then the solvent and water were distilled off under reduced pressure to remove the epoxy-containing polyorganosiloxane. Obtained as a viscous transparent liquid.
When this epoxy-containing polyorganosiloxane was subjected to 1H-NMR (Nuclear Magnetic Resonance) analysis, a peak based on the oxiranyl group was obtained at a chemical shift (δ) of around 3.2 ppm in accordance with the theoretical intensity. It was confirmed that no side reaction of the group occurred. This epoxy-containing polyorganosiloxane had a weight average molecular weight Mw of 2,200 and an epoxy equivalent of 186 g/mol.
Next, in a 100 mL three-necked flask, 10.1 parts by mass of the epoxy-containing polyorganosiloxane obtained above, acrylic group-containing carboxylic acid (manufactured by Toagosei Co., Ltd., Aronix M-5300, acrylic acid ω-carboxypolycaprolactone (degree of polymerization n ≈ 2)) 0.5 parts by mass, 20 parts by mass of butyl acetate, 1.5 parts by mass of the cinnamic acid derivative obtained by the method of Synthesis Example 1 of JP-A-2015-26050, and 0 of tetrabutylammonium bromide .3 parts by mass were charged and stirred at 90° C. for 12 hours. After completion of the reaction, the reaction solution was diluted with the same amount (mass) of butyl acetate and washed with water three times.
The operation of concentrating this solution and diluting it with butyl acetate was repeated twice to finally obtain a solution containing a polyorganosiloxane having a photo-orientation group (polymer A2 below). The weight average molecular weight Mw of this polymer A2 was 9,000. As a result of 1H-NMR analysis, the content of components having cinnamate groups in polymer A2 was 23.7% by mass.

Polymer A2

Low molecular weight compound B2
A low-molecular-weight compound B2 represented by the following formula (Nisshin Orio Co., Ltd., NOMUCORT TAB) was used.

Crosslinking agent C1
A cross-linking agent C1 represented by the following formula (Denacol EX411 manufactured by Nagase ChemteX Corporation) was used.

Compound D1
A compound D1 represented by the following formula (manufactured by Kawaken Fine Chemicals Co., Ltd., aluminum chelate A (W)) was used.

Compound D2
A compound D2 (triphenylsilanol manufactured by Toyo Science Co., Ltd.) represented by the following formula was used.

(Exposure of alignment film P-10)
The alignment film P-10 thus obtained was irradiated with polarized ultraviolet rays (20 mJ/cm ² , using an ultra-high pressure mercury lamp) to expose the alignment film P-10.

[Fabrication of λ/4 plate]
The optically anisotropic layer was formed by applying the composition A-1 described above onto the alignment film P-10.
The applied coating film is heated to 110°C on a hot plate, then cooled to 60°C, and then irradiated with ultraviolet rays having a wavelength of 365 nm at an irradiation dose of 500 mJ/cm ² using a high-pressure mercury lamp in a nitrogen atmosphere. By doing so, the orientation of the liquid crystal compound was fixed to produce an optically anisotropic layer. Finally, the optically anisotropic layer was transferred from the support to a quartz substrate having a thickness of 10 mm with an adhesive, and this was used as a λ/4 plate. Δn450×d (Re(450)) of the obtained λ/4 plate was 470 nm.

<Assembly of optical deflection element>
A liquid crystal optical phase modulation element, a λ/4 plate, and a liquid crystal diffraction element were laminated in this order from the front, and bonded with an adhesive to produce an optical deflection element as shown in FIG. A driving device was connected to the liquid crystal optical phase modulation element.
At this time, the polarization direction of the emitted light from the liquid crystal optical phase modulation element and the in-plane slow axis of the λ/4 plate were crossed at 45° so that the light was converted into circularly polarized light. Moreover, the center of the deflection direction of the liquid crystal optical phase modulation element was aligned with the center of the liquid crystal diffraction element, and they were bonded together so that the effect of amplifying the deflection angle of light was maximized.
A blue laser was prepared as a light source. This blue laser emits linearly polarized light with a wavelength of 450 nm, and the azimuth of the polarization axis is the extraordinary azimuth of the liquid crystal. The blue laser was arranged so that the emitted linearly polarized light was P-polarized with respect to the emission surface of the liquid crystal diffraction element.

[evaluation]
For the optical deflection element of Example 1, a blue laser beam is incident from the front of the optical deflection element on the side of the liquid crystal optical phase modulation element, and a predetermined voltage is applied to the individual electrodes so as to change the angle of the liquid crystal optical phase modulation element by ±3°. and confirmed the angle of light emitted from the liquid crystal diffraction element.
As a result, it was confirmed that the deflection angle (amount of deflection angle) by the liquid crystal optical phase modulation element was greatly enlarged by the liquid crystal diffraction element and increased to about ±55°.

In addition, a similar evaluation was performed by arranging a condenser lens (convex lens) between the blue laser and the liquid crystal optical phase modulation element of the optical deflection element. As a result, it was confirmed that the straightness of the light deflected by the light deflection element was improved.

[Example 2]
[Fabrication of diffraction element]
(Support and saponification treatment of the support)
As a support, a commercially available triacetyl cellulose film (Z-TAC manufactured by Fuji Film Co., Ltd.) was prepared. The support was passed through a dielectric heating roll at a temperature of 60°C to raise the surface temperature of the support to 40°C.
After that, on one side of the support, an alkaline solution shown below was coated using a bar coater at a coating amount of 14 mL (liter)/m ² , the support was heated to 110° C., and a steam type far infrared heater ( (manufactured by Noritake Co., Ltd.) for 10 seconds.
Subsequently, using the same bar coater, 3 mL/m ² of pure water was applied to the alkaline solution coated surface of the support. Then, after repeating water washing with a fountain coater and draining with an air knife three times, the support was dried by transporting it through a drying zone at 70° C. for 10 seconds to saponify the surface of the support with an alkali.

Alkaline solution――――――――――――――――――――――――――――――――
Potassium hydroxide 4.70 parts by mass Water 15.80 parts by mass Isopropanol 63.70 parts by mass Surfactant SF-1: C ₁₄ H ₂₉ O(CH ₂ CH ₂ O) ₂ OH
1.0 parts by mass Propylene glycol 14.8 parts by mass――――――――――――――――――――――――――――――――――

Coating liquid for forming undercoat layer ――――――――――――――――――――――――――――――――――
The following modified polyvinyl alcohol 2.40 parts by mass Isopropyl alcohol 1.60 parts by mass Methanol 36.00 parts by mass Water 60.00 parts by mass ――――――――――――

Alignment film forming coating solution――――――――――――――――――――――――――――――――――
Materials for optical alignment shown below 1.00 parts by mass Water 16.00 parts by mass Butoxyethanol 42.00 parts by mass Propylene glycol monomethyl ether 42.00 parts by mass ―――――――――――――――――― ―――――――――――――――

－Materials for optical alignment－

(Exposure of alignment film)
The alignment film was exposed using the exposure apparatus shown in FIG. 10 to form the alignment film P-1 having the alignment pattern shown in FIG.
In the exposure apparatus, a laser that emits laser light with a wavelength (325 nm) was used. The amount of exposure by interference light was set to 100 mJ/cm ² . One period of the alignment pattern formed by the interference of the two laser beams (the length of the 180° rotation of the optical axis (one period Λ)) can be changed by changing the crossing angle (crossing angle β) of the two lights. controlled by
Specifically, the exposure of the alignment film is performed by adjusting the crossing angle of the two laser beams and masking the unnecessary area for exposure, as described above. ° Rotation was carried out so that one period of rotation gradually became shorter from the center of the support toward both ends in one direction (direction of axis A) in which the optical axis rotates. In the following description, one direction in which the optical axis rotates will also be referred to as the "axis A direction" in accordance with the previous description.
One cycle of the orientation pattern was set so that the center of the support in the direction of the axis A was about 10 μm, and both ends of the support in the direction of the axis A were about 1 μm.

(Formation of B reflective cholesteric liquid crystal layer)
Composition A-1 below was prepared as a liquid crystal composition for forming a cholesteric liquid crystal layer.
This composition A-1 is a liquid crystal composition that forms a cholesteric liquid crystal layer (cholesteric liquid crystal phase) that has a selective reflection central wavelength of 450 nm and reflects right-handed circularly polarized light.
Composition A-1
―――――――――――――――――――――――――――――――――
Rod-shaped liquid crystal compound L-1 100.00 parts by mass Polymerization initiator (manufactured by BASF, Irgacure (registered trademark) 907)
3.00 parts by mass Photosensitizer (manufactured by Nippon Kayaku, KAYACURE DETX-S)
1.00 parts by mass Chiral agent Ch-1 6.77 parts by mass Leveling agent T-1 0.08 parts by mass Methyl ethyl ketone 268.20 parts by mass―――――――――――――――――――― ――――――――――――――

Rod-shaped liquid crystal compound L-1
Chiral agent Ch-1
Leveling agent T-1

The B reflective cholesteric liquid crystal layer was formed by coating the composition A-1 on the exposed alignment film P-1 in multiple layers.
Multi-layer coating means that the first layer composition A-1 is first applied on the alignment film, heated, cooled, and then UV-cured to prepare a liquid crystal fixing layer, and the second and subsequent layers are liquid crystal fixed. It refers to repeating the process of coating in multiple layers, heating and cooling in the same way, and then UV curing. By forming by multilayer coating, even when the total thickness of the liquid crystal layer is increased, the alignment direction of the alignment film is reflected from the bottom surface to the top surface of the liquid crystal layer.

For the first layer, the following composition A-1 was applied on the alignment film P-1, the coating film was heated on a hot plate to 95 ° C., then cooled to 25 ° C., and then under a nitrogen atmosphere. The alignment of the liquid crystal compound was fixed by irradiating the coating film with ultraviolet light having a wavelength of 365 nm at a dose of 100 mJ/cm ² using a high-pressure mercury lamp. At this time, the film thickness of the first liquid crystal layer was 0.2 μm.

The second and subsequent layers were overcoated on this liquid crystal layer, heated under the same conditions as above, cooled, and then UV-cured to prepare a liquid crystal fixing layer. In this manner, repeated coating was repeated until the total thickness reached a desired film thickness to form a B reflective cholesteric liquid crystal layer, thereby producing a B reflective layer. When the cross section of the coating layer was confirmed by SEM, the cholesteric liquid crystal phase of the B reflective layer was 8 pitches.
It was confirmed with a polarizing microscope that the B reflective cholesteric liquid crystal layer had a periodically oriented surface as shown in FIG. In the liquid crystal alignment pattern of the B-reflection cholesteric liquid crystal layer, one cycle of 180° rotation of the optical axis derived from the liquid crystal compound was 0.9 μm at both ends in the direction of the axis A of the support and 10 μm at the central portion. .

<Preparation of G reflective layer>
Alignment film P-2 having an alignment pattern shown in FIG. formed.
Composition A-2 for forming a cholesteric liquid crystal layer was prepared in the same manner as composition A-1, except that the amount of chiral agent Ch-1 added was changed to 5.68 parts by mass. This composition A-2 is a liquid crystal composition that forms a cholesteric liquid crystal layer that has a selective reflection central wavelength of 530 nm and reflects right-handed circularly polarized light.
A G reflective cholesteric liquid crystal layer was formed in the same manner as the B reflective cholesteric liquid crystal layer, except that the composition A-2 was applied in multiple layers on the alignment film P-2, to produce a G reflective layer.
It was confirmed with a polarizing microscope that the G-reflection cholesteric liquid crystal layer had a periodically oriented surface as shown in FIG. In the liquid crystal alignment pattern of this G-reflection cholesteric liquid crystal layer, one cycle in which the optical axis derived from the liquid crystal compound rotates by 180° was 1.1 μm at the end of the support in the direction of the axis A and 10 μm at the central portion. .

<Preparation of R reflective layer>
Alignment film P-3 having an alignment pattern shown in FIG. formed.
Composition A-3 for forming a cholesteric liquid crystal layer was prepared in the same manner as composition A-1, except that the amount of chiral agent Ch-1 added was changed to 4.69 parts by mass. This composition A-3 is a liquid crystal composition that forms a cholesteric liquid crystal layer that has a selective reflection central wavelength of 635 nm and reflects right-handed circularly polarized light.
An R reflective cholesteric liquid crystal layer was formed in the same manner as the B reflective cholesteric liquid crystal layer, except that the composition A-3 was applied in multiple layers on the alignment film P-3, thereby producing an R reflective layer.
It was confirmed with a polarizing microscope that the R-reflecting cholesteric liquid crystal layer had a periodically oriented surface as shown in FIG. In the liquid crystal alignment pattern of this R-reflecting cholesteric liquid crystal layer, one cycle in which the optical axis derived from the liquid crystal compound rotates by 180° was 1.3 μm at the end of the support in the direction of the axis A and 10 μm at the central portion. .

<Fabrication of first liquid crystal diffraction element>
The prepared B reflective layer, G reflective layer and R reflective layer are laminated in the order of the R reflective layer, G reflective layer and B reflective layer with an adhesive (SK Dyne 2057 manufactured by Soken Kagaku Co., Ltd.) to form the first liquid crystal. A diffraction element was produced. At the time of lamination, the next layer was laminated after peeling off the support and the alignment film.
As described above, the cholesteric liquid crystal layer has polarization properties in reflection, and diffracts and reflects circularly polarized light. Therefore, in the first liquid crystal diffraction element, a λ/4 plate (manufactured by Teijin Limited, trade name: Pure Ace WR-S, polycarbonate film, front retardation: 126 nm) is attached to a laminate of cholesteric liquid crystal layers. By arranging so that the laser light is incident on the four plate side, the light incident on the laminate of the cholesteric liquid crystal layers is made to be right-handed circularly polarized light. In addition, two similar λ/4 plates were bonded to the half region of the laminate of the cholesteric liquid crystal layers in the direction of the axis A in order to convert the incident light into left-handed circularly polarized light. That is, the two λ/4 plates act as λ/2 plates.

<Assembly of lighting device>
A blue laser was prepared as a light source. The blue laser was arranged so that the emitted linearly polarized light was P-polarized light with respect to the reflecting surface of the first liquid crystal diffraction element. The blue laser emits linearly polarized light with a wavelength of 450 nm, and the azimuth of the polarization axis is the extraordinary azimuth of the liquid crystal.
Also, a wavelength conversion member using phosphor (quantum dot phosphor containing InP/ZnS) was prepared. This phosphor is a phosphor that converts blue light into red and green light. Therefore, the light transmitted through the wavelength conversion member becomes white light.
Using this blue laser light source, a general mirror, a wavelength conversion member, and a first liquid crystal diffraction element, an in-vehicle lighting device as shown in FIG. 1 was manufactured.
Only one blue laser light source was used so that the laser light was directly incident on the mirror.
The first liquid crystal diffraction element was arranged so that the λ/2 plate side was the incident surface, and the laminate of the λ/2 plate, the λ/4 plate and the cholesteric liquid crystal layer was arranged in order from the light incident side.

[evaluation]
Using the manufactured in-vehicle lighting device of the present invention, a black paper 10 m ahead was irradiated with light, and the color and irradiation size of the light were confirmed.
In addition, an in-vehicle illumination device using a concave mirror and a projection lens instead of the first liquid crystal diffraction element was also prepared.
As a result, it was confirmed that the in-vehicle lighting device of the present invention emits white light and has substantially the same projection size as the in-vehicle lighting device using a concave mirror and a projection lens.
In terms of size and weight, the in-vehicle lighting device of the present invention was smaller and lighter.
From the above results, it is clear that the size and weight of the vehicle-mounted lighting device can be reduced by using the diffraction element, and the effect of the present invention is clear.

REFERENCE SIGNS LIST 101 laser light source 102

mirror

103, 111 lens 104 mirror 105 wavelength conversion member 106 first liquid crystal diffraction element 107 driving device (MEMS optical deflection element)
108 intermediate screen (diffusion plate)
109 λ/4 plate 110 Second liquid crystal diffraction element 112 Optical waveguide (optical fiber)
113 concave mirror 114 projection lens 12 support 13 alignment film 14a cholesteric liquid crystal layer 14b optically anisotropic layer 20 liquid crystal compound 22 optical axis 24

equal phase surface

50, 80

exposure device

52, 82

laser

54, 84 light source 56

beam splitter

58A, 58B , 90A, 90B Mirrors 60A, 60B, 96 λ/4 plate 70

Laser beams

72A,

72B Rays

86, 94 Polarizing beam splitter 92

Lenses

220, 224 Liquid crystal diffraction element 215 First optically anisotropic layer 216 Second optically anisotropic Layer 219 Third optically anisotropic layer L ₁ , L ₄₁ incident light L ₂ , L ₄₂ , L ₄₃ outgoing light P _O linearly polarized light P _R right circularly polarized light P _L left circularly polarized light M laser beam MP P polarized light MS S polarized light

Claims

An in-vehicle lighting device, comprising a light source, a diffusion member for diffusing light emitted by the light source, and a periodic structure pitch for diffracting the diffused light by the diffusion member, the pitch of which gradually changes from the center toward the outside. , an automotive lighting device for distributing light to an exterior space of a motor vehicle, comprising a first diffractive element.
The first diffraction element is a liquid crystal diffraction element formed using a composition containing a liquid crystal compound, wherein the direction of the optic axis derived from the liquid crystal compound rotates continuously along at least one in-plane direction. 2. A vehicle lighting device according to claim 1, comprising an optically anisotropic layer having a liquid crystal alignment pattern that varies with the orientation of the liquid crystal.
The vehicle-mounted lighting device according to claim 1, comprising an oxygen blocking layer adjacent to the first diffraction element.
an exit and an optical waveguide for distributing light to the exterior space of the automobile;
an optical deflection element that deflects the light emitted from the light source toward the first diffraction element or the optical waveguide;
2. The vehicle-mounted lighting device according to claim 1, further comprising a second diffraction element arranged on the light exit side of said light deflection element and having a periodic structure pitch that gradually changes from the center toward the outside.
The second diffraction element is a liquid crystal diffraction element formed using a composition containing a liquid crystal compound, wherein the orientation of the optic axis derived from the liquid crystal compound rotates continuously along at least one in-plane direction. 5. An automotive lighting device according to claim 4, comprising an optically anisotropic layer having a liquid crystal orientation pattern that varies while being oriented.
5. The vehicle-mounted lighting device according to claim 4, further comprising an oxygen blocking layer adjacent to said second diffractive element.
The vehicle-mounted lighting device according to claim 4, wherein the optical deflection element is a MEMS optical deflection element.
The in-vehicle lighting device according to claim 1, having a λ/4 plate.
A vehicle equipped with the in-vehicle lighting device according to any one of claims 1 to 8.
A diffraction element used in the vehicle-mounted lighting device according to any one of claims 1 to 8.