WO2022045167A1 - 画像表示ユニットおよびヘッドマウントディスプレイ - Google Patents

画像表示ユニットおよびヘッドマウントディスプレイ Download PDF

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Publication number
WO2022045167A1
WO2022045167A1 PCT/JP2021/031091 JP2021031091W WO2022045167A1 WO 2022045167 A1 WO2022045167 A1 WO 2022045167A1 JP 2021031091 W JP2021031091 W JP 2021031091W WO 2022045167 A1 WO2022045167 A1 WO 2022045167A1
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WIPO (PCT)
Prior art keywords
liquid crystal
image display
crystal layer
display unit
light
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/JP2021/031091
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English (en)
French (fr)
Japanese (ja)
Inventor
寛 佐藤
之人 齊藤
隆 米本
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Fujifilm Corp
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Fujifilm Corp
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Publication date
Application filed by Fujifilm Corp filed Critical Fujifilm Corp
Priority to JP2022545656A priority Critical patent/JP7431986B2/ja
Priority to CN202180052021.6A priority patent/CN115989433A/zh
Publication of WO2022045167A1 publication Critical patent/WO2022045167A1/ja
Priority to US18/172,807 priority patent/US20230204968A1/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/28—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for polarising
    • G02B27/281—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for polarising used for attenuating light intensity, e.g. comprising rotatable polarising elements
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
    • G02B1/08—Optical elements characterised by the material of which they are made; Optical coatings for optical elements made of polarising materials
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/01—Head-up displays
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/01—Head-up displays
    • G02B27/017—Head mounted
    • G02B27/0172—Head mounted characterised by optical features
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/02—Viewing or reading apparatus
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/42—Diffraction optics, i.e. systems including a diffractive element being designed for providing a diffractive effect
    • G02B27/4205—Diffraction optics, i.e. systems including a diffractive element being designed for providing a diffractive effect having a diffractive optical element [DOE] contributing to image formation, e.g. whereby modulation transfer function MTF or optical aberrations are relevant
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B3/00—Simple or compound lenses
    • G02B3/02—Simple or compound lenses with non-spherical faces
    • G02B3/08—Simple or compound lenses with non-spherical faces with discontinuous faces, e.g. Fresnel lens
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B3/00—Simple or compound lenses
    • G02B3/12—Fluid-filled or evacuated lenses
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/18—Diffraction gratings
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • G02B5/3016—Polarising elements involving passive liquid crystal elements
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/13363—Birefringent elements, e.g. for optical compensation
    • G—PHYSICS
    • G06—COMPUTING OR CALCULATING; COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F1/00—Details not covered by groups G06F3/00 - G06F13/00 and G06F21/00
    • G06F1/16—Constructional details or arrangements
    • G06F1/1613—Constructional details or arrangements for portable computers
    • G06F1/163—Wearable computers, e.g. on a belt
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/64—Constructional details of receivers, e.g. cabinets or dust covers
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • G02B5/3083—Birefringent or phase retarding elements

Definitions

  • the present invention relates to an image display unit used for a VR (virtual reality) head-mounted display and a head-mounted display.
  • VR virtual reality
  • a head-mounted display that has an image display unit that is attached to the user and guides the image to the user's eyes in order to experience the so-called immersive virtual reality (VR) that does not allow outside light in the real world to pass through.
  • An image display unit used in such a head-mounted display requires a lens in which the light emitted from the image display device collects the light at the position of the user's eyes.
  • the image display unit used for the head-mounted display by making the distance between the image display device and the lens close to the focal length of the lens, the user can visually recognize the image displayed by the image display device as a distant virtual image. ..
  • a Fresnel lens is generally used as a lens in order to reduce the thickness and weight.
  • a Fresnel lens there is a limit to shortening the focal length. Therefore, it is difficult to reduce the thickness of the entire image display unit (head-mounted display).
  • the light emitted from the image display device is reflected once by a reflective polarizing element or the like, and then reflected again by a mirror or the like to be reflected by the user's eyes.
  • a guiding structure has been proposed. As a result, the optical path length from the image display device to the user's eyes can be increased, and the entire image display unit can be made thinner.
  • Patent Document 1 has a linear splitter, a 1/4 wave plate, a half mirror, a 1/4 wave plate, and a reflection splitter in this order from the image display device side, and is used as an optical device for VR.
  • a head-mounted display that can be used is described.
  • light is reciprocated between the half mirror and the reflecting splitter to lengthen the optical path length.
  • an image display unit that uses a half mirror and a reflected polarizing element to reciprocate light between the half mirror and the reflected polarizing element to lengthen the optical path length, about 50% of the light incident on the half mirror.
  • the half mirror reflects about 50% of the light transmitted through the half mirror and reflected by the reflected polarizing element, and this light is emitted from the image display unit. Therefore, there is a problem that the utilization efficiency of light with respect to the amount of light of the image emitted by the image display device is as low as about 25%.
  • An object of the present invention is to provide an image display unit and a head-mounted display which are small in size, have high light utilization efficiency, and have little deterioration in image quality.
  • the present invention has the following configurations.
  • Image display device and A polarization diffractive element that diffracts the light emitted from the image display device, It has a polarizing plate that transmits the polarized light diffracted by the polarization diffractive element and absorbs the light that is not diffracted by the polarization diffractive element.
  • the polarization diffractive element is a polarization diffractive lens having a lens function. Let f be the focal length of the polarizing diffractive lens and d be the distance between the image display device and the polarizing diffractive lens. An image display unit that satisfies d ⁇ f.
  • the polarizing diffraction element diffracts circularly polarized light.
  • the image display device emits linearly polarized light.
  • the image display device emits unpolarized light.
  • the polarization diffractive element is a liquid crystal diffractive element having a liquid crystal layer containing a liquid crystal compound.
  • the liquid crystal layer has a liquid crystal orientation pattern in which the orientation of the optical axis derived from the liquid crystal compound changes while continuously rotating along at least one direction in the plane.
  • the liquid crystal layer has regions in the plane having different lengths of one cycle [1].
  • the image display unit according to any one of [8]. [10] The image display unit according to [9], wherein the liquid crystal layer gradually shortens one cycle from one side in one direction to the other side in the liquid crystal alignment pattern. [11] The image display unit according to [9] or [10], wherein the liquid crystal layer has one direction of the liquid crystal alignment pattern concentrically from the inside to the outside.
  • the liquid crystal layer has bright and dark parts derived from the liquid crystal phase with respect to the main surface of the liquid crystal layer.
  • the image display unit according to any one of [9] to [11], which has an inclined region.
  • the liquid crystal diffractive element has two or more liquid crystal layers, and has two or more liquid crystal layers. In the cross-sectional image of at least two liquid crystal layers cut in the thickness direction along one direction with a scanning electron microscope, bright and dark parts derived from the direction of the optical axis are observed.
  • the liquid crystal layer has a bright part and a dark part extending from one surface to the other surface in a cross-sectional image obtained by observing a cross section cut in the thickness direction along one direction with a scanning electron microscope.
  • the dark part has inflection points of two or more angles
  • an image display unit and a head-mounted display that are small in size, have high light utilization efficiency, and have little deterioration in image quality.
  • FIG. 5 is an enlarged plan view showing a part of the liquid crystal layer of the liquid crystal diffractive element shown in FIG.
  • FIG. 1 It is a figure which conceptually shows an example of the exposure apparatus which exposes the alignment film which forms the liquid crystal layer shown in FIG. It is a conceptual diagram for demonstrating the operation of a liquid crystal layer. It is a conceptual diagram for demonstrating the operation of a liquid crystal layer. It is a conceptual diagram which shows the operation of the liquid crystal diffraction element shown in FIG. It is a figure which conceptually shows an example of the SEM cross section of a liquid crystal layer. It is a conceptual diagram which shows the other example of the liquid crystal layer. It is a conceptual diagram which shows the other example of the liquid crystal layer.
  • the numerical range represented by using "-" in the present specification means a range including the numerical values before and after "-" as the lower limit value and the upper limit value. Further, “orthogonal” and “parallel” with respect to an angle mean a range of a strict angle of ⁇ 10 °, and “same” and “different” with respect to an angle mean whether or not the difference is less than 5 °. Can be judged on the basis of.
  • the "slow phase axis" means the direction in which the refractive index becomes maximum in the plane.
  • the inverse wavelength dispersibility means the property that the absolute value of the in-plane retardation increases as the wavelength becomes longer, and specifically, Re (450) which is the in-plane retardation value measured at a wavelength of 450 nm.
  • Re (550) which is an in-plane retardation value measured at a wavelength of 550 nm
  • Re (650) which is an in-plane retardation value measured at a wavelength of 650 nm
  • the image display unit of the present invention is Image display device and A polarization diffractive element that diffracts the light emitted from the image display device, It has a polarizing plate that transmits the polarized light diffracted by the polarization diffractive element and absorbs the light that is not diffracted by the polarization diffractive element.
  • the polarization diffractive element is a polarization diffractive lens having a lens function. Let f be the focal length of the polarizing diffractive lens and d be the distance between the image display device and the polarizing diffractive lens. An image display unit that satisfies d ⁇ f.
  • FIG. 1 is a diagram conceptually representing an example of the image display unit of the present invention.
  • FIG. 2 is an enlarged view of a part (a portion surrounded by a broken line) of the image display unit shown in FIG. 1, and is a diagram for explaining the operation of the image display unit.
  • the image display unit 10 shown in FIGS. 1 and 2 includes an image display device 52, a first circular polarizing plate 16, a polarizing diffraction element 20, and a second circular polarizing plate 26.
  • the first circular polarizing plate 16 has a first linear polarizing plate 12 and a first retardation plate 14.
  • the second circular polarizing plate 26 has a second linear polarizing plate 24 and a second retardation plate 22.
  • the second circular polarizing plate 26 is the polarizing plate in the present invention.
  • the image display device 52 emits unpolarized light as an image.
  • the first circularly polarizing plate 16 transmits circularly polarized light in a predetermined turning direction and shields the other circularly polarized light.
  • the first circular polarizing plate 16 transmits a predetermined linear polarization component of the incident light by the first linear polarizing plate 12, and is first by the first retardation plate 14.
  • the polarization diffractive element 20 diffracts the circular polarization transmitted through the first circular polarizing plate 16.
  • the polarizing diffraction element 20 converts the circularly polarized light into the circularly polarized light in the opposite turning direction.
  • the polarization diffractive element 20 is a polarization diffractive lens having a lens function of condensing light by diffracting circularly polarized light.
  • the second circular polarizing plate 26 transmits the light diffracted by the polarizing diffraction element 20 and absorbs the light that has not been diffracted.
  • the second circular polarizing plate 26 converts the circular polarization diffracted by the polarizing diffraction element 20 into linear polarization by the second retardation plate 22, and the second linear polarizing plate 24 converts the circular polarization into linear polarization.
  • the polarized light diffracted by the polarization diffractometer 20 is transmitted and the undiffused light is absorbed. ..
  • the polarized diffraction element 20 and the image display device are used. 52 is arranged so as to satisfy d ⁇ f.
  • the image display unit 10 when the image display device 52 emits light (image), the light passes through the first circular polarizing plate 16, the polarizing diffraction element 20, and the second circular polarizing plate 26, and is used. It is emitted toward the person U. At that time, the light emitted from the image display device 52 is focused on the position of the eye of the user U by the polarization diffractive element 20. As shown in FIG. 3, when the distance d between the polarizing diffraction element 20 and the image display device 52 is equal to or less than the focal length f of the polarizing diffraction element 20, the image display unit 10 displays an image to the user U in a distant virtual image. Visualize as VI.
  • the unpolarized light emitted from the image display device 52 is transmitted only by a predetermined linearly polarized light component by the first linear polarizing plate 12.
  • the first linear polarizing plate 12 transmits a linear polarization component perpendicular to the paper surface of FIG.
  • the linearly polarized light transmitted through the first linearly polarizing plate 12 is incident on the first retardation plate 14 and converted into right-handed circularly polarized light.
  • the right-handed circularly polarized light converted by the first retardation plate 14 is incident on the polarizing diffraction element 20 and diffracted.
  • the right circularly polarized light is converted to the left circularly polarized light.
  • the left circular polarization diffracted by the polarization diffractive element 20 is converted into linear polarization in the vertical direction in the figure by the second retardation plate 22.
  • the linearly polarized light converted by the second retardation plate 22 is transmitted through the second linear polarizing plate 24 and emitted.
  • the polarization diffractive element 20 since it is difficult to set the diffraction efficiency by the polarization diffractive element 20 to 100%, as shown by the arrow of the broken line in FIG. 2, a part of the right circular polarization incident on the polarization diffractive element 20 is not diffracted. It passes through the polarization diffractive element 20. In the absence of the second circular polarizing plate 26, the right circular polarization not diffracted by the polarization diffractive element 20 is emitted from the image display unit 10 and visually recognized by the user U. This right-handed circularly polarized image is visually recognized as a real image because it is not focused. Therefore, since the real image is superimposed on the virtual image and visually recognized by the user U, the image quality of the virtual image to be displayed deteriorates.
  • the image display unit 10 of the present invention has a second circular polarizing plate 26.
  • the right circular polarization that is, 0th-order light
  • the polarization diffractive element 20 is incident on the second retardation plate 22 of the second circular polarizing plate 26. It is converted into linear polarization in the direction perpendicular to the paper surface of FIG. 2, is incident on the second linear polarizing plate 24, and is absorbed. That is, the right circularly polarized light that has not been diffracted by the polarization diffractive element 20 is absorbed by the second circularly polarizing plate 26.
  • the image display unit 10 of the present invention uses a polarization diffraction element 20 that diffracts polarization as a lens. Therefore, since the polarization diffractive element 20 does not have a groove structure or the like, scattering and light streaks due to the groove structure do not occur, and the image quality does not deteriorate due to this.
  • the image display unit that uses the half mirror and the reflected reflector to reciprocate the light between the half mirror and the reflected deflector to lengthen the optical path length
  • about 50 of the light incident on the half mirror is used.
  • the half mirror reflects about 50% of the light transmitted through the half mirror and reflected by the reflected polarizing element, and this light is emitted from the image display unit. Therefore, the image display unit has a problem that the utilization efficiency of light with respect to the amount of light of the image emitted by the image display device is as low as about 25%.
  • the image display unit 10 of the present invention uses a polarization diffraction element 20 that diffracts polarization as a lens. Therefore, it is possible to increase the efficiency of light utilization with respect to the amount of light of the image emitted by the image display device 52.
  • the image display device 52 is assumed to emit unpolarized light, and the first circular polarizing plate 16 is provided between the image display device 52 and the polarizing diffraction element 20. Not limited to.
  • FIG. 3 is a partially enlarged view conceptually showing another example of the image display unit of the present invention.
  • the image display unit 10b shown in FIG. 3 includes an image display device 52b, a first retardation plate 14, a polarizing diffraction element 20, and a second circular polarizing plate 26.
  • the second circular polarizing plate 26 has a second linear polarizing plate 24 and a second retardation plate 22.
  • the second circular polarizing plate 26 is the polarizing plate in the present invention.
  • the image display device 52b emits linearly polarized light as an image. Further, the first retardation plate 14 converts the linearly polarized light emitted by the image display device 52b into circularly polarized light.
  • the polarized diffraction element 20 and the second circular polarizing plate 26 have the same configurations as the polarized diffraction element 20 and the second circular polarizing plate 26 of the image display unit 10 shown in FIG. 1. Further, the polarization diffraction element 20 and the image display device 52 are arranged so as to satisfy d ⁇ f.
  • the image display device 52b When the image display device 52b emits linearly polarized light (image) in the image display unit 10b, the light passes through the first retardation plate 14, the polarizing diffraction element 20, and the second circular polarizing plate 26. It is emitted toward the user U. At that time, the light emitted from the image display device 52b is focused on the position of the eye of the user U by the polarization diffractive element 20. Since the distance d between the polarizing diffraction element 20 and the image display device 52b is equal to or less than the focal length f of the polarizing diffraction element 20, the image display unit 10b causes the user U to visually recognize the image as a distant virtual image.
  • the image display device 52b emits linearly polarized light in the direction perpendicular to the paper surface of FIG.
  • the linearly polarized light emitted from the image display device 52b is incident on the first retardation plate 14 and converted into right-handed circularly polarized light.
  • the right-handed circularly polarized light converted by the first retardation plate 14 is incident on the polarizing diffraction element 20 and diffracted.
  • the right circularly polarized light is converted to the left circularly polarized light.
  • the left circular polarization diffracted by the polarization diffractive element 20 is converted into linear polarization in the vertical direction in the figure by the second retardation plate 22.
  • the linearly polarized light converted by the second retardation plate 22 is transmitted through the second linear polarizing plate 24 and emitted.
  • the right circular polarization (that is, 0th-order light) not diffracted by the polarization diffractive element 20 is incident on the second retardation plate 22 of the second circular polarizing plate 26 and is in the direction perpendicular to the paper surface of FIG. Is converted into linearly polarized light, and is incident on and absorbed by the second linear polarizing plate 24. That is, the right circularly polarized light that has not been diffracted by the polarization diffractive element 20 is absorbed by the second circularly polarizing plate 26. Therefore, only the virtual image due to the left circularly polarized light is visually recognized by the user U, and the undiffracted right circularly polarized light is not visually recognized. Therefore, it is possible to prevent the image quality of the virtual image displayed by the image display unit 10 from deteriorating.
  • the polarizing diffractive element 20 is assumed to diffract circularly polarized light, but the present invention is not limited to this.
  • the polarization diffraction element may be a polarization diffraction lens that diffracts linearly polarized light.
  • the polarized light diffusing element is a polarized light diffusing lens that diffracts linearly polarized light
  • the linearly polarized light diffracted by the polarized light diffusing element is transmitted, and the linear polarization element is not diffracted.
  • a linear polarizing plate that absorbs polarized light may be arranged. In such a configuration, this linear polarizing plate corresponds to the polarizing plate in the present invention.
  • the polarization diffusing element is a polarization diffractive lens that diffracts linear polarization
  • a linear polarizing plate is inserted between the image display device and the polarization diffractive element. If the image display device emits linearly polarized light, a linear polarizing plate, a retardation plate, or the like may not be arranged between the image display device and the polarization diffractive element.
  • the first retardation plate 14 is preferably a ⁇ / 4 plate from the viewpoint of converting the incident linear polarization into circular polarization. Since the image display device basically emits visible light, the first retardation plate 14 may be a ⁇ / 4 plate with respect to the wavelength in the visible light region. Further, when the light incident on the first retardation plate 14 is elliptically polarized light, the first retardation plate 14 has a phase difference that converts the incident light into circularly polarized light. good.
  • the second retardation plate 22 is preferably a ⁇ / 4 plate from the viewpoint of converting the incident circular polarization into linear polarization.
  • the second retardation plate 22 may be a ⁇ / 4 plate with respect to the wavelength in the visible light region.
  • the focal length f of the polarizing diffraction element is preferably less than 40 mm, more preferably 1 mm or more and 30 mm or less, and more preferably 3 mm or more. It is more preferably 15 mm or less.
  • the distance d between the image display system and the polarized diffraction element may be equal to or less than the focal length f of the polarized diffraction element, and from the viewpoint of displaying the virtual image in the distance, the distance d may be used.
  • the ratio d / f to the focal length f is preferably in the range of 0.8 to 1, more preferably in the range of 0.9 to 1, and preferably in the range of 0.95 to 1. More preferred.
  • the image display device illuminates an image (still image or moving image) displayed by the image display system.
  • the image display device is not limited, and for example, various known displays used for head-mounted displays and the like can be used. Examples of displays include liquid crystal displays (LCOS: including Liquid Crystal On Silicon), organic electroluminescence displays, and scanning display using DLP (Digital Light Processing) and MEMS (Micro Electro Mechanical Systems) mirrors. Is exemplified.
  • LCOS liquid crystal displays
  • organic electroluminescence displays organic electroluminescence displays
  • DLP Digital Light Processing
  • MEMS Micro Electro Mechanical Systems
  • the image display device may be a display that displays a monochromatic image or a display that displays a multicolor image.
  • the light emitted by the image display device may be unpolarized or linearly polarized.
  • the first and second linear polarizing plates are not particularly limited as long as they are linear polarizing plates having a function of transmitting linear polarization in one polarization direction and absorbing linear polarization in the other polarization direction, and are conventionally known straight lines.
  • a polarizing plate can be used.
  • the linear polarizing plate may be an absorption type linear polarizing plate or a reflection type linear polarizing plate.
  • an iodine-based polarizing element which is an absorption-type polarizing element, a dye-based polarizing element using a dichroic dye, a polyene-based polarizing element, and the like are used.
  • Iodine-based splitters and dye-based splitters include coated and stretched splitters, both of which can be applied.
  • a polarizing element produced by adsorbing iodine or a dichroic dye on polyvinyl alcohol and stretching it is preferable.
  • the absorption type polarizing element a splitter in which the dichroic dye is oriented by utilizing the orientation of the liquid crystal without stretching is particularly preferable.
  • the polarizing element has a very thin layer thickness of about 0.1 ⁇ m to 5 ⁇ m, is less likely to crack when bent as described in Japanese Patent Application Laid-Open No. 2019-194685, and has small thermal deformation. As described in Japanese Patent No.
  • a polarizing plate having a high transmittance of more than 50% has many advantages such as excellent durability and excellent heat moldability. Taking advantage of these advantages, it can be used for applications that require high brightness, small size and light weight, fine optical system applications, molding applications for parts having curved surfaces, and applications for flexible parts. It is also possible to peel off the support and transfer the polarizing element for use. It is also preferable to incorporate an absorption type polarizing element for the purpose of suppressing stray light in an in-vehicle display optical system such as a head-up display, an optical system such as AR glasses and VR glasses, an optical sensor such as LiDAR, a face recognition system, and polarization imaging.
  • an absorption type polarizing element for the purpose of suppressing stray light in an in-vehicle display optical system such as a head-up display, an optical system such as AR glasses and VR glasses, an optical sensor such as LiDAR, a face recognition system, and polarization imaging.
  • the reflective linear polarizing plate a film in which a layer containing two kinds of polymers is stretched, a wire grid splitter, or the like as described in JP-A-2011-053705 can be used. From the viewpoint of brightness, a film in which a layer containing a polymer is stretched is preferable.
  • a reflective splitter (trade name: APF) manufactured by 3M
  • a wire grid splitter (trade name: WGF) manufactured by Asahi Kasei Corporation, or the like can be preferably used.
  • a reflective linear polarizing plate in which a cholesteric liquid crystal film and a ⁇ / 4 plate are combined may be used.
  • the polarizing plate used in the present invention preferably has a smooth surface.
  • the average arithmetic roughness Ra of the surface is preferably 50 nm or less, more preferably 30 nm or less, further preferably 10 nm or less, and most preferably 5 nm or less.
  • the height difference of the surface unevenness within the range of 1 square millimeter is preferably 100 nm or less, more preferably 50 nm or less, and most preferably 20 nm or less.
  • Surface roughness and average arithmetic roughness can be measured using a roughness meter or an interferometer. For example, it can be measured using an interferometer "vertscan" manufactured by Ryoka System Co., Ltd.
  • the first and second phase difference plates are phase difference plates that convert the phase of the incident polarization.
  • the retardation plate is arranged by adjusting the direction of the slow phase axis depending on whether the incident polarization is converted to be closer to linear polarization or to be closer to circular polarization.
  • the retardation plate may be arranged so that the slow phase axis is + 45 ° or ⁇ 45 ° with respect to the transmission axis of the linear polarizing plate arranged adjacent to each other.
  • the retardation plate used in the present invention may be a single-layer type composed of one optically anisotropic layer, or may be composed of a stack of two or more optically anisotropic layers each having a plurality of different slow phase axes.
  • a multi-layer type is also good. Examples of the multi-layer type retardation plate are WO13 / 137464, WO2016 / 158300, JP-A-2014-209219, JP-A-2014-209220, WO14 / 157079, JP-A-2019-215416. Publication No., WO2019 / 16041, but not limited to this.
  • the retardation plate is preferably a ⁇ / 4 plate.
  • ⁇ / 4 plate there is no limitation on the ⁇ / 4 plate, and various known plates having a ⁇ / 4 function can be used. Specific examples of the ⁇ / 4 plate include those described in US Patent Application Publication No. 2015/0277006.
  • the ⁇ / 4 plate has a single-layer structure
  • a stretched polymer film a retardation film in which an optically anisotropic layer having a ⁇ / 4 function is provided on a support, and the like are used.
  • the ⁇ / 4 plate has a multi-layer structure
  • a wide band ⁇ / 4 plate formed by laminating a ⁇ / 4 plate and a ⁇ / 2 wavelength plate can be specifically mentioned.
  • the thickness of the ⁇ / 4 plate is not particularly limited, but is preferably 1 to 500 ⁇ m, more preferably 1 to 50 ⁇ m, and even more preferably 1 to 5 ⁇ m.
  • the retardation plate used in the present invention preferably has a reverse wavelength dispersibility. Having the inverse wavelength dispersibility makes the phase change in the phase difference plate ideal, and the conversion between linearly polarized light and circularly polarized light becomes ideal.
  • the polarization diffractive element is a polarization diffractive lens having a lens function of diffracting polarized light and condensing the diffracted polarized light.
  • the polarizing diffraction element may be one that diffracts linearly polarized light or one that diffracts circularly polarized light.
  • Examples of the polarizing diffraction element that diffracts circularly polarized light include a liquid crystal diffraction element.
  • FIG. 5 shows a conceptual diagram of a positive lens using a liquid crystal diffractive element.
  • FIG. 5 is a plan view conceptually showing the liquid crystal layer of the liquid crystal diffractive element.
  • the liquid crystal diffractometer has a liquid crystal layer having a predetermined liquid crystal orientation pattern in which the optical axis derived from the liquid crystal compound is rotated, which is formed by using the composition containing the liquid crystal compound.
  • the liquid crystal alignment pattern of the liquid crystal layer 36 has one direction in which the direction of the optical axis of the liquid crystal compound 40 changes while continuously rotating, concentrically from the inside to the outside. It is a pattern.
  • the concentric pattern is a pattern in which the lines connecting the liquid crystal compounds whose optical axes are oriented in the same direction are circular, and the circular line segments are concentric.
  • one direction in which the direction of the optical axis of the liquid crystal compound 40 changes while continuously rotating is provided radially from the center of the liquid crystal layer 36. It is a pattern.
  • the optical axis of the liquid crystal compound 40 (not shown) is the longitudinal direction of the liquid crystal compound 40.
  • the direction of the optical axis of the liquid crystal compound 40 is a number of directions from the center of the liquid crystal layer 36 to the outside, for example, the direction indicated by arrow A 1 , the direction indicated by arrow A 2 , and the direction indicated by arrow A 3 . It is changing while continuously rotating along the ... Arrows A 1 , arrow A 2 , and arrow A 3 are array axes, which will be described later.
  • the liquid crystal layer 36 of the liquid crystal diffractive element has a region in which one cycle ⁇ of the liquid crystal orientation pattern is different in the plane.
  • one cycle ⁇ of the liquid crystal alignment pattern is the length of the liquid crystal alignment pattern in which the optical axis of the liquid crystal compound 40 rotates 180 ° in one direction in which the direction of the optical axis continuously rotates and changes in the plane. It is (distance). Specifically, in the example shown in FIG. 5, in each direction in which the direction of the optical axis of the liquid crystal compound 40 changes while continuously rotating, one cycle ⁇ gradually shortens from the center to the outside. Has.
  • the diffraction angle by the liquid crystal diffractive element depends on the one cycle ⁇ of the liquid crystal alignment pattern, and the shorter the one cycle ⁇ , the larger the diffraction angle.
  • the liquid crystal layer 36 is provided radially from the center of the liquid crystal layer 36 in one direction in which the liquid crystal orientation pattern changes while the direction of the optical axis of the liquid crystal compound 40 continuously rotates, and is provided from the center to the outside in each direction.
  • the circular polarization incident on the liquid crystal layer 36 having this liquid crystal alignment pattern is caused by individual local areas in which the directions of the optical axes of the liquid crystal compound 40 are different.
  • the absolute phase changes in each region. At this time, the amount of change in each absolute phase differs depending on the direction of the optical axis of the liquid crystal compound 40 to which the circularly polarized light is incident.
  • each diffraction angle differs depending on one cycle in the region where the circularly polarized light is incident.
  • the liquid crystal layer 36 having a concentric liquid crystal alignment pattern that is, a liquid crystal alignment pattern in which the optical axis continuously rotates and changes radially, depends on the rotation direction of the optical axis of the liquid crystal compound 40 and the direction of incident circular polarization. Therefore, the incident light can be transmitted as focused light. That is, by making the liquid crystal alignment pattern of the liquid crystal layer concentric, the liquid crystal diffractive element exhibits a function as, for example, a convex lens.
  • FIG. 6 is a conceptual diagram of a locally viewed cross section of the liquid crystal layer 36 along one direction in which the direction of the optical axis 40A of the liquid crystal compound 40 changes while continuously rotating.
  • FIG. 7 is a plan view of FIG.
  • the liquid crystal diffraction element shown in FIG. 6 has a support 30, an alignment film 32, and a liquid crystal layer (hereinafter, also referred to as an optically anisotropic layer) 36.
  • the liquid crystal diffractometer has a liquid crystal layer having a predetermined liquid crystal orientation pattern in which the optical axis derived from the liquid crystal compound is rotated, which is formed by using the composition containing the liquid crystal compound. Further, as will be described later, the liquid crystal layer has regions in which one cycle ⁇ of the liquid crystal orientation pattern is different in the plane.
  • the liquid crystal diffractive element shown in FIG. 6 has a support 30, it is not necessary to provide the support 30.
  • the optical element of the present invention comprises the optical element of the present invention by peeling off the support 30 from the above configuration and using only the alignment film and the liquid crystal layer, or by peeling off the alignment film and using only the liquid crystal layer. You may.
  • liquid crystal diffusing element various layer configurations can be used as long as the liquid crystal layer has a liquid crystal orientation pattern in which the direction of the optical axis derived from the liquid crystal compound rotates in one direction.
  • the support 30 supports the alignment film 32 and the liquid crystal layer 36.
  • the support 30 various sheet-like materials (films, plate-like materials) can be used as long as they can support the alignment film and the liquid crystal layer.
  • a transparent support is preferable, and a polyacrylic resin film such as polymethylmethacrylate, a cellulose resin film such as cellulose triacetate, and a cycloolefin polymer film (for example, trade name "Arton", manufactured by JSR Corporation). Examples thereof include trade name "Zeonoa” (manufactured by Nippon Zeon Co., Ltd.), polyethylene terephthalate (PET), polycarbonate, and polyvinyl chloride.
  • the support is not limited to the flexible film, but may be a non-flexible substrate such as a glass substrate.
  • the support 30 may be a multi-layered support, and the multi-layered support includes one of the above-mentioned supports or the like as a substrate, and the surface of the substrate is provided with another layer or the like. Illustrated.
  • the thickness of the support 30 is not limited, and the thickness capable of holding the alignment film and the liquid crystal layer may be appropriately set according to the application of the liquid crystal diffractive element, the material for forming the support 30, and the like.
  • the thickness of the support 30 is preferably 1 to 1000 ⁇ m, more preferably 3 to 500 ⁇ m, still more preferably 5 to 250 ⁇ m.
  • the alignment film 32 is formed on the surface of the support 30.
  • the alignment film 32 is an alignment film for orienting the liquid crystal compound 40 in a predetermined liquid crystal alignment pattern when forming the liquid crystal layer 36 of the liquid crystal diffractive element.
  • the direction of the optical axis 40A (see FIG. 7) derived from the liquid crystal compound 40 is continuously along one direction in the plane (the direction of the arrangement axis D described later). It has a liquid crystal orientation pattern that changes while rotating. Therefore, the alignment film of the liquid crystal diffractive element is formed so that the liquid crystal layer can form this liquid crystal alignment pattern. Further, in the liquid crystal alignment pattern, the length in which the direction of the optical axis 40A rotates 180 ° in one direction in which the direction of the optical axis 40A changes while continuously rotating is defined as one cycle ⁇ (rotation cycle of the optical axis). ..
  • the direction of the optic axis 40A rotates is also simply referred to as “the optical axis 40A rotates”.
  • a rubbing-treated film made of an organic compound such as a polymer an oblique vapor deposition film of an inorganic compound, a film having a microgroove, and Langmuir of an organic compound such as ⁇ -tricosanoic acid, dioctadecylmethylammonium chloride and methyl stearylate.
  • an organic compound such as ⁇ -tricosanoic acid, dioctadecylmethylammonium chloride and methyl stearylate.
  • Examples thereof include a membrane obtained by accumulating LB (Langmuir-Blodgett) membranes produced by the Brodget method.
  • the alignment film by the rubbing treatment can be formed by rubbing the surface of the polymer layer with paper or cloth several times in a certain direction.
  • Materials 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 JP-A-2005-99228.
  • the materials used for forming the alignment film and the like described in JP-A-2005-128503 are preferably exemplified.
  • a so-called photo-alignment film in which a photo-alignable material is irradiated with polarized or non-polarized material to form an alignment film, is preferably used as the alignment film. That is, in the liquid crystal diffractive element, as the alignment film, a photoalignment film formed by applying a photoalignment material on the support 30 is preferably used. Polarized irradiation can be performed from a vertical direction or an oblique direction with respect to the photoalignment film, and non-polarized irradiation can be performed from an oblique direction with respect to the photoalignment film.
  • Examples of the photo-alignment material used for the photo-alignment film that can be used in the present invention include JP-A-2006-285197, JP-A-2007-76839, JP-A-2007-138138, and JP-A-2007-94071. JP-A-2007-121721, JP-A-2007-140465, JP-A-2007-156439, JP-A-2007-133184, JP-A-2009-109831, Patent No. 3883848 and Patent No.
  • Photodimrizable compounds described in Japanese Patent Application Laid-Open No. 2013-177561 and Japanese Patent Application Laid-Open No. 2014-12823, particularly cinnamate compounds, chalcone compounds, coumarin compounds and the like are exemplified as preferable examples.
  • azo compounds, photocrosslinkable polyimides, photocrosslinkable polyamides, photocrosslinkable esters, cinnamate compounds, and chalcone compounds are preferably used.
  • the thickness of the alignment film is not limited, and the thickness at which the required alignment function can be obtained may be appropriately set according to the material for forming the alignment film.
  • the thickness of the alignment film is preferably 0.01 to 5 ⁇ m, more preferably 0.05 to 2 ⁇ m.
  • the method for forming the alignment film there is no limitation on the method for forming the alignment film, and various known methods depending on the material for forming the alignment film can be used. As an example, a method of applying an alignment film to the surface of the support 30 and drying the alignment film and then exposing the alignment film with a laser beam to form an alignment pattern is exemplified.
  • FIG. 8 conceptually shows an example of an exposure apparatus that forms a concentric alignment pattern on the alignment film.
  • the exposure apparatus 80 includes a light source 84 provided with a laser 82, a polarization beam splitter 86 that splits the laser beam M from the laser 82 into an S-polarized MS and a P-polarized MP, and a mirror 90A arranged in the optical path of the P-polarized MP. It also has a mirror 90B arranged in the optical path of the S-polarized MS, a lens 92 arranged in the optical path of the S-polarized MS, a polarizing beam splitter 94, and a ⁇ / 4 plate 96.
  • the P-polarized MP divided by the polarizing beam splitter 86 is reflected by the mirror 90A and incident on the polarizing beam splitter 94.
  • the S-polarized MS divided by the polarizing beam splitter 86 is reflected by the mirror 90B, condensed by the lens 92, and incident on the polarized beam splitter 94.
  • the P-polarized MP and the S-polarized MS are combined by a polarizing beam splitter 94 and become right-handed circularly polarized light and left-handed circularly polarized light according to the polarization direction by the ⁇ / 4 plate 96, and the alignment film 32 on the support 30 is formed. Incident to.
  • the polarization state of the light applied to the alignment film changes periodically in the form of interference fringes. Since the intersection angle of the left circular polarization and the right circular polarization changes from the inside to the outside of the concentric circles, an exposure pattern in which the pitch changes from the inside to the outside can be obtained. As a result, in the alignment film, a concentric alignment pattern in which the alignment state changes periodically can be obtained.
  • one cycle ⁇ of the liquid crystal alignment pattern in which the optical axis of the liquid crystal compound 40 continuously rotates 180 ° along one direction is the focal length of the lens 92 (F number of the lens 92) and the focal length of the lens 92. It can be controlled by changing the distance, the distance between the lens 92 and the alignment film 32, and the like. Further, by adjusting the refractive power of the lens 92 (F number of the lens 92), the length ⁇ of one cycle of the liquid crystal alignment pattern can be changed in one direction in which the optical axis rotates continuously.
  • the length ⁇ of one cycle of the liquid crystal alignment pattern can be changed in one direction in which the optical axis continuously rotates by the spreading angle of the light spread by the lens 92 that interferes with the parallel light. More specifically, when the refractive power of the lens 92 is weakened, it approaches parallel light, so that the length ⁇ of one cycle of the liquid crystal alignment pattern gradually shortens from the inside to the outside, and the F number becomes large. On the contrary, when the refractive power of the lens 92 is increased, the length ⁇ of one cycle of the liquid crystal alignment pattern suddenly shortens from the inside to the outside, and the F number becomes small.
  • the direction of the optical axis of the liquid crystal compound in the liquid crystal layer formed on the pattern alignment film is at least one in the plane. It has an orientation pattern that orients the liquid crystal compound so that the liquid crystal alignment pattern changes while continuously rotating along the direction.
  • the pattern alignment film has an axis along the direction in which the liquid crystal compound is oriented as the alignment axis
  • the pattern alignment film changes while the orientation of the alignment axis continuously rotates along at least one direction in the plane. It can be said that it has an orientation pattern.
  • the alignment axis of the pattern alignment film can be detected by measuring the absorption anisotropy. For example, when the pattern alignment film is irradiated while rotating linearly polarized light and the amount of light transmitted through the pattern alignment film is measured, the direction in which the amount of light is maximum or minimum is gradually along one direction in the plane. It changes and is observed.
  • the alignment film is provided as a preferred embodiment and is not an indispensable constituent requirement.
  • the liquid crystal layer 36 or the like is optically derived from the liquid crystal compound 40. It is also possible to have a liquid crystal orientation pattern in which the orientation of the axis 40A changes while continuously rotating along at least one direction in the plane.
  • the liquid crystal layer 36 is formed on the surface of the alignment film 32.
  • the liquid crystal layer 36 shows only the liquid crystal compound 40 (liquid crystal compound molecule) on the surface of the alignment film. ing.
  • the liquid crystal layer 36 is the oriented liquid crystal compound 40 in the same manner as the liquid crystal layer formed by using a composition containing a normal liquid crystal compound. Have a structure stacked in the thickness direction.
  • the liquid crystal layer 36 is formed by using a composition containing a liquid crystal compound.
  • the liquid crystal layer functions as a general ⁇ / 2 plate, that is, two linearly polarized components orthogonal to each other contained in the light incident on the liquid crystal layer. It has a function of giving a phase difference of half wavelength, that is, 180 °.
  • the liquid crystal compound is rotated and oriented in the plane direction, the liquid crystal layer is transmitted by refracting (diffracting) the incident circular polarization in the direction in which the direction of the optical axis is continuously rotating.
  • the direction of diffraction differs depending on the turning direction of the incident circularly polarized light. That is, the liquid crystal layer transmits circularly polarized light and diffracts the transmitted light. Further, the liquid crystal layer changes the turning direction of the transmitted circularly polarized light in the opposite direction.
  • the liquid crystal layer has a liquid crystal orientation pattern in which the orientation of the optical axis derived from the liquid crystal compound changes while continuously rotating in one direction indicated by the arrangement axis D in the plane of the liquid crystal layer.
  • the optical axis 40A derived from the liquid crystal compound 40 is a so-called slow-phase axis having the highest refractive index in the liquid crystal compound 40.
  • the optical axis 40A is along the long axis direction of the rod shape.
  • array axis D direction is also simply referred to as "array axis D direction”.
  • each of the liquid crystal compounds 40 is two-dimensionally oriented in the liquid crystal layer in a plane parallel to the arrangement axis D direction and the Y direction orthogonal to the arrangement axis D direction.
  • the Y direction is a direction perpendicular to the paper surface.
  • FIG. 7 conceptually shows a plan view of the liquid crystal layer 36.
  • the liquid crystal compound 40 shows only the liquid crystal compound 40 on the surface of the alignment film 32.
  • the liquid crystal layer 36 has a structure in which the liquid crystal compound 40 is stacked from the liquid crystal compound 40 on the surface of the alignment film 32, as shown in FIG. 6 in the thickness direction. be.
  • the length of one cycle (one cycle ⁇ ) of the liquid crystal alignment pattern is different in each region of the liquid crystal layer. Other than that, it basically has the same configuration and action.
  • the liquid crystal layer 36 has a liquid crystal alignment pattern in which the orientation of the optical axis 40A derived from the liquid crystal compound 40 changes while continuously rotating along the arrangement axis D direction in the plane of the liquid crystal layer 36.
  • the fact that the orientation of the optical axis 40A of the liquid crystal compound 40 changes while continuously rotating in the array axis D direction is specifically arranged along the array axis D direction.
  • the angle formed by the optical axis 40A of the liquid crystal compound 40 and the arrangement axis D direction differs depending on the position in the arrangement axis D direction, and the angle formed by the optical axis 40A and the arrangement axis D direction along the arrangement axis D direction.
  • the difference in the angles of the optical axes 40A of the liquid crystal compounds 40 adjacent to each other in the arrangement axis D direction is preferably 45 ° or less, more preferably 15 ° or less, and further preferably a smaller angle. preferable.
  • the liquid crystal compound 40 forming the liquid crystal layer 36 is a liquid crystal having the same optical axis 40A in the Y direction orthogonal to the arrangement axis D direction, that is, in the Y direction orthogonal to one direction in which the optical axis 40A continuously rotates.
  • the compounds 40 are evenly spaced.
  • the angles formed by the direction of the optical axis 40A and the direction of the arrangement axis D are the same among the liquid crystal compounds 40 arranged in the Y direction.
  • the optical axis 40A of the liquid crystal compound 40 is 180 in the arrangement axis D direction in which the direction of the optical axis 40A continuously rotates and changes in the plane.
  • the length of rotation (distance) be the length ⁇ of one cycle in the liquid crystal alignment pattern.
  • the length of one cycle in the liquid crystal alignment pattern is defined by the distance from ⁇ to ⁇ + 180 ° between the optical axis 40A of the liquid crystal compound 40 and the arrangement axis D direction.
  • the distance between the centers of the two liquid crystal compounds 40 having the same angle with respect to the array axis D direction in the array axis D direction is defined as the length ⁇ of one cycle.
  • the distance between the centers of the two liquid crystal compounds 40 in which the direction of the arrangement axis D and the direction of the optical axis 40A coincide with each other in the direction of the arrangement axis D is the length ⁇ of one cycle.
  • the length ⁇ of this one cycle is also referred to as "one cycle ⁇ ".
  • the liquid crystal alignment pattern of the liquid crystal layer repeats this one cycle ⁇ in the direction of the array axis D, that is, in one direction in which the direction of the optical axis 40A continuously rotates and changes.
  • the liquid crystal compounds arranged in the Y direction have the same angle formed by the optical axis 40A and the arrangement axis D direction (one direction in which the direction of the optical axis of the liquid crystal compound 40 rotates).
  • the region in which the liquid crystal compound 40 having the same angle formed by the optical axis 40A and the arrangement axis D direction is arranged in the Y direction is defined as a region R.
  • the value of the in-plane retardation (Re) in each region R is preferably half wavelength, that is, ⁇ / 2.
  • the difference in refractive index due to the refractive index anisotropy of the region R in the liquid crystal layer is the refractive index in the direction of the slow axis in the plane of the region R and the refractive index in the direction orthogonal to the direction of the slow axis.
  • the incident light L 1 When incident, the incident light L 1 is given a phase difference of 180 ° by passing through the liquid crystal layer 36, and the transmitted light L 2 is converted into right circular polarization. Further, since the liquid crystal alignment pattern formed on the liquid crystal layer 36 is a periodic pattern in the arrangement axis D direction, the transmitted light L 2 travels in a direction different from the traveling direction of the incident light L 1 . In this way, the incident light L 1 polarized in the left circle is converted into the transmitted light L 2 polarized in the right circle, which is tilted by a certain angle in the direction of the array axis D with respect to the incident direction.
  • the incident light L 4 of right circular polarization is transmitted to the liquid crystal layer 36.
  • the incident light L 4 passes through the liquid crystal layer 36, is given a phase difference of 180 °, and is converted into the transmitted light L 5 of left circular polarization.
  • the liquid crystal alignment pattern formed on the liquid crystal layer 36 is a periodic pattern in the arrangement axis D direction, the transmitted light L 5 travels in a direction different from the traveling direction of the incident light L 4 .
  • the transmitted light L 5 travels in a direction different from that of the transmitted light L 2 , that is, in a direction opposite to the direction of the array axis D with respect to the incident direction.
  • the incident light L 4 is converted into the transmitted light L 5 of left circularly polarized light tilted by a certain angle in the direction opposite to the direction of the array axis D with respect to the incident direction.
  • the liquid crystal layer 36 can adjust the angle of refraction of the transmitted lights L 2 and L 5 by changing one cycle ⁇ of the formed liquid crystal alignment pattern. Specifically, in the liquid crystal layer 36, the shorter one cycle ⁇ of the liquid crystal orientation pattern, the stronger the interference between the lights that have passed through the liquid crystal compounds 40 adjacent to each other, so that the transmitted lights L 2 and L 5 are greatly refracted. Can be done. Further, by making the rotation direction of the optical axis 40A of the liquid crystal compound 40, which rotates along the arrangement axis D direction, the opposite direction, the refraction direction of the transmitted light can be made in the opposite direction. That is, in the examples shown in FIGS. 9 to 10, the rotation direction of the optical axis 40A toward the arrangement axis D direction is clockwise, but by making this rotation direction counterclockwise, the refraction direction of the transmitted light can be changed. , Can be done in the opposite direction.
  • ⁇ n 550 is the refractive index difference due to the refractive index anisotropy of the region R when the wavelength of the incident light is 550 nm
  • d is the thickness of the liquid crystal layer 36. 200 nm ⁇ ⁇ n 550 ⁇ d ⁇ 350 nm ...
  • the in-plane retardation Re (550) ⁇ n 550 ⁇ d of the plurality of regions R of the liquid crystal layer 36 satisfies the equation (1), a sufficient amount of circularly polarized light components of the light incident on the liquid crystal layer 36 can be obtained. , Can be converted into circular polarization traveling in a direction inclined in the forward direction or the opposite direction with respect to the arrangement axis D direction.
  • the in-plane retardation Re (450) ⁇ n 450 ⁇ d of the region R of the liquid crystal layer 36 with respect to the incident light having a wavelength of 450 nm and the in-plane of each region R of the liquid crystal layer 36 with respect to the incident light having a wavelength of 550 nm.
  • the retardation Re (550) ⁇ n 550 ⁇ d preferably satisfies the following formula (2).
  • ⁇ n 450 is the difference in refractive index due to the refractive index anisotropy of the region R when the wavelength of the incident light is 450 nm.
  • the formula (2) represents that the liquid crystal compound 40 contained in the liquid crystal layer 36 has reverse dispersibility. That is, when the equation (2) is satisfied, the liquid crystal layer 36 can cope with incident light having a wide band wavelength.
  • the liquid crystal layer is composed of a cured layer of a liquid crystal composition containing a rod-shaped liquid crystal compound or a disk-shaped liquid crystal compound, and the optical axis of the rod-shaped liquid crystal compound or the optical axis of the disk-shaped liquid crystal compound has a liquid crystal orientation pattern oriented as described above.
  • a liquid crystal layer made of a cured layer of the liquid crystal composition can be obtained by forming an alignment film on the support, applying the liquid crystal composition on the alignment film, and curing the liquid crystal composition.
  • the present invention includes an embodiment in which a laminate having a support and an alignment film integrally functions as a ⁇ / 2 plate.
  • the liquid crystal composition for forming the liquid crystal layer contains a rod-shaped liquid crystal compound or a disk-shaped liquid crystal compound, and further contains other components such as a leveling agent, an orientation control agent, a polymerization initiator and an orientation aid. May be.
  • the liquid crystal layer has a wide band with respect to the wavelength of the incident light
  • the liquid crystal layer is formed by using a liquid crystal material having a birefringence of reverse dispersion. It is also preferable to impart a twisting component to the liquid crystal composition and to stack different retardation layers so that the liquid crystal layer has a substantially wide band with respect to the wavelength of the incident light.
  • a method of realizing a wide-band patterned ⁇ / 2 plate by laminating two layers of liquid crystals having different twisting directions is shown in Japanese Patent Application Laid-Open No. 2014-089476 and the like. Can be preferably used in.
  • rod-shaped liquid crystal compound examples include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, and alkoxy-substituted phenylpyrimidines.
  • Phenyldioxans, trans and alkenylcyclohexylbenzonitriles are preferably used. Not only small molecule liquid crystal molecules as described above, but also high molecular weight liquid crystal molecules can be used.
  • the disk-shaped liquid crystal compound for example, those described in JP-A-2007-108732 and JP-A-2010-244033 can be preferably used.
  • the liquid crystal compound 40 rises in the thickness direction in the liquid crystal layer, and the optical axis 40A derived from the liquid crystal compound is an axis perpendicular to the disk surface, so-called. Defined as the phase advance axis.
  • a liquid crystal compound having a high refractive index anisotropy ⁇ n can be preferably used in order to obtain high diffraction efficiency.
  • the liquid crystal compound having a high refractive index anisotropy ⁇ n is not particularly limited, but the compound exemplified in WO2019 / 182129A1 and the compound represented by the following general formula (I) can be preferably used.
  • P 1 and P 2 independently represent a hydrogen atom, -CN, -NCS or a polymerizable group.
  • Sp 1 and Sp 2 each independently represent a single bond or a divalent linking group.
  • Sp 1 and Sp 2 do not represent a divalent linking group containing at least one group selected from the group consisting of aromatic hydrocarbon ring groups, aromatic heterocyclic groups and aliphatic hydrocarbon ring groups. ..
  • Z 1 , Z 2 and Z 3 are independently single-bonded, -O-, -S-, -CHR-, -CHRCHR-, -OCHR-, -CHRO-, -SO-, -SO 2- , respectively.
  • R represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. When there are a plurality of Rs, they may be the same or different. When a plurality of Z 1 and Z 2 are present, they may be the same or different. A plurality of Z3s may be the same or different. However, Z 3 linked to Sp 2 represents a single bond.
  • X 1 and X 2 independently represent a single bond or —S—, respectively.
  • a plurality of X 1 and X 2 may be the same or different from each other. However, at least one of the plurality of X 1 and the plurality of X 2 represents -S-.
  • k represents an integer of 2 to 4.
  • m and n each independently represent an integer of 0 to 3.
  • a plurality of m may be the same or different.
  • a 1 , A 2 , A 3 and A 4 are independently represented by any of the following general formulas (B-1) to (B-7), or the following general formulas (B-1) to A4. Represents a group formed by connecting two or more and three or less groups represented by any one of (B-7).
  • a plurality of A 2 and A 3 may be the same or different from each other. When a plurality of A1 and A4 are present, they may be the same or different.
  • W 1 to W 18 independently represent CR 1 or N, and R 1 represents a hydrogen atom or the following substituent L.
  • R 1 represents a hydrogen atom or the following substituent L.
  • Y 1 to Y 6 independently represent NR 2 , O or S, and R 2 represents a hydrogen atom or the following substituent L.
  • G 1 to G 4 independently represent CR 3 R 4 , NR 5 , O or S, and R 3 to R 5 independently represent a hydrogen atom or the following substituent L, respectively.
  • M 1 and M 2 independently represent CR 6 or N, respectively, and R 6 represents a hydrogen atom or the following substituent L. * Represents the bond position.
  • the substituent L is an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an alkylamino group having 1 to 10 carbon atoms, an alkylthio group having 1 to 10 carbon atoms, and 1 carbon atom number.
  • alkanoyl groups alkanoyloxy groups with 1 to 10 carbon atoms, alkanoylamino groups with 1 to 10 carbon atoms, alkanoylthio groups with 1 to 10 carbon atoms, alkyloxycarbonyl groups with 2 to 10 carbon atoms , Alkylaminocarbonyl group with 2 to 10 carbon atoms, alkylthiocarbonyl group with 2 to 10 carbon atoms, hydroxy group, amino group, mercapto group, carboxy group, sulfo group, amide group, cyano group, nitro group, halogen atom Or it is a polymerizable group.
  • the above-mentioned group described as the substituent L has -CH 2-
  • a group substituted with ⁇ C ⁇ is also included in the substituent L.
  • the group described as the substituent L has a hydrogen atom
  • at least one of the hydrogen atoms contained in the group is replaced with at least one selected from the group consisting of a fluorine atom and a polymerizable group.
  • the group is also included in the substituent L.
  • the refractive index anisotropy ⁇ n 550 of the liquid crystal compound is preferably 0.15 or more, more preferably 0.2 or more, further preferably 0.25 or more, and 0. .3 or more is the most preferable.
  • FIG. 11 is a conceptual diagram showing a part of a cross section of the liquid crystal layer 36 along one direction in which the direction of the optical axis 40A of the liquid crystal compound 40 changes while continuously rotating.
  • the liquid crystal diffractive element it is basically only the liquid crystal layer that exhibits the optical action. Therefore, in order to simplify the drawing and clearly show the configuration and the effect, in FIG. 11, the liquid crystal diffractive element shows only the liquid crystal layer 36.
  • the liquid crystal diffractive element has a liquid crystal layer 36.
  • the liquid crystal diffractometer targets circularly polarized light and refracts incident light in a predetermined direction to transmit it. In FIG. 11, the incident light is left circularly polarized.
  • the liquid crystal layer 36 has three regions A0, A1, and A2 from the left side in FIG. 11, and the length ⁇ of one cycle is different in each region. Specifically, the length ⁇ of one cycle is shortened in the order of regions A0, A1, and A2. Further, the regions A1 and A2 have a structure in which the optical axis is twisted and rotated in the thickness direction of the liquid crystal layer (hereinafter, also referred to as a twisted structure). The helix angle of each region may be the same or different, and can be appropriately set according to the required performance.
  • the helix angle of the region A1 in the thickness direction is smaller than the helix angle of the region A2 in the thickness direction, and the region A0 is a region having no twisting structure (that is, the helix angle is 0 °). Yes)
  • the helix angle is the helix angle in the entire thickness direction.
  • the direction of the optical axis of the liquid crystal compound is in the direction of the arrangement axis D with respect to the incident direction. It is refracted and transmitted at a predetermined angle in one direction, which is changing while continuously rotating.
  • the left circularly polarized LC2 is incident on the region A2 in the plane of the liquid crystal layer 36, it is refracted and transmitted by a predetermined angle in the arrangement axis D direction with respect to the incident direction.
  • the left circularly polarized LC0 when the left circularly polarized LC0 is incident on the region A0 in the plane of the liquid crystal layer 36, it is refracted and transmitted by a predetermined angle in the arrangement axis D direction with respect to the incident direction.
  • the angle of refraction by the liquid crystal layer 36 since the one cycle ⁇ A2 of the liquid crystal alignment pattern of the region A2 is shorter than the one cycle ⁇ A1 of the liquid crystal alignment pattern of the region A1, the incident light is as shown in FIG.
  • the angle of refraction with respect to is larger at the angle ⁇ A2 of the transmitted light in the region A2 than at the angle ⁇ A1 of the transmitted light in the region A1.
  • one cycle ⁇ A0 of the liquid crystal alignment pattern of the region A0 is longer than the one cycle ⁇ A1 of the liquid crystal alignment pattern of the region A1, as shown in FIG. 11, the angle of refraction with respect to the incident light is transmitted through the region A0.
  • the angle of light ⁇ A0 is smaller than the angle ⁇ A1 of transmitted light in region A1.
  • the light incident on the end side is refracted more than the light incident near the center of the liquid crystal diffractive element. It can function as a positive lens that collects light.
  • the diffraction efficiency may decrease as the diffraction angle increases. .. Therefore, when the liquid crystal layer has a region in which the direction of the optical axis of the liquid crystal compound rotates 180 ° in the plane and the length of one cycle is different, the diffraction angle differs depending on the incident position of the light. There is a possibility that the amount of diffracted light will differ depending on the incident position inside. That is, depending on the incident position in the plane, there may be a region where the transmitted and diffracted light becomes dark.
  • the liquid crystal diffractive element has a region in which the liquid crystal layer is twisted and rotated in the thickness direction, it is possible to suppress a decrease in the diffraction efficiency of the refracted light. Therefore, it is preferable that the liquid crystal diffractive element has a region in which the liquid crystal layer is twisted and rotated in the thickness direction, and has a region in which the size of the twist angle in the thickness direction is different. Specifically, the shorter the period ⁇ of the liquid crystal alignment pattern is, the larger the helix angle in the thickness direction is so that the amount of transmitted light becomes uniform regardless of the incident position in the plane. Can be done.
  • the liquid crystal diffraction element preferably has a region in which the size of the helix angle in the thickness direction is 10 ° to 360 °.
  • the helix angle in the thickness direction may be appropriately set according to one cycle ⁇ of the in-plane liquid crystal alignment pattern.
  • the liquid crystal diffractive element has a configuration having one liquid crystal layer, but the present invention is not limited to this, and the liquid crystal diffractive element may have two or more liquid crystal layers. Further, when the liquid crystal diffractive element has two or more liquid crystal layers, it may further have liquid crystal layers having different directions of twisting and rotation (direction of twist angle) in the thickness direction.
  • the optical axis has a region where the optical axis twists and rotates in the thickness direction of the liquid crystal layer, and Liquid crystal layers having different regions of rotation twist angle in the plane and having different rotation directions in the thickness direction may be laminated and used.
  • transmitted light is efficiently transmitted to incident light in various polarized states in a region having a helix angle in the thickness direction. Can be refracted.
  • the twist angle in the thickness direction is the same for each region in the plane.
  • the present invention is not limited to this, and the helix angle in the thickness direction of the liquid crystal diffraction element is not limited, and may be appropriately set according to the application of the optical element and the like.
  • liquid crystal diffractive element there is no limitation on the one cycle ⁇ in the orientation pattern of the liquid crystal layer, and it may be appropriately set according to the application of the optical element and the like.
  • the HTP of the chiral agent is reduced by irradiation with light.
  • the irradiation amount of light for example, in a region where the irradiation amount is large, the HTP is greatly reduced and the induction of the helix is reduced, so that the helix angle of the twisted structure is reduced.
  • the decrease in HTP is small, so that the helix angle of the twisted structure becomes large.
  • the method of changing the irradiation amount of light for each area is not particularly limited, and a method of irradiating light through a gradation mask, a method of changing the irradiation time for each area, a method of changing the irradiation intensity for each area, etc. are used. It is possible.
  • the gradation mask is a mask in which the transmittance for the irradiated light changes in the plane.
  • ⁇ (r) ( ⁇ / ⁇ ) [(r 2 + f 2 ) 1/2 ⁇ f]
  • ⁇ (r) represents the angle of the optical axis at the distance r from the center, ⁇ represents the wavelength, and f represents the target focal length.
  • one cycle ⁇ is gradually changed in one direction in which the optical axis continuously rotates, depending on the application of the liquid crystal diffractive element, for example, when it is desired to provide a light amount distribution in the transmitted light.
  • a configuration having a region in which one cycle ⁇ is partially different in one direction in which the optical axis rotates continuously is also available.
  • the liquid crystal diffractive element may have a liquid crystal layer in which one cycle ⁇ is entirely uniform and a liquid crystal layer having different regions in one cycle ⁇ .
  • the liquid crystal orientation pattern of the liquid crystal layer is concentric circles in which the direction in which the direction of the optical axis of the liquid crystal compound changes while continuously rotating is provided radially from the center of the liquid crystal layer.
  • the pattern is shaped like a pattern, but it is not limited to this as long as it can collect the incident polarization.
  • the liquid crystal alignment pattern of the liquid crystal layer may be an elliptical concentric pattern in which the direction of the optical axis of the liquid crystal compound changes while continuously rotating. That is, it may be a concentric pattern in which the lines connecting the liquid crystal compounds whose optical axes are oriented in the same direction are elliptical.
  • the concentric pattern may be a deformed pattern.
  • the liquid crystal diffractive element may have two or more liquid crystal layers.
  • the cross section cut in the thickness direction along one direction in which the direction of the optical axis of the liquid crystal compound changes while continuously rotating is observed with a scanning electron microscope.
  • the bright part and the dark part derived from the orientation of the optical axis are observed, and the inclination angles of the bright part and the dark part with respect to the main surface of the liquid crystal layer are different from each other in at least two liquid crystal layers. Further, it is preferable that the inclination directions of the bright part and the dark part are different from each other.
  • the liquid crystal diffractive element shown in FIG. 13 has a structure in which a first liquid crystal layer 217, a second liquid crystal layer 219, and a third liquid crystal layer 218 are laminated in this order.
  • the first liquid crystal layer 217 and the third liquid crystal layer 218 have a liquid crystal orientation pattern in which the orientation of the optical axis derived from the liquid crystal compound changes while continuously rotating along at least one direction in the plane. Moreover, it is twisted and oriented in the thickness direction.
  • the optical axis is twisted and oriented in the thickness direction means that the orientation of the optical axes arranged in the thickness direction from one main surface of the liquid crystal layer to the other main surface changes relatively in one direction.
  • the twisting property includes a right-handed twisting property and a left-handed twisting property, and may be applied depending on the direction to be diffracted.
  • the twist of the optical axis in the thickness direction is less than one rotation, that is, the helix angle is less than 360 °.
  • the twist angle of the liquid crystal compound in the thickness direction is preferably about 10 ° to 200 °, more preferably about 20 ° to 180 °.
  • twist angle In the case of cholesteric orientation, the twist angle is 360 ° or more, and it has selective reflectivity that reflects a specific circular polarization in a specific wavelength range.
  • the "twisting orientation" in the present specification does not include the cholesteric orientation, and selective reflectivity does not occur in the liquid crystal layer having the twisting orientation.
  • the cross section of the liquid crystal layer having such a liquid crystal alignment pattern is observed by SEM, the bright lines and dark lines shown in FIG. 13 are observed. As shown by overlapping the bright and dark lines in FIG. 13, the period of the bright and dark lines coincides with the period of the liquid crystal alignment pattern.
  • the first liquid crystal layer 217 and the third liquid crystal layer 218 have the same inclination angle of the bright line and the dark line with respect to the main surface of the liquid crystal layer, but the inclination directions are different from each other. Therefore, in the first liquid crystal layer 217 and the third liquid crystal layer 218, the bright lines and the dark lines are vertically symmetrical (symmetrical with respect to the center line in the thickness direction).
  • the direction of the optical axis derived from the liquid crystal compound is continuous along at least one direction in the plane. It has a liquid crystal alignment pattern that changes while rotating, and is not twisted or oriented in the thickness direction. Therefore, the bright and dark lines of the second liquid crystal layer 219 are along the normal of the interface of the second liquid crystal layer 219 and have no inclination.
  • One cycle in the liquid crystal orientation pattern of the first liquid crystal layer 217, the second liquid crystal layer 219, and the third liquid crystal layer 218 is different for each region in the plane, but at the same position in the plane.
  • One cycle in the liquid crystal orientation pattern of the first liquid crystal layer 217, the second liquid crystal layer 219, and the third liquid crystal layer 218 is equal.
  • the bright lines and the dark lines are vertically symmetrical.
  • the diffraction efficiency for the light incident from the normal direction is high, but the diffraction efficiency for the light incident from the diagonal direction is low.
  • the diffraction efficiency with respect to the light incident from the oblique direction can be improved. Therefore, the liquid crystal diffractive element obtained by laminating these liquid crystal layers can reduce the change in the diffraction efficiency depending on the incident angle, and can improve the average diffraction efficiency.
  • the liquid crystal diffractive element has a structure in which bright lines and dark lines are vertically symmetrical, but the present invention is not limited to this.
  • the twist in the thickness direction changes along one direction in which the direction of the optical axis derived from the liquid crystal compound changes.
  • the bright part and the dark part are vertically symmetrical on the central side of the liquid crystal diffusing element, and the bright part and the dark part are vertically asymmetrical on the central side of the liquid crystal diffusing element. It is also good.
  • the bright portion and the dark portion of the first liquid crystal layer 37a, the second liquid crystal layer 37b, and the third liquid crystal layer 37c are inclined to each other, and are inclined to each other. It may be configured to be vertically asymmetric with different angles.
  • the liquid crystal layer has a bright portion and a dark portion extending from one surface to the other surface in the SEM image, and has two dark portions.
  • a liquid crystal diffusing element having an inflection point having the above angles and having a region in which the inclination direction of the dark portion is different in the thickness direction can be preferably used.
  • the liquid crystal layer has a striped pattern of a bright part and a dark part, and each dark part has two places in the thickness direction, and the inclination angle with respect to the surface changes. That is, each dark part has two inflection points. Further, in any of the dark areas, the inclination direction in the upper region in the figure and the inclination direction in the lower region in the figure are opposite to each other. That is, each dark portion has a region having a different inclination direction.
  • the number of inflection points in the liquid crystal layer in which the inclination direction of the dark portion is folded back is an odd number.
  • the number of inflection points at which the inclination direction of the dark portion is folded back is one.
  • the average inclination angle of the dark part in the liquid crystal layer gradually changes along one direction.
  • the average tilt angle of the dark portion is the angle of the line segment connecting the points on one surface of one dark portion and the points on the other surface with respect to the main surface of the liquid crystal layer.
  • the refractive index difference ⁇ n 550 due to the refractive index anisotropy of the liquid crystal layer is 0.2 or more.
  • the image display unit of the present invention described above can be suitably used as an image display unit of a head-mounted display.
  • the following coating liquid for forming an alignment film was continuously applied onto the support by spin coating.
  • the support on which the coating film of the coating film for forming the alignment film was formed was dried on a hot plate at 60 ° C. for 60 seconds to form the alignment film.
  • Coating liquid for forming an alignment film ⁇ Material for photo-alignment A 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 ⁇ ⁇
  • the alignment film was exposed using the exposure apparatus shown in FIG. 8 to form an alignment film P-1 having an alignment pattern.
  • a laser that emits a laser beam having a wavelength (325 nm) was used.
  • the exposure amount due to the interference light was set to 1000 mJ / cm 2 .
  • one cycle of the orientation pattern was gradually shortened in the outward direction.
  • composition A-1 The following composition A-1 was prepared as the liquid crystal composition forming the first liquid crystal layer.
  • the liquid crystal layer was formed by applying the composition A-1 on the alignment film P-1 in multiple layers.
  • the composition A-1 of the first layer is first coated on the alignment film, heated and cooled, and then cured by ultraviolet rays to prepare a liquid crystal immobilization layer, and then the second and subsequent layers are immobilized with the liquid crystal. It refers to repeating the process of overcoating the layers, applying them, and then heating and cooling them in the same way, and then curing them with ultraviolet rays.
  • the orientation direction of the alignment film is reflected from the lower surface to the upper surface of the liquid crystal layer even when the total thickness of the liquid crystal layer is increased.
  • the following composition A-1 is applied on the alignment film P-1, the coating film is heated to 80 ° C. on a hot plate, and then the wavelength is increased using a high-pressure mercury lamp under a nitrogen atmosphere.
  • the orientation of the liquid crystal compound was fixed by irradiating the coating film with an ultraviolet ray of 365 nm at an irradiation amount of 300 mJ / cm 2 .
  • the second and subsequent layers were overcoated on this liquid crystal layer, heated under the same conditions as above, cooled, and then cured by ultraviolet rays to prepare a liquid crystal immobilized layer. In this way, recoating was repeated until the total thickness reached a desired film thickness to form the first liquid crystal layer.
  • the complex refractive index ⁇ n of the cured layer of the liquid crystal composition A1 is applied on a separately prepared support with an alignment film for retardation measurement, and the director of the liquid crystal compound is horizontally placed on the substrate. It was determined by measuring the refractive index value and the film thickness of the liquid crystal immobilization layer (cured layer) obtained by immobilizing the liquid crystal immobilization layer by irradiating it with ultraviolet rays after orienting it so as to be. ⁇ n can be calculated by dividing the retardation value by the film thickness. The retardation value was measured at a target wavelength using Axoscan manufactured by Axometrix, and the film thickness was measured using a scanning electron microscope (SEM).
  • SEM scanning electron microscope
  • the first liquid crystal layer finally has a liquid crystal ⁇ n 550 ⁇ thickness (Re (550)) of 160 nm, and has a concentric (radial) periodic orientation surface as shown in FIG. It was confirmed by a polarizing microscope.
  • the liquid crystal alignment pattern of the first liquid crystal layer was a liquid crystal alignment pattern in which the period became shorter toward the outside.
  • the helix angle of the first liquid crystal layer in the thickness direction was 80 ° in the plane and with a right twist.
  • measurements such as “ ⁇ n 550 ⁇ d” were carried out in the same manner.
  • composition A-2 was prepared as the liquid crystal composition forming the second liquid crystal layer.
  • Composition A-2 ⁇ Liquid Crystal Compound L-1 100.00 parts by mass Polymerization initiator (BASF, Irgacure (registered trademark) 907) 3.00 parts by mass Photosensitizer (manufactured by Nippon Kayaku, KAYACURE DETX-S) 1.00 parts by mass Leveling agent T-1 0.08 parts by mass Methyl ethyl ketone 1050.00 parts by mass ⁇ ⁇
  • the second liquid crystal layer was formed on the first liquid crystal layer in the same manner as the first liquid crystal layer except that the film thickness of the liquid crystal layer was adjusted using the composition A-2.
  • the second liquid crystal layer finally has a liquid crystal ⁇ n 550 ⁇ thickness (Re (550)) of 330 nm, and has a concentric (radial) periodic orientation surface as shown in FIG. It was confirmed by a polarizing microscope.
  • the liquid crystal alignment pattern of the second liquid crystal layer was a liquid crystal alignment pattern in which the period became shorter toward the outside.
  • the helix angle of the second liquid crystal layer in the thickness direction was 0 ° in the plane.
  • composition A-3 was prepared as the liquid crystal composition forming the third liquid crystal layer.
  • Composition A-3 Liquid crystal compound L-1 100.00 parts by mass Chiral agent H-1 0.63 parts by mass Polymerization initiator (BASF, Irgacure (registered trademark) 907) 3.00 parts by mass Photosensitizer (manufactured by Nippon Kayaku, KAYACURE DETX-S) 1.00 parts by mass Leveling agent T-1 0.08 parts by mass Methyl ethyl ketone 1050.00 parts by mass ⁇ ⁇
  • a third liquid crystal layer was formed on the second liquid crystal layer in the same manner as the first liquid crystal layer except that the film thickness of the liquid crystal layer was adjusted using the composition A-3.
  • the third liquid crystal layer finally has a liquid crystal ⁇ n 550 ⁇ thickness (Re (550)) of 160 nm, and has a concentric (radial) periodic orientation surface as shown in FIG. It was confirmed by a polarizing microscope.
  • the liquid crystal alignment pattern of the third liquid crystal layer was a liquid crystal alignment pattern in which the period became shorter toward the outside.
  • the helix angle of the liquid crystal layer in the thickness direction was 80 ° in the in-plane and left-handed twist.
  • Parallel light was incident on the liquid crystal diffractive element having the first to third liquid crystal layers, and the focal length of the condensed emitted light was measured.
  • the focal length was 30 mm.
  • a film having a cellulose acylate film, an alignment film and an optically anisotropic layer C was obtained in the same manner as the positive A plate described in paragraphs 0102 to 0126 of JP-A-2019-215416.
  • the optically anisotropic layer C is a positive A plate (phase difference plate), and the thickness of the positive A plate is controlled so that Re (550) is 138 nm.
  • An image display unit is manufactured using a first linear polarizing plate, a first retardation plate ( ⁇ / 4 plate), a liquid crystal diffraction element, a second retardation plate ( ⁇ / 4 plate), and a linear polarizing plate. (See Fig. 1).
  • a commercially available head-mounted display, Oculus Rift S manufactured by Oculus is disassembled, the display in it is used as an image display device, and the linear polarizing plate attached to the surface thereof is used as a first linear polarizing plate and a second linear polarizing plate. It was used as a linear polarizing plate of.
  • the first linear polarizing plate was arranged on the image display device side so that the angle of the absorption axis was 90 °.
  • the first phase difference plate was arranged so that the slow phase axis was 45 °.
  • the second phase difference plate was arranged so that the slow phase axis was ⁇ 45 °.
  • the second linear polarizing plate was arranged so that the angle of the absorption axis was 0 °.
  • the axis angle described is based on the horizontal direction of the head-mounted display (0 °), and the clockwise direction is positive when the image display unit is viewed from the viewing side.
  • the distance between the image display device and the liquid crystal diffractive element was set to 30 mm.
  • Example 2 In the production of the liquid crystal diffractive element, the same as in Example 1 except that the alignment pattern formed on the alignment film P-1 is changed, the focal length is set to 15 mm, and the distance between the image display device and the liquid crystal diffractive element is set to 15 mm. An image display unit was manufactured.
  • Example 3 In the production of the liquid crystal diffractive element, the same as in Example 1 except that the alignment pattern formed on the alignment film P-1 is changed, the focal length is set to 10 mm, and the distance between the image display device and the liquid crystal diffractive element is set to 10 mm. An image display unit was manufactured.
  • An image display unit was manufactured by arranging a Fresnel lens on the display surface side of the image display device.
  • the focal length of the Fresnel lens was 40 mm.
  • the distance between the image display device and the Fresnel lens was 40 mm.
  • the Fresnel lens used was the one that came with the Oculus Rift S.
  • the partial reflection mirror an aluminum film was formed by sputtering on the convex surface of a lens having a diameter of 5 cm and a radius of curvature of 10 cm so as to have a transmittance of 50% and a reflectance of 50%. That is, the partial reflection mirror has a curved shape.
  • the second reflective linear polarizing plate DBEF manufactured by 3M was used and arranged so that the transmission axis angle was 90 °.
  • a second absorption type linear polarizing plate was arranged so that the absorption axis angle was 0 °.
  • first phase difference plate and the second phase difference plate were arranged so that the slow phase axes were 45 ° and ⁇ 45 °, respectively.
  • the focal length of the partial reflection mirror was 20 mm.
  • the distance between the image display device and the partial reflection mirror was set to 20 mm.
  • Example 3 An image display unit was produced in the same manner as in Example 1 except that it did not have a second retardation plate and a second linear polarizing plate.
  • ⁇ Image quality evaluation 1> Similar to the above evaluation of light utilization efficiency, a laser pointer is used to inject light from the first linear polarizing plate side, place the paper at the focal length position, and observe the light displayed on the paper. It was evaluated according to the following criteria. A: A spot of light was observed at one focal point. B: Light was also observed at positions other than the focal point.
  • Examples 1 to 3 of the present invention have higher light utilization efficiency and higher image quality of the displayed image as compared with Comparative Examples.
  • the image quality was poor because the streaks of light due to the groove structure of the Fresnel lens were visually recognized in the displayed image.
  • the light utilization efficiency was low.
  • Comparative Example 3 since the light not diffracted by the liquid crystal diffractive element is emitted, the image quality is deteriorated.
  • Example 1-A2 In Example 1, the liquid crystal compound L-1 was changed to the liquid crystal compound L-2, the addition amounts of the chiral agent M-1 and the chiral agent H-1 were adjusted, and the same was performed except that the film thickness of the liquid crystal layer was adjusted. Then, a liquid crystal diffraction element was produced, and an image display unit of Example 1-A2 was produced.
  • the first liquid crystal layer finally has a liquid crystal ⁇ n 550 ⁇ thickness (Re (550)) of 160 nm, and has a concentric (radial) periodic orientation surface as shown in FIG. It was confirmed by a polarizing microscope.
  • the liquid crystal alignment pattern of the first liquid crystal layer was a liquid crystal alignment pattern in which the period became shorter toward the outside.
  • the helix angle of the first liquid crystal layer in the thickness direction was 80 ° in the plane and with a right twist.
  • the second liquid crystal layer finally has a liquid crystal ⁇ n 550 ⁇ thickness (Re (550)) of 330 nm, and has a concentric (radial) periodic orientation surface as shown in FIG. It was confirmed by a polarizing microscope.
  • the liquid crystal alignment pattern of the second liquid crystal layer was a liquid crystal alignment pattern in which the period became shorter toward the outside.
  • the helix angle of the second liquid crystal layer in the thickness direction was 0 ° in the plane.
  • the third liquid crystal layer finally has a liquid crystal ⁇ n 550 ⁇ thickness (Re (550)) of 160 nm, and has a concentric (radial) periodic orientation surface as shown in FIG. It was confirmed by a polarizing microscope.
  • the liquid crystal alignment pattern of the third liquid crystal layer was a liquid crystal alignment pattern in which the period became shorter toward the outside.
  • the helix angle of the liquid crystal layer in the thickness direction was 80 ° in the in-plane and left-handed twist.
  • Parallel light was incident on the liquid crystal diffractive element having the first to third liquid crystal layers, and the focal length of the condensed emitted light was measured.
  • the focal length was 30 mm.
  • Example 2-A2 In the production of the liquid crystal diffractive element, the alignment pattern formed on the alignment film P-1 was changed, the focal length was set to 15 mm, and the distance between the image display device and the liquid crystal diffractive element was set to 15 mm. An image display unit was produced in the same manner.
  • Example 3-A2 In the production of the liquid crystal diffractive element, the alignment pattern formed on the alignment film P-1 was changed, the focal length was set to 10 mm, and the distance between the image display device and the liquid crystal diffractive element was set to 10 mm. An image display unit was produced in the same manner.
  • Example 1-A3 In Example 1, the liquid crystal compound L-1 is changed to the liquid crystal compound L-3, the addition amounts of the chiral agent M-1 and the chiral agent H-1 are adjusted, and the heating temperature of the coating film when the liquid crystal layer is formed. In the same manner except that the temperature was changed to 55 ° C. and the thickness of the liquid crystal layer was adjusted, a liquid crystal diffraction element was produced, and an image display unit of Example 1-A3 was produced.
  • the first liquid crystal layer finally has a liquid crystal ⁇ n 550 ⁇ thickness (Re (550)) of 160 nm, and has a concentric (radial) periodic orientation surface as shown in FIG. It was confirmed by a polarizing microscope.
  • the liquid crystal alignment pattern of the first liquid crystal layer was a liquid crystal alignment pattern in which the period became shorter toward the outside.
  • the helix angle of the first liquid crystal layer in the thickness direction was 80 ° in the plane and with a right twist.
  • the second liquid crystal layer finally has a liquid crystal ⁇ n 550 ⁇ thickness (Re (550)) of 330 nm, and has a concentric (radial) periodic orientation surface as shown in FIG. It was confirmed by a polarizing microscope.
  • the liquid crystal alignment pattern of the second liquid crystal layer was a liquid crystal alignment pattern in which the period became shorter toward the outside.
  • the helix angle of the second liquid crystal layer in the thickness direction was 0 ° in the plane.
  • the third liquid crystal layer finally has a liquid crystal ⁇ n 550 ⁇ thickness (Re (550)) of 160 nm, and has a concentric (radial) periodic orientation surface as shown in FIG. It was confirmed by a polarizing microscope.
  • the liquid crystal alignment pattern of the third liquid crystal layer was a liquid crystal alignment pattern in which the period became shorter toward the outside.
  • the helix angle of the liquid crystal layer in the thickness direction was 80 ° in the in-plane and left-handed twist.
  • Parallel light was incident on the liquid crystal diffractive element having the first to third liquid crystal layers, and the focal length of the condensed emitted light was measured.
  • the focal length was 30 mm.
  • Example 2-A3 In the production of the liquid crystal diffractive element, the alignment pattern formed on the alignment film P-1 was changed, the focal length was set to 15 mm, and the distance between the image display device and the liquid crystal diffractive element was set to 15 mm. An image display unit was produced in the same manner.
  • Example 3-A3 In the production of the liquid crystal diffractive element, the alignment pattern formed on the alignment film P-1 was changed, the focal length was set to 10 mm, and the distance between the image display device and the liquid crystal diffractive element was set to 10 mm. An image display unit was produced in the same manner.
  • the ⁇ n 550 of the liquid crystal layer (liquid crystal compound) of Examples 1 to 3 is 0.15, and the ⁇ n 550 of the liquid crystal layer of Examples 1-A2 to 3-A2 is 0.25, Example 1-.
  • the ⁇ n 550 of the liquid crystal layer of A3 to Example 3-A3 was 0.32.
  • Example 1-A2 the light utilization efficiency (average value) of Example 1-A2 was improved with respect to Example 1, and the light utilization efficiency (average value) of Example 1-A3 was further improved. .. Similarly, the light utilization efficiency (average value) of Example 2-A2 was improved with respect to Example 2, and the light utilization efficiency (average value) of Example 2-A3 was further improved. The light utilization efficiency (average value) of Example 3-A2 was improved with respect to Example 3, and the light utilization efficiency (average value) of Example 3-A3 was further improved.
  • composition B-1 (Formation of liquid crystal layer) The following composition B-1 was prepared as the liquid crystal composition forming the first liquid crystal layer.
  • Liquid crystal compound L-1 100.00 parts by mass Chiral agent C-3 0.23 parts by mass Chiral agent C-4 0.82 parts by mass Polymerization initiator (BASF, Irgacure OXE01) 1.00 parts by mass Leveling agent T-1 0.08 parts by mass Methyl ethyl ketone 1050.00 parts by mass ⁇ ⁇
  • the chiral agent C-3 is 0.54 parts by mass and the chiral agent C-4 is 0.62 parts by mass.
  • the composition was changed to prepare the composition B-2.
  • the chiral agent C-3 was changed to 0.48 parts by mass and the chiral agent C-4 was changed to non-added in the composition B-1 of Example 1-B1.
  • Composition B-3 was prepared.
  • composition B-1 was applied in multiple layers on the alignment film P-1 to form a first liquid crystal layer.
  • the above composition B-1 is applied on the alignment film P-1, the coating film is heated to 80 ° C. on a hot plate, and then ultraviolet rays having a wavelength of 365 nm of an LED-UV exposure machine are used. Was applied to the coating film.
  • the coating film was irradiated by changing the irradiation amount of ultraviolet rays in the plane. Specifically, the coating film was irradiated by changing the irradiation amount in the plane so that the irradiation amount increased from the central portion to the edge portion. Then, the coating film heated to 80 ° C.
  • the second and subsequent layers were overcoated on the liquid crystal immobilization layer to prepare a liquid crystal immobilization layer under the same conditions as above. In this way, repeated coating was repeated until the total thickness reached a desired film thickness to form the first liquid crystal layer of the liquid crystal layer.
  • the first liquid crystal layer finally has a liquid crystal ⁇ n 550 ⁇ thickness (Re (550)) of 160 nm, and has a concentric (radial) periodic orientation surface as shown in FIG. It was confirmed by a polarizing microscope.
  • the liquid crystal layer had a liquid crystal orientation pattern in which the period became shorter toward the outside.
  • the helix angle in the thickness direction of the liquid crystal layer As for the helix angle in the thickness direction of the liquid crystal layer, the helix angle at a distance of about 5 mm from the center is 80 ° counterclockwise (-80 °), and one cycle at a distance of 15 mm from the center is 115 ° counterclockwise. It was (-115 °), and the helix angle increased toward the outside. As described above, the liquid crystal layer in which the helix angle changes in the plane is formed.
  • the composition B-2 was applied in multiple layers on the first liquid crystal layer to form a second liquid crystal layer.
  • the irradiation amount of ultraviolet rays irradiating the coating film from the center to the edges was applied in the same manner except that the total thickness was changed to a desired film thickness by changing (increasing the irradiation amount from the center to the edge).
  • the second and subsequent layers were overcoated on the liquid crystal immobilization layer to prepare a liquid crystal immobilization layer under the same conditions as above. In this way, recoating was repeated until the total thickness reached a desired film thickness to form a second liquid crystal layer.
  • the second liquid crystal layer finally has a liquid crystal ⁇ n 550 ⁇ thickness (Re (550)) of 330 nm, and has a concentric (radial) periodic orientation surface as shown in FIG. It was confirmed with a polarizing microscope.
  • the liquid crystal layer had a liquid crystal orientation pattern in which the period became shorter toward the outside.
  • the helix angle in the thickness direction of the liquid crystal layer As for the helix angle in the thickness direction of the liquid crystal layer, the helix angle at a distance of about 5 mm from the center is 6 ° counterclockwise (-6 °), and one cycle at a distance of 15 mm from the center is 76 ° counterclockwise. It was (-76 °), and the helix angle increased toward the outside. As described above, the liquid crystal layer in which the helix angle changes in the plane is formed.
  • the composition B-3 was applied in multiple layers on the second liquid crystal layer to form a third liquid crystal layer.
  • the irradiation amount of ultraviolet rays irradiating the coating film from the center to the edges was applied in the same manner except that the total thickness was changed to a desired film thickness by changing (increasing the irradiation amount from the center to the edge).
  • the second and subsequent layers were overcoated on the liquid crystal immobilization layer to prepare a liquid crystal immobilization layer under the same conditions as above. In this way, recoating was repeated until the total thickness reached a desired film thickness to form a third liquid crystal layer.
  • the third liquid crystal layer finally has a liquid crystal ⁇ n 550 ⁇ thickness (Re (550)) of 160 nm, and has a concentric (radial) periodic orientation surface as shown in FIG. It was confirmed with a polarizing microscope.
  • the liquid crystal layer had a liquid crystal orientation pattern in which the period became shorter toward the outside.
  • the helix angle in the thickness direction of the liquid crystal layer As for the helix angle in the thickness direction of the liquid crystal layer, the helix angle at a distance of about 5 mm from the center is 80 ° clockwise (twist angle 80 °), and one cycle at a distance of 15 mm from the center is 48 clockwise. The helix angle was 48 °, and the helix angle decreased toward the outside. As described above, the liquid crystal layer having the third liquid crystal layer was formed from the first liquid crystal layer.
  • the shapes of the bright part and the dark part had two inflection points in the dark part, and the average inclination angle increased from the center to the outside. rice field. Further, the focal length of the emitted light collected by incident parallel light on the liquid crystal diffractive element having the first to third liquid crystal layers was measured. The focal length was 30 mm.
  • Example 2-B1 In the production of the liquid crystal diffractive element, the alignment pattern formed on the alignment film P-1 was changed, the focal length was set to 15 mm, and the distance between the image display device and the liquid crystal diffractive element was set to 15 mm. An image display unit was produced in the same manner.
  • Example 3-B1 In the production of the liquid crystal diffractive element, the alignment pattern formed on the alignment film P-1 was changed, the focal length was set to 10 mm, and the distance between the image display device and the liquid crystal diffractive element was set to 10 mm. An image display unit was produced in the same manner.
  • Example 1-B2 In Example 1-B1, the liquid crystal compound L-1 is changed to the liquid crystal compound L-2, the addition amounts of the chiral agent C-3 and the chiral agent C-4 are adjusted, and the liquid crystal layer is produced from the center to the edge. A liquid crystal diffraction element was produced in the same manner except that the amount of ultraviolet rays irradiated to the coating film was adjusted toward the portion and the film thickness of the liquid crystal layer was adjusted, and the image display unit of Example 1-B2 was produced. ..
  • the first liquid crystal layer finally has a liquid crystal ⁇ n 550 ⁇ thickness (Re (550)) of 160 nm, and has a concentric (radial) periodic orientation surface as shown in FIG. It was confirmed by a polarizing microscope.
  • the liquid crystal layer had a liquid crystal orientation pattern in which the period became shorter toward the outside.
  • the helix angle in the thickness direction of the liquid crystal layer the helix angle at a distance of about 5 mm from the center is 80 ° counterclockwise (-80 °), and one cycle at a distance of 15 mm from the center is 115 ° counterclockwise. It was (-115 °), and the helix angle increased toward the outside.
  • the liquid crystal layer in which the helix angle changes in the plane is formed.
  • the second liquid crystal layer finally has a liquid crystal ⁇ n 550 ⁇ thickness (Re (550)) of 330 nm, and has a concentric (radial) periodic orientation surface as shown in FIG. It was confirmed by a polarizing microscope.
  • the liquid crystal layer had a liquid crystal orientation pattern in which the period became shorter toward the outside.
  • the helix angle in the thickness direction of the liquid crystal layer the helix angle at a distance of about 5 mm from the center is 6 ° counterclockwise (-6 °), and one cycle at a distance of 15 mm from the center is 76 ° counterclockwise. It was (-76 °), and the helix angle increased toward the outside.
  • the liquid crystal layer in which the helix angle changes in the plane is formed.
  • the third liquid crystal layer finally has a liquid crystal ⁇ n 550 ⁇ thickness (Re (550)) of 160 nm, and has a concentric (radial) periodic orientation surface as shown in FIG. It was confirmed by a polarizing microscope.
  • the liquid crystal layer had a liquid crystal orientation pattern in which the period became shorter toward the outside.
  • the helix angle in the thickness direction of the liquid crystal layer the helix angle at a distance of about 5 mm from the center is 80 ° clockwise (twist angle 80 °), and one cycle at a distance of 15 mm from the center is 48 clockwise.
  • the helix angle was 48 °, and the helix angle decreased toward the outside.
  • the liquid crystal layer having the third liquid crystal layer was formed from the first liquid crystal layer.
  • the shapes of the bright part and the dark part had two inflection points in the dark part, and the average inclination angle increased from the center to the outside. rice field. Further, the focal length of the emitted light collected by incident parallel light on the liquid crystal diffractive element having the first to third liquid crystal layers was measured. The focal length was 30 mm.
  • Example 2-B2 In the production of the liquid crystal diffractive element, the alignment pattern formed on the alignment film P-1 was changed, the focal length was set to 15 mm, and the distance between the image display device and the liquid crystal diffractive element was set to 15 mm. An image display unit was produced in the same manner.
  • Example 3-B2 In the production of the liquid crystal diffractive element, the alignment pattern formed on the alignment film P-1 was changed, the focal length was set to 10 mm, and the distance between the image display device and the liquid crystal diffractive element was set to 10 mm. An image display unit was produced in the same manner.
  • Example 1-B3 In Example 1-B1, the liquid crystal compound L-1 is changed to the liquid crystal compound L-3, the addition amounts of the chiral agent C-3 and the chiral agent C-4 are adjusted, and the liquid crystal layer is produced from the center to the edge. The amount of ultraviolet rays irradiated to the coating film was adjusted toward the portion, the heating temperature of the coating film when forming the liquid crystal layer was changed to 55 ° C., and the film thickness of the liquid crystal layer was adjusted in the same manner. A liquid crystal diffusing element was produced, and an image display unit of Example 1-B2 was produced.
  • the first liquid crystal layer finally has a liquid crystal ⁇ n 550 ⁇ thickness (Re (550)) of 160 nm, and has a concentric (radial) periodic orientation surface as shown in FIG. It was confirmed by a polarizing microscope.
  • the liquid crystal layer had a liquid crystal orientation pattern in which the period became shorter toward the outside.
  • the helix angle in the thickness direction of the liquid crystal layer the helix angle at a distance of about 5 mm from the center is 80 ° counterclockwise (-80 °), and one cycle at a distance of 15 mm from the center is 115 ° counterclockwise. It was (-115 °), and the helix angle increased toward the outside.
  • the liquid crystal layer in which the helix angle changes in the plane is formed.
  • the second liquid crystal layer finally has a liquid crystal ⁇ n 550 ⁇ thickness (Re (550)) of 330 nm, and has a concentric (radial) periodic orientation surface as shown in FIG. It was confirmed by a polarizing microscope.
  • the liquid crystal layer had a liquid crystal orientation pattern in which the period became shorter toward the outside.
  • the helix angle in the thickness direction of the liquid crystal layer the helix angle at a distance of about 5 mm from the center is 6 ° counterclockwise (-6 °), and one cycle at a distance of 15 mm from the center is 76 ° counterclockwise. It was (-76 °), and the helix angle increased toward the outside.
  • the liquid crystal layer in which the helix angle changes in the plane is formed.
  • the third liquid crystal layer finally has a liquid crystal ⁇ n 550 ⁇ thickness (Re (550)) of 160 nm, and has a concentric (radial) periodic orientation surface as shown in FIG. It was confirmed by a polarizing microscope.
  • the liquid crystal layer had a liquid crystal orientation pattern in which the period became shorter toward the outside.
  • the helix angle in the thickness direction of the liquid crystal layer the helix angle at a distance of about 5 mm from the center is 80 ° clockwise (twist angle 80 °), and one cycle at a distance of 15 mm from the center is 48 clockwise.
  • the helix angle was 48 °, and the helix angle decreased toward the outside.
  • the liquid crystal layer having the third liquid crystal layer was formed from the first liquid crystal layer.
  • the shapes of the bright part and the dark part had two inflection points in the dark part, and the average inclination angle increased from the center to the outside. rice field. Further, the focal length of the emitted light collected by incident parallel light on the liquid crystal diffractive element having the first to third liquid crystal layers was measured. The focal length was 30 mm.
  • Example 2-B3 In the production of the liquid crystal diffractive element, the alignment pattern formed on the alignment film P-1 was changed, the focal length was set to 15 mm, and the distance between the image display device and the liquid crystal diffractive element was set to 15 mm. An image display unit was produced in the same manner.
  • Example 3-B3 In the production of the liquid crystal diffractive element, the alignment pattern formed on the alignment film P-1 was changed, the focal length was set to 10 mm, and the distance between the image display device and the liquid crystal diffractive element was set to 10 mm. An image display unit was produced in the same manner.
  • Example 1-B1 the light utilization efficiency of Example 1-B1 was the same as that of Example 1 at the position of 5 mm from the center of the concentric circles of the liquid crystal diffractometer, and the utilization rate was improved at the position of 15 mm.
  • the light utilization efficiency of Example 2-B1 was the same as that of Example 2 at the position of 5 mm from the center of the concentric circles of the liquid crystal diffractive element, and the utilization rate was improved at the position of 15 mm.
  • Example 3-B1 the same at the position of 5 mm from the center of the concentric circles of the liquid crystal diffractometer, and the utilization rate was improved at the position of 15 mm.
  • the liquid crystal layer of the liquid crystal diffusing element has a region in which the size of the helix angle in the thickness direction is different, and the region in which one cycle ⁇ of the liquid crystal alignment pattern is shorter increases the helix angle in the thickness direction of the liquid crystal layer. It can be seen that the light utilization efficiency is improved in the region where the diffraction angle is large (in the above case, the position of 15 mm) by (increasing the average tilt angle of the dark portion).
  • Example 1-B2 As a result of the evaluation, the light utilization efficiency (average value) of Example 1-B2 was improved with respect to Example 1-B1, and the light utilization efficiency (average value) of Example 1-B3 was further improved.
  • the light utilization efficiency (average value) of Example 2-B2 is improved with respect to Example 2-B1, and the light utilization efficiency (average value) of Example 2-B3 is further improved.
  • the light utilization efficiency (average value) of Example 3-B2 was improved with respect to Example 3-B1, and the light utilization efficiency (average value) of Example 3-B3 was further improved.
  • Example 4 to 6 In the production of the image unit of Examples 1 to 3, the image unit was produced in the same manner except that the linear polarizing plate (polyvinyl alcohol layer type) was changed to the absorption type polarizing plate produced as described later.
  • the linear polarizing plate polyvinyl alcohol layer type
  • the coating liquid PA1 for forming an alignment layer was continuously coated on a cellulose acylate film (TAC substrate having a thickness of 40 ⁇ m; TG40 Fujifilm Co., Ltd.) with a wire bar.
  • the support on which the coating film was formed was dried with warm air at 140 ° C. for 120 seconds, and then the coating film was irradiated with polarized ultraviolet rays (10 mJ / cm 2 , using an ultrahigh pressure mercury lamp) to obtain a photoalignment layer.
  • PA1 was formed to obtain a TAC film with a photoalignment layer.
  • the film thickness was 0.3 ⁇ m.
  • ⁇ Formation of light absorption anisotropic layer P1> The following composition for forming a light absorption anisotropic layer P1 was continuously coated on the obtained alignment layer PA1 with a wire bar to form a coating layer P1. Then, the coating layer P1 was heated at 140 ° C. for 30 seconds, and the coating layer P1 was cooled to room temperature (23 ° C.). It was then heated at 90 ° C. for 60 seconds and cooled again to room temperature. Then, the light absorption anisotropic layer P1 was produced on the alignment layer PA1 by irradiating with an LED lamp (center wavelength 365 nm) for 2 seconds under an irradiation condition of an illuminance of 200 mW / cm 2 . The film thickness was 1.6 ⁇ m. This was designated as the laminated body 1B.
  • UV Adhesive Composition ⁇ ⁇ CEL2021P (manufactured by Daicel) 70 parts by mass ⁇ 1,4-butanediol diglycidyl ether 20 parts by mass ⁇ 2-ethylhexyl glycidyl ether 10 parts by mass ⁇ CPI-100P 2.25 parts by mass ⁇ ⁇
  • Technoloy S001G (methacrylic resin 50 ⁇ m thick, tan ⁇ peak temperature 128 ° C., Sumika Acrylic Sales Co., Ltd.) was applied as the resin base material S1 to the surface of the light absorption anisotropic layer of the laminate 1B using the above UV adhesive. I pasted them together. Then, only the cellulose acylate film 1 was peeled off to prepare an absorption-type polarizing film in which the resin base material / adhesive layer / light absorption anisotropic layer / alignment layer were arranged in this order. The thickness of the UV adhesive layer was 2 ⁇ m.
  • the average arithmetic roughness Ra of the obtained absorbent polarizing film was 10 nm or less.
  • the average arithmetic roughness Ra of the linear polarizing plate (polyvinyl alcohol layer type) was 20 nm or more.
  • the average arithmetic roughness Ra was measured using an interferometer "vertscan" manufactured by Ryoka System Co., Ltd.

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