CN107615119B - Method for manufacturing half mirror used on surface of image display part of image display device, half mirror, and mirror with image display function - Google Patents

Method for manufacturing half mirror used on surface of image display part of image display device, half mirror, and mirror with image display function Download PDF

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Publication number
CN107615119B
CN107615119B CN201680031885.9A CN201680031885A CN107615119B CN 107615119 B CN107615119 B CN 107615119B CN 201680031885 A CN201680031885 A CN 201680031885A CN 107615119 B CN107615119 B CN 107615119B
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liquid crystal
layer
image display
half mirror
light reflecting
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CN107615119A (en
Inventor
田口贵雄
冲和宏
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Fujifilm Corp
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Fujifilm Corp
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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/08—Mirrors
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/20—Filters
    • G02B5/26—Reflecting filters
    • 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
    • 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

Abstract

According to the present invention, there is provided a method of manufacturing a half mirror, comprising the steps of: preparing a transfer material including a circularly polarized light reflecting layer; bonding the surface of the circularly polarized light reflective layer of the transfer material and a transparent substrate with a curable adhesive; and curing the curable adhesive to form an adhesive layer having a thickness of 1.0 μm or more and 5.0 μm or less, wherein the pencil hardness of the surface of the transfer material bonded to the transparent substrate is HB or less. By using the half mirror manufactured by the manufacturing method of the present invention, it is possible to provide a mirror with an image display function capable of performing bright and clear image display and specular reflection image display.

Description

Method for manufacturing half mirror used on surface of image display part of image display device, half mirror, and mirror with image display function
Technical Field
The present invention relates to a method for manufacturing a half mirror used for a surface of an image display portion of an image display device, a half mirror manufactured by the method, and a mirror with an image display function.
Background
By disposing a half mirror composed of a reflective polarizing plate or the like on the surface of the image display unit of the image display device, a configuration can be obtained which not only displays an image when the image display unit displays an image, but also functions as a mirror surface when the image display unit does not display an image. For example, patent document 1 discloses a configuration in which a reflective polarizing plate formed on a transparent substrate is disposed in front of an image display unit of an image display device so as to be a reflective polarizing plate and a transparent substrate in this order from the image display unit side.
Documents of the prior art
Patent document
Patent document 1: japanese patent laid-open publication No. 2011-45427
Disclosure of Invention
Technical problem to be solved by the invention
The present invention addresses the problem of providing a method for manufacturing a half mirror that can be used as a half mirror on the surface of an image display unit of an image display device and that can display bright and clear images and specularly reflected images. It is another object of the present invention to provide a novel half mirror and a mirror with an image display function capable of displaying a bright and clear image and displaying a mirror-reflected image.
Means for solving the technical problem
The present inventors have made extensive studies in an attempt to produce a half mirror using a layer in which a cholesteric liquid crystal phase is fixed (hereinafter, also referred to as a cholesteric liquid crystal layer) as the reflective polarizing plate. Cholesteric liquid crystal layers are known to exhibit selective reflection at specific wavelengths, and films comprising cholesteric liquid crystal layers are used in a variety of applications as reflective members. In the cholesteric liquid crystal layer, a liquid crystal composition containing a polymerizable liquid crystal compound is usually applied to a support material, a cholesteric liquid crystal phase is formed in the coating film, and then the coating film is cured by ultraviolet irradiation, whereby the cholesteric liquid crystal phase is fixed to form the cholesteric liquid crystal layer.
As described in patent document 1, the present inventors have tried to form a cholesteric liquid crystal layer directly on the surface of a transparent substrate by using the transparent substrate as a support, and as a result, it is sometimes difficult to align a polymerizable liquid crystal compound in a desired direction and to form the polymerizable liquid crystal compound in a cholesteric liquid crystal phase. Then, the present inventors have formed a film by bonding the cholesteric liquid crystal layer formed on the temporary support to the transparent substrate and transferring the cholesteric liquid crystal layer.
However, distortion was visually observed in a specular reflection image obtained by observing the half mirror including the transparent substrate and the cholesteric liquid crystal layer thus produced from the transparent substrate side. The present inventors have found that the deformation is caused by Orange peel-like irregularities of a high-transparency adhesive transfer tape (OCA tape) used for bonding. OCA tapes are widely used as an adhesive used for the surface of an image display unit of an image display device.
Therefore, the present inventors have attempted to transfer using a curable adhesive in place of a highly transparent adhesive transfer tape, and have confirmed a distortion different from the distortion due to the irregularities of the orange peel in a specular reflection image when used as a mirror surface. The layer of the curable adhesive needs to have a thickness of about 20 to 30 μm in order to sufficiently adhere the cholesteric liquid crystal layer to the transparent substrate, and therefore the deformation is considered to be caused by the occurrence of thickness (film thickness) unevenness due to the coating step.
Based on the above findings, the present inventors have further studied and completed the present invention.
Namely, the present invention provides the following [1] to [19 ].
[1] A method of manufacturing a half mirror used for a surface of an image display portion of an image display device,
the half mirror comprises a circularly polarized light reflecting layer, an adhesive layer and a transparent substrate in this order,
the circularly polarizing light reflecting layer includes a cholesteric liquid crystal layer,
the manufacturing method comprises the following steps:
preparing a transfer material including the circularly polarized light reflecting layer;
bonding the surface of the circularly polarized light reflective layer of the transfer material and the transparent substrate with a curable adhesive; and
curing the curable adhesive to form the adhesive layer having a thickness of 1.0 μm or more and 5.0 μm or less,
the pencil hardness of the surface of the transfer material that is bonded to the transparent substrate is HB or less.
[2] The production method according to [1], wherein,
the above-mentioned transfer material comprises a temporary support,
the above manufacturing method includes a step of forming the above circularly polarized light reflecting layer in the above transfer material by a method including the steps of:
coating a liquid crystal composition containing a polymerizable liquid crystal compound on the temporary support to obtain a coating film; and
the cholesteric liquid crystal layer is obtained by curing the coating film.
[3] The production method according to [2], wherein,
the manufacturing method includes a step of peeling off the temporary support after the adhesive layer is formed.
[4] The production method according to any one of [1] to [3], wherein,
the transfer material includes an 1/4 wavelength plate.
[5] The production method according to [4], wherein,
the above-mentioned transfer material comprises a temporary support,
the above manufacturing method includes a step of forming the 1/4 wavelength plate in the above transfer material by a method including the steps of:
coating a liquid crystal composition containing a polymerizable liquid crystal compound on the temporary support to obtain a coating film; and
curing the coating film.
[6] The production method according to item [5], which comprises a step of applying a liquid crystal composition comprising a polymerizable liquid crystal compound to a surface of the 1/4 wavelength plate to obtain the cholesteric liquid crystal layer.
[7] A half mirror for use in a surface of an image display portion of an image display device,
the half mirror is manufactured by the manufacturing method of any one of [1] to [6],
the circularly polarized light reflecting layer and the adhesive layer are in direct contact,
the adhesive layer is in direct contact with the transparent substrate,
the thickness of the adhesive layer is 1.0 μm or more and 5.0 μm or less.
[8] A half mirror for use in a surface of an image display portion of an image display device,
the semi-reflecting mirror comprises a circular polarized light reflecting layer, an adhesive layer and a transparent substrate in sequence,
the circularly polarizing light reflecting layer includes a cholesteric liquid crystal layer,
the circularly polarized light reflecting layer and the adhesive layer are in direct contact,
the adhesive layer is in direct contact with the transparent substrate,
the adhesive layer is obtained by curing a curable adhesive,
the thickness of the adhesive layer is 1.0 μm or more and 5.0 μm or less,
the pencil hardness of the surface of the half mirror on the circularly polarized light reflecting layer side of the transparent substrate is HB or less.
[9] The half mirror according to [7] or [8], wherein,
the circular polarization light reflection layer includes 2 or more cholesteric liquid crystal layers, and the 2 or more cholesteric liquid crystal layers have mutually different central wavelengths of selective reflection.
[10] The half mirror according to [9], wherein,
the 2 or more layers of the cholesteric liquid crystal layer are in direct contact with each other.
[11] The half mirror according to [9] or [10], wherein,
the circular polarization light reflection layer includes 3 or more cholesteric liquid crystal layers, and the 3 or more cholesteric liquid crystal layers have mutually different central wavelengths of selective reflection.
[12] The half mirror according to [11], wherein,
the circularly polarizing light reflecting layer includes a cholesteric liquid crystal layer having a central wavelength of selective reflection at 400 to 500nm, a cholesteric liquid crystal layer having a central wavelength of selective reflection at 500 to 580nm, and a cholesteric liquid crystal layer having a central wavelength of selective reflection at 580 to 700 nm.
[13] The half mirror according to any one of [9] to [12], wherein,
in the circularly polarizing light reflecting layer, a cholesteric liquid crystal layer having a central wavelength of selective reflection of a shorter wavelength is disposed closer to the adhesive layer.
[14] The half mirror according to any one of [7] to [13], wherein,
the circularly polarized light reflecting layer includes a cholesteric liquid crystal layer having a center wavelength selectively reflecting in an infrared light region.
[15] The half mirror according to any one of [7] to [14], wherein,
the thickness of the circularly polarizing light reflecting layer is 25 μm or less.
[16] The half mirror according to any one of [7] to [15], wherein,
the transparent substrate is a glass plate or a plastic film with the front phase difference less than 10 nm.
[17] The half mirror according to any one of [7] to [16], which comprises an 1/4 wavelength plate,
and comprises the 1/4 wavelength plate, the circularly polarized light reflecting layer, the adhesive layer, and the transparent substrate in this order.
[18] A mirror with an image display function, comprising the half mirror of any one of [7] to [17],
and includes an image display device, the circularly polarized light reflecting layer, the adhesive layer, and the transparent substrate in this order.
[19] The mirror with image display function according to [18], wherein,
the image display device and the half mirror are directly bonded via an adhesive layer.
Effects of the invention
According to the present invention, it is possible to provide a method for manufacturing a half mirror capable of displaying a bright and clear image and displaying a mirror-reflected image. The present invention also provides a novel half mirror as a half mirror for use in the surface of an image display portion of an image display device. The half mirror of the present invention can provide a mirror with an image display function capable of displaying a bright and clear image and displaying a mirror-reflected image. The image display function-equipped mirror according to the present invention has an advantage that a display image and a specular reflection image can be observed even through a polarized sunglass lens.
Detailed Description
The present invention will be described in detail below.
In the present specification, "to" means that numerical values described before and after the "to" are included as a lower limit value and an upper limit value. In this specification, unless otherwise specified, angles such as "45 °", "parallel", "perpendicular", or "orthogonal" mean that the difference from the precise angle is in the range of less than 5 degrees. The difference from the precise angle is preferably less than 4 degrees, more preferably less than 3 degrees.
In the present specification, "(meth) acrylate" is used in the meaning of "either or both of acrylate and methacrylate".
In the present specification, the term "selective" as used with respect to circularly polarized light means that either one of right-handed circularly polarized light component and left-handed circularly polarized light component has a larger amount of light than the other circularly polarized light component. Specifically, in the case of the "selectivity", the circularly polarized light intensity of light is preferably 0.3 or more, more preferably 0.6 or more, and further preferably 0.8 or more. Substantially 1.0 is more preferable. Here, the circularly polarized light intensity means that the intensity of the right-handed circularly polarized light component of light is represented as IRAnd the intensity of the left-handed circularly polarized light component is set as ILFrom | IR-IL|/(IR+IL) The values indicated.
In the present specification, the term "handedness" as used with respect to circularly polarized light means right-handed circularly polarized light or left-handed circularly polarized light. The handedness of circularly polarized light is defined as that when viewed so that light advances toward the near side, the electric field vector is clockwise-rotated with time to be right-handed circularly polarized light, and counterclockwise-rotated to be left-handed circularly polarized light.
In this specification, the term "handedness" is sometimes used with respect to the direction of helical twist of cholesteric liquid crystal. The cholesteric liquid crystal reflects right-handed circular polarized light and transmits left-handed circular polarized light when the helical twist direction (handedness) is right, and reflects left-handed circular polarized light and transmits right-handed circular polarized light when the handedness is left.
The visible light is light of a wavelength visible to the human eye among electromagnetic waves, and represents light in a wavelength region of 380nm to 780 nm. Infrared (infrared) is a wavelength range electromagnetic wave longer than a visible light and shorter than an electric wave. The near infrared light in the infrared light is an electromagnetic wave in a wavelength range of 780nm to 2500 nm.
In the present specification, the case where the mirror with an image display function or the half mirror is referred to as "image" means that when the mirror with an image display function or the mirror with an image display function is used in combination, an image can be observed by viewing the half mirror from the transparent substrate side when an image is displayed on the image display portion. In the present specification, the term "mirror image" as used with respect to the mirror or half mirror with an image display function means an image that can be viewed by viewing from the transparent substrate side when no image is displayed on the image display portion when the mirror or half mirror with an image display function is used as the mirror with an image display function or in combination with the mirror with an image display function.
< half mirror >
As described later, the half mirror produced by the production method of the present invention (hereinafter referred to as a half mirror of the present invention) is a half mirror used for the surface of an image display portion of an image display device. The half mirror according to the present invention is used in particular in an image display unit of an image display device, and is preferably a half mirror used as a mirror surface when an image is not displayed on the image display unit.
As described above, the present inventors have found distortion in a specular reflection image of a half mirror including a transparent substrate and a cholesteric liquid crystal layer when viewed from the transparent substrate side. In this modification, it is considered that the orange-peel-like irregularities generated on the surface of the cholesteric liquid crystal layer are caused by scattering of reflected light in the visible light region at this portion. On the other hand, it is difficult to recognize the orange peel-like unevenness in the lamination of the film used in the image display device. Further, even when used on the surface of the image display unit of the image display device, orange peel-like irregularities are difficult to be recognized in a film having a low reflectance of visible light. The present inventors have found that providing a half mirror including a cholesteric liquid crystal layer as a visible light reflective half mirror for use on the surface of an image display portion of an image display device enables easy recognition of irregularities on such a half mirror. Further, further intensive studies have led to the discovery of a method for producing orange peel-like irregularities on the surface of a cholesteric liquid crystal layer, which can reduce the distortion of a specular reflection image.
The degree of the orange peel-like unevenness generated on the surface of the cholesteric liquid crystal layer can be determined from the degree of sharpness and the degree of no distortion (sharpness of image) of the image of the object that can be observed by the transmission mirror. Specifically, it is considered that the higher the resolution of the image, the less the orange peel-like irregularities. The measurement of the sharpness of the image can be performed in accordance with JIS K7374 as shown in examples. The definition of the image may be determined using ICM-IT manufactured by suma test instruments co.
The image clarity is preferably 70% or more, more preferably 80% or more, and further preferably 85% or more when an optical comb of 0.05mm is used, the image clarity being implemented at an incident light angle of 0 ° (the direction perpendicular to the sample surface) in the transmission system.
The half mirror of the present invention comprises a circularly polarized light reflecting layer, an adhesive layer and a transparent substrate in this order. In the half mirror of the present invention, the circularly polarized light reflecting layer and the adhesive layer may be in direct contact, and the adhesive layer and the transparent substrate may be in direct contact.
< method for manufacturing half mirror >
The half mirror can be formed by bonding a circularly polarized light reflecting layer to a transparent substrate. Specifically, the transfer material including the circularly polarizing light reflecting layer can be prepared, the surface of the circularly polarizing light reflecting layer of the transfer material and the transparent substrate can be bonded to each other with a curable adhesive, and then the curable adhesive can be cured.
[ transparent substrate ]
The material of the transparent substrate is not particularly limited. As the transparent substrate, a glass plate or a plastic plate used for manufacturing a general reflector can be used. The transparent substrate is preferably transparent in the visible light region and has a small birefringence. Examples of the plastic film include polyesters such as polyethylene terephthalate (PET), polycarbonates, acrylic resins, epoxy resins, polyurethanes, polyamides, polyolefins, cellulose derivatives, and silicones.
The thickness of the transparent substrate may be about 100 μm to 10mm, preferably 200 μm to 5.0mm, and more preferably 500 μm to 3.0 mm.
The transparent substrate may be larger in area of the main surface than the main surface of the circularly polarized light reflecting layer, may be the same as the transparent substrate, or may be smaller in area than the main surface of the circularly polarized light reflecting layer. In the present specification, the term "main surface" refers to a surface (front surface or back surface) of a plate-like or film-like member. A circularly polarized light reflecting layer may be bonded to a part of the main surface of the transparent substrate, and another type of reflecting layer such as a metal foil may be bonded or formed to another part. With this structure, an image can be displayed on a part of the mirror. On the other hand, the half mirror may be a half mirror in which a circularly polarized light reflecting layer is bonded to the entire main surface of the transparent substrate, and the half mirror may be bonded to an image display portion of an image display device having an image display portion having the same area as the main surface of the circularly polarized light reflecting layer. With this configuration, an image can be displayed on the entire surface of the mirror.
[ adhesive layer ]
In the production method of the present invention, the circularly polarizing light reflecting layer and the transparent substrate are bonded to each other through an adhesive layer having a thickness of 1.0 μm to 5.0 μm. That is, in the half mirror produced, the adhesive layer may be 1.0 μm or more and 5.0 μm or less. The present inventors have found that by controlling the thickness of the adhesive layer to be in the range of 1.0 μm to 5.0 μm, the orange peel-like irregularities on the surface of the circularly polarized light reflecting layer, that is, the surface of the cholesteric liquid crystal layer can be reduced in the obtained half mirror.
The thickness of the adhesive layer is more preferably 2.0 μm or more and 4.0 μm or less.
As the adhesive layer for bonding the circularly polarizing light reflecting layer and the transparent substrate, a layer obtained by curing a curable adhesive is used. As the curable adhesive, there are a thermosetting type, a photo-curing type and a reaction curing type from the viewpoint of the curing system, and as the raw materials, compounds such as acrylates, polyurethanes, urethane acrylates, epoxies, epoxy acrylates, polyolefins, modified olefins, polypropylenes, ethylene-vinyl alcohols, vinyl chlorides, chloroprene rubbers, cyanoacrylates, polyamides, polyimides, polystyrenes and polyvinyl butyrals can be used. From the viewpoint of workability and productivity, a photo-curing type is preferable as a curing system, and from the viewpoint of optical transparency and heat resistance, acrylates, urethane acrylates, epoxy acrylates, and the like are preferably used as a raw material.
[ transfer Material ]
A circularly polarized light reflecting layer may be prepared as a transfer material, and the surface of the circularly polarized light reflecting layer may be bonded to the transparent substrate. The transfer material may include a temporary support. As will be described later, a material for forming the circularly polarized light reflecting layer is used as a transfer material, and the circularly polarized light reflecting layer formed on the temporary support can be transferred onto the transparent substrate using the transfer material to produce a half mirror. The transfer material may have a circularly polarized light reflecting layer and an 1/4 wavelength plate. For example, the transfer material may include a temporary support, an 1/4 wavelength plate, and a circularly polarized light reflecting layer in this order.
When a transfer material having a temporary support is used, the temporary support may be peeled off after bonding the circularly polarized light reflecting layer to the transparent substrate. The temporary support may be peeled off when the circularly polarized light reflecting layer is bonded to the image display device, and may be bonded to the image display device on the obtained peeled surface. The temporary support may function as a protective film, for example.
The transfer material may be composed of an 1/4 wavelength plate and a circularly polarized light reflecting layer. For example, a half mirror can be obtained by forming a plurality of cholesteric liquid crystal layers in order on the surface of an 1/4 wavelength plate such as an extension film to form a circularly polarized light reflecting layer, and bonding the surface of the circularly polarized light reflecting layer to a transparent substrate.
When the circularly polarized light reflecting layer is bonded to the transparent substrate, the circularly polarized light reflecting layer in the transfer material and the transparent substrate are bonded together with a curable adhesive. The surface of the circularly polarized light reflecting layer is preferably coated with a curable adhesive, and the coated surface is preferably bonded to the transparent substrate. Then, the curing agent is cured based on the curing type adhesive used.
As described above, it has been difficult to ensure sufficient adhesive force for the surface of the image display unit of the image display device by the thickness of the adhesive layer being as thin as 1 μm or more and 5 μm or less, but the present inventors have found that the adhesiveness can be ensured by setting the pencil hardness of the surface of the transfer material bonded with the curable adhesive (the surface of the transfer material bonded to the transparent substrate) to HB or less. The surface of the transfer material bonded with the curable adhesive may be a circularly polarized light reflecting layer. That is, the outermost surface of the transfer material to be bonded to the transparent substrate may be a circularly polarized light reflecting layer.
Without being bound to any theory, it is considered that the reason why a sufficient adhesive force is obtained is that fine air bubbles are easily outgassed and the adhesive area is increased when the transfer material is bonded to the adhesive layer due to the softening of the bonding surface of the transfer material, some adhesiveness is observed on the surface of the transfer material due to the softening of the bonding surface of the transfer material, or the adhesive layer component is easily penetrated into the vicinity of the bonding surface of the transfer material due to the softening of the bonding surface of the transfer material.
The pencil hardness of the surface of the transfer material bonded to the transparent substrate is preferably HB, B, 2B, 3B, or 4B, and more preferably B, 2B, or 3B. In the present specification, the pencil hardness is a value obtained by evaluating the layer surface according to JIS K5400 (pencil scratch test method).
The pencil hardness of the transfer material can be adjusted by adjusting the amount of the crosslinking agent in the liquid crystal composition for bonding the outermost layer, that is, for forming the circularly polarizing light reflecting layer. Alternatively, the conditions of light irradiation or heating when the liquid crystal composition is cured to form a layer can be adjusted.
In the transfer material, the part of the cholesteric liquid crystal layer including the cholesteric liquid crystal layer closest to the adhesive layer side may be the pencil hardness of HB or less at the surface thereof in the production, or all the cholesteric liquid crystal layers of the circularly polarizing light reflecting layer may be the pencil hardness of HB or less at the surface thereof in the production, but the latter is preferable. When the transfer material includes an 1/4 wavelength plate, it is also preferable that the 1/4 wavelength plate has a pencil hardness of HB or less on the surface thereof during production. In particular, when the transfer material includes an 1/4-wavelength plate made of a liquid crystal composition, it is preferable that the 1/4-wavelength plate has a pencil hardness of HB or less on the surface thereof during production.
The present inventors have found that in a half mirror bonded to a transparent substrate with the pencil hardness of the surface of the transfer material bonded being HB or less, the pencil hardness of the surface of the half mirror on the side opposite to the transparent substrate when viewed from a circularly polarized light reflective layer is H or less. On the other hand, in the case where the pencil hardness of the transfer material surface to be bonded in the production method is higher than HB, a sufficient adhesive force cannot be obtained, but in this case, an example where the pencil hardness of the surface of the half mirror on the side opposite to the transparent substrate when viewed from the circularly polarized light reflecting layer is H is included. In the study of the present inventors, it was found that in a half mirror having a surface of the half mirror on the side opposite to the transparent substrate when viewed from the circularly polarized light reflecting layer, the pencil hardness of the transfer material surface bonded in the production method was higher than HB. Accordingly, it is considered that such a half mirror is manufactured so that the pencil hardness of the transfer material surface to be bonded is HB or less. Further, as described above, even in the case of a half mirror whose surface on the side opposite to the transparent substrate when viewed from the circularly polarized light reflecting layer has a pencil hardness of H, there is a possibility that the half mirror is manufactured so that the pencil hardness of the surface of the circularly polarized light reflecting layer to be bonded is HB or less.
The surface of the half mirror on the circularly polarized light reflecting layer side may be a circularly polarized light reflecting layer, an 1/4 wavelength plate, or the like, with respect to the transparent substrate.
[ circularly polarized light reflecting layer ]
The circularly polarizing light reflecting layer comprises at least 1 cholesteric liquid crystal layer exhibiting selective reflection in the visible light region. The circularly polarized light reflecting layer may include 2 or more cholesteric liquid crystal layers, or may include other layers such as an alignment layer. The circularly polarized light reflecting layer is preferably constituted by a cholesteric liquid crystal layer only. Also, when the circularly polarized light reflecting layer includes a plurality of cholesteric liquid crystal layers, it is preferable that these are in direct contact with adjacent cholesteric liquid crystal layers. The circularly polarizing light reflecting layer preferably includes 3 or more cholesteric liquid crystal layers such as 3 layers and 4 layers.
The thickness of the circularly polarizing light reflecting layer is preferably 2.0 to 30 μm, more preferably 4.0 to 25 μm, and still more preferably 5.0 to 20 μm.
In the half mirror, orange peel is more likely to occur as the thickness of the layer bonded to the transparent substrate is smaller. Therefore, when the thickness of the circularly polarizing light reflecting layer or the total thickness of a laminate of the circularly polarizing light reflecting layer and the 1/4 wavelength plate described later is 25 μm or less, particularly 20 μm or less, the effect of reducing orange peel in the present invention is remarkable.
(cholesteric liquid Crystal layer)
In the present specification, a cholesteric liquid crystal layer refers to a layer in which a cholesteric liquid crystal phase is fixed. The cholesteric liquid crystal layer is sometimes simply referred to as a liquid crystal layer.
A cholesteric liquid crystal phase is known to mean selective reflection of circularly polarized light in which either right-handed circularly polarized light or left-handed circularly polarized light is selectively reflected in a specific wavelength region while the other of the right-handed circularly polarized light and the left-handed circularly polarized light is transmitted. In this specification, selective reflection of circularly polarized light may be simply referred to as selective reflection.
As a film including a layer in which a cholesteric liquid crystal phase showing selective reflection of circularly polarized light is fixed, a large number of films formed of a composition including a polymerizable liquid crystal compound have been known, and as for a cholesteric liquid crystal layer, reference can be made to these conventional techniques.
The cholesteric liquid crystal layer is a layer that maintains the alignment of the liquid crystal compound in the cholesteric liquid crystal phase, and typically, a layer that is polymerized and cured by ultraviolet irradiation, heating, or the like to form a layer having no fluidity and that is in a state in which the alignment state is not changed by an external magnetic field or an external force is sufficient in order to set the polymerizable liquid crystal compound in the aligned state of the cholesteric liquid crystal phase. In addition, in the cholesteric liquid crystal layer, it is sufficient that the optical properties of the cholesteric liquid crystal phase are maintained in the layer, and the liquid crystal compound in the layer does not need to exhibit liquid crystallinity. For example, the polymerizable liquid crystal compound can be polymerized to a high molecular weight by a curing reaction and loses liquid crystallinity.
The central wavelength λ of the selective reflection of the cholesteric liquid crystal layer depends on the pitch P of the helical structures in the cholesteric structure (the period of the helix) and is in accordance with the relationship of the average refractive index n of the cholesteric liquid crystal layer and λ n × P. In the present specification, the central wavelength λ of selective reflection of the cholesteric liquid crystal layer is a wavelength at the center of gravity of a reflection peak of a circularly polarized light reflection spectrum measured from the normal direction of the cholesteric liquid crystal layer. In the present specification, the center wavelength of selective reflection means a center wavelength measured from a normal direction of the cholesteric liquid crystal layer.
As can be seen from the above equation, the center wavelength of selective reflection can be adjusted by adjusting the pitch of the helical structure. The center wavelength λ can be adjusted by adjusting the n value and the P value to selectively reflect either right-handed circularly polarized light or left-handed circularly polarized light with respect to light having a desired wavelength.
When light is obliquely incident with respect to the cholesteric liquid crystal layer, the center wavelength of selective reflection shifts to the short wavelength side. Therefore, it is preferable to adjust n × P so that λ calculated according to the above expression of λ ═ n × P becomes a long wavelength for a wavelength of selective reflection required for image display. Will be at refractive index n2The cholesteric liquid crystal layer (2) has a light angle theta with respect to a normal direction of the cholesteric liquid crystal layer (a helical axis direction of the cholesteric liquid crystal layer)2The central wavelength of the selective reflection in the angular transmission of (2) is set to λdWhen is lambdadRepresented by the following formula.
λd＝n2×P×cosθ2
By designing the central wavelength of selective reflection of the cholesteric liquid crystal layer included in the circularly polarizing light reflecting layer in consideration of the above, it is possible to prevent degradation of visibility when an image is observed from an oblique direction. Further, visibility when the image is viewed obliquely can be reduced. It is practical, for example, to prevent peeking in a smartphone or a personal computer.
Further, in the mirror with an image display function using a half mirror according to the present invention, due to the above-described property of selective reflection, a color tone may appear in a display image and a specular reflection image observed obliquely. This color tone can also be prevented by including a cholesteric liquid crystal layer having a central wavelength of selective reflection in the infrared light region in the circularly polarized light reflection layer. Specifically, the central wavelength of the selective reflection in the infrared region in this case is 780 to 900nm, preferably 780 to 850 nm.
The pitch of the cholesteric liquid crystal phase depends on the kind of the chiral agent used together with the polymerizable liquid crystal compound or the addition concentration thereof, and thus a desired pitch can be obtained by adjusting the above. In addition, as for the method of measuring the spiral direction or pitch, the method described in "liquid crystal chemistry experiment entry" published by Sigma 2007, page 46 and "liquid crystal review editorial committee MARUZEN 196 can be used.
In the half mirror of the present invention, the circularly polarized light reflecting layer preferably includes a cholesteric liquid crystal layer having a central wavelength of selective reflection in a wavelength region of red light, a cholesteric liquid crystal layer having a central wavelength of selective reflection in a wavelength region of green light, and a cholesteric liquid crystal layer having a central wavelength of selective reflection in a wavelength region of blue light. The reflective layer preferably includes, for example, a cholesteric liquid crystal layer having a central wavelength of selective reflection at 400nm to 500nm, a cholesteric liquid crystal layer having a central wavelength of selective reflection at 500nm to 580nm, and a cholesteric liquid crystal layer having a central wavelength of selective reflection at 580nm to 700 nm.
In the half mirror of the present invention, the center wavelength of selective reflection with the cholesteric liquid crystal layer can be adjusted as follows based on the emission peak of the image display device used in combination. That is, the central wavelength of selective reflection of the cholesteric liquid crystal layer may be different from the wavelength of the emission peak of the image display device by 5nm or more, preferably by 10nm or more. In particular, in the half mirror of the present invention not including the 1/4 wavelength plate described later, the adjustment is preferably performed. By deviating the center wavelength of the selective reflection from the light emission wavelength used for image display of the image display device, the light used for image display can brighten the display image without being reflected by the cholesteric liquid crystal layer. The wavelength of the emission peak of the image display device can be confirmed by the emission spectrum of the image display device at the time of white display. The peak wavelength may be a peak wavelength in the visible light region of the emission spectrum, and may be, for example, at least one selected from the group consisting of the emission peak wavelength λ R of red light, the emission peak wavelength λ G of green light, and the emission peak wavelength λ B of blue light in the image display device. The cholesteric liquid crystal layer has a center wavelength of selective reflection which differs by 5nm or more, preferably by 10nm or more, from any of the emission peak wavelength λ R of red light, the emission peak wavelength λ G of green light, and the emission peak wavelength λ B of blue light of the image display device. When the circularly polarized light reflecting layer includes a plurality of cholesteric liquid crystal layers, the center wavelength of selective reflection of all the cholesteric liquid crystal layers may be different from the wavelength of the peak of light emitted from the image display device by 5nm or more, preferably by 10nm or more. For example, in the case where the image display device is a full-color display device in which the emission spectrum at the time of white display indicates the emission peak wavelength λ R of red light, the emission peak wavelength λ G of green light, and the emission peak wavelength λ B of blue light, the center wavelength of selective reflection of the cholesteric liquid crystal layer may be different from any of λ R, λ G, and λ B by 5nm or more, preferably by 10nm or more.
Further, when the circularly polarized light reflecting layer includes a plurality of cholesteric liquid crystal layers, the cholesteric liquid crystal layer closer to the image display device preferably has a longer central wavelength of selective reflection. With this configuration, the diagonal color tone in the image and the specular reflection image can be suppressed.
The center wavelength of selective reflection of the cholesteric liquid crystal layer used is adjusted according to the emission wavelength region of the image display device and the use mode of the circularly polarizing light reflecting layer, whereby an image can be displayed with good light use efficiency. Examples of the mode of use of the circularly polarizing light reflecting layer include an incident angle of light with respect to the circularly polarizing light reflecting layer, an image observation direction, and the like.
As each cholesteric liquid crystal layer, a cholesteric liquid crystal layer in which the spiral direction is either right or left is used. The handedness of the reflected circularly polarized light of the cholesteric liquid crystal layer coincides with the handedness of the helix. When a plurality of cholesteric liquid crystal layers are included in the circularly polarizing reflective layer, the helices may all have the same handedness or may have different handedness. The cholesteric liquid crystal layer having a specific central wavelength of selective reflection may include a cholesteric liquid crystal layer having either right or left handedness, or may include a cholesteric liquid crystal layer having both right and left handedness.
In the half mirror including the 1/4 wavelength plate described later, a cholesteric liquid crystal layer having a helical direction of either right or left may be used depending on the direction of rotation of circularly polarized light of the direction of rotation obtained by emitting light from the image display device and transmitting 1/4 wavelength plate. Specifically, a cholesteric liquid crystal layer having a spiral handedness that transmits circularly polarized light having a handedness obtained by emitting light from the image display device and transmitting light through the 1/4 wavelength plate may be used. When the circularly polarized light reflecting layer includes a plurality of cholesteric liquid crystal layers, the spiral directions of the helices are preferably all the same.
In the half-value width Δ λ (nm) of the selective reflection band indicating selective reflection, Δ λ depends on the birefringence Δ n of the liquid crystal compound and the pitch P, and is in accordance with a relationship of Δ λ ═ Δ n × P. Therefore, the control of selecting the width of the reflection band can be performed by adjusting Δ n. The Δ n can be adjusted by adjusting the kind of the polymerizable liquid crystal compound or the mixing ratio thereof, or by controlling the temperature at which the alignment is fixed.
In order to form a cholesteric liquid crystal layer having the same central wavelength of selective reflection, a plurality of cholesteric liquid crystal layers having the same period P and the same spiral direction may be stacked. The cholesteric liquid crystal layer having the same lamination period P and the same spiral direction can improve the circularly polarized light selectivity at a specific wavelength.
[1/4 wavelength plate ]
The half mirror of the present invention may comprise an 1/4 wavelength plate. Also, the transfer material may include 1/4 wavelength plates. When the half mirror of the present invention is used as a mirror having an image display function, light from the image display device can be converted into circularly polarized light that transmits the handedness of the circularly polarized light reflecting layer and can be incident on the circularly polarized light reflecting layer by disposing 1/4 wavelength plates between the image display device and the circularly polarized light reflecting layer. Therefore, light reflected by the circularly polarized light reflecting layer and returned to the image display device side can be greatly reduced, and a bright image display can be performed.
The 1/4 wavelength plate may be a retardation layer functioning as a 1/4 wavelength plate in the visible light region. Examples of the 1/4 wavelength plate include a 1-layer 1/4 wavelength plate, and a broad-band 1/4 wavelength plate in which a 1/4 wavelength plate and a 1/2 wavelength retardation plate are laminated.
The front retardation of the former 1/4 wavelength plate is only required to be 1/4 of the emission wavelength of the image display device. Therefore, for example, if the emission wavelength of the image display device is 450nm, 530nm, or 640nm, a phase difference layer having a reverse wavelength dispersion property such as a phase difference of 112.5nm ± 10nm, preferably 112.5nm ± 5nm, more preferably 112.5nm at a wavelength of 450nm, or 132.5nm ± 10nm, preferably 132.5nm ± 5nm, more preferably 132.5nm at a wavelength of 530nm, or 160nm ± 10nm, preferably 160nm ± 5nm, more preferably 160nm at a wavelength of 640nm is most preferable as the 1/4 wavelength plate, and a phase difference plate having a small wavelength dispersion property of a phase difference or a phase difference plate having a normal wavelength dispersion property can be used. The inverse wavelength dispersion property is a property that the absolute value of the retardation becomes larger as the wavelength becomes longer, and the conventional wavelength dispersion property is a property that the absolute value of the retardation becomes larger as the wavelength becomes shorter.
The laminated 1/4 wavelength plate can be preferably used because it is formed by bonding a 1/4 wavelength plate and a 1/2 wavelength retardation plate to each other with a retardation axis of 60 ° angle, disposing the 1/2 wavelength retardation plate on the incident side of linearly polarized light, and using the 1/2 wavelength retardation plate with the retardation axis crossing at 15 ° or 75 ° with respect to the polarization plane of the incident linearly polarized light, and the reverse wavelength dispersion of the retardation is good.
In the present specification, the phase difference means a front retardation. The retardation can be measured using an axomatics inc. Alternatively, the measurement may be performed by causing light of a specific wavelength to be incident in the film normal direction in KOBRA 21ADH or WR (Oji scientific instruments co., ltd).
The 1/4 wavelength plate is not particularly limited and can be appropriately selected according to the purpose. Examples thereof include a quartz plate, an elongated polycarbonate film, an elongated norbornene polymer film, a transparent film oriented by containing inorganic particles exhibiting birefringence such as strontium carbonate, and a film obtained by depositing an inorganic electrolyte obliquely onto a support.
Examples of the 1/4 wavelength plate include (1) a retardation plate in which a birefringent film having a large retardation and a birefringent film having a small retardation are laminated so that optical axes thereof are orthogonal to each other as described in japanese patent application laid-open nos. 5-27118 and 5-27119, (2) a retardation plate in which a polymer film having a wavelength of λ/4 at a specific wavelength and a polymer film having a wavelength of λ/2 at the same wavelength and made of the same material as the polymer film are laminated to obtain a wavelength of λ/4 in a wide wavelength region as described in japanese patent application laid-open No. 10-68816, (3) a retardation plate in which a wavelength of λ/4 can be realized in a wide wavelength region by laminating two polymer films as described in japanese patent application laid-open No. 10-90521, (4) a retardation plate in which a modified polycarbonate film is used and which a wide wavelength region can be realized by laminating two polymer films as described in international patent application laid-open No. 00/26705 A retardation plate that realizes λ/4 wavelength in a wavelength region, and (5) a retardation plate that uses a cellulose acetate film and can realize λ/4 wavelength in a wide wavelength region as described in international publication No. 00/65384.
As the 1/4 wavelength plate, commercially available products can be used, and examples of commercially available products include the trade names: PURE-ACE (registered trademark) WR (manufactured by TEIJIN LIMITED, polycarbonate film), and the like.
The 1/4 wavelength plate can be formed by aligning and fixing a polymerizable liquid crystal compound or a polymer liquid crystal compound. For example, the 1/4 wavelength plate can be formed by applying a liquid crystal composition in which a polymerizable liquid crystal compound is aligned in a liquid crystal state to form a nematic alignment to a temporary support or an alignment film, and then fixing the liquid crystal composition by photo-crosslinking or thermal crosslinking. The 1/4 wavelength plate may be a layer in which a composition containing a polymer liquid crystal compound is obtained by applying a liquid crystal composition to the surface of a temporary support or an alignment film to form a nematic alignment in a liquid crystal state, and then cooling the liquid crystal composition to fix the alignment.
[1/4 wavelength plate and method for producing cholesteric liquid Crystal layer ]
Hereinafter, a material and a method for producing an 1/4 wavelength plate comprising a cholesteric liquid crystal layer and a liquid crystal composition will be described.
Examples of the material used for forming the 1/4 wavelength plate include a liquid crystal composition containing a polymerizable liquid crystal compound. The material used in the formation of the cholesteric liquid crystal layer preferably further contains a chiral agent (optically active compound). The liquid crystal composition described above, which is mixed with a surfactant, a polymerization initiator, or the like and dissolved in a solvent or the like, may be applied to a temporary support, an alignment film, an 1/4 wavelength plate, a cholesteric liquid crystal layer to be a bottom layer, or the like, and after the alignment aging, the liquid crystal composition may be cured and fixed to form a 1/4 wavelength plate or a cholesteric liquid crystal layer.
(polymerizable liquid Crystal Compound)
As the polymerizable liquid crystal compound, a rod-like liquid crystal compound may be used.
Examples of the rod-like polymerizable liquid crystal compound include rod-like nematic liquid crystal compounds. As the rod-like nematic liquid crystal compound, azomethines, azoxides, cyanobiphenyls, cyanophenyl esters, benzoates, phenyl cyclohexanecarboxylates, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines, phenyldioxanes, diphenylacetylenes, and alkenylcyclohexylbenzonitrile are preferably used. Not only a low molecular liquid crystal compound but also a high molecular liquid crystal compound can be used.
The polymerizable liquid crystal compound can be obtained by introducing a polymerizable group into a liquid crystal compound. Examples of the polymerizable group include an unsaturated polymerizable group, an epoxy group, and an aziridine group, an unsaturated polymerizable group is preferable, and an ethylenically unsaturated polymerizable group is particularly preferable. The polymerizable group can be introduced into the molecule of the liquid crystal compound by various methods. The number of the polymerizable groups having the polymerizable liquid crystal compound is preferably 1 to 6, and more preferably 1 to 3. Examples of the polymerizable liquid crystal compound include compounds described in Makromol. chem.,190, 2255 (1989), Advanced Materials 5, 107 (1993), U.S. Pat. No. 4683327, U.S. Pat. No. 5622648, U.S. Pat. No. 5770107, International publication No. WO95/22586, WO95/24455, WO97/00600, WO98/23580, WO98/52905, Japanese patent application laid-open No. 1-272551, Japanese patent application laid-open No. 6-16616, Japanese patent application laid-open No. 7-110469, Japanese patent application laid-open No. 11-80081, and Japanese patent application laid-open No. 2001-328973. Two or more polymerizable liquid crystal compounds may be used simultaneously. When two or more polymerizable liquid crystal compounds are used simultaneously, the alignment temperature can be lowered.
The amount of the polymerizable liquid crystal compound added to the liquid crystal composition is preferably 80 to 99.9 mass%, more preferably 85 to 99.5 mass%, and particularly preferably 90 to 99 mass% based on the mass of the solid content (mass excluding the solvent) of the liquid crystal composition.
(chiral agent: optically active Compound)
The material used in the formation of the cholesteric liquid crystal layer preferably comprises a chiral agent. The chiral agent has the function of initiating a helical structure of the cholesteric liquid crystal phase. The chiral compound may be selected according to the purpose, depending on the direction of helix or the pitch of helix induced by the compound.
The chiral agent is not particularly limited, and a known compound can be used. Examples of chiral agents include compounds described in the handbook of liquid crystal devices (chapter 3, items 4-3, TN, STN chiral reagents, page 199, published by the 142 th committee of Japan society of academic interest, 1989), Japanese patent application laid-open Nos. 2003-287623, 2002-302487, 2002-80478, 2002-80851, 2010-181852, and 2014-034581.
An axially asymmetric compound or a planar asymmetric compound, which generally contains an asymmetric carbon atom but does not contain an asymmetric carbon atom, can also be used as the chiral agent. Examples of the axial asymmetric compound and the planar asymmetric compound include binaphthyl, spirolene, p-cycloaralkyl, and derivatives thereof. The chiral agent may have a polymerizable group. When both the chiral agent and the liquid crystal compound have a polymerizable group, a polymer having a repeating unit derived from the polymerizable liquid crystal compound and a repeating unit derived from the chiral agent can be formed by a polymerization reaction of the polymerizable chiral agent and the polymerizable liquid crystal compound. In this embodiment, the polymerizable group of the polymerizable chiral agent is preferably the same type of group as the polymerizable group of the polymerizable liquid crystal compound. Accordingly, the polymerizable group of the chiral agent is also preferably an unsaturated polymerizable group, an epoxy group, or an aziridine group, more preferably an unsaturated polymerizable group, and particularly preferably an ethylenically unsaturated polymerizable group.
Also, the chiral agent may be a liquid crystal compound.
As the chiral agent, an isosorbide derivative, isomannide derivative, or binaphthyl derivative can be preferably used. As the isosorbide derivative, a commercially available product such as LC-756 manufactured by BASF corporation can be used.
The content of the chiral agent in the liquid crystal composition is preferably 0.01 to 200 mol%, more preferably 1 to 30 mol%, based on the total molar amount of the polymerizable liquid crystal compound.
(polymerization initiator)
In the mode of carrying out the polymerization reaction by ultraviolet irradiation, the polymerization initiator used is preferably a photopolymerization initiator capable of initiating the polymerization reaction by ultraviolet irradiation, and examples of the photopolymerization initiator include α -carbonyl compounds (described in each of the specifications of U.S. Pat. Nos. 2367661 and 2367670), acyloin ethers (described in U.S. Pat. No. 2448828), α -hydrocarbyl-substituted aromatic acyloin compounds (described in U.S. Pat. No. 2722512), polyquinone compounds (described in each of the specifications of U.S. Pat. Nos. 63 3046127 and 2951758), combinations of triarylimidazole dimers and p-aminophenyl ketones (described in U.S. Pat. No. 3549367), acridine and phenazine compounds (described in each of the specifications of Acridine-substituted-ketone-containing-substituted-olefin-substituted-ketone-containing compounds (described in U.S. Pat. No. 20157667 No. wo 2006, and phenazine-containing compounds (described in Japanese patent application Nos. wo 2006-60-105667-containing-and-4239850), acylphosphine oxide compounds (described in Japanese patent application Nos. ep. 8963-40409, jp-494, jp-5-29234-10-ep-kokai publication No. hei,028,2001,2001,2001,2001,2001,2001,2001,2001,2001,2001,8542, jp-kokai publication No. ep-hei,0519, ep-.
As the polymerization initiator, it is also preferable to use an acylphosphine oxide compound or an oxime compound.
As the acylphosphine oxide compound, for example, IRGACURE819 (compound name: bis (2,4, 6-trimethylbenzoyl) -phenylphosphine oxide) manufactured by BASF Japan Ltd. As the oxime compound, commercially available products such as IRGACURREOXE 01 (manufactured by BASF corporation), IRGACURE OXE02 (manufactured by BASF corporation), TR-PBG-304 (manufactured by Changzhou Tronly New electronic Materials CO., LTD.), Adeka Arkls NCI-831, Adeka Arkls NCI-930 (manufactured by ADEKA corporation), Adeka Arkls NCI-831 (manufactured by ADEKA corporation) and the like can be used.
One kind of the polymerization initiator may be used alone, or two or more kinds may be used simultaneously.
The content of the photopolymerization initiator in the liquid crystal composition is preferably 0.1 to 20% by mass, and more preferably 0.5 to 5% by mass, based on the content of the polymerizable liquid crystal compound.
(crosslinking agent)
The liquid crystal composition may optionally contain a crosslinking agent for the purpose of improving the strength and durability of the cured film. As the crosslinking agent, a crosslinking agent that is cured by ultraviolet rays, heat, moisture, or the like can be preferably used.
The crosslinking agent is not particularly limited and can be appropriately selected according to the purpose, and examples thereof include polyfunctional acrylate compounds such as trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, and pentaerythritol tetra (meth) acrylate; epoxy compounds such as glycidyl (meth) acrylate and ethylene glycol diglycidyl ether; aziridine compounds such as 2, 2-bis (hydroxymethyl) butanol-tris [3- (1-aziridinyl) propionate ], 4-bis (ethyleneiminocarbonylamino) diphenylmethane and the like; isocyanate compounds such as hexamethylene diisocyanate and biuret type isocyanate; a polyoxazoline compound having an oxazoline group in a side chain; and alkoxysilane compounds such as vinyltrimethoxysilane and N- (2-aminoethyl) 3-aminopropyltrimethoxysilane. Among these, a multifunctional acrylate compound is preferable. The multifunctional acrylate compound is preferably a 3-6 functional acrylate compound, and more preferably a 4-6 functional acrylate compound. In addition, a known catalyst can be used according to the reactivity of the crosslinking agent, and productivity can be improved in addition to the improvement of the strength and durability of the membrane. These may be used alone or in combination of two or more.
The content of the crosslinking agent in the liquid crystal composition is preferably 0 to 8.0 parts by mass, more preferably 0.1 to 7.0 parts by mass, and still more preferably 0.2 to 5.5 parts by mass, based on 100 parts by mass of the polymerizable liquid crystal compound in the liquid crystal composition. By adjusting the content of the crosslinking agent within the above range, the pencil hardness of the surface of the formed cholesteric liquid crystal layer can be adjusted to be HB or less.
(alignment controlling agent)
To facilitate stable or rapid planar alignment, an alignment controlling agent may be added to the liquid crystal composition. Examples of the orientation controlling agent include fluoro (meth) acrylate polymers described in the stages [ 0018 ] to [ 0043 ] of Japanese patent laid-open No. 2007-272185, and compounds represented by the formulae (I) to (IV) described in the stages [ 0031 ] to [ 0034 ] of Japanese patent laid-open No. 2012-203237.
Further, as the orientation controlling agent, one kind may be used alone, or two or more kinds may be used simultaneously.
The amount of the orientation-controlling agent added to the liquid crystal composition is preferably 0.01 to 10% by mass, more preferably 0.01 to 5.0% by mass, and particularly preferably 0.02 to 1.0% by mass, based on the total mass of the polymerizable liquid crystal compound.
(other additives)
In addition, the liquid crystal composition may contain at least one selected from various additives such as a surfactant and a polymerizable monomer for adjusting the surface tension of the coating film and making the film thickness uniform. If necessary, a polymerization inhibitor, an antioxidant, an ultraviolet absorber, a light stabilizer, a colorant, and metal oxide fine particles may be further added to the liquid crystal composition within a range not to deteriorate optical performance.
(solvent)
The solvent used for the preparation of the liquid crystal composition is not particularly limited and may be appropriately selected according to the purpose, but an organic solvent is preferably used.
The organic solvent is not particularly limited, and can be appropriately selected according to the purpose, and examples thereof include ketones, alkyl halides, amides, sulfoxides, heterocyclic compounds, hydrocarbons, esters, and ethers. These may be used alone or in combination of two or more. Of these, ketones are particularly preferable in view of the influence on the environment.
(coating, orientation, polymerization)
The method of coating the liquid crystal composition such as the temporary support, the alignment film, the 1/4 wavelength plate, and the cholesteric liquid crystal layer as the underlayer is not particularly limited and can be appropriately selected according to the purpose, and examples thereof include a wire bar coating method, a curtain coating method, an extrusion coating method, a direct gravure coating method, a reverse gravure coating method, a die coating method, a spin coating method, a dip coating method, a spray coating method, and a slide coating method. The liquid crystal composition can be transferred to a liquid crystal layer formed on a support. The liquid crystal molecules are aligned by heating the applied liquid crystal composition. The cholesteric liquid crystal layer may be formed by cholesteric alignment, and the 1/4 wavelength plate is preferably formed by nematic alignment. In the case of cholesteric alignment, the heating temperature is preferably 200 ℃ or lower, and more preferably 130 ℃ or lower. By this alignment treatment, an optical film can be obtained in which the polymerizable liquid crystal compound is twist-aligned so as to have a helical axis in a direction substantially perpendicular to the film surface.
In the case of nematic orientation, the heating temperature is preferably 50 to 120 ℃ and more preferably 60 to 100 ℃.
The aligned liquid crystal compound can be further polymerized and the liquid crystal composition is cured. The polymerization may be any of thermal polymerization and photopolymerization by irradiation with light, and photopolymerization is preferable. The light irradiation is preferably performed by using ultraviolet rays. The irradiation energy is preferably 20mJ/cm2～50J/cm2More preferably 100mJ/cm2～1,500mJ/cm2. In order to promote the photopolymerization reaction, light irradiation may be performed under heating conditions or under a nitrogen atmosphere. The wavelength of the ultraviolet radiation is preferably 350nm to 430 nm. From the viewpoint of stability, the polymerization reaction rate is preferably high, preferably 70% or more, and more preferably 80% or more. The polymerization reaction rate can be determined by measuring the consumption ratio of the polymerizable functional group using IR absorption spectroscopy.
The thickness of each cholesteric liquid crystal layer is not particularly limited as long as it is within a range showing the above characteristics, and is preferably within a range of 1.0 μm to 20 μm, and more preferably within a range of 2.0 μm to 10 μm.
The thickness of the 1/4 wavelength plate formed from the liquid crystal composition is not particularly limited, but is preferably 0.2 to 10 μm, and more preferably 0.5 to 2.0. mu.m.
[ temporary support ]
The liquid crystal composition may be applied to a temporary support or the surface of an alignment layer formed on the surface of the temporary support to form a layer. The temporary support or the temporary support and the alignment layer may be peeled off after the layer is formed. For example, the transfer material may be peeled off after being bonded to the transparent substrate. Examples of the temporary support include polyesters such as polyethylene terephthalate (PET), polycarbonates, acrylic resins, epoxy resins, polyurethanes, polyamides, polyolefins, cellulose derivatives, silicones, glass plates, and the like.
The thickness of the temporary support may be about 5 μm to 1000. mu.m, preferably 10 μm to 250. mu.m, and more preferably 15 μm to 120. mu.m.
The alignment layer can be provided by a method such as rubbing treatment of an organic compound such as a polymer (a resin such as polyimide, polyvinyl alcohol, polyester, polyarylate, polyamideimide, polyetherimide, polyamide, or modified polyamide), oblique deposition of an inorganic compound, formation of a layer having microgrooves, or accumulation of an organic compound (for example, tricosanoic acid, dioctadecylmethylammonium chloride, or methyl stearate) by the langmuir-blodgett method (LB film) utilization rate. Further, an alignment layer that generates an alignment function by application of an electric field, application of a magnetic field, or light irradiation may be used.
In particular, the alignment layer composed of a polymer is preferably subjected to a rubbing treatment and the rubbing-treated surface is coated with a liquid crystal composition. The rubbing treatment can be performed by rubbing the surface of the polymer layer in a predetermined direction a plurality of times using paper or cloth.
The liquid crystal composition may be applied to the surface of the temporary support or the surface of the temporary support subjected to rubbing treatment without providing an alignment layer.
The thickness of the alignment layer is preferably 0.01 to 5.0. mu.m, and more preferably 0.05 to 2.0. mu.m.
[1/4 laminate film of wavelength plate and cholesteric liquid Crystal layer ]
As described above, the cholesteric liquid crystal layer or the 1/4 wavelength plate can be formed by applying a liquid crystal composition in which a polymerizable liquid crystal compound and a polymerization initiator, and further a chiral agent, a surfactant and the like added as needed are dissolved in a solvent onto a temporary support, an alignment layer, a 1/4 wavelength plate, a cholesteric liquid crystal layer prepared in advance, or the like, drying the liquid crystal composition to obtain a coating film, aligning the polymerizable liquid crystal compound in a desired form on the coating film, and then polymerizing the polymerizable compound to fix the alignment.
The laminate of layers formed of the polymerizable liquid crystal compound can be formed by repeating the above steps. It is also possible to make a part of the layers or a part of the laminate film separately and attach these via an adhesive layer.
When a laminate film including a plurality of cholesteric liquid crystal layers, a laminate film including an 1/4 wavelength plate and a cholesteric liquid crystal layer, or a laminate film including a 1/4 wavelength plate and a plurality of cholesteric liquid crystal layers is formed, the step of directly applying a liquid crystal composition including a polymerizable liquid crystal compound or the like to the surface of the 1/4 wavelength plate or the cholesteric liquid crystal layer, and aligning and fixing the liquid crystal composition may be repeated, or a separately prepared cholesteric liquid crystal layer, a 1/4 wavelength plate, or a laminate thereof may be laminated using an adhesive or the like, but the former is preferable. The reason for this is that it is difficult to observe disturbance unevenness caused by thickness unevenness of the adhesive layer. The reason for this is that, in a laminated film of cholesteric liquid crystal layers, the following cholesteric liquid crystal layers are formed so as to be in direct contact with the surface of a previously formed cholesteric liquid crystal layer, and thus the alignment azimuth of the liquid crystal molecules on the air interface side of the previously formed cholesteric liquid crystal layer matches the alignment azimuth of the liquid crystal molecules on the lower side of the cholesteric liquid crystal layer formed thereon, and the polarization characteristics of the laminated body of cholesteric liquid crystal layers are good.
For example, a plurality of cholesteric liquid crystal layers may be sequentially formed on a temporary support to form a circularly polarized light reflecting layer as a transfer material. The semi-reflecting mirror can be obtained by bonding the surface of the circularly polarized light reflecting layer to a transparent substrate and then peeling off the temporary support as necessary. Alternatively, an 1/4 wavelength plate and a cholesteric liquid crystal layer may be sequentially formed on a temporary support to form a 1/4 wavelength plate and a circularly polarized light reflecting layer laminated body as a transfer material. The surface of the circularly polarized light reflecting layer is bonded to a transparent substrate, and then the temporary support is peeled off as necessary to obtain a half mirror having an 1/4 wavelength plate.
[ other adhesive layers ]
The half mirror of the present invention may further include an adhesive layer for bonding each layer in addition to the adhesive layer for bonding the circularly polarized light reflecting layer and the transparent substrate. As the adhesive layer in this case, a layer obtained by curing the curable adhesive, or a layer containing a hot-melt type adhesive or a pressure-sensitive adhesive type adhesive which does not need to be cured can be used. The thickness is not particularly limited, but is, for example, 1.0 μm or more and 5.0 μm or less, preferably 2.0 μm or more and 4.0 μm or less. The layer obtained by curing the curable adhesive may be used when the half mirror is bonded to an image display device described later. The thickness in this case may be 10 μm or more and 200 μm or less, and preferably 20 μm or more and 100 μm or less. When the half mirror is bonded to an image display device described later, a highly transparent adhesive transfer tape (OCA tape) or the like generally used on the surface of an image display portion of the image display device is preferably used.
< Reflector with image display function >
The half mirror of the present invention is used for the surface of an image display portion of an image display device. For example, the half mirror of the present invention can be combined with an image display device to be a mirror with an image display function. In this case, the half mirror may be disposed or bonded on the surface of the image display portion of the image display device. The reflector with image display function comprises an image display device, a circular polarization light reflection layer, an adhesive layer and a transparent substrate in sequence. When the 1/4 wavelength plate is included, the image display device, the 1/4 wavelength plate, the circularly polarized light reflecting layer, the adhesive layer, and the transparent substrate may be included in this order.
Another layer such as an adhesive layer may be included between the image display device and the half mirror, but it is preferable to include another layer other than the adhesive layer. That is, it is preferable that the image display device is in direct contact with the half mirror. The image display device may be formed by bonding a half mirror to at least a part of the image display portion. The area of the surface of the half mirror bonded may be smaller than, the same as, or larger than the area of the image display portion.
In the mirror with an image display function including the 1/4 wavelength plate, it is preferable that the 1/4 wavelength plate and the image display device are angularly adjusted so that the image becomes brightest. That is, in particular, in an image display device that displays an image by linearly polarized light, it is preferable that the relationship between the polarization direction (transmission axis) of the linearly polarized light and the retardation axis of the 1/4 wavelength plate is adjusted so that the linearly polarized light is optimally transmitted. For example, in the case of a 1-layer type 1/4 wavelength plate, the transmission axis and the retardation axis are preferably at an angle of 45 °. Light emitted from the image display device that displays an image by linearly polarized light passes through the 1/4 wavelength plate and then becomes circularly polarized light of either right or left handedness. The circularly polarized light reflecting layer described later is preferably formed of a cholesteric liquid crystal layer having a twist direction through which the circularly polarized light of the above handedness passes.
[ image display apparatus ]
The image display device is not particularly limited. The image display device is preferably an image display device that emits (emits) linearly polarized light to form an image, and more preferably a liquid crystal display device or an organic EL device.
The liquid crystal display device may be of a transmissive type or a reflective type, and is particularly preferably of a transmissive type. The liquid crystal display device may be any of an IPS (In Plane Switching) mode, an FFS (Fringe Field Switching) mode, a VA (Vertical Alignment) mode, an ECB (Electrically controlled birefringence) mode, an STN (Super Twisted Nematic) mode, a TN (Twisted Nematic) mode, an OCB (Optically Compensated Bend) mode, and the like.
The image displayed on the image display unit of the image display device may be a still image, a moving image, or simply character information. Further, the display may be performed in a single color such as black and white, or may be performed in a plurality of colors. It can also be displayed in full color.
The image display device preferably displays an emission peak wavelength λ R of red light, an emission peak wavelength λ G of green light, and an emission peak wavelength λ B of blue light in an emission spectrum in white display. By having such an emission peak wavelength, full-color image display can be performed. The λ R is preferably 580 to 700nm, more preferably 610 to 680 nm. The lambda G is preferably 500 to 580nm, more preferably 510 to 550 nm. λ B is preferably 400 to 500nm, more preferably 440 to 480 nm.
[ use of mirror with image display function ]
The use of the mirror with an image display function is not particularly limited. For example, the display device can be used as a crime prevention mirror, a mirror for a beauty shop or a barber shop, and the like, and can display images such as text information, still images, and moving images. The reflector with the image display function may be an indoor mirror for a vehicle, or may be used as a television, a personal computer, a smartphone, or a mobile phone.
Examples
The present invention will be described in more detail with reference to examples. The materials, reagents, amounts of substances, ratios thereof, operations and the like shown in the following examples can be appropriately modified within a range not departing from the gist of the present invention. Accordingly, the scope of the present invention is not limited to the following examples.
(1) Coating liquid 1 for forming a cholesteric liquid crystal layer, coating liquid 2, coating liquid 3, and coating liquid 4 for a 1/4 wavelength plate were prepared with the compositions shown in table 1 below. Further, the pencil hardness of the film of each coating liquid was changed by changing the amount of the crosslinking agent added.
[ Table 1]
Figure GDA0001489506820000241
[ chemical formula 1]
Rod-like liquid crystal compound: compound 1
Figure GDA0001489506820000242
Orientation controlling agent: compound 2
Figure GDA0001489506820000243
R1 R2 X
O(CH2)2O(CH2)2(CF2)6F O(CH2)2O(CH2)2(CF2)6F NH
Compound 2 is produced by the method described in Japanese patent application laid-open No. 2005-99248.
(2) (preparation of transfer Material A)
A temporary support (100 mm. times.150 mm) was made of TOYOB0C0, LTD PET film (COSMOSHINE A4100, thickness: 100 μm), and subjected to rubbing treatment (rayon cloth, pressure: 0.1kgf (0.98N), rotation speed: 1000rpm, conveyance speed: 10m/min, number of times: 1 round trip).
(3) Coating solution 1 (without A-TMMT addition) was applied to the rubbed surface of the PET film by a wire bar, dried, placed on a hot plate at 30 ℃ and subjected to a electrodeless lamp "D valve" (60 mW/cm) manufactured by Fusion UV Systems Ltd2) The cholesteric liquid crystal phase was fixed by irradiating UV for 6 seconds to obtain a cholesteric liquid crystal layer having a thickness of 3.5 μm. The same procedure was repeated with the use of coating liquid 2 and coating liquid 3 (neither A-TMMT was added) on the surface of the obtained layer, thereby obtaining a transfer material A having a cholesteric liquid crystal layer of 3 layers (layer of coating liquid 2: 3.0 μm, layer of coating liquid 3: 2.7 μm). The transmission spectrum of the transfer material A was measured by a spectrophotometer (manufactured by JASCO Corporation, V-670) to obtain transmission spectra having reflection peaks at 630nm, 540nm and 450 nm.
A temporary support (100 mm. times.150 mm) was made of a PET film (COSMOSHINEA4100, thickness: 100 μm) made of TOYOBO CO., LTD, and subjected to rubbing treatment (rayon cloth, pressure: 0.1kgf (0.98N), rotation speed: 1000rpm, conveyance speed: 10m/min, number of times: 1 round trip).
(3) (preparation of transfer Material B)
After coating liquid 4 (without A-TMMT addition) was applied to the rubbed surface of the PET film by a wire bar, it was dried and placed on a hot plate at 30 ℃ and an electrodeless lamp "D valve" (60 mW/cm) manufactured by Fusion UV Systems Ltd2) The cholesteric liquid crystal phase was fixed by irradiating UV for 6 seconds to obtain an 1/4 wavelength plate having a thickness of 0.8. mu.m. The same procedure was repeated with the use of coating liquid 1, coating liquid 2 and coating liquid 3 (all of which were not added with A-TMMT) on the surface of the obtained layer, thereby obtaining a transfer material B having a cholesteric liquid crystal layer of 3 layers on an 1/4 wavelength plate (coating liquid 1 layer: 3.5 μm, coating liquid 2 layer: 3 μm and coating liquid 3 layer: 2.7 μm). The transmission spectrum of the transfer material B was measured with V-670 to obtain transmission spectra having reflection peaks at 630nm, 540nm and 450 nm.
Transfer materials C to G were prepared in the same manner as the transfer material A, with the amount of A-TMMT (crosslinking agent) added in the coating solutions 1 to 3 and the temperature of the heating plate during UV irradiation being varied. The pencil hardness of the cholesteric liquid crystal layer-side surface of each transfer material was as follows. Further, pencil hardness was measured in accordance with JIS K5400 (pencil scratch test method).
[ Table 2]
Figure GDA0001489506820000251
(4-1) after coating TOAGOSEI CO, LTD adhesive LCR0631 on the surface of the cholesteric liquid crystal layer with a wire rod, the layer was laminated on a glass plate (50 mm. times.50 mm) having a thickness of 1.8mm using a laminator. At this time, the number of the wire rod and the nip roller pressure of the laminator were adjusted, thereby adjusting the thickness of the adhesive layer. Then, the plates were placed on a 50 ℃ hot plate and an electrodeless lamp "D-valve" (60 mW/cm) was manufactured by Fusion UVSystems Ltd2) After 30 seconds UV irradiation for bonding, the PET film was peeled off.
(4-3) an adhesive film for optical use (Panaclean (registered trademark) PD-S1) manufactured by PANAK Corporation was laminated on a glass plate (50 mm. times.50 mm) having a thickness of 1.8mm using a laminator, and then a PET film was peeled off.
(5) The adhesion of the film to glass was evaluated by a transverse cut test (according to JIS k5600, in which a checkered pattern consisting of 100 membrane sheets was used). The adhesive tape used was Nitto tape. A is defined as the value of 90 or more remaining patches. Less than 90 pieces of film remained was set as B. Regarding the crosscut (adhesiveness), the smaller the number of peeled film pieces, the more preferable the value is, and a is a practical range.
(6) The degree of orange peel-like unevenness was evaluated by evaluating the sharpness of an image according to JIS K7374 using a Suga test instruments co., ltd. For the measurement, the measurement was carried out in a transmission system at an incident light angle of 0 ° (vertical direction of the sample surface), and an optical comb of 0.05mm was used. More than 70% is defined as A, and less than 70% is defined as B. A is the practical range.
(7) The pencil hardness of the surface (PET interface side surface) obtained after peeling of the PET film was measured in accordance with JIS K5400 (pencil scratch test method).
[ Table 3]
Figure GDA0001489506820000261

Claims (20)

1. A method of manufacturing a half mirror used for a surface of an image display portion of an image display device,
the semi-reflecting mirror comprises a circular polarization light reflecting layer, an adhesive layer and a transparent substrate with the front phase difference less than 10nm in sequence,
the circularly polarizing light reflecting layer comprises a cholesteric liquid crystal layer showing selective reflection in the visible region,
the manufacturing method comprises the following steps:
preparing a transfer material including the circularly polarized light reflecting layer;
bonding the surface of the circularly polarized light reflecting layer of the transfer material and the transparent substrate with a photocurable adhesive; and
the adhesive layer is formed to have a thickness of 1.0 to 5.0 [ mu ] m by photocuring the photocurable adhesive,
the pencil hardness of the surface of the transfer material, which is attached to the transparent substrate, is B, 2B, 3B or 4B.
2. The manufacturing method according to claim 1,
the bonding is performed by coating the light-curable adhesive on the surface of the circularly polarizing light reflecting layer and bonding the coated surface to the transparent substrate.
3. The manufacturing method according to claim 1,
the transfer material includes a temporary support body,
the manufacturing method includes a step of forming the circularly polarized light reflecting layer in the transfer material by a method including the steps of:
coating a liquid crystal composition containing a polymerizable liquid crystal compound on the temporary support to obtain a coating film; and
curing the coating film to obtain the cholesteric liquid crystal layer.
4. The manufacturing method according to claim 3,
the manufacturing method includes a step of peeling off the temporary support after the adhesive layer is formed.
5. The manufacturing method according to claim 1,
the thickness of the transparent substrate is 500 mu m-3.0 mm.
6. The manufacturing method according to claim 1 or 2,
the transfer material comprises an 1/4 wavelength plate.
7. The manufacturing method according to claim 6,
the transfer material includes a temporary support body,
the transfer material has the temporary support, the 1/4 wavelength plate, and the circularly polarized light reflecting layer in this order,
the manufacturing method includes a step of forming the 1/4 wavelength plate in the transfer material by a method including the steps of:
coating a liquid crystal composition containing a polymerizable liquid crystal compound on the temporary support to obtain a coating film; and
curing the coating film.
8. The manufacturing method according to claim 7, comprising a step of coating a surface of the 1/4 wavelength plate with a liquid crystal composition containing a polymerizable liquid crystal compound to obtain the cholesteric liquid crystal layer.
9. A half mirror for use in a surface of an image display portion of an image display device,
the half mirror is manufactured by the manufacturing method of any one of claims 1 to 8,
the circularly polarized light reflecting layer and the adhesive layer are in direct contact,
the adhesive layer and the transparent substrate are in direct contact,
the transparent substrate is a glass plate or a plastic film with the front phase difference less than 10nm,
the thickness of the transparent substrate is 100 mu m-10 mm,
the thickness of the adhesive layer is 1.0 [ mu ] m or more and 5.0 [ mu ] m or less.
10. A half mirror for use in a surface of an image display portion of an image display device,
the semi-reflecting mirror comprises a circular polarized light reflecting layer, an adhesive layer and a transparent substrate with a front phase difference smaller than 10nm in sequence,
the circularly polarizing light reflecting layer comprises a cholesteric liquid crystal layer showing selective reflection in the visible region,
the circularly polarized light reflecting layer and the adhesive layer are in direct contact,
the adhesive layer and the transparent substrate are in direct contact,
the adhesive layer is a layer obtained by photocuring a photocurable adhesive,
the thickness of the adhesive layer is 1.0 [ mu ] m or more and 5.0 [ mu ] m or less,
the pencil hardness of the surface of the half mirror located on the circularly polarized light reflecting layer side with respect to the transparent substrate is B, 2B, 3B, or 4B.
11. The half mirror according to claim 9 or 10,
the circularly polarizing light reflecting layer includes 2 or more layers of cholesteric liquid crystal layers having center wavelengths of selective reflection different from each other.
12. The half mirror according to claim 11,
the cholesteric liquid crystal layers of 2 or more layers are in direct contact with each other.
13. The half mirror according to claim 10,
the circularly polarizing light reflecting layer includes 3 or more cholesteric liquid crystal layers having center wavelengths of selective reflection different from each other.
14. The half mirror according to claim 13,
the circularly polarized light reflecting layer includes: a cholesteric liquid crystal layer having a central wavelength of selective reflection within 400nm to 500 nm; a cholesteric liquid crystal layer having a central wavelength of selective reflection in a range of 500nm to 580 nm; and a cholesteric liquid crystal layer having a central wavelength of selective reflection in a range of 580 to 700 nm.
15. The half mirror according to claim 11,
in the circularly polarizing light reflecting layer, a cholesteric liquid crystal layer whose central wavelength of selective reflection is shorter is disposed at a position closer to the adhesive layer.
16. The half mirror according to claim 9 or 10,
the circularly polarized light reflecting layer includes a cholesteric liquid crystal layer having a center wavelength of selective reflection in an infrared light region.
17. The half mirror according to claim 9 or 10,
the thickness of the circular polarization light reflection layer is less than 25 μm.
18. The half mirror according to claim 9 or 10, comprising an 1/4 wavelength plate,
and comprises the 1/4 wavelength plate, the circular polarization light reflection layer, the bonding layer and the transparent substrate in sequence.
19. A mirror with an image display function comprising the half mirror according to claim 9 or 10,
and comprises an image display device, the circularly polarized light reflecting layer, the bonding layer and the transparent substrate in sequence.
20. The image display function-equipped mirror according to claim 19,
the image display device and the half mirror are directly bonded by means of an adhesive layer.
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