JP2017122776A - Mirror with image display function and half mirror - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mirror with an image display function that enables a wearer to observe a display image and a mirror reflection image even through polarized sunglasses and can display images with good hue, and a half mirror that achieves an image display device with the mirror function.SOLUTION: There is provided a mirror with an image display function including an image display device, a 1/4 wavelength plate, a circularly polarized light reflection layer, and a front plate in this order, where the circularly polarized light reflection layer includes a cholesteric liquid crystal layer; the cholesteric liquid crystal layer includes the center wavelength of selective reflection in a visible light region; the 1/4 wavelength plate includes a cycloolefin polymer; the film thickness of the 1/4 wavelength plate is 20 μm to 500 μm. Also provided is a half mirror including the 1/4 wavelength plate, the circularly polarized light reflection layer, and the front plate in this order.SELECTED DRAWING: None

Description

  The present invention relates to a mirror with an image display function and a half mirror.

  An image with a mirror function that provides a half mirror on the surface of the image display unit of the image display device, displays an image in the display mode, and displays a mirror reflection image as a mirror in a non-display mode such as when the image display device is turned off. The display device is described in Patent Documents 1 to 3, for example.

JP 2002-229494 A JP 2014-2011146 A JP 2011-45427 A

When a half mirror is disposed in the image display unit of the image display device, the image quality may be deteriorated due to a change in the color of the image due to the influence of the optical properties of the half mirror itself. Patent Documents 1 and 2 do not pay attention to such a problem. On the other hand, Patent Document 3 describes that image quality is improved by using a reflective polarizing plate as a half mirror to reduce reflection. However, in the configuration using a reflective polarizing plate as a half mirror, there is a problem that an image and a mirror reflection image cannot be confirmed when observed through polarized sunglasses.
An object of the present invention is to provide a mirror with an image display function capable of observing an image and a mirror reflection image without direction dependency even through polarized sunglasses, and capable of displaying an image with good color. Another object of the present invention is to provide a half mirror that realizes the image display device with a mirror function.

  The inventors of the present invention diligently studied to solve the above-mentioned problems, and have come up with the idea of designing the half mirror optically by paying attention to the characteristics of light for image display. An optical design was performed based on this idea, and a half mirror was manufactured using a material suitable for the optical design to complete the present invention.

That is, the present invention provides the following [1] to [12].
[1] A mirror with an image display function,
Including an image display device, a quarter-wave plate, a circularly polarized reflection layer, and a front plate in this order,
The circularly polarized light reflection layer includes a cholesteric liquid crystal layer,
The cholesteric liquid crystal layer has a central wavelength of selective reflection in the visible light region,
The quarter wave plate includes a cycloolefin polymer,
The said mirror with an image display function whose film thickness of the said 1/4 wavelength plate is 20 micrometers-500 micrometers.
[2] The mirror with an image display function according to [1], wherein the film thickness of the ¼ wavelength plate is 50 μm to 200 μm.
[3] The image display function according to [1] or [2], wherein the circularly polarized light reflection layer includes two or more cholesteric liquid crystal layers, and the two or more cholesteric liquid crystal layers have different selective reflection center wavelengths. mirror.
[4] The mirror with an image display function according to [3], wherein two or more cholesteric liquid crystal layers are in direct contact with each other.

[5] The circularly polarized light reflecting layer includes three or more cholesteric liquid crystal layers, and the three or more cholesteric liquid crystal layers have different selective reflection center wavelengths from each other. Mirror with image display function.
[6] The circularly polarized light reflection layer includes a cholesteric liquid crystal layer having a central wavelength of selective reflection in the wavelength range of red light, a cholesteric liquid crystal layer having a central wavelength of selective reflection in the wavelength range of green light, and the wavelength of blue light. The mirror with an image display function according to [5], including a cholesteric liquid crystal layer having a central wavelength of selective reflection in a region.
[7] The mirror with an image display function according to any one of [1] to [6], wherein the circularly polarized light reflection layer and the front plate are directly bonded via an adhesive layer.
[8] The mirror with an image display function according to any one of [1] to [7], wherein the circularly polarizing reflection layer and the quarter-wave plate are directly bonded via an adhesive layer.
[9] The mirror with an image display function according to any one of [1] to [8], wherein the image display device and the quarter-wave plate are directly bonded via an adhesive layer.
[10] The mirror with an image display function according to any one of [1] to [9], wherein the circularly polarized light reflection layer includes a cholesteric liquid crystal layer having a central wavelength of selective reflection in an infrared light region.

[11] A quarter wave plate, a circularly polarized light reflection layer, and a front plate are included in this order,
The front plate is a glass plate or a plastic film having a front phase difference of less than 10 nm,
The circularly polarized light reflection layer includes a cholesteric liquid crystal layer,
The cholesteric liquid crystal layer has a central wavelength of selective reflection in the visible light region,
The quarter wave plate includes a cycloolefin polymer,
The half mirror whose film thickness of the said quarter wavelength plate is 20 micrometers-500 micrometers.
[12] The half mirror according to [11], wherein the quarter-wave plate has a thickness of 30 μm to 200 μm.

  According to the present invention, there is provided a mirror with an image display function capable of displaying an image with good color. The mirror with an image display function of the present invention has an advantage that an image and a mirror reflection image can be observed without direction dependency even through polarized sunglasses. The present invention also provides a half mirror that realizes the image display device with a mirror function.

Hereinafter, the present invention will be described in detail.
In the present specification, “to” is used to mean that the numerical values described before and after it are included as a lower limit value and an upper limit value.
In the present specification, for example, an angle such as “45 °”, “parallel”, “vertical”, or “orthogonal”, unless otherwise specified, has a difference from an exact angle within a range of less than 5 degrees. Means. The difference from the exact angle is preferably less than 4 degrees, and more preferably less than 3 degrees.
In this specification, “(meth) acrylate” is used to mean “one or both of acrylate and methacrylate”.

In this specification, “selective” for circularly polarized light means that either the right circularly polarized light component or the left circularly polarized light component has more light than the other circularly polarized light component. Specifically, when referred to as “selective”, the degree of circular polarization of light is preferably 0.3 or more, more preferably 0.6 or more, and even more preferably 0.8 or more. More preferably, it is substantially 1.0. Table In _{/ (I R + I L)} | Here, the degree of circular polarization, the intensity of the right circularly polarized light component of the light I _R, when the strength of the left-handed circularly polarized light component and I _L, | I _R -I _L Is the value to be

  In this specification, “sense” for circularly polarized light means right circularly polarized light or left circularly polarized light. The sense of circularly polarized light is right-handed circularly polarized light when the electric field vector tip turns clockwise as time increases when viewed as the light travels toward you, and left when it turns counterclockwise. Defined as being circularly polarized.

  In this specification, the term “sense” may be used for the twist direction of the spiral of the cholesteric liquid crystal. The selective reflection by the cholesteric liquid crystal reflects right circularly polarized light when the twist direction (sense) of the cholesteric liquid crystal spiral is right, transmits left circularly polarized light, and reflects left circularly polarized light when the sense is left, Transmits circularly polarized light.

  Visible light is light having a wavelength visible to the human eye among electromagnetic waves, and indicates light having a wavelength range of 380 nm to 780 nm. Infrared rays (infrared light) are electromagnetic waves in the wavelength range that are longer than visible rays and shorter than radio waves. Among infrared rays, near infrared light is an electromagnetic wave having a wavelength range of 780 nm to 2500 nm.

  In this specification, the term “image” for a mirror with an image display function means an image that can be viewed and observed from the front plate side when the image is displayed on the image display unit of the image display device. Further, in this specification, the term “mirror reflection image” for a mirror with an image display function means an image that can be visually observed from the front plate when no image is displayed on the image display unit of the image display device. .

  In this specification, the front phase difference is a value measured using an AxoScan manufactured by Axometrics. The measurement wavelength is 550 nm unless otherwise specified. The front phase difference is a value measured by making light of a wavelength in the visible light wavelength region such as the central wavelength of selective reflection of the cholesteric liquid crystal layer incident in the film normal direction in KOBRA 21ADH or WR (manufactured by Oji Scientific Instruments). It can also be used. When selecting the measurement wavelength, the wavelength selection filter can be exchanged manually, or the measurement value can be converted by a program or the like.

<Mirror with image display function>
The mirror with an image display function of the present invention includes an image display device, a quarter-wave plate, a circularly polarizing reflection layer, and a front plate in this order. The mirror with an image display function of the present invention may include other layers such as an adhesive layer. In the present specification, among the above-described components of the mirror with an image display function, a portion including the quarter-wave plate, the circularly polarized reflection layer, and the front plate may be referred to as a half mirror. In the mirror with an image display function, the image display device and the half mirror may be in direct contact with each other, an air layer may be present therebetween, or may be directly bonded via an adhesive layer.
In the present specification, the surface on the front plate side with respect to the circularly polarized light reflection layer may be referred to as the front surface.

The image display device may be bonded to the quarter wavelength plate at least in a part of the image display unit. The area of the surface of the quarter wave plate to be bonded may be smaller than the area of the image display unit, may be the same, or may be larger. Moreover, it is preferable that the quarter wavelength plate and the circularly polarized light reflection layer are laminated with the same area.
The front plate may be larger than the circularly polarized light reflection layer, may be the same, or may be smaller. A circularly polarized light reflecting layer may be bonded to a part of the front plate, and another type of reflecting layer such as a metal foil may be bonded or formed at other portions. With such a configuration, an image can be displayed on a part of the mirror. On the other hand, a circularly polarized light reflection layer may be bonded to the entire surface of the front plate, and an image display device having an image display unit having the same area as the circularly polarized light reflection layer may be bonded to the quarter wavelength plate in the image display unit. With such a configuration, image display on the entire mirror surface is possible.

  In the mirror with an image display function of the present invention, it is preferable that the angle of the quarter wavelength plate is adjusted so that the image becomes brightest when bonded to the image display device. That is, the relationship between the polarization direction of the linearly polarized light (transmission axis) and the slow axis of the quarter-wave plate so that the linearly polarized light is transmitted best, particularly for an image display device displaying an image by linearly polarized light. Is preferably adjusted. For example, in the case of a single layer type quarter wave plate, it is preferable that the transmission axis and the slow axis form an angle of 45 °. The light emitted from the image display device displaying an image by linearly polarized light is circularly polarized light of either right or left sense after passing through the quarter wavelength plate. The circularly polarized light reflecting layer described later only needs to be composed of a cholesteric liquid crystal layer having a twist direction that transmits the circularly polarized light of the above-described sense.

  By including a quarter-wave plate between the image display device and the circularly polarized light reflection layer, light from the image display device can be converted into circularly polarized light and incident on the circularly polarized light reflection layer. Therefore, the light reflected by the circularly polarized light reflection layer and returning to the image display device side can be greatly reduced, and a bright image can be displayed. Further, it is difficult for image display quality to deteriorate due to multiple reflection between the image display device and the half mirror.

[Image display device]
The image display device is not particularly limited. The image display device is preferably an image display device that emits (emits light) linearly polarized light to form an image, and more preferably a liquid crystal display device.
The liquid crystal display device may be a transmission type or a reflection type, and is particularly preferably a transmission type. The liquid crystal display device includes 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, and a TN (Twisted Nematic) mode. Any liquid crystal display device such as an OCB (Optically Compensated Bend) mode may be used.

  The image displayed on the image display unit of the image display device may be a still image, a moving image, or simply text information. Further, it may be a monochrome display such as black and white, a multi-color display, or a full-color display.

[¼ wave plate]
The mirror with an image display function of the present invention includes a quarter wavelength plate. As described above, the use of the quarter-wave plate makes it possible to display an image with high light utilization efficiency, particularly when used in combination with an image display device displaying an image with linearly polarized light. Bright images can be displayed. For example, the central wavelength of selective reflection of the cholesteric liquid crystal layer included in the circularly polarized light reflection layer and the emission peak wavelength of blue light in the emission spectrum at the time of white display of the image display device are substantially the same (for example, the difference is less than 5 nm). However, the light emitted from the image display device can be transmitted to the front plate side without causing the circularly polarized light reflection layer to generate the sense circularly polarized light reflected to the image display device side.

  The quarter wave plate may be a retardation layer that functions as a quarter wave plate in the visible light region. Specifically, the front phase difference of the ¼ wavelength plate may be ¼ of the emission wavelength of the image display device.

(Cycloolefin polymer)
In the mirror with an image display function of the present invention, the quarter-wave plate includes a cycloolefin polymer. That is, a retardation film containing a cycloolefin polymer is used as the quarter wavelength plate. The quarter-wave plate is also preferably composed of only a retardation film containing a cycloolefin polymer, and is preferably a retardation film consisting essentially of a cycloolefin polymer. The present inventors have found that a mirror with an image display function using a retardation film containing a cycloolefin polymer as a quarter-wave plate can display an image with good color. This is considered because the retardation film containing a cycloolefin polymer has a small birefringence wavelength dependency. Specifically, as the birefringent wavelength dispersion characteristic of the cycloolefin polymer, Δn (λ = 400 nm) / Δn (λ = 550 nm) is about 1.01, Δn (λ = 700 nm) / Δn (λ = 550 nm) Is about 0.995, and when a retardation film having a front phase difference of 125 nm at λ = 550 nm is produced, the front phase difference in the visible light region of 380 to 780 nm is about 123 to 127 nm.

In this specification, a cycloolefin polymer represents a polymer having a cycloolefin structure, and so-called cycloolefin polymer (COP) and cycloolefin copolymer (COC) are both types of cycloolefin polymers.
Examples of cycloolefin polymers include (1) norbornene polymers, (2) monocyclic cycloolefin polymers, (3) cyclic conjugated diene polymers, (4) vinyl alicyclic hydrocarbon polymers, (5) Norbornene-based addition (co) polymers and hydrides of (1) to (5). A ring-opening (co) polymer containing at least one cyclic repeating unit can also be suitably used.

Norbornene polymer hydrides are disclosed in JP-A-1-240517, JP-A-7-196736, JP-A-60-26024, JP-A-62-19807, JP-A-2003-115767, or JP-A-2004-309799. As disclosed in each publication of No. 1, etc., it can be produced by subjecting a polycyclic unsaturated compound to addition polymerization or metathesis ring-opening polymerization and then hydrogenation.
The norbornene resin is marketed by JSR Corporation under the trade name Arton G or Arton F, and from Zeon Corporation, Zeoror ZF14, ZF16, Zeonex 250 or Zeonex 280. These are commercially available under the trade name and can be used.

  Norbornene-based addition (co) polymers are disclosed in JP-A-10-7732, JP-T 2002-504184, U.S. Published Patent No. 200029129157A1, WO2004 / 070463A1, and the like. It is obtained by addition polymerization of norbornene-based polycyclic unsaturated compounds. If necessary, norbornene-based polycyclic unsaturated compounds and ethylene, propylene, butene; conjugated dienes such as butadiene and isoprene; nonconjugated dienes such as ethylidene norbornene; acrylonitrile, acrylic acid, methacrylic acid, maleic anhydride It is also possible to carry out addition polymerization with linear diene compounds such as acid, acrylic acid ester, methacrylic acid ester, maleimide, vinyl acetate and vinyl chloride. Among these, a copolymer with ethylene is preferable. This norbornene-based addition (co) polymer is marketed by Mitsui Chemicals, Inc. under the name of Apel, and has different glass transition temperatures (Tg) such as APL8008T (Tg70 ° C), APL6013T (Tg125 ° C) or APL6015T ( Grades such as Tg145 ° C). Pellets such as TOPAS 8007, 6013, and 6015 are sold by Polyplastics Co., Ltd. The Appearn 3000 is available from Ferrania.

  The cycloolefin polymer unit content in the cycloolefin polymer is preferably 5 to 95% by mass. Moreover, although there is no restriction | limiting in the glass transition temperature (Tg) of a cycloolefin polymer, For example, high Tg cycloolefin polymer polymers, such as 200-400 degreeC, can also be used.

  As the film-like cycloolefin polymer, a film formed by a casting method or an extrusion method using a polymer solution or a molten polymer may be used. Moreover, as a cycloolefin polymer film and its manufacturing method, description of Paragraphs 0030 to 0107 of Unexamined-Japanese-Patent No. 2009-237376, description of 0025 to 0038 of WO2014 / 199934, etc. can be referred.

A retardation film containing a cycloolefin polymer is generally obtained by stretching a film-like cycloolefin polymer. By stretching, optical anisotropy is produced, and it can be used as a retardation film.
The stretched film is suitably obtained by uniaxially, biaxially or obliquely stretching an unstretched film obtained from a cycloolefin polymer. The stretching method is not particularly limited, and examples thereof include a roll-type, float-type longitudinal stretching method, tenter-type lateral uniaxial stretching and simultaneous biaxial stretching.
In the case of performing oblique stretching, there is no particular limitation as long as a long film can be obliquely stretched continuously, and various types of stretching machines can be used.

The temperature at which an unstretched film is stretched is preferably a temperature range of Tg-30 ° C to Tg + 60 ° C, more preferably Tg-10 ° C to Tg + 50 ° C, where Tg is the glass transition temperature of the cycloolefin polymer. . Moreover, a draw ratio is 1.01-30 times normally, Preferably it is 1.01-10 times, More preferably, it is 1.01-5 times.
The average thickness of the stretched film is preferably 20 to 80 μm, more preferably 30 to 60 μm, from the viewpoint of mechanical strength and the like.

  A method for forming an unstretched film for use in producing a stretched film is not particularly limited, and a known forming method can be employed. For example, either a hot melt molding method or a solution casting method can be employed, but from the viewpoint of reducing volatile components in the sheet, it is preferable to use the hot melt molding method. The hot melt molding method can be further classified into a melt extrusion molding method, a press molding method, an inflation method, an injection molding method, a blow molding method, a stretch molding method, and the like. Among these, in order to obtain a stretched film having excellent mechanical strength and surface accuracy, it is preferable to use a melt extrusion molding method. A thermoplastic norbornene resin is molded. The molding method is not particularly limited. Injection molding, melt extrusion, hot pressing, solvent casting, and the like, which are general molding methods for thermoplastic resins, can be used.

The molding conditions are appropriately selected depending on the purpose of use and the molding method. In the case of the melt extrusion molding method, the cylinder temperature is preferably set in the range of preferably 100 to 600 ° C, more preferably 150 to 350 ° C.
The thickness of the unstretched film can be appropriately determined according to the purpose of use of the stretched film obtained. The thickness of the film is preferably 10 to 300 μm, more preferably 30 to 200 μm, from the viewpoint of obtaining a uniform stretched film by a stable stretching process.

You may use the film which laminated | stacked the stretched film and the non-stretched film. Lamination may be performed using an adhesive.
In addition, as an example of a retardation film containing a cycloolefin polymer, a ZEONOR film manufactured by Nippon Zeon Co., Ltd. can be cited as a preferred example.

  As a retardation film containing a cycloolefin polymer, a film having a thickness of 20 to 500 μm is used. Since the cycloolefin polymer film generally has a low birefringence, it is possible to increase the rigidity by increasing the film thickness within the above range when forming a quarter-wave plate. Since the retardation film containing a cycloolefin polymer has high rigidity, even when pressing with a roller or the like when laminating the circularly polarized light reflection layer and the adhesive layer, the adhesive layer is less likely to be uneven. Further, for example, even if the adhesive layer shrinks due to aging, particularly in a high heat environment, unevenness is hardly generated. For this reason, image distortion hardly occurs even in a mirror with an image display function. In order to obtain sufficient rigidity, the thickness of the retardation film containing a cycloolefin polymer is more preferably 50 μm or more, and further preferably 80 μm or more. The upper limit of the thickness of the retardation film containing a cycloolefin polymer is preferably 400 μm, more preferably 300 μm, and even more preferably 200 μm.

  The λ / 4 wave plate may be adhered to the circularly polarized light reflecting layer by an adhesive layer or may be in direct contact therewith. For example, a separately produced λ / 4 wavelength plate and a circularly polarizing reflection layer may be adhered by an adhesive layer, and a circularly polarized light is passed through a step of directly applying a liquid crystal composition described later on the surface of the λ / 4 wavelength plate. A reflective layer may be formed.

[Circularly polarized reflective layer]
The circularly polarized light reflection layer functions as a semi-transmissive and semi-reflective layer in the mirror with an image display function. In other words, the circularly polarized light reflection layer functions to display an image on the front surface of the mirror with an image display function by transmitting the emitted light from the image display device during image display. On the other hand, when the image is not displayed, the circularly polarized light reflection layer reflects at least part of the incident light from the front plate direction and transmits the reflected light from the image display device. To function.
In the mirror with an image display function of the present invention, by using a circularly polarized light reflection layer for the half mirror, incident light from the front plate side is reflected as circularly polarized light, and incident light from the image display device is transmitted as circularly polarized light. be able to. Therefore, the mirror with an image display function of the present invention can observe a display image and a mirror reflection image without depending on the direction of the mirror with an image display function even through polarized sunglasses.

The circularly polarized light reflection layer includes at least one cholesteric liquid crystal layer exhibiting selective reflection in the visible light region. The circularly polarized light reflecting layer may include two or more cholesteric liquid crystal layers, and may include other layers such as an alignment layer. The circularly polarized light reflecting layer is preferably composed only of a cholesteric liquid crystal layer. Further, when the circularly polarized light reflection layer includes a plurality of cholesteric liquid crystal layers, it is preferable that they are in direct contact with adjacent cholesteric liquid crystal layers. The circularly polarized light reflection layer preferably includes three or more cholesteric liquid crystal layers such as three layers and four layers.
The thickness of the circularly polarized light reflecting layer is preferably in the range of 2.0 μm to 300 μm, more preferably in the range of 8.0 to 200 μm.

(Cholesteric liquid crystal layer)
In this specification, a cholesteric liquid crystal layer means 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.
The cholesteric liquid crystal phase selectively reflects circularly polarized light of either right circularly polarized light or left circularly polarized light in a specific wavelength region and selectively transmits circularly polarized light of the other sense. It is known to show. In this specification, the circularly polarized light selective reflection is sometimes simply referred to as selective reflection.

  Many films formed from a composition containing a polymerizable liquid crystal compound have been known as a film containing a layer in which a cholesteric liquid crystal phase exhibiting circularly polarized light selectively is fixed. You can refer to the technology.

  The cholesteric liquid crystal layer may be a layer in which the orientation of the liquid crystal compound in the cholesteric liquid crystal phase is maintained. Typically, the polymerizable liquid crystal compound is placed in the orientation state of the cholesteric liquid crystal phase and then irradiated with ultraviolet rays. Any layer may be used as long as it is polymerized and cured by heating or the like to form a layer having no fluidity, and at the same time, the layer is changed to a state in which the orientation is not changed by an external field or an external force. 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 may no longer exhibit liquid crystallinity. For example, the polymerizable liquid crystal compound may have a high molecular weight due to a curing reaction and may no longer have liquid crystallinity.

The central wavelength λ of selective reflection of the cholesteric liquid crystal layer depends on the pitch P (= helical period) of the helical structure in the cholesteric phase, and follows the relationship between the average refractive index n of the cholesteric liquid crystal layer and λ = n × P. In this specification, the central wavelength λ of selective reflection of the cholesteric liquid crystal layer means a wavelength at the center of gravity of the reflection peak of the circularly polarized reflection spectrum measured from the normal direction of the cholesteric liquid crystal layer. In the present specification, the center wavelength of selective reflection means the center wavelength when measured from the 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 in order to selectively reflect either the right circularly polarized light or the left circularly polarized light with respect to light of a desired wavelength by adjusting the n value and the P value.

When light is incident on the cholesteric liquid crystal layer at an angle, the center wavelength of selective reflection is shifted to the short wavelength side. Therefore, it is preferable to adjust n × P so that λ calculated according to the above formula λ = n × P becomes a long wavelength with respect to the wavelength of selective reflection required for image display. In the cholesteric liquid crystal layer having a refractive index n ₂ , the center wavelength of selective reflection when a light beam passes at an angle of θ ₂ with respect to the normal direction of the cholesteric liquid crystal layer (helical axis direction of the cholesteric liquid crystal layer) is λ _d . Λ _d is expressed by the following equation.
λ _d = n ₂ × P × cos θ ₂

Further, due to the selective reflection property described above, the mirror with an image display function of the present invention may have a color derived from an oblique view and an infrared light incident on the mirror reflection image from the oblique direction. is there. By including a cholesteric liquid crystal layer having a central wavelength of selective reflection in the infrared light region in the circularly polarized light reflecting layer, it is possible to prevent such a color. In this case, the center wavelength of selective reflection in the infrared region is specifically 780 to 900 nm, preferably 780 to 850 nm.
When a cholesteric liquid crystal layer having a central wavelength of selective reflection is provided in the infrared light region, this layer may be on the image display device side with respect to all cholesteric liquid crystal layers each having a central wavelength of selective reflection in the visible light region. preferable.

  Since the pitch of the cholesteric liquid crystal phase depends on the type of chiral agent used together with the polymerizable liquid crystal compound or the concentration of the chiral agent, the desired pitch can be obtained by adjusting these. For the method of measuring spiral sense and pitch, use the methods described in “Introduction to Liquid Crystal Chemistry Experiments”, edited by Japanese Liquid Crystal Society, Sigma Publishing 2007, p. be able to.

In the mirror with an image display function of the present invention, the circularly polarized light reflection layer includes a cholesteric liquid crystal layer having a central wavelength of selective reflection in the wavelength range of red light and a cholesteric liquid crystal layer having a central wavelength of selective reflection in the wavelength range of green light. And a cholesteric liquid crystal layer having a center wavelength of selective reflection in the wavelength range of blue light. Examples of the reflective layer include a cholesteric liquid crystal layer having a central wavelength of selective reflection at 400 nm to 500 nm, a cholesteric liquid crystal layer having a central wavelength of selective reflection at 500 nm to 580 nm, and a cholesteric liquid crystal having a central wavelength of selective reflection at 580 nm to 700 nm. It is preferable to include a layer.
Further, when the circularly polarized light reflection layer includes a plurality of cholesteric liquid crystal layers, it is preferable that the cholesteric liquid crystal layer closer to the image display device has a longer selective reflection center wavelength. With such a configuration, it is possible to suppress an oblique color tone in an image.

  By adjusting the central wavelength of selective reflection of the cholesteric liquid crystal layer to be used according to the emission wavelength region of the image display device and the usage mode of the circularly polarized light reflection layer, a bright image can be displayed with high light utilization efficiency. Examples of the usage of the circularly polarized light reflecting layer include an incident angle of light to the circularly polarized light reflecting layer, an image observation direction, and the like.

  The sense of reflected circularly polarized light in the cholesteric liquid crystal layer coincides with the sense of a spiral. Each cholesteric liquid crystal layer includes a cholesteric liquid crystal layer whose spiral sense is either right or left depending on the sense of circularly polarized light that is obtained from the image display device and transmitted through the quarter-wave plate. A liquid crystal layer is used. Specifically, a cholesteric liquid crystal layer having a spiral sense that transmits the circularly polarized light of the sense obtained from the image display device and transmitted through the quarter wavelength plate may be used. When a plurality of cholesteric liquid crystal layers are included in the circularly polarized light reflecting layer, it is preferable that the senses of the spirals are all the same.

The full width at half maximum Δλ (nm) of the selective reflection band showing selective reflection depends on the relationship of Δλ = Δn × P, where Δλ depends on the birefringence Δn of the liquid crystal compound and the pitch P. Therefore, the width of the selective reflection band can be controlled by adjusting Δn. Δn can be adjusted by adjusting the kind of the polymerizable liquid crystal compound and the mixing ratio thereof, or by controlling the temperature at the time of fixing the alignment.
In order to form one type of 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 sense may be stacked. By laminating cholesteric liquid crystal layers having the same period P and the same spiral sense, the circularly polarized light selectivity can be increased at a specific wavelength.

[Cholesteric liquid crystal layer production method]
Hereinafter, a method for producing a cholesteric liquid crystal layer will be described.
Examples of the material used for forming the cholesteric liquid crystal layer include a liquid crystal composition containing a polymerizable liquid crystal compound. The liquid crystal composition preferably further contains a chiral agent (optically active compound). If necessary, apply the above liquid crystal composition, which is further mixed with a surfactant or polymerization initiator and dissolved in a solvent, to a temporary support, a support, an alignment film, a lower cholesteric liquid crystal layer, and the like. After aging, the liquid crystal composition can be fixed by curing to form a cholesteric liquid crystal layer.

(Polymerizable liquid crystal compound)
A rod-like liquid crystal compound may be used as the polymerizable liquid crystal compound.
Examples of the rod-like polymerizable liquid crystal compound include a rod-like nematic liquid crystal compound. Examples of rod-like nematic liquid crystal compounds include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines. , Phenyldioxanes, tolanes and alkenylcyclohexylbenzonitriles are preferably used. Not only low-molecular liquid crystal compounds but also high-molecular liquid crystal compounds can be used.

  The polymerizable liquid crystal compound can be obtained by introducing a polymerizable group into the liquid crystal compound. Examples of the polymerizable group include an unsaturated polymerizable group, an epoxy group, and an aziridinyl group, preferably an unsaturated polymerizable group, and particularly preferably an ethylenically unsaturated polymerizable group. The polymerizable group can be introduced into the molecule of the liquid crystal compound by various methods. The number of polymerizable groups possessed by the polymerizable liquid crystal compound is preferably 1 to 6, more preferably 1 to 3. Examples of polymerizable liquid crystal compounds are described in Makromol. Chem. 190, 2255 (1989), Advanced Materials 5, 107 (1993), U.S. Pat. Nos. 4,683,327, 5,622,648, and 5,770,107, International Publication WO95 / 22586, WO95. / 24455, WO 97/00600, WO 98/23580, WO 98/52905, JP-A-1-272551, JP-A-6-16616, JP-A-7-110469, JP-A-11-80081, and JP-A-2001. -3282893 etc. are included. Two or more kinds of polymerizable liquid crystal compounds may be used in combination. When two or more kinds of polymerizable liquid crystal compounds are used in combination, the alignment temperature can be lowered.

  Moreover, it is preferable that the addition amount of the polymeric liquid crystal compound in a liquid-crystal composition is 80-99.9 mass% with respect to solid content mass (mass except a solvent) of a liquid-crystal composition, and 85-99. More preferably, it is 5 mass%, and it is especially preferable that it is 90-99 mass%.

(Chiral agent: optically active compound)
The material used for forming the cholesteric liquid crystal layer preferably contains a chiral agent. The chiral agent has a function of inducing a helical structure of a cholesteric liquid crystal phase. The chiral compound may be selected according to the purpose because the helical sense or helical pitch induced by the compound is different.
The chiral agent is not particularly limited, and known compounds (for example, liquid crystal device handbook, Chapter 3-4-3, TN, chiral agent for STN, page 199, Japan Society for the Promotion of Science, 142nd edition, 1989) Description), isosorbide, and isomannide derivatives can be used.

A chiral agent generally contains an asymmetric carbon atom, but an axially asymmetric compound or a planar asymmetric compound containing no asymmetric carbon atom can also be used as the chiral agent. Examples of the axial asymmetric compound or the planar asymmetric compound include binaphthyl, helicene, paracyclophane, and derivatives thereof. The chiral agent may have a polymerizable group. When both the chiral agent and the liquid crystal compound have a polymerizable group, they are derived from the repeating unit derived from the polymerizable liquid crystal compound and the chiral agent by a polymerization reaction between the polymerizable chiral agent and the polymerizable liquid crystal compound. A polymer having repeating units can be formed. In this aspect, the polymerizable group possessed by the polymerizable chiral agent is preferably the same group as the polymerizable group possessed by the polymerizable liquid crystal compound. Therefore, the polymerizable group of the chiral agent is also preferably an unsaturated polymerizable group, an epoxy group or an aziridinyl group, more preferably an unsaturated polymerizable group, and an ethylenically unsaturated polymerizable group. Particularly preferred.
The chiral agent may be a liquid crystal compound.
The content of the chiral agent in the liquid crystal composition is preferably 0.01 mol% to 200 mol%, more preferably 1 mol% to 30 mol% of the amount of the polymerizable liquid crystal compound.

(Polymerization initiator)
The liquid crystal composition preferably contains a polymerization initiator. In the embodiment in which the polymerization reaction is advanced by ultraviolet irradiation, the polymerization initiator to be used is preferably a photopolymerization initiator that can start the polymerization reaction by ultraviolet irradiation. Examples of the photopolymerization initiator include α-carbonyl compounds (described in US Pat. Nos. 2,367,661 and 2,367,670), acyloin ether (described in US Pat. No. 2,448,828), α-hydrocarbon substituted aromatics. Group acyloin compounds (described in US Pat. No. 2,722,512), polynuclear quinone compounds (described in US Pat. Nos. 3,046,127 and 2,951,758), combinations of triarylimidazole dimers and p-aminophenyl ketone (US patents) No. 3549367), acridine and phenazine compounds (JP-A-60-105667, US Pat. No. 4,239,850), oxadiazole compounds (US Pat. No. 4,221,970), and the like. .
The content of the photopolymerization initiator in the liquid crystal composition is preferably 0.1 to 20% by mass, and preferably 0.5 to 5% by mass with respect to the content of the polymerizable liquid crystal compound. Further preferred.

(Crosslinking agent)
The liquid crystal composition may optionally contain a crosslinking agent in order to improve the film strength after curing and improve the durability. As the cross-linking agent, one that can be cured by ultraviolet rays, heat, moisture, or the like can be suitably used.
There is no restriction | limiting in particular as a crosslinking agent, According to the objective, it can select suitably, For example, polyfunctional acrylate compounds, such as a trimethylol propane tri (meth) acrylate and pentaerythritol tri (meth) acrylate; Glycidyl (meth) acrylate , Epoxy compounds such as ethylene glycol diglycidyl ether; aziridine compounds such as 2,2-bishydroxymethylbutanol-tris [3- (1-aziridinyl) propionate], 4,4-bis (ethyleneiminocarbonylamino) diphenylmethane; hexa Isocyanate compounds such as methylene diisocyanate and biuret type isocyanate; polyoxazoline compounds having an oxazoline group in the side chain; vinyltrimethoxysilane, N- (2-aminoethyl) 3-aminopropylto Alkoxysilane compounds such as methoxy silane. Moreover, a well-known catalyst can be used according to the reactivity of a crosslinking agent, and productivity can be improved in addition to membrane strength and durability improvement. These may be used individually by 1 type and may use 2 or more types together.
3 mass%-20 mass% are preferable, and, as for content of a crosslinking agent, 5 mass%-15 mass% are more preferable. When the content of the crosslinking agent is 3% by mass or more, an effect of improving the crosslinking density can be obtained. Moreover, the stability of the layer formed can be maintained by setting it as 20 mass% or less.

(Orientation control agent)
In the liquid crystal composition, an alignment control agent that contributes to stable or rapid planar alignment may be added. Examples of the orientation control agent include fluorine (meth) acrylate polymers described in paragraphs [0018] to [0043] of JP-A-2007-272185, and paragraphs [0031] to [0034] of JP-A-2012-203237. Etc.] and the compounds represented by the formulas (I) to (IV).
In addition, as an orientation control agent, 1 type may be used independently and 2 or more types may be used together.

  The addition amount of the alignment control agent in the liquid crystal composition is preferably 0.01% by mass to 10% by mass, more preferably 0.01% by mass to 5% by mass with respect to the total mass of the polymerizable liquid crystal compound. 0.02% by mass to 1% by mass is particularly preferable.

(Other additives)
In addition, the liquid crystal composition may contain at least one selected from a surfactant for adjusting the surface tension of the coating film to make the film thickness uniform, and various additives such as a polymerizable monomer. . Further, in the liquid crystal composition, if necessary, a polymerization inhibitor, an antioxidant, an ultraviolet absorber, a light stabilizer, a colorant, metal oxide fine particles, and the like may be added as long as the optical performance is not deteriorated. Can be added.

(solvent)
There is no restriction | limiting in particular as a solvent used for preparation of a liquid-crystal composition, Although it can select suitably according to the objective, An organic solvent is used preferably.
The organic solvent is not particularly limited and may be appropriately selected depending on the intended purpose. For example, ketones, alkyl halides, amides, sulfoxides, heterocyclic compounds, hydrocarbons, esters, ethers, etc. Is mentioned. These may be used individually by 1 type and may use 2 or more types together. Among these, ketones are particularly preferable in consideration of environmental load.

(Coating, orientation, polymerization)
The method for applying the liquid crystal composition to the temporary support, the alignment film, the quarter wavelength plate, the underlying cholesteric liquid crystal layer, and the like is not particularly limited and can be appropriately selected according to the purpose. Examples of the coating method include curtain coating method, extrusion coating method, direct gravure coating method, reverse gravure coating method, die coating method, spin coating method, dip coating method, spray coating method, and slide coating method. It can also be carried out by transferring a liquid crystal composition separately coated on a support. The liquid crystal molecules may be cholesterically aligned by heating the applied liquid crystal composition. In the cholesteric orientation, the heating temperature is preferably 200 ° C. or lower, and more preferably 130 ° C. or lower. By this alignment treatment, an optical thin film in which the polymerizable liquid crystal compound is twisted and aligned so as to have a helical axis in a direction substantially perpendicular to the film surface is obtained.

The aligned liquid crystal compound can be further polymerized to cure the liquid crystal composition. The polymerization may be either thermal polymerization or photopolymerization by light irradiation, but photopolymerization is preferred. It is preferable to use ultraviolet rays for light irradiation. The irradiation energy is preferably ^{20mJ / cm 2 ~50J / cm 2} , 100mJ / cm 2 ~1,500mJ / cm 2 is more preferable. In order to accelerate the photopolymerization reaction, light irradiation may be performed under heating conditions or in a nitrogen atmosphere. The irradiation ultraviolet wavelength is preferably 350 nm to 430 nm. The polymerization reaction rate is preferably high from the viewpoint of stability, preferably 70% or more, and more preferably 80% or more. The polymerization reaction rate can determine the consumption rate of a polymerizable functional group using an IR absorption spectrum.

  The thickness of each cholesteric liquid crystal layer is not particularly limited as long as it exhibits the above characteristics, but is preferably in the range of 1.0 to 150 μm, more preferably in the range of 4.0 to 100 μm. Good. The thickness of the quarter wave plate formed from the liquid crystal composition is not particularly limited, but is preferably 0.2 to 10 μm, more preferably 0.5 to 2 μm.

(Temporary support, support, alignment layer)
The liquid crystal composition may be applied and layered on the surface of the temporary support or the alignment layer formed on the surface of the temporary support. The temporary support or the temporary support and the alignment layer may be peeled off after forming the layer.
In particular, a support may be used. The support does not have to be peeled off after forming the layer. Examples of the temporary support and the support include polyester such as polyethylene terephthalate (PET), polycarbonate, acrylic resin, epoxy resin, polyurethane, polyamide, polyolefin, cellulose derivative, silicone, or glass plate. The temporary support body should just be peeled, for example after adhere | attaching a circularly-polarizing reflection layer on a front plate. The temporary support may function as a protective film after the circularly polarized reflective layer is bonded to the front plate and further until the circularly polarized reflective layer is bonded to the image display device.

The alignment layer has a rubbing treatment of organic compounds such as polymers (resins such as polyimide, polyvinyl alcohol, polyester, polyarylate, polyamideimide, polyetherimide, polyamide, modified polyamide), oblique deposition of inorganic compounds, and microgrooves. It can be provided by means such as formation of a layer or accumulation of an organic compound (for example, ω-tricosanoic acid, dioctadecylmethylammonium chloride, methyl stearylate) by the Langmuir-Blodgett method (LB film). 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 made of a polymer is preferably subjected to a rubbing treatment and then a liquid crystal composition is applied to the rubbing treatment surface. The rubbing treatment can be performed by rubbing the surface of the polymer layer several times in a certain direction with paper or cloth.
The liquid crystal composition may be applied to the surface of the temporary support without providing the alignment layer, or the surface obtained by rubbing the temporary support.
The thickness of the alignment layer is preferably 0.01 to 5 μm, and more preferably 0.05 to 2 μm.

[Laminated film of cholesteric liquid crystal layer]
When forming a laminated film composed of a plurality of cholesteric liquid crystal layers, a liquid crystal composition containing a polymerizable liquid crystal compound or the like is applied directly to the surface of each cholesteric liquid crystal layer, and the alignment and fixing steps are repeated. Well, a separately prepared cholesteric liquid crystal layer or a laminate thereof may be laminated using an adhesive or the like, but the former is preferred. Usually, when an adhesive layer provided with a film thickness of 0.5 to 10 μm is used, interference unevenness derived from thickness unevenness of the adhesive layer may be observed. Therefore, it is preferable to laminate without using the adhesive layer. It is. In addition, by forming the next cholesteric liquid crystal layer so as to be in direct contact with the surface of the previously formed cholesteric liquid crystal layer, the orientation direction of the liquid crystal molecules on the air interface side of the previously formed cholesteric liquid crystal layer, and on that This is because the alignment orientations of the liquid crystal molecules below the cholesteric liquid crystal layer to be formed coincide with each other, and the polarization property of the laminate of the cholesteric liquid crystal layer is improved.

[Front plate]
The mirror with an image display function of the present invention has a front plate. The front plate may be in direct contact with the circularly polarizing plate, or may be directly bonded by an adhesive layer or the like.
The front plate is not particularly limited. As the front plate, a glass plate or a plastic film used for producing a normal mirror can be used. The front plate is preferably transparent in the visible light region. Here, “transparent in the visible light region” means that the light transmittance in the visible light region is 80% or more, preferably 85% or more. The light transmittance used as a measure of transparency is the light transmittance determined by the method described in JIS A5759. That is, the transmittance at each wavelength of 380 nm to 780 nm is measured with a spectrophotometer, and the weight obtained from the spectral distribution of CIE (International Commission on Illumination) daylight D65, the wavelength distribution of CIE light adaptation standard relative luminous sensitivity, and the wavelength interval. The visible light transmittance is obtained by multiplying the value coefficient and performing a weighted average. . The front plate preferably has a small birefringence. For example, the front phase difference may be 20 nm or less, preferably less than 10 nm, and more preferably 5 nm or less. Examples of the plastic film include polyester such as polyethylene terephthalate (PET), polycarbonate, acrylic resin, epoxy resin, polyurethane, polyamide, polyolefin, cellulose derivative, and silicone.
The film thickness of the front plate may be about 100 μm to 10 mm, preferably 200 μm to 5 mm, more preferably 500 μm to 2 mm, and further preferably 500 μm to 1000 μm.

[Adhesive layer]
The mirror with an image display function of the present invention may include an image display device, a circularly polarized light reflecting layer, a circularly polarized light reflecting layer and a front plate, and other adhesive layers for bonding the respective layers. The adhesive layer may be formed from an adhesive.
Adhesives include hot melt type, thermosetting type, photocuring type, reactive curing type, and pressure-sensitive adhesive type that does not require curing, from the viewpoint of curing method, and the materials are acrylate, urethane, urethane acrylate, epoxy , Epoxy acrylate, polyolefin, modified olefin, polypropylene, ethylene vinyl alcohol, vinyl chloride, chloroprene rubber, cyanoacrylate, polyamide, polyimide, polystyrene, polyvinyl butyral, etc. can do. From the viewpoint of workability and productivity, the photocuring type is preferable as the curing method, and from the viewpoint of optical transparency and heat resistance, it is preferable to use an acrylate, urethane acrylate, epoxy acrylate, or the like material.

<Half mirror>
The half mirror may be manufactured by adhering a circularly polarized light reflection layer and a quarter wave plate on the front plate in this order from the front plate side, or a lamination of the quarter wave plate and the circularly polarized light reflection layer. It may be produced by bonding the body to the front plate. For example, the circularly polarized light reflecting layer formed on the temporary support is transferred onto the surface of the quarter wavelength plate to form a laminate of the quarter wavelength plate and the circularly polarized reflective layer. A half mirror can be obtained by adhering to the front plate on the surface of the polarizing reflection layer and then peeling the temporary support as necessary.

<Manufacturing method of mirror with image display function>
The mirror with an image display function of the present invention can be produced by arranging the half mirror on the image display surface side of the image display device and integrating the image display device and the half mirror. The half mirror is arranged so that the image display device, the quarter-wave plate, the circularly polarized reflection layer, and the front plate are in this order.
The integration of the image display device and the half mirror may be performed by connection with an outer frame or a hinge or adhesion. For example, the mirror with an image display function of the present invention can be manufactured by adhering a half mirror including a front plate and a circularly polarized reflective layer to the image display surface of the image display device on the circularly polarized reflective layer side. Alternatively, a half mirror including a front plate, a circularly polarized light reflection layer, and a quarter wavelength plate can be bonded to the image display surface of the image display device on the quarter wavelength plate side.

<Use of mirror with image display function>
The use of the mirror with an image display function of the present invention is not particularly limited. For example, it can be used as a security mirror, a beauty salon or a barber mirror, and can display images such as character information, still images, and moving images. The mirror with an image display function of the present invention may be a vehicle rearview mirror. The mirror with an image display function of the present invention can observe the image and the mirror reflection image without depending on the direction even through the polarized sunglasses, so that the wearer of the polarized sunglasses can easily see the back and the like, and is safe for use as a vehicle rearview mirror. Sex can be secured. It may be used as a television, a personal computer, a smartphone, or a mobile phone.

  The present invention will be described more specifically with reference to the following examples. The materials, reagents, amounts and ratios of substances, operations, and the like shown in the following examples can be appropriately changed without departing from the gist of the present invention. Therefore, the scope of the present invention is not limited to the following examples.

<Production of 1/4 wavelength plate>
Resin pellets having an alicyclic structure as a transparent thermoplastic resin (ZEONOR 1420, glass transition temperature 136 ° C., manufactured by Nippon Zeon Co., Ltd.) are dried at 100 ° C. for 5 hours, supplied to an extrusion molding machine, and the lip opening is adjusted. The sheet was extruded from the adjusted die onto a cooling roll and cooled on the cooling roll to obtain a long unstretched film having an average thickness of 100 μm. Next, the film before stretching was continuously supplied to a longitudinal uniaxial stretching machine, and longitudinal uniaxial stretching with a stretching temperature of 150 ° C. and a stretching ratio of 1.3 times was performed to obtain a longitudinal uniaxially stretched film having an average film thickness of 87 μm.
Furthermore, a longitudinally uniaxially stretched film was continuously supplied to an oblique stretching machine, and oblique stretching was performed to obtain a quarter wavelength plate having an average thickness of 32 μm and an average orientation angle of 45 °.
Regarding the retardation value of the obtained quarter-wave plate at a wavelength of 550 nm, the retardation Rth in the thickness direction was 158 nm, and the retardation Re in the in-plane direction was 140 nm.

<Production of circularly polarizing film>
(Coating liquid for forming cholesteric liquid crystal layer)
The following compound 1, compound 1, fluorine-based horizontal alignment agent 1, fluorine-based horizontal alignment agent 2, chiral agent, polymerization initiator and solvent methyl ethyl ketone were mixed to prepare a coating solution having the following composition.
-Compound 1 80 parts by mass-Compound 2 20 parts by mass-Fluorine-based horizontal alignment agent 1 0.1 part by mass-Fluorine-based horizontal alignment agent 2 0.007 parts by mass-Right-turning chiral agent LC756 (manufactured by BASF)
Adjustment / polymerization initiator IRGACURE819 (manufactured by BASF) 3 parts by mass / solvent (methyl ethyl ketone) in accordance with the target reflection wavelength

  Coating liquids 1 to 3 were prepared by adjusting the amount of the chiral agent LC-756 having the coating liquid composition described above. Using each coating solution, a single layer of cholesteric liquid crystal layer was prepared on a temporary support in the same manner as in the preparation of the following circularly polarized reflective layer, and the reflection characteristics were confirmed. It was a circularly polarized light reflection layer, and the central reflection wavelength was as shown in Table 1 below.

(1) Toyobo Co., Ltd. PET film (Cosmo Shine A4100, thickness: 100 μm) was used as a temporary support (150 mm × 100 mm), and one side thereof was rubbed (rayon cloth, pressure: 0.1 kgf (0.98 N). ), Rotation speed: 1000 rpm, conveyance speed: 10 m / min, number of times: 1 reciprocation).

(2) The coating solution 1 for forming a cholesteric liquid crystal layer is applied to the rubbed surface of the PET film using a wire bar, then dried and placed on a hot plate at 30 ° C., and an electrodeless lamp “D” manufactured by Fusion UV Systems Co., Ltd. UV irradiation was performed with a “bulb” (60 mW / cm ² ) for 6 seconds, and the liquid crystal phase was fixed to obtain a cholesteric liquid crystal layer having a thickness of 3.5 μm. The same process was repeated using the coating liquid 2 and the coating liquid 3 in this order on the surface of the obtained cholesteric liquid crystal layer, and a laminate A of three cholesteric liquid crystal layers (layer of the coating liquid 2: 3.0 μm, A layer of coating solution 3 (2.7 μm) was obtained. When the transmission spectrum of the laminate A was measured with a spectrophotometer (manufactured by JASCO Corporation, V-670), transmission spectra having selective reflection center wavelengths at 630 nm, 540 nm, and 450 nm were obtained.

<Production of half mirror>
An OCA (Optically Clear Adhesive) (Acrylic OCA PDS1 manufactured by Panac Co., Ltd.) was bonded to the obtained quarter-wave plate using a laminator, and then bonded to the liquid crystal layer surface of the circularly polarizing film. Thereafter, the PET film was peeled off to obtain a half mirror.

[Example 2]
Resin pellets having an alicyclic structure as a transparent thermoplastic resin (ZEONOR 1420, glass transition temperature 136 ° C., manufactured by Nippon Zeon Co., Ltd.) are dried at 100 ° C. for 5 hours, supplied to an extrusion molding machine, and the lip opening is adjusted. The sheet was extruded from the adjusted die onto a cooling roll and cooled on the cooling roll to obtain a long unstretched film having an average thickness of 18 μm. This unstretched film and the stretched film of 32 μm prepared in Example 1 were bonded with OCA (acrylic OCA PDS1 manufactured by Panac Co., Ltd.) using a laminator to obtain a quarter wavelength plate. A circularly polarizing film was bonded to this quarter-wave plate in the same manner as in Example 1, and the PET film was peeled off to obtain a half mirror.

[Example 3]
The stretched film 32 μm produced in Example 1 and 100 μm of unstretched COP film ZF14 manufactured by Nippon Zeon Co., Ltd. were bonded with OCA (acrylic OCA PDS1 manufactured by Panac) to obtain a quarter-wave plate.
A circularly polarizing film was bonded to this quarter-wave plate in the same manner as in Example 1, and the PET film was peeled off to obtain a half mirror.
[Example 4]
A ZEONOR ZM16-138 (film thickness: 86 μm) manufactured by Nippon Zeon Co., Ltd. was used as a quarter-wave plate, and a half mirror was produced in the same procedure as in Example 1.

[Comparative Example 1]
A half mirror was produced in the same procedure as in Example 1 using a pure wavelength TT138 (film thickness: 40 μm) manufactured by Teijin Ltd., which is a main component polycarbonate (PC), as a ¼ wavelength plate.
[Comparative Example 2]
A half mirror was produced in the same procedure as in Example 1 by using Pure Ace TT138 (thickness: 70 μm) of Teijin Limited, which is a main component polycarbonate, as a quarter wavelength plate.

<Evaluation method of unevenness>
Each prepared half mirror was placed in a thermal environment at 95 ° C. for 1000 hours, and then the surface was visually checked for wrinkles. In addition, the indoor fluorescent lamp was projected on a half mirror, and the distortion of the reflected image was confirmed.
A: There are no wrinkles and the reflected image is not distorted.
B: Wrinkles are slightly generated, but the reflected image is hardly distorted.
C: There are many wrinkles, and the reflected image is distorted.

<Image evaluation method>
Each obtained half mirror is disposed on the surface of the image display unit of a liquid crystal display (LCD) (manufactured by Apple, iPad (registered trademark) Air), and a quarter-wave plate is opposed to the surface of the image display unit. The retardation axis of the / 4 wavelength plate and the transmission axis of the LCD (polarization direction of the light emission of the LCD) are 45 degrees.
A white image was projected on the LCD, observed from the front plate side of the half mirror, and the transmitted image was evaluated according to the following criteria.

Transparent image evaluation (transparent white image)
A: It looks white B: It looks almost white (the color is slightly bluish or yellowish)
C: Does not look white (the color is bluish or yellowish)

The results are shown in Table 2.

Claims (12)

A mirror with an image display function,
Including an image display device, a quarter-wave plate, a circularly polarized reflection layer, and a front plate in this order,
The circularly polarized light reflection layer includes a cholesteric liquid crystal layer,
The cholesteric liquid crystal layer has a central wavelength of selective reflection in the visible light region,
The quarter wave plate comprises a cycloolefin polymer;
The mirror with an image display function, wherein the film thickness of the ¼ wavelength plate is 20 μm to 500 μm. The mirror with an image display function according to claim 1, wherein the film thickness of the ¼ wavelength plate is 50 μm to 200 μm. 3. The mirror with an image display function according to claim 1, wherein the circularly polarizing reflection layer includes two or more cholesteric liquid crystal layers, and the two or more cholesteric liquid crystal layers have different selective reflection center wavelengths. The mirror with an image display function according to claim 3, wherein the two or more cholesteric liquid crystal layers are in direct contact with each other. 5. The image display function according to claim 1, wherein the circularly polarized light reflection layer includes three or more cholesteric liquid crystal layers, and the three or more cholesteric liquid crystal layers have different selective reflection center wavelengths. mirror. The circularly polarized reflective layer is selected as a cholesteric liquid crystal layer having a central wavelength of selective reflection in the wavelength range of red light, a cholesteric liquid crystal layer having a central wavelength of selective reflection in the wavelength range of green light, and a wavelength range of blue light. The mirror with an image display function according to claim 5, comprising a cholesteric liquid crystal layer having a central wavelength of reflection. The mirror with an image display function according to any one of claims 1 to 6, wherein the circularly polarizing reflection layer and the front plate are directly bonded via an adhesive layer. The mirror with an image display function according to any one of claims 1 to 7, wherein the circularly polarized light reflection layer and the quarter-wave plate are directly bonded via an adhesive layer. The mirror with an image display function according to any one of claims 1 to 8, wherein the image display device and the quarter-wave plate are directly bonded via an adhesive layer. The mirror with an image display function according to claim 1, wherein the circularly polarized light reflection layer includes a cholesteric liquid crystal layer having a central wavelength of selective reflection in an infrared light region. Including a quarter wave plate, a circularly polarizing reflection layer, and a front plate in this order,
The front plate is a glass plate or a plastic film having a front phase difference of less than 10 nm,
The circularly polarized light reflection layer includes a cholesteric liquid crystal layer,
The cholesteric liquid crystal layer has a central wavelength of selective reflection in the visible light region,
The quarter wave plate comprises a cycloolefin polymer;
The half mirror whose film thickness of the said quarter wave plate is 20 micrometers-500 micrometers. The half mirror according to claim 11, wherein the quarter-wave plate has a thickness of 30 μm to 200 μm.