WO2017188251A1

WO2017188251A1 - Transparent screen and image display system

Info

Publication number: WO2017188251A1
Application number: PCT/JP2017/016379
Authority: WO
Inventors: 雄二郎矢内; 永井　道夫; 昌山本
Original assignee: 富士フイルム株式会社
Priority date: 2016-04-27
Filing date: 2017-04-25
Publication date: 2017-11-02

Abstract

The objective of the invention is to provide: a transparent screen having excellent transparency and capable of reducing hot spots; and an image display system wherein, by using said transparent screen, visibility through the screen is excellent and hot spots are reduced. The objective is achieved by a transparent screen comprising a plurality of dot films in each of which dots made by fixing a cholesteric liquid crystal phase are arranged two-dimensionally on a support, wherein the dots in each of the dot films have the same selective reflection center wavelength.

Description

Transparent screen and image display system

The present invention relates to a transparent screen and an image display system using the transparent screen.

2. Description of the Related Art In recent years, a transparent screen that displays an image by diffusing and / or reflecting projection light from a projector and transmits light from the front and back surfaces is known as one of the screens constituting a projection display device. .

For example, in Patent Document 1, as a projection-type liquid crystal projection system, a transparent screen using cholesteric liquid crystal that reflects right- or left-circularly polarized red light, green light, and blue light is used, and red light projected onto the transparent screen is used. The green light and the blue light are polarized to the right circularly polarized light or the left circularly polarized light by the λ / 4 plate so that the right circularly polarized component or the left circularly polarized component of the external light irradiated on the transparent screen is transmitted. A projection type liquid crystal projection system is described.

Japanese Patent Laid-Open No. 5-107660

By the way, in the image display using the projector, there is a problem that a hot spot occurs. For example, in an image display system using a transparent screen as described in Patent Document 1, the hot spot is the side opposite to the projector of the transparent screen, and the light source of the projector observes in the straight direction of the light emitted from the projector. It is a phenomenon. When such a hot spot is generated by the transmitted light that has passed through the transparent screen, it feels dazzling when observed from the side opposite to the projector of the transparent screen.

In the transparent screen as shown in Patent Document 1, when the transparency of the screen is high, the hot spot is very dazzling. In particular, in a laser projector using a transparent screen and using a laser as a light source, the hot spot is extremely dazzling.

In a normal non-transparent screen, the regular reflected light in the straight traveling direction of the light emitted from the projector becomes a hot spot. In such a non-transparent screen, a concavo-convex structure is provided on the outermost surface of the screen to diffuse light and reduce hot spots caused by specularly reflected light.
However, in a transparent screen as shown in Patent Document 1, if a concavo-convex structure is imparted to the outermost surface, the transparency is significantly reduced, and this countermeasure cannot be used.

That is, in an image display system using a transparent screen, the appearance of a transparent screen that ensures good transparency and reduces hot spots caused by transmitted light is desired.

An object of the present invention is to solve such problems of the prior art, a transparent screen having good transparency and capable of reducing hot spots caused by transmitted light, and an image using the transparent screen To provide a display system.

In order to solve this problem, the transparent screen of the present invention has a plurality of dot films in which dots formed by fixing a cholesteric liquid crystal phase are two-dimensionally arranged on the surface of a support, and
A transparent screen characterized in that, in a plurality of dot films, the selective reflection center wavelength of the dots of at least two dot films and the rotation direction of the reflected circularly polarized light are equal to each other.

In such a transparent screen of the present invention, a dot film in which dots reflect right circularly polarized light, a dot film in which dots reflect left circularly polarized light, and a dot in which dots reflect right circularly polarized light, And it is preferable to have a plurality of dot films in which the dots reflect left circularly polarized light.
The in-plane retardation Re (550) at a wavelength of 550 nm of the support is preferably 0 to 20 nm, and the retardation Rth (550) in the thickness direction at a wavelength of 550 nm of the support is preferably 0 to 50 nm.
Moreover, it is preferable to have a λ / 4 plate.
Further, the in-plane retardation Re (550) of the λ / 4 plate at a wavelength of 550 nm is 120 to 150 nm, and the retardation Rth (550) in the thickness direction of the λ / 4 plate at a wavelength of 550 nm is −50 to 50 nm. Is preferred.

Moreover, the 1st aspect of the image display system of this invention is the transparent screen of this invention,
There is provided an image display system comprising: a projector in which outgoing light is non-polarized and a peak wavelength of the outgoing light is equal to a selective reflection center wavelength of a dot.

Furthermore, the second aspect of the image display system of the present invention includes a transparent screen of the present invention having a λ / 4 plate,
There is provided an image display system comprising: a projector, wherein the emitted light is polarized light, and a peak wavelength of the emitted light is equal to a selective reflection center wavelength of a dot.

In such an image display system of the present invention, the projector is preferably a laser projector.
Furthermore, it is preferable that the dot film of a transparent screen is arrange | positioned with the convex of a dot facing a projector.

According to the present invention, it is possible to realize a transparent screen having good transparency and capable of reducing hot spots caused by transmitted light, and an image display system using this transparent screen and reduced hot spots caused by transmitted light.

FIG. 1 is a diagram conceptually illustrating an example of an image display system of the present invention. FIG. 2 is a conceptual diagram for explaining the operation of the transparent screen of the present invention. FIG. 3 is a conceptual diagram for explaining the operation of the transparent screen of the present invention. FIG. 4 is a diagram conceptually showing another example of the image display system of the present invention. FIG. 5 is a conceptual diagram for explaining an evaluation method in an embodiment of the present invention. FIG. 6 is a conceptual diagram for explaining an evaluation method in an embodiment of the present invention. FIG. 7 is a conceptual diagram for explaining a measurement method in an embodiment of the present invention.

Hereinafter, the transparent screen and image display system of the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.

In this specification, a numerical range expressed using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.
In this specification, for example, an angle such as “45 °”, “parallel”, “vertical” or “orthogonal” is within a range where the difference from the exact angle is less than 5 ° unless otherwise specified. Means. The difference from the exact angle is preferably less than 4 °, more preferably less than 3 °.
In this specification, “(meth) acrylate” is used to mean “one or both of acrylate and methacrylate”.
In this specification, “same” includes an error range generally allowed in the technical field. In addition, in the present specification, when “all”, “any” or “entire surface” is used, it includes an error range generally allowed in the technical field in addition to the case of 100%, for example, 99% or more, The case of 95% or more, or 90% or more is included.

In this specification, visible light is light having a wavelength that can be seen by human eyes among electromagnetic waves, and indicates light having a wavelength range of 380 to 780 nm. Invisible light is light having a wavelength range of less than 380 nm or a wavelength range of more than 780 nm.
Although not limited to this, among visible light, light in the wavelength region of 420 to 490 nm is blue light, light in the wavelength region of 495 to 570 nm is green light, and wavelength of 620 to 750 nm. The light in the area is red light.

In this specification, retroreflection means reflection in which incident light is reflected in the incident direction.

In the present specification, “haze” means a value measured using a haze meter NDH-2000 manufactured by Nippon Denshoku Industries Co., Ltd.
Theoretically, haze means a value represented by the following equation.
(Scattering transmittance of natural light of 380 to 780 nm) / (scattering transmittance of natural light of 380 to 780 nm + direct transmittance of natural light) × 100%
The scattering transmittance is a value that can be calculated by subtracting the direct transmittance from the obtained omnidirectional transmittance using a spectrophotometer and an integrating sphere unit. The direct transmittance is a transmittance at 0 ° based on a value measured using an integrating sphere unit. That is, the low haze means that the direct transmitted light amount is large in the total transmitted light amount.

In this specification, Re (λ) and Rth (λ) represent in-plane retardation and retardation in the thickness direction at a wavelength λ, respectively. Unless otherwise specified, the wavelength λ is 550 nm.
In this specification, Re (λ) and Rth (λ) are values measured at a wavelength λ in AxoScan OPMF-1 (manufactured by Optoscience). By inputting the average refractive index ((Nx + Ny + Nz) / 3) and film thickness (d (μm)) in AxoScan,
Slow axis direction (°)
Re (λ) = R0 (λ)
Rth (λ) = ((Nx + Ny) / 2−Nz) × d
Is calculated.
Note that R0 (λ) is displayed as a numerical value calculated by AxoScan, and means Re (λ).

In this specification, the refractive indexes Nx, Ny, and Nz are measured using an Abbe refractometer (NAR-4T, manufactured by Atago Co., Ltd.) and a sodium lamp (λ = 589 nm) as a light source. Further, when measuring the wavelength dependency, it can be measured in combination with an interference filter using a multi-wavelength Abbe refractometer DR-M2 (manufactured by Atago Co., Ltd.).
In addition, as the refractive index, values in polymer handbooks (John Wiley & Sons, Inc.) and catalogs of various optical films can be used. The average refractive index values of the main optical films are exemplified below: cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), Polystyrene (1.59).

In this specification, the selective reflection center wavelength is a half-value transmittance represented by the following formula: T1 / 2 (%), where Tmin (%) is a minimum value of transmittance of a target object (member). ) Means the average value of two wavelengths.
Formula for calculating half-value transmittance: T1 / 2 = 100− (100−Tmin) ÷ 2
Further, “equal” for the selective reflection center wavelengths of a plurality of objects does not mean that they are strictly equal, and an error in a range that is not optically affected is allowed. Specifically, the phrase “selective reflection center wavelengths of a plurality of objects are equal” means that the difference between the selective reflection center wavelengths of the respective objects is 20 nm or less, and the difference is 15 nm or less. Preferably, it is 10 nm or less.

In this specification, the phrase “the peak wavelength of the light emitted from the projector is“ equal ”to the dot selective reflection center wavelength” does not mean that it is strictly equal, and an error in a range that is not optically affected is acceptable. Is done. Specifically, the peak wavelength of the light emitted from the projector is “equal” to the selective reflection center wavelength of the dot, which means that the difference between the two wavelengths is 50 nm or less, and this difference is 25 nm or less. And is more preferably 15 nm or less.

The transparent screen of the present invention has a plurality of dot films formed by two-dimensionally arranging dots formed by fixing a cholesteric liquid crystal phase on a support, and the plurality of dot films have a dot selective reflection center. The wavelength and the rotation direction of the reflected circularly polarized light have the same configuration. The image display system of the present invention includes such a transparent screen of the present invention and a monochromatic projector whose emitted light is polarized or non-polarized.
Such a transparent screen and image display system of the present invention is compatible with the display of a single color image such as a green image.

FIG. 1 conceptually shows an example of the image display system of the present invention using an example of the transparent screen of the present invention.
An image display system 10 illustrated in FIG. 1 includes the transparent screen 12 according to the present invention and a projector 14 that projects a green single-color image with non-polarized emitted light. That is, the image display system 10 is an image display system that displays a green single-color image on the transparent screen 12.

In the image display system 10, the transparent screen 12 has a configuration in which a right circular polarization laminate 20 and a left circular polarization laminate 24 are laminated. In FIG. 1, in order to clearly show the configuration of the transparent screen 12, the support 32 described later is hatched, and the interface between the right circularly polarized laminate 20 and the left circularly polarized laminate 24 is indicated by a thick line. .
In the following description, unless otherwise specified, not only the transparent screen of the image display system 10 shown in FIG. 1 but also various transparent screens of the present invention used in various image display systems of the present invention described later. The same is true.

Moreover, although illustration is abbreviate | omitted, the right circular polarization laminated body 20 and the left circular polarization laminated body 24 are bonded together by the bonding layer provided between both.
In the present invention, the bonding layer can be made of various known materials as long as the target plate-shaped material (sheet-shaped material) can be bonded. That is, the bonding layer may be a layer made of an adhesive or a layer made of an adhesive. An adhesive has fluidity when bonded and then becomes a solid. The adhesive is a gel-like (rubber-like) soft solid when pasted, and the gel-like state does not change thereafter. Moreover, the layer which consists of a material with the characteristic of both an adhesive agent and an adhesive may be sufficient as a bonding layer. Therefore, the bonding layer is a known material used for bonding sheet-like materials in optical devices and optical elements, such as optical transparent adhesive (OCA (Optical Clear Adhesive)), optical transparent double-sided tape, and ultraviolet curable resin. What is necessary is just to use.
Alternatively, the right circularly polarizing laminate 20 and the left circularly polarizing laminate 24 are laminated and held by a frame or a jig instead of being bonded together by the bonding layer to constitute the transparent screen of the present invention. May be.

In the transparent screen 12, the right circularly polarized laminate 20 is formed by laminating three right circularly polarized dot films 30R.
The right circularly polarized light dot film 30R embeds the support 32, the right circularly polarized light reflective dot 34R that is two-dimensionally arranged on one surface of the support 32, and the right circularly polarized light reflective dot 34R. And an overcoat layer 36 laminated on the substrate.
On the other hand, the left circularly polarized laminate 24 is formed by laminating three left circularly polarized dot films 30L.
The left circularly polarized light dot film 30L embeds the support 32, the left circularly polarized light reflective dot 34L that is two-dimensionally arranged on one surface of the support 32, and the left circularly polarized light reflective dot 34L. And an overcoat layer 36 laminated on the substrate.

Hereinafter, components of the right circularly polarized dot film 30R and the left circularly polarized dot film 30L will be described.
In the following description, when there is no need to distinguish between the right circularly polarized dot film 30R and the left circularly polarized dot film 30L, both are collectively referred to as “dot film”.
In the following description, when there is no need to distinguish between the right circularly polarized light reflecting dot 34R and the left circularly polarized light reflecting dot 34L, they are collectively referred to as “reflective dots”.

<Support>
Each of the dot film supports 32 supports reflective dots which are dots formed by fixing a cholesteric liquid crystal phase to be described later.

The support 32 preferably has a low light reflectance at the wavelength of light reflected by the reflective dots, and preferably does not include a material that reflects light at the wavelength of light reflected by the reflective dots.
The support 32 is preferably transparent in the visible light region. Further, the support 32 may be colored, but is preferably not colored or less colored. Further, the support 32 preferably has a refractive index of about 1.2 to 2.0, more preferably about 1.4 to 1.8.
In the present specification, when it is transparent, specifically, the non-polarized light transmittance (omnidirectional transmittance) at a wavelength of 380 to 780 nm may be 50% or more, preferably 70% or more, and preferably 85% or more. It is more preferable that

The haze value of the support 32 is preferably 30% or less, more preferably 0.1 to 25%, and further preferably 0.1 to 10%. Further, by using the support 32 having a high haze like an AG (anti-glare) support, it is possible to make adjustments that deteriorate the transparency and improve the front luminance and viewing angle characteristics.
The thickness of the support 32 may be selected according to the use and is not particularly limited, but may be about 5 to 1000 μm, preferably 10 to 250 μm, and more preferably 15 to 150 μm.

The support 32 preferably has a low Re (λ) and Rth (λ).
Specifically, the support 32 preferably has Re (550) of 0 to 20 nm, and more preferably 0 to 10 nm. In addition, the support 32 preferably has Rth (550) of 0 to 50 nm, more preferably 0 to 40 nm.

The support 32 may be a single layer or multiple layers. Examples of the support 32 in the case of a single layer include a support made of glass, triacetyl cellulose (TAC), polyethylene terephthalate (PET), polycarbonate, polyvinyl chloride, acrylic, polyolefin, and the like. As an example of the support body 32 in the case of a multilayer structure, a support body including any of the above-described single-layer support bodies as a substrate and another layer provided on the surface of the substrate can be cited.

In addition, you may provide a base layer between the support body 32 and the reflective dot mentioned later. The underlayer is preferably a resin layer, and more preferably a transparent resin layer. Examples of the underlayer include a layer for adjusting the shape of the reflective dots when forming the reflective dots, a layer for improving the adhesion characteristics between the support 32 and the reflective dots, and the polymerizability when forming the reflective dots. Examples thereof include an alignment film for adjusting the alignment of the liquid crystal compound.
Further, the base layer preferably has a low light reflectance at the wavelength of light reflected by the reflective dots, and preferably does not include a material that reflects light at the wavelength of light reflected by the reflective dots. The underlayer is preferably transparent. Further, the base layer preferably has a refractive index of about 1.2 to 2.0, more preferably about 1.4 to 1.8. The underlayer is also preferably a layer containing a resin obtained by curing a composition containing a polymerizable compound applied directly to the support surface. Examples of the polymerizable compound include non-liquid crystalline compounds such as (meth) acrylate monomers and urethane monomers.
The thickness of the underlayer is not particularly limited, but is preferably 0.01 to 50 μm, and more preferably 0.05 to 20 μm.

<Reflective dots>
As described above, the reflective dot is a dot formed by fixing the cholesteric liquid crystal phase.
In the right circularly polarized light laminate 20, the right circularly polarized light reflecting dots 34R that are two-dimensionally arranged on the right circularly polarized dot film 30R are dots that reflect green right circularly polarized light and transmit other light. .
On the other hand, in the left circularly polarized laminate 24, the left circularly polarized light reflecting dot 34L arranged two-dimensionally on the left circularly polarized dot film 30L reflects the green left circularly polarized light and transmits the other light. It is.

That is, in the three right circular polarization dot films 30R constituting the right circular polarization laminate 20, the selective reflection center wavelength of the arranged right circular polarization reflection dots 34R and the rotation direction of the reflected circular polarization are equal to each other. Further, in the three left circularly polarized dot films 30L constituting the left circularly polarized laminate 24, the selective reflection center wavelength of the arranged left circularly polarized reflective dots 34L and the rotation direction of the reflected circularly polarized light are equal to each other.
Further, the right circularly polarized light reflecting dot 34R of the right circularly polarized light dot film 30R and the left circularly polarized light reflecting dot 34L of the left circularly polarized light dot film 30L have the same selective reflection center wavelength, and the rotational direction of the circularly polarized light of the reflected light is the same. Different.

Each reflective dot is a dot formed by fixing a cholesteric liquid crystal phase. That is, the reflective dot is a dot made of a liquid crystal material having a cholesteric structure.
Here, the cholesteric liquid crystal phase that becomes a reflective dot gives a stripe pattern of a bright part and a dark part in the cross section of the reflective dot observed with a scanning electron microscope, and is maximum in the direction from the end of the reflective dot toward the center. An angle formed between the normal of the line formed by the first dark part from the surface of the reflective dot opposite to the support 32 and the surface of the reflective dot. Is preferably in the range of 70 to 90 °.
This point will be described in detail later.

In each dot film, the reflective dots may be arranged regularly or irregularly as long as they are arranged two-dimensionally.
When the reflective dots are regularly arranged, the arrangement pattern of the reflective dots in each dot film constituting the right circularly polarized laminate 20 and the left circularly polarized laminate 24 may be the same or different from each other. Here, when the arrangement pattern of the reflective dots in the respective dot films constituting the right circularly polarized laminate 20 and the left circularly polarized laminate 24 is the same, the positions in the surface direction of the reflective dots in each dot film are all dots. Even if it is the same position on the film, it may be a position shifted by two or more dot films.
Moreover, the arrangement density of the reflective dots in each dot film may be uniform over the entire surface, or may have regions with different arrangement densities.

The arrangement density of the reflective dots in the dot film is not particularly limited, and may be appropriately set according to the diffusibility (viewing angle) required for the transparent screen, transparency, and the like.
From the viewpoints of suppressing hot spots, obtaining a wide viewing angle, obtaining high transparency, and appropriate density that can be produced without defects such as coalescence or defect of reflective dots during production, the support 32 is provided. The area ratio of the reflective dots to the support 32 when viewed from the normal direction of the main surface is preferably 1 to 90.6%, more preferably 2 to 50%, and 4 to 30 % Is more preferable.
Note that the area ratio of the reflective dots was measured in a 1 × 1 mm area in an image obtained with a microscope such as a laser microscope, a scanning electron microscope (SEM), or a transmission electron microscope (TEM). For example, an average value of five locations may be used as the dot area ratio.

Similarly, the pitch of adjacent reflective dots is preferably 20 to 500 μm, more preferably 20 to 300 μm, in that hot spots can be suppressed, a wide viewing angle can be obtained, and high transparency can be obtained. More preferably, it is 20 to 150 μm. The pitch of the reflective dots is the distance between the centers of the reflective dots.

In the dot film, the diameters and / or shapes of the reflective dots may all be the same or may include different ones, but are preferably the same. For example, reflecting dots formed under the same conditions with the intention of forming dots having the same diameter and shape are preferable.

In this specification, when a reflective dot is described, the description is applicable to all the reflective dots in the transparent screen of the present invention. In addition, it is allowed that the transparent screen of the present invention including the reflection dots described includes dots not corresponding to the description due to an error or an error allowed in this technical field.

The reflective dots (the right circularly polarized reflective dot 34R and the left circularly polarized reflective dot 34L) are preferably circular when viewed from the normal direction of the main surface of the support 32, for example, hemispherical (substantially hemispherical), It is a dot having a spherical shape (substantially spherical shape), a truncated cone shape, a conical shape, a truncated cone shape, or the like. In the following description, the normal direction of the main surface of the support 32 is also referred to as “support normal direction”.
The circular shape does not have to be a perfect circle and may be a substantially circular shape. The center of the reflective dot means the center or the center of gravity of the circle. The reflective dots only need to have a circular average shape, and some of the reflective dots may have a shape that does not correspond to a circle.

The reflective dots preferably have an average diameter of 10 to 200 μm, more preferably 20 to 120 μm, when viewed from the normal direction of the support.
The diameter of the reflective dot is a straight line from the edge (edge or boundary of the reflective dot) to the edge in an image obtained with a microscope such as a laser microscope, a scanning electron microscope (SEM), or a transmission electron microscope (TEM). Thus, it can be obtained by measuring the length of a straight line passing through the center of the reflective dot. The number of reflection dots and the distance between the reflection dots can also be confirmed by a microscope image such as a laser microscope, a scanning electron microscope, or a transmission electron microscope.
When the shape of the reflective dot when viewed from the normal direction of the support is other than a circle, the diameter of the circle having the same circular area as the projected area of the reflective dot (equivalent circle diameter) is defined as the diameter of the reflective dot.
The average diameter is obtained by measuring the diameter of 10 randomly selected reflective dots by the above method and arithmetically averaging them.

The height of the reflective dot can be confirmed from a cross-sectional view of the dot obtained using a focus position scan with a laser microscope or a microscope such as SEM or TEM.
The average maximum height of the reflective dots is preferably 1 to 40 μm, more preferably 3 to 30 μm, and even more preferably 5 to 20 μm.

<< Optical properties of reflective dots >>
The reflective dot has wavelength selective reflectivity. As described above, the right circularly polarized light reflecting dot 34R and the left circularly polarized light reflecting dot 34L reflect green circularly polarized light.
The transparent screen 12 of the present invention is basically used as a screen that can be observed by superimposing an image of image light emitted from a single-color (green in the illustrated example) projector 14 and a background on the back side of the transparent screen 12. Therefore, it is preferable that the light whose reflective dots exhibit selective reflectivity is visible light.
Alternatively, the reflection wavelength of the reflection dot is preferably selected according to the wavelength of light emitted from the projector 14.

As described above, the reflective dot is a dot formed by fixing the cholesteric liquid crystal phase.
The wavelength of light at which the reflective dot exhibits selective reflectivity can be adjusted (selected) by adjusting the helical pitch of the cholesteric liquid crystal phase forming the reflective dot.
Further, the spiral axis direction of the cholesteric liquid crystal phase forming the reflective dots in the transparent screen of the present invention is controlled as will be described later. Therefore, the light incident on the reflective dots is reflected not only in regular reflection but also in various directions.

The reflective dots may be colored, but are preferably not colored or less colored. Thereby, the transparency of a transparent screen can be improved.

<< Cholesteric liquid crystal phase >>
It is known that the cholesteric liquid crystal phase exhibits selective reflectivity at a specific wavelength. The central wavelength λ of selective reflection depends on the pitch P (= spiral period) of the helical structure in the cholesteric liquid crystal phase, and follows the relationship between the average refractive index n of the cholesteric liquid crystal phase and λ = n × P. Therefore, the selective reflection center wavelength can be adjusted by adjusting the pitch of the spiral structure. Accordingly, in the illustrated example, the helical pitch of the cholesteric liquid crystal phase forming the reflective dots is adjusted so as to reflect green light.
Since the pitch of the cholesteric liquid crystal phase depends on the kind of chiral agent used together with the polymerizable liquid crystal compound or the concentration of the chiral agent when forming dots, a desired pitch can be obtained by adjusting these.
Regarding the pitch adjustment, Fujifilm Research Report No. 50 (2005) p. There is a detailed description in 60-63. For the measurement of spiral sense and pitch, it is possible to use the method described in “Introduction to Liquid Crystal Chemistry Experiments”, edited by the Japanese Liquid Crystal Society, Sigma Publishing 2007, p. it can.

The cholesteric liquid crystal phase gives a stripe pattern of a bright part and a dark part in a sectional view of a reflective dot observed by a scanning electron microscope. The two bright parts and the dark part 2 in the repetition of the bright part and the dark part correspond to one pitch of the spiral. From this, the pitch can be measured from the SEM sectional view. In the reflective dot, the normal line of each line of the striped pattern is the spiral axis direction of the cholesteric liquid crystal phase.

The reflected light of the cholesteric liquid crystal phase is circularly polarized light. That is, in the transparent screen 12 of the present invention, the reflective dots of each dot film reflect circularly polarized light. Whether the reflected light is right-handed circularly polarized light or left-handed circularly polarized light depends on the twist direction of the spiral in the cholesteric liquid crystal phase. The selective reflection of circularly polarized light by the cholesteric liquid crystal phase reflects right circularly polarized light when the twist direction of the spiral of the cholesteric liquid crystal phase is right, and reflects left circularly polarized light when the twist direction of the spiral is left.
Accordingly, in the illustrated transparent screen 12, the right circularly polarized reflective dot 34R of the right circularly polarized dot film 30R is a dot formed by fixing a right-twisted cholesteric liquid crystal phase, and the left circularly polarized dot film 30L has a left circle. The polarization reflection dot 34L is a dot formed by fixing a left twisted cholesteric liquid crystal phase.
The direction of rotation of the cholesteric liquid crystal phase can be adjusted depending on the type of liquid crystal compound forming the reflective dots (reflective layer) or the type of chiral agent added.

The half-value width Δλ (nm) of the selective reflection band (circular polarization reflection band) indicating selective reflection depends on Δn of the cholesteric liquid crystal phase and the pitch P of the helix, and follows the relationship of Δλ = Δn × P. Therefore, the width of the selective reflection band can be controlled by adjusting Δn. Δn can be adjusted by the type and mixing ratio of the liquid crystal compounds forming the reflective dots (solid film), and the temperature at the time of fixing the orientation. The half-value width of the reflection wavelength band is adjusted according to the application of the transparent screen 12, and may be, for example, 50 to 500 nm, and preferably 100 to 300 nm.

A reflective dot formed by fixing a cholesteric liquid crystal phase gives a stripe pattern of a bright part and a dark part in a cross section. The reflection dot formed by fixing such a cholesteric liquid crystal phase is a line formed by the first dark portion from the surface of the reflection dot opposite to the support 32 when confirmed by a cross-sectional view observed with a scanning electron microscope. The angle formed between the normal line and the surface of the reflective dot opposite to the support 32 is preferably in the range of 70 to 90 °.
In the following description, “the surface of the reflective dot opposite to the support 32” is also simply referred to as “the surface of the reflective dot”.
FIG. 2 shows a schematic diagram of a cross section of the reflective dot. In FIG. 2, the line formed by the dark part is indicated by a bold line. As shown in FIG. 2, it is preferable that the angle θ ₁ formed by the normal line (broken line) of the line Ld ₁ formed by the first dark portion and the surface of the reflective dot (its tangent line) is 70 to 90 °.

Here, when the position of the surface of the reflective dot is expressed by an angle α ₁ with respect to the perpendicular (dotted line) of the surface of the support 32 passing through the center of the reflective dot, the angle α ₁ is at a position of 30 ° and a position of 60 °. The angle between the normal of the line Ld ₁ formed by the first dark portion from the surface of the reflective dot and the surface of the reflective dot is preferably in the range of 70 to 90 °, and at all positions on the surface of the reflective dot, More preferably, the angle formed by the normal of the line Ld ₁ formed by the first dark portion from the surface of the reflective dot and the surface of the reflective dot is in the range of 70 to 90 °.
That is, the reflective dot does not satisfy the above angle at a part of the surface of the reflective dot, for example, does not intermittently satisfy the above angle at a part of the surface of the reflective dot, but continuously satisfies the above angle. It is preferable. In the sectional view, when the surface of the reflective dot is a curve, the angle formed between the normal line of the dark line and the surface of the reflective dot means the angle formed between the tangent line and the normal line of the reflective dot surface. To do. The angle is shown as an acute angle, which means a range of 70 to 110 ° when the angle formed between the normal line and the surface of the reflective dot is expressed as an angle of 0 to 180 °.

In the cross-sectional view, the reflection dot preferably has an angle θ ₂ formed by the normal of the line Ld ₂ formed by the second dark portion from the surface of the reflection dot and the surface of the reflection dot in the range of 70 to 90 °. It is more preferable that the angle formed between the normal line and the surface of the reflective dot is in the range of 70 to 90 ° with respect to the line formed by the third to fourth dark portions from the surface of the dot. More preferably, any of the lines formed by the 5th to 12th dark parts is in the range of 70 to 90 ° between the normal line and the reflective dot.

Furthermore, the angle formed between the normal line of the dark part and the surface of the reflective dot is more preferably 80 to 90 °, and further preferably 85 to 90 °.

Such a cross-sectional view of the reflective dot by SEM shows that on the surface of the reflective dot, the spiral axis of the cholesteric liquid crystal phase forms an angle in the range of 70 to 90 ° with the surface of the reflective dot (its tangent). .
With such a structure, the light incident on the reflective dot is parallel to the spiral axis direction of the cholesteric liquid crystal phase on the surface of the reflective dot when the light incident from the direction having an angle with respect to the normal direction of the support 32 is used. It can be incident at a close angle. Therefore, the light incident on the reflective dots can be reflected in various directions.

In addition, the reflective dots regularly reflect incident light on the basis of the helical axis of the cholesteric liquid crystal phase. Therefore, as conceptually shown in FIG. 3, the reflected light Ir reflected near the center of the reflective dot is parallel to the normal direction of the support with respect to the incident light In incident from the normal direction of the support 32. Is reflected. On the other hand, at a position deviated from the center of the reflective dot (a position where the helical axis of the cholesteric liquid crystal phase is inclined with respect to the normal direction of the support 32), the reflected light Ir is a direction different from the normal direction of the support 32. Is reflected. Therefore, the light incident on the reflective dots can be reflected in various directions, and the viewing angle can be increased. Further, since the light Ip that passes through the reflective dots is transmitted in the same direction as the incident light In, the scattered light can be suppressed from being scattered, haze can be reduced, and transparency can be increased.
Moreover, it is preferable that the reflective dot can reflect light incident from the normal direction of the support 32 in all directions. In particular, the reflection dot preferably has an angle (half-value angle) that is half the front luminance (peak luminance) of 35 ° or more and has high reflectivity.

The spiral axis of the cholesteric liquid crystal phase forms an angle in the range of 70 to 90 ° with the surface of the reflective dot, so that the angle formed between the normal direction of the first dark line from the surface and the normal direction of the support Preferably, the height continuously decreases as the height increases continuously.
The cross-sectional view is a cross-sectional view in an arbitrary direction including a portion having a height that continuously increases to the maximum height in the direction from the end of the dot toward the center, and typically includes and supports the center of the dot. Any cross-sectional view perpendicular to the body may be used.

<< Method for producing reflective dots >>
The reflective dots (the right circularly polarized reflective dot 34R and the left circularly polarized reflective dot 34L) can be obtained by fixing the cholesteric liquid crystal phase in a dot shape.
The structure in which the cholesteric liquid crystal phase is fixed may be any structure as long as the orientation of the liquid crystal compound in the cholesteric liquid crystal phase is maintained. Thus, any structure may be used as long as it is polymerized and cured by ultraviolet irradiation, heating, or the like to form a layer having no fluidity, and at the same time, the orientation state is not changed by an external field or an external force.
In the structure in which the cholesteric liquid crystal phase is fixed, it is sufficient that the optical properties of the cholesteric liquid crystal phase are maintained, and the liquid crystal compound may not exhibit liquid crystallinity. For example, the polymerizable liquid crystal compound may have a high molecular weight by a curing reaction and lose liquid crystallinity.

As an example of a material used for forming a reflective dot formed by fixing a cholesteric liquid crystal phase, a liquid crystal composition containing a liquid crystal compound can be given. The liquid crystal compound is preferably a polymerizable liquid crystal compound.
The liquid crystal composition containing the liquid crystal compound used for forming the reflective dots preferably further contains a surfactant. Moreover, the liquid crystal composition used for forming the reflective dots may further contain a chiral agent and a polymerization initiator.

--Polymerizable liquid crystal compound--
The polymerizable liquid crystal compound may be a rod-like liquid crystal compound or a disk-like liquid crystal compound, but is preferably a rod-like liquid crystal compound.
Examples of the rod-like polymerizable liquid crystal compound that forms the cholesteric liquid crystal phase 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 more 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, Volume 5, 107 (1993), US Pat. Nos. 4,683,327, 5,622,648, and 5770107, International Publication WO95 / 22586. No. 95/24455, No. 97/00600, No. 98/23580, No. 98/52905, JP-A-1-272551, JP-A-6-16616, and JP-A-7-110469. 11-80081 and JP-A-2001-328773, and the like. 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.

Specific examples of the polymerizable liquid crystal compound include compounds represented by the following formulas (1) to (11).

[In the compound (11), X ¹ is 2 to 5 (integer)]

Further, as polymerizable liquid crystal compounds other than the above, cyclic organopolysiloxane compounds having a cholesteric phase as disclosed in JP-A-57-165480 can be used. Further, the above-mentioned polymer liquid crystal compound includes a polymer in which a mesogenic group exhibiting liquid crystal is introduced into the main chain, a side chain, or both positions of the main chain and the side chain, and a polymer cholesteric in which a cholesteryl group is introduced into the side chain. A liquid crystal, a liquid crystalline polymer as disclosed in JP-A-9-133810, a liquid crystalline polymer as disclosed in JP-A-11-293252, or the like can be used.

The addition amount of the polymerizable liquid crystal compound in the liquid crystal composition is preferably 75 to 99.9% by mass with respect to the solid content mass (mass excluding the solvent) of the liquid crystal composition, and preferably 80 to 99. More preferably, it is more preferably 85% to 90% by weight.

--Surfactant--
By adding a surfactant to the liquid crystal composition used when forming the reflective dots, the present inventors align the polymerizable liquid crystal compound horizontally on the air interface side when forming the reflective dots, and the helical axis direction is as described above. It was found that reflective dots controlled in this way were obtained.
In general, in order to form dots, it is necessary to prevent the surface tension from being lowered in order to maintain the droplet shape during printing. Therefore, it was surprising that a reflective dot can be formed even when a surfactant is added, and a reflective dot having high retroreflectivity from multiple directions was obtained. According to the study by the present inventors, when a surfactant is used, dots having an angle formed by the surface of the reflective dot and the support 32 of 40 ° or more are formed at the end of the reflective dot. That is, by adding a surfactant when forming the reflective dots, the contact angle between the reflective dots and the support 32 is formed in an angle range that can achieve both a wide viewing angle and high transparency. Can do.
The surfactant is preferably a compound capable of functioning as an alignment control agent that contributes to stably or rapidly forming a planar cholesteric liquid crystal phase. Examples of the surfactant include a silicone-based surfactant and a fluorine-based surfactant, and a fluorine-based surfactant is preferably exemplified.

Specific examples of the surfactant include compounds described in paragraphs [0082] to [0090] of JP-A-2014-119605, and compounds described in paragraphs [0031] to [0034] of JP-A-2012-203237. , Compounds exemplified in paragraphs [0092] and [0093] of JP-A-2005-99248, paragraphs [0076] to [0078] and paragraphs [0082] to [0085] of JP-A 2002-129162 And compounds exemplified therein, and fluorine (meth) acrylate polymers described in paragraphs [0018] to [0043] of JP-A-2007-272185, and the like.
In addition, as a horizontal alignment agent, 1 type may be used independently and 2 or more types may be used together.
As the fluorine-based surfactant, compounds represented by the following general formula (I) described in paragraphs [0082] to [0090] of JP-A-2014-119605 are preferable.

In the general formula (I), L ¹¹ , L ¹² , L ¹³ , L ¹⁴ , L ¹⁵ , and L ¹⁶ are each independently a single bond, —O—, —S—, —CO—, —COO. —, —OCO—, —COS—, —SCO—, —NRCO—, —CONR— (in the general formula (I), R represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms), NRCO- and -CONR- have the effect of reducing the solubility, and more preferably -O-, -S-, -CO-, -COO-, -OCO- —COS— and —SCO—, and —O—, —CO—, —COO—, and —OCO— are more preferable from the viewpoint of the stability of the compound. The alkyl group that R can take may be linear or branched. The number of carbon atoms is more preferably 1 to 3, and examples thereof include a methyl group, an ethyl group, and an n-propyl group.

Sp ¹¹ , Sp ¹² , Sp ¹³ and Sp ¹⁴ each independently represent a single bond or an alkylene group having 1 to 10 carbon atoms, more preferably a single bond or an alkylene group having 1 to 7 carbon atoms. More preferably, it is a single bond or an alkylene group having 1 to 4 carbon atoms. However, the hydrogen atom of the alkylene group may be substituted with a fluorine atom. The alkylene group may or may not be branched, but a linear alkylene group having no branch is preferred. From the viewpoint of synthesis, it is preferable that Sp ¹¹ and Sp ¹⁴ are the same, and Sp ¹² and Sp ¹³ are the same.

A ¹¹ and A ¹² are monovalent to tetravalent aromatic hydrocarbon groups. The aromatic hydrocarbon group preferably has 6 to 22 carbon atoms, more preferably 6 to 14 carbon atoms, still more preferably 6 to 10 carbon atoms, and still more preferably 6. The aromatic hydrocarbon groups represented by A ¹¹ and A ¹² may have a substituent. Examples of such a substituent include an alkyl group having 1 to 8 carbon atoms, an alkoxy group, a halogen atom, a cyano group, or an ester group. For the explanation and preferred ranges of these groups, the corresponding description of T below can be referred to. Examples of the substituent for the aromatic hydrocarbon group represented by A ¹¹ and A ¹² include a methyl group, an ethyl group, a methoxy group, an ethoxy group, a bromine atom, a chlorine atom, and a cyano group. A molecule having a large number of perfluoroalkyl moieties in the molecule can align the liquid crystal with a small amount of addition, leading to a decrease in haze. Therefore, A ¹¹ and A ¹² have a large number of perfluoroalkyl groups in the molecule. It is preferably tetravalent. From the viewpoint of synthesis, A ¹¹ and A ¹² are preferably the same.

T ¹¹ is the following

(X in T ¹¹ represents an alkyl group having 1 to 8 carbon atoms, an alkoxy group, a halogen atom, a cyano group, or an ester group, and a divalent group or a divalent heterocyclic group represented by: Ya, Yb, Yc and Yd each independently represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and more preferably

And more preferably

It is.

The alkyl group that X contained in T ¹¹ can have 1 to 8 carbon atoms, preferably 1 to 5 carbon atoms, and more preferably 1 to 3 carbon atoms. The alkyl group may be linear, branched or cyclic, and is preferably linear or branched. Examples of preferable alkyl groups include a methyl group, an ethyl group, an n-propyl group, and an isopropyl group, and among them, a methyl group is preferable. The alkyl moiety of the alkoxy group X contained in the T ¹¹ can be taken, it is possible to refer to the description and the preferred range of the alkyl group X contained in the T ¹¹ can take. Examples of the halogen atom that X contained in T ¹¹ can take include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, and a chlorine atom and a bromine atom are preferable. Examples of the ester group that X contained in T ¹¹ can take include a group represented by R′COO—. Examples of R ′ include an alkyl group having 1 to 8 carbon atoms. For the explanation and preferred range of the alkyl group that R ′ can take, reference can be made to the explanation and preferred range of the alkyl group that X contained in T ¹¹ can take. Specific examples of the ester include CH ₃ COO— and C ₂ H ₅ COO—. The alkyl group having 1 to 4 carbon atoms which Ya, Yb, Yc and Yd can take may be linear or branched. For example, a methyl group, an ethyl group, an n-propyl group, an isopropyl group and the like can be exemplified.

The divalent heterocyclic group preferably has a 5-membered, 6-membered or 7-membered heterocyclic ring. A 5-membered ring or a 6-membered ring is more preferable, and a 6-membered ring is more preferable. As the hetero atom constituting the heterocyclic ring, a nitrogen atom, an oxygen atom and a sulfur atom are preferable. The heterocyclic group is preferably an aromatic heterocyclic group. Examples of heterocyclic rings include furan ring, thiophene ring, pyrrole ring, pyrroline ring, pyrrolidine ring, oxazole ring, isoxazole ring, thiazole ring, isothiazole ring, imidazole ring, imidazoline ring, imidazolidine ring, pyrazole ring, pyrazoline Ring, pyrazolidine ring, triazole ring, triazane ring, tetrazole ring, pyran ring, thiyne ring, pyridine ring, piperidine ring, oxazine ring, morpholine ring, thiazine ring, pyridazine ring, pyrimidine ring, pyrazine ring, piperazine ring and triazine ring included. The divalent heterocyclic group may have a substituent. For explanations and preferred ranges of examples of such substituents, reference can be made to the explanations and descriptions regarding the substituents that can be taken by the above-described monovalent to tetravalent aromatic hydrocarbons of A ¹ and A ² .

Hb ¹¹ represents a perfluoroalkyl group having 2 to 30 carbon atoms, more preferably a perfluoroalkyl group having 3 to 20 carbon atoms, and still more preferably a perfluoroalkyl group having 3 to 10 carbon atoms. The perfluoroalkyl group may be linear, branched, or cyclic, but is preferably linear or branched, and more preferably linear.

m11 and n11 are each independently 0 to 3, and m11 + n11 ≧ 1. In this case, a plurality of structures in parentheses may be the same or different from each other, but are preferably the same. M11 and n11 in the general formula (I) are determined by the valences of A ¹¹ and A ¹² , and the preferable range is also determined by the preferable ranges of the valences of A ¹¹ and A ¹² .
O and p contained in T ¹¹ are each independently an integer of 0 or more, and when o and p are 2 or more, a plurality of X may be the same or different from each other. O contained in T ¹¹ is preferably 1 or 2. P contained in T ¹¹ is preferably an integer of 1 to 4, and more preferably 1 or 2.

The compound represented by the general formula (I) may have a symmetrical molecular structure or may have no symmetry. Here, the symmetry means at least one of point symmetry, line symmetry, and rotational symmetry, and asymmetry means any of point symmetry, line symmetry, and rotational symmetry. Means not applicable.

The compound represented by the general formula (I) includes the perfluoroalkyl group (Hb ¹¹ ) and the linking group — (— Sp ¹¹ —L ¹¹ —Sp ¹² —L ¹² ) m ₁₁ —A ¹¹ —L ¹³ —. and ^{^{^{-L 14 -A 12 - (L 15}}} -Sp 13 -L 16 -Sp 14 -) n 11 -, and is preferably a compound which is a combination of T is a divalent group having the excluded volume effect. The two perfluoroalkyl groups (Hb ¹¹ ) present in the molecule are preferably the same as each other, and the linking group present in the molecule — (— Sp ¹¹ -L ¹¹ -Sp ¹² -L ¹² ) m ₁₁ -A ¹¹ -L ¹³ - and ^{^{^{-L 14 -A 12 - (L 15}}} -Sp 13 -L 16 -Sp 14 -) n 11 - preferably also the same. The terminal Hb ¹¹ -Sp ¹¹ -L ¹¹ -Sp ¹² -and -Sp ¹³ -L ¹⁶ -Sp ¹⁴ -Hb ¹¹ are preferably groups represented by any one of the following general formulas.
(C _a F _{2a + 1} )-(C _b H _2b )-
(C _a F _{2a + 1} ) — (C _b H _2b ) —O— (C _r H _2r ) —
(C _a F _{2a + 1} ) — (C _b H _2b ) —COO— (C _r H _2r ) —
(C _a F _{2a + 1} )-(C _b H _2b ) -OCO- (C _r H _2r )-

In the above formula, a is preferably from 2 to 30, more preferably from 3 to 20, and even more preferably from 3 to 10. b is preferably 0 to 20, more preferably 0 to 10, and still more preferably 0 to 5. a + b is 3 to 30. r is preferably from 1 to 10, and more preferably from 1 to 4.
Further, Hb ¹¹ -Sp ¹¹ -L ¹¹ -Sp ¹² -L ¹² -and -L ¹⁵ -Sp ¹³ -L ¹⁶ -Sp ¹⁴ -Hb ^{11 at} the terminal of the general formula (I) are any of the following general formulas: It is preferable that it is group represented by these.
(C _a F _{2a + 1} )-(C _b H _2b ) —O—
(C _a F _{2a + 1} )-(C _b H _2b ) —COO—
(C _a F _{2a + 1} )-(C _b H _2b ) —O— (C _r H _2r ) —O—
(C _a F _{2a + 1} )-(C _b H _2b ) —COO— (C _r H _2r ) —COO—
(C _a F _{2a + 1} )-(C _b H _2b ) —OCO— (C _r H _2r ) —COO—
The definitions of a, b and r in the above formula are the same as the definitions immediately above.

The addition amount of the surfactant in the liquid crystal composition is preferably 0.01 to 10% by mass, more preferably 0.01 to 5% by mass, and more preferably 0.02 to 1% with respect to the total mass of the polymerizable liquid crystal compound. More preferred is mass%.

--Chiral agent (optically active compound)-
The chiral agent has a function of inducing a helical structure of a cholesteric liquid crystal phase. The chiral agent may be selected according to the purpose because the twist direction or the spiral pitch of the spiral induced by the compound is different.
The chiral agent is not particularly limited, and is a known compound (for example, liquid crystal device handbook, chapter 3-4-3, chiral agent for TN (twisted nematic), STN (Super Twisted Nematic), 199 pages, Japan Science Foundation) 142), 1989), 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 that does not contain an 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 embodiment, 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. Accordingly, 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. Further preferred.
The chiral agent may be a liquid crystal compound.

It is preferable that the chiral agent has a photoisomerizable group because a pattern having a desired reflection wavelength corresponding to the emission wavelength can be formed by photomask irradiation such as actinic rays after coating and orientation. As the photoisomerization group, an isomerization site of a compound exhibiting photochromic properties, an azo group, an azoxy group, or a cinnamoyl group is preferable. Specific examples of the compound include JP2002-80478, JP200280851, JP2002-179668, JP2002-179669, JP2002-179670, and JP2002. Use the compounds described in JP-A No. 179681, JP-A No. 2002-179682, JP-A No. 2002-338575, JP-A No. 2002-338668, JP-A No. 2003-313189, and JP-A No. 2003-313292. Can do.

Specific examples of the chiral agent include compounds represented by the following formula (12).

In the formula, X is 2 to 5 (integer).

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 amount of the polymerizable liquid crystal compound.

--Polymerization initiator--
When the liquid crystal composition contains a polymerizable compound, it preferably contains a polymerization initiator. In the embodiment in which the polymerization reaction is advanced by ultraviolet irradiation, the polymerization initiator to be used is preferably a photopolymerization initiator that can start the polymerization reaction by ultraviolet irradiation. Examples of photopolymerization initiators 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), a combination of triarylimidazole dimer and p-aminophenyl ketone (US patent) 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, more preferably 0.5 to 12% by mass with respect to the content of the polymerizable liquid crystal compound. .

-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.
The content of the crosslinking agent is preferably 3 to 20% by mass and more preferably 5 to 15% by mass with respect to the solid content mass of the liquid crystal composition. If content of a crosslinking agent is in the said range, the effect of a crosslinking density improvement will be easy to be acquired, and stability of a cholesteric liquid crystal phase will improve more.

-Other additives-
When the inkjet method described later is used for forming the reflective dots, the liquid crystal composition may contain a monofunctional polymerizable monomer in order to obtain generally required ink properties. Examples of the monofunctional polymerizable monomer include 2-methoxyethyl acrylate, isobutyl acrylate, isooctyl acrylate, isodecyl acrylate, octyl / decyl acrylate, and the like.
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, etc., in a range that does not deteriorate the optical performance and the like. Can be added.

The liquid crystal composition is preferably used as a liquid when forming reflective dots.
The liquid crystal composition may contain a solvent. There is no restriction | limiting in particular as a solvent, 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 such as methyl ethyl ketone and methyl isobutyl ketone, alkyl halides, amides, sulfoxides, heterocyclic compounds, hydrocarbons , Esters, ethers and the like. These may be used individually by 1 type and may use 2 or more types together. Among these, ketones are preferable in consideration of environmental load. The above-described components such as the above-mentioned monofunctional polymerizable monomer may function as a solvent.

The liquid crystal composition is applied in the form of dots on the support 32 and then cured to form reflective dots.
When forming the reflective dots, the liquid crystal composition is applied onto the support 32 by, for example, a printing method, and preferably by droplet ejection. The printing method is not particularly limited, and an inkjet method, a gravure printing method, a flexographic printing method, or the like can be used, but an inkjet method is preferable. Reflective dot patterns can also be formed by applying known printing techniques.

The liquid crystal composition coated on the support 32 is dried or heated as necessary, and then cured to form reflective dots. It is sufficient that the polymerizable liquid crystal compound in the liquid crystal composition is aligned in the drying and / or heating step. When heating, the heating temperature is preferably 200 ° C. or lower, more preferably 130 ° C. or lower.

The aligned liquid crystal compound may be further polymerized. 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 20 to 50 J / cm ^{2 and} more preferably 100 to 1,500 mJ / cm ² . 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 250 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 (infrared) absorption spectrum.

<Overcoat layer>
The dot films (the right circularly polarized dot film 30 </ b> R and the left circularly polarized dot film 30 </ b> L) have an overcoat layer 36 that embeds the reflective dots and is laminated on the support 32.
The overcoat layer 36 may be provided on the surface side of the support 32 where the reflective dots are formed, and it is preferable to flatten the surface of the dot film.
In the illustrated example, the dot films are bonded to each other by the overcoat layer 36 to produce the right circular polarization laminate 20 and the left circular polarization laminate 24. Or similarly to the bonding layer which bonds the above-mentioned right circular polarization laminated body 20 and the left circular polarization laminated body 24, a dot film is bonded together by the bonding layer, and the right circular polarization laminated body 20 and the left circular polarization are combined. The laminate 24 may be produced.

The overcoat layer 36 is not particularly limited, but the smaller the difference from the refractive index of the reflective dots, the better, and the difference in refractive index is preferably 0.04 or less. Since the reflective dot has a refractive index of about 1.6, a resin layer having a refractive index of about 1.4 to 1.8 is preferable.
By using the overcoat layer 36 having a refractive index close to the refractive index of the reflective dot, the angle (polar angle) from the normal of the light incident on the reflective dot can be reduced. For example, when the overcoat layer 36 having a refractive index of 1.6 is used and light is incident on the transparent screen at a polar angle of 45 °, the polar angle actually incident on the reflective dot can be about 27 °. Therefore, by using the overcoat layer 36, the transparent screen 12 can widen the polar angle of light exhibiting retroreflectivity, and the angle formed between the surface of the reflective dot and the support 32 is small. However, high retroreflectivity is obtained in a wider range. The overcoat layer 36 may have a function as an antireflection layer or a hard coat layer.

Examples of the overcoat layer 36 include a resin layer obtained by applying a composition containing a monomer to the surface side of the support 32 on which the reflective dots are formed, and then curing the coating film.
The resin used for the overcoat layer 36 is not particularly limited, and may be selected in consideration of the adhesion to the support 32 and the reflective dots. For example, a thermoplastic resin, a thermosetting resin, an ultraviolet curable resin, or the like can be used. From the viewpoint of durability, solvent resistance, etc., a resin of a type that is cured by crosslinking is preferable, and an ultraviolet curable resin that can be cured in a short time is particularly preferable. Monomers that can be used to form the overcoat layer 36 include ethyl (meth) acrylate, ethylhexyl (meth) acrylate, styrene, methylstyrene, N-vinylpyrrolidone, polymethylolpropane tri (meth) acrylate, hexanediol (meta ) Acrylate, tripropylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl Examples include glycol di (meth) acrylate.

The thickness of the overcoat layer 36 is not particularly limited and may be determined in consideration of the maximum height of the reflective dots, may be about 5 to 100 μm, preferably 10 to 50 μm, and more preferably 20 ~ 40 μm. The thickness is the distance from the dot-forming surface of the support where there are no dots to the surface of the overcoat layer on the opposite surface.

The image display system 10 according to the present invention includes the transparent screen 12 formed by laminating the right circularly polarizing laminate 20 and the left circularly polarizing laminate 24 and the projector 14.

The projector 14 is a known projector that displays a picture on the transparent screen 12 by performing trapezoidal correction (distortion correction) as necessary and projecting projection light carrying the image onto the transparent screen 12.
In the image display system 10 of the present invention, the projector 14 projects a monochrome image, and in the illustrated example, projects a green monochrome image. That is, the projector 14 is a projector in which the peak wavelength of the emitted light is equal to the selective reflection center wavelength of the reflective dots.
Here, in the image display system 10 shown in FIG. 1 in which the transparent screen 12 has both a dot film corresponding to right circularly polarized light and a dot film corresponding to left circularly polarized light, the projector 14 is configured such that the emitted light is unpolarized. It is a projector. In the image display system 10, if the emitted light is non-polarized light, all known projectors that are not polarized light such as a DLP (Digital Light Processing) projector can be used.

In the image display system 10 of the present invention, the projector 14 is preferably a so-called short focus projector having a short focal length.
Further, the image display system 10 of the present invention is preferably a so-called front projection type in which the convex side of the reflective dot of the dot film is arranged toward the projector 14 side and the image is observed on the projector 14 side. Is preferred.
Furthermore, in the image display system 10 of the present invention, the projector 14 is arranged so that the incident angle of the light emitted from the projector 14 is 30 to 70 °, particularly 40 to 60 ° with respect to the normal line of the transparent screen 12. It is preferable to do this.
In addition, regarding the above points, the same applies to an image display system 50 using a projector 54 whose outgoing light is linearly polarized light, which will be described later. As will be described later, in the projector 54 in which the outgoing light is linearly polarized light, the outgoing light is P wave with respect to the transparent screen, and the incident angle of the light from the projector 14 with respect to the normal line of the transparent screen 12 is set. 56 ° ± 10 ° is also preferable.

As described above, the transparent screen 12 of the present invention reflects light by the reflective dots formed by fixing the cholesteric liquid crystal phase. Preferably, as shown in FIG. 2, the spiral axis of the cholesteric liquid crystal phase is An angle in the range of 70 to 90 ° is formed with the surface of the reflective dot. Thereby, as shown in FIG. 3, the transparent screen 12 can reflect not only retroreflection but also various directions on the light incident side, that is, the projector side, as well as retroreflection.
For this reason, the image display system 10 of the present invention is not projected from the normal direction of the transparent screen, but is disposed below the transparent screen, like a short focus projector, so that the image display system 10 is larger than the normal line of the transparent screen. Even when light is projected at an angle, an image can be suitably viewed from the projector side with a wide viewing angle.
Therefore, the image display system 10 of the present invention is a front projection type, and the projector 14 is arranged near the transparent screen by setting the incident angle of the projector 14 to the normal line of the transparent screen 12 to 30 to 70 °. Thus, the image display system can be reduced in size. In addition, by adopting the front projection type, the optical path from the projector 14 to the observer can be a folded optical path by a transparent screen, so that the overall optical distance can be shortened and the image display system can be further miniaturized.

Hereinafter, the operation of the image display system 10 will be described to describe the transparent screen 12 and the image display system 10 of the present invention in more detail.

In the image display system 10, the green projection light carrying the image emitted by the projector 14 first enters the right circularly polarized dot film 30 </ b> R of the first sheet (most projector 14 side) of the right circularly polarized laminate 20.
Of the light incident on the first right circularly polarized dot film 30R, only the green right circularly polarized light of the light incident on the right circularly polarized reflective dot 34R is reflected by the right circularly polarized reflective dot 34R. Passes through the right circularly polarized light reflecting dot 34R and passes through the first right circularly polarized light dot film 30R. Further, the light incident on the portion other than the right circularly polarized light reflecting dot 34R passes through the first right circularly polarized light dot film 30R as it is.

The light that has passed through the first right circularly polarized dot film 30R of the right circularly polarized laminate 20 then enters the second (second from the projector 14 side) right circularly polarized dot film 30R.
Similarly, in the light incident on the second right circularly polarized dot film 30R of the right circularly polarized laminate 20, only the green right circularly polarized light incident on the right circularly polarized reflective dot 34R is reflected by the right circularly polarized reflective dot 34R. The light other than the green right circularly polarized light incident on the right circularly polarized reflective dot 34R and the light incident on the portion other than the right circularly polarized reflective dot 34R pass through the second right circularly polarized dot film 30R. .

The light that has passed through the second right circularly polarized dot film 30R of the right circularly polarized laminate 20 is then incident on the third (third from the projector 14 side) right circularly polarized dot film 30R.
Similarly, in the light incident on the third right circularly polarized dot film 30R of the right circularly polarized laminate 20, only the green right circularly polarized light incident on the right circularly polarized reflective dot 34R is reflected by the right circularly polarized reflective dot 34R. The light other than the green right circularly polarized light incident on the right circularly polarized light reflecting dot 34R and the light incident on the portion other than the right circularly polarized light reflecting dot 34R are the third right circularly polarized dot film 30R, that is, the right circle. It passes through the polarizing laminate 20.

The light that has passed through the right circular polarization laminate 20 (the third right circular polarization dot film 30R) then enters the left circular polarization laminate 24.
The light incident on the left circularly polarizing laminate 24 first enters only the left circularly polarized light incident on the left circularly polarized light reflecting dot 34L after entering the first circularly polarized dot film 30L (most projector 14 side). Is reflected by the left circularly polarized light reflecting dot 34L and the light other than the green left circularly polarized light incident on the left circularly polarized light reflecting dot 34L and the light incident on the portion other than the left circularly polarized light reflecting dot 34L are It passes through the left circularly polarized dot film 30L.

The light that has passed through the first left circularly polarized dot film 30L of the left circularly polarized laminate 24 then enters the second left circularly polarized dot film 30L (second from the projector 14 side).
Similarly, in the light incident on the second left circularly polarized dot film 30L of the left circularly polarized laminate 24, only the green left circularly polarized light incident on the left circularly polarized reflective dot 34L is reflected by the left circularly polarized reflective dot 34L. The light other than the green left circularly polarized light incident on the left circularly polarized reflective dot 34L and the light incident on the portion other than the left circularly polarized reflective dot 34L pass through the second left circularly polarized dot film 30L. .

The light that has passed through the second left circularly polarized dot film 30L of the left circularly polarized laminate 24 then enters the third (third from the projector 14 side) left circularly polarized dot film 30L.
Similarly, in the light incident on the third left circularly polarized dot film 30L of the left circularly polarized laminate 24, only the green left circularly polarized light incident on the left circularly polarized reflective dot 34L is reflected by the left circularly polarized reflective dot 34L. The light other than the green left circularly polarized light incident on the left circularly polarized reflective dot 34L and the light incident on the part other than the left circularly polarized reflective dot 34L pass through the third left circularly polarized dot film 30L. Then, it passes through the left circularly polarizing laminate 24, that is, the transparent screen 12.

In the image display system 10, the green right circularly polarized light reflected by the right circularly polarized light reflecting dots 34R arranged on the three right circularly polarized dot films 30R of the right circularly polarized light laminated body 20, and the left circularly polarized light laminated body A green monochromatic image is displayed (projected) on the transparent screen 12 by the green left circularly polarized light reflected by the left circularly polarized reflective dots 34L arranged on the 24 left circularly polarized dot films 30L.

Thus, on the transparent screen 12 in the illustrated example, an image is displayed by light reflected by the reflective dots arranged on the dot film. Further, in the illustrated transparent screen 12, the light that has not been used for displaying an image passes through the transparent screen.
That is, in the case of a transparent screen that displays an image with dots that reflect or diffuse light, the light that has not entered the dot and the light that has passed through the dot pass through the transparent screen as it is with the projector of the transparent screen. Is observed from the opposite side. In the following description, the surface of the transparent screen opposite to the projector is also referred to as “back surface”.
Therefore, on the back side, when the emitted light of the projector is viewed from the straight direction through the transparent screen, the light source of the projector 14 is observed and a hot spot is generated. Hot spots are very dazzling. In particular, in the case of a laser projector using a laser as a light source as described later, the hot spots are extremely dazzling.

On the other hand, the transparent screen of the present invention has a plurality of dot films in which reflective dots formed by fixing the stick liquid crystal phase are two-dimensionally arranged, and among the plurality of dot films, 2 In the above dot film, the selective reflection center wavelength of the reflective dot and the rotation direction of the reflected circularly polarized light are equal to each other. The transparent screen 12 in the illustrated example has a right circularly polarized laminate in which three right circularly polarized dot films 30R in which right circularly polarized reflective dots 34R that reflect green right circularly polarized light are two-dimensionally arranged are laminated on the support surface. 20 and a left circularly polarized laminate 24 in which three left circularly polarized dot films 30L in which left circularly polarized reflective dots 34L that reflect green left circularly polarized light are two-dimensionally arranged are laminated on the support surface.
Therefore, even if the green right circularly polarized light projected from the projector 14 passes through the first right circularly polarized dot film 30R of the right circularly polarized laminate 20, it is reflected by the second right circularly polarized dot film 30R. Even when the green right circularly polarized light passes through the second right circularly polarized dot film 30R, it is reflected by the third right circularly polarized dot film 30R. Similarly, even if the green left circularly polarized light projected from the projector 14 passes through the first left circularly polarized dot film 30L of the left circularly polarized laminate 24, the second left circularly polarized dot film 30L Even if the green left circularly polarized light is reflected and passes through the second left circularly polarized dot film 30L, it is reflected by the third left circularly polarized dot film 30L.

Therefore, according to the transparent screen 12 of the present invention, the three right circularly polarized dot films 30R that reflect green right circularly polarized light and the three left circularly polarized dot films 30L that reflect green left circularly polarized light are used. Since most of the non-polarized green light projected from the projector 14 can be reflected, hot spots can be significantly suppressed.
Moreover, since the light passes through the gaps between the reflective dots and the reflective dots reflect only green light, the transparent screen 12 of the present invention can ensure good transparency while suppressing hot spots. Furthermore, as described above, the light passing through the dot film is not scattered but is transmitted as it is, so that the haze is small.

Further, as described above, in the present invention, an image is displayed on the transparent screen 12 by reflecting light with the reflective dots in which the cholesteric liquid crystal phase is fixed. Preferably, as shown in FIG. 2, the spiral axis of the cholesteric liquid crystal phase reflects light by the reflective dots that form an angle in the range of 70 to 90 ° with the surface of the reflective dots, whereby an image is displayed on the transparent screen 12. indicate.
Therefore, as shown in FIG. 3, the reflective dots of the transparent screen 12 reflect the incident light not only in retroreflection but also in various directions on the light incident side. Therefore, even when the short focus projector is disposed close to the transparent screen 12 and the projection light is incident on the transparent screen at a large angle with respect to the normal line of the transparent screen, a wide viewing angle can be achieved.
As a result, according to the present invention, it is possible to observe a high-quality monochromatic image with a sufficient amount of reflected light with a wide viewing angle by using a small image display system of the front projection type.

FIG. 4 conceptually shows another example of the image display system of the present invention using another example of the transparent screen of the present invention.
In addition, since the image display system 50 shown in FIG. 4 uses many the same members as the image display system 10 shown in FIG. 1 described above, the same members are denoted by the same reference numerals, and the following description mainly focuses on different parts. .

An image display system 50 shown in FIG. 4 includes the transparent screen 52 of the present invention and a projector 54. The image display system 50 is also an image display system that displays a green single-color image.
The transparent screen 52 includes a λ / 4 plate 56 and the right circularly polarizing laminate 20. In addition, although illustration is abbreviate | omitted like the previous example, (lambda) / 4 board 56 and the right circularly-polarized-light laminated body 20 are bonded together by the bonding layer.

The λ / 4 plate 56 converts linearly polarized light into right circularly polarized light. That is, the λ / 4 plate 56 has a slow axis so that the emitted light becomes right circular polarization corresponding to the right circular polarization reflection dot 34R of the right circular polarization dot film 30R constituting the right circular polarization laminate 20. Arranged together.
A λ / 4 plate (a plate having a λ / 4 function) is a plate having a function of converting linearly polarized light having a specific wavelength into circularly polarized light (or circularly polarized light into linearly polarized light). More specifically, the plate has an in-plane retardation value of Re (λ) = λ / 4 (or an odd multiple thereof) at a predetermined wavelength λnm. This expression only needs to be achieved at any wavelength in the visible light range (for example, 550 nm).
Note that the λ / 4 plate 56 has a configuration in which an optically anisotropic layer having a λ / 4 function is formed on a support, even though the optically anisotropic layer has only a λ / 4 function. However, when the λ / 4 plate 56 has a support, the combination of the support and the optically anisotropic layer is intended to be a λ / 4 plate.

As the λ / 4 plate 56, a known λ / 4 plate can be used. Accordingly, the in-plane retardation Re (550) at a wavelength of 550 nm is not particularly limited, but is preferably 120 to 150 nm, and more preferably 125 to 145 nm. Note that, even when the λ / 4 plate 56 includes a layer other than the optically anisotropic layer such as a support, the λ / 4 plate 56 preferably exhibits this in-plane retardation range. .

In the illustrated transparent screen 52, the λ / 4 plate 56 preferably has a small Rth (550) which is retardation in the thickness direction.
Specifically, Rth (550) is preferably −50 to 50 nm, more preferably −30 to 30 nm, and even more preferably Rth (550) is zero.
Thereby, a preferable result is obtained in that linearly polarized light incident obliquely on the λ / 4 plate 56 can be converted into circularly polarized light.

Here, as will be described later, an image display system 50 in the illustrated example includes a transparent screen 52 having a λ / 4 plate 56 and a right circularly polarized laminate 20 that reflects right circularly polarized light, and a projector 54 whose emitted light is linearly polarized light. The linearly polarized outgoing light emitted from the projector 54 is converted into right circularly polarized light by the λ / 4 plate 56, and this right circularly polarized light is incident on the right circularly polarized laminate 20 and reflected, thereby obtaining an image. Is displayed.

In the image display system of the present invention, when the transparent screen 52 displays an image with only one direction of circularly polarized light, a projector 54 whose output light is linearly polarized light is used. In other words, in the present invention, when a projector 54 whose output light is linearly polarized light is used, a λ / 4 plate that makes the output light of the projector 54 circularly polarized, and a dot that reflects right or left circularly polarized light. A transparent screen is comprised with the laminated body comprised with a film.
In the present invention, as described above, when the light emitted from the projector is non-polarized light, the λ / 4 plate is not used, and preferably right-circularly polarized light as in the transparent screen 12 shown in FIG. A transparent screen is composed of a laminate composed of a dot film that reflects light and a laminate composed of a dot film that reflects left polarized light.

As the projector 54, various known projectors such as an LCOS (Liquid crystal on silicon) projector and a laser projector can be used as long as the emitted light is linearly polarized light.
Especially, a laser projector is illustrated suitably for the reason mentioned later.

Here, in the case of using a linearly polarized projector 54, the light emitted from the projector 54 and incident on the transparent screen 52 is P wave with respect to the transparent screen 52, and the projector 54 transmits the transparent screen 52. It is preferable that the incident angle of light is 56 ° ± 10 ° with respect to the normal line of the transparent screen 52.
That is, when using a projector 54 with linearly polarized light, the light emitted from the projector 54 and incident on the transparent screen 52 is P wave with respect to the transparent screen 52, and the optical axis of the projector 54 is The angle is preferably 56 ° ± 10 ° with respect to the normal line of the transparent screen 52.

A hot spot in an image display system using a transparent screen is not only a hot spot in which the light source of the projector is observed through the transparent screen in the straight traveling direction of the light emitted from the projector, but also the straight traveling direction of the light emitted from the projector. The light source of the projector is indirectly observed even at a position where the emitted light is regularly reflected on the surface of the screen, and becomes a hot spot.

Here, as is well known, the reflectance of linearly polarized light varies depending on the angle of incidence on the reflecting surface. On the other hand, when light is incident at an angle of 56 °, the reflectance of light becomes substantially zero.
Accordingly, the light emitted from the linearly polarized projector 54 and incident on the transparent screen 52 is set as a P wave with respect to the transparent screen 52, and the incident angle of the light from the projector 54, that is, the optical axis of the projector 54 is set. By setting the angle to 56 ° ± 10 ° with respect to the normal line of the transparent screen 52, hot spots generated when the light from the projector 54 is regularly reflected by the transparent screen 52 can be greatly reduced.
Various known methods such as a method of rotating the light source of the projector 54 around the optical axis can be used as the method of making the linearly polarized light emitted from the projector 54 P wave with respect to the transparent screen 52.

Hereinafter, the operation of the image display system 50 will be described to describe the transparent screen 52 and the image display system 50 of the present invention in more detail.

As described above, the light emitted from the projector 54 is linearly polarized light and is a single green color.
The linearly polarized green light carrying the image emitted from the projector 54 is first made right circularly polarized by the λ / 4 plate 56.

The light that has been right-circularly polarized by the λ / 4 plate 56 enters the right-circularly polarized laminate 20.
As before, the light incident on the right circularly polarized laminate 20 is incident on the first right circularly polarized dot film 30R, and only the green right circularly polarized light incident on the right circularly polarized reflective dot 34R is on the right. The light other than the green right circularly polarized light reflected by the circularly polarized reflective dot 34R and incident on the right circularly polarized reflective dot 34R and the light incident on the portion other than the right circularly polarized reflective dot 34R are the first right circle. It passes through the polarizing dot film 30R.

The light that has passed through the first right circularly polarized dot film 30R of the right circularly polarized laminate 20 then enters the second right circularly polarized dot film 30R.
Similarly, in the light incident on the second right circularly polarized dot film 30R of the right circularly polarized laminate 20, only the green right circularly polarized light incident on the right circularly polarized reflective dot 34R is reflected by the right circularly polarized reflective dot 34R. The light other than the green right circularly polarized light incident on the right circularly polarized reflective dot 34R and the light incident on the portion other than the right circularly polarized reflective dot 34R pass through the second right circularly polarized dot film 30R. .

The light that has passed through the second right circularly polarized dot film 30R of the right circularly polarized laminate 20 is then incident on the third right circularly polarized dot film 30R.
Similarly, in the light incident on the third right circularly polarized dot film 30R of the right circularly polarized laminate 20, only the green right circularly polarized light incident on the right circularly polarized reflective dot 34R is reflected by the right circularly polarized reflective dot 34R. The light other than the green right circularly polarized light that has entered the right circularly polarized reflective dot 34R and the light that has entered the portion other than the right circularly polarized reflective dot 34R are supplied to the third right circularly polarized dot film 30R (right circle). It passes through the polarizing laminate 20), that is, the transparent screen 52.

As in the previous example, also in the image display system 50, an image is displayed (projected) on the transparent screen 52 by the green right circularly polarized light reflected by the right circularly polarized reflective dots 34R of the three right circularly polarized dot films 30R. The
Even if the green right circle emitted from the projector 54 and converted by the λ / 4 plate 56 passes through the first right circularly polarized dot film 30R of the right circularly polarized laminate 20, Even if green right circularly polarized light passes through the second right circularly polarized dot film 30R, it is reflected by the third right circularly polarized dot film 30R.

As described above, in the image display system 50, the light emitted from the projector 54 and incident on the right circularly polarized laminate 20 is green right circularly polarized light, and most of the green circularly polarized light is divided into three right circles. Since it can reflect with the polarizing dot film 30R, a hot spot can be suppressed significantly similarly to the previous example. Furthermore, as in the previous example, an image with a wide viewing angle can be displayed by light reflection with high diffusibility by the reflective dots.
Further, since the transparent screen 52 has a smaller number of films than the transparent screen 12 shown in FIG. 1, it can have higher light transmittance and lower haze.

As described above, in this example, the projector 54 whose outgoing light is polarized light is used.
Here, as will be described later, in the present invention in which an image is displayed with light reflected by a reflective dot formed by fixing a cholesteric liquid crystal layer, a projector having a narrow wavelength band of emitted light is used, such as a laser projector, and selection by a reflective dot is performed. By matching the wavelength band of the reflection center wavelength with the wavelength band of the light emitted from the projector, the transparency of the transparent screen can be further improved, and the light that becomes the display image can be reliably reflected by the reflective dots.
Considering this point, a laser projector is preferably used as the projector 54.

However, as is well known, laser light has high coherence.
For this reason, in an image display system using a laser projector as the projector 54, when the laser beam is disturbed due to unevenness or the like, the light is strengthened or weakened due to the high coherence of the laser beam. A phenomenon called speckle, in which a large number of fine bright and dark portions are formed in the display image, causing the display image to flicker, may be a problem.

On the other hand, the transparent screen of the present invention reflects the light so as to diffuse by the reflective dots and displays an image. Preferably, as shown in FIG. 2, the cholesteric liquid crystal phase spiral axis reflects the light with a high diffusivity by the reflective dot having an angle in the range of 70 to 90 ° with the surface of the reflective dot, thereby displaying an image. To do. In addition, the transparent screen of the present invention has a structure in which a plurality of dot films in which such reflective dots are two-dimensionally arranged are stacked, and the light diffused by the reflective dots of each dot film is applied to the transparent screen. The image is displayed, and the dot reflection films have the same selective reflection center wavelength of the reflection dots and the rotation direction of the reflected circularly polarized light.
Therefore, according to the present invention, when a laser projector is used, fine light and dark portions generated in the display image can be made inconspicuous due to the diffusion of light by the reflective dots, and speckle can be reduced. In particular, a transparent screen using a reflective dot in which the spiral axis of the cholesteric liquid crystal phase forms an angle in the range of 70 to 90 ° with the surface of the reflective dot can greatly reduce speckle due to its good light diffusibility.

In the image display system 50 shown in FIG. 4, when a projector with a narrow wavelength band of emitted light is used as the projector 54, such as a laser projector, the liquid crystal constituting the cholesteric liquid crystal phase that forms the right circularly polarized reflection dot 34R. As described above, using a liquid crystal compound having a low Δn (low ΔnLC (liquid crystal)), the right circularly polarized light reflecting dot 34R reflects only circularly polarized light in a narrow wavelength band corresponding to the wavelength band of the emitted light of the laser projector. It is preferable to do this.
By adopting such a configuration, the wavelength range of light that can be transmitted through the right circularly polarizing laminate 20 can be widened, the transparency of the transparent screen can be further increased, and the wavelength emitted by the projector 54 that has entered the reflective dot is emitted. An appropriate image can be displayed by reliably reflecting the light in the band.

Specifically, when a laser projector is used as the projector, Δn of the liquid crystal compound constituting the reflective dot is preferably 0.02 to 0.1, and preferably 0.04 to 0.06. More preferred.

Note that the transparent screen 52 shown in FIG. 4 uses the right circularly polarized laminate 20 that reflects green right circularly polarized light, and the light is converted to right circularly polarized light by the λ / 4 plate 56. There is no limitation.
That is, the same transparent screen and image can be obtained by using the left circularly polarized light laminate 24 that converts the linearly polarized light into the left circularly polarized light by the λ / 4 plate 56 and reflects the green left circularly polarized light instead of the right circularly polarized light laminate 20. A display system can be configured.

In the illustrated image display system 50, the linearly polarized light is incident on the λ / 4 plate 56 using the projector 54 that emits linearly polarized light. However, the present invention is not limited to this.
For example, in the image display system of the present invention that uses a dot film that reflects only right-handed circularly polarized light (or left-handed circularly polarized light only), light emitted from the projector using a non-polarized projector as in the projector 14 described above. May be incident on the linearly polarizing plate to obtain linearly polarized light, and light that has been linearly polarized by the linearly polarizing plate may be incident on the λ / 4 plate 56.

The transparent screen of the present invention is not limited to the configuration shown in FIGS. That is, the transparent screen of the present invention has a plurality of dot films in which reflective dots formed by fixing a cholesteric liquid crystal phase on a support are two-dimensionally arranged, and the selective reflection center wavelength of the reflective dots and the circularly polarized light that reflects. Various configurations can be used as long as the rotation directions of the plurality of dot films include a plurality of dot films having the same rotation direction.

For example, the transparent screen shown in FIGS. 1 and 4 displays a green single-color image having reflective dots that reflect green circularly polarized light, but the present invention is not limited to this.
That is, the transparent screen of the present invention displays a red single-color image having a configuration in which a plurality of dot films in which reflective dots that reflect red circularly polarized light are two-dimensionally arranged are laminated on the support surface. Or a blue monochromatic image having a configuration in which a plurality of dot films in which two-dimensionally arranged reflective dots that reflect blue circularly polarized light are two-dimensionally arranged are laminated on the support surface. Also good.
In this case, the projector used in the image display system of the present invention uses a projector that emits projection light that carries a red single-color image or a projector that emits projection light that carries a blue single-color image.

Further, in the example shown in FIGS. 1 and 4, each of the right circularly polarizing laminate 20 and the left circularly polarizing laminate 24 has three dot films, but the present invention is not limited to this. Not.
For example, regardless of the presence or absence of the λ / 4 plate 56 on the transparent screen, the right circularly polarizing laminate and / or the left circularly polarizing laminate may have two dot films, or four or more dot films. It may be a thing.
Further, in the case where the transparent screen has a right circular polarization laminate and a left circular polarization laminate, the number of dot films may be different between the right circular polarization laminate and the left circular polarization laminate. In addition, when the transparent screen has a right-circular polarizing laminate and a left-circular polarizing laminate, one of the right-circular polarizing laminate and the left-circular polarizing laminate reflects the selective reflection center wavelength of the reflective dot. If there are a plurality of dot films having the same rotational direction of circularly polarized light, the other may have only one dot film.

Further, in the present invention, in the configuration without the λ / 4 plate 56, the transparent screen may be configured only by the right circularly polarized laminate 20, or the transparent screen is configured only by the left circularly polarized laminate 24. May be.
That is, the transparent screen of the present invention may have a configuration having only two right circularly polarized dot films 30R, or may have a configuration having only two left circularly polarized dot films 30L.

The transparent screen and the image display system of the present invention have been described in detail above. However, the present invention is not limited to the above-described examples, and various improvements and modifications may be made without departing from the gist of the present invention. Of course.

Hereinafter, the features of the present invention will be described more specifically with reference to examples. The materials, reagents, used amounts, substance amounts, ratios, processing details, processing procedures, and the like shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

[Example 1]
<Preparation of underlayer>
The components shown below were stirred and dissolved in a container kept at 25 ° C. to prepare a base layer solution.
(Underlayer solution)
Mixture A of the following rod-like liquid crystal compound A 100 parts by mass IRGACURE 819 (manufactured by BASF) 3 parts by mass The following compound A 0.6 parts by mass Methyl ethyl ketone 932.4 parts by mass

Mixture A of rod-like liquid crystal compounds

The numerical value is mass%. R is a group bonded with oxygen.
Compound A

<Preparation of protective film 01>
A cellulose acetate film was prepared with reference to Examples ([0267] to [0270]) of JP2012-18396A. This is designated as a protective film 01. Re (550) and Rth (550) of the protective film 01 were 2 nm and 35 nm, respectively.
This protective film 01 was used as the support 32.
The prepared underlayer solution was applied to the support 32 (protective film 01) using a # 2.6 bar coater. Thereafter, the coating film was heated so that the coating film surface temperature became 50 ° C., dried for 60 seconds, and then irradiated with 500 mJ / cm ² of ultraviolet rays by an ultraviolet irradiation device under a nitrogen purge with an oxygen concentration of 100 ppm or less. Irradiation was performed to advance the cross-linking reaction, and an underlayer was prepared.
In addition, it was 0.8% when the haze value of the support body 32 in which the base layer was formed was measured.

<Formation of cholesteric liquid crystal dots>
The components shown below were stirred and dissolved in a container kept at 25 ° C. to prepare a cholesteric liquid crystal ink liquid R (liquid crystal composition).
(Cholesteric liquid crystal ink R)
Cyclopentanone 139.6 parts by mass Mixture A of the above-described rod-shaped liquid crystal compound 100 parts by mass IRGACURE 907 (manufactured by BASF) 3.0 parts by mass Kayacure DETX (manufactured by Nippon Kayaku Co., Ltd.) 1 part by mass The following chiral agent A 5. 78 parts by mass The following surfactant 0.08 parts by mass

Chiral agent A

Surfactant

The cholesteric liquid crystal ink liquid R is a material that forms dots that reflect light having a selective reflection center wavelength of 550 nm. The cholesteric liquid crystal ink liquid R is a material for forming dots that reflect right circularly polarized light. That is, the cholesteric liquid crystal ink liquid R is a material for forming the right circularly polarized light reflecting dot 34R.

The prepared cholesteric liquid crystal ink liquid R was placed on the base layer of the support 32 on which the base layer was prepared with an inkjet printer (DMP-2831, manufactured by FUJIFILM Dimatix Co., Ltd.) in which the platen was heated to 60 ° C. Drops were deposited on the entire surface of a 100 × 100 mm area with a distance (pitch) of 60 μm. After drying on the platen at 60 ° C. for 30 seconds or longer, the substrate 32 was cured by irradiating with ultraviolet rays of 500 mJ / cm ² at room temperature with an ultraviolet irradiation device to obtain the right circularly polarized reflecting dots 34R on the surface. .

<Dot shape and cholesteric structure evaluation>
Ten of the right circularly polarized light reflecting dots 34R were selected at random, and the shape of the dots was observed with a laser microscope (manufactured by Keyence Corporation). As a result, the dots have an average diameter of 30 μm, an average maximum height of 6 μm, and the angle (contact angle) formed by the contact surface between the dot surface at the dot end and the surface of the base layer is an average of 44 °, and is centered from the dot end. The height continuously increased in the direction toward.
One right circularly polarized light reflecting dot 34R located at the center of the support 32 was cut perpendicularly to the support 32 on the surface including the center of the dot, and the cross section was observed with a scanning electron microscope. As a result, a bright and dark stripe pattern as shown in FIGS. 2 and 3 was confirmed inside the dot.
Further, as shown in FIG. 2 from the cross-sectional view, the dark portion of the dot is formed at the position where the angle α ₁ with respect to the perpendicular (one-dot chain line) of the surface of the support 32 passing through the center of the dot is 30 ° and 60 °. The angles θ ₁ and θ ₂ formed by the normal direction of the line and the surface of the dot were measured. In the measurement, as conceptually shown in FIG. 7, the line formed by the outermost dark portion of the dot (the line Ld ₁ formed by the first dark portion in FIG. 2 (dot end portion)) and the innermost dark portion of the dot are formed. A line (dot center) and a line formed by three dark portions (between the dot end portion and the center) formed by an intermediate dark portion between the dot end portion and the dot center were performed.
As a result, they were 90 °, 89 °, and 90 ° in the order of the dot end, the dot end and the center, and the dot center. In other words, the angle between the normal direction of the line formed by the dark part of the dot and the surface of the dot is almost the same whether the dot is near the dot surface, in the center of the dot (innermost), or in the middle part of the dot. Met.

<Dot area ratio>
From the support 32 on which the right circularly polarized reflection dot 34R was formed, 5 locations were selected at random, and observed with a laser microscope (manufactured by Keyence Corporation), and the area ratio of the dots was measured in a 1 × 1 mm region. . As a result, the average value of the dot area ratios at the five locations was 20.2%.

<Formation of overcoat layer 36>
The components shown below were stirred and dissolved in a container kept at 25 ° C. to prepare an overcoat coating solution.
(Coating solution for overcoat)
Methyl ethyl ketone 103.6 parts by mass KAYARAD DPCA-30 (Nippon Kayaku Co., Ltd.) 40 parts by mass The following compound L 60 parts by mass Compound A 0.6 parts by mass IRGACURE 127 (manufactured by BASF) 3 parts by mass

Compound L

The prepared coating liquid for overcoat was applied onto the support 32 (underlayer) on which the right circularly polarized reflective dots 34R were formed, using a # 8 bar coater.
Then, after heating the coating film so that the coating surface temperature becomes 50 ° C. and drying for 60 seconds, the coating film is irradiated with UV light of 500 mJ / cm ² by an UV irradiation device to allow the crosslinking reaction to proceed. The coat layer 36 was produced to obtain a right circularly polarized dot film 30R.
In this example, three sheets of the same right circularly polarized dot film 30R were produced.

<Preparation of cholesteric liquid crystal ink liquid L>
A cholesteric liquid crystal ink liquid L was prepared in the same manner as the cholesteric liquid crystal ink liquid R except that the chiral agent A was changed to the chiral agent B and the addition amount of the chiral agent B was 8.09 parts by mass.

Chiral agent B

The cholesteric liquid crystal ink liquid L is a material for forming the left circularly polarized light reflecting dot 34L that reflects left circularly polarized light having a selective reflection center wavelength of 550 nm.

<Preparation of dot film>
A left circularly polarized dot film 30L was produced in the same manner as the right circularly polarized dot film 30R except that the prepared cholesteric liquid crystal ink liquid L was used instead of the cholesteric liquid crystal ink liquid R.
In this example, three same left circularly polarized dot films 30L were produced.

<Production of transparent screen>
Using the adhesive (manufactured by Soken Chemicals, SK Dyne), the three right circularly polarized dot films 30L and the three left circularly polarized dot films 30L so that the support 32 and the overcoat layer 36 face each other. Were bonded together to produce a transparent screen as shown in FIG. 1 having the left circularly polarizing laminate 24 and the right circularly polarizing laminate 20.

[Comparative Example 1]
A transparent screen was prepared in the same manner as in Example 1 except that one piece of the right circularly polarized dot film 30R and one piece of the left circularly polarized dot film 30L were used.
That is, this transparent screen is a transparent screen having one right circularly polarized dot film 30R and one left circularly polarized dot film 30L.

[Evaluation]
<Projector and arrangement>
The projector used PJWX4141 (manufactured by Ricoh Co., Ltd.) to irradiate an image from the lower part of the transparent screen so that white of 5 cm square was displayed at the center of the produced transparent screen.
This projector is a DLP projector, and the emitted light is non-polarized light.

<Evaluation of hot spot (transmission straight light)>
As shown in FIGS. 5 and 6, a full diffusion plate D made of barium sulfate is arranged on the extended line of the light emitted from the projector P and the center of the transparent screen S, and a color luminance meter is viewed from the normal direction of the complete diffusion plate D. The luminance was measured using B (Topcon, BM-5).
5 is a top view and FIG. 6 is a side view.
When the luminance measurement result using the transparent screen of Comparative Example 1 was normalized as 100, the luminance measurement result of the transparent screen of Example 1 was 8, and it was found that hot spots were significantly suppressed.

[Example 2]
<Preparation of alignment film>
On the surface of the protective film 01, an alignment film coating solution having the following composition was applied at 28 mL / m ² with a # 16 wire bar coater. Thereafter, the film was dried with warm air of 60 ° C. for 60 seconds and further with warm air of 90 ° C. for 150 seconds. A rubbing treatment was performed on the formed film surface with a rubbing roll in a direction parallel to the transport direction at a rate of 1000 rotations / minute to produce a protective film 01 with an alignment film.
(Alignment film coating solution)
The following modified polyvinyl alcohol 10 parts by mass Water 370 parts by mass Methanol 120 parts by mass Glutaraldehyde (crosslinking agent) 0.5 parts by mass

<Production of λ / 4 plate 56>
With reference to Examples ([0272] to [0282]) of JP2012-18396A, an optically anisotropic layer was formed on the protective film 01 with an alignment film, and a λ / 4 plate 56 was produced. Re (550) and Rth (550) were 138 nm and 5 nm, respectively.

<Preparation of dot film>
Three right circularly polarized dot films 30R were produced in the same manner as in Example 1 except that the protective film 01 with an alignment film was used instead of the protective film 01 on which the base layer was formed. That is, also in this example, the support 32 is the protective film 01.

<Production of transparent screen>
Using the adhesive (manufactured by Soken Chemical Co., Ltd., SK Dyne), the produced λ / 4 plate 56 and the three right circularly polarized dot films 30R were bonded together, and the λ / 4 plate 56 and the right as shown in FIG. A transparent screen having the circularly polarizing laminate 20 was produced.
The three right circularly polarized dot films 30R were bonded to each other with the support 32 and the overcoat layer 36 facing each other. The λ / 4 plate 56 was bonded to the overcoat layer 36 that is one surface of the right circularly polarizing laminate 20 with the protective film 01 with an alignment film facing each other.

[Comparative Example 2]
A transparent screen was produced in the same manner as in Example 2 except that the right circularly polarized dot film 30R was one.
That is, this transparent screen is a transparent screen composed of the λ / 4 plate 56 and one piece of the right circularly polarized dot film 30R.

[Evaluation]
<Projector and arrangement>
The projector used LSPX-P1 (manufactured by SONY) to irradiate an image from the lower part of the transparent screen so that white of 5 cm square was displayed on the center of the transparent screen.
This projector is a laser projector, and the emitted light is linearly polarized light.

<Evaluation of hot spot (transmission straight light)>
As in Example 1 and Comparative Example 1, the luminance was measured with a luminance meter B as shown in FIGS.
When the luminance measurement result using the transparent screen of Comparative Example 2 was normalized as 100, the luminance measurement result of the transparent screen of Example 2 was 10, and it was found that hot spots were significantly suppressed.
From the above results, the effects of the present invention are clear.

10, 50

Image display system

12, 52, S

Transparent screen

14, 54, P Prosector 20 Right circular polarization laminate 24 Left circular polarization laminate 30R Right circular polarization dot film 30L Left circular polarization dot film 34R Right circular polarization reflection dot 34L Left circularly polarized reflective dot 36 Overcoat layer B Luminance meter D Complete diffuser

Claims

On the surface of the support, it has a plurality of dot films in which dots formed by fixing a cholesteric liquid crystal phase are two-dimensionally arranged, and
In the plurality of dot films, the transparent reflection screen is characterized in that the selective reflection center wavelength of the dots of at least two of the dot films and the rotation direction of the reflected circularly polarized light are equal to each other.
The dot has a dot film that reflects right circularly polarized light, and the dot has a dot film that reflects left circularly polarized light, and
2. The transparent screen according to claim 1, comprising a plurality of at least one of a dot film in which the dots reflect right circularly polarized light and a dot film in which the dots reflect left circularly polarized light.
The in-plane retardation Re (550) at a wavelength of 550 nm of the support is from 0 to 20 nm, and the retardation Rth (550) in the thickness direction at a wavelength of 550 nm of the support is from 0 to 50 nm. Transparent screen as described.
The transparent screen according to any one of claims 1 to 3, comprising a λ / 4 plate.
The in-plane retardation Re (550) of the λ / 4 plate at a wavelength of 550 nm is 120 to 150 nm, and the retardation Rth (550) in the thickness direction of the λ / 4 plate at a wavelength of 550 nm is −50 to 50 nm. Item 5. The transparent screen according to Item 4.
A transparent screen according to any one of claims 1 to 5;
An image display system comprising: a projector in which the emitted light is non-polarized and the peak wavelength of the emitted light is equal to the selective reflection center wavelength of the dot.
The transparent screen according to claim 4 or 5,
An image display system comprising: a projector, wherein the emitted light is polarized light, and a peak wavelength of the emitted light is equal to a selective reflection center wavelength of the dots.
The image display system according to claim 7, wherein the projector is a laser projector.
The image display system according to any one of claims 6 to 8, wherein the dot film of the transparent screen is arranged with the convexity of the dots facing the projector.