JP2016114764A - Reflective film, optical member, display, and image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a novel reflective film; a novel optical member that can be used in a system that allows for manually entering information, such as characters or figures, on a display of an image display device, and digitizes and feeds the information to an information processing device; a display that features high read sensitivity for an optical pen in such a system; and an image display device.SOLUTION: A reflective film reflects light in the infrared wavelength range and includes circularly polarized light reflective layers 1-1, 1-2 comprising layers obtained by fixing cholesteric liquid crystal phases and containing particles having an average diameter of not less than 0.5 μm and less than a thickness of the circularly polarized light reflective layers.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a reflective film. The present invention also relates to an optical member including the reflective film, a display including the optical member, and an image display device including the display.

  In recent years, there is an increasing need for a system in which information such as characters or figures is input by handwriting on a display of an image display device, digitized, and input to an information processing device. In the form using an optical pen and a handwritten input sheet as the system, a handwritten input sheet having a layer in which information is written as an optical pattern and a reflective film can be used. Here, the reflective film is used to return light emitted from the optical pen to the image sensor incorporated in the optical pen as light reflecting information described as the optical pattern. For example, in Patent Document 1, an infrared reflecting layer having a characteristic of reflecting infrared light from one side and transmitting visible light is arranged with dots having a dot pattern in which coordinate information and / or code information is repeatedly defined. There is a description about an information input auxiliary sheet provided together with the dot pattern layer.

JP 2014-089443 A

  An object of the present invention is to provide a novel reflective film. This invention makes it a subject to provide the reflective film which can be used especially for the said system. Another object of the present invention is to provide a novel optical member that can be used as the above-mentioned handwriting input sheet. It is another object of the present invention to provide a display and an image display device with high sensitivity for reading with an optical pen.

  The inventors of the present invention have attempted to solve the above problems by using a layer in which a cholesteric liquid crystal phase that has been conventionally known to be used as a reflecting member is fixed. In the process, we faced a problem that sensitivity was lowered especially when the optical pen was tilted. A layer in which a cholesteric liquid crystal phase is fixed has the property of exhibiting maximum reflectivity at a desired wavelength in the normal direction, but the above problem is that the infrared light used when tilting the optical pen and reading from an oblique direction is used. It was thought that the reason was that sufficient reflected light could not be obtained at the wavelength of light. That is, it was considered that the layer in which the cholesteric liquid crystal phase was fixed had low retroreflectivity in the oblique direction. The inventors of the present invention have repeatedly studied to solve the above problems and complete the present invention.

That is, the present invention provides the following [1] to [16].
[1] A reflective film,
Reflects light in the infrared wavelength range,
Including a circularly polarized light reflection layer composed of a layer in which a cholesteric liquid crystal phase is fixed;
The circularly polarized reflective layer includes particles,
The reflective film having an average particle diameter of 0.5 μm or more and less than a film thickness of the circularly polarized reflective layer.
[2] The reflective film according to [1], wherein the particles are organic particles.
[3] The reflective film according to [1], wherein the particles are poly (meth) acrylate particles.
[4] The reflective film according to any one of [1] to [3], which has a haze value of 10% or less.
[5] The circularly polarizing reflective layer according to any one of [1] to [4], wherein the circularly polarized light reflecting layer is a layer formed from a liquid crystal composition containing the particles, a liquid crystal compound, a chiral agent, and a horizontal alignment agent. Reflective film.
[6] The circularly polarized light reflecting layer includes a right circularly polarized light reflecting layer that selectively reflects right circularly polarized light and a left circularly polarized light reflecting layer that selectively reflects left circularly polarized light,
The reflective film according to any one of [1] to [5], wherein the central wavelengths of circularly polarized light selective reflection of the right circularly polarized light reflecting layer and the left circularly polarized light reflecting layer are the same.

[7] The reflective film according to any one of [1] to [6], including a base material.
[8] The reflective film according to any one of [1] to [7], wherein the direct transmittance of non-polarized visible light is 50% or more.
[9] An optical member including the reflective film according to any one of [1] to [8] and an information presentation layer,
The information presentation layer is an optical member having a pattern of a material that absorbs or reflects light reflected by the reflective film.
[10] The optical member according to [9], wherein the pattern is a dot pattern.
[11] The optical member according to [9] or [10], wherein the pattern is formed by printing.
[12] The reflective film includes a substrate,
The optical member according to any one of [9] to [11], including the circularly polarized light reflecting layer, the base material, and the information presentation layer in this order.
[13] The reflective film includes a substrate,
The optical member according to any one of [9] to [11], including the base material, the circularly polarized light reflection layer, and the information presentation layer in this order.
[14] The reflective film includes a substrate,
The optical member according to any one of [9] to [13], wherein the pattern is formed on the substrate surface by printing.
[15] A display having the optical member according to any one of [9] to [14].
[16] An image display device having the display according to [15].

  According to the present invention, a novel reflective film is provided. In particular, the present invention provides a reflective film that can be used in a system for inputting information such as characters or figures on a display of an image display device by handwriting, digitizing the information, and inputting the information to an information processing device. The optical member including the reflective film can be used as a handwritten input sheet in the above-described system. By using the optical member, it is possible to provide a display and an image display device with high sensitivity of reading with an optical pen.

It is a figure which shows typically the cross section of the example of a reflective film. It is a figure which shows typically the cross section of the example of an optical member. It is a figure explaining the measuring method of the retroreflection signal strength performed in the Example.

Hereinafter, the present invention will be described in detail.
In the present specification, “to” is used to mean that the numerical values described before and after it are included as a lower limit value and an upper limit value.
In this specification, for example, an angle such as “45 degrees”, “parallel”, “vertical”, or “orthogonal”, unless otherwise specified, has a difference from an exact angle within a range of less than 5 degrees. Means. The difference from the exact angle is preferably less than 4 degrees, and more preferably less than 3 degrees.
In the present specification, for each numerical value, numerical range, and qualitative expression (for example, an expression such as “same”, etc.), a numerical value, a numerical range, and a property including an error generally allowed in this technical field are used. It shall be interpreted as showing. For example, when the wavelength is “same”, the difference is within 5 nm.
In this specification, “(meth) acrylate” is used to mean “one or both of acrylate and methacrylate”. The same applies to “(meth) polyacrylate” and the like.

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

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

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

  In this specification, “diffuse reflectance” or “regular reflectance” is a value calculated based on values measured using a spectrophotometer and an integrating sphere unit. When the regular reflectance is based on a value measured using an integrating sphere unit, it may be a measured value at an incident angle of, for example, 5 degrees for convenience of measurement. The diffuse reflectance is a value that can be calculated by subtracting the regular reflectance from the total reflectance (measured value of all angles of the integrating sphere). The direct transmittance is a transmittance at 0 degrees when based on a value measured using an integrating sphere unit.

In this specification, the “haze value” means a value measured using a haze meter NDH-2000 manufactured by Nippon Denshoku Industries Co., Ltd.
Theoretically, the haze value means a value represented by the following formula.
(Scattering transmittance of non-polarized light (natural light) of 380 to 780 nm) / (scattering transmittance of non-polarized light of 380 to 780 nm + direct transmittance of non-polarized light of 380 to 780 nm) × 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.
In the present specification, the term “reflected light” or “transmitted light” is used to mean scattered light and diffracted light.

In addition, the polarization state of each wavelength of light can be measured using a spectral radiance meter or a spectrometer equipped with a circularly polarizing plate. In this case, the intensity of light measured through the right circularly polarizing plate corresponds to I _R , and the intensity of light measured through the left circularly polarizing plate corresponds to I _L. In addition, ordinary light sources such as incandescent light bulbs, mercury lamps, fluorescent lamps, and LEDs emit almost non-polarized light. However, the characteristic of producing polarized light of films mounted on these light sources is, for example, a polarization phase difference analyzer manufactured by AXOMETRIC It can be measured using AxoScan or the like.
Moreover, even if it attaches a reflective film to an illuminance meter or an optical spectrum meter, it can measure. The ratio can be measured by attaching a right circular polarized light transmission plate, measuring the right circular polarized light amount, attaching a left circular polarized light transmission plate, and measuring the left circular polarized light amount.

<Reflection film>
The reflective film of the present invention includes a circularly polarized reflective layer. The reflective film of the present invention may include either one of a right circularly polarized light reflecting layer that selectively reflects right circularly polarized light or a left circularly polarized light reflecting layer that selectively reflects left circularly polarized light, or may include both. The reflective film of this invention may contain the base material and the oriented film other than a circularly-polarized-light reflection layer. FIG. 1 schematically shows a cross-sectional view of an example of the reflective film of the present invention. The reflective film shown to Fig.1 (a) is an example containing either the base material 5 and either (1-1) of a right circular polarization reflection layer or a left circular polarization reflection layer. The reflective film shown in FIG. 1B is an example including the base material 5 and both the right circularly polarized reflective layer and the left circularly polarized reflective layer (1-1 and 1-2).

[Optical properties of reflective film]
The reflective film of the present invention is a film that can reflect light in the infrared wavelength region. Although the wavelength of the infrared ray reflected by the reflective film of the present invention is not particularly limited, when the transmittance spectrum of the reflective film is confirmed, a reflective wavelength band having a center wavelength in the range of 780 to 2000 nm, preferably in the range of 800 to 1500 nm. It is preferable that can be confirmed. It is also preferable that the reflection wavelength is selected according to the wavelength of a light source such as an optical pen used in combination or the wavelength of an infrared ray sensed by a sensor of an image sensor. The half width of the reflection wavelength band is 50 to 500 nm, preferably 100 to 300 nm.

  The reflective film of the present invention is highly retroreflective with respect to the incidence of light from a direction that forms an angle from the normal line of the reflective film. Retroreflection means reflection in which incident light is reflected in the incident direction. For example, when light having an angle of 45 degrees with respect to the normal line of the reflective film is incident from the surface side of at least one of the reflective films of the present invention, the standard diffuser plate (Labsphere) The amount of retroreflective light is 10% or more of the amount of retroreflective light produced by the company. As will be described later, in the reflective film of the present invention, such a retroreflective property is obtained when the circularly polarized reflective layer contains particles. By having retroreflectivity, high sensitivity can be obtained even when light is incident at an angle from the normal of the reflective film and the reflected light is detected from the same direction.

  The reflective film of the present invention preferably has a reflection wavelength in the infrared wavelength region where the diffuse reflectance with respect to non-polarized light is 40% or more. This reflection wavelength may correspond to the center wavelength of circularly polarized light selective reflection of a cholesteric liquid crystal layer described later.

Further, the diffuse reflectance may be 50 or more, 60% or more, 70% or more, or 95% or less, 90% or less, 85% or less, and the like.
The reflective film of the present invention preferably has a regular reflectance of 50% or less for non-polarized light at the above reflection wavelength. Further, the regular reflectance may be 30% or less, or 20% or less.

The haze value of the reflective film of the present invention can be 10% or less. The haze value is preferably 5% or less, and more preferably 3% or less. The smaller the haze value is, the better. However, the reflective film of the present invention usually has a haze value of about 1% or more, or about 1.5% or more when the circularly polarizing reflection layer contains particles.
The reflective film of the present invention is preferably transparent in the visible light region. Specifically, the direct transmittance of non-polarized visible light having a wavelength of 380 to 780 nm is preferably 50% or more, more preferably 60% or more, further preferably 70% or more, and 80% or more. It is particularly preferred that

[Circularly polarized reflective layer]
The reflective film of the present invention includes a circularly polarizing reflective layer composed of a layer in which a cholesteric liquid crystal phase is fixed. It is known that the cholesteric liquid crystal phase has a circularly polarized light selective reflection property that selectively reflects either right circularly polarized light or left circularly polarized light. Many films formed from a liquid crystal composition containing a liquid crystal compound have been known as films exhibiting circularly polarized light selective reflectivity. For layers in which a cholesteric liquid crystal phase is fixed, those conventional techniques can be referred to. it can.

The layer in which the cholesteric liquid crystal phase is fixed may be a layer in which the alignment of the liquid crystal compound in the cholesteric liquid crystal phase is maintained, and typically, the polymerizable liquid crystal compound is in the alignment state of the cholesteric liquid crystal phase. On the other hand, if it is a layer that has been polymerized and cured by ultraviolet irradiation, heating, etc. to form a layer having no fluidity, and at the same time, it has been changed to a state that does not cause changes in the orientation form due to an external field or external force Good. In the layer in which the cholesteric liquid crystal phase is fixed, it is sufficient that the optical properties of the cholesteric liquid crystal phase are maintained in the layer, and the liquid crystalline compound in the layer may no longer exhibit liquid crystallinity. For example, the polymerizable liquid crystal compound may have a high molecular weight due to a curing reaction and may no longer have liquid crystallinity.
In this specification, a layer in which a cholesteric liquid crystal phase is fixed may be referred to as a cholesteric liquid crystal layer or a liquid crystal layer.

The cholesteric liquid crystal layer exhibits circularly polarized light selective reflection derived from the helical structure of the cholesteric liquid crystal. The central wavelength λ of the circularly polarized light selective reflection depends on the pitch P (= spiral period) of the helical structure in the cholesteric phase, and follows the relationship between the average refractive index n of the cholesteric liquid crystal layer and λ = n × P. Therefore, by adjusting the pitch of this spiral structure, the wavelength exhibiting circularly polarized light selective reflection can be adjusted. That is, in order to adjust the n value and the P value so as to exhibit circularly polarized light selective reflection in the near-infrared light wavelength region, the center wavelength λ is in the wavelength region of 750 nm to 2000 nm, preferably 800 nm to 1500 nm. You can do it. Since the pitch of the cholesteric liquid crystal phase depends on the type of chiral agent used together with the polymerizable liquid crystal compound or the concentration of the chiral agent, the desired pitch can be obtained by adjusting these.
In addition, the sense of the reflected circularly polarized light of the cholesteric liquid crystal layer coincides with the sense of the spiral. Therefore, a cholesteric liquid crystal layer having a spiral sense of right and left may be used as the right circular polarization reflection layer and the left circular polarization reflection layer, respectively.

When the reflective film of the present invention includes both a right circularly polarized reflective layer and a left circularly polarized reflective layer, the center wavelength of the circularly polarized selective reflection of each of the right circularly polarized reflective layer and the left circularly polarized reflective layer is the same or different. However, it is more preferable that they are the same. By including a right circularly polarized light reflecting layer and a left circularly polarized light reflecting layer having the same center wavelength of circularly polarized light, when the reflective film is used in a system using an optical pen, the irradiation light wavelength of the optical pen and the image sensor This is because the intensity of the reflected light can be improved by reflecting both the right circularly polarized light and the left circularly polarized light at a specific wavelength that matches the detected light wavelength.
For the method of measuring spiral sense and pitch, use the methods described in “Introduction to Liquid Crystal Chemistry Experiments”, edited by the Japanese Liquid Crystal Society, Sigma Publishing 2007, page 46, and “Liquid Crystal Handbook”, Liquid Crystal Handbook Editing Committee, page 196. be able to.

  The half-value width Δλ (nm) of the selective reflection band (circular polarization reflection band) showing the circularly polarized selective reflection follows that ΔΔ depends on the birefringence Δn of the liquid crystal compound and the pitch P, and Δλ = Δn × P. . Therefore, the width of the selective reflection band can be controlled by adjusting Δn. Δn can be adjusted by adjusting the kind of the polymerizable liquid crystal compound and the mixing ratio thereof, or by controlling the temperature at the time of fixing the alignment.

The reflection center wavelength and the half width of the cholesteric liquid crystal layer can be obtained as follows.
When the transmission spectrum of the reflective film is measured using a spectrophotometer UV3150 (Shimadzu Corporation), a peak of decrease in transmittance is observed in the selective reflection region. Of the two wavelengths having a transmittance of 1/2 the maximum peak height, the wavelength value on the short wave side is λ1 (nm) and the wavelength value on the long wave side is λ2 (nm). The reflection center wavelength and the half width can be expressed by the following formula.
Reflection center wavelength = (λ1 + λ2) / 2
Half width = (λ2−λ1)

  The half-value width of the circularly polarized light reflection band is usually about 50 nm to 150 nm for one kind of material. In order to widen the selection wavelength range, two or more cholesteric liquid crystal layers having different center wavelengths of reflected light with different periods P may be stacked. Alternatively, in one cholesteric liquid crystal layer, the control wavelength region can be widened by gradually changing the period P in the film thickness direction.

[particle]
The reflective film of the present invention contains particles in the circularly polarized light reflective layer. The present inventors have found that the retroreflectivity is improved as described above when the circularly polarized light reflection layer composed of a layer in which the cholesteric liquid crystal phase is fixed contains particles.
The cholesteric liquid crystal layer not containing particles is formed so that the spiral axis of the spiral is parallel to the normal direction, and the amount of retroreflected light in the circularly polarized light selective reflection band is the normal direction of the cholesteric liquid crystal layer (= spiral). It becomes the maximum in the incidence of light from the (axial direction), and there is almost no retroreflective light quantity for the incidence of light from the direction that makes an angle from the normal direction. That is, good retroreflectivity is exhibited only in the normal direction of the layer. On the other hand, when the cholesteric liquid crystal phase contains particles, the liquid crystal molecules are aligned along the surface of the particles, and a cholesteric liquid crystal phase having a normal to the surface of the particles as a helical axis direction is partially generated. It is considered that the retroreflectivity is improved by the reflection even with respect to the incidence of light from a direction that forms an angle with the normal line of the reflective film.

  The particles may be either inorganic particles or organic particles, but organic particles are preferable, and organic polymer particles are more preferable. Examples of the organic polymer particles include poly (meth) acrylate particles such as polymethyl methacrylate particles, crosslinked polymethyl methacrylate particles, or acrylic-styrene copolymer particles, melamine particles, polycarbonate particles, polystyrene particles, crosslinked polystyrene particles, poly Examples include vinyl chloride particles and benzoguanamine-melamine formaldehyde particles. Of these, poly (meth) acrylate particles are preferred.

The average particle diameter of the particles is 0.5 μm or more. By using particles having an average particle size of 0.5 μm or more, a preferable retroreflective property can be obtained from the circularly polarized light reflecting layer. Moreover, the average particle diameter of particle | grains should just be less than the film thickness of a circularly polarized light reflection layer. By making it less than the film thickness of the circularly polarized light reflecting layer, the haze value can be kept as low as 10% or less. This is presumably because the particles do not affect the surface shape of the circularly polarized light reflecting layer. The average particle size of the particles is more preferably 0.8 to 5 μm and even more preferably 1 to 3 μm in order to reduce the haze value while maintaining retroreflectivity. In addition, in order to impart scattering reflectivity and a low haze value, two or more kinds of particles having different particle diameters may be used in combination as appropriate.
In addition, in this specification, the average particle diameter of a particle | grain is a value calculated | required by the image process of an electron micrograph, and is an average value of the particle diameter which selected and measured 100 particle | grains at random.

  Although there is no restriction | limiting in particular in the refractive index of particle | grains, 1.0-3.0 are preferable, 1.2-1.6 are more preferable, 1.3-1.5 are still more preferable. The refractive index of the particles is determined by measuring the refractive index of the refractive liquid using, for example, an automatic refractive index measuring device (KPR-2000, manufactured by Shimadzu Corporation), and then a precision spectrometer (GMR-1DA, manufactured by Shimadzu Corporation). ) And can be measured by the Shribsky method.

  The particles may be contained in the circularly polarized reflection phase by being added to the liquid crystal composition used for forming the cholesteric liquid crystal layer. The content of the particles in the liquid crystal composition is preferably 0.01 to 5% by mass, more preferably 0.05 to 3% by mass, and still more preferably 0.1 to 2% by mass with respect to the total mass of the liquid crystal compound.

[Liquid crystal composition]
The liquid crystal composition includes a liquid crystal compound and the above particles. The liquid crystal compound is preferably a polymerizable liquid crystal compound. The liquid crystal composition preferably contains a chiral agent and a horizontal alignment agent. The liquid crystal composition may further contain a surfactant or a polymerization initiator. A cholesteric liquid crystal layer can be formed by applying the liquid crystal composition to a substrate, an alignment layer, or a cholesteric liquid crystal layer serving as a lower layer, fixing the cholesteric alignment, and then fixing it.

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

  The polymerizable liquid crystal compound can be obtained by introducing a polymerizable group into the liquid crystal compound. Examples of the polymerizable group include an unsaturated polymerizable group, an epoxy group, and an aziridinyl group, preferably an unsaturated polymerizable group, and particularly preferably an ethylenically unsaturated polymerizable group. The polymerizable group can be introduced into the molecule of the liquid crystal compound by various methods. The number of polymerizable groups possessed by the polymerizable liquid crystal compound is preferably 1 to 6, more preferably 1 to 3. Examples of polymerizable liquid crystal compounds are described in Makromol. Chem. 190, 2255 (1989), Advanced Materials 5, 107 (1993), US Pat. No. 4,683,327, US Pat. No. 5,622,648, US Pat. No. 5,770,107, International Publication WO95 / 22586. No. 95/24455, No. 97/00600, No. 98/23580, No. 98/52905, JP-A-1-272551, No. 6-16616, and No. 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.

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

(Chiral agent: optically active compound)
The chiral agent has a function of inducing a helical structure of a cholesteric liquid crystal phase. The chiral compound may be selected according to the purpose because the helical sense or helical pitch induced by the compound is different.
The chiral agent is not particularly limited, and known compounds (for example, liquid crystal device handbook, Chapter 3-4-3, TN, chiral agent for STN, page 199, Japan Society for the Promotion of Science, 142nd edition, 1989) Description), isosorbide, and isomannide derivatives can be used.
A chiral agent generally contains an asymmetric carbon atom, but an axially asymmetric compound or a planar asymmetric compound containing no asymmetric carbon atom can also be used as the chiral agent. Examples of the axial asymmetric compound or the planar asymmetric compound include binaphthyl, helicene, paracyclophane, and derivatives thereof. The chiral agent may have a polymerizable group. When both the chiral agent and the liquid crystal compound have a polymerizable group, they are derived from the repeating unit derived from the polymerizable liquid crystal compound and the chiral agent by a polymerization reaction between the polymerizable chiral agent and the polymerizable liquid crystal compound. A polymer having repeating units can be formed. In this aspect, the polymerizable group possessed by the polymerizable chiral agent is preferably the same group as the polymerizable group possessed by the polymerizable liquid crystal compound. Therefore, the polymerizable group of the chiral agent is also preferably an unsaturated polymerizable group, an epoxy group or an aziridinyl group, more preferably an unsaturated polymerizable group, and an ethylenically unsaturated polymerizable group. Particularly preferred.
The chiral agent may be a liquid crystal compound.

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 irradiation with a photomask such as actinic rays after coating and orientation. As a photoisomerization group, the isomerization part of the compound which shows photochromic property, an azo, an azoxy, and a cinnamoyl group are preferable. Specific examples of the compound include JP 2002-80478, JP 2002-80851, JP 2002-179668, JP 2002-179669, JP 2002-179670, and JP 2002-2002. 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.
The content of the chiral agent in the liquid crystal composition is preferably 0.01% by mass to 200% by mass and more preferably 1% by mass to 30% by mass based on the amount of the polymerizable liquid crystalline compound.

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

(Crosslinking agent)
The liquid crystal composition may optionally contain a crosslinking agent in order to improve the film strength after curing and improve the durability. As the cross-linking agent, one that can be cured by ultraviolet rays, heat, moisture, or the like can be suitably used.
There is no restriction | limiting in particular as a crosslinking agent, According to the objective, it can select suitably, For example, polyfunctional acrylate compounds, such as a trimethylol propane tri (meth) acrylate and pentaerythritol tri (meth) acrylate; Glycidyl (meth) acrylate , Epoxy compounds such as ethylene glycol diglycidyl ether; aziridine compounds such as 2,2-bishydroxymethylbutanol-tris [3- (1-aziridinyl) propionate], 4,4-bis (ethyleneiminocarbonylamino) diphenylmethane; hexa Isocyanate compounds such as methylene diisocyanate and biuret type isocyanate; polyoxazoline compounds having an oxazoline group in the side chain; vinyltrimethoxysilane, N- (2-aminoethyl) 3-aminopropylto Alkoxysilane compounds such as methoxy silane. Moreover, a well-known catalyst can be used according to the reactivity of a crosslinking agent, and productivity can be improved in addition to membrane strength and durability improvement. These may be used individually by 1 type and may use 2 or more types together.
3 mass%-20 mass% are preferable, and, as for content of a crosslinking agent, 5 mass%-15 mass% are more preferable. When the content of the crosslinking agent is less than 3% by mass, the effect of improving the crosslinking density may not be obtained. When the content exceeds 20% by mass, the stability of the cholesteric liquid crystal layer may be decreased.

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

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

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

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

[Method for producing cholesteric liquid crystal layer]
A cholesteric liquid crystal layer is obtained by applying the above liquid crystal composition to the surface of a substrate, the surface of another cholesteric liquid crystal layer or an alignment film, and drying to obtain a coating film. It can be formed by polymerizing a cholesteric liquid crystalline composition. The laminated film composed of a plurality of cholesteric liquid crystal layers may be formed by applying a liquid crystal composition on the cholesteric liquid crystal layer and repeating the manufacturing process of the cholesteric liquid crystal layer. For example, in the case of a reflective film including a right circularly polarized reflective layer and a left circularly polarized reflective layer, the induced spiral sense is induced on the surface on which the right circularly polarized reflective layer is formed from the composition containing the right chiral agent. A left circularly polarized light reflecting layer may be formed by applying a composition containing a chiral agent having a left spiral sense and performing orientation and polymerization. At this time, the order of forming the right circularly polarized light reflecting layer and the left circularly polarized light reflecting layer may be reversed.
A separately formed circularly polarized light reflecting layer, for example, a separately formed right circularly polarized light reflecting layer and left circularly polarized light reflecting layer may be bonded together with an adhesive layer. As the adhesive layer, an adhesive layer used for bonding each layer of the optical member may be used.

(Coating, orientation, polymerization)
The application method of the liquid crystal composition is not particularly limited and can be appropriately selected depending on the purpose. For example, a wire bar coating method, a curtain coating method, an extrusion coating method, a direct gravure coating method, a reverse gravure coating method, a die Examples thereof include a coating method, a spin coating method, a dip coating method, a spray coating method, and a slide coating method. Alternatively, a liquid crystal composition separately coated on a temporary support may be transferred and used. Liquid crystal molecules can be aligned in the process of drying the applied liquid crystal composition or by heating the applied liquid crystal composition. The heating temperature is preferably 200 ° C. or lower, and more preferably 130 ° C. or lower. By this alignment treatment, a layer in which the polymerizable liquid crystal compound is twisted and aligned so as to have a helical axis in a direction perpendicular to the surface of the substrate or the like is obtained. In the vicinity of the particle surface in this layer, A partial structure is obtained which is twisted and oriented so as to have a helical axis in a direction perpendicular to the particle surface.

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

The thickness of each cholesteric liquid crystal layer is not particularly limited as long as it exhibits the above characteristics, but is preferably in the range of 1.0 to 150 μm, more preferably in the range of 4.0 to 100 μm.
The total thickness of the cholesteric liquid crystal layer of the reflective film of the present invention, that is, the total thickness of the circularly polarized reflective layer is preferably 2.0 μm or more and 300 μm or less, more preferably 8.0 μm or more and 200 μm or less. It is a range. The selective reflection based on the periodic structure can be sufficiently ensured with a thickness of 2.0 μm or more. In addition, with a thickness of 300 μm or less, sufficient visible light transparency can be secured.

[Alignment layer]
The reflective film may include an alignment layer as a lower layer to which the liquid crystal composition is applied when forming the cholesteric liquid crystal layer. The alignment layer has a rubbing treatment of organic compounds such as polymers (resins such as polyimide, polyvinyl alcohol, polyester, polyarylate, polyamideimide, polyetherimide, polyamide, modified polyamide), oblique deposition of inorganic compounds, and microgrooves. It can be provided by means such as formation of a layer or accumulation of an organic compound (for example, ω-tricosanoic acid, dioctadecylmethylammonium chloride, methyl stearylate) by the Langmuir-Blodgett method (LB film). Furthermore, an alignment layer in which an alignment function is generated by application of an electric field, application of a magnetic field, or light irradiation is also known.

In particular, the alignment layer made of a polymer is preferably subjected to a rubbing treatment and then a liquid crystal composition is applied to the rubbing treatment surface. The rubbing treatment can be performed by rubbing the surface of the polymer layer several times in a certain direction with paper or cloth.
You may apply | coat a liquid-crystal composition to the base-material surface, or the surface which carried out the rubbing process of the base material, without providing an alignment layer.
In the case of forming a liquid crystal layer using a temporary support, the alignment film may not be peeled off together with the temporary support to form a layer constituting the optical member of the present invention.
The thickness of the alignment layer is preferably 0.01 to 5 μm, and more preferably 0.05 to 2 μm.

[Base material]
The reflective film of the present invention may contain a substrate as a support for the cholesteric liquid crystal layer. The base material may also serve as the alignment layer.
The substrate is not particularly limited. A plastic film can be used as the substrate. Examples of the plastic film include polyester such as polyethylene terephthalate (PET), polycarbonate, acrylic resin, epoxy resin, polyurethane, polyamide, polyolefin, cellulose derivative, and silicone.

The film thickness of the substrate may be about 5 μm to 1000 μm, preferably 10 μm to 250 μm, and more preferably 15 μm to 90 μm.
In forming the cholesteric liquid crystal layer, a temporary support may be used, and after forming the cholesteric liquid crystal layer, the cholesteric liquid crystal layer may be transferred to a substrate.
In addition, as a temporary support body, you may use glass etc. other than said plastic film.

<Optical member>
The reflective film of this invention can be used as a structural member of an optical member.
The optical member further includes an information presentation layer. The optical member may be in the form of a film or a sheet. FIG. 2 schematically shows a cross-sectional view of an example of the optical member of the present invention. The optical member shown in FIGS. 2A and 2B is an example in which an information presentation layer 11, a base material 5, and a circularly polarized light reflection layer (1-1, or 1-2 and 1-1) are laminated in this order. It is. The optical member shown in FIGS. 2C and 2D is an example in which a base material 5, a circularly polarized light reflection layer (1-1, or 1-2 and 1-1), and an information presentation layer 11 are laminated in this order. It is.

[Information presentation layer]
The information presentation layer has a pattern of a material that absorbs or reflects light having the reflection wavelength. That is, the information presentation layer has a pattern of a material that absorbs or reflects infrared rays. The pattern may be in the entire information presentation layer or in part. The material that absorbs or reflects the light having the reflection wavelength may be applied and printed on the surface of the reflective film by, for example, an ink jet method to form a pattern. Alternatively, for example, after being uniformly applied to the substrate surface, the pattern may be formed by printing and evaporation in units of 0.5 to 3000 μm using an infrared laser or the like. For the latter method, reference can be made to, for example, the description of JP-A-2011-152652.

  The pattern may be a pattern that can give at least the position or coordinate information of the selected partial region in the information presentation layer when the partial region is selected. The part to be selected may be a unit that can be photographed by a pen-type imaging device having, for example, a light source that emits infrared rays and a sensor that senses infrared rays. Examples of the pattern include a dot pattern described in paragraphs 0123 to 0152 of JP 2014-98943 A.

(Material that absorbs or reflects infrared rays)
Examples of materials that absorb or reflect infrared rays include carbon inks, inks containing inorganic ions (metals such as copper, iron, ytterbium), phthalocyanine dyes, dioctyl compound dyes, squalium dyes, croconium dyes, nickel complex dyes, etc. Other known organic dyes, other known infrared absorbing dyes, known infrared reflective particles, and the like can be used. The material that absorbs or reflects infrared rays preferably has no reflection or absorption in the visible wavelength region.

[Layer structure of optical member]
As an example of the layer configuration of the optical member when the reflective film includes a base material, the information presentation layer, the base material, the configuration in which the circularly polarized reflective layer is arranged in this order, and the information presentation layer, the circularly polarized reflective layer, the base material Are arranged in this order. In a configuration including two or more circularly polarized reflective layers, it is preferable that all the circularly polarized reflective layers are adjacent to each other, and neither the information presentation layer nor the substrate is included between the circularly polarized reflective layers.

(Adhesive layer)
The optical member of the present invention may include an adhesive layer for bonding the layers. The reflective film of the present invention may include an adhesive layer. The adhesive layer may be formed from an adhesive.
Adhesives include hot melt type, thermosetting type, photocuring type, reactive curing type, and pressure-sensitive adhesive type that does not require curing, from the viewpoint of curing method, and the materials are acrylate, urethane, urethane acrylate, epoxy , Epoxy acrylate, polyolefin, modified olefin, polypropylene, ethylene vinyl alcohol, vinyl chloride, chloroprene rubber, cyanoacrylate, polyamide, polyimide, polystyrene, polyvinyl butyral, etc. can do. From the viewpoint of workability and productivity, the photocuring type is preferable as the curing method, and from the viewpoint of optical transparency and heat resistance, the material is preferably an acrylate, urethane acrylate, epoxy acrylate, or the like. .

[Use of optical members]
Although it does not specifically limit as an application of the optical member of this invention, For example, it can use as a handwritten input sheet used with the system using the optical pen which digitizes handwritten information and inputs into information processing apparatus. In use, the composition of the cholesteric liquid crystal layer is adjusted and used so that the wavelength of infrared rays emitted from the optical pen is the wavelength at which the reflective film shows reflection. Specifically, the spiral pitch of the cholesteric liquid crystal phase may be adjusted by the above method. When the optical member is used as a handwritten input sheet, it is sufficient that light is irradiated from the information presentation layer side of the optical member and reflected light is detected from the information presentation layer side of the optical member.

  The optical member of the present invention is disposed, for example, on the display surface or in front of the image display device, and can be used as a handwriting input sheet. The optical member may be bonded directly to the display surface or via another film or the like, and may be integrated with the display. For example, the optical member may be detachably attached to the display surface. When integrated, the optical member of the present invention may be disposed between the forefront of the image display device or the protective front plate and the display panel. The optical member of the present invention is preferably arranged so that the reflective film and the information presentation layer side are in this order from the display surface side. It is preferable that the display does not emit infrared light in the reflection wavelength region of the reflective film in the optical member so that there is no false detection with the image sensor of the optical pen.

  Regarding a handwriting input system that digitizes handwritten information and inputs it to an information processing apparatus or an image display device that is equipped with a handwriting input sheet, JP2014-67398A, JP2014-98943A, JP2008-165385A. [0021] to [0032] of Japanese Patent Laid-Open No. 2008-108236, Japanese Patent Laid-Open No. 2008-077451, or Japanese Patent No. 4725417.

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

[Production of Reflective Films of Examples 1 and 3 and Comparative Examples 1 to 3 and 5]
The PET surface of Toyobo Co., Ltd. Cosmo Shine A-4100 (thickness 75 μm) that has not been subjected to easy adhesion treatment is subjected to rubbing treatment, and coating liquid A-1 or coating liquid A-5 shown in Table 1 is applied to the rubbing treated surface. The film was applied at room temperature so that the dry film thickness after drying was 8 μm. The coating layer was dried at room temperature for 1 minute, then heated in an atmosphere of 85 ° C. for 2 minutes, and then irradiated at 30 ° C. with a fusion D bulb (lamp 90 mW / cm) at an output of 60% for 6 to 12 seconds. A circularly polarized reflective layer was produced to obtain a reflective film.

[Production of Reflective Films of Examples 2 and 4 and Comparative Examples 4 and 6]
A rubbing treatment is performed on a PET surface of Toyobo Co., Ltd. Cosmo Shine A-4100 (thickness 75 μm) that has not been subjected to easy adhesion treatment, and either one of the coating liquid A-1 or the coating liquid A-5 shown in Table 1 is used. It apply | coated to the rubbing process surface at room temperature so that the thickness of the dry film after drying might be set to 8 micrometers. The coating layer was dried at room temperature for 1 minute, then heated in an atmosphere of 85 ° C. for 2 minutes, and then irradiated at 30 ° C. with a fusion D bulb (lamp 90 mW / cm) at an output of 60% for 6 to 12 seconds. A liquid crystal layer was obtained. On the obtained circularly polarized light reflective layer, the other of the coating liquid A-1 or the coating liquid A-5 shown in Table 1 was applied at room temperature so that the dry film thickness after drying was 8 μm, and then the same as described above. Then, drying, heating, and UV irradiation were performed to form a second circularly polarized reflective layer, and a reflective film was obtained.

One of the following particles was used.
SSX-101, manufactured by Sekisui Chemical Co., Ltd. (average particle size 1μm)
SSX-104, manufactured by Sekisui Chemical Co., Ltd. (average particle size 4μm)
SSX-110, manufactured by Sekisui Chemical Co., Ltd. (average particle size 10μm)
MEK-ST-ZL (30% dispersion) manufactured by Nissan Chemical Co., Ltd. (average particle size 0.1 μm)
When adding SSX-101, SSX-104, or SSX-110, 0.20 mass part was added, and when adding MEK-ST-ZL, 0.67 mass part was added.

[Evaluation of reflective film]
The obtained reflective film was evaluated as follows. The results are shown in Table 2.
(Haze value)
The haze value was measured using a haze meter NDH-2000 manufactured by Nippon Denshoku Industries Co., Ltd. When measuring the sample, the measurement was performed such that the incident light was applied from the substrate side.

(45 degree relative retroreflectivity)
Measurement was performed using an ultraviolet-visible near-infrared spectrophotometer V-670 (manufactured by JASCO Corporation) in combination with an absolute reflectance measurement unit ARV474S (manufactured by JASCO Corporation). As shown in FIG. 3, incident light is applied from a position inclined 45 degrees with respect to the normal direction of the sample surface, and a signal is detected at a position 8 degrees from the position (53 degrees with respect to the normal direction of the sample surface). This was taken as the retroreflective signal intensity. In FIG. 3, the detector is an InGaAs detector in the ultraviolet-visible near-infrared spectrophotometer V-670, and can detect near-infrared light. The incident light was adjusted to a wavelength of 850 nm, and the incident light was applied from the substrate side of the reflective film during measurement.

The retroreflective signal intensity when a standard diffuser (manufactured by Labsphere) is installed at the sample position is 100%, and the ratio of the retroreflective intensity when each of the reflection films prepared above is installed at the sample position is a relative recursion. The reflectance was calculated by the following formula.

(Relative retroreflectivity) = (Retroreflective signal intensity of reflective film) / (Retroreflective signal intensity of standard diffuser) × 100

Further, using a spectrophotometer V-670 manufactured by JASCO, the transmittance at a wavelength of 380 to 780 nm at an incident angle of 0 degree was averaged and calculated as a non-polarized direct transmittance.

  As can be seen from the results in Table 2, by adding particles having an average particle size of 0.5 μm or more and not more than the thickness of the circularly polarized reflective layer to the circularly polarized reflective layer, 45 ° with respect to the normal direction of the reflective film. Retroreflectivity in the direction forming the angle was improved, and the haze value could be suppressed to 10% or less.

[Production of optical member: formation of information presentation layer]
Carbon ink was apply | coated to the surface of Cosmo Shine A-4100 of each reflective film produced above. The coated surface was irradiated with infrared light having a YVO ₄ laser (wavelength: 1064 nm) beam diameter of 10 μm, and a predesigned dot pattern was formed by printing evaporation. That is, the carbon ink was removed according to the designed dot pattern.

1-1 Circular Polarized Reflective Layer 1-2 Circular Polarized Reflective Layer (1-1 reverse sense with circular polarized reflective layer)
5 Base material 11 Information presentation layer

Claims (16)

A reflective film,
Reflects light in the infrared wavelength range,
Including a circularly polarized light reflection layer composed of a layer in which a cholesteric liquid crystal phase is fixed;
The circularly polarized reflective layer includes particles,
The reflective film having an average particle diameter of 0.5 μm or more and less than a film thickness of the circularly polarized reflective layer. The reflective film according to claim 1, wherein the particles are organic particles. The reflective film according to claim 1, wherein the particles are poly (meth) acrylate particles. The reflection film according to any one of claims 1 to 3, wherein a haze value is 10% or less. The reflective film according to any one of claims 1 to 4, wherein the circularly polarized light reflective layer is a layer formed from a liquid crystal composition containing the particles, a liquid crystal compound, a chiral agent, and a horizontal alignment agent. The circularly polarized light reflecting layer includes a right circularly polarized light reflecting layer that selectively reflects right circularly polarized light and a left circularly polarized light reflecting layer that selectively reflects left circularly polarized light,
The reflective film according to any one of claims 1 to 5, wherein the center wavelength of circularly polarized light selective reflection of the right circularly polarized light reflecting layer and the left circularly polarized light reflecting layer is the same. The reflective film as described in any one of Claims 1-6 containing a base material. The reflective film according to claim 1, wherein the direct transmittance of non-polarized visible light is 50% or more. An optical member comprising the reflective film according to any one of claims 1 to 8 and an information presentation layer,
The information presentation layer is an optical member having a pattern of a material that absorbs or reflects light reflected by the reflective film. The optical member according to claim 9, wherein the pattern is a dot pattern. The optical member according to claim 9 or 10, wherein the pattern is formed by printing. The reflective film includes a substrate;
The optical member according to any one of claims 9 to 11, comprising the circularly polarizing reflection layer, the base material, and the information presentation layer in this order. The reflective film includes a substrate;
The optical member according to any one of claims 9 to 11, comprising the base material, the circularly polarized light reflecting layer, and the information presentation layer in this order. The reflective film includes a substrate;
The optical member according to any one of claims 9 to 13, wherein the pattern is formed on the surface of the base material by printing. The display which has the optical member as described in any one of Claims 9-14. An image display device comprising the display according to claim 15.