JP6582470B2 - Optical film and image display device - Google Patents

Description

  The present invention is applicable to an electronic pen input system that detects input coordinates using a dot pattern and inputs various types of information, and is applicable to an electronic pen input system configured to directly handwritten on the screen of a display device. About.

  2. Description of the Related Art Conventionally, an electronic pen input system that detects input coordinates using a dot pattern and inputs various types of information has been provided. As a typical example, an annot pen (Anoto (registered trademark) pen) developed by Anoto in Sweden has been provided. Electronic pen input systems are known.

  With regard to such an electronic pen input system, Patent Document 1 discloses a display by pattern-printing a layer that absorbs near infrared rays or ultraviolet rays on a film that transmits visible light and diffusely reflects near infrared rays or ultraviolet rays. There has been proposed an optical film applicable to an electronic pen input system of a type in which handwriting is directly performed on the screen of the apparatus.

  Patent Document 2 discloses a configuration of a reflector that can appropriately reflect and display white light by changing the spiral axis direction of the cholesteric liquid crystal in each region. Patent Document 3 discloses a configuration in which a diffuse reflection layer is formed with a cholesteric liquid crystal layer in a wave-like state.

  In the case of an input system in which handwriting is directly performed on the screen of the display device, it is considered that it will become more popular in the future. Accordingly, it is desired that an optical film applicable to such an input system can be easily created with a simpler configuration than in the past.

JP 2008-209598 A JP 2003-215342 A JP 2005-107296 A

  The present invention has been made in view of such a situation, and an optical film applicable to an electronic pen input system that detects input coordinates by a dot pattern and inputs various types of information is much simpler than conventional ones. An object of the present invention is to provide an optical film that can be easily produced with a simple structure.

  The present inventor has intensively studied to solve the above problems, and at least one surface of the translucent film material is made a rough surface, and a cholesteric liquid crystal layer is directly formed on the rough surface to perform diffuse reflection. The idea of producing a reflective layer made of a cholesteric liquid crystal layer on the other surface was completed, and the present invention was completed.

  Specifically, the present invention provides the following.

(1) An optical film that is transparent in the visible light region and diffusely reflects near infrared rays,
A substrate made of a translucent film material having at least one surface is a rough surface;
A diffuse reflection layer made of cholesteric liquid crystal produced on the rough surface of the substrate;
An optical film comprising: a reflective layer made of cholesteric liquid crystal formed on a surface opposite to the rough surface of the substrate.

  According to (1), by effectively utilizing the characteristics of cholesteric liquid crystals that selectively reflect near-infrared rays, the near-infrared rays can be obtained by a simple configuration and process that directly produces a liquid crystal layer of cholesteric liquid crystals on a rough surface. An optical film that diffusely reflects and transmits visible light can be provided. Further, the diffuse reflection layer made of cholesteric liquid crystal reflects only the right circularly polarized light or the left circularly polarized light, and transmits the left circularly polarized light or the right circularly polarized light in the opposite direction. Circularly polarized light can be reflected by the reflection layer formed on the opposite surface and incident on the diffuse reflection layer. This makes it possible to diffusely reflect near infrared rays more efficiently.

(2) In (1),
The surface opposite to the rough surface of the substrate is a rough surface,
An optical film in which the reflective layer formed on the opposite surface is a reflective layer that diffusely reflects near infrared rays.

  According to (2), since the reflective layer is a reflective layer that diffusely reflects near-infrared rays, the near-infrared rays can be diffusely reflected more efficiently without impairing the transmission of visible light. In addition, since the base of the reflective layer is a rough surface, the reflective layer that diffusely reflects near-infrared light can be manufactured by a simple configuration and process that directly forms a liquid crystal layer of cholesteric liquid crystal on the rough surface. it can.

  (3) In (1) or (2), the rough surface according to the diffuse reflection layer has an arithmetic average roughness Ra of 0.01 μm or more and 1 μm or less.

  According to (3), an optical film that diffusely reflects near infrared rays and transmits visible light can be provided with a more specific configuration.

(4) In any one of (1), (2) and (3),
An optical film with a dot pattern made of dots that absorb near infrared rays.

(5) In any one of (1), (2) and (3),
An optical film laminated with a dot pattern film in which a dot pattern with dots that absorb near infrared rays is produced.

  According to (4) or (5), the present invention can be applied to an electronic pen input system that detects input coordinates using a dot pattern and inputs various information, and for example, an electronic pen configured to be handwritten directly on the screen of a display device An optical film applicable to the input system can be provided.

  (6) An image display device in which the optical film according to (4) or (5) is disposed on a panel surface of an image display panel.

  According to (6), it is an electronic pen input system that uses an optical film with a simple configuration and process, detects input coordinates by a dot pattern, and inputs various information, and has a configuration in which handwriting is directly performed on the screen. An image display apparatus according to an electronic pen input system can be provided.

  The present invention relates to an optical film that can be applied to an electronic pen input system that inputs various information by detecting input coordinates using a dot pattern, and can be easily created with a simpler configuration than in the past. Can be provided.

It is a figure which shows the image display apparatus which concerns on 1st Embodiment of this invention. It is a figure which shows the optical film which concerns on the image display apparatus of FIG. It is a figure which shows the measurement result of the optical characteristic of the comparative example 1 of the diffuse reflection film which concerns on this invention. It is a figure which shows the reflectance by diffuse reflection in the measurement result of FIG. It is a figure which shows the measurement result of FIG. 4 in detail. It is a figure which shows the measurement result of the optical characteristic of the comparative example 2 of the diffuse reflection film which concerns on this invention. It is a figure which shows the measurement result of FIG. 6 in detail. It is a figure which shows the optical characteristic of Example 1-1 of the diffuse reflection film which concerns on this invention. It is a figure which shows the optical characteristic of Example 1-2 of the diffuse reflection film which concerns on this invention. It is a figure which shows the optical characteristic of Example 2 of the diffuse reflection film which concerns on this invention. It is a figure which shows the reflectance by diffuse reflection in the measurement result of FIG. It is a figure which shows the measurement result of FIG. 11 in detail. It is a figure which shows the optical characteristic of Example 3 of the diffuse reflection film which concerns on this invention. It is a figure which shows the measurement result of the comparative example 3. It is a figure which shows the reflectance by diffuse reflection in the measurement result of FIG. It is a figure which shows the measurement result of FIG. 15 in detail. It is a figure which shows the optical characteristic of Example 4 of the diffuse reflection film which concerns on this invention. It is a figure which shows the measurement result of FIG. 17 in detail. It is a figure which shows the measurement result of the comparative example 4. It is a figure which shows the reflectance by diffuse reflection in the measurement result of FIG. It is a figure which shows the measurement result of FIG. 20 in detail. It is a figure which shows the optical characteristic of Example 5 of the diffuse reflection film which concerns on this invention. It is a figure which shows the measurement result of FIG. 22 in detail. It is a figure which shows the measurement result of the comparative example 5. It is a figure which shows the reflectance by diffuse reflection in the measurement result of FIG. It is a figure which shows the measurement result of FIG. 25 in detail. It is a figure which shows the measurement result of the comparative example 6. It is a figure which shows the reflectance by diffuse reflection in the measurement result of FIG.

[First Embodiment]
FIG. 1 is a diagram showing an image display apparatus according to the first embodiment of the present invention. In this image display device 1, an optical film 3 related to an electronic pen input system is arranged on a panel surface (viewer side surface) of an image display panel 2, and an electronic pen input system is configured with a corresponding electronic pen or the like. .

  Here, the electronic pen input system is an electronic pen input system that detects input coordinates using a dot pattern and inputs various kinds of information, and is an electronic pen input system configured to directly handwritten on the screen of a display device. In this embodiment, the electronic pen input system transmits a near infrared ray for illumination from a corresponding electronic pen, and obtains and processes an imaging result of the reflected light of the near infrared ray with the electronic pen. A dot pattern provided on the film 3 is detected to detect input coordinates, thereby allowing data input by handwriting without any loss of viewing of the display image on the image display panel 2. Here, near infrared rays are electromagnetic waves having a wavelength of about 0.7 μm to 2.5 μm.

  Here, the image display panel 2 can widely apply various configurations such as a liquid crystal display panel and an organic EL image display panel. In addition, the electronic pen transmits a near infrared ray to illuminate a part that is in contact with the pen tip, an imaging unit that acquires an imaging result of the part that is in contact, and processes an imaging result acquired by the imaging unit A data processing circuit or the like for detecting the input coordinates of the pen tip from the dot pattern detected from the imaging result is provided.

[Optical film]
As shown in FIG. 2, the optical film 3 is produced by laminating a dot pattern film 4 and a diffuse reflection film 5 with a transparent adhesive such as an ultraviolet curable resin, and the diffuse reflection film 5 side is the image display panel 2. Is arranged on the panel surface of the image display panel 2 with a pressure sensitive adhesive, an adhesive made of an ultraviolet curable resin, or the like.

  Here, the dot pattern film 4 is a film in which a dot pattern that is transparent in the visible light range and selectively absorbs near infrared rays is formed. The diffuse reflection film 5 is a film that is transparent in the visible light range and diffusely reflects near infrared rays. As a result, the optical film 3 diffuses and reflects the near-infrared light for illumination from the electronic pen transmitted through the dot pattern film 4 by the diffuse reflection film 5 and selects the diffusely reflected near-infrared light by the dot pattern of the dot pattern film 4. Absorb. As a result, the optical film 3 is configured so that the dot pattern formed by the dot pattern film 4 can be photographed on a bright background of near infrared light diffusely reflected by the diffuse reflection film 5, and the input coordinates are detected by reliably detecting the dot pattern. Configured to be able to. Further, since it is transparent in the visible light range, it is configured so that the input coordinates can be reliably detected without causing any obstacle to the image display by the image display panel 2.

[Dot pattern film]
Here, the dot pattern film 4 is formed by printing the dots 7 which are relatively transparent in the visible light range and selectively absorb near infrared rays on the base material 8 made of a transparent film material. The image display by 2 is formed so as to absorb the near-infrared light for illumination from the electronic pen by this dot pattern without causing any obstacle.

  Here, the transparent film material according to the substrate 8 is disposed on the panel surface of the image display panel 2 such as a TAC (triacetyl cellulose) film material, a COP (cycloolefin polymer) film material, or a PET (polyethylene terephthalate) film material. The transparent film material applied to various optical films can be widely applied. The near-infrared absorber is relatively transparent in the visible light range, can absorb various near-infrared rays efficiently, and can be widely applied to various materials that can be printed on a transparent film material. Diimonium-based, phthalocyanine-based, cyanine-based compounds and the like can be used. Moreover, the printing method of the dot 7 is not specifically limited, A well-known method can be used, For example, a flexographic printing method, a gravure printing method, a stencil printing method, an ink jet printing method etc. can be applied. In addition, as for the dot pattern film 4, protective layers, such as a hard-coat layer, are produced in the outermost surface as needed.

  In addition, you may make it abbreviate | omit the base material 8 by producing a dot pattern on the surface of the diffuse reflection film 5 directly by the transfer method, printing, etc. Here, the transfer method means that, for example, when a desired layer is formed on a base material, the layer is not directly formed on the base material, but can be peeled once on a releasable support. After producing the transfer body by laminating the layers, according to the process, demand, etc., the layer formed on the support is finally placed on the substrate (transferred substrate) on which the layer is to be laminated. In this method, a desired layer is formed on the substrate by peeling and removing the support.

[Diffusion reflection film]
In the diffuse reflection film 5, the diffuse reflection layer 9 is provided on the surface on the dot pattern film 4 side, which is one surface of the substrate 10, and the reflection layer 11 is provided on the other surface of the substrate 10. The diffuse reflection layer 9 is a reflection layer that is transparent in the visible light range and selectively diffusely reflects near infrared rays. On the other hand, the reflective layer 11 is transparent in the visible light region and is a reflective layer that selectively reflects near infrared rays. In the diffuse reflection film 5, one surface of the substrate 10 is formed by a rough surface M, and a coating liquid is directly applied to the rough surface M, followed by drying and curing, thereby forming a liquid crystal layer of cholesteric liquid crystal. Thereby, the diffuse reflection layer 9 is produced. Further, a coating liquid similar to that of the diffuse reflection layer 9 is directly applied to the other surface of the substrate 10 and dried and cured to form a liquid crystal layer of cholesteric liquid crystal, whereby the reflection layer 11 is produced. .

  Here, it is well known that the liquid crystal layer made of cholesteric liquid crystal has a helical structure (cholesteric structure), is transparent in the visible light range, and selectively reflects near infrared rays. A liquid crystal layer made of such a liquid crystal material is produced on an uneven surface by aligning the liquid crystal material by the alignment regulating force of the alignment layer, as disclosed in, for example, JP-A-2003-215342. Accordingly, the near-infrared diffuse reflection can be achieved by variously changing the central axis direction (helical axis direction) related to the helical structure of the liquid crystal material. However, in the case of producing a diffuse reflection layer in this way, the configuration of the alignment layer is required, which not only complicates the configuration and process, but also causes the cloudiness in the visible light region if the spiral axis direction is extremely varied. It became clear that there was difficulty in application to a display etc. by becoming visible.

  Therefore, in this embodiment, the diffuse reflection film 5 has the surface of the substrate 10 as a rough surface M, and a coating liquid of cholesteric liquid crystal is directly applied to the rough surface M, followed by drying and curing. Produced. Here, when the liquid crystal layer is prepared by directly applying the cholesteric liquid crystal coating liquid onto the substrate 10 in this way, and the coated surface is a flat surface, the helical axis of the liquid crystal material related to the liquid crystal layer The direction is almost in the normal direction.

  However, when the coated surface is a rough surface M, it has been found that it exhibits diffuse reflectivity with respect to near infrared rays. This is considered to be due to the fact that the spiral axis direction of the liquid crystal material causes fluctuations according to the rough surface M and the influence of reflection from the rough surface M. As a result, the diffuse reflection film 5 is transparent in the visible region and emits near-infrared light by simply applying a coating liquid to the base material 10 having a rough surface to produce a liquid crystal layer made of a liquid crystal material. It is configured so that it can be selectively diffusely reflected.

  Particularly in this embodiment, since the cholesteric liquid crystal reflective layer 11 is also provided on the other surface of the base material 10, the diffuse reflective film 5 is simply compared with the case where only the diffuse reflective layer 9 is provided. Thus, it is possible to efficiently diffuse and reflect near infrared rays with a higher reflectance without impairing the transmission of visible light.

  That is, the cholesteric liquid crystal reflects right circularly polarized light or left circularly polarized light in a specific wavelength region λ represented by λ = n · p (λ is a wavelength, n is a refractive index, and p is a repeating pitch of a helical structure). It has the optical property of transmitting left circularly polarized light or right circularly polarized light that is opposite to the circularly polarized light that is used for reflection. Accordingly, if the diffuse reflection layer 9 on the dot pattern film 4 side reflects the right circularly polarized light in a specific wavelength region, the incident light of the left circularly polarized light is transmitted through the diffuse reflective layer 9. However, in the diffuse reflection film 5, the transmitted circularly polarized light is reflected by the reflective layer 11 and diffused by the rough surface M and the diffuse reflective layer 9, thereby further diffusely reflecting near infrared rays.

  Here, the light transmitted through the diffuse reflection layer 9 and incident on the reflection layer 11 is changed in polarization according to the retardation value of the substrate 10. Therefore, it is desirable to configure the reflective layer 11 so as to efficiently reflect the incident light due to the changed polarization.

  Specifically, when the value of retardation of the substrate 10 is near 0 or an integer multiple of the specific wavelength λ (nλ (n is 0 or an integer)), for example, when the specific wavelength λ is 900 nm. When the diffuse reflection layer 9 reflects the right circularly polarized light in this specific wavelength region, the reflection layer 11 has a retardation value of around 0 nm, around 900 nm, around 1800 nm, around 2700 nm, around 3600 nm,. Those having the optical property of reflecting the left circularly polarized light in this specific wavelength region are preferable. Note that the vicinity here refers to a range of ½ or less of the wavelength λ. For example, when the wavelength λ is 900 nm, the range is 900 nm ± 450 nm.

  When the retardation value of the substrate 10 is λ / 2 + nλ (n is 0 or an integer) (for example, when the specific wavelength λ is 900 nm, the retardation value is around 450 nm, around 1350 nm, around 2250 nm,... In the case where the diffuse reflection layer 9 reflects the right circularly polarized light in this specific wavelength region, the reflective layer 11 similarly has an optical property of reflecting the right circularly polarized light in this specific wavelength region. Those are preferred.

  Further, the transmitted light of the diffuse reflection layer 9 incident on the reflection layer 11 is already diffused and incident by the rough surface M of the diffuse reflection layer 9 and the base material 10, and this also reflects the reflection of the reflection layer 11. The light is sufficiently diffused with respect to the incident light of the diffuse reflection film 5, and the diffuse reflection film 5 can also efficiently diffuse and reflect near infrared rays.

  Furthermore, in this embodiment, the diffuse reflection film 5 is formed by the same rough surface M as the side surface of the diffuse reflection layer 9 even on the other surface of the base material 10 on the reflective layer 11 side of the base material 10. Thus, the reflection layer 11 is configured to function as a diffuse reflection layer that diffusely reflects near infrared rays. Thus, by making the reflective layer on the other surface side function as a diffuse reflective layer, the diffuse reflective film 5 can diffuse and reflect near infrared rays more efficiently.

  In this case, when a sufficient amount of diffusely reflected light can be secured in practice, the other surface of the substrate 10 may be a smooth surface and the reflective layer 11 may not function as a diffusely reflective layer.

  Here, when the roughness of the rough surface M is too rough, the display screen of the image display panel 2 is seen as blurred, thereby reducing the sharpness of the display screen and degrading the image quality. On the other hand, if the rough surface M does not have a sufficient roughness, the efficiency of diffuse reflection in the near-infrared region is reduced. In the electronic pen input system according to this embodiment, imaging is performed. As a result, a sufficient luminance ratio cannot be secured between the dot pattern and the background, and the position detection accuracy of the input coordinates is lowered.

  Accordingly, the roughness of the rough surface M is desirably an arithmetic average roughness Ra of 0.01 μm or more and 1 μm or less, more preferably 0.01 μm or more and 0.5 μm or less. The ten-point average roughness Rz is 0.05 μm or more and 3 μm or less, more preferably 0.1 μm or more and 1.5 μm or less. The arithmetic average roughness Ra and the ten-point average roughness Rz are based on JIS B 0601 (1994). Further, the roughness of the rough surface M may be different between the diffuse reflection layer 9 side and the reflection layer 11 side.

  By the way, the optical film 3 also needs to satisfy the haze value required for the film material disposed in this kind of image display panel. However, from the viewpoint of sufficiently ensuring the efficiency of diffuse reflection, it is necessary to sufficiently secure the roughness of the rough surface M. As a result, the optical film 3 has an increased haze value. However, when the diffuse reflection layer 9 and the reflection layer 11 are produced by applying a coating solution to the rough surface M, the haze value due to the rough surface M is lower than when the base material 10 is measured alone. . Thereby, the base material 10 has a haze value of 80 or less and 5 or more, preferably 40 or less and 5 or more, and more preferably 20 or less and 5 or more. The haze value after coating the coating liquid on the rough surface M is 20 or less and 1 or more, but when it is desired to make the image clearer, it is more preferably 10 or less and 0.5 or more. Thereby, the diffuse reflection film 5 is made to have a transmittance of 80% or more due to straight light and diffused light in the visible light region (wavelength range of 400 nm to 750 nm). In addition, the reflectance is 0.2% or more when incident at an angle of 5 degrees with respect to the normal and received at an angle of 60 degrees with respect to the normal.

  In addition, by making a coating surface into a rough surface in this way, the repellency of the coating liquid at the time of coating the coating liquid which concerns on the diffuse reflection layer 9 and the reflection layer 11 can also be reduced.

〔Base material〕
Here, the translucent film material according to the substrate 10 is a TAC (triacetyl cellulose) film material, a COP (cycloolefin polymer) film material, a PET (polyethylene terephthalate) film material, or the like on the panel surface of the image display panel 2. The translucent film material applied to the various optical films to be disposed can be widely applied.

  In the rough surface M according to the base material 10, in the case of roughening treatment by sandblasting, the base material is heated and pressed on a flat plate, a roll plate, or the like formed on the surface with a fine uneven shape corresponding to the rough surface M. In the case of producing a rough surface, various roughening treatments can be widely applied, for example, by etching. The roughening treatment by etching is represented by, for example, the case of etching a PET film with an alkaline solution (so-called chemical etching). Moreover, you may make it produce the rough surface M by mixing a filler in resin which comprises the base material 10. FIG.

  Moreover, it may replace with such a direct roughening process of the base-material surface, and you may make it provide the rough surface layer provided with the rough surface. Here, such a rough surface layer can be produced by a shaping process using a shaping resin layer. In addition, various types of antireflection layers applied to the antireflection film can be applied to such a rough surface layer. More specifically, as an antireflection layer having such a rough surface, in the case of embossing, when the surface is roughened by mixing light-transmitting fine particles, the solid component in the coating liquid is agglomerated. When making the surface uneven (so-called chemical matte surface), press the substrate coated with UV curable resin on a plate-shaped or roll-shaped mold with a lot of fine recesses to make the recess shape convex Various methods such as a transfer method (so-called shaping) can be widely applied.

(Diffuse reflection layer)
The diffuse reflection layer 9 is produced by coating, drying and curing a corresponding coating solution. Here, when the diffuse reflection layer 9 is thin, the fine uneven shape related to the rough surface M is likely to appear on the surface, and as a result, the display screen of the image display panel 2 is seen as blurred. As a result, the sharpness of the display screen decreases and the image quality deteriorates. On the other hand, if the thickness is too thick, the efficiency of diffuse reflection will decrease, and the position detection accuracy of the input coordinates will decrease in the electronic pen input system according to this embodiment. Therefore, the diffuse reflection layer 9 is formed with a thickness of 0.5 μm to 20 μm, more preferably 1 μm to 10 μm, and still more preferably 1 μm to 5 μm.

  The diffuse reflection layer 9 is made of a composition that reflects electromagnetic waves in the near-infrared wavelength region, and this composition contains a nematic liquid crystal having nematic regularity and a chiral agent having a turning property with respect to the nematic liquid crystal. . Further, the composition may contain a leveling agent, a polymerization initiator, an additive and the like.

(Nematic liquid crystal)
The nematic liquid crystal is not particularly limited as long as it is a liquid crystal material capable of forming a nematic liquid crystal structure, but it is polymerized at one or both ends of the molecule in that an optically stable diffuse reflection layer can be obtained after curing. A liquid crystal material having a functional group is preferable. A liquid crystal material having a polymerizable functional group at both ends is excellent in that the reliability upon heating is good, but the temperature range of the liquid crystal phase before coating and evaporating the solvent to cure (crosslink) In view of mass productivity, it is preferable to use a mixed material of a liquid crystal material having a polymerizable functional group at one end and a liquid crystal material having a polymerizable functional group at both ends.

Examples of such a liquid crystal material include compounds represented by the following formulas (2-i) to (2-xii) in addition to the compounds represented by the following general formula (1). These compounds can be used alone or in combination.

  In the general formula (1), R1 and R2 each represent hydrogen or a methyl group, but it is preferable that both R1 and R2 are hydrogen because of the wide temperature range showing the liquid crystal phase. X may be hydrogen, chlorine, bromine, iodine, an alkyl group having 1 to 4 carbon atoms, a methoxy group, a cyano group, or a nitro group, but is preferably a chlorine or methyl group. Moreover, in the said General formula (1), a and b which show the chain length of the alkylene group which is a spacer of the (meth) acryloyloxy group and aromatic ring of both ends of a molecular chain are arbitrary in the range of 2-12, respectively. Although it can take an integer, it is preferably in the range of 4 to 10, and more preferably in the range of 6 to 9. If a = b = 0, the stability is poor, the compound is easily hydrolyzed, and the compound itself has high crystallinity, which is not preferable because the temperature range showing the liquid crystal phase is narrow. Further, when either a or b is 13 or more, the isotropic transition temperature (TI) is low, which is not preferable in that the temperature range showing the liquid crystal phase is narrow.

(Chiral agent)
A chiral agent is a low molecular compound having an optically active site, and is mainly a compound having a molecular weight of 1500 or less. The chiral agent is mainly used for the purpose of inducing a helical structure in the positive uniaxial nematic regularity exhibited by the polymerizable liquid crystal material exhibiting nematic regularity. As long as this purpose is achieved, it is compatible with a polymerizable liquid crystal material exhibiting nematic regularity in a solution state or a molten state, without impairing the liquid crystal property of the polymerizable liquid crystal material exhibiting nematic regularity, The kind of the low molecular compound as the chiral agent is not particularly limited as long as it can induce a desired helical structure.

  Note that the chiral agent used for inducing the helical structure in the liquid crystal in this way needs to have at least some chirality in the molecule. Accordingly, the chiral agent used herein includes, for example, a compound having one or more asymmetric carbons, a compound having an asymmetric point on a heteroatom such as a chiral amine or a chiral sulfoxide, or cumulene. And compounds having an optically active site having axial asymmetry such as binaphthol.

However, depending on the nature of the selected chiral agent, the nematic regularity formed by the polymerizable liquid crystal material exhibiting nematic regularity, the degradation of orientation, or the liquid crystal material when the chiral agent is non-polymerizable There is a risk of lowering the curability of the film and lowering the reliability of the cured film. Further, the use of a large amount of a chiral agent having an optically active site causes an increase in the cost of the liquid crystal material. Therefore, when forming a selective reflection layer having a cholesteric regularity with a short helical pitch length, a chiral agent having a large effect of inducing a helical structure is selected as a chiral agent having an optically active site to be contained in the liquid crystal material. Specifically, axial asymmetry is represented in the molecule as represented by the following general formula (3), (4), (5), (6), (7) or (8). It is preferable to use a low molecular weight compound.

In the general formula (3) or (4), R4 represents hydrogen or a methyl group. Y is any one of formulas (i) to (xxiv) shown below, and among them, any one of formulas (i), (ii), (iii), (v) and (vii) Preferably there is. Moreover, although c and d which show the chain length of an alkylene group can each take arbitrary integers in the range of 2-12, it is preferable that it is the range of 4-10, and is the range of 6-9. Is more preferable. When the value of c or d is 0 or 1, since it lacks stability, is susceptible to hydrolysis, and has high crystallinity, compatibility with a polymerizable liquid crystal material exhibiting nematic regularity decreases, Depending on the concentration, phase separation is not preferable. On the other hand, when the value of c or d is 13 or more, the melting point (Tm) is low, so the compatibility with the polymerizable liquid crystal material exhibiting nematic regularity is lowered, and phase separation may occur depending on the concentration. This is not preferable.

  Such a chiral agent is not particularly required to have polymerizability. However, when the chiral agent has polymerizability, it is polymerized with a polymerizable liquid crystal material exhibiting nematic regularity, and the cholesteric regularity is stably fixed, which is preferable in terms of thermal stability and the like. In particular, it is preferable to have a polymerizable functional group at both ends of the molecule in order to obtain a selective reflection layer having good heat resistance.

(Leveling agent)
The leveling agent is used to promote the formation of a cholesteric structure of the liquid crystal material. The leveling agent is not particularly limited as long as it can promote the cholesteric alignment of the liquid crystal material in the diffuse reflection layer, and examples thereof include a silicon compound, a fluorine compound, and an acrylic compound. As a commercially available leveling agent, BYK-361N manufactured by Big Chemie Japan, S-241 manufactured by AGC Seikagaku Co., etc. can be used. The leveling agent may be one kind or two or more kinds.

  The content of the leveling agent is not particularly limited as long as it is within a range in which the cholesteric structure of the liquid crystal material can be formed with a desired regularity, but 0.01 parts by mass or more with respect to 100 parts by mass of the composition. The content is preferably 0 part by mass or less, and more preferably 0.03 part by mass or more and 1.0 part by mass or less. If it is less than 0.01 parts by mass, the cholesteric structure cannot be obtained with the desired regularity, which is not preferable. If it exceeds 5.0 parts by mass, the cholesteric structure cannot be obtained with the desired regularity, which is not preferable.

(Polymerization initiator)
The polymerization initiator is used to crosslink a liquid crystal material in which a cholesteric structure is formed by the action of a chiral agent and a leveling agent while maintaining the cholesteric structure so that the cholesteric structure is hardly disturbed. The polymerization initiator is not particularly limited as long as it can accelerate the polymerization reaction of the liquid crystal material, and may be appropriately selected according to the type of energy to be irradiated. Examples of the polymerization initiator include a photopolymerization initiator and a thermal polymerization initiator. Moreover, when a polymerization initiator is contained, the amount of the polymerization initiator is not particularly limited as long as a desired polymerization reaction occurs, and may be appropriately determined.

(solvent)
Further, in order to disperse the liquid crystal material, the chiral agent, the leveling agent, and the polymerization initiator, the composition is usually dispersed in a solvent. The solvent is not particularly limited as long as it can disperse the above-mentioned components, and examples thereof include cyclohexanone. In order to improve the drying speed, a solvent such as toluene, MEK, MIBK or the like is appropriately mixed. You may let them.

(Reflective layer)
In the diffuse reflection film 5 according to this embodiment, the reflective layer 11 functions as a diffuse reflective layer, so that the coating liquid is directly applied to the rough surface M of the substrate 10 in the same manner as the diffuse reflective layer 9. And then dried and cured. In addition, although process control can be simplified by producing with the same coating liquid as the diffuse reflection layer 9 by this, in the diffuse reflection film 5, after producing the diffuse reflection layer 9, the reflection layer 11 is produced. By manufacturing the reflective layer 11 or, on the contrary, by manufacturing the diffusive reflective layer 9, the coating liquid can be variously adjusted according to the manufacturing process, and manufactured. The damage of the diffuse reflection layer 9 and the reflection layer 11 in the process can be reduced. Moreover, you may produce with the material different from the diffuse reflection layer 11 from a viewpoint of reflecting the transmitted light of the diffuse reflection layer 11 mentioned above efficiently.

  Even when the other surface of the substrate 10 is made of a smooth surface and the reflective layer 11 is not given a diffuse reflection function, the reflective layer 11 preferably has a thickness of 0.5 μm or more and 20 μm in order to increase the reflectance. It is produced by the following, more preferably from 1 μm to 10 μm, and still more preferably from 1 μm to 5 μm.

〔Manufacturing process〕
The optical film 3 is manufactured through the following steps.

[Manufacturing process of dot pattern film]
(Dot pattern printing process)
This manufacturing process is performed by, for example, using a flexographic printing method, a gravure printing method, a stencil printing method, an ink jet printing method, etc. To print. Moreover, after producing protective layers, such as a hard-coat layer, as needed, it winds up on a roll and conveys to the following process.

[Manufacturing process of diffuse reflection film]
(Rough surface production process)
This manufacturing process roughens both surfaces of the base material 10 by, for example, sandblasting, while the base material 10 having a long film shape provided by the roll is pulled out from the roll and conveyed. In addition, in the case of producing a rough surface by heating and pressing a substrate on a flat plate, a roll plate or the like formed with a fine uneven shape corresponding to the rough surface M on the surface, in the case of etching, etc., it is replaced with a sand blast treatment. Thus, these processes are performed. Moreover, when producing a rough surface layer, the process of coating, drying, and hardening the coating liquid by the material corresponding to the various structure mentioned above is performed instead of a sandblasting process. Further, according to these roughening methods, the manufacturing process simultaneously roughens both surfaces, and roughens one surface at a time according to the roughening treatment, or produces the diffuse reflection layer 9 or the reflective layer 11. Then, the remaining surface of the substrate 10 is roughened. Moreover, when not making the reflective layer 11 function as a diffuse reflection layer, a manufacturing process roughens only one surface of the base material 10. FIG.

(Liquid crystal layer production process (diffuse reflection layer production process))
Then, the manufacturing process of the optical film 3 applies the coating liquid which concerns on the diffuse reflection layer 9, Then, it dries and hardens and the diffuse reflection layer 9 is produced. Here, various coating methods can be widely applied to the coating liquid coating, for example, slot die coating method, roll coating method, bar coating method, spin coating method, blade coating method and the like. it can.

  Here, drying after coating is performed in order to remove the solvent contained in the coating liquid, but the spectral curve changes depending on the drying temperature. If the drying temperature is low, not only the solvent is not sufficiently evaporated, but the liquid crystal alignment state is incomplete. On the other hand, when the drying temperature is high, the cholesteric phase shifts to an isotropic phase. Therefore, the drying temperature is preferably more than 65 ° C. and less than 120 ° C., more preferably more than 70 ° C. and less than 100 ° C. from the viewpoint of securing the intended characteristics.

  Curing after drying is performed by irradiation with electromagnetic waves, more specifically by irradiation with ultraviolet rays. A liquid crystal material that has formed a cholesteric structure by the action of a chiral agent and a leveling agent by this irradiation maintains the cholesteric structure. This is because the cholesteric structure is hardly disturbed by crosslinking as it is.

  The electromagnetic wave is preferably light having a wavelength range of 200 to 450 nm, and more preferably light having a wavelength range of 300 to 450 nm. The light source for supplying this light is not particularly limited. For example, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a carbon arc lamp, a mercury vapor arc, a fluorescent lamp, an argon glow lamp, a halogen lamp, an incandescent lamp, a low pressure mercury lamp, a flash Examples thereof include a UV lamp, a deep UV lamp, a xenon lamp, a tungsten filament lamp, and sunlight. By using these light sources and irradiating light so that the integrated light amount is in the range of 25 mJ / cm2 to 800 mJ / cm2, preferably 25 mJ / cm2 to 400 mJ / cm2, more preferably 50 mJ / cm2 to 200 mJ / cm2, The diffuse reflection layer 9 can be cured. If the integrated light amount is less than 25 mJ / cm 2, the polymerization of the liquid crystal material becomes insufficient, and as a result, the cholesteric structure of the liquid crystal material can be disturbed, which is not preferable. If it exceeds 800 mJ / cm 2, the leveling agent may appear on the surface of the diffuse reflection layer, which is not preferable.

(Reflection layer production process)
Subsequently, in the manufacturing process, the coating liquid related to the reflective layer 11 is directly applied to the other surface of the substrate 10 in the same manner as the diffuse reflective layer 9, and then dried and cured to produce the reflective layer 11. At this time, as described above, in the manufacturing process, a roughening process is performed in advance as necessary.

  In addition, after manufacturing the diffuse reflection layer 9 in this way, instead of the configuration in which the reflective layer 11 is manufactured, the reflective layer 11 may be manufactured and then the diffuse reflection layer 9 may be manufactured.

(Lamination process)
While transporting the dot pattern film produced in the manufacturing process of the dot pattern film and the diffuse reflection film produced in the manufacturing process of the diffuse reflection film, the coating liquid of the ultraviolet curable resin is applied to one film material. After drying, they are laminated and integrated by irradiation with ultraviolet rays. Then, after producing the adhesive bond layer used for arrangement | positioning to the image display panel 2, a separator film is arrange | positioned, it cuts to a desired magnitude | size, and the optical film 3 is produced.

  As a result, in the optical film 3, a transparent diffuse reflection film that selectively diffuses and reflects only near infrared rays is produced simply by producing a liquid crystal layer of cholesteric liquid crystal on a transparent film material having a rough surface. Accordingly, it is possible to provide an optical film applicable to a data input system of a type in which handwriting is directly performed on the screen of the display device with a simpler configuration and process than in the past.

  Although the Example and comparative example of the diffuse reflection film 5 which comprise the optical film 3 are explained in full detail below, this invention is not limited to a following example.

[Comparative Example 1]
The comparative example 1 is a configuration in which only the diffuse reflection layer 9 is prepared on the base material 10 and the reflection layer 11 is not prepared, and was prepared for confirmation of diffuse reflection by the diffuse reflection layer 9.

[Preparation of coating solution]
95.3 parts by mass of a liquid crystal material having a polymerizable acrylate at both ends and a spacer between the mesogen and acrylate at the center, and a right-turning chiral agent having a polymerizable acrylate at both ends ( (Product name: CNL-715, manufactured by ADEKA) 4.03 parts by mass was dissolved in 500 parts by mass of the cyclohexanone solution to prepare a coating solution for use in preparing the diffuse reflection layer. At this time, the cyclohexanone solution contains 5.0 parts by mass of a photopolymerization initiator (trade name: Irgacure 184, manufactured by BASF), 100 parts by mass of the liquid crystal monomer molecules and the chiral agent, and the liquid crystal monomer molecules and It contained 0.03 parts by mass of a leveling agent (trade name: BYK-361N, solid content: 30% by mass, manufactured by Big Chemie Japan) with respect to 100 parts by mass of the chiral agent in total.

In addition, the compound represented by the following structural formula was used for the liquid-crystal material used for coating of the coating liquid.

The chiral agent is a compound represented by the following structural formula.

[Formation of diffuse reflection layer]
Subsequently, using a bar coater, on a base material (arithmetic average roughness Ra 0.43 μm, ten-point average roughness Rz 4.1 μm, haze value 77.1, thickness 50 μm) with a PET film having a rough surface on one side, The coating solution was applied so that the film thickness after curing was 4 μm. This rough surface is due to sandblasting. Next, after cyclohexanone contained in this coating solution is evaporated at 80 ° C. for 2 minutes and dried, the integrated light quantity is adjusted to 50 mJ / cm 2 using an ultraviolet irradiation device “H bulb” (manufactured by Fusion). By irradiating with UV rays, the liquid crystal material and the chiral agent were three-dimensionally cross-linked and polymerized to form a diffuse reflection layer. In addition, the measurement of the integrated light quantity was measured according to JIS R1709 method using the ultraviolet light quantity meter "UV-351" (made by Oak Manufacturing Co., Ltd.). Note that the arithmetic average roughness Ra of the coating surface was reduced to 0.032 μm and the haze value was also reduced to 18.3 due to the production of the diffuse reflection layer. The haze value was measured in accordance with ISO 14782 (JIS K7136).

<Measurement of reflectance>
FIG. 3 is a diagram showing a measurement result of the diffuse reflection film 5. The symbol LT is the transmittance by the total transmitted light (straight-ahead light and diffuse transmitted light), and the symbol LR is the reflectance by the total reflected light (regular reflected light and diffuse reflected light). From this measurement result, the diffuse reflection film 5 However, it is transparent in the visible light region, and it can be seen that the reflectance selectively increases in the near infrared. The diffuse reflectance LR including regular reflection was measured by attaching an integrating sphere unit “ISN-723” (manufactured by JASCO Corporation) to an ultraviolet-visible spectrophotometer “V-670” (JASCO Corporation).

  The reflectivity at each light receiving angle is determined by applying a light ray at an angle of 5 degrees with respect to the normal direction of the film on which the diffuse reflection layer is formed, and the ultraviolet-visible near-spectrophotometer “V-670” (JASCO Corporation). The automatic absolute reflectance measurement unit “ARMN-735” (manufactured by JASCO Corporation) was attached to the measurement. Reference signs LR5 to LR60 (LR5, LR10, LR15, LR20, LR25, LR30, LR35, LR40, LR45, LR50, LR55, LR60) have reflection angles of 5 degrees, 10 degrees, 15 degrees, 20 degrees, 25 degrees, and 30 degrees, respectively. It is the reflectance by the received light quantity of the reflected light measured at degrees, 35 degrees, 40 degrees, 45 degrees, 50 degrees, 55 degrees, and 60 degrees. With the reflection characteristics LR10 to LR60 having a reflection angle of 10 degrees to 60 degrees, the situation of diffuse reflection in the near infrared can be seen.

  FIG. 4 is a diagram showing the reflectivity of the diffuse reflection layer 9 due to diffuse reflection. The measurement result in FIG. 4 is a partial enlargement of the measurement result in FIG. 3, and the incident angle and the reflection angle related to the measurement are the same as those in FIG. Note that the reflectance of the symbol LR5 in FIG. 4 includes the amount of reflected light of interface reflection with the air of the base material 10 on the side surface opposite to the diffuse reflection layer 9 because the reflection angle is 5 degrees equal to the incident angle. It does not show the correct diffuse reflectance.

  According to the measurement result of FIG. 4, it can be seen that the reflectance gradually decreases as the reflection angle becomes larger than the reflection angle of 5 degrees corresponding to the incident angle of 5 degrees. Can take a look. Moreover, the state of diffuse reflection in the near infrared can be seen in more detail by the reflection characteristics LR10 to LR60 having a reflection angle of 10 degrees to 60 degrees.

  FIG. 5 is an enlarged view showing the measurement result of FIG. According to FIG. 5, the state of diffuse reflection by the diffuse reflection layer 9 can be seen in more detail. By these, the function of the diffuse reflection layer 9 can be confirmed.

[Comparative Example 2]
6 and FIG. 7 show a PET film substrate that has not been subjected to any roughening treatment (arithmetic average roughness Ra 0.004 μm, ten-point average roughness Rz 0.025 μm, haze value 1 by comparison with FIGS. 3 and 4. 0.0 and a thickness of 50 μm) is a diagram showing measurement results when a liquid crystal layer made of cholesteric liquid crystal is produced on one side, and each measurement result is shown by the same reference numerals as in FIGS. The samples used for the measurement in FIGS. 6 and 7 were produced in the same manner as the diffuse reflection film subjected to the measurements in FIGS. 3 to 5 except that the rough surface was not produced.

  According to FIGS. 6 and 7, selective reflection characteristics in the near infrared can be seen. In addition, the increase / decrease (pulsation) other than the near infrared of the reflectance of the diffuse reflected light at a reflection angle of 5 degrees by the symbol LR5 is the reflected light from the substrate surface (interface with air) on the side where the liquid crystal layer is not formed. This is considered to be due to interference. However, it can be seen that the diffuse reflection component is hardly detected.

[Example 1-1]
FIG. 8 is a diagram showing the measurement results of the diffuse reflection film of Example 1-1 in comparison with FIGS. 3 and 6. This diffuse reflection film has a structure in which a diffused reflection layer 9 and a reflective layer 11 functioning as a diffuse reflection surface are produced using a base material having rough surfaces on both sides having the same roughness as in Comparative Example 1. It is. The diffuse reflection layer 9 and the reflection layer 11 were made the same as the diffuse reflection layer in Comparative Example 1. The base material had an arithmetic average roughness Ra of 0.43 μm, a ten-point average roughness Rz of 4.1 μm, a haze value of 77.1, and a thickness of 50 μm.

  In FIG. 8, although only the transmittance is shown, this transmittance is reduced in the near-infrared ray, and the reduction in the transmittance in the near-infrared ray is larger than that of Comparative Example 1, thereby functioning as a diffuse reflection layer. As the reflection layer is provided, an increase in the efficiency of diffuse reflection in the near infrared can be seen. Further, it is confirmed that the transmittance of visible light is not impaired by the transmittance of 80% or more in the visible light region.

[Example 1-2]
FIG. 9 is a diagram showing the measurement results of the diffuse reflection film of Example 1-2 in comparison with FIGS. 3 and 6. This diffuse reflection film has a configuration in which a diffuse reflection layer 9 and a reflection layer 11 are produced using the same base material as in Comparative Example 1 (one side is rough). The diffuse reflection layer 9 and the reflection layer 11 were made the same as the diffuse reflection layer in Comparative Example 1.

  According to Example 1-2, by providing the reflection layer 11 in more detail, it is possible to confirm an increase in diffuse reflection efficiency without any loss of visible light transmission.

[Example 2]
10-12 is a figure which shows the measurement result of the diffuse reflection film of Example 2 by contrast with FIGS. 3-5. The diffuse reflection film of Example 2 is configured the same as the diffuse reflection film of Example 1-1 except that both surfaces of the PET film are so-called chemical etched to be roughened. This transparent film material has a rough surface with an arithmetic average roughness Ra of 0.399 μm, a ten-point average roughness Rz of 1.618 μm, and a haze value of 85.5 and a thickness of 50 μm as a whole. In addition, the arithmetic mean roughness Ra of the coating surface after coating the diffuse reflection layer was reduced to 0.034 μm, and the haze value was also reduced to 6.2.

  According to the measurement results of FIGS. 10 to 12, as in the case of Example 1-1.1-2, the diffuse reflection in the near infrared can be confirmed, and the transparency in the visible light region can be confirmed. Thus, it can be seen that even in the case of a rough surface by chemical etching, near infrared rays can be selectively diffusely reflected.

Example 3
FIG. 13 is a diagram showing the measurement results of the diffuse reflection film of Example 3 in comparison with FIGS. 8 and 9. The diffuse reflection film of Example 3 is an example except that a translucent film material in which one surface is a rough surface by a so-called chemical mat surface and the other surface is a smooth surface is applied to a substrate. 1 is the same as the diffuse reflection film. In addition, the translucent film material of this Example 3 is the structure by which the rough surface layer which comprises a chemical mat | matte surface was laminated | stacked on one side of the base material by a translucent film material by this, It is produced by coating, drying and curing a coating liquid relating to the mat surface. The light-transmitting film material has a rough surface with an arithmetic average roughness Ra of 0.273 μm and a ten-point average roughness Rz of 0.98 μm, and has a haze value of 16.4 and a thickness of 128 μm as a whole. In addition, the arithmetic mean roughness Ra of the coating surface after coating the diffuse reflection layer was reduced to 0.011 μm, and the haze value was also reduced to 2.0.

[Comparative Example 3]
14-16 is a figure which shows the measurement result of the diffuse reflection film of the comparative example 3 by contrast with FIGS. 3-5. In the diffuse reflection film of Comparative Example 3, a rough surface with a so-called chemical mat surface is provided only on one side, a coating liquid is applied only on the side provided on the rough surface, and a diffuse reflection layer is produced. Except for the point that no reflective layer is provided, the configuration is the same as the diffuse reflective film of Example 3. The light-transmitting film material has a rough surface with an arithmetic average roughness Ra of 0.273 μm and a ten-point average roughness Rz of 0.98 μm, and has a haze value of 16.4 and a thickness of 128 μm as a whole. In addition, the arithmetic mean roughness Ra of the coating surface after coating the diffuse reflection layer was reduced to 0.011 μm, and the haze value was also reduced to 2.0.

  According to the measurement results of FIG. 13 and the measurement results of FIGS. 14 to 16, the diffuse reflection in the near infrared can be confirmed and the transparency in the visible light region can be confirmed as in the case of the above-described embodiment. Thus, it can be seen that even in the case of a rough surface with a chemical mat surface, near infrared rays can be selectively diffusely reflected.

Example 4
17 and 18 are diagrams showing the measurement results of the diffuse reflection film of Example 4 in comparison with FIG. The diffuse reflection film of Example 4 is made of PET containing a so-called filler, a part of the filler comes out on the surface of one surface to form a rough surface, and the other surface is a smooth surface. Except the point which applied the film material to the base material, it is comprised the same as the diffuse reflection film of Example 1-1. The light-transmitting film material has a rough surface with an arithmetic average roughness Ra of 0.024 μm and a ten-point average roughness Rz of 0.163 μm. The haze value as a whole is 7.1 and the thickness is 50 μm.

[Comparative Example 4]
19-21 is a figure which shows the measurement result of the diffuse reflection film of the comparative example 4 by contrast with FIGS. 3-5. The diffuse reflection film of Comparative Example 4 is made of PET containing a so-called filler. A part of the filler comes out only on one surface side, and only the surface on one side becomes a slightly rough surface. Applying the translucent film material to the base material, applying a coating liquid only to this rough surface to produce a diffuse reflection layer, except that no reflection layer is provided on the other surface, The same configuration as the diffuse reflection film of Example 4 is used. The light-transmitting film material has a rough surface with an arithmetic average roughness Ra of 0.024 μm and a ten-point average roughness Rz of 0.163 μm. The haze value as a whole is 7.1 and the thickness is 50 μm.

  According to the measurement results of FIGS. 17 and 18 and the measurement results of FIGS. 19 to 21, the diffuse reflection in the near infrared can be confirmed and transparent in the visible light region as in the above-described embodiment. Thus, it can be seen that even in the case of a rough surface by a chemical mat surface, near infrared rays can be diffusely reflected selectively and efficiently.

Example 5
22 and 23 are diagrams showing measurement results of the diffuse reflection film of Example 5 in comparison with FIG. The diffuse reflection film of Example 5 is formed by applying a light-transmitting film material made of a PET film material having a rough surface by shaping one surface and a smooth surface on the other surface, to the base material. The same configuration as that of the diffuse reflection film of Example 1 is adopted. This shaping process was performed by pressing a PET film coated with a transparent ultraviolet curable resin onto a roll-shaped mold provided with a large number of fine concave portions, and transferring the concave shape as a convex shape. The light-transmitting film material has a rough surface with an arithmetic average roughness Ra of 0.145 μm and a ten-point average roughness Rz of 0.741 μm, and has a haze value of 7.9 and a thickness of 100 μm as a whole. In addition, the arithmetic mean roughness Ra of the coating surface after coating the diffuse reflection layer was reduced to 0.012 μm, and the haze value was also reduced to 1.7.

[Comparative Example 5]
24-26 is a figure which shows the measurement result of the diffuse reflection film of the comparative example 5 by contrast with FIGS. 3-5. In the diffuse reflection film of Comparative Example 5, only the surface on one side of the substrate was roughened by the roughening method applied to Example 5, and the coating liquid was applied only to this rough surface to diffuse reflection. A layer is prepared, and the same configuration as that of the diffuse reflection film of Example 5 is adopted except that no reflective layer is provided on the other surface.

  According to the measurement results of FIGS. 22 and 23 and the measurement results of FIGS. 24 to 26, the diffuse reflection in the near infrared can be confirmed as in the above embodiment, and the transparent in the visible light region can be confirmed. Thus, it can be seen that even in the case of a rough surface by a shaping process, near infrared rays can be selectively diffusely reflected.

[Comparative Example 6]
27 and 28 are diagrams showing the measurement results of Comparative Example 6 in comparison with FIGS. 3 and 4. 27 and 28 show the measurement results of the copy paper. In the measurement results of FIGS. 27 and 28, it can be seen that the light is diffusely reflected from the visible light region to the near infrared region. Compared with the characteristics of selective diffuse reflection in the near infrared rays according to Examples 1 to 5, if a reflectance of less than 1% is obtained by the diffuse reflection layer, a diffuse reflectance equivalent to that of paper can be obtained. Conceivable.

  In the measurement results of FIGS. 3 to 27, although a sudden measurement change occurs at a wavelength of 850 nm, this change is due to the switching of the photoreceiver depending on the wavelength, and this is due to white copy paper ( It confirmed by measuring a diffuse reflectance using FIG.27 and FIG.28).

Example 6
In Example 6, a diffuse reflection film was produced in the same manner as in Examples 1 to 5 except that the near-infrared reflective layer coating solution was produced as follows. In Example 6, instead of the liquid crystal material described in (7-1) above, the liquid crystal material in (7-1) and the liquid crystal material in (9) were adjusted at a mass ratio of 7: 3, A coating solution was prepared from a mixed liquid crystal with a monofunctional liquid crystal. Thus, by using a mixed liquid crystal of a bifunctional liquid crystal and a monofunctional liquid crystal, the temperature range of the liquid crystal phase is expanded, and handling of the coating liquid becomes easy.

Further, the chiral agent (10) was applied to the chiral agent instead of the chiral agent (8-1). The chiral agent (10) has advantages such as low cost and easy synthesis compared with the chiral agent (8-1). In addition, the usage-amount of the chiral agent was increased about 8% of the usage-amount of Example 1-1, 1-2, and it adjusted so that a reflective wavelength might become substantially the same as Example 1. FIG.

  Instead of cyclohexanone, MEK (methyl ethyl ketone) and MIBK (methyl isobutyl ketone) were mixed at a mass ratio of 6: 4. According to this mixed solvent, compared with the case of using only cyclohexanone, the coating film is more easily dried, and a coating solution suitable for mass production can be obtained.

  Also in Example 6, the same effects as those of Examples 1 to 5 described above could be confirmed.

[Other Embodiments]
As mentioned above, although the specific structure suitable for implementation of this invention was explained in full detail, this invention can change the structure of the above-mentioned embodiment variously in the range which does not deviate from the meaning of this invention.

  That is, in the above-described embodiment, the case where the light diffusion layer is formed using the nematic liquid crystal and the cholesteric liquid crystal based on the chiral agent has been described. You may make it produce a layer.

  In the above-described embodiment, the case where the electronic pen input system is configured by arranging the optical film of the present invention on the panel surface of the image display panel has been described. The present invention can also be widely applied when an electronic pen input system is configured by being arranged on the surface of a member.

DESCRIPTION OF SYMBOLS 1 Image display apparatus 2 Image display panel 3 Optical film 4 Dot pattern film 5 Diffuse reflective film 7 Dot 8 Base material 9 Diffuse reflective layer 10 Base material 11 Reflective layer

Claims (7)

An optical film that is transparent in the visible light region and diffusely reflects near infrared rays,
A substrate made of a translucent film material having at least one surface is a rough surface;
A diffuse reflection layer made of cholesteric liquid crystal produced on the rough surface of the substrate;
An optical film comprising: a cholesteric liquid crystal reflective layer formed on a smooth surface opposite to the rough surface of the substrate. The specific wavelength of right circularly polarized light or left circularly polarized light reflected by the cholesteric liquid crystal is λ,
If n is 0 or an integer,
The retardation value of the substrate is nλ,
The circularly polarized light having the specific wavelength reflected by the diffuse reflection layer and the reflective layer is circularly polarized in different directions.
The optical film according to claim 1. The specific wavelength of right circularly polarized light or left circularly polarized light reflected by the cholesteric liquid crystal is λ,
If n is 0 or an integer,
The retardation value of the substrate is λ / 2 + nλ,
The circularly polarized light having the specific wavelength reflected by the diffuse reflection layer and the reflection layer is circularly polarized in the same direction.
The optical film according to claim 1. The optical film according to any one of claims 1 to 3, wherein the rough surface of the diffuse reflection layer has an arithmetic average roughness Ra of 0.01 µm or more and 1 µm or less. The optical film according to claim 1, further comprising a dot pattern made of dots that absorb near infrared rays. The optical film according to any one of claims 1 to 4 , wherein the optical film is laminated with a dot pattern film in which a dot pattern of dots that absorb near infrared rays is produced. The image display apparatus which has arrange | positioned the optical film of Claim 5 or Claim 6 on the panel surface of an image display panel.

Images