JP2016114661A - Manufacturing method for optical member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method for an optical member having dots, each being made of a liquid crystal material having a cholesteric structure and formed on a surface of a substrate and having a maximum height greater than a diameter thereof and, in particular, a manufacturing method that allows for forming the dots having a maximum height greater than a diameter thereof through a simple procedure that does not depend on a surface property and material of the substrate.SOLUTION: A manufacturing method for an optical member includes a step of forming dots 1 made of a liquid crystal material having a cholesteric structure on a surface of a substrate 2, which involves dropping droplets of a liquid crystal composition containing a liquid crystal compound and a chiral agent on the surface of the substrate 2, where the droplet is dropped twice or more per dot.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for manufacturing an optical member.

  A liquid crystal material having a cholesteric structure having light reflectivity can be used as a constituent material of various optical members by taking advantage of the characteristics. For example, Patent Documents 1 and 2 disclose a transparent sheet on which a dot pattern made of a liquid crystal material having a cholesteric structure that selectively reflects infrared rays is printed. This transparent sheet is attached to the display of an image display device, and is used in combination with an electronic pen equipped with an infrared sensor and an infrared irradiation unit that detects reflected light by the dot pattern, and data is input by handwriting on the display. The sheet can be

US Patent 8367189 Patent 5093034

  In order to detect reflected light from a dot pattern made of a light-reflective material with an electronic pen with a wide reading angle and high sensitivity, each dot forming the pattern may have a maximum height greater than the diameter. preferable. In particular, a liquid crystal material having a cholesteric structure has a maximum light reflectivity in the direction of the cholesteric spiral axis. For example, when formed in a planar shape, it exhibits the maximum reflectivity at a desired wavelength in the normal direction. Therefore, when the dot shape is flat, reflection from an oblique direction at a desired wavelength is weakened. In order to form dots having a maximum height with respect to the diameter, for example, in Patent Document 1, an ink-repellent primer layer is used as a base layer on which dots are provided. Further, in Patent Document 2, a liquid crystal material is filled in a concave portion of a roll in which a concave portion is formed, and a primer layer is formed on the surface thereof. And a method for forming a dot having a large maximum height is disclosed.

  However, both the methods of Patent Document 1 and Patent Document 2 have a problem that restrictions are imposed on the selection of the primer layer. In particular, the method described in Patent Document 1 also has a problem that the applicability of the overcoat layer is deteriorated. Further, the method described in Patent Document 2 has a problem that the manufacturing process becomes complicated.

  An object of the present invention is to provide a method capable of forming an optical member having a dot with a larger maximum height as a method for producing an optical member having dots made of a liquid crystal material having a cholesteric structure formed on the surface of a substrate. It is. In particular, an object of the present invention is to provide a method for producing an optical member capable of forming a dot having a larger maximum height by a simple method without depending on the properties and materials of the substrate surface.

  In order to improve the shape of dots formed from a liquid crystal material having a cholesteric structure, the present inventors have repeatedly studied various conditions. As a result, a composition for forming a liquid crystal material having a cholesteric structure is used as a substrate. It has been found that by applying droplets a plurality of times, a dot having a large maximum height can be obtained without particularly selecting a substrate surface material. Based on this finding, the present inventors have further studied and completed the present invention.

That is, the present invention provides the following [1] to [14].
[1] A method for producing an optical member,
Forming dots made of a liquid crystal material having a cholesteric structure on the substrate surface;
The formation of the dots includes depositing a liquid crystal composition containing a liquid crystal compound and a chiral agent on the substrate,
The droplet ejection is a method for producing an optical member that is performed twice or more per dot.
[2] The method for producing an optical member according to [1], wherein at least one of the second and subsequent droplet ejections is performed before drying the liquid crystal composition that has just been deposited.
[3] The method for producing an optical member according to [2], wherein the composition of the liquid crystal composition to be ejected is the same in at least one of the second and subsequent droplet ejections and in the immediately preceding droplet ejection. .
[4] The method for producing an optical member according to any one of [1] to [3], wherein at least one of the second and subsequent droplet ejections is performed after drying the liquid crystal composition that has just been deposited. .
[5] Manufacture of the optical member according to [4], wherein the liquid crystal composition used for the droplet ejection after the drying and the liquid crystal composition which has been deposited just before and dried by the drying have the same composition. Method.

[6] The production of the optical member according to [4], wherein a composition of the liquid crystal composition used for the droplet ejection after the drying is different from that of the liquid crystal composition ejected just before and dried by the drying. Method.
[7] The method for producing an optical member according to any one of [1] to [6], wherein at least one of the second and subsequent droplet ejections is performed after curing of the liquid crystal composition deposited immediately before. .
[8] The method for producing an optical member according to [7], wherein the composition of the liquid crystal composition used in the droplet ejection after the curing is the same as that of the liquid crystal composition ejected just before and cured by the curing. .
[9] The method for producing an optical member according to [7], wherein the composition of the liquid crystal composition used for the droplet ejection after curing is different from the composition of the liquid crystal composition ejected just before and cured by the curing. .
[10] The composition of the liquid crystal composition used in the droplet ejection after curing and the liquid crystal composition that has been ejected immediately before and cured by the curing are different in the chiral agent,
The method for producing an optical member according to [9], wherein the twist direction of the spiral induced by one chiral agent is right, and the twist direction of the spiral induced by the chiral agent contained in the other is left.
[11] The method for producing an optical member according to [10], wherein the liquid crystal composition first ejected on the surface of the substrate includes a chiral agent whose twist direction of the induced spiral is right.
[12] The composition according to [9], wherein the composition of the liquid crystal composition used in the droplet ejection after curing and the liquid crystal composition ejected just before and cured by the curing differ in concentration of the chiral agent. Manufacturing method of optical member.
[13] The concentration of the chiral agent in the liquid crystal composition used for the droplet ejection after the curing is larger than the concentration of the chiral agent in the liquid crystal composition that has been ejected immediately before and cured by the curing. Manufacturing method of the optical member.
[14] The method for manufacturing an optical member according to any one of [1] to [13], wherein the droplet ejection is performed by an inkjet method, and a plurality of the dots are formed in a pattern on the surface of the substrate.

  According to the present invention, a novel method for producing an optical member is provided. In the manufacturing method of the present invention, an optical member having dots having a maximum height larger than the diameter can be manufactured as the dots made of a liquid crystal material having a cholesteric structure. The optical member manufactured by the method of the present invention can be used, for example, as an optical member for mounting data on a display of an image display device and inputting data by handwriting on the display with an electronic pen or the like.

It is a figure which shows typically sectional drawing of an example of an optical member. It is the schematic of the system which used the optical member as a sheet | seat with which the surface or front of an image display apparatus (display apparatus which can display an image) is mounted | worn.

Hereinafter, the present invention will be described in detail.
In the present specification, “to” is used in the sense of including the numerical values described before and after it as lower and upper limits.
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 this specification, “(meth) acrylate” is used to mean “one or both of acrylate and methacrylate”.
In this specification, for each numerical value, numerical range, and qualitative expression (for example, expression of “identical”, etc.), numerical values, numerical ranges, and properties including errors generally allowed in this technical field are used. It shall be interpreted as showing. In particular, in the present specification, when referring to “all”, “any” or “entire surface”, etc., in addition to the case where it is 100%, including an error range generally allowed in the technical field, for example, 99% or more, The case of 95% or more, or 90% or more is included.

  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. Invisible light is light having a wavelength range of less than 380 nm or a wavelength range of more than 780 nm. Among infrared light, near infrared light is an electromagnetic wave having a wavelength range of 780 nm to 2500 nm. Ultraviolet light is light having a wavelength in the range of 10 to 380 nm.

In this specification, retroreflection means reflection in which incident light is reflected in the incident direction.
In this specification, “polar angle” means an angle with respect to the normal of the substrate.
In this specification, the surface of a dot means the surface or interface of a dot on the side opposite to the substrate, and means the surface not in contact with the substrate.
In the present specification, when it is transparent, specifically, the non-polarized light transmittance (omnidirectional transmittance) at a wavelength of 380 to 780 nm may be 50% or more, 70% or more, and 85% or more. Is preferred.

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

<Method for producing optical member>
The present invention relates to a method for manufacturing an optical member.
The shape of the optical member is not particularly limited, and may be, for example, a film shape, a sheet shape, or a plate shape. FIG. 1 schematically shows a cross-sectional view of an example of an optical member. In this example, dots 1 are formed on the surface of the substrate 2 composed of the support 3 and the substrate layer 4 on the substrate layer side, and an overcoat layer 5 is provided on the dot formation surface side of the substrate so as to cover the dots 1. It has been.
The manufacturing method of the present invention includes forming dots made of a liquid crystal material having a cholesteric structure on the substrate surface. Hereinafter, each material and procedure used in the production method of the present invention will be described.

<Board>
The substrate functions as a base material for forming dots on the surface.
The substrate preferably has a low light reflectivity at a wavelength at which the dots reflect light, and preferably does not include a material that reflects light at a wavelength at which the dots reflect light.
The substrate is preferably transparent in the visible light region. Moreover, although the board | substrate may be colored, it is preferable that it is not colored or there is little coloring. Further, the substrate preferably has a refractive index of about 1.2 to 2.0, more preferably about 1.4 to 1.8. In any case, for example, in an optical member used for an optical member used on the front surface of the display, the visibility of an image displayed on the display is not lowered.
The thickness of the substrate may be selected according to the use and is not particularly limited, but may be about 5 μm to 1000 μm, preferably 10 μm to 250 μm, and more preferably 15 μm to 150 μm.

  The substrate may be a single layer or a multilayer. Examples of the substrate in the case of a single layer include glass, triacetyl cellulose (TAC), polyethylene terephthalate (PET), polycarbonate, polyvinyl chloride, acrylic, polyolefin, and the like. Examples of the substrate in the case of a multilayer include those in which any of the above examples of the substrate in the case of a single layer is included as a support, and other layers are provided on the surface of the support.

Examples of other layers include a base layer provided between the support and the dots.
The production method of the present invention may include providing a base layer on the surface of the support.
The underlayer is preferably a resin layer, and particularly preferably a transparent resin layer. Examples of the underlayer include a layer for adjusting the surface shape when forming dots, a layer for improving adhesion characteristics with dots, and for adjusting the orientation of the polymerizable liquid crystal compound during dot formation. Examples include an alignment layer. Further, the base layer preferably has a low light reflectance at a wavelength at which the dot reflects light, and preferably does not include a material that reflects light at a wavelength at which the dot reflects light. The underlayer is preferably transparent. Further, the base layer preferably has a refractive index of about 1.2 to 2.0, and more preferably about 1.4 to 1.8. The underlayer is also preferably a thermosetting resin or a photocurable resin obtained by curing a composition containing a polymerizable compound applied directly to the support surface. Examples of the polymerizable compound include non-liquid crystalline compounds such as (meth) acrylate monomers and urethane monomers.
The thickness of the underlayer is not particularly limited, but is preferably 0.01 to 50 μm, and more preferably 0.05 to 20 μm.

As the substrate surface or the undercoat layer, an ink repellent material that easily repels ink composed of a liquid crystal composition described later may be used. However, in the manufacturing method of the present invention, an ink repellent material may not be used. , Dots having a large maximum height can be formed.
Further, the surface of the substrate or the underlayer may be subjected to surface processing before dot formation. For example, a hydrophilic treatment or an uneven shape may be formed to form a dot having a desired shape or a desired dot pattern. However, in the manufacturing method of the present invention, dots having a large maximum height can be formed in a desired pattern without performing surface processing on the substrate surface or the underlayer.

<Liquid crystal material having a cholesteric structure>
The dots formed by the manufacturing method of the present invention are made of a liquid crystal material having a cholesteric structure.
Cholesteric structures are known to exhibit selective reflectivity at specific wavelengths. The central wavelength λ of selective reflection depends on the pitch P (= helical period) of the helical structure in the cholesteric structure, and follows the relationship between the average refractive index n of the cholesteric liquid crystal and λ = n × P. Therefore, the selective reflection wavelength can be adjusted by adjusting the pitch of the spiral structure. Since the wavelength of the reflection peak approximates the center wavelength of selective reflection and changes in the same way as the center wavelength of selective reflection, the wavelength of the reflection peak can also be adjusted by adjusting the pitch of the helical structure.
Since the pitch of the cholesteric structure depends on the kind of chiral agent used together with the liquid crystal compound or the concentration of the chiral agent used when forming dots, a desired pitch can be obtained by adjusting these.

The selectively reflected light is circularly polarized light selective, and the selectively reflected light of one kind of cholesteric structure is right circularly polarized light or left circularly polarized light. Whether the reflected light is right-handed circularly polarized light or left-handed circularly polarized light depends on the twist direction of the helix of the cholesteric structure. When the twist direction of the spiral of the cholesteric structure is right, it reflects right circularly polarized light, and when the twist direction of the spiral is left, it reflects left circularly polarized light. The helix direction of the helix of the cholesteric structure generally depends on the chiral agent in the liquid crystal composition described later, and the helix direction of the helix to be induced is the right helix direction and the helix direction of the helix is the right cholesteric structure. And a cholesteric structure in which the helix direction of the helix is left can be formed using a chiral agent whose helix direction of induction is the left.
Regarding the pitch adjustment, Fujifilm Research Report No. 50 (2005) p. There is a detailed description in 60-63. For the method of measuring the twist direction and pitch of the spiral, use the method 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 Editorial Board Maruzen 196 pages. Can do.

  The cholesteric structure is observed as a stripe pattern of a bright part and a dark part with a scanning electron microscope (SEM). Two repetitions of this bright part and dark part (two bright parts and two dark parts) correspond to one pitch of the spiral. Therefore, the pitch can be measured from the SEM sectional view. The normal of each line of the striped pattern is the spiral axis direction.

  The full width at half maximum Δλ (nm) of the selective reflection band (circular polarization reflection band) indicating selective reflection follows the relationship of Δλ = Δn × P, where Δλ depends on the birefringence Δn of the liquid crystal compound and the pitch P. Therefore, the width of the selective reflection band can be controlled by adjusting Δn. Δn can be adjusted by adjusting the type of liquid crystal compound and its mixing ratio, or by controlling the temperature at the time of fixing the alignment. The half width of the reflection wavelength band is adjusted according to the use of the optical member, and may be, for example, 50 to 500 nm, and preferably 100 to 300 nm.

<Dot forming material: Liquid crystal composition>
In the production method of the present invention, a liquid crystal composition containing a liquid crystal compound and a chiral agent is used to form dots made of a liquid crystal material having a cholesteric structure. The liquid crystal compound is preferably a polymerizable liquid crystal compound. The liquid crystal composition may further contain a surfactant, a polymerization initiator, and the like.

[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.

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

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

  Moreover, it is preferable that the addition amount of the polymeric liquid crystal compound in a liquid-crystal composition is 75-99.9 mass% with respect to solid content mass (mass except a solvent) of a liquid-crystal composition, and 80-99. It is more preferable that it is mass%, and it is especially preferable that it is 85-90 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 twist direction or the spiral pitch of the spiral induced by the compound is different.
The helical pitch induced by the chiral agent may be represented by HTP (Helical Twisting Power) as an index of the force with which the chiral agent twists the liquid crystal. HTP is expressed by the formula HTP from the selective reflection wavelength λ, the average refractive index n, and the added chiral agent concentration C (mass%) of a cholesteric liquid crystal layer formed from a liquid crystal composition containing a chiral agent and a liquid crystal compound. = N / (λ × 0.01 × C).

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.

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

  The content of the chiral agent in the liquid crystal composition is preferably 0.01 mol% to 200 mol%, more preferably 1 mol% to 30 mol% of the amount of the polymerizable liquid crystal compound.

[Surfactant]
The liquid crystal composition may contain a surfactant. Examples of the surfactant include a silicone-based surfactant and a fluorine-based surfactant, and a fluorine-based surfactant is preferable.

Specific examples of the surfactant include compounds described in [0082] to [0090] of JP-A No. 2014-119605, compounds described in paragraphs [0031] to [0034] of JP-A No. 2012-203237, and JP-A No. Compounds exemplified in [0092] and [0093] of 2005-99248, and [0076] to [0078] and [0082] to [0085] of JP 2002-129162 A Compounds, fluorine (meth) acrylate polymers described in paragraphs [0018] to [0043] of JP-A-2007-272185, and the like.
In addition, as a horizontal alignment agent, 1 type may be used independently and 2 or more types may be used together.
As the fluorine-based surfactant, a compound represented by the general formula (I) described in [0082] to [0090] of JP-A No. 2014-119605 is particularly preferable.

  The addition amount of the surfactant 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.

[Polymerization initiator]
When it contains a polymerizable compound, 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 12% 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.

[Other additives]
When the ink jet method described later is used for dot formation, a monofunctional polymerizable monomer may be used to obtain generally required ink physical properties. Examples of the monofunctional polymerizable monomer include 2-methoxyethyl acrylate, isobutyl acrylate, isooctyl acrylate, isodecyl acrylate, octyl / decyl acrylate, and the like.
Further, in the liquid crystal composition, if necessary, a polymerization inhibitor, an antioxidant, an ultraviolet absorber, a light stabilizer, a colorant, metal oxide fine particles, etc., in a range that does not deteriorate the optical performance and the like. Can be added.

[solvent]
The liquid crystal composition is preferably used as a liquid when forming dots.
The liquid crystal composition may contain a solvent. There is no restriction | limiting in particular as a solvent, Although it can select suitably according to the objective, An organic solvent is used preferably.
The organic solvent is not particularly limited and may be appropriately selected depending on the intended purpose. For example, ketones such as methyl ethyl ketone and methyl isobutyl ketone, alkyl halides, amides, sulfoxides, heterocyclic compounds, hydrocarbons , Esters, ethers and the like. These may be used individually by 1 type and may use 2 or more types together. Among these, ketones are particularly preferable in consideration of environmental load. The above-described components such as the above-mentioned monofunctional polymerizable monomer may function as a solvent.

<Dot formation method>
In the method for producing an optical member of the present invention, dots are formed on the substrate surface. The dots may be formed on both sides of the substrate, but may be formed on one side, and are preferably formed on one side.
[Splashing]
In the production method of the present invention, the dots are formed by a method including ejecting the liquid crystal composition onto the surface of the substrate. Here, the droplet ejection is performed twice or more per dot.
The inventors of the present invention, when forming a dot, when droplets are ejected again on a portion where the liquid crystal composition has already been deposited, the shape of the dots does not become similar to the previously formed shape, It has been found that the height direction tends to increase with respect to the size viewed from the substrate normal direction. That is, it is easy to increase the maximum height of dots formed by a manufacturing method that includes forming a single dot twice or more by ejecting a liquid crystal composition.

By performing the second and subsequent liquid droplet ejections in accordance with the position of the liquid crystal composition deposited immediately before on the substrate, two or more liquid crystal composition ejections are performed for the formation of one dot. Drops can be made.
The second and subsequent liquid droplet ejection of the liquid crystal composition may be performed before or after drying of the liquid crystal composition deposited immediately before.
In the case where the liquid crystal composition contains a polymerizable liquid crystal compound, the second and subsequent liquid droplet ejection of the liquid crystal composition may be performed before or after curing of the liquid crystal composition deposited immediately before. In the liquid crystal composition ejected onto the surface of the cured liquid crystal composition, the orientation of liquid crystal compound molecules tends to be good.

The number of droplet ejections may be two or more for the formation of one dot, preferably 2 to 200 times, more preferably 2 to 100 times, and even more preferably 2 to 80 times. 2 to 50 times is particularly preferable.
For two or more times of droplet ejection, liquid crystal compositions having the same composition may be used, or liquid crystal compositions having different compositions may be used. For example, two or more liquid crystal compositions may be used in order, or two or more liquid crystal compositions may be used alternately or repeatedly. When a liquid crystal composition having a composition different from the liquid droplet composition that has just been deposited is ejected, the deposited liquid crystal composition is preferably dried before the droplet ejection, and may be dried and cured. preferable. For example, when a liquid crystal composition using a chiral agent that induces different twist directions is continuously ejected, the chiral agent that induces different twist directions becomes difficult to mix, and the effect as a chiral agent is offset and cholesteric. It can be prevented that the structure cannot be formed.
Examples of the dot formation procedure when using a liquid crystal composition containing a polymerizable liquid crystal compound include the following.

First Example (1) The first liquid crystal composition 1 is deposited on the substrate surface.
(2) Before the deposited liquid crystal composition 1 is dried, the second droplet ejection is performed with the liquid crystal composition 1 having the same composition.
(3) The liquid crystal composition 1 is dried and cured.
Second Example (1) First droplet deposition of the liquid crystal composition 1 is performed on the substrate surface.
(2) After the deposited liquid crystal composition 1 is dried, the second droplet ejection is performed with the liquid crystal composition 1 having the same composition.
(3) The liquid crystal composition 1 is dried and cured.

Third Example (1) The liquid crystal composition 1 is first deposited on the substrate surface.
(2) The deposited liquid crystal composition 1 is dried and cured.
(3) Second droplet ejection is performed with the liquid crystal composition 1 having the same composition.
(3) Drying and curing of the deposited liquid crystal composition 1 are performed.
Fourth Example (1) The liquid crystal composition 1 is ejected on the substrate 1 to 20 times without including the drying and curing steps.
(2) The deposited liquid crystal composition 1 is dried.
(3) The liquid crystal composition 2 different from the liquid crystal composition 1 is ejected 1 to 100 times.
(4) The dried liquid crystal composition 2 is dried and the entire liquid crystal composition 1 and liquid crystal composition 2 are cured.

Fifth Example (1) The liquid crystal composition 1 is ejected on the substrate 1 to 20 times without including the drying and curing steps.
(2) Drying and curing of the deposited liquid crystal composition 1 are performed.
(3) The liquid crystal composition 2 different from the liquid crystal composition 1 is ejected 1 to 100 times.
(4) Drying and curing of the deposited liquid crystal composition 2 are performed.

An example in which any one of the first to fifth examples is repeated twice or more, and an example in which any two or more selected from the group consisting of the first to fifth examples are combined are also given. be able to.
In the first example and the second example described above, the number of droplet ejections of the liquid crystal composition 2 may be, for example, 3 to 8 times the number of droplet ejections of the liquid crystal composition 1, and may be about 5 times.

  In the first to fifth examples, the liquid crystal composition 1 and the liquid crystal composition 2 may have different compositions in the chiral agent. For example, by using a chiral agent whose induced helix twist direction is on the right and on the other hand a chiral agent whose induced helix twist direction is on the left, both right and left circular polarizations are used. An optical member having a reflecting dot can be manufactured. In this case, the liquid crystal composition 1 to be ejected onto the substrate surface includes a chiral agent having a helical twist direction induced on the right and the liquid crystal composition 2 includes a chiral agent having a helical twist direction on the left. Is preferred. Alternatively, in the liquid crystal composition 1 and the liquid crystal composition 2, a dot having two reflection peak wavelengths of selective reflection can be formed by using a chiral agent having different HTP.

In the first to fifth examples, the liquid crystal composition 1 and the liquid crystal composition 2 may have different compositions in the concentration of the chiral agent. By using different compositions in the concentration of the chiral agent, it is possible to form dots having two reflection peak wavelengths for selective reflection. At this time, the concentration of the chiral agent in the liquid crystal composition 1 is preferably lower than the concentration of the chiral agent in the liquid crystal composition 2. If the concentration is lower in the liquid crystal composition applied earlier, the liquid crystal composition applied later is less likely to be affected by the penetration of the chiral agent from the liquid crystal composition previously applied or applied and cured. is there.
The liquid crystal composition 1 and the liquid crystal composition 2 may have different types and concentrations of liquid crystal compounds.

  The method of droplet ejection is not particularly limited, but it is particularly preferable to use an ink jet method. For the ink jet method, a known printing technique can be referred to. Dot pattern formation can also be performed by applying a known printing technique. A well-known alignment method in the printing technology field can also be applied to a technique in which the liquid crystal composition is ejected for the second time or later at the same position with respect to the position or position pattern of the liquid crystal composition previously ejected. .

The liquid crystal composition amount (ink amount) per droplet ejection may be, for example, 1 pL to 20 pL per dot, preferably 2 pL to 10 pL, and more preferably 5 pL to 6 pL. The total amount of liquid crystal composition to be ejected per dot may be, for example, 2 pL to 1200 pL, preferably 10 pL to 600 pL, more preferably 50 pL to 500 pL, and more preferably 100 pL to 400 pL. Further preferred.
Although droplet ejection may be performed on both sides of the substrate or on one side, it is preferably performed on one side. When the substrate includes a base layer, droplets may be deposited on the surface on the base layer side.

[Drying of liquid crystal composition]
The liquid crystal composition after droplet ejection on the substrate surface may be dried as necessary. Heating may be performed for drying or after drying, as long as the liquid crystal compound in the liquid crystal composition is aligned in the drying or heating step to form a cholesteric liquid crystal phase. When heating, the heating temperature is preferably 200 ° C. or lower, more preferably 130 ° C. or lower.
When drying is performed a plurality of times during the dot formation process, these conditions may be the same or different.

[Curing liquid crystal composition]
When the liquid crystal composition contains a polymerizable liquid crystal compound, the aligned polymerizable liquid crystal compound may be polymerized by curing the liquid crystal composition. Curing may be performed by light irradiation or heating, and is preferably performed by light irradiation. 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 of the liquid crystal compound by light irradiation, light irradiation may be performed under heating conditions or in a nitrogen atmosphere. The irradiation ultraviolet wavelength is preferably 250 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.
When curing is performed a plurality of times during the dot formation process, the conditions may be the same or different.

  It is sufficient that the cholesteric liquid crystal phase is fixed and a cholesteric structure is obtained by curing the liquid crystal composition. The cholesteric structure only needs to be a structure in which the alignment of the liquid crystal compound in the cholesteric liquid crystal phase is maintained. Typically, after the polymerizable liquid crystal compound is in the alignment state of the cholesteric liquid crystal phase, ultraviolet irradiation, Any structure may be used as long as it is polymerized and cured by heating or the like to form a layer having no fluidity, and at the same time, is changed to a state in which the orientation is not changed by an external field or external force. In the cholesteric structure, it is sufficient that the optical properties of the cholesteric liquid crystal phase are maintained, and the liquid crystal compound 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.

[Dots on the substrate surface]
One or more dots may be formed on the substrate surface. Two or more dots may be formed in close proximity to each other on the substrate surface, and the total surface area of the dots may be 50% or more, 60% or more, 70% or more, etc. of the area of the substrate on the dot forming side. In this case, the optical characteristics such as the selective reflectivity of the dots may be substantially the optical characteristics of the entire optical member, particularly the entire surface of the dot formation. On the other hand, even if two or more dots are formed in large numbers apart from each other on the substrate surface, the total surface area of the dots is less than 50%, 30% or less, 10% or less, etc. Good. In this case, etc., the optical characteristics of the optical member on the dot forming surface side may be confirmed as the contrast between the optical characteristics of the substrate and the optical characteristics of the dots.

In the optical member, the plurality of dots may be formed in a pattern and have a function of presenting information. For example, the optical member can be used as a sheet on which data can be input by being mounted on a display by being formed so as to be able to provide position information on the optical member formed in a sheet shape.
When forming dots in a pattern, for example, an average of 10 to 100 dots, preferably 15 to 50, more preferably 20 to 40 dots having a diameter of 20 to 200 μm per 2 mm square on the substrate surface. , So as to include.

  When a plurality of dots are formed on the surface of the substrate, the dots may be formed so that the diameters and shapes thereof are all the same or different from each other. For example, all dots may be formed under the same conditions, or dot formation under different conditions may be included. The formation of a plurality of dots under the same conditions can be realized by performing droplet ejection under the same conditions, preferably simultaneously, by an ink jet method or the like.

  In the present specification, when a dot is described, the description can be applied to all dots in the optical member. However, the optical member including the dot to be described depends on an error or an error allowed in the technical field. It shall be allowed to include dots that do not fall under the description,

[Dot shape]
In the production method of the present invention, the shape of the formed dots is not particularly limited, but is preferably circular when viewed from the normal direction of the substrate. The circular shape does not have to be a perfect circle and may be a substantially circular shape or an elliptical shape. For example, a plurality of circles may be slightly shifted and overlapped by two or more droplet ejections. In this specification, when the dot is referred to as the center, it means the center or the center of gravity of the shape when viewed from the normal direction of the substrate. When there are a plurality of dots on the substrate surface, the shapes of the dots may be the same or different, but are preferably the same or at least similar.

Although the diameter of a dot is not specifically limited, It is preferable to set it as 20-200 micrometers, and it is more preferable to set it as 70-150 micrometers. The diameter of the dot may be a circular diameter when the dot shape is approximated to a circle. The diameter of the dot can be adjusted by the droplet ejection amount per time of the liquid crystal composition. Specifically, when it is desired to reduce the dot diameter, the droplet ejection amount per time is reduced, and when it is desired to increase the dot diameter, the droplet ejection amount per time is increased.
The diameter of the dot is a straight line from the end (dot edge or boundary) to the end in an image obtained with a microscope such as a laser microscope, a scanning electron microscope (SEM), or a transmission electron microscope (TEM). And measuring the length of a straight line passing through the center of the dot. The number of dots and the distance between the dots can also be confirmed with a microscope image such as a laser microscope, a scanning electron microscope (SEM), or a transmission electron microscope (TEM).

  The dots are preferably formed so as to include a portion having a height that continuously increases to the maximum height in the direction from the end of the dot toward the center. In the present specification, the part may be referred to as an inclined part or a curved part. That is, it is preferable that the dots to be formed include an inclined portion or a curved surface portion whose height increases from the end portion of the dot toward the center. The shape of the dots can be adjusted by changing the droplet ejection amount of the liquid crystal composition or changing the timing of drying and curing of the liquid crystal composition with respect to two or more droplet ejections of the liquid crystal composition. Specifically, for example, in the second and subsequent droplets, the maximum is greater after the drying than when performed immediately after the first droplet, and more preferably after the curing than after the drying. You can get the height.

  In the present specification, when the dot is referred to as “height”, it means “the shortest distance from the dot surface point to the dot formation side surface of the substrate”. Further, when the substrate is uneven, the extension of the substrate surface at the end of the dot is defined as the dot-forming surface. The maximum height is the maximum value of the height, and is, for example, the shortest distance from the vertex of the dot to the dot formation side surface of the substrate. The height of a dot can be confirmed from a cross-sectional view of the dot obtained using a focus position scan with a laser microscope or a microscope such as SEM or TEM.

  Examples of the structure including the inclined part or the curved part include a hemispherical shape with the substrate side as a flat surface, a shape obtained by cutting and flattening the upper part of the hemispherical shape substantially parallel to the substrate (spherical base shape), A conical shape, a shape obtained by cutting and flattening the upper portion of the conical shape substantially parallel to the substrate (conical trapezoidal shape), and a shape that can approximate either of these. Of these, a hemispherical shape with the substrate side as a flat surface, a shape obtained by cutting and flattening the upper part of the hemispherical shape substantially parallel to the substrate, and a conical shape with the substrate side as a bottom surface being cut substantially parallel to the substrate and flattened. A shape that can be approximated to any one of these is preferable. Note that the above hemispherical shape includes not only a hemispherical shape having a plane including the center of the sphere as a plane, but also any one of a spherical shape obtained by arbitrarily cutting the sphere into two.

  The point on the dot surface that gives the maximum height of the dot may be at the apex of the hemispherical shape or the conical shape, or may be on the flat surface obtained by cutting substantially parallel to the substrate as described above. It is also preferred that all flattened planar points give the maximum dot height. It is also preferred that the center of the dot gives the maximum height.

  In the production method of the present invention, it is possible to easily obtain a large maximum height with respect to the dot diameter. For example, the dots formed by the manufacturing method of the present invention can be formed such that the maximum height divided by the dot diameter (maximum height / diameter) is 0.16 to 0.30. . (Maximum height / diameter) is adjusted by changing the composition of the liquid crystal composition, changing the droplet ejection amount of the liquid crystal composition, or drying the liquid crystal composition with respect to two or more droplet ejections of the liquid crystal composition, It can be adjusted by changing the timing of curing. In particular, a hemispherical shape with the substrate side as a plane, a shape obtained by cutting and flattening the upper part of the hemispherical shape substantially parallel to the substrate, and a shape obtained by cutting and flattening the conical shape with the substrate side as the bottom surface substantially parallel to the substrate For example, a dot satisfying the above maximum height / diameter is formed as a shape in which the dot height continuously increases from the end of the dot to the maximum height and the center indicates the maximum height. Can be formed. It is also possible to form such that the maximum height / diameter is further 0.18 to 0.28.

Moreover, in the manufacturing method of this invention, the dot (for example, average value) which the surface of a dot and the said board | substrate (the dot formation side surface of a board | substrate) make is 33 degrees-62 degrees can be formed. Furthermore, it is possible to form dots with the angle of 35 degrees to 60 degrees. A dot having such an angle can exhibit high retroreflectivity at an incident angle of light suitable for the use of an optical member described later.
The angle can be confirmed from a focus position scan by a laser microscope or a cross-sectional view of a dot obtained by using a microscope such as SEM or TEM. In this specification, the angle is perpendicular to the substrate including the center of the dot. It is assumed that the angle of the contact portion between the substrate and the dot surface is measured by the SEM image of the sectional view on the surface.

(Optical properties of dots)
The dots formed by the production method of the present invention are made of a liquid crystal material having a cholesteric structure and have wavelength selective reflectivity. The light with which the dot exhibits selective reflectivity is not particularly limited, and may be any of infrared light, visible light, ultraviolet light, and the like. For example, when an optical member is attached to a display and used as an optical member for inputting data directly by handwriting on the display device, the wavelength of light at which dots exhibit selective reflectivity does not affect the display image. Thus, the wavelength is preferably in the invisible light region, more preferably in the infrared light region, and particularly preferably in the near infrared light region. For example, in the reflection spectrum from the dots, it is preferable that a reflection wavelength band having a center wavelength in the range of 750 to 2000 nm, preferably in the range of 800 to 1500 nm can be confirmed. The reflection wavelength is preferably selected in accordance with the wavelength of light emitted from a light source used in combination or the wavelength of light sensed by an image sensor (sensor). The wavelength of light at which the dots exhibit selective reflectivity can be determined by adjusting the helical pitch in the cholesteric structure of the liquid crystal material forming the dots as described above.

  The dots are preferably transparent in the visible light region. The dots may be colored, but are preferably not colored or less colored. In either case, for example, when the optical member is used on the front surface of the display, the visibility of the image displayed on the display is not lowered.

Within the dot, the helical axis of the cholesteric structure is preferably in the range of angles in the range of 50 to 90 degrees with the dot surface. The angle is more preferably in the range of 60 degrees to 90 degrees, and further preferably in the range of 70 degrees to 90 degrees. In particular, the angle formed by the helical axis of the cholesteric structure on the surface of the dot is preferably in the range of 70 to 90 degrees.
The helical axis of the cholesteric structure is in the normal direction of the line formed by each dark portion when the cross section of the dot is observed with a scanning electron microscope (SEM). The angle formed by the spiral axis of the cholesteric structure on the surface of the dot is the angle formed by the normal of the line formed by the first dark portion from the surface of the dot and the surface. When the surface is a curve, the angle may be obtained using the surface as a tangent to the surface in the cross section. In particular, by satisfying the above angle also in the inclined portion or the curved surface portion, it is possible to exhibit high retroreflectivity even for light incident on the dots from a direction that makes an angle from the normal direction of the substrate. For example, according to the shape of the dot, high retroreflectivity can be exhibited for light incident on the dot at a polar angle of 27 degrees, and preferably for light incident on the dot at 45 degrees.

[Overcoat layer]
The production method of the present invention may further include forming an overcoat layer. The overcoat layer may be provided on the side of the substrate where the dots are formed, and the surface of the optical member is preferably flattened.
The overcoat layer is not particularly limited, but is preferably a resin layer having a refractive index of about 1.4 to 1.8. Difference between refractive index of overcoat layer and dot made of liquid crystal material to avoid scattering of image light from image display device when optical member is used as input medium such as input sheet on display surface such as image display device Is preferably 0.2 or less. More preferably, it may be 0.1 or less. The refractive index of a dot made of a liquid crystal material is about 1.6, but by using an overcoat layer having a refractive index of about 1.4 to 1.8, the polar angle of light actually incident on the dot is reduced. be able to. For example, when an overcoat layer having a refractive index of 1.6 is used and light is incident on the optical member at a polar angle of 45 degrees, the polar angle actually incident on the dots can be about 27 degrees. Therefore, by using an overcoat layer, it is possible to widen the polar angle of light where the optical member exhibits retroreflectivity, and even in the case of a dot having a small angle between the surface of the dot and the substrate, in a wider range, High retroreflectivity can be obtained. The overcoat layer may have a function as an antireflection layer, a pressure-sensitive adhesive layer, an adhesive layer, or a hard coat layer.

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

  The thickness of the overcoat layer is not particularly limited, and may be determined in consideration of the maximum dot height. For example, it may be about 5 μm to 100 μm, preferably 10 μm to 50 μm, more preferably 20 μm to 40 μm. The thickness is the distance from the dot formation surface of the substrate where there is no dot to the surface of the overcoat layer on the opposite surface.

<Applications of optical members>
The usage of the optical member is not particularly limited, and can be used as various reflecting members. The optical member may or may not be transparent in the visible light region depending on the application, but the optical member that is transparent can be particularly preferably used for the following applications. In the following uses, the haze of the optical member is preferably 5% or less, more preferably 3% or less, and particularly preferably 2% or less.

For example, an optical member in which a large number of dots are formed close to each other on the substrate surface can be used as a retroreflector that reflects only circularly polarized light having a specific wavelength.
In particular, an optical member having dots in a pattern, for example, an input means such as an electronic pen that digitizes handwritten information and inputs it to an information processing apparatus by forming the pattern as a coded dot pattern that gives positional information The input medium can be used in combination. In use, a liquid crystal material for forming dots is prepared and used so that the wavelength of light emitted from the input means becomes a wavelength at which the dots reflect. Specifically, the spiral pitch of the cholesteric structure may be adjusted by the method described above.

  The optical member can also be used as an input medium such as an input sheet on a display surface such as a liquid crystal display. 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. At this time, it is preferable that the wavelength range of light in which dots on the optical member exhibit selective reflection are different from the wavelength range of light emitted from the display. That is, it is preferable that the dots have selective reflectivity in the non-visible light region, and the display does not emit non-visible light so that there is no false detection by the detection device.

  Regarding a handwriting input system that digitizes handwritten information and inputs it to an information processing apparatus, Japanese Patent Application Laid-Open No. 2014-67398, Japanese Patent Application Laid-Open No. 2014-98943, Japanese Patent Application Laid-Open No. 2008-165385, and Japanese Patent Application Laid-Open No. 2008-108236. Reference may be made to [0021] to [0032], or Japanese Patent Application Laid-Open No. 2008-077451.

  As a preferable aspect in the case of using the optical member as a sheet mounted on the front surface or the front of a display device capable of displaying an image, the aspects described in [0024] to [0031] of Japanese Patent No. 4725417 can be exemplified. .

FIG. 2 shows a schematic diagram of a system in which the optical member is used as a sheet mounted on the surface or front of a display device capable of displaying an image.
In FIG. 2, any known sensor may be used as long as it emits infrared rays i and can detect the reflected light r having the above-described pattern. For example, a pen-type input terminal 106 may also read data processing device 107. As an example, it is disclosed in Japanese Patent Application Laid-Open No. 2003-256137, a pen (not including ink or graphite), a CMOS (Complementary Metal-Oxide Semiconductor) camera including an infrared irradiation unit, a processor, a memory, Bluetooth ( Examples thereof include a communication interface such as a wireless transceiver using a registered trademark technology and the like and a battery or the like built-in.

  As an operation of the pen-type input terminal 106, for example, when the pen tip is drawn so as to be in contact with the front surface of the optical member 100, the pen-type input terminal 106 detects the writing pressure applied to the pen tip, and CMOS The camera is activated to irradiate a predetermined range in the vicinity of the nib with infrared light having a predetermined wavelength emitted from the infrared irradiation unit and to capture a pattern (for example, the pattern is captured several tens to 100 times per second) ). When the pen-type input terminal 106 includes the read data processing device 107, the input trace associated with the movement of the pen tip during handwriting is digitized and converted into data by analyzing the captured pattern with a processor. And the input trajectory data is transmitted to the information processing apparatus.

Note that a processor, a memory, a communication interface such as a wireless transceiver using Bluetooth (registered trademark) technology, and a member such as a battery are a pen-type input terminal 106 as a read data processing device 107 as shown in FIG. It may be outside of. In this case, even if the pen-type input terminal 106 is connected to the read data processing device 107 with the code 108, the read data may be transmitted wirelessly using radio waves, infrared rays, or the like.
In addition, the input terminal 106 may be a reader described in Japanese Patent Laid-Open No. 2001-243006.

The read data processing device 107 calculates position information from continuous imaging data read by the input terminal 106, combines it with time information, and provides it as input trajectory data that can be handled by the information processing device. It does not specifically limit and it should just have members, such as a processor, memory, a communication interface, and a battery.
Further, the read data processing device 107 may be built in the input terminal 106 as described in Japanese Patent Laid-Open No. 2003-256137, or may be built in an information processing device including a display device. Further, the read data processing device 107 may transmit the position information wirelessly to an information processing device provided with a display device, or may transmit it by a wired connection connected by a code or the like.
The information processing apparatus connected to the display device 105 sequentially updates the image displayed on the display device 105 based on the trajectory information transmitted from the read data processing device 107, so that the trajectory input by handwriting on the input terminal 106 is obtained. It can be displayed on the display device as if it were written with a pen on paper.

  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.

[Example 1]
(Preparation of underlayer)
The composition shown below was stirred and dissolved in a container kept at 25 ° C. to prepare a base layer solution.
----------------------------------
Underlayer solution (parts by mass)
----------------------------------
Propylene glycol monomethyl ether acetate 67.8
Dipentaerythritol hexaacrylate (manufactured by Nippon Kayaku Co., Ltd., trade name: KAYARAD DPHA) 10.0
Megafuck RS-90 (manufactured by DIC Corporation) 26.7
IRGACURE 819 (manufactured by BASF) 0.5
----------------------------------

The base layer solution prepared above was applied to a transparent PET (polyethylene terephthalate, manufactured by Toyobo Co., Ltd., Cosmo Shine A4100) substrate with a thickness of 100 μm using a bar coater at a coating amount of 3 mL / m ² . Thereafter, the film surface is heated to 90 ° C., dried for 120 seconds, and then subjected to 700 mJ / cm ² (illuminance 200 mW / cm ² , 3.5 by an ultraviolet irradiation device under a nitrogen purge with an oxygen concentration of 100 ppm or less. For 2 seconds), the crosslinking reaction was allowed to proceed, and an underlayer was prepared.

(Cholesteric liquid crystal dot formation)
The compositions shown below were stirred and dissolved in a container kept at 25 ° C. to prepare cholesteric liquid crystal ink liquids A and B (liquid crystal compositions).

----------------------------------
Cholesteric liquid crystal ink A (parts by mass)
----------------------------------
Methoxyethyl acrylate 145.0
A mixture of the following rod-like liquid crystal compounds 100.0
IRGACURE 819 (manufactured by BASF) 10.0
Chiral agent with the following structure 3.8
Surfactant with the following structure 0.08
----------------------------------

The numerical value is mass%. Further, the group represented by R has a partial structure shown in the lower right, and is bonded at the position of the oxygen atom of this partial structure.

----------------------------------
Cholesteric liquid crystal ink liquid B (parts by mass)
----------------------------------
Methoxyethyl acrylate 145.0
Mixture of rod-like liquid crystal compounds used in ink liquid A 100.0
IRGACURE 819 (manufactured by BASF) 10.0
6.7 Chiral agent with the following structure
Surfactant used in ink liquid A 0.08
----------------------------------

Further, a cholesteric liquid crystal ink liquid C was prepared in the same manner as the ink liquid A, except that the addition amount of the chiral agent was 3.5 parts by mass.
The ink liquid A is adjusted to reflect 850 nm clockwise circularly polarized light, the ink liquid B is adjusted to counterclockwise circularly polarized light of 850 nm, and the ink liquid C is adjusted to reflect 900 nm clockwise circularly polarized light.

The above prepared cholesteric liquid crystal ink A was applied to the above-prepared PET underlayer with an inkjet printer (DMP-2831, manufactured by FUJIFILM Dimatix) at a dot center distance of 300 μm, a dot diameter of 64 μm, and 50 A droplet was sprayed on the entire surface of a × 50 mm region.
Further, the same ink liquid A was deposited on the surface of the dots prepared above, dried at 95 ° C. for 30 seconds, and then irradiated with ultraviolet rays of 500 mJ / cm ² (illuminance 200 mW / cm ² , 2.5 seconds) by an ultraviolet irradiation device. Were formed to form dots having a dot diameter of 109 μm (refractive index, 1.57) to obtain an optical member.

(Dot shape, cholesteric structure evaluation)
Of the dots of the optical member obtained above, 10 were randomly selected and the dot shape was observed with a laser microscope (manufactured by Keyence Corporation). The dots had an average diameter of 109 μm, an average maximum height of 22 μm, and dots The angle formed by the contact portion between the dot surface at the end and the surface of the underlayer is an average of 43 degrees, and the height continuously increases in the direction from the dot end toward the center.
One dot located at the center of the optical member obtained above was cut perpendicular to the PET substrate on the surface including the dot center, and the cross section was observed with a scanning electron microscope. Striped pattern was confirmed.

(Formation of overcoat layer)
The composition shown below was stirred and dissolved in a container kept at 25 ° C. to prepare an overcoat coating solution.

----------------------------------
Overcoat coating solution (parts by mass)
----------------------------------
Acetone 100.0
KAYARAD DPCA-30 (Nippon Kayaku Co., Ltd.) 100.0
IRGACURE 819 (BASF) 3.0
----------------------------------

The overcoat coating solution prepared above was applied at an application amount of 80 mL / m ² on the base layer on which the cholesteric liquid crystal dots were formed, using an applicator. Thereafter, the film surface temperature is heated to 50 ° C., and after drying for 60 seconds, 700 mJ / cm ² of ultraviolet rays is irradiated by an ultraviolet irradiation device to advance the crosslinking reaction, and the overcoat layer (refractive index: 1 .52) was produced.

(Dot performance evaluation)
About the optical member with an overcoat layer produced above, a light source for visible-near infrared irradiation (HL-2000) manufactured by Ocean Optics, an ultra-high resolution fiber multichannel spectrometer (HR4000), and a two-branch optical fiber are used. When measuring 5 spots at random with a 2 mm diameter field, the reflection peak wavelength was 850 nm in any field of view, and the normal of the optical member was 0 degree, and the polar angle was confirmed in the range of 0 to 50 degrees. Occasionally, retroreflection was observed from all dots.
In addition, in order to determine the direction (left and right) of the circularly polarized light reflected, both the λ / 4 plate attached to the polarizing microscope is inserted, and the observation when the angle of the analyzer is 0 degree and 90 degrees, It was judged whether it was circularly polarized light or one circularly polarized light.

[Examples 2 to 9 and Comparative Examples 1 and 2]
An optical member with an overcoat layer was prepared in the same manner as in Example 1 except that the cholesteric liquid crystal ink liquid used, whether or not drying was performed after the previous ink jet deposition, whether or not cured, and the dot diameter of the ink jet were changed as shown in the table below. did.
In addition, in the case of drying, drying was performed at 95 ° C. for 30 seconds, and in the case of curing, ultraviolet rays of 500 mJ / cm ² (illuminance 200 mW / cm ² , 2.5 seconds) were irradiated by an ultraviolet irradiation device. .

  The results of measuring the dot diameter, maximum height / diameter, reflection peak wavelength, and retroreflection angle range in the same manner as in Example 1 are shown in the table below.

  From the results shown in Table 1, it can be seen that dots having a larger “maximum height / diameter” and “an angle between the dot surface and the substrate” could be formed on the substrate by the manufacturing method of the present invention. . By the manufacturing method of the present invention, an optical member having dots with high reflection efficiency for natural light that reflects both right circularly polarized light and left circularly polarized light, and an optical member having dots having reflection peaks at a plurality of wavelengths can be easily obtained. I was able to.

1 dot 2 substrate 3 support 4 ground layer 5 overcoat layer 100 optical member 105 display device 106 pen-type input terminal 107 read data processing device 108 code

Claims (14)

A method of manufacturing an optical member,
Forming dots made of a liquid crystal material having a cholesteric structure on the substrate surface;
The formation of the dots includes depositing a liquid crystal composition containing a liquid crystal compound and a chiral agent on the substrate,
The droplet ejection is a method for producing an optical member that is performed twice or more per dot. The method for producing an optical member according to claim 1, wherein at least one of the second and subsequent droplet ejections is performed before drying the liquid crystal composition deposited immediately before. The method for producing an optical member according to claim 2, wherein the composition of the liquid crystal composition to be ejected is the same for at least one of the second and subsequent droplet ejections and the immediately preceding droplet ejection. The method for producing an optical member according to any one of claims 1 to 3, wherein at least one of the second and subsequent droplet ejections is performed after drying of the liquid crystal composition that has just been deposited. The method for producing an optical member according to claim 4, wherein the composition of the liquid crystal composition used for the droplet ejection after the drying is the same as that of the liquid crystal composition that has been deposited immediately before and dried by the drying. The method for producing an optical member according to claim 4, wherein the composition of the liquid crystal composition used in the droplet ejection after drying is different from the composition of the liquid crystal composition ejected immediately before the drying and dried by the drying. The method for producing an optical member according to any one of claims 1 to 6, wherein at least one of the second and subsequent droplet ejections is performed after curing of the liquid crystal composition deposited immediately before. The method for producing an optical member according to claim 7, wherein the composition of the liquid crystal composition used in the droplet ejection after curing is the same as that of the liquid crystal composition ejected immediately before the curing and cured by the curing. The method for producing an optical member according to claim 7, wherein the composition of the liquid crystal composition used in the droplet ejection after the curing is different from the composition of the liquid crystal composition ejected immediately before the curing and cured by the curing. The composition of the liquid crystal composition used in the droplet ejection after the curing and the liquid crystal composition that has been ejected immediately before and cured by the curing are different in the chiral agent,
The method of manufacturing an optical member according to claim 9, wherein the twist direction of the spiral induced by one chiral agent is right, and the twist direction of the spiral induced by the chiral agent contained in the other chiral agent is left. The method for producing an optical member according to claim 10, wherein the liquid crystal composition first deposited on the surface of the substrate contains a chiral agent whose induced spiral twist direction is right. 10. The optical member according to claim 9, wherein the composition of the liquid crystal composition used for the droplet ejection after curing and the liquid crystal composition that has been ejected immediately before and cured by the curing differ in concentration of the chiral agent. Production method. 13. The optical member according to claim 12, wherein the concentration of the chiral agent in the liquid crystal composition used in the droplet ejection after the curing is greater than the concentration of the chiral agent in the liquid crystal composition that has been ejected immediately before and cured by the curing. Manufacturing method. The method for producing an optical member according to claim 1, wherein the droplet ejection is performed by an inkjet method, and a plurality of the dots are formed in a pattern on the surface of the substrate.