JP6336948B2 - Infrared reflective pattern forming ink composition, infrared reflective pattern forming method, and infrared reflector - Google Patents

Description

  The present invention relates to an infrared reflective pattern forming ink composition, an infrared reflective pattern forming method, and an infrared reflector.

In recent years, there has been an increasing need to convert handwritten characters, pictures, symbols, and the like into electronic data that can be handled by an information processing device. In particular, handwritten information can be processed in real time without using a reading device such as a scanner. There is an increasing demand for input means that can be used for input. As such an input means, a sheet printed with an infrared reflection pattern is made transparent to visible light, the transparent sheet is placed in front of the display device, and the contents handwritten directly on the transparent sheet are input to the information processing device. Input devices that can do this have been proposed.
Such an input device is designed to recognize an infrared pattern as data in order to suppress the influence on the design and visibility of a printed matter and a display. The reading method may be designed to irradiate infrared rays obliquely and read the infrared rays reflected by the reflector with a light receiver near the infrared output unit.

By the way, various materials for forming a reflector that reflects infrared rays have been proposed in addition to the above applications.
For example, as an application for forming a glossy image on a recording medium, an ink composition containing flat metal particles, water, an organic solvent, and a resin having one or more unsaturated bonds has been proposed. (For example, refer to Patent Document 1).
In addition, as a use for forming a wiring pattern, a conductive pattern forming composition including flat silver particles and a binder resin has been proposed (for example, see Patent Document 2).

  In addition, an infrared shielding film having a metal particle-containing layer containing metal particles having 60% by number or more of hexagonal or circular tabular silver particles and containing a compound having absorption in the infrared region has been proposed. (For example, refer to Patent Document 3).

JP 2012-001581 A International Publication No. 2013/077447 JP 2014-066987 A

When forming the infrared reflection pattern in the input device as described above, it is advantageous to form the pattern by the ink jet method from the viewpoint of variable properties and process load reduction.
However, when the ink composition described in Patent Document 1 and the conductive pattern forming composition described in Patent Document 2 are ejected by the ink jet method, flat metal particles are formed on the outer peripheral portion of the liquid droplet after landing. There is a tendency that a pattern in which flat and flat metal particles are uniformly dispersed cannot be obtained. Therefore, the pattern has low infrared retroreflectivity and visible light transmittance, and tends to generate haze due to the unevenness of the flat metal particles.

  The present invention has been made in view of the above, and an ink composition for forming an infrared reflection pattern and an infrared reflection pattern forming method capable of obtaining an infrared reflection pattern having high infrared retroreflectivity and high visible light transmittance and low haze. In addition, an object of the present invention is to provide an infrared reflector using the ink composition for forming an infrared reflection pattern.

Specific means for solving the problems include the following aspects.
<1> Tabular grains, a dispersing agent for dispersing tabular grains, an organic solvent having a boiling point of 190 ° C. or higher and a solubility parameter of 24.0 MPa ^1/2 or higher, water, and a fluorine-based interface An infrared ray reflection agent, wherein the content ratio of the dispersant to the tabular grains is 0.01 to 0.5 by mass, and the content ratio of the organic solvent to the tabular grains is 10 to 150 by mass ratio. An ink composition for pattern formation.

<2> The ink composition for forming an infrared reflection pattern according to <1>, wherein the tabular particles are tabular metal particles.
<3> The flat metal particles have an aspect ratio of 6 to 40, and include at least one metal selected from silver, gold, aluminum, platinum, rhodium, copper, and nickel. Ink composition for forming an infrared reflection pattern.
<4> The ink composition for forming an infrared reflective pattern according to <3>, wherein the metal is silver.

<5> The ink composition for forming an infrared reflective pattern according to any one of <1> to <4>, wherein the dispersant is a water-soluble resin.
<6> The infrared reflective pattern forming ink composition according to any one of <1> to <5>, wherein the dispersant is gelatin having an average molecular weight of 20,000 to 200,000.
<7> The ink composition for forming an infrared reflection pattern according to any one of <1> to <6>, wherein the organic solvent is at least one selected from glycerin, ethylene glycol, formamide, and diethylene glycol.
<8> The fluorinated surfactant contains a perfluoro group in the molecule and has an index of refraction of 1.30 to 1.42, and the infrared reflection according to any one of <1> to <7>. An ink composition for pattern formation.

<9> An infrared reflective pattern forming method in which the infrared reflective pattern forming ink composition according to any one of <1> to <8> is applied on a support by an inkjet method to form an infrared reflective pattern.

<10> An infrared reflector having a support and an infrared reflective pattern formed of the ink composition for forming an infrared reflective pattern according to any one of <1> to <8>.

  According to the present invention, an infrared reflective pattern forming ink composition, an infrared reflective pattern forming method, and an infrared reflective pattern forming method capable of obtaining an infrared reflective pattern having high infrared retroreflectivity and high visible light transmittance and low haze. An infrared reflector using the ink composition is provided.

It is the schematic perspective view which showed the circular tabular grain which is an example of the shape of the tabular grain preferably used for an infrared reflector. It is the schematic perspective view which showed the hexagonal tabular grain which is an example of the shape of the tabular grain preferably used for an infrared reflector. It is the schematic which shows the cross section of an example of an infrared reflector. In an infrared reflector, it is a schematic sectional view showing the existence state of tabular grains in an infrared reflection pattern including tabular grains, and is a main plane (plane for determining equivalent circle diameter D) of tabular grains, and tabular It is a figure explaining the angle ((theta)) with the surface of the uneven structure nearest to a particle | grain. It is the schematic of an example by which tabular grain was arrange | positioned on the surface of the convex part of the uneven structure which an infrared reflector has. It is the schematic of another example by which tabular grain was arrange | positioned on the surface of the convex part of the uneven structure which an infrared reflector has. It is the schematic of the system which used the infrared reflector as the sheet | seat with which the surface or front of the display apparatus which can display an image is mounted | worn. It is the schematic which shows the upper surface of the other example of the infrared reflective pattern formation body of this invention. It is the schematic of the method of measuring the diagonal reflectance of an infrared reflector.

Hereinafter, the infrared reflective pattern forming ink composition, the infrared reflective pattern forming method, and the infrared reflector of the present invention will be described in detail.
In this specification, the numerical range indicated using “to” indicates a range including the numerical values described before and after “to” as the minimum value and the maximum value, respectively.

<Infrared reflective pattern forming ink composition>
The ink composition for forming an infrared reflection pattern of the present invention (hereinafter also simply referred to as “ink composition”) has tabular grains, a dispersant for dispersing the tabular grains, a boiling point of 190 ° C. or higher, and a solubility. Dispersion with respect to tabular grains, including an organic solvent (hereinafter also referred to as a specific organic solvent) having a parameter (hereinafter also referred to as SP value) of 24.0 MPa ^1/2 or more, water, and a fluorosurfactant. The mass ratio of the agent is 0.01 to 0.5, and the mass ratio of the specific organic solvent to the tabular grains is 10 to 150.
The ink composition of the present invention is used for forming an infrared reflection pattern. In particular, it can be suitably used for forming an infrared reflection pattern by an ink jet method.

Although the operation of the present invention is not clear, it is estimated as follows.
When the ink composition described in Patent Document 1 and the conductive pattern forming composition described in Patent Document 2 are ejected by an ink jet method, the flat plate-like particles are formed as droplets after the droplets are deposited. There was a tendency to be biased to the outer periphery. Therefore, there is a tendency that a pattern in which tabular grains are uniformly dispersed in a droplet cannot be obtained. This unevenness of the tabular grains is considered to be a cause of lowering the retroreflectivity and visible light transmittance of the formed pattern and increasing haze.
In addition, the ink composition described in Patent Document 1 and the conductive pattern forming composition described in Patent Document 2 have a composition in which the solvent contained in the composition is volatilized at the discharge port of the inkjet head even during discharge. The discharge property of the object may be lowered.
It is considered that there is the following relationship between the dischargeability of the ink composition and the uniformity of the dispersibility of the tabular grains in the droplets after landing.
When the ink composition dries, if the evaporation rate of water and organic solvent at the edge and center of the droplet is non-uniform, particles are deposited on the outer periphery of the droplet (so-called coffee stain phenomenon) May occur. This non-uniform evaporation rate of water and organic solvent is caused by the viscosity and surface tension of the ink composition, and thus affects the ejection properties. That is, it is considered that an ink composition in which a coffee stain phenomenon is likely to occur has a poor ejection property of the ink composition.
The ink composition of the present invention contains a specific organic solvent and a fluorosurfactant, and the mass ratio of the dispersant to the tabular grains and the mass ratio of the specific organic solvent to the tabular grains are within a predetermined range. . Therefore, it is considered that the ink composition is excellent in ejection properties, and the tabular grains in the droplets after landing on the support are present in a state with good uniformity. Furthermore, by including a fluorine-based surfactant, the infrared reflective pattern can maintain dispersibility while suppressing a decrease in transparency.
As described above, it is considered that the formed infrared reflection pattern is excellent in infrared retroreflectivity and visible light transmittance and has a low haze.

The content ratio of the dispersant to the tabular grains in the ink composition is 0.01 to 0.5 by mass ratio. When the content ratio is 0.01 or more, the amount of the dispersant is not excessively reduced with respect to the tabular grains, and the dispersibility of the tabular grains in the ink composition is improved. Therefore, the dischargeability of the ink composition is improved, the tabular grains are present in a uniform state even in the formed infrared reflection pattern, the infrared retroreflective property and the visible light transmittance are excellent, and the haze is low. Become. On the other hand, when the content ratio is 0.5 or less, the viscosity of the ink composition does not become excessively high, so that the ejection property is improved, and the formed infrared reflection pattern has a flat shape with good uniformity. Particles are present, the infrared retroreflectivity and visible light transparency are excellent, and the haze is low.
From the same viewpoint as described above, the content ratio of the dispersant to the tabular grains is preferably 0.05 to 0.25, and more preferably 0.07 to 0.13.

The content ratio of the specific organic solvent to the tabular grains in the ink composition is 10 to 150 by mass ratio. When the above content ratio is 10 or more, the viscosity of the ink composition does not become too high, so that the dischargeability of the ink composition is improved, and the formed infrared reflection pattern has a flat shape with good uniformity. Particles are present, the infrared retroreflectivity and visible light transparency are excellent, and the haze is low. On the other hand, when the content ratio is 150 or less, the viscosity of the ink composition does not become too low, so that the dischargeability of the ink composition is improved, and the formed infrared reflection pattern has good uniformity. There are tabular grains, which are excellent in infrared retroreflectivity and visible light transmittance, and have low haze.
From the same viewpoint as described above, the content ratio of the specific organic solvent to the tabular grains is preferably 20 to 120, and more preferably 50 to 100.

  Hereinafter, each component that can be contained in the ink composition of the present invention will be described.

[Fluorosurfactant]
The ink composition contains at least one fluorine-based surfactant.
In the case of urethane surfactants other than fluorine surfactants, for example, the retroreflective properties of infrared rays are likely to be lowered, but the infrared reflection formed when the ink composition selectively contains a fluorine surfactant. The surface tension of the ink composition can be adjusted without impairing the infrared retroreflectivity and visible light transmittance of the pattern. In addition, by using a fluorosurfactant, the above effect can be obtained in a small amount, which is advantageous in terms of cost.

The fluorosurfactant is not particularly limited and can be selected from known fluorosurfactants.
Examples of the fluorosurfactant include the fluorosurfactants described in “Surfactant Handbook” (Nishiichiro, Imai Tomoichiro, Kasai Shozo Edition, Sangyo Tosho Co., Ltd., 1960). .

Among these, as the fluorosurfactant, a fluorosurfactant having a perfluoro group in the molecule and a refractive index of 1.30 to 1.42 (preferably 1.32 to 1.40) is preferable. By including a perfluoro group in the molecule, the refractive index of the fluorosurfactant can be easily adjusted within the above range, and the surface tension of the ink composition can be adjusted with a relatively small amount.
Examples of the perfluoro group include a perfluoroalkyl group. As the perfluoroalkyl group, a perfluoroalkyl group having 10 or more carbon atoms is more preferable, and a perfluoroalkyl group having 14 to 18 carbon atoms is more preferable.
When the refractive index is within the above range, the infrared retroreflective property and visible light transmittance of the formed infrared reflective pattern can be more favorably maintained.
The refractive index can be measured by a Kalnew precision refractometer (manufactured by Shimadzu Corporation, KPR-3000). When the fluorosurfactant is liquid, the fluorosurfactant is accommodated in a cell and the refractive index is measured. When the fluorosurfactant is solid, the refractive index is measured by the V-block method in which the solid sample is placed on the V-block prism attached to the Kalnew precision refractometer (manufactured by Shimadzu Corporation, KPR-3000).

  Examples of the fluorosurfactant containing a perfluoro group in the molecule and having a refractive index of 1.30 to 1.42 include perfluoroalkyl carboxylates, perfluoroalkyl sulfonates, and perfluoroalkyl phosphates. Anionic type such as ester; amphoteric type such as perfluoroalkyl betaine; cationic type such as perfluoroalkyltrimethylammonium salt; containing perfluoroalkylamine oxide, perfluoroalkylethylene oxide adduct, perfluoroalkyl group and hydrophilic group Nonionic types such as oligomers, oligomers containing perfluoroalkyl groups and lipophilic groups, oligomers containing perfluoroalkyl groups, hydrophilic groups and lipophilic groups, urethanes containing perfluoroalkyl groups and lipophilic groups, etc. It is done. Moreover, the fluorine-type surfactant described in each gazette of Unexamined-Japanese-Patent No. 62-170950, 62-226143, and 60-168144 is also mentioned suitably.

  A commercially available fluorosurfactant may be used, for example, Surflon (registered trademark) series (for example, S-243, S-242) manufactured by AGC Seimi Chemical Co., Ltd., DIC Corporation. MegaFex (registered trademark) series (for example, F-444, F-410) manufactured by 3M, NOVEC (registered trademark) series (for example, 27002) manufactured by 3M, manufactured by EI Dupont Nemeras and Company Zonyl series (for example, FSE).

The content of the fluorosurfactant contained in the ink composition is preferably 0.01% by mass to 5.0% by mass, and 0.05% by mass to 1.0% by mass with respect to the total mass of the ink composition. Is more preferable, and 0.1% by mass to 0.5% by mass is even more preferable.
When the content of the fluorosurfactant is in the above range, it is easy to adjust the surface tension of the ink composition so that the dischargeability of the ink composition is better.

[Tabular grains]
The ink composition contains at least one tabular grain.
When the ink composition contains tabular grains, the formed infrared reflection pattern can retroreflect infrared rays.
Tabular grains are grains having a tabular shape. “Platform” means a shape having two main planes.

(Particle material)
There is no restriction | limiting in particular as a material of tabular grain, According to the objective, it can select suitably. The material for the tabular grains is preferably a metal such as silver, gold, aluminum, platinum, rhodium, copper, and nickel, and more preferably silver, from the viewpoint of high infrared reflectance.
That is, the tabular grains are preferably tabular metal grains, and more preferably tabular silver grains.

(Particle shape)
The tabular grain is not particularly limited as long as it is a grain having two main planes, and can be appropriately selected according to the purpose, for example, a triangular shape, a quadrangular shape, a hexagonal shape, an octagonal shape, a circular shape. Particles having a shape such as are preferable. Among these, in terms of high visible light transmittance, a hexagonal or more polygonal shape and a circular shape (hereinafter referred to as a hexagonal shape or a circular shape) are more preferable.
The circular tabular grains are not particularly limited as long as the tabular grains have no corners and are round when viewed from above the main plane with a transmission electron microscope (TEM), and are appropriately selected depending on the purpose. You can choose.
The hexagonal tabular grain is not particularly limited as long as it is a hexagonal shape when the tabular grain is observed from a direction perpendicular to the main plane with a transmission electron microscope (TEM), and is appropriately selected according to the purpose. For example, the hexagonal corner may be an acute angle or an obtuse angle, but an obtuse angle is preferable in that absorption in the visible light region can be reduced. There is no restriction | limiting in particular as an angle, According to the objective, it can select suitably.

  Among the tabular grains, hexagonal or circular tabular grains are preferably 60% by number or more, more preferably 65% by number or more, and more preferably 70% by number or more based on the total number of tabular grains. Particularly preferred. When the ratio of hexagonal to circular tabular grains is 60% by number or more, the visible light transmittance is increased.

(Average particle size and coefficient of variation)
There is no restriction | limiting in particular as a magnitude | size of a tabular grain, According to the objective, it can select suitably, 10 nm-500 nm are preferable, and 20 nm-300 nm are more preferable, and 50 nm-200 nm are more preferable.
The coefficient of variation in the particle size distribution of the tabular grains is preferably 35% or less, more preferably 30% or less, and particularly preferably 20% or less. The variation coefficient is preferably 35% or less because the reflection wavelength region of the heat ray in the infrared reflector becomes sharp.
The average particle diameter (average equivalent circle diameter) of the tabular grains can be obtained by a known method of correcting the photographing magnification by measuring the projected area of the grains on the electron micrograph. The equivalent circle diameter is represented by the diameter of a circle having an area equal to the projected area of individual particles obtained by this method. A particle size distribution (particle size distribution) is obtained by the statistics of the equivalent circle diameter D of 200 tabular grains, and the average particle diameter (average equivalent circle diameter) can be obtained by calculating the arithmetic average. The coefficient of variation in the particle size distribution of the tabular grains can be determined by a value (%) obtained by dividing the standard deviation of the particle size distribution by the aforementioned average particle diameter (average equivalent circle diameter)).

(Particle thickness)
The thickness of the tabular grains is preferably 20 nm or less, more preferably 5 nm to 14 nm, and more preferably 5 nm to 12 nm, from the viewpoints of dispersibility of the tabular grains in the ink composition and ejection properties. Particularly preferable is 5 nm to 10 nm.
The thickness of the tabular grains is determined by dropping a particle dispersion containing tabular grains onto a silicon substrate, drying, applying a coating process by carbon vapor deposition or metal vapor deposition, and performing cross-sectional slices by focused ion beam (FIB) processing. The transmission electron microscope (TEM) image of this cross section was photographed, the distance in the thickness a direction of any tabular grain was measured from the TEM image, and this operation was performed on 10 tabular grains. It was measured by calculating the arithmetic average value of 10 points.

(Aspect ratio of particles)
The aspect ratio of the tabular grains is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 6 to 40 from the viewpoint that the reflectance in the infrared region with a wavelength of 800 nm to 1,800 nm is increased. 10 to 35 are more preferable. When the aspect ratio is 6 or more, the reflection wavelength is longer than 800 nm, and when the aspect ratio is 40 or less, the reflection wavelength is shorter than 1,800 nm, so that the reflectance in a desired wavelength region can be increased. In addition, when the aspect ratio is 40 or less, aggregation of tabular grains in the ink composition can be suppressed, which is advantageous in terms of ejection properties and infrared retroreflectivity of the formed infrared reflection pattern.
The aspect ratio means a value obtained by dividing the average particle diameter (average equivalent circle diameter) of tabular grains by the average grain thickness of tabular grains.
For example, when the tabular grains are circular, the aspect ratio is a value obtained by dividing the diameter D shown in FIG. 1 by the thickness a. When the tabular grains are hexagonal, the aspect ratio is the diameter D (equivalent circle diameter D) obtained by approximating the area of the plane of the hexagonal tabular grains with a circle of the same area as shown in FIG. Is divided by the thickness a.
The grain thickness corresponds to the distance between the main planes of the tabular grains, and is, for example, as shown as a in FIGS. 1 and 2 and can be measured by a transmission electron microscope (TEM).
The aspect ratio of the tabular grains can be adjusted by the thickness and average particle diameter of the tabular grains.

(Method for synthesizing tabular grains)
The method for synthesizing tabular grains is not particularly limited and may be appropriately selected depending on the purpose.For example, when synthesizing triangular to hexagonal tabular metal particles, a chemical reduction method, a photochemical reduction method, Examples thereof include a liquid phase method such as an electrochemical reduction method. Among these, a liquid phase method such as a chemical reduction method or a photochemical reduction method is preferable in terms of shape and size controllability. After synthesizing triangular to hexagonal flat metal particles, for example, by performing etching treatment with a dissolved species that dissolves silver such as nitric acid and sodium sulfite, aging treatment by heating, etc., triangular to hexagonal flat plate shape Hexagonal or circular flat metal particles may be obtained by blunting the corners of the metal particles.

  As a method for synthesizing tabular grains, in addition to the above, after seed crystals are previously fixed on the surface of a transparent substrate such as a film or glass, metal particles (eg, Ag) may be grown in a tabular form.

  The tabular grains may be further processed to impart desired properties. The further treatment is not particularly limited and may be appropriately selected depending on the purpose. For example, formation of a high refractive index shell layer described in paragraphs [0068] to [0070] of JP-A No. 2014-184688 And adding various additives described in paragraphs [0072] to [0073] of JP-A No. 2014-184688.

(Preferred embodiment of tabular grains)
The tabular particles are preferably tabular metal particles from the viewpoint of infrared reflectance, and have an aspect ratio of 6 to 40, and at least one selected from silver, gold, aluminum, platinum, rhodium, copper, and nickel. Flat metal particles containing a metal are more preferable, an aspect ratio of 6 to 40, and flat silver particles containing silver are more preferable.

(Content of tabular grains)
The content of the tabular grains is preferably 0.40% by mass to 3.00% by mass, more preferably 0.50% by mass to 1.50% by mass, and 0.60% with respect to the total mass of the ink composition. The mass% to 1.00 mass% is more preferable.
The tabular grain content within the above range is advantageous in terms of the dispersibility of the tabular grains, the viscosity of the ink composition, and the dischargeability.

[Dispersant]
The ink composition contains at least one dispersant that disperses the tabular grains described above.
The content ratio of the dispersant to the tabular grains in the ink composition is 0.01 to 0.5 in terms of mass ratio as described above, and the preferable range is also as described above.

As a dispersing agent, it can select suitably from what can disperse a tabular grain.
The dispersant is preferably a water-soluble resin from the viewpoint of dispersibility of the tabular grains in the ink composition.
In the present specification, “water-soluble” means a property of dissolving 5 g or more (more preferably 10 g or more) in 100 g of water at 25 ° C.

  The water-soluble resin is preferably a water-soluble resin having visible light permeability. For example, polyvinyl acetal resin, polyvinyl alcohol resin, polyvinyl butyral resin, polyacrylate resin, polymethyl methacrylate resin, polycarbonate resin, polyvinyl chloride resin, ( Saturated) polyester resins, polyurethane resins, and polymers such as natural polymers such as gelatin and cellulose.

  Among the water-soluble resins, gelatin is preferable from the viewpoints of visible light transmittance and dispersibility of tabular grains.

  Gelatin includes so-called alkali-treated gelatin with treatment with lime in the process of induction from collagen, so-called acid-treated gelatin with treatment with hydrochloric acid, oxygen-treated gelatin with treatment with hydrolase, etc., contained in gelatin molecules Examples of treated and modified amino group, imino group, hydroxyl group, or carboxyl group as a functional group with a reagent having one group capable of reacting with them, such as phthalated gelatin, succinated gelatin, trimethylated gelatin, etc. Examples of so-called gelatin derivatives and modified gelatin include those commonly used in the art described in JP-A-62-215272, page 222, lower left column, line 6 to page 225, upper left column.

The molecular weight of gelatin is preferably from 5,000 to 1,000,000, more preferably from 10,000 to 500,000, and from 20,000 to 200,000, from the viewpoint of dispersibility of tabular grains in the ink composition. Further preferred.
The measurement of average molecular weight means the value of weight average molecular weight measured by gel permeation chromatograph (GPC).
The above GPC uses HLC-8020GPC (manufactured by Tosoh Corporation), and elution using TSKgel (registered trademark) and Super Multipore HZ-H (manufactured by Tosoh Corporation, 4.6 mm ID × 15 cm) as columns. This is performed using THF (tetrahydrofuran) as a liquid.
GPC is performed using a differential refractive index (RI) detector with a sample concentration of 0.45 mass%, a flow rate of 0.35 ml / min, a sample injection amount of 10 μl, and a measurement temperature of 40 ° C.
The calibration curve is “Standard sample TSK standard, polystyrene” manufactured by Tosoh Corporation: “F-40”, “F-20”, “F-4”, “F-1”, “A-5000”, “A -2500 "," A-1000 ", and" n-propylbenzene ".

The refractive index of the dispersant is preferably 1.40 to 1.70, more preferably 1.42 to 1.65, from the viewpoint of visible light transmittance and haze of the formed infrared reflection pattern. More preferably, it is 1.45 to 1.60.
The method for measuring the refractive index is as described above.

The content of the dispersant is preferably 0.01% by mass to 1.00% by mass, more preferably 0.03% by mass to 0.50% by mass, and 0.06% by mass with respect to the total mass of the ink composition. % To 0.30% by mass is more preferable.
When the content of the dispersant is within the above range, it is advantageous in terms of the dispersibility of the tabular grains, the viscosity of the ink composition, and the dischargeability.

[Specific organic solvent]
The ink composition contains at least one organic solvent (specific organic solvent) having a boiling point of 190 ° C. or higher and a solubility parameter (SP value) of 24.0 MPa ^1/2 or higher.
The content ratio of the specific organic solvent to the tabular grains in the ink composition is 10 to 150 in terms of mass ratio as described above, and the preferable range is also as described above.

When the boiling point of the specific organic solvent is 190 ° C. or more, the ink composition is excellent in dischargeability and excellent in the infrared retroreflectivity of the formed infrared reflection pattern. Moreover, when the boiling point is 190 ° C. or higher, the viscosity change of the ink composition due to the volatilization of the organic solvent when discharging the ink composition can be suppressed, the discharge property is excellent, and the formed infrared reflective pattern Excellent infrared retroreflectivity. The upper limit of the boiling point of the specific organic solvent is not particularly limited, but is preferably 300 ° C. or lower from the viewpoint of the viscosity of the ink composition.
A boiling point can be calculated | required with a boiling point measuring device (The product made by Titan Technologies, DosaTherm300).

When the SP value of the specific organic solvent is 24.0 MPa ^1/2 or more, the dispersibility of the tabular particles in the ink composition is excellent, and the infrared retroreflectivity of the formed infrared reflection pattern is excellent.
The upper limit of the SP value of the specific organic solvent is not particularly limited, but is preferably 45.0 MPa ^1/2 or less from the viewpoint of the viscosity of the ink composition.
In the present specification, the SP value (solubility parameter) is a value [unit: MPa ^1/2 ] obtained by the Okitsu method. The Okitsu method is one of the well-known methods for calculating the SP value. 29, no. 6 (1993) 249-259.

Specific examples of the specific organic solvent are shown below. In addition, the numerical value in a parenthesis shows a boiling point (unit: degreeC) and SP value (unit: MPa1 ^{/ 2} ) in the order described.
Examples of the specific organic solvent include ethylene glycol (197 ° C., 29.9 MPa ^1/2 ), diethylene glycol (244 ° C., 24.8 MPa ^1/2 ), triethylene glycol (125 ° C. (0.1 mmHg, literature value), 27.8 MPa ^1/2 ), propylene glycol (188 ° C., 27.6 MPa ^1/2 ), 1,4-butanediol (230 ° C., 30.7 MPa ^1/2 ), 1,2-pentanediol (206 ° C., 28.6 MPa ^1/2 ), 1,5-pentanediol (206 ° C., 29.0 MPa ^1/2 ), 1,6-hexanediol (250 ° C., 27.7 MPa ^1/2 ), glycerin (290 ° C., 33 .8MPa ^1/2), formamide (210 ℃, 39.3MPa ^1/2), dimethylformamide (153 ° C., 30.6 Pa ^1/2), methanol (65 ℃, 28.2MPa ^1/2), isopropyl alcohol (82 ℃, 28.7MPa ^1/2), triethanolamine (208 ℃ (20hPa), 32.3MPa 1/2) , Polyethylene glycol (250 ° C., 26.1 MPa ^1/2 ), 1,2-hexanediol (223 ° C., 24.1 MPa ^1/2 ), dipropylene glycol (230 ° C., 27.1 MPa ^1/2 ), 1 , 2-butanediol (191 ° C. (747 mmHg, literature value), 26.1 MPa ^1/2 ).

  Among these, glycerin, ethylene glycol, diethylene glycol, and formamide are preferable, glycerin and ethylene glycol are more preferable, and glycerin is still more preferable from the viewpoint of the dischargeability of the ink composition and the dispersibility of the tabular particles.

The content of the specific organic solvent is preferably 5% by mass to 80% by mass, more preferably 10% by mass to 70% by mass, and still more preferably 15% by mass to 65% by mass with respect to the total mass of the ink composition.
When the content of the specific organic solvent is within the above range, it is advantageous in terms of the dispersibility of the tabular grains, the viscosity of the ink composition, and the dischargeability.

[water]
The ink composition includes water.
Although there is no restriction | limiting in particular in content of the water in an ink composition, 10 mass% or more is preferable with respect to the total mass of an ink composition, 20 mass% or more is more preferable, 30 mass% or more is further more preferable.
The upper limit of the water content in the ink composition is appropriately set in consideration of the content of the tabular particles, the dispersant, the specific organic solvent, and the fluorosurfactant described above. 90 mass% or less is preferable with respect to the total mass of an ink composition, 85 mass% or less is more preferable, and 80 mass% or less is further more preferable.

[Other additives]
The ink composition may contain additives such as preservatives and antifoaming agents in addition to the above components.
As the preservative, reference can be made to the descriptions in paragraphs [0073] to [0090] of JP-A No. 2014-184688.
As the antifoaming agent, the description in paragraphs [0091] and [0092] of JP-A No. 2014-184688 can be referred to.

<Infrared reflective pattern forming method>
The infrared reflective pattern formation method of this invention forms an infrared reflective pattern by providing the above-mentioned ink composition on a support body by the inkjet method.
Since the infrared reflective pattern formed by the above method contains the ink composition described above, the infrared retroreflective property and visible light transmittance are high, and the haze is low.
As a method for forming an infrared reflection pattern, it is preferable to form an infrared reflection pattern by applying an ink composition on a support and then drying the ink composition.

  The support can be selected from materials having visible light permeability. Details of the support will be described later.

  The ink jet method is not particularly limited, and is a known method, for example, a charge control method for discharging ink using electrostatic attraction, a drop-on-demand method (pressure pulse method) using vibration pressure of a piezo element, An acoustic ink jet system that converts an electrical signal into an acoustic beam, irradiates the ink with ink, and ejects the ink using radiation pressure, and a thermal ink jet that forms bubbles by heating the ink and uses the generated pressure (bubble jet (registered) Trademark)) method or the like.

The ink jet head used in the ink jet method may be an on-demand method or a continuous method. In addition, as a discharge method, an electro-mechanical conversion method (for example, a single cavity type, a double cavity type, a bender type, a piston type, a shear mode type, a shared wall type, etc.), an electro-thermal conversion method (for example, a thermal type) Specific examples include an ink jet type, a bubble jet (registered trademark) type, an electrostatic suction type (for example, an electric field control type, a slit jet type, etc.) and a discharge type (for example, a spark jet type). However, any discharge method may be used.
In addition, there is no restriction | limiting in particular about the ink nozzle etc. which are used when discharging an ink composition by the inkjet method, According to the objective, it can select suitably.

As an inkjet head, a single serial head is used, and a shuttle system that performs recording while scanning the head in the width direction of the support, and a line head in which recording elements are arranged corresponding to the entire area of one side of the support There is a line system using. In the line system, an image can be recorded on the entire surface of the support by scanning the support in a direction perpendicular to the arrangement direction of the recording elements, and a carriage system such as a carriage for scanning a short head is not necessary. Further, since complicated scanning control of the carriage movement and the support is not required, and only the support is moved, the recording speed can be increased as compared with the shuttle system.
The infrared reflection pattern forming method of the present invention can be applied to any of these, but generally, when applied to a line system that does not use a dummy jet, the effect of improving ejection accuracy and image scratch resistance is great.
The amount of ink droplets can be adjusted by appropriately selecting the ejection conditions in the ink jet method according to the ink composition to be ejected.

The ink composition applied onto the support is preferably dried to form an infrared reflection pattern.
In the drying process, the ink composition applied on the support is evaporated with water and the specific organic solvent by, for example, a heating means, whereby an infrared reflection pattern is formed.

The heating means is not limited as long as water and the specific organic solvent can be dried, and a heat drum, hot air, an infrared lamp, a heat oven, a heat plate heating, or the like can be used.
The heating temperature is preferably 50 ° C or higher, more preferably about 60 ° C to 150 ° C, and still more preferably about 70 ° C to 100 ° C. The drying or heating time can be appropriately set in consideration of the composition of the ink composition to be used and the discharge amount of the ink composition. From the viewpoint of pattern uniformity, it is preferably 1 minute to 60 minutes, and 5 minutes to 40 minutes. Minutes are more preferred.

<Infrared reflector>
The infrared reflector of the present invention has a support and an infrared reflection pattern formed of the above-described ink composition.
Since the infrared reflector has an infrared reflection pattern formed by the ink composition described above, infrared retroreflectivity and visible light permeability are high, and haze is low.
The infrared reflector preferably further has an overcoat layer.
As an embodiment of the infrared reflector, as shown in FIG. 3, an embodiment of an infrared reflector 11 having a support 2, an infrared reflection pattern 1, and an overcoat layer 3 can be mentioned. In FIG. 3, the infrared reflector 11 includes a reflecting portion 21 in which the infrared reflecting pattern 1 is formed on the support 2 and a non-reflecting portion 22 in which the infrared reflecting pattern is not formed.

[Infrared reflection pattern]
The infrared reflector has an infrared reflection pattern formed of the above-described ink composition. The method for forming the infrared reflection pattern is as described above, and the preferred embodiment is also the same.
The infrared reflection pattern contains at least tabular grains, a dispersant, a specific organic solvent, and a fluorosurfactant.

(Flat orientation of tabular grains)
In the infrared reflector, the tabular grains are planarly oriented in an angle between the main plane of the tabular grains and the surface of the concavo-convex structure closest to the tabular grains in the range of 0 ° to ± 30 °. The tabular grains are preferably 50% by number or more based on the total tabular grains.

  Here, FIG. 4 is a schematic cross-sectional view showing an existence state of an infrared reflection pattern including tabular grains in the infrared reflector. FIG. 4 is a diagram for explaining an angle (± θ) between the main plane of the tabular grains 4 (the plane that determines the equivalent circle diameter D) and the surface of the concavo-convex structure closest to the tabular grains. .

  In FIG. 4, the angle (± θ) formed between the main plane of the tabular grains 4 and the surface of the concavo-convex structure closest to the tabular grains corresponds to a predetermined range in the plane orientation of the tabular grains. . That is, the plane orientation refers to a state where the tilt angle (± θ) shown in FIG. 4 is small when a cross section of the infrared reflector is observed. In particular, a state in which the main plane of the tabular grains is in contact with the surface of the concavo-convex structure closest to the tabular grains, that is, a state where θ is 0 ° is preferable. When the plane orientation angle of the main plane of the tabular grain with respect to the surface of the above-described uneven structure closest to the tabular grain, that is, θ in FIG. 4 is ± 30 ° or less, a predetermined wavelength of the infrared reflector (for example, The reflectance in the visible light region long wavelength side to the near infrared region is improved. The surface of the concavo-convex structure closest to the tabular grain from the main plane of the tabular grain is a perpendicular line directed from the main plane of the tabular grain to the surface of the concavo-convex structure closest to the tabular grain; Refers to an orthogonal plane. When the surface of the concavo-convex structure is flat as in the prism shape of FIG. 5, the angle formed between the main plane of the tabular grain and the surface of the concavo-convex structure closest to the tabular grain is tabular. It becomes the surface of the concavo-convex structure including the legs of the perpendicular line that are directed from the main plane of the grain toward the surface of the concavo-convex structure closest to the tabular grains. When the surface of the concavo-convex structure is a curved surface as in the hemispherical shape of FIG. 6, the angle formed between the main plane of the tabular grain and the surface of the concavo-convex structure closest to the tabular grain is tabular. It becomes a tangent plane between the perpendicular line and the surface of the concavo-convex structure, which is directed from the main plane of the grain toward the surface of the concavo-convex structure closest to the tabular grain.

  As an evaluation of whether or not the main plane of the tabular grain is plane-oriented with respect to the surface of the above-mentioned concavo-convex structure closest to the tabular grain, an infrared reflector is used as an infrared ray by using a focused ion beam (FIB). There is a method in which a cross-section sample or a cross-section sample of a reflector is prepared, and this is evaluated from an image obtained by observing using a transmission electron microscope (TEM) or the like.

[Support]
The infrared reflector has a support.
The support can be selected from materials having visible light permeability. There is no restriction | limiting in particular about the shape of a support body, a structure, a magnitude | size, etc., It can select suitably according to the objective.
Examples of the shape of the support include a flat plate shape and a shape having irregularities on one surface. The structure of the support may be a single layer structure or a laminated structure. The size of the support can be appropriately selected according to the size of the infrared reflector.

As the material of the support, a resin material is preferable from the viewpoint of moldability. Examples of the resin material include cycloolefin polymer (COP), cycloolefin copolymer (COC), polyolefin such as polyethylene, polypropylene, poly-4-methylpentene-1, polybutene-1, and polyester such as polyethylene terephthalate and polyethylene naphthalate; Polycarbonate, polyvinyl chloride, polyphenylene sulfide, polyether sulfone, polyethylene sulfide, polyphenylene ether, styrene resin, acrylic resin, polyamide, polyimide, cellulose resin such as triacetyl cellulose, and other cellulose acetates.
Among these, acrylic resin, COP, and polyethylene terephthalate film are preferable from the viewpoints of moldability, high visible light permeability, and low haze.

  When a resin is used as the material for the support, the glass transition temperature (Tg) is preferably low from the viewpoint of moldability. As Tg of a support body, 30 to 200 degreeC is preferable and 60 to 170 degreeC is more preferable. Further, from the viewpoint of moldability, the support preferably maintains high visible light permeability and low haze even when a temperature exceeding Tg is applied.

  The support may be a film containing the above resin material, or may be a laminated film of these. An optimal material can be used as needed.

There is no restriction | limiting in particular as thickness of a support body, According to the intended purpose of using an infrared reflector, it can select suitably. The thickness of the support is usually about 10 μm to 500 μm, but it is preferably thinner from the viewpoint of request for thinning, and is preferably thick from the viewpoint of moldability.
The thickness of the support is preferably 10 μm to 100 μm, more preferably 20 μm to 300 μm, and even more preferably 35 μm to 280 μm. If the thickness of the support is sufficiently thick, adhesion failure tends to be difficult to occur. Further, if the thickness of the support is sufficiently thin, it is advantageous in terms of weight reduction and cost.

(Uneven structure)
The infrared reflector preferably has an infrared reflection pattern formed on a support having an uneven structure.
As shown in FIG. 3, both the non-reflective portion 22 and the reflective portion 21 that reflects infrared light may have a concavo-convex structure. In addition, the non-reflective portion that does not retroreflect infrared rays does not have a concavo-convex structure, and only the reflective portion that retroreflects in the infrared irradiation direction of infrared rays may have a concavo-convex structure (not shown).

The concavo-convex structure may include only a plurality of convex portions, may include only a concave portion, or may include a plurality of convex portions and concave portions. Examples of the concavo-convex structure including only a plurality of convex portions include a structure in which hemispherical convex portions are formed. Examples of the concavo-convex structure including a plurality of convex portions and concave portions include a prism shape, a pyramidal prism shape, a corner cube shape, and the like.
In the infrared reflector, it is preferable that the uneven structure described above has a prism shape, a pyramidal prism shape, a hemispherical shape, or a corner cube shape.
The uneven structure described above preferably includes a plurality of convex portions and concave portions, particularly preferably a prism shape, a pyramidal prism shape, or a corner cube shape, and more preferably a corner cube shape.
In this specification, the corner cube shape refers to a shape in which three planes are combined so as to be orthogonal to each other, but in a range that is optically acceptable from a shape in which three planes are combined so as to be orthogonal to each other. Deformed shapes are also included. Since it is difficult to make the infrared irradiation unit and the light receiver completely optically coincident with each other, it is preferable that the infrared light irradiation unit and the light receiver are deformed so that reflected light can easily enter the light receiver rather than performing the retroreflection completely.

It is preferable that the concavo-convex structure has at least one of the convex portion and the concave portion at a periodic pitch.
The size of the convex part or the concave part means the distance between the lowest points when cut by a plane perpendicular to the support and passing through the highest point and the lowest point of the convex part in the case of the convex part. This is the distance between the highest points when cut vertically on a plane passing through the highest point and the lowest point of the recess. If the size of each pitch is different, the average value of the distances between the lowest points or between the highest points mentioned above It is. The pitch refers to the distance between the highest points in the case of convex portions, and is the distance between the lowest points in the case of concave portions.

  The size of the convex portion or the concave portion is preferably sufficiently larger than the diameter of the tabular grain. The ratio of the size of the convex portion or the concave portion and the diameter of the tabular grains is preferably 5 to 500 times, more preferably 10 to 300 times, and particularly preferably 25 to 250 times. It is preferable that the ratio of the size of the convex portion or the concave portion and the diameter of the tabular grain is equal to or more than the above-mentioned lower limit value because the infrared reflectance is increased. It is preferable that the ratio of the size of the convex portion or the concave portion and the diameter of the tabular grain is equal to or less than the above-described upper limit value.

The pattern size of the infrared reflection pattern is a diameter when a circle having the same area as that of one pattern is assumed. When the areas of the individual patterns are different, the average value of the diameters described above is used.
The pattern size is preferably sufficiently larger than the size of the convex portion or the concave portion. The ratio of the pattern size to the size of the convex portion or the concave portion is preferably 2 to 100 times, and more preferably 5 to 50 times. It is preferable that the ratio of the pattern size and the size of the convex portion or the concave portion is equal to or more than the above lower limit value because the pattern shape can be easily recognized. When the ratio between the pattern size and the size of the convex portion or the concave portion is equal to or less than the above-described upper limit value, the infrared reflectance is preferably increased.

~ Formation method of uneven structure ~
There is no restriction | limiting in particular as a method of forming an uneven structure in a support body. For example, a method of forming a concavo-convex structure by applying a mold having a desired concavo-convex structure shape to the support may be mentioned. The uneven structure on the support may be formed before the infrared reflection pattern is formed, or may be formed after the infrared reflection pattern is formed on the smooth support.
As a method for forming a concavo-convex structure on a support, in a state having an infrared reflection pattern on the support, a mold having a desired concavo-convex structure shape having a desired convexity or concave size is applied, and at least heating and pressing Providing the concavo-convex structure by doing one is preferable from the viewpoint of maintaining the planar orientation of the tabular grains, and the concavo-convex structure may be provided on the support by heating and pressing (hot pressing).
The heating and pressurizing conditions are not particularly limited, and can be changed depending on the shape, structure, material, thickness and the like of the support. The heating temperature is preferably 80 ° C to 200 ° C, and more preferably 120 ° C to 160 ° C. The pressurizing pressure is preferably 1 MPa to 100 MPa, and more preferably 5 MPa to 15 MPa.

[Overcoat layer]
The infrared reflector preferably further has an overcoat layer.
As shown in FIG. 3, the infrared reflector 11 has an overcoat layer 3 that fills and flattens the concave portions of the above-described concavo-convex structure on the surface side where the infrared reflective pattern 1 on the above-described support 2 is present. From the viewpoint of reducing haze.
In the infrared reflector, in order to prevent oxidation and sulfidation of tabular grains due to mass transfer and to provide scratch resistance, the infrared reflector is the one in which the aforementioned hexagonal or circular tabular grains are exposed. You may have the overcoat layer closely_contact | adhered to the surface of the above-mentioned infrared reflective pattern. Infrared reflectors, especially when tabular grains are unevenly distributed on the surface of the infrared reflection pattern, to prevent impurities in the manufacturing process due to peeling of tabular grains, to prevent disorder of tabular grain arrangement during coating of different layers, etc. You may have an overcoat layer.
The above-described overcoat layer may contain an ultraviolet absorber. The above-mentioned overcoat layer is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include binders, matting agents, low refractive index fillers such as hollow silica and hollow magnesium fluoride, and surfactants. And further contains other components as required. By containing the low refractive index filler described above, the visible light reflectance of the pattern portion and the non-pattern portion is reduced and the visible light transmittance is improved, which is more preferable in applications where an infrared reflector is attached to the front surface of the display. The binder is not particularly limited and may be appropriately selected depending on the purpose. For example, a thermosetting type or a photosetting type such as an acrylic resin, a silicone resin, a melamine resin, a urethane resin, an alkyd resin, or a fluororesin. Resin etc. are mentioned. As thickness of the above-mentioned overcoat layer, 0.01 micrometer-1,000 micrometers are preferable, 0.02 micrometer-500 micrometers are more preferable, 0.03-10 micrometers are more especially preferable.
In the infrared reflector, the difference in refractive index between the overcoat layer and the support is preferably 0.05 or less, more preferably 0.02 or less, and particularly preferably 0.01 or less. preferable.
In the infrared reflector, the overcoat layer is preferably transparent, and the above-described support and overcoat layer are more preferably transparent.

-Formation method of overcoat layer-
The overcoat layer is preferably formed by coating. The coating method at this time is not particularly limited, and a known method can be used. For example, a dispersion containing the above-described ultraviolet absorber can be used as a dip coater, a die coater, a slit coater, a bar coater, or a gravure coater. The method of apply | coating by etc. is mentioned.

[Other layers]
(Adhesive layer or adhesive layer)
The infrared reflector preferably has an adhesive layer or an adhesive layer. The adhesive layer can contain an ultraviolet absorber.
The material that can be used for forming the adhesive layer is not particularly limited and may be appropriately selected depending on the intended purpose. For example, polyvinyl butyral (PVB) resin, acrylic resin, styrene / acrylic resin, urethane resin, polyester resin And silicone resin. These may be used individually by 1 type and may use 2 or more types together. An adhesive layer made of these materials can be formed by coating.
Furthermore, you may add an antistatic agent, a lubricant, an antiblocking agent, etc. to the adhesion layer.
As thickness of the above-mentioned adhesion layer, 0.1 micrometer-10 micrometers are preferable.

~ Method for forming adhesive layer or adhesive layer ~
The adhesive layer or the adhesive layer is preferably formed by coating. For example, it can be laminated on the surface of the surface opposite to the surface having the infrared reflection pattern of the support. There is no limitation in particular as the coating method at this time, A well-known method can be used.
A film in which a pressure-sensitive adhesive or an adhesive is applied and dried in advance on a release film is prepared, and the pressure-sensitive adhesive or the adhesive of this film and the surface on the support side of the infrared reflector of the present invention are laminated. By doing so, an adhesive layer or an adhesive layer in a dry state may be laminated. The laminating method at this time is not particularly limited, and a known method can be used.

(Hard coat layer)
When the infrared reflector has an overcoat layer, a hard coat layer may be further provided on the overcoat layer from the viewpoint of adding scratch resistance. The hard coat layer can contain metal oxide particles.
As the hard coat layer, the description in paragraph [0144] of JP-A No. 2014-184688 can be referred to.

(Back coat layer)
In the infrared reflector, a back coat layer may be provided on the surface of the above support opposite to the above-described infrared reflection pattern. There is no restriction | limiting in particular as said backcoat layer, According to the objective, it can select suitably, A preferable composition and thickness are the same as the preferable composition and thickness of the above-mentioned overcoat layer.

(UV absorber layer)
The infrared reflector may have a layer containing an ultraviolet absorber (ultraviolet absorber-containing layer).
For the ultraviolet absorber-containing layer, the description in paragraphs [0148] to [0155] of JP-A No. 2014-184688 can be referred to.

(Refractive index adjustment layer)
The infrared reflector may be provided with one or more refractive index adjusting layers to make the above-mentioned infrared reflection pattern less noticeable. For example, the aspect which has an infrared reflective pattern on one surface of a support body, and has a low-refractive-index layer on the surface on the opposite side to the surface which has the infrared reflective pattern of a support body is mentioned. Further, in this aspect, a second refractive index adjusting layer may be provided between the support and the infrared reflection pattern. Furthermore, the aspect which is laminated | stacked in order of the support body, the 2nd refractive index adjustment layer, the 3rd refractive index adjustment layer, and the infrared reflective pattern may be sufficient.
By having the refractive index adjustment layer, the infrared light reflector has a higher visible light transmittance.

  As a material constituting the refractive index adjustment layer, materials described in paragraph [0065] of JP 2014-191224 A can be used.

The thickness of the refractive index adjusting layer is preferably 20 nm or more, more preferably 30 nm or more, and further preferably 40 nm or more. Although there is no restriction | limiting in particular about an upper limit, it is 1000 nm.
In addition, when a refractive index adjustment layer consists of two or more layers, it is preferable that the total thickness of each layer is in the said range.

  Regarding the other structure of the refractive index adjusting layer, the structure of the undercoat layer described in paragraphs [0066] to [0075] of JP-A No. 2014-191224 can be referred to.

<Applications of infrared reflectors>
The use of the infrared reflector is not particularly limited, and can be used for a system using a known infrared reflector.
When the infrared reflector is used as an application of the optical member, the applications described in paragraphs [0021] to [0032] of JP-A-2008-108236 can be given. For example, the optical member can be used as an optical member that is affixed to a display and handwritten with a pen or the like directly on the display device to input data.
In particular, an optical member having a wavelength selective reflection portion (for example, a dot) in a pattern can be used as an input sheet used in a system using an electronic pen that digitizes handwritten information and inputs the digitized information to an information processing apparatus.
The optical member can also be used as an input sheet on the surface of a display such as a liquid crystal display. At this time, the optical member is preferably transparent. 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, or may be detachably attached to the display surface, for example.
Regarding systems using an electronic pen that digitizes handwritten information and inputs it to an information processing apparatus, Japanese Patent Application Laid-Open Nos. 2014-98943, 2008-165385, 2008-108236, and 2008-077451 No. publication etc. can be referred.
The infrared reflector of the present invention is preferably a sheet mounted on the front surface or the front of a display device capable of displaying an image. As a preferable aspect of the sheet | seat with which the surface of the display apparatus which can display an image, or the front is mounted | worn, the aspect as described in Paragraph [0024]-[0031] of patent 4725417 can be mentioned.
FIG. 7 shows a schematic diagram of a system in which the infrared reflector of the present invention is used as a sheet mounted on the front surface or front of a display device capable of displaying an image.
As shown in FIG. 7, the system described above includes a display device 104, an infrared reflector 11, a pen-type input terminal 101, a code 102, and a read data processing device 103.
In FIG. 7, the input device is not particularly limited as long as it can emit infrared i and can detect the retroreflected light r of the infrared reflector 11 described above, and a known input device may be used. As an input device, for example, as a device that also includes a read data processing device 103 to which a pen-type input terminal 101 is connected by a code 102, ink, graphite, and the like disclosed in JP-A-2003-256137 are provided. Built-in communication interface, such as a wireless transceiver using Bluetooth (registered trademark) technology, etc., a battery, etc., without a nib, a CMOS (complementary metal oxide semiconductor) camera with an infrared irradiation unit, processor, memory, etc. Things.
As an operation of the pen-type input terminal 101, for example, when the pen tip is drawn so as to be in contact with the front surface of the infrared reflector 11 of the present invention, the pen-type input terminal 101 applies the pen pressure applied to the pen tip. Then, the CMOS camera is actuated to irradiate a predetermined range in the vicinity of the pen tip with an infrared ray having a predetermined wavelength emitted from the infrared irradiation unit, and image a pattern. About once). When the pen-type input terminal 101 includes the read data processing device 103, input trace data is obtained by quantifying and digitizing an input trace accompanying movement of the pen tip during handwriting by analyzing a 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 include a pen-type input terminal 101 as a read data processing device 103 as shown in FIG. It may be outside of. In this case, even if the pen-type input terminal 101 is connected to the read data processing apparatus 103 with the code 102, the read data may be transmitted wirelessly using radio waves, infrared rays, or the like.
In addition, the input terminal 101 may be a reader described in Japanese Patent Laid-Open No. 2001-243006.

The read data processing apparatus 103 applicable in the present invention has a function of calculating position information from continuous imaging data read by the input terminal 101, combining it with time information, and providing it as input trajectory data that can be handled by the information processing apparatus. If it has, it will not specifically limit, What is necessary is just to comprise members, such as a processor, memory, a communication interface, and a battery.
Further, the read data processing device 103 may be built in the input terminal 101 as disclosed in Japanese Patent Application Laid-Open No. 2003-256137, or may be built in an information processing device including a display device. Further, the read data processing apparatus 103 may transmit the position information wirelessly to an information processing apparatus 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 104 sequentially updates the images displayed on the display device 104 based on the trajectory information transmitted from the read data processing device 103, thereby obtaining the trajectory input by handwriting on the input terminal 101. It can be displayed on the display device as if it were written with a pen on paper.
Image display surface of image display device or image display device with infrared reflector of the present invention mounted in front of image display surface, image display surface of image display device or infrared reflector of the present invention mounted in front of image display surface A system including the image display device is also included in the invention disclosed in this specification.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist thereof. Unless otherwise specified, “parts” are based on mass.

<Preparation of flat metal particle dispersion>
-Preparation of tabular silver particle dispersion A-
Ion exchange water 13L (liter) is weighed in a reaction vessel made of high Cr-Ni-Mo stainless steel (NTKR-4, manufactured by Nippon Metal Industry Co., Ltd.), and NTKR-4 is made on a stainless steel (SUS316L) shaft. While stirring ion-exchanged water using a chamber equipped with four propellers and four NTKR-4 paddles, 1.0 L of 10 g / L trisodium citrate (anhydrous) aqueous solution was added. And kept at 35 ° C. To this solution, 0.68 L of 8.0 g / L polystyrene sulfonic acid aqueous solution was added, and further sodium borohydride prepared to 23 g / L using 0.04 N (mol / L) aqueous sodium hydroxide (NaOH). 0.041 L of aqueous solution was added. Further, 13 L of a 0.10 g / L aqueous silver nitrate solution was added at 5.0 L / min.
Thereafter, 1.0 L of 10 g / L trisodium citrate (anhydride) aqueous solution and 11 L of ion exchange water were added, and 0.68 L of 80 g / L potassium hydroquinone sulfonate aqueous solution was further added. The stirring speed was increased to 800 rpm, 8.1 L of a 0.10 g / L silver nitrate aqueous solution was added at 0.95 L / min, and then the temperature was lowered to 30 ° C.
A 44 g / L methylhydroquinone aqueous solution (8.0 L) was added, and then a 40 ° C. gelatin aqueous solution described later was added in its entirety. The stirring speed was increased to 1200 rpm, and a total amount of a silver sulfite white precipitate mixture described later was added to obtain a preparation.
When the pH change of the preparation solution stopped, 5.0 L of 1N (mol / L) aqueous sodium hydroxide (NaOH) was added at 0.33 L / min. Thereafter, 2.0 g / L of 1- (m-sulfophenyl) -5-mercaptotetrazole sodium aqueous solution (NaOH and citric acid (anhydride) was used to adjust to pH = 7.0 ± 1.0 and dissolve. 0.18 L) was added, and 0.078 L of 70 g / L 1,2-benzisothiazolin-3-one (the aqueous solution was adjusted to be alkaline with NaOH) was added. In this way, a tabular silver particle dispersion A was prepared.

-Preparation of gelatin aqueous solution-
16.7 L of ion-exchanged water was weighed in a dissolution tank made of SUS316L. 1.4 kg of alkali-treated beef bone gelatin (GPC weight average molecular weight 200,000) subjected to deionization treatment was added while stirring at low speed with an agitator made of SUS316L. Further, 0.91 kg of alkali-treated beef bone gelatin (GPC weight average molecular weight 21,000) subjected to deionization treatment, proteolytic enzyme treatment, and oxidation treatment with hydrogen peroxide was added. Thereafter, the temperature was raised to 40 ° C., and gelatin was swollen and dissolved simultaneously to completely dissolve it.

-Preparation of silver sulfite white precipitate mixture-
In a dissolution tank made of SUS316L, 5.7 L of ion-exchanged water was weighed, and 5.7 L of a 100 g / L silver nitrate aqueous solution was added. While stirring at a high speed with an agitator made of SUS316L, 1.9 L of a 140 g / L sodium sulfite aqueous solution was added in a short time to prepare a mixed liquid containing a white precipitate of silver sulfite. This mixture was prepared immediately before use.

When the flat silver particle dispersion A was diluted with ion-exchanged water and spectral absorption was measured using a spectrophotometer (manufactured by Hitachi, Ltd., U-3500), the absorption peak wavelength was 800 nm, and the full width at half maximum. Was 250 nm.
The physical properties of the tabular silver particle dispersion A are as follows: pH = 9.4 at 25 ° C. (measured with KR5E manufactured by ASONE Co., Ltd.), electric conductivity 8.1 mS / cm (CM-manufactured by Toa DKK Co., Ltd.) And a viscosity of 2.1 mPa · s (measured with SV-10 manufactured by A & D Co., Ltd.). The obtained flat silver particle dispersion A was stored in a 20 L container of a union container type II (a container made of low density polyethylene, manufactured by ASONE Co., Ltd.) and stored at 30 ° C.

-Preparation of tabular silver particle dispersion B-
800 g of the above-mentioned tabular silver particle dispersion A was collected in a centrifuge tube, and 1N (mol / L) sodium hydroxide (NaOH) and / or 1 N (mol / L) sulfuric acid was used at 25 ° C. and pH = Adjusted to 9.2 ± 0.2. Using a centrifuge (manufactured by Hitachi Koki Co., Ltd., himacCR22GIII, angle rotor R9A), centrifugation was performed at 9000 rpm for 60 minutes at 35 ° C., and then 784 g of the supernatant was discarded. A 0.2 mM (mg / mol) aqueous NaOH solution was added to the precipitated tabular silver particles B to make a total of 400 g, and the mixture was hand-stirred using a stir bar to obtain a coarse dispersion. In the same manner as this, 24 coarse dispersions were prepared to a total of 9600 g, added to a SUS316L tank and mixed. Furthermore, 10 ml of a 10 g / L solution of Pluronic 31R1 (manufactured by BASF, nonionic surfactant) (diluted with a mixed solution of methanol: ion-exchanged water = 1: 1 (volume ratio)) was added. Using an automixer type 20 manufactured by Primix Co., Ltd. (stirring section is homomixer MARKII), the crude dispersion mixture in the tank was subjected to batch dispersion treatment at 9000 rpm for 120 minutes. The liquid temperature during dispersion was kept at 50 ° C. After dispersion, the temperature was lowered to 25 ° C., and then single-pass filtration was performed using a profile II filter (manufactured by Nippon Pole Co., Ltd., MCY1001Y030H13).
In this manner, the tabular silver particle dispersion A is subjected to desalting and redispersion to prepare a tabular silver particle dispersion B containing 10% by mass of tabular silver particles B and 1% by mass of gelatin. did.

When the spectral transmittance of the tabular silver particle dispersion B was measured by the same method as that of the tabular silver particle dispersion A, the absorption peak wavelength and half width were almost the same as those of the tabular silver particle dispersion A. .
The physical properties of tabular silver particle dispersion B were pH = 7.6, electrical conductivity of 0.37 mS / cm, and viscosity of 1.1 mPa · s at 25 ° C. The obtained tabular silver particle dispersion B was stored in a 20 L container of Union Container II type and stored at 30 ° C. In addition, pH, electrical conductivity, and a viscosity were measured by the same method as said silver tabular grain dispersion liquid A.

-Evaluation of flat metal particles-
The shape of the tabular silver particles A in the tabular silver particle dispersion A was observed with a transmission electron microscope (TEM). In the tabular silver particle dispersion A, it was confirmed that hexagonal to circular and triangular tabular silver particles were generated.
Further, based on the shape of the 200 tabular silver particles A arbitrarily extracted from the TEM image of the tabular silver particle dispersion A, the number of the hexagonal or circular tabular silver particles was analyzed. Then, the ratio (number%) of the number of grains corresponding to hexagonal or circular tabular silver grains was determined. As a result, it was 80% by number or more based on the total number of tabular silver particles (hexagonal or circular tabular silver particles and triangular tabular silver particles).
An image obtained by TEM observation of the tabular silver particle dispersion A was taken into image processing software ImageJ and subjected to image processing. Image analysis was performed on 200 particles arbitrarily extracted from TEM images of several fields of view, and the equivalent circle diameter was calculated. As a result of statistical processing based on these populations, the average diameter was 100 nm.
The flat silver particle dispersion A was measured using a laser diffraction / scattering particle diameter / particle size distribution measuring apparatus Microtrac MT3300II (manufactured by Nikkiso Co., Ltd., particle permeability set to reflection), and the average particle diameter ( A result of 44 nm was obtained.
When the tabular silver particle dispersion B was measured in the same manner, the ratio of the tabular silver particles B to the total tabular silver particles, the particle size distribution of the tabular silver particles B, and the shape thereof were tabular in the tabular silver particle dispersion A. Almost the same results as the ratio of the metal particles A to the total tabular silver particles, the particle size distribution and the shape of the tabular silver particles A were obtained.

  The tabular silver particle dispersion B was dropped on a silicon substrate and dried, and the thickness of each tabular silver particle B was measured by FIB-TEM (Focused Ion Beam-Transmission Electron Microscope) method. 10 tabular silver particles B in the tabular silver particle dispersion B were measured, and the average thickness was 9 nm.

-Preparation of tabular silver particle dispersion C-
In the preparation of the flat silver particle dispersion A, 13 L (liter) of ion-exchanged water charged in a reaction vessel made of high Cr—Ni—Mo stainless steel (NTKR-4, manufactured by Nippon Metal Industry Co., Ltd.) was added to 103 L of ion-exchanged water. A tabular silver particle dispersion C was prepared through the same procedure as the preparation of the tabular silver particle dispersion A and the procedure of the tabular silver particle dispersion B, except for changing to (liter).

When the spectral transmittance of the obtained tabular silver particle dispersion C was measured by the same method as that for the tabular silver particle dispersion A, the absorption peak wavelength was 780 nm, and the full width at half maximum was almost the same as that of the tabular silver particles A. It was equivalent.
The physical properties of tabular silver particle dispersion C were pH = 9.0 at 25 ° C., electric conductivity 7.5 mS / cm, and viscosity 2.0 mPa · s. The obtained flat silver particle dispersion C was stored in a 20 L container of Union Container II type and stored at 30 ° C. In addition, pH, electrical conductivity, and a viscosity were measured by the same method as said silver tabular grain dispersion liquid A.

The shape, average diameter, and average thickness of the tabular grains C in the tabular silver grain dispersion C were measured in the same manner as the tabular grains A in the tabular silver grain dispersion A.
As a result, it was confirmed that hexagonal to circular and triangular tabular silver particles C were formed in the tabular silver particle dispersion C. The average diameter of the tabular silver particles C in the tabular silver particle dispersion C was 27 nm, and the average thickness was 9 nm.

Example 1
<Preparation of ink composition>
A specific organic solvent, a fluorosurfactant, and water were added to the tabular silver particle dispersion B obtained above to prepare an ink composition 1 having a composition shown below.

-Composition of ink composition-
Tabular silver particles B (tabular grains) ... 0.84 parts Gelatin (dispersant, mixture of gelatin having an average molecular weight of 20,000 and gelatin having an average molecular weight of 200,000) ... 0.08 parts Glycerin (specific) Organic solvent, boiling point 290 ° C., SP value 33.8 MPa ^1/2 )... 60 parts Surflon (registered trademark) S-243 (fluorinated surfactant 1 having a perfluoro group, refractive index = 1.35, AGC) Seimi Chemical Co., Ltd.) ... 0.14 parts Water ... Amount to be 100 parts in total

  The refractive index of the fluorosurfactant was measured with a Karnew precision refractometer (manufactured by Shimadzu Corporation, KPR-3000).

(Example 2 to Example 10, Comparative Example 1, Comparative Example 2, and Comparative Example 4 to Comparative Example 8)
Ink compositions of Examples and Comparative Examples were prepared in the same manner as in Example 1 except that the ink composition 1 used in Example 1 was prepared to have the compositions shown in Tables 1 and 2 below. .
In Examples 2 to 10, ink compositions 2 to 10 were used, and in Comparative Example 1, Comparative Example 2, and Comparative Examples 4 to 8, ink composition 11 and ink composition 12 were used. Ink composition 14 to ink composition 18 were used.

(Example 11 to Example 12)
Ink compositions of the respective examples were prepared in the same manner as in Example 1 except that the ink composition 1 used in Example 1 was prepared to have the composition shown in Table 2 below. In Examples 11 to 12, ink composition 19 to ink composition 20 were used.

Details of the components in Table 1 are as follows.
Urethane resin: DIC Corporation, Hydran HW-171

Details of the components in Table 2 are as follows.
Urethane surfactant: Permarin UC-20, manufactured by Sanyo Chemical Industries
MegaFac (registered trademark) F-410 (fluorine-based surfactant 2 having a perfluoro group, refractive index = 1.27, manufactured by DIC Corporation)
Surflon (registered trademark) S-242 (fluorinated surfactant 3 having a perfluoro group, refractive index = 1.37, manufactured by AGC Seimi Chemical Co., Ltd.)

(Comparative Example 3)
An ink composition 13 was prepared in the same manner as in Example 1 except that the ink composition 1 used in Example 1 was prepared to have the following composition without using the flat silver particle dispersion B.

-Composition of ink composition-
Titanium oxide particles (Ishihara Sangyo Co., Ltd., TTO-55, particle size 50 nm) ... 0.84 parts Glycerin (specific organic solvent) ... 60 parts Surflon (registered trademark) S-243 (perfluoro group) Fluorine-based surfactant 1 having refractive index = 1.35, manufactured by AGC Seimi Chemical Co., Ltd.) ... 0.14 parts Water ... Amount to be 100 parts in total

<Production of infrared reflector>
Hereinafter, preparation of an infrared reflector will be described.
An ink jet printer (FUJIFILM DIMATIX, DMP-2831) was prepared. The obtained ink composition of each Example and Comparative Example was loaded into the above-described ink jet printer, and the ink composition was prepared from the ejection port of the head, and the substrate (support) having irregularities on the surface prepared by the method described later A checkered pattern made up of the reflective portion 21 and the non-reflective portion 22 shown in FIG. 8 was formed. It should be noted that the ink droplet ejection amount of the reflection part in the pattern is 23 g / m ² , and the dot density is 1200 dpi (dot per inch). Further, the length 23 of one side shown in FIG. 8 is 200 μm, and is the length when the support is viewed from the direction perpendicular to the surface opposite to the uneven surface of the support.
The support provided with the checkered pattern was dried using an explosion-proof oven at an ambient temperature of 80 ° C. for 15 minutes to form an infrared reflective pattern.
The following overcoat layer coating solution is applied to the side of the support on which the infrared reflection pattern is formed using a wire bar so that the concavo-convex structure is filled, and is dried at 80 ° C. An overcoat layer obtained by drying was provided. The refractive index difference between the overcoat layer and the support was 0.01.
By using the method as described above, each of the examples and comparative examples is an infrared reflector having a support and an infrared reflection pattern, and an overcoat layer formed so as to cover the entire infrared reflection pattern portion. This ink composition was used.
A schematic diagram of the cross-sectional structure of the obtained infrared reflector is shown in FIG.

-Production method of support-
A hot press machine (Co., Ltd.) was applied to one side of an acrylic film (Escabo Sheet Co., Ltd., Technoloy S001G, thickness 250 μm, glass transition temperature = 103 ° C.) having a prism shape with a size of 50 μm. Using a mini test press MP-SNL, manufactured by Toyo Seiki Co., Ltd., an uneven structure was imparted to the acrylic film by hot pressing at 140 ° C. and 10 MPa. As described above, an acrylic film having a concavo-convex structure on one surface was used as a support.

-Coating liquid for overcoat layer-
Acrylic polymer aqueous dispersion: AS-563A 20 parts (Daicel Finechem Co., Ltd., solid content 27.5% by mass)
Crosslinking agent: Carbodilite (registered trademark) V-02-L2 0.46 parts (manufactured by Nisshinbo Chemical Co., Ltd., diluted with 20% by weight solid content distilled water)
Surfactant A: Lipar 870P ... 0.63 parts (manufactured by Lion Corporation, diluted with distilled water of 1 mass% solid content)
Surfactant B: NAROACTY (registered trademark) CL-95... 0.87 parts (manufactured by Sanyo Chemical Industries, Ltd., diluted with distilled water with a solid content of 1% by mass)
Urethane polymer aqueous solution: Olester UD350 0.13 parts (manufactured by Mitsui Chemicals, solid content 38% by mass)
Distilled water ... 77.91 parts

<Evaluation>
The following evaluation was performed on the ink compositions of Examples 1 to 12 and Comparative Examples 1 to 8 obtained above. The evaluation results are shown in Table 3 below.

−Dischargeability−
An ink jet printer (FUJIFILM DIMATIX, DMP-2831) was prepared. The obtained ink compositions of each Example and Comparative Example were loaded into the above-described ink jet printer, and the ink composition was discharged from the discharge port of the head, and the state was observed. The dischargeability was evaluated according to the following evaluation criteria by the continuous discharge time and the number of discharge ports (the number of non-discharge ports) from which the ink composition was not discharged.

Evaluation Criteria AA: The number of non-ejection ports when the ink composition can be ejected continuously for 20 minutes or more and ejected continuously for 20 minutes is less than 5% of all ejection ports.
A: The ink composition can be continuously ejected for 20 minutes or more, and the number of non-ejection ports when the ink composition is continuously ejected for 20 minutes is 5% or more and less than 8% of all ejection ports.
B: The number of non-ejection ports when the ink composition is continuously ejected for 20 minutes is 8% or more and less than 30% of the total number of ejection ports.
C: The number of non-ejection ports became 30% or more of the number of all ejection ports before 10 minutes had passed since the ink composition was continuously ejected.

-Pattern uniformity-
An ink jet printer (FUJIFILM DIMATIX, DMP-2831) was prepared. The obtained ink compositions of Examples and Comparative Examples were loaded into the above-described ink jet printer, and the ink composition was discharged from the discharge port of the head. A reflection pattern was formed. Arbitrary droplets in the formed infrared pattern were observed with an SEM, and the distribution of flat metal particles inside the droplets was determined. Pattern uniformity was evaluated according to the following evaluation criteria from the distribution of the obtained flat metal particles.

Evaluation criteria AA: The abundance of the flat metal particles in the region within 30% by area from the outer periphery of the dot is less than 25% by number of the whole.
A: The abundance of the flat metal particles in the region within 30% by area from the outer periphery of the dot is 25% by number or more and less than 35% by number.
B: The abundance of the plate-like metal particles in the region within 30% by area from the outer periphery of the dot is 35% by number or more and less than 50% by number.
C: The abundance of the flat metal particles in the region within 30% by area from the outer periphery of the dot is 50% by number or more of the whole.

-Retroreflectance-
The infrared reflectors of the examples and comparative examples were cut into 5 cm × 5 cm sizes to prepare samples. As shown in FIG. 9, the infrared reflector 113 is inclined 45 ° with respect to the light emitted from the light source 111, and the retroreflected light is bent by the half mirror 114 and put in the light receiver 112, and the oblique reflection spectrum of each sample. The reflectance of light having a wavelength of 300 nm to 2500 nm was measured at intervals of 5 nm using an ultraviolet-visible near-infrared spectrometer (manufactured by JASCO Corporation, V-670, using integrating sphere unit ISN-723). Obtain the 45 ° reflectance of the pattern portion and the 45 ° reflectance of the non-pattern portion at the wavelength (A) of the highest reflectance in the infrared region with a wavelength of 780 nm or more and 2500 nm or less, and (45 ° reflectance of the pattern portion) / (45 ° reflectance of non-patterned portion) was determined as retroreflectance (%).

Evaluation criteria AA: Infrared retroreflectance is 7% or more.
A: The infrared retroreflectance is 5% or more and less than 7%.
B: The infrared retroreflectance is 3% or more and less than 5%.
C: Infrared retroreflectance is less than 3%.

-Visible light transmittance-
The infrared reflectors of the examples and comparative examples were cut into 5 cm × 5 cm sizes to prepare samples. Using a UV-Vis near-infrared spectrometer (manufactured by JASCO Corp., V-670, using integrating sphere unit ISN-723), the transmittance of light with a wavelength of 300 nm to 2500 nm of the sample is measured at intervals of 5 nm. Using the transmittance (%) of light at 550 nm, the visible light effect rate was evaluated according to the following criteria.

Evaluation criteria AA: The transmittance of light at 550 nm is 85% or more.
A: The light transmittance at 550 nm is 80% or more and less than 85%.
B: The transmittance of light at 550 nm is 70% or more and less than 80%.
C: The transmittance of light at 550 nm is less than 70%.

-Haze-
The infrared reflectors of the examples and comparative examples were cut into 5 cm × 5 cm sizes to prepare samples. The haze (%) of the sample was measured using a haze meter (NDH-5000, manufactured by Nippon Denshoku Industries Co., Ltd.), and the haze was evaluated according to the following criteria.

Evaluation criteria AA: Haze is less than 3%.
A: The haze is 3% or more and less than 5%.
B: Haze is 5% or more and less than 10%.
C: Haze is 10% or more.

  From Table 3, it can be seen that the infrared reflection pattern formed using the ink composition of the example has high retroreflection and visible light transmittance of infrared rays and low haze.

DESCRIPTION OF SYMBOLS 1 ... Infrared reflective pattern 2 ... Support body 3 ... Overcoat layer 4 ... Tabular particle 11 ... Infrared reflector 21 ... Reflective part 22 ... Non-reflective part 23 ... Length 101 of one side of the reflective part which reflects infrared rays ... Pen type Input terminal 102 ... code 103 ... read data processing device 104 ... display device 111 ... light source 112 ... light receiver 113 ... infrared reflector 114 ... half mirror D ... (average) particle diameter or (average) circle equivalent diameter of tabular grains a ... (average) thickness θ of tabular grains ... angle i between tabular grains and support surface ... incident light r ... retroreflected light

Claims (10)

Tabular grains, a dispersant for dispersing the tabular grains, an organic solvent having a boiling point of 190 ° C. or higher and a solubility parameter of 24.0 MPa ^1/2 or higher, water, and a fluorosurfactant And including
For the formation of an infrared reflective pattern, the content ratio of the dispersant to the tabular grains is 0.01 to 0.5 by mass ratio, and the content ratio of the organic solvent to the tabular grains is 10 to 150 by mass ratio. Ink composition.   The ink composition for forming an infrared reflection pattern according to claim 1, wherein the tabular particles are tabular metal particles.   The infrared reflection according to claim 2, wherein the flat metal particles have an aspect ratio of 6 to 40 and contain at least one metal selected from silver, gold, aluminum, platinum, rhodium, copper, and nickel. An ink composition for pattern formation.   The ink composition for forming an infrared reflection pattern according to claim 3, wherein the metal is silver.   The ink composition for forming an infrared reflection pattern according to any one of claims 1 to 4, wherein the dispersant is a water-soluble resin.   The ink composition for forming an infrared reflection pattern according to any one of claims 1 to 5, wherein the dispersant is gelatin having an average molecular weight of 20,000 to 200,000.   The ink composition for forming an infrared reflective pattern according to any one of claims 1 to 6, wherein the organic solvent is at least one selected from glycerin, ethylene glycol, formamide, and diethylene glycol.   8. The infrared reflective pattern formation according to claim 1, wherein the fluorosurfactant includes a perfluoro group in a molecule and has a refractive index of 1.30 to 1.42. Ink composition.   The infrared reflective pattern formation method which provides the ink composition for infrared reflective pattern formation of any one of Claims 1-8 on a support body by the inkjet method, and forms an infrared reflective pattern. A support;
An infrared reflective pattern formed from the ink composition for forming an infrared reflective pattern according to any one of claims 1 to 8,
An infrared reflector.