JP2012006277A - Method for forming laminate and laminate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming a laminate in which a laminate is applied to recorded matter with an image formed by an ink composition containing particles each having a hollow structure, and which can suppress the discoloration of the image.SOLUTION: This method for forming the laminate comprises that a sheet having an adhesion layer containing a second polymer is adhered to a part of a recording medium in which at least the image is formed, where the recording medium includes the image formed by using a first polymer and the ink composition containing the particles each having the hollow structure. The glass transition temperature of the first polymer is higher than the glass transition temperature of the second polymer.

Description

  The present invention relates to a method for forming a laminate and a laminate.

  In ink jet recording, there is a demand for an ink composition containing a white color material. A typical example of the white color material is titanium oxide powder, which is often blended into an ink composition together with a dispersant and the like. In recent years, hollow particles as disclosed in Patent Document 1 have been used as a color material.

  On the other hand, conventionally, lamination has been performed on various printed materials for the purpose of protecting the printed materials (see, for example, Patent Document 2). As a general aspect of the laminate for a printed material, a sheet or film having an adhesive layer on the surface is bonded to the printed material by heat fusion or the like.

U.S. Pat. No. 4,880,465 JP 2000-318093 A

  However, when a laminate is applied to a printed matter formed using particles having a hollow structure as a color material, the original color of the color material may be impaired. As a specific example, when a laminate is performed on a printed matter using hollow particles as a white color material, the whiteness of a white printed portion may be reduced or become transparent. The inventors have obtained the knowledge that such a defect is caused by the hollow structure of the color material, and have made the present invention.

  One of the objects according to some embodiments of the present invention is a method of forming a laminate in which a laminate is applied to a recorded matter on which an image is formed with an ink composition containing particles having a hollow structure, An object of the present invention is to provide a method for forming a laminate that can suppress discoloration of the image. One of the objects according to some embodiments of the present invention is a laminate obtained by laminating a recorded material on which an image is formed with an ink composition containing particles having a hollow structure. An object of the present invention is to provide a laminate in which the discoloration is suppressed.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following aspects or application examples.

[Application Example 1]
One aspect of the method for forming a laminate according to the present invention is as follows.
For a recording medium comprising an image formed using an ink composition comprising a first polymer and particles having a hollow structure,
A laminate for adhering a sheet having an adhesive layer containing a second polymer to at least a portion of the recording medium on which the image is formed,
The glass transition temperature of the first polymer is higher than the glass transition temperature of the second polymer.

  According to the method for forming a laminate of this application example, it is possible to form a laminate that hardly causes discoloration of an image.

[Application Example 2]
In application example 1,
The content of the first polymer in the ink composition may be 5% by mass or more and 20% by mass or less.

  According to the method for forming a laminate of this application example, it is possible to form a laminate that is more unlikely to cause image discoloration.

[Application Example 3]
In application example 1 or application example 2,
The content of the particles in the ink composition may be 5% by mass or more and 20% by mass or less.

  According to the method for forming a laminate of this application example, it is possible to form a laminate that is more unlikely to cause image discoloration.

[Application Example 4]
In any one of Application Examples 1 to 3,
The average particle diameter d50 of the particles may be 0.4 μm or more and 0.8 μm or less.

  According to the method for forming a laminate of this application example, it is possible to form a laminate that is more unlikely to cause image discoloration.

[Application Example 5]
In any one of Application Examples 1 to 4,
The glass transition temperature of the first polymer may be 40 ° C. or higher.

  According to the method for forming a laminate of this application example, it is possible to form a laminate that is more unlikely to cause image discoloration.

[Application Example 6]
In any one of Application Examples 1 to 5,
The glass transition temperature of the first polymer may be lower than the glass transition temperature or thermal decomposition temperature of the particles having the hollow structure.

  According to the method for forming a laminate of this application example, it is possible to form a laminate that is more unlikely to cause image discoloration.

[Application Example 7]
One aspect of the laminate according to the present invention is:
A recording medium;
An image layer formed on the recording medium and containing particles having a first polymer and a hollow structure;
A sheet formed so as to cover at least the image layer, and adhered through an adhesion layer containing a second polymer;
Including
The glass transition temperature of the first polymer is higher than the glass transition temperature of the second polymer.

  According to the laminate of this application example, the color based on the particles of the image layer is unlikely to change, and the reliability of the image can be improved.

[Application Example 8]
In Application Example 7,
The glass transition temperature of the second polymer may be 40 ° C. or higher.

  According to the laminate of this application example, the color change of the image layer can be further suppressed.

  Hereinafter, embodiments of the present invention will be described. In addition, the following embodiment demonstrates an example of this invention. Therefore, this invention is not limited to the following embodiment, The various modifications implemented in the range which does not change a summary are also included. Note that not all of the configurations described in the following embodiments are indispensable constituent requirements of the present invention.

1. Laminate Forming Method The laminate body forming method of the present embodiment includes an image forming step and a laminating step.

1.1. Image Forming Step The image forming step is a step of forming an image on a recording medium using an ink composition containing a first polymer and particles having a hollow structure.

1.1.1. Recording medium The recording medium used in the image forming process is not particularly limited as long as it can attach or apply droplets of an ink composition (described later) by an ink jet recording apparatus. Examples of the recording medium used in the image forming process include absorptive recording media such as paper, cardboard, porous film, cloth (fiber product), and porous ceramic sheet, and ink absorption such as plastic and glass. In addition, an ink receiving layer or an ink absorbing layer may be formed on a surface to be coated of a substrate having no property.

  Further, the recording medium may be any of a gloss type, a mat type, and a dull type. Specific examples of the recording medium include, for example, surface-treated paper such as coated paper, art paper, and cast coated paper, and plastic films such as vinyl chloride sheets and PET films on which an ink receiving layer is formed. it can.

1.1.2. Ink composition The ink composition used in the image forming step includes at least a first polymer and particles having a hollow structure. The ink composition used in the image forming step may be either an aqueous system containing water as a solvent or a non-aqueous system not containing water as a solvent. In the following embodiments, an embodiment in which the ink composition is a water-based ink composition containing water as a solvent will be exemplified.

1.1.2.1. First polymer The first polymer contained in the ink composition used in the image forming step can be dissolved or dispersed in the ink composition, and has a glass transition temperature higher than the second polymer described later ( As long as it has Tg), it is not particularly limited.

  A wide range of polymers can be selected as the first polymer, and examples thereof include polymers such as polyurethane, polyolefin, polyol, polyamide, polycarbonate, and polyester, and modified products thereof.

  Of the polymers exemplified above, the first polymer is preferably polyurethane or a modified product thereof from the viewpoint of relatively easy adjustment of Tg. Furthermore, the first polymer is preferably a polycarbonate-based or polyether-based polyurethane from the viewpoint of good dispersibility in the water-based ink composition and good adhesion to the recording medium when attached to the recording medium. Hereinafter, an embodiment using polycarbonate-based or polyether-based polyurethane as the first polymer will be exemplified.

  When polyurethane is used as the first polymer, a known method can be applied to the synthesis of the polyurethane. For example, a compound having two or more isocyanate groups, a compound having two or more hydroxyl groups, Can be used. Hereinafter, a method for synthesizing polyurethane will be specifically described.

  Compounds having two or more isocyanate groups include, for example, chain aliphatic isocyanates such as tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, dodecamethylene diisocyanate, trimethylhexamethylene diisocyanate, lysine diisocyanate, 1,3-cyclohexane. Has a cyclic structure such as silylene diisocyanate, 1,4-cyclohexylene diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 3,3'-dimethyl-4,4'-dicyclohexylmethane diisocyanate Aliphatic isocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, m-phenylene diisocyanate, p-fluoro Nylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate, 2,2′-diphenylmethane diisocyanate, 3,3′-dimethyl-4,4′-biphenylene diisocyanate, 3,3′-dimethoxy-4 , 4′-biphenylene diisocyanate, 3,3′-dichloro-4,4′-biphenylene diisocyanate, 1,5-naphthalene diisocyanate, 1,5-tetrahydronaphthalene diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, and other aromatics Isocyanates. When synthesizing a polyurethane, compounds having two or more isocyanate groups may be used alone or in combination of two or more.

  Examples of the compound having two or more hydroxyl groups include polyether polyol and polycarbonate polyol.

  More specifically, as the polyether polyol, a cyclic ether compound such as ethylene oxide, propylene oxide, butylene oxide, styrene oxide, tetrahydrofuran, or epichlorohydrin, a compound having an active hydrogen atom as a catalyst, etc. Examples thereof include a polymer obtained by ring-opening polymerization alone or in combination of two or more. More specific examples include polyethylene glycol, polypropylene glycol, and polytetramethylene glycol.

  Further, as the polycarbonate polyol, diols such as 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, polyethylene glycol, polypropylene glycol, or polytetramethylene glycol, Examples thereof include dialkyl carbonates such as phosgene and dimethyl carbonate, and reaction products with cyclic carbonates such as ethylene carbonate.

  When synthesizing polyurethane, compounds having two or more hydroxyl groups may be used alone or in combination of two or more.

  The polyurethane may have an anionic property. For example, an anionic property can be imparted to the polyurethane by introducing a monomer having a carboxyl group or a sulfone group. Examples of such monomers include monohydroxycarboxylic acids such as lactic acid; dihydroxycarboxylic acids such as α, α-dimethylolacetic acid, α, α-dimethylolpropionic acid, α, α-dimethylolbutyric acid, and 3,4-diaminobutanesulfone. Examples include acids and diaminosulfonic acids such as 3,6-diamino-2-toluenesulfonic acid.

  Further, when the above-mentioned polyurethane is used as the first polymer, any type of polyurethane of the emulsion type in which the polyurethane is dispersed in the form of a solvent and the solution type existing in a state of being dissolved in the solvent is used. It may be used. The emulsion type can be classified into a forced emulsification type and a self-emulsification type depending on the emulsification method, and any type can be used in this embodiment. When an emulsion type polyurethane is adopted as the first polymer, it is more preferably a self-emulsifying type. The polyurethane in the form of such a self-emulsifying emulsion is superior in film-forming property and water resistance compared to the forced emulsification type, so that, for example, when an image is formed by adhering to a recording medium, the water resistance of the image Can be further enhanced.

  Examples of commercial products of the first polymer used in the ink composition used in the image forming step include forced emulsification type polyurethane emulsions such as “Takelac (registered trademark) W-6061” (manufactured by Mitsui Chemicals), “ Self-emulsifying polyurethane emulsions such as “Takelac (registered trademark) W-6021” (manufactured by Mitsui Chemicals), “WBR-016U” (polyether manufactured by Taisei Fine Chemical Co., Ltd., Tg = 20 ° C.), and the like.

  When the above-mentioned emulsion type polyurethane is employed as the first polymer, the average particle size of the polyurethane emulsion particles is preferably 50 nm to 200 nm, more preferably 60 nm to 200 nm. When the average particle diameter of the polyurethane emulsion particles is in the above range, the polyurethane can be uniformly dispersed in the ink composition.

  The content (solid content) of the first polymer in the ink composition used in the image forming step is preferably 1% by mass or more and 30% by mass or less, and more preferably based on the total mass of the ink composition. It is 5 mass% or more and 20 mass% or less. If the content (solid content) of the first polymer in the ink composition is in the above range, it is easy to enable good ejection and printing in an ink jet recording apparatus, and an image formed by adhering to a recording medium. It is possible to sufficiently ensure the scratch resistance. On the other hand, if the content of the first polymer exceeds 30% by mass, the reliability (clogging, ejection stability, etc.) in ink jet recording of the ink composition may be impaired, and appropriate physical properties (viscosity, etc.) ) May not be obtained. On the other hand, if it is less than 1% by mass, the fixability of the ink composition on the recording medium may be insufficient, and the formed image may have insufficient abrasion resistance.

  The glass transition temperature (Tg) of the first polymer blended in the ink composition used in the image forming step is higher than the glass transition temperature of the second polymer contained in the adhesive layer of the laminating sheet described later. Selected to be. The Tg of the first polymer can be changed, for example, by changing at least one of the type of polymer, the modification of the polymer, the polymerization conditions, and the type of monomer. The relationship between Tg in the first polymer and the second polymer will be described in the section “1.3. Relationship between Glass Transition Temperatures of First Polymer and Second Polymer”.

1.1.2.2. Particles The ink composition used in the image forming process of the present embodiment contains particles having a hollow structure as a coloring material.

  The particle | grains which have a hollow structure are not specifically limited, A well-known thing can be used. For example, particles described in specifications such as US Pat. No. 4,880,465 and Patent 3,562,754 can be preferably used.

  Here, the hollow structure refers to a structure in which particles have at least substances having different refractive indexes, for example, a so-called core-shell structure, that is, a structure in which a space is surrounded by a closed shell. Point to. Further, the substance of the hollow core (inner side surrounded by the shell) may be liquid or gas.

  The particles having such a hollow structure can exhibit an achromatic color or a chromatic color at least after being attached to a recording medium. For example, particles having a hollow structure that is not colored can exhibit an achromatic white to gray color when attached to a recording medium due to light scattering due to the difference in refractive index between the core and shell. . Further, the particles having a hollow structure can be colored, and when attached to a recording medium, it is also possible to impart saturation (color). Such a color can be imparted with color by, for example, coloring a substance disposed in the core or shell, or changing the optical dimension of the core or shell without coloring. .

  The terms “achromatic” and “chromatic” are defined in Japanese Industrial Standards JIS Z8105 Nos. 3008 and 0309, and Japanese Industrial Standards JIS Z8113 Nos. 03010 and 03011. Then, the achromatic color may have a slight hue.

  In this specification, “white ink” refers to the brightness (L *) of a printed material in which Epson genuine photographic paper <gloss> (manufactured by Seiko Epson Corporation) is ejected in an amount sufficient to cover the paper. ) And chromaticity (a *, b *) when measured using a colorimeter of Gretag Macbeth Spectrolino (manufactured by X-Rite), 70 ≦ L * ≦ 100, −3.5 ≦ a * ≦ 1, refers to ink showing a range of −5 ≦ b * ≦ 1.5.

  The material of the shell of the particles having a hollow structure can be formed of an organic compound such as a resin or an inorganic compound such as a metal oxide. Further, the substance disposed in the core is not particularly limited, and can be liquid or gas. In addition, the material arrange | positioned at a core can be substituted with the exterior through a shell by making the material of a shell into a high molecular compound (resin) or reducing the thickness of a shell, for example. Therefore, for example, when the particles are attached to the recording medium, the liquid such as moisture inside the particles is dried and replaced with the outside air, so that the core can be made hollow (substantially the atmosphere). Also, for example, if particles are present in the ink composition, the internal cavities can be filled with the medium of the ink composition, so that the ink has a specific gravity close to that of the external medium. Dispersion stability in the composition can be ensured. Thereby, the storage stability and ejection stability of the ink composition can be enhanced.

  The average particle diameter (outer diameter) (d50) of the particles having a hollow structure is preferably 0.2 μm or more and 1.0 μm or less, and more preferably 0.4 μm or more and 0.8 μm or less. If the outer diameter of the particles having a hollow structure is in such a range, the dispersion in the ink composition can be kept good, and a desired color can be exhibited when attached to the recording medium. . On the other hand, when the outer diameter exceeds 1.0 μm, the particles may settle and the dispersion stability may be impaired, and the reliability such as clogging of the ink jet recording head may be impaired. On the other hand, if the outer diameter is less than 0.2 μm, a desired color may not be obtained. The inner diameter of the particles having a hollow structure (that is, the outer diameter of the core described above) is suitably about 0.1 μm or more and 0.8 μm or less.

  The average particle diameter d50 of the particles having a hollow structure is measured using, for example, a particle size accumulation curve. The particle size accumulation curve is obtained by statistically processing the results of measurements that can determine the diameter of particles and the number of particles present in particles dispersed in a dispersion medium such as water. A kind of curve. The particle size accumulation curve in this specification is a particle having a small diameter with respect to the particle mass (the product of volume, particle density, and number of particles when the particle is regarded as a sphere) with the diameter of the particle on the horizontal axis. The value (integrated value) integrated from the large to large particles is plotted on the vertical axis.

  And, the particle size d50 is 50% (0.50) when the vertical axis is normalized (the total mass of the measured particles is 1) in the particle size accumulation curve. The value on the horizontal axis, that is, the diameter of the particle.

  The particle size accumulation curve of the particles can be obtained, for example, by using a particle size distribution measuring apparatus based on the dynamic light scattering method. In the dynamic light scattering method, dispersed particles are irradiated with laser light, and the scattered light is observed with a photon detector. In general, dispersed particles usually have a Brownian motion. The speed of particle movement is larger for particles with a larger particle diameter and smaller for particles with a smaller particle diameter. When laser light is irradiated onto particles that are in Brownian motion, fluctuations corresponding to the Brownian motion of each particle are observed in the scattered light. This fluctuation is measured, an autocorrelation function is obtained by a photon correlation method or the like, and the particle diameter and the frequency (number) of particles corresponding to the diameter can be obtained by using a cumulant method or a histogram method analysis. The dynamic light scattering method is suitable for a sample including submicron size particles such as the particles according to the present embodiment, and a particle size accumulation curve can be obtained relatively easily by the dynamic light scattering method. Can do. Examples of the particle size distribution measuring apparatus based on the dynamic light scattering method include Nanotrac UPA-EX150 (manufactured by Nikkiso Co., Ltd.), ELSZ-2, DLS-8000 (above, manufactured by Otsuka Electronics Co., Ltd.), LB-550 ( Manufactured by HORIBA, Ltd.).

  On the other hand, the particle size accumulation curve of the particles is an ink composition containing the particles of the present embodiment, a state where the ink composition is attached (for example, a printed material), or a state after forming a laminate. For example, it can be measured by electron microscopy. In this method, the size of particles is measured from an electron micrograph, and the particle size accumulation curve of the particles can be obtained by measuring the photograph, for example, by image processing. Specifically, the minor axis diameter and major axis diameter of each particle are measured, and a circle diameter (equivalent circle diameter) equal to the area is calculated arithmetically, and for example, 50 or more particles are randomly selected from a certain field of view. Can be selected and obtained. According to this method, even when particles other than particles (for example, pigments) are contained in the ink composition, the particles can be selected on the electron microscope image. Can be sought. In order to increase the reliability in this measurement, the number of particles to be measured should be increased. In the case of a laminate, the laminate sheet can be peeled off from the base material (recording medium such as paper) as a sample for observation with an electron microscope, and the release surface (lamination sheet side or base) By observing the surface on the material side, a particle size accumulation curve can be obtained.

  Furthermore, in the ink composition containing the particles of the present embodiment, as a method for obtaining the particle size accumulation curve of the particles, there is also a method using centrifugation (hereinafter referred to as a centrifugal method). ). As a specific example of the centrifugal method, an ink composition is filled into an appropriate length of a centrifuge tube, and after centrifugation, a centrifuge product in a specific position (depth) range of the tube is collected. Since the specific position of the particles in the centrifuge tube after centrifugation is specified by the specific gravity difference between the specific gravity of the particles and the other components of the ink composition, for example, the particles are concentrated in a specific range. Therefore, by collecting a part of the ink composition from an appropriate position of the centrifugal tube and measuring it by the above-mentioned dynamic light scattering method or the like, the particle size of the ink composition containing the particles can be increased. A product curve can be determined.

  The content (solid content) of the particles having the hollow structure is preferably 5% by mass or more and 20% by mass or less, more preferably 8% by mass or more and 15% by mass or less, with respect to the total mass of the ink composition. is there. If the content (solid content) of the particles having a hollow structure is within this range, for example, the dispersion of the particles in the ink composition can be kept good. On the other hand, if the content (solid content) of particles having a hollow structure exceeds 20% by mass, reliability such as clogging of the ink jet recording head may be impaired. If it is less than 5% by mass, the color density such as whiteness tends to be insufficient.

  The method for preparing the particles having a hollow structure is not particularly limited, and for example, the following known methods can be applied. As a method for preparing particles having a hollow structure, for example, a particle emulsion having a hollow structure is formed by stirring a vinyl monomer, a surfactant, a polymerization initiator, and an aqueous dispersion medium while heating in a nitrogen atmosphere. A so-called emulsion polymerization method can be applied.

  Examples of vinyl monomers used in the emulsion polymerization method include nonionic monoethylenically unsaturated monomers, such as styrene, vinyl toluene, ethylene, vinyl acetate, vinyl chloride, vinylidene chloride, acrylonitrile, (meth) acrylamide, (meth). Examples include acrylic acid esters. As (meth) acrylic acid ester, methyl acrylate, methyl methacrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-hydroxyethyl methacrylate, 2-ethylhexyl (meth) acrylate, benzyl (meth) acrylate, lauryl (Meth) acrylate, oleyl (meth) acrylate, palmityl (meth) acrylate, stearyl (meth) acrylate and the like can be mentioned. Moreover, a bifunctional vinyl monomer can also be used as a vinyl monomer. Examples of the bifunctional vinyl monomer include divinylbenzene, allyl methacrylate, ethylene glycol dimethacrylate, 1,3-butane-diol dimethacrylate, diethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, and the like. By copolymerizing the above monofunctional vinyl monomer and the above bifunctional vinyl monomer and highly cross-linking, not only the light scattering characteristics of the particles, but also the characteristics such as heat resistance, solvent resistance, solvent dispersibility, etc. It is possible to obtain particles having a hollow structure.

  The surfactant used in the emulsion polymerization method is not particularly limited as long as it forms a molecular aggregate such as micelles in water. For example, an anionic surfactant, a nonionic surfactant, a cationic surfactant, an amphoteric surfactant. Surfactant etc. are mentioned. As the polymerization initiator used in the emulsion polymerization method, a known compound soluble in water can be used, and examples thereof include hydrogen peroxide and potassium persulfate. Examples of the aqueous dispersion medium at this time include water and water containing a hydrophilic organic solvent.

1.1.2.3. Other Components (1) Water The ink composition used in the image forming process of the present embodiment can contain water. Examples of water that can be used in the ink composition include pure water such as ion exchange water, ultrafiltration water, reverse osmosis water, and distilled water, or ultrapure water. Ions or the like may be present in the water as long as the above-described particle dispersion is not hindered. In particular, water obtained by sterilizing these waters by ultraviolet irradiation or addition of hydrogen peroxide is more preferable because it can suppress the generation of mold and bacteria for a long period of time and can keep the ink composition stable for a long period of time. .

  The water content in the ink composition used in the image forming step of the present embodiment is not limited as long as the dispersion of particles having a hollow structure can be maintained, but is 50% by mass or more and 95% by mass with respect to the total amount of the ink composition. It is preferable that it is below mass%. When the content of water in the ink composition is within this range, the dispersibility of the particles having a hollow structure becomes better, and the storage stability can be further improved.

  In addition, that content of water is 50 mass% or more and 95 mass% or less has shown that content of components other than water is 5 mass% or more and 50 mass% or less. In the present specification, components other than water may be referred to as solid content, and the content of water is 50% by mass or more and 95% by mass or less means that the concentration of solid content in the ink composition is 5% by mass. % Or more and 50 mass% or less.

(2) Penetration aid The ink composition used in the image forming step of the present embodiment may contain a penetration aid as necessary. Examples of the penetration aid include polyhydric alcohols. Examples of polyhydric alcohols include ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, propylene glycol, butylene glycol, 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,2-heptanediol, 1,2-octanediol and other alkanediols having 4 to 8 carbon atoms, 1,2,6-hexanetriol, thioglycol, hexylene glycol, glycerin, trimethylolethane, trimethylol Examples include propane and glycol ethers.

  As glycol ethers, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, triethylene glycol Mention may be made of lower alkyl ethers of polyhydric alcohols such as monomethyl ether, triethylene glycol monobutyl ether and tripropylene glycol monomethyl ether. Among these, when triethylene glycol monobutyl ether is blended in the ink composition, even better recording quality can be obtained.

  One of the functions of such a penetration aid is to increase the wettability of the recording surface such as a recording medium to increase the permeability of the ink. These alkanediols may also have an effect of preventing the ink composition from drying and preventing clogging in the ink jet recording head portion when the ink composition is applied to an ink jet recording apparatus.

  The alkane diol has 4 to 8 carbon atoms such as 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,2-heptanediol, 1,2-octanediol. 1,2-alkanediol is preferred. Of these, 1,2-hexanediol, 1,2-heptanediol, and 1,2-octanediol having 6 to 8 carbon atoms are particularly good in enhancing the permeability of the ink composition to the recording medium. Therefore, it is more preferable.

  When the ink composition used in the image forming process of the present embodiment contains a penetration aid, the content of the penetration aid is preferably 0.1% by mass with respect to the total mass of the ink composition. It is 5 mass% or less, More preferably, it is 1 mass% or more and 5 mass% or less.

  In addition, the polyhydric alcohol can have a plurality of functions, and one of the other functions as the penetration aid is to suppress drying of the ink. When applied to a recording apparatus, the effect of preventing clogging of ink in the ink jet recording head portion can be enhanced. Furthermore, the polyhydric alcohol is a compound having a larger number of hydroxyl groups in one molecule than the size of the hydrophobic region, and has a higher function of trapping moisture and is more effective in suppressing drying of the ink composition. .

(3) Surfactant The ink composition used in the image forming process of the present embodiment can contain a surfactant. Examples of the surfactant suitable for the ink composition of the present embodiment include at least one of an acetylene glycol surfactant and a polysiloxane surfactant. When these surfactants are blended in the ink composition, the wettability of the recording medium to the recording surface increases, and the penetrability of the ink composition into the recording medium can be further improved.

  Examples of the acetylene glycol surfactant include 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol, 3, Examples include 5-dimethyl-1-hexyn-3-ol, 2,4-dimethyl-5-hexyn-3-ol, and the like. Moreover, a commercial item can also be utilized for acetylene glycol type-surfactant, for example, Orphine E1010, STG, Y (above, Nissin Chemical Co., Ltd. product), Surfinol 104, 82, 465, 485, TG (above , Air Products and Chemicals Inc.). Commercially available products can be used as the polysiloxane surfactant, and examples thereof include BYK-347, BYK-348, BYK-UV3500 (manufactured by Big Chemie Japan Co., Ltd.) and the like. Furthermore, you may add other surfactants, such as anionic surfactant, a nonionic surfactant, and an amphoteric surfactant, to the ink composition used with the formation method of the laminated body of this embodiment.

  When a surfactant is contained in the ink composition used in the image forming process of the present embodiment, the content of the surfactant is preferably 0.01% by mass with respect to the total mass of the ink composition. It is 5 mass% or less, More preferably, it is 0.1 mass% or more and 0.5 mass% or less.

(4) pH adjuster The ink composition used in the image forming step of the present embodiment can contain a pH adjuster. The pH adjuster suitable for the ink composition used in the image forming step of the present embodiment is not particularly limited, and for example, potassium dihydrogen phosphate, disodium hydrogen phosphate, sodium hydroxide, lithium hydroxide, water Examples thereof include at least one of potassium oxide, ammonia, diethanolamine, triethanolamine, triisopropanolamine, potassium carbonate, sodium carbonate, and sodium bicarbonate. Of these, when a tertiary amine such as triethanolamine or triisopropanolamine is selected as a pH adjuster, it becomes easier to adjust the pH of the ink composition. The content of the pH adjuster is preferably 0.01% by mass or more and 10% by mass, and more preferably 0.1% by mass or more and 2% by mass or less with respect to the total mass of the ink composition.

(5) Other components The ink composition used in the image forming process of the present embodiment can form, for example, a white (achromatic) image with particles having a hollow structure. You may contain a coloring material. Examples of such a color material include pigments and dyes, and a color material that can be used for ordinary inks can be used without particular limitation. The color of the color material that can be added to the ink composition used in the image forming process of the present embodiment may be chromatic or achromatic. When a color material is contained in the ink composition, for example, color can be imparted to an image formed when applied to a recording medium.

  As dyes that can be used in ink compositions, direct dyes, acid dyes, food dyes, basic dyes, reactive dyes, disperse dyes, vat dyes, soluble vat dyes, reactive disperse dyes, etc. are usually used for inkjet recording Various dyes can be used.

  Examples of the color material include pigments and dyes, and a color material that can be used for ordinary inks can be used without any particular limitation. In the case where a color material is included in the ink composition, for example, a glossy color can be imparted to the image formed when applied to the recording medium together with the metallic luster.

  As dyes that can be used in ink compositions, direct dyes, acid dyes, food dyes, basic dyes, reactive dyes, disperse dyes, vat dyes, soluble vat dyes, reactive disperse dyes, etc. are usually used for inkjet recording Various dyes can be used.

  Examples of pigments that can be used in the ink composition include inorganic pigments and organic pigments.

  As an inorganic pigment, for example. Carbon black can be used. Examples of organic pigments that can be used include azo pigments, polycyclic pigments, dye chelates, nitro pigments, nitroso pigments, and aniline black. Examples of pigment colors include black, yellow, magenta, and cyan. When the ink composition of the present embodiment contains a color material, it may contain a plurality of color materials. For example, in addition to the four basic colors of yellow, magenta, cyan, and black, the same series of dark and light colors can be added for each color. That is, in addition to magenta, light light magenta, dark red, cyan, in addition to light light cyan, dark blue, black, in addition to light gray, light black, and dark matte black Can be exemplified.

  When the pigment is contained in the ink composition used in the image forming process of the present embodiment, the pigment preferably has an average particle size in the range of 10 to 200 nm, more preferably about 50 to 150 nm. It is. When a color material is included in the ink composition used in the image forming process of the present embodiment, the amount of the color material added is preferably in the range of about 0.1 to 25% by mass, more preferably 0.5 to The range is about 15% by mass.

  In addition, when a pigment is contained in the ink composition, a pigment dispersant for dispersing the pigment may be further added. As a preferable dispersant, a dispersant conventionally used for preparing a pigment dispersion, for example, a polymer dispersant can be used. As such a dispersant, any dispersant used in normal ink can be used. The content when the pigment dispersant is contained in the ink composition is 5 to 200% by mass, preferably 30 to 120% by mass with respect to the content of the color material in the ink composition, and should be dispersed. It may be selected as appropriate depending on the color material.

  Examples of pigments that can be used in the ink composition used in the image forming process of the present embodiment include azo pigments, polycyclic pigments, dye chelates, nitro pigments, and nitroso pigments. Examples of pigment colors include yellow, magenta, and cyan. When the ink composition of the present embodiment contains a color material, it may contain a plurality of color materials. For example, in addition to the basic three colors of yellow, magenta, and cyan, the same series of dark and light colors can be added for each color. That is, in addition to magenta, light color light magenta, dark red and cyan, and light color light cyan and dark blue can be included.

  A white pigment may be used for the ink composition used in the image forming process of the present embodiment. Examples of white pigments that can be used in the ink composition include oxides of elements of Group IV of the periodic table, such as titanium dioxide and zirconia. Other white pigments include calcium carbonate, calcium sulfate, zinc oxide, barium sulfate, barium carbonate, silica, alumina (aluminum oxide), kaolin, clay (clay mineral), talc, white clay, aluminum hydroxide, magnesium carbonate , Magnesium oxide, and the like. Preferably, it may be one or a mixture of two or more selected from the group consisting of these.

  When the pigment is contained in the ink composition used in the image forming step of the present embodiment, the pigment preferably has an average particle size in the range of 10 nm to 200 nm, more preferably about 50 nm to 150 nm. belongs to. When a color material is contained in the ink composition used in the image forming process of the present embodiment, the amount of the color material added is preferably in the range of about 0.1% by mass or more and 25% by mass or less, more preferably 0. The range is from about 5% by mass to about 15% by mass.

  In addition, when a pigment is contained in the ink composition used in the image forming process of the present embodiment, a pigment dispersant for dispersing the pigment may be further added. As a preferable dispersant, a dispersant commonly used for preparing a pigment dispersion, for example, a polymer dispersant can be used. As such a dispersant, any dispersant used in normal ink can be used. The content when the pigment dispersant is contained in the ink composition is 5% by mass or more and 200% by mass or less, preferably 30% by mass or more and 120% by mass or less with respect to the content of the pigment in the ink composition. Yes, it may be appropriately selected depending on the pigment to be dispersed.

  Further, an organic solvent may be added to the ink composition used in the image forming process of the present embodiment. Such an organic solvent is not particularly limited, but a polar organic solvent, for example, alcohols (for example, methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, isopropyl alcohol, fluorinated alcohol, etc.), ketones (for example, Acetone, methyl ethyl ketone, cyclohexanone, etc.), carboxylic acid esters (eg, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, etc.), or ethers (eg, diethyl ether, dipropyl ether, Tetrahydrofuran, dioxane, etc.), 2-pyrrolidone, formamide, acetamide, dimethyl sulfoxide, sorbit, sorbitan, acetin, diacetin, triacetin, sulfolane, etc. can be used. .

  Furthermore, the ink composition used in the image forming step of the present embodiment may contain a polymer other than the first polymer. However, such a polymer is preferably selected to have a higher Tg than the second polymer. Examples of such polymers include acrylic acid, acrylic acid ester, methacrylic acid, methacrylic acid ester, acrylonitrile, cyanoacrylate, acrylamide, olefin, styrene, vinyl acetate, vinyl chloride, vinyl alcohol, vinyl ether, vinyl pyrrolidone, vinyl. Examples thereof include homopolymers or copolymers of pyridine, vinyl carbazole, vinyl imidazole, and vinylidene chloride, modified products thereof, polyurethane, fluororesin, and natural resin. The copolymer may be in any form of a random copolymer, a block copolymer, an alternating copolymer, and a graft copolymer.

  In addition, the ink composition used in the image forming process of the present embodiment includes a fixing agent such as water-soluble rosin, an antifungal agent / preservative such as sodium benzoate, an antioxidant such as allophanates, a wetting agent, and an ultraviolet ray. You may contain additives, such as an absorber, a chelating agent, an oxygen absorber, antiseptic | preservative, and a fungicide. These additives can be used singly or in combination of two or more.

  The ink composition used in the image forming process of the present embodiment is prepared in the same manner as the conventional pigment ink using a conventionally known apparatus such as a ball mill, a sand mill, an attritor, a basket mill, and a roll mill. Can do. In the preparation, it is preferable to remove coarse particles using a membrane filter or a mesh filter.

  In addition, the ink composition used in the image forming process of the present embodiment can be applied to various applications, and can be applied to, for example, writing instruments, stamps, recorders, pen plotters, ink jet recording apparatuses, and the like. it can. For example, when the use is printing by an inkjet recording system, the viscosity of the ink composition at 20 ° C. is preferably 2 to 10 mPa · s, more preferably 3 to 5 mPa · s. When the viscosity at 20 ° C. of the ink composition is within the above range, an appropriate amount of the ink composition is ejected from the nozzle, and the flying bending and scattering of the ink composition can be further reduced. In this case, it is more preferable.

1.1.3. Image Forming Method The specific method of image formation in the image forming step is not particularly limited as long as it is a method for forming an image on a recording medium. For example, thermal jet ink jet, piezo ink jet, continuous ink jet, It can be performed by a method such as a roller application or a spray application. However, the above ink composition is preferably ejected by an ink jet recording head and adhered to a recording medium. Hereinafter, an example of a method for forming a dot group by ejecting the above-described ink composition onto a recording medium using an inkjet recording apparatus and attaching the ink composition onto the recording medium will be described.

  As an ink jet recording head system, for example, a strong electric field is applied between a nozzle and an acceleration electrode placed in front of the nozzle, and ink is continuously ejected from the nozzle in the form of droplets. A method in which a print information signal is applied to a polarizing electrode for recording while flying or a method in which ink droplets are ejected in response to a print information signal without being deflected (electrostatic suction method). In addition, a system that forcibly ejects ink droplets by mechanically vibrating the nozzle with a crystal resonator, etc., a system that simultaneously applies pressure and printing information signals to ink liquid with piezoelectric elements, and ejects and records ink droplets (Piezo method), a method in which an ink liquid is heated and foamed with a microelectrode according to a print information signal, and an ink droplet is ejected and recorded (thermal jet method). Any of the ink jet recording heads described above may be used in the image forming process of the present embodiment.

  Examples of the ink jet recording apparatus used in the image forming process include those provided with the above ink jet recording head, main body, tray, head driving mechanism, carriage and the like. The ink jet recording head may include an ink cartridge that stores ink sets of at least four colors of cyan, magenta, yellow, and black, and may be configured to perform full color printing. In the present embodiment, at least one of these ink cartridges or a dedicated cartridge is provided and filled with the above-described ink composition. Other cartridges may be filled with normal ink. The ink jet recording apparatus includes a dedicated control board and the like, and can control ink ejection timing of the ink jet recording head and scanning of the head driving mechanism.

  By the image forming process as described above, an image can be formed on the recording medium using the ink composition. The form of the image formed on the recording medium is not particularly limited, and the ink composition is attached to the entire surface or a part of the recording medium.

1.2. Laminating process After the image is formed on the recording medium through the image forming process, the laminating process closely adheres a sheet having an adhesive layer containing the second polymer to at least a portion of the recording medium where the image is formed. It is a process to make. In the present specification, the sheet used in this step may be referred to as “laminate sheet” or simply “sheet”. The sheet has at least a substrate and an adhesion layer. A sheet | seat may have a layer which exhibits another function other than a base material and an adhesion layer. The laminating sheet may be provided on both sides of the recording medium. In this way, the effect of protecting the recording medium and the image can be further enhanced.

  In general, when a sheet is used for thermal lamination, an adhesion layer (sometimes referred to as a glue layer or a sealant layer) is made of a thermoplastic resin, and the thermoplastic resin is softened and melted by heating. It is made into a paste and is crimped to the adherend. Such thermoplastic resins include polypropylene, low density polyethylene (LDPE), linear low density polyethylene, ethylene-vinyl acetate copolymer (EVA), ethylene- (meth) acrylic acid copolymer, ethylene- (meth). Examples thereof include acrylic ester copolymers, ionomer resins (IO), ethylene / α-olefin copolymers, polyolefin resins such as amorphous polyester, polyester resins, and modified products thereof. The thickness of the adhesion layer can be, for example, 15 μm or more and 100 μm or less.

  The laminate sheet may be a commercially available sheet. For example, the base material and the adhesion layer are formed using a commonly used technique such as tandem extrusion lamination, sandwich extrusion lamination, or dry lamination. Can be manufactured. The processing temperature in this case is preferably 150 to 300 ° C, more preferably 200 to 280 ° C. In such processing, for example, an operation such as ozone treatment may be added between the base material and the adhesion layer.

1.2.1. Substrate The shape of the substrate can be, for example, a thin film, a film, or a sheet. The thickness of a base material is not specifically limited, For example, it can be 10 micrometers or more and 2 mm or less. One of the functions of the substrate is to cover at least a portion of the recording medium to which the ink composition is adhered and protect the portion from external force or the like. The base material is preferably transparent to such an extent that an image formed on the recording medium can be visually recognized through the base material. Furthermore, the base material may be colored as long as it is transparent to the extent that an image formed on the recording medium can be visually recognized through the base material.

  Although it does not specifically limit as a material of a base material, For example, a polypropylene, polyethylene, a polyethylene terephthalate, a polyvinyl chloride, a polycarbonate, and polystyrene, those copolymers, and those modified substances are mentioned, for example. In addition, these materials may be provided with uniaxial or multiaxial orientation by stretching or the like in the base material.

  The thickness of the substrate is preferably 6 μm or more and 100 μm or less, more preferably 7 μm or more and 40 μm or less. The base material may contain a lubricant, an anti-blocking agent, a stabilizer, an antioxidant, an antistatic agent, an antifogging agent, a colorant, and other additives.

1.2.2. Adhesion layer The adhesion layer is formed on one surface of the substrate. The thickness of the adhesion layer can be, for example, 1 μm or more and 100 μm or less. One of the functions of the adhesion layer is to adhere the recording medium and the base material by adhesion, pressure bonding, or fusion bonding to the recording medium.

  The adhesion layer is formed of, for example, a material that can be heat-sealed. The adhesion layer can be formed of, for example, a thermoplastic resin. The adhesion layer of the sheet used in the laminating process of the present embodiment includes a second polymer.

1.2.3. Second Polymer The type of the second polymer is not particularly limited, and examples thereof include polyethylene, ionomer, polyacrylic acid, ethylene vinyl acetate copolymer, and modified products thereof. As the type of the second polymer, it is preferable to select a type different from the first polymer. One of the functions of the second polymer is to provide adhesion between the adhesive layer and the recording medium and the substrate. The glass transition temperature (Tg) of the second polymer can be adjusted by the monomer composition, the degree of polymerization (molecular weight), and the amount of modification of the second polymer.

  Components other than the second polymer may be included in the adhesion layer. Examples of other components that can be included in the adhesion layer include polymers other than the second polymer, plasticizers, and additives (such as ultraviolet absorbers, antioxidants, and antistatic agents). In addition, when a polymer other than the second polymer is included in the adhesion layer, it is preferable to select a polymer having a Tg higher than that of the first polymer. The content of the second polymer in the entire adhesion layer is preferably 20% by mass or more and 100% by mass or less, and more preferably 50% by mass or more and 100% by mass or less.

1.2.4. Laminate Mode A general method can be used as the laminate mode in this step. Examples of such a method include a method in which a recording medium on which an image is recorded is sandwiched between lamination sheets, and heat is applied to such a laminate by pressing or roller pressing.

  In the laminating step, the heat applied to the laminate is applied so that at least the second polymer has a temperature higher than the glass transition temperature of the second polymer. In this step, it is preferable that the period during which the second polymer is at a temperature higher than the glass transition temperature is set to be, for example, not less than 0.1 seconds and not more than 100 seconds. Since the period during which the second polymer is at a temperature higher than the glass transition temperature varies depending on the material and thickness of the substrate, it can be appropriately adjusted within a range in which a good laminate can be obtained.

1.3. The relationship between the glass transition temperatures of the first polymer and the second polymer In the method for forming a laminate according to this embodiment, the relationship between the glass transition temperatures (Tg) of the first polymer and the second polymer described above is characterized. is there. That is, in the method for forming a laminate of this embodiment, both are selected so that the Tg of the first polymer is higher than the Tg of the second polymer.

  The laminating step is performed at a temperature higher than the glass transition temperature of at least the second polymer of the adhesion layer. In this embodiment, since the Tg of the first polymer is higher than the Tg of the second polymer, after the lamination step is finished (after the heating is finished and the temperature starts to drop), the second polymer Is in a temperature (rubber state) equal to or higher than Tg, and there is a state in which the temperature is lower than Tg (glass state) of the first polymer. That is, when the temperature drops after the laminating step, the fluidity (molecular mobility) of the first polymer is lowered first. Therefore, the first polymer is less likely to flow than the second polymer, and the shell of the particles having a hollow structure forming an image is surrounded by the first polymer having a low fluidity, so that the first polymer is surrounded by the first polymer. Invasion of the bipolymer is suppressed.

  With the above-described mechanism, according to the method for forming a laminate of the present embodiment, the second polymer is less likely to enter the particles having a hollow structure, and the original coloration of the particles having the hollow structure is maintained for a long time. Can be maintained over time.

  Further, when a polyether-based or polycarbonate-based polyurethane is employed as the first polymer, the following heterogeneous effects can be obtained. Generally, as a property of polyurethane, the main chain of polyurethane is loosely bonded by hydrogen bonds, so that a flexible and tough film structure can be formed. By using polyether-based or polycarbonate-based polyurethane as the first polymer, it is flexible while spreading on the recording medium while maintaining fluidity at a temperature (10 ° C. to 40 ° C.) at which ordinary inkjet printing is performed. A simple film structure can be formed, and the abrasion resistance of the formed image can be improved. In general, media used for printing (for example, exclusive recording paper for inkjet “OHP sheet” manufactured by Seiko Epson Corporation) are often positively charged, so anionic polyurethane is used as the first polymer. In this case, the adhesion can be further improved by electrostatic interaction.

  In addition, when a polyether-based or polycarbonate-based polyurethane is used as the first polymer, a highly flexible film is easily formed as compared with a case where a polyester-based polyurethane is used, and therefore, the abrasion resistance is higher. In addition, polyether-based or polycarbonate-based polyurethane is preferable when used in water-based inks because it has a property of being hardly deteriorated against water.

  The color of the image of the laminate formed by the laminate forming method of the present embodiment is light scattering due to the difference in the refractive index of light between the outer shell (shell) and the cavity (core) of particles having a hollow structure. Is used. Then, by making the fluidity of the first polymer smaller than the fluidity of the second polymer, the second polymer can be prevented from entering the cavity, and as a result, the coloration of the image of the laminate can be stabilized. It is considered possible.

  The glass transition temperature (Tg) of the first polymer is more preferably 0 ° C. or lower. Although the detailed reason is not clear, when the Tg of the first polymer is 0 ° C. or higher, the laminate has a certain degree of fluidity (lower fluidity than the second polymer). Leveling property in the laminate is improved. Thereby, a laminate with higher image quality can be obtained. Furthermore, the glass transition temperature of the first polymer is preferably lower than the thermal decomposition temperature of particles having a hollow structure.

  Furthermore, when a polycarbonate-based or polyether-based anionic polyurethane is used as the first polymer, the first polymer forms a film on the surface upon drying, and is a highly flexible film compared to a polyester-based polyurethane. Therefore, it is possible to further suppress the change in the scattering performance of the particles having a hollow structure in the ink composition.

2. Laminate As described above, the laminate formed by the laminate forming method of the present embodiment includes a recording medium, and an image layer formed on the recording medium and including particles having a first polymer and a hollow structure. A sheet formed so as to cover at least the image layer and adhered through an adhesion layer containing the second polymer, and the glass transition temperature of the first polymer is higher than the glass transition temperature of the second polymer It is characterized by being expensive. In such a laminate, the color based on the particles of the image layer hardly changes, and the reliability of the image can be improved.

  Further, as described above, when the glass transition temperature of the first polymer is 0 ° C. or higher, the laminate can further suppress the color change of the image layer. Furthermore, if the average particle diameter d50 of the particles having a hollow structure is 0.4 μm or more and 0.8 μm or less, the color change of the image layer can be further suppressed.

  When particles having a hollow structure are used as a white color material in an image formed on a recording medium by the ink composition described above, the whiteness of the image is determined by the Japanese Industrial Standard (JIS) Z8715: 1999 It can be quantified by an index (for example, whiteness index) described in “Expression Method—Whiteness”. The measurement for obtaining such a numerical value can be performed by, for example, the method described in Japanese Industrial Standard (JIS) Z8722: 2000 “Color Measurement Method—Reflection and Transmission Object Color”. Moreover, as a device capable of such measurement, a commercially available device can be used. On the other hand, when the whiteness is simply evaluated, for example, using an apparatus capable of evaluating the Lab color system, the L * value (brightness) can be used.

3. Examples and Comparative Examples Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but these do not limit the scope of the present invention.

3.1. Ink composition In the blending amounts shown in Tables 1 and 2, particles having a hollow structure (hollow particles), a first polymer, a polyhydric alcohol, a penetration aid, a pH adjuster, a surfactant, and ion-exchanged water The mixture was stirred and filtered with a metal filter having a pore size of 5 μm and deaerated using a vacuum pump to obtain ink compositions of Examples 1 to 11 and Comparative Examples 1 to 6. In addition, the unit of the numerical value described in Examples 1 to 11 in Table 1 and Comparative Examples 1 to 6 in Table 2 is mass%, and both the hollow particles and the first polymer are in terms of solid content. is there.

  As the hollow particles, commercially available products “SX8782 (D)” (manufactured by JSR Corporation) described in Tables 1 and 2 were used. SX8782 (D) is an aqueous dispersion type having an outer diameter of 1.0 μm and an inner diameter of 0.8 μm, and has a solid content concentration of 20.5%. The thermal decomposition temperature of “SX8782 (D)” is 300 ° C. to 330 ° C.

  As the first polymer, the following polyurethane, styrene acrylic acid copolymer, and polyacrylic acid were used.

  “U-1” is a polycarbonate anionic polyurethane, manufactured by Mitsui Chemicals, trade name “W-615”, and Tg = 85 ° C.

  “U-2” is “W-6061” (a polyether anionic polyurethane manufactured by Mitsui Chemicals, Tg = 25 ° C.).

  “U-3” is “WS-6021” (a polyether anionic polyurethane manufactured by Mitsui Chemicals, Tg = −60 ° C.).

  “SA-1” is “UC-3900” (manufactured by Toa Gosei Co., Ltd., styrene acrylic resin, Tg = 60 ° C.).

  “A-1” is “UG-4010” (manufactured by Toa Gosei Co., Ltd., anionic acrylic resin, Tg = −57 ° C.).

  Other components are as follows.

  As the polyhydric alcohol, glycerin obtained as a reagent was used.

  As the penetration aid, 1,2-hexanediol obtained as a reagent was used.

  As the pH adjuster, triethanolamine obtained as a reagent was used.

  As the surfactant, “BYK-348” (polysiloxane-based surfactant) or “BYK-U3500” (polyether-modified polysiloxane-based surfactant) (both manufactured by Big Chemie Japan Co., Ltd.) was used.

  As the water, ion-exchanged water obtained as a reagent was used.

  As the organic solvent, isopropyl alcohol obtained as a reagent was used.

3.2. Laminate Sheet As the laminate sheet, commercially available products each having an adhesive layer containing the second polymer shown in Table 1 and Table 2 were prepared.

  A laminate sheet containing low-density polyethylene in the adhesion layer was obtained from Prime Polymer Co., Ltd., under the trade name “Ultzex”. The Tg of low density polyethylene is -120 ° C.

  A laminate sheet containing an ethylene vinyl acetate copolymer in the adhesion layer was obtained from Mitsui-DuPont Polychemical Co., Ltd. under the trade name “Evaflex”. The Tg of the ethylene vinyl acetate copolymer is −25 ° C.

  A laminate sheet containing an ionomer resin in the adhesion layer was obtained from Mitsui DuPont Polychemical Co., Ltd., under the trade name “Himiran 1554”. The softening point of the ionomer resin is 72 ° C.

  The laminate sheet containing polyacrylic acid in the adhesion layer was obtained by using two types, “Almatex Z113” and “Almatex HWS-1140” manufactured by Mitsui Chemicals, Inc. The polyacrylic acid has Tg of 5 ° C. and 40 ° C., respectively.

  The sheets used in each example and each comparative example are indicated by ● in Tables 1 and 2.

3.3. Evaluation method 3.3.1. Preparation of Laminate First, the ink compositions of each example described in Table 1 and Table 2 were filled in the black ink chambers of a dedicated cartridge of an inkjet printer (“PX-G930” manufactured by Seiko Epson Corporation). Then, the ink cartridge was mounted on a printer, and printing was performed on a dedicated recording sheet for inkjet (“OHP sheet” manufactured by Seiko Epson Corporation) as a recording medium. Printing was performed at a resolution of 720 × 720 dpi, and the pattern was a solid pattern of 100% duty. The obtained printed matter was white in visual observation. Commercially available ink cartridges other than black were mounted. This was used as a dummy and was not used for printing.

In this specification, “duty” is a value calculated by the following equation.
duty (%) = number of actual printing dots / (vertical resolution × horizontal resolution) × 100
(Where “number of actual print dots” is the number of actual print dots per unit area, and “vertical resolution” and “horizontal resolution” are resolutions per unit area. 100% duty is a single color for a pixel. Means the maximum ink mass.)
Next, after drying the obtained printed matter, it was sandwiched by a laminating sheet having an adhesion layer described in Table 1, and a laminate was formed by a model LPA3301 laminator manufactured by Fuji Plastics. Lamination of the apparatus was performed at a temperature of about 90 ° C. and a sheet conveying speed of 600 mm / min.

3.3.2. Evaluation of Laminate An aging test was performed on the laminates of each Example and each Comparative Example.

  First, the whiteness of the laminates of each Example and each Comparative Example was evaluated by measuring L * values. The measurement was performed by placing each sample on a standard black paper. The apparatus used was Gretag Macbeth Spectroscan and Spectrolino (manufactured by X-Rite), and the light source was D50.

  Next, each sample was aged at 60 ° C. for 1 week. And the whiteness of the laminated body of each sample was evaluated by the L * value similarly to the above.

Evaluation criteria are
A: Difference between L * value immediately after lamination and L * value after aging is less than 3 B: Difference between L * value immediately after lamination and L * value after aging is 3 or more and less than 5 C: L * value immediately after lamination The difference between the L * value after aging and 5 or more and less than 10 D: The difference between the L * value immediately after lamination and the L * value after aging was set to 10 or more, and the results of each sample are also shown in Tables 1 and 2. In addition, as the difference between the L * value immediately after lamination and the L * value after aging was larger, there was a tendency for whiteness to be lowered by visual observation and to produce transparency.

3.4. Evaluation result When Table 1 and Table 2 were seen, all the samples of the Example were excellent in the aging characteristic after lamination. That is, it was found that the laminate of the example in which the Tg of the first polymer is higher than the Tg of the second polymer is less likely to cause image transparency. On the other hand, it was found that the laminate of the comparative example in which the Tg of the first polymer is lower than the Tg of the second polymer is likely to cause image transparency.

  The present invention is not limited to the above-described embodiments, and various modifications can be made. For example, the present invention includes substantially the same configuration (for example, a configuration having the same function, method, and result, or a configuration having the same purpose and effect) as the configuration described in the embodiment. In addition, the invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. In addition, the present invention includes a configuration that achieves the same effect as the configuration described in the embodiment or a configuration that can achieve the same object. In addition, the invention includes a configuration in which a known technique is added to the configuration described in the embodiment.

Claims (8)

For a recording medium comprising an image formed using an ink composition comprising a first polymer and particles having a hollow structure,
A laminate for adhering a sheet having an adhesive layer containing a second polymer to at least a portion of the recording medium on which the image is formed,
A method for forming a laminate, wherein the glass transition temperature of the first polymer is higher than the glass transition temperature of the second polymer. In claim 1,
The method for forming a laminate, wherein the content of the first polymer in the ink composition is 5% by mass or more and 20% by mass or less. In claim 1 or claim 2,
Content of the said particle | grain in the said ink composition is 5 mass% or more and 20 mass% or less, The formation method of the laminated body characterized by the above-mentioned. In any one of Claims 1 to 3,
The method for forming a laminate, wherein an average particle diameter d50 of the particles is 0.4 μm or more and 0.8 μm or less. In any one of Claims 1 thru | or 4,
The method for forming a laminate, wherein the glass transition temperature of the second polymer is 40 ° C or higher. In any one of Claims 1 thru | or 5,
The method for forming a laminate, wherein the glass transition temperature of the first polymer is lower than the glass transition temperature or thermal decomposition temperature of the particles having the hollow structure. A recording medium;
An image layer formed on the recording medium and containing particles having a first polymer and a hollow structure;
A sheet formed so as to cover at least the image layer, and adhered through an adhesion layer containing a second polymer;
Including
A laminate having a glass transition temperature of the first polymer higher than a glass transition temperature of the second polymer. In claim 7,
A laminate having the glass transition temperature of the second polymer of 40 ° C or higher.