JP2012006278A - Laminate and method for forming the same - 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 is adhered to a part of the recording medium in which at least the image is formed to a recording medium including the image formed by using the ink composition containing the first particles each having the hollow structure and second particles each having a polymerizable functional group on the surface.

Description

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

  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, there is an example in which particles having a hollow structure as disclosed in Patent Document 1 are used as a coloring 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.
At least the image of the recording medium is formed on a recording medium including an image formed using an ink composition including first particles having a hollow structure and second particles having a polymerizable functional group on the surface. It is characterized in that the sheet is brought into close contact with the raised portion.

  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 ink composition includes a thermal polymerization initiator,
The polymerizable functional group may react with heat applied in the step of bringing the sheet into close contact.

  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 with fewer steps.

[Application Example 3]
In application example 2,
The step of bringing the sheet into close contact may be performed at 40 ° C. or higher and 200 ° C. or lower.

  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 4]
In any one of Application Examples 1 to 3,
The ink composition includes a radiation polymerization initiator,
The polymerizable functional group may react with radiation given in the step of bringing the sheet into close contact.

  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 5]
In any one of Application Examples 1 to 4,
The average particle diameter d50 of the first 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 hardly causes discoloration of an image.

[Application Example 6]
One aspect of the laminate according to the present invention is:
A recording medium;
An image layer formed on the recording medium and comprising a polymer and first particles;
A sheet formed to cover at least the image layer;
It is characterized by including.

  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 7]
In Application Example 6,
The average particle diameter d50 of the particles may be 0.4 μm or more and 0.8 μm or less.

  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 first particles and second particles.

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 first particles and second particles. 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 Particle The ink composition used in the image forming process of the present embodiment contains first particles having a hollow structure.

  It does not specifically limit as 1st particle | grains which have a hollow structure, 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 substances having different refractive indexes are included in particles, for example, a so-called core-shell structure, that is, a structure in which a space is surrounded by a shell. . Further, the substance of the hollow core (inner side surrounded by the shell) may be liquid or gas.

  Such first particles can exhibit an achromatic color or a chromatic color at least after being attached to the recording medium. For example, the uncolored first particles can exhibit an achromatic white to gray color when attached to a recording medium due to light scattering caused by a difference in refractive index between the core and the shell. Further, the first particles can be colored, and when attached to the 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 first particles 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 the particles are present in the ink composition, the internal cavity can be filled with the ink composition, and thus has a specific gravity close to that of the external medium. Dispersion stability in the inside 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 first particles 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 first particles is within 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. In addition, the inner diameter of the first particles (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 first particles 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% (0.5) when the vertical axis is normalized in the particle size accumulation curve (the total mass of the measured particles is 1). 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. More 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 arithmetically calculated. For example, 50 or more particles are obtained from a certain field of view. There is a method of selecting at random. 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.

  Further, as a method for obtaining a particle size accumulation curve of dispersed particles in the ink composition, there is a method using centrifugation (hereinafter, this may be 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 radiation scattering method, 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 first particles is preferably 5% by mass to 20% by mass, and more preferably 8% by mass to 15% by mass with respect to the total mass of the ink composition. If the content (solid content) of the first particles 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 the first particles 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 density of a desired color such as whiteness tends to be insufficient.

  The method for preparing the first particles is not particularly limited, and for example, the following known methods can be applied. As a method for preparing the first particles, for example, a so-called emulsification weight, in which an emulsion of the first particles is formed by stirring a vinyl monomer, a surfactant, a polymerization initiator, and an aqueous dispersion medium while heating in a nitrogen atmosphere. Legal 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-butanediol dimethacrylate, diethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, and the like. First particles having not only light scattering characteristics but also heat resistance, solvent resistance, solvent dispersibility, and the like by copolymerizing and crosslinking the monofunctional vinyl monomer and the bifunctional vinyl monomer. Can be obtained.

  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.

1.1.2.2. Second Particle The ink composition used in the image forming process of the present embodiment contains second particles. The second particles are particles having a polymerizable functional group on the surface.

  The polymerizable functional group that the second particle has on the surface is a functional group having polymerizability, and is a functional group having at least one polymerizability of radical polymerizability, cationic polymerizability, and anion polymerizability. That is, the polymerizable functional group on the surface of the second particle may have a single polymerizable property of radical polymerizable property, cationic polymerizable property, and anionic polymerizable property, or may have a plurality of polymerizable properties. Good. The polymerizable functional group has at least one of the property of polymerizing by heat and the property of polymerizing by radiation such as light.

  One of the functions of the second particles contained in the ink composition is to fix the first particles to the surface of the recording medium. The content of the second particles in the ink composition is in the range of 0.01% by mass to 30% by mass, preferably in the range of 5% by mass to 30% by mass with respect to the ink composition. When the content of the second particles in the ink composition is less than 0.01% by mass, sufficient fixability may not be obtained. When the content exceeds 30% by mass, the ink particles are ejected from the nozzles of the inkjet head. Stability may be reduced.

(1) Structure Examples of the structure of the second particles include those having at least one polymerizable functional group on the surface of the particles. Examples of the second particle include a polymerizable oligomer having a molecular chain for forming a structure, such as a dendritic oligomer and a urethane oligomer, and a polymerizable functional group arranged at the peripheral edge of the structure. The second particle may be a particle in which the boundary between the center of the particle and the site where the polymerizable functional group is arranged is not clearly defined, such as the polymerizable oligomer. Since it has a structure, it is included in the range of the second particle, and is referred to as a second particle.

(2) Particle size The particle size d50 of the second particles is preferably about 400 nm or less, more preferably 5 nm to 300 nm. The particle diameter of the second particles can be similarly measured using, for example, dynamic light scattering used for the measurement of the particle diameter of the first particles described above.

(3) Material of Center Part The center part of the second particle refers to a region excluding the polymerizable functional group in the structure of the second particle. For example, in the second particle having a structure having at least one polymerizable functional group on the surface of the organic particle, the central portion refers to the organic particle, and in the second particle such as a dendritic oligomer or a urethane oligomer. Is the region excluding the polymerizable functional group. The structures of the polymerizable oligomer and the urethane oligomer will be described in the section of the polymerizable oligomer described later.

  Examples of the material of the center part (organic particle) of the second particle having a structure having at least one polymerizable functional group on the surface of the organic particle include poly (meth) acrylate and styrene- (meth) acrylate. Copolymer, styrene-maleic acid copolymer, styrene-itaconic acid ester copolymer, polyvinyl acetate, polyester, polyurethane, polyamide, ethylene-vinyl acetate copolymer, ethylene- (meth) acrylic acid ester copolymer , Polyethylene, polypropylene, polystyrene and the like.

  Such organic particles can be obtained, for example, by known emulsion polymerization. Moreover, simultaneously with emulsion polymerization, it is also possible to introduce a polymerizable functional group onto the surface of the obtained organic particles. As such an example, for example, when an unsaturated vinyl monomer (unsaturated vinyl monomer) is emulsion-polymerized in water in the presence of a polymerization catalyst and an emulsifier, the unsaturated vinyl monomer having a polymerizable functional group is used. Polymerization with the body. In addition, after forming organic particles, a polymerizable functional group may be separately introduced by graft polymerization or the like. Examples of unsaturated vinyl monomers used in these methods include acrylic acid ester monomers, methacrylic acid ester monomers, aromatic vinyl monomers, vinyl esters generally used in emulsion polymerization. Examples include monomers, vinylcyan compound monomers, halogenated monomers, olefin monomers, and diene monomers.

  Further, the material of the organic particles is more preferably one having a structure having a relatively reactive group such as a carboxyl group so that a polymerizable functional group can be easily introduced. Further, the chemical structure of the organic particles may or may not have a crosslinked structure. When the organic particles have a cross-linked structure, it is preferable to contain a structure derived from a cross-linkable monomer in an amount of 0.2% by mass to 4% by mass.

(4) Polymerizable functional group As the polymerizable functional group present on the surface of the second particle, an epoxy group, an isocyanate group, an amino group, a carboxyl group, a phenolic hydroxyl group, an N-methylol group, an N-methylol ether group,- Examples thereof include a COOCO- group, a (meth) acryloyl group, a glycidyl group, an itaconic acid group, an oxetane ring, and a β-acryloyloxyethyl hydrogen succinate group.

  Among these, as functional groups having cationic polymerizability, JP-A-6-9714, JP-A-2001-31892, JP-A-2001-40068, JP-A-2001-55507, JP-A-2001-310938, Examples thereof include groups introduced by epoxy compounds, vinyl ether compounds, and oxetane compounds described in JP-A Nos. 2001-310937 and 2001-220526.

  Moreover, as an epoxy group arrange | positioned on the surface of 2nd particle | grains, the epoxy group introduce | transduced by epoxy compounds, such as an aromatic epoxide and an alicyclic epoxide, is mentioned. Among epoxy compounds, an epoxy group derived from an aromatic epoxide and an alicyclic epoxide is preferable, and an alicyclic epoxide is particularly preferably used from the viewpoint of excellent curing speed. In addition, examples of the vinyl ether disposed on the surface of the second particle include a group introduced into the surface by a reaction with a vinyl ether compound such as a di- or trivinyl ether compound.

  The oxetane ring disposed on the surface of the second particle is introduced by a known oxetane compound described in JP-A No. 2001-220526, JP-A No. 2001-310937, and JP-A No. 2003-341217. An oxetane ring can be mentioned. The compound having an oxetane ring is preferably a compound having 1 to 4 oxetane rings in the structure. When such a compound is used, the adhesion to the recording medium can be further enhanced after the second particles are cured.

  Examples of the polymerizable functional group present on the surface of the second particle include various known radical polymerizable functional groups. Examples of the compound used for introducing the radical polymerizable functional group into the particle surface include (meth) acrylates, (meth) acrylamides, aromatic vinyls and the like. In the present specification, when referring to both or one of “acrylate” and “methacrylate”, when referring to “(meth) acrylate” and both or one of “acryl” and “methacryl”, “(meth)” "Acrylic" may be described respectively.

  Monofunctional (meth) acrylates include hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, tert-octyl (meth) acrylate, isoamyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, Stearyl (meth) acrylate, isostearyl (meth) acrylate, cyclohexyl (meth) acrylate, 4-n-butylcyclohexyl (meth) acrylate, bornyl (meth) acrylate, isobornyl (meth) acrylate, benzyl (meth) acrylate, 2 -Ethylhexyl diglycol (meth) acrylate, butoxyethyl (meth) acrylate, 2-chloroethyl (meth) acrylate, 4-bromobutyl (meth) acrylate, cyanoethyl (meth) ) Acrylate, benzyl (meth) acrylate, butoxymethyl (meth) acrylate, 3-methoxybutyl (meth) acrylate, alkoxymethyl (meth) acrylate, alkoxyethyl (meth) acrylate, 2- (2-methoxyethoxy) ethyl (meth) ) Acrylate, 2- (2-butoxyethoxy) ethyl (meth) acrylate, 2,2,2-tetrafluoroethyl (meth) acrylate, 1H, 1H, 2H, 2H-perfluorodecyl (meth) acrylate, 4-butyl Phenyl (meth) acrylate, phenyl (meth) acrylate, 2,4,5-tetramethylphenyl (meth) acrylate, 4-chlorophenyl (meth) acrylate, phenoxymethyl (meth) acrylate, phenoxyethyl (meth) acrylate , Glycidyl (meth) acrylate, glycidyloxybutyl (meth) acrylate, glycidyloxyethyl (meth) acrylate, glycidyloxypropyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, hydroxyalkyl (meth) acrylate, 2 -Hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, dimethylaminoethyl (meth) Acrylate, diethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylate, diethylaminopropyl (meth) acrylate, trimethoxysilylpropyl (meth) Acrylate, trimethoxysilylpropyl (meth) acrylate, trimethylsilylpropyl (meth) acrylate, polyethylene oxide monomethyl ether (meth) acrylate, oligoethylene oxide monomethyl ether (meth) acrylate, polyethylene oxide (meth) acrylate, oligoethylene oxide (meth) acrylate, Oligoethylene oxide monoalkyl ether (meth) acrylate, polyethylene oxide monoalkyl ether (meth) acrylate, dipropylene glycol (meth) acrylate, polypropylene oxide monoalkyl ether (meth) acrylate, oligopropylene oxide monoalkyl ether (meth) acrylate, 2 -Methacryloyloxyethyl succinic acid, 2-methacrylic acid Iroxyhexahydrophthalic acid, 2-methacryloyloxyethyl-2-hydroxypropyl phthalate, butoxydiethylene glycol (meth) acrylate, trifluoroethyl (meth) acrylate, perfluorooctylethyl (meth) acrylate, 2-hydroxy-3- Phenoxypropyl (meth) acrylate, EO modified phenol (meth) acrylate, EO modified cresol (meth) acrylate, EO modified nonylphenol (meth) acrylate, PO modified nonylphenol (meth) acrylate, EO modified-2-ethylhexyl (meth) acrylate Can be mentioned.

  Bifunctional (meth) acrylates include 1,6-hexanediol di (meth) acrylate, 1,10-decanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, and 2,4-dimethyl-1 , 5-pentanediol di (meth) acrylate, butylethylpropanediol (meth) acrylate, ethoxylated cyclohexanemethanol di (meth) acrylate, polyethylene glycol di (meth) acrylate, oligoethylene glycol di (meth) acrylate, ethylene glycol di (Meth) acrylate, 2-ethyl-2-butyl-butanediol di (meth) acrylate, hydroxypivalate neopentyl glycol di (meth) acrylate, EO-modified bisphenol A di (meth) acrylate, Sphenol F polyethoxydi (meth) acrylate, polypropylene glycol di (meth) acrylate, oligopropylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 2-ethyl-2-butyl-propanediol di ( And (meth) acrylate, 1,9-nonanediol di (meth) acrylate, propoxylated ethoxylated bisphenol A di (meth) acrylate, tricyclodecane di (meth) acrylate, and the like.

  Trifunctional (meth) acrylates include trimethylolpropane tri (meth) acrylate, trimethylolethane tri (meth) acrylate, alkylene oxide modified tri (meth) acrylate of trimethylolpropane, pentaerythritol tri (meth) acrylate, Dipentaerythritol tri (meth) acrylate, trimethylolpropane tri ((meth) acryloyloxypropyl) ether, isocyanuric acid alkylene oxide modified tri (meth) acrylate, dipentaerythritol tri (meth) acrylate propionate, tri (( (Meth) acryloyloxyethyl) isocyanurate, hydroxypivalaldehyde-modified dimethylolpropane tri (meth) acrylate, sorbitol tri (meth) acrylate DOO, propoxylated trimethylolpropane tri (meth) acrylate, and the like ethoxylated glycerol triacrylate.

  Examples of tetrafunctional or hexafunctional (meth) acrylates include pentaerythritol tetra (meth) acrylate, sorbitol tetra (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, dipentaerythritol tetra (meth) acrylate propionate, ethoxy Pentaerythritol tetra (meth) acrylate, sorbitol penta (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, sorbitol hexa (meth) acrylate, phosphazene alkylene oxide modified hexa (meth) Examples thereof include acrylate and caprolactone-modified dipentaerythritol hexa (meth) acrylate.

  Examples of (meth) acrylamides include (meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-propyl (meth) acrylamide, and Nn-butyl (meth) acrylamide. N-t-butyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N-methylol (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N- Examples include diethyl (meth) acrylamide and (meth) acryloylmorpholine.

  Aromatic vinyls include styrene, methyl styrene, trimethyl styrene, ethyl styrene, isopropyl styrene, chloromethyl styrene, methoxy styrene, acetoxy styrene, chloro styrene, dichloro styrene, bromo styrene, vinyl benzoic acid methyl ester, 3-methyl Styrene, 4-methylstyrene, 3-ethylstyrene, 4-ethylstyrene, 3-propylstyrene, 4-propylstyrene, 3-butylstyrene, 4-butylstyrene, 3-hexylstyrene, 4-hexylstyrene, 3-octyl Styrene, 4-octylstyrene, 3- (2-ethylhexyl) styrene, 4- (2-ethylhexyl) styrene, allyl styrene, isopropenyl styrene, butenyl styrene, octenyl styrene, 4-t-butoxy Rubonirusuchiren, 4-methoxystyrene, and a 4-t-butoxystyrene.

  In addition, the compounds used to introduce radical polymerizable compounds to the surface of the particles include vinyl esters (such as vinyl acetate, vinyl propionate, vinyl versatate), allyl esters (such as allyl acetate), and halogen-containing compounds. Monomers (vinylidene chloride, vinyl chloride, etc.), vinyl ethers (methyl vinyl ether, butyl vinyl ether, hexyl vinyl ether, methoxy vinyl ether, 2-ethylhexyl vinyl ether, methoxyethyl vinyl ether, cyclohexyl vinyl ether, chloroethyl vinyl ether, etc.), vinyl cyanide ((meta ) Acrylonitrile, etc.), olefins (ethylene, propylene, etc.) and the like may be used.

  Among these compounds, the second particles that can be suitably used in the ink composition used in the image recording process include polymerizable functional groups on the surface by (meth) acrylates and (meth) acrylamides from the viewpoint of curing speed. In particular, the second particles having a polymerizable functional group derived from (meth) acrylates are preferable from the viewpoint of curing speed.

  Further, the second particles may be particles having a core-shell structure and having a polymerizable functional group on the surface thereof. The second particles of this aspect may have a form in which the shell part completely covers the core part as well as a part of the core part. Further, a part of the polymer in the shell part may form a domain or the like in the core part. Furthermore, it may have a multilayer structure of three or more layers including layers having different compositions in the middle between the core part and the shell part. The second particles may have a polymerizable functional group disposed on the surface of such particles.

  Furthermore, in the case of the 2nd particle | grains which have a core-shell structure, the center part can be manufactured by multistage emulsion polymerization etc. by a well-known method. More specifically, it can be produced by the method disclosed in JP-A-4-76004. Examples of the unsaturated vinyl monomer used for the polymerization are the same as those exemplified above.

  The content of the second particles in the ink composition is appropriately 50% by mass to 95% by mass with respect to the total solid content of the composition, preferably 60% by mass to 92% by mass, and more preferably It is the range of 70 mass% or more and 90 mass% or less.

(5) Polymerizable oligomer The second particles may be those in which a polymerizable functional group is introduced at the end of the oligomer, in addition to those having a polymerizable functional group arranged on the surface of the particle as described above. . Here, the oligomer means a repeating structure of a small number of units substantially or conceptually obtained from a molecule having a small relative molecular mass (synonymous with molecular weight), generally about 2 to 20 times. A molecule having a medium relative molecular mass. The oligomer is sometimes called a polymerizable prepolymer, a base resin, or the like.

(5-1) Urethane oligomers As the second particles, urethane oligomers may be used. The urethane oligomer means one having at least one urethane bond and polymerizable unsaturated double bond in the molecule.

  Since the urethane oligomer has one or several acryloyl groups as functional groups, it has a property of causing a polymerization reaction and crosslinking polymerization.

  Examples of the urethane oligomer include oligomers generated by an addition reaction between a polyol and a polyisocyanate and a polyhydroxy compound. Examples of urethane oligomers include polyester urethane acrylate, polyether urethane acrylate, polybutadiene urethane acrylate, polyol urethane acrylate, and the like. Examples of commercially available urethane oligomers include U-4HA and U-15HA (both available from Shin-Nakamura Chemical Co., Ltd.).

  When a urethane oligomer is selected as the second particle, its molecular weight is preferably about 500 to 20000, more preferably about 500 to 10,000.

(5-2) Dendritic oligomer As the second particle, a dendritic oligomer may be used. As the dendritic oligomer, a polyfunctional (meth) acrylate compound represented by the following general formula (1) and a polyvalent mercapto compound represented by the following general formula (2) are polymerized by Michael addition (β position with respect to the carbonyl group). Can be mentioned.

[In the general formula (1), R ¹ represents hydrogen or an alkyl group having 1 to 4 carbon atoms, and R ² donates n hydroxyl groups of the compound R ³ (OH) _m to the ester bond in the formula. R ³ (OH) _m is a polyhydric alcohol based on a non-aromatic linear or branched hydrocarbon skeleton having 2 to 8 carbon atoms, and a plurality of molecules of the polyhydric alcohol. Is a polyhydric alcohol ether formed by dehydration of alcohol via an ether bond, or an ester of these polyhydric alcohol or polyhydric alcohol ether and hydroxy acid, where m ≧ n , N represents an integer of 2-20. ]

[In the above general formula (2), R ⁴ is a single bond, a hydrocarbon group having 1 carbon atom, or an oxygen atom in the skeleton having 2 to 5 carbon atoms, A hydrocarbon group which may be a branched chain, or a group having a carbonyloxy group bonded to at least a part of the thiomethyl group of formula 2 to these hydrocarbon groups, and p is an integer of 2 to 6 Wherein R represents 2 when R ⁴ represents a single bond, and p represents an integer of 2 to 4 when the carbon number of R ⁴ is 1. ]

  Michael addition of the polyvalent mercapto compound represented by the general formula (2) to the polyfunctional (meth) acrylate compound represented by the general formula (1) indicates that the resulting dendritic oligomer is still a carbon-carbon double bond. So that the carbon-carbon double bond of the compound represented by the general formula (1) remains in the range of 0.1% to 50% as a whole. It is preferable.

  For example, the addition ratio of the mercapto group of the polyvalent mercapto compound represented by the general formula (2) to the carbon-carbon double bond of the polyfunctional (meth) acrylate compound represented by the general formula (1) is The molar ratio of double bonds is preferably 1/200 to 1/2, more preferably 1/100 to 1/3, and more preferably 1/50 to 1/5. More preferably, it is particularly preferable to be 1/20 to 1/8.

  Further, the dendritic oligomer obtained by adding the polyvalent mercapto compound represented by the general formula (2) to the polyfunctional (meth) acrylate compound represented by the general formula (1) has a sufficient functional group for polymerization. It is preferable to have. For this purpose, the molecular weight of the dendritic oligomer is preferably in the range of 100 to 100,000 in terms of molecular weight per mole of carbon-carbon double bond. The molecular weight of the dendritic oligomer is preferably 1000 to 50000, more preferably 1500 to 40000, and particularly preferably 2000 to 30000.

  In the dendritic oligomer, the number (n) of acrylate groups in the general formula (1) is preferably 2 to 20, more preferably 2 to 10, and further preferably 2 to 6. Preferred specific examples of the polyfunctional (meth) acrylate compound represented by the general formula (1) include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, and tetraethylene glycol di (Meth) acrylate, tetramethylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, ethylene oxide modified trimethylolpropane tri (meth) acrylate, propylene oxide modified trimethylolprovantri (meth) acrylate, trimethylolethane Tri (meth) acrylate, pentaerythritol di (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) Acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, tripentaerythritol octa (meth) acrylate, tripentaerythritol hepta (meth) acrylate, caprolactone modified pentaerythritol tri (meth) acrylate, caprolactone modified Pentaerythritol tetra (meth) acrylate, caprolactone-modified dipentaerythritol hexa (meth) acrylate, epichlorohydrin-modified hexahydrophthalic acid di (meth) acrylate, hydroxypivalic acid neopentyl glycol di (meth) acrylate, neopentyl glycol di (meth) Acrylate, ethylene oxide modified neopentyl glycol di (meth) acrylate, Pyrene oxide modified neopentyl glycol di (meth) acrylate, caprolactone modified hydroxypivalate ester neopentyl glycol di (meth) acrylate, stearic acid modified pentaerythritol di (meth) acrylate, epichlorohydrin modified phthalic acid di (meth) acrylate, poly ( Ethylene glycol tetramethylene glycol) di (meth) acrylate, poly (propylene glycol tetramethylene glycol) di (meth) acrylate, polyester (meth) acrylate, polyethylene glycol di (meth) acrylate, polyethylene glycol-polypropylene glycol-polyethylene glycol di ( (Meth) acrylate, polypropylene glycol di (meth) acrylate, epichlorohydrin modification Propylene glycol di (meth) acrylate, propylene oxide modified bisphenol A diglycidyl ether di (meth) acrylate, silicone di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, tricyclo Decanedimethanol di (meth) acrylate, neopentyl glycol modified trimethylolpropane di (meth) acrylate, tripropylene glycol di (meth) acrylate, ethylene oxide modified tripropylene glycol di (meth) acrylate, triglycerol di (meth) acrylate , Dipropylene glycol di (meth) acrylate, epichlorohydrin modified glycerol tri (meth) acrylate, ethylene oxide modified Glycerol tri (meth) acrylate, propylene oxide modified glycerol tri (meth) acrylate, ethylene oxide modified phosphoric acid tri (meth) acrylate, caprolactone modified trimethylolpropane tri (meth) acrylate, HPA modified trimethylolpropane tri (meth) acrylate, Ethylene oxide modified trimethylolpropane tri (meth) acrylate, propylene oxide modified trimethylolpropane tri (meth) acrylate, trimethylolpropane benzoate (meth) acrylate, tris ((meth) acryloxyethyl) isocyanurate, alkoxy modified trimethylolpropane Tri (meth) acrylate, dipentaerythritol poly (meth) acrylate, alkyl-modified dipentaeri Ritorutori (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate of (meth) and acrylic acid ester. These compounds may be used alone or in combination of two or more.

In the dendritic oligomer, as the polyvalent mercapto compound represented by the general formula (2), 1,2-dimercaptoethane, 1,3-dimercaptopropane, 1,4-dimercaptobutane, bisdimercaptoethanethiol ( _{HS-CH 2 CH 2 -S-} CH 2 CH 2 -SH), trimethylolpropane tri (mercaptoacetate), trimethylolpropane tri (mercaptopropionate), pentaerythritol tetra (mercaptoacetate), pentaerythritol tri (mercapto Acetate), pentaerythritol tetra (mercaptopropionate), dipentaerythritol hexa (mercaptoacetate), dipentaerythritol hexa (mercaptopropionate) and the like.

  In synthesizing the dendritic oligomer, a polymerization inhibitor can be added as necessary. As the polymerization inhibitor, hydroquinone compounds and phenol compounds generally used for preventing polymerization of (meth) acrylate compounds can also be used in the present invention.

  Specific examples thereof include, but are not limited to, hydroquinone, methoxyhydroquinone, caterol, p-tert-butylcatechol, cresol, dibutylhydroxytoluene, 2,4,6-tri-tert-butylphenol (BHT) and the like.

  Completion of the synthesis of the dendritic oligomer can be confirmed by liquid chromatography, gel filtration chromatography, or other general analytical instruments.

  The Michael addition reaction of the polyvalent mercapto compound represented by the general formula (2) in the dendritic oligomer to the (meth) acrylate group of the polyfunctional (meth) acrylate compound represented by the general formula (1) is a polyfunctional (meta ) An acrylate compound (monomer) and a polyvalent mercapto compound are mixed, and a basic catalyst is added at room temperature to 100 ° C. The reaction time is usually about 30 minutes to about 6 hours.

  In the dendritic oligomer produced as illustrated above, molecular chains extend radially from the center, and these molecular chains have a spherical structure as a whole, and this spherical part forms the central part of the second particle. And has a structure in which a functional group having polymerizability is arranged in the periphery thereof.

  When the dendritic oligomer is blended in the ink composition, the coating film to be formed is improved in addition to the ability to fix the first particles, but the details of the mechanism are not clear. However, in general, the reaction using thiol and acrylate has a characteristic that it is hard to be inhibited by oxygen in radical polymerization and the like, and is cured with low energy, and has excellent adhesiveness due to less curing shrinkage. In the dendritic oligomer produced from thiol and acrylate as described above, there is no thiol residue at the end and it cannot be said that the reaction is exactly the same, but the properties (adhesion) such as strength of the film after curing, etc. It is estimated to improve.

(6) Properties of second particles The second particles are preferably added to the ink composition as an emulsion.

For such an emulsion, in the aqueous emulsion in which the second particles are dispersed in water at a concentration of 10% by mass, the second particles having a contact angle on a Teflon (registered trademark) plate of 70 ° or more are further selected. preferable. Furthermore, the surface tension of the aqueous emulsion in which the second particles are dispersed in water at a concentration of 35% by mass is preferably 40 × 10 ⁻³ N / m (40 dyne / cm, 20 ° C.) or more.

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 the first particles and the second particles can be maintained, but is 50% by mass with respect to the total amount of the ink composition. It is preferable that it is 95 mass% or less. When the water content in the ink composition is within this range, the dispersibility of the first particles 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) Polymerization initiator The ink composition used in the image forming method of the present embodiment may contain a polymerization initiator, if necessary. For example, when the ink composition contains second particles having a radical polymerizable functional group, the second particles can be polymerized by applying heat or irradiating with radiation. When it is necessary to further increase the speed of the polymerization, a thermal polymerization initiator or a radiation polymerization initiator can be added.

  As the thermal polymerization initiator, when the second particle has an epoxy group on the surface, an aliphatic amine, an aromatic amine, an organic dibasic acid anhydride, or the like, such as an isocyanate group on the surface, a carboxyl group, In the case of having a compound having a hydroxyl group, N-methylol group or N-methylol ether group on the surface, examples thereof include a compound having a carboxyl group, a hydroxyl group, an amino group and the like. The content of the thermosetting agent is selected depending on the type of the thermosetting agent, the type of the thermosetting polymer, the amount of use thereof, and the like. And about 1% by mass to about 500% by mass.

  Examples of the radiation polymerization initiator include aromatic ketones, aromatic onium salt compounds, organic peroxides, hexaarylbiimidazole compounds, ketoxime ester compounds, borate compounds, azinium compounds, metallocene compounds, active ester compounds, carbon Examples include compounds having a halogen bond. Specific examples of the radiation polymerization initiator include benzyl dimethyl ketal, α-hydroxyalkylphenone, α-aminoalkylphenone, acylphosphine oxide, oxime ester, thioxanthone, α-dicarbonyl, and anthraquinone. .

  Commercially available polymerization initiators include Vicure 10, 30 (manufactured by Stauffer Chemical), Irgacure 127, 184, 500, 651, 2959, 907, 369, 379, 754, 1700, 1800, 1870, 819, 819DW, OXE01, Darocur 1173, TPO, ITX (Ciba Specialty Chemicals), Quanture CTX (Aceto Chemical), Kayacure, DETX-S (Nippon Kayaku), ESACURE KIP150 (Lamberti) The polymerization initiator which can be obtained by name can be mentioned. Moreover, when the ink composition is a water-based ink composition, the polymerization initiator is more preferably water-soluble. Examples of such a polymerization initiator include Irgacure 819DW.

  In the case of using a water-based ink composition, the polymerization initiator is not necessarily water-soluble, may be oil-soluble, or may be poorly soluble. This is because, for example, when the polymerization initiator is oil-soluble, the polymerization initiator is present in the oil phase in the water-based ink composition, and when it is poorly soluble, the polymerization initiator is For example, after the image forming step, when water is removed to some extent on the recording medium, it comes into contact with the polymerizable functional group and can exhibit a desired action. Furthermore, the polymerization initiator may have a property of moving between phases, and can be appropriately selected according to the ink composition and as necessary.

(3) Penetration aid The ink composition used in the image forming step of the present embodiment may contain a penetration aid as required. 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. .

(4) Surfactant The ink composition used in the image forming step 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.

(5) pH adjuster The ink composition used in the image forming step of the present embodiment may 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. When the pH adjuster is contained in the ink composition, the content thereof is preferably 0.01% by mass or more and 10% by mass, and more preferably 0.1% by mass with respect to the total mass of the ink composition. % To 2% by mass.

(6) Other components The ink composition used in the image forming step of the present embodiment may contain a resin for the purpose of fixing the ink composition to a recording medium. Examples of such resins 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 pyridine. , Vinyl carbazole, vinyl imidazole, vinylidene chloride homopolymer or copolymer, or modified products thereof, polyurethane, fluororesin, natural resin, and the like. The copolymer may be in any form of a random copolymer, a block copolymer, an alternating copolymer, and a graft copolymer. One of the functions of the resin is to fix the first particles to the recording medium.

  The ink composition used in the image forming process of the present embodiment can form, for example, a white (achromatic) image with the first particles, but may further contain other color materials. . 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. When a color material is included in the ink composition, for example, a color of radiation can be imparted to an image formed when applied to a recording medium together with a metal radiation.

  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 included in the ink composition used in the image forming process of the present embodiment, a pigment dispersant for dispersing the pigment in the ink composition 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. .

  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.

  The ink composition used in the image forming process of the present embodiment can also be applied to other uses, 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 polarized radiation electrode during recording, or a method in which ink droplets are ejected in response to a print information signal without being deflected (electrostatic suction method). In addition, the nozzle is mechanically oscillated with a crystal oscillator, etc. to forcibly eject ink droplets. The pressure and print information signal are simultaneously applied to the ink liquid by a piezoelectric element to eject and record ink droplets. Examples include a method (piezo method), a method in which an ink liquid is heated and foamed with a microelectrode in accordance with a print information signal, and ink droplets are 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.

  The ink jet recording apparatus used in the image forming process may include an ultraviolet irradiation device. Furthermore, the ink jet recording apparatus used in the image forming process may include an apparatus for heating the recording medium. By using such an apparatus, the second particles in the ink composition can be cured on the recording medium before the lamination step.

  As an inkjet recording apparatus provided with an ultraviolet irradiation device, for example, a device in which a light irradiation device is mounted on a side surface of a carriage, or an optical fiber that guides light to a recording medium from an external light source separate from the inkjet recording device is configured. Can be mentioned.

When the ultraviolet ray irradiation device is provided in the ink jet recording apparatus, the wavelength of the irradiation light source is not particularly limited, but is preferably 350 nm or more and 450 nm or less. The dose of light, the recording medium, preferably 10 mJ / cm ² or more and 20000 mJ / cm ² or less, more preferably 50 mJ / cm ² or more, conducted at 15,000 mJ / cm ² or less. If it is the ultraviolet irradiation amount in this range, the curing reaction of the coating film of the ink composition formed on the recording medium can be sufficiently performed.

  In addition to the ultraviolet irradiation method, light from a metal halide lamp, a xenon lamp, a carbon arc lamp, a chemical lamp, a low-pressure mercury lamp, a high-pressure mercury lamp, or the like can be guided to the coating film by a light guide or the like. Moreover, as a light source, it can carry out using what was marketed, such as H lamp, D lamp, and V lamp which can be obtained from Fusion System etc., for example. Further, as the light source, an ultraviolet light emitting semiconductor element such as an ultraviolet light emitting diode (ultraviolet LED) or an ultraviolet light emitting semiconductor laser can be used, and ultraviolet light from such a light source can be irradiated.

  Examples of the ink jet recording apparatus provided with a heating device include a device that heats a recording medium by providing an infrared lamp on a carriage, and a device that heats a recording medium by heating a roller that conveys the recording medium. In addition, for example, heating is performed without bringing the recording medium into contact with the recording medium, such as heating by bringing a heat source into contact with the recording medium, irradiating infrared rays or microwaves (electromagnetic waves having a maximum wavelength of about 2,450 MHz), or blowing hot air. The method of heating can be mentioned. The recording medium may be heated at the same time as printing, after printing, or during printing.

  Examples of the method for heating the recording medium include a method in which a heater is provided on a guide roller to heat the recording medium, a method in which air is blown on the ink composition on the recording medium, and a method in which they are combined. Specifically, forced air heating, radiation heating, conductive heating, high frequency drying, microwave heating and the like are preferably used.

  The temperature range when heating the recording medium is preferably not less than a temperature capable of promoting volatilization of the liquid component present in the ink composition, for example, not less than 40 ° C., preferably 40 ° C. to 80 ° C. More preferably, it is in the range of 40 ° C to 60 ° C. When the temperature exceeds 80 ° C., problems such as deformation may occur depending on the type of the recording medium, which may hinder the conveyance of the recording medium, or may cause problems such as shrinkage when the recording medium cools to room temperature.

  The heating time is not particularly limited as long as the liquid component present in the ink composition can be volatilized by a desired amount, and is appropriately set in consideration of the liquid component to be used, the resin component / printing speed, the drying efficiency, and the like. can do.

  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 The laminating process is a process in which, after an image is formed on the recording medium through an image forming process, the sheet is brought into close contact with at least a portion of the recording medium on which the image is formed. In the present specification, the sheet used in this step may be referred to as “laminate sheet” or simply “sheet”. The sheet has, for example, a base material 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 sheet of this embodiment has an 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 bonded or thermally fused to the recording medium. The adhesion layer can be formed of, for example, an adhesive or a thermoplastic resin. The kind of the thermoplastic resin is not particularly limited, and examples thereof include polyethylene, ionomer, polyacrylic acid, ethylene vinyl acetate copolymer, and modified products thereof.

1.2.3. Laminate Mode A general method can be used as the laminate mode in this step. Examples of such a method include a method of sandwiching a recording medium on which an image is recorded with a laminating sheet and press-bonding such a laminate with a press or a roller. At this time, if the adhesion layer contains an adhesive and the second particles in the ink composition are already cured (polymerized) before the laminating step, it is necessary to perform heating, radiation irradiation, or the like. There is no.

  On the other hand, even when the adhesion layer contains an adhesive, when the second particles in the ink composition are uncured (unpolymerized), in this step, heating or irradiation with radiation is performed. On the other hand, when the adhesion layer includes a thermoplastic resin, the laminating step is performed by heating, but the second particles may be cured using the heat at this time. Furthermore, when the adhesion layer contains a thermoplastic resin and the second particles in the ink composition are uncured, the irradiation may be performed by irradiating with radiation in addition to heating.

  When heating is performed in the laminating step, the temperature achieved by heating is preferably 40 ° C. or higher and 200 ° C. or lower. Moreover, when performing irradiation of a radiation in a lamination process, this radiation can be irradiated through a sheet | seat, for example.

1.3. Curing of Second Particles In the method for forming a laminate according to the present embodiment, the second particles may be any one between the time when the ink composition is attached to the recording medium in the image forming process and the time when the laminating process is completed. Polymerization (curing) may be performed at the time. As described above, the polymerization of the second particles may be performed in the image forming process or may be performed in the laminating process.

  Thereby, a structure in which the polymer of the second particles covers the periphery of the first particles is formed. Therefore, according to the laminate forming method of the present embodiment, it is possible to make it difficult for, for example, a substance derived from the laminating sheet to enter the voids of the first particles in the formed laminate. Therefore, according to the method for forming a laminate of this embodiment, it is possible to form a laminate that is unlikely to cause image discoloration. Furthermore, in the method for forming a laminate according to the present embodiment, when the laminating step is performed by heating, the second particles can be polymerized (cured) by the heating, so that the image discoloration can be performed with fewer steps. It is possible to form a laminate that is less likely to cause the occurrence of the problem.

2. Laminate As described above, the laminate formed by the method for forming a laminate of the present embodiment includes a recording medium, an image layer formed on the recording medium and including a polymer and first particles, and at least an image layer. And a sheet formed to cover the sheet. 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. The polymer refers to a polymer formed by polymerizing the second particles.

  Moreover, if the average particle diameter d50 of the first particles is 0.4 μm or more and 0.8 μm or less, the color change of the image layer can be further suppressed.

  When the first particles 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 Japanese Industrial Standard (JIS) Z8715: 1999 “Color Expression Method. It can be quantified by an index (for example, whiteness index) described in “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 3.1.1. First Particle As the first particle, a commercially available product “SX8782 (D)” (manufactured by JSR Corporation) described in Table 1 was 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 the solid content concentration is 20.5%. The thermal decomposition temperature of “SX8782 (D)” is 300 ° C. to 330 ° C.

3.1.2. Second particles The following three types were prepared as the second particles. Moreover, the following two types of particles having no polymerizable functional group on the surface were prepared as comparison objects of the second particles.

(Second particle 1)
A reaction solution equipped with a stirrer, a reflux condenser, a dropping device, and a thermometer was charged with 900 g of ion-exchanged water and heated to 70 ° C. while purging with nitrogen under stirring. Maintain the internal temperature at 70 ° C, add 2 g of potassium persulfate as a polymerization initiator, dissolve and dissolve in advance 70 g of ion-exchanged water, 1.0 g of sodium lauryl sulfate, 53 g of styrene, 59 g of butyl acrylate, 48 g of glycidyl methacrylate, and molecular weight adjustment An emulsion prepared by adding 0.16 g of t-dodecyl mercaptan under stirring as an agent was continuously dropped into the reaction vessel over 1 hour. After completion of the dropwise addition, aging was performed for 1 hour. Subsequently, an emulsion prepared in advance by adding 70 g of ion-exchanged water, 1.0 g of sodium ralyl sulfate, 1 g of acrylamide, 79 g of styrene, 80 g of butyl acrylate, and 0.16 g of t-dodecyl mercaptan was added to the reaction vessel. It was dripped continuously over 1 hour. After completion of the dropwise addition, aging was performed for 1 hour. Subsequently, an aqueous solution in which 2 g of ammonium persulfate was dissolved in 20 g of ion exchange water as a polymerization initiator was added to the reaction vessel, and 300 g of ion exchange water, 2 g of sodium lauryl sulfate, 16 g of acrylamide, 298 g of styrene, 297 g of butyl acrylate, An emulsion prepared by adding 29 g of acid and 0.65 g of t-dodecyl mercaptan under stirring was continuously dropped into the reaction vessel over 3 hours. After completion of the dropwise addition, aging was performed for 3 hours. The obtained emulsion was cooled to room temperature, and then ion-exchanged water and ammonia water were added to adjust the solid content to 40% by weight and pH 8. The obtained emulsion, as the second particles, had resin cores having a core-shell structure, and exhibited properties of a surface tension of 57 × 10 ⁻³ N / m and a contact angle of 90 °. The particle size d50 of the second particles in this emulsion was 0.09 μm.

(Second particle 2)
As the second particles, a commercially available urethane oligomer, U-15HA (manufactured by Shin-Nakamura Chemical Co., Ltd.) was prepared.

(Second particle 3)
A dendritic polymer was prepared as the second particle. The dendritic polymer was placed in a 1 L four-necked flask with 20 g of pentaerythritol tetra (mercaptoacetate) (mercapto group 0.19 mol), 212 g of a mixture of dipentaerythritol hexaacrylate and dipentaerythritol pentaacrylate (carbon- Carbon double bond 2.12 mol), hydroquinone 0.1 g, and benzyldimethylamine 0.01 g were added and reacted at 60 ° C. for 12 hours. With respect to the obtained dendritic polymer, disappearance of mercapto groups was confirmed by iodometry. According to gel filtration chromatography, the molecular weight of the resulting dendritic polymer was 11000.

(Particle 1)
In a flask equipped with a stirrer, thermometer, reflux condenser, and dropping funnel, 0.5 part by weight of potassium persulfate and 80 parts by weight of pure water were added and dissolved, and the internal temperature was heated to 70 ° C. while stirring. . On the other hand, the following components were mixed and stirred to prepare an emulsion. This emulsion was gradually dropped into the flask using a dropping funnel over 3 hours to carry out emulsion polymerization. Ammonia was added to the obtained emulsion to adjust to pH 8, and an emulsion having a solid content of 40% by weight, an average particle diameter of 0.15 μm, a surface tension of 67 mN / m, and a contact angle of 88 ° was obtained. In addition, the polymerizable functional group was not introduce | transduced into the said particle | grains, and this was made into particle | grains 1.

(Particle 2)
First, 120 g of glycidyl methacrylate, 80 g of methyl methacrylate, and 300 g of propylene glycol monomethyl ether acetate are put into a 1 L four-necked flask, and 8 g of azobisisobutyronitrile (AlBN) is added as a polymerization initiator at 80 ° C. Polymerization was carried out for 6 hours. Subsequently, 61 g of acrylic acid and 1 g of triphenylphosphine were added and reacted at 120 ° C. for 24 hours. The acid value of the obtained solution was measured and found to be 0, confirming that the reaction was complete. The molecular weight of the polymer particles thus obtained was 15000. The particle 2 is a particle that does not have a polymerizable functional group.

3.1.3. Preparation of ink composition The first particles, the second particles 1 to 3, the particles 1 and 2, the polyhydric alcohol, the hydrophilic substance, the pH adjuster, the surfactant, and the ion exchange water described above are mixed and stirred to obtain a pore size. The ink compositions of Examples 1 to 8 and Comparative Examples 1 to 6 were obtained by filtration with a 5 μm metal filter and deaeration treatment using a vacuum pump. In addition, the unit of the numerical value described in Examples 1-8 of Table 1 and Comparative Examples 1-6 is mass%, and about particle | grains etc., all were described in conversion of solid content.

  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 resin, a styrene acrylic acid copolymer “UF-5022” (manufactured by Toa Gosei Co., Ltd., an anionic styrene acrylic resin) was used.

  As the surfactant, “BYK-348” (manufactured by Big Chemie Japan Co., Ltd.) (polysiloxane surfactant) was used.

  As a thermal polymerization initiator, Almatex H700 (obtained from Mitsui Chemicals) was used.

  Irgacure 819DW (available from Ciba Specialty Chemicals) was used as a photopolymerization initiator.

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

3.2. Laminating Sheet The laminating sheet was obtained from Prime Polymer Co., Ltd., a type containing low-density polyethylene in the adhesion layer, and used as a trade name “Ultzex”. The Tg of the low density polyethylene is −125 ° C.

3.3. Evaluation method 3.3.1. Preparation of Laminate First, the ink composition of each example described in Table 1 was filled in a black ink chamber 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 between sheets for laminating, and a laminate was formed by a model L-1-5 laminating apparatus manufactured by Eiwa Kako Co., Ltd. The laminating device comes with a temperature-adjustable heating device. The UV irradiation device uses a xenon lamp as the light source, and the optical fiber contains UV light just before the recording medium and the laminate sheet are joined together. It was installed so that it was irradiated.

  In each example and each comparative example, the set temperature was entered for those that were heated, and ● was entered for those that were irradiated with light.

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 radiation 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 Table 1. 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 was 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 formed using the ink composition containing the first particle having a hollow structure and the second particle having a polymerizable functional group on the surface hardly causes image transparency. On the other hand, the laminate of the comparative example formed using the ink composition containing the first particles having a hollow structure and the second particles having no polymerizable functional group on the surface easily causes image transparency. It has been found.

  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 (7)

  At least the image of the recording medium is formed on a recording medium including an image formed using an ink composition including first particles having a hollow structure and second particles having a polymerizable functional group on the surface. A method for forming a laminate in which a sheet is closely attached to a raised portion. In claim 1,
The ink composition includes a thermal polymerization initiator,
The method for forming a laminate, wherein the polymerizable functional group reacts with heat applied in the step of bringing the sheet into close contact. In claim 2,
The method for forming a laminate, wherein the step of bringing the sheet into close contact is performed at 40 ° C. or higher and 200 ° C. or lower. In any one of Claims 1 to 3,
The ink composition includes a radiation polymerization initiator,
The method for forming a laminate, wherein the polymerizable functional group reacts with radiation applied in the step of bringing the sheet into close contact. In any one of Claims 1 thru | or 4,
The average particle diameter d50 of the first particles is 0.4 μm or more and 0.8 μm or less. A recording medium;
An image layer formed on the recording medium and comprising a polymer and first particles;
A sheet formed to cover at least the image layer;
A laminate comprising: In claim 6,
The laminate has an average particle diameter d50 of 0.4 to 0.8 μm.