JP2008223188A - Composition for coating, and coated article - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composition for coating, exhibiting an iridescent color on the formed coated layer even on heat-treating, and to provide a coated article equipped with a coated layer consisting of such the coating composition. <P>SOLUTION: This coating composition comprises a pigment and a binder, wherein the pigment contains ≥60 mass% organic pigment, and the organic pigment is constituted by polymer particles consisting of a polymer composition containing ≥2 mass% cross-linkable radical polymerizable monomer, and the polymer particles have 150-5,000 nm number-average particle diameter. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a coating composition and a coated body, and more specifically, by applying to the surface of a body to be coated, an iris color develops even when the formed coating layer is heat-treated. For coating to form a coating layer with excellent printability, such as whiteness, pen-writing ability, offset printing suitability, and electrophotographic suitability when coated on a coated substrate such as coated paper The present invention relates to a composition and a coated body provided with a coating layer comprising such a coating composition.

  Conventionally, in order to give glossiness and a high-class feeling to a coated body such as a coated base paper, an accumulation layer in which uniform fine particles expressing an iris color are regularly arranged is formed on the coated body. ing. For example, as a composition for forming such a coating layer, an acrylic organic polymer or a styrene organic polymer is used (see, for example, Patent Documents 1 and 2). Further, Patent Document 1 discloses that an organic polymer is dried at 80 ° C. or lower to form an accumulation layer to develop an iris color. Patent Document 2 also describes the use of a bifunctional crosslinking monomer in order to maintain polymerization stability when producing uniform fine particles.

JP 2004-269922 A JP 2001-239661 A

  However, when an organic polymer as in Patent Documents 1 and 2 is used, the coating layer is dried at a high temperature, or in a process where high-temperature heat is applied, such as a heat roll part of electrophotographic printing or a high-temperature lamination process. When a temperature higher than the Tg of the organic polymer is applied, polymer particles are formed, and the whiteness and opacity are impaired, and the ordered arrangement structure of the polymer particles in the coating layer is impaired and the iris color disappears. End up. In addition, when characters are written with a pencil or ballpoint pen on the coating layer formed on the surface of the object to be coated, there is a problem that the pen writing aptitude such as readability, color developability and ease of writing is very poor. It was. Or, when used as printing paper, there are problems such as poor printability such as offset printability and electrophotographic suitability.

  Further, the conventional materials have drawbacks such that the angle at which the iris color of the coating layer appears (viewing angle) is narrow, the angle at which the iris color appears is limited, and the gloss is low. Depending on the viewing angle, it becomes a glossy coated body with a high gloss or a matte coated body with a low gloss. When used as paper, it has been desired to develop a composition having aptitude for offset printing and electrophotography.

  The present invention has been made in view of the above-mentioned problems of the prior art, and by applying a coating composition to the surface of an object to be coated, a rainbow is formed even if the coating layer to be formed is heat-treated. Coloration and whiteness are expressed, and for example, high gloss (glossy tone) and low gloss (matte tone) can be expressed without changing the calendar processing, and further, the viewing angle can be expressed. It is possible to express both glosses by changing the whiteness and pen writing suitability when applied to a substrate such as coated paper, or offset printing suitability when used as printing paper. The present invention provides a coating composition for forming a coating layer excellent in printability such as suitability for electrophotography and electrophotography, and a coating body provided with a coating layer comprising such a coating composition.

  An organic pigment that develops an iris color with a Tg (glass transition temperature) of 105 ° C. or less does not develop an iris color when particles are formed unless the coating layer is dried at 100 ° C. or less. Further, when the drying temperature is low, the coating speed must be suppressed, resulting in poor productivity.

  In addition, when electrophotographic printing is performed on the coated body after the coating layer is formed or high temperature laminating is performed (around 150 ° C.), high temperature processing (150 to 200 ° C.) is performed with a heat roll for toner fixation in electrophotographic printing. Therefore, particles are welded to each other by heat in the coating layer of the formed coating body, and the iris color and whiteness are lost.

  In order to solve the above-mentioned problems, the present invention provides the following coating composition and a coated body comprising a coating layer comprising such a coating composition.

[1] A coating composition comprising a pigment and a binder, wherein the pigment contains an organic pigment in an amount of 60% by mass or more, and the organic pigment has a structural unit derived from a crosslinkable radical polymerizable monomer. A coating composition comprising polymer particles comprising a polymer composition containing 2% by mass or more, wherein the number average particle diameter of the polymer particles is 150 to 5000 nm.

[2] The coating composition according to [1], wherein the organic pigment contains a hollow organic pigment having a hollowness of 15% by volume or more.

[3] The coating composition according to [2], wherein the organic pigment includes two or more hollow organic pigments having different number average particle diameters.

[4] The coating composition according to any one of the above [1] to [3], wherein the organic pigment contains a dense organic pigment.

[5] The coating composition according to [4], wherein the organic pigment contains two or more dense organic pigments having different number average particle diameters.

[6] The coating according to any one of [1] to [5], wherein the polymer particles constituting the organic pigment are solid and / or hollow polymer particles having a number average particle diameter of 150 to 700 nm. Composition.

[7] The coating composition according to any one of [1] to [5], wherein the polymer particles constituting the organic pigment are hollow polymer particles having a number average particle diameter of more than 700 nm and not more than 5000 nm. object.

[8] A coating provided with an object to be coated and a coating layer made of the composition for coating according to any one of [1] to [7] formed on the surface of the object to be coated. Engineering body.

[9] The coated body according to [8], wherein the coated body exhibits a black color.

[10] The coated body according to the above [8] or [9], wherein the coated body is a coated base paper or a film.

[11] The coated body according to any one of [8] to [10], wherein the coating amount of the coating layer is 0.5 to 30 g / m ² per one surface of the coated body.

[12] The coated body according to any one of [8] to [11], wherein the coating layer is laminated.

  The coating composition of the present invention is expressed without damaging the iris color and whiteness even when the coating layer formed by coating on the surface of the coated body is heat-treated, and has high gloss. In addition to being expressed, a coating layer having excellent whiteness and pen writing suitability can be formed when coated on a coated body such as a coated base paper. Further, the coated body of the present invention is provided with a coating layer comprising such a coating composition, exhibits an iris color at a wide angle or a desired angle, and has whiteness and pen writing suitability. And printing aptitude such as offset printing aptitude and electrophotographic aptitude. In addition, the coating composition of the present invention can exhibit, for example, a high gloss (glossy tone) and a low gloss (matte tone) by changing the viewing angle without calendering the coating layer. Furthermore, it is possible to express both glosses by changing the viewing angle.

  Hereinafter, the coating composition of the present invention and the coated body will be described based on specific embodiments, but the present invention is not limited to the following embodiments and departs from the spirit of the present invention. It should be understood that modifications and improvements to the following embodiments are also included in the scope of the present invention based on ordinary knowledge of those skilled in the art without departing from the scope.

[1] Coating composition:
The coating composition of the present embodiment is a coating composition containing a pigment and a binder, and the pigment contains 60% by mass or more of an organic pigment, and the organic pigment is crosslinkable. It includes polymer particles composed of a polymer containing 2% by mass or more of a structural unit derived from a polymerizable monomer, and the polymer particles have a number average particle diameter of 150 to 5000 nm.

  Such a coating composition can be expressed without damaging the iris color and whiteness even when the coating layer to be formed is heat-treated, and exhibits high gloss, and is coated on a coated base paper or the like. When applied to the body, a coating layer having excellent whiteness and pen writing suitability (for example, readability, color developability, ease of writing, etc.) can be formed. In addition, readability is the degree of readability and legibility of characters, sentences, symbols, etc. written on the coating layer with a pencil or ballpoint pen. In addition, the coating composition of the present embodiment can exhibit, for example, a high gloss (glossy tone) and a low gloss (matte tone) by changing the viewing angle without calendering the coating layer. Furthermore, it is possible to express both glosses by changing the viewing angle.

  In addition, the iris color in this specification means the hue change which arises when either of the wavelengths of visible light interferes. In the coating composition of the present embodiment, depending on the shape of the polymer particles constituting the organic pigment and / or the arrangement of these polymer particles, any of the wavelengths of visible light interferes to develop an iris color.

[1-1] Pigment:
The pigment used in the coating composition of the present embodiment preferably contains 60% by mass or more of an organic pigment. Further, the organic pigment includes polymer particles made of a polymer containing 2% by mass or more of a structural unit derived from a crosslinkable polymerizable monomer, and the number average particle diameter of the polymer particles is 150 to 5000 nm.

  When the content of such an organic pigment is less than 60% by mass, the amount of polymer particles contributing to interference with the wavelength of visible light is too small, and an iris color cannot be expressed in the formed coating layer. . In addition, it is preferable that content of such an organic pigment is 70 mass% or more, and it is still more preferable that it is 80 mass% or more. By comprising in this way, even if a coating layer is processed at high temperature, while being able to express an iris color satisfactorily, the coating layer excellent in whiteness and pen-writeability can be formed.

  Further, when the polymer particles constituting the organic pigment are composed of a polymer having a structural unit derived from a crosslinkable polymerizable monomer of less than 2% by mass, the polymer particles are deformed or deformed when the formed coating layer is treated at high temperature By forming a film, the coating layer becomes transparent so that iris color and whiteness cannot be expressed. Also, when coated on an object to be coated such as a coating base paper, the whiteness and pen Writability deteriorates remarkably.

  In addition, when the number average particle diameter of the polymer particles (particularly solid polymer particles) is less than 150 nm, the polymer particles are too small, so that interference of visible light wavelength by the polymer particles cannot be obtained, An iris color cannot be expressed in the coating layer. On the other hand, when the number average particle diameter of the polymer particles (particularly, hollow polymer particles) exceeds 5000 nm, the cost increases and further stable production is difficult.

  Examples of such organic pigments include hollow organic pigments and dense organic pigments. In this specification, the term “hollow” means a state in which a closed space (which can be observed with an electron microscope or the like, and in reality often contains gas or liquid) is present inside the polymer particles constituting the pigment. Say. On the other hand, “dense” is a concept with respect to the “hollow”, and refers to a state where the above-described closed space does not exist, that is, a state in which the inside is clogged.

  In addition, the “glass transition point (Tg)” in the present specification is a film prepared by heating and drying a latex containing polymer particles constituting an organic pigment at 130 ° C. for 30 minutes, and the glass transition point ( Tg) is a value measured using a differential scanning calorimeter (trade name “DSC-220C”, manufactured by Seiko Denshi Co., Ltd.) under conditions of a heating rate of 15 ° C./min.

  Further, the “number average particle diameter” in the present specification is a number average particle diameter measured by using a dynamic light scattering method. This measurement can be performed using, for example, a laser particle analyzer (trade name “Laser Particle Size Analysis System, LP-510 Model PAR-III”, manufactured by Otsuka Electronics Co., Ltd.).

  Moreover, the pigment used for the coating composition of this embodiment may contain a conventionally well-known inorganic pigment other than such an organic pigment.

  Here, the mechanism by which the coating layer obtained by coating the coating composition of the present embodiment on the surface of the coated body develops an iris color will be described. When the coating layer comprising the coating composition of the present embodiment expresses an iris color, two types of mechanisms are provided depending on the type and particle size of the polymer particles constituting the organic pigment in the coating composition. Conceivable.

  Specifically, when the polymer particles constituting the organic pigment form a regular three-dimensional accumulation structure, the mechanism that expresses the iris color according to the Bragg rule (hereinafter referred to as the “first iris color expression mechanism”) In the case of hollow polymer particles, the difference in refractive index between the outer shell (shell layer) of the hollow polymer particles and the inner air layer and the thickness of the outer shell contribute to the reflection of light. Two types of mechanisms are conceivable: a mechanism that causes a path difference to express an iris color (hereinafter, sometimes referred to as a “second iris color expression mechanism”).

  In the first iris color developing mechanism described above, the iris color appears well when the polymer particles whose number average particle diameter is about 1/2 of the wavelength of visible light form a regular three-dimensional integrated structure. To do. A preferred number average particle diameter of the polymer particles that express an iris color by such a first iris color expression mechanism is 150 to 700 nm. In this first iris color development mechanism, even an organic pigment composed of dense polymer particles (solid organic pigment), an organic pigment composed of hollow polymer particles (hollow organic pigment) Even in this case, an iris color is similarly developed, but a hollow organic pigment composed of hollow polymer particles is superior in a portion that is bulky, opaque, and excellent in whiteness.

  In the first iris color developing mechanism, for example, the degree of dispersion of the polymer particles having the number average particle diameter of 150 to 700 nm (hereinafter also referred to as “CV value (%)”) is 20% or less. Preferably, it is 15% or less. If the CV value exceeds 20%, the polymer particles in the coating layer are difficult to regularly arrange, and the intensity of the iris color may be reduced. The dispersity (CV value (%)) is a value obtained by dividing the standard deviation of polymer particles by the number average particle diameter (standard deviation / number average particle diameter) as a percentage.

  In this first iris color development mechanism, the number average particle size of the binder and other pigments (for example, inorganic pigments) contained in the coating composition is the number of polymer particles constituting the organic pigment. The average particle size is preferably ½ or less, more preferably １ ／ or less, and particularly preferably ¼ or less. When the number average particle diameter of the binder or other pigment (inorganic pigment) exceeds the above range, the three-dimensional accumulation structure of the polymer particles in the coating layer may be disturbed, and the intensity of the iris color may be reduced. .

  On the other hand, the second iris color expression mechanism is different from the first iris color expression mechanism described above, and is an expression mechanism specific to only an organic pigment composed of hollow polymer particles. In particular, the number average particle diameter is 700 nm. When using an organic pigment composed of an excess of hollow polymer particles (particularly, a hollow polymer particle having a number average particle diameter of more than 700 nm and not more than 5000 nm), an iris color is developed well. In this second iris color development mechanism, even if the polymer particles do not form a regular three-dimensional integrated structure as in the first iris color development mechanism described above, individual polymer particles can reflect light. An iris color can be expressed by causing a path difference.

[1-1a] A hollow organic pigment composed of polymer particles having a number average particle diameter of more than 700 nm and not more than 5000 nm:
As described above, the hollow organic pigment is an organic pigment in which a closed space exists inside the polymer particles constituting the organic pigment. As shown in FIG. 1, such a hollow organic pigment has an outer surface of the hollow polymer particle 2 when light (incident light 4 a and 4 b) is incident on the hollow polymer particle 2 constituting the hollow organic pigment 1. The reflected light 5a reflected on the surface forming the shell interferes with the reflected light 5b reflected on the inner surface forming the closed space 3 inside the polymer particle 2, whereby an iris color can be expressed. That is, the second iris color expression mechanism described above. Here, FIG. 1 is an explanatory view schematically illustrating an example of a light reflection state when light is incident on polymer particles constituting the hollow organic pigment.

  When such a hollow organic pigment is used, particularly when the coating layer is viewed at an angle of 75 ° or more (when the oblique angle of view is 75 ° or more), an iris color is produced with extremely strong interference light. Can be expressed. Further, when the coating layer is viewed at an angle of less than 75 °, the whiteness and pen writing ability are particularly excellent. In addition, when the coating layer is viewed perpendicularly to the surface of the coating layer, the visual oblique angle is 0 °.

  In the coating composition of this embodiment, as such a hollow organic pigment, a hollow organic pigment having a hollow ratio of 15% by volume or more can be suitably used, and a hollow organic pigment having a hollow ratio of 20% by volume or more can be used. Can be more suitably used. The number average particle diameter of the organic pigment is 150 to 5000 nm, but the hollow ratio of the hollow organic pigment composed of polymer particles particularly exceeding 700 nm (specifically, exceeding 700 nm and not more than 5000 nm) is 15% by volume or more. 1, as shown in FIG. 1, the optical path difference A when the incident lights 4 a and 4 b are reflected by the surface and the inner surface forming the outer shell of the polymer particle 2 is the wavelength of the incident lights 4 a and 4 b ( 400 to 700 nm), and interference of reflected light is favorably performed. The hollow organic pigment exceeding 700 nm is preferably 700 nm to 5000 nm, and more preferably 700 nm to 4000 nm. In addition, a hollow rate is a ratio (volume%) of the volume of the part (hollow part) which becomes hollow after drying with respect to the whole volume of a hollow organic pigment particle.

  In addition, it is preferable that the refractive index of the polymer particle which comprises this hollow organic pigment is 1.4 or more. By comprising in this way, interference of reflected light comes to be favorably performed by refraction caused by the outer shell of the polymer particles constituting the hollow organic pigment, and an iris color can be expressed more clearly.

  Moreover, the organic pigment used for the coating composition of this embodiment may contain 2 or more types of above-mentioned hollow organic pigments from which a number average particle diameter differs. For example, conventionally used inorganic pearl pigments, etc., exhibited an iris color due to interference of reflected light caused by Bragg reflection of the particle crystals constituting the pigment, so that the particles constituting the pigment do not have a uniform particle size. However, by using such a hollow organic pigment, even if it contains two or more types of hollow organic pigments having different number average particle diameters, an iris color can be favorably expressed.

[1-1a-1] Production of hollow organic pigment:
The hollow organic pigment used in the coating composition of the present embodiment can be produced, for example, as follows. In addition, it is also possible to manufacture the hollow organic pigment comprised from the polymer particle whose number average particle diameter is 700 nm or less by the following manufacturing methods.

  First, 5-80 mass% of unsaturated carboxylic acid (a-1), and 0-95 mass% of non-crosslinkable radically polymerizable monomer (a-2) copolymerizable with this unsaturated carboxylic acid (a-1). And the first polymerizable monomer (a) comprising the crosslinkable radically polymerizable monomer (a-3) 0 to 20 (where (a-1) + (a-2) + (a-3) = 100 mass%) Is emulsion-polymerized to obtain the first polymer particles (I).

  Next, in the presence of 2 to 1000 parts by mass of the obtained first polymer particles (I), 0 to 20% by mass of the unsaturated carboxylic acid (b-1) and the unsaturated carboxylic acid (b-1) Copolymerizable non-crosslinkable radical polymerizable monomer (b-2) 0 to 98% by mass and crosslinkable radical polymerizable monomer (b-3) 2 to 100% by mass (provided that (b-1) + (b− 2) + (b-3) = 100% by mass) second polymerizable monomer (b) 100 parts by mass is subjected to emulsion polymerization, and the surface layer of the first polymer particles (I) is converted to the second polymerizable monomer (b). The core-shell polymer particles (II) coated with the shell layer containing the second polymer derived from the above and the unreacted second polymerizable monomer (b) are obtained.

  Next, the pH of the obtained dispersion of the core-shell polymer particles (II) is adjusted to 7 or more with a volatile base, for example, and the core-shell polymer particles (II) are neutralized and swollen. The second polymerizable monomer (b) in the reaction is polymerized to produce a hollow organic pigment composed of hollow polymer particles (III). By comprising in this way, the hollow organic pigment which consists of hollow polymer particle (III) with a uniform particle diameter and high hollow ratio can be manufactured simply.

[1-1a-2] Preparation of first polymer particle (I):
The first polymer particles (I) described above are composed of 5 to 80% by mass of the unsaturated carboxylic acid (a-1) and other non-crosslinkable radical polymerizable compounds copolymerizable with the unsaturated carboxylic acid (a-1). 0 to 95% by mass of monomer (a-2) and 0 to 20% by mass of crosslinkable radical polymerizable monomer (a-3) (provided that (a-1) + (a-2) + (a-3) = 100 The first polymerizable monomer (a) comprising (mass%) can be obtained by emulsion polymerization.

  Examples of the unsaturated carboxylic acid (a-1) (hereinafter sometimes referred to as “monomer (a-1)”) include, for example, (meth) acrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid and the like. Or the dicarboxylic acid and the acid anhydride of the said dicarboxylic acid can be mentioned. Of these, (meth) acrylic acid and itaconic acid are preferred from the viewpoint of particle stability, and methacrylic acid is more preferred. These can be used individually by 1 type or in combination of 2 or more types.

  Examples of the non-crosslinkable radical polymerizable monomer (a-2) (hereinafter sometimes referred to as “monomer (a-2)”) include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, and propyl (meth) acrylate. , Unsaturated carboxylic acid esters such as butyl (meth) acrylate and 2-ethylhexyl (meth) acrylate, aromatic monomers such as styrene and α-methylstyrene, (meth) acrylonitrile, vinyl acetate, N, N-dimethyl (meth) Examples include acrylamide. Especially, unsaturated carboxylic acid ester is preferable and it is preferable that 50 mass% or more of monomer (a-2) is unsaturated carboxylic acid ester especially. If the unsaturated carboxylic acid ester is less than 50% by mass of the monomer (a-2), the hollow polymer particles (III) as the final target product may be distorted and the hollowness ratio may not be increased.

  As the crosslinkable radical polymerizable monomer (a-3) (hereinafter sometimes referred to as “monomer (a-3)”), a crosslinkable polymerizable monomer such as divinylbenzene or ethylene glycol di (meth) acrylate is used. The preferable compounding quantity is 0-20 mass% of the sum total of a 1st polymerizable monomer (a), More preferably, it is 0-5 mass%. When the ratio of the crosslinkable monomer is more than 20% by mass of the monomer (a), the swelling with the volatile base becomes insufficient, the hollowness becomes low, and the properties such as whiteness and gloss are insufficient, which is preferable. Absent.

  The method for emulsion polymerization of the first polymerizable monomer (a) in an aqueous medium is not particularly limited. For example, the first polymerizable monomer (a) may be added and polymerized at once, or continuously. However, the latter is preferable in order to obtain particles having a uniform particle size with good stability. The first polymer particles (I) may be prepared by one-stage polymerization or by two-stage or more multi-stage polymerization. Furthermore, the first polymerizable monomer (a) may be subjected to seed emulsion polymerization in the presence of seed particles. In particular, the seed particles may have a SP value (solubility parameter) close to that of the first polymerizable monomer (a). This is preferable in order to obtain particles having a uniform particle size with good stability. Examples of the emulsifier include an anionic surfactant, a nonionic surfactant, a cationic surfactant, an amphoteric surfactant, and an organic suspension protective agent. And anionic surfactants, nonionic surfactants, and organic suspension protecting agents are preferred. These emulsifiers can be used alone or in combination of two or more.

  Examples of the anionic surfactant include rosin salts such as potassium rosinate and sodium rosinate, sodium oleate, potassium laurate, sodium laurate, sodium laurate, sodium stearate, potassium stearate, and the like. Examples thereof include salts, sulfate esters of aliphatic alcohols such as sodium lauryl sulfate, and alkylaryl sulfonic acids such as sodium dodecylbenzene sulfonate.

  Examples of nonionic surfactants include polyethylene glycol alkyl esters, alkyl ethers, alkylphenyl ethers, and the like.

  Examples of the organic suspension protective agent include hydrophilic synthetic polymer materials such as polyacrylic acid, polymethacrylic acid, polyvinyl sulfonic acid, polyvinyl alcohol, polyvinyl pyrrolidone and polyethylene glycol, natural hydrophilic high substances such as gelatin and water-soluble starch. Examples thereof include molecular substances and hydrophilic semi-synthetic polymer substances such as carboxymethyl cellulose.

  Examples of the polymerization initiator include organic hydroperoxides represented by cumene hydroperoxide, diisopropylbenzene hydroperoxide, paramentane hydroperoxide, t-butyl hydroperoxide and the like, sugar-containing pyrophosphate prescription, sulfoxy Rate formulation, sugar-containing pyrophosphate formulation / sulfoxylate formulation mixed system formulation, redox initiator in combination with a reducing agent represented by formaldehyde resin formulation, persulfate such as potassium persulfate, ammonium persulfate, Azobisisobutyronitrile, benzoyl peroxide, lauroyl peroxide, etc. can be mentioned. Among them, persulfates such as potassium persulfate and ammonium persulfate in terms of particle stability and particle size uniformity, azobis Isobutyronitrile, Benzoyl peroxide are preferred. Moreover, a reducing agent can also be used in combination as needed.

  The polymerization temperature is preferably 5 to 95 ° C, more preferably 50 to 90 ° C. When the temperature is lower than 5 ° C., the reactivity of the unsaturated carboxylic acid is low and the particles may become unstable, and when the temperature exceeds 95 ° C., the particles may become unstable.

  The 1st polymer particle (I) obtained by the above turns into an alkali-swellable core particle, As a particle diameter of 1st polymer particle (I), Preferably it is 0.1-3 micrometers, More preferably Is 0.2-2 μm.

[1-1a-3] Preparation of core-shell polymer particles (II):
In the presence of 2 to 1000 parts by mass of the obtained first polymer particle (I), the core-shell polymer particle (II) is an unsaturated carboxylic acid (b-1) 0 to 20% by mass, and the unsaturated carboxylic acid 0 to 98% by mass of other radical polymerizable monomer (b-2) copolymerizable with acid (b-1) and 2 to 100% by mass of crosslinkable radical polymerizable monomer (b-3) (provided that (b -1) + (b-2) + (b-3) = 100% by mass) The second polymerizable monomer (b) (100 parts by mass) is subjected to emulsion polymerization, and the surface layer of the first polymer particles (I) is It can be obtained by coating with a shell layer containing the second polymer derived from the bipolymerizable monomer (b) and the unreacted second polymerizable monomer (b).

  The unsaturated carboxylic acid (b-1) (hereinafter sometimes referred to as “monomer (b-1)”) is the same as the unsaturated carboxylic acid shown as an example of the monomer (a-1) described above. Among them, (meth) acrylic acid, itaconic acid and the like are preferable from the viewpoint of particle stability.

  Examples of the radical polymerizable monomer (b-2) (hereinafter sometimes referred to as “monomer (b-2)”) include monoethylenic aromatic compounds such as styrene and α-methylstyrene, and methyl (meth) acrylate. , Ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate and other unsaturated carboxylic acid esters, (meth) acrylonitrile, vinyl acetate, N, Non-crosslinkable radically polymerizable monomers such as N-dimethyl (meth) acrylamide can be used.

  Examples of the crosslinkable radical polymerizable monomer (b-3) (hereinafter sometimes referred to as “monomer (b-3)”) include divinylbenzene, trivinylbenzene, allyl glycidyl ether, glycidyl (meth) acrylate, and ethylene. Glycol dimethacrylate or the like is preferably used, and divinylbenzene is more preferable. The addition of the crosslinkable radically polymerizable monomer (b-3) makes it possible to swell and decompose the shape of the hollow polymer particles (III) constituting the finally obtained hollow organic pigment by heat, mechanical stress, solvent or chemicals. It is preferable to hold it against the like.

[1-1a-4] Preparation of hollow polymer particles (III):
The hollow polymer particles (III) are neutralized and swollen by adjusting the pH of the dispersion of the core-shell polymer particles (II) prepared in the previous step to 7 or more with a volatile base such as ammonia or amine. The second polymerizable monomer (b) that has been unreacted and the second polymerizable monomer (b) that has been newly added can be obtained by polymerization.

  Moreover, it is preferable that after the core-shell polymer particles are once neutralized and swollen with a volatile base, (b-1), (b-2), and (b-3) are further added and polymerized. The preferred range is 0 to 10% by weight of unsaturated carboxylic acid (b-1) and other non-crosslinkable radically polymerizable monomer (b-2) copolymerizable with this unsaturated carboxylic acid (b-1). ) 0-70% by mass, and crosslinkable radical polymerizable monomer (b-3) 0-70% by mass (provided that (b-1) + (b-2) + (b-3) = 70% by mass) or less The second polymerizable monomer (b) consisting of can be obtained by emulsion polymerization. When the total amount of the second polymerizable monomer (b) after the core-shell polymer particles are once neutralized and swollen with a volatile base is more than 70% by mass (the total amount of the monomer b before being neutralized and swollen is 30% by mass) If it is less than the above, the hollow polymer particles (III) as the final target will be distorted or cracked, resulting in insufficient properties such as whiteness and gloss.

  Since the volatile base can penetrate into the second polymer derived from the second polymerizable monomer (b), the addition of the volatile base neutralizes the first polymer particle (I) component. Accordingly, the first polymer particle (I) component significantly absorbs water, and the core-shell polymer particle (II) becomes hollow polymer particles (III) having pores therein. The produced hollow polymer particles (III) contain water in the pores inside the particles in the aqueous dispersion. By drying the water-containing particles, the water as the dispersion medium volatilizes and the water inside the particles also volatilizes and becomes hollow.

  In addition, in the composition for coating of this embodiment, it can be used even in the state containing an aqueous medium inside the hollow polymer particles (III) as described above. When such a hollow polymer particle (III) is used, when the coating composition is applied to an object to be coated and the coated coating composition is dried, Water volatilizes and becomes hollow.

  The hollow particle production method described above is based on a swelling method using a volatile base. However, as another hollow particle production method, for example, a production method based on volume swelling utilizing polymerization shrinkage may be used (Patent Document). 1786888).

[1-1b] Dense organic pigment and hollow organic pigment composed of polymer particles having a number average particle size of 150 to 700 nm:
The dense organic pigment and the hollow organic pigment composed of polymer particles having a particle diameter of 150 to 700 nm can form an iris color according to the Bragg rule by forming a regular three-dimensional integrated structure. That is, it is the first iris color expression mechanism described above.

  The dense organic pigment is an organic pigment in which the inside of the polymer particle is clogged (solid), and the hollow organic pigment is an organic pigment in which a closed space exists inside the polymer particle constituting the organic pigment. . The number average particle size of the organic pigment used in the coating composition of the present embodiment is 150 to 5000 nm, but the number average particle size of the polymer particles constituting the solid organic pigment and the hollow organic pigment is 150 to 700 nm. 2, as shown in FIG. 2, in the polymer particles 12 constituting the organic pigment (in FIG. 2, the case of the dense organic pigment 11), the incident side of the polymer particles 12 on which the incident light 14 enters. The distance between the surface and the exit-side surface of the polymer particle 2, that is, the optical path difference B is about ½ of the wavelength of visible light (400 to 700 nm), and interference of reflected light is favorably performed. When such a solid organic pigment is used, the iris color can be expressed very well when viewed at an angle of 75 ° or less. In addition, even if the number average particle diameter of the polymer particles does not become about ½ of the wavelength of visible light (400 to 700 nm), a good iris color can be expressed in the dark field. Here, FIG. 2 is an explanatory view schematically showing an example of a reflection state of light when light is incident on polymer particles constituting the dense organic pigment. In addition, the code | symbol 15a has shown the reflected light reflected on the incident side surface of the polymer particle, and the code | symbol 15b has shown the reflected light reflected on the output side surface of the polymer particle.

  In addition, for example, in the hollow organic pigment, when the average particle diameter is reduced, the hollow portion of the polymer particle is reduced, so that the iris color is developed by the same mechanism as that of the dense organic pigment as shown in FIG. Specifically, for example, a hollow organic pigment composed of hollow polymer particles having a number average particle diameter of 150 to 700 nm can develop an iris color by the first iris color development mechanism.

  Moreover, it is preferable that the refractive index of the polymer particle which comprises such a solid organic pigment and a hollow organic pigment is 1.4 or more. By configuring in this way, interference of reflected light is further improved.

  Moreover, the organic pigment used for the coating composition of this embodiment may contain a 2 or more types of solid organic pigment and / or hollow organic pigment from which a number average particle diameter differs. In the coating composition of this embodiment, even if it contains two or more kinds of dense organic pigments and / or hollow organic pigments having different number average particle diameters as described above, an iris color can be expressed. it can.

  In the coating composition of the present embodiment, the organic pigment may contain two or more kinds of dense organic pigments, or two or more kinds of hollow organic pigments, or a hollow organic pigment. And a dense organic pigment.

[1-1b-1] Production of dense organic pigment:
The dense organic pigment used in the coating composition of the present embodiment can be produced, for example, by the following method.

  In addition, as a more specific structure of the polymer which comprises a dense organic pigment, structural unit 0-98 mass% derived from (a) aromatic vinyl monomer ((a ') monomer), ( b) Structural unit 0-60 mass% derived from aliphatic conjugated diene monomer ((b ′) monomer), (c) Derived from ethylenically unsaturated carboxylic acid monomer ((c ′) monomer) (D) vinyl cyanide monomer ((d ′) monomer) 0 to 60 mass%, (e) crosslinkable polymerizable monomer ((e ′) monomer) Body) 2 to 100% by mass and (f) a structural unit derived from another monomer (((f ′) monomer)) copolymerizable with these (a ′) to (e ′) monomers. A dense organic pigment containing 0 to 98% by mass (however, (a) + (b) + (c) + (d) + (e) + (f) = 100% by mass) Can do.

  Further, the structural unit of (e) the crosslinkable polymerizable monomer is preferably 5 to 100% by mass, and more preferably 10 to 100% by mass. (E) When the structural unit of the crosslinkable polymerizable monomer is less than 2% by mass, the degree of crosslinking of the polymer particles becomes low, and the particles are deformed when heat exceeding Tg of the polymer constituting the dense organic pigment is applied. In other words, the iris color and whiteness are not expressed because of film formation. Examples of the crosslinkable polymerizable monomer (e ′) include divinylbenzene, trivinylbenzene, allyl glycidyl ether, glycidyl (meth) acrylate, and ethylene glycol dimethacrylate. Among these, divinylbenzene is preferable. . These crosslinkable polymerizable monomers can be used singly or in combination of two or more.

  Examples of the ethylenically unsaturated carboxylic acid monomer ((c ′) monomer) include acrylic acid, methacrylic acid, fumaric acid, maleic acid, and itaconic acid. These ethylenically unsaturated carboxylic acid monomers can be used singly or in combination of two or more. The structural unit derived from (c) an ethylenically unsaturated carboxylic acid monomer ((c ′) monomer) is more preferably contained in an amount of 0.5 to 20% by mass.

  Examples of the vinyl cyanide monomer ((d ′) monomer) include acrylonitrile and methacrylonitrile. These vinyl cyanide monomers can be used alone or in combination of two or more. The structural unit derived from this (d) vinyl cyanide monomer ((d ′) monomer) is an optional component, but it is more preferable to contain, for example, 0 to 30% by mass.

  Examples of other monomers copolymerizable with these monomers (a ′) to (e ′) ((f ′) monomer)) include methyl acrylate and methyl methacrylate. These other monomers ((e ′) monomer) can be used singly or in combination of two or more.

  In addition, the dense organic pigment having such a composition is prepared by adjusting the particle size of the monomer component containing a predetermined amount of the above-described monomers (a ′) to (f ′) according to the number of parts used of the emulsifier. It can obtain by carrying out emulsion polymerization using. Further, when obtaining such a dense organic pigment, it is preferable to obtain a dense organic pigment by, for example, adjusting the pH to 2 or more with a volatile base after emulsion polymerization of the above monomer components. . By comprising in this way, the polymer particle which has a uniform particle diameter and expresses an iris color favorably can be obtained.

  As the emulsifier, anionic surfactants, nonionic surfactants, amphoteric surfactants and the like can be used alone or in combination of two or more. Here, examples of the anionic surfactant include higher alcohol sulfates, alkylbenzene sulfonates, aliphatic sulfonates, and polyethylene glycol alkyl ether sulfates. Examples of nonionic surfactants include ordinary polyethylene glycol alkyl ester types, alkyl ether types, and alkyl phenyl ether types. Examples of amphoteric surfactants include those having a carboxylate, sulfate, sulfonate, and phosphate ester salt as the anion moiety, and an amine salt and quaternary ammonium salt as the cation moiety. Betaines such as lauryl betaine and stearyl betaine, amino acid types such as lauryl-β-alanine, stearyl-β-alanine, lauryl di (aminoethyl) glycine, octyldi (aminoethyl) glycine, and the like are used.

  Examples of the polymerization initiator include water-soluble polymerization initiators such as sodium persulfate, potassium persulfate, and ammonium persulfate, and oil-soluble polymerization initiators such as benzoyl peroxide, lauryl peroxide, and 2,2′-azobisisobutyronitrile. Redox polymerization initiators in combination with a reducing agent can be used alone or in combination of two or more.

  Further, known molecular weight regulators, chelating agents, inorganic electrolytes and the like can be used. Examples of molecular weight regulators include halogenated hydrocarbons such as chloroform and carbon tetrabromide, mercaptans such as n-hexyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, and thioglycolic acid, dimethylxanthogen Xanthogens such as disulfide and diisopropylxanthogen disulfide, terpinolene (trade name), α-methylstyrene dimer, 1,1-diphenylethylene and the like which can be used in usual emulsion polymerization can be used.

[1-1c] Other pigments:
As long as the pigment used for the coating composition of the present embodiment contains 60% by mass or more of the hollow organic pigment and the dense organic pigment described so far, a conventionally known inorganic pigment, It may contain other organic pigments not included in the range described so far. In addition, it is preferable that such other pigments are contained so as not to impair the effects of the present embodiment. Specifically, such other pigments are usually less than 40% by mass, preferably less than 30% by mass, and more preferably less than 20% by mass.

  Examples of the inorganic pigment include calcium carbonate, kaolin, talc, aluminum hydroxide, titanium dioxide, barium sulfate, satin white, zinc oxide, and colloidal silica. As calcium carbonate, heavy calcium carbonate and / or light calcium carbonate having a cubic shape, a spherical shape, or a spindle shape can be used.

[1-2] Binder:
The binder used in the coating composition of the present embodiment is for causing the coating composition to exhibit an adhesive function and improving the strength of the formed coating layer. In the coating composition of the present embodiment, this binder is preferably contained in an amount of 0 to 60 parts by mass (solid content) with respect to 100 parts by mass of the pigment, and contained in an amount of 40 parts by mass or less (solid content). More preferably. When the binder content exceeds 60 parts by mass with respect to 100 parts by mass of the pigment, it becomes difficult to develop an iris color, and the whiteness of the coated paper is impaired, or the coated paper is caused by excessive adhesiveness. It may cause operational troubles in the manufacturing process and coated paper printing process. Here, the solid content of the binder refers to a component obtained by removing water as a dispersion medium or a solvent from the binder.

  As such a binder, latex such as styrene butadiene latex and acrylic latex can be used. In the coating composition of the present embodiment, as the latex, for example, the glass transition point (Tg) is −50 to 55 ° C., and the particle diameter is preferably 30 nm to 400 nm, and preferably 50 nm to 300 nm. More preferably. When the binder has a core / shell structure, the average Tg is preferably within the range of the Tg.

  Moreover, the binder used for the coating composition of this embodiment may contain starch, casein, soybean protein, etc. besides the latex mentioned above. Of these, starch is preferred. As the starch, processed starch such as phosphate esterified starch, hydroxyethyl etherified starch, oxidized starch, and enzyme-modified starch can be used. These can be used individually by 1 type or in combination of 2 or more types.

[2] Coated body:
Next, one embodiment of the coated body of the present invention will be specifically described. The coated body of this embodiment includes a coated body and a coating layer formed by coating the surface of the coated body with the coating composition of the present invention described so far. It is a coated body.

  The coated body according to the present embodiment has a coating layer in which an iris color appears at a wide angle or a desired angle even when heat-treated, and is excellent in whiteness and pen writing suitability. . In addition, the coating layer of the coated body of the present embodiment, for example, exhibits a high gloss (glossy tone) and a low gloss (matte tone) when the viewing angle is changed without calendering the coating layer. Further, it is possible to express both glosses by changing the viewing angle.

[2-1] Object to be coated:
The coated body used in the coated body of the present embodiment is not particularly limited as long as it can form a coating layer by coating the coating composition on the surface, for example, , Coated base paper, film and the like. In the present invention, “film” is a concept including both a film and a sheet.

  Although the kind of coating base paper used for the coating body of this embodiment is not specifically limited, What can be used as coating paper by coating the composition for coating mentioned above should just be used. The kind of raw material pulp of the coating base paper is not particularly limited, and examples thereof include mechanical pulp, chemical pulp, and waste paper pulp (DIP).

  In addition, for coated base papers, pigments such as calcium carbonate, clay and talc as internal additives, sizing agents such as alkyl ketene dimer, rosin acid soap, and sulfuric acid band, cationic starch, and paper strength enhancement such as polyacrylamide An agent, a bulking agent, etc. can also be used. Further, a surface sizing agent such as acrylamide or acrylic-styrene polymer can be applied to the surface of the coated base paper using a size press, a gate roll coater, a metered size press, or the like.

  As a film used for the coated body of the present embodiment, for example, a transparent film (trade name “Lumirror 100-T-60”, manufactured by Toray Industries, Inc.), a black film (trade name “Lumirror X30”, manufactured by Toray Industries, Inc.), etc. Can be suitably used.

  Moreover, there is no restriction | limiting in particular about the color of the to-be-coated body used for the coating body of this embodiment, A white thing may be sufficient and a predetermined color may be exhibited. In addition, when a to-be-coated body exhibits black, the viewing angle which iris color develops becomes wide, or iris color becomes clearer. This is because when the object to be coated is white, the object to be coated reflects all the light to show white, whereas when the object to be coated is black, it absorbs the light so that the organic pigment coating is applied. This is because the reflected light characteristic of only the light reflected by the construction layer (visible light in the wavelength region that expresses the iris color) is emphasized. In addition, when the coated body is coated paper or film, the coated body has high smoothness, so that it is possible to obtain very high gloss in addition to the expression of the iris color.

[2-2] Coating layer:
The coating layer of the coating body of this embodiment is formed by applying the coating composition described so far to the body to be coated. In addition, in the coating body of this embodiment, it is preferable that the coating amount of a coating layer is 0.5-30 g / m < ² > per coated body single side | surface, and 1-15 g per coated body single side | surface. further preferably / ^{m 2.} By comprising in this way, an iris color can be favorably expressed in a coating layer.

[2-3] Production of coated body:
The coated body of this embodiment can be manufactured by applying the coating composition described above to a coated body such as a coated base paper or a film to form a coating layer. When applying the coating composition, it is preferable to employ a coating method in which coating is performed with a blade coater, a bar coater, an air knife coater, or a curtain coater, because the coated surface can be smoothed and the gloss of white paper is improved.

  In producing the coated body of the present embodiment, in addition to the above-described step of forming the coating layer by the coating method, after applying the coating composition to produce an undried coated body. It is preferable to have a drying step of drying the undried coated body. The drying method in the drying step is not particularly limited, and for example, a method used in a general coated paper manufacturing method can be employed. For example, hot air drying, infrared drying, microwave drying, or the like can be employed. These can be used individually by 1 type or in combination of 2 or more types. In addition, when manufacturing the coated paper of this embodiment, you may have a desired process suitably other than the above-mentioned process.

  Moreover, in the coating body of this embodiment, you may perform a lamination process to the coating layer formed by coating the composition for coating. By applying such a laminating process, the coated body can be well protected, and durability against water and dirt can be imparted. For this reason, for example, the coated body of the present embodiment can be suitably used for articles that are frequently used, such as catalogs, manuals, menus, POPs, price cards, and membership cards.

  Examples of the above-described laminating process include, for example, a method in which a laminating film or the like is pressed and processed on a coating body provided with a coating layer formed by applying a coating composition. It can be performed using a laminating machine (sometimes called a laminator).

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples. In the examples and comparative examples, “parts” and “%” are based on mass unless otherwise specified. Moreover, the measuring method and evaluation method of various physical property values are shown below.

  [Glass transition point (Tg)]: An organic pigment was heated and dried at 130 ° C. for 30 minutes to prepare a film, and the temperature was raised using a differential scanning calorimeter (trade name “DSC-220C”, manufactured by Seiko Electronics Co., Ltd.). The measurement was performed at a speed of 15 ° C./min. The temperature at the peak of the observed peak was taken as the glass transition point.

  [Number average particle diameter (solid organic pigment)]: Using a laser particle analyzer (trade name “Laser Particle Size Analysis System, LP-510 Model PAR-III”, manufactured by Otsuka Electronics Co., Ltd.), the number average is obtained by a light scattering method. The particle size was measured.

  [Number average particle diameter (hollow organic pigment)]: In a transmission electron micrograph, the particle diameters of 20 randomly extracted polymer particles were measured and used as the average value of the obtained measurement results.

  [Hollow Ratio]: Measured by the difference in diameter between the surface and the inner surface forming the outer shell of the polymer particle in the transmission electron micrograph. In addition, the measurement was made into the average value of the measurement result of 20 polymer particles extracted at random.

  [Iris color]: The color and intensity of the iris color were evaluated by visual judgment at a visual oblique angle with regular reflection at an incident angle of 60 ° and 75 °. When no iris color was developed at any oblique angle, it was evaluated as “none”.

  [Blank gloss]: A gloss meter (Murakami Color Co., Ltd.) was used and measured according to JIS P8142. The measurement was made at two points of incident angles of 60 ° and 75 °.

  [Whiteness]: Measured using a spectral whiteness colorimeter (manufactured by Suga Test Instruments Co., Ltd.).

[Pen writing aptitude (readability)]: Five researchers wrote random letters with Pencil B (Mitsubishi Pencil Co., Ltd.), black ballpoint pen, and red ballpoint pen, and evaluated readability.
A: Very easy to read.
○: Easy to read.
Δ: Difficult to read

[Pen writing aptitude (coloring property)]: Five researchers wrote characters randomly with a pencil B (manufactured by Mitsubishi Pencil Co., Ltd.), a black ballpoint pen, and a red ballpoint pen, and evaluated the coloring property.
A: Color density and vividness are extremely good.
○: Good color depth and vividness.
Δ: Color density and vividness are inferior.

[Pen writing aptitude (writeability)]: Five researchers wrote random letters with pencil B (manufactured by Mitsubishi Pencil Co., Ltd.), black ballpoint pen, and red ballpoint pen, and evaluated the ease of writing.
A: Very easy to write.
○: Easy to write.
Δ: It is difficult to write.

“Electrophotographic suitability (toner fixability)”: A laser printer (trade name “IRC3220”, manufactured by Canon Inc.) was used, and a solid surface of black, indigo, red, yellow, and a patch of characters were prepared as a printing surface. Next, after sticking an adhesive tape (trade name “Cellophane Tape”, manufactured by Nichiban Co., Ltd.) evenly on the printed surface, the degree of toner peeling when slowly peeling by hand is confirmed with a loupe. Evaluation was performed in two stages.
○: Toner does not peel off.
X: Toner peeling occurs even a little.

"Electrophotographic suitability (image quality)": Using a laser printer (trade name "IRC3220", manufactured by Canon Inc.), print the black and solid areas of black, indigo, red and yellow on the printing surface and characters, and make the naked eye and loupe. It was used to evaluate the feeling. The presence / absence of gloss unevenness, printing unevenness, and unevenness was evaluated in three stages according to the following criteria: ○, Δ, and ×.
○: No gloss unevenness, printing unevenness, or uneven feeling.
(Triangle | delta): Gloss unevenness, printing unevenness, and a feeling of unevenness are somewhat seen.
X: Gloss unevenness, printing unevenness, and unevenness are clearly seen.

[Electrophotographic suitability (toner-resistant blister)]: A printed matter obtained by printing a solid surface on both sides of a coated body as a printing surface using a laser printer (trade name “IRC3220”, manufactured by Canon Inc.) at a temperature of 23 ° C. and humidity After humidity was adjusted for 24 hours in a 65% atmosphere, the printed matter was immersed in an oil bath for evaluation. The temperature of the oil was increased from 150 ° C. by 10 ° C., the coated paper was dipped in oil, visually confirmed up to a temperature of 230 ° C. where toner blisters were generated, and judged according to the following criteria.
○: Blister does not occur even at 230 ° C.
Δ: Blister is generated at 200 ° C. or higher and lower than 230 ° C.
X: Blister occurs at less than 200 ° C.

[Offset printing suitability (dry strength)]: Paper test ink (trade name “SD50 Red BT-8”, manufactured by TOKA) was kneaded in a printing roll by 0.6 cc on a printing roll using an RI printing machine (Made Seisakusho). The degree of picking when printing was performed once at the number of rotations was judged with the naked eye, and the printing strength was evaluated.
○: Picking does not occur at all.
Δ: Slight picking occurs.
X: A large amount of picking occurs.

[Applicability for offset printing (wet strength)]: Ink for paper test (trade name “SD50 Red BT-8”, manufactured by TOKA Co., Ltd.) was printed on a printing roll with an RI printing machine (manufactured by Meisei Seisakusho) Add an appropriate amount of water to the fountain solution transfer fountain roll, and knead it. After kneading for a certain period of time, the degree of picking when printing once through a dampening water roll at a rotation speed of 60 rpm was judged with the naked eye, and the printing strength was evaluated.
○: Picking does not occur at all.
Δ: Slight picking occurs.
X: A large amount of picking occurs.

[Offset printability (white paper blister resistance)]: After the coated body was conditioned for 24 hours in an atmosphere of a temperature of 23 ° C. and a humidity of 65%, the printed matter was immersed in an oil bath and evaluated. The temperature of the oil was increased from 150 ° C. by 10 ° C., and the coated paper was immersed in oil.
○: Blister does not occur even at 200 ° C.
(Triangle | delta): Blister generate | occur | produces at 170 degreeC or more and less than 200 degreeC.
X: Blister occurs at less than 170 ° C.

  [Lamination suitability]: The coated body was processed with a laminator (trade name “Lamiguard”, manufactured by Intercosmos) using a laminate film and a PET film. The appearance of the iris color after lamination was evaluated by visual judgment in the case of regular reflection with an incident angle of 60 ° and a 75 ° visual oblique angle of 60 ° and 75 °, respectively.

[1-1] Production of dense organic pigment A:
In an autoclave equipped with a stirrer and capable of temperature adjustment, 200 parts of water, 0.1 part of sodium dodecylbenzenesulfonate, 1.0 part of potassium persulfate and 0.5 part of sodium bisulfite were charged in advance. Next, 5.0 parts of styrene, 1.0 part of divinylbenzene, 1.0 part of acrylic acid, and 2.0 parts of itaconic acid are charged together as the first stage component and reacted at 55 ° C. for 3 hours to obtain a polymerization conversion rate. Was 90% or more (first stage polymerization).

  Thereafter, polymerization was continued at 65 ° C. while continuously adding 87 parts of styrene and 4 parts of divinylbenzene as the second stage components over 12 hours. After completion of the continuous addition, the mixture was further reacted at 70 ° C. for 3 hours (second stage polymerization) to obtain a dense organic pigment (this dense organic pigment is referred to as “dense organic pigment A”). The final polymerization conversion was 99.5%. The glass transition point and number average particle diameter of the obtained dense organic pigment A were measured. The polymerization composition and measurement results of the dense organic pigment A are shown in Table 1.

[1-2] Production of dense organic pigments B, C, E, F, G:
Except for the polymerization composition shown in Table 1, dense organic pigments B to G were obtained in the same manner as in “Production of dense organic pigment A” described above. The particle size was adjusted by the number of parts used of dodecylbenzenesulfonic acid (emulsifier). The glass transition points and number average particle diameters of the obtained dense organic pigments B to G were measured. The measurement results are shown in Table 1.

  When 10% by mass or more of divinylbenzene was used, there was no clear Tg peak due to crosslinking and gelation of the polymer with divinylbenzene.

[1-3] Production of dense organic pigment D:
In an autoclave equipped with a stirrer and capable of temperature adjustment, 200 parts of water, 0.1 part of sodium dodecylbenzenesulfonate, 1.0 part of potassium persulfate and 0.5 part of sodium bisulfite were charged in advance. Next, 10.0 parts of divinylbenzene and 0.5 part of acrylic acid were added as a first stage component and reacted at 55 ° C. for 3 hours to confirm that the polymerization conversion was 90% or more (first stage) Polymerization).

  Thereafter, polymerization was continued at 65 ° C. while continuously adding 89.5 parts of divinylbenzene as a second stage component over 12 hours. After completion of the continuous addition, the mixture was further reacted at 70 ° C. for 3 hours (second stage polymerization) to obtain a dense organic pigment (this dense organic pigment is referred to as “dense organic pigment A”). The final polymerization conversion was 99.5%. The glass transition point and number average particle diameter of the obtained dense organic pigment A were measured. The polymerization composition and measurement results of the dense organic pigment A are shown in Table 1.

[2-1] Production of hollow organic pigment H:
(Preparation of polymer particles (i))
In a reaction vessel having a capacity of 2 liters, 109.5 parts of water as a medium, 0.5 parts of sodium dodecylbenzenesulfonate (trade name “F65”, manufactured by Kao Corporation) as an emulsifier, and sodium persulfate as a polymerization initiator were added in an amount of 0.1 part. 5 copies were added. Meanwhile, 80 parts of methyl methacrylate, 20 parts of methacrylic acid, 0.5 part of octyl thioglycolate as molecular weight modifier, 0.1 part of emulsifier (trade name “F65”, manufactured by Kao Corporation) and 40 parts of water are mixed. Stirred and continuously added, polymerized over 5 hours, further aged for 2 hours, polymer particles (i) having a solid content of 40% and particle size of 140 nm (hereinafter referred to as “adjusted polymer particles (i)”) In some cases, an aqueous dispersion was obtained. The particle diameter of the adjusted polymer particles (i) was adjusted by the amount of the emulsifier. Table 2 shows the polymerization composition of the adjusted polymer particles (i).

(Preparation of hollow organic pigment H)
Into a reaction vessel having a capacity of 2 liters, 240 parts of water as a medium is put in advance, and 18 parts of an aqueous dispersion of polymer particles (i) prepared as described above is solid content, sodium persulfate as a polymerization initiator 0.4 part was added. Meanwhile, 59.5 parts of styrene, 0.5 part of acrylic acid, 0.1 part of an emulsifier (trade name “F65”, manufactured by Kao Corporation) and 40 parts of water were mixed and stirred to prepare an aqueous dispersion of the monomer. .

  Next, while stirring the liquid in the reaction vessel, the temperature is raised to 80 ° C., and then the liquid in the reaction vessel is kept at 80 ° C. with stirring to continuously add the monomer aqueous dispersion to the reaction vessel. It was added over 3 hours to obtain core-shell polymer particles (ii) in which styrene and acrylic acid were polymerized and laminated on the surface layer of the polymer particles (i). Approximately 15 minutes after the addition of all the monomers, 1.5 parts of 25% ammonium hydroxide was added all at once with stirring, the temperature was raised to 90 ° C., and then 40 parts of divinylbenzene were added all at once for 2 hours. To obtain an aqueous dispersion pair of hollow organic pigment (this hollow organic pigment is referred to as “hollow organic pigment H”). The hollow organic pigment H obtained was measured for glass transition point, number average particle diameter, and hollow ratio. The measurement results are shown in Table 2.

[2-2] Production of hollow organic pigments I, J, K, and L:
Except for the polymerization composition shown in Table 2, polymerization was carried out in the same manner as the hollow organic pigment H to produce hollow organic pigments I, J, K, and L. The second stage of the hollow organic pigment K polymer particles (i) was prepared as follows.

[2-3] Production of hollow organic pigment K:
(Polymer particles (i) second stage preparation)
Into a reaction vessel having a capacity of 2 liters, 186 parts of water was previously added as a medium, and 2.5 parts of an aqueous dispersion containing polymer particles (i) (seed particles) prepared in the production of hollow organic pigment I ( (Solid content) 0.5 parts of sodium persulfate was added as a polymerization initiator. Meanwhile, 70 parts of methyl methacrylate, 30 parts of methacrylic acid, and 40 parts of water were mixed and stirred to prepare an aqueous dispersion of the monomer mixture.

  Next, the temperature in the reaction vessel was increased to 80 ° C. while stirring, and the aqueous dispersion of the monomer mixture was continuously added to the reaction vessel over 5 hours. Thereafter, aging was further performed for 2 hours to obtain an aqueous dispersion of polymer particles (i) having a particle diameter of 1000 nm.

[3-1] Production of inorganic pigment (paint) a:
Kaolin clay (trade name “Miragros JP”, manufactured by Engelhard) 50 parts heavy calcium carbonate (trade name “Pimatech 90”, manufactured by Pimatech), starch (trade name “MS4600”, Japan Food Industry) 3 parts, dispersant (polyacrylic acid dispersant; trade name “Aron-T40”, manufactured by Toagosei Co., Ltd.) 0.1 part, and sodium hydroxide (trade name “sodium hydroxide grade 1”, Japanese Inorganic pigment a of offset-printed coated paper having a solid content of 65% was produced using 0.1 part (manufactured by Kojun Pharmaceutical Co., Ltd.). Table 3 shows the formulation of inorganic pigment a.

  As a specific method for producing the inorganic pigment a, adjustment water, a dispersant, and sodium hydroxide were charged into a stainless steel container, and the rotation speed of a coreless disperser (manufactured by Shimazaki Corporation) was set to 2000 rpm. Next, kaolin was gradually added into the stainless steel container, and after complete addition, the rotational speed of the disperser was set to 6000 rpm and stirring was continued for 30 minutes. Next, calcium carbonate was added, and then starch and sodium hydroxide were added, followed by further stirring for 15 minutes. Next, the number of revolutions of the disperser was set to 2000 rpm, latex was added, and stirring was performed for 10 minutes. Note that starch prepared in advance in a stainless steel container with cold water so as to have a concentration of 30% was prepared, and this was dissolved at 95 ° C. for 1 hour using a device with stirring capable of temperature adjustment. .

[4-1] Example 1:
(Preparation of coating composition)
100 parts of solid organic pigment A and 10 parts of latex (trade name “0696”, manufactured by JSR Corporation) as a binder are mixed, and the concentration is adjusted to 25% by mass with adjusted water to adjust the coating composition. Got. The coating composition was mixed with a lab stirrer (trade name “BL3000”, manufactured by Techjam) at a rotational speed of 1000 rpm for 2 minutes. Table 4 shows the coating composition.

(Manufacture of coated bodies)
Adjust the wire bar count so that the coating amount is 4.0 g / m ² on the black base paper (trade name “Kentrasia No. 402 Kuro”, manufactured by Special Paper Industries Co., Ltd.). After coating, the coated body was dried by drying at 150 ° C. for 20 seconds using a gear oven. Iris color and white paper gloss (incidence angles 60 ° and 75 °) of the obtained coated body were measured. Table 4 shows the measurement results.

[4-2] Examples 2 to 13:
A coating composition was prepared in the same manner as in Example 1 except that the organic pigment used for the preparation of the coating composition was changed as shown in Table 4. As shown in Table 4, the obtained composition for coating was coated with black base paper (trade name “Kentrasia No. 402 Black”, manufactured by Tokushu Paper Co., Ltd.), commercially available A2 matte paper (trade name “ A coated body was produced in the same manner as in Example 1, using “OK top coat mat N” (manufactured by Oji Paper Co., Ltd.) and a transparent film (trade name “Lumirror 100-T60”, manufactured by Toray Industries, Inc.). Iris color and white paper gloss (incidence angles 60 ° and 75 °) of the obtained coated body were measured. Table 4 shows the measurement results.

[4-3] Example 14:
(Preparation of coating composition)
100 parts of solid organic pigment C and 10 parts of latex (trade name “0696”, manufactured by JSR) as a binder are mixed, and the concentration is adjusted so that the solid content becomes 25% by mass with adjustment water, and the coating composition Got. The coating composition was mixed with a stirrer (trade name “Lab Stirrer”, manufactured by Tech Jam) at a rotational speed of 1000 rpm for 2 minutes. Table 5 shows the formulation of the coating composition.

(Manufacture of coated bodies)
Adjust the wire bar count so that the coating amount is 4.0 g / m ² on the white base paper (trade name “OK Prince Quality”, manufactured by Oji Paper Co., Ltd.). After coating, a coated body was produced by drying at 50 ° C. for 20 seconds using a gear oven.

[4-4] Examples 15 to 30:
A coating composition was prepared in the same manner as in Example 1 except that the organic pigment and inorganic pigment used for the preparation of the coating composition were changed as shown in Tables 5 and 6. A coated body was produced using the working composition.

  Iridescent colors (incidence angle 60 °, 75 ° specular reflection angle and incident angle 45 °, viewing angle 75 °), white paper gloss (incidence angles 60 ° and 75 °) of Examples 14 to 30 obtained , Whiteness, pen writing aptitude (readability), pen writing aptitude (color developability), pen writing aptitude (ease of writing), electrophotographic aptitude, offset printing aptitude and high temperature laminating aptitude. The measurement results are shown in Tables 5 and 6.

[4-5] Comparative Examples 1 to 6:
A coating composition was prepared in the same manner as in Example 1 except that the organic pigment used for preparing the coating composition was changed as shown in Table 7. A coated body was dried and produced at 50 ° C. using the obtained coating composition. Iris color (incidence angle 60 °, 75 ° specular reflection angle and incident angle 45 ° and viewing angle 75 °), white paper gloss (incidence angles 60 ° and 75 °), whiteness, pen writing Aptitude (readability), pen writing aptitude (color development), pen writing aptitude (writeability), electrophotographic aptitude, and high temperature laminating aptitude were measured. Table 7 shows the measurement results.

[4-7] Comparative Examples 7 and 8:
A coating composition was prepared in the same manner as in Example 1 except that the organic pigment used for preparing the coating composition was changed as shown in Table 7. A coated body was dried at 150 ° C. using the obtained coating composition. Iris color (incidence angle 60 °, 75 ° specular reflection angle and incident angle 45 ° and viewing angle 75 °), white paper gloss (incidence angles 60 ° and 75 °), whiteness, pen writing Aptitude (readability), pen writing aptitude (color development), pen writing aptitude (writeability), electrophotographic aptitude, and high temperature laminating aptitude were measured. Table 7 shows the measurement results.

[5] Consideration:
The coated bodies of Examples 1 to 13 are at least one of the coated bodies when viewed at a regular reflection angle of 60 ° and 75 ° even when the coated body is dried at 150 ° C. for 20 seconds in a gear oven. Iris color developed. Further, a matte tone with a low gloss at a visual oblique angle of 60 ° and a glossy tone with a very high gloss at a visual oblique angle of 75 °, both of which are unprecedented in which both characteristics are manifested by the visual oblique angle ( Examples 9, 11, 12, 13). Further, 75 ° white paper gloss is very high in a coated body using a commercially available A2 matte paper and a transparent film, in which the surface of the coated body is smooth or the coated body has little penetration into the coated body. It was found that the hollow organic pigment was not easily affected by the roughness of the coated body because the gloss of the white paper of the coated body using the hollow organic pigment was high. This seems to be because the light interference mechanism described above is different from the case of the polymer particles constituting the solid organic pigment. Moreover, the coating layer which the iris color expressed was able to be formed.

  Moreover, also in the coated bodies of Examples 14 to 21, when viewed at a regular reflection angle of 60 ° and 75 °, an iris color was developed in at least one of them. In addition, 75 ° white paper gloss was also high in the white paper gloss of the coated body using the hollow organic pigment, and in particular, the white paper gloss of the hollow organic pigment (for example, Examples 17 to 21) having a number average particle diameter exceeding 2000 nm was high. . Furthermore, these coated bodies have a matte appearance with a low gloss at a visual oblique angle of 60 °, and a glossy appearance with a very high gloss at a visual oblique angle of 75 °. It was not. Further, these coated bodies were all excellent in pen writing aptitude, electrophotographic aptitude, and offset printing aptitude. Further, even when the white paper portion after electrophotographic printing was viewed at a regular reflection angle of 60 ° and 75 °, an iris color was developed at least one of them. From this, it was found that the iris color was not impaired even when passing through a high-temperature roll for fixing toner in electrophotographic printing. In addition, even when dried at high temperature, the whiteness was 80% or more, and a coating layer in which an iris color was expressed could be formed without impairing the whiteness.

  The iris colors of the coated bodies subjected to the high-temperature laminating process of Examples 22 to 30 exhibited the same suitable iris color as before the laminating process. Thus, the coated body can be protected by laminating the coated layer of the coated body.

  On the other hand, in Comparative Examples 1 and 3, the iris color disappeared after electrophotographic printing and high temperature lamination. In Comparative Example 2, since the particle size of the polymer was small, no iris color was developed and the opacity of the white paper was low. In Comparative Examples 4 to 6, when 50 parts or more of the inorganic pigment was mixed, the iris color of the white paper did not appear, and the opacity and pen writing suitability were inferior. In Comparative Examples 7 and 8, the iris of the white paper portion disappeared by drying the coated body in a gear oven at 150 ° C. for 20 seconds. Moreover, the whiteness and pen writing ability were also inferior.

  The coating composition of the present invention can develop an iris color in the coating layer to be formed by coating on the surface of an object to be coated such as coating base paper or film. And it has the feature that an iris color is not spoiled even if a coated body is processed at high temperature, for example, can be used as coating materials, such as paper, textiles, and leather. Further, for example, the coating composition of the present invention can be used as a water-based paint such as a white paint. When numbers and letters are written on drawing paper (white) or the like using such a water-based paint, an iris color can be expressed by the degree of light hit. Moreover, the coated body of this invention can be used suitably for a coated paper, a film for packaging, a stationery etc., for example. Furthermore, it can be suitably used for electrophotographic printing and offset printing.

It is explanatory drawing which shows typically an example of the reflective state of light when light injects into the polymer particle which comprises the hollow organic pigment used for one Embodiment of the composition for coating of this invention. It is explanatory drawing which shows typically an example of the reflection state of light when light injects into the polymer particle which comprises the solid organic pigment used for one Embodiment of the composition for coating of this invention.

Explanation of symbols

1: hollow organic pigment, 2: polymer particle, 3: closed space, 4a, 4b: incident light, 5a, 5b: reflected light, 11: solid organic pigment, 12: polymer particle, 14: incident light, 15a, 15b : Reflected light, A, B: Optical path difference.

Claims (12)

A coating composition comprising a pigment and a binder,
The pigment contains 60% by mass or more of an organic pigment, and the organic pigment contains polymer particles having a polymer composition containing 2% by mass or more of a structural unit derived from a crosslinkable radical polymerizable monomer, and the number of the polymer particles The composition for coating whose average particle diameter is 150-5000 nm.   The coating composition according to claim 1, wherein the organic pigment contains a hollow organic pigment having a hollowness of 15% by volume or more.   The coating composition according to claim 2, wherein the organic pigment contains two or more kinds of hollow organic pigments having different number average particle diameters.   The coating composition according to any one of claims 1 to 3, wherein the organic pigment contains a dense organic pigment.   The coating composition according to claim 4, wherein the organic pigment contains two or more dense organic pigments having different number average particle diameters.   The composition for coating according to any one of claims 1 to 5, wherein the polymer particles constituting the organic pigment are solid and / or hollow polymer particles having a number average particle diameter of 150 to 700 nm.   The coating composition according to any one of claims 1 to 5, wherein the polymer particles constituting the organic pigment are hollow polymer particles having a number average particle diameter of more than 700 nm and not more than 5000 nm.   The coating body provided with the to-be-coated body and the coating layer which consists of a composition for coating as described in any one of Claims 1-7 formed in the surface of the said to-be-coated body.   The coated body according to claim 8, wherein the coated body is black.   The coated body according to claim 8 or 9, wherein the coated body is a coated base paper or a film. The coated body according to any one of claims 8 to 10, wherein a coating amount of the coating layer is 0.5 to 30 g / m ² per one surface of the coated body.   The coated body according to any one of claims 8 to 11, wherein the coating layer is laminated.

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