JP2005103898A - Inkjet recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording medium having an ink acceptance layer with a sufficiently secured void part despite the content, of each component, i.e. an inorganic fine particle and an organic polymer as a binder added in the ink acceptance layer, which is enough to fully display its respective function. <P>SOLUTION: This inkjet recording medium has the ink acceptance layer, which contains an organic polymer-compounded inorganic fine particle obtained by chemically bonding the inorganic fine particle with the organic polymer, formed on a support. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an ink jet recording medium such as ink jet recording paper and film used for ink jet printing and recording.

  The ink jet recording method is a method for recording characters and images by causing ink droplets to fly by various operating principles and adhere to a recording medium such as paper. This ink jet recording system has advantages such as relatively high speed, low noise, and easy multi-coloring.

  In addition, the fields of application that have attracted particular attention in recent years in the ink jet recording system include the creation of color proofs in the printing field where high image quality close to that of photographs is required, and the output of design images in the design field. Furthermore, it is generally performed that a character or image information created by a computer is output to a transparent recording sheet by an ink jet printer and used as a manuscript for an overhead projector for a conference presentation or the like.

  As the performance of the ink jet recording medium used in the ink jet recording method, the ink absorption is high, the image density is high, the color reproducibility is good, the dot reproducibility is good, the ink receiving layer is High gloss is required. In recent years, a great deal of research has been conducted to develop recording media having these performances.

  Here, high-quality paper or the like used for general printing is inferior in ink absorptivity and drying property, and inferior in image quality such as resolution. Therefore, currently, research is mainly conducted on a recording medium in which the above performance is improved by coating an ink-receiving layer on a support. Currently known recording media include those in which fine particles such as silica and alumina are contained in the ink receiving layer to form voids in the ink receiving layer, thereby improving the transparency and glossiness of the recording medium. Is the mainstream.

  In the recording medium using the inorganic fine particles, it is necessary to use an organic polymer as a binder in addition to the inorganic fine particles in order to maintain the strength of the ink receiving layer. However, when the amount of the organic polymer added is too large, the voids are blocked, and there is a problem that the ink absorbability improved by the addition of the inorganic fine particles is decreased. On the other hand, if the addition amount of the polymer is decreased in order to avoid clogging of the voids by the organic polymer, the purpose of adding the polymer is not achieved. That is, the strength of the ink receiving layer is not maintained to a necessary level. As a result, fine cracks were generated on the surface after the ink receiving layer was applied and dried, resulting in a decrease in gloss and blurring of the image.

  In order to solve this problem, for example, in an inkjet recording medium having at least one ink-receiving layer on a water-resistant support, the ink-receiving layer has inorganic fine particles and silanol groups having an average primary particle size of at least 3 to 30 nm. An ink jet recording medium characterized in that it contains polyvinyl alcohol having the above (see Patent Document 1). According to the recording medium described in the document 1, it is said that an ink-receiving layer having high ink absorption without cracks can be obtained.

However, also in the recording medium of Document 1, polyvinyl alcohol having a silanol group is used as a binder together with inorganic fine particles. Therefore, in some cases, there is a problem that the void formed by the inorganic fine particles is blocked by the binder, and the performance such as ink absorbability cannot be sufficiently ensured.
JP 2003-54120 A

  The object of the present invention is to provide a sufficient gap portion even though each component of the inorganic fine particles contained in the ink receiving layer and the organic polymer as the binder is contained in an amount capable of sufficiently exhibiting the respective functions. It is another object of the present invention to provide an ink jet recording medium having an ink receiving layer secured.

  The present invention is an ink jet recording medium comprising an ink receiving layer containing organic polymer composite inorganic fine particles formed by chemically bonding an organic polymer to inorganic fine particles on a support.

  According to the present invention, the inorganic fine particles and the organic polymer as the binder are contained in the ink receiving layer in a pre-bonded state. For this reason, the blockage | closure of the space | gap part by this polymer which was a problem in the conventional ink receiving layer which added each component separately is suppressed. As a result, an ink jet recording medium is provided in which a sufficient gap is ensured and the ink absorbency and the like are excellent.

  A first aspect of the present invention is an ink jet recording medium having an ink receiving layer containing organic polymer composite inorganic fine particles formed by chemically bonding an organic polymer to inorganic fine particles on a support.

  Conventionally, in the production of a recording medium containing an inorganic fine particle and an organic polymer as a binder in an ink receiving layer, a coating liquid to which inorganic fine particles and an organic polymer are separately added is applied onto a support, and the receiving layer is applied. It was common to install. For this reason, the space | gap part formed between inorganic fine particles may be obstruct | occluded with the organic polymer, and performance, such as ink absorptivity, may fall.

  On the other hand, in the ink jet recording medium of the present invention, the ink receiving layer coated on the support contains organic polymer composite inorganic fine particles formed by chemically bonding an organic polymer to inorganic fine particles. For this reason, the clogging of the voids, which has been a problem when the inorganic fine particles and the organic polymer are added separately, is suppressed, and an ink jet recording medium excellent in performance such as ink absorbability can be obtained.

  First, a preferred embodiment of the organic polymer composite inorganic fine particles contained in the ink receiving layer in the present invention will be described.

  The form of the organic polymer composite inorganic fine particles is not particularly limited as long as the organic polymer is chemically bonded to the inorganic fine particles.

  The inorganic fine particles contained in the organic polymer composite inorganic fine particles are not particularly limited as long as they are inorganic fine particles composed of an arbitrary element. The inorganic fine particles preferably contain atoms selected from the periodic table 2 to 6 and groups 12 to 16, more preferably atoms selected from the periodic table 3 to 5 and groups 13 to 15. Contained, more preferably an atom selected from Si, Al, Ti and Zr, and particularly preferably an Si atom.

  Furthermore, the inorganic fine particles used in the present invention are not particularly limited, but are preferably oxygen-containing compounds in which the above-described atoms constitute a three-dimensional network mainly through bonds with oxygen atoms.

  An organic polymer as described later is chemically bonded to the inorganic fine particles, but in addition to this, other organic groups or hydroxyl groups may be bonded, or condensability that can be a raw material of the inorganic fine particles as described later. Various groups derived from a compound may be bonded. Examples of the organic group include one or more selected from the group consisting of an optionally substituted alkyl group, cycloalkyl group, aryl group and aralkyl group having 20 or less carbon atoms. The In the present invention, as the inorganic fine particles, only one of the above embodiments may be used, or two or more embodiments may be used in combination. The shape of the inorganic fine particles is not particularly limited, and examples thereof include a spherical shape, a needle shape, a plate shape, a scale shape, and a crushed shape. Only one of these inorganic fine particles may be used alone, or two or more of them may be used in combination. In the ink jet recording medium of the present invention, the presence of the inorganic fine particles as described above in the ink receiving layer can provide an ink jet recording medium excellent in properties such as ink absorbability and water resistance.

  The organic polymer is not particularly limited as long as it can act as a binder in the ink receiving layer, and any organic polymer can be used, and the molecular weight, shape, composition, presence / absence of a functional group, and the like can be appropriately determined. Examples of the resin constituting the organic polymer include (meth) acrylic resins, polyvinyl alcohol resins, ether glycol resins, polyolefins such as polystyrene, polyvinyl acetate, polyethylene and polypropylene, polyvinyl chloride, polyvinylidene chloride, and polyethylene terephthalate. Examples thereof include polyesters such as these, copolymers thereof, resins partially modified with functional groups such as amino groups, epoxy groups, hydroxyl groups, and carboxyl groups. Only 1 type of these resin may be used independently, and 2 or more types may be used together. Here, (meth) acrylic resin, polyvinyl alcohol resin or ether glycol resin is preferably used as the resin constituting the organic polymer, and (meth) acrylic resin is particularly preferably used. The shape of the organic polymer is not particularly limited as described above, and examples thereof include linear, branched, and crosslinked structures. As for the shape of the organic polymer, only one of these may be used alone, or two or more may be used in combination. In addition, a copolymer containing a plurality of monomers constituting each of the above organic polymers may be used.

  The mode in which the organic polymer is chemically bonded to the inorganic fine particles is not particularly limited, but is preferably bonded by, for example, a covalent bond. This is because the covalent bonding allows the organic polymer to bind to the inorganic fine particles more firmly. In this case, it is more preferable that one atom constituting the organic polymer and one atom constituting the inorganic fine particle are directly bonded by a covalent bond.

Here, the organic polymer may contain, for example, a polysiloxane group, and may be bonded to inorganic fine particles via the polysiloxane group. The “polysiloxane group” is a group formed by connecting two or more silicon (Si) atoms in a linear or branched manner with a polysiloxane bond (Si—O—Si bond). In this case, the polysiloxane group preferably contains at least one Si-OR ¹ group. Here, the R ¹ group is a hydrogen atom, or one or two or more groups optionally selected from an alkyl group or an acyl group, and a plurality of R ¹ groups are present in one molecule of a polysiloxane group. If so, each R ¹ group may be the same or different. When an organic polymer having a polysiloxane group containing at least one Si—OR ¹ group is used, the R ¹ O group can be involved in the bonding of the organic polymer to the inorganic fine particles. That is, in such a case, although not particularly limited, for example, the R ¹ O group of the Si-OR ¹ group undergoes a condensation reaction with the condensable group in the condensable compound, whereby the condensable compound is hydrolyzed and condensed. An organic polymer can be bonded to the inorganic fine particles formed in the above manner.

On the other hand, the mode of introducing the polysiloxane group into the organic polymer is not particularly limited. For example, a condensable compound such as tetramethoxysilane (Si (OCH ₃ ) ₄ ) is added in the presence of a silane coupling agent. To polymerize the polymerizable polysiloxane, and polymerize the polymerizable polysiloxane with other polymerizable monomers, for example, radical polymerizable monomers such as (meth) acrylic acid monomers. Thus, an organic polymer having a polysiloxane group introduced can be synthesized. In the present specification, “polymerizable polysiloxane” refers to an organic polymer having a polysiloxane group, which can be copolymerized with a radical polymerizable monomer. Accordingly, the polymerizable polysiloxane has, for example, a double bond.

  Furthermore, the organic polymer may be, for example, an organic polymer containing a hydroxyl group (also referred to herein as “hydroxyl group-containing organic polymer”). In this case, the organic polymer can be bonded to the inorganic fine particles through oxygen atoms. That is, atoms in the inorganic fine particles and C atoms constituting the organic polymer skeleton can be bonded via O atoms therebetween. For example, when the inorganic fine particles are silica fine particles, a bonding form of Si—O—C exists in the organic polymer composite inorganic fine particles. The mode of bonding the organic polymer to the atom in the inorganic fine particle through an oxygen atom is not particularly limited. For example, a method of condensing a hydroxyl group-containing organic polymer together with a condensable compound can be used.

  Here, the organic polymer as described above acts as a binder in the ink receiving layer, and can improve properties such as strength and transparency of the ink receiving layer.

  In the organic polymer composite inorganic fine particle, the site in the inorganic fine particle when the organic polymer is bonded to the inorganic fine particle is not particularly limited. For example, when the inorganic fine particles have a three-dimensional structure, the organic polymer can be bound to the surface of the inorganic fine particles, and may be inside thereof. Thus, moderate softness and toughness can be imparted to the inorganic fine particles that are the core of the organic polymer composite inorganic fine particles by bonding the organic polymer inside the inorganic fine particles. Here, the presence or absence of the organic polymer in the inorganic fine particles in the organic polymer composite inorganic fine particles is, for example, the inorganic fine particles after thermally decomposing the organic polymer by heating the organic polymer composite inorganic fine particles at 500 to 700 ° C. This can be confirmed by comparing the measured value of the specific surface area with the theoretical value of the specific surface area calculated from the diameter of the inorganic fine particles. That is, when the inorganic fine particles include an organic polymer therein, many pores are generated in the inorganic fine particles due to decomposition of the organic polymer by heating. Therefore, in this case, the calculated value of the specific surface area of the inorganic fine particles after pyrolysis is a value that is considerably larger than the theoretical value calculated from the diameter of the inorganic fine particles.

  The average particle size of the organic polymer composite inorganic fine particles is preferably 5 to 200 nm, more preferably 5 to 100 nm. If the particle diameter is less than 5 nm, the surface energy of the organic polymer composite inorganic fine particles may increase and aggregation or the like may occur. On the other hand, when the particle diameter exceeds 200 nm, physical properties such as transparency of the ink receiving layer of the ink jet recording medium of the present invention may deteriorate.

  Moreover, the variation coefficient of the particle diameter of the organic polymer composite inorganic fine particles is preferably 50% or less, and more preferably 30% or less. If this value exceeds 50%, the particle size distribution of the organic polymer composite inorganic fine particles becomes wide, and irregularities occur on the surface of the ink receiving layer of the ink jet recording medium, so that a smooth surface may not be obtained.

Furthermore, the organic polymer composite inorganic fine particles may contain an alkoxy group. In this case, the content of the alkoxy group and the site thereof are not particularly limited, but preferably 0.01 to 50 mmol, more preferably 0.01 to 10 mmol, particularly preferably 0.01 to 1 g of organic polymer composite inorganic fine particles. 1 mmol is contained. Here, the “alkoxy group” refers to an R ² O group bonded directly to an atom constituting the inorganic fine particle. R ² is an optionally substituted alkyl group, and examples thereof include a methyl group, an ethyl group, an n-propyl group, and an n-butyl group. At this time, each R ² O group may be the same as or different from each other. By containing the above-mentioned amount of alkoxy groups, the affinity of the organic polymer composite inorganic fine particles with the organic medium and the dispersibility in the organic medium can be improved.

  The content of the inorganic fine particles in the organic polymer composite inorganic fine particles is not particularly limited, but is preferably 30 to 80% by mass, more preferably 50 to 70% by mass, and particularly preferably 55 to 65% by mass of the organic polymer composite inorganic fine particles. It is. If the content of the inorganic fine particles is less than 30% by mass, physical properties such as ink absorptivity, hardness and heat resistance of the ink receiving layer may be lowered. On the other hand, if it exceeds 80% by mass, the content of the organic polymer is relatively lowered, and the physical properties such as transparency and glossiness of the ink receiving layer may be lowered. Therefore, the content of the organic polymer in the organic polymer composite inorganic fine particles is complementary to the content of the above-mentioned inorganic fine particles, preferably 20 to 70% by mass, more preferably 30 to 50% by mass of the organic polymer composite inorganic fine particles. %, Particularly preferably 35 to 45% by mass.

  As described above, the ink jet recording medium of the present invention has an ink receiving layer containing organic polymer composite inorganic fine particles on a support.

  Here, the ink receiving layer of the ink jet recording medium of the present invention contains the organic polymer composite inorganic fine particles described above. Here, the content of the organic polymer composite inorganic fine particles in the ink receiving layer is not particularly limited, but is preferably 30 to 100% by mass, more preferably 50 to 70% by mass, and particularly preferably 55 to 70% by mass with respect to the total amount of the ink receiving layer. 65% by mass. When the content is less than 30% by mass, the ink absorbability of the ink receiving layer may be lowered.

  The thickness of the ink receiving layer is preferably 10 to 1000 μm, more preferably 15 to 45 μm, and particularly preferably 20 to 30 μm. Further, in the ink receiving layer, void portions are formed between the organic polymer composite inorganic fine particles contained therein. Here, the average diameter of the void portion is preferably 5 to 500 nm, more preferably 5 to 200 nm, and particularly preferably 10 to 100 nm. When the average diameter of the void portion is less than 5 nm, characteristics such as ink absorbability may not be sufficient, while when it exceeds 500 nm, transparency or color developability may not be sufficient.

  Hereinafter, although the preferable one aspect | mode of the manufacturing method of the inkjet recording medium of this invention is demonstrated, it is not restrict | limited to this.

  First, a method for producing organic polymer composite inorganic fine particles contained in the ink receiving layer in the ink jet recording medium of the present invention will be described.

  The organic polymer composite inorganic fine particles are not particularly limited, and can be produced, for example, by hydrolyzing and condensing a condensable compound in the presence of an organic polymer. Here, the “condensable compound” refers to a compound that can form a three-dimensional network structure by condensation reaction or hydrolysis and condensation reaction to form inorganic fine particles.

  Here, the condensable compound used for producing the organic polymer composite inorganic fine particles is not particularly limited, but preferably contains an atom selected from Groups 2 to 6 and Groups 12 to 16, and more Preferably, atoms selected from Group 3 to 5 and Groups 13 to 15 of the periodic table of elements are contained, and more preferably, atoms selected from Si, Al, Ti and Zr are contained. In particular, it is preferable that the condensable compound contains Si atoms because the condensation reaction is easily controlled. In addition, the condensable compound may contain only 1 type of said atoms, and may contain 2 or more types.

  Specific examples of the condensable compound include, for example, compounds listed as specific examples of the metal compound (G) and derivatives thereof on pages 6 to 8 of JP-A-7-178335, and JP-A-2001-64439. Examples of the condensable metal compound and its derivatives are given on pages 5 and 6 of the publication. Only 1 type of these condensable compounds may be used independently, and 2 or more types may be used together.

When the condensable compound forms a three-dimensional network structure, for example, when tetramethoxysilane (Si (OCH ₃ ) ₄ ) is used as the condensable compound, the following formula:

It is thought that it is represented by.

  Therefore, the organic polymer composite inorganic fine particles used in the present invention are formed by chemically bonding an organic polymer to inorganic fine particles in which a three-dimensional network structure is formed by the above reaction, for example. Here, as an example of a three-dimensional network structure, the inorganic fine particles containing Si atoms obtained by the above formula are not particularly limited. For example, in the tetrahedral structure formed by Si atoms, the bonding of Si atoms to each other is possible. It has a structure in which an O atom is inserted between them. Here, the method for forming the bond is not particularly limited, and the inorganic fine particles and the organic polymer are formed during or after the formation of the inorganic fine particles by hydrolysis and condensation of the condensable compound by the above reaction. Any method may be used as long as a chemical bond is formed.

Here, the mode for chemically bonding the organic polymer to the inorganic fine particles during or after the hydrolysis and condensation of the condensable compound is not particularly limited. For example, the organic polymer can undergo a condensation reaction with the condensable compound. There is a method using a reactive group having a reactive group such as a hydroxyl group or an alkoxy group. Therefore, a preferred embodiment of this method will be described below, but the present invention is not limited to this. Here, the “alkoxy group” means an R ² O group present in the organic polymer, and the definition of R ² is the same as described above.

  First, a case where a hydroxyl group-containing organic polymer is used as the organic polymer will be described.

  In this case, when the hydroxyl group-containing organic polymer is hydrolyzed and condensed together with the condensable compound, the hydroxyl group of the hydroxyl group-containing organic polymer is converted into a condensable group of the condensable compound, such as an alkoxy group, or the alkoxy group is hydrolyzed. It is considered that a dealcoholization reaction occurs with at least one of the hydroxyl groups generated by decomposition, and the carbon atom in the organic polymer and the atom in the condensable compound are bonded through an O atom. At this time, the condensable compound to which the organic polymer is bonded condenses with each other using a condensable group that has not participated in the reaction, thereby forming inorganic fine particles having a three-dimensional network structure. It is presumed that inorganic fine particles are produced. The technical scope of the present invention should be determined based on the description of the scope of claims, and the technical scope of the present invention is not limited at all even if the above mechanism is different from the fact.

  Specific examples of the hydroxyl group-containing organic polymer include compounds described in JP-A-2001-64439, pages 4 and 5, and the like.

  Next, the case where an organic polymer containing at least one alkoxy group, such as the organic polymer containing a polysiloxane group containing an alkoxy group, is used will be described.

  Also in this case, when the organic polymer is hydrolyzed and condensed together with the condensable compound, the alkoxy group of the organic polymer is hydrolyzed and reacts with the condensable compound in the same manner as described above, and the organic polymer and the condensable compound are reacted. It is thought that the atoms inside are bonded. Further, the mechanism by which inorganic fine particles are further formed and finally the organic polymer composite inorganic fine particles are produced is also assumed to be the same as described above.

  Here, specific examples of the organic polymer containing at least one alkoxy group and the production method thereof are described in, for example, JP-A-6-33015, JP-A-7-178335 and JP-A-2001-64439. The aspect currently performed is illustrated.

  By the method as described above, the organic polymer composite inorganic fine particles contained in the ink receiving layer in the ink jet recording medium of the present invention are produced. The organic polymer composite inorganic fine particles have a structure in which an organic polymer that can act as a binder is chemically bonded to inorganic fine particles serving as a nucleus. Therefore, since the inorganic fine particles and the organic polymer are contained in the ink receiving layer in a bonded state, the clogging of the void portion, which has been a problem when the inorganic fine particles and the binder are added separately, is suppressed, and the ink absorbability, etc. An ink jet recording medium having excellent performance can be obtained.

  Furthermore, although it does not restrict | limit in particular, The preferable one aspect | mode which forms the ink receiving layer containing an organic polymer composite inorganic fine particle on a support body is demonstrated below.

  First, an organic polymer composite inorganic fine particle dispersion containing the organic polymer composite inorganic fine particles is prepared. The dispersion is obtained by dispersing the organic polymer composite inorganic fine particles produced as described above in various dispersion media. In the dispersion, the dispersion medium for dispersing the organic polymer composite inorganic fine particles is not particularly limited, but preferably water or an organic solvent in which the organic polymer in the organic polymer composite inorganic fine particles can be dissolved, more preferably water or , Organic solvents such as esters, alcohols, ketones or aromatic hydrocarbons can be used. By using such a dispersion medium, the storage stability of the dispersion is excellent, and the dispersion stability in various organic solvents is also excellent.

  The content of the organic polymer composite inorganic fine particles in the dispersion is not particularly limited, but is preferably 25 to 50% by mass, more preferably 30 to 40% by mass. When the content is less than 25% by mass, a predetermined gap cannot be obtained at the time of drying, and the thickness of the ink receiving layer may be insufficient, resulting in a decrease in ink absorbability. On the other hand, if it exceeds 50% by mass, the coating workability is lowered, and it may be difficult to obtain a uniform and smooth coating film.

  The method for producing the dispersion is not particularly limited. For example, the method for directly obtaining the reaction mixture obtained in the production of the organic polymer composite inorganic fine particles as the dispersion, or the method for obtaining the organic polymer composite inorganic fine particles. The organic polymer composite inorganic fine particles are isolated from the reaction mixture obtained by removing the solvent in the obtained reaction mixture by distillation or the like and dispersing it in another dispersion medium, and the reaction mixture obtained in the production of the organic polymer composite inorganic fine particles. Thereafter, a method of dispersing in an arbitrary dispersion medium is exemplified.

  Next, a film-forming composition containing the organic polymer composite inorganic fine particle dispersion produced as described above is prepared. Since the film-forming composition contains the organic polymer composite inorganic fine particle dispersion produced as described above, the film-forming composition also contains a dispersion medium contained in the dispersion. Here, the content of the organic polymer composite inorganic fine particles in the film-forming composition is not particularly limited and can be appropriately determined. Preferably, it is 20-45 mass% with respect to the film-forming composition whole quantity, More preferably, it is 25-35 mass%. When the content is less than 20% by mass, a predetermined gap cannot be obtained at the time of drying, and the thickness of the ink receiving layer may be insufficient, resulting in a decrease in ink absorbability. On the other hand, if it exceeds 45% by mass, the coating workability is lowered, and it may be difficult to obtain a uniform and smooth coating film.

  The ink jet recording medium of the present invention can be produced by applying the film-forming composition prepared above onto a support to form an ink receiving layer.

  In the present invention, the film-forming composition used for forming the ink receiving layer is not particularly limited as long as it contains organic polymer composite inorganic fine particles, but preferably contains a crosslinking agent. . Thereby, in the formed ink receiving layer, the organic polymer portions of the organic polymer composite inorganic fine particles are cross-linked, and the properties such as weather resistance, heat resistance and surface hardness of the ink receiving layer can be improved.

  That is, the second of the present invention is an ink receiving layer obtained by coating a film-forming composition containing at least organic polymer composite inorganic fine particles formed by chemically bonding an organic polymer to inorganic fine particles and a crosslinking agent on a support. An ink jet recording medium.

  The second invention is characterized in that the ink receiving layer is formed by coating a film-forming composition containing at least organic polymer composite inorganic fine particles and a crosslinking agent on a support. Therefore, a preferred embodiment other than the fact that the film-forming composition contains a crosslinking agent is the same as in the first invention.

  Here, the relationship between the crosslinking agent and the organic polymer composite inorganic fine particles contained in the film-forming composition will be described below.

  In the present invention, as described above, when the film-forming composition contains a crosslinking agent in addition to the organic polymer composite inorganic fine particles, various properties of the ink receiving layer can be improved. This is because the organic polymer composite inorganic fine particles are crosslinked with each other by the contained crosslinking agent to form a network structure. Therefore, in order to be crosslinked by the crosslinking agent, it is necessary that the organic polymer composite inorganic fine particles have a functional group capable of reacting with the crosslinking agent. Here, as long as the organic polymer composite inorganic fine particle has a functional group capable of reacting with a crosslinking agent in the fine particle, the location, number and other aspects of the functional group are not particularly limited. Preferably it is present on the organic polymer. According to this aspect, as a result of the organic polymer being crosslinked by the crosslinking agent, the characteristics of the ink receiving layer can be effectively improved.

  Here, preferred embodiments of the crosslinking agent and the functional group on the organic polymer capable of reacting with the crosslinking agent are not particularly limited. For example, the organic polymer has a functional group (X), and the crosslinking agent has the functional group. The aspect which has 2 or more of functional groups (Y) which can react with (X) is mentioned. According to this aspect, as a result of effective cross-linking between organic polymers, an ink jet recording medium having an ink receiving layer that effectively suppresses clogging of voids between fine particles and has excellent properties such as ink absorbability is provided. sell.

  Here, the type of the functional group (X) and the functional group (Y) that can participate in the cross-linking reaction is not particularly limited, and can be appropriately determined within a range that does not impair the characteristics of the ink receiving layer. Although it does not restrict | limit especially as said functional group, For example, functional groups, such as a hydroxyl group, a carboxyl group, an amino group, an epoxy group, a mercapto group, an oxazoline group, and an aldehyde group, are illustrated. On the other hand, the functional group (Y) is not particularly limited, and examples thereof include an isocyanate group, an epoxy group, a hydroxyl group, a mercapto group, an amino group, an unsaturated group, and a carboxyl group. Such a functional group can be preferably used because it does not cause an undesirable reaction with, for example, the organic polymer composite inorganic fine particles and does not particularly impair the characteristics of the ink receiving layer. In addition, these functional groups (X) and functional groups (Y) may be used alone or in combination of two or more as long as they are within the range of combinations that can react with each other. Good.

  Here, the addition amount of the cross-linking agent in the film-forming composition is such that the functional group (Y) of the cross-linking agent is contained in an equivalent mole amount with respect to the functional group (X) of the organic polymer. Is preferred. Specifically, the molar ratio ((Y) / (X)) of the functional group (Y) to the functional group (X) is preferably 0.6 to 1.6, more preferably 0.8 to 1. .2. If the molar ratio is less than 0.6, the adhesion of the organic polymer composite inorganic fine particles to the support and the durability of the ink receiving layer may be lowered. On the other hand, when the molar ratio exceeds 1.6, voids formed in the ink receiving layer by the added crosslinking agent are reduced, and as a result, characteristics such as ink absorbability may be deteriorated.

  Moreover, the method in particular of apply | coating the film-forming composition on a support body is not restrict | limited, A conventionally well-known method can be used suitably. For example, the film-forming composition can be coated on a support by the method described in JP-A 2003-48368, page 10. Further, the film-forming composition may be used within a range not losing characteristics, for example, surfactants, pigments, dyes, fixing agents, ultraviolet absorbers, antioxidants, dispersants, antifoaming agents, leveling agents, antiseptics. Conventionally known additives such as an agent, a fluorescent brightening agent, a viscosity stabilizer, a pH adjuster, a light resistance stabilizer, an antistatic agent, a matting agent, an antiblocking agent, and a film forming aid may be contained. By containing the additive for the film-forming composition, it is possible to improve the ink-jet recording property of the obtained ink-receiving layer, the storage stability of the recording medium, the characteristics of the film-forming composition, and the like. In the ink jet recording medium of the present invention, the ink receiving layer need not be a single layer, and may have two or more layers. Further, the ink receiving layer need not be directly coated on the support, and an intervening layer may be formed between the support and the ink receiving layer.

  In the inkjet recording medium of the present invention, the support having an ink receiving layer on the surface is not particularly limited, and a conventionally known support can be used, and any of opaque, translucent and transparent can be used depending on the application. . Here, for example, when used as a recording sheet for an overhead projector (OHP), the support is usually transparent. The support is not particularly limited, and a conventionally known support can be used. Examples of the support include polyester resin, diacetate resin, triacetate resin, acrylic resin, polycarbonate resin, polyvinyl chloride resin, polyvinylidene chloride resin, polyimide resin, polystyrene resin, polyethylene phthalate resin, polyethylene naphthalate resin, nylon resin, Polyvinyl alcohol copolymer, ethylene-vinyl alcohol copolymer, ethylene-vinyl acetate copolymer, polyethylene resin, polyurethane resin, polystyrene resin, cellophane, celluloid, synthetic paper, resin-coated paper, opaque film, foam film, non-woven fabric, Synthetic resin moldings, plastic films, fine paper, corrugated paper, coated paper, wooden materials, metal-based building materials, metal structures such as metal structures and metal steel plates, cement-based materials such as cement-based building materials, concrete Concrete materials such bets building materials and concrete structures, as well as glass plate and the like. The thickness of these supports is not particularly limited, and can be appropriately determined according to the type of support, purpose of use, and the like.

  Furthermore, various back coat layers can be formed on the support of the present invention in order to impart properties such as antistatic properties, transportability, and anti-curl properties. The backcoat layer is not particularly limited, but may contain conventionally known additives such as inorganic or organic antistatic agents, hydrophilic binders, latexes, curing agents, pigments, surfactants and the like.

  In the ink jet recording medium of the present invention, as described above, various materials can be used as the support. Therefore, according to the present invention, for example, an inkjet recording medium (such as a signboard, a giant poster, and a banner) placed outdoors, an OHP sheet made of various resins having excellent properties such as ink absorbability and transparency, and inkjet recording are recorded. Clothing etc. can be provided.

  Hereinafter, the present invention will be described in more detail with reference to examples.

[Synthesis of polymerizable polysiloxane]
In a 300 mL four-necked flask equipped with a stirrer, a thermometer and a condenser tube, 144.5 g of tetramethoxysilane as a condensable compound, 23.6 g of γ-methacryloxypropyltrimethoxysilane as a silane coupling agent, and water as a solvent 19.0 g, 30.0 g of methanol, and 5.0 g of Amberlyst 15 (Rohm & Haas Japan Co.), which is a cation exchange resin, were charged and stirred at 65 ° C. for 2 hours for reaction. After the reaction mixture was cooled to room temperature, a distillation column was provided, the temperature was raised to 80 ° C. under normal pressure over 2 hours, and the temperature was maintained at 80 ° C. until methanol was not distilled. Further, the reaction was continued under a pressure of 200 mmHg until the methanol was not distilled at 90 ° C., and the reaction was further advanced.

After the reaction mixture was cooled again to room temperature, Amberlyst 15 was filtered off to obtain polymerizable polysiloxane (S-1) having a number average molecular weight of 1,800. The number average molecular weight was measured by HLC-8020 gel permeation chromatography and calculated in terms of polystyrene. At this time, TSKgel G3000H, TSKgel G2000H, and TSKgel GMH _XL (manufactured by Tosoh Corporation) were used as columns, and tetrahydrofuran was used as the solvent.

[Synthesis of organic polymers]
Into a 1 L flask equipped with a stirrer, a dripping port, a thermometer and an N ₂ gas introduction port, 200 g of n-butyl acetate was charged as a solvent, and then N ₂ gas was introduced, and the temperature in the flask was increased to 110 ° C. while stirring. Raised. Next, a mixed solution of 20 g of the polymerizable polysiloxane (S-1) synthesized above, 80 g of methyl methacrylate, 80 g of ethyl acrylate, 20 g of 2-hydroxyethyl methacrylate and 6 g of 2,2′-azobisisobutyronitrile was added to the dropping port. More dropwise over 2 hours. Thereafter, the mixture was stirred for 1 hour while maintaining at 110 ° C.

  Next, 0.4 g of 1,1′-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane was added twice every 30 minutes, and the reaction was allowed to proceed by further heating for 2 hours to obtain a number average molecular weight. Obtained an n-butyl acetate solution of an organic polymer (P-1) having a molecular weight of 12,000. The number average molecular weight was measured by the same method as described above. Moreover, the non-volatile polymer solid content of the obtained organic polymer (P-1) solution was 49.0%. The polymer solid content was measured by weighing 1 g of a sample, drying it at 105 ° C. for 1 hour with a hot air drier, and then calculating the percentage of the pre-drying weight as the polymer solid content.

[Preparation of organic polymer composite inorganic fine particle dispersion]
A 500 mL four-necked flask equipped with a stirrer, two dropping ports (dropping port A and dropping port B) and a thermometer was charged with 200 g of n-butyl acetate as a solvent and 50 g of methanol, and the temperature in the flask was set to 20 ° C. It was adjusted. Next, while stirring, a mixed solution A of an organic polymer (P-1) synthesized in the above-described organic polymer (P-1) 20 g, a condensable compound 30 g of tetramethoxysilane and 20 g of n-butyl acetate is added from a dropping port A. A mixed solution B of 20 g of 25% aqueous ammonia and 20 g of methanol was added dropwise from the dropping port B over 1 hour. Next, the mixture is stirred at 20 ° C. for 2 hours, and then a distillation column is provided. Under a pressure of 40 kPa, the temperature in the flask is increased to 100 ° C., and ammonia, methanol, water, and n-butyl acetate are distilled off. An organic polymer composite inorganic fine particle dispersion (Z-1) having an inorganic fine particle concentration of 34.8% by mass was obtained.

  The concentration was calculated by drying the obtained organic polymer composite inorganic fine particle dispersion at 130 ° C. for 24 hours under a pressure of 100 mmHg, and calculating the percentage of the mass after drying relative to the mass of the dispersion before drying.

  In addition, elemental analysis was performed on the remaining amount after drying in the measurement of the concentration of the organic polymer composite inorganic fine particles, and the inorganic content in the organic polymer composite inorganic fine particles was calculated as a percentage of the ash mass to the post-dry mass. As a result, the inorganic content in the organic polymer composite inorganic fine particles was 58.0% by mass.

  Furthermore, the average particle size of the organic polymer composite inorganic fine particles was measured using a submicron particle size analyzer (NICOMP MODEL 370: manufactured by Nozaki Sangyo Co., Ltd.). As a result, the particle size was about 55 nm. Further, the obtained dispersion (Z-1) was sealed in a Gardner viscosity tube and stored at 50 ° C. for 1 month. However, aggregation and sedimentation of particles and an increase in the viscosity of the dispersion were not observed.

[Preparation of OHP sheet]
An ink jet recording medium (OHP sheet) was prepared using the organic polymer composite inorganic fine particle dispersion (Z-1) obtained above.

Example 1
First, a solution obtained by diluting 10 g of Sumidur N3200 (isocyanate curing agent: manufactured by Sumika Bayer Urethane Co., Ltd.), which is a cross-linking agent, with 40 g of ethyl acetate was applied to a PET film having a thickness of 100 μm using a bar coater # 24. It was dried at 80 ° C. for about 1 minute by a dryer. Next, 90 g of the organic polymer composite inorganic fine particle dispersion (Z-1) obtained above, 2 g of Sumidur N32002, 6 g of ethyl acetate and 0.04 g of dibutyltin dilaurate as a curing accelerator were mixed and stirred well. The composition for coating was applied onto the PET film using a bar coater. Thereafter, the sheet was dried with a hot air dryer at 80 ° C. for about 1 minute to obtain an OHP sheet (1) having a dry thickness of the ink receiving layer of 25 μm.

Example 2
An OHP sheet (2) was obtained in the same manner as in Example 1 except that the amount of Sumidule N3200 added to the film-forming composition was 4 g.

Example 3
An OHP sheet (3) was obtained in the same manner as in Example 1 except that the amount of Sumidule N3200 added to the film-forming composition was 8 g.

Example 4
An OHP sheet (4) was obtained in the same manner as in Example 1 except that Sumidur N3200 was not added to the film-forming composition.

Comparative Example 1
First, a 10% by mass aqueous solution of PVA-CST (polyvinyl alcohol: manufactured by Kuraray Co., Ltd.) was applied onto a PET film having a thickness of 100 μm using a bar coater. Thereafter, the sheet was dried with a hot air dryer at 80 ° C. for about 15 minutes to obtain an OHP sheet (5) having a PVA ink receiving layer with a dry thickness of 25 μm.

Comparative Example 2
First, 100 g of Snowtex C (colloidal silica, particle size 20 to 40 μm: manufactured by Nissan Chemical Co., Ltd.) and 20 g of 10 mass% aqueous solution of PVA-CST (polyvinyl alcohol: manufactured by Kuraray Co., Ltd.) were mixed and stirred well. The product was coated on a 100 μm thick PET film using a bar coater. Thereafter, the sheet was dried at 80 ° C. for about 15 minutes with a hot air dryer to obtain an OHP sheet (6) having a PVA ink receiving layer with a dry thickness of 25 μm.

Performance Evaluation Test About the OHP sheets (1) to (6) obtained above, a color pattern is printed using an ink jet printer MJ-5000C (manufactured by Epson Corporation), ink drying property, color development property, dot reproducibility, water resistance And transparency were evaluated according to the following methods and evaluation criteria. The results are shown in Table 1.

1. Ink drying property Immediately after the color pattern was printed, the copy paper was superimposed on the print portion, and after rubbed well with a finger from above, the extent to which the print pattern was transferred to the copy paper was visually observed. The evaluation criteria are as follows.

○: not transferred at all;
○ △: Very slightly transferred;
Δ: Slightly transferred;
X: Pretty transferred.

2. When the color printed on the ink jet paper is used as a standard, and the printed part of the OHP sheet is observed directly (whether the color is reproduced or not) Middle, described as “direct view”) and when projected onto a screen using an OHP projector (denoted as “projection” in the table). The evaluation criteria are as follows.

○: Color development was good;
Δ: Slightly different color tone;
X: The color developability was poor.

3. Dot reproducibility The color pattern printed on the OHP sheet was enlarged and observed using a magnifying glass, and the dot shape was evaluated. The evaluation criteria are as follows.

○: It was a beautiful circle;
○ △: Very slightly deformed;
Δ: Slightly deformed;
×: It was considerably deformed.

4). Water resistance A few drops of water were dropped on the printed part, and the state of the ink receiving layer immediately after rubbing 10 times with a finger was evaluated. The evaluation criteria are as follows.

○: not changed;
○ △: ink melted very slightly;
Δ: Ink slightly melted;
X: The entire ink receiving layer was melted.

5). Transparency The presence or absence of transparency usable as an OHP sheet was evaluated by projecting using an OHP projector. The evaluation criteria are as follows.

○: There was no problem with transparency;
○ △: The projected image was slightly yellowish;
Δ: The projected image is slightly yellowish;
X: The projected image became very dark.

  As can be seen from Table 1, according to the present invention, the ink-receiving layer contains the organic polymer composite inorganic fine particles formed by chemically bonding the organic polymer to the inorganic fine particles. It can be seen that a recording medium is provided. This is because both the inorganic fine particles and the organic polymer as the binder are secured in an amount that can sufficiently exhibit their respective functions, and the clogging of the void portion by the organic polymer is effectively suppressed, so that the void portion is sufficient. It is thought that this is because

Claims (5)

  An ink jet recording medium comprising an ink receiving layer containing organic polymer composite inorganic fine particles formed by chemically bonding an organic polymer to inorganic fine particles on a support.   An ink jet recording medium comprising an ink receiving layer formed by coating on a support a film-forming composition containing at least organic polymer composite inorganic fine particles obtained by chemically bonding an organic polymer to inorganic fine particles and a crosslinking agent.   The inkjet recording medium according to claim 2, wherein the organic polymer has a functional group (X), and the cross-linking agent has two or more functional groups (Y) capable of reacting with the functional group (X).   The functional group (X) is selected from the group consisting of a hydroxyl group, a carboxyl group, an amino group, an epoxy group, a mercapto group, an oxazoline group and an aldehyde group, and the functional group (Y) is an isocyanate group, an epoxy group, a hydroxyl group, a mercapto group, The inkjet recording medium according to claim 3, which is selected from the group consisting of an amino group, an unsaturated group, and a carboxyl group.   The support is polyester resin, diacetate resin, triacetate resin, acrylic resin, polycarbonate resin, polyvinyl chloride resin, polyvinylidene chloride resin, polyimide resin, polystyrene resin, polyethylene phthalate resin, polyethylene naphthalate resin, nylon resin, polyvinyl alcohol Copolymer, ethylene-vinyl alcohol copolymer, ethylene-vinyl acetate copolymer, polyethylene resin, polyurethane resin, polystyrene resin, cellophane, celluloid, synthetic paper, resin-coated paper, opaque film, foamed film, non-woven fabric, synthetic resin 5. The material according to claim 1, which is selected from the group consisting of a molded body, plastic film, fine paper, corrugated paper, coated paper, wooden material, metal-based material, cement-based material, concrete-based material, and glass plate. Inkjet recording medium according to Re preceding paragraph.