JP2009160867A - Surface coating liquid, inkjet recording method, and inkjet recording apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface coating liquid which can improve the scratch resistance of a recorded article without spoiling the texture of a recording medium or the picture quality of an image being recorded with a pigment ink, and also, to provide an inkjet recording method and an inkjet recording apparatus which enables the superior image formation. <P>SOLUTION: This surface coating liquid is applied to a region which includes at least an image formed on the recording medium by using the pigment ink containing a pigment. The surface coating liquid contains at least a resin A which forms a resin layer on the surface of a pigment layer, and a resin B which is fixed by penetrating into pores of the pigment layer. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a surface coating solution for coating the surface of an image recorded using pigment ink by an inkjet method, an inkjet recording method and an inkjet recording apparatus using the surface coating solution.

  In recent years, along with high-definition of images formed by the ink jet method, ink jet recording apparatuses have been widely used in public exhibition uses such as photographs, posters and graphic prints, and commercial print uses. For this reason, the request | requirement with respect to improving robustness, such as long-term storage property in the image obtained, is increasing.

  Inks used in the ink jet recording method are roughly classified into dye inks containing dyes as color materials and pigment inks containing pigments as color materials. In the dye ink, a dye is dissolved in a molecular state in an aqueous medium. For this reason, the recorded matter formed using the dye ink has a characteristic that it has high transparency and excellent color developability. On the other hand, there is a problem that a recorded matter formed using dye ink tends to fade due to ultraviolet rays or active gas in the air. On the other hand, in the pigment ink, the pigment is present in a dispersed state in the aqueous medium. For this reason, the recorded matter formed using the pigment ink is excellent in fading resistance due to long-term storage.

  In recent years, due to advances in pigment-related technologies, ink jet recording images can achieve both long-term storage properties obtained with images formed with pigment inks and high color development properties comparable to images formed with dye inks. It is possible to provide pigment ink. For this reason, ink jet recording apparatuses using pigment inks have been popularized, mainly for commercial printing applications such as photographs and posters, which have a high demand for storing recorded matter for a long period of time.

  However, it has been pointed out that as a problem in the case of using pigment ink, an image recorded on a recording medium having high surface smoothness such as glossy paper is easily damaged. For example, there are cases where the image is severely damaged or peeled off due to contact that occurs during the handling of the recorded material, such as rolling the recorded material or sticking it to the wall.

  An ink jet recording medium is formed by forming an ink receiving layer for absorbing ink on a base material such as paper or film. The ink receiving layer contains a large amount of inorganic fine particles such as silica and alumina that have high absorbability of the aqueous medium constituting the ink in order to suppress bleeding of the ink. In particular, glossy paper requires high surface smoothness, and therefore, submicron order inorganic fine particles are often used as a material constituting the ink receiving layer. The gap between the inorganic fine particles in the ink receiving layer of the glossy paper, that is, the pore diameter is in the submicron order because it is proportional to the particle diameter of the inorganic fine particles.

  On the other hand, the pigment in the pigment ink is dispersed as particles having a diameter of about 100 nm (nanometers). For this reason, when the particle diameter of the pigment is larger than the pore diameter of the ink receiving layer, the pigment cannot enter the inside of the ink receiving layer, and remains on the surface of the ink receiving layer as if it has been screened.

  In general, glossy paper often has a smaller gap between the ink receiving layers than the particle size of the pigment. For this reason, in an image formed using pigment ink, a pigment layer is formed on the surface of the ink receiving layer. For this reason, an external force such as when contacting the image is directly applied to the pigment layer constituting the image. As a result, the image formed with the pigment ink is easily damaged, and in some cases, the problem of scratch resistance such that the pigment layer is peeled off remarkably occurs.

  In order to solve the problems described above, the following proposals have been made. For example, there is a proposal related to a laminate film system that covers an image with a film (see Patent Documents 1 and 2). There is also a proposal regarding a liquid laminating method in which the surface of an image is covered with a liquid containing a resin or the like (see Patent Documents 2 to 6). The present invention relates to a post-processing method in which a pigment ink layer and an ink receiving layer are adhered by heating the recording medium after recording using an ink receiving layer containing a thermoplastic resin particle in the recording medium. There are proposals (see Patent Documents 7 and 8).

Japanese Patent Laid-Open No. 2000-153677 JP 2004-1446 A JP 2004-99766 A JP 2004-243625 A JP 2005-47053 A JP 2005-81754 A JP 2003-170650 A Japanese Patent Laid-Open No. 2005-169943

  However, it is known that the following problems occur in the conventional techniques described above. First, in the laminate film system, scratch resistance is obtained by covering the surface of an image with a resin film having high film strength. However, since the surface of the image is covered with the above-described film, there is a problem that the original texture of the paper (recording medium) itself is impaired. In addition, since the laminating process is performed off-line using an apparatus different from the recording apparatus after the image is formed, there is a problem that the cost increases.

  In the liquid laminating method, it is possible to perform in-line laminating using the same recording apparatus immediately after forming an image. However, the material constituting the conventional laminating liquid needs to have a film thickness of several μm (micrometer) in order to obtain sufficient scratch resistance. Thus, when the film thickness is large, there is a problem that the texture of the recording medium and the image quality of the image are impaired. For example, Patent Document 6 describes that a film thickness of 1 μm or less is formed, but at present, even higher scratch resistance is required.

  Furthermore, in the post-processing methods described in Patent Document 7 and Patent Document 8, in addition to the need to use a special recording medium, there is a problem that the apparatus becomes large in order to perform heat treatment. There is.

  Accordingly, an object of the present invention is to provide a surface coating liquid that can improve the scratch resistance of a recorded matter without impairing the texture of the recording medium or the image quality of the image recorded with the pigment ink. Another object of the present invention is to provide an ink jet recording method and an ink jet recording apparatus capable of forming the above-described excellent image.

  The above object is achieved by the present invention described below. That is, the present invention is a surface coating liquid that is applied to a region containing at least an image formed on a recording medium using a pigment ink containing a pigment, and at least a resin A that forms a resin layer on the surface of the pigment layer, And a surface coating solution characterized by containing a resin B that penetrates and fixes into the pores of the pigment layer. A particularly preferred form is a surface coating solution in which the resin A is an emulsion resin and the resin B is a water-soluble resin.

  In another embodiment of the present invention, a step of forming an image on a recording medium by an inkjet recording method using a pigment ink containing a pigment, and a surface coating solution containing a resin at least in a region containing the image The surface coating liquid of the present invention described above, and the film thickness in at least a part of the resin layer is 0. The inkjet recording method is characterized in that it is 10 μm or more and 1.00 μm or less.

  In another embodiment of the present invention, there is provided a means for forming an image on a recording medium by an inkjet recording method using a pigment ink containing a pigment, and a surface coating liquid containing a resin at least in a region containing the image. An ink jet recording apparatus having means for applying and forming a resin layer, wherein the surface coating liquid is the surface coating liquid of the present invention described above.

  According to the present invention, there is provided a surface coating liquid capable of improving the scratch resistance of a recorded matter without impairing the texture of a recording medium such as paper or the image quality of an image recorded with pigment ink. Further, according to the present invention, it is possible to provide an ink jet recording method and an ink jet recording apparatus capable of forming the above excellent recorded matter by providing the step of applying the surface coating liquid.

Hereinafter, the present invention will be described in more detail with reference to preferred embodiments.
The present inventors effectively prevent the occurrence of scratches due to scratches or the like in an image formed on glossy paper using pigment ink without impairing the image quality of the formed image and the texture inherent to the recording medium. The present invention has been studied to achieve the present invention. That is, in the present invention, the surface coating liquid of the present invention containing the resin A that forms the resin layer on the surface of the pigment layer and the resin B that penetrates and fixes inside the pores of the pigment layer is used to achieve the above-described. Solved the problem. Hereinafter, the scratch resistance of an image formed using a pigment ink will be described, and the configuration of the surface coating liquid of the present invention that can contribute to the improvement of the scratch resistance of the image will be described.

<Abrasion resistance of images formed using pigment ink>
Hereinafter, the scratch generation mechanism in an image formed using pigment ink on glossy paper, which is the greatest problem of the present invention, will be described. FIG. 1 is a schematic diagram showing a cross section of an image formed on a glossy paper using pigment ink. 1-1 is an ink receiving layer of glossy paper, and 1-2 is a pigment layer, that is, an image formed with pigment ink.

  When an image is formed on a glossy paper using pigment ink, the gap of the ink receiving layer is smaller than the particle diameter of the pigment as described above, so that the pigment cannot enter the ink receiving layer. Therefore, as shown in FIG. 1, a pigment layer 1-2 having a porous structure, that is, an image is formed on the surface of the ink receiving layer 1-1. When an image in such a state is rubbed, an external force is directly applied to the pigment layer constituting the image, so that scratches are likely to occur and a problem arises in scratch resistance.

  The problem of scratch resistance can be effectively solved by applying the surface coating liquid of the present invention to an image formed with a pigment ink having the above-described characteristics. The reasons for this can be considered as follows. FIG. 2 shows that a pigment layer having a porous structure as shown in FIG. 1 contains a resin A that forms a resin layer on the surface of the pigment layer, and a resin B that penetrates and fixes into the pores of the pigment layer. It is a schematic diagram of the fixing process when a surface coating solution is applied. First, in a region including at least an image (pigment layer 2-4) formed on a recording medium having an ink receiving layer 2-5 using an ink containing a pigment, resin A (2-2) and resin B (2- A surface coating solution 2-1 containing 3) is applied [see FIG. 2 (a)]. When such a surface coating solution comes into contact with the pigment layer 2-4, the resin B (2-3) penetrates into the pigment layer 2-4 together with the aqueous medium in the surface coating solution [FIG. 2 (b). reference]. At that time, since the fluidity of the resin B (2-3) decreases as the aqueous medium is absorbed by the recording medium, the resin B (2-3) is fixed inside the pores of the pigment layer. . It is considered that the densified pigment layer 2-7 is formed by the resin B exhibiting such behavior. On the other hand, the resin A (2-2) does not penetrate into the pigment layer 2-4 like the resin B, and forms the resin layer 2-6 on the surface of the pigment layer 2-4. As a result, the resin layer 2-6 formed of the resin A (2-2) and the pigment layer 2-7 densified by the resin B (2-3) are firmly bound to each other [ See FIG. 2 (c)]. When the surface coating solution of the present invention containing the resin A forming the resin layer on the surface of the pigment layer and the resin B penetrating into the pores of the pigment layer and fixing is applied, the resins A and B are Thus, it is considered that the scratch resistance of the pigment layer (that is, the image) could be improved.

<Surface coating solution>
The present inventors have conducted a detailed study on a resin composition that can make the above-described behavior effective when a surface coating solution is applied on a pigment layer having a porous structure. As a result, it was found that the scratch resistance of the image can be improved more remarkably by using a surface coating solution containing resin A and resin B as described in detail below. In addition, it is preferable that the surface coating liquid and the resin layer of the present invention are substantially transparent, that is, use a resin having transparency within a range in which the image quality does not deteriorate. Specifically, it is preferable that the difference between the image density of the recorded material to which the surface coating liquid is applied and the image density of the recorded material to which the surface coating liquid is not applied is 0.3 or less, more preferably 0.1 or less. The image density can be measured using a reflection densitometer or the like.
Hereinafter, each component which comprises the surface coating liquid of this invention is demonstrated.

(Resin A forming a resin layer on the surface of the pigment layer)
The present inventors have studied a resin A that can form a better resin layer on the surface of a pigment layer having a porous structure when a coating liquid is applied to an area including an image on a recording medium. As a result, it was found that an emulsion resin as described below is preferably used as the resin A. Specific examples of the emulsion resin suitable as the resin A that is a constituent material of the surface coating liquid of the present invention include the following. Examples thereof include acrylic resins, urethane resins, polyester resins, vinyl acetate resins, vinyl chloride resins and ethylene-vinyl acetate copolymer resins, or composite resins thereof. From the viewpoint of imparting high transparency and film strength to the resin layer formed by the surface coating liquid of the present invention, among the above, it is preferable to use an acrylic resin, a urethane resin, a polyester resin, or the like. These emulsion resins can be synthesized by a known method such as an emulsion polymerization method or a phase inversion emulsification method. A commercially available emulsion resin may also be used. In order to further reduce the occurrence of scratches on the image, it is also preferable to select a resin in which the resin layer formed of the emulsion resin has slipperiness. For this purpose, for example, an emulsion resin such as a silicone resin, a fluorine resin, or a wax resin may be used. This point will be described later. As described above, it is necessary for the resin A to form a resin layer on the surface of the pigment layer. However, as long as the effect of the present invention is not impaired, a part of the resin A is applied to the pigment layer or the recording medium. It may be in an infiltrated state.

[Particle diameter of resin A]
The resin A constituting the surface coating solution of the present invention has a low permeability into the pores of the pigment layer having a porous structure when the coating solution is applied to the region containing the image, and the surface of the pigment layer It is preferable to use an emulsion resin having such a characteristic that the resin layer can be adhered to the resin. For this purpose, the emulsion resin is preferably configured as follows. First, the particle size of the emulsion resin at that time will be described. As described above, the pigment layer has a porous structure. Therefore, when the particle diameter of the resin A is larger than the pore diameter of the pigment layer, it is difficult to penetrate into the pores of the pigment layer, and thus the resin layer can be formed on the surface of the pigment layer. Here, the size of the pore diameter in the pigment layer can be considered that pores having a diameter comparable to this are formed since the particle diameter of the pigment is generally several tens to several hundreds of nm. . Therefore, the emulsion resin A constituting the surface coating solution of the present invention preferably has a 50% volume average particle diameter (D ₅₀ ) of the resin A of 20 nm or more and 300 nm or less. If D ₅₀ of the resin A is less than 20 nm, increases small resin particles the particle diameter than the pore size of the pigment layer, many resin A penetrates into the pores of the pigment layer, formation of the resin layer is efficiently There is a risk that it will not be performed well. On the other hand, when D _{50 of} resin A is larger than 300 nm, the resin layer does not penetrate into the pores of the pigment layer and the resin layer can be formed on the surface of the pigment layer, but the smoothness of the resin layer decreases, The glossiness of the image may be reduced. In the present invention, the average particle diameter was measured by a dynamic light scattering method.

[Glass transition temperature of resin A]
The resin A constituting the surface coating solution of the present invention is not limited to the emulsion resin as described above, but is preferably a resin having the following characteristics. First, the glass transition temperature of the resin A is preferably 20 ° C. or higher. In general, since the molecular structure of a resin can flow when the temperature is higher than the glass transition temperature, stickiness is generated and a sticky feeling is likely to occur. That is, it is not preferable that the glass transition temperature of the resin A used in the present invention is less than 20 ° C., because a sticky feeling may occur in the resin layer even at room temperature. Moreover, it is preferable that the glass transition temperature of resin A is 100 degrees C or less. When the glass transition temperature exceeds 100 ° C., the resin film-forming property is lowered, the resin film structure is hardened, and the brittleness is increased. Cracks may easily occur. From the above, in the present invention, the glass transition temperature of the resin A is preferably 20 ° C. or higher and 100 ° C. or lower. In addition, the glass transition temperature of resin can be adjusted by selecting the monomer which comprises resin suitably.

[Molecular weight of Resin A]
Moreover, as resin A which comprises the coating liquid of this invention, it is preferable that it is a molecular weight of 5,000 or more and 200,000 or less by the weight average molecular weight (Mw) of polystyrene conversion. This is because the strength of the resin layer is greatly affected by the degree of entanglement of the resin molecular chains. If the weight average molecular weight of the resin A is less than 5,000, the strength of the resin layer may not be sufficiently obtained. In this case, when producing a plurality of recorded materials, even if the recording surface of the previously prepared recording material is an extremely light contact such as contacting the back surface of the recording material prepared later, scratches are generated. There are things to do. That is, the image may not be sufficiently scratch resistant. On the other hand, if the weight average molecular weight of the resin A is greater than 200,000, when using an emulsion resin, the dispersion of the particle size distribution increases, and it may be difficult to obtain the resin A having a desired particle size. .

[Slidability of Resin A]
In the present invention, the coating liquid of the present invention is preferably configured so that the resin layer formed on the surface of the pigment layer by the resin A in the coating liquid has slipperiness. When the friction coefficient of the resin layer formed on the surface of the pigment layer by the resin A is small (that is, has slipperiness), the scratch resistance of the recorded matter becomes more excellent. For example, in order to reduce the occurrence of scratches on the image by suppressing the trapping of the friction material on the local unevenness of the resin layer, such as when a sharp friction material such as a nail contacts the image, the pigment layer The dynamic friction coefficient μ _k of the resin layer formed on the surface is preferably 0.40 or less. Furthermore, it is particularly preferable that the coating liquid of the present invention is configured so that the dynamic friction coefficient μ _k of the resin layer is 0.30 or less. Thus, if the coating liquid of the present invention is configured so that the friction coefficient of the resin layer formed on the surface of the pigment layer is small, scratches can be obtained even when scratched with sharp frictional objects such as nails. It is possible to provide images that are difficult to stick. The lower limit of the dynamic friction coefficient μ _k of the resin layer is 0.00 or more.

The dynamic friction coefficient of the resin layer formed on the pigment layer surface as defined above can be measured, for example, by a wear test performed in the following procedure. Using polymethylmethacrylate (PMMA) as a friction material, horizontal against the vertical load force when a PMMA ball is moved at a predetermined load and speed in an area on an image (pigment layer) on which a resin layer is formed. It can be determined as a ratio of directional forces. The measurement as described above can be performed by using a surface property tester (trade name: Haydon Tribogear TYPE 14DR; manufactured by Shinto Kagaku). However, the measurement of the dynamic friction coefficient μ _k of the resin layer, which is a problem in the present invention, is not limited to the above-described device, and other devices can be used as long as the same driving is possible.

In order that the dynamic friction coefficient μ _k of the resin layer formed on the pigment layer surface with the surface coating solution of the present invention is 0.40 or less, it is important to select the resin A for forming the resin layer. From the viewpoint of lowering the dynamic friction coefficient of the resin layer formed on the pigment layer surface, it is preferable to use an emulsion resin such as a silicone resin, a fluorine resin, or a wax resin.

  Examples of silicone resins that can be used at this time include acrylic silicone copolymer resins and urethane silicone copolymer resins. In the present invention, it is particularly preferable to use an acrylic silicone copolymer resin obtained by copolymerizing a dimethyl silicone having a dimethylsiloxane group and an acrylic monomer. When such an acrylic silicone copolymer resin is used as a constituent material for the surface coating liquid, silicone is effectively oriented on the surface of the resin layer to be formed. It becomes possible to form the resin layer which has.

  Specific examples of the fluororesin include the following. Examples thereof include polytetrafluoroethylene, polychlorotrifluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, polyvinylidene fluoride, and polyvinyl fluoride. Moreover, an ethylene-tetrafluoroethylene copolymer, an ethylene-chlorotrifluoroethylene copolymer, a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, and the like can be given. Moreover, an ethylene-trifluoroethylene-hexafluoropropylene copolymer, a tetrafluoroethylene-acrylic copolymer, etc. are mentioned. A fluororesin aqueous dispersion in which these resins are dispersed in an aqueous medium can be preferably used.

  As the wax resin, synthetic polyethylene emulsion, carnauba wax, paraffin wax, microcrystalline wax, candelilla wax, Fischer-Tropsch wax, and the like can be used. Furthermore, among the wax-based resins described above, those having a melting point of 60 ° C. or higher are preferably used. In addition, when using a wax-type resin, the film | membrane intensity | strength of the resin layer formed may not fully be obtained. In such a case, an acrylic resin or the like that can form a resin layer having a high film strength as mentioned above can be used in combination.

(Resin B that penetrates and fixes inside the pores of the pigment layer)
The coating liquid of the present invention comprises a resin A capable of forming a resin layer on the surface of a pigment layer having a porous structure when the coating liquid is applied to a region containing an image on a recording medium, and pores of the pigment layer. It contains at least a resin B that penetrates and fixes inside. According to the study by the present inventors, when an emulsion resin is used as the resin A and a water-soluble resin is used as the resin B, the resins A and B have the above-described functions well. The object of the present invention can be achieved in a state where it is exerted stably and exhibits a more remarkable effect. As described above, the resin B needs to penetrate into the pores of the pigment layer and be fixed. However, as long as the effect of the present invention is not impaired, a part of the resin B is composed of the resin A. The resin layer or the recording medium may be permeated.

Resin A (emulsion resin) and resin B (water-soluble resin) in the surface coating liquid having such a configuration are different in the state of these resins existing in water (in the aqueous medium constituting the surface coating liquid). Can be distinguished. That is, since the resin B in this case has a high affinity for water constituting the aqueous medium, the resin B exists in a state where water molecules and resin molecules are uniformly mixed. That is, it is considered that the resin B tends to hardly exist in a state where a large number of resin molecules are associated with each other in water. Therefore, in the present invention, when measuring the particle size distribution by the dynamic light scattering method, it is difficult to confirm the particle size of the resin in water, specifically, 50% volume average particle size (D ₅₀ ) Is a water-soluble resin. The present inventors use the water-soluble resin defined as described above as the resin B, and use it in combination with the resin A, which is an emulsion resin, so that the water-soluble surface coating solution that provides the remarkable effects described above can be obtained. It was confirmed that

  This means that by performing particle size distribution measurement by the dynamic light scattering method, it is possible to verify whether or not the surface coating liquid of the present invention has the above configuration. That is, when the aqueous solution used as the surface coating solution for the image formed with the pigment ink is measured for particle size distribution by the dynamic light scattering method, the following measurement results can be obtained. It can be said that it is liquid. For example, as a result of the particle size distribution measurement by the dynamic light scattering method, the aqueous solution coexists with resin particles having an average particle size of about 20 to 300 nm and resin in which it is difficult to confirm the particle size of the resin in water. It is a case where it is confirmed that it is a thing.

  Specific examples of the water-soluble resin that can be used in the surface coating solution of the present invention include acrylic, urethane, polyester, or polyvinyl alcohol resins, or composite resins thereof.

  The ionicity of the resin B that is preferably used for the resin as described above is roughly classified into anionicity, nonionicity, and cationicity. In the present invention, it is particularly preferable to use an anionic or nonionic resin as the resin B. This is because when the cationic resin B is used, the resin B may not be sufficiently penetrated into the pores of the pigment layer. The reason why this occurs is considered as follows. First, a pigment layer formed by an ink containing an anionic pigment widely used for ink jet recording becomes anionic. In such a case, when the surface coating liquid using the cationic resin B is applied to the constituent material, the anionic pigment layer captures the cationic resin B, and therefore the resin inside the pores of the pigment layer. B penetration is less likely to occur. As a result, it is considered that the function of the resin B described above is not sufficiently exhibited, and the effects of the present invention brought about by the resins A and B cannot be sufficiently obtained. The ionicity of the resin B is preferably selected in consideration of the compatibility with the resin A in addition to the ionicity of the pigment layer. In general, when a resin having opposite ionicity is mixed in an aqueous medium, aggregation easily occurs. Therefore, either the ionicity of the resin A and the resin B is made uniform, or one of the resins is made nonionic. preferable.

When an anionic resin B is used, the following resins can be used. That is, acidic groups such as a carboxyl group (—COOH), a sulfonic acid group (—SO ₃ H), and a phosphoric acid group (—PO ₄ H) are introduced into the resin as mentioned above, and these acidic groups are introduced. A resin neutralized with a base or the like. Moreover, when using a nonionic thing as the resin B, the acrylic resin etc. which introduce | transduced many hydrophilic groups, such as polyvinyl alcohol and polyvinylpyrrolidone, or a hydroxyl group and an ethylene oxide group, etc. can be used.

[Glass transition temperature of resin B]
The resin B used in the present invention penetrates into the pores of the pigment layer and is fixed inside the pores of the pigment layer. In order to select the resin B having the function of penetrating into the pores of the pigment layer, it is also important to specify the glass transition temperature of the resin B. As a result of the study by the present inventors, when a thermoplastic resin having a glass transition temperature of 0 ° C. or less is used as the resin B, the penetration of the resin B into the pores of the pigment layer occurs more effectively. I understood. The present inventors presume this reason as follows. When the thermoplastic resin reaches a glass transition temperature or higher, the molecular structure can flow. For this reason, a thermoplastic resin having a glass transition temperature of 0 ° C. or lower has high fluidity at normal temperature and is less likely to stay on the surface of the pigment layer. As a result, the resin penetrates into the pores of the pigment layer having a porous structure. It is thought that. In addition, the resin B in which a water-soluble resin or the like is used exists in the surface coating solution in a state of being mixed with the aqueous medium in the surface coating solution at a molecular level, and thus penetrates into the pores of the pigment layer together with the aqueous medium. It is thought that. In addition, it is particularly preferable to use a resin B having a low glass transition temperature of 0 ° C. or lower because the image strength can be further increased. This is because, when the resin B having a low glass transition temperature penetrates into the pores of the pigment layer, the resin B has adhesiveness at room temperature, so that the ink reception between the resin layer and the pigment layer, and further between the pigment layer and the recording medium. It is considered that the adhesiveness with the layer is increased, and as a result, the strength of the image is improved.

(Contents of Resin A and Resin B and their mass ratio and film thickness of the resin layer)
The content _{A A} (mass%) of the resin A in the surface coating liquid of the present invention is 0.50 mass% or more and 15.0 mass% or less, and further 1.0 mass based on the total mass of the surface coating liquid. % Or more and 5.0% by mass or less is preferable. The content W _B (% by mass) of the resin B in the surface coating solution of the present invention is 0.10% by mass or more and 5.0% by mass or less based on the total mass of the surface coating solution. It is preferable that it is 20 mass% or more and 3.0 mass% or less. Note that W _A and W _B are masses of solids, respectively.

In the surface coating solution of the present invention, the mass ratio of the content of the resin A W _A (% by mass) and the content W _B (% by mass) of the resin _B (W _A / W B) is 1.0 or more 5. It is preferably 0 or less. Incidentally, each of W _A and W _B, relative to the surface coating solution total weight, is that the mass of solids. When W _A / W _B is less than 1.0, the ratio of resin B to be present in the resin layer is increased, there is a case where the film strength of the resin layer can not be obtained sufficiently. On the other hand, if W _A / W _B exceeds 5.0, the binding effect by the resin B may not be sufficiently obtained, and the scratch resistance may not be sufficiently obtained.

In the surface coating solution of the present invention, the total content W _A of the resin A (mass%) and the content W _B (% by mass) of the resin B (W _A + W _B), based on the surface coating solution total weight 1.0 mass% or more and 20.0 mass% or less is preferable. When W _A + W _B is less than 1.0 wt%, it may be difficult to form a resin layer having a sufficient thickness on the surface of the pigment layer. Further, when W _A + W _B exceeds 20.0 mass%, since the film thickness of the resin layer is too large, there are cases where the texture of the recording material may be impaired.

  In the present invention, the resin layer is preferably formed so that the film thickness of at least a part of the resin layer is from 0.10 μm to 1.00 μm. Here, the film thickness of the resin layer is the film thickness on the pigment layer, and can be measured by cutting the image and observing the cross section with an electron microscope. It is also possible to measure the level difference between the region where the resin layer is formed and the region where the resin layer is not formed using a surface roughness measuring device such as an atomic force microscope.

  If the thickness of the resin layer exceeds 1.0 μm, the change in the quality of the recorded matter may increase. Further, if the thickness of the resin layer is less than 0.10 μm, the effect of improving the scratch resistance may not be obtained. Here, when the film thickness exceeds 1.0 μm, the quality of the recorded material is deteriorated because the surface of the recording surface is smoothed and the shape is greatly different due to the increase in the film thickness, which may cause glare. It is thought to be the main cause.

  The reason why the effect of improving the scratch resistance cannot be obtained when the film thickness is less than 0.10 μm is considered to be due to unevenness on the surface of the pigment layer. A pigment layer formed mainly of pigment particles is considered to have surface irregularities that are approximately the same as the particle diameter of the pigment particles. If the film thickness is smaller than 0.10 μm, the resin layer becomes smaller than the irregularities on the surface of the pigment layer, and the area where the pigment layer cannot be coated increases extremely, so the effect of improving the scratch resistance may not be obtained.

(Aqueous medium)
In the surface coating solution of the present invention, it is preferable to use water or an aqueous medium containing water and a water-soluble organic solvent. It is preferable to use ion-exchanged water (deionized water) instead of general water containing various ions. The content (% by mass) of water in the surface coating solution is 40.0% by mass or more and 90.0% by mass or less, and further 50.0% by mass or more and 90.0% by mass based on the total mass of the surface coating solution. The following is preferable. Moreover, it is preferable that content (mass%) of the water-soluble organic solvent in surface coating liquid shall be 10.0 to 50.0 mass% on the basis of the total mass of surface coating liquid.

Specific examples of the water-soluble organic solvent that can be used in the surface coating solution of the present invention include the following.
Alkyl alcohols having 1 to 6 carbon atoms such as methanol, ethanol, isopropanol, propanediol, butanol, isobutanol, butanediol, pentanol, pentanediol, 1,2- or 1,6-hexanediol; Polyhydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, glycerin and hexanetriol. Polyhydric alcohol ethers such as ethylene glycol monoethyl ether and ethylene glycol monobutyl ether. Amines such as ethanolamine and triethanolamine.

(Other ingredients)
In addition to the components described above, the surface coating solution of the present invention may contain a moisturizing solid content such as urea, urea derivatives, trimethylolpropane, trimethylolethane and the like in order to maintain the moisturizing property. Furthermore, a surface active agent, a rust inhibitor, an antifoaming agent, an antiseptic agent, an antifungal agent, an antioxidant, an anti-reduction agent, and an evaporation accelerator are used to obtain a surface coating solution having desired physical properties as required. Further, various additives such as a viscosity modifier, a film forming aid, a dispersant, and an ultraviolet absorber may be contained.

  The surfactant that can be used in the surface coating solution of the present invention is an anionic surfactant, a nonionic surfactant, or an amphoteric surfactant as long as it does not affect the storage stability of the surface coating solution. Any of these can be used. Specific examples of the anionic surfactant include fatty acid salts, higher alcohol sulfate esters, liquid fatty oil sulfate esters, alkylallyl sulfonates, and the like. Specific examples of the nonionic surfactant include polyoxyethylene alkyl esters, polyoxyethylene sorbitan alkyl esters, acetylene alcohol, and acetylene glycol. The content (% by mass) of the surfactant is preferably 0.10% by mass or more and 5.0% by mass or less based on the total amount of the surface coating solution.

(Method for applying surface coating solution)
The surface coating liquid of the present invention is for applying to a region containing at least an image formed on a recording medium using a pigment ink, and particularly in forming an inkjet recording image using a pigment ink. Preferably used. In the ink jet recording method of the present invention, a step of forming an image on a recording medium with pigment ink by an ink jet recording method, and a step of forming a resin layer by applying a surface coating solution containing a resin to a region containing the image. And the surface coating solution of the present invention is used as the surface coating solution. In order to sufficiently obtain the effect of using the surface coating liquid of the present invention, the surface coating liquid is applied to the outermost surface of the pigment layer constituting the image when applied to an area including an image formed using the pigment ink. It is particularly preferable to ensure that it is applied.

  The method for applying the surface coating solution of the present invention is not particularly limited as long as it can be applied to the surface of the pigment layer, particularly the outermost surface of the pigment layer. For example, known methods such as a roll coater method, a bar coater method, a blade coater method, and a gravure coater method can be used. Further, a non-contact method such as a spray method or an ink jet method can also be used.

  In order to achieve the application of the surface coating liquid to the outermost surface of the pigment layer, specifically, the following is preferable. When applying the surface coating solution by roll coater method, bar coater method, blade coater method, gravure coater method or spray method, the surface coating solution can be applied by these methods after forming an image with pigment ink. preferable.

  Even when the surface coating liquid is applied by an inkjet method, it is preferable to apply the surface coating liquid after forming an image with the pigment ink in the same manner as described above. More specifically, the arrangement order of the recording heads for discharging the pigment ink and the surface coating liquid can be configured such that the pigment ink is discharged first and the surface coating liquid is discharged later. It is also possible to control so that the surface coating liquid is discharged to the unit area where the image formation with the pigment ink has been completed.

  In the ink jet recording method of the present invention, it is particularly preferable to apply the surface coating liquid to the recording medium by the ink jet method among the methods for applying the surface coating liquid described above. If the surface coating solution is applied by an inkjet method, the time from image formation to application of the surface coating solution is small, and the area to which the surface coating solution is applied can be controlled appropriately, so that an optimum surface coating layer is formed. This is because that.

  By applying the surface coating solution of the present invention to the outermost surface of the pigment layer by the method as described above, the scratch resistance of the recorded matter can be greatly improved. However, when the surface coating liquid is applied only to the area where the image is formed, there is a possibility that the difference in slipping between the area where the image is formed and the area where the image is not formed becomes large. For this reason, in order to obtain uniform slipperiness over the entire region of the recording medium (recorded material), it is preferable to apply the surface coating liquid of the present invention to the region where no image is formed. In addition, after applying the surface coating liquid to the recording medium, a drying process using hot air or infrared rays may be performed in order to accelerate the formation of the formed resin layer.

<Pigment ink>
Examples of the ink used in the present invention include an ink using a pigment as a coloring material conventionally used, particularly a pigment ink for inkjet recording. Hereinafter, the components of the pigment ink will be described.
(Color material)
Any colorant can be used as long as it is a pigment used in conventional inks. Specifically, it is preferable to use inorganic pigments such as carbon black and titanium white, or organic pigments such as phthalocyanine, monoazo, disazo, or quinacridone. The average particle diameter of the pigment is a volume average particle diameter in the ink and is 0.05 μm or more and 0.30 μm or less (50 nm or more and 300 nm or less), and further 0.07 μm or more and 0.20 μm or less (70 nm or more and 200 nm or less). Is preferred. The content (% by mass) of the pigment in the pigment ink is 1.0% by mass or more and 20.0% by mass or less, and further 2.0% by mass or more and 12.0% by mass or less based on the total amount of the ink. preferable. Furthermore, a general dye or the like can be used in addition to the pigment as the color material.

  As the pigment used for the black ink, it is preferable to use carbon black such as furnace black, lamp black, acetylene black and channel black. Specifically, for example, the following commercially available products can be used. Ray Van: 7000, 5750, 5250, 5000 ULTRA, 3500, 2000, 1500, 1250, 1200, 1190 ULTRA-II, 1170, 1255 (above, manufactured by Colombian Chemical). Black Pearls L, Legal: 330R, 400R, 660R, Mogul L, Monak: 700, 800, 880, 900, 1000, 1100, 1300, 1400, 2000, Vulcan XC-72R, Stirling: MS, NSX76 (above, manufactured by Cabot ). Color Black: FW1, FW2, FW2V, FW18, FW200, S150, S160, S170, Printex: 35, U, V, 140U, 140V, Special Black: 4, 4A, 5, 6 (above, manufactured by Degussa). No. 25, no. 33, no. 40, no. 45, no. 47, no. 52, no. 900, no. 2200B, no. 2300, MCF-88, MA7, MA8, MA100, MA600 (above, manufactured by Mitsubishi Chemical).

  Carbon black newly prepared for the present invention can also be used. Of course, the present invention is not limited to these, and any carbon black can be used. Further, the present invention is not limited to carbon black, and magnetic fine particles such as magnetite and ferrite, titanium black, and the like may be used as a pigment for black ink.

  Specifically, for example, the following can be used as the organic pigment. Water-insoluble azo pigments such as Toluidine Red, Toluidine Maroon, Hansa Yellow, Benzidine Yellow, and Pyrazolone Red. Water-soluble azo pigments such as Ritolol Red, Helio Bordeaux, Pigment Scarlet, and Permanent Red 2B. Derivatives from vat dyes such as alizarin, indanthrone and thioindigo maroon. Phthalocyanine pigments such as phthalocyanine blue and phthalocyanine green. Quinacridone pigments such as quinacridone red and quinacridone magenta. Perylene pigments such as perylene red and perylene scarlet. Isoindolinone pigments such as isoindolinone yellow and isoindolinone orange. Imidazolone pigments such as benzimidazolone yellow, benzimidazolone orange, and benzimidazolone red. Pilanthrone pigments such as pyranthrone red and pyranthrone orange. Indigo pigments, condensed azo pigments, thioindigo pigments, diketopyrrolopyrrole pigments. Flavanthrone yellow, acylamide yellow, quinophthalone yellow, nickel azo yellow, copper azomethine yellow, perinone orange, anthrone orange, dianthraquinonyl red, dioxazine violet, etc. Of course, the present invention is not limited to these.

  Moreover, when an organic pigment is shown by a color index (CI) number, the following can be used, for example. C. I. Pigment Yellow: 1, 2, 3, 12, 13, 14, 16, 17, 20, 24, 74, 75, 83, 86, 93, 95, 97, 98, 109, 110, 114, 117, 120, 125 . In addition, C.I. I. Pigment Yellow: 128, 129, 137, 138, 147, 148, 150, 151, 153, 154, 166, 168, 180, 185 and the like. C. I. Pigment Red: 5, 7, 9, 12, 48 (Ca), 48 (Mn), 49, 52, 53, 57 (Ca), 97, 112, 122, 123, 149, 168, 175, 176, 177, 180, 184, 192, 202, 207, etc. In addition, C.I. I. Pigment Red: 215, 216, 217, 220, 223, 224, 226, 227, 228, 238, 240, 254, 255, 272, etc. C. I. Pigment Blue: 1, 2, 3, 4, 15, 15: 1, 15: 2, 15: 3, 15: 4, 15: 6, 16, 22, 60, 64, and the like. C. I. Bat Blue: 4, 6, 19, 23, 42, etc. Of course, the present invention is not limited to these.

(Dispersant)
As the dispersant for dispersing the pigment as described above in the aqueous medium, any water-soluble resin can be used. Specifically, the dispersant used for the ink can be appropriately selected in consideration of the ink dispersion stability and storage stability, as well as ink jet characteristics such as ejection performance and ejection stability. As the dispersant, it is preferable to use a dispersant having a weight average molecular weight of 1,000 to 30,000, more preferably 3,000 to 15,000. The content (% by mass) of the dispersant in the ink is preferably 0.1% by mass or more and 5.0% by mass or less based on the total mass of the ink.

  As the dispersant, a hydrophilic resin or a salt thereof obtained by copolymerizing two or more monomers (of which at least one of them is a hydrophilic monomer) consisting of the following groups can be used. Specific examples of the monomer include styrene, a styrene derivative, vinyl naphthalene, a vinyl naphthalene derivative, and an aliphatic alcohol ester of an α, β-ethylenically unsaturated carboxylic acid. Further, acrylic acid, acrylic acid derivatives, maleic acid, maleic acid derivatives, itaconic acid, itaconic acid derivatives, fumaric acid, fumaric acid derivatives, and the like can be given.

  In addition, a dispersant having a cationic property such as an acrylic copolymer obtained by using a quaternized compound of the following compound with methyl chloride, dimethyl sulfate, benzyl chloride, epichlorohydrin, or the like can also be used. Specific examples of such monomers include N, N-dimethylaminoethyl (meth) methacrylate, N, N-dimethylamino (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide and the like.

  In the present invention, it is particularly preferable to use a water-soluble resin having a structure such as a block copolymer or a graft copolymer as the dispersant. These resins have distinctly separated hydrophobic and hydrophilic parts in their molecular structure, and these resins exhibit strong adsorptive power to hydrophobic pigments, so the dispersibility of pigments in aqueous media is very good. Can be. In the present invention, it is particularly preferable to use a block-type water-soluble resin described in Japanese Patent No. 2635235 and Japanese Patent No. 2675965.

(Aqueous medium)
It is preferable to use water or an aqueous medium containing water and a water-soluble organic solvent for the pigment ink. It is preferable to use ion-exchanged water (deionized water) instead of ordinary water containing various ions. The water content (% by mass) in the pigment ink is 10.0% by mass or more and 90.0% by mass or less, and further 30.0% by mass or more and 80.0% by mass or less based on the total mass of the ink. It is preferable. Further, the content (% by mass) of the water-soluble organic solvent in the pigment ink is 3.0% by mass or more and 50.0% by mass or less, and further 3.0% by mass or more and 40.0% based on the total mass of the ink. It is preferable to set it as mass% or less.

  Specific examples of the water-soluble organic solvent used for the pigment ink include the following. Alkyl alcohols having 1 to 6 carbon atoms such as methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, tert-butanol, pentanol and hexanol. C3-C6 diols such as propanediol, butanediol, pentanediol, and hexanediol. Amides such as dimethylformamide and dimethylacetamide. Ketones or ketoalcohols such as acetone and diacetone alcohol. Ethers such as tetrahydrofuran and dioxane. Polyalkylene glycols such as polyethylene glycol and polypropylene glycol. Alkylene glycols having 2 to 6 carbon atoms such as propylene glycol, butylene glycol, triethylene glycol, 1,2,6-hexanetriol, thiodiglycol, hexylene glycol, diethylene glycol and the like. Alkyl ether acetates such as polyethylene glycol monomethyl ether acetate. Glycerin. Alkyl ethers of polyhydric alcohols such as ethylene glycol monomethyl (or ethyl) ether, diethylene glycol methyl (or ethyl) ether, triethylene glycol monomethyl (or ethyl) ether. N-methyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone and the like. Of these, polyhydric alcohols such as diethylene glycol and triethylene glycol, and alkyl ethers of polyhydric alcohols such as triethylene glycol monomethyl (or ethyl) ether are particularly preferable.

  The pigment ink used in the present invention has an ethanol or isopropyl alcohol (2-propanol) content of 1.0 mass in order to improve ejection stability when applied to an ink jet system that ejects ink by the action of thermal energy. % Or more is preferable. This is because by using an ink containing ethanol or isopropyl alcohol (2-propanol), the foaming of the ink on the thin film resistor of the recording head can be caused more stably.

(Other ingredients)
In addition to the components listed above, the pigment ink may contain a moisturizing solid content such as urea, urea derivatives, trimethylolpropane, trimethylolethane and the like in order to maintain the moisturizing property. Furthermore, a surfactant, a rust inhibitor, an antifoaming agent, an antiseptic agent, an antifungal agent, an antioxidant, an anti-reduction agent, an evaporation accelerator, etc. are used in order to obtain a pigment ink having desired physical properties as required. Various additives may be contained.

  The pH of the pigment ink is preferably adjusted to be neutral or alkaline. This is because the solubility of the resin can be improved, and the pigment ink can be made more excellent in long-term storage. However, the pH of the pigment ink is preferably 7.0 or more and 10.0 or less because it may cause corrosion in members constituting the ink jet recording apparatus. In order to bring the pH of the pigment ink into the range described above, it is preferable to use the following pH adjuster. Specifically, for example, organic amines such as diethanolamine and triethanolamine, inorganic alkali agents typified by alkali metal hydroxides such as sodium hydroxide, lithium hydroxide and potassium hydroxide, organic acids and mineral acids Etc.

  Any surfactant such as an anionic surfactant, a nonionic surfactant, and an amphoteric surfactant can be used for the pigment ink as long as it does not affect the storage stability of the ink. Can also be used. Specific examples of the anionic surfactant include fatty acid salts, higher alcohol sulfate esters, liquid fatty oil sulfate esters, and alkyl allyl sulfonates. Specific examples of the nonionic surfactant include polyoxyethylene alkyl esters, polyoxyethylene sorbitan alkyl esters, acetylene alcohol, and acetylene glycol. The surfactant content (% by mass) is preferably 0.01% by mass or more and 5.0% by mass or less based on the total amount of the ink, although it varies depending on the type of the dispersant in the ink.

(Ink preparation method)
The pigment ink used in the present invention can be prepared as follows. First, a pigment is added to an aqueous solution containing at least a dispersion resin and water, and the mixture is sufficiently stirred. Then, dispersion is performed using a dispersion means described later, and centrifugation is performed as necessary to obtain a desired dispersion. Next, the ink constituents listed above are added to the obtained dispersion, and then sufficiently stirred to obtain ink.

  At this time, it is preferable to perform premixing for 30 minutes or more before dispersing the liquid to which the pigment has been added. This is because the premixing operation can improve the wettability of the pigment surface and promote the adsorption of the dispersant onto the pigment surface. Here, any apparatus that performs distributed processing can be used as long as it is a commonly used disperser. Specifically, a ball mill, a roll mill, a sand mill, etc. are mentioned, for example. Among these, it is preferable to use a high-speed sand mill as listed below. Examples thereof include a super mill, a sand grinder, a bead mill, an agitator mill, a glen mill, a dyno mill, a pearl mill, and a cobol mill (all are trade names).

  Examples of a method for obtaining a pigment having a particle size distribution suitable for the pigment ink used in the present invention include the following (1) to (5). Of course, these methods can be combined appropriately. For example, (1) reduce the size of the grinding media of the disperser, (2) increase the filling rate of the grinding media, (3) increase the processing time, (4) slow the discharge speed, (5) grinding Thereafter, a method such as classification with a filter or centrifugation may be used.

<Recording medium>
In the present invention, a conventionally used recording medium, more preferably an inkjet recording medium suitable for image formation with pigment ink can be used. Hereinafter, a recording medium suitable for the present invention will be described. The surface coating liquid of the present invention is applied to a recorded material in which an image is formed by an inkjet recording method using a pigment ink on a glossy inkjet recording medium (glossy paper). A particularly remarkable effect is obtained for improvement. Of course, the coating liquid of the present invention can also be applied to recorded matter in which images are formed on various recording media other than glossy paper. Here, the definition of glossy paper in the present invention will be described. Of course, this is not an absolute reference, but it has been found that the glossiness occurs when the surface glossiness of 75-degree reflection is around 20. For this reason, in the present invention, a glossy paper is a recording medium generally classified as a glossy or semi-glossy, more specifically, a paper having a 75 degree reflection surface glossiness of 20 or more.

  Here, in a glossy or semi-glossy recording medium, submicron-order inorganic fine particles such as amorphous silica and alumina are often used as the material constituting the ink receiving layer. On the other hand, when the ink receiving layer is formed using inorganic fine particles of micron order, the surface roughness more than the light wavelength region is generated, so that glossiness cannot be obtained. As described above, when submicron-order inorganic fine particles are used as the material constituting the ink receiving layer, the pigment cannot penetrate into the ink receiving layer, so that the pigment layer is formed on the outermost surface of the ink receiving layer. For this reason, the effect of improving the scratch resistance achieved by applying the surface coating solution to the image is particularly great.

  The configuration of a glossy or semi-glossy recording medium will be described below. The recording medium generally has a layer structure in which at least one ink receiving layer is formed on a heat-resistant substrate. The ink receiving layer of the glossy or semi-glossy recording medium is composed of inorganic fine particles such as amorphous silica and alumina that are ultrafinely dispersed on the order of submicrons, and a binder that binds the inorganic fine particles. From the viewpoint of absorbability with respect to the aqueous medium in the ink, it is preferable to use inorganic fine particles having a large specific surface area such as gas phase method silica, colloidal silica, and hydroxide hydroxide sol.

  The inorganic fine particles are dispersed mechanically using a homogenizer, a pressure homogenizer, a colloid mill, a ball mill, a medium stirring mill, a high-speed rotary mill, etc., so that the secondary aggregates of the inorganic fine particles are on the order of submicrons. . Further, from the viewpoint of adjusting the secondary particle diameter of the inorganic fine particle dispersion and the stability of the dispersion, a dispersant can also be used.

(binder)
The following can be used for the binder. Polyvinyl alcohol or a modified product thereof, polyvinyl pyrrolidone, polyvinyl acetate and the like. In addition, oxidized starch, etherified starch, casein, gelatin, soy protein, carboxymethylcellulose and the like. SBR latex, NBR latex, acrylic latex, ethylene vinyl acetate latex, polyurethane, unsaturated polyester, etc.

  Among the above-mentioned binders, it is particularly preferable to use polyvinyl alcohol, and the reason is as follows. Polyvinyl alcohol is obtained by a saponification reaction in which polyvinyl acetate is neutralized with an alkali and a carboxyl group is substituted with a hydroxyl group. Depending on the degree of polymerization (molecular weight) and the degree of saponification, film strength, crystallinity, water solubility, viscosity, etc. It is possible to easily set the characteristics. In particular, it is preferable to use polyvinyl alcohol having a saponification degree of 90 mol% or more. This is because density unevenness caused by aggregation of ink not fixed on the recording medium can be suppressed, that is, the beading resistance of the pigment ink can be effectively improved. Polyvinyl alcohol having a high degree of saponification is known to easily form a film with high crystallinity. Accordingly, polyvinyl alcohol having higher crystallinity, that is, higher saponification degree, has lower water swellability. Therefore, when an image is formed using a pigment ink, the permeability of an aqueous medium in the ink to the ink receiving layer is increased. It is thought to be higher. Moreover, it is preferable that the polymerization degree of polyvinyl alcohol is 1,500 or more from a viewpoint of film | membrane intensity | strength.

(Crosslinking agent, binder having crosslinkability)
The binder mentioned above can also be used in combination with a crosslinking agent or a binder having crosslinking properties. Here, the crosslinking agent refers to a monomer (monomer) or oligomer (medium molecular weight component) having a functional group (reactive group) capable of forming a covalent bond or a coordinate bond by heating or the like. Examples of the inorganic crosslinking agent include metal oxides such as boric acid and sodium borate and salts thereof. Examples of the organic crosslinking agent include compounds such as isocyanate, epoxy, N-methylol, carbodiimide, triazine, aldehyde, vinylsulfone, acryloyl, ethyleneimine, and siloxane. As the crosslinkable binder, one having a reactive functional group in the resin can be used. Specifically, a water-soluble acrylic resin having a methylol group, an epoxy group, a silanol group, or the like, a modified polyvinyl alcohol, or the like can be used.

(Base material)
As the base material constituting the recording medium, paper made of natural pulp or synthetic pulp, heat resistant film, or the like can be used. Specific examples of the pulp include wood pulp such as softwood pulp, hardwood pulp and softwood hardwood mixed pulp, and regenerated pulp such as kraft pulp, sulfite pulp, and soda pulp. These pulps are usually bleached using chlorine, hypochlorite, chlorine dioxide, alkali extraction or alkali treatment, and if necessary, oxidative bleaching using hydrogen peroxide, oxygen, etc. It is preferable to use those subjected to the combination treatment.

  Various additives may be added to the base paper when preparing the paper slurry. For example, it is preferable to use a fatty acid or a salt thereof, a rosin derivative, or the like as the sizing agent. Further, by providing a layer such as a thermoplastic latex resin on the back surface of the recording medium, the water resistance, strength, and the like of the recording medium can be further improved.

  As the heat resistant film, a film composed of the following materials can be used. Polyesters such as polyethylene terephthalate (PET), polyethylene terephthalate / isophthalate copolymer, polybutylene terephthalate, and polyolefins such as polypropylene. Polyamide, polyimide, triacetyl cellulose, vinyl chloride resin, vinylidene chloride / vinyl chloride copolymer, acrylic resin, polyether sulfone, etc.

(Coating method of ink receiving layer)
In order to provide the ink receiving layer on the substrate described above, the following general coating apparatus can be used. Blade coater, roll coater, air knife coater, bar coater, gate roll coater, curtain coater, die coater, short dwell coater, gravure coater, flexo gravure coater, size press, etc. These coating apparatuses can be used on-machine or off-machine.

<Inkjet recording method and inkjet recording apparatus>
The ink jet recording method of the present invention mainly comprises forming a resin layer by applying the surface coating liquid of the present invention to a region containing an image formed on a recording medium by a pigment ink containing a pigment by the ink jet recording method. Features. At this time, the film thickness in at least a part of the formed resin layer is particularly preferably 0.10 μm or more and 1.00 μm or less. Further, the ink jet recording apparatus of the present invention comprises a means for forming an image on a recording medium using a pigment ink by an ink jet recording method, and a resin layer by applying the surface coating liquid of the present invention to at least the region containing the image. The main feature is to have means for forming. The method for applying the surface coat described above to the recording medium may be any method, but in the present invention, it is particularly preferable to use an ink jet method or a roll coat method. Hereinafter, an ink jet recording method and an ink jet recording apparatus will be described.

  FIG. 4 is an external perspective view of an ink jet recording apparatus that performs recording using an ink jet recording head (hereinafter referred to as a recording head). The ink jet recording apparatus has the following configuration. The carriage 11 detachably mounts a head cartridge in which a recording head and an ink cartridge containing ink are integrated.

  The carriage 11 is reciprocated by a carriage motor 12 (this moving direction is referred to as a main scanning direction). The driving force of the carriage motor 12 is transmitted to the carriage 11 by the belt 4. The movement of the carriage 11 in the main scanning direction is supported by the guide shaft 6. The flexible cable 13 transfers an electrical signal from the control unit to the recording head. The cap 141 and the wiper blade 143 are used for performing a recovery operation of the recording head. The cassette 15 stores recording media in a stacked state. The encoder sensor 16 optically reads the position of the carriage 11.

  FIG. 5 is a perspective view showing in more detail the configuration in the vicinity of the carriage in the ink jet recording apparatus of FIG. Here, black (K), light cyan (LC), dark cyan (C), light magenta (LM), dark magenta (M) and yellow (Y An example of an inkjet recording apparatus equipped with six types of inks) will be described. The recording head 22 includes recording heads 22K, 22LC, 22C, 22LM, 22M, and 22Y that discharge the six types of ink described above.

  The ink cartridge 21 includes ink cartridges 21K, 21LC, 21C, 21LM, 21M, and 21Y that respectively store ink supplied to the recording heads. The cap 141 caps each ink discharge port of the recording head 22, and includes six caps 141K, 141LC, 141C, 141LM, 141M, and 141Y. In addition, when these recording heads and ink cartridges are individually shown, they are indicated by using numbers assigned thereto, but when these are indicated comprehensively, the recording head is “22” as a generic number. The ink cartridge is indicated by “21” and the cap is indicated by “141”.

  Here, the description has been made using an example in which the recording head 22 and the ink cartridge 21 constitute a head cartridge. In the present invention, the head cartridge may be configured such that the recording head and the ink cartridge are integrated, or each may be configured to be separable.

  As shown in FIGS. 4 and 5, a carriage motor 12 is connected to the carriage 11 via a belt 4 and pulleys 5a and 5b. Then, the carriage 11 is reciprocated along the guide shaft 6 by driving the carriage motor 12.

  FIG. 6 is a schematic diagram of the recording head 22 as viewed from the discharge port side. The recording heads 22K, 22LC, 22C, 22LM, 22M, and 22Y have 1280 ejection ports arranged at a density of 1200 dpi to form ejection port arrays. These six recording heads are arranged in the main scanning direction. The ink ejected from one ejection port 23 is about 4 ng. The opening area of the discharge port 23 is adjusted in order to reduce the discharge amount as much as possible and perform high-quality recording.

  Hereinafter, a recording operation in the ink jet recording apparatus having the above-described configuration will be described in detail with reference to FIGS. A plurality of recording media 1 stacked in a cassette 15 are supplied one by one by a paper feed roller (not shown). In the recording operation area, the recording medium 1 is transported between the recording head 22 and a platen (not shown) to the transport roller pair 3 by the operation of auxiliary transport rollers (not shown) such as other spurs and rollers.

  Ink is supplied from the ink cartridge 21. The recording head 22 performs recording on the recording medium 1 with a width corresponding to the number of ejection ports of the recording head 22 according to the image signal while moving in the arrow B direction (forward scanning direction) in FIG. Specifically, according to the reading timing of the encoder sensor 16, it is driven based on the image signal, and an image is formed by ejecting and applying ink to the recording medium 1.

  When printing for one scan in the direction of arrow B (forward scan direction) is completed, the order of Y, M, LM, C, LC, and K moves while moving in the arrow B direction (return scan direction) toward the home position. Record with. In this way, reciprocal recording is performed. After one recording operation (one scan) in one direction is completed and before the next recording operation is started, the conveyance roller pair 3 is driven to intermittently move the recording medium 1 in the direction of arrow A by a predetermined amount. Transport it. In this manner, recording is performed on the recording medium 1 by repeating the recording operation for one scan and the conveyance of a predetermined amount of the recording medium.

  When the recording head 22 returns to the home position, the recovery mechanism can eliminate clogging of the discharge port 23 as necessary. The cap 141 caps the ejection port 23 of the recording head 22 in order to prevent ink from being sucked when the ejection port 23 is recovered or dried when left. The wiper blade 143 wipes the surface having the ejection port 23 of the recording head 22 while moving in the direction of arrow C to remove ink and the like.

  Next, a control configuration for executing recording control of the ink jet recording apparatus will be described. FIG. 7 is a block diagram for explaining a control system of the ink jet recording apparatus. Reference numeral 1700 denotes an interface for inputting a recording signal from a host device such as a microcomputer. Reference numeral 1701 denotes a CPU for controlling each part of the recording device. Reference numeral 1702 denotes a ROM for storing a control program executed by the CPU 1701, an error processing program, and the like.

  Reference numeral 1703 denotes a RAM for temporarily storing various data (such as recording signals and recording data supplied to the recording head 22). Reference numeral 1704 denotes a gate array that controls supply of print data to the print head 22 and also controls data transfer among the interface 1700, the CPU 1701, and the RAM 1703. Reference numeral 12 denotes a carriage motor for moving the recording head 22, and 1709 denotes a conveyance motor for conveying the recording paper 1. Reference numeral 1705 denotes a head driver for driving the recording head 22, and 1706 and 1707 denote motor drivers for driving the transport motor 1709 and the carriage motor 12. A recording signal input through the interface 1700 is converted into recording data by the gate array 1704 and the CPU 1701. Then, the motor drivers 1706 and 1707 are driven, and the recording head 22 is driven based on the recording data sent to the head driver 1705 to perform recording.

  The temperature control of the recording head 22 is performed based on the detected temperature of the environment where the ink jet recording apparatus is installed. The recording head 22 is provided with a discharge heater as discharge energy generating means, and a heat retaining heater 1710 for controlling the temperature of the ink is provided near the discharge port array. The CPU 1701 performs ON / OFF control of the heat retaining heater 1710 according to the environmental temperature detected by the thermistor 1708, whereby the recording head 22 is controlled to an optimum temperature. The temperature of the recording head 22 can also be controlled by monitoring the temperature inside the recording head output from the temperature sensor 1711 provided in the recording head 22.

Next, the present invention will be described more specifically with reference to examples and comparative examples. The present invention is not limited by the following examples unless it exceeds the gist. In the text, “parts” and “%” are based on mass unless otherwise specified. Further, the physical property values of the resin are values measured using the following apparatus. That is, the glass transition temperature (T _g ) was measured using EXSTAR / DSC6200S (trade name: manufactured by SII Nano Technology). The 50% cumulative volume average particle size (D ₅₀ ) was measured using a particle size distribution analyzer (trade name: Nanotrac UPA-150; manufactured by Nikkiso).

<Resin synthesis>
(Synthesis of Resin 1)
In a reaction vessel equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen blowing tube, 250 parts of propylene glycol monomethyl ether acetate (PMA) was charged. Nitrogen gas was introduced into the reaction vessel to replace the air in the reaction vessel so as not to contain oxygen, and then the internal temperature was raised to 80 ° C. Thereafter, a solution in which 3 parts of azobisisobutyronitrile as a polymerization initiator was dissolved was added to 20 parts of PMA. Furthermore, a monomer solution containing 85 parts of normal butyl acrylate (n-BA) and 15 parts of acrylic acid (AA) was added dropwise over 2 hours. Thereafter, the reaction was completed by stirring for 3 hours while maintaining the internal temperature. After completion of the reaction, PMA as a solvent was removed by drying under reduced pressure to obtain Resin 1. The weight average molecular weight in terms of polystyrene of the resin 1 was 10,000. The glass transition temperature of Resin 1 measured by a suggested scanning calorimeter (DSC) was −20 ° C.

(Synthesis of Resin 2)
Synthesis was carried out in the same procedure as that for Resin 1 except that 75 parts of isobutyl acrylate (i-BA) and 25 parts of acrylic acid (AA) were used as the monomer to be dropped. The polystyrene equivalent weight average molecular weight of Resin 2 was 9,000. The glass transition temperature of Resin 2 measured by a suggested scanning calorimeter (DSC) was 10 ° C.

<Preparation of surface coating solution>
Resins 1 and 2 obtained above are mixed with pure water and an aqueous potassium hydroxide solution, respectively, and the resin components are dissolved by heating and stirring to obtain resin solutions 1 and 2 having a solid content concentration of 10% by mass. Got. When the average particle diameter of the resin solutions 1 and 2 was measured by the dynamic light scattering method, the resin solution 1 was dissolved in a good state, and the particle diameter and the 50% volume average particle diameter (D ₅₀ ) were confirmed. I couldn't. Furthermore, each component was mixed so that it might become a composition shown in following Table 1, and it stirred sufficiently, and prepared surface coating liquids 1-4. The obtained surface coating solutions 1 to 4 were all colorless and transparent. In addition, the compounding quantity of resin A and B in Table 1 was shown by solid content (resin quantity in a resin solution).

<Preparation of pigment ink>
10 parts of carbon black (Printex 85; manufactured by Degussa), 4 parts of styrene-acrylic acid copolymer sodium salt (John Krill 555; manufactured by Johnson Polymer), and 86 parts of pure water were mixed and stirred for 30 minutes. As the styrene-acrylic acid copolymer sodium salt, one having an acid value of 200 mgKOH / g and a weight average molecular weight of 5,000 was used. This mixture was sufficiently dispersed using a bead mill (LMZ2; manufactured by Ashizawa Finetech Co., Ltd.) having a filling rate of zirconia beads having a diameter of 0.3 mm of 85%. Thereafter, centrifugal treatment was performed to remove coarse particles, and pressure filtration was performed with a filter having a pore size of 2.5 μm (trade name: HDCII 2.5 μm; manufactured by Pall) to obtain a pigment dispersion. The pigment concentration in the pigment dispersion thus obtained was 10.0%, and the dispersant (resin solid content) concentration was 4.0%.

The following components were sufficiently mixed and subjected to pressure filtration with a filter having a pore size of 2.5 μm (trade name: HDCII 2.5 μm; manufactured by Pall) to obtain a pigment ink. The average particle diameter of the pigment in the obtained ink was 120 nm.
-Pigment dispersion 35.0 parts-Glycerol 10.0 parts-Triethylene glycol 5.0 parts-Polyethylene glycol (average molecular weight 600) 5.0 parts-Acetylenol EH
(Surfactant; manufactured by Kawaken Fine Chemical Co., Ltd.) 0.5 part, 44.5 parts pure water

<Preparation of recording medium>
(Preparation of base paper)
After making paper using hardwood bleached kraft pulp as raw material pulp, machine calendering was performed at a linear pressure of 60 kg / cm to prepare a base paper having a basis weight of 150 g / m ² and a density of 0.95 g / cm ³ .

(Formation of ink receiving layer)
First, alumina hydrate, which is a component of the ink receiving layer, was prepared as follows. Aluminum octoxide was synthesized according to the method described in US Pat. No. 4,242,271 and hydrolyzed to prepare an alumina slurry. Water was added to the obtained alumina slurry so that the solid content concentration of the alumina hydrate was 5%. This liquid was heated to 80 ° C. and subjected to aging reaction for 10 hours to obtain a colloidal sol. The obtained colloidal sol was spray-dried to obtain alumina hydrate.

  The obtained alumina hydrate was dispersed in ion-exchanged water, and the pH of the liquid was adjusted to 10 using nitric acid. This liquid was aged for 5 hours to obtain a colloidal sol. After the obtained colloidal sol was desalted, acetic acid was added to carry out a peptization treatment. Thereafter, the colloidal sol of alumina hydrate was concentrated to obtain a dispersion having an alumina hydrate concentration of 15%.

Here, polyvinyl alcohol (trade name: PVA117; manufactured by Kuraray Co., Ltd.) was dissolved in ion-exchanged water to obtain a solution having a polyvinyl alcohol concentration of 10%. These two kinds of dispersions and solutions were mixed so that the solid content of alumina hydrate and the solid content of polyvinyl alcohol were 10: 1 by mass ratio, and then stirred to obtain a dispersion. The obtained dispersion was applied to the base paper obtained above so as to have a dry coating amount of 30 g / m ² to form an ink receiving layer.

<Preparation of recorded material>
Example 1
In this example, as described below, the surface coating solution 1 was applied to the image formed on the recording medium using the pigment ink by the ink jet recording method using a roll coat coating apparatus described later to obtain a recorded matter. . First, an ink cartridge of an ink jet recording apparatus (trade name: imagePROGRAF iPF5000; manufactured by Canon) was filled with the pigment ink obtained above and set at a position of a black ink cartridge. Further, the recording medium obtained as described above was cut into A4 size and set in the media cassette of the ink jet recording apparatus. The recording conditions were the number of dots per inch, that is, the resolution was 1200 dpi, and 8-pass bidirectional recording in which an image was formed by reciprocal scanning of 8 passes. Then, an image having a recording duty of 100% was formed using pigment ink, and immediately after recording, the surface coating solution 1 was applied by a roll coat coating device to produce a recorded matter.

  When a cross section of the obtained recorded matter was observed with an electron microscope, it was confirmed that the pigment layer was covered with a resin layer, and the resin layer was fixed with the resin inside the pores of the pigment layer. did it. Moreover, when the cross section of the recorded matter was observed with an electron microscope and the film thickness of the resin layer was measured, it was about 0.50 μm. The recorded matter obtained in this example kept the texture of the recording medium before image formation as it was.

  The roll coat coating apparatus used in Example 1 has the configuration shown in FIG. The drive mechanism of this roll coat coating apparatus is as follows. The surface coating liquid 110 is stored in the cartridge 103 and supplied to the porous body 100 via the supply pump 106, the supply path 102, and the surface coating liquid holding tank 101. In the application processing unit, the application roller 71A and the pressure conveyance roller 71B are rotatable. The regulation blade 111 is in contact with the application roller 71A.

  A coating roller driving motor (not shown) is driven to rotate at a predetermined value, whereby the surface coating liquid 110 is pumped from the porous body 100 to the coating roller 71A. The coating amount of the surface coating liquid 110 pumped up on the coating roller 71A can be adjusted by adjusting the pressing pressure of the regulating blade 111 and the rotation speed of the coating roller 71A. The recording medium is conveyed in the direction of the arrow L1 and enters the nip between the application roller 71A and the pressure conveyance roller 71B, so that the surface coating liquid is applied to the recording medium and then discharged from the roll coat application device. The

(Example 2)
In this example, a recorded material was obtained by applying the surface coating liquid 2 by an inkjet recording method to an image formed on a recording medium using a pigment ink by an inkjet recording method as described below. First, an ink cartridge of an ink jet recording apparatus (trade name: imagePROGRAF iPF5000; manufactured by Canon) was filled with the surface coating liquid 2 and the pigment ink, respectively. Each ink cartridge was set in the ink jet recording apparatus with the ink cartridge filled with the surface coating liquid in the yellow position and the ink cartridge filled with the pigment ink in the black position. Further, the recording medium obtained as described above was cut into A4 size and set in the media cassette of the ink jet recording apparatus.

  The recording conditions were the number of dots per inch, that is, the resolution was 1200 dpi, and 8-pass bidirectional recording in which an image was formed by reciprocal scanning of 8 passes. In order to apply the surface coating liquid onto the image formed with the pigment ink, among the eight-pass reciprocating scan, the pigment ink forms a mask pattern that forms an image with a recording duty of 100% in the first to seventh passes. Was used. The surface coating solution used was a mask pattern that formed an image with a recording duty of 100% in the final pass, that is, the 8th pass, without recording in the 1st to 7th passes. A recorded material was prepared using the pigment ink and the surface coating liquid 2. When a cross section of the obtained recorded matter was observed with an electron microscope, it was confirmed that the pigment layer was covered with a resin layer, and the resin layer was fixed with the resin inside the pores of the pigment layer. did it. Moreover, when the cross section of the recorded matter was observed with an electron microscope and the thickness of the resin layer was measured, it was about 0.30 μm. The recorded matter obtained in this example kept the texture of the recording medium before image formation as it was.

(Comparative Example 1)
In this comparative example, the surface coating liquid 3 was used in the same manner as in Example 1 except that the surface coating liquid 3 was used as the surface coating liquid. Coated liquid 3 was applied to obtain a recorded product. When the film thickness of the resin layer was measured in the same manner as in Example 1, it was about 0.30 μm. Further, when the cross section of the obtained recorded matter was observed with an electron microscope, the resin layer was formed on the surface of the pigment layer, but the resin was not fixed inside the pores of the pigment layer.

(Comparative Example 2)
In this comparative example, the surface coating liquid 4 was used in the same manner as in Example 1 except that the surface coating liquid 4 was used. Coated liquid 4 was applied to obtain a recorded product. When the film thickness of the resin layer was measured in the same manner as in Example 1, it was about 0.30 μm. Further, when the cross section of the obtained recorded matter was observed with an electron microscope, a resin layer was formed on the surface of the pigment layer, but clearly different from the example, the resin was placed inside the pores of the pigment layer. It was not in a state that can be said to exist and have become established.

<Evaluation>
(Image density)
The image density in the image area of each recorded matter obtained above was evaluated by measuring with a reflection densitometer (manufactured by X-Rite). The image density evaluation criteria are as follows. The evaluation results are shown in Table 2.
A: The image density is 2.0 or more.
B: The image density is less than 2.0.

(Glossy)
The surface glossiness (20-degree reflection) in the image area of each recorded matter obtained above was measured by a glossiness meter (product name: Microhaze Plus; manufactured by BYK Gardner) and evaluated. The evaluation criteria for glossiness are as follows. The evaluation results are shown in Table 2.
A: Glossiness is 30 or more.
B: Glossiness is 30 or less.

(Abrasion resistance)
The scratch resistance in the image area of each recorded matter obtained above was measured and evaluated with a surface property tester (product name: Haydon Tribogear TYPE 14DR; manufactured by Shinto Kagaku). Polymethylmethacrylic acid (PMMA) resin balls (4 mmΦ) were used as the friction member. The resin ball was fixed to a ball indenter folder, the resin ball was pressed perpendicularly to the image surface, and the resin ball was moved on the surface of the image area at a speed of 40 mm / sec. Subjective evaluation was made on the condition of the scratch when the vertical load applied to the resin ball was increased in steps up to 1,000 g. The evaluation criteria for scratch resistance are as follows. The evaluation results are shown in Table 2.
AA: Scratches due to image peeling do not occur and the gloss of the contact surface with the friction material does not decrease.
A: Although scratches due to image peeling do not occur, the gloss of the contact surface with the friction material is lowered.
B: Scratches due to image peeling occur at a vertical load of 200 g or less.

(Dynamic friction coefficient)
The dynamic friction coefficient with respect to the PMMA resin ball sphere in the image area of each recorded matter obtained above was measured using a surface property tester (product name: Haydon Tribogear TYPE14DR; manufactured by Shinto Kagaku). The vertical load applied to the PMMA resin ball is 50 g, the moving speed is 2 mm / sec, the horizontal force acting in the moving direction of the PMMA resin ball during movement is measured by the load cell, and the ratio of the horizontal force to the vertical load force is the dynamic friction coefficient. Calculated. The obtained dynamic friction coefficient values are shown in Table 2.

It is a schematic diagram which shows the cross section of the image formed in the glossy paper using the pigment ink. It is a schematic diagram of the fixing process when a surface coating solution is applied. It is a schematic diagram of a roll coat application device. 1 is an external perspective view of an ink jet recording apparatus. FIG. 5 is a perspective view illustrating a configuration in the vicinity of a carriage in the ink jet recording apparatus of FIG. 4. FIG. 3 is a schematic diagram of the recording head 22 as viewed from the discharge port side. It is a block block diagram of the control system of an inkjet recording device.

Explanation of symbols

1-1: Ink receiving layer 1-2: Pigment layer 2-1: Surface coating solution 2-2: Resin A
2-3: Resin B
2-4: Pigment layer 2-5: Ink receiving layer 2-6: Resin layer 2-7: Pigment layer 71A densified from B to resin 71: Application roller 71B: Pressure conveying roller 100: Porous body 101: Surface coating liquid holding tank 102: Supply path 103: Cartridge 106: Supply pump 110: Surface coating liquid 111: Regulation blade 1: Recording medium 3: Conveying roller pair 4: Belt 5a: Pulley 5b: Pulley 6: Guide shaft 11: Carriage 12: Carriage motor 13: Flexible cable 15: Cassette 16: Encoder sensor (optical position sensor)
21: Ink cartridge 22: Recording head 23: Ejection port 141: Cap 143: Wiper blade 1700: Interface 1701: CPU
1702: ROM
1703: RAM
1704: Gate array 1705: Head driver 1706: Motor driver 1707: Motor driver 1708: Thermistor 1709: Conveyance motor 1710: Insulation heater 1711: Temperature sensor

Claims (11)

A surface coating liquid that is applied to a region including at least an image formed on a recording medium using a pigment ink containing a pigment,
A surface coating liquid comprising at least a resin A that forms a resin layer on the surface of a pigment layer and a resin B that penetrates and fixes into the pores of the pigment layer.   The surface coating solution according to claim 1, wherein the resin A is an emulsion resin and the resin B is a water-soluble resin.   The surface coating solution according to claim 1 or 2, wherein the glass transition temperature of the resin A is 20 ° C or higher and 100 ° C or lower.   The surface coating liquid according to claim 1, wherein the resin B has a glass transition temperature of 0 ° C. or lower.   The surface coating liquid according to any one of claims 2 to 4, wherein an average particle size of the emulsion resin is 20 nm or more and 300 nm or less.   The surface coating solution according to any one of claims 1 to 5, wherein the resin layer formed of the resin A has slipperiness.   The surface coating liquid according to claim 2, wherein the emulsion resin is a silicone resin, a fluorine resin, or a wax resin.   The surface coating liquid according to claim 7, wherein the emulsion resin is an acrylic silicone copolymer resin obtained by copolymerizing dimethyl silicone and an acrylic monomer. A step of forming an image on a recording medium by an inkjet recording method using a pigment ink containing a pigment, and a step of forming a resin layer by applying a surface coating solution containing a resin to at least the region containing the image; An ink jet recording method comprising:
The surface coating liquid is the surface coating liquid according to any one of claims 1 to 8,
An ink jet recording method, wherein a film thickness of at least a part of the resin layer is from 0.10 μm to 1.00 μm.   The inkjet recording method according to claim 9, wherein the method for applying the surface coating liquid is an inkjet method or a roll coating method. Means for forming an image on a recording medium by an inkjet recording method using a pigment ink containing a pigment, and means for forming a resin layer by applying a surface coating solution containing a resin to at least the region containing the image An inkjet recording apparatus,
An ink jet recording apparatus, wherein the surface coating liquid is the surface coating liquid according to any one of claims 1 to 8.

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