JP2007076228A - Ink jet recording method and recorded matter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recording method, which gives a highly glossy and high quality ink jet print being excellent in high speed recordability, having high weatherability and excellent storage stability and scratch resistance, dye ink gives uniform lustrous feeling and excellent print weatherability and storage stability irrespective of an image density and pigment ink gives uniform lustrous feeling and excellent print storage stability irrespective of the image density. <P>SOLUTION: In the ink jet recording method for recording onto an ink jet recording medium with an ink recording ink including at least one kind of resin particles, the ink jet recording medium has at least one porous ink accepting layer including inorganic particles and a hydrophilic binder on a support and the topmost surface layer made of inorganic particles including substantially no hydrophilic binder and having self-fusibility on the porous ink accepting layer so as to employ the ink jet recording medium under the condition that the solid content of the topmost surface layer is 0.01-0.5 g/m<SP>2</SP>in order to execute this ink jet recording method and obtain a recorded matter. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ink jet recording method using a colorless ink containing resin fine particles, and more specifically, high glossiness and high durability with excellent environmental printing suitability, scratch resistance, high gloss uniformity, weather resistance, and storage stability. The present invention relates to a recording method capable of obtaining a high-quality inkjet print.

  In recent years, ink jet recording media (hereinafter also simply referred to as recording media) have been rapidly improved in image quality and approaching photographic quality. In particular, in order to achieve image quality comparable to that of photographic image quality by inkjet recording, improvements have been made from the aspect of inkjet recording media, and a porous layer composed of fine particles and a hydrophilic polymer is formed on a highly smooth support. The provided void-type recording medium is becoming one of the closest to the photographic image quality because it has high gloss, shows a vivid color, or has excellent ink absorption and drying properties. In particular, when a non-water-absorbing support is used, there is no occurrence of cockling after printing, as seen on a water-absorbing support, so-called “wrinkles”, and a high smooth surface can be maintained. Prints can be obtained and have gradually become the mainstream of photographic prints produced by ink jet recording.

  Inkjet recording is generally divided into those using water-based inks that use water and water-soluble solvents as ink solvents, and those that use non-aqueous oil-based solvents, and there are types that use dyes as coloring materials and types that use pigments, respectively. In order to obtain a high-quality recorded image, special paper suitable for each type is required. As for inks, a small amount of water-based ink is mainly used from the environmental and safety aspects.

  A color print comparable to a photographic image quality having high image sharpness and uniform surface gloss can be obtained with an inkjet pudding using a water-soluble dye ink. However, prints using this water-soluble dye have poor storage stability compared to pigment inks, and are subject to discoloration caused by sunlight, ozone, other oxidizing gases, or the like, and further image blurring. Yes. In particular, in a void-type recording medium provided with a fine porous layer, the contact area between the dye and the indoor air is widened, so that fading due to oxidizing gas in the air is greatly improved.

  For the purpose of improving light resistance and ozone gas resistance, a technique for adding latex or resin fine particles to ink has been disclosed (for example, see Patent Document 1). The method of adding latex or resin fine particles to the ink has a certain effect on the ozone gas fading prevention effect, but has been found to have the following problems.

  That is, the first problem is that the gloss level where ink is applied is improved, but the gloss level does not change on a white background. As a result, a difference in gloss occurs between the image part / non-image part.

  The second problem is that a good ozone fading prevention effect is recognized from the high density part to the intermediate density part where the ink amount is large, but the effect when the ink application amount is small is insufficient, so the ink application amount is rather small. The scarlet of will be conspicuous. Alternatively, a good ozone fading prevention effect is recognized in the secondary color and the multi-colored portion, but the fading is conspicuous in a portion close to a pure color, and unnaturalness becomes an image.

  A third problem is that an image fading effect against harmful gases such as ozone gas is not sufficiently obtained at an image portion adjacent to a white background. This is considered to be due to the ingress of ozone gas from the adjacent white background portion and the diffusion of ozone gas to the image portion.

  Means for improving the ozone fading and glossiness stably by changing the amount of colorless ink applied even when the image density range is different is disclosed (for example, refer to Patent Document 2), but stable even after hot and humid storage. It was found to be insufficient for exhibiting the effect. There is a problem of both the uniformity of film formation immediately after printing and the storage stability, and this problem is suppressed in the present invention.

  Further, by using a colorless ink containing resin fine particles, improvement in gloss unevenness and scratch resistance, which are weak points of pigment ink, has been proposed (for example, see Patent Document 3). .

On the other hand, a technique for improving absorptivity and gloss, particularly a gloss difference between a printed part and an unprinted part, is disclosed by using an outermost colloidal silica layer substantially free of an organic polymer adhesive (see, for example, Patent Document 4). Yes. When two or more kinds of colloidal silica having different particle diameters are used, the colloidal silica having a small particle diameter enters into the pores formed by the colloidal silica having a large particle diameter, and the porosity is lowered in return. In addition, when the outermost layer composed of ⁵ to 6 g / m ² of dry solid content of colloidal silica having a low porosity is coated, the absorbability is insufficient particularly when the resin fine particle-containing ink of the present invention is used. It has been found that gloss failure and scratch resistance deterioration due to non-uniformity of the above have not been sufficiently solved.
JP 2002-240413 A JP 2005-88411 A JP 2005-81754 A JP-A-6-183131

  An object of the present invention is a recording method which gives a high gloss and high quality ink jet print having good ink absorbability, excellent high-speed recording suitability, high weather resistance, and excellent storage stability and scratch resistance. Is to provide. In particular, when dye ink is used, uniform glossiness (glossiness, image clarity) and excellent weather resistance and storage stability are obtained regardless of image density. When pigment ink is used, it depends on image density. It is an object of the present invention to provide a recording method capable of providing uniform glossiness (glossiness, image clarity) and excellent print storage stability.

  The above object of the present invention can be achieved by the following configuration.

1. In an ink jet recording method for recording on an ink jet recording medium using an ink jet recording ink containing at least one kind of resin fine particles, the ink jet recording medium contains at least one layer of inorganic fine particles and a hydrophilic binder on a support. An ink receiving layer and an outermost layer made of inorganic fine particles having self-fusing properties substantially free of a hydrophilic binder on the porous ink receiving layer, and the solid content of the outermost layer is 0.01 to An ink jet recording method comprising using an ink jet recording medium of 0.5 g / m ² .

2. The ink jet recording ink containing the resin fine particles comprises a colored ink containing at least one colorant and a colorless ink substantially free of a colorant, and the resin fine particles in the colorless ink are applied to the ink jet recording medium. ^2. The ink jet recording method as described in 1 above, wherein the adhesion amount (g / m ² ) is varied in accordance with the adhesion amount of the resin fine particles of the colored ink for each recording region.

  3. 3. The inkjet recording method according to 1 or 2 above, wherein the inorganic fine particles having self-bonding property are at least one selected from colloidal silica and colloidal alumina.

  4). 4. The inkjet recording method according to any one of 1 to 3, wherein the inorganic fine particles having self-bonding property have an average primary particle size of 5 to 100 nm.

  5. A recorded matter produced by the inkjet recording method described in any one of 1 to 4 above.

  According to the present invention, there is provided a recording method for giving a high-gloss, high-quality inkjet print having good ink absorbability, excellent high-speed recording suitability, high weather resistance, and excellent storage stability and scratch resistance. In particular, when dye ink is used, uniform gloss (glossiness, image clarity) and excellent print weather resistance and storage stability are obtained regardless of image density. When pigment ink is used, image density Regardless of the recording method, it was possible to provide a recording method capable of providing uniform gloss (glossiness, image clarity) and excellent print storage stability.

  The present invention will be described in more detail.

An ink jet recording medium having an inorganic fine particle outermost layer having a solid content of 0.01 to 0.5 g / m ² that does not substantially contain a water-soluble binder of the present invention and colored ink containing at least a colorant are ejected to form an image. Recording with improved print quality and weather resistance by using an ink jet recording method that forms a protective film by discharging colorless ink containing fine resin particles and substantially no colorant. Media can now be provided.

The reason for these effects is not clear,
(I) When the outermost layer contains a polymer binder, it becomes an absorption inhibition factor due to swelling with an ink solvent, and causes poor adhesion such as surface aggregation of resin fine particles,
(Ii) It is presumed that the resin film formed on the surface of the recording medium is gradually impregnated into the pores of the porous layer due to heat and humidity during storage. For this purpose, it is considered that the elimination of the surface absorption inhibiting factor, the characteristics of the resin fine particles having a film forming ability, and the pore diameter design of the porous layer surface are important.

  First, the details of the outermost layer made of inorganic fine particles having self-bonding property, which is the surface layer according to the present invention, will be described.

The outermost layer according to the present invention is composed of inorganic fine particles having substantially no hydrophilic binder and having self-bonding properties, and the solid content of the outermost layer is 0.01 g / m ² or more and 0.5 g / m. ² or less.

  As the inorganic fine particles constituting the outermost layer according to the present invention, inorganic fine particles having self-bonding properties and having film-forming properties even in the absence of a binder are desirable. For example, light calcium carbonate, heavy calcium carbonate, carbonic acid Magnesium, kaolin, clay, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc hydroxide, zinc sulfide, zinc carbonate, hydrotalcite, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, synthetic amorphous Examples include white inorganic pigments such as silica, colloidal silica, alumina hydrate, colloidal alumina, pseudoboehmite, aluminum hydroxide, lithopone, zeolite, and magnesium hydroxide. Among them, alumina hydrate, cationic Colloidal silica, anionic colloidal silica Collectively referred to as colloidal silica) is preferable from the viewpoint of more exhibit the targeted effects of the present invention.

  The colloidal silica according to the present invention is obtained by dispersing silicon dioxide in water in a colloidal form, and has an average particle diameter of about 5 to 100 nm and is spherical. Examples of colloidal silica include the Snowtex series manufactured by Nissan Chemical Industries, Ltd., the Cataloid-S series manufactured by Catalytic Chemical Industry Co., Ltd., and the Rebacil series manufactured by Bayer. Also, beaded colloidal silica in which primary particles of cation-modified with alumina sol or aluminum hydroxide are bonded in a bead shape by bonding the particles with divalent or higher metal ions. There are beaded colloidal silicas such as SNOWTEX-AK series, SNOWTEX-PS series and SNOWTEX-UP series of Nissan Chemical Industries.

  As the shape of the inorganic fine particles, spherical fine particles are generally used. However, in the present invention, fine particles such as a pearl necklace shape in which spherical fine particles are connected may be used.

  The inorganic fine particles used in the outermost layer according to the present invention may be used as primary particles or in a state in which secondary aggregated particles are formed.

The solid content of the inorganic fine particles in the outermost layer according to the present invention is 0.01 g / m ² or more and 0.5 g / m ² or less, preferably 0.01 g / m ² or more, and 0.0. It is 3 g / m ² or less, more preferably 0.03 g / m ² or more and 0.2 g / m ² or less. If the solid content of the inorganic fine particles exceeds 0.5 g / m ² , overflow due to a decrease in the ink absorption rate, a decrease in the maximum density, and uneven gloss due to surface aggregation of the resin fine particles in the ink can occur, and a high-quality image can be obtained. Disappear. Further, if the solid content of the inorganic fine particles is less than 0.01 g / m ² , desired print weather resistance and storage stability cannot be obtained.

  The average particle diameter of the preferable primary particle diameter of the inorganic fine particles used in the outermost layer according to the present invention is 5 to 200 nm, preferably 5 to 100 nm, more preferably 10 to 50 nm. You may use together.

  In the above, the average particle size of the inorganic fine particles is obtained as a simple average value (number average) by observing the cross section and surface of the outermost layer with an electron microscope and determining the particle size of 100 arbitrary particles. Here, each particle size is represented by a diameter assuming a circle equal to the projected area.

  The outermost layer according to the present invention is preferably formed under the condition that the wet film thickness is 5.0 μm or more and 30 μm or less. By forming the outermost layer within the range of the wet film thickness specified in the present invention, the objective effect of the present invention becomes more prominent, and the effect can be enjoyed most in the range of 5.0 μm or more and 20 μm or less. Although the details of the effects obtained by setting the conditions specified above are not clear, the surface of the porous ink receiving layer does not dry quickly if the wet film thickness of the outermost layer exceeds a certain range. It is estimated that this is because a uniform film cannot be formed due to the adverse effects of the unevenness. On the contrary, when the wet film thickness is less than 5.0 μm, it is difficult to apply uniformly industrially, and application failure is likely to occur, resulting in deterioration of the quality of the ink jet recording medium.

  Moreover, various surfactants can be used for the said outermost layer for the purpose of improving the liquid physical property at the time of application | coating of an outermost layer, the applicability | paintability, and another objective. As such a surfactant, an anionic, cationic or nonionic surfactant is preferably used, but it is necessary to select ionicity so that resin fine particles in the ink do not aggregate on the surface of the recording medium. Among the active agents, acetylene glycol-based nonionic surfactants are particularly preferred from the viewpoints of print characteristics of the recording medium having the outermost layer coated on the porous layer, particularly glossiness, bleeding resistance and absorbability.

  The outermost layer according to the present invention is formed by coating an aqueous coating solution mainly containing inorganic fine particles on the porous ink receiving layer under the wet film thickness condition defined in the present invention. As the coating method, conventionally known coating methods can be applied. For example, a gravure coating method, a roll coating method, a rod bar coating method, an air knife coating method, an extrusion coating method, a curtain coating method, or a U.S. Pat. The extrusion coating method using the hopper described in Japanese Patent No. 2,681,294 can be used, but the outermost layer having a wet film thickness of 5.0 μm or more and 30 μm or less can be formed uniformly and with high accuracy. From the viewpoint of possible, it is particularly preferable to apply a slot nozzle spray coating apparatus.

  Hereinafter, a slot nozzle spray coating apparatus preferably used for forming the outermost layer according to the present invention will be described.

  In the formation of the outermost layer according to the present invention, the substrate to which the porous ink receiving layer is coated on the support is moved (conveyed) relative to the coating liquid nozzle of the coating apparatus, and continuously. The outermost layer is formed. The coating liquid (outermost layer coating liquid) nozzle of the coating device is at least applied to the coating width of the coated body (refers to the length of the coated portion of the coated body in the direction intersecting the transport direction of the coated body). The coating liquid is applied onto the coated body simply by transporting the coated body with respect to the coating apparatus by disposing the corresponding length so as to intersect the transporting direction of the coated body. When the object to be coated is a long belt-like support, the belt-like support itself is transported in the longitudinal direction of the belt-like support, and the coating liquid nozzle of the coating device is moved in the width direction of the belt-like support (perpendicular to the longitudinal direction). Preferably in the direction of An extremely thin coating film can be applied with high film thickness uniformity without a drying load by conveying the object to be coated in one direction to the coating apparatus and spraying the coating liquid as droplets over the coating width.

In addition, the outermost layer droplets sprayed from the coating liquid nozzle of the coating device, in the coating width direction,
1: the droplet size distribution is uniform,
2: The area range in which the droplets fall on the coated body has a uniform drop length in the transport direction,
3: The angle falling on the coated body is uniform,
4: The collision speed falling on the coated body is uniform,
By this, it becomes possible to ensure the uniformity of the coating film thickness.

  That the droplet diameter distribution is uniform in the coating width direction specifically means that the variation of the average droplet diameter is ± 20% or less in the coating width direction. More preferably, it is ± 10% or less.

  In addition, that the length in the transport direction of the area range in which the droplets fall on the coated body is uniform means that the variation in the length in the coating width direction is ± 10% or less. More preferably, it is ± 5% or less.

  Further, the spread angle of the liquid droplets falling on the coated body is uniform, the fluctuation of the falling angle of the liquid droplets falling on the coated body in the coating width direction with the coating liquid nozzle of the coating device as a base point, It means ± 10% or less. More preferably, it is ± 5% or less.

  Further, that the spatial density of the droplet group falling on the coated body is uniform means that the variation in the spatial density of the droplet group falling on the coated body in the coating width direction is ± 10% or less. To tell. More preferably, it is ± 5% or less.

  In order to achieve a uniform spray as described above, it is particularly preferable to use a slot nozzle spray device in the present invention.

  The slot nozzle spray device has a plurality of coating liquid nozzle holes for discharging the coating liquid in the coating width direction. The coating solution nozzle holes may be arranged in a line in the coating width direction or in a staggered manner. And a gas nozzle hole for ejecting gas in the vicinity of the coating liquid nozzle hole, and a mechanism for colliding the gas ejected from the nozzle with the coating liquid ejected from the coating liquid nozzle hole to form a droplet. Have.

  As a slot nozzle spray device that can be preferably used in the present invention, for example, a device described in JP-A-6-170308 can be applied. Japanese Patent Laid-Open No. 6-170308 discloses an example in which an adhesive for disposable diapers is applied onto a fiber using this slot nozzle spray device. However, an extremely high viscosity coating liquid (adhesive) is applied to the slot nozzle. It is dropped in a fiber form from a coating liquid nozzle (coating liquid discharge portion) of the spray device, and the coating apparatus and the object to be coated (fiber) are connected by the fiber-shaped coating liquid. That is, unlike the manufacturing method of the present invention, it is not applied as a discontinuous droplet on the object to be coated. The fiber-like coating liquid falling in parallel from each of the plurality of coating liquid nozzles provided over the coating width is disturbed by the gas ejected from the gas nozzle provided in the vicinity of the coating liquid nozzle, preventing vertical drop. And only land randomly within a certain area on the coated body. Without the gas nozzle, the fiber-like coating liquid falls vertically as it is, but by ejecting the gas from the gas nozzle, it is possible to disperse and land the coating liquid over a wider range. The coating layer is simply spread and placed, and is not a coating that requires strictly uniform coating film thickness over the entire surface of the coated body as described in the example of the ink jet recording medium. Further, since the adhesive is applied, the formed coating film is extremely thick.

  Further, a slot nozzle spray coating apparatus disclosed in JP-A-5-309310 can also be preferably used in the present invention. In the example disclosed in Japanese Patent Laid-Open No. 5-309310, a hot melt type adhesive is applied onto an object to be coated, as in the above-mentioned Japanese Patent Laid-Open No. 6-170308. Since this is also a very high viscosity coating liquid (adhesive), it is a method of continuously discharging the coating liquid to the surface of the coated body in the form of fibers, and there is no strict film thickness uniformity. The coating film to be formed is also very thick.

  In the present invention, the slot nozzle spray coating apparatus described in JP-A No. 2004-106378 can be preferably used particularly from the viewpoints of coating uniformity and coating ease.

  Next, a specific form of the slot nozzle spray coating apparatus used in the coating apparatus according to the present invention will be described.

  FIG. 1 is a schematic view for explaining the production method of the present invention. In the figure, reference numeral 1 is a slot nozzle spray portion of a slot nozzle spray device (the whole is not shown), and 9 is a long belt-like support-type coated body.

  The coated body 9 is transported at a constant speed by a transport means (not shown) in the transport direction indicated by the arrow in the drawing, which is the longitudinal direction of the coated body 9. The coating liquid nozzle C of the slot nozzle spray unit 1 has a length in the width direction of the object 9 to be applied, which is a direction orthogonal to the transport direction, and is disposed so as to face the application surface of the object 9 to be applied. Yes. From the coating liquid nozzle C, the outermost layer coating liquid is sprayed in the form of droplets, and coating is performed by landing the droplets on the substrate 9 to be transported. At this time, the length to which the outermost surface layer coating solution in the width direction of the body 9 is applied corresponds to the coating width indicated by the arrow in the figure. In FIG. 1, the application width is shorter than the length in the width direction of the article 9 to be applied, but it may of course be the same.

  FIG. 2 is a schematic cross-sectional view showing an example of a slot nozzle spray device including the slot nozzle spray unit described in FIG.

  The slot nozzle spray unit 1 includes a pair of internal die blocks 3a and 3b and external die blocks 2a and 2b on the outside of the pair of internal die blocks 3a and 3b. The coating liquid nozzle C is formed in the gas nozzle D between the internal die block 3a and the external die block 2a, and between the internal die block 3b and the external die block 2b.

  In FIG. 2, the slot nozzle spray unit 1 has a pair of gas nozzles D having a gas pocket A and a coating liquid nozzle C having a coating liquid pocket B. The outermost layer coating solution has a viscosity (preferably 0.1 to 250 mPa · s) capable of forming droplets without forming a fiber, and a coating solution such as a function-imparting compound-containing solution is placed in the preparation kettle 4, and the pump 5, It is supplied to the coating liquid pocket B through the flow meter 6 and guided to the coating liquid nozzle 3. On the other hand, pressurized air is supplied from the pressurized air source 7 to the gas pocket A via the valve 8 to the gas nozzle 2. At the time of application, the application liquid is supplied from the preparation kettle 4 so that the specified application amount is applied from the application liquid nozzle C, and at the same time, pressurized air is sprayed from the pair of gas nozzles D to form the application liquid in the form of droplets. It is sprayed and deposited on the body 9. In the production method of the present invention, the outermost layer coating liquid can be sprayed as fine droplets instead of in the form of fibers. By supplying the outermost layer coating liquid as fine droplets onto the surface of the object 9 to be coated, a highly uniform thin film can be formed at high speed without drying load.

  FIG. 3 shows an example of a coating production line in which the slot nozzle spray device as described above is arranged. Here, as the coated body, a substrate in which a porous ink receiving layer is coated is used. After applying the porous ink receiving layer, a plurality of (multistage) slot nozzle spray devices were arranged in the drying process. The formation of the porous ink receiving layer and the application of the outermost layer according to the present invention on the same line are called online coating.

  A porous material supplied from the flow-regulating slide bead coating device 20 in the process of passing the support roller 21 from the original winding of the support by a transport means (not shown) and further reversely transporting at the position of the backup roll 22. A coating solution for the quality ink receiving layer is applied. Since the coating liquid for the porous ink receiving layer contains a hydrophilic binder, it is cooled once in the cooling zone 30 and fixed. The substrate 9 having the porous ink receiving layer on the support is conveyed to the drying process. In the drying process, a reverser 23 that blows air and reversely conveys the coating film surface in a non-contact manner and a normal conveyance roller 24 that reversely conveys the reverse surface of the coated object 9 are provided alternately. Is meandering. In this drying step, hot air is blown to dry (the hot air blowing means is not shown). Application by droplet spraying as described above is performed by the two slot nozzle spray devices 1 in the middle of this drying process, preferably at a position after the reduced rate drying. Of the two slot nozzle sprays, at least one is preferably placed at a position after the drying end point from the viewpoint of drying properties. In this example, two slot nozzle spray devices are used, but one or of course three or more nozzles may be used.

  Next, the porous ink receiving layer, the support and other components constituting the ink jet recording medium of the present invention will be described.

  The porous ink receiving layer according to the present invention is composed of at least inorganic fine particles and a hydrophilic binder.

  As the inorganic fine particles, various kinds of solid fine particles known in ink jet recording media can be used.

  Examples of inorganic fine particles include, for example, light calcium carbonate, heavy calcium carbonate, magnesium carbonate, kaolin, clay, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc hydroxide, zinc sulfide, zinc carbonate, hydro White inorganic pigments such as talcite, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, synthetic amorphous silica, colloidal silica, alumina, colloidal alumina, pseudoboehmite, aluminum hydroxide, lithopone, zeolite, magnesium hydroxide, etc. Can be mentioned.

  The inorganic fine particles may be used as primary particles in a state of being uniformly dispersed in the hydrophilic binder, or may be added in a state of being dispersed in the hydrophilic binder by forming secondary agglomerated particles. However, the latter is more preferable from the viewpoint of achieving high ink absorbency. The shape of the inorganic fine particles is not particularly limited in the present invention, and may be spherical, rod-like, needle-like, flat-plate-like, or bead-like.

  The inorganic fine particles preferably have an average particle size of 3 to 200 nm. If the average particle size is 200 nm or less, high glossiness of the porous ink receiving layer can be achieved, and a clear image can be obtained by preventing the decrease in the maximum density due to irregular reflection on the surface.

  As the inorganic fine particles according to the present invention, composite particles composed of inorganic fine particles and a small amount of an organic substance (which may be a low molecular compound or a high molecular compound) are substantially regarded as inorganic fine particles. Also in this case, the particle diameter of the highest order particle observed in the dry film is defined as the particle diameter of the inorganic fine particles.

  The mass ratio of the organic matter / inorganic fine particle in the composite particle of the inorganic fine particle and a small amount of organic substance is approximately 1/100 to 1/4.

  The inorganic fine particles according to the present invention are preferably low refractive index fine particles from the viewpoint of low cost and high reflection density, and silica, particularly silica synthesized by a vapor phase method is more preferable.

  Further, cation surface-treated gas phase method silica, cation surface-treated colloidal silica and alumina, colloidal alumina, pseudoboehmite and the like can also be used.

The amount of inorganic fine particles used in the porous ink-receiving layer depends largely on the required ink absorption capacity, the void ratio of the void layer, the type of inorganic fine particles, and the type of hydrophilic binder, but in general, the recording sheet is 1 m ^2. Usually, it is 3 to 30 g, preferably 5 to 25 g. The ratio of inorganic fine particles and polyvinyl alcohol used in the porous ink receiving layer is usually 2: 1 to 20: 1 by mass ratio, and particularly preferably 3: 1 to 10: 1.

  The ink absorption capacity increases with the amount of inorganic fine particles added, but curling, cracking, etc. are likely to deteriorate, so a method of increasing the capacity by controlling the porosity is preferred. A preferable porosity is 40 to 85%. The porosity can be adjusted by the type of inorganic fine particles and binder selected, or by their mixing ratio, or by the amount of other additives.

  The porosity here refers to the ratio of the total volume of the voids to the volume of the void layer, and is calculated from the total volume of the layer components and the layer thickness. The total volume of the voids can be easily determined by measuring the amount of saturation transition and water absorption by Bristow measurement.

  Next, details of the hydrophilic binder will be described.

  The term “hydrophilic” as used in the present invention means that it is soluble in water or a mixed solvent of water and a water-miscible organic solvent such as methanol, isopropyl alcohol, acetone, and ethyl acetate. . In this case, the ratio of the water-miscible organic solvent is usually 50% by mass or less based on the total amount of the solvent. Further, the hydrophilic polymer refers to a polymer that normally dissolves in an amount of 1% by mass or more at room temperature, more preferably 3% by mass or more.

  Examples of the hydrophilic binder used in the porous ink receiving layer include polyvinyl alcohol, gelatin, polyethylene oxide, polyvinyl pyrrolidone, casein, starch, agar, carrageenan, polyacrylic acid, polymethacrylic acid, polyacrylamide, and polymethacrylic acid. Examples include hydrophilic polymers such as amide, polystyrene sulfonic acid, cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, dextran, dextrin, pullulan, and water-soluble polyvinyl butyral. In the present invention, a hydrophilic polymer having a hydroxyl group is used. It is preferable to use, and it is particularly preferable that the hydrophilic polymer having a hydroxyl group is polyvinyl alcohol.

  This polyvinyl alcohol includes, in addition to ordinary polyvinyl alcohol obtained by hydrolyzing polyvinyl acetate, modified polyvinyl alcohol such as cation-modified polyvinyl alcohol and anion-modified polyvinyl alcohol having an anionic group.

  As the polyvinyl alcohol obtained by hydrolyzing vinyl acetate, those having an average degree of polymerization of 1000 or more are preferably used, and those having an average degree of polymerization of 1500 to 5000 are particularly preferably used. 100% is preferable, and 80 to 99.5% is particularly preferable.

  Examples of the cation-modified polyvinyl alcohol have primary to tertiary amino groups and quaternary ammonium groups in the main chain or side chain of the polyvinyl alcohol as described in JP-A-61-110483. Polyvinyl alcohol, which is obtained by saponifying a copolymer of an ethylenically unsaturated monomer having a cationic group and vinyl acetate.

  Examples of the ethylenically unsaturated monomer having a cationic group include trimethyl- (2-acrylamido-2,2-dimethylethyl) ammonium chloride and trimethyl- (3-acrylamido-3,3-dimethylpropyl) ammonium chloride. N-vinylimidazole, N-vinyl-2-methylimidazole, N- (3-dimethylaminopropyl) methacrylamide, hydroxylethyltrimethylammonium chloride, trimethyl- (2-methacrylamidopropyl) ammonium chloride, N- (1, 1-dimethyl-3-dimethylaminopropyl) acrylamide and the like.

  The ratio of the cation-modified group-containing monomer of the cation-modified polyvinyl alcohol is 0.1 to 10 mol%, preferably 0.2 to 5 mol%, relative to vinyl acetate.

  Examples of the anion-modified polyvinyl alcohol include polyvinyl alcohol having an anionic group as described in JP-A-1-206088, and those described in JP-A-61-237681 and JP-A-63-307979. Examples thereof include a copolymer of vinyl alcohol and a vinyl compound having a water-soluble group, and modified polyvinyl alcohol having a water-soluble group as described in JP-A-7-285265.

  Nonionic modified polyvinyl alcohol is, for example, a polyvinyl alcohol derivative obtained by adding a polyalkylene oxide group to a part of vinyl alcohol as described in JP-A-7-9758, and described in JP-A-8-25595. And a block copolymer of a vinyl compound having a hydrophobic group and vinyl alcohol.

  Furthermore, polyvinyl alcohol modified with a silyl group is also included in the polyvinyl alcohol in the present invention as the modified polyvinyl alcohol.

  In addition, two or more kinds of polyvinyl alcohols having different types such as polymerization degree, saponification degree and modification may be used in combination.

  Further, gelatin, polyethylene oxide or polyvinyl pyrrolidone can be used in combination with polyvinyl alcohol, but these hydrophilic polymers are preferably in the range of 0 to 50% by mass, particularly preferably in the range of 0 to 20% by mass with respect to polyvinyl alcohol. Can be used.

  In the porous ink receiving layer according to the present invention, a cationic polymer can be used in combination with the hydrophilic polymer having a hydroxyl group.

Examples of cationic polymers that can be used in the present invention include polyethyleneimine, polyallylamine, polyvinylamine, dicyandiamide polyalkylene polyamine condensate, polyalkylene polyamine dicyandiamide ammonium salt condensate, dicyandiamide formalin condensate, epichlorohydrin dialkylamine addition polymer , diallyl dimethyl ammonium chloride polymer, diallyl dimethyl ammonium chloride-SO ₂ copolymer, polyvinyl imidazole, polyvinyl pyrrolidone, vinyl imidazole copolymers, polyvinyl pyridine, polyamidine, chitosan, cationized starch, vinylbenzyltrimethylammonium chloride polymers, (2-Methacryloyloxyethyl) trimethylammonium chloride polymer, dimethyla Roh methacrylate polymer, and the like.

  Alternatively, the cationic polymer described in the Chemical Industry Times, August 15 and 25, 1998, and the polymer dye fixing agent described in “Introduction to Polymer Drugs” issued by Sanyo Chemical Industries, Ltd. can be given as examples.

  The average molecular weight of the cationic polymer that can be used in the present invention is preferably in the range of 2000 to 500,000, and more preferably in the range of 3000 to 100,000.

  The average molecular weight is a number average molecular weight and refers to a polyethylene glycol equivalent value obtained from gel permeation chromatography.

  When the cationic polymer that can be used in the present invention is added to the coating solution in advance, it may be added not only uniformly to the coating solution but also in the form of forming composite particles together with inorganic fine particles. As a method for preparing composite particles by using inorganic fine particles and a cationic polymer, a method in which a cationic polymer is mixed with inorganic fine particles and adsorbed and coated, a method in which the coated particles are aggregated to obtain higher order composite particles, and further a mixing For example, the coarse particles obtained can be made into more uniform composite particles with a disperser.

  Although the cationic polymer that can be used in the present invention generally has a water-soluble group and exhibits water solubility, it may not be dissolved in water depending on, for example, the composition of the copolymerization component. Although it is preferable that it is water-soluble from the ease of manufacture, even if it is sparingly soluble in water, it can be dissolved and used using a water-miscible organic solvent.

  Here, the water-miscible organic solvent means alcohols such as methanol, ethanol, isopropanol, and n-propanol, glycols such as ethylene glycol, diethylene glycol, and glycerin, esters such as ethyl acetate and propyl acetate, acetone, and methyl ethyl ketone. An organic solvent that can dissolve approximately 10% or more in water, such as ketones and amides such as N, N-dimethylformamide. In this case, the amount of the organic solvent used is preferably equal to or less than the amount of water used.

The cationic polymer is generally used in the range of 0.1 to 10 g, preferably 0.2 to 5 g, per 1 m ² of the porous ink receiving layer.

  In the porous ink receiving layer according to the present invention, it is preferable to add a hydrophilic binder curing agent that forms the porous ink receiving layer.

  The curing agent that can be used in the present invention is not particularly limited as long as it causes a curing reaction with a water-soluble binder, but boric acid and its salts are preferable, but other known ones can be used. Specifically, it is a compound having a group capable of reacting with the hydrophilic binder or a compound that promotes the reaction between different groups of the hydrophilic binder, and is appropriately selected depending on the type of the hydrophilic binder.

  Examples of the curing agent that can be used in the present invention include epoxy curing agents (diglycidyl ethyl ether, ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-diglycidyl cyclohexane, N, N-diglycidyl-4-glycidyloxyaniline, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, etc.), aldehyde curing agents (formaldehyde, glioxal, etc.), active halogen curing agents (2,4-dichloro-4-hydroxy-1) , 3,5-s-triazine, etc.), active vinyl compounds (1,3,5-trisacryloyl-hexahydro-s-triazine, bisvinylsulfonylmethyl ether, etc.), aluminum alum and the like.

  Boric acid or a salt thereof refers to an oxygen acid having a boron atom as a central atom and a salt thereof, specifically, orthoboric acid, diboric acid, metaboric acid, tetraboric acid, pentaboric acid, and octaboron. Examples include acids and their salts.

  Boric acid having a boron atom and a salt thereof as a curing agent may be used alone or in combination of two or more. Particularly preferred is a mixed aqueous solution of boric acid and borax.

  The aqueous solutions of boric acid and borax can be added only in relatively dilute aqueous solutions, respectively, but by mixing both, a concentrated aqueous solution can be obtained and the coating solution can be concentrated. Further, there is an advantage that the pH of the aqueous solution to be added can be controlled relatively freely. The total amount of the curing agent used is preferably 1 to 600 mg per 1 g of the hydrophilic binder.

  An acid can be used for the purpose of lowering the film surface pH of the recording medium comprising the outermost layer and the porous ink receiving layer according to the present invention. For example, inorganic acids such as sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, citric acid, formic acid And organic acids such as acetic acid, phthalic acid, succinic acid, succinic acid, and polyacrylic acid.

  Examples of the alkali used for the purpose of increasing the film surface pH of the recording medium comprising the outermost layer and the porous ink receiving layer include sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, borax, sodium phosphate, Examples include calcium hydroxide and organic amines.

  The pH adjusting agent is particularly preferred when the pH in the coating solution for forming a porous film is different from the preferred film surface pH of the recording medium.

  The film surface pH of the porous ink receiving layer of the ink jet recording medium varies depending on the type of ink, but in general, the water resistance and bleeding of the dye are improved on the more acidic side, but the light resistance is higher on the higher pH side. Since there is a large tendency to improve, the optimum pH is selected in combination with the ink to be used. The membrane surface pH of the porous surface is preferably 3 to 7, more preferably 3.5 to 6.5, and particularly preferably 4.0 to 6.5. The film surface pH referred to here is J.I. It is a value measured in accordance with the paper surface pH measurement method specified in TAPPI 49. Specifically, 50 μl of pure water (pH = 6.2 to 7.3) is dropped onto the surface of the recording medium, and is commercially available. The value measured using a plane electrode.

  In the porous ink receiving layer according to the present invention, a water-soluble polyvalent metal compound may be used.

  Examples of the water-soluble polyvalent metal compound according to the present invention include metal hydrochlorides such as aluminum, calcium, magnesium, zinc, iron, strontium, barium, nickel, copper, scandium, gallium, indium, titanium, zirconium, tin, and lead. , Sulfate, nitrate, acetate, formate, succinate, malonate, chloroacetate and the like. Of these, water-soluble salts composed of aluminum, calcium, magnesium, zinc and zirconium are preferred because their metal ions are colorless. Furthermore, a water-soluble aluminum compound and a water-soluble zirconium compound are particularly preferable in that they are excellent in bleeding resistance during long-term storage.

  Specific examples of water-soluble aluminum compounds include polyaluminum chloride (basic aluminum chloride), aluminum sulfate, basic aluminum sulfate, aluminum potassium sulfate (alum), ammonium aluminum sulfate (ammonium alum), sodium aluminum sulfate, aluminum nitrate, phosphorus Examples thereof include aluminum oxide, aluminum carbonate, polysulfuric acid aluminum silicate, aluminum acetate, and basic aluminum lactate. Here, the water solubility in the water-soluble polyvalent metal compound means that it is dissolved in water at 20 ° C. by 1% by mass or more, more preferably 3% by mass or more.

  The most preferable water-soluble aluminum compound is basic aluminum chloride having a basicity of 80% or more from the viewpoint of ink absorbability, and can be represented by the following molecular formula.

[Al ₂ (OH) _n Cl _6-n ] _m
(However, 0 <n <6, m ≦ 10)
The basicity is represented by n / 6 × 100 (%).

  Specific examples of the water-soluble zirconium compound are preferably zirconyl carbonate, zirconyl ammonium carbonate, zirconyl acetate, zirconyl nitrate, zirconium oxychloride, zirconyl lactate and zirconyl citrate. Zirconyl ammonium carbonate and zirconyl acetate are particularly preferred. In particular, zirconium oxychloride and zirconyl acetate are preferred from the viewpoint of bleeding resistance during long-term storage.

  Various additives other than those described above can be added to the porous ink-receiving layer of the ink jet recording medium according to the present invention. In particular, image storability such as an ultraviolet absorber, an antioxidant, and a blurring inhibitor. It is preferable to contain an improver.

  These UV absorbers, antioxidants, and blurring inhibitors include alkylated phenol compounds (including hindered phenol compounds), alkylthiomethylphenol compounds, hydroquinone compounds, alkylated hydroquinone compounds, tocopherol compounds, thiodiphenyl ether compounds, two Compounds having the above thioether bonds, bisphenol compounds, O-, N-, S-benzyl compounds, hydroxybenzyl compounds, triazine compounds, phosphonate compounds, acylaminophenol compounds, ester compounds, amide compounds, ascorbic acid, amine antioxidants Agent, 2- (2-hydroxyphenyl) benzotriazole compound, 2-hydroxybenzophenone compound, acrylate, water-soluble or hydrophobic metal salt, organometallic compound, metal complex, Nardamine compounds (including so-called TEMPO compounds), 2- (2-hydroxyphenyl) 1,3,5, -triazine compounds, metal deactivators, phosphite compounds, phosphonite compounds, hydroxyamine compounds, nitrone compounds, Peroxide scavenger, polyamide stabilizer, polyether compound, basic auxiliary stabilizer, nucleating agent, benzofuranone compound, indolinone compound, phosphine compound, polyamine compound, thiourea compound, urea compound, hydrazide compound, amidine compound, sugar compound, Examples thereof include hydroxybenzoic acid compounds, dihydroxybenzoic acid compounds, and trihydroxybenzoic acid compounds.

  Among these, alkylated phenol compounds, compounds having two or more thioether bonds, bisphenol compounds, ascorbic acid, amine-based antioxidants, water-soluble or hydrophobic metal salts, organometallic compounds, metal complexes, hindered amine compounds, Hydroxyamine compounds, polyamine compounds, thiourea compounds, urea compounds, hydrazide compounds, hydroxybenzoic acid compounds, dihydroxybenzoic acid compounds, trihydroxybenzoic acid compounds, and the like are preferable.

  Organic latex fine particles such as polystyrene, polyacrylic acid esters, polymethacrylic acid esters, polyacrylamides, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, or copolymers thereof, urea resin, or melamine resin Oil droplet fine particles such as liquid paraffin, dioctyl phthalate, tricresyl phosphate, silicone oil, various surfactants such as cation or nonion, JP-A-57-74193, JP-A-57-87988, and JP-A-62-261476 JP-A-57-74192, JP-A-57-87989, JP-A-60-72785, JP-A-61-14659, JP-A-1-95091 and JP-A-3-13376. Anti-fading agent described in publications JP-A-59-42993, 59-52689, 62-280069, 61-242871, and JP-A-4-219266, etc. Contains various known additives such as pH adjusters such as phosphoric acid, citric acid, sodium hydroxide, potassium hydroxide, potassium carbonate, antifoaming agents, preservatives, thickeners, antistatic agents, matting agents, etc. You can also.

  Next, the support used for the ink jet recording medium of the present invention will be described.

  As the support used in the present invention, those conventionally known for inkjet recording media can be appropriately used.

  Examples of the water-absorbing support that can be used in the present invention include sheets and plates made of general paper, cloth, wood, etc., but especially paper is excellent in water absorption of the substrate itself and is cost-effective. It is most preferable because it is excellent. As the paper support, the main raw materials are chemical pulps such as LBKP and NBKP, mechanical pulps such as GP, CGP, RMP, TMP, CTMP, CMP, and PGW, and wood pulp such as waste paper pulp such as DIP. It is. In addition, various fibrous materials such as synthetic pulp, synthetic fiber, and inorganic fiber can be appropriately used as raw materials as necessary.

  If necessary, various conventionally known additives such as sizing agents, pigments, paper strength enhancers, fixing agents, fluorescent whitening agents, wet paper strength agents, cationizing agents and the like are added to the paper support. be able to.

  The paper support can be produced by mixing various fibrous materials such as wood pulp and various additives and using various paper machines such as a long net paper machine, a circular net paper machine, and a twin wire paper machine. If necessary, the paper can be subjected to size press treatment with starch, polyvinyl alcohol or the like, various coating treatments, or calendar treatment on a paper making stage or a paper machine.

  Examples of the non-water-absorbing support that can be preferably used in the present invention include a plastic resin film support or a support in which both surfaces of paper are coated with a plastic resin film.

  Examples of the plastic resin film support include a polyester film, a polyvinyl chloride film, a polypropylene film, a cellulose triacetate film, a polystyrene film, and a film support in which these are laminated. These plastic resin films can be transparent or translucent.

  A particularly preferred support in the present invention is a support in which both sides of paper are coated with a plastic resin, and most preferred is a support in which both sides of paper are coated with a polyolefin resin.

  Hereinafter, a non-water-absorbing paper support laminated with polyethylene, which is the most preferred polyolefin resin, will be described.

  The base paper used for the paper support is made from wood pulp as the main raw material, and if necessary, synthetic pulp such as polypropylene or synthetic fibers such as nylon or polyester is added to the wood pulp. As wood pulp, for example, any of LBKP, LBSP, NBKP, NBSP, LDP, NDP, LUKP, NUKP can be used, but more LBKP, NBSP, LBSP, NDP, LDP with more short fibers are used. Is preferred. However, the ratio of LBSP or LDP is preferably 10% by mass or more and 70% by mass or less.

  The pulp is preferably a chemical pulp (sulfate pulp or sulfite pulp) with few impurities, and a pulp having a whiteness improved by bleaching is also useful.

  In the base paper, sizing agents such as higher fatty acids and alkyl ketene dimers, white pigments such as calcium carbonate, talc and titanium oxide, paper strength enhancing agents such as starch, polyacrylamide and polyvinyl alcohol, fluorescent whitening agents, polyethylene glycols A water retaining agent such as a dispersant, a softening agent such as a quaternary ammonium, and the like can be appropriately added.

  The freeness of the pulp used for papermaking is preferably 200 to 500 ml as defined by CSF, and the fiber length after beating is a 24 mesh residual mass% defined by JIS-P-8207, and 42 30-70 mass% of sum with the mass% of a mesh remainder is preferable. In addition, it is preferable that the mass% of 4 mesh remainder is 20 mass% or less.

The basis weight of the base paper is preferably 50 to 250 g, particularly preferably 70 to 200 g. The thickness of the base paper is preferably 50 to 210 μm. The base paper can be given a high smoothness by subjecting it to a calendar process at the paper making stage or after paper making. The density of the base paper is generally 0.7 to 1.2 g / cm ³ (according to the method defined in JIS-P-8118). Furthermore, the base paper stiffness is preferably 20 to 200 g under the conditions specified in JIS-P-8143. A surface sizing agent may be applied to the surface of the base paper. As the surface sizing agent, the same sizing agents that can be added to the base paper can be used. The pH of the base paper is preferably 5 to 9 when measured by a hot water extraction method defined in JIS-P-8113.

  The polyethylene that covers the front and back surfaces of the base paper is mainly low-density polyethylene (LDPE) or high-density polyethylene (HDPE), but other LLDPE, polypropylene, and the like can also be used in part.

  In addition, the polyethylene layer on the side where the porous ink receiving layer is applied is improved in opacity and whiteness by adding rutile or anatase type titanium oxide to polyethylene as is widely done in photographic paper. Is preferred. The titanium oxide content is 1 to 20% by mass, preferably 2 to 15% by mass, based on polyethylene.

  In the polyolefin layer, a pigment having high heat resistance and a fluorescent brightening agent for adjusting the white background can be added. Examples of the color pigment include ultramarine blue, bitumen, cobalt blue, phthalocyanine blue, manganese blue, cerulean, tungsten blue, molybdenum blue, anthraquinone blue, and the like. Examples of the optical brightener include dialkylaminocoumarin, bisdimethylaminostilbene, bismethylaminostilbene, 4-alkoxy-1,8-naphthalenedicarboxylic acid-N-alkylimide, bisbenzoxazolylethylene, and dialkylstilbene. It is done.

  The amount of polyethylene used on the front and back of the paper is selected so as to optimize the curl at low and high humidity after the film thickness of the porous ink receiving layer and the back layer are provided. The thickness ranges from 15 to 50 μm on the porous ink receiving layer side and from 10 to 40 μm on the back layer side. The ratio of the front and back polyethylene is preferably set so as to adjust the curl which varies depending on the type and thickness of the porous ink receiving layer, the thickness of the inner paper, etc. It is about 3/1 to 1/3.

  Furthermore, the polyethylene-coated paper support preferably has the following characteristics.

1. Tensile strength: strength defined by JIS-P-8113, preferably 20 to 300 N in the vertical direction and 10 to 200 N in the horizontal direction. 2. Tear strength: 0.1 to 2N in the vertical direction and 0.2 to 2N in the horizontal direction are preferable according to a method defined by JIS-P-8116. Compression modulus: ≧ 9.8 kN / cm ²
4). Surface Beck smoothness: 500 seconds or more is preferable as a glossy surface under the conditions specified in JIS-P-8119, but it may be less than this for so-called molded products. Back surface Beck smoothness: 100 to 800 seconds are preferable under the conditions specified in JIS-P-8119. Opacity: Under the measurement conditions of linear light incidence / diffuse light transmission conditions, the transmittance for light in the visible range is 20% or less, particularly preferably 15% or less. Whiteness: Hunter whiteness specified in JIS-P-8123, preferably 90% or more. Further, when measured by JIS-Z-8722 (non-fluorescent) and JIS-Z-8717 (containing fluorescent agent) and displayed by the color display method defined in JIS-Z-8730, L ^* = 90 to 98, a ^* = − 5 to +5, b ^* = − 10 to +5 are preferable.

An undercoat layer can be provided on the porous ink receiving layer side of the support for the purpose of improving the adhesion to the porous ink receiving layer. The binder for the undercoat layer is preferably a hydrophilic polymer such as gelatin or polyvinyl alcohol, or a latex polymer having a Tg of −30 to 60 ° C. These binders are used in the range of 0.001 to ² g per m ² of the recording medium. In the undercoat layer, a small amount of a conventionally known antistatic agent such as a cationic polymer can be contained for the purpose of antistatic.

  A back layer may be provided on the surface of the support opposite to the surface of the porous ink receiving layer for the purpose of improving slipperiness and charging characteristics. The binder for the back layer is preferably a hydrophilic polymer such as gelatin or polyvinyl alcohol, a latex polymer having a Tg of −30 to 60 ° C., an antistatic agent such as a cationic polymer, various surfactants, and an average. A matting agent having a particle size of about 0.5 to 20 μm can also be added. The thickness of the back layer is generally 0.1 to 1 μm, but in the case where the back layer is provided for preventing curling, it is generally in the range of 1 to 20 μm. Further, the back layer may be composed of two or more layers.

  In the method for producing an ink jet recording medium of the present invention, examples of a coating method or a coating apparatus that can be used for coating a porous ink-receiving layer coating solution include a curtain coating method or US Pat. No. 2,761,419. The slide bead coating method using the hopper described in Japanese Patent No. 2,761,791 and the extrusion coating method can be used. In the present invention, in particular, the slide curtain coating device or the slide hopper is used. It is preferable to use a mold coating device, and these coating devices are capable of high-speed, thin film, and multilayer simultaneous coating, and are widely used as coating devices for photographic photosensitive materials, inkjet recording media, magnetic recording media, etc. Yes.

  In the ink jet recording medium of the present invention, the porous ink receiving layer and the outermost layer are formed on the support according to the above method, dried, and then laminated in a roll or cut into a sheet Thus, the heating treatment is performed at 35 ° C. or more for 12 hours or more, and further, the heating treatment is preferably performed in the range of 35 to 50 ° C. and 12 hours to 7 days.

  By applying the heating treatment specified above, it is possible to increase the coating strength of the outermost layer by imparting mild fusion between the inorganic fine particles constituting the outermost layer, resulting in excellent scratch resistance. Sex can be obtained.

  Next, a method for ink jet recording using the recording medium of the present invention will be described.

  The recording medium of the present invention is suitably used as a recording medium for aqueous pigment ink and dye ink.

  The water-based dye ink is an ink using a water-soluble dye as a coloring material, and is an ink obtained by mixing water or an organic solvent having high miscibility with water as an ink solvent. Examples of the dye include conventionally known azo dyes, xanthene dyes, phthalocyanine dyes, quinone dyes, anthraquinone dyes, etc., which are improved in water solubility by introducing a sulfo group or a carboxy group. Basic dyes are typically used.

  On the other hand, as the pigment used in the pigment ink, various conventionally known inorganic or organic pigment inks can be used by inkjet. Examples of inorganic pigment inks include carbon black, titanium oxide, and iron oxide. Examples of organic pigments include various azo pigments, phthalocyanine pigments, anthraquinone pigments, quinacridone pigments, indigo pigments, or lake pigments obtained by reacting water-soluble dyes with polyvalent metal ions. I can do it.

  These pigment particles are preferably used together with various dispersants and dispersion stabilizers such as hydrophilic polymers and surfactants. The pigment particles are preferably used in which the average particle size is dispersed to about 70 to 150 μm with these dispersed local dispersion stabilizers.

  The concentration of the dye and the pigment in the ink depends on the type of the dye or pigment, the form of the ink used (whether or not the dark and light ink is used), and the type of paper, but is generally 0.2 to 10 mass. %.

  Various solvents are used in the ink, and as such an ink solvent, water or an organic solvent having high miscibility with water can be used alone or mixed with water. Specifically, alcohol solvents such as ethanol, 2-propanol, ethylene glycol, propylene glycol, glycerin, 1,2-hexanediol, 1,6-hexanediol, diethylene glycol monomethyl ether, tetraethylene glycol monomethyl ether, 2- Amides such as pyrrolidinone, N-methylpyrrolidone, N, N-dimethylacetamide, amines such as triethanolamine, N-ethylmorpholine, triethylenetetramine, sulfolane, dimethyl sulfoxide, urea, acetonitrile, acetone, etc. These solvents may be used alone or in combination.

  In addition, various surfactants can be used in the ink for the purpose of increasing the permeability of the ink solvent and other purposes. As such a surfactant, an anionic or nonionic surfactant is preferably used. Of these, acetylene glycol surfactants are particularly preferred.

  Next, the substantially colorless ink containing the resin fine particles having the film forming ability according to the present invention will be described.

  The recording ink according to the present invention comprises resin fine particles having a film forming ability and a liquid medium, and preferably comprises resin fine particles, a water-soluble solvent and water as main components.

  In the resin fine particles according to the present invention, the glass transition temperature (Tg) is preferably −50 to 10 ° C., more preferably −20 to 10 ° C., and further preferably −10 to 10 ° C. If the glass transition point is −50 ° C. or higher, the effects of the present invention can be stably exhibited even after storage after printing, and if the glass transition point is 10 ° C. or lower, the film will be broken after storage. Failure prevention and uniform film formation immediately after printing can be obtained.

  In the resin fine particles according to the present invention, the minimum film-forming temperature (MFT) is used because the resin fine particles in the ink stably form a resin film on the surface of the porous layer of the recording medium by natural fusion regardless of the printing environment. ) Is preferably −60 to 10 ° C. In the present invention, a film-forming auxiliary may be added to control the minimum film-forming temperature of the resin fine particles. The film-forming aid is an organic compound that is also called a plasticizer and lowers the minimum film-forming temperature of the resin latex.

  The resin fine particles are not particularly limited as long as they exhibit the effects of the present invention. For example, the resin fine particles may be water-soluble resins or water-insoluble resins. And dispersed in water. Specific examples of the resin include acrylonitrile, styrene, acrylates (acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, 2-hydroxyethyl acrylate, 2-ethylhexyl acrylate, glycidyl acrylate, methacrylic acid, methyl methacrylate, butyl methacrylate), Vinyl acetate, butadiene, vinyl chloride, polyvinylidene chloride, silicone, urethane, olefin (ethylene, propylene), or a copolymer obtained by combining two or more of these monomers is preferable.

  The resin fine particles according to the present invention preferably have an average particle size of 10 to 200 nm, more preferably 10 to 150 nm, and still more preferably 10 to 100 nm.

  If the average particle diameter of the resin fine particles is 10 nm or more, the resin fine particles do not penetrate into the void layer and are present on the surface of the void layer, which is preferable in terms of gloss performance. If the average particle diameter of the resin fine particles is 200 nm or less, the resin fine particles are somewhat small, which is advantageous in terms of leveling properties on the surface of the void layer, and is preferable in terms of gloss performance.

  The average particle size of the resin fine particles can be easily measured using a commercially available particle size measuring device using a light scattering method or a laser Doppler method, for example, Zetasizer 1000 (Malvern).

  The thermoplastic resin to be used is preferably less residual monomer component from the viewpoint of odor and safety, preferably 3% or less, more preferably 1% or less, especially 0.1% with respect to the solid content mass of the polymer. % Or less is preferable.

  The liquid containing resin fine particles and substantially free of a colorant contains 0.1 to 10% by mass of resin and 1 to 50% by mass of a water-soluble medium, and optionally includes a surfactant and an ultraviolet absorber. Each functional compound such as an antioxidant and an antifungal agent may be contained. Furthermore, the liquid according to the present invention does not substantially contain a colorant, which means that it has substantially no function as a recording liquid. For other purposes, for example, for checking the remaining amount of ink. Or, for printing on a white background, the color may be slightly tinted for the purpose of adjusting the color tone of the white background or for confirming the discharge performance.

  As the organic solvent, surfactant, and other additives that can be added to the colorless ink according to the present invention, those that can be added to a recording liquid containing a coloring material can be used.

  For the recording ink and colorless ink according to the present invention, the surface tension of the ink is preferably 40 mN / m or less, and preferably 20 to 40 mN / m, in order to stably discharge, to increase the appearance of high gloss and to improve the ozone resistance. It is more preferable. For the same reason, the ink viscosity is preferably 1.5 to 10 mPa · s, more preferably 3.0 to 8.0 mPa · s.

  Next, the colorless ink application region on the ink jet recording medium will be described. The colorless ink application region can be applied to at least a part of the inkjet recording medium. In order to achieve the effect of the present invention, it is preferable to apply the colorless ink together to the area where the recording ink is not applied and the area where the recording ink is applied.

The amount of colorless ink applied varies depending on the characteristics of the recording ink, colorless ink, and ink jet recording medium, and the appropriate amount that provides the most effect is different, but it is preferable to apply at least 2 ml / m ² or more. However, if more colorless ink than 20 ml / m ² is applied, image quality degradation and gloss reduction are undesirable. The amount of colorless ink applied is preferably adjusted so that the recording ink amount and the total amount of colorless ink are within a certain range for each pixel. In this case, the minimum total amount is preferably ² ml / m ² or more, more preferably 8 ml / m ² or more.

It is also preferable to control the total amount of resin applied by both inks for each pixel in consideration of the resin fine particles contained in the recording ink and the amount of resin contained colorless. 0.3 In this case, the total resin amount of each pixel is preferably set to 0.5 g / m ² or more ^{0.05g / m 2 ~1g / m 2} , more preferably to 1.0 g / m ² or more 0.5 g / m ² .

  Next, a method for applying colorless ink will be described.

  As a method for applying the colorless ink, any method can be used as long as it can be selected and applied to at least a part of the image, but a method of applying using an ink jet head as in the recording ink is preferable. At this time, one or more heads for colorless ink may be prepared and colorless inks having different compositions may be applied. The colorless ink head may be fixed to the same carriage as the recording ink or may be separate. The colorless ink may be applied before, at the same time as, or after the recording ink is recorded, but it is preferable that the colorless ink is preferably fixed on the same carriage and applied at the same time or after the recording ink is recorded in order to achieve the effects of the present invention.

  Next, the ink of the present invention can use alkylamines and alkanolamines as pH adjusters. The pH adjuster has an effect of suppressing a rapid change in the ink pH when the ink lands on the recording medium. Regardless of whether or not it contains a coloring material, the inclusion of the amines in the ink suppresses precipitation and aggregation due to the interaction of the fine particles upon landing with the material contained in the recording medium. This is preferable.

  Specific examples of the alkylamines that can be applied include triethylamine, diethylamine, monoethylamine, and dimethylethylamine. Examples of the alkanolamines include triethanolamine, diethanolamine, monoethanolamine, dimethylethanolamine and the like.

  Examples of the present invention will be described below, but the present invention is not limited to these examples. In the examples, “%” represents mass% unless otherwise specified.

Example 1
<< Preparation of inkjet recording medium >>
[Preparation of Inkjet Recording Medium 101]
(Production of support)
For 100 parts by weight of wood pulp (LBKP / NBSP = 50/50), 1 part by weight of polyacrylamide, 4 parts by weight of ash (talc), 2 parts by weight of cationized starch, and 0.1 part of polyamide epichlorohydrin resin. Slurry liquid containing 5 parts by mass and various addition amounts of alkyl ketene dimer (sizing agent) was prepared, and a base paper was made with a long paper machine so that the basis weight was 170 g / m ² . After calendering this, a low-density polyethylene resin having a density of 0.92 containing 7% by mass of anatase-type titanium oxide and a small amount of a color tone adjusting agent was melt extruded at a temperature of 320 ° C. to a thickness of 28 μm. One side of the paper was coated and cooled immediately with a mirror cooling roller. Then, the opposite surface is coated with a mixed melt of high density polyethylene with a density of 0.96 / low density polyethylene with a density of 0.92 = 70/30 by the same melt extrusion method to a thickness of 32 μm. did.

  The surface on the side where the ink receiving layer is provided had a 60 ° glossiness of 56% and a centerline average roughness Ra of 0.12 μm.

After corona discharge on the titanium oxide-containing layer side of the support, 0.05 g / m ² of gelatin was applied as an undercoat layer.

  On the other side, a styrene / acrylic emulsion containing silica fine particles (matting agent) having an average particle diameter of about 1.0 μm and a small amount of cationic polymer (conductive agent) has a dry film thickness of about 0.5 μm. Thus, a support for applying the ink receiving layer was prepared.

  On the back surface side, the glossiness was about 18%, the center line average roughness Ra was about 4.5 μm, and the Beck smoothness was 160 to 200 seconds.

  The moisture content of the base paper of the support thus obtained was 7.0 to 7.2%.

The support had an opacity of 96.5% and whiteness of L ^* = 95.2, a ^* = 0.56, and b ^* = − 4.35.

(Preparation of ink receiving layer coating solution)
In accordance with the following procedure, an ink receiving layer coating solution having the following composition was prepared.

<Preparation of titanium oxide dispersion>
20 kg of titanium oxide having an average particle size of about 0.25 μm (Ishihara Sangyo: W-10), 150 g of sodium tripolyphosphate with pH = 7.5, 500 g of polyvinyl alcohol (Kuraray Co., Ltd .: PVA235), cationic polymer (P-1) is added to 90 L of an aqueous solution containing 150 g and 10 g of defoaming agent SN381 from Sannobuco, and dispersed with a high-pressure homogenizer (manufactured by Sanwa Kogyo Co., Ltd.). A titanium dispersion was obtained.

<Preparation of silica dispersion 1>
Water 71L
Boric acid 0.27kg
Borax 0.24kg
Ethanol 2.2L
Cationic polymer (P-1) 25% aqueous solution 17L
Anti-fading agent (AF1 * 1) 10% aqueous solution 8.5L
Optical brightener aqueous solution (* 2) 0.1L
The entire amount was finished to 100 L with pure water.

* 1: anti-fading agent (AF-1) HO-N (C 2 H 4 SO 3 Na) 2
* 2: UVITEX NFW LIQUID manufactured by Ciba Specialty Chemicals
As inorganic fine particles, 50 kg of vapor phase method silica (average primary particle diameter of about 12 nm) was prepared. The above liquid was supplied to a spiral pin mixer SPM25W (manufactured by Taiyo Koki Co., Ltd., hereinafter referred to as SPM) as a disperser 1 at a rate of 1.56 kg / min and gas phase method silica at a rate of 0.44 kg / min. Thereafter, the dispersion machine 2 was supplied to a fine flow mill FM-25 (continuous high-speed stirring dispersion machine, manufactured by Taiyo Kiko Co., Ltd., hereinafter referred to as FM). Thereafter, LMK-4 (continuous wet media type pulverizer, manufactured by Ashizawa, hereinafter referred to as LMK) is used as the disperser 3, and the dispersion liquid from the disperser 2 is added to the LMK at 2.0 kg / min using a mono pump. Supplied with. The SPM conditions are a peripheral speed of 36 m / sec, a residence time of 30 seconds, and the LMK conditions are a bead diameter of 0.5 mm zirconia, a residence time of 2 minutes, a rotor rotational peripheral speed of 8 m / sec, a material urethane, and a vessel material urethane. Dispersing in this way gave silica dispersion 1.

<Preparation of silica dispersion 2>
In the preparation of the silica dispersion 1, the silica dispersion 2 was prepared in the same manner except that the cationic polymer (P-1) was changed to the cationic polymer (P-2).

(Preparation of ink receiving layer coating solution)
A coating solution for each ink-receiving layer of the first layer, the second layer, the third layer, and the fourth layer was prepared by the following procedure.

<Coating liquid for first layer>
The following additives were sequentially mixed with 610 ml of silica dispersion 1 while stirring at 40 ° C.

5% aqueous solution of polyvinyl alcohol (Kuraray Industrial Co., Ltd .: PVA235)
220ml
5% aqueous solution of polyvinyl alcohol (Kuraray Industrial Co., Ltd .: PVA245)
80ml
Titanium oxide dispersion 30ml
15 ml of polybutadiene dispersion (average particle size: about 0.5 μm, solid content: 40%)
Surfactant (SF1) 5% aqueous solution 1.5ml
The whole amount was finished to 1000 ml with pure water.

<Second layer coating solution>
The following additives were sequentially mixed with 630 ml of silica dispersion 1 while stirring at 40 ° C.

5% aqueous solution of polyvinyl alcohol (Kuraray Industrial Co., Ltd .: PVA235)
180ml
5% aqueous solution of polyvinyl alcohol (Kuraray Industrial Co., Ltd .: PVA245)
80ml
15 ml of polybutadiene dispersion (average particle size: about 0.5 μm, solid content: 40%)
The whole amount was finished to 1000 ml with pure water.

<Coating liquid for third layer>
The following additives were sequentially mixed with 650 ml of silica dispersion 2 while stirring at 40 ° C.

5% aqueous solution of polyvinyl alcohol (Kuraray Industrial Co., Ltd .: PVA235)
180ml
5% aqueous solution of polyvinyl alcohol (Kuraray Industrial Co., Ltd .: PVA245)
80ml
The whole amount was finished to 1000 ml with pure water.

<Fourth layer coating solution>
The following additives were sequentially mixed with 650 ml of silica dispersion 2 while stirring at 40 ° C.

5% aqueous solution of polyvinyl alcohol (Kuraray Industrial Co., Ltd .: PVA235)
180ml
5% aqueous solution of polyvinyl alcohol (Kuraray Industrial Co., Ltd .: PVA245)
80ml
Saponin 50% aqueous solution 4ml
Surfactant (SF1) 5% aqueous solution 6ml
The whole amount was finished to 1000 ml with pure water.

  Each coating solution prepared as described above was subjected to two-stage filtration with a filter capable of collecting 20 μm.

  Each of the above coating solutions is 30 to 80 mPa · s at 40 ° C. and 30000 to 100,000 mPa.s at 15 ° C. The viscosity characteristic of s was shown.

(Application)
Each coating solution thus obtained was coated on the front side of the support coated on both sides with the above prepared polyolefin, on the first layer (35 μm), the second layer (45 μm), the third layer (45 μm), and the fourth layer. Each layer was applied simultaneously so as to be in the order of layers (40 μm). In addition, the numerical value in the parenthesis of each layer shows each wet film thickness. The coating was carried out simultaneously at a coating width of about 1.5 m and a coating speed of 100 m / min using a four-layer curtain coater at 40 ° C. for each coating solution.

  Immediately after coating, the film is cooled for 20 seconds in a cooling zone maintained at 8 ° C., then 20 to 30 ° C., relative humidity 20% or less for 30 seconds, 60 ° C., relative humidity 20% or less for 120 seconds, 55 ° C., relative humidity 20%. It dried by blowing each drying wind for 60 seconds below. The film temperature in the constant rate drying region is 8 to 30 ° C., and after the film temperature gradually rises in the decreasing rate drying region, the humidity is adjusted in a humidity control zone of 23 ° C. and relative humidity 40 to 60%. 101 was obtained.

[Preparation of inkjet recording medium 102]
(Preparation of outermost layer coating solution)
Cationic colloidal silica (Snowtex AK-M, average particle size 22 nm, manufactured by Nissan Chemical Industries, Ltd.) as 2% solid content concentration, polyvinyl alcohol (Kuraray Industrial Co., Ltd .: PVA235) as solid content 0.2% The outermost layer coating solution 1 was an aqueous solution composed of 0.3% using surfactant (Olfin E1010, manufactured by Nissin Chemical) as an active ingredient.

(Coating of outermost layer)
The prepared outermost layer coating application liquid 1 is applied on the ink receiving layer of the inkjet recording medium 101 using an air knife coater and dried so that the solid content is 1 g / m ^2, and then at 40 ° C. Heat treatment was performed for 24 hours, and the inkjet recording medium 102 was produced.

[Preparation of inkjet recording medium 103]
(Preparation of outermost layer coating solution)
Cationic colloidal silica (Snowtex AK, average particle size 12 nm, manufactured by Nissan Chemical Industries, Ltd.) 5% as solid content concentration, Cationic colloidal silica (Snowtex AK-L, average particle size 45 nm, Nissan Chemical Industries, Ltd.) The outermost layer coating solution 2 was an aqueous solution composed of 5% as a solid content concentration and 0.3% with surfactant (Olfin E1010, manufactured by Nissin Chemical) as an active ingredient.

(Coating of outermost layer)
The prepared outermost layer coating solution 2 is applied and dried on the ink receiving layer of the inkjet recording medium 101 using an air knife coater so that the solid content becomes 5 g / m ^2, and then 24 ° C. at 24 ° C. Heat treatment was performed for a time, and an inkjet recording medium 103 was produced.

[Preparation of inkjet recording medium 104]
(Preparation of outermost layer coating solution)
Cationic colloidal silica (Snowtex AK-M, average particle size 22 nm, manufactured by Nissan Chemical Industries, Ltd.) as a solid content concentration of 10%, surfactant (Olfin E1010, manufactured by Nissin Chemical) as an active ingredient is 0.3%. The outermost layer coating solution 3 was an aqueous solution consisting of%.

(Coating of outermost layer)
In the production of the ink jet recording medium 103, the outermost layer coating was replaced with an air knife coater, and the ink jet recording medium 104 was formed in the same manner except that the outermost layer coating liquid 3 was applied using the slot nozzle spray device described above. Produced.

[Preparation of Inkjet Recording Medium 105-109]
In the production of the ink jet recording medium 104, the solid content concentration of the cationic colloidal silica in the outermost layer coating solution is appropriately changed, and the solid content of the cationic colloidal silica is changed as shown in Table 1, so that the outermost layer is changed. Inkjet recording media 105 to 109 were prepared in the same manner except that was applied.

(Preparation of ink set)
<< Preparation of colored ink containing fine resin particles >>
An ink set was prepared as follows. The ink set is composed of six colors of ink, dark inks of yellow, magenta, cyan and black, and light inks of magenta and cyan.

<Preparation of dark ink (yellow, magenta, cyan and black)>
Diethylene glycol 10% by mass
Glycerin 10% by mass
10% by mass of triethylene glycol monobutyl ether
Dye (* 1) 3% by mass
Resin fine particles (SX1105: manufactured by Nippon Zeon, Tg 0 ° C., SBR) 1% by mass
Triethanolamine 1% by mass
Surfactant (Orphine E1010: manufactured by Nissin Chemical, acetylene glycol type activator)
0.5% by mass
Pure water remainder * 1: As for the dye, yellow used Direct Yellow 86, magenta used the following magenta dye-1, cyan used Direct Blue 199, and black used Food Black 2.

<Preparation of light ink (magenta and cyan)>
Diethylene glycol 10% by mass
Glycerin 10% by mass
10% by mass of triethylene glycol monobutyl ether
Dye (* 2) 0.8% by mass
Triethanolamine 1% by mass
Resin fine particles (SX1105: manufactured by Nippon Zeon, Tg 0 ° C., SBR) 1% by mass
Surfactant (Orphine E1010: manufactured by Nissin Chemical, acetylene glycol type activator)
0.5% by mass
Pure water remainder * 2: As for the dye, the following magenta dye-1 was used for magenta, and direct blue 199 was used for cyan.

<Preparation of colored ink not containing resin fine particles>
The resin fine particle-containing colored ink was prepared in the same manner as the resin fine particle-containing colored ink except that the resin fine particles were removed.

<Preparation of colorless ink containing resin fine particles>
Diethylene glycol 10% by mass
Glycerin 10% by mass
10% by mass of triethylene glycol monobutyl ether
Triethanolamine 1% by mass
Resin fine particles (SF300: manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Tg-42 ° C., urethane type)
1% by mass
Surfactant (Orphine E1010: manufactured by Nissin Chemical, acetylene glycol type activator)
0.5% by mass
Remaining pure water << Preparation of colorless ink containing no fine resin particles >>
The resin fine particle-containing colorless ink was prepared in the same manner as the resin fine particle-containing colorless ink except that the resin fine particles were removed.

<Inkjet recording device>
As shown in FIG. 4, the amount of ink droplets per discharge operation can be adjusted, and the recording inks are six colors of Y, M, C, K, LM (light magenta) and LC (light cyan) and colorless ink. A piezo-type ink jet recording apparatus equipped with each recording head was prepared.

  The recording head may be any of a piezo method, a thermal method, and a continuous method, but the piezo method is used from the viewpoint of the ejection stability of the ink containing resin fine particles.

  Each recording head is supplied with ink from a recording ink cartridge and a colorless ink cartridge (not shown) through a piping tube. Seven recording heads are arranged side by side along the scanning direction on the recording carriage, and are used for recording ink of six colors and colorless ink, respectively.

Under the above conditions, the image Nos. In the combinations shown in Table 1 depending on the presence or absence of resin fine particles. 100-109 were produced. (Image No. 100 was printed with an ink set of colored ink / colorless ink not containing resin fine particles. Image Nos. 101 to 109 were printed with an ink set of colored ink / colorless ink containing resin fine particles.)
Each ink was image-formed with a droplet amount of 4 pl, a recording resolution of 1440 dpi × 1440 dpi (dpi: representing the number of dots per 2.54 cm) and a maximum total ejected ink amount of 17 ml / m ² at the image recording site. .

Clear ink, the liquid adhesion amount with respect to proper amount and the inkjet recording medium is allowed to be variably controlled, the recording resolution in 1440 dpi × 1440 dpi, at the same time as the production of the recorded image, even in the ink deposition amount per all pixels minimum 17 ml / m ² Thus, printing was performed by varying the discharge amount of the colorless ink in accordance with the discharge amount of the recording ink.

(Evaluation of characteristics of ink jet recording media)
Each ink jet recording medium produced as described above was evaluated in accordance with the method described below.

[Environmental printability]
After printing 8 wedge images of B, G, R, and K under an environment of 27 ° C. and 80% RH, density unevenness and gloss unevenness of the printed portion were visually observed, and environmental printability was evaluated according to the following criteria. .

◎: No density unevenness or gloss unevenness occurred. ○: Density unevenness or gloss unevenness was observed, but there were no practical problems. △: Weak density unevenness or gloss unevenness was observed, but there were practical problems. Uneven gloss is observed.

[Ozone fading]
8 wedge images of Y, M, C, and K were printed in an environment of 23 ° C. and 55% RH, and left for 24 hours. Then, the reflection density was measured with a GretagMacbeth optical densitometer, and the ozone density was 10 ppm (24 Exposed to an environment at 60 ° C. for 60 hours, the reflection density is measured again, and the residual ratio of pigment = (density after exposure) / (density before exposure) × 100 (%) is determined. Evaluated.

A: The average dye residual ratio in the entire density range is 90% or more. ○: The average dye residual ratio average in the entire density area is 80% to less than 90%. Δ: The average dye residual ratio in the entire density area is 70% to 80%. Less than ×: The average dye residual ratio in the entire density range is 60% or more and less than 70% XX: The average dye residual ratio in the entire density range is less than 60%.

[Storage stability]
Print 8 wedge images of each of Y, M, C, and K in an environment of 23 ° C and 55% RH, leave it for 24 hours, and then measure the reflection density with a GretagMacbeth optical densitometer. After being left in the environment for 3 days, it was then exposed to an environment with an ozone concentration of 10 ppm (24 ° C., 60%) for 60 hours, and the reflection density was measured again. The residual ratio of pigment = (concentration after exposure) / (concentration before exposure) ) × 100 (%) was determined, and ozone fading was evaluated according to the following criteria.

A: The average dye residual ratio in the entire density range is 90% or more. ○: The average dye residual ratio average in the entire density area is 80% to less than 90%. Δ: The average dye residual ratio in the entire density area is 70% to 80%. Less than ×: The average dye residual ratio in the entire density range is 60% or more and less than 70% XX: The average dye residual ratio in the entire density range is less than 60%.

[Abrasion resistance]
Solid images of Y, M, C, K, B, G, and R are printed in an environment of 23 ° C. and 55% RH, and the printed portion of the print is rubbed 20 times with copy paper, and then the ozone concentration is 10 ppm (at 24 ° C. and 60 ppm). %) Was exposed to an environment for 20 hours, the surface condition was observed, and the following four grades were evaluated.

◎: No scratches or film peeling and no fading unevenness ○: Concentration unevenness due to ozone fading is observed in some scratched parts, but within the allowable range in practice △: Concentration due to ozone fading in scratching or film peeling parts Unevenness occurs and there is a practical problem ×: Concentration unevenness due to ozone fading occurs remarkably in the scratches and film peeling portions, and there is a practical problem.

  As shown in Table 1, the recording medium 101 having no outermost layer of the present invention is good for environmental printing even when printed using the ink containing the resin fine particles of the present invention. However, the effect of improving the color fading property is deteriorated and the scratch resistance is not sufficient in the storage stability evaluation by exposure to ozone after storage in a hot and humid environment. This is because the resin coating layer formed on the surface of the porous layer that is the ink absorption layer by adhering ink containing resin fine particles, a part of the resin that forms a film by heat and humidity during print storage It is considered that the pores of the porous layer were slowly impregnated, the uniform resin coating layer was locally broken, and the ozone gas blocking effect was lowered.

  In the recording medium 102 provided with the outermost layer containing the water-soluble binder and the recording mediums 103 to 105 in which the solid content of the outermost layer made of inorganic fine particles is outside the present invention, the ink containing the resin fine particles of the present invention is used. In this case, not only does the printability of the environment printed in a high humidity environment deteriorate significantly, but the resin fine particles in the ink aggregate on the surface of the recording medium even when printed in an environment of 23 ° C. and 55%. And a uniform film cannot be formed, and a sufficient ozone fading effect cannot be obtained. Further, even with the recording medium 109 in which the solid content of the outermost layer made of inorganic fine particles is outside the scope of the present invention, the effects of the present invention cannot be sufficiently obtained.

  When printing on the recording media 106 to 108 using the ink containing the resin fine particles of the present invention, the ozone fading is greatly improved, and the ozone fading is stable even after the print is stored in a hot and humid environment. It was found that an improvement effect can be obtained. Furthermore, it was found that it was excellent in scratch resistance.

Example 2
<< Preparation of colored ink and colorless ink containing resin fine particles >>
Ink containing resin fine particles in the same manner as in Example 1 except that the resin fine particles used in each ink were changed to the following in the preparation of colored ink and colorless ink containing resin fine particles prepared in Example 1, Each colorless ink was prepared.

Resin fine particles SF300: manufactured by Daiichi Kogyo Seiyaku, Tg -42 ° C, urethane-based SX1105: manufactured by Nippon Zeon, Tg 0 ° C, carboxy-modified SBR
P6030: Asahi Kasei, Tg 10 ° C., carboxy-modified SBR
As shown in Table 2, an image was produced in the same manner as in Example 1 except that the resin fine particles used in the ink were changed. Subsequently, in the same manner as in Example 1, environmental printability, ozone fading property, storage stability, and scratch resistance were evaluated.

  As can be seen from the results in Table 2, it can be seen that the effects of the present invention can be obtained stably regardless of the type of resin fine particles.

Example 3
<Preparation of pigment ink set>
(Preparation of pigment dispersion)
<Preparation of yellow pigment dispersion>
C. I. Pigment Yellow 74 20% by mass
Styrene-acrylic acid copolymer (molecular weight 10,000, acid value 120) 12% by mass
Diethylene glycol 15% by mass
100% by mass of ion-exchanged water The above additives are mixed, dispersed using a horizontal bead mill (System Zeta Mini, manufactured by Ashizawa) filled with 0.3 mm zirconia beads at a volume ratio, and yellow pigment dispersion Got the body. The average particle size of the obtained yellow pigment was 112 nm.

<Preparation of magenta pigment dispersion>
C. I. Pigment Red 122 25% by mass
Jonkrill 61 (acrylic-styrene resin, manufactured by Johnson)
18% by mass in solid content
Diethylene glycol 15% by mass
100% by mass of ion-exchange water The above additives are mixed and dispersed using a horizontal bead mill (System Zeta Mini, manufactured by Ashizawa Co., Ltd.) filled with 0.3% zirconia beads at a volume ratio of 60%, and magenta pigment dispersion Got the body. The average particle size of the obtained magenta pigment was 105 nm.

<Preparation of cyan pigment dispersion>
C. I. Pigment Blue 15: 3 25% by mass
Jonkrill 61 (acrylic-styrene resin, manufactured by Johnson)
15% by mass as solid content
Glycerin 10% by mass
100% by mass of ion-exchanged water The above additives are mixed and dispersed using a horizontal bead mill (System Zeta Mini manufactured by Ashizawa Co., Ltd.) filled with 0.3 mm zirconia beads at a volume ratio of cyan pigment dispersion. Got the body. The average particle diameter of the obtained cyan pigment was 87 nm.

<Preparation of black pigment dispersion>
Carbon black 20% by mass
Styrene-acrylic acid copolymer (molecular weight 7000, acid value 150) 10% by mass
Glycerin 10% by mass
100% by mass of ion-exchanged water The above additives are mixed, dispersed using a horizontal bead mill (System Zetamini, manufactured by Ashizawa) filled with 0.3% zirconia beads at a volume ratio of 60%, and black pigment dispersion Got the body. The average particle size of the obtained black pigment was 75 nm.

(Preparation of pigment ink set)
<Preparation of yellow ink>
Yellow pigment dispersion 15% by mass
20% by mass of ethylene glycol
Diethylene glycol 10% by mass
Surfactant (Surfinol 465 manufactured by Nissin Chemical Industry Co., Ltd.) 1% by mass
Amount to be 100% by mass of ion-exchanged water The above compositions were mixed, stirred, and filtered through a 1 μm filter to prepare a yellow ink which is an aqueous pigment ink of the present invention. The average particle diameter of the pigment in the ink was 120 nm, and the surface tension γ was 36 mN / m.

<Preparation of magenta ink>
Magenta pigment dispersion 15% by mass
20% by mass of ethylene glycol
Diethylene glycol 10% by mass
Surfactant (Surfinol 465 manufactured by Nissin Chemical Industry Co., Ltd.) 1% by mass
Amount to be 100% by mass of ion-exchanged water The above compositions were mixed, stirred, and filtered through a 1 μm filter to prepare a magenta ink that is the aqueous pigment ink of the present invention. The average particle size of the pigment in the ink was 113 nm, and the surface tension γ was 35 mN / m.

<Preparation of cyan ink>
Cyan pigment dispersion 10% by mass
20% by mass of ethylene glycol
Diethylene glycol 10% by mass
Surfactant (Surfinol 465 manufactured by Nissin Chemical Industry Co., Ltd.) 1% by mass
Amount to be 100% by mass of ion-exchanged water The above compositions were mixed, stirred, and filtered through a 1 μm filter to prepare a cyan ink which is an aqueous pigment ink of the present invention. The average particle size of the pigment in the ink was 95 nm, and the surface tension γ was 36 mN / m.

<Preparation of black ink>
Black pigment dispersion 10% by mass
20% by mass of ethylene glycol
Diethylene glycol 10% by mass
Surfactant (Surfinol 465 manufactured by Nissin Chemical Industry Co., Ltd.) 1% by mass
Amount to be 100% by mass of ion-exchanged water The above compositions were mixed, stirred, and filtered through a 1 μm filter to prepare a black ink which is the aqueous pigment ink of the present invention. The average particle diameter of the pigment in the ink was 85 nm, and the surface tension γ was 35 mN / m.

<Preparation of colorless ink>
Resin fine particles (any of the following) 2% by mass
SF300: Daiichi Kogyo Seiyaku, Tg -42 ° C, urethane-based SX1105: Nippon Zeon, Tg 0 ° C, carboxy-modified SBR
20% by mass of ethylene glycol
Diethylene glycol 10% by mass
Surfactant (Surfinol 465 manufactured by Nissin Chemical Industry Co., Ltd.) 1% by mass
Amount to be 100% by mass of ion-exchanged water The above compositions were mixed and stirred, filtered through a 1 μm filter, and a colorless ink dispersed in the aqueous system of the present invention was prepared. The surface tension γ of the ink was 35 mN / m.

  Further, even when the same amount of the ink and the pigment ink were mixed, the average particle diameter of the pigment was not changed and no aggregation occurred.

  Printing was performed on an inkjet recording medium with an inkjet printer equipped with a piezo-type head incorporating the ink and colorless ink cartridges described above. Image recording was performed using, for example, a cartridge of the type shown in FIG. 4 so that colorless ink is ejected immediately after image recording with image ink.

Each ink was image-formed with a droplet amount of 4 pl, a recording resolution of 1440 dpi × 1440 dpi (dpi: representing the number of dots per 2.54 cm) and a maximum total ejected ink amount of 17 ml / m ² at the image recording site. .

Colorless ink can be variably controlled with the appropriate amount of liquid and the amount of ink attached to the ink jet recording medium, and the recording resolution is 1440 dpi × 1440 dpi. Printing was performed by varying the discharge amount of the colorless ink in accordance with the discharge amount of the recording ink so as to be 17 ml / m ² .

  The image was evaluated for glossiness (60 degrees) and image clarity of a white background portion and a black solid print portion (reflection density≈2.0).

  As a comparative sample, prints in which colorless ink was not ejected onto the inkjet recording media 101 and 102 were simultaneously produced and evaluated. The obtained results are shown in Table 3.

(Environmental printability)
After printing 8 wedge images of B, G, R, and K under an environment of 27 ° C. and 80% RH, density unevenness and gloss unevenness of the printed portion were visually observed, and environmental printability was evaluated according to the following criteria. .

◎: No density unevenness or gloss unevenness occurred. ○: Density unevenness or gloss unevenness was observed, but there were no practical problems. △: Weak density unevenness or gloss unevenness was observed, but there were practical problems. Uneven gloss is observed.

(Evaluation of uneven gloss)
The gloss unevenness was determined by whether or not the color tone changed by changing the viewing angle of the recording medium.

  Gloss unevenness and glare were ranked according to the following rankings.

◎: None at all ○: Slightly recognized, but no problem in practical use △: Glossy unevenness is observed, which is a concern during viewing ×: Vigorous rainbow unevenness is observed.

(Abrasion resistance)
Solid images of Y, M, C, K, B, G, and R are printed in an environment of 23 ° C. and 55% RH, and the printed portion of the print is rubbed 20 times with copy paper, and then the ozone concentration is 10 ppm (at 24 ° C. and 60 ppm). %) Was observed for 80 hours, the surface condition was observed, and the following four grades were evaluated.

◎: No scratches or film peeling and no fading unevenness ○: Concentration unevenness due to ozone fading is observed in some scratched parts, but within the allowable range in practice △: Concentration due to ozone fading in scratching or film peeling parts Unevenness occurs and there is a practical problem ×: Concentration unevenness due to ozone fading occurs remarkably in the scratches and film peeling portions, and there is a practical problem.

  From the results shown in Table 3, the image No. according to the present invention. In 304 and 308, there is no problem in suitability for environmental printing, and the difference from the glossiness of the white background portion is small, and a uniform glossiness is obtained in the entire image area. Further, the scratch resistance is also good, and it has been shown that it is effective to use the inkjet recording medium of the present invention, and colored ink and colorless ink containing resin fine particles.

It is the schematic for demonstrating the coating method using the slot nozzle spray apparatus which concerns on this invention. It is a schematic sectional drawing which shows an example of the slot nozzle spray apparatus containing a slot nozzle spray part. It is a schematic diagram which shows an example of the coating production line which has arrange | positioned the slot nozzle spray apparatus. It is a perspective view which shows an example of the inkjet printer used with the inkjet recording method of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Slot nozzle spray part 1d Comb-tooth shim 2a, 2b External die block 2c, 2d Bottom surface of external die block 3a, 3b Internal die block 3c, 3d Bottom surface of internal die block 4 Adjustment pot 5 Pump 6 Flow meter 7 Pressurized air Source 8 Valve 9 Object to be coated 20 Coating device 21 Transport roller 22 Backup roll 23 Reverser 24 Transport roller 30 Cooling zone 31 Recording head 32 Carriage

Claims (5)

In an ink jet recording method for recording on an ink jet recording medium using an ink jet recording ink containing at least one kind of resin fine particles, the ink jet recording medium contains at least one layer of inorganic fine particles and a hydrophilic binder on a support. An ink receiving layer and an outermost layer made of inorganic fine particles having self-fusing properties substantially free of a hydrophilic binder on the porous ink receiving layer, and the solid content of the outermost layer is 0.01 to An ink jet recording method comprising using an ink jet recording medium of 0.5 g / m ² . The ink jet recording ink containing the resin fine particles comprises a colored ink containing at least one colorant and a colorless ink substantially free of a colorant, and the resin fine particles in the colorless ink are applied to the ink jet recording medium. ^2. The ink jet recording method according to claim 1, wherein the adhesion amount (g / m ² ) is varied according to the adhesion amount of the resin fine particles of the colored ink for each recording region. 3. The ink jet recording method according to claim 1, wherein the inorganic fine particles having self-bonding property are at least one selected from colloidal silica and colloidal alumina. The inkjet recording method according to claim 1, wherein an average primary particle size of the inorganic fine particles having self-bonding property is 5 to 100 nm. A recorded matter produced by the inkjet recording method according to claim 1.

Images