JP2002362023A - Ink-jet recording sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink-jet recording sheet relatively high in glossiness, which is improved when printing is done by an ink-jet method to produce a quality print. SOLUTION: In the ink-jet recording sheet, an ink absorbing layer comprising at least two void layers is provided, particles obtained by emulsifying/dispersing hydrophobic organic compound of a relatively large particle size are added into at least one layer of the void layers excluding the outermost layer, and the particles are substantially not added to the void layer most separated from a support.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording sheet, and more particularly to an ink jet recording sheet capable of obtaining high quality prints.

[0002]

2. Description of the Related Art Ink-jet recording is a method in which fine droplets of ink are caused to fly according to various operating principles and adhere to a recording sheet such as paper to record images and characters. It has advantages such as easy noise and multicoloring. With regard to nozzle clogging and maintenance, which has been a problem in the past, improvements have been made in both ink and equipment, and are now rapidly spreading in various fields such as various printers, facsimile machines, and computer terminals. .

[0003] The recording paper used in this ink jet recording system has a high density of print dots, a bright and vivid color tone, and the ink absorbs quickly so that even when the print dots overlap, the ink may flow out. It is required that bleeding does not occur, that the diffusion of print dots in the horizontal direction is not unnecessarily large, and that the periphery is smooth and not blurred.

[0004] In particular, when the ink absorption speed is low, when ink droplets of two or more colors are printed in an overlapping manner, the droplets cause a repelling phenomenon on the recording paper to become uneven, It is necessary for recording paper to have a high ink absorbency because the colors of each other are blurred in the boundary region of, and the image quality is easily deteriorated.

[0005] To solve these problems, a great many techniques have been proposed. For example, JP
JP-A-5-53012 describes a recording paper in which a coating for surface processing is wetted on a low-size base paper.
No. 5830, a recording paper provided with an ink-absorbing coating layer on the surface of a support, and a non-colloidal silica powder as a pigment in a coated layer described in JP-A-56-157. Recording paper, a recording paper using a combination of an inorganic pigment and an organic pigment described in JP-A-57-107878,
JP-A-58-11287 discloses a recording paper having two pore distribution peaks.
No. 1782, recording paper comprising two upper and lower porous layers, JP-A-59-68292 and JP-A-59-12.
Recording papers having irregular cracks described in JP-A Nos. 3696 and 60-18383.
No. 135786, No. 61-148092 and No. 62
And recording paper having a fine powder layer described in JP-A-149475, JP-A-63-252779,
-108083, 2-136279, 3-65
Nos. 376 and 3-27976, recording papers containing pigments having specific physical properties and fine-particle silica, JP-A-57-14091 and JP-A-60-2190.
No. 83, No. 60-210984, No. 61-20797
No. 61-188183, JP-A-5-278324
Nos. 6-92091, 6-183134, 7
Recording paper containing fine-particle silica such as colloidal silica described in JP-A-137431 and JP-A-7-276789, and JP-A-2-276671, JP-A-3-27671.
Nos. 67684, 3-215082 and 3-25
No. 1488, No. 4-67986, No. 4-263983
And a large number of recording papers containing alumina hydrate fine particles described in JP-A-5-16517 and the like.

[0006] Among them, a gap type recording paper using minute inorganic fine particles and a hydrophilic binder and having minute gaps formed in the ink receiving layer is preferable as a high quality glossy paper because relatively high gloss can be obtained. It is.

If the recording paper has an excessively high gloss, the surface friction is so high that it becomes easy to feed multiple sheets when a plurality of sheets are fed one upon another, or the gloss of the printed portion is reduced after inkjet recording. It turned out to be easy.

[0008] In the latter case, in particular, in a recording paper having a conventional high gloss, as the gloss of an unprinted portion becomes higher, the slight decrease in the gloss of the printed portion tends to greatly lower the print quality. In terms of print quality, simply improving the glossiness of an unprinted portion is not sufficient for print quality.

[0009] This point is not a major problem in the image quality of the conventional ink jet recording, which is mainly due to dot roughness and resolution. However, with the advent of a high quality printer in recent years, the print image quality has been significantly improved. It is becoming increasingly important as it approaches the level of photography.

[0010] It is not clear why the gloss of the printed portion is reduced, but the low-evaporation solvent contained in the ink recorded by ink-jet causes the hydrophilic binder of the ink absorbing layer to swell. It is presumed that this is caused by

In the conventional ink jet recording paper, no attempt has been made to improve the print quality from this point of view, and the present inventors have conducted intensive studies on this point, and as a result, have set the surface gloss to a specific range, It has been found that by increasing the glossiness of the part compared to the unprinted part, a very high quality print can be obtained.

[0012]

SUMMARY OF THE INVENTION An object of the present invention is to provide an ink jet recording paper which has a relatively high gloss and further increases the gloss when printed by an ink jet to provide a high quality print. It is in.

[0013]

The above object of the present invention is achieved by the following constitution. 1. It has an ink-absorbing layer composed of at least two void layers, and particles obtained by emulsifying and dispersing a hydrophobic organic compound having a relatively large particle size are added to at least one of the void layers other than the uppermost layer. An ink jet recording paper, wherein substantially no particles obtained by emulsifying and dispersing the hydrophobic organic compound are added to the void layer furthest from the body.

2. A latex polymer particle is added to at least one of the void layers other than the uppermost layer, and the latex polymer particles are substantially contained in the void layer farthest from the support. Ink jet recording paper characterized in that it is not added periodically.

[0015] 3. Ink-jet recording paper having an ink absorbing layer comprising at least two void layers, wherein at least one of the void layers other than the uppermost layer contains fine particles having a refractive index higher than that of inorganic fine particles forming voids. .

4. An ink absorbing layer substantially consisting of a swelling layer is provided on a support, and a void layer containing inorganic fine particles having a dispersity of 2 or less, a hydrophilic binder and a hardener is provided thereon. Ink jet recording paper.

As used herein, "substantially not added"
Means that no or very little is added.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The support used for the ink jet recording paper of the present invention may be any known support such as a water-absorbing support such as paper, a plastic resin film or a paper support whose surface is coated with a plastic resin film. The body is a non-absorbent support. In the case of a water-absorbing support, wrinkles are likely to be formed on the portion printed by ink jet, and the print quality is likely to deteriorate. Also,
The printed portion is more likely to be lower than the non-printed portion.

Examples of the non-water-absorbing support preferably used include, for example, polyester films, diacetate films, triacetate films, acrylic films, polycarbonate films, polyvinyl chloride films, polyimide films, cellophane and celluloid. A resin film (so-called RC paper) having a polyolefin resin coating layer obtained by adding a white pigment or the like to at least one of a base film and a transparent film made of a material such as
A translucent or opaque support such as a so-called white pet obtained by adding a white pigment such as titanium oxide or barium sulfate to polyethylene terephthalate is used. A support in which the effect of the present invention is particularly remarkable is an opaque support, which is used when a print is observed as a reflection image.

The support particularly preferably used in the present invention is an opaque polyester film, an opaque polyolefin resin film and a paper support in which both sides of a base paper support are laminated with polyethylene.

Particularly preferred is a paper support laminated with polyester, and the support described below has a relatively high glossiness, and the glossiness is further increased when printed by ink jet, so that high quality prints can be obtained. It is preferable to provide an ink jet recording paper giving the following.

The base paper used for the paper support is made of wood pulp as a main material, and if necessary, is made of synthetic pulp such as polypropylene or synthetic fiber such as nylon or polyester in addition to wood pulp. As wood pulp, LBKP, LBSP, NBKP, NBSP, LD
Any of P, NDP, LUKP, and NUKP can be used, but LBKP, NBSP, and LBS containing a large amount of short fibers
It is preferable to use more P, NDP, and LDP.
However, the ratio of LBSP and / or LDP is 10% by weight.
At least 70% by weight is preferred.

As the pulp, a chemical pulp containing less impurities (sulfate pulp or sulfite pulp) is preferably used, and pulp having improved whiteness by a bleaching treatment 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 agents such as starch, polyacrylamide and polyvinyl alcohol, fluorescent whitening agents, Water retention agents such as polyethylene glycols, dispersants, and softening agents such as quaternary ammonium can be appropriately added.

The freeness of the pulp used for papermaking is preferably 200 to 500 ml according to the CSF standard, and the fiber length after beating has a 24 mesh residual weight% and a 42 mesh residual weight specified in JIS-P-8207. 30% by weight
~ 70% is preferred. In addition, it is preferable that the weight% of the 4 mesh residue is 20% by weight or less. Base paper weight is 3
The amount is preferably from 0 to 250 g, particularly preferably from 50 to 200 g. The thickness of the base paper is preferably from 40 to 250 μm.

The base paper may be calendered at the papermaking stage or after the papermaking to provide high smoothness. The base paper density is generally 0.7 to 1.2 g / m ² (JIS-P-8118). Further, the rigidity of the base paper is preferably from 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 agent as that which can be added to the base paper can be used. Base paper pH is JIS-
When measured by the hot water extraction method specified in P-8113, it is preferably 5 to 9.

The polyethylene for covering the front and back surfaces of the base paper is mainly low-density polyethylene (LDPE) and / or high-density polyethylene (HDPE), but other LLDPE, polypropylene and the like can be partially used. Particularly, as the polyethylene layer on the coating layer side, it is preferable to add rutile or anatase type titanium oxide to polyethylene to improve opacity and whiteness as widely used in photographic printing paper. The content of titanium oxide is approximately 3 to 20% by weight, preferably 4 to 13% by weight, based on polyethylene.

The polyethylene-coated paper may be used as a glossy paper, or may be subjected to a so-called embossing process when the polyethylene is melt-extruded onto the base paper surface to carry out a so-called molding process. Those having a surface can also be used in the present invention.

The amount of polyethylene used on the front and back of the base paper is selected so as to optimize the film thickness of the aqueous coating composition and the curl in low and high humidity after the back layer is provided. The polyethylene layer on the side where the coating composition is applied is 2
The range is 0 to 40 μm, and the thickness of the back layer is 10 to 30 μm.

Further, the polyethylene-coated paper support preferably has the following characteristics. Tensile strength: The strength specified in JIS-P-8113 is preferably 2 to 30 kg in the vertical direction and 1 to 20 kg in the horizontal direction. The tear strength is preferably 10 to 200 g in the vertical direction and 20 to 200 g in the horizontal direction according to the method defined in JIS-P-8116. Compression elasticity ≧ 10 ³ Kgf / cm ² Surface Beck smoothness: 20 seconds or more is preferable as a glossy surface under the conditions specified in JIS-P-8119, but may be less than this for so-called molded products. Opacity: Under the measurement conditions of linear light incidence / diffuse light transmission conditions, the transmittance for visible light rays is preferably 20% or less, particularly preferably 15% or less.

The glossiness of the support on the ink absorbing layer side is as follows:
In order to obtain the effect of the present invention, the 60-degree specular gloss is 2
0% or more, and particularly preferably 20 to 60%. When the glossiness of the support is less than 20%, the glossiness as recording paper tends to be insufficient, and the glossiness is 8%.
If it exceeds 0%, a difference in glossiness between a printed portion and an unprinted portion is unlikely to occur, and the effect of the present invention tends to be reduced.

The recording paper of the present invention is composed of a void layer containing an inorganic fine particle having an average particle diameter of 100 nm or less and a dispersity of 2 or less and a hydrophilic binder as an ink absorbing layer.

In the case of a so-called swelling type ink absorbing layer in which the ink absorbing layer is substantially composed of only a hydrophilic binder and holds the ink by the swelling action of the hydrophilic binder, the ink absorbing layer absorbs ink droplets. -Since the gloss of the printed portion generally tends to be lower than that of the unprinted portion due to the increase and shrinkage of the film thickness due to drying, it is difficult to obtain the effect of the present invention. Then it is necessary.

Examples of the inorganic fine particles used in the ink absorbing layer include light calcium carbonate, heavy calcium carbonate,
Magnesium carbonate, kaolin, clay, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc chloride, zinc hydroxide, zinc sulfide, zinc carbonate, hydrotalcite,
Aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, synthetic amorphous silica, colloidal silica,
Examples include white inorganic pigments such as alumina, colloidal alumina, pseudoboehmite, aluminum hydroxide, lithopone, zeolite, and magnesium hydroxide. Such inorganic fine particles can be used as primary particles,
It can also be used in a state where secondary aggregated particles are formed.

In the present invention, silica or pseudo-boehmite is preferred from the viewpoint that particularly fine voids can be formed.
In particular, silica, colloidal silica, and pseudoboehmite synthesized by a gas phase method having an average particle diameter of 100 nm or less are preferable. Particularly preferred is particulate silica synthesized by a gas phase method. The average particle size of the inorganic fine particles can be determined by observing the cross section or surface of the particles or the void layer with an electron microscope.
The particle size of zero arbitrary particles is obtained, and is obtained as a simple average value (number average). Here, each particle size is represented by a diameter assuming a circle equal to the projected area.

The degree of dispersion in the present invention is defined as ({NV ² / Σ}) based on the particle diameter of a particle equivalent to a sphere obtained by measuring arbitrary 100 inorganic fine particles and measuring the particle size distribution.
NV) from the standard deviation and the average particle diameter calculated on the basis of:
It shows a value represented by the ratio of standard deviation / average particle size.

When inorganic fine particles having an average particle size of more than 100 nm and / or inorganic fine particles having a dispersity of more than 2 are used, the fine irregularities of the ink absorbing layer become large and high glossiness is obtained. It is difficult to obtain. The preferred average particle diameter of the inorganic fine particles is 80 nm or less, and the degree of dispersion is 1.
8 or less.

The hydrophilic binder used in the void layer can be appropriately selected from conventionally known ones. For example, gelatin, polyvinyl alcohol, polyvinylpyrrolidone, polyethylene oxide,
Examples include polyacrylic acid, polyacrylamide, agar, carrageenan, dextran, dextrin, pullulan, hydroxyethylcellulose, carboxymethylcellulose and the like. These hydrophilic binders are 2
More than one species may be used in combination.

A particularly preferred hydrophilic binder is polyvinyl alcohol. The polyvinyl alcohol preferably used in the present invention includes, in addition to normal polyvinyl alcohol obtained by hydrolyzing polyvinyl acetate, modified polyvinyl such as polyvinyl alcohol having a cation-modified terminal or an anion-modified polyvinyl alcohol having an anionic group. Also includes alcohol.

The polyvinyl alcohol obtained by hydrolyzing vinyl acetate preferably has an average degree of polymerization of 300 or more, and particularly preferably has an average degree of polymerization of 1,000 to 4,000. Saponification degree is 70-100%
Is preferable, and 80 to 99.5% is particularly preferable.

As the cation-modified polyvinyl alcohol, for example, as described in JP-A-61-10483, a tertiary amino group or a quaternary ammonium group is added to the main chain or side chain of the 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,
Hydroxyethyltrimethylammonium chloride,
Trimethyl-(-methacrylamidopropyl) ammonium chloride, N- (1,1-dimethyl-3-dimethylaminopropyl) acrylamide and the like. The ratio of the cation-modified group-containing monomer in the cation-modified polyvinyl alcohol is 0.1 to 10 mol%, preferably 0.2 to 5 mol%, based on vinyl acetate.

The anion-modified polyvinyl alcohol is described in, for example, polyvinyl alcohol having an anionic group as described in JP-A-1-2060888, JP-A-61-237681 and JP-A-63-307979. And a copolymer of vinyl alcohol and a vinyl compound having a water-soluble group,
Modified polyvinyl alcohol having a water-soluble group as described in -285265.

Examples of the nonionic modified polyvinyl alcohol include polyvinyl alcohol derivatives described in JP-A-7-9758, in which a polyalkylene oxide group is added to part of vinyl alcohol, and JP-A-8-25795. And a block copolymer of a vinyl compound having a hydrophobic group and vinyl alcohol described in Japanese Patent Application Laid-Open Publication No. H11-157,086. Polyvinyl alcohol may be used in combination of two or more kinds, such as different degrees of polymerization and types of modification.

The preferred amount of the inorganic fine particles used is 3 to 50 g, and particularly preferably 5 to 30 g, per 1 m ^{2 of} recording paper. Further, the preferred amount of the hydrophilic binder used is 0.5 to 10 g, particularly 1 to ⁵ g per 1 m ² of recording paper. The ratio of the inorganic fine particles to the hydrophilic binder is generally 3 to 10 by weight, and particularly preferably 4 to 8.

The 60-degree specular gloss of the surface of the ink absorbing layer of the ink jet recording paper of the present invention is 20% or more;
The glossiness after printing by inkjet is 3% or more higher than that of the unrecorded portion.

When the glossiness of the unprinted portion is less than 20%, a high-grade feeling is not obtained even if the glossiness of the printed portion is higher than that of the unprinted portion, and conversely, the glossiness of only the printed portion is abnormally high. If it is too much, the quality will be easily damaged. The upper limit of the glossiness of the unprinted portion is not particularly limited from the viewpoint of obtaining the effects of the present invention, but is generally less than 70%.

It is necessary that the glossiness of the printed portion is higher than that of the unprinted portion by 3% or more.
More preferably, it is higher. Further, it is preferable that the glossiness is higher than that of the unprinted portion as long as the difference in glossiness between the two does not exceed 15%. If it exceeds 15%, only the printed surface becomes abnormally glossy, making it difficult to achieve a natural texture finish.

Here, the glossiness of the printed portion is measured after printing with an ink jet printer under the condition that the maximum density can be obtained in black, and after leaving at 20 to 25 ° C. and a relative humidity in the range of 40 to 60% for 1 hour. The following values are shown.

In order to make the glossiness of the ink jet recording paper of the present invention 20% or more, it is necessary to make the particle diameter of the inorganic fine particles used 100 nm or less, as described above. Apply the absorbing layer onto the support by reducing the content of coarse particles in the coating solution as much as possible, or by applying pressure to the mirror surface roller by heating and applying pressure before the coating surface completely dries after coating. A combination of controlling the degree and the like can also be used in the present invention.

Next, a method of increasing the glossiness of a printed portion from an unprinted portion will be described. A first method for increasing the gloss of a printed portion over the gloss of an unprinted portion is to form the ink absorbing layer so as to include at least two or more void layers, and to relatively form at least one of the void layers other than the uppermost layer. Organic compound particles having a large particle diameter are added, and such particles are not added at all or only a very small amount is added to the void layer farthest from the support (uppermost void layer), and the distribution of such particles is reduced. It is obtained by having it between layers. The organic compound particles used in this case include particles obtained by emulsifying and dispersing a hydrophobic organic compound, and latex polymer particles.

These particles may have a relatively uniform particle size distribution or a wide particle size distribution, but a particle size component of about 1 to 5 μm is required to obtain the effects of the present invention. Is important. Therefore, when particles having a relatively uniform particle size distribution are used, particles having an average particle size of about 0.5 to 5 μm are preferably used. On the other hand, when the particle size distribution is wide, the average particle size is preferably 0.2 to 1 μm.

The particles of the above organic compound are added in an amount of about 10 to 50% by weight based on the hydrophilic binder in the layer containing the organic compound.

A second method for increasing the gloss of the printed portion over the gloss of the unprinted portion is to form the ink absorbing layer so as to include at least two or more void layers, and to form at least one of the void layers other than the uppermost layer. The use of fine particles having a higher refractive index than the inorganic fine particles used to form the voids.

Examples of such high refractive index fine particles include titanium oxide, zinc oxide and barium sulfate. It is preferred that these high refractive index inorganic fine particles are not added from the support to the uppermost void layer, since there is no reduction in the color density and the gloss of the printed portion is not reduced.

The average particle diameter of the high refractive index inorganic fine particles is preferably 1 μm or less, particularly preferably 0.5 μm or less. The lower limit of the average particle size is approximately 0.1μ
m or more. The amount of the inorganic particles having a high refractive index is generally 1 to 1 with respect to the inorganic particles contained in the void layer containing the same.
20% by weight.

A third method of increasing the gloss of the printed portion over the gloss of the unprinted portion is to form the ink absorbing layer so as to be composed of at least two or more void layers, and to remove the inorganic fine particles contained in the uppermost void layer. The ratio in the at least one void layer other than the uppermost layer is set to be at least 1 or more, preferably 2 or more, as compared with the ratio to the hydrophilic binder.

That is, at least one of the layers other than the uppermost layer
In the layer, gloss after printing can be increased by increasing the ratio of the hydrophilic binder to the inorganic fine particles. Such a layer having a high proportion of inorganic fine particles is preferably a layer adjacent to the uppermost layer.

A fourth method for increasing the gloss of a printed portion over the gloss of an unprinted portion is to use inorganic fine particles having different average particle sizes for the different void layers as the inorganic fine particles forming the void layer. The average particle size of the inorganic fine particles is preferably at least 2 nm, more preferably at least 5 nm, and can be achieved by using inorganic fine particles having different average particle sizes in separate layers. In this case, it is preferable that the layer forming the void layer with the inorganic fine particles having a larger average particle diameter be provided on the side closer to the support because the decrease in the maximum concentration is small. The average particle size of the inorganic fine particles in the uppermost layer is preferably the smallest among the plurality of void layers.

A fifth method of increasing the gloss of a printed portion over the gloss of an unprinted portion is to mix a gap layer formed from a coating solution that forms a weak agglomerate when two coating solutions are mixed. It is obtained by providing as a layer to be formed.

There are several types of coating solutions that form such aggregates. For example, when two types of coating solutions each having a different pH and stabilized at each pH are mixed, the pH may be reduced. A method of laminating and simultaneously applying coating liquids such that at least one of the liquids is aggregated due to fluctuations of the coating liquid, and simultaneously applying and laminating coating liquids whose pH rapidly changes when the respective coating liquids are mixed There are various methods, such as a method in which one coating solution is a cationic solution and the other is an anionic solution, and the two are simultaneously applied.

A sixth method for increasing the gloss of a printed portion over the gloss of an unprinted portion is to provide an ink absorbing layer substantially consisting of a swelling layer on a support and then providing a void layer of the present invention thereon. is there. The swelling layer referred to here is a layer whose thickness increases by swelling action when absorbing ink or water, and the layer is mainly composed of a hydrophilic binder. The swelling layer may contain an inorganic pigment, but the amount of the pigment used is about 3 times or less, preferably 2 times or less, by weight of the hydrophilic binder. This hydrophilic binder may be the same as or different from the hydrophilic binder constituting the void layer. Preferred hydrophilic binders used in the swelling layer are gelatin, polyvinyl alcohol, polyvinylpyrrolidone, and polyethylene oxide and mixtures thereof. Particularly, it is preferable that at least one kind is gelatin.

The hydrophilic binder contained in these swelling layers is preferably hardened with a hardener capable of cross-linking with the hydrophilic binder because cracking does not occur when the void layer is applied. The amount of the hydrophilic binder used in the swelling layer is generally 0.1 to 3 g per 1 m ² of recording paper. The swelling layer and the void layer may be applied simultaneously, or the void layer may be applied after the swelling layer is applied and dried, but the latter is preferred because it has less cracks.

In the present invention, the above method of increasing the glossiness of the printed portion over the glossiness of the unprinted portion may be performed alone or in combination of two or more.

It is necessary to harden the void layer of the present invention with a hardener in order to increase the glossiness of a portion printed by ink jet. If the film is not hardened, the glossiness of the printed portion is lower than before printing.

As the hardener, any hardener can be used as long as it can undergo a crosslinking reaction with the hydrophilic binder constituting the void layer. When the hydrophilic binder is particularly preferably used polyvinyl alcohol, It is preferable to use boric acid or a salt thereof as a hardener.
The boric acid or a salt thereof refers to an oxyacid having a boron atom as a central atom and a salt thereof, and specifically, orthoboric acid, metaboric acid, hypoboric acid, tetraboric acid, pentaboric acid and salts thereof. Is included.

The amount of boric acid or a salt thereof can vary widely depending on the amount of the inorganic fine particles and the hydrophilic binder in the coating solution.
Preferably it is 5 to 40% by weight.

Various additives other than those described above can be added to the void layer of the ink jet recording paper of the present invention.
Above all, a cationic mordant is preferable for improving water resistance and moisture resistance after printing. First-class cationic mordants
Although a polymer mordant having a tertiary amino group and a quaternary ammonium base is used, a quaternary ammonium base is used because the discoloration and deterioration of light resistance over time are small and the mordant ability of the dye is sufficiently high. Preferred are polymeric mordants having. Preferred polymer mordants are obtained as a homopolymer of the above-mentioned monomer having a quaternary ammonium salt group, as a copolymer with other monomers, or as a condensation polymer.

In addition to the above, see, for example, JP-A-57-741.
Nos. 93, 57-87988 and 62-2
UV absorber described in JP-A-61476;
Nos. 74192, 57-87989, 60
JP-A-72785, JP-A-61-146591, JP-A-1-95091 and JP-A-3-13376, etc., various kinds of anionic, cationic or nonionic surfactants, Showa 59-42993
JP-A-59-52689, JP-A-62-2800
No. 69, No. 61-242871, and Japanese Patent Laid-Open No.
Fluorescent brighteners described in -219266 and the like;
Known various additives such as a defoaming agent, a lubricant such as diethylene glycol, a preservative, a thickener, an antistatic agent and a matting agent can also be contained.

In particular, for the purpose of improving the slip property,
Silicone oil, a fluorine-based surfactant, and an organic or inorganic matting agent having an average particle size of 5 to 30 μm can be added within a range that does not impair the effects of the present invention.

In the recording paper of the present invention, the application of a plurality of void layers on the support can be appropriately selected from known methods, but it is preferable to apply all the void layers simultaneously.

Examples of the coating method include a roll coating method, a rod bar coating method, an air knife coating method, a spray coating method, a curtain coating method and an extrusion coating method using a hopper described in US Pat. No. 2,681,294. It is preferably used.

On the side opposite to the side having the void layer of the ink jet recording paper of the present invention, various types and back layers are provided in order to prevent curling and further improve sticking and ink transfer when superimposed immediately after printing. Is preferred.

The structure of the back layer varies depending on the type and thickness of the support and the structure and thickness on the front side, but generally a hydrophilic binder or a hydrophobic binder is used. The thickness of the back layer is usually in the range of 0.1 to 10 μm.

The surface of the back layer can be roughened in order to prevent sticking to other recording paper, to improve writing properties, and to improve transportability in an ink jet recording apparatus. Organic or inorganic fine particles having a particle size of 2 to 20 μm are preferably used for this purpose. These back layers may be provided in advance, or may be provided after applying the coating composition of the present invention.

Next, the water-soluble recording liquid used for ink-jet recording using the ink-jet recording paper of the present invention will be described below. The water-soluble recording liquid is usually a recording liquid comprising a water-soluble dye, a liquid medium, and other additives. As the water-soluble dye, a water-soluble dye such as a direct dye, an acid dye, a basic dye, a reactive dye, or a food dye known in the ink jet can be used, but a direct dye or an acid dye is preferable.

Although the solvent of the recording liquid is mainly water, the boiling point is usually 1 in order to prevent the dye from being deposited when the recording liquid is dried and clogging at the nozzle tip and the recording liquid supply path.
A high boiling organic solvent that is liquid at room temperature above 20 ° C. is used. High boiling organic solvents are required to have a vapor pressure much lower than that of water in order to prevent solid components such as dyes from being precipitated when water evaporates and to prevent generation of coarse precipitates. Must have high miscibility.

As such high-boiling organic solvents, high-boiling organic solvents are usually often used. Specific examples thereof include ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, glycerin, diethylene glycol monomethyl ether, and the like. Diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, glycerin monomethyl ether, 1,2,3-butanetriol, 1,2,4-
Butanetriol, 1,2,4-pentanetriol,
1,2,6-hexanetriol, thiodiglycol,
Alcohols such as triethanolamine and polyethylene glycol (average molecular weight of about 300 or less) are exemplified. In addition to the above, dimethylformamide,
N-methylpyrrolidone and the like can also be used.

Among these many high boiling organic solvents,
Polyhydric alcohols such as diethylene glycol, triethanolamine, glycerin and triethanolamine, and lower alkyl ethers of polyhydric alcohols such as triethylene glycol monobutyl ether are preferred.
The amount of these high boiling organic solvents used is 10 to 5 in the ink.
0% by weight, preferably in the range of 15 to 40% by weight.

Other additives contained in the recording liquid include, for example, a pH adjuster, a metal sealant, an anti-binder, a viscosity adjuster, a surface tension adjuster, a wetting agent, a surfactant, and a rust inhibitor. Is mentioned.

The recording liquid is 25 to 50 dyne / 25 ° C. for the purpose of improving the wettability to the recording paper and stabilizing the discharge from the ink jet nozzle.
cm, preferably in the range of 28 to 40 dyne / cm. The viscosity of the recording liquid is usually 2 to 10 cp at 25 ° C., preferably 2.5 to 10 cp.
8 cp. The pH of the recording liquid is preferably from 3 to 9.

It is preferable that the minimum ink droplet ejected from the ink nozzle has a capacity of 1 to 30 × 10 ⁻³ nl, since a minimum dot diameter of about 20 to 60 μm can be obtained on recording paper. A color print printed with such a dot diameter gives a high quality image. Preferably 2-20 ×
This is a case where a droplet having a volume of 10 ⁻³ nl is ejected as a minimum droplet.

The water-based ink may have at least two different densities of at least magenta and cyan.
In the method of printing with different types of ink, the low density ink is used in the highlight portion, so that it is difficult to identify the dots. However, the present invention can be applied to the case where such a printing method is adopted.

In the ink jet recording method, various conventionally known methods can be used as the recording method, and details thereof are described in, for example, the trend of the ink jet recording technology (Koichi Nakamura, edited by Koichi Nakamura, March 31, 1995, Nihon Kagaku). Information company).

[0086]

The present invention will be described below with reference to examples of the present invention.
The present invention is not limited to these examples. In addition,
In Examples, "%" indicates absolute dry weight% unless otherwise specified.

Comparative Example 1 The average particle diameter of the primary particles dispersed uniformly beforehand is about 0.5.
007 μm fumed silica (manufactured by Nippon Aerosil Co., Ltd .:
A300) of 18% aqueous solution A1 (pH = 2.6, containing 1% by weight of ethanol) was mixed with 450 liters of an aqueous solution C1 containing 18% by weight of the following cationic polymer P-1 and 1% by weight of ethanol (pH = 2). 0.3, containing 2 g of an antifoaming agent SN381 manufactured by Sannobuco) at room temperature with stirring. Next, boric acid and borax 1:
1 weight ratio of mixed aqueous solution D solution (concentration of 3% by weight each) 47
One liter was added slowly with stirring. Then, the mixture was dispersed at a pressure of 500 kg / cm ² with a high-pressure homogenizer manufactured by Sanwa Kogyo Co., Ltd., and the whole was finished to 630 liters with pure water.
An almost transparent dispersion B1 was obtained.

This dispersion has a filtration accuracy of 30 μm.
Filtration was performed using a TCP-10 type filter manufactured by Advantex Toyo.

[0089]

Embedded image

The following four kinds of coating liquids were prepared using the above-mentioned dispersion liquid for coating an ink jet recording paper having a four-layer structure. (All values are shown in the amount per liter of the coating solution, and the order of addition was mixed in the order described.)

First layer coating solution Silica dispersion B1 520 ml Polyvinyl alcohol (PVA203 manufactured by Kuraray) 10% aqueous solution 10 ml Polyvinyl alcohol (PVA235 manufactured by Kuraray) 5% aqueous solution 250 ml Fluorescent brightener dispersion (described below) 30 ml Ethanol 8 .5ml pure water (to make the total volume 1000ml)

Coating solution for second layer Dispersion B1 Silica dispersion B1 600 ml 10% aqueous solution of polyvinyl alcohol (PVA203 manufactured by Kuraray) 10 ml 5% aqueous solution of polyvinyl alcohol (PVA235 manufactured by Kuraray) 260 ml Fluorescent brightener dispersion (described below) 30ml ethanol 3.5ml pure water (total volume is 1000ml)

Coating Solution for Third Layer Dispersion B1 Silica Dispersion B1 620 ml 10% aqueous solution of polyvinyl alcohol (PVA203 manufactured by Kuraray Co., Ltd.) 10 ml 5% aqueous solution of polyvinyl alcohol (PVA235 manufactured by Kuraray Co., Ltd.) 265 ml Fluorescent brightener dispersion (described below) 10ml ethanol 10ml pure water (total volume is 1000ml)

Coating solution for fourth layer (top layer) Dispersion B1 Silica dispersion B1 590 ml Polyvinyl alcohol (PVA203 manufactured by Kuraray) 10% aqueous solution 5 ml Polyvinyl alcohol (PVA235 manufactured by Kuraray) 5% aqueous solution 240 ml Saponin aqueous solution (20%) 10 ml Matting agent dispersion containing 10% by weight of methyl methacrylate having an average particle size of 5 μm and a dispersity of 0.5 4 ml Ethanol 11 ml Pure water (total amount is finished to 1000 ml)

Fluorescent Whitening Agent Dispersion: An oil-soluble fluorescent whitening agent (UVITEX, manufactured by Ciba-Geigy) in 100 liters of a 3% acid-treated gelatin aqueous solution (containing 4 kg of saponin and 2 kg of cationic polymer P-1). -OB) 600 g
Then, a solution prepared by heating and dissolving 12 kg of diisodecyl phthalate in 25 liters of ethyl acetate was added, and the mixture was emulsified and dispersed with a high-pressure homogenizer to make the total amount 140 liters with pure water. As a result of measuring the particle size distribution of this dispersion using a Coulter counter, the average particle size was about 0.34 μm, and the percentage of particles having a particle size of 1 μm or more was 0.1% or less.

The above coating solution was simultaneously coated on a paper support (thickness: 240 μm, glossiness at 75 ° of the coated surface of 30%) coated on both sides with polyethylene at a wet film thickness of 4 layers as follows, and ink jet recording paper-1 I got First layer: 50 μm Second layer: 50 μm Third layer: 50 μm Fourth layer: 50 μm After applying the coating solution at 40 ° C. simultaneously, passing through a cooling zone at 0 ° C. for 20 seconds, then 30 to 50 ° C. And dried over 4 minutes. When the section of the obtained recording paper was observed with a microscope, the dry film thickness was about 40 in total.
μm.

Next, in the dispersion B1 used for the first to fourth layers of the recording paper-1, the dispersion B was obtained by adding the following changes.
2 to B7 were prepared in the same manner as for the dispersion B1, and
Recording papers-2 to 7 were prepared in the same manner as in No. 1.

Dispersion B2: The amount of the cationic polymer was 2
Dispersion B3: Silica particles except that the amount was reduced to the amount of / 3.
012 nm fumed silica (manufactured by Nippon Aerospace Co., Ltd., A
The same as the dispersion B1 except that the dispersion was changed to 200). Dispersion B4: Silica particles were used.
03 nm fumed silica (A5, manufactured by Nippon Aerospace Co., Ltd.)
Dispersion B5: Silica particles were the same as Dispersion B1, except that the average particle diameter of the primary particles used in Dispersion B1 was 0.1. 007 nm fumed silica and the fumed silica having an average primary particle size of 0.012 nm used in the dispersion B3 are:
Dispersion B6: Silica particles were the same as dispersion B1 except that the mixture was changed to a mixture having a weight ratio of 1. Vapor-phase silica having an average primary particle diameter of 0.007 nm used in dispersion B1 and dispersion B3 were used. Dispersion B7: Silica particles were the same as Dispersion B1, except that the mixture was changed to a mixture having a 4: 1 weight ratio of fumed silica having an average particle size of 0.03 nm of the primary particles used in Step B1. A 1: 1 weight ratio mixture of fumed silica having an average primary particle diameter of 0.007 nm and fumed silica having an average primary particle diameter of 0.03 nm used in dispersion B4. Same as Dispersion B1 except changed to

The particle size of the inorganic fine particles contained in the void layer of each recording paper was measured with an electron microscope, and the results shown in Table 1 were obtained. The glossiness of each recording sheet was measured using a gloss meter (VGS-1001DP) manufactured by Nippon Denshoku Industries Co., Ltd. at 60 degrees.

Further, as an ink jet printer,
The glossiness after performing black solid printing with the following three types of printers was measured in the same manner. (A): PM750C manufactured by Seiko Epson (b): BJC700J manufactured by Canon (c): PhotoSmart manufactured by Hewlett-Packard The results are shown in Table 1.

[0101]

[Table 1]

From the results shown in Table 1, the recording papers 1, 3, and 5 using inorganic fine particles having a dispersity of 2 or less and an average particle diameter of 100 nm or less have relatively high gloss, but were solid printed with an ink jet printer. The portions also have approximately the same gloss.

Example 1 When dispersing the fluorescent whitening agent dispersion used in the first to third layers in the recording papers 1 to 7 of Comparative Example 1, the amount of ethyl acetate was reduced to 2/3. Further, an emulsified dispersion was prepared in the same manner as in Comparative Example except that saponin was reduced to half.

The average particle size of this fluorescent whitening agent dispersion is about 0.1.
The ratio having a particle size of 7 μm but 1.0 μm or more was about 15%. Using this fluorescent brightener dispersion, recording papers 11 to 17 were prepared in the same manner as in Comparative Example 1. The glossiness before and after printing was measured in the same manner as in Comparative Example 1, and the results shown in Table 2 were obtained.

[0105]

[Table 2]

From the results shown in Table 2, by using the emulsified dispersion having a large particle diameter, the recording paper (1
1, 13, 15), the glossiness before printing is slightly lower than that of the recording paper (1, 3, 5) prepared in Comparative Example 1, but the glossiness increases after printing with an inkjet printer. However, as for the print, the print portion has become more clear and vivid.

On the other hand, recording paper (14, 17) using inorganic fine particles having a particle diameter of more than 100 nm and recording paper (12, 17) using inorganic fine particles having a dispersity of more than 2 were used.
In 16), the gloss was low, the gloss was hardly increased by printing with an ink jet printer, and the vividness of the entire print was low.

Example 2 In the recording papers 1 to 7 of Comparative Example 1, cationic latex particles (having an average particle size of about 0.75 μm,
1.0 μm or more occupies about 20%) was prepared by adding 25 ml per 1 liter of the coating liquid, and using the dispersions B1 to B7 in the same manner as in Comparative Example 1, the recording papers 21 to 21 were used.
27 was created. Evaluation was performed in the same manner as in Example 1, and the results shown in Table 3 were obtained.

[0109]

[Table 3]

From the results shown in Table 3, it is found that the glossiness of the recording paper (21, 23, 25) of the present invention before printing is slightly reduced by the addition of relatively large latex particles as in Example 1. On the contrary, the glossiness increased after printing, and it was found that very vivid prints could be obtained from this recording paper.

[0111] In the recording paper -1～7 Example 3 Comparative Example 1, except that the average particle size in the first layer was added to a titanium oxide of about 0.30μm in the recording sheet 1 m ² per 0.4g Recording papers 31 to 37 were prepared in the same manner as in Comparative Example 1. The gloss before and after printing was measured in the same manner as in Comparative Example 1, and the results shown in Table 4 were obtained.

[0112]

[Table 4]

From the results shown in Table 4, it can be seen that the same effects as in Examples 1 and 2 can be obtained by adding titanium oxide particles having a high refractive index to the first layer.

Example 4 In the recording papers 1 to 7 of Comparative Example 1, before coating the first to fourth layers, gelatin was previously coated on a support.
m ² per 2.0g was applied. This gelatin layer was hardened by adding 20 mg of 2,4-dichloro-6-hydroxy-s-triazine sodium salt as a hardener per 1 g of gelatin. The above-mentioned first to fourth layers were applied on this gelatin layer to prepare recording papers 41 to 47. The glossiness before and after printing was measured in the same manner as in Comparative Example 1, and the results shown in Table 5 were obtained.

[0115]

[Table 5]

From the results shown in Table 5, the recording paper (41, 43, 45) of the present invention has a relatively high gloss, and the gloss in the print is further increased. It can be seen that a more vivid print can be obtained.

[0117]

According to the present invention, it is possible to provide an ink jet recording paper which has a relatively high gloss and further increases the gloss when printed by an ink jet to give a high quality print.

Claims (4)

[Claims] An ink absorbing layer comprising at least two void layers, wherein at least one of the void layers other than the uppermost layer has
Particles obtained by emulsifying and dispersing a hydrophobic organic compound having a relatively large particle diameter are added, and particles obtained by emulsifying and dispersing the hydrophobic organic compound in a void layer furthest from the support are not substantially added. An ink jet recording sheet characterized by the above-mentioned. 2. An ink absorbing layer comprising at least two void layers, wherein at least one of the void layers other than the uppermost layer has
An ink jet recording paper comprising latex polymer particles, wherein the latex polymer particles are not substantially added to the gap layer furthest from the support. 3. An ink absorbing layer comprising at least two void layers, wherein at least one of the void layers other than the uppermost layer has
An ink jet recording paper comprising fine particles having a higher refractive index than inorganic fine particles forming voids. 4. An ink absorbing layer substantially consisting of a swelling layer is provided on a support, and a void layer containing inorganic fine particles having a degree of dispersion of 2 or less, a hydrophilic binder and a hardener is provided thereon. An ink jet recording sheet characterized by the above-mentioned.