JP3503016B2 - Inkjet recording paper - Google Patents

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 for recording using an aqueous ink, which can be produced at a low cost, provides a high quality image with a photographic texture, and prevents cracks on the recording surface. The present invention relates to an inkjet recording paper that can obtain high gloss.

[0002]

2. Description of the Related Art Ink-jet recording is a technique for ejecting minute droplets of ink to adhere to a recording sheet such as paper by various operating principles to record images, characters, etc. It has the advantages that it is noise and that it is easy to make multiple colors. Regarding nozzle clogging and maintenance, which have been a problem with this method,
Improvements have been made from both aspects of inks and devices, and are now rapidly spreading to various fields such as various printers, facsimiles, and computer terminals.

As a recording paper used in this ink jet recording system, the density of print dots is high, the color tone is bright and vivid, the ink is absorbed quickly, and the ink flows out even when the print dots overlap. It is required that the ink does not bleed, that the diffusion of the print dots in the lateral direction is not excessively large, and that the periphery is smooth and does not blur.

Particularly when the ink absorption speed is low, when ink droplets of two or more colors are overlapped and recorded, the droplets cause a cissing phenomenon on the recording paper to cause unevenness, or different colors. It is necessary to provide the recording paper with high ink absorbability because the colors tend to bleed each other in the border area of the recording medium and the image quality is likely to be greatly deteriorated.

In order to solve these problems, many techniques have been proposed in the past.

For example, a recording paper obtained by wetting a low-size base paper described in JP-A-52-53012 with a coating material for surface treatment, a surface of a support described in JP-A-55-5830. A recording paper having an ink-absorptive coating layer on it, a recording paper containing non-colloidal silica powder as a pigment in the layer to be coated, described in JP-A-56-157, and JP-A-57-107878. Recording paper using a combination of inorganic pigments and organic pigments described in JP-A-58-
No. 110287, a recording paper having two peaks of pore distribution, a recording paper having two upper and lower porous layers described in JP-A-62-111782, and JP-A-59-68292. Japanese Patent Publication No. 59-1236.
Recording papers having irregular cracks, such as those described in JP-A No. 96 and JP-A No. 60-18383, and JP-A-61-1.
Recording papers having a fine powder layer described in JP-A-35786, JP-A-61-148092 and JP-A-62-149475, JP-A-63-252779,
Recording paper containing pigment or fine particle silica having specific physical property values described in JP-A-1-108083, JP-A-2-136279, JP-A-3-65376 and JP-A-3-27976, JP-A-57-1409
No. 1, gazette 60-219083, gazette 60-21
No. 0984, No. 61-20797, No. 61-
188183, JP-A-5-278324,
No. 6-92011, No. 6-183134,
Recording papers containing fine particle silica such as colloidal silica described in JP-A Nos. 7-137431 and 7-276789, and JP-A-2-276671, JP-A-3-67684 and JP-A-3-67684. -215082, 3-251488, 4-67986, 4-263983, 5-16517, and the like, and recording sheets containing alumina hydrate fine particles. Many are known.

Among the above, when the ink receiving layer is a layer having a large number of voids for absorbing and holding ink, the ink absorbability is good, the bleeding at the boundary is small, and a high-quality image can be expected. .

When an ink-absorbing layer having such a void structure is provided on a non-water-absorbing support, a high-density clear image can be obtained, while the ink-absorbing layer provided on the support is Pore volume is limited.

For example, in the case of a film having a dry film thickness of 40 μm, assuming that the film has a uniform solid content of 22 μm, the void volume is the ink jet recording paper 1.
will be per m ² (40-22) = 18ml / m ² having only, depending on the recording method may occur or may not also as insufficient ink absorbing capacity in the vicinity of the maximum amount of ink.

In the ink absorbing layer having a void structure, the amount of ink absorbed is smaller than the dry capacity of the original film, so that it is necessary to make the dry film thickness sufficiently large to absorb a large amount of ink. The film is likely to crack under low humidity.

On the other hand, when an ink absorbing layer having a void structure is provided on a water-absorbing support, the support itself has a high absorption capacity and ink absorbency, which is preferable from the viewpoint of ink absorption. Therefore, the limitation on the ink absorbing layer as described above is reduced. However, since the support itself absorbs the ink solvent, there is a problem that the support becomes wavy after the ink solvent is dried after recording and wrinkles are likely to occur in an image.

The applicant has studied this point and found that
By providing an ink absorbing layer having a void structure on a water absorbing support having a thickness of 160 μm or more, it is possible to suppress wrinkling of the support after recording while maintaining ink absorbability and high-quality image quality. I found what I could do.

When an ink absorbing layer having a void structure is provided on a water absorbing support, the ink absorbing capacity of the recording paper is determined by the void capacity of the ink absorbing layer having a void structure and the absorbing capacity of the support itself. . If the ink absorption capacity of the recording paper is insufficient, the ink will overflow during recording, and the image quality will be greatly degraded.

However, as a result of the study by the present applicant, it has been found that a problem occurs even if the ink absorption capacity of the recording paper is too large. That is, a recording paper having an ink absorption layer having a void structure provided on a water-absorbent support can have a thinner ink absorption layer than a non-water-absorbent support, resulting in low cost and high production. The advantage is that the ink absorption layer itself has good properties and cracks can be reduced, but in order to achieve this purpose, it is generally necessary to reduce the void volume of the ink absorbing layer itself. Therefore, the ink absorption capacity of the recording paper is generally determined by the water absorption capacity of the support itself used. The voids of the ink absorbing layer are designed for controlling the spread of dots of ink droplets and fixing of dye, and the ink solvent is exclusively held by the water absorbing support.

In the production of such a recording paper, the solvent in the coating liquid of the support is absorbed quickly when the ink absorbing layer having a void structure is applied onto the support, so that the coating is fragile depending on the drying conditions. It was found that it is easy for the surface to become cracked and that a fine cracked state is likely to occur on the surface. When inkjet recording is performed on such an inkjet recording paper,
The ink spreads along these cracks and remarkably deteriorates the image quality. Therefore, the applicant of the present invention has earnestly studied the absorption of the recording paper when the ink absorption layer having a void structure is provided on the water-absorbent support, and has arrived at the present invention.

[0016]

The present invention has been made in view of the above circumstances, and the first problem to be solved by the present invention is to unnecessarily increase the thickness of the ink absorbing layer. Another object is to provide an inkjet recording paper having an increased ink absorption capacity.

A second problem to be solved by the present invention is to provide an ink jet recording paper which is low in cost, has no wrinkles in the image portion after recording, and has a high image quality and a photographic texture. It is in.

A third problem to be solved by the present invention is to provide an ink jet recording paper capable of preventing cracks on the recording surface and obtaining high gloss.

[0019]

The above objects can be achieved by the following ink jet recording paper.

1. A water-absorbent support having a thickness of 160 μm or more has a dry film thickness of 5 to 30 μm and an average particle size of 10
Silica fine particles synthesized by a gas phase method of 0 nm or less and
Containing fine hydrophilic binder, the hydrophilic of the fine particles
The weight ratio to the binder is 3 to 8, making it a hardener.
A Cobb obtained by using pure water containing a hardened ink absorbing layer having a void structure, a contact time of 10 seconds in the water absorption test method defined in JIS P8140, and containing 30% by weight of diethylene glycol. An ink jet recording paper having a water absorption of 20 to 60 g / m ² .

2. Water absorbing support having a thickness of 160 μm or more
The dry film thickness is 5 to 30 μm and the average particle size is 1
Contains fine particles of 00 nm or less and hydrophilic binder
The weight ratio of the fine particles to the hydrophilic binder
The rate is 3 to 8 and is hardened by boric acid or its salt
Has an ink absorption layer with a void structure
Contact time in the water absorption test method specified in 8140
Is 10 seconds and contains 30% by weight of diethylene glycol
Cobb water absorption determined using pure water
An inkjet recording paper characterized by having a size of m ² .

3 . Polyvinyl chloride as the hydrophilic binder
1 or 2 characterized by containing alcohol
Ink jet recording paper according to.

[0023]

[0024]

[0025]

[0026]

The present invention will be described in detail below.

In the present invention, as the water-absorbent support of the ink jet recording paper, any material having a desired water-absorption property can be used.

For example, there may be mentioned general paper, synthetic paper, cloth, sheets and plates made of wood, etc., among which paper is the most preferable because it is excellent in water absorption of the base material itself and also excellent in cost. . The paper support will be described below.

Examples of the paper support include chemical pulp such as LBKP and NBKP, GP, CGP, RMP, TMP and CTM.
Mechanical pulps such as P, CMP, PGW and the like, waste paper pulps such as DIP and the like, and wood pulps as the main raw material can be used. In addition, various fibrous substances such as synthetic pulp, synthetic fibers, and inorganic fibers can be appropriately used as raw materials, if necessary.

In the paper support, if necessary, a sizing agent,
Various conventionally known additives such as a pigment, a paper strengthening agent, a fixing agent, a fluorescent brightening agent, a wet paper strength agent and a cationizing agent can be added. Higher fatty acids, alkyl ketene dimers, etc. as sizing agents, calcium carbonate, talc, titanium oxide, etc. as pigments, starch as paper strengthening agents,
Examples of the fixing agent include polyacrylamide and polyvinyl alcohol, and examples of the fixing agent include, but are not limited to, a sulfuric acid band and a cationic polymer electrolyte.

The paper support is prepared by mixing the above-mentioned fibrous substance such as wood pulp with various additives, and using a Fourdrinier paper machine, a cylinder paper machine,
It can be manufactured with various paper machines such as a twin wire paper machine. If necessary, size press treatment with starch, polyvinyl alcohol, etc., various coat treatments, or calender treatment can be carried out at or after the paper making.

The thickness of the water absorbing support of the ink jet recording paper of the present invention is 160 μm or more. If it is thinner than this, the support itself absorbs the ink solvent, so that the support is likely to have wavy wrinkles in an image form after the ink solvent is dried after recording. Moreover, it is more preferable that the thickness of the water-absorbent support is 180 μm or more, since wrinkles are less likely to occur. There is no particular upper limit to the thickness of the water-absorbent support, but it is about 500 μm from the viewpoint of handleability.

According to the water absorption test method of JIS P8140 of the water-absorbent support, the contact time was 10 seconds,
Cobb water absorption was determined using pure water containing diethylene glycol 30% by weight is preferably from 10 to 50 g / m ^2, particularly preferably from 20 to 40 g / m ^2. If the Cobb water absorbency is less than 10 g / m ² , the ink absorbency of the absorptive support may be insufficient, the ink may overflow, and the image quality may deteriorate. ^{On the other hand} , when it exceeds 50 g / m ² , the support excessively absorbs the solvent in the coating liquid when the ink absorbing layer having a void structure is coated on the support, and the coating film is likely to be cracked depending on the drying conditions. Become.

In the present invention, for the purpose of increasing the adhesive strength between the support and the ink absorbing layer, the support may be subjected to corona discharge treatment, subbing treatment or the like prior to coating the ink absorbing layer. .

The ink jet recording paper of the present invention contains fine particles having an average particle diameter of 100 nm or less.

When fine particles having an average particle size of more than 100 nm are used, the glossiness of the recording paper is lowered, the roundness of the dots at the time of ink jet recording is lowered, and unnecessary dot spread occurs, or It becomes difficult to obtain a clear image because the maximum density is reduced due to irregular reflection on the surface.

The lower limit of the average particle size of the fine particles is not particularly limited, but it is about 10 n from the viewpoint of handleability and stability during production.
It is m or more.

As the fine particles, various inorganic or organic solid fine particles which are conventionally known in ink jet recording paper can be used.

Examples of the inorganic fine particles include 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, hydrotalcite, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, synthetic amorphous silica, colloidal silica, alumina, colloidal alumina, pseudoboehmite, water Aluminum oxide, lithopone,
Examples thereof include white inorganic pigments such as zeolite and magnesium hydroxide.

On the other hand, examples of the organic fine particles include polystyrene, polyacrylic acid esters, polymethacrylic acid esters, polyacrylamides, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, their copolymers, and urea resins. , Or melamine resin.

The above-mentioned fine particles may be used in a state of being uniformly dispersed in a binder as primary particles, or may be added in a state of forming secondary aggregated particles and being dispersed in a binder. Good, but the latter is more preferred.

When the fine particles are used in the form of secondary agglomerated particles of primary particles, it is preferable from the viewpoint of glossiness that the average particle diameter of the primary particles is 30 nm or less.

The lower limit of the average particle diameter of the primary particles is not particularly limited, but from the viewpoint of production of particles, it is generally 3 nm or more, especially 6
nm or more is preferable.

In the above, the average particle size of the fine particles is obtained by observing the particle itself or the cross section or the surface of the ink absorbing layer with an electron microscope, obtaining the particle size of 100 arbitrary particles, and taking it as a simple average value (number average). Desired. Here, each grain size is represented by a diameter assuming a circle equal to the projected area.

The method for producing silica fine particles is roughly divided into a dry method (gas phase method) and a wet method. As a dry method, a method by gas phase hydrolysis of silicon halide at high temperature (flame hydrolysis method), and There is known a method (arc method) in which silica sand and coke are heated and reduced by an arc in an electric furnace to be vaporized and air-oxidized. As a wet method, there is known a method in which activated silica is generated by acid decomposition of silicate and then excessively polymerized to cause aggregation / precipitation.

In the present invention, among the silica fine particles, silica synthesized by the gas phase method is most preferable.

The fine particle silica synthesized by the vapor phase method is usually a silica powder having an average primary particle diameter of 5 to 500 nm obtained by burning silicon tetrachloride with hydrogen and oxygen at a high temperature, and in the present invention, it is particularly 30 nm. Those having the following average primary particle diameters are preferable in terms of glossiness.

Various types of Aerosil manufactured by Nippon Aerosil Co., Ltd. are applicable as the commercially available vapor phase silica.

The colloidal silica preferably used in the present invention is obtained by heating and aging a silica sol obtained by metathesis of sodium silicate by an acid or the like or passing through an ion exchange resin layer. This colloidal silica is used for ink jet recording paper. For example, Japanese Unexamined Patent Publication No.
No. 7-14091, No. 60-219083,
60-219084, 61-20792, 61-188183, 63-17807.
JP-A-4-93284, JP-A-5-2783.
No. 24, No. 6-92011, No. 6-1831.
No. 34, No. 6-297830, No. 7-812.
No. 14, gazette 7-101142, gazette 7-179.
No. 029, No. 7-137431, and International Patent Publication No. WO94 / 26530.

The preferred average particle size of colloidal silica is usually 5 to 100 nm, but an average particle size of 7 to 30 nm is particularly preferred.

The silica and colloidal silica synthesized by the above vapor phase method may have their surfaces cation-modified, or may be those treated with Al, Ca, Mg, Ba and the like. Good.

The ink jet recording paper of the present invention contains fine particles and has an ink absorbing layer having a void structure.
When fine particles are contained to form voids, it is necessary to contain a hydrophilic binder in the layer in order to form a stable film.

Examples of the hydrophilic binder used include gelatin or gelatin derivatives, polyvinylpyrrolidone, pullulan, polyvinyl alcohol or its derivatives, polyethylene glycol, carboxymethyl cellulose, hydroxyethyl cellulose, dextran, dextrin, polyacrylic acid and its salts, agar, κ. -Carrageenan, λ-carrageenan, ι-carrageenan, xanthene gum, locust bean gum, alginic acid, gum arabic, pullulan, JP-A-7-195826 and 7
No. 9757, a polyalkylene oxide-based copolymerizable polymer, water-soluble polyvinyl butyral, or a vinyl monomer having a carboxyl group or a sulfonic acid group described in JP-A No. 62-245260, alone or a vinyl thereof. Examples thereof include polymers such as copolymers having repeating monomers. These hydrophilic binders may be used alone or in combination of two or more.

Above all, it is preferable to contain polyvinyl alcohol because of the hygroscopicity of the film, the stickiness under high humidity, and the less bleeding of the dye during ink jet recording.

The polyvinyl alcohol includes cation-modified, nonion-modified and anion-modified polyvinyl alcohol.

The average degree of polymerization of polyvinyl alcohol is preferably 1,000 to 5,000 from the viewpoint of film-forming property, and particularly preferably an average degree of polymerization of 2,000 or more.

The degree of saponification of polyvinyl alcohol is 70 to
100% is preferable, and 80 to 100% is particularly preferable. As the cation-modified polyvinyl alcohol, for example, polyvinyl having a primary to tertiary amino group or a quaternary ammonium group in the main chain or side chain of the polyvinyl alcohol as described in JP-A-61-110483. It is an alcohol and 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-vinyl imidazole, N-vinyl-2-methyl imidazole, N
-(3-dimethylaminopropyl) methacrylamide,
Hydroxylethyltrimethylammonium chloride, trimethyl- (methacrylamidopropyl) ammonium chloride, N- (1,1-dimethyl-3-dimethylaminopropyl) acrylamide and the like can be mentioned.

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

The anion-modified polyvinyl alcohol is described in, for example, polyvinyl alcohol having an anionic group as described in JP-A No. 1-206088, JP-A Nos. 61-237681 and 63-307979. Such as a copolymer of vinyl alcohol and a vinyl compound having a water-soluble group, and JP
A modified polyvinyl alcohol having a water-soluble group as described in JP-A-285265 can be used.

As the nonion-modified polyvinyl alcohol, 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, JP-A-8-25795. Examples thereof include block copolymers of a vinyl compound having a hydrophobic group and vinyl alcohol, which are described in Japanese Patent Laid-Open Publication No. 2003-242242.

In the ink jet recording paper of the present invention, the weight ratio of the fine particles to the hydrophilic binder is generally 2 to.
The range is 10, but 3 to 8 is particularly preferable. If the weight ratio of the fine particles to the hydrophilic binder is less than 3, a decrease in ink absorbency may be caused, and if it exceeds 8, the coating film of the void layer may be cracked during storage under low humidity.

The ink absorbing layer of the inkjet recording paper of the present invention preferably contains boric acid or a salt thereof as a hardener. The boric acid or a salt thereof means an oxygen acid having a boron atom as a central atom and a salt thereof, and specifically includes orthoboric acid, metaboric acid, hypoboric acid, tetraboric acid, pentaboric acid and salts thereof.

JIS of the ink jet recording paper of the present invention
In the water absorption test method specified in P8140, the contact time was set to 10 seconds, and diethylene glycol was added in an amount of 30% by weight.
The Cobb water absorption measured using pure water contained is 20 to 60.
a g / m ^2, particularly preferably from 30 to 50 g / m ^2. If the Cobb water absorption is less than 20 g / m ² , the water absorption capacity of the ink will be insufficient, the ink will overflow, and the image quality will be greatly deteriorated. When it exceeds 60 g / m ² , the support excessively absorbs the solvent in the coating liquid when the ink absorbing layer having a void structure is coated on the support, and the coating film may be cracked depending on the drying conditions. It will be easier.

The dry film thickness of the ink absorbing layer of the ink jet recording paper of the present invention is 5 to 30 μm. When it is less than 5 μm, the ink absorbency and gloss are deteriorated, and when it exceeds 30 μm, the coating film is cracked when it is stored in low humidity, and the cost is disadvantageous.

The ink jet recording paper of the present invention may have two or more ink absorbing layers containing fine particles. In this case, the kind or ratio of the hydrophilic binder and fine particles used in these plural ink absorbing layers. Is arbitrarily selected.

If necessary, various additives can be added to the ink absorbing layer of the ink jet recording paper of the present invention.

For example, JP-A-57-74193,
UV absorbers described in JP-A-57-87988 and JP-A-62-261476, JP-A-57-74192, JP-A-57-87989, and JP-A-60-72785.
JP-A No. 61-146591, JP-A No. 1-95
No. 091 and No. 3-13376, anti-fading agents, various anionic, cationic or nonionic surfactants, JP-A-59-42993 and JP-A-5-32993.
9-52689, 62-280069,
JP 61-242871 and JP-A 4-21926.
Various known additives such as fluorescent whitening agents, defoaming agents, lubricants such as diethylene glycol, preservatives, thickeners, antistatic agents, matting agents, etc., described in JP-A-6 No. 6 can be incorporated. .

Further, a cationic mordant may be contained in order to improve water resistance and moisture resistance after printing.

As the cationic mordant, a polymer mordant having a primary to tertiary amino group and a quaternary ammonium salt group is preferably used, but a cationic non-polymer mordant can also be used.

As the polymer mordant, a polymer mordant having a quaternary ammonium salt group is preferable from the viewpoint of weather resistance and robust dyeing property.

A preferable polymer mordant is obtained as a homopolymer of the above-mentioned monomer having a quaternary ammonium salt group, a copolymer with another monomer, or a condensation polymer.

This polymer mordant can be used either as a water-soluble polymer or in the form of water-dispersible latex particles.

On the other hand, as the non-polymeric mordant, a fourth compound having a total number of carbon atoms of 12 or more, preferably 18 or more
A compound having a primary ammonium base is used.

The amount of the above-mentioned polymer mordant and non-polymer mordant used is preferably 0.2 to 10 g, and more preferably 0.5 to 5 g per 1 m ² of the recording paper.

The ink absorbing layer of the present invention generally has a hard structure because it has a void structure. For this reason, cracks are likely to occur during production or during evaporation of the ink solvent after inkjet recording, but it is preferable to include oil droplets in order to further reduce this problem.

As the oil droplets, those obtained by emulsifying and dispersing a hydrophobic compound having a melting point of 40 ° C. or less and polymer latex particles having a glass transition temperature of 40 ° C. or less are used. The average particle size of the oil droplets is preferably 0.02-1 μm, more preferably 0.05-0.5 μm, and particularly preferably 0.05-0.
Those having a thickness of 3 μm are used.

The amount of oil droplets added is preferably 1 to 50% by weight, more preferably 2 to 20% by weight, based on the weight of the fine particles contained in the ink absorbing layer.

On the side opposite to the ink absorbing layer side of the ink jet recording paper of the present invention, various kinds of back layers are provided in order to prevent curling and further improve sticking and ink transfer when superposed immediately after printing. You can

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

The back layer may have a roughened surface in order to prevent sticking to other recording sheets, improve writing performance, and improve transportability in an ink jet recording apparatus. For this purpose, organic or inorganic fine particles having a particle size of 2 to 20 μm are preferably used.

The recording paper of the present invention having the above constitution can be obtained, for example, by the following method. First, the material for forming the ink absorbing layer having the void structure is added to a suitable solvent such as water, alcohol or various organic solvents to prepare a coating solution, which is coated on the water-absorbent support and dried. Thus, an ink absorbing layer having a void structure is formed.

The method for coating the ink absorbing layer on the support can be appropriately selected from known methods. The ink absorbing layer may have two or more layers. In this case, two or more layers can be coated at the same time, and in particular, simultaneous coating of all hydrophilic binder-containing layers is preferable.

The ink absorbing layer may be applied by a roll coating method, a rod bar coating method, an air knife coating method, a spray coating method, a curtain coating method, or the hopper described in US Pat. No. 2,681,294. The rouge coating method is preferably used, and particularly in the multilayer simultaneous coating method, the curtain coating method or the slide hopper coating method is preferable.

One of the preferable methods is to apply a hydrophilic binder-containing ink absorbing layer on a support, cool it to a gel state, and then dry it by a cold dry method. From the viewpoint of productivity, it is preferable to heat the coating liquid that has been set under the condition that it does not redissolve. Usually, after setting, after evaporating water to some extent within the range of room temperature to 30 ° C., it is heated to 40 ° C. to 50 ° C. and completely dried.

Drying after coating is preferably carried out by cooling once to increase the viscosity of the coating liquid or gelling and then blowing to dry.

The coating liquid temperature is usually 25 to 60 ° C.,
30-50 degreeC is preferable. For cooling, the film surface temperature after coating is 2
The temperature is preferably 0 ° C. or lower, preferably 15 to 5 ° C., and the subsequent drying is preferably performed by blowing air at 20 to 60 ° C. from the viewpoint of obtaining a uniform film surface.

The wet film thickness to be applied varies depending on the intended dry film thickness, but is generally 40 to 200 μm, preferably 50.
.About.150 .mu.m, and the coating speed is generally 20 to 200 m / min, although it depends largely on the drying ability. Drying time is generally 2-1
0 minutes.

Next, the water-soluble recording liquid to be used for ink jet recording using the recording paper of the present invention will be described below.

The water-soluble recording liquid is usually a recording liquid containing a water-soluble dye, a liquid medium, and other additives. As the water-soluble dye, a direct dye, an acid dye, a basic dye, a reactive dye or a water-soluble dye known as a dye for food, which is known in inkjet, can be used, but the direct dye or the acid dye is preferable.

The solvent of the recording liquid is mainly water, but the boiling point is usually 120 ° C. in order to prevent the dye from precipitating when the recording liquid is dried and clogging at the nozzle tip and the recording liquid supply path. Above, a high boiling organic solvent which is liquid at room temperature is used. The high-boiling organic solvent is required to have a vapor pressure much lower than that of water in order to prevent the formation of coarse precipitates by the precipitation of solid components such as dyes when water is evaporated. Must be highly miscible with.

For this purpose, many high boiling organic solvents are usually used. Specific examples include ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, glycerin, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, and triethylene. Glycol monobutyl ether, glycerin monomethyl ether, 1,2,3-butanetriol, 1,2,4-butanetriol, 1,
Examples thereof include alcohols such as 2,4-pentanetriol, 1,2,6-hexanetriol, 1,2-hexanediol, thiodiglycol, triethanolamine, and polyethylene glycol (having an average molecular weight of about 300 or less). In addition to the above, dimethylformamide, N-methylpyrrolidone and the like can also be used.

Among many of these high boiling organic solvents,
Polyhydric alcohols such as diethylene glycol, triethanolamine and glycerin, and lower alkyl ethers of polyhydric alcohols such as triethylene glycol monobutyl ether are preferable.

Other additives contained in the recording liquid include, for example, pH adjusting agents, sequestering agents, fungicides, viscosity adjusting agents, surface tension adjusting agents, wetting agents, surfactants, and rust preventives. Is mentioned.

The recording liquid is used in an amount of 25 to 50 dyne / 25 ° C. at 25 ° C. for the purpose of improving the wettability with respect to the recording paper and stabilizing the ejection from the ink jet nozzle.
It is preferred to have a surface tension in the range of cm, preferably 28-40 dyne / cm.

The viscosity of the recording liquid is usually 2 to 10 cp, preferably 2.5 to 8 cp at 25 ° C. The pH of the recording liquid is preferably 3-9.

When the minimum ink droplet ejected from the ink nozzle has a capacity of 1 to 30 pl, it is about 2 on the recording paper.
It is preferable because a minimum dot diameter of 0 to 60 μm can be obtained. A color print printed with such a dot diameter gives a high quality image. It is preferable that a droplet having a volume of 2 to 20 pl is ejected as the minimum droplet.

In addition, the water-based inks have different densities of at least two times for at least magenta and cyan.
In the method of recording with different types of ink, it is difficult to identify dots because low density ink is used in the highlight portion, but the present invention can also be applied when such a recording method is adopted.

In the ink jet recording method, various conventionally known methods can be used as the recording method. For details, see, for example, the trend of ink jet recording technology (edited by Koichi Nakamura, March 31, 1995, Nihon Kagaku). Information Co., Ltd.).

[0101]

EXAMPLES Examples of the present invention will be described below.
The invention is not limited to these examples. In addition,
The composition of the coating liquid is the amount per 1 L of the coating liquid. Further, the Cobb water absorption is determined by using a water absorption test method specified in JIS P8140, with a contact time of 10 seconds and using pure water containing 30% by weight of diethylene glycol.

Example 1 Coating solution 1 having the following constitution was applied to the recording surface side of a water-absorbent paper support having a thickness of 205 μm, and the coating temperature was 15
Cool rapidly within 30 seconds so that the temperature does not exceed ℃ 20 to 5
Quick dry for 2 minutes with a wind in the range of 0 ° C to obtain a dry film thickness of 15
A recording paper having an ink absorption layer having a pore structure layer of μm was obtained. The average particle diameter of the secondary agglomerated particles of the fine particles was 65 as observed by an electron microscope observation of the cross section of the ink absorption layer of this recording paper.
It was n m. The Cobb water absorption of the obtained recording paper was 42 g / m ² .

[Coating Solution-1] The following fine particle silica dispersion (1) 450 ml The following cationic polymer (1) (average molecular weight 10,000) 2 g Ethanol 35 ml n-Propanol 10 ml Ethyl acetate 5 ml Polyvinyl alcohol (PVA203 manufactured by Kuraray Co., Ltd.) 0 1 g Polyvinyl alcohol (PVA235 manufactured by Kuraray Co., Ltd.) 12 g Boric acid 2.0 g Borax 1.0 g Fine particle silica dispersion (1): A200 manufactured by Nippon Aerosil Co., Ltd. (vapor phase silica having an average primary particle diameter of 12 nm) 80 g of is added to 400 ml of pure water and dispersed by an emulsifying disperser, and then the total amount is made up to 450 ml with pure water.

[0104]

[Chemical 1]

The following items were evaluated for the obtained recording paper.

Cracks after coating: The number of cracks per 100 cm ² was examined.

Ink absorbency: A recording paper on which three colors of yellow, magenta and cyan are recorded is stored at room temperature (20 ° C., 5
0% RH) for 20 seconds, then the recording surface is overlaid with the back surface of another recording paper, and it is judged whether the ink adheres to the back surface when a load of 5 g per 10 cm ² is applied and held for 30 seconds. did.

[0108] ◎: No adhesion ○: It adheres in a trace state, but it is not a problem △: A little adhered and a little problem X: Clearly attached.

Gloss: 75 for the recording layer surface using a variable angle gloss meter (VGS-1001DP) manufactured by Nippon Denshoku Industries Co., Ltd.
The gloss was measured.

[0110] The low-humidity cracking: each 25 ° C. The ink jet recording sheet, a relative humidity of 20% printed surface after one day storage in a state of being in a cylindrical shape with a diameter of 200mm so that the outer, per 100 cm ² The number of cracks was checked.

Waviness after printing: Using an inkjet printer BJC-700J manufactured by Canon Inc., the sheet surface after solid printing of yellow, magenta and cyan was visually observed and judged according to the following criteria. It is A and B that do not cause a quality problem.

[0112] A: No swell is observed and aesthetics are not impaired. B: There is a small swell, but it is not so detrimental C: There is a large swell, which spoils the aesthetics.

Examples 2 to 4 and Comparative Examples 1 to 4 Same as the recording paper of Example 1 except that the water absorbent paper support used in Example 1 was changed to one having a thickness as shown in Table 1. Recording sheets of Examples 2 to 4 and Comparative Examples 1 to 4 were prepared and evaluated in the same manner as in Example 1. The average particle diameter of secondary aggregate particles of these particles by cross electron microscopy of the porous layer of the recording papers were both 65 n m.
The Cobb water absorption of each of the obtained recording papers is as shown in Table 1.

The evaluation results are shown in Table 1.

[0115]

[Table 1]

From the results shown in Table 1, it can be seen that the recording papers of Examples 1 to 4 of the present invention have good ink absorbency and gloss, and have no cracks in the coating film when applied. On the other hand, the recording paper of Comparative Example 1 having a Cobb water absorption of the present invention or less has poor ink absorbency, while the recording paper of Comparative Example 2 having a Cobb water absorption of the present invention or more has many cracks, The gloss is also greatly reduced. In addition, since the recording papers of Comparative Examples 3 and 4 have a thin support, the recording surface is wavy after printing, and the appearance is impaired.

Example 5 A recording sheet of Example 5 was prepared in the same manner as the recording sheet of Example 1 except that the dry film thickness of the coating liquid-1 was changed to 16 μm. The same evaluation as in Example 1 was performed. The average particle size of the secondary agglomerated particles of the fine particles was 65 as observed by electron microscopy of the cross section of the void layer of this recording paper.
It was n m. The Cobb water absorption of the obtained recording paper was 40 g / m ² .

Comparative Examples 5 and 6 Recordings of Comparative Examples 5 and 6 were carried out in the same manner as the recording paper of Example 1 except that the dry film thickness of the coating liquid-1 was changed as shown in Table 2. Paper was prepared and evaluated in the same manner as in Example 1. The average particle diameter of secondary aggregate particles of these particles by cross electron microscopy of the porous layer of the recording papers were both 65 n m. The resulting Cobb water absorption of the recording sheet were respectively ^{33g / m 2, 53g / m} 2.

Comparative Example 7 In Example 1, the fine particle silica dispersion (1) of the coating liquid-1 was changed to the fine particle silica dispersion (2) shown below,
A recording paper of Comparative Example 7 was prepared in the same manner as the recording paper of Example 1 except that the dry film thickness of the coating liquid-1 was changed to 16 μm, and evaluated in the same manner as in Example 1. The cross-section of the void layer of this recording paper was examined by electron microscopy and
The average particle size of the secondary agglomerated particles was 150 nm. The Cobb water absorption of the obtained recording paper was 41 g / m ² .

Fine particle silica dispersion (2): 80 g of TT600 manufactured by Nippon Aerosil Co., Ltd. (gas phase method silica having an average primary particle size of 40 nm) was added to 400 ml of pure water and dispersed by an emulsifying disperser, and then the whole amount was added. To 450 ml with pure water.

Table 3 shows the evaluation results.

[0122]

[Table 2]

[0123]

[Table 3]

From the results shown in Table 3, the recording paper of Comparative Example 3 had too thin an ink-absorbing layer to dry and the ink absorbency and gloss were deteriorated. The recording paper of Comparative Example 4 had a dry ink-absorbing layer. The film thickness is too thick and the film strength when stored under low humidity is poor.

Further, in Comparative Example 7 in which the average particle size of the fine particles is 100 nm or more, the gloss is greatly reduced.

Examples 6 to 9 The same as the recording paper of Example 1 except that the weight of polyvinyl alcohol in the coating liquid-1 was changed as shown in Table 4 and the dry film thickness was changed to 15 μm. Example 6
Recording sheets Nos. 9 to 9 were prepared and evaluated in the same manner as in Example 1.
The average particle size of secondary agglomerated particles of the fine particles by this way an electron microscopic observation of the cross section of the gap layer of the recording papers created was both 65 n m. Further, the Cobb water absorption of each of the obtained recording papers is as shown in Table 5.

Table 5 shows the evaluation results.

[0128]

[Table 4]

[0129]

[Table 5]

From the results shown in Table 5, the recording papers of Examples 6 to 9 of the present invention have good ink absorbency, film strength and gloss, but the weight ratio of fine particles to polyvinyl alcohol in the void layer is 3 to 8. It can be seen that the recording papers of Examples 7 and 8 having the range of 5 are particularly excellent.

Example 10 A coating liquid-2 having the following constitution was applied to the recording surface side of a water-absorbent paper support having a thickness of 185 μm and a Cobb water absorption of 8 g / m ² , and then the coating temperature was adjusted to 15 ° C. or lower. Rapidly within 30 seconds and rapidly dried with a wind in the range of 20 to 50 ° C. for 2 minutes to prepare a recording paper having a void layer having a dry film thickness of 20 μm, and evaluated in the same manner as in Example 1. did. The average particle size of secondary agglomerated particles of the fine particles by electron microscopic observation of the cross section of the gap layer of the recording sheet was 60 n m. The Cobb water absorption of the obtained recording paper was 22 g / m ² .

[Coating Liquid-2] The following fine particle silica dispersion (3) 450 ml The following cationic polymer (2) (average molecular weight 10000) 2 g Ethanol 35 ml n-Propanol 10 ml Ethyl acetate 5 ml Polyvinyl alcohol (PVA203 manufactured by Kuraray Co., Ltd.) 0 1 g Polyvinyl alcohol (PVA235 manufactured by Kuraray Co., Ltd.) 15 g Boric acid 2.0 g Borax 1.0 g Fine particle silica dispersion (3): Nippon Aerosil Co., Ltd. A300 (vapor-phase method silica having an average primary particle diameter of 7 nm)
80 g of is added to 400 ml of pure water and dispersed by an emulsifying disperser, and then the total amount is made up to 450 ml with pure water.

[0133]

[Chemical 2]

Examples 11 and 12 The same procedure as in Example 10 was repeated except that the water absorbent paper support used in Example 10 was changed to one having a thickness and a Cobb water absorbency as shown in Table 6. Examples 11 and 12
Each of the recording sheets was prepared and evaluated in the same manner as in Example 1. The average particle size of secondary agglomerated particles of the fine particles by such a cross section electron microscopy of the porous layer of the recording paper created was both a 60 n m. The Cobb water absorption of each of the obtained recording papers is as shown in Table 7.

Comparative Example 8 A comparative example was carried out in the same manner as the recording paper of Example 10 except that the water absorbent paper support used in Example 10 was changed to one having a thickness and a Cobb water absorbency as shown in Table 6. 8 recording sheets were prepared and evaluated in the same manner as in Example 1. The average particle size of secondary agglomerated particles of the fine particles by electron microscopic observation of the cross section of the gap layer of the recording sheet was 60 n m. The Cobb water absorption of each of the obtained recording papers is as shown in Table 7.

Table 7 shows the evaluation results.

[0137]

[Table 6]

[0138]

[Table 7]

From the results shown in Table 7, Examples 10, 11, 12 were obtained.
The recording paper of the present invention has good ink absorbency, film strength and gloss, but the support has a Cobb water absorption of 10 to 50 g.
It can be seen that Examples 11 and 12 having a range of / m ² are particularly excellent.

[0140]

According to the constitution of the present invention, an ink jet recording paper having good ink absorbency and good film strength and gloss can be obtained.

Claims (3)

(57) [Claims] 1. A dry film thickness of 5 to 30 μm and an average particle size of 10 on a water-absorbent support having a thickness of 160 μm or more.
Silica fine particles synthesized by a gas phase method of 0 nm or less and
Containing fine hydrophilic binder, the hydrophilic of the fine particles
The weight ratio to the binder is 3 to 8, making it a hardener.
A Cobb obtained by using pure water containing a hardened ink absorbing layer having a void structure, a contact time of 10 seconds in the water absorption test method defined in JIS P8140, and containing 30% by weight of diethylene glycol. An ink jet recording paper having a water absorption of 20 to 60 g / m ² . 2. A water-absorbent support having a thickness of 160 μm or more.
In addition, the dry film thickness is 5 to 30 μm, and the average particle size is 10
Containing fine particles of 0 nm or less and a hydrophilic binder,
The weight ratio of the fine particles to the hydrophilic binder is
3-8, hardened with boric acid or its salt
Having an ink absorption layer having a void structure, JIS P81
In the water absorption test method specified in 40, contact time is 1
0 seconds and contains 30% by weight of diethylene glycol
Cobb water absorption determined using pure water is 20 to 60 g / m ^2.
An inkjet recording sheet characterized by being 3. Polyvinyl as the hydrophilic binder
An alcohol is included, The claim 1 or 2 characterized by the above-mentioned.
Ink jet recording paper according to.