JPH0755580B2 - Inkjet recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a recording medium for recording using ink, and particularly, the density of images and characters recorded on the medium is high, and the light fastness of the image is high. The present invention relates to an inkjet recording medium having excellent ozone resistance. Further, the recording medium of the present invention may be used as any recording medium that uses a liquid ink during recording. Examples of such a recording medium include a thermal transfer recording medium, an inkjet recording medium using a solid ink at room temperature for heating and melting a wax or a resin component to form fine droplets, and flight recording, an inkjet recording medium using an oil-soluble dye ink, An image receiving recording medium of a photosensitive pressure-sensitive donor sheet using microcapsules containing a photopolymerizable monomer, a colorless or colored dye and / or a pigment, and the like can be given.

(B) Prior Art Ink jet recording is a method of ejecting minute droplets of ink by various operating principles and adhering them to a recording medium such as paper to record images, characters, etc.
It has features of low noise, easy multi-coloring, great flexibility of recording patterns, and no need for development and fixing. It is rapidly used in various applications as a recording device for various figures including Kanji and color images. Is popular in Further, an image formed by a multicolor ink jet method can obtain prints comparable to multicolor printing by a plate making method or printing by a color photographic method, and in an application that requires a small number of copies. Since it is cheaper than photographic technology, it is being widely applied to the field of full-color image recording.

As a recording medium used in this ink jet recording system, efforts have been made in terms of equipment and ink composition so as to use high-quality paper or coated paper used for ordinary printing and writing. However, with the improvement of the performance of the inkjet recording apparatus and the expansion of its applications such as the speeding up of the apparatus, the high definition and the full color, the recording medium is required to have higher characteristics. That is, as the recording medium, the density of the ink dots is high, the color tone is bright and vivid, the ink does not flow out or bleed even when the ink dots overlap and the ink dots overlap, The lateral spread of is not unnecessarily large, and the periphery is smooth and does not blur. Further, it is required that the resistance of the dye when the recorded image is exposed to ultraviolet rays, oxygen in the air, or water is not lowered, and preferably enhanced.

Several proposals have been made in the past to solve these problems. For example, in JP-A-52-53012,
An ink jet recording paper is obtained by wetting a low-sized base paper with a coating material for surface treatment, and in JP-A-53-49113, a sheet containing urea-formalin resin powder is impregnated with a water-soluble polymer. Ink jet recording paper is disclosed. These general paper type inkjet recording papers absorb ink quickly, but have drawbacks in that the periphery of dots is easily blurred and the dot density is low.

Further, JP-A-55-5830 discloses an inkjet recording sheet having an ink-absorbent coating layer on the surface of a support,
Further, in JP-A-55-51583, an example in which amorphous silica powder is used as a pigment in the coating layer is disclosed, and in JP-A-55-11829, a coating paper using a two-layer structure having different ink absorption rates is used. Examples are disclosed, and further, JP-A-59-174381 and JP-A-60-44.
No. 389, No. 60-132785, No. 60-171143, etc. disclose an ink jet recording sheet provided with a transparent ink receiving layer. These coated type inkjet recording media are improved from the general paper type inkjet paper in terms of dot diameter, dot shape, print density and color tone reproducibility, but the inks applied to these recording media There are many water-based inks that use water-soluble dyes, and when the image formed on the recording medium is exposed to water, etc., the dyes will dissolve again and bleed out, significantly reducing the value of the recorded matter. In addition, there is a defect that the dye is remarkably deteriorated due to the high light transmittance and air permeability of the ink receiving layer.

Therefore, among these drawbacks, in order to improve the water resistance,
For example, JP-A-55-53591 shows an example of applying a water-soluble salt of a metal to the recording surface, and JP-A-56-84992 shows an example of a recording medium containing a polycationic polymer electrolyte on the surface. Further, JP-A-55-150396 discloses a method of applying a water-resistant material which forms a lake with a dye in the ink after ink jet recording, and JP-A-56-58869 discloses coating a water-soluble polymer. After ink jet recording on a recording sheet, a method of making the water-soluble polymer insoluble to make it water resistant is further described in JP-A-56-99693 and 59-96987. JP-A-59-96988 discloses a method of making a dye insoluble by using a salt of the above, and JP-A-59-96988 discloses a method of making a dye by using a water-soluble salt of a metal.

On the other hand, in order to improve the light fastness of a recorded image, for example, JP-A-54-68303, JP-A-54-85804, and JP-A-56-18151 disclose examples in which an ultraviolet absorber is added to an ink liquid. ing. However, these ultraviolet absorbers have a problem that the jetting stability of the ink is deteriorated and the solubility thereof is low, so that a large amount cannot be added and a small amount thereof is not effective. As another solution, it is possible to add a benzophenone-based or benzotriazole-based ultraviolet absorber to the ink jet recording sheet.
Proposed in 7-74193 and 57-87988,
These have problems that they have poor solubility in water and are difficult to use in large amounts, they are ineffective when used in small amounts, and when they are used by emulsification, they are affected by emulsifiers. As another solution, it has been proposed in JP-A-61-43563 and JP-A-61-47290 to incorporate a metal salt such as a weak acid salt of an alkali metal. There are problems such as a decrease in colorability, and a small amount has little effect.

(C) Problems to be Solved by the Invention As is apparent from the above-mentioned conventional techniques, in order to solve the problems of the recording medium in the inkjet recording system,
Various proposals have been made for individual problems, and accordingly, recorded images have been improved year by year in accordance with the proposals. However, regarding the recording medium, (1) the ink dot density is high.

(2) The image density is high.

(3) Image colorability is good.

(4) The ink dot shape is good.

(5) Good ink absorbency.

(6) The storability of recorded images is good.

(Refers to resistance to fading and discoloration of recorded images on recording media, especially ultraviolet rays, sun rays, oxygen and ozone in the air, NO
Oxidizing gases such as x and SOx, fading resistance due to water and solvents, etc.) (7) In the case of the coated type, the coating liquid should be particularly easy to apply. Easy handling of recording media products after coating and processing. (In particular, if a coating liquid containing silica is applied, the adhesiveness of the coating layer will be deteriorated unless the amount of binder used is increased, and conversely, if the amount used is increased, a desired recorded image may not be obtained.) However, even if it is possible to solve individual characteristics, it will adversely affect other characteristics or it will be out of balance, so good quality with good balance in inkjet recording, especially colorization. Was difficult to obtain.

Conventionally, in order to improve the storability, it has been attempted to improve the storability by adding an additive to silica as described above. However, there is a limit to the improvement in the additive system, and if it is added so as to prevent discoloration and fading, there are drawbacks such as a decrease in absorption and color properties.

An object of the present invention is to solve the above problems, and in particular, the storability of recorded images (light resistance, ozone resistance, which is a drawback of pigments mainly composed of synthetic amorphous silica used in the field concerned). Etc.), adhesiveness, especially coating layer water resistance,
To improve the adhesiveness is to solve the problem that the ink absorption speed becomes slow.

(D) Means for Solving Problems That is, the present invention uses a water-based ink containing at least one water-soluble dye selected from direct dyes, acid dyes, basic dyes, reactive dyes and food dyes. An inkjet recording medium for forming a recorded image has a molecular weight of 1
An inkjet recording medium comprising at least 10,000 to 500,000 polyacrylamide, synthetic amorphous silica, and polyvinyl alcohol.

More specifically, synthetic amorphous silica has a BET specific surface area of 180 m ²
/ g or more, the refractive index is 1.43 to 1.48, the volume average particle diameter of the secondary agglomerated particles is 1 to 40 μm is 95% or more of synthetic amorphous silica, and more preferably polyvinyl alcohol has a saponification degree.
It has a degree of polymerization of 87 mol% or more and a degree of polymerization of 300 to 2000, and most preferably polyacrylamide is cationic or nonionic.

Polyacrylamide has particularly preferably a molecular weight of 10,000 to 50.
If it is less than 10,000, the adhesion of silica will be poor and 50
If it is larger than 10,000, the absorbency will be poor.

Further, the ionic property of polyacrylamide is good even if it is anionic, but the light resistance and ozone resistance of the recorded image are good, but the cationic property or nonionic property is more preferred from the viewpoint of ink absorption speed and the like.

Cationic polyacrylamide can be obtained without saponification of polyacrylamide, and nonionicity can be obtained by saponification up to about 20%.

Further, polyvinyl alcohol preferably has a saponification degree,
It is a complete saponification type of 87 mol% or more, more preferably 98 mot% or more, and the degree of polymerization is preferably 300 to 2000. If the degree of saponification is less than 87 mol%, the absorbability of the aqueous ink is deteriorated and the degree of polymerization is When the ratio is less than 300, the adhesion of silica is poor, and the water resistance when a coating layer is provided is poor.

When the degree of polymerization is more than 2000, when a coating liquid with silica is prepared, the viscosity becomes too high to control the desired coating amount, or the absorbability deteriorates.

Further, the synthetic amorphous silica has a BET specific surface area of less than 180 m ² / g, poor absorption, silica having a refractive index of less than 1.43,
Not currently on the market. If possible, a lower refractive index is preferable.

Silica having a refractive index larger than 1.48 has poor chromaticity, particularly in color superposition.

When the volume-average particle diameter of the secondary agglomerated particles is large, the amount of silica is less than 0.1 μm, the viscosity of the coating liquid is increased and the adhesiveness is deteriorated. On the other hand, if there is a large amount of silica larger than 40 μm, the unevenness of the surface will be large and the absorbency will be uneven, such being undesirable. Generally, preferably, the volume average particle size is 1 μm.
m to 20 μm is commercially available, and most of the amorphous silica particles have a particle size distribution within the above range by classification.

For example, Table 1 shows typical examples of commercially available silica.

As the method for producing the recording medium of the present invention, when pulp fibers are disintegrated into slurry to be made into paper by a paper machine, a size press liquid containing polyacrylamide and / or polyvinyl alcohol is immersed in a size press device provided on the way or A method of coating, and further applying a coating solution containing synthetic amorphous silica, further containing at least polyacrylamide, ponyvinyl alcohol and synthetic amorphous silica in the coating solution, and applying this coating solution to a roll coater or reverse. A method of forming an ink-receiving layer by coating and drying using a normal coating device such as a roll coater, an air knife coater, a blade coater, or a spray coater, or an ink including an ink-absorbing pigment and an adhesive provided on a support. There is a method of applying dissolved polyacrylamide on the receiving layer. In this case, commonly used fillers, pigments, adhesives and other additives can be used in combination.

Examples of fillers and pigments that can be used in the present invention include light calcium carbonate, heavy calcium carbonate, kaolin, talc,
Calcium sulfate, barium sulfate, titanium oxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, synthetic amorphous silica, aluminum hydroxide, alumina, lithopone, etc. White inorganic pigments and organic pigments such as styrene plastic pigments, acrylic plastic pigments, microcapsules, and urea resin pigments.

Examples of the adhesive used in the present invention include oxidized starch, etherified starch, cellulose derivatives such as carboxymethyl cellulose, hydroxyethyl cellulose, casein, gelatin, soybean protein, silanol-modified polyvinyl alcohol, maleic anhydride resin, and the like. Conjugated diene copolymer latex such as styrene-butadiene copolymer and methyl methacrylate-butadiene copolymer, acrylic polymer latex such as polymer or copolymer of acrylic acid ester and methacrylic acid ester, ethylene vinyl acetate copolymer Such as vinyl-based polymer latexes such as polymers, or functional group-modified polymer latexes with functional group-containing monomers such as carboxyl groups of these various polymers, thermosetting synthetic resin systems such as melamine resins, urea resins, etc. Water-based adhesive and polymethylmeth Acrylate, polyurethane resin, unsaturated polyester resin, vinyl chloride - vinyl acetate copolymer, polyvinyl butyral, synthetic resin-based adhesive such as alkyd resins, used alone or in combination. These polyacrylamide, polyvinyl alcohol, and the above adhesive are used in an amount of 2 to 100 parts by weight, preferably 5 to 30 parts by weight, based on 100 parts of the pigment, as long as the amount is sufficient for binding the pigment. The ratio is not particularly limited. However, it is not preferable to use 100 parts by weight or more of the adhesive because the film formation of the adhesive reduces the void structure or makes the void extremely small.
It is preferable to use the same amount even when the above adhesive is not used with only polyacrylamide and polyvinyl alcohol.

In the present invention, a cationic resin may be used in combination.
As the cationic resin to be used in combination, any of conventionally known monomers, oligomers or polymers that disintegrate to exhibit cationicity when dissolved in water can be used, but preferably has a tertiary and / or quaternary ammonium group. , For example, the compound of the following general formula (I) or the following general formula (II)
A compound having a monomer represented by (IV) as a constituent unit.

In the formula, R ₁ , R ₂ and R ₃ are hydrogen or an alkyl group, and m is 1 to
7, n represents 2 to 20, and Y represents an acid group.

R ₁ and R _{2 in} formulas (II) to (IV) are —CH ₃ , —CH ₂ —CH ₃ , and —C.
H ₂ CH ₂ OH and Y represent an acid group.

The compound represented by the general formula (I) is, for example, Nalpol
Examples include 607 (manufactured by Narco Chemical Co., Ltd.) and Polyfix 601 (manufactured by Showa High Polymer Co., Ltd.).

The compounds represented by the general formulas (II) to (IV) are polydiallylamine derivatives, which are obtained by cyclopolymerization of diallylamine compounds.
(Manufactured by Nitto Boseki Co., Ltd.) and Nefofix RPD (manufactured by Nichika Kagaku Co.).

Other additives include pigment dispersants, thickeners, fluidity improvers, defoamers, foam suppressors, release agents, foaming agents, penetrants, colored dyes, colored pigments, optical brighteners, and ultraviolet absorbers. Agents, antioxidants, preservatives, anti-bacterial agents, water-proofing agents and the like can also be appropriately added.

As the support, a sheet material such as paper or a thermoplastic resin film is used. In the case of paper, a paper without sizing agent or appropriately sized is not particularly limited, but preferably has a Steckigt sizing degree of 0.
Paper for about 40 seconds may or may not contain a filler.

The moderately sized paper used in the present invention is moderately sized with a neutral sizing agent and has a cold water extraction pH of 5.
Paper in the range of 2 to 10.5 with or without fillers. Further, so-called acid paper using a conventionally known rosin sizing agent may be used.

Examples of neutral sizing agents include higher organic ketene dimers (alkyl ketene dimers), cellulose-reactive sizing agents such as substituted cyclic dicarboxylic acid anhydrides, epoxidized higher fatty acid amides, cationized styrene-maleic anhydride copolymers. , Cationic self-fixing sizing agents such as cationized petroleum resins, and styrene-acrylic acid copolymers, styrene-maleic acid copolymers, α-olefin-maleic anhydride copolymers, petroleum resins, equal size press equipment, kate roll coaters, etc. It refers to a so-called externally added sizing agent or the like that exhibits sizing property by adhering to the paper surface with, but in the present invention, preferably one selected from alkyl ketene dimer or substituted cyclic dicarboxylic acid anhydride, particularly preferably Is an alkyl ketene dimer sizing agent. A support having a Steckigt size degree of 0 to 4 seconds can be produced by using one or a combination of these sizing agents. In particular, even if the Steckigt sizing degree is greater than 40 seconds, the effect on the effect of the present invention is small, so any sizing degree may be used, but excessively increasing the sizing degree does not make any sense. Oxidized starch that is usually used during production,
There is no problem in applying polyvinyl alcohol or the like with a size device.

When a filler is used, it is usually used in neutral papermaking systems such as talc, clay, heavy calcium carbonate, light calcium carbonate, calcined kaolin, aluminum oxide, aluminum hydroxide, titanium oxide, aluminum silicate, synthetic amorphous. Quality silica, urea-formalin resin and the like can be internally added. In the present invention, alkaline fillers such as heavy calcium carbonate, light calcium carbonate and aluminum hydroxide are preferably used.

In the case of a thermoplastic film, polyester, polystyrene, polyvinyl chloride, polymethylmethacrylate,
A transparent film of cellulose acetate, polyethylene, polycarbonate or the like, or a white opaque film filled with a white pigment or finely foamed is used. As the white pigment to be filled, for example, titanium oxide, calcium sulfate,
Many things such as calcium carbonate, silica, clay, talc, zinc oxide are used.

Further, so-called laminated paper or the like in which these resin films are attached to the surface of paper or processed with a molten resin can be used. An undercoat layer or corona discharge machining may be applied to improve the adhesion between the resin surface and the ink receiving layer.

The sheet just coated on the support can be used as a recording sheet according to the present invention as it is, but it is also possible to give the surface smoothness through a roll nip under heating and / or pressure with, for example, a super calender or a gloss calender. It is possible.

In this case, excessive processing by super calendering may reduce ink absorbability due to voids between the particles formed with a great deal of effort, and thus the degree of processing may be limited. The aqueous ink referred to in the present invention is a recording liquid composed of the following colorant, liquid medium, and other additives.

The colorant is a water-soluble dye such as a direct dye, an acid dye, a basic dye, a reactive dye or a food dye.

For example, as a direct dye, CIDirect Black 2,4,9,11,14,17,19,22,27,32,36,38,41,48,49,51,56,6
2,71,74,75,77,78,80,105,106,107,108,112,113,117,13
2,146,154,194 CIDirect Yellow 1,2,4,8,11,12,24,26,27,28,33,34,39,41,42,44,48,50,
51,58,72,85,86,87,88,98,100,110 CIDirect Orange 6,8,10,26,29,39,41,49,51,102 CIDirect Red 1,2,4,8,9,11,13, 17,20,23,24,28,31,33,37,39,44,46,4
7,48,51,59,62,63,73,75,77,80,81,83,84,85,90,94,99,
101,108,110,145,189,197,220,224,225,226,227,230 CIDirect Violet 1,7,9,12,35,48,51,90,94 CIDirect Blue 1,2,6,8,15,22,25,34,69,70,71,72,75,76, 78,80,81,82,
83,86,90,98,106,108,110,120,123,158,163,165,192,19
3,194,195,196,199,200,201,202,203,207,218,236,237,
239,246,258 CIDirect Green 1,6,8,28,33,37,63,64 CIDirect Brown 1A, 2,6,25,27,44,58,95,100,101,106,112,173,194,195,
209,210,211 CIAcid Black 1,2,7,16,17,24,26,28,31,41,48,52,58,60,63,94,107,1
09,112,118,119,121,122,131,155,156 CIAcid Yellow 1,3,4,7,11,12,13,14,17,18,19,23,25,29,34,36,38,40,
41,42,44,49,53,55,59,61,71,72,76,78,99,111,114,11
6,122,135,161,172 CIAcid Orange 7,8,10,33,56,64 CIAcid Red 1,4,6,8,13,14,15,18,19,21,26,27,30,32,34,35,37, 40,
42,51,52,54,57,80,82,83,85,87,88,89,92,94,97,106,1
08,110,115,119,129,131,133,134,135,154,155,172,17
6,180,184,186,187,249,254,256,317,318 CIAcid Violet 7,11,15,34,35,41,43,49,75 CIAcid Blue 1,7,9,22,23,25,27,29,40,41,43,45,49,51, 53,55,56,5
9,62,78,80,81,83,90,92,93,102,104,111,113,117,120,
124,126,145,167,171,175,183,229,234,236 CIAcid Green 3,12,19,27,41,9,16,20,25 CIAcid Brown 4,14 As a basic dye, CIBasic Black 2,8 CIBasic Yellow 1,2,11,12,14,21, 32,36 CIBasic Orange 2,15,21,22 CIBasic Red 1,2,9,12,13,37 CIBasic Violet 1,3,7,10,14 CIBasic Blue 1,3,5,7,9,24, 25,26,28,29 CIBasic Green 1,4 CIBasic Brown 1,12 As a reactive dye, CIReactive Black 1,3,5,6,8,12,14 CIReactive Yellow 1,2,3,13,14, 15,17 CIReactive Orange 2,5,7,16,20,24 CIReactive Red 6,7,11,12,15,17,21,23,24,35,36,42,63,66 CIReactive Violet 2,4 , 5,8,9 CIReactive Blue 2,5,7,12,13,14,15,17,18,19,20,21,25,27,28,37,38,4
0,41, CIReactive Green 5,7 CIReactive Brown 1,7,16 Furthermore, as a food dye, CIFood Black 2 CIFood Yellow 3,4,5 CIFood Red 2,3,7,9,14,52,87,92 , 94,102,104,105,106 CIFood Violet 2 CIFood Blue 1,2 CIFood Green 2,3.

The liquid medium of the water-based ink includes water and various water-soluble organic solvents such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, and t-butyl alcohol.
ert-butyl alcohol, isobutyl alcohol and other C1-4 alkyl alcohols; dimethylformamide, dimethylacetamide and other amides; acetone,
Ketones or ketone alcohols such as diacetoalcohol; ethers such as tetrahydrofuran and dioxane;
Polyalkylene glycols such as polyethylene glycol and polypropylene glycol; ethylene glycol,
Alkylene glycols having 2 to 6 alkylene groups such as propylene glycol, butylene glycol, triethylene glycol, 1,2,6-hexanetriol, thiodiglycol, hexylene glycol, diethylene glycol; glycerin, ethylene glycol methyl ether, diethylene glycol Examples thereof include lower alkyl ethers of polyhydric alcohols such as methyl (or ethyl) ether and triethylene glycol monomethyl ether.

Among these many water-soluble organic solvents, polyhydric alcohols such as diethylene glycol and lower alkyl ethers of polyhydric alcohols such as triethylene glycol monomethyl ether and triethylene glycol monoethyl ether are preferable.

Other additives include, for example, pH adjusters, sequestering agents,
Examples thereof include antifungal agents, viscosity modifiers, surface tension modifiers, wetting agents, surfactants, and rust preventives.

The recording medium in the present invention is not limited to use as an inkjet recording medium, and may be used as any recording medium that uses a liquid ink during recording. As such a recording medium, for example, a heat-meltable room temperature solid ink mainly composed of waxes and resin components and dyes and pigments is heat-melted on a thin support such as a resin film, high density paper or synthetic paper. Using the applied ink sheet as a donor sheet, heating from the ink back surface of the donor sheet, a heat-melting type transfer recording medium that melts and transfers the ink, heat-melting the heat-melting normal temperature solid ink as described above,
Inkjet recording medium for forming fine droplets, flight recording, inkjet recording medium using ink in which oil-soluble dye is dissolved in solvent, photopolymerizable monomer, microcapsule containing colorless or colored dye and / or pigment An image receiving recording medium such as a light and pressure sensitive donor sheet can be used.

What is common to these recording media is that the ink is in a liquid state during recording. The liquid ink permeates or spreads in the depth direction or surface direction of the ink receiving layer of the recording medium before being cured, solidified, or fixed. Therefore, the recording medium also needs to have absorptivity according to each method. Therefore, the recording medium according to the present invention may be used as the various recording mediums described above.

Further, in particular, the dye-based ink is weak in light resistance, ozone resistance, gas resistance, etc. and easily discolors, but on the recording medium of the present invention, it has a favorable effect on discoloration of recorded images. Is believed to give.

The inkjet suitability was measured by the following method.

Light resistance is based on Canon inkjet printer (A-12
The image part obtained by solid printing with black (hereinafter abbreviated as BK) ink using 10) was measured with a quinocene fade meter (FAL-25X-HCL type manufactured by Suga Test Instruments Co., Ltd.).
The sensory chromaticity (L ^* , a ^* , b ^* ) before and after exposure to xenon light or sunlight for 24 hours under irradiation at 40 ° C, illuminance 41W / m ² for 40 hours or exposure to direct sunlight is the color difference. Total (CR-
100, manufactured by Minolta Camera) and the color difference ΔE was obtained from the sensory color difference (ΔL ^* , Δa ^* , Δb ^* ) before and after irradiation. This value was shown as the amount of discoloration.

Ozone resistance is based on Canon inkjet printer (A
-1210), the image part obtained by solid printing with BK ink was exposed to an ozone generator (OS-1, Mitsubishi Electric Corporation) for 5 minutes in an air flow with an ozone concentration of 3 g / m ² The color difference ΔE before and after exposure was determined in the same manner as the light resistance, and this value was shown as the amount of discoloration. As for the amount of discoloration and fading, the smaller the numerical value is, the less the discoloration and fading is.

The water resistance of the coating layer is 30 ° C. for the image area obtained by solid printing with cyan (C), magenta (M), yellow (Y), and black (BK) inks using the same Canon inkjet printer. It was dipped in the ink for 3 minutes, and rubbed with a finger on the printed portion while it was wet, and the extent to which the ink became dirty and moved to a portion other than the printed portion was visually determined. Water resistance is better when it is not dirty.

The ink absorption speed is determined by using a Sharp or Canon inkjet printer to feed the paper immediately after solid printing of red printing (magenta + yellow) (after about 1 second), and then contacting it with a paper press roll or finger, etc. It was judged by whether or not it appeared. The ink that does not stain is good because the ink absorption speed is high.

(E) Action In the present invention, in the case where the ink receiving layer containing at least the specific polymerized amorphous silica and the specific polyvinyl alcohol is constituted, it is in the base paper layer and / or on the base paper layer and / or in the ink receiving layer and / or the ink. It has been found that the light resistance and ozone resistance of a recorded image with a water-soluble dye can be improved by providing a layer containing a specific polyacrylamide on the receiving layer.

The surface of the synthetic amorphous silica is generally strong in anion property and large in specific surface area although weak, so that it is active and well absorbs the dye ink and adsorbs the dye. Therefore, light or ozone exerts a catalytic action on the dye, and promotes discoloration and fading of the dye. However, due to its large specific surface area and low refractive index, it has the best chromaticity among various pigments.

Due to this large specific surface area, adhesion of silica is inevitably low and adhesiveness deteriorates with the usual amount of binder used, and therefore the adhesion must be increased. The polyvinyl alcohol in the present invention having a low degree of ketonization is not preferable because the absorbability of the water-based ink is deteriorated, and when it is used as a recording medium, the polyvinyl alcohol becomes tacky and causes blocking. Further, the degree of polymerization also needs to be in an appropriate range.

An object of the present invention is to obtain an inkjet recording medium which has good adhesiveness and absorbability of a coating layer and has little discoloration and fading of a recorded image. Therefore, polyacrylamide, particularly preferably cationic or nonionic polyacrylamide is used. It was found that by using acrylamide, it is possible to strongly adsorb on the surface of silica, which is anionic, and to significantly reduce discoloration and fading.

The reason is considered that the amidinium ion of the cationic or nonionic polyacrylamide is strongly adsorbed to the active groups on the surface of the anionic silica, and the silica is appropriately aggregated to weaken the surface activity, or the reducing property of the amide itself is considered to be the cause. To be
Further, although the polyacrylamide itself has a low refractive index and may not deteriorate the chromaticity, when used alone, the water resistance of the coating layer may deteriorate. Therefore, a combination of at least three is necessary, which cannot be achieved by normal use.
It was possible to find a completely new effect.

(F) Examples Examples of the present invention will be described below, but the invention is not limited to these examples. In the examples, parts and% mean parts by weight and% by weight.

Example 1 A pulp slurry comprising 80 parts of LBKP having a freeness of 370 ml CSF and 20 parts of NBKP having a freeness of 400 ml, 20 parts of talc and cationic starch (CA
TOF, manufactured by Oji National Co., Ltd.) 0.5 parts by weight, basis weight 65 g / m ²
Paper is made with a Fourdrinier paper machine and 2% of polyvinyl alcohol (PVA117, made by Kuraray Co., Ltd.) with a size press machine at the time of paper making,
Synthetic amorphous silica (Mizukasil P78A, manufactured by Mizusawa Chemical Co., Ltd.),
A size press liquid consisting of 1% of cationic polyacrylamide (polymerization degree: 100,000) was applied at 60 g / m ² , dried and finished through a machine calendar to obtain a recording paper of Example 1.

Examples 2-6 and Comparative Examples 1-2 Stockigt sizing degree of 0 sec fine paper having a basis weight 60 g / m ² as a base paper, polyvinyl alcohol (PVA117) 50 parts of synthetic amorphous silica (Fine Seal X-37B, Tokuyama Soda) 100
Parts, and 20 parts cationic polyacrylamide with a molecular weight of 80
00 (Comparative Example 1), 15000 (Example 2), 50,000 (Example 3) 100,000 (Example 4), 200,000 (Example 5), 500,000 (Example 6), 600,000 (Comparative Example) The coating liquid changed to 2) was coated with an air knife coater so that the solid content was 10 g / m ^2, and was supercalendered, and Examples 2 to 6 and Comparative Examples 1 to 1 were used.
The recording paper of No. 2 was used.

Example 7 and Comparative Example 3 50 parts of polyvinyl alcohol (PVA117) and 100 parts of synthetic amorphous silica (Fineseal X-37B,) were used as a base paper with a fine paper basis weight of 60 g / m ² of Steckigt sizing degree of 5 seconds. The coating liquid in which 20 parts of nonionic polyacrylamide (molecular weight 200,000) (Example 7) or 20 parts of anionic polyacrylamide (molecular weight 600,000) (Comparative Example 3) was used was changed to Examples 2 to 6 using an air knife coater. Similarly, coating was performed so that the solid content was 10 g / m ^2, and super calendering was performed to obtain recording papers of Example 7 and Comparative Example 3.

Examples 8 to 11 and Comparative Examples 4 to 5 Sekicht sizing degree of 10 seconds was used as a base paper of 60 g / m ² of fine paper, and the polymerization degree of polyvinyl alcohol 50 parts with a saponification degree of 98% was changed to 200 (comparison). Example 4), 300 (Example 8), 500
(Example 9) 1100 (Example 10), 2000 (Example 11), 24
As 00 (Comparative Example 5), 100 parts of synthetic amorphous silica (Mizukasil P78A) and a cationic polyacrylamide (polymerization degree of 100,000) were applied to each of them as a coating solution in the same manner as in Example 2. Then, it was processed and supercalendered to obtain recording papers of Examples 8 to 11 and Comparative Examples 4 to 5.

Example 12, Comparative Example 6 In Example 9, polyvinyl alcohol (polymerization degree: 500)
Example 12 and Comparative Example 6 were carried out in the same manner as in Example 9 except that the saponification degree was changed to 70% (Example 6) and 88% (Example 12).
I got the recording paper.

Example 13 and Comparative Example 7 100 parts of synthetic amorphous silica with a specific surface area of 260 m ² / g and a refractive index as a base paper with a fine paper basis weight of 60 g / m ² of Steckigt sizing degree of 20 seconds
1.436 Volume average particle size of secondary agglomerated particles is 0.1μm-40μ
Silica with m of 99% or more (Example 13), specific surface area of 150 m
² / g, refractive index 1.497, volume average particle size 0.1μm ~ 40μm 8
Example 4 except that it was changed to 5% silica (Comparative Example 7).
Recording sheets of Example 13 and Comparative Example 7 were obtained in the same manner as in.

Comparative Example 8 50 parts of polyvinyl alcohol having a saponification degree of 98% (polymerization degree of 10%) using a high quality paper basis weight of 60 g / m ² of Steckigt sizing degree of 10 seconds as a base paper.
1700) and 100 parts of synthetic amorphous silica (Mizukasil P78A) were applied in the same manner as in Example 2 and supercalendered to give a recording paper of Comparative Example 8.

Table 2 shows the results of measuring the inkjet suitability of the above recording papers.

As is clear from the above Examples and Comparative Examples, the present invention improves the storage stability (light resistance, ozone resistance) of recorded images when synthetic silica is used, and provides good coating layer water resistance and ink absorption speed. A recording medium having a good balance of quality was obtained.

(G) Effect of the Invention In the present invention, an inkjet recording medium is provided.
When synthetic amorphous silica having excellent color properties is used as a pigment, deterioration of storage stability of recorded images, poor coating layer water resistance, ink absorption speed, etc. are improved, and storage stability, coating layer water resistance, Inkjet recording such as ink absorption speed and color
In particular, it was possible to obtain a recording medium of good balance with few defects in terms of color recording.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location D21H 19/60 7199-3B D21H 1/32

Claims (4)

[Claims] 1. An inkjet recording medium for forming a recorded image using an aqueous ink containing at least one water-soluble dye selected from a direct dye, an acid dye, a basic dye, a reactive dye and a food dye. An ink jet recording medium, wherein the recording medium contains at least polyacrylamide having a molecular weight of 10,000 to 500,000, synthetic amorphous silica, and polyvinyl alcohol. 2. The synthetic amorphous silica has a BET specific surface area of 180 m ² / g.
The inkjet recording medium according to claim 1, wherein the synthetic amorphous silica has a refractive index of 1.43 to 1.48 and a volume average particle diameter of secondary aggregated particles of 1 to 40 µm of 95% or more. 3. Polyvinyl alcohol having a saponification degree of 87 mol%
The inkjet recording medium according to claim 1 or 2, wherein the degree of polymerization is 300 to 2000. 4. The inkjet recording medium according to claim 1, wherein the polyacrylamide is cationic or nonionic.