JPH01108083A - Recording material and recording method using the same - Google Patents

Abstract

PURPOSE:To obtain a recording material excellent which gives a recorded image with excellent preservability, particularly a reorded image hardly deteriorated due to discoloration in room, by causing an ink receiving layer to comprise an upper layer comprising a silicon-containing pigment having a low specific surface area and a lower layer comprising a pigment greater in average particle diameter than the pigment in the upper layer. CONSTITUTION:An upper layer of a recording material comprises as a main constituent an aqueous binder and a silicon-containing pigment having a BET specific surface area of 10-200m<2>/g, the pigment being particularly preferably a silica pigment from the viewpoint of a dye color developing property. The pigment preferably has an oil absorption according to, for example, JIS-K-5101 of at least 1.5ml/g. The average secondary particle diameter of the pigment in the upper layer is preferably not more than 15mum, whereas that of a pigment used as a main constituent of a lower layer is preferably about 2-30mum. The specific surface area of the pigment in the lower layer is preferably not less than that of the pigment in tie upper layer, more preferably, at least 200m<2>/g. The ink receiving layer is provided on a base by use of the pigments and a binder. A preferable weight ratio of the pigment to the binder used is 1/40-20/1.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a recording material suitably used in an inkjet recording method, and in particular has excellent absorbency and coloring properties for water-based inks, and improves the clarity of recorded images obtained. Regarding excellent recording materials.

Furthermore, the present invention relates to a recording material that provides recorded images with little indoor discoloration and excellent storage stability, and a recording method that provides the above-mentioned recorded images.

[Conventional technology]

Conventional recording materials for inkjet use include: (1) paper made from regular pulp-based paper to a low size, such as filter paper or blotting paper; (2) JP-A-Sho. As disclosed in Japanese Patent No. 56-148585, a coating layer is provided on a base material using a porous pigment such as silica or zeolite that has a large oil absorption capacity and adsorbs the coloring components in the ink. There is.

Recording material (1) can be made at low cost, but although it has excellent ink absorption, the ink penetrates deeply into the fiber layer of the paper, resulting in poor color development of the colorant in the ink. Since it is absorbed along the fibers on the surface, a phenomenon called feathering occurs, which causes the dots to become jagged instead of circular, and the resolution to deteriorate, making it impossible to obtain high-quality images.

For this reason, such uncoated paper has been used for applications that do not necessarily require relatively low-resolution (high-density images), such as monochrome recording and personal computer terminals.

Since the ink absorbing layer of the recording material (2) is porous and uniform, it is possible to obtain an appropriate ink absorbency and excellent dot shape and resolution.

However, in recording methods that require higher quality and higher resolution color images, on the recording material side, (1) multicolored ink droplets adhere to the same spot in layers. It also has an ink absorption capacity that prevents dots from flowing out and from spreading more than necessary.

(2) The ink absorption speed and ink fixing properties should be such that the attached ink droplets will not smear even if they are rubbed immediately afterwards.

(3) The recording agent in the ink received by the ink absorbing layer has excellent coloring properties.

(4) The periphery of the attached ink dot is smooth,
The shape should be close to a perfect circle.

In addition to the above requirements, the obtained recorded images must also have good storage properties such as water resistance and light resistance.

JP-A-59-185690 and JP-A-59-230
Publication No. 787 focuses on the physical properties of pigments in the ink absorption layer in order to obtain better coloring properties of dyes, and uses silica having a specific surface area of 200 m2/g or more and silica with a specific surface area of 240 mg-m0I/kg.
A recording material using silica having an acid value above has been introduced.

Furthermore, Japanese Patent Application Laid-Open No. 56-84992 discloses a method of enhancing the water resistance of inkjet recorded images by recording with an acidic/direct dye on a recording medium containing a polycationic polymer electrolyte in the ink absorbing layer. A method is described for preventing these dyes attached to the ink absorbing layer from flowing out even when the ink absorbing layer is immersed in water.

The light fastness of images is a problem of discoloration and discoloration of recorded images due to photodecomposition of dyes, and until now it was thought that the problem was a problem of the dye itself, which is a recording agent, but water fastening agents such as the above, especially polycationic substances It has come to be known that polycations promote the photodecomposition of dyes. The recording material to be
No. 0-72785 introduces a recording material containing polythione, an ultraviolet absorber, and an antioxidant.

[Problem that the invention seeks to solve]

However, recently, in addition to such water resistance and light resistance, a new problem regarding image storage stability, such as indoor discoloration of recorded images, has been brought into focus. The problem of indoor discoloration is also considered to be a problem caused by the decomposition of dyes, but this problem cannot be solved with conventionally known recording materials.

Visible light causes image fading, which has traditionally been a problem.

This phenomenon occurs when the dye in the recorded image is decomposed by ultraviolet light, and does not occur in areas that are not exposed to direct sunlight. In addition, when exposed to sunlight, do not use so-called general ppC paper or the above (
It is known that discoloration occurs in images recorded on any type of recording material (1) and (2), and is accelerated when the recording material contains a polycationic substance.

On the other hand, the indoor discoloration referred to in the present invention progresses even in the absence of direct sunlight, and does not occur in images recorded on general paper or non-coated paper. Furthermore, even if a polycation, which has little effect on light resistance as described above, is used or an ultraviolet absorber is contained, there is no significant effect, and discoloration of the image occurs.

Note that fading here refers to a phenomenon in which the saturation of a printed matter decreases, and discoloration refers to a phenomenon in which the saturation does not decrease, but rather changes in hue.

As described above, the problem of indoor discoloration referred to in the present invention is a phenomenon unique to coated paper having an ink absorbing layer, but its clear cause and countermeasure are still unknown.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a recording material that has excellent ink absorption properties and dye coloring properties, and is capable of producing high-quality, high-resolution images.

Another object of the present invention is to provide a recording material that provides a long shelf life of recorded images, particularly a recorded image that is less likely to deteriorate due to indoor discoloration, and a recording method for forming such an image.

The above and other objects of the present invention are achieved by the present invention as follows.

[Means and effects for solving the problem] That is, the present invention provides a recording material having a base material and an ink-receiving layer provided on the base material, in which the ink-receiving layer has a specific surface area determined by the BET method. A recording material comprising an upper layer containing a silicon-containing pigment whose average particle diameter is in the range of 10 to 200 IT1''/g and a lower layer containing a pigment having an average particle diameter larger than that of the pigment, and using the recording material. This is a recording method in which recording is performed using ink containing a water-soluble dye.

The present inventors have discovered that indoor discoloration does not occur on uncoated paper;
As this phenomenon only occurs on coated paper, we investigated the relationship between the pigments that form the coat layer and indoor discoloration, and found that it was previously considered unsuitable for inkjet applications.
The present invention was based on the discovery that when a pigment with a low specific surface area is used, the problem of indoor discoloration occurs.

Preferred embodiments of the recording material of the present invention will be described below, and the present invention will be explained in more detail accordingly.

A preferred embodiment of the recording material of the present invention has an ink-receiving layer formed by sequentially laminating a lower layer that absorbs ink and an upper layer that captures dye on the lower layer on a base paper as a substrate.

Conventionally, for example, in Japanese Patent Application Laid-Open No. 60-260376,
A recording material having two or more ink-receiving layers on a base material has been introduced, but as stated in Japanese Patent Application Laid-open No. 185690/1983, the pigment forming the outermost layer is based on the coloring property of the dye. Thyroid (manufactured by Fuji Davison) is used to improve
Silica with a high specific surface area, such as exemplified by silica, is used. As described above, such recording materials have the problem of indoor discoloration of images.

In the present invention, the dye-trapping upper layer means that when ink droplets attached to the surface are absorbed into the ink-receiving lower layer,
This layer traps the dye, and most of the ink solvent passes through this layer and is absorbed by the underlying layer or substrate.

The higher the proportion of dye that is not captured in this layer and reaches the lower layer together with the solvent, the lower the image density becomes.

The upper layer of the recording material of the present invention includes an aqueous binder and a silicon-containing pigment having a BET specific surface area of 10 to 200 m2/g, particularly preferably silica, a synthetic silicate, or a silicate from the viewpoint of dye color development. It is formed mainly from silica pigments such as minerals. When the specific surface area is less than 1 on-r/g, there is a significant decrease in ink absorbency as well as image density, and when it is more than 200 m2/g, indoor discoloration becomes noticeable.

According to the findings of the present inventor, indoor discoloration is due to oxidative decomposition of the dye, and when the dye is captured on the surface of the recording material, it comes into contact with the air and is more likely to be oxidized (particularly for pigments with a large specific surface area). When trapped, the area of contact with the air is maximized, causing indoor discoloration.

Therefore, in the present invention, it is essential to use a pigment with a specific surface area of 200rd/g or less.

Although such silica pigments have not been used for inkjet coated paper, various grades of silica pigments have been reprinted for use in paints, agricultural chemicals, and the like.

Furthermore, in the present invention, the silicon-containing pigment has an oil absorption amount of 1.0 according to JIS-5101. It is preferable that it is 5ml/g or more. That is, if it is less than 1.5 mA/g, the ink absorbency is insufficient.

In general, the specific surface area is measured as the amount of N2 molecules adsorbed, and the oil absorption amount is measured as the amount of linseed oil absorbed, and both are only indicators for understanding the pore structure of pigments, but based on the findings of the present inventor. For example, the specific surface area has a larger contribution to the color development and indoor discoloration of the dye, and the oil absorption has a larger contribution to the ink absorption.

Generally, there is a positive correlation between specific surface area and oil absorption, but depending on the manufacturing conditions, products with low specific surface area and high oil absorption can also be obtained.

Like the upper layer, the lower layer is formed using a water-based binder and a pigment, more preferably a silica-based pigment.

It is preferable to use a pigment that mainly forms the lower layer and has a larger average secondary particle diameter than the pigment that forms the upper layer. If the pigment forming the upper layer is larger than the pigment in the lower layer, the particle shape of the pigment will appear prominently on the surface, and due to the unevenness, the attached ink droplets will smear in a star shape, resulting in poor star shape. The resulting image appears grainy.

The average secondary particle diameter of the pigment that mainly forms the upper layer is 15μ
Further, the average secondary particle diameter of the pigment that mainly forms the lower layer is preferably in the range of about 2 to 30 μm. Generally 2
It goes without saying that the use of a pigment with a larger particle diameter is better in terms of image density and ink absorption.

In the present invention, by using a pigment with a large particle size in the lower layer and filling the fine irregularities on the surface with a pigment with a small particle size in the upper layer, we take advantage of the advantages of using a large pigment,
Furthermore, images with good dot shapes and no roughness can be obtained. This is an effect of the ink receiving layer having a two-layer structure.

It goes without saying that the average secondary particle size of the pigments forming each layer can be compared by observing the cross section of the recording material using an SEM or the like.

The specific surface area of the pigment forming the lower layer is preferably at least 200 rd/g, more preferably at least 200 rd/g, from the viewpoint of ink absorption. According to the findings of the present inventors, as long as the dye in the attached ink droplets is captured in the upper layer, the specific surface area of the pigment forming the ink absorption layer does not contribute much to indoor discoloration.

However, although the problem of indoor discoloration can be completely solved even with such a recording material having a specific pigment and a specific layer structure, it cannot be used for applications that require higher density images. I can't say it's enough.

A second feature of the present invention is that the ink-receiving layer contains aluminum oxide particles having a smaller average particle size than the silicon-containing pigment described above, and preferably contains aluminum oxide particles in the upper layer. It is. That is, it is possible to provide a recording material that has an excellent indoor discoloration suppressing effect and further excellent dye coloring properties by having the ink-receiving layer, especially the upper layer, both contain the above-mentioned pigment and aluminum oxide particles. can.

As described above, the mechanism by which aluminum oxide particles do not promote indoor discoloration and have the effect of improving dye color development is unknown, but according to the findings of the present inventors, aluminum oxide particles Compared to pigments, it has stronger dye adsorption properties, and by containing aluminum oxide, the dye capture property of the ink receiving layer is improved. it is conceivable that.

Furthermore, when the particle size of the aluminum oxide particles is larger than that of the silicon-containing pigment described above, which suppresses indoor discoloration,
It is preferable that the aluminum oxide particles have a smaller particle size than the silicon-containing pigment, since the effect on improving dye color development is small.

From the above, according to the inventor's imagination, even if the silicon-containing pigment and aluminum oxide particles are present separately in the ink-receiving layer, there is no significant effect; Since pigments have a negative surface potential and aluminum oxides have a positive surface potential, if the aluminum oxide particles have a smaller particle size than the pigment and are adsorbed on the surface of the pigment, the potential of the aluminum oxide particles is particularly high. It is believed that the dye adsorption properties of the silicon pigment are enhanced and that it is possible to provide excellent image density as a recording material.

In addition, the aluminum oxide mentioned here is industrially aluminum hydroxide obtained by treating bauxite, a natural mineral, with hot caustic soda, or water obtained by spark discharge of metal aluminum pellets in pure water. It is obtained by burning aluminum oxide, etc., and the manufacturing method itself is well known, and it comes in various crystal forms (α form, γ form, σ form, η form).

It includes all commercially available aluminas, including those with a θ-shape, ), and those with various particle sizes, bulk depths, and specific surface areas.

For example, in addition to general alumina powder, fused alumina, spherical alumina particles, α-alumina, and γ-alumina that are used as materials for ceramics, porcelain, and abrasive materials, ultrafine alumina produced by vapor phase method (manufactured by Aerosil), catalysts, Activated alumina for use as an adsorbent (manufactured by Iwatani Chemical Industry Co., Ltd.), colloidal aqueous dispersion of alumina hydrate (alumina sol; manufactured by Yasan Kagaku Co., Ltd.), and the like can all be used in the present invention.

Furthermore, in the present invention, silica-based pigments containing alumina in the crystal structure (activated clay, etc.) can be used, but Mg
O,Cab,ZuO,Cub.

Double salts of alumina containing basic oxides, such as N i O, M u O, F ez Os, etc., cannot be used because the color development of the dye becomes low.

More preferable physical properties of the aluminum oxide used in the present invention include particle size o, ooi μm to 10 μm, and specific surface area 10 to 10 μm.
300m2/g, more preferably 20-200m2/g
is within the range of If the particle size is too small, powder will fall off in the coating layer, and if it is too large, the dot shape will be poor.In addition, if the specific surface area is less than 10 m2/g, the ink absorption will be significantly reduced.
If it exceeds 00 m2/g, indoor discoloration will not be improved even when combined with these pigments, which is not preferable.

Further, the amount of aluminum oxide contained in the ink receiving layer is 50% by weight, more preferably 30% by weight based on the total pigment.
More preferably, the dye-trapping layer contains aluminum oxide in an amount of less than 50% by weight, more preferably less than 30% by weight, based on the total pigment in the ink-receiving layer. It is.

It goes without saying that it is more effective to contain aluminum oxide in the upper layer in order to improve the color development of the dye. Furthermore, when the ink receiving layer contains 80% by weight or more of aluminum oxide, there are not only problems of indoor discoloration, but also blurring of images and a decrease in resolution due to a decrease in ink absorption.

The base material used in the present invention includes conventionally known base materials such as paper 1 synthetic paper, plastic film, etc., but especially those with a basis weight of 50 to 250 glrd and a Steckigt sizing degree of 0 to 100 seconds. Paper is preferred. Basis weight is 50
If the paper is less than g/rd, the paper will not have firmness and there will be problems in feeding and discharging the paper in the printer. Also, the basis weight is 250g/
If the value exceeds +rf, powder falling off of the coat/layer becomes a problem.If the paper size exceeds 100 seconds, the adhesion between the coat layer and the base paper decreases, and powder falling also occurs.

The paper used as a base material in the present invention is a sheet containing a fibrous substance and, if necessary, a filler, and is made into paper within the above range using a suitable sizing agent by a conventionally known acidic papermaking method or neutral papermaking method. You can use any of them.

The fibrous material constituting the above paper used in the present invention is L
The main material is wood pulp represented by BKP and NBKP, but various synthetic fibers, glass fibers, etc. may be mixed if necessary.

The ink-receiving layer includes the above-mentioned pigment and binder on the above-mentioned base material,
Furthermore, if necessary, it is formed using a coating liquid mixed with various additives.

Next, as the binder used in the present invention, for example, water-soluble polymers such as polyvinyl alcohol, starch, oxidized starch, cationized starch, casein, carboxymethyl cellulose, gelatin, hydroxyethyl cellulose, SBR latex, MBR latex, acetic acid emulsion, One type or a mixture of two or more types of water-dispersible polymers such as acrylic emulsions are used.

In the present invention, the preferred ratio of pigment to binder used in the entire ink-receiving layer is in the range of 1/4 to 20/1 by weight. If the amount of binder is greater than 1/4, the ink receptivity of the ink-receiving layer is reduced, and if the amount of pigment is greater than 20/1, there is a serious problem of powder falling off of the coat layer.

Furthermore, in terms of color development and ink absorption, it is preferable that the ink absorption of the upper layer is slow enough that ink droplets attached to the surface smear to an appropriate size, and the ink absorption of the lower layer is high. For this purpose, it is preferable that the ratio of pigment to binder used in the upper layer is 1/4 to 5/1, and the ratio of pigment to binder in the lower layer is 1/1 to 20/l.

It is desirable that the ink droplet spread is appropriately large because it improves the resulting image density, but if the ink absorption of the recording material is good, the absorption of ink will be completed in a short time. Bleeding in the direction parallel to the surface is small (
Bleeding rate and ink absorbency are problems that are not compatible with conventional single-layer ink receiving layers.

In the present invention, it has become possible to achieve both by adjusting the structure of the two layers in the ink receiving layer.

Furthermore, in the present invention, the ink receiving layer may include, if necessary,
It may contain a dye fixing agent (waterproofing agent), a fluorescent whitening agent, a surfactant, an antifoaming agent, a PH regulator, a fungicide, an ultraviolet absorber, an antioxidant, and the like.

In particular, the addition of an antioxidant is effective because indoor discoloration is caused by decomposition caused by oxidation of the dye.

As the antioxidant, any of the conventionally known antioxidants such as hindered phenol type, phosphite type, thioether type, benzotriazole type, hindered amine type, and benzophenone type can be used.

When used, it is used in an amount of 0.5 to 30% by weight based on the pigment. If the content is 30% by weight or more, the recording material itself may change color and the color reproducibility of the dye may deteriorate.

All conventionally known methods such as a bar coater, blade coater, air knife coater, reverse roll coater, etc. can be used to coat the aqueous coating solution obtained by mixing the above-mentioned materials onto the above-mentioned substrate.

The dry coating amount of the aqueous coating liquid for the entire ink receiving layer is preferably 2 to 50 g/g.

In other words, if it is less than 2 g/rt, there is a problem of decreased ink absorption or feathering where the ink bleeds along the exposed fibers on the surface, and if it is applied more than 50 g/rt+', the coating layer becomes brittle. This results in the problem of powder falling off.

The ink-receiving layer is composed of two layers as described above, so the coating amount of the upper layer is 1 to 20 g/rr (and the total coating amount of the lower layer is 2 to 50 g/m2). Within this range, it is preferable that the coating amount be larger than that of the upper layer.

If the upper layer is less than Ig/m2, it will not have much effect compared to the case where it is not provided, and if it is more than 20g/m2, the effect of the lower layer will not be achieved and the ink absorption rate will be reduced.

Dye coloring properties etc. decrease.

After the aqueous coating liquid is applied under the above conditions, it is dried using a conventionally known drying method, such as a hot air drying oven, a hot drum, an infrared drying oven, etc., to obtain a recording material.

Further, in order to smooth the surface of the ink-receiving layer or to increase the surface strength of the ink-receiving layer, a supercalender may be used in the process.

In order to make the indoor discoloration suppressing effect of the recording material obtained as described above even more effective, the recording material formed using the above-mentioned specific material should be subjected to an ozone test such as c, r, hood black. The recording material is configured so that the color change ΔE''ab of No. 2 is 20 or less.

In other words, as a result of numerous investigations into indoor discoloration, the inventors found that (1) discoloration does not occur on uncoated paper, but occurs only on coated paper that has an ink-receiving layer (hereinafter referred to as the coat layer) containing pigment and binder; However, this phenomenon is particularly noticeable on coated paper, which has excellent inkjet recording properties such as recording agent color development and ink absorption.

(2) Discoloration occurs when exposed to strong light such as sunlight, but discoloration occurs when indoors, and it is thought that the decomposition mechanism of the recording agent dye is different. (3) The type of recording agent is acid dye. , basic dye.

(1) above even if you replace the direct dye with 1 food coloring.

It was found that the tendency of (2) did not change, and as a result, indoor discoloration was caused by (1) dye decomposition due to light and oxygen.

(2) The coat layer exhibits a catalytic effect on this phenomenon, and coated paper, which is particularly suitable for inkjet recording, exhibits a strong effect.

The conclusion was reached.

Based on this reasoning, we devised the following ozone test method as a method for measuring the catalytic activity of the coat layer.

The ozone test is considered to be a method of evaluating and measuring the catalytic activity of the coating layer when dyes are decomposed by oxygen, and is a method of evaluating and measuring new physical properties that could not be measured using various conventional methods. be.

In the present invention, the ozone test is carried out by the following procedure.

(a) Preparation of test piece (i) The test solution was a solvent consisting of 70 parts by weight of deionized water and 30 parts by weight of diethylene glycol as a dye.
, Food Black 2 dissolved in 2 parts by weight is used.

(ii) 0.4μl of test solution! ~0.5μI! /cm
It is applied to the coating layer at a ratio of 2 parts. Methods include applying the ink directly as droplets using a dropper or pipette, transferring the ink using a stamp, etc., applying the ink using a bar coater, etc., and applying the ink as small droplets using an inkjet recording method. Examples include methods.

(b) Test conditions (i) The inside of the test tank is shielded from light, and fresh ozone is constantly supplied from inside or outside the tank, so that the concentration is always 0.1 ± 0.05.
Set so that it is kept within the volume% range.

Also, the air inside is set so that convection is always caused by a fan.

(ii) Environmental conditions inside the tank are temperature 20℃±2℃ and humidity 65℃.
Set so that it is maintained within the range of %±3%RH. In order to complete the evaporation of the volatile matter in the ink and to keep the amount of moisture adsorbed within the test piece constant, the test piece used was one that had been stored under the above environment for two days after preparation.

(iii) After setting the conditions of (i) and (ii), the test chamber is exposed to ozone for 15 minutes.

(c) How to obtain measured values (i) The color difference ΔE"ab of the test piece before and after exposure to ozone in the above test tank for 15 minutes is determined according to JIS Z8730 and is defined as the color change ΔE"ab of C, 1, Food Black 2.

By using a recording material whose color difference (ΔE"ab) of the obtained test piece is 20 or less in the ozone test as described above, it is possible to obtain a recording material that provides an image without indoor discoloration, which is the objective of the present invention. can get.

C, i, food black 2 discoloration due to ozone test is 2
If it is 0 or more, it is not preferable because the effect against indoor discoloration is poor. More preferably, it is 10 or less.

C used in ozone test, 1. Food black 2 has a function as an indicator like a pH indicator, a redox indicator, etc., and can be used to evaluate and measure the catalytic activity of a coat layer by an ozone test.

It is well known that dyes are decomposed by ozone (see, eg, J. Soc. Dyers).

Col., Vol. 100 (1984), No.

4, P, 125-127 (M, Matsuitet, a
There are references such as 1, ).

However, uncoated paper does not show such noticeable discoloration even in the ozone test, but coated paper shows noticeable discoloration, so it is thought that the coat layer is still acting as a catalyst of some kind. In addition, the decomposition of dyes by ozone is caused by p
The thickness is thought to change depending on the surrounding environment such as H, ionic strength, and the adsorption status of the dye in the coating layer such as Van der Waalska and hydrogen bonding. or
If the coating layer adsorbs the dye to protect it from ozone attack, it is assumed that the decomposition of the dye will be suppressed.

C by ozone test, 1. Discoloration of food black 2 is 2
The recording material of the present invention having a particle size of 0 or less can also be considered as a recording material having such a special coating layer.

On the other hand, since the actual ozone concentration in the air around us is a few ppm, and the lethal dose is 50 ppm, it is hard to believe that ozone directly contributes to indoor discoloration, and it is difficult to believe that ozone directly contributes to indoor discoloration. Since oxygen in general oxygen molecules is in a triplet state and oxygen in ozone is in a singlet state, it is thought that the decomposition mechanisms are different, and it is difficult to directly link ozone tests and indoor discoloration. Ru.

Although some speculations regarding the relationship between ozone tests and indoor discoloration have been introduced above, it goes without saying that the correctness or wrongness of these speculations has nothing to do with the present invention.

In any case, according to the findings of the present inventors, recording materials having a coating layer in which the color change ΔE"ab of C, 1, and Food Black 2 is 20 or less in the ozone test described above can be Even if you hang it on a wall or store it in a desk drawer, no discoloration will occur indoors, and as a recording material with an ink absorbing layer, it has excellent ink absorbency, recording material's color properties, etc. It had excellent suitability for inkjet recording.

C,1, Food Black 2 referred to in the present invention is a commercially available dye represented by the following general formula and is easily available.

C used in the present invention: 1. Food Black 2 used has a purity of 90%. Generally, the purity of commercially available dyes is about 50-60%, and they contain a large amount of inorganic salts, especially NaCl!, as impurities. .

Although it contains Na2so4, etc., if it is used as it is, the effectiveness as an indicator for C,1, Food Black 2 will be low, and the test results will include the influence of impurities.

For this reason, the C,1, food black 2 referred to in the present invention is purified to a purity of 90% or more, NaC1゜N a a S
The concentration of Oa is 1% or less.

Any conventionally known purification method can be used as a purification method at this time, such as a method of salting out with sodium sulfate, dissolving in a solvent, and filtration, a treatment method with a cation exchange resin, and an aeration method. , a coagulation-sedimentation method using a flocculant, a filtration method, an electrolytic method, etc.

Using the inkjet recording method on the recording material with the above configuration, yellow (Y), magenta (M), cyan (
According to the recording method in which recording is performed using water-based ink of multiple colors such as C) and black (BK), the resulting image does not undergo discoloration indoors, and a recorded image with excellent storage stability can be obtained.

In the method of the present invention, the ink itself applied to the above-mentioned specific recording material by the inkjet recording method may be a known ink, such as a direct dye, an acid dye, a basic dye, or a reactive dye.

It is a water-soluble dye represented by food coloring, etc., and is particularly suitable as an ink for inkjet recording, and has good fixing properties when combined with the above-mentioned recording materials.

Preferred examples of those that provide an image that satisfies required properties such as color development, clarity, stability, and light fastness include C, 1, Direct Black 17, 19° 32.51,
71,108,146 c, r, Direct Blue 6.22, 25°71.
86,90,106,199 C, 1, Direct Red 1, 4.17° 28.83 C, 1, Direct Yellow 12, 24° 26.86,
98,142 C, 1, Direct Orange 34,39°44.46.
Direct dyes such as 60 C,1, Direct Violet 47.48 C,1, Direct Brown 109 C,1, Direct Green 59, C,1, Acid Black 2,7,24°26.31,
52.63, 112°C, 1, acid blue 9.22, 40°59.93,
102,104,11 3.117,120,167.22 9.234 C,1, Acid Red 1,6,32,37°51.5
2,80,85,87°92.94,115,180.25 6, 317. 315 c, r, acid yellow 11.17, 23°25
, 29. 42. 61. Acidic dyes such as 71C,1, Acid Orange 7.19 C,1, Acid Violet 49 are preferred, and others include: C,1, Basic Black 2 C,1, Basic Blue 1.3,5.7°9.24,
25.26, 28, 29 C, 1, Basic Red 1, 2, 9, 12° 13.1
4.37 c, r, basic violet 7.14°C, 1
, Food Black 1, 2, etc. can also be used.

The above examples of dyes are particularly preferable for inks applicable to the recording method of the present invention, but dyes for inks used in the present invention are not limited to these dyes.

Such water-soluble dyes are generally used in a proportion of about 0.1 to 20% by weight in conventional inks, and this proportion may be the same in the present invention.

The solvent used in the water-based ink used in the present invention is water or a mixed solvent of water and a water-soluble organic solvent, and a particularly preferable one is a mixed solvent of water and a water-soluble organic solvent. It contains polyhydric alcohol, which has the effect of preventing ink from drying. Further, as water, it is preferable to use deionized water rather than ordinary water containing various ions.

The content of the water-soluble organic solvent in the ink is generally in the range of 0 to 95% by weight, preferably 10 to 80% by weight, more preferably 15 to 50% by weight based on the total weight of the ink. .

In addition to the above-mentioned components, the ink used in the present invention may optionally contain a surfactant, a viscosity modifier, a surface tension modifier, and the like.

In the method of the present invention, any conventionally known inkjet recording method may be used to perform recording by applying the above-mentioned ink to the above-mentioned specific recording material.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples. In the text, parts or percentages are based on weight unless otherwise specified.

Examples 1-7. Comparative Examples 1 to 5 A high-quality paper with a basis weight of 100 g/d and a size degree of 22 seconds was used as a base material, and the following coating composition was applied on this base material with a dry coating amount of 15
Coating with a bar coater method so that it is 1 g/m2.
Hot air drying was performed at 10° C. for 5 minutes to form a lower layer.

4 parts polyvinyl alcohol (PVA
-117 Cra I, made by i) Polyvinyl alcohol 4 parts (PVA
-105 Kuraray) Water
200 parts The coating composition shown below was coated on the lower layer thus formed using a bar coater method so that the dry coating amount was 8 g/i, dried at 110°C for 5 minutes, and then coated on the upper layer. A recording material of the present invention and a recording material for comparison were obtained.

Pigment 25 parts Polyvinyl alcohol 6 parts (PVA-117
(manufactured by Kuraray) Polyvinyl alcohol 6 parts (PVA
-105 manufactured by Kuraray) Polyamine water resistant agent <28% aqueous solution> 4 parts (PAS
H-10L Nittobo) Water
200 copies Examples 1-7. Table 1 shows the pigments used to form the upper layer in Comparative Examples 1 to 5.

Comparative Example 6.7 As commercially available coated papers for inkjet, NM paper (manufactured by Mitsubishi Paper Industries) and FC-3 paper (manufactured by Jujo Paper Industries) were used as recording materials for comparison.

The suitability for inkjet recording of the recording material described above is as follows: Y and M inkjet heads equipped with 128 nozzles at a nozzle interval of 16 nozzles per 1 mm.

Inkjet printer with 4 colors of C and BK (a
) and an inkjet printer (b) having 24 nozzles for 4 colors at 8 intervals of 1 mm, inkjet recording was performed and evaluated using ink having the following composition.

◎Ink composition (I) Dye 5 parts ethanol 5 parts diethylene glycol 15 parts water
78 parts Dye (Ink I) Y: C, 1, Direct Yellow 86M: C, 1
, Acid Red 35C:C,1, Direct Blue 1998:C,r, Direct Black 17◎Ink composition (II) Dye 2 parts diethylene glycol 20 parts polyethylene glycol 8200 15 parts n-methyl-2-pyrrolidone
10 parts water
53 parts/dye (ink) Y:C, r, acid yellow 42M:C
, r, Acid Red 92C: C,1, Direct Blue 868: C,1, Direct Black 51◎ Ink Composition (III) C,1, Acid Black 26 was used as a dye in the ink composition (n).

Evaluation was performed on the following items. The results are shown in Table 2.

(1) Ink absorbency was evaluated using an inkjet printer (a) using ink (1).

In a mixed-color area of two-color ink in a recorded image, lines where the line thickness was worse than those in the monochrome area were rated x, those where there was no line were rated 0, and those where it was slightly thickened were rated Δ.

(2) Indoor storage stability (1) is ink (I), (II).

A color image was formed using printer (a), and it was hung on the wall of an office and left for 6 months. Same image similarly 6
When compared to the image stored in the Clear Pocket File for months, no discoloration was observed as ○, severe discoloration as ×, and moderate discoloration as △.

(3) Indoor storage stability (2) is ink (■).

A BK solid pattern was printed using printer (b), and as in (2), it was hung on the wall of the office and left for one month. Difference ΔE between the chromaticity of this image and the chromaticity of the image immediately after printing
``ab'' was determined and indoor discoloration was evaluated.

(4) Color properties are printed matter (Y, M) printed solidly using ink (I) and printer (a).

The saturation of C) was measured using a high-speed color analyzer CA-35 (manufactured by Murakami Color Science).

(5) Image density was measured using a Macbeth densitometer RD-914 for 0 and D of a solid print (BK) printed using ink (■) and printer (a).

(6) C by ozone test, 1. The discoloration E"ab of Food Black 2 was measured by the method described above.

〔Effect of the invention〕

Since the recording material of the present invention contains a large amount of pigment with high dye-capturing ability on the surface layer, there is a high probability that the dye in the ink droplet will be captured and absorbed by the pigment, and therefore the ink will not bleed or spread. As a result, the dot shape is improved and exhibits excellent ink absorption, resolution, color development, and color density.

Furthermore, the present invention exhibits inkjet recording suitability as a coated paper as shown above, particularly excellent image density, and there are fewer problems in image preservation peculiar to coated paper, and the recording material of the present invention and multicolor ink can be used as coated paper. In the recording method using the inkjet recording method, there is the problem of indoor discoloration when the resulting image is stored in an office wall or drawer that is not exposed to direct sunlight for one to several months. Does not occur.

Claims (11)

[Claims] (1) In a recording material having a base material and an ink-receiving layer provided on the base material, the ink-receiving layer is a silicon-containing material having a specific surface area in the range of 10 to 200 m^2/g by the BET method. 1. A recording material comprising an upper layer containing a pigment, and a lower layer containing a pigment having a larger average secondary particle diameter than the pigment. (2) The recording material according to claim 1, wherein the silicon-containing pigment has an oil absorption amount of 1.5 ml/g or more. (3) The recording material according to claim 1, wherein the silicon-containing pigment has an average secondary particle diameter of 15 μm or less. (4) The recording material according to claim 1, wherein the pigment contained in the lower layer has a specific surface area of 200 m^2/g or more by the BET method. (5) The average secondary particle diameter of the pigment contained in the lower layer is 2 to 30
The recording material according to claim 1, which has a range of μm. (6) In a recording material having a base material and an ink-receiving layer provided on the base material, the ink-receiving layer is a silicon-containing material having a specific surface area in the range of 10 to 200 m^2/g by the BET method. 1. A recording material comprising: an upper layer containing a pigment and aluminum oxide particles; and a lower layer containing a pigment having a larger average secondary particle diameter than the pigment. (7) The recording material according to claim 6, wherein the ratio of the silicon-containing pigment to the aluminum oxide particles is in the range of 20/1 to 1/4 (weight ratio). (8) The recording material according to claim 6, wherein the diameter of the aluminum oxide particles is smaller than the diameter of the silicon-containing pigment. (9) Claim 6, wherein the aluminum oxide particles have a specific surface area of 10 m^2/g or more as measured by the BET method.
Recording material described in section. (10) The average particle diameter of the aluminum oxide particles is 1
The recording material according to claim 6, which has a particle size of 0 μm or less. (11) In a recording method in which recording is performed by applying droplets of ink containing a water-soluble dye to a recording material, the recording material is B
The ink-receiving layer includes an upper layer containing a silicon-containing pigment having a specific surface area of 10 to 200 m^2/g by the ET method, and a lower layer containing a pigment having a larger average secondary particle size than the pigment. Characteristic recording method.