JPS59230787A - Ink jet recording paper - Google Patents

Abstract

PURPOSE:To provide the titled paper high in density of images or characters recorded on a sheet, clear in color tone of the images or characters, capable of absorbing an ink at high speed with little blur and suitable for recording in multiple colors, wherein an ink-receiving layer comprises synthetic amorphous silica having a specified surface activity. CONSTITUTION:The objective recording paper has the ink-receiving layer comprising synthetic amorphous silica (preferably, white carbon obtained by a wet process, silica gel or ultrafine silica obtained by a dry process, containing not less than 93% of SiO2, not more than 1% of Al2O3 and not more than 5% of Na2O on a dry basis) having a surface activity in terms of an acid value (the amount of dibutylamine adsorbed) of not less than 240mg-mol/kg. It is preferable that, when the ink-receiving layer is a sheet made from a material comprising a wood pulp as a main constituent to which synthetic amorphous silica is added, the content of said silica in the paper is set to be 10-30wt%, and when the layer is a sheet comprising a coated layer of synthetic amorphous silica and an adhesive on a base, the amount of said silica applied is set to be 10-50g/m<2>.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a recording sheet that is recorded using ink, and in particular, images and characters recorded on the sheet have high density, clear color tone, and ink absorption speed that is at least 100%. The present invention relates to an inkjet recording sheet that is suitable for multicolor recording and has little ink bleeding.

In recent years, inkjet recording methods have been characterized by high speed, low noise, easy multicolor printing, great flexibility in recording patterns, and no need for fixing. It is rapidly becoming popular for various uses including hard copy devices for r-type graphics and color images. Furthermore, the images formed by the multicolor inkjet method are comparable to those produced by normal multicolor printing, and when the number of copies to be produced is small, the multicolor inkjet recording method is cheaper than the normal plate making method. Attempts are being made to apply it to the fields of printing and color photographic printing.

High-quality paper used for general printing, coated paper, and so-called baryta paper used as a base for photographic paper have extremely poor ink absorption properties, so when used for inkjet recording, the ink remains on the surface for a long time. If a part of the device is touched or touched by the operator, or the recording surface is rubbed due to overlapping sheets ejected in succession, the residual ink will stain the image. In addition, if three or four color ink dots overlap in the same place in high-density image areas or multicolor recording, the amount of ink will be large, causing problems such as the ink mixing without being absorbed or flowing out. There is no gender.

This recording sheet can produce images with high density and clear tones, and it also absorbs ink quickly and does not run out, and it does not stain even if touched immediately after printing. At the same time, it is required to suppress the lateral diffusion of ink dots on the surface of the recording sheet and to obtain a high-resolution image without bleeding.

Several proposals have been made to solve these problems. For example, Japanese Patent Application Laid-Open No. 52-53012 discloses an inkjet recording paper made of a low-sized base paper moistened with a paint for surface treatment. Further, JP-A No. 53-49113 discloses an inkjet recording paper in which a sheet containing urea-formalin resin powder is impregnated with a water bathing polymer. Also, JP-A-55
No. 5830 discloses an inkjet recording paper having an ink-absorbing coating layer on the surface of the support, and JP-A No. 55-51583 discloses an example in which non-colloidal silica is used as a pigment in the coating layer. Disclosed in Japanese Patent Publication No. 55-146786
The issue discloses an inkjet recording paper provided with a water-soluble polymer coating layer. Furthermore, JP-A-55-11829
In this issue, it has a layer structure of two or more layers, the outermost layer has an ink absorbency of 1.5 to 5.5 mm/min, and the second layer has an ink absorbency of 5.5 to 60.0 mm/min. A method for adjusting the spread of ink dots and the absorption speed is disclosed.

However, the technical idea as typified by JP-A-52-58012 is to obtain resolution at the expense of some ink absorption;
Although the technical concept represented by No. 9113 provides a certain level of ink absorption and resolution, it has the disadvantage that the ink penetrates deep into the paper layer, making it difficult to achieve ink density.
Both are unsatisfactory as multicolor inkjet recording paper.

Therefore, as a method to improve these drawbacks, inkjet recording paper coated with non-colloidal silica powder was developed in JP-A-55
-51583, and Japanese Patent Publication No. 53-790 discloses an optically readable barcode printing paper coated with finely powdered silicic acid.

In this way, by providing a layer of non-colloidal silica etc. on the surface, the resolution, color density (chromaticity), absorbency, roundness, etc. suitable for inkjet are improved, but these non-colloidal silica and fine powder silicon The acid, that is, the synthetic amorphous silica referred to in the present invention, is
It has been found that there are large differences in absorption capacity, color density, and color reproducibility as inkjet suitability, depending on the reaction conditions, stirring conditions, drying method, drying conditions, etc. when producing this.

As a result of intensive research into the relationship between the physical properties of synthetic amorphous silica and inkjet suitability, the inventor of the present invention found that the acid value (dibutylamine absorption layer) is one of the guidelines for expressing the surface activity of synthetic amorphous silica. It was discovered that the color density and color reproducibility of the ink are particularly excellent when the ink is 240 tmol/Il1 or more, and the present invention has been accomplished based on this finding.

The present invention will be explained in detail below. In the present invention, the ink-receiving layer refers to the ink-receiving layer in the case where a sheet made from wood pulp and synthetic amorphous silica is used as a recording medium, the entire sheet becomes the ink-receiving layer, or paper with a size that is effective. When a sheet is used as a recording medium, in which a coating layer made of synthetic amorphous silica and an adhesive is provided on a support of a synthetic resin film, the coating layer becomes an ink-receiving layer. In other words, when inkjet recording is performed on a layer having voids that receive and absorb ink liquid, the surface thereof is called an ink-receiving layer.

The synthetic amorphous silica used in the present invention is 8% on a dry basis.
These include fine powder silica produced by a wet process, so-called white carbon or silica gel, and ultrafine powder silica produced by a dry process, with an i0.93% or more, an Al2O content of about 1% or less, and a Na2O content of about 5% or less.

Silica sol obtained by double decomposition of sodium silicate with acid, etc., or colloidal silica obtained by heating and aging this silica sol, gelling the silica sol and changing the production conditions to produce particles from a few millimeters to a few millimicrons. Silica gel, which is a three-dimensional secondary particle in which primary particles of about 10 millimicrons are bonded with siloxane, is mainly composed of silicic acid such as those obtained by heating silica sol, sodium silicate, sodium aluminate, etc. It is a synthetic silicon compound. The present invention requires that the surface activity of these synthetic amorphous silicas, that is, the acid value measured by the method described below, be 240 tmol/Ky or more.

The surface activity or acid value referred to in the present invention is used as one of the methods for quantifying the surface adsorption of fillers in the rubber and filler industries. It is considered to be one of the indicators of bonding strength. Typically diphenylguanidine (DPG) or dibutylamine (DBA) is used for measurements. Since DBAO has a lower molecular weight, it is considered to be more suitable for measuring the amount of surface adsorption of synthetic amorphous silica. For details about these, see D.
r, R, MEYER, HA BURG;Titrime
trische untersuchungen a
n F'ullstoffen; KAUT8CHUK
UND GUMMl, 7. Jahrgang, N.
r.

8/1951 P180-182, the following measurement method was used here.

Precisely weigh sample 1f and place it in a 250 g Erlenmeyer flask.

Then 50 rnl of N1500i solution of diptylamine dissolved in benzene (100-140°) are added.

Leave for 2 hours with frequent shaking and remove 25 tnl of supernatant.
Collect f, add 2 drops of 0.1% crystal violet glacial acetic acid solution as an indicator, add 5-chloroform, and back titrate with N/100 perchloric acid solution of glacial acetic acid solvent, and the point at which the color changes from violet to back green. is the end point. For the image, use the value calculated using the following formula.

Acid value (W-mol/Kg) = (Vo-VA)X20
Vo=N1500 Titration value of diptylamine 25-(,7
(Blank) VA = Titration value of measurement sample (-) If the acid value is 100 or more, reduce the sample amount to 0.25 f and measure.

In one embodiment of the present invention, the ink-receiving layer comprises a fibrous material and a synthetic amorphous silica filler.
l /Ky or more synthetic amorphous silica has an ash content of 5
Using a normal Fourdrinier paper machine, from a slurry to which a paper direction improver, a retention stain improver, an elbow coloring agent, etc. have been added as necessary, the weight is preferably 10 to 30 weight I-H. It is manufactured by making paper, and then adding oxidized starch, polyvinyl alcohol, etc., using a size press or the like that is normally used in paper making.

In addition, in an embodiment in which a coating layer is formed on a support, an acid value of 240
TILI-mol 7Kg or more of synthetic amorphous silica: 597w1 or more, preferably 10-50f/l
T? Charcoals commonly used as pigments include calcium, kaoli/(white clay), Merck, calcium sulfate, barium sulfate, titanium oxide, zinc oxide, zinc sulfide, zinc charcoal,
Inorganic pigments such as spotted/white, aluminum silicate, aluminum hydroxide, diatomaceous earth, calcium silicate, magnesium silicate, alumina, and lithopone can also be used in combination. The temporary support may be a sheet material such as paper or a thermoplastic adhesive film. There are no particular restrictions on the material, including appropriately sized paper, polyester, polystyrene, polyvinyl chloride, polymethyl methacrylate, cellulose acetate, polyethylene,
Films such as polycarbonate can be used. Even though these papers contain fillers, thermoplastic resin films
It may be a transparent film containing no solid pigment, or a white film filled with white pigment or formed by fine foaming. As the white pigment to be filled, many pigments can be used, such as titanium oxide, calcium sulfate, calcium carbonate, silica, clay, Merck, and zinc oxide. There are no particular limitations on the thickness of these supports, but those of 10 μm to 300 μm are usually used. There may also be a layer to improve adhesion between the film and the ink-receiving layer.

Formation of the ink-receiving layer on these supports consists of the synthetic amorphous silica described above and an aqueous adhesive to adhere it to the support. Examples of adhesives include oxidized starch, etherified starch, esterified starch, and dextrose.
Starches such as J-1, S-form cellulose such as carboxymethyl cellulose and hydroxyethyl cellulose, casein, gelatin, soybean protein, polyvinyl alcohol and its derivatives, maleic anhydride resin, ordinary styrene-butadiene copolymer, methyl methacrylate-butadiene Conjugated diene polymer latex such as a copolymer, acrylic polymer latex such as a polymer or copolymer of acrylic acid ester and methacrylic acid ester, vinyl polymer latex such as ethylene vinyl acetate copolymer, or Functional group-modified polymer latex with monomers containing functional groups such as carboxyl groups of these various polymers, water-based adhesives such as thermosetting synthetic resins such as melamine resins and urea resins, and polymethyl methacrylate, polyurethane resins, and Synthetic resin adhesives such as saturated plastic IJ ester resins, vinyl chloride-vinyl acetate copolymers, polyvinyl butyral, and alkyd resins are used. These adhesives are used in an amount of 2 to 50 parts, preferably 5 to 30 parts #'i, per 100 parts of the pigment, but the ratio is not particularly limited as long as the amount is sufficient to bind the pigment. . However, if 100 parts or more of adhesive is used, the peak of the pore distribution curve of the present invention may be shifted due to film formation of the adhesive, which is not very preferable.

Furthermore, if necessary, pigment dispersants, thickeners, flow modifiers, antifoaming agents, foam inhibitors, mold release agents, foaming agents, coloring agents, etc. may be added as appropriate. When forming the ink-receiving layer provided on the support in the present invention by applying a pigment coating liquid, etc., a blade coater, an air knife coater, a roll coater, a flash coater, a curtain coater, or a curtain coater, which is generally used as a coating machine, can be used. Coater, bar coater, gravure coater, spray etc. can all be applied. Furthermore, when the support is paper, it is also possible to apply a size press on a paper machine, a gate roll, a device, etc. A sheet simply provided with an ink-receiving layer on a support can be used as it is as a recording sheet according to the present invention, but it can be used as a recording sheet according to the present invention as it is, but it can be used, for example, with a super calender, a cross calender, etc., to achieve a different level of smoothness by passing it through the roll nip under heat and pressure. It is also possible to give. In this case, excessive processing by supercalender processing may change the size of the voids between the particles that have been formed, which may deviate from the range of the pore diameter according to the present invention, so the degree of processing may be limited.

The present invention will be described below with reference to examples, but it is not limited to these examples. In the Examples, parts and parts by weight refer to parts by weight and % by weight.

Methods for measuring various inkjet suitability values in Examples are shown below.

(1) Ink absorption speed Ink droplet of water-based ink for inkjet 0.0006-
Measure the time (in seconds) from the moment it is applied to the surface until it is completely absorbed.

(2) Resolution An ink droplet of aqueous inkjet ink with a diameter of 100 μm was attached to the surface, and after being absorbed, the area marked by the ink droplet was measured, and the value calculated as the diameter assuming a perfect circle was used. (μm) The smaller the diameter, the better the resolution.

(3) Ink absorption capacity The judgment was made by observing the ink flow when printing on the same surface with an inkjet device using water-based inks of four colors: cyan, magenta, yellow, and black.

(4) Color density Magenta, cyan,
Solid printing was performed in four colors, yellow and black, and the color density was measured using a Macbeth densitometer RD514.

Example I 70 parts of LBKP of F Suisan 350d and p Suisan 400T1
40 parts of synthetic amorphous silica (Nip Seal VN3 manufactured by Nippon Silica, [value 280 W-mol/Kt)] was added to a pulp slurry consisting of 30 parts of 1 ton of NBKP, 1 part of cationic starch (Cato F manufactured by Tamago National Co., Ltd.), and anion. Retention improver (Kinda Kagakusha JP-103)
Adding 0.01 part, 709/
lF? A paper with a basis weight of . A size press installed in the middle of the paper machine produces 1% polyvinyl alcohol (
PVAI 17) manufactured by Kuraray Co., Ltd. was attached.

The ash content of the paper-made inkjet recording paper is 20.
It was 3 chi.

For comparison, a comparative example was prepared in exactly the same manner as in Example 1, except that the synthetic amorphous silica was replaced with NipSeal E150J (acid value: 190 q-mol, 7 kg).

Table 1 shows the results of measuring the inkjet suitability of these papers.

Table 1 shows that the color densities of the Examples in which Nip Seal VN3 with an acid value of 280 was prepared were higher than those of the Comparative Examples, and the inkjet recorded images were clearly visible.

Table 1 Examples 2-3 Tsubo 163t/n? , Signal amorphous silica (Nip Seal N manufactured by Nippon Silica
8P, acid value 25111v-mol/Ky) 100
Polyvinyl alcohol (Cura V.
100 parts (10 parts as solid content) of PVA117) (manufactured by Co., Ltd.) were added, a small amount of an antifoaming agent was added, and the mixture was thoroughly stirred to prepare a coating liquid with a concentration of 20%.

This is 151/rr per side? The recording paper of Example 2 was obtained by applying the coating using an air knife coater and drying it, and then applying a super calender to smooth the surface.

Nip seal LP (instead of the above nip seal NAP)
The recording paper of Example 3 was prepared in exactly the same manner as in Example 2, using 4) with a g value of 286 q-mol/.

For comparison, instead of the above nip seals NSP and LP, nip seal E220A (acid value 232 W-mo
17Kg), nip seal E150K (acid value 190
Comparative Examples 2 to 4 were prepared in exactly the same manner using Tokusil GUN (manufactured by Tokuyama Soda Co., Ltd., acid value: 220 -mol/Kg). The inkjet suitability of these papers was measured and the results are shown in Table 2.

From Table 2, Example 2.3, which used synthetic amorphous silica with an acid value of 240 μm mol /Kg or more, had high color density;
It is recognized that it is excellent as an inkjet paper for color images because other suitability is also good. The higher the color density, the better the color density, but αn of 1.0 or more is required to obtain excellent recording.

Table 2

Claims (1)

[Claims] In an inkjet recording paper in which the ink-receiving layer contains synthetic amorphous silica, the surface activity of the synthetic amorphous silica is 240 key mol/Kg as an "acid value".
An inkjet recording paper characterized by the above.