JPH06219043A - Ink jet recording paper - Google Patents

Abstract

PURPOSE:To provide ink jet recording paper having appearance and touch like fine paper, rapid in ink absorption in a color ink jet recording system and obtaining an image good in density, resolving power and color developability. CONSTITUTION:Ink jet recording paper has a surface layer with a basis wt. of 60g/m<2> based on cellulose pulp and the surface layer provided on one surface or both surfaces of the surface layer and formed by a papermaking process and based on pulp wherein inorg. matter insoluble or hardly soluble in water is supported in the interior of a cellulose pulp fiber (e.g. silica supported pulp with silica content of 32wt.%). The surface layer is within the range of 10-100g/m<2> and the basis wt. of the sum of the surface layer and an inner layer is set to a range not exceeding 90wt.%. Thereafter, size press (e.g. PVA) and supercalender treatment are applied to obtain the ink jet recording paper.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording material used in an ink jet recording method, and more specifically, it is like high quality paper and has features such as excellent color development of color, dot shape and ink absorbability. The present invention relates to an aqueous inkjet recording paper.

[0002]

2. Description of the Related Art An ink jet recording system using a water-based ink is a system for recording by ejecting a small droplet of a recording liquid and adhering it onto a recording material such as paper, which is capable of high speed recording without noise. It has the feature that it can record on plain paper. However, in recent years, with the improvement of printer performance such as high-speed recording and multicolor recording, more advanced characteristics have been required for recording materials. That is, in the case of the color ink jet recording method using a plurality of ink nozzles, a plurality of different ink droplets collide with the same point on the paper, so that the ink droplets that collide first are not immediately absorbed inside the paper. Then, it overlaps with the ink droplets ejected at the same point on the paper, and the ink flows out,
It gets dirty when the paper surface is rubbed. Therefore, for multi-color recording, a recording material having a higher ink absorbing capacity than that for a single color is required.

Since high-quality papers and writing papers used for general printing have poor ink absorbency, the adhered ink remains on the paper surface for a long time and the ink is mixed without being absorbed to cause bleeding. When the recording surface is rubbed, it has a defect that the images cannot be overlaid for a while after printing because the image is soiled, so that it is not suitable as an inkjet recording paper. That is, in ink jet recording, the ink adhering to the paper surface is quickly absorbed inside the paper layer, and the appearance becomes dry, and in order to obtain a high density and clear image, the spread of ink dots is suppressed,
It is necessary to have the property of increasing the resolution,
Special paper is used that balances the absorption speed and spread of ink by adjusting the bulkiness, air permeability, and sizing degree. Particularly, in the color inkjet recording system, a so-called ink-receptive coating layer is provided on the surface of the paper. Coated paper is used.

From the above, the characteristics required for the recording material in order to obtain an image with good density, resolution and color reproducibility in the color ink jet recording system are as follows. (1) The ink absorbency is fast. (2) The diameter of the ink dot does not become larger than necessary and the spread of the dot is suppressed. (3) The shape of the ink dot is close to a perfect circle. (4) The density of ink dots is high and the area around the dots is not blurred. (5) The coloring property of the coloring component of the ink is excellent. (6) High whiteness. (7) The ink color should not change depending on the recording paper.

Many proposals have hitherto been made to satisfy these required performances. For example, as an example of high-quality paper type inkjet recording paper, Japanese Patent Laid-Open No. 52-530 is known.
Japanese Unexamined Patent Publication No. 12 discloses an ink jet recording paper obtained by slightly coating a base paper of low size with a paint and allowing the paint to penetrate into the paper layer. Further, JP-A-53-49113 discloses an ink jet recording paper in which a water-soluble polymer is coated on a paper in which a urea-formalin resin fine powder is internally added. However, all of these recording papers tend to improve resolution, recording density, etc. at the expense of ink absorbency, resulting in a decrease in ink absorbency, which is unsatisfactory as a color inkjet recording paper. It was a thing.

Further, Japanese Patent Laid-Open No. 52-74340 discloses an ink jet recording paper having a specific air permeability and ink absorption time. In the case of this recording paper, the absorption of ink is fast, but the dot diameter is likely to be large, the periphery of the dot is easily blurred, or the ink penetrates deep into the sheet layer, resulting in low image density and However, it is not satisfactory as a color ink jet recording sheet, because it has a defect that the ink may come off.
Further, Japanese Patent Laid-Open No. 58-110288 discloses an ink jet recording paper in which a filler having a specific pore distribution is internally added. In the case of this recording paper, a large amount of a filler such as synthetic silica or synthetic alumina must be added, resulting in a decrease in papermaking speed and powder drop of the product.

As a method for improving these drawbacks, a coated paper type ink jet recording paper has been proposed, and in JP-A-55-5830, an ink absorbing coating layer is provided on the surface of a support. Inkjet recording paper is disclosed,
Further, JP-A-55-51583 discloses an example in which non-colloidal silica is used as a pigment in a coating layer, and JP-A-55-146786 discloses a water-soluble polymer coating layer. An ink jet recording sheet provided is disclosed. These coated papers are certainly superior in ink absorbency, resolution, and color reproducibility to so-called high-quality paper type inkjet recording papers that do not have a coating layer on the surface, but they are fine paper-based papers. It looks and feels quite different from the paper. Therefore, customers who have used high-quality paper conventionally do not like the recording paper provided with the ink-absorptive coating layer as described above, and the so-called high-quality paper that has the appearance and feel similar to high-quality paper. There is a demand for a paper-like ink jet recording sheet with high print quality.

[0008]

SUMMARY OF THE INVENTION In view of the above situation, an object of the present invention is to obtain a high quality paper-like image, which has a high ink absorbency in a color ink jet recording system, and has good density, resolution and color reproducibility. The present invention intends to provide an ink jet recording sheet.

[0009]

An ink jet recording paper according to the present invention is formed of an inner layer containing cellulose pulp as a main component and one or both surfaces of the inner layer by papermaking, and is water-insoluble inside the cellulose pulp fiber. Or a surface layer containing as a main component a pulp supporting a poorly soluble inorganic substance, and the basis weight of the surface layer is 10 to 100 g / m ^2.
Of the total grammage of the surface layer and the inner layer
It can be obtained by coating and forming in a range not exceeding the weight%.

The present inventors have blended a pulp in which fibers of cellulose pulp carry a water-insoluble or sparingly soluble inorganic substance (hereinafter referred to as an inorganic substance-supporting pulp) on or on both sides of a pulp layer having a strong sizing property. By coating the surface layer with weak size, it is possible to manufacture ink jet recording paper that has fast ink absorbency, excellent image density, resolution and color reproducibility, and has the same appearance and touch as conventional high-quality paper. Heading out, the present invention has been completed.

Cellulose pulp used for producing the mineral-supporting pulp of the present invention is a chemical pulp such as sulfite pulp (SP), alkali pulp (AP), kraft pulp (KP) obtained from hardwood and softwood,
Examples include semi-chemical pulp, semi-mechanical pulp, mechanical pulp and the like, and waste paper pulp which is a deinked secondary fiber can also be used. Further, the pulp can be used without distinction between unbleached pulp and bleached pulp, beating and unbeating. Further, as the cellulose pulp, non-wood pulp grass, leaves, bast, fibers such as seed hair, for example, straw, bamboo,
Pulp such as hemp, bagasse, kenaf, honey and cotton linter can also be used. Further, as long as it is a hydrophilic fiber, regenerated fiber such as rayon, cellulose derivative fiber and hydrophilic synthetic polymer fiber such as polyvinyl alcohol and polyacrylamide can be used, but from the viewpoint of quality and cost, hardwood bleached kraft pulp (hereinafter LBKP). ), Or softwood bleached kraft pulp (hereinafter referred to as NBKP) is most suitable.

As a method for preparing an inorganic material-supporting pulp by supporting an inorganic material inside a cellulose fiber, there is disclosed in Japanese Patent Laid-Open No. Hei 3
No. 146766, No. 3-152295, No. 4-18193, No. 4-2429.
It can be carried out by the method described in Japanese Patent Laid-Open No. 9-57964. That is, a hydrophilic fiber material such as cellulose is impregnated with an aqueous solution containing as one component a water-soluble inorganic compound that reacts with a specific gas or an aqueous solution to produce an inorganic substance that is insoluble or hardly soluble in water. There may be mentioned a method in which a water-insoluble or sparingly-soluble inorganic substance is deposited and carried inside the hydrophilic fiber material by bringing the hydrophilic material into contact with a specific gas or an aqueous solution.

The water-insoluble or sparingly soluble inorganic compound is (A) a reaction between a water-soluble inorganic salt, an aqueous solution of an alkali metal salt of a hydroxide or a hydrate of a metal oxide, and an acidic or alkaline gas, (B) an inorganic It can be prepared by reacting an aqueous solution of a salt or hydroxide with an aqueous solution of an inorganic compound. As a method using an acidic gas, (1) an aqueous solution of an alkali metal salt of a hydrate of silicon or a metal oxide and an acidic gas (for example, sodium silicate and carbon dioxide gas), (2) hydroxylation of an alkaline earth metal Aqueous solution of substance and acid gas (eg magnesium hydroxide and carbon dioxide), (3) Aqueous solution of metal or alkaline earth metal salt and acid gas (eg calcium chloride and carbon dioxide)
There is a reaction such as. CO ₂ , SO ₂ , HC as acidic gas
1, HF, HBr, HI, H ₂ S, NO, NO ₂ , C
Examples thereof include l ₂ , F ₂ , Br _{2 and the} like.

As a method using an alkaline gas, there is a reaction between an aqueous solution of an alkaline earth metal or a metal salt and ammonia (for example, a reaction between magnesium chloride and ammonia). As a method of using an aqueous solution of an inorganic compound,
(1) Aqueous solution containing alkaline earth metal or metal ion and acid radical ion (eg, calcium hydroxide and phosphoric acid), (2) Alkali metal salt solution of hydrate of silicon or metal oxide and inorganic There is an acid reaction (for example, a reaction between sodium silicate and sulfuric acid). Further, in the method using an acidic gas or an alkaline gas, it is possible to react as an acid or an alkali in the liquid phase.

The inorganic substance to be supported may be any one that is insoluble or sparingly soluble in water, but white inorganic substances used as pigments and fillers are particularly preferable. By way of example, silica, aluminum hydroxide, magnesium carbonate, magnesium hydroxide, calcium carbonate, barium sulphate, calcium sulphate are suitable, but are not limited thereto. The cellulose pulp for producing the inorganic substance-supporting pulp of the present invention may be beaten to reduce the freeness or may be unbeaten. However, since strength as an inkjet recording paper becomes a problem, it is preferable to beat and use the pulp freeness in the range of 300 to 650 ml. The amount of the inorganic substance to be carried depends on the conditions, but it is possible to carry it up to about 65% as a content rate.

The ink jet recording paper having a multi-layer structure of the present invention comprises cellulose pulp as a main raw material, and an inorganic material-supporting pulp is blended on or on both sides of a pulp layer having a strong sizing property by a chemical such as a sizing agent. The surface layer having a weak sizing property is provided for papermaking, and the surface layer may contain 100% by weight of an inorganic substance-supporting pulp, or may be used by mixing with ordinary pulp containing no inorganic substance and other fibers. When the pulp is mixed, an appropriate mixing ratio is determined depending on the inorganic content of the inorganic-supported pulp used, but it is preferable that the inorganic content is 5 to 50% by weight. If necessary, synthetic pulp, synthetic fiber, glass fiber, inorganic fiber or the like can be mixed.

As the inner layer, a usual cellulose pulp containing no inorganic substance is used, but if necessary, synthetic pulp, synthetic fiber, glass fiber, inorganic fiber or the like can be mixed. As an additive for forming a sheet, rosin, alkyl ketene dimer, sizing agent such as alkenyl succinic acid, sulfuric acid band, fixing agent such as cationic polymer electrolyte, clay, talc, calcium carbonate, calcined kaolin, aluminum oxide, water Aluminum oxide, white carbon, organic pigment (plastic pigment), filler such as titanium oxide, polyacrylamide polymer, paper strength enhancer such as starch, melamine resin, urea resin, wet paper strength enhancement of polyamide / polyamine / epichlorohydrin resin etc. Agents, dyes, fluorescent dyes, defoamers, retention improvers, drainage improvers, slime control agents, etc. can be selected and added internally, but they must be of a strong size to suppress ink bleeding. If necessary, it is desirable to add the above sizing agent and fixing agent. On the other hand, the surface layer needs to have low sizing property, and it is desirable not to add a sizing agent.

The basis weight of the sheet is determined by the final use of the recording paper, but the total of the surface layer and the inner layer is 20 to 2
Papermaking is performed at 00 g / m ² , preferably 60 to 90 g / m ² . The raw material containing the inorganic material-supporting pulp as the surface layer has a basis weight of 10 to 1
The inner layer is coated in the range of 00 g / m ² and within the range of not more than 90% by weight of the total basis weight of the surface layer and the inner layer. When the basis weight of the surface layer is less than 10 g / m ² , the ink absorbency is insufficient, the ink absorption time is long, the ink bleeds, and the dot shape deteriorates. Further, when the basis weight of the surface layer is 100 g / m ² or more, the ink penetrates deep into the sheet layer and the image density decreases.
When the basis weight of the surface layer is 90% by weight or more of the total basis weight, the inner layer having a strong size property is substantially reduced,
Ink strike-through occurs. Therefore, unnecessarily thickening the layer of the inorganic material-carrying pulp not only deteriorates the quality but is also economically inadequate.

When the recording surface of the recording paper is only one side, it is made into two layers, and when the recording surface is both sides, it is made into three layers. As the multi-layered paper, a publicly known paper making machine such as a cylinder paper making machine and a multiple Fourdrinier paper machine can be used. At the time of forming into a sheet, a water-soluble polymer substance can be attached using a size press device or the like. Examples of the water-soluble polymer substance include oxidized starch,
There are starches such as dextrin, polyvinyl alcohol and its derivatives, carboxymethyl cellulose, gelatin, synthetic polymer latex, etc. Among them, polyvinyl alcohol and its derivatives and starches are preferable. Alternatively, a solution in which a water-soluble polymer substance is mixed with a filler may be applied. These water-soluble polymer substances are intended to prevent paper powder and filler from falling off the paper surface, improve the surface strength of the paper, and further impart printability. The adhesion amount is
The solid content of the water-soluble polymer is 0.1 to 10 g / m ² , preferably 0.5 to 5 g / m ² .

The recording paper of the present invention can be used as it is after being made into a paper, but it can be treated with, for example, a super calendar or a gloss calender to give its surface smoothness. The present invention will be described in more detail below with reference to Examples, but the measuring methods of the test items described in Examples and Comparative Examples are as follows. Measuring method of beating degree of pulp The beating degree of pulp is measured by TAPPI standard T2.
00 "Processing of pulp in the laboratory, beater process" and T227 "Freeness of pulp". Content of Inorganic Substances The content of inorganic substances in pulp and recording paper is JIS P-
According to 8128 "Method for testing ash content of paper and paperboard", measurement was performed by the following method.

1-2 from pulp or paper to be tested
A g sample is taken and dried in accordance with JIS P-8127 "Paper and board moisture test method", and then the mass is measured with an accuracy of 1 mg to obtain a test piece. The test piece is fully incinerated at a maximum temperature of 900 ° C. together with its lid in a crucible whose ignition mass (accuracy of 1 mg) was measured in advance. When completely burned and black particles are gone, with the lid on, move the crucible to a desiccator, let it cool to room temperature, weigh the contents of the crucible with an accuracy of 2 mg, and perform the same operation until the mass reaches a constant weight. Repeat. The ash content A (%) was calculated by Equation 1.

[0022]

[Formula 1] A = W / S × 100 (%) where W is the mass (g) of ash and S is the mass (g) of the dry test piece. Since the ash content of ordinary pulp itself is about 0 to 0.5% by weight, the ash content of pulp or paper carrying an inorganic substance can be considered as the amount of the oxide of the inorganic substance. Therefore,
The content of the inorganic substance was calculated by multiplying the ash value obtained by measuring the molecular weight ratio between the supported inorganic compound and the oxide of the inorganic compound. That is, in the case of silica-supported pulp,
Since SiO _{2 of the} supported material is still SiO ₂ after ashing, the content rate is ash%, and in the magnesium hydroxide supported pulp, M is
Since g (OH) ₂ is ashed to become MgO, the content rate =
It was calculated as ash × 58.33 / 40.31%.

[0023] The measurement of the basis weight basis weight, using a method according to JIS P-8124 "meter basis weight measurement method of paper". Density The density was measured by the method according to JIS P-8118 “Testing method for thickness and density of paper and paperboard”. The smoothness was measured by measuring the Beck's smoothness with an Oken smoothness tester. Steckigt sizing degree The measurement of Steckigt sizing degree is performed according to JIS P-8122.
The method according to the "Steckigt sizing test method for paper" was used. Tensile Strength The tensile strength was measured by the method according to JIS P-8113 “Test method for tensile strength of paper and paperboard”.

Recording Characteristics Inkjet Printer (IO-735: SHARP
Manufactured by K.K.) were used to evaluate the ink absorbency, color density, color developability, bleeding, and dot shape. (1) To evaluate the ink absorbency, the number of seconds until the printed ink dries was measured. 5 seconds or less ○, 6-10
Seconds are indicated by Δ, and 11 seconds or more are indicated by x. (2) As for the color density, the color density of yellow, magenta, and cyan color inks is determined by a Macbeth densitometer (Kollmor).
gen Corp). (3) With respect to the color forming property, the vividness of the color forming of the color inks of yellow, magenta and cyan was visually evaluated. The items with good color development are shown by O, Δ, and X. (4) As for bleeding, the degree of ink bleeding and flow-out at the overlapping printing boundary portion of magenta and cyan is indicated by good, good, and bad. (5) The shapes of dots are indicated by ◯, Δ, and x, starting from a shape close to a perfect circle. That is, when observing the dots with a stereoscopic microscope, a circle having a substantially circular shape was evaluated as a circle, a circle having a slightly broken shape as a triangle, and an irregular shape as a cross.

[0025]

EXAMPLES The present invention will be specifically described below with reference to examples, but the following examples do not limit the present invention. Example 1 (1) Manufacture of pulp carrying inorganic material Domestic hardwood mixed wood chips (volume weight: 550 kg / m ³ ).
LBKP containing as a main raw material was beaten to a freeness of 300 ml. This beaten pulp was immersed in a No. 3 sodium silicate (molar ratio 3.15, Be (Baume) = 42) solution for 1 hour, deliquored with a centrifugal dehydrator, defibrated with a mixer, and then in a treatment container. And was reacted with carbon dioxide under atmospheric pressure to generate silica inside and outside the fiber. After that, the pulp was disintegrated in water and further washed with water on a 150-mesh wire to wash and remove silica adhering to the outside of the fiber and sodium carbonate as a reaction by-product. The silica content of the silica-supported pulp was measured and found to be 32.0% by weight.

(2) To LBKP beaten to 400 ml of papermaking freeness, 1% by weight of cationic starch (Kate F: manufactured by Oji National Co., Ltd.) based on the pulp solid content, alkylketene dimer neutral sizing agent (SPK-287: Arakawa) Chemical industry) 0.3 similarly
% To make a papermaking raw material, and a high-quality paper having a basis weight of 60 g / m ² was made using a TAPPI type standard handmade machine. This sheet is placed on a filter paper, and then silica-supported pulp is made with a TAPPI-type standard hand-making machine at a basis weight of 10 g / m ² with no chemicals added. The silica-supported pulp sheet and the silica-supported pulp sheet were collected and dried. Then, polyvinyl alcohol (PVA117: made by Kuraray Co., Ltd.) was applied in a size press at a solid content of 2 g / m ² . 1 on the obtained sheet with a super calendar for experiments
A recording paper was manufactured by performing step processing. The results of paper quality analysis of this recording paper and evaluation of inkjet recording suitability are shown in Table 1.

Example 2 As in Example 1, a 60 g / m ² silica-supported pulp sheet and 10 g / m ² of high-quality paper (a sheet containing unsupported pulp and internally added with chemicals) are combined. , Manufactured recording paper.

Example 3 25 parts by weight of the silica-supporting pulp produced in Example 1 was mixed with 75 parts by weight of L-BKP beaten to a freeness of 400 ml to prepare a raw material for the surface layer. Recording paper was manufactured. The silica content of the surface material is
It was 6.8%.

EXAMPLE 4 As in Example 1, 10 g / m ² of silica-supported pulp sheet and 50 g / m ² of high-quality paper (a sheet containing unsupported pulp and internally added with chemicals) were combined. Further, a 10 g / m ² silica-supported pulp sheet was laminated on the back side to prepare a sheet having a three-layer structure, which was subjected to size press and super calender treatment in the same manner as in Example 1 to produce a recording paper.

Example 5 The beaten pulp of Example 1 was impregnated with a No. 3 sodium silicate (molar ratio 3.15, Be = 42) solution in the same manner as in Example 1 and deliquored. The pulp after the deliquoring was defibrated, immersed in a 1.8 N sulfuric acid aqueous solution for 30 minutes, and reacted to generate silica inside and outside the fiber. The pulp was washed with water on a 150-mesh wire to remove silica attached to the outside of the fiber and sodium carbonate as a by-product of the reaction. The silica content of the obtained supported pulp was measured and found to be 28.5% by weight. Furthermore, the silica-supported pulp in the same manner as in Example 1 with 100 parts by weight, silica-supported pulp 10 g / m ^2, and the combined paper making in the usual pulp 60 g / m ^2, size press, supercalendered to recording paper Was manufactured.

Example 6 The same beaten pulp as in Example 1 was immersed in an aqueous magnesium chloride solution having a concentration of 20% by weight at room temperature for 1 hour. The soaked pulp is deliquored by a centrifugal dehydrator, defibrated in the same manner as in Example 1, immersed in an aqueous sodium hydroxide solution having a concentration of 20% by weight for 30 minutes to cause reaction, and magnesium hydroxide is added inside and outside the fiber. Was generated. This pulp was washed with water on a 150-mesh wire to remove magnesium hydroxide adhering to the outside of the fiber and sodium chloride as a by-product of the reaction. When the content of magnesium hydroxide in this supported pulp was measured, it was 29% by weight. This example magnesium hydroxide supported pulp and conventional pulp Example 1 in the same manner as carried pulp 10 g / m ^2, usually combined paper making pulp 60 g / m ^2, similarly size press coating in Example 1, was treated supercalender To produce recording paper.

[0032] Comparative Example 1 freeness 400 ml LBKP the precipitated calcium carbonate was ^叩 solution in (PC: Shiraishi Kogyo Co., Ltd.) 15% by weight of the pulp solids, the same cationic starch as in Example 1, Kell Circe Ten dimer system in 1% by weight, 0.0%
5% by weight was added and a high-quality paper having a basis weight of 70 g / m ² was made with a TAPPI standard handmade machine. After papermaking, the same polyvinyl alcohol as in Example 1 was applied in a solid content of 2 g / m ² with a size press, and the paper quality and inkjet recording suitability of this recording paper were evaluated.

Comparative Example 2 The ratio of papermaking between silica-supported pulp sheet and woodfree paper was set to 5
A recording paper similar to that of Comparative Example 1 was manufactured except that g / m ² and 65 g / m ² were used, and the paper quality and inkjet recording suitability were evaluated.

Comparative Example 3 As in Example 1, a sheet of 105 g / m ² silica-supported pulp sheet and 5 g / m ² of high-quality paper (a sheet in which chemicals are internally added using unsupported pulp) is combined. , Recording paper was manufactured.

[0035]

[Table 1] As is clear from Table 1, the inkjet recording papers of the present invention obtained in Examples 1 to 6 were
In color inkjet recording, the ink absorbency was fast, the image density was high, the bleeding, color development, and dot shape were excellent, and there was no ink strikethrough.

[0036]

INDUSTRIAL APPLICABILITY The ink jet recording paper having the surface layer of the inorganic material-carrying pulp of the present invention has fast ink absorbency, and an image excellent in density, resolution and color reproducibility can be obtained.
There is no strike through of ink. Furthermore, since it has almost the same appearance and feel as the high quality paper, it is suitable as a color inkjet recording paper.

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Claims (1)

[Claims] 1. An inner layer containing cellulose pulp as a main component, and a pulp which is formed on one or both sides of the inner layer by sheeting and carries a water-insoluble or sparingly soluble inorganic substance inside the cellulose pulp fibers. It has a surface layer as a main component, and the basis weight of the surface layer is 10 to 100 g /
Within the range of m ² , and the total grammage of the surface and inner layers is 9
An ink jet recording paper, characterized in that it is formed by coating in a range not exceeding 0% by weight.