JPH074962B2 - Inkjet recording sheet - Google Patents

Description

TECHNICAL FIELD The present invention relates to an inkjet recording sheet, and more specifically, in an inkjet recording system using a water-based ink, the color of the ink absorbed and adhered in the sheet structure is clear, Also, it can give an image with a circular dot shape and sharp edges, and has a large surface strength of the sheet. It has the same tactile feel and usability as conventional plain paper, and can record high-resolution images at high speed. The present invention relates to an inkjet recording sheet.

[Prior Art] In an ink jet recording system, in order to obtain a high-quality recorded image, ink adhered to the base material (mainly paper) surface of a recording sheet does not spread irregularly on the surface, However, it is an important requirement to use a substrate that can be quickly absorbed and to have a surface structure that reinforces the color development of the adhered ink, and many proposals have heretofore been made for the means therefor. ing.

For example, by coating a pigment such as silica together with a binder on one side of paper, the whiteness and transparency of silica can be utilized to improve the color developability and liquid absorbability of ink over plain paper.

There is also a report [Japanese Patent Publication No. 60-27588] that a coated type base paper having a high sizing degree is used, but a low-size, non-size paper having a Steckigt sizing degree of 1 second or less is used.

However, such coated inkjet paper has a peculiar coating layer surface containing silica as a main component, and it is unpopular for general printing paper and office paper applications because it impairs the natural feeling of the paper and surface strength, Since the suitability for use such as paper passing property is also a problem, non-coated high-quality paper has been conventionally used for these applications.

In order to produce an uncoated inkjet paper, it is known that a liquid-absorbent pigment such as silica is internally added at the time of paper making, or a non-sized paper is made without adding a sizing agent.

[Problems to be Solved by the Invention] However, in non-sized inkjet papers containing these pigments internally, the ink is widely absorbed in the paper layer and is blocked by the pulp and the pigment, so that Intensity of color development and density are inferior, and dot spread and shape are often irregular and vague. A clear image similar to a coating type that selectively absorbs ink on the surface layer. Was not obtained.

Even when the coating layer is provided on the non-sized paper disclosed in the above-mentioned patent publication, there are problems such as almost the same edge blurring and irregular dot shape.

When a relatively large amount of water-absorbing pigment is added internally, the sheet manufacturing process by the papermaking method is also unstable, and the resulting irregular distribution of the pigment in the paper layer causes unevenness or variations in the images and colors. It may occur, and there may be troubles in use such as generation of paper dust.

The quality and physical / chemical properties of the paper layer structure composed of wood pipe and pigment, which are the main constituents of these coated and internally added inkjet papers, and especially the ink absorbability represented by sizing degree. The basic problem of the effect of functions on inkjet images has not been fully investigated.

The present invention, in an inkjet recording system using a water-based ink, absorbs the water-based ink promptly from the surface of the recording sheet, and the color of the image produced by the ink is fresh, and the ink dot shape is circular, resulting in a sharp edge. An ink jet recording sheet that can reproduce an image and therefore can record a high resolution image at a high speed, and can eliminate the drawbacks of the coating type, the internal addition type and the non-size type, which are the conventional techniques. It is an object of the present invention to provide an ink jet recording sheet having a size degree in a specific range and using a preferable internal addition pigment, and having a preferable surface size coating layer.

[Means for Solving Problems] As a result of research conducted by the present inventors, the above-mentioned problems were found in the ink-jet recording sheet with 70 to 95% by weight of wood pulp.
And 80% or more of particles with a particle size of 0.5 to 1.5 μm, JIS
The Stekihit sizing degree is 2 seconds or more when the main component is 5 to 30% by weight of light calcium composed of calcite whose oil absorption by K 5101 is 30 to 80 ml / 100g and the basis weight is 64 g / m ^2. It was found that setting it to 25 seconds or less can effectively solve the problem. With such a sheet, it is possible to perform high-resolution inkjet recording with clear color development.

In the present invention, the wood pipe used as the main component of the sheet is an ordinary papermaking pulp which can be produced by subjecting a natural wood pipe to a bleaching treatment.

As the pigment used together with the wood pulp, a color-developing white pigment having a high oil absorption and a high specific surface area is used. As the pigment main component, in particular, light calcium carbonate containing 80% or more of secondary particles having a particle diameter of 0.5 to 1.5 μm and having calcite as an oil absorption amount of 30 to 80 ml / 100 g is used. Light calcium carbonate having such a small particle size distribution gives particularly preferable results in improving the dot shape.

Other white pigments can be used in combination with the light calcium carbonate. As white pigments that can be blended, pigments used for internal addition to general paper, such as kaolin, clay, talc, diatomaceous earth, aluminum hydroxide, titanium dioxide, organic pigments (plastic pigment), Zeorex, silica, etc. are used. can do. The content of these white pigments should not exceed 10%.

The proportions of wood pulp and light calcium carbonate pigment are 70 to 95% by weight for the former and 30 to 5% by weight for the latter.

If the amount of light calcium carbonate added is 30% or more, there is a risk of quality problems such as a decrease in color density, impairing the feeling of natural paper, and generation of paper dust. Also, a large difference is not seen in the effects such as the roundness of the dot shape. When the addition of light calcium carbonate is 5% or less, the effect of improvement is not substantially seen.

In the production of the ink jet recording sheet of the present invention, the above-mentioned wood pulp is used together with the pigment in a usual paper making process. At this time, synthetic fibers with high whiteness,
You may use together a synthetic pulp. Paper strength enhancers, retention aids, wet paper strength enhancers, dyes and the like which are commonly used in papermaking can also be used in combination.

The sheet preferably has a thickness of ²⁰ to 200 μm and a basis weight of 20 to 180 g / m ² . Since an inkjet printer requires a sheet having good surface smoothness, it is preferable to set the Beck smoothness to 50 seconds or more by machine calendering or super calendering.

The inkjet recording sheet of the present invention further has a basis weight of 64
The Steckigt sizing degree of a sheet of / m ² must be 2 seconds or more and 25 seconds or less. If it is lower than 2 seconds, there will be problems such as large blurring, large edges, and blurred edges. On the other hand, when the Steckigt sizing degree is 25 seconds or more, absorption is slow, and problems such as stains on an inkjet printer occur, which tends to be difficult to use.

In the inkjet recording sheet of the present invention, in the surface size coating layer, by containing a low saponification degree of polyvinyl alcohol, water-based ink is adsorbed on the surface of the sheet to develop color, by a manufacturing method similar to that of general high-quality paper, Achieves clear coloring of ink dyes and precise reproduction of dots required for inkjet paper while having the same appearance.
It is possible to obtain an ink jet recording sheet that enables high resolution ink jet recording.

In the general manufacturing process, polyvinyl alcohol having a saponification degree of 98 mol% or more, which is called a completely saponified product, is used alone or in combination with starch as a surface sizing agent. However, by using a polyvinyl alcohol having a low saponification degree of 50 to 95 mol%, preferably 80 to 90 mol%, the affinity with the water-based ink causes a specifically high ink dot color density and roundness. I found that I can achieve it.

[Examples] Example 1 As a filler, an average particle size of secondary particles is 0.8 μm and 0.5 μm to 1.
Light calcium carbonate (calcite,
Albafil, Pfizer MSP, oil absorption 40ml / 100g) 10
A bleached kraft pulp that was mixed with a high-speed disperser after adding a dispersant and water using a part, and then beaten in a beater for 20 minutes.
Added to 100 parts. At this time, as an additive, 0.05 part of a sizing agent (Fibrin, manufactured by Oji National), 1 part of kaolin starch, and 0.002 part of methyl violet blue were added. The above was diluted with water to obtain a papermaking material having a concentration of 0.03%.

This raw material was paper-made into fine paper of 65 g / m ² using a fourdrinier paper machine to obtain an inkjet paper having a whiteness of 90%. The ash content (calcium carbonate) was 8.5%. The Stoeckigt sizing degree when the sheet was 64 g / m ² was 7 seconds.

Example 2 A polyvinyl alcohol having a saponification degree of 88% and an average polymerization degree of 1700 was applied to a paper made in the same manner as in Example 1 except that the content of light calcium carbonate (calcite) was changed to 20 parts. 4% concentration aqueous solution of 1 was applied by a size press method at a rate of 1 g / m ² to prepare an inkjet paper. Basis weight 64g / m ²
The degree of size at that time was 19 seconds.

Example 3 A 4% concentration aqueous solution of polyvinyl alcohol having a saponification degree of 99 mol% and a polymerization degree of 1700 was added to a paper made in the same manner as in Example 2 in the same manner as in Example ^{2 at} a rate of 1.0 g / m ² . An ink jet paper was prepared by applying the size press method. Basis weight 64
The Steckigt sizing degree, given as g / m ² , was 19 seconds.

Comparative Example 1 An inkjet paper was prepared in the same manner as in Example 1, except that the sizing agent was not added and the composition was the same as in Example 1. The ash content (calcium carbonate) was 8%. The Steckigt sizing degree was 1 second when the basis weight was 64 g / m ² .

Comparative Example 2 An inkjet paper was prepared in the same manner as in Example 1, except that 15 parts of fine particle silicic acid (Tokusil GUN) was added in place of calcium carbonate in the same composition as in Example 1. Ash (silicic acid)
Was 11%. The Steckigt sizing degree was 4 seconds when the basis weight was 64 g / m ² . Table 1 shows the evaluation results of the inkjet paper in these cases.

Recording Characteristic Evaluation Method The inkjet recording properties of the above-mentioned coated papers were evaluated by using a commercially available inkjet printer with respect to ink absorbency and color development and shape of recording dots.

For the evaluation of ink absorbency, a method of measuring the time (seconds) for the ink bleed on the printed dot portion to dry was used.

The dot shape is indicated by ◎, ○, △, × from the one that is close to the perfect circle of the shape of the dot printed on the paper by the ink jet printer observed under the microscope.

[Advantages of the Invention] The inkjet sheet of the present invention has excellent ink absorbency, dot diameter, and shape, and enables a high-resolution, high-speed inkjet printer that overcomes the drawbacks of the conventional methods. Is.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akira Kobayashi 1-10-6 Shinonome, Koto-ku, Tokyo Oji Paper Co., Ltd. Product Research Laboratory (72) Inventor Kenji Yasuda 1-10-6 Shinonome, Koto-ku, Tokyo (56) Reference JP 61-16885 (JP, A) JP 59-95187 (JP, A) JP 60-87089 (JP, A)

Claims (2)

[Claims] 1. 70 to 95% by weight of wood pulp and a particle size of 0.5
Includes 80% or more of ~ 1.5μm, oil absorption of 30-80ml / 10
5-30 light calcium carbonate consisting of 0g calcite
An ink jet recording sheet, characterized in that a Steckigt sizing degree is 2 seconds or more and 25 seconds or less when the basis weight is 64 g / m ² and the main component is wt%. 2. The ink jet recording sheet according to claim 1, which has a surface layer containing polyvinyl alcohol having a saponification degree of 50 mol% to 95 mol% in a ratio of 0.2 to 5.0 g / m ² .