JPS6356872B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an inkjet recording material (hereinafter also referred to as recording paper) used for recording characters, figures, etc. using a recording liquid. 2. Description of the Related Art Conventionally, recording with recording liquid, that is, ink, has been widely performed using writing instruments such as pens, fountain pens, and felt pens. Also, recently, the so-called
An inkjet recording system has also appeared, and recording liquid is also used here. Incidentally, this inkjet recording method uses various ink ejection methods (for example, an electrostatic suction method, a method that applies mechanical vibration or displacement to the ink using a piezoelectric element, a method that heats the ink to foam it, and uses the pressure applied at that time. ), the method using
Recording is performed by forming ink droplets and attaching some or all of them to a recording material such as paper. In this way, when recording using liquid ink, it is generally necessary that the ink does not bleed onto the surface of the recording paper and cause the print to become blurry, and that the ink is used as quickly as possible after recording. It is desirable that the ink does not dry and accidentally contaminate the paper surface, and that the pigment in the ink fixed on the paper does not discolor. In particular, in the inkjet recording method, the recording liquid (ink) must be absorbed quickly into the recording paper, especially when performing multicolor or full color recording.
Even if ink dots overlap, make sure that the later ink does not disturb or spill out the earlier ink, and that the ink droplets spread on the recording paper and the diameter of the ink dot becomes larger than necessary on the recording paper. The shape of the ink dot must be close to a perfect circle, and the area around it must be smooth. The density of the ink dot must be high and the area around the dot must not be blurred. The color of the recording paper must be white and the contrast with the ink dot must be high. be large, the color of the ink does not change depending on the type of recording paper, there is little scattering of ink drops around the ink dots, and there is no dimensional variation in the recording paper (e.g. wrinkles, spread).
It is necessary to satisfy various requirements such as having a small amount of data before and after recording. but,
Conventionally, it has been understood that meeting these requirements largely depends on the characteristics of the recording paper used, but in reality, plain paper and processed paper meet the above requirements. There is still no recording paper that can meet the requirements. For example, the processed paper for inkjet recording described in JP-A-52-74340 is
Although ink absorption is fast, the ink dots tend to have large diameters, the periphery of the dots tends to blur, and the size of the paper changes significantly after recording. Therefore, the main purpose of the present invention is to
The purpose of this invention is to satisfy the problems that the prior art could not solve in the technical field mentioned above. In particular, the present invention aims to provide a high-performance recording medium (recording paper) that satisfies almost all of the above-mentioned requirements in writing instruments or recording using liquid ink using an inkjet recording method. There is. Therefore, the recording material of the present invention that achieves the above object is composed of an ink-receptive coating layer provided on a liquid-absorbing substrate, and the surface of this coating layer is damaged by irregularly shaped cracks formed. It is characterized in that it is partitioned and the size of the partitioned portion is in the range of 10 μm×10 μm to several hundred μm×several hundred μm. Hereinafter, the present invention will be explained in detail with reference to illustrated examples and examples. First, the configuration of the present invention will be outlined using the schematic diagram of FIG. In the figure, reference numeral 1 denotes a liquid-absorbing substrate made of a porous material such as paper, porous plastic film, or cloth. 2 is a covering layer which receives ink. This coating layer 2 is basically composed of a film-forming resin paint, but various surfactants and porous inorganic particles may be further mixed into the paint. Such surfactants and porous inorganic particles are used in the coating layer 2.
It is a component that can increase the absorption and capture rate of pigments (for example, dyes) in ink, and is preferably used actively in the present invention. and,
As such a component, a white inorganic pigment that is porous and has ionicity on the particle surface can be particularly effectively used in the present invention. Specifically, natural zeolite, synthetic zeolite (e.g., molecular sieve [manufactured by Union Carbide]), calcium carbonate, diatomaceous earth, finely powdered silica (average particle size, 1μ
(below), silica (average particle size, 20μ or less), synthetic mica [general formula: M・Mg2.5(Si ₄・O ₁₀ )・F ₂ , however,
In the formula, M is a hydrogen atom or a metal atom. ], etc. can be used. In the present invention, a coating paint is prepared by mixing and dispersing these particles (generally particles from several hundred millimeters to several microns) alone or in combination in a resin paint. Incidentally, as the resin in this paint, either water-soluble or organic solvent-soluble resin can be used. For example, as a water-soluble resin,
Polyvinyl alcohol, starch, casein, gum arabic, SBR, gelatin, polyacrylamide, polyvinylpyrrolidone, carboxymethyl cellulose, sodium polyacrylate, sodium alginate, etc. Organic solvent-soluble resins include polyvinyl butyral, polyvinyl chloride, polyacetic acid These include vinyl, polyacrylonitrile, polymethyl methacrylate, polyvinyl formal, melamine resin, polyamide resin, phenolic resin, polyurethane resin, alkyd resin, and the like. The mixing ratio of the inorganic pigment particles and the resin component in such a paint is generally 5 to 20 parts by weight of the resin component to 100 parts by weight of the inorganic pigment. To form the coating layer 2, generally 1 g/m ² to 10 g/m 2 is coated on the substrate 1 by a known method (for example, roll coating method, rod bar coating method, spray coating method).
Apply an amount of paint about ² m2. Also, in practical terms,
It is best to apply the coating at a rate of about 2 g/m ² to 5 g/m ² . After such a coating amount is applied, the coating layer is dried as soon as possible. In the coating layer 2 obtained in this way, as shown in a partially enlarged view 2L of a partial area 2L enlarged approximately 50 times, there are irregularly shaped cracks 4 (...the majority of these cracks 4). (reaching the surface of the base 1), the scale-like coatings 3 are closely arranged in a two-dimensional arrangement. The size of one scale-like coating 3 is not particularly limited, but is approximately 10 μm.
×10 μm to several hundred μm×several hundred μm is common, and the width of the crack 4 is also not particularly limited in the present invention, but is usually about several μm. Incidentally,
Individual sizes and shapes of the scale-like coating 3, and cracks 4
The width etc. of the coating can be arbitrarily changed within the above-mentioned range by adjusting or controlling the composition of the coating material or the film forming conditions, especially the drying conditions after coating. When ink adheres to the coating layer 2 described above, the pigment (for example, dye) in the ink is selectively adsorbed to the area of the coating 3 and captured, while most of the solvent in the ink is After passing through the crack 4, it is quickly absorbed into the substrate 1.
As described above, in the present invention, since the pigment in the ink is captured almost at the outermost surface area of the recording paper, the color development is extremely good. In addition, the solvent in the ink quickly migrates to the underlying substrate through the cracks, so
An apparent dry state is quickly achieved on the surface of the recording paper. Furthermore, the scale-like coating 3 is particularly effective in preventing ink dots from becoming unnecessarily large, dots with high concentration, and the periphery of the dots from becoming blurred. This is because the dye is intensively adsorbed. The quality of this adsorption ability is determined mainly by the surface physical properties and chemical properties (for example, ionicity) of the coating 3 itself, surfactant, and pigment particles. Therefore, if the area occupied by the scale-like coating 3 in the coating layer 2 is extremely small, there is a disadvantage that the capture rate of the dye decreases and the color development and density of the dots decreases. If it is extremely large, the amount of ink transferred to the substrate increases, resulting in the so-called ink strike-through phenomenon, and there are disadvantages such as deterioration of the dot shape. Therefore, these aspects are preferably avoided. Here, more detailed examples will be described to illustrate the effects of the present invention. Example 1 Silica (100 parts by weight) and polyvinyl alcohol (20 parts by weight) were dispersed and dissolved in water, and then ground and mixed in a ball mill for 12 hours to obtain a slurry. The slurry was applied to 5 sheets of base paper (basis weight, 60 g/m ² ).
Each was coated on one side of the paper so that the dry solid content was approximately 4 g/m ² . Next, these were dried under the following conditions to prepare recording paper samples. *Drying conditions Sample: Naturally dried by leaving. Sample: 2 hours in oven (60℃). Sample: 30 minutes with 90℃ hot air. Sample: 1 minute with 110℃ hot air. Sample: 2 hours with 180℃ hot air. Then, take electron micrographs (X200) of the surface conditions of each of the above samples, faithfully reproduce them, and make a second
It is shown in Figs. Table 1 below summarizes the results of a comparative study of the characteristics in inkjet recording of each of the samples thus obtained. In addition, in Table 1 below, the dot density was measured using a Sakura microdensitometer PDM-5 (manufactured by Konishiroku Photo Industries Co., Ltd.), with a slit width of 30μ in width and 30μ in height, and a slit width in the X-axis direction. Electric speed 10μ/sec, chart feed speed 1mm/
The feed speed ratio of the sample to the sec chart is the result of measurement at 1/100 times. The dot diameter was determined by measuring the diameter of the printed dot using a stereomicroscope. The fixing time can be determined by using a device in which a rubber roller is placed a certain distance from the inkjet head used, and the paper feeding speed is varied to change the time it takes for the ink dot to contact the rubber roller. The time taken from when ink dots were generated to when ink no longer adhered to the roller was measured. In addition, the ink ejection opening diameter (orifice diameter) of the inkjet recording device used here was 50μ,
The ink used had the following composition. Water Black 187L (manufactured by Orient Chemical Co., Ltd.) 10 parts by weight diethylene glycol 30 〃 Water 60 〃 Ink physical properties: Viscosity 3.8 cps (measured with Tokyo Keiki E-type rotational viscometer) Surface tension 52.4 dyne/cm (Kyowa Kagaku hanging plate surface) (measured with a tension meter)

[Table] Example 2 Diatomaceous earth (100 parts by weight) and sodium alginate (15 parts by weight) were dispersed and dissolved in water, and ground and mixed in a ball mill for 15 hours to prepare a slurry. This slurry was applied to the surface of a base paper having a basis weight of 65 g/m ² so that the dry solid content was 4 g/m2, and was dried with hot air at 180° C. for several seconds to prepare a recording paper. When an electron micrograph was taken of the surface of this coating layer, a photograph almost equivalent to that shown in FIG. 6 was obtained. Further, when inkjet recording was performed on this recording paper in the same manner as in Example 1, the results were almost the same as in the case of the sample of Example 1. Examples 3 and 4 Inkjet recording was performed on the same sample as that obtained in Example 1 using the inks shown in Table 2 below in the same manner as in Example 1, and the results are shown in Table 2 below. It was hot.

[Table] Note that the numbers in parentheses in the ink composition column indicate parts by weight, and all other numbers are based on Example 1. Example 5 Using the same sample as in Example 1, cyan,
When full-color recording was performed using magenta, yellow, and black inks, the fixing time, dot density, and dot diameter were almost the same as in Example 1, and each color was extremely clear. Full-color photographs with good color reproducibility were reproduced. Example 6 When printing was performed using a commercially available fountain pen on the recording paper obtained in Example 2, there was no smearing, the ink was absorbed quickly, and very clean characters were written. As mentioned above, in the present invention, the attached recording liquid (ink) is quickly absorbed into the inside of the recording liquid (ink).
Even if different colors of recording liquid adhere to the same spot repeatedly within a short period of time, there is no phenomenon of the recording liquid flowing out or seeping out, and the spread of ink dots can be prevented.
It is possible to provide a recording material particularly suitable for multicolor inkjet recording, which can suppress image quality to a level that does not impair sharpness.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the structure of the present invention, and FIGS. 2 to 6 are all copies of electron micrographs of the surface of recording paper according to the present invention. In the figure, 1 is a base, 2 is a coating layer, 3 is a scale-like coating, and 4 is a crack.

Claims (1)

[Scope of Claims] 1 An ink-receptive coating layer is provided on a liquid-absorbing substrate, and the surface of this coating layer is divided by formed irregularly shaped cracks, and the size of the divided portion is However, the size ranges from 10μm×10μm to several hundred μm×several hundred μm.
A recording material for an inkjet, characterized in that the recording material is in the range of m. 2. The recording material for an inkjet according to claim 1, wherein the width of the crack is several μm. 3. The recording material for an inkjet according to claim 1, wherein the cracks reach the substrate.