JPS6365036B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a recording material (recording paper) used in an inkjet recording method, and particularly to a recording material that has high ink absorption and excellent ink color development. Recording methods using recording liquid have been common for a long time, such as writing with a fountain pen, but recently, a so-called inkjet recording method has also appeared, and recording liquid is also used here. The inkjet recording method generates small droplets of recording liquid using various operating principles, and performs recording by flying these droplets and adhering them to a recording material such as paper, but it generates little noise and can print at high speed. , is attracting attention as a recording method that allows multicolor printing. Water-based recording liquids are mainly used for inkjet recording in view of safety and printability. As the recording material used in this inkjet recording method, conventional paper has generally been used. However, as the performance of inkjet recording machines improves, such as faster recording and multicolor recording, recording materials for inkjet recording are also required to have more advanced characteristics. In other words, as a recording material for inkjet recording to obtain high resolution and high quality recorded images, 1) it should absorb ink as quickly as possible, and 2) it should not adhere later when ink dots overlap. 3) The diameter of the ink dot should not become larger than necessary; 4) The shape of the ink dot should be close to a perfect circle and the surrounding area should be smooth; 5) The density of the ink dot It is required that the required performance is high, and that the area around the dot is not blurred. Furthermore, in order to obtain a recorded image quality comparable to that of a color photograph using a multicolor inkjet recording method, in addition to the above-mentioned performance requirements, 6) high whiteness, and 7) excellent color development of the coloring components of the ink are required. 8) The number of ink droplets equal to the number of ink colors is
Since the ink may be deposited in layers on the same spot, additional performance is required, such as particularly excellent ink absorbency. However, the reality is that a recording material that satisfies all of these required performances has not yet been found. For example, the inkjet recording paper described in JP-A-52-74304 absorbs ink quickly, but the dot diameter tends to become large, the periphery of the dots tends to blur, and the dimensional change after recording is large. have. SUMMARY OF THE INVENTION An object of the present invention is to provide a full-color recording material for inkjet recording that satisfies the above-mentioned requirements and has particularly high ink absorption and excellent color development. The above and other objects are achieved by the following invention. That is, the present invention provides a recording material for inkjet recording in which a coating layer containing filler particles and a binder is provided on a support, in which filler particles having a size in the range of 3 to 25 μm are included in the coating layer. This is a recording material for inkjet recording, characterized in that 10,000 to 100,000 particles are exposed per 1 mm ² on the surface. The recording material of the present invention is characterized by the unique surface state of the coating layer that functions as a recording liquid receiving layer. In other words, relatively large, amorphous filler particles, which are the main component of the coating layer, appear on the surface of the coating layer in a randomly placed state, and function as ink absorption holes between these particles. It has a structure in which many large voids are scattered,
This is typically shown as the state shown in FIG. Of course,
These filler particles appearing on the surface are also fixed within the coating layer by the binder and do not easily separate from the coating layer. FIG. 1 is a scanning electron micrograph of the surface of the coating layer of the recording material of the present invention, magnified approximately 1,500 times, and clearly shows the surface condition, which could be described as having debris of various sizes scattered. On the other hand, FIG. 2 is an electron micrograph at the same magnification of the surface of a recording material having a conventional coating layer. These surfaces have a surface structure in which the coating layer is flattened while having many micropores that serve as absorption holes for the recording liquid, and are clearly distinguished from the recording material of the present invention. As described above, on the surface of the coating layer of the recording material of the present invention, there are large and numerous voids between the filler particles that serve as ink absorption holes, so when recording with ink is performed, the ink is absorbed into the filler particles. It is quickly absorbed into the gaps and has a large ink absorption capacity. As the support for the recording material of the present invention, it is appropriate to use paper, but cloth, resin film, synthetic paper, etc. can also be used. On the other hand, the coating layer of the recording material of the present invention is basically composed of filler particles and a binder. Examples of the filler particles include white inorganic pigments such as silica, clay, talc, diatomaceous earth, calcium carbonate, calcium sulfate, barium sulfate, titanium oxide, zinc oxide, satin white, aluminum silicate, lipoton, alumina, and zeolite. Examples include organic powders such as ion exchange resin powders and plastic pigments, and one or more of these may be used. In order for the irregular shape of the filler particles to appear on the surface of the coating layer as if scattered rubble, the particle size of the filler particles used should be about 1 to 30 μm, more preferably about 3 to 20 μm. is desirable.
If the particle size of the filler particles is too large, the roundness of the ink dots will be impaired and the resolution of the recorded image will be reduced, which is not preferable. The higher the dye adsorption ability of the filler particles, the more preferable they are, and it is more preferable that they have a porous structure. This is because the color development is better when the pigment in the ink absorbed into the gaps between the filler particles is captured in the outermost layer of the recording material. On the other hand, the binder includes water-soluble polymers such as starch, gelatin, casein, gum arabic, alginate, carboxymethyl cellulose, polyvinyl alcohol, polyvinylpyrrolidone, sodium polyacrylate, and polyacrylamide; synthetic resins such as synthetic rubber latex. Examples include organic solvent-soluble resins such as latex, polyvinyl butyral, polyvinyl chloride, polyvinyl acetate, polyacrylonitrile, polymethyl methacrylate, polyvinyl formal, melamine resin, polyamide resin, phenolic resin, polyurethane resin, and alkyd resin. Further, various additives such as a dispersant, a fluorescent dye, a PH adjuster, an antifoaming agent, a lubricant, a preservative, and a surfactant can be mixed in the coating layer. The recording material of the present invention is prepared by dispersing these coating layer components in a medium such as water, and applying a coating solution onto a support by a roll coating method, a load bar coating method, a spray coating method, an air knife coating method, etc. It can be manufactured by applying the coating to a substrate and then drying it as soon as possible. The mixing ratio of filler particles and binder in the coating liquid is generally 10 to 100 parts by weight of binder to 100 parts by weight of filler particles.
When the parts by weight are appropriate and the average particle size of the filler particles is large, good results are obtained by using as little binder as possible. The amount of the coating layer on the support is usually about 1 to 50 g/m ² (dry coating amount). Also, preferably 2~
It is recommended to apply ^{approximately} 30g/m2 (dry coating amount). The recording material of the present invention, in which a coating layer with a unique surface condition is provided on a support in this way, has extremely high ink absorbency, and recording liquids of different colors overlap in the same place within a short period of time. Even if the recording liquid adheres to the recording liquid, the recording liquid does not flow out or seep out, and provides a clear image with high resolution. Furthermore, it exhibits excellent color development properties and is suitable as a recording material for inkjet recording when performing full-color recording. Hereinafter, the present invention will be explained in more detail with reference to Examples. Example 1 Silica (Nipsil E150, trade name, manufactured by Nippon Silica Kogyo Co., Ltd., average particle size: 5 μm) as filler particles
using polyvinyl alcohol as a binder.
A coating composition was prepared using SBR latex based on the following composition. Silica 100 parts by weight Polyvinyl alcohol 25 〃 SBR latex 5 〃 Water 500 〃 On the other hand, general high-quality paper (basis weight 65 g/m ² ) with a size degree of 35 seconds based on JIS P8122 was used as the support. The above-mentioned coating composition was applied thereon by a blade coater method in a dry coating amount of 15 g/m ² and dried by a conventional method to obtain a recording material.
FIG. 1 shows a scanning electron micrograph of the surface of the coating layer of the recording material obtained, magnified approximately 1500 times. Color inkjet recording was performed on this recording material using the following four colors of ink, and the recording characteristics were evaluated. Yellow ink (composition) CI Acid Yellow 23 2 parts by weight Diethylene glycol 30 parts by weight Water 70 Agenta ink (composition) CI Acid Dred 92 2 parts by weight Diethylene glycol 30 parts by weight Water 70 Cyan ink (composition) CI Direct Blue 86 2 parts by weight Diethylene glycol 30 parts by weight Water 70 〃 Black ink (composition) CI Direct Black 19 2 parts by weight Diethylene glycol 30 parts by weight Water 70 〃 Table 1 shows the evaluation results of the recording characteristics of the recording material. 1) To measure the dot density, measure the printed dots using a Sakura Microdensidometer PDM-5 (Konishi Roku Photo Industry Co., Ltd.).
Measured using a product manufactured by Co., Ltd. 2) The shape of the dots was determined by observing the printed dots with a stereomicroscope, and marking the dots almost circular as ○, those with a slightly distorted circular shape as △, and the irregularly shaped dots as ×. 3) The degree of bleeding was determined by measuring the diameter of the printed dot using a stereomicroscope, and was expressed as how many times larger the diameter of the printed dot was than that of the ink droplet. 4) Color clarity is determined by visually comparing the color clarity of the inkjet recorded images, with the best one being ◎ and the worst being ×, ◎, 〇, △, ×.
We ranked them by rank. 5) Regarding the ink absorbency, when four colors of ink were recorded in layers, no ink flowed out and the image was clear, it was evaluated as ○, and other colors were evaluated as ×. Example 2 Calcium carbonate (average particle size
A coating composition was prepared based on the following composition using starch and SBR latex as a binder. Calcium carbonate 100 parts by weight Starch 30 〃 SBR latex 10 〃 Water 300 〃 On the other hand, the same general high-quality paper as in Example 1 was used as the support, and the dry coating amount of the above coating composition was applied onto this support. It was coated at a rate of 20 g/m ² by a blade coater method and dried by a conventional method to obtain a recording material. This recording material was evaluated in the same manner as in Example 1, and the results are shown in Table 1. Example 3 A coating composition was prepared based on the following composition using talc (average particle size: 7 μm) as filler particles and casein as a binder. Talc 100 parts by weight Casein 20 Water 500 On the other hand, the same general high-quality paper as in Example 1 was used as a support, and the above coating composition was applied onto this support in a dry coating amount of 20 g/m ² A recording material was obtained by coating by a blade coater method and drying by a conventional method. This recording material was evaluated in the same manner as in Example 1, and the results are shown in Table 1. Comparative Example 1 Inkjet recording characteristics were evaluated in the same manner as in Example 1 using commercially available art coat paper (trade name: SK Coat, manufactured by Sanyo Kokusaku Pulp Co., Ltd.) as a recording material. The results are shown in Table 4. In addition,
A scanning electron micrograph of the surface of the coating layer of this paper at a magnification of approximately 1500 times was as shown in FIG.

【table】

【table】 [Brief explanation of drawings]

FIG. 1 shows approximately the surface of the coating layer of the recording material of the present invention.
This is a scanning electron micrograph at 1500x magnification, and Figure 2 is an electron micrograph at the same magnification of the surface of commercially available art coat paper.

Claims (1)

[Claims] 1 In a recording material for inkjet recording in which a coating layer containing filler particles and a binder is provided on a support, filler particles having a size in the range of 3 to 25 μm are coated on the surface of the coating layer at 1 mm ² A recording material for inkjet recording, characterized in that 10,000 to 100,000 pieces are exposed per inkjet recording material.