JPH0237872B2 - - 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 relates to an ink (recording liquid)
The present invention relates to a recording material for inkjet recording which has high absorbency, has an appropriate degree of smearing, provides a good ink dot shape, and provides high pixel density, a method for manufacturing the same, and an inkjet recording method using the same. The inkjet recording method uses an ink ejection method, such as an electrostatic suction method using a high voltage application or a method that applies mechanical vibration or displacement to the ink using a piezoelectric element, to generate small droplets of ink, which are then flown onto paper, etc. This recording method generates little noise and allows high-speed printing and multicolor printing. Inks for inkjet recording are mainly water-based in view of safety and printability, and generally contain a recording agent and a liquid medium. 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 multi-color recording, recording materials for inkjet recording are also required to have more advanced characteristics. A recording material for such inkjet recording must: 1) absorb ink as quickly as possible; and 2) when ink dots overlap, ink that adheres later will not flow onto the previous dot. , 3) The diameter of the ink dot should be the desired size and uniform, 4) The shape of the ink dot should be close to a perfect circle, and the periphery should be smooth, 6) The degree of whiteness should be high, 7) Coloring of the ink The components must have excellent coloring properties, and must meet the following performance requirements. On the other hand, when recording on a recording material using the inkjet recording method, the image to be recorded (original image) is generally divided into evenly divided parts, and each unit (pixel) of the divided image is divided into The original image is reproduced on the recording material by a method of expressing it with one ink dot or a plurality of ink dots during recording. In such a recording method, in order to provide a sufficient recording density to a recorded image, it is necessary to obtain a sufficient pixel density (recording density for one pixel as a whole). To do this, for example, to explain the case where one pixel is expressed as one ink dot using the same amount of ink with the same recording material concentration, it is necessary to spread the ink dots recorded in one pixel as uniformly as possible over the entire pixel. Preferably, it is recorded in This is because, generally, when an ink dot with a small diameter is recorded in one pixel, the recording density of the ink dot itself becomes high, but the pixel density becomes low. On the other hand, as the diameter of the ink dot increases, the recording density of the ink dot itself decreases;
On the contrary, the pixel density increases. This is because the pixel density reaches its maximum when the ink dots spread uniformly over the entire pixel. This is because pixel density is mainly defined by the relative relationship between a recorded portion and a non-recorded portion within one pixel. Further, if recording is performed using a recording material with a higher degree of bleeding, a larger pixel area can be used for recording, and the recording speed can be increased. Therefore, in addition to meeting the above-mentioned required performance, it is necessary for the ink dots recorded in a pixel of a predetermined size to have an appropriate degree of smearing so that they spread uniformly over the entire pixel. required for the material. For example, when ordinary high-quality paper is used as a recording material, the ink absorbency is poor, making it impossible to obtain a sufficiently large ink dot diameter, the shape of the ink dots being extremely poor, and the desired pixel density being unable to be obtained uniformly. In addition, commercially available non-coated paper has sufficient ink absorption, but the ink runs through the fibers of the paper.
The degree of bleeding is uneven within the paper surface, making it difficult to control the shape and size of the ink dots, and local variations in ink dot density occur, making it impossible to obtain sufficient pixel density. Furthermore, inkjet recording paper having a structure in which a coating layer containing a pigment such as silica is provided on a base paper is disclosed, for example, in JP-A-55-51583 and JP-A-58-72495. However, these recording papers are designed to suppress the spread of dots by providing a coating layer on the base paper, and do not provide sufficient pixel density. It is an object of the present invention to satisfy the above requirements, to have high ink absorbency, and to have an appropriate degree of bleeding so that ink dots recorded in a pixel of a predetermined size spread uniformly over the entire pixel. Another object of the present invention is to provide a recording material for an inkjet that provides a good ink dot shape and excellent color development, a method for manufacturing the same, and an inkjet recording method using the same. The above objects are achieved by the following invention. The recording material for inkjet recording of the present invention has a dry coating amount of 1 g/m 2 or more and 5 g/m ² or more of a coating liquid containing at least a filler and a binder on a fibrous base material.
It is characterized by having a surface layer formed by coating an area less than m ² , in which the filler and the fibrous material of the base material are mixed, and a part of the fibrous material appears on the surface. do. The recording material of the present invention is characterized by the unique structure of the surface layer portion of the recording material that receives ink. That is, the recording material of the present invention basically has a base material mainly made of a fibrous material and filler particles attached to the surface of the base material in a very thin manner. The surface layer portion of the recording material that receives the ink of the recording material is a mixture of at least the filler particles and a portion of the fibers constituting the base material. The inkjet recording paper described in the above-mentioned Japanese Patent Application Laid-Open No. 55-51583 is one in which a coating layer containing silica powder and a polymeric binder is provided on a base paper.
That is, it has a structure in which the base paper is completely covered with a coating layer, and is clearly distinguished from the recording material of the present invention, which has a surface layer with a part of the fibrous material of the base material appearing on the surface. Therefore, the effects of the present invention cannot be obtained from the structure of the recording paper disclosed in the publication. Furthermore, the inkjet recording paper disclosed in JP-A-58-72495 also has a structure in which the base paper is completely covered with a coating layer, and a portion of the fibrous material of the base paper is covered with the coating layer. It does not have a surface layer that appears on the surface mixed inside. Therefore, this recording paper is clearly distinguished from the recording material of the present invention, and even if the recording paper disclosed in the publication is used, the effects of the present invention cannot be obtained. In addition, Table 1 in the lower right column of page 3 of JP-A No. 58-72495 shows a recording paper in which the dry coating amount of a coating liquid containing silica on the base paper was 5 g/m ² . Disclosed. However, even with such a small coating amount, the structure of the present invention described above cannot be obtained from the method described in the publication. In contrast, in the recording material of the present invention, as described above, a coating liquid containing at least a filler and a binder is coated on a fibrous base material in a dry coating amount of 1 g/m 2 or more and 5 g/m ² or more. It has a structure in which it is coated in an area of less than ² and includes a surface layer with a characteristic structure, and with this structure, the intended purpose of the present invention is achieved. FIG. 1 is a schematic partial cross-sectional view of a typical example of the recording material of the present invention, taken perpendicular to the thickness direction of the surface layer portion of the recording material. As shown in FIG. 1, the recording material of the present invention basically has a surface layer portion 3, a middle layer portion 2, and a lower layer portion 1. The surface layer portion 3 is made up of a mixture of at least filler particles 6 and some of the fibers 5 of the base material 4 mainly made of a fibrous material, and is a portion that mainly receives ink during recording. The middle layer portion 2 is located below the surface layer portion 3, is a portion made of a base material 4, and has no filler particles 6,
It mainly consists of fibers 5, and this part hardly absorbs ink. The lower layer portion 1 is a portion located below the middle layer portion 2, and may be made of the same type of base material 4 together with the middle layer portion 2, or may be made of a base material 4 different from the base material 4 constituting the middle layer portion 2. It may be constructed of a material or a suitable support. The filler particles 6 are attached and fixed to the surface of the base material 4 in a very thin manner, mainly by a binder (not shown). In the surface layer portion 3, some portions of the fibers 5 are lightly covered with filler particles 6, while other portions are in direct contact with the outside world. The filler particles 6 not only lightly cover the fibers 5 but also penetrate into the gaps between the fibers 5. In this way, the surface layer portion 3 of the recording material of the present invention is formed, in which at least some of the fibers 5 of the fibrous material mainly constituting the base material 4 and the filler particles 6 are mixed. FIG. 2 shows a cut surface of an example of the recording material of the present invention, cut perpendicular to the thickness direction of the surface layer of the recording material.
This is a scanning electron micrograph at 1500x magnification.The filler particles are mainly attached to the surface of the substrate by a binder (not shown), as if scattered very thinly, and are fixed on the surface of the recording material. The state of the surface layer portion of the recording material of the present invention, in which filler particles and some fibers constituting the base material are mainly mixed in the thickness direction, is clearly shown. On the other hand, Figure 3 shows the same magnification of the cut surface of the surface layer of a conventional recording material (product name: Inkjet Paper L, manufactured by Mitsubishi Paper Mills Co., Ltd.) cut perpendicular to the thickness direction of the recording material. This is an electron micrograph. FIG. 3 clearly shows the structure of the surface layer of this recording material, in which countless pulp fibers overlap, and it is clearly distinguished from the recording material of the present invention. When recording with ink is performed on the surface layer of the recording material of the present invention, the ink adhering to the surface of the recording material mainly forms the surface layer 3 where fibers 5 and filler particles 6 are mixed. be absorbed into. Then, it is hardly absorbed into the middle layer portion 2 inside the recording material, that is, hardly absorbed in the thickness direction of the recording material, and spreads in the surface layer portion 3 in the horizontal direction. This is because filler particles are smaller than fibers, so the specific surface area (surface area per unit weight) of filler particles is naturally larger than that of fibers. On the other hand, the ink (recording liquid) is absorbed into the recording material due to the surface energy of the filler or fibers. The ink is then absorbed faster in the areas formed by a large number of filler particles that have more surface energy, ie have a larger surface area, than in the areas made of fibers. Therefore, in the recording material of the present invention, the filler particles are adhered to the surface layer in a very thinly dispersed manner, so that the surface area of the surface layer portion is larger than the inside of the recording material. Because of the difference in absorption speed, the ink can travel faster in the lateral direction than in the thickness direction of the recording material. For this reason, the recording material of the present invention has a large ink smear and fast ink absorption, so that a sufficiently large ink dot can be recorded within the above-mentioned predetermined size pixel. As the base material 4 mainly made of fibrous material of the recording material of the present invention, it is appropriate to use paper.
Cloth or synthetic paper can also be used. In order to suppress the ink absorption in the thickness direction of the recording material as described above, it is recommended to use a base material 4 made of a fibrous material whose liquid absorption is suppressed by a method such as sizing. preferable. For the lower layer portion 1 of the present invention, in addition to the paper, cloth, or synthetic paper used for the base material 4, materials that can be used as a suitable support such as a resin film can be used. On the other hand, one of the other components that basically constitutes the surface layer portion 3 of the recording material of the present invention is the filler 6 fixed to the surface of the base material 4 mainly by a binder. Examples of the filler include silica, clay, talc, kaolin, diatomaceous earth, calcium carbonate, calcium sulfate, satin white, aluminum silicate, alumina, and zeolite, and one or more of these may be used. Particles of the filler are fixed onto the base material so that some of the fibers 5 mainly constituting the base material 4 and the filler 6 are mixed on the surface layer 3 of the recording material. In order to provide good ink absorption and a good degree of bleeding to the surface portion of the recording material, the particle size of the filler used is preferably 0.05 μm to 50 μm, more preferably
The thickness is preferably about 0.1 μm to 20 μm. If the particle size of the filler is too large, the degree of ink bleeding in the horizontal direction of the recording material becomes uneven, making it difficult to control the size and shape of the dots, which is not preferable. Furthermore, if a porous filler is used as the filler 6, the ink attached to the surface of the recording material will penetrate into the porous filler, and the recording agent components of the ink (for example, dyes and pigments) will be absorbed into the porous filler. It is possible to obtain good coloring properties by being adsorbed to a colored filler. On the other hand, the binder for fixing the filler to the surface of the base material 4 includes starch, gelatin, casein,
Water-soluble polymers such as gum arabic, sodium alginate, carboxymethylcellulose, polyvinyl alcohol, polyvinylpyrrolidone, sodium polyacrylate, polyacrylamide; synthetic resin latex such as synthetic rubber latex, polyvinyl butyral, polyvinyl chloride, polyvinyl acetate, polyacrylonitrile, Polymethyl methacrylate, polyvinyl formal, melamine resin,
polyamide, phenolic resin, polyurethane,
Examples include organic solvent soluble resins such as alkyd resins. In addition, the surface layer portion 3 of the recording material of the present invention may contain, in addition to the filler, other pigments such as plastic pigments, dispersants, fluorescent dyes, PH adjusters, etc., to the extent that the effects of the present invention are not impaired. Various additives such as antifoaming agents, lubricants, preservatives, and surfactants can also be mixed. The recording material of the present invention can be produced by coating a coating solution prepared by dispersing ingredients mainly consisting of these fillers and a binder in a medium such as water, using a roll coating method, a rod bar coating method, or a spray coating method. It can be manufactured by coating it on a substrate by an air knife coating method or the like, and then drying it as soon as possible. The mixing ratio of filler and binder in the coating solution is as follows:
Generally, the amount of binder is 10 to 100 parts by weight of filler.
150 parts by weight is appropriate, and when the average particle size of the filler is large, good results are obtained by using as little binder as possible. The coating amount of components including fillers, binders, etc. that are fixed on the substrate is determined by the desired dot diameter and the amount of ink that forms one ink dot and the size of the pixel in which the ink dot is recorded. Selected by. That is, by reducing the coating amount of these components, larger ink dots can be obtained. The coating amount is usually selected from the range of about 1 to 30 g/m ² (dry coating amount), but as shown in the examples below, the coating amount is 1 g/m ² or more
If it is less than g/m ² , for example about 3 g/m ² , it is possible to reliably obtain a recording material having a surface layer with the characteristic structure of the present invention. Further, the thickness of the surface layer portion 3 is approximately 0.5 μm to 10 μm. As described above, the recording material of the present invention, which has a unique structure in the surface layer portion of its cut surface, has high ink absorbency, and moreover, the ink dots recorded in a pixel of a predetermined size cover the entire pixel. Since it has an appropriate degree of smearing so that it spreads uniformly and a good ink dot shape is obtained, it is a recording material for inkjet that can obtain sufficient pixel density and has excellent coloration properties. Furthermore, by using the recording material of the present invention,
By changing the amount of coating components when the same amount of ink is used, it has become possible to control the ink dot diameter to a desired size that is compatible with the width of the pixel. Furthermore, compared to conventional recording materials, larger ink dots can be obtained, recording can be performed using a larger pixel area, and recording speed can be increased. Hereinafter, the present invention will be explained in more detail with reference to Examples. Example 1 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, as a fibrous base material, general high-quality paper with a sizing degree of 35 seconds based on JIS P 8122 (basis weight 65 g/m ² ) is used.
The above-mentioned coating composition was coated onto this support by a blade coater method at a dry coating weight of 3 g/m ² and dried by a conventional method to obtain a recording material. FIG. 2 shows a scanning electron micrograph of a cross section cut perpendicularly to the thickness direction of the obtained recording material at a magnification of 1500 times. For this recording material, the following four colors of ink were used, the droplet diameter was 90 μm, and the pixel size was 300.
Color inkjet recording was performed under recording conditions of ×300, and the recording characteristics of the recording material were evaluated. Yellow ink (composition) CI acid yellow 23 2 parts by weight diethylene glycol 30 〃 Water 70 〃 Magenta ink (composition) CI acid red 92 2 parts by weight diethylene glycol 30 〃 water 70 〃 Cyan ink (composition) CI Direct Blue 86 2 parts by weight diethylene glycol 30 〃 Water 70 〃 Black ink (composition) Direct black 19 2 parts by weight diethylene glycol 30 〃 Water 70 〃 Table 1 shows the evaluation results of the recording properties of the recording material.
When evaluating recording characteristics in Table 1, 1) Pixel density is the reflected optical density when recording is performed on all pixels using a photographic densitometer NML-STD-Tr.
(manufactured by Narumi Shokai). 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 stereoscopic microscope, and 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 ink absorbency, when ink was recorded in layers, no ink flowed out and the image was clear, it was evaluated as ○, and other cases were evaluated as ×. Example 2 Silica (product name: Nipsil) as a filler
E220A, Nippon Silica Kogyo, average particle size 1.0μm)
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, the same general high-quality paper as in Example 1 was used as the fibrous base material, and the above coating composition was dried and coated on this support. A recording material was obtained by coating with a blade coater method at a working amount of 2 g/m ² and drying by a conventional method. A scanning electron micrograph of a section cut perpendicularly to the thickness direction of this recording material at a magnification of 1500 times was almost the same as that obtained in Example 1 shown in FIG. The recording characteristics of this recording material were 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: 1 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 the fibrous base material, and the above coating composition was applied onto this support in a dry coating amount of 2 g/m A recording material was obtained by coating with a blade coater method at a ratio of ² :2 and drying by a conventional method. A scanning electron micrograph of a section cut perpendicularly to the thickness direction of this recording material at a magnification of 1500 times was also almost the same as that obtained in Example 1 shown in FIG. The recording characteristics of this recording material were evaluated in the same manner as in Example 1, and the results are shown in Table 1. Comparative Example 1 Commercially available inkjet paper as a recording material (product name: Inkjet Paper L, manufactured by Mitsubishi Paper Mills Co., Ltd.)
The inkjet recording characteristics were evaluated in the same manner as in Example 1 using the following. The results are shown in Table 1. FIG. 3 shows a scanning electron micrograph of a cross section cut perpendicularly to the thickness direction of this inkjet paper at a magnification of 1500 times. 【table】

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a cut section of an example of the recording material of the present invention cut perpendicularly to the thickness direction of the recording material;
Figure 2 is a drawing substituted for a scanning electron microscope with a magnification of 1500 times to show the particle shape of filler particles in a cross section of an example of the recording material of the present invention cut perpendicular to the thickness direction of the recording material. The photograph and Figure 3 show the second section of the conventional inkjet paper cut perpendicular to the thickness direction.
This is a similar photograph taken in place of a drawing taken by a scanning electron microscope at the same magnification as the photograph in place of the drawing in the figure. In the figure, 1 is the lower layer of the recording material, 2 is the middle layer of the recording material, 3 is the surface layer of the recording material, 4 is the base material mainly made of fibrous material, 5 is the fiber, and 6 is the base material. It is a filling material.

Claims (1)

[Claims] 1. A coating solution containing at least a filler and a binder is applied onto a fibrous base material in a dry coating amount of 1 g/m ² or more and less than 5 g/m ² . 1. A recording material for inkjet recording, characterized in that the filler and the fibrous material of the base material coexist and have a surface layer with a part of the fibrous material appearing on the surface. 2 A dry coating amount of 1 g/m 2 or ^more of a coating liquid containing at least a filler and a binder and having a weight ratio in the range of 10/1 to 10/15 on a fibrous base material 5
g/m ² to form a surface layer on the base material in which the filler and the fibrous material of the base material are mixed and a part of the fibrous material appears on the surface. 1. A method for producing a recording material for inkjet recording, the method comprising: forming an inkjet recording material. 3 It is formed by applying a coating solution containing at least a filler and a binder to a dry coating amount of 1 g/m ² or more and less than 5 g/m ² on a fibrous base material, and the filler By applying ink droplets to a recording material having a surface layer in which the fibrous material and the fibrous material of the base material are mixed, and a part of the fibrous material appears on the surface,
An inkjet recording method characterized in that recording is performed by spreading dots formed by the ink droplets over the entire pixel. 4. The inkjet recording method according to claim 3, wherein a color image is recorded using a plurality of color inks.