JPH0725225B2 - Receiving paper for thermal transfer paper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to an image-receiving paper for thermal transfer paper using a thermal head.

(B) Prior Art A thermal head is prepared by superimposing a coating layer surface of a thermal transfer paper, which has a heat-fusible substance as a main component on a support sheet, and is coated with ink layers of three primary colors of yellow, magenta, and cyan, and an image receiving paper. The thermal transfer system that heats and melts and transfers is currently widely used.

The image receiving paper used in this system obtains color recording by overlapping the inks of the three primary colors as in the case of color printing, and therefore the transfer amount of ink is 2-3 times that of single color. Therefore, as the ink layer on the image receiving paper becomes the first layer (yellow), the second layer (magenta), and the third layer (cyan), the overlapping of the ink becomes non-uniform and the image becomes uneven. That is, this is called ink spillage and has become a big problem.

On the other hand, if a plain paper is used as the image receiving paper, the above-mentioned drawback of ink overflow can be solved, but since the plain paper has irregularities on its surface, contact with a thermal head is prevented. It has a drawback that it becomes coarse and uneven transfer of ink is likely to occur on plain paper, resulting in a marked deterioration of image quality. In addition, since the ink penetrates too much, the vividness of the color is lacking. Therefore, improvements have been made in the image receiving paper and the thermal transfer paper and the apparatus.

For example, there is Japanese Patent Publication No. 59-16950. The publication describes an ink thermal transfer recording medium in which a water-based paint comprising a water-soluble binder and a pigment is applied on paper. However,
Only using these general materials is still insufficient for full-color printing that requires a clear image.

Further, JP-A-57-182487 describes a heat-sensitive recording sheet comprising an image receiving layer containing an oil absorbing pigment having an oil absorption of 30 ml / 100 g or more. Furthermore, it is described that various oil-absorbing pigments are mixed with various binders and applied. However, there is mutual suitability between a pigment having an oil absorption of 30 ml / 100 g or more and a binder, and there are many problems in obtaining a full color with high resolution.

Further, in JP-A-60-38192, the particle size is 0.1 to 1.0 μm.
It describes an image-receiving sheet containing vinyl polymer fine particles having m and Tg of 80 ° C. or higher. However, it is still insufficient to use fine particles of vinyl polymer as a pigment to obtain a good image quality.

(C) Object of the Invention It is an object of the present invention to provide a melt transfer type image-receiving paper for thermal transfer, which does not cause ink overflow and has a high resolution of a transferred image.

(D) Structure of the Invention As a result of intensive studies in view of the above, the present inventors have been able to provide an image-receiving paper for a melt transfer type thermal transfer paper which does not cause ink overflow and has a high resolution of a transferred image. .

That is, the image-receiving paper in combination with a thermal transfer recording sheet coated with a heat-meltable ink layer, nonionic low polymerization degree water-soluble adhesive with a polymerization degree of 1000 or less and oil absorption (JIS-K5101)
An image-receiving paper for thermal transfer paper, comprising a coating layer mainly composed of 30 to 200 ml / 100 g of a porous pigment and spherical non-porous particles.

More preferably, the average particle size of the non-porous particles is 3 to 25 μm.
m. Further, the non-porous particles are characterized by being selected from at least one of polyethylene resin, polystyrene resin, ethylene-vinyl acetate copolymer and vinyl chloride resin.

The present invention will be specifically described below.

First, the overflow will be described in detail. In the thermal transfer system, three primary colors of yellow, magenta, and cyan are sequentially printed, and red and yellow are used for magenta and cyan, green is used for yellow and cyan, blue is used for magenta and cyan, and black is created by mixing three colors. For this reason, when plain paper such as high-quality paper is used, its surface is rough, so the contact with the thermal transfer paper is rough and transfer unevenness is likely to occur. It does not look like a finish. It is also known to use coated paper as an alternative to plain paper. However, the image receiving paper coated with the pigment is improved in terms of resolution of the transferred image as compared with the plain paper, but as described above, yellow, magenta, and cyan are printed in the order of two colors and three colors. In addition, the oil absorption capacity of the image receiving paper becomes saturated, causing ink spillage, which eventually leads to uneven shading.
To improve ink spillage and transferred image resolution, an adhesive is required to control the oil absorption capacity of the ink with a porous pigment and apply the pigment to the base paper.

However, using only these porous pigments and water-soluble adhesives, there are limitations in terms of the oil absorption capacity of the ink and the reproducibility of the transferred image.

The image receiving paper of the present invention is mainly coated with a water-soluble adhesive, a porous pigment and spherical non-porous particles.

Next, the porous pigment, the spherical non-porous particles, and the adhesive will be specifically exemplified.

As the porous pigment having an oil absorption of 30 to 200 ml / 100 g, natural or synthetic zeolite, kaolin, calcined kaolin,
Talc, wax, diatomaceous earth, synthetic silica, clay, calcium carbonate, magnesium hydroxide, magnesium carbonate, magnesium silicate, titanium oxide, barium carbonate,
Urea-formalin resin filler, cellulose filler,
Aluminum hydroxide etc. are mentioned. Of these, preferably synthetic silica, synthetic zeolite, calcined kaolin,
It is calcium carbonate.

The spherical non-porous particles having a particle diameter of 3 to 25 μm include polymer fine particles containing vinyl monomers such as styrene, ethylene, vinyl chloride, vinyl acetate and acrylonitrile as a main component, and copolymers thereof. Examples thereof include inorganic fine particles such as glass beads and vegetable fine particles such as starch particles.

Next, examples of the adhesive include nonionic low-polymerization degree water-soluble adhesives having a polymerization degree of 1000 or less, such as polyvinyl alcohol, starch and derivatives thereof or cellulose derivatives.

Among the above-mentioned nonionic water-soluble adhesives, those that form a strong film with a high degree of polymerization are considered to reduce the oil absorption of the ink. In that sense, as in the present invention, a nonionic low-polymerization degree water-soluble adhesive having a polymerization degree of 1000 or less is used as an adhesive for an image-receiving paper for thermal transfer paper and has an oil absorption of 30 to 20.
By forming the image receiving surface with a porous pigment (0 ml / 100 g) and spherical non-porous particles having a particle size of 3 to 25 μm, the image receiving paper has excellent ink oil absorption and high resolution of the transferred image. Can be provided.

Incidentally, other than the above water-soluble adhesive, for example, a water-soluble adhesive having a carboxyl group such as anionic is
It is generally considered to have no affinity with non-polar ink. Further, a water-soluble adhesive having a high degree of polymerization of more than 1000 and a non-water-soluble adhesive such as latex and emulsion form a strong film, and thus the oil absorbency of the ink is poor.

On the other hand, when a porous pigment having an oil absorption of 30 to 200 ml / 100 g is used, the resolution of the transferred image is high in addition to the preferable oil absorption capacity of the ink. Further, when a pigment having an oil absorption of less than 30 ml / 100 g is used, the oil absorption of the pigment itself is too small and the ink overflows due to the problem of the film property of the adhesive. On the other hand, it has an oil absorption of 20 like synthetic silica and white carbon.
If the amount exceeds 0 ml / 100 g, the oil absorbency is good, but the adhesive is consumed more than necessary, resulting in a problem of adhesive strength.

In addition, in the case of spherical non-porous particles, if the particle size is less than 3 μm, there is no great difference from the size of the porous pigment, and the effect of addition is small. If the particle size exceeds 25 μm, problems of smoothness and ink fixability may occur. That is, in the case of large particles, the unevenness of the image receiving surface is correspondingly large, and since the voids between the particles are large, a large amount of ink is present in the voids, and ink peeling easily occurs.

The reason why the oil absorption capacity of the ink and the resolution of the transferred image are improved in the present invention is considered as follows. That is, by adding to the system of the porous pigment and the water-soluble adhesive, spherical non-porous particles slightly larger than the porous pigment, that is, having an average particle diameter of 3 to 25 μm, It is considered that the dispersibility is improved due to the uniformity, and that the ink is evenly distributed as if the ping-pong balls were just spread on the plane between the non-porous particles and the sand was scattered. Further, the porous pigment enters between the non-porous particles, and the ink tightly penetrates into the pores of the pigment, and the peeling of the ink is reduced. Further, the spherical non-porous particles do not consume much adhesive, and the amount of adhesive can be less than that of the porous pigment alone. Therefore, the oil absorbency of the ink is further improved.

Next, the mixing ratio will be described.

The mixing ratio of the porous pigment and the non-porous particles used in the present invention is, for example, 5 to 500 parts by weight, preferably 10 to 100 parts by weight, based on 100 parts by weight of the porous pigment. Further, the nonionic low-polymerization degree adhesive having a degree of polymerization of 1000 or less is, for example, 5 to 100 parts by weight, preferably 10 to 50 parts by weight with respect to 100 parts by weight of the porous pigment, but these water-soluble adhesives are The amount is not limited as long as the coating layer strength can be sufficiently maintained.

The base paper used for the image-receiving paper includes plain paper, coated paper for printing, high-quality paper that does not contain pigment, and glossy paper (for example, dried with a Yankee dryer), synthetic paper and synthetic resin film. It is what is coated on top.

Other additives include pigment dispersants, thickeners, fluidity improvers, defoamers, foam suppressors, release agents, foaming agents, penetrants, colored pigments, colored dyes, fluorescent whitening agents, and ultraviolet absorption. The addition of agents, antioxidants, antiseptics, antifungal agents, etc. is not limited in any way.

Example 1 A plain paper was used as a base paper, and a coating solution having the following composition was applied to this paper to obtain an image receiving paper having a dry coating amount of 10 g / m ² . A super calender was laid with a Becque smoothness meter for about 250 seconds.

Porous pigment Synthetic zeolite 100 parts by weight (oil absorption 50 ml / 100 g) Non-porous particles Polystyrene particles 100 parts by weight (Average particle size 3 μm) Water-soluble adhesive Polyvinyl alcohol 40 parts by weight (Polymerization degree 500) Water 330 parts by weight Evaluation method Is a color hard copy CHC33 made by Shinko Denki Co., Ltd., and the ink surface of the thermal transfer paper (made by Fuji Chemical Paper Co., Ltd.) provided is overlaid on the coating layer surface of the above-mentioned image receiving paper, and each of the three colors of yellow, magenta and cyan is a single color. The degree of ink spillage was evaluated by solid printing of two or three colors, and the dot depth of the transferred image was 250 μm, and the circular appearance was evaluated using the naked eye and an optical microscope. The results are shown in Table-1.

Examples 2, 3, 4 and Comparative Examples 1, 2, 3 Examples 2, 3, 4 and Comparative Examples 1, 2 are the same as Example 1 except that the average particle size of polystyrene particles is changed as shown in Table 1. Further, in Comparative Example 3, an image receiving paper was obtained and evaluated in the same manner as in Example 1 except that polystyrene particles were not added. The results are shown in Table-1.

As is clear from Table-1, when the polystyrene particles having an average particle size other than the range of 3 to 25 μm are used, the oil absorbency of the ink is deteriorated and the resolution is deteriorated. Has a significant adverse effect.

Example 5 and Comparative Examples 4 to 6 The same as Example 1 except that the water-soluble adhesive made of polyvinyl alcohol having a polymerization degree of 1000 used in Example 1 was replaced with the water-soluble adhesive listed in Table 2. Then, an image receiving paper was prepared and evaluated. The results are shown in Table-2.

Examples 6 to 8 and Comparative Examples 7 to 8 The porous particles made of the synthetic zeolite used in Example 1 were replaced by the porous particles listed in Table 3, and the porous particles and polystyrene particles were made non-porous. An image receiving paper was prepared and evaluated in the same manner as in Example 1 except that the mixing ratio with the particles was changed (in the same table, the mixing ratio is omitted). The results are shown in Table-3. The total amount of the porous particles and the non-porous particles is 200 weight.

Evaluation criteria Oil absorption of ink ○ Does not overflow even with multiplex printing △ Overflows slightly with multiplex printing × Slightly overflows with single color printing Transfer image resolution ○ Almost no dot splash △ Some dot splash × Dot splash Pretty much

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Sadao Morishita 1-4-1 Toganecho, Katsushika-ku, Tokyo Inside the Central Research Laboratory, Mitsubishi Paper Mills (72) Inventor Chiyoge Yamamoto 3-3 Yamato, Suwa-shi, Nagano Prefecture No. 5 Stock Company Suwa Seikosha (56) References JP-A-61-217289 (JP, A) JP-A-57-182487 (JP, A)

Claims (2)

[Claims] 1. An image-receiving paper used in combination with a thermal transfer recording sheet coated with a heat-meltable ink layer comprises a nonionic low-polymerization water-soluble adhesive having a polymerization degree of 1000 or less and an oil absorption (JIS-K).
5101) is a 30 to 200 ml / 100 g porous pigment and a coating layer mainly composed of spherical non-porous particles having an average particle size of 3 to 25 μm. Receiving paper. 2. The thermal transfer paper according to claim 1, wherein the non-porous particles are selected from at least one of polyethylene resin, polystyrene resin, ethylene-vinyl acetate copolymer and vinyl chloride resin. Image receiving paper.