JPS61286187A - Receiving paper for thermal transfer printer - Google Patents

Abstract

PURPOSE:To obtain a coated paper which has a matte tone on a visual basis and has a high surface smoothness required for use as a receiving paper for a thermal transfer paper, by chemically modifying the surface of a coated layer. CONSTITUTION:The coating amount of the coated paper is at least 5g/m<2> on an oven-dry weight basis. A calcium carbonate pigment with a particle diameter of 0.1-1.0mum is contained in the coating material in an amount of 40-100wt% based on the total amount of pigments. The coated paper is provided with a smoothness equivalent to a glossiness of at least 55% after providing the coated layer. The surface of the coated layer is modified by an acid or an acidic or basic salt. Accordingly, a receiving paper for a thermal transfer printer having a glossiness of at least 50% and an OKEN-type Bekk smoothness of not lower than 200sec can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to printer paper, and more specifically to a recording receiving paper for thermal transfer printers, which is used in thermal transfer printers using a heat-melting ink ribbon to sharply transfer molten ink and to improve the degree of decomposition. The present invention relates to a receiving paper on which characters and images with high quality can be easily obtained.The present invention also relates to a paper having a matte finish and high smoothness, which can be used as paper for thermal transfer type kanji printers, full-color printers, etc.

(Prior art and its problems) Recently, market demand for color printers has increased, especially as printers using the fusion type thermal transfer method can print on plain paper and can produce clear color images with relatively compact devices. It's attracting a lot of attention.

These melt-type thermal transfer printers can print film,
An ink sheet consisting of a base material such as thin paper and a layer of hot melt ink is used. A receiving paper made of plain paper, such as normal high-quality paper, is superimposed on this ink sheet, and the heat from the thermal head transfers the heat-melting ink to the receiving paper only in a necessary portion to form an image. Since pigments can be used as the main component of the colorant in the ink, it is possible to preserve the print permanently. However, even if such a melting type thermal transfer method is a plain paper recording method, it is not possible to print images of the same high standard on any paper, and it is necessary to provide printing suitability according to each application. Various technologies have been published.

For thermal transfer printer paper, in order to obtain good printing, the receiving paper should be high-quality paper, etc., which is calendered to have an Oken Peck smoothness of 100 seconds or more, preferably 200 seconds or more. It is known that images become clearer.

However, in color printing, when printing mixed colors such as blue, violet, and green obtained by overlapping monochromatic colors yellow, cyan, and i-zenta, when using high-quality paper as the receiving paper, the uniformity of hue and density cannot be achieved. However, it is difficult to obtain characters and images that are unnecessary and have great character.

Regarding decomposition power, printers with 16 dots/wa and 52 dots/gourd have been developed, but it is no longer possible to obtain satisfactory images when using so-called plain paper with exposed cellulose fibers on the surface. .

In order to improve these problems, a proposal has been made (Japanese Patent Laid-Open No. 57-182487) to obtain a good transferred image by providing an oil-absorbing pigment on the paper base material, and the method involves calendering the coated paper. A method has been proposed for increasing smoothness and improving dot reproducibility during thermal transfer.

Furthermore, most of the pigments used in coated printing paper are listed as the pigments, but strict reproducibility in the halftone dots of thermal transfer printing cannot be achieved with all of these pigments. Furthermore, due to the calendering process, the paper surface has a high level of gloss and glare to improve smoothness, making the paper surface difficult to read unlike plain paper.

The smoothing process is generally performed using a heating and pressurizing mechanism, e.g.
For example, it is carried out using finishing equipment called super calender, calender, machine calender, and thermal calender. For example, paper with a gloss level of 55 or higher is coated with a cross-like finish, paper with a gloss level of 40-554 is coated with a mid-gloss coat, paper with a gloss level of 20-40% is coated with a dull tone, and paper with a gloss level of 20% or less is coated with a dull tone. is called matte coated paper. Conventionally, these types of paper have been manufactured by varying the strength of the smoothing process described above.If the smoothing process is strong, the paper becomes coated paper with a strong gloss, which is visually different from plain paper.

In order to use pigment-coated paper as a receiving paper, it is necessary to perform a highly smoothing treatment, and the pigment-coated type receiving paper inevitably has a cross tone.

(Objective of the present invention) The present invention provides a novel coated paper that visually has a matte appearance and a coated paper surface that has high smoothness required as a receiving paper for thermal transfer printers. The purpose is to

That is, the object of the present invention is to provide a coated paper in which the image area transferred from the ink film has a high degree of gloss, and a printed matter with high contrast with the non-image area having a low white paper glossiness and high resolution can be obtained. .

(Structure of the Invention) The present invention provides 0.0% to all pigments in the paint. A coating film formed by single-stage coating of pigment-coated paper coated with a paint containing 40% by weight or more of calcium carbonate of ~1.0 μm at a ratio of 597 m'' or more by absolute dry weight, or This is a receiving paper for a thermal transfer printer, characterized in that the surface of the final coating layer formed by multi-stage coating is modified with an acid or an acidic to neutral salt.

However, in order to satisfy the seemingly contradictory relationship between white paper gloss and surface smoothness, which is the objective of the present invention, it is necessary to incorporate an innovative idea. Therefore, in order to break the balance between white paper gloss and surface smoothness, the inventors investigated the individual factors that influence each, namely, the coating layer surface's 0 to 1
Ultra-microscopic roughness with a width of 0.2 m, microscopic roughness with a width of 10 to 100 μm, macroscopic roughness represented by roughness of 100 μm or more,
Furthermore, physical properties such as pore size, distribution, and the microscopic interface state of the surface layer were examined in detail9.

They have also found that the white paper glossiness and the surface smoothness measured with a smoothness meter are not necessarily influenced by the same factors.

Therefore, as a result of intensive research and investigation into a method for forming a coating layer that can reduce the slight roughness of about 10 to 50 pongee widths, which is a necessary condition for making the white paper glossy like a pine tree, we have arrived at the present invention. did.

The objects of the present invention can be achieved by secondarily chemically modifying the surface of the coating layer once formed.

The base paper before the modification treatment used in the present invention may be coated in a single stage or in a multi-stage coating, but the coating amount of the single-stage coating layer or the final coating layer in the multi-stage coating is at least completely dry. 51/mj or more by weight, and generally the total pigment of coated paper for thermal transfer is 70 to 80% (weight ratio) of the total solid content in the paint.
However, in this total pigment, the particle size Q is 1 to 1.0 μm (
It is necessary that the pigment contains 40 to 100% by weight (preferably 60 to 80%) of calcium carbonate pigment having a diameter of α2 to 0.7 μm. Further, after the coating layer is formed, this base paper must be given smoothness with a gloss level of 55% or more by finishing equipment such as a super calender. If the final coating layer in a single-stage coating layer or multi-stage coating is less than 5 t/m, the internal permeation of the modifying liquid becomes significant, which may cause non-uniformity of the modified coating layer and result in formation. If calcium carbonate, which is easily reacted with the modifying solution, i.e., calcium carbonate with a particle size of α1 to 1.0 μm, is less than 40%, the white paper gloss after the modification treatment cannot be lowered to the desired level. Furthermore, even when the particle size of calcium carbonate is smaller than the above range, it is difficult to reduce the white paper gloss, and when extremely coarse calcium carbonate is used, or when the base paper If the smoothness of the pigment-coated paper (before modification) does not reach the above level, the surface of the modified coating layer will have an excessively rough structure, and the continuity of the ink film after transfer will deteriorate. As a result, the desired high surface smoothness cannot be obtained.In the present invention, there are no restrictions on the composition of the base paper, the components of the coating layer other than the pigment, the coating method, etc.

On the other hand, as a modification liquid, zinc sulfate, aluminum sulfate,
Acids or acids that are reactive with calcium carbonate, such as formic acid, calcium formate, sodium formate, calcium acetate, etc.
Although an aqueous solution of a neutral salt can be used, strong acids such as hydrochloric acid and sulfuric acid are not preferred from the viewpoint of adverse effects on the strength of the coating layer and the working environment. Moreover, ammonium salts of the above acids can also be used. Furthermore, by changing the concentration of the above-mentioned aqueous solution, the white paper glossiness can be set to an arbitrary level, but the concentration level differs depending on each treatment solution. The acids and salts used in the method of the present invention plug the ultramicroscopic pores with a width of 10 μm or less on the surface of the coating layer, suppress internal penetration of ink components, and maintain good coverage of the ink film. Ink transfer during thermal transfer tends to be somewhat lower than that of the coated layer before treatment. However, these coated papers are of a level comparable to commercially available coated papers.

There are several methods for surface modification, such as immersing the coated layer in a modifying solution and scraping off excess modifying fluid with a rond or air knife after application. I don't mind.

On the surface of the coating layer modified by the above treatment liquid, excess salt or fine powder, which is presumed to be a reaction product with the treatment liquid components, may adhere and easily detach. Therefore, in order to prevent such a phenomenon, it is preferable to incorporate a suitable amount of a substance having a binder effect. As the binder, synthetic binders such as starch, polyvinyl alcohol, and polyacrylamide can be used, but when salt is used as a modifying liquid component, nonionic-cationic substances that do not impair the activity of the salt's cations can be used. It is necessary to select

However, the purpose of the present invention can be achieved by satisfying the above requirements, but there is a need for countermeasures when bubbles occur during operation, or when it is desired to have a coloring function during reforming. When necessary, various chemicals can be added to the modification liquid, but in this case as well, it is preferable to select nonionic-cationic substances as the chemicals to be added.

Next, the present invention will be explained with reference to Examples, but the present invention is not limited by the Examples.

Example-1 A blade coater was used to coat the felt surface of a base paper of 8,017 m" square meter with a paint having the following composition at 20 t/m" (
Absolute dry weight) was coated, supercalendered, and smoothed to produce a base paper with a gloss level of 65To on the coated surface.

Paint composition first grade kaolinite clay...3
0 parts oxidized modified starch...
3-part styrene, butadiene latex 2
0 parts polyoxycarboxylate...
3 parts epoxy resin... 1 part 1.5, 2.0 and 50% aluminum sulfate (as A4 (804)s, 18 horse 0) and 4 parts of each on the surface of the above coated paper. An aqueous solution containing 1 amount of polyvinyl alcohol was passed through a metering rod at a water content of 55 t/m.
As a result, as shown in Table 1, white paper gloss levels corresponding to mid-gloss, dull and matte coated papers were obtained under each condition.

This was used to make transfer prints using Ze07x(X]nRO!) 240 (trade name: Telecopya thermal transfer printer), and as a result, it had good resolution comparable to commercially available art paper and was as clear as the original painting. It has been shown that the paper has a reed on the same level as commercially available coated paper that has been subjected to ordinary highly smoothing treatment, and is suitable for receiving paper for thermal transfer printers.

Table 1 also shows the evaluation results of the Oken-Beck smoothness and resolution of the coated paper obtained.

Comparative Example-1 The same base paper as in Example-1 was not subjected to finishing treatment, or was smoothed with a super calender under conditions where the gloss level was 50 or less, and then modified under the same conditions as in Example-1. As a result, as shown in Table 2, the glossiness of the white paper decreased as the concentration of the toshi modifier increased, but the surface smoothness did not improve much, and the resolution of printed copies was inferior to that of Example 1. Ta.

Table 2 Comparative Example-2 When treated in exactly the same manner as in Example-1 with the only difference being the paint composition of the base paper, as shown in Table 3), there was very little decrease in white paper glossiness. Although this could be reduced by increasing the concentration of the treatment liquid, the print gloss also decreased at the same time, making it impossible to obtain the desired coated paper.

Coating composition: First grade kaolinite clay... 75 parts ○ The rest is the same as Example-1 Table 3 Example-2 The same base paper surface as Example-1 was coated with 15.20 and 25% formic acid aqueous solution. As shown in Table 4, as a result of treatment using a modifying liquid, a thermal transfer printer-receiving paper was obtained that had white paper gloss equivalent to mid-gloss, dull, and matte coated paper, and had good resolution comparable to commercially available art paper. It was done.

Table 4 Example-5 Secondary kaolinite clay on the felt surface of the same base paper as in Example-1 40 parts
grade kaolinite clay...25 parts Oxidized modified starch/...5 parts Styrene phytadiene latex...18 parts Sodium polyphosphate...2 parts Epoxy resin...1 Using a blade coater, apply a base coat of 915 f/m'' (absolute dry coating weight), and apply /m! (absolute dry coating weight) on top of that using a blade coater. I did it.

As a result, white paper gloss levels corresponding to those of toshi, mid-gloss, dull and matte coated papers shown in Table 5 were obtained.
The surface smoothness is also at a high level comparable to commercially available art paper.
The resolution was also good.

Table 5 Example-4 The surface properties of the base paper obtained in Example-1 were changed to a glossiness value in the range of about 30 to 80% by supercalender, and
．． Modification treatment was carried out using a modification solution containing aluminum sulfate at a concentration of 5% and polyvinyl alcohol at a quarter of this amount. As a result, as shown in Table 6, the desired level of white paper glossiness can be obtained regardless of the glossiness of the base paper, but for high-resolution printing, the glossiness of the base paper must be 50 or higher. Obtained only under certain conditions.

Table 6 Example-5 Additives other than pigments were added to the surface of the base paper in Example-1 under the same conditions as above, but the pigment composition was primary kaolinite clay/
The calcium carbonate ratio was varied from 0/100 to 10010, and the coating was applied to give an absolute dry weight of 2017 m'', followed by finishing to a gloss level of 60% using a super calender, and the same treatment as in Example 4 was carried out.

As a result, as shown in Table 7, calcium carbonate accounts for 40% of the total pigments.
% or more, it was possible to reduce the white paper gloss to the desired dull tone.

Table 7 In addition to the above examples, the inventors have also
Experiments were also conducted regarding the particle size of calcium carbonate in the base paper coating. When the coated amount of the base paper was less than 597 m'' (absolute dry weight), the surface of the modified coating film became extremely uneven and was not worth evaluating. If the particle diameter of On the other hand, when coarser calcium carbonate was used, it was extremely difficult to develop gloss during the stage of smoothing the base paper, so finishing conditions were intentionally strengthened to achieve the desired level. When the paper was finished to a high level of gloss, the porosity of the base paper coating was lost and the reaction with the modifying liquid was insufficient, as described above.

Claims (1)

[Scope of Claims] 1. A paint containing 40% by weight or more of calcium carbonate with an average particle size of 0.1 to 1 μm based on the total pigment in the paint so that the ratio is 5 g/m^2 or more by absolute dry weight. It is characterized by modifying the surface of the coating film formed by single-stage coating or the final coating layer formed by multi-stage coating with an acid or an acidic or neutral salt. Receptive paper for thermal transfer printers. 2. The receiving paper for thermal transfer printers according to claim 1, which has a glossiness of 50% or less and a smoothness of 200 seconds or more as Oken Beck smoothness.