JP2725789B2 - Thermal transfer image recording sheet - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a thermal transfer image recording sheet using a hot-melt ink sheet. More specifically, the present invention provides a print and an image transferred to the surface of a recording sheet, in which the ink density is uniform, the dot shape is uniform, the resolution is high and clear, and moreover, compared with conventional plain paper. The present invention relates to a thermal transfer image recording sheet having a similar feel and suitability for use.

[Conventional technology]

Recently, a hot-melt type image transfer method using a thermal head or a dye sublimation type image transfer type printer can print clear prints and images with a compact device,
Widely used in Japanese word processors (word processors), facsimile machines, dry copiers, color graphics printers, color video printers, etc.

Image thermal transfer by a thermal fusion type image transfer system printer is performed by superposing an image recording sheet such as high quality paper on an ink sheet consisting of a thin film substrate and a thermal fusion ink layer, and heating from a thermal head corresponding to the image signal. , Heat the ink on the ink sheet according to the image,
An image is formed by transferring the hot-melted ink to a recording sheet. In the case of a monochrome printer, a single color ink is transferred once to form an image. In the case of a color printer, images of different colors such as yellow, magenta, cyan, and black are transferred, and these are superimposed to form a color image. To form

In a hot-melt image transfer system printer, the sharpness of the transferred image is affected by the smoothness of the recording surface of the recording sheet, etc.In order to enable high quality printing and image formation, the performance and characteristics of each printer Various inventions and inventions have been proposed for imparting the optimum image receiving suitability to a recording sheet according to the requirements.

For example, normal fine paper having a surface having a Beck smoothness of about 10 to 50 seconds is subjected to a smoothing process using a super calender or the like, and the Beck smoothness is improved to 100 seconds or more. Is known to be improved.

An invention in which an oil-absorbing pigment (most of pigments used for printing coated paper) layer is provided on a recording sheet to improve the receptivity of a thermal transfer ink image and obtain a transferred image without unevenness in density (Japanese Patent Laid-Open No. 57-182487). This has resulted in a considerable improvement in the receptivity of the recording sheet to the thermal transfer ink image.

The performance required for document printer paper in Japanese word processors, etc., which is an important application of the thermal image transfer system, has been further enhanced, and high quality paper with a Beck smoothness of 100 seconds or more is simply used as a recording sheet. Alone, it is difficult to make a highly clear print that satisfies the demand, and if the smoothness is too high, there are criticisms such as producing an unnatural gloss on the surface of the recording sheet and impairing the style of the recording sheet .

Further, by using a thermal transfer image recording sheet coated with an oil-absorbing pigment, it is possible to obtain a high-resolution print / image with a good dot shape, a low-gloss surface, less density unevenness of the image. . However, such a conventional recording sheet coated with an oil-absorbing pigment is unsatisfactory in terms of style, feeling, surface strength, and the like required for official documents and the like.

[Problems to be solved by the invention]

In view of the current situation of the thermal transfer image recording sheet as described above,
The present invention seeks to provide a thermal transfer image recording sheet that is uniform in the density and dot shape of a received ink image, and has the same style, feeling, and surface strength as conventional high-quality paper. is there.

[Means for solving the problem]

The thermal transfer image recording sheet of the present invention is composed of a paper mainly containing a mixture of 50 to 90% by weight of wood pulp and 10 to 50% by weight of light calcium carbonate particles, and has a Beck smoothness of 100 seconds or more. Having an image recording surface having, the light calcium carbonate particles have a hexagonal columnar calcite crystal structure, and 10
oil absorption of at least 50 ml / 100 g, of which at least 50 wt.
It has a particle diameter of about 1.5 μm.

In the paper forming the recording sheet of the present invention, the content of light calcium carbonate is 10 to 50% by weight,
Preferably it is in the range of 30% by weight. The content of the light calcium carbonate particles having a particle diameter of 0.5 to 1.5 μm is 50% by weight or more, and preferably 70% by weight or more.

The use of the thermal transfer image recording sheet of the present invention can improve the certainty and high density of dots and the intelligibility of characters when complex characters such as Chinese characters are clearly printed. Can be improved.

Generally, calcium carbonate is used as a preferred filler for neutral paper. Calcium carbonate is roughly divided into heavy calcium carbonate and light (precipitable) calcium carbonate. Heavy calcium carbonate is obtained by pulverizing naturally occurring limestone in a dry or wet manner. Light (precipitated) calcium carbonate is obtained by dissolving quicklime in water and blowing a carbon dioxide gas thereinto to cause a reaction. The particle size and distribution of the filler of heavy calcium carbonate are controlled by grinding conditions. Light calcium carbonate can change the particle shape, particle size, its distribution, and crystal structure by changing the reaction conditions.

The crystal structure of light calcium carbonate is divided into three types: calcite (hexagonal), aragonite (orthogonal), and vaterite (hexagonal).

The light calcium carbonate used in the present invention has a secondary particle diameter of 0.5 to 1.5 μm, but has a content of 50% or more, preferably 70% or more, and an oiling degree of 10 ml / 1.
It is not less than 00 g and has a hexagonal columnar calcite crystal structure. Calcite crystals may also form spindle-shaped particles. Aragonite crystals have a column shape that is narrower than a spindle shape. Natural calcium carbonate naturally has an irregular particle shape.

As a result of comparative evaluation of the recording characteristics of the neutral paper containing these various calcium carbonates using a thermal transfer printer, it was found that the paper containing hexagonal columnar calcite was most excellent. Although the detailed reason is not clear, it is presumed that since the filled filler is densely and uniformly distributed inside the paper, transfer ink receptivity is improved. Since the heavy calcium carbonate has an irregular crystal form and a small oil absorption, it is considered that the paper containing the calcium carbonate has poor acceptability of the transfer ink.

With respect to the light calcium carbonate particles, if the particle size is small, the oil absorption generally increases, and the receptivity of the transfer ink of paper containing the particles increases. However, if the particle size is too small, the yield at the time of filling becomes poor, and it becomes practically impossible to use this for papermaking. Further, when the content of the light calcium particles having an undersized particle becomes high, it is considered that the transfer ink receptivity and the quality of the transferred image of the paper obtained therefrom become poor. In the light calcium carbonate used in the present invention, the content of particles having a particle diameter (major axis) of 2 μm or more is preferably 50% by weight or more.

The light calcium carbonate used in the present invention has an oil absorption of 10 ml / 100 g or more, and this value is preferably larger, more preferably 20 ml / 100 g or more.

In the recording sheet of the present invention, when the content of light calcium carbonate is lower than 10% by weight, the obtained recording sheet has substantially no improvement effect. On the other hand, 50
If it is contained in an amount greater than 10% by weight, the resulting recording sheet may have a reduced color density of the ink image received, impair the feeling of natural paper, and may cause quality problems such as generation of paper dust. Even if light calcium carbonate is contained in an amount of more than 50% by weight, improvements in dot shape, stable reproduction and the like of an image received by the obtained recording sheet are not necessarily obtained.

In addition to light calcium carbonate having a hexagonal columnar calcite crystal structure, as a pigment to be incorporated into paper, light calcium carbonate, heavy calcium carbonate, etc. Clay, calcined clay, titanium dioxide, aluminum hydroxide,
Pigments such as talc, calcium silicate, calcium sulfate, magnesium silicate and synthetic amorphous silica may be used in combination.
The content of these combined pigments in the recording sheet is preferably 5% by weight or less.

The paper used in the present invention is a neutral paper, JIS-P
Those with a water extraction pH of 6 to 9.5, as measured according to -8133, are preferred. In general, paper produced by a normal papermaking process using wood pulp (particularly bleached wood pulp) and light calcium carbonate is used. However, synthetic fibers or synthetic pulp having high whiteness may be used in combination as long as the object of the present invention is not hindered. However, the combined amount is 30
It is preferable that the content be not more than weight%. General papermaking additives such as paper strength enhancers, retention aids, wet paper strength enhancers, and dyes can also be used.

The weight of the recording sheet of the present invention is 20 to 180 g / m ² , and the thickness is 2
It is preferably from 0 to 200 μm. The image recording surface of the recording sheet of the present invention has a smoothness of 100 seconds or more. For this purpose, it is preferable to perform a surface smoothing treatment using a calender or the like.

〔Example〕

Next, the thermal transfer image recording sheet of the present invention will be described with reference to examples. In the examples, "parts" means "parts by weight of solid content".

Example 1 As a filler, 30 parts of the following light calcium carbonate: Albafil Pfizer MSP Co., Ltd. Average particle diameter: 1.5 μm Content of particles having a particle diameter of 0.5 to 1.5 μm: 67% (weight) Oil absorption: 32 ml / A dispersant and water were added to 100 g of hexagonal columnar calcite crystals to perform high-speed dispersion mixing. Separately, 100 parts of bleached kraft pulp prepared by beating in a beater for 20 minutes were mixed with the light calcium carbonate. At this time, as an additive, a sizing agent (trade name: Fibran 81
Add 0.05 part of Oji National Co., Ltd.) and 1 part of cationic starch (trade name: CATO-F, manufactured by Oji National Co., Ltd.), dilute with water to adjust the total concentration to 0.03%, and make papermaking raw material. did. The raw material is paper-made using a fourdrinier multi-cylinder paper machine to produce a high-quality paper (papermaking sheet) having a whiteness of 72 g / m ² and a brightness of 93%. A recording sheet was prepared. Its ash (calcium carbonate) was 23.5%.

 The recording sheet was subjected to an image heat transfer test.

Using a commercially available Japanese word processor with a built-in fusion heat transfer printer, a kanji image is thermally transferred from a black ink sheet with an ink layer on a polyester substrate onto a recording sheet, and the sharpness and dot shape of the character image The uniformity of the ink density was visually evaluated.

 Table 1 shows the results.

Example 2 The same operation as in Example 1 was performed. However, as fillers, 20 parts of the same light calcium carbonate as described in Example 1 and 15 parts of the following heavy calcium carbonate were used.

Trademark: Whiten P-10, manufactured by Toyo Fine Chemical Co., Ltd. Average particle size: 2.0 μm Oil absorption: 26 ml / 100 g Content of those having a particle size of 2 μm or more: 55% Other stock components used were the same as those in Example 1. . The obtained papermaking sheet was smoothed with a super calender to produce a recording sheet having a Beck smoothness of 300 seconds. Its ash (calcium carbonate) was 22.0%.

 Table 1 shows the results of the thermal transfer test.

Comparative Example 1 The same operation as described in Example 1 was performed. However, 20 parts of the following light calcium carbonate was used as a filler.

Trademark: Agonite, manufactured by Shiroishi Kogyo Co., Ltd. Average particle size: 2.0 μm Oil absorption: 26 ml / 100 g Orthorhombic aragonite Content of particles having a particle size of 0.5 to 1.5 μm: 45% The same was used.

The recording sheet produced by smoothing this papermaking sheet with a super calender had a Beck smoothness of 300 seconds.
The ash content (calcium carbonate) was 17.1%.

 Table 1 shows the results of the thermal transfer test.

Comparative Example 2 The papermaking sheet of Example 1 was processed with a machine calendar,
The smoothness was set to 30 seconds.

 Table 1 shows the results of the thermal transfer test.

Comparative Example 3 The papermaking sheet of Example 2 was processed with a machine calendar,
The smoothness was set to 50 seconds.

 Table 1 shows the results of the thermal transfer test.

Comparative Example 4 The same operation as described in Example 1 was performed. However, 20 parts of heavy calcium carbonate (trademark: Whiten P-10, manufactured by Toyo Fine Chemical Co., Ltd.) was used as a filler. The other stock components were the same as in Example 1. The obtained papermaking sheet is smoothed with a super calender, and a Beck smoothness of 20
A recording sheet of 0 seconds was obtained. Its ash (calcium carbonate) was 15.5%.

 Table 1 shows the results of the thermal transfer test.

Comparative Example 5 The same operation as that described in Example 1 was performed. However, instead of light calcium carbonate, 20 parts of the following particulate silica (trade name: Fine Seal, manufactured by Tokuyama Soda) was used as a filler.

Average particle diameter: 2.6 μm Oil absorbent: 280 ml / 100 g This papermaking sheet was smoothed with a super calender to produce a recording sheet having a Beck smoothness of 150 seconds. Its ash content was 15%.

 Table 1 shows the results of the thermal transfer test.

[Effects of the Invention] The thermal transfer image recording sheet of the present invention is excellent in all of the ink transferability, the uniformity of the transferred ink image, the diameter and the shape of the dot, and eliminates the disadvantages of the conventional method. In addition, it enables high-resolution thermal transfer, and greatly contributes to the industry.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-281990 (JP, A) JP-A-2-3394 (JP, A) JP-A-2-26996 (JP, A) JP-A-61- 168524 (JP, A) JP-A-2-9688 (JP, A) JP-A-2-3393 (JP, A) JP-A-62-250299 (JP, A) JP-A-61-202891 (JP, A)

Claims (1)

(57) [Claims] 1. An image recording surface comprising a paper mainly comprising a mixture of 50 to 90% by weight of wood pulp and 10 to 50% by weight of light calcium carbonate particles and having a Beck smoothness of 100 seconds or more. The light calcium carbonate particles have a hexagonal columnar calcite crystal structure and an oil absorption of 10 ml / 100 g or more, and 50
A thermal transfer image recording sheet, characterized in that at least% by weight has a particle size of 0.5 to 1.5 μm.