JPS59187891A - Thermal transfer recording sheet - Google Patents

Abstract

PURPOSE:To provide the titled sheet capable of obtaining a thermal transfer recorded image excellent in resolution and minute line reproducibility without changing an ink doner sheet or raising cost, wherein the density of the sheet is set to be not lower than a specified value. CONSTITUTION:The density (according to JIS P-8118) of the thermal transfer recording sheet is set to be not lower than 0.87g/cm<2>. To obtain the high density, for example, a method of intensifying calendering at a calendering part is easy to carry out and is advantageous on an economical basis. Alternatively, a method of internally adding a pigment into the sheet or coating the pigment onto the sheet, or a method of coating a resin such as a styrene-butadiene latex or CMC onto the sheet may be employed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a thermal transfer recording medium (ink donor sheet) which is formed by coating a heat-melting or heat-sublimating ink on one or both sides of a base material such as paper or a plastic film. ) and a transfer sheet, the thermal recording medium is selectively heated according to the image information, and the ink melted or sublimated by the heat is transferred to the transfer sheet to record the image information.This is the so-called thermal transfer recording method. related.

Conventional technology Conventionally, the transfer sheet used for thermal transfer recording does not need to be special (such as printing paper or plain paper (with a density of 0.8
6 f/6! The paper below) is considered to be satisfactory,
There wasn't much interest.

However, with the increase in recording speed, the thermal transfer recording method has had drawbacks such as a decrease in resolution and the appearance of fine lines. However, none have achieved satisfactory results.

Purpose of the Invention The present invention improves the above-mentioned drawbacks and provides a transfer sheet that allows thermal transfer recording with high resolution and good fine line reproducibility to be obtained without making any changes to the ink donor sheet (or without increasing costs). The purpose is to

As a result of intensive research into the thermal transfer recording method, the inventor has discovered that
The inventors have discovered that the quality of transferred images can be significantly improved depending on the physical properties of the transfer sheet, leading to the present invention.

In other words, the image quality of the transferred image changes drastically when the density according to JIS P-8118 of the transfer sheet reaches 0.87'1 rad, and the resolution and reproduction of fine lines deteriorate at 0.8 x 7/crI. < , 0.87 t/crtl was exceeded, the resolution and fine line reproducibility were both significantly improved, and even if the density was further increased, there was almost no difference in image quality.Based on this knowledge, the present invention was completed. .

Structure of the Invention The present invention achieves the above object by adjusting the density of the transfer sheet to 0.87 t/cr1 or more, which is higher than that of commonly used plain paper. The details of why the performance of transferred sorting improves by increasing the density are not clear, but the fact that the density is higher than that of normal plain paper may cause the ink transferred from the toner sheet to smear or seep into it. This is thought to be due to the fact that the degree of blur and spread is small.

In order to obtain a transfer sheet with the required density, the method of applying strong calendering in the calendering part of the papermaking process is the easiest to dispose of, and is also advantageous in terms of cost. size press or offline application method, or styrene-butadiene latex,
There are various methods such as applying resins such as vinyl acetate resin emulsion and CMC (carboxymethyl cellulose) using a size press or off-line, but it is sufficient to change the density as required regardless of the method. The examples are not limited.

Note that the density of the transfer sheet in the present invention is determined according to JIS
According to P-8118, under the conditions of 20 ± 2 °C and 65 ± 2 inches relative humidity, the thickness of paper (,lI++1) and tsubo tW (f/
The value calculated from the measured value of m') by the following formula is adopted.

Next, the transfer sheet for thermal transfer recording of the present invention will be explained with reference to Examples and Comparative Examples.

Example 1 20% by weight of soft southern pulp (NBKP) as pulp
A mixture of hardwood pulp (LBKP) at a ratio of 80% by weight was beaten to a volume of 470 ml with a hardness of C, S, F, and passed through a calendar using a Fourdrinier paper machine with three swimming rolls and one paper pass. Calendar linear pressure is 70Kf/c with nip
T! Adjusted to 1641/m', moisture 6.5%, density o, 90? /crA to obtain transferred sorting.

Example 2 Pulp with a weight ratio of NBKP30 and LBKP70 was given a water degree of C, S, and F.

Beat it to 450 pieces, put it on a Fourdrinier paper machine, run a calendar with 3 swimming rolls, 2 nips, adjust the calender linear pressure to 67Kq/(-d, and make a basis weight of 645'/m'.
A transfer sheet was obtained with a moisture content of 6.5% and a density of 0.87f/counterfeit.

Example 3 A pulp containing 10% NBKP by weight and 90% by weight LBKP was mixed with water grades C, S, and F.

Beat it to 430 g, and use a fourdrinier paper machine to roll a calender into three swimming rolls, ii2. = Adjust the calender linear pressure to 73Kql- with the knob, and the basis weight ゛64f/m',
A transfer sheet was obtained with a moisture content of 7.0 and a density of 0.94.

Example 4 LBKP % Tomizu 3 C, S, F, 480 m7! The pulp was beaten, mixed with 9 widths of talc for the entire weight of the pulp, the water content was 6.5% using a Fourdrinier paper machine, the calender was used with two swimming rolls, and the nip pressure was 20Kf/ct with one nip of paper passing through!
And the basis weight is 602/lr? ′, smoothness (F, S,) 2
A coating base paper was made so that the coating time was 5 seconds, and a coating solution made by mixing and dispersing 100 parts by weight of clay, 10 parts by weight of casein, and 10 parts by weight of latex was applied to one side of the base paper using a saw blade coater to give a coated amount of 29. /rn'.
Finishing was performed using a super calender to obtain a transfer sheet with a density of 1.00.

Comparative Example 1 Pulp containing 30% by weight of NBKP and 70% by weight of LBKP was given a water degree of C and Sl.

Beat it to 500 ml, use a fourdrinier paper machine, apply a calender with 3 swimming rolls and 2 nips to adjust the calender linear pressure to 65 mm/d, and have a basis weight of 647 mm/d.
The paper was made to have a moisture content of 6.4% and a density of 0.86 to obtain a transferred notebook for comparison.

Comparative Example 2 A mixture of 15% by weight of NBKP and 85% by weight of LBKP was used as a valve at water ratings C, S, and F.

4607! The calender was beaten on a Fourdrinier paper machine with 3 swimming rolls and 2 nips, and the calender linear pressure was adjusted to 63 KqlcrA, and the basis weight was 61'/ff.
11', moisture content: 6.2%, density: 0°84&Double paper making to obtain a transferred notebook for comparison.

Papers obtained in Examples 1 to 4 and Comparative Examples 1 to 2 and commercially available 2
The density of the seed paper was measured. In addition, printing was performed using ink donor sheets from two companies using a Xerox printer P6, and the transferred images after printing were evaluated for the following items.

31ine pair and 41i per millimeter of resolution crab
Reproducibility of nepair printed test charts.

Reproduction of thin lines - Using a test chart with 10 8-point kanji characters printed on it, the reproducibility of the individual lines that make up each character.

The results are shown in the table below.

*20” O1 relative humidity from JIS P-8118 Ni (
R, H, ) Measured in a 65 room environment.

Hayashi evaluation criteria.

○; State where 41ine pair is reproduced △:
41ine pair has not been reproduced, but 31ine pair
Pair is successful again, state X; 31ine
Condition in which the pair is not reproduced Package evaluation criteria 20: ] 0 characters in the middle character or more C1 It is composed of ~
A state in which all lines are reproduced △; A state in which at least 70φ of the lines that make up the middle characters or more out of 10 characters are reproduced and are legible ×; A state in which at least 5 out of 10 characters are readable P) The current rate of the line that makes up the line is less than 70 and is unreadable.

Claims (1)

[Claims] In the transfer sheet used in the thermal transfer recording method, the density of the transfer sheet according to JIS P-8118 is 0.87.
1. A transfer sheet for thermal transfer recording, characterized in that it has a transfer rate of t/di or more.