JP2526536B2 - Sheet for thermal transfer recording - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a thermal transfer recording sheet.

[0002]

2. Description of the Related Art In recent years, the demand for color printers has expanded. In particular, thermal transfer recording, which is a kind of non-impact recording method, particularly fusion-type thermal transfer recording, is a simple device that has high reliability, can obtain a relatively high-resolution image, and is capable of color recording. Compared to the impact printer, it was extremely quiet and was highly evaluated because it was easy to use in the office. On the other hand, in the thermal transfer printer as well, there is a demand for higher printing speed, and there is an increasing demand for improvement in print omission, resolution, and print quality.

Further, in recent years, the corresponding ink sheet has been improved so that it can be printed sufficiently on plain paper having low smoothness. However, in order to meet the demands for further quality improvement in color recording, it is difficult to transfer ink evenly on conventional plain paper having a rough surface, and print faintness, dot dropouts, print unevenness, etc. occur. Not suitable for high speed recording.

For the purpose of improving these, some proposals of coated paper type thermal transfer image receiving papers have already been made. For example, Japanese Patent Publication No. 59-16950 proposes an image receiving paper provided with a coating layer composed of a water-soluble binder and a pigment. Further, in JP-A-59-182787, an image receiving paper having a coating layer mainly composed of a non-plate-like inorganic pigment and having a glossiness of 20% or more is disclosed, and in JP-A-60-192690, an aragonite-based light calcium carbonate. An image receiving paper using a synthetic polymer latex as a binder has been proposed. The basic idea of these conventional coated paper type image-receiving papers for thermal transfer recording is to obtain a uniform surface by smoothing the image-receiving paper surface and increasing gloss to achieve uniform transfer of the heat-meltable ink. It was

On the other hand, in these thermal transfer recordings, in order to improve the utilization efficiency of the color material of the ink sheet, which is a high-priced consumable item,
Various innovations have been made in the material, structure, and recording method of the ink sheet. For example, as an improvement of the recording method, there is seen that the part containing the coloring material of the ink sheet has a special structure such as a porous resin type or a stone wall structure so that the same ink sheet can be used many times. There is a method of reducing the relative speed of the ink sheet in the forward direction or the reverse direction with respect to the recording sheet. In the latter method, conventional thermal transfer recording paper, that is, uncoated plain paper type with high surface smoothness and coated paper type improved for high-definition recording and color recording, Uniform transferability is not obtained, and recording characteristics are deteriorated such as tailing and scumming. (2) Running stability such as sticking or misalignment between ink sheet and recording sheet deteriorates. There are some drawbacks.

In order to obtain the running stability of the ink sheet and the recording sheet, there is a method of adding a known lubricant to the recording layer, and as disclosed in JP-A-61-244589, polyalkylene silicone copolymer. There is a method of adding various lubricants, which has a different purpose, but is disclosed in JP-A-61-177289. However, these methods could not sufficiently satisfy the above-mentioned recording characteristics and running stability.

[0007]

SUMMARY OF THE INVENTION According to the present invention, in thermal transfer recording in which an ink sheet and a recording sheet have a relative speed, the recording density is high and there is almost no tailing or scumming.
An image-receiving sheet for thermal transfer recording having uniform transferability without print unevenness and having no sticking between the ink sheet and the recording sheet and having excellent running stability.

[0008]

In thermal transfer recording, general conditions required by the recording sheet for the thermal transfer ink to be transferred in a satisfactory state are as follows.

First, in order for the ink to be transferred uniformly and at a high speed, the surface of the recording sheet must be generally macroscopically smooth and highly smooth.

Secondly, in order to transfer the ink uniformly and surely, when the binding force between the ink and the recording sheet is Pa and the binding force between the ink and the support (base sheet) is Pb,
The condition Pa> Pb is necessary. Pb is determined by the ink and the ink support, and Pa is determined by the ink and the recording sheet. As the recording speed increases, the recording ink is required to be transferred and fixed on the recording sheet in a very short time.In thermal transfer recording, the viscosity is relatively high and the cohesive force is relatively high for the purpose of improving ink shortage. Strong inks are being used. Regarding these physical conditions, the problem in thermal transfer recording from the viewpoint of printing characteristics is the problem of dot reproducibility, and when arranging them side by side, (1) when Pa <Pb or when the unevenness of the recording sheet is large, The problem of missing dots, in which the dots that are generated are not transferred at all, (2) The problem of missing dots, in which some of the transferred dots are missing when Pa = Pb, (3) The smoothness around the dots is missing, and the unevenness is transferred. There is a problem.

In consideration of these points, the present invention mainly conducted a study on the case of thermal transfer recording in which the ink sheet and the recording sheet have a relative speed. The thermal transfer recording method in which the ink sheet and the recording sheet have a relative speed is mainly for the purpose of attempting to use the ink sheet economically. Specifically, the both are run in the same direction or in the opposite direction to record the feed amount of the ink sheet. 1 / n (n is larger than 1) of the sheet. When such a relative speed is provided, a frictional force is always generated between the two, so that tailing and background stain due to the ink, which cannot be considered before, occur in printing. The frictional force generated between the ink sheet and the recording sheet is considered as follows. F = (1-r) f1 + rf2 f1: frictional force between the recording sheet surface and the ink surface of the ink sheet f2: frictional force between the ink surface transferred to the recording sheet and the ink surface left on the ink sheet r : Ink transfer rate

It is considered that the generation of this frictional force causes the generation of tailing and scumming, and if the frictional force F is made as small as possible, it can be a great countermeasure against them. Since f2 is exclusively due to the constituent material of the ink, it is necessary to select f2 with as small a value as possible while considering the printing characteristics. On the other hand, in order to reduce f1, there is a method of adding a known lubricant or a means for enhancing the smoothness of the surface of the recording sheet as described above. However, if the entire surface (macroscopically) of the slipperiness is given to the surface of the recording sheet, Pa that contributes to the fixability of the ink is lowered, resulting in uneven printing, reduced print density, and missing print. That is, when the ink sheet and the recording sheet have relative velocities, a method of reducing f1 without lowering Pa can be obtained without tailing or scumming and having excellent printing characteristics.

Further, the problem of sticking between an ink sheet having a relative speed and a recording sheet will be examined. Although it varies depending on the recording method, the thermal transfer printer usually takes the form of changing the printing speed according to the ratio of the printing portion (solid ratio) in order to increase the printing speed. In many cases, sticking occurs when the solid ratio is high and a speed change occurs. When the sticking occurs, the image quality may be a problem such as a thin line break or a missing print on the solid portion, a peeling noise ("squeaking") between the stuck ink sheet and the recording sheet, and further a trouble of running the ink sheet or the recording sheet. Such problems occur. Sticking phenomenon is stick-slip phenomenon
(Stick-Slip Motion).
That is, when the relative speed between the ink sheet and the recording sheet is less than a certain speed, the contact area between the ink sheet and the recording sheet becomes large, or when a large speed change occurs, the frictional force rapidly increases. It is estimated that sticking will occur at any time. Therefore, in order to prevent sticking, not only the ink characteristics such as the cohesive force and the hot melt viscosity of the ink, but also the flatness / concavo-convex shape of the recording paper surface, the affinity between the surface and the ink, the ink absorbability,
It was found that surface characteristics such as ink capturing ability are greatly related.

From the above, the conditions required for the surface of the recording sheet to solve the above-mentioned problems include conditions that are contradictory to each other, and it is difficult to satisfy these conditions at the same time. .

The inventors of the present invention have made extensive studies as to how to realize these conditions, and have found that the state of the recording surface of the thermal transfer recording sheet is important. That is,
The recording surface is exposed with a mixture of pulp fibers and pigments, the exposure rate of the pulp fibers is 20% or less in area ratio, and the surface roughness of the recording surface measured by a print surf surface roughness meter is 2.5 to It must be in the range of 5 μm. In the case of a coated paper type thermal transfer recording sheet in which a recording layer is formed by coating or impregnating at least a paint consisting of a pigment and a water-based adhesive on a support, the recording layer is coated with the pigment. Solid content of 5 g / m ² or less, preferably 0.5 to 5 g
/ M ² was applied, by smoothing processing if necessary, also the plain paper type, that is, the thermal transfer recording sheet to create a pigment and pulp fibers to papermaking stock mainly, After mainly making paper by adjusting the papermaking conditions such as the type of pigment and the amount of pulp fiber and the dehydration rate,
It can be obtained by smoothing if necessary.

In the present invention, one of the important points is that the pulp fiber and the pigment are mixedly present on the surface of the recording layer, and the presence state is that the pigment fills the voids between the fibers and the surface of the pulp fiber. Most of the pigment should be evenly and thinly coated.

There are various methods for measuring the exposure ratio of the pigment on the surface of the sheet. For example, (1) divide the recording sheet as thinly as possible in the cross-sectional direction, ash the uppermost sheet and measure the pigment content, and (2) use a scanning electron microscope (SEM) to reflect electrons on the surface of the recording sheet. A method of obtaining an image and calculating the area ratio by dividing it into a pigment portion and a fiber portion. There is a method of calculating the area ratio on the recording sheet surface. In the present invention, the area (Fmm ²⁾ of the pulp fiber portion and the area (Pmm ^{2) of the} pigment portion are measured from the backscattered electron image of the recording layer surface in a certain area by the method (2), and the exposed area ratio f of the pulp fiber is measured. = 100 × F /
(F + P) was calculated.

The pigment used in the method of coating or impregnating the pigment mainly on the pulp fiber is preferably calcined kaolin, heavy calcium carbonate, light calcium carbonate, synthetic silica, synthetic silicate, magnesium carbonate,
Among these pigments, those having more excellent printing characteristics are those having a certain degree of porosity (having a large specific surface area) having an average particle size in the range of 1 to 20 μm. Calcium carbonate, synthetic silicate and magnesium carbonate are preferred. Particularly, plate-like or spherical basic magnesium carbonate is preferable. Other pigments may be appropriately added to these pigments as long as the printing characteristics of the present invention are not changed. Examples thereof include calcined kaolin, heavy calcium carbonate, light calcium carbonate, synthetic silica, synthetic silicate, clay, kaolin, acid clay, talc, aluminum hydroxide, zinc oxide, calcium silicate, titanium oxide, diatomaceous earth, Examples include barium sulfate, satin white, and organic resin pigments.

The pulp fibers used here include plant pulp fibers centering on wood fibers and pulp fibers regenerated from waste paper, and these pulp fibers include synthetic pulp fibers, synthetic fibers, inorganic fibers and the like. It can also be used in combination. As the fiber sheet as the support, it is possible to use either acidic or neutral ones such as uncoated paper mainly composed of the above pulp fibers, uncoated paper such as medium quality paper, recycled paper utilizing waste paper, etc. it can. It should be noted that the pulp fiber support may contain other pigments, additives, etc. to the extent that the object of the present invention is not impaired.

The water-based adhesive used in the coating material used for coating and impregnating the pigment on the support field is not particularly limited and may be a synthetic polymer latex or a water-soluble polymer adhesive. The solid content weight ratio of the pigment to the water-based adhesive in the coating material of the present invention is preferably 40/60 to 95/5, and more preferably 50/50 to 90/10. As the synthetic polymer latex, styrene-butadiene copolymer, modified styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, methylmethacrylate-
Butadiene copolymer, chloroprene latex, polymer or copolymer of acrylic acid ester and methacrylic acid ester, ethylene vinyl acetate copolymer, vinyl acetate-
Examples thereof include maleic acid ester copolymers, acrylic-vinyl acetate copolymers, vinyl acetate polymers and the like. As the water-soluble polymer adhesive, starch, cation-modified starch, polyvinyl alcohol, cellulose derivatives such as hydroxyethyl cellulose and carboxymethyl cellulose, polyacrylamides, polyvinyl pyridine,
To exemplify polyethylene oxide, polyvinylpyrrolidone, casein, gelatin, sodium alginate, sodium polystyrene sulfonate, sodium polyacrylate, starch-acrylonitrile graft polymer hydrolyzate, sulfonated chitin, carboxylated chitin and chitosan and their derivatives. You can

Various other additives can be added to the coating composition of the present invention as required. Dispersants, thickeners, release agents, surfactants, viscosity modifiers, flocculants, leveling agents, water-proofing agents and the like are used for improving coating suitability. Further, a lubricant, an antistatic agent, or the like is added to improve recording characteristics and conveyance of recording paper.

Examples of the method for applying or impregnating the coating material of the present invention include a size press, an air knife coater, a roll coater, a blade coater, a bar coater, a curtain coater and a spray method.

In the present invention, the coating layer is 5 g / m ²
It is an essential condition that the fine coating is as follows and the pulp fiber exposure rate is 20% or less. However, in general, when a coating material containing a pigment and an adhesive is applied onto a fibrous support such as high-quality paper, the coating amount of the pigment solid content is 5 g / m ² or less. Volume 24 Number 6 (June 1970)
It is known that considerable fibers are exposed, as also shown on pages 303-312. The ratio is 2
If it exceeds 0%, that is, if the surface is mainly composed of pulp fibers, the sticking property and the running property are slightly good, but the print density is lowered, and the image quality such as uneven transfer is deteriorated. If the exposure rate of the pulp fiber on the surface of the recording sheet is simply lowered, the amount of paint applied may be increased, but if this is done, the image quality will improve, such as increased print density, but problems such as sticking, squeaking, and running problems will occur. Occurs. Therefore, in order to achieve the object of the present invention, the paint is 5 g / m 2 in terms of pigment solid content.
² or less, and the pulp fiber exposure rate of the recording sheet surface is 20% or less, and the surface of the support is uniformly and thinly coated so that a surface recording layer without exposing most of the fibers can be obtained. To do.

As another means for achieving the object of the present invention, there is a method in which pulp fibers and pigments are mixed to make paper.
The pulp fibers and pigments used may be the same as those used in the coating method, and other pigments and additives may also be added within the scope of the object of the present invention.

Another important point of the present invention is that
The surface roughness of the recording sheet surface must be kept constant. The roughness is adjusted by the type and amount of the pigment used and the smoothing treatment. The smoothing treatment is usually a calendar treatment, which is a gloss calendar or a super calendar and a combination thereof.

As a tester for measuring the surface roughness or smoothness of paper, Bekk, Oken type smoothness tester, Wi
lliams Gurley Hill SPS, Sheffield, Bendsen, Pr
There are many methods such as int-surf (print surf), but each method has advantages and disadvantages and is adopted according to each purpose. In thermal transfer recording, the recording sheet is pressed by a thermal head under a certain constant pressure condition, the problem of adhesion between the ink sheet and the recording sheet, the effect of ink transfer efficiency on printing characteristics, the ink sheet and the recording sheet. Transportability and the like are problems. Especially in thermal transfer recording where the recording sheet and the ink sheet have a relative velocity, the flatness of the recording sheet surface in micro units has a large effect on each, so the micro surface roughness under pressure conditions Need to be accurately captured.
Among the above-mentioned equipment, the airflow width (0.051 mm) of the print surf surface roughness meter is the smallest, it is measured under a constant pressurizing condition, and the backing can be selected. It meets the conditions. The surface roughness of the recording sheet of the present invention measured by a print surf surface roughness meter is preferably 1 to 7 μm, more preferably 2.5 to
5 μm. If the surface roughness is too large, the ink fixability on the surface is deteriorated and print unevenness in solid print portions, print omissions, etc. are likely to occur, resulting in a non-uniform image as a whole, and sticking is also less likely to occur. Not preferable. On the other hand, if the surface roughness is too small, tailing and scumming are likely to occur. The preferred surface roughness varies depending on the type of thermal transfer printer, and the optimum value for the smoothing treatment of the recording sheet of the present invention needs to be adjusted to the printer without significantly changing other properties within the above range of surface roughness.

[0027]

When the thermal transfer recording sheet is made of a paper made of a pigment and fibers or has a coating layer having a solid content of 5 g / m ² or less, the recording surface of the recording sheet has a pulp fiber. And the pigment are mixed, the exposure rate of the pulp fiber on the recording surface is 20% or less in area ratio, and the surface roughness of the recording surface by a print surf surface roughness meter is 2.5 to 5 μm.
In the thermal transfer recording in which the ink sheet and the recording sheet have a relative speed,
A thermal transfer recording sheet with high recording density, almost no tailing or scumming, uniform transferability with no print unevenness, and no sticking between ink sheet and recording sheet, and excellent running stability. The reason for this was not clear enough, but it is thought that it would be roughly as follows.

On the recording surface of the recording sheet satisfying the above-mentioned conditions, the pigment fills the inter-pulp fiber voids and covers most of the fiber surface uniformly and thinly. Therefore, the recording layer is in a state in which macroscopic unevenness of the paper layer remains sufficiently. In some cases, the fibers form a special surface condition in which they appear randomly. By this surface condition, the frictional force F generated between the ink sheet and the recording sheet is dispersed and relaxed macroscopically, and an image with less trailing or character smearing is obtained, and print omission due to sticking, squeaking, and running You can get the one with almost no trouble. On the other hand, uneven printing and reduced printing density are expected due to the relaxation of the frictional force.However, due to the large number of microscopic pores composed of pigments filling the fibers or coating the fiber surface, heat It is considered that the ink having excellent absorbing property and capturing property of the molten ink, excellent forming property of printed dots and high recording density can be obtained.

[0029]

EXAMPLES The present invention will be specifically described below with reference to examples. In the following examples, parts and% are solid parts by weight and solid content% by weight, unless otherwise specified.

[Example 1] A concentration of 40% as a dispersant in water
2 parts of sodium acrylate is added to the solution, and plate-like basic magnesium carbonate (average agglomerated particle size:
100 parts (4.2 μm, oil absorption: 160 ml / 100 g) was added and dispersed by stirring. Next, as a binder, 50% styrene-butadiene copolymer emulsion (Tg:
-12 ° C) 10 parts, and further 10% concentration of polyvinyl alcohol (saponification degree: about 99%, average degree of polymerization: 1700) 3
Add 0 parts each with stirring to obtain a total solid content of 1
A 5% dispersion liquid was prepared and used as a coating liquid. 2.5 g of this coating solution on one side of a fine paper of 66 g / m ² with a Mayer bar.
g / m ² (pigment solid content) was applied and dried. The surface of the coating layer was smoothed with a test super calendar to obtain a recording sheet of Example 1 having a pulp fiber exposure rate of 5.6% and a print surf surface roughness of 3.4 μm.

[Example 2] A concentration of 40% as a dispersant in water
2 parts of sodium acrylate is added to the solution, and a synthetic aluminum silicate salt (average primary particle size 0.025 μm, B
50 parts of ET specific surface area 135 m ² / g) and 50 parts of plate-like basic magnesium carbonate (average agglomerated particle size: 5.6 μm, oil absorption: 140 ml / 100 g) are dispersed at a solid concentration of 25%, and then a binder is added. As a polyvinyl alcohol having a concentration of 10% (saponification degree: about 99%, average degree of polymerization: 170
0) 10 parts, 20 parts of 55% ethylene vinyl acetate resin (MFT: 0 ° C., viscosity: 1000 C.P./25° C.) were added with stirring, respectively, and the total solid content was 17%.
A dispersion liquid was prepared and used as a coating liquid. This coating solution was applied to a fine paper of 66 g / m ² with a Mayer bar at 3.2 g / side on one side.
After applying m ² (solid content), drying, and smoothing treatment, a recording sheet of Example 2 having a pulp fiber exposure rate of 10.5% and a print surf surface roughness of 3.2 μm was obtained.

[Comparative Examples 1 to 3] Calcined kaolin (particle size 2 µm or less 90%, true specific gravity 2.7, apparent specific gravity) was used in place of the basic magnesium carbonate of Example 2 in an aqueous solution to which an appropriate dispersant was added. 0.251g / cm
³ ), light fine calcium carbonate (columnar aragonite type,
Average particle size 2 μm), kaolin (particle size 2 μm or less 92%,
True specific gravity 2,58, apparent specific gravity (0.822g / cm ³ )
A coating material was prepared in the same manner as in Example 2 except that each of Comparative Example 1 and Comparative Example 1 was used.
A few recording sheets were obtained. The solid coating amount, surface roughness, and fiber exposure rate of each pigment are shown in Table 1.

[0033] The coating amount of each coating of the Comparative Examples 4 and 5 Example 1,2, 8.9g / m ^2, except that the 6.6 g / m ² in the same manner as in Examples 1 and 2 Recording sheets of Comparative Examples 4 and 5 were obtained. The solid coating amount of pigment, surface roughness, and fiber exposure rate are as shown in Table 1.

The recording sheets of Examples 1 and 2 and Comparative Examples 1 to 4 were evaluated by the following methods, and the results are shown in Table 1. (1) Recording Density A single color (black) recording was carried out using a thermal transfer printer in which the relative speed of the recording sheet and the ink sheet was 5/1, and the recording density in the solid recording section was measured with a Macbeth densitometer. (2) Tailing The amount of ink tailing at the boundary between the solid printed portion and the blank portion on the recording sheet flow direction side and at the character portion was visually determined. B and above were accepted. A: The trailing is good with almost no boundary portion or character portion. B: The trailing is slightly seen at the boundary part and also seen at the character part. C: The trailing can be seen in both the boundary part and the character part. (3) Print unevenness The above printer was used to visually evaluate the print unevenness in the solid print portion and the state of thin line dot omission. B and above were accepted. A: The image quality is good with almost no missing dots or unevenness. B: Some missing dots and unevenness are observed, and the image quality is slightly degraded. C: Many missing dots and unevenness are observed, and the image quality is poor. (4) Sticking The sticking state when a certain image is output by the printer is evaluated. B and above were accepted. A: Excellent printing stability with no printing omission in the printing section. B: Some print omissions in the print part are seen. C: A lot of missing prints are seen in the print part, and squeaking occurs. D: Not only print missing in the printing portion but also defective running of the recording sheet occurs. (5) Surface Roughness Parker Print Surf Surface Roughness Meter Model PPS
78 (manufactured by HE MESSMER), the surface roughness was measured using a hard backing with a clamping pressure of 10 kgf / cm ² . (6) Measurement of ratio of pulp fiber to pigment on recording paper surface Scanning electron microscope (JSM840A, JEOL Ltd.)
Backscattered electron image (magnification: 200)
(2 times) and divided into a pigment portion and a fiber portion, and using the image analysis device (IBAS system, manufactured by Carl Zeiss) from the image, the exposure rate of the pulp fiber on the recording layer surface of each sheet (area ratio% = Fiber area / (fiber + pigment area) was determined.

[0035]

[Table 1]

Examples 1 and 2 and Comparative Examples 1 to 5 are examples of a method of impregnating, coating, or spraying a paint comprising at least a pigment and an aqueous adhesive on a pulp fiber support. Looking at Table 1 showing the evaluation, it is found that with an appropriate coating amount, the fiber exposure rate is 20% or less in area ratio, and the surface roughness measured by the print surf surface roughness meter is 2.5 to 5 μm. While a recording sheet which has achieved the object of the present invention with extremely excellent results, is obtained other than the present invention, that is, the surface roughness of the print surf, the exposure rate of the fiber, and the coating amount are specified in the present invention. Those outside the range indicate that either or both of printability and running stability are lacking, and the object of the present invention cannot be achieved.

[Example 3 and Comparative Example 6] LB having a freeness (CSF) of 250 ml as a raw material pulp
Using 100 parts of KP, plate-like basic magnesium carbonate as a pigment (average aggregate particle size: 5.6 μm, oil absorption: 1
35 parts of 40 ml / 100 g), and further 0.5 parts of alkyl ketene dimer (cationic, pH 3.0, viscosity 30 C.PS) as a sizing agent, yield improver (polyacrylamide cation modified product, concentration 0.5%) 590C.PS)
A raw material slurry was obtained by adding and mixing 0.03 part, and papermaking was carried out by a Fourdrinier paper machine to obtain a sheet having a basis weight of 66 g / m ² . Further, this sheet was subjected to a surface smoothing treatment with a test super calendar to obtain a recording sheet of Example 3 having a surface roughness of 3.4 μm by a print surf surface roughness meter and a fiber exposure rate of 16.2%. In addition, the surface roughness of the print surf surface roughness meter is 2.3μ by changing the degree of smoothing treatment.
A recording sheet of Comparative Example 6 having m and a fiber exposure rate of 15.6% was obtained.

Comparative Example 7 100 parts of LBKP having a freeness (CSF) of 400 ml was used as a raw material pulp, and kaolin (kaolinite genus, spherical aggregate, average primary particle diameter 0.1 μ, specific gravity 2.2) was used as a pigment 30. In addition, 0.15 parts of a reinforced rosin sizing agent (Coropearl CS, manufactured by Seikou Kagaku Kogyo Co., Ltd.) as a sizing agent, and 1 part of a sulfuric acid band are added to make a paper with a paper machine and have a basis weight of 66 g / m ² . Was subjected to a smoothing treatment to obtain a recording sheet of Comparative Example 7 having a surface roughness of 2.3 μm and a fiber exposure rate of 35.5%.

Comparative Example 8 Comparative Example 8 was carried out in the same manner as in Example 3 except that the raw material pulp of Example 3 was changed to LBKP having a freeness of 400 ml and the amount of the basic magnesium carbonate as a pigment was changed to 20 parts. I got a recording sheet of.

[0040]

[Table 2]

Example 3 and Comparative Examples 6 to 8 were obtained by a method in which a slurry prepared by previously mixing pulp fibers and pigments was prepared so that pulp fibers and pigments were exposed in the above ratio with a paper machine. As shown in the results of Table 2, the recording sheet using the pigment of the present invention has excellent recording characteristics. Even if basic magnesium carbonate, which is a preferable pigment, is used. Fiber exposure rate is 2
If it exceeds 0%, the printing characteristics are deteriorated.

[0042]

As described above, the recording surface is composed of pulp fibers and pigments, the exposure rate of the pulp fibers on the recording surface is 20% or less in area ratio, and the print surf surface roughness of the recording surface is rough. Surface roughness of 2.5 ~ 5μ
m, and when the recording surface is obtained by coating as a recording layer, a recording sheet having a solid content of 0.5 to 5 g / m ² is used to obtain a high recording density in thermal transfer recording. Moreover, an excellent thermal transfer recording image-receiving sheet was obtained which had almost no tailing or scumming, uniform transferability with no print unevenness, and no print missing or squeaking caused by sticking.

Further, the recording sheet of the present invention not only exhibits excellent characteristics in the thermal transfer recording method in which the ink sheet and the recording sheet have relative velocities, but also stains or trails on the ink sheet which can be used many times. There is an effect that an excellent thermal transfer recording with a small amount can be obtained.

Claims (4)

(57) [Claims] 1. A recording provided by impregnating or coating a coating material containing at least a pigment and an aqueous adhesive with a pigment solid content of 0.5 to 5 g / m ² (square meter) on a support composed mainly of pulp fibers. In a recording sheet having a layer, the surface of the recording layer is a mixture of pulp fibers and pigments, the exposure rate of the pulp fibers is 20% or less in area ratio, and the surface roughness of the recording layer is measured by a print surf surface roughness meter. Surface roughness is 2.5-5 μm
A sheet for thermal transfer recording characterized by: 2. A solid content weight ratio of the pigment to the aqueous adhesive is 5
It is 0 / 50-90 / 10, It is characterized by the above-mentioned.
The thermal transfer recording sheet described. 3. A recording sheet prepared by making a raw material from a mixture of at least pulp fiber and pigment, wherein the recording layer surface is a mixture of pulp fiber and pigment, and the exposure rate of the pulp fiber on the surface of the recording layer is area. A thermal transfer recording sheet having a ratio of 20% or less, and a surface roughness of the recording layer surface measured by a print surf surface roughness meter of 2.5 to 5 μm. 4. The thermal transfer recording sheet according to claim 1, wherein the pigment is magnesium carbonate.