JPH06278381A - Image receiving paper for thermal transfer recording - Google Patents

Abstract

PURPOSE:To obtain thermal transfer recording image receiving paper suitably used in the application to a railroad ticket, a commutation ticket, a flight ticket and other ticket paper, a POS label and other labels, and a prepaid card and other cards, especially required to be recorded or read at a high speed in thermal transfer recording image receiving paper available for a copying machine, a printer, and a facsimile terminal equipment, and the like of a hot melt ink- type thermal transfer recording system. CONSTITUTION:In thermal transfer recording image receiving paper, a coating composition mainly composed of a synthetic polymeric resin and a porous pigment is applied on one surface of base paper to form an image receiving layer for receiving hot melt ink. Especially, as the synthetic polymeric resin, a synthetic polymeric resin having a glass transition point of -60--5 deg.C and a surface tension of 38-58mN/m is used. Furthermore, as the porous pigment, a porous pigment having an apparent specific gravity of 0.1-0.5g/cm<3> in accordance with JIS-K-6220 is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image receiving paper used in a copying machine, a printer, a facsimile, etc., which uses a thermal transfer ink type thermal transfer recording system, and particularly to a ticket which requires high speed recording or high speed reading. The present invention relates to a thermal transfer recording image receiving paper suitable for ticket papers such as commuter tickets and airline tickets, labels such as POS labels, and cards such as prepaid cards.

[0002]

2. Description of the Related Art In recent years, with the rapid development of OA and FA,
Copiers, printers, facsimiles and the like that utilize various recording systems such as electrophotographic systems and thermal transfer recording systems are used according to their respective purposes, and are widely used for CAD / CAM, for example. Colored color materials are used for image formation in such a thermal transfer recording system, and usually, the color materials are melted, evaporated, and sublimated and transferred onto a recording medium, for example, an image receiving paper such as paper or a film sheet, and adhesive. The recorded image is formed by adsorption and dyeing.

By the way, in this type of recording system, an ink transfer sheet having a heat-fusible ink layer composed of a coloring material and waxes, a resin or the like is melted by heat generated by a thermal head or an energizing head, The heat-fusion type thermal transfer recording method, in which a color material is transferred to an image receiving paper to obtain a recorded image, has advantages such as a simple apparatus, easy compactness, and maintenance-free. Therefore, reliability and security are required. Attention is being paid to the use of such as passenger tickets, commuter tickets, ticket papers such as airline tickets, labels such as POS labels, and cards such as prepaid cards. Further, the heat-melt type transfer recording method has a feature that plain paper can be used as a recording medium.

However, like the other recording systems, such a thermal transfer recording system is also required to improve full-color recording, high-speed recording, clear image, high resolution, etc., together with the performance improvement and improvement of the recording apparatus. Plain paper is becoming less than satisfactory. For example, in the case of labels, when a bar code or the like recorded at high speed is read using a reading device, if the image quality is poor and there are many missing dots or line breaks, the bar code or the like Since it cannot be read, it is unacceptable as an image receiving paper. Also,
For ticket papers and cards that combine magnetic recording systems, transfer them to the image receiving paper in order to pass the cards at high speed through the device with the built-in magnetic head or to be used repeatedly for a long period of time. When the transferred image is rubbed and soiled, or when dots are lost due to scratches or the like, the fixability and the robustness become problems, and the card cannot serve its function.

For this reason, many proposals have been made regarding the image receiving paper. For example, the Beck smoothness of the surface of the image receiving layer is specified in order to improve transferability (JP-A-59-1330).
92, 59-187892), provided with an image receiving layer containing a specific emulsion or latex (JP-A-61-158497).
No. 61-158498), or an image receiving layer containing a specific pigment and a binder such as polyvinyl alcohol or latex (JP-A-60-110489, 60-192690).
Issue 61-217289, Issue 61-266296, Issue 61-284486
No. 62-32085, No. 62-257888, JP-A 1-2024
No. 93) and the like. However, even these conventional methods have not completely eliminated the effect of improving the ink transfer property. That is, the image is blurred due to lack of reproducibility of the edge portion or sharpness of the image, or the image receiving layer surface is rolled up together with the transfer ink by a pick when the ink transfer sheet and the image receiving paper are separated during thermal transfer recording, The actual situation is that a satisfactory recorded image has not yet been obtained due to problems such as dot loss and line breakage.

Further, recently, there have been more and more occasions when printing such as gravure printing or offset printing is performed on the image receiving paper for thermal transfer recording, and accordingly, demands for quality of the image receiving paper such as smoothness, surface strength and opacity become severe. It's coming. In addition, the image quality is reduced due to paper dust generated due to the image receiving paper, and paper passing problems with printers are also exposed.
There is an urgent need to solve these problems.

[0007]

DISCLOSURE OF THE INVENTION The present invention is free from the uneven transfer, line breakage and dot omission as in the prior art, and is excellent in ink transfer acceptability, reproducibility and sharpness, and also the fixability and fastness of a transferred image. The present invention provides a high-quality and high-quality image-receiving paper for thermal transfer recording, which is excellent in full-color recording, has excellent high-speed recording suitability, and has excellent printing suitability.

[0008]

According to the present invention, an image receiving layer for receiving a hot-melt ink is provided by applying a coating composition containing a synthetic polymer resin and a porous pigment as a main component on one side of a base paper. In the thermal transfer recording image-receiving paper, (A) the synthetic polymer resin has a glass transition point and a surface tension of −60, respectively.
A synthetic polymer resin having a temperature of -5C and 38-58mN / m is used, and (B) the porous pigment is JIS-K-
Apparent specific gravity according to 6220 is 0.1-0.5g / cm ³
The image-receiving paper for thermal transfer recording is characterized by using a porous pigment.

[0009]

From the actual situation as described above, the present inventors have improved the adhesion between the ink transfer sheet and the recording image receiving surface, and are capable of high-quality thermal transfer recording with excellent ink transferability without transfer unevenness or missing dots. We have made extensive studies on paper. As a result, in order to obtain a desired effect, by forming an ink image-receiving layer containing a specific synthetic polymer resin and a porous pigment as main components on the base paper, the characteristics of the synthetic polymer resin and the porous pigment It has been found that a synergistic effect can bring about a remarkable effect that cannot be expected from the conventional techniques, and has completed the present invention.

First, the synthetic polymer resin contained in the image receiving layer will be described as the first feature. The synthetic polymer resin used in the present invention has a glass transition point (hereinafter, referred to as Tg) and a surface tension (hereinafter, referred to as γ),
The important requirements are -60 to -5 ° C and 38 to 58 mN / m, respectively. That is, in the present invention, by forming a relatively soft film as the image receiving layer, the surface of the image receiving layer formed of the synthetic polymer resin is appropriately plasticized (heat transfer) by the heat from the thermal head to form a transfer ink. Since the affinity of the ink is increased and the effect of improving the wettability of the image receiving layer surface is excellent, the transfer ink melted by the thermal head permeates properly into the image receiving layer and is remarkably effective in improving the fixing property of the ink. Is. In particular, since the time during which the heat-melting components (waxes, etc.) in the ink transfer sheet are melted is short, transfer and penetration of the transfer ink to the image-receiving layer are likely to be insufficient, and for example, high at 4 inches / second or more. The effect is extremely large in the case of a method in which thermal transfer recording is performed at a speed.

The Tg of the synthetic polymer resin can be appropriately adjusted according to the polymerization conditions such as the type and composition of the constituent monomers, the composition ratio (copolymerization rate) and the polymerization temperature. For example, Tg of polybutadiene is about -90 ° C, polyisobutylene is about -73 ° C, polystyrene is about 90 ° C, polymethylmethacrylate is about 105 ° C, butylpolyacrylate is about -55 ° C, or polyethylene is about -125 ° C. C is generally known. Further, these constituent monomers can be appropriately combined and the polymerization temperature and the like can be variously adjusted to form a copolymer, and the Tg thereof can be appropriately adjusted. For example,
Styrene / butadiene copolymer latex is widely used as a binder for paper coating in the paper manufacturing industry because of its excellent printing strength and printing gloss, etc. Usually, the Tg of such a binder is about 0 to 60 ° C. There are many things.

On the other hand, the surface tension (γ) of synthetic polymer resin
Is a state of a protective layer obtained by forming a surfactant or a protective colloid (water-soluble polymer), which is used as an emulsifier during emulsion polymerization, on the surface of a synthetic polymer resin particle by adsorption or chemical bonding, or particles It depends on the remaining amount (concentration) of the emulsifier that is not adsorbed on the surface and is liberated. Of course, γ of synthetic polymer resin, like Tg,
It can be adjusted by the polymerization conditions and particle size, the type and amount of emulsifier, addition of water-soluble salts, and the like.

Incidentally, in the present invention, when the Tg of the synthetic polymer resin exceeds -5 ° C., dot dropout or line breakage phenomenon is recognized due to poor affinity with the ink on the surface of the image receiving layer, and dot reproducibility. The image quality is poor and the sharpness of the image area is lost. Further, dots are more likely to be lost or scratched due to scratches, resulting in poor fixability and fastness. On the other hand, if the temperature is lower than -60 ° C, blocking of the image receiving paper, ink bleeding phenomenon, or poor printability due to a decrease in surface strength is not preferable.

The synthetic polymer resin has a γ of 38 mN / m.
When it is less than the above range, the wettability of the surface of the image receiving layer with respect to the transfer ink is deteriorated, the transfer failure of the ink, the ink swimming phenomenon on the surface of the image receiving layer, etc. occur, and the quality of the obtained image is remarkably deteriorated. On the other hand, when it exceeds 58 mN / m, the transferability of the ink is increased, but the ink (dots) spreads and bleeds, and a non-uniform transfer image is likely to be formed. Furthermore, since the dispersion stability of the synthetic polymer resin is rapidly deteriorated, a coating composition having good coating suitability cannot be obtained. From the above, the Tg of the synthetic polymer resin is −60 to −5 ° C., more preferably −5.
5 to −10 ° C. and γ are specified to be 38 to 58 mN / m, and more preferably 40 to 56 mN / m.

The synthetic polymer resin is not particularly limited, and examples thereof include styrene / butadiene copolymer, methacrylic acid ester / butadiene copolymer, acrylonitrile / butadiene copolymer, polybutadiene, polyisobutylene, Synthetic rubber type such as polychloroprene, methacrylic acid ester / acrylic acid ester copolymer, ethyl acrylic acid ester / acrylic acid ester copolymer, styrene / acrylic acid ester copolymer, acrylic type such as polyacrylic acid ester, ethylene / Vinyl acetate copolymer, maleate / vinyl acetate copolymer, ethyl acrylate / vinyl acetate copolymer,
Vinyl acetate type such as polyvinyl acetate, vinyl chloride type, vinylidene chloride type, and various modified polymers obtained by introducing functional groups such as carboxyl group, hydroxyl group, amide group and amino group into these polymers or copolymers, polyethylene, polystyrene,
Examples thereof include latex such as polyisoprene or emulsion. Among these, one kind or two or more kinds are appropriately selected and used according to the quality target of the image receiving paper for thermal transfer recording. Among these synthetic polymer resins, the synthetic rubber latex is excellent in the adhesive strength of the image receiving layer surface and excellent in dispersion stability of the pigment, and forms a flexible and elastic film to fix the transfer ink. It is particularly preferably used because it exhibits excellent properties and reproducibility of dot shape.

The second feature of the present invention is that the apparent specific gravity (hereinafter, simply apparent specific gravity) according to JIS-K-6220 as a pigment in the image receiving layer is 0.1 to 0.5 g / cm ³ . This is where the porous pigment is included. The porous pigment contains a large amount of air in its particles, and by having such a pigment conveniently contained in the image receiving layer, it is possible to impart appropriate voids and cushioning properties. Therefore, the heat insulating property of the image receiving layer can be well maintained, and the heat from the thermal head can be appropriately stored on the surface of the image receiving layer. As a result, the acceptability of the transfer ink and the sharpness of the image are more outstanding. The quality characteristics of the image receiving paper for thermal transfer recording are drastically improved because of its excellent effect of improving transfer unevenness and dot omission.

As a method for measuring the apparent specific gravity of a pigment, for example, "bulk" defined in JIS-K-5101.
There is also a method of measuring the bulk specific gravity or converting the bulk density (ml / g) into the apparent specific gravity (g / cm ³ ) and handling. But,
As a result of earnest studies by the present inventors, the thermal transfer recording of the present invention, which is obtained by applying a coating composition containing a porous pigment to form an image receiving layer, or by smoothing the paper through a pressure nip. In the case of image-receiving paper for use, the apparent specific gravity value obtained by measuring the pigment in a dense state to a certain degree by applying a constant load specified in JIS-K-6220 is more effective than the desired effect of the present invention. We find that the correlation is higher.

The porous pigment is not particularly limited as long as it satisfies the above conditions, and examples thereof include diatomaceous earth, calcined diatomaceous earth, flux calcined diatomaceous earth, calcined kaolin, zeolite, white carbon, and amorphous silica. Examples thereof include magnesium aluminosilicate, fine particle calcium silicate, fine particle alumina, fine particle titanium oxide, fine particle magnesium carbonate, and fine particle light calcium carbonate.

Incidentally, even with the above-mentioned porous pigments, when the apparent specific gravity exceeds 0.5 g / cm ³ , the characteristics of the porous pigment are reduced by half and the voids in the image receiving layer are reduced, resulting in a dense structure. , The adiabatic efficiency of the image receiving layer drops sharply. As a result, the receptivity and fixability of the transfer ink are poor, and it is not possible to obtain the thermal transfer recording image-receiving paper excellent in image quality without the transfer unevenness and dot omission desired in the present invention. On the other hand, 0.1 g / cm
If it is less than ³ , the voids in the image receiving layer increase, and the heat insulation effect becomes higher than necessary, so that the heat of the thermal head is difficult to cool on the surface of the image receiving layer, and heat is accumulated and transfer ink bleeding and dot bridging occur. The phenomenon is induced, and the image quality becomes poor. Further, since the strength of the image receiving layer surface becomes extremely weak, the image receiving layer surface is rolled up together with the transfer ink by a pick when the ink ribbon and the image receiving paper are separated.
Dots are lost, which causes deterioration of image quality. Therefore, the apparent specific gravity is 0.1 to 0.5 g / cm ³ , preferably 0.15.
To 0.45 g / cm ³ , more preferably 0.20 to 0.4
It is in the range of 0 g / cm ³ .

In the coating composition (image-receiving layer), in addition to the above specific porous pigment and synthetic polymer resin, other pigments and water-soluble (or water-dispersible) polymer compounds may be used in combination, if necessary. can do. In order to obtain the desired effect of the present invention, at least a specific synthetic polymer resin is added to the pigment in an amount of 20 to 20.
It is preferable that the amount is 150% by weight, more preferably 25 to 125% by weight. By the way, if it is less than 20% by weight, the strength of the image receiving layer becomes extremely weak, resulting in defective transfer dots and easy generation of paper dust, resulting in remarkable deterioration of image quality. On the other hand, if the amount exceeds 150% by weight, blocking of the surface of the image receiving layer or bleeding of the ink may cause poor sharpness of the image area, which is not preferable.

Examples of the water-soluble (or water-dispersible) polymer compound include cationic starch, amphoteric starch, oxidized starch, enzyme-modified starch, thermochemically modified starch, pregelatinized starch, esterified starch, Starch such as etherified starch, cellulose derivative such as carboxymethyl cellulose and hydroxyethyl cellulose, natural or semi-synthetic polymer compound such as natural rubber, gelatin, casein, soybean protein; polyvinyl alcohol, polyvinylpyrrolidone, polyethyleneimine, polyether, polyurethane Examples thereof include synthetic polymer compounds such as polyamide, olefin / maleic anhydride resin, polyamide / epichlorohydrin resin, polyester resin, epoxy resin and melamine resin. In addition to these, various auxiliaries such as surfactants, pH adjusters, viscosity adjusters, softeners, gloss imparting agents, waxes, dispersants, flow modifiers, conductive agents, stabilizers, antistatic agents. Agents, cross-linking agents, sizing agents, optical brighteners, colorants, ultraviolet absorbers, antifoaming agents, water resistance agents, plasticizers, lubricants, preservatives, fragrances, etc. can be appropriately used as necessary. is there.

As the pigments other than the porous pigments, various pigments used for general coated paper, for example, kaolin, deramikaolin, aluminum hydroxide, satin white, heavy calcium carbonate, light calcium carbonate, calcium sulfate,
Mineral pigments such as barium sulfate, titanium dioxide, talc, zinc oxide, zinc carbonate, alumina, magnesium oxide, magnesium carbonate, silica, colloidal silica, bentonite, zeolite, sericite and polystyrene resins,
Examples thereof include fine particles of urea resin, melamine resin, acrylic resin, benzoguanamine resin and the like, fine hollow particles and other organic pigments. The mixing ratio of the above-mentioned pigments other than the porous pigment is up to about 30% by weight with respect to the porous pigment in order to obtain the desired effect of the present invention.

The coating amount of the coating composition is 5 to 25 g / m ^{2 on} one side in terms of dry weight, and more preferably 6 to 20.
A range of g / m ² is suitable. Incidentally, if it is less than 5 g / m ² , it is difficult to obtain the desired effect of the present invention. On the other hand, 2
If it exceeds 5 g / m ² , the surface of the image-receiving layer is likely to be blocked, and the image quality may be deteriorated due to ink bleeding, which is not preferable.

As a coating method, generally known publicly-used coating equipment such as blade coater, air knife coater, roll coater, reverse roll coater, bar coater, champlex coater, curtain coater, die slot coater, gravure coater, brush. A coater, a two-roll, or a metering blade type size press coater, a short dwell coater, a bill blade coater, a gate roll coater, a sprayer, or the like is appropriately used. These devices are applied or impregnated in the form of an on-machine coater or an off-machine coater.

In forming the image receiving layer, 1
It is also possible to have a layer, or a multilayer structure of two or more layers as required. In the case of a multi-layer structure, each coating composition does not have to be the same, and may be appropriately adjusted and blended according to the required quality level, and is not particularly limited. It is also possible to provide a synthetic resin layer, a coating layer composed of a pigment and an adhesive, an antistatic layer, etc. on the back surface of the base paper to prevent curling, impart printability, and feedability.

In order to obtain the image-receiving paper for thermal transfer recording having excellent recording suitability desired by the present invention, the method for preparing the base paper as the support of the present invention cannot be overlooked.

The base paper as the above-mentioned support is prepared by appropriately adjusting the kind of pulp as a raw material, its manufacturing method, kind of beating machine and processing conditions, added chemicals, paper-making method, post-processing method such as calender. Manufactured. Among these conditions, specifying the type and properties of the raw material pulp, and imparting appropriate smoothness and cushioning property to the base paper is one of the more preferable factors in obtaining the desired effect of the present invention. Become. For example, although smoothing of the paper surface can be achieved to some extent by pressure treatment using a super calender in the post-treatment process,
Depending on the type and properties of the pulp, no matter how much the calendering process is strengthened, it is difficult to obtain a high-quality thermal transfer recording image receiving paper with a sharp image and no transfer unevenness.

The characteristics of the pulp fiber constituting the base paper of the present invention are described in J. It is preferable that the water retention of the pulp in accordance with TAPPI No. 26 is 125% or less in the measured value before beating, and the following conditional expressions are satisfied. By using pulp fibers that satisfy such specific conditions, the obtained base paper has a relatively bulky paper layer structure, has appropriate voids and excellent cushioning properties, and is homogeneous and highly smooth. Since it is extremely effective in forming a base paper, it can be a more preferable embodiment. : 0.3 ≤ L ≤ 1.0: 0.3 ≤ d / D ≤ 0.8 L: J. Length-weighted average fiber length (mm) measured according to TAPPI No. 52 D: Average fiber diameter measured by micrograph (μm) d: Average lumen diameter measured by micrograph (μm)

Here, the water retention of pulp is defined by the amount of water held by a certain amount of pulp fiber, and serves as a quantitative measure of the swelling state and porosity of pulp. . Specifically, J. It is a value measured by a method based on TAPPI No. 26, and is called WRV. Ordinary pulp is produced from lignocellulosic fibers such as wood, straw, bacas, bamboo, and kenaf as a raw material through a cooking process and a bleaching process. Although there are differences depending on the types of raw materials and the pulp manufacturing process, it is generally said that the water retention of pulp fibers after bleaching is 125 to 200%.

Most of the pulp fibers used in the present invention are those having a water retention of 125% or less and very low swelling properties. Such pulp fibers are
Since there is little water penetration into the fiber wall, there is little change in expansion and contraction of the fiber due to moisture absorption and desorption. That, of course, effectively acts to improve the dimensional stability, because the bonding strength between the fibers is relatively small, and the number of contact points between the fibers is small,
It was found that it gives the base paper proper voids and cushioning properties. Furthermore, when it is finished as a base paper using a pulp fiber having such characteristics, its heat insulating property is remarkably improved, and heat from the thermal head or the current-carrying head can be appropriately stored on the surface of the image receiving layer. It was found that the quality characteristics as a thermal transfer recording image receiving paper can be improved.

In order to obtain such a pulp fiber, the kind and production method thereof are not particularly limited, but for example, slurry-like or porridge-like pulp fiber produced through a cooking and a bleaching step. (Wet pulp)
Examples thereof include dry pulp that has been once dried into a sheet using a dryer, or waste paper pulp that has undergone a papermaking process and has been at least once formed into a paper, and has undergone a drying process.

Incidentally, when the water retention of the pulp fiber specified in the present invention exceeds 125%, as the value increases, the voids and cushioning properties in the paper layer are gradually lost, and the heat insulating effect becomes poor. As a result, in the image receiving paper finished with such pulp, not only the sharp, high quality thermal transfer image receiving layer without missing dots desired by the present invention cannot be formed, but also the expansion and contraction degree of the paper is large. As a result, curling is likely to occur, which causes running troubles in the printer. On the other hand, if the water retention is too small, the number of voids in the paper layer becomes too large, and the bond strength between fibers becomes extremely small, leading to a decrease in the paper layer strength and the generation of paper dust.
As a result, there is a possibility that the image reproducibility may be deteriorated, a line break may occur in the image area due to picking, and further, the printability may be deteriorated, which is not preferable. Therefore, the water retention of the pulp fiber is preferably 125% or less, more preferably about 75 to 120%.

During the production of the base paper, the wet pulp is usually introduced as a paper stock to the wire part of the paper machine, and subjected to a paper making process to be finished as a so-called paper sheet. in this case,
As a method for preparing the stock material, various types of refiners, such as various refiners, can be used so that appropriate paper layer strength and smoothness can be obtained when wet pulp (in the case of dry pulp, the pulp is once disintegrated and made into a slurry) is finished as a base paper. A beating machine is used to perform the required beating, and various internal additives, dyes, fillers, etc. are appropriately added to the pulp slurry as needed to give a concentration of 0.3 to
It is prepared as a stock (pulp slurry) of about 1% by weight.

In the case of the conventional image receiving paper for thermal transfer recording,
The pulp fiber constituting the base paper, which is the support, has a water retention of about 160 to 250% after the beating step. On the other hand, the present inventors have diligently studied the characteristics of pulp fiber to obtain the desired effect of the present invention. As a result, they have found that the water retention of pulp fibers before being subjected to beating is an important factor.

That is, the water retention (before beating) at the time of disaggregation was J. 1 in the measured value according to TAPPI No.26
It is important to be 25% or less. Of course, in the preparation of the stock, as described above, the beating is performed with a beating machine. However, if the beating is excessively performed, the original characteristics of the specific pulp fiber as described above will not be obtained. Since it may be lost and the desired function may not be exhibited, the water retention of the pulp fiber after beating is 180% or less, preferably 90 to 1
It is desirable to adjust the range to about 60%.

Next, examples of pulp fibers satisfying the above conditional expressions (1) and (2) include maple, hippo, oak, oak,
K made from hardwood such as beech, aspen and eucalyptus
The chemical pulp obtained by P, SP, AP method etc. is mentioned. By the way, if the length-weighted average fiber length of pulp fibers (hereinafter referred to as L value) exceeds 1.0 mm, the dispersibility of the stock material in the papermaking process becomes poor, and the formation is poor and the uniform image-receiving layer is obtained. It is difficult to obtain the surface. On the other hand, if the thickness is less than 0.3 mm, the paper layer strength becomes extremely small, and paper dust is liable to be generated, which is liable to cause deterioration of an image due to paper dust and a line break phenomenon of an image area due to a pick. In addition, printability is also reduced, which is not preferable. Therefore, the L value is 0.3 to
1.0 mm, more preferably 0.35 to 0.85 mm is desirable.

On the other hand, in the conditional expression, when the d / D ratio exceeds 0.8, the texture is good and the smoothness of the paper surface is improved, but the paper is easily crushed and the cushioning property of the base paper is There is a possibility that the image may be lost, and the desired high-definition image formation without dot omission and sharp and high image quality may not be performed. On the other hand, when it is less than 0.3, the fibers become too hard, the paper is hard to be crushed, and there is a concern that the smoothness of the paper surface and the image quality may deteriorate. Further, the strength of the paper layer is reduced. Therefore, the d / D ratio is preferably 0.3 ≦ d / D ≦ 0.8, and more preferably 0.35 ≦ d / D ≦ 0.75.

As a method for measuring the pulp fiber length,
Pulp fiber length measurement method by sieving method (TAPPI-STD
T233 hm-82) or projection method for measuring pulp fiber length
(TAPPI-STD T232hm-85) and the like. Unlike these methods, the method of measuring the length-weighted average fiber length according to TAPPI No. 52 has a high detection power, and the width of the fiber, the thickness of the fiber wall,
It has the feature that the fiber length distribution can be automatically measured without being affected by the flexibility of the fiber. The measured values in each example of the present invention are KAJ of Finland.
It was measured using an FS-100 model manufactured by AANI.

The average fiber diameter and the average lumen diameter were measured from micrographs. When taking a micrograph,
Pulp fibers were embedded in an acrylic resin, and a thin section made with a microtome was used to measure 25 fibers for each, and an average value was obtained.

The content of the above specific pulp fiber is 50% by weight or more based on the total pulp fibers constituting the base paper.
More preferably, it is important to contain 60% by weight or more. By the way, if the amount is less than 50 parts by weight, not only the base paper having the desired proper voids and cushioning property of the present invention cannot be obtained, but the obtained base paper is subjected to a pressure treatment by a calender or the like. However, a sufficient smoothing effect cannot be expected. As a result, it is not possible to obtain a high-quality image-receiving paper without the transfer unevenness and dot omission desired by the present invention.
As described above, the desired effect of the present invention is efficiently exhibited when the pulp water content, the physical property value, and the blending amount are all satisfied as the pulp fiber.

In the present invention, chemical pulp fibers other than the above can be appropriately blended, if necessary, as long as the specific pulp fibers are contained in an amount of 50 parts by weight or more. Furthermore, SGP, RGP, BCTMP, CTMP
Mechanical pulp and deinked pulp such as kenaf, bamboo,
Non-wood pulp such as straw and hemp, organic synthetic fibers such as polyamide fiber, polyester fiber and polynosic fiber, and inorganic fibers such as glass fiber, ceramic fiber and carbon fiber can also be used.

In the present invention, when the stock material is prepared, the filler is contained in an amount of 2 to 30% by weight, more preferably 4 to 25% by weight, based on the pulp fiber content. It was found to be effective in improving moderate voids, cushioning properties, and smoothness. The image-receiving paper finished with the base paper obtained under such conditions has particularly excellent heat insulating properties and excellent quality properties as a thermal transfer recording image-receiving paper, and can be a more preferable embodiment.

The filler in this case is not particularly limited, but includes, for example, talc, kaolin, clay, calcined kaolin, deramikaolin, heavy calcium carbonate, light calcium carbonate, magnesium carbonate, titanium dioxide, aluminum hydroxide, Mineral fillers such as calcium hydroxide, magnesium hydroxide, zinc oxide, magnesium sulfate, magnesium silicate, calcium sulfate, calcium silicate, white carbon, aluminosilicate, amorphous silica, sericite, bentonite and smectite, and polystyrene resin fine particles, Examples thereof include organic synthetic fillers such as urea formalin resin fine particles and fine hollow particles, and the fillers contained in waste paper, brokes, etc. can be recycled. Among these various fillers, a porous filler having an apparent specific gravity defined by JIS-K-6220 of 0.10 to 0.50 g / cm ³ , preferably 0.15 to 0.45 g / cm ³ is used. It is more preferably used because it can more efficiently impart the heat insulating properties of the base paper.

In addition to pulp fibers and fillers, various amounts of conventionally used anionic, nonionic, cationic or amphoteric compounds are used in the paper material as long as the desired effects of the present invention are not impaired. A retention aid, a drainage improver, a paper-strengthening agent, a paper-making internal additive such as an internal sizing agent, and the like are appropriately selected and used as necessary. Also, dyes, optical brighteners, p
An internal additive for papermaking such as an H-adjusting agent, a defoaming agent, a pitch control agent, and a slime control agent can be appropriately added if necessary. Further, it is possible to surface sizing using adhesives such as starch, polyvinyl alcohol, carboxymethyl cellulose, latex and derivatives or modified products thereof, various surface sizing agents, pigments, dyes, optical brighteners and antistatic agents. Is.

The papermaking method is not particularly limited. For example, an acidic papermaking method having a papermaking pH of about 4.5, or an alkaline filler such as calcium carbonate as a main component,
The papermaking pH is set to a weak acidity of about 6 to a weak alkalinity of about 9,
All papermaking methods such as the so-called neutral papermaking method can be applied.

The thus prepared image-receiving paper for thermal transfer recording is subjected to smoothing treatment in a usual drying process or surface treatment process so that the Z-axis strength defined in TAPPI-STD UM 403 is 0.05 to 0.18 ft.lb. , And more preferably 0.08-
It is adjusted and finished in a range of about 0.16 ft · lb and a water content of 3 to 10% by weight, more preferably 4 to 8% by weight.

When the smoothing process is performed, the above-mentioned quality is satisfied and, at the same time, the JIS-B
The ten-point average roughness (R _Z ) specified in −0601 is 3 to 15 μm.
m, and more preferably 4 to 12 μm, to obtain a more excellent and high-quality recorded image desired by the present invention. By the way,
When the ten-point average roughness of the surface of the image receiving paper exceeds 15 μm, the smoothness of the paper becomes poor, and there is a concern that dot dropout or image quality deterioration may occur. On the other hand, if the smoothing is promoted to less than 3 μm, as a result, the properties such as cushioning properties and heat insulating properties of the base paper are lost, and ink transfer failure, ink swimming and uneven density on the surface of the image receiving layer occur. It becomes easy and not preferable. In addition, the fixability of the ink becomes poor, and dot defects due to scratches, rubbing stains, and the like are likely to occur.

The ten-point average roughness specified here is a standard length according to the method defined in JIS-B-0601 using a universal surface profile measuring instrument SE-3C (manufactured by Kosaka Laboratory Ltd.). It was measured at 8 mm. The method of measuring such surface roughness is
The vertical movement of the stylus is converted into an electrical quantity, and the unevenness of the paper surface, that is, the smoothness is read. Therefore, it is possible that the air permeability of the paper may affect the fine roughness of the paper surface, which was considered difficult with measuring equipment such as Beck's smoothness meter and Parker Print Surf, which are general air leak type smoothness measuring tools. It was possible to measure accurately without Moreover, according to the detailed study results of the present inventors, the measured value of the ten-point average roughness is more than the value of the center line average roughness obtained by cutting off the waviness of the image receiving paper surface. It has been clarified that the effect of the desired smoothing treatment is highly correlated.

When smoothing the image-receiving paper for thermal transfer recording, it is carried out by a normal smoothing device such as a super calender, a gross calender, a soft calender, etc. without any particular effort. More desirable results can be obtained by passing the paper through a pressure nip composed of a metal roll heated to 50 ° C. or higher, more preferably 80 ° C. or higher, and a heated or unheated elastic roll for smoothing. . In addition, it is appropriately used in on-machine and off-machine, the form of the pressurizing device,
The number of pressure nips and the like are also appropriately adjusted according to a normal smoothing device.

[0050]

EXAMPLES The present invention will be described in more detail with reference to examples, but the scope of the invention is not limited thereto. Unless otherwise specified, "part" and "%" in the examples mean "part by weight" and "% by weight", respectively.

[Measurement of Physical Properties of Pulp Fiber] The water retention and the fiber morphology of the pulp fiber were measured by the following methods, and the obtained results are shown in Table 1. (Measurement of water retention) J. The water retention (%) of the pulp fiber was measured according to TAPPI No. 26.

(Measurement of Length Weighted Average Fiber Length) J. TAP
The length-weighted average fiber length (L value; mm) of the pulp fiber was measured according to PI No.52.

(Measurement of d / D) 2 made by microtome
A thin section of 5 pulp fibers was photographed with a micrograph, and the average fiber diameter (D; μm) and the average lumen diameter (d; μm) were measured to calculate d / D.

[Measurement of Physical Properties of Synthetic Polymer Resin] Tg and γ of the synthetic polymer resin were measured by the following methods, and the obtained results are shown in Table 2. (Tg) It measured using the differential scanning calorimeter (DSC-10 / made by Seiko Instruments Inc.).

(Γ) It was measured using a surface tension tester (manufactured by Ohira Rika Kogyo Co., Ltd.) manufactured by Junoi.

Example 1 [Preparation of base paper] 90 parts of LBKP [dry pulp of pulp, freeness = 480 ml of CSF], NBKP [dry pulp of pulp, freeness = 500 ml of CSF] 10
20 parts of talc [apparent specific gravity = 0.75 g / cm ³ ] as filler, 2.0 parts of sulfuric acid band, 1.5 parts of rosin emulsion sizing agent,
After adding 1.0 part of cationic starch and 0.2 part of cationic polyacrylamide and diluting them with white water, a paper stock having a pH of 5.2 and a solid content concentration of 1.0% was prepared. Papermaking this stock with a twin wire paper machine,
Then, using a size press device, size press coating was performed so that the dry starch coating amount was 2 g / m ² , followed by drying and passing through a 3-nip machine calender to obtain a weight of 80 g. A base paper of / m ² was obtained.

[Preparation of Coating Composition] 100 parts (solid content; hereinafter the same) of calcined kaolin [apparent specific gravity = 0.34 g / cm ³ ] and 0.4 parts of carboxymethyl cellulose (solid content ratio to pigment; The same) and 0.5 parts of sodium polyacrylate were added, and the mixture was dispersed and mixed using a Choles disperser to prepare a pigment slurry. To this pigment slurry, 70 parts of resin A shown in Table 2, 5 parts of oxidized starch, 1 part of optical brightener and water were added and mixed by stirring to prepare a coating composition having a solid content concentration of 45% by weight.

[Formation of Image Receiving Layer] The coating composition thus obtained was coated on one surface of the above-mentioned base paper using a blade coater so that the dry coating amount was 15 g / m ^2, and after drying ,
Using a super calender, smoothing treatment under the conditions of nip number 11, metal roll temperature of 50 ° C. and nip linear pressure of 150 Kg / cm to obtain an image receiving paper for thermal transfer recording having a basis weight of 95 g / m ^2. It was

Examples 2 to 5 Resin B (Example 2), Resin C (Example 3), Resin D (in the preparation of the coating composition of Example 1 were changed by changing the kind of the synthetic polymer resin. Example 1) except that Example 4) and Resin E (Example 5) were used to prepare coating compositions respectively.
An image receiving paper was obtained in the same manner as.

Example 6 In the preparation of the coating composition of Example 1, the type of porous pigment was changed to obtain amorphous silica (apparent specific gravity = 0.20 g / c).
m ³ ] 100 parts was used and the resin A was also changed to 100 parts to prepare a coating composition, and an image receiving paper was obtained in the same manner as in Example 1.

Example 7 In the preparation of the coating composition of Example 1, the type of the porous pigment was changed and the coating composition was prepared by using calcined kaolin having an apparent specific gravity of 0.42 g / cm ^3. Example 1 except prepared
An image receiving paper was obtained in the same manner as.

Examples 8 to 9 In the preparation of the coating composition of Example 1, as a pigment, 75 parts of calcined kaolin and 25 parts of spindle-shaped light calcium carbonate [apparent specific gravity = 0.56 g / cm ³ ] were mixed pigments. Example 1 was repeated except that 125 parts of Resin A (Example 8) and 150 parts of Resin A (Example 9) were added to the pigment slurry obtained by dispersing and mixing these, respectively, to prepare a coating composition. An image receiving paper was obtained in the same manner as.

Example 10 In the preparation of the coating composition of Example 8, the compounding parts of the pigment were 60 parts of calcined kaolin and 40 parts of spindle-shaped light calcium carbonate.
An image receiving paper was obtained in the same manner as in Example 8 except that the coating composition was prepared by changing the parts.

Example 11 In the formation of the image receiving layer of Example 1, the coating amount was changed to
An image receiving paper was obtained in the same manner as in Example 1 except that the dry weight was 8 g / m ² .

Comparative Examples 1 to 5 Resin F (Comparative Example 1), Resin G (Comparative Example 2) and Resin H (in the preparation of the coating composition of Example 1 were changed by changing the kind of the synthetic polymer resin. An image receiving paper was obtained in the same manner as in Example 1 except that Comparative Example 3), Resin J (Comparative Example 4) and Resin K (Comparative Example 5) were used to prepare coating compositions.

Comparative Examples 6 to 8 In the preparation of the coating composition of Example 1, the type of porous pigment was changed to give kaolin [apparent specific gravity = 0.58 g / cm3].
³ ] (Comparative Example 6), amorphous silica [apparent specific gravity = 0.55 g
/ Cm ³ ] (Comparative Example 7) and amorphous silica [apparent specific gravity = 0.07 g / cm ³ ] (Comparative Example 8) were used, and the coating composition was prepared respectively. An image receiving paper was obtained in the same manner.

Example 12 [Preparation of base paper] LBKP [Pulp dry pulp, C
SF 480 ml] 95 parts and NBKP [dry pulp of pulp, CSF 500 ml] 5 parts were added to a pulp slurry, and spherical agglomerated light calcium carbonate [apparent specific gravity = 0.38 g / cm ³ ] and heavy calcium carbonate were used as fillers. 20 parts of mixed filler (apparent specific gravity = 0.80 g / cm ³ ) (mixing ratio 3: 2), 0.5 part of sulfuric acid band, and 1. of cationic starch.
5 parts, 0.2 parts of cationic polyacrylamide, and 0.1 part of alkyl ketene dimer were added, and the mixture was diluted with white water to have a pH of 7.9 and a solid content concentration of 1.
A 1% stock was prepared. This paper material was paper-made using a Fourdrinier paper machine, and then a size press machine was used to apply the oxidized starch and the maleic anhydride-based surface sizing agent in a dry weight of 2 g / m ² and 0.2 g / m ² , respectively. After size press coating so as to be ² , it was dried and passed through a machine calender with 3 nip to obtain a base paper having a basis weight of 75 g / m ² .

[Preparation of coating composition] 0.2 parts of carboxymethyl cellulose and 0.5 parts of sodium polyacrylate were added to 100 parts of spherical agglomerated light calcium carbonate [apparent specific gravity = 0.38 g / cm ³ ]. A pigment slurry was prepared by dispersing and mixing with a Corless disperser. To this pigment slurry, 35 parts of resin A, 5 parts of polyvinyl alcohol, 1 part of optical brightener and water were added, and mixed by stirring to give a solid content of 5
A coating composition of 0% by weight was prepared.

[Formation of Image Receiving Layer] The coating composition thus obtained is coated on one surface of the above base paper using a bar coater so that the dry coating amount is 20 g / m ^2, and then dried. Soft calender with 4 nips and metal roll temperature of 100
Smoothing treatment was carried out under the conditions of ℃ and nip linear pressure of 200 Kg / cm to obtain a thermal transfer recording image-receiving paper having a basis weight of 95 g / m ² .

Examples 13 to 14 In the preparation of the base paper of Example 12, pulps (Example 13) and pulp (Example 14), all of which are dry pulps, were used by changing the type of pulp fiber. Example 12 except that the base paper was prepared by mixing 95 parts each.
A base paper and an image receiving paper were obtained in the same manner as in.

Examples 15 to 16 In the formation of the image receiving layer of Example 1, the coating amount was changed to
5 g / m ^{2 of} dry weight (Example 15), and 25 g / m ²
An image receiving paper was obtained in the same manner as in Example 1 except that the coating was carried out so that m ² (Example 16) was obtained.

Comparative Example 9 In the preparation of the coating composition of Example 12, the porous pigment was replaced by spindle-shaped light calcium carbonate [apparent specific gravity = 0.56 g / cm 3].
³ ] except that the coating composition was prepared by changing to 100 parts
An image receiving paper was obtained in the same manner as in Example 12.

Comparative Example 10 Same as Example 12 except that in the preparation of the coating composition of Example 12, the synthetic polymer resin was changed and the resin L was used to prepare the coating composition. To obtain an image receiving paper.

The 26 types of image-receiving papers for thermal transfer recording thus obtained were subjected to quality measurement and evaluation by the following methods, and the obtained results are shown in Table 3.

(Measurement of Image Density) A test pattern having a bar code print, a solid print and a halftone dot print was transferred and recorded using a thermal transfer printer, and the density of a black solid print portion of the obtained recorded image was measured by a Macbeth densitometer ( RD914 type / manufactured by Macbeth).

(Evaluation of transfer unevenness on recording surface) The degree of transfer unevenness of the solid printing portion was visually evaluated according to the following evaluation criteria. ⊚: Excellent in light and shade and no swimming ◯: Good with little unevenness in shade and swimming. Δ: Inferior due to uneven shade and swimming.

(Evaluation of sharpness of recording surface) The sharpness of the thin line (edge portion) printed with the bar code was visually evaluated according to the following evaluation criteria. ⊚: There are no dot bleeding or line breaks, and fine lines are sharp and excellent. ◯: There is almost no dot blurring or line breaks, and the sharpness of fine lines is good. Δ: Dot bleeding and line breaks were recognized, and the fine lines were unclear and slightly inferior, but there was no problem in practical use. X: There are many dot bleeds and line breaks, and the fine lines are unclear and inferior.

(Evaluation of dot reproducibility on recording surface) The halftone dot printing portion was enlarged 30 times by a dot analyzer (DA-3000 / KS Systems Co., Ltd.), and the dot shape (roundness) and missing dots were confirmed. The degree was visually evaluated according to the following evaluation criteria. ⊚: There is no dot dropout and the dot shape is excellent. ◯: There are almost no missing dots, and the dot shape is good. Δ: Missing dots were observed and the dot shape was slightly inferior, but there was no problem in practical use. X: Many dots are missing and the dot shape is inferior.

(Evaluation of Rubbing Stain on Recording Surface) The above bar code printing part was rubbed 100 times with a load of 200 g using a friction tester for dyeing fastness (manufactured by Toyo Seiki Seisakusho Co., Ltd.), and the degree of stain was as follows. Visual evaluation was performed according to the evaluation criteria of. ⊚: Excellent with no stains on the print. ◯: There is almost no stain on the print, which is good. Δ: Staining of the print is recognized and slightly inferior. X: Marked stains are noticeable and inferior.

(Evaluation of Printing Strength) Printing was carried out using a RI printability tester (manufactured by Akira Seisakusho Co., Ltd.) and visually evaluated according to the following evaluation criteria. ⊚: Excellent without any pick. ◯: Good with almost no picking. Δ: Picking occurred and was slightly inferior. X: There are many picks, which is inferior.

(Measurement of Ten-Point Average Roughness of Image Receiving Layer Surface of Recording Paper) Using a universal surface shape measuring device (SE-3C / manufactured by Kosaka Laboratory Ltd.), a standard length of 8 m according to JIS-B0601.
The ten-point average roughness (Rz; μm) of the image receiving layer surface at m was measured.

[0082]

[Table 1]

[0083]

[Table 2]

[0084]

[Table 3]

[0085]

As is clear from the results shown in Table 3, the thermal transfer recording image-receiving paper according to the embodiment of the present invention has no particular transfer unevenness or dot omission and is excellent in sharpness and dot reproducibility. It was Further, it was a thermal transfer recording image-receiving paper capable of forming a high image quality, having excellent fastness without generation of rubbing stains on the transferred print, and having excellent printability.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Fudou Yasuda 4-3-1, Jokoji, Amagasaki City, Hyogo Prefecture Kanzaki Paper Co., Ltd. Kanzaki Mill

Claims (5)

[Claims] 1. A thermal transfer recording image-receiving paper comprising an image-receiving layer for receiving a hot-melt ink by coating a coating composition containing a synthetic polymer resin and a porous pigment as main components on one side of a base paper.
(A) The synthetic polymer resin has a glass transition point and a surface tension of −60 to −5 ° C. and 38 to 58 mN /, respectively.
m, a synthetic polymer resin, and (b) a porous pigment having an apparent specific gravity of 0.1 to 0.5 g / cm ³ according to JIS-K-6220 as the porous pigment. An image-receiving paper for thermal transfer recording characterized by. 2. A pulp fiber constituting a base paper is described in J. T
The pulp according to APPI No. 26 has a water retention value of 125% or less as measured before beating, and pulp fibers satisfying the following conditional expressions are 50 to 10 of all pulp fibers.
The image receiving paper for thermal transfer recording according to claim 1, which contains 0% by weight. : 0.3 <L <1.0: 0.3 <d / D <0.8 Here, L: J. Length-weighted average fiber length (mm) measured according to TAPPI No. 52 D: Average fiber diameter measured by micrograph (μm) d: Average lumen diameter measured by micrograph (μm) 3. The synthetic polymer resin is 20 to 150 relative to the pigment.
The image-receiving paper for thermal transfer recording according to claim 1, which is blended in a weight percentage. 4. The image-receiving paper for thermal transfer recording according to claim 1, wherein the synthetic polymer resin is a synthetic rubber latex. 5. The image-receiving paper for thermal transfer recording according to claim 1, wherein the coating amount of the coating composition is 5 to 25 g / m ^{2 on} one side in dry weight.