JP3089737B2 - Image receiving paper for thermal transfer recording - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer recording paper used in a copying machine, a printer, a facsimile machine, etc., utilizing a thermal transfer recording system. The present invention relates to an image-receiving paper for thermal transfer recording, which is excellent as an image-receiving paper and has excellent suitability for office paper such as writing and stamping properties.

[0002]

2. Description of the Related Art In recent years, with the progress of OA, copying machines and printers using various recording methods such as an electrophotographic method and a thermal transfer recording method have been widely used. These are used in, for example, CAD / CAM and the like according to their respective uses. In this type of recording method, an ink ribbon having a heat-fusible ink layer composed of a coloring material is melted by heat, and the coloring material is transferred to recording paper, and is adhered, adsorbed, and dyed to form a recorded image. The hot-melt type thermal transfer recording method for obtaining has recently attracted attention, and is characterized by the fact that plain paper can be used as recording paper.

[0003] In this thermal transfer recording system, as in other recording systems, there is a movement toward colorization, high speed, high resolution, and the like, and there is a demand for full color recording, higher speed recording, clearer printing, and the like. Is getting stronger. For example, when performing single-color or multi-color recording with a color thermal transfer printer or the like, a recording material is combined with an ink ribbon having a coloring material such as yellow, magenta, cyan, and black and a wax, and is applied by a thermal head to be transferred onto the recording paper. However, when plain paper is used as the recording paper, the smoothness of the surface of the image receiving layer is inferior, and defects such as transfer unevenness and missing dots occur.

For this reason, many proposals have been made for improving the smoothness of the surface of an image receiving layer. For example, Beck smoothness is specified (Japanese Patent Laid-Open Nos. 59-133092 and 59-187892),
Those provided with a thermal transfer image-receiving layer containing a specific pigment or binder (JP-A-57-182487, JP-A-59-182787, JP-A-60-114)
No. 89, No. 60-110492, No. 60-192690, No. 61-217289
No. 61-286187 and No. 63-21185).
However, although the improvement effect is recognized to some extent in these conventional methods, the image sharpness due to uneven density and color misalignment in overlapping color inks in multi-color recording, or missing ink dots and poor dot diameter reproducibility, etc. However, difficulties such as a decline in the number have not been completely solved. Therefore,
It is not sufficient to simply enhance the calendering treatment etc. to improve smoothness or to include a pigment in the thermal transfer image receiving layer, and it is not enough to eliminate the above-mentioned drawbacks and obtain a recording that is sufficiently satisfactory in ink transferability and dot reproducibility. At present it has not been obtained.

[0005]

SUMMARY OF THE INVENTION The present invention is particularly suitable for recording paper having good transferability and reproducibility of ink, good resolution, sharpness and color density, no transfer unevenness and missing dots, moderate glossiness. An object of the present invention is to provide a high-quality and high-quality image receiving paper for thermal transfer recording, which is excellent in office paper such as writing properties and sealability, and is excellent in writing properties and sealability.

[0006]

Means for Solving the Problems The present invention relates to a thermal transfer recording image receiving paper provided with an image receiving layer for receiving the transfer of the heat-fusible ink on a base paper, wherein the image receiving layer has a single particle having a long diameter and a short diameter. Coating composition containing light calcium carbonate having an average ratio of 1.5 to 15 and satisfying the following formula, in an amount of 40% by weight or more based on all pigments, and containing the light calcium carbonate and an adhesive as main components: Having a coating solid content of 0.3 to 4.0 g / m ² per side, and a surface of the image receiving layer of JIS B
[0601] An image receiving paper for thermal transfer recording, characterized by having a ten-point average roughness of 3 to 22 μm as specified in No. 0601. 1.5 ≦ d / D ≦ 8.0 d = 0.2-3.0 μm D = 0.1-0.6 μm d: average particle diameter μm by Cedigraph X-ray transmission type particle size distribution measurement D: BET ratio Average particle diameter μm calculated based on specific surface area by surface area measurement method

[0007]

[Function] Industrial calcium carbonate is roughly divided into heavy calcium carbonate obtained by physically pulverizing natural limestone and light calcium carbonate obtained by synthesis by a chemical method. , Calcite type, aragonite type and vaterite type. In the papermaking industry, these calcium carbonates are widely used as fillers or pigments. As a method for producing light calcium carbonate, there are a carbon dioxide compounding method in which carbon dioxide gas is blown into lime milk to cause a reaction, and a carbonate solution compounding method obtained by reacting a carbonate with an aqueous solution of calcium chloride or the like. ,
The former carbon dioxide compounding method is often employed.

In general, light calcium carbonate has primary particles in the shape of a spindle, needle, column, or cubic or rectangular parallelepiped with a rounded local part, and a primary particle diameter of 0.05.
It is about 1.0 μm. Usually, such fine primary particles of light calcium carbonate often form so-called secondary particles in which an aggregate of a plurality or a large number of bonded primary particles is formed. By the way, these secondary particles lose their original primary particle characteristics as if they behave like primary particles, and as a result, the unique effects of the light calcium carbonate cannot be sufficiently obtained. Rather, the characteristics of the secondary particles may appear strongly. That is, the light calcium carbonate has properties such as the smoothness and gloss of the formed paper, the viscosity of the coating liquid, and the like, depending on the shape, agglomeration form, or particle diameter of the secondary particles, together with the characteristics of the primary particles that the primary primary particles have. Significantly affects properties. Therefore, the light calcium carbonate to be used must sufficiently exhibit the characteristics of the secondary particles.

The inventors of the present invention have particularly improved the adhesion between the ink ribbon and the recording image receiving surface, have excellent ink receptivity, and can reproduce high quality images. Therefore, the present invention is suitable not only for monochrome printing but also for full color printing. As a result of intensive studies on a method of obtaining a thermal transfer recording image receiving paper having excellent quality characteristics such as writability and sealability, a coating liquid containing light calcium carbonate having a specific particle morphology as a pigment was identified. By providing a 10-point average roughness of the surface of the image receiving layer by applying an amount of the coating, and by specifying the ten-point average roughness of the surface of the image receiving layer, a remarkable effect that cannot be predicted from the prior art can be obtained by a synergistic effect of these conditions. And finally completed the present invention.

Specifically, a coating composition containing a specific light calcium carbonate and an adhesive as main components is prepared as a coating solution, and the solid content of the coating is 0.3 to 4.0 g / m ² per side. Coating and drying to form an image receiving layer, and the image receiving layer surface is smoothed so as to have a ten-point average roughness of 3 to 22 μm as defined in JIS B0601, thereby obtaining the desired thermal transfer recording image of the present invention. An image receiving paper is obtained.

Light calcium carbonate originally has a very strong cohesive force between primary particles, and usually a large number of primary particles are bonded to form aggregates. The light calcium carbonate constituting the aggregate is in the form of a slurry.
Is not completely separated into individual primary particles even if it is treated, for example, in a wet mill.

Therefore, the present inventors disperse light calcium carbonate in water, treat the mixture with a stirrer such as a desktop propeller mixer, and measure the slurry by a Sedigraph X-ray transmission type particle size distribution measuring method. Average particle diameter d obtained by
Is measured as a particle diameter of an aggregate in which a large number of primary particles aggregate into a so-called secondary particle, as if it were a primary particle. Thus, d should be interpreted correctly as the average secondary particle size. (Hereafter, d is referred to as the secondary particle diameter)

On the other hand, the average particle diameter D of light calcium carbonate calculated from the value measured by the BET specific surface area measurement method is as follows:
Approximately, it can be defined as the original average particle diameter, that is, the average primary particle diameter. (D is hereinafter referred to as the primary particle diameter)

The light calcium carbonate used in the present invention is:
The average particle diameter d of the secondary particles is 0.2 to 3 when measured in an aqueous dispersion by a Sedigraph X-ray transmission type particle size distribution measuring method.
0 μm, preferably 0.3 to 2.5 μm, and the ratio (d / D value) of the average particle diameter d of the secondary particles to the average particle diameter D of the primary particles is 1.5 to 8.0, preferably 2.0 to 7.0.
It is. By the way, when d is less than 0.2 μm, the ink receptivity of the obtained image receiving layer is inferior, and the reproducibility of dots is reduced. On the other hand, if it exceeds 3.0 μm, the effect of the smoothing treatment of the paper is reduced and a uniform image receiving layer surface cannot be obtained, resulting in transfer unevenness. Further, since the frictional resistance becomes large, the running property of the paper at the time of recording deteriorates, and particularly in the case of the color recording in which the multi-color ink is overprinted, it causes the color shift of the recorded image, which is not preferable.

On the other hand, when the value of d / D exceeds 8.0, light calcium carbonate forms large aggregates, so that a uniform and smooth image receiving layer cannot be obtained, resulting in transfer unevenness and image quality. In addition, when used as office paper, ink such as a pen or a stamp penetrates into the voids of the aggregated particles of light calcium carbonate, spreads over the coating layer, oozes out from the paper surface, and has ink resistance and vermilion. Poor suitability for office paper such as sealability. On the other hand, if it is less than 1.5, the number of fine particles close to a single crystal becomes relatively large, and as a result, the strength of the surface of the image receiving layer is weakened. Since the surface is rolled up together with the transfer ink, dots are missing, which causes deterioration in image quality.
For this reason, it is not possible to cope with recording such as high speed printing and color printing for multicolor printing.

Further, the light calcium carbonate of the present invention has a ratio (D _L / D _S ) of the average value of the major axis (D _L ) and the minor axis (D _S ) of the single particles of 1.5 to 15, Preferably
It is desirable to be in the range of 2.0 to 12. By setting such a specific range, appropriate gloss and smoothness can be imparted,
The desired excellent effects of the present invention can be obtained.

Here, the ratio of the average value of the major axis to the minor axis of the light calcium carbonate (the value of D _L / D _S ) is measured by a microscopic method or the like, and the value of this ratio increases. As the light calcium carbonate particles become oriented in the flow direction of the base paper, the optical characteristics such as glossiness and rigidity are improved, and the relatively flat particles are increased. It has the characteristic that it can be obtained.

If the value of D _L / D _S exceeds 15, the fluidity of the coating liquid becomes unstable, and the above-mentioned orientation characteristics are impaired, making it difficult to obtain the desired effects of the present invention. On the other hand, when it is less than 1.5, the number of cubic (granular) particles increases, the effect of smoothing the surface of the image receiving layer is reduced, transfer unevenness is likely to occur, and the image quality is deteriorated.

Examples of the precipitated calcium carbonate in the form that satisfies such D _L / D _S value described above, for example fusiform, acicular, stump-like side columnar, pillar, hexagonal prism, a plate shape, the shape of a rectangular parallelepiped, etc. Among them, in the case of the present invention, particularly, light calcium carbonate having a spindle shape, a column shape, or a hexagonal column shape is more preferably used. The crystal structure and production method of the light calcium carbonate are not particularly limited. For example, any of calcite type, aragonite type and vaterite type can be used in the crystal structure. Among them, aragonite-type light calcium carbonate is preferably used because it has high ink acceptability and excellent coating suitability.

As a method for producing light calcium carbonate,
For example, JP-B-42-14706, JP-B-54-28397, JP-B-55-51852
No. 59-12607, No. 60-33765, JP-A-59-57913
No. 59-26927, No. 60-86067, No. 62-17020, and the like, but there is no particular limitation.

The light calcium carbonate used in the method of the present invention includes a slurry-like or cake-like water-containing product, and a powdery product obtained by further drying the slurry-like or cake-like product. There is no particular limitation on the presence or absence of, for example. The light calcium carbonate used in the present invention has a primary particle diameter D of 0.1 to 0.1.
Those having a thickness of 0.6 μm can more preferably be used because satisfactory optical characteristics such as whiteness and opacity can be obtained. Fillers having a powder whiteness of 75% or more, preferably 80% or more are effective in improving the whiteness.

By the way, it is well known that plain paper such as high-quality paper has a porous structure and a paper layer, so that it originally has good thermal characteristics and high transfer ink receptivity. That is. Thus, the thermal transfer recording image-receiving paper according to the present invention can be used as long as the thermal properties of the base paper are not obliterated and the suitability for office paper such as writing and stamping properties is not destroyed. The image receiving layer is provided by applying a coating liquid containing light calcium carbonate as a pigment. That is, the coating amount is 0.3 to 4.0 g / solid on one side on the base paper.
m ² , preferably 0.5 to 3.5 g / m ² . Incidentally, when the coating amount is less than 0.3 g / m ² , the surface of the image receiving layer becomes rough and non-uniform, resulting in transfer unevenness and poor image quality. On the other hand, if it exceeds 4.0 g / m ² ,
This is not preferable because the thermal characteristics of the base paper are not effectively exhibited, the ink receptivity is reduced, and the dot reproducibility becomes poor. In addition, the texture as a plain paper type is lost, the erasability with an eraser, the sealability with vermilion, etc. are reduced, and the paper is not suitable for writing paper.

In the coating composition, it is possible to prepare the coating liquid by using the light calcium carbonate used in the present invention alone or in combination with other pigments, but the desired effects of the present invention can be obtained. In order to obtain it, it is desirable that at least 40% by weight or more, preferably 50% by weight or more of the light calcium carbonate is added to the total pigment. The proportion of the blended pigment in the coating composition is adjusted in the range of 20 to 90% by weight, preferably 30 to 80% by weight, based on the solid content.

The thus-prepared image receiving paper for thermal transfer recording is subjected to a smoothing treatment in a usual drying step, surface treatment step, etc., and is finished into a paper having a water content of about 3 to 10% by weight, preferably about 4 to 8% by weight. Further, in the thermal transfer recording image-receiving paper of the present invention, when performing the smoothing treatment, the surface of the image-receiving paper has a ten-point average roughness defined by JIS B0601 of 3 to 22 μm, preferably 5 to 20 μm. By adjusting so that the desired effect of the present invention becomes more prominent. Incidentally, if the ten-point average roughness of the image receiving paper surface exceeds 22 μm, the smoothness of the paper is inferior and a high-quality recorded image desired by the present invention cannot be obtained. Further, since the frictional resistance is increased, the running property of the paper at the time of recording is deteriorated, which causes a color shift of a recorded image in the case of color recording. On the other hand, 3 μm
If it is less than 1, the smoothness of the image receiving paper surface is high and the ink receptivity itself is not bad, but the dot diameter of the ink is too thin, color misregistration and uneven shading occur, resulting in poor color reproducibility. Become. Further, the fixing property of the ink is inferior, which causes deterioration in image quality due to dropping of ink dots and rubbing stains, which is not preferable.

The ten-point average roughness specified here was measured using a universal surface profile measuring instrument SE-3C (manufactured by Kosaka Laboratory Co., Ltd.) and a standard length of 8 m according to the method specified in JIS B0601.
m. In this method for measuring the surface roughness, 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. For this reason, the fineness of the paper surface, which has been difficult with measuring instruments such as the Beck Smoothness Meter and Parker Print Surf, which are common air leak-type smoothness measuring instruments, is affected by the air permeability of the paper. It is possible to measure accurately without, and according to the detailed study results of the present inventors,
The measured value of the ten-point average roughness is more highly correlated with the effect of the smoothing process desired by the present invention than the value of the center line average roughness determined by cutting off the waviness of the image receiving paper surface. It became clear.

The smoothing processing of the image receiving paper for thermal transfer recording is carried out by a normal smoothing apparatus such as a super calender, gross calender, soft calender, etc. Particularly desirable results can be obtained by passing the paper through a pressure nip composed of a metal roll heated to 50 ° C. or higher, preferably 80 ° C. or higher, and a heated or non-heated elastic roll to smooth the paper. It is appropriately used in an on-machine or an off-machine, and the form of the pressure device, the number of pressure nips, and the like are appropriately adjusted according to a general smoothing device.

In the present invention, pigments used in combination with light calcium carbonate include various pigments used for general coated papers, for example, kaolin, delamikaolin, aluminum hydroxide, satin white, heavy calcium carbonate, calcium sulfate, and the like. Barium sulfate, titanium dioxide, calcined kaolin, talc, zinc oxide, zinc carbonate, alumina, diatomaceous earth, magnesium oxide, magnesium carbonate, silica, white carbon, aluminosilicate, colloidal silica,
Mineral pigments such as bentonite, zeolite, and sericite; fine particles such as polystyrene resin, urea resin, melamine resin, acrylic resin, and benzoguanamine resin; fine hollow particles; and other organic pigments. One or two or more of them can be used in combination according to the quality target of the recording paper.

The adhesive is a water-soluble polymer compound and / or a water-dispersible polymer compound, and is not particularly limited. For example, starches such as positive starch, amphoteric starch, oxidized modified starch, and esterified starch; cellulose derivatives such as carboxymethylcellulose and hydroxyethylcellulose; natural or semi-synthetic polymers such as gelatin, casein, soybean protein, and natural rubber; polyvinyl alcohol;
Polydienes such as isoprene, neoprene, and polybutadiene; polyalkenes such as polybutene, polyisobutylene, polypropylene, and polyethylene; vinyl halide, vinyl acetate, styrene, (meth) acrylic acid, (meth) acrylic acid ester, (meth) acrylamide, and methyl Vinyl polymers and copolymers such as vinyl ether,
Synthetic rubber latex such as styrene / butadiene, methyl methacrylate / butadiene, polyurethane resin,
Known and publicly-known adhesives such as synthetic polymers such as polyester resins, poly (meth) acrylate resins, polyamide resins, olefin / maleic anhydride resins, melamine resins, and other synthetic resins are included. One or more types are appropriately selected and used according to the quality target of the image receiving paper. The amount of the adhesive is adjusted in the range of about 10 to 80% by weight based on the solid content.

In the coating solution, in addition to these pigments and adhesives, various auxiliaries, such as anionic, cationic, nonionic or amphoteric surfactants, pH adjusters, viscosity adjusters, softeners, gloss, etc. Imparting agents, waxes, stabilizers, antistatic agents,
A crosslinking agent, a sizing agent, a fluorescent whitening agent, a coloring agent, a defoaming agent, a waterproofing agent, a preservative, a fragrance, and the like can be appropriately used as needed.

The coating apparatus is not particularly limited, and includes, for example, a blade coater, an air knife coater, a roll coater, a reverse roll coater, a bar coater, a curtain coater, a die slot coater, a gravure coater, a champlex coater, and a brush. An ordinary coating apparatus such as a coater, a roll, or a metering blade type size press coater, a bill blade coater, a short dwell coater, a gate roll coater or the like can be used as appropriate. Of course, these devices may be on-machine or off-machine coaters.

The base paper used as the base paper is not particularly limited. For example, the base paper is mainly made of wood pulp. If necessary, non-wood pulp such as kenaf, bamboo, hemp, polyester or polyolefin may be used. And synthetic fibers, and also inorganic fibers such as glass fibers and ceramic fibers. The type and production method of the pulp fiber are not particularly limited. For example, as wood pulp, in addition to chemical pulp and SCP such as softwood pulp and hardwood pulp obtained by the KP, SP, AP method, etc., various high speed Retained pulp (SGP, BSGP, BCTMP, CTMP, CGP, TMP, RG
P, CMP, etc.) or general high-quality paper or medium-grade paper including waste paper pulp or recycled pulp such as DIP can be used.

Of course, the base paper is generally known and used as a filler for papermaking, such as talc, kaolin, calcined kaolin, clay, diatomaceous earth, heavy calcium carbonate, light calcium carbonate, magnesium carbonate, aluminum hydroxide, titanium dioxide, Mineral fillers such as magnesium sulfate, silica, white carbon, aluminosilicate, bentonite, zeolite, sericite and polystyrene resin,
Fine particles such as urea resin, melamine resin, acrylic resin, and benzoguanamine resin, and organic synthetic fillers such as fine hollow particles can be appropriately selected and used in combination. Pigments contained in waste paper, broke, etc. can also be used effectively as fillers. The excellent effect desired by the present invention is obtained when the base paper contains an ash content measured at a combustion temperature of 500 ° C. of 8 to 30% by weight, preferably about 10 to 25% by weight.

In addition, various kinds of anionic, nonionic, cationic or amphoteric retention improvers, drainage improvers, paper strength enhancers, internal sizing agents, etc., which have been conventionally used when making the base paper, etc. The internal additive for papermaking is appropriately selected and used. For example, polyvalent metal compounds such as Al, Fe, Sn, and Zn (basic aluminum compounds such as a sulfate band, aluminum chloride, sodium aluminate, basic aluminum chloride, and basic polyaluminum hydroxide, and alumina sol easily dispersible in water) Water-soluble aluminum compounds or ferrous sulfate, ferric chloride, etc.) and various sizing agents (rosin-based such as alkyl ketene dimer system, rosin emulsion, alkenyl succinic anhydride system, styrene-acrylic system, higher fatty acid system, etc.) Petroleum resin sizing agent, etc.) and various starches, polyacrylamide, urea resin, melamine resin, epoxy resin, polyamide resin, polyamide / polyamine resin, polyethyleneimine, polyamine, vegetable gum, polyvinyl alcohol, latex, polyethylene oxide,
Examples thereof include hydrophilic cross-linked polymer particle dispersions and derivatives or modified products thereof, and various compounds such as colloidal silica and bentonite.

Incidentally, internal additives for papermaking such as dyes, fluorescent brighteners, pH adjusters, defoamers, pitch control agents, slime control agents and the like can be added as appropriate according to the use of paper.

When preparing the stock according to the method of the present invention, the specific conductivity (SC) of the stock is maintained at 1.5 mS / cm or less in both the preparation step and the papermaking step. Further, it is preferable that the zeta potential is also adjusted to around zero. Water-soluble polymer compounds such as starch, polyvinyl alcohol, latex, and carboxymethyl cellulose can be applied to the surface of the paper using a two-roll or metering blade type size press, gate roll coater, bill blade, short dwell coater, spray, etc. Various surface sizing agents such as alkyl ketene dimer type, rosin type such as rosin emulsion, styrene-acrylic type, olefin-maleic anhydride type, higher fatty acid type, etc., waterproofing agent such as epoxy compound, fluorescent brightener, defoaming agent It is also possible to apply a conductive agent, a pigment, a dye and the like.

The papermaking method is not particularly limited. For example, an acidic papermaking method having a papermaking pH of about 4.5, an alkaline filler such as calcium carbonate as a main component, and a papermaking pH of about 6 to about 9 It can be applied to all papermaking methods such as a so-called neutral papermaking method to be weakly alkaline,
The paper machine is also made using a fourdrinier paper machine, a twin wire paper machine, a round net paper machine, a Yankee paper machine or the like as appropriate.

The thermal transfer recording paper thus obtained is
In particular, since it is excellent in ink transferability and reproducibility, it can be preferably used as a high-quality thermal transfer recording image receiving paper for full color as well as monochrome. Moreover, it is excellent in suitability for office paper such as pen writing suitability and sealability, and can be suitably used as ordinary writing paper.

[0038]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but it is needless to say that the present invention is not limited to these ranges. In the examples, “parts” and “%” indicate “parts by weight” and “% by weight”, respectively, unless otherwise specified.

[Light calcium carbonate] Eleven types (AK) of light calcium carbonate having physical properties shown in Table 1 were prepared by a carbon dioxide gasification method. Among the obtained light calcium carbonates, A, F, G, H, and K are powder products, and C,
I is a cake-like hydrate having a solid content of 65%,
E and J indicate the concentration of solids produced by adding sodium polyacrylate (trade name: Alon A-9 / Toa Gosei Co., Ltd.) to the synthesized light calcium carbonate and dispersing it in water using a turbine blade type stirrer. Is a slurry product of 60 to 65%. B was prepared by dispersing the synthesized light calcium carbonate A in water using a turbine blade type stirrer, and using a sand grinder (type 32G, manufactured by Igarashi Kikai Seisakusho Co., Ltd.) to rotate at 1000 rpm and a flow rate of 15 l / l. min and wet-milled slurry.

The primary particle size of light calcium carbonate is as follows:
The secondary particle diameter, particle shape, and the like were measured or observed by the following methods, respectively, and the obtained results are shown in Table 1.

(Measurement of Primary Particle Diameter D) The primary particle diameter was calculated by the following formula based on the specific surface area S measured by the BET specific surface area measurement method. D = 6 / (S · η) D: Average primary particle diameter of light calcium carbonate (μm) S: Specific surface area measured by BET specific surface area measurement method (m
² / g) η: True specific gravity of light calcium carbonate (g / cm ³ )

(Measurement of Secondary Particle Diameter d) Into a 500 ml container, water was previously charged so that the total amount was 300 g and the finished concentration was 25%, and then the required light calcium carbonate was added. While using a desktop propeller mixer for 800
The mixture was stirred at rpm for 10 minutes to prepare a slurry. The thus obtained slurry of light calcium carbonate was measured for its particle size when the cumulative weight reached 50% using a Sedigraph X-ray transmission type particle size distribution analyzer (manufactured by Shimadzu Corporation). The value was taken as the average secondary particle size.

(Observation of Particle Shape) The shape of the particles was observed with a secondary electron beam using a scanning electron microscope.

(Measurement of ratio D _L / D _S between major axis and minor axis) The actual major axis and minor axis of a single particle were measured by the above-mentioned scanning electron microscope, and the major axis and minor axis were calculated from the average value of each. (D _L / D _S ) was determined.

Example 1 [Preparation of base paper] NBKP (freeness = csf: 520 ml), 10 parts, LB
To a pulp slurry containing 90 parts of KP (freeness = csf: 460 ml), talc was used as a filler, and 15 parts of rosin size (trade name: Size Pine N-771 / Arakawa Chemical Industries) was added.
1.5 parts and 2 parts of a sulfuric acid band were added, and the pulp slurry was diluted with white water to prepare a stock having a pH of 5.1 and a concentration of 1.0%. The stock was made using a Fourdrinier paper machine and dried to obtain a base paper having a rice tsubo of 80.5 g / m ² .

[Preparation of coating liquid] As shown in Table 2, 90 parts of light calcium carbonate A (solid content; the same applies hereinafter) and 10 parts of titanium oxide were added to 0.4 part of sodium polyacrylate (solid content ratio to pigment; the same applies hereinafter). ) Was added thereto, and the mixture was dispersed in water using a CORES disperser to prepare a pigment slurry. This pigment slurry
25 parts of 28% oxidized starch (trade name: Ace A / Oji Cornstarch), polyvinyl alcohol (trade name: P)
VA-105 / 25 parts of Kuraray Co., Ltd., 1 part of a fluorescent whitening agent and water were mixed, stirred and mixed to prepare a coating solution having a concentration of 25%.

[Formation of Image-Receiving Layer] The coating solution thus obtained was applied to both sides of the base paper obtained as described above so that the total amount of coating was 4.5 g / m ^{2 in} terms of dry weight. Coated using a ring blade type size press, temperature is 50 ℃
Paper through a pressure nip (11 nips, nip linear pressure 200Kg / cm) consisting of a metal roll and an elastic roll
g / m ² of an image receiving paper for thermal transfer recording was obtained.

Examples 2 to 6 and Comparative Examples 1 to 5 The same procedures as in Example 1 were carried out except that the coating liquid was prepared by partially changing the kind of light calcium carbonate and the number of parts as shown in Table 2. In the same manner as in Example 1, an image-receiving paper for thermal transfer recording having a rice area of 85 g / m ² was obtained.

Example 7 [Preparation of base paper] In Example 1, the pulp content was changed to NBKP10
Parts, LBKP 40 parts, and recycled pulp made from OA waste paper
Parts as well as the internal chemicals, and as a filler, a mixed filler of heavy calcium carbonate (trade name: Softon-1200 / Bihoku Powder Chemical Industry Co., Ltd.) and kaolin (mixing ratio 4: 1)
15 parts, 0.5 part of sulfate band, cationic starch (trade name:
Amilofax T-2200 / Matsuya Chemical Industries)
And 0.5 part of an alkyl ketene dimer (trade name: Size Pine K-287 / Arakawa Chemical Industry Co., Ltd.) was added. After diluting the pulp slurry with white water, colloidal silica (trade name: BMA / Eka Nobel) was added. 0.2 parts were added to prepare a stock having a pH of 7.9 and a concentration of 0.95%. The stock is made using a twin-wire machine, dried and dried.
A base paper of 82.5 g / m ² was obtained.

[Preparation of coating liquid] As shown in Table 2, 50 parts of light calcium carbonate A and heavy calcium carbonate (trade name:
Same as Example 1 except that 40 parts of FMT-90 / Fimatic Co.) and 0.6 part of sodium polyacrylate were added to 10 parts of titanium oxide, and the mixture was dispersed in water using a Cores disperser to prepare a pigment slurry. To prepare a coating solution.

[Formation of Image-Receiving Layer] The coating amount of this coating solution was 2.% by dry weight on only one side of the base paper obtained as described above.
The procedure was performed except that the coating was performed using a gate roll coater to 5 g / m ² and the paper was passed while changing the temperature of the metal roll and the linear pressure of the pressure nip to 80 ° C-150 Kg / cm, respectively. In the same manner as in Example 1, an image-receiving paper for thermal transfer recording having a rice area of 85 g / m ² was obtained.

[0052] In Comparative Example 6 Example 7, except that by changing the compounding parts of pigment as shown in Table 2 to prepare a coated liquid, in the same manner as in Example 7, the basis weight of 85 g / m ² An image receiving paper for thermal transfer recording was obtained.

Examples 8 to 9 and Comparative Example 7 In Example 7, the amount of the coating liquid was changed to 0.7 g.
/ M ² (Example 8), 3.4 g / m ² (Example 9), 5.2
Except for using g / m ² (Comparative Example 7), the same procedure as in Example 7 was carried out to obtain a thermal transfer recording image-receiving paper having a rice area of 85 g / m ² .

Example 10 and Comparative Example 8 In Example 7, the temperature of the metal roll and the linear pressure of the pressure nip were changed to 150 ° C.-100 kg / cm (Example 10) and 30 ° C., respectively.
(Room temperature) Except for -40 Kg / cm (Comparative Example 8), an image receiving paper for thermal transfer recording having a rice area of 85 g / m ² was obtained in the same manner as in Example 7.

Comparative Example 9 In Example 6, the amount of the coating liquid was changed to 7.5 g /
m ² , and the same as in Example 6, except that the temperature of the metal roll and the linear pressure of the pressure nip were each set to 150 ° C.-250 Kg / cm. ^Thus, an image receiving paper for thermal transfer recording was obtained.

Comparative Example 10 In Example 1, as shown in Table 2, a pigment slurry containing 100 parts of heavy calcium carbonate (trade name: Softon-2200 / manufactured by Bihoku Powder Chemical Industry Co., Ltd.) without blending light calcium carbonate was used. Was used in the same manner as in Example 1 except that a coating liquid was prepared using the above method to obtain a thermal transfer recording image-receiving paper having a rice area of 85 g / m ² .

The thus-obtained 20 kinds of image receiving papers for thermal transfer recording were measured and evaluated for quality by the following methods. The results are shown in Table 3.

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

(Measurement of Image Density) Using a thermal transfer type color printer (CHC-443 type / manufactured by Shinko Electric Co., Ltd.), a test pattern having grids, solids, and halftone dots was recorded. Using a Macbeth densitometer (R
D-100 R / Macbeth).

(Evaluation of Transfer Unevenness on Recording Surface) The degree of transfer unevenness on the solid portion of the recording surface was visually evaluated according to the following evaluation criteria. A: Extremely excellent without transfer unevenness. ：: Good with almost no transfer unevenness. Δ: Transfer unevenness was observed and slightly inferior. ×: Many transfer irregularities are inferior.

(Evaluation of color misregistration on recording surface) The grid portion on the recording surface was magnified 30 times by a dot analyzer (DA-3000), and the degree of color misregistration in the overprinted portion was visually evaluated according to the following evaluation criteria. . A: Extremely excellent without color shift. ：: good with almost no color shift. Δ: Inferior color shift.

(Evaluation of dot reproducibility on recording surface) The halftone dots on the recording surface were measured by a dot analyzer (DA-3000).
The degree of dot dropout and sharpness (bleeding) was visually evaluated according to the following evaluation criteria. ：: The dots are sharp and have no dropout, and are extremely excellent. ：: good with almost no blurring or dropping of dots. Δ: Slightly inferior due to bleeding or missing dots. X: Many of the dots are blurred or missing.

(Measurement of pen writing size on paper) "J.TAPP
The pen writing size of paper was measured according to the method described in "I. Pulp and Paper Test Method" No. 27-78.

(Evaluation of Markability of Vermilion) The state of dirt due to rubbing immediately after stamping vermilion on paper was visually evaluated according to the following evaluation criteria. A: There is no generation of stains and the sealability is excellent. ：: Good with almost no stain. Δ: Slightly generated and slightly inferior.

[0065]

[Table 1]

[0066]

[Table 2]

[0067]

[Table 3]

[0068]

As is clear from the results of the examples, the image receiving paper for thermal transfer recording of the present invention has high recording characteristics, particularly high image density, no transfer unevenness and color misregistration, and extremely excellent dot reproducibility. This thermal transfer recording paper had excellent suitability as a thermal transfer recording paper for high-quality full color as well as monochrome, and also excellent office paper suitability such as pen writing suitability and sealability.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-124896 (JP, A) JP-A-3-197188 (JP, A) JP-A-60-110490 (JP, A) JP-A-1- 221282 (JP, A) JP-A-2-88293 (JP, A) JP-A-2-3394 (JP, A) JP-A-60-192690 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41M 5/38-5/40

Claims (1)

(57) [Claims] 1. In a thermal transfer recording image receiving paper provided with an image receiving layer for receiving the transfer of the heat-fusible ink on a base paper, the ratio of the average value of the major axis to the minor axis of the single particle is 1.5. ~ 15
The light-weight calcium carbonate which satisfies the following formula is formed from a coating composition containing 40% by weight or more with respect to the total pigment and containing the light-weight calcium carbonate and an adhesive as main components. Is from 0.3 to 4.0 g / m ² and the surface of the image receiving layer has a ten-point average roughness of 3 to 22 μm as defined in JIS B0601. 1.5 ≦ d / D ≦ 8.0 d = 0.2-3.0 μm D = 0.1-0.6 μm d: average particle diameter μm by Cedigraph X-ray transmission type particle size distribution measurement D: BET ratio Average particle diameter μm calculated based on specific surface area by surface area measurement method