JP3863199B2 - Thermal transfer recording material - Google Patents

Description

ＰＶＢ：ポリビニルブチラール
添加剤A:イトワックスJ420 伊藤製油(株)製
添加剤B:ア−マイドHTP ライオンアクゾ(株)製
添加剤C:アエロジルR972 日本アエロジル(株)製
【００２５】
次に、インキ層の引張破断応力とインキ層／受像層と１８０度剥離力を測定した。
インキ層の引張破断応力の測定方法を示す。鏡面仕上げしたステンレス板にインキ層液を流延し、室温で３日間乾燥後さらに６０℃の恒温槽で12時間乾燥することにより約３０μmの厚みのインキ膜を作製し,幅３０ｍｍ，長さ６０ｍｍにカットした。できたサンプルを120℃10分加熱処理後、液体窒素で急冷した後、２３℃／６５％条件下、３００ｍｍ／分の速度でテンシロンで引っ張り、切断する時の応力を測定した。
次にインキ層／受像層の１８０度剥離力の測定方法を示す。厚み５μmのPETベ−スにSBRラテックスを３μmの厚みに塗布し、その上にインキ層液を厚みが０．３μmになるよう塗布した。また、厚み１００μmのPETベ−ス上にSBRラテックスを０．３μmの厚みに塗布し、その上に受像第2層を厚みが２μmになるよう塗布した。両者を重ねてサ−マルヘッドで全面印字した後、幅３５ｍｍ、長さ６０ｍｍに切断し、インキ層と受像層の面との接着力をテンシロンにより引っ張り速度５００ｍｍ／分で１８０度剥離した値より求めた。 結果を表２に示す。
上記全面印字は薄膜サ−マルヘッドを用い、ドット密度６００dpi、ヒ−タ−サイズ７０μｍＸ８０μｍ、抵抗値３１００Ω、電圧１５V、ストロ−ブ幅２．５msecの条件でおこなった。
【００２６】
【表２】

○：優れている
△：実用上問題なし
×：実用上問題あり
【００２７】
参考例２
各々、表１に示すインキ組成にした以外は参考例１と同様に記録材料を作製し、評価した。結果を表２に示す。参考例１と同様に良好な画質が得られた。
【００２８】
比較例１，２
表１中の比較例に示すインキ組成にした以外は参考例１と同様に記録材料を作製し、評価した。結果を表２に示す。ドットの欠陥やギザが多く、また階調再現数も低かった。
【００２９】
実施例１〜３
各々、表１に示すインキ組成にした以外は参考例１と同様に記録材料を作製し、評価した。結果を表２に示す。参考例１に比べさらに良好なドット形状、再現階調数が得られた。
【００３０】
【発明の効果】
本発明によれば面積階調のみで、画像のエッジシャープネスも含めたドット形状が良好で、階調再現性に優れた記録材料が得られる。[0001]
[Industrial application fields]
The present invention is a thermal head printer or a laser light source, and is used to thermally transfer a thermal ink layer containing a pigment onto an image receiving sheet material to form a high-quality multi-tone color image with only area gradation. The present invention relates to a thermal transfer recording material.
[0002]
[Prior art]
Conventionally, as a thermal transfer recording method for forming a color image using a thermal head printer or a laser light source, a sublimation dye transfer method and a thermal melting transfer method are known.
In the sublimation dye transfer method, a transfer sheet comprising a transfer layer consisting of a sublimation dye and a binder is placed on a support and the image receiving sheet is overlaid, and heat is applied to the image by a thermal head from the back side of the transfer sheet support. In this method, a sublimation dye is sublimated and transferred to an image receiving sheet to form an image on the image receiving sheet. A color image can be formed by using a transfer sheet made of yellow, magenta, and cyan.
[0003]
However, the sublimation dye system has the following drawbacks.
(1) The gradation expression of the image mainly uses density gradation (controlling the seed type or amount of the dye) and is suitable for some consumer purposes who prefer gradation similar to photography. For example, it is not suitable for a color proof used in the printing field in which gradation expression is performed only by area gradation.
(2) Since the image formation uses dye sublimation, the edge sharpness of the finished image is unsatisfactory, and the solid density of the thin line is thinner than that of the thick line. These are serious drawbacks regarding the quality of the character image.
(3) Since the durability of an image is inferior, development in fields requiring heat resistance and light resistance is limited.
(4) Since the thermal recording sensitivity is lower than that of the thermal melting type transfer system, it is not suitable as a high-speed recording material using a high resolution thermal head expected in the future.
(5) The photosensitive material is more expensive than the heat melting type transfer material.
[0004]
On the other hand, in the heat-melt transfer method, a transfer sheet provided with a heat-meltable transfer layer composed of a coloring material such as pigment or dye and a binder such as wax on the support is overlapped with the image-receiving sheet, and the transfer sheet support In this method, heat is applied imagewise from the back side by a thermal head, and the transfer layer is melted and fused to an image receiving sheet image to form an image.
Compared with the sublimation dye transfer system, the heat-melt transfer system has advantages such as (1) higher heat sensitivity, (2) less expensive materials, and (3) better light resistance of images. Yes.
However, one of the biggest drawbacks of the hot melt transfer system is that the quality of the color image is inferior to that of the sublimation dye transfer system. This is because this method is not a gradation reproduction by density gradation but a binary recording. Of course, various proposals have been made for an ink transfer layer for improving the binary recording property and achieving density gradation for the purpose of forming a multi-gradation color image in the hot melt transfer system. However, the basis of these ideas is that the thermal head heats up using the property that the ink layer binder melts and the viscosity decreases as a result of heating with the thermal head, resulting in increased adhesion to the image-receiving sheet and transfer. Is to control the cohesive failure inside the ink layer and soften the gamma characteristic of the thermal transfer recording. Therefore, the hot melt transfer method is inferior in terms of multi-gradation as compared with the sublimation dye transfer method. In general, the reproducibility of image density such as a fine line is also inferior.
[0005]
In addition, since the thermal melting type transfer system usually uses a low-melting crystalline wax as a binder for the ink layer, the resolution is lowered or the strength of the transfer-fixed image is weak due to blurring during thermal printing in the recording medium. There are problems such as. Furthermore, crystalline waxes have the disadvantage that it is difficult to obtain a transparent image due to light scattering of the crystalline phase. This is a major drawback when forming a color image as an overlap of yellow, magenta, cyan, and the like. Further, the factor for deteriorating the transparency is related to the pigment ratio with respect to the total amount of the ink layer. As described in Japanese Patent Publication No. 63-65029, the colorant is usually 20% by weight based on the total amount of the ink layer. If it is used below this part, the transparency will be reduced.
[0006]
Various proposals have been made to improve the color reproduction of the color image of the hot melt transfer system. For example, in JP-A-61-244592 (Japanese Patent Publication No. 5-13072), at least 50% by weight or more is desired for the purpose of improving transparency, fixed image strength and the like while maintaining continuous tone. There has been proposed a thermal ink layer comprising a crystalline polymer, a releasable substance, and a colorant (dye or pigment).
In this publication, first, regarding the transparency, if the amorphous polymer is 50% by weight or less, the transparency of the thermal ink material is remarkably deteriorated and good color reproducibility cannot be obtained. It is stated that 70% by weight is necessary to show particularly good transparency. Further, it is stated that the thickness of the thermal ink layer is preferably 0.5 μm to 50 μm, usually 1 μm to 20 μm. However, particularly in terms of image formation, cyan, magenta, and yellow require a reflection density of about 1.4, and particularly black requires about 1.7 for the purpose of image formation. There is no description of how much density can be obtained while maintaining transparency with a pigment diameter ink layer thickness of 1 μm or less. Further, in the examples as well, the film thickness of the ink layer is about 3 μm, almost the same as the normal wax system. That is, in this specification, there is no technical disclosure for maintaining the transparency of the pigment and making the optical reflection density at least 1.0 or more with a film thickness of 1.0 μm or less.
[0007]
On the other hand, the technical progress of thermal head printers is remarkable. As a printing method that enables multi-tone recording not only with high resolution of the thermal head itself but also with area gradation only, the sub-scanning division method described in JP-A-4-19163, JP-A-5-1555057, In addition, the heat-intensive method described in "Annual Meeting of the Electrophotographic Society of Japan 1992/7/6" has been proposed.
[0008]
[Problems to be solved by the invention]
From the material side, the following characteristics are important as factors for obtaining a color image having a high multi-gradation with only the area gradation of binary recording in the thermal transfer system.
(1) Each color has a predetermined image density.
(2) Excellent gradation reproducibility.
(3) The edge sharpness of a line or point image is excellent and the dot shape is good.
(4) The transparency of the transfer ink layer is good.
(5) High sensitivity.
(6) The image transferred to the printing paper is excellent in printed matter approximation such as texture and glossiness of the image.
[0009]
If the above factors are greatly improved by the pigment transfer method with area gradation only, and multi-gradation high-quality color images and monochrome images can be achieved, color proof not only for consumer use but also in the printing field, Utilizing the durability of originals or pigments, it will be possible to expand into the card field, outdoor display field and meter display field.
However, the technological development from the sensitive material side of the conventional heat-melt transfer method is mainly to reduce the ink layer's low gamma characteristics, or to improve it as an independent item of the previous factors, and multi-tone recording with only area gradation There has been no proposal or solution for what should be a thermal transfer material suitable for the system.
The object of the present invention is to propose just this solution.
[0010]
[Means for Solving the Problems]
As a result of intensive research, the present inventors have determined that this is a method that should be called a thermal adhesive thin film peeling method compared to the conventional sublimation dye thermal transfer method and melt transfer method, and the mechanical strength and image receiving sheet of the thermal ink layer. The present inventors have found that the image quality (particularly dot quality and gradation reproducibility) is improved by setting the adhesive strength to the image receiving surface to a certain value.
That is, the object of the present invention is to
30 to 70 parts by weight of pigment and 25 to 60 parts by weight of an amorphous organic polymer having a softening point of 150 ° C. or less, a film thickness of 0.2 μm to 1.0 μm, and a tensile breaking stress of 10 MPa or less An ink sheet having a thermal ink layer containing a magenta pigment (CI . PR . 57: 1) as the pigment ;
An image receiving sheet provided with an image receiving layer (excluding an image receiving sheet provided with an image receiving layer having a glass transition point (Tg) of 100 ° C. or higher);
180, at a peeling speed of 500 mm / min between the image-receiving surface of the image-receiving sheet and the heat-sensitive ink layer of the ink sheet after thermal printing with the lowest energy that the thermal ink layer of the ink sheet is transferred to the entire surface of the image-receiving layer . This was achieved by a thermal transfer recording material characterized in that the peel strength was 0.3 dyn / mm or more . If the tensile rupture stress of the thermal ink layer exceeds 10 MPa, the dot quality may not be satisfactory, such as missing dots, jagged dots, large variations in dot size, and no small dots. The number of gradation reproduction is low due to the collapsed portion.
[0011]
In the present invention, the thermal ink layer is further subjected to thermal printing with the minimum energy that can be transferred onto the entire surface of the image receiving sheet, and then the peeling speed between the image receiving surface of the image receiving sheet and the surface of the ink sensitive ink layer is 500 mm / min. The above defects could be further improved by setting the 180 degree peeling force to 0.3 dyn / mm or more.
Hereinafter, the present invention will be described in detail.
[0012]
As the support for the heat-sensitive transfer recording material (ink sheet and image receiving sheet) of the present invention, various known supports are used as conventional supports for melt transfer and sublimation transfer. Similarly, a polyester film having a release treatment on the back surface having a thickness of about 5 μm is particularly preferable. The thermal transfer material is as follows:
As the pigment contained in the ink layer of the ink sheet of the present invention, various known pigments can be used, such as carbon black, azo, phthalocyanine, quinacridone, thioindigo, anthraquinone, isoindolinone, and the like. Pigments. Two or more of these may be used in combination, and a known dye may be added for hue adjustment.
[0014]
Examples of the amorphous organic polymer conjugate having a softening point of 50 ° C. to 150 ° C. contained in the ink layer of the ink sheet of the present invention include, for example, butyral resin, polyamide resin, polyethyleneimine resin, sulfonamide resin, polyester polyol resin, Petroleum resin, styrene, α-methyl styrene, 2-methyl styrene, chlorostyrene, vinyl benzoic acid, vinyl benzene sulfonic acid soda, aminostyrene and other styrenes and their derivatives, homopolymers and copolymers of substitution products, methyl methacrylate, ethyl methacrylate, Methacrylic acid esters such as hydroxyethyl methacrylate and acrylic acid esters such as methacrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, α-ethylhexyl acrylate, acrylic acid, butadiene, Dienes such as ene and isoprene, acrylonitrile, vinyl ethers, maleic acid and maleic esters, maleic anhydride, cinnamic acid, vinyl chloride, vinyl acetate, and other monomers alone or other monomers These copolymers can be used. These resins can be used in combination of two or more. Of these, butyral resin and styrene / maleic acid half ester resin are preferable from the viewpoint of dispersibility. The softening point of these resins should be selected in the range of 50 ° C to 150 ° C. If it exceeds 150 ° C., the thermal recording sensitivity is low, and if it is less than 50 ° C., the adhesion resistance of the ink layer is poor.
[0015]
In these ink layers, various releasing agents and softening agents are added in an amount of 1 to 20% by weight with respect to the total amount of the ink layer from the viewpoint of releasing the ink layer from the support during thermal printing and improving thermal sensitivity. It is also possible to add within the range.
Specifically, higher fatty acids such as palmitic acid and stearic acid, fatty acid metal salts such as zinc stearate, fatty acid esters or partially saponified products thereof, fatty acid derivatives, higher alcohols, derivatives of polyhydric alcohols, and the like, Waxes such as paraffin wax, carnauba wax, montan wax, beeswax, wood wax, candelilla wax, low molecular weight polyethylene having a viscosity average molecular weight of about 1,000 to 10,000, polyolefins such as polypropylene, polybutylene, or olefin , Α-Olefins and organic acids such as maleic anhydride, acrylic acid and methacrylic acid, low molecular weight copolymers with vinyl acetate, low molecular weight oxidized polyolefins, halogenated polyolefins, lauryl methacrylate, stearyl methacrylate Methacrylic acid ester having long alkyl side chain, acrylic acid ester or acrylic acid ester having perfluoro group, methacrylic acid ester alone or copolymer with vinyl monomer such as styrene, polydimethylsiloxane, poly Low molecular weight silicone resins such as diphenylsiloxane and silicone-modified organic substances, as well as cationic surfactants such as ammonium salts and pyridinium salts having long chain aliphatic groups, or anions having long chain aliphatic groups as well as nonions Surfactants, perfluorosurfactants and the like can be mentioned, and one or more can be selected and used.
[0016]
As for the optical density of these thermal ink layers, the reflection density is preferably 1.0 or more when transferred onto a white support for the reason described above . The film thickness ranges from 0.2 μm to 1.0 μm . In a thick ink layer larger than 1.0 μm, in the area gradation reproducibility, the shadow part is easily crushed and the highlight part is easily skipped, resulting in poor gradation reproducibility. On the other hand, when the film thickness is less than 0.2 μm, it is difficult to obtain a predetermined concentration. In order to obtain a predetermined concentration with these thin films, the pigment in the ink layer is added in an amount of 30 to 70 parts by weight, and the amorphous organic polymer conjugate is added in an amount of 25 to 60 parts by weight. It is preferable that the total amount of the releasable substance and the softener is 1 to 15 parts by weight. When the pigment ratio does not reach this, it is difficult to obtain the density with the predetermined film thickness. The particle diameter of the pigment is preferably 70% or more and 1.0 μm or less of the pigment . When the particle size is large, the transparency of the overlapping portion of each color at the time of color reproducibility is impaired, and it becomes difficult to satisfy both the relationship between the film thickness and the density.
[0017]
With respect to the dispersion of these pigments into the amorphous organic polymer conjugate, various dispersion methods used in the paint field such as a ball mill are applied by adding an appropriate solvent.
[0018]
The heat-sensitive ink layer of the present invention is mainly composed of a pigment and an amorphous organic polymer combination, and has a higher pigment ratio than the conventional wax melt type, and has a viscosity at the time of thermal transfer of 10 ² compared to the normal melt type. Since it is not as low as 10 ³ cps and is higher than at least 10 ⁴ cps at a temperature of 150 ° C., the present invention provides thermal adhesiveness of the image receiving sheet or thermal adhesiveness between the ink layers in the case of color image formation. It can be said that this is image formation of a thin film peeling phenomenon type utilizing the above. This, combined with the effect of thinning the ink layer, enables high gradation reproducibility from the shadow area to the highlight area while maintaining high resolution, and also improves edge sharpness and further 100%. For example, the uniformity of the density of small characters and solid portions of 4 points was reproduced.
[0019]
As the image receiving sheet, it is possible to use heat-softening synthetic paper or the image receiving sheet technology described in US Pat. Nos. 4,486,225, 4,766,053 and 4,933,258. As the support for an image receiving sheet on which a thermal adhesive layer containing at least an organic polymer conjugate is provided, a plastic film such as paper, polyester film, polycarbonate film, polypropylene film, polyvinyl chloride film, or the like can be used. When used for proofing, an image may be formed by retransferring a transfer image formed on a plastic film to the printing paper in order to form an image on the same paper as the printing paper.
[0020]
Examples of the present invention are shown below, but the present invention is not limited thereto. The following thermal transfer material means an ink sheet.
[0021]
Reference example 1
(Creation of thermal transfer material)
An ink layer coating solution having the following composition was prepared.
-Polyvinyl butyral 12 parts by weight (Denka butyral # 2000-L, manufactured by Denki Kagaku Kogyo Co., Ltd.)
・ Magenta pigment (C.I.PR.57: 1) 12 parts by weight ・ Dispersing aid 0.8 parts by weight (Solsperse S-20000, manufactured by ICI Japan Co., Ltd.)
-Solvent 110 parts by weight of n-propyl alcohol Using a spin coater (whiler) on a polyester film (manufactured by Teijin Ltd.) having a release treatment on the back surface having a thickness of 5 μm, the dry film thickness is 0 A thermal transfer material was prepared by coating to a thickness of .38 μm. The prescription is shown in Table 1.
[0022]
(Creation of image receiving sheet)
A coating solution for the first image-receiving layer and the second image-receiving layer having the following composition was prepared.
(Coating solution for first image receiving layer)
・ 25 parts by weight of vinyl chloride / vinyl acetate copolymer (MPR-TSL, manufactured by Nissin Chemical Co., Ltd.)
・ Dioctyl phthalate 12 parts by weight (DOP, manufactured by Daihachi Chemical Co., Ltd.)
・ Surfactant 4 parts by weight (Megafac F-177, manufactured by Dainippon Ink & Chemicals, Inc.)
・ Solvent Methyl ethyl ketone 75 parts by weight (image receiving second layer coating solution)
・ 16 parts by weight of polyvinyl butyral (Denkabutyral # 2000-L, manufactured by Denki Kagaku Kogyo Co., Ltd.)
・ N, N-dimethylacrylamide / butyl acrylate copolymer 4 parts by weight ・ Surfactant 0.5 part by weight (Megafac F-177, manufactured by Dainippon Ink & Chemicals, Inc.)
-Solvent n-propyl alcohol 200 parts by weight On a polyethylene terephthalate (PET) film support having a thickness of 100 µm, the above-mentioned coating solution for the first image receiving layer is applied at 300 rpm using a spin coater, and in an oven at 100 ° C For 2 minutes. The film thickness of the obtained first image receiving layer was 20 μm.
Further, on the first image receiving layer, a coating solution for the second image receiving layer was applied at 200 rpm using a spin coater and dried in an oven at 100 ° C. for 2 minutes. The film thickness of the obtained second image receiving layer was 2 μm.
[0023]
The heat-sensitive transfer material and the image-receiving sheet were overlapped and printed by a thermal head recording apparatus using a sub-scanning division method. This principle is a system that performs multi-step modulation of only area gradation by turning on and off a 75 μm × 50 μm head in a 50 μm direction with a minute feed of 3 μm pitch. The polyester film of the heat-sensitive transfer material was peeled off, and an image consisting only of area gradation was formed on the image receiving sheet. Next, the image-receiving sheet on which the image is formed is overlapped with art paper, passed through a heat roller at a pressure of 4.5 kg / cm ² , 130 ° C. and 4 m / sec, and then the polyester film of the image-receiving sheet is peeled off to obtain an ink image. The image-receiving second layer with the image was formed on art paper. At this time, the reflection density of each single color was 1.43.
The gradation reproducibility was 10 to 95%, and there was no defect due to dust and the dot shape was good. Further, the surface following the unevenness of the paper was matted, and the surface gloss was an image very similar to the printed matter. The results are shown in Table 2.
[0024]
[Table 1]

PVB: Polyvinyl butyral additive A: Ito wax J420 Additive made by Ito Oil Co., Ltd. B: Ahamide HTP Additive made by Lion Akzo Co., Ltd. C: Aerosil R972 Made by Nippon Aerosil Co., Ltd.
Next, the tensile breaking stress of the ink layer, the ink layer / image receiving layer, and the 180-degree peeling force were measured.
The measuring method of the tensile breaking stress of an ink layer is shown. An ink layer solution is cast on a mirror-finished stainless steel plate, dried at room temperature for 3 days, and further dried in a thermostatic bath at 60 ° C. for 12 hours to produce an ink film having a thickness of about 30 μm, with a width of 30 mm and a length of 60 mm. Cut into. The resulting sample was heat-treated at 120 ° C. for 10 minutes, quenched with liquid nitrogen, then pulled with Tensilon at a rate of 300 mm / min under conditions of 23 ° C./65%, and the stress at the time of cutting was measured.
Next, a method for measuring the 180 ° peeling force of the ink layer / image receiving layer will be described. An SBR latex was applied to a PET base having a thickness of 5 μm to a thickness of 3 μm, and an ink layer solution was applied thereon to a thickness of 0.3 μm. Further, SBR latex was applied to a thickness of 0.3 μm on a PET base having a thickness of 100 μm, and an image receiving second layer was applied thereon to a thickness of 2 μm. After overlapping the two and printing the entire surface with a thermal head, the sheet was cut to a width of 35 mm and a length of 60 mm, and the adhesive strength between the ink layer and the surface of the image receiving layer was determined from the value peeled 180 degrees at a pulling speed of 500 mm / min. It was. The results are shown in Table 2.
The whole surface printing was performed using a thin film thermal head under the conditions of a dot density of 600 dpi, a heater size of 70 μm × 80 μm, a resistance value of 3100Ω, a voltage of 15 V, and a strobe width of 2.5 msec.
[0026]
[Table 2]

○: Excellent △: No problem in practical use ×: Problem in practical use [0027]
Reference example 2
Recording materials were prepared and evaluated in the same manner as in Reference Example 1 except that the ink compositions shown in Table 1 were used. The results are shown in Table 2. Good image quality was obtained as in Reference Example 1 .
[0028]
Comparative Examples 1 and 2
A recording material was prepared and evaluated in the same manner as in Reference Example 1 except that the ink compositions shown in Comparative Examples in Table 1 were used. The results are shown in Table 2. There were many dot defects and jagged edges, and the number of gradations was low.
[0029]
Examples 1-3
Recording materials were prepared and evaluated in the same manner as in Reference Example 1 except that the ink compositions shown in Table 1 were used. The results are shown in Table 2. Compared to Reference Example 1 , a better dot shape and number of reproduced gradations were obtained.
[0030]
【The invention's effect】
According to the present invention, it is possible to obtain a recording material that has only area gradation, a good dot shape including image edge sharpness, and excellent gradation reproducibility.

Claims (2)

30 to 70 parts by weight of pigment and 25 to 60 parts by weight of an amorphous organic polymer having a softening point of 150 ° C. or less, a film thickness of 0.2 μm to 1.0 μm, and a tensile breaking stress of 10 MPa or less An ink sheet having a thermal ink layer containing a magenta pigment (CI.PR.57: 1) as the pigment;
An image receiving sheet provided with an image receiving layer (excluding an image receiving sheet provided with an image receiving layer having a glass transition point (Tg) of 100 ° C. or higher);
180, at a peeling speed of 500 mm / min between the image-receiving surface of the image-receiving sheet and the heat-sensitive ink layer of the ink sheet after thermal printing with the minimum energy that the entire surface of the ink-sensitive sheet is transferred onto the image-receiving layer of the image-receiving sheet. A heat-sensitive transfer recording material having a peel strength of 0.3 dyn / mm or more. 2. The thermal transfer recording material according to claim 1, wherein the optical reflection density of the transferred image is at least 1.0 or more on the white support.