JP2010253759A - Thermal transfer receptive sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermal transfer receptive sheet that provides a clear print image having high image density and high light-resistance, that causes little bleeding of image even if prints are left under the high temperature and high humidity environment, and that has excellent image preservability. <P>SOLUTION: The heat transfer receptive sheet comprises a sheet-like support and a barrier layer and an image receptive layer which are laminated at least on one surface of the sheet-like support, The image receptive layer contains polyurethane resin synthesized from a specific polymerization component while the barrier layer contains inorganic pigment having an aspect ratio (ratio of average particle major diameter/thickness of pigment) of 5-5,000. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The thermal transfer receiving sheet of the present invention has a high printing density, a clear and excellent light fastness printed image is obtained, and even when the printed material is placed in a high-temperature and high-humidity environment, there is very little image bleeding, and thermal transfer with excellent image storage stability. It relates to a receiving sheet.

  The dye thermal transfer system is a thermal transfer receiving sheet (hereinafter also referred to as “receiving layer”) having a dye thermal transfer sheet (hereinafter also referred to as “ink ribbon”) and an image receiving layer (hereinafter also referred to as “receiving layer”) that receives the dye. The dye layer and the receiving layer are superposed, and the dye is transferred onto the receiving layer by heating to form an image. Heating is performed with a thermal head, and a full-color image is formed with multicolored dots. Since the dye is used, the image is clear and highly transparent, and a high-quality image usable for photographic use is obtained.

  As the resin for forming the receptor layer, dyeable thermoplastic resins such as vinyl chloride resins, polyester resins, polyurethane resins, polyvinyl acetal resins, acrylic resins, and cellulose resins have been proposed. Generally, such a thermoplastic resin is dissolved or dispersed in water or an organic solvent to prepare a receiving layer coating solution, which is applied to a sheet-like support and dried to form a receiving sheet, Commercialized.

The vinyl chloride resin has high water resistance, and when used in the receiving layer, the printed matter is excellent in image storability in a high-temperature and high-humidity environment. In addition, acrylic resins and polyester resins have a problem that it is difficult to achieve both releasability of the receiving layer and adhesion to the heat transferable protective layer. Cellulosic resins have good releasability of the receiving layer, but have a problem that the printing density is low and the image blurs in a high temperature and high humidity environment.
As for the polyurethane resin, a urethane resin containing 5 to 90 parts by weight of an aromatic component has been proposed as an example of a thermal transfer recording resin. (Patent Document 1)
However, the receiving layer using urethane resin can obtain high printing density, but there is a problem that image bleeding occurs when the printed material is placed in a high humidity environment. Color control is achieved only by controlling the content ratio of aromatic components. It is difficult to balance image bleeding with density.

  Patent Document 2 proposes a urethane resin synthesized from a non-aromatic polyisocyanate and a polyol. However, a urethane resin that does not contain a certain amount or more of an aromatic component has poor dyeability and is not suitable for high-speed thermal transfer printing. Further, Patent Document 2 proposes the use of an aliphatic polyol. However, the aliphatic polyol has a low heat resistance, and there is a problem that image blur occurs when a printed material is placed in a high temperature environment.

JP-A-10-337968 (pages 1 to 3) JP-A-10-337969 (pages 1 and 2)

  The object of the present invention is to improve the above-mentioned disadvantages of the prior art, and at the time of high-speed printing, a printed image having a high printing density, a clear and good light resistance can be obtained, and the printed matter can be placed in a high-temperature and high-humidity environment. It is an object of the present invention to provide a thermal transfer receiving sheet with very little image bleeding and excellent image storage stability.

The present invention includes the following inventions.
(1) In a thermal transfer receiving sheet in which a barrier layer and an image receiving layer are sequentially laminated on at least one surface of the sheet-like support, the image receiving layer includes the following (A) to (C): A thermal transfer receiving sheet comprising a polyurethane resin synthesized from a polymerized component containing an inorganic pigment having an aspect ratio (ratio of average particle diameter / thickness of pigment) of 5 to 5000. .
(A) Polyisocyanate comprising 90% by mass or more of alicyclic polyisocyanate and / or aliphatic polyisocyanate.
(B) A polyol comprising 50% by mass or more of an aromatic diol.
(C) Low molecular weight polyamine compound.
(2) The blending ratio of the (A) and the (B) at the time of synthesizing the polyurethane resin is 100: 40 in terms of a molar ratio of the isocyanate group that the (A) has and the hydroxyl group that the (B) has. The thermal transfer receiving sheet according to (1), which is in a range of ˜100: 90.
(3) The polyurethane resin is further synthesized from a polymerization component containing the following (D), and the carboxyl group content is 0.3 to 6% by mass with respect to 100% by mass of the polyurethane resin. The thermal transfer receiving sheet according to (1) or (2).
(D) A diol having a carboxyalkyl group as a side chain.
(4) The thermal transfer receiving sheet according to any one of (1) to (3), wherein the inorganic pigment is a swellable inorganic layered compound.
(5) The thermal transfer receiving sheet according to any one of (1) to (4), wherein the barrier layer contains a polyvinyl alcohol derivative.
(6) The thermal transfer receiving sheet according to (5), wherein the barrier layer contains 1 to 100% by mass of the inorganic pigment with respect to 100% by mass of the polyvinyl alcohol derivative.
(7) The thermal transfer receiving sheet according to any one of (5) to (6), wherein the polyvinyl alcohol derivative is at least one selected from silanol-modified polyvinyl alcohol and an ethylene-vinyl alcohol copolymer.
(8) The thermal transfer receiving sheet according to (1) to (7), wherein an intermediate layer containing hollow particles is further provided between the sheet-like support and the barrier layer.

  According to the present invention, a print image having a high print density, a clear and good light resistance can be obtained, and a thermal transfer receiving sheet excellent in image storability can be obtained without image blurring even when the print is placed in a high temperature and high humidity environment. .

Hereinafter, the present invention will be described in more detail.
(Sheet support)
As the sheet-like support used in the receiving sheet of the present invention, papers and synthetic resin sheets mainly composed of cellulose pulp are used. Examples of paper include high-quality paper (acidic paper, neutral paper), medium-quality paper, coated paper, art paper, glassine paper, and resin-laminated paper.
Examples of the sheet mainly composed of a synthetic resin include polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate, polyamide, polyvinyl chloride, polystyrene, polycarbonate, and polyvinyl chloride.
Examples of the porous stretched sheets include, for example, synthetic paper, porous polyester sheet and the like mainly composed of a thermoplastic resin such as polyolefin and polyester. These materials may be used alone, or may be a laminate sheet obtained by laminating and adhering porous stretched sheets, porous stretched sheets and other sheets and / or papers.
The sheet-like support may have a structure in which a first base layer on which a receiving layer is formed, an adhesive layer, a release agent layer, and a second base layer are sequentially laminated. Of course, a sheet-like support having a structure of (also referred to as a seal type) can be used.
Among the sheet-like supports, papers mainly composed of cellulose pulp are preferable. The texture of the resulting receiving sheet is close to that of photographic paper, is low in cost, and has little environmental impact.

(Image receiving layer)
The image receiving layer of the present invention contains a polyurethane resin synthesized from a polymerization component containing a polyisocyanate, a polyol and a low molecular weight polyamine compound.

(Polyurethane resin)
In the present invention, the method for synthesizing the polyurethane resin to be used is not particularly limited. Generally, after synthesizing a urethane prepolymer obtained from polyisocyanate and polyol as raw materials, a low molecular weight polyamine compound is used, Obtained by chain extension of urethane prepolymer.

(Urethane prepolymer)
The urethane prepolymer used as an intermediate raw material for the polyurethane resin is synthesized by polycondensation of polyisocyanate and polyol. In this invention, it is preferable to synthesize | combine in ratio of polyisocyanate and polyol in the range of 100: 40-100: 90 in the molar ratio of the isocyanate group: hydroxyl group of a raw material, More preferably, it is 100: 55-100: 85 It is preferable to synthesize in the range, even more preferably in the range of 100: 60 to 100: 70. When the ratio of the polyol to the polyisocyanate is less than 40, the synthesized polyurethane resin has an excessive crystal region, the dyeability is lowered, and the color density of the printed matter printed by thermal transfer is lowered. On the other hand, if it exceeds 90, the amorphous region of the synthesized polyurethane resin becomes excessive, the heat resistance of the resulting receiving layer is lowered, and troubles such as fusion with the dye ribbon and peeling of the receiving layer are likely to occur during printing. . In addition, the prints that have been heat-transfer printed have bleeding over time, which impairs the storage stability of the prints.

(Polyisocyanate)
The polyisocyanate combines with a low molecular weight polyamine compound to form a hard block in the polyurethane resin. The hard block forms a crystalline region by electrical or chemical bonding with the hard block of another molecular chain. This crystal region imparts heat resistance to the polyurethane resin.
Polyisocyanates are mainly classified into alicyclic, aliphatic, and aromatic types. Among these, when aromatic polyisocyanates are used as raw materials for polyurethane resins, the light resistance of images is significantly reduced. The reason why the aromatic polyisocyanate reduces the light resistance of the image is not clear, but the hard block in which the aromatic rings of the polyisocyanate are regularly arranged prevents the dye molecules from penetrating into the image receiving layer, This is presumably because the dye tends to be unevenly distributed in the surface layer portion of the image receiving layer which is easily affected by ultraviolet rays.

  The present invention is characterized by containing 90% by mass or more of alicyclic polyisocyanate and / or aliphatic polyisocyanate in 100% by mass of polyisocyanate used for the synthesis of urethane prepolymer, more preferably 95% by mass. As described above, it is more preferably 98% by mass or more. When the content of the alicyclic polyisocyanate and / or the aliphatic polyisocyanate is less than 90% by mass, the light resistance of the printed matter thermally transferred to the obtained thermal transfer receiving sheet is remarkably lowered. Moreover, it is preferable to adjust content of aliphatic polyisocyanate to the range of 20 mass% or less of the polyisocyanate used for the synthesis | combination of a urethane prepolymer. When the content of the aliphatic polyisocyanate exceeds 20% by mass, the heat resistance of the obtained polyurethane resin is lowered, and the peelability between the dye thermal transfer sheet and the receiving sheet is lowered or the bleeding of the printed matter is deteriorated. It becomes easy to do.

Examples of the aliphatic polyisocyanate that can be used in the present invention include hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, lysine diisocyanate, and hexamethylene triisocyanate. Among these, hexamethylene diisocyanate is preferably used.
Examples of the alicyclic polyisocyanate that can be used in the present invention include isophorone diisocyanate, dicyclohexylmethane diisocyanate, cyclohexane diisocyanate, and triisocyanate cyclohexane. Among these, isophorone diisocyanate, dicyclohexylmethane diisocyanate, and cyclohexane diisocyanate are preferably used. The aliphatic polyisocyanate and alicyclic polyisocyanate that can be used in the present invention are not limited to the above examples, and can be used alone or in combination of two or more.

  In addition to the aliphatic polyisocyanate and the alicyclic polyisocyanate, an aromatic polyisocyanate can be used within a range that does not impair the effects of the present invention. Examples of aromatic polyisocyanates include aromatics such as phenylene diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, triphenylmethane triisocyanate, and polyisocyanates such as xylylene diisocyanate, tetramethylxylylene diisocyanate, and triisocyanate methylbenzene. Group polyisocyanate etc. are mentioned, These can be used independently and can also use 2 or more types together.

(Polyol)
The polyol that forms a urethane prepolymer together with the polyisocyanate forms a soft block in the polyurethane resin. The soft block contributes to the dyeing property of the image receiving layer. The polyurethane resin used in the present invention is characterized by containing 50% by mass or more of an aromatic polyol with respect to 100% by mass of all polyol components as a polyol component, preferably 60% by mass or more, more preferably 70% by mass or more. Further, it is preferable to contain 80% by mass or more. When the aromatic polyol is less than 50% by mass, the dyeing property of the obtained image receiving layer is lowered, and a highly sensitive thermal transfer receiving sheet cannot be obtained, or the heat resistance of the image receiving layer is lowered, and the dye ribbon Problems such as fusing and peeling of the receiving layer occur.

  Examples of aromatic polyols that can be used in the present invention include aromatic polyester polyols such as polyethylene terephthalate diol, polyethylene isophthalate diol, polyhexamethylene isophthalate adipate diol, polyethylene oxide adducts and ethylene oxide adducts of aromatic polyesters. These may be used alone or in combination of two or more.

  Also, it is possible to use a polyol other than the aromatic polyol in combination as long as the effects of the present invention are not hindered. Examples of polyols other than aromatic polyols include polyethylene adipate diol, polybutylene adipate diol, polyethylene butylene adipate diol, polyethylene succinate diol, polybutylene succinate diol, polyethylene sebacate diol, polybutylene sebacate diol, and poly-ε. -Polyester polyols such as caprolactone diol, poly (3-methyl-1,5-pentylene adipate) diol, polytetramethylene carbonate diol, polyhexamethylene carbonate diol, poly (1,4-cyclohexanedimethylene carbonate) diol, poly (Hexamethylene-1,4-cyclohexanedimethylene) polycarbonate polyol such as carbonate diol, polyethylene glycol , Polypropylene glycol, polyether polyol such as polytetramethylene glycol, and acrylic polyols and the like, which can be used alone or may be used in combination of two or more.

  Examples of the low molecular weight polyol include ethylene glycol, propylene glycol, neopentyl glycol, 1,4-butanediol, 1,6-hexanediol, trimethylolpropane, pentaerythritol, sorbitol, and the like. It can be used or two or more types can be used in combination.

(Polyamine compound)
The polyurethane resin used in the present invention is obtained by synthesizing the urethane prepolymer and then chain-extending the urethane prepolymer with a low molecular weight polyamine compound. The low molecular weight polyamine compound forms a hard block in the polyurethane resin together with the polyisocyanate. As described above, it is preferable that the low molecular weight polyamine compound is non-aromatic because the light resistance of the dye thermally transferred to the receiving layer is reduced when a large amount of aromatic component is contained in the crystalline region.

  Examples of the low molecular weight polyamine compound that can be used in the present invention include hydrazine, ethylenediamine, propylenediamine, hexamethylenediamine, bisaminomethylcyclohexane, di (aminocyclohexyl) methane, piperazine, 2-methylpiperazine, isophoronediamine, diethylenetriamine, and imino. Examples thereof include low molecular weight polyamines such as bispropylamine and triethylenetetramine, and these can be used alone or in combination of two or more.

The method for synthesizing the polyurethane resin of the present invention is not particularly limited, and is synthesized using various known methods, reaction catalysts, and reaction inhibitors.
The urethane resin of the present invention may be a solvent-soluble type or a water-dispersed type such as a self-emulsifying type or a forced emulsifying type using a dispersing agent. In recent years, it is preferable to use a water-dispersed type in consideration of the environment, and among the water-dispersed types, a self-emulsifying type is preferable because a film-forming property during coating can be obtained and a uniform image-receiving layer can be obtained.

  The method of self-emulsification or forced emulsification of the polyurethane resin is not particularly limited, and various known methods can be used. By adding a diol having a carboxyl alkyl as a side chain as a raw material to the polyurethane resin. A method of introducing a carboxyl group to make it hydrophilic is preferable. The content ratio of the carboxyl group derived from the diol having the carboxyl alkyl as a side chain is preferably 0.3 to 6% by mass, more preferably 0.5 to 5% by mass, more preferably 100% by mass of the polyurethane resin. Preferably it is 2.5-4 mass%. When the content ratio of the carboxyl group is less than 0.3% by mass, the polyurethane resin becomes unstable in the coating liquid, smears occur in the coating drying process, and the print image quality may deteriorate. Further, when the content ratio of the carboxyl group exceeds 6% by mass, the water resistance of the obtained receiving layer is poor, and when the printed matter is stored in a high-temperature and high-humidity environment, bleeding of the printed matter may occur or the storage stability may be reduced. There is.

The lower limit value of the glass transition temperature of the polyurethane resin used in the present invention is preferably −30 ° C., more preferably −10 ° C., and still more preferably 0 ° C. When the glass transition temperature of the polyurethane resin is less than −30 ° C., fusion between the image receiving layer and the dye thermal transfer sheet is likely to occur. The upper limit of the glass transition temperature of the polyurethane resin used in the present invention is preferably 60 ° C, more preferably 50 ° C, and even more preferably 40 ° C. When the glass transition temperature of the polyurethane resin exceeds 60 ° C., the dyeing property of the image receiving layer is inferior, and a sufficient print density cannot be obtained, which is not preferable.
In addition, the glass transition temperature of the said polyurethane resin was measured according to ISO-11359-2.
(Example of measuring glass transition temperature of polyurethane resin)
Measuring instrument: Dynamic viscoelasticity measuring device DMS6100 type (manufactured by Seiko Instruments Inc.)
Drive frequency: 10Hz
Measurement mode: Tensile mode Distance between chucks: 20 mm
Temperature increase rate: 5 ° C / min
From the measurement results of the viscoelasticity / temperature characteristics of the resin, a viscoelasticity / temperature graph was created, and the glass transition temperature was determined as the peak value of tan δ.

The coating amount of the image-receiving layer, 0.5 to 10 g / m ² is preferred. The coating amount of the image-receiving layer is less than 0.5 g / m ^2, sometimes sufficient printing quality and image light resistance can not be obtained, exceeds 10 g / m ^2, the heat insulating effect of the sheet-like support In some cases, sufficient print density cannot be obtained.

(Crosslinking agent)
The dyeable resin used in the receiving layer of the present invention is preferably crosslinked with a crosslinking agent after coating. Examples of the crosslinking agent used in the receiving layer of the present invention include an isocyanate crosslinking agent, a titanium chelate crosslinking agent, a carbodiimide crosslinking agent, and an oxazoline crosslinking agent.
A carbodiimide-based crosslinking agent is particularly preferable because it has good reactivity with the carboxyl group of the polyurethane resin. The content ratio of the carbodiimide-based crosslinking agent is preferably 0.5 to 40% by mass and more preferably 1 to 30% by mass with respect to 100% by mass of the resin used in the receiving layer.

(Release agent)
The image receiving layer of the present invention can also contain a conventionally known release agent. As the release agent used in the image receiving layer of the present invention, waxes, hydrophilic group-containing silicone oil, silicone oil emulsion, polysiloxane segment-containing aqueous resin, and the like are preferable.
(Other additives)
In the image-receiving layer of the present invention, conventionally known surfactants, thickeners, antifoaming agents, pigments, and the like can be used as necessary in the range not impairing the effects of the present invention.

(Barrier layer)
The barrier layer of the present invention is characterized by containing an inorganic pigment having an aspect ratio (ratio of average particle diameter / thickness of pigment) of 5 to 5000.
The barrier layer of the present invention is a layer in which an inorganic pigment having a high aspect ratio is folded to form a layer through which the dye does not permeate, and the dye dyed on the image receiving layer is prevented from diffusing into the sheet-like support. In addition, image bleeding caused by dye diffusion is prevented.

  The aspect ratio (Z) is indicated by the relationship Z = L / a, where L is the average particle diameter of inorganic pigment in water (measured by laser diffraction method. Using a particle size distribution analyzer LA-910 manufactured by Horiba, Ltd.) , Volume distribution 50% median diameter), and a is the thickness of the inorganic pigment. The thickness is a value obtained by observing a cross section of the barrier layer by photographic observation using a scanning electron microscope (SEM) or a transmission electron microscope (TEM).

  The inorganic pigment used in the barrier layer of the present invention has an aspect ratio of 5 to 5000, preferably 100 to 5000, and more preferably 300 to 5000. If the aspect ratio is less than 5, the effect of preventing dye penetration is small, and image bleeding cannot be prevented. On the other hand, if the aspect ratio exceeds 5000, the flexibility of the barrier layer is lost, and depending on the paper feeding method of the printer, the barrier layer may be cracked during printing, and the print image quality may deteriorate.

  The average particle diameter of the inorganic pigment used in the barrier layer of the present invention is generally in the range of 0.1 to 20 μm, preferably 0.3 to 18 μm, and more preferably 0.5 to 16 μm. When the average particle major axis is less than 0.1 μm, the aspect ratio becomes small, and it becomes difficult to spread in parallel on the intermediate layer, and image bleeding cannot be completely prevented. If the average particle major axis exceeds 20 μm, the inorganic pigment protrudes from the barrier layer, and irregularities are generated on the surface of the barrier layer, and the smoothness of the surface of the receiving layer may be lowered to deteriorate the image quality.

  Examples of inorganic pigments used in the barrier layer of the present invention include heavy calcium carbonate, light calcium carbonate, kaolin, calcined kaolin, structural kaolin, deramikaolin, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, and alumina. , Magnesium carbonate, magnesium oxide, silica, white carbon, zeolite, swellable inorganic layered compound, etc., having an aspect ratio in the range of 5 to 5000 can be selected and used. Among these, a swellable inorganic layered compound is preferable because a shape with a high aspect ratio can be easily obtained.

(Swellable inorganic layered compound)
Specific examples of the swellable inorganic layered compound preferably used in the barrier layer of the present invention include graphite, phosphate-based derivative compounds (such as zirconium phosphate compounds), chalcogenides, hydrotalcite compounds, lithium aluminum Examples thereof include composite hydroxides and clay minerals (for example, synthetic mica and synthetic smectite).

  Graphite, phosphate derivative compounds (zirconium phosphate compounds, etc.), chalcogenides, hydrotalcite compounds, and lithium aluminum composite hydroxides are compounds or substances in which unit crystal layers are stacked on each other and have a layered structure. Here, the layered structure refers to a structure in which surfaces in which atoms are strongly bonded by a covalent bond or the like and densely arranged are stacked substantially in parallel by a weak binding force such as van der Waals force.

A “chalcogenide” is a dichalcogenide of a group IV (Ti, Zr, Hf), a group V (V, Nb, Ta) and / or a group VI (Mo, W) element, which has the formula MX2 (M The element X represents a chalcogen (S, Se, Te).
Clay-based minerals generally have a two-layer structure having an octahedral layer with aluminum, magnesium, etc. as the central metal at the top of the silica tetrahedral layer, and a silica tetrahedral layer, with aluminum, magnesium, etc. It is classified into a type having a three-layer structure in which an octahedral layer made of a central metal is confined from both sides. Examples of the former two-layer structure type include kaolinite group and antigolite group. Examples of the latter three-layer structure type include smectite group, vermiculite group, mica group, etc. depending on the number of interlayer cations. Can do.

  Specific examples of clay minerals include kaolinite, dickite, nacrite, halloysite, antigolite, chrysotile, pyrophyllite, montmorillonite, hectorite, tetrasilic mica, sodium teniolite, margarite, talc, vermiculite, Examples include xanthophyllite and chlorite. For other examples, reference can be made to articles such as Haruo Shiramizu, “Clay Mineralogy”, 1988, Asakura Shoten Co., Ltd.

  As the swellable inorganic layered compound used in the barrier layer of the present invention, among clay minerals, a smectite group, a vermiculite group, a mica group, or the like is preferably used. As the smectite group, for example, montmorillonite, hydelite, nontronite, saponite, iron saponite, hectorite, soconite, stevensite and the like are more preferably used.

In addition to natural products (clay minerals), these swellable inorganic layered compounds may be either synthetic products or processed products (for example, surface-treated products of silane coupling agents). For example, as synthetic smectite, those represented by the formula _{Na 0.1~1.0 Mg 2.4~2.9 Li 0.0~0.6 Si 3.5~4.0} O 9.0~10.6 (OH and / or F) _{1.5 to 2.5} and the like.
The synthetic smectite and synthetic mica can be produced by three synthesis methods: a hydrothermal reaction method (see JP-A-6-345419), a solid-phase reaction method, and a melting method (see JP-A-5-270815). There is.

Examples of the synthetic swellable inorganic layered compound include fluorine phlogopite (KMg ₃ AlSi ₃ O ₁₀ F, melting method or solid phase reaction method), potassium tetrasilicon mica (KMg _2.5 Si ₄ O ₁₀ F ₂ , melting method), Sodium tetrasilicon mica (NaMg _2.5 Si ₄ O ₁₀ F ₂ , melting method), sodium teniolite (NaMg ₂ LiSi ₄ O ₁₀ F ₂ , melting method), lithium teniolite (LiMg ₂ LiSi ₄ O ₁₀ F ₂ , melting method) ) synthetic mica, such as, or sodium hectorite _{(Na 0.33 Mg 2.67 Li 0.33 Si} 4.0 O 10 (OH or F) _2, hydrothermal reaction method or a fusion method), lithium hectorite _{(Na 0.33 Mg 2.67 Li 0.33 Si} 4.0 O ₁₀ (OH or F) _2, hydrothermal reaction method or a fusion method), synthetic smectite such as saponite _{(Na 0.33 Mg 2.67 AlSi 4.0 O} 10 (OH) 2, hydrothermal reaction method)

  Among the swellable inorganic layered compounds, synthetic mica such as sodium tetrasilicon mica, sodium teniolite, lithium teniolite, synthetic smectite such as sodium hectorite, lithium hectorite, saponite, and natural smectite such as montmorillonite are more preferable. used. Among these, sodium tetrasilicon mica is particularly preferable, and a desired particle size, aspect ratio, and crystallinity can be obtained by a fusion synthesis method.

  Examples of commercially available clay minerals include natural bentonite commonly called sodium bennite, kunipia (: trade name, natural montmorillonite, manufactured by Kunimine Industries), smecton (: trade name, hydrothermal reaction method synthetic smectite, kunimine industry). Co., Ltd.), Bee Gum (: trade name, manufactured by Vanderbilt), Laponite (: trade name, manufactured by Laporte), DM Clean A, DMA-350, Na-Ts (: Trade name, all three types are fused synthetic mica) , Sodium tetrasilicon mica, manufactured by Topy Industries, Ltd.), Bengel (: trade name, manufactured by Toyoshun Yoko Co., Ltd.) and the like. These may be used alone or in combination of two or more.

  The swellable inorganic layered compound preferably used in the present invention is a swellable inorganic layered compound that easily swells, cleaves and disperses in water. The degree of the “swelling / cleavage” property of the swellable inorganic layered compound to the solvent can be evaluated by a “swelling / cleavage” test. The swelling property of the swellable inorganic layered compound is preferably about 5 ml / 2 g or more, more preferably about 20 ml / 2 g or more.

  Specifically, the swelling power of the swellable inorganic layered compound is, for example, Kunipia (swelling power: 65 ml / 2 g or more), Smecton (swelling power: 60 ml / 2 g or more), DM Clean A, DMA-350, Na-Ts (swelling) Force: 30 ml / 2 g or more), ME-100 (: trade name, manufactured by Coop Chemical Co., swelling power: 20 ml / 2 g or more) and bengel (swelling force: 38 ml / 2 g or more).

  The swelling test will be described in detail. Using a 100 ml graduated cylinder as a test container, 2 g of the swellable inorganic layered compound was slowly added to 100 ml of the solvent and allowed to stand, and then the interface between the swellable inorganic layered compound dispersion layer and the supernatant layer after 24 hours at 23 ° C. From the scale, read the volume of the swellable inorganic layered compound dispersion layer. The larger this value (ml / 2g), the higher the swellability and the better. As the solvent, water is preferably used.

  On the other hand, the cleavage property of the swellable inorganic layered compound is preferably about 5 ml or more, more preferably about 20 ml or more. As a solvent for cleavage measurement, a solvent having a density smaller than that of the swellable inorganic layered compound is used, and preferably water is used.

  The cleavage test will be described in detail. Slowly add 30 g of a swellable inorganic layered compound to 1,500 ml of swelling solvent, and disperser (trade name: Desper MH-L, manufactured by Asada Tekko Co., Ltd., blade diameter 52 mm, rotation speed 3100 rpm, container capacity 3 L, bottom surface-blade After being dispersed for 90 minutes at a peripheral speed of 8.5 m / sec at a distance of 28 mm (solvent temperature: 23 ° C.), 100 ml of the dispersion was taken, placed in a graduated cylinder and allowed to stand for 60 minutes, and then swellable inorganic layered The volume of the swellable inorganic layered compound dispersion layer is read from the interface between the compound dispersion layer and the supernatant layer. The larger this numerical value (ml), the higher the cleavage property of the swellable inorganic layered compound, which is preferable.

In the present invention, the barrier layer preferably contains a polyvinyl alcohol derivative. The polyvinyl alcohol derivative has good dispersibility of the inorganic pigment, particularly the swellable inorganic layered compound, in the coating material, is excellent in film formability during coating, and provides a uniform barrier layer.
Polyvinyl alcohol derivatives include fully saponified polyvinyl alcohol (saponification degree 97-100%), partially saponified polyvinyl alcohol (saponification degree less than 76-97%), silanol-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, and acetoacetyl-modified polyvinyl alcohol. In addition, one or more kinds selected from cation-modified polyvinyl alcohol, mercapto group-containing polyvinyl alcohol and the like can be used.
Among the above polyvinyl alcohol derivatives, fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, silanol-modified polyvinyl alcohol, ethylene vinyl alcohol copolymer, etc. are preferably used, solvent resistance barrier property and dye migration preventing property, flexibility, coating Excellent in aptitude.
Furthermore, when a silanol-modified polyvinyl alcohol or ethylene-vinyl alcohol copolymer is used for the barrier layer, a barrier layer having high water resistance can be obtained. When an image receiving layer is formed on the barrier layer with a water-based paint, the barrier layer receives the barrier layer. A uniform image-receiving layer is obtained without dissolving in the layer coating.

  Silanol-modified polyvinyl alcohol can be produced by a conventionally known synthesis method, and vinyl trimethoxysilane and vinyl acetate are copolymerized in methanol or the like, and then vinyl acetate is saponified by methanolysis using sodium hydroxide as a catalyst. Can be obtained. The silanol-modified polyvinyl alcohol preferably has a saponification degree of 85% or more and a silanol group content in the molecule of 0.05 to 3 mol% as a monomer unit.

  The viscosity of the barrier layer coating solution prepared by containing silanol-modified polyvinyl alcohol and ethylene-vinyl alcohol copolymer is preferably moderately low, and since the inorganic pigment is uniformly dispersed, a clear image can be obtained. can get. The degree of polymerization is preferably 200 to 2000.

  In addition, various water-soluble resins and aqueous polymer compounds such as water-dispersible resins can be used in combination as appropriate, as long as the effects of the present invention are not impaired. Examples of water-soluble resins that can be used in combination include starch, modified starch, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, isobutylene-maleic anhydride copolymer salt, styrene-maleic anhydride copolymer salt, styrene. -Resins such as acrylic acid copolymer salts and ethylene-acrylic acid copolymer salts, urea resins, polyurethane resins, melamine resins, amide resins, etc., and water dispersible resins include styrene-butadiene copolymer Examples thereof include coalesced latex, acrylic ester resin latex, methacrylic ester copolymer latex, ethylene-vinyl acetate copolymer latex, polyester polyurethane ionomer, and polyether polyurethane ionomer.

  1-100 mass parts is preferable with respect to 100 mass parts of polyvinyl alcohol derivatives, and, as for the solid content compounding quantity of the inorganic pigment in a barrier layer, 1-20 mass parts is more preferable. If the amount is less than 1 part by mass, the effect of preventing the permeation of the dye is small and image bleeding may not be sufficiently prevented. On the other hand, if it exceeds 100 parts by mass, the adhesive strength of the barrier layer may be insufficient.

The coating amount of the barrier layer, 0.5 to 10 g / m ² is preferred. When the coating amount of the barrier layer is less than 0.5 g / m ² , a sufficient image bleeding prevention effect may not be exhibited, and when it exceeds 10 g / m ² , the heat insulating effect of the sheet-like support cannot be exhibited, A sufficient print density may not be obtained.

(Middle layer)
An intermediate layer containing hollow particles can be provided between the sheet-like support and the barrier layer. Since the intermediate layer containing hollow particles can impart heat insulation and cushioning properties, it can improve image clarity and image uniformity. The material and production method of the hollow particles used in the intermediate layer are not particularly limited, and specific examples of the material for forming the walls of the hollow particles include acrylonitrile, vinylidene chloride, styrene acrylate polymer. .
As a method for producing these hollow particles, a method of heating and foaming microcapsules in which butane gas is sealed in resin particles, an emulsion polymerization method, and the like can be mentioned.
The coating amount of the intermediate layer, 1 to 30 g / m ² is preferred. If the coating amount of the intermediate layer is less than 1 g / m ² , sufficient heat insulating properties and cushioning properties cannot be expected, and if it exceeds 30 g / m ² , the effect obtained for the increase in cost is small.
The particle size of the hollow particles is preferably 0.1 to 10 μm. When the particle size of the hollow particles is less than 0.1 μm, the walls of the hollow particles become thin and the heat resistance is insufficient, and is easily broken in the coating and drying process. On the other hand, when the thickness exceeds 10 μm, surface irregularities of the obtained receiving sheet are increased and image uniformity may be deteriorated.
The volume hollow ratio of the hollow particles is preferably 50 to 90%. When the volumetric hollow ratio of the hollow particles is less than 50%, the effect of imparting heat insulating properties and cushioning properties may be insufficient. If it exceeds 90%, the walls of the hollow particles become thin and the durability may be lowered.

(Back layer)
A back surface layer can be appropriately provided on the surface (back surface) of the sheet-like support on which the image receiving layer is not provided.
The purpose of the back layer is to improve runnability, prevent static electricity, prevent scratching of the receiving layer due to friction between the receiving sheets, and prevent dye transfer to the back surface when the receiving sheets are stacked. The back layer contains a resin, a pigment, an antistatic agent and the like depending on the purpose.

(Calendar processing)
The receiving sheet may be calendered. By the calendering process, the unevenness of the surface of the obtained receiving sheet can be reduced and a uniform image can be obtained. The calendar process may be performed at any stage. As the calendar apparatus used for the calendar process, a calendar apparatus generally used in the paper industry such as a super calendar, a soft calendar, a gloss calendar, and a clearance calendar can be appropriately used.

  Various auxiliary agents such as wetting agents, dispersants, thickeners, antifoaming agents, colorants, antistatic agents, preservatives and the like used in the production of general coated papers are appropriately added to each coating layer. The

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. Further, “parts” and “%” in the examples represent “parts by mass” and “% by mass”, respectively, unless otherwise specified, and are solid contents.

Examples [Polyurethane resin synthesis examples UP1 to UP5]
After the urethane prepolymer obtained from polyisocyanate and polyol was synthesized by the following method, the urethane prepolymer was chain-extended using low molecular weight polyamine compounds to synthesize polyurethane resins UP1 to UP5.
To a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer and a nitrogen blowing tube, the polyol components shown in Table 1 and 2,2-dimethylolbutanoic acid were added in the amounts shown in Table 1, and further dibutyl 0.001 g of tin dilaurate and 120 g of methyl ethyl ketone were added and mixed uniformly. Next, the amount of the isocyanate component shown in Table 1 was added to this and the amount shown in Table 1 was added, and the mixture was reacted at 80 ° C. for 5 hours to obtain a methyl ethyl ketone solution of a prepolymer.
The resulting prepolymer solution of methyl ethyl ketone was cooled to 30 ° C., neutralized by adding triethylamine in the amount shown in Table 1, and then 403 g of water was gradually added to emulsify and disperse. To this emulsified dispersion, a 20% by mass aqueous solution of ethylenediamine was added in the amount shown in Table 1 (in terms of solid content) and stirred for 2 hours. The solvent was removed while the temperature was raised to 50 ° C. over 2 hours under reduced pressure to obtain a polyurethane resin emulsion having a nonvolatile content of about 39% by mass. In the present invention, the nonvolatile content of the polyurethane resin emulsion means the residual weight ratio after the aqueous dispersion is dried at 105 ° C. for 3 hours.

  Polyisocyanate, polyol, low molecular weight polyamine compound used for the synthesis of polyurethane resins UP1 to UP5, and types of diol having carboxylalkyl as a side chain, alicyclic polyisocyanate, aliphatic polyisocyanate and aromatic polyisocyanate in polyisocyanate component Table 2 shows the content ratio (mass ratio) of the isocyanate, the ratio of polyisocyanate and polyol in the prepolymer (isocyanate group: molar ratio of hydroxyl groups), and the content ratio of carboxyl groups to the polyurethane resin obtained by synthesis. there were.

Example 1
(Formation of sheet-like support and intermediate layer)
As a sheet-like support, art paper having a thickness of 150 μm (trade name: OK Kanto N, manufactured by Oji Paper Co., Ltd., basis weight 174.4 g / m ² ) was used. An intermediate layer was formed by coating and drying an intermediate layer coating solution having the following composition on one side of the sheet-like support so that the solid content coating amount was 10 g / m ² .
(Preparation of intermediate layer coating solution)
An intermediate layer coating solution was prepared by stirring materials having the following composition.
45 parts of pre-expanded hollow particles made of a copolymer mainly composed of acrylonitrile and methacrylonitrile (average particle diameter: 3.2 μm, volume hollow ratio: 85%)
10 parts of polyvinyl alcohol (trade name: PVA205, manufactured by Kuraray)
45 parts of styrene-butadiene copolymer resin dispersion (trade name: 0695, manufactured by JSR, Tg-4 ° C.)
200 parts of water (preparation of receiving sheet)
The barrier layer coating liquid B1 obtained by the following preparation method was coated on the intermediate layer so as to have a solid content coating amount of 1.5 g / m ² and dried to form a barrier layer. Next, the receiving layer coating liquid R1 was coated on the barrier layer so that the solid coating amount was 3 g / m ² and dried to obtain a receiving sheet.
(Preparation of barrier layer coating solution B1)
10 parts of swelling synthetic mica (trade name; NTS-10, manufactured by Topy Industries, Ltd.,
Main component: Sodium 4 Silicon mica, particle average major axis 12 μm, aspect ratio 2400)
Silanol-modified polyvinyl alcohol 100 parts (trade name: R2105, manufactured by Kuraray, polymerization degree 500)
1100 parts of water (preparation of receiving layer coating solution R1)
Polyurethane resin UP1 of the above synthesis example 88 parts Carbodiimide type cross-linking agent 10 parts (trade name: Carbodilite E-02, Nisshinbo Co., Ltd.)
2 parts polysiloxane graft acrylic resin (trade name: US450, manufactured by Toagosei)
300 parts of water

<Example 2>
A receiving sheet was obtained in the same manner as in Example 1 except that in the preparation of the receiving layer coating liquid R1 of Example 1, the polyurethane resin UP2 of the above synthesis example was used instead of the polyurethane resin UP1.
<Example 3>
A receiving sheet was obtained in the same manner as in Example 1 except that the polyurethane resin UP3 of the above synthesis example was used instead of the polyurethane resin UP1 in the preparation of the receiving layer coating solution R1 of Example 1.

<Example 4>
A receiving sheet was obtained in the same manner as in Example 1 except that the barrier layer coating liquid B2 obtained by the following method was used instead of the barrier layer coating liquid B1 in the preparation of the receiving sheet.
(Preparation of barrier layer coating solution B2)
10 parts of swelling synthetic mica (trade name; NTS-10, manufactured by Topy Industries, Ltd.,
Main component: Sodium 4 Silicon mica, particle average major axis 12 μm, aspect ratio 2400)
100 parts of ethylene-vinyl alcohol copolymer (trade name: RS4105, manufactured by Kuraray, polymerization degree 500)
1100 parts of water

<Example 5>
A receiving sheet was obtained in the same manner as in Example 1 except that the barrier layer coating solution B3 obtained by the following method was used instead of the barrier layer coating solution B1 in the preparation of the receiving sheet.
(Preparation of barrier layer coating solution B3)
Deramikaolin 10 parts (trade name: Astra Plate, manufactured by Huba,
Particle average major axis 1μm, aspect ratio 40)
Silanol-modified polyvinyl alcohol 100 parts (trade name: R2105, manufactured by Kuraray, polymerization degree 500)
1100 parts of water

<Example 6>
A receiving sheet was obtained in the same manner as in Example 1 except that the barrier layer coating liquid B4 obtained by the following method was used instead of the barrier layer coating liquid B1 in the preparation of the receiving sheet.
(Preparation of barrier layer coating solution B4)
10 parts of swelling synthetic mica (trade name; NTS-10, manufactured by Topy Industries, Ltd.,
Main component: Sodium 4 Silicon mica, particle average major axis 12 μm, aspect ratio 2400)
100 parts of fully saponified polyvinyl alcohol (trade name: PVA117, manufactured by Kuraray, degree of polymerization 1700)
1100 parts of water

<Comparative Example 1>
A receiving sheet was obtained in the same manner as in Example 1 except that the polyurethane resin UP4 of the above synthesis example was used instead of the polyurethane resin UP1 in the preparation of the receiving layer coating liquid R1 of Example 1.
<Comparative example 2>
A receiving sheet was obtained in the same manner as in Example 1 except that in the preparation of the receiving layer coating liquid R1 of Example 1, the polyurethane resin UP5 of the above synthesis example was used instead of the polyurethane resin UP1.

<Comparative Example 3>
A receiving sheet was obtained in the same manner as in Example 1 except that the barrier layer coating liquid B5 obtained by the following method was used instead of the barrier layer coating liquid B1 in the preparation of the receiving sheet.
(Preparation of barrier layer coating solution B5)
100 parts of ethylene-vinyl alcohol copolymer (trade name: RS4103, manufactured by Kuraray)
1100 parts of water

<Comparative example 4>
A receiving sheet was obtained in the same manner as in Example 1 except that the barrier layer coating solution B6 obtained by the following method was used instead of the barrier layer coating solution B1 in the preparation of the receiving sheet.
(Preparation of barrier layer coating solution B6)
10 parts of heavy calcium carbonate (trade name; Softon 2200, manufactured by Bihoku Flour Industry, particle average major axis 1 μm, aspect ratio 2)
Silanol-modified polyvinyl alcohol 100 parts (trade name: R2105, manufactured by Kuraray, polymerization degree 500)
1100 parts of water

[Evaluation]
The following tests were conducted on the receiving sheets obtained in the above examples and comparative examples. The obtained results are shown in Table 3.
[Image density]
Using a commercially available thermal transfer video printer (trade name: UP-50, manufactured by Sony Corporation) equipped with a sublimation dye thermal transfer sheet (trade name: UP-540, manufactured by Sony Corporation) A solid image was printed. Using a Macbeth reflection densitometer RD914, the print density of the black solid image was measured. The image clarity of the receiving sheet was evaluated according to the following criteria.
A: Black solid print density is 2.2 or more, and can be used as a high-sensitivity receiving sheet without problems.
◯: The black solid print density is 2.0 or more and less than 2.2, and can be used practically without any problem.
(Triangle | delta): The printing density of black solid is 1.7 or more and less than 2.0, and it is practical.
X: The black solid print density is less than 1.7, which is not suitable for practical use.

[Image clarity]
Using a commercially available thermal transfer video printer (trade name: UP-50, manufactured by Sony Corp.) equipped with a sublimation dye thermal transfer sheet (trade name: UP-540, manufactured by Sony Corp.), Macbeth The image was printed so that the image density when measured with a reflection densitometer RD914 was 0.6 to 0.7, and the dot reproducibility of the image was visually evaluated according to the following criteria.
(Double-circle): There is no missing dot and it is excellent in sharpness.
○: Slightly missing dots can be seen, but can be used practically without any problem.
(Triangle | delta): Although dot missing is seen, it is practical.
X: Missing dots are conspicuous and are not suitable for practical use.

[Image bleeding]
Using a commercially available thermal transfer video printer (trade name: UP-50, manufactured by Sony Corporation) equipped with a sublimation dye thermal transfer sheet (trade name: UP-540, manufactured by Sony Corporation), black thin lines were printed in a room temperature environment. After the print was placed in an environment of 40 ° C. and 75% RH for 48 hours, bleeding of the black thin line was evaluated according to the following criteria.
A: The black thin line does not show any blur even when observed with a magnifier, and there is no problem in practical use.
○: The black thin line is slightly blurred by magnifying glass, but is practical.
Δ: The black thin line is slightly blurred by visual observation, but is practical.
X: Bleeding is clearly observed by visual observation of black thin lines, and is not suitable for practical use.

(Image light resistance)
Using a commercially available thermal transfer video printer (trade name: UP-50, manufactured by Sony Corporation) equipped with a sublimation dye thermal transfer sheet (trade name: UP-540, manufactured by Sony Corporation), solid black printing was performed at room temperature. The obtained black solid image print was processed with an Xe fade meter until the accumulated illuminance reached 10,000 kJ / m ² .
The color tone before and after the light resistance test of the image was measured using a color difference meter (Gretag) in accordance with JIS Z 8721. The measured values were recorded in the L ^* a ^* b ^* color system based on JIS Z 8729, and the color difference (ΔE ^* ) before and after treatment was calculated by the method based on JIS Z 8730 to evaluate the light resistance.
A: ΔE ^* is less than 7, and there is no problem in practical use.
○: ΔE ^* is 7 or more and less than 10 and is practical.
Δ: ΔE ^* is 10 or more and less than 13 and is practical.
×: ΔE ^* is not less than 13, not suitable for practical use.

表３から明らかなように、実施例１〜７の熱転写受容シートは、印画濃度が高く、画像の鮮明性、画像の耐光性に優れ、高温高湿度環境での画像滲みが極めて少ない、優れた熱転写受容シートである。

As is apparent from Table 3, the thermal transfer receiving sheets of Examples 1 to 7 have a high printing density, excellent image sharpness and image light resistance, and excellent image blurring in a high temperature and high humidity environment. It is a thermal transfer receiving sheet.

  The present invention provides a thermal transfer receiving sheet having a high image density, a clear and excellent light fastness, a very low image bleeding even when the printed material is placed in a high temperature and high humidity environment, and excellent image storage stability. This is extremely useful in practice.

Claims (8)

In a thermal transfer receiving sheet in which a barrier layer and an image receiving layer are sequentially laminated on at least one surface of the sheet-like support and the sheet-like support, the image receiving layer includes a layer containing the following (A) to (C) A thermal transfer receiving sheet comprising a polyurethane resin synthesized from a composite component, wherein the barrier layer contains an inorganic pigment having an aspect ratio (ratio of average particle diameter / thickness of pigment) of 5 to 5000.
(A) Polyisocyanate comprising 90% by mass or more of alicyclic polyisocyanate and / or aliphatic polyisocyanate.
(B) A polyol comprising 50% by mass or more of an aromatic diol.
(C) Low molecular weight polyamine compound. The blending ratio of the (A) and the (B) at the time of synthesizing the polyurethane resin is a molar ratio of the isocyanate group possessed by the (A) and the hydroxyl group possessed by the (B), from 100: 40 to 100: The thermal transfer receiving sheet according to claim 1, which is in the range of 90. The polyurethane resin is further synthesized from a polymerization component containing (D) below, and the carboxyl group content is 0.3 to 6% by mass with respect to 100% by mass of the polyurethane resin. Item 3. The thermal transfer receiving sheet according to Item 1 or 2.
(D) A diol having a carboxyalkyl group as a side chain.   The thermal transfer receiving sheet according to claim 1, wherein the inorganic pigment is a swellable inorganic layered compound. The thermal transfer receiving sheet according to any one of claims 1 to 4, wherein the barrier layer contains a polyvinyl alcohol derivative. The thermal transfer receiving sheet according to claim 5, wherein the barrier layer contains 1 to 100% by mass of the inorganic pigment with respect to 100% by mass of the polyvinyl alcohol derivative. The thermal transfer receiving sheet according to any one of claims 5 to 6, wherein the polyvinyl alcohol derivative is at least one selected from silanol-modified polyvinyl alcohol and an ethylene-vinyl alcohol copolymer. The thermal transfer receiving sheet according to any one of claims 1 to 7, further comprising an intermediate layer containing hollow particles between the sheet-like support and the barrier layer.