JP3517691B2 - Thermal transfer recording medium - 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 medium, and more specifically, it has good fixing property to a receptor, strong resistance to heat, rubbing, chemicals, etc., and high performance in terms of transfer performance such as thermal sensitivity. Thermal transfer recording medium.

[0002]

2. Description of the Related Art A thermal transfer recording medium requires an ink layer having a low softening temperature in order to improve thermal transfer performance, and does not stain the background by rubbing the tail even if the thermally transferred image is rubbed during heating. Moreover, an ink having a good fixing property, which does not dissolve in a chemical such as an organic solvent, is required. However, since there are contradictory requirements to these requirements, it is extremely difficult to easily form an ideal ink layer. For example, Japanese Examined Patent Publication (Kokoku) No. 60-59159 discloses a thermal transfer recording medium having a thermal transfer ink layer composed of an epoxy resin having a softening temperature of 60 to 110 ° C. and a colorant, and the ink layer has a storage stability. It gives a transferred image with good abrasion resistance, but this transferred image is 70 ℃
There is a defect that the image is disturbed when rubbed under moderate heating. Further, since the lubricity of the transferred image surface is low, there is a drawback that it can be easily peeled off by metal corners, claws and the like.

For this reason, studies have been conducted to make the thermal transfer recording layer a multi-layer structure, to search for a combination of a specific binder resin and a specific heat-meltable ink, and the like. For example, in JP-A-3-99885, a polyester resin having a glass transition temperature of 50 to 70 ° C., a colorant, and a lubricant are main components on a release layer formed of a heat-melting substance having a melting point of 60 to 120 ° C. A thermal transfer recording material having a thermal transfer ink layer is disclosed. In Japanese Unexamined Patent Publication (Kokai) No. 3-211090, at least one of the thermal transfer recording layers formed of a plurality of layers such as a release layer and an ink layer is a layer containing a thermoplastic resin having a glass transition temperature of 120 ° C. or higher as a main component, Discloses a thermal transfer recording medium capable of obtaining a transferred image having high heat resistance and chemical resistance. Further, in JP-A-3-178488, a release layer containing a wax having a softening point of 70 to 120 ° C. as a main component, and an inorganic pigment or a resin powder having a softening point of 100 ° C. or more is contained in a colorless thermoplastic binder resin. A thermal transfer recording medium having a three-layer structure having the above-mentioned layer and an ink layer is disclosed in Japanese Patent Laid-Open No.
No. 189189 proposes a thermal transfer recording medium having a heat-meltable ink layer composed of a heat-meltable ink and a resin matrix having releasability for the ink by the present applicant. Further, the present applicant has conducted research for the purpose of improving abrasion resistance, heat resistance and chemical resistance of a transferred image, and uses a copolymer of methyl methacrylate, acrylonitrile and glycidyl methacrylate as an alkanolamine as a binder resin for an ink layer. A modified resin has been proposed (JP-A-2-258294). For the same purpose, a method of using a copolymer formed of acrylonitrile or methacrylonitrile and an unsaturated ester as a binder resin for an ink layer, and providing a lubrication agent layer and / or an adhesion improver layer under the ink layer. A method and a method of providing a sensitivity improving agent layer on the ink layer have been proposed (JP-A-2-258295).
Issue).

Although many proposals have been made for the thermal transfer recording medium as described above, generally, when the abrasion resistance of the transferred image is high, the thermal sensitivity is poor, and when the thermal sensitivity is high, the abrasion resistance is problematic. There are many problems, and no simple method that can improve both of them is found.
For example, the provision of the release layer improves the thermal sensitivity, but significantly reduces the wear resistance, and the addition of a lubricant, resin, or the like to the release layer to improve the wear resistance causes the thermal sensitivity to decrease. Also,
Providing the sensitivity improver layer (polyester) improves the fixability to the receptor, but the ink layer remains fragile.

[0005]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems and provides a transfer image having abrasion resistance, excellent chemical resistance and heat resistance, and high image resolution and heat sensitivity.
It is an object of the present invention to provide a thermal transfer recording medium that can be easily manufactured.

[0006]

According to the present invention, first, in a thermal transfer recording medium in which a release layer containing wax as a main component and an ink layer containing a colorant are sequentially laminated on a support, the ink layer is formed on the ink layer. Provided is a thermal transfer recording medium characterized by containing a copolymer resin containing acrylonitrile or methacrylonitrile as a monomer component and a polyester resin having a Tg of 30 to 50 ° C. as a binder resin. Secondly, in the thermal transfer recording medium described in the first item, the copolymer resin is a copolymer resin composed of methyl methacrylate (l), acrylonitrile (m), and glycidyl methacrylate (n). A thermal transfer recording medium is provided. Third, in the thermal transfer recording medium described in the second, the weight composition ratio (l) :( m) :( n) of each monomer is (10-60) :( 20-6.
0): (10 to 60), a thermal transfer recording medium is provided. Fourthly, there is provided a thermal transfer recording medium according to the above first thermal transfer recording medium, wherein the polyester resin is contained in the ink layer in an amount of 20 to 50% by weight of the solid content of the ink layer. Fifth, in the thermal transfer recording medium described in the first or fourth,
The number average molecular weight of the polyester resin is 15,000 to 200
The thermal transfer recording medium according to claim 1 or 3, wherein the thermal transfer recording medium is 00.

The present invention will be described in detail below. As described above, the present invention is a thermal transfer recording medium in which a release layer containing wax as a main component and an ink layer containing a colorant are sequentially laminated on a support, and as a binder resin of the ink layer, acrylonitrile or methacrylonitrile is used as a monomer. Copolymer resin contained as a component and Tg 30 to 50 ° C in addition to this
It is characterized by containing the polyester resin of. With such a constitution, particularly with the copolymer resin, a transferred image having excellent heat resistance and chemical resistance can be obtained. However, it was difficult to improve not only these properties but also abrasion resistance and thermal sensitivity with the above-mentioned copolymer resin alone, but by adding a polyester resin having a Tg of 30 to 50 ° C. to the above-mentioned polymer resin, this problem is solved. I was able to overcome it. This Tg (glass transition point) range is important, and polyester resins having a Tg of less than 30 ° C. have problems such as a trailing phenomenon in the transferred image.
With a polyester resin having a temperature of higher than 0 ° C., the fixing to the receptor becomes insufficient and the thermal sensitivity also deteriorates. Other features of the configuration of the present invention will be described in detail in the following embodiments of the invention.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION First, acrylonitrile-methylmethacrylate, acrylonitrile-methylmethacrylate, as specific examples of an acrylic copolymer resin based on acrylonitrile or methacrylonitrile, which is the main material of the thermal transfer ink layer in the present invention,
Acrylonitrile-methyl acrylate, acrylonitrile-ethyl methacrylate, acrylonitrile-ethyl acrylate, acrylonitrile-n-butyl methacrylate, acrylonitrile-glycidyl methacrylate, acrylonitrile-glycidyl acrylate, acrylonitrile-2-hydroxyethyl methacrylate,
Examples thereof include acrylonitrile-iso-butyl methacrylate, acrylonitrile-tert-butyl methacrylate, acrylonitrile-2-hydroxypropyl methacrylate, and copolymer resins of all the above combinations in which acrylonitrile is replaced with methacrylonitrile.

Among these copolymer resins, those having particularly excellent heat resistance, chemical resistance, and abrasion resistance and which can be easily produced industrially include acrylonitrile-glycidyl methacrylate and acrylonitrile-methyl methacrylate. , Acrylonitrile-ethyl methacrylate. In addition to the above, various other vinyl monomers other than the above may be used as the comonomer component in these copolymer resins to form a terpolymer.

Among the acrylic copolymer resins described above, the terpolymer represented by the following general formula (I) is particularly preferable.

[Chemical 1] (However, in the formula, R ¹ , R ² , 1, m, and n each represent the following. R ¹ : —H or —CH ₃ , R ² : —H, —CH ₃ , —C ₂ H ₅ , _{-C 3 H 7, -C 4 H} 9 or _{-C 2 H 4 OH, l,} m, n: integer).

In the copolymer represented by the above general formula (I), the function of each comonomer is as follows. (Meth) acrylic acid ester: imparting thermoplasticity, Tg
Control of (glass transition point), imparting chemical resistance, (meth) acrylonitrile: imparting chemical resistance, imparting mechanical strength, imparting heat resistance, glycidyl (meth) acrylate: imparting adhesiveness, crosslinkability Addition and heat resistance.

The composition ratio of these comonomers is preferably in the following range. l: m: n (weight ratio) = (0 to
80): (10-70): (0-80), more preferably (10-60): (20-60): (10-60).
Is. If this composition is out of balance, sufficient mechanical strength cannot be ensured, and problems such as deterioration of chemical resistance and curling of the thermal transfer ink layer occur. The molecular weight of the acrylic copolymer resin affects the melt viscosity and influences the sensitivity during thermal transfer. Therefore, the molecular weight of these copolymer resins is G
The weight average molecular weight (hereinafter, referred to as MW) of 2000 to 1,000,000 and the number average molecular weight (hereinafter, referred to as MN) of 1,000 to 500,000, and more preferably MW of 3,000 to 500,000 and MN of 1,500 to 250,000, in terms of polystyrene converted by PC. is there. The acrylic copolymer resin can be easily prepared by a known method. For example, it can be obtained by using a radical initiator such as benzoyl peroxide or azobisisobutyronitrile as a polymerization initiator and polymerizing at a suitable temperature in a solvent. Further, these compositions can be synthesized by a conventionally known method by emulsion polymerization and can be used as an emulsion.

Next, another main material, Tg30-5
The 0 ° C. polyester resin will be described. Tg 30 ° C
When a polyester resin of less than 1 is used, the transferred image may have tailing, transfer to the protective layer during storage at high temperature, and the resistance of the transferred image may decrease. Also, Tg50 ° C
When a polyester resin having a viscosity of more than 5 is used, the fixing to the receptor is not sufficient, high energy is required for transfer, and the thermal sensitivity is poor.

An acrylic copolymer resin containing the acrylonitrile or methacrylonitrile as a monomer component and T
The two main ink layer materials of the polyester resin having a g of 30 to 50 ° C. can be selected in an appropriate amount depending on the required resistance and printing characteristics, but in consideration of adaptability to a wide range of receptors, the polyester resin is It is desirable that the solid content of the ink layer is 20 to 50% by weight based on the total weight of the solid content. If the polyester resin content in the ink layer is less than 20%, the fixing to the receptor is not sufficient and the resistance is poor, especially because it is weak against scratching due to sharp edges. On the other hand, when the polyester resin content in the ink layer exceeds 50% by weight, the transfer may not be sufficient, such as when the image is faint on a low-smooth receptor. The number average molecular weight of the polyester resin in the ink layer is preferably 15,000 to 20,000. If the number average molecular weight is less than 15,000, the resistance of the transferred image, such as abrasion resistance, decreases, and if the number average molecular weight exceeds 20,000, the transferability decreases and a clear image cannot be obtained.

These polyester resins are prepared by a conventionally known synthesis method such as polycondensation of polyhydric alcohol and polybasic acid, ring-opening polymerization of cyclic ester such as lactone, polycondensation of dibasic acid and glycol. Manufactured.

Various additives may be added to the ink layer of the present invention for the purpose of improving thermal transferability and resolution. For example, the addition of waxy fatty acid amides, various lubricants, synthetic waxes such as paraffin wax, natural waxes such as candelilla wax and carnauba wax, oils such as silicone oil and perfluoroalkyl ether, etc. And the resolution can be improved. As the lubricant in this case, in addition to phosphoric acid ester and the like, resins such as silicone resin, tetrafluoroethylene resin and fluoroalkyl ether resin, and inorganic lubricants such as silicon carbide and silica can be used.

The release layer is a layer provided adjacent to the support, and is mainly composed of wax having a melting point or a softening point of 70 to 120 ° C. This layer is a layer provided to improve the releasability between the support and the thermal transfer layer when heat is applied, and therefore it is desirable that the layer be composed of a component that melts into a low-viscosity liquid when heat is applied by a thermal head, Further, the layer components may be adjusted so that the layer is easily cut near the interface between the heated portion and the non-heated portion.

Specific examples of the wax used in the release layer include natural waxes such as beeswax, whale wax, wood wax, rice bran, carnauba wax, candelilla wax and montan wax; paraffin wax, microcrystalline wax. , Oxidized wax, ozokerite,
Synthetic waxes such as ceresin, ester wax, polyethylene wax; higher saturated fatty acids such as margaric acid, lauric acid, myristic acid, palmitic acid, stearic acid, furoic acid and behenic acid; higher such as stearyl alcohol and behenyl alcohol Saturated monohydric alcohols; higher esters such as fatty acid esters of sorbitan; higher fatty acid amides such as stearic acid amide and oleic acid amide.

It is also possible to impart elasticity to the peeling layer to improve the adhesion between the thermal transfer recording medium and the transferred material. To achieve this object, the release layer is made of isoprene rubber,
Rubbers such as butadiene rubber, ethylene propylene rubber, butyl rubber and nitrile rubber are added. other than this,
In order to prevent the release layer from falling off, it is possible to add a resin having a strong adhesive property to the layer, and as the resin added for this purpose, an ethylene-vinyl acetate copolymer, an ethylene-ethyl acrylate copolymer, etc. Is preferred.

As the support, a known film or paper may be used as it is. For example, a plastic film having relatively high heat resistance such as polyester such as polyethylene terephthalate, polycarbonate, triacetyl cellulose, nylon, polyimide, etc .; cellophane; sulfuric acid. Paper or the like is preferably used.

If desired, the thermal transfer recording medium of the present invention may be provided with a protective layer on the back surface of the support. The protective layer is a layer to protect the support from high temperature when heat is applied by the thermal head, and in addition to thermoplastic resin and thermosetting resin with high heat resistance, UV curable resin and electron beam curable resin can be used Is. Resins suitable for forming the protective layer are fluororesins, silicone resins, polyimide resins, epoxy resins, phenol resins, melamine resins and the like, and these resins may be used in a thin film form. Further, since the heat resistance of the support can be remarkably improved by installing the protective layer, it becomes possible to use a material which has been conventionally unsuitable as the support by installing the protective layer.

As the colorant used in the present invention, carbon black, organic pigment,
An inorganic pigment or various dyes can be used by selecting an appropriate one.

The release layer and the ink layer provided on the support are
It can be carried out by a known method such as a hot melt coating method, an aqueous coating method, a coating method using an organic solvent. The thermal transfer layer provided by such a coating method has an overall thickness of 0.5 to
10 μm, preferably 0.5 to 6.0 μm, the ink layer thickness is 0.5 to 6.0 μm, preferably 1.0 to 4.0 μm, and the peeling layer thickness is 0.3 to 2 in the thermal transfer layer. 0.0μ
m, preferably 0.5 to 1.5 μm.

[0024]

EXAMPLES Next, the present invention will be described more specifically with reference to examples. The parts here are based on the weight of the solid content.
A polyester film having a thickness of 4.5 μm was used as a support. Release layer 1.0 μm in order from the support side
The thickness of the ink layer was 1.0 μm, and the compositions of the following Examples and Comparative Examples were dissolved or dispersed in methyl ethyl ketone as a solvent and then applied to prepare thermal transfer recording media of the present invention and comparison.

[Example 1]   Release layer: Carnauba wax 100 parts   Ink layer: Carbon black 15 parts             Acrylonitrile-methyl methacrylate-                     Glycidyl methacrylate copolymer                               (Weight ratio 25:55:20)                       (MW = 6400, MN = 3600) 25 copies             Polyester resin                       (Tg 47 ° C., Mn = 25,000) 60 parts

[Example 2]   Release layer: Carnauba wax 100 parts   Ink layer: Carbon black 15 parts             Acrylonitrile-methyl methacrylate-                     Glycidyl methacrylate copolymer                               (Weight ratio 25:55:20)                       (MW = 6400, MN = 3600) 75 copies             Polyester resin                       (Tg 47 ° C., Mn = 25,000) 10 parts

[Embodiment 3]   Release layer: Carnauba wax 100 parts   Ink layer: Carbon black 15 parts             Acrylonitrile-methyl methacrylate-                     Glycidyl methacrylate copolymer                               (Weight ratio 25:55:20)                       (MW = 6400, MN = 3600) 35 copies             Polyester resin                       (Tg 47 ° C., Mn = 25,000) 50 parts

[Embodiment 4]   Release layer: Carnauba wax 100 parts   Ink layer: Carbon black 15 parts             Acrylonitrile-methyl methacrylate-                       Glycidyl methacrylate copolymer                               (Weight ratio 25:55:20)                       (MW = 6400, MN = 3600} 50 copies             Polyester resin                       (Tg 47 ° C., Mn = 25,000) 35 parts

[Embodiment 5]   Release layer: Carnauba wax 100 parts   Ink layer: Carbon black 15 parts             Acrylonitrile-methyl methacrylate-                       Glycidyl methacrylate copolymer                               (Weight ratio 25:55:20)                       (MW = 6400, MN = 3600) 65 copies             Polyester resin                       (Tg 47 ° C., Mn = 25,000) 20 parts

[Embodiment 6]   Release layer: Carnauba wax 100 parts   Ink layer: Carbon black 15 parts             Acrylonitrile-methyl methacrylate-                     Glycidyl methacrylate copolymer                               (Weight ratio 25:55:20)                       (MW = 6400, MN = 3600) 50 copies             Polyester resin                       (Tg 30 ° C., Mn = 25,000) 35 parts

[Embodiment 7]   Release layer: Carnauba wax 100 parts   Ink layer: Carbon black 15 parts             Acrylonitrile-methyl methacrylate-                     Glycidyl methacrylate copolymer                               (Weight ratio 25:55:20)                       (MW = 6400, MN = 3600) 50 copies             Polyester resin                       (Tg 45 ° C., Mn = 17,000) 35 parts

[Embodiment 8]   Release layer: Carnauba wax 100 parts   Ink layer: Carbon black 15 parts             Acrylonitrile-methyl methacrylate-                     Glycidyl methacrylate copolymer                               (Weight ratio 25:55:20)                       (MW = 6400, MN = 3600} 50 copies             Polyester resin                         (Tg 45 ° C., Mn = 6000) 35 parts

Comparative Example 1   Release layer: Carnauba wax 100 parts   Ink layer: Carbon black 15 parts             Epoxy resin (softening point 70 ° C) 50 parts             Polyester resin                         (Tg 45 ° C., Mn = 6000) 35 parts

Comparative Example 2   Release layer: Carnauba wax 100 parts   Ink layer: Carbon black 15 parts             Styrene-methyl methacrylate copolymer                                     (Weight ratio 25:75)                       (MW = 6700, MN = 3800) 50 copies                     Polyester resin                         (Tg 45 ° C., Mn = 6000) 35 parts

Comparative Example 3   Release layer: Carnauba wax 100 parts   Ink layer: Carbon black 15 parts             Acrylonitrile-methyl methacrylate                     -Glycidyl methacrylate copolymer                               (Weight ratio 25:55:20)                       (MW = 6400, MN = 3600) 50 copies             Polyester resin                         (Tg 67 ° C., Mn = 17,000) 35 parts

[Comparative Example 4]   Release layer: Carnauba wax 100 parts   Ink layer: Carbon black 15 parts             Acrylonitrile-methyl methacrylate                     -Glycidyl methacrylate copolymer                               (Weight ratio 25:55:20)                       (MW = 6400, MN = 3600) 50 copies             Polyester resin                         (Tg 25 ° C., Mn = 16000) 35 parts

[Comparative Example 5]   Ink layer: Carbon black 15 parts             Acrylonitrile-methyl methacrylate                     -Glycidyl methacrylate copolymer                               (Weight ratio 25:55:20)                       (MW = 6400, MN = 3600) 75 copies   Over layer: Polyester resin                         (Tg 47 ° C., Mn = 25000) 35 parts

The thermal transfer recording media obtained in Examples 1 to 8 and Comparative Examples 1 to 5 were evaluated by the following method. Although the evaluation test was performed on the transferred image,
As the image-receiving paper (transferred paper), label-shaped white PET or synthetic paper having a back surface paste-processed was used, and what was printed under the following conditions was used for the test. <Printing conditions> Thermal head: Partial glaze thin film head type platen pressure: 150 g / cm Peeling angle of thermal transfer recording medium: 3 for transfer paper
0 degree peeling torque value: 200 g Applied energy: 10 to 30 mJ / mm ² Printing speed: 10 cm / sec

The various characteristics evaluated are as follows. 1. Image formation status White PET (Bekk smoothness 25000 seconds) and synthetic paper (B
Ekk smoothness 2000 seconds) was used as the transfer paper, and the transfer image under the applied energy of 20 mJ / mm ² was evaluated according to the following criteria. ◎ There are no voids or scratches, and the edges of the image are sharp. * Almost no voids or blurring. △ There are some voids and scratches. × No transfer at all. 2. Abrasion resistance of about 1 t / cm ² Stainless steel edge objective 30 cm /
A 50 round trip image was love tested at a speed of sec.
(Transfer paper: white PET) ◎ The image is not destroyed at all. 〇 Images are hardly destroyed. △ The image is slightly destroyed. × The image is completely destroyed. 3. Place a transfer image sample on a glass plate in a tank set to heat resistance of 100 ° C or 150 ° C, perform a reciprocating rub test 20 times at a speed of 30 cm / sec, and transfer paper (white PET)
The results of visually observing the surface are shown in Table 1. The symbols in the table have the following meanings. ◎ As a result of the love test, there is no change from before the test. 〇 As a result of the love test, the image can be read, but it can be scratched. △ As a result of the love test, the image becomes unreadable. × As a result of the love test, the transfer paper surface is exposed. 4. Chemical resistance After 0.5 cc of each chemical was applied to the transferred image with a cotton swab, this sample was tested under a load of 10 g / mm ² for 3 times.
20 round-trip love tests were performed at a speed of 0 cm / sec.
Table 1 shows the results of observing the surface of the transferred paper (white PET).
The symbols in the table have the following meanings. ◎ As a result of the love test, there is no change from before the test. 〇 As a result of the love test, the image can be read, but it can be scratched. △ As a result of the love test, the image becomes unreadable. × As a result of the love test, the transfer paper surface is exposed.

[0040]

[Table 1]

[0041]

As described above, according to the thermal transfer recording medium of the present invention, the ink is used in the thermal transfer recording medium in which the release layer containing wax as the main component and the ink layer containing the colorant are sequentially laminated on the support. By using an acrylic copolymer resin containing acrylonitrile or methacrylonitrile as a monomer component and a polyester resin having a Tg of 30 to 50 ° C. as a binder resin for the layer, transfer excellent in abrasion resistance, heat resistance, and chemical resistance is achieved. It is possible to obtain an image and also to obtain excellent thermal transferability such as thermal sensitivity.

─────────────────────────────────────────────────── ─── Continuation of front page (72) Masayuki Wakabayashi Masayuki Wakabayashi 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (56) References JP-A-4-80090 (JP, A) JP-A 63-295292 (JP, A) JP-A-3-197092 (JP, A) JP-A-2-258295 (JP, A) JP-A-3-32886 (JP, A) JP-A-9-30125 (JP, A) A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B41M 5/38-5/40

Claims (5)

(57) [Claims] 1. A thermal transfer recording medium in which a release layer containing wax as a main component and an ink layer containing a colorant are sequentially laminated on a support, wherein acrylonitrile or methacrylonitrile is used as a binder resin in the ink layer. A thermal transfer recording medium characterized by containing a copolymer resin as described above and a polyester resin having a Tg of 30 to 50 ° C. 2. The thermal transfer recording medium according to claim 1, wherein the copolymer resin is a copolymer resin composed of methyl methacrylate (l), acrylonitrile (m), and glycidyl methacrylate (n). 3. A weight composition ratio (l) of each monomer:
(M): (n) is (10-60): (20-60):
The thermal transfer recording medium according to claim 2, wherein the thermal transfer recording medium is (10 to 60). 4. The thermal transfer recording medium according to claim 1, wherein the polyester resin is contained in the ink layer in an amount of 20 to 50% by weight of the solid content of the ink layer. 5. The thermal transfer recording medium according to claim 1, wherein the polyester resin has a number average molecular weight of 15,000 to 20,000.