JP3032605B2 - 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 particularly to a thermal transfer recording medium for bar codes.

[0002]

2. Description of the Related Art In recent years, thermal transfer recording systems using thermal heads have been reported to be noise-free, to make devices relatively inexpensive and compact, to be easy to maintain, and to have stable printed images. It has come to be used frequently due to its advantages. Representative examples of the thermal transfer recording medium employed in such a thermal transfer recording system include: (1) a heat-meltable ink layer comprising a colorant and a binder provided directly on a support; One in which a hot-melt ink layer made of a binder is provided on a support via a release layer containing wax as a main component, and the like.

The type (1) has good thermal sensitivity,
In order to facilitate the transfer of the ink to the receiving paper or to help transfer the ink to a relatively rough receiving paper having a Beck smoothness of 400 to 500 seconds, a method in which the heat-fusible ink is finely divided has conventionally been employed. I was

For example, a) forming a plurality of hot-melt ink layers containing organic or inorganic fine particles on a base material,
The size is made smaller in the order of the middle, the surface, and the base material (JP-A-60-166484).

B) A thermal transfer sheet in which an ink layer in which a plurality of types of heat-meltable ink fine particles having different melting points are mixed is formed on a base material (JP-A-61-22992).

C) Ink comprising a vinyl acetate acrylic copolymer, an acrylic ester resin emulsion, a wax emulsion and a colorant (JP-A-62-1241980,
Id.-218461).

D) It is formed of an aqueous ink dispersed as an O / W emulsion using a paraffin wax containing a colorant and a surfactant (JP-A-62-2228).
92).

However, as the relatively rough receiving paper, there are many papers coated with a resin on a plain paper and those obtained by applying a super calender, and have the disadvantage that they are expensive. When printing was performed on a receiving paper having a Beck smoothness of 400 seconds or less and a low surface smoothness, an image was missing (void) due to insufficient cutting of the ink layer.

In addition, these thermal transfer recording media have a problem in that since the content of carbon black is large, the friction resistance of the image is low and smear is generated.

The thermal transfer recording medium of the type (2) includes, for example, e) two or more types of domains formed of a heat-fusible material on a first ink layer containing heat-fusible resin fine particles. (Japanese Patent Application Laid-Open No. 62-215)
86).

F) A thermal transfer recording medium wherein the surface roughness of the uppermost layer of the ink layer on the support is 50 seconds or less in Beck smoothness (Japanese Patent Laid-Open No. 60-253589).

G) The surface of the ink layer is rough and has an amplitude of 1 to 10 μm at a cycle of 10 to 30 cycles (JP-A-61-252194).

However, in the above e), since the second ink layer is composed of the non-particulate phase and the fine particles, the shear strength of the non-particulate portion is too high, and the cut of the ink layer is deteriorated. The thermal sensitivity is low, and there is a drawback that when a ladder bar code is printed on highly smooth paper such as mirror-coated paper, a dropping phenomenon (a phenomenon in which a non-applied heat portion is transferred to the receiving paper side) occurs.

On the other hand, when the surface of the ink layer is roughened as in the above f) and g), the area in contact with the receiving paper is reduced, and the ink layer is not in contact with the receiving paper even when softened. Due to the occurrence of parts, white voids occur in the image.

Conventionally, in order to prevent this, the melt viscosity of the ink layer has been increased to bridge between the convex portions of the receiving paper. The disadvantage is that the sensitivity is low.

[0016]

SUMMARY OF THE INVENTION The present invention solves the above problems, has excellent thermal sensitivity, enables high-speed printing, and obtains a good image even on a receiving paper having low surface smoothness. An object of the present invention is to obtain a thermal transfer recording medium which is excellent in friction resistance and clarity of ladder bar code printing on highly smooth paper.

[0017]

The structure of the present invention for solving the above problems is a thermal transfer recording medium as described in the claims.

The structure of the present invention will be described in detail. In a thermal transfer recording medium having at least a first ink layer and a second ink layer each containing a heat-fusible material on a support, the first ink layer, the second ink layer The ink layer is composed of a layer containing heat-fusible particles as the heat-fusible material.
The heat fusible particles of the ink layer have an average particle size of 0.15 to 0.5.
35 μm particle group A and average particle size of 2.0 to 20.0 μm
Particles B having a particle size of 5 to 20 μm per 10 ⁴ μm ² area of the surface of the second ink layer by setting the ratio of the particle group A to the particle group B to 95: 5 to 80:20. There are 5 to 50 projections.

Hereinafter, the present invention will be described with reference to the accompanying drawings.
This will be described in more detail.

FIG. 1 shows a thermal transfer recording medium 1 according to the present invention.
FIG. In this drawing, 2 is a film-like support, 3 is a release layer, 4 is an ink layer, and 5 is a heat-resistant protective layer. 6 is heat-fusible particles, 71 is particle group A
, And 72 represent the heat-fusible particles belonging to the particle group B.

Examples of the support 2 include a plastic film having relatively high heat resistance, such as polyester, polycarbonate, triacetyl cellulose, nylon, and polyimide, glassine paper, condenser paper, and metal foil. The length is about 2 to 15 μm, preferably 3 to 1.
The range is 0 μm.

The surface of the support 2 which is in contact with the thermal head (the surface opposite to the side where the ink layer 4 is present) may be provided, if necessary, with a silicone resin, a fluororesin, a polyimide resin or an epoxy resin. By providing a heat-resistant protective layer 5 made of phenol resin, melamine resin, nitrocellulose, or the like, the heat resistance of the support can be improved, or a support material that could not be used conventionally can be used. . The release layer 3 is mainly 40 to 10
Paraffin wax having a melting point of 0 ° C., microcrystalline wax, oxidized paraffin wax, candelilla wax, carnauba wax, montan wax, ceresin wax, polyethylene wax, polyethylene oxide wax, caster wax, hardened tallow oil,
Wax materials such as lanolin, wood wax, sorbitan stearate, sorbitan palmitate, stearyl alcohol, polyamide wax, oleylamide, stearylamide, hydroxystearic acid, synthetic ester wax, and synthetic alloy wax are constituted. Particle formation can be easily achieved by applying a solvent-dispersed coating liquid and drying. The average particle size of the heat-fusible particles 6 in the release layer is 0.20 to 5.0 μm, preferably 0.60 to 2.0 μm. In order to obtain an average particle diameter of 0.60 to 3.0 μm, it can be formed by applying an aqueous emulsion type or aqueous dispersion type coating solution and drying.

If the average particle size is smaller than 0.20 μm, problems such as voids in high-speed printing, voids in low-smooth paper, or falling off of the ink layer occur. Further, the average particle size is 5.
If it is larger than 0 μm, the thermal sensitivity is reduced and large characters are missing.

The average particle size mentioned here is determined from the particle morphology observed from the cross section of the thermal transfer recording medium. To observe the cross section, a sample is formed by a conventional method, and a transmission electron microscope (T
EM). The particle size in the TEM observation and the particle size of the coating liquid forming the ink layer substantially match. Therefore, it can be appropriately set according to the average particle size in the state of the coating liquid. The particle size of the coating liquid can be easily measured by LA-700 manufactured by HORIBA, Ltd. using a laser diffusion method.

If necessary, the release layer 3 may be made of an elastomer such as rubber, polyvinyl butyral, a vinyl chloride-vinyl acetate copolymer resin, nitrocellulose, an epoxy resin, an ethylene-vinyl acetate copolymer resin, or an ethylene-α-olefin copolymer. One or more resins such as a polymer resin, an α-olefin-maleic anhydride copolymer resin, an ethylene-methacrylic acid copolymer resin, ethyl cellulose, and polyvinyl alcohol may be mixed in an appropriate amount.

The thickness of the release layer 3 is 0.5 to 5.0 μm, preferably 0.8 to 2.0 μm. When the thickness is less than 0.5 μm, the function as a release layer is reduced, and the transferability to paper having relatively low smoothness is deteriorated. On the other hand, when the thickness is more than 5.0 μm, the adhesive strength is reduced and the ink layer peels off. .

The ink layer 4 is a conventionally known heat-fusible layer, which contains a coloring agent and a heat-fusible material as main components, and is made of a resin as required.

The colorant is appropriately selected from conventionally known dyes and pigments. Examples of the heat-fusible material include paraffin wax, microcrystalline wax,
Paraffin wax, candelilla wax, carnauba wax, montan wax, ceresin wax, polyethylene wax, polyethylene oxide wax, caster wax, tallow hardened oil, lanolin, wood wax, sorbitan stearate, sorbitan palmitate, stearyl alcohol, polyamide wax , Oleylamide, stearylamide, hydroxystearic acid, synthetic ester wax, synthetic alloy wax, and the like. In order to reduce the penetration at 25 ° C. to 2 or less, for example, carnauba wax (penetration of 1) It is advisable to mainly mix candelilla wax (degree of penetration 1), lanolin derivative synthetic wax (degree of penetration 2) and the like. In particular, when carnauba wax is used, the friction resistance of the image surface becomes excellent.

If the penetrability of the heat-fusible material of the main component at 25 ° C. is larger than 2, the transfer surface after printing becomes a soft material, and the image is disturbed when rubbed with a pen scanner or the like. There is a problem that reading cannot be performed again.

As the resins, polyamide-based, polyester-based, polyurethane-based, vinyl chloride-based, cellulose-based,
In addition to petroleum-based, styrene-based, butyral-based, and phenol-based resins, examples include ethylene-vinyl acetate copolymers and ethylene-acrylic resins.

The ratio of each material constituting the ink layer 4 is as follows: colorant / wax / resin = 5/50/30
~ 90/5 to 50 is suitable.

As shown in FIG. 1, the ink layer 4 is composed of heat-fusible particles as a heat-fusible material. Particles of the above-mentioned material can be achieved by using the same method as that for the release layer. .

The heat-fusible particles in the ink layer 4 are composed of a particle group A71 having an average particle diameter of 0.15 to 0.35 μm and a particle group B72 having an average particle diameter of 2.0 to 20.0 μm. . The heat fusible particles of the particle groups A and B are easily melted even with a small amount of heat and easily transferred to the receiving paper as a result of the increase in the specific surface area due to the granulation of the heat fusible material.

The function of the particle group B is that the particle diameter is larger than the particle diameter of the particle group A, so that it is somewhat difficult to melt, so that the boundary between the non-heated part and the heated part is clarified. It plays a role like a filler. With this function, the ladder bar code can be printed clearly.

The ratio of the particle group A to the particle group B is 95: 5
It is preferable to set it to 80:20. 95% of particle group A
When the number of particles increases, the function as a filler of the particle group B decreases, and when the ladder bar code is printed, co-fall occurs. On the other hand, when the amount of the particle group B exceeds 20%, the thermal sensitivity decreases and the number of voids increases.

When the average particle diameter of the particle group A is smaller than 0.15 μm, the layer becomes a layer close to a continuous layer, and the interparticle force is increased. On the other hand, if the average particle diameter of the particle group A is larger than 0.35 μm, the properties are close to those of the particle group B, and the thermal sensitivity is lowered. On the other hand, when the average particle diameter of the particle group B is smaller than 2.0 μm, the properties of the particle group A become closer to
Co-falling occurs in ladder barcode printing. or,
When the average particle diameter of the particle group B is larger than 20.0 μm, the thermal sensitivity is reduced and the number of voids is increased.

The thickness of the ink layer 4 is 0.5 to 5.0 μm, preferably 1.0 to 2.5 μm.

When the thickness is less than 0.5 μm, insufficient density or lack of printing on paper having a relatively low smoothness occurs. On the other hand, when the thickness exceeds 5.0 μm, the ink layer drops off.

On the surface of the ink layer 4 formed as described above, relatively large particle protrusions of 5.0 to 20.0 μm can be easily observed by a scanning electron microscope (SEM).
5 to 50 of these particle protrusions can be confirmed per 10 ⁴ μm ² area. If the number of protrusions is less than 5, the layer becomes a layer close to a continuous layer as a so-called layer, and the interparticle force is increased. It is easy to cause falling off at the same time.
On the other hand, when the number is more than 50, the thermal sensitivity is lowered and voids are generated.

Here, the size of the particle protrusion is a value obtained by measuring the largest diameter r of the particle as shown in FIG.

Next, the present invention will be specifically described with reference to Examples and Comparative Examples. The amounts of the components described in Examples and Comparative Examples are based on weight.

[0042]

EXAMPLE The following first ink layer aqueous emulsion (I) was applied on a 4.5 μm polyethylene terephthalate (PET) film so as to have a dry film thickness of 1.5 μm to form a first ink layer (comparative). Example 1 is not formed).

Next, a second ink layer was formed by applying a water-based emulsion (II) for a second ink layer on the first ink layer so as to have a dry film thickness of 1.5 μm, thereby producing a thermal transfer recording medium. .

The conditions are shown in Tables 1 and 2 below.

[0045]

[Table 1]

[0046]

[Table 2] Recycled paper {paper source (manufactured by Ricoh Company)} having a Beck smoothness of about 50 seconds and about 400
0 second surface-treated mirror coated paper (Kanzaki Paper)
, A barcode thermal transfer printer (Atech: S
Using WEDOT196 and TEC Co .; B-600), printing was performed by applying standard energy at 20 ° C. and 60% RH. The results were as shown in Tables 3 and 4.

[0047]

[Table 3]

[0048]

[Table 4] Transferability: The evaluation was made based on whether the barcode portion printed on the recycled paper by SWEDOT196 was clearly printed.

…: The bar code portion is clearly printed and transferred.

X: There are bar codes which are not clearly transferred and the bar code portion is unclearly printed.

Bar code reading rate: SWEDOT196
Laser check LC-2 on bar code part printed with
811 (Symbol Technologies, I
nc. (Manufactured by the company), the laser was scanned 100 times at random, and the number of readings was shown as a percentage.

That is, a reading rate of 100% indicates that the laser was scanned 100 times and the reading was performed 100 times, indicating that the bar code was clear.

Abrasion resistance (cardboard test): SWED
A 4 cm × 7 cm cardboard board is placed on the bar code portion printed on the mirror-coated paper in OT196, and the same place is rubbed 50 times with a love tester while applying a load of 1 kgf at 25 ° C., and then the bar code reading rate is obtained. Was measured.

Co-fall: The reading ratio of the ladder bar code printed on the mirror-coated paper by TEC B-600 was calculated by laser check LC-2811.

[0055]

As described above, the present invention is excellent in thermal sensitivity, enables high-speed printing, obtains a good image even on a receiving paper having a low surface smoothness, and has good rub resistance of the image and smooth paper. This is a thermal transfer recording medium that also has excellent ladder barcode printing clarity.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing a structure of a thermal transfer recording medium of the present invention.

FIG. 2 is an explanatory diagram of the size of a particle projection.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 thermal transfer recording medium 2 film support 3 release layer 4 ink layer 5 heat-resistant protective layer 6 heat-meltable particles 71 particle group A 72 particle group B

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Nobuyuki Maeda 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Kumi Surizaki 1-3-6 Nakamagome, Ota-ku, Tokyo (56) References JP-A-62-169686 (JP, A) JP-A-63-183882 (JP, A) JP-A-63-89383 (JP, A) JP-A 64-24791 (JP, A) JP-A-61-125894 (JP, A) JP-A-62-21582 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41M 5/38-5 / 40

Claims (4)

(57) [Claims] 1. A thermal transfer recording medium having at least a first and a second ink layer each containing a heat-fusible material on a heat-resistant support in order, wherein the heat-fusible material is particles. Thermal transfer recording wherein the heat-fusible particles of the two ink layers comprise a particle group A having an average particle diameter of 0.15 to 0.35 μm and a particle group B having an average particle diameter of 2.0 to 20.0 μm. Medium. 2. The thermal transfer recording medium according to claim 1, wherein the ratio of the particle group A to the particle group B in the second ink layer is 95: 5 to 80:20. 3. The thermal transfer recording medium according to claim 1, wherein the material of the heat-fusible particles of the second ink layer is mainly carnauba wax. 4. The method according to claim 1, wherein there are 5 to 50 particle projections having a size of 5 to 20 μm per 10 ⁴ μm ² of the surface of the second ink layer. Thermal transfer recording medium.