JP2019166747A - Thermosensitive recording medium - Google Patents

Abstract

To provide a thermosensitive recording medium that facilitates reading of bar code or the like without background printing.SOLUTION: A thermosensitive recording medium 1 has a thermosensitive recording layer 3 and a top coat layer 5 laminated on a base material 2. The thermosensitive recording layer 3 contains hollow particles 6 and has an opacity of 20% or more as measured in accordance with JISP8149.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a thermal recording material, and more particularly, to a thermal recording material excellent in reading characteristics such as a barcode.

  The thermal recording medium is colored by a chemical reaction when heated by a thermal head or the like, and a recorded image is obtained. It is not only used as a recording medium for facsimiles, automatic ticket vending machines, and scientific measuring instruments, but also for POS systems such as retail stores. Is used in a wide range of applications as a heat-sensitive recording label (see, for example, Patent Document 1).

  Moreover, since it is possible to print while being a packaging material in which a packaged product can be seen, a highly transparent thermal recording material is used for the packaging material and the like. By using such a highly transparent thermal recording material, a separate label or the like is not necessary, and convenience is improved (for example, see Patent Document 2).

Japanese Patent Laid-Open No. 2002-362027 International Publication No. 2015/012386

  Here, in the case of using a heat-sensitive recording material having high transparency, the base material may be colored by printing or the like in order to improve the reading characteristic of a barcode or the like. In particular, since barcodes, QR codes (registered trademark), and the like may be difficult to read by a reader when the background is transparent, the background is often printed in white.

  However, the provision of a new printing process only for such background printing has a problem that the manufacturing process of the thermal recording member becomes complicated and the cost increases.

  Moreover, when the printing on the back surface side which contacts with a packaged article becomes a problem on food hygiene, printing itself was difficult.

  Therefore, the present invention has been made in view of the above-described problems, and an object of the present invention is to provide a thermal recording material excellent in reading characteristics such as a barcode without performing background printing.

  In order to achieve the above object, in the first invention, on the premise of a thermosensitive recording material in which at least a thermosensitive recording layer and a topcoat layer are laminated on a substrate, the thermosensitive recording layer contains hollow particles, and JIS The opacity measured according to P8149 is 20% or more.

  According to the above configuration, it is possible to provide a thermal recording material excellent in reading characteristics such as a barcode without performing background printing.

  In the second invention, in the first invention, the haze value measured in accordance with JIS-K7136: 2000 is set to 70% or more.

  According to the above configuration, it is possible to reliably prevent deterioration in reading characteristics such as a barcode.

  Moreover, in 3rd invention, in 1st or 2nd invention, the hollow particle is comprised with the acrylic resin.

  According to the above configuration, by providing opacity by the light scattering effect, the barcode can be read and the sensitivity on the low energy side can be improved. In addition, since it is melted by heat from the thermal head, it is possible to prevent a decrease in print quality.

  According to a fourth invention, in any one of the first to third inventions, an intermediate layer is provided between the heat-sensitive recording layer and the topcoat layer.

  According to the said structure, the thermal recording body which has the barrier property with respect to water or oil can be provided.

  According to the present invention, it is possible to provide a thermal recording material excellent in reading characteristics such as a barcode without performing background printing.

FIG. 1 is a cross-sectional view for explaining the heat-sensitive recording material of this embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the following embodiments.

  FIG. 1 is a cross-sectional view for explaining the heat-sensitive recording material of this embodiment.

  As shown in FIG. 1, the thermal recording body 1 of the present embodiment has a structure in which a thermal recording layer 3, an intermediate layer 4, and a topcoat layer 5 that are colored by heating are laminated on a sheet-like substrate 2. It has become.

  As the base material 2, a transparent synthetic resin film, for example, a polypropylene film, a polyethylene terephthalate film, a polystyrene film, a polycarbonate film, etc. can be used. Although the thickness of the base material 2 is not specifically limited, For example, about 10 micrometers-about 100 micrometers are excellent in coating property and transparency, and preferable.

  The material for forming the heat-sensitive recording layer 3 includes a color former that develops color when heated, a developer, a binder, and a lubricant.

  In order to improve the transparency of the thermosensitive recording layer 3, it is preferable to use materials having a small particle diameter. By using a material having a small particle diameter in this way, irregular reflection of particles can be suppressed.

  Specifically, examples of the leuco dye that is a color former include 2-aniline-3methyl-6- (N-methyl-P-toluidino) fluorane, and the particle size thereof is 0.8. It is preferable that it is 1-1. Here, the particle diameter means a 50% average particle diameter measured by a microtrack laser analysis / scattering particle size analyzer.

  Examples of the developer include 3,3′-diallyl-4,4′-dihydroxydiphenylsulfone, and the particle diameter thereof is preferably 0.1 to 1.0 μm. .

  Examples of the binder include a styrene-butadiene copolymer.

  Examples of the lubricant include polyethylene, zinc stearate, paraffin and the like, and the particle diameter thereof is preferably 0.5 μm or less.

  In order to improve transparency, it is particularly effective to contain paraffin, and this paraffin is less than the color development temperature of the thermal recording layer 3, preferably less than 80 ° C, more preferably less than 50 ° C. A melting point paraffin is preferred.

The particle diameter of the low melting point paraffin is preferably 0.5 μm or less as described above. The content of this paraffin is preferably 0.1 to 1.0 g / m ² by dry weight.

  By including the low melting point paraffin in this way, the surface of the particles constituting the thermosensitive recording layer 3 is melted when the coating liquid for forming the thermosensitive recording layer is applied onto the substrate 2 and dried. It is possible to improve the transparency by suppressing irregular reflection on the particle surface.

  The intermediate layer 4 having a barrier property against water and oil is mainly formed of a resin. Examples of the resin of the intermediate layer 4 include an acrylic resin emulsion, a water-soluble resin such as a polyvinyl alcohol (PVA) resin, and an SBR resin.

  In order to improve transparency, the above resin is water-soluble resin such as polyvinyl alcohol (PVA) resin, which is a resin having a hydroxy group as a hydrophilic structural unit, or hydrophobic core particles. A core-shell structure resin coated with a conductive shell polymer, for example, a core-shell type acrylic resin is preferable.

  Water-soluble polyvinyl alcohol (PVA) and core-shell type acrylic resins have good film formability, and when the coating liquid for forming the intermediate layer is applied onto the thermosensitive recording layer 3 and dried, the water-soluble part Since the resin having saturates the heat-sensitive recording layer 3 to form the smooth intermediate layer 4, irregular reflection at the heat-sensitive recording layer 3 is suppressed and transparency is improved.

  As the core-shell type resin, for example, a core-shell type acrylic resin that is commercially available under the name Barrier Star (Mitsui Chemicals) can be used.

  The top coat layer 5 improves the matching of the thermal recording body 1 to the thermal head so that the color of the thermal recording layer 3 is smoothly formed. This top coat layer 5 is contained in the binder. In addition, a filler, a lubricant, a crosslinking agent and the like are added.

  As resin which is a binder, an acrylic resin etc. are mentioned, for example. Examples of the lubricant include polyethylene and zinc stearate. Examples of the crosslinking agent include zirconium carbonate.

  Examples of the filler include colloidal silica, calcium carbonate, zirconium carbonate, polymethyl methacrylate (PMMA), and polystyrene (PS). In addition, it is preferable that the particle diameter of these fillers is 1.0 micrometer or less. In order to improve transparency, colloidal silica having a small particle diameter is preferable as the filler.

  Here, in the heat-sensitive recording material 1 of the present embodiment, as shown in FIG. 1, the heat-sensitive recording layer 3 contains hollow particles 6 in order to reduce transparency and improve reading characteristics such as barcodes. It is characterized by

  As the hollow particles, publicly known known hollow particles may be used, and examples of the material of the hollow particles include acrylic resins (for example, polyacrylic acid ester, polyacrylonitrile, etc.), polystyrene, polychlorinated chloride. Thermoplastic resins such as vinyl, polyvinylidene chloride, polyvinyl acetate, polybutadiene, and copolymers thereof can be used.

  Among these, it is preferable to use an acrylic resin as a material for the hollow particles. By using an acrylic resin, it is possible to read a barcode and to improve sensitivity on the low energy side by imparting opacity by a light scattering effect. In addition, since it is melted by heat from the thermal head, it is possible to prevent a decrease in print quality.

  Then, when the coating liquid for forming the heat-sensitive recording layer is applied onto the substrate 2, a part of the coating liquid for forming the heat-sensitive recording layer containing such hollow particles (that is, a bar) The portion to be printed such as a code) is applied only to 2a to form the thermosensitive recording layer 3, and the other portion (that is, the portion requiring transparency) 2b on the substrate is made of, for example, the hollow particles Instead, a coated liquid for forming a heat-sensitive recording layer containing a general filler such as kaolin and calcium carbonate is applied to form another heat-sensitive recording layer 7 having excellent transparency, thereby confirming the package. It is possible to manufacture the heat-sensitive recording material 1 having excellent reading characteristics such as a barcode without impairing the transparency that can be achieved.

  In addition, since the hollow particles themselves are dissolved and become transparent when heated, the hollow particles do not shield the black color that has been thermally developed. Accordingly, the thermal recording body 1 having excellent reading characteristics such as a barcode is manufactured without causing the disadvantage that the printing density is lowered (that is, the black color of the portion to be blackened is reduced to become gray). It becomes possible to do.

  In the thermal recording material 1 of the present embodiment, as described in the examples described later, in order to improve the barcode reading characteristics, the opacity measured in accordance with JIS P8149 is 20% or more. It is necessary to be.

  In addition, the haze value of the heat-sensitive recording material 1 is preferably 70% or more. This is because when the haze value is less than 70%, the ratio of the diffused light to the total transmitted light is small, and the transparency of the thermal recording body 1 becomes too high, so that the inconvenience that the reading characteristics such as the barcode are deteriorated occurs. Because there is.

  In addition, the “haze value” here refers to a haze value measured according to JIS-K7136: 2000.

  Hereinafter, the present invention will be described based on examples. In addition, this invention is not limited to these Examples, These Examples can be changed and changed based on the meaning of this invention, and they are not excluded from the scope of the invention. Absent.

Example 1
(Preparation of thermal recording material)
<Thermal recording layer>
A coating liquid for forming a thermosensitive recording layer shown in Table 1 was prepared, and the coating amount for forming the thermosensitive recording layer was prepared on a 40 μm-thick OPP (biaxially oriented polypropylene) film as a base material. After applying to a dry weight of 4.0 g / m ² , drying was performed to form a heat-sensitive recording layer having a thickness of 4.0 μm on the substrate. In Table 1, the numerical value of each compounding agent shows the weight ratio at the time of drying.

  As the compounding material, the leuco dye uses 2-aniline-3methyl-6- (N-methyl-P-toluidino) fluorane having a particle size of 0.5 μm, and the developer has a particle size of 0. 4 μm of 3,3′-diallyl-4,4′-dihydroxydiphenylsulfone was used, and the binder (binder) was SBR having a glass transition temperature Tg of “−3 ° C.”. The lubricant is polyethylene (PE) having a melting point of 100 ° C. and a particle size of 0.6 μm, paraffin having a melting point of 66 ° C. and a particle size of 0.3 μm, and paraffin having a melting point of 46 ° C. and a particle size of 0.2 μm. It was used. Moreover, the particle | grains (The product made from Dow Chemical, brand name: ULTRA E, a particle size: 0.4 micrometer, hollow rate: 45%) which consist of acrylic resins were used for the hollow particle.

<Intermediate layer>
A coating solution for forming an intermediate layer using a core-shell type acrylic resin is prepared, and the coating amount of the prepared coating solution for forming an intermediate layer is 2.0 g / m ² by dry weight on the above-mentioned heat-sensitive recording layer. After the coating as described above, drying was performed to form an intermediate layer having a thickness of 2.0 μm on the thermosensitive recording layer.

<Topcoat layer>
The top coat layer forming coating solution shown in Table 1 was prepared, and the prepared top coat layer forming coating solution was applied on the above-mentioned intermediate layer so that the coating amount was 1.5 g / m ^{2 in} dry weight. After the coating, drying was performed to form a top coat layer having a thickness of 1.5 μm on the intermediate layer.

  In addition, an acrylic resin was used as a binder (binder), and polyethylene (PE) and zinc stearate (St-Zn) were used as a lubricant. Further, colloidal silica having a particle diameter of several nm and colloidal silica having a particle diameter of several tens of nm were used as fillers, and zirconium carbonate was used as a crosslinking agent.

  The heat-sensitive recording material of this example was produced by the above method.

(Opacity measurement)
Using a reflectometer (trade name: TC-6DS / A type, manufactured by Tokyo Denshoku Co., Ltd.), the opacity of the obtained thermal recording material was measured in accordance with JIS P8149. The results are shown in Table 2.

(Measurement of haze value)
Using a haze meter (trade name: NDH7000, manufactured by Nippon Denshoku Co., Ltd.), the haze value of the obtained thermal recording material was measured in accordance with JIS-K7136: 2000. The results are shown in Table 2.

(Registration exam)
A bar code was printed on the surface of the produced thermal recording material on the substrate side, and placed on a concealment rate test paper (black background) standardized in JIS K5600.

Next, using a register (manufactured by Toshiba Tec Corporation, trade name: MA-1955), the barcode reading was attempted 20 times, and the rate at which the barcode could be read (that is, the number of barcodes actually read / 20 Times x 100) [%] was calculated. The results are shown in Table 2.
(Dynamic sensitivity evaluation)
A commercially available thermal printer (Ishida Co., Ltd .; BP4300) was used for the produced thermal recording paper, with a printing speed of 50 mm / sec, an applied voltage of 24.0 V, a head resistance value of 1533Ω, and a pulse width of 0.157 to 0.354 ms. And printing is performed under the conditions of printing energy of 0.077 mJ / dot, 0.104 mJ / dot, and 0.171 mJ / dot, and the printing density under each printing energy condition is measured by a spectrophotometer (manufactured by X-rite, (Trade name: eXact). The results are shown in Table 2.

(Example 2)
As hollow particles, instead of particles made of acrylic resin (Dow Chemical, trade name: ULTRA E, particle size: 0.4 μm, hollow rate: 45%), hollow particles made of acrylic resin (made by Dow Chemical, trade name) : HP-1055, particle size: 1 μm, hollow ratio: 55%) was used in the same manner as in Example 1 to prepare a thermal recording material.

  Next, in the same manner as in Example 1 above, opacity measurement, haze value measurement, registration test, and dynamic sensitivity evaluation were performed. The results are shown in Table 2.

Example 3
As hollow particles, instead of particles made of acrylic resin (Dow Chemical, trade name: ULTRA E, particle size: 0.4 μm, hollow rate: 45%), hollow particles made of acrylic resin (made by Dow Chemical, trade name) : HP-1055, particle size: 1 μm, hollow ratio: 55%), and the thermosensitive recording material was prepared in the same manner as in Example 1 except that the blending amount was changed to 20% by weight.

  Next, in the same manner as in Example 1 above, opacity measurement, haze value measurement, registration test, and dynamic sensitivity evaluation were performed. The results are shown in Table 2.

Example 4
As hollow particles, instead of particles made of acrylic resin (Dow Chemical, trade name: ULTRA E, particle size: 0.4 μm, hollow rate: 45%), hollow particles made of acrylic resin (made by Dow Chemical, trade name) : HP-1055, particle size: 1 μm, hollow ratio: 55%, blending amount: 5% by weight, and further kaolin as a filler (trade name: HYDRAGLOSS90, particle size: 0.40 μm, blending) A heat-sensitive recording material was prepared in the same manner as in Example 1 except that 5% by weight was used.

  Next, in the same manner as in Example 1 above, opacity measurement, haze value measurement, registration test, and dynamic sensitivity evaluation were performed. The results are shown in Table 2.

(Example 5)
As hollow particles, instead of particles made of acrylic resin (Dow Chemical, trade name: ULTRA E, particle size: 0.4 μm, hollow rate: 45%), hollow particles made of acrylic resin (made by Dow Chemical, trade name) : HP-1055, particle size: 1 μm, hollow ratio: 55%, blending amount: 7.5% by weight), and further kaolin (made by Kamin, trade name: HYDRAGLOSS 90, particle size: 0.40 μm) as a filler. , Compounding amount: 2.5% by weight) was used in the same manner as in Example 1 to produce a thermosensitive recording material.

  Next, in the same manner as in Example 1 above, opacity measurement, haze value measurement, registration test, and dynamic sensitivity evaluation were performed. The results are shown in Table 2.

(Comparative Example 1)
Instead of particles (made by Dow Chemical, trade name: ULTRA E, particle size: 0.4 μm, hollow ratio: 45%) made of acrylic resin as hollow particles, kaolin (made by Kamin, trade name: HYDRAGLOSS 90) as a filler A heat-sensitive recording material was produced in the same manner as in Example 1 except that the particle size: 0.4 μm) was used.

  Next, in the same manner as in Example 1 above, opacity measurement, haze value measurement, registration test, and dynamic sensitivity evaluation were performed. The above results are shown in Table 3.

(Comparative Example 2)
Instead of particles made of acrylic resin that is hollow particles (manufactured by Dow Chemical, trade name: ULTRA E, particle size: 0.4 μm, hollow ratio: 45%), silica particles that are fillers (manufactured by Nippon Shokubai Co., Ltd.) , Trade name: KE-050W, particle size: 0.5 μm) was used in the same manner as in Example 1 to prepare a heat-sensitive recording material.

  Next, in the same manner as in Example 1 above, opacity measurement, haze value measurement, registration test, and dynamic sensitivity evaluation were performed. The above results are shown in Table 3.

(Comparative Example 3)
As hollow particles, instead of particles made of acrylic resin (Dow Chemical, trade name: ULTRA E, particle size: 0.4 μm, hollow rate: 45%), hollow particles made of acrylic resin (made by Dow Chemical, trade name) : HP-1055, particle size: 1 μm, hollow ratio: 55%, blending amount: 2.5% by weight), and further kaolin (product of Kamin, trade name: HYDRAGLOSS90, particle size: 0.40 μm) as a filler. , Blending amount: 7.5% by weight) was used in the same manner as in Example 1 to prepare a thermosensitive recording material.

  Next, in the same manner as in Example 1 above, opacity measurement, haze value measurement, registration test, and dynamic sensitivity evaluation were performed. The above results are shown in Table 3.

(Comparative Example 4)
Polymethylmethacrylate as a filler (solid particles) instead of particles made of acrylic resin as hollow particles (manufactured by Dow Chemical, trade name: ULTRA E, particle size: 0.4 μm, hollow rate: 45%) A thermosensitive recording material was produced in the same manner as in Example 1 except that a resin (manufactured by Seiden Chemical Co., Ltd., trade name: PG-5, particle size: 2 μm) was used.

  Next, in the same manner as in Example 1 above, opacity measurement, haze value measurement, registration test, and dynamic sensitivity evaluation were performed. The above results are shown in Table 3.

(Comparative Example 5)
A polystyrene resin (Mitsui) as a filler (solid particles) instead of particles (made by Dow Chemical, product name: ULTRA E, particle size: 0.4 μm, hollow ratio: 45%) made of acrylic resin as hollow particles A thermosensitive recording material was produced in the same manner as in Example 1 except that Chemical Co., Ltd., trade name: 110M, particle size: 0.8 μm) was used.

  Next, in the same manner as in Example 1 above, opacity measurement, haze value measurement, registration test, and dynamic sensitivity evaluation were performed. The above results are shown in Table 3.

(Comparative Example 6)
Instead of particles made of acrylic resin that is hollow particles (manufactured by Dow Chemical, trade name: ULTRA E, particle size: 0.4 μm, hollow ratio: 45%), silica particles that are fillers (manufactured by Nippon Shokubai Co., Ltd.) , Trade name: KE-050W, particle size: 0.5 μm, blending amount: 20% by weight) was used in the same manner as in Example 1 to produce a thermosensitive recording material.

  Next, in the same manner as in Example 1 above, opacity measurement, haze value measurement, registration test, and dynamic sensitivity evaluation were performed. The above results are shown in Table 3.

(Comparative Example 7)
Instead of particles made of acrylic resin that is hollow particles (manufactured by Dow Chemical, trade name: ULTRA E, particle size: 0.4 μm, hollow rate: 45%), titanium oxide particles that are fillers (manufactured by Teika Co., Ltd.) , Product name: JR600A, particle size: 0.3 μm) was used in the same manner as in Example 1 to produce a heat-sensitive recording material.

  Next, in the same manner as in Example 1 above, opacity measurement, haze value measurement, registration test, and dynamic sensitivity evaluation were performed. The above results are shown in Table 3.

(Comparative Example 8)
Instead of particles made of acrylic resin that is hollow particles (manufactured by Dow Chemical, trade name: ULTRA E, particle size: 0.4 μm, hollow rate: 45%), titanium oxide particles that are fillers (manufactured by Teika Co., Ltd.) , Trade name: JR600A, particle size: 0.3 μm, blending amount: 20% by weight) was used in the same manner as in Example 1 to produce a thermosensitive recording material.

  Next, in the same manner as in Example 1 above, opacity measurement, haze value measurement, registration test, and dynamic sensitivity evaluation were performed. The above results are shown in Table 3.

  As shown in Table 2, the thermal recording paper of Examples 1 to 5 (in which the content of hollow particles is 5 to 20% by weight) in which the thermal recording layer contains hollow particles and the opacity is 20% or more is a bar. It can be seen that the code reading characteristics are very good. On the other hand, it can be seen that the barcode is not read at all in the thermal recording papers of Comparative Examples 1 and 2 in which the thermal recording layer contains kaolin or silica particles but does not contain hollow particles.

  It can also be seen that the barcode is not read at all on the thermal recording paper of Comparative Example 3 having an opacity of less than 20% (18.4).

  In Comparative Examples 4 to 5 containing solid particles, it can be seen that the barcode is not read at all. This is presumably because the solid particles, unlike the hollow particles, are solid and are not easily melted by heat, and as a result, transparency due to dissolution did not occur. Further, it is considered that the solid particles have a light scattering effect that is less than that of the hollow particles, so that a contrast that allows the barcode to be read cannot be obtained.

  Further, as shown in Tables 2 to 3, it can be seen that the thermal recording papers of Examples 1 to 5 have higher dynamic sensitivity characteristics and superior printing characteristics as compared with Comparative Examples 1 to 8. As described above, the hollow particles are considered to be transparent because the hollow particles themselves dissolve and become transparent when heated, so that the hollow particles do not shield the heat-sensitive black color.

  On the other hand, in Comparative Example 6 containing 20% by weight of silica particles, the barcode can be read, but the dynamic sensitivity characteristic is low (particularly the dynamic sensitivity characteristic on the low energy side is low) and the printing characteristic is poor. I understand that.

  Further, in Comparative Examples 7 to 8 containing titanium oxide particles, barcode reading is possible, but it can be seen that the dynamic sensitivity characteristic is low and the printing characteristic is poor. This is because, unlike hollow particles, titanium oxide does not change by heating (that is, it does not become transparent when heated), so if there is a large amount (that is, 10% by weight or more), heat-sensitive black This is considered to be because the print density was lowered as a result (ie, the black color of the portion desired to be blackened was reduced, resulting in a grayish appearance).

  As described above, the present invention is particularly useful for a thermal recording material on which a barcode or the like is printed.

DESCRIPTION OF SYMBOLS 1 Thermal recording body 2 Base material 3 Thermal recording layer 4 Intermediate layer 5 Topcoat layer 6 Hollow particle 7 Other thermal recording layers

Claims (4)

A heat-sensitive recording material in which at least a heat-sensitive recording layer and a topcoat layer are laminated on a substrate,
The thermosensitive recording layer contains hollow particles;
A heat-sensitive recording material, wherein the opacity measured in accordance with JIS P8149 is 20% or more.   The heat-sensitive recording material according to claim 1, wherein the haze value measured in accordance with JIS-K7136: 2000 is 70% or more.   The heat-sensitive recording material according to claim 1, wherein the hollow particles are formed of an acrylic resin.   The thermal recording material according to claim 1, further comprising an intermediate layer between the thermal recording layer and the topcoat layer.

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