JP3092081B2 - Thermal recording medium for laser marking and printing ink - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-speed and efficient marking method for in-line production and packaging of labels and other display materials to be affixed to products shipped from factories, and more particularly to thermosensitive coloring. The present invention relates to a thermosensitive recording medium capable of easily forming a laser coloring agent layer in an arbitrary pattern by a printing method and performing high-preservation laser marking, and a printing ink therefor.

[0002]

2. Description of the Related Art In general, a heat-sensitive recording medium having a heat-sensitive recording layer mainly comprising an electron-donating usually colorless or pale-color dye precursor and an electron-accepting color developing agent on a support is known as a laser light, heat-sensitive recording medium. By heating with a head, a hot pen or the like, the dye precursor and the developer react instantaneously to obtain a recorded image, and are used in a wide range of fields such as facsimile, computer terminals, labels and the like.

[0003] In recent years, as the use of receipts, such as cashier sheets, and label applications for foodstuffs has expanded, record images have been displayed in monetary values and dates on receipts, and on the date of manufacture and expiration date on foods. Due to the importance of this image, a heat-sensitive recording medium is required to have a long-term record holding characteristic under a severe use and storage environment.

However, in the conventional thermosensitive recording medium provided with a thermosensitive recording layer mainly composed of a dye precursor and an electron-donating developer, the storage stability (water resistance, chemical resistance, etc.) of the recorded image is low. It is still inadequate and has a serious practical problem that the recorded image is decolored due to long-term immersion in water and adhesion of chemicals such as ester-based oil compounds and vegetable oils, causing serious troubles as labels. Was.

[0005] In particular, in the case of recycled bottles for recycling beer bottles and the like, ester-based oil-based compounds and silicone oils are used for the purpose of repairing the appearance of scratches generated during transportation and bottle washing, maintaining the strength of the bottles, and suppressing the occurrence of scratches. A coating solution for a water-based or oil-based bottle containing oil is applied, and when a thermosensitive recording medium is used for such a bottle, the coating solution for the bottle is applied to the thermosensitive recording medium from above, or Contact, so that the recorded image loses its color, resulting in insufficient storage stability.

[0006] To improve the water resistance and chemical resistance of the recorded image of thermosensitive recording material using a basic leuco dye and a developer, JP 62-135567, JP 63-957 No. 3,
JP-A-3-13385 and the like have proposed a dimerized basic leuco dye. When the leuco dye shown here is used, the chemical resistance of the recorded image is improved, and the color is not erased even when it comes into contact with the bottle coating solution. Dissolve and react as a result, resulting in color development (ground color development) or for cooling the contents of the bottle,
When immersed in water for a long time, there is a problem that a recorded image cannot be held.

[0007]

SUMMARY OF THE INVENTION In view of the above-mentioned circumstances, the present invention provides an efficient and high-speed and high-sensitivity laser beam.
In addition, it is possible to perform labeling on paper base labels etc. only by heat-sensitive coloring and not to cause material destruction (no contamination due to laser marking), and high water resistance and chemical resistance of recorded images and uncolored parts (background parts) An object of the present invention is to provide a thermal recording medium.

[0008]

Means for Solving the Problems In view of such a situation, the present inventors have made intensive studies on a heat-sensitive recording material that non-destructively develops color by laser irradiation. As a result, a color former such as a leuco dye and its developer have been developed. A printing ink containing, for example, a gravure printing ink is produced, and after printing on a base material, when a printed portion is irradiated with a laser, even if the base material is paper, the color is formed without being destroyed and marking can be easily performed, In addition, a heat-sensitive recording medium having excellent water resistance and plasticizer resistance was found, and was disclosed in Japanese Patent Application No. 4-3200.
No. 86 (JP-A-6-166266).

However, a heat-sensitive recording medium having high storage stability of a recorded image which can be used even under severe conditions for a long period of time or in a recycled bottle which comes into contact with a bottle coating solution, further requires a coloring agent and a developing agent. The need for a special choice was felt.

Accordingly, the inventors of the present invention have proposed a method for improving the water resistance of a recorded image,
As a result of intensive studies to improve storage stability such as chemical resistance, a fluoran derivative represented by the following general formula (1) as a basic leuco dye, and a fluoran derivative represented by the following general formula (2) as a developer
The phenolic compound shown in the above, borates are contained as a multifunctional additive, and an inorganic binder is contained as a binder.
Laser marking for heat-sensitive recording material that does not have a high storage stability (water resistance, chemical resistance) to have, and excellent heat-sensitive recording material of the printing ink containing the components is the, especially to bring the label compound Was found. General formula (1)

[0011]

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[In the above formula, R ₁ represents a methyl group or an ethyl group. General formula (2)

[0013]

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[Wherein R is a methyl group, a phenyl group, p
-Represents a tolyl group, an α-naphthyl group or a β-naphthyl group, and n represents an integer of 0 or 1.]

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the basic leuco dye represented by the general formula (1), which is a color former, is preferably a case where the substituent R ₁ is a methyl group. Can be used as well.

Examples of the phenol compound represented by the general formula (2), which is a developer, include 4-hydroxyphenylmethylsulfone, 2,4-dihydroxyphenylmethylsulfone, and 3,4-dihydroxyphenylmethylsulfone. ,
4-hydroxyphenylphenylsulfone, 2,4-dihydroxyphenylphenylsulfone, 3,4-dihydroxyphenylphenylsulfone, 4-hydroxyphenyl-p-tolylsulfone, 2,4-dihydroxyphenyl-p-tolylsulfone, 3,4 -Dihydroxyphenyl-p-tolylsulfone, 4
-Hydroxyphenyl-α-naphthyl sulfone, 2,4-dihydroxyphenyl-α-naphthyl sulfone, 3,4-dihydroxyphenyl-α-naphthyl sulfone, 4-hydroxyphenyl-β-naphthyl sulfone, 2,4-dihydroxyphenyl
-β-Naphthyl sulfone, 3,4-dihydroxyphenyl-β-
And naphthyl sulfone.

These are appropriately selected in consideration of the type of solvent used in forming the ink, the required degree of image durability, and a slight difference in the color density by laser.
Among them, hydroxyphenyl-p-tolylsulfone is preferable, and 3,4-dihydroxyphenyl-p-tolylsulfone is particularly excellent.

In the present invention, the mixing ratio of the basic leuco dye and the developer is not particularly limited since it is appropriately selected, but generally, the basic leuco dye and the developer are mixed with the developer. / The weight ratio of the color former is 0.1 / 1 to 5/1
The weight ratio is 0.5 / 1 to 1
A range of 3/1 is preferable.

In order to enhance the durability of the heat-sensitive recording medium and the stability of the heat-sensitive coating solution for obtaining the same or the printing ink, one or both of the basic leuco dye and the developer of the present invention are used. Can also be used.

Further, the basic leuco dye and the developer do not prevent the combined use of a plurality of compounds included in the general formulas (1) and (2) as desired, and the effects of the present invention are expected. The combination of other compounds is not prevented as far as possible.

The borate used in the present invention is a multifunctional additive, and has the first performance as a laser sensitizer for converting laser light into heat. In addition, the borates suppress the background color development of the heat-sensitive coloring layer comprising the leuco dye of the present invention and the color developer due to various solvents and the like, and further increase the water resistance and chemical resistance of the recorded image. The borates themselves are hardly soluble or insoluble in thermal coating liquids and printing inks and are therefore dispersed in particles. The particle size is usually 10 μm or less, and particularly preferably 0.1 to 4 μm. Also,
These may be previously surface-treated with a titanium coupling agent, a silane coupling agent, a metal soap, a surfactant, a resin, or the like, in order to enhance dispersibility.

The mixing ratio of the borate is 5 to 1 with respect to 100 parts by weight of the total amount of the basic leuco dye and the developer.
It is 50 parts by weight, preferably 20 to 80 parts by weight. Examples of the borate used here include zinc borate, which is a metal salt of boric acid, calcium borate, magnesium borate, lithium borate, aluminum borate, sodium borate, manganese borate, barium borate, and the like, which contain bound water. Or anhydrous. These may be used in combination of two or more.

As the binder resin for fixing the basic leuco dye, the developer and the borates used in the heat-sensitive recording medium of the present invention, generally used polymer materials can be used. For example, polyamide resin, polybutyral resin,
Polyvinyl butyral resin, polyvinyl alcohol resin, nitrocellulose resin, acrylic resin, vinyl chloride-vinyl acetate copolymer resin, urethane resin, petroleum resin, chloride rubber resin, cyclized rubber resin, alkyd resin, phenol Resin, epoxy resin and the like. These can be used in a state of being dissolved or dispersed in a suitable organic solvent, water or the like, depending on the method of forming the thermosensitive recording medium.

In the thermosensitive coloring layer, if necessary, fillers such as calcium carbonate, silica, alumina, magnesia, talc, mica, titania, cordierite, barium sulfate, etc., metal stearate, stearamide, lauryl A lubricating agent such as an acid metal salt, lauric amide, oleic acid metal salt, or oleic amide may be appropriately present to enhance the sharpness of a recorded image.

The support of the present invention is appropriately selected and is not particularly limited, but may be a conventional paper, art paper, coated paper, aluminum-evaporated paper, vinyl chloride resin, polyester resin, polyolefin resin, metal, etc. Sheet, synthetic paper, laminated paper or the like can be used.

In order to enhance the smoothness of the support, a nitrocellulose resin, a polyamide resin, an acrylic resin, a polyurethane resin, a polyester resin, an epoxy resin, a silicone resin, An undercoat layer containing a resin containing various polymers as a main component such as a fluororesin or a filler may be formed.

Further, in order to increase the durability of the thermosensitive coloring body,
Polyethylene resin, polypropylene resin, ethylene-vinyl acetate resin, ethylene-ethyl acrylate resin, acetate nitrocellulose resin, polyamide resin, acrylic resin, polyurethane resin,
Resins containing various polymers such as polyester resins, epoxy resins, silicone resins, and fluororesins as main components, and fillers, lubricants, ultraviolet absorbers, antioxidants, water producing agents, oil producing agents, etc. An overcoat layer to which an auxiliary agent has been added can be used on the thermosensitive coloring layer. The addition of an ultraviolet absorber or an antioxidant to the heat-sensitive coloring layer or the overcoat layer suppresses deterioration of the recorded image or uncolored portion (background portion) due to light, and further enhances the long-term storability of the heat-sensitive recording medium.

In order to increase the laser coloring sensitivity and coloring density,
The undercoat layer and the overcoat layer may contain a basic leuco dye, a developer, and a sensitizer for laser marking.

The coating method for forming the thermosensitive coloring layer of the thermosensitive coloring body is not particularly limited.
Conventional methods can be used, for example, gravure printing,
Examples include offset printing, flexographic printing, screen printing, air knife coating, and blade coating.

The thickness of the heat-sensitive coloring layer of the present invention is usually a heat-sensitive recording material dry coating amount a is 5 to 10 g / m may be less than ² 1.0 g / m ² or more, preferably 1.5~4g /
It is sufficient if there is a dry coating amount of m ² . In order to produce an inexpensive label with a small amount of coating, if the printing ink is partially formed in a desired pattern only at the place where laser marking is desired, the thickness of the applied portion and the uncoated portion does not greatly differ. Therefore, for example, there is an effect that the cutting accuracy in the case where a large number of labels are stacked and cut in order to produce a label, and the handling when the labeling is performed by a labeler using a bundle in which a large number of labels are stacked are significantly improved.

The preparation of the heat-sensitive coating liquid or the printing ink is not particularly limited, but in order to prevent color formation in the coating liquid,
A method in which a basic leuco dye and a developer are separately dispersed and mixed immediately before coating (both salts may be added in either dispersion at this time), a basic leuco dye, a developer, boric acid There is a method of dispersing the salts together.

In the case of dispersing together, Japanese Patent Application No. 4-32
No. 0086 (Japanese Patent Application Laid-Open No. 6-166266) is effective from the viewpoint of high workability and easy management of the coating liquid, in which a one-ink printing ink to which a background color development inhibitor is added is effective.

The heat-sensitive coating liquid or printing ink includes a dispersant,
Viscosity modifiers, fillers, leveling agents, lubricants, ultraviolet absorbers, antioxidants, antistatic agents, colorants, heat-sensitive sensitizers,
Auxiliaries classified as preservatives and the like can be added.

Further, in order to adjust the hue and the color sensitivity of the recorded image, a leuco dye, a developer, a pigment precursor and the like other than the present invention can be added within a range where the water resistance, chemical resistance and the like are not reduced. .

The laser apparatus for coloring the thermosensitive coloring material for laser marking of the present invention by applying a color has an output of at least 0.1 joule / cm ² · pulse, preferably at least 0.1 joule / cm ² · pulse.
A pulsed laser capable of giving an energy of 2 Joules / cm ² · pulse or more to the irradiation surface or a scanning laser having an output of 0.5 W or more is preferable, for example, a carbon dioxide laser, a carbon monoxide laser, a semiconductor laser, and yttrium aluminum.・ Garnet (YAG) laser,
Excimer laser, etc., among which Transve
rselly Excited Atomopheri
c Pressure (TEA) type carbon dioxide gas laser and scanning type carbon dioxide laser are particularly preferable in that black marking with good visibility can be obtained.

In the case of a pulse laser in which the energy of one shot is limited, the thermosensitive coloring member of the present invention, which can print with low energy, is very suitable. The thermosensitive recording medium for laser marking of the present invention can record with a conventional thermosensitive head, hot pen or the like in addition to the laser beam, and the storage stability performance of the thermosensitive recording body does not change.

[0037]

The present invention will be described in more detail with reference to the following Examples and Comparative Examples, but it should not be construed that the invention is limited thereto. The parts and percentages in the examples are on a weight basis.

Example 1 Compound of Structural Formula I 8 parts Compound of Structural Formula II 5 parts Calcium borate 6 parts Polyamide resin {K-80 manufactured by Toray Industries, Inc.} 3 parts Saturated aqueous ammonium chloride solution 5 parts Ethanol 23 parts

[0039]

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Structural formula II

[0041]

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The above components were shaken for 3 hours together with glass beads in a paint conditioner to prepare a one-part type heat-sensitive coating liquid. The viscosity of the heat-sensitive coating solution was adjusted by adding ethanol so that the viscosity was 25 ± 3 seconds in a # 3 Zahn cup method viscosity measurement. Next, an angle of 0, 70 lines /
cm and printed with a Helio gravure plate.
Further, a nitrocellulose-based gravure OP varnish [SF815 manufactured by Dainippon Ink and Chemicals, Inc.] was gravure-printed and dried to obtain a thermosensitive recording medium.

The laser marking was performed using a TEA-type carbon dioxide laser irradiator through a metal mask with characters cut out, and an irradiation energy amount of 0.40 to 0.57 joules / c.
Irradiation was performed with an m ² pulse laser.

The measurement of the laser irradiation energy amount is as follows.
A detector {Model No. ED-500 manufactured by GENTEC Co., Ltd.) is installed at the position of the metal mask, and one pulse of carbon dioxide laser light is irradiated to the detector, and the output voltage of the detector is measured by a laser energy meter {Model No. EM-1 manufactured by GENTEC Co., Ltd.}. Read in. Further, the total irradiation energy was divided by the area of the irradiation area on the marking surface to derive the irradiation energy per unit area per pulse.

Example 2 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that aluminum borate was used instead of calcium borate.

Example 3 A thermosensitive recording medium was obtained in the same manner as in Example 1, except that zinc borate was used instead of calcium borate.

Comparative Example 1 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that kaolin clay was used instead of calcium borate.

Comparative Example 2 A heat-sensitive recording material was obtained in the same manner as in Example 1, except that zinc phosphate was used instead of calcium borate.

Comparative Example 3 A heat-sensitive recording material was obtained in the same manner as in Example 3, except that bisphenol S was used in place of 3,4-dihydroxyphenylparatolylsulfone.

Test Examples Water resistance tests and chemical resistance tests were performed as storage stability tests on the laser-marked thermosensitive recording material samples of Examples 1 to 3 and Comparative Examples 1 to 3 . In the water resistance test, the sample was immersed in city water, and evaluated by the brightness of the colored portion after two weeks. The chemical resistance was evaluated by preparing a bottle coating solution having the following composition, applying the solution on a sample with a sponge, and examining the brightness of the laser colored portion and the laser non-irradiated portion two weeks later.

Table 1 shows the evaluation results of the compositions shown in Examples 1 to 3 and Comparative Examples 1 to 3 . Table 1 shows the results of evaluation based on the lightness of the colored portion and the uncolored portion (background portion) before and after the storage stability test. The numerical values before the test indicate lightness values measured by a colorimeter.

Evaluations after the water resistance test and the chemical resistance test were as follows: increase in the brightness of the colored portion was less than 10: 10 or more to less than 15: 15 or more to less than 20: Δ 20 or more: × brightness of the uncolored portion Less than 10: ◎ 10 or more to less than 15: 15 or more to less than 20: Δ 20 or more: x

Composition of bottle coating liquid Isopropyl myristate 20 parts Isopropyl palmitate 10 parts Capric acid triglyceride 45 parts Sorbitan sesquiolate 6 parts Polyoxyethylene nonylphenyl ether 6 parts Polyoxyethylene (20) sorbitan oleate 3 parts Silicone oil (Toshiba Silicone TSF451-350) 10 parts

[0054]

[Table 1]

[0055]

According to the heat-sensitive recording material for laser marking of the present invention, the recorded image and the background have excellent water resistance and chemical resistance, and exhibit long-term record retention characteristics under severe use and storage environments. A recording medium is obtained. In particular, the present invention is suitable for a label which is used for a bottle which uses a drug such as a bottle coating liquid which remarkably decolors an image, such as a recycled bottle, and which comes into contact with the drug.

In the recording medium of the present invention, nondestructive marking is performed at a rate of 60 to 600 per minute due to high sensitivity to laser light.
Zero high-speed and large-area marking can be efficiently performed. Therefore, the thermal recording medium of the present invention is particularly suitable for labels, receipts, nameplates, cards, and the like that require high storage stability of recorded images.

Continuation of the front page (51) Int.Cl. ⁷ Identification code FI B41M 5/18 108 (72) Inventor Tadashi Kobayakawa 2-10-1 Shinkawa, Chuo-ku, Tokyo (56) References JP-A-63-209992 (JP) JP-A-3-13385 (JP, A) JP-A-5-57463 (JP, A) JP-A-6-166266 (JP, A) JP-A 9-1936 (JP, A) JP-A Sho 63-9573 (JP, A) JP-A-8-25809 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41M 5/30 C09D 11/02 G09F 3/02

Claims (8)

(57) [Claims] 1. A fluoran derivative represented by the general formula (1) as a basic leuco dye in a thermosensitive recording medium containing a basic leuco dye on a support and a color developing agent which causes the leuco dye to develop a color by heating. And the general formula (1) [In the above formula, R1 represents a methyl group or an ethyl group. As a color developer, a phenol compound represented by the general formula (2) and a phenol compound represented by the general formula (2): [Wherein R is a methyl group, a phenyl group, a p-tolyl group,
represents an α-naphthyl group or a β-naphthyl group;
Or a whole number of 1]. A heat-sensitive recording material for laser marking, comprising a borate as a multifunctional additive and no inorganic binder as a binder . 2. The heat-sensitive recording material for laser marking according to claim 1, which is used for a bottle to which a bottle coating liquid is applied. 3. The heat-sensitive recording material for laser marking according to claim 1, wherein the recording material is a label. 4. A laser marking heat-sensitive recording material according to any one of claims 1 to 3 as a binder resin containing polyamides resin. 5. A laser marking heat-sensitive recording material according to claim 4, the binder resin are both contain ethanol. 6. A basic leuco dye represented by the following general formula (1):
And a fluoran derivative represented by the general formula (1): [In the above formula, R1 represents a methyl group or an ethyl group. A phenol compound represented by the general formula (2) as a color developer, and a phenol compound represented by the general formula (2): [Wherein R is a methyl group, a phenyl group, a p-tolyl group,
represents an α-naphthyl group or a β-naphthyl group, and n represents an integer of 0 or 1.] It is characterized in that it contains borates as a multifunctional additive and does not contain an inorganic binder as a binder. Printing ink for laser marking. 7. The laser marking printing ink according to claim 6 as a binder resin containing polyamides resin. 8. binder resin are both laser marking printing ink according to claim 7 containing ethanol.