JP7017996B2 - Thermal paint and laser marking method using it - Google Patents

Description

The present invention relates to a heat-sensitive paint and a laser marking method using the same.

Non-contact industrial inkjet printers and laser markers capable of high-speed printing are used in a wide range of fields such as foods, cosmetics, and electronic parts. However, many of these marking devices print in a single color, and it is difficult to print in multiple colors. In order to print in multiple colors in an inkjet printer, a plurality of inks, ink tanks, and nozzles for ejecting ink are required. Laser marking is a method of printing by irradiating an object with laser light to melt, burn, peel, oxidize, scrape, or discolor the surface. In order to print in multiple colors in a laser marker, it is necessary to apply a paint that develops multiple colors depending on the laser wavelength in advance on the printed surface. Examples of the paint that develops multiple colors include a paint containing a substance whose material changes its structure at a specific wavelength and causes a color change. Therefore, in order to develop multiple colors, it is necessary to irradiate laser beams of various wavelengths. In addition, a high-power laser device is often required in order to cause a structural change in the material.

On the other hand, in a thermal printer provided with a thermal head, a technique of printing in multiple colors using a multicolor heat-sensitive recording material is known.

Patent Document 1 states that at least an electron donating compound, an electron accepting compound, and a part or all of the composition system are reversible crystalline-amorphous transition or two phase-separated or phase-separated states-non. A temperature indicating material containing a reversible material that expresses a change in a phase separation state and a temperature indicating characteristic controlling material is disclosed. The temperature indicating property controlling agent is solid at room temperature, and at least a part of the temperature indicating property controlling agent is compatible with the electron-accepting compound or the reversible material or the electron-accepting compound and the reversible material, and the crystalline-amorphous transition thereof. Alternatively, the rate of the crystalline-amorphous transition or the phase-separated state-non-phase separated state of the composition system is changed by the change of the phase-separated state-non-phase separated state, and after the phase separation, the electron-donating compound and the electron-accepting compound are used. It is stated that it does not inhibit the interaction of.

Japanese Unexamined Patent Publication No. 2001-348568

The temperature indicating material disclosed in Patent Document 1 becomes a fluid state when heated from the color-developed state to above its melting point, and the electron-donating compound and the electron-accepting compound weaken the interaction, and the electron-accepting compound or the reversible material is used. Alternatively, the electron-accepting compound and the reversible material are compatible with at least a part of the temperature-indicating property controlling agent, and the interaction between the temperature-indicating property controlling agent and the color developer and the reversible material becomes stronger and the color is extinguished. When rapidly cooled from that state, it solidifies in an amorphous state and maintains a decolorized state while strengthening the interaction between the three components of the reversible material, the electron-accepting compound, and the temperature-indicating property control agent.

In this amorphous state temperature indicating material, the reversible material and the temperature indicating characteristic controlling agent crystallize at a rate corresponding to the heating temperature, and the color develops. By atomizing this amorphous temperature-indicating material into fine particles and mixing them in the paint, it is possible to produce a paint that develops color by heating with a laser.

Laser marking is required to have a high printing speed. In order to increase the printing speed, it is desirable to use a temperature indicating material having a high color developing speed.

However, since the high color development speed means that it is easy to crystallize, it is difficult to solidify it in an amorphous state while it is in a decolorized state. The temperature-indicating material in the amorphous state is formed by heating to a temperature higher than the melting point and melting the material, and then quenching to a temperature below the glass transition point. At this time, it passes through a temperature that is easily crystallized, which is an intermediate temperature between the melting point and the glass transition point. If the temperature indicating material is crystallized at a temperature at which it is easy to crystallize in the quenching step of the temperature indicating material, the temperature indicating material does not become an amorphous state but crystallizes and develops color. Therefore, it cannot be used as a paint that develops color by heating with a laser.

Therefore, an object of the present invention is to provide a heat-sensitive paint which can be colored by a laser and has a high coloring speed.

In order to solve the above problems, the heat-sensitive coating material according to the present invention contains a leuco dye, a color developer and a decoloring agent, has amorphous first particles, and has a melting point from a temperature below the glass transition point of the first particles. When heated at a heating rate of 30 ° C./min, the color develops at a temperature equal to or higher than the glass transition point of the first particle and lower than the melting point.

According to the present invention, it is possible to provide a heat-sensitive paint which can be colored by a laser and has a high coloring speed.

It is a graph which shows the relationship between the temperature and the color density of the temperature sensitive material used in 1st Embodiment. It is a DSC curve of a temperature sensitive material with a fast crystallization rate. It is a DSC curve of a temperature sensitive material with a slow crystallization rate. It is a graph which shows the relationship between the temperature and the color density of the temperature sensitive material used in 2nd Embodiment. It is a schematic diagram which shows the color change of the paint which concerns on 2nd Embodiment. It is a graph which shows the relationship between the temperature and the color density of the temperature sensitive material used in 3rd Embodiment. It is a graph which shows the relationship between the temperature and the color density of the temperature sensitive material used in 3rd Embodiment. It is a schematic diagram which shows the color change of the paint which concerns on 3rd Embodiment. It is a photograph which shows the temperature dependence of the paint which concerns on Example 3. FIG. It is a photograph which shows the laser printing result of the paint which concerns on Example 3. FIG.

Hereinafter, embodiments for carrying out the present invention (hereinafter referred to as “embodiments”) will be described in detail with reference to the drawings as appropriate. In each figure, the same reference numerals are given to common parts, and duplicate description will be omitted.

[First Embodiment]
The heat-sensitive paint according to the first embodiment relates to a paint for laser marking that forms markings by locally heating the paint by irradiating the paint with a laser beam and discoloring the paint.

The heat-sensitive coating material contains a temperature-sensitive material that changes color due to heat generated by irradiation with laser light, and a solvent. A resin, a viscosity adjusting agent, a surface tension adjusting agent, or the like may be added to the heat-sensitive paint for adjusting the viscosity and the strength of the coating film (paint after the solvent has dried).

<Solvent>
The laser marking paint is applied to the printed surface in advance for printing by a laser beam. A solvent (paint solution) is required to apply to the printed surface. The solvent can be selected according to the properties of the material forming the printed surface. In the case of a printed surface having hydrophilicity such as paper, it is preferable to use a hydrophilic solvent.

<Temperature sensitive material>
The temperature-sensitive material is particles containing a leuco dye, a color developer, and a decolorizing agent, and is a material that changes color due to an amorphous-crystalline phase transition. Further, the temperature-sensitive material exhibits a hysteresis characteristic in the color density-temperature curve and has reversibility.

The temperature-sensitive material according to the first embodiment has a feature that the color develops by crystallization when the temperature is raised from the amorphous and decolorized state. FIG. 1 shows the relationship between the color density and the temperature of the temperature-sensitive material according to the first embodiment. The broken line shows the relationship between the color density and the temperature when the cooling rate is slow. In FIG. 1, the vertical axis is the color density, the horizontal axis is the temperature, Ta is the developing temperature of the temperature-sensitive material, Td is the decoloring temperature, and the shaded area is the operating temperature of the marking object. The temperature-sensitive material according to the first embodiment starts to develop color at Ta in the process of raising the temperature, and starts decolorization when it reaches Td. Further, when the temperature is lowered from the decolorized state, if the cooling rate is high, the solidified state remains in the decolorized state. When the cooling rate is slow, color development starts at Ta'as shown by the broken line, and solidifies in the developed state.

Therefore, by applying thermal energy corresponding to the temperature Ta to the temperature-sensitive material decolorized in the amorphous state, the paint can be developed only in the laser-irradiated portion. After color development, the color development state can be maintained by cooling without raising the temperature above Td. Further, by setting Ta to a temperature higher than the range of the operating temperature of the marking object (a temperature not expected in the process of use), new color development can be suppressed. For example, when the marking object is stored and used at room temperature, it is preferable to use a material that develops color at 60 ° C. or higher.

2 and 3 are DSC curves obtained by differential scanning calorimetry (DSC) of the temperature sensitive material. FIG. 2 is a DSC curve of a temperature-sensitive material having a high crystallization rate, and is a schematic diagram when measured at a temperature rising rate of 30 ° C./min and a temperature lowering rate of 20 ° C./min. FIG. 3 is a DSC curve of a temperature-sensitive material having a slow crystallization rate, and is a schematic diagram when measured at a temperature rising rate of 5 ° C./min and a temperature-decreasing rate of 20 ° C./min. The vertical axis is the heat flux (W), the horizontal axis is the temperature, Tg is the glass transition point, Ta is the start temperature of the exothermic peak due to crystallization in the temperature rise process (hereinafter referred to as the crystallization start temperature in the temperature rise process), and Td. Is the melting point. The melting point Td in FIGS. 2 and 3 and the crystallization start temperature Ta in the temperature raising process correspond to the decoloring temperature Td and the developing color temperature Ta in FIG. 1, respectively.

In FIGS. 2 and 3, as the temperature is increased, the baseline decreases with the glass transition at the glass transition point Tg. Crystallization starts at the crystallization start temperature Ta in the temperature rise process, and an exothermic peak is observed. The leuco dye and the color developer, which had been dissociated due to the start of crystallization, combine with each other to start color development. An endothermic peak is observed at the melting point Td. The temperature-sensitive material that has reached the melting point melts, and the bond between the leuco dye and the developer dissociates, resulting in decolorization. When the temperature rise rate is slow, the crystallization start temperature Ta in the temperature rise process appears at a lower temperature, and when the temperature rise rate is faster, the crystallization start temperature Ta in the temperature rise process appears at a higher temperature, or crystallization. It melts at the melting point Td without the starting temperature Ta appearing.

As shown in FIG. 2, when the temperature-sensitive material having a high crystallization rate is cooled from a temperature equal to or higher than the melting point Td, crystallization occurs and an exothermic peak is observed. As a result, the dissociated leuco dye and the color developer combine to start color development. When heated again in this state, since it has already crystallized, a decrease in baseline due to glass transition and an exothermic peak due to crystallization are not observed.

As shown in FIG. 3, when the temperature-sensitive material having a slow crystallization rate is cooled from a temperature equal to or higher than the melting point Td, crystallization does not occur and no exothermic peak due to crystallization is observed. Since the temperature-sensitive material solidifies while the leuco dye and the color developer are dissociated, the decolorized state is maintained. Although not shown in FIG. 3, when the temperature lowering rate is slow, the leuco dye and the color developer are combined and solidified in a colored state. The coloration state differs depending on the cooling rate. In the case of a material that is easily crystallized, it easily crystallizes at a temperature higher than the glass transition point, so that the crystallization start temperature Ta and the glass transition point Tg are often the same temperature.

As mentioned above, laser marking is required to have a high printing speed. In order to increase the printing speed in laser marking, it is desirable to use a material with a high crystallization rate as the temperature sensitive material.

However, in laser marking, it is necessary to make the temperature sensitive material in a decolorized state before laser irradiation. This is to develop the color of the temperature-sensitive material by irradiating the temperature-sensitive material in the decolorized state with a laser beam so as to have a temperature of Ta or more and Td or less. As can be seen from FIGS. 2 and 3, in the case of a temperature-sensitive material that is difficult to crystallize, the temperature-sensitive material can be kept in a decolorized state before laser irradiation by melting the temperature-sensitive material and then quenching it. .. On the other hand, in the case of a temperature-sensitive material that easily crystallizes, it cannot be left in a decolorized state because it crystallizes and develops color in the cooling process.

Various cooling methods are assumed as the quenching method, but due to the heat capacity of the temperature-sensitive material, the crystallization rate is such that a crystallization peak is observed in the DSC measurement at a heating rate of 30 ° C./min or higher. It is difficult to make a fast temperature sensitive material. Further, it is difficult to produce a heat-sensitive material that crystallizes and develops color when heated at a heating rate of 1000 ° C./min or more, such as spot heating by laser irradiation.

As a result of diligent studies by the inventors, a solvent rapid evaporation method in which a temperature-sensitive material containing a leuco dye, a developer and a decoloring agent is dissolved in a volatile solvent and the solvent is dried below the glass transition point Tg of the temperature-sensitive material. It was found that a material having a high crystallization rate and a decolorized state in an amorphous state can be produced by using the above.

Examples of the solvent rapid evaporation method include a freeze-drying method, a spray drying method, a vacuum drying method, and a cold air drying method for a temperature-sensitive material consisting of a leuco dye, a color developer, and a decolorizing agent dissolved in a volatile solvent. Can be applied. In either method, the volatile solvent can be rapidly volatilized. Although it depends on the drying rate, if it is below the glass transition point, the temperature-sensitive material does not crystallize, so that even a material that easily crystallizes can be made amorphous. As the volatile solvent, a solvent having high volatility and capable of dissolving the leuco dye, the developer and the decoloring agent can be used. Specifically, ketones such as acetone, methyl ethyl ketone and cyclohexanone, esters such as ethyl acetate, methyl acetate, ethyl propionate and methyl propionate, ethers such as dimethyl ether and tetrahydrofuran, non-polar solvents such as hexane, benzene and toluene. Etc. can be used.

The paint containing the temperature-sensitive material produced by the above method is above the glass transition point of the temperature-sensitive material and has a melting point when heated from a temperature below the glass transition point of the temperature-sensitive material to the melting point at a heating rate of 30 ° C./min. It develops color at temperatures below and decolorizes at the melting point of the temperature sensitive material. A material having a high crystallization rate (coloring rate) develops color at a temperature equal to or higher than the glass transition point and lower than the melting point regardless of whether the heating rate is slow or fast. On the other hand, a material with a slow crystallization rate (color development rate) develops color at a temperature above the glass transition point and below the melting point when the heating rate is slow, but does not develop color when the heating rate is high and at the melting point. Melt. Therefore, when heated from a temperature below the glass transition point of the temperature-sensitive material to the melting point at a heating rate of 30 ° C./min, the color is developed at a temperature equal to or higher than the glass transition point of the temperature-sensitive material and below the melting point, and the temperature-sensitive material is developed. It can be said that the material that decolorizes at the melting point is a material having a high crystallization rate (color development rate). By using a material having a high crystallization rate, the printing speed in laser marking can be improved.

Further, in the DSC measurement, when the temperature-sensitive material is heated from the temperature below the glass transition point to the melting point at a heating rate of 30 ° C./min, the temperature at the temperature above the glass transition point of the temperature-sensitive material and below the melting point is felt. It is preferable to observe the exothermic peak derived from the crystallization of the warm material.

As already explained, in the material having a high crystallization rate, an exothermic peak derived from crystallization is observed in the temperature range above the glass transition point and below the melting point regardless of whether the temperature rise rate is slow or fast in the DSC measurement. .. On the other hand, for a material having a slow crystallization rate, an exothermic peak derived from crystallization is observed when the temperature rise rate is slow in DSC measurement, but an exothermic peak derived from crystallization is observed when the temperature rise rate is high. It melts at the melting point without appearing. Therefore, when heated at a heating rate of 30 ° C./min, a material in which an exothermic peak derived from crystallization of the temperature-sensitive material is observed at a temperature above the glass transition point of the temperature-sensitive material and below the melting point is a crystal. It can be said that it is a material with a high crystallization rate.

From the viewpoint of improving the laser marking speed, when the temperature-sensitive material is heated from a temperature below the glass transition point to the melting point at a heating rate of 100 ° C./min, it appears at a temperature above the glass transition point of the temperature-sensitive material and below the melting point. It is more preferable to color and decolorize at the melting point of the temperature sensitive material.

The speed of spot heating by a laser varies depending on the laser output and the spot area, but for example, when a high power laser (500 W) is used to heat a diameter of 14 mm, the speed becomes about 6000 ° C./min. However, the rate of spot heating actually applied to the base material to which the heat-sensitive paint is applied takes into consideration the thickness of the paint, the thickness of the base material, the spot area, the thermal conductivity of the paint and the materials constituting the base material, and further. It is necessary to consider the heating rate and heat relaxation rate. Considering these points, for example, when a 10 W CO ₂ laser is applied to a substrate having a thickness of 100 μm and a heat-sensitive paint applied to the substrate to a diameter of 1 mm, the heating rate of spot heating by the laser becomes about 1000 ° C./min. It is presumed that it will be. Therefore, when spot heating is performed with a laser at a heating rate of 1000 ° C./min from a temperature below the glass transition point of the temperature-sensitive material to the melting point, color development occurs at a temperature above the glass transition point of the temperature-sensitive material and below the melting point. It is more preferable to do so.

(Leuco dye)
The leuco dye is an electron-donating compound, and conventionally known dyes for pressure-sensitive copying paper and heat-sensitive recording paper can be used. For example, triphenylmethanephthalide, fluorane, phenothiazine, indrillphthalide, leukooramine, spiropyran, rhodamine lactam, triphenylmethane, triazene, spirophthalanxanthene, naphtholactam, Azomethine type and the like can be mentioned. Specific examples of the leuco dye include 9- (N-ethyl-N-isopentylamino) spiro [benzo [a] xanthene-12,3'-phthalide] and 2-methyl-6- (Np-tolyl-N-). Ethylamino) Fluoran 6- (diethylamino) -2-[(3-trifluoromethyl) anilino] xanthene-9-spiro-3'-phthalide, 3,3-bis (p-diethylaminophenyl) -6-dimethylamino Phenyl, 2'-anilino-6'-(dibutylamino) -3'-methylspiro [phthalide-3,9'-xanthene], 3- (4-diethylamino-2-methylphenyl) -3- (1-ethyl) -2-Methylindole-3-yl) -4-azaphthalide, 1-ethyl-8- [N-ethyl-N- (4-methylphenyl) amino] -2,2,4-trimethyl-1,2-dihydro Spiro [11H-chromeno [2,3-g] quinoline-11,3'-phthalide can be mentioned.

One kind or a combination of two or more kinds of leuco dyes may be used for one temperature sensitive material.

(Color developer)
The color developer changes the structure of the leuco dye and causes color development by contacting with the electron-donating leuco dye. As the color developer, a known color developer used for heat-sensitive recording paper, pressure-sensitive copying paper, and the like can be used. Specific examples of such a developer include benzyl 4-hydroxybenzoate, 2,2'-biphenol, 1,1-bis (3-cyclohexyl-4-hydroxyphenyl) cyclohexane, and 2,2-bis (3). -Cyclohexyl-4-hydroxyphenyl) propane, bisphenol A, bisphenol F, bis (4-hydroxyphenyl) sulfide, paraoxybenzoic acid ester, phenols such as galvanic acid ester and the like can be mentioned. The color developer is not limited to these, and may be any compound that is an electron acceptor and can change the color of the leuco dye. In addition, metal salts of carboxylic acid derivatives, salicylic acid and salicylic acid metal salts, sulfonic acids, sulfonates, phosphoric acids, phosphoric acid metal salts, acidic phosphoric acid esters, acidic phosphoric acid ester metal salts, phosphites, sulphite. Metal salts and the like may be used. In particular, those having high compatibility with leuco dyes and decoloring agents described later are preferable, and organic coloring agents such as 2,2'-bisphenol, bisphenol A, and gallic acid esters are preferable.

Two or more kinds of color-developing agents may be combined with one temperature-sensitive material. The color density at the time of coloration of the leuco dye can be adjusted by combining with a color developer. The amount of the developer to be used is selected according to the desired color density. For example, it may be selected within the range of about 0.1 to 100 parts by weight with respect to 1 part by weight of the leuco dye.

(Decolorizing agent)
The decoloring agent is a compound capable of dissociating the bond between the leuco dye and the color developer, and is a compound capable of controlling the color development temperature of the leuco dye and the color developer. Generally, in the temperature range in which the leuco dye is colored, the decolorizing agent is solidified in a phase-separated state. Further, in the temperature range in which the leuco dye is in the decolorizing state, the decoloring agent is melted, and the function of dissociating the bond between the leuco dye and the color developer is exhibited. As the decoloring agent, as the material of the decoloring agent, a wide range of materials capable of dissociating the bond between the leuco dye and the color developer can be used. Various materials can be decolorants if the polarity is low and the leuco dye does not show color developability and the polarity is high enough to dissolve the leuco dye and the developer. Among them, when used as a decoloring agent in a paint for laser marking, a material that easily crystallizes is preferable as the decoloring agent. Typically, hydroxy compounds, ester compounds, peroxy compounds, carbonyl compounds, aromatic compounds, aliphatic compounds, halogen compounds, amino compounds, imino compounds, N-oxide compounds, hydroxyamine compounds, nitro compounds, azo compounds, diazos. Various organic compounds such as compounds, hydrangea compounds, ether compounds, oil and fat compounds, sugar compounds, peptide compounds, nucleic acid compounds, alkaloid compounds, and steroid compounds can be used. Specifically, tricaprin, isopropyl myristate, m-tolyl acetate, diethyl sebacate, dimethyl adipate, 1,4-diacetoxybutane, decyldecanoate, diethyl phenylmalonate, diisobutyl phthalate, triethyl citrate, phthal. Benzyl butyl acid, butyl phthalyl butyl glycolate, methyl N-methylanthranylate, ethyl anthranylate, 2-hydroxyethyl salicylate, methyl nicotinate, butyl 4-aminobenzoate, methyl p-torylate, 4-nitrobenzoic acid Ethyl, 2-phenylethyl phenylacetate, benzyl silicate, geranyl acetate, dimethyl succinate, dimethyl sebacate, diethyl oxalacetate, monoolein, butyl palmitate, ethyl stearate, methyl palmitate, stearic acid Methyl, linaryl acetate, di-n-octyl phthalate, benzyl benzoate, diethylene glycol dibenzoate, methyl p-anisate, m-tolyl acetate, cinnamyl silicate, 2-phenylethyl propionate, butyl stearate, myristic acid Ethyl, methyl myristate, methyl anthranilate, neryl acetate, isopropyl palmitate, ethyl 4-fluorobenzoate, cyclanderate (isomer mixture), butopyronoxyl, ethyl 2-bromopropionate, tricaprylin, ethyl levulinate, hexadecyl palmitate , Ethyl acetate, 1,1-ethanediol diacetate, dimethyl arsenate, tristea, methyl acetylsalicylate, benzaldiasetate, methyl 2-benzoylbenzoate, ethyl 2,3-dibromobutyrate, 2-furan Ethyl carboxylate, ethyl acetopylbate, ethyl vanirate, dimethyl itacone, methyl 3-bromobenzoate, monoethyl adipate, dimethyl adipate, 1,4-diacetoxybutane, diethylene glycol diacetate, ethyl palmitate, terephthal Diethyl acid, phenyl propionate, phenyl stearate, 1-naphthyl acetate, methyl behenate, methyl arachidate, methyl 4-chlorobenzoate, methyl sorbate, ethyl isonicotinate, dimethyl dodecanoate, methyl heptadecanoate, α -Ethyl cyanosilicate, N-phenylglycine ethyl, diethyl itacone, methyl picolinate, methyl isonicotinate, DL-methyl mandelate, 3-aminobenzoate Chill, Methyl 4-methylsalicylate, diethyl benzilidenmalate, Isoamyl DL-mandelate, Triethyl methanetricarboxylate, diethyl formaminomalonate, 1,2-bis (chloroacetoxy) ethane, methyl pentadecanoate, ethyl arachidate, 6 -Ethyl bromohexanate, monoethyl pimelliate, hexadecyl lactate, ethyl benzylate, mephenpyr-diethyl, procaine, dicyclohexyl phthalate, 4-tert-butylphenyl salicylate, isobutyl 4-aminobenzoate, butyl 4-hydroxybenzoate, tri Palmitin 1,2-diacetoxybenzene, dimethyl isophthalate, monoethyl fumarate, methyl vanirate, methyl 3-amino-2-thiophenecarboxylate, etomidate, cloquintoset-mexil, methyl benzylate, diphenyl phthalate, benzoate Phyl acid, propyl 4-aminobenzoate, ethylene glycol dibenzoate, triacetin, ethyl pentafluoropropionate, methyl 3-nitrobenzoate, 4-nitrophenyl acetate, methyl 3-hydroxy-2-naphthoate, trimethyl succinate, Ethyl 3-hydroxybenzoate, methyl 3-hydroxybenzoate, trimebtin, 4-methoxybenzyl acetate, pentaerythritol tetraacetate, methyl 4-bromobenzoate, ethyl 1-naphthalene acetate, 5-nitro-2-flualdehydedia Setato, ethyl 4-aminobenzoate, propylparaben, 1,2,4-triacetoxybenzene, methyl 4-nitrobenzoate, diethylacetamide malonate, valetamate bromide, 2-naphthyl benzoate, dimethyl fumarate, adifenin Hydrochloride, benzyl 4-hydroxybenzoate, ethyl 4-hydroxybenzoate, vinyl butyrate, vitamin K4, methyl 4-iodoide benzoate, methyl 3,3-dimethylacrylate, propyl asbestosate, 1,4-diacetoxybenzene Diethyl mesosilicate, dimethyl 1,4-cyclohexanedicarboxylate (cis-, trans-mixture), triethyl 1,1,2-ethanetricarboxylate, dimethyl hexafluoroglutarate, amyl benzoate, ethyl 3-bromobenzoate , 5-bromo-2-chloroethyl benzoate, bis (2-ethylhexyl) phthalate, diethyl allylmalonate, diethyl bromomalonate, diethyl ethoxymethylenemalonate, diethyl ethylmalonate, fu Diethyl maleate, diethyl maleate, diethyl malonate, diethyl phthalate, dimethyl 1,3-acetone dicarboxylate, dimethyl phthalate, ethyl 3-aminobenzoate, ethyl benzoate, ethyl 4- (dimethylamino) benzoate, Ethyl nicotinate, ethyl phenylpropiorate, ethyl pyridine-2-carboxylate, ethyl 2-pyridyl acetate, ethyl 3-pyridyl acetate, methyl benzoate, ethyl phenylacetate, amyl 4-hydroxybenzoate, 2,5-diacetoxy Toluene, ethyl 4-oxazolcarboxylate, trimethyl 1,3,5-cyclohexanetricarboxylate (cis-, trans-mixture), methyl 3- (chlorosulfonyl) -2-thiophenecarboxylate, pentaerythritol disteaert, lauric acid Benzyl, diethyl acetylenedicarboxylate, phenyl methacrylate, benzyl acetate, dimethyl glutarate, ethyl 2-oxocyclohexanecarboxylate, ethyl phenylcyanoacetate, ethyl 1-piperazin carboxylate, methyl benzoylate, methyl phenylacetate, phenyl acetate, Diethyl succinate, tributyrin, diethyl methylmalonate, dimethyl arsenate, diethyl 1,1-cyclopropanedicarboxylic acid, dibenzyl malonate, methyl 4-tert-butylbenzoate, ethyl 2-oxocyclopentanecarboxylate, cyclohexanecarboxylic acid Methyl, 4-methoxyphenylacetate, methyl 4-fluorobenzoylacetate, dimethyl maleate, methyl terephthalaldehyde, ethyl 4-bromobenzoate, methyl 2-bromobenzoate, methyl 2-iodobenzoate, 3-iodobenzoate Ethyl acid, ethyl 3-furancarboxylate, diallyl phthalate, benzyl bromoacetate, dimethyl bromomalonate, methyl m-tolurate, diethyl 1,3-acetone dicarboxylate, methyl phenylpropiolate, 1-naphthyl butyrate, o-toluyl Ethyl 2-oxocyclopentanecarboxylate, isobutyl benzoate, ethyl 3-phenylpropionate, di-tert-butyl malonate, dibutyl sebacate, diethyl adipate, diethyl terephthalate, dipropyl phthalate, 1, 1 -Etandiol diacetate, diisopropyl adipate, diisopropyl fumarate, ethyl silicate, 2-cyano-3, 2-ethylhexyl 3-diphenylacrylate, neopentylglycoldiacrilate, g. Riorain, ethyl benzoyl acetate, ethyl p-anisate, diethyl sverate, sorbitan tristearate, sorbitan monostearate, stearate amide, glycerol monostearate, glycerol distearate, 3- (tert-butoxycarbonyl) phenylboronic acid , Lasecadotril, 4-[(6-acryloyloxy) hexyloxy] -4'-cyanobiphenyl, 2- (dimethylamino) vinyl 3-pyridylketone, stearyl acrylate, ethyl 4-bromophenylacetate, dibenzyl phthalate, 3 , 5-Dimethoxymethylbenzoate, eugenol acetate, didodecyl 3,3'-thiodipropionate, vanillin acetate, diphenyl carbonate, ethyl oxanate, methyl terephthalaldehyde, dimethyl 4-nitrophthalate, acetic acid (4-nitrobenzoyl) Ethyl, dimethyl nitroterephthalate, methyl 2-methoxy-5- (methylsulfonyl) benzoate, methyl 3-methyl-4-nitrobenzoate, dimethyl 2,3-naphthalenedicarboxylate, bis adipate (2-ethylhexyl), 4'-acetoxyacetophenone, trans-3-benzoylacrylate ethyl, coumarin-3-carboxylate ethyl, BATTA tetraethyl ester, 2,6-dimethoxybenzoate methyl, iminodicarboxylate di-tert-butyl, p-benzyloxybenzoic acid Benzyl acid, methyl 3,4,5-trimethoxybenzoate, methyl 3-amino-4-methoxybenzoate, diethylene glycol distearate, ditetradecyl 3,3'-thiodipropionate, ethyl 4-nitrophenylacetate, 4-chloro -3-Methyl nitrobenzoate, 1,4-dipropionyloxybenzene, dimethyl terephthalate, ethyl 4-nitrosilicate, dimethyl 5-nitroisophthalate, triethyl 1,3,5-benzenetricarboxylate, N- ( 4-Aminobenzoyl) -diethyl L-glutamate, 2-methyl-1-naphthyl acetate, 7-acetoxy-4-methylcoumarin, methyl 4-amino-2-methoxybenzoate, 4, 4'-diacetoxybiphenyl, 5 -Ester compounds such as dimethyl aminoisophthalate 1,4-dihydro-2, 6-dimethyl-3, 5-pyridinedicarboxylate diethyl, 4,4'-biphenyldicarboxylate dimethyl, cholesterol, cholesteryl bromide, β-estradiol , Methyl androstengio Cholesterol, pregnenolone, cholesterol benzoate, cholesterol acetate, cholesterol linoleate, cholesterol palmitate, cholesterol stearate, cholesterol n-octanoate, cholesterol oleate, 3-chlorocholesterol, trans-cholesterol silicate, cholesterol decanoate , Hydrocholesterol, Cholesterol laurate, Cholesterol butyrate, Cholesterol formate, Cholesterol heptanate, Cholesterol hexanoate, Cholesterol hydrogen oxalate, Cholesterol myristate, Cholesterol propionate, Cholesterol valerate, Cholesterol hydrogen phthalate, Phenylacetic acid Cholesterol, Cholesterol Chlorogitate, Cholesterol 2,4-dichlorobenzoate, Cholesterol Peralgonate, Cholesterol Nonyl Carbonate, Cholesterol Heptyl Carbonate, Cholesterol Oleyl Carbonate, Cholesterol Methyl Carbonate, Cholesterol Ethyl Carbonate, Cholesterol Isopropyl Carbonate, Cholesterol Butyl Carbonate, Cholesterol Isobutyl Carbonate, Cholesterol Amyl Carbonate, Cholesterol n-octyl Carbonate, Cholesterol Hexil Carbonate, Allyl Estrenol, Altrenogest,
9 (10) -dehydronandrolone, estradiol, ethynyl estradiol, estradiol, estradiol benzoate, β-estradiol 17-cipionate, 17-estradiolate β-estradiol, α-estradiol, β-estradiol, 17-heptanate, guestlinone, Mestranol, 2-methoxy-β-estradiol, nandrolone, (-)-norgestrel, kinestrol, trenborone, tiboron, stanolone, androsterone, avirateron, avirateron acetate, dehydroepiandrosterone, dehydroepiandrosterone acetate, ethisterone, epi Androsterone, 17β-hydroxy-17-methylandrosta-1,4-dien-3-one, methylandrostendiol, methyltestosterone, Δ9 (11) -methyltestosterone, 1α-methylandrostan-17β-ol-3 -On, 17α-methylandrostan-17β-all-3-one, stanozolol, testosterone, testosterone propionate, altrenogest, 16-dehydropregnenolone acetate, 16,17-epoxypregnenolone acetate, 11α-hydroxyprogesterone, 17α -Hydroxyprogesterone caproate, 17α-hydroxyprogesterone, pregnenolone acetate, 17α-hydroxyprogesterone acetate, megestrol acetate, medroxyprogesterone acetate, pregnenolone acetate, 5β-pregnenolone-3α, 20α-diol, budesonide, corticosterone , Cortisone acetate, cortisone, cortexolone, deoxycorticosterone acetate, defrazacoat, hydrocortisone acetate, hydrocortisone, 17-hydrocortisone butyrate, 6α-methylpregnenolone, pregnenolone, predonison, sodium acetate, sodium deoxycholate Examples thereof include steroid compounds such as methyl, methyl hyodeoxycholate, β-cholestanol, cholesterol-5α, 6α-epoxide, diosgenin, ergosterol, β-citosterol, stigmasterol and β-citosterol acetate. From the viewpoint of compatibility with leuco dyes and color developers, it is preferable to contain these compounds. Further, two or more kinds of these decoloring agents may be combined. The freezing point and melting point can be adjusted by combining with a decolorizing agent.

The temperature sensitive material contains at least the above-mentioned leuco dye, color developer, and decolorizing agent. However, when a material having a color-developing effect and a decolorizing effect is used in one molecule, the color-developing agent and the decoloring agent may be omitted. Further, as long as the ability to change the color by crystallization is maintained, a material other than the leuco dye, the color developer, and the decolorizing agent can be included. For example, by including a pigment, it is possible to change the color at the time of decolorization and the time of color development.

(Particle)
In the paint according to the first embodiment, amorphous particles containing at least a leuco dye, a developer and a decoloring agent constituting the temperature-sensitive material need to be independently present in the paint.

As a method for forming a paint that satisfies the above conditions, there are a method in which amorphous particles are directly dispersed in a paint and a method in which the amorphous particles are microencapsulated and the microcapsules are dispersed in the paint.

For example, the temperature-sensitive material can be made into fine particles by forming an amorphous material containing a leuco dye, a color developer and a decoloring agent by a solvent rapid evaporation method and then pulverizing the material. The method of micronization is not particularly limited, and various pulverization methods such as a mortar, a ball mill, a rod mill, a bead mill, and a homogenizer can be used. When the spray drying method is used in the solvent rapid evaporation method, it can be used as it is as particles.

The particle size of the amorphous particles is not particularly limited, but is preferably not less than the resolution of visual observation and the camera, and is preferably 20 μm or less from the viewpoint of visibility. On the other hand, it has been experimentally shown that if the particle size is too small, the color-developing property is impaired, and it is preferably 100 nm or more.

Further, the leuco dye, the color developer and the decoloring agent may be dispersed in the paint by encapsulating them in microcapsules. By microencapsulating, the environmental resistance of the composition to humidity and the like is improved, and storage stability and discoloration characteristics can be stabilized. Further, when the paint is prepared, it is possible to suppress the influence of the leuco dye, the color developer, and the decoloring agent on the compounds such as other resin agents and additives. As used herein, microencapsulation means protecting the inclusions with a resin wall membrane.

The resin film used for the microcapsules includes a urea resin film composed of a polyvalent amine and a carbonyl compound, a melamine resin film composed of a melamine / formarin prepolymer, a methylol melamine prepolymer, and a methylated melamine prepolymer, and a polyvalent isocyanate and a polyol compound. Examples thereof include a urethane resin film composed of a urethane resin film, an amide resin film composed of a polybasic acid chloride and a polyvalent amine, and a vinyl resin film composed of various monomers such as vinyl acetate, styrene, (meth) acrylic acid ester, acrylonitrile, and vinyl chloride. However, it is not limited to these. Further, by performing the surface treatment of the formed resin film and adjusting the surface energy at the time of making ink or paint, it is possible to perform additional treatment such as improving the dispersion stability of the microcapsules.

From the viewpoint of storage stability, the diameter of the microcapsules is preferably in the range of about 0.1 to 100 μm, more preferably in the range of 0.1 to 1 μm.

<Additives>
Additives may be added to the temperature-sensitive material and the paint to the extent that the temperature-sensitive function is not affected. As the additive, for example, a resin, a dye, a pigment, a heat storage material, a high heat conduction material, and a light absorption material can be used. By adding a dye or pigment to the temperature sensitive material, it is possible to adjust the hue at the time of color development and / or at the time of decolorization. By adding a heat-storing material such as a heat-storing capsule or a high heat-conducting material to a temperature-sensitive material or paint, the outside of the temperature-sensitive material reaches the developing temperature or the decoloring temperature, and the temperature-sensitive material itself changes color. It is possible to adjust the heat energy required for the paint.

By adding the light absorbing material to the temperature sensitive material or the paint, it is possible to increase the thermal energy applied to the temperature sensitive material at a specific wavelength, and it is possible to reduce the required laser output.

<Laser marking method>
When laser marking with the paint according to the first embodiment, the wavelength, output, and irradiation time of the laser beam are set to a temperature-sensitive material (a combination of leuco dye, a developer, and a decoloring agent), additives, and microcapsules. It is adjusted appropriately depending on the type of resin coating used for.

In the present embodiment, since printing is performed by utilizing the heat generated by the paint due to the irradiation of the laser beam, the wavelength of the laser beam may be selected from the temperature-sensitive material and the wavelength absorbed by the paint. Since many organic materials are used in paints, it is preferable that the laser beam is infrared rays having a large absorption. The output of the laser beam is not particularly limited. By selecting a wavelength at which the temperature sensitive material and the paint have a large absorption, the paint can be discolored and markings can be formed even when a low power laser beam is used.

[Second Embodiment]
<Thermal paint>
The paint according to the second embodiment contains two types of temperature-sensitive materials (hereinafter, referred to as first temperature-sensitive material and second temperature-sensitive material) having different color tones at the time of color development in order to make the marking multicolored. .. In the following embodiments, the description of the same configuration as that of the first embodiment will be omitted.

As the first temperature-sensitive material and the second temperature-sensitive material, the temperature-sensitive material used in the first embodiment can be used. The first temperature-sensitive material and the second temperature-sensitive material have different glass transition points or color development temperatures. In the DSC measurement, when the temperature rising rate becomes high, the glass transition point and the temperature of the crystallization start temperature Ta approach each other.

Hereinafter, the color change of the paint using the two types of temperature-sensitive materials will be described with reference to FIGS. 4 and 5. FIG. 4 is a graph showing the relationship between the temperature and the color density of the two types of temperature-sensitive materials used in the paint according to the second embodiment. In FIG. 4, the vertical axis is the color density, the horizontal axis is the temperature, Ta 1 is the color developing temperature of the first temperature sensitive material, Ta ₂ is the color developing temperature of the second temperature sensitive material, and T _{d 1} is the first temperature sensitive material. The decoloring temperature (melting point) of the material, T _d2 is the decoloring temperature (melting point) of the second temperature-sensitive material, and the shaded area is the operating temperature range of the marking object.

As shown in FIG. 4, the first temperature-sensitive material and the second temperature-sensitive material have different developing colors and different thermal energies required for discoloration. The first temperature-sensitive material begins to develop color at a temperature T _a1 and decolorizes at a temperature T _d1 . The second temperature-sensitive material begins to develop color at a temperature T _a1 and decolorizes at a temperature T _d2 . Further, the decoloring temperature and the developing color temperature of the first and second temperature-sensitive materials have a relationship of _Ta1 <T _a2 <T _d1 <T _d2 . The relationship may be T _a1 <T _a2 <T _d2 <T _{d 1} .

FIG. 5 is a schematic diagram showing a state of color change of the paint containing the first temperature-sensitive material and the second temperature-sensitive material. Before irradiation with the laser beam, both the first temperature-sensitive material and the second temperature-sensitive material are in a decolorized state (FIG. 5A).

Thermal energy that is greater than the heat energy ( _Ta1 ) required for the first temperature-sensitive material to develop color and less than the thermal energy of heat _Ta2 required for the second temperature-sensitive material to develop color. When applied to the paint by a laser beam, the first temperature sensitive material develops color, but the second temperature sensitive material remains decolorized. Therefore, only the first temperature-sensitive material exhibits a developed color (FIG. 5 (b)).

When the heat energy of the heat (T _a2 ) required for the second temperature-sensitive material to develop color or more and less than T _d1 and T _d2 is applied to the paint by the laser beam, the first temperature-sensitive material and the first. 2 Both temperature-sensitive materials develop color. Therefore, both the first temperature-sensitive material and the second temperature-sensitive material exhibit a developed color (FIG. 5 (c)).

In this way, it is possible to make the markings multicolored by mixing a plurality of temperature-sensitive materials. Even if the paint once developed is decolorized at a temperature higher than T _d1 and T _d2 , if a material with a high crystallization rate is used, it will crystallize in the cooling process, so the decolorized state should be maintained. It is difficult. Therefore, irreversible printing is possible.

The heat-sensitive paint has a melting point T _d1 of the first temperature-sensitive material and a second temperature-sensitive material from the lowest temperature T _g of the glass transition point T _g1 of the first temperature-sensitive material and the glass transition point T _g2 of the second temperature-sensitive material. When heated to a lower temperature T _m of the melting point T _d2 at a heating rate of 30 ° C./min, the color develops in two stages in a temperature range of the temperature T _g or more and less than the temperature T _m . Further, in the differential scanning calorimetry (DSC), when heating from the temperature T _g to the temperature T _m at a heating rate of 30 ° C./min, the temperature is derived from crystallization in the temperature range of the temperature T _g or more and less than the temperature T m. It is preferable to observe two exothermic peaks. For example, when the characteristic temperature of the first temperature-sensitive material and the second temperature-sensitive material has a relationship of T _g1 <T _g2 <T _d1 <T _d2 , crystallization occurs in a temperature range of T _g1 or more and less than T _g2 . It is preferable that the first exothermic peak derived from the exothermic peak is observed, and the second exothermic peak derived from crystallization is observed in the temperature range of T _{g 2} or more and less than T _{d 1} .

Further, when spot heating is performed with a laser at a heating rate of 1000 ° C./min from a temperature of T _g to a temperature of T _m , the color is developed in two stages in a temperature range of the temperature T _g or more and less than the temperature T _m . It is more preferable to make it a feature.

In the present embodiment, the paint containing two kinds of temperature-sensitive materials has been described, but the heat-sensitive paint may contain two or more kinds of temperature-sensitive materials.

<Laser marking method>
As the laser marking method, the same method as in the first embodiment can be used.

In the case of the second embodiment in which the paint contains a plurality of temperature-sensitive materials, the color tone of the heat-sensitive paint is controlled by irradiating the laser light by changing the output of the laser light or the irradiation time without changing the wavelength of the laser light. It is preferable to do so. When the temperature-sensitive materials have absorption in the same wavelength region, the color tone of the coating film can be adjusted by changing the output or irradiation time with only one wavelength laser by using a laser with a wavelength in which all the temperature-sensitive materials have absorption. Can be controlled.

Therefore, it is preferable that the first temperature-sensitive material and the second temperature-sensitive material are colored by a laser beam having the same wavelength.

[Third Embodiment]
<Thermal paint>
The laser marking paint according to the third embodiment has the same configuration as that of the second embodiment except that the color development time of the temperature sensitive material is changed. In the third embodiment, the crystallization speed of the first temperature-sensitive material and the second temperature-sensitive material, that is, the color development time is different. For example, as the first temperature-sensitive material, when the temperature rise rate is less than _RA (for example, the temperature rise rate is 100 ° C./min), the color is developed by crystallization, but the temperature rise rate _RA (for example, the temperature rise rate is 100 ° C./min). In the above, a material that reaches the melting point without crystallization and does not develop color is used. As the second temperature-sensitive material, a material that crystallizes and develops color even at a temperature rise rate _RA (for example, a temperature rise rate of 100 ° C./min) or higher is used.

The color change of the paint will be described with reference to FIGS. 6 to 8. FIG. 6 is a graph showing the relationship between the temperature and the color density of the first temperature-sensitive material and the second temperature-sensitive material contained in the paint at a temperature rise rate _RA (for example, a temperature rise rate of 100 ° C./min) or less. FIG. 7 is a graph showing the relationship between the temperature and the color density of the first temperature-sensitive material and the second temperature-sensitive material contained in the paint at a temperature rise rate _RA (for example, a temperature rise rate of 100 ° C./min) or less. In FIGS. 6 and 7, the vertical axis is the color density, the horizontal axis is the temperature, _Ta1 is the color developing temperature of the first temperature-sensitive material, _Ta2 is the developing temperature of the second temperature-sensitive material, and T _d1 is the first. 1 The decoloring temperature (melting point) of the temperature-sensitive material, T _d2 is the decoloring temperature (melting point) of the second temperature-sensitive material, and the shaded area is the operating temperature range of the marking object.

As shown in FIG. 6, when the temperature rise rate is less than _RA (for example, the temperature rise rate is 100 ° C./min), the first and second temperature-sensitive materials have different color development temperatures and are necessary for discoloration. The heat energy is different. The first temperature-sensitive material begins to develop color at a temperature T _a1 and decolorizes at a temperature T _d1 . The second temperature-sensitive material begins to develop color at a temperature T _a1 and decolorizes at a temperature T _d2 . Further, the decoloring temperature and the developing color temperature of the first and second temperature-sensitive materials have a relationship of _Ta1 <T _a2 <T _d1 <T _d2 . The relationship may be T _a1 <T _a2 <T _d2 <T _{d 1} . This configuration is the same as in the first embodiment.

On the other hand, when the temperature rise rate _RA (for example, the temperature rise rate is 100 ° C./min) or higher, as shown in FIG. 7, the first temperature-sensitive material does not develop color, and only the second temperature-sensitive material develops a color temperature. The color develops at T _a2 or higher.

FIG. 8 is a schematic diagram showing a state of color change of the paint according to the third embodiment. The first heat-sensitive material and the second temperature-sensitive material are materials that change from a decolorized state to a developed state by applying heat energy, and both the first and second temperature-sensitive materials are used before laser beam irradiation. It is in a decolorized state (FIG. 8 (a)).

Thermal energy that is greater than or equal to the heat energy of the heat ( _{Ta1) required for the first temperature-sensitive material to develop color and less than the thermal energy of the heat (Ta2 )} required for the second temperature-sensitive material to develop color. When the paint is applied to the paint with a laser beam so that the temperature rise rate is less than _RA (for example, the temperature rise rate is 100 ° C./min), only the first temperature-sensitive material develops color and the second temperature-sensitive material develops color. It remains decolorized. Therefore, only the first temperature-sensitive material exhibits a developed color (FIG. 8 (b)).

The heat energy equal to or higher than the heat energy (T _a2 ) required for the second temperature-sensitive material to develop color and less than T _d1 and T _d2 is applied to the temperature rise rate _RA (for example, the temperature rise rate 100 ° C./min). ) Is applied to the paint with a laser beam so that the color of the paint is developed by both the first temperature-sensitive material and the second temperature-sensitive material. Therefore, both the first temperature-sensitive material and the second temperature-sensitive material exhibit a developed color (FIG. 8 (c)).

The heat energy of the heat (T _a2 ) required for the second temperature-sensitive material to develop color and less than T _d1 and T _d2 is applied to the temperature rise rate _RA (for example, the temperature rise rate 100 ° C./min). ) As described above, when the paint is applied with a laser beam, the first temperature-sensitive material does not develop color, and only the second temperature-sensitive material develops color. Therefore, only the second temperature-sensitive material exhibits a developed color (FIG. 8 (d)).

As described above, by including the temperature-sensitive materials having different crystallization speeds (color development speeds), it is possible to print three kinds of colors with two kinds of temperature-sensitive materials.

Further, in order to control the crystallization rate, it is possible to mix not only the temperature-sensitive material having a high crystallization rate as shown in FIG. 2 but also the temperature-sensitive material having a slow crystallization rate as shown in FIG.

<Laser marking method>
As the laser marking method, the same method as in the first embodiment can be used.

In the case of the third embodiment in which the paint contains a plurality of temperature-sensitive materials, the laser light is irradiated by changing the output or irradiation time of the laser light without changing the wavelength of the laser light as in the second embodiment. , It is preferable to control the color tone of the heat-sensitive paint.

Further, in order to change the rate of temperature rise of the coating material by the laser beam, the output of the laser beam may be controlled.

Next, the present invention will be described in more detail with reference to examples. The present invention is not limited to these examples.

<Making thermal paint>
As a temperature-sensitive material, as a leuco dye, 2'-methyl-6'-(N-p-trill-N-ethylamino) spiro [isobenzofuran-1 (3H), 9'-[9H] xanthene] -3-one (RED520 manufactured by Yamada Chemical Co., Ltd.) was used by 1 part by weight, octyl gallate manufactured by Tokyo Chemical Industry Co., Ltd. was used by 1 part by weight as a developer, and methyl androstendiol manufactured by Tokyo Chemical Industry Co., Ltd. was used by 100 parts by weight as a decolorizing agent.

Leuco dye, color developer, and decolorizing agent constituting the temperature sensitive material are mixed with 1000 parts by weight of tetrahydrofuran as a volatile solvent, and the tetrahydrofuran is vacuum dried at 0 ° C., which is below the glass transition point of the temperature sensitive material. A temperature-sensitive material in an amorphous and decolorized state was produced. Amorphous particles of the temperature-sensitive material were produced by crushing the prepared temperature-sensitive material in a mortar. The temperature sensitive material was colorless and transparent.

Next, a heat-sensitive paint was prepared as follows using the prepared temperature-sensitive material. A copolymer of polyvinyl alcohol and polyvinyl acetate having a number average molecular weight (Mn) of 10,000 as pure water and a resin in a container provided with stirring blades (number of repetitions of polyvinyl alcohol unit: number of repetitions of polyvinyl acetate unit ≈ 36: 64, the hydroxyl value was 285), and the amorphous particles of the temperature-sensitive material were added and mixed for about 1 hour to prepare a paint containing the temperature-sensitive material.

<DSC measurement>
The prepared paint is heated by differential scanning calorimetry (DSC) from 0 ° C, which is below the glass transition point of the temperature-sensitive material, to 220 ° C, which is above the melting point of the temperature-sensitive material, at a heating rate of 30 ° C / min. did. As a result, an exothermic peak derived from crystallization was observed around 80 ° C., and an endothermic peak derived from the melting point was observed around 195 ° C.
Then, the prepared paint was cooled at a temperature lowering rate of 20 ° C./min by differential scanning calorimetry (DSC). As a result, an exothermic peak derived from crystallization was observed in the temperature lowering process. From the above results, it was confirmed that the temperature-sensitive material used in Example 1 was a material that was easily crystallized.

<Confirmation of color development function>
The prepared paint was heated at a heating rate of 30 ° C./min from 0 ° C., which is a temperature below the glass transition point of the temperature-sensitive material, to 220 ° C., which is a temperature equal to or higher than the melting point of the temperature-sensitive material. As a result, it was confirmed that the color developed red at 80 ° C. and disappeared at the melting point of 195 ° C.

(Comparative Example 1)
The temperature-sensitive material was cooled by a liquid quenching method to prepare a temperature-sensitive material in the same manner as in Example 1 except that an attempt was made to produce amorphous particles.

Specifically, the same leuco dye, color developer, and decolorizing agent as in Example 1 are mixed, heated to 220 ° C., which is above the melting point of the temperature-sensitive material, melted, and then the sample container is placed in liquid nitrogen. Was rapidly cooled by impregnating with. The temperature-sensitive material after cooling was colored red. It is probable that it crystallized and developed color during the cooling process. Therefore, it was not possible to obtain a temperature-sensitive material in an amorphous and decolorized state.

As described above, from Example 1 and Comparative Example 1, the leuco dye, the color developer, and the decoloring agent constituting the temperature-sensitive material are dissolved in a highly volatile organic solvent, and the solvent is evaporated below the glass transition point. As a result, it was found that an amorphous temperature-sensitive material having a high crystallization rate can be obtained.

As a temperature-sensitive material, 1 part by weight of 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (CVL manufactured by Yamada Chemical Industry Co., Ltd.) as a leuco dye, and octyl gallate manufactured by Tokyo Chemical Industry Co., Ltd. as a color developer. A temperature-sensitive material and a paint were prepared in the same manner as in Example 1 except that 1 part by weight was used and 100 parts by weight of 17α-hydroxyprogesterone octatate manufactured by Tokyo Chemical Industry Co., Ltd. was used as a decoloring agent. The prepared paint was subjected to DSC measurement in the same manner as in Example 1 to confirm the color development function.

In the DSC measurement, an exothermic peak derived from crystallization was observed around 110 ° C. and an endothermic peak derived from the melting point was observed around 215 ° C. in the heating process. An exothermic peak due to crystallization was observed during the temperature lowering process. From the above results, it was confirmed that the temperature-sensitive material used in Example 2 was a material that was easily crystallized.

Further, the produced paint was heated at a heating rate of 30 ° C./min from 0 ° C., which is a temperature below the glass transition point of the temperature-sensitive material, to 220 ° C., which is a temperature equal to or higher than the melting point of the temperature-sensitive material. As a result, it was confirmed that the color developed in blue at 110 ° C. and disappeared at the melting point of 215 ° C.

(Comparative Example 2)
The temperature-sensitive material was cooled by a liquid quenching method to prepare a temperature-sensitive material in the same manner as in Example 2 except that an attempt was made to produce amorphous particles.

Specifically, the same leuco dye, color developer, and decolorizing agent as in Example 2 are mixed, heated to 220 ° C., which is above the melting point of the temperature-sensitive material, melted, and then the sample container is placed in liquid nitrogen. Was rapidly cooled by impregnating with. The temperature-sensitive material after cooling was colored blue. It is probable that it crystallized and developed color during the cooling process. Therefore, it was not possible to obtain a temperature-sensitive material in an amorphous and decolorized state.

(Comparative Example 3)
As a temperature-sensitive material, 1 part by weight of 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (CVL manufactured by Yamada Chemical Industry Co., Ltd.) as a leuco dye, and octyl gallate manufactured by Tokyo Chemical Industry Co., Ltd. as a color developer. A temperature-sensitive material and a heat-sensitive paint were prepared in the same manner as in Example 1 except that 1 part by weight of vitamin K4 manufactured by Tokyo Chemical Industry Co., Ltd. was used as a decoloring agent. The prepared paint was subjected to DSC measurement in the same manner as in Example 1 to confirm the color development function.

The temperature-sensitive material of Comparative Example 3 could be in an amorphous and decolorized state even by the liquid quenching method. The leuco dye, the color developer, and the decolorizing agent that compose each of the temperature-sensitive materials were mixed, and the sample container was rapidly cooled by impregnating the sample container into liquid nitrogen from 220 ° C., which is above the melting point of the temperature-sensitive material. Amorphous particles were obtained by crushing the temperature-sensitive material in a mortar. The produced amorphous particles were colorless and transparent.

In the DSC measurement, only the endothermic peak derived from the melting point was observed in the heating process. In addition, no exothermic peak was observed during the temperature lowering process. From this result, it was confirmed that the third temperature-sensitive paint is a material that is difficult to crystallize.

Further, the produced paint was heated at a heating rate of 30 ° C./min from 0 ° C., which is a temperature below the glass transition point of the temperature-sensitive material, to 220 ° C., which is a temperature equal to or higher than the melting point of the temperature-sensitive material. As a result, the melting point reached 120 ° C. without developing color. Since the crystallization rate is slow, it is considered that the color did not develop because it did not crystallize at a heating rate of 30 ° C./min.

<Preparation of temperature sensitive paint>
A paint containing both the temperature-sensitive materials prepared in Examples 1 and 2 was prepared by the following method.

A copolymer of polyvinyl alcohol and polyvinyl acetate having a number average molecular weight (Mn) of 10,000 as pure water and a resin in a container provided with stirring blades (number of repetitions of polyvinyl alcohol unit: number of repetitions of polyvinyl acetate unit ≈ 36: 64, the hydroxyl value is 285), the amorphous temperature-sensitive material particles prepared in Example 1 and the amorphous temperature-sensitive material particles prepared in Example 2 are charged and mixed for about 1 hour. A temperature-sensitive paint containing two types of temperature-sensitive materials was prepared.

The prepared paint was impregnated with a base material (paper) for 10 minutes each to absorb the paint on the surface of the base material. Then, the base material was taken out from the paint and the pure water was volatilized to prepare a base material in which the paint was absorbed.

<Confirmation of color development function>
Thermal energy was applied to the prepared substrate with a hot plate. FIG. 9 shows a state of color change due to heat energy of the paint according to the embodiment. The temperature was raised at 30 ° C./min, and when the surface temperature of the base material reached 80 ° C., which is the developing color temperature _Ta1 of the first temperature-sensitive material, the heated portion of the base material turned red. On the other hand, when the heating rate is increased to 100 ° C./min and heat energy is applied at high speed, when the surface temperature of the base material reaches 110 ° C., which is the developing color temperature _Ta2 of the second temperature-sensitive material, The heated part of the base material turned blue. Further, when the discolored substrate was placed in an environment of 20 ° C., it was confirmed that the discolored state was maintained.

Next, regarding the prepared base material, the discoloration function of the paint was confirmed when the laser was irradiated at a low output and when the laser was irradiated at a high output.

First, heat energy was applied to the prepared substrate by irradiating the produced substrate with a CO ₂ laser having an output of 0.5 W. When the surface temperature of the base material that absorbed the paint reached 80 ° C., which is the color development temperature _Ta1 of the first temperature-sensitive material, the laser-irradiated portion of the base material turned red.

Next, for the prepared substrate, the laser output was increased to 1.5 W and heat energy was applied at high speed. It was confirmed that when the surface temperature of the base material that absorbed the paint reached 110 ° C., which is the developing temperature _Ta2 of the second temperature-sensitive material, the laser-irradiated portion of the base material turned blue. FIG. 10 shows a state of color change of the paint according to the embodiment when the laser output is increased and heated to 110 ° C. The heating rate up to 110 ° C. was 100 ° C./min.

Further, when the laser irradiation was stopped and the base material once discolored was placed in an environment of 20 ° C., it was confirmed that the discolored state was maintained.

From the above, it was confirmed that by using the paint according to this example, it is possible to discolor in multiple colors by laser irradiation.

Claims (8)

A heat-sensitive paint that contains a heat-sensitive material that changes color with heat .
The temperature-sensitive material includes a first temperature-sensitive material and a second temperature-sensitive material having different crystallization rates from each other.
The first temperature-sensitive material contains amorphous first particles mixed with a leuco dye, a color developer and a decoloring agent, and when the temperature is raised below a predetermined temperature rise rate _RA , the color development temperature _Ta1 It is a material that develops color in a temperature range equal to or higher than the decolorization temperature T _d1 and does not develop color when the temperature is raised above _RA .
The second temperature-sensitive material contains amorphous second particles mixed with a leuco dye, a color developer and a decoloring agent, and in both cases of temperature rise below RA and temperature rise above _{RA .} , A material that develops color in a temperature range of more than the developing color temperature T _a2 and less than the decoloring temperature T _d2 .
It is characterized in that there is a relationship of "T _a1 <T _a2 <T _d1 <T _d2 " or "T _a1 <T _a2 <T _d2 <T _d1 " between the T _a1 , T _d1 , T _a2 , and T _d2 . Thermal paint. In the heat-sensitive paint according to claim 1 ,
When the differential scanning calorimetry for raising the temperature of the temperature- sensitive material to the higher temperature of T _d1 or T _d2 under the condition of less than _RA is performed, the amorphous first particles and the non-amorphous particles are measured. Two exothermic peaks derived from the crystallization of the second crystalline particle were observed .
When differential scanning calorimetry is performed in which the temperature is raised to the higher temperature of T _d1 or T _d2 under the conditions of _RA or higher, one exothermic peak derived from the crystallization of the amorphous second particles is obtained. A heat-sensitive paint characterized by being observed . In the heat-sensitive paint according to claim 1 or 2 .
A heat-sensitive paint characterized in that when the temperature rise rate and the reached temperature of the temperature-sensitive material are controlled, the color develops in three stages. In the heat-sensitive paint according to any one of claims 1 to 3 ,
The amorphous first particle and the amorphous second particle are heat-sensitive paints characterized in that they are developed by a laser beam having the same wavelength. In the heat-sensitive coating material according to any one of claims 1 to 4 .
A thermal coating material, wherein the amorphous first particles and / or the amorphous second particles are microencapsulated. It is a laser marking method using heat- sensitive paint.
The heat-sensitive paint is the heat-sensitive paint according to any one of claims 1 to 5.
By irradiating the heat-sensitive paint with the laser light while controlling the output or irradiation time without changing the wavelength of the laser light , the temperature rise rate and the reached temperature of the irradiation region are controlled , so that the color tone of the heat-sensitive paint can be adjusted. A laser marking method characterized by control. In the laser marking method according to claim 6,
The amorphous first particle and the amorphous second particle dissolve the leuco dye, the developer and the decolorizing agent in a volatile solvent, respectively, and then volatilize at a temperature equal to or lower than the glass transition point. A laser marking method characterized by being produced by a solvent rapid evaporation method for drying a sex solvent. In the laser marking method according to claim 6 or 7.
The laser marking method, wherein the laser beam is an infrared laser beam.

Images