Two-color heat-sensitive material as well as preparation method and application thereof

Abstract

The invention discloses a two-color heat-sensitive material as well as a preparation method and application thereof, and relates to the technical field of heat-sensitive color development materials. The invention provides a double-color heat-sensitive material. The double-color heat-sensitive material is prepared from the following components in parts by weight: 20 to 50 parts of color developing agent dispersion liquid, 5 to 15 parts of dye precursor microcapsule emulsion A, 15 to 45 parts of dye precursor microcapsule emulsion B, 5 to 15 parts of adhesive and 5 to 30 parts of filler. According to the invention, the dye precursor microcapsule emulsion A and the dye precursor microcapsule emulsion B with specific structures are mixed, and the two microcapsule emulsions are matched for use, so that two high-definition hues can be printed at the same time based on the magnitude of printing energy by utilizing different softening points of wall materials of the two microcapsule emulsions; the two-color heat-sensitive material has excellent hue isolation (high-definition low-temperature color development hue and clear high-temperature color development hue can be obtained at the same time) and aging resistance, the problems that an existing two-color heat-sensitive material can only achieve two-color printing under high-energy-level printing and printing is not clear are solved, and the application field of the two-color heat-sensitive material is widened.

Description

Technical Field

[0001] The invention relates to the technical field of thermosensitive chromogenic materials, in particular to a dual-color thermosensitive material and a preparation method and application thereof. Background Art

[0002] Thermal materials are widely used in the retail, catering, express delivery, medical, financial and other industries. With the promotion of these applications, it is necessary to record images in multiple colors. In particular, the advantage of recording images in multiple colors is that the text to be emphasized can be recorded with a different hue from other parts. However, traditional thermal materials are monotonous in color and cannot clearly highlight the key content.

[0003] Application number CN117227345A discloses a two-color thermal printing paper, which sequentially coats a pre-coating layer, a high melting point thermal layer, a low melting point thermal layer and a protective layer on a paper base. It utilizes the 30°C difference in the melting points of the two layers of dyes in the high melting point and low melting point thermal layers to avoid interference in printing and color development and achieve two-color separation. Application number CN114277610A discloses a two-color inkless printing paper isolation protective layer coating and its preparation method and two-color inkless printing paper. In order to solve the problem that when the color development temperatures of two different color thermal layers are similar, the colors are easily affected by each other and cannot display their respective colors, an isolation protective layer is added between the high melting point thermal layer and the low melting point thermal layer to avoid the two coating colors from affecting each other. When the melting points of the two layers of dyes in the high melting point thermosensitive layer and the low melting point thermosensitive layer of the above-mentioned two-color thermal paper differ by 30°C, they need to be coated in two layers; when the color developing temperatures of the thermal layers are similar, an isolation layer needs to be coated between the high melting point thermosensitive layer and the low melting point thermosensitive layer. These processes for preparing two-color thermal paper are cumbersome and the structure is complex.

[0004] Therefore, preparing a two-color thermosensitive material with excellent hue isolation and aging resistance is an urgent problem to be solved. Summary of the invention

[0005] Based on this, the purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a two-color thermal sensitive material with excellent color separation and aging resistance.

[0006] To achieve the above-mentioned purpose, in the first aspect of the present invention, the present invention provides a two-color thermosensitive material, comprising the following components in parts by weight: 20-50 parts of a developer dispersion, 5-15 parts of a dye precursor microcapsule emulsion A, 15-45 parts of a dye precursor microcapsule emulsion B, 5-15 parts of an adhesive, and 5-30 parts of a filler; the particle size D90 of the dye precursor microcapsule emulsion A is 0.6-2 μm; the dye precursor microcapsule emulsion A comprises a core material and a wall material, the core material is the dye precursor A, the wall material is polyurethane, and the softening point of the wall material of the dye precursor microcapsule emulsion A is 70-100°C; the particle size D90 of the dye precursor microcapsule emulsion B is 0.6-1 μm; the dye precursor microcapsule emulsion B comprises a core material and a wall material, the core material is the dye precursor B, the wall material is polyurea, and the softening point of the wall material of the dye precursor microcapsule emulsion B is ≥130°C.

[0007] Preferably, the particle size D90 of the dye precursor microcapsule emulsion A is 0.6-1 μm.

[0008] The present invention mixes a dye precursor microcapsule emulsion A with a specific structure and a dye precursor microcapsule emulsion B, uses the two microcapsule emulsions in combination, utilizes the different softening points of the wall materials of the two microcapsule emulsions, and can realize printing of two high-definition hues simultaneously based on the level of printing energy. The present invention has excellent hue isolation (capable of simultaneously obtaining a high-definition low-temperature color-developing hue and a clear high-temperature color-developing hue) and aging resistance, overcomes the problem that the existing two-color thermal paper needs to be printed at a higher energy level to realize two-color printing and the printing is unclear, and broadens the application field of the two-color thermal material.

[0009] The present invention uses an interfacial polymerization method to microencapsulate a dye precursor in a polyurethane shell to form a dye precursor microcapsule emulsion A, thereby avoiding direct contact between a colorless dye and a developer; in addition, the soft and hard segments of the microcapsule polyurethane shell are matched and unsaturated double bonds are added to reduce its softening point (increase the heat sensitivity of the microcapsule) and enhance its waterproof performance, so as to achieve the purpose of high-definition color development at low temperatures (70°C-100°C) and have excellent aging resistance. The present invention uses an interfacial polymerization method to microencapsulate a dye precursor in a polyurea shell to form a high-temperature dye precursor microcapsule, so as to achieve the purpose of high-definition color development at high temperatures (≥130°C).

[0010] Preferably, the weight ratio of the dye precursor microcapsule emulsion A to the dye precursor microcapsule emulsion B is 1:(2-3).

[0011] The inventors found in the actual experimental process that the weight ratio of the dye precursor microcapsule emulsion A and the dye precursor microcapsule emulsion B affects the hue isolation and aging resistance of the finally prepared two-color thermosensitive material. When the above-mentioned specific weight ratio is adopted, the hue isolation and aging resistance of the finally prepared two-color thermosensitive material are better.

[0012] The inventors found in the actual experimental process that the dye precursor microcapsule emulsion A (low-temperature dye precursor microcapsule emulsion) and the dye precursor microcapsule emulsion B (high-temperature dye precursor microcapsule emulsion) at the above-mentioned specific weight ratio can simultaneously obtain two different hues of thermosensitive materials based on the high and low printing heat energy levels, that is, various hues can be combined, wherein the low-temperature dye precursor microcapsule emulsion A in the low-temperature region presents one hue when developing color, and the two dye precursor microcapsules simultaneously develop color in the high-temperature region to present a superimposed hue different from the former. For example, in the case of a combination of red and black, the red color is first developed in the low temperature region (70°C-100°C, i.e., low printing heat or energy level), and the superimposed color of red and black, i.e., black, is developed in the high temperature region (≥130°C, i.e., high printing heat or energy level); in the case of a combination of blue and black, the blue color is first developed in the low temperature range, and the superimposed color of blue and black, i.e., black, is developed in the high temperature region (≥130°C, i.e., high printing heat or energy level); in the case of a combination of yellow and black, the yellow color is first developed. The color is developed in the low temperature range, and the superimposed color of yellow plus black is black in the high temperature area (≥130℃, i.e. high printing heat or energy level); in the case of a combination of red and blue, red is first developed in the low temperature range, and the superimposed color of red plus blue is purple in the high temperature area (≥130℃, i.e. high printing heat or energy level); in the case of a combination of yellow and blue, yellow is first developed in the low temperature range, and the superimposed color of yellow plus blue is green in the high temperature area (≥130℃, i.e. high printing heat or energy level).

[0013] Preferably, the dye precursor A and the dye precursor B are two dye precursors exhibiting different hues.

[0014] Preferably, the dye precursor may use any known compound, and specifically the following compounds may be mentioned:

[0015] <Black dye precursor>

[0016] 2-phenylamino-3-methyl-6-diethylfluoran;

[0017] 2-phenylamino-3-methyl-6-dibutylaminofluoran;

[0018] 3-Diethylamino-6-methyl-7-phenylaminofluoran;

[0019] 3-Diethylamino-6-methyl-7-benzylaminofluoran;

[0020] 3-Diethylamino-6-methyl-7-dibenzylaminofluoran;

[0021] 3-Diethylamino-6-ethoxyethyl-7-anilinofluoran;

[0022] 3-Diethylamino-7-(m-trifluoromethylanilino)fluoran;

[0023] 3-Diethylamino-7-(o-chloroanilino)fluoran;

[0024] 3-Diethylamino-7-(p-chloroanilino)fluoran;

[0025] 3-Diethylamino-7-(o-fluoroanilino)fluoran;

[0026] <Blue dye precursor>

[0027] 3,3-bis(4-dimethylaminophenyl)-6-dimethylaminophenyl peptide;

[0028] 3-Diethylamino-6-methyl-7-n-octylaminofluoran;

[0029] 3-Diethylamino-6-methyl-7-benzylaminofluoran;

[0030] 3-Diethylamino-7-dibenzylaminofluoran;

[0031] 3-Diethylamino-6-methyl-7-diphenylmethylaminofluoran;

[0032] <Green dye precursor>

[0033] 3-Diethylamino-7-anilinofluoran;

[0034] 3-Diethylamino-6-methyl-7-dibenzylanilinofluoran;

[0035] 3-(N-ethyl-N-hexylamino)-7-anilinofluoran;

[0036] 3-Diethylamino-7-cyclohexylaminofluoran;

[0037] 3-(N-p-Tolyl-N-ethylamino)-7-(N-methyl-N-phenylamino)fluoran;

[0038] <Red dye precursor>

[0039] 3,3-Bis(N-octyl-2-methylindolyl)phthalide fluoran;

[0040] 3-Diethylamino-7-chlorofluoran;

[0041] 3-(N-ethyl-p-toluamino)-7-methylfluoran;

[0042] 3-Diethylamino-6-methyl-7-chlorofluoran;

[0043] 3-(N-ethyl-N-isopentyl)amino-7-phenoxyfluoran;

[0044] 3-Diethylamino-6,8-dimethylfluoran;

[0045] 3-Di(n-butyl)amino-6-methyl-7-bromofluoran;

[0046] 3-Toluamino-7-methylfluoran;

[0047] 3-Toluamino-7-ethylfluoran;

[0048] <Yellow dye precursor>

[0049] 3,6-dimethoxyfluoran;

[0050] N,N-dimethyl-4-[2-[2-(octyloxy)phenyl]-6-phenyl-4-pyridyl]-aniline;

[0051] The above dye precursors can be used alone or simultaneously to provide different hues.

[0052] Preferably, the developer dispersion liquid comprises a developer and a dispersing aid, wherein the weight ratio of the developer to the dispersing aid is (1-2): (0.5-1).

[0053] Preferably, the developer can use an organic developer known in the field of thermosensitive materials; the developer is at least one of bisphenol A, bisphenol sulfones, hydroxyphenyl aryl sulfones, 4-hydroxyphenyl aryl sulfonates, zinc salts of aromatic carboxylic acids such as salicylic acid; in one embodiment, the bisphenol A is at least one of 4,4'-isopropylidene diphenol, 4,4'-cyclohexylene diphenol, and 1,7-bis(hydroxyphenylthio)-3,5-dioxepane; the bisphenol sulfones are 4,4'-dihydroxydiphenyl sulfone, 4,4'-sulfonyl diphenol, 2,4'-sulfonyl diphenol, bis(3-1-butyl-4-hydroxy-6-methylphenyl) sulfone, bis(3-ethyl-4-hydroxyphenyl) sulfone, bis(3-propyl-4-hydroxyphenyl) sulfone, bis(3-methyl-4-hydroxyphenyl) sulfone, bis(2-isopropyl-4-hydroxyphenyl) sulfone The hydroxyphenyl aryl sulfones are at least one of 2,4-diphenylsulfone phenol, 4-hydroxy-4′-n-propoxydiphenyl sulfone and 4-hydroxy-4′-n-butoxydiphenyl sulfone. The 4-hydroxyphenyl aryl sulfonates are at least one of 4-hydroxyphenyl p-toluenesulfonate, 4-hydroxyphenyl methylenesulfonate, 4-hydroxyphenyl p-chlorobenzenesulfonate and 4-hydroxyphenyl-2′-naphthalenesulfonate. The zinc salts of aromatic carboxylic acids such as salicylic acid are at least one of 4-(n-octyloxycarbonylamino)salicylic acid zinc, 4-[2-(p-methylphenoxy)ethoxy]salicylic acid zinc, 4-[3-(p-toluenesulfonyl)propoxy]salicylic acid zinc and 5-[p-(2-p-methoxyphenoxyethoxy)cumyl]salicylic acid.

[0054] Preferably, the dispersing aid is a mixture of polyvinyl alcohol, silicate and deionized water; the silicate is at least one of aluminum silicate, calcium silicate, lithium silicate, lithium aluminum metasilicate, lead silicate, potassium silicate and sodium silicate; further preferably, the silicate is sodium silicate.

[0055] Preferably, the weight ratio of the polyvinyl alcohol to the silicate is (10-50):(1-10).

[0056] Polyvinyl alcohol promotes the uniform dispersion of solid particles in liquids and prevents particle agglomeration, thereby improving the stability and uniformity of the system. Silicates have good dispersibility and can further effectively disperse and stabilize suspended particles through the interaction between their molecules and developer molecules, as well as their adsorption ability on the surface of suspended particles, preventing them from agglomerating and precipitating, thereby improving grinding efficiency to meet the requirements of micro-particle size.

[0057] Preferably, the developer dispersion is ground and dispersed to a particle size of 0.2≤D90≤1μm. Too large a particle size will affect the color clarity performance, while too small a particle size will increase the production cost. After the developer dispersion is ground to the required particle size, it is heat-sterilized at 70℃-80℃ for 1-3h.

[0058] Preferably, the adhesive is at least one of vinyl acetate polymer, vinyl acetate copolymer, polyvinyl alcohol, polyacrylic acid latex, polyurethane, epoxy resin, and styrene-butadiene latex.

[0059] Preferably, the filler is at least one of aluminum silicate, talc, kaolin, calcined kaolin, magnesium carbonate, calcium carbonate, barium carbonate, titanium dioxide, zinc oxide, silicon dioxide, and aluminum hydroxide.

[0060] Preferably, the method for preparing the dye precursor microcapsule emulsion A comprises the following steps:

[0061] (1) mixing oligomer polyol, polyisocyanate, unsaturated double bond compound, organic solvent and dye precursor A uniformly to obtain an oil phase;

[0062] (2) The protective colloid and the emulsifier are mixed uniformly to obtain an aqueous phase, and the oil phase and the aqueous phase are homogenized and emulsified. During the emulsification process, a catalyst, a chain extender, a neutralizer and a free radical initiator are added respectively to obtain the dye precursor microcapsule emulsion A.

[0063] Preferably, in step (1), the weight ratio of oligomer polyol, polyisocyanate, unsaturated double bond compound, organic solvent and dye precursor A is oligomer polyol: polyisocyanate: unsaturated double bond compound: organic solvent: dye precursor A = (4-6): 1: (1-2): (2-4): (8-16);

[0064] And / or, in the step (2), the weight ratio of the protective colloid to the emulsifier is (2-4): (0.5-2);

[0065] And / or, in step (2), the catalyst accounts for 0.05-0.5% of the total mass percentage of the water phase and the oil phase solution, the chain extender accounts for 0.5-1.5% of the total mass percentage of the water phase and the oil phase solution, the neutralizer accounts for 0.1-1% of the total mass percentage of the water phase and the oil phase solution, and the free radical initiator accounts for 0.1-1% of the total mass percentage of the water phase and the oil phase solution.

[0066] Preferably, the raw materials for preparing the dye precursor microcapsule emulsion A include at least one of the following (a)-(j):

[0067] (a) The oligomer polyol is a polyether polyol and / or a polyester polyol; preferably, the oligomer polyol is ethylene glycol, neopentyl glycol, 1,2-propylene glycol, 2,2-dimethyl-1,3-propylene glycol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol and 1,2-cyclohexanedimethanol, as well as polyols such as fatty acid triols, such as ethylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7 -heptanediol, 1,8-octanediol, propylene glycol, 2,3-dihydroxybutane, 1,2-dihydroxybutane, 1,3-dihydroxybutane, 2,2-dimethyl-1,3-propanediol, 2,4-pentanediol, 2,5-hexanediol, 3-methyl-1,5-pentanediol, 1,4-cyclohexanedimethanol, dihydroxycyclohexane, diethylene glycol, 1,2,6-trihydroxyhexane, styrene glycol, 1,1,1-trimethylolpropane, hexanetriol, pentaerythritol or glycerol, at least one of adipic acid polyester polyol; further preferably, the oligomer polyol is adipic acid polyester polyol;

[0068] (b) The polyisocyanate is phenylene diisocyanate, 2,6-toluene diisocyanate, 2,4-toluene diisocyanate, naphthalene-1,4-diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, xylylene diisocyanate, tetramethylxylene diisocyanate, 4 ,4'-diphenylpropane diisocyanate, hexamethylene diisocyanate, 1,2-butanediisocyanate, cyclohexene-1,2-diisocyanate, cyclohexene-1,4-diisocyanate, 4,4',4"-triphenylmethane triisocyanate, toluene-2,4,6-triisocyanate, diphenylmethane-4,4'-diisocyanate; preferably, the polyisocyanate is 2,4-toluene diisocyanate;

[0069] (c) the unsaturated double bond compound is at least one of pentaerythritol triacrylate, glycerol allyl ether, terminal hydroxyl polybutadiene, and diacetone acrylamide; preferably, the unsaturated double bond compound is terminal hydroxyl polybutadiene;

[0070] (d) the organic solvent is at least one of methyl ether, ethyl ether, acetone, ethyl ether, dichloromethane, methyl formate, ethyl acetate, methyl acetate, butyl acetate, ethyl butyrate, ketone, ethyl ketone, acetone, dichloromethane, 1-chlorobutane, and chloropropane; preferably, the organic solvent is diethyl ether;

[0071] (e) the protective colloid is polyvinyl alcohol;

[0072] (f) the emulsifier is at least one of polyoxyethylene fatty alcohol ether (AEO), glyceryl monostearate (GMS), dodecylphenol polyoxyethylene ether (DPEO), octylphenol polyoxyethylene ether (OPE), polyoxyethylene sorbitan monooleate (Tween 80), and sorbitan monooleate (Span 80); further preferably, the emulsifier is a mixture of polyoxyethylene sorbitan monooleate (Tween 80) and sorbitan monooleate (Span 80), with a weight ratio of (10-20):1;

[0073] (g) the catalyst is at least one of stannous octoate, stannous oleate, dibutyltin dilaurate, triethylenediamine, triethylenediamine, dimethylethanolamine, dimethylethanolamine, N-methylmorpholine, N,N-dimethylcyclohexylamine, and tetramethylethylenediamine; preferably, the catalyst is dibutyltin dilaurate;

[0074] (h) the chain extender is at least one of 1,4-butanediol, 1,6-hexanediol, glycerol, trimethylolpropane, diethylene glycol (DEG), and triethylene glycol; preferably, the chain extender is 1,6-hexanediol;

[0075] (i) the neutralizing agent is at least one of sodium bicarbonate, sodium acetate, sodium pyrophosphate, sodium carbonate, hydrochloric acid, phosphoric acid, formic acid, acetic acid, AMP-95, diethanolamine, triethanolamine, and aminoacetic acid; preferably, the neutralizing agent is triethanolamine;

[0076] (j) The free radical initiator is at least one of azobisisobutyronitrile, azobisisoheptylnitrile, dibenzoyl peroxide, potassium persulfate, and ammonium persulfate; preferably, the free radical initiator is ammonium persulfate.

[0077] The oligomer polyol, chain extender, unsaturated double bond compound and the like in the dye precursor microcapsule emulsion A are used together as the soft segment of the polyurethane wall material, wherein the oligomer polyol is used as the main soft segment; and the polyisocyanate is used as the hard segment of the polyurethane wall material.

[0078] The invention controls the ratio of the soft segment and the hard segment of the polyurethane wall material in the dye precursor microcapsule emulsion A and the particle size D90 of the dye precursor microcapsule emulsion A finally prepared by selecting specific raw material components and dosages, so that the softening point of the wall material of the dye precursor microcapsule emulsion A finally prepared is 70-100 DEG C, the particle size D90 is 0.6-1μm, and the finally prepared two-color thermosensitive material has better hue isolation and aging resistance.

[0079] Preferably, the method for preparing the dye precursor microcapsule emulsion B comprises the following steps:

[0080] S1, mixing polyisocyanate, silane coupling agent containing isocyanate active group, organic solvent and dye precursor B to obtain oil phase;

[0081] S2, mixing the protective colloid and the emulsifier evenly to obtain an aqueous phase, homogenizing the oil phase and the aqueous phase, and adding a chain extender during the emulsification process to obtain the dye precursor microcapsule emulsion B.

[0082] Preferably, in step S1, the weight ratio of the polyisocyanate, the silane coupling agent containing isocyanate active groups, the organic solvent, and the dye precursor B is polyisocyanate: the silane coupling agent containing isocyanate active groups: the organic solvent: the dye precursor B = (8-16): 1: (1-4): (8-16);

[0083] And / or, in step S2, the weight ratio of the protective colloid to the emulsifier is (2-6): (0.5-5);

[0084] And / or, in step S2, the chain extender accounts for 0.1-1% of the total mass percentage of the aqueous phase and the oil phase solution.

[0085] Preferably, the raw materials for preparing the dye precursor microcapsule emulsion B include at least one of the following (m)-(r):

[0086] (m) the polyisocyanate is an aromatic isocyanate; preferably, the polyisocyanate is at least one of toluene diisocyanate, diphenylmethane diisocyanate, and naphthalene 1,5-diisocyanate;

[0087] (n) the silane coupling agent containing an isocyanate reactive group is at least one of 3-isocyanate propyl trimethoxy silane, 3-isocyanate propyl triethoxy silane, isocyanate methyl trimethoxy silane, and 3-isocyanate propyl methyl dimethoxy silane;

[0088] (o) the organic solvent is at least one of methyl ether, ethyl ether, acetone, ethyl ether, dichloromethane, methyl formate, ethyl acetate, methyl acetate, butyl acetate, ethyl butyrate, ketone, ethyl ketone, acetone, dichloromethane, 1-chlorobutane, and chloropropane; preferably, the organic solvent is diethyl ether;

[0089] (p) the protective colloid is polyvinyl alcohol;

[0090] (q) the emulsifier is at least one of polyoxyethylene fatty alcohol ether (AEO), polyoxyethylene sorbitan monooleate (Tween 80), glyceryl monostearate (GMS), dodecylphenol polyoxyethylene ether (DPEO), octylphenol polyoxyethylene ether (OPE), and sorbitan monooleate (Span 80); further preferably, the emulsifier is a mixture of polyoxyethylene sorbitan monooleate (Tween 80) and sorbitan monooleate (Span 80), with a weight ratio of (10-20):1;

[0091] (r) The chain extender is an amine chain extender; preferably, the chain extender is at least one of 3,3′-dichloro-4,4′-diaminodiphenylmethane, 3,5-diaminoisobutyl p-chlorobenzoate, diethyltoluenediamine, 3,5-dimethylthiotoluenediamine, ethanolamine, diethanolamine, and triethanolamine.

[0092] The invention selects specific raw material components and dosages, so that the softening point of the wall material of the dye precursor microcapsule emulsion B finally prepared is ≥130°C, the particle size D90 is 0.6-1μm, and the finally prepared two-color thermosensitive material has better hue isolation and aging resistance.

[0093] In the second aspect of the present invention, the present invention provides a method for preparing the dual-color thermosensitive material, which is as follows: the developer dispersion, dye precursor microcapsule emulsion A, dye precursor microcapsule emulsion B, adhesive, and filler are uniformly mixed according to weight parts to obtain the dual-color thermosensitive material.

[0094] In the third aspect of the present invention, the present invention provides the use of the two-color thermal-sensitive material in the preparation of two-color thermal paper and / or film.

[0095] In the fourth aspect of the present invention, the present invention provides a two-color thermal paper and / or film, wherein a substrate, a two-color chromogenic layer, and a protective layer are arranged in sequence; the protective layer comprises the following components in parts by weight: 20-50 parts of filler, 30-60 parts of adhesive, 5-20 parts of lubricant, and 1-3 parts of cross-linking agent.

[0096] Preferably, the substrate is a paper base and / or a polymer film.

[0097] Preferably, the paper base is at least one of coated paper, coated base paper and white cardboard.

[0098] Preferably, the polymer film is a film made of at least one of polyethylene (PE), polyvinyl chloride (PVC), polystyrene (PS), polyester (PET), polypropylene (PP), and polyimide (PI).

[0099] Preferably, the filler is at least one of aluminum silicate, talc, kaolin, calcined kaolin, magnesium carbonate, calcium carbonate, barium carbonate, titanium dioxide, zinc oxide, silicon dioxide, and aluminum hydroxide; the adhesive is at least one of vinyl acetate polymer or copolymer, polyvinyl alcohol, polyacrylate, polyurethane, epoxy resin, and styrene-butadiene latex; the lubricant is at least one of paraffin emulsion, carnauba wax, polyethylene wax, zinc stearate emulsion, and zinc stearamide emulsion; the cross-linking agent is at least one of aziridine, glyoxal, acetic acid, and acetonitrile.

[0100] Preferably, the present invention provides a method for preparing the two-color thermal paper, which is specifically as follows: coating a two-color chromogenic layer and a protective layer on a paper base layer in sequence to obtain the two-color thermal paper.

[0101] The coating method is at least one of coating rod coating, blade coating, air knife coating, curtain coating, and anilox roller coating. The coating amounts of the two-color chromogenic layer and the protective layer are 2-10 g / m 2 and 1-10g / m 2 .

[0102] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention mixes a dye precursor microcapsule emulsion A with a specific structure and a dye precursor microcapsule emulsion B, uses the two microcapsule emulsions in combination, and utilizes the different softening points of the wall materials of the two microcapsule emulsions. Based on the level of printing energy, it is possible to print out two high-definition hues at the same time, has excellent hue isolation (capable of simultaneously obtaining a high-definition low-temperature color-developing hue and a clear high-temperature color-developing hue) and aging resistance, overcomes the problem that the existing two-color thermal paper needs to be printed at a higher energy level to achieve two-color printing and the printing is unclear, and broadens the application field of two-color thermal materials. DETAILED DESCRIPTION

[0103] In order to better illustrate the purpose, technical scheme and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments. Its purpose is to understand the content of the present invention in detail, rather than to limit the present invention. All other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Unless otherwise specified, the experimental reagents and instruments designed for the implementation and comparative examples of the present invention are all commonly used ordinary reagents and instruments, which can be obtained from commercial channels. In the implementation and comparative examples, the experimental methods used are conventional methods unless otherwise specified; and unless otherwise specified, the raw materials used in parallel experiments are the same batch of raw materials.

[0104] Examples 1-10 and Comparative Examples 1-11

[0105] Example 1

[0106] The invention provides a two-color thermosensitive material, comprising the following components in parts by weight: 40 parts of a developer dispersion, 10 parts of a dye precursor microcapsule emulsion A, 15 parts of a dye precursor microcapsule emulsion B, 10 parts of an adhesive (polyacrylic acid latex-BASF Vinofan W 3109ap), 25 parts of a filler (30% kaolin-Zhong African kaolin Maoming new material in mass concentration), and 50 parts of deionized water;

[0107] The preparation method of the developer dispersion is as follows: 30 parts of a polyvinyl alcohol aqueous solution (Kuraray PVA-203) with a mass concentration of 15% are added to a dispersion tank for stirring, and then 60 parts of 2,4-diphenylsulfonephenol (DBSP, Wuhan Shuer Biotechnology Co., Ltd.) are added. After stirring for 30 minutes, 2 parts of sodium silicate with a concentration of 12% and 8 parts of defoaming agent BYK-024 (BYK, Germany) are added respectively, and stirred for 30 minutes; the dispersion is put into a vertical rod-cut ball mill and ground for 3 hours to a particle size D90 = 0.2-1 μm; the dispersion is transferred to an insulation tank, heated to 70°C, maintained at 70°C for thermal qualitative treatment for 1 hour, and diluted to a concentration of 40% with deionized water after natural cooling.

[0108] The preparation method of the dye precursor microcapsule emulsion A is as follows: 40 parts of 3,6-dimethoxyfluoran (yellow dye precursor, Wuhan Shuer Biotechnology Co., Ltd.), 20 parts of adipic acid polyester polyol (oligomer polyol, BASF), 5 parts of terminal hydroxyl polybutadiene (unsaturated double bond compound, Hubei Xinghengye), 5 parts of 2,4-toluene diisocyanate (polyisocyanate, Sigma-Aldrich (Shanghai)), and 10 parts of ether (organic solvent, Sigma-Aldrich (Shanghai)) are heated and dissolved (90°C) to obtain an oil phase, and the obtained oil phase is slowly added to an aqueous solution containing 10 parts of polyvinyl alcohol (Japan Kuraray PVA-203) with a mass concentration of 10% as a protective colloid and 5.5 parts of Tween with a mass concentration of 100% as an emulsifier. 80 (emulsifier, Merck Chemicals) and 0.5 parts of Span 80 (emulsifier, Merck Chemicals) with a mass concentration of 100%, the mixture was emulsified and dispersed at 90°C for 1 hour by stirring at 9000 rpm using a homogenizer, 0.1% dibutyltin dilaurate (catalyst, Merck Chemicals) and 0.9% 1,6-hexanediol (chain extender, Merck Chemicals) based on the mass percentage of the oil phase and the aqueous phase mixed solution were gradually added to carry out chain extension reaction for 2 hours, then the mixture was cooled to 40°C and neutralized with 0.5% triethanolamine (neutralizer, Merck Chemicals) based on the mass percentage of the oil phase and the aqueous phase mixed solution, 0.5% ammonium persulfate (free radical initiator, Merck Chemicals) based on the mass percentage of the oil phase and the aqueous phase mixed solution was added to the above emulsion, and the mixture was reacted at 40°C for 1 hour to obtain a dye precursor microcapsule emulsion A.

[0109] The preparation method of the dye precursor microcapsule emulsion B is as follows: 40 parts of 2-phenylamino-3-methyl-6-diethylfluoran (black dye precursor, Wuhan Shuer Biotechnology Co., Ltd.), 5 parts of ether (organic solvent, Sigma-Aldrich (Shanghai)), 40 parts of toluene diisocyanate (polyisocyanate, Merck Chemical), 5 parts of 3-isocyanate propyl trimethoxy silane (silane coupling agent containing isocyanate active group, Sigma-Aldrich (Shanghai)) are heated and dissolved (100°C) to obtain an oil phase, and the obtained oil phase is slowly added to an aqueous solution containing 6 parts of 10% by mass polyvinyl alcohol (Japan Kuraray PVA-203) as a protective colloid and 3.7 parts of 100% by mass Tween as an emulsifier. 80 (emulsifier, Merck Chemical) and 0.3 parts of Span 80 (emulsifier, Merck Chemical) with a mass concentration of 100%, use a homogenizer to stir at 8000 rpm and heat at 90°C for emulsification and dispersion for 0.5 h, slowly add 0.5% diethyltoluenediamine (chain extender, Merck Chemical) based on the mass percentage of the oil phase and the aqueous phase mixed solution, and keep the reaction at 90°C for 4 h to obtain a high-temperature dye precursor microcapsule emulsion.

[0110] The preparation method of the dual-color thermosensitive material is as follows: the developer dispersion, dye precursor microcapsule emulsion A, dye precursor microcapsule emulsion B, adhesive, filler and deionized water are uniformly mixed according to weight parts to obtain the dual-color thermosensitive material.

[0111] Example 2

[0112] The invention provides a two-color thermosensitive material. Compared with Example 1, only the raw materials for preparing a dye precursor microcapsule emulsion A are different, that is, 40 parts of 3,6-dimethoxyfluoran (a yellow dye precursor, Wuhan Shuer Biotechnology Co., Ltd.) are replaced by 20 parts of N,N-dimethyl-4-[2-[2-(octyloxy)phenyl]-6-phenyl-4-pyridyl]-aniline (a yellow dye precursor, Wuhan Shuer Biotechnology Co., Ltd.) and 20 parts of 3,6-dimethoxyfluoran (a yellow dye precursor, Wuhan Shuer Biotechnology Co., Ltd.), and the rest remain unchanged.

[0113] Example 3

[0114] The invention provides a two-color thermosensitive material. Compared with Example 1, only the raw materials for preparing a dye precursor microcapsule emulsion B are different, that is, 40 parts of 2-phenylamino-3-methyl-6-diethylfluoran (a dye precursor that develops black, Wuhan Shuer Biotechnology Co., Ltd.) are changed into 20 parts of 2-phenylamino-3-methyl-6-diethylfluoran (a dye precursor that develops black, Wuhan Shuer Biotechnology Co., Ltd.) and 20 parts of 3-diethylamino-6-methyl-7-phenylaminofluoran (a dye precursor that develops black, Wuhan Shuer Biotechnology Co., Ltd.), and the rest remain unchanged.

[0115] Example 4

[0116] The present invention provides a two-color thermosensitive material. Compared with Example 1, only in the step of preparing the developer dispersion, 60 parts of 2,4-diphenylsulfonephenol (DBSP, Wuhan Shuer Biotechnology Co., Ltd.) are replaced by 60 parts of 4,4'-isopropylidene diphenol (BPA, Wuhan Shuer Biotechnology Co., Ltd.), and the rest remain unchanged.

[0117] Example 5

[0118] The invention provides a two-color thermosensitive material. Compared with Example 1, only the proportions of oligomer polyol, polyisocyanate, unsaturated double bond compound, organic solvent and dye precursor A raw materials in the preparation process of dye precursor microcapsule emulsion A are different, which is specifically as follows: 40 parts of 3,6-dimethoxyfluoran (yellow dye precursor, Wuhan Shuer Biotechnology Co., Ltd.), 18 parts of adipic acid polyester polyol (oligomer polyol, BASF), 6 parts of terminal hydroxyl polybutadiene (unsaturated double bond compound, Hubei Xinghengye), 3 parts of 2,4-toluene diisocyanate (polyisocyanate, Sigma-Aldrich (Shanghai)), and 10 parts of ether (organic solvent, Sigma-Aldrich (Shanghai)) are heated and dissolved (90°C) to obtain an oil phase, and the rest remain unchanged.

[0119] Example 6

[0120] The invention provides a two-color thermosensitive material. Compared with Example 1, only the weight ratio of the raw materials of the monoisocyanate, the silane coupling agent containing isocyanate active groups, the organic solvent and the dye precursor B in the preparation process of the dye precursor microcapsule emulsion B is different, which is specifically as follows: 40 parts of 2-phenylamino-3-methyl-6-diethylfluoran (black dye precursor, Wuhan Shuer Biotechnology Co., Ltd.), 10 parts of ether (organic solvent, Sigma-Aldrich (Shanghai)), 36 parts of toluene diisocyanate (polyisocyanate, Merck Chemical), and 3 parts of 3-isocyanatepropyltrimethoxysilane (silane coupling agent containing isocyanate active groups, Sigma-Aldrich (Shanghai)) are heated and dissolved (100°C) to obtain an oil phase, and the rest remain unchanged.

[0121] Example 7

[0122] The present invention provides a two-color thermosensitive material. Compared with Example 1, the weight parts of the two-color thermosensitive material are different, and the two-color thermosensitive material includes the following components in weight parts: 40 parts of a developer dispersion, 8 parts of a dye precursor microcapsule emulsion A, 17 parts of a dye precursor microcapsule emulsion B, 10 parts of an adhesive (aqueous acrylic latex-BASF Vinofan W3109ap), 25 parts of a filler (30% kaolin-Central African kaolin Maoming new material in a mass concentration), and 50 parts of deionized water, and the rest remain unchanged.

[0123] Example 8

[0124] The present invention provides a two-color thermosensitive material. Compared with Example 1, the weight parts of the two-color thermosensitive material are different, and the two-color thermosensitive material comprises the following components in weight parts: 40 parts of a developer dispersion, 6.5 parts of a dye precursor microcapsule emulsion A, 18.5 parts of a dye precursor microcapsule emulsion B, 10 parts of an adhesive (aqueous acrylic latex-BASF Vinofan W3109ap), 25 parts of a filler (kaolin with a mass concentration of 30%-Zhongfei Kaolin Maoming new material), and 50 parts of deionized water, and the rest remain unchanged.

[0125] Example 9

[0126] The preparation method and steps thereof are different from those of Example 1 in that in the preparation step of dye precursor microcapsule emulsion A, 5 parts of 100% Tween 80 by mass and 0.5 parts of 100% Span 80 by mass are changed to 5.25 parts of 100% Tween 80 by mass and 0.25 parts of 100% Span 80 by mass, and the rest remain unchanged.

[0127] Example 10

[0128] The preparation method and steps thereof are different from those of Example 1 in that in the preparation step of dye precursor microcapsule emulsion A, 5 parts of 100% Tween 80 by mass and 0.5 parts of 100% Span 80 by mass are changed to 4.95 parts of 100% Tween 80 by mass and 0.55 parts of 100% Span 80 by mass, and the rest remain unchanged.

[0129] Comparative Example 1

[0130] The preparation method and steps thereof are different from those of Example 1 in that in the preparation step of dye precursor microcapsule emulsion A, 40 parts of 3,6-dimethoxyfluoran (a yellow dye precursor, Wuhan Shuer Biotechnology Co., Ltd.) are replaced with 40 parts of 2-phenylamino-3-methyl-6-diethylfluoran (a black dye precursor, Wuhan Shuer Biotechnology Co., Ltd.), and the rest remain unchanged.

[0131] Comparative Example 2

[0132] The preparation method and steps thereof are different from those of Example 1 in that in the preparation step of dye precursor microcapsule emulsion A, 5 parts of terminal hydroxyl polybutadiene are changed to 0 parts, that is, no unsaturated double bond compound is contained, and the rest remain unchanged.

[0133] Comparative Example 3

[0134] The preparation method and steps thereof are different from those of Example 1 in that in the preparation step of dye precursor microcapsule emulsion A, 0.5 parts of ammonium persulfate (free radical initiator) are changed to 0 parts, that is, no free radical initiator is contained, and the other parts remain unchanged.

[0135] Comparative Example 4

[0136] The preparation method and steps thereof are different from those of Example 1 in that in the preparation step of the developer dispersion, 2 parts of 12% sodium silicate are replaced with 0 parts, and the rest remain unchanged.

[0137] Comparative Example 5

[0138] The preparation method thereof is different from that of Example 1 in that in the preparation step of the developer dispersion, 30 parts of a polyvinyl alcohol aqueous solution with a mass concentration of 15% is replaced by 0 parts, and the rest remains unchanged.

[0139] Comparative Example 6

[0140] The preparation method and steps thereof are different from those of Example 1 in that in the preparation step of the dye precursor microcapsule emulsion A, the proportions of the oligomer polyol, the polyisocyanate, the unsaturated double bond compound, the organic solvent, and the raw materials of the dye precursor A are different, specifically as follows: 40 parts of 3,6-dimethoxyfluoran (a yellow dye precursor, Wuhan Shuer Biotechnology Co., Ltd.), 35 parts of adipic acid polyester polyol (oligomer polyol, BASF), 15 parts of terminal hydroxyl polybutadiene (unsaturated double bond compound, Hubei Xinghengye), 5 parts of 2,4-toluene diisocyanate (polyisocyanate, Sigma-Aldrich (Shanghai)), and 10 parts of ether (organic solvent, Sigma-Aldrich (Shanghai)) are heated and dissolved (90°C) to obtain an oil phase, and the rest remain unchanged.

[0141] Comparative Example 7

[0142] The preparation method and steps thereof are different from those of Example 1 in that: in the preparation step of the dye precursor microcapsule emulsion A, the proportions of the oligomer polyol, the polyisocyanate, the unsaturated double bond compound, the organic solvent, and the raw materials of the dye precursor A are different, specifically as follows: 40 parts of 3,6-dimethoxyfluoran (a yellow dye precursor, Wuhan Shuer Biotechnology Co., Ltd.), 10 parts of adipic acid polyester polyol (oligomer polyol, BASF), 3 parts of terminal hydroxyl polybutadiene (unsaturated double bond compound, Hubei Xinghengye), 5 parts of 2,4-toluene diisocyanate (polyisocyanate, Sigma-Aldrich (Shanghai)), and 10 parts of ether (organic solvent, Sigma-Aldrich (Shanghai)) are heated and dissolved (90°C) to obtain an oil phase, and the rest remain unchanged.

[0143] Comparative Example 8

[0144] The preparation method and steps thereof are different from those of Example 1 in that, compared with Example 1, only the weight ratio of the raw materials of the monoisocyanate, the silane coupling agent containing isocyanate active groups, the organic solvent, and the dye precursor B in the preparation process of the dye precursor microcapsule emulsion B is different, specifically as follows: 40 parts of 2-phenylamino-3-methyl-6-diethylfluoran (black dye precursor, Wuhan Shuer Biotechnology Co., Ltd.), 5 parts of ether (organic solvent, Sigma-Aldrich (Shanghai)), 25 parts of toluene diisocyanate (polyisocyanate, Merck Chemical), and 5 parts of 3-isocyanatepropyltrimethoxysilane (silane coupling agent containing isocyanate active groups, Sigma-Aldrich (Shanghai)) are heated and dissolved (100° C.) to obtain an oil phase, and the rest remain unchanged.

[0145] Comparative Example 9

[0146] The preparation method and steps thereof are different from those of Example 1 in that, compared with Example 1, only the weight ratio of the raw materials of the monoisocyanate, the silane coupling agent containing isocyanate active groups, the organic solvent, and the dye precursor B in the preparation process of the dye precursor microcapsule emulsion B is different, specifically as follows: 40 parts of 2-phenylamino-3-methyl-6-diethylfluoran (black dye precursor, Wuhan Shuer Biotechnology Co., Ltd.), 5 parts of ether (organic solvent, Sigma-Aldrich (Shanghai)), 90 parts of toluene diisocyanate (polyisocyanate, Merck Chemical), and 5 parts of 3-isocyanatepropyltrimethoxysilane (silane coupling agent containing isocyanate active groups, Sigma-Aldrich (Shanghai)) are heated and dissolved (100° C.) to obtain an oil phase, and the rest remain unchanged.

[0147] Comparative Example 10

[0148] The preparation method and steps thereof are different from those of Example 1 in that the weight parts of the two-color thermosensitive material are different, and the two-color thermosensitive material includes the following components in weight parts: 40 parts of developer dispersion, 3 parts of dye precursor microcapsule emulsion A, 50 parts of dye precursor microcapsule emulsion B, 10 parts of adhesive (water-based acrylic latex - BASF Vinofan W 3109ap), 25 parts of filler (mass concentration of 30% kaolin - Central African kaolin Maoming new material), and 50 parts of deionized water, and the rest remain unchanged.

[0149] Comparative Example 11

[0150] The preparation method and steps thereof are different from those of Example 1 in that the weight parts of the two-color thermosensitive material are different, and the two-color thermosensitive material includes the following components in weight parts: 40 parts of developer dispersion, 20 parts of dye precursor microcapsule emulsion A, 5 parts of dye precursor microcapsule emulsion B, 10 parts of adhesive (water-based acrylic latex - BASF Vinofan W 3109ap), 25 parts of filler (mass concentration of 30% kaolin - Central African kaolin Maoming new material), and 50 parts of deionized water, and the rest remain unchanged.

[0151] Application Example 1

[0152] A two-color thermal paper, wherein a coated base paper, a two-color color-developing layer, and a protective layer are arranged in sequence;

[0153] The two-color chromogenic layer is formed by coating and drying the two-color thermosensitive material prepared in Example 1 (uniform coating with a rod scraper, coating amount 4g / m 2 , drying temperature is 70℃)

[0154] The protective layer is formed by coating and drying the protective layer protection liquid (the air knife is evenly coated, and the coating amount is controlled at 3g / m 2 , drying temperature is 90°C); the protective layer protection liquid is as follows: 32 parts of kaolin dispersion with a mass concentration of 30%, 12 parts of silica dispersion with a mass concentration of 30%, 15 parts of polyvinyl alcohol with a mass concentration of 15% (Kuraray PVA-217), 32 parts of water-based styrene-butadiene latex (Yoshida Chemical 106#), 4 parts of zinc stearate dispersion with a mass concentration of 40% (Sigma-Aldrich (Shanghai)), 3 parts of paraffin and 2 parts of glyoxal aqueous solution with a mass concentration of 40% (Sigma-Aldrich (Shanghai)).

[0155] Application Example 2-Application Example 10

[0156] Compared with Application Example 1, the other application examples are exactly the same except that the two-color thermosensitive materials used in the two-color color-emitting layer are different; specifically, Application Example 2 is coated with the two-color thermosensitive material prepared in Example 2, Application Example 3 is coated with the two-color thermosensitive material prepared in Example 3, and so on.

[0157] Comparative Application Example 1-Comparative Application Example 11

[0158] Compared with Application Example 1, Comparative Application Example 1 differs only in the two-color thermosensitive material used in the two-color color-emitting layer, and the rest are exactly the same; specifically, Comparative Application Example 1 is coated with the two-color thermosensitive material prepared in Comparative Example 1, and Comparative Application Example 2 is coated with the two-color thermosensitive material prepared in Comparative Example 2, and so on.

[0159] Performance Testing

[0160] The particle sizes of the dispersions of the above examples and comparative examples were tested, and the two-color thermal paper prepared in the application example was evaluated for static color development, image printing and other properties. The test results are shown in Table 1 below.

[0161] Average particle size of dispersion: The particle sizes of developer dispersion, dye precursor microcapsule emulsion A and dye precursor microcapsule emulsion B were measured using Malvern Mastersizer 3000 laser diffraction particle size analyzer.

[0162] Thermal paper performance test method: Refer to the National Standard of the People's Republic of China GB / T 28210-2011 "Thermal Paper" to test the image color development performance and image preservation performance, and the results are shown in Table 1. Brother QL-800 printer was used for image printing test (the printer automatically identifies two different hues in the image and gives low energy level (printing temperature 70℃-100℃) and high energy level (printing temperature ≥130℃) printing to obtain a two-color image of the thermal material), where the color development optical density of 0.08 is the color development optical density of the blank, and the color development optical density of 1.3 is the saturated color development optical density. The results are shown in Table 1 below.

[0163] Table 1

[0164]

[0165]

[0166] It can be seen from Examples 1-3 in Table 1 that if the dye precursors are of the same hue, they can be used alone or mixed in the dye precursor microcapsule emulsion, and it can be seen from Table 1 that both hues are clearly visible in the image at the same time. It can be seen from Examples 1 and 4 in Table 1 that the color developer can be replaced with other known developers, and it can be seen from Table 1 that both hues are clearly visible in the image at the same time.

[0167] Combining Examples 1 and 5-6 in Table 1, and Comparative Examples 6-9, it can be seen that a larger ratio of polyols and unsaturated double bonds in the dye precursor microcapsule emulsion A (Comparative Example 6) will lead to a violent reaction, uncontrollable microcapsule particle size (large particle size), and unclear color development in the yellow area; a lower ratio of polyols and unsaturated double bonds in the dye precursor microcapsule emulsion A (Comparative Example 7) will make its color optical density lower (the softening point of the microcapsule shell is higher), resulting in unclear color development in the yellow area; The ratio of polyisocyanate in capsule emulsion B is low (Comparative Example 8), which causes it to start coloring at low temperatures (low softening point of microcapsule shell), covering up the yellow hue of coloring at low temperatures, further causing unclear coloring in the yellow area; the ratio of polyisocyanate in dye precursor microcapsule emulsion B is high (Comparative Example 9), resulting in violent reaction, uncontrollable microcapsule particle size (large particle size), and high softening point of its shell (high coloring temperature), further causing unclear coloring in the black area. Therefore, in the preparation process of dye precursor microcapsule emulsions A and B, good results can only be achieved if the raw materials are within a certain range.

[0168] Combining Examples 1 and 7-8 in Table 1, and Comparative Examples 10-11, it can be seen that when the weight ratio of the dye precursor microcapsule emulsion A to the dye precursor microcapsule emulsion B is 1:(2-3), the black hue developed at high temperature can basically completely cover the yellow hue that can be developed at low temperature, so that excellent hue isolation can be achieved (high-definition low-temperature color development hue and clear high-temperature color development hue can be obtained at the same time).

[0169] Combining Example 1 and Examples 9-10 in Table 1, it can be seen that the mass ratio of emulsifier Tween 80 and Span 80 in the two dye precursor microcapsule emulsions is most suitable at (10-20):1. A ratio greater than or less than this ratio will cause the capsule emulsion particle size to change, thereby resulting in a decrease in the image color optical density value.

[0170] Combining Example 1 and Comparative Example 1 in Table 1, it can be seen that if two dye precursor capsules use dyes of the same hue, the print will only show one hue, and there will be no two-color effect.

[0171] Combining Example 1 and Comparative Examples 2-3 in Table 1, it can be seen that Comparative Example 2 does not have the unsaturated double bond compound terminal hydroxyl polybutadiene, and its waterproof performance (image retention rate) is lower than that of Examples 1-4, while Comparative Example 2 does not have the free radical initiator ammonium persulfate, and its waterproof performance (image retention rate) is lower than that of Examples 1-4. The deterioration of waterproof performance leads to deterioration of heat resistance and moisture resistance (the color development optical density of the blank part becomes higher and the color development optical density of the image becomes lower). Therefore, in order to reduce the softening point of the shell, a large proportion of soft segment polyol substances is used (there are more hydrophilic groups in the molecular chain), which leads to poor water resistance of the microcapsule. Therefore, by introducing unsaturated double bond compounds and reacting with the hydrophilic groups of the soft segment polyol (initiating the reaction through the free radical initiator), the waterproof performance and aging resistance of the microcapsule and the color-forming layer are enhanced.

[0172] Combining Example 1 and Comparative Examples 4-5 in Table 1, it can be seen that polyvinyl alcohol and sodium silicate in the developer dispersion must be used together. The lack of one of them will lead to a larger particle size of the dispersion, thereby resulting in a decrease in the image color optical density value. Among them, Comparative Example 5 does not contain polyvinyl alcohol. Due to the large particle size of the dispersion, the image color optical density value is low and the image clarity is also deteriorated.

[0173] In summary, the color of the two-color thermal paper prepared by the present invention is clearly visible and has excellent color isolation and aging resistance.

[0174] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A two-color thermal sensitive material, characterized in that: The invention comprises the following components in parts by weight: 20-50 parts of developer dispersion, 5-15 parts of dye precursor microcapsule emulsion A, 15-45 parts of dye precursor microcapsule emulsion B, 5-15 parts of adhesive, and 5-30 parts of filler; The particle size D90 of the dye precursor microcapsule emulsion A is 0.6-2 μm; the dye precursor microcapsule emulsion A comprises a core material and a wall material, the core material is the dye precursor A, the wall material is polyurethane, and the softening point of the wall material of the dye precursor microcapsule emulsion A is 70-100° C.; The particle size D90 of the dye precursor microcapsule emulsion B is 0.6-1 μm; the dye precursor microcapsule emulsion B comprises a core material and a wall material, the core material is the dye precursor B, the wall material is polyurea, and the softening point of the wall material of the dye precursor microcapsule emulsion B is ≥130°C.

2. The two-color thermosensitive material according to claim 1, characterized in that: The weight ratio of the dye precursor microcapsule emulsion A to the dye precursor microcapsule emulsion B is 1:(2-3).

3. The two-color thermosensitive material according to claim 1, characterized in that: The dye precursor A and the dye precursor B are two dye precursors showing different hues.

4. The two-color thermosensitive material according to claim 1, characterized in that: The preparation method of the dye precursor microcapsule emulsion A comprises the following steps: (1) mixing oligomer polyol, polyisocyanate, unsaturated double bond compound, organic solvent and dye precursor A uniformly to obtain an oil phase; (2) The protective colloid and the emulsifier are mixed uniformly to obtain an aqueous phase, and the oil phase and the aqueous phase are homogenized and emulsified. During the emulsification process, a catalyst, a chain extender, a neutralizer and a free radical initiator are added respectively to obtain the dye precursor microcapsule emulsion A.

5. The two-color heat-sensitive material according to claim 4, characterized in that: In the step (1), the weight ratio of the oligomer polyol, the polyisocyanate, the unsaturated double bond compound, the organic solvent, and the dye precursor A is oligomer polyol: polyisocyanate: unsaturated double bond compound: organic solvent: dye precursor A = (4-6): 1: (1-2): (2-4): (8-16); And / or, in the step (2), the weight ratio of the protective colloid to the emulsifier is (2-4): (0.5-2); And / or, in step (2), the catalyst accounts for 0.05-0.5% of the total mass percentage of the water phase and the oil phase solution, the chain extender accounts for 0.5-1.5% of the total mass percentage of the water phase and the oil phase solution, the neutralizer accounts for 0.1-1% of the total mass percentage of the water phase and the oil phase solution, and the free radical initiator accounts for 0.1-1% of the total mass percentage of the water phase and the oil phase solution.

6. The two-color heat-sensitive material according to claim 4, characterized in that: The raw materials for preparing the dye precursor microcapsule emulsion A include at least one of the following (a)-(j): (a) The oligomer polyol is a polyether polyol and / or a polyester polyol; preferably, the oligomer polyol is ethylene glycol, neopentyl glycol, 1,2-propylene glycol, 2,2-dimethyl-1,3-propylene glycol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol and 1,2-cyclohexanedimethanol, as well as polyols such as fatty acid triols, such as ethylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7 -heptanediol, 1,8-octanediol, propylene glycol, 2,3-dihydroxybutane, 1,2-dihydroxybutane, 1,3-dihydroxybutane, 2,2-dimethyl-1,3-propanediol, 2,4-pentanediol, 2,5-hexanediol, 3-methyl-1,5-pentanediol, 1,4-cyclohexanedimethanol, dihydroxycyclohexane, diethylene glycol, 1,2,6-trihydroxyhexane, styrene glycol, 1,1,1-trimethylolpropane, hexanetriol, pentaerythritol or glycerol, at least one of adipic acid polyester polyol; further preferably, the oligomer polyol is adipic acid polyester polyol; (b) The polyisocyanate is phenylene diisocyanate, 2,6-toluene diisocyanate, 2,4-toluene diisocyanate, naphthalene-1,4-diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, xylylene diisocyanate, tetramethylxylene diisocyanate, 4 ,4'-diphenylpropane diisocyanate, hexamethylene diisocyanate, 1,2-butanediisocyanate, cyclohexene-1,2-diisocyanate, cyclohexene-1,4-diisocyanate, 4,4',4"-triphenylmethane triisocyanate, toluene-2,4,6-triisocyanate, diphenylmethane-4,4'-diisocyanate; preferably, the polyisocyanate is 2,4-toluene diisocyanate; (c) the unsaturated double bond compound is at least one of pentaerythritol triacrylate, glycerol allyl ether, terminal hydroxyl polybutadiene, and diacetone acrylamide; preferably, the unsaturated double bond compound is terminal hydroxyl polybutadiene; (d) the organic solvent is at least one of methyl ether, ethyl ether, acetone, ethyl ether, dichloromethane, methyl formate, ethyl acetate, methyl acetate, butyl acetate, ethyl butyrate, ketone, ethyl ketone, acetone, dichloromethane, 1-chlorobutane, and chloropropane; preferably, the organic solvent is diethyl ether; (e) the protective colloid is polyvinyl alcohol; (f) the emulsifier is at least one of polyoxyethylene fatty alcohol ether, polyoxyethylene sorbitan monooleate, glyceryl monostearate, polyoxyethylene dodecylphenol ether, polyoxyethylene octylphenol ether, and sorbitan monooleate; further preferably, the emulsifier is a mixture of polyoxyethylene sorbitan monooleate and sorbitan monooleate, with a weight ratio of (10-20):1; (g) the catalyst is at least one of stannous octoate, stannous oleate, dibutyltin dilaurate, triethylenediamine, triethylenediamine, dimethylethanolamine, dimethylethanolamine, N-methylmorpholine, N,N-dimethylcyclohexylamine, and tetramethylethylenediamine; preferably, the catalyst is dibutyltin dilaurate; (h) the chain extender is at least one of 1,4-butanediol, 1,6-hexanediol, glycerol, trimethylolpropane, diethylene glycol (DEG), and triethylene glycol; preferably, the chain extender is 1,6-hexanediol; (i) the neutralizing agent is at least one of sodium bicarbonate, sodium acetate, sodium pyrophosphate, sodium carbonate, hydrochloric acid, phosphoric acid, formic acid, acetic acid, AMP-95, diethanolamine, triethanolamine, and aminoacetic acid; preferably, the neutralizing agent is triethanolamine; (j) The free radical initiator is at least one of azobisisobutyronitrile, azobisisoheptylnitrile, dibenzoyl peroxide, potassium persulfate, and ammonium persulfate; preferably, the free radical initiator is ammonium persulfate.

7. The two-color heat-sensitive material according to claim 1, characterized in that: The preparation method of the dye precursor microcapsule emulsion B comprises the following steps: S1, mixing polyisocyanate, silane coupling agent containing isocyanate active group, organic solvent and dye precursor B to obtain oil phase; S2, mixing the protective colloid and the emulsifier evenly to obtain an aqueous phase, homogenizing the oil phase and the aqueous phase, and adding a chain extender during the emulsification process to obtain the dye precursor microcapsule emulsion B.

8. The two-color heat-sensitive material according to claim 7, characterized in that: In the step S1, the weight ratio of the polyisocyanate, the silane coupling agent containing isocyanate active groups, the organic solvent, and the dye precursor B is polyisocyanate: the silane coupling agent containing isocyanate active groups: the organic solvent: the dye precursor B = (8-16): 1: (1-4): (8-16); And / or, in step S2, the weight ratio of the protective colloid to the emulsifier is (2-6): (0.5-5); And / or, in step S2, the chain extender accounts for 0.1-1% of the total mass percentage of the aqueous phase and the oil phase solution.

9. The two-color heat-sensitive material according to claim 7, characterized in that: The raw materials for preparing the dye precursor microcapsule emulsion B include at least one of the following (m)-(r): (m) the polyisocyanate is an aromatic isocyanate; preferably, the polyisocyanate is at least one of toluene diisocyanate, diphenylmethane diisocyanate, and naphthalene 1,5-diisocyanate; (n) the silane coupling agent containing an isocyanate reactive group is at least one of 3-isocyanate propyl trimethoxy silane, 3-isocyanate propyl triethoxy silane, isocyanate methyl trimethoxy silane, and 3-isocyanate propyl methyl dimethoxy silane; (o) the organic solvent is at least one of methyl ether, ethyl ether, acetone, ethyl ether, dichloromethane, methyl formate, ethyl acetate, methyl acetate, butyl acetate, ethyl butyrate, ketone, ethyl ketone, acetone, dichloromethane, 1-chlorobutane, and chloropropane; preferably, the organic solvent is diethyl ether; (p) the protective colloid is polyvinyl alcohol; (q) the emulsifier is at least one of polyoxyethylene fatty alcohol ether, polyoxyethylene sorbitan monooleate, glyceryl monostearate, polyoxyethylene dodecylphenol ether, polyoxyethylene octylphenol ether, and sorbitan monooleate; further preferably, the emulsifier is a mixture of polyoxyethylene sorbitan monooleate and sorbitan monooleate, with a weight ratio of (10-20):1; (r) The chain extender is an amine chain extender; preferably, the chain extender is at least one of 3,3′-dichloro-4,4′-diaminodiphenylmethane, 3,5-diaminoisobutyl p-chlorobenzoate, diethyltoluenediamine, 3,5-dimethylthiotoluenediamine, ethanolamine, diethanolamine, and triethanolamine.

10. Use of the two-color thermal-sensitive material according to claim 1 in preparing two-color thermal paper and / or film.

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