JPH0417155B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a heat-sensitive recording sheet with excellent water resistance, solvent resistance, and color-forming properties, and more specifically, a heat-sensitive recording sheet in which a heat-sensitive color-forming component layer is provided on a supporting substrate. In or on the coloring component layer,
Modified polyvinyl alcohol containing a silyl group in the molecule and one or more of melamine-formaldehyde resin, urea-formaldehyde resin, or polyamide-epoxy resin as a water-resistant agent for water resistance, solvent resistance, and color development. The present invention relates to a heat-sensitive recording sheet with excellent properties. Heat-sensitive recording sheets that are usually colorless or light-colored leuco dyes, organic acids, electron acceptors such as phenolic compounds, binders, etc. are provided on a support substrate, and are colored by applying heat are used for facsimiles, computer terminals, calculator printers, etc. Widely used for barcode labels in medical measuring instruments, POS, and other applications. Prior Art Conventionally, it has not been possible to manufacture a heat-sensitive recording sheet by coating a colorless or light-colored lactone compound such as crystal violet lactone and an acidic compound such as a phenol compound together with a water-soluble binder onto a supporting substrate. It is publicly known. Conventional water-soluble binders include polyvinyl alcohol (hereinafter abbreviated as PVA), methyl cellulose,
Carboxymethyl cellulose, polyacrylic acid,
Water-soluble polymers such as styrene-maleic acid copolymer or starch are used, and among them, PVA is widely used because of its excellent adhesive performance. However, in the case of a heat-sensitive recording sheet manufactured using such a water-soluble binder, the colored lines obtained by the compatibility and reaction of the color-forming lactone compound and the acidic compound are resistant to moisture or organic solvents. Although it is stable, it has the disadvantage that the colored part tends to fade and disappear when it comes into contact with water or the plasticizer in PVC synthetic leather. As a way to overcome these shortcomings,
−33117, Special Publication No. 1983-33119, Special Publication No. 1983-
As seen in No. 33839 and Special Publication No. 59-30555, formalin, glyoxal, dialdehyde starch,
A method is known in which a water-resistant agent such as glutaraldehyde, aldehyded polyacrylamide, or alkali metal tetraborate is used in combination with a water-soluble binder. Other JP-A-58-191194, JP-A-58-
As shown in No. 193189, it has also been proposed to impart crosslinking properties to PVA itself to improve water resistance. Problems to be solved by the invention However, in order to react PVA and dialdehyde and make PVA sufficiently water resistant, it is necessary to heat treat it at a high temperature of 100℃ or higher.On the other hand, if the temperature is 100℃ or higher, color development Because lactone compounds and acidic compounds are compatible with each other and coloration occurs due to the reaction, it is impossible to use heat treatment at such high temperatures, and in reality heat treatment must be performed at low temperatures, resulting in insufficient water resistance. However, the method using cross-linked PVA does not require heat treatment at high temperatures, but recent
It did not necessarily fully satisfy the strict water resistance and solvent resistance requirements required for POS, etc. Means for Solving the Problems In view of the current situation, the present inventors have conducted intensive research to improve the above-mentioned drawbacks. As a result, in a heat-sensitive recording sheet in which a heat-sensitive color forming component layer is provided on a supporting substrate, silyl is present in the molecule. One or more of melamine-formaldehyde resin, urea-formaldehyde resin, or polyamide-epoxy resin is contained as a binder in the thermosensitive coloring component layer, or on the layer. By imparting this color to the dye, high water resistance and high barrier properties against organic solvents can be obtained under normal manufacturing conditions without the need for special conditions such as high-temperature heat treatment, as well as good color development and storage stability of colored lines. The inventors have discovered that a heat-sensitive recording sheet with excellent properties can be obtained and have completed the present invention. The present invention will be explained in more detail below. The modified PVA containing a silyl group in the molecule used in the present invention may be any type as long as it contains a silyl group in the molecule, but the silyl group contained in the molecule may be an alkoxyl group, an acyloxyl group, or any of these. Particularly preferably used are those having a reactive substituent such as a silanol group or a salt thereof, which is a hydrolyzate. As a method for producing such modified PVA, PVA
Alternatively, a method in which a silyl group is introduced into modified polyvinyl acetate containing a carboxyl group or a hydroxyl group by post-modification using a silylating agent, or a method in which a copolymer of a vinyl ester and an olefinic unsaturated monomer containing a silyl group is introduced. and a method of saponifying a polyvinyl ester having a silyl group at the end obtained by polymerizing a vinyl ester in the presence of a mercaptan having a silyl group. In the method of post-modifying PVA or modified polyvinyl acetate using a silylating agent, organic solvents that do not react with the silylating agent, such as benzene, toluene, xylene, hexane, heptane,
A silylating agent is dissolved in ether or acetone, and powdered PVA or the above-mentioned modified polyvinyl acetate is suspended in the solution with stirring, and the silylating agent is mixed with the silylating agent at a temperature ranging from room temperature to the boiling point of the silylating agent.
Silyl group-containing modified PVA can be obtained by reacting PVA or the above modified polyvinyl acetate, or by further saponifying vinyl acetate units using an alkali catalyst or the like. Examples of silylating agents used in post-modification include organohalogensilanes such as trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane, vinyltrichlorosilane, diphenyldichlorosilane, and triethylfluorosilane, trimethylacetoxysilane, and dimethyldichlorosilane. Organosilicon esters such as acetoxysilane, organoalkoxysilanes such as trimethylmethoxysilane and dimethyldimethoxysilane, organosilanols such as trimethylsilanol and diethylsilanediol, aminoalkylsilanes such as N-aminoethylaminopropyltrimethoxysilane, and trimethylsilicon isocyanate. Examples include organosilicon isocyanates such as . The introduction rate of the silylating agent, that is, the degree of modification, can be arbitrarily adjusted by adjusting the amount of the silylating agent used and the reaction time. Further, the degree of polymerization and saponification of the obtained silyl group-containing modified PVA can be arbitrarily adjusted by adjusting the degree of polymerization and saponification of the PVA used or the degree of polymerization and saponification of the above-mentioned modified polyvinyl acetate. In addition, in a method of saponifying a copolymer of a vinyl ester and a silyl group-containing olefinic unsaturated monomer, for example, the vinyl ester and the silyl group-containing olefinic unsaturated monomer are combined with a radical initiator in alcohol. A silyl group-containing modified PVA can be obtained by copolymerizing the copolymer using PVA and then saponifying the copolymer by adding an alkali or acid catalyst to the alcohol solution of the copolymer. Vinyl esters used in the above method include vinyl acetate, vinyl propionate, vinyl formate, etc., but vinyl acetate is preferred from an economical standpoint. In addition, the silyl group-containing olefinic unsaturated monomer used in the above method has the following formula ()
Examples include vinylsilanes represented by () and (meth)acrylamide-alkylsilanes represented by (). [Here, n is 0 to 4, m is 0 to 2, R ¹ is an alkyl group having 1 to 5 carbon atoms (methyl, ethyl, etc.), R ²
is an alkoxyl group or acyloxyl group having 1 to 40 carbon atoms (here, the alkoxyl group and acyloxyl group may have an oxygen-containing substituent),
R ³ is a hydrogen atom or a methyl group, R ⁴ is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, and R ⁵ is a carbon number 1
It represents a divalent organic residue in which ~5 alkylene groups or chain carbon atoms are interconnected by oxygen or nitrogen, respectively. Note that when two or more R ¹ 's exist in the same monomer, R ¹ may be the same or different. Also R ²
Even when two or more are present in the same monomer, R ²
may be the same or different. ] Specific examples of the vinylsilane represented by formula () include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris-(β-methoxyethoxy)silane, vinyltriacetoxysilane, allyltrimethoxysilane, allyltriacetoxysilane, Vinylmethyldimethoxysilane, vinyldimethylmethoxysilane, vinylmethyldiethoxysilane, vinyldimethylethoxysilane, vinylmethyldiacetoxysilane, vinyldimethylacetoxysilane, vinylisobutyldimethoxysilane, vinyltriisopropoxysilane, vinyltributoxysilane, vinyltributoxysilane Hexyloxysilane, Vinylmethoxydihexyloxysilane, Vinyltrioctyloxysilane, Vinyldimethoxyoctyloxysilane, Vinylmethoxydioctyloxysilane, Vinylmethoxydilauryloxysilane, Vinyldimethoxylauryloxysilane, Vinylmethoxydioleyloxysilane , vinyldimethoxyoleyloxysilane, and also general formula (Here, R ¹ and m are the same as above, and x is 1 to 20). Further, specific examples of the (meth)acrylamide-alkylsilane represented by the formula () include:
3-(meth)acrylamidopropyltrimethoxysilane, 3-(meth)acrylamidopropyltriethoxysilane, 3-(meth)acrylamidopropyltri(β-methoxyethoxy)
Silane, 2-(meth)acrylamido-2-methylpropyltrimethoxysilane, 2-(meth)acrylamido-2-methylethyltrimethoxysilane, N-(2-(meth)acrylamido-ethyl)-aminopropyltrimethoxysilane , 3-
(meth)acrylamide-propyltriacetoxysilane, 2-(meth)acrylamide-ethyltrimethoxysilane, 1-(meth)acrylamide-methyltrimethoxysilane, 3-(meth)acrylamide-propylmethyldimethoxysilane, 3-(meth)acrylamide-propylmethyldimethoxysilane, ) acrylamide-propyldimethylmethoxysilane, 3-(N-methyl-(meth)
acrylamide)-propyltrimethoxysilane,
3-((meth)acrylamide-methoxy)-3-
Hydroxypropyltrimethoxysilane, 3-
((meth)acrylamide-methoxy)-propyltrimethoxysilane, N,N-dimethyl-N-trimethoxysilylpropyl-3-(meth)acrylamide-propylammonium chloride,
Examples include N,N-dimethyl-N-trimethoxysilylpropyl-2-(meth)acrylamido-2-methylpropylammonium chloride. In addition, when copolymerizing the vinyl ester and the silyl group-containing olefinic unsaturated monomer to produce the modified PVA used in the present invention, it is necessary to use other monomers other than the above two components. Other copolymerizable unsaturated monomers, such as styrene, alkyl vinyl ethers, vinyl versatate,
(meth)acrylamide, ethylene, propylene,
Olefins such as α-hexene and α-octene,
Unsaturated acids such as (meth)acrylic acid, crotonic acid, (anhydrous) maleic acid, fumaric acid, and itaconic acid; their alkyl esters and alkali salts; trimethyl-3-(1-(meth)acrylamide-1,1)
-dimethylpropyl)ammonium chloride, trimethyl-3-(1-(meth)acrylamidopropyl)ammonium chloride, 1-vinyl-2-
It is also possible to have a cationic monomer such as methylimidazole and its quaternized product present in a small proportion. In addition, in a method for saponifying a polyvinyl ester having a silyl group at the end obtained by polymerizing a vinyl ester in the presence of a mercaptan having a silyl group, for example, when vinyl ester is polymerized using a radical initiator, , a mercaptan having a silyl group is added to the polymerization system all at once, in parts, or continuously, so that the mercaptan having a silyl group is present in the polymerization system, and by chain transfer to the mercaptan, a polyvinyl ester having a silyl group at the end is produced. After the polyvinyl ester is produced, an alkali or acid catalyst is added to the alcohol solution of the polyvinyl ester to saponify the polyvinyl ester, thereby producing a modified product having a silyl group.
You can get PVA. As the mercaptan having a silyl group used in this method, 3-(trimethoxysilyl)-propyl mercaptan, 3-(triethoxysilyl)-propyl mercaptan, etc. can be used. When producing modified PVA by this method, it is also possible to include a small proportion of an unsaturated monomer copolymerizable with the vinyl ester used in the method. Modified PVA containing a silyl group in the molecule has been described in detail above, but among these, from the viewpoint of ease of industrial production, one based on copolymerization is preferable to one based on post-modification. In addition, among PVA modified by copolymerization, the saponified copolymer with a silyl group-containing olefinic unsaturated monomer represented by the formula () has a high viscosity stability in an aqueous solution, and a resistance to alkali when made into an alkaline aqueous solution. It is preferably used because it is excellent in terms of stability and water resistance when formed into a film. On the other hand, in terms of the saponified copolymer with the silyl group-containing olefinic unsaturated monomer shown by the formula (), the viscosity stability of aqueous solutions, and the stability against alkali, the silyl group-containing olefinic monomer shown by the formula () Although it is slightly inferior to saponified copolymers with unsaturated monomers, it has the characteristics that it is difficult to foam in aqueous solutions and can exhibit superior performance in terms of barrier properties against organic solvents when formed into a film. and is preferably used in some cases. The degree of modification of the modified PVA obtained by the above three methods, that is, the content of silyl groups in the modified PVA, can be appropriately selected depending on the purpose, but it is usually 0.01 to 10% as a monomer unit containing a silyl group in the molecule. mol%, preferably 0.1 to 5 mol%. Also denatured
PVA (post-modified PVA and modified PVA by copolymerization)
The polymerization degree of (both) is usually 300-3000, preferably 500-
3000, more preferably 1000 to 3000, and the degree of saponification is selected from the range of 70 to 100 mol%. Further, as the waterproofing agent in the present invention, melamine-formaldehyde resin, urea-formaldehyde resin, or polyamide-epoxy resin is suitable, and these may be generally commercially available ones.
One or a combination of two or more of these can be used. The weight mixing ratio of the modified polyvinyl alcohol containing a silyl group in the molecule and the above water resistant agent is
1 to 50 parts of water resistance agent (solid content equivalent) per 100 parts,
Preferably 5 to 30 parts is suitable. If it is less than 1 part, it will not be effective, and if it is more than 50 parts, the film will be too weak to be used. Typical examples of the heat-sensitive color-forming component in the heat-sensitive recording sheet of the present invention include a color-forming substance and a color-developing substance that reacts with the color-forming substance when heated to form a color. Among thermosensitive coloring components, a typical coloring substance is a chromogenic lactone compound. The color-forming lactone compound may be any compound that can develop color by reacting with an acidic compound when heated, such as triphenylmethane, triphenylmethane phthalide, fluoran, leucoauramine, spiropyran, etc. Examples include leuco compounds. Further, among the heat-sensitive coloring components, the color-developing substance may be an acidic compound that generally liquefies or vaporizes at 70°C or higher and has the property of reacting with the leuco compound to develop color, such as 4-phenylphenol, 4-hydroxyacetophenone, 2,2'-diacetoxyphenyl,
2,2'-methylenebis(4-chlorophenol),
2,2'-methylene bis(4-methyl-6-t-butylphenol), 4,4'-isopropylidene diphenol, 4,4'-isopropylidene bis(2
-chlorophenol), 4,4'-isopropylidene bis(2-methylphenol), 4,4'-sec-
Examples include phenolic compounds such as butylidenephenol, 4,4'-ethylenediphenol, and 4,4'-ethylenebis(2-methylphenol). Examples of the supporting substrate used in the heat-sensitive recording sheet of the present invention include papers such as wood-free paper, medium-quality paper, and coated paper, as well as plastic films, film-laminated papers, and woven fabric sheets. Next, regarding the heat-sensitive recording sheet of the present invention, a general method for producing a heat-sensitive recording sheet using a color-forming lactone compound and a phenol compound will be specifically described. The color-forming lactone compound and the phenol compound are separately pulverized into fine particles, and if necessary, fillers such as various clays such as talc and calcium carbonate, waxes, and sea surfactants are added.
Furthermore, a heat-sensitive coating liquid is prepared by adding PVA modified with silyl groups in the molecule and a water-resistant agent, and this is coated onto a supporting substrate and dried to form a recording layer. Modification containing a silyl group in
It can be manufactured by forming a layer containing PVA and a waterproofing agent. At this time, it is also effective to apply the above-mentioned modified PVA and water-resistant agent on the support substrate in advance to form a layer containing the modified PVA and water-resistant agent, and then apply the above-mentioned heat-sensitive coating liquid. be. In addition, we created a heat-sensitive coating liquid containing modified PVA containing a silyl group in the molecule and without adding a water-resistant agent;
A heat-sensitive coloring component layer is formed by coating on a support substrate coated with or without PVA and a water-resistant agent, and a modified PVA containing a silyl group in the molecule is coated on the layer.
It is also possible to add a waterproofing agent. Here, as a method for applying modified PVA containing a silyl group in the molecule and a water resistance agent to the heat-sensitive coloring component layer, after dispersing the modified PVA in water, in some cases, a small amount of sodium hydroxide, hydroxide, etc. There is a method in which an alkali such as potassium, ammonium hydroxide, or amine is added, a water resistance agent is added thereto to form a uniform aqueous solution, and this is applied onto the heat-sensitive coloring component layer by coating or spraying. Furthermore, a small proportion of conventional Kochi water-soluble resins, such as unmodified PVA, may be combined with the above-mentioned modified PVA. When the above-mentioned modified PVA and water resistant agent are used as a binder in the heat-sensitive coloring component layer, the amount to be used is 1 to 1 to 100 parts by weight of the heat-sensitive coloring component.
500 parts by weight, preferably 2 to 200 parts by weight. In addition, when applying modified PVA and a water-resistant agent on the heat-sensitive coloring component layer, the coating amount as a solid content is 0.5 to 5.
It is preferable to set it so that it is g/m ² . Further, in this case, the concentration of the coating aqueous solution consisting of the modified PVA and the waterproofing agent is 0.5 to 20% by weight, preferably 2 to 15% by weight. Function and Effects of the Invention The heat-sensitive recording sheet of the present invention has remarkable water resistance,
It is characterized by excellent solvent resistance and good color development. Although the details of the reason why such remarkable performance is obtained are unknown, it is presumed as follows. That is, an alkoxyl group, an acyloxyl group, a silanol group which is a hydrolyzate thereof, or a salt thereof bonded to a silyl group in the modified PVA containing a silyl group in the molecule used in the present invention reacts with a waterproofing agent, This is thought to be because when it is dried to form a film, it easily self-condenses and crosslinks, and also reacts with the filler or supporting substrate, forming a film that is insoluble in water and has high barrier properties against organic solvents. . EXAMPLES The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited thereto. In the examples, "%" and "part" are based on weight unless otherwise specified. Example 1 As Inventive Examples 1 to 3, copolymers of vinylmethoxysilane and vinyl acetate were saponified to contain 0.2 mol% of silyl groups as vinyl silane units, and the degree of saponification of vinyl acetate units was 98.5 mol%, and the degree of polymerization was A modified PVA containing a silyl group in the molecule of 1750 was obtained. This modified PVA was dissolved in water to prepare a 15% aqueous solution.
This is called liquid A. Next, 8 parts of crystal violet lactone,
Solution B is a 30% solution made by adding 25 parts of talc, 15 parts of stearamide, a small amount of dispersant, and water. Separately, 25 parts of bisphenol A, 25 parts of talc, a small amount of a dispersant, and water were added to prepare a 30% solution, and this was designated as Solution C. Put these B liquid and C liquid separately into a paint shaker, crush and disperse them using glass beads of 5 mm diameter, and then add 30 parts of B liquid and C liquid.
A heat-sensitive coating liquid was prepared by mixing 30 parts of liquid, adding 30 parts of liquid A to the solution, and then adding three types of waterproofing agents at a ratio of 20% based on the modified PVA in terms of solid content. Comparative Example 1: Modification containing a silyl group in the molecule
A heat-sensitive coating liquid was prepared using a 15% PVA aqueous solution and liquids B and C in the same manner as in Examples 1 to 3, except that no water-resistant agent was used. As Comparative Example 2, a 15% aqueous solution of unmodified PVA (Kuraray Popal PVA-117) and a 40% glyoxal aqueous solution as a waterproofing agent were added at a ratio of 20% to PVA-117 in terms of solid content, and the other examples were as follows. A heat-sensitive coating liquid was prepared in the same manner as in 3. These heat-sensitive coating liquids were applied to 50g/ ^m2 of high-quality paper using a wire bar so that the coated amount after drying was 7g/ ^m2 . After drying at 50℃,
3 on the calender roll under the conditions of cm ² and 10 m/min.
The paper was passed through several times to obtain heat-sensitive recording sheets. These heat-sensitive recording sheets were immersed in water for one day and night, and then a water resistance test was conducted in which the degree of elution was judged on a five-point scale by rubbing the coated surface with a finger.
The results are shown in Table-1. In addition, these heat-sensitive recording sheets were heated to develop color and measured using a Macbeth densitometer, and then the color-developing surface was brought into contact with a commercially available soft vinyl chloride resin film, and the sheet was placed in a thermostat at 45°C for 2 days with a load placed on it. After that, the color density was measured and the browning properties caused by the plasticizer were compared. The results are also listed in Table-1.

[Table] As shown in Table 1, modifications containing silyl groups
When using PVA and a melamine-formaldehyde resin, urea-formaldehyde resin or polyamide-epoxy resin as a water-repellent agent, the above-mentioned modification
It can be seen that the water resistance and solvent resistance are superior to PVA alone or PVA-117 to glyoxal series. Example 2 Inventive Examples 4 to 6 contain 0.6 mol% of silyl groups obtained by saponifying a copolymer of vinyltriacetoxysilane and vinyl acetate as vinyl silane units, and the degree of saponification of vinyl acetate units is 99.0 mol. %, modified PVA with a degree of polymerization of 500 is dissolved in water and modified.
A 10% aqueous solution of PVA was created. Example 1
A mixed solution was prepared by adding 15% of the three types of waterproofing agents used in PVA based on solid content. These mixed solutions were overcoated onto the surface of a commercially available thermal paper for printing so that the solid content coating amount was 3 g/m ² , and after drying at 50° C., calendering was performed. As Comparative Example 3, unmodified PVA (Kuraray Poval
Prepare a 10% aqueous solution of PVA-117) and add 40% glyoxal aqueous solution to PVA-117 in terms of solid content.
15% was added and similarly overcoated on the surface of thermal paper, dried at 50°C and calendered. These overcoated thermal papers have water resistance,
The color development and browning property (solvent resistance) due to the plasticizer in PVC were measured and compared. The results are shown in Table-2. Modification containing silyl groups even by overcoating
It can be seen that the combined use of PVA and a waterproofing agent provides excellent water resistance and solvent resistance.

【table】

Claims (1)

[Scope of Claims] 1. A heat-sensitive recording sheet in which a heat-sensitive coloring component layer is provided on a supporting substrate, wherein a modified polyvinyl alcohol containing a silyl group in the molecule and a melamine-formaldehyde resin, a urea-formaldehyde resin, or a polyamide are used as a water resistance agent. -Epoxy resin 1
1. A heat-sensitive recording sheet, characterized in that a species or two or more species are contained in the heat-sensitive coloring component layer or provided on the layer. 2. The heat-sensitive recording material according to claim 1, wherein the modified polyvinyl alcohol containing silicon in the molecule is a saponified product of a copolymer of a vinyl ester and an olefinic unsaturated monomer containing a silyl group in the molecule. sheet. 3. The heat-sensitive recording sheet according to claim 1, wherein the modified polyvinyl alcohol contains 0.01 to 10 mol% of a monomer unit containing a silyl group in the molecule. 4. The heat-sensitive recording sheet according to claim 1, wherein the modified polyvinyl alcohol contains 0.1 to 5 mol% of a monomer unit containing a silyl group in the molecule. 5. Claim 1, wherein the weight mixing ratio of the modified polyvinyl alcohol containing a silyl group in the molecule and the waterproofing agent is 1 to 50 parts of the waterproofing agent (in terms of solid content) per 100 parts of the modified polyvinyl alcohol. The heat-sensitive recording sheet described.