JPS6345087A - Thermal recording sheet - Google Patents

Abstract

PURPOSE:To contrive higher plasticizer resistance and higher transparency, by providing a thermal recording layer comprising a sulfonium salt of a specified general formula and a colorless or light-colored electron-donative dye. CONSTITUTION:A thermal recording layer comprising a colorless or light-colored dye and a sulfonium salt of formula I is provided. In formula I, each of R1 and R2, which may combine with each other to form a ring, is a substd. or unsubstd. hydrocarbon group, A is allyl substd. by at least one aliphatic group, a tertiary aliphatic group or a hydrocarbon group having a 6-20C monovalent aromatic group at alpha-position with respect to the cationic sulfur atom, and X is a non-nucleophilic anion. The sulfonium salt scarcely performs a color reaction even when being dissolved in the same solvent together with the electron- donative dye, and displays an extremely excellent effect in, for example, a thermal recording sheet provided with a colorless transparent coating layer and required to have a high degree of transparency. In addition, the sulfonium salt has extremely excellent resistance to plasticizers, so that recorded images will not fade even in contact with a plastic film.

Description

DETAILED DESCRIPTION OF THE INVENTION "Graduation field of application" The present invention relates to a heat-sensitive recording sheet, and particularly to a heat-sensitive recording sheet suitable for a recording sheet that has excellent print fading resistance against plasticizers and requires transparency. It is something.

``Prior art'' A thermosensitive recording material utilizes a coloring reaction between a colorless or light-colored electron-donating dye and an organic or inorganic coloring agent to obtain a recorded image by bringing both coloring substances into contact with each other using heat. well known. Such heat-sensitive recording media are relatively inexpensive, and the recording devices are compact and relatively easy to maintain, so they are used not only as recording media for facsimiles and various computers, but also in a wide range of fields.

Generally, such heat-sensitive recording materials are prepared by mixing an appropriate water-soluble polymer such as polyvinyl alcohol or carboxymethyl cellulose with an electron-donating dye and a coloring agent, and if necessary, pigments such as calcium carbonate and titanium oxide, antioxidants, etc. brightener,
An aqueous dispersion prepared by adding various auxiliary agents such as lubricants and thickening agents is applied to a suitable support such as paper, synthetic paper, or film.
Manufactured by drying.

``Problems to be solved by the invention'' However, the conventional heat-sensitive recording material manufactured in this way is
If plasticizers (for example, phthalate esters such as dioctyl phthalate, phosphate esters such as tricresyl phosphate, etc.) or oils contained in plastic films such as polyvinyl chloride come into contact, the recorded image may fade. However, countermeasures have been proposed, such as providing an overcoat layer on the heat-sensitive recording layer, but satisfactory results have not always been obtained. In addition, when a plastic film is used as a support, it is inevitably affected by the plasticizer contained in the film, so at present it is difficult to obtain products with commercial value.

In view of the current situation, the present inventors have developed the conventional rS! As a result of extensive research into improving the above-mentioned poor plasticizer resistance of thermal recording materials, they discovered a material with completely different characteristics from conventional coloring agents. By combining it with a colorless or light-colored electron-donating dye, we have completed an outside-the-window recording sheet that has extremely excellent plasticizer resistance and is especially suitable for recording sheets that require transparency.

"Means for Solving the Problem" The present invention uses a colorless or light-colored electron-donating dye and the following general formula (
This is a heat-sensitive recording sheet characterized by being provided with a heat-sensitive recording layer containing the sulfonium salt shown in 1).

[In the formula, R+ and Rz each represent a substituted or unsubstituted hydrocarbon group, and may be bonded to each other to form a ring.

A is an allyl group substituted with at least one aliphatic group,
It represents a tertiary aliphatic group or a hydrocarbon group having one C5-2o monovalent aromatic group at the alpha position to the cationic sulfur atom, and X represents a non-nucleophilic anion. ] "Action" The specific sulfonium salt represented by the above general formula (1) used in the present invention hardly causes a coloring reaction even when dissolved together with an electron-donating dye in a solvent, and the resulting ? Even when the 8 liquid is applied to a support, only a virtually colorless and transparent coating layer is formed. However, it is a material that has extremely unique properties in that when it is thermally recorded with a thermal recording device, a color reaction occurs and a clear recorded image is formed.

The present inventors speculate that the specific sulfonium salt represented by the above general formula [I] is a unique compound that decomposes when heated and generates an electron-accepting substance that causes the electron-donating dye to develop color. It is presumed that if it is simply dissolved together with an electron-donating dye in a solvent, it will have almost no coloring ability, and that it will only thermally decompose and acquire coloring ability when heated.

Therefore, since it can be used together with electron-donating dyes by dissolving it in a solvent, it forms a highly transparent coating layer, unlike the aqueous dispersion coating liquid used in ordinary thermosensitive recording media. be done. Therefore, it exhibits extremely excellent effects in heat-sensitive recording sheets that require a high degree of transparency, such as recording sheets for overhead projectors.

Moreover, the outside-window recording sheet of the present invention using the specific sulfonium salt represented by the above general formula (1) has extremely excellent resistance to plasticizers, and the recorded image will not fade even if it comes into contact with a plastic film. For example, even if a plastic film is used as the support, a heat-sensitive recording sheet having sufficient plasticizer resistance can be obtained. The reason why the fastness of recorded images to plasticizers is significantly improved is not necessarily clear, but it may be because the relationship between the electron-accepting substance produced by thermal decomposition and the electron-donating dye is adjusted in a well-balanced manner. It is assumed that there is no such thing.

Therefore, the above-mentioned formula-a C exhibiting excellent properties as described above
The specific sulfonium salt represented by I) will be explained in more detail. The substituents R8 and R2 in the general formula [I] each represent the same or different substituted or unsubstituted hydrocarbon groups, but preferably represent an aliphatic or alicyclic group. R
1 and R2 may combine with each other to form a ring, and the group includes an unsaturated bond, an alkoxy group, a nitro group, a halogen group, a hydroxyl group, a carboxyl group, an ester group, an ether group, a cyano group, a carbonyl group, and a sulfone group. It can contain functional groups such as a group, a 1,000-oneythyl group, and the like.

Substituent A is an allyl group or tertiary aliphatic group substituted with at least one aliphatic group represented by the following general formula (II) or [■], [wherein R3-R6 are hydrogen atoms] or a substituted or unsubstituted aliphatic group, preferably an alkyl group, and at least one of R3-R4 must be a substituted or unsubstituted aliphatic group, preferably an alkyl group. R7~R7
is selected from substituted or unsubstituted aliphatic groups, preferably alkyl groups. ] Or it is a hydrocarbon group having one C8-28 monovalent aromatic group at the α-position with respect to the cationic sulfur atom.

The aromatic group may be substituted with a group including an aliphatic group, an alkoxy group, a nitro group, a halogen group, a hydroxyl group, a carboxyl group, an ester group, a cyano group, a carbonyl group, a sulfone group, a 1,000-onythyl group, and the like.

Substituent X is a non-nucleophilic anion, 2MQm- (M is an atom selected from BXP, Sb, As, Fe, AI, Sn, Zn, 7i or Cd, preferably B, P, As
Or sb. Q is a halogen atom, and m is a number from 1 to 6. ], but a preferred specific example is B F 4-+ P F ;.

Examples include A S F6-, S b F-&, and the like. In addition, as the non-nucleophilic anion X, 2MQ,
, ○H (in the formula, M, Q, and m are the same as above) can also be used.Furthermore, as other non-nucleophilic anions, perchlorate ion (C1○4-), trichloride ion, Examples include fluoromethyl sulfite ion (CF3SO31, fluorosulfonate ion (FS○3-), )'luenesulfonate anion, trinitrohenzenesulfonate anion, and the like.

Specific examples of the specific sulfonium salt represented by the general formula (1) include the following compounds.

Furthermore, benzyltetramethylenesulfonium hexafluorophosphate, benzyltetramethylenesulfonium hexafluoroarsenate, penzyltetramethylenesulfonium hexafluoroantimonate, p-methoxybenzyltetramethylenesulfonium hexafluoroantimonate, p-methoxybenzyltetramethylenesulfonium Hexafluoroarsenate, p-nitropenzyltetramethylenesulfonium trifluoroarsenate, o-nitrobenzyltetramethylenesulfonium hexafluoroarsenate, benzyldimethylsulfonium hexafluoroantimonate, benzyldiethylsulfonium hexafluorophos Fae
For example,

In the present invention, the colorless or light-colored electron-donating dye used in combination with the specific sulfonium salt as described above is not particularly limited, and various conventionally well-known dyes may be appropriately selected and used. Of course, two or more types can also be used in combination.

Examples of such electron-donating dyes include 3,3-bis(
p-dimethylaminophenyl)-6-dimethylaminophthalide, 3,3-bis(p-dimethylaminophenyl)
Phthalide, 3-(p-dimethylaminophenyl)-3-
(1,2-dimethylindol-3-yl)phthalide,
3-(p-dimethylaminophenyl')-3-(2-methylindol-3-yl>phthalide, 3,3-bis(
1゜2-dimethylindol-3-yl)-5-dimethylaminophthalide, 3,3-bis(1,2-dimethylindol-3-yl)-6-dimethylaminophthalide,
3.3~bis(9-ethylcarbazol-3-yl)-
6-dimethylaminophthalide, 3,3-bis(2-phenylindol-3-yl)-6-dimethylaminophthalide, 3-p-dimethylaminophenyl-5-(1-methylpyrrol-3-yl) -triallylmethane dyes such as -6-dimethylaminophthalide, 4,4'-bis-dimethylaminobenzhydrylbenzyl ether, N-halophenyl-leucoauramine, N-2,4,5-t')
') Diphenylmethane dyes such as lorophenyl leuco auramine, thiazine dyes such as benzoyl leucomethylene blue, p-nitrobenzoyl leucomethylene blue, 3-methyl-spiro-dinaphthopyran, 3-ethyl-
Spiro-dinaphthopyran, 3-phenyl-spiro-dinaphthopyran, 3-benzyl-spiro-dinaphthopyran,
Spiro dyes such as 3-methyl-naphtho-(6'-methoxyhenzo)spiropyran, 3-propyl-spiro-dibenzopyran, rhodamine-B-anilinolactam, rhodamine(p-nitroanilino)lactam, rhodamine (
Lactam dyes such as 0-chloroanilino)lactam, 3
-Dimethylamino-7-methoxyfluoran, 3-diethylamino-6-methoxyfluoran, 3-diethylamino-7-methoxyfluoran, 3-diethylamine-
7-chlorofluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-6,
7-dimethylfluorane, 3-(N-ethyl-p-)luidino)-7-methylfluorane, 3-diethylamino-7-N-acetyl-N-methylaminofluorane, 3
-diethylamino-7-N-methylaminofluorane,
3-diethylamino-7-dibenzylaminofluorane, 3-diethylamino-7-N-methyl-N-benzylaminofluorane, 3-diethylamino-7-N-chloroethyl-N-methylaminofluorane, 3-diethylamino- 7-N-diethylaminofluorane, 3-(N
-ethyl-p-toluidino)-6-methyl-7-phenylaminofluorane, 3-(N-ethyl-p-)luidino)-6-methyl-7-(p-toluidino)fluorane, 3-(N- cyclopentyl-N-ethylamino)-
6-Methyl-7-anilite fluorane, 3-diethylamino-6-methyl-7-phenylaminofluorane, 3
-diethylamino-7-(2-carbomethoxy-phenylamino)fluorane, 3-(N-ethyl-N-isoamylamino)-6-methyl-7-phenylaminofluorane, 3-(N-cyclohexyl-N -methylamino)
-6-Methyl-7-phenylaminofluorane, 3-pyrrolidino-6-methyl-7-phenylaminofluorane, 3-piperidino-6-methyl-7-phenylaminofluorane, 3-diethylamine-6-methyl- 7-xylidinofluorane, 3-diethylamino-7-(o-chlorophenylamino)fluoran, 3-dibutylamino-7-(o-chlorophenylamino)fluoran, 3-
Pyrrolidino-6-methyl-7-p-butylphenylaminofluorane, 3-(N-methyl-Nn-amyl)amino-6-methyl-7-phenylaminofluorane, 3
-(N-ethyl-Nn-amyl)amino-6-methyl-7-phenylaminofluorane, 3-(N-ethyl-
N-4so-amyl)amino-6-methyl-7-phenylaminofluorane, 3-,(N-methyl-Nn-hexyl)amino-6-methyl-7-phenylaminofluorane, 3-(N -ethyl-N-n-hexyl)amino-6-methyl-7-phenylaminofluorane, 3-(
Examples include fluoran dyes such as N-ethyl-N-β-ethylhexyl)amino-6-methyl-7-phenylaminofluoran.

The heat-sensitive recording sheet of the present invention is generally produced by dissolving or dispersing the specific sulfonium salt and electron-donating dye in an appropriate solvent and applying a coating solution to various supports. . However, when using a film as a support, it is also possible to knead a sulfonium salt and an electron-donating dye into the recording sheet when forming the film, and furthermore, it is possible to mix the film/thermal recording layer/
It is also possible to form a recording sheet in a laminated state like a film.

When producing an outside recording sheet using a coating method, it is preferable to use a binder together when forming a heat-sensitive recording layer.
It is also a preferred embodiment to incorporate appropriate auxiliary agents in consideration of the required quality characteristics of the recording sheet, such as heat resistance, wearability with the support, solvent resistance, scuffing resistance, and abrasion resistance. For example, a lubricant is added to improve the running properties of the film, and antioxidants, ultraviolet absorbers, and image storage improvers are added to improve storage stability. Further, if necessary, a sensitizer, a dye or a pigment for adjusting the color tone, etc. can be added as appropriate.

Examples of solvents used in preparing coating solutions include aromatic solvents such as benzene and toluene, ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone, ester solvents such as ethyl acetate and butyl acetate, and the like. Examples include mixtures.

The combined ratio of the electron-donating dye and the specific sulfonium salt is about 0.1 to 50 parts by weight, more preferably about 0.5 to 5 parts by weight, per 1 part by weight of the electron-donating dye. is desirable. Further, the coating amount of the coating liquid when forming the recording layer is generally about 0.1 to 5 g/d, more preferably 0.5 to 2 g/d based on the amount of the mixture of the electron donating dye and the specific sulfonium salt. It is desirable to adjust within a range of approximately tri.

"Examples" The present invention will be described in more detail with reference to Examples below, but the present invention is not limited thereto unless it goes beyond the gist of the present invention. In addition, parts in the examples indicate parts by weight unless otherwise specified.

Example 1 A coating liquid obtained by uniformly dissolving the following components was coated with a thickness of 25 μm.
The mixture was coated on a polyester film with a solid content of 3 g/m'' and dried at 100° C. for 30 seconds to obtain a heat-sensitive recording sheet.

・3-dibutylamino-7-(o-chlorophenylamino)fluoran 1 part ・Prenyltetramethylenesulfonium hexafluorophosphate 2 parts ・Methyl methacrylate/methacrylic a = 95/5 (wt/wt) copolymer
Part 7/Toluene
10 parts methyl ethyl ketone
10 parts Example 2 A heat-sensitive recording sheet was obtained in the same manner as in Example 1, except that a coating liquid obtained by uniformly dissolving the following components was used.

・3-(N-cyclohexyl-N-methylamino) = 6
-Methyl-7-phenylaminofluorane 1.5 parts, dimethylprenylsulfonium hexafluoroarsenate 2.5 parts, butyral resin (trade name: Esresoku BM-3゜Building Chemical Industry - 6 parts, benzene)
8 parts methyl ethyl ketone
12 parts Example 3 A thermosensitive recording sheet was obtained in the same manner as in Example 1 except that a coating liquid obtained by uniformly dissolving the following components was used.

・3-(N-ethyl-N-1so-amyl)amino-
2 parts of 6-methyl-7-phenylaminofluorane, 2 parts of t-butyltetramethylenesulfonium hexafluorophosphate, 20 parts of acrylic copolymer, and toluene
4 parts methyl ethyl ketone
10 parts Example 4 A thermosensitive recording sheet was obtained in the same manner as in Example 1, except that a coating liquid obtained by uniformly dissolving the following components was used.

・1 part of 3-diethylaminohenzo(a) fluoran ・2 parts of p-methoxybenzyltetramethylenesulfonium hexafluoroarsenate ・7 parts of methyl methacrylate/methacrylic acid-9515 (wt/wt) copolymer ・Toluene
10 parts methyl ethyl ketone
10 parts Example 5 3-dibutylamino-7-(O-chlorophenylamino)fluoran was added to crystal violet lactone (CV
A thermosensitive recording sheet was obtained in the same manner as in Example 1 except that L) was used instead.

Comparative Example I Preparation of Liquid A・3-dibutylamino-7-(o-chlorophenylamino)fluoran 2 parts・5% methylcellulose aqueous solution 5 parts・water
40 parts B solution preparation 4.4-isopropylidenediphenol 20 parts 5%
Methylcellulose aqueous solution 5 parts/water
55 parts Preparation of liquid C/Stearic acid amide 20 parts/5%
Methylcellulose aqueous solution 5 parts/water
55 parts Lacquer preparation 25% acetoacetyl group-modified polyvinyl alcohol aqueous solution 400 parts 40% glyoxal water? Yong night 2.5 parts/Wednesday
300 parts of each of the above solutions A, B, and C were ground using a sand grinder until the average particle size was 3 μm. Thereafter, a coating liquid obtained by mixing 55 parts of liquid A, 80 parts of liquid B, and 80 parts of liquid C was applied to a 25 μm thick polyester film to a solid content of 6 g/m and dried, and the recording layer was Liquid D was coated on top so that the solid content was 5 g/m and dried to obtain a heat-sensitive recording sheet.

Comparative Example 2 3-(N-cyclohexyl-N instead of 3-dibutylamino-7-(O-chlorophenylamino)fluorane
A thermosensitive recording sheet was obtained in the same manner as in Comparative Example 1 except that 6-methyl-7-phenylaminofluorane (-methylamino)-6-methyl-7-phenylaminofluoran was used.

Comparative Example 3 3-dibutylamino-7-(O-chlorophenylamino,
') A thermosensitive recording material was obtained in the same manner as in Comparative Example 1 except that crystal violet lactone was used instead of fluoran.

The following quality evaluation tests were conducted on the eight types of heat-sensitive recording sheets prepared in this way, and the results are listed in Table 1.

(2) Color development test: Recorded images were obtained by bringing the polyester film surface (opposite side to the surface coated with the recording layer) for Examples and the surface coated with the recording layer in contact with a hot plate at 200° C. for 5 seconds for Comparative Examples.

■Plasticizer resistance: A wrap film was placed in close contact with the recorded image, and the image was left at 40°C for 2 days to check the degree of discoloration.

■Transparency of recording sheet: Judging visually.

Table 1 [Remarks] The evaluation criteria for the water quality evaluation test is: ○...
・ Excellent for scratching.

△... Slightly inferior.

×...Extremely inferior.

"Effects" As is clear from the results in Table 1, the heat-sensitive recording sheets of each example of the present invention all have excellent printing fastness against plasticizers, and are obtained by using a film as a support. The resulting recording sheet exhibited extremely excellent transparency.

Claims (1)

[Scope of Claims] A heat-sensitive recording sheet comprising a heat-sensitive recording layer containing a colorless or light-colored electron-donating dye and a sulfonium salt represented by the following general formula [I]. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ [In the formula, R_1 and R_2 each represent a substituted or unsubstituted hydrocarbon group, and may be bonded to each other to form a ring. A is an allyl group substituted with at least one aliphatic group,
It represents a tertiary aliphatic group or a hydrocarbon group having one monovalent aromatic group of C_6_ to_2_0 at the α-position with respect to the cationic sulfur atom, and X represents a non-nucleophilic anion. ]