JPS6334836B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to recording materials. Specifically, the present invention relates to an electron-accepting color developer that develops color upon contact with an electron-donating color former. Conventionally, recording materials that utilize the coloring phenomenon caused by contact between an electron-donating color former and an electron-accepting color developer include thermal copying paper, electrically conductive thermal recording paper, pressure-sensitive recording paper, and the like. Representative examples of these recording materials include pressure-sensitive recording paper and heat-sensitive recording paper. Pressure-sensitive recording paper is prepared by placing a sheet coated with microcapsules of an electron-donating color former solution and a sheet coated with a color developer facing each other, overlapping the coated surfaces of the two so that they are facing each other, and writing on the pressure-sensitive recording paper. With the destruction of the capsule, the oil containing the color former is transferred to the color developer surface, and the color former and the color developer react to form a color.
In recent years, it has come into widespread use with the progress of administrative streamlining. On the other hand, thermal recording paper, especially thermal recording paper called a two-component coloring system, is made by dispersing an electron-donating coloring agent and an electron-accepting coloring developer in the form of fine particles, and adding a binder or the like to these. They are applied to a support such as paper so as to be separated from each other, and when heated, one or both of them melt and come into contact, resulting in a chemical reaction that produces a colored image. Thermal recording paper and thermal recording methods are used in recorders, facsimile machines, copying machines, etc., and have features such as no noise when recording, no need for developing and fixing, and easy maintenance and management of the equipment. As a result, demand in the facsimile field has grown significantly in recent years. The dye coloring method, which is the mainstream among thermosensitive recording methods, utilizes the coloring reaction of electron-donating colorless dyes, such as triphenylmethane phthalide dyes such as crystal violet lactose (CVL), 3-diethylamino-6-
Fluoran dyes such as methyl-7-anilinofluorane, substituted indolinobenzospiropyran dyes, and bisphenol A [2,2'bis-
(4-Hydroxyphenyl)propane] Combinations with other phenol compounds, organic acids or salts thereof, etc. are disclosed. However, color developers with even better performance have been desired for pressure-sensitive copying paper and heat-sensitive recording paper that utilize color reactions with electron-donating color formers. In particular, in the recording paper of the present invention using bisphenol A, which has conventionally been widely used as a color developer for heat-sensitive recording paper, (1) the melting point of bisphenol A is
Because the temperature is as high as 157℃, in order to obtain sufficient color image density,
(2) the light fastness of the colored image is insufficient; (3) the colored image has a tendency to decrease in density or disappear upon contact with plasticizers, etc.; (4) The moisture resistance of thermal recording paper is low;
There are many points that would like to be improved, such as (5) the tendency for natural color development (contamination) when stored under high temperature and high humidity conditions, and (5) the tendency for color developers to sublimate during color development and storage. An excellent color developer was desired. In particular, in recent years, a new color developer has been developed as a color developer for thermal recording paper for high-speed printers with short heating pulse widths, which develops color at low temperatures, reaches sufficient color density within a narrow temperature range from the color initiation temperature, and develops color instantly when heated. The appearance of was requested. As a result of various studies on color developers, the present inventors found that the general formula () (In the formula, R ₁ represents an alkyl group having 1 to 3 carbon atoms, a halogenated alkyl group, a cyclohexyl group, a phenyl group, a hydroxyl group, or a halogen atom, and R ₂ and R ₃ represent an alkyl group having 1 to 15 carbon atoms. bis-( _{4 -} hydroxy The inventors have discovered that a heat-sensitive recording material with significantly superior performance can be obtained by using phenyl sulfide derivatives, and have arrived at the present invention. That is, by using the above-mentioned bis-(4-hydroxyphenyl) sulfide derivatives in thermal recording paper, the 2,
Compared to thermal recording sheets that use 2-bis(4-hydroxyphenyl)propane (i.e., bisphenol A) as a color developer, (1) there are many compounds with low melting points that melt at low temperatures; When applied, the amount of auxiliary agents such as melting point depressants can be significantly reduced or even eliminated, (2)
A sufficient color density is reached within a narrow range from the color initiation temperature, and the color image is extremely deep. (3) The color image has excellent storage stability and exhibits excellent light fastness and plasticizer fastness. (4) Extremely low sublimability.
(5) A thermal recording sheet with excellent handling and storage stability, such as less staining and less natural coloring tendency when stored under humid heat conditions, can be obtained, solving the problems of conventional thermal recording paper. It is something. The color developer of the present invention has the general formula () (In the formula, R ₁ , R ₂ and R ₃ have the same meanings as in the general formula ()) by reacting a substituted phenol with sulfur chloride (SCl ₂ ) in the presence of a catalyst. Obtainable. Specifically, the color developer of the present invention is bis-(4
-Hydroxy-2,5-dimethylphenyl) sulfide, bis-(4-hydroxy-2-methyl-
5-ethyl phenyl) sulfide, bis-(4-
Hydroxy-2-methyl-5-iso-propylphenyl) sulfide, bis-(4-hydroxy-
2,3-dimethylphenyl) sulfide, bis-
(4-hydroxy-2,5-diethylphenyl)
Sulfide, bis-(4-hydroxy-2,5-
diisopropylphenyl) sulfide, bis-
(4-hydroxy-2,5-dichlorophenyl sulfide), bis-(4-hydroxy-2,5-
dibromophenyl) sulfide, bis-(4-hydroxy-2,3,6-trimethylphenyl) sulfide, bis-(2,4,5-trihydroxyphenyl) sulfide, bis-(4-hydroxy-2- cyclohexyl-5-methylphenyl) sulfide, bis-(4-hydroxy-2,5-ditrichloromethylphenyl) sulfide, bis-
(2,3,4-trihydroxyphenyl) sulfide, bis-(2-tert-butyl-4,5-dihydroxyphenyl) sulfide, bis-(4-hydroxy-2,5-diphenylphenyl) sulfide , bis-(4-hydroxy-2-tert-octyl-5-methylphenyl) sulfide and the like, but are not limited to these. As the color forming agent used together with the color developer of the present invention, various electron-donating dyes that develop color by melting reaction with the color developer are used, but specifically,
3,3'-bis(4-dimethylaminophenyl)-
6-dimethylaminophthalide [crystal violet lactone], 3,3'-bis(4-dimethylaminophenyl)phthalide [malachite green lactone], 3-diethylamino-6-methyl-
7-anilinofluorane, 3-diethylamino-
7-(0-chloroanilino)fluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-piperidino-6-methyl-7-anilinofluorane, 3-methyl cyclohexylamino-6-methyl- 7-anilinofluorane, 3-ethyl-p-tolylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-(p-tert-butylanilino)fluorane, 3-diethylamino-6 -Methyl-7-chlorofluorane, 3-diethylamino-7-dibenzylaminofluorane, 3-cyclohexylamino-7-chlorofluorane, 3-diethylamino-7-methylfluorane, 1,3,3-trimethylindo Lino-6'-chloro-8'-methoxy-benzospiropyran, 3-(4-diethylamino-2
-ethoxyphenyl), 3-(1-ethyl-2-
Examples include methylindol-3-yl)-4-azaphthalide and tris-4-dimethylphenylmethane. As an example of the recording material of the present invention, a general manufacturing method for heat-sensitive recording paper is as follows. First, the color developer of the present invention and the usually colorless to light color former are separately mixed or pulverized and dispersed together with a binder in a medium that does not dissolve them (for example, an organic solvent such as water or petroleum). Make a liquid. Binders used in the preparation of these dispersions include polyvinyl alcohol, carboxymethylcellulose, methylcellulose, hydroxyethylcellulose, styrene-maleic acid copolymer or salt, diimbutylene-maleic acid copolymer or salt, alginate sodium salt, modified Examples include starch, gum arabic, styrene-butadiene rubber latex, terpene resin, synthetic polymers such as cyclized rubber, and natural or modified natural polymers. The resulting dispersion is coated onto a support such as paper and dried to produce a heat-sensitive recording sheet. Generally, both dispersions are mixed and coated on the support, but both dispersions may be applied separately in two parts. Suitable amounts of color former, developer and binder are 1 to 15 parts by weight of color former, 1 to 95 parts by weight of color developer and 1 to 40 parts by weight of binder. When preparing the heat-sensitive recording sheet of the present invention, if necessary, inorganic or Organic pigments, water-soluble binders with crosslinking properties, dialdehyde starch or crosslinking accelerators, compounds with two or more ethyleneimine groups, compounds with two or more 1,2-epoxy ring structures, protein-based adhesives and water-resistant agents such as glutaraldehyde. Animal-based waxes such as beeswax and serrata wax, vegetable-based waxes such as carnauba wax, synthetic waxes such as petroleum waxes, paraffin waxes, microcrystalline waxes, and polyethylene waxes, and metallic soaps such as calcium stearate and zinc stearate ( Use of lubricants such as higher fatty acid metal salts, pressure coloring inhibitors, melting point depressants such as stearic acid amide, palmitic acid amide, and ethylene bistes aromaamide, sensitivity improvers, various surfactants, antifoaming agents, etc. It is also possible to improve the coating suitability and properties of the recording sheet. The present invention will be explained below using examples. The following methods were used to prepare the recording sheet and to measure various performances. () How to make a heat-sensitive recording sheet [A] Liquid Crystal Violet Lactone
10.5g 10% polyvinyl alcohol (Kuraray #117) 45.0g Water 44.5g Total 100.0g [B] Liquid Developer 105g 10% polyvinyl alcohol 450g Water 445g Total 1000g [C] Liquid Talc 105g 10% polyvinyl alcohol 450g Water 445 g Total 1000g Prepare a dispersion of the above [A], [B], and [C] liquids using a sand grinding mill, and prepare 7 parts by weight of liquid [A], 27 parts by weight of liquid [B], and 36 parts by weight of liquid [C]. Mix the parts and apply it on high-quality paper until the dry coating amount is reached.
It was coated and dried to give a weight of 4.0±0.5 g/m ² to obtain a blue color thermosensitive recording sheet. () Method for evaluating the performance of heat-sensitive recording sheets (1) Color density The coated recording sheet is brought into contact with a metal block at a surface temperature of 200°C for 5 seconds to develop color. Ten minutes after color development, determine the color density using a Macbeth densitometer. (2) Storage stability of colored images The recording sheet colored by the method in (1) is left indoors in a dark place for 6 months, and then the change in color density is measured. (3) Light fastness of colored image The recording sheet colored by the method in (1) is exposed to light for 3 hours using a carbon arc fed meter. The color density after the test is measured using a Macbeth densitometer. (4) Plasticizer resistance of colored images 30% with dioctyl phthalate as a plasticizer component
A commercially available vinyl chloride sheet containing 10% of the coloring was brought into close contact with the colored side of the recording sheet colored by method (1), and a load of 1 kg/100 cm ² was placed on the sheet and stored in a constant temperature bath at 60°C for 24 hours. Determine the subsequent color density. (5) Degree of scumming on the recording sheet The degree of scumming on the coated recording sheet is measured using a Macbeth densitometer. (6) Moisture resistance of recording sheet The coated recording sheet was stored in a constant temperature and humidity chamber at 45°C and 90% RH for 24 hours, and the degree of self-coloring after the test was measured using a Macbeth densitometer. The higher the reflection density value after the test, the more intense the natural color development under humidification. (7) Sublimation property of color developer In order to obtain a colored image on a thermosensitive recording sheet through thermal color development using a thermal head, the color developer is exposed to high temperature conditions. If the vapor pressure of the color developer is high, problems such as head staining due to sublimation or evaporation of the color developer, dusting on the paper surface, and decreased coloring ability are likely to occur during color development or during high-temperature storage. As a guide to the sublimability of the color developer, use a thermobalance.
Weight loss rate up to 200℃ (heating rate 2℃/min,
room temperature to 200°C). The smaller the weight reduction rate, the lower the degree of sublimation and volatilization of the color developer in the practical temperature range. Examples 1 to 4 and Comparative Examples 1 to 2 Heat-sensitive recording sheets were prepared using the compounds having the following structural formulas, respectively, according to the method for producing heat-sensitive recording paper described above. Example 1 Bis-(4-hydroxy-3,6-dimethylphenyl) sulfide (melting point 181-183℃) Example 2 Bis-(4-hydroxy-3-isopropyl-
6-methylphenyl) sulfide (melting point 152-153.5℃) Example 3 Bis-(4-hydroxy-2,5-dichlorophenyl) sulfide (melting point 175-176℃) Example 4 Bis-(4-hydroxy-2-isopropyl-
5-methylphenyl) sulfide (melting point 170-172℃) Comparative example 1 Bisphenol A (melting point 157℃) Comparative example 2 Bis-(4-hydroxy-3-tert-butyl-
6-methylphenyl) sulfide (melting point 160-161℃) Comparative example 3 Bis-(4-hydroxy-3-tert-butyl-
6-Methylphenyl) sulfide (melting point 125-126°C) Table 1 shows the results of evaluating the performance of the prepared heat-sensitive recording sheet. 【table】

Claims (1)

[Claims] 1. General formula () as a color developer on a support (In the formula, R ₁ represents an alkyl group having 1 to 3 carbon atoms, a halogenated alkyl group, a cyclohexyl group, a phenyl group, a hydroxyl group, or a halogen atom, and R ₂ and R ₃ represent an alkyl group having 1 to 15 carbon atoms. bis-( _{4 -} hydroxy A heat-sensitive recording material characterized by using a (phenyl) sulfide compound.