JPH01154162A - Electrophotographic toner - Google Patents

Abstract

PURPOSE:To extinguish color by heat and to render a copy legible at the time of secondary copying by incorporating a specified mateliable to discolor by heat, a toner binder resin, and an electric charge controller. CONSTITUTION:The toner contains a color developing agent, optionally selected so long as it develops color on reaction with an acidic material, a compound having a phenolic hydroxyl group, such as tertiary butylphenol, or nonylphenol, a heat discoloring material composed of alcohol, ester and/or ketone, preferably having a melting point of 10-45 deg.C, the toner binder resin, and the charge controller. The copy obtained by using this toner can be easily read at temperatures below room temperature, but the image part is made colorless by heat at the time of recopying, thus permitting legible secondary copies cannot be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrophotographic toner for preventing secondary copying.

[Conventional technology]

With the spread of copying machines, especially electrophotographic copying machines, copies can be easily made and secondary copies can be easily made from copies, making it difficult to preserve important information. Therefore, in order to maintain the confidentiality of important information, there are methods to prevent secondary copying by electrophotographic copying machines, such as (1) using copy paper coated with a photochromic material that changes color when exposed to light, and (2) using a fluorescent material test. There are methods using mixed toner. Method (1) utilizes the fact that a photochromic material coated on paper develops color when exposed to light during copying.
Copying is prevented by eliminating the density difference between the image area and the non-image area.

However, this method has the disadvantage that it inevitably produces a blurred but legible secondary copy.

Method (2) uses a toner containing a fluorescent substance instead of a dye, but with this method, the primary copy is almost unreadable under visible light, so special equipment is required for reading, such as an ultraviolet irradiator. , black light, etc. are required.

[Structure of the invention]

The present invention provides a thermochromic material comprising a coloring agent (a), a compound having a phenolic hydroxyl group (b), an alcohol, an ester and/or a ketone, and a toner binder resin and an electric charge. This is an electrophotographic toner characterized by containing a control agent.

Copies made using the electrophotographic toner of the present invention are easy to read at temperatures below room temperature, but when recopied using an electronic copying machine, the image area becomes colorless (white) due to heat during exposure. It has the advantage that no readable secondary copies are obtained.

The coloring agent (a) used in the present invention may be one that develops color by reacting with an acidic substance, and examples thereof include the following compounds. Triaryl compounds such as 3,3-
Bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (crystal violet lactone), 3
．． 3-bis(p-dimethylaminophenyl)phthalide,
3-(p-dimethylaminophenyl)-3-(1,2-
dimethylindol-6-yl) phthalide, 3,6-bis(9-ethylcarbazol-6-yl)-5-dimethylaminophthalide, 6,6-bis(2-phenylindol-6-yl)-5- Dimethylaminophthalide, 5-
p-dimethylaminophenyl-3-(1-methylvirol-2-yl)-6-dimethylaminophthalide, diarylmethane compounds such as 4,4'-bis-dimethylaminobenzhydrin benzyl ether, N-halophenyl leuco Oh6ramin, N-2,4,5-)! J
Chlorophenylleucoauramine, xanthine compounds such as rhodamine B-anilinolactam, rhodamine B
-p-Nitroanilinolactam, Rhodamine B -p-
Chloroanili.

Noractam, fluoran compounds such as 3-dimethylamino-7-medoxyfluoran, 3-diethylamine-7-chlorofluoran, 6-diethylamine-6.8-
Dimethylfluorane, 3-diethylamine-7-methylaminofluorane, 3--)ethylamino-7-7enylamino-6-methylfluorane, 6-dinitylamino-7-dichloroethylaminofluorane, thiazine compounds such as benzoylleucomethyl Lev, Q/-
, p-nitrobenzylleucomethylene blue, spiro compounds such as 3-methyl-spirosinaphthohyran, 6
-Nitylose virodinaphthopyran, 3,3'-cyclolose virodinaphthopyran, 6-benzyl-spiro-
Dinaphthopyran, 3-propyl-spiro-dibenzopyran. These can also be used as a mixture.

Examples of the compound (b) having a phenolic hydroxyl group include the following compounds. Tertiary butylphenol, nonylphenol, dodecylphenol, 2,2'-
Bis(4-methyl-6-tert-butylphenol), α-
or β-naphthol, hydroquinone monomethyl ether, guaiacol, eugenol, p- or 0-chlorophenol, p- or O-bromophenol, (p-or hao-chlorophenyl)-p- or 〇-phenol, p
- Methyl, N-/l/, propyl, butyl, octyl or dodecyl esters of oxybenzoic acid, 3-ingropylcatechol, p-tert-butylcatechol, bisphenol A.

Bisphenol S, 1,2- or 2,3-dioxynaphthalene, chlorocatechol, bromocatechol, 2.4
-dihydroxybenzophenone, phenolphthalein, 0-cresolphthalein, methyl, ethyl, propyl, octyl or dodecyl esters of protocatechuic acid, 2,4,6-trioxymethylbenzene, 2,3.
4-) Lioxyethylbenzene, methyl, ethyl, propyl, butyl, hexyl, octyl, dodecyl, cetyl or stearyl ester of gallic acid, 2,3.5-)
Dioxynaphthalene, tannic acid, phenolic resin.

The alcohol, ester, and ketone (c) are preferably compounds with a melting point of 10 to 45°C, such as stearyl alcohol, myristyl alcohol, cetyl alcohol,
Examples include lauryl alcohol, butyl stearate, methyl stearate, lauryl stearate, methyl 1,2-dihydroxystearate, methyl myristate, cetyl myristate, and benzophenone.

For example, a lactone-based leuco dye changes color from a leuco type to a colored type due to the ring opening of the lactone ring within the molecule. Although the mechanism of action of alcohols, esters, and ketones 0→ is not clear, it is thought that they are the main elements governing the opening and closing of the lactone ring and its temperature characteristics.

The ratio of each component in the thermochromic material is 1 to 5 parts by weight of component (B) and 1 to 5 parts by weight of component (C) to 1 part by weight of component (A).
500 parts by weight, particularly 5 to 150 parts by weight, is preferred.

The binder resin for toner used in the present invention can be obtained by (co)polymerizing the following monomers. styrene,
Styrenes such as parachlorostyrene, α-methylstyrene, tertiary-butylstyrene, methyl acrylate, ethyl acrylate, n-propyl acrylate, stearyl acrylate, 2-ethylhexyl acrylate, phenyl acrylate, methacrylic acid α-methylene aliphatic monocarboxylic acid esters such as methyl, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, and phenyl methacrylate; vinyl nitriles such as acrylonitrile and methacrylaterile; vinyl methyl ether; and vinyl isobutyl. Vinyl ether of ether nato, vinyl pyridine such as 2-vinylpyridine and 4-vinylpyridine, N-vinyl cyclic compounds such as N-vinylpyrrolidone, vinyl ketone of vinyl methyl ketone, vinyl ethyl ketone, methyl isopropenyl ketone,
Unsaturated hydrocarbons such as ethylene, propylene, imbutylene, butadiene, imprene, → melon,
- Monofunctional vinyl monomers such as halogen-containing unsaturated hydrocarbons such as chlorobrene. In addition, for example, the following polyfunctional vinyl monomers can also be used. Ethylene glycol dimethacrylate, diethylene glycol diacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, neopentyl glycol dimethacrylate, dipropylene glycol dimethacrylate,
Polyhydric alcohol methacrylates such as trimethylolpropane trimethacrylate, trimethylolethane trimethacrylate, hentaerythritol tetramethacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, neopentyl glycol diacrylate, trimethylol propane triacrylate,
Trimethylolethane triacrylate, pentaerythritol diacrylate, etc. - polyhydric alcohol acrylate, polyfunctional vinylbenzene such as divinylbenzene. Polyfunctional monomers may be used in combination with monofunctional monomers.

When a polyfunctional monomer is used, the obtained polymer becomes crosslinked, and the durability of the finally obtained toner can be increased. The polymer may be crosslinked by using other crosslinking agents.

Examples of charge control agents include organic amine compounds (BONDRON AFP-B manufactured by Orient Chemical Co., Ltd.), chromium-containing dyes (BONDRON E-84 manufactured by Orient Chemical Co., Ltd.), and quaternary ammonium described in Japanese Patent Publication No. 44308/1983. Colorless or white dyes such as salts are used.

The toner of the present invention is obtained by melting and kneading a thermochromic material, a toner binder resin, a charge control agent, and, if necessary, toner additives, followed by pulverization and classification.

For example, the following compounds are used as toner additives. Anti-blocking agents such as fatty acid metal salts such as cadmium stearate, barium stearate, zinc oleate and cobalt palmitate, relatively low molecular weight polyethylene or polypropylene, higher fatty acids having 28 or more carbon atoms, paraffin, etc., infrared absorbers , plasticizers for modifying resin components, compatibility improvers between charge control agents and resin components, etc.

The toner of the present invention preferably has a thermochromic material encapsulated in microcapsules. These microcapsules can be manufactured by conventional methods. In order to produce a toner in which a thermochromic material is microencapsulated, it is preferable to disperse the microcapsules, toner binder resin, and charge control agent in a solvent, and then spray-dry the mixture using a spray dryer.

For example, toluene, xylene, etc. are used as the solvent.

〔Effect of the invention〕

Using the toner of the present invention, copies with sharp images can be obtained. However, when making a secondary copy of this copy, the image is discolored by heat, making it impossible to obtain a readable copy. A halogen lamp is used as a light source for an electronic copying machine, and since 80% or more of the emitted light is infrared rays, a large amount of heat is generated during exposure. In particular, since the object to be copied becomes extremely high in temperature when exposed to light, even when looking at the electrons that are irradiated with light, it is thought that the image will quickly fade away.

Example 1 1 part by weight of crystal violet lactone and 2 parts by weight of bisphenol A are dispersed in 80 parts by weight of liquid myristyl alcohol heated to 50°C. This dispersion was added dropwise to a dispersion of 5 parts by weight of urea resin and 100 parts by weight of water at 60°C, stirred at high speed, and formalin was added as a hardening agent.
By adding 5 parts by weight and drying, microcapsules having a particle size of 1 to 3 μm in which the thermochromic material is encapsulated are obtained.

When 50 parts by weight of this microcapsule, 950 parts by weight of toluene, 50 parts by weight of epoxy resin and electricity are spray-dried,
A positively charged toner for electrophotography is obtained. This toner 5
y was mixed with 100 g of iron powder carrier to prepare a developer. When I loaded this into an electronic copying machine and made copies, the room temperature was 25°C.
C! A primary copy with a clear image was obtained below.

When this secondary copy was recopied as a manuscript, no legible secondary copy was obtained. Note that the temperature of the glass plate of the document table of the electronic copying machine at this time was 62°C. Furthermore, when the second copy was returned to room temperature, the original clear image was reproduced.

Example 2 50 parts by weight of microcapsules of the thermochromic material obtained in Example 1, 950 parts by weight of toluene, 50 parts by weight of styrene-acrylate copolymer, and a charge control agent (Bondron E-84 manufactured by Orient Chemical Co., Ltd.) ) An electrophotographic toner was prepared in the same manner as in Example 1 using 20 parts by weight. When the obtained toner was evaluated in the same manner as in Example 1, similar results were obtained.

Claims (1)

[Claims] It is characterized by containing a color former (a), a thermochromic material consisting of a compound having a phenolic hydroxyl group (b) and an alcohol, an ester and/or a ketone (c), a binder resin for toner, and a charge control agent. Toner for electrophotography.