JPH073605B2 - Liquid developer for electrophotography - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a liquid developer for electrophotography,
In particular, it relates to a liquid developer for electrophotography which is excellent in positive charge stability.

(B) Prior Art and Problems Thereof A liquid developer used in a developing step of electrostatic photography is generally a dispersion of toner particles mainly composed of a pigment or dye and a resin in a highly insulating carrier liquid. . In general, such a developer has insufficient charge characteristics or lacks stability, and therefore resin acid, fatty acid,
It is well known to use metal salts such as alkylbenzenesulfonic acid, alkylphosphoric acid, naphthenic acid, and various other compounds.

Nevertheless, conventional liquid developers have insufficient charge characteristics and cannot provide sufficient image density unless they are latent images of high potential, and in particular, they have insufficient stability and gradually charge during long-term storage. It has the drawbacks that the characteristics change to lower the image density and cause fog.

In particular, JP-A-53-54029, JP-A-53-52588, and JP-A-53-1231.
38, Dosho 57-48738, Dosho 57-129450, Dosho 58-55939,
Liquid developers containing polymer particles as toner particles, such as those described in JP-A-59-83174 and JP-A-59-212851, have good fixability and are suitable for offset printing plates because they accept printing ink well. It is preferably used. However, since the polymer particles generally have almost no chargeability, they are charged with a charge control agent, but a charge control agent that strongly adheres to the surface of polymer particles and gives good charge characteristics stably for a long time is The reality is that there are very few. In addition, JP-A-49-
8239, 53-123138, 55-95955 and the like, it is disclosed to use a salt of a fatty acid and a basic nitrogen atom-containing compound such as an aliphatic amine or a guanidine derivative, but it is not stable over time. In terms of points, it was still not enough.

(C) Object of the Invention An object of the present invention is to provide a liquid developer for electrophotography which is excellent in charging characteristics and stability over time.

(D) Structure of the Invention The above object of the present invention is to provide, in a highly insulating carrier liquid, polymer particles as toner particles, a basic nitrogen atom-containing compound as a charge control agent (provided that a nitrogen-containing heterocyclic compound having an amino group and It is achieved by a positively chargeable liquid developer for electrophotography, which comprises a salt of a polymeric carboxylic acid soluble in the carrier liquid (excluding dyes having an amino group).

However, as the basic nitrogen atom-containing compound, a nitrogen-containing heterocyclic compound having an amino group and a dye having an amino group have been previously proposed, and are therefore excluded.

As the high molecular weight carboxylic acid used in the present invention,
It may be at least partially soluble in the carrier liquid. Preferably, an addition polymerizable carboxylic acid such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic acid or fumaric acid and the following formula, A polymer acid which is soluble in the carrier liquid obtained by copolymerizing the monomer shown by can be used.

The addition polymerizable carboxylic acid is 1 to 20 mol% in the copolymer,
Preferably, it is desirable to include the range of 1 to 10 mol%.
The molecular weight of the copolymer may be any molecular weight as long as it is soluble in the carrier liquid.

-COO for the carboxyl group of high-molecular carboxylic acid
・ N A basic nitrogen-containing compound for forming a salt of ≡
Then, ammonia, various amines, guanidines, etc.
Compounds Containing Carboxyl Group and Salt-Reactive Nitrogen Atom
Things are included. Specific examples are ammonia and butyric acid.
Ruamine, octylamine, decylamine, stearyl
Amine, laurylamine, ethylenediamine, butanedi
Amine, octanediamine, ethanolamine, dieta
Nolamine, triethanolamine, propanol
Min, 1,6-hexanediamine, P-phenylenediami
N, N-lauryl-2-hydroxypropylene diami
1,3-diphenylguanidine, 1,3-O-tolylgua
There is a carrot.

As for the ratio of the high molecular weight carboxylic acid and the basic nitrogen-containing compound, an amount of the basic nitrogen-containing compound in which all or part of the carboxyl groups form a salt can be used. The salt formation reaction is
It can be easily obtained by mixing both and preferably heating. Methanol to add salt to the carrier liquid,
It can be added as a solution of an organic solvent such as ethanol, butyl acetate, toluene or xylene, or a mixed solvent.

As a method for producing a liquid developer using the charge control agent according to the present invention, various known methods can be used, for example, a colorant, a resin and a charge control agent are mixed to obtain a petroleum-based aliphatic hydrocarbon. A method of diluting the concentrated toner obtained by dispersing in a carrier liquid such as an aromatic hydrocarbon or a halogenated aliphatic hydrocarbon with a disperser such as an attritor or a ball mill, and a carrier liquid having a low dielectric constant and a high insulating property. A method of obtaining toner particles by dropping a concentrate of a colorant, a resin and a charge control agent into the carrier liquid, or after polymerizing monomers in a low dielectric constant, highly insulating carrier liquid to obtain polymer particles. , A colorant and a charge control agent are added.

The carrier liquid used in the present invention has a low dielectric constant and high electric insulation, and includes, for example, normal paraffin hydrocarbons, isoparaffin hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, halogenated aliphatic hydrocarbons. Examples of the hydrogen include isoparaffinic hydrocarbons such as Shell Sol 71 (Shell Petroleum), Isopar G and Isopar H, Isopar K and Isopar L (Esso Petroleum) IP Solvent (Idemitsu Petroleum). .

As the toner particles, a pigment or dye such as carbon black coated with a resin, for example, an alkyd resin, an acrylic resin, a rosin, a styrene-acrylic acid ester copolymer or the like, or as described above, JP-A-53-123138 is used. , Polymer particles such as those described in JP-A-57-129450, JP-A-59-83174, and JP-A-59-212851, and oil-soluble azo dyes such as oil black and oil red; and bases such as Bismarck Brown and chrysoidine. Acid azo dyes, wool black, amide black green, blue black HF and other acidic azo dyes, direct day black E, congo red and other direct dyes, sutan violet, acid blue and other anthraquinone dyes, auramine, malachite green, crystal bi Lett, Carbonium dyes such as Victoria Blue, Rhodami Rhodamine dyes as B, safranin, nigrosine, such as those colored with colorants such as quinone imine dyes such as methylene blue can be used.

The charge control agent according to the present invention described above is preferably used in an amount of 0.001 to 0.5 parts by weight per 1000 parts by weight of the carrier liquid.

Hereinafter, the present invention will be described in more detail with reference to Examples.

(E) Example Example 1 [Comparative Developer A] 500 g of an IP solvent (manufactured by Idemitsu Petroleum Co., Ltd.) composed of isoparaffin hydrocarbon in a flask equipped with a stirrer, a thermometer and a nitrogen inlet tube, 100 g of lauryl methacrylate,
5 g of methacrylic acid was added, 1 g of BPO (benzoyl peroxide) was added as a polymerization initiator, and polymerization was carried out for 5 hours on a water bath at 85 ° C. to obtain a polymer solution.

Then, 100 g of the product solution was taken, transferred to a flask equipped with a stirrer, thermometer, dropping funnel and nitrogen introducing tube, 300 g of IP solvent was added, and insoluble co-weight was added from the dropping funnel on a 70 ° C water bath. As a monomer giving a coalescence, 100 g of vinyl acetate, 10 g of N-vinylpyrrolidone, 5 g of methyl acrylate (Tg 3 ° C) and a polymerization initiator A
A mixture of 1 g of IBN (azobisisobutyronitrile) was added dropwise over 3 hours. Then, after heating for 3 hours under a nitrogen atmosphere, it was cooled to room temperature. The product was a composite resin-dispersed white emulsion having extremely excellent dispersion stability. Then, to this emulsion solution, a solution prepared by dissolving 5 g of oil black HBB in 20 g of xylene was added dropwise with stirring. Aluminum stearate as a charge control agent
After adding 1 g, the toner solution was diluted 50 times in IP solvent. The obtained toner was a positively chargeable toner showing good dispersion stability, and as a result of observation of an electron micrograph, it was found to be particles having a uniform distribution of 0.2 μm.

[Comparative developer B]

A toner solution was prepared in the same manner except that the charge control agent of Comparative Developer A was replaced with 1 g of aluminum salt of steberite rosin.

[Comparative developer C]

A toner solution was prepared in the same manner except that the charge control agent of comparative developer A was changed to 1 g of laurylamine palmitate.

[Developer of the Invention-1] A mixture of 50 g of a 10% solution of a lauryl methacrylate-methacrylic acid copolymer synthesized as shown in Comparative Developer A and an ethanol solution of 1.0 g of octylamine was mixed and heated to obtain aluminum stearate. A toner solution was prepared in the same manner as Comparative Developer A except that it was used instead.

These toners were used as a liquid developer for zinc oxide electrophotographic offset masters and used as a plate making machine EP-11 (manufactured by Mitsubishi Paper Mills).
Used in. 40 ℃ to check the charge stability of the toner
Table 1 shows the maximum reflection densities obtained by the developers stored at 3, 7, and 14 days.

From the results shown in Table 1, the comparative developers A to C show a remarkable change in maximum density over time because of poor charge stability, but the developer 1 of the present invention shows almost no change in density over time. It turns out that it is extremely stable.

Example 2 Instead of the octylamine used in the developer 1 of the present invention in Example 1, the same amounts of octanediamine, ethanolamine and P- were used.
The same procedure was performed except that phenylenediamine and 1,3-diphenylguanidine were used. All of the developers were extremely stable like the developer 1 of the invention.

Example 3 100 g of stearyl methacrylate and methoxy polyethylene glycol methacrylate And 1.8 g of AIBN are put in one flask equipped with a stirrer, a thermometer and a nitrogen introducing tube, and 500 g of IP solvent.
Was added and the mixture was heated at 75 ° C. for 5 hours and stirred. Then take 100 g of the product solution, 50 g of methyl methacrylate, 35 g of styrene, 10 g of hydroxyethyl methacrylate and
AIBN 1.0g was added and it heat-stirred at 75 degreeC for 5 hours. The product was a stable emulsion with an average particle size of 0.15μ. Then, Orient Chemical Oil Black HBB 8g was added to xylene.
It was dissolved in 60 g, and this was added dropwise to the above-mentioned emulsion liquid and stirred, and then the charge control agent used in Example 1 was added to the same amount as in Example 1 per toner resin weight, and an IP solvent was added to the solid content. The developer was diluted to a concentration of 0.9%.

The result was almost the same as the result of Example 1.

(F) Effect of the Invention The liquid developer of the present invention has good positive chargeability and is extremely excellent in charge stability over time.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-59-160153 (JP, A) JP-A-49-8239 (JP, A) JP-A-55-95955 (JP, A) JP-B-46- 21195 (JP, B1)

Claims (1)

[Claims] 1. A polymer particle as a toner particle, a basic nitrogen atom-containing compound as a charge control agent (excluding a nitrogen-containing heterocyclic compound having an amino group and a dye having an amino group) in a highly insulating carrier liquid. A positively chargeable liquid developer for electrophotography, comprising: a salt of a high-molecular carboxylic acid soluble in the carrier liquid.