JPH0619596B2 - Liquid developer for electrostatic photography - Google Patents

Description

The present invention relates to a liquid developer for electrostatic photography,
More specifically, it relates to an improved liquid developer containing a novel charge control agent useful for converting an electrostatic latent image into a visible image in an electrophotographic or electrostatic recording process. This improved developer is particularly suitable for developing electrostatic latent images on insulating surfaces with positively charged toner particles.

(Prior Art) In the process of electrophotography, for example, first, a surface of a recording material such as a photosensitive layer made of photoconductive zinc oxide provided on a support having relatively high conductivity is uniformly formed in a dark place. Is charged negatively. Then, by projecting the optical image of the original document onto the charged photosensitive layer, a uniform partial discharge of the charged surface is generated according to the intensity of the irradiated light to form an electrostatic latent image. Let it form.

A visible image is formed by causing electroscopic toner particles to act on the electrostatic latent image. This visible image is fixed directly to the photoconductive surface in the electrochromic process.
Alternatively, the electrostatic latent image or the visible image is transferred and fixed on a desired support surface through a transfer process such as charge transfer, pressure transfer and magnetic transfer.

Further, in normal copying, it is required to obtain a positive copy from a positive original. Therefore, when the surface of the photosensitive layer is used while being negatively charged, the electroscopic toner particles are required to have a strong and stable positive charge. Many types of liquid developers containing toner particles having a positive charge are already on the market.

However, all of these commercially available developers are designed for reproduction of line drawing originals or halftone dot image originals and are not suitable for continuous tone image reproduction. That is, when a continuous tone image is copied using these developers,
It has been found that a sufficient image density cannot be obtained, a flow-like defect (so-called streak) is likely to occur in the image, and further, toner deposition (fogging) to the non-image area is likely to occur.

As a developer capable of improving these problems and obtaining a good continuous tone image, a developer using a half-alkylamide compound of diisobutylene-maleic acid copolymer as a charge control agent is disclosed in JP-B-49-26594. Publication (US Patent 406
No. 2789).

However, according to the experimental results of the present inventors, the positive charge retention of the toner particles in the developer is strong and does not cause the polarity to be changed. It has been found that the sharpness of the copied image is gradually lost when it is repeatedly used more than once and repeatedly. This is also a problem in that the amount of toner particles adhering to the image surface decreases, the above-mentioned drawbacks occur, and the strength of the formed image after fixing becomes insufficient.
Therefore, when an image was formed on a zinc oxide photosensitive paper using these developers and used as an offset printing plate, there was a problem that the oil sensitivity to the printing ink and the number of printed sheets became insufficient. . In addition, the image quality of the copied image obtained through the transfer process was significantly deteriorated.

(Object of the Invention) The present invention solves the above problems of the conventional liquid developer.

An object of the present invention is to provide a good liquid developer which gives excellent image quality of a continuous tone image and does not cause image quality deterioration even when continuously used for a long time.

Another object of the present invention is to provide a liquid developer capable of continuously producing a large number of offset printing original plates having excellent printing ink oil sensitivity and printing durability by electrophotography.

Another object of the present invention is to provide a liquid developer suitable for various types of electrostatic photography and various types of transfer such as charge transfer, in addition to the above applications.

(Structure of the Invention) The present invention relates to a toner containing a resin as a main component and at least one of the following as a charge control agent in a non-aqueous solvent having an electric resistance of 10 ⁹ Ω · cm or more and a dielectric constant of 3.5 or less. General formula (I
A liquid developer for electrostatic photography, comprising a half-maleic acid amide copolymer containing repeating units a) and (Ib).

General formula (Ia) General formula (Ib) In the formula, X represents a hydrocarbon group having a total carbon number of 10 or more, and Y
₁ and Y ₂ may be the same or different and each represents a hydrogen atom or an alkyl group.

R ₁ and R ₂ may be the same or different and each represents a hydrogen atom, an aliphatic group, an alicyclic hydrocarbon group, an aromatic group or a heterocyclic group. R ₁ and R ₂ may be closed by a carbon atom, and the ring may contain a hetero atom.

However, the total number of carbon atoms contained in X, R ₁ and R ₂ is 14
That is all.

M represents a hydrogen atom, a metal atom, or an ammonium salt or a quaternary salt of an organic base.

In addition, the component represented by the general formula (Ia) and the general formula (Ib)
The compositional ratio of the components shown by 10 to 99.5: 0.5 to
90 (parts by weight).

The charge control agent used in the present invention will be described in detail.

In the general formula (Ia), X preferably has a total carbon number of 10
To 30 optionally substituted alkyl groups (eg, decyl group, dodecyl group, tetradecyl group, hexadecyl group,
Octadecyl group, docosanyl group, 10-methoxycarbonyloctamethylene group, 10-hexyloxycarbonyloctamethylene group, etc .; Aralkyl group having 10 to 32 total carbon atoms which may be substituted (for example, 4-butylphenylmethyl group) A 4-methoxycarbonylphenylethyl group, a 4-butoxycarbonylphenylmethyl group, etc.); a cycloalkane group having 10 to 32 total carbon atoms which may be substituted (for example, a 4-butylcyclohexyl group, a 4-octylcyclohexyl group, 4-dodecylcyclohexyl group,
3,5-dibutylcyclohexyl group, 3-hexylcyclooctyl group, etc.) or an aryl group having 10 to 32 total carbon atoms which may be substituted (for example, 4-butylphenyl group, 4-octylphenyl group, 4- Dodecylphenyl group, 4-octyloxyphenyl group, 4-octyloxycarbonylphenyl group, etc.) and the like.

Y ₁ and Y _2, connexion different even the same may be, preferably more preferably represents a hydrogen atom or a methyl group, Y ₁ and Y ₂ are both either methyl group a hydrogen atom or Y ₁ or Y ₂ Represent.

R ₁ and R ₂ may be the same or different, and a hydrogen atom,
An optionally substituted alkyl group having 1 to 28 carbon atoms (eg, methyl group, ethyl group, propyl group, butyl group, hexyl group, octyl group, 2-ethylhexyl group, decyl group,
Dodecyl group, tetradecyl group, hexadecyl group, octadecyl group, docosanyl group, 3-methoxypropyl group, 3
-Chloropropyl group, 2-cyanoethyl group and the like), aralkyl group having a total carbon number of 7 to 32 and which may be substituted (for example, benzyl group, phenethyl group, 4-chlorobenzyl group, 4-
Butylbenzyl group, 4-methoxybenzyl group and the like, alkenyl group having a total carbon number of 2 to 32 and which may be substituted (for example, allyl group, 2-pentenyl group, isobutenyl group, 2-
A decenyl group, an oleyl group, etc.) A cycloaliphatic hydrocarbon group having a total carbon number of 5 to 32 (for example, cyclopentyl group, cyclohexyl group, etc.), an aryl group (a total of 6 to 32 carbon number, which may be substituted) For example, phenyl group, naphthyl group, 2-chlorophenyl group, 4-chlorophenyl group, 4
-Methylphenyl group, 4-methoxyphenyl group, 4-butylphenyl group, 4-octylphenyl group, 4-butoxyphenyl group, etc.) or an optionally substituted heterocyclic group having 5 or more atoms (for example, furyl group, etc.) Represents Furthermore R ₁
And R ₂ may be closed with a carbon atom and may contain a hetero atom in the ring (eg, morpholyl group, piperidyl group, etc.).

M is organic such as hydrogen atom, alkali metal (eg, sodium, potassium, lithium), alkaline earth metal (eg, barium, calcium, aluminum, etc.), transition metal (eg, copper, iron, titanium, cobalt, tin, etc.) A metal atom capable of forming a salt with a carboxylic acid, or an ammonium salt or a quaternary salt of an organic base (for example, trimethylamine, dimethylamine, triethylamine, M, N-dimethylaniline, pyridine, morpholine, etc.) (for example, tetramethylammonium, Trimethyl dodecyl ammonium).

The composition ratio of the components represented by the general formulas (Ia) and (Ib) is 10:90 to 99.5: 0.5 by weight,
It is preferably 70:30 to 30:70.

The molecular weight of the copolymer containing the components represented by the general formulas (Ia) and (Ib) of the present invention is 1,000 to 500,000,
It is preferably 5000 to 50,000.

General formula (Ia) and general formula (Ib) which are the features of the present invention
The semi-maleic acid amide copolymer represented by can be produced by reacting a maleic anhydride copolymer containing a repeating unit represented by the following general formulas (IIa) and (IIb) with an amino compound.

General formula (IIa) General formula (IIb) The general formula (IIa) represents the same symbol as the general formula (Ia).

The maleic anhydride copolymer represented by the general formula (II) can be produced by a conventionally known method.

For example, Ryohei Oda, “Modern Industrial Chemistry, Volume 16, Polymer Industrial Chemistry I,” page 281 (published by Asakura Shoten), Otsu et al.
"Polymer Letters, 2, 973 (1964), MMMart
in, J. Org. Chem. 27, 1201 (1962) and the like.

Some specific examples are listed below.

(1) (2) (3) (Four) (Five) (6) (7) (8) (9) (Ten) On the other hand, with respect to the amino compound, as described above, as preferable compound examples, butylamine, pentylamine, hexylamine, octylamine, decylamine, dodecylamine, tetradecylamine, hexadecylamine,
Octadecylamine, docosanylamine, 2-ethylhexylamine, 3,3-dimethylpentylamine, allylamine, hexenylamine, dodecenylamine, tetradecenylamine, hexadecenylamine, octadecenylamine, 2-nonyl-2-butenylamine and the like. To be

The novel charge control agent used in the present invention is a reaction product of the above-mentioned copolymer of maleic anhydride represented by the general formula (II) and various amino compounds, which is edited by the Chemical Society of Japan. , "New Experimental Chemistry," Vol. 14, p. 1145,
(Maruzen Publishing Co., Ltd.) and the like, it can be synthesized by applying the reaction conditions in the reaction of an ordinary low molecular weight compound carboxylic acid anhydride with an amino compound.

That is, in an organic solvent capable of dissolving the carboxylic acid anhydride and the amino compound without causing a reaction and at the following reaction temperatures [for example, hydrocarbons (for example, decane, Isopar G, Isopar H, cyclohexane, benzene, toluene , Xylene), ketones (methyl ethyl ketone, methyl isobutyl ketone, etc.), ethers (dioxane, THF, anisole, etc.), halogenated hydrocarbons (chloroform, dichloroethylene, methyl chloroform, etc.), dimethylformamide or dimethylsulfone. And the like, and the compounds are mixed at a temperature of 20 ° C to 200 ° C.
The reaction is carried out at ° C, preferably 25 ° C to 150 ° C, for 1 hour to 80 hours, preferably 3 to 15 hours. In this reaction, the use of a catalytic amount of an organic base (eg, triethylamine, dimethylaniline, pyridine, morpholine, etc.) or an inorganic or organic acid (eg, sulfuric acid, methanesulfonic acid, benzenesulfonic acid, etc.) promotes the reaction.
It is similar to the case of the low molecular weight compound.

The reaction product obtained by this reaction is a polymer containing a half-maleic acid amide product by the reaction of an acid anhydride and an amino compound in the polymer. The above-mentioned US Pat. No. 40627.
In comparison with the half-alkylamide compound of the diisobutylene-maleic acid copolymer described in No. 89, the novel charge control agent of the present invention has a substituent X in the copolymer component of the half-maleic acid alkylamide compound having a carbon number. However, it was found that the number of times of development and use was dramatically improved.

Specific examples of the compound of the present invention are shown below, but the invention is not limited thereto.

(1) (2) (3) (Four) (Five) (6) (7) (8) (9) (Ten) (11) (12) (13) (14) (15) (16) (17) (18) (19) The non-aqueous solvent used in the present invention having an electric resistance of 10 ⁹ Ω · cm or more and a dielectric constant of 3.5 or less, preferably a linear or branched aliphatic hydrocarbon, alicyclic hydrocarbon, or aromatic Hydrocarbons or halogenated hydrocarbons can be used. More preferably from the viewpoint of volatility, stability, odor, etc., octane, isooctane, decane, isodecane, nonane, dodecane, isododecane, decalin, isoparain-based petroleum solvent, Isopar E, Isopar G,
Isopar H, Isopar L (manufactured by Exxon), Cielsol-71 (manufactured by Ciel), Amsco OMS (manufactured by Spirits) and the like are used alone or in combination.

The toner particles used in the present invention are not particularly specified, and conventionally known particles can be used. For example, the resin that is the main constituent of the toner particles may be any resin that is substantially insoluble in the organic solvent, such as acrylic resin, ester resin, amide resin, alkylene resin, phenol-modified alkyd resin, and epoxy resin. Examples thereof include synthetic resins such as resins, rosins and synthetic rubbers, and natural resins. The resin dispersion that can be used for the liquid developer can be prepared by a method known to those skilled in the art.

For example, there is a method in which a desired resin is dispersed in a non-polar solvent and then dispersed by a ball mill or a high speed stirrer to produce the resin.
As for the monomer, a so-called polymerization granulation method is known, in which a monomer which is dissolved in a nonpolar solvent and becomes insoluble in the solvent when polymerized into a solvent is polymerized to obtain a resin dispersed in the solvent. ing. For example, K. E. J. Barrett, "Dispersion Polymerization in Organic Media" John Willy and Sons. , London (1974), US Pat. No. 3,637,569.
No. 3,753,760 and the like.

The particle size of the obtained dispersed resin is preferably 5 μm or less, particularly 2 μm or less in order to obtain a continuous tone image.

If necessary, a colorant may be used as a constituent of the toner particles. These colorants are not particularly specified, and various conventionally known pigments or dyes can be used. The colorant may be used alone by dispersing it in the non-aqueous solvent in combination with a dispersion promoter or the like, or may be a graft type particle in which a polymer is chemically bonded to the surface of the colorant (for example, graft carbon: It may be used under the name of Mitsubishi Gas Chemical Co., Ltd.). Further, a colorant may be contained in the above resin for use.

As a method for coloring the dispersed resin, for example, JP-A-48-7
There is a method of physically dispersing in a resin using a disperser (paint shaker, colloid mill, vibration mill, ball mill, etc.), which is a known method in Japanese Patent No. 5242, etc., and very many pigments and dyes are used. Are known. Examples thereof include magnetic iron oxide iron powder, carbon black, nigrosine, alkali blue, Hansa yellow, quinacridone red, phthalocyanine blue, phthalocyanine black, and benzidine yellow.

As another coloring method, there is a method of heating and dyeing a dispersed resin material with a preferable dye as described in JP-A-57-48738.

Examples thereof include Hither Yellow, Crystal Violet, Victoria Blue, Malachite Green, Seriton Hua Streddo, Desperce Yellow, Desperce Red, Desperce Blue, Solvent Red and the like.

Further, as another coloring method, there is a method of chemically bonding a dispersion resin and a dye. For example, Japanese Patent Laid-Open No. 53-5402
No. 9 and the like use a method of reacting a resin with a dye, and Japanese Patent Publication No. 44-22955 and the like use a method of previously binding a dye to a monomer of a resin which is insoluble and can be dispersed by polymerization. can do.

In order to stably disperse the above-mentioned resin or colorant in the non-aqueous solvent, a conventionally known dispersion stabilizer can be used.

That is, various synthetic resins or natural resins can be used alone or in combination of two or more kinds. For example, an alkyl chain having a total carbon number of 4 to 30 [may contain a substituent such as a halogen atom, a hydroxyl group, an amino group, an alkoxy group or a hetero atom such as an oxygen atom, and the main chain carbon-carbon atom bond is Acrylic acid or methacrylic acid alkyl ester, fatty acid vinyl ester, vinyl alkyl ether or a polymer of a monomer such as olefin such as butadiene, isoprene or diisobutylene, or a combination of two or more thereof. And a copolymer of the above-mentioned monomer forming a polymer soluble in an aliphatic hydrocarbon solvent and one or more of the following various monomers. be able to.

For example, vinyl acetate, acrylic acid, or methacrylic acid methyl, ethyl, n-propyl or iso-propyl ester, styrene, vinyltoluene, styrene derivatives such as α-methylstyrene, acrylic acid, methacrylic acid, crotonic acid, maleic acid. , Itaconic acid, unsaturated carboxylic acids or their anhydrides, hydroxyethyl methacrylate, hydroxyethyl acrylate, diethylaminoethyl methacrylate, N-vinylpyrrolidone, acrylamide, acrylonitrile, 2-chloroethyl methacrylate, 2,2,2-trifluoro Hydroxy group, amino group, amide group, cyano group, sulfonic acid group, carbonyl group, halogen atom, such as ethyl methacrylate,
Examples thereof include monomers containing various polar groups such as heterocycles.

Alternatively, in addition to the above synthetic resins, resins such as alkyd resins, alkyd resins modified with various fatty acids, and linseed oil-modified polyurethane resins can be used.

The amount of each main component of the liquid developer of the present invention will be described below.

The toner particles containing a resin and a colorant as main components are preferably 0.5 to 50 parts by weight with respect to 1000 parts by weight of the carrier liquid.

When the amount is 0.5 parts by weight or less, the image density is insufficient, and when the amount is 50 parts by weight or more, fog easily occurs on the non-image part. A carrier liquid-soluble resin such as the above-mentioned dispersion stabilizer is also used if necessary, and can be added in an amount of about 0.5 to 100 parts by weight with respect to 1000 parts by weight of the carrier liquid. The copolymer of the present invention, which is a charge control agent, produces a remarkable effect with a very small amount on the carrier liquid, and has a ratio of 0.
001 to 0.5 parts by weight is the best.

Below this lower limit, the positive charge retention of the toner particles becomes unstable, and above the upper limit, the electrical resistance of the developer decreases and the image density obtained is lowered.

In addition, various additives may be added as required. Specific examples are given in Yuji Harazaki, “Electrophotography”, Vol. 16, No. 2, page 44.

The upper limit of the total amount of the liquid developer additives as described above is restricted by the electric resistance of the developer. That is, when the electric resistance of the liquid developer with the toner particles removed is 10 ⁹ Ω · cm or less, it becomes difficult to obtain a good quality continuous tone image. Therefore, the amount of each additive added should be within this range. It is necessary to control.

Examples of the present invention will be presented below, but the invention is not limited thereto.

Intermediate Production Example 1: Intermediate Specific Example (2) A mixture of 98 g of maleic anhydride, 252 g of 1-dodecene and 816 g of toluene was heated to a temperature of 85 ° C. with stirring under a nitrogen atmosphere.

At that temperature, 6.0 g of initiator: benzoyl peroxide was added and stirred for 3 hours, and further 6.0 g of benzoyl peroxide was added and stirred for 4 hours.

The solid content of the obtained polymer solution was 22.5%.

Intermediate Production Example 2: Intermediate Specific Example (4) A mixture of 49 g of maleic anhydride, 152 g of 1-hexadecene and 494 g of toluene was heated to a temperature of 90 ° C. with stirring under a nitrogen atmosphere.

At that temperature, 3.50 g of benzoyl peroxide was added and stirred for 3 hours, and then 3.5 g of benzoyl peroxide was added to add 4
Stir for hours.

The solid content of the obtained polymer solution was 24.8%.

Intermediate Production Example 3: Intermediate Specific Example (5) A mixture of 98 g of maleic anhydride, 378 g of 1-octadecene, and 1850 g of toluene was heated to 90 ° C. with stirring under a nitrogen atmosphere.

At that temperature, 7.0 g of benzoyl peroxide was added and stirred for 3 hours, and then 7.0 g of benzoyl peroxide was added and stirred for 5 hours.

The solid content of the obtained polymer solution was 14.8%.

Compound Production Example 1: Present Compound Example (2) A mixture of 100 g of the polymer solution obtained in Intermediate Production Example 1, 23.2 g of n-octadecylamine and 2 g of pyridine was stirred at 70 ° C. for 8 hours. After cooling, this reaction solution was added to 800 m of methanol with stirring for 15 minutes, and the mixture was further stirred for 1 hour.

The precipitated solid is collected by filtration and dried under reduced pressure to give a pale white yellow solid 37g
Got The molecular weight measured by high performance liquid chromatography was 11,000.

Compound Production Example 2: Inventive Compound Specific Example (6) A mixture of 100 g of the polymer solution obtained in Intermediate Production Example 2, 25 g of N-methyl-n-octadecylamine, 1.8 g of N, N-dimethylaniline and toluene was heated. 100
Stirred at 15 ° C for 15 hours. After cooling, the mixture was added to methanol 1 with stirring for 15 minutes, and the mixture was further stirred for 1 hour.

The precipitated solid was collected by filtration and dried under reduced pressure to give a pale white yellow solid 3
5 g was obtained. The molecular weight measured by high performance liquid chromatography was 11,000.

Compound Production Example 3: Present Compound Example (9) A mixture of 100 g of the polymer solution obtained in Intermediate Production Example 3, 3.1 g of n-butylamine and 0.5 g of pyridine was stirred at a temperature of 50 ° C. for 50 hours.

After cooling, this solution was added to 800 m of methanol with stirring for 15 minutes, and the mixture was further stirred for 1 hour.
The precipitated solid was collected by filtration and dried under reduced pressure to give a pale white yellow solid 1
5 g was obtained. The molecular weight measured by high performance liquid chromatography was 7,500.

Compound Production Example 4: Present Compound Example (10) A mixture of 100 g of the polymer solution obtained in Intermediate Production Example 3, n-octadecylamine 10.2 g and pyridine 2 g was stirred at a temperature of 70 ° C. for 10 hours.

After cooling, while stirring this solution in methanol 1,
The mixture was added over 15 minutes and stirred as it was for 1 hour. The precipitated solid was collected by filtration and dried under reduced pressure to obtain 21 g of a pale white-yellow solid.
The molecular weight measured by high performance liquid chromatography is 7500.
It was.

Example 1) 12 g of poly (lauryl methacrylate), 1 vinyl acetate
A mixed solution of 00 g and Cielsol 71 385 g was heated to a temperature of 70 ° C. while stirring under a nitrogen stream. 2,2 '
-Add 1.7 g of azobis (isobutylnitrile) and add 4
After reacting for a period of time, a 200 mesh nylon cloth was used for cooling.

A white resin dispersion having a polymerization rate of 83% and an average particle size of 0.20 μm was obtained.

Poly (lauryl methacrylate) 10g, Nigrosine 1
0 g and 30 g of Sielsol 71 were put in a paint shaker together with glass beads and dispersed for 2 hours to obtain a fine dispersion of nigrosine.

32 g of the above-mentioned white resin dispersion, 2.5 g of the above-mentioned nigrosine dispersion, and 0.03 g of the compound (2) of the present invention obtained in the compound production example 1) were dispersed in a shell sol 71 1 to prepare a liquid developer. It was made.

The liquid developer obtained is used as a Fuji fully automatic plate-making machine ELP280.
(Fuji Photo Film Co., Ltd.) developer and ELP master (Fuji Photo Film Co., Ltd.) as an electrophotographic photosensitive material for printing master, using a positive tone original having continuous gradation to form an image on the ELP master. To form a master plate. The image of the obtained master plate was a good continuous tone image, and the maximum optical density of the image was 1.51 and the minimum (fog) was 0.06. The color tone of the image was temperature control. Similarly, 2000 ELP masters were processed and the optical density of the image on the 2000th master plate was examined. The maximum was 1.48, the decrease in density was small, and the minimum was 0.06, which showed no change. It was Further, when the images of the first processed image and the 2000th image were observed, both were very clear images.

Next, the non-image areas of the first and 2000th master plates were desensitized to make printing plates, and 3000 sheets were printed. In all of the plates printed, the 3000th printed matter was clear, there were no fine line breaks, and there was no fog.

For comparison, a liquid developer was prepared in the same manner as described above except that the following comparative compound Y ₁ (Comparative Example 1) or Y ₂ (Comparative Example 2) was used instead of the compound (2) of the present invention. Then, the characteristics were examined in the same manner as above.

Comparative compound Y ₁ Comparative compound Y ₂ The obtained results are shown in Table A below together with the results of Example 1.

From the results in Table A, when the liquid developer containing the comparative compound Y ₁ or Y ₂ was used, the change rate of the image density of the 2,000th master plate was large, and the fine line was observed even in the printed image. The cuts were conspicuous, the fog in the non-image area was increased, and the density was decreased. On the other hand, when the compound of the present invention was used, the rate of change in the image density of the master plate was small, and the printed image also had fine lines. It can be seen that a clear product can be obtained with no cuts or increased fog.

Examples 2 to 4 and Comparative Example A In the preparation of the liquid developer of Example 1, the charge control agent of the present invention shown in Table 1 was used instead of the charge control agent of the compound (2) of the present invention. A liquid developer for electrostatic photography was prepared in the same manner as in 1.

For comparison, a known charge control agent, diisobutylene-maleic acid half-octadecylamide copolymer, was also prepared.

The obtained liquid developer was tested in the same manner as in Example 1, and the maximum density of the image of the first master plate and the maximum density of the 2000th master plate of the same image part were measured, and both were measured. The change rate of was calculated by the following formula.

Next, the 1st and 2000th master plates were used as printing plates in the same manner as in Example 1 to print 3000 sheets, and the image of the printed matter was observed. The results are shown in Table 1.

As is clear from Table 1, in Examples 2 to 4 using the charge control agent of the present invention, the maximum image of the obtained master plate is high, and the density decrease is small even after processing 2000 sheets. However, in Comparative Example A conducted for comparison, the first sheet has a high master density, but the 2000th sheet has a large decrease in density, and the printed matter printed using this shows conspicuous cuts of fine lines in the printed image. Fog was seen in the image area (200
The density of the non-image area of the 0th master plate is 0.1
There was 0 and it was more than the first one).

Examples 5 to 8 The same as Example 1 except that the charge control agent of the present invention shown in Table 2 was used instead of the charge control agent of the compound (2) of the present invention in the preparation of the liquid developer of Example 1. Thus, a liquid developer for electrostatic photography was prepared.

The resulting liquid developer was tested as in Example 1 and
The maximum densities of the 1st and 2000th master plates were measured to determine the change rate. The results are shown in Table 2.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hidefumi Sera, 210 Nakanuma, Minamiashigara City, Kanagawa Prefecture Fuji Photo Film Co., Ltd. Kai 50-39549 (JP, A) JP 49-110349 (JP, A)

Claims (1)

[Claims] 1. A toner containing a resin as a main component and at least one of the following general formulas () in a non-aqueous solvent having an electric resistance of 10 ⁹ Ω · cm or more and a dielectric constant of 3.5 or less: A liquid developer for electrostatic photography, comprising a half-maleic acid amide copolymer containing repeating units represented by Ia) and (Ib). General formula (Ia) General formula (Ib) In the formula, X represents a hydrocarbon group having a total carbon number of 10 or more, and Y
₁ and Y ₂ may be the same or different and each represents a hydrogen atom or an alkyl group. R ₁ and R ₂ may be the same or different and each represents a hydrogen atom, an aliphatic group, an alicyclic hydrocarbon group, an aromatic group or a heterocyclic group. R ₁ and R ₂ may be closed by a carbon atom, and the ring may contain a hetero atom. However, the total number of carbon atoms contained in X, R ₁ and R ₂ is 14
That is all. M represents a hydrogen atom, a metal atom, or an ammonium salt or a quaternary salt of an organic base.