JPH11133677A - Negative charge type liquid developer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a negative charge liquid developer which is less in electrostatic charge fluctuation, has a high printing density and is capable of yielding a good printing image of low fogging by preventing the electrostatic charge fluctuation occurring in the cutting of the mechanical adsorptive force of pigments and resins by continuous printing and preventing the adverse influence on printing characteristics, such as the degradation in image densities by the stain of the non-image part by the fine toners and the lower resistance of toners. SOLUTION: The negative charge liquid developer prepd. by dispersing the toners consisting essentially of the coloring agents and the resins into a highly insulating low-dielectric constant carrier liquid is formed by introducing an acidic group into the molecules or surfaces of the coloring agents. The developer described above comprises a solvation part having affinity to the carrier liquid and a non-solvation part not having the affinity. The unit from the monomer having the acidic group is included in the solvation part and the unit from the monomer having the basic group is included in the non-solvation part in the negative charge liquid developer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a negatively chargeable liquid developer. The present invention particularly prevents charge fluctuations caused by cutting of mechanical attraction force between the pigment and the resin due to forced circulation in continuous printing, further stains non-image areas due to finer toner, and reduces image resistance due to lower toner resistance. The present invention relates to a negatively chargeable liquid developer capable of preventing a decrease in concentration and the like.

[0002]

Conventionally, as the liquid developer, the electric resistance is 10 ¹⁴ [Omega] cm approximately resin petroleum solvent, that the toner particles comprising a charge control agent and a colorant dispersed is known. The toner particles are charged on the contact surface with the solvent, attract counter ions on the solvent side, and form an electric double layer at the interface. The toner particles are electrophoresed along the electric field, and the electrostatic latent image on the photoconductor is developed.

The constituent part of the resin for liquid developer contains a non-solvate part insoluble in the carrier liquid and a stabilizer for the solubilized part, and further contains a monomer that contributes to the chargeability. Furthermore, it has been reported that it contains amphiphilic particles (organosol) as shown in JP-A-4-225369. The advantage of using an organosol is that it is excellent in dispersion stability because it crosslinks in a resin three-dimensionally. The organosol is sterically stabilized by using a graft copolymer stabilizer having an anchor group introduced by an esterification reaction of the epoxy (glycidyl) function with an ethylenically unsaturated carboxylic acid. In this esterification reaction, a tertiary amine or a pyridine derivative is used as a catalyst.

[0004] The unsolvated part is the dispersed phase of the polymer dispersion, is prepared from a thermoplastic polymer having a Tg of 25 ° C. or lower, and is insoluble in the carrier liquid of the liquid toner. The unsolvated polymer is prepared in situ by a copolymerization reaction with a stabilizer monomer. Examples of suitable monomers for the unsolvated part include methyl methacrylate and ethyl methacrylate.

[0005] Stabilizers are graft copolymers prepared by the polymerization reaction of at least two comonomers. It may be selected from comonomers having an anchor group, a polar group and a solubilizing group. The anchor group reacts with the functional group of the ethylenically unsaturated compound to form a graft copolymer stabilizer. The ethylenically unsaturated portion of the anchor group is
The copolymerization reaction with the comonomer in the organic solvent can provide a stable dispersion. As a further feature, the at least two polymer components include one component being a polymer component soluble in the continuous phase and the other being a polymer component insoluble in the continuous phase. The function of the soluble component is to form a lyophilic layer that completely covers the surface of the particles. As a result, mutual approach between the particles is hindered, a three-dimensionally stable colloidal component is generated, and stabilization against aggregation of the dispersion can be achieved. Examples of the monomer that works for solubility include n-hexyl acrylate, n-hexyl methacrylate, 2-ethylhexyl acrylate,
Examples thereof include 2-ethylhexyl methacrylate, lauryl acrylate, lauryl methacrylate, stearyl acrylate, and stearyl methacrylate. Also,
The anchor group is an insoluble component and has a low content in the dispersant. The function of the anchor group is to form a covalent bond between the unsolvated portion of the particle and the soluble portion of the stabilizer. Glycidyl acrylate, glycidyl methacrylate and the like can be mentioned as a monomer that functions as an anchor group. The polar group reacts with the base to give the particles a negative permanent charge. Further, as another function, it is chemically bonded to the anchor group by an ester reaction or the like, thereby contributing to the bonding between the non-solvated portion and the stabilizer. Further, it is involved in the adsorptivity with the colorant, and is also effective in binding called ionic affinity between the polar group in the resin and the colorant. Examples of the monomer that functions as a polar group include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, vinylbenzoic acid, and anhydrides of these carboxylic acids.

The charge controlling agent ionizes the carboxylic acid, which is a polar group, in a non-aqueous solvent. Therefore, when a base is added as a proton acceptor, the toner charge increases. The amount of toner charge greatly depends on the dielectric constant and amount of the resin, the dissociation constant of the monomer and the dissociation constant of the base. Usually, resin 100
When added in a range of 0.05 g to 1 g per g, the dielectric constant of the toner also becomes a desirable value of 1 × 10 ⁻¹¹ to 1 × 10 ⁻⁹ Scm ⁻¹ . As the base, diethanolamine, triethanolamine, ethylamine, diethylamine, triethylamine, ethylenediamine, cyclohexylamine, butylamine, hexylamine, dihexylamine, methylamine, dimethylamine, trimethylamine, nitroaniline, methylaniline, chloroaniline, glycine, imidazole, Pyridine, aminopyridine and the like can be mentioned.

Examples of the colorant include phthalocyanine blue, phthalocyanine green, rhodamine lake, peacock blue lake, sky blue, and organic pigments.
Naphthol Green B, Naphthol Green Y, Naphthol Yellow S, Risor Fast Yellow 2G, Permanent Red 4R, Brilliant Fast Scarlet, Hansai Yellow, Benzidine Yellow, Risor Red, Lake Red C, Lake Red D, Brilliant Carmine 6B, Permanent Red F5R, etc. Is mentioned. Further, carbon black or the like can be used as an inorganic colorant.

As a method for producing a liquid developer, the above-described method in which a resin, a charge controlling agent and a colorant are individually mixed into a carrier liquid such as a petroleum solvent and dispersed by an attritor or a ball mill is used. it can.

[0009]

Conventionally, the polar monomer in the resin plays both roles of the chargeability of the developer and the adsorptivity of the colorant, so that the resin and the colorant are forcedly circulated by continuous printing or the like. , The charge fluctuation of the toner itself becomes very large. In addition, non-polarized particles are scattered in the carrier liquid to cause the toner to be finer, which adversely affects printing characteristics such as contamination of non-image areas and reduction in image density due to lower resistance of the toner. There were drawbacks to do.

Accordingly, the present invention prevents fluctuations in charging caused by the mechanical attraction of pigment and resin caused by continuous printing, reduces contamination of non-image areas due to finer toner, and lowers image density due to lower toner resistance. It is an object of the present invention to provide a negatively chargeable liquid developer capable of preventing adverse effects on printing characteristics, such as low charge fluctuation, high print density, and providing a good printed image with low fog.

[0011]

According to the present invention, it has been found that the above objects can be achieved by using the following electrostatic liquid developer. 1. In a negatively chargeable liquid developer obtained by dispersing a toner containing a colorant and a resin as main components in a high-insulating low-dielectric carrier liquid,
An acidic group is introduced in the molecule or on the surface of the colorant, and
The resin is composed of a solvation part having an affinity for the carrier liquid and a non-solvation part having no affinity.The solvation part contains a unit from a monomer having an acidic group, and the non-solvation part contains a base. A negatively chargeable liquid developer comprising a unit composed of a monomer having a functional group.

2. The negatively-chargeable liquid developer according to 1, wherein the weight ratio of the solvated part to the non-solvated part of the resin is 95: 5 to 60:40. 3. The above-mentioned 1 wherein the proportion of units derived from monomers having an acidic group present in the solvated part of the resin is 1 to 20% by weight.
Or 2 negatively chargeable liquid developer. 4. The negatively chargeable liquid developer according to any one of the above items 1 to 3, wherein the monomer having an acidic group contains a carboxyl group.

5. The ratio of units from monomers having a basic group present in the unsolvated part of the resin is 0.01 to 10
The negatively chargeable liquid developer according to any one of the above 1 to 4, which is% by weight. 6. The negatively chargeable liquid developer according to claim 1, wherein the charge amount is −10 to −400 μC / g.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The reason why the negatively chargeable liquid developer of the present invention is excellent is considered to have the following features. First, in order to impart the effects of chargeability and adsorption of a pigment to a solvated part and a non-solvated part of the resin, respectively, a unit made of a monomer having an acidic group in the solvated part (hereinafter referred to as an acid) is used. It is necessary to contain a unit derived from a monomer having a basic group in the unsolvated part (hereinafter referred to as a basic monomer unit). At this time, it is preferable that the solvation part occupies 60 to 95% by weight of the whole resin. This is a condition suitable for keeping the dispersion of the resin in the carrier liquid stable, and also a condition suitable for allowing re-dispersion even if the resin settles. 60 solvates
When the content is less than 10% by weight, the sedimentation of the resin becomes remarkable, the non-solvated portions are bound together, and the redispersion of the developer becomes undesirable as a resin for a liquid developer.

Further, the weight ratio of the acidic monomer unit present in the solvate part is preferably 1 to 20%. If the amount of the acidic monomer unit exceeds 20% by weight, the affinity of the resin with the carrier liquid is reduced, and the resin gels, which may hinder the dispersion in the carrier liquid. Further, even if the resin can be dispersed in the carrier liquid, the resin has a very high viscosity, so that the viscosity of the developer at the time of producing the developer is high, and squeeze defects in development are likely to occur, which causes a problem of fogging of a printed image. Sometimes. The acidic monomers include acrylic acid, methacrylic acid,
Itaconic acid, maleic acid, fumaric acid, vinylbenzoic acid,
Further, anhydrides of these carboxylic acids are suitable,
Among them, acrylic acid and methacrylic acid are particularly preferred from the viewpoint of resin production.

The weight ratio of the basic monomer unit present in the unsolvated part of the resin is preferably from 0.01 to 10%. When the amount of the basic monomer unit exceeds 10% by weight, the chargeability of the resin is biased positively, and the resin may not be a negatively chargeable developer. Examples of the basic monomer include vinylamine containing nitrogen, N, N-dimethylaminoethyl acrylate, N, N-dimethylaminoethyl methacrylate,
N, N-diethylaminoethylaminoethyl acrylate, N, N-diethylaminoethyl methacrylate,
N, N-dipropylaminoethyl acrylate, N, N
-Dipropylaminoethyl methacrylate and the like, and in addition, hydroxyacrylate, hydroxymethacrylate, butylene glycol methacrylate and the like can be considered.

The colorant preferably contains an acidic group in the molecule of the colorant or, in the case of a type in which a resin is coated on the surface of a pigment such as a flushing pigment, in the resin. Examples include those containing a carboxyl group, a sulfonic group, a nitro group, and the like. By preparing a developer using the coloring agent having the acidic group introduced therein and the resin shown above, the non-solvated portion of the resin and the pigment selectively exhibit extremely strong electrostatic adsorption. The effect of preventing separation of the resin and the pigment is exhibited. Furthermore, even if a part of the pigment is separated from the resin, the pigment itself has an acidic group and exhibits a negative charge, so that the pigment does not become non-polar, so that the problem of fogging in development is unlikely to occur. This effect is particularly remarkable when the colorant contains a metal complex such as cyan. In most cases, the colorant used for cyan is positively charged because copper phthalocyanine is used. Therefore, when copper phthalocyanine is used as a coloring agent for a negatively chargeable liquid developer, it is necessary to cover the pigment with a resin, and if a part of the pigment surface is exposed, the charge of the pigment itself becomes a charge of the toner. Will have an effect. Therefore, the liquid developer of the present invention is also effective from the viewpoint of suppressing the influence of the charging of the pigment.

The developer of the present invention prepared from the following resin and pigment has a charge amount of -10 to -400 µC / g.
Is appropriate. A method of measuring the charge amount is to apply a bias between electrodes having an appropriate width, obtain the charge amount from the integration of time and current value, and obtain the charge amount from the charge amount and the amount of developer attached to the electrode. Yes. This charge amount is -4
If it is larger than 00 μC / g, a large amount of floating charge of the toner is present, the surface of the toner particles is not charged, the movement of the developer to the electrode is hindered, and the image density becomes low. In addition, -10 μC / g
If it is smaller, the charge of the toner itself is too low, and the movement of the developer to the electrode is slowed down, resulting in a disadvantage that the image density is lowered.

By dispersing a resin and a colorant satisfying the above conditions in a carrier liquid having a high insulation and a low dielectric constant, the fluctuation of the charge is small, the contamination of the non-image area caused by finer toner and the lowering of the resistance of the carrier liquid. A negatively charged liquid developer in which a decrease in image density is prevented can be obtained. The high-insulating low-dielectric-constant carrier liquid useful in the present invention has a resistance value that does not disturb the electrostatic latent image of the photoreceptor or the like, that is, approximately 10 ¹¹ to 10 ¹⁶ Ωc.
m, preferably one having a resistance value of about 10 ¹² to 10 ¹⁶ Ωcm. Furthermore, it is particularly preferable to use a solvent having no odor and toxicity and having a relatively high flash point. The state of the carrier liquid at normal temperature is not particularly limited as long as it is liquid when used as a dispersion medium. For example, aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons, polysiloxanes, and the like can be used. Isoparaffin-based solvents are preferred from the viewpoints of harmlessness, odor, and cost. Specifically, Isopar G, Isopar H, Isopar L, Isopar K
(From Esso), Shellsol 71 (from Shell Petrochemical), IP Solvent 1620, IP Solvent 2028 (from Idemitsu Petrochemical).

According to the present invention, the resin is composed of a solvated portion having an affinity for the carrier liquid and an unsolvated portion having no affinity, in which an acidic group is introduced into the molecule or on the surface of the colorant. By preparing a developer from a resin that contains an acidic monomer unit in the sum part and a basic monomer unit in the unsolvated part, the adsorption power between the resin and the colorant is increased, and forced circulation by continuous printing is performed. Print characteristics such as non-image area stains due to finer toner, and lower image density due to lower toner resistance, by preventing the resulting mechanical adsorption force between the colorant and resin from being cut off. Adverse effects can be prevented.

[0021]

The present invention will be further described below with reference to examples. Example 1 A 1.0-L flask equipped with a stirrer, a condenser, and a dropping funnel was charged with 400 mL of Isopar L (manufactured by Exxon) and mixed with 19 g of methacrylic acid, 71 g of lauryl methacrylate, and 4 g of azoisobutyronitrile. Was added dropwise over 1 hour and copolymerized at 80 ° C. for 6 hours. Next, using 5 g of glycidyl methacrylate and 0.1 g of vinylpyridine, an esterification reaction was performed at 120 ° C. for 12 hours. Next, methyl methacrylate 4.5
g, 0.5 g of dimethylaminoethyl methacrylate and 1 g of azoisobutyronitrile were added dropwise over 30 minutes and copolymerized at 80 ° C. for 6 hours. As a result, a resin dispersion having a polymerization rate of 98% was obtained. Next, 50 g of a pigment obtained by introducing a sulfonic acid group into a copper phthalocyanine pigment (manufactured by Toyo Ink) and dimethylamine 1.
A mixture of 0 g and Isopar L 500 g was dispersed in a ball mill for 10 hours to obtain a liquid developer. Subsequently, as an evaluation, the charge amount of the liquid developer at the initial stage and after printing 50,000 sheets was measured by applying a voltage of 1 between electrodes (width 2 mm, electrode area 20 × 30 mm).
The amount of charge (Q / M) was determined from the application time, the amount of charge (Q), and the amount of toner (M) attached to the electrode when 00V was applied. As printing characteristics, image density and fog were measured by a colorimeter (manufactured by X-RITE) on an image printed by a liquid developing copier (manufactured by SAVIN). The image density is a status A density of 1.2 or more, and the fog is a color difference ΔE between before and after printing the stamp paper.
Was 0.5 or less. The obtained results are shown in Table 1. Even after printing 50,000 sheets, the charge amount, the image density, and the fog showed good characteristics with almost no change from the initial stage. Example 2 The experiment was performed under the same conditions as in Example 1 except that the amount of methacrylic acid was changed to 12 g, the amount of lauryl methacrylate was changed to 43 g, the amount of methyl methacrylate was changed to 36 g, and the amount of dimethylaminoethyl methacrylate was changed to 4 g. . The evaluation results are shown in Table 1. As shown in Table 1, even after printing 50,000 sheets, good characteristics were obtained with little change from the initial stage. Example 3 An experiment was performed under the same conditions as in Example 1 except that the amount of methacrylic acid was changed to 0.95 g and the amount of lauryl methacrylate was changed to 89.05 g. Table 1 shows the evaluation results.
Even after printing 000 sheets, good characteristics were obtained which were almost unchanged from the initial stage. Example 4 The amount of methacrylic acid was changed to 0.6 g, the amount of lauryl methacrylate to 54.4 g, the amount of methyl methacrylate to 36 g, and the amount of dimethylaminoethyl methacrylate to 4 g.
The experiment was performed under the same conditions as in Example 1 except for the above conditions. The evaluation results are shown in Table 1. As shown in Table 1, even after printing 50,000 sheets, good characteristics were obtained with little change from the initial stage. Example 5 An experiment was performed under the same conditions as in Example 1 except that the amount of methyl methacrylate was changed to 4.95 g and the amount of dimethylaminoethyl methacrylate was changed to 0.05 g. The evaluation results are shown in Table 1. As shown in Table 1, even after printing 50,000 sheets, good characteristics were obtained with little change from the initial stage. Example 6 The amount of methacrylic acid was 12 g, the amount of lauryl methacrylate was 43 g, the amount of methyl methacrylate was 39.6 g,
The experiment was performed under the same conditions as in Example 1 except that the amount of dimethylaminoethyl methacrylate was changed to 0.4 g.
The evaluation results are shown in Table 1. As shown in Table 1, even after printing 50,000 sheets, good characteristics were obtained with little change from the initial stage. Example 7 The amount of methacrylic acid was changed to 0.95 g, the amount of lauryl methacrylate was changed to 89.05 g, the amount of methyl methacrylate was changed to 4.95 g, and the amount of dimethylaminoethyl methacrylate was changed to 0.05 g. The experiment was performed under the same conditions as described above. The evaluation results are shown in Table 1. As shown in Table 1, even after printing 50,000 sheets, good characteristics were obtained with little change from the initial stage. Example 8 The amount of methacrylic acid was 0.6 g, the amount of lauryl methacrylate was 54.4 g, and the amount of methyl methacrylate was 39.
6 g, the amount of dimethylaminoethyl methacrylate was reduced to 0.
The experiment was performed under the same conditions as in Example 1 except that the amount was changed to 4 g. The evaluation results are shown in Table 1. As shown in Table 1, even after printing 50,000 sheets, good characteristics were obtained with little change from the initial stage. Comparative Example 1 400 mL of Isopar L (manufactured by Exxon) was placed in a 1.0 L flask equipped with a stirrer, a cooling tube, and a dropping funnel, and 19 g of methacrylic acid and lauryl methacrylate 71 were added thereto.
g and 4 g of azoisobutyronitrile were added dropwise over 1 hour and copolymerized at 80 ° C. for 6 hours. Next, an ester reaction was performed at 120 ° C. for 12 hours using 5 g of glycidyl methacrylate and 0.1 g of vinylpyridine. Next, a mixture of 5 g of methyl methacrylate and 1 g of azoisobutyronitrile was added dropwise over 30 minutes, and copolymerized at 80 ° C. for 6 hours. As a result, a colored resin dispersion having a polymerization rate of 98% was obtained. Next, a pigment obtained by introducing a sulfonic acid group into a copper phthalocyanine pigment (manufactured by Toyo Ink) 5
0 g, dimethylamine 1.0 g and Isopar L50
0 g of the mixture was dispersed in a ball mill for 10 hours to obtain a liquid developer. Subsequently, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1. After printing 50,000 sheets, the charge amount sharply increased, the image density decreased and fog increased from the initial stage, and there was a problem in printing characteristics. Comparative Example 2 A mixture of 90 g of lauryl methacrylate, 4.5 g of methyl methacrylate, 5 g of azoisobutyronitrile and 0.5 g of dimethylaminoethyl methacrylate was copolymerized at 80 ° C. for 6 hours. An experiment was performed under the same conditions as in Comparative Example 1 except that the resin dispersion obtained as described above was used. The results are shown in Table 1. As shown in Table 1, reverse charging occurred after printing 50,000 sheets, resulting in a negative image due to a decrease in image density and an increase in fog, and there was a problem in printing characteristics. Comparative Example 3 An experiment was performed under the same conditions as in Example 1 except that the colorant was changed to untreated copper phthalocyanine pigment. The results are shown in Table 1, where the charge amount rapidly increased after printing 50,000 sheets,
The image density decreased and fog increased from the initial stage, and there was a problem in printing characteristics.

[0022]

[Table 1]

[0023]

According to the present invention, a negatively charged resin prepared from a resin composed of a colorant having an acidic group introduced into the molecule or on the surface thereof, a solvate part containing an acidic monomer unit and a non-solvate part containing a basic monomer unit. By using a liquid developer,
Prevents fluctuations in charging caused by the mechanical attraction between pigment and resin due to continuous printing, and adversely affects printing characteristics such as contamination of non-image areas due to finer toner and lowering of image density due to lower resistance of toner. , And a good print image with low charge fluctuation, high print density and low fog can be provided for a long time.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Katsuharu Hu 4-1-1, Kamidadanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture Inside Fujitsu Limited (72) Takahiro Kashiwakawa 4-chome, Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa No. 1 in Fujitsu Limited

Claims (6)

[Claims] In a negatively chargeable liquid developer obtained by dispersing a toner containing a colorant and a resin as main components in a carrier liquid having a high insulation and a low dielectric constant, an acidic group is introduced into a molecule or a surface of the colorant, And, the resin is composed of a solvation part having an affinity for the carrier liquid and a non-solvation part having no affinity, and the solvation part contains a unit from a monomer having an acidic group, and the unsolvation part A negatively-chargeable liquid developer, characterized by containing a unit from a monomer having a basic group. 2. The negatively chargeable liquid developer according to claim 1, wherein the weight ratio of the solvated part to the non-solvated part of the resin is 95: 5 to 60:40. 3. The negatively chargeable liquid developer according to claim 1, wherein the proportion of the unit from the monomer having an acidic group present in the solvated part of the resin is 1 to 20% by weight. 4. The negatively chargeable liquid developer according to claim 1, wherein the monomer having an acidic group contains a carboxyl group. 5. The negative according to claim 1, wherein the proportion of the unit derived from the monomer having a basic group present in the unsolvated part of the resin is 0.01 to 10% by weight. Chargeable liquid developer. 6. The negatively chargeable liquid developer according to claim 1, wherein the charge amount is from −10 to −400 μC / g.