JPH06138713A - Developer of wet process for developing electrostatic latent image - Google Patents

Abstract

PURPOSE:To improve the quality of the developer by using a compd. having a hydroxyl group as an essential component and a resin as a dispersion medium. CONSTITUTION:This developer wet process contains the dispersion medium, coloring agents, resin and charge imparting agent. The resin is copolymerized by using the compd. expressed by formula as an essential component in addition to components of an arom. group, alkyl group, oxyethylene group and acetoacetoxy group in its side chain so that the resin is soluble in the dispersion medium. In the formula, R, R', R'' are to 20C straight chain or branched alkyl group, arom. ring or straight chain or branched alkyl group having an ether group, ester group or arom. ring. The resin plays a surfactant-like role and the hydroxy group existing in the side chains is adsorbed on the surface of coloring agent particles of pigments, etc., by which the pigments, etc., are stably dispersed in the dispersion medium even in a high-temp. region.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wet developer for developing an electrostatic latent image for developing an electrostatic latent image in an electrophotographic process or the like. More specifically, it relates to the composition of the resin contained in the developer.

[0002]

2. Description of the Related Art In the field of image forming technology, a photoconductor or a photoconductor uniformly charged is selectively irradiated with light according to an image signal to develop the formed electrostatic latent image. The method is commonly referred to as the electrophotographic process.
The electrophotographic process is roughly classified into a dry developing method and a wet developing method.

In principle, the dry developing method has an advantage that it is excellent in handleability and storability of the developing toner agent, since the powder of the colorant is simply scattered and attached to the electrostatic latent image in principle. However, in order to meet the increasing demand for high-quality images as seen in video printers and the like that print electronic still photographs, it is the actual situation that the wet development method must be given up.

On the other hand, the wet development method is a method using a liquid developer in which a dye or a pigment as a colorant is dispersed in an insulating medium. According to the wet development method, it is possible to obtain a resolution and gradation that are comparable to those of silver salt photographs, and particularly when a pigment is used as a colorant, the formed image has excellent weather resistance. , Is being developed in various fields.

Conventionally, as the developer used in the wet development method, the insulating medium is a substance which is liquid at room temperature, represented by, for example, saturated hydrocarbon Isopar G (manufactured by Esso Co.). Wet developers (hereinafter referred to as liquid toners) are known. Further, as described in JP-A-2-6966, a wet developer (hereinafter referred to as a solid toner) in which colorant particles are dispersed in an electrically insulating organic medium which is solid at room temperature and liquefies when heated. Called) is also proposed. This solid toner or solidified toner is
Since it is solid when stored, it has advantages such as easy handling and little change in composition.

In such a wet type developer, a resin component such as styrene or dodecyl acrylate has been conventionally used for charging the colorant particles. This resin component is dispersed in the developer and forms a complex by interacting with the colorant particles. Since the charge-providing agent is incorporated in this resin component, the colorant particles are electrically charged through the resin component.

[0007]

By the way, in the technique using the resin component as described above, it is necessary to add 2 to 5 times the amount of the resin component to the colorant particles. Changes and sticking of resin to the developing device are problems. In addition, since the adsorption of the resin component to the colorant particles is in an equilibrium state, if there is a large amount of excess resin component that is not adsorbed to the colorant particles, the colorant particles may not be absorbed during the development of the electrostatic latent image. It is considered that the adsorption of the resin component which is not adsorbed onto the photoconductor results faster than the fixing of the colorant particles onto the photoconductor. Due to such a decrease in the fixing property of the colorant particles, a sufficient development density may not be obtained.

When stored for a long period of time, the resin component adsorbed on the colorant particles is desorbed with the lapse of time, causing aggregation and sedimentation of the colorant particles, resulting in a marked decrease in resolution during reuse and reuse. There were problems such as being impossible. On the contrary, if the concentration of the colorant particles is increased in advance, the colorant particles agglomerate and the resolution is remarkably lowered during development.

Such a drawback is particularly remarkable in the solid toner which needs to be heated in order to dissolve the dispersion medium during development. That is, in the solid toner, the equilibrium state of the adsorption of the resin component to the colorant particles is easily broken by heating, and the colorant particles may be aggregated or the fixing property may be deteriorated. Therefore, it becomes difficult to obtain high resolution.

Therefore, the present invention has been proposed in view of the above problems of the prior art, and shows an electrostatic property which exhibits good charge characteristics and dispersion stability and is excellent in resolution and gradation. An object is to provide a wet type developer for latent image development.

[0011]

The present inventors have taken the following means in order to achieve the above-mentioned object. That is, the wet developer for developing an electrostatic latent image of the present invention contains a dispersion medium, colorant particles, a resin and a charge-donating agent, and the resin has an aromatic ring, an alkyl group or oxyethylene in its side chain. In addition to components such as a group and an acetoacetoxy group, a compound represented by the following chemical formula is used as an essential component for copolymerization and dissolution in a dispersion medium.

[Chemical 1]

Here, the resin plays a role of a surfactant, and the hydroxy group in the side chain is adsorbed on the surface of the colorant particles such as the pigment, so that the pigment and the like are stably maintained in the dispersion solvent even in a high temperature region. Can be dispersed.

Examples of usable colorant particles include conventionally known inorganic pigments, organic pigments, dyes and mixtures thereof. Examples of the inorganic pigments include chrome pigments, cadmium pigments, iron pigments, cobalt pigments, ultramarine blue and dark blue. As organic pigments and dyes, Hansa Yellow (C.I. 11680), Benzidine Yellow G (C.I. 21090), Benzidine Orange (C.I. 21110) and Fast Red (C.I.
37085), Brilliant Carmine 3B (C.I.
6015-Lake), phthalocyanine blue (C.I.
I. 74160), Victoria Blue (C.I. 504)
15), oil blue (C.I. 74350), alkali blue (C.I. 42770A), first scarlet (C.I. 12315), rhodamine 6B (C.I.
I. 45160), Rhodamine Rake (C.I. 451)
60-Lake), Fast Sky Blue (C.I.
74200-Lake), Nigrosine (C.I. 504)
15), carbon black and the like. These can be used alone or as a mixture of two or more kinds, and those having a desired color development can be selected and used.

In the present invention, the hydroxy group contained in the resin improves the stability as a developer,
It is intended to obtain good resolution and gradation, and particularly to obtain dispersion stability.

The wet developer of the present invention contains a dispersion medium, a charge donor, a charge enhancer and the like, in addition to the resin component and the colorant particles described above. First, as the dispersion medium, any electrically insulating organic material can be used, and an electrically insulating organic material that is liquid at room temperature or an electrically insulating organic material that is solid at room temperature and liquefies by heating can be used.

As the electrically insulating organic substance which is liquid at room temperature,
For example, aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons, polysiloxanes and the like can be used, and among the aliphatic hydrocarbons from the viewpoint of volatility, safety, toxicity, odor, etc. Isoparaffinic petroleum solvent is preferred. Examples of the isoparaffin-based petroleum solvent include Isopar G, Isopar H, Isopar L, Isopar K (all manufactured by Esso), Shellsol 71 (manufactured by Shell Petroleum).
And so on.

Further, regarding the electrically insulating organic solid toner which is solid at room temperature, the melting point is preferably 30 ° C. or higher, more preferably 40 ° C. or higher, in consideration of the normal use environment and handleability. . Although the upper limit of the melting point is not particularly specified, it is practically about 100 ° C. or lower, more preferably 80 ° C. or lower. The reason is that even if the melting point is too high, extra energy is consumed for heating,
This is because it is considered that the heat resistance temperature of the material generally used as the substrate should not be exceeded when it is used while being held on the substrate. Materials that meet these requirements include paraffins, waxes, and mixtures thereof.
First, as paraffins, there are various normal paraffins having 19 to 60 carbon atoms ranging from nonadecane to hexacontane. Examples of waxes include plant waxes such as carnauba wax and cotton wax, animal waxes such as beeswax, ozokerite, and petroleum waxes such as paraffin wax, microcrystalline wax and petrolatum. These materials have a dielectric constant of 1.9 to
It is a dielectric of about 2.3. Furthermore, polyethylene,
Crystalline polymers with long alkyl groups on the side chains such as polyacrylamide, homopolymers or copolymers of polyacrylates such as poly-n-stearyl acrylate and poly-n-stearyl methacrylate (copoly-n-stearyl acrylate ethyl methacrylate) can also be used. However, the above paraffins and waxes are preferable in consideration of the viscosity at the time of heating.

A charge donor is added to the wet developer.
Examples of charge donors that can be used include metal salts of fatty acids such as naphthenic acid, octenoic acid, oleic acid, isostearic acid and lauric acid, metal salts of sulfosuccinic acid esters, oil-soluble sulfonic acid ester metal salts and abietic acid. Metal salts, aromatic carboxylic acid metal salts, aromatic sulfonic acid metal salts, and the like.

Further, in order to improve the charging potential of the colorant particles, SiO ₂ , Al ₂ O ₃ , TiO ₂ , ZnO, Ga _{2 are used.}
O ₃ , In ₂ O ₃ , GeO ₂ , SnO ₂ , PbO ₂ , M
Metal oxide particles such as gO or a mixture thereof may be added as a charge enhancer.

Regarding the blending ratio of the above-mentioned respective components, first, the colorant particles are 0.01 to 100 g per 1 liter of the dispersion medium.
Is preferable, and more preferably 0.1 to 10 g. In order to carry out particularly efficient development and suppress the amount of waste toner, the concentration (ratio of the dispersion medium and the colorant (dilution ratio)) to the dispersion medium is preferably 2 to 10% by weight.
The concentration range of the colorant is only the concentration in the developing step, and may be concentrated to a higher concentration during storage, for example.

The charge-providing agent is added in a range of not more than the same amount as the colorant particles, and is generally 0.001 to 10 g, preferably 0.01 to 10 g per 1 liter of the dispersion medium like the colorant particles. It is in the range of 1 g. Furthermore, the charge enhancer is added in a weight ratio of not more than 2 times, preferably not more than the same amount with respect to the colorant particles.

[0022]

By introducing the hydroxy group into the resin, the hydroxy group effectively acts as a binding element between the resin and the colored particles such as pigments, while the resin itself has good compatibility with the dispersion solvent, Since it also dissolves in, it effectively acts as a dispersant for dispersing pigments and the like. Especially at high temperature, since the hydroxy group is adsorbed on the pigment, the resin is not desorbed from the pigment, which greatly contributes to the improvement of the dispersibility of the developer.

[0023]

The preferred embodiments of the present invention will be described in detail below. Prior to the preparation of the developer, several resin syntheses were first performed, which will be described.

(Synthesis-1) Stearyl acrylate (S
A), methyl acrylate (MA), monomer having oxyethylene CH ₂ ═C (CH ₃ ) COO (CH ₂ C
H ₂ O) ₄ CH ₃ (M40G) was charged in a molar ratio of 30 each.
%, 69%, 1%, and 0.5% of the monomer weight of the initiator AIBN was added. After adding about 5 times the amount of solvent (toluene), bubbling with dry nitrogen gas N ₂ and sealing under a nitrogen atmosphere at about 75 ° C.
Polymerization reaction was carried out for about 24 hours. Then, it refine | purified twice by n-hexane and methanol. After completely removing the solvent, toluene was added in an amount equal to that of the resin to disperse and store the resin. This resin is designated as YD1-1. In addition, YD1-1
Does not contain a hydroxy group and is used to prepare a comparative example as described below. (Synthesis-2) 2-hydroxypropyl acrylate (HPA) was added together with SA, MA and M40G, and they were weighed out so that the charged molar ratios were 70%, 19%, 1% and 10%, respectively. This synthesis was performed in the same manner as (Synthesis-1). This resin is designated as YD8-5. Y due to the addition of HPA
D8-5 contains a certain amount of hydroxy groups. (Synthesis-3) SA, MA, M40G, and HPA were weighed out so that the charged molar ratios were 30%, 59%, 1%, and 10%, respectively. This synthesis was performed in the same manner as (Synthesis-1).
This resin is designated as YD8-7. (Synthesis-4) SA, MA, M40G, and HPA were weighed out so that the charged molar ratios were 50%, 19%, 1%, and 30%, respectively. This synthesis was performed in the same manner as (Synthesis-1).
This resin is designated as YD8-10.

Next, the following comparative examples and examples were prepared using the resins obtained by the above-mentioned synthesis. (Comparative Example 1) First, about 0.50 g of an azo yellow pigment and about 0.55 g of an isoparaffinic solvent were kneaded and then subjected to Hoover Mahler to pulverize the pigment. Add it with 0.50 g of YD1-1 to 50 ml of Isopar H,
Furthermore, the charge donor Zr octylate is added in an amount of several μl to several
Add nl and stir with a paint shaker for about 6 hours. Development was performed using this. (Comparative Example 2) First, about 0.50 g of an azo yellow pigment and about 0.55 g of an isoparaffinic solvent were kneaded and then subjected to Hoover Mahler to pulverize the pigment. 50 ml of paraffin (melting point 42 ~ with 0.50 g of YD1-1)
44 ° C.), and then several μl to several nl of Zr octylate, which is a charge-donating agent, was added, and the mixture was stirred by a paint shaker for about 6 hours. Using this, development was carried out at 55 ° C. (Example 1) First, about 0.50 g of an azo yellow pigment and about 0.55 g of an isoparaffinic solvent were kneaded and then subjected to Hoover Mahler to pulverize the pigment. Add it along with 0.50 g of YD8-5 to 50 ml of Isopar H,
Furthermore, the charge donor Zr octylate is added in an amount of several μl to several
Add nl and stir with a paint shaker for about 6 hours. Using this, development was performed in the same manner as in Comparative Example 1. (Example 2) First, about 0.50 g of an azo yellow pigment and about 0.55 g of an isoparaffinic solvent were kneaded and then subjected to Hoover Mahler to pulverize the pigment. With 0.50 g of YD8-5, 50 ml of paraffin (melting point 42 ~
44 ° C.), and then several μl to several nl of Zr octylate, which is a charge-donating agent, was added, and the mixture was stirred by a paint shaker for about 6 hours. Using this, development was performed in the same manner as in Comparative Example 2. (Example 3) YD8-7 was used as a resin, a developer was prepared and developed in the same manner as in Example 1. (Example 4) YD8-10 was used as a resin, and Example 1 was used.
A developer was prepared and developed in the same manner as in. (Example 5) YD8-10 was used as a resin, and Example 2 was used.
A developer was prepared and developed in the same manner as in.

The results of development and development as described above are shown in the table below. The evaluation item was dispersibility, and the development density was also measured. The dispersibility was evaluated by visual observation. A mark "○" indicates that no aggregation was observed, a mark "△" indicates that a little aggregation was observed, and a symbol "X" indicates that aggregation occurred.

[Table 1]

From the above table, it can be seen that the dispersibility is greatly different between the case where there is a hydroxy group and the case where there is no hydroxy group. This is because the hydroxy group is adsorbed on the surface of the pigment, and thereby high dispersion stability is obtained.

[0028]

As is apparent from the above description, in the present invention, the quality of the developer is improved by using a compound having a hydroxy group as an essential component and a resin soluble in a dispersion solvent. Therefore, in the dispersion system of the electrostatic latent image wet developer, the resin does not come off even at high temperature, and high dispersion stability can be maintained. Therefore, even if the dispersion medium is a solid dispersion medium at room temperature, the charge-donating agent does not separate from the colorant particles when heated to liquefy the dispersion medium.
It is possible to perform wet development excellent in resolution, gradation, and particularly dispersion stability even at a high temperature of about 0 ° C., and it is useful when applied to a solidified wet toner developer. Further, since the alkyl group in the side chain of the resin provides better dispersion stability, the colorant particles are not likely to aggregate even if the concentration of the colorant particles is increased.

Claims (1)

[Claims] 1. A resin containing a dispersion medium, colorant particles, a resin and a charge-providing agent, wherein the resin is a resin soluble in the dispersion medium and containing a hydroxy group as an essential component. A wet type developer for developing an electrostatic latent image characterized by: