JP2822245B2 - Wet developer for electrostatic latent image development - Google Patents

Description

Description: TECHNICAL FIELD 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.

[Summary of the Invention]

In the present invention, the colorant particles contained in the wet developer are surface-treated with a silane coupling agent having an acrylic double bond, and a resin component is copolymerized with the silane coupling agent, so that the developer is used as a developer. The purpose is to improve stability and obtain good developing characteristics, gradation properties, and fixing properties.

[Conventional technology]

In the field of image forming technology, a method of selectively irradiating light onto a uniformly charged photoconductor in accordance with an image signal and developing a formed electrostatic latent image is generally called an electrophotographic process. ing. This electrophotographic process is roughly classified into a dry developing method and a wet developing method.

The dry developing method has an advantage that it is excellent in handling property and preservation property of the developed toner because, in principle, it merely sprays and attaches a colorant powder to the electrostatic latent image. However, as seen in video printers and the like for printing electronic still photographs, in reality, in order to respond to the demand for high-quality images, which has been increasing in recent years, it is necessary to give a step to wet development.

On the other hand, the wet development method uses a liquid developer in which a dye or pigment as a colorant is dispersed in an insulating medium. According to the wet development method, it is possible to obtain resolution and gradation comparable to silver halide photography, and especially when a pigment is used as a colorant, the formed image is excellent in weather resistance, and Development is under way.

Conventionally, as a developer used in a wet developing method, a wet developer (hereinafter referred to as a wet developer) in which an insulating medium is a liquid substance at normal temperature represented by, for example, a saturated hydrocarbon-based Isopar G (manufactured by Esso) or the like , And liquid toner) are widely known.

[Problems to be solved by the invention]

By the way, in the wet developer used in the above-mentioned wet developing method, a resin component for adsorbing the colorant particles and taking in the charge donor is added. And as a polymer conventionally used as such a resin component,
Copolymers such as styrene and dodecyl acrylate are mainly used for the purpose of increasing the solubility in nonpolar solvents.

However, when the above-mentioned copolymer is used as the resin component, the adsorptivity to the colorant particles and the fixability to the photoreceptor film are not sufficient, and satisfactory resolution, gradation and fixability are obtained. The fact is that it has not been done.

Further, in the above-mentioned conventional copolymer, it is necessary to add a resin component in an amount of 2 to 5 times the amount of the colorant particles, which causes problems such as a change in composition due to repeated development and sticking of the resin to a developing device. Become.

As the surface treatment of the colorant particles, for example, JP-A-58-80
Although techniques for treating the surface of a dry toner with a silane compound are known from, for example, Japanese Patent Application Laid-Open No. 651, 651, these techniques do not take into account the interaction with the resin component and cannot solve the above-mentioned problems.

Accordingly, the present invention has been proposed in view of the above-described conventional circumstances, and has as its object to improve the adsorption characteristics of a resin component to a colorant particle in a wet developer, whereby the charge of the colorant particle is improved. It is an object of the present invention to provide a wet developer for developing an electrostatic latent image having excellent characteristics and excellent resolution, gradation and fixability.

A further object of the present invention is to provide a wet developer for developing an electrostatic latent image which is excellent in stability by suppressing a composition fluctuation of a resin component and sticking to a developing device.

[Means for solving the problem]

The present inventors have conducted various studies focusing on the interaction between the resin component and the colorant particles.Then, a silane coupling agent having an acrylic double bond was allowed to act on the surface of the colorant particles, In addition, by copolymerizing the resin component with this acrylic double bond, the resin component and the colorant particles can be chemically linked, the charging structure can be strengthened and the stability greatly improved. I came to the knowledge that I could do it.

The present invention has been completed based on such knowledge, and comprises a dispersion medium, colorant particles, a resin component, and a charge donor, and the colorant particles have an acrylic double bond. The surface treatment is carried out with the silane coupling agent, and the acrylic double bond of the silane coupling agent is copolymerized with a resin component.

As the silane coupling agent having an acrylic double bond, the following formula (I) [Where R represents hydrogen or a methyl group, and n is 1 to 4
Is an integer. At least one of X, Y, and Z is preferably a compound represented by halogen or alkoxy (methoxy, ethoxy, etc.)].

When the surface of the colorant particle is treated with the silane coupling agent, the colorant particle reacts with a hydroxyl group (for example, a hydroxyl group by adsorbed water or the like) present on the surface of the colorant particle and is chemically bonded to the surface.

Therefore, the colorant particles preferably have a hydroxyl group on the surface thereof, but these functional groups are not necessarily required because the reactivity of the silane coupling agent is extremely high.

From such a viewpoint, the colorant particles that can be used include conventionally known inorganic pigments, organic pigments, dyeings, and mixtures thereof.

For example, examples of the inorganic pigment include a chromium pigment, a cadmium pigment, an iron pigment, a cobalt pigment, ultramarine, navy blue, and the like. Organic pigments and dyes include Hansa Yellow (CI11680) and Benzidine Yellow G (CI2109
0), benzidine orange (CI21110), fast red (CI37085), brilliant carmine 3B (CI160
15-Lake), Phthalocyanine Blue (CI74160), Victoria Blue (CI42595-Lake), Spirit Black (CI50415), Oil Blue (CI74350), Alkaline Blue (CI42770A), Fast Scarlet (CI12315), Rhodamine 6B (CI45160), Rhodamine Lake (CI45160-Lake), Fast Sky Blue (CI74200-Lake), Nigrosine (CI50415), 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 may be selected and used.

The silane coupling agent is chemically bonded to the surface of the colorant particles by the surface treatment with the silane coupling agent. In the present invention, the silane coupling agent further includes an acrylic double bond. A copolymerizable monomer is copolymerized to obtain a resin component.

Examples of the monomer copolymerizable with the acrylic double bond include acrylates such as methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, isobutyl acrylate, pentyl acrylate, hexyl acrylate, heptyl acrylate, and octyl acrylate. Methacrylates such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, butyl methacrylate, isobutyl methacrylate, pentyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, styrene, vinyl acetate, vinyl toluene,
Acrylonitrile and the like can be mentioned. Of course, not limited thereto, any monomer having a double bond copolymerizable with an acrylic double bond can be used.

Further, particularly for the purpose of increasing the interaction with the charge donor, even if a monomer having a structure in which the resin component copolymerized with the silane coupling agent has a polyoxyethylene structure in a side chain is selected. Good.

The polyoxyethylene structure has a repeating unit that becomes —O—CH ₂ CH ₂ —, and a coordination field is formed by its oxygen atom. In this case, it is necessary that the polyoxyethylene structure is introduced into the side chain of the copolymer, and even if the polyoxyethylene structure is introduced into the main chain, the effect of forming a coordination field cannot be expected.

In particular, in consideration of compatibility with a dispersion medium, formation of a coordination field due to a carboxyl group, and the like, it is preferable to use an acrylate copolymer represented by the following formula (II).

However, in the copolymer represented by the formula (II),
R ¹ , R ² and R ³ each represent hydrogen or a methyl group, and j is 1
And m represents an integer of 10 to 30. As for j and m, two or more kinds of j and m may be combined within the above range.

In addition, x, y, and z indicate the composition ratio of each monomer, but it is preferable that x is 0.2 to 0.8, y is 0.2 to 0.8, and z is 0.001 to 0.05. When the value of x is out of the above range, the coordination field due to the ester bond portion is reduced and it becomes difficult to take in the charge donor, and when the value of y is out of the above range, problems such as solubility in the dispersion medium occur. Furthermore, when the value of z is 0.
If it is less than 001, the effect of introducing a polyoxyethylene structure will be insufficient, and if it exceeds 0.05, the solubility will decrease.

On the other hand, the number n of repeating unit units in the polyoxyethylene structure is preferably 2 to 6. If n is too large, it will be difficult to dissolve in a nonpolar solvent. If it is too small, the solubility will be improved, but the function as a functional group will be reduced.

The molecular weight of the above-mentioned copolymer is 3000 to 3,000 in number average molecular weight Mw.
It is preferably 100,000, more preferably 5,000 to 50,000.

The copolymer having a polyoxyethylene structure itself is excellent not only in the adsorptivity to the colorant particles but also in the interaction with the charge donor.

This means that, as shown in FIG. 1, the polyoxyethylene chain present in the side chain of the copolymer behaves as if it were a crown ether, and the coordination field formed by the polyoxyethylene chain provides a charge donating. This is because the metal ions of the agent are surrounded.

Further, in the copolymer, a coordination field is also formed by the carboxyl oxygen in the ester bond portion derived from the acrylic monomer, and this portion also surrounds the metal ion as shown in FIG.

Therefore, by using the copolymer represented by the formula (II) as the resin component, the interaction with the charge donor is ensured, and the charge characteristics of the colorant particles are improved.

The wet developer of the present invention contains a dispersing medium, a charge-donating agent, a charge-enhancing agent, and the like in addition to the colorant particles and the resin component, but the dispersing medium is not particularly limited.
Usually, a liquid electrically insulating organic solvent at room temperature is used.

As the liquid electrically insulating organic solvent, for example, aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons, polysiloxanes, and the like can be used. Volatility, safety, toxicity, odor, etc. In view of this, isoparaffinic petroleum solvents are 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 the like.

Further, in addition to a resin component having a polyoxyethylene structure in a side chain directly bonded to the colorant particles, a known resin material may be appropriately selected and used in combination. Examples of such resin materials include butadiene rubber, styrene-butadiene rubber, cyclized rubber, rubbers such as natural rubber, styrene resins,
Synthetic resins such as vinyl toluene resin, acrylic resin, polycarbonate resin, polyvinyl acetate resin, rosin resin, hydrogenated rosin resin, alkyd resins including modified alkyd such as linseed oil modified alkyd resin, polyterpene And other natural resins. In addition, modified phenol resins such as phenol resins and phenol formalin resins, pentaerythritol phthalate, coumarone-indene resins, ester gum resins, vegetable oil polyamide resins, etc. are also useful, and polyvinyl chloride, chlorinated Halogenated hydrocarbon polymers such as polypropylene, synthetic rubbers such as vinyl toluene-butadiene, butadiene-isoprene, and long-chain alkyl groups such as 2-ethylhexyl methacrylate, lauryl methacrylate, stearyl methacrylate, lauryl acrylate, and actyl acrylate Acrylic monomer polymers having the above or copolymers thereof with other polymerizable monomers (eg, styrene-lauryl methacrylate copolymer, acrylic acid-lauryl methacrylate copolymer), polyethylene, etc. Polyolefins, polyterpenes, and the like can also be used.

Usually, a charge donor is added to a wet developer. Usable charge donors include, for example, metal salts of fatty acids such as naphthenic acid, octenoic acid, oleic acid, stearic acid, isostearic acid or lauric acid, metal salts of sulfosuccinates, metal salts of oil-soluble sulfonic acid, phosphoric acid Metal salts such as ester metal salts and abietic acid; metal salts of aromatic carboxylic acids; and metal salts of aromatic sulfonic acids.

Further, in order to improve the charge of the colorant particles, SI
O ₂ , Al ₂ O ₃ , TiO ₂ , ZnO, Ga ₂ O ₃ , In ₂ O ₃ , GeO ₂ , SnO ₂ , Pb
Metal oxide particles such as O ₂ and MgO or a mixture thereof may be added as a charge enhancer.

Regarding the mixing ratio of each of the above-mentioned components, first, the colorant particles are preferably 0.01 to 100 g, more preferably 0.1 to 10 g, per liter of the dispersion medium. In order to perform particularly efficient development and suppress the amount of waste toner, the concentration with respect to the dispersion medium [the ratio of the dispersion medium to the colorant (dilution ratio)] is 2 to 10% by weight.
It is preferable that

Note that the concentration range of the coloring agent is a concentration in the developing step to the last, and may be concentrated to a higher concentration during storage, for example.

The resin component is added in the range of about the same amount or less as the colorant particles.
It is preferably from 0.1 to 100 g, more preferably from 0.1 to 1 g.
It is 0g.

The charge donor is also usually 0.001 to 10 per 1
g, preferably in the range of 0.01 to 1 g. Further, the charge enhancer is added in a weight ratio of not more than twice, preferably not more than the weight of the colorant particles.

[Action]

When the colorant particles are surface-treated with a silane coupling agent having an acrylic double bond, they react with hydroxyl groups on the surface of the colorant particles and are chemically bonded to the surface of the colorant particles.

Then, when a monomer copolymerizable with an acrylic double bond acts on the colorant particles to which the silane coupling agent is chemically bonded, a copolymer is formed at an end of the silane coupling agent. Resin component.

Here, the resin component is chemically bonded to the colorant particles via a silane coupling agent,
The charged structure is firmly formed together with the charge donor. Therefore, aggregation of the colorant particles is suppressed, and high resolution and high gradation can be obtained. At the same time, fluctuations in the composition of the resin component and sticking to the developing device are also suppressed.

〔Example〕

Hereinafter, the present invention will be described based on specific experimental results.

Preparation of Surface Treated Toner The silane coupling agent used here is 3-methacryloyloxypropylmethyldichlorosilane.

A yellow toner (3,3'-dichlorobenzidine) was used as the colorant particles, and this yellow toner was
Fineness was achieved by the Mahler method, and 3-methacryloyloxypropylmethyldichlorosilane in an amount of 1 to 20% by weight of the toner was added to directly bond to the hydroxyl groups of the toner. At this time, a paraffin solvent (Isoper H) was used as a solvent.

The reaction formula between the toner (3,3'-dichlorobenzidine) and 3-methacryloyloxypropylmethyldichlorosilane is as follows.

Then, methyl acrylate (79
% Molar ratio), stearyl acrylate (20% molar ratio) and methoxytotetraethylene glycol methacrylate (1% molar ratio), and polymerization was carried out using AIBN as a polymerization initiator. At this time, the reaction temperature was set to 75 ° C., and ultrasonic waves were continuously applied during the polymerization reaction to prevent aggregation of the toner.
Each acrylate was sufficiently dehydrated before the reaction.

After the reaction, it was confirmed by ¹ H-NMR (270 MHz) that a polymer was formed on the toner surface.

Synthesis of Resin The resin synthesized here is simply for dispersing in a developer without being bound by a silane coupling agent.

The acrylic monomer was weighed and 0.5% of a reaction initiator [α, α'-azobis (isobutyronitrile)] was added. After adding a 5-fold amount of a solvent (dimethylformamide), the mixture was degassed and sealed using a vacuum line. After reaction at 70 ° C. for 18 hours, the tube was opened, a reaction terminator (hydroquinone) was added, and the mixture was purified three times from a mixed solvent of n-hexane and ethanol for purification. After the solvent was completely removed, the same amount of toluene as the synthesized resin was added, dispersed, and stored.

The resins shown in Table 1 were synthesized according to the above synthesis method. These resins are synthesized from methyl acrylate, stearyl acrylate, and methoxytetraethylene glycol methacrylate (or methoxydiethylene glycol methacrylate). In the above formula (II), j = 1 and m = 18. The methyl acrylate is copolymerized for the purpose of improving the flexibility of the resin, and the stearyl acrylate is copolymerized for the purpose of improving the solubility in a paraffinic solvent.

Experimental Example 1 In this experimental example, the charge was measured.

Developer composition Toner 1g; (Use a solution equivalent to 1g when surface-treated) Resin when using FR-101, AS1-1 and AD2-2
1 g; Dispersion medium (Isoper) 1; 20 drops each of charge donors (Zr octylate, Ca octylate); A developer was prepared from the above composition, and the charge was measured.
When FR-101, AS1-1, and AD2-2 were used as composition resins, the same yellow pigment as the surface-treated product was used as colorant particles kneaded with oleic acid. The results are shown in Table 2.

As is clear from this table, AD2 after surface treatment
-2 when the resin component is polymerized,
The surface charge is further improved as compared with the case where 2-2 is used.

Experimental Example 2 In this experimental example, development characteristics were examined.

For the purpose of evaluating the development resolution, gradation, and fixability, development was performed using the developer prepared in Experimental Example 1.
Table 3 shows the developing characteristics of each developer.

The above resolution is the result when a yellow pigment, which is generally difficult to develop, is used. When using a pigment that has been polymerized after surface treatment, the resolution is extremely good, 70 lines / mm
The above resolution was obtained.

Experimental Example 3 In this experimental example, the concentration dependency of the charge donor was examined.

Development was performed using the surface-treated yellow pigment while changing the amount of the charge donor. In this case, the charge donor added was only Zr octylate. The charge donor has only 12% by weight of Zr. Note that the developer is further diluted into two media for the purpose of comparing the development densities. Table 4 shows the concentration dependency of the charge donor.

If an excessive amount of the charge donor is added, the development density naturally decreases. In the case of a developer to which a resin is added, the development density is significantly affected by the concentration of the added charge donor. However, what is characteristic in this case is that the concentration of the charge donor Zr is 1 × 10 5
^-8 to 1.times.10.sup.- ⁵ Mol / can be developed at a substantially constant developing density.

〔The invention's effect〕

As is clear from the above description, in the present invention, since the resin component is chemically bonded to the colorant particles via the silane coupling agent having an acrylic double bond, the resin component and the colorant The binding of the particles becomes very strong, and the charging characteristics can be secured.

Further, problems such as aggregation of colorant particles due to detachment of the resin component can be solved, and wet development excellent in resolution, gradation, and fixability can be performed.

Further, it is possible to solve problems such as variation in the composition of the resin component and sticking to the developing device, and to provide a wet developer excellent in stability.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a state of capturing metal ions by a polyoxyethylene structure, and FIG. 2 is a schematic diagram showing a state of capturing metal ions in an ester bond.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-55-83057 (JP, A) JP-A-58-80651 (JP, A) JP-A-62-7718 (JP, A) JP-A-62 7717 (JP, A) JP-A-60-11853 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 9/12

Claims (2)

(57) [Claims] 1. A colorant comprising a dispersion medium, colorant particles, a resin component and a charge donor, wherein the colorant particles are surface-treated with a silane coupling agent having an acrylic double bond, and A wet developer for developing an electrostatic latent image, wherein a resin component is copolymerized with an acrylic double bond of a coupling agent. 2. The wet developer for developing an electrostatic latent image according to claim 1, wherein the dispersion medium is a liquid electrically insulating organic solvent at room temperature.