JP3081637B2 - Color liquid developer for electrostatic photography - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an electrostatic latent image formed on an electrophotographic photoreceptor or an electrostatic recording medium, and electrostatically attaches toner particles to a visible image to form a visible image and color superposition. The present invention relates to a color liquid developer for electrostatography used in a process for performing electrophotography.

[Conventional technology]

In order to obtain a full-color image by electrophotography or electrostatic recording, an electrostatic latent image is formed on an electrophotographic photoreceptor or electrostatic recording paper by a conventional method, and a color liquid developer of a primary color according to an extinguishing color mixing method is used. It is obtained by electrostatically attaching toner particles to form a visual image and superimposing colors.

The liquid developer used in this method is a resin such as rosin, linseed oil, soybean oil, modified alkyd resin, styrene butadiene resin, acrylic resin, etc. It is obtained by pulverizing and dispersing in a carrier liquid having a high insulating property and a low dielectric constant as described above.

In color electrophotography, liquid developers are desired to have various performances in order to superimpose toners of the respective primary colors as described above, but it is necessary that particularly good color reproduction be obtained. is there.

However, when the formation and development of the electrostatic latent image are repeated in the order of black, cyan, magenta, and yellow using the liquid developer obtained by the method described above,
When the toner in the next step is developed with respect to the residual potential of the previously developed portion, there is a problem that extra toner is attached and color reproducibility is deteriorated. This development is referred to herein as "color overlap fog" due to residual potential.

It is known that the residual potential can be reduced by adding a static elimination mechanism such as light, heat, or ion irradiation to the machine side. As an example, when a photoconductive monomer is introduced into the resin constituting the toner, and a process of irradiating light after development is added, the residual potential after development with the toner is quickly neutralized by irradiation with light, Next, when a latent image is formed and developed with another toner, the portion where the latent image is not provided does not have an unnecessary color overlap fog. However, such a method is not an advantageous method because the structure on the machine side becomes complicated, leading to an increase in cost.

Therefore, a method has been proposed for improving the color fogging due to the residual potential on the side of the liquid developer, but there are two ideas in this method. One is a method of sufficiently neutralizing an electrostatic latent image with toner particles, and the other is a method of leaking electric charges into a carrier liquid constituting a liquid developer.

When these methods are used alone or in combination, although there is almost no "color overlap fog" in the initial quality,
When toner is consumed during running, "color overlap fogging" occurs, or when the ion concentration in the liquid increases due to running, the image density decreases rapidly, or the image density is not sufficiently obtained even in the initial quality. However, it is hard to say that an image with good color reproducibility can be stably obtained. Under such circumstances, there has been a demand for a liquid developer capable of obtaining a color image without "color overlap fog" without external static elimination and without impairing performance such as image density.

The present inventors have previously proposed a liquid developer capable of obtaining a color image without "color overlap fog" (Japanese Patent Application No. 62-203389).
issue). This is a resin dispersion obtained by graft-polymerizing a soluble monomer in a liquid carrier of a liquid developer onto a styrene-butadiene resin, and a gel resin comprising a monomer having a soluble monomer, an insoluble monomer, and a crosslinkable group in the carrier liquid. It is characterized in that it is combined with a resin dispersion in which insoluble resin particles are dispersed therein. However, it has been found that the latter resin dispersion has a practical problem in terms of dispersion stability.

Further, a toner capable of obtaining an image with high transparency is desired for full-color color reproducibility. In general, transparency can be improved to some extent by lowering the pigment concentration contained in the toner particles.However, this method has a disadvantage that the image density is reduced, and sufficient transparency is obtained when a certain image density is to be obtained. Did not.

[Problems to be solved by the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a color liquid developer suitable for color superposition type electrostatography, which eliminates the above-mentioned disadvantages.

[Means for solving the problem]

The present inventors have been studying in order to achieve the above object, but have found that it can be solved by using a specific resin in combination at a certain ratio, and have completed the present invention.

That is, the present invention relates to a color liquid developer used in a process of electrostatically adhering toner particles containing a pigment and a resin dispersed in a carrier liquid as a main component to form a visual image and color superimpose, wherein the resin comprises the following resin It consists of a combination of (I) and resin (II), and preferably the ratio of resin (I) and resin (II) is
95: 5 to 5:95, more preferably the particle size of the material
A color liquid developer for electrostatography, having a particle size of 0.15 μm or less.

Resin (I) A non-aqueous resin dispersion obtained by graft-polymerizing at least one of styrene-butadiene resin or vinyltoluene-butadiene resin and at least one monomer selected from the following formula (III).

Resin (II) At least one monomer selected from the group of monomers of the following general formula (III) and at least one type of monomer selected from the group of monomers that become insoluble in the solvent when homopolymerized in a non-aqueous solvent. Non-aqueous resin solution obtained by polymerizing

In the present invention, it is estimated that the electric resistance, the capacitance, and the like of the toner become values particularly effective for reducing fog and secondary color reproducibility by a specific resin combination.

The effect of resin (I) and resin (II) on image quality can be explained as follows.

The toner obtained by using the resin (I) is excellent in rechargeability, so that color superposition is sufficiently performed and an image without color unevenness can be obtained. Color reproducibility of primary colors such as cyan, cyan and magenta is insufficient.

On the other hand, although the resin (II) is excellent so that color overlap fog can hardly be felt, the rechargeability is slightly inferior to the resin (I). Further, the resin (II) has a feature of being excellent in dispersion stability.

In the present invention, the ratio of resin (I) to resin (II) is 9
By using the toner obtained by specifying the ratio of 5: 5 to 5:95, preferably 95: 5 to 60:40, it is possible to obtain a sufficient color superposition for excellent rechargeability, and a residual potential. As a result, a color image having good color reproducibility was obtained, and the problem of dispersion stability as disclosed in Japanese Patent Application No. 62-303389 was solved.

In order to produce the resin (I), a styrene-butadiene copolymer is dissolved in a non-aqueous solvent, and then a monomer of the general formula (III) is dropped, and azobisisobutyronitrile (AIB
N), 60-120 in the presence of a polymerization initiator such as benzoyl peroxide (BPO) which initiates polymerization at a relatively low temperature.
The polymerization reaction may be performed at a temperature of about ° C.

On the other hand, in order to produce the resin (II), a monomer of the general formula (III) and at least one monomer selected from a monomer group which is insoluble in a nonaqueous solvent when homopolymerized in the solvent are mixed with a nonaqueous solvent. The polymerization reaction may be performed at a temperature of about 60 to 120 ° C. in a solvent in the presence of a polymerization initiator such as AIBN or BPO.

The monomer represented by the general formula (III) is a monomer that can be a solvation component even after polymerization, and specific examples thereof include lauryl methacrylate, lauryl acrylate,
Stearyl methacrylate, stearyl acrylate,
2-ethylhexyl methacrylate, 2-ethylhexyl acrylate, dodecyl methacrylate, dodecyl acrylate, hexyl methacrylate, hexyl acrylate, octyl methacrylate, octyl acrylate, cetyl methacrylate, cetyl acrylate, vinyl laurate, vinyl stearate, nonyl methacrylate, nonyl acrylate, decyl methacrylate , Decyl acrylate, cyclohexyl methacrylate, cyclohexyl acrylate, and the like.

Next, some specific examples of the production examples of the resin (I) and the resin (II) will be described.

[Production Example (1) of Resin (I)] A stirrer, a thermometer, a cooling pipe, and a dropping funnel were provided.
Toluene 400g in a 2.0 flask, styrene-butadiene resin (Priolite S-5, manufactured by Goodyear) 300g
While stirring at 80 ° C., a monomer solution comprising 400 g of 2-ethylhexyl methacrylate and 10 g of benzoyl peroxide was added dropwise thereto over 2 hours. Thereafter, polymerization was carried out at this temperature for 5 hours. As a result, the polymerization rate is 95%.
Was obtained.

[Production Example (2) of Resin (I)] 400 g of cyclohexane was placed in the same flask as in Resin Example (1).
Vinyltoluene / butadiene resin (Priolite VT,
300 g of Goodyear (manufactured by Goodyear) was charged and a monomer solution composed of 10 g of lauroyl peroxide was added dropwise thereto over 2 hours while heating and stirring at 90 ° C. Thereafter, polymerization was carried out at this temperature for 5 hours. As a result, a resin dispersion having a polymerization rate of 94% was obtained.

[Production Example (1) of Resin (II)] A stirrer, a thermometer, a cooling pipe, and a dropping funnel were provided.
In a 2.0 flask, 750 g of Isopar H were charged, and while heating and stirring at 80 ° C., 400 g of 2-tylhexyl methacrylate, 200 g of styrene, and 200 g of n-butyl methacrylate were added thereto.
A monomer solution consisting of 150 g and 10 g of benzoyl peroxide was added dropwise over 3 hours while purging with nitrogen. Thereafter, polymerization was carried out at this temperature for 10 hours. As a result, a resin solution having a polymerization rate of 94% was obtained.

[Production Example (2) of Resin (II)] A stirrer, a thermometer, a cooling pipe, and a dropping funnel were provided.
2.0 g of Isopar H was charged into a flask, and while heating and stirring at 80 ° C., lauryl methacrylate 50 was added into the flask.
0 g, styrene 250 g, and benzoyl peroxide 10
g of a monomer solution was added dropwise over 3 hours while purging with nitrogen. Thereafter, polymerization was carried out at this temperature for 10 hours. As a result, a resin solution having a polymerization rate of 94% was obtained.

In order to obtain a color liquid developer for electrostatography using the resin thus obtained, 1 to 5 parts by weight of the resin (I) and the resin (II) of the present invention together with 1 part by weight of the colorant is used. A concentrated toner is obtained by kneading and dispersing (as a resin solid content) and 10 to 30 parts by weight of a carrier liquid with an attritor, a ball mill, a sand mill, or the like, and may be diluted with a similar carrier liquid as necessary.

Further, at the time of adjusting the concentrated toner or after the adjustment, a charge control agent such as a resin acid metal salt can be added as necessary.

As the colorant, general inorganic or organic pigments can be used, but the following are more preferable for a color superposition type electrophotographic liquid developer.

≪ Black カ ー ボ ン Carbon black (furnace black, channel black, acetylene black, etc.) ≪ Cyan ≫ Phthalocyanine blue (β-type) ≪ Magenta フ Naphthol AS-based insoluble monoazo pigment ≪ Yellow ≫ Acetoacetate arylamide-based insoluble disazo pigment In the present invention, Furthermore, the primary particle diameter of the pigment is 0.15μm
By using the following, the transparency of the image can be increased without increasing the light transmittance and the pigment concentration in the toner, so that the color reproducibility can be enhanced without the side effect of the decrease in the image density.

As the carrier liquid used in the liquid developer of the present invention, an aliphatic hydrocarbon or a derivative thereof is preferable.

Specific examples thereof include, for example, paraffinic or isoparaffinic hydrocarbons (Esso's Isopar H, Isopar G, Isopar L, Isopar K, etc.), ligroin, n-hexane, isooctane, cyclohexane, etc., alone or in combination of two or more. Are used in combination.

〔Example〕

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

Example 1 {Cyan} phthalocyanine blue (primary particle size 0.10 μm) 5 parts Resin (I) Production Example 1 (solid content conversion) 8.5 parts Resin (II) Production Example 1 (solid content conversion) 1.5 parts Isopar H (in resin) 85 parts {Magenta} Naphthol carmine (primary particle size 0.10 μm) 5 parts Production example 1 of resin (I) (solid content conversion) 8.5 parts Production example 1 of resin (II) (solid content conversion) 1.5 Part Isopar H (including solvent in resin) 85 parts ≪Yellow≫ Disazo Yellow AAA (primary particle diameter 0.10 μm) 5 parts Resin (I) Production Example 1 (solid content conversion) 10 parts Isopar H (solvent in resin also) 85 parts {Black} Carbon black 5 parts Nigrosine 2 parts Resin (I) Production Example 1 (solid content conversion) 8.5 parts Resin (II) Production Example 1 (solid content conversion) 1.5 parts Zirconium naphthenate (metal content 4%) ) 0.25 parts Isopar H (in resin) 82.75 parts The mixture having the above composition was dispersed in a ball mill for 24 hours to obtain a concentrated toner, and 50 g of the concentrated toner was diluted in Isopar 1 to prepare a set of electrophotographic color liquid developers. Subsequently, this was repeatedly subjected to latent image formation and development in the order of black, cyan, magenta, and yellow with an electrostatic color plotter CE-3436 (manufactured by Versat Tech Co., Ltd.). A color image was obtained.

Example 2 A liquid developer was prepared in exactly the same manner as in Example 1 except that the resin (I) and the resin (II) were replaced with the resin of Production Example 2.

When a color image was printed using this liquid developer in the same manner as in Example 1, almost no color fogging was observed.
Secondary color reproducibility was also good.

Comparative Example 1 A liquid developer was prepared in exactly the same manner as in Example 1 except that the resin (II) was omitted for each of the cyan, magenta and black toners.

When a color image was printed using this liquid developer in the same manner as in Example 1, other toner adhered to the black, cyan, and magenta images, and the color overlapped fog was large.

Comparative Example 2 A liquid developer was prepared for each of the cyan, magenta and block toners of Example 1, except that the resin (I) was omitted.

When a color image was printed using this liquid developer in the same manner as in Example 1, color reproducibility of the secondary color was slightly inferior, though no color overlap was formed on the black, cyan, and magenta images. .

Comparative Example 3 A liquid developer was prepared in the same manner as in Example 1 except that the liquid developer of Example 1 was replaced with the liquid developer of Example 1 of Japanese Patent Application No. Sho 62-303389. The dispersion stability of each magenta toner was poor, causing a problem in practical use.

Comparative Example 4 A liquid developer was prepared in the same manner as in Comparative Example 3, except that the primary particle size of the cyan, magenta and yellow pigments was changed to 0.10 μm.

Table 1 shows the image quality, the dispersion stability of the liquid developer itself, and the total transmittance using the liquid developers of the above Examples and Comparative Examples.
Shown in

Evaluation method 1. Image density Macbeth reflection densitometer RD-914 2. Color overlay fog The change in color before and after color overlay in the CIE-1976Lab * color system was measured by a colorimeter.

 Ideal color overlay is zero color difference.

3. Secondary color reproducibility Using RGB of afset process printing as reference color, color difference of 15 or less is ○ 15 or more x 4. Dispersion stability The percentage of the solids settled after natural sedimentation (one month) with respect to the total solids. Measured and ranked according to the following criteria.

○ Less than 30% △ 30% or more and less than 50% × 50% or more [Effect] As is clear from the comparison between the examples and comparative examples, the color liquid developer for electrophotography according to the constitution of the present invention has a color fog. Almost no reproducibility of secondary colors due to high transparency. When used for color superposition type electrophotography or electrostatic recording, it has a remarkable effect on color reproducibility and color discrimination. .

 Further, it has sufficient dispersion stability for practical use.

Continuation of the front page (56) References JP-A-1-145665 (JP, A) JP-A-1-145666 (JP, A) JP-A-55-7713 (JP, A) JP-A-55-22718 (JP) , A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 9/13

Claims (3)

(57) [Claims] A color liquid developer used in a process of electrostatically attaching toner particles containing a pigment and a resin as main components dispersed in a carrier liquid to an electrostatic latent image to visualize and color overlap. A color liquid developer for electrophotography, wherein the resin comprises a combination of a resin (I) and a resin (II). Resin (I) A non-aqueous resin dispersion obtained by graft-polymerizing at least one kind of styrene-butadiene resin or vinyl toluene-butadiene resin with at least one kind of monomer selected from the following formula (III). Resin (II) at least one monomer selected from the group of monomers represented by the following general formula (III) and at least one monomer selected from the group of monomers insolubilized in a non-aqueous solvent when homopolymerized in the solvent: Non-aqueous resin solution obtained by polymerizing 2. The electrophotographic color liquid developer according to claim 1, wherein the resin (I) and the resin (II) are used in a ratio of 95: 5 to 5:95. 3. The color liquid developer for electrophotography according to claim 1, wherein the pigment has a particle size of 0.15 μm or less.