JPS635351A - Liquid developing agent for electrostatic photography - Google Patents

Abstract

PURPOSE:To obtain the titled agent capable of improving a fixing and a dispersion properties by using a resin obtd. by cross-linking a copolymer of specific monomers with isocyanate to the titled agent. CONSTITUTION:The copolymer obtd. by copolymerizing the monomers shown by formulas I and II is cross-linked with the isocyanate compd. In the formulas, R1 is H or CH3 group, R2 is 6-20C alkyl, R3 is OH or -O(CH2)nOH [(n) is a positive integer of 1-4] or -NHCH2OH. As the polymer having the cross- linking type structure has properties of swelling and dispersing in a carrier solution, in case that said polymer is used for a toner (a particle absorbed a resin to an image forming agent), the resin is fixed on a cured image whereby the toner does not peel in the printing, and has an excellent anti-printing and anti-rubbing properties of the image in an electrostatic printer.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to a liquid developer for electrophotography, particularly to a developer for electrophotographic offset and a wet developer for printer plotters.

In the case of the conventional wet development method, the fat content of the toner is mainly that which is adsorbed to the pigment, so the resin content in the image area is lower than that of the dry toner, and the fixation is due to the evaporation of the solvent, so the dry toner The disadvantage is that the fixing power is weaker than that of . For this reason, images obtained using the wet method have superior resolution and fine line reproducibility compared to images using dry toner, but when used as a master for offset printing, the toner tends to fall off during printing. It has the disadvantage of poor durability during printing (printing durability). Recently, wet toner copiers have begun to incorporate dryers in order to quickly remove solvent from the master and improve fixing performance, but due to the aforementioned properties of wet toner, For,
It's still not effective. Additionally, electrostatic printers are used for CAD and CAM output.

Electrostatic printer plotters are mainly used for large drawings due to their fast printing speed, and a developer with good fixing properties is desired.

In addition, in order to improve the fixing properties of wet type developers, conventionally, for example, carbon black is glat-polymerized with vinyl monomer, or polymerized dyes are used (Japanese Patent Publication No. 47-33778, Japanese Patent Publication No. 47-18035).
A toner in which a pigment is coated with a resin insoluble in a carrier solvent has been proposed (Japanese Patent Publication No. 48-24905), but the toner in which carbon black is graft-polymerized has a low grafting rate, so vinyl heptanomer may remain. , it polymerizes as it is, has little effect, and requires purification, so it has low practical value. On the other hand, in the case of polymer dyes, the dispersion stability is still insufficient, and if a monomer that would cause the polymer to be solvated in the carrier liquid is copolymerized with the dye, it will dissolve in the carrier liquid. Another problem is that it is difficult to form a black image using a single polymer dye.

Toners in which the pigment is coated with a resin insoluble in the carrier solvent have problems such as large particle diameters and poor dispersion stability.

Purpose It is an object of the present invention to provide a developer having excellent fixing properties and dispersibility, which overcomes the above-mentioned conventional drawbacks.

As a result of intensive research to achieve the above object, the present inventors have developed an electrostatic photographic liquid comprising a toner mainly composed of a colorant and a resin dispersed in a carrier liquid comprising an aliphatic hydrocarbon solvent. In the developer, the resin has the general formula (I), R1CH2=C-COOR, [R; H or CM, group, R2: C. ~C2.

Alkyl group] A monomer represented by the general formula (n), RO CH, = C-C-R3 [R: H or CH, group, R,: -OH, - O (
CH2)nOH (n is a positive integer of 1 to 4), NHCH20H] is a resin obtained by crosslinking a copolymer with a monomer represented by the following formulas with isocyanate. It has been found that the above object can be achieved by providing an electrostatographic liquid developer which has the following properties.

The resin used in the present invention is a polymer having a crosslinked structure as described above, and this polymer has the property of swelling and dispersing in a carrier liquid. Because of these properties, when used as a toner (particles in which a resin is adsorbed to an imager), this polymer will evaporate after the carrier liquid evaporates from the image area during fixing.
It hardens and adheres to the image.

The method for producing the resin used in the present invention includes (i) a step of copolymerizing an acrylic monomer having a higher ester and an acrylic monomer having a -COOH group or 10H group, and (n) the step (i). The process consists of crosslinking the obtained copolymer with an isocyanate compound.

The copolymerization step (i) and the crosslinking step (it) are known methods.

Examples of acrylic monomers of general formula I with higher esters include hexyl acrylate, hexyl methacrylate, n-octyl acrylate, n-octyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, n-nonyl acrylate,
Examples include n-nonyl methacrylate, lauryl acrylate, lauryl methacrylate, dodecyl acrylate, dodecyl methacrylate, stearyl acrylate, and stearyl methacrylate.

Examples of acrylic monomers of general formula (■) include acrylic acid, methacrylic acid, 2-hydroxyacrylate,
Examples include 2-hydroxy methacrylate, hydroxypropylacrylate, hydroxy methacrylate, N-methylol acrylamide, N-methylol methacrylamide, and the like.

Examples of the isocyanate compound include hexamethylene-1,6-diisocyanate, diphenylmethane diisocyanate, naphthamene-1,5-diisocyanate, and toluylene diisocyanate. Examples of commercially available products include Nipporan Coronate L and H (manufactured by Nippon Polyurethane Co., Ltd.), and Susidur N-75 and L-75 (manufactured by Sumitomo Bayer).

The appropriate weight ratio of the heptanomer of general formula (1) to the monomer of general formula (2) is about 99:1 to 70:30.

The proportion of the isocyanate compound used as a crosslinking agent is suitably 0.01% to 5% by weight based on the copolymer.

The polymer thus obtained can be used in combination with a conventional resin for liquid toners. Known coloring agents such as carbon black, crystal violet, and phthalocyanine blue are used.

As the carrier liquid, known petroleum-based aliphatic hydrocarbons and their halides are used.

To prepare the liquid developer of the present invention, as in the conventional method, a concentrated toner is prepared by kneading a polymer, a colorant, and if necessary a polarity control agent such as a higher fatty acid metal salt with a small amount of a carrier liquid, and this is mixed with a large amount of the carrier liquid. You can dilute it with The appropriate ratio of polymer to colorant is about 1:1 to 9:1 (by weight).

Examples of manufacturing the resin used in the present invention will be specifically shown below.

Preparation Example 1 400 g of isooctane is placed in a 4-tube flask equipped with a stirrer, a thermometer, a dropping funnel, and a condenser, and the internal temperature is heated to 90° C. in an oil bath, and the inside of the flask is purged with nitrogen.

Apart from this, 2-ethylhexyl methacrylate 194
g, 6 g of 2-hydroxy acrylate, and 1 g of penzoyl peroxide were prepared and added dropwise from a dropping funnel over about 2 hours. After the dropwise addition, the temperature was maintained at 90°C for 5 hours to carry out polymerization to form 2-ethylhexyl methacrylate. A copolymer of 2-hydroxymethacrylate was obtained. 200 g of isooctane and 1.5 g of toluylene diisocyanate solution (80% methyl ethyl ketone solution) were added to the flask containing this copolymer, and the mixture was reacted at 80° C. for 3 hours to obtain a crosslinked polymer. Thixotopic index of this crosslinked product (according to ASTM D 2556-66T)
was 2.1.

Production Examples 2 to 4 The same method as Production Example 1 was used except that 2-ethylhexyl methacrylate and 2-hydroxyacrylate copolymers consisting of monomers having the weight ratios shown in Table 1 below were used to obtain the thixotovic index shown in the table below. A polymer with the following properties was created.

(Margin below) Table 1 Production Example 5 A crosslinked product with a thixotopic index of 2.3 was obtained in the same manner as Production Example 1 except that lauryl methacrylate was used instead of 2-ethylhexyl methacrylate.

Production Example 6 A crosslinked product with a thixotopic index of 3.4 was prepared in the same manner as in Production Example 1, except that lauryl methacrylate was used in place of 2-ethylhexyl methacrylate and acrylic acid was used in place of 2-hydroxyacrylate. I got it.

Production Example 7 A crosslinked product of thixotopic indenox 1.8 was obtained in the same manner as in Production Example 1 except that stearyl methacrylate was used in place of 2-ethylhexyl methacrylate.

Production Example 8 A crosslinked product with a thixotopic index of 1.9 was obtained in the same manner as in Production Example 1, except that hydroxypropyl methacrylate was used in place of 2-hydroxyacrylate in Production Example 1.

Production Example 9 Production Example 1 except that hexamethylene 1,6 diisocyanate was used instead of toluylene diisocyanate in Production Example 1.
A crosslinked product with a thixotopic pink index of 2.3 was obtained in the same manner as above.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to the following Examples and Comparative Examples, but it should be understood that the present invention is not limited thereto.

Example 1 Carbon black #40 (manufactured by Mitsubishi Kasei): 4g Victoria Blue: 1g Isopar G (manufactured by Exxon Chemical): 53g was kneaded in a ball mill for 72 hours to obtain an a-condensed toner, and 10g of the mixture was mixed with Isopar H.
(Aliphatic hydrocarbon manufactured by Esso Oil) A liquid developer for electrostatic photography was prepared by partitioning during 2Q.

Also, as a comparative example, in this example, 2-
A similar liquid developer was prepared using an ethylhexyl methacrylate: hydroxyethyl methacrylate (95:5 weight ratio) copolymer.

Next, when plates were made using a commercially available wet-type electrophotographic plate making machine using these developers, the product of the present invention produced a clear image with an image density of 1.45 and the background density of 0.23, while the comparative example produced a clear image with an image density of 1.45 and a background density of 0.23. 1.39. A similar image with a background density of 0.24 was formed, and a Macbeth densitometer was used to measure the density.

In addition, when we conducted a peeling test using a commercially available adhesive tape (I peeled it off after rubbing the tape on the image), it was found that the product of the present invention did not adhere well. 4; ((image j degrees after peeling) XIOO/(original L1
・1 image j3? t)〕'r8=%, and also rub the soil with your hands). The +I+i image could hardly be removed, but the comparative product had a constant γf〈U〈U〈〈〉〈U〉〈〈〉〉〉〈U〉〈〈〉〈〉〉〈〉〉〈〉〈〉〉〈〉〉〉〉〉〉〈〉〉〈〉〉〈〉〉〉〈〈〈〈〈〉〈〉〈〈〉〈〉〈〈〉 After printing with a similar agent (mainly composed of carbon and acrylic copolymer), the paper was subjected to a peel test using an adhesive tape, and the fixing rate was 75%.

Example 2 Calcium hexyl salicylate: 0.2 g Isopar G: 14.8 g was mixed in a ball mill in the same manner as in the example to obtain a concentrated toner, and 10 g of the concentrated toner was dispersed in Isopar GIQ to prepare an electrostatic photographic liquid. A developer was prepared. Hereinafter, when plate making was carried out in the same manner as in Example 1 using this developer, the image size was 1.28 degrees per degree.
A clear blue-black positive image was formed. The fixation rate of this image was 96%.

When printing with a printing press (Ricoh AP-.1600) using the plate made in this way, clear marks were obtained.
10,000 sheets were obtained, and there was no toner peeling even after printing 10,000 sheets.

Example 3 Rikiichi Bon Black #40: 5g Nickel naphthenate: 0.5g Isopa G (manufactured by Exxon Chemical): 12.5 g was kneaded in a ball mill for 72 hours to obtain a concentrated toner, and 10 g of the concentrated toner was dispersed in Alsopar-HIQ. A liquid developer for electrostatic photography was prepared. Using this developer, an electrostatic printer plotter (BE)
When an image was formed with NSON9211), the image density was 1.22, and after rubbing this image with a finger about 5 times, the density was 1.16.For comparison, instead of the crosslinked resin of Example 3, A developer was prepared in the same manner as in Example 3 except that a copolymer of lauryl methacrylate and hydroxypropyl acrylate (98:2 weight ratio) was used, and an image was formed. The image density was 1.20, and the density after rubbing with a finger was 0.58.

Examples 4 to 1l Example 1 except that the polymers of Production Examples 2 to 9 were used instead of the polymer obtained in Production Example 1 in Example 1.
A developing solution was prepared in the same manner as in Example 1, and plate making was performed in the same manner as in Example 1. The results shown in Table 2 below were obtained.

(Margin below) Table 2 Effects The toner of the present invention has good dispersion stability and excellent fixing properties, so when used for offset purposes, there is no toner peeling during printing, and it has excellent printing properties, making it suitable for electrostatic printers. Resistant to image scratching.

Claims (1)

[Scope of Claims] 1. An electrostatographic liquid developer comprising a toner containing a colorant and a resin as main components dispersed in a carrier liquid comprising an aliphatic hydrocarbon solvent, wherein the resin has the general formula (I ), ▲There are mathematical formulas, chemical formulas, tables, etc.▼ [R_1: H or CH_3 group, R_2: C_6-C_
2_0 alkyl group] There are monomers represented by the general formula (II), ▲mathematical formulas, chemical formulas, tables, etc.▼ [R_1: H or CH_3 group, R_3: -OH, -O
(CH_2)nOH (n is a positive integer from 1 to 4), -NH
A liquid developer for electrostatic photography, characterized in that it is a resin obtained by crosslinking a copolymer with a monomer represented by CH_2OH with isocyanate.