JPS5995544A - Liquid developer for electrophotography - Google Patents

Abstract

PURPOSE:To obtain the titled developer capable of forming an high density image even on transfer paper with low smoothness by dispersing a thermoplastic resin, a coloring agent, and a specified ethylene-vinyl acetate copolymer in a liq. carrier. CONSTITUTION:An ethylene-vinyl acetate copolymer having 5-35wt% vinyl acetate content, 0.91-0.96 density and 60-106 deg.C softening point, e.g., ''TMREV 720'' of Hoechst Co. is used. 1 Part by weight of a coloring agent (A) such as carbon black, about 0.5-4 parts thermoplastic resin (B) such as (co)polymer of acrylic acid (ester), styrene (deriv.) or vinylpyridine, and about 0.5-3 parts said ethylene-vinyl acetate copolymer (C) are dispersed in a liq. carrier (D) which is aliphatic petroleum hydrocarbon such as ''Isoper E'' of Esso Standard Oil Co.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrophotographic liquid developer containing an image density enhancer.

As a liquid developer for electrophotography, a toner whose main component is a coloring agent consisting of a thermoplastic resin such as an acrylic resin or a styrene resin, or a pigment or dye such as Carzen Black is contained in a carrier liquid consisting of a petroleum-based aliphatic hydrocarbon. It is known that it is dispersed.

This type of liquid developer generally transfers a toner image formed on an electrophotographic photoreceptor onto a transfer paper using the toner's electrophoretic properties, and then thermally fixes it using the toner's thermal adhesive properties. It is used in type electrophotography. This conventional liquid developer has poor transferability, especially on paper with low smoothness.
・Therefore, there was a drawback that a transferred image with high density, sharpness, and uniformity could not be obtained.

The purpose of the present invention is to disperse and contain a specific ethylene-vinyl acetate copolymer, so that it can be used not only for highly smooth transfer paper but also for low smoothness transfer paper at a higher concentration than before. An object of the present invention is to provide a liquid developer for electrophotography which can form transferred images with excellent sharpness and uniformity.

That is, the liquid developer of the present invention is an electrophotographic liquid developer comprising a toner mainly composed of a thermoplastic resin and a colorant dispersed in a petroleum-based aliphatic hydrocarbon carrier liquid, and further has a vinyl acetate content of 5 to 5. 35% by weight, density 0.91-0.96,
It is characterized by having a dispersion property of an ethylene-vinyl acetate copolymer having a softening point of 60 to 106°C.

The ethylene-vinyl acetate copolymer used in the present invention and having the properties described above has toner electrophoresis properties even on transfer paper with low smoothness, and has good spreadability and permeability when heated, so that fine lines can be formed. It is possible to form a transferred image with sharp parts and uniform density even in wide parts. However, if the content of vinyl acetate in the copolymer is less than 5% by weight, it is difficult to obtain the desired effect of the present invention, and if it is more than 40% by weight, the compatibility with the carrier liquid becomes poor and the toner is mixed in the carrier liquid. This tends to cause agglomeration and reduces the sharpness of the image. If the density of the copolymer is less than 0.91, the transferability of the toner image will be poor and the image density will be reduced, and if it is more than 0.96, a wide width image with uniform density will not be obtained. Furthermore, if the softening point of the copolymer is below 60°C, the sharpness of the image will decrease, and
If the temperature exceeds 06° C., a wide-width image with uniform density cannot be obtained.

Examples of commercially available ethylene-vinyl acetate copolymers having the above-mentioned properties include those shown in the table below.

As the thermoplastic resin, (meth)acrylic acid or its ester (for example, 2-ethylhexyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate)
Acrylate, butyl (meth)acrylate, ethyl (
(meth)acrylate, methyl (meth)acrylate, dimethylamine ethyl (meth)acrylate, 2-hydroxy (meth)acrylate, glycidyl (meth)acrylate, etc.), styrene or its derivatives (such as vinyltoluene, chlorstyrene, aminostyrene, dimethyl aminostyrene, nitrostyrene, vinylbenzoic acid, etc.),
Polymers or copolymers of vinylpyridine, vinylpyrrolidone, etc. are used.

As a coloring agent, carbon black (commercially available products include Printex G, 1Bjv, Special Black 15, 4, and 4-B manufactured by Degussa; Mitsubishi # manufactured by Mitsubishi Carzen);
44, #30. MA-11, MA-100; G-Pen 30 manufactured by Casette. 40. Same 1o35, Conductex SC1 Mogul L1 Elftex 8, Thor-1
There are J Le 400, etc. ), Phthalocyanine Blue, Phthalocyanine Green, Sky Blue, Rhodamine Lake, Malachite Green Lake, Methyl Violet Lake, Peacock Flu Lake, Naphthol Green B,
Naphthol Green Y1 Naphthol Yellow S, Linole Fast Yellow 2G, Permanent Red 4R.

Brilliant Fast Scarlet, Hansa Yellow, Linur Red, Benzidine Yellow, Lake Red C, Lake Red D, Brilliant Carmino 6B, Permanent Red F5R.

Pigment Scarlet 3B, alkali blue, oil blue, oil violet, methyl orange, fast red, methyl violet and the like. When carbon black is used as a colorant to obtain a black image, organic colorants among the above colorants are usually used in combination with carbon black as a complementary color to black.

As carrier liquids, petroleum-based aliphatic hydrocarbons such as cyclohexane, n-xane, n-hebutane, n-nonane, n-octane, isooctane, isododecane, ligroin, and mixtures thereof (commercially available products manufactured by Esso Standard Oil Co., Ltd.) are used. (Isobar E, G, H, L, K, Shell Sol 71, Tsurpez 150, etc. manufactured by Shell Oil Company) are used.

In addition to the above components, additives such as thermosetting polyester and rosin-modified polyester can be used in the present invention. Further, up to 50 wt% of polyethylene wax may be used in combination with the ethylene-vinyl acetate copolymer of the present invention.

To make the liquid developer of the present invention, a colorant, a thermoplastic resin,
The above-mentioned ethylene-vinyl acetate copolymer may be kneaded with a small amount of carrier liquid using a means such as Zeel Mill or Kedi Mill to obtain a concentrated toner, and this may be dispersed in an appropriate amount of carrier liquid.

The amount of thermoplastic resin and ethylene-vinyl acetate copolymer used is 0.5 to 4 parts by weight, respectively, per 1 part by weight of the colorant.
Approximately 0.5 to 3.0 parts by weight is appropriate.

Examples of the present invention are shown below. Note that the ratio is a weight ratio.

Example 1 Ethylenotovinyl acetate copolymer (TMREV720)
15.9 Carbon Black (Raven 103
5) 12g Alkaline Blue
After thoroughly dispersing a composition consisting of 90 g of 2I Isopar H with 2-lumil, 350 g of Isopar H was added and redispersed to obtain a concentrated toner.
A liquid developer was prepared by diluting 140 g of the developer with Aituno<-H12.

Example 2 A liquid developer was prepared in the same manner as in Example 1 except that 400 & 400A were used instead of TR4REV7200.

Example 3 TMREV720 cr) Generation Q NiBA S pis
A liquid developer was prepared in the same manner as in Example 1 except that C9626 was used.

Comparative Example A liquid developer was prepared in the same manner as in Example 1 except that TMREV720 was not used.

Next, the liquid development blue 11 obtained as described above was placed in a commercially available transfer type wet electrophotographic copying machine, and image retention transfer was carried out on two types of transfer papers with a flat (10 seconds and 150 seconds), respectively. However, the result in the table below is 4%.

Furthermore, regarding the developer of Example 1 and Comparative Example (
When copying 9000 sheets in a row using second transfer paper, the image density of Example 1 was maintained at a high value of 1.0 to 1.25, but in the case of comparison fl12, it was 0.4. ~0
．． A force/vine that can only be obtained with a low value of 6.

Claims (1)

[Claims] 1. An electrophotographic liquid developer comprising a toner containing a thermoplastic resin and a colorant as main components dispersed in a petroleum-based aliphatic hydrocarbon carrier liquid, further comprising a vinyl acetate content of 5 to 35.
Weight%, density 0.91-0.96, softening point 60-106
1. A liquid developer for electrophotography, characterized in that it contains an ethylene-vinyl acetate copolymer dispersed therein.