JPS5997157A - Electrophotographic liquid developer - Google Patents

Abstract

PURPOSE:To obtain an electrophotographic liquid developer capable of obtaining a transferred image not deteriorated in image density and sharpness during transfer and fixing by using an oxidized type polyethylene wax having a specified property as a toner component. CONSTITUTION:The liquid developer is obtained by dispersing a toner composed essentially of a thermoplastic resin, a colorant, and an oxidized type of polyethylene wax having 1,000-4,000mol.wt., 0.90-1.02 density, 5-50 acid value, and 80-120 deg.C softening point into a liquid carrier of a petroleum type aliphatic hydrocarbon. Image crushing is prevented, sharpness is enhanced, and deterioration of image density is avoided during transfer and fixing by using such an oxidized type of polyethylene wax having specified properties.

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, the main components are a thermoplastic resin such as styrene resin or acrylic resin, a coloring agent such as a pigment or dye such as carbon black, and polyethylene wax in a carrier liquid consisting of a petroleum-based aliphatic hydrocarbon solvent. There are known toners in which toner is dispersed. Including polyethylene wax in the developer has the effect of improving the density of the developed image, but this is because the wax gets between the colorant and resin that make up the toner particles.
It is thought that this is because increasing the particle size of the toner increases the amount of development and adhesion. However, on the other hand, the addition of conventionally known polyethylene wax has the drawback that it reduces the sharpness of the copied image during the transfer process, and in particular, the copied image obtained by developing, transferring, and fixing fine text images becomes flattened. Moreover, a decrease in image density also occurred.

The object of the present invention is to provide an electrophotographic liquid that uses a specific polyethylene wax, more specifically a specific oxidized polyethylene wax, as an image density improver to obtain a transferred image without deterioration in image density or sharpness during transfer and fixing. By providing the developer.

That is, the liquid developer of the present invention contains a thermoplastic resin, a colorant, and a molecular weight of 1000 to 40 in a petroleum-based aliphatic hydrocarbon carrier liquid.
00, a density of 0.90 to 1902, an acid value of 5 to 50, and a softening point of 80 to 120°C.

In the present invention, by using such a specific oxidized polyethylene wax, there is no image collapse, therefore high sharpness, and no reduction in image density during transfer and fixing.

The oxidized polyethylene wax used in the present invention is obtained by oxidizing low-molecular polyethylene, and has a molecular weight of 1000 to 1000.
4000, density 0.90-1.02, acid value 5-50
, the softening point should be 80-120°C. It is difficult to obtain those with a molecular weight of 900 or less, and when the molecular weight is 4,000 or more, the image density decreases. If the density is outside the above range, the image density will decrease. In addition, the acid value greatly affects the particle size of the toner, and if the acid value is less than 5, the particle size becomes too large and it is difficult for the toner to electrophoretically adhere to the transfer paper during transfer, resulting in the image density being below the standard value9. If the particle size is 50 or more, the particle size of the toner becomes too small, and even if the toner easily migrates onto the transfer paper during transfer, it tends to seep into the inside, and thus the image density similarly falls below the standard value.

Commercially available oxidized polyethylene waxes having the above-mentioned specific properties include the following.

(Left below) Thermoplastic resins include acrylic acid, methacrylic acid, or esters thereof (for example, 2-ethylhexyl (meth)
Acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, butyl (meth)acrylate, ethyl (meth)acrylate, methyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, 2-hydroxy (meth)acrylate, glycidyl (
(meth)acrylate, etc.), styrene or its derivatives (e.g., vinyltoluene, chlorstyrene, aminostyrene, dimethylaminostyrene, nitrostyrene, vinylbenzoic acid, etc.), vinylpyridine, vinylpyrrolidone, etc. are used. Ru.

Carbon black is used as a coloring agent (commercially available product is Printex 01 V manufactured by Degussa.

Special Black 15, 4, 4-B; Mitsubishi Su44, Na30, MA-11, MA-10 manufactured by Mitsubishi Carbon Co., Ltd.
0; Raben 30, 40, 103 manufactured by Cabot
5, Condextex SC1 Mogull L1 Elftex 8, Zigull 400, etc. ), Fuclocyanine Blue, Phthalocyanine Green, Sky Blue, Rhodamine Lake, Malachite Green Lake, Methyl Violet Lake, P=1 Ivy Blue Lake, Naphthol Green B1 Naphthol Green Y1 Naphthol Yellow S1 Litho-Schifst Yellow 2G, Permanent Red 4R1 brilliant first scarlet,
Hansa Yellow, Resole Red, Pencil Shin Yellow, Lake Red C Lukiretsudo D1 Brilliant Carmine 6B, Permanent Red F5R, Pigment Scarlet 3B, Alkali Blue, Oil Blue, Oil Violet, Methyl Orange, Fast Red, Methyl Violet, etc. Can be mentioned. Note that when carbon black is used as a coloring agent 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 a carrier liquid, cyclohexane, n-hexane is used. , n-hebutane, n-nonane, n-octane, isooctane, isododecane, ligroin, and mixtures thereof. and Shell Sol 71 and Tsurpez 150 manufactured by Shell Oil Co., Ltd.) are used.

The unmodified polyethylene wax used in combination with the oxidized polyethylene wax preferably has a softening point of 80 to 130°C, a molecular weight of 500 to 12,000, and a density of 0.90 to 0.98. Commercially available products include the following.

(Hereinafter, blank spaces) 8- In addition to the above components, additives such as thermosetting polyester and rosin-modified polyester can be used in the present invention.

The trap for making the liquid developer of the present invention is a colorant, a thermoplastic resin,
The oxidized polyethylene wax and, if necessary, the unmodified polyethylene wax may be kneaded with a small amount of a carrier liquid using a ball mill, a kedimir, or the like to obtain a concentrated toner, and the concentrated toner may be dispersed in an appropriate amount of the carrier liquid. The appropriate amounts of the thermoplastic resin and oxidized polyethylene wax to be used are approximately 0.9 to 5.0 parts by weight and 0.5 to 3.5 parts by weight, respectively, per 1 part by weight of the colorant. When unmodified polyethylene wax is used, the amount used is 0.5 in terms of oxidized polyethylene wax/unmodified polyethylene wax ratio (weight).
~9.5/ The range of 9.5 to 0.5 is preferable.

The present invention will be explained below with reference to Examples. Note that all percentages and ratios are by weight.

Example 1 Carbon black (Raven 1035) 12I!
Methylene blue 21 Isopar H
After kneading 90 g of the same composition in a ball mill for 72 hours, 360.9 g of Isopar H was added and kneaded for another 1 hour to obtain a concentrated toner, and 140 g of the same was dispersed and diluted in Isopar HIJ to prepare a liquid developer. .

Examples 2 to B A liquid developer was prepared in the same manner as in Example 1 using the compositions shown in the table below.

(The following is a blank space.) Next, the liquid developer obtained as described above was placed in a commercially available transfer type wet electrophotographic copying machine, and copies were made, and the results shown in the table below were obtained. In addition, the toner particle size of each developer is added to the same table.

(The following is a margin) Furthermore, the smoothness of the developer of Example 7 and Comparative Example 2 was 10.
When 12,000 sheets were continuously copied using transfer paper, Example 7 maintained a high image density of 1.2 to 1.3, but Comparative Example 2 maintained a high image density of 0.55 to 0.7. Only low values were obtained.

Example 9 Carbon black (Printex G) 12.9
Phthalocyanine blue 21! After kneading the composition consisting of Isopar HLoll for 72 hours in a ball mill, Isopar H350.9 was added and kneaded for an additional hour to obtain a concentrated toner, and 130 g of it was dispersed and diluted in Isopar HIA to prepare a liquid developer.

151 Examples 10 to 15 Liquid developers were prepared in the same manner as in Example 9 using the compositions shown in the table below.

(The following is a blank space) 16- Example 1 regarding the liquid developer obtained as above
A performance test was conducted in the same manner as in 8 to 8, and the results shown in the table below were obtained. Furthermore, the uniformity and fixability of the wide image (both visually evaluated) were added.

(Margin below)

Claims (1)

[Claims] 1. A thermoplastic resin in a petroleum-based aliphatic hydrocarbon carrier liquid,
Colorant and molecular weight 1000-4000, density 0.90-
1.02, an acid value of 5 to 50, and a softening point of 80 to 120C. 2. The liquid developer according to claim 1, further comprising unmodified polyethylene wax as a toner component.