JPH0623863B2 - Liquid developer for electrophotography - Google Patents

Description

TECHNICAL FIELD The present invention relates to a liquid developer for electrophotography in which a specific wax-like substance is contained in a toner.

As a liquid developer for electrophotography, styrene resin, thermoplastic resin such as acrylic resin, colorant composed of pigment or dye such as carbon black, and polyethylene wax are contained in a carrier liquid composed of petroleum-based aliphatic hydrocarbon solvent. A toner in which a toner as a main component is dispersed is known. By including polyethylene wax in the developer, it has the effect of improving the developed image density. This is because wax enters between the colorant and the resin forming the toner particles,
It is considered that this is because the particle size of the toner is increased, which increases the amount of toner attached to development. However, on the other hand, the addition of the conventionally known polyethylene wax reduces the sharpness of the copy image in the transfer step, and the copy image obtained by developing, transferring and fixing a fine character image is crushed. In addition to the drawbacks, the image density also decreased.

OBJECT The object of the present invention is to provide a liquid developer for electrophotography, which can obtain image quality without lowering of image density and sharpness during transfer / fixing and has good fixability.

Structure The present invention is a liquid developer for electrophotography, comprising a toner having a colorant and a resin as main components dispersed in a carrier liquid having a high insulating and low dielectric constant, wherein the toner contains polyhydroxypolyolefin. It is characterized by that.

The melting point of polyhydroxypolyolefin is 50 to 1
00 ℃, specific gravity 0.8-1.0, hydroxyl value (KOHmg / g) is 2
Those of 0 to 70 are suitable. Commercially available products are Polytail H, Polytail HA, and Polytail H manufactured by Mitsubishi Kasei.
E, polytail KH, polytail HC, polytail HU, etc. These are novel reactive polymers that take advantage of the excellent electrical and mechanical properties of polyolefin, and also have the property of being dissolved in a carrier liquid of a liquid developer at a melting point or higher.

As the resin for forming the toner, known resins such as thermoplastic resins can be used.

As the thermoplastic resin, acrylic acid, methacrylic acid or their esters (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 (eg vinyltoluene, chlorostyrene, aminostyrene, dimethylaminostyrene, nitrostyrene, vinylbenzoic acid etc.), vinylpyridine, vinylpyrrolidone or other polymers or copolymers are used. It

Carbon black as a colorant (commercially available products such as Printex G and V from Degussa, Special blacks 15, 4 and 4-B from Degussa; Mitsubishi # 4 from Mitsubishi Carbon)
4, # 30, MA-11, MA-100; Raven 30, 40, 1035, Conductex SC, Mogar L, Elftex 8, Legal 4 manufactured by KYABOT CORPORATION.
There is 00 etc. ) Phthalocyanine Blue, Phthalocyanine Green, Sky Blue, Rhodamine Lake, Malachite Green Lake, Methyl Violet Lake, Peacock Blue Lake, Naphthol Green B, Naphthol Green Y, Naphthol Yellow S, Resorfarst Yellow 2G, Permanent Red 4R, Brilliant Farst Scarlett, Hansa Yellow, Resole Red, Benzidine Yellow, Lake Red C, Lake Red D, Brilliant Carmine 6B, Permanent Red F5R, Pigment Scarlet 3B, Alkali Blue, Oil Blue, Oil Violet, Methyl Orange, Fares Red, Methyl. Examples include bio-reset. When a carbon black is used as a colorant for obtaining a black image, an organic type of the above colorants is usually used in combination with the carbon black for a complementary color of black.

Oxidized polyethylene wax or unmodified polyethylene wax may be added to the toner in addition to polyhydroxypolyolefin. It is preferable that the softening point is 80 to 130 ° C., the molecular weight is 500 to 12000, and the density is 0.90 to 0.98. Commercially available products include those shown in Examples below.

Examples of the carrier liquid include petroleum-based aliphatic hydrocarbons such as cyclohexane, n-hexane, n-heptane, n-nonane, n-octane, isooctane, isododecane, ligroin, and mixtures thereof (ISOPAR E manufactured by Esso Standard Petroleum Co., Ltd. as a commercial product). , G, H, L, K and Ciel-Polly Co. Cielsol 71, Solbetso 150, etc.) are used.

To make the liquid developer of the present invention, a colorant, a thermoplastic resin,
Polyhydroxypolyolefin and, if necessary, unmodified polyethylene wax or oxidized polyethylene wax may be kneaded with a small amount of carrier liquid by means such as a ball mill or a eddy mill to form a concentrated toner, which may be dispersed in an appropriate amount of carrier liquid. . Alternatively, the colorant may be subjected to flashing with a wax in a kneader and then dispersed with the thermoplastic resin carrier liquid. The particle size of the toner is preferably 0.2 to 1.0 μm. The amounts of the thermoplastic resin and polyhydroxypolyolefin used are 0.5 to 3.0 parts by weight and 0.1% by weight per 1 part by weight of the colorant, respectively.
About 3.0 parts by weight is suitable. When unmodified polyethylene wax or oxidized polyethylene wax is used, the amount thereof is preferably in the range of 0.5 to 9.5 / 9.5 to 0.5 in terms of polyhydroxypolyolefin / polyethylene wax ratio (weight).

Effects According to the present invention, by adding polyhydroxypolyolefin to the toner, it is possible to obtain image quality without lowering image density or sharpness.

Hereinafter, the effects of the present invention will be specifically shown by examples.

Example 1 Polytail H (manufactured by Mitsubishi Kasei Co., Ltd.) 20 g 2-ethylhexyl methacrylate / lauryl methacrylate / methacrylic acid / methyl methacrylate (30 /
20/10/40) Copolymer 35 g Carbon black (Raven 1035) 12 g Isopar H 90 g A composition was kneaded in a ball mill for 48 hours, then 360 g Isopar H was added and further kneaded for 1 hour to obtain a concentrated toner. A liquid developer was prepared by dispersing and diluting 140 g in Isopar H1.

Examples 2 to 8 Liquid developers were prepared in the same manner as in Example 1 using the compositions shown in the table below.

Next, the liquid developer obtained as described above was placed in a commercially available transfer type wet electrophotographic copying machine and copied, and the results shown in the following table were obtained. In the table, the toner particle size of each developer is additionally shown.

The present invention provides a liquid developer for electrophotography, which contains a polyhydroxypolyolefin in a toner and has a high transferability of the toner to the transfer paper regardless of the smoothness of the transfer paper and a good image density and sharpness. It is a thing.

Next, to clarify that the effect is excellent,
A test example in which a developer containing no polyhydroxypolyolefin as a comparative developer is shown below.

Test Example 1) Test developer a) Developer of Example 1 b) Sun wax E250P (Sanyo Kasei Co., Ltd.) in Example 1
Developer containing 5.0 g of polyolefin wax) c) Developer using 20 g of sun wax (polyolefin wax) in place of polyral H (polyhydroxypolyolefin) of Example 1 2) Test method Test method described in Examples 3) Test results As described above, the developers (a) and (b) of the present invention are comparative developers (c)
In comparison, the toner particle size is small and the image density and resolution are excellent.

Claims (1)

[Claims] 1. A liquid developer for electrophotography comprising a toner having a colorant and a resin as main components dispersed in a carrier liquid having a high insulating property and a low dielectric constant, wherein the toner contains polyhydroxypolyolefin. A liquid developer for electrophotography, characterized in that