JPS6330857A - Dry toner - Google Patents

Abstract

PURPOSE:To obtain a dry process toner not causing offset trouble even when a releasing agent, such as silicone oil, is not supplied to a heat roll, by using as a main binder an organic compound having a melting point above normal temperature, and a melt viscosity of <=10<3> poise at a shearing speed of 10<2>sec<-1> at temperatures from the melting point up to 30 deg.C above it. CONSTITUTION:The organic compound having a melting point above normal temperature, and a melt viscosity of <=10<3> poise at a shearing speed of 10<2>sec<-1> at temperatures from the melting point up to 30 deg.C above it is used as the main binder of a heat fixable dry process toner. This toner has high hardness at normal temperature and abruptly lowers in viscosity in the range of from the melting point to 30 deg.C above it, thus permitting offset trouble to be avoided even without using the releasing oil, such as silicone oils, and fixing to be efficiently executed at high speed, and further, the fixed image to be small in thickness and comparable in quality with prints.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrostatic charge developing toner used for development in electrophotography, electrostatic recording, etc. Regarding this.

[Conventional technology]

In electrophotography, a static image is formed on the photoreceptor. The Lm image is usually developed with resin powder containing pigment, and the resulting visible painter is transferred onto transfer paper and fixed using heat, pressure, or a combination thereof, but it is possible to perform this fixing process at high speed and with high efficiency. In recent years, the hot roll fixing method has been widely adopted due to these demands.

In the hot roll fixing method, in order to perform high-speed fixing with low power consumption, it is effective to lower the softening point of the toner binder material and reduce the melt viscosity. When lowering the softening point of the binder polymer (binder resin) used as a bonding material, a decrease in fluidity due to caking occurs when toner is stored, and when the melt viscosity is lowered, offset phenomenon and other problems can occur. This will cause stains and stains. For this reason, a device is installed to supply a release agent such as silicone oil to the heated roll to prevent offset, and the glass transition point of the main binder polymer is increased, or ultrafine inorganic powder such as silica is added to the toner surface. A method of preventing caking during storage by using it as an external additive has been proposed.

[Problem that the invention seeks to solve]

However, supplying silicone oil to the heat roll requires a supply groove, which inevitably increases the cost of the device and requires maintenance for oil replenishment.

Furthermore, if the glass transition point of the main binder polymer is set high, the softening temperature will increase, making low-temperature fixing difficult.

In addition to these, since the conventional toner is fixed by adhering and solidifying the resin to the paper by heat and pressure before fixing, unless the toner is atomized, especially in high density areas, The image is too thick and looks unnatural compared to printing.

An object of the present invention is to improve the above-mentioned problems in heat fixing toners.

That is, an object of the present invention is to provide a dry toner that does not cause an offset phenomenon even if a release agent such as silicone oil is not supplied to a heated roll.

Another object of the present invention is to provide a dry toner that can be fixed efficiently at high speed.

Furthermore, another object of the present invention is to reduce the thickness of the fixed image.
It is an object of the present invention to provide a dry toner capable of forming a good image having a naturalness similar to that of printing.

[Means for solving problems]

The present invention provides a dry toner for heat fixing using, as a main binder, an organic compound having a melting point above room temperature and a melt viscosity of 10 spoise or less at a shear rate of 102 sec-'' at a temperature within 30°C of the melting point. This is what I did.

Conventionally, high-molecular-weight resins are used as binding materials for toners, and pigments such as carbon black and charge control agents are mixed into the resins using a kneading method, and the toners are made by finely pulverizing the resin. In this case, the binder resin holds and fixes elemental materials such as pigments, and during fixing, the toner is softened by heat and pressure, or a combination thereof, and has the function of adhering along the unevenness of the paper surface. .

In the case of hot roll fixing, during the fixing process the toner usually flows with a high viscosity of 10'poise or more, so the penetration of the toner into the inside is only small, and the overmaterial is 1μ+ni.
This is not enough. It is thought that the adhesive force that determines the degree of fixation of toner to paper is largely due to the adhesive force caused by expansion on the paper surface. In this case, the effect of penetration ζ into the paper fibers, which improves toner adhesion, is not necessarily fully utilized.

When a material that exhibits extremely low viscosity when the temperature rises after melting is used as the binder resin, as in the dry toner of the present invention, it is expected that the toner will penetrate into the paper fibers, and the gap between the toner and the paper will increase. The bonding area can be greatly expanded, and as a result, an image with high image strength can be obtained at a relatively low temperature.

For high-speed fixing 1, in order to improve the permeability of toner into paper, it is necessary for the toner to be instantly melted by the heat from the heated roll, and experimentally it has been shown that heating to within 30°C of the melting point can reduce the viscosity. It turns out that being able to transform is a necessary condition.

The viscosity at that time is the melt viscosity of normal toner, 104
~10' poise (shear rate 10" 5ee-
When the main binder contains a material with a shear rate of 103 poise (shear rate 102 formula-1), which is much lower than The degree of fixation and the offset toner t depend on the total amount of toner on the paper before fixing, but when a material exhibiting the above-mentioned physical properties is used, a sufficient number of strokes a degrees and a sufficient degree of fixation in high-speed fixing are both achieved.

Furthermore, by reducing the viscosity at a temperature within 30° C. of the melting point, disturbances and offsets in fixed images can be minimized.

Examples of organic compounds that can be instantaneously dissolved by heating with a hot roll and exhibit low viscosity change include urethane oligomers, polyether oligomers, and others such as styrene,
Styrenes such as parachlorostyrene, vinylnaphthalene, vinyl esters such as vinyl chloride, vinyl bromide, vinyl fluoride, vinyl acetate, vinyl propionate, vinyl benzoate, vinyl butyrate, such as methyl acrylate, ethyl acrylate , I'1tn-butyl acrylate, isobutyl acrylate, dodecyl acrylate, n-octyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, methyl α-chloroacrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate Methylene aliphatic carboxylic acid esters such as acrylonitrile, methacrylonitrile, acrylamide, vinyl ethers such as vinyl methyl ether, vinyl isobutyl ether, vinyl ethyl ether, vinyl ketones such as vinyl methyl ketone, vinyl xyl ketone, etc. In addition to homooligomers of vinyl monomers such as N-vinyl compounds such as N-vinylpyrrole, N-vinylcarbazole, N-vinylindole, and N-vinylpyrrolidone or co-oligomers with other monomers, carnauba wax and montan wax , relatively hard waxes such as paraffin wax, montanic acid ester wax, and amide wax, or compounds made by adding alcohols to incyanate compounds.
These substances can be used alone or in combination.

Among these organic compounds, they have high hardness at room temperature and have a melting point of ~
In the range of melting point +30℃, melt viscosity is shear rate 1
Any material can be used as long as it has a molecular weight of 10' poise or less at 0" 5ee-1. Regarding the molecular weight, one with a relatively low molecular weight, preferably 500 or less, more preferably 2000 or less. Those with good crystallinity and high crystallinity are preferred.

The dry toner of the present invention has a physical characteristic of low viscosity change when melted, so it can be used not only for hot roll fixing but also for
Conventional heat fixing methods for each fence such as flash, radiant or oven methods may also be used.

If care is taken to ensure that the toner of the present invention contains a large amount of these instant-dissolving, low-viscosity components as the main binder component, other binders may be used in combination as sub-binder materials.

As the secondary binder, a high molecular weight polymer of the raw material monomer of the oligomer mentioned above, that is, a binder similar to that conventionally used as a binder resin, can be used. Similarly, polyethylene can be used as a mold release material. Wax, polypropylene wax, etc. may be used in combination, and as colorants, in addition to ordinary carbon black, various pigments and even magnetic substances may be added.

However, the content of these sub-binder resins or additives, etc.
From here, melt! Care must be taken to avoid a significant increase in lI viscosity.

〔Example〕

Hereinafter, the dry toner for heat fixing of the present invention will be explained with reference to Examples. In the following explanation, parts represent parts by weight.

Example 1 The composition shown in Table 1 below was kneaded with three rolls to obtain a low-viscosity material of components A and B, and this material was used to make a toner with the following composition by ordinary kneading and pulverization methods. A and B were obtained.

Toner A: 70 parts of component A, styrene-n-butyl methacrylate resin (Mn=12000. MW=50000
) 15 parts, carbon black (Cabot BPL) 15
Department.

Toner B: 70 parts of component B, other components are the same as toner A.

The average particle size was 11.0 μm for both toners 7A and B. Copying was performed using a modified Fuji Zerotsu 3500 machine using a fluororesin coated carrier, and a fixing test was conducted while changing the temperature of the Teflon-coated heat roller. . A, H
A slight offset was observed with both toners above 160°C, but the degree of fixation at 130°C (according to the li!lii elephant rag rubbing test) was much finer than that of toner A. They were separated.

Further, when a caking test was conducted by leaving toners A and B at 50° C. for 1 hour, toner A showed more agglomeration than toner B.

Example 2 The composition shown below was mixed using a three-roll mixer to obtain a low-viscosity material of components D and E. Using this material and E, kneading was carried out in a conventional manner.
Toner D and Toner E having the following compositions were obtained by the pulverization method.

Toner D: 60 parts of component D, 30 parts of styrene-n-butyl methacrylate, carbon black (Cabot BPL
) 10 copies.

Toner E: 60 parts of component E, other components are the same as toner D.

The average particle size was 11.5μ for both toners D and E, and Example 1
A retention test was conducted in the same manner.

Off-cent was slightly observed for toner D at 170°C and for toner E at 180°C or higher. When comparing the degree of fixation at 130°C, Toner E was inferior to Toner D. In the caking test 1 under the same conditions as in Example 1, Toner E was more crumbly than Toner D.

〔Effect of the invention〕

The dry toner for heat fixing of the present invention has high hardness at room temperature;
The main binder is an organic compound whose viscosity decreases rapidly in the temperature range from melting point to melting point +30°C, and no offset phenomenon occurs even without the use of a release agent such as silicone oil during hot roll fixing. , fixing can be carried out efficiently at high speed, and the fixed image has a small thickness and has a quality comparable to that of printing.

Claims (1)

[Claims] As a main binder, it has a melting point above room temperature and 30° below the melting point.
The melt viscosity at a temperature within ℃ is the shear rate of 10^2
A dry toner for heat fixing, characterized in that an organic compound having a poise of 10^3 or less in sec^-^1 is used.