JP2767700B2 - Toner for developing electrostatic images - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner for developing an electrostatic image in electrophotography, and more particularly, to a toner in which the temperature of a hot roll in a hot roll fixing is lowered, or a hot roll. The present invention relates to a toner for a low-energy fixing, which is required as a thermal characteristic of a toner for a high-speed copying machine in which a roll pressing pressure is made weaker than the conventional one, and a toner for a high-speed copying machine in which a roll rotation speed is increased.

<Prior Art> With the spread of copiers and printers using the electrophotographic method, as the spread of the copiers and printers has become widespread, the so-called gray area located at the border between the printing machine and the copier has been reduced in energy mainly for home use. Higher speeds for the purpose of dissemination to the market, or lower roll pressure accompanying the simplification of the fixing roll to reduce machine cost, and lower energy accompanying the multifunctionality of copiers and printers are desired. I have.

In response to the above demands, it is desired that the toner has low energy at the time of fixing. In the prior art, studies have been made mainly on lowering the energy of the resin of the toner, for example, those in which the molecular weight and distribution of the resin are improved. A composition in which the composition of the resin is changed, a composition in which an additive is added to the resin, and the like have been proposed.

As a method of changing the molecular weight or the distribution of the resin of the toner, a method of broadening the molecular weight distribution by lowering the molecular weight of the low molecular weight part and increasing the molecular weight of the high molecular weight part, or crosslinking the high molecular weight part is used. Is being done. However, in this method, it is inevitable that the glass transition point of the resin must be lowered in order to have sufficient fixability, and the storage stability of the toner is impaired. Further, there is a disadvantage that it is difficult to provide sufficient fixability even if the fixability is improved while maintaining the storage stability.

As another energy-saving method, a method has been proposed in which a sub-resin as a second component is added to the resin of the toner to improve the fixability of the toner. In this method, a high-crystalline sub-resin is added under the premise that the glass transition point of the resin system is not lowered, so that good results can be obtained in the fixing property and the storage stability of the toner. Therefore, the melt viscosity at the time of fixing the toner on a hot roll is sharply reduced, and the cohesive force of the toner at the time of melting is weak, so that the offset phenomenon is likely to occur. It has also been proposed to add a polycrystalline wax having high crystallinity in order to improve the above-mentioned disadvantages. Has the disadvantage that it is difficult to

<Problem to be solved by the invention> The present invention has been made in view of the above circumstances.
That is, the object of the present invention is to lower the fixing temperature and not deteriorate the storability of the toner, and to cause no practical problem in the offset property. An object of the present invention is to provide a low-energy fixing toner which does not cause a problem even in a certain life property and image quality.

<Means for Solving the Problems> As a result of intensive studies to solve the above problems, the present inventors have found that a hardened castor oil having a polar group such as a hydroxyl group or a carboxyl group or a modified product thereof is blended in a toner. Have shown very good results. That is, the present invention is a toner for developing an electrostatic image containing a styrene-acrylic copolymer resin or a polyester resin and a hardened castor oil or a modified product thereof. 1 to 25% by weight,
The present invention relates to a toner for developing an electrostatic image for hot roll fixing, wherein the cured castor oil or a modified product thereof has an acid value of 200 or less and a melting point of 60 ° C. to 100 ° C.

 Hereinafter, the present invention will be further described.

The hardened castor oil referred to in the present invention is also called caster wax and is a hydrogenated product of castor oil. The modified product of the hardened castor oil is obtained by reacting with a dibasic acid or the like using a hydroxyl group in a side chain and introducing an acid such as a carboxyl group to change the acid value. The acid to be introduced is not particularly limited as long as it is a dibasic acid, but oxalic acid, succinic acid,
Dibasic acids having about 2 to 20 carbon atoms, such as adipic acid, are preferred. If too much acid is introduced and the acid value is increased, the hygroscopicity of the toner is increased, which causes a problem in practical use especially at high temperature and high humidity. Further, as the acid value increases, the melting point tends to decrease. Therefore, those having an acid value of 200 or less are used in the present invention so as not to deteriorate storage stability.

The amount of the hardened castor oil or a modified product thereof to be added to the toner is suitably from 1 to 25% by weight, and if the amount is less than 1%, the fixability is not significantly improved.
%, The fixing property is extremely good, but the image quality is deteriorated such as the glossiness of the fixing surface of the toner being too high, and therefore, it is not preferable.

The melting point of the hardened castor oil or its modified product mainly depends on the degree of hardening by hydrogenation and the type and amount of the acid to be introduced, but those having a melting point of 60 ° C to 100 ° C are used in the present invention.
If the melting point is lower than 60 ° C., it tends to cause a problem in the storability of the toner, and if the melting point is higher than 100 ° C., the fixing property is undesirably deteriorated.

The toner for developing an electrostatic image of the present invention is composed of a hardened castor oil or a modified product thereof, a thermoplastic resin composed of a styrene-acrylic copolymer resin or a polyester resin, a colorant, and other additives. Examples of the colorant include facial dyes used as colorants for ordinary toners, for example, carbon black, nigrosine dye, aniline dye, chrome yellow, ultramarine blue, methylene blue chloride, rosebergan, magnetite, and ferrite. Furthermore, various auxiliary agents may be used as necessary as other additives, for example, a charge control agent, a lubricant such as waxes or metal soaps, an antioxidant, an extender,
Fluidity modifiers such as colloidal silica and colloidal alumina are included.

<Operation> The toner for developing an electrostatic charge image of the present invention has a melting point because the hardened castor oil or a modified product thereof is a crystalline substance, and has a temperature of 60 ° C to 100 ° C. At the fixing temperature at which the toner is melted almost completely, it effectively works to improve the fixing strength. Further, since the cohesive force is strong or the affinity with the heat roll is weak, the offset phenomenon does not occur. In addition, at around 50 ° C., which is considered to be the storage limit of general toner, no change occurs, so that the storage stability does not deteriorate. Furthermore, it is possible to produce waxes of various polarities by reacting with an acid or the like using the hydroxyl groups present in the hardened castor oil. -Affinity with the thermoplastic resin as the first component of the acrylic copolymer resin and the polyester resin can be improved, so that the material composition in the toner can be easily made uniform.

<Example> Hereinafter, the present invention will be described in detail with reference to examples.

[Example 1] The mixture having the above composition was subjected to hot melt kneading and pulverization and classification to obtain a toner for developing an electrostatic image according to the present invention having an average particle diameter of 11 μm.

Comparative Example 1 A comparative toner was obtained in the same manner as in Example 1, except that the castor oil was changed to 88.5% by weight except for the hardened castor oil.

Example 2 Instead of the styrene-acrylic copolymer resin A of Example 1, a styrene-acrylic copolymer resin B (St / BA / MMA, M
n = 6500, Mw = 124000, Mw / Mn = 19.1)
In the same manner as in Example 1, an electrostatic image developing toner according to the present invention was obtained.

Comparative Example 2 A comparative toner was obtained in the same manner as in Example 2 except that the hydrogenated castor oil was used and the styrene-acrylic copolymer resin B was changed to 88.5% by weight.

[Examples 3 and 4, Comparative Examples 3 and 5] A mixture having the composition shown in Table 1 was subjected to hot-melt kneading and then pulverized and classified to obtain an electrostatic image developing toner and an average toner having an average particle diameter of 11 μm according to the present invention. I got

[Examples 5 to 7, Comparative Examples 6 to 8] Modified hardened castor oil (caster wax) with dibasic acid to prepare a modified product of hardened castor oil having a different acid value, and blended as shown in Table 2. Was subjected to hot-melt kneading, pulverization and classification to obtain a toner for developing an electrostatic charge image and a toner for comparison according to the present invention having an average particle diameter of 11 μm. Maleic acid was used as a dibasic acid to modify the hardened castor oil.
As a method for introducing maleic acid, a normal esterification method was used.

Comparative Example 9 A comparative toner was obtained in the same manner as in Example 1, except that the hardened castor oil having a melting point of 45 ° C. was used instead of the hardened castor oil of Example 1.

[Comparative Example 10] In place of the hydrogenated castor oil of Example 1, the acid value was 1, and the melting point was 1.
Example 1 except that a modified product of 105 ° C hydrogenated castor oil was used.
In the same manner as described above, a comparative toner was obtained.

The following items were tested for Examples 1 to 7 and Comparative Examples 1 to 10 described above.

(1) Minimum fixing temperature (A) A fixing device consisting of a heat roller having a surface layer formed of Teflon and a pressure roller having a surface layer formed of silicon rubber is set to a roll pressure of 30 kg / cm and a roll speed of 170 mm / sec. Then, the set temperature of the heat roller is changed stepwise to fix the toner image with the sample toner transferred to the transfer paper at each set temperature. The formed fixed image was rubbed with a cotton pad (PPC pad (trade name, manufactured by Dynic)), and the lowest set temperature for the fixed image showing sufficient rub resistance was defined as the lowest fixing temperature.

(2) Offset Occurrence Temperature (B) The operation of transferring a toner image onto transfer paper, performing a fixing process by the above-described fixing device, and observing whether or not toner stain occurs in a margin portion of the transfer paper is performed by the fixing device. This was repeated with the set temperature of the heat roller changed, and the lowest set temperature at which toner contamination occurred was taken as the offset occurrence temperature.

(3) Fixing temperature width ((B)-(A)) The side obtained by subtracting the minimum fixing temperature from the offset occurrence temperature was defined as the fixing temperature width.

(4) Preservation The sample toner was placed in an atmosphere of 45 ° C for 2 weeks or
After being left in an atmosphere at 50 ° C. for 8 hours, the fluidity of the toner was visually checked to evaluate the storage stability.

(5) Image quality A continuous copy test was performed using the sample toner, and the image quality after copying was visually evaluated.

Of the above items, the minimum fixing temperature, offset occurrence temperature,
Table 3 shows the results of the fixing temperature range and the storage stability. Regarding image quality, all of Examples 1 to 7 showed good images in continuous copying of 20,000 sheets or more. On the other hand, among the comparative examples, in Comparative Example 4, unevenness of the image portion occurred after 5,000 copies, and in Comparative Example 5, the image quality deteriorated after 1,000 copies, and gloss occurred in the image portion.

As is clear from Table 3 and the results of the image quality, the toner for developing an electrostatic image of the present invention obtained good results in all evaluation items, but in Comparative Examples, any of the evaluation items was insufficient. Results were obtained.

That is, in Comparative Examples 1 to 3 and Comparative Example 10, the minimum fixing temperature was high, and it was insufficient as a low energy fixing toner. Further, in Comparative Examples 4 to 9, the storage stability was poor and the image quality after copying was insufficient.

<Effects of the Invention> The toner for developing an electrostatic image of the present invention has good fixability and offset property, and further has good storability by blending a specific amount of a hardened castor oil or a modified product thereof with the toner as described above. Thus, a low energy fixing toner having good image quality can be provided.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G03G 9/08

Claims (1)

(57) [Claims] An electrostatic image developing toner comprising a styrene-acrylic copolymer resin or a polyester resin and a hardened castor oil or a modified product thereof, wherein the hardened castor oil or the modified product is based on the weight of the toner. A toner for developing an electrostatic charge image for hot roll fixing, comprising 1 to 25% by weight, wherein the acid value of the hardened castor oil or a modified product thereof is 200 or less and the melting point is 60 ° C to 100 ° C.