JP-7855973-B2 - Wax composition for toner

Inventors

• 森重 貴裕
• 吉村 健司
• 清水 湧太郎

Assignees

• 日油株式会社

Dates

Publication Date

20260511

Application Date

20220902

Claims (1)

1. A wax composition for toner containing an ester compound A represented by the following structural formula (1) and an aliphatic ketone compound B represented by the following structural formula (2), wherein the mass ratio of ester compound A to aliphatic ketone compound B [(A):(B)] is 0.1:99.9 to 30:70. Ester compound A: (In structural formula (1), R1 represents a linear saturated alkyl group with 15 to 24 carbon atoms, and n represents an integer from 2 to 6.) Aliphatic ketone compound B: (In structural formula (2), R2 and R3 each independently represent a linear alkyl group, and the total number of carbon atoms in R2 and R3 is 30 to 48.)

Description

This invention relates to a wax composition for toners suitably used in developing electrostatic images recorded by electrophotography, electrostatic recording, and other methods in devices such as photocopiers and laser printers. Toner used in image forming devices such as photocopiers and printers contains a thermoplastic resin that serves as a binder resin, a coloring agent (such as carbon black, magnetic powder, or pigment), a charge control agent, and a wax, and optionally further contains a fluidity enhancer, a cleaning aid, and a transfer aid. In this context, the wax functions as a release agent to prevent toner from remaining on the fixing roll during fixing (filming), and also has the function of promoting the softening of the thermoplastic resin to improve its fixability. On the other hand, wax can cause toner particles to block each other due to bleeding during toner storage, so efforts are being made to improve the storage stability of the toner. For example, Patent Document 1 describes a method for producing an ester wax for toner, characterized by a condensation reaction between a linear saturated monocarboxylic acid or a mixture thereof selected from among those having 14 to 30 carbon atoms, a linear saturated monohydric alcohol or a mixture thereof selected from among those having 14 to 30 carbon atoms, or a dihydric to hexahydric polyhydric alcohol or a mixture thereof selected from among those having 2 to 30 carbon atoms, followed by neutralization with an alkaline aqueous solution and removal of the neutralized salt by centrifugation. It is stated that by using this wax, a toner with excellent storage stability can be provided. Furthermore, in recent years, copying devices such as multifunction printers and commercial printing presses have required toners that can handle ultra-high-speed printing beyond conventional limits, from the perspective of improving production efficiency and saving energy. For example, Patent Document 2 describes that by mixing hydrocarbon wax and ester wax, a toner can be obtained that has excellent low-temperature fixing and fixing/separation properties, is less likely to cause mold release agent to adhere to components of image forming equipment, and can form images with excellent scratch resistance. It is expected that using such a toner will enable high-speed printing. Furthermore, in the commercial printing field where these devices are used, there is a need to consistently provide high-quality printed materials with a uniform, high gloss equivalent to or better than photographs and posters obtained by silver halide photography or gravure printing, even under the aforementioned ultra-high-speed printing conditions. However, wax presents a challenge because differences in the crystalline state on the surface of the printed material can cause uneven gloss, and there is a need for wax that can solve these problems. For example, Patent Document 3 introduces a toner using synthetic monoester wax as an electrophotographic toner that exhibits high gloss close to photographic gloss over a wide fixing temperature range, and achieves excellent low-temperature fixing properties, high resistance to hot offsets, and good storage stability. However, even such toners are not sufficiently suitable for ultra-high-speed printing and cannot reduce gloss unevenness in printed materials. Furthermore, Patent Document 4 introduces a toner that uses an ester wax in which the difference between the endothermic peak temperature during heating and the exothermic peak temperature during cooling, i.e., the difference between the melting point and the solidification point, is within a specific range, thereby adjusting the affinity between the wax and the polyester resin binder, and consequently suppressing the amount of wax bleeding during image fixing and enabling the suppression of gloss unevenness caused by the wax. However, even when using such a wax, it is not sufficient to suppress gloss unevenness due to differences in crystalline state, and the amount of wax bleeding may be insufficient during high-speed printing. Also, because the difference between the melting point and the solidification point is large, there is a risk that the melting and solidification of the wax will be insufficient, and it cannot be said that high-quality printed materials can be stably supplied. Toner has many required characteristics, and there is a need for a toner wax that can simultaneously satisfy all of these requirements. Japanese Patent Publication No. 2012-32479Japanese Patent Publication No. 2020-187270Japanese Patent Publication No. 2019-53322Japanese Patent Publication No. 2021-170100 Embodiments of the present invention will be described below. The wax composition for toner of the present invention contains, as essential components, the ester compound A and aliphatic ketone compound B shown below. In this specification, numerical ranges defined using the symbol "～" include the numbers at bot