Toner for developing electrostatic images

Abstract

To provide a toner for electrostatic image developing that contains a certain amount or more of aliphatic diol-derived structural units while achieving printed images with excellent bending resistance in low-temperature environments. [Solution] A toner for developing electrostatic images, wherein an external additive is attached to the surface of toner particles containing a binder resin, the binder resin contains amorphous polyester resin A which is a polycondensate of an alcohol component and a carboxylic acid component containing 60 mol% or more of aliphatic diol A having 2 to 5 carbon atoms, the external additive contains silica particles, the fluorescence X-ray intensity of the Si element of the toner measured by fluorescence X-ray analysis exceeds 50 kcps, and the silica adhesion strength is 80% or more.

Claims

1. A toner for electrostatic image development in which an external additive is attached to the surface of toner particles containing a binder resin, The aforementioned binder resin contains amorphous polyester resin A, which is a polycondensate of an alcohol component and a carboxylic acid component containing 60 mol% or more of aliphatic diol A having 2 to 5 carbon atoms. The aforementioned external additive contains silica particles, The fluorescence X-ray intensity of the Si element in the toner, as measured by fluorescence X-ray analysis, exceeds 50 kcps. A toner for developing electrostatic images, having a silica adhesion strength of 80% or higher, as calculated by the silica adhesion strength measurement method described below. <Method for measuring silica adhesion strength> 5 g of toner and 20 mL of a 5% by mass aqueous solution of polyoxyethylene(9) lauryl ether are added to a 300 mL beaker containing 150 mL of distilled water and stirred for 1 minute. Then, the aqueous solution is irradiated with 150 W of ultrasound using an ultrasonic device for 5 minutes. 500 mL of distilled water is added to the aqueous solution after ultrasonic irradiation and stirred for 5 minutes. The solution is then filtered by suction using qualitative filter paper, and the residue on the filter paper is dried under reduced pressure at 40°C for 3 hours to obtain the toner after ultrasonic treatment. The fluorescence X-ray intensity of the Si element in the toner before and after ultrasonic treatment is measured using an X-ray fluorescence analyzer, and the silica adhesion strength of the toner is calculated using the obtained measurements according to the following formula 1. Silica adhesion strength (%) = (Fluorescence X-ray intensity of Si element in toner after ultrasonic treatment / Fluorescence X-ray intensity of Si element in toner before ultrasonic treatment) × 100 (Equation 1)

2. The electrostatic image developing toner according to claim 1, wherein the content of the external additive per 100 parts by mass of the toner particles is 0.05 parts by mass or more and 5 parts by mass or less.

3. The electrostatic image developing toner according to claim 1, wherein the content of the amorphous polyester resin A in the binder resin is 50% by mass or more.

4. The electrostatic image developing toner according to claim 1, wherein the content of the binder resin in the electrostatic image developing toner is 60% by mass or more.

Images