JPH02123371A - Method for evaluating characteristic of toner for developing electrostatic charge image - Google Patents

Abstract

PURPOSE:To exactly grasp characteristics of a toner corresponding to print quality during printing by filling the toner in a cell, applying a vertical load from above the toner, measuring a shearing stress at this stage and evaluating the toner basing on a coeffts. of friction calculated from the values of the vertical load and the shearing stress. CONSTITUTION:After measuring a weight of a cover 3 of a cell 2, a frictional force between an upper part and a lower part of the separable cell 2, and a sectional area of the cell 2, a toner 1 is filled in the cell 2, mounting the cover 3 and a weight 4 thereon, and a thickness and a bulk density of the toner 1 filled on the shearing surface are measured. Thereafter, a shearing force is applied slowly by a cylinder 6 to an upper-half part of the cell 2. When the value reaches a limit value, a layer of the toner 1 causes separation into the upper cell and the lower cell, and the upper part 5 of the cell moves. At this stage, the limit value is measured as a shearing load. A vertical load and a shearing stress are obtd. based on each above described value. The toner is evaluated based on a coefft. of friction calculated from the vertical load and the shearing stress. Thus, evaluation of characteristics of a toner is attained exactly.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for evaluating the characteristics of toner for developing electrostatic images used in fields such as electrophotography, and particularly for selecting a toner suitable for high-speed development. This invention relates to an effective toner characteristic evaluation method.

(Prior art) The electrophotographic method is described in US Pat. No. 2,297,691, British Patent No. 1,165,406 and British Patent No. 1,165.
．． As described in No. 405.

A charging process that uses a photoconductive substance to apply a static charge to the photoreceptor, an exposure process that irradiates light to form an electrostatic latent image, and a development process that attaches toner to the latent image area. A transfer step in which the toner image is transferred to an image support such as paper according to the image quality, a fixing step in which the toner image is fixed to the image support by heat, pressure, flash light, etc., a cleaning step in which toner remaining on the photoreceptor is removed, and It consists of a static electricity removal process that removes the static charge on the photoreceptor and returns it to its initial state, and this process is repeated to obtain a number of printed materials.

The electrostatic image developing toner (hereinafter referred to as toner) referred to in the present invention is used in computer output devices using an electrophotographic method. Computer output device (hereinafter referred to as
Printers (abbreviated as "printers") are becoming faster and more diversified, and in order to keep up with these trends, it is natural to improve the machines, but the toner used in printers and the combination of toner and carrier are improving. It is also essential to improve the developer composition.

In particular, in recent years, recognition of the usefulness of printers has increased, and the field of use has expanded from processing important information such as insurance cards and certificates to bookbinding. For these reasons, the form of information is also printed.

There is a wide range of printing needs, from thin lines such as ruled lines to printing on large areas, and there is a desire to develop toners that can process these at high speed.

In developing toners, it is important to evaluate the physical properties of toners, such as fluidity, electrical resistance, and charge amount, which will be described below. In particular, the fluidity of toner has a large effect on print quality (image density, etc.) during high-speed printing with printers, and if the fluidity of toner is poor.

It is said that when toner is replenished to the developer in a developing machine, the toner is not uniformly mixed into the developer in an instant, and a sufficient developing function cannot be achieved.

Conventionally, the fluidity of toner was as shown in Figure 2.

The toner 1 was simply put into the funnel 7, and the toner receiver was evaluated based on the angle θ (so-called angle of repose) of the peak of the toner 1 formed on the portion 8.

(Problems to be Solved by the Invention) However, the conventional method of evaluating toner fluidity as described above has a problem in that it is not possible to accurately evaluate toner characteristics suitable for use in an actual machine.

The present invention solves the above problems and provides an evaluation method for accurately grasping toner characteristics corresponding to print quality during actual printing.

(Means and effects for solving the problems) The present invention is to fill a cell with toner for developing an electrostatic image, apply a vertical load from above the core toner, measure the shear stress at this time, and calculate the vertical load and shear stress. The present invention relates to a method for evaluating characteristics of toner for developing electrostatic images, characterized in that the toner is evaluated based on a friction coefficient determined from a stress value.

In the present invention, the coefficient of friction (α) is calculated by e.g. the vertical load (δ) in the primary measuring device and the measured shear stress (τ
) can be derived.

The measuring device is shown in Figure 1. The nuclear measuring device consists of a cell 2 which can be divided in the center into which the toner 1 is placed. It consists of a cell lid 3, a weight 4 that applies a vertical load to the toner, and a cylinder 6 that applies a shear load to the upper part 5 of the divisible cell 2.

Furthermore, the cylinder 6 is configured to be able to detect the applied shear load. Furthermore, 0 weight 4 is 200 to 30
009 is preferable, and it is preferable to have one-weight rice plants or a large number of them so that the vertical load can be varied variously.

An example of a method of measuring using the measuring device and determining the ♀friction coefficient (α) will be described below.

First, in this device, the weight of the cell lid 3.

The friction force between the upper and lower parts of the divisible cell 2 and the cross-sectional area of the cell are measured in advance.

Next, fill the cell with the toner to be evaluated, and close the cell lid 1.
Place the weight on it. At this time, the thickness of the filled toner on the sheared surface (h in FIG. 1) and the bulk density of the toner are determined.

Next, a shearing force is gradually applied to the upper half of the cell by the cylinder 6. When the value of shear force reaches a critical value, the toner layer separates between the upper and lower cells, and the upper part of the cell moves. This limit value is measured and the shear load (shear load due to cylinder 6,
K).

From the above, the vertical load (δ) and shear stress (τ) are determined by the following formula.

Here, We: Weight of the cell lid (91We: Weight of the weight (9) F: Cell cross-sectional area (cm") h: Thickness of the filled toner on the shear surface (cm) ρ: When filling the toner Bulk density (u/cm3) K Shear load due to cylinder 6 (9) Wd: Frictional force between the top and bottom of cell 2 + 9) By changing the weight of the weight for one type of toner.

It is preferable to perform the same operation multiple times to obtain δ and τ. The obtained values are plotted on a graph with vertical load (δ) on the horizontal axis and shear stress (τ) on the vertical axis.

Based on the plot, a straight line passing through the origin can be drawn. The slope of the straight line obtained at this time is the friction coefficient (α).

Therefore, the coefficient of friction (α) is obtained from the straight line obtained.

It can be determined by the formula.

The value of the coefficient of friction (α) of the toner determined as described above has a good correlation with the properties of the toner when mixed with a carrier and used in an actual machine Kl'i'. For example, regarding the density of one image, a correlation is obtained in which the larger the coefficient of friction (α) is, the lower the density of the zero image is. Therefore, as a preliminary evaluation of toner characteristics, a more accurate friction coefficient (α
) is a very effective method.

(Example) Next, the present invention will be described in detail with reference to Examples.
It is not limited to LVc.

(1) Copolymer synthesis 200 parts by weight of water and 0.3 parts by weight of a suspending agent (polyvinyl alcohol, Tenkahohar W-24 (Denki Kagaku Kogyo ■ trade name)) were charged into a reaction vessel and dissolved uniformly. The monomers and polymerization initiator having the composition shown in 1 were added, and the mixture was heated under a stream of 9 atoms while continuing to stir.

It was held at 80-90°C for 10 hours. Thereafter, the mixture was cooled and filtered, and then sufficiently dried to obtain copolymers a- and e.

(2) Production of toner The materials shown in Table 2 were premixed all at once in a Henschel mixer, and then melted and kneaded at 90°C using a -shaft kneader. Next, the cooled kneaded material was pulverized using a bottle mill and a jet mill, and classified using a vibrating sieve to obtain an average particle size of 10 to 15.
A μm toner was obtained.

Note 1) Monomer■: Monomer■: (3) Measurement of friction coefficient (α) A measuring device as shown in FIG. 1 is commercially available.

- Using a surface shear type automatic recording powder shear tester (Model DS-086, manufactured by Tsutsui Rikagaku Kiki ■), the friction coefficients (α) of the toners A to E obtained above were determined. In this device, the weights that apply the vertical load are 2009.4009.
aoog, so.

The values were changed to 9.1 and 9, and measurements were taken for each. In addition.

In this device, the coefficient of friction (α) is automatically calculated using the above-mentioned calculation formula.

Table 2 shows the friction coefficient (α) of each toner obtained.

Further, as comparative data, the angle of repose (θ) of each toner was determined by a conventional method and is also shown in Table 2.

(4) Measurement of image density in actual machine test The above-mentioned combinations of each toner and carrier (TSV-200: manufactured by Nippon Tetsuko Powder ■) are used. A two-component developer with a toner concentration of 3 mass was prepared.

Using this developer, a selenium drum rotating at a circumferential speed of approximately 60 m/sec was uniformly positively charged with a corona voltage of +4 kV, and then information was written using a He-Ne laser.

Reversal development was performed using a magnetic brush method. Next, the image carried on the recording paper was fixed with a Teflon heat roll.

A large printed area of 25 x 25 mm of the print was measured using a Macbeth densitometer.

The data obtained here are summarized and the relationship between the friction coefficient (α) and image density is shown in FIG. Furthermore, the angle of repose (θ)
The relationship between image density and image density is shown in FIG.

As is clear from these data, with the conventional evaluation method, there was not much correlation between the measured data and the characteristics of the actual machine, but with this evaluation method.

It has been shown that there is a good correlation with the characteristics of the actual machine.

(Effects of the Invention) According to the evaluation method of the present invention, preliminary evaluation results that correspond well with the results of the actual machine can be obtained, making it possible to accurately evaluate toner characteristics at the toner development stage.

And it can be done easily.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a measuring device used in the toner characteristic evaluation method of the present invention, Fig. 2 is a schematic diagram of a conventional toner fluidity measuring device, and Fig. 3 is a sectional view of a measuring device used in the toner characteristic evaluation method of the present invention. FIG. 4 is a graph showing the relationship between the toner friction coefficient and image density determined by the conventional evaluation method. FIG. 4 is a graph showing the relationship between the toner repose angle and image density determined by the conventional evaluation method. Explanation of symbols 1...Toner 2...Cell 3...Cell lid 4...Weight 5...Cell top
6... Cylinder 7... Funnel 8.
...The toner tray is shown in the open diagram (00) (09 愼まａｷ 4 文 (be)) Figure Jθ 4ρ 5θ zu 1!.

Claims (1)

[Claims] 1. A cell is filled with toner for developing an electrostatic image, a vertical load is applied from above the toner, and the shear stress at this time is measured;
Based on the friction coefficient obtained from the values of vertical load and shear stress,
A method for evaluating the characteristics of a toner for developing electrostatic images, the method comprising evaluating the toner. 2. Claim 1, wherein the environmental temperature at the time of evaluation is 30 to 50°C.
A method for evaluating the characteristics of the electrostatic image developing toner described above.