JPH02153363A - Defoaming agent for developer - Google Patents

Abstract

PURPOSE:To prevent foaming of a developer without adversely affecting the developer by adding a specified modified dimethylsilicone as the defoaming agent to the developer. CONSTITUTION:The modified dimethylsilicone to be used as the defoaming agent is represented by the formula in which n:m is 70:30 - 0:100. This agent can be added to either or both of a concentrated toner or a liquid carrier dispersion, and it may be added at the time of adjusting the developer. The misoperation of a toner concentration sensor when a heating and pressing means coated with a releasing liquid is used in a wet copying machine for copying on both of the front and opposite sides of a transfer paper, occurrence of an abnormal image like raindrops due to poor squeezing of a reverse roller, troubles of suction of the developer due to foaming in a pump, and the like problems can be solved by using this defoaming agent.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to improvements in technology in wet double-sided copying.

[Prior art]

Fixing in wet copying is a simple mechanism, as the solvent present in the toner layer on the photoreceptor or transfer paper simply evaporates.

For example, fixing was completed by using hot air or a simple plotter roller (squeezing roller made of nonwoven fabric, etc.). However, as copying machines become faster these days, transfer paper carrying a developer is passed between a heating roller and a pressure roller that are in pressure contact with each other, and thermal fixation is now being implemented in both wet-type and dry-type copying machines. The adoption of the method is oriented. When paper passes between heated and pressure rollers, even in wet copying machines,
It is known that the hot offset phenomenon to the rollers and transfer paper occurs as in the dry copying method. As a countermeasure against this problem, it has been considered to apply a releasing liquid such as silicone oil to the surface of the heating roller.

FIG. 1 explains the mechanism of a transfer type wet electrophotographic apparatus. The latent image on the photoreceptor is developed with a developer by a developing roller 6.8 which is rotationally driven while maintaining a small distance from the photoreceptor drum 1.
This developing roller is cleaned by a cleaning member (scraper) 7.6 The photosensitive drum 1 is driven to rotate at a constant speed in the direction of the arrow by a drive device during copying, and the main charger 1
4, after the document is charged negatively, an exposure device projects an image of the document to form a latent image, and an eraser removes the charge outside the image forming area. The latent image on the photoreceptor drum 1 is developed by a wet developing device, and transferred to a transfer paper 21 that is fed from a paper feeding device (not shown) via a conveying roller as indicated by a broken line arrow.
The image is transferred by the transfer charger 11.

This transfer paper 21 is separated from the photosensitive drum by a separation roller and conveyed by a conveyor belt.

The toner is fixed by the fixing device and discharged to the outside.

After the transfer paper is separated from the photosensitive drum 1, residual toner is removed by a cleaning unit, and residual potential is removed by a static eliminator (static eliminator 15 or static eliminator charger) in preparation for the next copy.

In the above-mentioned wet type developing device, the first. Second
Developing rollers 6.8 are arranged respectively, squeeze rollers (R, R,) 9 are arranged, and the first . The second developing roller 6.8 is held at a small distance from the surface of the photosensitive drum 1. This interval is adjusted to 0.1-0.2 rrn, and the first. The second developing roller 6.8 is driven by a drive device to rotate in the opposite direction to the photosensitive drum 1 as shown by the arrow, and a cleaning member (scraper) 7 fixed to the developing container is applied to each developing roller 6.8. Always clean the toner on the developing roller.

The developer supplied from the developer supply nozzle 5 by the developer supply means is uniformly conveyed to the surface of the photoreceptor drum 1 by the rotation of the developer roller 6.8 and the scraper 7, and is further transferred to the surface of the photoreceptor drum 1 and the developer roller 6. After developing the latent image on the photoreceptor drum 1, the developer is discharged from the developer outlet 12.
collected and reused.

The squeeze rollers (R, R,) 9 are rotated by a drive device in the opposite direction to the photoreceptor drum 1 to scrape off excess developer on the photoreceptor drum 1, and the developer on the surface is removed by the scraper 7. scraped off.

Furthermore, as shown in FIG. 2, the fixing device is of a type in which the heating roller 31 comes into direct contact with the toner image surface, and is pressed against the heating roller 31 across the paper passage path of the transfer paper 2I carrying unfixed toner. The rollers 32 are arranged so as to be in pressure contact with each other. A pressure lever 34 is pressed against the shaft portion of the pressure roller 32 based on the biasing force of a spring 35, so that a predetermined pressure is applied to the pressure roller 32. Further, nips are formed on the pressure roller and the heating roller. Next, the heating roller 31 has a built-in heater 33 as a heat source of, for example, 100V and 750W.

A thermistor 36 and a temperature fuse 37 are attached to the heater 33 outside the heating roller 31 to control the temperature. Further, a separation claw 38 and a mold release liquid coated felt 39 are arranged on the outer peripheral surface of the heating roller 31 so as to be in contact with each other.

However, if this wet-type copying machine is applied to a double-sided copying machine that has recently become popular for boat fishing, that is, a wet-type copying machine that copies on both sides of transfer paper, the heating and pressurizing means coated with the above-mentioned release liquid is applied. , ■ Malfunction of the toner density sensor, ■ Abnormal images like rain drips due to poor squeezing of the reverse roller, etc., (c) Poor pumping of the developer due to bubbles entering the pump, L4) The developer is leaking outside the machine. It was found that problems such as leakage occurred.

We investigated the causes of these phenomena.

■ Malfunction of toner concentration sensor When using a light transmission type sensor, which is used as an inexpensive and stable toner concentration sensor, bubbles may enter between the light receiving part and the light emitting part, as shown in Figure 4, causing the light to emit light. As the transparency improves, it is detected that the concentration of the developer is low, and more toner is replenished than necessary, resulting in a developer with excessive toner concentration and abnormal images such as streaks.

■ Occurrence of abnormal image like raindrops due to poor squeezing of R, R. Figure 5 shows the original diagram of the reverse roller (R,, R,).1 The liquid film on the photoreceptor after development is Depending on the tension, the number 1
00μ, and a flow with a speed of U is generated on the photosensitive drum surface.On the other hand, a flow with a speed of ① is generated only in R, R, (reverse rotation roller). Therefore, a combined flow of U+V=W occurs at the joint between the drum and R, R, and the liquid is torn left and right.

Here, if the speed (2) of R, R, increases, the speed (2) increases, so the removed liquid t2 increases and remains along with the photoreceptor. The liquid t gradually decreases, and becomes constant when the relative velocity between V□ and v2 exceeds a certain level6. Determined by surface condition.

Bubbles in the developer enter between these R, R and the photoreceptor,
The action of R, R, is no longer transmitted in the bubble area, and failure to squeeze the developer occurs locally, resulting in a transferred image with a large amount of developer attached in the form of raindrops (FIG. 6).

■ Poor pumping of developer (see Figure 6) Bubbles enter the pump casing 23 in the developer tank 22, causing the rotating blade 2
4 and the casing 24 to pump up the developer decreases, resulting in poor pumping of the developer.

As a result, the amount of liquid accumulated in the developing section decreases, causing uneven development.

(1. Developing solution flows out of the machine) Bubbles are generated in the liquid agitation, pump, liquid recovery port, etc. in the imaging tank, and as the volume of the foamy developer increases, it overflows from the liquid recovery port of the developing tank. and leaked out of the aircraft.

From the above studies, it has been found that the above phenomenon is caused by a large amount of bubbles generated in the developer.

〔the purpose〕

An object of the present invention is to solve the problem of the mouth.

〔composition〕

As a result of investigating the cause of the bubbling phenomenon of the developer, the present inventors discovered that after the front side of the copy paper has been copied, when the back side is subsequently copied, the following method is commonly used in a dry copying machine when fixing the front side. When a dimethylsiloxane-based silicone oil release agent with the formula is used, this silicone oil gets mixed into the developer little by little through the copy paper and photoreceptor, which is the cause of foaming in the developer. was investigated.

In other words, evenly applied silicone oil, which is a conventional release agent, does not cause any problems when copying only one side. The copy operation is performed again, but at this time, when the transfer paper comes into close contact with the photoconductor, the evenly applied silicone oil adheres to the photoconductor (at this time, the silicone oil that adheres The weight is IIng per sheet of A-4 size transfer paper.
0.5mg adheres. Of course.

(Varies depending on the type of transfer paper) These adhered silicone oils will be mixed into the developer via the photoreceptor surface, and will cause deformed surface copying of about 1000 to 5000 sheets.
In synthetic copies, 1 g to 0.5 g of silicone oil is mixed. However, the silicone oil mixed in the developer is also consumed during development and taken out of the machine.
When about 000 to 10,000 sheets are deformed, about 1 g is definitely mixed in.

Therefore, the present inventors conducted research on a material that has an antifoaming effect when added to a developer. However, these are subject to many restrictions, and although various studies have been attempted, it has been difficult to find a material that has a good defoaming effect. The reason for this is that the developer (dispersed carrier liquid) used in a wet type copying machine is required. The following points can be raised regarding physical properties.

■ Must have high electrical resistance (X10140 or more) ■
Low dielectric constant (ε=3 or less) ■ Low dissolving power ■ Low odor ■ Low flammability (50°C or higher) t'Q+ Fast drying As a dispersed carrier that satisfies these conditions Aliphatic hydrocarbons, such as isoparaffinic hydrocarbons such as 15opar (EXXSON), have been selected as representative examples and have been used as developers in wet-type copying machines. Various materials with an anti-foaming effect as mentioned above were also considered as candidates, and their effectiveness was confirmed by adding them to the developer. It is difficult to find effective solutions because they cause problems and side effects, such as causing problems, emitting strange odors, or increasing the dissolving power and similarly decreasing the electrical resistance, shortening the life of the developer. No defoaming material was found.

However, it was surprisingly discovered that modified dimethylsiloxane, in which a fluoro group was introduced into the dimethylsiloxane that caused foaming, exhibits antifoaming properties without losing the six properties necessary for the developer, and the present invention has been made. has been reached.

That is, the present invention is an antifoaming agent for a developer in wet electrostatic copying, which is made of a modified dimethyl silicone represented by the following structural formula.

In the formula, n: m ~ 10: 30 ~ 0: 100
The antifoaming agent of the present invention can be added in advance to either the Funktner or the dispersion carrier liquid, or both, or can be added when preparing the developer.

The amount of antifoaming agent used in the present invention is 0.1 part by weight or more, preferably 0.5 part by weight, per 100 parts by weight of development ti, to have a sufficient effect, and even if the amount used is increased beyond that, There is no particular problem, but it is not economical.6 [Example] The effectiveness of the antifoaming agent of the present invention is clarified from Example 1.

By variously changing the ratio of n; Test 1 was conducted regarding the copying condition of the copy paper. The test conditions are Tsopar]Q.

To the solution, 50 hours of toner and 0.5 grams each of antifoaming agent were added to prepare a developer. The results are shown in Table 1.

(Left below) 1) Regarding affinity (add Isopar I, 20mQ for 11 hours and stir, check the state of the liquid), 0 indicates no affinity, that is, no dissolution;
It shows that it easily separates into two phases.

(2) corresponds to an intermediate level of affinity, and indicates that even if left for a long time, the degree of two-phase separation is small and the sample becomes cloudy.

× indicates affinity and dissolution.

A similar study was conducted on the above-mentioned developers, and a similar trend was found.6 2) Measurement of the amount of bubble generation was performed according to JIS K3362, 3.1.
5.

That is, water at 40°C is circulated through the vertically installed outer cylinder of the measuring device shown in Fig. 7 to keep it at a constant temperature, and 50 cc of a developer sample containing a release agent is gently poured along the outer cylinder over the entire side surface. Pour 200 cc of the above sample into pipette A, hold the lower end of the pipette at a height of 90 cm from the liquid level in section B, attach a capillary tube to the upper end of the pipette, and When the active chamber is opened, the sample should flow out in about 30 seconds, and the droplet should be allowed to fall to the center of the liquid surface in part B. After all the sample liquid has flowed out, measure the amount of bubbles and measure this. It has foaming power. Perform the measurement operation three times,
The average value of three measurements was taken as the measurement result.

According to the above measurement method, the results when dimethyl silicone oil (KF.96), which is a mold release agent, was mixed are shown in FIG.

According to this, if 1g of dimethyl silicone oil (KF 96) is mixed in with Jsopar] Q, 6 bubbles will be generated.
5m (approximately 2 g is generated, and if it is 3 g or more, it tends to be slightly saturated.) Note that no bubbles were generated when the aliphatic hydrocarbon liquid was used alone without dimethyl silicone oil.

3) Regarding image density, This is a value measured with a Macbeth densitometer.

4) Regarding sharpness, solid uniformity, and background stains,
All are based on the following 5-level evaluation.

5 Excellent 4 Slightly excellent 3 Good 2 Slightly poor 1 Poor In addition, the data on the copying characteristics are as follows:
The results were obtained for copies made using a Ricoh CT-5085 copying machine, with a developer obtained by adding toner sog prepared by the method disclosed in Japanese Patent No. 139426 to 15opar LIQ as a control. From the above results, it can be seen that a n:m ratio of 70:30 is the limit, and a good antifoaming effect can be obtained if the n:m ratio is 30 or more, preferably 50 or more.

〔effect〕

The antifoaming agent of the present invention can prevent foaming of the developer without having any adverse effect on the developer.

Therefore, by adding the antifoaming agent of the present invention, the problem of foaming does not occur even if the developer is used at 200K, whereas when it was not added, the developer had to be replaced at an average temperature of 80 to 100K. We were able to achieve excellent results.

[Brief explanation of the drawing]

Figure 1 is an overall view of a wet copying device, Figure 2 is an enlarged view of its fixing device, Figure 3 is a graph showing the relationship between the amount of conventional silicone mixed in and the amount of bubbles generated, and Figure 4 is a toner density sensor. FIG. 5 is a diagram of the principle of the reverse squeeze roller, FIG. 6 is an explanatory diagram of an abnormal image of raindrops, and FIG. 7 (a) is a foaming force measurement device. Figure 7 (
b) is a partially enlarged view. 1... Photosensitive drum 2... Pumping pump 3...
・Toner concentration sensor 4...Developer supply pipe 5...Developer supply nozzle 6
...First developing roller 7...Scraper 8...
Second developing roller 9...Reverse squeeze roller 10...Paper feed roller 11...Transfer charger 12...Developer discharge port 13...Eraser 14
Main charger 15 Static elimination lamp 17 Liquid diffusion plate 19 Liquid collection hole 2 Transfer paper 23 Pump casing 24 Toner sensor lamp (light emitting part) 25 ...Photodetector (light receiving part) 26...Developer drain hole 31...Heating roller 32...Pressure roller 33...Heater 34...Pressure lever 35...Spring
36...Thermistor 37...Temperature fuse
38...Separation Claw 39...Silicone coated felt 16...Cleaning plate] 8...Cleaning 20...Transport belt 22...Developer tank

Claims (1)

[Claims] 1. An antifoaming agent for a developer in wet electrostatic copying made of modified dimethyl silicone represented by the following structural formula ▲ There are numerical formulas, chemical formulas, tables, etc. ▼ In the formula, n: m = 70 :30~0:100