JPS60217367A - Image forming method - Google Patents

Abstract

PURPOSE:To obtain stably vivid visible images of a sufficient image density for a long period by allowing a toner to contain a binder resin and a release agent whose penetration is lower than a prescribed value. CONSTITUTION:A carrying belt 20 which is moved along a passage reaching a toner receiving and distributing device 12 of a developing device 9 by rolls 22 and 23 is stretched on the outside peripheral face of a rotary drum 19. The toner gathered from the surface of the photosensitive drum 19 by a cleaning device 10 is sent to a recovery drum and is supplied to the toner receiving and distributing device 12 of the developing device 9 and is used for development of an electrostatic latent image on the photosensitive drum 19 again. This toner contains the binder resin and the release agent whose penetration is <=4.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a method for developing an electrostatic charge image formed in an electrophotographic method, an electrostatic printing method, an electrostatic recording method, etc. The present invention relates to an image forming method for forming an image.

[Prior art]

Currently, in order to form a visible image from image information, methods using electrostatic images such as electrophotography are widely used. In this method, for example, according to electrophotography, an electrostatic image formed on an electrostatic image support made of a photoconductive photoreceptor by a charging process and an exposure process is developed using electrodetecting colored particles called toner. This toner image is usually transferred to a transfer material and fixed to obtain a visible image, while the electrostatic charge image support after transfer is cleaned/cleaned and used for the next image formation. It is. Such a method allows repeated formation of visible images.

In the process of developing an electrostatic image, charged fine particles are attracted by electrostatic attraction and attached to the next surface of the electrostatic image support.
This is the process of visualizing the electrostatic charge image.

A specific method (8) for carrying out such a tax-receiving process is a wet development method using a liquid developer in which pigments or dyes are finely dispersed in an insulating organic liquid.

A powder developer is used, which is composed of a toner containing a coloring agent such as carzen black dispersed in an inder composed of a natural or synthetic resin. Cascade method.

Hair brush method, magnetic brush method, impression method.

There are dry developing methods such as powder cloud method.

The image visualized in the developing step may be fixed as is on the support, but usually it is transferred to another support such as transfer paper and then fixed. In this way, the toner is not only subjected to the development process, but also to the subsequent processes, that is, the transfer process and the fixing process, so the toner has not only good developability but also the following processes: It is required to have good transferability and good tackiness. this house.

One condition regarding fixability is the strictest.

Research on improving the fixing properties of this toner and its results have been published in numerous documents.

It is generally advantageous to use a heat fixing method to fix the toner image formed in the first step or the image to which it is transferred.This heat fixing method includes a non-contact heat fixing method such as oven fixing, There is a contact heating fixing method such as roller fixing. The contact heat fixing method is excellent in that it has high thermal efficiency, and is particularly capable of high-speed fixing and is suitable for fixing in high-speed copying machines. Furthermore, since a relatively low-temperature heat source can be used, this method requires less power consumption, making it possible to downsize the copying machine and save energy. Furthermore, there is no risk of fire even if paper accumulates oil in the fixing device, which is also preferable.

Although the contact heating fixing method is preferable in these respects, this method has a serious problem of occurrence of an offset phenomenon. this is.

This is a phenomenon in which a part of the toner constituting the image is transferred to the surface of the heat roller during fixing, and this is transferred again to the next transferred transfer paper or the like, staining the image. In order to prevent this offset phenomenon, various proposals have been made and some have been put into practical use. One is to apply release oil such as silicone oil six times on a hot roller (5) while fixing is performed, and the other is to make the toner itself have anti-offset properties. The latter means does not require a silicone oil application mechanism, so the structure of the fixing device is simple.

It is superior in that it does not require maintenance such as replenishing silicone oil.

Therefore, the offset phenomenon occurs when the temperature of the heat roller increases. Therefore, the higher the minimum temperature at which the offset phenomenon occurs (hereinafter referred to as "offset occurrence temperature"), the better the non-offset property is. However, in order to form a specific toner layer, it is necessary to heat the toner to a temperature above its softening point. Therefore, in an actual heat roller fixing device, the temperature of the heat roller is The temperature is set to a specific temperature within the four fixable temperature ranges that are above the toner's softening point and below the offset generation temperature.

On the other hand, it is naturally desirable that the minimum temperature required for toner fixation (hereinafter referred to as "minimum fixing temperature") be low, and it is also desirable to In order to achieve the formation of image t(6), it is necessary that the toner used for development can be fixed at a low temperature.

Hitherto, as a technical means for obtaining a toner having non-offset properties and a low minimum fixing temperature, there has been known a means of incorporating a release agent such as a low softening point wax such as polyethylene wax.

However, in the case of simply incorporating a low softening point wax into the toner, the fluidity of the powdered toner decreases, resulting in a decrease in developability and transferability, making it impossible to form a good visible image. They also tend to be nest-saving. And the power of wax! In order to obtain this effect, it is necessary to increase the content of the wax, and as a result, the wax component adheres to the surface of the developer support, electrostatic image support, or carrier particles. The so-called toner filming phenomenon in which a film is formed occurs, and these functions are inhibited, leading to problems such as a decrease in the amount of electricity of toner particles (7). be.

On the other hand, in order to improve the fluidity of the toner, it is effective to add a fluidity improver made of fine hydrophobic silica powder to the toner powder, but it is effective to add a fluidity improver made of fine hydrophobic silica powder to the toner powder. In order to obtain sufficient fluidity in toner, it is necessary to add a large amount of hydrophobic silica fine powder, and as a result, the optical surface of the electrostatic charge image support is If the support is a photoconductive photoreceptor, this can be a serious problem, and if surface cleaning of the electrostatic image support is carried out with a sam blade, the blade may be damaged. If the surface wears unevenly, cleaning failures may occur early.

Furthermore, from the perspective of efficient use of toner.

Although it was submitted to the recycling system, that is, development, I [!
Toner that did not participate in the formation of the II image (1>20-80
h) In an image forming method that employs a system in which the toner is cleaned and collected, and the collected toner is returned to the developing device for reuse, when the toner described in i is applied, the optical surface of the toner particles is Hydrophobic silica particles become embedded, which may reduce the fluidity of the toner.When the toner is used repeatedly, the wax component separates from the toner particles, preventing toner offset. Performance deteriorates, and visible images with excellent resolution cannot be stably obtained over a long period of time.

[Purpose of the invention]

The present invention has been made based on the above-mentioned circumstances, and the object thereof is to provide a toner for developing electrostatic images that can be fixed at a low temperature and has excellent non-offset properties and fluidity, and that provides sufficient image brightness. An object of the present invention is to provide an image forming method that can stably and efficiently form large and clear visible images over a long period of time.

[Structure of the invention]

The purpose of the above is to develop an electrostatic image by supplying a toner for developing an electrostatic image to an electrostatic image support, and to recover the toner for developing an electrostatic image that does not participate in electrophoretic formation and use it again for development. Image using the system (9) Image forming method, characterized in that the toner for developing an electrostatic image contains a binder resin and a release agent having a penetration degree of 4 or less. This is achieved by an image forming method.

The present invention will be explained in detail below.

In the present invention, in image formation in which an electrostatic charge image is developed with an electrostatic charge image developing toner to form an image, a so-called silent image developing toner recycling system is employed. FIGS. 1 and 2 each show an example of such a toner recycling device.

In the apparatus shown in FIG. 1, reference numeral 19 denotes a collection drum, which is coaxially connected to a position outside one end of the photosensitive drum (not shown in the figure) constituting the electrostatic image support through a partition wall. A magnet 18 is arranged inside the magnet. A part of the collecting drum 19 is handled by the cleaning device IO and the screw conveyor 17, and the other part is connected to the developing device 9, which is extended from one end of the S optical drum 11tlJ1c. A conveyor belt 20 is suspended on the outer peripheral surface of the photosensitive drum and is moved along a path leading to the toner receiving and distributing device 12 (lO) of the developer h9 by a roller 2I2゜z8. 1
The toner collected by the screw conveyor 17
The waste is then sent to the recovery drum 19, but this recovery drum 51
A brush is formed on the conveyor belt 2θ on the conveyor belt 9 by a mixture of the developer, that is, the toner supplied from the developing device 9, and the carrier. The toner is picked up by the toner and conveyed by the conveyor belt 20 which is conveyed by the rotation of the first collection drum 19, and is thereby supplied to the toner receiving and distributing device 12 of the developing device 9, where it is again used to collect the electrostatic charge image on the photosensitive drum. Subjected to development. Reference numeral 14 denotes a magnetic brush device, which is composed of a rotating sleeve 14a and a magnet 14b disposed inside the rotating sleeve 14a. 15 is a developer stirring device, and 21 is a casing.

On the other hand, in the apparatus shown in FIG. 2, 1 is a developing device.

2 is a cleaning device, 81'i) a toner receiving and distributing device, 4 is a magnetic brush device, 5 is a photosensitive drum, 6 is a screw conveyor, 7 is a wIl star screw, 81-J (11) a second screw, this device The first screw 7 and the second screw 8 supply toner from the screw conveyor 6 to the toner receiving and distributing device 8. That is, each of the first screw 7 and the second screw 8 does not have a rotating shaft inside and a blade spirally provided along the rotating shaft.
, the toner carried by the screw conveyor 6 is pushed up by the blades as the rotating shaft rotates and is sent to the second screw 8.
In this case, toner is sequentially fed in the horizontal direction on the same principle as the first screw 7 and supplied to the toner receiving/distributing device, where it is again applied to the 3A image of the electrostatic charge image on the photosensitive P ram 5.

In the present invention, two examples are a toner for developing an electrostatic image in an image forming method using a toner recycling device as described above. A toner powder containing any other necessary toner components is preferably mixed with a fluidity improver such as stone, for example, hydrophobic silica fine powder.

The toner image obtained by developing with the electrostatic charge image developing toner is transferred to a transfer material such as paper, and subjected to a multi-contact heat fixing process using, for example, a heating roller to form a visible image. The toner remaining on the electrostatic image support without being transferred to the transfer material is cleaned and collected by a cleaning device such as a cleaning blade, and the cleaned electrostatic image support is used in the next image forming process. served.

In the above, the penetration degree of the llll type agent is JIS K22.
85-1980. Melt the sample mold release agent by heating, pour it into a sample container, let it cool, and then warm it to a constant temperature of 25C in a constant temperature water bath. Enter the mold release agent vertically for 5 seconds.

The depth of penetration of the needle is measured to the nearest 0.1 degree, and the value obtained by multiplying this by 10 is defined as the degree of penetration.

In the present invention, the release agent rL used in the toner (18
) is required to be 4 or less, and the ratio of use thereof is preferably 1 to 20'M with respect to the total amount of toner. If a release agent with a penetration level of more than 4 is used, the fluidity and non-cohesiveness of the toner will be reduced, resulting in poor development and, as a result, it will not be possible to obtain a clear visible image. Moreover, if the ratio of the mold release agent used is less than 1 weight, the effect as a WM mold agent will not be exhibited and the non-offset property will decrease, and on the contrary, 20! If the amount exceeds the limit, toner filling occurs, resulting in poor development, and fluidity also decreases.

Examples of release agents that can be used in the toner in the present invention include polyolefins, 8-fat modified metal salts, fatty acid esters, partially saponified fatty acid esters, higher fatty acids, higher alcohols, and liquid or solid paraffin wax. , amide thread wax, polyhydric alcohol ester, silicone varnish, aliphatic fluorocarbon, etc., which have a penetration degree of 4 or less can be mentioned. These mold release agents can be used in any one form or in combination of two or more types (14). In addition, these mold release agents have melting points of 60 to 16
It is preferable that the temperature is within the range of 0C because low-temperature fixability can be obtained.

Examples of the polyolefin having a penetration degree of 4 or less include resins such as polypropylene, polyethylene, and polyethylene 7y, which have a melting point of 80 to 180G when measured by the ring and ball method specified in JIS K 2581-1960;
Preferably it is 80 to 150C. Penetration is 4
Examples of the fatty acid metal salts include maleic acid, zinc, and magnesium.

Metal salts with calcium, etc.; stearin modified and zinc.

Metal salts with cadmium, norium, lead, iron, nickel, cobalt, copper, aluminum, magnesium, etc.; dibasic lead stearate; zinc with oleic acid, magnesium, iron, cobalt, copper, lead, power A/Gold M salt with sium, etc.; Kinho salt of nogrumitic acid with aluminum, calcium, etc.; lead casorylate; lead caproate; metal salt of linoleic acid with zinc, cobalt, etc.: ricinoleic acid with calcium, zinc , metal salts with cadmium, etc., and mixtures thereof (15). Examples of the fatty acid ester having a penetration degree of 4 or less include montanic acid ethylene glycol ester. Examples of the partially saponified fatty acid ester having a penetration degree of 4 or less include partially saponified calcium of Id moretanic acid ester. Penetration is 4
Examples of the higher fatty acids listed below include stearic acid, arachinic acid, behenic acid, lignocerin, and mixtures thereof. If the penetration degree is 4 or less, the higher alcohol is 1, for example, behenyl 7.
Examples include Lecor et al. The paraffin wax has a penetration level of 4 or less.

Examples include synthetic paraffins and chlorinated hydrocarbons. Examples of the amide waxes having a penetration degree of 4 or less include stearamide, oleic acid amide, palmitic acid amide, lauric acid amide, behenic acid amide, methylene bis stearamide, ethylene bis stearamide, etc. Can be mentioned. Examples of the polyhydric alcohol ester having a penetration degree of 4 or less include glycerin stearate, glycerin lysyl, glycerin monobehenate, sorbitan mono, nostearate, and sorbitan triolate. Examples of the silicone varnish having a penetration degree of 4 or less include methyl silicone varnish, phenyl silicone varnish, and the like. Penetration is 4
Examples of the following aliphatic 70 carbons include low polymer compounds such as tetrafluoroethylene and hexafluoropropylene.

Among the above-mentioned mold release agents, specifically preferred ones include those shown in No. 1 fi below.

(17) Table 1 (18) Examples of the fluidity improver include hydrophobic silica, alumina, titanium oxide, talc, and metal stearate, among which hydrophobic silica is preferred. Specifically, examples of this hydrophobic silica include [Ryo ErogiyyR-9724, "Aerosil R-812J,
“Aerosil R-805j (manufactured by Nippon Aerosil Co., Ltd.)
, "D-17" (manufactured by Degussa), etc. These fluidity improvers are preferably retained on the toner particles in a state where they are attached to the surfaces of the particles.
For example, it is used by being mixed and added to toner powder. The proportion of the fluidity improver to be used is preferably 0.01 to 10% by weight based on the total amount of the toner.

The toner used in the present invention is obtained by dispersing a release agent with a penetration degree of 4 or less in a non-inner resin together with a colorant, a magnetic material, a property improver, and other necessary additives. It is a particle powder obtained by further mixing and adding a fluidity improver to the toner powder, and the average particle size thereof is usually in the range of 5 to 30 μm.

(19) The resin used as the above-mentioned inder resin is not particularly limited, and resins that are normally used for this type of purpose can be used, but for practical purposes, polyester resins, styrene resins, acrylic resins, styrene resins, etc. - Acrylic copolymer resins, other vinyl resins, and others are preferred.

As a coloring agent, Cargino black, Niclonone dye (
C,1,/1650415B), aniline blue (C
, l4t50405 ), Calco Oil Blue (C,
I.

4 azoec Blue3), riC'mui x c;
-(,C,1,A14090), Ultramarine Blue (C, 1.1tfL77103), DuPont Oil Red ('C,1, Knob 626105), Quinoline Yellow (C0■, /1647005), Methylene Blue Chloride (C,1 , Scrap 52015), Phthalocyanine Blue (C, 1, 74160), Malachite Green Oxale) (C, 1, 42000), Lamp Black (C, 1, A 77266), A-Z Bengal (C, 1, A 45435) , mixtures thereof, and others. These colorants need to be contained in a sufficient proportion to form a visible image with sufficient concentration, and are usually 1 to 20 parts by weight per 100 parts by weight of Ingu resin. It is said that

The magnetic material may be a metal or alloy that exhibits ferromagnetism such as ferrite, magnetite, iron, conortite, nickel, or a compound containing these elements, or a material that does not contain a ferromagnetic element but is subjected to appropriate heat treatment. Alloys that exhibit ferromagnetic properties, such as manganese-copper-
Aluminum, a type of alloy called Heusler alloy containing manganese and copper such as manganese-copper-tin, or sulfur dioxide, and others.
The magnetic material is uniformly dispersed in the inder in the form of a fine powder with an average particle size of 0.1-1 microns. The content thereof is 20 to 70 parts by weight, preferably 40 to 70 parts by weight, per 100 parts by weight of toner.

Examples of the property improving agent include a charge control agent and others.

The toner used in the present invention is mixed with a carrier consisting of iron powder, glass beads, etc. to form a two-component developer (21), but when it contains a magnetic material, it can be used as a single-component developer to form electrostatic images. Subjected to development.

[Effects of the Invention] As described above, the image forming method of the present invention adopts a recycling system in which residual toner that is not involved in image formation is collected and the collected toner is again used for development, and in addition, it uses a recycling system that collects residual toner that is not involved in image formation and uses the collected toner again for development. Since development is carried out using a product containing an H-type agent with a degree of 4 or less, low-temperature fixing is possible, as well as good non-offset properties and fluidity, as will be understood from the examples described below. Excellent visible images with sufficient image density, clearness, and no background smudge can be formed stably and efficiently over a long period of time. Since the same toner is repeatedly used for development, the amount of toner consumed corresponds to the amount of toner actually transferred and fixed to the transfer material, etc., and the toner that is considered invalid is virtually exhausted, so toner replenishment is possible. It is possible to provide a margin for the timing interval, and the labor required for replenishing toner can be considerably reduced, making it possible to reduce running costs.

(22) The reason why the above effects can be obtained is that the toner used in the present invention contains a release agent with a penetration degree of 4 or less, so that the toner particles are not given release properties. In addition, the addition of this release agent suppresses the occurrence of offset phenomenon, and the increase in stickiness of toner particles caused by the addition of this release agent is small, making it difficult for toner agglomeration to occur.Furthermore, it has high durability against friction or agitation, and can be used many times. It is conceivable that the above-mentioned characteristics of the toner can be stably exhibited even after repeated use.

Such effects are particularly significant when a one-screw type toner recycling device as shown in FIG. 2 is used. That is, in the one-screw type, the toner is conveyed while being subjected to a considerable impact, and therefore great durability is required of the toner, and the toner used in the method of the present invention fully satisfies such requirements.

〔Example〕

Examples of the present invention will be described below, but the present invention is not limited thereto.

(23) Examples 1 to 4 and Comparative Examples 1 to 3 Mix each composition according to the composition shown in Table 2, and follow the usual toner manufacturing method by melting, cooling, crushing, and classifying steps. Toner powder with an average particle size of 11 μm was obtained, and each toner powder was further coated with hydrophobic silica [Aerosil R-97
2J (manufactured by Nippon Aerosil Co., Ltd.) was mixed and added at a concentration of 0.8% by weight to obtain a total of seven types of toners 1 to 4 and comparative toners 1 to 3.

In the table, numerical values represent parts by weight. In the production of Comparative Toners 1 to 3, many aggregates were present in the toner powder when hydrophobic silica was added after the classification process, so the toner powder was sieved using a 100-mesh sieve to obtain toner.

(25) A two-component developer having a toner concentration of 2.5% by weight by mixing each of these Toners 1 to 4 and Comparative Toners 1 to 3 with a resin-coated carrier made of iron powder. and each of them was used to create an electrophotographic copying machine rU-Bix equipped with a recycling device similar to the configuration shown in FIG.
4500'' (manufactured by Konishiroku Photo Industry Co., Ltd.), the electrostatic charge image is developed, the toner image is transferred to transfer paper, the toner image is fixed by a heat roller fixing device, the residual toner is collected by a cleaning plate r, and the recovered toner is The initial charge amount of toner particles and the charge amount after 30,000 copies, the toner concentration in the developer after 30,000 copies, the quietness density at the initial stage and after 30,000 copies, and the occurrence of offset phenomenon are recycled to the developing device. Next, check the existence and minimum fixing temperature. The results are shown in Table 3. The copying speed was approximately 30 sheets/min using A4 size transfer paper. In actual copying tests using Comparative Toners 1 to 3, fogging or a decrease in image density became noticeable before the number of copies reached 30,000, so Comparative Toner 1 was used for 5,000 copies, and Comparative Toner 2 was used for 5,000 copies. The actual copying test was discontinued after 2,500 copies and 8,000 copies for comparative toner 8, and the measurement results at that point are shown in parentheses in the column "After 80,000 copies" in Table 8. Furthermore, the quietness density evaluates the fluidity of the toner, and the higher the fluidity, the higher the quietness density.

Specifically, a toner sample was loosely packed into a container having a diameter of 281ζ and a volume of 100 fflAI from above through a 100 mesh sieve, and the weight of the toner sample at this time was measured to determine the quietness density. Regarding the minimum fixing temperature, a fixing device comprising a heat roller whose surface layer is made of Teflon and a pressure roller whose surface layer is made of silicone beam is used.

The operation of fixing the toner image of the sample toner transferred onto the transfer paper of 649/m2 at a linear speed of 200 u/s is as follows:
The set temperature of the heat roller was increased from 100C to 100C, and the temperature was increased by 5C repeatedly, and the formed fixed image was subjected to 1,000 degrees of rubbing.

The minimum setting temperature for a fixed image with sufficient af resistance was defined as the minimum fixing temperature.

(28) When we investigated the image quality of the obtained copied images, we found that when toners 1 to 4 were used, clear images with sufficient image density and no fogging were obtained even after 30,000 copies were made. When toners 1 to 3 were used, fogging occurred early in all cases, and comparative toner 1 was copied 5000 times, and comparative toner 2 was copied 2500 times.
With comparison toner 3, after 3000 copies, fog increased and sharpness decreased significantly, and toner fireflies (toner fused and aggregated due to agitation in the developing device, which adhered to the surface of the photoreceptor) Furthermore, when the toner is transferred and fixed to paper, a phenomenon in which the periphery of the toner aggregates becomes white, and the quality of the image is significantly deteriorated. This is because when Comparative Toners 1 to 3 were used, a large number of toner aggregates were generated in the developing device.

As described above, according to the method of the present invention, even when the copying speed is high, sufficiently good images can be stably formed over many times, and especially when the copying speed is 30 sheets per A4 size transfer paper. The effect of the present invention becomes even greater when the time is longer than 1 minute.

[Brief explanation of the drawing]

FIGS. 1 and 2 are explanatory cross-sectional views showing an example of a toner recycling device that can be suitably used in the image forming method of the present invention, respectively. 9...Developer lO...Cleaning device 12...
- Toner receiving and distributing device 14... Magnetic brush device 14a... Rotating sleeve 14b... Magnet 15... Developer stirring device 1
7...Screw conveyor 18...Magnet 19...Collection drum 20...Transportation heald 21...Casing 22.23...Roller 1...Developer 2...Cleaning device 3...・Toner receiving and distributing device 4...Magnetic plan device 5...Photosensitive r ram 6...
screw conveyor

Claims (1)

[Scope of Claims] l) The electrostatic charge image developing toner is supplied to the electrostatic charge image support to develop the electrostatic charge image, and the electrostatic charge image developing toner not involved in image formation is collected and subjected to development again. An image forming method employing a recycling system, wherein the toner for developing an electrostatic image contains a 1,6 inder resin and a release agent having a penetration of 4 or less. formative force method. 2) The image forming method according to claim 1, wherein the toner for developing an electrostatic image is mixed with a fluidity improver. 3) The image forming method according to claim 2, wherein the fluidity improver is hydrophobic silica.