JPH0467044A - Image forming method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention supplies a non-magnetic one-component developer externally added with an auxiliary agent as necessary to a rotating developer carrier, The developer is carried and conveyed on the surface of the developer carrier, and an electrostatic latent image is formed on the latent image carrier in a development area where the latent image carrier and the developer carrier face each other. The present invention relates to an image forming method in which images are visualized using the developer carried on a developer carrier.

[Conventional technology]

Image forming devices such as electronic copying machines, printers, and facsimile machines that form an electrostatic latent image on a latent image carrier and visualize it with a developer to obtain a recorded image use a dry type that uses a powdered developer. This developing device is widely used. recent years,
In particular, a method using a developing magnet roller having a sleeve provided with a magnetic field generating means inside and a magnetic one-component toner is popular.

However, magnetic toner has a drawback in that it is unsuitable for color printing because the magnetic substance mixed inside it is black. Furthermore, in a method using magnetic single-component toner, the electrostatic latent image is developed by rotating the sleeve, by rotating the internal magnet, or by rotating both. When developing, the rotation speed of the sleeve or magnet must be selected so that the moving speed of the magnetic toner is usually 2 to 4 times the speed of the latent image so that the pitch of the magnetic poles does not affect the image. However, in order to ensure sufficient uniformity of image density, the rotation speed of the magnet becomes very high, which brings about the inconvenience of requiring a powerful motor to drive it, which naturally leads to an increase in the size of the mechanical device. become.

Against this background, with the intention of using a single-component toner that does not have magnetism, Japanese Patent Publication No. 41-9475 discloses a method in which a donor member having a thin toner layer on the surface is disposed close to the latent image forming member. , a method has been proposed in which the toner is ejected only to the latent image area while making them non-contact. Thus, in this proposal, toner retention is carried out on a suitably adhesive web or pre-charged film sheet.
This is achieved by suctioning and adsorbing the toner. However, this method has a limit on the length of sheets and webs, making it unsuitable for continuous copying and printing.

The above problem can be solved by making the toner carrier endless so that it can be used repeatedly, but such a method using a non-magnetic component toner was developed
It is disclosed in Japanese Patent No. 0-229065. In this proposal, an elastic equalizing member is brought into contact with a developer carrier roller to form a thin layer, and an alternating current and direct current developing bias is applied.
Developing the latent image. However, with this method, the toner layer formed is almost one layer, and it is difficult to obtain good image quality with high image density and sharp contrast.
Have difficulty. Furthermore, Japanese Patent Application Laid-Open No. 50-30537 discloses a developing device using a pulse bias method, which is said to improve image quality, but even with this method, the effect of increasing image density and sharpening contrast has not been observed. .

Furthermore, JP-A-47-12635 and JP-A-50-1
No. 0143 discloses a structure of a developer carrier having an insulating and conductive micro pattern on its surface.

These utilize a minute electric field to form peaks and valleys of toner in accordance with the minute pattern, and adhere toner that corresponds to the potential level of the latent image. The manufacturing process is complicated and causes cost increases.

As a method to solve these problems, the present inventors
First, a one-component developer consisting of a non-magnetic toner to which an auxiliary agent has been externally added as necessary is supplied to a rotationally driven developer carrier, and the developer is carried on the surface of the carrier. In a developing area where the latent image carrier and the developer carrier face each other, the electrostatic latent image formed on the latent image carrier is transferred by the developer carried by the developer carrier. In the developing device for visualization, a carrier having a chargeable and photoconductive surface is used as the developer carrier, and a charging means charges the surface to a polarity opposite to that of the toner; Light is selectively irradiated onto the surface of the subsequent developer carrier to form a large number of minute electric fields near the surface, and the developer used to visualize the electrostatic latent image is developed by the closed electric field. A developing device characterized by being provided with a light source means for causing the agent to adhere to the surface of the agent carrier.

In such a device, many minute electric fields (microfields) are formed near the surface of the developer carrier, so the electric field strength can be significantly increased compared to conventional ones, and the developer carrier can be sufficiently charged and a large amount of This has many advantages, such as being able to carry non-magnetic toner on a developer carrier and transport it to a development area.

[Problem to be solved by the invention]

However, even in the above-mentioned development method using a developing device that forms a large number of micro-fields near the surface of the developer carrier, if the conventional toner is used as is.

It is difficult to keep the toner layer on the developer carrier stable with two or more layers, and the toner layer becomes thinner and the amount of toner to be developed decreases, resulting in low density in the image area and the toner layer becoming thinner. This may cause uneven development, resulting in uneven density in the image area, or the toner on the developer carrier may have opposite polarity, causing toner to adhere to non-image areas, causing fog. Furthermore, if the developer carrier is stirred for a long period of time and a large number of prints are made, the toner may fuse to the surface of the developer carrier, resulting in streaks in the image. It turns out that points occur.

Therefore, an object of the present invention is to be able to stably and uniformly laminate toner in two or more layers on a developer carrier in the image forming method described above, and to prevent the toner from fusing to the developer carrier. An object of the present invention is to provide an image forming method capable of obtaining high-quality images with high image density, sharp contrast, and no background stains.

[Means to solve the problem]

As a result of extensive studies, the present inventors have found that the above object can be achieved by using a toner that contains a binder resin and a colorant, and is further blended with a powder substance that has specific thermal properties. Based on this knowledge, we have completed the present invention.

That is, according to the present invention, after the surface of the developer carrier having a chargeable and photoconductive surface is charged, the surface is selectively irradiated with light, so that the surface of the developer carrier near the surface of the developer carrier is charged. A large number of micro-closed chamber fields are formed, and a non-magnetic one-component developer made of toner to which an adjuvant is externally added as necessary is supplied onto this developer carrier, and the developer is transported by the micro-closed chamber fields. In an image forming method in which an electrostatic latent image is visualized by the developer carried on the surface of a developer carrier,
The toner consists of at least a binder resin and a colorant,
Moreover, the amount of powder material having a thermal conductivity of 6 W/mK or more at 300 K is 5 to 10 per 100 parts by weight of the binder resin.
There is provided an image forming method characterized in that 0 parts by weight of the compound is used.

In the present invention, in a developing method in which a large number of microfields are formed near the surface of a developer carrier, by using a toner containing a specific amount of a powder substance having high thermal conductivity, the toner is particularly absorbed on the developer carrier. Fusing is prevented, and even after long-term printing, images are as clear as the initial image, and no streaks appear on the image. The reason for this is not clear, but by incorporating a specific amount of a powder substance with high thermal conductivity into the toner, heat accumulation on the surface and inside of the toner is prevented, and heat is easily released from the toner.
As a result, melting of the resin is prevented, and it is presumed that the toner is prevented from fusing to the developer carrier even during long-term stirring.

Examples of the powder substance having a thermal conductivity of 6 W/mK or more at 300 K used in the toner used in the present invention include, for example,
Metals such as Ag, AQ, Au-B: Graphite: AQ20
．． , Fe3O4, Fe2O, and various other alloys.

In addition, if the blending amount of the powder substance having a thermal conductivity of 61/mK or more at 300K in the toner is less than 5 parts by weight per 100 parts by weight of the binder resin in the toner, it may be added to the developer carrier by long-term stirring. If the amount exceeds 100 parts by weight, the amount of the binder resin actually decreases, and the fixability may become insufficient.

As the binder resin used in the toner used in the present invention, all binders that have been used hitherto as binders for toners can be used. Specifically, styrene such as polystyrene, styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, and styrene-butadiene copolymer Examples include saturated polyester resins, unsaturated polyester resins, epoxy resins, phenol resins, maleic acid resins, coumaronic acid resins, chlorinated paraffins, xylene resins, vinyl chloride resins, polypropylene, and polyethylene. It goes without saying that two or more of these binder resins may be appropriately mixed and used. Among these, polystyrene,
Preference is given to using styrenic resins and epoxy resins.

Further, as the colorant used in the toner used in the present invention, all pigments and dyes that have been conventionally used as a colorant for toners can be used. Specifically, carbon black, lamp black, iron black, ultramarine blue, nigrosine dye, aniline blue calco oil blue, DuPont oil red, quinoline yellow, methylene blue chloride,
Phthalocyanine blue, phthalocyanine green, Hansa yellow G, rhodamine 6C lake, chrome yellow, quinacridone, benzidine yellow, malachite green, malachite green hexalate, oil black, azo oil black, rose bengal, monoazo dye and pigment, disazo dye and pigment, Examples include trisazo dyes and pigments and mixtures thereof.

Furthermore, the toner used in the present invention may contain a charge control agent, a fluidizing agent, or a releasing agent, if necessary. In this case, as a charge control agent.

Things that give positive polarity to the toner include nigrosine dyes, quaternary ammonium salts, basic dyes, amino acid-containing polymers, and things that give negative polarity include chromium-containing monoazo dyes, chlorine-containing organic dyes, Examples include metal salts of salicylic acid derivatives.

Examples of the fluidizing agent include 5102 whose surface has been made hydrophobic, inorganic oxides such as TiO2, inorganic fine particles such as SiC, and metal soaps such as stearin. In addition, as a mold release agent, in addition to synthetic waxes such as low molecular weight polyethylene and polypropylene, vegetable waxes such as candelilla wax, carnauba wax, rice wax, tree wax, and jojoba oil; beeswax, lanolin, and whale oil. Animal waxes such as wax; Mineral waxes such as montan wax and osikelite; Hydrogenated castor oil, hydroxystearic acid, and fatty acid amides.

Examples include oil-based waxes such as phenol fatty acid esters.

Furthermore, in addition to the above-mentioned components, the toner used in the present invention may optionally contain various plasticizers (dibutyl phthalate, dioctyl phthalate, etc.) for the purpose of adjusting the thermal properties, electrical properties, physical properties, etc. of the toner. Resistance adjusters (tin oxide, lead oxide,
It is also possible to add auxiliary agents such as antimony oxide (antimony oxide, etc.).

As described above, in the image forming method of the present invention, the surface of the developer carrier having a chargeable and photoconductive surface is charged, and then the surface is selectively irradiated with light to form an image. A large number of minute closed electric fields are formed near the surface of the developer carrier, and a non-magnetic one-component developer consisting of toner to which an auxiliary agent is externally added as necessary is supplied onto the developer carrier. The developer is supported on the surface of the developer carrier by an electric field.

The electrostatic latent image is visualized by the supporting developer.

This image forming method will be explained below.

FIG. 1 shows a developer carrier (developing roller) having a chargeable and photoconductive surface, which is useful for carrying out this image forming method.
1 schematically shows a developing device 2 equipped with a.

In FIG. 1, a developing device 2 is arranged close to a photoreceptor tram 3 that holds a latent image. Around the developing roller 1, there is a plate member 4 that regulates the thickness of the toner layer.
It is provided to be elastically pressed on the lower left side of the developing roller 1, and is configured to uniformly thin the toner 7 supplied from the toner tank 5 with the rotation of the agitator 6. The agitator 6 moves the toner 7 in the clockwise direction F2 by the resistance at its tip. An elastic roller member 8 for supplying toner is arranged on the lower right side of the developing roller l.

The toner supply roller 8 is made of a sponge material made of foamed urethane rubber, or a brush-shaped material made of fibers made of polyester, polytetrafluoroethylene, or the like. The toner supply roller 8 is connected to the developing roller 1 which has been given a deposition charge in advance by a method to be described later.
The toner 7 moved by the agitator 6 is rubbed onto the surface of the toner.

The toner 7 rubbed by the toner supply roller 8 is combined with the frictional scribble effect generated by the mutual friction between the toner supply roller 8 and the developing roller l to
Since the electricity is stabilized, the toner can be stably held on the surface of the developing roller 1 even though there is a relatively large toner layer. Then, the toner 7 is uniformly made into a thin layer as the developing roller 1 rotates by a plate member 4 provided to be elastically pressed on the lower left side of the developing roller 1, and then supplied to the developing area.

The plate member 4 is made by laminating a material having toner distribution performance such as urethane rubber to an elastic cylindrical plate spring.
Alternatively, an elastic member may be used as is.

Development of the latent image on the photosensitive drum 3 is carried out by transferring a desired amount of toner according to the latent image by a developing bias means 9 connected to the developing roller 1 and the toner supply roller 8. There is. The developing roller 1 is in a relationship of 30 to 50 mm so that it does not substantially contact the photoreceptors I to ram 3.
0R1 is preferably arranged at intervals of 50 to 250 squares. As a result, it is no longer necessary to apply an excessive load such as when developing a latent image by bringing the developing roller into contact with the photoreceptor, and it becomes possible to replace the rotary motor with a smaller one. If the photoreceptor is in the form of a flexible belt, the developing roller 1 may essentially be in contact with the photoreceptor. In this case, the thickness of the toner layer held on the surface of the developing roller 1 separates the two. If the circumferential speed of the photoreceptor drum 3 and the circumferential speed of the developing roller are approximately equal, then
Furthermore, it is possible to reduce the knocking torque.

In this relationship, if the developing bias applying means 9 is provided, a desired amount of toner can be transferred to the photosensitive drum 3. Of course, the level and polarity of the bias potential can be changed between normal development and reverse development. For the developing bias, an alternating current electric field can be used in combination in addition to a direct current electric field. As for the alternating current electric field, a rectangular wave pulsed electric field is set at a frequency of 300 to 2,000 Hz, preferably 500 to 1,500 Hz, and the time of the high potential part and the time of the low potential part are set at different ratios. When used with a waveform of
Moreover, it is possible to obtain an excellent developed image with less dirt on the background. The optimum ratio of the above ratio (duty ratio) differs depending on the polarity of the latent image and the polarity of the toner. The ratio of the time to the time of the low potential portion (-800V or less) may be 5 to 18:2 to 8. During regular development, if this ratio is generally reversed, the sharpness of the low latent image potential area will also be good, the image density will be high in the high latent image potential area, and the background will be less smudged.

Excellent developed images can be obtained.

A developing roller charging member 10 is arranged above and in contact with the developing roller 1 . The charging member 1o is made of a conductive sponge material made of foamed urethane rubber, or a brush-shaped fiber made from polyester, polytetrafluoroethylene, or the like with a conductive substance dispersed therein. The charging member 10 removes toner from the surface of the developing roller 1.

The function is to apply a voltage to the surface by applying a voltage from the power source 11. The removed toner is collected by the scraper 12 and will be used again. The charging member 1o may be any device that can apply a charge to the developing roller, and may be a normal corona charging device. The power source 11 may be one that superimposes alternating current in addition to direct current. In the example shown in FIG. 1, the potential applied to the developing roller 1 is 50-500V, preferably 100-300V, and therefore the voltage at which the power supply 11 operates is 300 to 2,000V, preferably 500V. to 1,000-no.

On the right side of the developing roller 1, there is a small point light source, for example, L.
A light irradiation member 13 consisting of an ED array element is arranged to erase the charges on the developing roller 1 in a desired pattern. As a result, on the surface of the developing roller 1, there are countless minute portions that have electrical charges and those that do not, and countless minute electric fields are formed between them.

Since these electric fields cause a phenomenon well known as the "edge effect" over the entire surface of the developing roller 1,
The adsorption and adhesion force of toner increases significantly compared to the case of a uniform electric field. In general, the increase rate is 5 to 2 times, and the amount of toner adhesion also increases at this rate. Through the above operation steps, the toner 7 moved by the agitator 6 is
The attraction and adsorption force of the charged charges held by the developing roller 1 and the frictional charging effect generated by the mutual friction between the toner supply roller 8 and the developing roller 1 combine to stabilize the charging of the toner. Even though there are relatively many toner layers on one surface, the toner is stably retained.

In general, the state called a thin layer with non-magnetic toner is 0.2 to 0.
．． 4mg/c+n2, and the state called multilayer is about 0.5
mg/cm" or more1 means that an amount of 0.8-1.2 mg/cm2 is usually present on the developing roller.

FIG. 2 shows another method for erasing the electrical charges on the developing roller 1 in a desired pattern, in which uniform irradiation light from a cold cathode tube light source 21 is transmitted through a transparent film 22 on which a minute electric field pattern is printed. The irradiation is performed in synchronization with the rotation of the developing roller 1. Since a staggered pattern is printed on the transparent film 22, a staggered charge pattern is also formed on the surface of the developing roller 1.

FIG. 3 shows yet another method for erasing the electrical charges on the developing roller 1 in a desired pattern. In this method, the light beam 32 emitted from the semiconductor laser light source 31 is made into a predetermined beam diameter with a collimator lens 33, and then rotated. A polygonal mirror 34 changes the direction, and a reflecting mirror 35 such as a prism scans the surface of the developing roller l. An arbitrary minute electric field can be formed on the developing roller 1 depending on the emission pattern of the laser beam.

The surface of the developing roller 1 is made of a chargeable and photoconductive material, and any material that can be generally used as an electrophotographic photoreceptor can be used. is available. For example, Se,
Pb, Cd, Zn, Si-based inorganic photoconductive materials and their compounds alone or dispersed in a binder material, carbocyclic compounds, heterocyclic compounds, pigment dyes, azo types,
The photoreceptor may be made of phthalocyanine-based, arylamine/arylmethane-based organic photoconductive materials, or polymeric photoconductive materials such as polyvinylcarbazole-based materials, either alone or in combination.

From the viewpoint of abrasion durability, it is preferable to use an amorphous silicon type material, and from the viewpoint of cost performance, it is preferable to use an organic photoreceptor or a dispersion type inorganic photoreceptor such as tin oxide. By configuring the structure of the developing roller 1 as described above,
A sufficient amount of toner with a stable charge is electrically adsorbed and maintained on the surface of the developing roller, so even if the photoreceptor and developing roller are used at the same speed, there is no reduction in image density. It never comes to life.

As is clear from the above description, according to the present method, the surface of the developer carrier is made of a chargeable and photoconductive material, so the structure of the developer carrier can be simplified. Costs can be reduced, and a sufficient amount of toner with a stable charge can be retained on the surface. Then, the rectangular wave pulsed electric field applied as a developing bias acts on a sufficient amount of toner with a stable charge amount, providing suitable mechanical energy for developing the latent image, resulting in good sharpness in low potential areas. , it is possible to obtain an excellent developed image with high image density in high potential areas and less dirt on the background. Furthermore, by configuring the structure of the developer carrier, the photoreceptor and the developer carrier can be used in a constant velocity relationship, so that the developer carrier can be used without reducing the image density. This reduces rotational load and also helps stabilize image quality. These effects also reduce the load placed on the toner, thereby prolonging its lifespan.

However, even in such a development method that forms many minute closed electric fields (microfields) near the surface of the developer carrier, if conventionally known toner is used as is, the It is difficult to keep the toner layer bi-stabilized by setting it to 2N or more, and the toner layer becomes thinner and the amount of toner developed decreases, resulting in low density in the image area and uneven toner layer. Uneven development may occur, resulting in non-uniform density in image areas, or toner on the developer carrier may have opposite polarity, causing toner to adhere to non-image areas and causing fog.

Furthermore, if the developer carrier is stirred for a long period of time and printing is performed many times, the toner may fuse to the surface of the developer carrier, resulting in streaks in the image.

However, when a toner containing a powder substance having the above-mentioned specific thermal properties is used, it is possible to form a stable multi-layer toner on the developer carrier, resulting in high image density, background smudges, and characters. It is possible to obtain high-quality images that do not cause bleeding, etc., and there is no fusion (filming) of the toner to the developer carrier, even during long-term printing, and it is possible to obtain high-density, high-quality images over a long period of time. You can get quality images.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples. Note that parts represent parts by weight.

Example 1 Low molecular weight polypropylene (mold release agent) 5.5 parts Azo pigment (coloring agent) 6 parts Zinc salicylate salt (
Charge control agent) 4 parts The above composition was mixed and melted and kneaded in a heated roll mill.

After cooling, it is pulverized using a hammer mill, and then pulverized using an air jet type pulverizer. The obtained finely pulverized product was classified to have an average particle size of 11 tones.

To 100 parts of the present particles, 0.2 parts of 5in2@ powder was added and mixed to obtain a toner.

Next, the developing roller shown in FIG. 2 was attached to the developing device shown in FIG. 1.

When the toner was loaded into the developing device and developed by rotating the developing roller and photoreceptor at a constant speed, a clear image with high image density and no background stains or fog was obtained. (The charged part of the photoreceptor is 1800V, the tip part is 1100V, and the toner is developed in the exposed part.) Furthermore, as a result of printing 5,000 sheets, the same clear image as the initial one was obtained. No abnormality in the image due to toner fusion to the developing roller was observed.

Comparative Example A toner for comparison was prepared in the same manner as in Example 1 except that AQ fine powder was not blended, and the toner was charged into the same developing device as in Example 1. When images were taken under these conditions, clear images were obtained.

However, after printing an additional s, ooo sheets, the toner was fused to the surface of the developing roller, and black streaks appeared on the image.

Example 2 Styrene/acrylic copolymer 100 parts (binding resin) Low molecular weight polypropylene (mold release agent) 5.5 parts Azo pigment (coloring agent) 10 parts Nigrosine dye (charge control agent) 3 parts Above composition The mixture was treated in the same manner as in Example 1 to obtain particles with an average particle size of 12 particles. To 100 parts of the present particles, 0.2 parts of TiO□ fine powder was added and mixed to obtain a toner.

The obtained toner was charged into the same developing device as in Example 1,
When the developing roller and the photoreceptor were rotated at a constant speed to perform development, a clear image with high image density and no background stains or fog was obtained.

(The charging part of the photoreceptor is -800V, and the exposure part is -100V.

Toner is developed on the charging section. Furthermore, as a result of printing 5,000 sheets, a clear image similar to the initial image was obtained, and no abnormality in the image due to toner fusion to the developing roller was observed.

Example 3 In Example 2, AQ20 was used instead of rutile titanium oxide.
A toner was prepared in the same manner as in Example 2, except that 20 parts of 3 fine powder (thermal conductivity at 300:361 m/nK) was blended.

When the obtained toner was evaluated in the same manner as in Example 2, clear images were obtained. Further, when 5,000 sheets were printed, a clear image similar to the initial image was obtained, and no abnormality in the image due to toner fusion to the developing roller was observed.

〔Effect of the invention〕

In the image forming method of the present invention, since a toner containing a powder substance having the above-mentioned specific thermal properties is used, a developer carrier having a chargeable and photoconductive surface is used. In a development method in which a large number of minute electric fields are formed near the surface of a developer carrier by selectively irradiating the surface with light after charging the surface of the developer carrier.
It is possible to form a stable multilayer toner on the developer carrier, and a high-quality image with high image density and no background stains or blurred characters can be obtained. Further, even if printing is performed for a long period of time, toner does not adhere to the developer carrier, and high-density, high-quality images can be obtained for a long period of time.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of a developing device that is useful in carrying out the present invention and is equipped with a developer carrier (developing roller) having a chargeable and photoconductive surface. FIG. 2 is a schematic cross-sectional view showing a method using a cold cathode tube light source for erasing the charges on the developing roller in a desired pattern. Furthermore, FIG. 3 is a schematic perspective view showing a method using a semiconductor laser light source for erasing the charges on the developing roller in a desired pattern. DESCRIPTION OF SYMBOLS 1... Developer carrying member (developing roller), 2... Developing device, 3... Photosensitive drum, 4... Toner layer thickness regulation blade member, 5... Toner tank, 6... Agitator, 7... Toner, 8... Toner supply roller, 9...
・Developing bias applying means, 10... Charging member, 11.
...Power supply, 12..Scraper, 13..Light irradiation member, 21..Cold cathode tube light source, 22.Transparent film, 31
... semiconductor laser light source, 32... light beam, 33.
... Collimator lens, 34 Rotating polygon mirror, 35 Reflector.

Claims (1)

[Claims] (1) After charging the surface of a developer carrier having a chargeable and photoconductive surface, by selectively irradiating the surface with light, a large number of minute closed electric fields are created near the surface of the developer carrier. A non-magnetic one-component developer consisting of toner to which an auxiliary agent is externally added as necessary is supplied onto this developer carrier, and the developer is transferred to the surface of the developer carrier by the minute closed electric field. In an image forming method in which an electrostatic latent image is visualized by the supported developer, the toner comprises at least a binder resin and a colorant, and has a thermal conductivity of 6 W/mK or more at 300K. An image forming method characterized in that a powder material is used in an amount of 5 to 100 parts by weight per 100 parts by weight of the binder resin.