JP2828173B2 - Image forming device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an image forming apparatus used for a printer, a copying machine, and the like.

(Prior Art) Conventionally, when an image is formed on a printer, a copying machine, or the like, an electrophotographic recording method based on the Carlson method is generally used.

FIG. 10 is a conceptual diagram of the image forming method based on the Carlson method.

In the figure, an image on a document read by an optical unit is first exposed by an exposure device 3 of a photosensitive drum 2 charged by corona discharge of a corona discharger 1, and is formed as an electrostatic latent image. After the electrostatic latent image is developed by the developing device 4, it is transferred onto the recording medium 8 by the transfer device 5 and fixed by the fixing device 6 to form an image.

Since the photosensitive drum 2 is used repeatedly, the residual toner after the transfer is cleaned by the cleaning device 7.

However, in the above conventional image forming apparatus,
Since the transfer process using the electrostatic action is used, the transfer rate is low, a process for cleaning the residual toner on the photosensitive drum 2 after the transfer is required, and further, maintenance work for discarding the collected toner is required. Required.
When the toner is discarded, there are problems such as soiling of the body and clothing and scattering of the toner inside and outside the apparatus.

In addition, there are many processes from the formation of the electrostatic latent image to the fixing of the toner image on the recording medium 8, which causes a problem that not only the device becomes complicated but also the size becomes large. Therefore, a cleaning device on the photosensitive drum 2 is unnecessary,
2. Description of the Related Art An image forming apparatus capable of downsizing the apparatus has been provided.

FIG. 11 is a schematic diagram of an image forming apparatus which does not require a cleaning device on a photosensitive drum.

In the figure, a drum-shaped electrostatic latent image carrier 101 formed by providing a photoconductive layer 101b on a conductive support 101a is rotated at a constant peripheral speed in the direction of an arrow by a driving unit (not shown). The electrostatic latent image carrier 101 has a photoconductive layer 101b formed on a conductive support 101a, and includes a selenium photoconductor,
Any of organic photoconductors, zinc oxide photoconductors, and amorphous silicon photoconductors can be used.

Reference numeral 102 denotes an endless developing object, which is stretched between the electrostatic latent image carrier 101, the pressure roll 103, and the pulling roll 111.
The object to be developed 102 is formed in a film shape having an insulating property, and moves in the direction of the arrow due to a frictional force with the electrostatic latent image carrier 101. A tension mechanism (not shown) is provided on the pulling roll 111 so that the developing object 102 moves at the same speed as the electrostatic latent image carrier 101, and applies an appropriate tension to the developing object 102.

The developing member 102 used here needs to generate lines of electric force corresponding to the electrostatic latent image formed on the electrostatic latent image holding member 101 between the developing member 102 and the toner holding member 107 during development. Therefore, it is insulative and thin, and is heated during transfer and fixing, so that heat resistance is required. In consideration of these, it is preferable to use a heat-resistant insulating film such as polyester, polyimide, polyetherimide, polyethersulfone, and polyetheretherketone.

Next, the operation of the image forming apparatus having the above configuration will be described.

First, the electrostatic latent image carrier 101 is uniformly and uniformly charged by using the charging device 104 provided to face the surface.
As the charging device 104, a corona charger as shown in the figure is generally used, but a brush charger or the like can also be used. Then, between the charging process and the exposure process, the developing object 102 moves at a constant speed while being in close contact with the electrostatic latent image carrier 101.

Next, the exposure device 105 irradiates the electrostatic latent image carrier 101 with light corresponding to an image signal after passing through the developing object 102 to form an electrostatic latent image. As the exposure device 105, in addition to the combination of the LED array and the Selfoc lens (trade name), any combination such as a combination of a laser and an image forming optical system can be used.

The developing device 106 is disposed so as to face the developing object 102 that is in close contact with the electrostatic latent image carrier 101, and the toner is placed on the toner carrier 107.
108 is sucked and conveyed in the direction of the arrow, and adheres to the developing object 102 corresponding to the electrostatic latent image formed on the electrostatic latent image carrier 101.

Here, reversal development is performed, and a bias potential is applied between the conductive support 101a of the electrostatic latent image carrier 101 and the toner carrier 107. With such a configuration, the toner carrier
In the space between 107 and the developing object 102, lines of electric force associated with the electrostatic latent image formed on the electrostatic latent image carrier 101 are generated through the developing object 102. For this reason, the charged toner 108 on the toner carrier 107 adheres to the portion of the developer 102 where the charge has disappeared due to the electrostatic force, and is developed to form a toner image.
As the developing device 106, any one of a two-component magnetic brush developing device, a one-component magnetic brush developing device, and a one-component non-magnetic developing device can be used.

Thereafter, the developing object 102 separated from the electrostatic latent image carrier 101 is conveyed to a transfer / fixing unit composed of a pressure roll 103 and a heating roll 113. Here, the final recording support 114 (generally paper) accommodated in the paper cassette 120 is
The skew of the final recording support 114 is corrected by being fed to the paper feed roll 116 that has been taken out by the paper feed roll 115 and stopped rotating.

Here, the paper feed roll 116 is activated, and the final recording support 114
Is sent to the transfer / fixing unit. The developing member 102 on which the toner image is formed and the recording support 114 are superposed here, and heated and pressed. At the time of transfer and fixing, the heat of the heat generating roll 113 melts the toner 108 on the developing object 102 via the final recording support 114 and penetrates between the fibers of the final recording support 114 by a pressurizing action. Transfer and fixing are performed simultaneously. The final recording support 114 on which the transfer and fixing have been performed in this manner is the discharge roll 1
The paper 17 is discharged outside the image forming apparatus.

On the other hand, a small amount of toner 108 may remain on the development target 102 after transfer and fixing, but is removed by a fixing cleaner 118 provided so as to press the pressure roll 103 against the pressure. At this time, the state of the toner 108 is still in the molten state in the fixing section, so that the residual toner can be easily wiped off.

On the other hand, after the electrostatic latent image carrier 101 is separated from the object to be developed 102 after the development process, the entire surface is irradiated with light by a charge removing lamp 119 serving as a charge removing means, and residual charges are removed. Thus, the electrostatic latent image carrier 101 is repeatedly used.

(Problems to be Solved by the Invention) However, in the conventional image forming apparatus,
In some cases, toner adheres to the non-image area to cause “ground fogging”, thereby deteriorating the image.

The present invention solves the above-mentioned problems of the conventional image forming apparatus, reduces the adhesion of the toner to the non-image portion without lowering the transfer rate, prevents the occurrence of "ground fogging", and provides an image with good contrast. It is an object of the present invention to provide an image forming apparatus capable of obtaining the following.

(Means for Solving the Problems) In order to achieve this, in the image forming apparatus of the present invention, an electrostatic latent image carrier, a developing member that partially contacts the electrostatic latent image carrier, Means for charging the surface of the electrostatic latent image carrier provided opposite the latent image carrier, means for exposing the charged electrostatic latent image carrier to form an electrostatic latent image, Means for forming a toner image corresponding to the electrostatic latent image on the electrostatic latent image carrier, provided on the surface of the latent image carrier with the object to be developed in close contact with the latent image carrier; A recording support is superimposed on a developing member on which an image is formed, and is provided to face the recording medium,
A means for transferring the toner image to the recording support;

The developing member is formed of a fluororesin film or a film serving as a substrate, which is coated with a fluororesin, and the surface on which the toner image is formed is formed of the fluororesin.

The toner used for development is a positively charged toner.

(Operation) According to the present invention, as described above, the electrostatic latent image carrier, the developing member that is partially in contact with the electrostatic latent image carrier, and the electrostatic latent image carrier facing the electrostatic latent image carrier. Means for charging the surface of the electrostatic latent image carrier, means for exposing the charged electrostatic latent image carrier to form an electrostatic latent image, and Means for forming a toner image corresponding to an electrostatic latent image on an electrostatic latent image carrier on a developing object, and a developing object on which the toner image is formed; Since a recording support is provided on the recording support and opposed to the recording support, a means for transferring a toner image to the recording support is provided. An electrostatic latent image is formed on the surface of the electrostatic latent image carrier.

Then, the electrostatic latent image carrier and the developing object are closely overlapped with each other, and a toner image corresponding to the electrostatic latent image is formed on the developing object by attaching toner to the developing object. .

The toner image is sent to a transfer unit, transferred to a recording support, and fixed simultaneously with or after the transfer.

The developing member is formed of a fluororesin film or a substrate film coated with a fluororesin, and the surface on which the toner image is formed is formed of the fluororesin. As the toner used for development is of a positive charge type, the toner is further positively charged by friction between the non-developers.

Therefore, the positively charged toner does not adhere to the non-image portion.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

In the image forming apparatus of the present invention, the toner 108 adhered to the developing object 102 in the transfer / fixing process is
To increase the transfer rate when transferring to 114,
The material 02 is made of a fluororesin film or a film coated with a fluororesin. FEP (Fluolinated Ethylene Propylene copo
limer, tetrafluoroethylene-6-propylene copolymer, PTFE (Polytetra Fluoro Ethylene, tetrafluoroethylene), PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer), CTFE (Poly Chloro Tri Fluo)
ro Ethylene, trifluoroethylene chloride, ETFE (Ethylene
-Tetre Fluoro Ethylene Copolymer, tetrafluoroethylene-ethylene copolymer), and any of them can be used.

FIG. 1 is a diagram showing the result of development using two types of toners, one having a positive (+) polarity and the other having a negative (-) polarity. The vertical axis indicates the recording density, and the horizontal axis indicates the developing bias potential.

In these toners, a binder resin such as a styrene-acrylic copolymer or polyester is used as a charge control agent. A positively charged toner is mixed with a nigrosine metal complex, and a negatively charged toner is mixed with an azo dye metal complex. Obtained.

At the time of development, a one-component non-magnetic development method in which non-magnetic toner is adhered to a toner carrier and developed is used. In addition to this, for example, any of a developing method such as a developing method using a magnetic toner as a single component and a two-component developing method using a mixture of a carrier and a toner may be used. The method of writing light on the electrostatic latent image carrier uses a reversal developing method in which an image portion is irradiated with light to form an electrostatic latent image, and toner is attached to a portion where the charge has disappeared. The developing object 102 is made of FEP (Fluolinated Ethylene Propy-lene) which is a fluororesin.
A Teflon (trademark) coated Kapton (trademark) film in which Copolimer (tetrafluoroethylene-6-fluoropropylene copolymer) is coated on a polyimide resin film is used.

The right part of the vertical axis in the drawing shows the recording density when the positively charged toner 108 is used. Since the reversal development is performed, the photoconductor used for the electrostatic latent image carrier 101 is of a positive charging type. On the other hand, as the positively charged photoconductor, a selenium-based photoconductor, a positively charged organic photoconductor, or the like can be used.

On the other hand, the left side of the vertical axis shows the negatively charged toner 108.
4 shows the recording density when using. Here, as the photosensitive member, a negatively charged organic photosensitive member, that is, a zinc oxide-based or cadmium sulfide-based photosensitive member can be used.

Both the plus and minus toners 108 increase the bias potential and the recording density of the image area increases and saturates to obtain a sufficient recording density. On the other hand, with regard to "ground fog", toner using negatively charged toner 108 exceeds the allowable limit density of "ground fog", and reduces toner adhesion to non-image areas in all development bias ranges. I can't. On the other hand, the image recorded using the positively charged toner 108 has a small amount of toner attached to the non-image portion.

FIG. 2 is a diagram showing the principle of adhesion of the negatively charged toner, FIG. 3 is a model diagram of the adhesion potential of the negatively charged toner, FIG. 4 is a diagram showing the principle of the adhesion of the positively charged toner, and FIG. It is a potential model diagram.

Both of them use reversal development in which the electrostatic latent image carrier 101 is irradiated with light and the toner 108 is attached to a portion where the charge has disappeared.

In FIG. 2, a charging process and an exposure process are performed on an electrostatic latent image carrier 101 before a developing process, so that an electrostatic latent image is formed. Then, before the development process,
102 moves at the same speed in close contact with the electrostatic latent image carrier 101. Here, a one-component toner developing method will be described as a developing method.

Also, since the development is reverse, a developing bias applying unit 121 is provided between the toner carrier 107 and the conductive support 101a of the electrostatic latent image carrier 101, and a developing bias potential is applied to the toner carrier 107. I have.

The toner carrier 107 rotates in the direction of the arrow shown in the figure, and the toner 108 supplied from a toner supply unit (not shown) adheres thereto. The toner 108 is charged by the frictional charging applying unit (here, charged negatively) and is conveyed to the developing unit. In the developing section, when a part of the toner 108 on the toner carrier 107 comes into contact with the object to be developed 102, the surface thereof is a fluororesin FEP (Fluolinated Ethylene Propylene).
(Copol-imer, tetrafluoroethylene-6-fluoropropylene copolymer), so that it is charged to the positive side with the opposite polarity. This is because the fluorine-based resin is located at the most negative side in the triboelectric series ("Electrostatic Handbook" edited by the Electrostatics Society of Japan, p. 59; "Plastic Film" edited by the Plastic Film Research Society, p. 137, published by Gihodo).

As a result, as shown in FIG.
On the image 102, in addition to the normally charged toner 108a (here, a negatively charged toner) adhering to the portion of the electrostatic latent image carrier 101, which is the image portion, where the charge has disappeared, there is a non-image portion. Toner charged to the opposite polarity even in areas where charges exist
108b (here, positively charged toner) adheres.

In the figure, on the negative side with respect to OV, the exposed residual potential V _r that forms the image portion of the electrostatic latent image carrier 101,
Developing bias potential V _b of the toner carrying member 107, the non-exposed portion potential V _s to form a non-image portion is provided. The arrows in the figure indicate the direction of the electric field.

In this case, the developing bias potential V _b, the toner 108a charged to a normal is set to a potential lower than the non-exposed portion potential V _s in order to suppress the adhesion of the non-image portion.

Of the toner 108 held on the toner carrier 107, the normally negatively charged toner 108a receives a force opposite to the direction of the electric field due to the Coulomb force and adheres to the image portion. Further, in the developing unit, the toner 108b charged to the positive side having the opposite polarity due to friction with the developing member 102 receives a force in the direction of the electric field and adheres to the non-image portion. As a result, the amount of the toner 108b attached to the non-image portion increases, and “ground fogging” occurs to deteriorate the image quality.

Referring to FIG. 4, a description will be given of a developing process when a positively charged toner is used. Again, the toner carrier
The toner 108 attached to the toner 107 is charged to a predetermined positive polarity by a charging means (not shown) before reaching the developing unit. When the surface of the toner 108 comes into contact with a film made of a fluorine-based resin in the developing section, the toner 108 is charged to a positive side more than the charged portion until the toner 108 reaches the developing section.
Therefore, as shown in FIG. 5, in the developing object 102, the charge corresponding to the image portion of the electrostatic latent image formed on the electrostatic latent image carrier 101 disappears, and the charged toner 108a
(Here, a positively charged toner) adheres. Since the amount of the negatively charged toner having the opposite polarity is very small, the toner 108 does not adhere to the portion where the charge corresponding to the non-image portion exists. In other words, image quality with high contrast can be obtained with very little "ground fog".

Next, a description will be given of the toner adhesion state when the normal development is performed.

FIG. 6 is a diagram showing the principle of adhesion of the negatively charged toner, FIG. 7 is a diagram showing the adhesion potential of the negatively charged toner, FIG. 8 is a diagram showing the principle of the adhesion of the positively charged toner, and FIG. It is a potential model diagram.

As shown in FIG. 6, an electrostatic latent image is formed on the electrostatic latent image carrier 101, and the object to be developed 102 is superimposed on the electrostatic latent image carrier 101 in close contact. Since the development is the regular development, the developing bias applying means 122 is provided so as to have the opposite polarity to that in the case of the reversal development in FIG.

When a negatively charged toner is used, as shown in FIG. 7, the electrostatic latent image carrier is
Residual potential V _r of the non-image portion is exposed to form the 101, developing bias potential V _b, the non-exposed portion potential V _s to form an image portion of the toner carrying member 107 is provided.

Then, the normally negatively charged toner 108a adheres to the image portion which is the non-exposed portion to form an image.

However, in the developing unit, a part of the toner 108a that has been charged to the negative side comes into contact with the developing object 102 and is frictionally charged to the positive side and adheres to the non-image part. Therefore, “ground fog” increases, and the image quality deteriorates.

On the other hand, when a positively charged toner is used, since the toner is not charged to the opposite polarity due to contact with the object to be developed 102 in the developing process, it is possible to perform recording with less "ground fog" and sufficient contrast. it can.

It should be noted that the present invention is not limited to the above embodiment, and various modifications are possible based on the gist of the present invention.
They are not excluded from the scope of the present invention.

For example, in addition to the FEP used here, PTFE (Polytetra Fluoro Ethylene, tetrafluoroethylene), PFA (Polytetrafluoroethylene-perfluoroalkoxyethylene copolymer), CTFE (Poly Chloro Tri Fluo
ro Ethylene, chlorofluoroethylene (ETF), ETFE (Ethylene
All fluororesins such as -Tetra Fluoro Et-hylene Copoylmer, tetrafluoroethylene-ethylene copolymer) can be used.

Further, in the present embodiment, the one-component developing method has been described, but other developing methods such as a two-component magnetic brush developing method can be applied.

Further, in the present embodiment, the electrostatic latent image body, which is the photosensitive member on which the electrostatic latent image is formed, and the film, which is the developing object, are overlapped,
A configuration is described in which a toner image is formed on a developing object corresponding to an electrostatic latent image in the form of an electrostatic latent image carrier, and this toner image is superimposed on recording paper and fixed simultaneously with transfer. It is not limited.

For example, the same effect can be obtained by a configuration in which a developing medium on which a toner image is formed and a recording sheet are superimposed and transferred, and then the toner on the recording sheet is fixed.

Further, a reversible thermosensitive recording medium is used as a developing object, an image is written on the reversible thermosensitive recording medium using a thermosensitive head, this is superposed on a photoconductor, and the entire surface is exposed. It may be used for an apparatus for forming.

(Effects of the Invention) As described above in detail, according to the present invention, the object to be developed is formed by coating a surface of a fluororesin film or a substrate film with a fluororesin,
The surface on which the toner image is formed is made of a fluorine-based resin, and the toner used for development is of a positive charge type, so that the toner is not charged to the opposite polarity during development, Further, it is charged to the normal polarity side.

Therefore, the amount of toner adhered to the non-image portion is reduced, and an image with less “ground fog” and sufficient contrast can be formed.

[Brief description of the drawings]

FIG. 1 is a diagram showing the result of development using two types of toners, one having a positive polarity (+) and the other having a negative polarity (−). FIG.
FIG. 3 is a diagram showing the adhesion potential model of the negatively charged toner, FIG. 4 is a diagram showing the principle of adhesion of the positively charged toner, FIG. 5 is a diagram showing the adhesion potential of the positively charged toner, and FIG. FIG. 7 is a diagram showing an adhesion potential model of a negatively charged toner during normal development, FIG. 8 is a diagram showing an adhesion principle of a positively charged toner during normal development,
FIG. 9 is a model diagram of the adhesion potential of the positively charged toner during normal development, FIG. 10 is a conceptual diagram of an image forming method using the Carlson method, and FIG. 11 is an image forming apparatus which does not require a cleaning device on the photosensitive drum. FIG. 101: electrostatic latent image carrier, 101a: conductive support, 101b: photoconductive layer, 102: developing object, 104: charging device, 105: exposure device, 106: developing device, 107: toner carrier, 108 ... toner, 111: pulling roll, 114: final recording support.

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Claims (1)

(57) [Claims] 1. An electrostatic latent image carrier, (b) an object to be developed that is partially in contact with the electrostatic latent image carrier, and (c) an electrostatic latent image carrier facing the electrostatic latent image carrier. (D) means for exposing the charged electrostatic latent image carrier to form an electrostatic latent image; and (e) means for exposing the charged electrostatic latent image carrier to form an electrostatic latent image. Means for forming a toner image corresponding to the electrostatic latent image on the electrostatic latent image carrier on the object to be developed, the means being provided so as to oppose the image bearing member on which the image developer is closely adhered; And (g) means for transferring the toner image to the recording support, which is provided so as to oppose the recording support on the development target on which the toner image has been formed; (H) a positively chargeable toner is used as the toner.