JP3652619B2 - Developing apparatus, charging method used therefor, and printing apparatus including the developing apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a developing device used in an electrophotographic image forming apparatus such as a copying machine, a printer, and a facsimile machine, a charging method used therefor, and a printing apparatus including the developing device.
[0002]
[Prior art]
In general, an electrophotographic image forming apparatus (electrophotographic apparatus) such as a copying machine, a printer, and a facsimile has an LSU, a photosensitive drum, and a developing device. Here, the LSU forms an electrostatic latent image on the surface of the photosensitive drum by irradiating the rotating photosensitive drum with laser light. The developing device develops (visualizes) the electrostatic latent image by supplying toner to the photosensitive drum.
[0003]
Further, the developing device has a developing roller provided so as to be adjacent to the photosensitive drum. Then, while supplying toner to the surface of the developing roller and rotating the developing roller in the opposite direction to the photosensitive drum, the toner can be sequentially supplied to the entire electrostatic latent image on the photosensitive drum. Is set.
[0004]
By the way, in such a developing device, development is performed by electrostatically adsorbing toner to the electrostatic latent image on the photosensitive drum. Therefore, it is necessary to charge the toner by some method.
[0005]
For example, in a developing device using a non-magnetic one-component toner or a magnetic one-component toner (a toner containing magnetic powder), a supply roller disposed opposite to the developing roller, and a downstream side (developing roller) And a layer thickness regulating blade (blade) provided on the downstream side in the rotation direction.
[0006]
Then, the toner is sequentially supplied to the surface of the rotating developing roller by the supply roller, and the thickness of the toner layer that stands on the developing roller is regulated by the blade. Further, the blade is a charging unit, and is set so as to frictionally charge the toner by rubbing against the toner as the charging unit. As a result, the toner for development can be charged.
[0007]
Further, in a developing device using a two-component developer in which a carrier is mixed with toner, the toner and the carrier are agitated and mixed in the toner tank before being supplied to the developing roller, and the friction between them is applied. In the same manner as described above, the toner is triboelectrically charged. In this case, the carrier becomes the charging means.
[0008]
[Problems to be solved by the invention]
However, in the configuration in which the toner is charged by friction with the blade (mechanical rubbing), it is necessary to increase the speed difference between the toner and the blade in order to obtain a sufficient charge amount. On the other hand, toner / blade is subjected to a mechanical / thermal load proportional to the speed difference.
[0009]
Therefore, if the speed difference is increased in order to obtain a sufficient charge amount, the mechanical / thermal load applied to the toner and the blade also increases, causing a problem that the toner is destroyed and deteriorated. Furthermore, the toner softened by frictional heat (sliding heat) is fused to the blade and the developing roller, leading to deterioration of the charging characteristics of the toner and failure of the developing device.
[0010]
Also, in the configuration in which the toner is charged by friction with the carrier, as in the configuration using the blade, it is necessary to stir the toner and the blade at a high speed to obtain a sufficient charge amount and to increase the speed difference between them. There is. Accordingly, an excessive mechanical / thermal load is applied to the toner and the carrier, which causes a problem that the toner carrier is destroyed and deteriorated. In addition, the toner softened by frictional heat is fused to the carrier, leading to deterioration of the charging characteristics of the toner.
[0011]
As described above, in a developing device using a method (contact charging method) in which a toner is brought into contact with a charging means such as a blade carrier with a large speed difference and the toner is charged by friction at that time (contact charging method), Large mechanical / thermal load on charging means such as blade carrier.
[0012]
The present invention has been made in view of the above-described conventional problems, and its purpose is to reduce the mechanical / thermal load on the toner and charging means for charging the toner to prevent the toner and the apparatus from deteriorating. Another object of the present invention is to provide a developing device that can perform the charging, a charging method used therefor, and a printing device including the developing device.
[0013]
[Means for Solving the Problems]
In order to solve the above-described problems, a developing device of the present invention is a developing device that is used in an electrophotographic apparatus and develops an electrostatic latent image on a latent image holding member with a charged developer. Holding means for transporting to the latent image holding body, an electron inducing part for inducing its own electrons by receiving light irradiation, and an irradiating means for irradiating the electron inducing part with light, Charging means for charging the developer by applying electrons to the developer, and a gap is provided between the charging means and the conveying means, and the flow of the electrons is controlled in the gap. It is characterized by having a grid electrode.
[0014]
According to the above configuration, since the gap is provided between the charging unit and the conveying unit, the developer and the charging unit have a large speed difference when charging the developer on the conveying unit. There is no contact in the state. Therefore, the mechanical / thermal load applied to the developer and the charging means can be suppressed. Thereby, the deterioration of the developer (development of the developer) and the deterioration of the apparatus can be prevented. In addition, it is possible to prevent deterioration of the charging characteristics of the developer due to the developer softened by the frictional heat between the charging unit and the conveying unit being fused to the charging unit or the conveying unit.
[0015]
Further, since the grid electrode is arranged, the flow of photoelectrons from the charging unit to the transport unit can be controlled. Therefore, variation in the charge amount in the developer can be suppressed, and the surface potential of the developer can be stabilized at a desired value. Thereby, the reliability of the developing device can be improved.
[0016]
In the developing device, the developer is negatively charged, and the absolute value of the charge amount is preferably 5 μc / g or more and 30 μc / g or less.
[0017]
When the charge amount of the developer is −5 μc / g or more, the developer and the transporting unit can adhere to each other in the developer transport process, and an increase in the scattering of the developer during transport can be prevented. . Further, when developing the electrostatic latent image on the latent image holding member, the developer can be adsorbed to the latent image holding member. For example, when the developing device is provided in the printing device, the printing density is lowered. Can be prevented.
[0018]
On the other hand, when the charge amount of the developer is −30 μc / g or less, when developing the electrostatic latent image on the latent image holding member, the developer is not excessively attracted to the latent image holding member. Thereby, for example, when the developing device is provided in the printing device, it is possible to prevent the print density from rising and the occurrence of print fogging. Thus, a charge amount of −5 μc / g to −30 μc / g is an appropriate charge amount when developing using a developer. Thereby, the reliability of the developing device can be improved.
[0019]
In the developing device, it is preferable that a voltage having a value obtained by adding a voltage value for charging the developer to a value of the voltage applied to the conveying unit is applied to the grid electrode.
[0020]
According to the above configuration, the developer on the transport unit can be charged by the difference between the voltage applied to the grid electrode and the voltage applied to the transport unit. Therefore, the surface potential of the developer can be stabilized at a desired value.
[0021]
In the developing device, the electron inducing portion is preferably made of a semiconductor or metal.
[0022]
According to said structure, the charging means which has an electron induction part can discharge | release an electron easily (it has a photoelectric effect). Therefore, since electrons induced by light irradiation can be directly imparted to the developer, the developer can be easily charged. As a result, the developer can be charged even if a gap is provided between the charging unit and the conveying unit.
[0023]
In the developing device, it is preferable that a bias voltage is applied between the electron inducing unit and the transport unit.
[0024]
According to said structure, the electron induced from the electron induction part is accelerated toward the conveyance means, causing the electron multiplication by an avalanche phenomenon between a charging means and a conveyance means. At this time, the accelerated electrons become gas molecules in the air (for example, O ₂ , N ₂ Etc.) and ionizing them, new electrons can be generated one after another.
[0025]
In the developing device, a supply unit that supplies the developer to the conveyance unit and a charging unit are arranged on the conveyance unit in the order along the direction in which the developer is conveyed, and the supply unit is conveyed. It is preferable to regulate the thickness of the developer on the conveying means to a constant thickness.
[0026]
According to said structure, the thickness of the developer on a conveyance means can be controlled with a supply means. In this way, the developer can be reliably charged by keeping the thickness of the developer constant. Therefore, it is possible to prevent variation in the charge amount of the developer and improve the charge performance of the developer. Thereby, the reliability of the developing device can be improved.
[0027]
In the developing device, voltages having the same polarity are applied to the charging unit, the grid electrode, and the transport unit, respectively, and the absolute value of these voltages is
Applied voltage to charging means> Applied voltage to grid electrode> Applied voltage to conveying means
It is preferable to satisfy the relationship.
[0028]
According to said structure, the absolute value of the applied voltage to a charging means is larger than the absolute value of the applied voltage to a grid electrode. Thereby, the electrons jumping out from the charging means can be discharged from the grid electrode to the developer.
[0029]
Further, the absolute value of the voltage applied to the grid electrode is larger than the absolute value of the voltage applied to the conveying means. As a result, the developer can be charged by the difference between the voltage applied to the grid electrode and the voltage applied to the conveying means.
[0030]
In the developing device, the developer is preferably a one-component toner.
[0031]
According to the above configuration, when toner is used as the developer of the developing device, image quality deterioration and device failure due to melting thereof can be effectively prevented.
[0032]
In the developing device, it is preferable that a wavelength changing unit that changes the wavelength of light emitted from the irradiation unit is disposed between the electron induction unit and the irradiation unit that irradiates the electron induction unit with light.
[0033]
According to the above configuration, the wavelength of the light can be changed without separately preparing an irradiating unit that irradiates light having an optimum wavelength in the charging unit. Thereby, the wavelength of the light irradiated to an electron induction part can be changed easily, without changing an irradiation means. Therefore, the wavelength can be adjusted according to the material of the electron inducing portion, and the charging efficiency can be improved. In addition, the cost of the irradiation means can be reduced.
[0034]
In the above developing device, it is preferable that the irradiation unit is arranged to face the transport unit with the electron inducing portion interposed therebetween.
[0035]
According to said structure, the light from an irradiation means can reach | attain an electron induction part, without irradiating a developing agent etc. Accordingly, it is possible to prevent the light amount of the irradiation unit from being attenuated by hitting the developer, and to secure the light amount of the irradiation unit. In addition, the irradiation unit can be prevented from being contaminated by the developer.
[0036]
The charging method of the present invention is a charging method for charging a developer that develops an electrostatic latent image into a visible image, and irradiates light to an electron inducing material that induces its own electrons by being irradiated with light. The developer is charged by discharging the induced electrons to the developer via the grid electrode.
[0037]
According to the above configuration, development is performed by irradiating light to an electron inducing material that induces its own electrons by being irradiated with light, and charging the developer by discharging the induced electrons to the developer. The mechanical / thermal load applied to the charging means for charging the developer and developer can be suppressed. Thereby, destruction of the developer can be prevented. In addition, it is possible to prevent deterioration of the charging characteristics of the developer.
[0038]
In addition, by discharging the induced electrons to the developer via the grid electrode, it is possible to suppress variation in the charge amount in the developer, and to stabilize the surface potential of the developer at a desired value. .
[0039]
A printing apparatus according to the present invention includes a latent image holding body that holds an electrostatic latent image formed based on an image signal, and the above-described developing device that develops the electrostatic latent image. Yes.
[0040]
According to the above configuration, a printing device with high reliability can be provided by including the developing device.
[0041]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to FIGS. 1 to 9 as follows.
[0042]
FIG. 1 is an explanatory diagram illustrating a configuration of a printing apparatus according to the present embodiment. As shown in FIG. 1, the printing apparatus according to the present embodiment includes a developing unit (developing apparatus) 1, a photosensitive drum 2, a charging roller 3, a transfer roller 4, a fixing roller pair 5, and an LSU (laser beam scanner). Unit) 6. As the developer, a one-component non-magnetic toner is used.
[0043]
The photoreceptor drum 2 has a photoreceptor on its surface and has a drum shape. The photosensitive drum 2 is rotationally driven in the direction of arrow A at a speed of 50 to 150 mm / s.
[0044]
The charging roller 3 uniformly charges the surface of the photosensitive drum 2 to a predetermined potential. The charging roller 3 is driven to rotate in the direction of arrow B (the direction opposite to the direction of arrow A) at the same speed as the photosensitive drum 2.
[0045]
The LSU (laser beam scanner unit) 6 exposes the surface of the charged photosensitive drum 2 with laser light (arrows in FIG. 1). The surface of the photosensitive drum 2 has a function of forming an electrostatic latent image according to image data input from the outside.
[0046]
The developing unit 1 forms a toner image on the photosensitive drum 2 by developing the electrostatic latent image formed by the LSU 6. The developing unit 1 will be described in detail later.
[0047]
As described above, the surface of the photosensitive drum 2 uniformly charged to a predetermined potential by the charging roller 3 is exposed by the laser light from the LSU 6. As a result, an electrostatic latent image corresponding to image data (image signal) input from the outside is formed on the surface of the photosensitive drum 2. Then, toner is attached to the electrostatic latent image on the photosensitive drum 2 by a later-described developing roller 11 in the developing unit 1, and the electrostatic latent image is developed to form a toner image.
[0048]
The transfer roller 4 transfers the toner image on the photosensitive drum 2 to the sheet P.
[0049]
The fixing roller pair 5 heat-fixes the toner image on the sheet P by heat-pressing the sheet P on which the toner image is transferred.
[0050]
Next, the developing unit 1 that is a characteristic configuration of the printing apparatus according to the present embodiment will be described.
[0051]
As shown in FIG. 1, the developing section 1 includes a developing tank 10, a developing roller (conveying means) 11, a toner supply roller (supplying means) 12, a toner charging roller (charging means) 13, a stirring roller 14, and a grid electrode. 40.
[0052]
The developing tank 10 is a storage tank (toner tank) for storing the toner T.
[0053]
The agitating roller 14 agitates the toner T, which is the toner in the developing tank 10, and conveys the toner T to the vicinity of the toner supply roller 12 in an open state, that is, without applying any load.
[0054]
The developing roller 11 has a cylindrical shape in which a rubber layer 21 made of a conductive rubber elastic material is provided on an Al (aluminum) element 22. The developing roller 11 is a rotating roller provided so as to face the photosensitive drum 2, and has a speed of 50 to 150 mm / s (photosensitive drum 2 in the direction of arrow B (the direction opposite to the photosensitive drum 2)). At the same speed), while being held in contact with the photosensitive drum 2 while being held in toner. As a result, the toner T can be adhered to the electrostatic latent image on the photosensitive drum 2, and the electrostatic latent image can be developed to form a toner image.
[0055]
The toner supply roller 12 is a rotating roller made of a cylindrical foaming rubber elastic material. Further, the toner supply roller 12 is disposed opposite to the developing roller 11 in the developing tank 10. A predetermined bias voltage is applied to the toner supply roller 12 so that the toner T in the developing tank 10 can be adsorbed and held. The toner T is held in contact with the developing roller 11 while rotating at the same speed as the developing roller 11 in the opposite direction (A direction) to the rotating direction (B direction) of the developing roller 11 while holding the toner T. Yes. As a result, the toner T in the developing tank 10 is supplied to the outer peripheral surface of the developing roller 11. Hereinafter, the toner layer on the outer peripheral surface of the developing roller 11 is referred to as a toner layer. At this time, by supplying the toner T to the developing roller 11 while the toner supply roller 12 rotates, the thickness of the toner layer on the developing roller 11 can be made constant (aligned). That is, the toner supply roller 12 also has a function of regulating the thickness of the toner layer.
[0056]
A toner charging roller 13 is disposed so as to face the toner supply roller 12 with the grid electrode 40 interposed therebetween.
[0057]
The toner charging roller 13 is disposed so as to face the downstream side of the toner supply roller 12 and the upstream side of the photosensitive drum 2 along the rotation direction (B direction) of the developing roller 11. The toner charging roller 13 is a rotating roller and rotates at a constant speed in the opposite direction (A direction) to the developing roller 11.
[0058]
Further, as shown in FIG. 2, the toner charging roller 13 has an ITO layer 31 and a metal layer 32 formed on a base roller 30, and an ultraviolet irradiator (irradiation means) 33 in the base roller 30. It is the structure equipped with.
[0059]
The ultraviolet irradiator 33 is an ultraviolet lamp (low pressure mercury lamp), and is a light source that irradiates ultraviolet rays from the inside of the base roller 30 toward the outside. By irradiating the ultraviolet rays on the toner layer, charging of the toner on the developing roller 11 is induced.
[0060]
The base roller 30 is a cylindrical roller made of quartz glass or transparent acrylic resin having ultraviolet transparency.
[0061]
The ITO layer 31 is an electrode made of conductive ITO (Indium-Tin-Oxide: oxide of indium and tin) that can transmit ultraviolet rays, and is formed on the base roller 30 by coating. A bias voltage of −900 V to −1500 V is applied between the ITO layer 31 and the developing roller 11 according to the rotational speed of the photosensitive drum 2.
[0062]
The metal layer (electron inducing part) 32 is formed on the ITO layer 31 and has a function of emitting electrons (photoelectrons) by the photoelectric effect when irradiated with ultraviolet rays from the ultraviolet irradiator 33. The metal layer 32 is made of a semiconductor or a metal such as aluminum (Al).
[0063]
The material of the metal layer 32 is not particularly limited as long as the material has a photoelectric effect (electron induced material). Moreover, titanium oxide used for a photocatalyst may be used.
[0064]
As described above, the toner supply roller 12 also has a function of regulating the thickness of the toner layer. By making the thickness of the toner layer on the developing roller constant, the toner in the toner layer is reliably charged. Can be done. Therefore, it is possible to prevent variation in the charge amount of the toner and to improve the charging performance of the toner. As a result, the reliability of the developing unit 1 can be improved.
[0065]
Hereinafter, the operation of the developing unit 1 will be described.
[0066]
When development is started, the toner supply roller 12 sequentially forms toner layers on the surface of the development roller 11 along the circumferential direction. Thereafter, the toner layer of the developing roller 11 is conveyed between the developing roller 11 and the toner charging roller 13. Then, the toner charging roller 13 imparts electrons emitted from the metal layer 32 to the toner, so that the toner is photoelectron charged.
[0067]
Thereafter, the charged toner is sent to a portion facing the photosensitive drum 2 and electrostatically attracted (supplied) to the electrostatic latent image on the photosensitive drum 2. Thereby, the electrostatic latent image is developed (visualized) as a toner image.
[0068]
Next, photoelectric charging by the toner charging roller 13 will be described.
[0069]
In the toner charging roller 13, electrons e are induced and emitted from the metal layer 32 to the outside by the photoelectric effect due to the irradiation of ultraviolet rays by the ultraviolet irradiator 33.
[0070]
A bias voltage of −900 V to −1500 V is applied between the ITO layer 31 and the developing roller 11. Accordingly, the electrons e induced from the metal layer 32 are accelerated toward the developing roller 11 by the bias voltage and causing electron multiplication due to the avalanche phenomenon between the rollers 12 and 13. Then, after the amount of electrons e reaching the toner on the developing roller 11 is adjusted in the grid electrode 40 described later (the flow of electrons e is controlled), the electrons e that are supposed to reach the toner on the developing roller 11 are controlled. Only reaches the toner.
[0071]
With this electron e, the toner is charged to a desired charge amount of −5 μC / g or more, more preferably −10 μC / g or more. The toner e charges the toner layer to a desired charge amount of −30 μC / g or less, more preferably −20 μC / g or less.
[0072]
As described above, when the charge amount of the toner is −5 μc / g or more, when the toner is transported by the developing roller 11, the toner and the developing roller 11 can adhere to each other, and the scattering of the toner during transport is increased. Can be prevented. Further, when developing the electrostatic latent image on the photosensitive drum 2, the toner can be attracted to the photosensitive drum 2. For example, when the developing unit 1 is provided in the printing apparatus, the printing density is reduced. Can be prevented.
[0073]
On the other hand, when the charge amount of the toner is −30 μc / g or less, when the electrostatic latent image on the photosensitive drum 2 is developed, the toner is not excessively attracted to the photosensitive drum 2. Thereby, for example, when the developing unit 1 is provided in a printing apparatus, it is possible to prevent an increase in printing density and occurrence of printing fog. Thus, a charge amount of −5 μc / g to −30 μc / g is an appropriate charge amount when developing using a developer. As a result, the reliability of the developing unit 1 can be improved.
[0074]
Here, the photoelectric effect will be described. Electrons (surface electrons) on the surface of a metal or semiconductor are induced and emitted to the outside by receiving energy of a predetermined value (work function) or more from the outside. The photoelectric effect is a phenomenon in which energy as described above is imparted to surface electrons by light irradiation and emitted as electrons.
[0075]
Further, an example of photoelectric charging used in the developing unit 1 will be specifically shown. Here, an example of a photoelectron charging experiment in which electrons are induced from the toner charging roller 13 by the irradiation of ultraviolet rays will be described with reference to FIG.
[0076]
First, a pseudo flat plate is produced instead of the toner charging roller 13. The flat plate is formed by first vacuum depositing ITO 61 and a semiconductor 62 made of GaAs on the surface of the transparent acrylic plate 60 in this order. Then, instead of the toner T as the member to be charged, a polyester resin PES 63 which is a toner material is placed on the flat plate.
[0077]
Here, the thickness k of the transparent acrylic plate 60 is 1 to 5 mm, the thickness m of the ITO 61 is several tens of nm, the thickness l of the semiconductor 62 is several tens of nm, and the thickness n of the PES 63 is 10 to 100 μm.
[0078]
Thereafter, the ultraviolet irradiator 33 irradiates ultraviolet rays having a wavelength λ of 350 nm from the side of the flat plate facing the surface on which the PES (polyethersulfone) 63 is formed. At this time, the irradiation energy is 0.1 to 10 mW / cm 2 and the irradiation time is several seconds.
[0079]
As a result, the surface of PES63 could be charged to -150 to -30V. This indicates that the toner can be charged even when there is no speed difference between the toner as the member to be charged and the toner charging roller 13 as the charging member.
[0080]
The avalanche phenomenon is as follows. That is, the electrons induced from the metal layer 32 and accelerated by the bias voltage are gas molecules (O in the air) between the toner charging roller 13 and the developing roller 11. ₂ , N ₂ Etc.) and ionize them to emit electrons. Then, new electrons generated by this ionization are accelerated by the bias voltage, further ionize other molecules, and emit new electrons. Such an increase in electrons is an avalanche phenomenon.
[0081]
In this way, if the avalanche phenomenon is used, the electrons generated by the photoelectric effect are accelerated by the bias voltage, collide with gas molecules in the air, and ionize them to generate new electrons, which in turn are ionized. It becomes possible to participate in. Further, with the number of electrons increased by this avalanche phenomenon as a target value, the ultraviolet irradiation intensity and the applied voltage are determined.
[0082]
As described above, the toner charging roller 13 rotates at a constant speed with the developing roller 11 in a non-contact manner with the developing roller 11 so that the toner layer on the developing roller 11 is charged to a predetermined voltage value by photoelectric charging. It has become. As a result, the region of the metal layer 32 that is irradiated with light by the ultraviolet irradiator 33 and induces electrons to be applied to the toner is not always constant, and moves as the toner charging roller 13 rotates. Therefore, it is possible to irradiate the refresh surface with light, thereby promoting the generation of electrons and reducing the amount of irradiation light.
[0083]
In addition, since the metal layer 32 is made of a semiconductor or metal, the metal layer 32 can easily emit electrons (has a photoelectric effect). Therefore, electrons induced by light irradiation can be directly applied to the toner, so that the toner can be easily charged. Thus, even if a gap is provided between the developing roller 11 and the toner charging roller 13, the toner on the developing roller 11 can be charged.
[0084]
The distance between the toner charging roller 13 and the grid electrode 40 is preferably 50 to 500 μm, and the distance between the grid electrode 40 and the developing roller 11 is preferably 50 to 500 μm.
[0085]
In addition, since a gap is provided between the developing roller 11 and the toner charging roller 13, the toner and the toner charging roller 13 have a large speed difference when charging the toner on the developing roller 11. There is no contact. Therefore, the mechanical / thermal load applied to the toner and the toner charging roller 13 can be suppressed. As a result, toner deterioration (toner destruction) and apparatus deterioration can be prevented. In addition, it is possible to prevent toner charging characteristics from deteriorating due to the toner softened by the frictional heat between the developing roller 11 and the toner charging roller 13 being fused to the developing roller 11 and the toner charging roller 13.
[0086]
As described above, the one-component toner is charged by photoelectron charging. As a method for charging the toner, a method using a toner containing a P compound is also conceivable. In this method, the chemical structure of the P compound is changed by irradiating the toner with light in the developing tank, and this is brought into a free radical state. Then, the toner is charged (+ charged) by extracting the electrons of the toner with the P compound in the free radical state.
[0087]
However, in this method, since it is necessary to contain the P compound in the toner, there is a problem that the normal toner cannot be used and the operation cost becomes high. In this method, in order to quickly and sufficiently charge the toner, it is necessary to increase the amount of the P compound. However, the increase in the P compound as a crystalline substance increases the density of the toner image obtained by development ( (Concealment ratio) is lowered, and the toner is fragile, causing a toner crash.
[0088]
Hereinafter, the grid electrode 40 will be described in detail.
[0089]
As shown in FIG. 4, the grid electrode 40 is an electrode that is disposed between the developing roller 11 and the toner charging roller 13 and controls the flow of electrons e from the toner charging roller 13. Moreover, the shape is a net shape as shown in FIG.
[0090]
First, control of the flow of electrons e in the grid electrode 40 will be described with reference to FIG.
[0091]
As shown in FIG. 6, the grid electrode 40 is disposed between the developing roller 11 and the toner charging roller 13. Further, it is assumed that the X (V) voltage is applied to the toner charging roller 13 and the Y (V) voltage (grid voltage) is applied to the grid electrode 40. The relationship between the absolute value of X and the absolute value of Y is | X |> | Y |.
[0092]
In this way, by making the absolute value of the voltage applied to the toner charging roller 13 larger than the absolute value of the voltage applied to the grid electrode 40, electrons that have jumped out of the metal layer 32 of the toner charging roller 13 can be transferred to the grid electrode. The toner on the developing roller 11 can be discharged from 40.
[0093]
In the grid electrode 40, the electron e jumping out from the toner charging roller 13 has a potential (hereinafter referred to as a surface potential) of a surface (surface layer) facing the toner charging roller 13 of the toner on the developing roller 11 as Y (V). Until it becomes, it releases to the toner. Here, e1 emitted to the toner side is assumed to be e1.
[0094]
On the other hand, when the surface potential of the toner layer becomes Y (V), the electronic e is controlled so as not to jump out to the developing roller 11 side. Here, an electron e that is regulated by the grid electrode 40 and cannot be emitted from the grid electrode 40 to the developing roller 11 side is represented by e2.
[0095]
As described above, the grid electrode 40 controls the flow of electrons from the toner charging roller 13 to the developing roller 11. As a result, the surface potential of the toner layer is stabilized, and hence variation in the charge amount in the toner layer can be suppressed. As a result, charging in the toner layer can be stabilized, and the reliability of the developing unit 1 can be improved.
[0096]
Next, the surface potential of the toner layer between the case where the grid electrode 40 is arranged between the developing roller 11 and the toner charging roller 13 and the case where the grid electrode 40 is not arranged is compared based on FIG. FIG. 7 is a graph showing the relationship between the displacement in the rotation direction of the developing roller 11 and the surface potential of the toner layer in the toner layer. Further, it is assumed that the grid electrode 40 controls the flow of electrons e so that the surface potential of the toner becomes Z.
[0097]
As shown in FIG. 7, when the grid electrode 40 is provided, the surface potential is stable at Z as indicated by the dotted line 51. On the other hand, as shown by the solid line 52, when the grid electrode 40 is not disposed, the surface potential of the toner layer is Z with respect to Z due to the fluctuation of the applied toner voltage and the toner material. Become unstable.
[0098]
Further, as shown in FIG. 8, the applied voltage to the toner charging roller 13 is -900 to -1500 V, and the applied voltage to the developing roller 11 is -400 to -500 V. At this time, in order to set the charge amount of the toner layer to, for example, −10 μC / g to −20 μC / g, which is an appropriate charge amount during development, a voltage of −50 V is required. Therefore, the surface potential of the toner layer needs to be −450 to −550V.
[0099]
On the other hand, a voltage having the same potential as the surface potential of the toner layer is applied to the grid electrode 40. Therefore, in order to set the surface potential of the toner layer to −450 to −550V, the grid voltage is also set to −450 to −550V. That is, since the grid voltage and the surface potential of the toner layer have the same value, it is only necessary to apply a voltage to the grid electrode 40 as much as the surface potential of the desired toner layer. Thus, by providing the grid electrode 40, the charge amount of the toner can be set to a desired value.
[0100]
Thus, the absolute value of the voltage applied to the grid electrode 40 is larger than the absolute value of the voltage applied to the developing roller 11. Thereby, the toner in the toner layer can be charged by the difference between the voltage applied to the grid electrode 40 and the voltage applied to the developing roller 11.
[0101]
In addition, a voltage having a value obtained by adding a voltage value for charging the toner layer to the value of the voltage applied to the developing roller 11 is applied to the grid electrode 40, thereby applying the voltage to the grid electrode 40. The toner can be charged by the difference between the voltage applied to the developing roller 11 and the voltage applied to the developing roller 11. Therefore, the surface potential of the toner layer can be stabilized at a desired value.
[0102]
The developing unit 1 described above is not limited to a printing apparatus, and can be applied to an electrophotographic image forming apparatus (electrophotographic apparatus) such as a copying machine, a printer, or a facsimile.
[0103]
Further, a wavelength conversion element (wavelength changing means) 70 may be provided between the toner charging roller 13 and the ultraviolet irradiator 33 as shown in FIG. At this time, it is assumed that a light beam having a wavelength of 700 nm is emitted from the ultraviolet irradiator 33.
[0104]
Here, a photoelectrostatic charging experiment in which electrons are induced from the toner charging roller 13 by the irradiation of ultraviolet rays using the same plate as that used in the experiment shown in FIG. An example will be described with reference to FIG.
[0105]
The wavelength conversion element 70 is made of a nonlinear optical material. In this case, light having a wavelength of 700 nm emitted from the ultraviolet irradiator 33 is converted into ultraviolet light having a wavelength of 350 nm by the wavelength conversion element 70 and irradiated to the semiconductor 62. Accordingly, it is not necessary to separately prepare an ultraviolet light emitter that irradiates the semiconductor 62 with ultraviolet light having an optimum wavelength of 350 nm, and the wavelength can be easily changed to ½ using the existing ultraviolet light emitter 33. Thus, the wavelength can be easily adjusted according to the material of the metal layer 32, and the charging efficiency can be improved. Further, the cost of the ultraviolet irradiator 33 can be reduced.
[0106]
【The invention's effect】
As described above, the developing device of the present invention is a developing device that is used in an electrophotographic apparatus and develops an electrostatic latent image on a latent image holding member with a charged developer, and holds the developer. A transporting means for transporting the latent image holding member; an electron inducing part for inducing electrons by being irradiated with light; and an irradiating means for irradiating the electron inducing part with light. Charging means for charging the developer by being applied to the agent, and a gap is provided between the charging means and the conveying means, and the gap is provided with a grid electrode for controlling the flow of electrons. It is the composition which is.
[0107]
Thus, when charging the developer on the conveying unit, the developer and the charging unit do not come into contact with each other with a large speed difference. Therefore, the mechanical / thermal load applied to the developer and the charging means can be suppressed. Thereby, the deterioration of the developer (development of the developer) and the deterioration of the apparatus can be prevented. In addition, it is possible to prevent deterioration of the charging characteristics of the developer due to the developer softened by the frictional heat between the charging unit and the conveying unit being fused to the charging unit or the conveying unit.
[0108]
In addition, the flow of electrons from the charging unit to the transport unit can be controlled. Therefore, variation in the charge amount in the developer can be suppressed, and the surface potential of the developer can be stabilized at a desired value. As a result, the reliability of the developing device can be improved.
[0109]
The developing device of the present invention is configured such that the developer is negatively charged and the absolute value of the charge amount is 5 μc / g or more and 30 μc / g or less.
[0110]
Thereby, in the developer transporting step, the developer and the transporting unit can adhere to each other, and an increase in the scattering of the developer being transported can be prevented. Further, when developing the electrostatic latent image on the latent image holding member, the developer can be adsorbed to the latent image holding member. For example, when the developing device is provided in the printing device, the printing density is lowered. Can be prevented.
[0111]
Further, when developing the electrostatic latent image on the latent image holding member, the developer is not excessively attracted to the latent image holding member. Thereby, for example, when the developing device is provided in the printing device, it is possible to prevent the print density from rising and the occurrence of print fogging. Therefore, there is an effect that the reliability of the developing device can be improved.
[0112]
The developing device of the present invention is configured such that the grid electrode is applied with a voltage value obtained by adding a voltage value for charging the developer to a voltage value applied to the conveying means.
[0113]
As a result, the developer on the transport unit can be charged by the difference between the voltage applied to the grid electrode and the voltage applied to the transport unit. Therefore, there is an effect that the surface potential of the developer can be stabilized at a desired value.
[0114]
In the developing device of the present invention, the electron inducing portion is made of a semiconductor or metal.
[0115]
Thereby, the charging means having the electron inducing portion can easily emit electrons (has a photoelectric effect). Therefore, since electrons induced by light irradiation can be directly imparted to the developer, the developer can be easily charged. As a result, the developer can be charged even if a gap is provided between the charging unit and the conveying unit.
[0116]
The developing device of the present invention has a configuration in which a bias voltage is applied between the electron inducing portion and the conveying means.
[0117]
As a result, the electrons induced from the electron inducing portion are accelerated toward the conveying means while causing electron multiplication due to the avalanche phenomenon between the charging means and the conveying means. At this time, the accelerated electrons become gas molecules in the air (for example, O ₂ , N ₂ Etc.) and ionizing them, it is possible to generate new electrons one after another.
[0118]
In the developing device of the present invention, a supply means for supplying the developer to the conveyance means and a charging means are arranged oppositely in this order along the conveyance direction of the developer on the conveyance means. In this configuration, the thickness of the developer on the conveying means is regulated to a constant thickness.
[0119]
Thereby, it is possible to prevent variation in the charge amount of the developer, and to improve the charging performance of the developer. Therefore, there is an effect that the reliability of the developing device can be improved.
[0120]
In the developing device of the present invention, voltages of the same polarity are respectively applied to the charging unit, the grid electrode, and the transport unit, and the absolute value of these voltages is
Applied voltage to charging means> Applied voltage to grid electrode> Applied voltage to conveying means
It is the structure which satisfies the relationship.
[0121]
Thereby, the electrons jumping out from the charging means can be discharged from the grid electrode to the developer. In addition, the developer can be charged by the difference between the voltage applied to the grid electrode and the voltage applied to the conveying means.
[0122]
The developing device of the present invention is configured such that the developer is a one-component toner.
[0123]
As a result, when toner is used as the developer of the developing device, it is possible to effectively prevent image quality deterioration and device failure due to melting.
[0124]
The developing device of the present invention has a configuration in which a wavelength changing unit that changes the wavelength of light emitted from the irradiation unit is disposed between the electron induction unit and the irradiation unit that irradiates light to the electron induction unit.
[0125]
Accordingly, the wavelength of the light can be changed without separately preparing an irradiating unit that irradiates light having an optimum wavelength in the charging unit. Therefore, it is possible to easily change the wavelength of light applied to the electron inducing portion without changing the irradiation means. As a result, the wavelength can be adjusted according to the material of the electron inducing portion, the charging efficiency can be improved, and the cost of the irradiation means can be reduced.
[0126]
The developing device of the present invention has a configuration in which the irradiation unit is arranged to face the conveying unit with the electron inducing portion interposed therebetween.
[0127]
Thereby, the light from an irradiation means can reach | attain an electron induction part, without irradiating a developing agent etc. Therefore, it is possible to prevent the light amount of the irradiation unit from being attenuated and to secure the light amount of the irradiation unit. Further, there is an effect that the irradiation unit can be prevented from being contaminated by the developer.
[0128]
The charging method of the present invention is a charging method for charging a developer that develops an electrostatic latent image into a visible image, and irradiates light to an electron inducing material that induces its own electrons by being irradiated with light. The developer is charged by discharging the induced electrons to the developer via the grid electrode.
[0129]
Thereby, the mechanical / thermal load applied to the developer and the charging means for charging the developer can be suppressed. Therefore, the developer can be prevented from being destroyed. In addition, it is possible to prevent deterioration of the charging characteristics of the developer. In addition, it is possible to suppress variation in the charge amount in the developer, and it is possible to stabilize the surface potential of the developer at a desired value.
[0130]
A printing apparatus according to the present invention includes a latent image holding body that holds an electrostatic latent image formed based on an image signal, and the above-described developing device that develops the electrostatic latent image.
[0131]
Thereby, there is an effect that a highly reliable printing apparatus can be provided.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram illustrating a configuration of a printing apparatus according to an embodiment of the present invention.
FIG. 2 is a detailed diagram illustrating a configuration of a toner charging roller.
FIG. 3 is an explanatory diagram showing an example of a photoelectron charging experiment.
FIG. 4 is an explanatory diagram illustrating configurations of a developing roller, a toner charging roller, and a grid electrode.
FIG. 5 is a detailed view showing the shape of a grid electrode.
FIG. 6 is an explanatory diagram showing control of an electron flow by a grid electrode.
FIG. 7 is a graph showing the relationship between the displacement in the rotation direction of the developing roller in the toner layer and the surface potential of the toner layer.
FIG. 8 is an explanatory diagram showing a voltage applied to a developing unit.
FIG. 9 is an explanatory diagram showing an example of a photoelectron charging experiment in which a wavelength conversion element is provided.
[Explanation of symbols]
1 Development unit (developing device)
2 Photosensitive drum (latent image carrier)
3 Charging roller
4 Transfer roller
5 Fixing roller pair
6 LSU
10 Developer tank
11 Developing roller (conveying means)
12 Toner supply roller (supply means)
13 Toner charging roller (charging means)
14 Stirring roller
31 ITO layer
32 Metal layer (electron induction part)
33 UV irradiator (irradiation means)
40 Grid electrode
70 Wavelength conversion element (wavelength changing means)

Claims (11)

A developing device used in an electrophotographic apparatus for developing an electrostatic latent image on a latent image holding member with a charged developer,
Conveying means for holding the developer and conveying it to the latent image holding body;
It has an electron inducing part that induces its own electrons by receiving light irradiation, and an irradiating means for irradiating light to the opposite part of the electron inducing part that faces the conveying means, and is induced in the opposite part of the electron inducing part. Charging means for charging the developer by applying the generated electrons to the developer on the conveying means ,
A gap is provided between the charging unit and the conveying unit, and the gap includes a grid electrode for controlling the flow of electrons .
2. A developing apparatus according to claim 1, wherein said charging means comprises a rotating roller having a built-in irradiation means and an electron inducing portion on the surface .   2. The developing device according to claim 1, wherein the developer is negatively charged, and the absolute value of the charge amount is not less than 5 [mu] c / g and not more than 30 [mu] c / g.   2. A voltage having a value obtained by adding a voltage value for charging the developer to a value of a voltage applied to the conveying unit is applied to the grid electrode. 2. The developing device according to 2.   The developing device according to claim 1, wherein the electron inducing portion is made of a semiconductor or a metal.   5. The developing device according to claim 1, wherein a bias voltage is applied between the electron inducing unit and the conveying unit. On the conveying means, a supply means for supplying the developer to the conveying means and the charging means are arranged in this order opposite to each other along the direction in which the developer is conveyed.
The developing device according to claim 1, wherein the supply unit regulates a thickness of the developer to be transported on the transport unit to a constant thickness. Voltages of the same polarity are applied to the charging unit, grid electrode, and transport unit, and the absolute values of these voltages are
7. The developing device according to claim 1, wherein a relationship of an applied voltage to the charging unit> an applied voltage to the grid electrode> an applied voltage to the transport unit is satisfied.   The developing device according to claim 1, wherein the developer is a one-component toner.   The wavelength changing means for changing the wavelength of light emitted from the irradiating means is disposed between the electron inducing section and the irradiating means for irradiating the electron inducing section with light. The developing device according to any one of 1 to 8. A charging method for charging a developer for developing an electrostatic latent image into a visible image,
An electron-inducing material that induces its own electrons when irradiated with light is arranged on the surface of the rotating roller, and light is irradiated from the irradiation means built in the rotating roller to the opposite part of the electron-inducing material facing the conveying means. And
A charging method, wherein a developer is charged by discharging electrons induced in an opposing portion of an electron inducing material to the developer via a grid electrode. A latent image holding body for holding an electrostatic latent image formed based on an image signal;
A printing apparatus comprising: the developing device according to claim 1, which develops the electrostatic latent image.

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