JP4976026B2 - Charger, image forming device - Google Patents

Description

  The present invention relates to a charger that emits electrons using a novel material, and an image forming apparatus using the charger.

  Conventional charging systems in image forming apparatuses are mainly corotron and scorotron using corona discharge. However, since corona discharge applies an electric field in the air, it generates a large amount of harmful substances such as ozone and NOx, and the charging efficiency is low. Therefore, there are drawbacks such as high cost and danger to human body. In view of environmental considerations in recent years, there is an urgent need to improve such a charging method, and a shift to roller charging is being made.

  With roller charging, for example, in the case of an image forming apparatus, a conductive rubber roller is brought into contact with a charged body such as a photoconductor, and a discharge is caused in a minute gap between the charged body and the charging roller to charge the surface of the charged body. The generation of ozone is remarkably reduced (reduced to 1/100 to 1/500) compared to corotron. Such a method is shown in Patent Documents 1 to 3, for example. However, since the charging roller also applies a voltage to the minute gap between the member to be charged and the charging roller to cause corona discharge, the generation of ozone cannot be made zero in principle. Further, since ozone is generated in the vicinity of the member to be charged, deterioration of the member to be charged due to ozone still remains a problem.

  There are various theories about the cause of deterioration of the member to be charged. One of them is that unnecessary products (ozone and NOx) due to discharge are chemically bonded to the surface of the member to be charged. Possible causes of chemical bonding include strong oxidizing power of ozone and nitrides produced by NOx. For this reason as well, it is desired that unnecessary substances are not generated as much as possible in the charging step. In addition, since the roller type is far closer to the charged body than the corona, the deterioration of the charged body due to ozone still remains a problem. In recent years, a high electric field in the vicinity of the photoconductor is suspected as a factor for deteriorating the photoconductor. In order to eliminate such a concern, a charging method at a low voltage is desired. Further, in principle, discharge has a threshold value according to Paschen's law, and charging cannot be performed unless a voltage is applied beyond that. For this reason, for example, when it is desired to charge to 100 V, it is 150 V for charge injection, but it is necessary to apply several hundred V for discharge. Even if future low-voltage development is realized, a voltage higher than the threshold must be applied, and the merit is diminished. If possible, a method satisfying an applied voltage comparable to the required surface potential is desired.

  In recent years, under such a background, a charging method using field emission that is non-contact and does not use discharge is being studied, and Non-Patent Document 1 reports the possibility. The point is that field emission occurs at a low voltage by forming a microprojection or a material having a high field emission capability on the surface of the charger. As a result, charging below the threshold of Paschen's law is possible, and there are few by-products such as ozone, and damage to the photoreceptor can be reduced.

In response to this, various electron emission materials have been proposed in recent years. However, for practical use, it is particularly required that resistance to high voltage is high and that current density is large. One of the new materials that has been actively developed is carbon nanotube. However, this material does not have remarkably excellent emission characteristics, and it is necessary to devise in order to improve the current density. Specifically, processing such as controlling the growth position and patterning to grow a thin film, or using a print transfer technique to etch into a shape suitable for electron emission properties is required. However, even if such a laborious and difficult process is performed, the current performance is that the current density is at most in the order of mA / cm ² . Furthermore, there is a limit in the electric field strength to be used, and if it exceeds the limit, the material is deteriorated and peeled off and cannot be used for a long time under a high voltage.

On the other hand, SP ³ -bonded 5H-BN (BN: boron nitride / boron nitride) (hereinafter referred to as “SP ³ -bonded BN”) shown in Patent Document 4 is based on such a current situation, It is a material developed based on the prediction that this type of field electron emission technology will become more promising in the future. It has high electric field strength and high efficiency (high current) even when used for a long time. It is a material that can be released stably at a density. Originally, BN is a material that is extremely stable even at high temperatures in the atmosphere, as used in high-temperature crucibles, and an electron-emitting device using this material has high-efficiency, stable and extremely low field electron emission characteristics. Show. Detailed description and definition of SP ³ binding BN will be given later.
Japanese Patent Publication No. 7-89248 JP-A-64-73365 JP-A 64-54471 JP-A-2005-76035 Japan HardCopy97 Proceedings P221

The SP ³ bonding conventional field emission-type charger using BN, to realize a uniform charge voltage in the plane of the SP ³ bonding BN has become an issue. It has been found that this is because it is difficult to control the film thickness and volume resistance of the SP ³ bonding BN in the plane, and the current value is not uniform in the plane. In addition, the resistance value also varies greatly in a region where the charging potential such as a pinhole portion existing in the photosensitive member is lowered, so that the current is concentrated, causing a voltage drop temporarily, and the surrounding charging potential is lowered. This nonuniformity of the charged potential is a fatal problem in image formation, and a mechanism for controlling this nonuniformity is required. In view of such circumstances, the present invention provides a charger using a field emission phenomenon that can be uniformly charged, and an image forming apparatus that forms a high-quality image using the charger.

An aspect of the present invention that achieves the above object includes an insulating substrate, an electrode formed on the insulating substrate, and an SP ³ -bonded boron nitride body formed on the electrode. A charger for performing field emission from the SP ³ -bonded boron nitride body, wherein the electrode is divided at a predetermined interval, and current control by the electrode is performed independently. It is.

Here, the SP ³ bonded boron nitride body has an insulating property in a direction parallel to the surface of the insulating substrate, and an anisotropic conductivity having conductivity in a direction perpendicular to the surface of the insulating substrate. It has the property.

Further, a catalyst for growing the SP ³ -bonded boron nitride body is provided between the electrode and the SP ³ -bonded boron nitride body.

  In addition, the electrode contains Ni.

  Moreover, it has a peeling prevention body between the said insulating substrate and the said electrode, The said peeling prevention body is good to contain Cr.

Further, characterized in that the direction of division of the electrodes, the angle between the direction of rotation forms the image bearing member on which an image forming apparatus has a 1 ° to 89 °.

  According to another aspect of the present invention, in the image forming apparatus having the charger, the image carrier, the exposure device, and the developing device, image information is transferred to the charger, and the electrode is used based on the image information. The present invention relates to an image forming apparatus characterized by performing current control.

  In the charger of the present invention, since the electrodes are divided, current control can be performed at an arbitrary position. The nonuniformity of the current value can be improved by the control. In addition, since the electrodes are divided, the area where the charging potential drops can be limited to a limited area, and the problem in image formation is solved.

  The best mode for carrying out the charger of the present invention will be described below. In the description, the drawings submitted at the same time as this specification will be referred to as appropriate.

In the conventional field emission-type charger using a SP ³ bonding BN, where it is required to achieve uniform charging voltage in the plane of the SP ³ bonding BN, the present form of charger 1 As shown, since the electrode (lower electrode 12) of the charger 101 of this embodiment is divided, current control at an arbitrary position can be performed, and nonuniformity of the current value can be improved. Further, since the lower electrode 12 is divided, it is possible to limit a region where the charging potential drops such as a pinhole portion existing in the photosensitive member, and the problem in image formation is solved.

However, in order to divide the lower electrode and independently control the current, crosstalk in which a current flows between adjacent lower electrodes occurs, making current control difficult. Although there is a method of performing a process for dividing the SP ³ -bonded BN film, SP ³ -bonded BN is a ceramic and is difficult to process by a general dry etching technique. In the charger of this embodiment, SP ³ bonding BN has conductivity anisotropy. The SP ³ bonding BN can provide anisotropy of conductivity by using a method described later. This anisotropy is substantially an insulator in a direction parallel to the substrate surface of the insulating substrate 11 in FIG. 1, and exhibits high conductivity in a direction perpendicular to the substrate surface. The presence of conductivity in the vertical direction does not reduce the field emission capability. Moreover, since it is an insulator in a direction parallel to the insulating substrate 11, crosstalk to adjacent electrodes can be suppressed.

Further, a conventional SP ³ bonding BN film has been formed on a Si substrate. However, in order to divide the lower electrode 12 as in this embodiment, it is desirable to form a SP ³ bonding BN film on the divided electrode. However, SP ³ bonding BN cannot be formed on a general metal. There is a need for a method of forming SP ³ -bonded BN on a divided metal. Where a layer having a catalytic function is necessary on the divided lower electrode 12, the charger of this embodiment forms a Si film as the catalyst layer 15 on the lower electrode 12 layer as shown in FIGS. As a result, the growth of SP ³ bonding BN can be performed directly on the lower electrode 12. In forming an SP ³ bonding BN film, as shown in Patent Document 4, it is known that a Si substrate serves as a catalyst, but this time, its function is manifested by Si formed by sputtering or CVD. I found out that Si may be a single crystal or an amorphous state. Although the mechanism is unknown, it is thought that nitrogen existing in the atmosphere can be taken into Si because nitrogen easily binds to Si. It is believed that boron is bonded to the nitrogen-rich Si surface and SP ³ -bonded BN grows.

Further, in the conventional SP ³ bonding BN film, film formation has been performed on a Si substrate. It is known that Si has a catalytic function on the Si substrate, and an SP ³ bonded BN film grows. As described above, a method of forming a Si film as the catalyst layer 15 is employed. However, in this method, it is necessary to form a separate Si film, and the number of steps is increased. A method of forming SP ³ bonding BN without forming Si is desired. A catalyst layer is required for growth of SP ³ -bonded BN. As a catalyst, Si is disclosed by Patent Document 4, but is not known otherwise.
When various materials were tried this time, it was found that SP ³ bonding BN grows in Ni. Ni acts as a catalytic function, and it is considered that nitrogen in the atmospheric gas during film formation is taken into the catalyst layer and promotes the growth of SP ³ -bonded BN. Therefore, as shown in FIGS. 1 and 3, it was found that the charger of this embodiment can simultaneously perform the catalytic function and the electrode function by using Ni as the lower electrode 12 this time. Thereby, a production process can be reduced without producing the previous catalyst layer.

In addition, there is a problem of peeling that occurs between the insulating substrate of the lower electrode due to heating and light irradiation necessary for film formation of the SP ³ bonding BN. In conventional semiconductor processes, electrode materials have been selected using general adhesion as an index. However, the heating and light irradiation necessary for the formation of the SP ³ -bonded BN are very specific processes. In addition, there are still many unclear points about the mechanism at the time of film formation of SP ³ -bonded BN. However, when the lower electrode is Ni, the nitrogen once melted into the inside of Ni and becomes supersaturated is boron ( It is considered that SP ³ binding BN precipitates by binding to B). At this time, it is conceivable that Ni containing supersaturated nitrogen deteriorates adhesion with the substrate and peels off. There is a need for metallic materials or improved processes that can withstand this unique process. In the charger of this embodiment, as shown in FIG. 6, a base layer 16 is formed between the lower electrode 12 and the insulating substrate 11. This underlayer 16 was formed of Cr or the like, improved adhesion, and improved peeling at the time of SP ³ bonding BN film formation. Also, in the film formation process of SP ³ -bonded BN, it is expected that Cr hardly melts nitrogen because of its high melting temperature. This prevents diffusion of nitrogen into the substrate, promotes efficient generation of SP ³ binding BN, and maintains close contact with the substrate.

Further, in order to divide the lower electrode and perform electrically independent current control, it is also necessary to divide the SP ³ bonding BN film. However, it is difficult to apply the deep RIE (reactive ion etching) process, which has been used in the conventional MEMS semiconductor process, to SP ³ -bonded BN. This is because SP ³ -bonded BN is a ceramic and has a poor chemical reaction with a general reactive gas. Etching exceeding several μm is difficult because the fluorine-based gas that deeply etches quartz or the like has a poor chemical reaction with the SP ³ bonding BN that is a nitride. There is a need for a method for simply patterning an SP ³ -bonded BN film. In view of this, the charger of this embodiment can selectively increase the temperature by causing a current to flow during the formation of the SP ³ bonding BN by making an arbitrary region of the lower electrode 12 high resistance. For example, the resistivity is controlled by controlling the thickness of the Ni film, and heat is generated when a current is passed through the thin Ni region. By controlling this heat generation during the SP ³ bonding BN film formation, the substrate temperature can be controlled to an arbitrary region and an arbitrary temperature. It has been found that the film formation of SP ³ bonding BN shows high dependence on the substrate temperature. This temperature dependency is converted into a database and used for film formation of SP ³ -binding BN. If this method is used, SP ³ -bonded BN can be selectively grown in an arbitrary region, and patterning of the SP ³ -bonded BN film, which has been difficult with the conventional method, becomes possible. Since the SP ³ bonding BN film can be patterned, crosstalk between adjacent electrodes obtained by dividing the lower electrode can be reduced.

  As described above, the nonuniformity of the charged potential is a fatal problem in image formation. There is a need for a mechanism that controls this non-uniformity. In particular, when the lower electrode 12 is divided, there is a region that cannot be charged between the electrodes. Means to avoid this are necessary. The charger mounted on the image forming apparatus of this embodiment divides the lower electrode 12 diagonally with respect to the rotation direction of the image carrier (see FIG. 1). By dividing obliquely, it is possible to prevent the distribution of the charged potential in the portion where there is no electrode. This is because the region without electrodes apparently moves in the horizontal direction by the rotation of the image carrier, and the charging potential becomes uniform. Thereby, the charging potential can be made uniform.

  In addition, it is required to form a high-quality image by applying a uniform charging potential. However, even if uniform charging is performed, a high-quality image cannot be formed unless controlled exposure is performed during exposure. The image forming apparatus of this embodiment takes in image information required for charging and applies a required charging potential to a required position. As a result, it is possible to form a high-quality image without disturbing the image state due to exposure.

  Hereinafter, the specific implementation form of the said form is demonstrated.

  An image forming apparatus of this embodiment is shown in FIG. The image forming apparatus includes a charging device, an image carrier 61, a developing device 63, and the like. The charging device includes a charger 101 and a charger cover 100. As the image carrier 61, a generally used organic photoreceptor is used. In this embodiment, the charger 101 forms a latent image on the uniformly charged photoconductor with the laser beam L, and the developing device 63 converts the latent image into a toner image. The image is formed by transferring it onto paper.

  As shown in FIG. 2, the charger 101 is disposed close to the image carrier 61 and separated by the gap G. The distance of the gap G from the image carrier 61 varies greatly depending on parameters such as applied voltage and field emission capability, but may be between 1 μm and 10 mm, and this time is controlled to about 50 μm.

Enlarged views of the charger 101 are shown in FIGS. FIG. 1 is a view of the charger 101 as viewed from the image carrier side, and FIG. 3 is a cross-sectional view of the charger 101 in the short direction. A lower electrode 12 and a catalyst layer 15 are formed on an insulating substrate 11, and an SP ³ bonding BN film 14 is formed thereon. The insulating substrate 11 can use various materials such as Si, quartz, a polymer substrate, and a sapphire substrate. This time, a quartz substrate was used because a large substrate could be obtained at low cost. The quartz substrate was polished and finished so that its flatness was Ra <10 nm or less. The lower electrode 12 only needs to have a thickness in the range of 0.1 nm to 10 μm, and this time is about 100 nm. The material of the lower electrode 12 may be any metal material such as Ni, Cr, Au, Cu, W, Pt, Al, Fe, Mo, Ti, Ag, Mn, Zr, Co, Pb, Ru, Ta. This time, Cr, which is excellent in terms of productivity and heat resistance, was used.

  The lower electrode 12 is divided obliquely with respect to the rotation direction of the image carrier 61. This is because the distribution of the charged potential is prevented from occurring in the portion where there is no electrode by dividing it diagonally. If the angle formed by the rotation direction and the dividing direction of the image carrier 61 is within a range of 1 ° to 89 °, a uniform effect of the charging potential can be seen, but this time it is set to about 40 °. The distance between the electrodes is preferably about 1 μm to 10 μm, and this time about 2 μm. The number of electrode divisions may be any number between 2 and 100,000, but an optimum division number is selected depending on the complexity of the process, the cost, or the required uniformity of the charged potential. In this embodiment, the number of divisions is set to about 1000, and the width L of one electrode is designed to be about 300 μm. The length T of the electrode is determined from many parameters such as the current value of field emission and the printing capability of the copying machine, but about 10 μm to 10 mm is appropriate. This time, it designed to about 1mm. The lower electrode 12 is wired in each divided state, and a transistor capable of controlling the current value is arranged in each of them.

A Si film is formed as a catalyst layer 15 on the lower electrode 12. The catalyst layer 15 is made of a material that has conductivity and promotes the formation of SP ³ -bonded BN. While the present inventors searched for a film formation method for SP ³ -bonded BN, this catalytic function was expressed in Si and Ni. Although the detailed mechanism of the catalytic effect in Si and Ni is unknown, it seems that the amount of nitrogen melted at a high temperature has an influence. Here, a film obtained by doping boron into the Si film was formed by CVD. The boron doping amount is about 10 ¹⁸ cm ⁻³ , indicating sufficient conductivity. In the film formation process of SP ³ bonding BN, if the film thickness of Si is too thin, the function of the catalyst is not exhibited. It is difficult to form a thick Si film. Therefore, the optimum film thickness of Si is about 0.1 nm to 10 μm, but this time it is about 500 nm.

  The lower electrode 12 and the catalyst layer 15 are patterned by a photolithography process. The pattern is a shape that requires an accuracy of the order of several μm, as shown when the shape of the lower electrode 12 is explained earlier. A resist is applied after forming the lower electrode 12 and the catalyst layer 15 on the quartz substrate. In this step, the film thickness can be arbitrarily and uniformly applied by using a spin coater. A positive resist was used with a resist thickness of about 2 μm. The quartz substrate coated with the resist is baked in an oven at a baking temperature of 100 ° C.

  In the photolithography process, exposure is performed using a laser exposure apparatus instead of a general stepper so that the entire charger 101 can be processed at once. The laser exposure apparatus is an apparatus that performs exposure by irradiating a laser beam only at an arbitrary position. It is most suitable for the case where the electrode is removed only in a part with a small area as in this case and the area is large. Here, the irradiation location is determined by the pattern of the lower electrode 12 described above, and the data is input to the exposure apparatus. After exposure, the resist is developed with a developer to form a pattern.

  The patterned resist is dry etched with a chlorine-based gas. The etching height can be controlled by controlling the etching time. Thereafter, the catalyst layer 15 and the lower electrode 12 can be patterned by peeling and cleaning the resist.

The SP ³ bonding BN film 14 is not formed on the wiring portion as shown in FIG. In this case, the SP ³ bonding BN film 14 can be selectively formed at an arbitrary position by patterning the catalyst layer 15. The pattern formation of the lower electrode 12 and the SP ³ bonding BN can be independently designed by forming the lower electrode 12, forming the catalyst layer 15, and performing the above-described photolithography process. it can.

An SP ³ -bonding BN film 14 is formed on the catalyst layer 15. This material is excellent in field electron emission characteristics when boron nitride produced under specific conditions is formed into a film shape while searching for a material exhibiting excellent electron emission characteristics. It has been found that a product having a surface shape can be produced. Hereinafter, the SP ³ binding BN invented by the present inventors will be described in detail.

This SP ³ -bonded BN (Sp ³ -bonded 5H-BN) is a preferable material that is particularly excellent in electron emission characteristics in air. SP ³ bonding BN film excellent surface shape field electron emission characteristics, i.e., SP ³ bonding nitride shape exhibited sharp state of the tip has a peculiar structure formed by self-shaped formed A boron film body can be produced. This makes it possible to produce a new material that is ideal as a field electron emission material with a low field electron emission threshold, a high current density, and a long electron emission lifetime, without any special processing means or processing process. .

  When boron nitride is produced and deposited on a substrate by a reaction from the gas phase, boron nitride is formed in a film shape on the substrate when irradiated with high energy ultraviolet light in the vicinity of the substrate, and a tip is formed on the film surface. Boron nitride having a pointed state is generated and grown in a self-organizing manner in the light direction at appropriate intervals. And the resulting film easily emits electrons when an electric field is applied to it, and considering this kind of material so far, while maintaining a large current density that can be said to be exceptional, deterioration of the material, It has been confirmed and found to be an extremely excellent electron emission material that can maintain a very stable state and performance without damage or dropout.

  In order for this material to form a surface shape excellent in field electron emission characteristics in a self-modeling manner by reaction from the gas phase, irradiation with ultraviolet light is necessary. This will be clarified in the detailed conditions of material generation to be described later, but the reason is not necessarily clear at this stage. However, it can be considered as follows.

  That is, surface morphogenesis by self-organization is grasped as a so-called “Turing structure”, and appears under certain conditions where the surface diffusion of the precursor material and the surface chemical reaction compete. Here, it is considered that ultraviolet light irradiation is related to the photochemical promotion of both, and affects the regular distribution of initial nuclei. The growth reaction on the surface is promoted by irradiation with ultraviolet light, which means that the reaction rate is proportional to the light intensity. Assuming that the initial nucleus is hemispherical, the light intensity is large near the apex and the growth is promoted, whereas the light intensity is weakened and the growth is delayed at the peripheral part. This is considered to be one of the formation factors of the surface formation with a sharp tip. In any case, ultraviolet light irradiation plays an extremely important role, and it cannot be denied that this is an important point.

The method for producing this material will be described in detail below. The CVD reaction vessel having the structure shown in FIG. 4 is an SP ³ bonding BN having excellent electron emission characteristics that is suitably used for an electron source substrate using the electron-emitting device of this embodiment and an image display device using the substrate. It was used to carry out the gas phase reaction to obtain

  In FIG. 4, a reaction vessel 41 includes a gas introduction port 42 for introducing a reaction gas and its dilution gas, and a gas outlet 43 for exhausting the introduced reaction gas and the like out of the vessel. And maintained at a reduced pressure below atmospheric pressure. An insulating substrate 44 on which boron nitride is deposited is set in the gas flow path in the vessel, and an optical window 48 is attached to a part of the wall of the reaction vessel 41 facing the substrate 44 on which the boron nitride is deposited. Then, excimer ultraviolet laser light (thick arrow in the figure) is irradiated onto the substrate 44 through the window 48.

The reaction gas introduced into the reaction vessel 41 is excited by ultraviolet light irradiated on the surface of the substrate 44, and a nitrogen source and a boron source in the reaction gas undergo a gas phase reaction, and are represented by a general formula: BN on the substrate. Then, SP ³ -bonded BN having a 5H type polymorphic structure is generated, precipitated, and grown into a film.

  In this case, the pressure in the reaction vessel 41 can be implemented in a wide range of 0.001 to 760 Torr. Further, the temperature of the substrate placed in the reaction space can be carried out in a wide range of room temperature to 1300 ° C., but the pressure is low and the temperature is high in order to obtain the desired reaction product with higher purity. It is more preferable to carry out with.

  In addition, when irradiating and exciting the surface of the substrate 44 or a space region in the vicinity thereof with ultraviolet light, it is also a good method to irradiate with plasma. In FIG. 4, a plasma torch 47 shows this mode, and the reaction gas inlet 42 and the plasma torch 47 are integrated toward the substrate 44 so that the reaction gas and plasma are irradiated toward the substrate 44. Is set to

The following description is based on more specific conditions. However, the conditions disclosed below are disclosed only as an aid for understanding the SP ³ binding BN suitably applied to the present invention, and the present invention is not limited only by these conditions. Needless to say.

<Generation condition example 1>
A diborane flow rate of 10 sccm and an ammonia flow rate of 20 sccm were introduced into a mixed dilution gas flow having an argon flow rate of 2 SLM and a hydrogen flow rate of 50 sccm, and simultaneously maintained at 800 ° C. by heating in an atmosphere maintained at a pressure of 30 Torr by exhausting with a pump. Excimer ultraviolet laser light was irradiated on the silicon substrate (see FIG. 4). The desired thin film was obtained after 60 minutes of synthesis time. As a result of identifying the thin film product by X-ray diffraction, the crystal system of this sample is hexagonal, and it is a 5H type polymorphic structure with SP ³ bonds, and the lattice constants are a = 0.25 nm, c = 1.04 nm. Met.

  As a result of observation with a scanning electron microscope image, this thin film is self-shaped with a unique surface shape covered with a conical protrusion structure (0.001 μm to several μm in length) with a sharp tip that tends to cause electric field concentration. Formation was observed.

In order to investigate the field electron emission characteristics of this thin film, a cylindrical metal electrode having a diameter of 1 mm was separated from the surface by 30 μm, a voltage was applied between the thin film and the electrode in vacuum, and the amount of electron emission was measured. At 20 (V / μm), an increase in current density is observed, and at 20 (V / μm), it is clear that the current is saturated at the limit current value (equivalent to 1.3 A / cm ² ) of the high-voltage power supply for measurement. It became.

  Further, when the time change of the current value at this time was examined, the current value was slightly fluctuated for about 15 minutes, but the average current value was maintained, and the current value due to material deterioration was maintained. No decrease was observed, confirming that the material was stable. Furthermore, even if this evaluation was performed in the air, almost the same characteristics were shown. Moreover, the thin film was pulverized into fine particles (0.0005 μm to 1 μm), made into a paste, coated, dried, and evaluated for its performance, but the same performance was obtained.

<Production Comparative Example 1>
For comparison, the field electron emission characteristics of a portion of the thin film that was simultaneously produced under the same conditions as those in Production Condition Example 1 except for the irradiation with ultraviolet light were examined. As a result, the threshold electric field intensity at the start of electron emission is 42 (V / μm), which is significantly higher than 15 (V / μm) in the case of generation condition example 1 manufactured by performing ultraviolet light irradiation. I understood. Further, when this portion was observed with a scanning electron microscope, damage and peeling of the thin film due to field electron emission were observed. On the other hand, no damage was found in the portion showing the protruding surface shape grown under ultraviolet light irradiation after the field electron emission experiment.

<Generation condition example 2>
In an atmosphere maintained at a pressure of 30 Torr by introducing a diborane flow rate of 10 sccm and an ammonia flow rate of 20 sccm into a mixed dilution gas flow with an argon flow rate of 2 SLM and a hydrogen flow rate of 50 sccm, and simultaneously evacuating with a pump, the output is 800 w and the frequency is 13.56 MHz. RF plasma was generated, and excimer ultraviolet laser light was irradiated onto a silicon substrate maintained at 900 ° C. by heating (see FIG. 4).

A thin film product was obtained after a synthesis time of 60 minutes. As a result of identifying this product by the same method as in Production Condition Example 1, the crystal system was hexagonal, a 5H polymorphic structure with SP ³ bonds, and the lattice constants were a = 0.25 nm, c = 1. It was 04 nm.

  As a result of observation with a scanning electron microscope image, this thin film is self-shaped with a unique surface shape covered with a conical protrusion structure (0.001 μm to several μm in length) with a sharp tip that tends to cause electric field concentration. Formation was observed.

In order to investigate the field electron emission characteristics of this thin film, a cylindrical metal electrode having a diameter of 1 mm was separated from the surface by 40 μm, a voltage was applied between the thin film and the electrode in vacuum, and the amount of electron emission was measured. As a result, an increase in current density was observed at an electric field strength of 18-22 (V / μm), and the limit current value (equivalent to 1.3 A / cm ² ) of the high voltage power supply for measurement was observed at 22 (V / μm). It became clear that it was saturated. Similar results were also obtained in air evaluation or fine particle evaluation. That is, it was confirmed that a stable material was obtained as in Production Condition Example 1.

<Generation condition example 3>
In an atmosphere maintained at a pressure of 30 Torr by introducing a diborane flow rate of 10 sccm and an ammonia flow rate of 20 sccm into a mixed dilution gas flow with an argon flow rate of 2 SLM and a hydrogen flow rate of 50 sccm, and simultaneously evacuating with a pump, the output is 800 w and the frequency is 13.56 MHz. RF plasma was generated, and excimer ultraviolet laser light was irradiated onto a nickel substrate maintained at 900 ° C. by heating (see FIG. 4).

  A thin film product was obtained after a synthesis time of 60 minutes. As a result of identifying this product by the same method as in Production Condition Example 1, the crystal system was hexagonal, and it was a 5H polymorphic structure with Sp3 bonds, and the lattice constants were a = 0.251 nm, c = 1.05 nm. Met.

  As a result of observation with a scanning electron microscope image, this thin film is self-shaped with a unique surface shape covered with a conical protrusion structure (0.001 μm to several μm in length) with a sharp tip that tends to cause electric field concentration. Formation was observed.

In order to investigate the field electron emission characteristics of this thin film, a cylindrical metal electrode having a diameter of 1 mm was separated from the surface by 40 μm, a voltage was applied between the thin film and the electrode in vacuum, and the amount of electron emission was measured. As a result, an increase in current density was observed at an electric field strength of 18-22 (V / μm), and the limit current value (corresponding to 1.2 A / cm ² ) of the high-voltage power supply for measurement was observed at 22 (V / μm). It became clear that it was saturated. Similar results were also obtained in air evaluation or fine particle evaluation. That is, it was confirmed that a stable material was obtained as in Production Condition Example 1.

As described above, the SP ³ -bonded BN having excellent electron emission characteristics used suitably for the electron source substrate using the electron-emitting device of the present embodiment and the image display device using the substrate has the field electron emission characteristics. It has a unique configuration in which a surface shape excellent in the shape, that is, a shape having a pointed tip is formed in a self-modeling manner.

The SP ³ binding BN is not limited to a shape with a sharp tip, but may be in the form of fine particles. The fine particle film described here is a film in which a plurality of fine particles are aggregated, and the fine structure is not only in a state where the fine particles are individually dispersed and arranged, but also in a state where the fine particles are adjacent to each other or overlap (some fine particles are aggregated). And the case where an island shape is formed as a whole is also taken.) The particle diameter of the fine particles is several 0.1 μm to 1 μm, preferably 0.1 nm to 20 nm.

An SP ³ -bonded BN film produced under the above conditions was formed as shown in FIG. It has been found that the SP ³ bonding BN film 14 exhibits conductivity anisotropy by the above-described production method. The SP ³ bonding BN film 14 has a high conductivity in the thickness direction, but has a very low conductivity in the direction parallel to the insulating substrate 11. This was clarified by measuring the resistance value between adjacent electrodes. Although the mechanism of the conductivity anisotropy appearing in the SP ³ -bonded BN film 14 is unknown, the SP ³ -bonded BN film 14 is an insulator in the first place, but there is some conductive path in the film thickness direction. It may be formed. It can be understood that this conductive path has anisotropy.

An image forming apparatus of this embodiment is shown in FIG. The image forming apparatus includes a charging device, an image carrier 61, a developing device 63, and the like. The image carrier 61 is not a commonly used photoreceptor, but an insulator having a function of simply maintaining a charged potential. This insulator may be a polymer material such as polycarbonate, polyethylene, polyterephthalate, or an inorganic material such as SiO ₂ or SiN. This time, polycarbonate was used from the viewpoint of mass production of materials. The polycarbonate was about 100 μm thick and coated on the surface of an aluminum tube.

  In this embodiment, image information to be obtained is transmitted to the charger 101, an arbitrary latent image is formed only at a necessary portion for charging, and the developing device 63 converts the latent image into a toner image. The image is formed by transferring it onto paper.

  As shown in FIG. 5, the charging device 101 is disposed close to the image carrier 61 and separated by the gap G. The distance of the gap G from the image carrier 61 varies greatly depending on parameters such as applied voltage and field emission capability, but may be between 1 μm and 10 mm, and this time is controlled to about 50 μm.

FIG. 6 is an enlarged cross-sectional view of the charger 101. A base layer 16 and a lower electrode 12 are formed on an insulating substrate 11, and an SP ³ bonding BN film 14 is formed thereon. The insulating substrate 11 can use various materials such as Si, quartz, a polymer substrate, and a sapphire substrate. This time, a quartz substrate was used because a large substrate could be obtained at low cost. The quartz substrate was polished and finished so that its flatness was Ra <10 nm or less.

The underlayer 16 has a function of bringing the lower electrode 12 into close contact with the insulating substrate 11 and a function of preventing nitrogen from diffusing into the insulating substrate 11 when the SP ³ bonding BN film 14 is formed. Thus, nitrogen is efficiently supplied to SP3 binding BN film 14, can make a good SP ³ bonding BN film 14 quality. This time, Cr was adopted as the underlayer 16. Cr was formed to a thickness of about 10 nm by a heating vapor deposition device.

A lower electrode 12 is formed thereon. The material of the lower electrode 12 may be Ni, and the thickness may be in the range of 0.1 nm to 10 μm, and this time is about 100 nm. It has been found from the research results of the inventors that Ni has a catalytic function of the SP ³ -bonded BN film 14 as shown in the previous generation condition example 3.

  The lower electrode 12 is divided perpendicularly to the rotation direction of the image carrier 61. The distance between the electrodes is preferably about 1 μm to 10 μm, and this time about 2 μm. The number of electrode divisions may be any number between 2 and 100,000, but is selected depending on the complexity of the process, the cost, or the required image quality. In this embodiment, the number of divisions is about 5000, and the width L of one electrode is designed to be about 70 μm. This is equivalent to 400 dpi as an image. The length T of the electrode is determined from many parameters such as the current value of field emission and the printing capability of the copying machine, but about 10 μm to 10 mm is appropriate. This time, it designed to about 0.1mm. The electrodes are wired in respective divided states, and a transistor capable of controlling the current value is arranged in each of them. A desired image is formed by transferring required image information to the transistor.

  The lower electrode 12 and the underlayer 16 are patterned by a photolithography process. The pattern is a shape that requires an accuracy of the order of several μm, as shown when the shape of the lower electrode 12 is explained earlier. A resist is applied after the lower electrode 12 and the underlayer 16 are formed on a quartz substrate. In this step, the film thickness can be arbitrarily and uniformly applied by using a spin coater. A positive resist was used with a resist thickness of about 2 μm. The quartz substrate coated with the resist is baked in an oven at a baking temperature of 100 ° C.

  In the photolithography process, exposure is performed using a laser exposure apparatus instead of a general stepper so that the entire charger 101 can be processed at once. The laser exposure apparatus is an apparatus that performs exposure by irradiating a laser beam only at an arbitrary position. It is most suitable for the case where the electrode is removed only in a part with a small area as in this case and the area is large. Here, the irradiation location is determined by the pattern of the lower electrode 12 described above, and the data is input to the exposure apparatus. The resist is developed with a developer to form a pattern.

  The patterned resist is dry etched with a chlorine-based gas. The etching height can be controlled by controlling the etching time. Thereafter, the base layer 16 and the lower electrode 12 can be patterned by removing the resist and washing.

In this embodiment, the thickness of the lower electrode 12 is reduced only in the film formation region of the SP ³ bonding BN film 14. This can be realized by dividing the resist thickness into two stages by controlling the exposure amount in the photolithography process. The shape of the lower electrode in the thin part of the resist is then transferred in a dry etching process to produce a thin lower electrode. The thin lower electrode 12 exhibits a high resistivity when a current is passed, and becomes a heating element. The SP ³ bonding BN film 14 has different growth conditions depending on the substrate temperature, and can be selectively formed in the heat generation region. This is a method of forming the SP ³ bonding BN film 14 in a fine shape, which is difficult to finely process such as dry etching.

An SP ³ bonding BN film 14 is formed on the lower electrode 12. This material is excellent in field electron emission characteristics when boron nitride produced under specific conditions is formed into a film shape while searching for a material exhibiting excellent electron emission characteristics. It has been found that a product having a surface shape can be produced.

The SP ³ bonding BN film 14 was formed under substantially the same conditions as in Production Condition Example 1. However, in this example, when a film was formed, a current was passed through the electrode to generate heat in a region having a high resistance value. This controlled the temperature of the heat generating region to about 800 ° C. and the other substrate temperatures to 700 ° C. As a result, the SP3-bonded BN film 14 was selectively formed. The film quality and field emission capability were almost the same as in Production Condition Example 1.

An SP ³ -bonded BN film produced under the above conditions was formed as shown in FIG. It has been found that the SP ³ bonding BN film 14 exhibits conductivity anisotropy by the above-described production method. The SP ³ bonding BN film 14 has a high conductivity in the thickness direction, but has a very low conductivity in the direction parallel to the insulating substrate 11.

  In addition, although the form mentioned above is the best thing for implementing the charger of this invention, it is not the meaning limited to this implementation form. Therefore, various modifications can be made to the implementation form without changing the gist of the present invention.

FIG. 2 is an enlarged view of the surface of a charger 101 of the present embodiment. FIG. 3 is an explanatory diagram illustrating an arrangement of a charger 101 and an image carrier 61 in the image forming apparatus according to the first exemplary embodiment. 1 is a cross-sectional view of a charger 101 according to a first embodiment. It is the figure which shows the schematic and outline | summary of a reaction apparatus. FIG. 6 is an explanatory diagram illustrating an arrangement of a charger 101 and an image carrier 61 in an image forming apparatus according to a second embodiment. 6 is a cross-sectional view of a charger 101 according to Embodiment 2. FIG.

Explanation of symbols

11 Insulating substrate 12 Lower electrode 13 Wiring 14 SP ³ Bonding BN film 15 Catalyst layer 16 Underlayer 41 Reaction vessel (reactor)
42 Gas inlet 43 Gas outlet 44 Boron nitride deposition substrate 45 Optical window 46 Excimer ultraviolet laser device 47 Plasma torch 61 Image carrier 63 Developing device 63a Developer carrier 64 Cleaning device 64a Cleaning brush 64b Cleaning blade 100 Charger cover 101 Charger G Gap L Laser light

Claims (8)

An insulating substrate;
An electrode formed on the insulating substrate;
Having SP ³ bonded boron nitride formed on the electrode;
In a charger that performs field emission from the SP ³ -bonded boron nitride body by controlling the current of the electrode,
The charger is characterized in that the electrode is divided at a predetermined interval, and current control by the electrode is performed independently. The SP ³ bonded boron nitride body has an anisotropy of conductivity such that it has an insulating property in a direction parallel to the surface of the insulating substrate and a conductivity in a direction perpendicular to the surface of the insulating substrate. The charger according to claim 1. The charger according to claim 1, further comprising a catalyst for growing the SP ³ -bonded boron nitride body between the electrode and the SP ³ -bonded boron nitride body.   The charger according to claim 1, wherein the electrode contains Ni.   The charger according to any one of claims 1 to 4, further comprising an anti-peeling body between the insulating substrate and the electrode.   The charger according to claim 5, wherein the peeling prevention body contains Cr. The direction of division of the electrode, charging device according to any of claims 1 to 6, characterized in that the angle of the rotation direction forms of the image bearing member is 1 ° to 89 ° to the image forming apparatus. A charger according to any one of claims 1 to 7 ,
An image carrier;
An exposure device;
In an image forming apparatus having a developing device,
An image forming apparatus, wherein image information is transferred to the charger, and current control by the electrodes is performed based on the image information.

Images