JP2012078724A - Developing device and image forming apparatus - Google Patents

Abstract

A developing device and an image forming apparatus capable of improving developing ability while suppressing carrier adhesion.
A small particle size magnetic carrier having a small average particle size, a large particle size magnetic carrier having an average particle size larger than that of the small particle size magnetic carrier, and a toner particle having a particle size smaller than that of the small particle size magnetic carrier. A developer containing portion for containing the developer contained therein, a developer carrying member for carrying the developer in the developer containing portion on a surface that moves around itself, and a loop inside the circumferential surface of the developer carrying member on the inner side. In a developing device having magnetism generating means for attracting a developer to the peripheral surface of the developer carrier by a magnetic force generated by a plurality of magnetic poles arranged so as to be arranged along the peripheral surface, The resistance is 10 ¹² to 10 ¹³ [Ω] in terms of dynamic resistance, and the electrical resistance of the large particle size magnetic carrier is 10 ⁸ to 10 ⁹ [Ω] in terms of dynamic resistance.
[Selection] Figure 1

Description

  The present invention relates to a developing device used for development by supporting a developer containing a magnetic carrier and toner particles on the surface of the developer carrier by the magnetic force of a magnetic generating means contained in the developer carrier, and the development thereof. The present invention relates to an image forming apparatus such as a printer, a facsimile machine, and a copier provided with the apparatus.

  In this type of image forming apparatus, when a small particle size magnetic carrier having a relatively small average particle size is used as the magnetic carrier of the developer, compared to a case where a large particle size magnetic carrier having a relatively large average particle size is used, The surface area of the particles accommodated per unit volume increases. As a result, a large amount of toner particles can be carried on the surface of the magnetic carrier, and the image can be developed delicately and without unevenness. On the other hand, there is a demerit that the flowability of the developer is deteriorated, or the so-called carrier adhesion in which the magnetic carrier adheres to the photoreceptor due to the small amount of magnetization. On the other hand, when a large particle size magnetic carrier is used, the flowability of the developer can be improved, and the occurrence of carrier adhesion can be suppressed because the amount of magnetization is large. On the other hand, since the amount of toner particles carried is smaller than that of a small particle size magnetic carrier, there is a demerit that an image cannot be developed delicately and an image having a blur or density unevenness is formed.

  In Patent Document 1, a small particle size magnetic carrier is used as a magnetic carrier in order to compensate the disadvantages of a small particle size magnetic carrier with a large particle size magnetic carrier and to supplement the disadvantages of a large particle size magnetic carrier with a small particle size magnetic carrier. A developer containing two types of magnetic carriers, a carrier and a large particle size magnetic carrier, is disclosed.

Normally, the magnetic carrier is held on the developer carrying member by magnetic force, but at the same time, electric charge due to electrostatic induction or charge injection exists in the magnetic carrier, and electrostatic force works between the electric charge on the photoconductor. Yes. In particular, as the electric resistance of the magnetic carrier decreases, the electrostatic force increases due to electrostatic induction or charge injection. Further, the developing ability can be improved by using a low-resistance magnetic carrier to lower the electrical resistance of the entire developer and increase the strength of the developing electric field.
However, the smaller the particle size of the magnetic carrier, the smaller the amount of magnetization of the magnetic carrier, so the magnetic force acting on the magnetic carrier becomes weaker. For this reason, if the electric resistance of the small particle size magnetic carrier is made too small, the electrostatic force generated between the small particle size magnetic carrier and the photoconductor is reduced by the magnetic force generated between the small particle size magnetic carrier and the developer carrier. In this case, the problem arises that the small-diameter magnetic carrier easily adheres to the photosensitive member and the carrier adheres.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a developing device capable of improving the developing ability while suppressing carrier adhesion, and an image forming apparatus including the developing device. .

In order to achieve the above object, the invention of claim 1 includes a small particle size magnetic carrier having a small average particle size, a large particle size magnetic carrier having a larger average particle size than the small particle size magnetic carrier, and the small particles. A developer container that contains a developer containing toner particles having a particle diameter smaller than that of the magnetic carrier, and a developer carrier that carries the developer in the developer container on a surface that moves around itself. Magnetic force attracting the developer to the peripheral surface of the developer carrier by the magnetic force generated by a plurality of magnetic poles arranged along the peripheral surface inside the loop of the peripheral surface of the developer carrier Generating means, and transporting the developer to a development area facing the latent image carrier of the image forming apparatus by moving the surface of the developer carrier, and the toner in the developer is transferred to the latent image in the development area. Develop the latent image by transferring it to the latent image on the carrier The developing device that the electric resistance of the small diameter magnetic resistance carrier is ¹⁰ 12 ^{~10 13 [Ω]} in the dynamic resistance, the large diameter magnetic resistance ¹⁰ 8 electric resistance in the dynamic resistance of the carrier to 10 ⁹ [Omega] It is characterized by being.
The invention of claim 2 is the developing apparatus according to claim 1, wherein the small particle size magnetic carrier has a weight average particle size of 20 [μm] to 40 [μm], and the large particle size magnetic carrier has a weight average particle size. The particle size is 60 [μm] to 90 [μm].
According to a third aspect of the present invention, there is provided the developing device according to the first or second aspect, wherein the magnetic poles located at the position facing the development region of the magnetism generating unit are formed between the latent image carrier and the developer carrier. It is characterized by being provided at a position shifted from the closest part to the downstream side in the circumferential direction.
According to a fifth aspect of the present invention, in the developing device of the first, second, third, or fourth aspect, the above-described small particle size magnetic carrier using a resin material as a base material is used.
According to a sixth aspect of the present invention, an image obtained by developing a latent image formed on a latent image carrier by developing the latent image by supplying a developer by a developing means is finally recorded on a recording material. In an image forming apparatus that forms an image on the recording material by transferring the image on the recording material, the developing device according to claim 1, 2, 3, 4, or 5 is used as the developing means.

In the present invention, the electric resistance of the small particle size magnetic carrier is 10 ¹² to 10 ¹³ [Ω] in terms of dynamic resistance, and the electric resistance of the large particle size magnetic carrier is 10 ⁸ to 10 ⁹ [Ω] in terms of dynamic resistance. Thus, as clarified in an experiment described later, it is possible to improve the developing ability by reducing the resistance of the entire developer while suppressing carrier adhesion.

1 is a schematic configuration diagram showing a copier according to an embodiment. FIG. 3 is a partial configuration diagram illustrating an enlarged part of an internal configuration of an image forming unit. The elements on larger scale which show a part of tandem part which consists of four process units. The schematic block diagram of the measuring apparatus of dynamic resistance DR. 6 is a graph showing the relationship between developer and toner adhesion amount γ. FIG. 2 is an enlarged schematic diagram illustrating a photoconductor and a developing device. The figure showing the relationship between the magnetic pole angle of the magnetic pole N1, and the carrier adhesion amount. The figure showing the developer carrier vibration apparatus which vibrates a developing sleeve. 6 is a graph showing the relationship between the vibration frequency of the developing sleeve vibration device and the toner adhesion amount γ. 6 is a graph showing the results of evaluating the toner adhesion amount γ when a small particle size magnetic carrier using a resin material as a base material is used and when a small particle size magnetic carrier using a ferrite material as a base material is used.

  Hereinafter, an embodiment in which the present invention is applied to an electrophotographic copying machine (hereinafter simply referred to as a copying machine) will be described.

First, a basic configuration of the copying machine according to the embodiment will be described.
FIG. 1 is a schematic configuration diagram illustrating a copying machine according to an embodiment. The copying machine includes an image forming unit 1, a blank paper supply device 40, and an image reading unit 50. The image reading unit 50 as an image reading apparatus includes a scanner 150 fixed on the image forming unit 1 and an automatic document feeder (hereinafter referred to as ADF) 51 as a sheet conveying device supported by the scanner 150. ing.

  The blank paper supply device 40 includes two paper feed cassettes 42 arranged in multiple stages in the paper bank 41, a feed roller 43 that feeds recording paper from the paper feed cassette, and separates the sent recording paper into a paper feed path 44. A separation roller 45 to be supplied is provided. In addition, a plurality of conveyance rollers 47 that convey recording paper as a sheet-like member are provided in a paper feed path 37 as a conveyance path of the image forming unit 1. Then, the recording paper in the paper feeding cassette is fed into the paper feeding path 37 in the image forming unit 1.

  The image forming unit 1 includes an optical writing device 2, four process units 3K, 3Y, 3M, and 3C that form black, yellow, magenta, and cyan (K, Y, M, and C) toner images, and a transfer unit 24. , A paper transport unit 28, a registration roller pair 33, a fixing device 34, a switchback device 36, a paper feed path 37, and the like. Then, a light source such as a laser diode or LED (not shown) disposed in the optical writing device 2 is driven to irradiate the four drum-shaped photosensitive members 4K, Y, M, and C with the laser light L. . By this irradiation, electrostatic latent images are formed on the surfaces of the photoreceptors 4K, 4Y, 4M, and 4C, and the latent images are developed into toner images through a predetermined development process.

  FIG. 2 is an enlarged partial configuration diagram illustrating a part of the internal configuration of the image forming unit 1. FIG. 3 is a partially enlarged view showing a part of a tandem part composed of four process units 3K, 3Y, 3M, 3C. The four process units 3K, 3Y, 3M, and 3C have substantially the same configuration except that the colors of the toners to be used are different, and therefore, K, Y, M, and C attached to the respective reference numerals in FIG. The subscript is omitted.

  Each of the process units 3K, 3Y, 3M, and 3C supports the photosensitive member 4 and various devices disposed around the photosensitive member 4 as a single unit on a common support. Can be removed. Taking the process unit 3K for black as an example, this has a charging device 23, a developing device 6, a drum cleaning device 15, a static elimination lamp 22 and the like around the photosensitive member 4. This copying machine has a so-called tandem configuration in which four process units 3K, 3Y, 3M, and 3C are arranged so as to face an intermediate transfer belt 25, which will be described later, along the endless movement direction. Yes.

  As the photoreceptor 4, a drum-shaped member is used in which a photosensitive layer is formed by applying a photosensitive organic photosensitive material to a base tube made of aluminum or the like. However, an endless belt may be used.

  The developing device 6 develops the latent image using a developer containing a magnetic carrier (not shown) and a non-magnetic toner. A stirrer 7 that conveys the developer contained in the developing device while stirring and supplies the developer to the developing sleeve 12, and development for transferring toner in the developer carried on the developing sleeve 12 to the photoreceptor 4. Part 11.

  The stirring unit 7 is provided at a position lower than the developing unit 11, and includes two conveying screws 8 arranged in parallel to each other, a partition plate provided between the screws, and a developing case 9 that is a developer containing unit. A toner concentration sensor 10 provided on the bottom surface of the toner.

  The developing unit 11 includes a developing sleeve 12 that faces the photosensitive member 4 through an opening of the developing case 9, a magnet roller 13 that serves as a magnetism generator that is provided in a non-rotatable state inside the developing sleeve 12, and a doctor blade that approaches the developing sleeve 12. 14 and so on. The developing sleeve 12 as a developer carrying member has a non-magnetic rotatable cylindrical shape. The magnet roller 13 has a plurality of magnetic poles that are sequentially arranged from the position facing the doctor blade 14 in the rotational direction of the sleeve. Each of these magnetic poles applies a magnetic force to the developer on the sleeve at a predetermined position in the rotational direction. As a result, the developer sent from the stirring unit 7 is attracted and carried on the surface of the developing sleeve, and a magnetic brush is formed along the magnetic field lines on the sleeve surface.

  The magnetic brush is regulated to an appropriate layer thickness when passing through the position facing the doctor blade 14 as the developing sleeve 12 rotates, and then conveyed to the developing region facing the photoconductor 4. Then, the toner is transferred onto the electrostatic latent image by the potential difference between the developing bias applied to the developing sleeve 12 and the electrostatic latent image on the photosensitive member 4, thereby contributing to development. Further, as the developing sleeve 12 rotates, the developing sleeve 12 is returned to the developing portion 11 again, and after being separated from the sleeve surface by the influence of the repulsive magnetic field formed between the magnetic poles of the magnet roller 13, the developing sleeve 12 is returned to the stirring portion 7. An appropriate amount of toner is supplied to the developer in the stirring unit 7 based on the detection result by the toner density sensor 10. Note that the doctor blade 14 also plays a role of promoting frictional charging of the toner by sliding with the magnetic carrier in the developer.

  As the drum cleaning device 15, a system in which the cleaning blade 16 made of an elastic body is pressed against the photoconductor 4 is used, but another system may be used. In order to improve the cleaning property, this example employs a system having a contact conductive fur brush 17 whose outer peripheral surface is in contact with the photosensitive member 4 so as to be rotatable in the direction of the arrow in the figure. The fur brush 17 also serves to apply the lubricant to the surface of the photoreceptor while scraping off the lubricant from a solid lubricant (not shown) to form a fine powder. A metal electric field roller 18 for applying a bias to the fur brush 17 is rotatably provided in the direction of the arrow in the figure, and the tip of the scraper 19 is pressed against it. The toner attached to the fur brush 17 is transferred to the electric field roller 18 to which a bias is applied while rotating in contact with the fur brush 17 in the counter direction. Then, after being scraped from the electric field roller 18 by the scraper 19, it falls onto the recovery screw 20. The collection screw 20 conveys the collected toner toward the end of the drum cleaning device 15 in the direction orthogonal to the drawing sheet surface, and transfers it to the external recycling conveyance device 21. The recycle transport device 21 sends the delivered toner to the developing device 6 for recycling.

  The neutralization lamp 22 neutralizes the photoreceptor 4 by light irradiation. The surface of the photoreceptor 4 that has been neutralized is uniformly charged by the charging device 23 and then subjected to optical writing processing by the optical writing device 2. As the charging device 23, a charging device that rotates a charging roller to which a charging bias is applied while contacting the photosensitive member 4 is used. A scorotron charger or the like that performs a non-contact charging process on the photoreceptor 4 may be used.

  In FIG. 2 described above, K, Y, M, and C toner images are formed on the photoreceptors 4K, 4Y, 4M, and 4C of the four process units 3K, 3Y, 3M, and 3C by the processes described above. Is done.

  A transfer unit 24 is disposed below the four process units 3K, 3Y, 3M, and 3C. The transfer unit 24 as a belt driving device moves the intermediate transfer belt 25 stretched by a plurality of rollers endlessly in the clockwise direction in the drawing while contacting the photoreceptors 4K, 4Y, 4M, and 4C. As a result, primary transfer nips for K, Y, M, and C in which the photoreceptors 4K, 4Y, 4M, and 4C contact the intermediate transfer belt 25 that is an endless belt member are formed.

  In the vicinity of the primary transfer nips for K, Y, M, and C, the intermediate transfer belt 25 is moved to the photoreceptors 4K, 4Y, 4M, and 4C by primary transfer rollers 26K, 26Y, 26M, and 26C disposed inside the belt loop. It is pushing toward. A primary transfer bias is applied to the primary transfer rollers 26K, 26Y, 26M, and 26C by a power source (not shown). As a result, a primary transfer electric field for electrostatically moving the toner images on the photoconductors 4K, 4Y, 4M, and 4C toward the intermediate transfer belt 25 is formed in the primary transfer nips for K, Y, M, and C. Yes.

  In the drawing, a toner image is sequentially formed at each primary transfer nip on the front surface of the intermediate transfer belt 25 that sequentially passes through the primary transfer nips for K, Y, M, and C along with the endless movement in the clockwise direction. Overlaid and primary transferred. By this primary transfer of superposition, a four-color superposed toner image (hereinafter referred to as a four-color toner image) is formed on the front surface of the intermediate transfer belt 25.

  Below the transfer unit 24 in the figure, a paper transport unit 28 is provided between the drive roller 30 and the secondary transfer roller 31 to endlessly move the endless paper transport belt 29. The intermediate transfer belt 25 and the paper transport belt 29 are sandwiched between the secondary transfer roller 31 and the lower stretching roller 27 of the transfer unit 24. As a result, a secondary transfer nip is formed in which the front surface of the intermediate transfer belt 25 and the front surface of the paper transport belt 29 abut. A secondary transfer bias is applied to the secondary transfer roller 31 by a power source (not shown). On the other hand, the lower stretching roller 27 of the transfer unit 24 is grounded. Thereby, a secondary transfer electric field is formed in the secondary transfer nip.

  A registration roller pair 33 is disposed on the right side of the secondary transfer nip in the drawing. A registration roller sensor (not shown) is disposed near the entrance of the registration nip of the registration roller pair 33. The recording paper P conveyed from the blank paper supply device (not shown) toward the registration roller pair 33 is temporarily stopped after a predetermined time when the leading edge of the recording paper P is detected by the registration roller sensor. Touch the tip to the resist nip. As a result, the posture of the recording paper P is corrected, and preparations for synchronization with image formation are completed. In this way, the posture of the recording paper P is corrected, but the correction may not be performed successfully. Then, a skew of the recording paper P occurs on the downstream side of the registration roller pair 33.

  When the prior application of the recording paper P hits the registration nip, the registration roller pair 33 resumes roller rotation driving at a timing at which the recording paper P can be synchronized with the four-color toner image on the intermediate transfer belt 25, and the recording paper P To the secondary transfer nip.

  In the secondary transfer nip, the four-color toner image on the intermediate transfer belt 25 is secondarily transferred onto the recording paper under the influence of the secondary transfer electric field and the nip pressure, and becomes a full color image combined with the white color of the recording paper. The recording paper that has passed through the secondary transfer nip is separated from the intermediate transfer belt 25 and is conveyed to the fixing device 34 along with its endless movement while being held on the front surface of the paper conveying belt 29.

  On the surface of the intermediate transfer belt 25 that has passed through the secondary transfer nip, untransferred toner that has not been transferred to the recording paper at the secondary transfer nip adheres. This transfer residual toner is scraped off and removed by a belt cleaning device in contact with the intermediate transfer belt 25.

  The recording paper conveyed to the fixing device 34 is fixed to a full color image by pressurization or heating in the fixing device 34, and then sent from the fixing device 34 to the paper discharge roller pair 35, and then to the outside of the apparatus. Discharged.

  In FIG. 1 described above, a switchback device 36 is disposed under the paper transport unit 22 and the fixing device 34. As a result, the recording paper that has undergone the image fixing process on one side is switched by the switching claw to the recording paper path to the recording paper reversing device, where it is reversed and enters the secondary transfer transfer nip again. Then, after the secondary transfer process and the fixing process of the image are performed on the other side, the sheet is discharged onto a discharge tray.

  The scanner 150 fixed on the image forming unit 1 and the ADF 51 fixed on the scanner 150 have a fixed reading unit and a moving reading unit 152. The moving reading unit 152 is disposed immediately below a second contact glass (not shown) fixed to the upper wall of the casing of the scanner 150 so as to come into contact with the document MS, and is a moving body equipped with a light source, a reflection mirror, and the like. The carriage can be moved in the horizontal direction in the figure. Then, in the process of moving the carriage from the left side to the right side in the figure, the light emitted from the light source is reflected by a document (not shown) placed on the second contact glass, and then passed through a plurality of reflecting mirrors. Read with an image sensor such as a CCD.

  On the other hand, the fixed reading unit includes a first surface fixed reading unit 151 disposed in the scanner 150 and a second surface fixed reading unit (not shown) disposed in the ADF 51. The first surface fixed reading unit 151 having a light source, a reflection mirror, an image reading sensor such as a CCD, etc. is arranged directly below a first contact glass (not shown) fixed to the upper wall of the casing of the scanner 150 so as to contact the document MS. It is installed. Then, when a document MS conveyed by the ADF 51 described later passes over the first contact glass, the light emitted from the light source is sequentially reflected on the document surface and received by the image reading sensor via a plurality of reflecting mirrors. To do. Thus, the first surface of the document MS is scanned without moving the optical system including the light source and the reflection mirror. The second surface fixed reading unit scans the second surface of the document MS after passing through the first surface fixed reading unit 151.

  The ADF 51 disposed on the scanner 150 includes a document placing table 53 for placing the document MS before reading on the main body cover 52, a transport unit 54 for transporting the document MS as a sheet-like member, and reading. A document stacking table 55 for stacking the subsequent document MS is held. A hinge (not shown) fixed to the scanner 150 is supported so as to be swingable in the vertical direction. Then, by swinging, it moves like an open / close door, and the first contact glass 154 and the second contact glass 155 on the upper surface of the scanner 150 are exposed in the opened state.

  In the case of a single-sided original such as a book in which one corner of the original bundle is bound, the originals cannot be separated one by one and cannot be transported by ADF. Therefore, in the case of a single-sided original, the ADF 51 is opened as shown in the figure, and then the single-sided original with the page to be read open facing down is placed on the second contact glass 154 and then the ADF is closed. Then, the image of the page is read by the moving reading unit 152 shown in FIG.

  On the other hand, in the case of a document bundle in which a plurality of independent documents MS are simply stacked, the document MS is automatically conveyed one by one by the ADF 51 while the first surface fixed reading unit 151 in the scanner 150 or the first document in the ADF 51 is used. The two-surface fixed reading unit can sequentially read.

  In this case, after setting the document bundle on the document placing table 53, a copy start button (not shown) is pressed. Then, the ADF 51 sends the originals MS of the original bundle placed on the original placement table 53 into the conveyance unit 54 in order from the top, and conveys the original MS toward the original stack table 55 while inverting it. In the course of this conveyance, immediately after the document MS is reversed, the original MS is passed directly over the first surface fixed reading unit 151 of the scanner 150. At this time, the image on the first surface of the document MS is read by the first surface fixed reading unit 151 of the scanner 150.

  As the K, Y, C, and M toners used in the process units 3K, 3Y, 3M, and 3C of the respective colors, those having a weight average particle diameter of 4 to 8 [μm] are used in order to realize a high-quality image. ing. If the weight average particle size is less than 3 [μm], it is easy to cause problems such as in-machine contamination due to scattering, image density reduction in a low humidity environment, and poor photoconductor cleaning. . On the other hand, when the weight average particle diameter exceeds 8 [μm], it becomes easy to generate scattering around the spot when developing a micro spot of 100 [μm] or less. The weight average particle diameter and circularity of the toner can be measured using a flow type particle image analyzer FPIA-1000 (manufactured by Toa Medical Electronics Co., Ltd.).

  As the resin constituting the toner base particles, polystyrene resin, epoxy resin, polyester resin, polyamide resin, styrene acrylic resin, styrene methacrylate resin, polyurethane resin, vinyl resin, polyolefin resin, styrene butadiene resin, phenol resin, polyethylene resin, Silicone resin, butyral resin, terpene resin, polyol resin and the like are listed. Examples of the vinyl resin include styrene such as polystyrene, poly-p-chlorostyrene and polyvinyltoluene, and homopolymers thereof: styrene-p-chlorostyrene copolymer, styrene-propylene copolymer, styrene-vinyl. Toluene copolymer, styrene-vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene -Methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether Copolymer, styrene-vinylethyl Ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester Styrene copolymers such as copolymers: polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate and the like.

  The polyester resin is composed of a divalent alcohol in group A and a dibasic acid salt in group B as exemplified below, and further a trivalent or higher alcohol or carboxylic acid in group C. It may be added as a component.

Group A: ethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4 butanediol, neopentyl glycol, 1,4 butenediol, 1,4-bis (hydroxymethyl) Cyclohexane, bisphenol A, hydrogenated bisphenol A, polyoxyethylenated bisphenol A, polyoxypropylene (2,2) -2,2′-bis (4-hydroxyphenyl) propane, polyoxypropylene (3,3) -2 , 2-bis (4-hydroxyphenyl) propane, polyoxyethylene (2,0) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (2,0) -2,2′-bis ( 4-hydroxyphenyl) propane and the like.

Group B: maleic acid, fumaric acid, mesaconic acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebacic acid, malonic acid, linolenic acid, Or esters of these acid anhydrides or lower alcohols.

Group C: Trivalent or higher alcohols such as glycerin, trimethylolpropane and pentaerythritol, and trivalent or higher carboxylic acids such as trimellitic acid and pyromellitic acid. As the polyol resin, an alkylene oxide adduct of an epoxy resin and a dihydric phenol, or a compound having one active hydrogen in the molecule that reacts with the glycidyl ether and the epoxy group, and an active hydrogen that reacts with the epoxy resin in the molecule. A product obtained by reacting two or more compounds.

  Examples of the pigment to be contained in the toner include the following. That is, examples of the black pigment include azine dyes such as carbon black, oil furnace black, channel black, lamp black, acetylene black, and aniline black, metal salt azo dyes, metal oxides, and composite metal oxides. Examples of yellow pigments include cadmium yellow, mineral fast yellow, nickel yellow, navel yellow, naphthol yellow S, Hansa Yellow G, Hansa Yellow 10G, Benzidine Yellow GR, Quinoline Yellow Lake, Permanent Yellow NCG, Tartrazine Lake, etc. Is mentioned.

  Examples of the orange pigment include molybdenum orange, permanent orange GTR, pyrazolone orange, Vulcan orange, indanthrene brilliant orange RK, benzidine orange G, indanthrene brilliant orange GK and the like. Examples of red pigments include Bengala, Cadmium Red, Permanent Red 4R, Resol Red, Pyrazolone Red, Watching Red Calcium Salt, Lake Red D, Brilliant Carmine 6B, Eosin Lake, Rhodamine Lake B, Alizarin Lake, Brilliant Carmine 3B, and the like. Can be mentioned.

  Examples of purple pigments include fast violet B and methyl violet lake. Examples of blue pigments include cobalt blue, alkali blue, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, phthalocyanine blue partially chlorinated, first sky blue, and indanthrene blue BC. Examples of the green pigment include chrome green, chromium oxide, pigment green B, and malachite green lake.

  These pigments may be used alone or in combination of two or more. In color toners, uniform dispersion of good pigment is essential, so instead of putting the pigment directly into a large amount of resin, a master batch in which the pigment is dispersed at a high concentration is prepared and diluted. The charging method is used. In this case, a solvent is generally used to help dispersibility, but it may be dispersed with water in consideration of the environment. When water is used, temperature control is important so that residual moisture in the masterbatch does not become a problem.

  A charge control agent is dispersed (internally added) in the toner particles. The charge control agent makes it possible to optimally control the charge amount according to the development system, and to stabilize the balance between the particle size distribution and the charge amount. For controlling the toner to be positively charged, nigrosine and quaternary ammonium salts, triphenylmethane dyes, imidazole metal complexes and salts can be used alone or in combination of two or more. Further, salicylic acid metal complexes, salts, organic boron salts, calixarene compounds, and the like are used for controlling the toner to be negatively charged.

  Further, a release agent can be internally added to the toner in the present invention to prevent offset at the time of fixing. Release agents include natural waxes such as candelilla wax, carnauba wax, rice wax, montan wax and derivatives thereof, paraffin wax and derivatives thereof, polyolefin wax and derivatives thereof, sazol wax, low molecular weight polyethylene, and low molecular weight polypropylene. And alkyl phosphate esters. The melting point of these release agents is preferably 65 to 90 ° C. If it is lower than this range, blocking during storage of the toner tends to occur, and if it is higher than this range, offset tends to occur in the region where the fixing roller temperature is low.

  Additives may be added to the toner particles for the purpose of improving releasability and even improving dispersibility. As additives, styrene acrylic resin, polyethylene resin, polystyrene resin, epoxy resin, polyester resin, polyamide resin, styrene methacrylate resin, polyurethane resin, vinyl resin, polyolefin resin, styrene butadiene resin, phenol resin, butyral resin, terpene resin, A polyol resin etc. are mentioned, You may mix them 2 or more types. Crystalline polyester may be used as the polyester resin. It is an aliphatic polyester having crystallinity, having a sharp molecular weight distribution, and increasing the absolute amount of its low molecular weight as much as possible. This resin undergoes a crystal transition at the glass transition temperature (Tg), and at the same time, the melt viscosity suddenly decreases from the solid state and exhibits a fixing function to paper. By using this crystalline polyester resin, low-temperature fixing can be achieved without excessively reducing the Tg and molecular weight of the resin. Therefore, there is no decrease in storage stability associated with a decrease in Tg. Further, there is no excessively high gloss and offset resistance deterioration due to low molecular weight. Therefore, the introduction of the crystalline polyester resin is very effective for improving the low-temperature fixability of the toner.

  In order to improve the fluidity, the inorganic fine powder may be adhered or fixed to the toner surface. The average particle size of the inorganic fine powder is suitably 10 [nm] to 200 [nm]. When the particle size is smaller than 10 [nm], it is difficult to create an uneven surface having an effect on fluidity, and when the particle size is larger than 200 [nm], the powder shape becomes rough, which is a problem of toner shape. Occurs.

  Examples of the inorganic fine powder include Si, Ti, Al, Mg, Ca, Sr, Ba, In, Ga, Ni, Mn, W, Fe, Co, Zn, Cr, Mo, Cu, Ag, V, and Zr. Examples thereof include oxides and composite oxides. Of these, fine particles of silicon dioxide (silica), titanium dioxide (titania), and alumina are preferably used. Furthermore, it is effective to perform a surface modification treatment with a hydrophobizing agent or the like. Typical examples of the hydrophobizing agent include the following. Namely, dimethyldichlorosilane, trimethylchlorosilane, methyltrichlorosilane, allyldimethyldichlorosilane, allylphenyldichlorosilane, benzyldimethylchlorosilane, bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, p-chloroethyltrichloro Silane, chloromethyldimethylchlorosilane, chloromethyltrichlorosilane, hexaphenyldisilazane, hexatolyldisilazane and the like.

  The inorganic fine powder is preferably added at a ratio of 0.1 to 2% by weight with respect to the toner. If it is less than 0.1 [wt%], the effect of improving toner aggregation is poor, and if it exceeds 2 [wt%], there are problems such as toner scattering between fine wires, contamination in the machine, scratches and abrasion of the photoreceptor. This is because it tends to occur.

  In addition, at least a charge control agent may be attached or fixed to the surface of the powder made of resin or pigment so that the powder surface shape has a small period and a large period. The average particle size is optimally as small as 10 to 200 [nm]. When the particle size is smaller than 10 [nm], it is difficult to create an uneven surface having an effect on fluidity, and when the particle size is larger than 200 [nm], the powder shape becomes rough, which is a problem of toner shape. Occurs.

  In addition, other additives such as Teflon (registered trademark) powder, zinc stearate powder, polyvinylidene fluoride powder, lubricant powders; or cerium oxide powder, silicon carbide powder, titanium, as long as they do not have a substantial adverse effect. A small amount of an abrasive such as strontium acid powder may be added as a developability improver.

  It may be a toner or a capsule toner produced by a spray drying method or the like produced without using a kneading step or a pulverizing step.

The toner resistance is adjusted by adjusting the amount of the conductive material contained and dispersed in the base resin. Examples of the carbon-based conductive material include acetyl black, oil furnace black, thermal black, carbon fiber, and graphite. Examples of the metallic conductive material include metal powders such as tin oxide (SnO ₂ ), zinc oxide (ZnO), Cu, and Ni. These are appropriately dispersed in the toner binder resin to adjust the electric resistance.

Next, features of the present invention will be described.
Each of the developing devices 6K, 6Y, 6C, and 6M shown in FIG. 2 performs development using a developer containing two types of magnetic carrier, a small particle magnetic carrier and a large particle magnetic carrier. It has become. As described later, the small particle size magnetic carrier and the large particle size magnetic carrier are processed so as to have different electric resistances, but the same magnetic material is used as the base material. The magnetic material is a ferrite material having a mass magnetization of 80 to 100 [emu / g]. In the copying machine according to the embodiment, a small particle size magnetic carrier and a large particle size magnetic carrier are mixed in a weight ratio of 50 [%]: 50 [%].

  In the developers used in the developing devices 6K, 6Y, 6C, and 6M, the weight average particle size of the small particle size magnetic carrier is adjusted to about 25 [μm], and the weight average particle size of the large particle size magnetic carrier is adjusted. It is adjusted to about 80 [μm]. As the base material, a base ferrite material is fired at 1250 to 1300 [° C.] for about 3 to 5 hours, pulverized with a crusher or the like, and then processed into a desired particle size. In addition, about the weight average particle diameter and circularity of a magnetic carrier, it is possible to measure using the flow type particle image analyzer FPIA-1000 (made by Toa Medical Electronics Co., Ltd.).

  The weight average particle diameter of the small particle size magnetic carrier is preferably 20 [μm] to 40 [μm], and more preferably 25 [μm] to 35 [μm]. The weight average particle size of the large particle size magnetic carrier is preferably 60 [μm] to 90 [μm], and more preferably 70 [μm] to 80 [μm]. If the small particle size magnetic carrier is too small, it will be disadvantageous for carrier adhesion, and if it is too large, blur and density unevenness will occur and the image quality will deteriorate, so the above range is suitable. On the other hand, if the magnetic particle carrier is too small, it is not sufficient to cause a disturbance, and if it is too large, blur and density unevenness occur and the image quality is lowered.

The electrical resistance of the small particle size magnetic carrier is adjusted to 10 ¹² to 10 ¹³ [Ω] by the dynamic resistance DR, and the large particle size magnetic carrier is adjusted to 10 ⁸ to 10 ⁹ [Ω] by the dynamic resistance DR. ing.

  The dynamic resistance DR can be measured using the measuring device shown in FIG. A rotatable sleeve 512 having a diameter of 20 [mm] including a magnet roller 513 is set above the pedestal 500 that is electrically grounded. The free end of the counter electrode (doctor) 502 is opposed to the surface of the sleeve 512 with a gap of 0.9 [mm]. The size of the counter electrode 502 is width = 65 [mm] and length L = 0.5 to 1 [mm]. In this state, the sleeve 512 is rotationally driven at a rotational speed of 600 [rpm] (linear speed of 628 [mm / sec]). Then, a predetermined amount (14 g) of the magnetic carrier C to be measured is carried on the rotating sleeve 512, and the magnetic carrier C is stirred for 10 minutes as the sleeve 512 rotates. Next, the current IRII [A] flowing between the sleeve 512 and the counter electrode 502 is measured by the ammeter 503 without applying a voltage to the sleeve 512. Next, a voltage E [V] of a withstand voltage upper limit level (400 [V] for high resistance silicon-coated carrier to several [V] for iron powder carrier) is applied to the sleeve 512 from the DC power source 504 for 5 minutes. Then, a current IRQ [A] flowing between the sleeve 512 and the counter electrode 502 in a state where the voltage E is applied is measured by an ammeter 503. Finally, the dynamic resistance DR is obtained by substituting each measured value into the equation “DR = E / (IRQ−IRII)”.

The dynamic resistance of the magnetic carrier mixed under the conditions described above was 10 ¹⁰ to 10 ¹¹ [Ω].

  By mixing the above-mentioned small particle size magnetic carrier and large particle size magnetic carrier for use in development, the electric resistance of the developer is smaller than when using a small particle size magnetic carrier alone. As a result, the strength of the developing electric field is increased, and the developing ability can be improved.

[Experiment]
In order to confirm the effect of the present invention, the present inventor uses the image forming apparatus according to the embodiment, and includes developer 1, developer 2 and developer 3 each containing toner and the magnetic carrier shown in Table 1. The image was output using.

  The details of the magnetic carrier contained in developer 1, developer 2 and developer 3 are as follows.

<Developer 1>
As a magnetic carrier, only a large particle size magnetic carrier having a weight average particle diameter of 60 [μm] to 90 [μm] and an electric resistance of 10 ⁸ to 10 ⁹ [Ω] in terms of dynamic resistance DR was contained.

<Developer 2>
As a magnetic carrier, only a small particle size magnetic carrier having a weight average particle diameter of 20 [μm] to 40 [μm] and an electric resistance of 10 ¹² to 10 ¹³ [Ω] in terms of dynamic resistance DR was contained.

<Developer 3>
The magnetic carrier has a weight average particle diameter of 60 [μm] to 90 [μm], an electric resistance of 10 ⁸ to 10 ⁹ [Ω] as a dynamic resistance DR, and a weight average particle diameter of 20 [μm] to 40 [μm], mixed with a small particle size magnetic carrier whose electric resistance is 10 ¹² to 10 ¹³ [Ω] in dynamic resistance DR at a weight ratio of 50 [%]: 50 [%] Contained.

  Further, the toners used in the developer 1, the developer 2, and the developer 3 are those described in the present embodiment, and the same toner is used in all the developers.

  FIG. 5 and Table 2 show the experimental results.

  In the evaluation of carrier adhesion shown in Table 2, “◯” indicates a case where carrier adhesion does not occur, and “x” indicates a case where carrier adhesion occurs. In the evaluation of image uniformity, “◯” indicates that the image is uniform, and “x” indicates that the image is not uniform.

  The toner adhesion amount γ shown in FIG. 5 is an index indicating how much toner has adhered to the latent image on the photosensitive member 4 per 1 [kv] of the developing bias. The larger the value, the better the developing ability. It represents that. As shown in the figure, by using the developer 3 composed of a carrier obtained by mixing a low-resistance large-particle magnetic carrier and a high-resistance small-particle magnetic carrier and a toner, the carrier alone of the small-particle magnetic carrier is used. The developing ability is improved as compared with the case where the developer 2 composed of toner and toner is used.

  Further, as shown in Table 2, a uniform image can be obtained without carrier adhesion by using the developer 3 in which a low-resistance large-particle magnetic carrier and a high-resistance small-particle magnetic carrier are mixed. it can.

Next, FIG. 6 is a schematic diagram showing the photoreceptor 4 and the developing device 6 in an enlarged manner.
The magnetic carrier in the developer on the surface of the developing sleeve 12 rises on the surface of the sleeve by the magnetic flux generated by the magnet roller 13 serving as magnetism generating means to form a magnetic brush.

  The magnet roller 13 has six magnetic poles arranged in the order of N1 (N pole), S1 (S pole), N2 (N pole), S2 (S pole), S3 (S pole), and S4 (S pole) in the circumferential direction. It has. The magnetic pole S1 is a pumping magnetic pole that generates a magnetic flux for pumping up the developer in the stirring unit 7 shown in FIG. The magnetic pole N1 is a developing magnetic pole for causing the developer to spike in the developing region where the photosensitive member 4 and the developing sleeve 12 face each other. Further, the magnetic pole S2 and the magnetic pole N2 are transport poles for transporting the developer that has passed through the development region, and the magnetic pole S3 and the magnetic pole S4 are the developer transported by the magnetic pole S2 and the magnetic pole N2 from the surface of the developing sleeve. It is a repulsion magnetic pole for making it detach | leave and return to the stirring part 7 shown in FIG.

  In the figure, the broken line indicated by reference numeral L2 represents the direction of the magnetic pole N1, which is the developing magnetic pole, and its position is shifted in the circumferential direction of the sleeve from the closest contact point between the developing sleeve surface and the photosensitive member surface indicated by reference numeral L1. It is arranged at the position. When the magnetic pole N1 is disposed at the closest position, the developer is strongly pressed at the closest position, and carrier adhesion is likely to occur.

  FIG. 7 is a diagram illustrating the relationship between the magnetic pole angle of the magnetic pole N1 and the carrier adhesion amount. The carrier adhesion was calculated by counting the number of carrier adhesions within a certain area of the photoreceptor surface. As shown in the figure, compared with the case where the closest contact and the magnetic pole N1 coincide (magnetic pole angle 0 [°]), the magnetic pole angle is shifted in the developing sleeve circumferential direction downstream direction from the closest contact (magnetic pole angle). By providing the magnetic pole N1, the recovery effect by the magnetic force can be obtained after the developer has passed through the development region, and carrier adhesion can be suppressed. In the copier according to the present embodiment, the magnetic pole N1 is disposed at a position shifted in the circumferential direction by 5 [°] from the closest point. The developing gap, which is the gap between the photosensitive member 4 and the developing sleeve 12 at the closest point, is set to 300 [μm].

  Next, a modification of the copying machine according to the embodiment will be described. Unless otherwise specified, the configuration of the copying machine according to the modification is the same as that of the copying machine described with reference to FIG. FIG. 8 is a diagram illustrating a developing sleeve vibrating device that vibrates the developing sleeve 12.

  The developing sleeve 12 is provided with a gear 601 for transmitting driving to one side of the shaft, and a bearing 602 for supporting the shaft of the developing sleeve 12 is provided on the other side.

  Further, an elastic member 603 made of a spring is in contact with the end surface of the shaft on the side where the gear 601 of the developing sleeve 12 is disposed, and the developing sleeve vibrates on the end portion of the shaft on the side where the bearing 602 is disposed. A piezoelectric element 604 made of a piezoelectric material such as lead zirconate titanate or barium titanate, which constitutes the apparatus, is in contact. The developing sleeve 12 can be vibrated in the axial direction by outputting a voltage from the AC power supply 605 connected to the piezoelectric element 604 to the piezoelectric element 604.

  Since the developing sleeve 12 is vibrated in the axial direction in this manner, the adhesive force between the magnetic carrier and the toner particles on the developing sleeve 12 is weakened, so that the supply capability of the toner from the developing sleeve 12 to the photosensitive member 4 is increased and the developing ability is increased. Can be further improved.

  FIG. 9 is a graph showing the relationship between the vibration frequency of the developing sleeve vibration device and the toner adhesion amount γ. As shown in the figure, the toner adhesion amount γ can be increased by vibrating the developing sleeve 12 at a certain frequency.

  In the copying machine according to the modified example, the developing device 6 for each color uses a small particle size magnetic carrier of the developer contained therein, in which magnetic particles are mixed into a resin as a base material. Since the specific gravity of the resin material is smaller than that of the ferrite material described above, the movement that is pushed away by the movement of the large particle size magnetic carrier in the development region becomes active. For this reason, the probability of contact with the photosensitive member 4 is increased, and accordingly, the toner supply performance to the photosensitive member 4 is improved, so that the developing ability is improved.

FIG. 10 is a graph showing the results of evaluating the toner adhesion amount γ under such conditions.
As shown in the figure, when a small particle size magnetic carrier using a resin material as a base material is used, the toner adhesion amount γ is smaller than when a small particle size magnetic carrier using a ferrite material as a base material is used. It has improved.

As described above, according to the present embodiment, a small particle size magnetic carrier having a small weight average particle size, a large particle size magnetic carrier having a weight average particle size larger than that of the small particle size magnetic carrier, and smaller than the small particle size magnetic carrier. A developing case 9 that is a developer containing portion that contains a developer containing toner particles having a particle size, and a developing sleeve that is a developer carrying member that carries the developer in the developing case 9 on a surface that moves around itself. 12 and magnetism generating means for attracting the developer to the peripheral surface of the developing sleeve 12 by a magnetic force generated by a plurality of magnetic poles arranged so as to be aligned along the peripheral surface inside the loop of the peripheral surface of the developing sleeve 12 The developer roller is transported to the developing region facing the photosensitive member 4 which is a latent image carrier of the image forming apparatus by moving the surface of the developing sleeve 12, and in the developing region, G The developing device 6 for developing the latent image by transferring over to the latent image on the photosensitive member 4, the electric resistance of the small-diameter magnetic resistance carrier is ¹⁰ 12 ~10 13 ^[Ω] in the dynamic resistance, large diameter magnetic properties The electrical resistance of the carrier is 10 ⁸ to 10 ⁹ [Ω] in terms of dynamic resistance. Thereby, as clarified in the above-described experiment, it is possible to improve the developing ability by reducing the resistance of the entire developer while suppressing carrier adhesion.
Further, according to the present embodiment, the weight average particle size of the small particle size magnetic carrier is 20 [μm] to 40 [μm], and the weight average particle size of the large particle size magnetic carrier is 60 [μm] to 90 [90]. μm]. If the small particle size magnetic carrier is too small, it will be disadvantageous for carrier adhesion, and if it is too large, blur and density unevenness will occur and the image quality will deteriorate, so the above range is suitable. On the other hand, if the magnetic particle carrier is too small, it is not sufficient to cause a disturbance, and if it is too large, blur and density unevenness occur and the image quality is lowered.
Further, according to the present embodiment, the magnetic pole N1 existing at the position facing the developing region of the magnet roller 13 is provided at a position shifted from the closest portion of the photosensitive member 4 and the developing sleeve 12 to the downstream side in the circumferential direction. Therefore, after the developer passes through the development area, a recovery effect by magnetic force is obtained, and carrier adhesion can be further suppressed.
Further, according to the present embodiment, by providing the developing sleeve vibrating device that is a vibrating means for mechanically vibrating the developing sleeve 12, the adhesion force between the magnetic carrier on the developing sleeve 12 and the toner particles is weakened, and the toner Thus, the developing ability can be further improved.
In addition, according to the present embodiment, by using a small particle size magnetic carrier using a resin material as a base material, since the specific gravity of the small particle size magnetic carrier is small, the movement in the development area becomes active and the photosensitive region is exposed. Since the probability of contact with the body 4 increases, the developing ability is further improved.

DESCRIPTION OF SYMBOLS 1 Image formation part 2 Optical writing apparatus 3 Process unit 4 Photoconductor 6 Developing apparatus 7 Stirring part 8 Conveying screw 9 Developing case 10 Toner density sensor 11 Developing part 12 Developing sleeve 13 Magnet roller 14 Doctor blade 15 Drum cleaning apparatus 16 Cleaning blade DESCRIPTION OF SYMBOLS 17 Fur brush 18 Electric field roller 19 Scraper 20 Collecting screw 21 Recycling conveyance apparatus 22 Paper conveyance unit 22 Static elimination lamp 23 Charging apparatus 24 Transfer unit 25 Intermediate transfer belt 26 Primary transfer roller 27 Lower tension roller 28 Paper conveyance unit 29 Paper conveyance belt 30 Drive roller 31 Secondary transfer roller 33 Registration roller pair 34 Fixing device 35 Paper discharge roller pair 36 Switchback device 37 Paper feed path 40 Blank paper supply device 41 Paper bank 42 Feed Cassette 43 Delivery roller 44 Paper feed path 45 Separating roller 47 Conveying roller 50 Image reading unit 52 Main body cover 53 Document placement table 54 Conveying unit 55 Document stacking table 150 Scanner 151 Surface fixed reading unit 152 Moving reading unit 154 Contact glass 155 Contact glass 500 Pedestal 502 Counter electrode 503 Ammeter 504 DC power supply 512 Sleeve 513 Magnet roller 601 Gear 603 Elastic member 604 Piezoelectric element 605 AC power supply

Japanese Patent No. 3306730

Claims (6)

A small particle size magnetic carrier having a small average particle size, a large particle size magnetic carrier having a larger average particle size than the small particle size magnetic carrier, and a toner particle having a smaller particle size than the small particle size magnetic carrier. A developer accommodating portion for accommodating the developer;
A developer carrying member for carrying the developer in the developer containing portion on a surface that circulates by itself; and
Magnetic force that attracts the developer to the peripheral surface of the developer carrier by the magnetic force generated by a plurality of magnetic poles arranged along the peripheral surface inside the loop of the peripheral surface of the developer carrier. Generating means,
By moving the surface of the developer carrier, the developer is transported to a development area facing the latent image carrier of the image forming apparatus, and the toner in the developer is transferred to the latent image of the latent image carrier in the development area. In the developing device for developing the latent image,
The electric resistance of the small particle size magnetic carrier is 10 ¹² to 10 ¹³ [Ω] in dynamic resistance, and the electric resistance of the large particle size magnetic carrier is 10 ⁸ to 10 ⁹ [Ω] in dynamic resistance. A developing device. The developing device according to claim 1.
The small particle size magnetic carrier has a weight average particle size of 20 [μm] to 40 [μm], and the large particle size magnetic carrier has a weight average particle size of 60 [μm] to 90 [μm]. A developing device. The developing device according to claim 1 or 2,
The magnetic pole present at a position facing the developing area of the magnetism generating means is provided at a position shifted from the closest portion between the latent image carrier and the developer carrier to the downstream side in the circumferential direction. Development device The developing device according to claim 1, 2 or 3,
A developing device comprising a vibrating means for mechanically vibrating the developer carrying member. The developing device according to claim 1, 2, 3 or 4,
A developing device using the above-mentioned small particle size magnetic carrier using a resin material as a base material. An image obtained by developing the latent image by supplying a developer to the latent image formed on the latent image carrier by developing means is finally transferred onto the recording material, and the recording material In an image forming apparatus that forms an image on top,
An image forming apparatus using the developing device of claim 1, 2, 3, 4 or 5 as the developing means.

Images