JP2003076060A - Developing device for forming micr image - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device for an MICR printer which does not cause the lowering of the image density in spite of use for a long time. SOLUTION: A magnetic developer 62 housed in a hopper 61 contains magnetic toners consisting of at least a binder and magnetic powder and a large- grain size silica powder of >=1.5 mass% of the magnetic toners and <100 m<2> /g in BET specific surface area. The magnetic developer 62 is captured by a sponge-like elastic supply roller 64 and is supplied to a developing roller 10c consisting of an elastic rubber material and develops an electrostatic latent image of a photosensitive drum 9 conveyed without the aid of magnetic force. When the printer is used for a long time, the large-grain size silica powder prevents the degradation in the image density of printed matter by the desorption of the magnetic powder in the magnetic toners the occurrence of clogging, etc., in the supply roller 64 and the decrease of the supply rat of the magnetic developer 62 to the developing roller 10. The large-grain size silica powder regulates the electrostatic chargeability and flow properties of the magnetic developer 62 to the values suitable for the supply roller 64 and the developing roller 10c.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an MICR printer for forming an MICR image, and more particularly to a MICR image forming developing device having an elastic developing roller and using a contact developing system.

[0002]

2. Description of the Related Art MICR is used to prevent counterfeiting and alteration when issuing securities such as bills and checks in the financial market.
(Magnetic Ink Character R
An MICR printer equipped with an (ecognition) system is used. Here, the MICR system prints (image-forms) a magnetic identification mark called MICR font on a predetermined area of the face of securities, and reads it with a magnetic reader (reader sorter) (the identification mark is visually recognized by a person. It is possible to confirm the authenticity by being able to roughly recognize it.

Conventionally, printing of the above MICR font has been performed in the past.
Although offset printing and dot printer methods were exclusively used, the so-called dry magnetic development type electrophotographic printer that conveys and develops with a magnetic roller using a magnetic developer can be applied to the printing of the magnetic identification mark. Therefore, in recent years, it is replacing the conventional printer. An electrophotographic printer using this magnetic developer is generally unsuitable for color printing because the toner contains magnetic powder, but it can be said that it is suitable for MICR image formation. Therefore, a dedicated MICR printer has been provided in which the magnetic developer is changed to a composition suitable for MICR image formation.

On the other hand, with the progress of electrophotographic printers,
Recently, full-color printers with high-speed and high-definition color tone and saturation have also been provided, and have become widely used as office equipment in various offices. Further, such a full-color printer is capable of not only office printing but also design printing of the entire face of securities such as securities. Therefore,
In the financial market and the like, a printer capable of full-color printing and also capable of forming the MICR image has been desired. However, in such a full-color printer, generally, a developing method using a non-magnetic developer, particularly a non-magnetic one-component developing method having a simple structure is preferably adopted. Therefore, it was considered difficult to achieve both full-color printing and MICR image formation.

By the way, in an electrophotographic full-color printer, usually Y (yellow: yellow) and M (magenta:
A total of four color toners of red dye), C (cyan: blue with a greenish tint), and K (black: black) toner dedicated to printing black portions of characters and images on a single sheet of paper. Overwrite and transfer. Therefore, it is necessary to perform the image forming process for each color toner, and printing (printing) is repeated four times on one page of paper.

An image forming section of a non-magnetic one-component developing system of four colors is provided in parallel so that the printing process of successively superposing and transferring the four kinds (four colors) of toner on a sheet is performed in one step. The tandem type full color printer has been put into practical use. With this tandem type full color printer,
It has become possible to perform high-resolution, high-definition color tone and saturation printing at high speed.

Therefore, it has been proposed to make use of such a tandem type feature and to make it a MICR printer without making a large structural change. That is, in such a tandem type full-color printer, as described later in the embodiment of the present invention, the magnetic developer is put in the developing device of the K (black) image forming portion, and the other Y (yellow), M ( As in the conventional case, a non-magnetic developer such as chromatic toner is put in the developing device of the magenta) and C (cyan) image forming portions. By doing so, it becomes possible to form high-resolution and high-definition color printing (including black printing) and MICR image formation, and to provide a desirable printer in the financial market.

[0008]

However, in the non-magnetic one-component developing system of the tandem type full-color printer, unlike the magnetic roller of the magnetic developing system described above, a developing roller made of an elastic rubber material (contacting the photoconductor) is used. It is premised that the non-magnetic one-component developer is conveyed by a type) without the aid of magnetic force, and the non-magnetic one-component developer is frictionally charged by a doctor blade or the like to form a thin layer on the developing roller.

Therefore, the magnetic developer (toner for MICR printer) is simply stored in the black developing device of the tandem type full color printer, which is basically a non-magnetic developing system.
When the CR printer was constructed, the following problems were found.

That is, although there is relatively no problem in the initial stage, the image density gradually decreases as it is used. Since the image density corresponds to the magnetic reading intensity, the magnetic reading intensity decreases as the image density decreases. Therefore, even if the information on securities such as checks printed by the MICR printer is attempted to be recognized through the reader / sorter, it cannot be correctly recognized.

In general, magnetic toner contains a large amount of magnetic powder (40 to 50% by mass), so that the true specific gravity is large and the resistance is low. Therefore, so-called photoconductor fogging, such as paper stains and poor conveyance to the developing roller. The image defect based on is likely to occur. Further, since it contains magnetic powder, the performance at the time of fixing after being transferred to paper is also poor. Therefore, although it is preferable to contain the minimum amount of magnetic powder that has a magnetic force that can be recognized as MICR, sufficient consideration has not been conventionally given to the above-described developing method premised by the present invention.

As the magnetic powder, there are needle-shaped and octahedral magnetic powders. Of these, needle-shaped magnetic powder has a high remanent magnetization and a small amount can be added for magnetic reading, but if the remanent magnetization is high. It is known that magnetic agglomeration easily occurs to cause poor dispersion with the toner resin.
Magnetic toners that use mixed types of magnetic powders have also been proposed. Therefore, such a mixed use of two kinds of magnetic powders is preferably used in the developing method of the present invention, but the above-mentioned problem of reduction in image density still exists.

Further, in the non-magnetic one-component developing system, it is substantially only the doctor blade that imparts the triboelectric charging property to the developer, and the developer is required to have a very fast charging rise. Further, the higher the speed (for example, the printer described later in the embodiment of the present invention is 29 sheets / minute for A4 size), the faster the triboelectric charging property is required. Further, the developer is required to have very fast fluidity because of the mechanism in which the developer is supplied from the developing hopper through the supply roller to the developing roller to be used for development.

In the conventional developing method, various substances are externally added to the toner (for example, 0.1 to 1.0% by mass of small particle silica is externally added) in order to improve the rapid triboelectric charging start-up characteristics and fluidity. However, when the so-called "black solid" is printed, the substance causes remarkable image defects commonly called "comet" and "filming". Therefore, the external additive is also required to have a proper composition suitable for the developing system.

If the triboelectrification property is not sufficiently taken into consideration, the triboelectrification property will be excessively increased when the developing roller or the like runs idle until the printer is switched on and reaches the ready state, and as a result, the adhesive force to the developing roller is increased. A phenomenon occurs in which the image density at the leading edge of the paper becomes thin when printing is performed due to the excessive strength.

Therefore, an object of the present invention is to provide a MICR printer in which a magnetic developer is accommodated in a non-magnetic developing type developing device having an elastic developing roller, and various developing problems as described above are caused. The present invention provides a developer for MICR image formation and a developing device capable of performing stable image formation without causing the above-mentioned phenomenon and suppressing a decrease in image density due to long-term use thereof. And by this,
The reader sorter enables accurate reading of information on securities.

[0017]

In order to achieve the above object, the inventors of the present invention have made earnest studies, and as a result, pay attention to the transport compatibility between a magnetic toner and a specific developing member such as an elastic developing roller or a supply roller. However, they have found that the above various problems can be solved by devising the composition of the magnetic developer containing an external additive, and have completed the present invention.

The developing device for MICR image formation according to the first aspect of the present invention is a contact developing system in which a magnetic developer is contained and an elastic developing roller is brought into pressure contact with a photosensitive member, which is the premise of the present invention.

According to the invention described in claim 1,
A developing hopper having an opening to face a photoconductor on which an electrostatic latent image is formed and containing a magnetic developer; and a developing hopper provided so as to partially come into contact with the photoconductor to press the photoconductor. An elastic developing roller that holds the magnetic developer housed inside and conveys the magnetic developer to the electrostatic latent image of the photoconductor, and conveys the elastic developing roller rather than the opening. A doctor blade that regulates the magnetic developer so as to form a thin layer on the elastic developing roller on the upstream side in the direction, and the doctor blade disposed in the hopper on the upstream side in the conveying direction of the elastic developing roller with respect to the doctor blade. When the supply roller is in pressure contact with the elastic developing roller, and the magnetic developer is allowed to return to the developing hopper by light pressure contact with the elastic developing roller on the downstream side of the opening in the conveying direction of the elastic developing roller. A conductive regulating sheet member for regulating the outflow of the magnetic developer from the inside of the developing hopper, and a bias voltage applying means for applying a bias voltage to at least the elastic developing roller and the supply roller are provided, and the magnetic developer is By providing a developing device for MICR image formation, which comprises a magnetic toner comprising at least a binder resin and a magnetic powder, and a fine silica powder having a large particle diameter of 1.5% by mass or more based on the magnetic toner. Can be achieved.

The large particle size silica fine powder has a BET specific surface area of less than 100 m ² / g. As a result, it is possible to achieve the above-described object of suppressing a decrease in image density that occurs when printing (using) a magnetic developer and filling it.

The magnetic powder is formed by mixing needle-shaped magnetic powder and octahedral magnetic powder. As a result, it is possible to satisfy the magnetic reading performance and suppress the deterioration of the fixability to a low level.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail below with reference to embodiments of the present invention. FIG. 1 schematically shows an internal configuration of a tandem type full color printer including the developing device of the present invention and suitable as an MICR printer. First, the overall configuration of the printer device according to the present invention will be described with reference to FIG.

The internal structure of the printer device 1 shown in FIG. 1 includes an image forming section 2, a double-sided printing transport unit 3, and a paper feeding section 4.
Etc. Here, the image forming unit 2 has a configuration in which four image forming units 5 to 8 are arranged side by side, and magenta (M), cyan (C), and yellow (Y) from the right side to the left side of the drawing. , And black (K) in that order. Here, the magenta (M), cyan (C), and yellow (Y) image forming units 5 to 7 are configured to perform color printing by subtractive color mixing, and the black (K) image forming unit 8 will be described later. Used for MICR image formation (MICR font printing).

Each of the image forming units 5 to 8 has a drum unit DU and a toner unit (developing device) T.
It has the same configuration except that the developer is U and is stored in the developing hopper of the toner unit TU. That is, the toner units TU of the image forming units 5 to 7 have three subtractive primary colors of M (magenta), C (cyan), and Y.
The toners (non-magnetic developers) of respective colors (yellow) are stored. On the other hand, the toner unit TU of the image forming unit 8 is a developing device that contains the magnetic developer of the present invention for printing MICR fonts, as described later.

Therefore, the configuration will be described by taking the image forming unit 8 including the developing device of the present invention as an example. The drum unit DU accommodates the photosensitive drum 9, the charger 10a, the cleaner 10e, and the like, and the print head 10b is arranged above the drum unit DU. The toner unit TU is configured such that the developing roller 10c and the developer are housed in the developing device 44.

The peripheral surface of the photosensitive drum 9 is made of, for example, an organic photoconductive material, and in the vicinity of the peripheral surface of the photosensitive drum 9, a charger 10a, a print head 10b, and a developing roller 10 are provided.
c, a transfer device 10d, and a cleaner 10e are sequentially arranged. The photoconductor drum 9 rotates in the direction of the arrow, and first, the peripheral surface of the photoconductor drum 9 is uniformly charged by the charge applied from the charger 10a. Then, an electrostatic latent image is formed on the peripheral surface of the photosensitive drum 9 by optical writing based on the print information from the print head 10b, and a toner image is formed by the developing process by the developing roller 10c. In this way, the toner image formed on the peripheral surface of the photoconductor drum 9 reaches the position of the transfer device 10d as the photoconductor drum 9 rotates in the arrow direction, and the toner image immediately below the photoconductor drum 9 is shown in the arrow direction. Transferred to the paper that moves to.

On the other hand, the sheet is conveyed by the sheet feeding cassette 11 constituting the sheet feeding unit 4, the standby roller pair 12, the conveying belt 13, the driving roller 14, etc., and the sheet feeding roller 11a.
By the rotation of, the paper carried out from the paper feeding cassette 11 is sent to the standby roller pair 12, and further, is sent on the conveyor belt 13 at the timing corresponding to the toner image, and reaches each transfer device 10d. Then, the toner image is transferred in each of the transfer devices 10 d, and the sheet on which the toner image is transferred moves on the conveyor belt 13 in the direction of the arrow in accordance with the movement of the conveyor belt 13, and is subjected to heat fixing processing in the fixing unit 15. .

The above-mentioned paper includes not only the paper carried out from the paper feed cassette 11 but also the paper supplied from the MPF tray 16. In this case, the paper is the paper feed roller 16
It is carried in by a, and the printing process is performed by the above-mentioned route.

The fixing unit 15 includes a heat roller 15a (hereinafter referred to as a fixing roller) and a press roller 1.
5b and an oil applying roller 15c, etc., for example, while the paper is nipped and conveyed between the fixing roller 15a and the press roller 15b, toner images of, for example, a plurality of colors transferred to the paper are melted and heat-fixed to the paper. To do. The oil applying roller 15c has a function of applying a releasing oil to the peripheral surface of the fixing roller 15a and removing the toner remaining on the fixing roller 15a. The sheet on which the toner image is fixed by the fixing unit 15 is conveyed upward or leftward on the sheet surface via the switching flap 17. And usually
The switching flap 17 is located at the broken line position, and the paper is guided to the paper output unit 21 via the paper output roller pair 20.

On the other hand, the double-sided printing conveyance unit 3 is detachably attached to the main body of the apparatus and is a unit to be mounted when double-sided printing is performed by the printer apparatus 1 of the present embodiment. Pairs 18a to 18e are provided. For double-sided printing, the switching flap 1
The sheet is once sent upward by 7 and, for example, when the rear end of the sheet reaches the pair of conveying rollers 19, the conveyance of the sheet is stopped and the sheet is conveyed in the reverse direction. By this control, the sheet is carried into the sheet conveying path of the double-sided printing conveying unit 3 at the lower position, the sheet is fed in the reverse direction by the pair of reverse conveying rollers 18a to 18e, and reaches the standby roller pair 12 again, as described above. Then, the toner image is sent to the transfer portion at the same timing as the toner image, and the toner image is transferred to the back surface of the paper.

FIG. 2 is an external perspective view of the printer device 1 shown in FIG. The printer device 1 shown in FIG. 1 is composed of an upper part 22 and a lower part 23 of the device,
An operation panel 33 is disposed on the above, and a print sheet discharging section 21 is also formed on the upper surface thereof. Operation panel 33
Is composed of a key operation unit 33a in which a plurality of keys are arranged, and a display unit 33b such as a liquid crystal display which performs display based on display information output from the CPU 30 of FIG. 3 described later. Further, the paper discharge section 21 includes a pair of paper discharge rollers 20.
With the rotation of, the print sheets created by each image forming unit are output and sequentially stacked on the paper output unit 21.

Further, a front cover 24 that can be opened and closed is provided on the front surface of the lower portion 23 of the apparatus main body. The front cover 24 is opened, for example, during jam clearance or maintenance.

FIG. 3 is a circuit block diagram of the printer device 1 having the above-mentioned configuration. 3, the circuit block includes an interface controller (hereinafter referred to as I / F controller) 26, a printer controller 28, a printer printing unit 29, a CPU 30, a ROM 31, an operation panel 33, and an EEPROM 32. The I / F controller 26 converts the print data supplied from the host device into bitmap data and expands it in the frame memory 27. In the frame memory 27, a storage area is set for each of magenta (M), cyan (C), yellow (Y), and black (K), and data of each color is expanded in the corresponding area.

The data expanded in the frame memory 27 is output to the printer controller 28 and output to the printer printing unit 29 under the control of the CPU 30. At this time, magenta (M), cyan (C), yellow (Y),
The data of each color of black (K) is supplied to the corresponding print head 10b of FIG.

The system program of this example is stored in the ROM 31, and the CPU 30 performs processing in accordance with this system program.

Next, the basic operation of the printer device 1 described above will be described. First, when the power is turned on and the paper quality, number of sheets, print mode, and other designations of the paper to be used are input by key input or as a signal from the host device to be connected, the paper feed roller 11a is driven by a drive mechanism (not shown).
Rotates once to feed the sheets placed and stored in the sheet feeding cassette 11 toward the pair of standby rolls 12. The pair of standby rolls 12 temporarily stops the rotation and waits for the conveyance timing in a state where the leading end of the sheet is brought into contact with the nip portion formed by the pair of rollers.

Subsequently, the drive roller 14 rotates counterclockwise and the driven roller 14 'is driven to rotate counterclockwise as well. As a result, the conveyor belt 13
, The upper circulation portion contacts the four photoconductor drums 9, and the whole is circularly moved counterclockwise.

At the same time, each drum unit DU and toner unit TU are sequentially driven at the print timing. The photoconductor drum 9 rotates clockwise, the charger 10a applies a uniform high negative charge to the peripheral surface of the photoconductor drum 9, and the print head 10b outputs an image signal to the peripheral surface of the photoconductor drum 9. Exposure is performed accordingly to form a low potential portion. As a result, an electrostatic latent image composed of a high negative potential portion due to the charger 10a and a low negative potential portion due to exposure is formed. The developing roller 10c of the developing device 44 transfers the toner to the low potential portion of the electrostatic latent image to form a toner image on the peripheral surface of the photosensitive drum 9 (reverse development).

At the timing when the front end of the toner image on the peripheral surface of the most upstream photosensitive drum 9 is rotationally conveyed to a point facing the conveying belt 13, the print start position of the paper coincides with the facing point. Then, the pair of standby rollers 12 starts to rotate and feeds the paper to the paper carry-in section. The sheet is attracted to the transport belt 13 and is transported to the first transfer unit formed by the photoconductor drum 9 and the transfer unit 10d.

The transfer device 10d applies the transfer current output from the transfer bias power source to the sheet via the conveyor belt 13. The transfer current applied from the transfer unit transfers the M (magenta) toner image on the photosensitive drum 9 onto the sheet. Next, C at the second transfer part from the upstream
The (cyan) toner image is transferred, and further, the Y (yellow) toner image is transferred at the third transfer portion from the upstream side. Then, the K (black) toner image formed by the magnetic developer of the present invention is transferred at the fourth (ie, most downstream) transfer portion from the upstream side.

The sheet on which the four color toner images have been transferred in this manner is separated from the conveyor belt 13 and carried into the fixing unit 15. The fixing unit 15 heat-fixes the toner image on the sheet. After the image is fixed, the sheet is discharged onto the upper sheet discharge section 21 with the toner image downward by the pair of sheet discharge rollers 20, for example.

The printer device 1 according to the embodiment of the present invention is provided with a full color mode in which four image forming units are operated to form a full color image and a monochrome mode in which only one image forming unit is operated. In this case, MICR image formation can be performed. In addition,
The full-color mode can be configured by operating the three image forming units of M (magenta), C (cyan), and Y (yellow).

In the printer device 1 which operates as described above, each developing device 44 has the following structure in order to form a stable toner image on the photosensitive drum 9.

FIG. 4 is a side sectional view schematically showing a main part of the developing device 44 of the present invention. Developing device 44 shown in FIG.
Is a toner unit TU which is detachably attached to the printer device 1 and constitutes one image forming unit 8 together with the drum unit DU. The developing device 44 includes the hopper 6
1, the developing roller 10c made of a conductive rubber roller is rotatably held in the lower opening of the hopper 61, and the developer 62 is accommodated in the hopper 61.
A stirring member 63 is disposed so as to be buried in the developer 2 and stirs the developer.

At the lowermost part of the developing device 44, a supply roller 64 made of a sponge body is arranged in pressure contact with the developing roller 10c. The developing roller 10c is provided with a metal blade spring-shaped doctor blade 65 in pressure contact with the obliquely upper right peripheral surface thereof, and is provided with a squeeze sheet (conductive regulation sheet) 66 in contact with the lower peripheral surface thereof. There is. The squi sheet 66 is provided with a conductivity regulating sheet bias means including a bias power source 71. A sealing member 6 is provided on both sides of the doctor blade 65 to prevent the developer 62 from leaking by separating the inside and the outside of the opening of the hopper 61.
7 are provided.

By the way, in order to eliminate the developing memory, the developer 62 in the non-developing portion remaining on the peripheral surface of the developing roller 10c after the development on the photosensitive drum 9 is finished is scraped off in the developing device. The required rubbing force of the supply roller 64 differs depending on the adhesive force of the developer 62 to the developing roller 10c. That is, a strong rubbing force is required for a developer having a strong adhesive force, but a weak rubbing force is sufficient for a developer having a weak adhesive force. Developing roller 1 for this developer 62
It can be said that the adhesion force to 0c is substantially determined by the charging ability of the developer 62. That is, the smaller the triboelectric charge amount is, the weaker the adhesive force is, and the easier it is to scrape off the developing roller 10c.

However, the triboelectric charge amount of the developer 62 has a close relationship with the adhesion development (so-called photoconductor fog) on the non-image portion which occurs during development and causes a problem, and the developer with a small charge amount is involved. The more easily photoconductor fogging occurs.
Therefore, in order to prevent such photoconductor fogging, it is necessary to increase the triboelectric charge amount of the developer 62. When the triboelectric charge amount of the developer 62 is increased, the adhesive force to the developing roller 10c increases, so that it becomes necessary to apply a strong rubbing force to the supply roller 64.

Repeating the rotation for a long time with such a strong rubbing force causes deterioration of developing characteristics such as deterioration of charging ability and deterioration of fluidity of the developer, which is not preferable. For example, when the charge amount decreases, the above-described photoconductor fogging occurs, and when the fluidity decreases, the lack of development in halftone dot printing occurs.

Therefore, the developing device 4 according to the embodiment of the present invention.
In No. 4, first, the developing roller 10c is formed of a cored bar and a cylindrical semiconductive (10 ⁶ Ωcm) urethane rubber surrounding the cored bar, and a development bias of "-250 V" is applied to the cored bar. It is applied from the bias power source 68. Further, the supply roller 64 is composed of a core metal and a cylindrical semiconductive (10 ⁶ Ωcm) urethane sponge surrounding the core metal,
A supply bias of "-500 V" is applied to the core metal from the bias power source 69.

Further, the doctor blade 65 is formed of an elastic metal plate, and a "-500V" doctor bias is applied to the doctor blade 65 from the bias power source 69. Then, the squeeze sheet 66 located on the upstream side of the supply roller 64 is composed of a conductive member (10 ³ Ωcm), and a sheet bias voltage in the range from 0 V (0 volt) to the developing bias voltage of the developing roller 10c is applied to this. The bias power source 71 is used to apply the voltage.

As described above, when the squeeze sheet 66 is made of a conductive material and a sheet bias voltage in the range from 0 V to the developing bias voltage of the developing roller 10c is applied to the squi sheet 66, the developer 62 adhering to the developing roller 10c is removed. The charge can be reduced. As a result, the supply roller 64
Even the weak rubbing force caused by the developing roller 10c
The non-developed portion of the developer that has adhered and returned to the top can be scraped off.

As described above, the developing device 44 of the present invention employs the contact developing (roller) system in which the developing roller 10c made of elastic rubber is brought into pressure contact with the surface of the photosensitive drum 9. The high-speed and high-quality development by the non-magnetic developer is obtained by the above device configuration. Further, even with this contact developing method, development with MICR toner (magnetic developer) can be performed in the same manner as with non-magnetic developer.

However, as described in the conventional example, when printing such as continuous printing is performed using the magnetic toner in the developing device 44 having such a structure, the image density gradually decreases. This is because the formation of a stable toner layer on the developing roller 10c and the transfer from the developing roller 10c to the photosensitive member are gradually hindered.

The cause of this is considered to be the compatibility of conveyance between the magnetic toner and the developing member. That is, in the developing device 44 of the present invention, the developing roller 1 made of elastic rubber is used.
0c and a supply roller 64 made of a sponge body are used. On the other hand, in the magnetic toner, hard magnetic powder is exposed on the surface of the toner resin, and the magnetic powder is detached as it is used, and the detached magnetic powder firmly adheres to the developing roller 10c and the supply roller 64 and is conveyed. It is thought that it inhibits sex. In this case, the acicular magnetic powder having a high residual magnetization suitable for the MICR toner as the magnetic powder tends to promote the above-mentioned impediment to the transportability. In addition, since the magnetic toner contains magnetic powder and has a lower charge amount than the non-magnetic toner, in order to compensate for this,
Even if an external additive such as conventionally known small particle size silica is used,
Some of them may be detached as they are used, and the force of electrically attracting them becomes small, so that it is not possible to prevent a decrease in the toner supply amount to the developing roller 10c.

In particular, the supply roller 64 takes in the developer 32 in the hopper 61 and supplies it to the developing roller 10c. However, since the supply roller 64 of the present embodiment is made of a sponge-like elastic body, the above magnetic powder is used. It is conceivable that the amount of toner supplied to the developing roller 10c is significantly reduced when printing such as continuous printing is performed as a result of clogging.

Therefore, in the present invention, the composition itself of the magnetic developer is devised as described below, in addition to the above-mentioned developing device configuration.

[0057]

EXAMPLES Examples of the present invention will be shown below to more specifically describe the present invention. First, a production example of the magnetic toner used in the following examples will be described.

[Magnetic toner production example] Polyester resin (MW: 97,000, MN: 4,400, SP: 140 ° C) …… 62 mass% Magnetic powder 1 granular (octahedral) magnetic powder Toda Kogyo MAT222 …… 11 mass % (BET specific surface area 3.8 m ² / g, particle size 0.4 μm, remanent magnetization 18.1 emu / g) Magnetic powder 2 Needle-shaped magnetic powder Toda Kogyo MAT230 …… 24 mass% (BET specific surface area 16.0 m ² / g , Particle size 0.6 μm, remanent magnetization 31.8 emu / g) Wax polypropylene Mitsui Chemicals Co., Ltd. NP056 2% by mass Negative charge control agent 1% by mass Mix the above materials with a Henschel mixer and mix them at 2 The mixture was kneaded with a shaft extruder. Then, after cooling and coarse crushing, classification was performed to obtain a classified magnetic toner having an average particle diameter of 8.5 μm.

The magnetic powders 1 and 2 are set to 11% by mass and 24% by mass, respectively, for the following reason.
That is, the MICR toner requires a predetermined magnetic strength for magnetic reading, and it is not preferable to add 40 to 50% by mass of magnetic powder as in the conventional case in consideration of the fixing property. It has been described above that it is preferable for the developing system of the present invention to use a mixture of two kinds of magnetic powders having different shapes and magnetism. Therefore, the magnetic powders 1 and 2 having different shapes and magnetism were manufactured in advance in various mixing ratios, and the compounding amount that can satisfy the magnetic strength and reduce the total amount was obtained. This is because we have obtained the knowledge that

FIG. 5 is a diagram showing the residual magnetization and magnetic read value of the magnetic toner obtained by manufacturing the magnetic powders 1 and 2 at various mixing ratios. The magnetic read value is 100 to 15
It has been confirmed that if it is about 0%, no reading error occurs in the actual MICR system reader sorter. Therefore, in order to obtain a magnetic read value of 100 to 150%, it was found from FIG. 5 that the residual magnetization of the magnetic toner should be designed to 9 to 12 emu / g. As a mixing ratio of the magnetic powders 1 and 2, the magnetic powder 1 was 5 to 20% by mass and the magnetic powder 2 was 30 to 15% by mass. . Therefore, as an intermediate example of a preferable mixing ratio, the magnetic powders 1 and 2 are 11% by mass and 24%, respectively.
It is defined as% by mass. Incidentally, the residual magnetization of the magnetic toner having this mixing ratio was about 10 emu / g.

Example 1 An external additive having a BET specific surface area of 50 + −15 m ² / g was added to the classified magnetic toner.
1.0 mass%, 1.5 mass% of a large particle size silica fine powder (hydrophobic silica RX-50 manufactured by Nippon Aerosil Co., Ltd.)
2.0% by mass, 2.5% by mass, and 3.0% by mass were respectively added at five mixing ratios and mixed by a Henschel mixer, and magnetic developers A, B, C corresponding to the above mixing ratios were added.
D and E were obtained.

Comparative Example 1 With respect to the classified magnetic toner obtained in Example 1 above, the BET specific surface area as an external additive was 300 + −30 m ² /
0.3 mass% of a small particle size silica fine powder (hydrophobic silica R812 manufactured by Nippon Aerosil Co., Ltd.) was added * and mixed with a Henschel mixer to obtain a magnetic developer F. * Since the BET specific surface area of the small particle size silica fine powder of Comparative Example 1 is about 6 times the BET specific surface area of the large particle size silica fine powder of Example 1 above, Addition amount 1.8
A 1/6 amount corresponding to mass% was used as a comparative example.

Next, the magnetic developers A to F obtained as described above are quantitatively filled into dedicated toner cartridges, and then the tandem type full color printer (printer manufactured by Casio Computer Co., Ltd .: color page) shown in FIG. Prest N-
5: Set to the most downstream toner unit TU with a print speed of A4 horizontal (29 sheets / minute), and set MI in monochrome mode.
CR image formation (MICR font printing) was performed and image quality was evaluated. In addition, a life test of continuous printing was performed up to 14,000 sheets.

The results are shown in FIGS. FIG. 6 is a diagram showing the relationship between the externally added amount of silica and the image density (at the initial stage), which was obtained for each of the magnetic developers A to F. As shown in the figure, in the magnetic developer A, the amount of silica added externally was not sufficient, and there was a tendency that an image density difference occurred between the image leading edge portion and the image trailing edge portion of the paper. With the magnetic developers B to E, good printed images with almost no difference in image density between the image leading edge and the image trailing edge were obtained.
On the other hand, the magnetic developer F of silica having a small particle size resulted in a large difference in image density between the leading edge portion and the trailing edge portion of the image on the paper, and at the same time, the image density was generally low.

FIG. 7 and FIG. 8 show the above-mentioned life test for the magnetic developer E of which the silica external addition amount is 3% by mass among the magnetic developers B to E with good results shown in FIG. FIG. 7 shows the result of the image density transition,
FIG. 8 shows a graph and numerical values of the transition of the read value obtained by reading the obtained MICR font with a reader sorter. In FIG. 8, only the average value is shown as a numerical value in the figure.

As shown in both figures, with the magnetic developer E, a stable image density was obtained from the beginning of printing to 14,000 sheets, and the magnetic reading performance was also satisfactory (as a magnetic reading value). Of about 115% was obtained, and this value was a value with sufficiently few reading errors.).

From the above, it was considered that if the silica having a large particle diameter of 1.5% by mass or more was externally added, there would be no problem in MICR image formation even with the above-described developing apparatus configuration. Therefore, the MICR printer can be provided without significantly changing the structure of the tandem type full color printer of FIG. Further, since both full-color image formation and MICR image formation can be achieved, full-color printing of an image on the face of a check, for example, can be facilitated by the same printer.

FIG. 9 shows a color developer and the magnetic developer of the present invention in the tandem type full color printer (printer manufactured by Casio Computer Co., Ltd .: Color Page Presto N-5: print speed A4, 29 sheets / minute). It is a figure which shows the check printed using.

[0069]

As described above, according to the present invention, by changing the composition of the magnetic developer, the magnetic developer is accommodated in the non-magnetic developing type developing device provided with the elastic developing roller, and the MICR is accommodated. Even if the printer is configured, stable image formation can be performed, and a decrease in image density due to long-term use can be suppressed. Therefore, if the developing device of the present invention is applied to a tandem type full-color printer, office printing and design printing of the entire bill face such as securities can be performed, and at the same time, MICR images can be easily formed.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing an internal configuration of a printer device according to the present invention.

FIG. 2 is an external perspective view of a printer device according to the present invention.

FIG. 3 is a circuit block diagram of a printer device according to the present invention.

FIG. 4 is a diagram schematically showing a main part of a developing device according to an embodiment of the present invention.

FIG. 5 is a graph showing a residual magnetization and a magnetic reading value of a magnetic toner obtained by mixing two kinds of magnetic powders.

FIG. 6 is a graph showing the relationship between the externally added amount of silica and the image density (at the initial stage).

FIG. 7 is a graph showing the transition of image density obtained by continuous printing with the magnetic developer of the present invention.

FIG. 8 is a graph showing the transition of the read value obtained by reading the MICR font obtained by performing continuous printing on the magnetic developer of the present invention with a reader sorter.

FIG. 9 is a diagram showing a check printed by using a non-magnetic developer for color and a magnetic developer for MICR in the printer device according to the present invention.

[Explanation of symbols]

1 Printer device 2 Image forming section 3 Transport unit for double-sided printing 4 Paper feeder 5-8 Image forming unit 9 Photosensitive drum 10a Charger 10b print head 10c developing roller 10d transfer device 10e cleaner 11 paper cassettes 11a Paper feeding roller 12 Standby roller pair 13 Conveyor belt 14 Drive roller 14 'driven roller 15 Fixing unit 15a heat roller 15b Press roller 15c Oil coating roller 16 MPF tray 16a Paper feed roller 17 Switching flap 18a to 18e Reverse transport roller pair 19 Conveyor roller pair 20 Paper ejection roller pair 21 Paper output section 22 Upper part of device 23 Device bottom 24 Front cover 26 I / F controller 27 frame memory 28 Printer controller 29 Printer printing section 30 CPU 31 ROM 32 EEPROM 33 Operation panel 33a Key operation part 33b display section 44 Developing device 62 developer 63 Stirrer 64 supply roller 65 doctor blade 66 Squishy sheet 67 sealing member 68 Bias power supply 69 Bias power supply 71 Bias power supply

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) G03G 15/08 507 G03G 9/08 101 (72) Inventor Yoshio Nomura 4084 Miyaji, Iruma-shi, Saitama Casio Electronic Industrial Co., Ltd. In-house (72) Inventor Yasuo Kamoshita 4084 Miyaji, Iruma-shi, Saitama Casio Electronics Co., Ltd. F-term (reference) 2H005 AA08 AA29 CB13 EA05 EA07 EA10 FA06 2H077 AA12 AC04 AD06 AD13 CA11 EA13 FA21 GA03

Claims (3)

[Claims] 1. A developing hopper having an opening to face a photoconductor on which an electrostatic latent image is formed and containing a magnetic developer; and a part of the developing hopper to come into pressure contact with the photoconductor. An elastic developing roller which is provided and holds the magnetic developer contained in the developing hopper on its surface and conveys the magnetic developer to impart it to the electrostatic latent image of the photoconductor; A doctor blade that regulates the magnetic developer to form a thin layer on the elastic developing roller on the upstream side in the conveying direction of the elastic developing roller; and a conveyance of the elastic developing roller that is disposed in the hopper rather than the doctor blade. A supply roller that is in pressure contact with the elastic developing roller on the upstream side in the direction, and a light pressure contact with the elastic developing roller that is downstream from the opening in the conveying direction of the elastic developing roller, and the magnetic developer returns to the developing hopper. A conductive regulating sheet member that regulates the outflow of the magnetic developer from the developing hopper at the same time, and a bias voltage applying unit that applies a bias voltage to at least the elastic developing roller and the supply roller, The magnetic developer contains a magnetic toner composed of at least a binder resin and magnetic powder, and a fine silica powder having a large particle size of 1.5% by mass or more based on the magnetic toner.
R image forming developing device. 2. The MIC according to claim 1, wherein the large particle size silica fine powder has a BET specific surface area of less than 100 m ² / g.
R image forming developing device. 3. The magnetic powder is a mixture of acicular magnetic powder and octahedral magnetic powder.
The developing device for MICR image formation described.