JP3284728B2 - Color image forming method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming method in a printer, an electrophotographic copying machine, etc., and more particularly, to an image forming method capable of controlling the glossiness of an image on a recording material.

[0002]

2. Description of the Related Art Generally, in an image forming apparatus using an electrophotographic system, a fixing means includes an upper roll and a lower roll facing a front surface (a surface on which a toner image is formed) and a back surface of a recording material, respectively. A heated roll fixing device configured to heat these rolls to a predetermined temperature by a heating means such as a heater lamp is widely used. The glossiness of the output image mainly depends on the formation of the toner used, the recording material, the amount of toner on the recording material, and the configuration and fixing conditions of the fixing device used in the image forming apparatus. In particular, when the above conditions are not changed, the glossiness of the output image is almost uniquely determined regardless of the glossiness of the document image. On the other hand, there are various types of original images, such as high-gloss photographic images and low-gloss general business documents. The image forming apparatus using the electrophotographic method described above is not sufficient, and it is an important issue to change the above-mentioned factor that governs the glossiness as necessary.

[0003] As a conventional image forming apparatus for changing the factor governing the glossiness, for example, an image forming apparatus having means for changing a fixing condition is disclosed in Japanese Patent Application Laid-Open No. 60-51.
No. 866 discloses this. FIG. 5 shows a configuration diagram of this conventional image forming apparatus. The operation will be briefly described below. The original on the platen passes through mirrors 501 and 502 and a lens 503 and is color-separated through a color filter 504, and a primary charger 505, a static eliminator 507, and an exposure lamp 50 are provided.
8, a light image is projected onto the photoreceptor 506 to form an electrostatic latent image. The electrostatic latent image is then developed 5
At 09, the image is visualized by the first color toner, reaches the transfer section, and the toner image is transferred. Similarly, the second color toner image and the third color toner image are transferred onto the recording material 511 in synchronization with each other.
The recording material 511 is peeled off from the transfer drum 510 by a peeling unit 512, passes through a conveying unit 513, and a toner image is fixed by a fixing unit 514, and is discharged. At this time, the fixing device 514
An appropriate fixing condition can be selected by changing the operation speed according to the type of the recording material 511. Also,
Similarly, an image forming apparatus having means for changing fixing conditions, which is advantageous for miniaturization, is disclosed in Japanese Patent Application Laid-Open No. H4-1670. FIG. 6 shows a configuration diagram of this conventional image forming apparatus. The operation will be briefly described below.

A document on a document table is subjected to color separation by a reading unit 601 and converted into image signals. The surface of the photoconductor 603 is uniformly charged by the first charger 604, and then the laser light modulated by the laser scanning optical device 602 according to the image information of the first color is applied to the photoconductor 603.
And a first color electrostatic latent image is formed on the photoreceptor 603. Next, the electrostatic latent image of the first color on the photoconductor 603 is developed by the developing device 605 with the toner of the first color and is visualized to form a toner image of the first color. The first color toner image formed on the photoconductor is conveyed to the transfer section according to the rotation of the photoconductor 603. At this time, the transfer belt 606 is separated from the photoconductor surface as shown in FIG. Yes, the image passes undisturbed. Further, the fur brush 607 is also separated from the photosensitive member surface, and the image passes without being disturbed. The photoreceptor is recharged again by the first charger 604 and is developed with the second color toner by the laser scanning optical device 602 to form a two-color toner image on the photoreceptor. Similarly, after the third and fourth color toner images are formed on the photoconductor, the transfer belt 606 is moved to the position of the toner image and the registration roll 60.
8 and is pressed against the photosensitive member at the same time as the recording material transport by the recording material 61, and the toner image is formed by the second charger 609.
0. Recording material 610 onto which toner image has been transferred
Is conveyed while being attached to the transfer belt 606, is separated by curvature separation, and is fixed by a fixing device 611.
Is discharged. Also in this apparatus, the fixing condition can be selected by changing the operation speed of the fixing device.

Japanese Patent Application Laid-Open No. 3-116175 discloses an image forming apparatus having two fixing means in series. The image forming apparatus includes a primary fixing unit that irradiates a toner image on a recording material with heat rays from a lamp to melt the toner, and a heating roller and a heating roll after the toner image is fused and fixed by the primary fixing unit. The secondary fixing unit includes a secondary fixing unit that fixes the toner image by passing through the pressure-contacted backup roll, and the secondary fixing unit includes a unit that separates the heating roll and the backup roll. Japanese Patent Application Laid-Open No. 4-157482 discloses an image forming apparatus having two fixing units in parallel. This image forming apparatus includes a first fixing device set to a normal fixing condition and a second fixing device set to an enhanced fixing setting for sufficiently fusing and fixing the toner image so as to have gloss. Two fixing devices are provided, and the fixing is performed by one of the fixing devices by switching the recording material conveyance by the recording material conveyance unit. In addition, actual opening Hei 4-4265
Japanese Patent Application Laid-Open No. 8 (1999) -1995 discloses that a rotary developing device is provided with three types of chromatic color developing devices and a high glossy color image forming device from the viewpoint of achieving both high gloss color images and low gloss monochrome image quality in a color image forming device. There is disclosed an image forming apparatus provided with a black developing unit for black and white and a black developing unit for forming a low gloss black and white image separately from a rotary developing device. On the other hand, Japanese Patent Application Laid-Open No. 4-204566 discloses a method for controlling the gloss of an output image by using a black toner having a softening point higher than that of the three chromatic toners by, for example, 10 ° C. or more, and changing the black toner to the final color. There is disclosed an image forming apparatus that forms an image and adjusts an undercolor removal ratio in accordance with a desired degree of gloss, thereby changing the gloss of an output image.

[0006]

However, Japanese Patent Application Laid-Open No. 60-51866 and Japanese Patent Application Laid-Open No.
In the method using an image forming apparatus having a configuration as described in Japanese Patent Application Publication No. 70-70, when the process speed of the photoconductor or the transfer drum and the speed of the fixing device are different from each other, when the leading end of the recording material enters the fixing device, The recording material must have been separated from the transfer drum or photoconductor after the transfer separation operation has been completed. That is, when recording is performed with the speed of the fixing device and the speed of the image forming means such as the photoconductor and the transfer drum different, the distance between the transfer separation unit and the fixing unit is determined by the distance of the paper used in the image forming apparatus. It is required to be longer than the maximum length, and there is a drawback that the device becomes large. Also, JP-A-3-116175, JP-A-4-157
In the case of the method using the image forming apparatus having the configuration disclosed in Japanese Patent Publication No. 482, two fixing units are required, and it is difficult to say that the fixing unit is appropriate in terms of power consumption and cost.

As described above, in the case of using the conventional image forming apparatus, in order to control the glossiness of the output image, it has been mainly dealt with by changing the fixing conditions or devising the structure of the fixing device. However, there is no mention of the composition of the toner itself that finally visualizes an image on a recording material.
In general, the factor that governs the fixing characteristics of a toner is the physical properties of a binder resin, which is a main component of the toner. Typical examples of the binder resin for a toner include a styrene-acrylic resin and a polyester resin. Can be Styrene-
Acrylic resins generally have a relatively high softening point and are suitable for obtaining low-gloss output images, but in order to obtain high-gloss output images, it is necessary to apply a very high amount of heat. However, it is difficult to achieve this within a limited range of power consumption, so that an increase in the size of the device and an increase in power consumption are inevitable. In addition, it is possible to lower the softening point temperature by lowering the molecular weight of the styrene-acrylic resin, thereby reducing the amount of heat required for fixing. However, lowering the molecular weight of the styrene-acrylic resin reduces the image strength. And the output image has cracks due to bending and the like.

Further, polyester resins are widely used in toners of electrophotographic color image forming apparatuses currently on the market, and generally have a relatively low softening point and are suitable for obtaining high gloss output images. ing. However, currently available toners using polyester resins are:
In order to obtain a low-gloss output image, it is difficult to achieve low-gloss even if the amount of fixing heat is reduced. Has a drawback such as poor fixing such as low temperature offset. In view of this point, the image forming apparatus having the configuration disclosed in Japanese Utility Model Laid-Open Publication No. Hei 4-42658 is required. However, two black developing units are required, and power consumption and cost are also reduced. It is hard to say that it is an appropriate means.

On the other hand, when an image forming apparatus having the structure disclosed in Japanese Patent Application Laid-Open No. 4-204566 is used, it is necessary to lower the undercolor removal rate in order to obtain a high gloss color image. This has the disadvantage that the sharpness of the image is reduced, the amount of toner consumption is increased, and fixing defects such as offset are likely to occur. In order to obtain a low-gloss color image, it is necessary to increase the undercolor removal ratio. In a low-saturation area, a low-gloss image is obtained, but a high-saturation area ( The glossiness in the area mainly composed of two or less chromatic toners) remains high, and high glossy and low glossy areas are mixed in one output image, which is not preferable. The present invention has been made in view of the above-described conventional problems, has a small size, does not involve an increase in power consumption, and does not reduce the number of discharged images per unit time.
To provide an image forming method capable of controlling the glossiness of an image on a recording material without causing a fixing defect such as offset regardless of the presence or absence of gloss, and specifically, for an image in which a monochrome image is mixed with a full-color image. It is another object of the present invention to provide an image forming method capable of outputting a full-color image with high gloss and a monochrome image with low gloss.

[0010]

Means for Solving the Problems The present invention provides at least:
A latent image forming step of exposing a uniformly charged photoreceptor to form an electrostatic latent image, a developing step of developing the electrostatic latent image using toner, and transferring the formed toner image to a recording material And a transfer separation step of separating the toner image from the toner development holding member, and a fixing step of fixing the transferred toner image on a recording material. A full-color image is formed using three types of chromatic toner and black toner by a four-color full-color image forming developing device, and the full-color image formed on the recording material is formed of the three chromatic colors. And a black toner image formed by superimposing four black toner images, and developing the black toner image so as to be formed on the lowermost layer. The black toner comprises at least a resin component and a colorant, and the resin component It contains a polyester resin containing no tetrahydrofuran-insoluble component obtained by polycondensation of an alcohol monomer and a carboxylic acid monomer, and has a molecular weight and a molecular weight distribution of the resin component measured by gel permeation chromatography. Is the weight average molecular weight (M
w) A black toner having a number average molecular weight (Mn) of 2,000 to 10,000, a weight average molecular weight / number average molecular weight (Mw / Mn) of 10 or more, and an apparent black toner by a flow tester method. Has a melt viscosity of 1
The temperature at which x10 ⁴ poises is obtained is in the range of 120 ° C. to 140 ° C. In the present invention, it is preferable that the black toner has a higher softening point than at least the three types of chromatic toners. More preferably, in the image portion composed of the three types of chromatic colors, the three types of chromatic colors are used. It is preferable that an achromatic gray component is separated from the density and an undercolor removal operation is performed to replace the gray component with black toner, and that the undercolor removal coefficient be 0.8 or less at the maximum.

Hereinafter, the present invention will be described. First, to describe the black color toner used in the present invention,
In the present invention, the black toner comprises at least a resin component and a colorant, and the resin component does not contain a tetrahydrofuran-insoluble component obtained by polycondensation of an alcohol monomer and a carboxylic acid monomer. The molecular weight and the molecular weight distribution of the toner resin component measured by gel permeation chromatography were as follows: weight average molecular weight (Mw) 25,
000 to 80,000, number average molecular weight (Mn) 2,
It is necessary to have a weight average molecular weight / number average molecular weight (Mw / Mn) of 10 or more. When the resin component of the black toner contains a tetrahydrofuran-insoluble component, it is difficult to obtain high gloss for a full-color image, and when the weight average molecular weight is larger than the above range, it is similarly difficult to obtain a high gloss image. . Also,
When the weight average molecular weight is smaller than the above range, it is difficult to obtain low gloss for black and white images. When the number average molecular weight is larger than the above range, the fixing temperature rises, and thus the power consumption increases. When the number average molecular weight is smaller than the above range, the storage stability of the toner is deteriorated. Further, if the weight average molecular weight (Mw) / number average molecular weight (Mn) is less than 10, it becomes difficult to obtain a low gloss image.

Further, in the black toner used in the present invention, the temperature at which the apparent melt viscosity of the toner by the flow tester method becomes 1 × 10 ⁴ poise needs to be 120 ° C. to 140 ° C. This temperature is
It means the softening point of the resin component. When this temperature is lower than 120 ° C., it is difficult to obtain a low gloss image, and when this temperature is higher than 140 ° C., fixing such as low-temperature offset in a high density region. Defects are more likely to occur. The softening point of the resin component was measured using a Shimadzu Flow Tester CFT as a measuring device.
Using 500-A, as a measurement condition, die = 0.5 m
mx 1.0 mm, heating rate = 5 ° C / min, load = 10
kg, preheating time = 300 sec, measurement temperature range = 80 ~
It was measured at 190 ° C. The molecular weight of the resin component was determined by using a fully automatic high-temperature high-speed chromatograph (WATERS ALC / GPC 150C) as a measuring device, using tedrahydrofuran as a solvent, and using a flow rate =
1.0 ml / min, temperature = 40 ° C., is measured under the condition of the detector = indicates Sa屈 folding meter (RI).

In the present invention, a polyester obtained by polycondensing an alcohol monomer and a carboxylic acid monomer is used as the resin component containing no tetrahydrofuran-insoluble component. Examples of the alcohol monomer include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3
Diols such as propylene glycol, 1,4-butanediol, neopentyl glycol, 1,4-butenediol, bisphenols such as bisphenol A, hydrogenated bisphenol A, polyoxyethylenated bisphenol A, and polyoxypropylenated bisphenol A A
Alkylene oxide adducts and other dihydric alcohols can be mentioned. Further, a trihydric or higher polyhydric alcohol is used to make the polyester non-linear so as not to generate tetrahydrofuran insoluble components. For example, sorbitol, 1,2,3,6-hexanetetraol, 1,4-sorbitan, pentaerythritol,
1,2,4-butanetriol, 1,2,5-pentanetriol, glycerin, 2-methylpropanetriol, 2-methyl-butanetriol, trimethylolethane, trimethylolpropane, 1,3,5-trihydroxymethyl Benzene and others can be mentioned.

Examples of the carboxylic acid monomer include maleic acid, fumaric acid, mesaconic acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, terephthalic acid, isophthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, Sebacic acid, malonic acids, or alkyl succinic acids, their anhydrides, alkyl esters, and other divalent carboxylic acids can be mentioned. In addition, 3
Polyvalent carboxylic acids having a valency or higher can be used, for example,
1,2,4-benzenetricarboxylic acid, 1,2,5-benzenetricarboxylic acid, 1,2,4-cyclohexanetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,
4-butanetricarboxylic acid and others can be mentioned. In the present invention, the resin component may be composed of one kind of polyester, or may be a mixture of linear polyester and non-linear polyester. In this case, the molecular weight and the molecular weight distribution of the toner can be arbitrarily controlled within a suitable range by adjusting the mixing ratio between the linear polyester and the non-linear polyester.

The black toner preferably has a higher softening point than the three chromatic toners. In particular, the softening point of the black toner is higher than the softening point of the three chromatic toners by 10 ° C. or more. preferable. If the softening point of the black toner is about the same as the softening point of the chromatic toner, only the same degree of gloss can be obtained under the same fixing conditions. In other words, in an image in which a full-color image that requires high gloss and a character image that requires low gloss are mixed, using the image tone recognition unit,
Even if it is separated into a color image portion and a character image portion, it is impossible to satisfy the requirement for gloss at the same time. In an image in which a full-color image and a character image are mixed as described above, in order to obtain an effective gloss difference, the softening point of the black toner is preferably 10 ° C. or more higher than the softening points of the three chromatic toners. . In the present invention, known magenta, cyan, and yellow color toners can be used as the other three chromatic toners.

Next, the image forming method of the present invention will be described. The image forming method of the present invention includes, at least, a latent image forming step of forming an electrostatic latent image by exposing on a uniformly charged photoconductor, a developing step of developing the electrostatic latent image using toner, Transfer the formed toner image to the recording material, a transfer separation step of separating from the toner development holding member, and a fixing step of fixing the transferred toner image on the recording material, and
In the developing step, a full-color image is formed using the above three types of chromatic toner and black toner. In this case, the full-color image formed on the recording material is formed by superimposing the three types of chromatic colors and the four-color black toner image, and development is performed so that the black toner image is formed in the lowermost layer. Do. Further, in the present invention, it is preferable to perform an undercolor removal operation of separating an achromatic gray component from three types of chromatic color densities and replacing it with black toner. In this case, the undercolor removal coefficient is preferably at most 0.8 or less, particularly preferably in the range of 0.4 to 0.7. The undercolor removal coefficient indicates the ratio of replacing the achromatic gray component separated from the three chromatic color densities with the black toner, and the amount of the achromatic gray component separated from the three chromatic color densities. Is represented by B / A, and B is the amount of black substitution therein. The undercolor removal coefficient is 0.
If it is higher than 8, in a full-color image, low gloss due to black toner becomes noticeable in a low-saturation portion,
A high-saturation portion with high saturation and a low-gloss portion with low saturation are mixed in the full-color image, which is not preferable.

FIG. 1 is a schematic structural view of an example of an image forming apparatus for carrying out the color image forming method of the present invention.
Around the photoconductor 101 rotating in the direction of the arrow, a charger 102, a rotary developing device 103, a transfer drum 104, a cleaner 105, a pre-exposure device 106, a potential sensor 108 and the like are arranged. The photoconductor 101 has a charger 1 in a dark area.
02 is uniformly charged. The density signals of R (red), G (green), and B (blue) supplied from the image input device 110 and the like are converted by the color conversion processing circuit 140 into Y (yellow), M (magenta), and C (cyan). , K (black)
The photoconductor 101 is converted into density signals of the respective colors, and the photoconductor 101 is exposed by the light beam scanning device 120 according to the converted density signals to form an electrostatic latent image. The light beam scanning device 120 includes a semiconductor laser 121, a collimator lens 1
22, a polygon mirror 123, an image forming optical system 124, a light beam pulse width conversion (PWM) circuit 130, and the like. The light beam converted into a pulse width signal corresponding to the density by the light beam PWM circuit 130 is used as a photosensitive member. 101
Is scanned.

The rotary developing device 103 includes yellow, cyan,
It is composed of four developing devices each having magenta and black toners. In this example, each developer is
A reversal development system using two-component magnetic brush development is employed. As appropriate, the rotary developing device 103 rotates to develop the electrostatic latent image with a desired toner. An alternating electric field is applied to the rotary developing device 103 by a developing bias circuit (not shown). The developing bias circuit includes a high-voltage AC power supply for supplying an AC bias and a high-voltage DC power supply for supplying a DC bias. The transfer drum 104 rotates with a recording material mounted on the outer periphery. The developed toner image on the photoconductor is transferred to a transfer charger 1
The multi-color toner image is transferred to the recording material 107 for each color by 04b. 104a is a recording material absorbing charger, 104c is a peeling charger, 104
d is a peeling nail, and 104e is a charger for static elimination. In this image forming apparatus, formation, development, and transfer of an electrostatic latent image are performed in the order of black, yellow, magenta, and cyan, respectively. The toner image on the transfer material formed by development has a structure in which toner images of black, yellow, magenta, and cyan are superimposed, and the black toner image is the lowermost layer. The transfer material onto which the toner image obtained by these steps has been transferred is separated from the transfer drum 104 by the peeling claw 104d, and then fixed by the fixing device 109 to form a multicolor image.

The color conversion processing circuit 140 has, for example, a configuration as shown in FIG. That is, R, G, and B color separation signals (R, G,
G, B) are subjected to light intensity-density conversion by a density conversion circuit 202 (Y1, M1, C1), a black component (K1) is extracted by a black component extraction circuit 203, and signals Y2, M2, C2 are output by a masking circuit 204. , K2, and a color conversion process is performed by an under color removal (UCR) circuit 205 to obtain a signal Y3.
, M3, C3, K3. The signal subjected to the color conversion processing is taken out as an output image by the image output device 206. In the under color removal (UCR) processing, a full black method (100%) is used as a method for determining the amount of removal of the equivalent neutral density (gray component) in the three signals and the amount of black signal generation.
(URC) and skeleton black systems, which are known to have the effect of expanding the color reproduction range of high-density areas, supplementing sharpness, and reducing running costs by reducing toner consumption.

Referring to FIG. 3, UCR according to the above-described method is used.
The processing will be described. In FIG. 3, (a) is URC
The relationship between each of the Y, M, and C color signals before processing and the gray component is shown. When the toner amount is plotted on the vertical axis, the gray component at the time of mixing the three colors becomes an amount that matches the minimum value among the three colors, which is indicated by oblique lines in the figure. In the full black method, as shown in FIG. 3B, the K color component is equal to the gray component, and Y, M, C
Each color component has a value obtained by subtracting the gray component. In the skeleton black method, UCR is added to the gray component.
The coefficient a (0 <a <1) is multiplied to determine the subtraction amount of the gray component and the generation amount of the K color component from each of the Y, M, and C color components (see FIG. 3C). FIG. 3D shows the relationship between the gray component before URC processing and each of the Y, M, C, and K color signals.
(E) and (f) show the relationship between the gray component and the Y, M, C, and K color signals according to both of the above methods, respectively.
As shown in FIG. 3D, before the UCR process, the gray component is equal to the same amount of each of the Y, M, and C color signals. In the full black system, as shown in FIG. 3E, all the gray components are replaced by K color signals, and the Y, M, and C color signals are 0.
The CR processing has a problem that image quality is significantly degraded due to generation of a K color component in a bright portion. On the other hand, in the skeleton black method, as shown in FIG. 3F, when the gray component is small (the brightness of the input image is high or the saturation is high), the gray component is represented by three colors of Y, M, and C. K component is generated as the gray component increases,
It is generally designed to increase it and is more practical than the full black system.

The fixing device preferably used in the present invention comprises a heating roll and a pressure roll which rotate while being pressed against each other, and a mold release for preventing toner offset on at least one outer peripheral surface of the heating roll and the pressure roll. A release agent supply unit for providing an agent, and fixing the toner image by passing the sheet on which the unfixed toner image is formed on the heating roll and the pressure roll. A pressure roll has a substrate roll having a heating source inside, an inner elastic layer provided with a metal-containing filler provided on the substrate roll, and a single layer or a plurality of layers provided with the inner elastic layer. And an external elastic body layer.

FIG. 4 is a schematic structural view of one example. The main part of the fixing device is constituted by a heating roll 401 and a pressure roll 402. The heating roll 401 includes a substrate roll 404 having a Colts lamp 403 therein, an inner elastic body 405 provided thereon, and an outer elastic body 406 provided thereon. On the other hand, the pressure roll 402 includes a substrate roll 407 having a Colts lamp 418 therein, an inner elastic body 408 provided thereon,
And an outer elastic body 409 provided thereon. The heating roll 401 and the pressure roll 402 are pressed by a heating mechanism (not shown). Note that reference numeral 413 denotes a releasing agent supply unit for applying the silicone composition 414 to the pressure roll 401. 415 is an oil pan, 416 is a supply roll, and 417 is a coating roll. The recording material 410 carrying the toner image 411 is inserted between the heating roll 401 and the pressure roll 402 to perform fixing.

Next, the materials used for the fixing device having the above-described configuration will be described. The substrate roll constituting a part of the heating roll and the pressure roll requires high heat transferability and rigidity capable of transferring heat energy from a heating source provided therein to the inner elastic layer. Can be made of a metal material such as a stainless alloy or aluminum.
In addition, the inner elastic layer provided on these substrate rolls has an elasticity and a thickness that allow the heating roll and the pressure roll to come into contact with the sheet on which the toner image is formed with an appropriate pressing force and a contact width, and a thickness from the heating source. the thermal energy required for heat transfer can be high thermal conductivity outside the elastic layer, specifically e last-mer metal-containing filler dispersed therein, e.g., fluorosilicone elastomers, silicone carbon elastomer, various other It can be composed of silicone rubber, fluoroelastomer, various organic rubbers such as ethylene-propylene-diene rubber, various copolymers, and the like. Here, the upper limit of the rubber hardness of the elastomer forming the inner elastic layer of both rolls is 80 ° in JIS hardness, and generally 40 ° to 70 ° when the filler is dispersed.

On the other hand, the outer elastic layer provided on the inner elastic layer has a high heat transfer property capable of transferring the heat energy from the heating source to the toner image on the recording material, and has a function of preventing toner offset. It requires affinity and abrasion resistance with a mold release agent, and as the constituent material,
Fluoroelastomers and silicone elastomers are preferred. As a specific example, the fluoroelastomer is a commercially available copolymer of vinylidene fluoride and hexanefluoropropylene, which is commercially available as Viton (Vito).
n) Viton B, a terpolymer of vinylidene fluoride, hexafluoropropylene and tetrafluoroethylene, known as A (trade name of EI Dupont) (trademark of EI Dupont) And Fluorel 21
70, Fluorell 2174, Fluorell 2176, Fluorell 2177, Fluorell IVS76 (the above Fluorel is a brand name of 3M), Viton GH, Viton EGO
C, Viton E430 and the like can be applied. As a specific example of the silicone elastomer, a high temperature curing type (HT
V), room temperature curing type (RTV) or low temperature curing type (LT)
V) can be used. In the case of a silicone elastomer, it is preferable to provide an oil-resistant layer in the intermediate layer in order to prevent the release agent from entering the inner elastic layer. Further, a mixture of a fluoroelastomer containing vinylidene fluoride as a main component and another material, for example, a mixture of tetrafluoroethylene, silicone rubber, fluorosilicone rubber and the like may be used. As the metal-containing filler for appropriately adjusting the heat conductivity, copper, tin, silver, zinc, aluminum, iron,
Metals such as lead, polybutene, platinum, gold, beryllium, nickel, chromium, iridium, ruthenium, tungsten, cadmium, and vanadium, alloys of these metals, metal oxides, and metal salts thereof can be used.

[0025]

Next, the present invention will be described by way of examples. In the following examples, the color image forming apparatus shown in FIG. 1 was used to form an image under the following conditions. The photoconductor 101 is
The charging unit 102 is set to be uniformly charged to -650 V in the dark part, and the process speed is 160 m
m / sec. The four developing devices using the yellow, cyan, magenta, and black toners in the rotary developing device 103 adopt a reversal developing method using two-component magnetic brush development, and use a toner having an average particle diameter of 7 μm. Using. An alternating electric field is applied to the rotary developing device 103 by a developing bias circuit (not shown). In this embodiment, the alternating electric field is applied under the conditions of a DC voltage of -500 V, an AC voltage of 1500 Vp-p, and 6 kHz.

As the fixing device, one having the structure shown in FIG. 4 was used. As the heating roll 401, 500
A W-shaped Colt lamp 403 was used, in which an inner elastic body 405 and an outer elastic body 406 were provided on a substrate roll 404 formed of an aluminum core material having an outer diameter of 43 mm. The inner elastic body is composed of 100 parts by weight of crystalline silica and 100 parts by weight of crystalline silica and vulcanizing agent (RC4, manufactured by Toray Industries) based on 100 parts by weight of silicone compound (SH841U, manufactured by Toray Industries, Inc.).
It was formed by filling and mixing with 0.8 part, had a thermal conductivity λ of 0.0017 cal / cm sec deg, a rubber hardness of 60 ° in JIS hardness, and an approximate thickness of 3.0 mm. The outer elastic body is made of Viton rubber (E-60C,
It is formed by filling and mixing 100 parts by weight of DuPont, 2 parts by weight of carbon (manufactured by Tokyo Materials) and 10 parts by weight of magnesium oxide (Mgo: # 30, manufactured by Kyowa Chemical Co., Ltd.). Is 0.0005 cal / cm sec deg and the thickness is 2
It was 0 μm. On the other hand, as the pressure roll 402, a 500 W Colts lamp 418 is provided inside, and an inner elastic body 408 and an outer elastic body 409 are provided on a substrate roll 407 formed of an aluminum core material having an outer diameter of 49 mm. One used. The inner elastic body is formed by filling and mixing 50 parts by weight of crystalline silica and 0.8 parts of a vulcanizing agent (RC-4, manufactured by Toray Industries) with respect to 100 parts by weight of the silicone compound (SH841U, manufactured by Toray Industries, Inc.). When the thermal conductivity λ is 0.0015 cal / cm sec deg and the rubber hardness is JIS
The hardness was 70 ° and the approximate thickness was 1.0 mm. The outer elastic body is made of 100 parts by weight of Viton rubber (E-60C, manufactured by DuPont) and carbon (manufactured by Tokyo Material).
Parts by weight and 10 parts by weight of magnesium oxide (Mgo: # 30, manufactured by Kyowa Chemical Co., Ltd.), and the mixture is formed. Its heat transfer coefficient λ is 0.0005 cal / cm sec deg, and its thickness is 20 μm.
Met. The heating roll 401 and the pressure roll 4
02 is pressed by a heating mechanism (not shown) to form a nip width of 6.0 mm at the center, the surface temperature of the heating roll 401 is 155 ° C., and the pressure roll 40
2 are set to 150 ° C., respectively, so that they rotate at a surface speed of 160 mm / sec in the directions of the arrows.

Next, the formulation of the developer used in the present invention will be shown. Example 1 (1) 100 parts by weight of non-linear bisphenol-based polyester (polyester A) (bisphenol A-ethylene oxide adduct / bisphenol A-propylene oxide adduct / terephthalic acid / dodecenyl succinic acid / trimellitic anhydride condensate) Molecular weight (Mw) = 83,000 Number average molecular weight (Mn) = 3,600 Weight average molecular weight (Mw) / Number average molecular weight (Mn) = 23 Tedahydrofuran insoluble matter = 0% Apparent melting by flow tester method 1 × 10 ⁴ viscosity
Poise temperature T is T = 130 ° C. (2) 4 parts by weight of carbon black having a primary particle diameter of 45 μm The above components are melted by an extruder, kneaded, cooled, and ground by a jet mill, The obtained pulverized product was classified to prepare a black toner having a volume average particle size of 7 μm. Table 1 shows the molecular weights and molecular weight distributions of the resin components constituting the toner for the obtained black toner. Table 1 also shows the temperature at which the apparent melt viscosity of the black toner by the flow tester method becomes 1 × 10 ⁴ poise. The black toner and hydrophobic silica (R972, manufactured by Nippon Aerosil Co., Ltd.) were mixed using a high-speed rotary mixer, and further mixed with an acrylic polymer-coated 50 μm ferrite carrier to prepare a black developer.

Example 2 (1) Non-linear bisphenol-based polyester (polyester A) 90 parts by weight (bisphenol A-ethylene oxide adduct / bisphenol A-propylene oxide adduct / terephthalic acid / dodecenyl succinic acid / trimellitic anhydride condensate) Weight average molecular weight (Mw) = 83,000 Number average molecular weight (Mn) = 3,600 Weight average molecular weight (Mw) / Number average molecular weight (Mn) = 23 Tedahydrofuran insoluble matter = 0% By flow tester method Apparent melt viscosity is 1 × 10 ⁴
Poise temperature T is T = 130 ° C. (2) Nonlinear bisphenol-based polyester (polyester B) 10 parts by weight (bisphenol A-propylene oxide adduct / fumaric acid) Weight average molecular weight (Mw) = 13,000 Average molecular weight (Mn) = 2,700 Weight average molecular weight (Mw) / number average molecular weight (Mn) = 4.
8 Apparent melt viscosity by flow tester method is 1 × 10 ⁴
Poise temperature T is 105 ° C. (3) 4 parts by weight of carbon black having a primary particle diameter of 45 μm The above components are melted by an extruder, kneaded, cooled, and pulverized by a jet mill. The obtained pulverized product was classified to prepare a black toner having a volume average particle size of 7 μm. Table 1 shows the molecular weights and molecular weight distributions of the resin components constituting the toner for the obtained black toner. Table 1 also shows the temperature at which the apparent melt viscosity of the black toner by the flow tester method becomes 1 × 10 ⁴ poise. The black toner and hydrophobic silica (R972, manufactured by Nippon Aerosil Co., Ltd.) were mixed using a high-speed rotary mixer, and further mixed with an acrylic polymer-coated 50 μm ferrite carrier to prepare a black developer.

Example 3 (1) Nonlinear bisphenol-based polyester (polyester A) 70 parts by weight (bisphenol A-ethylene oxide adduct / bisphenol A-propylene oxide adduct / terephthalic acid / dodecenyl succinic acid / trimellitic anhydride condensate) Weight average molecular weight (Mw) = 83,000 Number average molecular weight (Mn) = 3,600 Weight average molecular weight (Mw) / Number average molecular weight (Mn) = 23 Tedahydrofuran insoluble matter = 0% By flow tester method Apparent melt viscosity is 1 × 10 ⁴
Poise temperature T is T = 130 ° C. (2) Non-linear bisphenol-based polyester (polyester B) 30 parts by weight (bisphenol A-propylene oxide adduct / fumaric acid) Weight average molecular weight (Mw) = 13,000 Average molecular weight (Mn) = 2,700 Weight average molecular weight (Mw) / number average molecular weight (Mn) = 4.
8 Apparent melt viscosity by flow tester method is 1 × 10 ⁴
Poise temperature T is 105 ° C. (3) 4 parts by weight of carbon black having a primary particle diameter of 45 μm The above components are melted by an extruder, kneaded, cooled, and pulverized by a jet mill. The obtained pulverized product was classified to prepare a black toner having a volume average particle size of 7 μm. Table 1 shows the molecular weights and molecular weight distributions of the resin components constituting the toner for the obtained black toner. Table 1 also shows the temperature at which the apparent melt viscosity of the black toner by the flow tester method becomes 1 × 10 ⁴ poise. The black toner and hydrophobic silica (R972, manufactured by Nippon Aerosil Co., Ltd.) were mixed using a high-speed rotary mixer, and further mixed with an acrylic polymer-coated 50 μm ferrite carrier to prepare a black developer.

Example 4 (Comparative Example) (1) Non-linear bisphenol-based polyester (polyester A) 30 parts by weight (bisphenol A-ethylene oxide adduct / bisphenol A-propylene oxide adduct / terephthalic acid / dodecenyl succinic anhydride / trihydric anhydride) (Mellitic acid condensate) Weight average molecular weight (Mw) = 83,000 Number average molecular weight (Mn) = 3,600 Weight average molecular weight (Mw) / Number average molecular weight (Mn) = 23 Tetrahydrofuran insoluble matter = 0% Flow tester method Melt viscosity is 1 × 10 ⁴
Poise temperature T is T = 130 ° C. (2) Non-linear bisphenol-based polyester (polyester B) 70 parts by weight (bisphenol A-propylene oxide adduct / fumaric acid) Weight average molecular weight (Mw) = 13,000 Average molecular weight (Mn) = 2,700 Weight average molecular weight (Mw) / number average molecular weight (Mn) = 4.
8 Apparent melt viscosity by flow tester method is 1 × 10 ⁴
Poise temperature T is 105 ° C. (3) 4 parts by weight of carbon black having a primary particle diameter of 45 μm The above components are melted by an extruder, kneaded, cooled, and pulverized by a jet mill. The obtained pulverized product was classified to prepare a black toner having a volume average particle size of 7 μm. Table 1 shows the molecular weights and molecular weight distributions of the resin components constituting the toner for the obtained black toner. Table 1 also shows the temperature at which the apparent melt viscosity of the black toner by the flow tester method becomes 1 × 10 ⁴ poise. The black toner and hydrophobic silica (R972, manufactured by Nippon Aerosil Co., Ltd.) were mixed using a high-speed rotary mixer, and further mixed with an acrylic polymer-coated 50 μm ferrite carrier to prepare a black developer.

Example 5 (Comparative Example) (1) Non-linear bisphenol-based polyester (polyester B) 100 parts by weight (bisphenol A-propylene oxide adduct / fumaric acid) Weight average molecular weight (Mw) = 13,000 Number average molecular weight (Mn) = 2,700 weight average molecular weight (Mw) / number average molecular weight (Mn) = 4.
8 Apparent melt viscosity by flow tester method is 1 × 10 ⁴
Poise temperature T = 105 ° C. (2) 4 parts by weight of carbon black having a primary particle diameter of 45 μm The above components are melted by an extruder, kneaded, cooled, and ground by a jet mill, The obtained pulverized product was classified to prepare a black toner having a volume average particle size of 7 μm. Table 1 shows the molecular weights and molecular weight distributions of the resin components constituting the toner for the obtained black toner. Table 1 also shows the temperature at which the apparent melt viscosity of the black toner by the flow tester method becomes 1 × 10 ⁴ poise. The black toner and hydrophobic silica (R972, manufactured by Nippon Aerosil Co., Ltd.) were mixed using a high-speed rotary mixer, and further mixed with an acrylic polymer-coated 50 μm ferrite carrier to prepare a black developer.

[0032]

[Table 1] Using the black developer (toner) shown in Examples 1 to 5 above, a toner image was formed on a recording material by the above-described image forming apparatus, and an image sample after fixing was evaluated. Table 2 shows the evaluation results at that time. The evaluation was performed on the glossiness of the black toner at an image weight of 1.0 mg / cm ² . The glossiness of the fixed image is measured using a glossmeter (Gloss Guard II [incident angle 75 °], Gardner, USA)
Was measured by

[0033]

[Table 2] As shown in the evaluation results shown in Table 2, when the toners of Examples 1 to 3 were used, a low gloss image (gloss level of 30 or less) could be obtained at a fixing speed of 160 mm / s. When the toners of Nos. 4 and 5 were used, a low gloss image could not be obtained.

Further, the black toner of Example 1 and yellow, magenta and cyan toners (Mw: 10,000, Mn: A-Color 635 manufactured by Fuji Xerox Co., Ltd.)
3,300, the temperature at which the apparent melt viscosity by the flow tester method becomes 1 × 10 ⁴ poise: 110 ° C.)
The image forming apparatus described above changed the undercolor removal coefficient, formed an image on paper in the order of black, yellow, magenta, and cyan, and fixed the image. The glossiness of the obtained color image was evaluated. Table 3 shows the evaluation results.

[0035]

[Table 3] The image toner weight (TMA) of each color of Y, M, and C when the UCR coefficient is 0 is 0.5 mg / cm ² ,
The TMA of K when the coefficient is 1 is 1.0 mg / cm ² . As shown in the evaluation results shown in Table 3, the undercolor removal coefficient was 0.8.
If it is below (when the toners of Examples 1 to 3 are used), a high gloss image (gloss degree of 50 or more) can be obtained, but if the undercolor removal coefficient is 0.8 or more, a high gloss image is obtained. I couldn't do that.

Further, the black toner of Example 1 and yellow, magenta, and cyan toners (Mw: 10,000, Mn: A-Color635 for Fuji Xerox Co., Ltd.)
3,300, the temperature at which the apparent melt viscosity by the flow tester method becomes 1 × 10 ⁴ poise: 110 ° C.)
With the undercolor removal coefficient set to 0.7, the order of image formation was changed by the above-described image forming apparatus, and the glossiness of the color image when fixed was evaluated. Table 4 shows the evaluation results at that time.

[0037]

[Table 4] In Table 4, A means a case where the layers are stacked on the recording material in the order of K, Y, M, and C (that is, K is the lowermost layer),
B means that the layers are stacked in the order of Y, M, C, and K on the recording material. The image toner weight (TMA) of each color of Y, M and C was 0.15 mg / cm ² , and the TMA of K was 0.7 mg / cm ² . As shown in the evaluation results shown in Table 4, when the black toners of Examples 1 to 3 were formed in the lowermost layer, high gloss images (gloss degree of 50 or more) could be obtained. When the toner was formed on the uppermost layer, a high gloss image could not be obtained.

[0038]

Since the image forming method of the present invention has the above configuration, it is small in size, does not increase power consumption, does not decrease the number of image discharges per unit time, and has a gloss like a photographic image. It is possible to control the glossiness of the image on the recording material for an image in which a full-color image with a high degree and a black-and-white image with a low gloss level such as a general business document are mixed. There is an effect that the image quality does not deteriorate and the image quality does not deteriorate.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an example of a color image forming apparatus used in an image forming method of the present invention.

FIG. 2 is a flowchart for performing a background removal operation.

FIG. 3 is a graph showing a relationship between a toner amount and each color component and a relationship between a color signal and a gray component when a background removal operation is performed.

FIG. 4 is a schematic configuration diagram of a transfer device.

FIG. 5 is a schematic configuration diagram of an example of a conventionally used color image forming apparatus.

FIG. 6 is a schematic configuration diagram of another example of a conventionally used color image forming apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 101 ... Photoconductor, 102 ... Charging device, 103 ... Rotary developing device, 104 ... Transfer drum, 105 ... Cleaner, 106
... pre-exposure device, 107 ... recording material, 108 ... potential sensor, 1
09: fixing device, 110: image input device, 120: light beam scanning device, 121: semiconductor laser, 122: collimator lens, 123: polygon mirror, 124: imaging optical system, 130: light beam PWM circuit, 140: Color conversion processing circuit, 201 image input device, 202 density conversion circuit, 203 black component extraction circuit, 204 masking circuit, 205 under color removal (UCR) circuit, 206 image output device, 401 heating roll, 402 ... pressure roll, 4
03: Colt lamp, 404: substrate roll, 405: inner elastic body, 406: outer elastic body, 407: substrate roll,
408: inner elastic body, 409: outer elastic body, 410: recording material, 411: toner image, 413: release agent supply means, 4
14 ... silicone composition, 415 ... oil pan, 416
... supply roll, 417 ... application roll, 418 ... Colt lamp, 501 and 502 ... mirror, 503 ... lens,
504 ... color filter, 505 ... primary charger, 506 ...
Photoconductor, 507: static eliminator, 508: exposure lamp, 509
Developing unit 510 Transfer drum 511 Recording material 51
2: peeling section, 513: transport section, 514: fixing device, 601
... Reading unit, 602 ... Laser scanning optical device, 603
.., Photoreceptor, 604, first charger, 605, developer, 60
Reference numeral 6: transfer belt, 607: fur brush, 608: resist roll, 609: second charger, 610: recording material, 6
11: Fixing device.

Continuation of the front page (72) Inventor Hiroshi Sugizaki 1600 Takematsu, Minamiashigara-shi, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. (56) References JP-A-5-249742 (JP, A) JP-A-1-142740 (JP, A) JP-A-3-1644753 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 9/087 G03G 9/09 G03G 13/01 G03G 15/01 111

Claims (1)

(57) [Claims] At least a latent image forming step of exposing a uniformly charged photoconductor to form an electrostatic latent image, a developing step of developing the electrostatic latent image using toner, In a color image forming method including a transfer separation step of transferring a toner image to a recording material and separating the toner image from a toner development holding member, and a fixing step of fixing the transferred toner image on the recording material, the developing step includes three types. A full-color image is formed using three types of chromatic toner and black toner by a developing device for forming a full-color image of four colors of chromatic color and black, and the full-color image formed on the recording material is Developing so that a black toner image is formed in the lowermost layer, the black toner being formed by superimposing the three types of chromatic colors and four black toner images. Coloring The resin component contains a polyester resin containing no tetrahydrofuran-insoluble component obtained by polycondensation of an alcohol monomer and a carboxylic acid monomer, and is used for gel permeation chromatography of the resin component. Weight average molecular weight (Mw) of 25,000 to 8
000, number average molecular weight (Mn) 2,000 to 1
0000, weight average molecular weight / number average molecular weight (Mw / M
n) A color image forming method having a temperature of at least 10 and having a temperature at which the apparent melt viscosity of a black toner by the flow tester method becomes 1 × 10 ⁴ poise is in the range of 120 ° C. to 140 ° C.