JP3093412B2 - Multi-color fixing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a full-color toner image formed by heating and fixing a multicolor toner image which has not been fixed on a recording material by an appropriate image forming process means such as electrophotography, electrostatic recording and magnetic recording. The present invention relates to a mixed color fixing device for forming images.

[0002]

2. Description of the Related Art In recent years, a full-color image forming apparatus such as a copying machine has become widespread in addition to a black-and-white image forming apparatus.

In this full-color machine, a yellow toner image, a magenta toner image, and a cyan toner image are stacked on a recording material,
The plural colors of toner are mixed and fixed by heat and pressure.

A full-color color toner must have good color mixing properties and good meltability when heat is applied, and it is preferable to use a sharp-melt toner having a low softening point and a low melt viscosity. . That is, by using such a sharp melt toner, the color reproduction range of a copy can be widened and a color copy faithful to a document image can be obtained.

However, such a sharp-melting color toner has a large affinity and is likely to be offset.

FIG. 6 shows an example of a fixing device for performing color mixture fixing.

In FIG. 6, reference numeral 1 denotes a fixing roller having an outer diameter of 40 mm.
A rubber elastic body layer 6 having a thickness of 00 μm is coated. As shown in FIG. 7, the rubber elastic body layer 6 is formed on a phenyl HTV (high-temperature vulcanization type) silicone rubber layer 6-2 having a thickness of 360 μm and an LTV (low temperature vulcanization type) silicone rubber having a thickness of 40 μm as an anti-offset layer. The layer 6-1 is formed, and has a two-layer configuration.

Reference numeral 2 denotes a pressure roller having an outer diameter of 40 mm, which is formed by forming an LTV silicone rubber 9 with a thickness of about 6 mm on a cored bar 8 made of aluminum, and covering the surface with a 50 μm-thick fluorine resin tube. Consisting of

Reference numeral 3 denotes a release agent coating device, which is a dimethyl silicone oil KF9 contained in an oil pan 13.
6 (manufactured by Shin-Etsu Chemical Co., Ltd.) is sucked up by the felt 16 and applied on the fixing roller 1.

Next, reference numeral 4 denotes a cleaning device, which presses a conventionally known web against the fixing roller 1 with a pressing roller 4-1, thereby cleaning off stains such as toner offset on the fixing roller.

In the fixing device as described above, the heater is intermittently controlled by a control device (not shown) so that the fixing roller 1 is heated by the heater 11 and the surface temperature becomes 180 ° C. by the thermistor 12. Further, it is rotationally driven in a direction of an arrow by a driving device (not shown).
Therefore, the transfer material P on which the visible images (toners) T of a plurality of layers are formed enters between the fixing roller and the pressure roller driven by heating and rotation, is heated and fixed at the nip N, and is out-of-machine by the paper discharging roller 16. Is discharged to

[0012]

FIG. 8 shows the direction in which the recording material of the fixing device is discharged from the nip.

The recording material P that has passed through the nip N is discharged along the fixing roller 1 as shown in FIG.

When the recording material is discharged along the fixing roller 1 as described above, the toner T receives radiant heat from the fixing roller 1 not only during the nip N but also after exiting the nip. When it moves to the separation claw 14 while adhering to the toner, it receives excessive heat and becomes excessively melted, resulting in an extremely high glossiness as an image and a so-called offset phenomenon in which toner is transferred to the fixing roller. Was.

On the other hand, the above-mentioned phenomenon has hardly been a problem in conventionally known black-and-white copying.

This is because black-and-white copying is mainly for copying character information and line drawings, and there is no problem at all even if there is a slight change in glossiness.

Further, since the toner used for black-and-white copying is a high melting point toner that melts at a high temperature, the glossiness is hard to change even if the heating time of the toner slightly varies.

For this reason, in black-and-white copying, the pressure roller is made very soft with respect to the heating roller, and the recording material is discharged along the heating roller.

However, many multicolor image originals have a so-called solid image having a large area, so that unevenness in gloss of the solid toner image due to the length of the heating time is conspicuous, causing a decrease in copy quality. This is particularly noticeable when a sharp melt color toner is used.

Further, a low melting point sharp melt toner is
Offset is likely due to high affinity with the roller, and if the heating time is extended beyond the heating time in the nip portion, the toner is excessively melted and immediately offset to the fixing roller.

[0021]

Embodiments of the present invention will be described below.

First, the definition of the roller end discharge position used in the description of the present invention will be described.

As shown in the sectional view of FIG. 9, a perpendicular line h is drawn on a line 1 connecting the center A of the fixing roller 1 and the center B of the pressure roller passing through both ends of the nip.

Further, a common tangent m on the discharge side of the fixing roller and the pressure roller is drawn.

The line m is defined as a roller end discharge position reference line, and a point intersecting with the perpendicular h is defined as a 0 (zero) position. From the 0 position, the fixing roller side is set to a + (plus) position, and the pressure roller side is set to-
(Minus) position.

Under the above conditions, the position where the recording material passes through the nip N and crosses the line m is expressed in mm from the 0 position, and is defined as a roller end discharge position. For example, FIG. 10 shows the discharge position of the transfer material after passing through the nip described with reference to FIG. 8. When the transfer material P ′ after passing through the nip intersects the line m at the point x and the distance from the line h is +5 mm. The roller end discharge position of the fixing device is +5 mm.

First, FIG. 4 illustrates a full-color image forming apparatus using a multi-color image fixing device.

This apparatus is capable of forming a full-color image by mixing different color toners. As shown in FIG. 4, the image forming apparatus includes a transfer material transport system I provided from the right side of the apparatus main body 100 to a substantially central part of the apparatus main body 100, and the transfer material transfer system I provided at a substantially central part of the apparatus main body 100. A latent image forming section II provided in close proximity to the transfer drum 28 constituting the material conveying system I, and a developing means provided in close proximity to the latent image forming section II, that is, a rotary developing device I
II.

First, the transfer material transport system I will be described.

An opening is formed in the right wall of the apparatus main body 100, and detachable transfer material supply trays 101 and 102 are provided in the opening so as to partially protrude outside the apparatus. Paper feed rollers 103 and 104 are disposed almost directly above the trays 101 and 102.
The paper feed rollers 106 and 104 are connected to transfer drums 3 and 104 and a transfer drum 28 that is rotatable in the direction of arrow A disposed to the left.
Paper feed guides 24a and 24b having 107 at both ends are provided. In the vicinity of the outer peripheral surface of the transfer drum 28, the contact roller 27 moves from the upstream side to the downstream side in the rotation direction,
A gripper 26, a transfer material separating charger 22 and a separating claw 40 are sequentially arranged. A transfer charger 29 and a transfer material separating charger 23 are arranged on the inner peripheral side of the transfer drum 28. At the upper right side of the transfer drum 28, a transport belt means 25 is provided in proximity to the separation claw 40, and at the end (right) end of the transport belt means 25 in the transfer material transport direction, a multicolor image fixing device (hereinafter referred to as a fixing device) 21) is provided. A discharge tray 41 that extends to the outside of the apparatus main body 100 and is detachable from the apparatus main body 100 is provided downstream of the fixing device 21 in the transport direction.

Next, the configuration of the latent image forming section II will be described. First, a photosensitive drum 32 as an image carrier rotatable in the direction of arrow B in FIG. 4 is provided with its outer peripheral surface in contact with the outer peripheral surface of the transfer drum 28. Above the photosensitive drum 32 and in the vicinity of the outer peripheral surface thereof, a static eliminator 30, a cleaning means 31, and a primary charger 33 are sequentially arranged from the upstream side to the downstream side in the rotation direction of the photosensitive drum 32. An image exposure means 42 such as a laser beam for forming an electrostatic latent image on the outer peripheral surface of the photosensitive drum 32 and an image exposure reflection means 43 are provided.

Next, the configuration of the rotary developing device III is as follows. A rotatable housing (hereinafter referred to as a “rotator”) is provided at a position facing the outer peripheral surface of the photosensitive drum 32.
34, four types of developing devices are mounted in the rotating body 34 at four positions in the circumferential direction, and the electrostatic latent image formed on the outer peripheral surface of the photosensitive drum 32 is visualized (that is, developed). ). The above four types of developing devices are:
Each of the yellow developing device 34Y and the magenta developing device 3
4M, cyan developing device 34C and black developing device 34
BK.

The sequence of the entire image forming apparatus having the above-described configuration will be briefly described by taking a full color mode as an example. When the above-described photosensitive drum 32 rotates in the direction of arrow B in FIG. 4, the photoconductor on the photosensitive drum 32 is uniformly charged by the primary charger 33. When the photosensitive member is uniformly charged by the primary charger 33,
Image exposure is performed by the laser light E modulated by the yellow image signal of the document, and an electrostatic latent image is formed on the photosensitive drum 32. And the electrostatic latent image of this yellow image is
By the rotation of the rotator 34, the image is developed by the yellow developing device 34Y previously set at the developing position.

On the other hand, the paper feed guide 24a, the paper feed roller 10
6. The transfer material (not shown) conveyed via the paper feed guide 24b is held by the gripper 26 at a predetermined timing, and the contact roller 27 and the contact roller 27
The transfer drum 28
Wrapped around. The transfer drum 28 is a photosensitive drum 32
4, the visible image (toner image) developed by the yellow developing device 34Y is in contact with the outer peripheral surface of the photosensitive drum 32 and the outer peripheral surface of the transfer drum 28. The transfer is performed by the transfer charger 29 at the portion where the transfer is performed. The transfer drum 28 continues to rotate as it is,
Prepare for the transfer of the next color (magenta in FIG. 4).

On the other hand, the photosensitive drum 32 is neutralized by the neutralizing charger 30, and is cleaned by the cleaning means 31. Thereafter, the photosensitive drum 32 is charged again by the primary charger 33, and the above image exposure is performed by the next magenta image signal. receive. The rotary developing device III includes a photosensitive drum 3
2 while the electrostatic latent image based on the magenta image signal is formed by the image exposure on the magenta developing device 34.
M is fixed at the above-described predetermined developing position, and predetermined magenta development is performed. Subsequently, the process as described above is also performed for cyan and black, respectively.
When the transfer of the four colors is completed, the four-color visible image (toner image) formed on the transfer material is discharged by the chargers 22 and 23, and the gripping of the transfer material by the gripper 26 is released. The transfer material is separated from the transfer drum 28 by the separation claw 40, sent to the fixing device 21 by the transport belt 25, and fused and fixed by heat and pressure to complete a series of full-color print sequences, thereby forming a required full-color print image. Will be done.

The above color toner needs to have good melting property and color mixing property when heat is applied, and a sharp melt toner is used.

Such a sharp melt toner includes, for example, a binder resin such as a polyester resin or a styrene-acryl ester resin, a colorant (a dye, a sublimable dye),
It is manufactured by melt-kneading, pulverizing, and classifying a toner-forming material such as a charge control agent. If necessary, an external addition step of adding various external additives (for example, hydrophobic colloidal silica) to the toner may be added. As such a color toner, a toner using a polyester resin as the binder resin is particularly preferable in consideration of the fixing property and the sharp melt property. Examples of the sharp-melt polyester resin include a polymer compound having an ester bond in the main chain of a molecule synthesized from a diol compound and a dicarboxylic acid.

In particular, the following equation

[0039]

[Outside 1] (Wherein R is an ethylene or propylene group, x, y
Is a positive integer of 1 or more, respectively, and the average value of x + y is 2 to 10. ), And a carboxylic acid component comprising a divalent or higher carboxylic acid or an acid anhydride thereof or a lower alkyl ester thereof (for example, fumaric acid, maleic acid, maleic anhydride, Phthalic acid, terephthalic acid,
A polyester resin obtained by at least co-condensation polymerization with trimellitic acid, pyromellitic acid, etc. is more preferable because it has sharp melting characteristics.

The softening point of the sharp-melt polyester resin is preferably from 75 to 150 ° C., more preferably from 80 to 120 ° C.

FIG. 5 shows an example of the softening characteristics of a sharp melt toner containing this polyester resin as a binder resin. The measurement conditions are as follows.

Using a flow tester CFT-500A type (manufactured by Shimadzu Corporation), a die (nozzle) diameter of 0.2 m
m, a thickness of 1.0 mm, a 20 kg extrusion load, an initial set temperature of 70 ° C., a preheating time of 300 seconds, and a constant temperature rise at a rate of 6 ° C./min. A curve (hereinafter referred to as a softening S-shaped curve) was obtained. The toner used as the sample is a fine powder precisely weighed from 1 to 3 g, and the cross-sectional area of the plunger is 1.0 cm ² . Softening S
The character curve becomes a curve as shown in FIG. As the temperature rises at a constant speed, the toner is gradually heated and starts to flow (plunger descent A → B). When the temperature is further raised, the toner in a molten state flows out greatly (B → C → D), and the lowering of the plunger stops and ends (D → E).

The height H of the S-shaped curve indicates the total amount of outflow, and H /
The temperature T0 corresponding to the point C of 2 indicates the softening point of the toner or the resin.

Whether or not the toner and the binder resin have a sharp melt property can be determined by measuring the apparent melt viscosity of the toner or the binder resin.

The toner or the binder resin having such a sharp melt property means that the temperature when the apparent melt viscosity shows 10 ³ poise is T1, and the temperature when the apparent melt viscosity shows 5 × 10 ² poise is T2. T1 = 90 to 150 ° C. | ΔT | = | T1−T2 | = 5 to 20 ° C.

The sharp-melt resin having these temperature-melt viscosity characteristics is characterized in that the viscosity decreases sharply when heated. Such a decrease in viscosity causes appropriate mixing between the uppermost toner layer and the lowermost toner layer, and furthermore, the transparency of the toner layer itself is sharply increased, and good color reduction mixing is caused.

<First Embodiment> First, a first embodiment of the present invention will be described with reference to FIGS.

FIG. 1 shows a multicolor image fixing apparatus according to this embodiment. In FIG. 1, reference numeral 51 denotes a fixing roller having an outer diameter of 40 mm. A rubber elastic body layer 53 having a thickness of 1 mm is coated on a cored bar 52 made of aluminum. The rubber elastic layer 53 is composed of two layers as shown in FIG. 2, and a phenyl HTV silicone rubber layer 53-1 is formed as an elastic layer below the rubber elastic layer 53-1.
A one-component RTV (room temperature vulcanization type) silicone rubber layer 53-2 is formed as a 200 μm thick layer as an elastic layer for preventing offset with a thickness of 00 μm.

Further, the roller has an effective hardness of 80 ° (A
The lower layer phenyl HTV silicone rubber has a piece rubber hardness of about 34 ° (JIS-A 1 kg weight), and the upper layer one-part RTV silicone rubber has a piece rubber hardness of about 50 ° (J load).
The fixing roller is formed by using rubber of IS-A (1 kg weight).

The fixing roller has an effective hardness of 80 ° (Aske
The term “r-C1 kg load” refers to the surface hardness when the rubber layer wound around the core is measured as it is, including the core, and each rubber hardness of each layer is measured by a single rubber according to JIS standards. Since the hardness of the aluminum core is different from the measured rubber hardness, when the rubber thickness is thin as in the present fixing roller, the hardness becomes higher than the JIS standard hardness of the rubber.

As for the rubber hardness, the piece rubber hardness was measured by a JIS-A measuring method in accordance with JIS standard, but the effective hardness of the roller was measured with a 1 kg weight of an Asker-C hardness meter in order to avoid damage to the roller. Done.

Reference numeral 54 denotes a pressure roller having an outer diameter of 40 mm. A phenyl HTV silicone rubber 56 having a thickness of about 2 mm is formed as an elastic layer on a metal core 55 made of aluminum. A thick fluororesin tube is coated.

Further, the roller has an effective hardness of 86 ° (A
phenyl-HTV silicone rubber having a hardness of about 70.
° (JIS-A 1 kg weight) rubber is used.

The elastic layer may be made of rubber or resin such as fluorine rubber or silicone resin, in addition to silicon rubber or fluorine resin.

The other components, such as an oil application device, a cleaning device, a heating mechanism, and a temperature control method, are the same as those of the conventional fixing device, and thus the description thereof is omitted.

Although the fixing roller is heated by the heater 11, no heater for heating the pressure roller is provided. Naturally, the toner receives a larger amount of heat from the fixing roller than the pressure roller.

With the conventional full-color electrophotographic image forming apparatus, the transfer material P carrying the multicolor image T enters between the rollers driven to rotate.

The transfer material P mixed and fixed in the nip N and discharged from the nip is at a roller end discharge position of 0 as shown in FIG.
Below the position.

Therefore, the transfer material P does not receive excessive radiant heat from the fixing roller after passing through the nip.

As described above, in this embodiment, the roller end discharge position can be set to the zero position because the roller diameter, the rubber thickness, and the effective rubber hardness of each of the fixing roller and the pressure roller are appropriately selected and the nip is set. This is because N is substantially flat.

In order to make the nip N substantially flat as described above, in order to obtain a large nip, the surface effective hardness of the pressure roller having a thick rubber layer on the core is 85 ° or more, The surface effective hardness of the fixing roller having a rubber layer thinner than the roller may be set to 85 ° or less.

In particular, the fixing roller elastom
Since the total thickness of the fixing roller is smaller than the total thickness of the pressure roller, it is preferable that the effective surface hardness of the fixing roller be smaller than the surface effective hardness of the pressing roller.

Further, it is preferable that the rubber piece hardness of the pressure roller is larger than that of the fixing roller.

The roller end discharge position does not largely depend on the type of transfer material. In the present invention, 84 g of A4 size paper is used, but the difference in the stiffness of various transfer materials is not so much affected by the proximity of the nip to the roller end discharge position. Measurement of the roller end discharge position is preferred.

Next, a comparison between the fixing device of this embodiment and the conventional device shown in FIG. 6 will be described.

[0066]

[Outside 2]

The structural comparison is as described above.

In such a conventional apparatus, when a so-called solid image on which the toner is applied on the entire surface of the transfer material is fixed, uneven gloss occurs over the entire surface. In addition, the number of sheets until the so-called offset occurs when the toner on the transfer material is transferred to the fixing roller is as short as 2,000 sheets. On the other hand, in the fixing device of this embodiment, even when the solid image was fixed, no gloss unevenness was generated at all, and the number of sheets until the offset was performed was significantly improved to 20,000 sheets.

Next, a comparative example will be described. The rubber layers of the fixing roller and the pressure roller used for comparison have the same thickness as in this embodiment.

[0070]

[Outside 3]

In both the embodiment and the comparative example, the surface effective hardness of the pressure roller is larger than that of the fixing roller.

Under these conditions, when a color image obtained by the full-color electrophotographic image forming apparatus described above was fixed in the comparative apparatus, an offset occurred on 6,000 sheets. This is because the surface effective hardness of the pressure roller is higher than that of the fixing roller, but the discharge end position of the roller is +2.
mm, it is on the plus side, so if you use a toner that is disadvantageous for mold release, such as color toner,
The offset occurs early in the case where there are a plurality of toner layers on the transfer material. That is, in a fixing device such as a multi-color image for various copying needs in recent years, if the roller end discharge position is not configured to be more appropriate than a conventional heat fixing device, unevenness in gloss and offset can be achieved in a short life. Failure occurs.

Incidentally, NP-Color T.C.
In the color laser copier-1, by making the rubber thickness of the fixing roller larger than the rubber thickness of the pressure roller, the roller end discharging position is set to be lower.

However, when the rubber thickness of the fixing roller is made larger than the rubber thickness of the pressure roller, the rubber thickness of the fixing roller becomes large and becomes 2 mm or more even when it is thin. Is very high, and the heat of the internal heater is blocked by the rubber layer even if the rubber of the fixing roller is destroyed by heat, In some cases, there was a problem in fixing.

For this reason, it is conceivable to heat the fixing roller from the outside, but the apparatus becomes complicated and the reliability decreases.

Therefore, as in this embodiment, the fixing roller e
The total thickness of the lastomer is preferably smaller than that of the pressure roller, and particularly preferably smaller than 2 mm.

<Second Embodiment> Next, a second embodiment of the present invention will be described. The description of the common parts with the first embodiment is omitted.

As the fixing roller 51, the same roller as used in the first embodiment is used. The outer diameter of the pressure roller is 40 mm, the thickness of the rubber is 3 mm, the surface layer of the fluororesin tube is 50 μm, and the effective hardness is 87 ° (weight of Asker-C 1 kg). When a color image was fixed in the same manner, the discharge position at the roller end was 0 mm, and satisfactory fixing was possible up to 20,000 sheets.

Next, a table including other examples and comparative examples is shown.

[0080]

[Table 1]

In the fifth to tenth embodiments, although the paper is discharged without being wound, problems such as paper wrinkles are likely to occur. This is because the difference between the effective surface hardness of the fixing roller and the pressure roller is as large as 15 °. In order to further prevent paper wrinkling, it is preferable that the difference between the effective surface hardnesses is 10 ° or less.

In the ninth and tenth embodiments, the fixing roller el
Since the hardness of the rubber forming the astomer is less than 20 ° and the restoration property of distortion due to pressure is reduced, it is preferable that the effective surface hardness of the fixing roller is 60 ° or more.

Further, if the effective surface hardness of the pressure roller is increased, the nip width cannot be increased, so that the effective surface hardness of the pressure roller is preferably 100 ° or less.

In the embodiment described above, a two-layer rubber is used for the fixing roller. However, a single-layer or three or more-layer rubber may be used.

When a large amount of release agent oil is applied,
It is preferable that the intermediate layer has three or more layers having an oil barrier layer such as a fluoro rubber layer.

Although the heat conductivity was not mentioned, the heat conductivity of the elastomer was 1.0 × 10 ⁻³ c in order to efficiently transfer the heat of the heater inside the fixing roller to the surface layer.
It is preferably at least al / cm · sec · ° C.

Further, although the pressure roller used was a roller having a surface layer of a fluorine resin tube coating, the invention is not limited to this, and a conventionally known material (eg, silicone rubber, fluorine rubber, etc.) may be used, and the tube thickness is not limited. However, a roller having a surface layer coated with a fluorine resin tube having a thickness of 20 μm to 120 μm for transporting paper and the like, particularly for wrinkles of paper, is preferable.

The outer diameter of the fixing roller and the pressure roller is also 40 m.
Although the example of m is shown, it is not limited to this. As for the rubber thickness, the rubber thickness of the fixing roller is 1 mm, 1.5
mm, and the rubber thickness of the pressure roller is 2 mm and 3 mm, but the invention is not limited thereto.

Although the embodiments of the present invention have been described above, the present invention can be modified in various ways within the technical idea without being limited to these embodiments.

[0090]

As described above, according to the present invention, the toner on the transfer material does not receive radiant heat more than necessary. Therefore, even when used in a multi-color image forming apparatus using a sharp melt toner, a good image can be obtained without extremely increasing the glossiness of the image. Also,
No offset is generated.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a schematic configuration of a first embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a configuration of an elastic layer of a fixing roller of the apparatus in FIG.

FIG. 3 is a cross-sectional view showing a roller end discharge position of a transfer material in the apparatus of FIG. 1;

FIG. 4 is a cross-sectional view illustrating a schematic configuration of a full-color electrophotographic image forming apparatus.

FIG. 5 is a view showing a softening S-shaped curve of a sharp melt toner used in the apparatus of FIG. 4;

6 is a cross-sectional view illustrating a schematic configuration of a multicolor image fixing device provided in the apparatus in FIG. 4;

7 is a cross-sectional view illustrating a configuration of an elastic layer of a fixing roller of the apparatus in FIG. 6;

FIG. 8 is a cross-sectional view showing a roller end discharge position of a transfer material in the apparatus shown in FIG. 6;

FIG. 9 is a diagram illustrating a definition of a roller end discharge position.

FIG. 10 is a diagram illustrating an example of a case where a roller end discharge position is a plus position.

[Explanation of symbols]

 51 fixing roller 53 elastic layer 54 pressure roller 56 elastic layer

Claims (1)

(57) [Claims] 1. A heating roller having a core material and an elastic layer provided on the core material, a heating means provided inside the heating roller, and a core material and an elastic layer provided on the core material. A color mixing fixing device having the heating roller and a pressure roller forming a nip, wherein the recording material supporting a plurality of color toners is nipped and conveyed in the nip to perform mixed color fixing, wherein the elastic layer of the heating roller Wherein the total thickness of the heating roller is smaller than the total thickness of the elastic layer of the pressure roller, and the effective surface hardness of the heating roller is smaller than the effective surface hardness of the pressure roller.