JPH09171322A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high-speed fixing device capable of fixing at high speed, being miniaturized and securing the transparency of a color toner image on a transparent sheet by deciding such a fixing condition that a nip passing time satisfies a specified expression. SOLUTION: In this fixing device provided with a heating member and a pressure member coming into press-contact with each other, a body to be heated carrying the unfixed color toner image is held and carried by a press-contact part (nip) between the heating member and the pressure member so as to fix the unfixed color toner image. The fixing condition is decided so that the nip passing time (t) (ms) may satisfy the expression based on A>=-4.6. In the expression, Tm: the melting point of toner ( deg.C). Th: the surface temperature of the heating member ( deg.C), P: pressing force per unit area in the nip (total weighting/ nip area) (kgf/cm<2> ), and A: a constant expressing transparency. The carrying speed is decided so that the ratio v1/v2 of carrying speed v1 in the case of fixing on the transparent sheet being the body to be heated to the carrying speed v2 in the case of fixing on plain paper may be 0.5 to 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat fixing device particularly applied to an electrophotographic image forming apparatus.
More specifically, the heating target having an unfixed color toner image is sandwiched and conveyed by a heating member and a pressing member that are in pressure contact with each other, and the heating target holding the unfixed color toner image is nipped and conveyed at the pressing contact portion between the heating member and the pressing member. The present invention relates to a fixing device that fixes a color toner image on a body.

[0002]

2. Description of the Related Art Conventionally, a heat fixing device such as a heat roller or a belt is used as a fixing device for color toner, and a plain paper (thick letter, postcard, thin normal paper, etc.) is used as a heated object.
Alternatively, a transparent sheet used for an overhead projector (hereinafter abbreviated as OHP) is used, and when fixing the transparent sheet, a method of slowing the transport speed of transporting the transparent sheet to secure transparency by fixing the transparent sheet is slower than that of plain paper. Was commonly used.

For example, in Japanese Patent Laid-Open No. 59-188673, a technique for fixing a transparent sheet in a color fixing device at a fixing roller peripheral speed (hereinafter, referred to as a fixing speed) lower than that of plain paper is used. Is proposed.

In Japanese Patent Laid-Open No. 60-78462, a buffer space is provided between a fixing device and a separation point (separation of a photoconductor or a transfer intermediate medium from paper) in transfer to fix a transparent sheet. Has proposed a technique of making the fixing speed slower than the peripheral speed of the photosensitive drum.

Further, Japanese Patent Application Laid-Open No. 60-86574 proposes a technique for reducing both the fixing temperature and the fixing speed when fixing a transparent sheet in a color fixing device.

[0006]

Generally, the high speed of a laser printer is used to convey the transparent sheet at a high speed even in a fixing device, and if the transparent sheet is fixed at a high speed, the transparent sheet cannot be sufficiently heated. The color toner image becomes opaque, and the projection image projected by the OHP becomes black or a color that is substantially black.

Therefore, in order to secure the transparency, the techniques proposed in JP-A-59-188673, JP-A-60-78462 and JP-A-60-86574 have been conventionally used. . However, if the transport speed of the fixing device during the fixing of the transparent sheet is extremely slower than that during the fixing of the plain paper, it is not desirable because the high speed of the laser printer cannot be utilized and wasteful time is consumed.

Further, in the technique disclosed in Japanese Patent Laid-Open No. 60-78462, a buffer space is required, so that the image forming apparatus becomes large, and a fixing device which secures a long fixing time by the buffer space is used. Even in the single-color or two-color mode, it is necessary to wait until the fixing of the transparent sheet on which the image is previously formed is completed, then transfer the color toner image to the next transparent sheet and convey it to the fixing device. Alternatively, the printing speed (the number of printed sheets per unit time) in the single-color mode or the two-color mode cannot be made higher than that in the three-color mode, and again, the high speed of the laser printer cannot be utilized and wasteful time is consumed. Was not desirable.

The present invention has been made in view of the above conventional problems, and an object of the present invention is to fix a transparent sheet at a high speed at a speed almost equal to a process speed (the same speed as a photosensitive member), and to fix the apparatus. An object of the present invention is to provide a high-speed fixing device capable of ensuring the transparency of a color toner image on a transparent sheet with a structure that is downsized.

[0010]

In order to solve the above-mentioned problems, a fixing device of the present invention has a heating member and a pressure member which are in pressure contact with each other, and a pressure contact portion between the heating member and the pressure member. A fixing device for fixing an unfixed color toner image by sandwiching and transporting an object to be heated carrying an unfixed color toner image (hereinafter referred to as a nip) at a nip passage time t
It is characterized in that the fixing condition is determined so that (ms) satisfies the expression 3 in the element of A ≧ −4.6.

[0011]

(Equation 3)

Further, in the fixing device of the present invention, the object to be heated is a transparent sheet or plain paper, and the first conveying speed v1 in the fixing device when fixing the transparent sheet and the fixing when fixing the plain paper. Ratio of the second transport speed v2 in the device v1 /
It is characterized in that each transport speed is determined so that v2 is 0.5 to 2.

Further, the fixing device of the present invention is characterized in that the fixing condition is determined so as to satisfy the expression A ≧ 0 in the equation (3).

Further, the fixing device of the present invention is characterized in that the fixing condition is set so as to satisfy the equation of A ≧ 10.9 in Formula 3.

Further, the fixing device of the present invention is characterized in that the fixing condition is determined so that the color melting point Tm is 105 ° C. ≤ Tm ≤ 125 ° C. and the formula 3 is satisfied.

Further, the fixing device of the present invention is characterized in that the fixing condition is set so as to satisfy the equation (4).

[0017]

(Equation 4)

Further, the fixing device of the present invention is characterized in that the surface temperature Th of the heating member is controlled to 180 ° C. or lower.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments and drawings.

First, the structure of the fixing device of the present invention will be described with reference to FIG. 1, and then the structure for ensuring transparency when using such a fixing device will be described.

FIG. 1 is a schematic view of a fixing device according to an embodiment of the present invention, in which a metal cylinder having good heat conductivity such as aluminum, a heating roller 1 made of a rubber layer formed on the outer peripheral surface thereof, and a heating roller. A heating member configured by a heating body 7 such as a halogen lamp disposed inside the roller 1, and a pressure member configured by a pressure roller 2 in which an elastic body such as silicone rubber is formed on the outer peripheral surface of a metal shaft. The heating roller 1 and the pressing roller 2 are pressed against each other by a pressing means (not shown) to form a pressing portion 11.
It should be noted that the heating roller 1 has an HTV, RT on a metal cylinder in order to improve the contact property with the object 12 to be heated such as a transparent sheet.
A layer of silicone rubber such as V or LTV or a fluororubber may be provided, and silicone or PFA may be coated or formed as a release layer by a tube to improve the release property. Since the surface roughness of the heating roller 1 affects the transparency of the toner image on the transparent sheet, the surface roughness is 1 μmRa (JI
The center line average roughness defined by S B0601) or less. Moreover, the wall thickness of the metal cylinder was 0.5 to 6 mm. Further, a temperature detecting member 8 such as a thermistor is installed so as to come into contact with the outer peripheral surface of the heating roller 1 or in the vicinity of the outer peripheral surface of the heating roller 1, and a temperature control means is provided by a temperature detection signal from the temperature detecting member 8. The power supply to the heating element 7 is controlled by 13 to control the heating member to a desired temperature. The heating roller 1 and the pressure roller 2 are rotationally driven by a driving device (not shown), and the transparent sheet as the heated body 12 enters the pressure contact portion (nip) between the heating roller 1 and the pressure roller 2 in the direction of the arrow. Then, after fixing is performed in the nip of the fixing device, the sheet is discharged from the fixing device. Further, a peeling claw 9 for peeling the heated body 12 after fixing from the heating roller 1, and a discharge roller 10 for smoothly discharging the paper discharged from the nip of the fixing device from the fixing device.
Alternatively, a releasing agent such as a silicone oil is applied to the surface of the heating roller 1 and a cleaner such as an oil impregnated pad for removing the toner adhering to the surface of the heating roller 1 is provided in the fixing device as required. May be. Also, the object to be heated 1
2 is plain paper such as thin normal paper, thick letters, postcards, etc.
A transparent sheet used for HP is used.

As described above, the results of the intensive studies conducted by the present inventors on the structure in which the process speed and the fixing speed are equal to each other and the transparent sheet is fixed at a high speed to provide transparency will be described below.

A heating roller is used as a heating member, a halogen lamp arranged inside the heating roller is used as a heating member, a pressure roller is used as a pressure member, and the surface temperature of the heating roller (hereinafter referred to as fixing temperature Th) is detected by a temperature detecting member. The fixing temperature is detected, and the pressure roller is pressed against the heating roller by spring pressure to form a nip having a length L (mm), and the heating roller and the pressure roller are conveyed by a motor at a conveying speed v (mm).
The relationship between each parameter that determines the transparency and the transparency will be described by taking a fixing device that is rotationally driven at / s) as an example.

As shown in Equation 5, the toner temperature Tt is the fixing temperature T
It is expressed as a function of h and the nip passage time t (ms).

[0025]

(Equation 5)

Further, the toner viscosity is expressed as a function of the toner temperature as shown in the equation (6).

[0027]

(Equation 6)

Further, as in the equation (7), the toner deformation amount is represented by a function of the toner viscosity, the pressure P, and the pressure application time (that is, the nip passage time t).

[0029]

(Equation 7)

By the way, in the unfixed color toner, when heat and pressure are applied, the toner particles are deformed, the toner particles are eventually connected to each other, and an interface between the toner particles (hereinafter referred to as a grain boundary).
Disappears, bubbles in the toner layer disappear, and the surface of the toner layer becomes flat. According to this process, the transparency of the toner layer is improved. Therefore, the transparency is expressed by a function of the amount of toner deformation and the amount of grain boundaries as shown in Expression 8.

[0031]

(Equation 8)

Since the toner deformation amount and the grain boundary amount decrease almost at the same time, equation 8 can be written as equation 9.

[0033]

[Equation 9]

From Equations 5-9, the transparency can be expressed by Equation 10.

[0035]

(Equation 10)

From equation 10, equation 11 holds when the transparency is constant.

[0037]

[Equation 11]

As expressed by the equations 5 to 9, the toner deformation amount increases as the pressure increases, and the toner viscosity decreases and the toner deformation amount increases as the toner temperature rises. That is, when the pressure increases, the toner deforms as if the toner temperature rises. Therefore, the effect of pressure on transparency can be formulated as a temperature correction term. In the present invention, the effect of pressure is formulated as a correction term for the fixing temperature.
The specific formula will be shown later by Equation 14.

By the way, as is well known, the toner temperature Tt after the nip passage time t is qualitatively expressed by Expression 12.
However, as the initial condition, the toner temperature Tt at t = 0 was set to the room temperature Tr (Tt = Tr).

[0040]

(Equation 12)

The equation 12 is transformed into the equation 13.

[0042]

(Equation 13)

We have used HAZE as a measure of the transparency of color toner images formed on transparent sheets. HAZ
E was measured by a haze meter (NDH-1001DP, manufactured by Nippon Denshoku Industries Co., Ltd.). As a result of diligent examination,
We have found that Haze is suitable for quantifying the transparency of color toner images formed on transparent sheets.

Therefore, we experimentally verified which parameters are involved in HAZE and how, and as a result of earnest study, the following was found. In addition, the transparency becomes higher as the Haze becomes smaller.

[Equation 13] as basic form
When it is approximated to the fixing condition of 0, the time constant τ = 115 m
and the toner melting point is Tm (° C.), the toner temperature Tt =
It was found that Tm-4.6 (° C) can be obtained, and (25.7 / P-6.43) can be subtracted from the fixing temperature as a pressure correction term, and if the fixing condition is defined by Equation 14, a transparency of 50 can be obtained with Haze. .

[0046]

[Equation 14]

The toner melting point Tm was measured by a flow tester method.

Next, if the fixing conditions are defined by the equation 15, HAZ
E gives a transparency of 35.

[0049]

(Equation 15)

If the fixing condition is defined by the equation 16, HAZ
A transparency of 15 is obtained with E.

[0051]

(Equation 16)

By substituting the fixing temperature Th, the toner melting point Tm, and the pressure P into these equations 14 to 16, the respective HAZE values are obtained.
We have found that if the nip passage time t having a value is obtained and the nip width L and the transport speed v are controlled so that the nip passage time is longer than the nip passage time t, transparency higher than desired can be secured.

That is, equations (14) to (16) show the minimum nip passage time for ensuring the desired transparency, and in order to obtain higher transparency, the nip passage time is lengthened or the fixing temperature is raised to make the transparency transparent. It is sufficient to increase the amount of heat applied to the sheet. Alternatively, the transparent sheet is detected by a sensor, and the total load is increased by using the total load changing device proposed in Japanese Patent Laid-Open No. 61-294475 to increase the nip width L.
May be increased, or the pressure P may be increased.

However, if the amount of heat applied is too large, the intermolecular bonding force in the toner layer becomes small, so-called offset occurs, and the printed matter is stained.

Next, the mechanism of generating the offset will be described. When the unfixed toner is heated in the nip of the fixing device, the toner temperature rises. When the toner temperature rises, the toner particles bond with each other. At this time, since the bonding force between the toners is larger than the adhesive force between the toner and the heating roller, peeling occurs at the interface between the toner and the heating roller, and offset does not occur. However, when the toner temperature is further increased, the toner viscosity decreases, the binding force between the toners decreases, and the adhesive force between the toner and the heating roller exceeds the binding force between the toners, causing separation in the toner layer. The toner upper layer portion adheres to the surface of the heating roller, causing offset.
Therefore, it is necessary to keep the toner temperature lower than a certain temperature in order to prevent the offset.

The relationship among the nip passage time, the fixing temperature, and the toner temperature is as shown in Expression 13. By using this formula as a basic form and approximating the fixing conditions (fixing temperature, nip passage time, toner melting point) at which offset occurred, Formula 17 was obtained.

[0057]

[Equation 17]

Therefore, if the fixing condition is defined by the equation 18, no offset occurs.

[0059]

(Equation 18)

Expression 18 is the same expression as Expression 2 described in claim 7.

[0061]

EXAMPLES Hereinafter, more detailed examples of the present invention will be described using Experimental Examples 1 to 5.

<Experimental Example 1> In this experimental example, an experimental example corresponding to claims 1 and 7 will be described.

The fixing device used in this experimental example is shown in FIG.
In the nip between a pair of heating roller and pressing roller that are pressed against each other as shown in Fig. 5, the transparent sheet that is the object to be heated is nipped and conveyed, and the image forming surface of the paper comes into contact with the heating roller and inside the heating roller. A halogen lamp was arranged as a heating body (heater) to perform fixing.

An RTV rubber (outer diameter φ18 mm, wall thickness 0.5 mm) was formed on the outer peripheral surface of an aluminum cylinder (outer diameter φ17 mm, wall thickness 0.6 mm) as a heating roller, and a PFA tube was wound as a release layer. The surface roughness after polishing was 0.3 μmRa.

Since the fixing device for color uses a soft heating roller, the heat resistance of the surface rubber is large and the fixing temperature is 18
If the temperature is not lower than 0 ° C., the temperature of the internal metal part exceeds 230 ° C. which is the heat resistant temperature of the adhesive part during continuous passage of narrow paper, and the adhesive part between the metal part and the rubber part melts and peels off. Therefore, the fixing temperature Th is preferably 180 ° C. or lower, and in this embodiment, the fixing temperature is 140 ° C. to 180 ° C.

As the pressure roller, a roller (outer diameter φ18 mm, wall thickness 4 mm) having a silicone rubber layer of JIS-A hardness of 24 degrees formed by injection molding on the outer peripheral surface of a steel shaft was used. The heating roller and the pressure roller were brought into pressure contact with each other with a total weight of 5 kgf by a pressure means (not shown). Nip width is 2.2 mm
And the nip length of the pressure roller in the axial direction is 225
mm. Therefore, the pressure P is P = 5 / (0.22 × 2
2.5) = 1.0 kgf / cm ² .

Further, the heating roller is rotationally driven by a driving device (not shown), and the conveying speed is 33.0 mm / sec-10.
It was set to 1.5 mm / sec. The environmental temperature was 25 ° C. and the environmental humidity was 50%.

The melting point (Tm) of the color toner is 1 for each color.
A toner of 02 ° C. was used. The melting point of the toner was measured by the flow tester method. Further, the toner adhesion amount on the transparent sheet is set to 0.6 mg / cm ^2, and 4c is applied on the transparent sheet.
An m × 4 cm color batch was formed and fixed at a predetermined fixing temperature and transport speed. As described above, the transparency after fixing is HA
ZE is used as a scale, and HAZE is a haze meter (NDH-
1001DP, manufactured by Nippon Denshoku Industries Co., Ltd.). The transparent sheet is XE made by FUJI XEROX.
ROXFILM (REORDER No. V515) was used.

Table 1 shows combinations of the fixing temperature and the conveying speed at which HASE was 50.

[0070]

[Table 1]

All the combinations shown in Table 1 satisfied the formula 1 described in claim 1. The fixing condition may be set in this way. Further, when the nip passage time is longer than that shown in Table 1, the transparency is further improved.

Even when a narrow paper such as an envelope was continuously fed, the temperature of the inner wall of the metal cylinder did not exceed the heat resistance temperature 230 ° C. of the adhesive portion, the adhesive portion between the metal portion and the rubber portion did not melt and did not peel off. .

Experimental Example 2 In this experimental example, an experimental example corresponding to claim 3 will be described.

Fixing device size, conveying speed range, desired HA
The ZE value is different from that of Experimental Example 1, but the basic structure of the fixing device, the material used, the fixing temperature range, the toner melting point Tm, the transparency (Haze) measuring method, etc. are used unless otherwise specified.
Is the same as

In Experimental Example 1, the setting of the fixing condition was set to 50 in Haze, but 35 in Haze is more transparent. Therefore, in this experimental example, HAZE
The setting of the fixing condition of 35 will be described.

In this experimental example, an RTV was mounted on a cylinder made of aluminum (outer diameter φ39 mm, wall thickness 3 mm) as a heating roller.
Rubber (outer diameter φ40 mm, wall thickness 0.5 mm) was formed, and a PFA tube was wound as a release layer.

Two types of pressure rollers were prepared, one for high pressure and the other for low pressure. Silicone rubber layer with ASK-C hardness of 83 degrees (outer diameter φ) by injection molding on the outer peripheral surface of an aluminum cylinder (outer diameter φ39 mm, wall thickness 3 mm) for high pressure.
A roller having a thickness of 40 mm and a thickness of 2 mm) was used. Further, the heating roller and the pressure roller were pressed against each other with a total weight of 56.7 kgf. The nip width was 4.5 mm, and the nip length of the pressure roller in the axial direction was 315 mm. Therefore,
The pressure P is P = 56.7 / (0.45 × 31.5) = 4.
0 kgf / cm ² .

As a low-pressure pressure roller, a steel shaft (outer diameter φ10 mm) on the outer peripheral surface of which a silicone rubber layer having an ASK-C hardness of 55 degrees is formed by injection molding (outer diameter φ4).
0 mm, wall thickness 15 mm) was used. Further, the heating roller and the pressure roller were pressed against each other with a total weight of 17.0 kgf. The nip width is 4.5 mm, the nip length of the pressure roller in the axial direction is 315 mm, and the pressure P is 1.2 kgf / cm.
^{And 2} .

The heating roller is rotationally driven by a driving device (not shown), and the conveying speed is 43.7 mm / sec to 34.
It was set to 7.0 mm / sec.

Table 2 shows combinations of the fixing temperature and the conveyance speed at which HASE became 35.

[0081]

[Table 2]

All the combinations shown in Table 2 satisfy claim 3. The fixing condition may be set in this way. Also,
When the nip passage time is longer than that shown in Table 2, the transparency is further improved.

<Experimental Example 3> In this experimental example, an experimental example corresponding to claim 5 will be described.

Further, this experimental example is the same as the experimental example 2 except for the toner melting point Tm.

In this experimental example, the toner melting point Tm is 105 ° C. ≦
A toner having Tm ≦ 125 ° C. was used.

When the melting point Tm of the toner is less than 105 ° C., the molecular weight of the toner is small, so that the intermolecular bonding force in the toner layer becomes small and so-called offset occurs and the printed matter is stained. In order to prevent this, it is necessary to apply a large amount of release agent such as silicone oil to the heating roller, the paper head is soiled with oil, the applied oil evaporates, and it adheres to the photoconductor and charging device, causing image distortion. However, the oil consumption was high and the running cost was high. Therefore,
It is more preferable to use a toner having a toner melting point Tm of 105 ° C. or higher.

Further, when a toner having a toner melting point Tm of more than 125 ° C. is used, a considerably large amount of heat needs to be added to the transparent sheet to obtain a desired transparency, so that a higher fixing temperature or a longer nip passage time is required. It needed to be established. However, the toner melting point Tm is 125
When a large amount of heat is used to obtain a desired transparency to a transparent sheet using a toner having a temperature higher than 0 ° C., stretching strain of the transparent sheet is relaxed, the transparent sheet shrinks, and image distortion occurs,
Further, when a large amount of heat is applied to improve the transparency, the transparent sheet is deformed and paper jam occurs, or the transparent sheet is melted and separated in the fixing device. Therefore, a toner having a toner melting point Tm of 125 ° C. or lower is more preferable.

The pressure roller used was the one for high pressure of Experimental Example 2, and the total weight was 56.7 kgf.

Table 3 shows combinations of the fixing temperature and the conveying speed at which HASE became 35.

[0090]

[Table 3]

The combinations shown in Table 3 all satisfy claim 5, and the fixing conditions may be set in this way. Further, when the nip passage time shown in Table 3 was exceeded, the transparency was further improved.

Further, the oil consumption was small, the running cost was low, the oil adhered to the photoconductor and the charger was small, there was no offset, and the image was not disturbed.

Moreover, the shrinkage, deformation, and melting of the transparent sheet did not occur, and the image disorder did not occur.

<Experimental Example 4> In this experimental example, an experimental example corresponding to claims 2 and 4 will be described.

If the transparent sheet is conveyed at a high speed in the fixing device and fixed, and high-speed printing is performed, the high speed of the laser printer can be utilized, there is no waiting time for the user, and unnecessary time is not consumed. Further, if the transparent sheet is fixed at a high speed, the same speed as that at the time of fixing the plain paper can be obtained. As described above, it is necessary to change the oil supply amount when the transport speed is different between plain paper and transparent sheet. For this reason, the control device has been increased in size.

However, if the ratio v1 / v2 of the transport speed v1 for fixing the transparent sheet and the transport speed v2 for fixing the plain paper is 0.5 to 2, no offset occurs even with the same oil supply amount. And the oil consumption was also low.

Further, in Experimental Example 2, the fixing condition with Haze of 35 was described. However, with Haze 35, the stability is poor, and depending on the conditions, the transparency between the initial transparent sheet and the final transparent sheet during continuous printing is high. Different. Further, when it deteriorated further, the transparency was different between the front end and the rear end of the transparent sheet in one sheet, and the image quality was deteriorated. This is Haze
In the fixing condition of about 35, the transparency greatly depends on the fixing temperature, the nip passage time, and the environment, and the transparency greatly changes due to these variations.

On the other hand, in the case of HAZE, the transparency is almost saturated near 15, and the transparency hardly changes due to the above-mentioned fluctuation factors, and the change in the transparency during continuous printing or one sheet becomes negligible. Therefore, in this experimental example, HAZ
The setting of the fixing condition of 15 will be described.

In this experimental example, the dimensions of the fixing device, the conveying speed range, and the desired Haze value are different from those in the experimental example 2, but the basic structure of the fixing device, the materials used, the fixing temperature range, the toner melting point Tm, and the transparency (Haze). The measurement method and the like are the same as in Experimental Example 2 unless otherwise specified.

In this experimental example, an RTV was mounted on a cylinder made of aluminum (outer diameter φ78 mm, wall thickness 6 mm) as a heating roller.
A rubber (outer diameter φ80, wall thickness 1 mm) was formed, and a PFA tube was wound as a release layer.

Further, a silicone rubber layer (outer diameter φ80 mm, wall thickness 4 mm) having an ASK-C hardness of 83 degrees was formed on the outer peripheral surface of an aluminum cylinder (outer diameter φ72 mm, wall thickness 6 mm) as a pressure roller by injection molding. A roller was used.
In addition, the heating roller and the pressure roller have a total weight of 113.4 kg.
Pressed with f. The nip width was 9.0 mm, and the nip length in the axial direction of the pressure roller was 315 mm. Therefore, the pressure P is P = 113.4 / (0.90 × 31.5)
= 4.0 kgf / cm ² . In addition, the transport speed is 8
It was set to 9.8 mm / sec to 297 mm / sec.

Table 4 shows combinations of the fixing temperature and the conveying speed at which HASE is 15.

[0103]

[Table 4]

All of the combinations shown in Table 4 satisfy claim 4, and if the fixing conditions are set in this way, the transparency is unlikely to change with respect to changes in the fixing temperature, the nip passage time, and the environmental temperature, and continuous sheet passing is possible. The transparency of the initial transparent sheet and that of the final stage were almost the same, and the fluctuation of the transparency in one sheet was negligible, which was good.

Further, the desired transparency can be obtained even at a high conveying speed, the color printed matter can be obtained at a high speed as in the case of fixing the plain paper, and wasteful time such as waiting time can be reduced.

Even if the oil supply amount was not switched, there was no offset, no image smearing occurred, and the oil consumption amount was small.

Further, the cost can be reduced because the oil supply amount switching device is unnecessary. In particular, when the transport speed of the fixing device is the same for plain paper and transparent sheet, the operation of switching the oil supply amount is unnecessary, and the complexity of the user's printer operation can be reduced.

<Experimental Example 5> In Experimental Examples 1 to 4, the minimum nip passage time for ensuring the desired transparency is shown. In order to obtain higher transparency, the nip passage time is lengthened or the fixing temperature is increased. It is said that the amount of heat applied to the transparent sheet may be increased by performing the same process. However, if the amount of heat applied is too large, the toner temperature becomes too high, the intermolecular bonding force in the toner layer becomes small, and so-called offset occurs, which stains the printed matter.

Therefore, in the present experimental example, the toner temperature is controlled to be equal to or lower than the predetermined temperature based on the second aspect of the sixth aspect to prevent the offset.

In this experimental example, the transport speed range was set to Experimental example 4
However, the basic structure of the fixing device, dimensions, materials used, fixing temperature range, toner melting point Tm, transparency (HAZ
The measuring method of E) and the like are the same as in Experimental Example 4. The transport speed was 38.0 mm / sec to 152.5 mm / sec.

First, when the nip passage time and the conveyance speed at which offset occurs at each fixing temperature were examined, the results are shown in Table 5.

Therefore, when the conveying speed was increased and the nip passage time was shortened at each fixing temperature, offset did not occur. Table 6 shows a specific example of the transport speed. These combinations satisfy claim 4, and 1 in HAZE
The transparency was better than 5.

[0113]

[Table 5]

[0114]

[Table 6]

As described above, the fourth aspect is satisfied, and
By setting the fixing conditions satisfying the mathematical expression 2 of claim 6, a desired transparency can be ensured, an offset does not occur, and a good transparent image can be obtained.

Although the detailed embodiments of the present invention have been described above, the fixing device of the present invention is not limited to the above embodiments. For example, the object to be heated is nipped and conveyed by a film and a pressure roller,
It is also possible to use a fixing device in which a heated body is heated through a film by a heating body such as a ceramic heating body.

[0117]

According to the fixing device of the first aspect, the color toner image on the transparent sheet can be fixed and printed at a high speed, and a desired transparency can be secured in the color toner image on the transparent sheet. It is possible to obtain a good transparent image, and the buffer space between the transfer device and the fixing device is not required, so that the image forming apparatus can be downsized, and in the single-color or two-color mode, the four-color or three-color mode can be obtained. The printing speed (the number of printed sheets per unit time) can be further increased, the high speed of the laser printer can be utilized, and waste of time can be prevented.

According to the fixing device of the second aspect, the process speed and the fixing speed are almost equal, and
Since it is possible to fix a transparent sheet at the same speed as plain paper, there is no need to switch the oil supply amount to the fixing device, and an oil supply amount switching device is not required, enabling downsizing and cost reduction of the image forming apparatus. Thus, the complexity of the user's operation of the device can be reduced. Further, even with a transparent sheet, a color printed matter can be obtained at high speed as in the case of fixing plain paper, and wasteful time such as waiting time can be reduced.

According to the fixing device of the third aspect, a better transparency can be secured.

Further, according to the fixing device of the fourth aspect, it is possible to secure even better transparency, and it is possible to make the transparency less likely to change with respect to changes in the fixing temperature, the nip passage time, and the environmental temperature. It is possible to make the transparency of the initial transparent sheet and the transparent sheet of the last stage of continuous paper feeding substantially the same, and it is possible to reduce the fluctuation of the transparency in one sheet to a negligible level.

Further, according to the fixing device of the fifth aspect, the oil consumption can be reduced, the running cost can be reduced, and the oil adhesion to the photoconductor and the charger can be reduced.
Offset can be prevented, image disturbance can be prevented, and shrinkage, deformation, and melting of the transparent sheet can be prevented, and image disturbance can be prevented.

According to the fixing device of the sixth aspect, offset can be prevented, the fixing device can have a long life, and a good transparent image can be obtained.

Further, according to the fixing device of the seventh aspect, the temperature of the inner wall of the metal cylinder does not exceed the heat resistant temperature of 230 ° C. of the adhesive portion even if the narrow paper such as the envelope is continuously passed, so that the metal portion and the rubber portion It is possible to prevent melting of the bonded portion with the portion and prevent peeling.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a fixing device according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heating roller 2 Pressure roller 7 Heating body 8 Temperature detection member 11 Pressure contact part 12 Heated body 13 Temperature control means

Claims (7)

[Claims] 1. A heating member having a heating member and a pressing member which are in pressure contact with each other, and a heating target carrying an unfixed color toner image is sandwiched at a pressing contact portion (hereinafter referred to as a nip) between the heating member and the pressing member. A fixing device that conveys and fixes an unfixed color toner image, and has a nip passage time t (ms) of several 1
The fixing device is characterized in that the fixing condition is determined so as to satisfy A ≧ -4.6. [Equation 1] 2. The object to be heated is a transparent sheet or plain paper, and is the first in a fixing device when fixing the transparent sheet.
The respective transport speeds are determined so that the ratio v1 / v2 of the transport speed v1 of 1 to the second transport speed v2 of the fixing device when fixing the plain paper is 0.5 to 2. Item 2. The fixing device according to item 1. 3. The fixing device according to claim 1, wherein the fixing condition is determined so as to satisfy the expression of A ≧ 0 in Expression 1. 4. The fixing condition is set so as to satisfy the equation of A ≧ 10.9 in Formula 1.
3. The fixing device according to claim 1. 5. The melting point Tm of the toner is 105 ° C. ≦ Tm.
The fixing device according to any one of claims 1 to 4, wherein the fixing condition is set so as to satisfy the expression (1) using a color toner having a temperature of ≤ 125 ° C. 6. The fixing device according to claim 1, wherein the fixing condition is set so as to satisfy Expression 2. [Equation 2] 7. The surface temperature Th of the heating member is 180 ° C.
The fixing device according to claim 1, wherein the fixing device is controlled as follows.