JP3377672B2 - Color image forming equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming apparatus such as a copying machine or a laser printer using an electrophotographic process mechanism.

[0002]

2. Description of the Related Art As a color image forming apparatus of this type,
For example, there is a color laser printer. In a color laser printer, various image forming methods, for example, a multi-developing method in which developing devices of four colors are developed on a photosensitive drum in a multiple manner to form a color image, four color developing devices are transferred to an intermediate transfer medium in a multiplex manner and color images are transferred. There is an intermediate transfer system for forming an image, but recently, a 4-tandem tandem system having a high printing speed is becoming the mainstream.

As shown in FIG. 13, this four-drum tandem type color laser printer is a yellow (Y) unit in which electrophotographic process mechanisms such as a photosensitive drum 101, a charger 102, an exposure device 103 and a developing device 104 are integrated. , Magenta (M), cyan (C), and black (K) printing stations 1001, 1002, 1003, and 1004 are arranged in parallel with a sheet conveying belt 110 as a medium conveying belt stretched in an endless belt shape. It Each developing device 104
The toners of yellow (Y), magenta (M), cyan (C), and black (K) are stored in the respective cartridges.

Each printing station 1001, 1002,
At the position where 1003 and 1004 face each other, the paper transport belt 11 is provided.
A transfer roller 105 is provided via the transfer roller 105 to transfer the transfer roller 10 to the recording medium conveyed on the paper conveyance belt 110.
5, multiple transfer is performed to form a color image, and the color image is fixed by the fixing device 106 provided on the downstream side.

By the way, in recent years, there is an increasing demand for using OHP (overhead projector) for presentations at academic conferences and product presentations. Therefore, OHP
The OHP sheet as a transparent sheet used in 1. is used as a recording medium to perform desired printing in the image forming apparatus described above.

However, since the OHP sheet transmits the light and projects the image drawn on the screen on the screen, the normal recording for recognizing the image by visually observing the light reflected from the drawn image. Different from the paper. Therefore, OH
When printing on a P sheet, a toner image that allows light to pass through must be formed, unlike printing on a normal recording sheet. That is, when printing on an OHP sheet, it is necessary to sufficiently melt the toner on the OHP sheet when fixing the toner image. If this is not done, the light transmittance of the toner deteriorates and a desired transmitted image cannot be obtained.

For this reason, conventionally, when printing on an OΡΡ sheet, the fixing speed is made slower than in the case of a normal recording sheet so that the toner image is sufficiently fixed on the OΗΡ sheet, or the recording sheet provided in the fixing device 106. The nip width of the fixing roller 106a sandwiching the sheet is widened.

In some cases, the output of the fixing device 106 is increased to fix the toner image at a higher temperature than that of the normal recording paper. This is 2 as shown in FIG.
As can be seen from the relationship between the transparency rank after printing and the fixing surface temperature at the time of fixing in the types of OHP sheets X and Y, the higher the fixing surface temperature, the higher the transparency rank after printing. This is because the transparency of the OHP sheet after printing is good.

The transparency rank in FIG. 15 is 1
Is not permeable, 2 is slightly permeable, 3 is slightly turbid, 4 is slightly turbid but not difficult to see, and 5 is sufficiently permeable. The average rank is shown.

Further, in order to improve the transparency of the OHP sheet after printing, there is also one that uses a toner having a relatively low softening point to sufficiently fix the toner.

[0011]

However, in the color image forming apparatus which slows down the fixing speed at the time of fixing the OHP sheet as described above, there is a problem that the overall printing speed decreases. Further, in a color image forming apparatus that raises the fixing temperature at the time of fixing an OHP sheet, there is a problem that waviness or winding of the OHP sheet is likely to occur at the time of fixing.

That is, as shown in FIG. 15, since the transparency of the printed portion of the OHP sheet is good at rank 4 or higher, the fixing temperature of about 180 ° C. or higher for the OHP sheet X and about 190 ° C. or higher for the OHP sheet Y. Required, but OH
Since the P sheet is generally vulnerable to heat, if the fixing temperature is set too high, waviness, wrapping, or the like will occur. This wave is OH
The P sheet may cause a jam, or the actual OH
When used with P, there arises a problem that it is inconvenient to handle.

That is, when the fixing temperature in the fixing device 106 is higher than a certain temperature, the OHP sheet 111 bends by the heat as shown in FIG. For this reason, the OHP sheet 111 is entangled with the fixing roller 106a and is rolled up, causing a jam. For example, as shown in FIG.
The fixing surface temperature of the P sheet X is about 187 ° C. or more, and waviness or entrainment occurs, and even if the OHP sheet Y is a special coating of a resin having a low softening point in order to improve the transparency of the toner, the fixing surface is When the temperature is about 176 ° C. or higher, waviness or entrainment occurs. In addition, the OHP sheet Y which has been specially processed so as to have good transparency as described above has a problem that the corrugation, the wrapping, and the like occur at a temperature lower than that of an ordinary one.

Further, in the color image forming apparatus for improving the transparency of the toner by lowering the softening point of the toner, the developing devices 103y, 103m, 103c, 1 are selected depending on the frequency of use.
The 03k developing blade sticks or the developing roller filming (a state in which the developing roller thinly dissolves the toner and sticks to it) is likely to cause white or color streaks on the output image. There was a problem that soft caking (soft blocking) occurs in which the toner easily collapses and hardens in the developing device when the temperature rises, resulting in uneven image density, and in particular, halftone unevenness in which image roughening occurs and where image roughening does not occur. .

Therefore, according to the present invention, it is possible to fix the transparent sheet such as an OHP sheet in a fixing temperature range in which waviness or winding does not occur, and thereby, the transparency of the toner in the printing on the transparent sheet is stably improved. It is an object of the present invention to provide a color image forming apparatus capable of maintaining the printing speed and the image quality.

[0016]

According to the present invention of claim 1, the surface of an electrostatic latent image holding member is charged, an electrostatic latent image is formed by exposure, and the electrostatic latent image is visualized. Multiple printing stations are arranged on an endless belt-shaped medium conveyance belt, and the toner image visualized by the printing station is transferred onto the recording medium conveyed by the medium conveyance belt in an overlapping manner, and the image is heated and fixed by a fixing device to form a color image. in the color image forming apparatus that forms a comprises a fluidized material to fluidize the resin material and the resin material having a lower softening point than the toner, the toner constant
An image forming auxiliary means for supplying an image forming auxiliary material that becomes colorless and transparent by heating and melting while lowering the deposition temperature is provided separately from the printing station on the medium conveying belt, and wavy or wound at a predetermined heating temperature as a recording medium. When a transparent sheet that causes sticking is used, the image forming auxiliary means supplies the image forming auxiliary material on the transparent sheet on which the color image is printed, and the fixing device lowers the temperature of the transparent sheet lower than a predetermined heating temperature. In order to fix the printed color image while heating and melting the image forming auxiliary material.

In the present invention having such a configuration, when color printing is performed on a transparent sheet such as an OHP sheet as a recording medium, the transparent sheet is conveyed to each printing station by a medium conveying belt and each color is transferred in an overlapping manner. It In this case, an image forming auxiliary material including a resin material having a softening point lower than that of the toner and a fluidizing material for fluidizing the resin material, which becomes colorless and transparent after heating and melting, is supplied onto a transparent sheet and then fixed by heating. As a result, it is possible to lower the melting temperature of the toner when fixing the transparent sheet. Further, since the image forming auxiliary material contains resin fine powder which becomes colorless and transparent after heating and melting as a main component, it does not affect the toner image on the transparent sheet after fixing. Furthermore, by including a fluidizing material for fluidizing the resin material in the image forming auxiliary material, the image forming auxiliary material can be uniformly supplied.

According to the second aspect of the present invention, the image forming auxiliary means carries the image forming auxiliary material in the hopper portion and the image forming auxiliary material in the hopper portion, and conveys them by the medium conveying belt. The color image forming apparatus according to claim 1, further comprising: an auxiliary material supply roller that supplies the transparent sheet; and an auxiliary material restricting unit that restricts an amount of the image forming auxiliary material carried on the auxiliary material supply roller.

A third aspect of the present invention is the color image forming apparatus according to the second aspect, wherein the auxiliary material supply roller of the image forming auxiliary means has a roughened surface so that an appropriate toner conveyance amount can be secured.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment in which the present invention is applied to a color laser printer will be described below with reference to FIGS.

FIG. 1 is a cross-sectional view showing the structure of a color laser printer according to the present embodiment. Reference numerals 21 to 24 are continuous with a sheet conveying belt 1 as an endless belt-shaped medium conveying belt stretched inside the main body of the apparatus. 4 printing stations arranged in parallel.

In each of the printing stations 21 to 24, a charging device 4, an exposure device 5, a developing device 6, a drum cleaner 7, and a discharging lamp 8 are provided around a photosensitive drum 3 as an electrostatic latent image holder.
, And the transfer roller 9 is also opposed to the photosensitive drum 3 via the sheet conveying belt 1.

The developing devices 6 of the printing stations 21 to 24 store yellow (Y), magenta (M), cyan (C), and black (K) toners, respectively, and the developing roller 10 is rotatably provided at the bottom. The toner is supplied to the photosensitive drum 3 by the contact charging. The transfer roller 9 is made of a conductive material.

A tension roller 12 which gives a predetermined tension to the sheet conveying belt 1 is arranged on the sheet conveying belt 1. The sheet conveying belt 1 is made of a conductive material, and its surface is covered with an insulating layer. Then, a pair of guide rollers 14, maintaining a predetermined tension so that the conductive material contacts,
It has been passed over to 15.

Below the paper carrying belt 1, a paper feeding device 19 in which recording papers 18 are stacked and accommodated is detachably provided. A paper feed roller 23 for picking up the recording paper 18, a carrying roller 24 for guiding the recording paper 18 to the carrying path 13, and a registration roller 25 are provided above the paper feeding device 19. A suction roller 26 is provided on the upstream side of the paper transport belt 1 for electrostatically attracting the recording paper 18 guided to the paper transport belt 1 so as not to shift the recording paper 18.

A conveyance path 13 for guiding the recording paper 18 from the paper feeding device 19 to the end of the paper conveyance belt 1 is provided near one guide roller 14. Further, the fixing device 20 is arranged close to the outside of the other guide roller 15.

In this printer, the paper feeding belt 1 is driven at a predetermined speed by a motor (not shown) to feed the paper feeding device 1.
The recording paper 18 fed from the sheet 9 is adsorbed by the adsorption roller 26 and conveyed to each of the printing stations 21 to 24. Then, the printing station 21 transfers a yellow (Y) image, the printing station 22 transfers a magenta image, and the printing station 23 transfers a cyan image to perform color printing by superimposing colors. The fixing device 20 thermally fixes and discharges the sheet to the sheet discharge unit 21 or 22.

Further, on the above-mentioned paper conveying belt 1, the printing stations 2 to 24 are arranged side by side, and the printing station 2
An image forming assisting device 31 as an image forming assisting device is provided on the downstream side of the belt 4 in the belt conveying direction. The image forming auxiliary device 31 is for uniformly depositing and supplying the image forming auxiliary material on the color image by the printing stations 21 to 24, and the electrophotographic process mechanism such as the photosensitive drum 3 like the printing stations 21 to 24. Not equipped.

The image forming auxiliary device 31 is provided so as to be able to come into contact with and separate from the sheet conveying belt 1, and is usually separated from the sheet conveying belt 1, and when printing on an OHP film as a recording medium or designated by an operator. Thus, it comes into contact with the paper transport belt 1.

Further, as shown in FIG. 2, the image forming auxiliary device 31 is provided with a hopper portion 34 for accommodating a predetermined image forming auxiliary material 33, and a sheet conveying device provided in an opening formed under the hopper portion 34. O transported by belt 1
The auxiliary material supply roller 35 that supplies the image forming auxiliary material 33 in contact with the HP sheet 30 and the auxiliary material supply roller 35 OH
A conveyance regulating blade 36 as an auxiliary material regulating means for keeping the amount of the image forming auxiliary material 33 supplied to the P sheet 30 at a constant amount, a high voltage power source 37 for applying a constant voltage to the auxiliary material supplying roller 35, The transfer roller 38 is provided at a position opposite to the auxiliary material supply roller 35 via the sheet conveying belt 1. The auxiliary material supply roller 35 is rotationally driven in the same direction at substantially the same speed as the paper transport belt 1 when the image forming auxiliary material 33 is supplied by a motor (not shown).

The auxiliary material supply roller 35 is constructed by attaching an elastic member such as urethane rubber impregnated with carbon dispersion or ionic conductive material having a minute rough surface on the shaft 35a. The high voltage power supply 37 is connected to the shaft 35a.

By rotating the auxiliary material supply roller 35, the image forming auxiliary material 33 in the hopper portion 34 is moved as shown by an arrow a and sent to the vicinity of the conveyance regulation blade 36, and the auxiliary material supply roller 35 can be restrained. In addition, the necessary amount of the image forming auxiliary material 33 is regulated while being charged and is conveyed to the OHP sheet 30 on the paper conveying belt 1. In this way, the charged image forming auxiliary material 33 conveyed by the auxiliary material supplying roller 35 becomes O due to the potential difference between the auxiliary material supplying roller 35 and the transfer roller 38.
It is attached and supplied to the HP sheet 30. In this case, the transfer roller 38 is charged with the same polarity as that of the image forming auxiliary material 33 by 50.
A voltage of about V to several hundreds V is applied.

The image forming auxiliary material 33 is formed by mixing a resin such as polyester which becomes colorless and transparent after heating and melting, silica (hydrophobic silicon dioxide) and the like.
The resin having a low resin softening point is suitable so that the toner can be sufficiently fixed on the OHP sheet even at a low temperature. For example, the softening point level of a color toner is generally lower than that of a monochrome toner, but a softening point level lower than that of the color toner is used. In addition, the silica is added for the purpose of uniformly attaching the resin on the OHP sheet so as to adhere to the particle surface of the resin to give the electrification power.

The relationship between the amount of silica added to the image forming auxiliary material 33 and the amount of the image forming auxiliary material 33 conveyed to the auxiliary material supply roller 35 is shown in FIG. According to FIG. 3, as the amount of silica added increases, the image forming auxiliary material 33
However, the amount is gradually saturated. -One
When the amount of silica added is reduced, the amount of the image forming auxiliary material 33 conveyed decreases, and when silica is not added, the image forming auxiliary material 33 is
It is almost never conveyed onto the auxiliary material supply roller 35. From this, it is found that at least silica needs to be added (externally added) to the image forming auxiliary material 33, and a region suitable for the conveyance of the image forming auxiliary material 33 is a region where the amount of silica added is about 0.5% or more. It can be seen that it is.

It should be noted that even if silica is added to the resin as the image forming auxiliary material 33, the carrying amount can be secured, but if this is the only amount, peeling may be easy. Therefore, in order to more stably and uniformly attach the image forming auxiliary material 33 to the OHP sheet, a charge control material may be further added.

As the charge control material, for example, a quaternary ammonium salt material is used, and after kneading with a pressure kneader,
A pulverizer such as an elbow jet is pulverized to about 5 to 20 μm, and then silica (hydrophobic silicon dioxide) is externally added by a mixer such as a Henschel mixer.

The properties of the image forming auxiliary material 33 as described above are actually different depending on the kind of resin and the composition ratio of resin, silica, charge control material, etc. Good results have been obtained when the image forming auxiliary material 33 is constituted by. For example, the resin softening point is about 91.
Image forming auxiliary material A consisting of 99.4% of resin at 0 ° C and 0.6% of silica, and 99.5% of resin having a softening point of about 98 ° C.
%, Silica 0.5%, image forming auxiliary material B, 99.5% resin having a resin softening point of about 110 ° C., 0.5% silica
Image forming auxiliary material C consisting of 98.4% resin having a softening point of about 91 ° C., silica 0.6%, charge control material 1%, and resin softening point of about 98 ° C. Image forming auxiliary material E consisting of 98.5% resin, 0.5% silica and 1% charge control material, and 9% resin having a softening point of about 105 ° C.
The image forming auxiliary material E and the like are composed of 8.5%, silica 0.5%, and charge control material 1%.

Here, FIG. 4 shows the relationship between the resin softening point of the resin forming the image forming auxiliary material 33 and the fixing surface temperature which improves the permeability of the toner on the OHP sheet. This Figure 4
According to the above, it can be seen that the fixing surface temperature in the fixing device can be further lowered by using a resin having a lower softening point of the resin in a region of a temperature lower than the temperature at which the corrugation or winding of the OHP sheet occurs.

The amount of the image forming auxiliary material 33 conveyed also differs depending on the surface roughness of the auxiliary material supply roller 35. Here, the relationship between the surface roughness of the auxiliary material supply roller 35 and the transport amount of the image forming auxiliary material is shown in FIG. According to FIG. 5, the conveyance amount of the image forming auxiliary material 33 increases as the surface roughness of the auxiliary material supply roller 35 increases, but the surface roughness is 50 μm.
If it exceeds the above range, the amount of the image forming auxiliary material 33 conveyed is too large, and the consumption of the image forming auxiliary material 33 in the hopper portion 34 is remarkably accelerated, resulting in waste.

On the other hand, when the surface roughness of the auxiliary material supply roller 35 is less than 1 μm, the amount of the image forming auxiliary material 33 conveyed is too small to obtain the effect of the image forming auxiliary material 33 sufficiently, and the OPP sheet printing is performed. The toner transparency at the time is not obtained, and the image becomes cloudy (blackened) at the time of OHP projection. From this, the range of usable surface roughness is 1 μm to 50 μm.
It is found that the optimum region is 8 μm to 15 μ
It turns out that it is m.

Instead of applying a high voltage to the auxiliary material supply roller 35, a high voltage power supply 39 may be provided on the transfer roller 38 side as shown in FIG. In this case, a voltage of about 50V to several hundreds of V is applied to the transfer roller 38 with a polarity opposite to the charging polarity of the image forming auxiliary material 33.

In the present embodiment having such a configuration, when performing color printing on the OHP sheet, the image forming auxiliary device 31 is brought into contact with the paper transport belt 1. Then, when a signal for forming an image is input from a host computer (not shown) or the like, the OHP sheet is sent onto the sheet conveyance belt 1 at a predetermined timing. Then, the OHP sheet is printed at the printing stations 2 together with the sheet conveying belt 1.
Move toward 1-24.

On the other hand, an image signal from the host computer or the like is sent to each exposure device 5 as a signal corresponding to each color, and, for example, a yellow signal is input to the yellow exposure device 5. The exposure device 5 emits a laser beam in response to this signal and exposes the photosensitive drum 3 charged in the same manner by the charging device 4 to form an electrostatic latent image. The photosensitive drum 3 is rotating in the direction of the arrow shown in FIG. 1, the electrostatic latent image on the photosensitive drum 3 is developed by the developing device 5, and the image is formed on the OHP sheet on the sheet conveying belt 1 by the transfer roller 9. Is transcribed. After that, the surface of the photosensitive drum 3 is cleaned by the cleaning device 7, and further, the residual potential on the photosensitive drum 3 is reduced by the illumination of the charge removing device 8 to prepare for the next electrophotographic process. Magenta,
The same processing is performed on the cyan and black printing stations 22 to 24, and the OHP on the paper transport belt 1 is performed.
Color images are sequentially transferred and superposed on the sheet.

The OHP sheet that has passed through the black printing station 24 is conveyed to the image forming auxiliary device 31. At this time, the auxiliary material supply roller 35 of the image forming auxiliary device 31 is rotationally driven. Then, the image forming auxiliary material 33 is uniformly attached on the auxiliary material supplying roller 35. Then, due to the contact pressure and the potential difference between the auxiliary material supply roller 35 to which the high voltage is applied and the transfer roller 38, the image forming auxiliary material 3 is transferred from above the toner of the conveyed OHP sheet.
3 is uniformly attached and supplied.

A state sectional view of the OHP sheet at this time is shown in FIG. As shown in FIG. 6, since the image forming auxiliary material attached on the toner of each color is transparent, the toner layer of each color (yellow (Y), magenta (M), black (K))
Does not affect the quality of the color image.

After that, the OHP sheet is conveyed by the sheet conveying belt 1 and separated from the sheet conveying belt 1 by the curvature of the guide roller 15, and is sent to the fixing device 20. Then, the toner on the OHP sheet is fixed together with the image forming auxiliary material 33 by heating and melting by the fixing device 20 at a relatively low temperature, and is discharged to the outside of the printer.

Here, as the image forming auxiliary material 33, 98.5% of the above-mentioned resin having a resin softening point of about 98 ° C.,
An image forming auxiliary material E composed of 0.5% silica and 1% charge control material was used, and the fixing surface temperature was about 150 ° C. to about 200 ° C.
FIG. 8 shows the result of an experiment in which the effect of changing the temperature to 0 ° C., that is, the change in the transparency of the toner on the OHP sheet was examined.
In FIG. 8, the transparency rank is as follows: 1 is not transparent, 2 is slightly transparent, 3 is slightly cloudy, 4 is slightly cloudy but not difficult to see, 5 is sufficiently transparent ,
Based on the standard, 50 subjects visually evaluated and the average rank is shown.

According to FIG. 8, the transparency (transparency) of the toner on the OHP sheet is compared with the conventional experimental result shown in FIG. 15 in the case where the image forming auxiliary material 33 is not provided.
It can be seen that the fixing surface temperature becomes significantly lower when the transparency on the OHP sheet is 4 or more, which is sufficient for transparency. Specifically, in FIG. 15, good transparency (transparency rank 4 or higher) could not be obtained unless the fixing surface temperature was set to about 180 to about 190 ° C. or higher.
Then, it can be seen that sufficiently good transparency (transparency rank 4 or higher) can be obtained at about 160 ° C. or higher.

Further, in the present embodiment, the fixing surface temperature of about 160 ° C. to about 186 ° C. is the area where the corrugation and winding of the OHP sheet do not occur, so the fixing surface temperature of the fixing device 20 is set to this area. If it is set by, it is possible to prevent the corrugation and the winding of the OHP sheet.

As described above, by providing the image forming auxiliary device 31 and uniformly supplying and fixing the predetermined image forming auxiliary material 33 on the OHP sheet onto which the toner has been transferred, the OHP sheet is not corrugated or wound. The toner can be sufficiently fixed in the fixing temperature range where it does not occur, the transparency of the toner in the printing on the transparent sheet such as the OHP sheet can be stably improved, and the printing speed and the image quality can be maintained. . That is, the OHP of the OHP sheet
It is possible to prevent turbidity (blackening) of an image when projected.

In order to supply such an image forming auxiliary material 33, it may be possible to put it in the printing stations 21 to 24 together with the toner. However, by doing so, the softening of the image forming auxiliary material 33 is reduced. This is not suitable because sticking filming occurs on the developing roller 10 described above due to the point resin. Therefore, in the present invention, by providing the image forming auxiliary device 31 as a separate body from the printing stations 21 to 24, it is possible to obtain the effect of preventing the occurrence of sticking filming.

By providing the image forming auxiliary device 31 on the sheet conveying belt 1, the image forming auxiliary device 31 and the fixing device 20 are separated from each other. As a result, the image forming auxiliary device 31 is less likely to be affected by the temperature of the fixing device 20. That is, it is possible to prevent poor flow or soft caking of the image forming auxiliary material due to excess heat from the fixing device 20,
It is possible to prevent defective supply of the image forming auxiliary material agent onto the auxiliary material supply roller and prevent occurrence of uneven image density, especially halftone unevenness.

In the present embodiment, the image forming auxiliary device 31 is provided on the downstream side of the printing station 24 on the sheet conveying belt 1 in the belt conveying direction, but the invention is not limited to this. However, if the image forming auxiliary device 31 is provided on the sheet conveying belt 1, the same effect can be obtained. Therefore, the place where the image forming auxiliary device 31 is provided can be selected according to the circumstances such as the vacant space of the color image forming apparatus to which the present invention is applied, the arrangement of each mechanism, and the gear train. For example, as an example thereof, FIG. 9 shows a case where the image forming auxiliary device 31 is provided between the printing stations 23 and 24 on the sheet conveying belt 1.
Shown in.

Next, a second embodiment in which the present invention is applied to a color laser printer will be described with reference to FIGS. In the present embodiment, the same parts as those in the above embodiment are designated by the same reference numerals and detailed description thereof will be omitted.

FIG. 10 is a sectional view showing the arrangement of a color laser printer according to this embodiment. The difference from the above embodiment is that an image forming auxiliary device 31 as an image forming auxiliary means is attached to the sheet conveying belt 1. An image forming auxiliary device 41 as an image forming auxiliary means is provided apart from the sheet conveying belt 1 instead of being provided so as to be able to come into contact with and separate from the OHP without contact.
The point is to supply the image forming auxiliary material to the sheet.

Specifically, the image forming auxiliary device 41
11, as shown in FIG. 11, a hopper unit 4 for accommodating an image forming auxiliary material 33 similar to that described in the above embodiment.
3, an auxiliary material supply roller 44 for supplying the image forming auxiliary material 33 to the OHP sheet conveyed by the sheet conveying belt 1 in a non-contact manner provided in the opening formed in the lower part of the hopper portion 43, and this auxiliary material supply A conveyance regulating blade 45 as an auxiliary material regulating means for keeping the amount of the image forming auxiliary material 33 supplied to the OHP sheet by the roller 44 at a constant amount.
Composed of.

The auxiliary material supply roller 44 is the shaft 4
A foam material is attached to 4a, and the motor is rotated in the arrow direction by a motor (not shown). By the rotation of the auxiliary material supply roller 44, the image forming auxiliary material 33 in the hopper portion 43 is moved as shown by an arrow b to be sent to the vicinity of the conveyance regulation blade 45, and a necessary amount of the image forming auxiliary material 42 is supplied.
While the sheet is regulated by the conveyance regulation blade 2, the OHP sheet conveyed below the image forming auxiliary device 41 is naturally dropped and scattered. In this case, the rotation speed of the auxiliary material supply roller 44 is set slightly slower so that a sufficient amount of the image forming auxiliary material 33 can be attached and supplied to the OHP sheet.

Even with such a structure, the same effect as that of the above-described embodiment can be obtained. Further, in this embodiment, since the auxiliary material supply roller 44 is made of the foam material, the image formation per rotation can be performed. It is possible to increase the carry amount of the auxiliary material 33, and it is also unnecessary to apply almost any electric charge.

Further, in order to allow the image forming auxiliary material 33 to be attached and supplied onto the OHP sheet of the paper transport belt 1 by natural fall, the high voltage power source and the transfer roller, which are necessary in the above-described embodiment, and the paper. The contact / separation mechanism for the conveyor belt 1 can be eliminated. Therefore, the same effect as that of the above-described embodiment can be obtained with a simpler configuration.

In the present embodiment, the image forming auxiliary device 41 is provided on the downstream side of the printing station 24 on the sheet conveying belt 1 in the belt conveying direction, but the invention is not limited to this. However, if the image forming auxiliary device 41 is provided on the sheet conveying belt 1, the same effect can be obtained. Therefore, similarly to the above-described embodiment, the place where the image forming auxiliary device 41 is provided can be selected according to the circumstances such as the empty space of the color image forming apparatus to which the present invention is applied, the arrangement of each mechanism, and the gear train. For example, as an example thereof, the image forming auxiliary device 41 may be installed in the printing stations 23 and 24 on the paper transport belt 1.
FIG. 12 shows the case where it is provided between the first and the second terminals.

[0061]

As described above in detail, according to the present invention, an image forming which becomes colorless and transparent after heat fixing, including a resin material having a softening point lower than that of the toner and a fluidizing material for fluidizing the resin material is formed. By supplying the auxiliary material onto the transparent sheet and then fixing the heat, the melting of the toner at the time of fixing the transparent sheet can be lowered in temperature. As a result, it is possible to sufficiently fix the transparent sheet such as an OHP sheet in a comparatively low fixing temperature region where waviness and winding do not occur, improve the transparency of the toner, and maintain the printing speed and the image quality. You can That is, for example, O of an OHP sheet
It is possible to prevent turbidity (blackening) of an image during HP projection.

Further, by using as a main component a resin that becomes colorless and transparent after the image forming auxiliary material is melted by heating, the transparency of the transparent sheet can be improved without damaging the toner image. Further, by adding a fluidizing material to the image forming auxiliary material,
The efficiency of conveyance of the image forming auxiliary material by the auxiliary material supply roller can be improved.

Further, by providing the image forming auxiliary means containing the image forming auxiliary material separately from the printing station, the developing roller and the developing blade generated when the image forming auxiliary material is mixed in the toner at the printing station are provided. It is possible to prevent sticking filming. This makes it possible to prevent the generation of white stripes or color stripes on an image even when an image forming auxiliary agent made of a low softening point resin is used.

Further, by providing the image forming assisting means on the sheet conveying belt 1 and keeping the image forming assisting means away from the fixing section, it is possible to prevent poor flow of the image forming auxiliary material or soft caking due to excess heat from the fixing section. However, it is possible to prevent the defective supply of the image forming auxiliary material on the auxiliary material supplying roller of the image forming auxiliary means, and to prevent the occurrence of the image density unevenness, especially the halftone unevenness.

Further, the image forming auxiliary means is provided with the auxiliary material supplying roller and the blade for regulating the amount of the image forming auxiliary material conveyed by the auxiliary material supplying roller, so that the image forming auxiliary material is placed on the auxiliary material supplying roller. It became possible to form a uniform layer. As a result, the necessary amount of the image forming auxiliary material can be uniformly supplied to the transparent sheet.

Further, by roughening the surface of the auxiliary material supply roller to the extent that an appropriate toner transfer amount can be secured, the image forming auxiliary material can be stably and continuously transferred.

[Brief description of drawings]

FIG. 1 is an overall cross-sectional view showing the configuration of a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the configuration of the image forming auxiliary device shown in FIG.

FIG. 3 is a diagram showing the relationship between the amount of silica added to the image forming auxiliary material and the amount of conveyance of the image forming auxiliary material onto the auxiliary material supply roller in the embodiment.

FIG. 4 is a diagram showing a relationship between a resin softening point of a resin forming an image forming auxiliary material and a fixing surface temperature for improving toner permeability on an OHP sheet in the embodiment.

FIG. 5 is a diagram showing the relationship between the surface roughness of the auxiliary material supply roller and the conveyance amount of the image forming auxiliary material in the embodiment.

FIG. 6 is a state cross-sectional view of an OHP sheet supplied with an image forming auxiliary material according to the same embodiment.

FIG. 7 is a view showing a modified example of the configuration of the image forming auxiliary device in the same embodiment.

FIG. 8 is a diagram showing an experimental result of examining a change in transparency of the toner on the OHP sheet in the embodiment.

FIG. 9 is a diagram showing a modification example in which the arrangement position of the image forming auxiliary device in the embodiment is changed.

FIG. 10 is an overall sectional view showing a configuration of a second embodiment of the present invention.

11 is a cross-sectional view showing the configuration of the image forming auxiliary device shown in FIG.

FIG. 12 is a diagram showing a modification example in which the arrangement position of the image forming auxiliary device in the embodiment is changed.

FIG. 13 is an overall sectional view showing a configuration of a conventional color image forming apparatus.

FIG. 14 is a diagram showing an operation in a conventional color image forming apparatus.

FIG. 15 is a diagram showing an operation in a conventional color image forming apparatus.

[Explanation of symbols]

2 ... Photosensitive drum (electrostatic latent image holder) 4 ... Charger 5 ... Exposure device 6 ... Developing device 20 ... Fixing device 30 ... OHP sheet (transparent sheet) 31, 41 ... Image forming auxiliary device 33 ... Image forming auxiliary material 35, 44 ... Auxiliary material supply roller 36, 45 ... Transport regulation blade (auxiliary material regulation means)

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-7-72696 (JP, A) JP-A-4-362960 (JP, A) JP-A-5-323781 (JP, A) JP-A-5- 281863 (JP, A) JP 62-218980 (JP, A) JP 7-152221 (JP, A) JP 6-342225 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G03G 13/01 G03G 15/01-15/01 117 G03G 21/00 370 G03G 15/20-15/20 302

Claims (3)

(57) [Claims] 1. A plurality of printing stations are provided on an endless belt-shaped medium carrying belt for charging the surface of an electrostatic latent image carrier, forming an electrostatic latent image by exposure, and visualizing the electrostatic latent image. In the color image forming apparatus, the toner image visualized by the printing station is superposed and transferred onto the recording medium conveyed by the medium conveying belt, and the toner image is heated and fixed by the fixing device to form a color image. Lowering the fixing temperature of the toner, including a resin material having a lower softening point and a fluidizing material that fluidizes the resin material.
An image forming auxiliary means for supplying an image forming auxiliary material which becomes colorless and transparent when heated and melted is provided separately from the printing station on the medium conveying belt, and wavy at a predetermined heating temperature as the recording medium. When a transparent sheet that causes wrapping is used, an image forming auxiliary material is supplied from the image forming auxiliary means onto the transparent sheet on which a color image is printed, and the fixing device heats the transparent sheet at a predetermined heating temperature. A color image forming apparatus, which heats and melts the image forming auxiliary material at a lower temperature than the above to fix the printed color image. 2. The image forming auxiliary means carries a hopper portion for accommodating the image forming auxiliary material, and conveys the image forming auxiliary material in the hopper portion, and the transparent sheet conveyed by the medium conveying belt. 2. The color image forming apparatus according to claim 1, further comprising: an auxiliary material supply roller that supplies the auxiliary material supply roller to the auxiliary material supply roller; and an auxiliary material restriction unit that restricts the amount of the image formation auxiliary material carried on the auxiliary material supply roller. 3. The color image forming apparatus according to claim 2, wherein the auxiliary material supply roller of the image forming auxiliary means has a roughened surface so that an appropriate toner conveyance amount can be secured.