DE2152466B2 - Device for producing a fixed toner image on an image receiving material - Google Patents

Description

The invention relates to an apparatus for manufacturing ^ ⁰ lung of a fixed toner image on an image receiving material by transferring a toner image from an intermediate image carrier in the molten state, in a continuous operation with an endless circulating elastic intermediate image carrier, a Übertragungsein direction to contact an image receiving material to the intermediate image carrier and an inside the transfer zone on the rear side of the intermediate image carrier facing the image receiving material and directed onto the transfer zone.

In a known device of this type (DE-OS 37 616 Fig. 6) an applicator roll transfers a multi-layer of a thermoplastic toner powder to a pre-treated for printing, with a Stomer Siiikonela- ^M covered, the image carrier forming roller. From this, at least one monolayer of the toner is applied to an endlessly rotating over several rollers, the Transferring the tape forming the intermediate image carrier with a silicone elastomer surface, using an infrared lamp one shield is close to the bottom of the Arranged on the belt that carries the infrared radiation absorbing toner powder, Pa the belt is radiation-permeable, the toner is directly through Radiation absorption heated. It is also possible that the intermediate image carrier is heated as a whole, so that the toner is heated by contact heat transfer. By means of a further roller, an oil-shaped image receiving material is coated with the toner powder on the Tape brought into contact. This known device is not suitable for rapid copying operations, since the intermediate image carrier does not have a suitable heat capacity in the transfer area that has a rapid Ensure heating by absorption of radiation, as well as rapid cooling of the strip and thus would ensure that the intermediate image carrier only within the immediate transmission area the has a high temperature required for melting the toner

Is z. B. the toner image with a conventional roller forming the intermediate image carrier of one semiconducting image carrier (z. B. photoconductive recording roller) added, the direct Contact of the roller on which the thermoplastic toner powder is melted together with the semiconducting image carriers because of their sensitivity to heat.

Also known is a device (US-PS 34 52 181) in which in a rotatable transparent The drum is provided with a stationary heat radiation source. The toner is here from the onto the toner image directional heat radiation source melted before it comes into contact with the transparent drum is brought, whereby the fixation is terminated on contact with the drum. Such devices are also not suitable as so-called "fast copiers" with which more than fifty copies of 8.5 by 11 inches and preferably more than sixty copies can be made can.

The invention is based on the object of a device for producing a fixed toner image to make on an image receiving material according to the type mentioned in such a way that a fast Copying, d. H. at least fifty copies per minute with primary formation of the toner image on one photoconductive recording roller is achievable.

According to the invention, this object is achieved by the characterizing features of claim I. solved.

Advantageous further developments of the device according to the invention emerge from the subclaims.

It proves to be particularly advantageous that the thin, the toner-carrying. Thermal radiation absorbing, elastic layer of the intermediate image carrier, depending on the material from which it is made, it is so thin that it is sufficiently small Has heat capacity, as a result of which they heat up very quickly by absorption of radiation, but can also cool down again very quickly, which enables very fast copying.

An embodiment of the device according to the invention will now be based on the single figure of the Drawing described:

A roller 20 forming an intermediate image carrier is rotatably mounted on a shaft 15 and with a one

Transfer device representing pressure roller 21 jn can be brought into engagement, which is rotatably mounted on a shaft π. In addition, a roller 30 having scoring images on its surface can be brought into contact with the roller 20 carrying toner images 31 which can be transferred to the roller 20. The roller 20 can be brought into contact with an image receiving material 18 onto which the toner is fused, with permanent toner images 33 being produced. The pressure roller 21 can be provided with an elastic and compressible cover 16 and heated from the inside. A drive device, not shown, sets the two rollers 20 and 21 in rotation in the direction of rotation shown, into the gap between the two rollers

20 and 21, the imaging material can be inserted manually or by an automatic device will.

The roller 20 consists of a drum 10 which is permeable to thermal radiation and which is rotatable by the shaft 15 is carried, from a covering the drum 10 and the thermal radiation conducting, elastic and compressible Layer Ii and a thin layer that carries the toner. Absorbing thermal radiation, elastic layer 12 on the layer 11. Inside the Drum 10, a heat radiation source 13 and a reflector 14 are fixedly arranged, which the heat radiation band-shaped on the thermal radiation absorbing layer 12 within the contact zone align the image receiving material.

The drum 10 is made of a rigid material, e.g. B. made of glass or quartz, which has good thermal conductivity.

The elastic, compressible layer 11 consists of a material with good thermal conductivity and sufficient mechanical strength so that the layer does not tear in use. To this end the layer 11 should have a thickness of at least 0.76 mm exhibit. In order to save material, the thickness of the layer 11 should preferably be less than 3.8 mm be. The elastic layer 11 can consist of a cloth exist, which is attached to the drum 10 in a suitable manner, or have the shape of a sleeve that can be drawn onto the drum 10. As can be seen from the single figure, the distance between the rollers 20 and

21 so dimensioned that the pressure roller 21 covers the coating of the roller 20 formed by the layers 11 and 12 deformed so that a relatively wide gap area is formed which extends over the full length of the Transfer zone only corner. Layer 11 of the > o Roller 20 is sufficiently soft to create a suitable gap area and its hardness is sufficient suitably about 2-60 and preferably 2-30 according to the Shore A durometer.

The thermal radiation absorbing layer 12v > also has a high tear strength, is sufficiently sticky to be able to absorb the toner powder 31 from the roller 30 and, on the other hand, has an adhesive force for the thermoplastic toner softened by the heat, ie a low affinity for eo the latter on. Silicone elastomers with these surface properties emerge from US Pat. No. 3,554,836. The thin layer 12 with the thickness preferably of 0.013 to 0.1 is rapidly heated by the focused-heat-radiation and>"> radiation as quickly cooled after completion of the heat * mm. The layer 12 is also sufficiently flexible to fit the outside of the elastic layer 11 when it is deformed in the gap area, and has a hardness of about 15-50 according to Shore A iPurometer.

The thin layer i2 absorbs the heat flow directed towards it, preferably a little. Part of the thermal radiation penetrates through the layer 12 and is absorbed by the toner forming the toner image, so that the toner is heated both by direct contact with the heated layer 12 and by absorption of the thermal radiation in the toner image itself. In this way, large image areas can be melted even if the thermal capacity in the thin layer 12 absorbing the thermal radiation is insufficient. Smaller image areas, e.g. B, thin lines, are easily melted together on contact with the heated layer 12. The heating is compensated for by the roller 20, so that large and small image areas are melted equally well. In the preferred embodiment, approximately 36% of the thermal radiation penetrates the layer 12,

This effect is achieved in that both the elastic layer 11 and the Schviht 12 from one Silicone elastomer can be produced. With <! He preferred Embodiment, both layers consist of the same silicone elastomer and are a single unit Hot melt cloth connected to one another. The silicone elastomer of layer 12 is up to 5% by weight or more dark pigments added, e.g. B. carbon black to the To increase the absorption capacity of the layer 12.

In conventional devices, the use of silicone elastomers for Israeli towels has been unlikely. In the case of the conventional rollers with a hot-melt cloth, the thermal conductivity was used to create an effect on the surface of the hot-melt cloth maintain the required temperature. So that the melting mi: the required high speed can take place, the silicone hot melt cloth would have to be very thin to avoid the poor thermal conductivity to be able to compensate. It is known that silicone elastomers are mechanically weak, so that for a desired thermal conductivity required thin layers in the operation of the copier would tear.

U.N. to increase the mechanical strength Silicone polymers usually with an addition of silicon oxide in an amount of 20 G2W.- ° A> or provided with another filler material. However, the addition of conventional fillers creates undesirable ones Surface properties, d. H. when irradiating the After use, filler particles are generated in places that generally have a high affinity for the have softened thermoplastic toner powders. Softened and lingering on the surface Toner powder leads to the generation of so-called ghost images on subsequent image receiving materials. Such conventional and with. Silicone elastomers with additives are therefore undesirable for hot-melt cloths.

In the case of the roller 20 of the device according to the invention that forms the intermediate image carrier, it is not the thermal conductivity of the silicone cloth that is decisive, but rather the thermal radiation falling through the silicone cloth onto the layer 12 which absorbs the thermal radiation. The melt cloth of the roller 20 b ^r therefore also does not have to be particularly thin. It is also possible to use thicker hot melts made of silicone elastomers, which have a greater tear strength. The use of thicker hot melt fabrics also enables larger gap areas to be formed between the

Rollers, so that the thermoplastic toner powder a lingers in the gap for a long time and to its softening such as sticking to the image receiving material more Time is available.

The cured silicone elastomers useful for the device according to the invention are characterized by that they transmit the thermal radiation very well and are preferably optically clear. to for this purpose the silicone elastomer must be essentially free of conventional fillers.

A silicone elastomer which can be used advantageously in the device according to the invention is, for. B. a cross-linked product of silicone rubber and polymerized vinyldimethylpolysiloxane. that when curing z. B. with benzoyl peroxide leads to the production of a suitable, albeit somewhat cloudy, elastomer. The cured elastomer has a Shore A hardness of 15-20. a tensile strength of 3.4 kg / cm ² , an elongation of 150% up to / um break and

The preferred hot melt cloth consists of an elastomer which is produced from a mixture of the above-mentioned rubber with a clear silicone resin. The elastomer produced from the cured mixture is optically clear, tough and also well suited as a hot melt cloth for the roller 20. The preferred hot melt cloth is made from a mixture of equal parts by weight of said rubber and resin, although other proportions, e.g. B. 30-100 parts rubber and 70-0 parts resin lead to the production of a usable hot melt sheet. Hot-melt cloths consisting of silicone resin with a content of less than 30% by weight silicone rubber have a hard surface and are therefore not suitable for the roller 20. An elastomer, which consists of a cured composition of equal parts rubber and resin, has a hardness of 20 - 30 according to Shore A, a tensile strength of 26.5 kg / cm ² , an elongation of 240% to break and a tear strength of 107 g / cm on.

During preparation, curing agents are added to the rubber and resin, such as 2,4-dichlorobenzoyl peroxide. tertiary butyl perbenzoate. Dicumyl peroxide or the like. The curing agent preferably consists of a low molecular weight polydimethylsoloxane containing silane groups and an initiating catalyst. The curing conditions required for these agents vary somewhat depending on the curing agent and silicone rubbers or resins, with effective cures being obtained at temperatures up to 127 ° ^C.

According to a suitable method for producing the hot melt cloth, the centrifugal force is used. A Mixture of silicone rubber. Silicone resin and a suspension agent as well as a radiation adsorptive Pigment in a volatile liquid carrier, such as toluene or heptene, will first become evenly up to the desired thickness sprayed onto a preliminary support surface or by means of a doctor blade or a roller applied. During the drying of the film, the carrier is at least partially removed by evaporation. The resulting film can have a clear layer or the same mixture without pigment, so that a thicker film on drying is generated in the subsequent process stages is more resilient. The film is carefully removed and with the pigmented side on the smooth Inside of a cylinder or drum. The drum is set in rapid rotation, and it becomes a mixture of silicone rubber, silicone resin and an alis hardener in a volatile one Carrier slowly and evenly into the drum ■■> introduced, whereby a coating with the desired uniform thickness is produced on the inside of the film. As the drum continues to rotate, the composition is further dried by heating and hardened. The finished, pliable and elastic

κι sleeve is then carefully removed from the drum, if necessary cut to size and placed on the transparent drum of the copier as an outer cover raised.

Be under a different procedure first

r, silicone rubber and a curing agent in one Processed suitable device to a homogeneous mixture, which in a suitable mold to a Foil is pressed, which is heated until the elastomer has hardened sufficiently, and that in the previously

a film is coated. The film can either be through before or after the connection is made Heating can be hardened. On the other hand, it is also possible to wait until curing at room temperature

; -, temperature has occurred by itself. The curing at Room temperature is generally over after 72 hours. The melting cloth can be attached to the outside of a transparent drum can be attached using mechanical V * "itel or with the help of a

in transparent adhesive.

According to a third method, a homogeneous mixture of silicone resin, silicone rubber and a curing agent is produced. from a radiation-absorbing pigment and a volatile, liquid carrier into one

r> Mold sprayed, which is dimensioned a little larger than the transparent melting drum, after which the topping is dried by evaporation of the volatile liquid carrier will. After that, the drum is inserted into the mold cavity provided with the lining so that a

jn even space between the cylindrical Outside of the drum and the mold wall is created, which space with a Silicone elastomer composition is filled and then cured. Suitable for this purpose

r. Compositions consist of curable and low viscosity polydimethylsiloxane resins or from curable mixtures of low viscosity polydimethylsiloxane oils and resins of the above for the preferred

, ι, composition mentioned melt cloth. Before the Spraying the material can release the mold cavity with a coating of a suitable; ittel provided, e.g. B. with a soap solution or a liquid household detergent, and the drum surface

v, can be provided with a suitable primer coating beforehand to promote adhesion.
Suitable toners with the roller consist of compositions containing thermoplastic materials such as those from GB-PS 1128 464

mi emerge, e.g. ß. Epoxy resins and polystyrene resins.

Some examples of advantageous compositions are given below; with all information about Parts and percentages are by weight unless otherwise specified.

example 1

Forty weights of a mixture of the same Parts of said silicone rubber and said

60 parts of heptane were added to silicone resin. The mixture was stirred using a conventional mechanical stirrer for approximately 2 hours, until a homogeneous solution was formed. With continued stirring for a period of 5 minutes this solution added an amount of the curing agent from polydimethylsoloxane with a low Molecular weight containing silane groups and an initiating catalyst equal to 10% by weight of the klki-'n silicone resin added. This solution was divided into two unequal parts. So much carbon black was added to the smaller part of the solution that its weight percentage was 5%. This portion was then placed in a ball mill for 24 hours processed to mix the black pigment with the solution. The dark solution was made using a Squeegee on a peelable polytetrafluoroethylene film applied. The covering was then dried with evaporation of the solvent for approximately 10 minutes, leaving a dark self-supporting sheet with a Thickness of 0.025 mm was built. The dried one dark foil was applied using a doctor blade along with some of the remaining non-pigmented solution applied to a surface, with a coating on the dark film with a thickness of approximately 0.25 mm after drying and evaporating the solvent for approximately 20 minutes became.

The dried film and liner were cut into a format that, with the edges butting but not overlapping, into a SO cm centrifugal casting drum fits into it. The foil ji the drum was inserted so that the coating on the drum surface, after which the drum was set in rotation. The rest of the larger portion the solution was then slowly poured into the drum rotating at 400 rpm for approximately 4 to 5 hours. During the The solvent vapor was removed by means of a fan during the last hour of the The drum was heated to about 100 ° C during circulation, to fully cure the elastomer shell. The multilayer casing had a wall thickness of 3.8 mm.

After curing and removal of the solvent had ended, the casing was removed from the centrifugal casting drum and the coating was stripped off. The cover was cut to size and placed on a A glass drum with a diameter of 31 cm is drawn, which is connected to a tubular heating lamp with a consumption of 2700 watts, and which was used in a test copier became. The roller 20 was used in a copying process in which at a speed of 230 Copies per minute of thermoplastic toner from images in the format 21.5 χ 28 cm on paper was melted together. After making more than 25,000 copies with excellent Results, the investigation was voluntarily canceled, π. . . " Example 2

A homogeneous mixture was produced from 98 parts of the silicone rubber mentioned and from 1.8 parts Parts by weight of a mixture of equal parts of benzoyl peroxide in a silicone paste. The mixture was spread on the polished surface of a heated plate supported by the piston of a hydraulic press was carried. The position of the plate was determined by means of inserts so that a thickness of approximately 3.8 mm was achieved. With the plate heated to about 127 ° C, the mixture was under a pressure of 70.3 kg / cm ^{2 for} 15 minutes ten long pressed, being somewhat cloudy and hardened Elastomer film was produced. The cured film was bonded to a 0.025 mm thick dark silicone elastomer film, which was produced according to the method described in Example 1 described method was generated. Like in

π Example I described, the transparent coating applied to the cured film and pressed under a slight pressure. The compound The film was cured for one hour at a temperature of 100 ° C. After that, the merged set the film by means of a transparent silicone adhesive ies on the transparent surface of a smelting drum attached as described in Example 1. The roller 20 was used to transfer toner images from a semiconducting material web and for melting together zen of the toner of the images on sheets of paper in at a rate of 180 copies per minute with excellent results.

Example 3

In the case of a shape whose cavity corresponded to the cylindrical outside of a glass melting drum, such as described in Example 1, and with dimensions that are obtained after inserting the drum into the mold To allow space with a width of 5 mm, the area of the mold cavity was first covered with a Cover made of a liquid cleaning agent. A homogeneous mixture was then formed on this topping from 95 parts by weight of said clear silicone resin zes and from 5 parts by weight of carbon black and from 500 After processing for four hours in a ball mill, divide heptane to a thickness of approximately 0.025 mm sprayed on and dried by evaporating the solvent. The cylindrical surface of the glass melt drum was used to promote adhesion with a Covering made of special silicone rubber, after which the drum is centered in the mold cavity and the Gap between the outside of the drum and the mold wall then with a silicone cast together Composition were filled by mixing 40 parts by weight of silicone oil with 60 parts of the aforementioned silicone resin and 6 parts of the aforementioned Curing agent was prepared. The composition was in an air oven for 3 hours hardened at a temperature of 75 ° C. After hardening, the melting roller was out of the mold taken out.

The roller 20 was used for fusing together toner images in the format 21.5 × 28 cm on paper at a speed of 150 copies per minute excellent results

1 sheet of drawings

Claims (6)

Claims; 1. Apparatus for producing a fixed toner image? on an image receiving material Transferring a toner image from an intermediate image carrier in the molten state, in a continuous process with an endlessly rotating elastic Intermediate image carrier, a transfer device for contacting an image receiving material with the intermediate image carrier and one arranged within the transfer zone on the rear side of the intermediate image carrier facing away from the image receiving material, onto the transfer zone directed heat radiation source, characterized in that the intermediate image carrier '5 (20) a thin, the toner carrying, heat radiation absorbing, elastic layer (12) with a has such a heat capacity that it only a temperature required for softening the toner within the transfer range having 2. Apparatus according to claim 1, characterized in that the thin, thermal radiation absorbing layer (12) of the intermediate image carrier (20) an elastically compressible, heat-radiation-permeable and heat-insulating further Layer (11) is arranged 3. Apparatus according to claim 2, characterized in that the further layer (11) consists of one pigment-free silicone elastomer coating. » 4. Apparatus according to claim 1 and 2, characterized in that the thin layer (12) consists of a pigmented silicone elastomer coating. 5. Apparatus according to claim 2, characterized in that the layers (11 and 12) of the intermediate image carrier (20) are arranged on the casing of a rotatable drum (10) within which the heat radiation source (13) is arranged in a stationary manner, that the thermal radiation through the drum (10) and the layer (11) in the form of an elongated, narrow band onto the thin layer (12) which absorbs the thermal radiation is focused in the transmission zone. 6. Apparatus according to claim 1, characterized in that the thickness of the thin layer (12) * "> is preferably in the range from 0.013 to 0.1 mm.