JP2000081718A - Electrophotographic image forming transparent film and toner image forming method using same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an electrophotographic OHP film capable of giving an image free from transfer and conveyance defects such as voids, reduced density and a discharge pattern. SOLUTION: The electrophotographic image forming transparent film has one or more surface coating layers on at least one face of a transparent substrate 11. The contact angle of the coating layers to pure water at 23 deg.C and 50% RH is 55-90 deg., an electron-conductive electrically conductive agent is used as a surface resistance regulator and the surface resistivity of the coating layers at 23 deg.C and 50% RH is 1×108 to 1×1012Ω/sq.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transparent film suitable for forming an image using a copying machine or a printer using an electrophotographic method, and a toner image forming method using the same.

[0002]

2. Description of the Related Art It is common practice to form an image on a transparent film using an electrophotographic copying machine and project the image on an OHP. However, forming an image on a film using an electrophotographic method has many problems as compared with forming an image on paper. Thus, various problems have been solved by forming a coating layer on the surface of the film and giving it a function.

[0003] For example, a problem in forming an image using a typical polyethylene terephthalate film as a transparent film is a transportation failure. For example, a matting agent is contained in a coating layer on the surface. Then, the friction is adjusted to cope with the problem (Japanese Patent Application Laid-Open No. 1-315768).

In addition, since a polyethylene terephthalate film has a high surface resistivity, when an image is to be formed as it is, when a toner image on an image carrier such as a photoconductor is transferred to the film, it is applied to a contact transfer member. It is necessary to increase the bias transfer potential, and this may cause image failure due to abnormal discharge. To cope with this problem, an antistatic agent is applied to the film surface to suppress the surface resistivity to a certain specified value.
As a result, it is also possible to suppress a conveyance failure with charging. As means for adjusting the surface resistance, many proposals have been made, and among them, a method of applying an antistatic agent to the surface of a support is generally used. Examples of the antistatic agent include an ion conductive agent (anionic antistatic agent, cationic antistatic agent, amphoteric antistatic agent, etc.) and an electron conductive agent (zinc oxide, tin oxide, titanium oxide, etc.). (Japanese Patent Laid-Open No. 62
-94332, JP-A-6-75419, etc.).

[0005] When an image was formed using the above-mentioned conventional film, a state in which toner was partially missing was found particularly in a character image or a fine line image. This phenomenon is a "dropout"
It is called, when transferring from the photosensitive drum to the OHP film, the toner part which is thickly overlapped, especially in the high resolution character pattern output in the image pattern, the toner in the central part of the character pattern is lost without being transferred, A blank state occurs. It has been found that this "void" occurs particularly remarkably in a model using a contact transfer method such as a transfer roller.

Here, an electrophotographic image forming apparatus using a transfer roller will be described with reference to FIG. In FIG. 5, reference numeral 1 denotes a photosensitive drum, which is one of image carriers, and is driven to rotate at a predetermined peripheral speed (process speed) in a direction indicated by an arrow. In the course of rotation, the peripheral surface of the photosensitive drum 1 is uniformly charged to a predetermined polarity by the charger 2, and image exposure means such as laser beam scanning exposure means (not shown) and document image projection exposure means (not shown). As a result, an image exposure L corresponding to the image information is performed on the charged surface,
An electrostatic latent image corresponding to the exposure pattern is formed. The electrostatic latent image is developed as a toner image Ta by the developing device 4. The toner image Ta is transferred to a transfer nip n between the photosensitive drum 1 and a transfer roller 5 which is a contact transfer member pressed against the photosensitive drum 1. Then, the toner is sequentially transferred as transfer toner Tb to the transfer material P fed at a predetermined timing from a paper feeding unit (not shown). In FIG. 5, reference numerals 6 and 7 denote an inlet side guide plate and an outlet side guide plate which are guide members for guiding the transfer material P to the transfer nip portion n, which are fixed to the apparatus main body. ing.

The transfer material P that has passed through the transfer nip n is separated from the surface of the photosensitive drum 1 and conveyed to a fixing device (not shown), where the transfer toner image Tb is fixed.
It is output as an image formed product (print / copy).
After the transfer, the surface of the photosensitive drum 1 is cleaned by a cleaning device 8 to remove residual contaminants such as transfer residual toner, and is repeatedly used for image formation. The transfer roller 5 is composed of a cored bar 5a and a conductive elastic layer 5b of conductive rubber or the like formed into a roller shape by molding the cored bar with a mold or the like. It is rotatably supported by the illustrated support member.

The transfer roller 5 is disposed in parallel with the photosensitive drum 1, is pressed against the surface of the photosensitive drum 1 with a predetermined pressing force, and rotates at the same peripheral speed as the photosensitive drum 1.
Then, when a bias voltage having a polarity opposite to that of the toner image Ta on the photosensitive drum 1 is applied to the transfer roller 5 from the power supply 9, the transfer material P introduced into the transfer nip n is formed as an electrostatic latent image, and The toner image Ta on the drum 1 side is transferred to the transfer material P side as a transfer toner image Tb.

The toner and the transfer material P transferred at this time are:
A predetermined pressure when passing through the transfer nip is received from the contact transfer member, and the toner aggregates due to this pressure. At this time, when the adhesion between the toner and the transfer material P is strong, the toner is transferred onto the transfer material P.
If the adhesive force of the toner is weak, but rather the adhesive force between the toner and the photosensitive drum 1, the aggregated toner may be carried to the drum side. Such a phenomenon,
This also occurs when the toner image on the photosensitive drum side is transferred to an intermediate transfer member and further transferred from the intermediate transfer member to a transfer material.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a transparent film for electrophotographic image formation capable of obtaining an image free from transfer defects and conveyance defects such as hollow portions, low density and discharge patterns. It is in.

Another object of the present invention is to provide a toner image forming method using such a transparent film.

[0012]

According to the present invention, there is provided a transparent support having at least one surface coating layer on at least one surface thereof. The contact angle with water is not less than 55 degrees and not more than 90 degrees, and an electronic conductive agent is used as a surface resistance adjusting agent.
A transparent film for forming an electrophotographic image, wherein the surface specific resistance of the surface coating layer at a humidity of 50% RH is 1 × 10 ⁸ to 1 × 10 ¹² Ω / □.

According to the present invention, in a toner image forming method for transferring and fixing a toner image formed on an image carrier to a transfer material, the transparent film for forming an electrophotographic image is used as the transfer material. Is a method for forming a toner image.

[0014] The transparent film according to the present invention is obtained by setting the contact angle of the surface coating layer to 55 to 90 degrees and using an electron conductive material as a resistance adjusting agent contained in the surface coating layer. , Can solve the problem of pitfalls,
Further, the surface specific resistance of the surface coating layer is set to 1 × 10 ⁸ to 1 × 1.
When the transfer material is set to 0 ¹² Ω / □, the transfer material is pressed onto the toner image formed on the image carrier by the contact transfer member to transfer the toner image to the transfer material. And the occurrence of a defective image due to abnormal discharge can be prevented.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The contact angle of the surface coating layer of the transparent film according to the present invention with pure water is 55 to 90 degrees at 23 ° C. and 50% RH. This is the angle between the tangent line at the contact point between the interface of pure water and the film surface and the plane of the image receiving layer when water drops are gently dropped on the surface of the film placed horizontally as shown in FIG. . When the contact angle is in the range of 55 degrees or more and 90 degrees or less, there is no "hollow", and when the contact angle is less than 55 degrees, the contact between the toner and the film is low and the degree of "hollow" is acceptable. If it exceeds 90 degrees, the surface energy of the film is much lower than the surface energy of the toner.
The adhesiveness is reduced, and the degree of “hollow-out” is reduced. This contact angle is more preferably 60 degrees or more and 90 degrees or less.
In addition, by using an electron conductive conductive agent for adjusting the surface resistance of the surface coating layer, there is no adverse effect on “hollow-through” as in a surfactant-based antistatic agent.

The surface specific resistance of the surface coating layer is 1 × 10 ⁸ to 1 × 10 ¹² Ω / □ at 23 ° C. and 50% RH. If it is less than 10 ⁸ Ω / □, the transfer amount when transferring the toner to the image receiving layer is not sufficient, resulting in an image having a low density. If it exceeds 1 × 10 ¹² Ω / □, it is abnormal especially in a dry environment. Discharge may occur, resulting in a defective image, or being charged with static electricity, causing dust or dirt to be adsorbed, or film sticking to each other, resulting in poor paper feed.

FIG. 1 shows a film according to the present invention in which image receiving layers 12a and 12b are formed on both surfaces of a transparent support 11.

As the transparent support 11, any material can be used as long as it is transparent and has the property of withstanding heat during heat fixing. It is desirable that the heat resistant temperature does not cause thermal deformation at 100 ° C. or higher. If the temperature is lower than 100 ° C., there is a high possibility that the toner image will be deformed during heat fixing.

Examples of the material of the transparent support include polyesters (eg, polyethylene terephthalate), cellulose esters (eg, nitrocellulose, cellulose acetate, cellulose acetate butyrate), and polysulfone, polyphenylene oxide, polyimide, polycarbonate, polyamide, and the like. be able to. Of these, polyethylene terephthalate is preferred from the viewpoints of heat resistance, transparency, cost and the like.

The thickness of the support is not particularly limited.
Those having a thickness of 50 to 200 μm are preferred. If the thickness is smaller than this, there is often a problem in paper permeability due to problems such as the stiffness of the film. Sex, price, etc. are also disadvantageous.

The image receiving layers 12a and 12b are layers containing an antistatic agent, a matting agent, a binder and the like. Examples of the electron conductive conductive agent used as an antistatic agent include SnO.
₂ , ZnO, TiO, Al ₂ O ₃ , In ₂ O ₃ , SiO
₂ , MgO, BaO and MoO ₃ . These may be used alone or as a composite oxide thereof. Further, SnO ₂ whose performance is improved by antimony doping or the like is preferable. The average particle diameter of the electron conductive agent is preferably 0.1 μm or less. If it exceeds 0.1 μm, haze will increase. Among them, particularly preferred is SnO ₂ having an average particle size of 10 to 100 nm.

The average particle size of the conductive agent is also the average particle size measured by a so-called microscope method. That is, for each particle placed in the field of view of the electron microscope, the distance between two parallel lines in any given direction is measured, and the arithmetic average value of the distance is obtained. The number of measurement particles is 200 or more.

Examples of the matting agent include a fluorine resin, a low molecular weight polyolefin organic polymer (a polyethylene matting agent, a paraffinic or microcrystalline wax emulsion, etc.), and inorganic fine particles (SiO ₂ , Al
₂ O ₃ , talc, kaolin, etc.) and bead-shaped plastic powders (cross-linked PMMA, polycarbonate, polyethylene terephthalate, polystyrene, etc.). The average particle size of the matting agent is 1 to 20 μm.
Is preferable. A larger average particle size is preferable for preventing double feed, etc., but when too large, fogging (haze) occurs.
Is increased, the above range is preferable.

The average particle size of the matting agent is a value measured by a laser light scattering optical particle size distribution meter (trade name: Microtrack, manufactured by Nikkiso Co., Ltd.).

As the binder, water-soluble polymers (polyvinyl alcohol, polyacrylic acid, polyacrylamide, polyhydroxyethyl acrylate, polyvinyl pyrrolidone, water-soluble polyester, water-soluble polyurethane, water-soluble nylon, water-soluble epoxy resin, gelatin,
Hydroxyethyl cellulose, hydroxypropylcellulose, carboxymethylcellulose and derivatives thereof, water-dispersible resins (water-dispersed acrylic resins, water-dispersed polyesters, etc.), emulsions (acrylic resin emulsions, polyvinyl acetate emulsions, styrene-butadiene rubber) Emulsion type) and organic solvent soluble type resin (acrylic resin, polyester resin, etc.). Further, a crosslinking agent may be further added to these polymers.

In order to more effectively prevent the hollow phenomenon, and according to the present invention, at least one surface coating layer is provided on at least one surface of the transparent support,
Hardness of the surface at 23 ° C. in a humidity 50% RH is, the universal hardness value when pushed 1μm diamond indenter at the surface film physical property test 150 N / mm ² or more, in particular, be a 160 N / mm ² or more It is suitable.

FIG. 6 shows a universal hardness measuring apparatus. In this measurement, the opposing angle was 136 in a square pyramid.
The sample (transparent film) 61 fixed to the sample support 62 is attached to the diamond indenter 63 specified in °.
The weight is gradually pushed into the surface. The indentation depth under the load is electrically detected and read, and the load applied to the indenter at that time is detected by the load cell.

The universal hardness value is expressed by the indentation load at the set maximum indentation depth (1 μm in the present invention).

The surface coating layer may be formed, for example, by dispersing or dissolving the polymer, antistatic agent, matting agent, etc. in pure water or an organic solvent, and coating the obtained coating solution on the transparent support. , By heating and drying. The coating can be performed by a known coating method such as an air doctor coater, a blade coater, a rod coater, a knife coater, a squeeze coater, a reverse roll coater, and a bar coater.

The coating thickness of the surface coating layer is optional,
It is desirable that the thickness be from 0.01 to 10 μm. If the coating thickness is too thin, there is a problem in the fixability and coating workability of the toner. On the other hand, if the coating thickness is too thick, when the surface softens during heat fixing, there is a risk of winding around the heat fixing member (roller, film, etc.). In addition, the coating cost increases. As the OHP film for black and white, the amount of toner transferred to the surface coating layer is small, so that the coating thickness of the surface coating layer is 0.1 to 2 μm. The upper portion is desirably 1 to 10 [mu] m from the necessity of sufficiently embedding the upper portion in the surface coating layer in the fixing process to smooth the surface, suppress the light scattering, and obtain an image having a high light transmittance.

The surface coating layer may contain known materials such as an antioxidant, a coloring agent, and an ultraviolet absorber, if necessary. The structure of the surface coating layer of the transparent film of the present invention is not limited to the above-described structure in which one image-receiving layer is formed on each side of the transparent support, and also includes a transparent support material as shown in FIG. 31 in which an image receiving layer 32 is formed only on one side (this requires discrimination between front and back, but the cost is suppressed);
As shown in FIG. 4, there is a transparent support 41 in which conductive layers 42a and 42b are formed on both sides (or one side) and image receiving layers 43a and 43b are formed thereon (this has a wide selection range of materials). Here, the electron conductive conductive agent as a resistance adjusting agent is added to the conductive layer or both the conductive layer and the image receiving layer.

[0032]

The present invention will be described below by way of specific examples.

(Example 1-1) A 100 μm-thick polyethylene terephthalate film (trade name: F56, manufactured by Toray Co., Ltd.) stretched by a biaxial stretching method was coated on both surfaces using a bar coater as a surface coating layer. Speed 20m / mi
At n, the following materials were applied and dried at 120 ° C. for 30 seconds. The layer thickness at this time was 0.2 μm (dry film thickness). Table 1 shows the evaluation results of this film.

Binder 10 parts by weight of water-soluble polyester (Tg = 65 ° C.) (trade name: WAC-20, manufactured by Takamatsu Yushi) Antistatic agent SnO ₂ (average particle size: 10 nm) 4 parts by weight Matting agent SiO ₂ (average particle size) 10 μm) 2 parts by weight Pure water 84 parts by weight

(Example 1-2) In Example 1-1,
Table 1 shows the evaluation results of the films obtained by performing the coating in the same manner as in Example 1-1, except that TiO (average particle size: 10 nm) was used instead of SnO ₂ as the antistatic agent.

(Comparative Example 1-1) In Example 1-1,
Coating was performed in the same manner as in Example 1-1, except that the same amount of an anionic surfactant (trade name: Plysurf A212C, manufactured by Daiichi Kogyo Seiyaku) was used instead of SnO ₂ as an antistatic agent. Table 1 shows the evaluation results of the obtained films.

(Comparative Example 1-2) In Example 1-1,
A film obtained by performing coating in the same manner as in Example 1-1 except that a nonionic surfactant (trade name: Derektor RL, manufactured by Meisei Chemical Co.) was used instead of SnO ₂ as an antistatic agent. Table 1 shows the evaluation results.

[0038]

[Table 1]

In Tables 1 to 3, evaluations "A" to "Blank" were made.
E is as follows.

When a toner image of 16-point characters is formed on a transparent film, A: the number of voids per 50 characters is 0 B: the number of voids per 50 characters is 1 to 5 C: The number of voids per 50 characters is 6 10 to 10 D: Hollow spots per 50 characters 11 to 15 E: Hollow spots per 50 characters 30 or more

(Example 2-1) The following materials were coated on both sides of a 100 μm-thick polyethylene terephthalate film stretched by a biaxial stretching method at a coating speed of 20 m / min using a bar coater as a surface coating layer. And dried at 120 ° C. for 30 seconds.

Binder 8 parts by weight of water-dispersible polyester (Tg = 70 ° C.) (trade name: WR905, manufactured by Nippon Synthetic Chemical Industry) Antistatic agent SnO ₂ (average particle size: 10 nm) 4 parts by weight Matting agent SiO ₂ (average particle size) Diameter 6 μm) 1.5 parts by weight Pure water 86.5 parts by weight

At this time, the layer thickness was 0.2 μm. Further, this film was subjected to a heat treatment in an oven at an atmosphere temperature of 150 ° C. for 60 seconds. Table 2 shows the evaluation results of this film.

(Example 2-2) In Example 2-1:
Table 2 shows the evaluation results of the films obtained in the same manner as in Example 2-1 except that the heat treatment after coating and drying was performed at 150 ° C. for 30 seconds.

(Example 2-3) In Example 2-1.
Table 2 shows the evaluation results of the films obtained in the same manner as in Example 2-1 except that the heat treatment after coating and drying was performed at 130 ° C. for 15 seconds.

(Example 2-4) In Example 2-1,
Example 2-1 except that the heat treatment after coating and drying was not performed
Table 2 shows the evaluation results of the films obtained in the same manner as in the above.

[0047]

[Table 2]

(Example 3) In Example 1-1, the following coating material was used at a coating speed of 50 m / min using a gravure coater, dried at 160 ° C for 15 seconds, and dried to a thickness of 0.2 µm. A coating layer was formed.

Binder Polyester resin (tg = 67 ° C.) 11.5 parts by weight (trade name: Byron-200, manufactured by Toyobo) Antistatic agent SmO ₂ (average particle size: 10 nm) 4 parts by weight Matting agent Polymethyl methacrylate resin (average) (Particle size: 6 μm) 2 parts by weight MEK / toluene (weight ratio: 1: 1) 82.5 parts by weight Table 3 shows the evaluation results of the obtained films.

[0050]

[Table 3]

The films obtained in Examples and Comparative Examples were evaluated by the following methods.

<Punching> Copier NP manufactured by Canon Inc.
Using a 6030, a character image and a thin line image were formed in an environment of 23 ° C. and a humidity of 5% RH, and the void was evaluated.

<Contact Angle> Using a contact angle meter CA-X Roll manufactured by Kyowa Interface Science Co., Ltd., at 23 ° C. and a humidity of 50% RH.
The measurement was carried out under the environment of (1) with a drop amount of 1.8 μl.

<Universal Hardness Value> The hardness was measured under an environment of 23 ° C. and a humidity of 50% RH using a hardness meter Fischerscope H100 manufactured by Helmut Fischer.

<Surface resistivity> Advanced Test Co., Ltd.
The measurement was performed using an ultra-high resistance meter R8340 manufactured at 23 ° C. under an environment of 50% RH with an applied voltage of 100 V.

[0056]

As described above, the present invention has the following features.
An object of the present invention is to provide a transparent film for electrophotography capable of obtaining an image free from poor transfer and poor transfer such as a low density and discharge pattern.

The transparent film is effective as a film for OHP, a film for illumination, and the like.

[Brief description of the drawings]

FIG. 1 is a view showing a basic structure of a transparent film in the present invention.

FIG. 2 is a schematic diagram showing a contact angle between an image receiving layer and pure water.

FIG. 3 is a cross-sectional view illustrating an example of a configuration of a transparent film according to the present invention.

FIG. 4 is a cross-sectional view illustrating an example of a configuration of a transparent film according to the present invention.

FIG. 5 is a configuration diagram illustrating an example of an electrophotographic image forming apparatus using a transfer roller.

FIG. 6 is a schematic diagram of a measurement test of a surface film physical property test used in the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photosensitive drum 2 charger 4 developing device 5 transfer roller 5a cored bar 5b conductive elastic layer 11, 31, 41 transparent support 12a, 12b, 32, 42a, 42b image receiving layer 43a, 43b conductive layer 61 sample 62 sample support Stand 63 diamond indenter

Claims (14)

[Claims] 1. A transparent support having at least one surface with:
It has at least one or more surface coating layers, and the contact angle of the surface coating layer with pure water at 23 ° C. and a humidity of 50% RH is 5
The surface specific resistance of the surface coating layer at 23 ° C. and a humidity of 50% RH is 1 × 10 ⁸ to 1 × 10 5 to 90 °, an electronic conductive agent is used as a surface resistance adjusting agent.
^A transparent film for forming an electrophotographic image, which has a resistance of ¹² Ω / □. 2. The transparent film for forming an electrophotographic image according to claim 1, wherein the electron conductive conductive agent is SnO ₂ particles. 3. The transparent film for forming an electrophotographic image according to claim 1, wherein the contact angle is 60 degrees or more and 90 degrees or less. 4. The hardness of the surface at 23 ° C. and a humidity of 50% RH is 150 N / cm when a diamond indenter is pushed in by 1 μm in a surface film physical property test.
The transparent film for forming an electrophotographic image according to claim 1, which has a thickness of ² mm2 or more. 5. The transparent film for forming an electrophotographic image according to claim 4, wherein the hardness is 160 N / mm ² or more. 6. After the surface coating layer is applied, a heat treatment is performed to make the surface hardness at 23 ° C. and a humidity of 50% RH equal to or less than 1 μm in the surface film physical property test.
The universal hardness value when pushed in is 150 N / mm
^The transparent film for forming an electrophotographic image according to claim 4, wherein the number is ² or more. 7. The transparent film for forming an electrophotographic image according to claim 1, wherein a matting agent particle is contained in the surface coating layer. 8. The transparent film for forming an electrophotographic image according to claim 1, wherein the transparent support is a polyester film. 9. The transparent film for forming an electrophotographic image according to claim 1, wherein the thickness of the transparent support is 50 to 200 μm. 10. An electron conductive agent having an average particle size of 0.1.
The transparent film for forming an electrophotographic image according to claim 1, which has a thickness of not more than μm. 11. The transparent film for forming an electrophotographic image according to claim 7, wherein the matting agent has an average particle size of 1 to 20 μm. 12. A toner image forming method for transferring and fixing a toner image formed on an image carrier to a transfer material, wherein the transfer material is any one of claims 1 to 11. A toner image forming method, which is a transparent film for forming an image. 13. A method for transferring a toner image onto a transfer material by pressing a transfer material onto a toner image formed on an image carrier by a contact transfer member to which a bias voltage having a polarity opposite to that of the toner image is applied. Item 13. The toner image forming method according to Item 12. 14. The toner image forming method according to claim 12, wherein the contact transfer member is a transfer roller.