JPS63311263A - Intermediate transfer body - Google Patents

Abstract

PURPOSE:To improve transfer efficiency of an intermediate transfer body and to obtain stably distinct picture images by constituting the intermediate transfer body of aromatic polyamide film or aromatic polyimide film contg. 5-20wt.% carbon black and having a specified surface resistivity. CONSTITUTION:The title intermediate transfer body is constituted of aromatic polyamide film or aromatic polyimide film contg. 5-20wt.% carbon and having 10<7>-10<15> surface resistivity Rs (OMEGA/square cm<2>). In a recording device using this intermediate transfer body 6, an electrostatic latent image is developed to form a toner image by a developing device 4, and the toner image is transferred electrostatically to the endless intermediate transfer body 6 by charging the toner image with a counter polarity at an electrode 7. By this method, an intermediate transfer body having superior mechanical characteristics and thermal characteristics is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an intermediate transfer body used in electrophotographic recording devices and the like.

(Prior Art) Conventionally, in an electrophotographic recording device, an electrostatic latent image is formed on an image carrier such as a photoreceptor drum, this is developed with toner, and the obtained toner image is electrostatically transferred onto a recording paper, for example. It is transcribed into.

However, with the above methods, the transfer efficiency is poor and it is difficult to obtain clear images.

Further, when a paper jam occurs, the photoreceptor drum is seriously damaged by the paper, resulting in a disadvantage that the life of the photoreceptor is shortened. Therefore, recently, methods using intermediate transfer bodies have been proposed in Japanese Patent Publication No. 46-41679 and Japanese Patent Application Laid-open No. 59-7746.
It is disclosed in No. 7, etc. That is, this is a method in which a toner image formed on an image carrier is once transferred to an intermediate transfer member by pressure, and then transferred again from the intermediate transfer member onto recording paper.

Furthermore, as a method using an intermediate transfer body, a method is also known in which a toner image is electrostatically transferred to the intermediate transfer body.

This is a method in which a toner image is electrostatically transferred onto an intermediate transfer member made of an insulating film such as polyethylene terephthalate, and then retransferred onto recording paper. Although this method requires a device for removing static electricity from the intermediate transfer body, which increases the size of the device, it is possible to obtain very clear images.

(Problems to be Solved by the Invention) However, the method of transferring a toner image to an intermediate transfer member by pressure requires considerable suppression in order to improve transfer efficiency, and there is a problem that the photoreceptor drum etc. are easily damaged. .

In comparison, the method of transferring toner images to an intermediate transfer member using static electricity has very good transfer efficiency, resolution, and photosensitive drum life, but since the intermediate transfer member is an insulator, it is necessary to remove static electricity. The drawbacks are that a device is required, the device becomes very large, and the cost of the device is also high.

In order to compensate for the above-mentioned structural defects, the intermediate transfer member is made to have appropriate conductivity so that the static electricity can be easily removed after the toner image is electrostatically transferred to the intermediate transfer member. There is an attempt. For example, films to which conductive fillers such as carbon black are added are being considered, but even if carbon is added to films obtained by melt-forming films such as PET (polyethylene terephthalate), conductivity does not develop, or If the amount added is increased, there is a problem that the physical properties of the film will be significantly deteriorated.

In comparison, in the case of solution-cast films, it is easier to uniformly disperse inorganic fillers such as carbon, but polycarbonate and fluorine-based polymers have poor affinity with carbon, etc., resulting in uneven resistance and rough surfaces. However, there are problems such as insufficient strength.

According to the present invention, when a toner image is transferred to an intermediate transfer member, the transfer can be performed electrostatically, and the static electricity of the transferred toner can be easily removed by providing the intermediate transfer member with appropriate conductivity. The object of the present invention is to provide an intermediate transfer member having excellent mechanical properties and thermal properties.

(Means for solving the problem) The present invention provides carbon black of 5 to 20゛ and 1 lIt%.
Contains surface resistivity Rs (Ω/□) of 107≦R6≦1
The present invention relates to an intermediate transfer member for an electrophotographic recording device, characterized in that it is made of an aromatic polyamide film or an aromatic polyimide film falling within the range of No. 015.

The present invention will be explained using figures.

FIG. 1 is a side view showing an example of a recording apparatus using an intermediate transfer body according to the present invention.

In this recording apparatus, an image carrier 1 such as a rotating drum type photoreceptor drum rotates in the direction of the arrow, and after its surface is cleaned by a cleaning device 5, a charging device 2
is uniformly charged, and an electrostatic latent image is formed on its surface by exposure 3.

The electrostatic latent image is developed into a toner image by a developing device 4, and the toner image is charged with an opposite charge to that of the toner by an electrode 7 and electrostatically transferred to an endless belt-shaped intermediate transfer member 6. The toner image on the intermediate transfer member is roughly retransferred to the recording paper 11 at the application roll 8, and then
．． Fixed by 10. The intermediate transfer body 6 is grounded 12
Since it is grounded from the back side and static electricity escapes, no special static electricity cleaning device is required.

The aromatic polyamide of the present invention refers to the basic structural unit (1-I
It is made of a polymer containing 50 mol% or more of N-Ar1-NHOC-Ar2-Co).

Here, Ar1 and Ar2 refer to structures (1) and (2) below.

Here, RSX is a halogen group, a nitro group, a C1-C3 alkyl group, a C1-C3 alkoxy group, and Y is 10-1
-Cf-tz -, -〇-1-3O2-0p, m, n
represents O-3, and α represents O or 1.

Q Here, S is a halogen group, a nitro group, a C1-C3 alkyl group, or a C1-C3 alkoxy group. q is O~4゜Among these, polymers having substituents such as halogen (especially chlorine) or alkyl groups (especially methyl group) in R or S, or polymers having an alkyl group or -CH2- in X or Y are The solubility in a polymer solution is improved compared to that without a substituent, and the compatibility with carbon black is improved, which is preferable. Furthermore, the moisture absorption rate is also reduced, which is preferable because the change in resistance value due to moisture absorption is small. For example, a polymer containing 50 mol% or more of (where p+q≧1) -HNCH21NHOC((history co-Iq (here Q=0 to 4) (here q=O to 4)) can be mentioned.

This aromatic polyamide is produced by the reaction of acid chloride and diamine.
Alternatively, it can be obtained by reacting an isocyanate with a carboxylic acid.

Taking the combination of acid chloride and diamine as an example, as a single acid chloride, terephthalic acid chloride, isophthalic acid chloride, and these aromatic nuclei have halogen, nitro, alkyl, or alkoxy groups. Examples include 2-chloroterephthalic acid chloride, 2-chloroisophthalic acid chloride, 2,5-dichloroterephthalic acid chloride, 2-nitroterephthalic acid chloride, and 2-methylisophthalic acid chloride. In addition, on the diamine side, p-phenylenediamine, m-phenylenediamine,
4,4-diaminodiphenylketone, 3,3°-diaminodiphenylketone, 4,4-diaminodiphenylmethane, 3.4°-diaminodiphenylmethane, 3,3゛-
Diaminodiphenylmethane, 4,4-diaminodiphenyl ether, 3,3°-diaminodiphenyl ether,
Benzidine, and those having the above substituents on their aromatic nuclei, such as 2-chloro-p-phenylenediamine, 2-chloro-m-phenylenediamine, 2-methyl-m-phenylenediamine, 3,3-dimethyl Examples include bench gin.

Taking the combination of isocyanate and carboxylic acid as an example, on the isocyanate side, phenylene-1,4-diisocyanate, phenylene-1,3-diisocyanate,
Diphenylketone-4,4-diisocyanate, diphenylmethane-4,4'-diisocyanate, diphenyl ether-4,4°-diisocyanate, diphenylsphone-4,4°-diisocyanate, and those having the above substituents on their aromatic nuclei. Examples include toluylene-2,6-diisocyanate and toluylene-2,4-diisocyanate. The carboxylic acid side includes terephthalic acid, isophthalic acid, and those having substituents on their aromatic nuclei.

The present invention needs to contain 50 mol% or more, preferably 70 mol% or more of the basic structural unit represented by the above general formula. If the amount is less than the above range, the compatibility with carbon black will deteriorate, making it impossible to form a film with sufficient mechanical properties. The copolymerization component of less than 50 mol% is not particularly limited, and may contain ester bonds, urethane bonds, imide bonds, heterocyclic bonds, and the like. In order to obtain a film with excellent mechanical properties and heat resistance, the polymer should have an intrinsic viscosity (0.5 g of polymer was mixed with N-methylpyrrolidone containing 2.5 wt% of lithium bromide for 100 m
The value measured at 30°C as a solution of 1) is 0.5 to 6.0
is preferred.

Further, the aromatic polyimide of the present invention is mainly composed of the structural unit represented by the following formula (3).

Here, R1 contains at least one aromatic ring and preferably has 25 or less carbon atoms, and the two carbonyl groups forming the imide ring are organic groups bonded to adjacent carbon atoms. .

In the formula, -R2- is a divalent organic group, which is derived from an aromatic diamine having the general formula H2N-R2-NH2. R1M is provided by an aromatic tetracarboxylic acid component having the general formula %. Representative examples of such aromatic tetracarboxylic acids include the following.

Pyromellitic dianhydride, 3.3', 4.4°-bisphenyltetracarboxylic dianhydride, 2,3,6.7
-naphthalene dicarboxylic dianhydride, 2,2-bis(3
, 4-dicarboxyphenyl)ether dianhydride, pyridine-2,3,5,6-tetracarboxylic dianhydride, 3
．． Examples thereof include 3',4,4°-benzophenonetetracarboxylic dianhydride and their tetracarboxylic acid esters.

On the other hand, as an aromatic diamine, it is preferable that two amino acids are bonded via at least one carbon, and R2 contains at least one aromatic ring, and the carbon The number is preferably 25 or less, such as para-xylylene diamine, meta-phenylene diamine, and benzidine.

4,4-diaminodiphenyl ether, 4,4-sia
.

Minodiphenylmethane, 4,4'-diaminodiphenylsulfone, 3,3'-dimethyl-4,4°-diaminodiphenylmethane, 1,5-diaminonaphthalene, 3,
Examples include 3'-dimethoxybenzidine and 1,4-bis(3-methyl-5-aminophenyl)benpine.

It goes without saying that these acid components may be used alone or in combination.

Furthermore, the aromatic polyamide and aromatic polyimide of the present invention may be blended with lubricants, antioxidants, other additives, and other polymers to the extent that the physical properties of the film are not impaired.

The carbon black used in the present invention may be any one having electrical conductivity, but furnace black and acetylene black are preferable.

Further, carbon black that has been surface-treated to improve conductivity may also be used. In addition, these carbon blacks preferably have a specific surface area of 5 Td/q to 1000 Td/q to 1000 Td/g, particularly preferably 10 Td/g to 950 Td/g, and a particle size of -a few particles of preferably 5 mμ to 500 mμ, Especially from 10mμ
The carbon purity is preferably 100 mμ, and the carbon purity is preferably 90% or more, more preferably 97% or more.

The amount of carbon black added is 5 to 20 wt per polymer.
%, and the surface resistivity R3 must satisfy 107≦R3≦1015. If carbon black is less than 5wt% or Rs exceeds 1015, transfer from the image carrier to the intermediate transfer member is possible, but static electricity cannot escape just by grounding, so a device that applies the opposite static electricity is required. Therefore, the purpose of the present invention cannot be achieved. In addition, if carbon black is more than 20 wt% or Rs is less than 107, when the toner image is transferred from the image carrier, the charge on the intermediate transfer body will escape and the force to attract the toner image to the intermediate transfer body will not work properly. The image will not be transferred and a clear image will not be obtained. More preferably carbon 5 to 15
The surface resistivity in wt% is 109≦R5≦1014.

In addition, in the present invention, the volume resistivity RV is 107≦RV≦
1015 is preferable in order to achieve the object of the present invention. As a result, static electricity on the intermediate transfer body is removed by grounding it from the back surface.

Moreover, the film thickness of the present invention is preferably 10 to 150μ, more preferably 20 to 100μ.

The film of the present invention preferably has a strength of 8 kg/m2 or more in at least one direction, such as the longitudinal or lateral direction, but 10 kg/m2 or more.
More preferably, it is 5F/rM112 or more. The upper limit is not particularly limited, but is 80K! j/ It is about #2. If the strength is less than 8Ky/Ky2, the workability of the intermediate transfer member deteriorates, and when used as an intermediate transfer member, tearing and wrinkles occur frequently, making it unsuitable for practical use.

Furthermore, at least one direction, vertical or horizontal, is '
Dimensional change at 200℃ under +Kg/lrim” load is 5
% or less. More preferably it is 2% or less. This enables thermal fixation on the intermediate transfer member, and furthermore allows the apparatus to be made smaller. Generally, the elongation of the film of the present invention is preferably 10% or more, more preferably 15 to 100%. Furthermore, the moisture absorption rate of the film is preferably 4% or less. If it is larger than this, the resistance of the film will change greatly due to humidity, making stable printing difficult.

Further, the surface of the present invention (the surface in contact with the image carrier) is preferably smooth, and has a center line average roughness (Ra) of 0.1.
5μ or less, maximum roughness g (Rtll, preferably 5μ or less. Ra exceeds 0°15μ or Rt 1.5
If it exceeds μ, the image quality will deteriorate and the photosensitive drum will be damaged, shortening its lifespan. More preferably, Ra is 0.1
μ or less, R1 is 1.0 μ or less. Also, for the same reason, there is one coarse protrusion with a diameter of 50 μ or more on the surface.
It is preferable that it is below m2.

Next, the manufacturing method of the present invention will be explained. To achieve the present invention, the above carbon is present in a solution of aromatic polyamide, aromatic polyimide, or polyamic acid (polyimide precursor), and the film is formed from this solution.

First, aromatic polyamides made from acid chlorides and diamines can be solution polymerized in aprotic organic polar solvents such as N-methylpyrrolidone, dimethylacetamide, or dimethylformamide, or interfaced using an aqueous medium. Synthesized by polymerization etc. When acid chloride and diamine are used as monomers in the polymer solution, hydrogen chloride becomes a side effect, so in order to neutralize this, an inorganic neutralizing agent such as calcium hydroxide or an organic neutralizing agent such as ethylene oxide is used. Added.

Further, the reaction between isocyanate and carboxylic acid is carried out in an aprotic organic polar solvent in the presence of a catalyst.

These polymer solutions may be used directly as a film-forming stock solution to form a film, or the polymer may be isolated once and then redissolved in the above-mentioned solvent to prepare a film-forming stock solution. In some cases, an inorganic salt such as calcium chloride or magnesium chloride may be added to the membrane forming stock solution as a solubilizing agent. The polymer concentration in the membrane forming stock solution is preferably about 2 to 40% by weight.

On the other hand, aromatic polyimide or polyamic acid can be obtained as follows. That is, polyamic acid can be prepared by reacting a tetracarboxylic dianhydride and an aromatic diamine in an aprotic organic polar solvent such as N-methylpyrrolidone, dimethylacetamide, or dimethylformamide. Further, aromatic polyimide can be prepared by heating a solution containing the above-mentioned polyamic acid or adding an imidizing agent such as pyridine to obtain a polyimide powder, which is then dissolved again in a solvent. The polymer concentration in the membrane forming stock solution is 5
It is preferably about 40% by weight.

Carbon black can be sufficiently dispersed in an organic solvent or a small amount of polymer solution in advance and then added to the film-forming stock solution, directly added to the film-forming stock solution, or dispersed in a polymerization solvent before polymerization. There is a way to do this.

The film-forming stock solution to which carbon black has been added and mixed is formed into a film by a so-called solution film-forming method. Prior to film formation, it is necessary to filter the film forming stock solution to remove coarse foreign matter.

The filter medium used is preferably 50μ or less, more preferably 30μ or less. Solution film forming methods include a wet-dry method, a dry method, a wet method, etc., and the wet-dry method and the dry method are preferable in order to obtain a film with good surface properties.

It is preferable to adjust the polymer concentration and temperature of the film-forming stock solution so that the viscosity during casting is 100 to 10,000 voids. The viscosity here refers to a value measured using a rotating B-type viscometer under the same conditions (degrees and temperatures) as during casting. Casting is performed on a support such as a metal drum or endless metal belt, where the drying or imidization reaction is accelerated until the film becomes self-retaining. At this time, it is necessary to control so that the solvent does not suddenly scatter and cause surface roughening, and the treatment is generally carried out at room temperature to 300°C, preferably 50 to 250°C, within 60 minutes.

Once the film has become self-retaining, it is peeled off from the support and introduced into a wet bath when a wet-dry process is employed. This bath generally consists of an aqueous medium and may contain an organic solvent, an inorganic salt, etc. in addition to water. The remaining solvent, inorganic salt, and imidizing agent in the film are extracted in the bath. Further, the film is stretched or relaxed in the longitudinal direction. After leaving the bath, the film is then dried, stretched, relaxed, and heat treated. These treatments are generally carried out at 100-500°C.

In the case of a dry method, a self-retaining film generally has a residual volatile content of at least 3% by weight after peeling from the support.
It is dried, stretched, relaxed, and heat treated until it becomes: These treatments are generally carried out at 150-500°C.

As mentioned above, when using either the dry-wet method or the dry method, the area magnification is preferably 0.8 to 5.0 times, more preferably 1.1 to 3.0 times, and stretching or relaxing is performed. Let's do it. The areal magnification is the product of the stretching ratio in the longitudinal direction (MD force direction) of the film and the stretching magnification in the width direction (TD force direction).If the areal magnification is less than 0.8, the physical properties of the film will deteriorate and the flatness will deteriorate. Moreover, if it exceeds 5.0, the carbon in the film will be oriented in the plane direction, the distance between the carbons will be widened, and conductivity will not be developed. It is possible to adjust the resistivity by changing.

The film obtained in the above manner is processed such as being cut to a required size and made into an endless belt, and if necessary, edge reinforcement and perforation processing are performed to form an intermediate transfer member.

(Method for Measuring Properties) The method for measuring film physical properties in the present invention will be described below.

(1) Surface resistivity R5 circular main electrode with a diameter of 50 m, an inner diameter of 70 rM1, and an outer diameter of 80 m.
m ring-shaped counter electrodes were fixed so that the centers of each circle were the same, and placed on the film surface with a load of 1 kg. When a current was passed through the counter electrodes, the resistance value was read and calculated using the following formula.

Rs = (P/g) x R where, Rs two-surface resistivity (Ω/□) P: Effective circumference of electrode (18.8 cm) g: Distance between electrodes (1.0 cm> R: Actual value of resistance (Ω) (2) Strength and elongation When the film breaks when set in a tensilon type tensile testing machine according to ASTM-D-882 with a sample width of 10 m and a sample length of 50 s1, and pulled at a tensile speed of 300 m/min. Strength and elongation are measured.The atmosphere is 25°C and 155%RH.

(3> Center line average roughness, maximum roughness.
), the stylus radius is 2μ, the load is 70η, and the cutoff value is 0.08IN! Under condition 1, magnify 5,000 to 20,000 times in the surface roughness direction and draw a chart with a cross-sectional curve film length of 4#! For the portion corresponding to II+, the centerline average roughness Ra and R roughness R1 were determined.

(4> Number of coarse protuberances Aluminum was deposited on the surface to be measured, observed with a differential interference microscope at 100x magnification, and the number of protrusions with a diameter of 50 μm or more was counted.

(Example) The present invention will be described below based on Examples. However, it is not limited to this.

Example 1 2-chloro-p-phenylenediamine and 2-chloroterephthalic acid chloride were converted into NMP (N-methylpyrrolidone)
After reacting in the reactor and neutralizing the generated hydrogen chloride with lithium hydroxide, carbon black was added to the polymer in an amount of 14wt.
% was added, and the polymer concentration was adjusted to 10 wt% to prepare a film-forming stock solution. This stock solution was filtered through a 30μ cut filter, then uniformly cast on a metal drum at 30°C and dried for 10 minutes in an atmosphere of 120°C. After that, it was peeled off from the drum and continuously immersed in a water tank for 30 minutes while MD force direction 1.1
Stretched twice. 30 minutes after introducing the rough film into the tenter
MD stretched 1.1 times in the TD force direction at 0°C to a thickness of 45μ,
A uniform film with well-balanced physical properties in the TD force direction was prepared (q).As shown in Table 1, this film had excellent mechanical properties and heat resistance, and R6 was 2 x 109Ω/□. The properties were also very good as shown in Table 1, and the number of coarse protrusions was very small at 0.0002.An endless belt was made from the obtained film and tested using the apparatus shown in Figure 1. , the transfer to the intermediate transfer body and recording paper was very clear.Static charge removal after transfer to the recording paper was also carried out naturally by grounding, and very good recording was possible even when printing continuously. .

Example 2 A polymer synthesized from 4.4°-diaminodiphenylmethane and 2-chloroterephthalic acid chloride was once isolated,
After purification, it is dissolved again in NMP at a polymer concentration of 15 wt%. Add carbon black to this solution at a ratio of 8% to the polymer.
The film-forming stock solution obtained by adding wt% was formed into a film in the same manner as in Example 1 to obtain the films shown in Table 1.

Shun, who used an endless belt, conducted the same test as in Example 1, and 17 clear images were obtained.

Example 3 4.4-Diaminodiphenyl ether and pyromellitic dianhydride were reacted in DMAc (N,N-dimethylacetamide) to obtain a polyamic acid solution with a polymer concentration of 18 wt%. To this solution, 12 wt % of the polyimide from which carbon black was obtained was added to obtain a film forming stock solution. This stock solution was filtered through a 30 μ cut filter, and was uniformly cast onto a metal drum at 30°C for 10 min in an atmosphere of 120°C.
It was dried for a while.

Thereafter, it was peeled off from the drum, stretched 1.1 times in the MD force direction, introduced into a tenter, and stretched 1 degree in the TD force direction at 380° C. to obtain a polyimide film with a thickness of 55 μm. It has the properties shown in Table 1, and the results of actual machine tests were also very excellent, just like polyamide.

Comparative Example 1 1 q of film was prepared in the same manner as in Example 1 from a solution in which 3 wt % of carbon black was added to the polymer in a polymer solution having the same composition as in Example 1. R3 is a film larger than the claimed scope of the present invention, and when it was processed into an endless belt and tested, a clear image was obtained, but static electricity could not be removed by grounding alone, and transfer more than two times was not possible. There wasn't.

Comparative Example 2 Example 1 was prepared from a solution in which 25 wt% of carbon black was added to the polymer solution with the same composition as in Example 1.
A film was obtained in a similar manner. The Rs of this film was smaller than the claimed range of the present invention, and when tested, even when a charge was applied, static electricity escaped and no toner image was transferred and no image was obtained.

Comparative Example 3 A film made by adding carbon black to polyethylene terephthalate (PET) in Swt% based on the polymer cost Rs.
is 1×10 16 , which is higher than the claimed range of the present invention, and the actual test results were similar to those of Comparative Example 1. Attempts to add more carbon resulted in a brittle film that could not be used.

(Effects of the Invention) The intermediate transfer body of the present invention has appropriate electrical insulation and conductivity. During the short period when the toner image is transferred from the image carrier to the intermediate transfer member, the intermediate transfer member exhibits insulating properties and the electric field from the electrode acts effectively on the toner without being shielded. The toner image is effectively transferred to the toner image.

On the other hand, the toner transferred to the intermediate transfer body has static electricity, but because the intermediate transfer body is slightly conductive, this static electricity escapes from the ground before reaching the application roll.
The toner image is easily transferred to recording paper. Therefore, the transfer efficiency is high, clear images can be stably obtained, and there is no need to remove static electricity on the transfer body after transfer, so the apparatus can be made very small. Furthermore, it has good mechanical properties, so it is less likely to tear or wrinkle during use, and it is also heat resistant, allowing for heat fixing at the same time as transfer from the intermediate transfer body, making it possible to roughly downsize the device. become.

[Brief explanation of the drawing]

FIG. 1 is a schematic side view of an example of an electrophotographic recording apparatus using an intermediate transfer member according to the present invention.

Claims (1)

[Claims] It is characterized by being made of an aromatic polyamide film or an aromatic polyimide film containing 5 to 20 wt% of carbon black and having a surface resistivity Rs (Ω/□) in the range of 10^7≦Rs≦10^1^5. Intermediate transfer body for electrophotographic recording devices.