JPH04163558A - Electrophotographic sensitizer - Google Patents

Abstract

PURPOSE:To secure such an electrophotographic sensitizer that is high sensitivity and low in residual potential by containing oxytitanium phthalocyanine and an azo pigment of work function Wf>=5.45eV in a photoconductive layer. CONSTITUTION:Oxytitanium phthalocyanine TiOPC and an azo pigment of work function Wf>=5.45eV are contained in a photoconductive layer. Since this TiOPC has a high sensitivity in wavelength light in and around 600-800nm, it is useful as a photosensitive material for an electrophotographic printer or digital copying machine using a light emitting diode and a semiconductor laser beam as an illuminant, but it has a defect, say, residual potential. Therefore, with a yet higher azo pigment in the work function Wf added, this Wf of the azo pigment being added in order to lower the residual potential without preventing the intrinsic characteristic, is set down to more than 5.45eV. With this constitution, such an electrophotographic sensitizer that is high sensitivity and low in the residual potential is securable.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an electrophotographic photoreceptor and an electrophotographic device equipped with the photoreceptor, and more particularly to an extremely high-sensitivity electrophotographic photoreceptor containing oxytitanium phthalocyanine in the photosensitive layer. The present invention relates to an electrophotographic photoreceptor and an electrophotographic apparatus equipped with the photoreceptor.

[Prior Art] Electrophotographic photoreceptors using organic materials have come to be installed in large numbers in copying machines and optical printers, and materials are making remarkable progress.

Among these materials, oxytitanium phthalocyanine (hereinafter abbreviated as Ti0Pc) has attracted attention in recent years. Ti
Since 0Pc has high sensitivity to light with a wavelength around 600 to 800 nm, it is useful as a photoreceptor material for electrophotographic printers or digital copying machines that use LEDs or semiconductor lasers as light sources.

[Problem to be solved by the invention] However, although Ti0Pc has high sensitivity,
It has the disadvantage of a large residual potential.

Incidentally, Ti0Pc is known to take many crystal forms, but among them, the diffraction angle 2θ±0.2° in the X11 diffraction spectrum of CuK is 9.0°,
Crystalline Ti0Pc, which has strong peaks at 14.2@, 23.9°, and 27.1", clearly exhibits the above characteristics. That is, although it has extremely high sensitivity, it has a high residual potential. In terms of characteristics, it has the disadvantage that it becomes difficult to obtain a potential contrast in systems where the process speed of electrophotography is high or the process cycle is short, and furthermore, in systems where the laser spot is small when using laser exposure. Ti0Pc
When attempting to form a laminated photoreceptor using the charge-generating layer, the formulation design latitude of the charge transport layer, intermediate layer, surface protective layer, etc. becomes narrow, which is undesirable.

Therefore, an object of the present invention is to improve the above-mentioned drawbacks and provide an electrophotographic photoreceptor using Ti0Pc with very high sensitivity and low residual potential.

[Means for Solving the Problems] That is, the present invention provides an electrophotographic photoreceptor j having an organic photoconductive layer on a conductive support, wherein the photoconductive layer contains (A) oxytitanium phthalocyanine; B) An electrophotographic photoreceptor containing an azo pigment having a work function Wf≧5.45 eV, and an electrophotographic apparatus and facsimile equipped with the photoreceptor.

The present invention will be explained in detail below.

When using Ti0Pc in combination with a charge transport material,
Since the work function Wf of Ti0Pc is lower than that of commonly used charge transport materials, sufficient carrier injection is not performed in the region of low electric field strength, which is considered to be a cause of the residual potential.

The present inventors focused on this point, and after conducting extensive studies, discovered that by adding an azo pigment with a higher Wf content, the residual potential could be lowered without impeding the original characteristics.
This led to the present invention. The Wf of Ti0Pc varies depending on its crystal form, but takes a value of about 5.1 to 5.4 eV. On the other hand, the effect of the present invention can be obtained when the Wf of the azo pigment added is 5.45 eV or more.

The addition ratio of azo pigment to Ti0Pc is 100% by weight ~
5% by weight (hereinafter abbreviated as %) is suitable, and even 70% by weight is suitable.
% to 10% is preferred. If the addition ratio of the azo pigment exceeds 100%, the inherent high sensitivity characteristics of TioPc may be significantly impaired. That is, when it is 100% or less, the residual potential of the photoreceptor can be lowered by increasing the Wf of the photoconductive layer as a whole without impairing the sensitivity. Further, if the addition ratio is lower than 5%, the effect of the present invention will be insufficient, which is not preferable.

Furthermore, as can be inferred from the above description, it is desirable that the azo pigment has a certain degree of photosensitivity. It is preferable to have high sensitivity to.

Such azo pigments are as follows - Ritual (1).

Those represented by (II) are preferred.

B-N=N-A-N=N-C (I) where A, A' are diamines or triamine central skeletons, B, C, and D are compounds having phenolic hydroxyl groups, and are the same compounds. It's okay.

Specific examples of A and Ao are given below.

■ Next, specific examples of B, C, and D will be given.

Next, the general formula of oxytitanium phthalocyanine used as a charge generating material is shown.

However, x,,x2. x , , x4 is 1 or Br
, and n, m, and β are integers of O to 4.

Documents related to synthesis methods and electrophotographic properties include, for example, JP-A-57-148745. 59-36254. Same 59-
44054゜59-31965. 61-2392'
48. 62-67094, etc. Ti0Pc obtained according to these methods is used as a charge generating material.

Ti0Pc, like other phthalocyanines, exists in polymorphism. For example, Japanese Patent Application Laid-Open No. 59-49544 (USP
4, 444.861), JP-A-59-166959, JP-A-61-239248 (USP 4.72)
8.592), Japanese Patent Application Laid-Open No. 62-67'094 (US
P4.664.997), Japanese Patent Application Laid-Open No. 63-366,
JP-A-63-116158, JP-A-63-198
Oxytitanium phthalocyanine having different crystal forms is reported in Q67 and JP-A-64-17066.

Among these, (1) Bragg angle 2θ±0.2° in X-ray diffraction of Cu/K is 9.0° and 14.2°.
.

A novel crystalline oxytitanium phthalocyanine having strong peaks at 23.9° and 27.1° is preferred because it has high sensitivity and the present invention works effectively.

The structure of the photoreceptor of the present invention may be either a laminated type including a charge generation layer and a charge transport layer, or a single layer type in which a charge generation material and a charge transport material are mixed. Furthermore, in the former case, there are two lamination orders, of which the charge generation layer and the charge transport layer are generally laminated in this order from the substrate side. The aspect of the photoreceptor will be explained by taking its configuration as an example.

The conductive support may be any material as long as it has conductivity, such as metals such as aluminum and stainless steel, metals with conductive layers, plastics, and paper, and the shape may be cylindrical or film-like. It will be done.

Furthermore, a subbing layer having barrier and adhesive functions may be provided between the conductive support and the photosensitive layer.

As the material for the undercoat layer, polyvinyl alcohol, polyethylene oxide, ethyl cellulose, methyl cellulose, casein, polyamide, glue, gelatin, etc. are used.

These are dissolved in a suitable solvent and applied onto a conductive support.

Further, it is preferable to provide a conductive layer between the support and the undercoat layer for the purpose of covering unevenness and defects on the substrate and preventing interference fringes due to scattering when the image input is a laser beam.

This can be formed by dispersing conductive powder such as carbon black, metal particles, metal oxide, etc. in a binder resin. The thickness of the conductive layer is 5 to 40 microns, preferably 1
0 to 30 microns is suitable.

A charge generation layer is provided on the undercoat layer. That is, Ti0Pc
It is formed by applying and drying a paint in which azo pigment and azo pigment are dispersed in a binder resin dissolved in a solvent.

Examples of the binder resin used here include polyester resin, acrylic resin, polyvinyl carbazole resin, phenoxy resin, polycarbonate resin, polyvinyl butyral resin, polystyrene resin, polyvinyl acetate resin, polysulfone resin, polyarylate resin, and vinylidene chloride/acrylonitrile resin. Main examples include polymer resins.

The ratio of the total pigment to the binder resin (weight ratio: the same applies hereinafter) of Ti0Pc and azo pigment is preferably 175 to 5/1, more preferably 172 to 3/1.

The charge transport layer is mainly formed by applying and drying a paint in which a charge transport material and a binder resin are dissolved in a solvent.

Examples of the charge transport material used include various triarylamine compounds, hydrazone compounds, stilbene compounds, pyrazoline compounds, oxazole compounds, thiazole compounds, and triallylmethane compounds. As the binder resin, the same resin as that used for the charge generation layer can be used.

Coating methods for these photosensitive layers include dipping,
Spray coating method, spinner coating method,
A bead coating method, a blade coating method, a beam coating method, etc. can be used.

FIG. 1 shows a schematic configuration example of a general transfer type electrophotographic apparatus using the electrophotographic photoreceptor of the present invention.

In the figure, reference numeral 1 denotes a drum-type photoreceptor of the present invention as an image carrier, which is rotated at a predetermined circumferential speed in the direction of the arrow around an axis 1a. The photoreceptor 1 is charged by charging means 2 during its rotation process.
The peripheral surface thereof is uniformly charged with a predetermined positive or negative potential, and then subjected to optical image exposure (slit exposure, laser beam scanning exposure, etc.) by an image exposure means (not shown) in the exposure section 3. As a result, electrostatic latent images corresponding to the exposed images are sequentially formed on the circumferential surface of the photoreceptor.

The electrostatic latent image is then developed with toner by a developing means 4, and the toner developed image is transferred by a transfer means 5 from a paper feed section (not shown) between the photoreceptor 1 and the transfer means 5 in synchronization with the rotation of the photoreceptor 1. The images are sequentially transferred onto the surface of the transfer material P that is fed.

The transfer material P that has undergone the image transfer is separated from the photoreceptor surface and introduced into the image fixing means 8, where the image is fixed and a copy is produced.
will be printed out on the outside of the aircraft.

After the image has been transferred, the surface of the photoreceptor 1 is cleaned by a cleaning means 6 to remove residual toner, and is further subjected to a charge removal process by a pre-exposure means 7, and is used repeatedly for image formation.

As the uniform charging means 2 for the photoreceptor 1, a corona charging device is generally used. Also, as the transfer device 5, a corona transfer means is generally used. A plurality of components such as the cleaning means and the cleaning means may be combined together as an apparatus unit, and this unit may be configured to be detachable from the apparatus main body.For example, the photoreceptor l and the cleaning means The means 6 may be integrated into one device unit, and configured to be detachable using a guide means such as a rail of the device body.In this case, the charging means and/or the developing means may be attached to the device unit. It may also be configured with

When using an electrophotographic device as a copying machine or printer, light image exposure involves scanning the reflected light or transmitted light from the original, or reading the original into a signal, and using this signal to scan the laser beam and drive the LED array. , or by driving a liquid crystal shutter array.

When used as a facsimile printer, the optical image exposure is exposure for printing received data.

FIG. 2 is a block diagram showing an example of this case.

The controller 11 controls the image reading section 10 and the printer 19. The entire controller 11 is controlled by the PU 17. Read data from the image reading unit 10 is transmitted to the other station through the transmission circuit 13. Data received from the other station is sent to the printer 1 through the reception circuit 12.
Sent to 9th. Predetermined image data is stored in the image memory 16. Printer controller 18 is printer 1
It controls 9. 14 is a telephone.

Image information received from the circuit 15 (image information from a remote terminal connected via a line) is demodulated by the receiving circuit 12, decoded by the CPU 17, and sequentially stored in the image memory 16. Ru. and at least 1
When the image information of the page is stored in the memory 16, the image of the page is recorded. CPU 17 is memory 16
One page of image information is read out, and the decoded one page of image information is sent to the printer controller 18. The printer controller 18 is one from the CPU 17.
When the image information of the page is received, the printer 19 is controlled to record the image information of the page.

Note that during recording by the printer 19, the CPU 17
The next page is being received.

Images are received and recorded in the manner described above.

The electrophotographic photoreceptor of the present invention can be used not only in electrophotographic copying machines, but also in a wide range of electrophotographic application fields such as laser beam printers, CRT printers, LED printers, liquid crystal printers, and laser plate making.

Next, an example of manufacturing Ti0Pc used in the present invention will be shown.

In 100 g of α-chlornaphthalene, 5.0 g of 0-phthalodinitrile, titanium tetrachloride 2. After heating and stirring Og at 200°C for 3 hours, the mixture was cooled to 50°C and the precipitated crystals were filtered off to obtain a paste of dichlorotitanium phthalocyanine. Next, this was washed with N,N'-dimethylformamide 100n+42 heated to 100° C. under stirring, then washed twice with methanol 100n+42 heated to 60° C., and filtered. Further, the resulting paste was stirred in 100 ml of deionized water at 80° C. for 1 hour and filtered to obtain blue oxytitanium phthalocyanine crystals. Yield 4.
3g.

The elemental analysis values of this compound were as follows.

Elemental analysis value fc, □H+ 6N+ Ji01 Next, this crystal was dissolved in 30 nl of concentrated sulfuric acid and added dropwise to 300+ tl of deionized water at 20'C under stirring to cause reprecipitation, filtration, and thorough washing with water. Crystalline oxytitanium phthalocyanine was obtained.

4.0 g of the thus obtained amorphous oxytitanium phthalocyanine was added to 100 mβ of methanol at room temperature (2
The mixture was suspended and stirred for 8 hours at 2° C.), filtered, and dried under reduced pressure to obtain low-crystalline oxytitanium phthalocyanine. Next, add n to 2.0 g of this oxytitanium phthalocyanine.
40 mj2 of -butyl ether was added, and milling was carried out at room temperature (22°C) for 20 hours with glass beads of 1 mmψ.

The solid content was taken out from the dispersion, thoroughly washed with methanol and then with water, and dried to obtain the novel crystalline oxytitanium phthalocyanine of the present invention. The yield was 1.8 g, and the Bragg angles 2θ±0.2° in X-ray diffraction of this oxytitanium phthalocyanine were 9.0°, 14.2°,
It had strong peaks at 23.9° and 27.1'.

1 dish main l Japanese Patent Application Laid-Open No. 61-239248 (USP 4.728.
592), the so-called α
A crystalline form of oxytitanium phthalocyanine, which is called a type, was obtained.

Amorphous oxytitanium phthalocyanine was obtained in the same manner as in Production Example 1. 15 parts of sodium chloride and 7 parts of diethylene glycol were mixed with 10 parts by weight (hereinafter abbreviated as "parts") of the oxy-titanium phthalocyanine thus obtained, and the mixture was milled in an automatic mortar under heating at 80°C for 60 hours. Ta. Next, sufficient water washing was performed to completely remove the sodium chloride and diethylene glycol contained in this treated product. After drying this under reduced pressure, 200 parts of cyclohexanone and 1 mmφ glass beads were added.
Processing was performed using a sand mill for 0 minutes to obtain oxytitanium phthalocyanine crystals. Bragg angle 2θ±0 in X-ray diffraction of this oxytitanium phthalocyanine crystal
．． 2° is 95°.

9.7@, 11.7°, 15.0°, 23
．． 5', 24.1@.

It had a strong peak at 27.3°.

[Example] Next, the present invention will be explained according to examples.

50 parts of titanium oxide powder coated with tin oxide containing 10% antimony oxide, 25 parts of resol type phenolic resin
parts, 20 parts of methyl cellosolve, 5 parts of methanol, and silicone oil (polydimethylsiloxane polyoxyalkylene copolymer, average molecular weight 3000) 0.002
2 parts with a sand mill machine using φ1mm glass beads.
A coating material for a conductive layer was prepared over time.

Aluminum cylinder (φ30 mm x 260 mm
), the above paint was applied by dip coating and dried at 140° C. for 30 minutes to form a conductive layer with a thickness of 20 μm.

On top of this, a solution of 5 parts of 6-66-610-12 quaternary polyamide copolymer resin dissolved in a mixed solvent of 70 parts of methanol and 25 parts of butanol was applied by dipping and dried to form a 1 μm thick undercoat layer. Established.

Next, 3 parts of the oxytitanium phthalocyanine crystal (Wf = 5.28 eV) obtained in Production Example 1 of the present invention and a trisazo pigment having the following structure (Wf = 5.52 eV)
2 parts of polyvinyl butyral resin (product name: S-LEC BM-2, manufactured by Miki Chemical) dissolved in 100 parts of cyclohexanone was dispersed for 2 hours using a sand mill using 1φ glass beads, and 100 parts of methyl ethyl ketone was dispersed in this. was added, diluted, collected, coated on the undercoat layer, and dried at 80°C for 10 minutes to form a film with a thickness of 0.15 μm.
A charge generation layer was formed.

Next, a solution was prepared by dissolving 10 parts of a charge transport material represented by the following structural formula and 10 parts of bisphenol 2 type polycarbonate resin in 60 parts of monochlorobenzene, and the solution was applied onto the charge generation layer by a dipping method. This was dried at a temperature of 110° C. for 1 hour to form a charge transport layer with a thickness of 20 ILm.

Comparison (1) A photoreceptor was prepared in the same manner as in Example 1 except that no trisazo pigment was added.

These Example 1 and Comparative Example 1 were installed in a laser beam printer (product name: LBP-3X: manufactured by Canon),
Charging was set so that the dark area potential was -700 m, and a laser beam with a wavelength of 802 nm was irradiated to this, and the amount of light required to lower the potential at -700 m to -150 (Vl) was measured and was defined as the sensitivity. The potential at a light intensity of uJ/Cm2 was measured and used as the residual potential.The results are shown in Table 1.

Table 1 Note that the laser beam spot diameter in this printer is 85 μm in the main scanning direction and 100 μm in the sub-scanning direction. Further, the process speed is 47IlaI/SeC.

Disazo pigments with the following structural formula are used as Yuazo pigments (Revised 5.
A photoreceptor was prepared in the same manner as in Example 1, except that a voltage of 76 eV was used.

CI C1 A disazo pigment with the following structural formula (l[=5
．． A photoreceptor was prepared in the same manner as in Example 1, except that a charge transport material having the following structure was used as the charge transport material.

Bleed ■A Ti0Pc obtained in Production Example 2 (Wf=5.18eV
) A photoreceptor was produced in the same manner as in Example 1, except that the photoreceptor was used.

Ti0Pc (Wf=5.34eV
) A photoreceptor was produced in the same manner as in Example 2, except that the photoreceptor was used.

These photoreceptors were evaluated in the same manner as in Example 1. The results are shown in Table 2.

Table 2 A photoreceptor was prepared in the same manner as in Example 1 except that an 80φ x 360mm aluminum cylinder was used.

A photoreceptor was prepared in the same manner as in Comparative Example 1, except that an 80φ x 360 mm aluminum cylinder was used.

These photoreceptors are used in a digital color copying machine (product name: C
LC-500, manufactured by Canon), and the dark potential is -7
00 (V), and apply a wavelength of 790V to this.
The amount of light required to lower the voltage to -700 (V) by irradiating a laser beam of nm was measured and defined as the sensitivity. Also, 5μJ/c
The potential at a light intensity of m'' was measured and used as the residual potential. The results are shown in Table 3.

Table 3 Note that the laser beam spot diameter in this copying machine is 40 μm in the main scanning direction and 60 μm in the sub-scanning direction. The process speed is 160 mm/sea.

A protective layer was provided on the photoreceptor obtained in Example 1 by the following procedure. 1 part of polytetrachloroethylene powder (trade name Nilbrone L-2, manufactured by Daikin Industries) was mixed with bisphenol 2
Type Bolicarbonate! - A paint was prepared by dispersing 3 parts of the resin in a monochlorobenzene solution and adding 2 parts of the charge transport material used in Example 1 thereto. This was spray coated onto the photoreceptor to form a 2 μm thick protective layer.

Comparative Example A protective layer was provided on the photoreceptor obtained in Comparative Example 1 in the same manner as in Example 7.

These photoreceptors were evaluated in the same manner as in Example 1 using a laser beam printer. The results are shown in Table 4.

Table 4 A photoreceptor was produced in the same manner as in Example 2, except that the ratio of the azo pigment added to Ti0Pc was changed as follows.

Example 8 2.5 parts of Ti0Pc, 2.5 parts of disazo pigment.
5 parts Example 9 4.7 parts of Ti0Pc, 0.3 parts of disazo pigment These photoreceptors were evaluated in the same manner as in Example 1, and the results are shown in Table 5.

Table 5 [Effects of the Invention] As is clear from the above examples, the photoreceptor in which an azo pigment with a work function Wf≧5.45 eV is added to oxytitanyl phthalocyanine has a low residual potential (and the characteristics of the highly sensitive Ti0Pc are sufficiently maintained). In addition, the effect becomes more pronounced in systems with a small laser beam spot diameter or systems with a high process speed.Similarly, the effect works well in photoreceptor structures such as surface protective layers. .

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a general transfer type electrophotographic apparatus. FIG. 2 is a block diagram of a facsimile machine using an electrophotographic device as a printer. 1: Photoreceptor 2: Charging means 3: Exposure section 4: Developing means 5: Transfer means 6: Cleaning means 7: Pre-exposure means 8: Image fixing means. Agent Patent Attorney Jo Yamashita Hirahaku Figure 1 Figure 2

Claims (7)

[Claims] (1) In an electrophotographic photoreceptor having an organic photoconductive layer on a conductive support, the photoconductive layer includes (A) oxytitanium phthalocyanine and (B) a work function Wf≧5.45e.
An electrophotographic photoreceptor comprising a V azo pigment. (2) The electrophotographic photosensitive material according to claim 1, wherein the photoconductive layer is composed of two layers: a charge generation layer containing the component (A) and the component (B), and a charge transport layer. body. (3) The electrophotographic photoreceptor according to claim (2), wherein the charge transport layer is laminated on the charge generation layer containing the component (A) and the component (B). (4) The weight ratio of component (B) to component (A) is
The electrophotographic photoreceptor according to claim 1, wherein the electrophotographic photoreceptor has a content of 5 to 100%. (5) Component (A) has a diffraction angle 2θ±0.2° of 9.0° in the X-ray diffraction spectrum of CuK_α; 14.
4. The electrophotographic photoreceptor according to claim 1, wherein the electrophotographic photoreceptor is a crystal having strong peaks at 2°, 23.9°, and 27.1°. (6) An electrophotographic apparatus comprising the electrophotographic photoreceptor according to any one of claims (1) to (5). (7) A facsimile machine comprising the electrophotographic photoreceptor according to any one of claims (1) to (5) and having a receiving means for receiving image information from a remote terminal.