Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Radiation-sensitive composition or product
Reexamination Certificate
2001-10-15
2003-01-07
Goodrow, John (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Radiation-sensitive composition or product
C430S078000, C540S141000
Reexamination Certificate
active
06503673
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a phthalocyanine composition, a process for the production thereof and an electrophotographic photoreceptor. More specifically, it relates to a phthalocyanine composition suitable for use in an electrophotographic photoreceptor that has a high charge potential and high sensitivity and which is capable of exhibiting stable performances without causing a change in various properties in repeated use, a process for efficiently producing the above phthalocyanine composition and an electrophotographic photoreceptor to which the above phthalocyanine composition is applied and which has the above excellent properties.
2. Related Art Statement
In recent years, electrophotography is not only used in the field of copying machines, but also it now has come into wide use in the fields of a printing plate, a slide film and a microfilm where photography has been conventionally used. Further, studies are being made on the application of electrophotography to a high-speed printer using a laser, an LED or a CRT as a light source. Further, studies have recently also begun concerning the application of photoconductive materials to uses other than the electrophotographic photoreceptor, such as electrostatic recording elements, sensor materials and EL devices. A photoconductive material and an electrophotographic photoreceptor using the same are therefore being demanded to satisfy higher levels in wider fields of applications. For an electrophotographic photoreceptor, inorganic photoconductive materials such as selenium, cadmium sulfide, zinc oxide and silicon have been known, and these have been widely studied and put into practical use. These inorganic materials have various advantages and at the same time have various disadvantages. For example, selenium has defects that production conditions with it are severe and that it is easily crystallized due to heat or mechanical impact. Cadmium sulfide and zinc oxide are poor in humidity resistance and durability. It is pointed out that silicon has poor chargeability and difficulty of production. Further, selenium and cadmium sulfide also involve toxicity problems.
In contrast, organic photoconductive materials have advantages that they are excellent in film-formability and also excellent in flexibility, that they are light in weight and excellent in transparency and that they are feasible for designing a photoreceptor to light in a wide wavelength region according to a proper sensitizing method. For these reasons, practical use thereof is gradually attracting attention.
Meanwhile, a photoreceptor for use in electrophotography is required to satisfy the following general basic properties. That is, (1) it is to have a high chargeability to corona discharge in a dark place, (2) it is to be free of much leakage of an obtained charge in a dark place (dark decay), (3) it is to readily dissipate a charge upon irradiation with light (light decay), and (4) it is to be free of residual charge after irradiation with light.
However, as organic photoconductive materials, photoconductive polymers including polyvinylcarbazole have been so far studied in various ways, while these are not necessarily satisfactory in film formability, flexibility and adhesion and cannot be said to fully have the above basic properties as a photoreceptor.
Organic low-molecular-weight photoconductive compounds can give a photoreceptor excellent in film formability, adhesion and mechanical properties such as flexibility by selecting a binder for forming the photoreceptor, while it is difficult to find out a compound suitable for retaining high-sensitivity properties.
For overcoming the above problems, there have been developed organic photoreceptors having higher sensitivity properties imparted by using different materials which separately have charge generation function and a charge transportation function. These photoreceptors called a function-separation type have a feature in that materials suitable for individual functions can be selected from a broad range of materials, and a photoreceptor having predetermined performances can be easily produced, so that studies have been extensively under way.
Of these materials, various materials such as phthalocyanine pigments, squarilium dyes, azo pigments and perylene pigments have been studied as a material having the function of charge generation. Above all, azo pigments have been studied in various ways and practically have been in wide use since they can have diversified molecular structures and can be expected to show high charge generation efficiency. However, it has not yet been clear what relationships are there between the molecular structure and the charge generation efficiency of the azo pigments. Under the circumstances, a huge volume of studies have been made on syntheses thereof to find out optimum structures, while there have not yet been obtained any azo pigments which satisfy demands of the above basic properties and high durability as a photoreceptor.
In recent years, further, laser beam printers having advantages of a high speed, a high-quality image and non-impact properties by using laser beam in place of conventional white light are widely used together with advanced data processing systems, and it is accordingly desired to develop materials that can comply with requirements therefor. Of laser beams, a semiconductor laser, which has been and is increasingly applied to a compact disc, an optical disc, etc., in recent years and has been remarkably technically developed, is actively applied to the field of printers as a compact and highly reliable light source material. In this case, the wavelength of the light source is approximately 780 to 830 nm, and it is therefore intensely desired to develop a photoreceptor having high-sensitivity properties to light in a near infrared region. Under the circumstances, developments of photoreceptors using phthalocyanines particularly having light absorption in a near infrared region are actively under way.
Not only phthalocyanines differ in absorption spectrum, photoconductivity, etc., depending upon central metals, but also phthalocyanines having an identical central metal differ in the above various properties depending upon crystal forms, and it is reported that phthalocyanines having specific crystal forms are selected for an electrophotographic photoreceptor.
For example, concerning oxytitanium phthalocyanine (to be sometimes abbreviated as “TiOPc” hereinafter), JP-A-61-217050 discloses an &agr;-form TiOPc having main diffraction peaks at Bragg angles (2&thgr;±0.2°) of 7.6°, 10.2°, 22.3°, 25.3° and 28.6° in X-ray diffraction spectrum, and JP-A-62-67094 discloses a &bgr;-form TiOPc having main diffraction peaks at Bragg angles of 9.3°, 10.6°, 13.2°, 15.1°, 15.7°, 16.1°, 20.8°, 23.3°, 26.3° and 27.1°. However, these phthalocyanines fail to fully satisfy required high properties.
Even if phthalocyanines are limited to those which have a peak at Bragg angle (2&thgr;±0.20°) of 27.2° in X-ray diffraction spectrum, II type TiOPc reported in JP-A-62-67094 has poor chargeability and low sensitivity. JP-A-64-17066 discloses a Y-form TiOPc that has a main diffraction peaks at 9.5°, 9.7°, 11.7°, 15.0°, 23.5°, 24.1°, 27.3° and exhibits relatively good sensitivity. However, it has a problem that it causes transformation to other crystal form during dispersing and that its dispersion is poor in stability with the passage of time.
Further, there are reports on the use of a mixed crystal or a simple mixture of two or more phthalocyanines as a charge-generating material for an electrophotographic photoreceptor. For example, JP-A-1-142659 discloses an &agr;-form TiOPc composition containing &agr;-TiOPc and metal-free phthalocyanine (to be sometimes referred to as “H
2
Pc” hereinafter). JP-A-2-170166 discloses a mixed crystal formed of two or more phthalocyanines having different central metals. JP-A-2-272067 discloses an X-form H
2
Pc composition containing TiOPc and H
2
Pc. JP-A-4-351673 discloses a m
Horiuchi Tamotsu
Nagamura Hideki
Okaji Makoto
Goodrow John
Mitsubishi Paper Mills Limited
Nixon & Vanderhye P.C.
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