JPS6130267B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a photosensitive material for electrophotography, which comprises β-type copper phthalocyanine as a photoconductive substance, a mixture of an isocyanate compound having an aromatic ring and a polyol compound having an aromatic ring as a binder. An electrophotographic photosensitive material in which a photoconductive layer containing as a main component is formed on a conductive substrate, wherein the number of moles of isocyanate residues in the isocyanate compound N〓NCO ₎ and the number of moles of hydroxyl groups in the polyol compound It is characterized by containing a mixture of an isocyanate compound and a polyol compound such that the ratio N〓 _{NCO) /} N〓 OH) to N〓 _OH) is within the range of 1.0 to 1.6. be.

The electrophotographic photosensitive material (also referred to as photosensitive plate) of the present invention can use visible light to form an electrostatic latent image, and has excellent charging-light irradiation repetition characteristics against corona discharge.

Generally, electrophotographic photosensitive materials are obtained by forming a photoconductive layer on a conductive substrate. The photoconductive layer is
It is formed from an inorganic or organic photoconductive material such as vapor deposited amorphous selenium, zinc oxide-resin mixtures, poly-N-vinylcarbazole, etc. As mentioned above, the present invention uses β-type copper phthalocyanine as a photoconductive substance. Phthalocyanine pigments generally have excellent light resistance and heat resistance, and are non-polluting, so they can be used in various ways as photoconductive substances. Proposals and attempts have been made regarding the production of phthalocyanine and its application to electrophotographic light-sensitive materials. An example is shown below.

Regarding the manufacturing method of ε-type copper phthalocyanine and X-type metal-free phthalocyanine,
Disclosed in No. 2780 and Japanese Patent Publication No. 45-8102,
Regarding the application of phthalocyanine pigments to photosensitive materials for electrophotography, Japanese Patent Publication No. 49-4338, 50-3853
No. 47-6580, respectively.

The above-mentioned Japanese Patent Publication No. 49-4338 discloses that metal-free phthalocyanine, especially X-type metal-free phthalocyanine, has superior sensitivity compared to metal phthalocyanine.
It is stated that it gives good quality images, and it was published in Japanese Patent Application Publication No. 1989-
Publication No. 38543 states that ε-type copper phthalocyanine has superior charge acceptance compared to other crystalline forms of copper phthalocyanine, and may have better sensitivity than metal-free phthalocyanine, thus producing high-quality images. It is written that it is given.

The present inventors used β-type copper phthalocyanine, which has conventionally been considered to have low sensitivity and low charge acceptance, as a photoconductive substance, and contained a relatively large amount of an isocyanate compound having an aromatic ring as a binder. , an electrophotographic photosensitive material which has excellent electrophotographic properties by forming a photoconductive layer using a mixture of an isocyanate compound having an aromatic ring and a polyol compound having an aromatic ring, and is therefore capable of providing high-quality copied images. I discovered that it is possible to obtain The present invention is based on this discovery, and will be described below.

The β-type copper phthalocyanine used in the present invention is more stable than other crystalline forms of copper phthalocyanine. - Stable unless 4-dioxane or the like is used. That is, it does not change to a crystal form other than the β type due to the solvent effect. Therefore, a solvent capable of dissolving both the above-mentioned isocyanate compound and polyol compound, such as tetrahydrofuran, 1,2-dichlorothane, methyl ethyl ketone, cellosolve acetate, etc., is used.

Polyurethane resins with isocyanate active groups have excellent adhesion to metals, as well as excellent weather resistance, oil resistance, solvent resistance, abrasion resistance, tensile strength, and electrical insulation properties, and are flame retardant. As is well known, such an isocyanate compound is added to a polyol compound having an aromatic ring in a mixture in which N〓 _NCO) /N〓 _OH) is in the range of 1.0 to 1.6. 5-50% by weight of phthalocyanine
By forming a photoconductive layer consisting of a mixture preferably added in an amount of 10 to 30% by weight on a conductive support, electrophotographic properties such as corona discharge withstand voltage or its repetition properties are excellent. Furthermore, an electrophotographic light-sensitive material having excellent bending strength and capable of forming high-quality images can be obtained.

The isocyanate compound having an aromatic ring is as follows: A compound containing as a main component (Desmudur L manufactured by Bayer AG, West Germany), Compounds consisting of (Desmodyur T-65, Desmodyur T-80, Desmodyur T-100 manufactured by Nippon Polyurethane Co., Ltd.), (Diphenylmethane-4,4-diisocyanate) (Millionate MT manufactured by Nippon Polyurethane Co., Ltd.) (Polymethylene polyphenyl isocyanate) (Millionate MR manufactured by Nippon Polyurethane Co., Ltd.) Phenyl isocyanate, orthochlorophenyl isocyanate, methachlorophenyl isocyanate, parachlorophenyl isocyanate, 2,5-dichlorophenyl isocyanate, 3,4-dichlorophenyl isocyanate, 1,5-naphthalene diisocyanate, triphenylmethane triisocyanate , 4,4-dimethyl-3,3'-diphenyl isocyanate, and the like.

The above-mentioned polyol compound having an aromatic ring is a polymer compound obtained by polycondensation of diol, triol, and phthalic acid (adipic acid may be further added), and the above-mentioned diol is poly(oxypropylene) glycol. , poly(oxypropylene) poly(oxyethylene glycol,
Poly(oxybutylene) glycol and poly(oxytetramethylene) glycol are used, and the triols include poly(oxypropylene) triol, poly(oxypropylene) poly(oxyethylene) triol, and poly(oxypropylene) poly(oxyethylene). ) poly(oxypropylene) triol, etc. are used. Polyol compounds having an aromatic ring are commercially available under the trade names of Desmofene 800, Nitsuporan 125, and Nitsuporan 131 (manufactured by Nippon Polyurethane Co., Ltd.).

Examples of the present invention are shown below.

Example 1 A photoconductive layer forming liquid was prepared by grinding and mixing the following components using a ball mill.

Photoconductive layer forming liquid components: Part by weight β-type copper phthalocyanine (Sumitomo Cyanine Blue
LBG; manufactured by Sumitomo Chemical Co., Ltd.) 30 Isocyanate (Desmodyur T-65; manufactured by Nippon Polyurethane Co., Ltd.) 25 Polyol (Nituporan 125; manufactured by Nippon Polyurethane Co., Ltd.) 45 1,2-dichloroethane 900 The above photoconductive layer forming liquid was applied to an aluminum-deposited polyester film. It was applied on top by a casting method using a doctor blade, and after air drying for 10 minutes,
Heat and dry at 150℃ for 30 minutes to determine the thickness of the photoconductive layer.
An electrophotographic photosensitive material of the present invention having a thickness of 15.5 μm was obtained.
In this case, the value of N〓 _NCO) /N〓 _OH) of the isocyanate and polyol used as binders was 1.0.

The photosensitive material obtained as described above was subjected to +6 kV corona discharge for 20 seconds in a dark place to positively charge the photoconductive layer. Surface potential at this time
Vs, surface potential when left in the dark for 20 seconds after charging
V ₀ , then irradiated using a 20 lux white tungsten lamp, and the exposure amounts required to attenuate the surface potential by 1/2, 1/5, and 1/10 are E _1/2 , E _1/5 , and E _{1 . /
10} (lux/second) was measured, and the values shown below were obtained.

Vs = 1380V V ₀ = 1080V E _1/2 = 11.4 E _1/5 = 13.4 E _1/10 = 14.6 (lux seconds) The above photosensitive material was wound around a drum with a diameter of 15 cm.
It is rotated at a linear speed of 210 mm/sec, and the charging voltage of the corona discharge is set so that the surface potential becomes 600 V after about 1 second after being positively charged by corona discharge in the dark. The charging voltage at this time was +5.7kV.
Next, the surface of the photosensitive material is irradiated with an 8W fluorescent lamp to bring the surface potential to 0V, and then it is charged a second time. After repeating charging and light irradiation in this way 10,000 times, the surface potential becomes V _10,000. was measured and a value of 540V was obtained. This is 90% of the first surface potential. It can be seen that the repeatability against corona discharge is excellent.

Example 2 A photoconductive layer forming solution was prepared in the same manner as in Example 1 using the following components.

Photoconductive layer forming liquid component: Part by weight β-type copper phthalocyanine (Sumitomo Cyanine Blue
LBG) 20 Isocyanate (Desmodyur T-100) 38 Polyol (Desmofene 800) 42 Methyl ethyl ketone 900 Using the above photoconductive layer forming solution and in the same manner as in Example 1, a photoconductive layer of the present invention having a thickness of 10.9 μm was prepared. A photosensitive material for electrophotography was obtained. In this case N _{= NCO)} /N
The value of 〓 _OH) was 1.0.

Using the above photosensitive material, the properties were measured in the same manner as in Example 1, and the values shown below were obtained.

Vs = 1010V V ₀ = 780V E _1/2 = 23.4 E _1/5 = 42.9 E _1/10 = 56.6 (lux seconds) Using the above photosensitive material, perform the first charging in the same manner as in Example 1. The surface potential V ₁₀₀₀₀ after charging and light irradiation is repeated 10000 times with +600V is
At 570V, it showed 95% of the first time.

Example 3 A photoconductive layer forming solution was prepared in the same manner as in Example 1 using the following components.

Photoconductive layer forming liquid component: Part by weight β-type copper phthalocyanine (Sumitomo Cyanine Blue
LEG) 25 Isocyanate (Desmodyur T-65) 35 Polyol (Nituporan 125) 40 Tetrahydrofuran 900 Using the above photoconductive layer forming solution and in the same manner as in Example 1, electrophotographic photosensitive material with a photoconductive layer thickness of 10.4 μm was prepared. I got the material. In this case, the value of N〓 _NCO) /N〓 _OH) was 1.6.

Using the above photosensitive material, the properties were measured in the same manner as in Example 1, and the values shown below were obtained.

Vs = 1240V V ₀ = 1040V E _1/2 = 9.4 E _1/5 = 11.7 E _1/10 = 13.4 (lux seconds) V ₁₀₀₀₀ = 540V Using the above photosensitive material, conduct a +9.5kV corona discharge in a dark place. The surface potential Vs when the test was carried out for 20 seconds was 1440V. After leaving this in a dark place for 3 seconds, it was irradiated with a 500 lux white tungsten lamp, and after the light was attenuated, a 19.5 kV corona discharge was performed again and the surface potential Vsr was measured.
I got 1440V. It can be seen that the withstand voltage of the photoconductive layer against corona discharge is at least +9.5 kV.

Comparative examples are shown below for comparison with the electrophotographic light-sensitive material of the present invention.

Comparative Example 1 A photosensitive material was obtained in the same manner as in Example 1 except that a photoconductive layer forming liquid prepared with the following components was used.

Photoconductive layer forming liquid component: Part by weight β-type copper phthalocyanine (Sumitomo Cyanine Blue
LBG) 20 Isocyanate (Desmodyur T-65) 38 Polyol (Nituporan 125) 42 1,2-dichloroethane 900 The value of N〓NCO ₎ /N〓OH ₎ in the case of this light-sensitive material was 1.8.

Using the above photosensitive material, the properties were measured in the same manner as in Example 1, and the values shown below were obtained.

Vs = 910 V ₀ = 650 E _1/2 = 4.9 E _1/5 = 5.4 E _1/10 = 6.0 (lux seconds) Also, compared to the initial surface potential of 600 V due to the same corona discharge as in Example 1, charging and 10000 light irradiation
After repeating the test several times, the surface potential V ₁₀₀₀₀ was measured and found to be 300V. It can be seen that the charging characteristics due to corona discharge and the repetition characteristics of light irradiation are inferior.

Comparative Example 2 A photosensitive material was obtained in the same manner as in Example 1, except that a photoconductive layer forming liquid prepared with the following components was used.

Photoconductive layer forming liquid component: Part by weight β-type copper phthalocyanine (Sumitomo Cyanine Blue
LBG) 20 Isocyanate whose main component is hexamethylene diisocyanate (Coronate HL; manufactured by Nippon Polyurethane Co., Ltd.) 40 Polyol (Nituporan 125) 40 1,2-dichloroethane 900 In the case of the above photosensitive material, N〓 _NCO) /N〓 _OH) teeth
1.0, but there is no aromatic ring in the isocyanate component.

Using the above photosensitive material, the properties were measured in the same manner as in Example 1, and the values shown below were obtained.

Vs = 1180 V ₀ = 1000 E _1/2 = 18.3 E _1/5 = 22.9 E _1/10 = 26.9 (lux seconds) Also, for the initial surface potential of 600 V due to corona discharge, which is the same as in Example 1, charging and The surface potential V ₁₀₀₀ after repeating light irradiation 1000 times is 420V, and V ₁₀₀₀₀ after repeating 10000 times decreases to 250V, indicating that the charging characteristics due to corona discharge and the repetition characteristics of light irradiation are inferior.

As described above, when an isocyanate compound and a polyol compound are used as binders to form a photoconductive layer of an electrophotographic photosensitive material using β-type copper phthalocyanine, the number of moles of isocyanate residues in the isocyanate compound is N. 〓NCO ₎ and
Number of moles of hydroxyl groups in the above polyol compound N〓 _NCO)
When the ratio N〓 _NCO) /N〓 _OH) exceeds 1.6, or when an aromatic ring is not present in the isocyanate compound and the polyol compound, the repeatability of charging by corona discharge and light irradiation is poor.

Claims (1)

[Claims] 1. A photosensitive material for electrophotography in which a photoconductive layer made of a mixture of fine powder of β-type copper phthalocyanine dispersed in a binder is formed on a conductive substrate,
The binder has a ratio of the number of moles of isocyanate residues N〓 _NCO) in the isocyanate compound having an aromatic ring to the number of moles of hydroxyl groups N〓 _OH) in the polyol compound having an aromatic ring, N〓 _NCO) /N〓 _OH). The value is 1.0 or
The electrophotographic photosensitive material described above is a resin obtained by blending the isocyanate compound and the polyol compound so as to fall within the range of 1.6.