JP2001242649A - Electrophotographic method and electrophotographic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic method and an electrophotographic device with improved sensitivity of white color or enhanced sensitivity for short wavelength. SOLUTION: In the electrophotographic method and the device therefor, the photoreceptor used has photosensitive layers containing a charge generating material and a charge transfer material in the same layer or separated layers formed on a conductive supporting body and contains a fluorescent material having the wavelength of fluorescent light in the absorption wavelength region of the charge generating material. The photoreceptor is irradiated with light of 380 nm to 420 nm wavelengths.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic method and an electrophotographic apparatus having high sensitivity, particularly excellent blue sensitivity.

[0002]

2. Description of the Related Art Conventionally, inorganic materials such as selenium, cadmium sulfide, and zinc oxide have been used as a photoconductive material of a photoreceptor used in an electrophotographic system. Generally, the electrophotographic method is to charge a photoconductive photoreceptor in a dark place, for example, by corona discharge, then expose the image, and selectively dissipate the charge only in the exposed area to form an electrostatic latent image. An image forming method in which an image is formed by developing and visualizing the latent image portion with fine particles (toner) composed of a colorant such as a dye or a pigment and a binder such as a polymer substance to form an image. one of.

In such an electrophotographic system, the basic characteristics required of a photoreceptor are (1) that it can be charged to an appropriate potential in a dark place, (2) that there is little charge dissipation in a dark place, And (3) charge can be quickly dissipated by light irradiation.

[0004] The above-mentioned inorganic substances have many advantages and also have various disadvantages. For example, selenium, which is widely used at present, sufficiently satisfies the above conditions (1) to (3), but the production conditions are difficult, the production cost is high, there is no flexibility, and the selenium is processed into a belt shape. Difficult to do,
Since it is sensitive to heat and mechanical shock, it also has drawbacks such as requiring careful handling. Cadmium sulfide and zinc oxide are dispersed in resin as a binder and used as photoreceptors, but they are used repeatedly as they are due to mechanical defects such as smoothness, hardness, tensile strength, and friction resistance. Can not do it.

In recent years, electrophotographic photoreceptors using various organic substances have been proposed in order to eliminate the disadvantages of these inorganic substances, and some of them have been put to practical use. For example, a photoreceptor containing an organic pigment as a main component (JP-A-47-37543)
JP-A-47-10735), a eutectic complex of a kind of polymer formed of a pyrylium-type dye and a carbonate polymer having an alkylidene diarylene group in a repeating unit. Described in the official gazette). Although these photoreceptors have excellent properties and are considered to be of high practical value, in electrophotography, considering various requirements for photoreceptors, these requirements are still insufficient. At present, no satisfactory products have been obtained.

On the other hand, the spectral absorption of a photoreceptor is governed by the spectral absorption of an organic pigment or a polymer eutectic complex as a main component. A photoreceptor using these materials has excellent sensitivity in the visible region of 500 nm or more. Is remarkably reduced at 500 nm or less. This is because the absorbance of the above-mentioned material is sharply reduced below 500 nm. As a result, of course, the sensitivity of the photoconductor to white light is reduced, but in particular, considering analog color electrophotography, high-speed image processing cannot be performed due to its low sensitivity to blue light (blue sensitivity). Have

In order to improve this disadvantage, for example, Japanese Patent Laid-Open
0-16538 describes a single-layer photoreceptor in which a distyryl compound as a blue sensitivity sensitizer is added in addition to a eutectic complex of a pyrylium salt and a polycarbonate, a photoconductor that does not absorb blue light.

On the other hand, Japanese Patent Application Laid-Open No. 1-312549 reports that in a laminated photoreceptor comprising a charge generation layer and a charge transport layer, the sensitivity is increased by adding a blue sensitivity sensitizer to a layer containing a charge generation substance. Have been. In the inventions described in these publications, the reason why the blue sensitivity is improved is not clearly understood, but is merely described according to some chemical or electrical mechanism.
For this reason, even in a single-layer photoreceptor or a laminated photoreceptor, only attempts have been made to add a blue sensitivity sensitizer to a layer in which a charge generating substance is present.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrophotographic method and an electrophotographic apparatus in which white sensitivity is improved or short-wavelength sensitivity is increased.

[0010]

According to the present invention, a photosensitive layer containing a charge-generating substance and a charge-transporting substance in the same or separate layers is provided on a conductive support. An electrophotographic method comprising irradiating light of 380 nm to 420 nm using a photoreceptor containing a fluorescent substance having a fluorescent wavelength in a wavelength region. An electrophotographic photoreceptor characterized by further containing a substance is provided. Also provided is a case where the fluorescent substance having a fluorescence wavelength in the absorption wavelength region of the charge generation substance is the charge transport substance itself.

Next, the present invention will be described in more detail with reference to the drawings. 1 and 2 are cross-sectional views of two representative examples of the photoreceptor according to the present invention, wherein 1 is a conductive support, 2 is a photosensitive layer, 3 is a charge generating material, 4 is a charge transport layer,
5 is a charge generation layer, 6 is a layer containing a fluorescent substance, and 7 is a fluorescent substance.

FIG. 1 shows a structure in which a charge generation layer 5 mainly composed of a charge generation substance 3 and a charge transport layer 4 are sequentially provided on a conductive support 1. At this time, the fluorescent substance 7 is contained in the charge transport layer (the fluorescent substance may be a continuous phase in a completely solid solution state with the charge transport substance and the medium). In this photoreceptor, when light is irradiated on the charge transport layer, light in a wavelength region having no wavelength region absorbed by the fluorescent substance and the charge transport substance directly reaches the charge generation layer and generates charges. On the other hand, light absorbed by the fluorescent substance is also converted into fluorescence having a wavelength in a region where the charge generating substance has absorption, and finally absorbed by the charge generating substance and used for charge generation. Therefore, as a result, light in a wavelength region that is not absorbed by the charge generating material is also effectively used because it is converted into light in a wavelength region in which the charge generating material has absorption. When the charge transport substance has fluorescence, the fluorescent substance may be the charge transport substance itself.

FIG. 2 shows a structure in which a charge generation layer 5, a charge transport layer 4, and a layer 6 containing a fluorescent substance are sequentially laminated on a conductive support. In this case, the layer 6 may include a charge transport material for transporting charges. In this case, there is an advantage that the rate of absorption of the fluorescent substance by the charge transporting substance is hidden by the charge transporting substance, as compared with the case where the fluorescent substance is contained in the charge transporting layer. In addition,
Also in this case, when the charge transport material has fluorescence, the fluorescent material may be the charge transport material itself.

In the present invention, the thickness of the charge transport layer is 5 to 5.
50 μm, preferably 10-20 μm, the charge transport layer 4
The amount of the charge transporting material in the above is 10 to 95% by weight, preferably 30 to 90% by weight. The thickness of the charge generation layer 5 is 5 μm or less, preferably 2 μm or less, and the amount of the charge generation substance occupying the charge generation layer is 10 to 10 μm.
It is 100%, preferably 50-90% by weight. Also,
The layer 6 containing the fluorescent substance has a thickness of 0.05 to 5 μm. When the fluorescent substance does not have charge transporting ability, it is desirable to add a charge transporting substance to the layer 6 at the same time in order to prevent a residual potential. The amount of the fluorescent substance added depends on the film thickness and the extinction coefficient of the substance, but only an amount sufficient to absorb light is necessary. Cause. Of course, this does not apply to the case where the fluorescent substance has the charge transporting ability. On the other hand, depending on the compound, the fluorescence may be reduced when the added concentration is high. When a fluorescent substance is contained to increase the sensitivity of the electrophotographic photoreceptor at the fluorescent substance absorption wavelength, if the concentration of the fluorescent substance is too high, the fluorescence generation yield is reduced and the sensitivity may be reduced. . The reason for this is not clear at present, but is considered as follows. That is, assuming that the charge transport substance is A, the fluorescent substance is B, and the excited state of the B molecule is B *, if the concentration of the B molecule is high and the distance between the B molecules is short, the excited state easily moves between the B molecules, Accordingly, non-radiative deactivation occurs between the excited B molecules (B *) or by contact between the B * and the B molecules. Conversely, by reducing the B molecule concentration, non-radiative deactivation is suppressed, and the fluorescence generation efficiency is increased. Therefore, in the present invention, it is preferable that the molar ratio between the fluorescent substance (B) and the charge transport substance (A) is set to 1/1 to 1/400. If the molar ratio of the two is less than 1/400, the energy transfer rate from A to B decreases and the fluorescence from B decreases, which is not desirable.

The above is the main constitution of the photoreceptor in the present invention, but a method of giving a gradient to the concentration of the fluorescent substance in the charge transport layer is also a preferred embodiment.

The mechanism of sensitization by the addition of these fluorescent substances is not always clear at the present time, but the following are considered to be the main factors. That is, the fluorescence emitted by the fluorescent substance absorbing visible light is absorbed by the charge generating substance by overlapping with the absorption of the charge generating substance, leading to charge generation (of course, other mechanisms, such as, for example, However, factors such as the fact that the exciton of the fluorescent substance transfers energy over a long distance to act on the charge generating substance are not completely denied.)

As in this presumed mechanism, the fluorescent substance does not need to be present in the layer containing the charge generating substance as in the above-mentioned prior art, but has a sensitizing effect even if it is contained in other layers. The present inventors have found. That is, it is considered that, due to the large refractive index in the photosensitive layer, a large amount of fluorescent light is absorbed by the charge generating substance without being removed from the surface to the outside under the condition of total reflection, thereby enabling sensitization.

An advantage of these photoreceptors is that light having a wavelength in a region where the absorption of the charge generating substance is small is also converted into light in the absorption area of the charge generation substance by the fluorescent substance and is effectively used for charge generation. Is mentioned. Further, in the case of a photoconductor in which a layer containing at least a charge transport material from the irradiation light side, a layer containing a charge generation material, and then a conductive support are laminated in this order, the charge transport material irradiates the charge generation material with light. In the case where the fluorescent substance is partially hidden at a specific wavelength, it is better to add such a fluorescent substance to the charge transport layer or to the irradiation side layer than to add the fluorescent substance to the charge generation layer.
Light is not absorbed by the charge transport material due to the generation of fluorescence, but is converted to the wavelength side where the absorption of the charge generation material exists, so that more effective light utilization may be possible.

Of course, as expected from these estimation mechanisms, in order to enhance sensitization, the fluorescence generation efficiency is high and the absorption is in the wavelength region where the absorption of the charge generating substance is small. For example, a method of selecting a substance that emits fluorescence in a wavelength region having a large wavelength according to the type of the charge generating substance is effective. The fluorescent substance must have a fluorescence generation efficiency of at least 0.05 or more, preferably 0.3 or more, and below that, the sensitizing effect is small.

As the conductive support 1 used for the photoreceptor of the present invention, a metal plate or metal foil of aluminum or the like,
Examples include a plastic film on which a metal such as aluminum is vapor-deposited, or a paper subjected to a conductive treatment.

As the binder, polyamide, polyurethane, polyester, epoxy resin, polyketone,
Condensation resins such as polycarbonate, and vinyl polymers such as polyvinyl ketone, polystyrene, poly-N-vinyl carbazole, and polyacrylamide are used. Insulating and adhesive resins can all be used. If necessary, a plasticizer is added to the binder. Examples of such a plasticizer include halogenated paraffin, polychlorinated biphenyl, dimethylnaphthalene, and dibutylphthalate.

As the charge transport material in the present invention, any of conventionally known materials can be used, and it is not limited to a specific material. Such charge transport materials include
For example, triphenylamine type, hydrazone type, stilbene type and the like can be mentioned. Examples of the charge generating substance in the present invention include inorganic pigments such as selenium, selenium-tellurium, cadmium sulfide, cadmium sulphide-selenium, α-silicon, and organic pigments such as C.I. Pigment Blue 25 (color index CI 21180) and C.I. Pigment Red 41 (CI 21200), CI Acid Red 52 (CI 45100), CI Basic Red 3 (CI45210), an azo pigment having a carbazole skeleton (described in JP-A-52-95033), and having a distyrylbenzene skeleton Azo pigments (JP-A-53-133445) and azo pigments having a triphenylamine skeleton (JP-A-53-13234)
No. 7), azo pigments having a dibenzothiophene skeleton (JP-A-54-21728), azo pigments having an oxadiazole skeleton (described in JP-A-54-12742), and azo pigments having a fluorenone skeleton (Described in JP-A-54-22834), an azo pigment having a bisstilbene skeleton (described in JP-A-54-17733), and an azo pigment having a distyryloxadiazole skeleton (described in JP-A-54-2129). Azo pigments having a distyrylcarbazole skeleton (JP-A-54-149).
Azo pigments such as C.I. Pigment Blue 16 (CI 74100), and C.I.
73410), C-I Bad Die (CI7303)
0) and perylene pigments such as Argo Scarlet B (manufactured by Bayer) and Indanthrene Scarlet R (manufactured by Bayer). These charge generating substances may be used alone or in combination of two or more.

The fluorescent substance used in the present invention includes:
For example, the following may be mentioned, but the present invention is not limited to these, and any one may be used as long as it has fluorescence in a wavelength region where the charge generating substance has absorption and has relatively high fluorescence generation efficiency. it can.

[0024]

Embedded image (R ¹ : alkyl group, aryl group, R ² : 2- (4-aminostyryl) group, X : Is oxygen or sulfur) [Representative example] 4- (dicyanomethylene) -2-methyl-6
-[2- (9-durolidyl) ethenyl] -4H-pyran 4- (dicyanomethylene) -2-methyl-6- (p-dimethyl-aminostyryl) -4H-pyran

Embedded image

Embedded image (R ¹ , R ² : alkyl group, halogen, haloalkyl group, etc.)

[Representative Example] N, N'-di (p-tolyl) -3,4,9,10-perylenebis- (dicarboximide) N, N'-diphenyl-3,4,9,10-perylenebis -(Dicarboximide)

[0026]

Embedded image (R ¹ , R ² : hydrogen, carboxy group, alkanoyl group, aryl group, etc. R ² : hydrogen, alkyl group, haloalkyl group, carboxy group, etc. R ³ : hydrogen, alkyl group R ⁴ : amino group, hydroxy group)

[Representative example] 4,6-dimethyl-7-ethylaminocoumarin 7-amino-3-phenylcoumarin 7-dimethylamino-4-methylcoumarin 7-hydroxy-3-acetylcoumarin 7-hydroxy-3-cyano Coumarin

Embedded image (R ¹ : hydrogen, substituted or unsubstituted alkyl group, A: hydrogen, cyano group, halogen, carboxy group, arylsulfonyl group, alkylsulfonyl group, etc. B: hydrogen, hydroxy group, mercapto group, amino group, arylamino group [Representative Examples] R ¹ ; Methyl, A; Chlorine, B; Hydroxy group R ¹ ; Methyl, A; Chlorine, B; —O ⁻ Na ⁺ ion

Various Carbostyril Dyes [Typical Examples] 7-Amino-4-methylcarbostyril 7-Dimethylamino-4-methylcarbostyril

Embedded image (R ¹ ; hydrogen, methyl group, tertiary amino group, R ² ; alkyl group Y ; Enzymes, sulfur X ^-; anion)

[Representative example] 4- (4-dimethylaminophenyl) -2- (4-methoxyphenyl) -6-phenylpyrylium perchlorate 4,6-diphenyl-2- (4-ethoxyphenyl)-
Thiapyrylium p-toluenesulfonate

Various polymethine dyes [Typical examples]

Embedded image (N = 1 to 3 R ¹ ; alkyl group X ⁻ ; anion) [Representative example] 2,2′-diethyloxacarbocyanine iodid

Embedded image (N = 1 to 3 R ¹ ; alkyl group X ⁻ ; anion)

[Representative example] 1,1'-diethyl-2,2'-carbocyanine iodide

Embedded image (N = 1 to 3 R; alkyl group X ⁻ ; anion)

[Representative Example] 2- (2-anilino-1-ethylenyl) -benzothiazoleethiodide

Arylbutadienes [Typical Examples] 1-phenyl-4- (p-biphenylyl) -butadiene 1,4-di- (β-naphthyl) -butadiene 1,4-di- (p-methoxyphenyl) -butadiene Condensed cyclic hydrocarbon perylene, trinaphthylene, pentacene, naphthacene,
9,10-diphenylanthracene polycyclic hydrocarbon terphenyl, quarterphenyl and other various xanthene dyes

[Typical example]

Embedded image

Embedded image

Benzoxazole derivative [Representative example] 2-p-tolyl-6-hydroxybenzoxazole 2-phenyl-6-hydroxy-5-trioxazole

Acridine Derivatives [Typical Examples] 4-ethyl-9-aminoacridine 3-aminoacridine 9-aminoacridine

Quinoline derivatives (Example) 3,4-diamino-6,7-benzoquinoline

Oxazole derivative [Representative example] 2,5-diphenyloxazole 5-phenyl-2-styryloxazole 2-phenyl-5- (p-anisyl) oxazole

Embedded image (A ^{1 and} A ² each represent a substituted or unsubstituted alkyl group or aryl group and may be the same or different.) Ar is a substituted or unsubstituted polycyclic or condensed polycyclic compound. )

[Typical example]

[Table 1]

[0040]

Embedded image [Wherein A ¹ and A ² are carbazolyl, pyridyl, thienyl, indolyl, furyl or substituted or unsubstituted phenyl, styryl, naphthyl or anthryl, respectively. Is a dialkylamino group containing a substituted alkyl group, a substituted or unsubstituted diarylamino group, an alkyl group, an alkoxy group, a carboxy group or an ester thereof, a halogen atom, a cyano group, an amino group, a nitro group and an acetylamino group. Represents a selected group. R ^{1 to} R ⁴ represent a hydrogen atom, a cyano group,
Represents an acyl group, a substituted or unsubstituted alkyl group or an aryl group. ]

[Typical example]

[Table 2]

[0042]

Embedded image [In the formula, n is an integer of 0 or 1, R ₁ has a hydrogen atom, an alkyl group containing a substituted alkyl group, or a substituted or unsubstituted phenyl group, and Ar ₁ represents a substituted or unsubstituted aryl group, R ₅ represents an alkyl group including a substituted alkyl group, or a substituted or unsubstituted aryl group or a hydrogen atom;

Embedded image

Embedded image Represents a 9-anthryl group or a substituted or unsubstituted carbazolyl group, wherein R ₃ and R ₄ represent an alkyl group containing a substituted alkyl group, a substituted or unsubstituted aryl group, and R ₃ and R ₄ represent May be the same or different,
R ₄ may form a ring), and m is 0, 1, 2,
Or, it is an integer of 3 and when m is 2 or more, R ₂ may be the same or different. When n is 0, A and R ₁ may form a ring together. ]

[Typical example]

[Table 3]

[0044]

Embedded image [In the formula, R represents an alkyl group containing a substituted alkyl group, or a substituted or unsubstituted aryl group, and A represents a substituted amino group, a substituted or unsubstituted aryl group, or an allyl group. ]

[0045]

Embedded image [Wherein, X represents a hydrogen atom or a halogen atom;
Represents a substituted alkyl group or a substituted or unsubstituted aryl group, and A represents a substituted amino group, or a substituted or unsubstituted aryl group or allyl group. ]

[0046]

Embedded image [In the formula, R ₁ , R ₂ and R ₃ represent hydrogen, a lower alkyl group, a lower alkoxy group, a dialkylamino group or a halogen atom, and n represents 0 or 1. ]

[0047]

Embedded image Wherein, R ₁ represents an alkyl group, a substituted or unsubstituted phenyl group or a heterocyclic group 1 to 11 carbon atoms, R _2,
R ₃ may be respectively identical or different and are hydrogen, an alkyl group having 1 to 4 carbon atoms, a hydroxyalkyl group, chloroalkyl group, a substituted or unsubstituted aralkyl group or aryl group, also, R ₂ and R ₃ may combine with each other to form a nitrogen-containing heterocyclic ring. R ₄ may be the same or different and represents hydrogen, an alkyl group having 1 to 4 carbon atoms, an alkoxy group or halogen. ]

[0048]

Embedded image [In the formula, R represents a hydrogen atom or a halogen atom, and Ar represents a substituted or unsubstituted phenyl group, naphthyl group, anthryl group or carbazolyl group. ]

[0049]

Embedded image [Wherein R ₁ is hydrogen, halogen, cyano group, carbon number 1-4)
Represents an alkoxy group or an alkyl group having 1 to 4 carbon atoms, and Ar is

Embedded image

Embedded image R ₂ represents an alkyl group containing a substituted alkyl group or a substituted or unsubstituted phenyl group; R ₃ represents hydrogen, halogen, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms or a dialkylamino group; Wherein n is 1 or 2, and when n is 2, R ₃ may be the same or different, and R ₄ and R ₅ are hydrogen, a substituted or unsubstituted alkyl group having 1 to 4 carbon atoms or a substituted or unsubstituted alkyl group. Or an unsubstituted benzyl group,
Alternatively, it represents a substituted or unsubstituted phenyl group. ]

[0050]

Embedded image [Wherein, R ₁ represents an alkyl group containing a substituted alkyl group, or a substituted or unsubstituted phenyl group, and R ₂ represents a hydrogen atom, a lower alkyl group, a lower alkoxy group, a halogen atom, a nitro group, an amino group, A dialkylamino group containing an alkyl group or a substituted or unsubstituted diarylamino group; n represents an integer of 1 or 2; ]

The photosensitive member of the present invention may be provided with an adhesive layer or a barrier layer between the conductive support and the photosensitive layer, if necessary. Materials used for these layers include polyamide, nitrocellulose, aluminum oxide and the like, and the thickness thereof is preferably 1 μm or less. In order to perform copying using the electrophotographic photoreceptor of the present invention, the photoreceptor is charged, exposed, developed, and, if necessary, transferred to paper or the like. The photoreceptor of the present invention has excellent advantages such as high sensitivity and flexibility.

[0052]

The present invention will be described in more detail with reference to the following examples. All parts are by weight. Example 1 As a charge generating material, 76 parts of the following bisazo pigment, 1260 parts of a 2% tetrahydrofuran solution of a polyester resin (Vylon 200, manufactured by Toyobo Co., Ltd.) and 3700 parts of tetrahydrofuran were pulverized and mixed in a ball mill to obtain. The dispersion was applied on an aluminum surface on a conductive support made of a polyester base on which aluminum was deposited by using a doctor blade, and was naturally dried to form a charge generation layer having a thickness of about 1 μm. Further, a mixture of the following fluorescent substance and the following charge transport substance (weight ratio (1: 6)) 2
Part, polycarbonate resin (Panlite K1300,
2 parts and 16 parts of tetrahydrofuran were mixed and dissolved to form a solution. The solution was applied on the charge generation layer using a doctor blade, and was applied at 80 ° C. for 2 minutes at 120 ° C.
The resultant was dried at a temperature of 5 ° C. for 5 minutes to form a charge transporting layer containing a fluorescent substance having a thickness of about 20 μm.

[Table 4]

Example 2 A photoconductor of Example 2 was prepared in the same manner as in Example 1, except that the fluorescent substance was perylene and the weight ratio of the fluorescent substance to the charge transporting substance was 1:15.

Example 1-2 Example 1 was repeated in the same manner as in Example 1 except that the amount of the charge transporting substance was 2 parts and the fluorescent substance was not added.
Example 1-2 was obtained in which the charge transport layer was 20 μm.

Example 3 As a charge generating substance, 76 parts of the same bisazo pigment as in Example 1, 1260 parts of a 2% tetrahydrofuran solution of a polyester resin (Vylon 200, manufactured by Toyobo Co., Ltd.) and 3700 parts of tetrahydrofuran were charged in a ball mill. The resulting dispersion is applied on an aluminum surface on a conductive support made of aluminum-evaporated polyester base using a doctor blade, and dried naturally to form a charge generation layer having a thickness of about 1 μm. did. On the other hand, 2 parts of the same compound as in Example 1 was used as a charge transport material, and a polycarbonate resin (Panlite K1300, manufactured by Teijin Limited)
After mixing and dissolving 2 parts and 16 parts of tetrahydrofuran to form a solution, the solution was applied on the charge generation layer using a doctor blade and dried at 80 ° C. for 2 minutes and at 120 ° C. for 5 minutes to obtain a solution having a thickness of about 18 μm. A charge transport layer was formed. Further, 2 parts of the same fluorescent substance as in Example 1, 2 parts of a polycarbonate resin (Panlite K1300, manufactured by Teijin Ltd.) and 16 parts of tetrahydrofuran were mixed and dissolved to form a solution, which was then placed on the charge transport layer. The resultant was coated with a doctor blade and dried at 80 ° C. for 2 minutes and at 120 ° C. for 5 minutes to form a fluorescent layer having a thickness of about 2 μm. Thus, a photoreceptor of Example 3 was obtained.

Example 4 A photoconductor of Example 4 was obtained in the same manner as in Example 3 except that the following compound was used as the fluorescent substance.

Embedded image Next, in order to examine the sensitivity of the thus obtained laminated electrophotographic photosensitive member in the visible region, an electrostatic copying paper test apparatus (SP428, manufactured by Kawaguchi Electric Works) was used for the photosensitive member in a dark place. After charging by performing a −6 kv corona discharge for 20 seconds, the device is left in a dark place for another 20 seconds, and then subjected to surface potential V.
o (V) was measured. Then, a tungsten lamp light is irradiated so that the illuminance on the surface of the photoreceptor becomes 4.5 lux, and an exposure amount E1 / 2 (lux seconds) until the potential from -800 volts becomes 1/2 and 1/10. , E1 / 10
(Looks second) was calculated. Table 5 shows the results.

[Table 5]

Further, in order to examine the photosensitive wavelength range of the photosensitive member obtained above, the spectral sensitivity was measured by the following measuring procedure. First, the surface potential of the photoreceptor is charged to −800 volts or more by corona discharge in a dark place.
Dark decay was performed until the voltage reached 0 volt, and when the surface potential reached -800 volts, the photosensitive member was irradiated with monochromatic light of 1 μW / cm ² , which was separated using a monochromator. Then, the time (second) until the surface potential attenuated to -400 volts was obtained, and the half-exposure amount (μW · sec / cm ² ) was calculated. On the other hand, a potential difference actually obtained by exposure is obtained by subtracting a potential attenuation due to dark decay from an apparent potential difference of 400 volts obtained by exposure, and a light decay rate (Volt) is obtained from this potential difference and the half-exposure amount.
· Cm ² · μW ^-1 · sec ^-1 ) was calculated and used as the sensitivity. The results are shown in FIGS.

Example 5 A photoconductor of Example 5 was obtained in the same manner as in Example 1, except that the charge generating substance and the fluorescent substance were changed to those shown in Table 6 below.

[Table 6] The light decay rate of this photoreceptor at a wavelength of 430 nm was measured by the same method as in Example 1.
m ² · μm ^-1 · sec ^-1 .

Example 5-2 Example 5-2 was the same as Example 5 except that the addition amount of the charge transporting substance was 2 parts and no fluorescent substance was added. Was obtained. The light decay rate of this photoreceptor at a wavelength of 430 nm was 210 Volt · cm ² · μm ^-1 · sec ^-1 .

Example 6 A charge generation layer (thickness: about 0.3 μm) composed of the following bisazo pigment (10 parts) and polyvinyl butyral (trade name: XYHL: manufactured by Union Carbide Plastics) 3 parts as a charge generation substance was used. A dispersion of a mixed solvent of 4-methoxy-4-methylpentanone and dimethoxyethane was formed on a conductive support made of a polyester base on which aluminum was vapor-deposited, using a doctor blade. Further, 2 parts of the following charge transport material, polycarbonate resin (Panlite K1300, manufactured by Teijin Limited) 2
And 16 parts of tetrahydrofuran were mixed and dissolved to form a solution. The solution was applied onto the charge generating layer using a doctor blade, and dried at 80 ° C. for 2 minutes and at 120 ° C. for 5 minutes to obtain a fluorescent layer having a thickness of about 20 μm. A charge transport layer containing the generated substance was formed. Further thereon, 1.5 parts of the following charge transport material,
A fluorescent layer having a composition of 0.5 part of the following fluorescent substance and 2 parts of a polycarbonate resin (Panlite K1300, manufactured by Teijin Limited) was prepared, and a photoreceptor of Example 6 was obtained.

[Table 7] The light decay rate of this photoconductor at a wavelength of 460 nm is 43
It was 0 Volt · cm ² · μW ^-1 · sec ^-1 .

Example 6-2 Example 6-2 was the same as Example 6 except that the addition amount of the charge transport material was 2 parts and no fluorescent material was added. Was obtained. The light decay rate of this photoreceptor at a wavelength of 460 nm was 58 Volt · cm ² · μW ^-1 · sec ^-1 .

Example 7 An intermediate layer (approximately 0.2 μm) of a polyamide resin (trade name: CM8000, manufactured by Toray) was formed on an aluminum-evaporated polyester film, and 66% of the following charge-generating substance and polyester resin ( (Byron 200, manufactured by Toyobo Co., Ltd.) A thin layer of about 0.02 μm having a composition of 34% was provided. On top of this, the following fluorescent substance 1%, charge transport substance 49
%, And a charge transport layer (thickness: about 20 μm) having a composition of 50% polycarbonate resin, and -8 by corona charging.
It was charged to 00 V and irradiated with monochromatic light of about 1 μW / cm ² to measure the wavelength change of the potential attenuation. FIG. 8 shows the result.

[Table 8] As a result, it can be seen that those in the wavelength region of the fluorescent substance show higher sensitivity than the wavelength directly irradiating the charge generation substance. Further, the following becomes clear from this result. This photoreceptor is characterized in that the charge generation layer is thinner than those of the other embodiments. Therefore, the vertically incident light, which has a small absorption of the charge generating substance, is reflected without being absorbed, and thus has a slightly lower sensitivity. But,
In the wavelength region of the fluorescent substance, it is converted to fluorescent light, so that the reflection at the electrode and the reflection at the interface between the charge transport layer and air satisfy the total reflection condition, and most of the light is confined inside the photoreceptor. Repeat multiple reflections until absorbed by the charge generating material. Therefore, the sensitivity is higher in the wavelength region that is once converted into fluorescence than in the wavelength that is directly absorbed by the charge generation material. Thus, it can be seen that conversion to fluorescence also has the effect of increasing sensitivity due to multiple reflection.

Example 8 A polyamide resin intermediate layer (about 0.2 μm) was formed on an aluminum-evaporated polyester film, and a 50% titanyl phthalocyanine butyral resin (trade name: XYHL, Unican Carbide) was formed thereon as a charge generating substance. A layer having a composition of 50% (made by Plastics Co., Ltd.) was formed with a thickness of about 0.3 μm. On top of that, the same fluorescent substance as in Example 5,
A charge transport layer having the same thickness as the charge transport material was provided (the composition is shown in FIG. 9) to obtain a photoreceptor of Example 8. Example 7
In the same manner as in the above, the wavelength change of the potential attenuation was measured. FIG. 9 shows the result. From FIG. 9, it can be seen that the wavelength region of the fluorescent substance shows higher sensitivity than directly irradiating the charge generation substance. The reason for this is not clear yet, but the absorption of the charge generating substance is quite high. In this example, the absorption at the interface between the charge generation layer and the charge transport layer increased due to oblique incidence due to conversion to fluorescence rather than the effect of multiple reflection. Conceivable. As described above, it is considered that the conversion into the fluorescent light also has the effect of increasing the absorption ratio near the interface by oblique incidence.

It is apparent from the following experiments that these sensitizations are due to the fluorescence emitted by the sensitizer being absorbed by the charge generating substance. That is, Table 9 below
The compound shown in (1) is a charge-transporting substance and also absorbs blue light and has fluorescence in the absorption wavelength region of the charge-generating substance.

When this was used in place of the charge transport material in the same manner as in Example 1, the quantum efficiency (φ (sensitivity)) obtained from the sensitivity of the photoconductor at each wavelength (surface charge on the photoconductor with respect to the amount of irradiation light) For neutralization). Table 9 shows the results. As shown in Table 9, the long wavelength (φ
It can be seen that there is a difference between the quantum efficiency in 2) and the quantum efficiency (φ1) at a wavelength where the charge carrier substance is absorbed. If the efficiency of fluorescence generation by the charge transport substance is added to the efficiency at the short wavelength, the relative ratio to the efficiency at the long wavelength (φ2
/ Φ1) indicates the fluorescence generation and the efficiency with which it is absorbed by the charge generating material. On the other hand, the light emission efficiency (φ3 (fluorescence)) was determined by irradiating light to the charge transport layer alone. In this case, the fluorescence was largely internally reflected, so that the film was cut to take out the fluorescence to the outside. Table 9 shows the fluorescence generation efficiency at that time. As is clear from Table 9, there is a correlation between the fluorescence generation efficiency and the above value. That is, it is understood that the generation of fluorescence and the absorption to the charge generating substance are the main factors for improving the sensitivity at a short wavelength.

[0066]

[Table 9]

Example 9 As a charge generating substance, a charge generating layer having a composition of 2.5 parts of the following bisazo pigment and 1 part of polyvinyl butyral resin (trade name: XYHL, Union Carbide Plastics Co.) was used in an amount of about 0.1 to 0. It was formed in a thickness of 0.2 μm. Further, 2 parts of a mixture of a fluorescent substance (B) having the following charge transporting ability and the following charge transporting substance (A) (weight ratio is shown in Table 7), 2 parts of a polycarbonate resin (Panlite K1300: manufactured by Teijin Limited) And 16 parts of tetrahydrofuran were mixed and dissolved to form a solution. The solution was applied onto the charge generation layer using a doctor blade, and dried at 80 ° C. for 2 minutes and at 120 ° C. for 5 minutes to generate a fluorescent light having a thickness of about 20 μm. A charge transport layer containing the substance was formed to obtain a photoreceptor of Example 9.

[Table 10] As a result, the quantum efficiency (φ2) when irradiated with light having a wavelength of 420 nm (the absorption region of the charge transport layer) was as shown in Table 11 below. Further, a correlation as shown in FIG. 10 was observed between the ratio (φ2 / φ1) to the quantum efficiency (φ1) of the region where the charge transport layer does not absorb light and the fluorescence yield (φ3) obtained separately.
From the above results, to increase the quantum efficiency of the absorption region of the charge transport layer, the ratio of the fluorescent substance to the amount of the charge transport substance (B /
It is understood that it is effective to set A) to about 1/1 to 1/200 (wt / wt). The molecular weight of the charge transport substance is 423.58, and the molecular weight of the fluorescent substance is 672.96.
Therefore, when expressed as a molar ratio, it is about 1/1 to 1/300.

[Table 11]

Example 10 As a charge generating substance, a charge generating layer composed of 2.5 parts of a bisazo pigment and 1 part of a polyvinyl butyral resin (trade name: XYHL, Union Carbide Plastics Co.) was used in an amount of about 0.1 to 0.1. It was formed with a thickness of 2 μm. Furthermore, 2 parts of a mixture of a fluorescent substance (B) having the following charge transporting ability and the following charge transporting substance (A) (weight ratio is shown in Table 10) and 2 parts of a polycarbonate resin (Panlite K1300: manufactured by Teijin Limited) After mixing and dissolving 16 parts of tetrahydrofuran to form a solution, the solution was applied on the charge generation layer using a doctor blade, dried at 80 ° C. for 2 minutes and at 120 ° C. for 5 minutes to obtain a fluorescent substance having a thickness of about 20 μm. Thus, a photoreceptor of Example 10 was obtained.

[Table 12] As a result, the quantum efficiency (φ2) when light having a wavelength of 420 nm (absorption region of the charge transport layer) was applied was as shown in Table 13 below. As in Example 9, the quantum efficiency is higher when the concentration of the fluorescent charge carrier is appropriate.

[Table 13]

[0069]

As is clear from the above results, according to the present invention, the photosensitive material used in the present invention is a photosensitive material in which a fluorescent substance is added to a charge transport layer or another layer, or a photosensitive material. By using a photoreceptor in which the carrier substance itself has strong fluorescence or a photoreceptor in which the charge carrier substance itself has strong fluorescence, an electrophotographic photosensitive method in which the sensitivity particularly at 380 to 420 nm is significantly enhanced can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a representative electrophotographic photosensitive member according to the present invention.

FIG. 2 is a schematic sectional view of another representative electrophotographic photosensitive member according to the present invention.

FIG. 3 shows a spectral sensitivity curve of the electrophotographic photosensitive member obtained in Example 1.

FIG. 4 shows a spectral sensitivity curve of the electrophotographic photosensitive member obtained in Example 2.

FIG. 5 shows a spectral sensitivity curve of the electrophotographic photosensitive member obtained in Example 3.

FIG. 6 shows a spectral sensitivity curve of the electrophotographic photosensitive member obtained in Example 4.

FIG. 7 shows a spectral sensitivity curve of the electrophotographic photosensitive member obtained in Example 1-2.

FIG. 8 shows a spectral sensitivity curve of the electrophotographic photosensitive member obtained in Example 7.

FIG. 9 shows a spectral sensitivity curve of the electrophotographic photosensitive member obtained in Example 8.

FIG. 10 is a graph showing the relationship between the quantum efficiency and the fluorescence yield of the photoreceptor obtained in Example 9.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) G03G 15/04 (72) Inventor Tomoyuki Shimada Ricoh Co., Ltd. (72) 1-3-6 Nakamagome, Ota-ku, Tokyo Inventor Hiroshi Adachi 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd.

Claims (8)

[Claims] 1. A fluorescent material having a photosensitive layer containing a charge-generating substance and a charge-transporting substance in the same or separate layers on a conductive support, and having a fluorescence wavelength in the absorption wavelength region of the charge-generating substance. 380n using photoreceptor containing substance
An electrophotographic method characterized by irradiating light of m to 420 nm. 2. The electrophotographic method according to claim 1, wherein the fluorescent substance having a fluorescence wavelength in the absorption wavelength region of the charge generating substance is different from the charge transporting substance. 3. The electrophotographic method according to claim 1, wherein the fluorescent substance having a fluorescence wavelength in the absorption wavelength region of the charge generating substance is the same as the charge transporting substance. 4. The electrophotographic method according to claim 1, wherein the charge generating substance is an azo pigment. 5. The electrophotographic method according to claim 1, wherein the charge generating substance is a phthalocyanine pigment. 6. The electrophotographic method according to claim 1, wherein the irradiation light is monochromatic light. 7. The electrophotographic method according to claim 1, wherein the charge transporting substance is an aromatic amine compound. 8. A photosensitive layer containing a charge-generating substance and a charge-transporting substance in the same or separate layers on a conductive support, and a fluorescent substance having a fluorescence wavelength in the absorption wavelength region of the charge-generating substance is provided. 380n using the contained photoreceptor
An electrophotographic apparatus characterized by irradiating light of m to 420 nm.