JPS61175645A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To form the titled body having excellent properties of a sensitivity, a repeating property and a durability by incorporating a charge transfer substance contg. a hydrazone compd. having a specific structure to the titled body. CONSTITUTION:The charge transfer substance comprises at least one of the compds. shown by formula (I) wherein R1 is a halogen atom and may be substd. an alkyl or an alkoxy group, R2 is a hydrogen atom, or a halogen atom, and may be substd. an alkyl or an alkoxy group, R1 and R2 are different with each other, R3 may be substd. an alkyl or an alkoxy group, R4 and R5 may be substd. an alkyl, an aralkyl or an aryl group or R4 and R5 together with each other may form a heterocyclic ring residue. The representative example of the hydrazone compd. can give the compds. shown by formulas (1) and (2).

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to an electrophotographic photoreceptor, and more specifically, the present invention relates to an electrophotographic photoreceptor, and more specifically, a photoconductive layer formed on a conductive support has a ,
By containing a novel hydrazone compound, an electrophotographic photoreceptor having excellent photosensitivity and durability is provided.

(Prior Art) The electrophotographic method has already been published by Carlson in US Patent No. 2.297.
As disclosed in No. 691, this photographic method is a clever combination of electrostatic phenomena and photoconductive phenomena, in which the surface of a photoconductive photoreceptor is uniformly charged by corona discharge etc. in a dark place. After that, the optical image is converted into an electrostatic latent image using photoconductivity,
This is one of the image forming methods in which colored charged powder (toner) is attached to this to turn it into a visible image.

The basic electrical and photoelectric properties required of a photoreceptor in such electrophotography are that it can be charged to an appropriate potential in a dark place, that this potential can be maintained for an appropriate amount of time, and that it can be charged quickly by light irradiation. For example, the electric charge can be dissipated.

In such photoreceptors, amorphous selenium,
Inorganic photoconductive materials such as cadmium sulfide and zinc oxide have been widely used. Although these inorganic materials satisfy the above conditions, they also have some drawbacks. For example, cadmium sulfide or zinc oxide is used as a photoreceptor by dispersing it in a resin as a binder.

Since it has mechanical defects such as smoothness, flexibility, hardness, tensile strength, and abrasion resistance, it cannot withstand repeated use as it is. Furthermore, when using cadmium sulfide, consideration must also be given to hygiene issues.

In addition, amorphous selenium must be manufactured by vapor deposition, which not only increases manufacturing costs but also has no flexibility and is difficult to process into a belt shape.
It has drawbacks such as the toxicity of selenium and its sensitivity to heat and mechanical shock, so care must be taken when handling it.

In recent years, in order to eliminate the drawbacks of these inorganic photoreceptors,
Research on organic photoreceptors is progressing, and organic photoreceptors.

Easy to form a film, easy to manufacture, lightweight.

1 for flexibility and 2 for having many advantages of polymorphism in spectral sensitivity.
Various organic photoreceptors have been proposed, and some are in practical use.

For example, poly-N-vinylcarbazole and 2,4°7-
Photoreceptor consisting of dolinitrofluoren-9-one (US Pat. No. 3,484,237), poly-N-vinylcarbazole sensitized with pyrylium salt dye (Japanese Patent Publication No. 48-25658), Photoreceptor whose main component is a eutectic complex consisting of a dye and a resin
Publication No.) etc.

Furthermore, an electrophotographic photoreceptor has been proposed that combines a substance that generates electric charge with light (called a charge-generating substance) and a substance that can transport the generated electric charge (called a charge-transporting substance). . For example, U.S. Patent No. 3.791.
No. 826 describes a photoreceptor in which a charge transport layer is provided on a charge generation layer, and U.S. Pat. No. 3,764,315 describes a photoreceptor in which a charge generation material is dispersed in a charge transport material A photoreceptor with a This kind of charge generation and charge transport.

By sharing the functions with different substances,
In other words, by the combination of a charge generating substance and a charge transporting substance,
Its properties are better and a useful photoreceptor is provided.

Until now, many charge generating substances useful in this type of photoreceptor have been known. On the other hand, various materials have been proposed as charge transport materials.

The current situation is that it is difficult to say that the situation is necessarily satisfactory.

The basic properties of an excellent charge transport material are:

When charged, it must be able to maintain a sufficient potential, it must be able to sufficiently transmit light of an effective wavelength to generate charges from the charge-generating substance, and it must also be able to sufficiently hold the electric charge generated by the charge-generating substance. It has the ability to promptly transport. In addition, as for the practically required properties, it can be used alone or dissolved in a binder.

Able to form a uniform film2. It is necessary that the electrostatic properties do not deteriorate or change under harsh environmental conditions due to temperature, humidity, ozone, NOx, etc. generated during corona discharge. So far, as this type of charge transport material, polyphenyl compounds such as triphenyl have been classified by chemical structural formula, and U.S. Patent No. 3.717.462
No., U.S. Patent No. 4.150.987, JP-A-55-55
hydrazone compound described in specification No. 2064,
Diarylalkane compounds described in U.S. Pat. No. 3.820.989, U.S. Pat. No. 3.189.
2,5-bis(P-diethylaminophenyl)-1,3,4-oxadiazole described in U.S. Pat. No. 477, pyrazoline compounds described in U.S. Pat. No. 3'837.851, etc. is a relatively excellent charge transport material that has been proposed in recent years. However, the current situation is that these charge transport materials do not satisfy all of the above conditions.

(Problems to be Solved by the Invention) The present invention provides an electrophotographic photoreceptor having excellent sensitivity, repeatability, durability, and the like.

[Structure of the invention]

(Means for Solving the Problem) As a result of intensive research, the present inventors discovered that a hydrazone compound with a specific structure is a truly useful charge transport material for electrophotographic photoreceptors, and further discovered that The present invention was completed by discovering that an electrophotographic photoreceptor using a charge transporting material has excellent properties.

That is, the present invention relates to an electrophotographic photoreceptor having excellent properties and is provided using a hydrazone derivative having a novel structure.

An object of the present invention is to provide an electrophotographic photoreceptor that has high sensitivity and low residual potential by containing a novel charge transport substance, and has high charge transport efficiency and thus has a high copying speed. Another object of the invention is when it is used as a photoreceptor for repetitive transfer type electrophotography in which charging exposure, development, and transfer steps are repeated.

To provide an electrophotographic photoreceptor with excellent durability and environmental friendliness, which has little fatigue deterioration due to repeated use, maintains stable characteristics under various harsh environments such as high temperature rather than low temperature, and high humidity than low humidity. It is in.

This object of the present invention is achieved by containing at least one compound represented by the following general formula (1) as a charge transport substance.

General formula (1) (wherein, Re is a halogen atom, an alkyl group or an alkoxy group which may have a substituent, and R2 is water.

It represents an elementary atom, a halogen atom, an alkyl group or an alkoxy group which may have a substituent, and R2 and R2 are different from each other. RJ represents an alkyl group or an alkoxy group that may have a substituent, R4L or R represents an alkyl group, an aralkyl group, or an aryl group that may have a substituent, or R and R represent a heterocyclic residue. Indicates that a group may be formed. ) To further explain the substituents, among the above substituents R1R1, Rj, R≠ or Rf, alkyl groups include methyl group, ethyl group, straight or branched propyl group, butyl group, pentyl group, hexyl group.

Among @RI+ Rx- or R3, which are substituents such as heptyl group, octyl group, and stearyl group, alkoxy group refers to substituents such as methoxy group, ethoxy group, propoxy group, butoxy group, hexyloxy group, and benzyloxy group. It is a substituent. Among R and R1, the aralkyl group is a substituent such as benzyl group, phenethyl group, cinnamyl group, benzhydryl group, trityl group, and naphthylmethyl group, and when R and R5 form a heterocyclic residue, is a piperidino group.

When a substituent such as a morpholino group has zero or more substituents, the substituent includes a halogen atom, a nitro group, and the like.

The compound of the present invention represented by the general formula (T) can be produced, for example, by the method shown below.

One method is to react hydrazine represented by the following general formula (1) or its mineral acid salt with an aldehyde represented by the general formula (I[[) in an organic solvent.

General formula (II) (In the formula, Re or Rf is the same as the general formula (1)) General formula CDI) (In the formula, R, R, or RJ is the same as the general formula CI) Non-reactive as a solvent Although a wide variety of organic solvents can be used, preferably alcohols such as methanol and ethanol, dimethylformamide, dioxane, etc. can be used alone or in combination.

In another method, hydrazine represented by the following general formula (mV) or its mineral acid salt is reacted with an aldehyde compound represented by the above general formula (V) in a solvent.

General formula (IV) H,N-NH-R exposure (wherein R is the same as in general formula (f)) Then, in a solvent with a compound represented by the following general formula (V), preferably under basic conditions. By reacting with 7, the hydrazone compound of the present invention can be obtained.

General formula (V) R, -X (wherein, X represents a negative group such as a halogen atom, and R
5 is the same as in general formula (1)) As the solvent, a wide range of non-reactive solvents can be used, but preferably protic solvents such as water and alcohols, or aprotic polar solvents such as dimethyl sulfoxide and dimethyl formamide. Solvents, acetone, ketones such as methyl ethyl ketone, benzene.

Aromatic hydrocarbons such as toluene and xylene, ethers such as tetrahydrofuran and dioxane, dichloromethane,
Chlorinated hydrocarbons such as 1,2-dichloroethane or amines such as pyridine and triethylamine can be used alone or in combination.

Bases include sodium hydroxide and potassium hydroxide.

Potassium carbonate, sodium methylate, sodium hydride, etc. are used.

Representative examples of the nine hydrazone compounds used in the present invention obtained by such a synthesis method are listed below.

[Hydrazone compound]

These compounds can be used alone or in combination of two or more.

The photoreceptor of the present invention contains the above-mentioned hydrazone compounds, and photoreceptors with various characteristics can be obtained depending on how these hydrazone compounds are applied. For example, a hydrazone compound as a charge transporting substance is provided on a conductive support substrate in the same layer as a charge generating substance, which is usually referred to as a single-layer photoreceptor, or a first layer mainly containing a charge generating substance. and.

It can be used in a structure commonly called a laminated type photoreceptor, which is formed by laminating two second layers mainly containing a charge transporting substance on a conductive support substrate.

These configurations are appropriately selected depending on the polarity of the photoreceptor used. Further, examples of the charge generating substance used in the present invention include the following.

Inorganic compounds include selenium, selenium alloys, and CdS.

Although inorganic optical semiconductors such as ZnO, CdSe, and amorphous silicon can also be used, it is preferable to use organic charge-generating substances. Examples of organic charge-generating substances include phthalocyanine pigments such as metal phthalocyanine and metal-free phthalocyanine, azo dyes such as monoazo dyes and disazo dyes, indigo pigments, quinacridone pigments, indanthrene pigments, xanthine dyes, and benzimidazoles. Pigments, dyes and pigments such as perylene pigments and squalic menane dyes, eutectic complexes formed from pyrylium salt dyes and polycarbonate resins, and charge transfer complexes formed from electron-donating substances such as polyvinylcarbazole and electron-accepting substances such as TNF. Among them, it is particularly preferable to use phthalocyanine pigments.

Since the hydrazone compound in the present invention does not have film-forming ability by itself, a binder resin is used to form it as a photosensitive layer. Further, since charge generating substances cannot form a film by themselves except for polymeric resins such as polyvinylcarbazole, a binder may be used as necessary.

The binder preferably used in the present invention is a highly electrically insulating film-forming polymer or copolymer. These high molecular weight polymers and copolymers are 1
Binders preferably used in the present invention include phenolic resin, polyester resin, vinyl acetate resin, polycarbonate resin, polypeptide resin, cellulose resin, polyurethane resin, polyvinylpyrrolidone, polyethylene oxide, polyvinyl chloride resin, starch, and polyvinyl alcohol. .

Acrylic copolymer resin, methacrylic copolymer resin.

silicone resin, polyacrylonitrile copolymer resin,
Polyacrylamide, polyvinyl butyral.

Examples include polyvinyl carbazole and polyvinylidene chloride resin. These polymer binders may be used alone or in combination of two or more, but the binders that can be used in the present invention are not limited to these. Further, in the photoreceptor of the present invention, a charge generation layer containing a charge generation substance as a main component is provided on the conductive support via an intermediate layer if necessary, and adjacent to the charge generation layer the charge generation layer containing a charge transport substance as a main component is provided. A stacked structure including a charge transport material may also be used. Also, if such a laminated structure is used.

Which of the charge generation layer and the charge transport layer is to be used as the upper layer is determined depending on whether the chargeability is positive or negative.

Generally, when negatively charged, it is advantageous in terms of characteristics to have a charge transport layer as an upper layer. - Also in the photoreceptor of the present invention.

In the case of a laminated structure consisting of separate layers of a charge generation layer and a charge transport layer, the charge generation layer may be formed directly on the conductive support or, if necessary, with an intermediate layer such as an adhesive layer or a barrier layer provided thereon. ■ Apply vacuum evaporation, ■ Apply a solution of the charge-generating substance dissolved in an appropriate solvent, or ■ Minimize the charge-generating substance in a dispersion solvent using a ball mill, attritor, etc., and add a polymer binder as necessary. It can be provided by a method such as coating a dispersion obtained by mixing and dispersing with. The polymer binder used at this time may be the same as that used for the charge transport layer.

Alternatively, it may be a single photosensitive layer comprising a hydrazone compound according to the present invention and a binder.

In addition, the hydrazone compound according to the present invention has a binding agent of 10
Preferably, the amount of the charge transport material is 10 to 300 parts by weight per 0 parts by weight. However, the present invention is not limited to this range only. The thickness of this photosensitive layer is determined by the required photosensitivity and durability, as well as the mixing ratio of the charge generating substance and the charge transporting substance to the binder. , the thickness of the photosensitive layer on the supporting conductive substrate is 50 microns or less.

Preferably, the thickness is about 7 to 30 microns, which is suitable from the viewpoint of flexibility of the film.

The photosensitive layer can also be coated with a layer that serves as a protective layer, if necessary.

The support used in the electrophotographic photoreceptor of the present invention includes:

Any type of conductive layer conventionally used may be used as long as it is imparted with conductivity. Specifically, aluminum and copper.

Metals such as stainless steel and brass, aluminum, plastics on which indium oxide, tin oxide, etc. are vapor-deposited or laminated, or conductive particles 1 For example, carbon black,
Examples include plastics in which tin particles and aluminum particles are dispersed. Also, regarding its shape, it can be sheet-like or cylinder-like.

Other items are also acceptable. 2. When using the electrophotographic photoreceptor according to the present invention, the light source is usually a halogen lamp or the like, and if the charge generating substance is phthalocyanine, the sensitivity is 750 NO+ or more.
Laser light such as a gallium-aluminum-arsenic semiconductor laser (oscillation wavelength 780 rv+) can also be used.

Next, the present invention will be explained in more detail with reference to synthesis examples and examples, but the present invention is not limited to the following examples. In the following examples, "part j" indicates parts by weight.

Synthesis example 1 A synthesis example of the hydrazone compound (1) of the present invention will be shown.

After adding 31 parts of phosphorus oxychloride to 73 parts of dimethylformamide at 15-20°C, N-(4-methyl) was added at the same temperature.
Add 32 parts of benzyl-N-(4-ethyl)benzyl-m-toluidine and stir at 50-60°C for 3 hours. Next, the reaction mixture is cooled and poured into 2000 parts of ice water. Next, the mixture is neutralized with sodium hydroxide to bring the PL to 9 to 10, and then cooled, filtered, washed with water, and dried to obtain 30 parts of an aldehyde having the structure shown below.

Next, 28 parts of the above aldehyde was added to 96 parts of ethanol and 1.
Add 19 parts of 1-diphenylhydrazine hydrochloride and 2 parts of acetic acid as a catalyst and stir at 70 to 80°C for 2 hours. After cooling the reaction solution and filtering the precipitated crystals, compound (1) 31 is obtained by drying. part is obtained. 24 parts of pure product are obtained by recrystallization from acetonitrile.

Synthesis example 2 A synthesis example of the hydrazone compound (6) of the present invention will be shown.

After adding 25 parts of phosphorus oxychloride to 58 parts of dimethylformamide at 15 to 20°C, 29 parts of N-(2-methoxy)benzyl-N-(4-ethyl)benzyl-m-anisidine was added at the same temperature. Stir at 60-70°C for 3 hours.

After cooling the reaction solution, pour it into 1,600 parts of ice water.Next, neutralize with sodium hydroxide to bring the pH to 9-10, cool, filter, wash with water, and dry to obtain an aldehyde having the following structure. 24 parts are obtained.

Next, 23 parts of the above aldehyde, 7 parts of phenylhydrazine, and 0.8 parts of p-)luenesulfonic acid as a catalyst are added to 72 parts of ethanol, and the mixture is stirred at 70 to 80°C for 2 hours. Cool the reaction solution and filter the precipitated crystals.

By drying, 23 parts having the following structure are obtained.

Next, 1 part of sodium hydride was added to 38 parts of dimethylformamide.
．． After adding 4 parts at 15-20°C, the above hydrazone 19
1 part at the same temperature. Then, 9 parts of octyl bromide are added dropwise at 20-25°C. After stirring at the same temperature for 3 hours, ice water 1
000 parts, filtered and washed with water.

By drying, 19 parts of compound (6) are obtained.

15 parts of pure product are obtained by recrystallization from ethyl acetate.

Synthesis example 3 A synthesis example of the compound (10) of the present invention will be shown.

N-(
By using 35 parts of 3-ethyl)benzyl-N-(3-methoxy)benzyl-0-)luidine, 33 parts of an aldehyde having the following structure are obtained.

Next, 30 parts of the above aldehyde and 1.1 parts of ethanol were added to 94 parts of ethanol.
- Add 19 parts of diphenylhydrazine hydrochloride and 2 parts of acetic acid as a catalyst, and stir at 70-80°C for 2 hours. After cooling the reaction solution and filtering the precipitated crystals, 34 parts of compound (10) are obtained by drying. 27 parts of pure product are obtained by recrystallization from acetonitrile.

Example 1 40 parts of copper phthalocyanine and 0.5 part of tetranitrocopper phthalocyanine are dissolved in 500 parts of 98% concentrated sulfuric acid with thorough stirring. The dissolved solution was poured into 5000 parts of water to precipitate a composition of fI phthalocyanine and tetranitrocopper phthalocyanine, passed through once, washed with water, and dried at 120° C. under reduced pressure.

Next, 1 part of this composition, 2.5 parts of compound (1), acrylic polyol (manufactured by Narita Pharmaceutical Co., Ltd., Takerank A-70)
2) A composition consisting of 3.6 parts, 0.5 parts of epoxy resin (manufactured by Shell Chemical Co., Ltd., Epon 1007), 1.2 parts of methyl ethyl ketone, and 1.2 parts of cellosolve acetate was kneaded in a magnetic ball mill for 48 hours. A photoconductive composition is obtained.

Next, this photoconductive composition was roll coated onto the aluminum of a laminate film of 5 micron thick aluminum foil and 75 micron polyester film to a dry film thickness of 8 microns, and uniformly heated to 110°C. Place in the heated oven for 1 hour.

It was used as an electrophotographic photoreceptor. +5.7KV for the sample obtained in this way, Konagi Jr. whelk 10mm, 10
A corona discharge is applied at a charging speed of m/ll1 inch, and after 10 seconds after the discharge is stopped, exposure is performed using a 2854 tungsten light source at an illuminance of 10 Lux. The amount of light irradiation required for the potential immediately before exposure to decrease by 50% at this time was defined as the sensitivity. The sample measured in this way has a maximum surface charge of 5
70V, dark decay rate 17%, sensitivity 4. l Lux.

sec, the residual potential was 22 V, and both chargeability and sensitivity were values sufficient for practical use. No induction was observed in one surface potential decay during charging exposure, and a light decay curve of 5 curves was exhibited. In addition, this photoconductor is positively charged with a copying machine.
I made ooo copies in a row.

The resulting image has excellent gradation.9 Even when copying an ordinary photograph as an original, a beautiful image can be obtained in terms of detail intermediate color density, there is no change in sensitivity, and there is no scratch on the photoreceptor. However, a clear image with no such scratches was obtained in the copied image.

Examples 2 to 4 In Example 1, compound (2) was used instead of compound (1).
, (5) or (9), respectively, Example 1
When tested in the same manner as in Example 1, both chargeability and sensitivity were sufficient for practical use.

No induction was observed in 9 surface potential decay upon charging exposure, and the repeatability was also good.

Example 5 40 parts of copper phthalocyanine and 1.5 parts of dinitrometal-free phthalocyanine are dissolved in 100 parts of 98% concentrated sulfuric acid with thorough stirring. Pour the dissolved liquid into 1000 parts of water,
After the phthalocyanine composition is precipitated, it is filtered once, washed with water, and dried at 120° C. under reduced pressure. 1 part of this composition, 3 parts of compound (3)
Panlite L-1250) 4 parts and tetrahydrofuran 1
After dispersing in a ball mill with part 0, and spraying this liquid to a thickness of 10 μm on an aluminum cylinder,
It was dried and used as an electrophotographic photoreceptor. The electrophotographic properties of the thus obtained sample were measured in the same manner as in Example 1. The sample measured in this manner had a maximum surface charge of 590 parts, a sensitivity of 3.7 Lux, sec, and its light attenuation curve showed a 5-curve curve with no induction. After making 10,000 copies, clear images with excellent gradation and no change in sensitivity were obtained both in the initial and final images.

Example 6 2 parts of compound (8) for 1 part of ε-type copper phthalocyanine,
Disperse 0.8 parts of triphenylmethane, 4 parts of acrylic resin, and 20 parts of cellosolve acetate in a ball mill,
Thereafter, the samples were measured in the same manner as in Example 1.

The obtained light attenuation curve is one curve with no induction, the maximum surface potential at this time is 570 V, and the dark attenuation rate is 16.
%, sensitivity 3.3 Lux, sec, residual potential 19V, and also in live-action tests.

The same results as in Example 1 were obtained.

Example 7 10 parts of copper phthalocyanine obtained in Example 1.

Thermosetting acrylic resin 32 parts, melamine resin 8 parts and butyl acetate (cellosolve acetate) (1:1) 50
A photoconductive coating material was prepared by kneading the composition consisting of the following parts in a ball mill for 24 hours, and this coating material was coated on an aluminum support to a thickness of about 1 .mu.m and cured to form a charge generating layer.

Next, polycarbonate resin (Panlite L-1250
) and 3 parts of polyester resin (manufactured by Gutdeyer) were mixed with tetrahydrofuran and 100 parts of toluene solvent. The weight ratio of solvents is 9:1.

9 parts of compound (1) were added together with 0.02 part of silicone oil. This liquid was applied onto the charge generation layer to a thickness of about 15μ and dried at 80° C. to form a charge transport layer to obtain a laminated photoreceptor.

When this photoreceptor was corona charged at -6.5 KV for 0.2 seconds, the surface potential was -860 V, and the sensitivity was 3.
4 Lux, sec, and was an extremely highly sensitive photoreceptor.

Examples 8 to 9 In Example 7, compound (4) was used instead of compound (1).
When tested in the same manner as in Example 7 using (6) and (6), the chargeability was the same as in Example 7.

Both sensitivity values are sufficient for practical use, and are suitable for charging exposure.

No inductance was observed in surface potential decay.

Furthermore, the repeatability was also good.

Example 11 98 parts of tetrahydrofuran was added to 2 parts of Guianpoule (CI21180), and the mixture was crushed and mixed in a ball mill to obtain a charge-generating pigment coating liquid. This was applied using a doctor blade onto a polyester film on which aluminum had been vapor-deposited, and air-dried to form a charge generation layer with a thickness of 0.5 μm. Next, a charge transport layer forming coating liquid obtained by mixing 2 parts of compound (5), 2 parts of polycarbonate (Panlite L) and 45 parts of tetrahydrofuran was applied onto the charge generation layer using a doctor blade.
A photoreceptor of the present invention was prepared by drying at .degree. C. for 30 minutes to form a charge generating layer with a thickness of 10 .mu.m. This photoreceptor is -5
, 5KV corona charging for 0.2 seconds, the surface potential was -89OV, and the sensitivity E% was 4. I Lux
, sec.

〔Effect of the invention〕

The present invention has the above configuration, and when using it,
High sensitivity even in positive and negative charging, and
There is little deterioration of the photoreceptor due to repetition, and in practical use, it has excellent charge retention ability from low to high temperatures and from low humidity to high humidity, environmental friendliness with respect to sensitivity changes, and durability.

Claims (1)

[Scope of Claims] 1. An electrophotographic photoreceptor characterized by having a photosensitive layer containing at least one compound represented by the following general formula [I]. General formula [I] ▲ Numerical formulas, chemical formulas, tables, etc. R_1 and R_2 are different from each other, R_3 represents an alkyl group or alkoxy group that may have a substituent, R_4 or R_5
represents an alkyl group, aralkyl group, or aryl group that may have a substituent, or that R_4 and R_5 may form a heterocyclic residue. )