JPH09289346A - Optical sensor, photoconductive layer forming material therefor, and photoconductive layer forming ink composition therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical sensor which enables stable supply of constant performance and has excellent durability, a photoconductive layer forming material therefor, and a photoconductive layer forming ink composition therefor. SOLUTION: An optical sensor having a photoconductive layer on an electrode and an information recording medium having an information recording layer on an electrode are arranged to face each other. The photoconductive layer is caused to contain an azo compound having an azo group coupled with a coupler residue expressed by the formula in a molecule. In the formula, X represents a condensation ring with a benzene ring, and Y represents a group with n being an integer of 0 to 4 selected from a halogen atom, cyano group, alkyl group and alkoxyl. R1 and R2 represent hydrogen, alkyl group, aromatic ring group and aromatic complex ring group. R1 and R2 may be the same or different, and may form a ring with a nitrogen atom.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical sensor capable of recording optical information in the form of visible information or electrostatic information on an information recording medium, a material for forming the photoconductive layer, and an ink for forming the photoconductive layer. It relates to a composition.

[0002]

2. Description of the Related Art In order to record optical information on an information recording medium, a photosensor comprising a photoconductive layer having an electrode on the front surface and a charge holding layer having an electrode on the rear surface facing the photosensor. The information recording medium consisting of is arranged on the optical axis,
A method of exposing while applying a voltage between both electrodes, recording an electrostatic charge on the charge holding layer according to the incident optical image, and developing the electrostatic charge with a toner or reproducing with a potential reading device, for example, It is described in JP-A-1-290366 and JP-A-1-289975. Further, the charge holding layer in the above method is a thermoplastic resin layer, the electrostatic charge is recorded on the surface of the thermoplastic resin layer, then heated, and the electrostatic charge recorded by forming a frost image on the surface of the thermoplastic resin layer. A method for visualizing is described in, for example, JP-A-3-1
No. 92288.

Furthermore, the present applicants have disclosed that the information recording layer in the information recording medium is a liquid crystal-polymer composite type liquid crystal recording layer, which is exposed when a voltage is applied in the same manner as described above, and which is exposed to an electric field formed by an optical sensor. The information recording and reproducing method of reproducing information as visible information by transmitted light or reflected light when reproducing information is described in Japanese Patent Application Nos. Hei 4-3394 and Hei 4-24722.
And Japanese Patent Application No. 5-266646. This information recording / reproducing method can visualize recorded information without using a deflection plate.

[0004] The present applicant has found that in the above-mentioned information recording system, by making the optical sensor semiconductive and having an amplifying action, it is possible to improve the information recording performance on an information recording medium. First, Japanese Patent Application No. 6
Although the application was filed as Japanese Patent No. -6437, there is a demand for providing an optical sensor that has stable information recording performance and that can withstand repeated use.

[0005]

DISCLOSURE OF THE INVENTION The present invention relates to an optical sensor used for forming information on an information recording medium, a material for forming the photoconductive layer, and an ink composition for forming the photoconductive layer. An object is to provide an optical sensor that can stably supply performance and is excellent in durability, a material for forming the photoconductive layer, and an ink composition for forming the photoconductive layer.

[0006]

The optical sensor of the present invention comprises:
An optical sensor having a photoconductive layer on at least an electrode, which is arranged to face an information recording medium having an information recording layer on at least an electrode, and a voltage is applied between both electrodes in an exposed state, or a voltage is applied. In a photosensor capable of forming information on the information recording medium by an electric field or an amount of electric charge, in a photoconductive layer of the photosensor, a coupler residue represented by the following general formula (1): It is characterized by containing an azo compound having at least one bound azo group in the molecule.

[0007]

Embedded image

(In the formula, X is condensed with a benzene ring to be substituted.
Atom group necessary for forming an unsubstituted aromatic hydrocarbon ring or a substituted / unsubstituted aromatic heterocycle, Y is selected from hydrogen, halogen atom, cyano group, substituted / unsubstituted alkyl group, and alkoxy group N is an integer group of 0 to 4. R ₁ and R ₂ represent hydrogen, a substituted / unsubstituted alkyl group, a substituted / unsubstituted aromatic hydrocarbon ring group or a substituted / unsubstituted aromatic heterocyclic group. Here, R ₁ and R ₂ may be the same or different, and may form a ring in cooperation with the nitrogen atom. ) Further, the above-mentioned optical sensor of the present invention is semi-conductive, and when a voltage is applied between both electrodes in an exposed state, or when an exposure is performed while a voltage is applied, a current caused by the exposure to the information recording medium is generated. Information can be recorded with the intensity amplified as described above, and the behavior of gradually decreasing the conductivity when the voltage is continuously applied after the exposure is finished, and the function of continuing the information recording on the information recording medium It is characterized by having.

Further, the above-mentioned optical sensor of the present invention is 10
^When a voltage with an electric field strength of ⁵ to 10 ⁶ V / cm is applied,
The passing current density in the unexposed area is 10 ⁻⁴ to 10 ⁻⁷ A / cm ²
It is characterized by being.

In the photoconductive layer forming material in the photosensor of the present invention, a photosensor having a photoconductive layer on at least an electrode and an information recording medium having an information recording layer on at least an electrode are arranged to face each other. For forming a photoconductive layer in an optical sensor capable of forming information on an information recording medium by applying an electric field or an electric charge to the information recording medium by applying a voltage in an exposed state between both electrodes A material, which is an azo compound having at least one azo group bonded to the coupler residue represented by the general formula (1) in the molecule.

The ink composition for forming a photoconductive layer of the present invention comprises
An optical sensor having a photoconductive layer on at least an electrode and an information recording medium having an information recording layer on at least an electrode are arranged to face each other, and a voltage is applied between both electrodes in an exposed state or a voltage is applied. An ink composition for forming a photoconductive layer in an optical sensor, which is capable of forming information on an information recording medium by an electric field or an electric charge when exposed to light in a state of being exposed, and is a coupler residue represented by the general formula (1). It is characterized by comprising an azo compound having at least one azo group bonded to a group in a molecule and a binder.

The ink composition for forming a photoconductive layer of the present invention comprises
An optical sensor having a photoconductive layer composed of a charge transport layer and a charge generation layer on at least an electrode and an information recording medium having an information recording layer on at least an electrode are arranged to face each other, and a voltage between both electrodes in an exposed state is a voltage. Ink composition for forming a photoconductive layer for forming a charge generation layer in an optical sensor capable of forming information on an information recording medium by an electric field or an amount of electric charge by exposing under an applied voltage or a voltage. It is characterized by comprising a binder and an azo compound having at least one azo group bonded to the coupler residue represented by the above general formula (1) in the molecule.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
The photosensor according to the present invention is formed by laminating a photoconductive layer on an electrode, and the photoconductive layer is a single layer type and a stacked type in which a charge generation layer and a charge transport layer are stacked. The photoconductive layer generally has a function of generating photo-induced charge carriers (electrons, holes) in the irradiated portion when irradiated with light and allowing the carriers to move in the layer width. In the present invention, a specific azo compound described below is contained in the photoconductive layer in the case of a single-layer type, and in the charge generation layer in the case of a multilayer type, thereby providing an optical sensor. When light is applied to the information recording medium, the electric field or charge applied to the information recording medium is amplified over time with the light irradiation, and the increased conductivity gradually attenuates when voltage is applied even after the light irradiation is completed. While maintaining the electric field or the amount of electric charge to the information recording medium, not only stably exhibiting a certain electric property, but also having good film properties and repeated use. It can be an optical sensor with little deterioration.

The photo-induced current amplifying action in the optical sensor of the present invention will be described. A gold electrode of 0.16 cm ² is laminated on the photoconductive layer of the optical sensor for measuring an amplification effect. A constant DC voltage is applied between the two electrodes with the ITO electrode as a positive electrode, and 0.5 seconds after the start of the voltage application, light is irradiated from the substrate side for 0.033 seconds, and the current value of the optical sensor during the measurement time is measured. At the start of light irradiation (t = 0)
Measure from. The irradiation light was a green light obtained by a green filter (manufactured by Nippon Vacuum Optical Co., Ltd.) using a xenon lamp (L2274 manufactured by Hamamatsu Photonics) as a light source.
The intensity of irradiation light irradiated at the intensity of looks was measured with an illuminometer (manufactured by Minolta), and the characteristics of the filter used are shown in FIG.

When irradiated with light at this light intensity, the transparent substrate, I
Considering the light transmittance of the TO film and the spectral characteristics of the filter, 4.2 × 10 ¹¹ photons / cm ² seconds enter the photoconductive layer. When all the incident photons are converted into optical carriers, a photocurrent of 1.35 × 10 ⁻⁶ A / cm ² per unit area is theoretically generated. Here, when measuring with the measuring device, the ratio of the photo-induced current actually generated in the optical sensor to the theoretical photo-current, that is, apparent quantum efficiency = (photo-induced current actually generated in the optical sensor) Value / theoretical photocurrent value) is defined as the apparent quantum efficiency of the optical sensor. The light-induced current is a value obtained by subtracting a base current value, which is a current flowing in a portion not irradiated with light, from a current value of a light irradiation portion. The current that flows due to
This is different from a so-called photocurrent. The photo-induced current amplification action in the photo-sensor of the present invention is defined as such a behavior of the photo-induced current.

An optical sensor having a photo-induced current amplifying action and an optical sensor having no photo-induced current amplifying action (hereinafter referred to as a comparative sensor) according to the present invention will be described using the measurement results of the measuring device. . First, an example of the measurement result of the comparative sensor is shown in FIG. In FIG.
The (m) line is the theoretical value (1.35 × 10 ⁻⁶ A / cm ² ).
Indicates a state in which light irradiation was performed for 0.033 seconds and voltage application was continued after light irradiation. The line (n) is an actual measurement line of the comparative sensor, and the increase of the photocurrent during light irradiation is small, and the value does not exceed the theoretical value (1.35 × 10 ⁻⁶ A / cm ² ). The quantum efficiency is only up to about 0.4. FIG. 7 shows changes in quantum efficiency during light irradiation.

On the other hand, in the photosensor of the present invention, as an example, as shown in FIG. 8, the photo-induced current increases at the time of light irradiation, and as is clear from FIG. It can be seen that the quantum efficiency exceeds 1 at 01 seconds and continues to increase thereafter.

Further, in the comparative sensor, the photocurrent is rapidly attenuated at the same time after the light irradiation is completed, so that even if the voltage is continuously applied after the light irradiation, the effective current as the light information cannot be obtained. On the other hand, in the optical sensor of the present invention, by continuing the voltage application even after the light irradiation, the photoinduced current flows continuously while gradually attenuating, and the photoinduced current can be subsequently taken out. Optical information can be continuously obtained.

Although the detailed reason is not clear, in the photosensor of the present invention, all of the photoinduced charge carriers generated by the irradiation of the information light are applied in the layer width direction of the photoconductive layer in the voltage applied state. Instead of moving, some of the photo-induced charge carriers become trapped in trap sites existing in the photoconductive layer or at the interface between the electrode and photoconductive layer, and these trapped charges accumulate over time. In addition to the photocurrent generated by exposure when a voltage is applied, the injection current from the electrode induced by this trapped charge flows, and the apparent amount of photoinduced current is considered to be amplified over time. To be However, this phenomenon occurs when charge carriers are appropriately injected from the electrode to the charge generation layer, and when appropriate injection is not performed, that is, when injection is too small or injection is too large. There is almost no amplification effect.

In the present invention, by using an optical sensor containing a specific azo compound in the photoconductive layer, injection of charge carriers from the electrode to the charge generation layer is appropriately performed, and a photoinduced current amplification effect is effectively produced. be able to. And
When the exposure is terminated while maintaining the voltage applied, the photocarriers generated by the exposure are immediately attenuated and disappear, but the decay of the trapped charges is gentle, so the electrode induced by the trapped charges is an electrode. It is speculated that a sufficient amount of the injection current from the device flows while it is attenuated, and the attenuation gradually occurs. This photo-induced current is an effect of current amplification triggered by light in the optical sensor of the present invention, and a current larger than the photocurrent caused by the incident light expected in a normal photoconductor flows in the information recording medium. On the other hand, it enables effective optical information provision.

On the other hand, the photoconductor element used for general electrophotography has a dark resistivity of 10 ¹⁴ to 10 ¹⁶ Ω.
cm, the photosensor of the present invention cannot achieve its purpose in electrophotography, and a photosensor having a photoconductive layer having a large dark resistivity for general electrophotography is: It cannot be used for the purpose of the present invention.

Further, the specific resistance ρ (Ω · cm) of the optical sensor
And the current density J (A / cm ² ), the film thickness of the optical sensor is d, the electrode area is S, and the applied electric field strength is E (V / c).
m), ρ = (E · d / J · S) × (S / d) =
Since the relational expression of E / J holds, the specific resistance ρ (Ω · c
m) can be obtained from the applied electric field strength and the current density, and in each embodiment of the present invention, is expressed by the current density.

The present inventors have studied to improve this kind of optical sensor, and as a result, an electrophotographic photoreceptor containing an azo compound having a specific coupler group represented by the above general formula (1) is known. (Japanese Patent Laid-Open No. 1-177041)
However, the present invention has been found out that, by containing it in the photoconductive layer in the photosensor of the present invention, the unique performance as a photosensor can be stably exhibited.

Among the azo compounds having at least one azo group bonded to the coupler residue represented by the general formula (1) in the molecule, particularly preferred are bisazo compounds, trisazo compounds represented by the following general formula (2) or It is a tetrakis compound.

[0025]

[Chemical 6]

In the formula, A is an m-valent group (a) a hydrocarbon having at least one benzene ring, (b) a nitrogen-containing hydrocarbon group having at least two benzene rings, and (c) at least 2 Of one hydrocarbon group having at least one benzene ring and at least one heterocycle, m is an integer of 1 to 4, and X, Y, R ₁ , R ₂ and n are generally It has the same meaning as in formula (1).

The benzene ring in the above (a) and (b) may be condensed with one or more other benzene rings to form a condensed ring, and the benzene ring in (c) may be the other one. It may be condensed with the above benzene ring or heterocycle to form a condensed ring.

The above-mentioned hydrocarbon group, nitrogen-containing hydrocarbon group, benzene ring and heterocycle in (a), (b) and (c) are a halogen atom, an alkyl group, an alkoxy group, an alkylamino group and an arylamino group. It can also be substituted with an organic residue such as a group, an acylamino group, a nitro group, a cyano group, or a hydroxy group.

More specifically, the above (a),
Specific examples of (b) and (c) are as follows.

As an example of (a),

[0031]

Embedded image

And the like.

As an example of (b),

[0034]

Embedded image

And the like.

As an example of (c),

[0037]

Embedded image

And the like.

The optical sensor of the present invention has the above general formula (2).
By utilizing the excellent carrier generating function of the azo compound represented by, as a charge generating substance of the optical sensor, not only can it stably show certain electric characteristics,
The optical sensor has good film properties and little deterioration due to repeated use.

Specific examples of the azo compound represented by the general formula (2) are shown below, but the azo compound in the present invention is not limited thereto.

Specific examples of the azo compound represented by the general formula (2)

[0042]

Embedded image

[0043]

Embedded image

[0044]

[Chemical 12]

[0045]

Embedded image

[0046]

Embedded image

[0047]

Embedded image

[0048]

Embedded image

[0049]

Embedded image

[0050]

Embedded image

[0051]

Embedded image

[0052]

Embedded image

[0053]

[Chemical 21]

[0054]

Embedded image

The above compounds can be synthesized by known methods. For example, the compound of the general formula A- (NH ₂ )
_m {wherein _m is an integer of 1 to 4 and A has the same meaning as in general formula (2). } By diazotizing the amine represented by the following formula and subjecting the resulting diazonium salt to a coupling reaction with the coupler of the general formula (1) in the presence of an alkali.

An example of the synthesis example will be described below. Azo compounds having another structure represented by the general formula (2) can also be synthesized according to the following synthesis examples. Note that the following synthesis examples do not limit the content of the present invention.

Synthesis Example (In the case of Exemplified Compound No. 1) 10.1 parts by weight of 3.3'-dichlorobenzidine was added to water 2
Disperse in a mixed solution of 00 parts by weight and concentrated hydrochloric acid 33 parts by weight. 61 parts by weight of a 10% sodium nitrite aqueous solution was added dropwise over 10 minutes while maintaining good agitation of this dispersion while maintaining it at 0 to 5 ° C., followed by further stirring for 15 minutes to obtain a diazonium salt solution.

Next, the coupler 3 of the following structural formula (3)
After 2.0 parts by weight was dissolved in 700 parts by weight of a 2% aqueous sodium hydroxide solution, the solution was cooled and kept at 0 to 5 ° C., and the diazonium salt aqueous solution obtained above was dropped into this solution over 15 minutes. did.

[0059]

Embedded image

After completion of the dropping, the mixture was stirred for additional 2 hours, the resulting azo compound was filtered off and washed thoroughly with water to prepare Exemplified Compound No. 1
37.6 parts by weight of a crude product of This was washed with DMF, methanol, and then with water in that order and dried to obtain a purified product.

The optical sensor of the present invention will be described. FIG. 1 is a cross-sectional view for explaining a stacked optical sensor,
In the figure, 13 is an electrode, 14 'is a charge generation layer, 14''is a charge transport layer, and 15 is a substrate.

The charge generation layer 14 'has the above-mentioned general formula (1).
The azo compound represented by the fine particles in a suitable medium,
After adding a binder if necessary, on the electrode, for example, blade coating method, dip coating method,
Spinner coating method, slide coating method,
It is formed by applying after coating by an α coating method, a kiss coating method, a roll coating method, or the like.
The azo compound is preferably dispersed with a primary average particle size of 1 μm or less, preferably 0.7 μm or less, and most preferably 0.5 μm or less.

The binder is not particularly limited,
A hydrophobic, high dielectric constant, insulating polymer compound is preferable, and various thermoplastic or thermosetting synthetic resins can be suitably used. For example, silicone resin, polycarbonate resin, vinyl acetal resin such as vinyl formal resin, vinyl butyral resin, styrene resin, styrene-butadiene copolymer resin, epoxy resin, acrylic resin, saturated or unsaturated polyester resin, methacrylic resin, vinyl chloride Resin, vinyl acetate resin, vinyl chloride
A vinyl acetate copolymer resin and the like can be mentioned, and they can be used alone or in combination.

In the ink composition for forming a photoconductive layer in a laminated photosensor, the mixing ratio of the azo compound and the binder is
The binder is 0.1-10 with respect to 1 part by weight of the azo compound.
The weight ratio is preferably 0.2 to 1 part by weight. Examples of the medium include 1,2-dichloroethane,
1,1,2-trichloroethane, chlorobenzene, tetrahydrofuran, cyclohexanone, dioxane, 1,
2,3-trichloropropane, ethyl cellosolve, 1,
Examples include 1,1, -trichloroethane, methyl ethyl ketone, chloroform, toluene, and xylene, and solid content of 0.2% by weight by ball mill dispersion, disperser dispersion, sand mill dispersion, triple roll dispersion, ultrasonic dispersion, or the like.
It is set to 20% by weight, preferably 1% to 5% by weight.

The charge generation layer has a film thickness of 0.01 after drying.
２2 μm, and preferably 0.1-0.5 μm. With such a film thickness, good sensitivity and image quality are exhibited.

The charge-transporting layer 14 "is formed by dispersing or dissolving a charge-transporting substance in a suitable medium described in the charge-generating layer, applying the charge-transporting material on the charge-generating layer 14 ', and drying. It is preferable to use a binder, unless the organic substance is a substance such as poly-N-vinylcarbazole or polyglycidylcarbazole which itself functions as a binder. Is a substance having a good transport property of the carrier generated in, for example, oxadiazole-based, oxazole-based, triazole-based, thiazole-based, triphenylmethane-based, styryl-based, pyrazolone-based, hydrazone-based, aromatic amine-based, carbazole-based , Polyvinylcarbazole type, stilbene type, enamine type, azine type, triphenylamine type, butadie And a polycyclic aromatic compound, a stilbene dimer, a biphenyl, and the like, and it is necessary to use a substance having good hole transporting properties.

As the binder, the same binders as those used in the charge generation layer described above, and polyarylate resin and phenoxy resin can be used, but styrene resin, styrene-butadiene copolymer resin and polycarbonate resin are preferable. Binder is charge transporting substance 1
0.1 to 10 parts by weight, preferably 0.1
It is desirable to use at a ratio of 1 part by weight.

The thickness of the charge transport layer after drying is 1 to 50 μm.
m, preferably 3 to 20 μm, whereby good sensitivity and image quality can be obtained. Further, the above-described charge transporting substance that can be formed into a film by the vapor deposition method can be formed into a film without using a binder.

Next, a single-layer type optical sensor will be described. FIG. 2 is a cross-sectional view for explaining the single-layer type optical sensor, in which 13 is an electrode, 14 is a photoconductive layer, and 15 is a substrate. In order to form a single-layer photoconductive layer, the above-described charge transporting substance may be dissolved or dispersed in the above-described dispersion for forming a charge generation layer, and may be similarly coated on an electrode. The charge-transporting substance can be arbitrarily selected, but it is preferable to use the binder described in the above-mentioned laminated optical sensor, except for using the substance which itself serves as a binder as described above.

In the ink composition for forming the photoconductive layer in the single-layer type photosensor, the mixing ratio of the azo compound and the binder is
The binder may be used in an amount of 0.1 to 10 parts by weight, preferably 0.3 to 3 parts by weight, based on 1 part by weight of the azo compound.

The charge-transporting substance is 0.5 parts by weight to 1 part by weight with respect to 1 part by weight of the azo compound represented by the general formula (1).
The binder may be used in an amount of 0 part by weight, preferably 1 part by weight to 3 parts by weight. When the charge transporting substance does not function as a binder, the binder is 0 parts by weight based on 1 part by weight of the total amount of the azo compound and the charge transporting substance. 1 to 10 parts by weight, preferably 0.1 to 1 part by weight.

Examples of the medium in the ink composition include the medium described in the above laminated photosensor,
By the same dispersing method, the solid content is adjusted to 0.2 to 20% by weight, preferably 1 to 5% by weight.

The photoconductive layer in the single-layer type photosensor has a thickness after drying of 5 μm to 30 μm, preferably 1 μm.
The thickness is preferably 0 to 20 μm, whereby good sensitivity and image quality can be obtained.

The electrode 13 in the optical sensor is required to have transparency if the information recording medium described later is opaque, but if the information recording medium is transparent, it may be transparent or opaque. ^A material that stably gives a specific resistance of ⁶ Ω · cm or less, for example, a metal thin film conductive film of gold, platinum, zinc, titanium, copper, iron, tin, etc., tin oxide, indium oxide, zinc oxide, titanium oxide, tungsten oxide. , A metal oxide conductive film such as vanadium oxide, an organic conductive film such as a quaternary ammonium salt, or the like can be used alone or as a composite material of two or more kinds. Among them, metal oxide conductors are preferable, and indium tin oxide (ITO) is particularly preferable. The electrode is formed by a method such as vapor deposition, sputtering, CVD, coating, plating, immersion, and electric field polymerization, and is formed on the entire surface between the information recording layer and an arbitrary pattern. Further, two or more kinds of materials can be stacked and used.

The substrate 15 is required to have transparency if the information recording medium described later is opaque. However, if the information recording medium has transparency, it may be transparent or opaque. It has the shape of a film, tape, disk, etc. and strongly supports the optical sensor. If the optical sensor itself has a supporting property, it is not necessary to provide it. However, the material and thickness are not particularly limited as long as the optical sensor has a certain strength capable of supporting the optical sensor. For example, a flexible plastic film, or a plastic sheet or card of glass, polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polymethyl acrylate, polyester, polycarbonate, or the like is used.

If the electrode 13 is transparent, a layer having an antireflection effect may be laminated on the other surface of the substrate on which the electrode 13 is provided, or an antireflection effect may be exhibited. The antireflection property may be imparted by adjusting the thickness of the transparent substrate or by combining the two.

Next, an information recording medium used in combination with the optical sensor of the present invention will be described. Examples of the information recording medium include a case where the information recording layer is a liquid crystal-polymer composite (hereinafter, referred to as LCPC). LCPC
Has a structure in which resin particles are dispersed in a liquid crystal phase,
As the liquid crystal material, a smectic liquid crystal, a nematic liquid crystal, a cholesteric liquid crystal, or a mixture thereof can be used. As a liquid crystal, from the viewpoint of so-called memory properties, it retains its orientation and retains information permanently.
It is preferred to use smectic liquid crystals.

As the smectic liquid crystal, a liquid crystal substance exhibiting a smectic A phase such as a cyanobiphenyl type, a cyanoterphenyl type, a phenyl ester type having a long terminal carbon group of a substance exhibiting liquid crystallinity, a fluorine type or the like, a ferroelectric substance Examples thereof include a liquid crystal substance exhibiting a smectic C phase used as a liquid crystal, a liquid crystal substance exhibiting a smectic H, G, E, G phase and the like.

The material for forming the resin particles is, for example, an ultraviolet curable resin which is compatible with the liquid crystal material in the monomer or oligomer state, or a solvent which is common to the liquid crystal material in the monomer or oligomer state. Those having compatibility with can be preferably used. Examples of such an ultraviolet-curable resin include acrylic acid esters and methacrylic acid esters. In addition, a solvent-soluble resin having compatibility with a common solvent with the liquid crystal material, for example, an acrylic resin, a methacrylic resin, a polyester resin, a polystyrene resin, and a copolymer containing these as a main component,
Epoxy resins, silicone resins and the like can be mentioned.

The ratio of the liquid crystal material to the resin used is such that the liquid crystal content is 10% by weight to 90% by weight, preferably 40% by weight.
The content is preferably used so as to be 80% by weight. If it exceeds 90% by weight, phenomena such as oozing out of liquid crystal occur, and image unevenness occurs, which is not preferable.

Since the film thickness of the information recording layer affects the resolution, the film thickness after drying is 0.1 μm to 10 μm, preferably 3 μm.
The operating voltage can be reduced while maintaining high resolution. If the film thickness is too small, the contrast of the information recording portion is low, and if it is too large, the operating voltage is undesirably high.

Next, two information recording devices using this information recording medium and the above-mentioned optical sensor will be described.

First, in the first information recording apparatus, as shown in FIG. 3, the information recording medium 2 uses the above-mentioned optical sensor 1 and the insulating resin film spacer 19 such as a polyimide film, and has a thickness of 2 μm to 20 μm. The two electrodes 13 and 13 'are connected to each other via the voltage source V, and the information recording device is formed. One or both of the electrodes 13 and 13 'in this device may be transparent.

Further, a second information recording device as shown in FIG. 4 may be used. FIG. 4 is a cross-sectional view of the information recording apparatus. In the figure, reference numeral 20 denotes a dielectric layer, and the same reference numerals as those in FIG. 3 indicate the same contents.

In this information recording device, the optical sensor 1 and the information recording medium 2 are laminated with the dielectric layer 20 interposed therebetween without providing a gap. This information recording device is particularly suitable when the photoconductive layer in the optical sensor is formed by applying a solvent. That is, when the information recording layer is directly applied and formed on the photoconductive layer, the liquid crystal in the information recording layer elutes due to the interaction between them, and the image due to the elution of the photoconductive material by the solvent for forming the information recording layer. The occurrence of unevenness can be prevented. In addition, the optical sensor and the information recording medium can be integrated.

When forming the dielectric layer 20, it is necessary that its constituent components have no solubility in the photoconductive layer forming material and the information recording layer forming material.
Further, it is necessary that the material does not have conductivity. In the case of having conductivity, the space charge is diffused and the resolution is deteriorated, so that the insulating property is required. Further, since the dielectric layer applies a distribution voltage applied to the liquid crystal layer or deteriorates the resolution, it is preferable that the film thickness is small,
m or less. However, if the thickness is too small, image noise due to the interaction with time is generated, and there is a problem of permeation due to defects such as pinholes during lamination coating. Since the permeability due to defects such as pinholes differs depending on the solid content ratio of the material to be laminated, the type of solvent, and the viscosity, the thickness of the dielectric layer is appropriately set, but it is preferable that the thickness be at least 10 μm or less. Preferably, the thickness is 0.1 to 3 μm. Further, in consideration of the distribution of the voltage applied to each layer, a material having a high dielectric constant as well as a thin film is preferable.

As a material for forming the dielectric layer, inorganic materials such as SiO ₂ , TiO ₂ , CeO ₂ , Al ₂ O ₃ and G are used.
eO ₂ , Si ₃ N ₄ , AlN, TiN, MgF ₂ , Zn
S, using a combination of silicon dioxide and titanium dioxide, a combination of zinc sulfide and magnesium fluoride, a combination of aluminum oxide and germanium, etc.
It is preferable to form the layers by a CVD method or the like. In addition, a water-soluble resin having low compatibility with an organic solvent, for example, an aqueous solution of polyvinyl alcohol, hydrogenated urethane, water glass, or the like is used, and a spin coating method, a blade coating method, a roll coating method, a bead coating method, a slide coating method is used. It may be laminated by a method or the like. Further, a coatable fluororesin may be used. In this case, the resin is dissolved in a fluorine-based solvent and applied by a spin coat method, or a blade coat method, a roll coat method, a bead coat method, a slide coat method, or the like. May be laminated. As a fluorine resin that can be applied,
For example, an organic material such as polyparaxylene which is formed into a film by a vacuum system and a fluororesin disclosed in JP-A-4-24722 can be preferably used.

Next, the information recording method of the present invention will be described.

FIG. 10 is a diagram for explaining the information recording method in the first information recording apparatus. The same applies to the second information recording device. In the figure, 11 is an information recording layer, 13
Is the electrode of the optical sensor, 13 'is the electrode of the information recording medium, 1
4 is a photoconductive layer, 21 is a light source, 22 is a shutter having a driving mechanism, 23 is a pulse generator serving as a power supply, 2
4 indicates a dark box.

When information light is made incident from the light source 21 while applying an appropriate voltage by the pulse generator 23 between the electrodes 13 and 13 ', the photoconductive layer 1 at the portion where the light is made incident.
The photocarrier generated in step 4 moves to the interface on the information recording layer 11 side by the electric field formed by the two electrodes, redistributes the voltage, and the liquid crystal layer in the information recording layer 11 is oriented according to the electric field or the amount of charge. Then, recording according to the pattern of the information light is performed.

In this information recording method, planar analog recording is possible, and recording at the liquid crystal level can be obtained, so that high-resolution recording is achieved, and the exposure pattern is visualized by the orientation of the liquid crystal phase. Retained. The information recorded by the orientation of the liquid crystal is visible information that can be read visually, but it can be read by enlarging it with a projector, and the information is read with high precision using laser scanning or CCD. be able to.

[0092]

Embodiments of the present invention will be described below. In the following examples, "parts" or "%" indicates parts by weight or% by weight, respectively. Further, the following embodiments do not limit the contents of the present invention.

Example 1 An ITO film having a sheet resistance of 80 Ω / □ and a film thickness of 100 nm formed on a glass substrate having a thickness of 1.1 mm was thoroughly washed and dried.

Exemplified azo compound (1) having the following structure on this ITO film

[0095]

Embedded image

3 parts and 1 part of polyvinyl formal resin, 98 parts of 1,4-dioxane and 98 parts of cyclohexanone.
After being mixed with 1 part, the mixture was sufficiently dispersed using a paint shaker and a super-dispersing device (Nanomizer LA31 manufactured by Nanomizer Co., Ltd.) to obtain a cumulative 50% average particle size (measured by "MICROTRAC2" manufactured by Nikkiso). A dispersion coating solution having a thickness of 21 μm was prepared, which was then coated with a blade coater, air-dried and then dried at 100 ° C. for 1 hour to form a charge generation layer having a thickness of 0.3 μm.

Next, on this charge generation layer, 15 parts of p-diethylaminobenzaldehyde-N-phenyl-N-benzylhydrazone and 10 parts of a polycarbonate resin were added.
1,1,2-trichloroethane: dichloroethane = 69
Part: 46 parts, and uniformly dissolved in a solvent consisting of 46 parts to obtain a coating solution, which was coated with a spinner at 500 rpm for 0.4 seconds. After coating, the film is left on the surface of the coating film in a windless state until the surface of the coating film is not adhered to the surface of the coating film, and then dried at 80 ° C. for 2 hours. Were laminated to produce an optical sensor having a photoconductive layer having a thickness of 10 μm.

[0098] To measure the resulting electric characteristics of the photoelectric sensor (electrical characteristics of the photoelectric sensor), 0.16 cm ² on the charge transport layer in an optical sensor, a thickness of 10 nm, surface resistance 1 k [Omega / □ gold electrode A current measuring device as shown in FIG. 11 was constructed by vapor deposition to form an electrode and a medium for measurement.

In the figure, 15 is a photosensor support, 13 is a photosensor electrode, 16 is a concentration gradient region, 14 is a photoconductive layer,
Reference numeral 30 is a gold electrode, 31 is a light source, 32 is a shutter (No. 0 electromagnetic shutter manufactured by Copal), 33 is a shutter drive mechanism, 34 is a pulse generator (manufactured by Yokogawa Hewlett-Packard), and 35 is an oscilloscope.

In this current measuring device, the electrode 13 in the photosensor is positive and the gold electrode is negative, and the distance between both electrodes is 15
0 V (1.5 × 10 ⁵ V / c electric field strength to optical sensor)
m) was applied, and 0.5 seconds after the start of the voltage application, light irradiation was performed from the glass substrate side for 0.033 seconds, and the light irradiation start time was set to t = 0, and the current flowing through the optical sensor was measured. The irradiation light was a green light obtained by a green filter (manufactured by Nippon Vacuum Optical Co., Ltd.) using a xenon lamp (L2274 manufactured by Hamamatsu Photonics) as a light source.
Irradiation at 1 ux intensity. The irradiation light intensity was measured with an illuminometer (manufactured by Minolta), and the characteristics of the filter used are shown in FIG.

The voltage application was continued even after the light irradiation was completed, and the voltage application was continued for 0.15 seconds from the light irradiation start time. The result of measuring the change over time in the current with an oscilloscope is shown by line A in FIG. The line (B) is a case where only voltage is applied without exposure. The horizontal axis represents voltage application time (seconds), and the vertical axis represents current density (A / cm ² ).
As shown by the line A, two inflection points (a) and (b) are observed in the current value by the optical sensor of the present invention. The amount of current below the inflection point (a) is considered to be a current (light-induced current) corresponding to the amount of exposure. Further, the inflection point (b) is a change point of the current amount following the end of the exposure, and it can be seen that the current according to the voltage change continuously flows and gradually attenuates even when the exposure is not performed yet. . That is, from this figure, it can be seen that, in the optical sensor of the present invention, the light-induced current continues to increase during exposure, continues after the exposure is completed, and gradually decreases after a certain period of time. The value of the base current density (passing current density in the unexposed portion) of this photosensor is 2.8.
It was × 10 ^-6 A / cm ² .

The optical sensor of the present invention is 10 ⁵ to 10 ⁶ V
It is preferable that the passing current density in the unexposed portion is 10 ⁻⁴ to 10 ⁻⁷ A / cm ² when a voltage with an electric field intensity of 10 / cm is applied, and the passing current density in the unexposed portion is 10 ⁻⁴ to. 10 ^-7 A
In the range of / cm ^2, the amplification effect is remarkable, and the optical sensor can be excellent in information recording performance.

(Production of Information Recording Medium) An ITO film having a thickness of 100 nm was formed by sputtering on a glass substrate having a thickness of 1.1 mm to obtain an electrode, and then the surface was washed.

On this electrode, a polyfunctional monomer (dipentaerythritol hexaacrylate, manufactured by Toagosei Kagaku Kogyo, M-400) 40 parts, a photocuring initiator (2-hydroxy-2-methyl) -1-Phenylpropan-1-on, Ciba Geigy, Glocure 1173) ... 2 parts, liquid crystal {Smectic liquid crystal (Merck, S-6) 90%, nematic liquid crystal (Merck, E31LV) ) Is contained by 10%} ... 50 parts, -Surfactant (Sumitomo 3M, Fluorad FC-430)-3 parts are uniformly dissolved in 96 parts of xylene to obtain a coating solution of 5 parts.
After coating using a blade coater with an interval of 0 μm, the coating film was dried at 47 ° C. for 3 minutes, then dried under reduced pressure at 47 ° C. for 2 minutes, and immediately cured by irradiation with 0.3 J / cm ² of ultraviolet light. Thus, an information recording medium having an information recording layer having a thickness of 6 μm was obtained.

After the liquid crystal was extracted from the information recording layer surface with hot methanol and dried, the internal structure was observed with a scanning electron microscope (Hitachi, S-800) at 1000 times. It is covered with a UV-curable resin of 0.6 μm and has a particle size of 0.1 μ in the liquid crystal phase forming a continuous layer inside the layer.
m had a structure filled with a resin particle phase.

(Information recording method and recording characteristics) The obtained optical sensor and an information recording medium were combined as shown in FIG. 3, and an air layer was provided to face each other via a spacer of a polyimide film having a thickness of 10 μm, Laminated.

This laminated body was mounted on an image pickup camera (RB67 manufactured by Mamiya Co., Ltd.) as shown in FIG. 10 with the photographic film replaced, and 700 V was applied between both electrodes of the optical sensor and the information recording medium.
Was applied for 0.04 seconds, and at the same time, a projection exposure was performed from the optical sensor side for 1/30 seconds at a gray scale exposure of 2-200 lux. After the exposure, the information recording medium was taken out. When observing the information recording medium with transmitted light,
In the information recording layer, a recording portion composed of a light transmitting portion corresponding to a gray scale was observed.

Then, the recorded information on the information recording medium was read by an image scanner using a CCD line sensor, and the information was output using a sublimation transfer printer (SP-5500 manufactured by Victor Company of Japan). As a result, a good printed matter having a gradation property corresponding to the above was obtained.

Further, when a color image was recorded in the same manner by separating the three colors of R, G, and B with a prism and a color filter, the recorded image was good, and the recorded information of the color image was read in the same manner to obtain information. As a result of outputting, good printed matter was obtained.

Example 2 5 parts by weight of polyvinyl alcohol (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., AH-26, saponification degree 97-) on the photoconductive layer in the optical sensor prepared in Example 1.
99%) was dissolved in 95 parts by weight of ion-exchanged water, and this was applied with a spinner to give a film thickness of 1 μm.
m dielectric layers were laminated.

Then, an information recording layer was formed on this dielectric layer in the same manner as the method for forming the information recording layer shown in Example 1, and ITO was sputtered on the information recording layer.
Was deposited to a thickness of 20 nm to form a conductive layer, thereby producing an information recording medium.

A DC voltage of 700 V was applied between both electrodes of this information recording medium, and at the same time, a gray scale was projected and exposed from the optical sensor side for 1/30 seconds as in Example 1. The voltage application time was 0.05 seconds. After the exposure, the information recording medium was taken out and read and output by the same information output device as in Example 1. As a result, a good printed matter was obtained.

(Embodiment 3) (Electrical Characteristics of Optical Sensor) The electrical characteristics of the optical sensor manufactured in Example 1 were measured 100 times. It was found that the optical sensor of the present invention was excellent in durability.

(Information recording characteristic) The above-mentioned electric characteristic measurement is performed 1
The optical sensor and the information recording medium after repeating 00 times,
In the same manner as in Example 1, as shown in FIG.
An air layer was provided via a spacer of a polyimide film having a thickness of μm, and the layers were laminated to face each other.

As shown in FIG. 10, this laminated body was mounted on an image pickup camera (RB67 manufactured by Mamiya Co., Ltd.) with the photographic film replaced, and a 700-mm film was placed between both electrodes of the optical sensor and the information recording medium.
At the same time as applying a direct voltage of V for 0.04 seconds, the gray scale exposure amount is 2 to 200 lux for 1/30 seconds,
Projection exposure was performed from the light sensor side. After the exposure, the information recording medium was taken out. When the information recording medium was observed with the transmitted light, a recording portion including a light transmitting portion corresponding to a gray scale similar to that of Example 1 was observed in the information recording layer. Next, the information recorded on the information recording medium is read by an image scanner using a CCD line sensor, and the information is read by a sublimation transfer printer (SP- made by Victor Company of Japan, Ltd.).
5500), a good printed matter having the same gray scale gradation as in Example 1 was obtained.

When a color image was recorded in the same manner by decomposing it into three colors of R, G and B with a prism and a color filter, the image recorded in the same manner as in Example 1 was good and the recording information of the color image was the same. As a result of reading and outputting information, good printed matter was obtained.

[0117]

In the photosensor of the present invention, by using the photosensor containing this specific azo compound in the photoconductive layer, the conductivity of the entire photosensor element can be brought to an appropriate state. It is possible to obtain an optical sensor suitable for the operating voltage and range of the liquid crystal recording medium. Therefore, the recording image density can be kept within a certain range, and stable recording of optical information can be performed.
That is, the optical sensor according to the present invention can be an optical sensor having high sensitivity, stable electrical characteristics, good film properties, and little deterioration due to repeated use.

[Brief description of drawings]

FIG. 1 is a cross-sectional view illustrating an optical sensor of the present invention.

FIG. 2 is a sectional view illustrating another optical sensor according to the present invention.

FIG. 3 is a sectional view illustrating a first information recording device according to the present invention.

FIG. 4 is a sectional view illustrating a second information recording device according to the present invention.

FIG. 5 is a diagram showing a spectral characteristic of a green filter in a measurement system used for explaining a photocurrent amplification action of the photosensor of the present invention.

FIG. 6 is a diagram showing a measurement result of a photocurrent amplifying action of a comparative sensor.

FIG. 7 is a diagram showing a change in quantum efficiency during light irradiation of a comparative sensor.

FIG. 8 is a diagram showing measurement results of photocurrent amplification action in the optical sensor of the present invention.

FIG. 9 is a diagram showing changes in quantum efficiency during light irradiation of the photosensor of the present invention.

FIG. 10 is a diagram for explaining the information recording method of the present invention.

FIG. 11 is a diagram for explaining a current measuring device.

FIG. 12 is a diagram showing current measurement results of the optical sensor of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Optical sensor, 2 ... Information recording medium, 11 ... Information recording layer, 13, 13 '... Electrode, 14 is a photoconductive layer, 14' ... Charge generating layer, 14 "... Charge transport layer, 15 ... Substrate, 19 ... Spacer, 20 ... Dielectric layer, 21 ... Light source, 22 ... Shutter having drive mechanism, 23 ... Pulse generator (power supply), 24 ... Dark box, 30 ... Gold electrode, 31 ... Light source, 32 ...
Shutter, 33 ... Shutter drive mechanism, 34 ... Pulse generator, 35 ... Oscilloscope

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location G03G 5/06 367 (72) Inventor Osamu Suda 1-7-6 Nihonbashi-Bakurocho, Chuo-ku, Tokyo Large Within Nissei Kagaku Co., Ltd. (72) Inventor Masanori Akada 1-1-1, Ichigaya-Kagacho, Shinjuku-ku, Tokyo Within Dai Nippon Printing Co., Ltd. (72) In-house Hironori Ueyama 1-1-1-1 Ichigaya-Kagacho, Shinjuku-ku, Tokyo No. 1 in Dai Nippon Printing Co., Ltd. (72) Inventor Daigo Aoki 1-1-1, Ichigaya-Kagacho, Shinjuku-ku, Tokyo No. 1 within Dai-Nippon Printing Co., Ltd. (72) Inventor Osamu Shimizu 1-chome, Ichigaya-Kagacho, Shinjuku-ku, Tokyo No. 1 in Dai Nippon Printing Co., Ltd.

Claims (6)

[Claims] 1. An optical sensor having a photoconductive layer on at least an electrode, which is arranged to face an information recording medium having an information recording layer on at least an electrode, and a voltage is applied between both electrodes in an exposed state. Alternatively, in an optical sensor capable of forming information on an information recording medium by an electric field or an amount of electric charge by exposing under an applied voltage, a photoconductive layer of the optical sensor is represented by the following general formula (1). An optical sensor comprising an azo compound having at least one azo group bonded to a coupler residue in the molecule. Embedded image (In the formula, X is a group of atoms necessary for being condensed with a benzene ring to form a substituted / unsubstituted aromatic hydrocarbon ring or a substituted / unsubstituted aromatic heterocycle, and Y is hydrogen, a halogen atom, or a cyano group. A group, a substituted / unsubstituted alkyl group, an alkoxy group, and an integer group of n = 0 to 4. Further, R ₁ and R
₂ represents hydrogen, a substituted / unsubstituted alkyl group, a substituted / unsubstituted aromatic hydrocarbon ring group or a substituted / unsubstituted aromatic heterocyclic group. Here, R ₁ and R ₂ may be the same or different, and may form a ring in cooperation with the nitrogen atom. ) 2. The light sensor is semi-conductive, and when a voltage is applied between both electrodes while being exposed, or when a light is exposed while a voltage is applied, the information recording medium is exposed to more than a current caused by the exposure. Information can be recorded with the amplified intensity, and the behavior is such that the conductivity gradually decreases when voltage is continuously applied after the exposure is completed, and it has the effect of continuing information recording on the information recording medium. The optical sensor according to claim 1, wherein: 3. The passing current density in the unexposed portion is 10 ⁻⁴ to 10 ⁻⁷ A / cm ² when an electric field strength of 10 ⁵ to 10 ⁶ V / cm is applied to the photosensor. The optical sensor according to claim 1 or 2. 4. An optical sensor having a photoconductive layer on at least an electrode and an information recording medium having an information recording layer on at least the electrode are arranged to face each other, and a voltage is applied between both electrodes in an exposed state. Or a material for forming a photoconductive layer in an optical sensor capable of forming information on an information recording medium by an electric field or an amount of electric charge, which is represented by the following general formula (1). A material for forming a photoconductive layer in an optical sensor, which is an azo compound having at least one azo group bonded to a coupler residue in a molecule. Embedded image (In the formula, X is a group of atoms necessary for being condensed with a benzene ring to form a substituted / unsubstituted aromatic hydrocarbon ring or a substituted / unsubstituted aromatic heterocycle, and Y is hydrogen, a halogen atom, or a cyano group. A group, a substituted / unsubstituted alkyl group, an alkoxy group, and an integer group of n = 0 to 4. Further, R ₁ and R
₂ represents hydrogen, a substituted / unsubstituted alkyl group, a substituted / unsubstituted aromatic hydrocarbon ring group or a substituted / unsubstituted aromatic heterocyclic group. Here, R ₁ and R ₂ may be the same or different, and may form a ring in cooperation with the nitrogen atom. ) 5. An optical sensor having a photoconductive layer on at least an electrode and an information recording medium having an information recording layer on at least an electrode are arranged to face each other, and a voltage is applied between both electrodes in an exposed state. Or an ink composition for forming a photoconductive layer in an optical sensor capable of forming information on an information recording medium by an electric field or an amount of electric charge, which is exposed by applying a voltage, and is represented by the following general formula (1): An ink composition for forming a photoconductive layer, comprising an azo compound having at least one azo group bonded to the coupler residue shown in the molecule and a binder. Embedded image (In the formula, X is a group of atoms necessary for being condensed with a benzene ring to form a substituted / unsubstituted aromatic hydrocarbon ring or a substituted / unsubstituted aromatic heterocycle, and Y is hydrogen, a halogen atom, or a cyano group. A group, a substituted / unsubstituted alkyl group, an alkoxy group, and an integer group of n = 0 to 4. Further, R ₁ and R
₂ represents hydrogen, a substituted / unsubstituted alkyl group, a substituted / unsubstituted aromatic hydrocarbon ring group or a substituted / unsubstituted aromatic heterocyclic group. Here, R ₁ and R ₂ may be the same or different, and may form a ring in cooperation with the nitrogen atom. ) 6. An optical sensor having a photoconductive layer composed of a charge transport layer and a charge generation layer on at least an electrode, and an information recording medium having an information recording layer on at least the electrode are arranged to face each other, and between both electrodes, Photoconductivity for forming a charge generation layer in an optical sensor capable of forming information on an information recording medium by an electric field or an amount of electric charge by applying a voltage in an exposed state or by applying a voltage in an exposed state An ink composition for forming a layer, which comprises a binder and an azo compound having at least one azo group bonded to a coupler residue represented by the following general formula (1) in a molecule and a binder. Ink composition. Embedded image (In the formula, X is a group of atoms necessary for being condensed with a benzene ring to form a substituted / unsubstituted aromatic hydrocarbon ring or a substituted / unsubstituted aromatic heterocycle, and Y is hydrogen, a halogen atom, or a cyano group. A group, a substituted / unsubstituted alkyl group, an alkoxy group, and an integer group of n = 0 to 4. Further, R ₁ and R
₂ represents hydrogen, a substituted / unsubstituted alkyl group, a substituted / unsubstituted aromatic hydrocarbon ring group or a substituted / unsubstituted aromatic heterocyclic group. Here, R ₁ and R ₂ may be the same or different, and may form a ring in cooperation with the nitrogen atom. )