JP2000133493A - Electrode for discharge treatment, discharge treating method and device using the electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably generate the discharge plasma for a long time and to execute the surface treatment for a short time by lining surface of a conductive base material of at least one of opposite surfaces of a pair of opposite electrodes for discharge treating to a substrate, with an inorganic material hardenable at not more than a predetermined temperature. SOLUTION: The conductive base materials 21A, 22A are metal such as gold, platinum or the like, or a composite material of metal and ceramic. The base materials 21A, 22A are coated with a normal temperature hardenable glass as a dielectric of an inorganic material hardneable at not more than 100 deg.C to manufacture the electrodes 21, 22. The base materials are optionally coated with various glass such as pyrex or the like as the inorganic solid dielectric 21B, 22B meltable at a high temperature, ceramic, or metallic oxide such as titanium oxide or the like. A substrate F for a photographic photosensitive material, is placed between a pair of opposite electrodes 21, 22 to form a discharge treatment chamber 30, and a mixture gas 54 including the Ar gas of at least 60 pressure % is introduced thereto to perform the discharge treatment onto the surface of the substrates F continuously conveyed with above 7.5 kW/m2 of discharge output.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode for electric discharge treatment, an electric discharge treatment method and an electric discharge treatment apparatus using the electrode, and more particularly, to a durable electric discharge capable of stably generating a discharge plasma for a long time. The present invention relates to a processing electrode, a discharge processing method and a discharge processing apparatus for performing discharge processing with good surface performance on a supporting pair by discharge plasma using the electrode.

[0002]

2. Description of the Related Art Conventionally, there has been known an electrode used in a discharge processing apparatus for discharging a surface of a support with discharge plasma at a pressure of about 0.01 to 10 Torr. However, this discharge processing apparatus requires a vacuum apparatus. Since the apparatus becomes complicated, a technique that enables discharge plasma at or near atmospheric pressure is disclosed as an improvement. Therefore, it is necessary to cover the surface of the electrode with a solid dielectric in order to generate discharge plasma, and this technique has been disclosed (Japanese Patent Publication No. 2-48626).

However, when the solid dielectric material is an organic material, the material changes with time, so that it is difficult to obtain a stable discharge plasma for a long time, and the organic material adheres to the support and adversely affects the quality. was there. Therefore, as an improvement, there has been disclosed a technique relating to an electrode in which a solid dielectric is formed using a ceramic spraying method in which a sprayed material powder heated to a molten state is sprayed onto a metal base material surface to form a film as an inorganic coating. (JP-A-6-96718). Further, there is disclosed a technique relating to an electrode in which a solid dielectric is formed on the surface of a metal base material by using a glass lining method of forming a film by melting glass.

[0004]

As described above, as a problem of the prior art, all of the above-mentioned electrodes for generating discharge plasma have glass, ceramics, or the like on at least one electrode surface in order to prevent arc discharge. The cover is provided with plastic or the like. However, in the ceramic spraying method, the base material is unlikely to be deformed, but the dielectric of the coated ceramic has a porous structure, and the discharge concentrates there, and pinholes are likely to be generated and strong discharge occurs. It is impossible and lacks uniformity. In particular, when used continuously for a long time, dielectric breakdown occurs and the transition from glow discharge to arc discharge tends to occur. In addition, the coated dielectric formed by the glass lining method also has a large difference in thermal shrinkage from the base material, which causes distortion and bending, making it impossible to produce an electrode capable of long-term discharge treatment. As mentioned above,
All of the conventional electrodes have low durability and cannot stably generate discharge plasma for a long time.

In order to avoid this, even if rubber is used, the rubber which is an organic substance has a bad effect on the surface of the support, and since it gradually wears out, the durability is poor and the frequent replacement is required.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a discharge plasma electrode capable of stably generating discharge plasma for a long time and performing surface treatment in a short time. . Another object of the present invention is to provide a surface treatment method and a surface treatment apparatus which stably generate discharge plasma for a long period of time and have good surface performance in a short time and can perform surface treatment.

[0007]

This object is achieved by any one of the following technical means (1) to (17).

(1) A support is positioned between a pair of opposed electrodes, and a voltage is applied between the electrodes to perform a discharge process on the support. Characterized in that at least one of the opposing surfaces is coated with a conductive base material surface by lining an inorganic material which cures at 100 ° C. or lower.

(2) The electrode for electric discharge treatment according to the above (1), wherein the inorganic material is a glass which is curable at room temperature.

(3) The electrode for discharge treatment according to (1) or (2), wherein the electrode is an electrode for performing a discharge treatment near atmospheric pressure.

(4) At least one of the electrodes has a cylindrical shape.
Item 10. An electrode for electric discharge treatment according to item 9.

(5) At least one of the cylindrical electrodes
The electrode for discharge treatment according to item (4), wherein the electrode is a roll type that rotates while being in contact with the support.

(6) Provided on at least one of the opposing surfaces of the pair of opposing electrodes is an electrode lined with an inorganic material whose conductive base material surface is cured at 100 ° C. or lower as a dielectric, and A discharge treatment chamber is formed by positioning a support between the opposing electrodes, and a mixed gas containing Ar gas of 60% by pressure or more is introduced into the discharge treatment chamber, and a voltage is applied to the electrodes, and an atmospheric pressure is applied. Alternatively, a discharge treatment method is characterized in that a discharge plasma is excited under a pressure near the atmospheric pressure to perform a discharge treatment on the surface of a support that is continuously conveyed at a discharge output of 7.5 kW / m ² or more.

(7) An electrode lined on at least one of the opposing surfaces of the pair of opposing electrodes with a dielectric material of an inorganic material whose surface is cured at a temperature of 100 ° C. or less; A discharge treatment chamber for performing a discharge treatment by positioning a support between electrodes to be filled, a filling means for introducing and filling a mixed gas containing Ar gas at 60% by pressure or more into the treatment chamber, and applying a voltage between the electrodes. And a discharge generating means for exciting a discharge plasma under an atmospheric pressure or a pressure close to the atmospheric pressure to discharge the surface of a support continuously transported at a discharge output of 7.5 kW / m ² or more. Discharge treatment device.

(8) In an electrode used in a discharge treatment apparatus for performing a discharge treatment on the support by applying a voltage between the pair of opposed electrodes and positioning a support between the pair of opposed electrodes, Characterized in that at least one of the opposing surfaces is made of a composite material of metal and ceramic as a base material, and the surface of the base material is coated with a dielectric material.

(9) The electrode for discharge treatment according to item (8), wherein the electrode is an electrode for performing discharge treatment near atmospheric pressure.

(10) The electrode for discharge treatment according to the above mode (8) or (9), wherein at least one of the electrodes has a cylindrical shape.

(11) The electrode for discharge treatment according to item (10), wherein at least one of the cylindrical electrodes is of a roll type which rotates while being in contact with a support.

(12) Provided on at least one of the opposing surfaces of the pair of opposing electrodes is an electrode having a base material surface of a composite material of metal and ceramic lined with a dielectric, and a support is provided between the pair of opposing electrodes. To form a discharge treatment chamber, a mixed gas containing Ar gas at 60% by pressure or more is introduced into the discharge treatment chamber, and a voltage is applied to the electrode;
A discharge treatment method characterized by exciting a discharge plasma under an atmospheric pressure or a pressure close to the atmospheric pressure and performing a discharge treatment on a surface of a support continuously transported at a discharge output of 7.5 kW / m ² or more.

(13) An electrode having a base material surface of a composite material of a metal and a ceramic lined with a dielectric material on at least one facing surface of the pair of facing electrodes, and a support between the pair of facing electrodes. A discharge processing chamber for performing discharge processing while being positioned; filling means for introducing and filling a mixed gas containing Ar gas at 60% by pressure or more into the processing chamber; and voltage generating means for applying a voltage between the electrodes. And a discharge treatment apparatus that excites discharge plasma at or near atmospheric pressure to discharge the surface of the support that is continuously transported at a discharge output of 7.5 kW / m ² or more.

(14) The discharge treatment method according to the above (6) or (12), wherein the support is a plastic film.

(15) The method according to the item (14), wherein the plastic film is a support for a photosensitive material.

(16) The discharge treatment apparatus according to the above (7) or (13), wherein the support is a plastic film.

(17) The discharge processing apparatus according to item (16), wherein the plastic film is a support for a photosensitive material.

The inventor of the present invention has found that electrodes coated with a dielectric material necessary for electric discharge treatment, and in particular, cylindrical electrodes are important in producing distortion, deflection, and cracks during production due to differences in heat shrinkage, and We focused on the fact that it was a highly accurate inorganic dielectric coating without any porosity.

In other words, the difference in thermal expansion between the base material and the dielectric material is not limited to the fabrication of the electrode at room temperature by the dielectric coating on the base material or the fabrication of the electrode at a high temperature by the dielectric coating on the base material. It is necessary to reduce the size as much as possible. Therefore, it is understood that the former manufacturing method can be achieved by using a cold-setting glass as a dielectric, and the latter manufacturing method can be realized as a base material (for example, Kyocera). Cermet (trade name) manufactured by Co., Ltd.)
It has been found that this can be achieved by using a metal-ceramic composite material as described above.

The electrode thus produced, and a discharge treatment method and a discharge treatment apparatus using the same are the present invention.

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a discharge treatment electrode, a discharge treatment method, and a discharge treatment device according to the present invention will be described below with reference to the drawings, but the present invention is not limited thereto. In the following description, although there is a definite expression for a term or the like, it shows a preferable example of the present invention, and does not limit the meaning of the term or the technical scope of the present invention.

FIG. 1 is a cross-sectional view showing one example of the flat electrode of the present invention, FIG. 2 is a cross-sectional view showing another example of the flat electrode of the present invention, and FIG. FIG. 2 is a cross-sectional view of the discharge processing apparatus. FIG. 4 is a perspective view showing an example of a cylindrical and roll-type electrode according to the present invention.
FIG. 5 is a perspective view showing an example of a cylindrical fixed electrode, and FIGS. 6 and 7 are cross-sectional views of a discharge treatment apparatus using a cylindrical electrode.

In FIG. 1, a pair of electrodes is composed of a lower electrode 21 and an upper electrode 22. The pair of electrodes has a support F placed between the electrodes and generates discharge plasma to generate a discharge plasma. This is for performing discharge treatment on both surfaces. The structure of the electrodes 21 and 22 is a parallel plane type, but is not limited thereto. As shown in a sectional view of another discharge processing apparatus of the present invention in FIG. As shown in the cross-sectional view of the discharge processing apparatus of the present invention in FIG. The fixed electrode 26 is opposed to the electrode 26, and the other is not shown in the drawings. Such an electrode can be used as an electrode for discharge plasma treatment, corona discharge treatment and the like.

First, the parallel plane type electrode shown in FIGS. 1 and 2 and the discharge processing method and apparatus shown in the sectional view of FIG. 3 using the same will be described.
6 and 7 will be described in detail.

As shown in FIG. 1A, the electrode 21 is a combination of a conductive base material 21a such as a metal and the like coated with a dielectric material 21b of an inorganic material which cures at 100 ° C. or less. As shown in the figure, the base material 21A is a combination of a base material 21A of a composite material of metal and ceramics coated with a solid dielectric 21B such as a glass material that melts at a high temperature.
The electrode 22 has the following configuration, similarly to the electrode 21 described above.

The electrode 22 is a combination of a conductive base material 22a such as a metal coated with a dielectric material 22b of an inorganic material which cures at 100 ° C. or lower, as shown in FIG. As shown in (1), the base material 22A is a combination of a base material 22A of a composite material of metal and ceramics coated with a solid dielectric 22B such as a glass material that melts at a high temperature.

Of course, the electrode 21 in FIG.
The electrode 21 shown in FIG. 1B may be replaced, or the electrode 22 shown in FIG. 1B may be replaced with the electrode 22 shown in FIG.

Here, a conductive base material 21 such as a metal is used.
Metals such as silver, platinum, stainless steel, and aluminum are used for a and 22a, and cermet (trade name, manufactured by Kyocera Corporation) is used for the base materials 21A and 22A of the composite material of metal and ceramic. The dielectrics 21b and 22b, which are inorganic materials that cure at a temperature of 100 ° C. or less, are made of, for example, room temperature curable glass, and the solid dielectrics 21B and 22B, such as a glass material that melts at a high temperature, are made of various types of glass (Pyrex, quartz). Etc.), ceramics, metal oxides (titanium oxide, zirconium oxide, aluminum oxide) and the like.

Next, in FIG. 2, a pair of electrodes is a lower electrode 2
1 and the upper electrode 23. The electrode 21 is shown in FIG.
And the electrode 23 is an electrode provided with no solid dielectric. The support F is placed on the lower electrode 21 of the pair of electrodes, and one side of the support is subjected to discharge treatment.

FIG. 3 is a sectional view showing an example of a discharge processing apparatus using discharge plasma according to the present invention. In FIG. 3, the discharge processing apparatus includes electrodes 21 and 22, a holding unit 60, a gas filling unit 50,
It comprises a voltage generating means 40, a discharge processing chamber 30, and the like.

The support F is a photographic material support (also referred to as a film) in the embodiment. The electrodes 21 and 22 are shown in FIG.
(A), (b) and the like, the gap between the electrodes is, for example, about 10 mm.

The holding unit 60 holds the support F between the electrodes 21 and 22 by the pair of conveying rollers 62 and 63.
The support F is transported in the direction of the arrow while being driven by the transport roller pairs 62 and 63.

The gas filling means 50 is a means for filling the discharge processing chamber 30 with a mixed gas of an inert gas and a reactive gas.
The mixed gas is helium (He) and / or argon (A
r) an inert gas and a reaction gas such as nitrogen (N), oxygen (O), carbon dioxide, hydrogen, and water (H ₂ O).
It is desirable to use a relatively inexpensive discharge with argon gas.

The voltage generating means 40 applies a voltage from the power supply 41 to the conductive electrode portions 21a, 22a or 21A, 22A. The value is determined as appropriate, for example, the voltage is about 3 to 5 kV, and the power supply frequency is 1 to 100 kHz.

The discharge processing chamber 30 is composed of a processing vessel 31 made of Pyrex glass, and the processing vessel 31 is filled with a mixed gas. In the embodiment, the processing container 31 is made of Pyrex glass, but may be made of metal as long as it is insulated from the electrodes.

The electrodes 21 and 22 are arranged at predetermined positions in the processing vessel 31, and the mixed gas 5 generated by the gas generator 51 is
4 by a pump 55, and the discharge processing chamber 30 through the air supply port 52.
The processing container 31 is filled with the mixed gas 54 and discharged from the exhaust port 53. Next, a voltage is applied to the electrodes 21 and 22 by the power supply 41 to generate discharge plasma. Here, the support F is supplied from the roll-shaped film 61 and transported between the electrodes in the discharge processing chamber 30 by the transport roller pairs 62 and 63. The surface of the support F is subjected to a discharge treatment by a discharge plasma during transportation,
It is then discharged.

Although an example in which the discharge treatment is performed on both surfaces of the support F has been described, the support F is placed on the lower electrode, and
Only the upper side of the support F may be subjected to the discharge treatment.

FIG. 6 shows a configuration in which a plurality of cylindrical electrodes 26 are opposed to both sides of a straight-moving support member.
Both surfaces of the support F transported at a constant speed to the discharge processing chamber 30 through the discharge processing chambers 2 and 63 are uniformly discharged. A mixed gas 54 similar to that described above is supplied from the gas supply port 52 to the discharge processing chamber 3.
The processing container 31 is filled with the mixed gas 54 and discharged from the exhaust port 53. As shown in the perspective view of FIG. 5, the cylindrical electrode 26 is a combination of a conductive base material 26a such as a metal coated with a dielectric material 26b of an inorganic material that cures at 100 ° C. or less, or a combination of a metal and a metal. Base material 26A of composite material with ceramics
And a combination of a solid dielectric 26B such as a glass material that melts at a high temperature.

FIG. 7 shows a plurality of cylindrical fixed electrodes 2 with respect to a roll-shaped electrode 25 on which a support F is wound and conveyed and rotated.
6, the support F is wound around the roll-shaped electrode 25 and pressed by the nip rollers 65 and 66, and the support F is moved into and out of the discharge processing chamber 30 via the guide rollers 64 and 67 and is conveyed at a constant speed. You. The charging of the discharge processing chamber 30 with the mixed gas similar to that described above is performed in the same manner as in FIGS. As a result, the interval between the electrodes becomes extremely stable, and a good discharge treatment is performed on the support F. However, the discharge treatment is performed only on one side of the support. In addition, as shown in the perspective view of FIG. 4, the cylindrical roll-shaped electrode 25 is a combination of a conductive base material 25a such as a metal coated with a dielectric material 25b of an inorganic material that cures at 100 ° C. or lower, or It is configured by combining a base material 25A of a composite material of metal and ceramic with a solid dielectric 25B such as a glass material that melts at a high temperature.

The details of the gas filling means 50 including the pump 55 and the voltage generating means 40 are exactly the same as those in FIG.

For the composite base material of metal and ceramic, instead of lining a dielectric material that melts at a high temperature, 1
An inorganic material that cures at a temperature of 00 ° C. or less may be lined.

[0049]

EXAMPLE A dielectric material was coated on a base material by the method shown in Table 1 below, 20 cylindrical electrodes each having a width of 150 cm were manufactured, and a gap between the base material film F and the support film F was set to 1 mm as a discharge condition.
The discharge treatment was continued for 1 hour by applying a voltage of 10 kHz and 200 W / m in Ar gas, and various performances were compared and summarized in the table. The thickness of the dielectric was 1 mm.

[0050]

[Table 1]

As can be seen from the results shown in Table 1, a cylindrical electrode made of a conductive ceramic, that is, a composite material of metal and ceramic as a base material and lined with high-temperature molten glass or room temperature glass, or a conductive material such as metal. It is recognized that the cylindrical electrode in which the room temperature glass was lined with a good base material had no cracks, had almost no deflection, had good uniformity in the discharge treatment, was stable, and had significantly improved durability. However, the conventional cylindrical electrode in which high-temperature molten glass is lined with a highly conductive base material such as a metal has considerable cracks, has a large amount of deflection, and the discharge treatment is not uniform with the width of the support. The durability and workability were poor. Further, a metal base material obtained by spraying ceramic onto the metal base material had a poor durability and an arc discharge in the discharge treatment, even if the cracking and the bending amount were good, so that it was not practical at all.

[0052]

According to the present invention, it is possible to obtain an electrode for electric discharge treatment which has no distortion such as bending or the like, does not crack, and has high processing accuracy. The durability of the electrode was also improved, and a stronger discharge treatment became stable and sustainable.

Further, the adhesion between the surface of a support such as a photosensitive material or the like and the coating solution was increased by the electric discharge treatment method and the electric discharge treatment device using the electrode, and the coatability was greatly improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example of a flat electrode of the present invention.

FIG. 2 is a cross-sectional view showing another example of the flat electrode of the present invention.

FIG. 3 is a sectional view showing an example of a discharge processing apparatus using discharge plasma according to the present invention.

FIG. 4 is a perspective view showing an example of a cylindrical and roll-type electrode of the present invention.

FIG. 5 is a perspective view showing an example of a cylindrical fixed electrode of the present invention.

FIG. 6 is a sectional view showing another example of the discharge processing apparatus using discharge plasma of the present invention.

FIG. 7 is a cross-sectional view showing another example of a discharge processing apparatus using discharge plasma according to the present invention.

[Explanation of symbols]

21, 22, 23, 25, 26 Electrodes 21a, 22a, 25a, 26a Conductive base material such as metal 21A, 22A, 25A, 26A Base material of composite material of metal and ceramics 21b, 22b, 25b, 26b 100 ° C. Inorganic dielectric material that cures below (such as room temperature curable glass) 21B, 22B, 25B, 26B Solid dielectric material that fuses at high temperature (such as quartz glass) 30 Discharge processing chamber 31 Processing container 40 Voltage generating means 41 Power supply 50 Gas filling Means 51 Gas generator 52 Air supply port 53 Exhaust port 54 Mixed gas 60 Holder 61 Rolled film 62, 63 Conveying roller pair F Substrate (photosensitive material support, film)

Claims (17)

[Claims] 1. An electrode used in a discharge treatment apparatus which performs a discharge treatment on a support by applying a voltage between the electrodes and positioning a support between the pair of opposed electrodes, wherein An electrode for discharge treatment, characterized in that at least one of the opposing surfaces is formed by coating a surface of a conductive base material with a material having an inorganic property which cures at 100 ° C. or less by lining. 2. The electrode for electric discharge treatment according to claim 1, wherein the inorganic material is a room temperature curable glass. 3. The electrode for discharge treatment according to claim 1, wherein the electrode is an electrode for performing discharge treatment near atmospheric pressure. 4. The electrode for discharge treatment according to claim 1, wherein at least one of said electrodes has a cylindrical shape. 5. The electrode for discharge treatment according to claim 4, wherein at least one of said cylindrical electrodes is a roll type which rotates while being in contact with a support. 6. An electrode lined with at least one opposing surface of a pair of opposing electrodes using a dielectric material made of an inorganic material whose surface is cured at a temperature of 100 ° C. or lower, and the pair of opposing electrodes is provided. A discharge treatment chamber is formed by locating a support between the electrodes to be treated, and a mixed gas containing Ar gas of 60% by pressure or more is introduced into the discharge treatment chamber, and a voltage is applied to the electrodes so that atmospheric pressure or atmospheric pressure is applied. A discharge treatment method comprising: exciting a discharge plasma under a pressure near the atmospheric pressure to perform a discharge treatment on a surface of a support continuously transported at a discharge output of 7.5 kW / m ² or more. 7. An electrode lined on at least one of opposing surfaces of a pair of opposing electrodes with a dielectric material of an inorganic material whose surface of a conductive base material is cured at 100 ° C. or lower, and the pair of opposing electrodes A discharge treatment chamber for performing discharge treatment with a support positioned between the electrodes, filling means for introducing and filling a mixed gas containing Ar gas at 60% by pressure or more into the treatment chamber, and applying a voltage between the electrodes. A voltage generating means, wherein the discharge plasma is excited under an atmospheric pressure or a pressure close to the atmospheric pressure, and a discharge treatment is performed on the surface of the support which is continuously conveyed at a discharge output of 7.5 kW / m ² or more. Discharge treatment equipment. 8. An electrode used in a discharge treatment apparatus for performing a discharge treatment on the support by applying a voltage between the electrodes, wherein the support is positioned between the pair of opposed electrodes, An electrode for discharge treatment, wherein at least one of the opposing surfaces is made of a composite material of metal and ceramic as a base material, and the base material surface is coated with a dielectric. 9. The electrode for discharge treatment according to claim 8, wherein the electrode is an electrode for performing discharge treatment near atmospheric pressure. 10. The electrode according to claim 8, wherein at least one of the electrodes has a cylindrical shape. 11. The electrode for discharge treatment according to claim 10, wherein at least one of said cylindrical electrodes is a roll type rotating while being in contact with a support. 12. An electrode having a base material surface of a composite material of a metal and a ceramic lined with a dielectric material is provided on at least one facing surface of a pair of facing electrodes, and a support is provided between the pair of facing electrodes. A discharge processing chamber, and a mixed gas containing Ar gas at 60% by pressure or more is introduced into the discharge processing chamber, a voltage is applied to the electrode, and the pressure is reduced under atmospheric pressure or a pressure close to atmospheric pressure. A discharge treatment method characterized by exciting a discharge plasma and performing a discharge treatment on a surface of a support continuously transported at a discharge output of 7.5 kW / m ² or more. 13. An electrode in which a base material surface of a composite material of metal and ceramic is lined with a dielectric material on at least one opposing surface of a pair of opposing electrodes, and a support is positioned between the pair of opposing electrodes. A discharge processing chamber for performing discharge processing by charging, a filling means for introducing and filling a mixed gas containing Ar gas at 60% by pressure or more into the processing chamber, and a voltage generating means for applying a voltage between the electrodes. 6. Discharge plasma is excited at atmospheric pressure or a pressure close to atmospheric pressure to discharge output.
An electric discharge treatment apparatus, which performs an electric discharge treatment on the surface of a support continuously transported at 5 kW / m ² or more. 14. The discharge treatment method according to claim 6, wherein the support is a plastic film. 15. The method according to claim 14, wherein the plastic film is a support for a photosensitive material. 16. The discharge treatment apparatus according to claim 7, wherein the support is a plastic film. 17. The discharge processing apparatus according to claim 16, wherein the plastic film is a support for a photosensitive material.