JPH08222537A - Surface cleaning and reforming apparatus - Google Patents

Abstract

PURPOSE: To provide a surface cleaning and reforming apparatus by which the attenuation coefficient of a quantity of ultraviolet rays is hardly changed within a definite distance range from an ultraviolet source by utilizing the interference of light by a method wherein a low-pressure mercury cold cathode tube whose heat generation amount is very small is used so as to form a surface light source. CONSTITUTION: In a surface cleaning and reforming apparatus, the surface of an object to be treated is irradiated with ultraviolet rays which are emitted from a mercury lamp 24, and its surface is cleaned or reformed. In the surface cleaning and reforming apparatus, a low-pressure mercury cold cathode tube is used as the mercury lamp 24. Thereby, a surface light source is achieved, and the interference of light is utilized. As a result, a quantity of ultraviolet rays can be made uniform within a definite distance range from the light source.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface cleaning / modifying apparatus for irradiating ultraviolet rays to clean and modify a glass material, a plastic material, a metal material and a solid surface of a product such as an optical disk substrate.

[0002]

2. Description of the Related Art Generally, liquid crystal display devices, compact discs, semiconductor elements, etc. are manufactured on LCD glass substrates, CD substrates,
CVD (Chemical)
It is formed by repeatedly performing an operation of forming a thin film using Vapor Deposition), sputtering, etc., and applying etching by applying a photolithography technique, etc., but with the miniaturization and high integration of processing, The reduction of product yield due to the presence of fine organic substances or inorganic substances is a serious problem. Also, when bonding or painting a thin film on a solid surface,
The presence of organic stains on the interface also causes a problem of deterioration in adhesive strength.

Therefore, prior to the formation of a thin film on a solid surface, a cleaning operation for removing dirt and particles of an organic substance or an inorganic substance and a modification for improving the adhesive force by modifying the chemical or physical composition of the surface. Operations are being performed. As these cleaning / modifying treatments, a wet treatment that uses a liquid at the time of treatment and a dry treatment that performs treatment while the surface of the object to be treated are dry are known. Due to its relatively small size, a dry cleaning and reforming apparatus using ultraviolet rays has been attracting attention.

The principle of cleaning and modification by ultraviolet rays is that the high energy of short-wavelength ultraviolet rays excites the molecules of an organic substance to break their bonds, and at the same time, the following formulas (1), (2) and (3) are applied by ultraviolet ray irradiation. As described above, ozone is generated to oxidize it to modify its surface or remove dirt. Note that chlorine or the like is used together with the inorganic particles. O ₂ + h · ν 1 → O + O (1) O ₂ + O → O ₃ (2) O ₃ + h · ν 2 → O ₂ + O (3) where h is Planck's constant and ν 1 is wavelength 184.9 nm.
, Ν2 is an ultraviolet ray having a wavelength of 253.7 nm.

With respect to the inorganic substance, the generated active species of ozone and oxygen oxidize the surface of the inorganic substance, thereby improving the wettability and enhancing the adhesiveness to the thin film. Here, a conventional surface cleaning and reforming apparatus will be described with reference to FIG. As shown in the figure, this device has a mounting table 4 for holding an object to be processed 2 such as an optical disk substrate and a glass substrate, and a mercury lamp 6 of high output power is provided above the mounting table 4.
Of a predetermined wavelength, that is, 184.9 nm and 25, which contribute to the generation of ozone and the activation of the enzyme.
It is designed to irradiate ultraviolet rays mainly having a wavelength of 3.7 nm.

By the way, since the mercury lamp has a very large amount of ultraviolet rays per unit number, a low-pressure mercury hot cathode tube is used. However, this hot cathode tube uses a large amount of electric power, for example, about several hundred W. It consumes power and emits high heat. In order to obtain the ultraviolet rays of the above-mentioned preferable wavelength and to maintain the object to be treated at an appropriate temperature, the lamp temperature must be considerably low, for example, about 40 ° C to 60 ° C. Cooling jacket 8 nearby
Is provided to cool the lamp to a predetermined temperature. Then, a reflection plate 10 is provided on the back surface side of the mercury lamp 6, that is, on the upper side, to enhance the ultraviolet irradiation efficiency.
Further, an exhaust duct 14 for exhausting the internal atmosphere is provided in the hood 12 on the ceiling, and an ozone separator 16 for removing unreacted ozone is provided in the middle of the exhaust duct 14.

[0007]

By the way, in the above-mentioned conventional apparatus, since the hot cathode tube which emits high heat is used as the mercury lamp, as a forced cooling means for cooling the same, for example, A large-scale water cooling jacket 8 has to be provided, which not only increases the size of the apparatus itself, but also increases the cost. Further, the distance between the mercury lamp and the object to be processed 2 is set to be extremely small, for example, about 1 cm in consideration of the uniform distribution state of the ultraviolet rays, but since the hot cathode tube 6 generates a large amount of heat as described above. For example, when processing an object to be processed made of a material that is easily affected by heat such as resin, heat management becomes strict, and in the worst case,
There is also a problem that processing may not be possible.

Further, since the unit cost of the low-pressure mercury hot cathode tube itself is very high, the cost is higher than this point. Further, since the intensity distribution of ultraviolet rays from the lamp toward the object to be processed weakens in proportion to the square of the distance as the distance from the lamp increases, the processed surface of the object to be processed is in a substantially flat state in order to perform uniform processing. However, it is difficult to perform uniform treatment on a product having an uneven surface or a product molded into a certain uneven shape.

In this case, by arranging a plurality of mercury lamps 6 in parallel so as to form a surface light source, the intensity distribution of ultraviolet rays within a certain distance range close to the light source can be made constant regardless of the distance. Although it is conceivable, since the heat generation amount of each lamp is large as described above, it is necessary to set the distance between adjacent lamps to a considerably large value, which causes unevenness in the intensity distribution of ultraviolet rays, Not applicable. The present invention was devised in order to effectively solve the above problems. The object of the present invention is to reduce the amount of ultraviolet light within a certain distance range from an ultraviolet light source by utilizing the interference of light by making a surface light source using a cold cathode tube of low-pressure mercury, which has a very small amount of heat generation. An object of the present invention is to provide a surface cleaning reforming device whose amount is almost unchanged.

[0010]

In the conventional cleaning and improving apparatus of this type, since the apparatus was designed from the viewpoint of applying a large amount of power and generating a large amount of ultraviolet rays at a stroke for processing, In order to meet such requirements, a hot cathode tube lamp that emits a large amount of ultraviolet rays with one lamp was used, but as a result of earnest research on a cleaning and reforming operation using ultraviolet rays, the present inventor found that the amount of ultraviolet rays per unit number was Even if the number of cold cathode tubes is smaller than that of hot cathode tubes, it is possible to obtain a similar amount of ultraviolet rays by arranging many cold cathode tubes closely and side by side. It was found that the amount of ultraviolet rays can be made uniform without depending on the distance from the light emitting source by keeping the light attenuation rate substantially unchanged within a small distance range of about 10 mm to 40 mm. Which has led to the present invention by Rukoto.

In order to solve the above problems, the present invention provides
In a surface cleaning and reforming apparatus for irradiating the surface of an object to be treated with ultraviolet rays emitted from a mercury lamp to clean or modify the surface, the mercury lamp is a low-pressure mercury-cooled type that mainly emits ultraviolet rays of a specific wavelength. It is composed of a cathode tube.

[0012]

Since the present invention is constructed as described above, a plurality of parallel light sources can be arranged at a very narrow pitch, so that it can be constructed as a pseudo surface light source. For example, it is possible to make the amount of ultraviolet rays uniform by making light interfere with each other regardless of the distance within a range of about 10 mm to 40 mm from the light source and over substantially the entire surface parallel to the lamp array surface. A uniform surface treatment can be performed on the treated body. Further, since the cold cathode tube has a very small amount of heat generation as compared with the hot cathode tube used in the conventional apparatus, it is possible to solve various problems caused by the heat generation.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the surface cleaning / modifying apparatus according to the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a perspective view showing an example of a surface cleaning / modifying apparatus according to the present invention, and FIG.
1 is a sectional view of the apparatus shown in FIG. 3, FIG. 3 is a partially cutaway perspective view showing a mounting portion of the low-pressure mercury cold cathode tube of the apparatus shown in FIG. 1, and FIG.
4 is a plan view showing the arrangement of cold cathode tubes of the apparatus shown in FIG.
FIG. 6 is a side view of the portion shown in FIG. 6, and FIG. 6 is a schematic plan view showing the reflector.

As shown in the figure, this surface cleaning and reforming device 18
Is a housing 20 that forms the outside of the apparatus, and a mounting table 2 on which a target object 2 such as an optical disk substrate or a glass substrate is mounted.
2 and a mercury lamp that irradiates it with ultraviolet light of a specific wavelength 2
It is mainly composed of 4. Specifically, the housing 20
Includes two stainless steel plates 20A placed opposite each other, with a mercury lamp 24
A lamp accommodating portion 26 for accommodating and holding the lamp is provided, and a mounting table holding plate 28 is set below the lamp accommodating portion 26. Therefore, the two plates 20A and the lamp housing portion 26 are
And a space defined by the mounting table holding plate 28 is configured as a processing space S. Further, the lower end of the plate 20A is bent at a right angle, and an elastic member 30 such as rubber is provided there.
Is provided to support the entire apparatus.

The mounting table 22 is formed as, for example, a disk having a size sufficient for mounting and holding the object 2 to be processed, and the material thereof is, for example, stainless steel. The shape of the mounting table 22 is not limited to a disk, and may be any shape according to the shape of the object to be processed. For example, when processing a rectangular LCD substrate, the mounting table 22 is correspondingly formed. Also, it may be formed in a square shape. This table 22
A rotary shaft 34 is provided at the center of the lower surface of the rotary shaft 34.
Is rotatably provided on the table holding plate 28 via a bearing 36. The lower end of the rotary shaft 34 is connected to the rotary motor 38 so that the mounting table 32 can be rotated.

At the plate side end of the mounting table holding plate 28,
A sliding portion 40 is provided, and the sliding portion 40 is provided on the plate 2
It is slidably held on a guide rail 42 provided inside 0A, and the object 2 can be carried in and out from the outside by sliding the mounting table holding plate 28. The slide mechanism is not limited to such a configuration, and a roller member or another mechanism may be used. Further, partition walls 44 for partitioning the processing space S are provided upright at both ends of the mounting table holding plate 28 in the sliding direction. In FIG. 1, the partition wall on the opposite side is not shown.

Two plates 20A forming the housing 20
An outer air intake hood 46 having a rectangular cross section is formed at an upper end of the lamp and the mounting portion of the lamp housing portion 26, and an outer air intake port 48 is formed at a lower portion of the hood 46 and the plate 20A.
A large number of inflow holes 50 are formed along the hood 46 on the side so that outside air can be taken into the processing space S.

On the other hand, the lamp accommodating portion 26 is formed of, for example, stainless steel into a substantially box shape, and the mercury lamp 24 is provided at a predetermined distance L1 from the mounting table 22. As the mercury lamp 24, a low-pressure mercury cold cathode tube, which has a very small calorific value, is used instead of the hot cathode tube that emits high heat used in the conventional apparatus.

The mercury lamp 24, which is a cold cathode fluorescent lamp,
As shown in FIGS. 4 and 5, a large number are arranged at a predetermined pitch L2 along a surface parallel to the mounting surface of the mounting table 24. For example, a diameter of 6 mm for an area of about 300 mm × 300 mm. About 30 cold cathode tubes 24 are collectively arranged with a pitch L2 of about 10 mm to form a so-called surface light source. Here, the predetermined pitch means that the lights from the arranged cold cathode tubes 24 interfere with each other and are approximately 10 m in the direction orthogonal to the arrangement surface of the tubes.
It is a pitch within a range of m to 40 mm and which provides a substantially uniform amount of ultraviolet rays over substantially the entire surface parallel to the array surface. That is, in the space area defined here, the attenuation rate of light hardly changes even if the distance from the light source changes, so that the amount of ultraviolet rays becomes substantially uniform as described above. In this case, since the power consumption per cold cathode tube 24 is as low as about 7 to 9 W, the calorific value is low, and as a result, the switch L is very narrow as described above.
Even if they are arranged in two, problems due to heat hardly occur. In addition, the cold cathode tube 24 efficiently emits ultraviolet rays having wavelengths of 184.9 nm and 253.7 nm, which are useful for cleaning and reforming, substantially equally as compared with the hot cathode tube, and emits ultraviolet rays of other wavelengths much. Since this is not done, good cleaning and modification treatments are possible.

The distance L1 between the mounting table 22 and the cold cathode tubes 24 is set to about 40 mm, for example. The reason for this is that, by arranging the cold cathode tubes 24 so as to form a pseudo surface light source as described above, light interference causes a range of 10 mm to 40 mm from the tubes and is parallel to the array surface. This is because it is possible to form a spatial region in which the amount of ultraviolet rays is substantially constant regardless of the distance over substantially the entire surface. Further, the tube pitch L2 may be appropriately increased or decreased as long as a region where the amount of ultraviolet rays is uniform can be formed within a certain distance range regardless of the distance from the light source.

A reflection plate 52 for reflecting the ultraviolet rays emitted from the cold cathode tubes 24 toward the mounting table 22 side in the downward direction is provided over almost the entire surface immediately above the arranged cold cathode tubes 24. It enables efficient irradiation. The reflector 52 is formed of a material that is difficult to oxidize, such as stainless steel. In addition, the exhaust duct 5 having a rectangular cross section is provided on the socket portion 54 side that supports both ends of the cold cathode fluorescent lamp 24.
8 is provided, and a fan mechanism 56 for exhausting the atmosphere in the processing space S to generate an upward flow in the duct 58.
Is provided.

FIG. 6 is a plan view showing the reflection plate 52. As shown in the drawing, the reflection plate 52 has a large number of ventilation holes 60 formed therein. In this case, the ventilation hole 60 is formed by the reflection plate 52.
Although it may be uniformly provided over the front surface of the cold cathode tube 24, the vent holes 60 are provided so as to be unevenly distributed between the portions corresponding to both ends of the cold cathode tube 24 and the central portion in the longitudinal direction of the tube 24 as illustrated. As a result, the heat generated in the filament portion of the cold cathode tube 24 can be efficiently discharged, and moreover, the atmosphere in the processing space S can be directed substantially uniformly upward. still,
In the illustrated example, the vent holes 6 in the central portion and the end portion of the reflector 52 are shown.
The case where the array of 0s is arranged in 4 columns and the case where it is arranged in 2 columns is shown, but this is only an example, and it goes without saying that the number of arrays can be appropriately selected.

The exhaust duct 58 provided on both sides of the lamp accommodating portion 26 is formed with a large number of communicating holes 62 for communicating the space above the reflecting plate 52 with the exhaust duct 58, and the rear end side of the duct 58. A duct outlet 64 is provided in the. A fan mechanism 56 composed of a rotary fan is provided near the duct outlet 64 to exhaust the internal atmosphere to the outside of the apparatus. Further, a connector 59 for connecting a plug for supplying power to the apparatus main body is provided on the side of the exhaust duct 58, as shown in FIG. FIG.
As shown in FIG. 3, a power source unit 66 for supplying various kinds of electric power required on the apparatus body side is arranged on the side portion of the apparatus body.

Next, the operation of the present embodiment configured as described above will be described. First, in a state where the object 2 to be processed such as an optical disk substrate and a glass substrate is placed and held on the mounting table 22, this is loaded into the processing space S, and the cleaning or modification processing of this surface is started. That is, by rotating the mounting table 22, the object 2 to be processed is rotated and the cold cathode tube 2 is rotated.
4 is turned on, and at the same time, outside air (O ₂ ) is taken into the processing space S from the outside air intake hood 46 to generate an ascending flow inside, and this is discharged from the exhaust duct 58 to the outside of the apparatus.

Now, as described above, the specific wavelength (184.9)
(25 nm, 253.7 nm) is applied to the surface of the processing space S and the object 2 to be treated, ozone and active species are generated, and organic contaminants on the surface of the object 2 are decomposed and removed for cleaning. Alternatively, in the case of surface treatment, modification is performed by breaking the linkage of organic molecules. Also,
When the object 2 to be processed is a metal material, a metal oxide is formed on the surface of the object 2 for modification.

Here, in the present invention, since a large number of cold cathode tubes 24 having a very small amount of heat generation are arranged densely to form a surface light source, the lights from the cold cathode tubes interfere with each other, As a result, there is almost no distance attenuation of ultraviolet rays within a range of 10 to 40 mm from the light source, and the amount of ultraviolet rays becomes substantially constant within this distance range. FIG. 9 schematically shows a region where the amount of ultraviolet rays is substantially uniform, and the amount of ultraviolet rays in the shaded area in the figure is substantially uniform. Therefore, even if the surface of the object to be processed 2 has irregularities within the above distance range, uniform cleaning and modification treatment can be performed, and the in-plane uniformity of the treatment can be improved. Therefore, in the conventional device, for example, a cube-shaped device or a device having unevenness on the surface and a difference in height could not be subjected to surface homogenization treatment, but according to the present invention,
Even if there is a difference in height within the above-mentioned certain range, the uniform surface treatment can be performed as described above, so that the object to be treated can be uniformly surface-treated even after molding.

Further, since the amount of heat generated by the cold cathode fluorescent lamp 24 is small, the cold cathode fluorescent lamp 24 can be air-cooled by the fan mechanism 56.
Can be cooled to about 40 ° C., which emits an ultraviolet ray having an effective wavelength, and can prevent excessive heating of the object to be processed, so that a large and expensive cooling jacket conventionally required can be provided. It can be lost. Furthermore,
Since the cold cathode tube 24, which has a long life, is inexpensive, and consumes less power, is used, it is possible to contribute to power consumption reduction and cost reduction. FIG. 7 is a graph showing the contact angle (wettability) when the surface is actually modified using the device of the present invention, but the modification time increases for both acrylic resin (marked with Δ) and glass (marked with ×). It was found that the better the result, the lower the contact angle.

Table 1 shows the relationship between the distance from the light source and the illuminance of ultraviolet rays (253.7 nm) when the fan mechanism is driven. The measurement point is the center of the mounting surface. As is clear from Table 1, it was found that there was almost no difference in the amount of ultraviolet rays within the range of 10 mm to 40 mm, and that the dose was uniform, but when the distance was too close to 10 mm, the amount of ultraviolet rays increased rapidly. If it exceeds 40 mm, on the contrary, the amount of ultraviolet rays sharply decreases, which is not preferable. Further, FIG. 10 shows that in Table 1 above, the light source distance is 30 mm.
It is the result of measuring the illuminance at five places on the mounting surface at the time.
The configuration at this time was such that 30 cold cathode tubes were arranged at a pitch of 10 mm and the mounting table was circular. Further, at the time of measurement, a fan is driven for cooling. As is apparent from the figure, the illuminance of the central portion P1 is 11.
4 mW / cm ² and peripheral portions P1 and P3 at the upper and lower ends in the figure
At 11.8 mW / cm ² , 11.4
mW / cm ² , which is 10.8 mW / cm at the inner portions P4 and P5 30 mm from the left and right ends in the figure.
^{It was 2} , 10.9 mW / cm ² , and it was found that there was almost no difference in the amount of ultraviolet light over the entire surface. In the above embodiment, the case where the power supply unit 66 is provided separately from the apparatus main body and the fan mechanism 56 is also provided on the side part has been described, but the present invention is not limited to this, and is configured as shown in FIG. 8, for example. You may. In the illustrated apparatus, the power supply unit 66 is incorporated in the lower portion of the apparatus body, and only one fan mechanism 56 is provided directly above the apparatus body. In this case, since the atmosphere in the processing space is uniformly sucked upward, the ventilation holes 60 of the reflection plate 52 are formed uniformly over the entire surface,
In addition, in order to ensure the uniformity of the ascending flow, two reflecting plates 52 are provided.
Are arranged vertically.

Further, in the above embodiment, the mounting table 22 is rotatably provided on the slidable mounting table holding plate 28, but in order to achieve mass productivity, for example, a belt conveyor or the like may be used as the mounting table 22. You may Further, in this embodiment, air is introduced into the processing space S, but clean air having high cleanliness or pure oxygen may be introduced as this air.

[0030]

As described above, according to the surface cleaning / modifying apparatus of the present invention, the following excellent operational effects can be exhibited. Since a cold cathode tube that is inexpensive and has a long life is used as a mercury lamp as an ultraviolet ray source, it is not necessary to use a large cooling mechanism such as a cooling jacket for cooling, and downsizing and cost reduction of the device can be achieved. Can be significantly promoted. Further, since the power consumption is small, the running cost can be reduced. Furthermore, by arranging multiple cold-cathode tubes with a small amount of heat generation in close proximity to each other, it becomes a surface light source and the light from each cold-cathode tube can be made to interfere with each other. Therefore, within a predetermined distance from the light source. In addition, it is possible to obtain a uniform dose by substantially eliminating the distance attenuation of ultraviolet rays over substantially the entire surface parallel to the array surface. Therefore, it is possible to perform uniform cleaning and modification treatment even on an object having an uneven surface, for example, performing uniform surface treatment on an object having an uneven surface after molding. Therefore, the degree of freedom in designing the manufacturing process can be increased.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of a surface cleaning / modifying apparatus according to the present invention.

2 is a cross-sectional view of the device shown in FIG.

3 is a partially cutaway perspective view showing a mounting portion of a low-pressure mercury cold cathode tube of the apparatus shown in FIG.

FIG. 4 is a plan view showing an arrangement of cold cathode tubes of the apparatus shown in FIG.

5 is a side view of the portion shown in FIG. 4. FIG.

FIG. 6 is a schematic plan view showing a reflector.

FIG. 7 is a graph showing the relationship between surface modification time and contact angle.

FIG. 8 is a perspective view showing another embodiment of the device of the present invention.

FIG. 9 is a diagram schematically showing a region where the amount of ultraviolet rays is substantially uniform.

FIG. 10 is a diagram showing an ultraviolet illuminance on a mounting surface when a light source distance is 30 mm.

FIG. 11 is a schematic configuration diagram showing a conventional surface cleaning / modifying apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Object to be treated 18 Surface cleaning and reforming apparatus 20 Housing 22 Mounting table 24 Mercury lamp (low-pressure mercury cold cathode tube) 26 Lamp housing section 28 Mounting table holding plate 46 Outside air intake hood 52 Reflector plate 56 Fan mechanism 58 Exhaust duct L1 Predetermined pitch S processing space

Claims (8)

[Claims] 1. A surface cleaning / modifying apparatus for irradiating the surface of an object to be processed with ultraviolet rays emitted from a mercury lamp to clean or modify the surface, wherein the mercury lamp mainly emits ultraviolet rays of a specific wavelength. A surface cleaning and reforming device, which is a low-pressure mercury cold cathode tube for discharging. 2. The surface cleaning reforming according to claim 1, wherein a plurality of the low-pressure mercury cold cathode tubes are arranged at a predetermined pitch along a surface parallel to the mounting surface of the mounting table. apparatus. 3. The predetermined pitch is substantially within a range of approximately 10 mm to 40 mm in a direction orthogonal to the array surface of the cold cathode tubes and substantially due to light interference over substantially the entire surface parallel to the array surface. The surface cleaning / modifying apparatus according to claim 1 or 2, wherein the pitch is such that a uniform amount of ultraviolet rays is obtained. 4. A surface cleaning / modifying apparatus for irradiating a surface of an object to be treated with ultraviolet rays to clean or modify the surface, the mounting table on which the object to be processed is mounted, and the mounting table. A case forming a space between the processing chambers, a low-pressure mercury cold cathode tube which is arranged to face the mounting table and mainly emits ultraviolet rays of a specific wavelength, and a fan mechanism for moving the atmosphere between the processing chambers. A surface cleaning and reforming apparatus, characterized in that it is configured to include. 5. The surface cleaning reforming according to claim 4, wherein a plurality of the low-pressure mercury cold cathode tubes are arranged at a predetermined pitch along a surface parallel to the mounting surface of the mounting table. apparatus. 6. The surface cleaning and reforming apparatus according to claim 4, further comprising a reflecting plate that reflects ultraviolet rays near the low-pressure mercury cold cathode fluorescent lamp. 7. The mounting table is provided so as to be rotatable or slidably movable.
7. The surface cleaning / modifying apparatus according to any one of 6 to 6. 8. The predetermined pitch is within a range of approximately 10 mm to 40 mm in a direction orthogonal to the array surface of the cold cathode tubes and over substantially the entire surface parallel to the array surface due to light interference. 8. The surface cleaning / modifying apparatus according to claim 5, wherein the pitch is such that the amount of ultraviolet rays is substantially uniform.