JP2014064996A - Light irradiation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an illuminance adjusting mechanism for adjusting a central illuminance of a surface to be irradiated while keeping a light quantity received by an object to be processed constant in a light irradiation apparatus including a pair of vertical reflectors surrounding a linear light source A light irradiation apparatus is provided.
A pair of saddle-shaped reflecting mirrors are arranged to face each other in a letter C shape on a cross section M orthogonal to the central axis C of the light source, and a space between the light source and the saddle-shaped reflecting mirror. With respect to the rotation axis R formed in the above, the reflection mirror symmetry plane A including the central axis C and orthogonal to the irradiated surface is configured to be rotatable symmetrically with respect to each other. The pair of saddle-shaped reflecting mirrors has an angle α1 corresponding to an open state in which the central illuminance on the irradiated surface is maximized as a lower limit, and the reflecting mirror is the largest that does not come into contact with the constituent members constituting the light irradiation device casing. The illuminance adjustment is performed by rotating the reflecting mirror in the opening direction or the closing direction with reference to the state of an angle α selected within an angle range with the angle α2 corresponding to the open state as an upper limit.
[Selection] Figure 3

Description

  The present invention relates to a light irradiation apparatus including an illuminance adjustment mechanism.

  An ultraviolet irradiator mounted on a sheet-fed printing press or the like is a type of light irradiator equipped with a reflecting mirror that controls the direction of light emitted from a light source. As a device that cures the object to be treated such as printing ink on the workpiece surface by light (ultraviolet rays) irradiation (ultraviolet ray curing) while passing through the region (irradiated surface) facing the irradiation port for a predetermined short time. Conventionally known. As the light source, a linear ultraviolet lamp such as a high output straight tube type mercury lamp is often used in order to handle a workpiece having a large area. A typical example of such an ultraviolet irradiator is disclosed in Patent Document 1. The pair of reflecting mirrors has a so-called double-spread structure, and the symmetry plane formed by the two (hereinafter referred to as “reflecting mirror symmetry plane” or simply “symmetry plane”) includes the central axis of the linear lamp and is irradiated. The planes coincide with the plane orthogonal to the plane, and can be rotated symmetrically with respect to the plane of symmetry, and the opening angle of the two can be adjusted so that the required irradiation conditions can be realized. However, in the conventional ultraviolet irradiator, once the conditions are set, the ultraviolet irradiation is performed with the opening angle of the reflecting mirror fixed.

  The object to be processed on the workpiece surface is required to receive predetermined light energy required for photocuring while passing through the front surface (irradiated surface) of the light irradiation port. The magnitude of this light energy varies depending on the type of object to be processed, and the intensity of light energy that the object to be processed receives instantaneously (hereinafter referred to as “illuminance”) and the front surface of the light irradiation port. It is defined by both the time integration of the intensity of light energy received during passage. The photocuring reaction on the workpiece surface does not occur unless it receives light energy with an illuminance of a predetermined magnitude or more. Also, assuming that the workpiece is a flat plate, the illuminance in the workpiece conveyance direction is symmetrical with respect to the symmetry plane, and is distributed in a certain shape (typically, a mountain shape in which the center of the irradiated surface is high and decreases toward the edge. However, since the work passes through the irradiated surface at a constant speed, the light energy received by the object to be processed is expressed by the time integral value of the illuminance in the work conveyance direction on the irradiated surface. (This integrated value is hereinafter referred to as “light quantity”).

  If the light irradiation condition is set so that the illuminance at the center of the irradiated surface (hereinafter referred to as “center illuminance”) is maximized in the workpiece conveyance direction, The central illuminance matches the peak illuminance of the illuminance distribution in the workpiece conveyance direction, and an approximate value of the light quantity can be estimated from the central illuminance. Therefore, for the sake of convenience, the management of the light energy received by the object to be processed is performed by the central illuminance measured by the illuminometer installed at the center of the irradiated surface.

  By the way, when it is understood that the light energy irradiated from the light irradiation device is insufficient with respect to a required value, conventionally, (a) a method of bringing the distance between the light irradiation port and the surface to be irradiated close, (b) As a countermeasure, a method of increasing the input power to the lamp and increasing the light output from the light irradiation device has been adopted.

  However, in the case of (a), the central illuminance (the intensity of light energy received instantaneously) may be insufficient depending on the opening angle of the reflecting mirror even if the distance between the light irradiation port and the irradiated surface is reduced. In the case of (b), since the lamp is lit with an overload, there may be a case where a stable lighting state cannot be maintained and the lamp life is shortened. .

  On the other hand, if it is excessive with respect to the required energy value, (c) reduce the center illuminance by increasing the distance between the light irradiation port and the irradiated surface, and (d) reduce the input power to the lamp. However, in the case of (c), the amount of light always decreases as the distance increases, and in the case of (d), the input power is from the viewpoint of stable lamp lighting. There was a problem that there was a restriction on the amount of decrease.

Japanese Patent Laid-Open No. 11-244663

  The present invention provides a light irradiation apparatus including a pair of vertical reflectors that surround a linear light source, and includes an illuminance adjustment mechanism that adjusts the central illuminance of the irradiated surface while keeping the amount of light received by the object to be processed constant. It is an object to provide a light irradiation apparatus.

In order to achieve the above object, a light irradiation apparatus of the present invention comprises a linear light source having a central axis C, and reflects light from the light source, extends along the light source, and is opposed to the light source. In a light irradiation apparatus including a pair of vertical reflectors, and a housing including at least the light source and a light irradiation port that accommodates the pair of vertical reflectors and is disposed to face the irradiated surface. ,
The pair of saddle-shaped reflectors are arranged to face each other in the shape of a letter C extending toward the light irradiation port on a cross section M orthogonal to the central axis C, and between the light source and the saddle-shaped reflector. Centering on a rotation axis R formed in a space between them, the mirror A is configured to be rotatable symmetrically with respect to a mirror symmetry plane A including the center axis C and orthogonal to the irradiated surface that receives light from the light source. In addition, when the magnitude of the angle of rotation of one of the saddle type reflectors about the rotation axis R on the cross section M is defined by an angle α measured in the direction in which the reflector is opened, The angle α is an angle α2 corresponding to the maximum open state in which the reflecting mirror is not in contact with the components constituting the housing, with the lower limit being the angle α1 corresponding to the open state where the central illuminance on the irradiated surface is maximum. Is selected within an angle range with the upper limit of Characterized in that it has an illuminance adjusting mechanism for illuminance adjustment by rotating the direction or closing direction open each trough reflector.

  According to the present invention, it is possible to provide a light irradiation apparatus that can irradiate a surface to be irradiated with light having a desired illuminance by changing a rotation angle of a reflecting mirror without changing an irradiation distance or a lighting condition of a light source. it can.

  By using the light irradiation device of the present invention, it is possible to significantly adjust the illuminance of the irradiated surface only by adjusting a slight rotation angle of the reflecting mirror about several degrees, and the light necessary for the reaction can be adjusted. It is possible to adapt to the photocuring process of the to-be-processed object from which the magnitude | size of energy differs.

It is a partial notch schematic side view which shows the whole external shape of the light irradiation apparatus of embodiment of this invention. It is a figure for demonstrating the schematic sectional drawing of the direction orthogonal to the central axis of a light source of the light irradiation apparatus shown in FIG. 1, and the outline of an illuminance measuring method. It is a schematic diagram for demonstrating the effect | action of the illumination intensity adjustment mechanism with which the light irradiation apparatus of embodiment of this invention was equipped. It is a graph which shows the illumination intensity distribution and the change of light quantity when changing the rotation angle of a pair of saddle type reflecting mirrors. It is a graph which shows the illumination intensity distribution and the change of light quantity when changing the distance of a light irradiation opening and a to-be-irradiated surface. It is a graph which shows the influence which the symmetry of how to open a pair of saddle type reflectors has on illuminance distribution.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

<Example>
FIG. 1 is a partially cutaway schematic side view showing the overall outer shape of a light irradiation apparatus according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of the central portion of the light irradiation device shown in FIG. 1 in the direction orthogonal to the central axis of the light source, and also shows an outline of the illuminance measurement method. FIG. 3 is a schematic diagram for explaining the operation of the illuminance adjusting mechanism provided in the light irradiation device using the main part of the cross-sectional view of FIG.

  The light irradiation apparatus of the present invention is, for example, an ultraviolet irradiation apparatus that irradiates an object to be processed such as a resin compound with ultraviolet rays and cures the ultraviolet rays. The ultraviolet irradiation device 1 stores, for example, a straight tube type high-pressure mercury lamp 10 as a light source, a pair of vertical reflecting mirrors 20 and 20 extending along the lamp 10, and the lamp 10 and the reflecting mirrors 20 and 20. And a housing 30 provided with a light irradiation port 40 disposed opposite to the irradiated surface S. The straight tube type high-pressure mercury lamp 10 has specifications of, for example, a light emission length of 1050 mm, an input power of 16.8 kW, and an arc tube outer diameter of 28 mm. The length of the light irradiation port 40 in the direction along the lamp 10 has a sufficient length that does not hinder the direct light from the lamp 10.

  The pair of vertical reflectors 20, 20 have a length in the longitudinal direction that covers the entire length of the lamp 10, and are constituted by, for example, a metal water cooling block in which cooling water flow paths 22, 22 are formed. Then, a light reflecting film made of a dielectric multilayer film is formed on the reflecting surfaces 21 and 21 on the surface facing the lamp 10. The reflecting surface is defined by a part of an ellipse having the light source central axis as one focal point in a cross section orthogonal to the light source central axis. The light emitted from the light source is reflected by the reflecting surfaces 21 and 21 and is irradiated from the light irradiation port 40 which is an opening.

  The ultraviolet irradiation device 1 is, for example, a water-air cooling type, and the housing 30 includes a metal water-cooling block 50 in which a cooling water flow path is formed, and an air-cooling cylinder 60 that forms a cooling air flow path. In the example of the apparatus shown in FIG. 2, a light irradiation port 40 that is an opening is formed between the vertical reflectors 20 and 20 and the irradiated surface S, and air for air cooling can be taken from here.

  A work such as paper is transported to the front surface of the light irradiation port 40 so that the surface to which the object to be processed such as printing ink is attached coincides with the irradiated surface S, and is kept at a constant speed while facing the light irradiation port 40. And let it cure with ultraviolet light. You may comprise the periphery of the to-be-irradiated surface S so that it may become inert gas atmosphere, such as nitrogen gas. The workpiece such as paper may be a sheet that is divided for each sheet, or may be a continuous body such as roll paper. The plane formed by the light irradiation port 40 and the irradiated surface S are parallel to each other, and the distance between the two is appropriately adjusted and changed according to the type of the object to be processed.

  Here, the angle α at which the outer periphery of the light source rotates around the virtual axis R existing between the one saddle-shaped reflecting mirror 20 and the lamp 10 is referred to as a “rotation angle”. The angle α is plus (+) when measured in the direction in which the reflecting mirror opens, and minus (−) when measured in the closing direction. In FIG. 3, the position of the reflecting mirror after rotation is indicated by a broken line. In order to adjust the central illuminance of the irradiated surface S to a desired value, both the bowl-shaped reflecting mirrors 20 and 20 are rotated symmetrically with respect to the plane A by the angle α in a direction to open the reflecting mirror. Although the axis R is not shown in FIG. 3, the axis R actually coincides with the central axis of the reflecting mirror rotating shaft member installed at both ends in the longitudinal direction of the housing 30. In general, the pair of saddle-shaped reflecting mirrors 20 and 20 are configured to be rotated by the same angle α in conjunction with each other.

  The reflecting mirror is rotated as follows. That is, as shown in FIG. 1 and FIG. 2, for example, the illuminance is measured with an illuminometer 80 installed at the center of the irradiated surface, and the illuminance value is taken into a sequencer (not shown). A signal is sent to the motor 72 to operate the reflecting mirror. Reference numeral 71 denotes a rotating gear of the reflecting mirror. The rotation gear 71, the motor 72, the sequencer, the illuminance meter 80, and other members and equipment involved in the rotation of the reflecting mirror constitute an illuminance adjustment mechanism. If this illuminance adjustment mechanism is used, the reflecting mirror can be rotated at a minute angle of 0.1 °.

Here, in order to investigate the relationship between the rotating state of the reflecting mirror and the illuminance and the amount of light, the following experiment was performed.
The pair of saddle-shaped reflecting mirrors 20 and 20 has the following curves defining the reflecting surfaces 21 and 21 on the cross section M in the open state of the reflecting mirror where the illuminance at the center point O of the irradiated surface S is maximum. The one that matches the part of the ellipse defined as follows was used.
That is, this ellipse has a long axis on the cross-section M that coincides with the mirror symmetry plane A, one focal point that coincides with the central axis C of the lamp 10, and the other focal point that coincides with the central point O of the illuminated surface S. It is an ellipse whose distance from the focal point (inter-focal distance) L1 is 90 mm. This distance L1 is referred to as “irradiation distance” in the present invention, and a distance of 90 mm is standard.

  The distance (irradiation surface distance) L2 from the plane formed by the light irradiation port 40 to the surface to be irradiated S2 is appropriately selected depending on the device design and the optical system employed, but is approximately half the irradiation distance L1. The irradiation width L3 of the light irradiated from the light irradiation port 40 is defined by the movement distance in the workpiece conveyance direction D immediately below the light irradiation port 40, and one of the reflecting mirrors on the cross section M orthogonal to the central axis C of the lamp 10 The length in the direction from 20 toward the other reflecting mirror 20 was set to 200 mm. This length is set to be slightly larger than the opening width of the light irradiation port 40 in consideration of oblique irradiation from the end. In FIG. 2, the length in the vertical direction is exaggerated and is different from the actual aspect ratio.

  The illuminance meter 80 has a center point O of the irradiated surface S, the center of the light receiving portion opening surface (circular having a diameter of 1 mmφ) separated from the lamp central axis C by the irradiation distance L1 (the irradiation surface distance L2 from the light irradiation port 40). , I.e., 100 mm from the end of the irradiated surface S in the irradiation width direction. The workpiece conveyance speed when passing through the irradiated surface S was 4.8 m / min.

  The rotation angle α of the reflecting mirror 20 is based on the opening state of the reflecting mirror where the illuminance at the center point O of the irradiated surface S is maximum, and the rotation angle at this time (lower limit rotation angle α1) is 0 °. And On the other hand, the rotation angle at which the reflecting mirror 20 is in the maximum open state without contacting the water cooling block 50 and the inner wall of the housing 30 (upper rotation angle α2) was + 6 °.

Therefore, first, changes in the illuminance distribution and the amount of light in the irradiation width L3 when the rotation angle α was changed in the range of 0 ° to + 6 ° were examined. The result is shown in FIG. FIG. 4A is a graph showing the illuminance distribution with the horizontal axis representing the irradiation position in the irradiation width direction and the vertical axis representing the illuminance (unit: mW / cm ² ). FIG. 4B is a graph showing the integrated value of illuminance, that is, the change in the amount of light in the irradiation width L3. In FIG. 4B, the vertical axis represents the light amount, and the unit is illuminance (mJ / cm ² ). The same applies to FIG. 5B described later.

  As shown in FIG. 4A, the illuminance distribution was symmetric in the irradiation width direction with respect to the center position of the irradiated surface even when the rotation angle was changed. On the other hand, the illuminance distribution near the center of the irradiated surface changed greatly depending on the rotation angle of the reflecting mirror. That is, as the rotation angle changed from 0 ° to 4 °, the central illuminance decreased by about 30%. In addition, as for the form of the illuminance distribution, the distribution giving the maximum value at the center position is shown in the range of the rotation angle from 0 ° to 4 °, but when the angle exceeds 4.2 °, the illuminance value is the center position. And the M-shaped distribution is the largest on both sides of the depression.

  On the other hand, as shown in FIG. 4B, the amount of light that is the integrated value of illuminance does not coincide slightly with the angle near the center of the irradiated surface even when the rotation angle is changed from 0 ° to 6 °. However, there was no difference when reaching the position of the irradiation width of 200 mm where the light irradiation was completed. That is, it is confirmed that the amount of light that the object to be treated receives again after passing through the front of the light irradiation port of the ultraviolet irradiation device does not vary even if the rotation angle of the reflecting mirror is changed from 0 ° to about 6 °. It was done.

The intensity of light energy necessary for curing the printing ink varies depending on the type of ink, but in the case of the ink used in this example, it is known to be in the range of 1000 to 1800 mW / cm ² . Therefore, in the case of the vertical reflector of the present embodiment, if the rotation angle is adjusted within the range of 0 to 4 °, the desired peak can be obtained without changing the distance between the light irradiation port and the irradiated surface. Illuminance can be achieved, and increase / decrease adjustment of peak illuminance of up to about 30% is possible. Moreover, at this time, the amount of light received by the printing ink is constant, and reliable photocuring is ensured. In this light irradiation process, the light output from the lamp is constant even if the rotation angle of the reflecting mirror is changed. Therefore, during this period, the lamp is lit under a certain condition, and stable light emission can be expected. Further, since an excessive load is not applied, there is an advantage that the lamp life is not shortened.

  In the case of the present embodiment, the illuminance adjustment is specifically performed as follows. That is, (a) when the central illuminance of the irradiated surface is simply increased or decreased, the reference rotation angle α is set to 0 ° (lower limit rotation angle α1) to + 6 ° (upper limit rotation angle α2). To select the range and increase its center illuminance, the reflector is rotated from the rotation angle α to the closing direction (minus direction), and to decrease, the direction from the state to open (plus direction) ). (B) In order to adjust the illuminance after ensuring the peak illuminance on the irradiated surface to be the intensity of light energy necessary for photocuring, the reference rotation angle α is set to 0 ° to + 4 °. The range is selected, and the reflecting mirror is rotated in the closing direction (minus direction) or opening direction (plus direction) from the state of the rotation angle α to increase or decrease the peak illuminance.

  In this illuminance adjustment, the pair of saddle-shaped reflecting mirrors 20 and 20 are naturally rotated symmetrically with respect to the surface A orthogonal to the irradiated surface S. If the reference rotation angle α is selected as 0 °, the illuminance adjustment can be performed only in the direction of decreasing the central illuminance, and if the reference rotation angle α is selected as + 6 °, the illuminance adjustment can be performed only in the direction of increasing the central illuminance. Is possible.

  Next, the irradiation distance L1 was 90 mm as a reference, and the change in the illuminance distribution and the amount of light in the irradiation width L3 when changing in the range of 50 to 150 mm before and after that was examined. The result is shown in FIG. FIG. 5A is a graph showing the illuminance distribution in the irradiation width direction, and FIG. 5B is a graph showing the change in the amount of light in the irradiation width direction.

  As shown in FIG. 5A, the illuminance distribution changes depending on the irradiation distance while maintaining symmetry, but the central illuminance of the irradiated surface increases as the irradiation distance approaches from an irradiation distance of 150 mm to 90 mm. On the contrary, the central illuminance decreased even when the distance was closer than 90 mm. On the other hand, as shown in FIG. 5B, the amount of light monotonously increased as the irradiation distance was shortened.

This means that the peak illuminance may not reach even 1000 mW / cm ² in the conventional method of making up for the shortage of illuminance and light quantity by reducing the irradiation distance, and the required peak illuminance is not necessarily guaranteed. ing.

  Here, the relationship between the symmetry of the open state of the pair of reflecting mirrors and the illuminance distribution will be described. FIG. 6A shows a case where a pair of reflecting mirrors are in an open state maintaining symmetry with respect to a surface (surface A) orthogonal to the irradiated surface S, and only one of the reflecting mirrors is artificially formed from that state. The illuminance distribution in the irradiation width direction is shown for each of cases where the angle is rotated by 10 ° or 10 °. FIG. 6B shows a trajectory of light rays emitted from the light source when the reflecting mirror corresponding to FIG. In the figure, the left reflecting mirror is fixed, and only the right reflecting mirror is rotated.

As shown in FIG. 6, when the pair of reflecting mirrors are rotated without maintaining symmetry with respect to the plane A, the central illuminance and the peak illuminance are greatly reduced even at a slight rotation angle, and the peak illuminance is 1000 mW / cm. ^It can be seen that the desired light irradiation condition cannot be realized.

  Even when the intensity of the light energy required for curing the printing ink is other than the above-described embodiment, the peak illuminance is reduced while keeping the light amount constant by simply rotating the reflecting mirror by several degrees as in the above-described embodiment. It has been confirmed that it can be adjusted on a scale of about 10%.

  In the embodiment described above, the rotation angle (upper limit rotation angle α2) at which the reflecting mirror is in the maximum open state where the reflecting mirror does not come into contact with the components constituting the housing such as the water cooling block is the center point of the irradiated surface S. The opening state of the reflecting mirror where the illuminance at O is maximum is the reference (0 °), and the angle in the opening direction of the reflecting mirror is + 6 °. However, the present invention is not limited to this. The magnitude of the rotation angle α2 depends on the arrangement of the light source 10 and the reflecting mirror 20, the shape of the reflecting surface 21, and the size of the irradiation distance L1, and may be appropriately selected according to these specifications.

  In the embodiment described above, the shape of the reflecting surfaces of the pair of reflecting mirrors is a parabolic shape in which a cross section perpendicular to the central axis of the light source is focused on the central axis of the light source, but the present invention is limited to this. However, other geometric shapes can be selected as appropriate according to the intended light distribution.

  In the embodiment described above, the light applied to the object to be processed is ultraviolet light. However, in the present invention, the light is not limited to light in this wavelength region, and other wavelength regions such as visible light and infrared light are used. May be irradiated.

  Furthermore, each component of the light irradiation apparatus described in the description of the above embodiments can be arbitrarily modified within the scope of the gist of the present invention. In the above-described embodiment, for example, the vertical reflectors 20 and 20 are provided with shutters that block the light irradiation from the light irradiation port 40 by closing the edges of both reflection mirrors when they are not irradiated with light. You may also serve.

  In the embodiment described above, the ultraviolet irradiation device has arranged the ultraviolet transmissive plate-like member that forms the light irradiation port between the vertical reflector and the irradiated surface, but the present invention is not limited to this. The light source uses an ultraviolet lamp (so-called ozone-less lamp) that suppresses ultraviolet irradiation in the wavelength range that contributes to ozone generation, and the light irradiation port is configured in an open state without any members disposed there. May be. Further, although there is only one ultraviolet irradiation device, a plurality of ultraviolet irradiation devices may be arranged in a row so as to ensure a wide irradiated surface.

  The present invention is applicable to an ultraviolet irradiator mounted on a printing machine or the like.

DESCRIPTION OF SYMBOLS 1 ... Ultraviolet irradiation apparatus 10 ... Straight pipe type high pressure mercury lamp 20 ... Vertical reflector 21 ... Reflecting surface 22 ... Cooling water flow path 30 ... Housing 40 ... Light irradiation port 50 ... Water cooling block 60 ... Air cooling cylinder 70 ... Reflecting mirror circuit Moving mechanism 71 ... Rotating gear 72 ... Drive motor 80 ... Illuminance meter A ... Symmetric plane S ... Irradiated surface O ... Center point C of irradiated surface S ... Central axis R of lamp 10 ... Rotary axis L1 ... Irradiation distance L2 ... irradiation surface distance L3 ... irradiation width D ... conveying direction α ... rotation angle

Claims (1)

A linear light source having a central axis C, a pair of vertical reflectors that reflect the light from the light source, extend along the light source, and are opposed to each other, the light source, and the pair of vertical patterns In a light irradiation apparatus comprising a housing that includes at least a light irradiation port that houses a reflecting mirror and is disposed opposite to the irradiated surface,
The pair of saddle-shaped reflectors are arranged to face each other in the shape of a letter C extending toward the light irradiation port on a cross section M orthogonal to the central axis C, and between the light source and the saddle-shaped reflector. Centering on a rotation axis R formed in a space between them, the mirror A is configured to be rotatable symmetrically with respect to a mirror symmetry plane A including the center axis C and orthogonal to the irradiated surface that receives light from the light source. In addition, when the magnitude of the angle of rotation of one of the saddle type reflectors about the rotation axis R on the cross section M is defined by an angle α measured in the direction in which the reflector is opened, The angle α is an angle α2 corresponding to the maximum open state in which the reflecting mirror is not in contact with the components constituting the housing, with the lower limit being the angle α1 corresponding to the open state where the central illuminance on the irradiated surface is maximum. Is selected within an angle range with the upper limit of The light irradiation device characterized by having an illumination adjustment mechanism for illuminance adjustment by rotating the direction or closing direction open each trough reflector.

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