Super-high pressure lamp

Providing a super-high pressure lamp having increased pressure resistance. The super-high pressure lamp includes: an arc tube; and a sealing portion in which a front end of an exhaust pipe capable of exhausting gas in the arc tube or supplying gas into the arc tube is sealed, wherein, in the sealing portion, a height of a first sealed space, which has a tapered shape that becomes narrower toward a front end of the sealing portion, is larger than twice an inner diameter of the first sealed space.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a super-high pressure lamp.

Description of the Related Art

A super-high pressure lamp in which a high pressure gas is sealed in an arc tube is known. In recent years, there is a laser sustained plasma (LSP) lamp used as an ultraviolet light source used in an inspection process of a semiconductor substrate, a liquid crystal substrate, a color filter, and the like as one of the super-high pressure lamps (see Patent Document 1). The LSP lamp emits an excitation laser from the outside of the arc tube toward the inside of the arc tube to turn a target inside the arc tube into plasma. A super-high pressure luminescent gas is sealed in the arc tube. High-brightness and broadband light radiated from the lamp is utilized simultaneously with the generation of plasma.

PRIOR ART DOCUMENT

Patent Document

SUMMARY OF THE INVENTION

Higher brightness and longer life of a super-high pressure lamp are required by the market. In order to meet the market requirement, it is necessary to further increase the pressure resistance strength of the super-high pressure lamp. Therefore, an object of the present invention is to provide a super-high pressure lamp having increased pressure resistance.

The present inventors have found that pressure resistance of a super-high pressure lamp is not uniform, and a portion having a particularly low pressure resistance exists in a sealing portion. Therefore, the shape of the sealing portion for improving the pressure resistance strength has been devised.

A super-high pressure lamp of the present invention includes:an arc tube; anda sealing portion in which a front end of an exhaust pipe capable of exhausting gas in the arc tube or supplying gas into the arc tube is sealed,in which, in the sealing portion, a height h1 of a first sealed space, which has a tapered shape that becomes narrower toward a front end of the sealing portion, is larger than twice an inner diameter d1 of the first sealed space.

The “super-high pressure lamp” refers to a lamp in which a pressure of 8 MPa or more (pressure during lighting) is applied to the inside of the arc tube. That is, pressure resistance of the “super-high pressure lamp” is 8 MPa or more. Hereinafter, the “super-high pressure lamp” may be simply referred to as a “lamp”.

The “sealing portion” is a trace of the exhaust pipe attached to the lamp at the time of manufacturing the lamp. A method of forming the sealing portion will be described later.

A front end of the first sealed space may have an unbranched shape. In a case where the front end of the first sealed space has an unbranched shape, pressure resistance of the lamp is improved.

The super-high pressure lamp may further include a first branch and a second branch formed by branching the front end of the first sealed space,in which an interval between a front end of the first branch and a front end of the second branch may be 1.5 mm or less. In a case where the interval between the front end of the first branch and the front end of the second branch is 1.5 mm or less, the pressure resistance of the lamp is improved.

The interval between the front end of the first branch and the front end of the second branch may be shorter than an interval between a root of the first branch and a root of the second branch. Since the interval between the front end of the first branch and the front end of the second branch is narrowed, the pressure resistance of the lamp is improved.

The first branch and the second branch may be twisted in a pair. If the first branch and the second branch are twisted in a pair, the interval between the front end of the first branch and the front end of the second branch is narrowed and the pressure resistance of the lamp is improved.

An outer diameter d2 of the sealing portion may be three times or more the inner diameter d1 of the first sealed space. The thickness of the sealing portion increases, and the pressure resistance of the lamp is improved.

The super-high pressure lamp may further include two side tubes connected to the arc tube and disposed opposite to each other with the arc tube interposed between the two side tubes,in which the sealing portion may be provided on a curved surface or inside of any one of the two side tubes.

The super-high pressure lamp may further include two side tubes connected to the arc tube and disposed opposite to each other with the arc tube interposed between the two side tubes,in which an electrode may be disposed inside each of the two side tubes, andthe sealing portion may be provided on the arc tube or a curved surface of any one of the two side tubes.

The super-high pressure lamp may be a laser sustained plasma lamp.

As a result, it is possible to provide the super-high pressure lamp having increased pressure resistance.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be described with reference to the drawings. It should be noted that the drawings disclosed herein merely show schematic illustrations except for graphs. The dimensional ratios on the drawings do not necessarily reflect the actual dimensional ratios, and the dimensional ratios are not necessarily the same between the drawings.

Some of the drawings are illustrated in an XYZ orthogonal coordinate system. The vertical direction is defined as a Z direction, and two directions orthogonal to each other in a horizontal plane orthogonal to the vertical direction are defined as an X direction and a Y direction. Positive and negative orientations distinguished from each other for directional expression will be described as a “+Z direction” and a “−Z direction” by adding positive and negative signs, while a direction expressed without distinction between positive and negative orientations will be described simply as the “Z direction”. The −Z direction is a gravity direction.

First Embodiment

An outline of a super-high pressure lamp of a first embodiment will be described with reference toFIG.1.FIG.1illustrates an LSP lamp10(hereinafter may be simply referred to as a “lamp10”), which is a type of the super-high pressure lamp. The lamp10includes an arc tube2, a first side tube3connected to one end of the arc tube2, a second side tube4connected to the other end of the arc tube2, a sealing portion5, and two starting electrodes EL.

The arc tube2, the first side tube3, and the second side tube4are arranged along the Z1axis. The Z1axis is an axis parallel to the Z direction. Except for the sealing portion5, the arc tube2, the first side tube3, and the second side tube4have a shape of a rotating body centered on the common Z1axis. However, the arc tube2, the first side tube3, and the second side tube4may not have the common Z1axis, or may not have a shape of a rotating body. The lamp10of the embodiment has a socket6on each of the first side tube3and the second side tube4. In the lamp10, a fixture7for fixing the lamp10to a light source device is provided at a front end of each socket6.

In the present embodiment, the arc tube2, the first side tube3, and the second side tube4are made of glass material (for example, quartz glass). In the present embodiment, the arc tube2and the first side tube3have a hollow shape. The second side tube4has a solid shape. However, the second side tube4may have a hollow shape, or the first side tube3may have a solid shape. For example, the thicknesses of the arc tube2and the hollow side tube (3,4) are preferably 2.5 mm or more and are preferably 4 mm or less. The variation in thickness of the arc tube2and the side tubes (3,4) is preferably 15% or less, and is more preferably 10% or less.

The arc tube2is formed to bulge from the Z1axis to the periphery of the Z1axis including the X direction and the Y direction. The arc tube2has a space therein. An inner diameter i2in the space of the arc tube2increases from the upper end and the lower end of the arc tube2in the Z direction toward a center plane C1located at the center of the arc tube2.

In the lamp10of the present embodiment, a working gas is sealed in the space inside the arc tube2. The working gas comes to a high pressure, in particular during lighting. The lamp10has strength to withstand the pressure from the working gas of 8 MPa or more during lighting. The pressure resistance of the lamp10is preferably 15 MPa or more, and more preferably 25 MPa or more. Examples of the working gas include a rare gas such as argon, krypton, or xenon, or a mixed gas thereof.

In the arc tube2, laser sustained plasma Pr is generated and light is emitted. Specifically, in the lamp10, when an excitation laser is emitted toward the intersection of the Z1axis and the center plane C1of the arc tube2and the working gas sealed in the lamp10is turned into plasma to form plasma Pr, light containing desired light is emitted from the plasma Pr. When lighting is started, preliminary discharge is performed using the two starting electrodes EL to assist generation of plasma by the laser.

[Outline of Light Source Device]

FIG.2is a view illustrating an example of the light source device incorporating the lamp10. A light source device100includes the lamp10, a laser oscillation unit21that oscillates a laser (for example, a laser having a wavelength band of infrared light) to be applied to the lamp10, and a condensing optical system25that condenses laser light from the laser oscillation unit21. The laser light emitted from the laser oscillation unit21is shaped by a beam shaping optical system22including a collimator, a beam expander, and the like, is reflected by a reflecting mirror23, passes through a wavelength selection type optical element24such as a dichroic mirror, is reflected by the condensing optical system25, is condensed in a predetermined region, and enters the lamp10. As a result, the excitation laser is applied to the lamp10. InFIG.2, the excitation laser is indicated by solid lines.

Light radiated from the lamp10is reflected by the condensing optical system25, reflected by the optical element24, passes through a beam shaping optical system26such as a homogenizer and a filter for making the light uniform, and travels toward a device (for example, a substrate inspection device) using laser light, not illustrated. InFIG.2, the light generated by the lamp10is indicated by broken lines.

The sealing portion5will be described. In the present embodiment, the sealing portion5is disposed on the arc tube2.FIGS.3A and3Bare enlarged views of an E1region inFIG.1. Details of the sealing portion5will be described with reference toFIGS.3A and3B.FIGS.3A and3Bare views of the same sealing portion5viewed from the same direction, butFIGS.3A and3Bare illustrated separately in order to make reference signs, auxiliary lines, and the like easily viewable.FIGS.3A and3Bare both illustrated in the ABC orthogonal coordinate system in which the protruding direction of the sealing portion5is an A direction, and the directions orthogonal to the protruding direction are a B direction and a C direction. Note thatFIGS.3A and3Bhave changed orientation from the XYZ orthogonal coordinate system ofFIG.1.

The sealing portion5includes an outer surface5aand an inner surface (5b,5c). Points p3and p4are portions having a large curvature on a second inner surface5cto be described later. Points p5and p6are portions having a large curvature on the outer surface5a. In the present specification, the boundary between the arc tube2and the sealing portion5includes the point p3, the point p4, the point p5, and the point p6. The boundary line between the arc tube2and the sealing portion5is defined as line segment p3-p5and line segment p4-p6. A region (hatched region inFIG.3A) on the +A side with respect to the line segment p3-p5and the line segment p4-p6, which are the boundary line is defined as the sealing portion5.

InFIG.3A, the outer surface5aof the sealing portion5extends from the point p5to the point p6via an outer apex5t. The outer apex5tis a point located at the most front end (maximum in the A direction) of the outer surface5a. The outer surface5ahas a shape in which the outer diameter d2 generally decreases toward the front end of the sealing portion5. The outer surface5amay partially have a shape in which the outer diameter d2 does not decrease toward the front end of the sealing portion5. The outer surface5ais preferably a substantially conical surface as a whole.

InFIG.3A, the inner surface (5b,5c) of the sealing portion5includes a first inner surface5bon the front end side and the second inner surface5con the rear end side. The first inner surface5bextends from the point p1to the point p2via an inner apex5i. The inner apex5iis a point located at the most front end (maximum in the A direction) of the first inner surface5b. The first inner surface5bhas a tapered shape in which the inner diameter of the sealing portion5decreases toward the front end.

As illustrated inFIG.3B, a space (cross-hatched region inFIG.3B) which is located on the front end side with respect to line segment p1-p2connecting the point p1and the point p2and is surrounded by the first inner surface5bis referred to as a first sealed space5s. The width of the first sealed space5sin the A direction is referred to as a height h1 of the first sealed space5s. An inner diameter d1 of the first sealed space5sis the interval between the point p1and the point p2.

The present inventors have found, through intensive research, that a portion having low pressure resistance strength in the sealing portion5is near the front end of the first sealed space5swhere stress concentrates. The present inventors have found that if the taper angle θ1(seeFIG.3A) of the first sealed space5sis decreased, the pressure resistance strength is improved. Improvement of the pressure resistance strength of the sealing portion5leads to improvement of the pressure resistance strength of the entire lamp10.

In order to realize the taper angle θ1for enhancing the desired pressure resistance strength, the height h1 of the first sealed space5sis preferably larger than twice the inner diameter d1 of the first sealed space5s. The taper angle θ1is preferably 15 degrees or less. The inner diameter d1 is preferably 1 mm or more and is preferably 3 mm or less. The height h1 is preferably 3 mm or more and is preferably 9 mm or less.

A height h3 of the sealing portion5is represented by the interval between the outer apex5tand the point p5(point p6) in the A direction. The height h3 is preferably twice or more the interval between the point p5and the point p6.

Line segment p1-p3and line segment p2-p4corresponding to the inner surface of the sealing portion5extend substantially in a direction along the direction A. A region (hatched region inFIG.3B) sandwiched between line segment p1-p3and line segment p2-p4is referred to as a second sealed space5v. The inner diameter of the second sealed space5vis substantially constant in the A direction and is the inner diameter d1.

The outer diameter d2 of the sealing portion5is represented by the interval between the point p5and the point p6in the C direction. The inner diameter of the sealing portion5is represented by the interval between the point p1and the point p2or the interval between the point p3and the point p4in the C direction. In the present embodiment, the outer diameter d2 is three times or more the inner diameter d1. As a result, the thickness of the sealing portion5can be sufficiently secured, so that the pressure resistance is improved. The outer diameter d2 is preferably 3 mm or more and is preferably 10 mm or less. The outer diameter d2 is more preferably 4 mm or more and is more preferably 9 mm or less.

FIG.4Ais a view obtained by rotating the view illustrated inFIG.3Bby 90 degrees about an axis parallel to the A axis. The sealing portion5is preferably a rotationally symmetric figure, but the sealing portion5may not be a rotationally symmetric figure. In the sealing portion5of the lamp10of the present embodiment, the front end of the first sealed space5sis branched into a first branch B1and a second branch B2.

The front ends of the first branch B1and the second branch B2are portions having low pressure resistance strength, and cracks are likely to occur from the first branch B1or the second branch B2toward the outer surface5a. The present inventors have considered that an interval KL between the front end of the first branch B1and the front end of the second branch B2affects the pressure resistance strength, and conducted the following experiment.

In order to examine the relationship between the interval KL between the front end of the first branch B1and the front end of the second branch B2and the pressure resistance strength, the lamps10ware prepared in which only the intervals KL were different and the other conditions were the same. Alcohol was gradually injected into each lamp10, and the internal pressure of each lamp10was measured while increasing the internal pressure of each lamp10. A pressure value when each lamp10is broken is defined as a fracture pressure BP.

FIG.5is a graph illustrating the relationship between the interval KL between the front end of the first branch B1and the front end of the second branch B2and a fracture pressure BP. Each point illustrated inFIG.5indicates the measurement results of the interval KL and the fracture pressure BP of each lamp10. As indicated by the regression line ofFIG.5, it has been found that the fracture pressure BP tends to increase as the interval KL decreases.

As the interval KL decreases, a thickness t1abetween the first branch B1and the outer surface5aand a thickness t1bbetween the second branch B2and the outer surface5acan be increased (seeFIG.4A). As a result, it is considered that the pressure resistance strength of the lamp10is improved. The interval KL between the front end of the first branch B1and the front end of the second branch B2is preferably 1.5 mm or less, and more preferably 1 mm or less. The interval KL between the front end of the first branch B1and the front end of the second branch B2is preferably designed to be shorter than the interval between the root of the first branch B1and the root of the second branch B2.

The smaller the interval between the front end of the first branch B1and the front end of the second branch B2is, the thicker the thickness t1a/t1bcan be, which is preferable. In a case where there is no branch at the front end of the first sealed space5s, the thickness t1a/t1bcan be maximized, which is more preferable.

Note that it is determined that there is no branch at the front end of the first sealed space5sin a case where no branch is observed at the front end of the first sealed space5sat any rotation angle when the sealing portion5is rotated by 360 degrees about the axis passing through the outer apex5t.

Details of a method of reducing the interval KL between the front end of the first branch B1and the front end of the second branch B2will be described later, but one of the methods is a method of twisting the branches.FIG.4Bis a cross-sectional view of line segment F1-F1inFIG.4A.FIG.4Billustrates the first branch B1and the second branch B2sandwiched between a central region of the sealing portion5and a peripheral region of the sealing portion5. It is observed that the front end of the first branch B1and the front end of the second branch B2both extend while bending in the w1direction and are twisted in a pair. Due to the shape in which the front end of the first branch B1and the front end of the second branch B2are twisted in a pair, the interval KL between the front end of the first branch B1and the front end of the second branch B2can be made close to each other.

The interval between the front end of the first branch B1and the front end of the second branch B2in the B direction may be reduced, or the length (route) from the front end of the first branch B1to the front end of the second branch B2along the boundary of the first sealed space5smay be reduced.

As described above, examples of the parameters related to the sealing portion5include the height h3, the outer diameter d2, and the thickness (t1a, t1b) of the sealing portion5, the height h1, the inner diameter d1, the interval KL, and the taper angle θ1of the first sealed space5s. There is a possibility that all the parameters relating to the sealing portion5change when the sealing portion5is rotated about a straight line passing through the outer apex5tof the sealing portion5and parallel to the A axis. In the present specification, the parameters related to the sealing portion5indicate maximum values in a case where the parameters are measured by rotating the sealing portion5about the straight line passing through the outer apex5tof the sealing portion5and parallel to the A axis.

[Method of Forming Sealing Portion]

The method of forming the sealing portion5will be described. When the lamp10is manufactured, an exhaust pipe8is attached to the arc tube2. The exhaust pipe8is used to exhaust gas in the space inside the arc tube2and supply a working gas to the space. After the working gas is supplied into the space, the exhaust pipe8is disconnected from the arc tube2. At this time, part of the exhaust pipe8remains on the arc tube2. The remaining exhaust pipe8becomes the sealing portion5which seals the inside of the arc tube2from the outside.

A method of disconnecting the exhaust pipe8from the arc tube2will be described with reference toFIG.6. An E2region of the exhaust pipe8close to the arc tube2is heated, and the exhaust pipe8is contracted to close the hole of the exhaust pipe8.FIG.6illustrates a state after the hole of the exhaust pipe8is closed. Then, in order to cut the exhaust pipe8in the vicinity of line segment C2-C2, the arc tube2is gradually separated from the exhaust pipe8in a state where the vicinity of line segment C2-C2is heated. The exhaust pipe8may be separated from the arc tube2.

The shape of the sealing portion5(the taper angle of the first sealed space5sor the like) can be changed by adjusting the heating temperature, the heating range, the separating speed, the separating direction, and the like. When the exhaust pipe8is separated, for example, if the arc tube2is separated from the exhaust pipe8while being rotated in the B3direction in a state where the exhaust pipe8is fixed, the branches (B1, B2) at the front end of the first sealed space5scan be formed in a twisted shape. Of course, the arc tube2may be fixed, and the exhaust pipe8may be separated from the arc tube2while being rotated in the B3direction.

Second Embodiment

A super-high pressure lamp of a second embodiment will be described with reference toFIG.7. The matters to be described below will be described focusing on portions different from those of the first embodiment. Description of matters similar to those in the first embodiment will be omitted. The same applies, too, from the third embodiment onward.

A lamp20is an LSP lamp not including two starting electrodes EL. A sealing portion5is provided on an arc tube2as in the first embodiment.

Third Embodiment

A super-high pressure lamp of a third embodiment will be described with reference toFIGS.8A and8B. In a lamp30illustrated inFIG.8A, a sealing portion5is provided on a curved surface of a second side tube4. An arc tube2is not provided with the sealing portion5. The same applies to a lamp40illustrated in a modification ofFIG.8B. The lamp30illustrated inFIG.8Adoes not include two starting electrodes EL, whereas the lamp40illustrated inFIG.8Bincludes two starting electrodes EL.

Fourth Embodiment

A super-high pressure lamp of a fourth embodiment will be described with reference toFIG.9. In a lamp50, a sealing portion5is provided inside a second side tube4.

The embodiments of the super-high pressure lamp and the modification thereof have been described above. The present invention is not limited to the embodiments and the modification thereof described above, and various changes or improvements may be made to the embodiments and the modification thereof and two or more of the embodiments and the modification thereof may be combined without departing from the spirit of the present invention.

In the embodiments and the modification thereof described above, the LSP lamp has been indicated as an example of the “super-high pressure lamp”. However, a super-high pressure mercury lamp used as a light source of an exposure device, used for curing or drying a resin adhesive, or used as a light source of a projector or the like is also a kind of the super-high pressure lamp. The above embodiments can also be applied to a super-high pressure mercury lamp.

EXAMPLES

A pressure resistance test was performed by using the lamps10of the first embodiment. Samples S1to S15are the lamps10different from one another in the inner diameter d1 of the first sealed space5s, the height h1 of the first sealed space5s, and the interval KL between the front end of the first branch B1and the front end of the second branch B2. Type 1 has a non-twisted sealing portion obtained by pulling out the exhaust pipe8without rotating the arc tube2. Type 2 has a twisted sealing portion obtained by pulling out the exhaust pipe8while rotating the arc tube2. Type 3 has a sealing portion in which d1 and h1 are fixed and the front end of the first sealed space5sis not branched.

The pressure resistance test of each sample was performed as follows. Alcohol was gradually injected into the lamp10of each sample, and the internal pressure of the lamp10was measured while increasing the internal pressure of the lamp10. The pressure value when the lamp10is broken is defined as “fracture pressure”.

As a result of the pressure resistance test, in any sample, the starting point of fracture was the sealing portion5. A case where the fracture pressure is 25 MPa or more is evaluated as grade A, a case where the fracture pressure is 15 MPa or more is evaluated as grade B, and a case where the fracture pressure is less than 15 MPa is evaluated as grade C. Since the lamp10is superior as the fracture pressure increases, grade A, grade B, and grade C are ranked in this order of excellence. Note that the actual pressure resistance of the lamp10is a value obtained by considering the safety factor in the fracture pressure.

The evaluation results are analyzed. h1/d1 of type 2, which is grade A or type 1, which is grade B is greater than 2. In contrast, h1/d1 of type 3, which is grade C is smaller than 2. That is, it has been confirmed that the height h1 of the sealed space where the inner diameter of the sealing portion changes is preferably larger than twice the inner diameter d1 of the sealing portion.

If type 2, which is grade A and type 1, which is grade B are compared, no significant difference of h1/d1 is observed between type 2 and type 1. However, the interval KL of type 2, which is grade A, is much smaller than the interval KL of type 1, which is grade B. As a result, it was confirmed that the interval KL is preferably smaller. The interval KL is preferably smaller than 1000 μm, and more preferably smaller than 500 μm.