EP2190005A2

EP2190005A2 - Light-emitting container for high-intensity discharge lamp and high-intensity discharge lamp

Info

Publication number: EP2190005A2
Application number: EP09176841A
Authority: EP
Inventors: Keiichiro Watanabe
Original assignee: NGK Insulators Ltd
Current assignee: NGK Insulators Ltd
Priority date: 2008-11-25
Filing date: 2009-11-24
Publication date: 2010-05-26
Also published as: EP2190005A3; JP2010153372A; JP5340896B2

Abstract

A light-emitting container 5A for a high-intensity discharge lamp has an arc tube comprising a translucent polycrystalline ceramics. The arc tube has a central light-emitting portion 2 and side end portions 3 provided on both sides of the central light-emitting portion 2, respectively, and tubular portions 1 protruding from both of the side end portions, respectively. The inner surfaces of the side end portions are roughened surfaces.

Description

TECHNICAL FIELD

The present invention relates to a light-emitting container for a high-intensity discharge lamp.

BACKGROUND ARTS

Translucent ceramics transmit visible light, and therefore, have been used for a light-emitting container for a high-intensity discharge lamp. Particularly, translucent alumina ceramics are being used for a light-emitting container for a high-intensity discharge lamp.
For the purpose of improving stability of color temperature of a ceramic metal halide lamp, vapor pressure of metal halide in a plasma arc is required to be raised. There is disclosed that when a ceramic tube is partially coated with zirconium oxide and infrared radiation emitted from a plasma arc is reflected at an inside of an arc tube, a temperature within the arc tube is raised, thereby improving the metal halide vapor pressure (European Patent No. 0869540A1 : Japanese Patent Laid-open Publication No. Hei10-335059A ). In European Patent No. 0869540A1 : Japanese Patent Laid-open Publication No. Hei10-335059A , also disclosed is that when both end faces (end plugs) of the arc tube and surfaces of elongated tubular portions (leg parts) attached to the arc tube are coated with zirconium oxide films, liquefaction and temperature reduction of a metal-halide filling are prevented and excellent color rendering properties are secured.
Disclosed is that an arc tube for a metal halide lamp rated for not more than 150 W has an internal capacity of less than 1 cc and further is coated at both ends with a heat reflective coating so that the arc tube can be operated in either a horizontal or vertical position without a change in color temperature or light-emitting efficiency ( U.S. Patent No. 5708328B ).
Japanese Patent Laid-open Publication No. 2006-93045A (0054) discloses that in the high-pressure discharge lamp used as a automobile headlight in which the light-emitting portion with average linear light transmittance of visible light of 15% or more and a plug end part with that of less than 15% are manufactured by the shrinkage fitting method, when a light shielding film is further formed on a surface of an arc tube, light radiation in an undesired direction is shielded.
Further, Japanese Patent Laid-open Publication No. 2004-6198A discloses that in a high-pressure discharge lamp used as an automobile headlight, the intensity center is located in a central portion by thinning a wall thickness of the central portion of an arc tube, and the light collection efficiency onto a focus of a projection beam is improved.

DISCLOSURE OF THE INVENTION

In a high-intensity discharge lamp, discharge between electrodes is first caused in a starting gas such as mercury vapour and argon gas, and sodium and metal iodides as light-emitting materials are evaporated and gasified by using thermal energy due to its discharge energy. Further, the light-emitting materials are excited by the energy of electrons emitted between the electrodes, and light generated at the time when electrons of the light-emitting materials are returned from the excited state to the ground state is used as a light source.
Accordingly, as the vapour pressure of the light-emitting materials is higher, the probability of collision between the emitting electrons and the light-emitting materials becomes higher. Therefore, the excitation of the light-emitting materials is easy to be caused, and the light-emitting efficiency becomes higher. For the purpose of raising the vapor pressure of the light-emitting materials, a temperature of the light-emitting materials is required to be raised, and it is important that a gas temperature within the arc tube is kept high.
As described above, in the high-intensity discharge lamp, electron emission between the electrodes is used to produce luminescence, and a temperature of a light-emitting portion becomes the highest and a temperature of a root part or back part of the electrodes becomes low. This portion in which the temperature is the lowest is referred to as a coolest point. Since the vapor pressure of the light-emitting materials within the lamp is controlled by this coolest point, raising the temperature of the coolest point is important for increasing the vapor pressure of the light-emitting materials.
For the purpose of raising the temperature of the coolest point, as in the conventional technology, powder of zirconium oxide is baked onto a surface of an end plug of the electrode root part or a tubular part (leg part) at a temperature of 400 to 500°C, whereby formation of a light shielding film is effective (European Patent No. 0869540A1 : Japanese Patent Laid-open Publication No. Hei10-335059A : U.S.Patent No. 5708328B ). When light energy emitted from the light-emitting materials is absorbed by the light shielding film, a temperature of the arc tube is raised and also a temperature of the metal halide vapor is raised. As a result, the vapor pressure of the light-emitting materials is raised and the light-emitting efficiency (lm/W) can be improved, thereby providing an arc tube for a high-intensity discharge lamp with excellent color temperature stability at the same time. However, since a surface coating layer made of the above-described heterogeneous material powder has weak adherence to a surface of the arc tube and also weak binding power of powders, the layer is easy to be peeled off at the time of long hours of lighting or repetition of lighting on and off. Also, there arises a problem that when the surface coating layer is gradually peeled off, the light-shielding properties are deteriorated, and a temperature of the arc tube is gradually lowered, resulting in gradually deteriorated the lamp characteristic.
Since the ceramic arc tube generally has translucent properties but is not transparent, the entire arc tube produces luminescence by light generated and emitted by the plasma arc, and thus, a size of the light source is the same as that of the arc tube. Therefore, a light-emitting portion is hard to be controlled in conformity to the performance of lighting equipment used in combination of the arc tube. In lamps in which a relatively large size of the light source is allowed as in lamps for general lighting, there is not much problem of a large size of the light source as compared with that of the lighting equipment. However, for a headlight for an automobile or a lamp for a projector, since the ceramic arc tube has an extremely large size of the light source, it is hard to be combined with lighting equipment.
To cope with the problem, it is known that the light collection efficiency using a projection beam is improved by emitting light from a narrow area of the central portion of the arc tube (Japanese Patent Laid-open Publication No. 2006-93045A : Japanese Patent Laid-open Publication No. 2004-6198A ). The methods disclosed in these documents are effective in improving the light collection efficiency, but since a light shielding effect at the ends of the arc tube is not sufficiently exerted, the color stability is not sufficiently obtained. Also, a shape of the arc tube is limited to a small cylindrical shape.
An object of the present invention is to provide a high-intensity discharge lamp capable of improving the color temperature stability during the light emitting and of keeping durability at the time of repeating lighting on and off. Further, the present invention can narrow a light-emitting area of the arc tube in conformity with specifications of the entire light-emitting apparatus.
A light-emitting container for a high-intensity discharge lamp of the invention comprises:

an arc tube comprising a translucent polycrystalline ceramics, the arc tube comprising a central light-emitting portion and side end portions provided on both sides of the central light-emitting portion, respectively; and
tubular portions protruding from both of the side end portions, respectively,

Further, a light-emitting container for a high-intensity discharge lamp of the invention comprises:

an arc tube comprising a translucent polycrystalline ceramics, the arc tube comprising a central light-emitting portion and side end portions provided on both sides of the central light-emitting portion, respectively; and
tubular portions protruding from the respective side end portions,

A high-intensity discharge lamp of the invention comprises:

the light-emitting container;
electrodes provided in an internal space of the arc tube; and
electrode holding members inserted into the respective tubular portions and holding the electrodes, respectively.

According to the present invention, the roughened surface is formed on an inner surface of the side end portion of the arc tube, a light shielding part with relatively low light transmittance is formed, and the intensity center is disposed in the central light-emitting portion. These enable the light collection efficiency of the projection beam to be improved.
At the same time as the above, it is proved that when the roughened surface is formed on the inner surface of the side end portion, liquefaction or temperature reduction of a gas at the coolest point of the arc tube can be appropriately controlled.
Since a surface roughness of the arc tube has been known to cause scattering of light, the arc tube is conventionally manufactured using a mold with a smooth surface roughness. The surface roughness has not been intentionally increased in part and irregularities have not been formed.
Further, when employing an extrusion molding method widely used as a molding method of translucent polycrystalline ceramics, a ferrule for specifying a shape and a molded body are uniformly rubbed with each other. Therefore, a surface state becomes uniform and the surface roughness fails to be intentionally increased in part.
Further, since the surface roughness exerts an influence on the strength of ceramics, the ceramics have been manufactured so as to have a preferably smooth surface. The present invention has been made contrary to these common knowledges in a field of the high-intensity arc tube.
When only outer surfaces of the side end portions and the tubular portions are coated with the light shielding films, sealing members are deteriorated due to rise in temperature of the sealing members. As a result, the color temperature stability is deteriorated and the durability during repetition of the lighting on and off is deteriorated. The reason is considered that a gas temperature at the end plug is higher than expected and further a corrosive gas is easy to flow into the tubular part to corrode a sealing portion. Further, adhesion to a ceramic surface of the light shielding film is considered to be reduced in a long-term use to impair the ability for controlling the coolest point.
Further, it is examined that the coolest point generated at the side end portion is controlled by forming the roughened surface on the outer surface of the side end portion. However, in this case, it is proved that an effect of controlling the coolest point is not sufficiently exerted. The reason is that when emitted light is scattered on the outer surface of the side end portion, the heat quantity used for rise in temperature at the coolest point is smaller than expected.
Furthermore, it is confirmed that the same operation and effect as in the above is obtained also by forming the concave or convex pattern on the inner surface of the side end portion of the light-emitting container.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1(a) is an appearance view of a light-emitting container for a ceramic metal halide lamp (Comparative Embodiment), and FIG. 1(b) is a cross-sectional view of the same light-emitting container for a ceramic metal halide lamp.
FIG. 2(a) is an appearance view of a light-emitting container for a ceramic metal halide lamp (Embodiment), and FIG. 2(b) is a cross-sectional view of the same light-emitting container.
FIG. 3(a) is an appearance view of the light-emitting container for a ceramic metal halide lamp (Comparative Embodiment), and FIG. 3(b) is a cross-sectional view of the same light-emitting container.
FIG. 4(a) is an appearance view of the light-emitting container for a ceramic metal halide lamp (Embodiment), and FIG. 4(b) is a cross-sectional view of the same light-emitting container.
FIGS. 5(a) to 5(c) are cross-sectional views of the light-emitting container for a ceramic metal halide lamp. FIG. 5(a) illustrates an example in which a stripe-shaped roughened surface is formed on an inner surface of a side end portion. FIG. 5(b) illustrates an example in which a roughened surface is formed on the inner surface of the side end portion and a roughness of the roughened surface is stepwise increased. FIG. 5(c) illustrates an example in which a dotted concave or convex pattern is formed on the inner surface of the side end portion.
FIGS. 6(a) to 6(c) are cross-sectional views of the light-emitting container for a ceramic metal halide lamp. FIG. 6(a) illustrates an example in which a linear concave part is formed on the inner surface of the side end portion. FIG. 6(b) illustrates an example in which a netted concave part is formed on the inner surface of the side end portion. FIG. 6(c) illustrates an example in which the netted concave part and the roughened surface are formed on the inner surface of the side end portion.
FIG. 7(a) is an appearance view of the light-emitting container for a ceramic metal halide lamp (Embodiment), and FIG. 7(b) is a cross-sectional view of the same light-emitting container.
FIG. 8(a) is an appearance view of a light-emitting container for a high-pressure sodium lamp (Embodiment), and FIG. 8(b) is a cross-sectional view of the same light-emitting container.
FIG. 9 is a cross-sectional view illustrating a state in which electrodes are fitted to the light-emitting container for a ceramic metal halide lamp.
FIG. 10(a) is an appearance view of the light-emitting container for a ceramic metal halide lamp (Embodiment), and FIG. 10(b) is a cross-sectional view of the same light-emitting container.
FIG. 11(a) is an appearance view of the light-emitting container for a ceramic metal halide lamp (Embodiment), and FIG. 11(b) is a cross-sectional view of the same light-emitting container. A light shielding part with a rough surface is formed on an outer surface in a strip shape in the vertical direction with respect to the discharge direction of a central portion of an arc tube. In the same manner, a wall thickness of the central portion of the arc tube is thinned in a strip shape in the vertical direction with respect to the discharge direction, and a light transmission part is formed in combination of control over the surface roughness and the wall thickness.
FIG. 12(a) is an appearance view of the light-emitting container for a ceramic metal halide lamp (Embodiment), and FIG. 12(b) is a cross-sectional view of the same light-emitting container. Multiple strip-shaped light transmission parts are formed in two places on the front side and the opposite side thereof.
FIG. 13(a) is an appearance view of the light-emitting container for a ceramic metal halide lamp (Embodiment), FIG. 13(b) is a cross-sectional view of the same light-emitting container, and FIG. 13(c) is a transverse cross-sectional view of the same container. The light shielding parts with the rough surface are formed on the outer surface such that the strip-shaped light transmission parts are formed in two places in the same direction as the discharge direction in the central portion of the arc tube. In the same manner, the wall thickness of the central portion of the arc tube is thinned in the same direction as the discharge direction, and the light transmission parts are formed in combination of control over the surface roughness and the wall thickness.
FIG. 14(a) is an appearance view of the light-emitting container for a ceramic metal halide lamp (Embodiment), FIG. 14(b) is a cross-sectional view of the same light-emitting container, and FIG. 14(c) is a transverse cross-sectional view of the same container. The light shielding parts with the rough surface are formed on the inner and outer surfaces, and the light transmission parts are formed like a dot in the central portion of the arc tube. In this view, the dotted light transmission parts are formed in 24 places, and the light transmission parts are formed such that a virtual center of each light transmission part converges on the center of the arc tube.
FIG. 15(a) is an appearance view of the light-emitting container for a ceramic metal halide lamp (Embodiment), FIG. 15(b) is a cross-sectional view of the same light-emitting container, and FIG. 15(c) is a transverse cross-sectional view of the same container. The light shielding parts with the rough surface are formed on the inner and outer surfaces such that the light transmission parts are formed like a dot in the central portion of the arc tube. In the same manner, the wall thickness of the central portion of the arc tube is thinned like a dot, and the dotted light transmission parts are formed in combination of control over the surface roughness and the wall thickness. In this view, the dotted light transmission parts are formed in 8 places, and the light transmission parts are formed such that the virtual center of each light transmission part converges on the center of the arc tube.

BEST MODES FOR CARRYING OUT THE INVENTION

An inner surface of a side end portion is a roughened surface. It means that Ra of the inner surface is larger than those of an inner surface and an outer surface of a central light-emitting portion. In a preferred embodiment, a center line average surface roughness Ra of the inner surface of the side end portion is 2.0 µm or more, and particularly preferably 2.5 µm or more.
From a viewpoint that strength of an arc tube is not deteriorated, the center line average surface roughness Ra of the inner surface of the side end portion is preferably 20 µm or less.
The outer surface of the side end portion may be a smooth surface, or a roughened surface. In a preferred embodiment, the center line average surface roughness Ra of the outer surface of the side end portion is 2.0 µm or more, and particularly preferably 2.5 µm or more, which enables light-emitting efficiency to be more improved. From a viewpoint that the strength of the arc tube is not deteriorated, the center line average surface roughness Ra of the outer surface of the side end portion is preferably 20 µm or less. From this viewpoint, the outer surface of the side end portion is a smooth surface and the center line average surface roughness Ra is preferably 1.0 µm or less, for example.
In a preferred embodiment, the center line average surface roughness Ra of the inner and outer surfaces of the central light-emitting portion is 1.0 µm or less, thereby further improving the light-emitting efficiency from the central light-emitting portion. Further, since visible light emitted from a plasma arc generated by the discharge between electrodes is used in a high-intensity discharge lamp, it is preferred that as to the surface roughness of the light transmission part, both the inner and outer surfaces are smooth, and light scattering and light loss are reduced. When translucent alumina ceramics have an average particle size of 15 to 50 µm, both of the translucent properties and the mechanical strength are preferably satisfied.
Further, in a preferred embodiment, the central light-emitting portion has the light transmission part and the light shielding part with linear light transmittance lower than that of this light transmission part. This makes it possible to further narrow emitting regions in conformity with specifications of the entire light-emitting apparatus.
The case in which a concave or convex pattern is formed on the inner surface (and the outer surface) of the side end portion includes a case in which a concave pattern is formed, and a case in which a convex pattern is formed. From a viewpoint of the present invention, a height difference (step) of the concave part or the convex part is preferably 0.05 mm or more. Further, from a viewpoint that release after the molding is made easy, a height difference of the concave part or the convex part is preferably 0.2 mm or less.
FIG. 1(b) is a schematic cross-sectional view of a conventional light-emitting container for a high-intensity discharge lamp used for a metal halide lamp, and FIG. 1(a) is a front view illustrating an appearance of the light-emitting container. The light-emitting container has a central light-emitting portion 2, side end portions 3 of both sides of the central light-emitting portion 2, and tubular portions (leg parts) 1 outside the respective side end portions 3. Both of the inner and outer surfaces of the side end portions 3 and the central light-emitting portion 2 are flat and smooth, and the surface roughness is almost uniform.
FIG. 2 illustrates an embodiment of the light-emitting container 5A for a high-intensity discharge lamp used for a metal halide lamp. In the embodiment, the inner surface 2a and the outer surface 2b of the central light-emitting portion 2 are smooth surfaces, and the outer surfaces 3b of the side end portions 3 are smooth surfaces. However, on the inner surfaces 3a of the side end portions 3, roughened surfaces 6 are formed. In an internal space 4 of the arc tube, arc discharge is executed and light is emitted.
FIG. 3 relates to a comparative embodiment outside of the present invention. In a light-emitting container 5B of the comparative embodiment, the inner surface 2a and the outer surface 2b of the central light-emitting portion 2 are smooth surfaces, and also, the inner surfaces 3a of the side end portions 3 are smooth surfaces. However, on the outer surfaces 3b of the side end portions 3, the roughened surfaces 6 are formed.
FIG. 4 illustrates an embodiment of the light-emitting container 5C for a high-intensity discharge lamp used for the metal halide lamp. In the embodiment, the inner surface 2a and the outer surface 2b of the central light-emitting portion 2 are smooth surfaces. However, on the inner surface 3a and the outer surface 3b of the side end portions 3, the roughened surfaces 6 are formed, respectively.
FIGS. 5 and 6 illustrate an embodiment in which the roughened surface and the concave or convex pattern are formed on the inner surfaces of the side end portions of the light-emitting container used for the metal halide lamp.
In a light-emitting container 5D of FIG. 5(a), the inner surface 2a and the outer surface 2b of the central light-emitting portion 2 are smooth surfaces, and the outer surfaces 3b of the side end portions 3 are smooth surfaces. However, on the inner surfaces 3a of the side end portions 3, the roughened surfaces 6 are formed. In particular, the roughened surface 6 has a strip shape which is formed in the circumferential direction around a tube axis A of the arc tube, and the adjacent roughened surfaces 6 are parallel to each other.
In a light-emitting container 5E of FIG. 5(b), the inner surface 2a and the outer surface 2b of the central light-emitting portion 2 are smooth surfaces, and the outer surfaces 3b of the side end portions 3 are smooth surfaces. However, on the inner surfaces 3a of the side end portions 3, the roughened surfaces 6A are formed. In the embodiment, the average surface roughness Ra of the roughened surface 6A is gradually reduced toward the central light-emitting portion from an end on the tubular part side of the side end portion.
In a light-emitting container 5F of FIG. 5(c), the inner surface 2a and the outer surface 2b of the central light-emitting portion 2 are smooth surfaces, and the outer surfaces 3b of the side end portions 3 are smooth surfaces. However, on the inner surfaces 3a of the side end portions 3, concave or convex patterns 7 are formed. In the embodiment, the concave or convex pattern 7 has a shape in which a number of dimple-shaped concave parts are formed.
In a light-emitting container 5G of FIG. 6(a), a concave or convex pattern 9 has a shape in which a number of elongated groove-like concave parts are formed. Further, in a light-emitting container 5H of FIG. 6(b), the concave or convex pattern 10 has a shape in which elongated grooves are formed in a net shape.
In a light-emitting container 5I of FIG. 6(c), the inner surface 2a and the outer surface 2b of the central light-emitting portion 2 are smooth surfaces, and the outer surfaces 3b of the side end portions 3 are smooth surfaces. However, on the inner surfaces 3a of the side end portions 3, both of the netted concave or convex pattern 10 and the roughened surface 6 are formed.
FIG. 7 illustrates a light-emitting container 5J for a metal halide lamp. In the embodiment, the inner surface 2a and the outer surface 2b of the central light-emitting portion 2 are smooth surfaces, and the roughened surfaces 6 are formed on the inner surface 3a and the outer surface 3b of the side end portions 3. Further, since a wall thickness of the side end portion 3 is larger than that of the central light-emitting portion 2, convergence of emission to the central light-emitting portion is more accelerated.
FIG. 8 illustrates a light-emitting container 5K used for a high-pressure sodium lamp. In the embodiment, the inner surface 2a and the outer surface 2b of the central light-emitting portion 2 and the outer surfaces 3b of the side end portions 3 are smooth surfaces. The roughened surfaces 6 are formed on the inner surfaces 3a of the side end portions 3.
FIG. 9 illustrates the metal halide lamp using the light-emitting container 5A (see FIG. 2) according to an embodiment of the present invention. The light shielding part with a rough surface is formed on an electrode root part and a rear part behind the top of the electrode. An electrode holding member 12 is inserted into the tubular part 1, and an electrode 14 is attached to an inner end of the electrode holding member. An outer end of the electrode holding member 12 is sealed by a sealing member 13 to an inner wall surface of the tubular part 1 as well as to an outer wall surface of the tubular part 1. A pair of the electrodes 14 is located in the internal space 4 of the arc tube, and the light-emitting container 5A is designed such that discharge is executed between the electrodes 14.
FIG. 10 illustrates the embodiment in which a light transmission part 20 is formed in a strip shape in the central portion of a light-emitting container 5L for a metal halide lamp. In the embodiment, the roughened surfaces are formed on the inner and outer surfaces of the side end portions 3, and at the same time, the roughened surfaces are partially formed also on the inner and outer surfaces of the central light-emitting portion 2, thereby forming the elongated strip-shaped light transmission part 20 and the light shielding parts 21.
FIG. 11 illustrates the embodiment in which the light transmission part 20 is formed in a strip shape in the central portion of a light-emitting container 5M for a metal halide lamp. In the embodiment, the light-emitting container 5M is further molded and processed such that the wall thickness of the light transmission part 20 is thinned in the central light-emitting portion 2. After the sintering, a surface of the light transmission part 20 is polished and the surface roughness becomes smoother. Meanwhile, the surface roughness is increased in all the surfaces except an inner surface of the central portion, thereby forming the light shielding parts 21 in a strip shape.
FIG. 12 illustrates the embodiment in which the light transmission parts 20 are formed in a strip shape at the respective places at the front and at the back on the opposite side in the longitudinal direction in the central portion of a light-emitting container 5N used for a metal halide lamp. In the embodiment, since the light shielding parts 21 in which the surface roughness is increased are formed on the inner and outer surfaces of the central light-emitting portion 2, the light transmission parts 20 in which scattering and absorption of light is relatively reduced are formed.
FIG. 13 illustrates the embodiment in which the light transmission parts 20 are formed in a strip shape at places at the front and at the back on the opposite side in the longitudinal direction in the central portion of a light-emitting container 5P for a metal halide lamp. In the embodiment, since the light shielding parts 21 in which the surface roughness is increased are formed on the inner and outer surfaces of the central light-emitting portion 2, the light transmission parts 20 in which scattering and absorption of light 15 is relatively reduced are formed. Further, as illustrated in FIG. 13(c), the wall thicknesses of the light transmission parts 20 are thinned, thereby forming the light transmission parts 20 at two places.
FIG. 14 illustrates the embodiment in which the light transmission parts 20 are formed as dots in a light-emitting container 5Q for a metal halide lamp. In the embodiment, since the light shielding parts 21 in which the surface roughness is increased are formed on the inner and outer surfaces of the central light-emitting portion 2, the dotted light transmission parts 20 in which scattering and absorption of light 15 is relatively reduced are formed. The dotted light transmission parts 20 are formed in 24 places. The light transmission parts 20 are formed such that the virtual center of each light transmission part 20 converges on the center of the arc tube.
FIG. 15 illustrates the embodiment in which the dotted light transmission parts 20 are formed in a light-emitting container 5R for a metal halide lamp. Since the light shielding parts 21 in which the surface roughness is increased are formed on the inner and outer surfaces of the central light-emitting portion 2, the dotted light transmission parts 20 in which scattering and absorption of light 15 is relatively reduced are formed. As illustrated in FIG. 14(c), the wall thicknesses of the light transmission parts 20 are thinned. In this view, the dotted light transmission parts 20 are formed in eight places. The light transmission parts 20 are formed such that the virtual center of each light transmission part 20 converges on the center of the arc tube.
Since the ceramic arc tube has translucent properties but is not transparent, the entire arc tube produces luminescence due to light generated and emitted by the plasma arc. Accordingly, a size of a light source is the same as that of the arc tube. Therefore, in a headlight for an automobile or light source lamp for a projector in which a small light source size is required, the ceramic arc tube is hard to be adjusted to meet a light source size matched to the performance of lighting equipment. However, according to the present invention, the light source size is limited to a predetermined size, thereby providing a lamp matched to the performance of lighting equipment.
The light transmission part is reduced, for example, in the arc tube for an automobile, and a size of a light source can be adjusted to meet that of 2 mm ϕ × 4 mm which is the same as that of a filament of a halogen lamp. Further, for applying the arc tube to a light source for a projector, the light source size can be adjusted to a diameter of 1 mm or less.
A high-pressure discharge lamp according to the present invention may be applied to various kinds of lighting systems using pseudo point light sources, including a headlight for an automobile, an OHP (over head projector) and liquid crystal projector.
In the present invention, the central light-emitting portion means a portion interposed between the side end portions on the both sides in the arc tube. The side end portion means a portion which occupies both ends of the arc tube, that is, a portion between from the end of the tubular part to that of the central light-emitting portion.
In the present invention (see FIG. 2), when the entire inner surface area of the central light-emitting portion 2 and the side end portions 3 (the arc tube) is defined as L, an inner surface area P of each side end portion 2 is set to 5% of the entire inner surface area L. In short, when the inner surface areas of the respective side end portions are summed up, the area is 10% of the entire inner surface area of the arc tube. In the present invention, these inner surfaces of the side end portions are at least required to be roughened.
As semi-transparent and translucent ceramics forming the arc tube, the followings can be exemplified: polycrystalline Al₂O₃, AlN, AlON, and single crystal of Al₂O₃, YAG, Y₂O₃ having a surface roughness Ra of 1.0 µm or less.
The semi-transparency means the following light transmittance:

a total light transmittance of not lower than 85% and a linear light transmittance of not higher than 45%.

The intensity center means a part having the highest intensity in the light emitting portion. The intensity center is not required to be defined as a single point, and may be defined as a part elongating in the longitudinal cross-sectional direction of the arc tube.
The high-intensity discharge lamp means a mercury lamp which uses mercury as a light-emitting material, a high-pressure sodium lamp which uses sodium as a light-emitting material, and a metal halide lamp which uses a metal iodide as a light-emitting material.
Polycrystalline ceramics are molded by a molding method adapted to a desired shape, such as an extrusion molding method, a press molding method such as a dry bag molding method, a slip casting method, an injection molding method, and a gel cast molding method.
In the extrusion molding method, since its shape is formed by friction with a shape of a die, the surface roughness is smoothed and therefore, hard to be partially changed.
In the slip casting method, since an inner surface of a molded body is formed as a free surface, the surface roughness is prevented from being partially increased.
In the press molding method, since an outer surface of the molded body is formed by generally using a rubber die, the surface roughness is hard to be precisely controlled. However, when the surface roughness of a cored bar is increased in relation to the inner surface, the surface roughness of the light emitting portion and the electrode part can be intentionally changed.
In the injection molding method and the gel cast molding method, a shape of the inner surface is formed by the transfer using an inner mold, and a shape of the outer surface is formed by the transfer using an outer mold, respectively. At that time, the surface roughness of the mold is also transferred at the same time. Accordingly, the arc tube is formed such that the surface roughness is increased and irregularities are provided in the portion corresponding to the light shielding part of the mold and further the surface roughness is smoothed in the portion corresponding to the light transmission part of the mold. This processing enables the light shielding part and the light transmission part to be formed. Further, using the injection molding method and the gel cast molding method, the surface roughness can be changed and the wall thickness can be controlled independently in both of the inner surface and the outer surface.

EXAMPLES

(Manufacture of Comparative Embodiment 1, Embodiment 1, Embodiments 3 to 8)

Using a translucent alumina raw material powder, the molded bodies of the light-emitting containers for metal halide lamp in the comparative embodiment 1 illustrated in FIG. 1, the embodiment 1 illustrated in FIG. 2, and the embodiments 3 to 8 illustrated in FIGS. 5(a) to 5(c) and FIGS. 6(a) to 6(c) were prepared using the gel cast molding method.
The wall thicknesses of the portions corresponding to the capillary part and the light transmission part of the molded body were uniformly 1.3 mm. The wall thickness of a part in which the light shielding part was formed by processing of the surface roughness was 1.3 mm. The outer surface of the mold was finished to have a uniform surface roughness Ra of 0.1 µm.
As to the shape of the inner side, a pin for forming a capillary and a core of a wax component were integrated with each other in advance to produce an inner mold. The inner mold is then inserted into an outer mold. Slurry for the gel cast molding was poured into a gap formed between the outer and inner molds, and hardened. Then, the pin was taken out from the core and the wax core was heated and melted to be removed from the hardened slurry. The molded body was fired at 1300°C in air to remove binder, and pre-sintered. The alumina calcined body was further fired for 3 hours at 1800°C in a hydrogen atmosphere, and a hollow light-emitting container for a high-intensity discharge lamp made of translucent polycrystalline alumina ceramics was prepared.
A surface of the core forming mold was finished to have a uniform surface roughness Ra of 0.1 µm in the comparative embodiment 1, and the entire surface was finished to have a surface roughness Ra of 0.1 µm in the embodiments. Thereafter, in the embodiments 1, 3, and 4, a surface of the portion corresponding to the light shielding part each illustrated in FIGS. 2, 5(a) and 5(b) was roughly finished partly to have a surface roughness Ra of 5 µm by electric discharge machining. In the same manner, in the embodiments 5, 6, and 7, a pattern each illustrated in FIGS. 5(c), 6(a), and 6(b) was engraved to a depth of 150 µm by machining to thereby form the light shielding part 3. In the embodiment 8, the same pattern as in the embodiment 7 was performed by machining, and then the electric discharge machining was performed to form the light shielding part 3 in which the net pattern was formed and the surface roughness was increased.
The surface shape of the core forming mold was transferred to the core surface by using the above-described core forming mold, and the inner surface roughness of the molded body can be further controlled, thereby forming the light transmission part 2 and the light shielding part 3. The inner surface area of the light shielding part was from 10 to 20% of the entire inner surface area of the arc tube.
A crystal of the light-emitting container after the sintering had an average particle size of 25 µm, the capillary part and the light transmission part each had a uniform wall thickness of 0.9 mm, and the portion corresponding to the light transmission part had a surface roughness Ra of 0.15 µm and showed sufficient translucent properties. Meanwhile, the portion corresponding to the light shielding part formed by increasing the surface roughness had a surface roughness Ra of 3 µm, and showed translucent properties worse than that of the light transmission part. The concave part having the maximum depth of 0.1 mm was further formed in the light shielding part formed by irregularities.

(Comparative Embodiment 2, Embodiments 2 and 9)

The molded bodies of the light-emitting containers for metal halide lamp according to the comparative embodiment 2 illustrated in FIG. 3, embodiment 2 illustrated in FIG. 4 and embodiment 9 illustrated in FIG. 7 were prepared by the gel cast molding method using a translucent alumina raw material powder. In the comparative embodiment 2 and the embodiment 2, the molded bodies each had a uniform wall thickness of 1.3 mm. In the embodiment 9, as to the wall thickness of the molded body, the light shielding body had a wall thickness of 1.3 to 3 mm, and the light transmission part had a wall thickness of 1.3 mm.
The outer surface of the mold was finished to have a uniform surface roughness Ra of 0.1 µm, and then the portion corresponding to each light shielding part was roughened by the electric discharge machining. The surface roughness Ra was 5 µm. As to the shape of the inner side, a pin for forming a capillary and a core of a wax component were integrated with each other in advance to produce an inner mold. The inner mold is then inserted into an outer mold. Slurry for the gel cast molding was poured into a gap formed between the outer and inner molds, and hardened. Then, the pin was taken out from the core and the wax core was heated and melted to be removed from the hardened slurry. The molded body was fired at 1300°C in air to remove binder, and pre-sintered. The alumina calcined body was further fired for 3 hours at 1800°C in a hydrogen atmosphere, and the hollow light-emitting container made of translucent polycrystalline alumina ceramics was prepared.
The surface of the core forming mold according to the comparative embodiment 2 was finished to have a uniform surface roughness Ra of 0.1 µm in the same manner as in the comparative embodiment 1. In the embodiments 3 and 9, the entire surface was finished to have a surface roughness Ra of 0.1 µm, and then surfaces of the portions corresponding to the light shielding parts illustrated in FIGS. 4 and 7 were roughly finished partly to have a surface roughness Ra of 5 µm using the electric discharge machining.
Since the above-described outer and inner molds are used in combination thereof, the inner and outer surface roughnesses and the wall thickness of the molded body can be controlled, thereby forming the light transmission part and the light shielding part.
In the embodiments 2 and 3, the inner surface area of the light shielding part was 30% of the inner surface area of the arc tube.
A crystal of the light-emitting container after the sintering had an average particle size of 25 µm. In the comparative embodiment 2 and the embodiment 2, the capillary part, the light transmission part and the light shielding part each had a uniform wall thickness of 0.9 mm, and had the maximum wall thickness of 2.1 mm in the embodiment 9. The portion corresponding to the light transmission part had a surface roughness Ra of 0.15 µm, and showed sufficient translucent properties. Meanwhile, the portion corresponding to the light shielding part had a outer surface roughness Ra of 3 µm.

(Manufacture of Comparative Embodiment 3)

The arc tube having a pattern as illustrated in FIG. 3 was prepared in the same manner as in the comparative embodiment 2. However, it is noted that the roughened surface was not formed on the outer surface of the side end portion 3. Instead of forming the roughened surface, a light shielding film with a thickness of 5 µm made of a cermet of tungsten-alumina was formed on the outer surface 3b of the side end portion 3.

(Embodiment 10)

The molded body of the light-emitting container for a high-pressure sodium lamp illustrated in FIG. 8 was prepared by the press molding method using the translucent alumina raw material powder.
A cylindrical rubber die was prepared in the outer side, then, there is fixed a cored bar called a mandrel, in which the entire surface was finished to have a surface roughness Ra of 0.1 µm and the surface of the portion corresponding to the light shielding part 3 illustrated in FIG. 8 was roughly finished partly to have a surface roughness Ra of 5 µm by a sand blast method. A gap formed between the rubber die and the mandrel was further filled with the translucent alumina raw material powder, and a hydrostatic pressure of 1 ton/cm² was applied from the outside of the rubber die for the molding. The outer side of the molded body was lathed such that the molded body had a uniform wall thickness of 1.1 mm after the molding.
Since the above-described mandrel cored bar is used, the surface shape of the mandrel cored bar can be transferred to an inner surface of the molded body of the light-emitting container to control the inner surface roughness of the molded body, thereby forming the light transmission part and the light shielding part. A surface area of the light shielding part was in the range of 10% of the entire surface area obtained by summing up two surface areas of the light transmission part and the light shielding part.
The molded body was further combined with a plug which had been previously molded by the press molding method, and sintered at 1300°C in air to remove the binder and pre-sintered. The alumina calcined body was further fired for 3 hours at 1800°C in a hydrogen atmosphere, and a hollow light-emitting container 5 for a high-intensity discharge lamp made of translucent polycrystalline alumina ceramics was prepared.
A crystal of the light-emitting container after the sintering had an average particle size of 25 µm, the light transmission part and the light shielding part each had a uniform wall thickness of 0.8 mm, and the portion corresponding to the light transmission part had an inner surface roughness Ra of 0.2 µm, and showed sufficient translucent properties. Meanwhile, the portion corresponding to the light shielding part formed by increasing the surface roughness had a surface roughness Ra of 3 µm, and showed translucent properties worse than that of the light transmission part. The outer surfaces of the light transmission part and the light shielding part of the light-emitting container each had a uniform surface roughness Ra of 1 µm.

(Embodiments 11 and 12)

The molded bodies of the light-emitting container for a metal halide lamp according to the embodiment 11 illustrated in FIG. 10 and the embodiment 12 illustrated in FIG. 11 were prepared by the gel cast molding method using the translucent alumina raw material powder. In the embodiments 11 and 12, the molded bodies each had a uniform wall thickness of 1.3 mm.
The outer surface of the mold was finished to have a uniform surface roughness Ra of 0.1 µm, and then a surface of the portion corresponding to the light shielding part of FIGS. 10 and 11 was roughened by the electric discharge machining. The surface roughness Ra was 5 µm.
As to the shape of the inner side, a pin for forming a capillary and a core of a wax component were integrated with each other in advance to produce an inner mold. The inner mode is than inserted into an outer mold. Slurry for the gel cast molding was poured into a gap formed between the outer mold and the core, and hardened. Then, the pin was taken out from the core and the wax core was heated and melted to be removed from the hardened slurry. The molded body was fired at 1300°C in air to remove binder, and pre-sintered. The alumina calcined body was further fired for 3 hours at 1800°C in a hydrogen atmosphere, and a hollow light-emitting container made of translucent polycrystalline alumina ceramics was prepared.
The entire surface of the core forming mold according to the embodiments 11 and 12 was finished to have a surface roughness Ra of 0.1 µm, and then the surface of the light shielding part illustrated in FIGS. 10 and 11 was roughly finished partly to have a surface roughness Ra of 5 µm using the electric discharge machining.
Since the above-described outer and inner molds were used in combination thereof, the inner and outer surface roughnesses and the wall thickness of the molded body could be controlled, thereby vertically forming the annular light transmission part with respect to the discharge direction in the central portion of the light-emitting container. In the embodiments 11 and 12, the surface area of the light transmission part was 25%, and the surface area of the light shielding part was 75%.
In the embodiment 12, the wax core was removed and then the light transmission part was ground to a wall thickness of 1 mm from the outside. A crystal of the light-emitting container after the sintering had an average particle size of 25 µm. In the embodiment 11, the capillary part, the light transmission part and the light shielding part each had a uniform wall thickness of 0.9 mm. The polishing was performed such that the light transmission part according to the embodiment 12 had a wall thickness of 0.7 mm and a surface roughness Ra of 0.01 µm. The light shielding part and the capillary part each had a wall thickness of 0.9 mm.

(Embodiments 13 and 14)

The molded bodies of the light-emitting container for a high-intensity discharge lamp used for the metal halide lamp according to the embodiment 13 illustrated in FIG. 12 and an embodiment 14 illustrated in FIG. 13 were prepared by the gel cast molding method using the translucent alumina raw material powder. In the embodiment 13, the molded body had a uniform wall thickness of 1.3 mm. In the embodiment 14, the portion corresponding to the light transmission part had a wall thickness of 0.5 to 0.6 mm, the portion corresponding to the light shielding part had a wall thickness of 0.6 to 3 mm, and the capillary part had a wall thickness of 1.3 mm. The outer surface of the mold was finished to have a uniform surface roughness Ra of 0.1 µm, and then surfaces of the portions corresponding to the light shielding parts of FIGS. 12 and 13 were roughened by the electric discharge machining. The surface roughness Ra was 5 µm.
As to the shape of the inner side, a pin for forming a capillary and a core of a wax component were integrated with each other in advance to produce an inner mold. The inner mode is than inserted into an outer mold. Slurry for the gel cast molding was poured into a gap formed between the outer mold and the core, and hardened. Then, the pin was taken out from the core and the wax core was heated and melted to be removed from the hardened slurry. The molded body was fired at 1300°C in air to remove binder, and pre-sintered. The alumina calcined body was further fired for 3 hours at 1800°C in a hydrogen atmosphere, and a hollow light-emitting container 5 for a high-intensity discharge lamp made of translucent polycrystalline alumina ceramics was prepared.
The entire surface of the core forming mold according to the embodiments 13 and 14 was finished to have a surface roughness Ra of 0.1 µm, and then surfaces of the portions corresponding to the light shielding parts illustrated in FIGS. 12 and 13 were roughly finished partly to have a surface roughness Ra of 5 µm using the electric discharge machining.
Since the above-described outer and inner molds were used in combination thereof, the inner and outer surface roughnesses and the wall thickness of the molded body could be controlled, thereby forming the strip-shaped light transmission part in parallel with the discharge direction of the light-emitting container. In the embodiments 13 and 14, the inner surface area of the light shielding part is 90% of the entire inner surface area of the arc tube.
A crystal of the light-emitting container after the sintering had an average particle size of 25 µm. In the embodiment 13, the capillary part, the light transmission part and the light shielding part had a uniform wall thickness of 0.9 mm. In the embodiment 14, the light transmission part had a wall thickness of 0.3 to 0.4 mm, the light shielding part had a wall thickness of 0.4 to 2.1 mm, and the capillary part had the wall thickness of 0.9 mm. As described above, when the surface roughness and a wall thickness were controlled, the strip-shaped light transmission part formed on the light-emitting container showed translucent properties sufficiently larger than those of the light shielding part.

(Embodiments 15 and 16)

The molded bodies of the light-emitting containers for high-intensity discharge lamp used for the metal halide lamp according to the embodiment 15 illustrated in FIG. 14 and embodiment 16 illustrated in FIG. 15 were prepared by the gel cast molding method using the translucent alumina raw material powder. In the embodiment 15, the molded body had a uniform wall thickness of 1.3 mm. In the embodiment 16, the portion corresponding to the light transmission part had a wall thickness of 1.3 mm, the portion corresponding to the light shielding part had a wall thickness of 1.3 to 2.1 mm, and the portion corresponding to the capillary part had a wall thickness of 1.3 mm. The outer surface of the mold was finished to have a uniform surface roughness Ra of 0.1 µm, and then surfaces of the portions corresponding to the light shielding parts of FIGS. 14 and 15 were roughened by the electric discharge machining. The surface roughness Ra was 5 µm.
As to the shape of the inner side, a pin for forming a capillary and a core of a wax component were integrated with each other in advance to produce an inner mold. The inner mode is than inserted into an outer mold. Slurry for the gel cast molding was poured into a gap formed between the outer mold and the core, and hardened. Then, the pin was taken out from the core and the wax core was heated and melted to be removed from the hardened slurry. The molded body was fired at 1300°C in air to remove binder, and pre-sintered. The alumina calcined body was further fired for 3 hours at 1800°C in a hydrogen atmosphere, and a hollow light-emitting container 5 for a high-intensity discharge lamp made of translucent polycrystalline alumina ceramics was prepared.
The entire surface of the core forming mold according to the embodiments 15 and 16 was finished to have a surface roughness Ra of 0.1 µm, and then surfaces of the portions corresponding to the light shielding parts illustrated in FIGS. 14 and 15 were roughly finished partly to have a surface roughness Ra of 5 µm using the electric discharge machining.
Since the above-described outer and inner molds were used in combination thereof, the inner and outer surface roughnesses and the wall thickness of the molded body could be controlled, thereby forming the dotted light transmission parts on the light-emitting container. In the embodiment 15, the inner surface area of the light shielding part is 70% of the entire inner surface area of the arc tube. In the embodiment 16, the inner surface area of the light shielding part is 90% of the entire inner surface area of the arc tube.
A crystal of the light-emitting container after the sintering had an average particle size of 25 µm. In the embodiment 15, the capillary part, the light transmission part, and the light shielding part each had a uniform wall thickness of 0.9 mm. In the embodiment 16, the light transmission part had a wall thickness of 0.9 mm, the light shielding part had a wall thickness of 0.9 to 1.5 mm, and the capillary part had a wall thickness of 0.9 mm. As described above, since the surface roughness and the wall thickness were controlled, the strip-shaped light transmission part formed on the light-emitting container showed translucent properties sufficiently larger than those of the light shielding part.

(Assembly of Arc Tube)

A metal component in which an electrode part including a coil made of tungsten and an introducing conductor made of niobium were joined via molybdenum was inserted into one capillary part in each of the above-described light-emitting containers. A position of a joined portion between the introducing conductor and the molybdenum was temporarily fixed using a jig such that the introducing conductor was located outside the capillary part near the end of the capillary part. Further, annular frit materials for sealing were inserted into the introducing conductor and put on the end of the capillary part, and then that portion was heated and melted up to a predetermined temperature to be hermetically sealed.
Within a glove box in an argon atmosphere, mercury and an appropriate amount of iodide such as Na, Tl, or Dy as light emitting metal were further put in the composite light-emitting container having hermetically sealed therein the one end from another capillary part which is not sealed. In the same manner as in the above-described case, a metal component in which an electrode part including a coil made of tungsten and an introducing conductor made of niobium were joined via molybdenum was inserted into one capillary part in each of the above-described light-emitting containers. A position of a joined portion between the introducing conductor and the molybdenum was temporarily fixed using a jig such that the introducing conductor was located outside the capillary part near the end of the capillary part. Further, annular frit materials for sealing were inserted into the introducing conductor and put on the end of the capillary part, and then that portion was heated and melted up to a predetermined temperature to be hermetically sealed, thereby preparing a high-pressure discharge lamp.
A lead wire for supplying current was welded to the introducing conductor of this light-emitting container for a high-intensity discharge lamp, and inserted into a glass outer bulb to prepare a lamp. Then, since a current was flown using a predetermined ballast power supply, the lamp could be lighted as a metal halide high-pressure discharge lamp.

(Test Method)

The following tests were performed with respect to the obtained discharge lamps. The test method and the results are shown.
A lead wire for supplying current is welded to an electrode holding member of the discharge lamp, and inserted into a glass outer bulb to prepare a lamp. Then, when a current is flown using a predetermined ballast power supply, the lamp is lighted as the metal halide high-pressure discharge lamp.

(Initial Light-emitting Efficiency)

An initial light-emitting efficiency was measured. The light-emitting efficiency according to the comparative embodiment 1 was set to 100, and the measured light-emitting efficiency was shown in the table using relative values.

(Color Stability)

Color stability of the lamp was evaluated by evaluating time dependence of color rendering properties. A color rendering index Ra under an initial condition according to the comparative embodiment 1 was set to 100, and the color rendering index after a lighting test of 400 hours was shown in the table.

(Lighting On and Off Durability)

Lighting on and off was repeatedly performed and change in the light-emitting efficiency of the lamp was confirmed, whereby durability of the lamp was evaluated. An initial lamp light-emitting efficiency according to the comparative embodiment 1 was set to 100, and relative values of the lamp light-emitting efficiency after the lighting on and off test of 300 cycles were shown.
A light-emitting container 5A for a high-intensity discharge lamp has an arc tube comprising a translucent polycrystalline ceramics. The arc tube has a central light-emitting portion 2 and side end portions 3 provided on both sides of the central light-emitting portion 2, respectively, and tubular portions 1 protruding from both of the side end portions, respectively. The inner surfaces of the side end portions are roughened surfaces.

Table 1

		Comparative Example 1	Example 1	Comparative Example 2	Comparative Example 3
	Figure	1	2	3	Fig. 3 light-shielding film
	Molding method	Gel Casting	Gel casting	Gel Casting	Gel Casting
Light Shielding Part	Sintered body: Outer surface roughness Ra (µm)	0.1	0.1	3	0.1
	Sintered body: Inner surface roughness Ra (µm)	0.1	3	0.1	0.1
	Sintered body: Surface Concave-convex (µm)	-	-	-	-
	Concave-convex pattern	-	-	-	-
	Thickness (mm)	0.9	0.9	0.9	0.9
	Area (%)	0	20	20	20
Light Transmitting Part	Sintered body: Outer surface roughness Ra (µm)	0.15	0.15	0.15	0.15
	Sintered body: Inner surface roughness Ra (µm)	0.15	0.15	0.15	0.15
	Thickness (mm)	0.9	0.9	0.9	0.9
	Area (%)	100	80	80	80
	Number	-	One	One	One
Thickness of capillary portion(mm)		0.9	0.9	0.9	0.9
Initial light-emitting Efficiency (Relative value)		100	110	95	95
Color rendering property after 400 hours (Relative value)		100	110	95	90
Light emitting efficiency after 300 cycles of ons and offs (Relative value)		100	110	95	85

Table 2

		Example 2	Example 3	Example 4	Example 5	Example 6
	Figure	4	5(a)	5(b)	5(c)	6(a)
	Molding method	Gel casting	Gel casting	Gel Casting	Gel Casting	Gel Casting
Light Shielding Part	Sintered body: Outer surface roughness Ra (µm)	3	0.1	0.1	0.1	0.1
	Sintered body: Inner surface roughness Ra (µm)	3	3	3	0.1	0.1
	Sintered body: Surface Convex-concave (µm)	-	-	-	150	150
	Concave-convex pattern	-	-	-	Dimple	Stripe
	Thickness (mm)	0.9	0.9	0.9	0.9	0.9
	Area (%)	25	15	15	10	15
Light Transmitting Part	Sintered body: Outer surface roughness Ra (µm)	0.15	0.15	0.15	0.15	0.15
	Sintered body: Inner surface roughness Ra (µm)	0.15	0.15	0.15	0.15	0.15
	Thickness (mm)	0.9	0.9	0.9	0.9	0.9
	Area (%)	75	85	85	90	85
	Number	one	one	one	one	one
Thickness of capillary portion(mm)		0.9	0.9	0.9	0.9	0.9
Initial light-emitting Efficiency (Relative value)		105	112	112	115	112
Color rendering property after 400 hours (Relative value)		105	110	110	110	110
Light emitting efficiency after 300 cycles of ons and offs (Relative value)		105	112	112	115	112

Table 3

		Example 7	Example 8	Example 9	Example 10
	Figure	6(b)	6(c)	7	8
	Molding method	Gel casting	Gel Casting	Gel Casting	Press
Light Shielding Part	Sintered body: Outer surface roughness Ra (µm)	0.1	0.1	3
	Sintered body: Inner surface roughness Ra (µm)	0.1	3	3	3
	Sintered body: Concave-convex (µm)	150	150	-	-
	Concave-convex pattern	Net	Net	-	-
	Thickness (mm)	0.9	0.9	0.9~2.1	0.9
	Area (%)	20	20	30	0.8
Light Transmitting Part	Sintered body: Outer surface roughness Ra (µm)	0.15	0.15	0.15	1
	Sintered body: Inner surface roughness Ra (µm)	0.15	0.15	0.15	0.2
	Thickness (mm)	0.9	0.9	0.9	0.8
	Area (%)	80	80	70	90
	Number	one	one	one	one
Initial light-emitting Efficiency (Relative value)		110	110	108	130
Color rendering property after 400 hours (Relative value)		110	110	110	25
Light emitting efficiency after 300 cycles of ons and offs (Relative value)		110	110	108	130

Table 4

		Example 11	Example 12	Example 13
	Figure	10	11	12
	Molding method	Gel casting	Gel casting	Gel casting
	Average grain size (µm)	25	25	25
Light Shielding Part	Sintered body: Outer surface roughness Ra (µm)	3	3	3
	Sintered body: Inner surface roughness Ra (µm)	3	3	3
	Sintered body: surface convex/concave (µm)	-	-	-
	Convex or concave pattern	-	-	-
	Thickness (mm)	0.9	0.9	0.9
	Shielding film material	-	-	-
	Shielding film thickness (µm)	-	-	-
	Area (%)	75	75	90
Light Transmitting Part	Sintered body: Outer surface roughness Ra (µm)	0.15	0.01	0.15
	Sintered body: Inner Surface roughness Ra (µm)	0.15	0.15	0.15
	Thickness (mm)	0.5~0.9	0.7	0.9
	Area (%)	25	25	10
	Number	One	One	Two
Initial light-emitting Efficiency (Relative value)		75	75	60
Color rendering property after 400 hours (Relative value)		110	110	110
Light emitting efficiency after 300 cycles of ons and offs (Relative value)		75	75	60

Table 5

		Example 14	Example 15	Example 16
	Figure	13	14	15
	Molding method	Gel casting	Gel casting	Gel casting
	Average grain size (µm)	25	25	25
Light Shielding Part	Outer mold: Surface roughness Ra (µm)	5	5	5
	Sintered body: Inner surface roughness Ra (µm)	3	3	3
	Sintered body: Inner surface roughness Ra (µm)	3	3	3
	Sintered body: surface convex/concave (µm)	-	-	-
	Convex or concave pattern	-	-	-
	Thickness (mm)	0.4 ~2.1	0.9	0.9 to 1.5
	Shielding film material	-	-	-
	Shielding film thickness (µm)	-	-	-
	Area (%)	90	70	90
Light Transmitting Part	Sintered body: Outer surface roughness Ra (µm)	0.15	0.15	0.15
	Sintered body: Inner surface roughness Ra (µm)	0.15	0.15	0.15
	Thickness (mm)	0.3~0.4	0.9	0.9
	Area (%)	10	30	10
	Number	Two	Twenty four	Eight
Initial light-emitting Efficiency (Relative value)		60	80	60
Color rendering property after 400 hours (Relative value)		110	110	110
Light emitting efficiency after 300 cycles of ons and offs (Relative value)		60	80	60

Claims

A light-emitting container for a high-intensity discharge lamp, the container comprising:
an arc tube comprising a translucent polycrystalline ceramics, said arc tube comprising a central light-emitting portion and side end portions provided on both sides of the central light-emitting portion, respectively; and

tubular portions protruding from both of the side end portions, respectively,
wherein said side end portions comprise inner surfaces comprising roughened surfaces, respectively.
The light-emitting container of claim 1, wherein
the inner surface of the side end portion has a center line average surface roughness Ra of 2.0 µm or more.
The light-emitting container of claim 1 or 2, wherein
the side end portion comprises an outer surface having a center line average surface roughness Ra of 2.0 µm or more.
The light-emitting container of any one of claims 1 to 3, wherein
the central light-emitting portion comprises an inner surface and an outer surface each having a center line average surface roughness Ra of 1.0 µm or less.
The light-emitting container of any one of claims 1 to 3, wherein
the central light-emitting portion comprises a light transmission part and a light shielding part having a linear light transmittance lower than that of the light transmission part.
The light-emitting container of claim 5, wherein
the central light-emitting portion has a plurality of the light transmission parts; and
each light transmission part is formed as a strip and formed in parallel with a tube axis of the light-emitting container.
The light-emitting container of claim 5, wherein
the central light-emitting portion has a plurality of the light transmission parts; and
each light transmission part is formed like a dot.
A high-intensity discharge lamp comprising:
the light-emitting container of any one of claims 1 to 7;

electrodes provided in an internal space of the arc tube; and

electrode holding members inserted into the respective tubular portions and holding the electrodes, respectively.
A light-emitting container for a high-intensity discharge lamp, the container comprising:
an arc tube comprising a translucent polycrystalline ceramics, said arc tube comprising a central light-emitting portion and side end portions provided on both sides of the central light-emitting portion, respectively; and

tubular portions protruding from the respective side end portions, wherein said side end portion comprises an inner surface comprising a concave or convex pattern.
The light-emitting container of claim 9, wherein
the inner surface of the side end portion has a center line average surface roughness Ra of 2.0 µm or more.
The light-emitting container of claim 9 or 10, wherein
the side end portion comprises an outer surface comprising a concave or convex pattern.
The light-emitting container of any one of claims 9 to 11, wherein
the central light-emitting portion comprises a light transmission part and a light shielding part having a linear light transmittance lower than that of the light transmission part.
The light-emitting container of claim 12, wherein
the central light-emitting portion has a plurality of the light transmission parts; and
each light transmission part is formed as a strip and in parallel with a tube axis of the light-emitting container, or wherein
the central light-emitting portion has a plurality of the light transmission parts; and
each light transmission part is formed like a dot.
A high-intensity discharge lamp comprising:
the light-emitting container of any one of claims 9 to 13;

electrodes provided in an internal space of the arc tube; and

electrode holding members inserted into the respective tubular portions and holding the electrodes, respectively.
The high-intensity discharge lamp of claim 8 or 14, comprising a high-pressure sodium lamp, or a metal halide lamp.