JPH04370644A - Arc tube for high luminance discharge lamp and its manufacture - Google Patents

Abstract

PURPOSE:To shorten the starting time of a thick arc tube by providing an outer surface layer which consists of a translucent aluminum nitride including a specific oxide, and an inner surface thin layer which consists of an aluminum oxide. CONSTITUTION:An aluminum oxide thin layer 1f is formed on the inner surface of an arc tube 1F which furnishes electrode holding holes 1a and 1b at both ends, and a sealing material sump 1c, and consists of an outer surface layer of a translucent nitride including 0.5 to 8wt% of one or more oxides selected from yttrium oxide, calcium oxide, and magnesium oxide. And, even though the thickness of the arc tube 1F is increased to secure the mechanical strength under a high temperature and a high pressure condition, in such a constitution, the transmission of the heat generated in an arc discharge time is increased owing to the high thermal conductivity of the aluminum nitride, the temperature rise of the luminous tube 1F itself by the heat of the arc discharge is expedited, and the starting time of the luminous tube 1F can be shortened.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-intensity discharge lamp arc tube used in a high-intensity discharge lamp and a method for manufacturing the same.

0002

[Prior Art] This type of arc tube for high-intensity discharge lamps (hereinafter referred to as
Arc tubes (simply referred to as arc tubes) are roughly divided into arc tubes made from quartz glass and arc tubes made from translucent ceramic, and are generally used outside of high-pressure discharge lamps (hereinafter simply referred to as lamps) such as metal halide lamps. It is used by being built into the pipe. For light-transmitting ceramic arc tubes, Mg
Arc tubes made of translucent aluminum oxide, in which a small amount of sintering aids such as O, La2O3, Y2O3, etc. are added to aluminum oxide and sintered to uniformly coarsen crystal grains, are commonly used. Note that these sintering aids are added for the purpose of suppressing abnormal grain growth and developing translucency.

A conventional arc tube made of translucent aluminum oxide has the following physical properties. Linear transmittance for wavelength 380-760nm: 40-6
0% (thickness: 0.5 mm) Mechanical strength (JIS R1601) Bending strength St (room temperature) = 20 to 40 kg/cm2 (900°C) = 6 to 20 kg/cm2 Weibull coefficient (room temperature) = 1.9 to 3 .1 (900°C) = 1.2 to 1.6 Thermal conductivity (thermal constant measuring device TC-3000 manufactured by Shinku Riko)
by. (Same below) (Room temperature) = 52W/m・K (900℃) = 9W/m・K

[0004] In general, an arc tube is filled with a rare gas for starting and a metal component (solid) for discharge that emits light in various colors at an internal pressure of several tens of Torr, and during discharge, the tube wall temperature reaches 900°C.
℃, and as the temperature rises, the internal pressure also increases. Therefore, in order to prevent the arc tube from breaking even under high temperature and high internal pressure, the wall thickness of the arc tube (approximately 0.6
mm) is shown.

[0005]

However, as the thickness increases, the heat capacity of the arc tube itself also increases, so it takes time for the temperature of the entire light emitting section to rise due to the heat of the arc discharge formed between the main electrodes. For this reason, the time required for the temperature of the arc tube to rise to a predetermined temperature in a steady state at which the discharge metal component within the tube evaporates and reaches a saturated vapor pressure is increased. As a result, the starting time until the light emission becomes stable becomes longer, and it takes about 30 seconds or more to reach the above-mentioned steady state.

The present invention has been made to solve the above-mentioned problems, and aims to provide an arc tube with a short starting time even if the arc tube is thick to ensure mechanical strength under high temperature and high pressure. purpose.

[0007]

[Means for Solving the Problems] The means adopted by the present invention to achieve the above object is an arc tube for a high-intensity discharge lamp, which is made of one or more types selected from yttrium oxide, calcium oxide, and magnesium oxide. 0.5-8w of oxide
an outer layer made of translucent aluminum nitride containing t%;
Its gist is that it has a thin inner layer made of aluminum oxide.

[0008]The procedure adopted by the present invention in manufacturing the arc tube for a high-intensity discharge lamp made of such translucent aluminum nitride is to use one or more oxides selected from yttrium oxide, calcium oxide, and magnesium oxide. A process of adding an organic binder to a mixed fine powder containing 0.5 to 8 wt% of aluminum nitride and the balance of aluminum nitride, and forming a tubular molded body of a desired shape by a predetermined molding method; A step of sintering at a temperature of 1750 to 1950°C in an atmosphere, and a treatment temperature of 1
700-1900℃ and processing pressure 1000-2000a
tm condition, and the tubular sintered body after the hot isostatic pressing is heated to
The gist thereof is that it includes a step of heat treatment at a temperature of 1300°C.

[0009] Here, the reason why the sintering was carried out in the temperature range of 1750 to 1950°C was because the density after sintering was set to be 95% or more of the theoretical density so that hot isostatic pressing in the post-process was applied. This is to avoid the formation of coarse crystals in the sintered body. In other words, the above sintering was performed at 17
If the temperature is less than 50°C, the density after sintering will be less than 95% of the theoretical density, and hot isostatic pressing will not be applied, resulting in 195
This is because at temperatures above 0°C, the frequency of formation of coarse crystals in the sintered body increases, which is disadvantageous in terms of strength.

Furthermore, the reason why hot isostatic pressing is carried out in the above temperature and pressure ranges is to obtain practical light transmittance (in-line transmittance for wavelengths of 380 to 760 nm: 40 to 60 nm).
%), improve mechanical strength, and avoid breakage during hot isostatic pressing. In other words, hot isostatic pressing is carried out at temperatures below 1700°C or 100°C.
If the temperature is less than 0 atm, translucency will be developed but only low translucency will be obtained; conversely, if the temperature exceeds 1,900°C, abnormal grain growth will be promoted, leading to a decrease in mechanical strength and translucency. This is because, if it exceeds the limit, even if the pores, scratches, etc. present in the sintered body are extremely minute, stress concentration will occur at the location where the scratches, etc. are present, and cracks may occur.

[0011] Also, heat treatment in the air at a temperature range of 1000 to 1300°C is necessary to control the thickness of the aluminum oxide thin layer when nitrogen and oxygen are substituted to form aluminum oxide. This is to make the formation time of the thin layer industrially appropriate, and to avoid oxygen from penetrating into the bulk. In other words, if the temperature is below 1000°C, nitrogen and oxygen will replace each other to form aluminum oxide, and it will take a long time to obtain a thin layer of aluminum oxide with the desired thickness. 2AlN+O2 may occur due to rapid substitution of oxygen and the formation of a thin layer of aluminum oxide with a thickness greater than the desired thickness, or oxygen may penetrate into the bulk of 2AlN+O2.
→2 This is because a reaction of AlON occurs and AlON is produced which inhibits the improvement of heat conduction.

0012

[Function] The arc tube for high-intensity discharge lamps of the present invention having the above structure is composed of an outer layer of aluminum nitride and a thin inner layer of aluminum oxide, so it is the same as the above-mentioned conventional arc tube for high-intensity discharge lamps. Even with a thick wall, the diffusion transfer of heat generated during arc discharge is enhanced due to the high thermal conductivity of aluminum nitride, and the temperature rise of the arc tube itself due to the heat of arc discharge is promoted.

Furthermore, what is exposed to the highly reactive metal gas that fills the arc tube and the high temperature and high pressure is a thin layer of aluminum oxide in which there is no impregnation of metal into the crystal grains due to free metal ions. Therefore, this suppresses deterioration on the inner surface of the arc tube.

[0014] Furthermore, the method for manufacturing a luminous tube for a high-intensity discharge lamp made of translucent aluminum nitride includes, first, a method of manufacturing an arc tube made of aluminum nitride and one or more oxides selected from yttrium oxide, calcium oxide, and magnesium oxide; Add organic binder to mixed fine powder, injection molding, extrusion molding,
A tubular molded body having a desired shape is formed by a predetermined molding method such as press molding. Then, this tubular molded body is sintered at a temperature of 1750 to 1950° C. in a nitrogen atmosphere to obtain a tubular sintered body of aluminum nitride containing the above-mentioned selected oxide. At this time, the added oxide promotes sintering and suppresses abnormal grain growth, and even by sintering at a relatively low temperature, the crystal grain size becomes minute and dense.

[0015] Thereafter, the sintered tubular compact is subjected to hot isostatic pressing in a nitrogen atmosphere at a processing temperature of 1,700 to 1,900°C and a processing pressure of 1,000 to 2,000 atm to create isotropic pressure. The tubular sintered body is then heat-treated to develop translucency.

Furthermore, by heat-treating the tubular sintered body that has undergone hot isostatic pressing at a temperature of 1000 to 1300°C in the atmosphere, nitrogen and oxygen are replaced on the surface (including the inner surface) of the tubular compact. A thin layer of aluminum oxide is formed.

[0017]

[Embodiment] Next, a preferred embodiment of the arc tube according to the present invention will be explained based on the drawings.

First, the arc tube 1F of the first embodiment to be manufactured will be explained, and then its manufacturing process will be explained. As shown in FIG. 1, the arc tube 1F has a large diameter electrode holding hole 1a and a small diameter electrode holding hole 1b (approximately 1
It is a cylindrical aluminum nitride arc tube equipped with a sealing material reservoir 1c (within a diameter of about 10 μm) on its inner surface.
A thin aluminum oxide layer 1f having the following thickness is provided. Next, the manufacturing process of this arc tube 1F will be explained using the process diagram of FIG. 2.

First, aluminum nitride (purity: 99.5
mol% or more) fine powder (particle size 1 μm or less) and yttrium oxide fine powder (particle size 1 μm or less) are weighed and mixed so that aluminum nitride: 96 wt% and yttrium oxide: 4 wt%. An organic binder mainly composed of acrylic thermoplastic resin is added to the mixed fine powder, and this is wet-mixed using an organic solvent (benzene) in a plastic (nylon) ball mill for about 24 hours. Wet the fine alumina powder thoroughly. Furthermore, the solvent is removed by distillation drying, and the desired viscosity (5
0,000 to 100,000 cps) is kneaded and prepared (Step 1).

The organic binder is a mixture of an acrylic thermoplastic resin, paraffin wax, and atactic polypropylene. The amount of these organic binders added to 100g of the above mixed fine powder is as follows:
The total amount is 25g.

[0021] Each component in the organic binder is blended as follows, and the sum of each component is the total amount (25 g) of the organic binder. Acrylic thermoplastic resin 20-23g (preferably 21.5g) Paraffin wax 3g or less (preferably 2.0g) Atactic polypropylene 2g or less (preferably 1.5g)

[0022] In the distillation drying during the preparation of the compound, it is distilled and dried at 130°C for 24 hours, and then heated and kneaded (130°C) using a roll mill to obtain a compound with a desired viscosity.

[0023] Thereafter, a molded body is obtained by injection molding using the mold apparatus 100 shown in FIG. 3 (step 2). Note that the molded body and the injection molding process (step 2) will be explained following the explanation of the configuration of the mold apparatus 100.

As shown in FIG. 3, this mold apparatus 100 includes an upper mold 101 fixed to a frame (not shown), and a lower mold 105 installed on a base 103 that can be raised and lowered and raised and lowered together with the base 103. Equipped with The upper surface of the upper mold 101 has a recess 10 into which a nozzle 107 of an injection machine (not shown) fits.
A sprue 111 is formed downward from the bottom of the recess 109 and communicates with the injection hole of the nozzle 107 . Further, a cavity 112 is formed in this upper mold 101 in parallel to the sprue 111.

As shown in detail in FIG. 4, which shows an enlarged view of the sprue 111 and the cavity 112, the upper mold 101
A runner 113 that communicates the sprue 111 and the cavity 112, a ring gate 115, and a film gate 117 are formed at the joint of the lower die 105 and the lower die 105. Therefore, the compound injected into the sprue 111 from the nozzle 107 passes through the runner 113 and is transferred to the ring gate 11.
5. It flows into the film gate 117 and then reaches the cavity 112.

As shown in FIG. 4, the molding pin 119 that enters the cavity 112 and determines the shape of the injection molded product is
A molding part 120 is provided that is located inside the cavity 112 during mold clamping, which will be described later. Furthermore, the tip of the molding part 120 is provided with a small diameter part 123 that enters the center hole 121 of the upper die 101 and forms the electrode holding hole 1b (see FIG. The large diameter portion 125 is inserted into the lower mold 105, and the male screw 127 is continuous with the large diameter portion 125. By screwing this male screw 127 into a threaded hole 129 formed in the lower mold 105, the molding pin 119 is integrated with the lower mold 105, and is inserted into the cavity 112 through the stripper plate 130.
facing the center of Note that the diameter of the center hole 121 is set to be very slightly larger than the small diameter portion 123 at the tip of the molding pin 119, so that air is removed from the cavity during injection molding. Furthermore, a conical projection 121a that projects into the cavity is formed at the end of the center hole 121 on the side of the cavity 112. This protrusion 121a
As a result, a sealant reservoir 1c is formed during injection molding, which will be described later.

A tapered hole 131 that widens downward is formed in the lower central surface of the stripper plate 130, and a guide having a tapered surface that fits the tapered hole 131 is provided in the large diameter portion 125 of the forming pin 119. Member 133
is fitted externally. Therefore, the molding pin 119 enters the cavity 112 along its central axis while being centered during mold clamping, and the molding part 120 is located at the center of the cavity 112.

The gap between the molding part 120 and the cavity 112 is an injection space SK into which the compound is injected, as will be described later, and the volume shrinkage when the molded body is sintered, the desired wall thickness of the sintered body, etc. It is determined in advance through experiments, etc., taking into consideration the following. In this example, this gap is adjusted so that the thickness of the molded body before sintering is approximately 0.79 mm. Note that the inner diameter of the molded body before sintering is approximately 4.85 mm.

[0029] Furthermore, at the connecting portion between the molded part 120 and the large diameter part 125, there is a tapered part 135 which becomes smaller in diameter on the large diameter part 125 side.
is formed. Therefore, after molding, the molded body is held by the molding pins 119 by the tapered portion 135, so that the molded body can be easily released from the cavity 112.

Next, a mechanism for raising and lowering the lower die 105 will be explained. As shown in FIG. 3, the lower mold 105 and the first movable plate 137 located on the lower surface thereof are connected by bolts 141 with a first spring 139 biased to widen the gap between the two members. has been done. For this reason,
The first movable plate 137 is prevented from falling by the head of the bolt 141, and the first movable plate 137 is prevented from falling by the head of the bolt 141.
39, it is constantly urged downward.

Furthermore, the first movable plate 137 and the stripper plate 130 are fixed by a rod 143. Furthermore, the first movable plate 137 and the second movable plate 145 located below the lower mold 1
05 and the first movable plate 137, the second spring 14 has a larger elastic force than the first spring 139.
They are connected by bolts 149 with 7 interposed therebetween.

The second movable plate 145 has the sprue 111, the runner 113, and the ring gate 1 which pass through the first movable plate 137 and have their tips mentioned above.
15 and a predetermined location of the film gate 117, an ejector pin 151 is provided upright. Further, a buffer rod 153 is erected on the second movable plate 145, passing through the first movable plate 137 and the lower mold 105 and having its tip end facing the lower surface of the upper mold 101. 153 includes the lower mold 105 and the first movable plate 137.
The third spring 15 is biased to increase the distance between the third spring 15 and the third spring 15.
5 is installed.

Furthermore, as shown in FIG. 5, which is a view taken from the direction of arrow A in FIG.
An upper member 158 of this portal frame 157 is located on the lower surface of the gate-shaped frame 157.
A stopper bolt 159 passing through is fixed. Therefore, the lower die 105 descends as the base 103 descends until the head of the stopper bolt 159 comes into contact with the lower surface of the upper member 158 of the portal frame 157.

Next, the injection molding process (step 2) for producing a molded article using the mold apparatus 100 having the above-described configuration will be described in detail, along with an explanation of the operation of the mold apparatus 100. First, the lower mold 105 is raised together with the base 103 to bring the mold apparatus 100 into the mold clamping state shown in FIG. 6 . Accordingly, as shown in FIGS. 4 and 6, the molding pin 119 is positioned along the central axis of the cavity 112 with the small diameter portion 123 at the tip inserted into the center hole 121 of the upper mold 101. Thus, an injection space SK is formed between the molding pin 119 and the cavity 112.

[0035] In this mold-clamped state, the uniform compound obtained in step 2 is heated at 900 to 1800 kg/cm2
It is injected from the nozzle 107 of the injection machine at an injection pressure of . In addition, the compound has a temperature of 130 to 200 when injected.
℃ (preferably 180 ℃). The compound injected from the nozzle 107 passes through the sprue 111, runner 113, ring gate 115, and film gate 117, and fills the injection space SK between the cavity 112 and the molding pin 119.

[0036] After that, maintain the holding pressure state under predetermined conditions (holding pressure of 180 to 800 kg/cm2 to 0.5 to
(continues for 5 seconds), during which time the compound is solidified in the injection space SK to form a molded body W0 (FIG. 6). The molded body W0 thus obtained has a transferability (dimensions of the molded body/dimensions of the mold) of 0.99 or more, and has a transferability of 0.99 or more (dimensions of the molded body/dimensions of the mold).
It has a roundness of 99 or more and a shrinkage rate (radial direction/axial direction) of 0.99 or more. Note that this molded body W0 includes a runner 113, a ring gate 115, and a film gate 117.
It is one with what has solidified within.

After carrying out the above-described injection molding step (step 2), the base 103 is lowered to take out the molded object W0 from the mold apparatus 100 as follows (step 3). First, as the first step of taking out the molded body W0,
As shown in FIG. 7, the molded body W0 is pulled out from the cavity 112. That is, the lower die 105, the first and second movable plates 137, 145, and the forming pin 119 descend together with the base 103, and furthermore, the tapered portion 135 of the forming pin 119 underlies the formed object W0. In order to form the cut portion, the molded body W0 is attached to a molding pin 119 as shown in FIG.
is held and pulled out from the cavity 112.

Thereafter, in the second step, the forming pins 119 are pulled out from the molded body W0 and the molded body W0 is released from the mold device 100.

In other words, when the lower mold 105 and the like are continuously lowered together with the base 103 and the head of the stopper bolt 159 comes into contact with the lower surface of the upper member 158 of the portal frame 157, at that point the second movable Plate 145 stops. When the second movable plate 145 stops in this way, the biasing force of the second spring 147, which has a larger elastic force than the first spring 139, acts upward on the first movable plate 137, so that the first movable plate 145 stops. A brake is applied to the descent of the plate 137. Therefore, as shown in FIG. 8, the stripper plate 130 is raised relative to the lower mold 105 by the rod 143, and the molding pin 119 integrated with the lower mold 105 is pulled out from the molded body W0.

After that, the lower mold 10 is further mounted together with the base 103.
5 is lowered and the lower surface of the lower mold 105 hits the upper surface of the first movable plate 137, the first movable plate 137 is pushed up and the lower mold 105 is moved to the second movable plate 145.
be relatively close to. Therefore, as shown in FIG. 9, the ejector pin 151 rises and the molded object W0 is lifted from the upper surface of the stripper plate 130. The thus separated molded body W0 is taken out from the mold device 100. FIG. 10 shows the molded body W0 taken out.

Next, the released molded body W0 is cut along the cutting line X near the connecting portion between the runner 113 and the ring gate 115, as shown by the dashed line in FIG.
Arc tube sintered part H1 that will become the arc tube described later and sprue 1
11, the runner 113, the ring gate 115, and the film gate 117 are separated into unnecessary sintered parts H2, and the unnecessary sintered parts H2 are removed (step 4).

Thereafter, the arc tube sintered portion H1 is subjected to an initial heat treatment in a nitrogen atmosphere to a temperature at which the organic binder such as an acrylic thermoplastic resin is thermally decomposed and completely carbonized. (Step 5). The specific upper limit heating temperature in this initial heat treatment may be determined depending on the capacity of the heat treatment furnace used and the thermal decomposition temperature of the organic binder, and in this example, from room temperature (20°C) to 45°C.
The temperature was raised to 0°C over 72 hours. Other processing conditions are as follows. In addition, during the temperature increase up to 450℃,
A constant pressure was maintained. Processing pressure 1-8kg/cm2 (
Optimum pressure 8kg/cm2) Time to raise temperature from 20℃ to 450℃
72 hours or less In other words, by performing the initial heat treatment, organic binders such as acrylic thermoplastic resin, paraffin wax, and atactic polypropylene, which were blended at the time of compound preparation, are thermally decomposed and carbonized, and the arc tube sintered part H1
Degrease.

Next, the arc tube sintered portion H1 that has undergone this initial heat treatment is calcined in the atmosphere, and the carbides metamorphosed during the initial heat treatment are burned and removed from the arc tube sintered portion H1 (step 6). During this calcination, it is sufficient to heat the carbide to a temperature sufficient to burn and remove it, and in this example, room temperature (2
The temperature was raised from 0°C to 700°C over 8 hours. By the time this calcining process is completed, the carbides transformed during the initial heat treatment are completely burned and removed from the sintered body.

Next, a sintering process is performed under the following conditions in a nitrogen atmosphere to sinter the calcined arc tube sintered portion H1 (step 7). At this time, the temperature was raised at a rate of 100°C/hour. Processing temperature 1750-1950℃ (
Optimum temperature: 1800℃) Holding time at the above treatment temperature: 4 hours or less

0
[045] By performing the above initial heat treatment and calcination/sintering treatment, the volume shrinkage becomes 82.5% of the compact before sintering, and the filling rate after sintering is approximately 98.5% (bulk density 3 .2
85).

Thereafter, this sintered body is subjected to hot isostatic pressing under the following conditions in a nitrogen gas atmosphere (step 8).
. At this time, the temperature was raised at a rate of 200°C/hour. In this way, the densification of the sintered body W through step 7 is completed, and the filling rate is 10.
0% (bulk density 3.300). Furthermore, this sintered body W
Translucency appears. In addition, when performing this hot isostatic pressing, the sintered body was heated with aluminum nitride beads (
The particles were buried in a titanium sponge (particle size: 2 mm) and then placed in a pod made of aluminum nitride. Processing temperature 1700-1900℃ (
Optimum temperature 1750℃) Processing pressure 1000-2000at
m (optimal pressure 1000 atm) Processing time 1~
4 hours (optimal processing 2 hours)

Subsequently, as shown in FIGS. 11(a) and 11(b), the sintered body W is
The end face is ground and polished to form a seating surface for a sealing member, which will be described later, on the side with a larger opening degree (Step 9).

After this step 9, as shown in FIG. 11(b), an arc tube 1F having electrode holding holes 1a, 1b at both ends is fabricated. This arc tube 1F has an inner diameter d of the light emitting region of about 4.0 mm, a wall thickness of about 0.65 mm, and a total length of about 40 mm. Note that the diameter of the small-diameter electrode holding hole 1b is 1 mm or less.

Next, this arc tube 1F was exposed to 100
By performing heat treatment at a temperature of 0 to 1300°C, for example 1300°C, nitrogen and oxygen in aluminum nitride on the inner and outer surfaces of the arc tube are replaced to form a thin aluminum oxide layer (step 10). At this time, heat treatment is performed to 1300° C. with a temperature gradient of about 150° C./hour, held at that temperature for about 1 hour, and then cooled to room temperature with a temperature gradient of about the same degree. The thickness of the aluminum oxide thin layer to be formed is determined by the processing temperature, holding time, etc., and in this example, the thickness is approximately 10 μm or less in order to avoid a significant decrease in the light transmittance of the arc tube. It is set like this.

The outer surface of the obtained arc tube 1F is ground and polished to a thickness of about 0.6 mm using a brush coated with diamond abrasive grains (step 11). This surface polishing removes irregularities on the outer surface of the arc tube, prevents scattering of light on the surface, and improves transmittance. On this occasion,
The aluminum oxide thin layer formed on the outer surface of the arc tube in step 10 above is removed along with the irregularities.

The thus completed arc tube 1F has the following physical properties. Linear transmittance for wavelengths 380 to 760 nm: 40% or more (thickness: 0.5 mm) Mechanical strength (JIS R1601) Bending strength St (room temperature) = 38 kg/cm2 (900°C) = 23 kg/cm2 Weibull coefficient (room temperature) =3.1 (900℃)=2.6 Thermal conductivity (room temperature)=181W/m・K (900℃)=93W/m・K

In other words, the arc tube 1F of this example has mechanical strength and linear transmittance comparable to those of the conventional arc tube made of translucent aluminum oxide, but its thermal conductivity is three times higher at room temperature. The temperature increases approximately 10 times at 900°C.

For measuring the intensity, the arc tube 1 of this embodiment described above was used.
A separately prepared sample (shape, thickness, etc. conforms to JIS R1601) was used as a replacement for F. In addition, in preparing the sample, various conditions in the above-described steps were followed. Thermal conductivity was also measured using this sample.

[0054] The in-line transmittance was measured using a double beam spectrophotometer after lapping the above-mentioned separately prepared sample to a thickness of 0.5 mm on both sides.

Then, as shown in FIG. 11(c), the main electrode coil 2 is inserted and set into the electrode holding hole 1b of the arc tube 1F from the inside of the tube, and the tapered sealing material is connected to the electrode holding hole 1b. The main electrode coil 2 is fixed by filling the reservoir 1c with a predetermined sealing material. Thereafter, in the arc tube 1F with one side sealed in this way, a predetermined rare gas metal for starting and a discharge material (Sn-based, Na-Tl-In
As shown in FIG.
Ceramic sealing member 4 sintering and fixing the main electrode coil 3
is fixed to the open end of the arc tube 1F with a predetermined sealing material. Note that the distance between the main electrode coils 2 and 3 is approximately 30 mm. Furthermore, when filling the discharge material, the internal pressure of the arc tube is adjusted to several tens of Torr using a rare gas such as argon.

The sealing member 4 and the sealing material for fixing it may be made of, for example, aluminum oxide cermet containing CuO or NiO for surface improvement, or CaO-Al2O3-MgO solder. Glass etc. can be illustrated. When the sealing member 4 made of solder glass is used, the sealing material is locally heated to a predetermined temperature (approximately 1370°C) and melts, and after cooling, it solidifies and connects the arc tube 1F and the sealing member. 4 and completely airtight and sealed. The arc tube 1F with the main electrode attached in this manner is generally used by being incorporated into the outer bulb of a high-pressure discharge lamp such as a metal halide lamp.

[0057] Then, Hg-NaI (
When a voltage of 100V (46W) was applied to the arc tube of this example, which was sealed with 0.11g of 0.11g), it was turned on. The time required for the pressure to reach a steady state (starting time) was approximately 12 seconds. Note that the brightness in this steady state was 98,000 nt. In addition, Hg-TlI-InI3 (0.1
3g) was sealed and the above lighting test was conducted, 10
It took about 13 seconds to stabilize at a brightness of 8,000 nt. Note that if the wall thickness is made thinner, the startup time will be further shortened.

Furthermore, when light emission was continued at each of the above luminances, the arc tube of this example filled with Hg-NaI showed no signs of damage even after being lit for a long period of 4,000 hours. No abnormalities were observed. Also, Hg-TlI
-In the arc tube of this example filled with InI3, 3
No abnormality was observed in the arc tube even after continued lighting for a long period of ,000 hours. In other words, these highly corrosive discharge metal components such as Hg-NaI and Hg-Tl
Even when I-InI3 is sealed, no abnormality is observed even if the lighting is continued for the long period of time described above.

As explained above, the arc tube 1F of the first embodiment has the same thickness (approximately 0.6 mm) as the conventional arc tube made of translucent aluminum oxide, and can withstand high temperatures and high pressures. Even if the mechanical strength is maintained as the same as in the past, the arc tube quickly warms up due to the high thermal conductivity of the arc tube itself, so the starting time can be shortened to less than half of the conventional one. In addition, the inner surface is equipped with a thin layer of aluminum oxide that does not impregnate the interior of the crystal grains with metal ions, so it is exposed to highly reactive metal gas that fills the arc tube during lighting and high temperature and high pressure. Deterioration is suppressed even if As a result, no abnormality was observed even when the lamp was turned on continuously for a long period of 3,000 to 5,000 hours or more at the brightness when the light emission state became a steady state.

Furthermore, according to the arc tube 1F of this embodiment, the area of the sealing material exposed to the discharge metal vapor components (ions) in the arc tube can be reduced, so that the discharge metal vapor components (ions) can be reduced. ) The amount of cracks that occur in the sealing material due to corrosion is reduced, and the probability of leakage of discharge metal vapor components to the outside of the arc tube is reduced. For this reason, the amount of residual metal vapor components for discharge in the arc tube is maintained at the initial sealed amount for a long period of time, which is better than a simple cylindrical arc tube (not shown) with large diameter electrode holding holes at both ends. Longer life can be achieved. However, it goes without saying that even such a simple cylindrical arc tube is included in the present invention as long as it is made of transparent aluminum nitride with a thin layer of aluminum oxide on the inner surface. do not have.

Furthermore, according to the method for manufacturing an arc tube according to the embodiment described above, an arc tube made of transparent aluminum nitride and having a thin layer of aluminum oxide on the inner surface can be easily manufactured.

Next, the arc tube 1A of the second embodiment will be explained. In the explanation, the external features of the arc tube 1A of the second embodiment to be manufactured will be explained,
After that, the manufacturing process will be explained. Figure 13(a)
, (b), the arc tube 1A is a U-shaped aluminum nitride arc tube with a tubular body provided with electrode holding holes 1a at both ends and curved at the center.
A thin aluminum oxide layer 1f with a thickness of μm is provided. Next, the manufacturing process of this arc tube 1F will be explained using the process diagram of FIG. 14. Note that FIG. 13(b) is similar to FIG. 13(b).
It is a Y plane sectional view of (a).

First, in the same manner as in the first embodiment described above, fine powder of aluminum nitride (purity: 99.5 mol% or more) (particle size of 1 μm or less) and fine powder of yttrium oxide (particle size of 1 μm or less) are mixed. , aluminum nitride: 96wt%,
Yttrium oxide: Weighed and mixed to 4wt%, and mixed fine powder with acrylic organic binder, deflocculant such as butyl acetate, and antifoaming agent such as octanol with benzene. are wet-mixed in a plastic (nylon) ball mill for about 24 hours to prepare a slurry in which the mixed fine powder is uniformly present in the solvent (Step 1).

The blending ratio (weight ratio) of the organic binder, etc. to the mixed fine powder is as follows, per 100 g of the mixed fine powder. Organic binder 3g deflocculant 1g antifoaming agent
0.1g Benzene 60g

Next, air bubbles are removed from the prepared slurry (Step 2). Specifically, the slurry taken out from the ball mill is placed in a resin container in a vacuum desiccator, and while the slurry in the resin container is stirred using a magnetic stirrer, the air in the desiccator is pumped out using a vacuum pump for several minutes (for example, about 1 hour). (minutes) aspirate.

[0066] After that, the following steps are performed to obtain the image shown in Fig. 13(a).
The desired molded body shown in FIG. 15(b) is molded using the mating mold 10 shown in FIG. 15(a). The mating molds 10 are symmetrical molds 11a and 11b made of a porous inorganic material such as gypsum or a porous resin having pores having the same function as gypsum, as shown in FIG. 15(a). A slurry injection space 13 is formed at the joint surface of the molds 11a and 11b.

As shown in FIG. 15(b), each of the molds 11a and 11b has grooves (cavities) 13a and 13b curved at the lower end of the mold on their joint surfaces 15a and 15b. The grooves 13a, 13b are cut into the joint surfaces 15a, 15b in the following manner using an end mill having spherical cutting teeth at the tip.

That is, as shown in FIG. 16(a), the radius r
An end mill EM equipped with spherical cutting teeth at the tip was cut into type 11.
A, 11b are moved along arrow A in the figure, with the cutting depth from the joint surfaces 15a, 15b set to r. In this case, the cutting locus of the end mill EM from the cutting start position S to the cutting end position E is the locus shown by arrow A in FIG. The interval L is set smaller than 2r.

Therefore, the bonding surfaces 15a and 15b are as shown in FIG.
As shown in FIG. 16(C), which is a cross-sectional end view taken along line X-X in FIG.
The end mill EM
Cutting and forming. Note that, as described above, the groove 13a
, 13b, it is also possible to shape the grooves 13a, 13b so that protrusions 14a, 14b are formed in the center thereof.

The molds 11a and 11b described above are joined together at their joint surfaces to fix both molds to form a mating mold 10 (see FIG. 15).
a)).

Next, the slurry from which air bubbles were removed in step 2 is injected into the slurry injection space 13 of this mating mold 10, and left for a predetermined time (step 3). When injecting the slurry, as shown in FIG. 17, the slurry is poured into a cylindrical body 17 placed on the upper surface of the mating mold 10. Note that a slurry larger than the volume of the slurry injection space 13 is injected into the cylindrical body 17 . Further, the lower surface of the cylindrical body 17 and the upper surface of the mating mold 10 are sealed by placing clay 19 in a tubular shape at the lower end of the cylindrical body 17. Rubber may be used instead of clay.

[0072] The solvent component (here, benzene) in the slurry thus injected into the slurry injection space 13
As described above, while the slurry is left for a predetermined period of time after being injected, it is sucked into the pores of the porous molds 11a and 11b by capillary action and absorbed into the molds. Therefore, on the wall surface of the slurry injection space 13, the mixed fine powder bound by an organic binder etc. is evenly deposited along the surface of the wall surface, and as shown in FIG. A bonded layer SA is formed.

The standing time after this slurry injection determines the thickness of the above-mentioned inking layer SA, that is, the inner diameter of the molded body, which will be described later. For this reason, the above-mentioned leaving time is determined in advance through experiments or the like so that the inner diameter etc. of the formed inked layer SA become a predetermined value. Further, in setting the standing time and the size of the mold, volume shrinkage during sintering and the like are taken into consideration. The standing time in this example was such that the inner diameter of the inking layer SA was approximately 4
．． It is set to be 82 mm and the filling rate is about 57%, and in this case, the time is 10 minutes or less. The outer diameter of the inking layer SA is determined by the slurry injection space 13, and is approximately 6.27 mm in this embodiment.

[0074] It should be noted that a configuration may be adopted in which the outside of each mold is maintained at a negative pressure while the mold is left to stand, and the solvent component in the slurry is forcibly sucked out of the mold. In this way, the filling rate can be further increased by shortening the standing time, directly removing air bubbles in the slurry through the mold, and strengthening the suction.

[0075] After leaving it for a predetermined time, the slurry remaining inside the cylindrical body 17 and the inside of the inking layer SA is removed (step 4). After that, the mating mold 10 is separated and FIG.
The molded body of the arc tube 1A having the shapes shown in a) and (b) is released from the mold, and the molded body is dried until the solvent is completely removed from the molded body (Step 5).

Thereafter, the dried compact is calcined in the atmosphere to burn off the organic binder (step 6). During this calcination, it is sufficient to heat the organic binder to a temperature sufficient to burn and remove it, and in this example, room temperature (20
The temperature was raised from 700°C to 700°C over 8 hours. and,
By the completion of this calcination process, the organic binder has been completely burned off from the compact.

Next, this molded body was heated to 175% in a nitrogen atmosphere.
The molded body is sintered by heat treatment at a predetermined sintering temperature of 0 to 1950°C, for example, about 1800°C for about 4 hours (Step 7). At this time, the temperature was raised at a rate of 100° C./hour. By sintering in this manner, the volume shrinkage becomes about 82.5% of the compact before sintering, and the desired dimensions are obtained. At this time, the filling rate is approximately 98.5% (bulk density 3.2
85).

Thereafter, this sintered body is subjected to hot isostatic pressing under the following conditions in a nitrogen gas atmosphere (step 8).
. At this time, the temperature was raised at a rate of 200°C/hour. In this way, the densification of the sintered body W through step 7 is completed, and the filling rate is 10.
0% (bulk density 3.300). Further, this sintered body develops translucency, and becomes an arc tube 1A made of translucent aluminum nitride. In addition, when performing this hot isostatic pressing, the sintered body was coated with aluminum nitride beads (particle size 2
mm) and titanium sponge, and then placed in a pod made of aluminum nitride. Processing temperature 1700-1900℃ (
Optimum temperature 1750℃) Processing pressure 1000-2000at
m (optimal pressure 1000 atm) Processing time 1~
4 hours (optimal processing 2 hours)

The manufactured arc tube 1A has an inner diameter of approximately 4.0
mm, the wall thickness is approximately 0.3 mm, and the height from the opening to the bent portion is approximately 20 mm.

Next, this arc tube 1A was exposed to 100
By performing heat treatment at a temperature of 0 to 1300°C, for example 1300°C, nitrogen and oxygen in aluminum nitride on the inner and outer surfaces of the arc tube are replaced to form a thin aluminum oxide layer (step 9). At this time, heat treatment is performed up to 1300°C with a temperature gradient of about 150°C/hour, and 1
It is held for about an hour and then cooled to room temperature with the same temperature gradient. The thickness of the aluminum oxide thin layer to be formed is determined by the processing temperature, holding time, etc., and in this example, the thickness of the aluminum oxide thin layer is set to be about 10 μm or less.

The outer surface of the obtained arc tube 1A is ground and polished to a thickness of about 0.6 mm using a brush coated with diamond abrasive grains (step 10). This surface polishing removes irregularities on the outer surface of the arc tube, prevents scattering of light on the surface, and improves transmittance. On this occasion,
The aluminum oxide thin layer formed on the outer surface of the arc tube in step 9 is removed along with the irregularities.

The arc tube 1A thus completed has the following physical properties. Linear transmittance for wavelengths 380 to 760 nm: 40% or more (thickness: 0.5 mm) Mechanical strength (JIS R1601) Bending strength St (room temperature) = 36 kg/cm2 (900°C) = 20 kg/cm2 Weibull coefficient (room temperature) = 3.2 (900℃) = 2.8 Thermal conductivity (room temperature) = 180W/m・K (900℃) = 91W/m・K

In other words, the arc tube 1A of this example has mechanical strength and linear transmittance comparable to those of the conventional arc tube made of translucent aluminum oxide, but its thermal conductivity is three times higher at room temperature. The temperature increases approximately 10 times at 900°C.

For measuring the intensity, the arc tube 1 of this embodiment described above was used.
A separately prepared sample (shape, thickness, etc. conforms to JIS R1601) was used as a replacement for A. In addition, in preparing the sample, various conditions in the above-described steps were followed. Thermal conductivity was also measured using this sample.

[0085] The in-line transmittance was measured using a double beam spectrophotometer after lapping the above-mentioned separately prepared sample to a thickness of 0.5 mm on both sides.

[0086] Inside the arc tube 1A, a predetermined starting rare gas and a discharge material (Sn-based, N
a-Tl-In series, Sc-Na series, Dy-Tl series alloys or halides of each metal) amalgam is placed, and
As shown in (c), a ceramic (aluminum oxide) sealing member 4 (Fig. 1
9) is fixed to both electrode holding holes 1a of the arc tube 1A with a predetermined sealing material. At this time, the internal pressure is adjusted to several tens of Torr using a rare gas such as argon. Note that the sealing member 4 and the sealing material may be the same as those in the first embodiment. After the main electrode is attached in this manner, the arc tube 1A is used by being incorporated into the outer bulb of a high pressure discharge lamp such as a metal halide lamp.

Hg-NaI (0.11
A voltage of 100 V (4
When 6W) was applied and the light was turned on, the starting time was approximately 12
It was seconds. Note that the brightness when the light emission reached a steady state was 98,000 nt. Furthermore, when the above lighting test was conducted with Hg-TlI-InI3 (0.13 g) sealed as a discharge material, it took about 13 seconds to stabilize at a brightness of 108,000 nt.

Furthermore, when light emission was continued at each of the above luminances, the arc tube of this example filled with Hg-NaI showed no signs of damage even after being lit for a long period of 4,000 hours. No abnormalities were observed. Also, Hg-TlI
- In the arc tube of this example filled with InI3, 3
No abnormality was observed in the arc tube even after continued lighting for a long period of ,000 hours. In other words, these highly corrosive discharge metal components such as Hg-NaI and Hg-Tl
Even when I-InI3 is sealed, no abnormality is observed even if the lighting is continued for the long period of time described above.

As explained above, the arc tube 1A of the second embodiment has the same thickness (approximately 0.6 mm) as the conventional arc tube made of translucent aluminum oxide, and can withstand high temperature and high pressure conditions. Even if the mechanical strength is maintained as the same as in the past, the arc tube quickly warms up due to the high thermal conductivity of the arc tube itself, so the starting time can be shortened to less than half of the conventional one. In addition, the inner surface is equipped with a thin layer of aluminum oxide that does not impregnate the interior of the crystal grains with metal ions, so it is exposed to highly reactive metal gas that fills the arc tube during lighting and high temperature and high pressure. Deterioration is suppressed even if As a result, no abnormality was observed even when the lamp was turned on continuously for a long period of 3,000 to 5,000 hours or more at the brightness when the light emission state became a steady state.

In addition, since the shape is a U-shape in which the side surfaces of the electrode holding hole 1a at both ends are joined to each other, the distance from the center position of the light emission that corresponds to the curved part to the electrode holding hole 1a where the main electrode is arranged ( In the case of symbol L in FIG. 13(c), the distance is short and the lamp is compact with respect to the lighting direction. As a result,
Since the high-intensity discharge lamp can be miniaturized, the high-intensity discharge lamp using the arc tube 1A of this embodiment is suitable as a consumer lighting fixture.

Further, according to the method for manufacturing an arc tube according to the second embodiment described above, the arc tube is made of transparent aluminum nitride and has a thin layer of aluminum oxide on the inner surface, and is curved at the center. It is possible to easily manufacture a U-shaped arc tube whose sides are joined to each other, that is, an arc tube with a complicated shape that can be used in consumer electric lights that are required to be compact in the lighting direction. .

Although one embodiment of the present invention has been described above, the present invention is not limited to this embodiment in any way, and can be implemented in various ways without departing from the gist of the present invention. Of course. For example, instead of the arc tube 1A in the second embodiment, as shown in FIG. 20, an arc tube 1B in which tubular bodies with square cross sections are joined at the center may be used. If it has such a square shape, it will sit well and the grinding process will be easy. Further, the step of heat treatment in the atmosphere may be performed after the step of grinding and polishing (step 11 in the first embodiment, step 9 in the second embodiment) for removing irregularities on the outer surface. In this way, even if a thin aluminum oxide layer is formed on the outer surface, light scattering on the outer surface is avoided due to the lack of irregularities, so there is no need to remove the thin aluminum oxide layer on the outer surface. do not have.

[0093]

Effects of the Invention As described in detail above, the arc tube for a high-intensity discharge lamp of the present invention has a translucent outer layer made of aluminum nitride and a thin inner layer made of aluminum oxide, so that it can withstand high temperatures and pressures. Although it is thick to ensure mechanical strength, it increases the transfer of heat generated during arc discharge due to the high thermal conductivity of aluminum nitride, and promotes the temperature rise of the arc tube itself due to the heat of arc discharge. . As a result, the starting time can be shortened even though the aluminum oxide arc tube has the same wall thickness as the conventional aluminum oxide arc tube, which has increased particle size to exhibit translucency.

Furthermore, according to the manufacturing method of the present invention, it is possible to easily manufacture an arc tube for a high-intensity discharge lamp, which has an outer layer made of translucent aluminum nitride and a thin inner layer made of aluminum oxide. can.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an arc tube 1F of a first embodiment.

FIG. 2 is a process diagram for explaining the manufacturing process of the arc tube 1F.

FIG. 3 is a schematic cross-sectional view of the mold device 100 used for manufacturing the arc tube 1F in a mold clamped state.

4 is an enlarged view of the main part of FIG. 3 used to explain the vicinity of the compound injection space SK formed by the cavity 112 and the molding pin 119. FIG.

FIG. 5 is a view taken in the direction of arrow A in FIG. 3;

FIG. 6 is an explanatory diagram for explaining a state in which the compound is injected into the injection space SK in the cavity 112.

FIG. 7 is an explanatory diagram for explaining a state in which the molded body is pulled out from the cavity 112.

FIG. 8 is an explanatory diagram for explaining a state in which the forming pin 119 is pulled out from the formed object W0.

FIG. 9 is an explanatory view for explaining a state in which the molded body W0 is lifted from the upper surface of the stripper plate 130.

FIG. 10 is a sectional view of the molded body W0 separated from the mold apparatus 100.

FIG. 11 is an explanatory diagram for explaining the grinding process performed on the molded body W0 after sintering and the assembled state.

FIG. 12 is a perspective view of the sealing member 4 fixed to the electrode holding hole of the arc tube 1F.

FIG. 13 is an explanatory diagram for explaining the shape of the arc tube 1A of the second embodiment.

FIG. 14 is a process diagram for explaining the manufacturing process of the arc tube 1A.

FIG. 15 is a perspective view of a mating mold 10 used for manufacturing the arc tube 1A.

FIG. 16 is an explanatory diagram for explaining the mold manufacturing process in the mating mold 10.

FIG. 17 is an explanatory diagram for explaining the manufacturing process of the arc tube 1A.

FIG. 18 is an explanatory diagram for explaining the manufacturing process of the arc tube 1A.

FIG. 19 is a perspective view of the sealing member 4 fixed to the electrode holding hole of the arc tube 1A.

FIG. 20 is an explanatory diagram for explaining an arc tube 1B in another embodiment.

[Explanation of symbols]

1A Arc tube 1B Arc tube 1F Arc tube 1a Electrode holding hole 1b Electrode holding hole 1c Encapsulant pool 1f Aluminum oxide thin layer 2 Main electrode coil 3 Main electrode coil 4 Sealing member 10 Combined type 13 Slurry injection space 100 Mold equipment 112 Cavity 119 Molded pin SK injection space SA Inking layer

Claims (3)

[Claims] Claim 1: An arc tube for a high-intensity discharge lamp, wherein the outer surface layer is made of translucent aluminum nitride and contains 0.5 to 8 wt% of one or more oxides selected from yttrium oxide, calcium oxide, and magnesium oxide. and an inner thin layer made of aluminum oxide. 2. The arc tube for a high-intensity discharge lamp according to claim 1, wherein the pair of main electrodes are sealed and a metal component necessary for light emission is sealed inside the tube. [Claim 3] Yttrium oxide, calcium oxide,
0.0 or more oxides selected from magnesium oxide.
A step of adding an organic binder to a mixed fine powder containing 5 to 8 wt% of aluminum nitride as the balance, and forming a tubular molded body of a desired shape by a predetermined molding method; A step of sintering at a temperature of ~1950°C, and a treatment temperature of 1700°C under a nitrogen atmosphere.
A process of hot isostatic pressing at ~1900°C and a processing pressure of 1000 to 2000 atm, and a step of applying hot isostatic pressing to the tubular sintered body after the hot isostatic pressing in the atmosphere at a pressure of 1000 to 130 atm.
1. A method for manufacturing an arc tube for a high-intensity discharge lamp, comprising the step of heat treatment at a temperature of 0°C.