JP4190366B2 - Method for manufacturing glass reflector for projector - Google Patents

Description

  The present invention relates to a glass reflector used together with a light source such as a high-pressure mercury discharge lamp and a manufacturing method thereof, and more particularly to a glass reflector suitable for a light source of a projector such as a liquid crystal projector or a DLP projector and a manufacturing method thereof.

  As a light source for liquid crystal projectors and DLP projectors (herein, these are collectively referred to as projectors), a combination of a halogen lamp and a heat-resistant glass reflector such as borosilicate glass was initially used. High pressure discharge lamps, which are superior in terms of light color nearer white and lamp life, have been replaced by this. This replacement has contributed to the progress of miniaturization and higher output of discharge lamps.

  With the spread of video equipment such as personal computers and DVDs, projectors have been used for a wide range of applications, from business presentations to home use. As a result, the projector itself has become smaller and the brightness has been lost. There is no need to reduce the output of the lamp. An increase in lamp output causes an increase in the amount of heat generated from the lamp, and due to the effect of miniaturization of the projector housing, the temperature rise of the light source portion is significant and may exceed 600 ° C. at the neck portion of the reflector.

  In the conventional projector, the maximum temperature of the glass surface is about 400 to 450 ° C., but in the latest projector, the maximum temperature of the glass surface is increased to 450 to 550 ° C. Therefore, for use in projectors, low thermal expansion crystallized glass reflectors, which are superior in heat resistance to the conventional heat resistant glass reflectors using borosilicate glass or the like, have become the mainstream (for example, patent documents). 1).

  This is because the rising temperature of the reflector may exceed the transition point of the conventionally used borosilicate glass, and the probability that a conventional borosilicate glass reflector will crack or break at temperatures reaching 550 ° C. Because it was believed to be expensive.

On the other hand, a glass reflector is manufactured by press molding molten glass using a mold manufactured based on a desired optical design.

By the way, since the reflecting mirror for the light source needs an aperture to insert and fix the light source lamp on the top of the reflecting surface, the neck that protrudes along the optical axis of the reflecting mirror on the back surface side of the reflecting surface during press molding. This is done by forming a part and cutting or perforating it.

In general, in a flat glass product, if there is a scratch on the peripheral edge, even if the scratch is fine, when the stress is applied, the scratch may stretch and lead to the destruction of the flat glass. A part is chamfered by mechanical grinding to remove scratches and prevent chipping. Conventionally, chamfering is performed for each sheet glass by mechanical grinding. However, since this method takes time, a method for simultaneously chamfering a plurality of sheet glasses by etching is also known (Patent Document 2).

Japanese Patent Publication No. 7-37334 Japanese Patent Laid-Open No. 54-25

  In the above-mentioned crystallized glass reflecting mirror, since it is necessary to crystallize the glass, it is reheated to a temperature higher than the glass transition point of the mother glass. As a result of deviating from the ideal curved surface, the reflection direction of the light from the light source is disturbed and the reflection efficiency is deteriorated, the brightness (illuminance) of the projected image is lowered in the projector.

In addition, in this kind of reflecting mirror, a dielectric multilayer film that reflects visible light and transmits infrared rays is deposited on the reflecting surface, and means for preventing heating of the irradiated object by infrared rays is taken. Therefore, the infrared rays emitted from the light source pass through the multilayer film and pass through the reflector substrate, but since crystallized glass scatters infrared rays at the crystal interface, etc., heat is trapped around the reflector in a projector or other housing. Cheap.

Reflector using amorphous heat-resistant glass that does not require a crystallization process is not subject to reheating after molding, so its reflection surface accuracy is closer to the ideal curved surface than crystallized glass, and it was used for a projector light source. Although the projection surface illuminance in this case is excellent, there is a risk of damage in a high-temperature use environment as described above, and therefore, the present situation is that it is limited to use in combination with a relatively low output light source.

As a result of analysis of the amorphous glass reflector that resulted in breakage, it was found that most of them were cracked starting from the cut surface or the drilled surface of the hole provided in the neck did.

As described above, chamfering processing is performed on plate glass products to remove scratches on the peripheral edge, but the chamfering processing is difficult because the aperture of the reflector is on the end surface or inner peripheral surface of the neck portion. There is very inefficiency. In addition, since the chamfering process itself is a machining process, it is difficult to completely remove even minute microcracks.

The present invention has been made in view of the problems of the conventional reflectors for projectors as described above, has heat resistance that can withstand a combination with a high-output light source, has excellent reflection surface accuracy, and is inexpensive. An object of the present invention is to provide a reflecting mirror and a manufacturing method thereof.

In order to achieve the above object, according to claim 1 of the present invention, the reflecting surface portion is made of amorphous glass having a thermal expansion coefficient of 30 to 45 × 10 ⁻⁷ / ° C. and reflects light emitted from a light source. and opening for inserting the light source bulb, a manufacturing method of a projector for a glass reflector having open at a position recessed from said reflecting surface portion by a mold having a bottom mold and a plunger of molten glass A press molding step for press molding into a predetermined reflector shape having a predetermined hole portion, and an opening for forming the aperture portion by removing the glass at the portion corresponding to the aperture portion of the reflector formed by this step And a surface smoothing step that removes mechanical damage of the processed portion by etching the apertures formed by this step and smoothing the surface thereof. A method for producing a glass reflector for a projector is provided.

Here, when the thermal expansion coefficient is lower than 30 × 10 ⁻⁷ / ° C., the moldability is deteriorated, and the yield of the reflector requiring a precise reflecting surface is lowered. When the thermal expansion coefficient exceeds 45 × 10 ⁻⁷ / ° C., the heat resistance is decreased. Insufficient performance to withstand the combination with a high output light source. Preferably, it is up to 40 × 10 ⁻⁷ / ° C.

  The removal of mechanical damage in the processed part means that there is no chipping due to mechanical processing, surface roughness, or micro-cracks of several μm existing on the surface, and the origin of reflector breakage. Since the mechanical damage is removed, the occurrence of breakage can be suppressed even in a reflecting mirror in which the temperature of the glass surface becomes very high.

According to the present invention , it is preferable that the reflection surface portion has a shape of a spheroidal surface or a rotation paraboloid, and the reflection surface accuracy in the vicinity of the aperture is within ± 20 μm with respect to an ideal curved surface .

  The vicinity of the opening in this case means a range from the neck opening end to about 20 mm in the radial direction, and the surface accuracy in the vicinity of the opening may be within ± 20 μm with respect to the ideal curved surface. Since the accuracy around the neck portion has the most influence on the brightness of the projection light from the reflecting mirror, it is particularly effective to improve the accuracy of the reflecting surface in this portion.

According to claim 2 of the present invention, the etching amount of the opening processing surface which is removed by the etching process, producing a projector glass reflector according to claim 1, wherein a is 30μm or more Provide a method.

  As will be described later, the processed surface of the hole portion that has been drilled by machining is in a state in which many fine irregularities and cracks exist, and an etching amount of 30 μm or more is required to eliminate the influence.

In the step of forming the opening portion, the opening portion may be formed by a drill from the reflective surface side, or a portion corresponding to the opening portion is cut by a cutter to form the opening portion. Also good. The reason why the hole is formed by the drill by inserting the drill from the reflecting surface side is to drop the cutting waste and the glass piece without attaching to the reflecting surface.

ADVANTAGE OF THE INVENTION According to this invention, the glass reflective mirror suitable for projectors with high heat resistance, excellent reflective accuracy, and low price, and its manufacturing method are obtained.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Two types of glass (A) and (B) having the following components and the like were used as the reflector glass of the examples and comparative examples. % Is mass%.

(A) SiO ₂ 80.9%, Al ₂ O ₃ 2.3%, Na ₂ O 4%, B ₂ O ₃ 12.7%, thermal expansion coefficient (0 to 300 ° C.): 32.5 × 10 ^{− 7} / ° C.

(B) SiO ₂ 78%, Al ₂ O ₃ 2.1%, Na ₂ O 5.2%, B ₂ O ₃ 14.5%, coefficient of thermal expansion (0 to 300 ° C.): 38 × 10 ⁻⁷ / ° C.

Further, the sample of the example and the comparative example is a deformed reflecting mirror having a spheroid with an outer dimension of 50 mm and a width of 50 mm when viewed from the optical axis direction and a focal length F of 6 mm. The length of the neck portion was 5 mm from the boundary with the reflecting surface, the thickness in the vicinity of the focal point was 4.5 mm, the neck portion inner diameter (opening surface diameter) φ10 mm, and the opening diameter φ9 mm.

<Example 1>
As Example 1, the raw materials were prepared so as to have the above glass composition, melted at about 1600 ° C., and then a glass gob having a predetermined weight was dropped into a bottom mold 41 as shown in FIG. And is pressed into the shape of the reflecting mirror 4 having the above dimensions (the same applies to Example 2 and Comparative Example 1 described below). When this pressing is performed, if the glass temperature is pressed to about 800 ° C. or less, the transfer accuracy of the plunger shape serving as the reflection surface is good, and the accuracy of the reflection surface can be improved.

  A reflector 1 press-molded as described above is shown in FIG. In Example 1, when pressing, it is preferable to set the thickness d of the planned opening portion 11 as thin as possible within a range that does not hinder the drilling process. The thickness d of this portion is determined by the gap between the molds. For example, the thickness is 1.5 to 3 mm.

  In addition, if the thickness of the planned opening portion 11 is thick, it takes time for drilling and etching of the processed surface, and if it is too thin, cracks of a size that cannot be removed by etching at the time of drilling may occur. Absent. In addition, in this type of glass, when the molten glass is pressed, the glass is rapidly deprived of heat and solidified as the thickness decreases due to contact with the mold. It is a limit.

Further, it is desirable that the planned opening portion 11 is provided at a position as far as possible from the reflecting surface that is recessed from the reflecting surface 13. Since this portion is etched after the drilling process, if only the neck portion 12 is immersed in the etching solution by providing a distance between the opening surface and the reflecting surface 13, the influence of the etching solution on the reflecting surface 13 is affected. Can be small.

Next, the reflecting mirror 1 is placed on the die 14, and a hole such as a diamond core drill 15 is applied from the reflecting surface side and rotated in the direction of the arrow 16 to open a hole in the planned opening portion 11. A portion 17 is formed (FIG. 1B).

  When the inner peripheral surface of the aperture was observed in this state, the surface had fine ground glass-like irregularities, and the surface roughness was a rough surface with irregularities of Ra of about 1 μm and a maximum of 17-18 μm.

  As shown in FIG. 1C, the reflecting mirror 1 in which the opening 17 is formed is immersed in an etching solution 20 and etched. That is, the reflecting mirror 1 whose opening end of the reflecting surface is held by the holding device 18 is immersed or pulled up and down the liquid surface until the processed surface of the opening portion is immersed in the etching solution 20 stretched in the corrosion-resistant liquid tank 19. Was repeated as appropriate. As the etching solution 20, hydrofluoric acid having a weight concentration of 5% was used and the solution temperature was 25 ° C.

  During etching, if the etchant adheres to the reflective surface, a stain-like mark remains, which may adversely affect the subsequent reflective film formation and reflection characteristics. Apply heat softening wax to the reflective surface in advance. The reflective surface may be protected. In this case, it is possible to immerse the entire reflecting mirror substrate in the etching solution. The heat-softening wax applied to the reflecting surface is softened by heating after the etching process is finished and separated from the reflector substrate, and the adhering matter is removed by washing with a detergent.

  The etched reflecting mirror was sufficiently washed and dried to obtain a sample substrate.

<Example 2>
In the second embodiment, the reflector 3 having the neck portion rear end 32 in a closed state is formed by press working using a mold in which the neck portion 31 is set longer than in the first embodiment (FIG. 2 (A). )). Next, after slowly cooling the reflecting mirror 3, the rear end of the neck portion 31 is left with the cutter 34 on the surface 33 perpendicular to the optical axis, where the length of the remaining neck portion is the same position as in the first embodiment. The rear end of the neck portion is cut and removed (FIG. 2B).

  Next, as shown in FIG. 2C, the cut surface 33 was etched in the same manner as in Example 1, washed, and dried to obtain a sample substrate (FIG. 2D).

<Comparative Example 1>
In Comparative Example 1, a reflector was manufactured by press molding using borosilicate glass, and after slow cooling, a hole was formed by a core drill in the same manner as in Example 1 above. There is nothing.

<Comparative example 2>
In Comparative Example 2, a borosilicate glass was used to manufacture a reflecting mirror in which the neck end rear end was closed as in Example 2 described above by press working, and after slow cooling, the neck end rear end was excised. The hole is processed, but the processed surface is not etched after that.

<Comparative Example 3>
Comparative Example 3 is an example using crystallized glass, made of crystallized glass according to Example (1) of Japanese Patent Publication No. 7-37334, and after molding in the same manner as in Example 3 above, The rear end of the neck portion is cut and removed by a plane orthogonal to the optical axis, but the subsequent cut plane is not etched.

Specifically, in Comparative Example 3, SiO ₂ 60%, Al ₂ O 3 21%, Li ₂ O 5.5%, TiO ₂ + ZrO ₂ 4%, P ₂ O ₅ 5%, B ₂ O ₃ 2.5 %, ZnO + MgO 4%, K ₂ O + Na ₂ O 1.5%, and the raw materials were mixed, melted at 1500 ° C. and vitrified, and formed into the shape of a reflector substrate by a press method. The glass molded body was held at 570 ° C. for 1 hour, and then heated to 770 ° C. at a rate of 3 ° C. per minute. After holding at this temperature for 1 hour, it was cooled. The molded product that was transparent before the heat treatment turned milky white and consisted of a β-spodumene solid solution. It is a crystallized glass having a thermal expansion coefficient of 6 × 10 ⁻⁷ / ° C.

  Accordingly, an annular protrusion 21 as shown in FIG. 1 (D) remains on the inner periphery of the neck portion of the reflector produced in Example 1 and Comparative Example 1, but is produced in Example 2 and Comparative Examples 2 and 3. There is no protrusion on the inner periphery of the neck of the reflecting mirror.

As described above, a reflective film comprising 30 layers of TiO ₂ films and SiO ₂ films alternately laminated by vacuum deposition on the reflective surface of the reflective mirror substrate prepared in the examples and comparative examples, did.

<Evaluation results of Examples and Comparative Examples>
The evaluation results for these Examples and Comparative Examples are shown in FIG. 4 as the average value of 10 samples. In addition, the column of relative illuminance in the table indicates the ratio of the projection surface average illuminance of each example and the comparative example to the projection surface average illuminance of Comparative Example 3.

(1) Presence / absence of mechanical damage in the processed part First, scratches, chips and surface roughness of the processed part were visually observed. All of the reflectors of the above examples were in a smooth surface state in which no scratches or chips were observed and the edge of the open end was removed. On the other hand, the machined surface of each of the above comparative examples was found to have a trace of machining, was a ground glass-like rough surface, and a fine chip was observed at the edge of the aperture. Next, a laser beam was incident on the surface of the processed part, and the scattered light was observed. In any of the reflectors of the examples, no light scattering due to cracks was observed, and it was determined that mechanical damage of the processed part was removed.

In addition, by changing the immersion time in the etching solution, the surface states of the processed parts of the samples with the etching amounts of about 10 μm, 20 μm, 30 μm, 50 μm, and 100 μm were compared. When the etching amount is 10 μm, the surface unevenness still remains, and at 20 μm, the surface unevenness is almost removed and the surface is in a smooth state. Scattering of light that seems to be due to was observed. On the other hand, since laser light scattering was hardly observed at 30 μm or more, an etching amount of 30 μm or more was used for the following evaluation.

Therefore, it is preferable that the etching amount necessary for removing the mechanical damage of the processed part is at least 30 μm or more, and more preferably 50 μm or more in consideration of the influence of processing accuracy due to wear of the machining jig. It is preferable that the thickness is about 100 μm in consideration of the etching processing time and the accuracy of other parts.

(2) Surface roughness of processed part The surface roughness of the processed part of each sample was measured using a stylus type surface roughness meter. In Examples 1 and 2 and Comparative Example 1, the reflecting mirror was divided into two along the optical axis, the inner peripheral surface of the neck portion was exposed, and the inner peripheral surface of the aperture portion was measured over 1 mm in the optical axis direction, Comparative Example 2 , 3, the end surface of the neck portion was measured along the cut surface. Each example had an average roughness Ra of about 0.03 μm, whereas each comparative example had a rough surface with irregularities having an average roughness Ra of about 1 μm and a maximum of 17-18 μm.

(3) Reflection surface accuracy As a result of measuring the reflection surface of each sample along the radial direction using a stylus type three-dimensional shape measuring apparatus, Examples 1 and 2 and Comparative Examples 1 and 2 with respect to the reflection surface design value. Then, the accuracy was ± 10 to 15 μm. On the other hand, in Comparative Example 3, it was confirmed that there was a deviation of about ± 70 μm. The measurement results of the three-dimensional measurement data of Example 1 (A) and Comparative Example 3 are shown in FIGS. In these figures, measured values are shown enlarged in the normal direction of each measurement point with respect to an ideal curved surface (curve). The reflection surface curve (measured value) is an enlarged display of 50 times, and the distance between the center line and the upper and lower lines is 50 μm.

(4) Lighting evaluation A 150 W ultra-high pressure mercury lamp (UHP) is attached to each sample mirror, an electric fan with a diameter of 10 cm is installed at a distance of 10 cm from the neck of the reflector, and the reflector neck of the reflector is mounted with a thermocouple. While measuring the temperature, control the fan's air volume so that the temperature after the temperature rise reaches the set temperature (450 ° C, 550 ° C), and turn it on continuously for 2.5 hours. Carried out. This was performed for each of the examples and comparative examples for the number of samples, 10 pieces each.

As a result, the results shown in the table of FIG. 4 were obtained. In the lighting evaluation shown in FIG. 4, the numerator means the number of samples in which cracks or cracks occur in 10 samples. Thus, in the Example and Comparative Example 3 using glass (A), no cracks or cracks occurred in the reflector even after 2000 hours. On the other hand, in Comparative Examples 1 and 2, cracks occurred at 450 ° C. for 1000 hours, and at 550 ° C., half of the 10 samples were cracked or cracked in 50 hours. This is considered to be a result of removing the mechanical damage of the processed part in each embodiment of the present invention. Here, the removal of the mechanical damage in the processed part means that there are no chips, scratches or micro cracks of several μm or less existing on the surface due to the mechanical processing.

(5) Projection surface illumination (lx)
A 150 W ultra high pressure mercury lamp (UHP) was mounted on the reflectors of Examples 1 and 2 and Comparative Example 3 where cracking and cracking did not occur in the above lighting evaluation, and mounted on an actual liquid crystal projector. Measure the illuminance with an illuminometer that projects light of no image on the screen at a distance of 40 inches diagonally, and places the projection surface equally in 9 sections of 3 x 3 rows. Evaluated.

  When compared with the average of the illuminance of 9 sections, the measured value of each example exceeded the measured value of Comparative Example 3 by about 3 to 5%. In the case of using the reflecting mirror of each example, in the comparison with the same optical system, the difference in illuminance between the central section and the surrounding section is smaller than when using the reflecting mirror of Comparative Example 3, A relatively uniform projection illuminance up to the periphery was obtained. From this result, it was judged that the reflecting mirror according to the present invention using no crystallized glass was superior in reflecting surface accuracy.

In addition, although the said Example demonstrated the example using borosilicate glass, the amorphous glass used for this invention should just have a thermal expansion coefficient of the range of 30-45 * 10 < ^-7 > / degreeC. When the thermal expansion coefficient is lower than 30 × 10 ⁻⁷ / ° C., the moldability is deteriorated, and the yield is lowered in a reflector that requires a precise reflecting surface. On the other hand, if the thermal expansion coefficient exceeds 45 × 10 ⁻⁷ / ° C., the heat resistance is not sufficient and it cannot be combined with a high output light source. More preferably, the amorphous glass in the present invention has a thermal expansion coefficient in the range of 30 to 40 × 10 ⁻⁷ / ° C. Specifically, an aluminosilicate glass can be suitably used in addition to the borosilicate glass.

  The etching solution to be used is not limited to hydrofluoric acid but may be a mixed acid aqueous solution of hydrofluoric acid and sulfuric acid, and the concentration and etching treatment time may be appropriately adjusted according to the glass material of the reflector substrate and the etching amount. .

  In the present invention, by removing mechanical damage due to drilling, an amorphous glass is used, but there is an effect that a highly heat-resistant reflecting mirror that does not generate cracks or cracks can be obtained.

  In addition, since the reflecting mirror according to the present invention uses amorphous glass, there is no deformation or shrinkage caused by the crystallization process that is unavoidable in crystallized glass, and the accuracy of the reflecting surface can be made closer to the ideal phase. The projection illuminance is bright and the difference in illuminance between the central portion and the peripheral portion is small, that is, there is an effect that a reflecting mirror suitable for a projector light source can be obtained.

  In addition, in the case of amorphous glass that is transparent to infrared rays, unlike crystallized glass, a light source is emitted, passes through the multilayer film, and transmits infrared rays that are incident on the reflector substrate in a straight line without being scattered. There is an advantage that it is easy to take intensive heat dissipation measures.

The figure for demonstrating the process of manufacturing the reflective mirror by Example 1 of this invention. The figure for demonstrating the process of manufacturing the reflective mirror by Example 2 of this invention. The figure which shows the structure of the metal mold | die used for the press work of reflectors, such as the Example of this invention. The figure which shows the measurement result of the characteristic of each Example and comparative example of this invention. The figure which shows the result of the reflective surface three-dimensional shape measurement of the reflective base body by Example 1 (A) of this invention. The figure which shows the result of the reflective surface three-dimensional shape measurement of the reflective base body by the comparative example 3. FIG.

Explanation of symbols

1, 3, 4 ... Reflector,
11 ... planned opening part,
12 ... Neck part,
14 ... Dice,
15 ... Core drill,
17 ... opening part,
19 ... Liquid tank,
20 ... Etching solution 31 ... Neck part,
32 ... rear end of neck,
34 ... Cutter,
4 1 ... Bottom mold,
4 2 ... Plunger,

Claims (2)

Glass projector reflection made of amorphous glass having a thermal expansion coefficient of 30 to 45 × 10 ⁻⁷ / ° C. , and having a reflective surface portion that reflects light emitted from the light source and an aperture portion into which the light source bulb is inserted. A method for manufacturing a mirror, comprising: pressing a molten glass into a predetermined reflecting mirror shape having a planned opening portion at a position recessed from the reflecting surface portion by a die having a bottom die and a plunger; and The step of forming the hole part by removing the glass at the portion corresponding to the hole part of the reflector formed by this process, and the etching of the hole part formed by this process And a surface smoothing step for removing the mechanical damage of the processed part by smoothing the surface by applying the method. The etching amount of etching the openings machined surface to be removed by the process of claim 1 Projector glass reflector, wherein a is 30μm or more.

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