JP4476257B2 - Glass tube processing method, glass tube manufacturing method, and fluorescent lamp manufacturing method - Google Patents

Description

The present invention is a processing method of a glass tube, a method of manufacturing a manufacturing method and fluorescent lamp glass tube.

Among the fluorescent lamps, a cold cathode fluorescent lamp in which a phosphor layer is formed on the inner surface side of a tubular glass bulb and a cold cathode is provided as an internal electrode at both ends is suitable for reducing the diameter. For this reason, it is suitably used as a light source of a backlight unit that is required to be thin (downsized).
As a material of a glass tube used for a glass bulb of a small-diameter fluorescent lamp, conventionally, borosilicate glass that is excellent in terms of strength has been used.

  As the glass tube, a glass tube formed by a tube forming method such as the Danner method or the bellows method and cut into an appropriate length is used (Patent Documents 1 and 2). Further, the glass tube is slightly bent in a bow shape because of its manufacturing method. When a coating liquid containing a phosphor is applied while being curved to form the phosphor layer, unevenness occurs in the thickness of the finally obtained phosphor layer, which appears as uneven luminance when lit. Therefore, when used as a light source for a backlight that requires strict luminance uniformity, the curved glass tube is straightened. This correction is performed as follows.

First, a glass tube made of borosilicate glass (hereinafter referred to as “borosilicate glass tube”) to be corrected has an inner diameter sufficiently larger than the outer diameter and is held horizontally in a heating furnace. It is inserted into a straight tube made of quartz glass (hereinafter referred to as “quartz tube”). Then, while rotating the quartz tube around its axis, the temperature in the heating furnace is raised to such an extent that the surface of the borosilicate glass tube becomes 560 to 660 ° C. and held at this temperature for a certain time. By doing in this way, the borosilicate glass tube is gradually straightened by its own weight while rotating in the quartz tube. In view of the above principle, it seems that the surface of the borosilicate glass tube may be raised to the vicinity of 780 ° C., which is the softening point, but if it exceeds 660 ° C., the borosilicate glass tube in the quartz tube is on the contrary. Has been observed to be irregularly curved.
JP-A-8-283031 JP 2005-162532 A

By the way, the material of the glass tube used for the glass bulb constituting the cold cathode fluorescent lamp is mainly borosilicate glass from the viewpoint of strength as described above, but there is a demand for using soda glass from the viewpoint of cost. is there.
Soda glass is currently used as a bulb material in fluorescent lamps for general lighting such as indoor lighting. When used for general lighting, the brightness uniformity is not as severe as it is used for backlights, so the above-mentioned correction treatment is not performed. However, when used for backlights, this correction is similar to borosilicate glass. Processing is required.

  In addition, when using soda glass, it is necessary to reinforce a glass tube made of the soda glass (hereinafter referred to as “soda glass tube”). As this strengthening method, there is a method of raising the temperature of the glass tube to the vicinity of the softening point (hereinafter referred to as “heat strengthening treatment”). The glass tube manufactured by the above-mentioned tube drawing method has a minute scratch called a microcrack on its surface, and the microcrack is a main factor that weakens the strength of the glass tube. . Therefore, by raising the temperature of the glass tube to the vicinity of the softening point, the surface of the glass tube is softened, the microcracks are closed, and the strength is improved. In the borosilicate glass tube, since the material itself has sufficient strength, the heat strengthening treatment is not required (even if there is a microcrack).

However, for the purpose of cost reduction, in spite of using soda glass tubes, if a borosilicate glass tube is used, an unnecessary heat strengthening process will be added. It will be rejected.
In view of the above problems, an object of the present invention is to provide a glass tube processing method and a glass tube manufacturing method capable of reducing costs by using soda glass. Another object is to provide a method for manufacturing a fluorescent lamp using a glass tube produced by such a production how.

  In order to achieve the above object, a glass tube processing method according to the present invention is a glass tube processing method made of soda glass, made of a material having a softening point higher than that of soda glass, and held substantially horizontally. The glass tube is inserted into a cylindrical body and placed on the inner surface of the cylindrical body, and the glass tube is heated to a temperature lower by 60 ° C. to 120 ° C. than its softening point while rotating the cylindrical body around its axis. It is characterized by doing.

The method for producing a glass tube according to the present invention is a method for producing a glass tube made of soda glass, which is made of a material having a softening point higher than that of soda glass and is held in a substantially horizontal cylindrical body. The glass tube is heated to a temperature lower by 60 ° C. to 120 ° C. than its softening point while the cylindrical body is rotated around its axial center. .
  Moreover, the manufacturing method of the glass tube which concerns on this invention is a manufacturing method of the glass tube which consists of glass in the range whose content rate of sodium oxide is 5 mol% or more and 20 mol% or less, Comprising: Material with a softening point higher than the said glass The glass tube is inserted into a cylindrical body held substantially horizontally and placed on the inner surface of the cylindrical body, and the glass tube is rotated from its softening point while rotating the cylindrical body around its axis. It is characterized by heating to a temperature lower by 60 ° C to 120 ° C.
Furthermore, the fluorescent lamp manufacturing method according to the present invention is a fluorescent lamp manufacturing method using a glass tube manufactured by the glass tube manufacturing method, and includes a step of sealing both ends of the glass tube. It is characterized by that.

According to the above processing method and manufacturing method according to the present invention, the glass tube made of soda glass is heated at a temperature relatively close to the softening point, such as 60 ° C. to 120 ° C. lower than the softening point. The microcracks existing on the surface are closed, and the strength is improved (strengthened). In addition, in a glass tube made of soda glass, when placed in a rotating cylinder and heated to the above temperature, it is corrected without problems, without irregular bending as seen with borosilicate glass. It has been confirmed by experiments that That is, since the strengthening process and the straightening process can be performed in one step, it is economical, and the cost reduction effectiveness by using a glass tube made of soda glass can be secured.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a perspective view showing a part of a glass tube processing apparatus 10 used in one manufacturing process of a fluorescent lamp. The processing apparatus 10 is an apparatus for straightening a glass tube formed by a tube drawing method such as the Danner method or the bellows method (hereinafter referred to as “correction process”).
The glass tube used in the present embodiment is made of lead glass, lead-free glass, soda lime glass, or other soda glass. Soda glass is a glass material containing sodium oxide (Na ₂ O) in a range of 5 mol% to 20 mol%. In this example, lead-free glass (Na ₂ O content 5-12 mol%) is used, and the softening point is 680 ° C. The reason why lead-free glass is used is that natural environment protection is taken into consideration. However, even lead-free glass may contain lead as an impurity in the manufacturing process. Therefore, glass containing lead at an impurity level of 0.1 Wt% or less is also defined as lead-free glass.

The processing apparatus 10 includes a cylindrical body 14 having an inner diameter sufficiently larger than the outer diameter of the glass tube 12 to be processed and longer than the glass tube 12. The cylindrical body 14 is made of a glass material having a sufficiently higher softening point than the glass tube 12. In this example, the cylindrical body 14 is formed of quartz glass (softening point: 1000 ° C.).
The cylindrical body 14 is placed in a continuous furnace (not shown) while being held horizontally by a transport mechanism (not shown), and is transported through the continuous furnace. Further, the cylindrical body 14 is rotated in the direction of the arrow R around its axis by a rotation driving mechanism (not shown) while being conveyed by the conveying mechanism.

  When the glass tube 12 is inserted into the cylindrical body 14 outside the continuous furnace in a substantially parallel manner and placed on the inner surface of the cylindrical body 14, the glass tube 12 rotates following the rotating cylindrical body 14, It is carried into the continuous furnace, heated to a predetermined temperature while passing through the continuous furnace, and then carried out of the continuous furnace. During this time, the glass tube 12 is heated from room temperature to the predetermined temperature and maintained at the predetermined temperature for a predetermined time, and then naturally cooled again to room temperature. Here, the predetermined temperature is a temperature on the surface of the glass tube 12 (glass material) to be processed, and is a temperature lower by 60 ° C. to 120 ° C. (including 60 ° C., not including 120 ° C.) than the softening point. is there. In this example, since the softening point of the glass tube 12 is 680 ° C. as described above, the predetermined temperature (hereinafter referred to as “processing temperature”) X is in the range of 560 ° C. <X ≦ 620 ° C. In addition, even if it is a glass material which falls into the classification of the same soda glass, since the softening point takes different values depending on the component composition ratio and the like, the processing temperature is also different.

  The glass tube 12 is straightened by receiving the above-described processing by the processing device 10 (by passing through the manufacturing process), and the microcracks existing on the surface thereof are blocked to increase the strength. (It will be strengthened). If heating is performed at a temperature lower than the softening point by 60 ° C. to 120 ° C. (including 60 ° C. but not including 120 ° C.), correction and strengthening can be performed well, but the point of strengthening is taken into consideration. In this case, the processing temperature is preferably set in a range lower by 60 ° C. to 100 ° C. (including 60 ° C. and 100 ° C.) than the softening point.

  For the heat strengthening treatment, it is necessary to set the heating temperature (processing temperature) of the glass tube in the vicinity of the softening point. However, in the case of borosilicate glass, as described in [Background Art]. In addition, it was recognized that when the heat strengthening process was performed using the processing apparatus 10, the glass tube was bent irregularly. Thus, it has been expected that soda glass must also be subjected to a heat strengthening process separately from the correction process by the processing apparatus 10. However, in the case of soda glass, even if the temperature of the glass tube surface is raised to the vicinity of the softening point (a temperature lower by 60 ° C. to 120 ° C. than the softening point) in the processing apparatus 10, it does not bend, of course. The inventor of the present application has found that correction can be made. Of course, a heating strengthening process is also performed simultaneously with the correction process.

That is, since the straightening process and the heat strengthening process are performed at the same time, even if soda glass is used as the material of the glass tube, the initially estimated man-hour (heat strengthening process man-hour) does not increase. It has become possible to obtain a glass tube having a small diameter and a required strength suitable for a cathode fluorescent lamp.
Moreover, according to the processing apparatus 10, since the glass tube is heated while rotating, the surface is heated uniformly. As a result, the microcrack portion distributed on the surface of the glass tube is heated without any problem and is uniformly strengthened over the entire surface. Accordingly, the glass tube is strong against bending in all directions, and therefore, the handling in the manufacturing process of the backlight unit of the fluorescent lamp using the glass tube becomes easy. In addition, the fluorescent lamp can withstand vibration during transportation of the finished product (backlight unit).

The inventor of the present application conducted a destructive test on the glass tube subjected to the heat strengthening treatment and the untreated glass tube, and investigated the breaking strength of both.
The destructive test was performed by a three-point bending method using a universal testing machine and applying a concentrated load to the center of a glass tube supported by a span of 50 mm and applying a bending load to the glass tube as shown in FIG. The load value [kgf] when the glass tube broke (when it broke) was recorded as the breaking strength. The moving speed of the indenter for applying the concentrated load was 1 [mm / min].

In either case, a glass tube having an outer diameter of 4.0 [mm] and an inner diameter of 3.0 [mm] was used. For reference, a destructive test was also conducted on a glass tube made of borosilicate glass.
The types of glass tubes subjected to the test are as follows.
(I) Glass tube A0 ... material: soda glass, heat strengthening treatment: none (ii) Glass tube A1 ... material: soda glass, heat strengthening treatment: present (heating temperature 620 ° C.)
(Iii) Glass tube B0 ... material: borosilicate glass, heat strengthening treatment: none (iv) Glass tube B1 ... material: borosilicate glass, heat strengthening treatment: present (heating temperature 665 ° C.)
The glass tube A0 is not subjected to correction processing, and each of A1, B0, and B1 is subjected to correction processing. Needless to say, the heat strengthening treatment of the glass tube B <b> 1 is not performed using the processing apparatus 10.

Each of the above four types of glass tubes was prepared and tested. The test results are shown in FIG. In addition, what is shown in FIG. 3 is 50% intensity | strength in the Weibull determination with respect to various glass tubes.
The soda glass is subjected to a heat strengthening treatment by the processing apparatus 10 so that the breaking strength is improved from 6.1 to 8.3. When the breaking strength is 8.3 [kgf], the strength of the fluorescent lamp used as the light source of the backlight unit of the liquid crystal display device is satisfactory.

Originally, the glass tube made of borosilicate glass has sufficient strength, so even if it is used for a fluorescent lamp of a backlight unit, it is not subjected to heat strengthening treatment. As a result, it was found that the fracture strength decreased. The reason for this is currently unknown.
Moreover, the correction result of the glass tube which consists of soda glass processed using the processing apparatus 10 is demonstrated.

Glass tube before processing (glass tube S0), glass tube heat treated at 640 ° C. (glass tube S1), glass tube heat treated at 620 ° C. (glass tube S2), and glass tube heat treated at 560 ° C. (glass Five tubes S3) were prepared for each.
Each glass tube has an outer diameter of 4.0 [mm], an inner diameter of 3.0 [mm], and a total length of 950 [mm].

And the straight tube degree was investigated about each glass tube. The investigation method is shown in FIG.
With the glass tube supported at two points at positions 50 mm from both ends, the maximum radial deflection d when the glass tube was rotated once was measured at three locations. The measurement was performed from one end of the glass tube at positions of 275 mm (position PL), 475 mm (position PC), and 675 mm (position PR), respectively.

The measurement results are shown in FIG. In the drawing, “maximum” and “minimum” indicate the maximum value and the minimum value of the shake d among the five lines. Further, “average” is an average value of five of each. “Σ” is the standard deviation of the measured value. In either case, the unit is mm.
Here, the problem is the maximum value. If this maximum value is 0.1 mm or less at any measurement position (PL, PC, PR), the necessary brightness uniformity for the backlight unit can be obtained when the phosphor layer is formed. I know.

As shown in FIG. 5, the maximum value in the glass tube S0 before processing is significantly higher than 0.1 mm, whereas in the glass tube S2 and the glass tube S3, the maximum value is significantly lower than 0.1 mm, which is good. It can be seen that proper correction has been made. Although detailed data is omitted, both the glass tube S2 and the glass tube S3 have satisfactory breaking strength.
The maximum value of the glass tube S1 is not much different from the maximum value of the glass tube S0 before processing, or is increased depending on the measurement position. This indicates that even soda glass cannot be corrected correctly if the heating temperature (processing temperature) is too close to the softening point.

FIG. 6 is a longitudinal sectional view showing a schematic configuration of a cold cathode fluorescent lamp 20 manufactured using the glass tube 12 made of the soda glass.
The cold cathode fluorescent lamp 20 has a glass bulb 22 in which both ends of a glass tube are sealed. The total length of the glass bulb 22 is 950 mm, the outer diameter is 4 mm, and the inner diameter is 3 mm (thickness is 0.5 mm). In addition, you may change the full length in the range of 300-1500 mm. According to the present invention, as described above, an excellent strengthening treatment is performed and the film is strong against bending. Therefore, the present invention is particularly suitable for a long glass bulb (glass tube) of 900 to 1500 mm. Moreover, you may change the internal diameter of a glass bulb in the range of 1.0-10.0 mm, and thickness 0.2-0.6 mm.

Further, inside the glass bulb 22, a mixed gas (not shown) composed of about 2 mg of mercury (not shown) and plural kinds of rare gases such as argon (Ar) gas and neon (Ne) gas is enclosed. . The mixed rare gas in this example is sealed at a pressure of 50 Torr with a mixing ratio of 10% argon and 90% neon.
Lead wires 24 and 26 are supported at both ends of the glass bulb 22. The lead wires 24 and 26 are connection lines of internal lead wires 24A and 26A made of dumet wires and external lead wires 24B and 26B made of nickel, respectively. Both ends of the glass tube are hermetically sealed with internal lead wires 24A and 26A. Both the inner lead wires 24A and 26A and the outer lead wires 24B and 26B have a circular cross section. The inner lead wires 24A and 26A have a wire diameter of 1.0 mm and a total length of 3.0 mm, and the outer lead wires 24B and 26B have a wire diameter of 0.8 mm and a total length of 3.0 mm.

  Electrodes 28 and 30 are joined to the inner lead wires 24A and 26A on the inner side of the glass bulb 22 by laser welding or the like, respectively. The electrode 28.30 is a so-called hollow electrode having a bottomed cylindrical shape, and is obtained by processing a niobium rod. The reason why the hollow electrodes are used as the electrodes 28 and 30 is that they are effective in suppressing sputtering in the electrodes caused by the discharge when the lamp is lit (for details, see JP-A-2002-289138). ).

A protective film 32 is formed on the inner surface of the glass bulb 22, and a phosphor layer 34 is formed on the protective film 32.
The protective film 32 is made of SiO ₂ (silica). The protective film 32 is provided to block sodium that is a component of the glass bulb from eluting into the discharge space, and to prevent the mercury from being consumed by the reaction between the sodium and mercury.

The phosphor layer 32 includes blue phosphor particles that emit blue light, green phosphor particles that emit green light, and red phosphor particles that emit red light, and emits white light as a whole.
As mentioned above, although this invention was demonstrated based on embodiment, of course, this invention is not restricted to an above-described form, For example, it can also be set as the following forms.
(1) In the above embodiment, a cold cathode fluorescent lamp (CCFL) has been described as an example. However, the present invention is not limited to this and can be applied to a so-called external electrode fluorescent lamp. The external electrode fluorescent lamp is, for example, a dielectric barrier discharge fluorescent lamp (EEFL: External Electrodes Fluorescent) in which, instead of the internal electrode, an external electrode is provided on the outer periphery of the glass bulb at both ends of the glass bulb and the glass tube wall is used as a capacitance. Lamp).

When applied to an external electrode fluorescent lamp, the dark startability particularly required as the light source of the backlight unit is improved because the glass bulb is made of soda glass. That is, since soda glass contains a large amount of sodium oxide (Na ₂ O), the sodium (Na) component elutes on the inner surface of the glass bulb over time. This is because sodium has a low electronegativity, and sodium eluted at the inner end of the glass bulb (without a protective film) is considered to contribute to the improvement of the dark startability.

The present invention is also applicable to a hot cathode fluorescent lamp having a hot cathode as an internal electrode.
(2) Although the protective film is formed of silica (SiO ₂ ) in the above embodiment, it may be formed of alumina (Al ₂ O ₃ ).

  The processing method of the glass tube which concerns on this invention can be utilized suitably for the correction | amendment and reinforcement | strengthening process of the comparatively thin diameter glass tube used for the fluorescent lamp used as a light source of a backlight unit, for example.

It is a perspective view which shows a part of processing apparatus for a heat strengthening process. It is a figure which shows the method of a fracture strength test. It is a figure which shows the result of a fracture strength test. It is a figure which shows the measuring method of a straight pipe degree. It is a figure which shows the measurement result by the measuring method shown in FIG. It is a longitudinal cross-sectional view of the cold cathode fluorescent lamp which concerns on embodiment.

Explanation of symbols

12 Glass tube 14 Cylindrical body 20 Cold cathode fluorescent lamp 22 Glass bulb

Claims (4)

A method of processing a glass tube made of soda glass,
Made of a material with a softening point higher than soda glass, inserted into the cylindrical body and inserted into the cylindrical body held substantially horizontally, while rotating the cylindrical body around its axis, A method of processing a glass tube, wherein the glass tube is heated to a temperature lower by 60 ° C. to 120 ° C. than its softening point. A method of manufacturing a glass tube made of soda glass,
Made of a material with a softening point higher than soda glass, inserted into the cylindrical body and inserted into the cylindrical body held substantially horizontally, while rotating the cylindrical body around its axis, A method for producing a glass tube, comprising heating the glass tube to a temperature lower by 60 to 120 ° C. than its softening point. A method for producing a glass tube made of glass having a sodium oxide content of 5 mol% or more and 20 mol% or less,
Made of a material with a softening point higher than that of the glass, the glass tube is inserted into a cylindrical body held approximately horizontally and placed on the inner surface of the cylindrical body, while rotating the cylindrical body around its axis, A method for producing a glass tube, comprising heating the glass tube to a temperature lower by 60 to 120 ° C. than its softening point. A method for producing a fluorescent lamp using a glass tube produced by the method for producing a glass tube according to claim 2 or 3,
A method for manufacturing a fluorescent lamp, comprising: sealing both ends of the glass tube.

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