JP2007005035A - Manufacturing method of lamp, lamp, and fluorescent lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of lamp capable of forming a phosphor film with little unevenness of thickness even on a longitudinal glass tube. <P>SOLUTION: The phosphor film is formed on an inner face of the glass tube 22 through a process of painting suspension 36 containing phosphor on the inner face of the glass tube 22, and a process of drying the painted suspension 36 by blowing drying air 38 in the glass tube 22. On the painting process, the suspension 36 filled in the glass tube is exhausted by turning the other end of the glass tube 22 downward, and on the drying process, the drying air 38 is started to blow at least 30 seconds after the start of exhaustion of the suspension 36. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a lamp manufacturing method, a lamp, and a fluorescent lamp having a coating film formed by drying a suspension coated on the inner surface of a glass tube on the inner surface of the glass tube.

As a lamp having a coating film on the inner surface of the glass tube through a coating process for applying the suspension to the inner surface of the glass tube and a drying process for drying the applied suspension, for example, there is a cold cathode fluorescent lamp. . The suspension in this case is for a phosphor film. For example, in the coating process, after the suspension is filled into a straight tubular glass tube, the lower end of the glass tube faces downward, that is, standing upright. In the state, the suspension is discharged from the lower end of the glass tube, and in the drying process, air is blown into the glass tube coated with the suspension (for example, Patent Documents 1 and 2). Note that the air is often temperature-controlled air.
JP-A-4-280031 JP 2001-23518 A

The cold cathode fluorescent lamp described above is, for example, used as a light source in the field of backlights of liquid crystal display devices. In this field, as the display screen becomes larger, the length of the cold cathode fluorescent lamp is increased. Strong demand.
The inventors have formed a phosphor film using the above method in response to a request for lengthening, and the difference in thickness of the phosphor film between the upper end side and the lower end side of the lamp is very large. There arises a problem that the thickness unevenness of the phosphor film is large. This problem may occur similarly when the glass tube to which the suspension is applied is long (the ratio between the total length of the glass tube and the inner diameter of the glass tube is large).

  The present invention has been made in view of the above problems, and provides a lamp manufacturing method and a lamp capable of reducing the thickness unevenness of a coating film even with a long glass tube. For the purpose.

  In order to achieve the above object, a lamp manufacturing method according to the present invention has a coating film formed by drying a suspension applied to the inner surface of a glass tube by blowing air from one end of the glass tube. In the production method, the suspension is applied to the inner surface of the glass tube by discharging the suspension filled in the glass tube with the other end of the glass tube facing downward. The air is blown from one end of the glass tube after at least 30 seconds have elapsed from the start of discharge of the suspension filled in the glass tube.

The “lamp” here refers to a lamp having a coating film obtained by applying a suspension to the inner surface of a glass tube and drying the suspension. An example of such a lamp is a fluorescent lamp. Examples of the fluorescent lamp include a cold cathode fluorescent lamp, a hot cathode fluorescent lamp, and an external electrode fluorescent lamp. The suspension includes, for example, a phosphor film and a protective film.
On the other hand, when the suspension of the air filled in the glass tube starts to be discharged from the air, the liquid level of the suspension starts from the discharge of the glass tube. After the time required to reach the lower end of the tube has elapsed, it is blown from the one end.

Further, the glass tube is characterized in that it rotates around the axis of the glass tube as the center of rotation after discharging the suspension. The rotation of the glass tube here is performed continuously before the suspension is discharged, when the suspension is started after the suspension is discharged, and when the suspension is discharged. This includes the case where it is performed only after discharging.
Further, during the discharge of the suspension, the air flow of air within a range in which the discharge of the suspension in the glass tube is promoted and the liquid level of the suspension that is descending in the glass tube stops once during the descent. It is characterized by being blown.

On the other hand, in order to achieve the above object, the lamp according to the present invention is manufactured by the above manufacturing method, the coating film is a phosphor film, and the thickness of the phosphor film has a design value of S (μm). The film thickness (μm) at a predetermined position is within the range of ± 3 (μm) with respect to the design value S.
The “design value” here is, for example, a film thickness that increases conversion efficiency for converting ultraviolet rays emitted from a luminescent material (for example, mercury) into a predetermined wavelength.

Furthermore, the “predetermined position” referred to here does not indicate an arbitrary position, but includes at least a position within a total of three areas, that is, an end area (15 mm from the end) on both sides of the glass tube and a central area. Further, it is preferable to include a position in a total of five regions including an intermediate region between the two end regions and the central region.
Note that the film thickness in each region is not simply indicated by a measurement result, but is indicated by an average value obtained by measuring a plurality of points, for example, four points at equal intervals in the circumferential direction.

On the other hand, in order to achieve the above object, a lamp according to the present invention comprises a phosphor film on the inner surface of a glass tube, and the glass tube has a length of 500 mm or more and an inner diameter of 2 mm or more and 3 mm or less,
Regarding the film thickness of the phosphor film, when the design value is S (μm), the film thickness (μm) at a predetermined position is within a range of ± 3 (μm) with respect to the design value S. It is characterized by that.

When the lamp manufacturing method according to the present invention is used, since the thickness of the suspension applied to the glass tube can be made substantially uniform before drying, the thickness unevenness of the obtained coating film is reduced. .
The lamp according to the present invention can make the thickness of the coating film uniform. Further, when a phosphor film is used as the coating film, the thickness of the phosphor film can be made uniform, so that the luminance unevenness of the entire lamp can be reduced. Further, when a protective film is applied to the coating film, the transmittance of the light converted by the phosphor layer can be made constant, so that the luminance unevenness of the entire lamp can be reduced.

Hereinafter, a cold cathode fluorescent lamp manufactured using the manufacturing method according to the present invention and a backlight unit using the cold cathode fluorescent lamp will be described as embodiments with reference to the drawings.
<Configuration of backlight unit>
First, the configuration of the backlight unit will be described.
FIG. 1 is a schematic perspective view showing the configuration of the backlight unit. In FIG. 1, a part of the front panel 16 is cut away to show the internal structure of the backlight unit 1.

The backlight unit 1 is for a liquid crystal display device. As shown in FIG. 1, the backlight unit 1 has a straight tubular cold cathode fluorescent lamp (hereinafter referred to as “lamp”) 20 and an opening having the lamp 20. A housing 10 to be housed and a translucent front panel 16 covering an opening of the housing 10 are provided.
The backlight unit 1 is a so-called direct type, and uses a plurality of lamps 20, here, 14 lamps 20. The lamps 20 are electrically connected in parallel, and the configuration of the lamps 20 will be described later.

The housing 10 is made of, for example, polyethylene terephthalate (PET) resin, and a reflective surface formed by depositing a metal such as silver is formed on the inner surface 11 thereof. The front panel 16 is configured by depositing a diffusion plate 13, a diffusion sheet 14, and a lens sheet 15.
The diffuser plate 13 and the diffuser sheet 14 scatter and diffuse the light emitted from each lamp 20, and the lens sheet 15 aligns the scattered and diffused light in the normal direction of the sheet 15. is there. The light emitted from each lamp 20 by these sheets 13, 14, 15 irradiates the front uniformly from the entire surface (light emitting surface) of the front panel 16.

<Lamp configuration>
The structure of the lamp 20 will be described with reference to FIG. FIG. 2 is a partially cutaway perspective view showing a schematic configuration of the lamp 20.
The lamp 20 uses, for example, a glass tube 22 having a substantially circular cross section. The electrodes 24 and 26 are sealed at both end portions 22a and 22b of the glass tube 22, and, for example, mercury is contained therein. In addition, a predetermined amount of rare gas (for example, argon, neon) or the like is enclosed. Note that when the electrodes 24 and 26 are sealed in the glass tube 22 and mercury or the like is sealed therein, the glass tube becomes a discharge vessel.

The electrodes 24 and 26 include bottomed cylindrical electrode bodies 24a and 26a and electrode bars 24b and 26b attached to the bottoms of the electrode bodies 24a and 26a. Sealed to 22a and 22b. In FIG. 2, the bead glass on the electrode 26 side is not shown because of the configuration of the drawing.
A protective film 32 is formed on the inner surface of the glass tube 22, and a phosphor film 34 is further formed on the protective film 32. The protective film 32 is for preventing the glass tube 22 and mercury enclosed in the glass tube 22 from reacting. The phosphor film 34 contains a phosphor, and the phosphor converts ultraviolet rays emitted from mercury into visible light.

<Method for forming phosphor film>
Next, a method for forming the phosphor film 34 on the inner surface of the glass tube 22 will be described. Since the protective film 32 can be formed by the same method as the method of forming the phosphor film 34, the description thereof is omitted here. In addition to the step of forming the phosphor film 34 (protective film 32), the lamp 20 is manufactured by a step of sealing the electrodes 24 and 26 to the glass tube 22, a step of sealing mercury or the like inside the glass tube 22, If necessary, there is a step of deforming the glass tube into a predetermined shape, etc., but these steps are the same as in the prior art, and the description thereof is omitted.

The phosphor film is formed by a coating process in which a suspension containing phosphor is applied to the inner surface of the glass tube, a film surface uniformizing process in which the thickness of the applied suspension is uniform, and a film surface is uniform. And a drying step of drying the formed suspension.
Here, the coating process is performed through a filling process for filling the suspension for the phosphor film into the glass tube and a discharging process for discharging the filled suspension. In this form, it starts immediately after the suspension filled in the glass tube starts to be discharged.

FIG. 3 is a diagram for explaining a method of forming a phosphor film.
First, a glass tube 22 and a suspension 36 containing a phosphor are prepared. As the suspension 36, for example, a mixture of a phosphor, a binder, a binder, and an organic solvent is used. Now, each step will be described.
(1) Filling Step In this filling step, as shown in FIG. 3A, first, the glass tube 22 is erected so that its axis is vertical, and then the lower end opening of the glass tube 22 is suspended. It is immersed in the turbid liquid 36 and the suspension 36 is sucked into the glass tube 22. The suspension 36 is sucked by, for example, sucking air inside the glass tube 22 from the upper end opening of the glass tube 22 to make the inside of the glass tube 22 have a negative pressure.

(2) Discharge process In this discharge process, the suspension 36 is sucked to a predetermined position inside the glass tube 22, that is, when the liquid level of the suspension reaches a predetermined position, the suction is stopped, and the glass The lower end opening of the tube 22 is pulled up from the suspension 36, and the suspension 36 is discharged from the lower end opening of the glass tube 22, as shown in FIG. The suspension 36 is discharged, for example, by opening the upper end opening of the glass tube 22 and utilizing the weight of the suspension 36 (by natural fall). As a result, the suspension 36 is applied to the inner surface of the glass tube 22. It is preferable that the glass tube 22 be rotated after the suction of the suspension is stopped.

(3) Film surface homogenization process In this film surface homogenization process, as shown in FIG. 3C, after the discharge of the suspension 36 is completed, the glass tube 22 is rotated about its axis. While rotating, the outer surface of the glass tube 22 is heated. Here, a coil heater 37 is used for heating the glass tube 22. The reason for heating the glass tube 22 is to apply heat to the portion where the coating film is formed thick to reduce the viscosity of the suspension in that portion, thereby promoting uniform film surface.

Further, the time for this film surface homogenization step is from the start of discharging the suspension from the glass tube until several tens of seconds have elapsed, and here, after the suspension is completely discharged. . The time when the suspension is completely discharged from the glass tube is the time when the liquid level of the suspension in the glass tube reaches the lower end of the glass tube.
(4) Drying step In this drying step, as shown in FIG. 3D, a predetermined temperature is controlled from the upper end opening of the glass tube 22 while rotating the glass tube 22 in the same manner as the film surface equalizing step. Then, the drying air 38 is introduced to dry the suspension 36 applied to the inner surface of the glass tube 22.

(5) Summary When the drying process is completed, a phosphor film is formed on the inner surface of the glass tube 22. To be precise, after completion of the drying process, for example, through a process of baking at 660 (° C.), the formation of the original phosphor film is completed (changes in the film thickness of the coating film before and after baking) Does not occur).
And the process of providing the electrodes 24 and 26 in the edge part of the glass tube 22, enclosing rare gas etc. inside the glass tube 22, or changing a glass tube into a predetermined shape if necessary is performed. Thus, the cold cathode fluorescent lamp 20 is completed.

<Example>
Specific examples of the method for forming the phosphor film described above will be described. The specific examples, numerical values, and the like described here are described as embodiments of the invention, and the present invention is not limited to the specific examples, numerical values, and the like.
The glass tube 22 used in the above description is made of borosilicate glass. The glass tube 22 has an inner diameter Di of 2.0 (mm), an outer diameter Do of 3.0 (mm) (see FIG. 2), a length of 1075 (mm), and a phosphor film. The area to be done (the length of the glass tube) is 1000 (mm). Needless to say, the thickness of the glass tube 22 is 0.50 (mm).

The phosphor film 34 to be formed is for a three-wavelength region having a color temperature of 10,000 (K). For example, europium-activated yttrium oxide (Y ₂ O ₃ : Eu ³⁺ ) is used for red, and cerium terbium is used for green. It contains activated rare-earth phosphors of activated lanthanum phosphate (LaPO ₄ : Ce ³⁺ , Tb ³⁺ ) and europium-activated barium magnesium aluminate (BaMgAl ₁₆ O ₂₆ : Eu ²⁺ ) in blue.

Further, as the organic solvent, for example, a base of butyl acetate, as a binder, for example, nitrocellulose, as a binder, for example, boron, calcium phosphate, barium, etc., the specific gravity of the suspension 36 is 1.46. In the Ford Cup viscometer with an inner diameter of 2.6 (mm), the viscosity at this time was 130 (sec) at 25 (° C.).
After the suspension having the above structure is filled in the glass tube, the upper end of the glass tube is opened and the suspension is discharged. After opening the upper end, the suspension starts to be discharged using the natural fall of the suspension, and the time until the liquid level of the suspension reaches the lower end of the glass tube is about 45 (seconds). In this embodiment, the film surface uniformizing time is longer than 45 seconds. Specifically, it is from the start of discharging the suspension until about 100 seconds have passed. This time corresponds to about twice the time (45 seconds) from when the suspension is discharged until the liquid level reaches the lower end.

That is, after filling the glass tube with the suspension, the drying air is blown in 100 seconds after the suspension is started to be discharged. Further, the rotation speed of the glass tube 22 in the film surface homogenization step is 60 (rotation / min), and the glass tube 22 is heated from the outside so that the outer peripheral temperature of the glass tube 22 is 42 (° C.). Is set.
The temperature of the drying air 38 is controlled within the range of 25 (° C.) to 45 (° C.), and further 30 (° C.) to 40 (° C.), and the flow rate is the inner diameter of the glass tube 22. Per unit area of Di, it is set within the range of 7 (ml / (min · mm ² )) to 162 (ml / (min · mm ² )), for example, 40 (ml / (min · mm ² )). Yes. Here, the reason why the temperature of the drying air 38 is set to 30 (° C.) to 40 (° C.) is to dry the applied suspension earlier at a high temperature.

Further, the air volume of the drying air is within a range of 7 (ml / (min · mm ² )) to 162 (ml / (min · mm ² )) per unit area of the inner diameter Di of the glass tube 22, for example, 40 The reason why it is set to (ml / (min · mm ² )) is to suppress the unevenness of the film thickness (to make the film thickness uniform) and to shorten the drying time as much as possible.
<About phosphor film thickness and film surface uniformity time>
FIG. 4 is a diagram showing the film thickness of the phosphor film at a predetermined position of the glass, and FIG. 5 shows the relationship between the film surface homogenization time and the film thickness difference of the phosphor film. The film thickness shown in FIG. 4 was measured at four locations in the circumferential direction of the glass tube at a total of six positions of 15, 240, 470, 693, 806, and 919 (mm) with reference to the upper end of the glass tube. The average film thickness difference shown in FIG. 5 is the difference between the minimum and maximum film thickness measured at each point of the glass tube.

The film surface homogenizing time shown in FIGS. 4 and 5 is 24 seconds, in which the phosphor film is dried by blowing drying air before the liquid level of the suspension reaches the lower end of the glass tube. This is the time conventionally employed for glass tubes having a length of, for example, 750 (mm) or less.
It can be seen from FIGS. 4 and 5 that the film thickness difference of the phosphor becomes smaller when the film surface uniformizing time is lengthened. That is, the film thickness uniformity time is 60 (sec) corresponding to about twice the time in the conventional method, and 96 (sec) corresponding to about four times the time in the conventional method. The difference is getting smaller.

As described above, the longer the film surface homogenization time, the smaller the film thickness difference of the phosphor film. At the end of the application of the suspension, the phosphor film is placed on the upper part of the glass tube due to the surface tension of the suspension. Is applied (adhered), but due to the uniform film surface, the adhering suspension flows out due to the surface tension, resulting in a more uniform film thickness.
Here, when the state at the time of discharge of the suspension in the glass tube is briefly described, the suspension is temporarily stopped before the liquid level of the suspension descending in the glass tube reaches the lower end of the glass tube. This is considered to be caused by the balance between the surface tension and the weight of the coating liquid.

The time from the start of the suspension discharge until the liquid level stops temporarily (this time is also referred to as “balance time”) is about 45 (sec). The film surface homogenization time is 60 (sec) after 15 (sec) from the balance time, and 96 (sec) is about 50 (sec) after the balance time.
<Discussion>
(1) About discharge speed The inventors have found that the film thickness difference of the phosphor film can be reduced, that is, the film thickness can be uniformly applied, by taking a long film surface uniformization time. Next, the inventors considered that the reason why the difference in film thickness became smaller was that the discharge of the suspension ended (the liquid level of the suspension) because a predetermined time had passed since the suspension began to be discharged. It was confirmed by a test whether or not a predetermined time had elapsed since the end of That is, it was confirmed by a test whether the suspension discharge start time was a reference or the suspension discharge end time was a reference.

This test will be described below.
In the test, the drying air was blown immediately after the suspension was discharged in about 50 seconds corresponding to the free fall described above, and the suspension was about twice as fast as the free fall. Three types of coating conditions: when drying air is blown immediately after the air is discharged, and when drying air is blown immediately after the suspension is discharged at about 1/2 times the speed of free fall The thickness difference of the phosphor film was measured.

That is, the film surface homogenization time under the above three types of application conditions is the time when the suspension discharge is completed, and the elapsed time after the suspension discharge is “0”. The suspension discharge speed is adjusted by controlling the inside of the glass tube to a negative pressure.
FIG. 6 is a diagram showing the elapsed time from the suspension discharge (start) to the end time and the film thickness difference between the phosphor films. Moreover, FIGS. 7-9 is a figure which shows the film thickness measurement result in the predetermined position of the glass tube in each elapsed time of FIG.

As can be seen from FIG. 6, the discharge time becomes longer, that is, the film thickness difference of the phosphor film becomes smaller in the order of elapsed time 25 (sec), 50 (sec), 100 (sec). This has the same tendency as the result shown in FIG.
In particular, the elapsed time in FIG. 6 and the elapsed time in FIG. 5 are substantially the same value, specifically, the elapsed time in FIG. 5 is 24 (sec), the elapsed time in FIG. 6 is 25 (sec), FIG. The elapsed time in FIG. 6 is 60 (sec), the elapsed time in FIG. 6 is 50 (sec), the elapsed time in FIG. 5 is 96 (sec), and the elapsed time in FIG. 6 is 100 (sec). The thickness difference is the same or close. Note that the tests in FIG. 5 and FIG. 6 differ from each other in the apparatus for performing the coating process and the drying process, and it is considered that a certain degree of variation has occurred in the film thickness difference.

Therefore, the thickness difference of the phosphor film in the glass tube is not related to the passage of time from the end of the suspension discharge, and is not much related to the suspension discharge speed (currently speculated). )), It is considered that if the time from the start of discharging the suspension elapses for a predetermined time, the suspension becomes smaller. That is, the reference is the time from the start of the suspension discharge.
(2) Confirmation test The inventors are able to reduce the difference in the thickness of the phosphor film if a predetermined time elapses from the start of discharging the suspension through an experiment for adjusting the discharging time of the suspension. I found. In order to further confirm this, when drying air is blown when about 75 (sec) has elapsed after the suspension has been discharged under the condition that the discharging time in FIG. 6 is 25 (sec), that is, The film thickness distribution of the phosphor film of the glass tube was measured when 100 (sec) had elapsed since the discharge was started.

FIG. 10 is a diagram showing the thickness distribution of the phosphor film when the drying air is blown when 100 (sec) has elapsed after the suspension discharge speed is changed and the suspension discharge is started. .
Speed 2 in FIG. 10 is a measurement result when the discharge speed of the suspension is twice the discharge speed due to the natural drop of the suspension (the discharge time is half of the discharge time due to the natural drop). There is an elapsed time of about 75 (sec).

On the other hand, the speed 1/2 is a measurement result when the discharge speed of the suspension is 1/2 times the discharge speed due to the natural drop of the suspension (the discharge time is twice the discharge time due to the natural drop) There is no elapsed time after discharge, and drying air is blown in immediately.
As shown in FIG. 10, if the elapsed time from the start of discharge of the suspension is the same, for example, even if the discharge speed is different, the difference in thickness of the phosphor film is substantially the same, and The distribution is similar to that of the body membrane.

For this reason, in order to make the thickness of the phosphor film uniform, it is only necessary to set not only the elapsed time after the suspension is discharged but also the elapsed time after starting the suspension discharge to a predetermined time or more. it is conceivable that.
As described above, the present invention has been described based on the embodiments. However, the content of the present invention is not limited to the specific examples shown in the above embodiments, and for example, the following modifications are further provided. Can be implemented.

1. About Suspension Although the suspension in the above embodiment is for the phosphor film 34, other suspension may be used. Other suspensions include, for example, a protective film 32. The protective film 32 is made of, for example, yttria (Y ₂ O ₃ ) fine particles. Instead of yttria, titania (TiO ₂ ), ceria (CeO ₂ ), magnesia (MgO), lanthanum (La ₂ O ₃ ), alumina (Al ₂ O ₃ ), or a mixture of two or more of these Is used.

As the organic solvent, for example, the base of butyl acetate may be used as the phosphor film suspension in the embodiment, and, for example, nitrocellulose may be used as the binder. The suspension described in the embodiment Although the liquid is for a predetermined phosphor film, other suspensions may be used when forming another phosphor film. In this case, since the viscosity of the suspension, the composition ratio of the suspension, etc. also change, the time from the start of discharging the suspension until the air is blown may be slightly changed. Therefore, the effect that the film surface of the suspension applied to the inner surface of the glass tube is made uniform can be obtained by leaving the predetermined time.

2. Regarding the application process In the above embodiment, the glass tube in the discharge process and the application process was in an upright state, but at least when the suspension in the glass tube is discharged, the glass tube may be installed upright, For example, the posture of filling the suspension into the glass tube may be such that the axis of the glass tube is inclined with respect to the vertical direction.

3. About the discharge process In the discharge process of the embodiment, the discharge of the suspension is promoted from the upper end of the glass tube during the discharge of the suspension, that is, when the liquid level of the suspension is lowered in the glass tube. Therefore, air may be blown. At this time, the amount of air blown is preferably 13 (ml / (min · mm ² )) or less.

If the blowing amount is more than 13 (ml / (min · mm ² )), drying is promoted and it becomes difficult to make the film thickness uniform.
4). About the drying air (1) About the direction of air In the embodiment, the drying air 38 flows downward from the upper end opening of the glass tube 22. For example, the drying air 38 flows upward from the lower end opening of the glass tube. Also good. That is, drying air in the direction opposite to the direction in which the suspension flows may be allowed to flow.

The time until blowing the drying air is good after 60 (sec) from the start of discharging the suspension. This is because when the phosphor film (coating film) is formed under these conditions, the film thickness difference can be controlled within 6 (μm).
Further, the time until blowing the drying air is more preferably after 100 (sec) from the start of discharging the suspension. This is because if the phosphor film is formed under these conditions, the difference in film thickness can be controlled within 4 (μm).

Furthermore, by adjusting the viscosity of the suspension, the diameter of the glass tube, the heater heating setting until blowing dry air, the blowing condition of air during drying (so-called air profile), etc., 30 seconds from the start of the suspension discharge If it passes after (sec), it can control within 6 (micrometers) of film thickness differences.
(2) Airflow In the embodiment, the air flow for drying in the drying step is constant from the start to the end of drying, but the air flow rate may be changed during the drying step.

For example, the drying air may be increased stepwise or decreased stepwise. However, since the conductance changes as the total length of the glass tube increases, it is necessary to set the flow rate based on the measured value of the flow rate at the end of the glass tube. The drying speed can be controlled, that is, the film thickness can be controlled by adjusting the drying air.
Also, since the viscosity of the suspension is considered to be lower than that during the injection of the suspension due to the heat during drying, the flow rate gradually increases (linear, curvilinear, stepwise). It is desirable to let them.

FIG. 11 shows the film thickness distribution when the air volume is increased stepwise.
In addition, this FIG. 11 is the same as the application | coating conditions shown in FIG. 9, and only changed the air volume of the drying air in a drying process, and the case where the air volume is increased in steps (FIG. 11). When the air volume is not changed (FIG. 9), the effect when the air volume is changed can be seen.
The stepwise increase in the air volume is performed in the order of 80 (ml / min), 100 (ml / min), and 120 (ml / min), and the blowing time for each air volume is about 7 minutes each.

  In FIG. 11, the thickness difference of the phosphor film after the formation is 4 (μm), whereas in FIG. 9, the thickness difference is 5 (μm). Comparing FIG. 9 and FIG. 11, it can be seen that the film thickness difference is smaller in FIG. That is, it can be seen that a uniform phosphor film can be obtained by increasing the air volume stepwise. Therefore, it is considered that the thickness of the phosphor film can be made more uniform than when the air volume is constant by optimizing the air for drying such as gradually increasing the air volume of the drying air.

5. Regarding the shape of the discharge vessel In the embodiment, the shape of the discharge vessel was substantially the same as the shape of the glass tube on which the suspension was applied. For example, after forming the coating film by drying the suspension, It may be processed (deformed) into a shape other than a straight tube, for example, a shape such as “U” or “W”. Furthermore, it may be processed into an annular shape (deformed).

6). Regarding the lamp In the above embodiment, the case where the phosphor is applied to the glass tube for the cold cathode fluorescent lamp has been described. However, other lamps such as a fluorescent lamp, a bulb-type fluorescent lamp, a compact fluorescent lamp, etc. The manufacturing method according to the present invention can be applied to a cathode fluorescent lamp, and also to an external electrode fluorescent lamp arranged on the outer periphery of both ends of a glass tube.

7). Regarding inner diameter and length of glass tube In the above embodiment, the inner diameter of the glass tube was 2.0 (mm), the outer diameter was 3.0 (mm), and the length was 1075 (mm). Not what you want. However, the effects of the present invention are remarkably exhibited when the inner diameter of the glass tube is 10 (mm) or less and the length is up to 2500 (mm).

  Regarding the inner diameter of the glass tube, further, when it becomes 3.0 (mm) or less, the viscosity of the suspension changes due to the influence of the ambient temperature of the glass tube, and in the conventional coating method, However, it is difficult to suppress the film thickness unevenness (the film thickness difference is 6 μm or less) within ± 3 (μm), but in the present invention, the film thickness unevenness can be suppressed within the above range. That is, the present invention is particularly effective when the inner diameter of the glass tube is 3.0 (mm) or less.

When the inner diameter of the glass tube becomes smaller than 2.0 (mm), it is necessary to lower the viscosity of the suspension in order to efficiently discharge the suspension in the glass tube. It becomes difficult.
In the manufacturing method according to the present invention, air is blown into the glass tube after a predetermined time has elapsed since the discharge of the suspension was started. That is, the liquid level of the suspension is made uniform by leaving it for a predetermined time. This homogenization is performed regardless of the length of the glass tube, and the present invention can be carried out regardless of the length of the glass tube.

On the other hand, in the conventional manufacturing method, the film thickness unevenness tends to increase as the length of the glass tube increases. In particular, when the length of the glass tube is 500 (mm) or more, it becomes difficult to suppress the film thickness unevenness (the film thickness difference is 6 μm or less) within ± 3 (μm) with respect to the set value. Then, it is particularly effective when the length of the glass tube is 500 (m) or longer.
Further, in the conventional method, when the length of the glass tube is 500 (mm) or more, the temperature of the outer periphery of the glass tube, the heating method, the viscosity of the suspension, etc. are adjusted to form a coating film. The thickness is set within ± 3 (μm) with respect to the set value. In this method, it is particularly difficult to manage various conditions when the length of the glass tube is 700 mm or more.

8). About the thickness of a glass tube Although the thickness of the glass tube was 0.5 (mm) in the said embodiment, it is not limited to this dimension. However, when heating the outer circumference of the glass tube, it is necessary to lengthen the heating time when the glass tube is thick, and shorten the heating time when the glass tube is thin, to make the film surface uniform. There is.

9. About rotation of a glass tube In the said embodiment, although the glass tube was autorotating by making the axis | shaft into the rotation center, it does not need to rotate. However, the difference in film thickness tends to be smaller when the glass tube is rotated.
The rotation speed is determined by the inner diameter of the glass tube, but is preferably 1500 (rpm) or less. This is because when the speed is higher than this, color separation due to the difference in specific gravity of the phosphor particles, separation between the phosphor and the binder, and the like occur.

10. Regarding the heating of the glass tube In the above embodiment, the outer surface of the glass tube is heated with a coil heater when the suspension applied in the glass tube is discharged, and the drying air is used when the suspension is dried. Is blown into the glass tube, and the outer surface of the glass tube is heated by a coil heater.
First, it is necessary to determine the heating at the time of discharging the suspension in consideration of the viscosity of the suspension, that is, the ease of discharging the suspension. It may not be necessary to heat the.

Further, in the drying step, it is only necessary to dry the suspension in the glass tube. For example, it is sufficient to blow air for drying, and conversely, heating may be performed from the outer surface to dry. However, it goes without saying that it is more efficient to dry the suspension using both.
In the embodiment, a coil heater is used as the heating means. However, for example, a hot air set to a desired temperature may be applied to the outer surface of the glass tube, or the drying process may be performed in a drying furnace. You can go.

11. Regarding Film Thickness In this embodiment, europium-activated yttrium oxide is used for red, cerium / terbium-activated lanthanum phosphate is used for green, and europium-activated barium magnesium aluminate is used for blue. When the film thickness is in the range of about 16 (μm) to 24 (μm), this phosphor film has high conversion efficiency for converting ultraviolet light from mercury into visible light.

Therefore, the design value S of the coating film in the present invention is a value in the vicinity of the highest conversion efficiency of the phosphor film (here, 20 (μm)), and this value varies depending on the phosphor film to be used.
As the phosphor, for example, when blue is the above-described phosphor, and europium and manganese-activated barium magnesium aluminate are used for green and europium-activated yttrium vanadate is used for red, the thickness of the phosphor film is 18 (μm). The conversion efficiency becomes the highest in the vicinity of ˜26 (μm), and the set value S is 22 (μm).

  The production method according to the present invention can be used to make the thickness of a coating film formed by drying a suspension coated in a glass tube uniform.

It is a partial schematic perspective view which shows the structure of a backlight unit. It is a partially cutaway perspective view showing a schematic configuration of a lamp according to an embodiment. It is a figure explaining the formation method of a fluorescent substance film. It is a figure which shows the film thickness of the fluorescent substance in the predetermined position of glass upper end. The relationship between the film surface uniformization time and the phosphor film thickness difference is shown. It is a figure which shows the schematic of the drying apparatus in the process for drying. It is a figure which shows the elapsed time from liquid discharge to completion time, and the film thickness difference of a fluorescent substance film. It is a figure which shows the film thickness measurement result in the predetermined position of the glass tube in elapsed time 25 (sec). It is a figure which shows the film thickness measurement result in the predetermined position of the glass tube in elapsed time 50 (sec). It is a figure which shows the film thickness measurement result in the predetermined position of the glass tube in elapsed time 100 (sec). It is a figure which shows distribution of the film thickness of the fluorescent substance film when the air for drying is blown when 100 (sec) passes after changing the discharge speed of a suspension and starting discharge of a suspension. The film thickness distribution when the air volume is increased stepwise is shown.

Explanation of symbols

1 Backlight Unit 20 Cold Cathode Fluorescent Lamp 22 Glass Tube 32 Protective Film 34 Phosphor Film 36 Suspension 38 Drying Air

Claims (7)

The suspension applied to the inner surface of the glass tube is a method for producing a lamp having a coating film that is dried by blowing air from one end of the glass tube,
Application of the suspension to the inner surface of the glass tube is performed by discharging the suspension filled inside the glass tube with the other end of the glass tube facing downward,
The method of manufacturing a lamp, wherein the air is blown from one end of the glass tube after at least 30 seconds have elapsed from the start of discharge of the suspension filled in the glass tube.   From the start of discharge of the suspension filled in the glass tube, when the air naturally drops the suspension filled in the glass tube, the liquid level of the suspension is lower than the lower end of the glass tube. The method for manufacturing a lamp according to claim 1, wherein the lamp is blown from the one end after a time required to reach the temperature reaches.   3. The method of manufacturing a lamp according to claim 1, wherein the glass tube rotates at least about the axis of the glass tube after the suspension is discharged.   During the discharge of the suspension, the air flow is blown within the range in which the discharge of the suspension in the glass tube is promoted and the liquid level of the suspension that is descending in the glass tube stops once in the middle. The method for manufacturing a lamp according to any one of claims 1 to 3, wherein: A lamp having a coating film on the inner surface of a glass tube,
The said lamp | ramp is manufactured by the manufacturing method of any one of Claims 1-4, The lamp | ramp characterized by the above-mentioned.   The coating film is a phosphor film, and when the design value is S (μm), the film thickness (μm) at a predetermined position with respect to the design value S The lamp according to claim 5, wherein the lamp is within a range of ± 3 (μm). A fluorescent lamp having a phosphor film on the inner surface of a glass tube,
The glass tube has a length of 500 mm or more and an inner diameter of 2 mm or more and 3 mm or less,
Regarding the film thickness of the phosphor film, when the design value is S (μm), the film thickness (μm) at a predetermined position is within a range of ± 3 (μm) with respect to the design value S. A fluorescent lamp characterized by that.

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