JP2006173063A - Manufacturing method of cold-cathode fluorescent lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a cold-cathode fluorescent lamp capable of preventing the thickness of a phosphor layer formed on an inner wall of a glass tube from becoming uneven in a tube axis direction. <P>SOLUTION: After a process of applying phosphor solution 2, the phosphor solution is dried by a drying machine 3 in a state of slanting a glass tube 1. Thus, by providing the process drying the phosphor solution in a state of slanting the glass tube 1, fluidity of the phosphor solution in the glass tube 1 can be reduced, and the thickness of phosphor layer formed on an inner wall of a glass tube can be prevented from becoming uneven in tube axis direction. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method of manufacturing a cold cathode fluorescent lamp used as a light source for backlighting a liquid crystal display device or a small illumination light source, and in particular, the thickness of a phosphor layer formed on the inner wall of a glass tube is the axis of the tube. The present invention relates to a method of manufacturing a cold cathode fluorescent lamp capable of preventing non-uniformity in direction.

  Generally, a cold cathode fluorescent lamp is used as a light source for back lighting of a liquid crystal display device such as a personal computer, a word processor, a monitor, etc., or as a small illumination light source, and has a pair of cold cathodes inside both ends of a glass tube. It has a configuration. A phosphor layer is formed by applying a phosphor solution to the inner wall of the glass tube and drying it.

  FIG. 7 is a diagram showing steps of applying and drying a phosphor solution in a conventional method for manufacturing a cold cathode fluorescent lamp.

  First, in the coating process, the inner wall of the glass tube 1 is sucked up from a lower end portion of the glass tube 1 fixed upright to a predetermined position of the phosphor solution 2 in which the phosphors of red, green and blue are mixed. The phosphor solution is applied to In the next drying step, air is blown into the glass tube by the dryer 3. At this time, the phosphor solution inside is dried and adheres to the inner wall to form a phosphor layer. On the other hand, the surplus phosphor solution that has not adhered to the liquid flows and falls in the glass tube 1.

  In the phosphor solution used in the conventional cold cathode fluorescent lamp manufacturing method described above, the specific gravity of the green phosphor is larger than the specific gravity of the phosphors of other colors. Faster than things, and therefore easier to flow down. On the other hand, since the specific gravity of the blue phosphor is lower than that of the phosphors of other colors, the fluidity in the glass tube is lower than that of the other colors, and therefore tends to remain at the top in the glass tube. Therefore, there has been a problem that in the axial direction of the cold cathode fluorescent lamp, the blending ratio of the phosphors of the three colors slightly changes and the film thickness becomes nonuniform.

  The present invention has been made in view of the above problems, and its object is to prevent the thickness of the phosphor layer formed on the inner wall of the glass tube from becoming uneven in the axial direction of the tube. Another object of the present invention is to provide a method for manufacturing a cold cathode fluorescent lamp.

  In order to solve the above-mentioned problem, the manufacturing method of the cold cathode fluorescent lamp according to claim 1 includes the step of applying a phosphor solution to the inner wall of the glass tube. And drying the applied phosphor solution with the glass tube tilted.

  According to the manufacturing method of the first aspect, since the flowability of the phosphor solution in the glass tube can be lowered by providing the step of drying the phosphor solution while the glass tube is inclined, the inner wall of the glass tube It is possible to prevent the thickness of the phosphor layer formed from becoming uneven in the axial direction of the tube.

  A manufacturing method of a cold cathode fluorescent lamp according to claim 2 is characterized in that, in the manufacturing method according to claim 1, the angle of the inclined glass tube is adjusted.

  According to the manufacturing method of claim 2, in addition to preventing the film thickness of the phosphor layer from becoming uneven in the axial direction of the tube, by adjusting the angle of the inclined glass tube, Since the fluidity of the phosphor solution can be adjusted, the thickness of the phosphor layer in the axial direction of the tube can be adjusted.

  The manufacturing method of the cold cathode fluorescent lamp according to claim 3 is the manufacturing method according to claim 1 or 2, wherein the inclined glass tube has an angle of 70 degrees or more and 80 degrees with respect to the vertical direction. It is characterized by the following.

  According to the manufacturing method of claim 3, in addition to preventing the film thickness of the phosphor layer from becoming non-uniform in the axial direction of the tube, the angle of the tilted glass tube with respect to the vertical direction By setting the angle to 70 degrees or more and 80 degrees or less, it is possible to manufacture a cold cathode fluorescent lamp in which the thickness of the phosphor layer in the axial direction is appropriate.

  In the manufacturing method according to any one of claims 1 to 3, the tilted glass tube may be rotated about its axis.

  According to this manufacturing method, in addition to preventing the thickness of the phosphor layer from becoming non-uniform in the axial direction of the tube, the phosphor solution can be obtained by rotating the tilted glass tube about its axis. Since the film is dried while rotating, it is possible to prevent the phosphor layer from becoming uneven in the circumferential direction.

  Further, in this manufacturing method, the glass tube has an elliptical or flat cross section, and the rotation speed when the major axis in the cross section is vertical may be slower than the rotation speed when horizontal. .

  According to this manufacturing method, in addition to preventing the phosphor layer thickness from becoming uneven in the axial direction and circumferential direction of the tube, the rotational speed when the major axis in the cross section is vertical is By making it slower than the rotation speed, the time when the major axis becomes vertical becomes longer, and the phosphor solution flows against the surface tension, so that the glass tube having an elliptical shape or a flat shape is used for the cross section. It is possible to prevent the thickness of the phosphor layer to be formed from becoming uneven in the circumferential direction.

  According to the manufacturing method of the cold cathode fluorescent lamp of the present invention, the flow of the phosphor solution in the glass tube can be lowered by providing the step of drying the phosphor solution while the glass tube is inclined. It is possible to prevent the phosphor layer formed on the inner wall from becoming uneven in the axial direction of the tube.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram illustrating a drying process of a phosphor solution in the present embodiment. Here, it demonstrates as the application | coating process demonstrated using FIG. 7 having been performed.

  After the application process of the phosphor solution 2, as shown in FIG. 1, the glass tube 1 is inclined and the applied phosphor solution is dried by the dryer 3 disposed at the upper end of the tube. For example, the glass tube 1 can be tilted by rotating the glass tube 1 around the position of the dryer 3.

  As described above, by providing the step of drying the phosphor solution while the glass tube 1 is inclined, the flowability of the phosphor solution in the glass tube 1 can be lowered, so that it is formed on the inner wall of the glass tube 1. It is possible to prevent the thickness of the phosphor layer from becoming nonuniform in the axial direction of the tube.

  Moreover, since the non-uniformity of the phosphor content of each color can be prevented, the chromaticity difference in the axial direction can be reduced.

  Moreover, since the fluidity | liquidity of a fluorescent substance solution can be adjusted by adjusting the angle of the glass tube 1 of the inclined state, the film thickness and chromaticity difference of the fluorescent substance layer in the axial direction of a pipe | tube can be adjusted.

  Further, drying may be performed while changing the angle of the glass tube 1.

  In particular, in order to prevent non-uniform film thickness in the axial direction of the tube, it is desirable that the angle of the tilted glass tube with respect to the vertical direction is 70 degrees or more and 80 degrees or less.

  Further, the manufacturing method of the present embodiment can be applied to, for example, a cold cathode fluorescent lamp using a glass tube having an inner diameter of 0.8 mm or more and 8.0 mm or less.

  Next, in the present embodiment, the tilted glass tube 1 is rotated about the axis of the tube. Thus, by rotating the glass tube 1 about the axis of the tube, the phosphor solution is dried while circling around the inner wall of the glass tube 1, so that the thickness of the phosphor layer is not uniform in the circumferential direction. Therefore, the occurrence of unevenness can be prevented.

  In addition, you may make it rotate, adjusting the angle of the glass tube 1 of the inclined state.

  By the way, when the manufacturing method described above is applied to a cold cathode fluorescent lamp using a glass tube 1 having a flat cross section, as shown in FIG. 2, the phosphor solution has a long diameter of the cross section due to its surface tension. There is a tendency to accumulate in the vicinity of the end, and therefore it is difficult to make the film thickness in the circumferential direction uniform.

  In order to prevent this inconvenience, in the present embodiment, when the glass tube 1 having a flat cross section is used, the rotation speed when the major axis in the cross section is vertical is made slower than the rotation speed when it is horizontal. ing.

  FIG. 3 is a graph showing the transition of the rotational speed when the glass tube 1 having a flat cross section is used.

  At the rotation angles a and b shown on the horizontal axis in FIG. 3, that is, when the major axis of the cross section of the flat glass tube 1 is vertical, the rotation speed is the lowest. On the other hand, at the rotation angle c shown in FIG. 3, that is, when the major axis is horizontal, the rotation speed becomes maximum. For example, the rotation speed when the major axis is vertical is 10 to 20 rpm (rotation / min), and the rotation speed when the major axis is horizontal is 120 rpm (rotation / min).

  FIG. 4 is a view showing each cross section when the glass tube 1 having a flat cross section is rotated about the tube axis.

  As shown on the left side of the figure, when the major axis of the cross section is vertical and the phosphor solution 2 is accumulated near the lower end of the major axis, if the glass tube 1 is rotated 180 degrees, the center of the figure As shown, the phosphor solution 2 apparently moves to the vicinity of the upper end of the long diameter. In the present embodiment, as shown in the center of the figure, since the rotation speed when the major axis is vertical is slower than the rotation speed when horizontal, the phosphor solution flows against the surface tension, Thereby, as shown on the right side of the figure, the film thickness near the upper end of the major axis and the film thickness near the lower end can be made equal.

  Thus, by making the rotational speed when the major axis in the cross section is vertical lower than the rotational speed when it is horizontal, the time when the major axis becomes vertical becomes longer, and the phosphor solution resists the surface tension. Since it flows, it can prevent that the film thickness of the fluorescent substance layer formed in the glass tube which has an elliptical shape or a flat shape in a cross section becomes uneven in the circumferential direction.

  Note that the control of the rotational speed described above can also be applied to a method for manufacturing a cold cathode fluorescent lamp using a glass tube having an elliptical cross section.

  FIG. 5A is a table showing the film thicknesses of the phosphor layers of the cold cathode fluorescent lamps manufactured by the conventional manufacturing method and the manufacturing method of the present embodiment, respectively. FIG.5 (b) is a cross-sectional view of the glass tube which shows the film thickness measurement location. In particular, these are for glass tubes having a flat cross section.

  As shown in FIG. 5A, in the conventional manufacturing method, the film thickness of the phosphor layer at the short-diameter end of the cross section (indicated by the arrow Y1 in FIG. 5B) is about 9 μm. It becomes thinner than the film thickness of 20 μm at the long-diameter end of the surface (indicated by the arrow Y2 in FIG. 5B). On the other hand, according to the manufacturing method of the present embodiment, the thickness of the phosphor layer at the end portion of the short diameter can be increased until it is substantially equal to the film thickness at the end portion of the long diameter. The layer thickness can be made uniform.

  FIG. 6 is a diagram showing chromaticity deviations of cold cathode fluorescent lamps manufactured by a conventional manufacturing method and a manufacturing method of the present embodiment using a glass tube having a circular cross section. In particular, FIG. 6A is a graph in which the chromaticity deviation (x deviation) in the circumferential direction is taken on the vertical axis, and the distance from a point in the circumferential direction is taken on the horizontal axis, and FIG. 3 is a graph in which the chromaticity deviation (y deviation) in the axial direction is taken on the vertical axis and the distance from the end of the glass tube is taken on the horizontal axis. These are graphs of a cold cathode fluorescent lamp provided with a glass tube having an inner diameter of 2.4 mm and a length of 300 mm and a lamp current of 6 mA.

  As shown in FIG. 6 (a), the chromaticity deviation in the circumferential direction is not the chromaticity deviation of the cold cathode fluorescent lamp by the conventional manufacturing method, but the color of the cold cathode fluorescent lamp by the manufacturing method of the present embodiment. The degree deviation can be reduced. Further, as shown in FIG. 6B, the chromaticity deviation in the axial direction was about 0.008 by the conventional manufacturing method, but according to the manufacturing method of the present embodiment, the color deviation is The degree deviation can be reduced to about 0.002.

FIG. 1 is a diagram illustrating a drying process of a phosphor solution in the present embodiment. FIG. 2 is a cross-sectional view showing a state in which the phosphor solution accumulates in the vicinity of the end portion of the long diameter of the flat cross section. FIG. 3 is a graph showing the transition of the rotational speed when the glass tube 1 having a flat cross section is used. FIG. 4 is a view showing each cross section when the glass tube 1 having a flat cross section is rotated about the tube axis. FIG. 5A is a table showing the film thicknesses of the phosphor layers of the cold cathode fluorescent lamps manufactured by the conventional manufacturing method and the manufacturing method of the present embodiment, and FIG. It is a cross-sectional view of the glass tube which shows the measurement location. FIG. 6 is a diagram showing the chromaticity deviations of the cold cathode fluorescent lamps manufactured by the conventional manufacturing method and the manufacturing method of the present embodiment, using a glass tube having a circular cross section. a) is a graph of chromaticity deviation in the circumferential direction, and FIG. 6B is a graph of chromaticity deviation in the axial direction. FIG. 7 is a diagram showing a conventional phosphor solution coating and drying process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Glass tube 2 ... Phosphor solution 3 ... Dryer

Claims (3)

  A method of manufacturing a cold cathode fluorescent lamp, comprising: applying a phosphor solution to an inner wall of a glass tube; and drying the applied phosphor solution while the glass tube is inclined.   2. The method of manufacturing a cold cathode fluorescent lamp according to claim 1, wherein an angle of the tilted glass tube is adjusted. 3. The method of manufacturing a cold cathode fluorescent lamp according to claim 1, wherein the inclined glass tube has an angle of 70 degrees or more and 80 degrees or less with respect to the vertical direction.

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