JPH02276151A - Fluorescent lamp - Google Patents

Abstract

PURPOSE:To form a high luminance part in the vicinity inside a translucent plate so as to improve the symmetry of luminous intensity distribution property by providing a discharge throttling member which throttles a positive column in each luminous chamber in the vicinity of the translucent plate. CONSTITUTION:For a fluorescent lamp 21, anodes 22a, 22b, 22c, and 22d being plural electrodes are formed respectively in columnar shape of thin diameter, and auxiliary partition plates 23a, 23b, 23c, and 23d being four discharge throttling members are provided inside a taper case(fluorescent film-coated body)6. A positive column alpha, which passes inside a luminous chamber 8b in the taper case 6, is throttled by the narrowing recess 25b of this auxiliary partition plate 23b. Accordingly, by narrowing the positive column alpha, more watts can be input, so the ultraviolet-ray irradiation intensity around this throttling recess 25b improves.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a fluorescent lamp suitable for display fluorescent lamps, which are display elements of electronic display panels, and light emitting elements of decorative lighting, for example. In particular, fluorescent lamps with higher brightness and improved light distribution characteristics are used.

(Prior Art) In general, surface water fluorescent lamps suitable for display elements of electronic display panels include single-tube monochromatic or single-tube multicolor fluorescent lamps. An example of this, although not previously known, is shown in Figure 7 (
There is a fluorescent lamp 1 constructed as shown in A), (B) and FIG.

As shown in FIG. 8, this fluorescent lamp 1 has a button stem 4 with a cathode 3 erected inside an envelope 2 made of stainless steel or the like and formed into a cylindrical shape with a bottom, and the outer periphery of the button stem 4 is filled with 7 liters of glass. then insert it tightly.

Next, this button stem 4 is welded to the inner bottom of the envelope 2, and the exhaust pipe 4a is airtightly extended to the outside from the bottom center hole 2h of the envelope 2.

The envelope 2 has an upper step portion 2a having a rectangular planar shape, for example, by sequentially widening the upper part of the opening into a rectangular tube shape in two stages.
and a lower step portion 2b, respectively.

In addition, the entire inner peripheral surface of the envelope 2 is coated with a glass film (not shown), and when an electric discharge occurs within the envelope FS2, the metal envelope 2 is coated with impurities contained therein. The glass coating prevents gas from being released.

Next, in the envelope 2, as shown in FIG. 14, a tapered tube 6 that tapers downward is filled with frit glass around its outer periphery, and then coaxially inserted and fixed. ing.

A partition plate 8 having a cross-shaped planar shape, for example, is coaxially inserted and fixed into the tapered cylinder 6, and a partition plate 8, for example, a seventh
As shown in the figure (A>, four light emitting chambers 8a, 8b, 8c,
It is divided into 8d.

Each of the inner surfaces of the tapered surface 6C of the tapered tube 6 facing each of the light emitting chambers 8a to 8d and each outer surface of the partition plate 8 have, for example, each light emitting chamber 8a.
Fluorescent films 9 that emit light of different colors are adhered every ~8d, and the tapered cylinder 6 is configured as a fluorescent film adhered body.

The upper part of the taper n6 (see Fig. 8) is formed into a truncated quadrangular pyramid tapering downward, and each corner of the upper end is formed into a notch 6a, 6a... with a cylindrical lower part. A circular discharge hole 6 is formed at the bottom of this cylindrical lower part.
b is open.

The tapered tube 6 is supported by being engaged with the inner surface of each corner of the lower step 2b in the envelope 2.

The anodes 10a to 10d, which are a plurality of electrodes, are formed in a circular loop shape, and each of the light emitting chambers 8a to 10d in the tapered cylinder 6
They are arranged coaxially at the inner upper end of 8d.

Each of the anodes 10a to 10d has the upper end of each pin-shaped lead wire 11, 11, . The distal end portion vertically and airtightly penetrates the bottom of the step portion 2b of the t portion of the envelope 2 and extends to the outside to be electrically connected to a lighting circuit (not shown).

Next, the outer periphery of the rectangular flat transparent glass transparent plate 12 is filled with frit glass, and the outer periphery is fitted into the upper step 2a of 2, and the transparent plates 1 and 12 are inserted into the upper step. It is fixed inside 2a.

As a result, the envelope 2 is airtightly sealed, and while the exhaust pipe 4a is passed through the envelope 2, mercury and a rare gas are sealed, and the transparent plate 12 is connected to the fluorescent lamp 1.
be the light emitting surface.

(Problem to be Solved by the Invention) However, in such a conventional fluorescent lamp 1, when only one of the plurality of light emitting chambers 8a to 8d emits light, so-called single chamber light emission, the light distribution characteristics become asymmetrical. However, there is a problem in that it is difficult to equalize the brightness.

Furthermore, due to this asymmetric groove, there is a problem that the chromaticity of white light during whole-room light emission deteriorates.

That is, as shown in FIG. 9, when the cathode 3 and the anode of ji-, for example, IOC, are energized to generate a tIi current,
A positive column α is formed between the cathode 3 and a single anode 10c, and a portion of this positive column α passes through the light emitting chamber 8C containing the energized anode 10c in the tapered tube 6.

At this time, the positive column α excites the mercury atoms in the light emitting chamber 8C to generate ultraviolet (UV) light, and this ultraviolet light excites the fluorescent light wA9 on the inner surface of the tapered cylinder 6 to emit light in a desired color, transmitting light. It is emitted from brakes 1 and 12 to the outside.

However, the fluorescent light wA9 is deposited only on the inner peripheral surface of the tapered surface 6c of the tapered tube 6 and on each outer surface of the partition plate 8, and moreover, the sunlight column α passes through the shortest distance between the cathode 3 and the anode 10c. Therefore, the left end of the positive column α in the figure is the anode 10c.
The radial gap between the positive column α and the fluorescent film 9 of the tapered tube 6 becomes maximum at the large diameter end of the tapered tube 6 (the end on the side of the transparent brakes 1 to 12). .

Therefore, at the end of the large span ['' of the taper n6, the radial distance between the positive column α and the fluorescent film 9 becomes maximum, and tJV (
Ultraviolet (UV) light) 1 strong current is the minimum, resulting in low brightness.

On the other hand, the Uv (ultraviolet) irradiation intensity is maximum at the reduced diameter end of the tapered tube 6 where the radial distance between the positive column α and the fluorescent light g19 is the minimum, and here the brightness section J111 (10th
(see figure) are distributed. For convenience of illustration, FIG. 10 shows the light emitting state of the light emitting chamber 8C in the adjacent room 8d.

And such a high brightness part J! As shown in FIG. 10, the light emitted at h1 is the fluorescence II of both the tapered tube 6 and the partition plate 8 on the outer circumference G side of the transparent plate 12! While the light emitted from J9 is mainly 1g and 1g2, on the center 0 side only the light 10 from the fluorescent film 9 of the tapered tube 6 is the main, and 1o10-1o2>Iol.

However, the light emitted from the central part G side) is emitted by 1! 01 is
In addition to the fact that there is no light emitted from the fluorescent film 9 of the partition plate 8, the light emission JO is emitted from the high-intensity portion Jh1 of the tapered tube 6 on the reduced diameter side than the light emission position at the left end of the partition plate 8 in the figure. The light will be blocked.

Therefore, as shown by the broken line in FIG. 11, the light distribution characteristic of such a single room light emission is such that the amount of light on the outer peripheral side G of the fluorescent lamp 1 is greater than the light amount on the center side O, and the amount of light in the single light emitting room 8C increases. The light distribution characteristics when the center O6 is the central axis are asymmetrical inside and outside (left and right).

This asymmetry in the light distribution characteristics during single-chamber light emission is caused by light-emitting chamber 8C.
The same phenomenon as b occurs in other light emitting chambers 8a, 8b, and 8d.

In addition, since there is asymmetric light distribution in such a single room light emission,
All the anodes 10a to 10d are energized, and all the light emitting chambers 88 to
8d to emit light and synthesize each emitted color to output white light, the light distribution characteristics at that time will also be asymmetrical between the inside and outside (left and right) with the center O of the fluorescent lamp 1 as the central axis, so the white balance The difference is that the chromaticity of white color decreases.

For this reason, depending on the direction from which the fluorescent lamp 1 is viewed,
White light appears to have a reddish or dark tinge to it.

The present invention has been made in consideration of the above circumstances, and an object thereof is to provide a fluorescent lamp capable of improving light distribution characteristics and increasing brightness.

[Structure of the invention]

(Means for Solving the Problems) This defense has been made to solve the above problems, and the invention according to claim 1 (hereinafter referred to as the first invention):
Opening towards the transparent plate and this transparent brake 1,
a q2-light film body with a fluorescent film coated on its inner surface; a partition member that divides the light-emitting chamber formed by the light-transmitting plate and the fluorescent film covering body into a plurality of light-emitting chambers; A tIC is provided corresponding to each chamber, and has a plurality of electrodes for selectively energizing, and another electrode paired with the plurality of electrodes and spaced apart in a direction substantially perpendicular to the light-transmitting plate; By energizing between one electrode and the other electrode, a part of the positive column formed approximately perpendicular to the light-transmitting plate is selectively passed through the light-emitting chamber, causing the fluorescent film on the inner surface of the light-emitting chamber to emit light. and outputs the emitted light to the outside through the light-transmitting plate 1 (in the fluorescent lamp 2, a discharge diaphragm member is provided that narrows the diameter of the positive column passing through the light-emitting chamber near the inner surface of the light-transmitting plate; A feature of the discharge diaphragm member is that a fluorescent film is attached to the outer surface of the discharge diaphragm member.

In addition, the invention according to claim 2 (hereinafter referred to as the second invention)
is characterized in that the fluorescent film adherend in the first invention is tapered and expanded toward the light-transmitting plate.

Furthermore, the invention according to claim 3 (hereinafter referred to as the third invention) is characterized in that the discharge diaphragm member in the first invention is formed into a tapered cylinder that expands toward the inner surface of the light-transmitting plate. .

(Function) First invention> The diameter of the positive light column passing through the light emitting chamber is narrowed near the inner surface of the transparent plate I by the discharge diaphragm member.

Therefore, the amount of straw 1-(W
), the brightness can be increased accordingly.

In addition, since the diameter of the positive column is narrowed near the inner surface of the transparent plate by the discharge aperture member, the intensity of ultraviolet (U) irradiation near the inner surface of this transparent plate increases, and a high-brightness area is formed here. to be distributed.

Therefore, the light emitted from this high-brightness portion is not blocked by the partition plate, and is output from the transparent plate toward the center portion to the outside.

Therefore, by increasing the amount of light emitted toward the center of the light-transmitting plate, it is possible to both increase the brightness of the fluorescent lamp and improve the symmetry of the light distribution characteristics.

Second invention> The fluorescent film adherend has a fluorescent film adhered surface formed into a tapered surface that expands in a tapered shape toward the inner surface of the light-transmitting plate. The visible area of the fluorescent film adherend when viewed from above is expanded by the tapered surface.

Therefore, more of the light emitted from the fluorescent film attached to the tapered tube of the fluorescent film adherend is visible from the light-transmitting plate side, so that the brightness can be increased accordingly.

Third Invention> The discharge diaphragm member has a fluorescent film coated outer surface formed into a tapered surface toward the inner surface of the transparent plate 1, so that the discharge diaphragm member can be accessed from the transparent plate side. The visible area when visually recognized is expanded by the amount of the tapered tube.

Therefore, more of the light emitted from the fluorescent film attached to the tapered tube of the discharge diaphragm member is visible from the transparent plate side, so that the brightness can be increased accordingly.

(Example) Examples of the first to third inventions of the present application are shown in Figs. 1 to 6 below.
This will be explained based on the diagram.

In FIGS. 1 to 4, parts common to those shown in FIGS. 7 and 8 are designated by the same reference numerals, and redundant explanation thereof will be omitted.

1 to 3 respectively show the overall configuration of a first embodiment of the first to third inventions of the present application, FIG. 1 is a plan view, and FIG. 2 is a cross section taken along the line T] in FIG. Figure 3 shows ■-■ of Figure 1.
FIG.

As shown in FIGS. 1 to 3, the fluorescent lamp 21 of the tree theory example has, for example, four anodes 22a, 22, which are multiple electrodes.
b, 22c, and 22d are each formed in the shape of a cylinder with a small diameter instead of the conventional ring shape, and there are four auxiliary discharge diaphragm members, for example, in the tapered tube (fluorescent film adherend) 6. Partition plate 23a.

The feature is that 23b, 23c, 23d are provided.

As shown in FIGS. 1 to 3, each of the anodes 22a to 22d has a straight bottle-shaped lead Ii at its lower end (the right end in FIGS. 2 and 3). 24a.

24b, 24c, and 24d are fixed coaxially, and the tips of these lead wires 24a to 24d are connected to the lower step 2b of the envelope 2.
vertically outwardly in a gas-tight manner and electrically connected to the required lamp lighting circuits, respectively.

Each anode 22a to 22d is a tapered tube (fluorescent film adherend)
They are arranged close to the outside of each of the inwardly convex arcuate notches 6a cut out at each corner of the large-diameter opening end of No. 6.

On the other hand, each of the auxiliary partition plates 23a to 23d is arranged in the tapered cylinder 6 on a diagonal line connecting each outer end of the cross-shaped partition plate 8, as shown in FIG.
One sheet is arranged for each d.

Each of the auxiliary partition plates 23a to 23d is made of a cape plate, and as shown in FIG. 2, the right end in the figure on the cathode 3 side is formed into a chevron shape, while the other end (left end in the figure) is formed into a chevron shape. It adheres almost perpendicularly to the inner surface.

In addition, each auxiliary partition plate 23a to 23d is a transparent plate 1-1.
Each abutment surface that abuts the inner surface of 2 has arc-shaped aperture recesses 25a and 25b at the middle portion thereof in the direction of the handle.

25c and 25d are cut out, and these four parts 2
A positive column is passed through 5a to 25d to narrow down its diameter.

Each of the auxiliary partition plates 23a to 23d has a light emitting chamber 88 to 88 which accommodates each of the auxiliary partition plates 23a to 23d, respectively, on its outer surface.
Each fluorescence II of 8d! A fluorescent film (not shown) that emits light in the same color as 9 is respectively coated.

Therefore, when the fluorescent lamp 21 configured in this way performs so-called single-chamber light emission by energizing only the required anode, for example 22b, and the cathode 3, the positive column α shifts to the envelope as shown in FIG. 2 between the cathode 3 and the anode 22b.

This positive column α enters the light emitting chamber 8b located next to the inside of the anode 22b which is energized, and further causes the fluorescent films on each side of the auxiliary partition plate 23b in the light emitting chamber 8b to emit light, and also causes the diaphragm recess thereof to emit light. After passing through 25b and being reduced in diameter, it reaches 7 nodes 22b.

For this purpose, the positive column α excites mercury atoms in the light emitting chamber 8b to generate ultraviolet rays (UV), and the ultraviolet rays excite the fluorescent film 9 in the light emitting chamber 8b and the fluorescent film of the auxiliary partition plate 23b, respectively. Then, light is emitted as required, the light is emitted in a single chamber, and this light is emitted from the transparent plate 12 to the outside.

By the way, since the auxiliary partition plate 23b is disposed within the light emitting chamber 8b, the sunlight column α passing through the light emitting chamber 8b within the taper 916 is narrowed down by the concave portion 25b of the auxiliary partition plate 23b.

Therefore, by narrowing down the positive column α, more watts can be input, so this aperture recess 25b
The surrounding ultraviolet (UV) irradiation intensity is improved.

Furthermore, since the aperture concave portion 25b is arranged near the inner surface of the light-transmitting plate 1, 12, the UV irradiation intensity near the inner surface of the light-transmitting plate 12 is improved, as shown in FIG. 4(A). A second high brightness portion h is provided at the large diameter opening end of the taper n6.
2 is formed.

That is, as shown in FIG. 4(A), in the fluorescent lamp 21 of this embodiment, the positive column α is narrowed down at the diameter-reduced end and the open end of the tapered tube 6, so that the high-brightness portion JF1 is
．． 1h2 is distributed respectively.

Moreover, this latter high brightness section Ih2 is a transparent brake 1-
Since it is located near the inner surface of 12, that is, inside the large diameter opening end of taper M6, the light emitted in this high brightness part 1 [) is not blocked by the left end of the partition plate 8 in the figure. The light is emitted toward the center G side in the direction GJ.

Therefore, 02・
03 The amount of light emitted to the center G side increases.

Due to the bundling, the light emitted toward the center G side of the fluorescent lamp 21 is 1°1. '02. '03, light emitted to the outer circumference G side 'G1. iG2. 'G3 is almost equal, and the 4th
As shown in Figure (B), the light distribution characteristics of a single light emitting chamber, for example 8d, with the axis O as the central axis are also approximately symmetrical between the center G side and the outer peripheral G side (left and right).

Such improvement in the symmetry of light distribution characteristics is achieved not only in the light emitting chamber 8b but also in the auxiliary partition plates 23a and 23G.

The same phenomenon is observed in other light emitting chambers 8a, 8c, and 8d having 23d.

In other words, in FIG. 4, the light distribution state of the light emitting chamber 8b is shown in the adjacent light emitting chamber 8d for convenience of illustration, but each of the light emitting chambers 88 to 8d has auxiliary partition plates 23a to 23d. etc., each of the light emitting chambers 8a to 8d has the same structure.
The symmetry of the light distribution characteristics is improved.

Therefore, even if the anodes 22a to 22d and the cathode 3 are energized and white light is not synthesized as a whole, the chromaticity of the white light can be improved by improving the symmetry of the light distribution characteristics of the light emitting chambers 8a to 8d. can be increased.

5 and 6 show the overall structure of another embodiment of the present invention, and the fluorescent lamp 31 of this embodiment has the outer surfaces of auxiliary partition plates 32a, 32b, 32c, and 32d, which are discharge diaphragm members. It is characterized in that it is formed on the tapered surface t.

That is, as shown in FIG. 6, the fluorescent lamp 31 is connected to the open end (
The bottom of a right bottom cylindrical upper envelope 35 having a slightly larger diameter than the lower outer knee envelope 34 is coaxially and airtightly fixed to the left end in FIG.

A center hole 36 is bored in the bottom of the upper envelope 35, and the upper part,
The insides of both lower envelopes 34 and 35 are communicated.

The upper envelope 35 has a cross-shaped partition plate 3 as shown in FIG.
For example, four light emitting chambers 38a, 38b, 38c,
It is evenly divided into 38d, each light emitting room is 388~38d.
Cylindrical anodes 39a, 39b,
39c and 39d are provided, respectively.

Each of the light emitting chambers 38a to 38d has horizontal auxiliary partition plates 32a to 32d, which are discharge diaphragm members, erected on the bottom of the upper envelope 35 at the outer periphery of the center hole 36. The top end surfaces of the partition plates 32a to 32d are connected to the upper envelope 3.
It is in airtight contact with the inner surface of a transparent plate 40 that airtightly seals the open end of 5.

Therefore, each of the auxiliary partition plates 32a to 32d has its outer surface facing the light-transmitting plate 40 and is formed into a tapered surface t, and these tapered surfaces t... Almost the entire surface is coated with a fluorescent film that emits light in the same color.

Each of the auxiliary partition plates 32a to 32d is a transparent plate I.
On the abutment surface that abuts the inner surface of 40, an arc-shaped aperture recess 41a is provided at approximately the middle portion in the longitudinal direction.

41b, 41c, and 41d are each cut out, and the diameter of the positive column α passing through each of the light emitting yen 38a to 38d is narrowed down by these aperture recesses 41a to 41d.

Therefore, when a so-called single-chamber light emission is performed by energizing only the required anodes, for example 39c, and the cathode 33 of the fluorescent lamp 31 configured in this way, the positive column α is connected to the cathode 3 as shown in FIG. It is formed between the anode 39G and the energized anode 39G; its positive light column α passes through the light emitting chamber 38C.

The positive column α in this light emitting chamber 38C is the auxiliary partition plate 3.
2c, and is narrowed down here.

Therefore, by adjusting the positive column α, more watts can be inputted, the UV irradiation intensity can be increased, and high brightness can be achieved.

Furthermore, since the aperture recess 41C is located near the inner surface of the light-transmitting plate 40, the second bright melon portion oh2 is formed near the inner surface of the light-transmitting plate 40.

In other words, the auxiliary partition plates 328 through which the positive column α is narrowed down
32d and 2 around each aperture recess 41a to 41d.
Brightness portions Jh and h2 are formed at these locations, respectively.

Since the latter high-brightness part Ih2 is located near the inner surface of the transparent plate 40, the back of the light emitted around the aperture recess 41G of this brightness part Oh2, the center 0 side of the fluorescent lamp 31,
In other words, since the light exiting toward the cross-shaped partition plate 37 is not blocked by the tip of the partition plate 37 (the left end in FIG. 6), the amount of light exiting toward the center O is increased, and the amount of light exiting from the inside and outside (left and right) is increased. It is possible to improve light distribution characteristics.

Roughly speaking, each of the auxiliary partition plates 328 to 32d has its outer surface formed into a wide tapered surface t... that widens toward the light-transmitting plate 40, so that each auxiliary partition plate 328 when viewed from the light-transmitting plate 40 An attempt is made to expand each visible area of 32d to 32d.

Therefore, much of the light emitted from the fluorescent films of these tapered surfaces t... can be seen from the light-transmitting plate 40 side, and the brightness can be increased accordingly.

Incidentally, the tapered tube 6, the cross-shaped partition plate 8, and the auxiliary partition plates 23a to 23d of the fluorescent lamp 21 shown in FIG.
Compared to the case where these 6.8.23a to 23d are formed separately and assembled, work efficiency can be improved and work costs can be significantly reduced.

〔Effect of the invention〕

As explained above, in the present invention, since the discharge diaphragm member that narrows down the positive column in each light emitting chamber near the light-transmitting plate is provided, a high-brightness portion can be formed near the inner side of the light-transmitting plate.

Since the light emitted near the inside of the light-transmitting plate is not blocked by the partition and is emitted toward the lamp center axis, the amount of light emitted to the center of the lamp is increased, and the amount of light between the center and outer periphery of the lamp is increased. can be made almost equal, and the symmetry of the light distribution characteristics can be improved.

As a result, the chromaticity of white light can be increased.

[Brief explanation of drawings]

FIG. 1 is a plan view of an embodiment of a fluorescent lamp according to the present invention;
Figure 2 is a sectional view taken along line I[, -II in Figure 1, and Figure 3 is a cross-sectional view of Figure 1.
4(A) is a sectional view taken along the line ■-■ in FIG. 1, which explains the operation of the embodiment shown in FIGS.
FIG. 4(B) is a light distribution characteristic diagram of the embodiment shown in FIGS. 1 to 3, FIG. 5 is a plan view of another embodiment of the present invention, and FIG. Figure 7 (A) is a plan view of a conventional fluorescent lamp, and Figure 7 (B) is a cross-sectional view of the conventional fluorescent lamp.
-■ A sectional view taken along the line B, Figure 8 is an assembled and disassembled perspective view of the fluorescent lamp shown in Figures 7 (A>, (F3), Figures 9 and 10)
The figure is Fig. 7 (
△) VI B-■B line cross-sectional view, FIG. 11 is shown in FIG.・Hoopa tube (fluorescent film adherend), 8...partition plate, 88~8d・
...Light-emitting chamber, 12.40... Translucent brake 1, 21゜31... Fluorescent lamp, 22a-22d... Anode, 23a-23d, 32a-32d-... Auxiliary partition plate (discharge aperture members), 25a to 25d, 41a to 41d
...Aperture recess.

Claims (1)

[Claims] 1. A transparent plate, a fluorescent film adherend having an opening toward the transparent plate and a fluorescent film coated on the inner surface, and the transparent plate and the fluorescent film adherend. a partition member that divides the light-emitting chamber formed by the light-emitting chamber into a plurality of light-emitting chambers; a plurality of electrodes that are provided corresponding to the light-emitting chambers and selectively energize; One of the positive pillars has a light-transmitting plate and another electrode spaced apart from each other in a substantially perpendicular direction, and is formed in a direction substantially perpendicular to the light-transmitting plate by energization between the plurality of electrodes and the other electrode. In the fluorescent lamp, a part of the light emitting chamber is selectively passed through the light emitting chamber to cause a fluorescent film on the inner surface of the light emitting chamber to emit light, and the emitted light is outputted to the outside through the light transmitting plate. A fluorescent lamp characterized in that a discharge diaphragm member is provided that narrows the discharge diaphragm near the inner surface of the transparent plate, and a fluorescent film is coated on the outer surface of the discharge diaphragm member. 2. A fluorescent lamp, wherein the fluorescent film adherend according to claim 1 is expanded in a tapered shape toward the light-transmitting plate. 3. A fluorescent lamp, wherein the discharge aperture member according to claims 1 and 2 has an outer surface tapered toward the inner surface of the light-transmitting plate.