GB2291533A - Fluorescent lamp and display device - Google Patents

Abstract

A display fluorescent lamp includes a cylindrical dielectric container 2, e.g. of glass, fitted with a rare gas e.g. xenon, and having a large diameter portion 2a and a small diameter portion 2b. An internal electrode 3 is inserted into the small diameter portion 2b and an external electrode 4 is mounted on an outer surface of the large diameter portion 2a. Therefore, even when the large diameter portion 2a of the glass valve 2 has a small diameter, it is possible to ensure a sufficient leakage distance between the internal electrode 3 and the external electrode 4. A fluorescent layer 7 is excited by a discharge between the electrodes and emits light with leaves the lamp via a cap portion 8 which may be fitted with a filter. An arrangement of such lamps, e.g. emitting respectively red, blue or green light, may together provide a display. <IMAGE>

Description

FLUORESCENT LAMP AND DISPLAY DEVICE The present invention relates to a display fluorescent lamp used as a light emitting device for use in, for example, a large image display unit or an electric sign board, and further relates to a display device.

Figs. 1 and 2 are a perspective view partially broken away of, and a sectional view of a conventional display fluorescent lamp disclosed in, for example, Japanese Patent Publication (Kokai) No. 5-190152. In the drawings, reference numeral 1 means a display fluorescent lamp, 2 is a cylindrical glass valve forming the display fluorescent lamp 1, and 3 is an internal electrode inserted into the glass valve 2 through a lower end surface of the glass valve 2. Further, reference numeral 4 means an external electrode mounted on an outer surface of the glass valve 2, 7 is a fluorescent substance layer formed on inner walls of a side surface and the lower end surface of the glass valve 2, and 8 is a light emitting portion having permeability mounted onto an upper end surface of the glass valve 2.A power source 6 is connected between the internal electrode 3 and the external electrode 4 via lead wires 5a and 5b.

A description will now be given of the operation.

When the power source 6 applies ac voltage across the internal electrode 3 and the external electrode 4, and voltage is applied to a rare gas in the glass valve 2 through glass serving as dielectric material, thereby causing discharge. Ultraviolet rays are generated by the discharge to excite the fluorescent substance layer 7, and are thereafter converted into specific visible rays which are determined depending upon fluorescent substances.

Since a fluorescent substance itself has a white body, the visible rays emitted from the fluorescent substance are substantially totally reflected off the fluorescent substance layer 7 mounted on the inner wall of the glass valve 2, and are thereafter sent back into the glass valve 2. The visible rays can be outputted and emitted out of the glass valve 2 through the light emitting portion 8 exclusively having permeability.

Thus, the display fluorescent lamp 1 serves as a light emitting device having high luminance.

The conventional display fluorescent lamp can serve as the light emitting device in a large image display unit to provide suitable emission with high luminance.

However, with higher resolution of the large image display unit, it is necessary to reduce a diameter of the glass valve 2 for higher density arrangement of the display fluorescent lamps 1. Hence, a distance between the external part of the internal electrode 3 and the external electrode 4 is reduced, resulting in problems in that, for example, a sufficient leakage distance cannot be ensured for electrical insulation.

In order to overcome the above problems, it is an object of the present invention to provide a display fluorescent lamp in which a sufficient leakage distance can be ensured between an internal electrode and an external electrode even when a glass valve has smaller diameters It is another object of the present invention to provide a display fluorescent lamp in which an external electrode can continuously be printed to have a constant thickness.

It is still another object of the present invention to provide a display fluorescent lamp in which a sufficient connecting space for connecting a lead wire to an external electrode can be provided within an extended cylindrical surface of a cylindrical container.

It is a further object of the present invention to provide a display fluorescent lamp in which prevention can be made of shorts between adjacent external electrodes.

It is a still further object of the present invention to provide a display fluorescent lamp in which an external electrode can be more easily printed onto a cylindrical container.

It is another object of the present invention to provide a display fluorescent lamp in which an external electrode can be formed by simply fitting a preformed cylindrical conductor material into a cylindrical container without complex process required in printing.

A further object of the present invention is to provide a display fluorescent lamp in which reduction can be made of an increase and a decrease in luminance due to reflection at a fluorescent substance layer.

A still further object of the present invention is to provide a display fluorescent lamp in which constant transmittance can be provided in an entire range of visible rays.

Another object of the present invention is to provide a display fluorescent lamp in which an increase and a decrease in luminance can be reduced by utilizing a transmittance characteristic corresponding to a wavelength of visible rays.

Still another object of the present invention is to provide a display fluorescent lamp in which durability of a filter cap can be improved.

A further object of the present invention is to provide a display device in which display fluorescent lamps can be arranged in high density for higher resolution of a display image.

A still further object of the present invention is to provide a display device in which color image display can be carried out by using luminescent colors including red, green, and blue.

Another object of the present invention is to provide a display device in which control can be made to selectively turn ON each of a plurality of display fluorescent lamps by using few signal wires.

Still another object of the present invention is to provide a display device in which insulating tube coating can surely prevent shorts between external electrodes of display fluorescent lamps adjacently disposed in parallel.

A further object of the present invention is to provide a display device which an insulating tube is reliably fixed to a display fluorescent lamp.

A still further object of the present invention is to provide a display device in which an insulating tube is mounted and fixed to a display fluorescent lamp by using heat shrinkage of the tube.

Another object of the present invention is to provide a display device in which insulating caps cover display fluorescent lamps adjacently disposed in parallel, thereby surely avoiding shorts between mutual external electrodes and waterproofing the entire display fluorescent lamps.

Still another object of the present invention is to provide a display device in which reduction can be made of an increase and a decrease in luminance due to reflection at a fluorescent substance layer even when an insulating cap is used.

A further object of the present invention is to provide a display device in which constant transmittance can be provided in an entire range of visible rays even when an insulating cap is used.

A still further object of the present invention is to provide a display device in which an increase and a decrease in luminance can be reduced by using a transmittance characteristic corresponding to a wavelength of visible rays even when an insulating cap is used.

Another object of the present invention is to provide a display device in which durability of an insulating cap can be improved.

Still another object of the present invention is to provide a display device in which an insulating cap can surely and unremovably be secured to a display fluorescent lamp.

A further object of the present invention is to provide a display device in which an insulating cap can be easily fixed onto a cylindrical convex portion.

A still further object of the present invention is to provide a display device in which an insulating cap can be easily mounted to a cylindrical convex portion, and more tight engagement can be provided therebetween.

Another object of the present invention is to provide a display device in which reduction can be made of an increase and a decrease in luminance due to reflection at a fluorescent substance layer by avoiding entrance of external light such as sunlight.

According to the present invention, there is provided a display fluorescent lamp including a cylindrical dielectric container into which a rare gas is sealed, having a large diameter portion and a small diameter portion, a light emitting portion, mounted to the cylindrical container at an end surface on the side of the large diameter portion, an internal electrode inserted into the cylindrical container through an end surface portion on the side of the small diameter portion of the cylindrical container, a fluorescent substance layer formed on an inner surface of the cylindrical container except the light emitting portion, and an external electrode mounted to an outer surface of the large diameter portion of the cylindrical container except the light emitting portion.

In the display fluorescent lamp, an axial length of the small diameter portion of the cylindrical container is longer than a leakage distance required for voltage which is applied across the internal electrode and the external electrode.

In the operation, when voltage is applied by an external power source across the internal electrode and the external electrode, the voltage is applied to the rare gas in the display fluorescent lamp through the cylindrical container made of dielectric material, resulting in discharge. Ultraviolet rays are generated by the discharge to excite the fluorescent substance layer, and are converted into specific visible rays determined depending upon fluorescent substances. Since the fluorescent substance itself typically has a white body, the visible rays emitted from the fluorescent substance are substantially totally reflected off the fluorescent substance layer which is formed on an inner surface of the cylindrical container on the side of the large diameter portion.Thereafter, the visible rays are sent back into the cylindrical container and are finally emitted through the light emitting portion.

In general, the voltage applied across the internal electrode and the external electrode is in an approximate range of 200 to 2000 V while varying depending upon a type of the sealed rare gas or sealing pressure. For example, when the cylindrical container has the large diameter portion having diameter of 6.45 mm, and xenon is sealed as the rare gas at pressure of 200 Torr, it is necessary to apply voltage of about 600 V or more. In this case, a leakage distance of 5.6 mm and more is required for application of, as an example, IEC380 standard of creepage distance.In the display fluorescent lamp of the present invention, with the cylindrical container including the large diameter portion having diameter of 6.45 mm and the small diameter portion having diameter of 2.4 mm, it is possible to provide a leakage distance of about 6 mm or more by setting a length of the small diameter portion to about 4 mm or more. Further, the applied voltage may exceed the above voltage depending upon the type of the sealed rare gas, the sealing pressure, and so forth. In such a case, it is also possible to provide a required leakage distance and sufficiently ensure electrical insulation between the internal electrode and the external electrode by appropriately setting the length of the small diameter portion.

In one preferred mode, an external electrode includes conductor paste formed by printing on an outer peripheral surface of a cylindrical container.

Consequently, by printing the conductor paste, it is possible to continuously print and form the external electrode on an outer surface of the cylindrical container to have a constant thickness.

Alternatively, an external electrode preferably extends onto at least a part of an outer surface of a small diameter portion of a cylindrical container. Since the external electrode extends to reach the outer surface of the small diameter portion of the cylindrical container, it is possible to connect a lead wire to the external electrode at the small diameter portion.

Further, a sufficient connecting space can be provided within an extended cylindrical surface of the cylindrical container, thereby enabling high density arrangement of display fluorescent lamps.

An insulating film may be formed on the outer surface of the external electrode except a position to which power for driving the lamp is supplied. When a plurality of display fluorescent lamps are adjacently disposed to form a display device, the insulating films formed on the external electrodes can prevent shorts between the respective external electrodes.

In another preferred mode, there is provided a display fluorescent lamp in which a circular or slopeshaped boundary portion is provided between a large diameter portion and a small diameter portion of a cylindrical container. With the smooth connecting portion between the large diameter portion and the small diameter portion, it is possible to facilitate printing operation in which conductor paste serving as the external electrode is formed on an outer surface of a cylindrical container.

The external electrode preferably includes a cylindrical conductor material, and is fitted into the outside of the cylindrical container. The cylindrical conductor material is formed by methods such as pressing to have a given shape and given dimensions.

Subsequently, the conductor material is fitted into the outer surface of the cylindrical container, thereby enabling integration of the external electrode with the cylindrical container.

A filter cap having wavelength selecting transmittance may be mounted on the outside of a light emitting portion. The filter cap serves to reduce an increase and a decrease in luminance due to reflection at a fluorescent substance layer.

Alternatively, a filter cap preferably includes a neutral density filter. The neutral density filter has a constant transmittance characteristic in an entire range of visible rays, thereby reducing the increase and the decrease in luminance in a fluorescent substance.

The filter cap may includes a color filter. The color filter has a transmittance characteristic corresponding to a wavelength of the visible rays emitted from the fluorescent substance. As a result, it is possible to reduce the increase and the decrease in luminance due to the reflection at the fluorescent substance.

The filter cap is preferably made of silicon rubber, resulting in improved durability and enhanced weather resistance.

According to the present invention, there is provided a display device in which the plurality of display fluorescent lamps as described above are disposed in parallel in a flat form. Since the display fluorescent lamps having small outside diameter can be arranged in high density in the flat form, the display device enables high-resolution image display.

In one preferred mode, in the display device, three types of display fluorescent lamps, including a red emitting lamp, a green emitting lamp, and a blue emitting lamp, are disposed in parallel for each type. As a result, it is possible to carry out high-resolution color image display.

In the display device, display fluorescent lamps are preferably disposed in a matrix form, with external electrodes or internal electrodes of the display fluorescent lamps interconnected for each row through one connecting members, and the internal electrodes or the external electrodes of the display fluorescent lamps interconnected for each column through the other connecting members. As a result, it is possible to reduce the number of wires used for power supply to the electrodes.

Alternatively, in the display device having a base member to attach the respective display fluorescent lamps, cylindrical convex portions may be provided for the base member at positions opposed to the respective lamps. Further, the convex portion and a position of the display fluorescent lamp except a light emitting portion may be also coated with a common insulating tube. As a result, it is possible to surely prevent shorts between the external electrodes of the respective display fluorescent lamps.

In another preferred mode, the display device includes an adhesive layer interposed between a display fluorescent lamp and an insulating tube, thereby surely fixing the insulating tube to the display fluorescent lamp.

The insulating tube preferably includes a heatshrinkable tube. That is, the display fluorescent lamp and the convex portion are covered with the heatshrinkable tube which is thereafter heated. As a result, the heat-shrinkable tube can be secured to an outer surface of the display fluorescent lamp by shrinkage force inherent in the heat-shrinkable tube, resulting in insulation between the respective external electrodes.

Alternatively, in the display device, the cylindrical convex portions may be provided to attach the display fluorescent lamps for a base member at positions opposed to the display fluorescent lamps. Further, the convex portion and the light emitting portion of the display fluorescent lamp may be coated with a common insulating cap. It is thereby possible to waterproof the entire display fluorescent lamps.

In another preferred mode, an insulating cap of each display fluorescent lamp is made of material having wavelength selecting transmittance. As a result, with the insulating cap made of the material having the wavelength selecting transmittance, it is possible to eliminate the need for discretely preparing a filter cap or the like.

The insulating cap of each display fluorescent lamp preferably includes a neutral density filter. The filter has constant transmittance in an entire range of visible rays, thereby reducing an increase and a decrease in luminance due to reflection at a fluorescent substance layer.

Alternatively, the insulating cap of each display fluorescent lamp may include a color filter. The color filter has a transmittance characteristic corresponding to a wavelength of visible rays to reduce the increase and the decrease in luminance due to the reflection at the fluorescent substance layer.

The insulating cap of each display fluorescent lamp is preferably made of silicon rubber, resulting in improved durability and enhanced weather resistance.

In another preferred mode, an adhesive layer is interposed between an insulating cap of each display fluorescent lamp and the display fluorescent lamp. The insulating cap is secured by adhesive to the display fluorescent lamp, thereby reliably preventing the insulating cap from dropping out of the display fluorescent lamp.

In the display device, a projecting portion preferably extends from an outer surface of each cylindrical convex portion of a base member. As a result, with the projecting portion extending from the outer surface of the cylindrical convex portion, it is possible to prevent the insulating cap from dropping out of the convex portion, and to stabilize a mounting state.

In another preferred mode, a concave portion is provided in an outer surface of each cylindrical convex portion of a base member, and a projecting portion for engaging the concave portion extends from an inner surface of an insulating tube or an insulating cap of each display fluorescent lamp. It is thereby possible to easily fit the insulating tube or insulating cap with the cylindrical convex portion, and to stabilize a fitting state.

The display device is preferably provided with light shielding means for shielding external light into a light emitting portion of the display fluorescent lamp. The light shielding means can prevent high intensity external light such as sunlight from directly entering the display fluorescent lamp, and can previously avoid an increase and a decrease in luminance of the display fluorescent lamp due to the irradiation. As a result, bright display image can be observed.

The above and further objects and novel features of the invention will more fully appear from the following detailed description when the same is read in connection with the accompanying drawings. It is to be expressly understood, however, that the drawings are for purpose of illustration only and are not intended as a definition of the limits of the invention.

Fig. 1 is a perspective view partially broken away of a conventional display fluorescent lamp; Fig. 2 is a sectional view showing the conventional display fluorescent lamp; Fig. 3 is a sectional view showing one embodiment of a display fluorescent lamp according to the present invention; Fig. 4 is a sectional view showing another embodiment of the display fluorescent lamp according to the present invention; Fig. 5 is a sectional view showing still another embodiment of the display fluorescent lamp according to the present invention; Fig. 6 is a sectional view showing still another embodiment of the display fluorescent lamp according to the present invention; Fig. 7 is a sectional view showing still another embodiment of the display fluorescent lamp according to the present invention;; Fig. 8 is a sectional view showing still another embodiment of the display fluorescent lamp according to the present invention; Fig. 9 is a sectional view showing still another embodiment of the display fluorescent lamp according to the present invention; Fig. 10 is a sectional view showing still another embodiment of the display fluorescent lamp according to the present invention; Fig. 11 is a perspective view showing a cylindrical conductor material in Fig. 10; Fig. 12 is a sectional view showing still another embodiment of the display fluorescent lamp according to the present invention; Fig. 13 is a perspective view showing one embodiment of a display device according to the present invention; Fig. 14 is a perspective view showing another embodiment of the display device according to the present invention;; Fig. 15 is a plan view showing electric connection in another embodiment of the display device according to the present invention; Fig. 16 is a perspective view showing still another embodiment of the display device according to the present invention; Fig. 17 is a perspective view showing a base member having cylindrical convex portions in the display device in Fig. 16; Fig. 18 is a sectional view showing a display fluorescent lamp in Fig. 16; Fig. 19 is a sectional view showing a display fluorescent lamp in still another embodiment of the display device according to the present invention; Fig. 20 is a sectional view showing a display fluorescent lamp in still another embodiment of the display device according to the present invention;; Fig. 21 is a sectional view showing a display fluorescent lamp in still another embodiment of the display device according to the present invention; Fig. 22 is a sectional view showing a display fluorescent lamp in still another embodiment of the display device according to the present invention; Fig. 23 is a sectional view showing a display fluorescent lamp in still another embodiment of the display device according to the present invention; Fig. 24 is a perspective view showing still another embodiment of the display device having light shielding means, according to the present invention; Fig. 25 is a front view showing the light shielding means in Fig. 24; and Fig. 26 is a side view showing the light shielding means in Fig. 24.

Embodiments of the invention will now be described in detail referring to the accompanying drawings. In Fig. 3, reference numeral 1 means a display fluorescent lamp, and 2 is a cylindrical container forming the display fluorescent lamp 1, that is, a glass valve serving as a cylindrical container including portions having different diameters in an axial direction.

Further, reference numeral 2a means a large diameter portion of the glass valve 2, and 2b is a small diameter portion of the glass valve 2.

Reference numeral 3 means an internal electrode inserted into the glass valve 2 through an end surface portion of the glass valve 2 on the side of the small diameter portion 2b, 4 is an external electrode mounted on an outer surface of the large diameter portion 2a of the glass valve 2, and 7 is a fluorescent substance layer formed on an internal side surface and an internal lower end surface of the large diameter portion 2a of the glass valve 2.

Reference numeral 8 means a light emitting portion, mounted at an upper end (i.e., at the left end in the drawing) of the large diameter portion 2a of the glass valve 2. The internal electrode 3 and the external electrode 4 are connected to a power source 6 via lead wires 5a and 5b.

A description will now be given of the operation.

When voltage is applied by the power source 6 across the internal electrode 3 and the external electrode 4, the voltage is applied to a rare gas in the display fluorescent lamp 1 through glass serving as dielectric material, resulting in discharge. Ultraviolet rays are generated by the discharge to excite the fluorescent substance layer 7, and are converted into specific visible rays determined depending upon fluorescent substances.

Since the fluorescent substance itself has a white body, the visible rays emitted from the fluorescent substance are substantially totally reflected off the fluorescent substance layer 7 which is formed on the inner surface of the glass valve 2 on the side of the large diameter portion 2a. Thereafter, the visible rays are sent back into the glass valve 2, and are finally outputted and emitted out of the glass valve 2 through the light emitting portion 8 having permeability.

The voltage applied across the internal electrode 3 and the external electrode 4 is in an approximate range of 200 to 2000 V while varying depending upon a type of the sealed rare gas or sealing pressure. For example, when the glass valve 2 has the large diameter portion 2a having diameter of 6.45 mm, and xenon is sealed as the rare gas at pressure of 200 Torr, it is necessary to apply voltage of about 600 V or more. In this case, a leakage distance of 5.6 mm or more is required for application of, as an example, IEC380 standard.

In the conventional display fluorescent lamp, it is impossible to extend the leakage distance between the internal electrode and the external electrode to be half the diameter of the glass valve or more. Therefore, the glass valve having diameter of 6.45 mm provides an insufficient leakage distance of about 3 mm.

On the other hand, in the display fluorescent lamp 1 of the present invention, when the glass valve 2 has the large diameter portion 2a having diameter of 6.45 mm and the small diameter portion 2b having diameter of 2.4 mm, it is possible to provide a leakage distance of about 6 mm or more by setting a length of the small diameter portion 2b to about 4 mm or more. Further, the applied voltage may exceed the above voltage depending upon the type of the sealed rare gas, the sealing pressure, and so forth. In such a case, it is also possible to provide a required leakage distance and sufficiently ensure electrical insulation between the internal electrode 3 and the external electrode 4 by appropriately setting the length of the small diameter portion 2b.

The external electrode 4 can efficiently and easily be formed by printing conductor paste on the outer surface of the glass valve 2 by using printing methods such as screen printing.

Fig. 4 is a sectional view showing another embodiment of the display fluorescent lamp according to the present invention. In the display fluorescent lamp 1 of the embodiment, the external electrode 4 extends onto a part of the small diameter portion 2b of the glass valve 2. In such a structure, it is possible to provide a sufficient space required to connect the lead wire 5b with the external electrode 4 within an extended cylindrical surface of the large diameter portion 2a of the glass valve 2. Consequently, the connecting portion for the lead wire 5b does not require an unnecessarily large outside diameter, resulting in high density arrangement of the display fluorescent lamps 1.

Fig. 5 is a sectional view showing still another embodiment of the display fluorescent lamp according to the present invention. In the display fluorescent lamp 1 of the embodiment, an external electrode 4 partially extends onto a part of a small diameter portion 2b of a glass valve 2. As in the second embodiment shown in Fig.

4, it is possible to provide a sufficient connecting space required for a lead wire within an extended cylindrical surface of the glass valve 2, resulting in high density arrangement of the display fluorescent lamps 1.

Fig. 6 is a sectional view showing still another embodiment of the display fluorescent lamp according to the present invention. In the display fluorescent lamp 1 of the embodiment, an insulating film 9 extends across an outer periphery of an external electrode 4 to cover the external electrode 4 except a position to which a driving signal is supplied for the external electrode 4. A lead wire 5b, for supplying driving power to the external electrode 4, is connected via an opening in the insulating film 9 to the external electrode 4 mounted on a large diameter portion 2a of a glass valve 2.

According to the embodiment, if the plurality of display fluorescent lamps 1 are arranged to form a display device, it is possible to provide an effect in that prevention can be made of shorts between the adjacent external electrodes 4.

Fig. 7 is a sectional view showing still another embodiment of the display fluorescent lamp according to the present invention. In the display fluorescent lamp 1 of the embodiment, an external electrode 4 partially extends onto a part of a small diameter portion 2b of a glass valve 2, and an insulating film 9 extends across an outer periphery of the external electrode 4 to cover the external electrode 4 except a position to which a driving signal is supplied for the external electrode 4. A lead wire 5b, for supplying driving power to the external electrode 4, is connected to an end of the external electrode 4 extending onto the small diameter portion 2b of the glass valve 2.In the embodiment, as in the above embodiment, it is possible to provide high-density arrangement of the display fluorescent lamps 1, and prevent shorts between the external electrodes 4 of the adjacent display fluorescent lamps 1.

Fig. 8 is a sectional view showing still another embodiment of the display fluorescent lamp according to the present invention. In the display fluorescent lamp 1 of the embodiment, a boundary portion is provided in a circular form between the large diameter portion 2a and the small diameter portion 2b of the glass valve 2. An external electrode 4 partially extends onto a part of the small diameter portion 2b of the glass valve 2. Further, an insulating film 9 extends across an outer periphery of the external electrode 4 to cover the external electrode 4 except a position to which a driving signal is supplied for the external electrode 4. A lead wire Sb, for supplying driving power to the external electrode 4, is connected to an end of the external electrode 4 extending onto the small diameter portion 2b of the glass valve 2.

According to the embodiment, when the external electrode 4 is formed to extend from the large diameter portion to the small diameter portion 2b of the glass valve 2 by printing conductor paste, there are the following advantages. That is, the printing operation can continuously and easily be carried out through the circular portion 2c, and formation of the insulating film 9 is facilitated.

Fig. 9 is a sectional view showing still another embodiment of the display fluorescent lamp according to the present invention. In the display fluorescent lamp 1 of the embodiment, a slope-shaped portion (a boundary portion) is formed to connect a large diameter portion 2a and a small diameter portion 2b of a glass valve 2.

Further, an external electrode 4 partially extends onto a part of the small diameter portion 2b of the glass valve 2. In addition, an insulating film 9 extends across an outer periphery of the external electrode 4 to cover the external electrode 4 except a position to which a driving signal is supplied for the external electrode 4. A lead wire 5b, for supplying driving power to the external electrode 4, is connected to an end of the external electrode 4 extending onto the small diameter portion 2b of the glass valve 2. According to the embodiment, through the slope-shaped portion 2d provided between the large diameter portion 2a and the small diameter portion 2b of the glass valve 2, it is also possible to continuously, easily and rapidly form conductor paste serving as the external electrode 4, or the insulating film 9 by printing.

Fig. 10 is a sectional view showing still another embodiment of the display fluorescent lamp according to the present invention. In the display fluorescent lamp 1 of the embodiment, an external electrode 4 includes a cylindrical conductor material 10 as shown in Fig. 11, and the external electrode 4 is fitted into an outer periphery of a large diameter portion 2a of a glass valve 2. The cylindrical conductor material 10 of the external electrode 4 is cut out of a plate and formed by pressing or the like. A connecting strip lOa is bent on the side of a center of the cylindrical conductor material 10 to contact a lead wire 5b.

Therefore, according to the embodiment, it is possible to eliminate process required to print and form conductor paste, including printing, drying, and baking, thereby providing an advantage of improved assembling efficiency.

Fig. 12 is a sectional view showing still another embodiment of the display fluorescent lamp according to the present invention. In the display fluorescent lamp 1 of the embodiment, a filter cap 11 having wavelength selecting permeability is mounted on a light emitting portion 8 of a glass valve 2. External light enters the glass valve 2 through the light emitting portion 8 to be reflected off a fluorescent substance layer 7, and the external light is emitted from the light emitting portion 8 again, thereby increasing or decreasing luminance.

According to the embodiment, the increase or decrease in luminance can be reduced by damping the external light through two filtering operations, that is, entrance filtering operation and emission filtering operation. As a result, more enhanced contrast can be obtained in a display image. Although the construction of the display fluorescent lamp 1 is similar to that of the lamp shown in Fig. 3 in this embodiment, it is available to utilize the construction shown in Fig. 8 or Fig. 9.

The filter cap 11 having the wavelength selecting permeability may include a neutral density filter having constant transmittance in an entire range of visible rays. In this case, a constant transmittance characteristic can be provided in the entire range of the visible rays to efficiently reduce the increase and the decrease in luminance due to reflection at a fluorescent substance. Alternatively, the filter cap 11 may include a color filter having a transmittance characteristic corresponding to a wavelength of visible rays emitted from the fluorescent substance, resulting in an effect of improved contrast as described above. Alternatively, the filter cap 11 may be made of silicon rubber, thereby improving durability and weather resistance.

Fig. 13 is a perspective view showing one embodiment of a display device according to the present invention.

In a display device 21 of the embodiment, a plurality of display fluorescent lamps 1 as shown in Figs. 3 to 12 are arranged on a base member 22 in a flat matrix form. As shown in Fig. 13, small diameter portions of the respective display fluorescent lamps 1 are mounted to the base member 22 with light emitting portions 8 of glass valves 2 directed upwardly.

According to the embodiment, the display fluorescent lamp 1 has the small diameter portion of the glass valve, in which a leakage distance can be extended. Hence, an outside diameter of a large diameter portion can be made as small as possible, thereby providing the display device which can form a large high-resolution image display unit.

Fig. 14 shows another embodiment of the display device according to the present invention. In the display device 21 of the embodiment, the plurality of lamps of three types including a red emitting lamp 1R, a green emitting lamp 1G, and a blue emitting lamp 1B, are arranged on the base member 22 in the regular order.

According to the embodiment, the emitting lamps 1R, 1G, and 1B are turned ON with their intensity set to different rates, thereby reproducing various types of luminescent colors. As a result, it is possible to provide a high-resolution color image display unit.

Fig. 15 is a plan view showing electric connection in another embodiment of the display device according to the present invention. In the display device 21 of the embodiment, display lamps 1 are arranged in a matrix form, with external electrodes 4 of the display fluorescent lamps 1 mutually connected for each row, and internal electrodes 3 of the display fluorescent lamps 1 mutually connected for each column. There are provided connecting members 23 for interconnecting the external electrodes 4, and connecting members 24 for interconnecting the internal electrodes 3. This structure can realize an interface between the display device 21 and an external display device drive circuit (not shown) by only eight signal lines (i.e., four connecting members 23 and four connecting members 24).

Fig. 15 shows the display device 21 formed by interconnecting the external electrodes 4 of the display fluorescent lamps 1 for each row, and by interconnecting the internal electrodes 3 of the display fluorescent lamps 1 for each column. However, for the purpose of the same effect, the display device 21 may be formed by connecting the mutual internal electrodes 3 of the display fluorescent lamps 1 for each row, and by connecting the mutual external electrodes 4 of the display fluorescent lamps 1 for each column.

Fig. 16 shows still another embodiment of the display device according to the present invention. In the display device 21 of the embodiment, cylindrical convex portions 25 extend to attach display fluorescent lamps 1 as shown in Fig. 17 from a base member 22 of the display device 21 at positions opposed to the display fluorescent lamps 1. As shown in Fig. 18, the convex portions 25 and the position of the display fluorescent lamps 1 except light emitting portions 8 are coated with common insulating tubes 26.

In the embodiment, as shown in Fig. 18, a small diameter portion 2b of a glass valve 2 of each display fluorescent lamp 1 is inserted into a center hole 25a of the convex portion 25. Further, the display fluorescent lamp 1 and the convex portion 25 are simultaneously coated with the insulating tube 26 after a lower surface of a large diameter portion 2a is opposed to a top surface of the convex portion 25. It is thereby possible to more reliably prevent shorts between the adjacent external electrodes 4 of the display fluorescent lamps 1.

In the drawing, omission is made of the external electrode 4 and so forth.

Fig. 19 is a sectional view mainly showing an external construction of a display fluorescent lamp in still another embodiment of the display device according to the present invention. In each display fluorescent lamp 1, an adhesive layer 27 is provided on an inner surface of an insulating tube 26. According to the embodiment, it is possible to enhance adhesion between the display fluorescent lamp 1 and the insulating tube 26, and between a cylindrical convex portion 25 extending from a base member 22 and the insulating tube 26. If the insulating tube 26 includes a heat-shrinkable tube, the adhesion can be more enhanced after heat shrinkage.

Fig. 20 is a sectional view showing an external construction of a display fluorescent lamp in still another embodiment of the display device according to the present invention. In each display fluorescent lamp 1, the cylindrical convex portion 25 as shown in Fig. 17 extends from a base member 22 of the display device at a position opposed to the display fluorescent lamp 1.

Further, the convex portion 25 and a light emitting portion 8 of the display fluorescent lamp 1 are coated with a common insulating cap 28.

According to the embodiment, waterproofness of the display fluorescent lamp 1 can be established. Further, the insulating cap 28 may be made of material having wavelength selecting transmittance, thereby eliminating the need for discretely preparing a filter cap. The insulating cap 28 may be made of silicon rubber, resulting in an advantage of improved weather resistance.

Alternatively, the insulating cap 28 may include a neutral density filter having constant transmittance in an entire range of visible rays, or a color filter having a transmittance characteristic corresponding to a wavelength of the visible rays emitted from a fluorescent substance. It is thereby possible to reduce an increase and a decrease in luminance due to reflection at the fluorescent substance.

Fig. 21 is a sectional view mainly showing an external construction of a display fluorescent lamp in still another embodiment of the display device according to the present invention. In each display fluorescent lamp 1, a cylindrical convex portion 25 extends from a base member 22 of the display device at a position opposed to the display fluorescent lamp 1. Further, the convex portion 25 and a light emitting portion 8 of the display fluorescent lamp 1 are coated with a common insulating cap 28. An adhesive layer 29 is provided on an inner surface of the insulating cap 28. According to the embodiment, it is possible to more enhance adhesion between the display fluorescent lamp 1 and the insulating cap 28, and between a cylindrical convex portion 25 and the insulating cap 28.

Fig. 22 is a sectional view mainly showing a display fluorescent lamp in still another embodiment of the display device according to the present invention. In each display fluorescent lamp 1, a cylindrical convex portion 25 extends from a base member 22 of the display device at a position opposed to the display fluorescent lamp 1. Further, the convex portion 25 and a light emitting portion 8 of the display fluorescent lamp 1 are coated with a common insulating cap 28. An adhesive layer 29 is provided on an inner surface of the insulating cap 28. In addition, a projecting portion 30 is provided on a circumferential surface of the cylindrical convex portion 25 extending from the base member 22 of the display device 21.In the embodiment, the insulating cap 28 is fitted to cover the display fluorescent lamp 1, thereby securely fitting a lower portion of the insulating cap 28 with the cylindrical convex portion 25. Thus, it is possible to prevent the insulating cap 28 from being easily released from the cylindrical convex portion 25. Though the insulating cap 28 has been described in the embodiment, the projecting portion 30 may be provided for the insulating tube 26 as shown in Figs. 16, 18, and 19, resulting in the same effect.

Fig. 23 is a sectional view showing an external construction of a display fluorescent lamp in still another embodiment of the display device according to the present invention. In each display fluorescent lamp 1, a cylindrical convex portion 25 extends from a base member 22 of the display device at a position opposed to the display fluorescent lamp 1. Further, the convex portion 25 and a light emitting portion 8 of the display fluorescent lamp 1 are coated with a common insulating cap 28. An adhesive layer 29 is provided on an inner surface of the insulating cap 28. In addition, a projecting portion 31 is provided on an inner surface of the insulating cap 28 at a position covering the cylindrical convex portion 25, and a concave portion 32 is provided in a circumferential surface of the cylindrical convex portion 25 at a position corresponding to the projecting portion 31.

According to the embodiment, the projecting portion 31 is fitted with the concave portion 32, thereby providing an advantage to more reliably prevent the insulating cap 28 from being released from the cylindrical concave portion 25. Though the insulating cap 28 is shown in the drawing, the projecting portion 31 and the concave portion 32 may be provided for the insulating tube 26 as shown in Figs. 16, 18, and 19, resulting in the same effect.

Fig. 24 is a perspective view, Fig. 25 is a front view, and Fig. 26 is a side view, showing still another embodiment of the display device according to the present invention. Light shielding means 33 is mounted to the display device 21 to prevent intensive external light such as sunlight from directly reaching light emitting portions 8 of display fluorescent lamps 1. The light shielding means 33 includes light shielding plate 34 interposed between lateral arrays of the plurality of display fluorescent lamps 1, for shielding direct sunlight travelling from the upper side or the diagonally upper side. It is thereby possible to reduce an increase and a decrease in luminance by reducing reflection from a fluorescent substance of the display fluorescent lamp 1, and to realize more improved contrast in a display image.

Though the display device includes four by four (i.e., sixteen) display fluorescent lamps in the embodiment described above, it must be noted that the present invention should not be limited to sixteen display fluorescent lamps, and may employ any number of display fluorescent lamps to form one display device.

As set forth above, the present invention can provide many effects.

An axial length of the small diameter portion of the cylindrical container is longer than the leakage distance required for voltage which is applied across the internal electrode and the external electrode. As a result, even when the glass valve has smaller diameters, it is possible to provide a sufficient leakage distance between the internal electrode and the external electrode.

The external electrode includes the conductor paste formed by printing on the outer peripheral surface of the cylindrical container. Consequently, it is possible to continuously print and form the external electrode to have a constant thickness.

The external electrode extends onto the outer surface of the small diameter portion of the cylindrical container. As a result, the sufficient connecting space for connecting the lead wire to the external electrode can be provided within the extended cylindrical surface of the cylindrical container.

The insulating film is formed on the outer surface of the external electrode except the position to which the driving signal for the external electrode is supplied. As a result, it is possible to avoid shorts between adjacent external electrodes.

The circular or slope-shaped boundary portion is provided between the large diameter portion and the small diameter portion of the cylindrical container. As a result, it is possible to facilitate the external electrode printing operation to the cylindrical container.

The external electrode includes a cylindrical conductor material, and is fitted into the outside of the cylindrical container. As a result, without complex process required in printing, it is possible to easily form the external electrode by simply fitting the preformed cylindrical conductor material into the cylindrical container.

The filter cap having the wavelength selecting transmittance is mounted on the outside of the light emitting portion, thereby reducing the increase and the decrease in luminance due to the reflection at the fluorescent substance layer.

The filter cap includes the neutral density filter, resulting in constant transmittance in the entire range of visible rays.

The filter cap includes the color filter to utilize the transmittance characteristic corresponding to the wavelength of the visible rays. As a result, it is possible to reduce the increase and the decrease in luminance due to the reflection at the fluorescent substance layer.

The filter cap is made of silicon rubber, resulting in improved durability and enhanced weather resistance of the filter cap.

The plurality of display fluorescent lamps having small diameter are disposed in a flat and parallel form.

Consequently, the display fluorescent lamps can be arranged in high density, resulting in higher resolution of the display image.

The emitting lamps of three types including the red emitting lamp, the green emitting lamp, and the blue emitting lamp, are disposed in parallel for each type.

As a result, color image display can be carried out by using the luminescent colors including red, green, and blue.

The display fluorescent lamps are disposed in a matrix form, with the external electrodes or internal electrodes of the display fluorescent lamps interconnected for each row through one connecting members, and the internal electrodes or external electrodes of the display fluorescent lamps interconnected for each column through the other connecting members. As a result, control can be made to selectively turn ON each of the plurality of display fluorescent lamps by using few signal wires.

The cylindrical convex portion is provided for the base member at the position opposed to the display fluorescent lamp. Further, the convex portion and the position of the display fluorescent lamp except the light emitting portion are coated with the common insulating tube. As a result, it is possible to surely prevent shorts between the external electrodes of the display fluorescent lamps adjacently disposed in parallel.

The adhesive layer is interposed between the display fluorescent lamp and the insulating tube, thereby surely fixing the insulating tube to the display fluorescent lamp.

The insulating tube includes the heat-shrinkable tube. As a result, by using the heat shrinkage of the tube, it is possible to easily mount and fix the insulating tube to the display fluorescent lamp.

The cylindrical convex portion to attach the display fluorescent lamp is provided for the base member at the position opposed to the display fluorescent lamp.

Further, the convex portion and the light emitting portion of the display fluorescent lamp are coated with the common insulating cap. With the insulating caps covering the respective display fluorescent lamps adjacently disposed in parallel, it is possible to surely avoid the shorts between the mutual external electrodes, and to waterproof the entire display fluorescent lamps.

The insulating cap is made of material having the wavelength selecting transmittance. As a result, even when the insulating cap is used, it is also possible to reduce the increase and the decrease in luminance at the light emitting portion.

The insulating cap includes the neutral density filter. As a result, even when the insulating cap is used, it is also possible to provide constant transmittance in the entire range of visible rays.

The insulating cap includes the color filter. As a result, even when the insulating cap is used, it is also possible to reduce the increase and the decrease in luminance by using the transmittance characteristic corresponding to the wavelength of visible rays.

The insulating cap is made of silicon rubber, resulting in improved durability and enhanced weather resistance of the insulating cap.

The adhesive layer is interposed between the insulating cap and the display fluorescent lamp. As a result, it is possible to surely and unremovably secure the insulating cap to the display fluorescent lamp.

The projecting portion extends from the outer surface of each cylindrical convex portion of the base member, thereby easily fixing the insulating cap onto the cylindrical convex portion.

The projecting portion extends from the inner surface of the insulating tube or insulating cap at the position covering the outer surface of the cylindrical convex portion. Further, the concave portion for engaging the projecting portion is provided in the outer surface of the cylindrical convex portion at the position corresponding to the projecting portion. As a result, it is possible to more tightly fit the insulating cap with the cylindrical convex portion.

There is provided the light shielding means for shielding the external light into the light emitting portion of the display fluorescent lamp. As a result, it is possible to avoid entrance of the external light such as sunlight, thereby reducing the increase and the decrease in luminance due to the reflection at the fluorescent layer.

While preferred embodiments of the invention have been described using specific terms, such description is for illustrative purposes only, and it is to be understood that changes and variations may be made without departing from the scope of the following claims.

Claims (28)

1. A display fluorescent lamp comprising: a cylindrical dielectric container into which a rare gas is sealed, having a large diameter portion and a small diameter portion; a light emitting portion, mounted to said cylindrical container at an end surface portion on the side of said large diameter portion; an internal electrode inserted into said cylindrical container through an end surface portion on the side of the small diameter portion of said cylindrical container; a fluorescent substance layer formed on an inner surface of said cylindrical container except said light emitting portion; and an external electrode mounted to an outer surface of the large diameter portion of said cylindrical container except said light emitting portion; wherein an axial length of said small diameter portion is longer than a leakage distance require for voltage which is applied across said internal electrode and said external electrode.

2. A display fluorescent lamp according to claim 1, wherein said external electrode includes conductor paste formed by printing on an outer peripheral surface of said cylindrical container.

3. A display fluorescent lamp according to claim 1, wherein said external electrode extends onto at least a part of an outer surface of said small diameter portion of said cylindrical container.

4. A display fluorescent lamp according to any one of claims 1 to 3, wherein an insulating film is formed on an outer surface of said external electrode except a position to which power for driving said lamp is supplied.

5. A display fluorescent lamp according to any one of claims 1 to 3, wherein a circular or slope-shaped boundary portion is provided between said large diameter portion and said small diameter portion of said cylindrical container.

6. A display fluorescent lamp according to claim 1, wherein said external electrode includes a cylindrical conductor material, and is fitted into the outside of said cylindrical container.

7. A display fluorescent lamp according to any one of claims 1 to 3, wherein a filter cap having wavelength selecting transmittance is mounted on the outside of said light emitting portion.

8. A display fluorescent lamp according to claim 7, wherein said filter cap includes a neutral density filter.

9. A display fluorescent lamp according to claim 7, wherein said filter cap includes a color filter.

10. A display fluorescent lamp according to claim 8 or 9, wherein said filter cap is made of silicon rubber.

11. A display device comprising a plurality of display fluorescent lamps disposed in a flat form, said display fluorescent lamp including: a cylindrical dielectric container into which a rare gas is sealed, having a large diameter portion and a small diameter portion; a light emitting portion mounted to said cylindrical container at an end surface portion on the side of said large diameter portion; an internal electrode inserted into said cylindrical container through an end surface portion on the side of the small diameter portion of said cylindrical container; a fluorescent substance layer formed on an inner surface of said cylindrical container except said light emitting portion; and an external electrode mounted to an outer surface of the large diameter portion of said cylindrical container except said light emitting portion; wherein an axial length of said small diameter portion is longer than a leakage distance required for voltage which is applied across said internal electrode and said external electrode.

12. A display device according to claim 11, wherein said plurality of display fluorescent lamps of three types including a red emitting lamp, a green emitting lamp, and a blue emitting lamp, are disposed in parallel for each type.

13. A display device according to claim 11 or 12, wherein said plurality of display fluorescent lamps are disposed in a matrix form, with the external electrodes or the internal electrodes of said display fluorescent lamps interconnected for each row through one connecting members, and the internal electrodes or the external electrodes of said display fluorescent lamps interconnected for each column through the other connecting members.

14. A display device according to claim 11 or 12, further comprising a base member to attach said plurality of display fluorescent lamps, wherein cylindrical convex portions are provided for said base member at positions opposed to said display fluorescent lamps, and said convex portion and a position of said display fluorescent lamp except a light emitting portion being coated with a common insulating tube.

15. A display device according to claim 14, wherein said insulating tube includes a heat-shrinkable tube.

16. A display device according to claim 15, wherein an adhesive layer is interposed between each display fluorescent lamp and the insulating tube covering said lamp.

17. A display device according to claim 11 or 12, further comprising a base member to attach said plurality of display fluorescent lamps, wherein cylindrical convex portions for attaching said display fluorescent lamps are provided for said base member at positions opposed to said display fluorescent lamps, and said convex portion and a light emitting portion of said display fluorescent lamp being coated with a common insulating cap.

18. A display device according to claim 17, wherein said insulating cap is made of material having wavelength selecting transmittance.

19. A display device according to claim 18, wherein said insulating cap includes a neutral density filter.

20. A display device according to claim 18, wherein said insulating cap includes a color filter.

21. A display device according to claim 17, wherein said insulating cap is made of silicon rubber.

22. A display device according to claim 17, wherein an adhesive layer is interposed between each display fluorescent lamp and the insulating cap covering said lamp.

23. A display device according to claim 14, wherein a projecting portion extends from an outer surface of said cylindrical convex portion.

24. A display device according to claim 17, wherein a projecting portion extends from an outer surface of said cylindrical convex portion.

25. A display device according to claim 14, wherein a concave portion is provided in an outer surface of each cylindrical convex portion of said base member, and a projecting portion for engaging said concave portion extending from an inner surface of an insulating tube of each display fluorescent lamp.

26. A display device according to claim 17, wherein a concave portion is provided in an outer surface of each cylindrical convex portion of said base member, and a projecting portion for engaging said concave portion extending from an inner surface of the insulating cap of each display fluorescent lamp.

27. A display device according to claim 11 or 12, further comprising light shielding means for shielding external light into the light emitting portion of each display fluorescent lamp.

28. A display device substantially as hereinbefore described with reference to any one of Figures 3 to 26 of the accompanying drawings.