JP2000251839A - Cold cathode fluorescent lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve color shifting and attenuation of brightness through a relatively simple constitution. SOLUTION: Electrodes 3, 3 are arranged at respective ends of a glass bulb 1 of a straight tube formed by laminating a light transmissive protective layer 5A and a luminescent layer 2 in its inner face, rare gas and mercury are sealed in the inner space of the glass bulb 1, and the protective layer 5A is formed by mixing two kinds of oxides selected from the group comprising the oxides of aluminum, lanthanum and cerium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cold cathode fluorescent lamp, and more particularly to an improvement of a cold cathode fluorescent lamp of a backlight unit applied to a liquid crystal display device in OA equipment such as a personal computer and a word processor.

[0002]

2. Description of the Related Art Generally, a cold cathode fluorescent lamp of this kind is obtained by mixing a plurality of phosphors which emit light in, for example, blue, green and red regions on the inner surface of a glass bulb 1 as shown in FIG. A light-emitting layer 2 is formed of the mixed phosphor, electrodes 3 and 3 are arranged at the end of the glass bulb 1, and a rare gas such as argon and mercury are sealed in the interior space of the glass bulb 1. I have. The electrodes 3,
Lead wires 4 and 4 are connected to 3 and are led out from the end of the glass bulb 1 to the outside.

In this cold cathode fluorescent lamp, for example, the outer diameter of the glass bulb 1 is reduced to 6 mm or less.
It is suitable for a backlight unit of a liquid crystal display device in an OA device such as a notebook personal computer or a word processor in which a display screen is colorized, since the lamp brightness is high.

In this cold-cathode fluorescent lamp, the bulb temperature tends to increase with an increase in the tube wall load at the time of lighting due to the reduction in the diameter of the glass bulb 1, and the brightness is attenuated based on this. In addition, the color misregistration may impair the display function of the liquid crystal display device.

Specifically, for example, the light-emitting layer 2 is a europium-activated strontium-calcium-barium phosphor [(Sr.Ca.
Ba) ₅ (PO ₄ ) ₃ Cl: Eu], a cerium / terbium-activated lanthanum phosphate phosphor [LaPO ₄ : Ce · Tb] which emits light in a green region, and a europium which emits light in a red region. Active yttrium oxide phosphor [Y ₂ O
₃ : Eu].
Phosphors that emit light in the blue region are more susceptible to degradation than other phosphors, and tend to have a greater decrease in brightness. For this reason, when the x value and the y value in the CIE chromaticity coordinates are shifted in the plus direction by, for example, about 0.002 to 0.004, the color balance of the blue area, the green area, and the red area is lost, and the light color becomes yellowish. In addition, the display quality of the liquid crystal display device is significantly impaired.

Further, as the bulb temperature of the glass bulb 1 increases, a change in color occurs due to the reaction of a part of the precipitated components and the phosphor from the glass bulb 1 with mercury, and the brightness is reduced based on this. It becomes larger, and furthermore, a color shift or the like occurs.

[0007]

Therefore, conventionally, in order to solve such a problem, for example, as shown in FIG. 4, the average particle size between the inner surface of the glass bulb 1 and the light emitting layer 2 is increased. For example, a cold cathode fluorescent lamp in which a translucent protective layer 5 made of alumina (Al ₂ O ₃ ) having a thickness of about 0.05 to 0.1 μm has been proposed.

According to this proposal, the plurality of phosphors constituting the light-emitting layer 2 emit light when the phosphors facing the discharge side are stimulated by mercury resonance lines (ultraviolet rays), Since the phosphor facing the luminous layer is stimulated by the ultraviolet rays transmitted through the light emitting layer 2 and reflected by the protective layer 5 to emit light, the initial luminance tends to increase. Therefore, as the display screen of the liquid crystal display device becomes more colorized, it becomes possible to achieve the higher brightness required for the cold cathode fluorescent lamp.

However, although the discoloration of the glass bulb 1 due to the formation of the protective layer 5 is improved to some extent as compared with the cold cathode fluorescent lamp shown in FIG. 3, the color shift and the decay of the brightness are reduced as shown in FIG. The level is equivalent to that of a cathode fluorescent lamp, and further improvement is required.

Therefore, an object of the present invention is to provide a cold cathode fluorescent lamp which can improve color misregistration, brightness attenuation and the like with a relatively simple structure.

[0011]

SUMMARY OF THE INVENTION Accordingly, in order to achieve the above-mentioned object, the present invention provides a straight tubular glass bulb formed by laminating a light-transmitting protective layer and a light-emitting layer on the inner surface. An electrode is disposed at an end of the cold cathode fluorescent lamp in which a rare gas and mercury are sealed in an inner space of a glass bulb, wherein the protective layer is formed by mixing a plurality of metal oxides. And

According to a second aspect of the present invention, the protective layer is formed by mixing two or more selected from the group consisting of an oxide of aluminum, lanthanum and cerium. According to the invention, a specific metal oxide 1 is contained in a weight ratio of a mixing ratio of a plurality of metal oxides forming the protective layer.
In contrast, another metal oxide is set in the range of 0.7 to 1.3.

Further, a fourth invention of the present invention is characterized in that said light emitting layer is formed by mixing a plurality of phosphors which emit light in blue, green and red regions. Means that the outer diameter of the glass bulb is 1.5 to 6.0 mm.
Is set within the range of.

[0014]

Next, an embodiment of a cold cathode fluorescent lamp according to the present invention will be described with reference to FIG.
The same parts as those of the conventional example shown in FIGS. 3 and 4 are denoted by the same reference numerals, and detailed description thereof will be omitted. This embodiment is characterized in that a protective layer 5 having a light-transmitting property formed by mixing a plurality of metal oxides on the inner surface of the glass bulb 1 in order from the inner surface side.
A: The light emitting layer 2 is formed by lamination. The protective layer 5A is formed by mixing, for example, two or more selected from the group consisting of oxides of aluminum, lanthanum, and cerium (Al ₂ O ₃ , La ₂ O ₃ , and CeO ₂ ).
As a combination, for example, Al ₂ O ₃ + La ₂ O ₃ , A
I ₂ O ₃ + CeO ₂ and La ₂ O ₃ + CeO ₂ are recommended. In these combinations, the mixing ratio of the plurality of metal oxides is set in the range of 0.7 to 1.3 with respect to the specific metal oxide 1 and the other metal oxides by weight ratio. However, the mixing ratio of other metal oxides is 0.7
If it is less than 1.3 or more than 1.3, depending on the combination, the attenuation of the brightness or the color shift can be obtained only at the level of the conventional example. Therefore, it is desirable to set within the above range.

The glass bulb 1 is made of, for example, silicon oxide,
It is composed of a lead-free borosilicate glass based on boron oxide (hereinafter referred to as BFK glass for convenience), and has an outer diameter of 1.5 to 6.0 mm, preferably 1. It is set in the range of 5 to 3.0 mm. This B
FK glass includes, for example, silicon oxide (SiO ₂ ), alumina (Al ₂ O ₃ ), boron oxide (B ₂ O ₃ ), sodium oxide (Na ₂ O), potassium oxide (K ₂ O), and lithium oxide (Li ₂ O). 0), titanium oxide (TiO ₂ ), etc., and the composition ratio is, for example, 67.6% of silicon oxide, 4% of alumina, 18% of boron oxide, 1% of sodium oxide, 8% of potassium oxide, 1% of lithium oxide. , 0.4% titanium oxide
Although it is set to a degree, the composition ratio can be appropriately changed depending on desired glass characteristics. The glass bulb 1 can be made of lead glass, soda glass, low lead glass or the like.

On the inner surface of the glass bulb 1, a protective layer 5 is provided.
A, the light emitting layer 2 is formed by lamination. In particular, the light emitting layer 2 located on the discharge path side has, for example, a blue region, a green region,
It is composed of a mixed phosphor obtained by mixing a plurality of rare-earth phosphors that emit light in the red region, but may be composed in combination with another phosphor such as a halophosphate phosphor, or depending on the purpose. It is also possible to use one kind of phosphor alone. In addition, this light emitting layer 2
For example, it can be composed of a mixture containing a plurality of phosphors, α-alumina and metal borate. In particular, the proportion of the mixture of α-alumina and metal borate is 0.5 to 0.5% of the phosphor weight. By setting them in the range of 4.0% and 0.1 to 1.0%, it is possible to reduce peeling of the light emitting layer 2 due to application of vibration, impact, and the like, and to improve starting characteristics in a dark state.

According to this embodiment, since the protective layer 5A is formed of a plurality of metal oxides, the initial luminance, the color shift and the attenuation of the brightness can be effectively improved as compared with the conventional example. Depending on the combination of metal oxides, a metal oxide having a relative life of 50,000 hours (life defined as the life when the luminous flux maintenance ratio becomes 50%) is obtained. This is presumed to be because each metal oxide exhibits a complementary action.

In particular, when the combination of metal oxides is Al ₂ O ₃ +
In the case of La ₂ O ₃ , Al ₂ O ₃ + CeO ₂ , an excellent effect on the initial luminance and the color shift is recognized. When the combination of metal oxides is La ₂ O ₃ + CeO ₂ , the initial luminance and the color are improved. The latter combination is recommended because excellent effects are recognized in all of the shift and the brightness attenuation.

The light emitting layer 2 is made of, for example, a plurality of phosphors and α
-If it is composed of a mixture containing alumina and metal borate, the light emitting layer 2 comes closer to the electrodes 3 and 3 because the diameter of the glass bulb 1 is reduced, and the gap between the electrodes in the dark state When a high-frequency high voltage is applied to the substrate, not only the electron emitted from α-alumina can be used as a trigger to reliably start the device in a short time, but also the peeling of the light emitting layer 2 can be reduced.

Further, the outer diameter of the glass bulb 1 is 1.5
It is desirable that the diameter be within the range of about 6.0 mm in accordance with the technical trend of lightening and shortening of the OA equipment. In particular, when the outer diameter is in the range of 1.5 to 3.0 mm, the above-mentioned effect becomes more remarkable. Tends to appear.

The present invention is not limited to the above-described embodiment. For example, the light-emitting layer may form an aperture portion (a portion where the light-emitting layer is not formed) depending on the application.
Further, the supply of mercury to the internal space of the glass bulb can be performed by, for example, attaching a mercury-titanium alloy to the electrode or in the vicinity thereof and performing high-frequency heating after completion of the evacuation operation. Further, the protective layer can be made of an oxide other than aluminum, lanthanum and cerium.

[0022]

Next, an experimental example will be described. First, it contains isopropyl alcohol, dispersant, metal oxide particles,
An outer diameter of 3 m is applied to a coating solution prepared by adjusting the particle concentration to 2%.
One end of a glass bulb made of borosilicate glass having a length of 230 mm is immersed, applied by suction by vacuum suction, dried and fired to form a protective layer. Next, europium-activated strontium-calcium-barium chlorophosphate, cerium / terbium-activated lanthanum phosphate-based phosphor, and europium-activated yttrium oxide-based phosphor are provided on the inner surface (on the protective layer) of the glass bulb. Are applied at a weight ratio of 2: 1: 2, and a coating solution containing a mixed phosphor is applied by suction using vacuum suction, dried and fired to form a light emitting layer. Thereafter, a mixed rare gas of neon (95%)-argon and 5 mg of mercury were sealed in the interior space of the glass bulb, and the lamp section A shown in FIG.
~ F to complete the production of the cold cathode fluorescent lamp. The combination of a plurality of metal oxides in the protective layer of these cold cathode fluorescent lamps is such that the lamp category A is Al ₂ O ₃ + La.
₂ O ₃ , lamp section B is Al ₂ O ₃ + CeO ₂ , lamp section C is La ₂ O ₃ + CeO ₂ , and the mixing ratio is set to 1: 1. The protective layer of the lamp section D is formed only of Al ₂ O ₃ , the lamp section E is formed of only La ₂ O ₃ , and the lamp section F is formed of only CeO ₂ .

The cold cathode fluorescent lamps were measured for initial luminance, color shift during 100 hours of operation, and attenuation of brightness. The results shown in FIG. 2 were obtained. In the drawing, the mark ◎ indicates that a remarkable effect was obtained as compared with the conventional example shown in FIG. 4, and the mark ○ indicates that the effect was obtained as compared with the conventional example shown in FIG. The marks indicate that only the same level of effect as that of the conventional example shown in FIG. 4 was obtained.

As is clear from these results, Al
Among the three types of metal oxides, ₂ O ₃ , La ₂ O ₃ , and CeO ₂ , lamp categories A to 2 in which two are appropriately combined.
In the case of C, the initial luminance, color shift, and attenuation are all favorable effects as compared with the conventional example shown in FIG. The life of these lamp sections was prolonged. In particular, the lamp section C had a luminous flux maintenance rate of 55% when operated for 50,000 hours.

However, the lamp section D using only Al ₂ O ₃ has excellent initial luminance, but the color shift and the attenuation are at the level of the conventional example. The lamp section E using only La ₂ O ₃ has the attenuation. Is excellent, but the color shift is at the level of the conventional example, and when applied to a backlight unit of a liquid crystal display device in OA equipment, sufficient display quality cannot be expected. Further, the lamp category F using only CeO ₂ is generally improved from the level of the conventional example, and when applied to a backlight unit of a liquid crystal display device, display quality can be expected to be improved. It is not enough.

[0026]

As described above, according to the present invention, since the protective layer is formed of a plurality of metal oxides, the initial luminance, the color shift, and the attenuation of the brightness can be reduced as compared with the conventional example. In addition to the improvement, the relative life can be improved.

[0027] Particularly, when a combination of a metal oxide is Al ₂ O ₃ and _{La 2 O 3, Al 2 O} 3 and CeO ₂ are obtained excellent effects with respect to the initial luminance and the color misregistration, metal oxides Is a combination of La ₂ O ₃ and CeO ₂ , excellent effects can be obtained in all of the initial luminance, the color shift, and the attenuation of the brightness. Therefore, for example, when applied to a backlight unit of a liquid crystal display device, the display quality of the liquid crystal display device can be improved.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing one embodiment of the present invention.

FIG. 2 is a diagram showing results of determining various characteristics with respect to combinations of metal oxides.

FIG. 3 is a side sectional view of a conventional cold cathode fluorescent lamp.

FIG. 4 is a side sectional view of a different conventional cold cathode fluorescent lamp.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Glass bulb 2 Light emitting layer 3 Electrode 4 Lead wire 5A Protective layer

Claims (5)

[Claims] An electrode is disposed at each end of a straight tube-shaped glass bulb formed by laminating a light-transmitting protective layer and a light-emitting layer on its inner surface, and a rare gas and A cold-cathode fluorescent lamp in which mercury is sealed, wherein the protective layer is formed by mixing a plurality of metal oxides. 2. The cold cathode fluorescent lamp according to claim 1, wherein said protective layer is formed by mixing two or more members selected from the group consisting of aluminum, lanthanum and cerium oxide. 3. The mixing ratio of a plurality of metal oxides forming the protective layer is within a range of 0.7 to 1.3 with respect to a specific metal oxide 1 with respect to a specific metal oxide 1. The cold cathode fluorescent lamp according to claim 1, wherein the cold cathode fluorescent lamp is set. 4. The cold cathode fluorescent lamp according to claim 1, wherein the light emitting layer is formed by mixing a plurality of phosphors that emit light in blue, green, and red regions. 5. The outer diameter of the glass bulb is 1.5-6.
2. The cold cathode fluorescent lamp according to claim 1, wherein the cold cathode fluorescent lamp is set within a range of 0 mm.