JP2006190545A - Cold-cathode fluorescent lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable to radiate heat of a phosphor without relying on an extra heat-radiating member. <P>SOLUTION: In the cold-cathode fluorescent lamp exciting the phosphor to emit light by irradiating electrons on a phosphor screen of the phosphor 14, a surface area of the phosphor screen is increased by providing ruggednesses 18 on nearly a whole surface of the phosphor screen, whereby, improvement in heat radiation is attained by increasing an emission volume of secondary electrons e2 without the need of extra heat-radiating members. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a cold cathode fluorescent lamp that emits light by exciting a phosphor with electrons.

In this type of cold cathode fluorescent lamp, various types such as a surface conduction type, a field emission type, and an MIM type have been proposed. For example, in the field emission type, although not shown, a phosphor and an anode part are provided in a vacuum envelope, and a high electric field is applied between the anode part and the cathode part, and electrons (primary electrons) are emitted from the cathode part. The phosphor is accelerated and collided with the phosphor at high speed so that the phosphor is excited to emit light. In the light emission of such a phosphor, energy obtained by subtracting the emission energy from the acceleration energy of electrons is applied to the phosphor. As a result, the phosphor generates heat, resulting in a decrease in luminous efficiency and deterioration of the phosphor. This heat generation increases as the area of the anode portion increases. Therefore, when such a cold cathode fluorescent lamp is incorporated as a backlight of a liquid crystal display device that tends to be thin, light, and have a large screen, the heat dissipation is becoming increasingly important. Although many techniques for radiating heat generated by phosphors have been proposed in the past (see Patent Documents 1, 2, 3, etc.), these existing heat radiating techniques are provided with an additional heat radiating member. If the cost of the backlight is reduced, in addition to thinning and weight reduction, it is difficult to adopt it.
JP 2000-173550 A JP 2000-208077 A JP 2003-237126 A

  The present invention makes it possible to manufacture a thin, lightweight, and low-cost cold cathode fluorescent lamp by enabling the heat dissipation of the phosphor without adding an extra heat dissipation member to the heat dissipation of the phosphor. This is a problem to be solved.

  The cold cathode fluorescent lamp according to the present invention is a cold cathode fluorescent lamp in which secondary electrons are emitted from the phosphor screen when the phosphor is irradiated with electrons and excited to emit light. Irregularities for increasing the amount of secondary electron emission are formed on almost the entire surface irradiated with. The unevenness of the phosphor screen consists of a combination of recesses and protrusions. If the depth of the recesses, the height of the projections, and the pitch of the recesses and projections are the same over the entire phosphor screen, the amount of secondary electron emission is evenly distributed throughout the phosphor screen This is preferable because the heat radiation associated with the emission of the secondary electrons can be made uniform, the luminous efficiency can be made uniform, and the uneven emission can be eliminated. The phosphor is composed of a large number of amorphous phosphor particles. The phosphor particles are irregular, but the particle size is about 4 to 9 μm, and it is preferable to set the number of laminated phosphor particles corresponding to the concave and convex portions in each part of the phosphor screen. Unevenness can be formed by laminating other fine particles having a particle diameter smaller than that of the phosphor particles on the laminated surface of the laminated phosphor particles and setting the amount of the fine particles to be laminated. It is preferable that the uneven pitch, the inner wall surface of the concave portion, and the outer wall surface shape of the convex portion are set so that secondary electrons do not return to the inside of the phosphor due to reflection on the wall surfaces. The unevenness of the phosphor screen of the present invention is an unevenness defined as described above. Unlike the technique disclosed in Japanese Patent Laid-Open No. 1800-90847 as a technique for providing an unevenness on the phosphor screen, Instead of returning the electrons back to the phosphor, heat is radiated so that secondary electrons are not emitted and returned to the phosphor. In addition, if we add to the technique described in the above publication, if the secondary electrons are returned to the phosphor again, the probability that the electrons and holes formed by the generation of secondary electrons recombine and emit light is large. There is almost no heat. Therefore, it should be noted that in the present invention, even if secondary electrons are emitted to the outside, the light emission efficiency is not reduced thereby. Furthermore, as a result of the surface area being increased due to the unevenness of the phosphor, the primary electron irradiation area is enlarged and increased, so that a remarkable effect can be exhibited that the emission intensity does not decrease and heat can be dissipated. It is.

  The shape of the irregularities may be any shape such as a semicircular shape, a semielliptical shape, a sine wave shape, a wave shape, or a sawtooth shape. According to the present invention, since the surface area of the phosphor screen is increased by providing irregularities over almost the entire surface of the phosphor screen, the area in which secondary electrons can be emitted from the phosphor into the tube is greatly expanded. The amount of secondary electrons remaining in the body is greatly reduced, and heat can be radiated by suppressing heat accumulation due to secondary electrons. And since this heat dissipation structure is simply provided with unevenness for increasing the heat dissipation area over the entire surface of the phosphor screen, it is not necessary to attach an extra heat dissipation member for heat dissipation of the phosphor, and it is thin and lightweight, A low-cost cold cathode fluorescent lamp can be manufactured. The depth, height, uneven pitch and the like of the unevenness to be applied to the phosphor screen can be appropriately set by experiments or the like. For example, the phosphor particles have a particle size of, for example, several μm, and irregularities can be formed on the phosphor screen by changing the stacking height of the phosphor particles.

  According to the present invention, it is possible to efficiently dissipate heat generated from the phosphor without providing an extra heat dissipating member for the heat radiation of the phosphor.

  Hereinafter, a cold cathode fluorescent lamp according to an embodiment of the present invention will be described with reference to the accompanying drawings. In the embodiment, the present invention is applied to a field emission type cold cathode fluorescent lamp as a cold cathode fluorescent lamp, but may be applied to other forms of cold cathode fluorescent lamps that emit light by colliding primary electrons from the cold cathode. it can. 1 is a sectional view of a field emission type cold cathode fluorescent lamp (hereinafter referred to as the present lamp) of the present embodiment, FIG. 2 is a sectional view taken along line AA of FIG. 1, and FIG. It is sectional drawing which expands and shows a principal part. In these drawings, the lamp has a vacuum vessel 10 whose inside is set to a predetermined vacuum pressure. The shape of the vacuum vessel 10 can take various forms depending on the use of a light source including a backlight. In the embodiment, a relatively flat box shape is used for convenience of explanation. The vacuum vessel 10 includes a front panel 10a, a back panel 10b, and a spacer panel 10c. The front panel 10a includes a glass substrate, quartz, sapphire, and the like, and can irradiate light source light to the outside. A planar anode 12 is formed on the inner surface of the front panel 10a in a thin film by sputtering, EB vapor deposition, or the like, such as ITO (indium oxide / tin) or aluminum. The material of the anode 12 may be either ITO or aluminum in the type in which the fluorescence emission is directly seen (direct view type), but it is preferable to use ITO in the transmission type in which the fluorescence emission is seen through the anode. In the direct view type, there is no particular limitation on the material, but examples include inorganic materials such as indium oxide, tin oxide, zinc oxide, zinc chalcogenide, gallium nitride, indium nitride, and CdTe in addition to the above indium oxide and tin. it can. However, when the electron velocity is high, electrons can pass through aluminum, so that either a transmissive type or ITO or aluminum may be used.

  The phosphor 14 is formed in a planar shape by being applied to the anode 12 by a slurry coating method, screen printing, an electric perturbation method, a sedimentation method, or the like. A known material (fluorescent material) can be used as the material of the phosphor 14. The thickness of the phosphor 14 is set to about 1 to 5 times the particle size of the phosphor material. It is preferable that the phosphor 14 can emit light with high efficiency by electron beam excitation. The fluorescent material is preferably a material that does not easily react with the conductive material. For example, there is a rare earth oxide fluorescent material. The average particle diameter of the fluorescent particles constituting the phosphor 14 is preferably a value that contributes to the improvement of the light emission efficiency with less unevenness on the fluorescent screen and less uneven light emission.

  The cathode 16 is arranged to extend in a wire shape in one direction at a distance from the anode 12. The cathode 16 is a field emission type cathode that emits electrons so as to cover the entire planar area of the anode 12 by an electric field generated between the anode 12 and the anode 12 by applying an anode voltage of about 3 to 15 kV. The cathode 16 is formed by a conductive wire 16a and a carbon thin film 16b having a number of nanotube-shaped or nanowall-shaped fine protrusions formed on the surface of the conductive wire 16a. The cathode 16 may have a configuration in which one or a plurality of conductors are meandered and bent so as to cover the entire planar area of the anode 12 or the grid 18, or the entire planar area of the anode 12 or the grid 18 may be combined with the plurality of conductors. The structure which covers may be sufficient. The conducting wire 16a is made of nickel or an alloy thereof. The carbon thin film 16b has nanotube-like or nanowall-like fine protrusions. The nanowall-like carbon thin film can be formed by a plasma CVD method, for example, an electron cyclotron resonance method (ECR-PCVD method).

  The cathode 16 is positively set to have a surface roughness that makes it easier for the surface of the conductive wire 16a to generate electric field concentration, and the surface roughness irregularities 16c are further formed on the fine protrusions of the carbon thin film 16b only. 16d is formed and acts as an electric field concentration assisting part that promotes electric field concentration at the fine protrusions. This surface roughness is microscopic but may be visible irregularities. For example, the unevenness | corrugation which twists several conducting wires and the unevenness | corrugation which carries out the threading process of the conducting wire surface may be sufficient.

  In the present lamp having the above configuration, the unevenness 18 is formed on the entire back surface of the phosphor 14. The unevenness 18 can be formed, for example, by randomly setting the number of phosphor particles 14a. The unevenness 18 can be formed by pressing an unevenness forming jig into the surface of the phosphor 14. The depth of the concave portion 18a, the height of the convex portion 18b, the pitch between the concave portions 18a, the pitch of the convex portions 18b, and the like can be appropriately set according to the heat radiation level.

  From the above, in the lamp of the embodiment, the secondary electrons e2 generated when the primary electrons e1 collide with the phosphor 14 are emitted from the back side of the phosphor 14, and the amount of emission is the surface area of the phosphor 14. Since it is increased by the unevenness 18, it can be released in a larger amount compared to the case of a flat surface area, and the heat generated by the light emission on the surface is more effectively dissipated and the phosphor 14 generates heat. As a result, it is possible to prevent the light emission efficiency from being lowered or deteriorated.

  Therefore, in the embodiment, the heat radiation of the phosphor 14 can be improved by simply providing the irregularities 18 on the phosphor 14 without using the heat radiating member. The lamp can be applied to a backlight of a large-sized, lightweight, high-performance and low-cost liquid crystal display device.

  In this lamp, as shown in FIG. 4, the unevenness 10 a 1 can be formed on the inner surface of the front panel 10 a and the unevenness 18 can be formed on the back surface of the phosphor 14.

  The present invention is not limited to the above-described embodiment, and includes various changes or modifications within the scope described in the claims.

It is sectional drawing of the cold cathode fluorescent lamp which concerns on embodiment of this invention. It is sectional drawing of the AA line of FIG. It is sectional drawing which expands and shows the principal part of FIG. It is an expanded sectional view of the principal part of the cold cathode fluorescent lamp which concerns on other embodiment.

Explanation of symbols

12 Anode 14 Phosphor 16 Cathode 18 Concavity and convexity

Claims (1)

  In the cold cathode fluorescent lamp that irradiates the phosphor surface with electrons and excites the phosphor to emit light, the phosphor surface has irregularities formed on almost the entire surface irradiated with electrons to increase the amount of secondary electron emission. A cold cathode fluorescent lamp characterized by comprising:

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