JPH0495338A - Discharge lamp - Google Patents

Abstract

PURPOSE:To enhance light flux by forming on the inner or outer surface of a glass envelop an ultraviolet radiation reflecting layer which reflects ultraviolet radiation and which allows transmission of visible light therethrough. CONSTITUTION:A thin dielectric multilayed film 6 which roughly completely reflects ultraviolet radiation in the vicinity of 253.7nm which is the main exciting wavelength of mercury and which allows visible light of wavelength from 380 to 780nm to be roughly transmitted therethrough is formed on the inner surface of a glass envelop 2. As a result, ultraviolet radiation generated at the lighting of a discharge lamp from gas sealed in the glass envelope 2 is converted to visible light when applied to particles of fluorescent material in a fluorescent material particle layer 4. The visible light converted from the ultraviolet radiation is roughly completely transmitted through the thin dielectric multilayered film 6. Ultraviolet radiation transmitted through the fluorescent material particle layer 4 is roughly completely reflected by the thin dielectric multilayered film 6 and is therefore reflected by the thin dielectric film 6 until it is applied to the fluorescent material particles in the fluorescent material particle layer 4 and converted to visible light; i.e., the thin dielectric multilayered film 4 reflects ultraviolet radiation and also has complete wavelangth selectivity by which it allows transmission of visible light therethrough and is capable of converting roughly all ultraviolet radiation generated from the gas sealed in the glass envelop 2 to visible light.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a discharge lamp having a fluorescent substance that converts ultraviolet rays around 253°7 nm, which is the main excitation wavelength of mercury, into visible light. This invention relates to fluorescent lamps and cold cathode discharge lamps with improved efficiency.

[Prior Art] Generally, discharge lamps including fluorescent lamps, cold cathode discharge lamps, etc. consist of a glass envelope and a phosphor particle layer coated on the inner surface of the glass envelope. After being evacuated, the envelope is filled with rare scum such as alcon, krypton, neon, helium, etc., and mercury vapor, although the type varies depending on the type of lamp. In a discharge lamp, when the lamp is lit, the phosphor in the phosphor particle layer is excited mainly by ultraviolet light around 253.7 nm, which is the main excitation wavelength of mercury, and the wavelength 3 B On, m b)
is converted into visible light over a wavelength of 780 nm. The converted visible light passes through the glass envelope and exits, but on the other hand,
The ultraviolet rays that have passed through the phosphor particle layer and reached the glass envelope are substantially absorbed by the glass envelope.

In order to effectively utilize the ultraviolet rays absorbed by the glass envelope, for example, referring to U.S. Pat. No. 4,079,288, A.
It is disclosed that by providing an ultraviolet reflection layer made of 12O3, ultraviolet light transmitted through the phosphor particle layer is reflected to excite the phosphor particles, thereby improving the luminous flux of the discharge lamp.

[Problems to be Solved by the Invention] However, since the conventional ultraviolet reflection layer is made by applying white powder such as Al2O3 to the inner surface of a glass bulb, it also reflects visible light having a wavelength of 380nrn to 780nm. For this reason, it is extremely effective for reflective discharge lamps in which a specific area is provided in a part of the glass bulb where no phosphor particle layer or ultraviolet reflection layer is coated, and the reflected light is emitted from this specific area, but it is not effective for reflective discharge lamps. In a full-circumference discharge lamp, the luminous flux is only slightly improved by the ultraviolet reflection layer, and there is a strong need for an ultraviolet reflection layer that reflects ultraviolet light and transmits visible light.

Therefore, an object of the present invention is to provide a discharge lamp with improved luminous flux by forming an ultraviolet reflection layer that reflects ultraviolet rays and transmits visible light on the inner or outer surface of a glass envelope.

[Means for Solving the Problems] In view of the above-mentioned circumstances, the present inventors first focused on the technology of multilayer thin film dielectric reflecting mirrors. In this multilayer thin film dielectric reflector technology, by forming a reflective film consisting of several to tens of layers of dielectric thin films with high refractive index and low refractive index stacked alternately, absorption is reduced and arbitrary It is possible to select a spectral reflectance of 100% and obtain a reflectance close to 100% for a specific wavelength.

As a result of intensive research, the above purpose was to create a film with the main excitation wavelength of mercury on the inner surface of the glass envelope or, if the material of the glass envelope is made of a material that almost transmits ultraviolet rays, on the outer surface of the glass envelope. This problem is solved by providing a discharge lamp characterized by forming a dielectric pot N thin film that almost completely reflects ultraviolet rays around 253.7 nm and substantially transmits visible light with wavelengths from 380 nm to 780 nm. .

Preferably, in this discharge lamp, the dielectric multilayer thin film has T
a high refractive index layer made of at least one substance selected from the group consisting of iO2, Ta2O5 and ZnS, and 5j02
and low refractive index layers made of at least one substance selected from the group consisting of MgF2 and MgF2.

In addition, in this invention, even if the discharge lamp is a fluorescent lamp in which the main part of the light emission is photoluminescence of a fluorescent substance excited by ultraviolet radiation from the discharge, the discharge lamp is a cold cathode discharge lamp that emits light by the sunlight of the glow discharge. In the case of a fluorescent lamp, the dielectric multilayer thin film is preferably a reflective film in which three or more layers of TlO2 layers and 5102 layers are stacked alternately, while in the case of a cold cathode discharge lamp. It is preferable that the reflective film is a reflective film in which nine or more dielectric multilayer thin films are stacked.

[Function] For example, on the inner surface of the glass envelope, a dielectric multilayer thin film is formed that almost completely reflects ultraviolet light around 253.7 nm, which is the main excitation wavelength of mercury, and almost transmits visible light with wavelengths from 380 nm to 780 nm. As a result, as shown in the schematic diagram of FIG. 1, when the discharge lamp is lit, the ultraviolet rays generated from the gas sealed in the glass envelope 2 are emitted as shown in item 2 a in FIG. , when the phosphor particles of the phosphor ion N4 are irradiated, it is converted into visible light. The converted visible light almost completely passes through the dielectric multilayer thin film 6. on the other hand,
The ultraviolet rays that have passed through the phosphor particles N4 are almost completely reflected by the dielectric multilayer thin film 6, as shown in No. 2 in FIG. The light that is converted into light is reflected by the dielectric thin film 6.

That is, in the past, part of the ultraviolet rays generated from the gas sealed in the glass envelope 2 was absorbed by the glass envelope 2, resulting in transmission loss, but in the present invention, the dielectric multilayer thin film 4 has perfect wavelength selectivity, reflecting ultraviolet rays and transmitting visible light, so almost all of the ultraviolet rays emitted from the gas sealed within the glass envelope 2 are ideally converted into visible light. A discharge lamp is realized.

As a result, the luminous efficiency of the discharge lamp is improved to an astonishing degree.

[Example] Examples of the present invention will be described below.

First, the present inventors investigated a dielectric multilayer thin film from the viewpoint that it completely reflects ultraviolet rays around 253.7 nm, which is the main excitation wavelength of mercury, and transmits visible light with wavelengths ranging from 380 nm to 780 nm.

First, if the glass envelope is made of an ultraviolet-transparent material such as high-purity quartz glass, a dielectric multilayer thin film may be formed on the outer surface of the glass envelope, but if the glass envelope is not made of high-purity material, Since this method absorbs ultraviolet rays, which reduces luminous efficiency, it was assumed that a dielectric multilayer thin film would be formed on the inner surface of the glass envelope.

As the high refractive index layer, T i 02, Ta2O5, Zn
S, etc. are good, and as a low refractive index layer, 5102, Mg
F2 etc. is good.

Next, various methods such as vacuum evaporation method, vapor phase method (CVD method), etc. can be considered as a method for producing a dielectric multilayer thin film.
On the premise of selecting a dipping method that is excellent in mass production, we selected TiO2 as the high refractive index layer and SiO2 as the low refractive index layer, and laminated the high refractive index layer - low refractive index layer - high refractive index layer. By doing this, we considered how many layers to add.

That is, as shown in FIG. 1, a discharge lamp has a glass envelope 2, and a dielectric multi-N thin film is disposed between a phosphor particle layer 4 to be coated on the inner surface of the glass envelope 2. M6 is formed. The glass envelope 2 is a silica (Si02) glass substrate, and the refractive index of T i 02 of the optical refractive index layer is n, = 2.
．． 76, the refractive index of SiO2 of the low refractive index layer is n, :=1
．． 48, and the configuration is assumed to be a bandpass filter having a periodic multilayer film of a high refractive index layer and a low refractive index layer, and the configuration is expressed by the following equation.

NS/ (0,5H)(L -H)”L (0,5H)
/N.

Ns glass substrate (n, = 1.48) 0.5H: High refractive index layer (n Hd: 0.125λ)
L: Low refractive index layer (nLd=0.25λ) H: High refractive index F
(n, d=0.25λ) NO=phosphor particle layer Note that d is the film thickness, and d is the wavelength (253.7 nm).

For example, when the number of layers is 9, it is as follows.

NS/ (0,5H) (L -H) ”L (0,
5H) /N.

That is, a specific example of the configuration, expressed in terms of constituent materials and their film thicknesses, is as follows.

Glass substrate/(Ti02: 12.2n-)(Si
02:45.6nm) (Ti02:24.5n@)
(Si02:45.6r++w) (Ti02:24
．． 5nw) (Si02: 45.6n*) (T1
02: 24.5rv) (Si02:45.6n*)
(T102: 12.2 ns) / Phosphor particle layer Figure 2 shows the results of calculating the reflectance at normal incidence for a wavelength of 253.7 nm for the 5th to 15th layers of dielectric length N thin film 6 with such a configuration. is shown.

As is clear from FIG. 2, when the dielectric multilayer thin film 6 has nine or more layers, the reflectance at a wavelength of 253.7 nm can be about 97% or more.

Also, as a matter of course, the more layers the dielectric multilayer thin film 6 has, the closer the reflectance can be to 100%.
As is clear from FIG. 2, the reflectance exceeds 99% with 13 layers and 15N, and 13 layers is economically sufficient.

Next, although it is not shown in the figure, the lower limit of lamination is about 82% even in the case of 3 layers, the reflectance at 253.7 layers m is about 82%, and in the case of these 3 layers, it feels the brightest to the eye Transmits almost completely at 550%m of the visible range, which is said to be 380nm.
Since it has a reflectance of approximately 10% or less at m to 780 nm, three layers are sufficient when economical efficiency is considered while improving brightness.

The reflectance curve of the dielectric multilayer thin film 60 constructed in this way will be described.

3 to 6 show reflectance curves when the number of layers of the dielectric multilayer thin film 6 is 9 to 15, respectively.

As is clear from FIGS. 3 to 6, the visible light region,
In other words, the reflectance at wavelengths from 381 Dnm to 780% m is all 20% or less, and it can be said that the film is highly transparent.

Next, the characteristics of a discharge lamp in which such a dielectric multilayer thin film 6 is formed will be described.

(Example 1) As a discharge lamp, the dielectric multilayer thin film 6 of the present invention was applied to a cold cathode discharge lamp that emits light by the sunlight of glow discharge.

Color temperature 5500'K, outer diameter 8.0mmφ, total length 2
In a cold cathode discharge lamp for back illumination of a liquid crystal display device with a diameter of 60 mm, high-purity stone T glass with excellent ultraviolet transmission is used for the glass envelope 2, TiO2 is used as a high refractive index layer, and TiO2 is used as a low refractive index layer. S i 02 was selected and a dielectric multilayer thin M6 having nine layers was formed on the inner surface of the glass envelope 2 by a dipping method.

A conventional cold cathode lamp that does not form a dielectric multilayer thin film 6,
At 25°C, 30 kHz, and a rated current of 5 mA, the brightness is 4500 nt, whereas the cold cathode discharge lamp of the present invention can have a brightness of about 6000 nt under the same conditions, and has a brightness half-life of 4500 nt. The lifespan was approximately 20,000 hours long.

(Example 2) Next, as a discharge lamp, a normal low-pressure mercury lamp whose main part of light emission is photoluminescence of a fluorescent substance excited by ultraviolet radiation from a discharge, and in particular a three-wavelength high color rendering fluorescent lamp. The dielectric multilayer thin film 6 of the present invention was applied to this.

The color temperature is set to 3000°, and the glass envelope 2 is set to FL40S.
In a three-wavelength fluorescent lamp with an S bulb, TlO2 is selected as the high refractive index layer and 5102 is selected as the low refractive index layer, and a dielectric multilayer thin film 6 having three layers is dipped on the inner surface of the glass envelope 2. Formed by law.

The luminous flux of a conventional discharge lamp in which 2 g/m2 of α-A12O3 powder with a particle size of 0.3 μm was coated on the inner surface of the FL40SS bulb as an ultraviolet reflection layer was 35001 m, whereas a dielectric material was used instead of the ultraviolet reflection layer. The luminous flux of the fluorescent lamp of the present invention, which is the same except that the multilayer thin film 6 is formed, is extremely bright at 42001 m.

In addition, other lamp characteristics such as color rendering, luminous flux maintenance rate, and color shift (color change) were almost the same as those of conventional fluorescent lamps.

Although the above description has been made regarding cold cathode discharge lamps and fluorescent lamps, it is understood that the present invention may be applied to various discharge lamps such as other discharge lamps, such as hot cathode discharge lamps and high-pressure discharge lamps. Needless to say.

[Effects of the Invention] As explained above, according to the present invention, a discharge lamp with improved luminous flux is provided by forming an ultraviolet reflection layer on a glass envelope that reflects ultraviolet rays and transmits visible light. be able to.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a part of a cross section of a discharge lamp according to the present invention, FIG. 2 is a graph diagram showing the relationship between the number of layers and reflectance of the dielectric multilayer thin film in FIG. 1, and FIG. 6 to 6 are graphs showing reflectance curves of the dielectric multilayer thin film shown in FIG. 1. 2°° glass envelope, 4. Phosphor particle layer, 6. Dielectric multilayer thin film. Figure 1

Claims (6)

[Claims] (1) Apply ultraviolet rays near 253.7 nm, which is the main excitation wavelength of mercury, to the inner surface of the glass envelope or the outer surface of the glass envelope when the material of the glass envelope is made of a material that almost transmits ultraviolet rays. Approximately reflective and wavelength 380nm to 780nm
A discharge lamp characterized by forming a dielectric multilayer thin film that substantially transmits visible light over a wide range. (2) The dielectric multilayer thin film consists of a high refractive index layer made of at least one substance selected from the group consisting of TiO2, Ta2O5, and ZnS, and at least one substance selected from the group consisting of SiO2 and MgF2. The discharge lamp according to claim 1, characterized in that the discharge lamp is formed of alternating layers of low refractive index layers. (3) The discharge lamp is a fluorescent lamp whose main part of light emission is photoluminescence of a fluorescent substance excited by ultraviolet radiation from a discharge. Discharge lamp described in. (4) The discharge lamp according to claim 3, wherein the dielectric multilayer thin film is made of a reflective thin film in which three or more TiO2 layers and SiO2 layers are stacked alternately. (5) The discharge lamp according to claim 1 or 2, wherein the discharge lamp is a cold cathode discharge lamp that emits light by the sunlight of glow discharge. (6) The discharge lamp according to claim 5, wherein the dielectric multilayer thin film is a reflective thin film in which nine or more TiO2 layers and SiO2 layers are stacked alternately.