JPS6337459B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fluorescent lamp with high efficiency and improved color rendering, and more particularly to an improvement in a fluorescent lamp having a two-layer phosphor structure to reduce lamp cost.

Recently, based on the results of research on the color vision of the human eye, a phosphor that emits blue light around 450 nanometers, a green phosphor around 540 nanometers, and a red phosphor around 610 nanometers has been mixed. Fluorescent lamps with light bodies have been proposed. This fluorescent lamp has the highest lamp efficiency and is the most widely used conventional fluorescent lamp.
It also has excellent properties, being equivalent to the brightest white fluorescent lamp, and its color rendering properties are almost the same as conventional fluorescent lamps with improved color rendering. However, since the phosphors used in these fluorescent lamps are all made from rare earth metals, they are extremely expensive, and therefore the lamps have to be expensive as well.

As a countermeasure against this, for example, the phosphor can be coated in two layers, i.e., an inexpensive phosphor is coated on the glass tube side, and an expensive phosphor is coated on the discharge side. It has been proposed to significantly reduce the amount of phosphor used. What is important in this case is the chromaticity point of the phosphor layer coated on the glass tube side (hereinafter referred to as the first phosphor layer) and the chromaticity point of the phosphor layer coated on the discharge side (hereinafter referred to as the second phosphor layer). It is necessary to bring the chromaticity points of the body layers as close as possible. This means that approximately 90% or more of the ultraviolet rays generated within the fluorescent lamp are absorbed by the second phosphor layer, converted into visible light having the desired emission spectrum, and emitted, but the remaining approximately 10%
% or less of ultraviolet light is absorbed by the first phosphor layer and
It is converted into visible light having the emission spectrum of the phosphor, and is emitted from the fluorescent lamp together with the visible light emitted by the second phosphor layer. Therefore, if the chromaticity point of the first phosphor layer is different from the chromaticity point of the second phosphor layer, the light emitted from the lamp will deviate from the intended chromaticity point.

As a result of a more detailed study by the present inventors on this point, we found that even if the chromaticity point of the first phosphor layer and the chromaticity point of the second phosphor layer are the same, We have found that the color rendering properties are greatly affected by the type of phosphor.

The present invention was made based on the recognition of this fact, and an object of the present invention is to provide a fluorescent lamp with high efficiency and improved color rendering properties.

Conventionally, the phosphor used in the first phosphor layer of a fluorescent lamp with a two-layer structure that has high efficiency and high color rendering properties has been used as a phosphor that is highly efficient, inexpensive, and has a relatively large change in chromaticity point. Antimony- and manganese-activated calcium halophosphate phosphors have been mainly used because they are easily produced.This phosphor is coated as the first phosphor layer, and the emission spectrum is determined as the second phosphor layer. The peak wavelength of is approximately 450
A fluorescent lamp coated with three types of phosphors, each of which has a narrow emission spectrum half-width of 30 to 60 nanometers, 5 to 30 nanometers, and 5 to 30 nanometers, respectively. As shown in Figure 1, we created lamps with different coating amounts of each phosphor layer and calculated the spectral energy distribution and color rendering index.As shown in Figure 1, the light amount of the first phosphor layer relative to the total light amount was It was found that as the color rendering index increases, the average color rendering index decreases. Furthermore, as a result of a detailed study of the spectral energy distribution determined using the amount of light from the first phosphor layer as a parameter, as shown in Figure 2,
It has been found that the energy from lamps around 500-530 nanometers and 560-580 nanometers increases. Here, curve 1 is when the light amount from the first phosphor layer is mixed with the light amount from the second phosphor layer by 10%, curve 2 is when the light amount is mixed by 20%, and curve 3 is when the light amount is mixed by 30%. This shows the spectral energy distribution of light emitted from a fluorescent lamp. From the above, the average color rendering index decreases in the wavelength ranges mentioned above, namely 500 to 530 nanometers and 560 nanometers.
It became clear that this was due to an increase in energy of ~580 nanometers. Furthermore, as a result of examining color rendering properties, it was found that in addition to the average color rendering index, R ₉ for red, which is particularly important among special color rendering indexes, and R ₁₅ for Japanese skin tones also decreased significantly, and that It was found that energy in the wavelength region of 560 to 580 nanometers has a large influence. Since this wavelength almost coincides with the manganese emission peak wavelength of the phosphor of the first phosphor layer shown by curve 5 in FIG. 3, there is no other way than to reduce this emission intensity. Note that curve 4 shows the spectral energy distribution consisting only of the second phosphor layer. In order to improve color rendering, the thickness of the second phosphor layer is increased to reduce the emission intensity of the first phosphor layer, and the second phosphor layer converts most of the ultraviolet rays into visible light. There is no choice but to convert, but this is inappropriate because it increases costs and goes against the purpose of the present invention. As a result of various studies on solutions, it has been found that a phosphor that does not have an emission peak in the range of 560 to 580 nanometers may be used for the first phosphor layer. The phosphors that meet this purpose are firstly the green region of 500 to 600 nanometers;
In the red region of ~700 nanometers, the phosphor in the second phosphor layer has a narrow half-width in that wavelength range, and because it has high efficiency and high color rendering properties, the half-width is narrow. A wide phosphor is inappropriate. In addition, there is no inexpensive and highly efficient phosphor with a narrow half-width in the green and red regions. From the above, as a result of examining phosphors in the blue region, we found that the blue-emitting phosphor in the second phosphor layer has a relatively wide half-width. It has been found that the color rendering index is not affected at all even when the light is mixed with light from the second phosphor.

As described above, the chromaticity point of the first phosphor layer and the
It has become clear that simply matching the chromaticity points of the phosphor layer does not necessarily provide high color rendering properties, and that the spectral energy distribution of the phosphor used in the first phosphor layer is important. This means that if you simply match the chromaticity points as in the past, the color rendering index will decrease unless you control the coating amount of the first phosphor layer and the coating amount of the second phosphor layer very strictly. However, by using a phosphor in the first phosphor layer that does not emit light in the wavelength range that causes a decrease in color rendering properties, as in the present invention, it is possible to precisely control the coating amount. It has the great advantage that a high color rendering index can be obtained without any control. Examples of phosphors suitable for the first phosphor layer for the purpose of the present invention include antimony-activated calcium halophosphate, calcium tungstate, magnesium tungstate, and tin-activated strontium pyrophosphate. 400
These include those in the range of ~500 nanometers.
2.2g of antimony-activated calcium halophosphate with a peak emission spectrum wavelength of 480 nanometers is applied to the inner wall of a glass tube for a 40W fluorescent lamp.
Next, 2.3 gr of a mixed phosphor consisting of 12.8% europium-activated barium magnesium aluminate, 38.2% terbium-activated cerium magnesium aluminate, and 49% europium-activated yttrium oxide was applied thereon. A fluorescent lamp was manufactured using this method. As a result of measuring the spectral energy distribution of the completed fluorescent lamp and then calculating the color rendering index, the lamp chromaticity point is x =
0.345, y=0.356, the average color rendering index was 84, the special color rendering index _R9 was 40, and _R15 was 98. The spectral energy distribution is shown in FIG. Curve 6 is the spectral energy distribution of the fluorescent lamp according to this example. For comparison, as the first phosphor layer, 5000K
2.2 gr of antimony and manganese-activated calcium halophosphate was applied, and then 15.8 gr of europium-activated barium magnesium aluminate was applied on top.
%, 37.2% terbium-activated cerium magnesium aluminate, and 47% europium-activated yttrium oxide, and a fluorescent lamp was then fabricated in the usual manner. As a result of measuring the spectral energy distribution of the completed fluorescent lamp, the chromaticity point is x = 0.346, y = 0.358, the average color rendering index is 82, the special color rendering index R ₉ is 24, R ₁₅
was 93.

As explained above, the fluorescent lamp of the present invention has higher average and special color rendering index than conventional ones.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the relationship between the ratio of the light amount of the first phosphor layer to the total amount of light emitted from the fluorescent lamp and the average color rendering index. Figure 2 is a diagram showing the relationship between the average color rendering index and the light emitted from the fluorescent lamp. Figure 3 shows the spectral energy distribution of the first phosphor layer in the first phosphor layer.
Figure 4 shows a comparison of the spectral energy distribution of a fluorescent lamp coated with only a phosphor layer and a second phosphor layer. FIG. 6... Spectral energy distribution curve of the fluorescent lamp of the example of the present invention.

Claims (1)

[Claims] 1 The inner wall of the glass tube is coated with two layers of phosphor, of which the first phosphor layer coated on the glass tube side consists of a blue-emitting phosphor, while the second phosphor layer coated on the discharge side A fluorescent lamp characterized in that the phosphor layer is composed of three types of phosphors whose emission spectra have peak wavelengths in the ranges of 430 to 490 nanometers, 520 to 570 nanometers, and 600 to 640 nanometers.