JPS61174291A - Phosphor emitting blue light - Google Patents

Abstract

PURPOSE:To provide a blue light-emitting phosphor having high luminance under electric current and excellent temperature characteristic, prepared by activating a matrix consisting of Sr, Ca or Ba and Mg-contg. silicate with divalent Eu. CONSTITUTION:The phosphor is prepared by activating a matrix consisting of a silicate of formula, M3Mg Si2O3 (where M is Sr, Ca or Ba) with 0.1-10mol% of divalent Eu per mol of matrix. The phosphor emits blue light which has a y value of less than 0.1 on a CIE chromaticity diagram. It does not cause saturation of luminance under a sufficiently high current density and has excellent high temperature properties. Even when used for a high- brightness cathode ray tube for projectors, is does not cause unbalance of white color due to saturated luminance. It also does not lose balance of white color as a result of optical quenching at elevated temperature in prolonged continuous use and produces high quality color images.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a blue-emitting phosphor, particularly a blue-emitting phosphor suitable for use in, for example, a high-brightness cathode ray tube for a projector.

[Conventional technology]

In recent years, projectors that project reproduced images from a television picture tube, that is, a cathode ray tube, onto a screen have become rapidly popular.

As mentioned above, the cathode ray tube used in such a projector needs to project the reproduced image onto the screen as a bright image, so the fluorescent surface of the cathode ray tube is required to have high brightness. . Therefore, in this type of cathode ray tube for a projector, the fluorescent surface is excited with an extremely high current density compared to a normal cathode ray tube. Therefore, a phosphor forming this type of fluorescent surface is required to have a brightness that is difficult to saturate even with a large current, that is, to have excellent current brightness characteristics. In addition, in this type of cathode ray tube, the phosphor is excited with an extremely high current density as described above, and the electron beam is bombarded with high excitation energy, that is, a high accelerating voltage. The surface temperature rise is considerably higher than that of ordinary cathode ray tubes. In order to avoid this temperature increase, methods such as liquid cooling the front panel of the cathode ray tube, which has a fluorescent surface, are taken to avoid a decrease in brightness due to an increase in the temperature of the fluorescent material, that is, temperature quenching. However, even with this method, the phosphor in this type of cathode ray tube is a phosphor with excellent temperature characteristics that does not cause temperature quenching even at a constant temperature of 100°C or 120°C. Something is desired.

In order to obtain such a high-brightness cathode ray tube, a phosphor with excellent current-luminance characteristics and excellent temperature characteristics is required, and currently only blue phosphors meet these requirements. something has not been provided yet. That is, as a blue phosphor, for example, ZnS:Ag can be mentioned, but although this has excellent temperature characteristics, it has poor current brightness characteristics, and brightness saturation occurs at large currents.

[Problem that the invention seeks to solve]

As mentioned above, currently there is no blue light-emitting phosphor that satisfies both current brightness characteristics and temperature characteristics at the same time. That is, under a large current, the blue phosphor undergoes brightness saturation or temperature quenching, resulting in a loss of white balance and color distortion in the projected image.

The present invention provides a blue-emitting phosphor having excellent current brightness characteristics and temperature characteristics.

c) Means for Solving Problems] In the present invention, a silicate having a composition formula represented by M3MgSi2Oe, in which N is composed of at least one element selected from Sr, Ca, and Ba, is used as a matrix, To this, 0.1 to 10 mol% of divalent Eu is added to 1 mol of the base material.
A blue phosphor is formed by activating the blue phosphor.

[Effect]

The phosphor according to the present invention described above has a y value of y in the CIE chromaticity diagram.
A phosphor was obtained which exhibited blue light emission of <o, i, did not exhibit brightness saturation at a sufficiently large current density, and had excellent temperature characteristics.

〔Example〕

SrCO3, CaCl2+ BaCl2+ MgO+
Carbide and oxide powders such as 1Eu2O3 are used as starting materials, and BaCl2+ BaP2+ C is added as a fluxing agent.
Add an appropriate amount of either aCl2+ H3BO3+ NH4Cl and mix thoroughly using a ball mill or the like.

This mixed raw material is placed in an aluminum crucible and fired at a temperature of 1000 to 1300° C. for several hours in a reducing atmosphere. The luminescence properties of the Eu2+-activated silicate phosphor thus synthesized under electron beam excitation were measured. This measurement was carried out by coating the phosphor on the inner surface of a panel of a cathode ray tube body to produce a cathode ray tube.

Example 1 5rC with a purity of 99.99% (h is 70.2 Og, 6.39 g of MgO with a purity of 99.99%, respectively)
19.05g of 5tO2.

Add 0.279 g of EL12O3 as an activator. and,
Add 3.3 g of [1aCI2] as a fluxing agent and mix thoroughly. This mixture was placed in an aluminum crucible, activated carbon was placed on top of it, or Ar gas containing 8% H2 was flowed and fired at a temperature of 1200°C for 3 hours to produce a fluorescent sample (sample number (1)). Obtained.

In Example 1, the activator Eu2O3 and the flux B
Each phosphor (sample numbers (2) to (31)
) was obtained. In this case, the blending amount of carbide as the raw material in each sample (1) to (31), the composition of each obtained phosphor (sample numbers (11 to (31)), and the emission peak wavelength,
The chromaticity values (CIE chromaticity) are shown in the table of FIG. As is clear from this, by changing the mixing ratio of Sr, Ca, and Ba, the emission spectrum changes to a peak wavelength of 428
It varies continuously between ~475 nm.

Figure 2 shows the molar ratios of Sr, Ca, and Ba for the phosphors of sample numbers (1) to (31).
It is plotted as a black point on a ternary diagram with +Ca+Ba as the apex, and the plot points corresponding to each sample (1) to (31) are given a corresponding number. Now, if we define blue light emission as having a chromaticity value y of 0.1 or less, the combinations that satisfy this condition will be in the shaded range in the ternary diagram of FIG. That is, (5rt-x −)' Cax
Bay)3 Mg5i2Oe: In the composition of Eu, O≦X≦0.7 and O≦Y≦1 (however, 0.35X
≦0.7 and 0≦Y≦0.2, and 0.15<X<
0.25 and excluding X+Y=1).

Moreover, FIGS. 3 and 4 each show the emission spectra measured for representative samples, and the emission spectra for each sample are given numbers corresponding to each sample number.

Example 2 By the same method as in Example 1, in this example, 5
rC (h 56.16g, CaCO3 9.518g
, using 6.39 g of MgO, 19.0 h of 5i02, 3.3 g of BaCl2 as a flux, and l1o2O as an activator.
3 was varied in the range of 0.028 to 1.39 g to obtain phosphors. The composition of the phosphor in this case is (Sro, 8Cao, 2) 3M, which is the same as sample number (2) shown in the table of Figure 1.
gSi2Oe: Eu, and Eu11 degrees is 0.1 to 10 mol% with respect to 1 mol of the base material. FIG. 5 shows the results of measuring the relationship between Eu8 degrees and luminance of each phosphor with the Eu concentration changed in this way. The effective luminance can be changed by changing the Eu concentration from 0.1 to 10 mol%, but
As is clear from Figure 5, I! u? Ii degree shows maximum brightness of 1 to 2 mol%.

Example 3 In Example 2, Eu2O3 was 0.279g (1 mol% concentration), and BaCl2 was 3.3g (1 mol% concentration) as a fluxing agent.
'0 mol%). In this Example 3,
BaCl2 from 0.165 to 6. '6g (0,5~2O
FIG. 6 shows the measurement results of the relationship between the BaCl2 concentration and the brightness when the BaCl2 concentration was varied within the range of (mol %). According to this, it can be seen that the brightness is maximum when the amount of BaCl2 in Example 3 is 3.3 g (10 mol%), and the brightness decreases when BaCl2 is less than 1 mol%. In addition, in this case, adding more than 20 mol % of BaCl2 caused sintering of the sample, which was undesirable.

In other words, the appropriate concentration range for this BaCl2 is 1-2O
It becomes mole%.

Incidentally, BaF2. CaC
1z.

Similar results were obtained using H3BO3.

Further, the results of measuring the current luminance characteristics of the phosphor according to Example 3 were as shown in curve (71) in FIG. In addition, the curve (72) in the same figure shows the conventional blue phosphor ZnS.
: Similar current brightness characteristics of A'g are shown in comparison. As is clear from this, almost no brightness saturation was observed in the phosphor according to Example 3 of the present invention even at high current density. In addition, the table of FIG. 8 shows the ZnS:A at each current density.
The relative brightness against g is shown. That is, the phosphor according to the present invention has a luminance of about 50 μA/a compared to the conventional ZnS:Ag.
It can be seen that the luminance is low in a range lower than J as a boundary, but that the luminance is conversely high in a current density higher than this, indicating excellent linearity.

Furthermore, Fig. 9 shows the measurement of the temperature characteristics of the phosphor according to Example 3, and it shows that the decrease in brightness due to temperature rise is extremely small, and at 100°C, the brightness decreases by only about 5%. It only shows that. Incidentally, the current brightness characteristics and temperature characteristics of each phosphor according to the present invention were almost the same as those of Example 3 described above.

〔Effect of the invention〕

As described above, the blue phosphor according to the present invention improves brightness saturation at high current density, and also impairs improvement in temperature characteristics, so when used in the high-brightness cathode ray tube for the projector described above, Even in bright images, it is possible to obtain high-quality color images without disrupting the white balance due to brightness saturation, and even when the temperature rises due to long-term continuous use, without disrupting the white balance due to temperature quenching. It is of practical use and its benefits are great.

[Brief explanation of drawings]

Fig. 1 is a characteristic chart of each phosphor sample, Fig. 2 is a ternary diagram of Ba-5r-Ca of the phosphor matrix used to explain the present invention, and Figs. 3 and 4 are according to the present invention. Figures 5 and 6 are emission spectrum diagrams of a blue-emitting phosphor, and Figures 5 and 6 are measurement curves of luminescence brightness versus concentration of activator Eu and flux RaCI2, respectively. Figure 7 is a diagram showing a blue-emitting phosphor according to the present invention. FIG. 8 is a diagram showing the current/luminance characteristic curves of each of the conventional phosphors, FIG. 8 is a numerical table thereof, and FIG. 9 is a temperature characteristic curve diagram of the phosphor according to the present invention. Saisei Reiki (嬰爾行が) ward μ) Tsuka O) Tsuka ward p,
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Claims (1)

[Claims] A silicate having a composition formula represented by M_3MgSi_2O_8, in which M is made of at least one element selected from Sr, Ca, and Ba, is used as a base material, and divalent Eu is added to this base material per mole of the above base material. A blue-emitting phosphor activated by 0.1 to 10 mol%.