JP2007138007A - Fluorescent substance and el element using the same and method for producing fluorescent substance - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluorescent substance which is a mixed crystal fluorescent substance of ZnS with a group IIA sulfide and can emit short wavelength EL in high brightness, when an AC electric field is applied, and to provide a method for producing the same. <P>SOLUTION: This mixed crystal fluorescent substance represented by the formula: Zn<SB>(1-x)</SB>M<SB>x</SB>S:Cu [M is at least one group IIA element selected from the group consisting of Be, Mg, Ca, Sr and Ba; the mixed crystal ratio of x satisfies 0.05≤x<] is characterized by having macle therein and having a light-emitting component in a UV ray region of ≤400 nm. The method for producing the fluorescent substance comprises a process for mixing group IIA sulfide powder with ZnS:Cu intermediate fluorescent substance powder having macle therein, and a process for firing the mixture. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electroluminescence (hereinafter referred to as “EL”) light emitting phosphor and a method for manufacturing the same. In particular, the present invention relates to a phosphor having many twins necessary for EL emission and a method for manufacturing the same.

Due to recent environmental problems, a function of separating, decomposing or sterilizing harmful substances, bacteria, viruses and the like is strongly demanded. Photocatalytic materials are attracting attention as a means for performing such decomposition and sterilization. A typical photocatalyst is anatase TiO ₂ , which generally exhibits a photocatalytic function with ultraviolet rays having a wavelength of 400 nm or less. Recently, a rutile TiO ₂ that has a lower function than anatase TiO ₂ but functions up to a wavelength of about 420 nm has been developed.

  Devices that emit light of such a wavelength include mercury lamps and light emitting diodes, but they are point or line light sources and are not suitable for uniformly exciting a large area photocatalyst. An inorganic EL device is a device that uniformly emits light over a large area. In this method, phosphor powder having a function of emitting light is dispersed in a dielectric resin, and light is emitted mainly by applying an alternating electric field.

  As a phosphor that emits light with high efficiency, there is a ZnS phosphor. This phosphor has a large number of twins (stacking faults) formed therein, and a highly conductive Cu—S compound exists in a needle shape along the twin interface. When an electric field is applied, electric field concentration occurs at the tip of the acicular conductive phase, and the phosphor matrix, ZnS, is excited, and this energy moves to various levels in the phosphor to emit EL. That is, electrons are trapped in a shallow trap and holes are trapped in an acceptor level of a Cu activator. When an electric field is reversed, electrons are ejected and recombined with holes to emit light (see Non-Patent Document 1).

  The ZnS: Cu phosphor described in Non-Patent Document 1 is the most famous phosphor that generates EL light emission when an alternating electric field is applied, and includes a plurality of types such as a Blue-Cu type and a Green-Cu type. Luminescence occurs. However, even the Blue-Cu type light emission having the light emitting component in the shortest wavelength region does not have the light emitting component in the ultraviolet region having a wavelength of 400 nm or less.

On the other hand, as a method for shortening the emission wavelength of the ZnS: Cu phosphor, for example, a group IIA sulfide is added to ZnS which is a phosphor base material to form a mixed crystal, and the band gap of the phosphor base material is increased. It is effective to increase.
A phosphor obtained by adding a group IIA sulfide to ZnS to form a mixed crystal is reported in Patent Document 1, but here, "other than main emission (DA pair emission, that is, Green-Cu emission)" is reported. In this case, it is impossible to cause light emission having a high-intensity component due to Blue-Cu light emission in an ultraviolet region having a wavelength of 400 nm or less.

Further, even if a Zn _(1-x) M _x S: Cu phosphor is prepared by the method as described, twins are hardly formed when the mixed crystal ratio of x exceeds 0.05, and the EL The emission intensity was weak. In general, it is effective to grow a phosphor at a temperature condition in which zinc blende type crystals are stable in order to form twins with high density. However, Zn _(1-x) M _x S: Cu is a mixture of x. When the crystal ratio exceeds 0.05, the wurtzite type becomes stable at any temperature, and even if the crystal type is the wurtzite type and the phosphor is grown, twins are hardly formed.

JP 2002-231151 A JP 61-296085 "Copper-activated phosphor" Ceramics 26 (1991) No. 7

  An object of this invention is to provide the fluorescent substance which enables EL light emission with high brightness | luminance, and its manufacturing method. In particular, it is a mixed crystal phosphor of ZnS and Group IIA sulfide, and has a large number of needle-like conductive phases due to the presence of a large number of twins therein, and has high brightness and short wavelength EL when an alternating electric field is applied. It is an object of the present invention to provide a phosphor capable of emitting light and a method for manufacturing the same. It is another object of the present invention to provide an EL element using these phosphors.

As a result of intensive studies to solve the above problems, the present inventors have prepared a ZnS: Cu intermediate phosphor, and then mixed a Group IIA sulfide powder to form a mixed crystal under preferable heat treatment conditions. The present inventors have found that a Zn _(1-x) M _x S: Cu phosphor having a large number of twins remaining therein can be produced.

The present invention employs the following configuration.
(1) A mixed crystal phosphor represented by a general formula Zn _(1-x) M _x S: Cu, wherein M is selected from the group of Be, Mg, Ca, Sr and Ba The mixed crystal ratio of x satisfies 0.05 ≦ x <1, and has a twin crystal inside, and a light emitting component in the ultraviolet region having a wavelength of 400 nm or less. It is a characteristic phosphor.
(2) The phosphor according to (1), wherein the mixed crystal ratio of x is 0.3 ≦ x ≦ 0.5.
(3) The phosphor according to (1) or (2), wherein the average number of twin boundaries per μm ² is 5 or more in the phosphor cross section.
(4) The phosphor according to (3), wherein the average number of twin boundaries per μm ² is 10 or more in the phosphor cross section.

In order for the phosphor to emit EL, it is necessary that twins are formed inside and a conductive phase is present at the twin boundary. Furthermore, in order to have a light emitting component in the ultraviolet region having a wavelength of 400 nm or less, it is essential to emit Blue-Cu light. In order to shorten the wavelength of Blue-Cu type light emission of ZnS: Cu and to have a light emitting component in the region of 400 nm or less, a mixed crystal with a group IIA element, that is, Zn _(1-x) M _x S: Cu is used. Therefore, it is necessary to increase the band gap of the phosphor base material. However, when the mixed crystal ratio of x is less than 0.05, the band gap is not sufficiently increased, and EL light emission having a light emitting component in the ultraviolet region having a wavelength of 400 nm or less cannot be obtained.

Further, when the mixed crystal ratio of x is in the range of 0.3 ≦ x ≦ 0.5, the integrated intensity of the light emitting component having a wavelength of 400 nm or less is preferably 5% or more of the total integrated light intensity. In addition, when the average number of twin boundaries in the phosphor cross section is 5 or more per square μm, it is preferable that EL light emission with an emission luminance of 0.1 cd / m ² or more is possible. In particular, the number of 10 or more is more preferable because EL light emission with a light emission luminance of 1 cd / m ² or more can be obtained.

(5) An EL device having at least an anode, a cathode, and a light emitting layer, wherein the light emitting layer includes the phosphor according to any one of (1) to (4). .
(6) In the above (5), the EL emission is characterized in that when an AC electric field is applied to the light emitting layer, the integrated emission intensity in the ultraviolet region with a wavelength of 400 nm or less is 0.5% or more with respect to the total integrated emission intensity. The EL element described.
(7) The EL element according to (6), which emits EL light emission when an alternating electric field is applied, and an emission integrated intensity in an ultraviolet region having a wavelength of 400 nm or less is 5% or more with respect to a total emission integrated intensity. .

  By using the phosphor of the invention according to any one of (1) to (4), it is possible to provide an EL element that emits light having a light emitting component in an ultraviolet region having a wavelength of 400 nm or less. Further, EL light emission having a luminance that can be visually recognized even in a dark place can be obtained.

(8) The method for producing a phosphor according to any one of (1) to (4), wherein a ZnS: Cu intermediate phosphor powder having twins inside and a group IIA sulfide powder are mixed. And a method for producing a phosphor, comprising a step of firing the mixture.
By such a method for producing a phosphor, it becomes possible to produce a Zn _(1-x) M _x S: Cu phosphor having many twins remaining therein. For this reason, it is possible to increase the amount of the Cu ₂ S conductive phase precipitated on the twin boundary surface and increase the EL emission intensity.
Here, the ZnS: Cu intermediate phosphor is a mixture of ZnS powder, Cu salt powder such as Cu ₂ S, and flux powder such as KCl, and then the ZnS crystals are fired at a temperature at which the zinc blende type is stable. This means a ZnS: Cu phosphor having twins inside.
In addition, the ZnS: Cu intermediate phosphor used in the present invention may be manufactured by various methods known in the prior art as long as it is formed so as to have many twins inside.
In order to fire a twin-rich ZnS: Cu intermediate phosphor, for example, a mixed powder composed of a ZnS raw material powder, a Cu ₂ S powder, and a KCl powder as a flux is melted with KCl, and the ZnS crystal is flashed. What is necessary is just to heat-process in the temperature range where a zinc ore type becomes stable, ie, the temperature range of 750 degreeC or more and 1020 degrees C or less, and carry out liquid phase growth of the phosphor crystal. As the Cu supply source, not only Cu ₂ S but also a salt containing Cu, for example, CuSO ₄ , CuCl ₂ , CuBr ₂ , Cu (CH ₃ COO) _2, or the like may be used. Further, not only KCl but also a low melting point halide such as NaCl may be used as the flux.

(9) In the method for producing a phosphor according to (8), the addition amount of Cu in the ZnS: Cu intermediate phosphor powder is 0.002 to 0.1 in terms of a Cu / ZnS molar ratio. is there.
(10) In the method for producing a phosphor according to (9), an addition amount of Cu in the ZnS: Cu intermediate phosphor powder is 0.005 to 0.05 in terms of a Cu / ZnS molar ratio. is there.

  Conventionally, a method for producing a phosphor after producing an intermediate phosphor is known (for example, see Patent Document 2). Such a production method has a large particle size in order to obtain a long-life phosphor. The purpose is to produce a zincblende (cubic) phosphor. For this reason, a phosphor is produced by firing a mixture containing zinc sulfide, a copper compound, and a halogen compound to produce an intermediate phosphor and then applying a predetermined heating and pressurization. However, in the conventional method, the intermediate phosphor grows as a wurtzite type (hexagonal type) and is converted into a zinc blende type by heating and pressurization, so that a growth twin cannot be formed. This is because the growth twins are formed in the process of crystal growth, and no new growth twins are formed even if the phosphor once crystal-grown is heated and pressurized.

  On the other hand, the present invention is characterized in that after a zinc blende type intermediate phosphor containing a large amount of twins is produced, a mixed crystal with a group IIA sulfide is formed without annihilating the twins. . Therefore, it is possible to obtain a phosphor capable of EL emission of light in a low wavelength region with higher luminance than a phosphor manufactured by a conventional method.

When the addition amount of Cu in a ZnS: Cu phosphor having internal twins (hereinafter referred to as ZnS: Cu intermediate phosphor) is 0.002 to 0.1 in terms of a Cu / ZnS molar ratio, the wavelength is 400 nm or less. Is preferable since a phosphor that emits EL light with an integrated emission intensity in the ultraviolet region of 0.5% or more of the total integrated emission intensity and a luminance of 0.1 cd / m ² or more can be obtained. When the added amount of Cu is less than 0.002 in terms of the Cu / ZnS molar ratio, Blue-Cu type light emission does not occur, and a phosphor with extremely low EL light emission luminance is obtained. On the other hand, if it exceeds 0.1, the phosphor having an EL emission luminance of less than 0.1 cd / m ² is not preferable.

Furthermore, it is particularly preferable that the addition amount of Cu in the ZnS: Cu intermediate phosphor is 0.005 to 0.05 in terms of a Cu / ZnS molar ratio. In this case, it is possible to produce a phosphor capable of obtaining EL light emission with an integrated emission intensity in the ultraviolet region having a wavelength of 400 nm or less of 0.5% or more of the total integrated emission intensity and a luminance of 1 cd / m ² or more. It becomes.

(11) The method for producing a phosphor according to any one of (8) to (10), wherein a firing temperature in the firing step is 500 to 1000 ° C.
(12) The production of the phosphor according to any one of (8) to (11), wherein a time of 500 ° C. or more is 30 to 480 minutes at a firing temperature in the firing step. Is the method.
(13) The method for producing a phosphor as described in (12) above, wherein a time of 500 ° C. or more is 45 to 90 minutes at a firing temperature in the firing step.

In the present invention, if the firing temperature is too low, the ZnS: Cu intermediate phosphor and the group IIA sulfide will not be mixed, and conversely if the firing temperature is too high, the twin and acicular Cu ₂ S conductive phases will disappear. End up. For this reason, it is necessary to produce a phosphor within an appropriate firing temperature range.

Therefore, by setting the firing temperature to 500 ° C. to 1000 ° C., ZnS: Cu intermediate phosphor and IIA sulfide are mixed and Zn _(1-x) M _x S: Cu fluorescence in which many twins remain. A body can be produced. When the firing temperature is less than 500 ° C., the solid phase reaction between the ZnS: Cu intermediate phosphor and the group IIA sulfide does not occur, and therefore EL emission having a light emitting component in the ultraviolet region of 400 nm or less does not occur. Further, if the temperature during firing exceeds 1000 ° C., twins disappear and EL light emission does not occur, which is not preferable.

  Further, the time during which the temperature during firing is 500 ° C. or higher is preferably 30 minutes to 480 minutes. When the time is less than 30 minutes, the solid phase reaction between the ZnS: Cu intermediate phosphor and the group IIA sulfide is not sufficient, and EL light emission having a light emitting component in the ultraviolet region of 400 nm or less cannot be obtained. On the other hand, if it exceeds 480 minutes, twins disappear and EL light emission does not occur.

Furthermore, the time when the temperature during firing is 500 ° C. or higher is particularly preferably 45 minutes to 90 minutes. In this case, it is preferable to obtain a phosphor that has EL emission integrated intensity in the ultraviolet region having a wavelength of 400 nm or less of 0.5% or more of the total emission integrated intensity and emits EL light having a luminance of 1 cd / m ² or more.

(14) The phosphor manufacturing method according to any one of (8) to (13), wherein annealing is performed after the firing step.
(15) The method for manufacturing a phosphor according to (14), wherein a temperature during the annealing treatment is 400 ° C. to 850 ° C.
(16) The method for producing a phosphor as described in (14) or (15) above, wherein at the temperature during the annealing treatment, a time of 400 ° C. or more is 1 hour to 24 hours.

By annealing the phosphor after firing, it is possible to increase the amount of precipitation of the acicular Cu ₂ S conductive phase at the twin interface without losing the twins. For this reason, since the fluorescent substance which improved EL emitted light intensity is obtained, it is preferable.
Further, it is preferable to set the temperature during the annealing process to 400 ° C. to 850 ° C. because a phosphor that emits EL light with higher luminance than the phosphor before the annealing process can be obtained. When the temperature during the annealing process is less than 400 ° C., there is no change in the EL emission luminance due to the phosphor before the annealing process. Further, when the temperature exceeds 850 ° C., twins are reduced and the EL emission luminance is lower than that of the phosphor before the annealing treatment, which is not preferable.

  Furthermore, it is preferable to obtain a phosphor that emits EL light with higher luminance than that of the phosphor before the annealing treatment by setting the time at which the annealing temperature is 400 ° C. or more to 1 hour to 24 hours. In the case of less than 1 hour, there is no change in the phosphor before annealing and the EL emission luminance. Further, if it exceeds 24 hours, twins are reduced, and the EL emission luminance is lower than that of the phosphor before the annealing treatment, which is not preferable.

  According to the present invention, it is possible to obtain a phosphor capable of emitting EL with high luminance. In particular, it is a mixed crystal phosphor of ZnS and Group IIA sulfide, and has a large number of needle-like conductive phases due to the presence of a large number of twins therein, and has high brightness and short wavelength EL when an alternating electric field is applied. A phosphor capable of emitting light is obtained. Furthermore, it is possible to provide a light-emitting device that emits light having a wavelength in the ultraviolet region by EL using a surface light source by using an EL element using these phosphors.

  First, a method for obtaining Blue-Cu light emission will be described. As described in Non-Patent Document 1, when an addition amount of Cu as an activator is added at a higher molar concentration than a coactivator such as Cl or Al, Blue-Cu type light emission can be obtained. However, the concentration ratio between the activator and the coactivator is the concentration ratio contained in the phosphor, not the mixing ratio of the raw material powder. That is, KCl or NaCl, which is a Cl supply source, also has an effect as a flux, and is mixed in a large amount in order to improve the crystallinity of the phosphor. However, since the solid solubility limit of Cl with respect to ZnS is as low as about 0.1 mol%, the concentration of the activator can be shared regardless of the amount of flux by increasing the Cu salt as the Cu supply source to be higher than 0.1 mol%. It can be higher than the activator concentration.

Next, a method for obtaining a Zn _(1-x) M _x S: Cu phosphor having twins inside is described. As described above, when raw material powders such as ZnS powder, group IIA sulfide powder, Cu salt and the like are fired at once, twins are hardly formed for the above reasons. Therefore, first, ZnS powder, Cu salt powder such as Cu ₂ S, and flux powder such as KCl are mixed, and then the ZnS crystal is fired at a temperature at which the zinc blende type is stable to have twins inside. A ZnS: Cu intermediate phosphor is prepared. Thereafter, ZnS: Cu intermediate phosphor powder and Group IIA sulfide powder are mixed and crystallized under preferable heat treatment conditions, so that Zn _(1-x) M _x S: Cu phosphor in which twins remain inside is mixed. Can be produced.

The preferable heat treatment condition mentioned here is a condition in which the twin and acicular Cu ₂ S conductive phases are not lost by thermal diffusion, and the mixed crystal formation of the ZnS: Cu intermediate phosphor and the group IIA sulfide is sufficiently caused. Point to. Usually, the remaining of twin and acicular Cu ₂ S conductive phase and the mixed crystallization of ZnS: Cu intermediate phosphor and group IIA sulfide are in a trade-off relationship with each other. Is necessary.

As a result of diligent search, the inventors found that the ZnS: Cu intermediate phosphor powder and the group IIA sulfide powder having a Cu addition amount of 0.002 to 0.1 in terms of Cu / ZnS molar ratio were inert gases of 500 ° C to 1000 ° C. by baking 30 minutes to 480 minutes at medium has 0.5% more UV components of whole emission intensity below the ultraviolet region wavelength 400 nm, and visible to the naked eye in a dark room 0.1 cd / m ² or more Invented a Zn _(1-x) M _x S: Cu phosphor having an x mixed crystal ratio of 0.05 or more, which produces luminance EL emission. Under particularly preferable firing conditions, 1 cd that has a UV component of 5% or more or 10% or more of the total emission integrated intensity in an ultraviolet region having a wavelength of 400 nm or less and can be sufficiently visually recognized even in a bright room using a fluorescent lamp for illumination. Invented a Zn _(1-x) M _x S: Cu phosphor having an x mixed crystal ratio of 0.05 or more, which generates EL emission with a luminance of / m ² or more.

  Further, when the temperature rising rate is low, there is a high possibility that twins disappear during the temperature raising process. Therefore, it is preferable that the temperature rising rate is fast. For this purpose, it is preferable to perform firing using equipment capable of rapid superheating, such as a lamp heating device, a laser annealing device, and a plasma superheating device.

  In this method, since the group IIA sulfide is diffused from the surface of the ZnS: Cu intermediate phosphor grown to a certain extent (about 20 μm), there is a slight difference in the amount of IIA element solid solution between the phosphor surface and the inside. It is a feature that occurs. Distribution of solid solution of group IIA elements varies with elemental analysis such as X-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS), X-ray analysis with transmission electron microscope (TEM-EDX), and acceleration voltage It can also be measured by CL emission characteristic analysis.

Further, the Zn _(1-x) M _x S: Cu phosphor produced by the above process is annealed at a temperature of 400 ° C. to 850 ° C. to eliminate twins and eliminate the twin from the phosphor base material. By diffusing the Cu component to the crystal interface, the amount of acicular Cu ₂ S conductive phase deposited can be increased, and as a result, the EL intensity can be further increased. Here, the annealing treatment is preferably performed at a temperature of 400 ° C. or higher for 1 hour to 24 hours.
In order to increase the EL intensity by increasing twins, it is also effective to form slip twins by applying mechanical stress to the phosphor powder with a ball mill or uniaxial press before annealing.

Hereinafter, the present invention will be described in detail based on examples.
[Preparation of ZnS: Cu intermediate phosphor]
ZnS powder (purity 99.999%), Cu ₂ S powder (purity 99.9%) in an amount of 0.001 to 0.2 in terms of Cu / ZnS molar ratio, and 0.025 in terms of Cl / ZnS molar ratio. Weigh each KCl powder (purity 99.9%) to a total of 10 g, put them in 100 ml of ethanol, apply ultrasonic vibration with an ultrasonic mixer to disperse and mix. After performing, the raw material mixed powder was naturally dried. The dried raw material mixed powder was filled in a quartz crucible with a lid, heated and fired in argon gas at 950 ° C. for 120 minutes, washed with water and dried to prepare a ZnS: Cu intermediate phosphor powder.

[Preparation of Zn _(1-x) M _x S: Cu phosphor]
The prepared ZnS: Cu intermediate phosphor powder and the group IIA sulfide powder with an x mixed crystal ratio of 0.01 to 0.6 were weighed to a total of 10 g, and these were added to 100 ml of ethanol. After mixing and dispersing and mixing by applying ultrasonic vibration with an ultrasonic mixer, the mixed powder is dried using an evaporator into which N ₂ gas is introduced to prevent oxidation of the group IIA sulfide. It was. The dried mixed powder was filled in a quartz crucible with a lid, and baked under a predetermined condition (lot Nos. 1-48, see Table 1) in an argon gas using a lamp heating device. In addition, lots No. 30 to 44 were annealed after firing. To the obtained powder, 250 cc of ammonia water and 75 cc of hydrogen peroxide water are added to remove excess Cu ₂ S component deposited on the surface of the powder, followed by washing with water and drying to obtain Zn _(1-x) M _x S. : Cu phosphor was produced. The number of twins of the prepared Zn _(1-x) M _x S: Cu phosphor was observed by cross-section of the phosphor at a magnification of 30000 times by TEM, and 1 square near the center of any 10 phosphor powders. The number of twin boundaries per μm was counted, and the average value was obtained.
FIG. 1 is a TEM image showing an example of a phosphor in lot No. 6 obtained by the above-described manufacturing method. As is clear from FIG. 1, a large number of twins are formed inside the phosphor, and a needle-like conductive phase exists on the twin boundary surface. When an alternating electric field is applied to an EL element including such a phosphor in a light emitting layer, EL light emission with high brightness and short wavelength is possible.

The prepared Zn _(1-x) M _x S: Cu phosphor was passed through a 30 μm mesh, and 1 g of the phosphor was dispersed in 2 ml of castor oil to prepare a phosphor slurry. The produced phosphor slurry was injected into the gap between the ITO transparent conductive glass and the steel plate, the interval of which was adjusted using a glass plate spacer, to produce an EL device.

An electrode was placed on the transparent conductive glass with ITO and the steel plate of the produced EL element, and a triangular wave AC electric field of 1000 Hz and 200 V was applied to cause the phosphor to emit EL. Luminance and emission spectra were measured using a luminance meter and a spectrometer.
The experimental results are shown in Table 1.

Lots No. 1 to 9 are examples and comparative examples corresponding to the inventions of claims 1 to 5.
When the mixed crystal ratio of x of Zn _(1-x) M _x S: Cu was less than 0.05, EL light emission having a light emitting component in the ultraviolet region having a wavelength of 400 nm or less was not obtained (No. 1). When the mixed crystal ratio of x is in the range of 0.05 to 0.5, EL light emission having a light emission component of 0.5% or more of the total light emission intensity in the ultraviolet region having a wavelength of 400 nm or less was obtained (No. 2 to No). .8). In particular, when the mixed crystal ratio of x is in the range of 0.3 ≦ x ≦ 0.5, EL light emission having a light emission component of 5% or more of the total light emission intensity in the ultraviolet region having a wavelength of 400 nm or less can be obtained (No. 5). ~ No. 8). When the mixed crystal ratio of x exceeds 0.5, an excessive group IIA sulfide is precipitated alone, and as a result, the mixed crystal ratio of x is equivalent to that of 0.5 (No. 9). .

Lots Nos. 10 to 16 are examples and comparative examples corresponding to the inventions according to claims 9 and 10.
When a ZnS: Cu intermediate phosphor having a Cu addition amount of less than 0.002 in terms of Cu / ZnS molar ratio is used, Blue-Cu type light emission does not occur, and EL light emission luminance is as weak as less than 0.1 cd / m ^2. (No. 10). When the added amount of Cu is 0.002 to 0.1 in terms of Cu / ZnS molar ratio, EL light emission having a luminance of 0.1 cd / m ² or more having a light emitting component in the ultraviolet region having a wavelength of 400 nm or less associated with Blue-Cu type light emission is obtained. (No. 6, No. 11 to No. 15). In particular, it is preferable because the EL emission with a luminance of 1 cd / m ² or more can be obtained when the Cu addition amount is 0.005 to 0.05 in terms of Cu / ZnS molar ratio (No. 6, No. 12 to No. 14). If the Cu addition amount exceeds 0.1 in terms of the Cu / ZnS molar ratio, the EL emission intensity decreases and the luminance is less than 0.1 cd / m ^2, which is not preferable (No. 16).

Lots No. 17 to 21 are examples and comparative examples corresponding to the invention described in claim 11.
When the firing temperature is less than 500 ° C., the reaction between the ZnS: Cu intermediate phosphor and the group IIA sulfide does not occur, and thus EL light emission having a light emitting component in the ultraviolet region having a wavelength of 400 nm or less was not obtained (No. 17). EL light emission having a light emission component of 0.5% or more of the total light emission intensity in an ultraviolet region having a wavelength of 400 nm or less at a baking temperature of 500 ° C. to 1000 ° C. was obtained (No. 18 to No. 20). When the firing temperature exceeded 1000 ° C., twins disappeared and EL emission was not obtained (No. 21).

Lots No. 22 to 29 are examples and comparative examples corresponding to the inventions of claims 12 and 13.
When the firing temperature is 500 ° C. or more for less than 30 minutes, the reaction between the ZnS: Cu intermediate phosphor and the group IIA sulfide is not sufficient, and light emission having a light-emitting component in the ultraviolet region with a wavelength of 400 nm or less cannot be obtained (No). .22). When the firing temperature is 500 ° C. or higher for 30 minutes to 480 minutes, an EL having a luminance of 0.1 cd / m ² or more having a light emitting component of 0.5% or more of the total light emission intensity in an ultraviolet region having a wavelength of 400 nm or less. Luminescence was obtained (No. 6, No. 23 to No. 28). In particular, it is preferable since the EL emission with a luminance of 1 cd / m ² or more having a light emission component of 8.4% or more of the total emission intensity in the ultraviolet region having a wavelength of 400 nm or less can be obtained at a baking temperature keeping time of 45 minutes to 90 minutes (No. 6, No. 24, No. 25). When the firing temperature keep time exceeded 480 minutes, twins disappeared and no EL emission was obtained (No. 29).

Lots No. 30 to 35 are examples and comparative examples corresponding to the inventions of claims 14 and 15.
When the annealing temperature after firing was less than 400 ° C., there was no change in the luminance of EL emission before annealing (No. 30). When the annealing temperature was 400 ° C. to 850 ° C., EL light emission with higher luminance than before annealing was obtained (No. 31 to No. 34). If the annealing temperature exceeds 850 ° C., twins disappear, which is not preferable (No. 35).

Lots No. 36 to 44 are examples and comparative examples corresponding to the invention described in claim 16.
When the annealing temperature was 400 ° C. or higher for less than 1 hour, there was no change in the EL emission luminance before annealing (No. 36). When the annealing temperature was 400 ° C. or higher for 1 to 24 hours, EL light emission having a luminance higher than that before annealing was obtained (No. 37 to No. 42). If the annealing temperature exceeds 400 ° C. for more than 24 hours, the EL emission luminance is lower than before annealing (No. 43, No. 44).

Lots No. 45 to 48 are examples corresponding to the invention described in claim 1.
In the group IIA elements where M is Be, Mg, Ca, Sr, or Ba, an EL component having a light emitting component of 0.5% or more of the total light emission intensity in an ultraviolet region having a wavelength of 400 nm or less and a luminance of 1 cd / m ² or more Luminescence was obtained (No. 6, No. 45 to No. 48).

(Comparative example)
[Zn _(1-x) M _x S: Cu phosphor by conventional fabrication method 1]
ZnS powder (purity 99.999%), Cu ₂ S powder (purity 99.9%) in an amount of 0.01 in terms of Cu / ZnS molar ratio, KCl powder in an amount of 0.025 in terms of Cl / ZnS molar ratio (Purity 99.9%), and MgS powder (purity 99.9%) in an amount such that the mixed crystal ratio of x is 0.01 ≦ x ≦ 0.5, each of which is weighed to 10 g, After putting them into 100 ml of ethanol, applying ultrasonic vibration with an ultrasonic mixer to disperse and mix, raw material mixed powder using an evaporator into which N ₂ gas was introduced to prevent oxidation of MgS Was dried. The dried raw material mixed powder was filled in a quartz crucible with a lid and baked by heating in argon gas at 950 ° C. for 120 minutes. Thereafter, the fired powder is washed with distilled water, 250 cc of ammonia water and 75 cc of hydrogen peroxide water are added to remove excess Cu ₂ S component deposited on the powder surface, and further, washed with water and dried to obtain Zn _{( 1-x) A} Mg _x S: Cu phosphor was prepared.

The prepared Zn _(1-x) Mg _x S: Cu phosphor was passed through a 30 μm mesh, and then 1 g of the phosphor was dispersed in 2 ml of castor oil to prepare a phosphor slurry. The produced phosphor slurry was injected into the gap between the ITO transparent conductive glass and the steel plate, the interval of which was adjusted using a glass plate spacer, to produce an EL device.

  A 1000 Hz, 200 V triangular wave AC electric field was applied between the transparent conductive glass with ITO of the produced EL element and the steel sheet to cause the phosphor in the phosphor slurry layer to emit EL. Regarding the EL emission characteristics, the luminance and emission spectrum were evaluated using a luminance meter and a spectrum analyzer.

The crystal phase of the phosphor powder was identified by XRD. In addition, the number of twins was observed by a TEM at a magnification of 30000 times, and the number of twin boundaries per square μm near the center of any 10 phosphor powders was counted. The average value was obtained.
The experimental results are shown in Table 2.

When the mixed crystal ratio of x is less than 0.05, EL light emission occurs, but the light emission wavelength is hardly shortened, and light emission having a component in the ultraviolet region having a wavelength of 400 nm or less was not obtained (lot numbers 0-1, 0- 2). It was confirmed that when the mixed crystal ratio of x was 0.05 or more (lot numbers 0-2 to 0-7), the crystal phases were all wurtzite, almost no twins were formed, and almost no EL emission was generated.

As described above, when all the raw materials of Zn _(1-x) M _x S: Cu phosphor are mixed and fabricated by one firing as described in Patent Document 1, if the mixed crystal ratio of x is 0.05 or more, Almost no EL emission is obtained.
[Zn _(1-x) M _x S: Cu phosphor by conventional fabrication method 2]
9.074 g of ZnS powder (purity 99.999%), Cu (CH ₃ COO) ₂ powder (purity 99.9%) in an amount of 0.01 in terms of Cu / ZnS molar ratio, 0 in terms of Br / ZnS molar ratio An NH ₄ Br powder (purity: 99.9%) in an amount of 0.01 was mixed with stirring in 200 ml of distilled water, and then dried in the atmosphere at 120 ° C. To the obtained dry powder, 0.926 g of MgS powder (purity 99.9%) and 1 g of S powder (purity 99.9%) were added and mixed in a mortar. The obtained mixed powder was calcined in hydrogen sulfide at 800 ° C. for 1 hour and then in nitrogen at 800 ° C. for 2 hours. Thereafter, the calcined powder is washed with distilled water, 250 cc of ammonia water and 75 cc of hydrogen peroxide water are added to remove excess Cu ₂ S component deposited on the powder surface, and further washed with water and dried to obtain Zn _0.85. A Mg _0.15 S: Cu phosphor was prepared.

The prepared Zn _0.85 Mg _0.15 S: Cu phosphor was passed through a 30 μm mesh, and then 1 g of the phosphor was dispersed in 2 ml of castor oil to prepare a phosphor slurry. The produced phosphor slurry was injected into the gap between the ITO transparent conductive glass and the steel plate, the interval of which was adjusted using a glass plate spacer, to produce an EL device.
A 1000 Hz, 200 V triangular wave AC electric field was applied between the transparent conductive glass with ITO of the produced EL element and the steel sheet to cause the phosphor in the phosphor slurry layer to emit EL. Regarding the EL emission characteristics, the luminance and emission spectrum were evaluated using a luminance meter and a spectrum analyzer.
The crystal phase of the phosphor powder was identified by XRD. In addition, the number of twins was observed by a TEM at a magnification of 30000 times, and the number of twin boundaries per square μm near the center of any 10 phosphor powders was counted. The average value was obtained.
The experimental results are shown in Table 3.

It was confirmed that the Zn _0.85 Mg _0.15 S: Cu phosphor produced by this method has a wurtzite crystal phase, almost no twins are formed, and hardly emits EL.

It is a TEM image of the fluorescent substance in which the twin boundary surface was formed.

Claims (16)

A mixed crystal phosphor represented by a general formula Zn _(1-x) M _x S: Cu, wherein M is at least one selected from the group consisting of Be, Mg, Ca, Sr and Ba. It represents a type IIA element, and the mixed crystal ratio of x satisfies 0.05 ≦ x <1, has twins inside, and has a light emitting component in an ultraviolet region having a wavelength of 400 nm or less. Phosphor.   2. The phosphor according to claim 1, wherein a mixed crystal ratio of x is 0.3 ≦ x ≦ 0.5. ^{3. The} phosphor according to claim 1, wherein an average number of twin boundaries per 1 μm ² in the phosphor cross section is 5 or more. 4. The phosphor according to claim 3, wherein an average number of twin boundaries per μm ² in the phosphor cross section is 10 or more. 5.   An EL element having at least an anode, a cathode, and a light emitting layer, wherein the light emitting layer includes the phosphor according to any one of claims 1 to 4.   6. The EL element according to claim 5, wherein when an alternating electric field is applied to the light emitting layer, EL light emission having an emission integrated intensity in an ultraviolet region having a wavelength of 400 nm or less of 0.5% or more with respect to a total emission integrated intensity is generated. .   The EL element according to claim 6, wherein when an alternating electric field is applied to the light emitting layer, EL light emission having an emission integrated intensity in an ultraviolet region having a wavelength of 400 nm or less of 5% or more with respect to a total emission integrated intensity is generated.   A method for producing a phosphor according to any one of claims 1 to 4, wherein a step of mixing a ZnS: Cu intermediate phosphor powder having twins therein and a group IIA sulfide powder, and the mixture A method for producing a phosphor, comprising a step of firing the material.   9. The method for producing a phosphor according to claim 8, wherein an addition amount of Cu in the ZnS: Cu intermediate phosphor powder is 0.002 to 0.1 in terms of a Cu / ZnS molar ratio.   The method for producing a phosphor according to claim 9, wherein the addition amount of Cu in the ZnS: Cu intermediate phosphor powder is 0.005 to 0.05 in terms of a Cu / ZnS molar ratio.   The method for producing a phosphor according to any one of claims 8 to 10, wherein a firing temperature in the firing step is 500 ° C to 1000 ° C.   12. The method for manufacturing a phosphor according to claim 8, wherein a time of 500 ° C. or more is 30 minutes to 480 minutes at a firing temperature in the firing step.   13. The method for manufacturing a phosphor according to claim 12, wherein a time of 500 ° C. or more is 45 minutes to 90 minutes at a firing temperature in the firing step.   The method for manufacturing a phosphor according to any one of claims 8 to 13, wherein an annealing treatment is performed after the firing step.   The method for manufacturing a phosphor according to claim 14, wherein a temperature during the annealing treatment is 400 ° C to 850 ° C.   The method for manufacturing a phosphor according to claim 14 or 15, wherein a time of 400 ° C or higher is 1 hour to 24 hours at the annealing temperature.