JP5881427B2 - Display using inorganic EL elements - Google Patents

Description

  The present invention relates to a display using an inorganic electroluminescence (hereinafter referred to as inorganic EL) element.

  Inorganic EL elements can be used as auxiliary illumination light sources as flexible and low-cost sheet-like light emitters, and can also be used as displays that display characters and figures by forming or dividing electrode layers into predetermined patterns. it can.

  For example, in Patent Document 1, positive characters are displayed by cutting a back electrode along the outline of a displayed character and dividing it into a character portion and its peripheral portion (the character portion is lit), or negative. It has been proposed to obtain a letter-like character display (lighting up the surrounding area).

  Moreover, in patent document 2, the light emission surface of one inorganic EL element is divided into two areas, and the frequency of the alternating voltage applied to each area is different to obtain different emission colors for each area. Has been proposed. This display device includes a waveform generation device that outputs an inorganic EL element with different frequencies of alternating voltages in two light emitting regions. The waveform generation device includes an input unit and a conversion unit, and a user sets a light emission pattern in the waveform generation device using the input unit. The light emission pattern setting method is a color level corresponding to a color level corresponding to a plurality of colors to be emitted, a light emission time that is a time for emitting each color, a light luminance value, and a repetition number of input light emission patterns. It is set by inputting the number of setting repetitions. The conversion unit extracts a frequency corresponding to the light emission pattern (color level) input by the user from the frequency conversion table. The conversion unit converts the input luminance value into a voltage value corresponding to the AC frequency.

Japanese Patent No. 2770100 JP 2010-135175 A (paragraphs [0036] to [0040], claims 3 and 4)

  However, the display of Patent Document 1 cannot simultaneously emit characters and background. That is, since the light emitting layer is formed of a single phosphor material and is only cut into the back electrode, the light emitting surface in an unlit state looks uniform and the characters are hidden. For this reason, an effect is obtained that characters appear only when they are lit. However, if the character and the background are turned on at the same time, it is difficult to recognize the character because the emitted color is the same. For this reason, it is possible to realize only one of the display modes for displaying characters positively or negatively.

  Although the display of Patent Document 2 has a wide variety of colors that can be displayed, it requires a complicated operation for the user to input a light emission pattern having a number of parameters, and the configuration of the waveform generation device is complicated. is there.

  The present invention has been made in view of the above-described problems, and has a simple configuration, and an inorganic EL element is lit so that light is emitted in a color different from a background of a pattern such as a character and a figure, and excellent visual performance is achieved. It is an object of the present invention to provide a display device that obtains a display with effective effects.

  The display device of the present invention is a simple structure, and lights an inorganic EL element so that it emits light with a color different from that of characters, graphics, etc., to obtain a display with an excellent visual effect.

  A ZnS (zinc sulfide) phosphor used for an inorganic EL element has a feature that an emission color changes depending on a driving frequency. Figure 1 shows the CIE x and y chromaticity points of the luminescent color when a dispersion type inorganic EL element is created and the drive frequency is changed for two types of phosphors manufactured by OSRAM Sylvania, product numbers GG25 and GG45. ing. Both emit green light when the drive frequency is low, and change to blue light when the drive frequency is high. The GG45 phosphor emits green light at 500 Hz and greenish blue light at 10 kHz. The GG25 phosphor emits green near blue-green at 500 Hz and blue at 10 kHz.

  There are various types of driving of the inorganic EL element, and an inorganic EL element that is a capacitive (C) load is connected in series with the inductor (L), and a self-oscillation type driving system is used at the resonance frequency. Can do. When a dispersion-type inorganic EL element having a different light emission area is turned on by such a self-oscillation type driving method, the L × C value of the load is different, so that the oscillation frequency is changed. Can be obtained.

  Based on the characteristics of the phosphor in the inorganic EL element and the driving method thereof, the display of the present invention includes the inorganic EL element and the high-frequency oscillator configured as follows.

  That is, the inorganic EL element has a pair of planar electrodes formed continuously over substantially the entire lighting area. One of the pair of planar electrodes is electrically insulated from the inside and outside of the pattern by a gap formed so as to be bordered along the outer shape of the pattern such as characters and figures. The other of the pair of planar electrodes is formed on a solid surface.

  The high-frequency oscillator includes a common electrode between the inside of the pattern of the one planar electrode and the other planar electrode that is a common electrode, and between the outside of the pattern of the one planar electrode and the common electrode. A high frequency voltage having a different frequency is applied between the other planar electrode.

  According to the configuration of this display, the lighting area of the inorganic EL element is divided into a pattern such as characters and figures to be displayed and a background which is outside thereof. Also, the area of characters, figures, etc. is different from the area of the background unless it is intentionally set the same. In the division, the one planar electrode (either the back electrode or the transparent electrode) is provided with a cut (gap) bordered along the outer shape of the pattern so that the pattern portion and the background portion are insulated from each other. Since the other planar electrode is formed as a single plane, it is common. Then, by applying high frequency voltages having different frequencies to the pattern portion and the background portion having different areas, the inorganic EL element is lit so that the pattern portion and the background portion emit light in different colors.

  As a configuration example of the high-frequency oscillator, there is a configuration in which two self-excited oscillation units are respectively connected between the divided electrode pattern portion and the common electrode, and between the divided electrode background portion and the common electrode. Can be mentioned. The two self-excited oscillation units may have the same circuit configuration, or may have different circuit configurations only in a portion that determines the resonance frequency.

  As another configuration of the high-frequency oscillator, a single self-excited oscillation unit can be provided between the divided electrode pattern portion and the common electrode, and between the divided electrode background portion and the common electrode. And the output of the self-excited oscillation unit may be switched by the switching unit so that the voltage is alternately applied to the pattern portion and the background portion. When the output of the self-excited oscillation unit is switched at a high speed of 30 times or more per second, the pattern portion and the background portion appear to emit light simultaneously.

  According to the present invention, it is possible to obtain a display having an excellent visual effect by lighting an inorganic EL element with a simple configuration so as to emit light in a color different from the background of patterns such as characters and figures. It becomes.

It is a figure which shows the CIE x, y chromaticity point of the luminescent color when a dispersion-type inorganic EL element is produced about two types of fluorescent substance, and a drive frequency is changed. It is a schematic block diagram which shows the indicator which concerns on the 1st Embodiment of this invention. It is sectional drawing which shows an example of the inorganic EL element used for a display same as the above. It is the elements on larger scale of the back electrode in an inorganic EL element same as the above. It is a schematic block diagram which shows the indicator which concerns on the 2nd Embodiment of this invention. It is a schematic block diagram which shows the display which concerns on the 3rd Embodiment of this invention.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

  FIG. 2 is a schematic configuration diagram illustrating the display according to the first embodiment. As shown in FIG. 2, the display 1 includes an inorganic EL element 10 and a high frequency oscillator 20.

  FIG. 3 is a cross-sectional view showing an example of an inorganic EL element. As shown in FIG. 2, the structure of the inorganic EL element 10 is a general inorganic EL element composed of a transparent film substrate 16, a transparent electrode 15, a light emitting layer 14, a dielectric layer 13, and a back electrode 12. As a method, both a thin film process and a thick film process are possible. When using a thin film process, the general material and structure used for a thin film type inorganic EL element can be used. In the case of a thick film process, those of a dispersion type inorganic EL element can be used. The transparent electrode 15 and the back electrode 12 constitute a pair of planar electrodes referred to in the present invention, and are continuously formed over substantially the entire lighting area of the inorganic EL element 10.

  Below, an example of the manufacturing method of the inorganic EL element by a thick film process is demonstrated. A phosphor paste was applied and baked on almost the entire ITO surface of the PET film (transparent film substrate 16) on which the ITO transparent electrode 15 was formed, thereby forming a light emitting layer 14 having a thickness of about 70 μm. The phosphor used was GTP product number GG45 (Osram Sylvania product number GG45 equivalent), and the binder resin was fluororubber. In the same manner, a dielectric layer 13 having a thickness of about 30 μm was formed from the dielectric paste. The dielectric material was barium titanate powder, the binder resin was fluororubber, and the weight ratio of barium titanate powder to resin was about 3: 1, but this is also an example and is not particularly limited. On the dielectric layer 13 thus formed, Ag paste was pattern printed and baked to form the back electrode 12.

  FIG. 4 is an enlarged plan view showing a part of the back electrode in the inorganic EL element. As shown in FIG. 2 and FIG. 4, the back electrode 12, which is one planar electrode, is formed inside the pattern by a gap 123 formed as an example along the outline of the character pattern “TAZMO” ( Hereinafter, the pattern portion is divided into 121 and the outside of the pattern (hereinafter referred to as the background portion) 122, which are electrically insulated from each other. The gap 123 can be formed, for example, by mechanically cutting a conductor layer formed on one side of the dielectric layer 13 with a substantially constant width along the outer shape of the pattern.

  Note that the pattern is not limited to characters, but may be any shape having an outline such as a figure, symbol, or illustration. A variety of patterns such as a mark-like pattern combining characters and figures can be selected arbitrarily.

  The transparent electrode 15 which is the other planar electrode is formed on a solid surface with no gap.

  The high frequency oscillator 20 includes a DC power source 21, a first inverter circuit 22, and a second inverter circuit 23. The inverter circuit is an example of the self-excited oscillation unit referred to in the present invention. As an example of the inverter circuit, a self-excited oscillation circuit known as a Royer circuit is used. The resonance (oscillation) frequency f of this type of circuit is 1 / (2π√LC) where L is the inductance of the coil connected in series with the load and C is the capacitance of the load (see Equation 1).

  f = 1 / (2π√LC) (Equation 1)

  The DC power supply 21 outputs a DC voltage.

  As shown in FIG. 2, one of the outputs of the first inverter circuit 22 is connected to the pattern portion 121 in the back electrode 12. One of the outputs of the second inverter circuit 23 is connected to the background portion 122 of the back electrode 12. The other of the outputs of the first inverter circuit 22 and the second inverter circuit 23 is connected to the transparent electrode 15 in common.

  Two inverter circuits 22 and 23 having the same circuit configuration can be used. Usually, since the pattern portion 121 of the back electrode 12 has a smaller area than the background portion 122, the capacitances of the pattern portion 121 are different. If the capacitance of the pattern portion 121 is C1 and the capacitance of the background portion 122 is C2, the smaller the area, the smaller the capacitance, and C1 <C2. Therefore, even if the circuit configurations of the two inverter circuits 22 and 23 are the same, if the inductance L of the inverter circuit is appropriately selected, for example, a high frequency voltage with a frequency f1 = 1 kHz is present in the pattern portion 121 and a background portion 122 is present. A high-frequency voltage having a frequency of f2 = 5 kHz is applied (f1> f2 from the relationship of Expression (1)). That is, high-frequency voltages having different frequencies are applied to the pattern portion 121 and the background portion 122 in the back electrode 12. As a result, the characters emit light in blue and the background emits green.

  Since the same layer is uniformly applied to the entire surface of the light-emitting layer 14 immediately below the transparent electrode 15, characters cannot be seen when the inorganic EL element 10 is not lit. However, when the inorganic EL element 10 is turned on, the characters and the background appear in different colors, and a high visual effect can be obtained.

  Note that two inverter circuits 22 and 23 having different inductance L values may be used. In that case, since the frequency of the high frequency voltage applied to both can be arbitrarily selected irrespective of the area ratio of the pattern part 121 and the background part 122 in the back electrode 12, a larger color difference can be given.

  Two or more inverter circuits may be used. For example, if a plurality of inverter circuits corresponding to the characters of the pattern portion 121 are provided and driven by separate inverter circuits for one character or several characters, it becomes possible to vary the drive frequency in units of one character or several characters. Therefore, the pattern portion 121 can emit light with a different color for each unit.

  FIG. 5 is a schematic configuration diagram illustrating a display according to the second embodiment. As a characteristic structure of the display 1 according to the present embodiment, the high frequency oscillator 20 has only one inverter circuit 22 as shown in FIG. One of the outputs of the inverter circuit 22 is connected to the pattern portion 121 and the background portion 122 of the back electrode 12 via the switching unit 24, and the other output of the inverter circuit 23 is connected to the transparent electrode 15. The inverter circuit 22 is the same as that described in the first embodiment. The switching unit 24 may be one that switches the connection destination by a contact like a mechanical relay, or may be a semiconductor switch such as a solid state relay.

  When the switching of the output of the inverter circuit 22 by the switching unit 24 is performed at a high speed of, for example, 30 times or more per second, the characters and the background seem to emit light simultaneously. Also in this case, as in the first embodiment, since the light emission colors of the character and the background are different, a high visual effect can be obtained.

  According to this embodiment, since only one inverter circuit is required, the cost is low.

  FIG. 6 is a schematic configuration diagram showing a display device according to the third embodiment. As a characteristic structure of the display 1 according to the present embodiment, as shown in FIG. 6, the inorganic EL element 10 includes a pattern portion 151 in which the transparent electrode 15 is electrically insulated from each other through a gap 153 and the background. While being divided into portions 152, the back electrode 12 is formed as a single surface. This is the reverse of the first embodiment.

  One of the outputs of the first inverter circuit 22 is connected to the pattern portion 151 of the transparent electrode 15, and the other of the outputs of the second inverter circuit 23 is connected to the background portion 152 of the transparent electrode 15. The other of the outputs of the first inverter circuit 22 and the second inverter circuit 23 is connected in common to the back electrode 12. The other configuration of the display 1 is the same as that of the first embodiment.

  The transparent electrode 15 can be formed on the transparent film substrate 16 as a thin film having a thickness of about several hundred nm. Therefore, according to the present embodiment, there is an advantage that the gap 153 can be easily formed by cutting (etching) the conductive layer formed on the transparent film substrate 16 with a solid surface at a high speed with a laser beam or the like.

  The above description of the embodiment is to be considered in all respects as illustrative and not restrictive. The scope of the present invention is shown not by the above embodiments but by the claims. Furthermore, the scope of the present invention is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

DESCRIPTION OF SYMBOLS 1 ... Display 10 ... Inorganic EL element 12 ... Back electrode 121 ... Pattern part 122 ... Background part 123 ... Gap 13 ... Dielectric layer 14 ... Light emitting layer 15 ... Transparent electrode 151 ... Pattern part 152 ... Background part 153 ... Gap 16 ... Transparent film substrate 20 ... high frequency oscillator 21 ... DC power supply 22 ... first inverter circuit 23 ... second inverter circuit 24 ... switching unit

Claims (9)

A display device that displays an inorganic EL element by lighting so that the background of characters, figures, and the like emits light in a different color,
It has a pair of planar electrodes formed continuously over substantially the entire lighting area, and includes a dielectric layer and a light emitting layer between the pair of on-surface electrodes, one of the pair of planar electrodes being one of The inside and the outside of the pattern are electrically insulated by a gap formed so as to border the outer shape of the pattern such as characters and figures, and the other of the dielectric layer, the light emitting layer, and the pair of planar electrodes Are both inorganic EL elements formed on a solid surface,
Between the inside of the pattern of the one planar electrode and the other planar electrode which is a common electrode, and the outside of the pattern of the one planar electrode and the other planar electrode which is a common electrode A high-frequency oscillator configured such that high-frequency voltages having different frequencies are applied to each other,
Comprising a display. The high-frequency oscillator is
A first self-oscillating portion connected between the inside of the pattern in the one planar electrode and the other planar electrode;
A second self-oscillating portion connected between the outside of the pattern in the one planar electrode and the other planar electrode;
The display according to claim 1, comprising:   The display device according to claim 2, wherein the first self-excited oscillation unit and the second self-excited oscillation unit have the same circuit configuration.   The display device according to claim 2, wherein the first self-excited oscillation unit and the second self-excited oscillation unit differ in circuit configuration only in a portion that determines an oscillation frequency. The high-frequency oscillator is
A switching unit is provided between the inside of the pattern and the other planar electrode in the one planar electrode, and between the outside of the pattern and the other planar electrode in the one planar electrode. The display according to claim 1, further comprising a single self-excited oscillation unit connected via each other.   The display according to claim 5, wherein the switching unit switches the output of the self-excited oscillation unit at 30 times or more per second.   The display device according to claim 2, wherein the self-excited oscillation unit is a self-excited oscillation type inverter circuit.   The inorganic EL element includes at least a light emitting layer and a dielectric layer between a transparent electrode and a back electrode, the one planar electrode is a back electrode, and the other planar electrode is a transparent electrode. The display according to any one of claims 1 to 7.   The inorganic EL element includes at least a light emitting layer and a dielectric layer between a transparent electrode and a back electrode, the one planar electrode is a transparent electrode, and the other back electrode is a transparent electrode. Item 8. The display according to any one of Items 1 to 7.