JP2007059667A - Light emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the degradation of a zinc-oxide-based semiconductor layer which is generated when an LED chip is sealed with a resin when it the LED chip is applied to the zinc-oxide-based semiconductor layer. <P>SOLUTION: Such a light emitting device as an LED lamp 10 has an LED chip 11 having a zinc-oxide-based semiconductor layer as its light emitting layer, etc., and has a fluorescent substance 24 so excited by the light radiated from the LED chip 11 as to emit visible rays. The LED chip 11 is covered with a silicone resin 23 emitting substantially no amines, no carbonic-acids, and no oximes. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a light emitting device such as an LED lamp.

  LED lamps using light emitting diodes (LEDs) are rapidly expanding in various fields such as backlights for liquid crystal displays, mobile phones, information terminals, indoor / outdoor advertisements, and the like. In addition, LED lamps have long life and high reliability, and have features such as low power consumption, impact resistance, high-purity display color, and lightness and thinness. Application is also under consideration. When such an LED lamp is applied to various uses, it is important to obtain white light emission.

  Typical methods for realizing white light emission with LED lamps are (1) a method using three LED chips that emit blue, green and red colors, and (2) a blue light emitting LED chip and yellow or orange light emission. And (3) a combination of a three-color mixed phosphor of blue, green and red (hereinafter referred to as RGB phosphor). Of these, the method (2) is generally widely used. Also in the method (3), improvement of luminous efficiency and luminous color is being promoted.

  As the structure of the LED lamp to which the above methods (2) and (3) are applied, a transparent resin mixed with a phosphor is poured into a cup-shaped frame equipped with an LED chip, and the phosphor is cured by curing it. Known is a structure in which a transparent resin layer is formed, or a structure in which a phosphor sheet is disposed on a transparent resin layer after the resin is poured into a cup-shaped frame equipped with LED chips and cured. Yes.

In the LED lamp as described above, an LED chip having a nitride semiconductor layer typified by GaN as a light emitting layer is frequently used in consideration of luminous efficiency, luminous intensity, etc., but the LED chip itself is expensive. There is a difficulty that there is. For such a point, it has been studied to apply an LED chip using an inexpensive zinc oxide-based semiconductor layer as a light emitting layer to an LED lamp (see, for example, Patent Document 1).
JP 2004-356273 A

  As described above, an LED chip using a zinc oxide based semiconductor layer as a light emitting layer is less expensive than an LED chip having a GaN based semiconductor layer or the like, but because zinc oxide is an amphoteric oxide. It has a drawback that it is weak against acids and alkalis and is also soluble in acetic acid. For this reason, for example, when resin-sealing LED chips, there is a problem that the zinc oxide-based semiconductor layer is deteriorated by a by-product generated during the curing reaction of the sealing resin, and the light emission intensity, light emission efficiency, and the like are likely to decrease. Yes.

  The present invention was made to cope with such a problem, and when using an LED chip having a zinc oxide based semiconductor layer as a light emitting layer, the deterioration of the zinc oxide based semiconductor layer that occurs during resin sealing is suppressed, An object of the present invention is to provide a light emitting device in which the light emission intensity, the light emission efficiency, and the like are improved.

  The light-emitting device according to claim 1; a light-emitting element having a zinc oxide-based semiconductor layer; a silicone resin that is disposed so as to cover the light-emitting element and substantially does not emit amines, carboxylic acids, and oximes; And a phosphor that emits visible light when excited by light emitted from the element.

  In the invention described in claim 1, the definitions and technical meanings of terms are as follows unless otherwise specified.

  A light-emitting element excites a phosphor with emitted light to emit visible light, and has, for example, a zinc oxide-based semiconductor layer as a light-emitting layer. The zinc oxide-based semiconductor constituting the light emitting layer is not limited to a ZnO semiconductor, but may be one in which Mg, Cd, or the like is added to ZnO. Examples of the light emitting element used in the present invention include an ultraviolet light emitting type LED chip and a blue light emitting type LED chip.

  The phosphor is excited by the light emitted from the light emitting element to emit visible light, and is emitted by the color mixture of the visible light emitted from the phosphor and the light emitted from the light emitting element or from the phosphor. As a light emitting device, a desired light emission color is obtained by the visible light or the color mixture of visible light itself. The type of the phosphor is not particularly limited, and is appropriately selected according to the intended emission color, light emitted from the light emitting element, and the like.

  The transparent resin functions as a sealing resin for the light emitting element, and a silicone resin is used here. The silicone resin used in the present invention does not substantially release amines, carboxylic acids and oximes. Here, the silicone resin that does not substantially release amines, carboxylic acids, and oximes means a product that does not generate amines, carboxylic acids, and oximes as a by-product based on the curing reaction, and serves as a light emitting layer. In such a case, a trace amount of amines, carboxylic acids and oximes which do not adversely affect the zinc oxide-based semiconductor layer is generated as a secondary or derivative.

  According to the light emitting device of the first aspect, it is possible to suppress deterioration of the zinc oxide based semiconductor layer constituting the light emitting layer or the like of the light emitting element. Therefore, it is possible to improve the light emission intensity, light emission efficiency, and the like of a light emitting device to which a light emitting element having an inexpensive zinc oxide based semiconductor layer is applied.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing a configuration of an embodiment in which a light emitting device of the present invention is applied to an LED lamp used as a lighting device or the like. The LED lamp 10 shown in the figure has an LED chip 11 as a light emitting element. The LED chip 11 has a zinc oxide based semiconductor layer as a light emitting layer. A configuration example of such a zinc oxide-based LED chip 11 is shown in FIG.

  A zinc oxide LED chip 11 shown in FIG. 2 has a structure in which an n-type light-emitting layer 13 made of n-type ZnO and a p-type light-emitting layer 14 made of p-type ZnO are stacked on an n-type ZnO substrate 12 as a main part. Have On the p-type light emitting layer 14, an ohmic electrode having translucency is formed as an upper electrode (p-type electrode) 15. For the upper electrode 15, for example, an ITO film or a light-transmitting metal film is used. An ohmic electrode is formed as a lower electrode (n-type electrode) 16 on the lower surface side of the n-type ZnO substrate 12. For the lower electrode 16, for example, a metal film such as an Al film, a Ti film, or a Ni film is used.

  In addition, the zinc oxide type LED chip 11 shown in FIG. 2 shows an example of the LED chip which has a zinc oxide type semiconductor layer as a light emitting layer, and is not limited to the structure. The zinc oxide-based LED chip 11 only needs to have a zinc oxide-based semiconductor layer as a light-emitting layer, and the structure of the light-emitting layer is a lower electrode / n-type ZnO substrate / n-type MgZnO clad layer / non-doped MgZnO—ZnO light-emitting layer / It may be p-type MgZnO clad layer / upper electrode or the like.

  The zinc oxide-based LED chip 11 can be used as a light-emitting element that emits blue light or ultraviolet light because ZnO constituting the light-emitting layer has a band gap substantially equal to that of GaN, for example. The wavelength of light emitted from the zinc oxide-based LED chip 11 is controlled in the range from the blue region to the ultraviolet region by changing the band gap by adding, for example, Mg or Cd to ZnO constituting the light emitting layer. Can do. Accordingly, the zinc oxide-based LED chip 11 can be used as a blue light emitting type light emitting element or an ultraviolet light emitting type light emitting element. In particular, the zinc oxide-based LED chip 11 is effective as an ultraviolet light emitting type light emitting element.

  The zinc oxide LED chip 11 as described above is mounted on a substrate 18 having a metal circuit 17. The metal circuit 17 has a first circuit pattern portion 17 a connected to the lower electrode 16 of the zinc oxide LED chip 11 and a second circuit pattern portion 17 b connected to the upper electrode 15. The zinc oxide-based LED chip 11 is mounted on the first circuit pattern portion 17a, and the lower electrode 16 is electrically connected to the first circuit pattern portion 17a based on this mounting structure. On the other hand, the upper electrode 15 of the zinc oxide-based LED chip 11 is electrically connected to the second circuit pattern portion 17 b through the bonding wire 19.

  As the substrate 18 on which the zinc oxide LED chip 11 is mounted, an Al substrate, a Ni substrate, a glass epoxy substrate or the like having heat dissipation and rigidity are used. When a substrate having conductivity such as an Al substrate or a Ni substrate is applied to the substrate 18, the metal circuit 17 is formed through the insulating layer 20 as shown in FIG. On such a substrate 18, for example, a resin frame 22 having a truncated cone-shaped recess (cavity) 21 is provided, and the zinc oxide LED chip 11 is disposed in the recess (cavity) 21. . That is, the zinc oxide based LED chip 11 is disposed in the cavity 21, and its periphery is surrounded by the frame 22.

  A transparent resin 23 is filled and cured in the cavity 21 in which the zinc oxide LED chip 11 is disposed, and the zinc oxide LED chip 11 is covered with the transparent resin 23. A silicone resin is used for the transparent resin 23 for sealing the zinc oxide-based LED chip 11. Here, since a silicone resin is excellent in light resistance and heat resistance as compared with a general epoxy resin as a sealing resin, it is suitable as a sealing resin for a light emitting element. In particular, when the zinc oxide-based LED chip 11 is an ultraviolet light emitting type, the epoxy resin may be deteriorated and colored with UV light, whereas the silicone resin has excellent UV resistance. Efficiency and luminescent color can be maintained over a long period of time.

  Further, a silicone resin that does not substantially generate amines, carboxylic acids and oximes is used as the transparent resin 23 as a by-product based on the curing reaction. By applying such a silicone resin to the transparent resin 23, it is possible to suppress degradation of the zinc oxide-based LED chip 11. As described above, since zinc oxide is an amphoteric oxide, when amines and oximes are released during the curing process of the transparent resin 23, the zinc oxide LED chip 11 (the n-type ZnO light-emitting layer 13 and the p-type is released by these. ZnO light emitting layer 14 and the like) deteriorate. Moreover, also when carboxylic acid represented by acetic acid is released in the curing process of the transparent resin 23, dissolution of zinc oxide proceeds and the zinc oxide LED chip 11 deteriorates.

  On the other hand, by applying a silicone resin that does not substantially generate amines, carboxylic acids and oximes as a by-product based on the curing reaction to the transparent resin 23, the deterioration of the zinc oxide LED chip 11 is deteriorated. Can be suppressed. Therefore, it is possible to stably maintain the light emission characteristics (light emission wavelength, light emission intensity, light emission efficiency, etc.) inherent to the zinc oxide-based LED chip 11. The LED lamp 10 excites the phosphor with the light emitted from the zinc oxide LED chip 11 to emit visible light, and the visible light emitted from the phosphor by the color mixture of the visible light and the light of the LED chip 11. A desired emission color is obtained by mixing the colors of the light itself. Therefore, by maintaining the light emission characteristics of the zinc oxide-based LED chip 11, it is possible to stably maintain the light emission color, light emission intensity, and the like as the LED lamp 10.

  For the transparent resin 23 to which the silicone resin is applied, a silicone resin composition in which a silicone base polymer (polyorganosiloxane polymer), a curing agent, and a filler, an additive and the like are uniformly dispersed is used as a dispenser. The zinc oxide-based LED chip 11 is filled in the cavity 21 and is cured under the conditions corresponding to the curing reaction mechanism of the silicone base polymer. Here, as a curing reaction mechanism of the silicone resin composition, a crosslinking reaction curing type, a condensation reaction curing type, an addition reaction curing type, and the like using an organic peroxide are known. Among these, the addition reaction type silicone resin composition does not generate by-products such as amines, carboxylic acids, and oximes during the curing process.

  From such points, it is preferable to use an addition reaction type silicone resin for the transparent resin 23. The addition reaction type silicone resin is a composition obtained by blending an addition reaction type silicone base polymer with a curing agent and, if necessary, a filler or an additive to make a composition and curing the composition at room temperature or under heating. is there. For the addition reaction type silicone base polymer, polyorganosiloxane in which at least two of the organic groups bonded to silicon atoms in one molecule are vinyl groups is used. As the curing agent, a platinum-based catalyst such as chloroplatinic acid or platinum olefin complex is used, and if necessary, polyorganohydrogensiloxane having two or more hydrogen atoms bonded to silicon atoms in one molecule is used as a crosslinking agent. Used together.

  Further, as fillers and additives to be added to the addition reaction type silicone resin composition, those that do not release amines, carboxylic acids and oximes in addition to not inhibiting transparency are used. . As such a filler or additive, alumina, silica, or the like can be used. Furthermore, in the LED lamp 10 of this embodiment, the phosphor can be dispersed in a transparent resin (silicone resin in this embodiment) 23 that seals the zinc oxide-based LED chip 11. Is also applicable as an additive.

  On the transparent resin 23 made of the silicone resin as described above, a phosphor sheet 24 containing a phosphor that is excited by light emitted from the zinc oxide LED chip 11 and emits visible light is disposed. The phosphor sheet 24 is produced by dispersing a phosphor having a desired emission color in a transparent resin sheet. Such a phosphor sheet 24 is disposed so as to cover the opening of the recess (cavity) 21 in which the zinc oxide LED chip 11 is disposed.

  The light emitted from the zinc oxide LED chip 11 is emitted in the light emitting direction of the LED lamp 10 through the phosphor sheet 24. Therefore, part or all of the light emitted from the zinc oxide-based LED chip 11 is emitted from the LED lamp 10 after being converted into light having a longer wavelength by the phosphor in the phosphor sheet 24. In this way, a color based on the color of light emitted from the zinc oxide LED chip 11 and the emission color of the phosphor, or a color based on the emission color of the phosphor itself, such as white light, is emitted from the LED lamp 10. The That is, the LED lamp 10 having a desired emission color can be configured.

  The phosphor contained in the phosphor sheet 24 emits visible light when excited by light emitted from the zinc oxide-based LED chip 11, for example, ultraviolet light or blue light. The type of phosphor is appropriately selected according to the emission color, excitation spectrum, and the like of the target LED lamp 10, and is not particularly limited. When the ultraviolet light emitting type zinc oxide LED chip 11 is used, it is preferable to use a phosphor having an excitation spectrum in the ultraviolet region. The same applies to the case where the blue light emitting type zinc oxide LED chip 11 is used.

When white light emission is obtained using the ultraviolet light emission type zinc oxide LED chip 11, ultraviolet excitation type RGB phosphors are mainly used. As such a blue light-emitting phosphor in the RGB phosphor, for example, AE ₁₀ (PO ₄ ) ₆ Cl ₁₂ : Eu phosphor (AE is an alkaline earth element such as Sr, Ba, Ca, etc. The same shall apply hereinafter). And halophosphate phosphors and aluminate phosphors such as (Ba, Mg) Al ₁₀ O ₁₇ : Eu phosphors. Examples of the green light emitting phosphor include an aluminate phosphor such as a (Ba, Mg) Al ₁₀ O ₁₇ : Eu, Mn phosphor. Examples of the red light-emitting phosphor include oxysulfide phosphors such as La ₂ O ₂ S: Eu phosphor.

When white light emission is obtained using the blue light emitting type zinc oxide LED chip 11, yellow to orange light emitting phosphors are mainly used. In order to improve color rendering properties, a red light emitting phosphor may be used in combination with a yellow or orange light emitting phosphor. Examples of yellow to orange light emitting phosphors include YAG phosphors such as RE ₃ (Al, Ga) ₅ O ₁₂ : Ce phosphor (RE represents at least one selected from Y, Gd and La, the same shall apply hereinafter). Silicate phosphors such as AE ₂ SiO ₄ : Eu phosphor.

Further, in place of the above phosphors, nitride phosphors (for example, AE ₂ Si ₅ N ₈ : Eu) and oxynitride phosphors (for example, Y ₂ ) capable of obtaining various emission colors depending on the composition. Si ₃ O ₃ N ₄ : Ce), sialon-based phosphors (for example, AE _x (Si, Al) ₁₂ (N, O) ₁₆ : Eu), or the like may be applied. Note that the LED lamp 10 is not limited to a white light-emitting lamp, and an LED lamp 10 having a light-emitting color other than white can be configured. When the LED lamp 10 emits light other than white, for example, light of intermediate color, various phosphors are appropriately used according to the target light emission color.

  In this embodiment, the structure in which the phosphor sheet 24 is arranged on the transparent resin 23 has been described, but the arrangement structure of the phosphor is not limited to this. For example, as shown in FIG. 3, the phosphor may be directly dispersed in a transparent resin 23 made of a silicone resin. Moreover, as shown in FIG. 4, after potting the zinc oxide LED chip 11 with a silicone resin 23a that does not contain a phosphor, it may be filled with a silicone resin 23b in which the phosphor is dispersed. The reverse is also possible. These structures can be obtained by filling and curing a liquid silicone resin composition in which a phosphor is dispersed. Furthermore, a modification such as providing a reflective layer between the transparent resin 23 and the phosphor sheet 24 is possible. Thus, the configuration other than the arrangement structure and basic structure of the phosphor is not particularly limited, and various modifications are possible.

  The LED lamps 10 having the above-described configuration are arranged in a matrix as shown in FIGS. 5 and 6, for example, and thereby an LED lamp module is configured. 5 and 6 show an LED lamp module in which nine LED lamps 10 are arranged in a matrix of 3 rows and 3 columns. Each zinc oxide LED chip 11 is mounted on a metal circuit 17 having a continuous pattern, and is connected in series. Such an LED lamp module is applied to various uses from a backlight of a liquid crystal display device to a general lighting device.

  Next, the results of evaluating the characteristics of the LED lamp 10 will be described. First, an LED chip having an emission wavelength of 350 to 370 nm is prepared as the zinc oxide-based LED chip 11, and this is mounted on the substrate 18 and sealed with an addition reaction type silicone resin to produce an LED lamp (Example 1). Produced. A phosphor sheet containing RGB phosphors was disposed on the silicone resin. JCR 6140 (trade name) manufactured by Toray Dow Corning was used as the addition reaction type silicone resin. On the other hand, as a comparative example with the present invention, an LED lamp was prepared in the same manner as in Example 1 except that a thermosetting epoxy resin (Comparative Example 1) and a condensation reaction type silicone resin (Comparative Example 2) were used as transparent resins. Produced.

  The light output of each LED lamp according to Example 1 and Comparative Examples 1 and 2 described above was evaluated. As a result, while the LED lamp of Example 1 maintained the light output, each LED lamp according to Comparative Examples 1 and 2 became cloudy, and the light output decreased. Thus, an LED lamp manufactured by sealing a zinc oxide LED chip with an addition reaction type silicone resin that does not substantially release amines, carboxylic acids and oximes during the curing reaction is a zinc oxide LED. Since the deterioration of the chip can be suppressed, the emission intensity, emission color, and the like can be kept stable. On the other hand, the LED lamps of Comparative Examples 1 and 2 in which a thermosetting epoxy resin or a condensation reaction type silicone resin is applied to the transparent resin are inferior to the light emission characteristics of Example 1. From this, it is understood that the zinc oxide LED chip is deteriorated during the curing reaction of the transparent resin.

It is sectional drawing which shows the structure of the LED lamp by one Embodiment of this invention. It is sectional drawing which shows one structural example of the zinc oxide type LED chip applied to the LED lamp shown in FIG. It is sectional drawing which shows the structure of the LED lamp by other embodiment of this invention. It is sectional drawing which shows the structure of the LED lamp by other embodiment of this invention. It is a top view which shows the structural example of the illuminating device comprised using the LED lamp shown in FIG. It is sectional drawing along the AA line of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... LED lamp, 11 ... Zinc oxide type LED chip, 12 ... n-type ZnO substrate, 13 ... n-type ZnO light emitting layer, 14 ... p-type ZnO light emitting layer, 17 ... Metal circuit, 18 ... Substrate, 21 ... Recess (cavity) ), 22 ... frame, 23 ... transparent resin made of silicone resin, 24 ... phosphor sheet.

Claims (3)

A light emitting device having a zinc oxide based semiconductor layer;
A silicone resin disposed over the light emitting element and substantially free of amines, carboxylic acids and oximes;
A phosphor that emits visible light when excited by light emitted from the light emitting element;
A light-emitting device comprising:   2. The light emitting device according to claim 1, wherein the silicone resin is an addition reaction type silicone resin.   The light emitting device according to claim 1 or 2, wherein the light emitting element emits ultraviolet light, and the phosphor emits visible light when excited by the ultraviolet light.

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