JP2014183192A - Polarized led and display device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarized LED having improved luminance and high use efficiency of light, and to provide a backlight unit, a liquid crystal display device, a head-up display unit and a liquid crystal projector using the polarized LED.SOLUTION: The polarized LED has such a configuration that: at least one LED element is mounted on a substrate; the LED element is covered with a phosphor dispersed resin layer containing a phosphor that absorbs light emission of the LED element; a wire grid polarizing element is disposed on an exiting surface side of the LED element; and preferably, the LED element is mounted on a bottom of a recessed portion formed on the substrate and the inner surface of the recess portion has a reflection surface.

Description

  The present invention relates to a polarized LED using a wire grid polarizing element and a phosphor, a backlight unit having the polarized LED, a liquid crystal display device, a head-up display, and a liquid crystal projector.

  A liquid crystal display (LCD) has advantages such as thinning, low voltage driving, and low power consumption, and therefore has been widely applied to desktop and notebook personal computer displays and projectors. The main structure of the liquid crystal display device is a light source, a liquid crystal panel, and two polarizing elements located on both front and rear sides of the liquid crystal panel. After the light beam is emitted from the light source, when it reaches the polarizing element closer to the light source of the liquid crystal panel, about half of the light beam is transmitted. Thereafter, the transmitted light passes through the liquid crystal panel and the polarizing element on the opposite side to display an image.

In recent years, light emitting diodes (LEDs) with low energy consumption have been widely used as light sources for image display devices such as liquid crystal display devices. An LED is a semiconductor diode that emits light, and converts electrical energy into visible light or ultraviolet light.
Conventionally, it has been known that a polarized light source is also used in the above display device. In recent years, an LED with low energy consumption has been frequently used as the polarized light source. In addition, a technique is also known in which a wire grid polarizing element is used to obtain polarized light, and a reflector or the like is provided in order to improve the light utilization rate of the LED light source (Patent Documents 1 and 2).

JP-A-2005-79104 JP 2005-328042 A

  Due to the above-described technology and the like, the light use efficiency in the LED has been considerably improved. However, due to the downsizing of the display device, the display image becoming clearer, the use of polarized light in projectors, the use in automobile headlights, etc. There is a demand for efficient use of light in LEDs.

  In view of the above problems, the object of the present invention is to efficiently convert non-polarized light emitted from an LED into linearly polarized light, and to further improve the amount of light emitted from the LED, thereby increasing polarization of the light. It is intended to obtain an LED (polarized LED light source), particularly a white polarized LED.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have directly covered the entire light emitting portion of the LED with a resin containing a phosphor, and the wire grid polarization element is reflected light from the polarization element. It has been found that the above problem can be solved by arranging the wire grid polarizing element so as to return to the resin containing the phosphor, and the present invention has been completed.

Specifically, the present invention relates to the following (1) to (19).
(1) At least one LED element is mounted on the substrate, and the phosphor-dispersed resin containing a phosphor that emits light by absorbing light emitted from the LED element is a portion other than the mounting part of the LED element. A polarized LED that is arranged so as to cover directly, and is arranged such that a wire grid polarization element is disposed on the light emission surface side of the LED element, and reflected light from the wire grid polarization element returns to the phosphor-dispersed resin.
(2) The polarization LED according to (1), wherein the period of the wire grid of the wire grid polarization element is 150 nm or less.
(3) The polarizing LED according to (2), wherein the wire grid period of the wire grid polarizing element is 120 nm or less.
(4) The polarization LED according to any one of (1) to (3), wherein a dielectric layer having a refractive index different from that of the wire grid is provided on the wire grid in the wire grid polarization element.
(5) The LED element is mounted on the bottom of the recess formed in the substrate, the phosphor is filled with the phosphor-dispersed resin, and at least light from the phosphor and a wire grid polarization element are formed on the inner surface of the recess. Polarized LED as described in any one of said (1)-(4) which has a reflective surface which reflects the reflected light from.
(6) The polarizing LED according to (5), wherein the wire grid polarizing element is disposed so as to be in close contact with the end portion of the reflecting surface.
(7) The polarizing LED according to any one of (1) to (4), further including a quarter-wave plate between the wire grid polarizing element and the LED element.
(8) Any of the above (1) to (7), wherein the wire grid polarizing element is a polarizing element having a wire grid on the surface of a glass substrate, and the wire grid forming surface is arranged to face the LED element. The polarized LED according to claim 1.
(9) The above LED element is an LED element that emits blue light or light having a shorter wavelength than blue, and includes the phosphor that emits green or longer wavelength fluorescence than green as the phosphor. The polarized LED according to any one of the above.
(10) The polarized LED according to any one of (1) to (9), wherein the LED element is an LED element that emits blue light having a light emission maximum wavelength of 400 to 500 nm.
(11) The polarized LED according to any one of (1) to (10), wherein the phosphor is a phosphor that emits fluorescence having an emission maximum wavelength of 500 to 650 nm.
(12) The polarized LED according to any one of (1) to (11), wherein the emitted light is white.
(13) The wire grid polarizing element according to any one of (1) to (12), wherein the single transmittances of light having a wavelength of 450 nm and light having a wavelength of 550 nm are both 45% or more. The polarized LED as described.
(14) The polarized LED according to any one of (1) to (13), wherein the LED element is mounted in plural on the substrate.
(15) A display device using the polarized LED according to any one of (1) to (14).
(16) A plurality of the polarized LEDs according to any one of (1) to (13) are arranged on a circuit board, or a liquid crystal back using the polarized LED according to (14). Light.
(17) A liquid crystal display device having the liquid crystal backlight according to (16).
(18) A head-up display comprising the polarized LED according to any one of (1) to (14) as a light source.
(19) A liquid crystal projector including the polarizing LED according to any one of (1) to (14) as a light source.

  According to the present invention, in a polarized LED, a polarized LED having good durability and high luminance can be obtained. In particular, the present invention is suitable for a polarized LED that emits white light, and a polarized LED having higher luminance can be obtained by using a highly transmissive wire grid polarizing element.

It is sectional drawing which shows the structure of the surface mount-type polarization LED of this invention. It is sectional drawing which shows the structure of the bullet-type polarized LED of this invention. In the surface mount type polarization LED of the present invention, it is a sectional view showing the composition provided with a plurality of LED elements on a substrate. 1 shows a configuration example of a liquid crystal display device to which a surface-mounted polarization LED of the present invention is applied. The structural example of the head up display unit (HUD unit) to which the surface mount type polarization LED of the present invention is applied is shown.

  1 to 3 are schematic cross-sectional views of a polarized LED according to the present invention. As shown in FIGS. 1 to 3, the polarized LED of the present invention includes at least one LED element mounted on a substrate and a phosphor that absorbs light emitted from the LED element and emits light. A phosphor-dispersed resin layer that directly covers the element, and a wire-grid polarizing element provided on the light-emitting surface side of the light from the LED element so that reflected light from the wire-grid polarizing element returns to the phosphor-dispersed resin Prepare.

As a substrate used for the polarized LED of the present invention, for example, ceramics such as alumina and aluminum nitride (AlN), glass, epoxy resin and the like are used. Since the heat dissipation effect of the system can be enhanced and the temperature rise of the polarized LED can be suppressed, it is preferable to use a material having high thermal conductivity such as alumina or aluminum nitride.
Electrodes are formed on the substrate. As the electrode, for example, a metal electrode made of Ag, Pt, Ru, Pd, Al, or the like is used.

As shown in FIG. 1 or FIG. 2, it is preferable that the substrate used for the polarized LED of the present invention has a recess for mounting the LED element. In that case, the LED element is mounted on the bottom of the formed recess. The concave portion may be formed on the substrate itself, or the concave portion may be formed by forming a convex portion on the substrate on which the LED element is mounted so as to surround the LED element. The depth of the recess is such that the LED element can be completely accommodated in the recess and the upper portion of the LED element can be covered with the phosphor dispersion resin when the recess is filled with the phosphor dispersion resin. Is preferable.
In a preferred embodiment of the polarized LED of the present invention, at least the reflected light from the wire grid polarizing element is provided on the inner surface (LED element side) of the substrate surrounding the LED element, particularly on the inner surface where the concave portion is formed. And the light emitted from the phosphor is reflected, passes through the phosphor dispersion resin, and returns to the light emission side from the LED element. The reflecting surface usually reflects light from the LED element and returns it to the light emitting side. Therefore, all of the light from the LED element, the light emitted from the phosphor, and the light reflected by the wire grid are again returned to the light emission side from the LED element through the phosphor dispersion resin. Become. By repeating this, all the light emitted from the LED element is used for light emission of the phosphor and emitted as polarized light without being wasted.
The reflecting surface is polished so that the inside of the substrate itself can reflect light, or a reflecting surface is formed by attaching a metal film or the like to the inside, and the reflecting plate is placed inside the substrate. It may be provided to form a reflective surface. Usually, the method of providing a reflector is simple and preferable.
Further, the bottom reflective surface may be formed of a conductive metal film.
The LED element used in the polarized LED of the present invention may be an LED element connected to an electrode of a substrate by a flip-chip method. In that case, it is preferable to use the transparent electrode which consists of indium tin oxide (ITO), for example for the electrode of an LED element.

As the LED element used in the present invention, any LED element that emits light having a wavelength of blue or longer wavelength can be used. The LED element used in the present invention can be obtained, for example, by forming a light emitting layer made of a semiconductor such as GaP, GaAsP, GaAlAs, GaN, InGaN, AlGaN or InGaAlP on a silicon carbide (silicon carbide) substrate.
In the polarized LED of the present invention, use of an LED element that emits blue light is preferable, and use of a blue LED element that emits blue light having a maximum wavelength of 400 to 500 nm is more preferable. As the blue LED element, a known blue LED element can be used, and for example, a GaN-based LED element can be used.
The LED element is mounted at a predetermined position on the substrate and is bonded to the electrode with AuSn eutectic solder or other various solders, silver paste, or the like, or connected to the electrode using a lead wire or the like.

In the polarized LED of the present invention, the phosphor-dispersed resin is disposed so as to directly cover the entire portion other than the mounting portion of the LED element, particularly the entire light emitting portion. By doing so, the light from the LED element efficiently causes the phosphor to emit light, and the light not used for the light emission of the phosphor directly reaches the wire grid polarization element as it is. In the wire grid polarization element, half of the light arriving at the polarization element (light directly arrived from the LED element, light emitted from the phosphor, etc.) is emitted as polarized light through the polarization element, and the remaining half amount Is reflected by the wire grid polarization element. The reflected light returns to the phosphor-dispersed resin, enhances the light emission of the phosphor, and increases the light emission amount of the phosphor. Therefore, the quantity of emitted light can be increased and the luminance can be increased.
In particular, when the light reflecting surface is provided on the inner side surface of the substrate, the light from the LED element is emitted as polarized light without waste, so that the luminance of the emitted light can be further increased.
As the phosphor used in the present invention, a phosphor that absorbs light emitted from the LED element and emits fluorescence having a longer wavelength than the light emitted from the LED element is used.
As the phosphor that can be used in the polarized LED of the present invention, any phosphor can be used as long as it absorbs blue or shorter wavelength light than blue and emits longer wavelength fluorescence than absorbed light. A phosphor that emits longer wavelength fluorescence is more preferable. For example, a green phosphor, a yellow phosphor, or a red phosphor that absorbs blue to blue-violet light and emits green, yellow, or red light. In addition, when an LED element that emits ultraviolet light is used, a blue phosphor, a green phosphor, a yellow phosphor, or a red phosphor that absorbs ultraviolet light and emits blue, green, yellow, or red fluorescence is used alone. Or it can be used in combination of 2 or more types.

  As the green phosphor, for example, a green phosphor having an emission maximum wavelength of about 490 to 575 nm is used. Examples of the green phosphor include a green phosphor comprising at least one of a green phosphor composed of europium manganese activated aluminate and a green phosphor composed of europium manganese activated silicate.

  As the yellow phosphor, for example, a yellow phosphor having an emission maximum wavelength of about 500 to 650 nm, preferably about 520 to 620 nm is used. Examples of the yellow phosphor include at least one of a YAG yellow phosphor using cerium-doped yttrium aluminum garnet and a TAG yellow phosphor using cerium-doped terbium aluminum garnet. Examples thereof include yellow phosphors.

As the red phosphor, for example, a red phosphor having a light emission maximum wavelength of about 620 to 780 nm is used. Examples of the red phosphor include a red phosphor composed of at least one of a red phosphor composed of europium activated lanthanum oxysulfide and a red phosphor composed of europium activated CaSiAlN ₃ .

  As the blue phosphor, for example, a blue phosphor having a light emission maximum wavelength of about 400 to 490 nm is used. Examples of the blue phosphor include a blue phosphor mainly composed of barium / aluminum oxide (BAM).

The phosphor used in the phosphor dispersion resin may be a single phosphor or a combination of a plurality of phosphors. For example, a blue LED element is used as the LED element, and a yellow phosphor that absorbs blue light is used alone as a phosphor, or both a green phosphor and a red phosphor that absorb blue light are combined. By using it, a polarized LED that emits white light can be obtained.
The particle size of the phosphor used in the present invention is not particularly limited, but the average particle size is usually 10 μm or more, preferably 10 μm to 100 μm, more preferably 20 μm to 80 μm. Here, the average particle diameter means a value measured by a laser diffraction method.
In the polarized LED of the present invention, a yellow phosphor having an absorption maximum wavelength of 400 to 500 nm and an emission maximum wavelength of 520 to 620 nm is used alone, or an absorption maximum wavelength is 400 to 500 nm and light is emitted. It is more preferable to use both a green phosphor having a maximum wavelength of 490 to 575 nm and a red phosphor having an absorption maximum wavelength of 400 to 500 nm and an emission maximum wavelength of 520 to 620 nm. It is particularly preferable to use a yellow phosphor alone having an absorption maximum wavelength of 400 to 500 nm and an emission maximum wavelength of 520 to 620 nm.

The method of directly covering the portion other than the LED element mounting portion with the phosphor dispersion resin is not particularly limited as long as the portion other than the LED element mounting portion (mounting portion on the substrate) can be directly covered. For example, a heat or photocurable resin composition in which the phosphor is dispersed in a transparent resin may be filled around the mounted LED element and the resin composition may be cured. The resin composition can be cured by ultraviolet irradiation or heating according to a normal curing method for a curable resin composition.
The amount of the phosphor-dispersed resin that covers the LED element is usually not particularly limited as long as it is an amount that can sufficiently cover the entire LED element. In a preferred embodiment, the polarized LED of the present invention emits white light. Therefore, in that case, for example, the blue light emitting LED may be covered with a phosphor-dispersed resin in an amount capable of emitting light emitted from the blue light emitting LED as white light. In the polarized LED of the present invention in which the LED element is mounted on the bottom of the concave portion of the substrate, the phosphor-dispersed resin is provided in the concave portion in such an amount that the light emitted from the LED element can be converted into white light. Fill. As long as the effect of the present invention is achieved, the filling amount is not hindered and a gap may be formed in the upper portion of the concave portion. Preferably, the filling amount is such that the concave portion is filled. When the wire grid polarizing element is attached, the phosphor dispersed resin and the wire grid polarizing element are in close contact with each other, and the reflected light from the wire grid polarizing element is more efficiently reflected in the phosphor. Increase luminescence.

If the transparent resin used for dispersion | distribution of fluorescent substance is a resin generally used in an optical member and has a high visible light transmittance, there is no particular problem.
In order to form the phosphor-dispersed resin used in the present invention, it can be obtained, for example, by dispersing the phosphor uniformly in a commercially available curable resin composition for optical members. As a commercially available curable resin composition for optical members, a commercially available resin composition such as a heat- or photo-curable silicone resin or epoxy resin is used.
What is necessary is just to adjust suitably content of the fluorescent substance in fluorescent substance dispersion resin so that the emitted light which has a desired hue, Preferably white is obtained. The ratio of each phosphor when using a plurality of phosphors is appropriately adjusted so that a desired hue can be obtained.

The polarized LED of the present invention can obtain polarized light having an arbitrary hue from an LED element that emits monochromatic light by appropriately selecting an LED element and a phosphor.
A preferable polarized LED of the present invention includes a polarized LED using a blue LED element that emits blue light. Along with the blue LED element, a yellow phosphor that absorbs blue light from the blue LED and emits yellow light and / or a green phosphor that absorbs the blue light and emits green light and / or a red phosphor is used. The obtained white polarized LED is more preferable, and the white polarized LED obtained using the blue LED element and the yellow phosphor is further preferable.
In the polarized LED of the present invention, an LED element that emits blue light having an emission maximum wavelength of 400 to 500 nm, a yellow phosphor having an absorption maximum wavelength of 400 to 500 nm, and an emission maximum wavelength of 500 to 650 nm; It is particularly preferable to use in combination.

The preferable white polarized LED includes the phosphor in the phosphor-dispersed resin layer so that the blue light emitted from the blue LED element and the light emitted from the phosphor are mixed to emit white light. Adjust the amount.
As the white light in the present invention, when shown in the XYZ color system proposed by CIE (Commission Internationale d'Eclairage), the white chromaticity is X = 0.270 to 0.320, and Y = 0.270 to 0.320 is preferable, and more preferably, X = 0.280 to 0.310 and Y = 0.280 to 0.310 are more preferable. More preferably, it is preferable to adjust so as to approach X = 0.3 and Y = 0.3 in the above range.
In addition, although the combination of the LED element and fluorescent substance in polarization LED of this invention is not restricted above, the said white polarization LED is preferable.

  The polarizing LED of the present invention is also referred to as a wire grid polarizing element (also referred to as a wire grid polarizing plate) on the light emission surface side (hereinafter also referred to as LED light emitting side) from the LED element covered with the phosphor dispersion resin as described above. ) So that the reflected light from the wire grid polarization element returns to the phosphor-dispersed resin covering the LED element again. By providing the wire grid polarization element as described above, a part of the light emitted from the LED element causes the phosphor in the phosphor resin layer to emit light, and the remaining light together with the light emitted from the phosphor, A wire grid polarization element is reached. Only the light in the direction parallel to the transmission axis of the wire grid polarizing element (the direction orthogonal to the wire in the wire grid polarizing element) reaches the outside as polarized light. On the other hand, light in a direction orthogonal to the transmission axis (direction parallel to the wire in the wire grid polarizing element) is reflected by the wire grid polarizing element. The reflected light is again guided to the phosphor-dispersed resin layer. As a result, the reflected light from the wire grid polarizing element causes the phosphor in the phosphor-dispersed resin layer to emit light, and the amount of light emitted from the phosphor increases. In a preferred embodiment of the present invention, the LED element is mounted on the bottom of the recess of the substrate, the phosphor-dispersed resin is filled inside the recess so as to cover the LED element, and the inside of the recess Since the side has a reflective surface that reflects light, the light reflected from the wire grid polarization element is not used for light emission of the phosphor, and the light emitted from the phosphor is in a direction other than the LED output side. The light emitted from the LED and the light emitted from the LED and emitted in the direction other than the LED light emission side and not used for the light emission of the phosphor are all reflected on the reflecting surface. It is reflected and returns to the phosphor-dispersed resin layer again. In this preferred embodiment, this circulation of light is repeated, and as a result, theoretically, all (100%) of the light emitted from the LED element and the light emitted from the phosphor is not wasted and is polarized. Emitted. Actually, there is a loss when reflecting on the wire grid polarization element, a loss due to passing through the resin layer, a loss when reflecting on the reflecting surface, etc. The luminance can be greatly improved.

The wire grid polarizing element used in the present invention will be described below.
The wire grid polarizing element used in the present invention is not particularly limited, and any wire polarizing element can be used as long as it can be polarized by arranging wires in parallel on a transparent substrate, but the single transmittance is a wavelength of 450 nm. And light having a wavelength of 550 nm, both of which are preferably greater than 45%. More preferably, the single transmittance of the above wavelength is preferably 46% or more, and more preferably 47% or more. The upper limit of the single transmittance of the wire grid polarizing element may be up to 50%, but is usually about 49% or less. By using the high transmittance wire grid polarizing element, the luminance of light emitted as polarized light can be greatly improved.
Also preferred is a wire grid polarizing element in which the transmittance of polarized light parallel to the transmission axis of the wire grid polarizing element is greater than 90% at a wavelength of 450 nm and a wavelength of 550 nm. More preferably, the transmittance is 92% or more. This is because the brightness of light emitted as polarized light is improved by using such a wire grid polarization element. Furthermore, it is more preferable that the transmittance of at least one of the polarized light exceeds 94% at a wavelength of 450 nm and a wavelength of 550 nm. Most preferably, the transmittance at a wavelength of 450 nm and a wavelength of 550 nm is 94% or more.
Also, in the above, a wire grid polarizing element in which the transmittance of polarized light perpendicular to the transmission axis of the polarizing element is 450 nm and 550 nm is less than 1%, and both are preferably less than 0.6%. Smaller ones are more preferable.
In addition, “single transmittance” in this specification means a transmittance when a single polarizing plate is used and irradiated with natural light (non-polarized light), and a spectrophotometer is used according to a method based on JIS Z8701: 1999. Measured. The transmittance of polarized light parallel or perpendicular to the transmission axis of the polarizing element is the transmittance when one polarizing element is used and the polarizing element is irradiated with light parallel or perpendicular to the transmission axis. , Measured using a spectrophotometer. In the wire grid polarization element, the transmission axis means a direction orthogonal to the wire of the wire grid.

As the transparent substrate of the wire grid polarizing element, a conventional transparent resin substrate or glass substrate can be used, and it is preferable to use a glass substrate from the viewpoint of heat resistance. As a material constituting the wire grid, for example, metals such as aluminum, silver, copper, chromium, titanium, nickel, tungsten and iron, or alloys thereof can be used.
When the period (pitch) of the wire of the wire grid is sufficiently short compared to the incident electromagnetic wave, the wire grid acts as a polarizer, and reflects the polarization component in which the direction of the wire and the electric field is parallel in the electromagnetic wave, Transmits orthogonal polarization components.
By making the period of the wire shorter than at least half of the wavelength of incident light, a wire grid polarizing element having excellent polarization characteristics can be obtained. The wire period (pitch) of the wire grid polarizing element used in the polarizing LED of the present invention is preferably 150 nm or less, more preferably 145 nm or less. More preferably, the period is 125 nm or less, and most preferably 120 nm or less. The lower limit of the period is not particularly limited, but is about 70 nm due to technical problems. When commercial production is considered, about 90 to 125 nm is most preferable.
Such a wire grid polarizing element has a high transmittance of polarized light parallel to the transmission axis at a wavelength of 450 nm as high as 82% and a high transmittance of polarized light parallel to the transmission axis at a wavelength of 550 nm as high as 86%. Since the reflectance of polarized light orthogonal to the transmission axis is high at about 85 to 90% at both wavelengths, the amount of polarized light emitted from the polarized LED can be increased, and the luminance of the emitted light from the polarized LED is increased. be able to.

Wire grid polarization elements that can be used in the polarized LED of the present invention can be obtained from the market as, for example, product names ProFlux PPL05C and ProFlux PFU01C (both manufactured by Polatechno Co., Ltd., glass substrate, aluminum wire grid).
Moreover, in the wire grid polarizing element used for the polarized LED of the present invention, a dielectric layer having a refractive index different from that of the material constituting the wire is formed on the wire grid formed on the substrate (the side opposite to the wire grid substrate). May be formed. The thickness of the dielectric layer is preferably about 80 to 120 nm, and more preferably 90 to 110 nm. By forming such a dielectric layer, the reflectance of polarized light orthogonal to the transmission axis of the wire grid at a wavelength of 450 nm can be improved up to about 90%. As a material constituting such a dielectric layer, an oxide, nitride or oxynitride of a substance selected from silicon, aluminum, chromium, titanium, nickel and tungsten can be used, but is not limited thereto.

In the polarized LED of the present invention shown in FIG. 1 to FIG. 3 having a substrate having a recess formed as a preferred embodiment of the present invention, the wire grid polarization element is disposed so as to completely close the opening of the recess of the substrate. The The wire grid polarizing element has no problem as long as it completely closes the opening of the concave portion of the substrate, but from the viewpoint of economy, a shape and a size that match the shape of the opening of the concave portion of the substrate are preferable. In this case, even if each LED element has a wire grid polarizing element as shown in FIG. 1, a plurality of LED elements are mounted on the bottom of the substrate recess as shown in FIG. In addition to filling the phosphor-dispersed resin that covers the elements together, one wire grid polarizing element may be provided so as to close the opening.
In the polarized LED of the present invention, it is preferable to use a wire grid polarizing element in which a wire grid is formed on the transparent glass substrate surface from the viewpoint of durability, transmission and reflection performance improvement. The surface facing the LED element when the wire grid polarizing element is disposed on the LED element may be either the substrate surface on which the wire grid is formed or the substrate surface on which the wire grid is not formed. The polarizing element is preferably disposed so that the wire grid forming surface faces the LED element.
In the polarized LED of the present invention, since the polarizer is placed very close to the LED element, it is assumed that the LED element is heated to a high temperature during use. Therefore, the polarized LED of the present invention having a wire grid polarizing element using a glass substrate is preferable, and the polarized LED always exhibits stable polarization characteristics because of excellent heat resistance.

The polarized LED of the present invention obtained as described above may be further sealed with a transparent resin as necessary. As such an example, the bullet-type polarized LED shown in FIG. 2 can be mentioned.
As the transparent resin for sealing, a curable transparent resin having a high visible light transmittance, which is generally used in an optical member, can be used, similarly to the resin used for the phosphor dispersion resin. The dispersion medium of the phosphor-dispersed resin layer and the transparent resin used as the sealing resin may be the same or different, and are preferably the same.
What is necessary is just to seal the polarizing LED of this invention like the normal LED sealing for sealing with this transparent resin.

Hereinafter, a typical configuration of the polarized LED of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing a configuration of a surface-mounted polarization LED of the present invention. Regarding the action of the polarized LED of the present invention, in the polarized LED shown in FIG. 1, a blue LED element that emits blue light is used as the LED element, and the yellow phosphor that absorbs the blue light and emits yellow light as the phosphor. The case of using will be described as an example.
In FIG. 1, when non-polarized blue light is emitted from the LED element 20, a part of the blue light is absorbed by the phosphor in the phosphor-dispersed resin layer 30, causing the yellow phosphor to emit light, and the remainder being phosphor-dispersed. It passes through the resin layer 30 and reaches the wire grid polarization element 40 as white light together with the light from the yellow phosphor. One polarization of the light reaching the wire grid polarization element 40 is transmitted and emitted to the outside, and the polarized light orthogonal thereto is reflected. The light reflected by the wire grid polarizing element 40 returns to the phosphor-dispersed resin layer 30 and enhances the light emission of the phosphor. In addition, the light reflected by the wire grid polarization element is not used for light emission of the phosphor, the light emitted from the phosphor is emitted in a direction other than the LED light emission side, and emitted from the LED element. The light emitted in the direction other than the LED light emission side and the light that was not used for the light emission of the phosphor is all reflected by the reflecting surface, and again returns to the phosphor-dispersed resin layer, The same as above is repeated in the polarized LED. As a result, theoretically, if the loss in the light path is ignored, the light emitted from the LED element is partly used for light emission of the phosphor, and the remaining part is left as it is together with the light from the phosphor. As a result, 100% is emitted.

  As described above, the polarized LED of the present invention, particularly the polarized LED having a reflecting surface in the concave portion, utilizes light in all directions emitted from the LED element, and increases the light emission amount of the phosphor and the remaining light. Is finally emitted as polarized light from the wire grid polarization element together with the light from the phosphor, so that the polarized LED of the present invention can improve the brightness of the emitted light and suppress power consumption.

As shown in FIGS. 1-3, when using the board | substrate with which the recessed part is formed as a board | substrate of polarization LED of this invention, a reflective surface is provided in the inner surface and bottom face of a board | substrate recessed part. The reflecting surface is preferably installed so as to reflect the reflected light to the LED light output side. In addition, the reflective surface is made of a highly reflective material, thereby increasing the use efficiency of the emitted light of the LED element in the phosphor and the amount of emitted light emitted from the phosphor to the outside, thereby increasing the brightness of the polarized LED. Further improvement can be achieved. The reflectivity (ratio of reflected light with respect to incident light) on the reflecting surface is preferably 90% or more, more preferably 95% or more, and still more preferably 98% to 100%.
As the high reflectivity material, a diffuse reflection material such as a white ceramic such as alumina or a heat-resistant white resin can be preferably used.

  In the polarized LED of the present invention, in some cases, a phase difference plate such as a quarter-wave plate and a half-wave plate can be installed between the wire grid polarization element and the LED element. It is preferable to install a single wavelength plate. When a quarter-wave plate is installed, by arranging the angle between the transmission axis of the wire grid polarization element and the fast axis (slow axis) of the quarter-wave plate to be 45 °, The polarized light reflected by the wire grid polarization element is transmitted through the first quarter-wave plate, reflected by the reflecting surface of the concave portion of the substrate, and transmitted through the second quarter-wave plate. Therefore, the amount of emitted light can be increased.

The manufacturing method of the polarized LED of the present invention will be described by taking the surface mount type polarized LED shown in FIG. 1 as an example. In addition, the manufacturing method of polarized LED of this invention is not limited to the following method.
First, the LED element 20 is installed using paste in the substrate recess 11 for mounting the LED element, and connected to each electrode 12 by the lead wire 13. At this time, instead of using one lead wire 13, the LED element may be bonded onto one electrode using a conductive paste. Next, the phosphor-dispersed resin layer 30 is formed by applying or dropping the phosphor-dispersed resin in which the phosphor is dispersed so as to cover the LED element 20 and curing the resin. If necessary, the sealing resin layer may be formed by filling the gap between the concave portions 11 that cannot be filled with the phosphor-dispersed resin layer 30 with a transparent resin and curing the transparent resin. In the polarized LED of the present invention, the entire space surrounded by the wire grid polarizing element 40 and the substrate recess 11 may be filled with the phosphor dispersed resin layer 30. The polarized LED of the present invention shown in FIG. 1 is manufactured by placing the wire grid polarizing element 40 on the exit surface side of the LED package thus obtained.
The polarized LED manufactured by the above manufacturing method emits white light with less variation in chromaticity and good reproducibility compared with a conventional white LED light source, and the emission intensity for the same supply power also increases. .

FIG. 2 is a cross-sectional view showing a configuration of a bullet-type polarized LED of the present invention. The same members as those in the surface-mounted polarization LED of FIG.
The bullet-type polarized LED of the present invention includes a substrate 10, a lead wire 13, a lead frame 14, an LED element 20 having an LED element 20 and a phosphor-dispersed resin layer 30, and a wire grid polarizing element 40, and the LED package and the wire. It is manufactured by forming a shell-shaped transparent mold resin 50 so as to surround the grid polarizing element 40. The surface mount type polarization LED of FIG. 1 described above except that the wire grid polarization element 40 is disposed on the light emitting surface side of the LED package, then sealed with a transparent mold resin 50, formed into a shell shape and cured. The bullet-type polarized LED of the present invention can be manufactured in the same manner as the manufacturing method.

  As the resin used as the mold resin in the bullet-type polarized LED of the present invention, a curable resin transparent in visible light that can be used as a dispersion medium or a sealing resin for the phosphor-dispersed resin layer can be used. By appropriately processing the convex shape protruding in the light emission direction of the mold resin, it becomes possible to control the light extraction direction or the light emission spread angle.

In the polarized LED shown in FIGS. 1 and 2, one LED element (hereinafter also referred to as a phosphor-coated element) covered with the phosphor-dispersed resin layer is mounted on each substrate. However, the polarized LED according to the present invention may have a plurality of phosphor-coated elements on each substrate, and have blue, green, red, yellow, and other structures having other configurations together with the phosphor-coated elements. LED elements having respective emission colors such as white may be mounted on the same substrate.
In FIG. 3, a plurality of LED elements 20 are mounted on one substrate recess 11, the plurality of LED elements 20 are covered with a phosphor-dispersed resin layer 30, and one wire grid polarizing element 40 is disposed on the exit surface. The structure of the polarization LED of this invention formed is shown.

The polarized LED of the present invention can be preferably used as a light source for various display devices. For example, as shown in FIG. 4, a surface-mounted polarization LED of the present invention is arranged on a circuit board on a matrix to produce a planar polarization LED, which can be used as a backlight unit for a liquid crystal display device. .
A liquid crystal display device can be manufactured by combining a backlight unit including the planar polarization LED of the present invention with an optical component such as a liquid crystal cell.
FIG. 4 shows an example of a liquid crystal display device using a backlight unit including the planar polarization LED of the present invention. As the liquid crystal cell used in the liquid crystal display device, a conventional liquid crystal cell in which a liquid crystal layer is sandwiched between two conventional linearly polarizing elements can be used. When using a conventional liquid crystal cell having two linearly polarizing elements, the plane of polarized light of the planar polarization LED of the present invention may be arranged so that the polarization plane of the incident light is parallel to the transmission axis of the incident side linearly polarizing element. . Further, since the planar polarization LED of the present invention emits polarized light, a liquid crystal cell having a transparent substrate having no polarization ability on the incident side and having a linearly polarizing element only on the emission side can be used as the liquid crystal cell. .

  As shown in FIG. 5, the liquid crystal display device of the present invention can be used for a head-up display unit (HUD unit). In FIG. 5, the liquid crystal display device of the present invention is mounted on a predetermined device for projecting display light onto a display object (for example, a front window of an automobile). Specifically, the HUD unit of the present invention has at least a liquid crystal display device having at least the polarizing LED of the present invention and a liquid crystal cell, and a concave mirror. The display light emitted from the liquid crystal display device is reflected by the concave mirror and projected onto the front window or the like. Such a vehicle-mounted HUD unit is used to display information necessary for driving a vehicle (for example, direction indication, inter-vehicle distance, travel distance, various warning information, road information, etc.).

The polarized LED of the present invention can also be used as a white light source for a small liquid crystal projector such as a micro projector. At this time, it is preferable to use the bullet-type polarized LED of the present invention.
By using the polarized LED of the present invention as a light source, various displays such as a liquid crystal display device, a HUD unit, and a small liquid crystal projector having excellent characteristics of low power consumption and low chromaticity variation even at high luminance. The device can be manufactured.

  Examples of the present invention will be shown below, but the present invention is not limited to these examples.

Example 1
It has a recess on the substrate, a reflector on the bottom and side surfaces of the recess, a blue LED element is mounted on the bottom of the recess, and the entire recess is covered with yellow light so that the LED element is completely covered LED unit (manufactured by Nichia Corporation, product name NS6W083BT) filled with a phosphor dispersion resin, and a wire grid polarizer (wavelength of 450 nm having a wavelength of 144 nm formed on the glass surface) Single transmittance 46.5%, single transmittance 47.1% at 550 nm (product name PPL05C, manufactured by Polatechno Co., Ltd.) with the wire grid forming surface facing the LED element, and the concave portion of the substrate is completely covered Thus, the polarizing LED of the present invention was obtained.

Example 2
In the first embodiment, the wire grid polarizing element is a wire grid having a single transmittance of 47.1% at a wavelength of 450 nm and a single transmittance of 47.7% at 550 nm, in which a wire grid having a period of 120 nm is formed on the glass surface. A polarizing LED of the present invention was obtained in the same manner as in Example 1 except that the polarizing element (product name: PFU01C, manufactured by Polatechno Co., Ltd.) was used.

[Comparative Example 1]
A comparative polarized LED was produced in the same manner as in Example 1 except that an absorption linear polarizing plate (Polatechno dye-based polarizing plate, product name SHC-115U) was used instead of the wire grid polarizing element.
Table 1 below shows the transmittance at wavelengths of 450 nm and 550 nm with respect to polarized light parallel to or orthogonal to the transmission axis of each polarizing plate used in Example 1, Example 2, and Comparative Example 2. In Table 1, Tp represents the transmittance for polarized light parallel to the transmission axis, and Ts represents the transmittance for polarized light orthogonal to the transmission axis.

For the polarized LED obtained in each of the examples and comparative examples, the illuminance (hereinafter referred to as polarized illuminance) of the component parallel to and orthogonal to the transmission axis of the wire grid in the emitted light is referred to in the following method. It was measured.
A light receiving part of a reference polarizing plate and a spectral irradiance meter (product name Spectroradiometer USR-40, manufactured by Ushio Electric Co., Ltd.) is installed in this order on the output surface of the polarized LED, and the reference in the wavelength range of the visible light region The illuminance when the reference polarizing plate was arranged so that the transmission axis of the polarizing plate was parallel or perpendicular to the transmission axis of the polarizing LED was measured. As the reference polarizing plate, a dye-based polarizing plate (manufactured by Polatechno Co., Ltd., product name SHC-125U) was used.
Table 2 shows the illuminance measurement results for each polarization component at 450 nm and 550 nm. In Table 2, Tpol represents the illuminance when the transmission axis of the reference polarizing plate is parallel to the transmission axis of the polarized LED of the present invention or the polarizing LED for comparison, and Tpol-c represents the transmission axis of the reference polarizing plate and the present invention. Illuminance when the transmission axis of the polarizing LED or the comparative polarizing LED is orthogonal to each other is shown.

  As shown in Table 2, the polarized LED of the present invention using a wire grid polarizing element has a Tpol at 450 nm corresponding to blue light as compared with the polarized LED of Comparative Example 1 using a conventional absorption linearly polarizing plate. In Example 1, it is improved by about 1.04 times, in Example 2 is improved by about 1.16 times, and Tpol at 550 nm corresponding to yellow light is improved by about 1.32 times in Example 1, In Example 2, it improved about 1.57 times. Furthermore, compared to the polarization LED of Comparative Example 1, Tpol-c at 450 nm is reduced to about 77% in Example 1, is reduced to about 65% in Example 2, and Tpol-c at 550 nm is In Example 1, it decreased to about 94%, and in Example 2, it decreased to about 88%. Therefore, when the polarized LED of the present invention using a wire grid polarizing element is used, the amount of emitted light is increased as compared with a polarized LED using a conventional dye-based polarizing element, and when used in a liquid crystal display device. In black display, display without light leakage is possible.

  Since the polarized LED of the present invention can emit emitted light with high brightness as described above, it is useful as various light sources used in various display devices such as liquid crystal display devices, HUD units, and microprojectors.

DESCRIPTION OF SYMBOLS 10 Substrate 10-1 Concave formation part 11 Substrate reflective surface 12 Electrode 13 Lead wire 14 Lead frame 20 LED element 30 Phosphor dispersed resin layer 40 Wire grid polarizing element 50 Mold resin

Claims (19)

  At least one LED element is mounted on the substrate, and a phosphor dispersion resin containing a phosphor that absorbs light emitted from the LED element and emits light directly covers a portion other than the mounting part of the LED element. And a wire grid polarizing element arranged on the light emission surface side of the light from the LED element, and a reflected LED from the wire grid polarizing element is returned to the phosphor-dispersed resin.   The polarization LED according to claim 1, wherein a period of the wire grid of the wire grid polarization element is 150 nm or less.   The polarization LED according to claim 2, wherein the period of the wire grid of the wire grid polarization element is 120 nm or less.   The polarization LED according to any one of claims 1 to 3, wherein a dielectric layer having a refractive index different from that of the wire grid is provided on the wire grid in the wire grid polarization element.   The LED element is mounted on the bottom of the recess formed in the substrate, the phosphor is filled with the phosphor-dispersed resin, and at least light from the phosphor and reflection from the wire grid polarizing element are formed on the inner surface of the recess. The polarized LED according to claim 1, further comprising a reflective surface that reflects light.   The polarization LED according to claim 5, wherein the wire grid polarization element is disposed so as to be in close contact with the end portion of the reflection surface.   The polarization LED according to any one of claims 1 to 4, further comprising a quarter-wave plate between the wire grid polarization element and the LED element.   The said wire grid polarizing element is a polarizing element which has a wire grid on the surface of a glass substrate, and is arrange | positioned so that a wire grid formation surface may oppose an LED element. Polarized LED.   The LED element is an LED element that emits blue light or light having a shorter wavelength than blue, and includes a phosphor that emits green or fluorescence having a longer wavelength than green as the phosphor. The polarized LED according to 1.   The polarized LED according to any one of claims 1 to 9, wherein the LED element is an LED element that emits blue light having a light emission maximum wavelength of 400 to 500 nm.   The polarizing LED according to any one of claims 1 to 10, wherein the phosphor is a phosphor that emits fluorescence having an emission maximum wavelength of 500 to 650 nm.   Output light is white, Polarized LED as described in any one of Claims 1-11.   The polarization LED according to any one of claims 1 to 12, wherein the wire grid polarization element is a wire grid polarization element in which single transmittances of light having a wavelength of 450 nm and light having a wavelength of 550 nm are both 45% or more.   The polarized LED according to any one of claims 1 to 13, wherein there are a plurality of LED elements mounted on the substrate.   The display apparatus using the polarization LED as described in any one of Claims 1-14.   The backlight for liquid crystals using the polarization LED as described in any one of Claims 1-13.   A liquid crystal display device comprising the liquid crystal backlight according to claim 16.   A head-up display comprising the polarized LED according to any one of claims 1 to 14 as a light source.   A liquid crystal projector provided with the polarized LED according to claim 1 as a light source.

Images