WO2012093765A1

WO2012093765A1 - Lighting apparatus and method for controlling the same

Info

Publication number: WO2012093765A1
Application number: PCT/KR2011/007231
Authority: WO
Inventors: Youngjoo Yee; Jeongsoo Lee; Chihwan JEONG
Original assignee: Lg Electronics Inc.
Priority date: 2011-01-07
Filing date: 2011-09-30
Publication date: 2012-07-12
Also published as: KR101414643B1; KR20120080340A

Abstract

The present invention relates to a lighting apparatus and a method for controlling the same which can adjust characteristics of a light, such as a color temperature. The lighting apparatus includes an LED light source, and an adjustable color filter operative by an electrowetting principle for transmitting or shielding a light of a specific wavelength band from the LED light source, selectively.

Description

LIGHTING APPARATUS AND METHOD FOR CONTROLLING THE SAME

The present invention relates to a lighting apparatus and a method for controlling the same, and more particularly, to a lighting apparatus and a method for controlling the same which can adjust characteristics of a light from an LED, actively.

The LED (Light Emitting Diode) is a semiconductor device which emits the light by an electro-luminescence effect when a forward direction voltage is applied thereto. Recently, owing to high efficiency and a long lifetime of the LED compared to a fluorescent lamp or an incandescent lamp, the LED is spot lighted as a lighting apparatus. A color of the light from the LED varies with materials of the LED, and the LED can be fabricated to emit a light, starting from a UV light to a visible light, or an infrared light.

It is preferable that a white LED is used in the lighting apparatus. However, due to a problem in fabrication of the LED, the white LED has a problem in that mass production of the lighting apparatuses having the same chromaticity is difficult, and adjustment of a color temperature and a color rendering index CRI which are important performance indices are very difficult, too. In the meantime, currently, since the color temperature of the light is known to affect user’s concentration, mental fatigability, and so on, this is a time for taking even a service of the lighting as a so called ‘sensibility lighting’ into account. Consequently, technologies which can adjust the color temperature of the LED lighting are being suggested, currently.

In a related art LED lighting apparatus, there are two methods for adjusting the color temperature. A first method is application of a principle in which the light from the LED device involved in a color temperature change as the light passes through a fluorescent material disposed around the LED device. A second method is arrangement of two or more than two LED devices having different color temperatures within one package for adjusting brightness of each of the LED devices or a number of turned on LED devices, thereby adjusting the color temperature.

However, the first method has a drawback in that the color temperature can not be adjusted actively, and requires a complicate fabrication process and management for fabrication of a LED device having various color temperatures. Though the second method enables active color temperature adjustment, the second method has drawbacks in that a plurality of LED devices are required without fail, and a complicate control system is required for adjustment of the color temperature.

Currently, a technology used for the color temperature adjustment in the LED lighting apparatus is use of two kinds of LED devices having different color temperatures. That is, an LED package having a warm white color temperature characteristic and an LED package having a cool white color temperature characteristic are used for adjustment of the color temperature, or an LED package having a cool white color temperature characteristic and a red LED package are used for adjustment of the color temperature. However, since those methods require additional LEDs, the methods fail to become popular due to price. Therefore, development of an LED lighting apparatus is required, which does not use a plurality of LED devices, and enables active adjustment of characteristics of the light, such as color tone, and the color temperature, and easy control and fabrication thereof.

To solve the problems, an object of the present invention is to provide a light emitting device and a method for controlling the same which enables adjustment of characteristics of a light, such as color tone, and the color temperature, more effectively.

Another object of the present invention is to provide a light emitting device and a method for controlling the same which enables easy fabrication.

To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, a lighting apparatus includes an LED light source, and an adjustable color filter operative by an electrowetting principle for transmitting or shielding a light of a specific wavelength band from the LED light source, selectively.

Preferably, the adjustable color filter includes a hydrophobic dielectric material portion, a polar liquid provided to the hydrophobic dielectric material portion, and a driving unit for applying a voltage to the hydrophobic dielectric material portion, selectively. And, more preferably, the hydrophobic dielectric material portion has a nonpolar liquid further provided thereto, the nonpolar liquid having a transmissive spectrum different from a transmissive spectrum of the polar liquid. In this instance, the nonpolar liquid is a colored liquid having predetermined color tone and a color rendering index. Moreover, preferably, the nonpolar liquid is an oleaginous liquid. And, the polar liquid is a transparent liquid, and the polar liquid is an aqueous liquid.

In the meantime, preferably, the driving unit includes a first electrode positioned on one side of a hydrophobic dielectric material, and a second electrode positioned on the other side of a hydrophobic dielectric material. And, preferably, the driving unit applies a voltage to a portion of the hydrophobic dielectric material portion. Moreover, more preferably, the first electrode has a first transparent portion provided on an underside of the first electrode, and a second transparent portion provided over the first electrode.

In the meantime, preferably, the adjustable color filter includes a plurality of cells. And, preferably, the cells have at least one of shapes and an arrangement thereof made in random or pseudo-random. Moreover, preferably, the cells are a set of a plurality of cells having transmissive spectrum characteristics different from one another. The plurality of cells can be arranged on the same plane, or the plurality of cells can be stacked in multiple layers.

In another aspect of the present invention, a method for controlling a lighting apparatus includes the steps of arranging a polar liquid on a hydrophobic dielectric material, and selectively applying a voltage to the hydrophobic dielectric material to move the polar liquid selectively for transmitting or shielding a light of a specific wavelength band from an LED light source.

Preferably, the hydrophobic dielectric material has a nonpolar liquid provided thereto further for cohering or spreading the nonpolar liquid following the selective movement of the polar liquid. And, more preferably, the voltage is applied to a portion of the hydrophobic dielectric material, selectively. Preferably, the polar liquid is a transparent aqueous liquid and the nonpolar liquid is a colored oleaginous liquid.

The lighting apparatus and the method for controlling the same present invention have following advantageous effects.

First, the utilization of the electrowetting enables easy adjustment of a color temperature and so on, and active adjustment of different color temperature suit to a taste of a user.

Second, since the LED device or the LED package used as a light source can be embodied with one or one kind of LEDS having a predetermined color temperature characteristic, the lighting apparatus costs lower than the related art lighting apparatus which uses two or a plurality of LEDS having color temperature characteristics different from one another.

Third, since fine adjustment of color temperature of the LED device is possible, uniformity of characteristics between devices can be secured.

The accompanying drawings, which are included to provide further understanding of the disclosure and are incorporated in and constitute a part of this application, illustrate embodiments of the disclosure and together with the description serve to explain the principle of the disclosure.

In the drawings:

FIG. 1 illustrates a schematic view showing a principle of electrowetting.

FIG. 2 illustrates a section of an LED lighting apparatus in accordance with a preferred embodiment of the present invention.

FIG. 3 illustrates a section of a unit adjustable color filter in the LED lighting apparatus in FIG. 2.

FIG. 4 illustrates a graph showing a voltage vs. a colorless area ratio of the unit adjustable color filter in the LED lighting apparatus in FIG. 2.

FIG. 5 illustrates a plan view of an LED lighting apparatus in accordance with another preferred embodiment of the present invention.

FIG. 6 illustrates a section of an LED lighting apparatus in accordance with another preferred embodiment of the present invention, schematically.

FIG. 7 illustrates a section of an LED lighting apparatus in accordance with another preferred embodiment of the present invention, schematically.

FIG. 8 illustrates a perspective view of an bulb type LED lighting apparatus in accordance with preferred embodiment of the present invention.

Reference will now be made in detail to the specific embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

In the present invention, a color temperature is adjusted by using an adjustable color filter which serves as an optical shutter to transmit only a light of a specific wavelength band from the LED device, i.e., an LED. The adjustable color filter is embodied by utilizing an electrowetting principle. The electrowetting is discovered by G. Lippmann et al who are physicists in an early part of 1900s, and is a phenomenon in which a wetting property of a hydrophobic surface varies with electric fields applied thereto.

The electrowetting will be described with reference to FIG. 1.

A drop of water or water solution has a property of maintaining a surface area thereof to be a minimum on a hydrophobic dielectric material layer owing to surface tension of the liquid itself. Therefore, in an ordinary state, the liquid exists in a shape 100 which forms a great contact angle θ1 to a surface of the hydrophobic dielectric material layer. However, upon application of a voltage to the liquid and a conductive plate 110 through a first electrode 130 and a second electrode 140, electrostatic energy is accumulated between the liquid and the hydrophobic dielectric material layer. Then, in order to make an energy balance between interfaces with respect to the electrostatic energy added thus, since the contact angle θ2 to the hydrophobic dielectric material layer becomes smaller, the liquid drop is spread to a large area, leaving the liquid drop to exist in a spread state. The LED lighting apparatus of the present invention embodies the adjustable color filter by utilizing the electrowetting principle for adjusting a color temperature and so on.

The LED lighting apparatus in accordance with a preferred embodiment of the present invention will be described with reference to FIG. 2. At first, an overall configuration of the LED lighting apparatus of the embodiment will be described.

There is the adjustable color filter 320 provided on an LED light source 310, i.e., in a direction of light travel. The LED light source 310 can include an LED device, a package having the LED device, and phosphor for producing a predetermined color spectrum, and so on. And, it is preferable that the adjustable color filter 320 has a plurality of unit adjustable color filters which serve as micron optical shutters. For an example, it is preferable that the adjustable color filter 320 is divided into a plurality of cells each with the unit adjustable color filter 321 so that the color temperature and so on can be adjusted at each of the cells.

The unit adjustable color filter 321 will be described in detail, with reference to FIGS. 3A and 3B. FIG. 3A illustrates a state in which no external electric field is applied to the adjustable color filter 320, and FIG. 3B illustrates a state in which an external electric field is applied to the adjustable color filter 320.

The plurality of unit cells 322 have the unit adjustable color filters 321, respectively. It is preferable that the plurality of unit cells 322 are partitioned with barriers 230, and it is preferable that the cells 322 are arranged in a form a pixels. The unit adjustable color filter 321 or the adjustable color filter 320 will be described, in detail.

The unit adjustable color filter 321 serves to transmit or shield a light of a specific waveband from the LED light source (not shown), selectively. For this, the unit adjustable color filter 321 includes a hydrophobic dielectric material portion 240, a polar liquid 260 and a nonpolar liquid 270 on the hydrophobic dielectric material portion 240, a

driving unit

220, 250 and 280 for applying a voltage to the hydrophobic dielectric material portion 240, selectively.

That is, upon application of the voltage to the hydrophobic dielectric material portion 240 with the driving

unit

220, 250 and 280, the nonpolar liquid 270 moves to cause the nonpolar liquid 270 to cohere making the nonpolar liquid 270 to transmit or shield a light of the specific wavelength region, selectively. For an example, if the nonpolar liquid 270 is in a cohered state, the light from the LED light source transmits through the polar liquid 260 and travels to an outside of the color filter 320. If the nonpolar liquid 270 is in a spread state, since the light from the LED light source transmits through the nonpolar liquid 270 and the polar liquid 260 and travels to an outside of the color filter 320, the color temperature and so on can be adjusted, which will be described in more detail, later.

In the meantime, it is preferable that the polar liquid 260 and the nonpolar liquid 270 have transmissive spectrum characteristics different from each other. For an example, the nonpolar liquid 270 can be a colored liquid having predetermined color tone and a color rendering index, and the colored liquid can be formed by scattering one or a plurality of dyes. And, the polar liquid 260 can be a colorless transparent polar liquid including a water solution, a polar liquid having a predetermined transmissive spectrum, or a polar liquid prepared to scatter and dissolve pigments therein to have a predetermined transmissive spectrum different from the nonpolar liquid. Moreover, it is preferable that the polar liquid 260 is an aqueous liquid and the nonpolar liquid 270 is an oleaginous liquid, which do not mix with each other.

As described before, though various types of the polar liquid 260 and the nonpolar liquid 270 can be used, for conveniences’ sake, the embodiment will be described taking a case as an example in which the polar liquid 260 is a transparent aqueous liquid and the nonpolar liquid 270 is the oleaginous liquid such that the color temperature and so on are adjusted with the nonpolar liquid 270. FIG. 3 illustrates the example.

In the meantime, the driving unit for applying the voltage to the hydrophobic dielectric material portion 240 selectively will be described. It is preferable that the driving unit includes a first electrode 250 positioned on an underside of the hydrophobic dielectric material portion 240, a second electrode 220 positioned on an upper side of the color filter 320 spaced from the hydrophobic dielectric material portion 240, and a control power source 280 connected between the first electrode 250 and the second electrode 220. And, it is preferable that the first electrode 250 is provided to a portion excluding a portion of the hydrophobic dielectric material portion 240. That is, it is preferable that a non-electrode region 251 is provided to a portion of the hydrophobic dielectric material portion 240, and it is preferable that the non-electrode region 251 is disposed to be non-transparent, optically. That is, it is preferable that, when the voltage is applied to the unit adjustable color filter 321, the nonpolar liquid 270 coheres to the non-electrode region 251. And, it is preferable that the first electrode 250 and the second electrode 220 are transparent to transmit the light as it is. And, it is preferable that a first transparent portion 290 is provided on an underside of the first electrode 250, and a second transparent portion 210 is provided on the second electrode 220 to serve as a housing of the unit adjustable color filter 321.

As explained above, the control power source 280 is provided for controlling the adjustable color filter 320. Additionally, a power source for controlling the LED light source 310 is also provided.

The operation of the LED lighting apparatus of the present invention will be described with reference to FIGS. 3A and 3B. FIG. 3A illustrates a state in which no external electric field is applied to the adjustable color filter, and FIG. 3B illustrates a state in which an external electric field is applied to the adjustable color filter.

The embodiment will describe a case in which the unit cell 322 contains the polar liquid 260 (Called as ‘a transparent polar liquid’, for convenience’s sake), such as water or a water solution, and a nonpolar colored oleaginous liquid 270 (Called as ‘a colored nonpolar liquid’ for convenience’s sake), particularly, focused on movement at an interface of the transparent polar liquid 260 and the colored nonpolar liquid 270.

A state will be described at first, in which no external electric field is applied to the unit adjustable color filter 321, with reference to FIG. 3A.

In an ordinary state in which no external electric field is applied to the unit adjustable color filter 321, according to a relation between surface tensions expressed as [[γo,w + γo,i < γw,i] ( γ:surface tension, o: oil, w: water or saline, i: insulating material), the colored nonpolar liquid 270 positions between the transparent polar liquid 260 and the hydrophobic dielectric material portion 240. That is, the colored nonpolar liquid 270 is spread to an entire surface of the unit cell 322 such that the cell 322 transmits only a light of a spectrum distribution the colored nonpolar liquid 270 transmits. Since the cell 322 has very small size, preferably below 2mm, it is preferable that the surface tension which is force acting on the interface is greater than the gravity, significantly. If it is done so, a film of the colored nonpolar liquid 270 is maintained in a stable and continuous state in all directions.

Next, referring to FIG. 3B, a state will be described, in which the external electric field is applied to the unit adjustable color filter 321.

Upon application of the voltage between the transparent polar liquid 260 and the first electrode 250 through the second electrode 220, static electric energy is added to a system under an energy balance. According to this, a stacked state of the colored nonpolar liquid 270 and the transparent polar liquid 260 can be maintained no more. That is, the transparent polar liquid 260 moves in a direction to lower entire energy of the system by moving so as to be brought into contact with a surface of the hydrophobic dielectric material portion 240. According to this, the colored nonpolar liquid 270 is pushed away from the surface of the hydrophobic dielectric material portion 240 to cohere at the non-electrode region 251 of the cell 322. That is, the transparent polar liquid 260 becomes to be positioned at a region excluding a region having the colored nonpolar liquid 270 cohered therein, making the region transparent. According to this, the cell 322 transmits the light from the LED light source (not shown) without transition of a color.

That is, as described before, the LED lighting apparatus of the embodiment can adjust the color temperature and so on of the light from the LED light source by cohering or spreading the colored nonpolar liquid 270, selectively. And, by controlling the voltage applied to the first electrode 250 and the second electrode 220, fine adjustment of the light from the LED light source is possible.

A method for making fine adjustment of the light from the LED light source by controlling the voltage applied to the first electrode 250 and the second electrode 220 will be described, with reference to FIG. 4.

FIG. 4 illustrates a graph showing a voltage vs. a colorless area ratio of the unit cell. In a case the voltage is between (0 ~ Vth), there is almost no cohesion of the colored nonpolar liquid 270. Accordingly, since it is in a state the colored nonpolar liquid 270 is spread to an entire surface of the cell 322, a ratio of the transparent area to a cell 322 area is close to zero. Therefore, the light from the LED light source transmits through the colored nonpolar liquid 270, coloring the cell 322 with the colored nonpolar liquid 270. That is, as shown in FIG. 4A, an entire area of the cell 322 is colored. As shown in FIG. 4B, the colored nonpolar liquid 270 coheres following increase of the voltage, to increase a region without the colored nonpolar liquid 270, i.e., a region having only the transparent polar liquid 260 present thereto. This case is a state in which a color of the LED light source and a predetermined transmitted color of the colored nonpolar liquid 270 are mixed. As shown in FIG. 4C, if the voltage increases further, to a voltage higher than a predetermined value Vfull, the transparent area becomes greater than 80%. In this case, the light from the plurality of unit cells 322 transmits almost without mix of the colors. Therefore, as described before, by controlling the voltage to the unit adjustable color filter, fine adjustment of color intensity of the unit adjustable color filter is possible.

A unit adjustable color filter in accordance with another preferred embodiment of the present invention will be described with reference to FIG. 5.

A basic principle of the embodiment is identical to the foregoing embodiment, except that the embodiment has a shape of the cell 322 or the unit adjustable color filter 321 different from the foregoing embodiment. The foregoing embodiment has the cells or the unit adjustable color filters arranged at predetermined intervals. However, a spatial distribution of light intensity can be non-uniform due to refraction caused by arrangement of, and space between, the adjustable color filter and the LED light source, and a size of the LED light source. For an example, if the unit cells are arranged at the predetermined intervals, a periodic arrangement of slits through which the light can pass, can cause refraction and interference, and the like.

Therefore, in order to suppress this, shapes and arrangement of the cells 322 or the unit adjustable color filters of the adjustable color filter are made in random or pseudo-random. For an example, the shapes of the cells 322 can be made in random or pseudo-random. Or, the arrangement of the cells 322 can be made in random or pseudo-random in which no spatial periodicity exists or the periodicity is suppressed. Or, cells with a variety of sizes can be arranged in random or pseudo-random, spatially. Of course, those methods may be combined.

FIG. 5A illustrates a colored state in which a predetermined color of the light transmitted through the colored nonpolar liquid spread on the surface of the cell 322 is filtered, and FIG. 5B illustrates a state in which the colored nonpolar liquid is cohered to a predetermined cohesion region and the light from the LED light source transmits through a transparent portion except the cohesion region without color transition.

An adjustable color filter in accordance with another preferred embodiment of the present invention will be described with reference to FIGS. 6 and 7.

The embodiment has a basic principle identical to the foregoing embodiments. However, the embodiment has the unit cells or the unit adjustable color filters each configured for a wavelength band or a color. This configuration enables free color adjustment within a visible light range. The embodiment will be descried, in detail.

The foregoing embodiment (See FIG. 3) suggests using singular colored nonpolar liquid for all cells, which is selected to have a transmissive characteristic of a light that enables to obtain a color tone or a color rendering index a consumer of user prefers. And, by controlling an area the colored nonpolar liquid is brought into contact with the cell electrically, color intensity can be adjusted, freely. In the meantime, since the embodiment suggests the cells to have different characteristics of wavelength bands and colors, free color adjustment is possible within the visible light range.

For an example, referring to FIG. 6, a plurality of

cells

321a, 321b and 321c having different characteristics of wavelength bands and colors can be formed on the same layer in single layer. Or, as shown in FIG. 7, a plurality of

cells

321a, 321b and 321c can be stacked in multiple layers having different characteristics of wavelength bands and colors. Though FIG. 7 illustrates

cells

321a, 321b and 321c or filters having different characteristics of wavelength bands schematically for convenience’s sake, each of the

cells

321a, 321b and 321c has the unit adjustable color filter mounted thereto as shown in FIG. 3.

In the meantime, the embodiment enables independent voltage application to the

cells

321a, 321b and 321c, enabling independent adjustment of the contact areas of the colored nonpolar liquid spread on the surfaces of the

cells

321a, 321b and 321c, respectively. As a result of this, a characteristic, such as different and fine color tones, color intensity and the color temperature, of the light from the LED light source 310 can be adjusted with the adjustable color filter.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. For an example, though the foregoing embodiments illustrate and describe using the colored nonpolar liquid and the transparent polar liquid, single liquid, for an example, the colored nonpolar liquid, can also be used. Though the foregoing embodiments describe using the LED light source as a light source, the present invention is not limited to this.

Referring to Fig. 8, a bulb type LED light apparatus, as an example of the embodiment of this invention, will be explained. Generally, a LED module 620 with the LED light source is disposed in a heat sink 610, since the LED module 620 generates heat. A bulb 640 and a housing 650 are connected to the heat sink 610, respectively. Electric parts such as a power source are disposed within the housing 650. The adjustable color filter 630 is disposed over the LED module 620. Since light from the LED module 620 is transmitted to the bulb 630 through the adjustable color filer 630, optic characteristics such as color temperature is controllable by controlling the adjustable color filer 630.

This invention is not limited to the bulb type LED light apparatus. For example, it is possible to apply this invention to a planar type LED light apparatus.

Claims

A lighting apparatus comprising:

an LED light source; and

an adjustable color filter operative by an electrowetting principle for transmitting or shielding a light of a specific wavelength band from the LED light source, selectively.
The lighting apparatus as claimed in claim 1, wherein the adjustable color filter includes;

a hydrophobic dielectric material portion,

a polar liquid provided to the hydrophobic dielectric material portion, and

a driving unit for applying a voltage to the hydrophobic dielectric material portion, selectively.
The lighting apparatus as claimed in claim 2, wherein the hydrophobic dielectric material portion has a nonpolar liquid further provided thereto, the nonpolar liquid having a transmissive spectrum different from a transmissive spectrum of the polar liquid.
The lighting apparatus as claimed in claim 3, wherein the nonpolar liquid is a colored liquid having predetermined color tone and a color rendering index.
The lighting apparatus as claimed in claim 4, wherein the nonpolar liquid is an oleaginous liquid.
The lighting apparatus as claimed in claim 4, wherein the polar liquid is a transparent liquid.
The lighting apparatus as claimed in claim 6, wherein the polar liquid is an aqueous liquid.
The lighting apparatus as claimed in any one of claims 2 to 8, wherein the driving unit includes;

a first electrode positioned on one side of a hydrophobic dielectric material, and

a second electrode positioned on the other side of a hydrophobic dielectric material.
The lighting apparatus as claimed in claim 8, wherein the driving unit applies a voltage to a portion of the hydrophobic dielectric material portion.
The lighting apparatus as claimed in claim 9, wherein the first electrode has a first transparent portion provided on an underside of the first electrode, and a second transparent portion provided over the first electrode.
The lighting apparatus as claimed in claim 2 or 3, wherein the adjustable color filter includes a plurality of cells.
The lighting apparatus as claimed in claim 11, wherein the cells have at least one of shapes and an arrangement thereof made in random or pseudo-random.
The lighting apparatus as claimed in claim 11, wherein the cells are a set of a plurality of cells having transmissive spectrum characteristics different from one another.
The lighting apparatus as claimed in claim 13, wherein the plurality of cells are arranged on the same plane.
The lighting apparatus as claimed in claim 13, wherein the plurality of cells are stacked in multiple layers.
A method for controlling a lighting apparatus comprising the steps of:

arranging a polar liquid on a hydrophobic dielectric material; and

selectively applying a voltage to the hydrophobic dielectric material to move the polar liquid selectively for transmitting or shielding a light of a specific wavelength band from an LED light source.
The method as claimed in claim 16, wherein the hydrophobic dielectric material has a nonpolar liquid provided thereto further for cohering or spreading the nonpolar liquid following the selective movement of the polar liquid.
The method as claimed in claim 17, wherein the voltage is applied to a portion of the hydrophobic dielectric material, selectively.
The method as claimed in claim 18, wherein the polar liquid is a transparent aqueous liquid and the nonpolar liquid is a colored oleaginous liquid.