Patent Publication Number: US-2020298016-A1

Title: Light irradiation device

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is a non-provisional application of Provisional Application No. 62/820,490 filed Mar. 19, 2019, the content of which is incorporated herein by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a light irradiation device. More particularly, the present disclosure relates to a light irradiation device used for treatment. 
     BACKGROUND 
     Recently, various treatment devices using ultraviolet light have been under development. In general, ultraviolet light is known to have a sterilization effect, and conventional ultraviolet-light treatment devices are utilized by using conventional UV lamps and operating the UV lamps near a skin to irradiate the UV light to an area requiring treatment. 
     However, besides the sterilization effect, the ultraviolet light irradiation causes harmful effects such as skin aging and cancer. Accordingly, there is a demand for a method of obtaining sterilization and treatment effects with ultraviolet light irradiation in a safe manner for treatment purpose. 
     SUMMARY 
     The present disclosure provides a light irradiation device having high sterilization and skin regeneration effects while minimizing adverse effects on a human body. 
     Embodiments of the present disclosure provide a light irradiation device including a light source unit emitting a light to a wounded skin and a controller controlling the light source unit. The light source unit includes a substrate, at least one first light source disposed on the substrate and emitting a first light in a blue wavelength band, and at least one second light source disposed on the substrate and emitting a second light in a red to a near-infrared wavelength band. The first and second lights have different skin penetration depths from each other depending on a wavelength, and a difference in the skin penetration depth between the first light and the second light is equal to or greater than about 1.8 mm. 
     In some embodiments, the first light has the skin penetration depth equal to or greater than about 1.0 mm. Additionally, or alternatively, the second light has the skin penetration depth equal to or greater than about 4.3 mm. For example, the first light has a wavelength band of about 370 nm to about 500 nm. As another example, the second light has a wavelength band of about 610 nm to about 940 nm. 
     In some embodiments, he first light and the second light are substantially simultaneously irradiated for a predetermined time. In other embodiments, the first light is irradiated for a first time, and the second light is irradiated for a second time longer than the first time. The second light starts to be irradiated before the irradiation of the first light is completed, and at least a portion of the first time overlaps at least a portion of the second time. 
     In some embodiments, the second light is irradiated continuously. The first light is irradiated discontinuously. At least one of the first light and the second light is periodically irradiated. 
     The light irradiation device according to embodiments of the present disclosure is used for treatment. An irradiation area of the first light on the skin is smaller than an irradiation area of the second light on the skin. 
     The substrate faces the skin and includes a first region in which the first light source is disposed and a second region in which the second light source is disposed, and the second region surrounds the first region. A surface corresponding to the first region is disposed to be more spaced apart from the skin than a surface corresponding to the second region is. 
     According to the above, the light irradiation device having the high sterilization and the skin regeneration effects while minimizing the adverse effects on the human body may be provided. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other advantages of the present disclosure will become readily apparent by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein: 
         FIG. 1  is a plan view showing a light irradiation device according to an exemplary embodiment of the present disclosure; 
         FIG. 2  is a block diagram showing a light irradiation device according to an exemplary embodiment of the present disclosure; 
         FIGS. 3A to 3F  are graphs showing a method of driving a light irradiation device according to an exemplary embodiment of the present disclosure to show on/off time of first and second light sources, where: 
         FIG. 3A  illustrates a first method of driving the light irradiation device according to embodiments of the present disclosure. 
         FIG. 3B  illustrates a second method of driving the light irradiation device according to embodiments of the present disclosure. 
         FIG. 3C  illustrates a third method of driving the light irradiation device according to embodiments of the present disclosure. 
         FIG. 3D  illustrates a fourth method of driving the light irradiation device according to embodiments of the present disclosure. 
         FIG. 3E  illustrates a fifth method of driving the light irradiation device according to embodiments of the present disclosure. and 
         FIG. 3F  illustrates a sixth method of driving the light irradiation device according to embodiments of the present disclosure; 
         FIG. 4  is a view showing an operation mechanism of a light irradiation device according to an exemplary embodiment of the present disclosure; 
         FIGS. 5A to 54D  are conceptual views showing the operation mechanism of  FIG. 4  sequentially in the order of occurrence, where: 
         FIG. 5A  illustrates an exemplary view of damaged epidermis and dermis in a wounded site of skin; 
         FIG. 5B  illustrates an exemplary view of pathogens in the dermis in the wounded site of skin as shown  FIG. 5A ; 
         FIG. 5C  illustrates an exemplary view of new cells generated in the wounded site shown  FIG. 5B ; and 
         FIG. 5D  illustrates an exemplary view of a cured wounded site; 
         FIG. 6A  is a plan view showing a light irradiation device according to an exemplary embodiment of the present disclosure; 
         FIG. 6B  is a cross-sectional view taken along a line A-A′ of  FIG. 6A ; 
         FIG. 7A  is a plan view showing a light irradiation device according to an exemplary embodiment of the present disclosure; 
         FIG. 7B  is a cross-sectional view taken along a line B-B′ of  FIG. 7A ; 
         FIG. 8  is a graph showing sterilization effects in accordance with irradiation conditions when a light is irradiated to a wound using a conventional light irradiation device and a light irradiation device according to an exemplary embodiment of the present disclosure; and 
         FIG. 9  is a graph showing a recovery period of the wound in accordance with the irradiation conditions when the light is irradiated to the wound using a conventional light irradiation device and a light irradiation device according to an exemplary embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     The present disclosure may be variously modified and realized in many different forms, and thus specific embodiments will be exemplified in the drawings and described in detail hereinbelow. However, the present disclosure should not be limited to the specific disclosed forms, and be construed to include all modifications, equivalents; or replacements included in the spirit and scope of the present disclosure. 
     Hereinafter, exemplary embodiments of the present disclosure will be explained in detail with reference to the accompanying drawings. 
       FIG. 1  is a plan view showing a light source unit  10  of an irradiation device according to an exemplary embodiment of the present disclosure. Referring to  FIG. 1 , the light source unit  10  according to the exemplary embodiment of the present disclosure emits a light to a selected area of a skin such as a wounded area of the skin. 
     The light source unit  10  includes a substrate  20 , at least one first light source  30  disposed on the substrate  20  and emitting a first light in a blue wavelength band, and at least one second light source  40  disposed on the substrate  20  and emitting a second light in red to an infrared wavelength band. 
     The substrate  20  should not be particularly limited as long as the first and second light sources  30  and  40  are available to be mounted thereon. The substrate  20  may be provided in various forms. In some embodiments, the substrate  20  may be provided with wires to supply a power to the first and second light sources  30  and  40 . The substrate  20  may include, for example, a metal substrate or a printed circuit board, on which the wires are formed. 
     The first light source  30  may emit the first light in the blue wavelength band of a visible light wavelength band. The first light may correspond to a light with a wavelength band from about 370 nm to about 500 nm. In some embodiments, the first light may be a light with a wavelength band from about 385 nm to about 435 nm. More particularly, the first light may be a light with a wavelength band from about 400 nm to about 420 nm, preferably, about 410 nm. In other embodiments, the wavelength band of the first light is not limited thereto. 
     The first light has a higher penetration force into an area of a skin than an ultraviolet light and corresponds to a wavelength band that is harmless to the human body. The first light corresponds to an absorption wavelength of porphyrins present in pathogens such as bacteria. When the first light is applied to the bacteria, the porphyrins in the bacteria absorb the first light, and reactive oxygen species (ROS) are produced in cells of the bacteria by the energy of the first light. The reactive oxygen species are accumulated in the cells of the bacteria and oxidize cell walls of bacteria, and as a result, that bacteria are killed. That is, the pathogens may be killed by inducing an oxidative stress in the pathogens by the ROS. 
     The second light source  40  emits the second light in a red visible light to a near-infrared wavelength band. The second light may correspond to a light in the wavelength band from about 610 nm to about 940 nm. In the exemplary embodiment of the present disclosure, the second light may be a light with a red visible light wavelength band, for example, from about 610 nm to about 750 nm, or an infrared light wavelength band, for example, from about 750 nm to about 940 nm. As another example, the second light according to the exemplary embodiment of the present disclosure may be a light with the infrared light wavelength band of about 830 nm, about 850 nm, or about 890 nm. 
     The second light is applied to a certain area of a skin to dilate blood vessels and promote a blood circulation. That is, the second light improves a blood flow, and as a result, immune response is promoted. 
     In more detail, the red visible light to the near-infrared light acts on a certain area of a skin to be treated and stimulates mitochondria in cells to produce adenosine tri-phosphate (ATP), the reactive oxygen species (ROS), and/or nitrogen oxide (NO). The ATP, ROS, and/or NO act on a wounded site to promote wound healing. The ATP and ROS induce the expression of genes involved in inflammatory response that is an immune response required for wound healing and genes needed for cell growth. In addition, the ROS and/or NO have an ability to sterilize pathogens such as bacteria that penetrate into the wounded site. Accordingly, the inflammatory response and the cell growth are induced in damaged tissue areas, resulting in wound healing. The NO promotes migration of immune cells and increases supply of oxygen and nutrients to accelerate tissue healing processes. In addition, the NO expands capillaries in surrounding tissues and induces formation of new capillaries. 
     In some embodiments, when the first and second lights are irradiated substantially simultaneously, or alternatively, the first and second lights are irradiated not simultaneously, i.e., at different timings, but sequentially in a predetermined time, a higher wound healing effect may be achieved than when each of the first and second lights is irradiated alone. 
     According to the embodiments of the present disclosure, as the pathogens in the wounded site are sterilized by the first light and an immune mechanism is promoted by the second light, the wound may be efficiently healed. When a certain area of the skin is injured, not only the sterilization of the pathogens but also treatment of infected cells are required for the complete wound healing. Although the first light is effective to sterilize the pathogens, the function of inducing the immune mechanism in the skin of the wounded site is not large when only the first light is used. In particular, in the case of deep or complex wounds, a penetration depth of the light varies depending on the wavelength of the light, and the sterilization effect is lowered. As a result, unsterilized pathogens in the wound may be re-proliferated. When unsterilized pathogens are re-proliferated, the wound healing is delayed. The second light promotes the immune mechanism of the skin before unsterilized pathogens are re-proliferated, and thus, the wound may be effectively healed in a relatively short time. 
     In the present embodiment, the pathogens refer to microorganisms that cause diseases, such as viruses, bacteria, fungi, protozoa, and hosts. In general, anything that causes diseases may be included in the pathogens. 
     The light irradiation device  100  according to the exemplary embodiment of the present disclosure may be used to heal the wound that requires treatment. For example, the light irradiation device  100  may be used not only for simple wounds but also may be used for chronic diseases, such as a normal ulcer, a pressure ulcer, or an ischemic ulcer due to diabetes. In addition, the light irradiation device  100  may be used for a variety of wounds, e.g., a surgical site infection due to surgery, a laceration in which tissues are torn apart, an incised wound in which skin and tissues are cut with a sharp instrument, a punctured wound caused by a sharp object such as a knife or spear, etc. 
     According to the exemplary embodiment of the present disclosure, the wounded site may be sterilized without using the ultraviolet light. Although the ultraviolet light may reduce the amount of pathogens, the ultraviolet light induces mutations in DNA of skin cells. Therefore, overexposure to the ultraviolet light may cause a skin cancer, and there is a need to control a dose of the ultraviolet light. In the case of the ultraviolet light, since the wavelength is very short and the penetration into the skin is low, the sterilization of pathogens in wounds outside the skin may be partially possible. However, in the case of wounds with a predetermined depth or more, it is impossible to sterilize the pathogens inside. This is because there is a difference in penetration depth into the wounded skin depending on a wavelength of external light, and the shorter the wavelength is, the thinner the penetration depth may be in the skin. 
     According to the exemplary embodiment of the present disclosure, as a combination of the first light and the second light having different penetration depths is used, it is possible to enhance the healing effect on the wounded site as a whole rather than a specific position. This will be described in detail later. 
       FIG. 2  is a block diagram showing the light irradiation device  100  according to an exemplary embodiment of the present disclosure. Referring to  FIG. 2 , the light irradiation device  100  according to the exemplary embodiment of the present disclosure may include the light source unit  10  having the first light source  30  emitting the first light and the second light source  40  emitting the second light, a controller  50  controlling the first and second light sources  30  and  40  such that the second light source  40  emits the second light after the first light source  30  emits the first light, and a power supply unit  60  supplying a power to the first and second light sources  30  and  40 . 
     As described above, the first and second light sources  30  and  40  may emit the first light with the blue wavelength band and the second light with the red visible light to the near-infrared wavelength band, respectively. 
     The controller  50  may control whether to emit the light from the first and second light sources  30  and  40 , an amount of the light, an intensity of the light, emission time, and the like. The power supply unit  60  may be electrically connected to the first and second light sources  30  and  40  and the controller  50  and may supply the power to the first and second light sources  30  and  40  and the controller  50 . In  FIG. 2 , the power supply unit  60  supplies the power to the first and second light sources  30  and  40  via the controller  50 ; however, it should not be limited thereto or thereby. That is, the power supply unit  60  may be connected directly to the first and second light sources  30  and  40  to supply the power to the first and second light sources  30  and  40 . 
     In some embodiments, the light irradiation device  100  may further include an optical unit that selectively focuses or disperses the lights emitted from the first and second light sources  30  and  40 . The optical unit may focus the lights generated by the first and second light sources  30  and  40  into a narrow range or a wide range as necessary. The optical unit may focus or disperse the light in a uniform or non-uniform form depending on a position to which the light is irradiated. The optical unit may include at least one lens as needed, and the lens may perform various functions, such as focusing, dispersing, uniformizing, and non-uniformizing the lights from the first and second light sources  30  and  40 . 
     For example, in the case where the light is irradiated to a small area using the light irradiation device  100  according to the exemplary embodiment of the present disclosure, a lens for focusing the light may be used in the first and second light sources  30  and  40 . On the contrary, in the case where the light is irradiated to a wide area, for example, a whole room, using the light irradiation device  100  according to the exemplary embodiment of the present disclosure, a lens for dispersing the light may be used. For example, additional lenses may be added to the first light source  30  and the second light source  40  to allow the first light source  30  to irradiate the light to a relatively small area directly corresponding to the wounded site and to allow the second light source  40  to irradiate the light to a relatively wide area corresponding to the wounded site and surrounding area adjacent to the wound. 
     In the present exemplary embodiment, the controller  50  individually drives the first light source  30 , the second light source  40 , or both. That is, the first and second light sources  30  and  40  may be substantially simultaneously turned on/off, or the first and second light sources  30  and  40  may be individually turned on/off. In addition, the intensity of the lights emitted from the first light source  30  and the second light source  40 , i.e., the intensity of the first and second lights, may be simultaneously or individually controlled. However, the controller  50  drives the first light source  30  and the second light source  40  such that a process of applying the first light and the second light within a predetermined range of time is included when driving the first light source  30  and the second light source  40 . 
     According to the exemplary embodiment of the present disclosure, the first light may be applied to an object to be sterilized during a predetermined time, and the second light may be irradiated simultaneously with the first light or after the first light is irradiated. Accordingly, in addition to the effect obtained from the second light, it is possible to prevent the re-proliferation of the unsterilized pathogens again as much as possible after the irradiation of the first light. As a result, an improved wound-healing effect may be obtained compared with irradiation of the first light alone. In the exemplary embodiment of the present disclosure, a synergy effect of the wound healing may be obtained through the irradiation of both the first light and the second light. When turning on/off the first light source  30  and the second light source  40  to obtain the above-described effects, various implementations are available. For instance, as to the first light source  30  and the second light source  40 , a method of emitting lights simultaneously, a method of continuously emitting lights, a method of sequentially decreasing or increasing the intensity of lights, a flickering method, or a mixed method may be employed. 
       FIGS. 3A to 3F  illustrate various implementations of methods for driving the light irradiation device according to an exemplary embodiment of the present disclosure to show on/off time of the first and second light sources. In  FIGS. 3A to 3F , the first and second lights of the light irradiation device according to the exemplary embodiment of the present disclosure are respectively referred to as “L 1 ” and “L 2 ”, and a time lapse is represented by “T”. 
       FIG. 3A  illustrates a first method of driving the light irradiation device according to embodiments of the present disclosure. Referring to  FIG. 3A , the first light source is turned on for a first time t 1  to irradiate the first light L 1 , and the second light source is turned on for a second time t 2  to irradiate the second light L 2 . In the present exemplary embodiment, the second time t 2  for which the second light L 2  is irradiated may be longer than the first time t 1  for which the first light L 1  is irradiated. Since the first light L 1  is to sterilize the wounded site, the first light L 1  may be irradiated until a time point where the wounded site is sufficiently sterilized. The second light L 2 , which is the light with the red to the near-infrared wavelength band, may be irradiated for a longer time while the wound is healed to promote the immune response. 
     The irradiation time and the irradiation amount of the first and second lights L 1  and L 2  respectively emitted from the first and second light sources may be changed in various ways. In the exemplary embodiment of the present disclosure, the first light L 1  and the second light L 2  may be simultaneously irradiated, and as described above and shown in  FIG. 3A , the irradiation of the second light L 2  may be performed for a longer time than the irradiation of the first light L 1 . In the case of the first light L 1 , a total dose may be set in various ranges within a range that is harmless to the human body depending on the object to be sterilized. In the case of the second light L 2 , a total dose may be set within a limit that is harmless to the human body, for example, within a range where there is no risk of low temperature burn. 
     In the present exemplary embodiment, the application frequency and the timing of application of the first light L 1  and the second light L 2  may vary.  FIG. 3B  illustrates a second method of driving the light irradiation device according to embodiments of the present disclosure. As one example, referring to  FIG. 3B , when the first light L 1  and the second light L 2  are applied, both the first light L 1  and the second light L 2  may be applied continuously. 
       FIG. 3C  illustrates a third method of driving the light irradiation device according to embodiments of the present disclosure. As another example, referring to  FIG. 3C , the second light L 2  may not be provided continuously and provided in a discontinuous manner with the first light L 1 , while the first light L 1  is continuously applied without interruption to the object to be sterilized. 
     Referring to  FIGS. 3A to 3C , the irradiation of the first light L 1  and the second light L 2  may be performed once for a predetermined time period. However, as shown in  FIGS. 3D and 3E , the first light L 1  or the second light L 2  may be irradiated a plurality of times at intervals.  FIG. 3D  illustrates a fourth method of driving the light irradiation device according to embodiments of the present disclosure.  FIG. 3E  illustrates a fifth method of driving the light irradiation device according to embodiments of the present disclosure. 
     For example, referring to  FIGS. 3D and 3E , the first light L 1  may be applied three times during the first time t 1 , the second time t 2 , and a third time t 3 , and the second light L 2  may be applied during a fourth time t 4 . The first light L 1  may be applied periodically at regular intervals or aperiodically at irregular intervals. 
     Referring to  FIG. 3B , at least a portion of the irradiation time of the first light L 1  may overlap a portion of the irradiation time of the second light L 2 . As shown in  FIG. 3B , although the irradiation of the first light L 1  does not start together with the irradiation of the second light L 2  at the same time point, the irradiation of the second light L 2  may start before the application of the first light L 1  is completed. 
     In the exemplary embodiment of the present disclosure, the time point at which the first light L 1  starts to be applied may be different from the time point at which the second light L 2  starts to be applied. For example, the first light L 1  and the second light L 2  may start to be applied at the same time point as shown in  FIGS. 3A and 3D , or may start to be applied at different time points from each other as shown in  FIGS. 3B, 3C, 3E, and 3F .  FIG. 3F  illustrates a sixth method of driving the light irradiation device according to embodiments of the present disclosure. In the case of  FIG. 3C , the application of the second light L 2  starts before the application of the first light L 1 , and in the case of  FIGS. 3B, 3E, and 3F , the application of the first light L 1  starts before the application of the second light L 2 . 
     Referring to  FIG. 3E , both the first light L 1  and the second light L 2  may be applied three times. In this case, the first light L 1  may be applied during the first time t 1 , the second time t 2 , and the third time t 3 , and the second light L 2  may be applied during the fourth time t 4 , a fifth time t 5 , and a sixth time t 6 . A repetition cycle and the number of repetitions of irradiation of the first and/or second lights L 1  and L 2  may vary depending on types of objects to be cured and total amount of light. 
     In the embodiments of the present disclosure as discussed above, the first light L 1  may be irradiated to overlap with the time during which the second light L 2  is applied, or alternatively may not overlap. For example, referring to  FIGS. 3A and 3D , during the time that the second light L 2  is applied, the first light L 1  may be irradiated to overlap the second light L 2 . Referring to  FIG. 3E , the time that the first light L 1  is applied does not overlap the time that the second light L 2  is applied, and the first and second lights L 1  and L 2  may be applied during different times from each other. Referring to  FIG. 3F , the time that the first light L 1  is applied may or may not overlap the time that the second light L 2  is applied. In the case of  FIG. 3F , the first and third times t 1  and t 3  during which the first light L 1  is applied do not overlap with the fourth time t 4  during which the second light L 2  is applied, and the second time t 2  during which the first light L 1  is applied overlaps the fourth time t 4  during which the second light L 2  is applied. 
     In the exemplary embodiment of the present disclosure, in the case where the first light L 1  and/or the second light L 2  are applied several times, the time during which the irradiation of the first light L 1  is maintained and the time during which the irradiation of the second light L 2  is maintained may be the same as each other or different from each other. For example, as shown in  FIGS. 3D and 3E , the first time t 1 , the second time t 2 , and the third time t 3  each during which the first light L 1  is applied may be the same value. On the other hand, as shown in  FIG. 3F , the first time t 1 , the second time t 2 , and the third time t 3  each during which the first light L 1  is applied may be different values. This is the same with the second light L 2 . 
     In the exemplary embodiment of the present disclosure, the second light L 2  may start to be applied after the irradiation of the first light L 1  is completed, however, as shown in  FIGS. 3B, 3E, and 3F , the second light L 2  may start to be applied while the irradiation of the first light L 1  is in progress, or at the moment that the irradiation of the first light L 1  is completed. This is to prevent the re-proliferation of unsterilized bacteria as much as possible after the sterilization of the pathogens by the first light L 1 . In some embodiments of the present disclosure, when the irradiation of the second light L 2  starts after the irradiation of the first light L 1  is completed as shown in  FIG. 3E , the second light L 2  is required to be applied as soon as possible after the irradiation of the first light L 1  is completed for the efficient curing. 
     As described above, the light irradiation device according to the exemplary embodiment of the present disclosure irradiates the first light L 1  and the second light L 2  using the first light source and the second light source to treat the wound, and the first light L 1  and the second light L 2  have different penetration depths from each other when being applied to area(s) of the skin. Hereinafter, an operation mechanism of the light irradiation device according to the exemplary embodiment of the present disclosure will be described. 
       FIG. 4  is a view showing the operation mechanism of the light irradiation device according to an exemplary embodiment of the present disclosure, and  FIGS. 5A to 5D  are conceptual views showing the operation mechanism of  FIG. 4  sequentially in the order of occurrence. In  FIG. 4 , a first light and a second light of the light irradiation device according to the exemplary embodiment of the present disclosure are indicated by “L 1 ” and “L 2 ”, respectively. 
     In some embodiments of the present disclosure, referring to  FIG. 4 , the lights emitted from the first and second light sources of the light irradiation device are applied to a certain area of the skin. The skin protects the human body from external pathogens  2000  and includes an epidermis SK 1 , which is a stratified squamous epithelium, a dermis SK 2 , which is a tight connective tissue, and a subcutaneous tissue (not shown), which is a loose connective tissue. For the convenience of explanation,  FIG. 4  shows mainly the epidermis SK 1 , the dermis SK 2 , and a blood vessel  1100  in the dermis SK 2 . The epidermis SK 1  provides a waterproofing function and acts as a barrier to infection. The dermis SK 2  is a layer of skin beneath the epidermis SK 1  that consists of the connective tissue and cushions the body from stress and strain. The dermis SK 2  is tightly connected to the epidermis SK 1  through a basement membrane SKM. The epidermis SK 1  contains no blood vessel  1100  and the dermis SK 2  contains the blood vessel  1100 . 
     When a wound occurs in the skin, the pathogens  2000  may penetrate the body through the wound. The human body responds to the pathogens  2000  penetrated into tissues in the skin, and as a result, a cytokine  1200  is secreted by immune cells. The cytokine  1200  secreted from one cell affects other cells or the secreting cell itself. For example, the cytokine  1200  may induce proliferation of macrophages or may promote differentiation of the secreting cell itself. When the first light L 1  and the second light L 2  are irradiated by the light irradiation device according to the exemplary embodiment of the present disclosure in the above-described process, the wound may heal relatively quickly. This will be described with reference to drawings. 
     Referring to  FIGS. 4 and 5A , when the wound occurs in the skin, the epidermis SK 1  may be damaged, or the epidermis SK 1  and the dermis SK 2  may be damaged depending on the extent of the wound.  FIG. 4  shows the wound in which the epidermis SK 1  and a portion of the dermis SK 2  are damaged. 
     In the case where the epidermis SK 1  and the portion of the dermis SK 2  are damaged, the pathogens  2000  penetrate into the human body through the damaged portions of the epidermis SK 1  and the dermis SK 2 . The pathogens  2000  may be most commonly present around the wound and may partially penetrate into the tissue in the skin. 
     According to the exemplary embodiment of the present disclosure, the first light L 1  and the second light L 2  may be provided to the wounded site. 
     As described above, the first light L 1  and the second light L 2  may have different wavelength bands from each other. The first light L 1  has a relatively short wavelength, and the second light L 2  has a relatively long wavelength. The first light L 1  and the second light L 2  have different penetration distances into the skin depending on their wavelengths. When a maximum penetration depth in the skin of the first light L 1  is referred to as a first distance and a maximum penetration depth in the skin of the second light L 2  is referred to as a second distance, the second distance is larger than the first distance. In  FIG. 4 , an area into which the first light L 1  may penetrate and an area into which the second light L 2  may penetrate are indicated by a first zone A 1  and a second zone A 2 , respectively. The first zone A 1  may be in the epidermis SK 1 , and the second zone A 2  may be positioned in a corresponding area from the epidermis SK 1  to the dermis SK 2 . 
     In more detail, the first light L 1  may have the wavelength from about 370 nm to about 500 nm and more particularly, in the wavelength band from about 370 nm to about 420 nm. The second light L 2  may have the wavelength from about 610 nm to about 940 nm and more particularly, in the wavelength band from about 610 nm to about 750 nm or from about 750 nm to about 940 nm. The first light L 1  may penetrate into the epidermis SK 1  of the skin, and the second light L 2  may penetrate into the dermis SK 2  of the skin as well as the epidermis SK 1 . In more detail, the first light L 1  may have the skin penetration depth of about 1 mm or more, and the second light L 2  may have the skin penetration depth of about 4.3 mm or more. In addition, the maximum penetration depth in the skin of the first light L 1  may be about 2.5 mm, and thus, a difference in the skin penetration depth between the first light L 1  and the second light L 2  may be equal to or greater than about 1.8 mm. 
     The penetration depth into the skin according to the wavelength of each light is as shown in Table 1 below. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Wavelength (nm) 
                 Depth (mm) 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 300 
                 0.5 
               
               
                   
                 350 
                 0.8 
               
               
                   
                 400 
                 1 
               
               
                   
                 450 
                 1.5 
               
               
                   
                 500 
                 2.5 
               
               
                   
                 550 
                 3 
               
               
                   
                 600 
                 4.3 
               
               
                   
                 650 
                 4.8 
               
               
                   
                 700 
                 5.2 
               
               
                   
                 750 
                 5.4 
               
               
                   
                   
               
            
           
         
       
     
     The first light L 1  acts on the epidermis SK 1  of the wounded site to sterilize the pathogens  2000  present around the wound or penetrated into the skin. Since the first light L 1  has the relatively short wavelength, it may be difficult to sterilize all pathogens  2000  in the dermis SK 2  when the wound reaches or affects the dermis SK 2 . 
     Referring to  FIGS. 4 and 5B , most of the pathogens  2000  in the epidermis SK 1  may be sterilized and removed by the first light L 1 , but some pathogens  2000  in the dermis SK 2  may remain. The immune system in the skin tissue confirms the infection by recognizing the pathogens  2000  remaining in the dermis SK 2  and releases an immune-active substance (e.g., the cytokine  1200 ). Through the immune response, the blood vessel  1100  of the wounded site are expanded, and cells for immunity, such as leukocytes  1110  and macrophages, migrate to the wounded site to activate the inflammatory mechanism. The second light L 2  penetrates into the dermis SK 2  through the epidermis SK 1  and acts on the dermis SK 2 , and thus, the blood vessel  1100  in the wounded site is more expanded. The second light L 2  also promotes the migration of immune cells (e.g., leukocytes  1110 ) from the expanded blood vessel  1100 . The immune cells migrate to the wounded site, and ingest and remove the infiltrated foreign material, i.e., pathogens  2000 . As the immune mechanism in the dermis SK 2  is activated by the second light L 2 , the pathogens  2000  unsterilized by the first light L 1  may be effectively removed. In  FIG. 4 , a reference numeral “ 1120 ” denotes erythrocyte. 
     Referring to  FIGS. 4 and 5C , new cells are generated in the wounded site where the pathogens are removed by the first light L 1  and the second light L 2 , and the wounded site is gradually reduced. 
     As shown in  FIGS. 4 and 5D , as the wounded site may be regenerated and healed, the wound may be completely cured, and the expanded blood vessel  1100  contracts again. 
     The light irradiation device  100  according to the exemplary embodiment of the present disclosure may be implemented in various forms for the treatment of the skin.  FIG. 6A  is a plan view showing a light irradiation device  100  according to an exemplary embodiment of the present disclosure, and  FIG. 6B  is a cross-sectional view taken along a line A-A′ of  FIG. 6A . 
     Referring to  FIGS. 6A and 6B , the light irradiation device  100  according to the exemplary embodiment of the present disclosure may include a first light source  30 , a second light source  40 , and a substrate  20  on which the first and second light sources  30  and  40  are mounted. More specifically,  FIG. 6A  illustrates a plan view of the light irradiation device  100  and  FIG. 6B  illustrates a cross sectional view of  FIG. 6B . 
     In the present exemplary embodiment, the first light source  30  may be provided in a plural number, and the second light source  40  may also be provided in a plural number. However, the number of the first and second light sources  30  and  40  should not be particularly limited, and the number of the first light sources  30  may be greater than, smaller than, or equal to the number of the second light sources  40 . In addition, according to the exemplary embodiment of the present disclosure, the first light sources  30  and the second light sources  40  may be regularly or irregularly arranged depending on the number of the first light sources  30  and the number of the second light sources  40 . 
     In the exemplary embodiment of the present disclosure, the first and second light sources  30  and  40  may be arranged such that an area on the skin to which a first light from the first light sources  30  is provided and an area on the skin to which a second light from the second light sources  40  is provided are different from each other. 
     In some embodiments, since the first light is to sterilize pathogens penetrating through the wound, the sterilization may be sufficiently performed even though the first light is irradiated only in a relatively small area. The second light is to expand the blood vessel around the wound and to activate the immune mechanism, so that the second light needs to be irradiated to an area wider than the area where the wound is formed. 
     To this end, the second light sources  40  may be provided in large numbers so as to cover a relatively larger area than the first light sources  30 , or may be arranged to have a wide light directivity angle. On the other hand, the first light sources  30  may be provided in relatively small numbers so as to cover a relatively smaller area than the second light sources  40  or may be arranged to have a narrow light directivity angle. As another way, depending on devices, additional components, such as a lens or a shade, for controlling a light irradiation area of the first light sources  30  and the second light sources  40  may be further disposed in the light irradiation device  100 . 
     In the substrate  20  of the exemplary embodiment shown in  FIGS. 6A and 6B , when an area in which the first light sources  30  are arranged, which faces the skin, is referred to as a “first region R 1 ” and an area in which the second light sources  40  are arranged is referred to as a “second region R 2 ”, the second region R 2  surrounds the first region R 1 . A surface corresponding to the first region R 1  may be concaved from a surface corresponding to the second region R 2 , so that the first region R 1  is more spaced apart from the skin than the second region R 2  is. Accordingly, the second region R 2  around the first light sources  30  arranged in the first region R 1  has a protruding shape, and the light emitted from the first light sources  30  may be partially blocked by the protruding portion. Therefore, the light emitted from the first light sources  30  may travel in a direction that is not blocked by the protruding portion. As a result, the area of the skin to which the light emitted from the first light sources  30  is applied may be relatively reduced. Since the second light sources  40  are arranged in the portion that is more protruded than the first region R 1 , a periphery of the second light sources  40  is in a relatively open state, and thus, there is less limitation in the traveling direction of the light emitted from the second light sources. Thus, the second light may be applied to the area of the skin, which is relatively wider than the area of the skin to which the first light is applied. 
     In the exemplary embodiment of the present disclosure, the substrate  20  on which the first and second light sources  30  and  40  are mounted includes the first region R 1  and the second region R 2  and has the shape varying depending on the first region R 1  and the second region R 2 . The shape of the substrate  20  should not be limited thereto or thereby. For example, the substrate  20  may have a flat shape in other embodiments. It should not be particular limited, and arrangements of the first and second light sources  30  and  40  and the substrate  20  may be changed depending on separate components, for example, a separate support member. For example, the substrate  20  may be disposed on a flat support member without a step difference, and the first and second light sources  30  and  40  may be disposed on the substrate  20 . Alternatively, the substrate  20  may be disposed on a support member having a stepped portion, and the first and second light sources  30  and  40  may be disposed on the substrate  20 . Further, one substrate  20  is provided in the present exemplary embodiment, however, the substrate  20  may be provided in a plural number, i.e., one or more substrates may be provided. 
     Although not shown in figures, the light irradiation device  100  according to the exemplary embodiment of the present disclosure may further include a housing that accommodates the first and second light sources  30  and  40  and the substrate  20 . The housing may be provided with a transmission window through which the lights emitted from the first and second light sources  30  and  40  pass, the lights emitted from the first and second light sources  30  and  40  may be provided to the human body after passing through the transmission window. 
     In the exemplary embodiment of the present disclosure, a controller may be disposed on the substrate  20  in various ways. For instance, the controller may be formed on the substrate  20  as separate circuit wirings or may be mounted on the substrate  20  after being formed in a separate chip. 
     The light irradiation device according to an exemplary embodiment of the present disclosure may be implemented in various forms.  FIG. 7A  is a plan view showing a light irradiation device  100  according to an exemplary embodiment of the present disclosure, and  FIG. 7B  is a cross-sectional view taken along a line B-B′ of  FIG. 7A . 
     Referring to  FIGS. 7A and 7B , in the light irradiation device  100  according to the exemplary embodiment of the present disclosure, a shape or size of an area to which the light is provided may be set differently depending on a shape or condition of the skin or wound. For example, in the present exemplary embodiment, the light irradiation device  100  extends in a direction (direction B-B′ in  FIGS. 7A and 7B ). This light irradiation device  100  may be used for a portion elongated in one direction, such as an arm, or when the wound itself is formed long. 
     In the present exemplary embodiment, the substrate  20  may include a first region R 1  disposed at a center portion and corresponding to a concave portion, a second region R 2  surrounding the first region R 1  and corresponding to a convex portion, and a third region R 3  disposed between the first region R 1  and the second region R 2  and corresponding to an inclined portion. The inclination of the third region R 3  is formed inwardly, that is, in a direction toward the center portion. 
     First light sources  30  may be arranged in the first and third regions R 1  and R 3 , and second light sources  40  may be arranged in the second region R 2 . Since the first light sources  30  are arranged in the concave portion or the portion inclined inwardly, the area of the skin to which the light emitted from the first light sources  30  is applied may be relatively reduced. Since the second light sources  40  are arranged in the portion that is more protruded than the first region R 1 , a periphery of the second light sources  40  is in a relatively open state, and thus, there is less limitation in the traveling direction of the light emitted from the second light sources  40 . Thus, the second light may be applied to the area of the skin, which is relatively wider than the area of the skin to which the first light is applied. 
     In the embodiments described above, the light irradiation device may be implemented in various forms and used for various purposes. For example, the light irradiation device according to the exemplary embodiment of the present disclosure may be applied to various places where a lighting and a sterilization are necessary, and in particular, may be used as a lighting device. For example, the light irradiation device may be used for medical facilities, such as operating rooms and hospitals, lighting facilities for public health or personal hygiene. In particular, the light irradiation device according to the exemplary embodiment of the present disclosure may be used for the purpose of treating patients. 
     The light irradiation device according to the present disclosure may be applied to public facilities, public spaces, and shared products to be used for the purpose of public treatment, or may be applied to personal facilities, personal spaces, and personal use products to be used for the purpose of personal treatment. In addition, the light irradiation device according to the present disclosure may be used in addition to other treatment devices. That is, the light irradiation device according to the present disclosure may be additionally mounted to a variety of light treatment devices. Further, the light irradiation device according to the present disclosure may be used as a lighting device mounted on walls and a ceiling that form a predetermined space (e.g., a chamber). 
       FIG. 8  is a graph showing sterilization effects in accordance with irradiation conditions when a light is irradiated to a wound using a conventional light irradiation device and a light irradiation device according to an exemplary embodiment of the present disclosure.  FIG. 9  is a graph showing a recovery period of the wound in accordance with the irradiation conditions when the light is irradiated to the wound using a conventional light irradiation device and a light irradiation device according to an exemplary embodiment of the present disclosure. 
     In  FIG. 8 , a comparative example indicates a state in which none of the first light and the second light is irradiated, an experimental example 1 indicates a state in which the ultraviolet light is irradiated using a sterilizing ultraviolet light irradiation device, and an experimental example 2 indicates a state in which the first light and the second light are irradiated using the light irradiation device according to the exemplary embodiment of the present disclosure. 
     For the comparative example, the experimental example 1, and the experimental example 2, a hair on the back of a laboratory mouse was removed, and a 10-mm wound was produced in a 10 mm by 100 mm area on the back of the mouse using a sharp blade. In this case, the wound was induced by scratching the dermis layer and causing the laboratory rat to bleed from the back. Then, a pathogenic bacterium, e.g., Methicillin-resistant  Staphylococcus aureus  (MRSA), was inoculated as a pathogen. Tissues of the wound were collected on the specified dates to check the number of bacteria and measure the length of the wound. The light used in experimental example 1 was the ultraviolet light, a wavelength of the ultraviolet light was about 254 nm, and a dose of the ultraviolet light was about 150 mJ/cm 2 . A wavelength of the first light used in the experimental example 2 was about 410 nm, and a dose of the first light was about 120 J/cm 2 . A wavelength of the second light used in the experimental example 2 was about 850 nm, and a dose of the second light was about 60 J/cm 2 . The lights of experimental example 1 and experimental example 2 were irradiated three times in total for three consecutive days. Table 2 shows the sterilization effect depending on irradiation conditions as the number of bacteria when the light is irradiated to the wound using a conventional light irradiation device and the light irradiation device according to the exemplary embodiment of the present disclosure, and the number of bacteria is presented on a log scale. 
     
       
         
           
               
               
               
               
               
             
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                   
                 Comparative 
                 Experimental 
                 Experimental 
               
               
                   
                 Date (days) 
                 example 
                 example 1 
                 example 2 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 0 (the day of 
                 4.62 
                 4.62 
                 4.62 
               
               
                   
                 inoculation) 
               
               
                   
                 1 
                 4.62 
                 2.78 
                 2.56 
               
               
                   
                 3 
                 6.27 
                 3.56 
                 1.47 
               
               
                   
                 7 
                 8.18 
                 4.75 
                 0.00 
               
               
                   
                 14 
                 4.62 
                 1.56 
                 0.00 
               
               
                   
                   
               
            
           
         
       
     
     Referring to Table 2 and  FIG. 8 , in the comparative example in which none of the lights is irradiated, the number of bacteria did not decrease even after 14 days had passed, but rather, the number of bacteria increased in the middle of the process. In particular, after the wound was infected with bacteria, the number of bacteria continued to increase from day 1 to day 7, and after more time elapsed, the number of bacteria decreased. The reason why the number of bacteria increased gradually from day 1 to day 7 was thought to be caused by the result of the growth of bacteria in the wound and the wounded site without being terminated. Since then, some of the bacteria were killed by the immune response, and thus, the number of bacteria seemed to have decreased. 
     In Experimental example 1, it was observed that the number of bacteria was decreased on day 1 by applying the ultraviolet light to the wound. It seemed that the ultraviolet light had the sterilization effect on the skin. However, it was observed that the number of bacteria increased from day 3 to day 7 after day 1. This is because some of the bacteria in the epidermis close to the surface of the skin were killed by the ultraviolet light, but bacteria located at an inner portion of the epidermis and in the dermis remain without being terminated and then re-proliferate when the skin is sterilized by using the ultraviolet light. Since the ultraviolet light has a very small penetration depth in the skin, it is difficult to thoroughly kill bacteria located at the inner portion the epidermis and in the dermis. 
     In Experimental example 2, the number of the bacteria was gradually decreased as time went on. This is interpreted as the case where the sterilization of bacteria in the epidermis by the first light is substantially performed with the sterilization of bacteria at the inner portion of the epidermis and in the dermis by the promotion of immune response. 
     Table 3 shows the recovery period of the wound depending on irradiation conditions when the light is irradiated to the wound using a conventional light irradiation device and the light irradiation device according to the exemplary embodiment of the present disclosure, and the length of the wound as a function of the elapse of time is shown. 
     
       
         
           
               
               
               
               
               
             
               
                   
                 TABLE 3 
               
               
                   
                   
               
               
                   
                   
                 Comparative 
                 Experimental 
                 Experimental 
               
               
                   
                 Date (days) 
                 example 
                 example 1 
                 example 2 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 0 (the day of 
                 10.00 
                 10.00 
                 10.00 
               
               
                   
                 inoculation) 
               
               
                   
                 1 
                 10.00 
                 10.00 
                 10.00 
               
               
                   
                 3 
                 9.73 
                 8.83 
                 6.93 
               
               
                   
                 7 
                 8.98 
                 6.26 
                 3.37 
               
               
                   
                 14 
                 7.50 
                 4.79 
                 0.00 
               
               
                   
                   
               
            
           
         
       
     
     Referring to Table 3 and  FIG. 9 , in Comparative example in which none of the lights is irradiated, the recovery of the wound was very slow even after 14 days had passed. 
     In Experimental example 1, the recovery of the wound was faster than the comparative example; however, the recovery of the wound is still slow, and only about 50% of the wound was recovered on the 14th day. 
     In Experimental example 2, the recovery of the wound was very faster than the comparative example and experimental example 1. On the 14th day, the wound was 0 mm in length, and the wound was healed completely. In experimental example 2, it was observed that immune response and skin regeneration response by the improvement in blood flow were promoted in addition to sterilization. 
     As described above, the light irradiation device according to the exemplary embodiment of the present disclosure may effectively sterilize the wound and may significantly reduce the recovery period of the wound. 
     Although the exemplary embodiments of the present disclosure have been described, it is understood that the present disclosure should not be limited to these exemplary embodiments but various changes and modifications can be made by one ordinary skilled in the art within the spirit and scope of the present disclosure as hereinafter claimed. 
     Therefore, the disclosed subject matter should not be limited to any single embodiment described herein, and the scope of the present inventive concept shall be determined according to the attached claims.