JP2010067442A - Light source module and illuminating device having the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light source module and a display device which improves light extraction efficiency and uniforms illuminance distribution as well. <P>SOLUTION: According to the light source module, in consideration of reflection light from a reflective plate 5 disposed on a second end face 1B of a light guide member 1, the density of a diffusion structure 4 is increased from the position of a first end face 1A on which light from a light source 2 is incident to a position of a half or more of the dimension L in the light guide direction X of the light guide member 1, and is kept constant in an area beyond the position of the half or more of the dimension L. As a result, light extraction efficiency is determined to be practically needed efficiency 80% or higher, and illuminance distribution is made uniform in the light guide direction X. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a light source module using a light guide plate and an illumination device including the same.

  2. Description of the Related Art Conventionally, linear light source modules using a light guide plate have attracted attention and are being developed for applications such as backlights for liquid crystal televisions, scanners, and copiers. An example of a linear light source module using a light guide plate is described in Patent Document 1 (Japanese Patent Laid-Open No. 2002-44378).

  FIG. 9 is a schematic diagram for explaining a linear light source module 300 using the light guide plate disclosed in Patent Document 1. As shown in FIG. A linear light source module 300 shown in FIG. 9 has a light source 302 disposed at one end of a light guide plate 301 and a reflector 305 disposed at the other end. Further, the light guide plate 301 is formed with a light extraction structure 304 for radiating the light being guided from the light guide plate 301.

  The light emitted from the light source 302 is coupled to the light guide plate 301 and is guided in the light guide plate 301 by repeating total reflection. At this time, light incident on the light extraction structure 304 formed on the light guide plate 301 is reflected and scattered, and light that does not satisfy the total reflection condition is emitted from the light guide plate 301. In addition, since the light reaching the end of the light guide plate 301 is reflected by the reflection plate 305, the light is guided through the light guide plate 301 again and finally emitted by the light extraction structure 304.

  Here, the light extraction structure 304 has a distance from the light source 302, the magnitude of reflected light from the reflection plate 305, and the reflection plate 305 in order to make the illuminance in the longitudinal direction (X direction) of the light guide plate 301 uniform. The width is changed in consideration of the distance from the center, and is substantially triangular in the longitudinal direction (X direction).

  However, the linear light source module 300 using the conventional light guide plate 301 has the following problems.

  In the linear light source module 300 described in Patent Document 1, the width of the light extraction structure 304 is changed, and a triangular shape is formed in the longitudinal direction (X direction). In the linear light source module 300, since the light reflected and scattered by the light extraction structure 304 is emitted from the light guide plate 301, the light extraction structure 304 serves as a light emitting unit. Therefore, the width (dimension in the Y direction) of the light emitting portion varies depending on the position in the longitudinal direction (X direction), and the illuminance distribution in the Y direction in FIG. 9 varies depending on the position in the longitudinal direction (X direction).

  When forming a surface light source module used for a backlight of a liquid crystal television or the like, a plurality of linear light source modules 300 in FIG. In this surface light source, if the width of each light emitting part is different in the longitudinal direction, the interval between adjacent light emitting parts will be different, and it will be difficult to make the illuminance in the light emitting surface uniform.

  In the conventional linear light source module 300, the reflection plate 305 is disposed at the end portion and the reflected light is returned to the light guide plate 301 again. In this way, the light remaining without being emitted by the light extraction structure 304 can be returned to the light guide plate 301 and reused, so that the light extraction efficiency can be increased. The light extraction efficiency is a value obtained by dividing the amount of light emitted from the light guide plate by the amount of light combined from the light source to the light guide plate.

However, if the amount of light reflected by the reflection plate 305 is large, the distance that light is guided in the light guide plate 301 before the light is emitted becomes long. In this case, coupling loss, reflection loss, light guide loss, and the like are increased, and the light extraction efficiency is reduced as compared with the case where the reflected light from the reflection plate 305 is small.
JP 2002-44378 A

  SUMMARY OF THE INVENTION An object of the present invention is to provide a light source module and a display device that can achieve both improved light extraction efficiency and uniform illuminance distribution.

In order to solve the above problems, a light source module of the present invention includes a light source,
The first end face on which light from the light source is incident, the second end face opposite to the first end face, and the first end face and the second end face are located between the first end face and the second end face. A light guide member including a light exit surface that emits light incident from the first end surface, and a back surface opposite to the light exit surface;
A reflecting plate that is disposed on the second end face of the light guide member and reflects light reaching the second end face;
A diffusion structure formed on at least one of the back surface and the light exit surface of the light guide member and having a plurality of diffusion portions for diffusing light incident from the first end surface;
The density of the diffusion structure, which is the ratio of the dimension in the light guide direction of the diffusion portion occupying per unit dimension in the light guide direction from the first end face to the second end face along the light exit surface,
The position of the first end face increases from the first end face to the second end face to a position that is at least one-half of the dimension of the light guide member and at least one half of the position. It is characterized by being constant or decreasing in the region exceeding.

  According to the light source module of the present invention, the light guided to the second end face without being emitted from the light guide member is reflected by the reflecting plate and recombined with the light guide member. The recombined light is again guided in the light guide member, diffused by the diffusion structure, and emitted from the light exit surface of the light guide member. In this way, the light reaching the second end surface of the light guide member is reflected by the reflecting plate, returned into the light guide member, and reused, so that the light extraction efficiency (= (the amount of light emitted from the light guide member) ÷ A light source module with a large (the amount of light coupled from the light source to the light guide member)) can be realized.

  In the present invention, in consideration of the reflected light from the reflection plate disposed on the second end face of the light guide member, the density of the diffusion structure (light extraction structure) is set to the first end face on which light from the light source enters. From this position, it is increased to a position that is at least a half of the dimension of the light guide member, and is made constant or decreased in a region that exceeds the position that is at least a half. Thereby, the light extraction efficiency can be set to 80% or more which is practically required, and the illuminance distribution in the light guiding direction (longitudinal direction) can be made uniform.

  Moreover, in the light source module of one Embodiment, the said reflecting plate has a reflection characteristic with many diffusion components compared with a regular reflection component.

  According to this embodiment, since the reflecting plate has reflection characteristics with many diffusing components, light is scattered by this reflecting plate. A part of the reflected light scattered by the reflecting plate is directly emitted from the light emitting surface. In this case, since the reflecting plate itself functions as a diffusing structure (light extraction structure), the density of the diffusing structure near the reflecting plate can be reduced. Therefore, the material for forming the diffusion structure and the processing cost can be reduced.

  Moreover, in the light source module of one Embodiment, the said reflecting plate has a reflection characteristic with many regular reflection components compared with a diffusion component.

  According to this embodiment, the influence of Fresnel loss and the like can be suppressed, and more light can be recombined in the light guide member. Therefore, it is possible to realize a light source module with high light extraction efficiency. In addition, as a substance whose reflection characteristics include a lot of regular reflection components, there is a metal such as aluminum. By forming a metal film such as aluminum directly on the end face of the light guide member by a method such as vapor deposition or plating, the light guide member is formed without forming an air layer between the end face of the light guide member and the reflector plate. It can be arranged on the end face of.

In the light source module of one embodiment, the density of the diffusion structure is
It increases from the position of the first end face to a position of 75% of the dimension of the light guide member from the first end face to the second end face, and is constant in a region exceeding the position of 75%. Is or is decreasing.

  According to this embodiment, the amount of light reflected by the reflecting plate can be 20% or less of the amount of light combined from the light source to the light guide member, and the light extraction efficiency can be improved.

  That is, the theoretical limit value of the light extraction efficiency of the linear light source module is considered to be about 95% in consideration of the loss due to the diffusion structure (light extraction structure), the reflection plate, and the like. In order to obtain light extraction efficiency of 85% or more, which is 90% of the theoretical limit, it is necessary to suppress the amount of light reflected by the reflector to 20% or less of the amount of light coupled from the light source to the light guide member.

Moreover, in the light source module of one embodiment, the plurality of diffusion units included in the diffusion structure are:
The light guide member has a linear shape extending in a direction orthogonal to the light guide direction from the first end surface toward the second end surface on the back surface or the light emitting surface of the light guide member, and a plurality of diffusion portions having the linear shape. The density of the diffusion structure is set by changing at least one of the line width and the spacing between the lines of the plurality of diffusion portions.

  According to this embodiment, the dimension in the direction orthogonal to the light guide direction (the width dimension of the light emitting portion) can be made constant. Thereby, the illuminance distribution in the width direction of the light source module can be made constant regardless of the position in the light guide direction (length direction).

  Moreover, in the light source module of one Embodiment, the said diffusion structure was formed in both the back surface and the light-projection surface of the said light guide member.

  According to this embodiment, by forming the diffusion portion of the diffusion structure (light extraction structure) dispersed on each of the back surface of the light guide member and the light emission surface, compared with the case where the diffusion structure is formed only on one side Thus, the density of the diffusion portion formed on each surface can be reduced. Therefore, it becomes easy to form a diffusion structure. That is, when the light extraction efficiency is increased, the required maximum diffusion portion density is considerably increased. When the density of the diffusion part is increased, the interval between the diffusion parts is narrowed, and it becomes difficult to form the diffusion part. In such a case, it is effective to disperse and form the diffusion portions of the diffusion structure on a plurality of surfaces parallel to the light guide direction.

  That is, a plurality of diffusion portions of the diffusion structure are dispersedly arranged on each of the plurality of surfaces parallel to the light guide direction, and the diffusion portions formed on each of the plurality of surfaces are added. Fill the density distribution. By doing so, it is possible to realize the density distribution of the high-density diffusion part necessary for realizing a large light extraction efficiency.

  Moreover, in the light source module of one Embodiment, the said diffusion structure was formed by patterning the resin ink which mixed the diffusion particle.

  According to this embodiment, when producing the diffusion structure, a method with excellent cost performance such as screen printing can be used, and a light source module can be produced at low cost. As the diffusion structure, there is a manufacturing method for forming a macro prism or the like in addition to a manufacturing method for patterning a resin ink mixed with diffusion particles. However, in order to form a microprism, since fine processing is required, the processing cost increases.

  Moreover, in the illuminating device of one Embodiment, it is the structure of single or multiple arrangement | sequence.

  According to this embodiment, it is possible to realize a more efficient lighting device.

  Further, the display device according to an embodiment has a structure in which a plurality of the light source modules are arranged.

  According to this embodiment, a high-luminance display device such as a liquid crystal television using the light source module as a backlight can be realized.

  According to the light source module of the present invention, the density of the diffusion structure (light extraction structure) is set so that the light from the light source is incident in consideration of the reflected light from the reflection plate disposed on the second end face of the light guide member. It is increased from the position of the end face of 1 to a position that is at least a half of the dimension of the light guide member, and is made constant or decreased in a region that exceeds the position of the half or more. Thereby, the light extraction efficiency can be set to 80% or more which is practically required, and the illuminance distribution in the light guiding direction (longitudinal direction) can be made uniform.

  Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.

(First embodiment)
FIG. 1 is a schematic diagram showing a schematic configuration of a light source module as a first embodiment of the light source module of the present invention. The light source module is attached to the light guide member 1, the coupling member 3 attached to the first end face 1A of the light guide member 1, and the second end face 1B opposite to the first end face 1A. A reflection plate 5 and a diffusion structure 4 formed on the back surface 1C of the light guide member 1 are provided.

  The coupling member 3 has a recess 7 facing the first end surface 1 </ b> A, and the light source 2 is disposed on the bottom surface of the recess 7. The inner surface 7A of the recess 7 serves as a reflector that reflects the emitted light of the light source 2 toward the first end surface 1A. Here, in this embodiment, the angle formed by the inner surface 7A of the recess 7 and the bottom surface of the recess 7 is set to 135 °. The shape of the inner side surface 7A constituting the reflector is not limited as long as the light emitted from the light source 2 can be efficiently combined with the light guide member 1, and other shapes may be used. In this embodiment, the light source 2 is configured by a light emitting element (LED), but may be configured by an LD (laser diode) element or the like.

  The light guide member 1 has a light extraction surface 1D that is positioned between the first end surface 1A and the second end surface 1B and emits light incident from the end surface 1A. It faces in the opposite direction to the direction in which the light extraction surface 1D faces. The back surface 1C and the light extraction surface 1D are substantially parallel.

  The diffusing structure 4 includes a plurality of diffusing portions 4A for diffusing light, and the plurality of diffusing portions 4A are optical axes from both ends in the optical axis direction of the back surface 1C of the light guide member 1 toward the center. The number per unit dimension in the direction (light guide direction) is increasing.

  Moreover, the said light guide member 1 is produced by the acrylic resin of width 10mm * height 6mm * length 536mm as an example. Here, the width is a dimension in the direction Z shown in FIG. 1, the height is a dimension in the normal direction Y of the light extraction surface 1 </ b> D shown in FIG. 1, and the length is the optical axis J of the light source 2. Direction (light guide direction) X. The shape of the light guide member 1 is not limited to the above shape, and the cross-sectional shape of the light guide member 1 may be a polygonal shape other than the quadrangle shown in FIG. 1 or a round shape. . Moreover, the length of the light guide member 1 can also be changed according to the use. The light guide member 1 may be made of a material having good transparency and high transmittance such as polystyrene resin, methacrylic resin, polycarbonate resin or glass in addition to acrylic resin. The reflective plate 5 may be made of a material having a high reflectivity such as a metal film such as aluminum, a high reflectivity polycarbonate, or a white scattering plate.

  In the lighting device using the light guide member 1, in order to increase the light extraction efficiency (= the amount of light emitted from the light guide member ÷ the amount of light combined from the light source to the light guide member) It is important to emit as much light as possible from the light guide member 1. If there is light that is incident on the first end surface 1A and is not emitted from the light guide member 1 and remains on the opposite end surface 1B, the light extraction efficiency decreases accordingly. The linear light source module in this embodiment has a structure in which the remaining light is reflected into the light guide member 1 and recombined by providing a reflector 5 at the end of the opposite end face 1B. The recombined light is guided again in the light guide member 1 and taken out by the diffusion structure 4. Thereby, more light can be extracted and the light extraction efficiency can be improved.

  In the present embodiment, a reflecting plate (not shown) may be installed at a position facing the back surface 1 </ b> C of the light guide member 1. In this case, the light emitted from the back surface 1C of the light guide member 1 can be reflected toward the light extraction surface 1D, and the illuminance at the light extraction surface 1D can be increased.

  In this embodiment, each diffusing portion 4A forming the diffusing structure 6 formed on the light guide member 1 is a mixture of diffusing fine particles in a transparent resin, and the back surface of the light guide member 1 by screen printing. 1C is patterned into a line extending in the direction Z. In the linear light source module according to this embodiment, the diffusing structure 4 has each diffusing portion in order to make the illuminance distribution in the longitudinal direction (optical axis direction X) of the light guide member 1 uniform and to realize a large light extraction efficiency. A density distribution of 4A is determined.

  Here, FIG. 2A shows an example of the pattern distribution of the diffusion portion 4A of the diffusion structure 4 in the present embodiment. 2A is a rear view showing a state in which the rear surface 1C of the light guide member 1 is viewed in the direction Y. FIG. In the example shown in FIG. 2A, the diffusion units 4A extending in the direction Z have the same dimension in the optical axis direction X, and the number per unit dimension in the optical axis direction increases in the optical axis direction X. . FIG. 2B shows another example of the pattern distribution of the diffusion portion 14A of the diffusion structure 14 in a modification of the present embodiment. 2B is a rear view showing a state in which the rear surface 1C of the light guide member 1 is viewed in the direction Y, as in FIG. 2A. In the example shown in FIG. 2B, in the diffusing portion 14 </ b> A extending in the direction Z, the dimension in the optical axis direction X increases toward the optical axis direction X.

  The density of the diffusing parts 4A and 14A of the diffusing structures 4 and 14 shown in FIGS. 2A and 2B is the size of the diffusing parts 4A and 14A in the optical axis direction occupied per unit size in the optical axis direction X of the light guide member Defined as a percentage.

  2A and 2B, since the light diffusion structures 4 and 14 are formed in the same size as the width direction Z of the linear light source module of this embodiment, the width of the light extraction surface 1D forming the light emitting portion The dimensions can be constant. For this reason, it is easy to control the illuminance when a plurality of the linear light source modules of this embodiment are arranged in the width direction Z to form a surface light source device. In this embodiment, as shown in FIG. 2A, the density is controlled by controlling the interval between patterns forming each diffusion portion 4A. In this embodiment, the pattern size of each diffusion portion 4A is 0.2 mm in the optical axis direction X, 10 mm in the direction Z, and 0.01 mm in the direction Y.

(Diffusion structure density)
Next, the density of the diffusion structure 4 as the patterned light extraction structure will be described in detail. The density distribution of the diffusion structure 4 as the light extraction structure employing the light guide member 1 can be calculated based on the model of the light source module shown in FIG. Consider a case in which light guided from the light source 2 into the light guide member 1 is extracted from the light guide member 1 at a position X separated from the one end surface 1A of the light guide member 1 in the direction X by the dimension X. Here, when the light amount of the light at the position X is S1 (X), the light amount Q1 (X) per unit length (dimension in the X direction) extracted from the light guide member 1 is expressed by the following equation (1). Is done.
Q1 (X) = a (X) · S1 (X) (1)

In the above formula (1), a (X) is the emissivity of light from the light guide member 1 at the position X, and is a value determined by the density of the diffusion structure 4 as the light extraction structure. The light quantity S1 (X) at the position X can be expressed by the following equation (2).

  In this equation (2), P0 is the amount of light coupled from the light source 2 to the light guide member 1.

The light guided into the light guide member 1 is reflected by the reflecting plate 5 at the position of X = L, which is the length of the light guide member 1 in the optical axis direction, and the light guide member 1 is light source 2 side. Is guided to. The amount of light Q2 (X) per unit length (dimension in the X direction) emitted from the light guide member 1 by the diffusion structure 4 serving as the light extraction structure of the reflected light is expressed as follows. It is represented by the following formula (3).
Q2 (X) = a (X) · S2 (X) (3)

In the above equation (3), a (X) is the emissivity of light from the light guide member 1 at the position X, and is a value determined by the density of the diffusion structure 4 as the light extraction structure. The light quantity S2 (X) at the position X can be expressed by the following equation (4).

  Further, the light emitted from the light source 2, reflected by the reflecting plate 5 and returned to the light source 2 side is reflected again by the coupling member 3 attached around the light source 2 and is coupled to the light guide member 1 again. Thus, the light guided in the light guide member 1 is emitted from the light guide member 1 by the diffusion structure 4 as a light extraction structure while being repeatedly reflected at both ends of the light guide member 1.

And if the light quantity per unit length radiated | emitted from the light guide member 1 is equal, the value of the light quantity Qtotal per unit length radiated | emitted from the light guide member 1 will be calculated by following Formula (5). .
Qtotal (X) = Q1 (X) + Q2 (X) +... + Qn-1 (X) + Qn (X)
= P0 / L (5)

Therefore, by realizing the emissivity a (X) of the light from the light guide member 1 at the position X that satisfies the above formulas (1) to (5), the illuminance in the optical axis direction X can be made uniform. Can do. This light emissivity a (X) is proportional to the density of the diffusion structure 4 as the light extraction structure as described above, and can be expressed by the following equation (6).
a (X) = c × D (X) (6)

  In Expression (6), D (X) is the density of the diffusion structure 4 even at the position X, and c is a proportionality constant.

  In this embodiment, as the diffusion structure 4 which is a light extraction structure, a transparent resin mixed with diffusion fine particles is used, and the proportionality constant between the emissivity and the density of the diffusion structure is 0.018. Therefore, the density distribution of the diffusion structure 4 is obtained by multiplying a (X) obtained from the above expression by 0.018.

  As described above, the density of the diffusing structure 4 is obtained assuming that all the reflected light reflected by the reflecting plate 5 is recombined with the light guide member 1. That is, this is a case where the reflection characteristics of the reflecting plate 5 are all regular reflection. However, the actual reflection characteristics of the reflection plate 5 include a diffusion component. When the reflecting plate 5 contains a diffusing component, a part of the reflected light is scattered and emitted from the light guide member 1 as it is. In this case, since the reflecting plate 5 itself plays the role of the diffusing structure 4, the density of the diffusing structure 4 required near the reflecting plate 5 is smaller than that obtained by the above calculation. Therefore, in order to fully consider the influence of the reflection characteristics of the reflection plate 5, the illuminance distribution was analyzed using the density of the diffusion structure 4 as the light extraction structure obtained by the above formula, and the density was optimized.

  FIG. 4 is a graph showing the density distribution of the diffusion structure 4 finally obtained in the present embodiment. The horizontal axis of the graph of FIG. 4 indicates a value obtained by normalizing the position X of the light guide member 1 in the optical axis direction by the length L of the light guide member 1 in the optical axis direction (light guide direction). The position of the end face 1A is X = 0.

  Also, the vertical axis of the graph of FIG. 4 is the density of the diffusing portion 4A of the diffusing structure 4, and indicates the ratio of the dimension in the optical axis direction of the diffusing portion 4A formed per unit dimension in the optical axis direction X. ing. In FIG. 4, the density distribution K1 indicated by a solid line has a diffusion component of 10% in the reflection characteristic of the reflecting plate 5, and the density distribution K2 indicated by a broken line has a diffusion component of 90% of the reflection characteristic of the reflecting plate 5. belongs to. In the density distributions K1 and K2 of the diffusion structure 4 shown in FIG. 4, the density gradually increases from the end face of the light guide member 1 on which the light source 2 is arranged, and is approximately 75% of the total distance from the light source 2. The slope has changed since then (turned to decrease).

  Next, the reason why the inclination is changed will be described. As described above, the light guided into the light guide member 1 is scattered by the diffusion structure 4 and emitted from the light guide member 1. The emissivity is determined by the density of the diffusion structure 4. Further, since the light guided in the light guide member 1 is guided while being emitted by the diffusion structure 4, the amount of light guided decreases as the distance from the light source 2 increases. Therefore, in order to make the light quantity radiated | emitted from the light guide member 1 constant along an optical axis direction, the spreading | diffusion structure 4 gradually goes along the optical axis direction from the end surface 1A of the light guide member 1 in which the light source 2 is arrange | positioned. It is necessary to increase the density.

  However, since the light source module in this embodiment uses reflected light, there is light that is guided to the light source 2 from the reflecting plate 5 disposed on the end surface 1B of the light guide member 1. For this reason, it is not necessary to increase the density of the diffusing structure 4 so much in the vicinity of the reflecting plate 5, and the gradient of the density distribution changes (decreases) in the middle of reaching the end face 1B.

  Further, in the case of the reflecting plate 5 having more diffusing components, most of the light reflected by the reflecting plate 5 is scattered and emitted from the light guide member 1 as it is. In this case, since the reflection plate 5 itself functions as a light extraction structure, the density of the diffusion structure 4 as the light extraction structure near the reflection plate 1 is further reduced. Therefore, the density of the diffusion structure 4 is set as shown by a distribution K2 indicated by a broken line in FIG. In this density distribution K2, the density increases as the distance from the light source 2 increases, but the density decreases halfway. Therefore, it is preferable to use the reflecting plate 5 having a large amount of diffusing components in that the material for forming the diffusing structure 4 and the processing cost can be reduced.

  On the other hand, since the reflection plate 5 having a large number of regular reflection components has a small amount of scattered light, the reflection light reflected by the reflection plate 5 and emitted as it is from the light guide member 1 is small. In this case, since the effect of the reflecting plate 5 functioning as the diffusing structure 4 is small, the density of the diffusing structure 4 as the light extraction structure near the reflecting plate 5 is higher than that of the reflecting plate 5 having a large amount of diffusing components. It does not become so small around 5. For this reason, the density of the diffusion structure 4 is as shown by the density distribution K1 shown by the solid line in FIG. That is, the density increases as the distance from the light source 2 increases, but the density becomes constant while approaching the reflector 5.

  Examples of the reflection plate 5 containing a lot of regular reflection components include metal films such as aluminum. If the metal film such as aluminum is directly formed on the end surface 1B of the light guide member 1 by a method such as vapor deposition or plating, an air layer is formed between the end surface 1B of the light guide member 1 and the reflection plate 5. Instead, the reflector 5 can be disposed in close contact with the light guide member 1. In this case, the influence of Fresnel loss and the like can be suppressed, and more light can be recombined with the light guide member 1. Therefore, it is preferable in that a linear light source module with high light extraction efficiency can be realized.

  As described above, the density distribution of the diffusing portion 4A of the diffusing structure 4 for making the illuminance distribution in the optical axis direction X uniform is obtained by performing calculation and illuminance analysis using the model shown in FIG. Is possible.

  Next, the density distribution of the diffusion portion 4A for increasing the light extraction efficiency (a value obtained by dividing the light amount emitted from the light guide member 1 by the light amount coupled from the light source 2 to the light guide member 1) will be described.

  There are several solutions for a (X) (emissivity distribution) that satisfy the above formulas (1) to (5), and the light intensity emitted from the light guide member 1 is constant for each, and the illuminance distribution is uniform. Can be.

  The density distributions K3 and K4 shown in FIGS. 5A and 5B are obtained by calculating the density distribution different from the density distribution of the diffusion portion 4A of the diffusion structure 4 shown in FIG. 4 from the model calculation and illuminance analysis shown in FIG. is there. In the density distribution K3 shown in FIG. 5A and the density distribution K4 shown in FIG. 5B, the gradient of the density distribution of the diffusing structure 4 increasing from the light source 2 side toward the reflecting plate 5 side is inclined toward zero (constant density). The position where it starts to decrease is different. Further, as shown in FIG. 5A, in the distribution K3 where the slope of the density distribution of the diffusion structure 4 starts to decrease toward the slope zero (constant density) in the distribution K3 closer to the light source 2 side than the distribution K4 in FIG. 5B, The density is generally lower than the distribution K4 in FIG. 5B. In the distribution K3 having a generally low density, the amount of light extracted by the diffusing structure 4 is small, so that the amount of light reflected by the reflector 5 increases. Therefore, in the density distribution K3, the amount of light reflected by the reflecting plate 5 and guided toward the light source 2 increases, so that the slope of the density distribution K3 starts to decrease toward the zero slope (constant density). It is closer to the light source 2 side than the density distribution K4 in FIG. 5B.

  In the light source module having the density distribution K <b> 3 shown in FIG. 5A, approximately 41.8% of the light coupled from the light source 2 to the light guide member 1 is reflected by the reflecting plate 5. On the other hand, in the light source module having the density distribution K <b> 4 shown in FIG. 5B, approximately 7.8% of the light coupled from the light source 2 to the light guide member 1 is reflected by the reflector 5.

  In the light source module having the density distribution K1 shown in FIG. 4, approximately 21.6% of the light coupled from the light source 2 to the light guide member 1 is reflected by the reflector 5.

  FIG. 6 shows the relationship between the light extraction efficiency of the linear light source module having the density distributions K1, K3, and K4 of the diffusion structure 4 shown in FIGS. 4, 5A, and 5B and the amount of light reflected by the reflector 5. It is a thing. As shown in FIG. 6, it can be seen that the light extraction efficiency increases as the amount of light reflected by the reflector 5 decreases. This suggests that in order to increase the light extraction efficiency, it is necessary to radiate a large amount of light from the light guide member 1 with as few reciprocations as possible.

  This is because if the reflection is repeated at the end surface 1B of the light guide member 1, the light guide distance is extended, and losses such as reflection loss, coupling loss, and light guide loss at the end surface 1B are integrated and increased. In particular, the light emitted from the light source 2 and returned to the light source 2 by the reflecting plate 5 on the end face 1B of the light guide member 1 is reflected and combined by the coupling member 3 attached to the light source 2 again. Since the coupling loss is a large loss, it is better that the amount of light returning to the light source 2 is as small as possible. In other words, it is preferable to emit all the light as much as possible during a round trip of the light. In order to reduce the light returning to the light source 2, it is necessary to reduce the amount of light reflected at the position of the reflecting plate 5.

  From the characteristics shown in FIG. 6, when the amount of light reflected by the reflecting plate 5 is 50% or less of the amount of light coupled from the light source 2 to the light guide member 1, 80% or more light extraction required for practical use is required. It can be seen that efficiency can be obtained.

  There is a correlation between the amount of light reflected by the reflector 5 and the density distribution of the diffusing structure 4 as described above. In the density distribution of the diffusing structure 4, the amount of light reflected by the reflector 5 is guided by setting the density distribution so that the inclination starts to decrease from the position of 50% or more of the dimension in the optical axis direction of the entire light guide member 1 from the light source 2. It becomes possible to make it 50% or less of the light quantity couple | bonded with the optical member 1, and it becomes possible to implement | achieve the light extraction efficiency of 80% or more.

  Further, the density distribution K3 of the diffusion structure 4 shown in FIG. 5A has a density value much smaller than the density distributions K1, K2, and K4 shown in FIGS. 4 and 5B. It becomes easy to form.

  In addition, the theoretical limit value of the light extraction efficiency of the light source module is considered to be about 95% in consideration of the loss due to the light extraction structure and the reflector. From the characteristics of FIG. 6, it can be seen that in order to obtain a light extraction efficiency of 85% or more, which is 90% of the theoretical limit, it is necessary to suppress the amount of light reflected by the reflecting plate 5 to 20% or less. The density of the diffusing structure 4 is increased in the region from the first end face 1A to 70% of the optical axis direction dimension L of the light guide member 1, and is formed so that the density is decreased or made constant in the region beyond it. Thus, the amount of light reflected by the reflecting plate 5 is 20% or less of the amount of light coupled from the light source 2 to the light guide member 1. As a result, a light source module with high light extraction efficiency can be realized.

(Second embodiment)
Next, FIG. 7A shows a second embodiment of the light source module of the present invention. In the second embodiment, only the diffusion structure (light extraction structure) is formed not only on the back surface 1C of the light guide member 1 of the first embodiment but also on the light extraction surface 1D. And different. Therefore, in the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and different points from the first embodiment will be mainly described.

  In the second embodiment, a diffusion structure 24 having a diffusion portion 24A corresponding to each diffusion portion 4A of the diffusion structure 4 formed on the back surface 1C is formed on the light extraction surface 1D of the light guide member 1. According to this embodiment, since the diffusion structures 4 and 24 forming the light extraction structure are formed separately on the back surface 1C of the light guide member 1 and the light extraction surface 1D, the density of the diffusion portions 4A formed on the back surface 1C is increased. Without increasing the density of the diffusion structures 4 and 24 as a whole.

  Therefore, the desired density of the diffusion structure as a whole can be achieved while suppressing the density of the diffusion portions 4A and 24A formed on the back surface 1C and the light extraction surface 1D of the light guide member 1, respectively, and the light extraction efficiency can be improved. .

  Further, as described above, in order to increase the light extraction efficiency, it is necessary to bring the position where the density gradient of the diffusing portion starts to decrease closer to the reflector 5 on the opposite side of the light source 2. In this case, the maximum density required is quite large. When the density of the diffusing parts increases, the distance between the diffusing parts becomes narrow, and it becomes difficult to form the diffusing parts by screen printing or the like. In such a case, the diffusion surfaces 4A and 24A of the diffusion structures 4 and 24 are dispersedly arranged on the back surface 1C and the light extraction surface 1D of the light guide member 1 as in this embodiment, so that the surfaces 1C and 1D are distributed. The increase in density at the substrate is suppressed, and the diffusion portion can be easily formed.

  In the second embodiment, the diffusion portions 24A and 4A having the same pattern are formed on both the light extraction surface 1D and the back surface 1C of the light guide member 1. However, as shown in FIG. Diffusion structures 26 and 27 may be formed by diffusing portions 26A and 27A arranged in different patterns on the back surface 1C and the light extraction surface 1D.

  That is, it is not necessary to form the density distribution of the diffusing portion of the diffusing structure constituting the light extraction structure shown so far only on one back surface 1C of the light guide member 1 parallel to the optical axis direction (light guide direction). Each diffusion portion may be dispersed and formed on each of the back surface 1C and the light extraction surface 1D parallel to the back surface 1C. That is, the sum of the densities of the diffusion portions formed on the surfaces 1C and 1D only needs to satisfy the density distribution necessary for the diffusion structure. By doing so, it is possible to realize a high density distribution necessary for realizing a large light extraction efficiency.

  Next, FIG. 8 shows an analysis result of the illuminance distribution of the light source module having the density distribution K1 shown in FIG. In FIG. 8, the horizontal axis indicates a value obtained by normalizing the position X of the light guide member 1 in the optical axis direction by the length L of the light guide member 1 in the optical axis direction. In FIG. 8, the vertical axis represents the relative value of illuminance. According to FIG. 8, the uniformity of the illuminance distribution (= minimum illuminance ÷ maximum illuminance) is 93.3%, indicating a very uniform illuminance distribution. In the density distribution K1 shown in FIG. 4, the density gradient of the diffusion structure 4 as the light extraction structure is 75% (0.75 L) of the dimension L in the optical axis direction from the end face 1A of the light guide member 1. Turning to the decrease, it is almost constant in the region exceeding the 75% position. Thereby, the light extraction efficiency shows a very large value of 85.1%.

  As described above, in the light source module according to this embodiment, the light guided to the end surface 1B of the light guide member 1 without being emitted from the light guide member 1 is again coupled to the light guide member 1 by the reflector 5. And reuse. Further, in the region where the density distribution of the diffusing structure 4 exceeds 50% of the entire dimension L in the optical axis direction X of the light guide member 1 from the light source 2, the density is constant or the density is reduced. As a result, it is possible to obtain light utilization efficiency of 80% or more, and to make the illuminance distribution in the optical axis direction (longitudinal direction) of light constant. In particular, the density distribution of the diffusing structure 4 is set so that the inclination starts to decrease from a position of 75% or more of the entire dimension L in the optical axis direction X of the light guide member 1 from the light source 2 and the density is constant or the density decreases. As a result, the light extraction efficiency can be 85% or more, which is 90% of the theoretical limit, and the illuminance distribution in the optical axis direction (longitudinal direction) of light in the linear light source can be made almost constant. Become.

  In the example of the diffusion structures 4 and 14 shown in FIGS. 2A and 2B described above, the diffusion portions 4A and 14A are guided in the light guide direction from the first end surface 1A to the second end surface 1B on the back surface 1C of the light guide member 1. A linear shape extending in a direction Z orthogonal to the direction Z. The light guide member 1 of the light source module includes the diffusion structure 4 that changes the line width of the diffusion portion 4A as shown in FIG. 2B and the diffusion structure 14 that changes the distance between the lines of the diffusion portion 14A as shown in FIG. 2A. Therefore, the illuminance distribution in the width direction Z can be made equal at any position in the optical axis direction X of the light source module. Note that the density distribution of the diffusing portions of the diffusing structure may be set by changing both the line width and the inter-line spacing of each diffusing portion in the optical axis direction X.

  The light source modules of the first and second embodiments control light on a photoconductor such as a light source for image reading, a copier, and a printer that are used in backlights, copiers, and scanners for liquid crystal televisions. Therefore, it can be widely used for other light sources such as a light source for static elimination, a thin light source for interiors, and a guide light.

It is a schematic diagram which shows the cross section of 1st Embodiment of the light source module of this invention. It is a rear view which shows an example of the density distribution of the diffusion part of the diffusion structure of the said 1st Embodiment. It is a rear view which shows an example of the density distribution of the spreading | diffusion part of the diffusion structure in the modification of the said 1st Embodiment. It is a figure which shows the model of a linear light source module. It is a distribution map which shows an example of the density distribution of the diffusion structure 4 which makes the light extraction structure of the said 1st Embodiment. It is a distribution map which shows another example of the density distribution of the diffusion structure 4 which makes the light extraction structure of the said 1st Embodiment. It is a distribution map which shows another example of the density distribution of the diffusion structure 4 which makes the light extraction structure of the said 1st Embodiment. It is a characteristic view showing the relationship between the light extraction efficiency of the light source module of the first embodiment and the amount of light reflected by the reflecting plate. It is a schematic diagram which shows the cross section of 2nd Embodiment of the light source module of this invention. It is a schematic diagram which shows the cross section of the modification of the said 2nd Embodiment. It is a graph which shows the analysis result of the illumination intensity distribution of the light source module which has the density distribution K1 shown in FIG. It is a figure which shows the conventional light source module.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light guide member 1A, 1B End surface 1C Back surface 1D Light extraction surface 2 Light source 3 Coupling components 4, 14, 24 Diffusion structure (light extraction structure)
4A, 14A, 24A Diffuser 5 Reflector

Claims (9)

A light source;
The first end face on which light from the light source is incident, the second end face opposite to the first end face, and the first end face and the second end face are located between the first end face and the second end face. A light guide member including a light exit surface that emits light incident from the first end surface, and a back surface opposite to the light exit surface;
A reflecting plate that is disposed on the second end face of the light guide member and reflects light reaching the second end face;
A diffusion structure formed on at least one of the back surface and the light exit surface of the light guide member and having a plurality of diffusion portions for diffusing the light incident from the first end surface;
The density of the diffusing structure, which is the ratio of the dimension in the light guide direction of the diffusing portion per unit dimension in the light guide direction from the first end face to the second end face along the light exit surface,
The position of the first end face increases from the first end face to the second end face to a position that is at least one half of the dimension of the light guide member and at least one half of the position. A light source module characterized by being constant or decreasing in a region exceeding. The light source module according to claim 1,
The light source module according to claim 1, wherein the reflection plate has a reflection characteristic having a larger diffusion component than a regular reflection component. The light source module according to claim 1,
The light source module according to claim 1, wherein the reflection plate has a reflection characteristic having more regular reflection components than diffusion components. The light source module according to any one of claims 1 to 3,
The density of the diffusion structure is
It increases from the position of the first end face to a position of 75% of the dimension of the light guide member from the first end face to the second end face, and is constant in a region exceeding the position of 75%. A light source module characterized by being or being reduced. In the light source module according to any one of claims 1 to 4,
The plurality of diffusion portions that the diffusion structure has,
The light guide member has a linear shape extending in a direction orthogonal to the light guide direction from the first end surface toward the second end surface on the back surface or the light emitting surface of the light guide member, and a plurality of diffusion portions having the linear shape. The light source module, wherein the density of the diffusion structure is set by changing at least one of a line width and / or an interval between lines of the plurality of diffusion portions. The light source module according to any one of claims 1 to 5,
A light source module, wherein the diffusion structure is formed on both a back surface and a light emitting surface of the light guide member. The light source module according to any one of claims 1 to 6,
A light source module, wherein the diffusion structure is formed by patterning a resin ink mixed with diffusion particles.   8. A lighting device having a structure in which one or a plurality of the light source modules according to claim 1 are arranged.   8. A display device having a structure in which a plurality of light source modules according to claim 1 are arranged.

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