JP4331313B2 - Light guide element and light source device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light guide element for internally changing the direction of light supplied from the side and emitting the light from an emission surface, and a light source device using the light guide element. The present invention can be applied to backlighting or front lighting of various devices such as a liquid crystal display, an in-vehicle device, and an advertising panel.
[0002]
[Prior art]
A light source device of a type that introduces light from a side end face of a light guide plate, which is a plate-like light guide element, and uses one of two major faces (surface having a larger area than the end face) of the light guide plate as an exit face Is widely applied, for example, to backlighting and front lighting of liquid crystal displays. The basic performance of this type of light source device depends largely on the light guide element used.
[0003]
The basic role of the light guide element is to change the traveling direction of light introduced into the light guide element from the side end face (substantially parallel to the exit surface of the light guide element) and emit the light from the exit surface. As is well known, if a simple transparent plate is used as it is as the light guide element, the direction is hardly changed and sufficient luminance cannot be obtained. Therefore, a direction changing means that promotes emission from the emission surface is required.
[0004]
Means for promoting emission of the light guide element are (1) scattering power inside the light guide element, (2) light diffusibility given to the emission surface, (3) light diffusivity given to the back surface, (4) It is supported by one or two or more of the refractive uneven shape provided on the exit surface and (5) internal reflection means provided on the back surface.
[0005]
The method (1) is easy to obtain high-efficiency and uniform outgoing light. However, the preferential emission direction from the emission surface is greatly inclined from the front direction (usually, an inclination of about 60 to 75 degrees with respect to the normal line standing on the emission surface). Therefore, in order to obtain the illumination output to the periphery in the front direction, output directivity characteristic correcting means such as a prism sheet is indispensable. Even if the light diffusing sheet is used, the output in the front direction increases to some extent, but light diffusion occurs in a wide range and the energy efficiency decreases.
[0006]
In the methods (2) and (3), it is difficult to obtain outgoing light with high efficiency. Further, similarly to the method (1), the emission from the emission surface strongly occurs obliquely. Increasing light diffusivity does not increase efficiency due to factors such as wide-range scattering and absorption by light diffusing elements (white ink, etc.).
[0007]
The method (4) facilitates the escape of light from the exit surface, but it is difficult to make a positive change of direction. Therefore, it is difficult to obtain outgoing light with high efficiency. In particular, it is not advantageous that light traveling from the back surface of the light guide element toward the exit surface is not generated.
[0008]
The method (5) positively generates light traveling from the back surface of the light guide element toward the exit surface. In addition, orderly internal reflection hardly causes wide-range scattering. Therefore, there is a possibility that an output having directivity in a desired direction (typically, almost in the front direction) can be obtained efficiently. However, in the prior art, the problem of light leakage has hindered efficient direction change as described below.
[0009]
FIG. 1 is a cross-sectional view for explaining an application example of the method (5). In the figure, reference numeral 1 denotes a light guide element made of a transparent material such as acrylic resin, and one side end face thereof provides an incident end face 2. The primary light source L whose back is covered with the reflector 8 is disposed in the vicinity of the incident end surface 2 and supplies light to the incident end surface 2. One of the two major surfaces 3 and 4 of the light guide element 1 provides the exit surface 3. The other major surface 4 provides the back surface. The back surface 4 includes a large number of internally reflecting slopes 5a to 5f for changing the direction. For the sake of illustration, a small number of internally reflecting slopes are shown.
[0010]
The light emitted from the primary light source L is introduced into the light guide element 1 through the incident end face 2. When light propagating in the light guide element 1 (light beam group) encounters the internal reflection slopes 5 a to 5 f, the direction is changed to the emission surface 3 by internal reflection, and illumination lights 6 a to 6 f are output from the emission surface 3. Such an action is called an edge lighting effect. FIG. 1 shows illumination lights 6a to 6f that are emitted almost in the front direction according to a typical design.
[0011]
It should be noted that, in general, not only “total reflection” but also “normal reflection” occur in the internal reflection surfaces 5a to 5f.
As is well known, normal reflection occurs under an internal incident angle below the critical angle and involves light leakage. For example, in the case of a light guide element made of acrylic resin having a refractive index of 1.49, the critical angle is about 42 degrees.
[0012]
The internal incident angle below the critical angle particularly occurs on the internal reflection slope (for example, 5a) close to the incident end face 2, and tends to cause light leakage (for example, 7a). This is because, as can be understood from the drawing, the inclination of the internal incident light (the extending direction of the light guide element 1 or the inclination with respect to the emission surface 3; the same applies hereinafter) is relatively large.
Further, even on an internal reflection inclined surface (for example, 5c) that is relatively far from the incident end surface 2, light that has undergone internal reflection by the exit surface 3 causes light leakage (for example, 7b) according to an internal incident angle that is less than the critical angle.
[0013]
Further, in the case where the light guide element 1 has a scattering ability (light scattering light guide element), or in the case where the exit surface 3 has light diffusibility for promoting emission, more light leakage is considered to occur. It is done.
[0014]
Needless to say, such light leakage reduces the illumination light output efficiency, and thus the luminance of the light source device. If a reflective sheet is disposed along the back surface 4, a certain amount of light leakage can be collected and returned to the light guide element 1. However, it is difficult to direct the reflected light from the reflection sheet in the intended illumination output direction (usually the front direction periphery). Therefore, leakage light collection that relies on a reflective sheet is not a satisfactory solution.
[0015]
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art. That is, an object of the present invention is to improve a light guide element for emitting light introduced from a side end face (incident end face) from an exit face, to provide a leakage light collecting function, thereby increasing direction change efficiency. There is.
Another object of the present invention is to provide a light source device with high illumination light output efficiency by employing such an improved light guide element.
[0016]
[Means for Solving the Problems]
  The present invention improves a light guide element having a major surface that provides an output surface and a back surface for light emission, and an incident end surface for light introduction. In this improvement, the rear surface of the light guide element is provided with a projection row having both a direction changing function and a light leakage collecting function.At the same time, a projection row having another direction correcting function is provided on the exit surface.Is based on the basic idea.Note that the direction correcting function provided in the projection row provided on the exit surface is a function of correcting the output directivity characteristic in a plane parallel to the incident end surface.
[0017]
  Follow the basic idea aboveFirstA large number of protrusion rows P1, P2, P3,... Are provided on the back surface of the light guide element to change the light traveling direction. Each protrusion row Pi (i = 1, 2, 3...) Extends substantially parallel to the incident end face. Note that the numbers are for convenience in defining the leakage light collection function, and are assigned in the order closer to the incident end face.In addition, the projection surface of the light guide element is provided with a large number of protrusion rows extending substantially perpendicular to the incident end surface and for correcting output directivity characteristics. This correction of the directional characteristic is to correct the output directivity characteristic in the plane parallel to the incident end face.
[0018]
  The protrusion row Pi provided on the back surface of the light guide element is:It includes a first surface Si that is relatively close and sharp with respect to the incident end surface, and a second surface Ti that is relatively far and inclined with respect to the incident end surface.
  The second surface Ti has an internal reflection function for generating light toward the exit surface and a leakage function for generating leakage light. The projection row Pj (j = 2, 3,...) Collects leaked light from the second surface Tj-1 of the preceding projection row Pj-1 through the first surface Sj, and the second surface Tj. Are arranged to cooperate in a chain for internal incidence.
[0019]
Each protrusion row Pi (i = 1, 2, 3...) May include a tip portion having a non-sharp cross-sectional shape. Such a shape reduces the risk of causing harmful deformation or damage to the tip of the light guide element during transportation, assembly of the light source device or liquid crystal display, or during use. The light leakage recovery function in the present invention relies mainly on the vicinity of the base of the projection row. Therefore, the non-sharp cross-sectional shape does not significantly reduce the leakage light collection function.
[0020]
The protrusion row may be integrated with the substrate portion of the light guide element or may be a separate body coupled to the substrate portion. Further, the protrusion row may be made of either the same material as the substrate portion or a different material.
[0021]
  The light guide element may have a structure including a light guide plate and a sheet-like member coupled thereto. The sheet-like member may be made of either the same material as the light guide plate or a different material. The light guide plate and the sheet-like member may be bonded using an optical adhesive..
[0022]
  When the improved light guide element is applied to the light source device, a primary light source for supplying primary light toward the incident end face of the light guide element is disposed. The advantages of the improvement of the light guide element are reflected in a light source device using the light guide device and a device (for example, a liquid crystal display) in which the light source device is applied to backlighting or front lighting, and bright illumination light, bright display, low power consumption, etc. can get.
[0023]
  NaRegarding the inclination angles of the first surface Si and the second surface Ti with respect to the vertical surface perpendicular to the extending surface on which the exit surface of the light guide element rides, the former is α and the latter is β, and 0 degree ≦ α ≦. It is desirable that 10 degrees and 30 degrees ≦ β ≦ 60 degrees.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
  (1) Basic embodiment
  FIG. 2 illustrates the present invention.The fruitIt is a sketch showing the outline of arrangement according to an embodiment.However, in this figure, FIG. 9, and FIG. 10, illustration of the protrusion row formed on the light exit surface of the light guide element is omitted for convenience of explanation.Referring to FIG. 2, one side end face of the light guide element 10 made of a transparent material such as an acrylic resin or polycarbonate (PC) provides an incident end face 12. The light guide element 10 in the present embodiment is an integrally molded product as a whole. Also, the thickness tends to decrease from the incident end face 12 toward another end face (terminal face) 15. Such a shape is suitable for obtaining a uniform luminance distribution.
[0025]
  A rod-shaped primary light source (cold cathode tube) L is disposed along the incident end face 12 and supplies light to the incident end face 12. One of the two major surfaces 13 and 14 of the light guide element 10 is an emission surface 13. The other surface (back surface) 14 is provided with a large number of projection rows P1, P2, P3... Pi.(Note that, as described above, protrusion rows are also formed on the emission surface 13, which will be described later). On back 14Each projection row Pi includes a first surface Si and a second surface Ti, and extends substantially parallel to the incident end face 12. For each projection row Pi, the first surface Si is closer to the incident end face than the second surface Ti.
[0026]
The first surface Si is a sharp surface. That is, an angle close to perpendicular to the extending surface of the light guide element 10 represented by the emission surface 13 is formed. On the other hand, the second surface is an inclined surface that is not as sharp as the first surface. The inclination angle is designed according to the desired priority output direction (main emission direction from the emission surface 13).
[0027]
If a known liquid crystal panel is arranged outside the emission surface 13, a backlight type liquid crystal display is configured. The front light type liquid crystal display will be described later.
[0028]
  The light emitted from the primary light source L is introduced into the light guide element 10 through the incident end face 12. When light propagating through the light guide element 10 enters any one of the projection rows Pi, internal reflection occurs on the second surface Ti. The internally reflected light is redirected to a direction determined according to the internal incident angle and the inclination angle of the second surface Ti and travels toward the exit surface 13. As long as the internal incident angle on the exit surface 13 is smaller than the critical angle, an illumination output can be obtained from the exit surface 13. Light diffusion on exit surface 13SexualIf any exit facilitating means is provided, the illumination output can be obtained more easily.
[0029]
As for the incident beam whose internal incident angle is smaller than the critical angle, a part of the incident beam is internally reflected and the rest leaks. In other words, the second surface Ti has an internal reflection function for generating light toward the emission surface 13 and a leakage function for generating leakage light from the projection row Pi.
[0030]
  SuddenThe arrays Pj (j = 2, 3,...) Are arranged so as to cooperate in a chained manner for light leakage recovery. That is, the leakage light from the second surface Tj-1 of the preceding projection row Pj-1 is collected through the first surface Sj of the subsequent projection row Pj and is incident on the second surface Tj internally. This internal incidence gives the recovered light an opportunity to change direction to the exit surface 13. If light leaks again, it will be recovered from the first surface Sj + 1 of the next projection row Pj + 1 into the projection row Pj + 1.
[0031]
A broken line 9 drawn along the back surface 14 represents the inner surface of the frame or housing for mounting or housing the illustrated elements. This inner surface has diffuse reflection or regular reflection. A reflecting member such as silver foil may be interposed between the light guide element 10 and the frame or housing. Such reflecting surface means can also contribute somewhat to the collection of light leakage.
[0032]
Importantly, however, the present invention does not rely on recovery by external reflecting means. As described above, it is difficult to expect high efficiency in the recovery by such an external reflecting means, and the direction changing function in the controlled direction is not sufficient.
[0033]
FIG. 3 is a view for explaining the direction change and leakage light collection by the projection rows, and shows the cross section of two adjacent projection rows Pj-1 and Pj and the behavior of the light beam.
3, the incident end face 12 (not shown) is on the left side, and therefore the general light supply direction in the light guide element 10 is from the left to the right. Each of the projection rows Pj and Pj-1 It has a shape including one surface Sj-1, Sj, second surface Tj-1, Tj, and the intersection of the first surface Sj-1, Sj and the second surface Tj-1, Tj has a sharp tip. Bj and Bj-1 are formed.
[0034]
As described in the circle, the angles formed by the first surface S and the second surface T with respect to the vertical surface M (an arrow direction is a plus sign) for an arbitrary projection row P are α and β. The vertical surface M is defined with respect to the extended surface on which the light exit surface 13 (see FIG. 2) rides. In this example, α = 0 degrees and β = 48 degrees. This value is a preferred example. In general, the angle α is preferably about 0 to 10 degrees. α <0 degrees is also acceptable, but it may be inferior in terms of manufacturing difficulties, mechanical strength, and the like. The inclination angle β is designed according to the desired output direction (the main emission direction from the emission surface 13). Of course, the refractive index n of the material (here n = 1.49) is also taken into account. In the normal case, the tilt angle β will be in the range of 30-60 degrees.
[0035]
Now, the second surface Tj-1 of the projection row Pj-1 is represented by a point A in order to consider the basic cooperative action of the projection rows Pj-1 and Pj-1. The point A is on the second surface Tj-1, and is close to the base of the projection row Pj-1 (that is, far from the tip Bj-1).
[0036]
A perpendicular line with respect to the second surface Tj-1 at the point A is N (broken line). Symbol C represents a critical angle, which is 42 degrees in this example. Most of the internally incident rays at the point A can be roughly classified as follows according to the internal incident angle.
[0037]
Ray group I: A ray group in which the internal incident angle is sufficiently smaller than the critical angle C. Most of these light rays leak from the second surface Tj-1 and enter the first surface Sj of the subsequent projection row Pj. Since the first surface Sj is raised, most of the leaked light is introduced into the subsequent projection row Pj through the first surface Sj. Then, it is incident on the second surface Tj of the subsequent projection row Pj.
[0038]
It should be noted that the internal incident angle on the second surface Tj is larger than the internal incident angle (experienced previously) on the second surface Tj-1 as can be understood from the illustrated passing area. Is also getting bigger. As a result, the light group I easily satisfies the total reflection condition in the internal reflection at the second surface Tj, and is redirected to the light group toward the exit surface 13 (see FIG. 2) as illustrated by I '. In this example, the light beam group I 'is output substantially in the front direction.
[0039]
There will be many such light groups I in the vicinity of the incident end face 12. In other regions, a part of the light totally reflected by the exit surface 13 will belong to the light beam group I. Referring to FIG. 1, it can be understood that the former corresponds to the collection of the leaked light 7a and the latter corresponds to the collection of the leaked light 7b.
[0040]
Ray group II: A ray group whose internal incident angle is smaller than the critical angle C but does not belong to the ray group I. A considerable part of these light rays leak from the second surface Tj-1 and enter the first surface Sj of the subsequent projection row Pj. Since the first surface Sj is raised, most of the leaked light is introduced into the subsequent projection row Pj through the first surface Sj.
[0041]
However, as can be understood from the illustrated passing area, it is difficult to internally enter the second surface Tj of the subsequent projection row Pj, so that the light beam group II 'is formed as illustrated. Since the ray group II 'has not experienced a large reorientation, most of it will be totally reflected at the exit surface 13 and again incident on the second surface of another projection row. The internal incident angle at that time can be slightly larger than the internal incident angle on the second surface Tj-1 in consideration of refraction on the second surface Tj-1 and the first surface Sj. As a result, like ray group I, there will be a chance to be redirected.
[0042]
Ray group III: a ray group having an internal incident angle larger than the critical angle C. These light rays are totally reflected by the second surface Tj-1, and are redirected to a light ray group III 'toward the emission surface 13 (see FIG. 2). In this example, the light beam group III 'is output substantially in the front direction.
[0043]
The above is the basic form of the direction changing action with light leakage recovery, but the action can vary depending on the angles α and β and the refractive index n. For example, if the angle β (= 48 degrees) is corrected downward, total reflection on the second surface Tj is difficult to occur. Even in that case, a chance to change the direction by total reflection is given to the subsequent protrusion row Pj + 1.
[0044]
FIG. 4 shows an example of such a situation. Referring to FIG. 4, the cross-sections of three protrusion rows Pj-1, Pj, Pj + 1 that are adjacent to each other and the behavior of light rays are depicted. In FIG. 4, the angle of the first surface is α = 0 degrees, and the angle of the second surface is β = 40 degrees. This value is an example that gives a situation in which collection is performed in cooperation with the three parties.
[0045]
The light ray group IV represents a light ray group in a certain range in which the internal incident angle is sufficiently smaller than the critical angle C (substantially corresponding to the light ray group I described above). Most of these light rays leak from the second surface Tj-1 and enter the first surface Sj of the subsequent projection row Pj. Since the first surface Sj is raised, most of the leaked light is introduced into the subsequent projection row Pj through the first surface Sj. Then, it is incident on the second surface Tj of the subsequent projection row Pj.
[0046]
This internal incidence has a slightly larger internal incidence angle than internal reflection at the second surface Tj-1. However, since the angle β is small, the internal reflection at the second surface Tj is not sufficient to satisfy the total reflection condition. As a result, most of the light rays leak again from the second surface Tj and further enter the first surface Sj + 1 of the subsequent projection row Pj + 1. Since the first surface Sj + 1 stands upright, most of the leaked light is incident on the second surface Tj + 1 of the projection row Pj + 1 via the first surface Sj + 1.
[0047]
This internal incidence has a slightly larger internal incidence angle than internal reflection on the second surface Tj. In this example, as a result, total reflection occurs on the second surface Tj + 1. The light beam group IV 'is output by the direction change accompanying the total reflection. In this example, the light beam group IV 'is output substantially in the front direction.
[0048]
If the second surface Tj + 1 cannot be totally reflected, the light leakage is further relayed to the subsequent projection row Pj + 2... Through such a process, it is expected that a large amount of light leakage is redirected on the second surface of one of the protrusion rows.
[0049]
(2) Other embodiments
The present invention allows various other embodiments that maintain the basic function described in (1) above. Hereinafter, they will be described by way of example.
[0050]
1. Modifications on the shape of the protrusion row
(A) The angle α of the first surface of the projection row in the embodiment shown in FIGS. 2 to 4 is α = 0. However, as shown in FIGS. 5 and 6, the angle α> 0 degrees or α <0 degrees of the first surface S of the projection row P may be used. The shape as shown in FIG. 6 may be advantageous in bringing the incident angle on the first surface S close to vertical. On the other hand, as described above, it may be undesirable from the viewpoint of manufacturing difficulty, mechanical stability, and the like.
[0051]
In contrast, the shape as shown in FIG. 5 is generally easier to manufacture and has higher mechanical strength than the shape as shown in FIG.
[0052]
(B) The tip B of the projection row shown in FIGS. 2 to 4 has a sharp shape. However, as shown in FIG. 7, the tip end portion of the protrusion row P may have a non-sharp shape B ′. By doing so, it is possible to prevent the protrusion row P from being deformed or damaged due to handling after manufacture (assembly, transportation, operation, etc.) and causing adverse effects such as deterioration of characteristics. As indicated by the broken line, it is more preferable to have a roundness.
[0053]
(C) The bases of the protrusion rows shown in FIGS. 2 to 4 are in contact with each other. However, as long as the leakage light collecting performance and the direction changing function are not impaired, as shown in FIG. 8, there may be a small interval between the adjacent protrusion rows Pj-1 and Pj. A large interval may degrade the light leakage collection performance and direction change function.
[0054]
2. Modifications related to the arrangement of protrusions on the light guide element
(A) The light guide element in the embodiment shown in FIGS. 2 to 4 is integrally formed of the same material including the protrusion rows. However, as shown in FIG. 9, the substrate portion 21 and the protrusion row 22 of the light guide element 20 may be made of different materials, for example, polymethyl methacrylate (PMMA) and polycarbonate (PC).
[0055]
(B) As shown in FIG. 10, the light guide element 30 may be configured by being combined with the prism sheet 32 including the substrate portion 31 and the protrusion row 321. An optical adhesive may be used for bonding. In that case, the material of each part is as follows, for example.
[0056]
The substrate part 31 of the light guide element 30 = polymethyl methacrylate (PMMA / refractive index n = 1.49)
Substrate portion of prism sheet 32 = polyethylene terephthalate (PET film / refractive index n = 1.52)
Projection row of prism sheet 32 = polymethyl methacrylate (PMMA / refractive index n = 1.49)
Adhesive layer between substrate portion 31 of light guide element 30 and substrate portion of prism sheet 32
= Epoxy adhesive / refractive index n = 1.55)
In this way, some refraction and reflection occur at the interface of each layer. Therefore, it is preferable that the difference in refractive index is small as in the above material example. Needless to say, even if some refraction and reflection occur, the basic action (leakage light collection and direction change) described with reference to FIGS. 3 and 4 is not lost.
[0057]
3. Modification of the light scattering element's internal scattering ability
One or both of the substrate portion of the light guide element, the protrusion row, or both may have internal scattering ability. For example, a well-known so-called light scattering light guide may be employed as the material of the light guide element. However, if the internal scattering ability is too strong, the degree of contribution to the change in direction of the basic action of the present invention is reduced. In general, it is preferable to impart weak internal scattering ability.
[0058]
4). Modification of the cross-sectional shape (thickness distribution) of the light guide element
The light guide element 10 shown in FIGS. 2 to 4 has a thin wedge-shaped cross section (excluding protrusion rows). In general, this is advantageous in obtaining uniform brightness across the exit surface. However, a uniform-thickness light guide element having a rectangular (excluding protrusion rows) cross section may be employed.
[0063]
  Here, the protrusion row formed on the exit surface of the light guide element will be described with reference to FIG.FIG.1As shown in FIG. 5, the light guide element 10 itself has a large number of protrusion rows Q on the exit surface for correcting the output directivity.The theseProtrusion row QIsExtends almost perpendicular to the incident end face. Therefore,The output directivity is corrected with respect to the plane parallel to the incident end face. For example, preferential transmission in the front direction can be performed in a plane parallel to the incident end face.
[0064]
  Note that FIG.As shown in FIG. 4, a sheet-like light diffusion member 70 may be disposed on the light exit surface side of the light guide element 10. The light diffusing member 70 reduces the sharpness of the emission directivity of the light source device and prevents a minute periodic structure such as the protrusion row P from being noticeable.
[0065]
  Also,Primary light source is rod-shaped light source (fluorescent lamp) LInstead ofOther types of primary light sources may be employed. For example, FIG.3As shown in FIG. 4, a light source using an LED stack having a linear array of light emitting diode arrays may be employed.
[0066]
  publicAs with many known light source-based light source devices, one typical application of the light source device according to the present invention is a backlight type liquid crystal display. However, the light source device according to the present invention is also applicable to a front light type liquid crystal display. FIG.4The cross-sectional view shows the basic arrangement and the typical optical path.
[0067]
  FIG.4, The light guide element 10 of the light source device used for front lighting is arranged on the front surface (observation surface side) of the liquid crystal panel LCDP. The liquid crystal panel LCDP includes a light diffusion sheet, a polarizing plate, a glass substrate (equipped with a transparent electrode), a color filter, a liquid crystal cell, and the like, and a reflector RS is disposed on the back side. The reflector RS may be mounted in the liquid crystal panel LCD.
[0068]
Light from the primary light source L (represented by an arrow optical path) is introduced into the light guide element 10. When propagating light is input to the projection row, it is emitted substantially perpendicularly from the exit surface 13 through leakage, refraction, internal reflection, and the like, and enters the liquid crystal panel LCDP by the above-described action.
[0069]
This light is reflected by the reflector RS through a light diffusion sheet, a polarizing plate, a glass substrate (equipped with a transparent electrode), a color filter, a liquid crystal cell, and the like in the liquid crystal panel LCDP. The reflected light reaches the polarizing plate (observation side) again through the liquid crystal cell, the color filter, and the glass substrate. As is well known, transmission / cutoff of the polarizing plate is determined depending on ON / OFF (polarization state) of the electrode of the corresponding pixel. If transmission is allowed, the light is emitted to the outside as display light through the light guide element 10 and reaches the eyes of the observer OB. The display light encounters the protrusion P and causes some refraction. Therefore, the brightest observation is performed from a direction slightly inclined from the direction of the direction as shown in the figure.
[0070]
【The invention's effect】
  As described above, according to the present invention, efficient direction change with little light energy loss is performed inside the light guide element based on leakage light collection and direction change by the projection row formed on the back surface of the light guide element. It is. The direction characteristic of the output light can be adjusted by the angle of the first surface and the second surface of the projection row.In particular, the output directivity characteristic in the plane parallel to the incident end face is realized by a projection row formed on the exit surface of the light guide element.Combination with additional arrangement of the light diffusing sheet and directional characteristic correction means such as formation of protrusions on the exit surface of the light guide element is also possible. Further, it can be applied not only to a backlight type liquid crystal display but also to a front light type liquid crystal display.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a conventional technique.
[Figure 2]BookFIG. 4 is a sketch representing an outline of an arrangement according to a basic embodiment of the invention(However, the projection rows formed on the light exit surface of the light guide element are not shown).
FIG. 3 is a diagram for explaining direction change and light leakage recovery by a protrusion row;
FIG. 4 is a diagram for describing direction change and leakage light collection related to a plurality of subsequent protrusion rows.
FIG. 5 is a cross-sectional view showing a case where the angle α of the first surface of the protrusion row is α> 0 degrees.
FIG. 6 is a cross-sectional view showing a case where the angle α of the first surface of the protrusion row is α <0 degrees.
FIG. 7 is a cross-sectional view illustrating an example in which the tip end portion of the protrusion row P has a non-sharp shape.
FIG. 8 is a cross-sectional view illustrating an example in which there is a small gap between adjacent protrusion rows.
FIG. 9 is a cross-sectional view illustrating an example in which the substrate portion of the light guide element and the protrusion row are made of different materials(However, the projection rows formed on the light exit surface of the light guide element are not shown).
FIG. 10 is a cross-sectional view illustrating a light guide element in which a prism sheet is coupled to the back surface of a substrate.(However, the projection rows formed on the light exit surface of the light guide element are not shown).
FIG. 11 Light guide elementA number of protrusion rows for correcting the output directivity characteristic that itself has on its exit surfaceA sketch to explain about.
FIG. 12 shows light on the exit surface side of the light guide element.Example of diffusing memberA sketch to explain about.
FIG. 13LED stack was used as the primary light sourceA floor plan explaining an example.
FIG. 14The light source device according to the present invention is applied to a front light type liquid crystal display.Sectional drawing explaining an example.
[Explanation of symbols]
  1, 10, 20, 30 Light guide element
  2, 12 Incident end face
  3, 13 Output surface (one major surface)
  4, 14 Back (the other major surface)
  5a-5b Internal reflection slope
  6a-6b Illumination light
  7a, 7b Leakage light
  8 Reflector
  9 External reflective surface
  15 End face
  21, 31  Light guide element substrate
  P,Q  ProtrusionColumn
70 Light diffusion member
  L Primary light source (fluorescent lamp)
  LCDP LCD panel
  LS Primary light source (LED array)

Claims (8)

A light guide element having a major surface providing an exit surface and a back surface for light emission, and an incident end surface for light introduction;
On the back side, a plurality of projection rows P1, P2, P3,...
Each projection row Pi (i = 1, 2, 3...) Extends substantially parallel to the incident end face, and is relatively close to the incident end face, and is separated from the first face Si and the incident end face. A relatively far and inclined second surface Ti with respect to
The second surface Ti has an internal reflection function for generating light traveling toward the emission surface and a leakage function for generating leakage light from the projection row Pi.
The projection row Pj (j = 2, 3,...) Collects the leaked light from the second surface Tj-1 of the preceding projection row Pj-1 through the first surface Sj, and internally enters the second surface Tj. Arranged to work together in a chain to make it incident ,
The light emitting element, wherein the output surface includes a plurality of protrusion rows for correcting output directivity characteristics, and the protrusion rows extend substantially perpendicular to the incident end face .   2. The light guide element according to claim 1, wherein each projection row Pi (i = 1, 2, 3...) Includes a tip portion having a non-sharp cross-sectional shape.   The sheet-like member combined with the light-guide plate and the said light-guide plate is provided, The said sheet-like member is equipped with the said many protrusion row | line | columns P1, P2, P3 .... Light guide element. A light source device including a primary light source and an optical element for converting the light supplied from the primary light source into a redirected illumination light;
The optical element includes a major surface that provides an emission surface and a back surface for light emission, and an incident end surface for light introduction,
On the back side, a plurality of projection rows P1, P2, P3,...
Each projection row Pi (i = 1, 2, 3...) Extends substantially parallel to the incident end face, and is relatively close to the incident end face, and is separated from the first face Si and the incident end face. A relatively far and inclined second surface Ti with respect to
The second surface Ti has an internal reflection function for generating light traveling toward the emission surface and a leakage function for generating leakage light from the projection row Pi.
The projection row Pj (j = 2, 3,...) Collects the leaked light from the second surface Tj-1 of the preceding projection row Pj-1 through the first surface Sj, and internally enters the second surface Tj. Arranged to work together in a chain to make it incident,
The light source device , wherein the exit surface includes a plurality of protrusion rows for correcting output directivity characteristics, and the protrusion rows extend substantially perpendicular to the incident end face . 5. The light source device according to claim 4, wherein each projection row Pi (i = 1, 2, 3...) Includes a tip portion having a non-sharp cross-sectional shape. Light guide plate and comprises a sheet-like member coupled to the light guide plate, said sheet-like member is provided with the plurality of projection rows P1, P2, P3 · · · · ·, claim 4 or claim 5 light source device. When the angles of inclination of the first surface Si and the second surface Ti with respect to the vertical surface perpendicular to the extending surface on which the exit surface rides are α and β, 0 degrees ≦ α ≦ 10 degrees and 30 The light guide element according to claim 1 , wherein degree ≦ β ≦ 60 degrees . When the inclination angles of the first surface Si and the second surface Ti with respect to the vertical surface perpendicular to the extending surface on which the exit surface rides are α and β, respectively, 0 degree ≦ α ≦ 10 degrees and 30 The light source device according to claim 4 , wherein degree ≦ β ≦ 60 degrees .

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