JP4669799B2 - Edge input type backlight - Google Patents

Description

  The present invention relates to a liquid crystal display device, and more particularly to a backlight that illuminates a liquid crystal panel from the back side.

  Thin and light liquid crystal display devices capable of displaying images have rapidly spread due to price reduction and development of high image quality technology due to progress in manufacturing technology, and are widely used in monitors for personal computers and TV receivers. As the liquid crystal display device, a transmissive liquid crystal display device is generally used. The transmissive liquid crystal display device includes a planar light source called a backlight, and spatially modulates illumination light emitted from the backlight by a liquid crystal panel to form and display an image. As the backlight, a system using a cold cathode tube which is a substantially linear light source and entering from a side surface of a thin light guide plate is often used.

  A backlight using the above-described cold cathode ray tube will be described with reference to FIG. FIG. 10A shows a state in which the backlight BLc is viewed from the exit surface side. FIG. 10B shows a cross section of the backlight BLc with respect to the straight line VIIb-VIIb in FIG. The backlight BLc includes a light guide plate 110 and a cold cathode ray tube 120.

  As shown in FIG. 10B, the cold cathode ray tube 120 is covered with a reflector 130 having a substantially U-shaped cross section. The open end of the reflector 130 is connected to one end of the light guide plate 110. In FIG. 10A, the reflector 130 is not displayed for the sake of visibility.

  The light emitted from the cold cathode ray tube 120 enters the light guide plate 110 from the incident surface 111 of the light guide plate 110. Then, the light propagates while repeating total reflection between the opposing main surfaces of the light guide plate 110. On the surface of the reflection surface 113 which is the surface opposite to the emission surface 112, a diffuse reflection layer or reflection unevenness having a specific density distribution and size is formed so that a part of the propagating light is emitted.

  By appropriately setting the density distribution and the size distribution for forming the diffuse reflection layer or the reflection irregularities, it is possible to perform almost uniform illumination over the entire surface of the liquid crystal panel. By providing the reflective sheet 140 on the reflective surface 113 side of the light guide plate 110, a part of the light leaking from the reflective surface 113 to the outside of the light guide plate 110 is reflected toward the light guide plate 110 to prevent light loss. .

  In addition, in order to control the directivity of light emitted from the backlight BLc and illuminate the liquid crystal panel with desired light distribution characteristics, a diffusion film, a prism sheet, or the like is generally provided on the light emission surface 112 side of the light guide plate 110. The optical film 150 is installed. In addition, a reflector 130 that surrounds the cold cathode ray tube 120 and opens toward the incident surface 111 of the light guide plate 110 is provided. Thereby, the light emitted from the cold cathode ray tube can be guided to the light guide plate without any excess.

  Furthermore, recently, a light emitting diode (hereinafter referred to as “LED”) having high luminous efficiency has been developed, and it has been proposed to use it as a light source for a liquid crystal backlight. As a method for obtaining planar light emission that can be used as a backlight from an LED that is a point light source, a method in which a large number of LEDs are arranged on the end face of a light guide plate and light is directly input is common.

  With reference to FIG. 11, a method using a side emitter type LED light emitting element, which is one of the methods for obtaining planar light emission by the plurality of LEDs described above, will be described. In the side emitter type, the light emitting element itself is provided with a box-shaped reflecting member. 11A shows a partial cross section of the main part centering on the light source part, and FIG. 11B shows a state in which the light source part is observed from the incident surface 211 of the light guide plate 210.

  The LED chip 221 is bonded on the element substrate 222, the reflection member 223 is provided around the LED chip 221, and further sealed with a transparent resin sealing resin portion 224. Then, the connection electrode 225 is provided, and the side emitter type LED element 220 is configured. A plurality of LED elements 220 are arranged and connected on the flexible substrate 270 to constitute a light source unit.

  Then, the light source unit is fixed on the resin frame 260 so that the openings of the plurality of side emitter LED elements 220 face each other close to the incident surface of the light guide plate 210. In FIG. 11B, the transparent sealing resin portion 224 shown in FIG. 11A is omitted. With this configuration, the light emitted from the light source unit can be guided to the light guide plate 210 while being stably held at a predetermined position facing the light guide plate 210.

  Furthermore, a method of obtaining planar light emission using an LED array module in which a plurality of LED chips are linearly arranged on one substrate and sealed is also proposed (for example, Patent Document 1). Such a method will be described with reference to FIG. Unlike the method shown in FIGS. 10 and 11, this method is configured as an LED array module in which a plurality of LED chips are sealed in a linear array on a single substrate (for example, Patent Documents). 1) FIG. 12A shows a partial cross section of the main part centering on the light source part, and FIG. 12B shows a state where the light source part is observed from the incident surface 311 of the light guide plate 310. FIG.

  The LED array module 320 is configured by linearly arranging a plurality of LED chips 321 on an array module substrate 322 and sealing them with a sealing resin portion 324 made of a transparent resin. As described above, the LED array module 320 can be efficiently produced by arranging and sealing the LED chips 321 in a matrix on one large array module substrate (322) and then cutting the LED chips. Moreover, by using a wiring board as the array module substrate 322, a plurality of LED chips 321 in the LED array module 320 can be connected internally, and the number of connection points can be reduced.

  The cross section of the sealing resin portion 324 of the LED array module 320 configured as described above is rectangular. As a result, the sealing resin portion 324 becomes a light emitting portion capable of emitting light not only from the surface facing the array module substrate 322 but also from the side surface portion adjacent thereto. Then, the reflective film 330 is provided on the side surfaces of the sealing resin portion 324 and the array module substrate 322. Thereby, it is possible to prevent light from leaking from the side surface portion of the LED array module 320 to a portion other than the incident surface 311 of the light guide plate 310 and to effectively use the light.

When this LED array module 320 is used, significant effects such as reduction in manufacturing cost and simplification of wiring can be expected as compared with the case of using LED light emitting elements in which LED chips are individually sealed.
JP 2004-235139 A

  Light cannot be effectively used in a structure that obtains planar light emission using an LED array module in which a plurality of conventional LED chips described with reference to FIG. 12 are linearly arranged on one substrate and sealed. The inventors of the present invention have found. With reference to FIG. 13, the reason why light cannot be effectively used in the conventional structure will be described.

  First, FIG. 13 shows a cross section of the LED array module 320 as in FIG. 12, except that light leaking from the side surface of the LED array module 320 is returned to the inside of the sealing resin portion 324 by the reflective film 330. A broken line is shown in the locus. The light leaked to the outside from the side surface of the LED array module 320 is reflected by the reflective film 330 and re-enters the sealing resin portion 324, and then the surface Po (hereinafter referred to as “the surface of the sealing resin portion 324” facing the module substrate 322). This is called the “module board facing surface”. And since light is totally reflected by the said surface, it cannot be radiate | emitted outside toward the entrance plane 311 of the light-guide plate 310. FIG.

  Generally, epoxy, silicon or the like which is transparent and has excellent heat resistance and weather resistance is used for sealing an LED, but its refractive index is about 1.5. In this case, the critical angle at the interface between the air and the sealing member (module substrate facing surface Po) is about 42 °, and light incident on one of the orthogonal surfaces from the air side is always totally reflected by the other surface. . Incident light from the air side cannot be 42 ° or more from the normal direction of the incident surface in the sealing member. Therefore, the fact that the light cannot enter at an angle of 48 ° or less from the normal line of the interface is apparent from the light guide plate mechanism in which light incident from the side surface of the parallel plate propagates while repeating total reflection.

  The light L totally reflected by the module substrate facing surface Po of the sealing resin portion 324 returns to the LED chip 321 or the module substrate 322 along a locus as indicated by a broken line. A part of the light L reaching the module substrate 322 is reflected and travels in the direction of the module substrate facing surface Po, but is absorbed by the electrode material or the resist material to generate a component that causes a loss.

  Thus, in the method of simply disposing the reflective film 330 on the side surface portion of the LED array module 320, it is possible to completely prevent the light from being emitted from the illumination invalid portion. However, the light reflected by the reflective film 330 is not necessarily effectively emitted from the facing surface of the module substrate.

Furthermore, as shown in FIG. 12, the LED chips 321 that are light emitters are provided in a scattered manner, so that the portion facing the LED chip 321 is bright in the vicinity of the incident surface 311 of the light guide plate 310, and the intermediate portion thereof is A dark and light distribution is likely to occur, and a portion where the light and dark are remarkable cannot be used as an effective surface.
In consideration of the above problems, the present invention realizes a backlight with high light utilization efficiency by suppressing the generation of illumination invalid areas in the light guide plate as much as possible while using a plurality of LEDs as point light sources. An object is to provide a display device.

The present invention provides a light emitting element array module in which a plurality of light emitting elements are arranged on an array module substrate and the light emitting elements are sealed with a transparent material to form a light emitting portion, and a plurality of the light emitting element array modules are arranged. A wiring board disposed on the wiring board, a pressing member provided in the lateral direction of the light emitting element array module on the wiring board in the vicinity of the light emitting part of the light emitting element array module, and a light emitting part of the light emitting element array module A light guide plate that has a light incident surface on which the light from the light is incident on the side surface portion and that emits light introduced from the light incident surface from one of the two light emitting surfaces facing each other to perform planar illumination; and A reflective sheet that faces the light-exiting surface facing the light-exiting surface of the light plate and reflects light leaking from the counter-exiting surface in the direction of the light-exiting surface; At least two reflecting surfaces provided so as to surround a space between the incident surface of the light guide plate, and a width in a direction perpendicular to the arrangement direction of the light emitting portions of the light emitting element array module is incident on the light guide plate The reflection surface provided between the light emitting portion of the light emitting element array module and the incident surface of the light guide plate is spaced from the light emitting element array module toward the light guide plate. The reflection sheet is configured to be large, and one end of the reflection sheet protrudes from the incident surface of the light guide plate toward the light emitting element array module, and the protrusion is a light emitting part of the light emitting element array module. It arrange | positions so that it may exist between and the said pressing member .

  In the present invention, the light emitted from the side surface of the light emitting element array module can also be used effectively, and the light use efficiency of the ineffective region having a small uniformity from the vicinity of the incident surface of the light guide plate is not reduced without impairing the light use efficiency. High backlight can be realized.

(First embodiment)
The edge input type backlight according to the first embodiment of the present invention will be described below with reference to FIGS. 1, 2, 3, 4, 5, 6, and 7. Incidentally, FIG. 1 shows a configuration of a light source unit which definitive to edge input type backlight, FIG. 2 shows an essential part of the light guide portion Pog, 3 was formed by combining the light source unit Pos and the light guide portion Pog It shows a state.

In FIG. 1 (a), represents a top view of a light source unit Pos 1 used in such edge input type backlight in this embodiment from the light guide plate, IB shown in FIG. 1 (a) in FIG. 1 (b) -IB cross section is shown. As shown in FIG. 1 (a), are connected and disposed to so that a plurality of LED chips 421 are arranged on an elongated rectangular array module substrate 422, by sealing with a transparent sealing resin portion 424, LED An array module 420 is formed. Then, a plurality of LED array modules 420 are arranged on the wiring board 430 to be substantially linear. Then, the side surface direction before Symbol LED array module 420 on the wiring board 430 (parallel to the direction in which an array of LED array module 420) is pressing member 440 close to the light emitting portion of the LED array module 420 is provided Yes .

As shown in FIGS . 2 and 3 , in the light guide portion Pog, a reflection sheet 450, a light guide plate 410, a prism sheet 460, and a diffusion sheet 470 are sequentially stacked on a frame 480. The reflection sheet 450 is made of a white PET (polyethylene terephthalate) resin sheet, and is formed so that one end of the reflection sheet 450 protrudes from the incident surface 411 of the light guide plate 410 toward the LED array module 420 , and the protrusion Pexb is the LED array. The module 420 is disposed so as to exist between the light emitting portion of the module 420 and the pressing member 440. Further, in the protruding portion Pexb of the reflection sheet 450, a mirror reflection sheet 451 on which silver is vapor-deposited is pasted on the surface facing the light guide plate 410 to form a mirror reflection layer 461b.

  The prism sheet 460 has a transparent PET sheet as a base material, and a fine prism array is formed on one surface of the prism sheet 460 using an ultraviolet curable resin or the like. Then, by installing the prism sheet 460 so that the prism surface is located on the side opposite to the light guide plate 410, the light leaking in a scattered manner from the side surface of the light guide plate 410 is condensed in the front direction and the front direction. The effect of brightening is obtained.

The prism sheet 460 is formed so that one side protrudes from the incident surface 411 of the light guide plate 410 to the LED array module 420 side as in the case of the reflection sheet 450, and the protruding portion Pext is emitted from the LED array module 420. It arrange | positions so that it may exist between a part and the said pressing member 440. FIG. A specular reflection sheet 451 is bonded to the surface of the protrusion Pext facing the light guide plate 410, that is, the surface where the prism is not formed, so that a specular reflection layer 461t is formed. The specular reflection sheet 451 may be a silver vapor deposition film.

As shown in FIG. 3, a combination of light guide portion Pog shown in the light source unit Pos 1 and 2 shown in FIG. 1, the edge input type backlight is configured. Specifically, the reflection sheet 450 of the light guide part Pog and the protrusions Pexb and Pext of the prism sheet 460 are inserted between the LED array module 420 and the pressing member 440 to fix the wiring board 430 to the frame 480.

Note that when the LED array module 420 is brought into close contact with the incident surface 411 of the light guide plate 410, light and darkness occurs in which the portion corresponding to the LED chip 421 is bright and the middle portion is dark, and the vicinity of the incident surface 411 of the light guide plate 410 is in the effective region. It can be considered that it cannot be used. In order to prevent or reduce such a situation, in the present invention, an appropriate gap d is set between the two. Assuming that the gap d is the distance between the incident surface 411 of the light guide plate 410 and the exit surface of the sealing resin portion 424 of the LED array module 420, the appropriate gap d depends on the arrangement interval p of the LED chips and the arrangement interval is 0. About 2 to 0.8 times is desirable.

The thickness of the light guide plate 410 and have set larger than the width of the LED array module 420, the distance between the specular reflection layer 461b and 461t surround the entrance surface 411 and the LED array module 420 of the light guide plate 410 is an LED array module 420 side To the incident surface 411 of the light guide plate 410.

Hereinafter, the reason for providing a gap d of the above-described reason for setting the specular reflection layer 461b and 461t to open toward the both spacing When mirror reflection layer on the light guide plate 410 side. The reason why the gap d is provided between the LED array module 420 and the incident surface 411 of the light guide plate 410 is that illumination spots occur on the incident surface 411 of the light guide plate 410 due to the LED chips 421 being scattered. This is to ease it.

  With reference to FIG. 4, it is effective to provide a gap d between the LED array module 420 and the incident surface 411 of the light guide plate 410, and how much gap d is effective. I will explain it. FIG. 4 shows a simple illumination model with four point light sources K1, K2, K3 and K4, each having the same luminous intensity, arranged at a predetermined interval p. Note that the point light sources K1 to K4 are collectively referred to as a point light source K.

  A straight line l2 imagining the light incident surface of the light guide plate is set at a position away from the straight line l1 connecting the point light sources K1, K2, K3, and K4 by the distance d, and the illuminance at the point M on the straight line l2 is calculated. As described above, the distance d is used as a parameter representing the air gap. In an actual light source arrangement, it is common to use more than four light sources, but since it is assumed that d / p is relatively small, the influence at the point M of the light source far from the calculation point is small, and this is ignored. It is enough to get a quantitative outlook.

  The point M is located at a distance of x from the point that opposes the second point light source K2 (more precisely, the intersection C2 of the straight line Lr and the straight line L2 that passes through the point light source K2 and is perpendicular to the straight line 11). The illuminance is displayed as a function of x. The illuminance S at the point M is calculated as the sum of the illuminances at the points M of the point light sources K1 to K4. The illuminance at the point M of the point light sources K1 to K4 depends on the distance between the point light sources K1 to K4 and the point M formed by the light trace and the angle θ formed between the point M and the normal to the line l2. In addition, this angle (theta) is called the desired angle which looked at the point M from each of the point light sources K1-K4.

  In general, the illuminance of the surface illuminated by the point light source decreases in inverse proportion to the square of the distance from the point light source. However, in this case, as shown in FIG. 3, it is assumed that propagation in one direction is constrained by the reflection sheet 450, and thus is inversely proportional to the first power of the distance. The distance can be expressed as d / Cos (θ) by the angle θ. Therefore, the distance factor is proportional to Cos (θ) / d. This relationship is applied to the surface on which the illumination light is perpendicularly incident.

Since the surface along the straight line 12 is illuminated with an inclination of the angle θ, the illuminance thereof is Cos (θ) times the illuminance in the case of normal incidence (the illumination amount is constant and the illumination area is 1 / cos (θ ) Doubled). As a result, the illuminance from the point light source with the desired angle θ is proportional to cos (θ) ^ 2 / d.
The distance can be expressed as d / Cos (θ) by the above θ. Accordingly, the illuminance is proportional to cos (θ) with respect to the distance factor, and the illuminance is proportional to the square of Cos (θ).

Accordingly, the illuminances S1, S2, S3, and S4 at point M by the point light sources K1, K2, K3, and K4 are respectively expressed by the following equations where the desired angles from the angular light source are θ1 to θ4 and the proportional multiplier is A: Expressed by (1), (2), (3), and (4).
S1 = A · Cos (θ1) ^ 2 / d (1)
S2 = A · Cos (θ2) ^ 2 / d (2)
S3 = A · Cos (θ3) ^ 2 / d (3)
S4 = A · Cos (θ4) ^ 2 / d (4)

Desired angles θ1 to θ4 from the point light sources K1 to K4 are expressed by the following equations (5), (6), (7), and (8), respectively.
θ1 = atan {(p + x) / d} (5)
θ2 = atan (x / d) (6)
θ3 = atan {(p−x) / d} (7)
θ4 = atan {(2p−x) / d} (8)

  Desired angles θ1 to θ4 are calculated using the above equations (5) to (6) based on the values of the distance x and the interval p, and the above equations (1) to (4) are calculated based on the calculated values of θ1 to θ4. The illuminances S1 to S4 are obtained using, and the sum is taken to obtain the illuminance at the point M.

  FIG. 5 shows the illuminance calculated by changing the interval d in the range of 0.1 to 1 time the interval p of the point light source K and changing the calculation point M from x = 0 to x = p in each state. Show the distribution. In FIG. 5, the horizontal axis is a value obtained by dividing the previously defined distance x by the interval p and indicates the illuminance calculation position, and the vertical axis is the relative illuminance normalized based on the maximum illuminance at each setting of the gap d. The state of illumination spots is shown as the illuminance distribution.

  From FIG. 5, the maximum illuminance is shown at the point of x / p = 0 and x / p = 1 facing the point light source K, and the minimum illuminance is shown at x / p = 0.5 which is an intermediate part thereof. Can be seen. This tendency is (naturally) larger as the distance d between the point light source K and the incident surface is smaller (d / p is smaller) than the arrangement interval p of the point light sources K, and the distance d is larger than the distance p. As the distance d becomes equal to the distance d (d / p = 1), it becomes almost completely uniform.

FIG. 6 shows a graph displaying the illuminance ratio as a function of d / p. In FIG. 6, the horizontal axis indicates a value obtained by dividing the distance d between the straight line 11 formed by the point light source K and the setting surface by the arrangement interval p of the point light sources K. The vertical axis represents the illuminance ratio in the light source setting = maximum illuminance / minimum illuminance, and represents the size of the illumination spots. When d / p is 0.1, the illuminance ratio is as extremely large as about 12 times. However, the d / p = 0.2 3.5 times, both illumination ratio when twice and d / p is increased at 0.3 drops sharply.

  Visual evaluation was also performed using an actual LED light source and light guide plate. The result confirms a remarkable effect when d / p is less than 3.5 when the illuminance ratio is 3.5 times or less, and if the illuminance ratio is greater than 0.3, it becomes a level that can hardly be recognized as a light / dark pattern. Was confirmed.

  Based on the above calculation results and visual evaluation results, it can be seen that it is effective to set d / p to 0.2 or more in order to reduce illumination spots. Also, since d / p is 0.8 and the illuminance ratio is almost 1 and the illumination spots are eliminated, setting the distance d to a value larger than that has no effect and creates an invalid space. become. Therefore, d / p is desirably 0.8 or less.

Next, with reference to FIG. 7, the specular reflection layer 461b and 461t surround the entrance surface 411 and the LED array module 420 of the light guide plate 410 together when the specular reflection layer, open towards the gap in the light guide plate 410 as The reason for setting to is explained. An experiment was conducted using an LED array module 420 in which three 0.3 mm square LED chips 421 were arranged at 10 mm intervals on a 1 mm × 30 mm long module substrate 422 and sealed with a transparent resin 424.

Specifically, the LED array module 420 is installed at a distance d from the incident surface 411 of the light guide plate 410 having a thickness of 2 mm, and two spaces between the LED array module 420 and the incident surface 411 of the light guide plate 410 are provided. The specular reflection sheet 451 is used. In this state, the LED array module 420 was energized to cause the LED chip 421 to emit light, and the total amount of light emitted from the exit surface 411 of the light guide plate 410 was measured.

Although the value obtained by dividing the total luminous flux emitted from the light guide plate 410 by the total luminous flux of the light generated by the LED array module 420 is considered to be the optical coupling efficiency in this light guiding state, the driving condition of the LED array module 420 is constant. The total luminous flux of light generated from the LED array module 420 is constant. Therefore, the total luminous flux emitted from the light guide plate 410 is proportional to the optical coupling efficiency.

  Two types of reflection sheets were prepared: a white PET sheet having diffuse reflection characteristics and a silver vapor deposition sheet having specular reflection characteristics. In addition, as shown in the upper right of FIG. 7, two reflective sheets are set in parallel along the side surface portion of the LED array module 420, and as shown in the lower right of FIG. 7, the two reflective sheets Was compared with the case where the distance was gradually increased from the LED array module having a width of 1 mm toward the incident surface of the light guide plate having a thickness of 2 mm.

  At the same time that the total luminous flux was measured, the light and dark spots of the light emitted from the vicinity of the incident end of the light guide plate were observed. As a result, the occurrence of light and dark spots hardly depends on the difference in the material of the reflection sheet and the difference in setting method, and is greatly influenced by the distance d. In either case, the light guide plate 410 and the LED array module 420 are brought into close contact with each other. As a result, remarkable light and dark spots were generated. The distance d was remarkably relaxed at 2 mm or more, which is 0.2 times the arrangement interval P of the LED chips 421 = 10 mm, and was almost eliminated at 3 mm or more.

  The graph on the left side of FIG. 7 shows the results of measuring the total emitted light flux under each condition. In the graph, the horizontal axis represents the distance d between the LED array module 420 and the incident surface 411 of the light guide plate 410, the vertical axis represents the total measured luminous flux under each condition, and the silver vapor deposition sheet (specular reflection sheet 451) represents the LED array module 420. And the value obtained by dividing the surface of the array module and the incident surface 411 of the light guide plate 410 by the total luminous flux in the contact state (d = 0). Represents the effective coupling efficiency.

When two white PET sheets similar to the reflection sheet 450 of the light guide plate 410 are used as the reflection sheets, and the distance d is changed in a state where they are set to be parallel to each other, the distance d increases rapidly. Coupling efficiency decreased. Specifically, when the distance d is 3 mm, the coupling efficiency is about 0.6 times that of the close contact state (dotted line of rhombus marks in the graph). This is presumed to be due to the occurrence of a component that returns to the incident light source side without going to the light guide plate side when the light emitted from the LED array module 420 is reflected by the reflection sheet.

  When a specular reflective silver vapor-deposited sheet is used as the reflection sheet, the reduction in coupling efficiency is slight even if the distance d is increased. For example, the relative light intensity of 90% or more can be maintained even if the distance d is set to 3 mm so as to substantially eliminate bright and dark spots (broken lines indicated by triangular marks in the graph). The cause of this is thought to be because the above-mentioned component of the return light is reduced by the mirror reflection.

  Further, using a mirror-reflecting silver vapor-deposited sheet, as shown in the lower right of FIG. 7, the interval between the reflective sheets gradually increases from the LED array module 420 side to the incident surface 411 side of the light guide plate 410. When set to, the coupling efficiency in the close contact state (d = 0) was improved by about 4% as compared with the case where the silver vapor deposition sheet was arranged along the side surface. This is considered to be because the regression absorption phenomenon of the side emission component shown in FIG.

  Further, by installing the reflection sheet so as to open toward the light guide plate 410 in this way, the reduction in the coupling efficiency with respect to the distance d is further reduced, and even if the distance is set to 3 mm so as to almost eliminate the bright and dark spots. Although it was possible to maintain a coupling efficiency equivalent to that of a simple installation, it was confirmed. The cause is that the light is emitted from the LED array module 420 and reflected by the reflective layer because it is surrounded by two specular reflective layers that gradually open from the LED array module 420 toward the light guide plate. Since the angle approaches the normal direction of the incident surface 411 of the light plate 410, even if the distance between the light guide plate 410 and the LED array module 420 is increased, the light can be efficiently incident on the light guide plate without generating return light. This is thought to be possible.

As described above, in the present embodiment, since an appropriate interval is provided between the incident surface 411 of the light guide plate 410 and the LED array module 420, uniform light emission is possible from the vicinity of the light guide plate incident end, and since the reflective layer surrounding the incident surface and the LED array module 420 of the light guide plate 410 when the specular reflection layer are both set to open the gap in the light guide plate 410 side can maintain high coupling efficiency.

  In addition, as the reflective sheet to be installed on the back surface of the light guide plate, a diffuse reflective white PET sheet which is lower in price than a specular reflective silver deposited sheet and can be expected to reduce spots by diffuse reflection is often used. Although a white PET sheet is used in the form, the present invention is not limited to this, and a specular reflective sheet may be used. In this case, it is not necessary to form a specular reflection layer again on the reflection sheet, and the reflection sheet may be simply extended.

In the edge input type backlight BLE1 according to the first embodiment described above, the distance between the reflection layer (specular reflection sheet 451) surrounding the incident surface 411 of the light guide plate 410 and the LED array module 420 is set as the light guide plate 410. It is set to open as it approaches. Therefore, the distance between the two specular reflection sheet 451 of the light guide plate 410 side, both when regulated by the thickness of the light guide plate 410 itself by the member extending from the light guide plate 410 side providing the reflective layer, LED array module 420 side Then, a reflection sheet (specular reflection sheet 451) is inserted between the pressing member 440 provided on the wiring board and the side surface portion of the LED array module 420. However, this invention is not limited to this, For example, a structure as shown in FIG. 8 may be sufficient.

Hereinafter, an edge input type backlight according to a second embodiment of the present invention will be described with reference to FIG. 8 (a) is in the same manner as described above FIG. 1 (a), depicts a top view of a light source unit Pos2 used in such edge input type backlight in this embodiment from the light guide plate side. FIG. 8B shows a VB-VB cross section in FIG.

A slit 590 is provided near the side surface of the LED array module 520 of the wiring board 530 of the light source unit Pos2. On the other hand, both the light guide unit Pog2 Figure 7 and is projected to the reflective sheet 550 and the prism sheet 560 from the light guide plate 510 as well, providing a specular reflection layer 561b and 561t into its protruding portion, the each cutting edge portion light source Convex portions Phb and Pht corresponding to the slits 590 of the portion Pos2 are formed.

  If comprised in this way, the sealing resin part 524 used as the light-projection part of the LED array module 520 will be completely enclosed by the two specular reflection layers 561b and 561t, and from the light source Pos2 side toward the light guide plate Pog2 side It is possible to maintain a stable state in which the interval gradually increases.

Oite the first embodiment and the second edge input type backlight according to the embodiment of the embodiment of the present invention described above, to form a specular reflective layer to extend the optical sheet. This means that a new member is not required for light guide from the light source part to the light guide plate, and the opening of the light guide part surrounded by the reflective layer can be completely and automatically matched with the light guide plate incident surface. Although there is an advantage, the present invention is not limited to this. For example, as shown in FIG. 9, a reflection sheet having a specular reflection layer may be provided so as to extend from the back surface of the wiring substrate of the light source unit.

Next, with reference to FIG. 9, a description will be given to the edge input type backlight according to a third embodiment of the present invention. Edge input type backlight according to the present embodiment, Oite the edge input type backlight shown in FIG. 3, the pressing member 440 located on the light emitting surface side of the light guide plate 410, extending from the back surface of the wiring board 430 This is shared by the specular reflection plate 670. A specular reflection surface 671 is provided on the surface of the specular reflection plate 670 facing the LED chip 421.

Oite according to edge input type backlight in this embodiment, it is provided with appropriate intervals between the entrance surface 411 and the LED array module 420 of the LED chip 42 1 when closely arranged together light guide plate 410 Thus, uniform light emission is possible from the vicinity of the incident end of the light guide plate 410. Further, a reflective layer surrounding the incident surface 411 and the LED array module 420 of the light guide plate 410 together when the specular reflection layer 461b and 461T, since the set to open the gap in the light guide plate 410 side, LED array module Even when an interval is provided between 420 and the incident surface 411 of the light guide plate 410, high coupling efficiency can be maintained.

  The edge input type backlight and the liquid crystal display device according to the present invention can be particularly compact because a device capable of uniform light emission from the side surface portion that becomes the incident surface can be made compact while using a plurality of point light sources. It is useful for video display units such as portable information terminals and notebook personal computers that are required to be lightweight.

The lineblock diagram of the light source part and light guide part in the edge input type backlight concerning a 1st embodiment of the present invention Sectional drawing of the principal part of the light guide part shown in FIG. 1 is a cross-sectional view of a main part showing a combined state of the light source part of FIG. 1 and the light guide part of FIG. Illustrative diagram of illuminance distribution calculation model Graph showing calculated illuminance distribution Graph showing calculated light / dark ratio Graph showing experimental results of coupling efficiency The block diagram of the light source part and light guide part in the edge input type backlight concerning the 2nd Embodiment of this invention Sectional drawing which shows the principal part which shows the edge input type backlight concerning the 3rd Embodiment of this invention The figure which shows the structure of the backlight using the conventional cold cathode ray tube The figure which shows the structure of the conventional edge input type backlight using a side emitter type LED light emitting element. The figure which shows the structure of the conventional edge input type backlight using an LED array module Explanatory drawing of the trajectory of light emitted from the side of the joule of the LED array

110, 210, 310, 410, 510 Light guide plate 111, 211, 311, 411, 511 Entrance surface 112 Exit surface 113 Reflection surface 120 Cold cathode ray tube 130, 230 Reflector
220 LED light emitting elements 221, 321, 421, 521 LED chip 222 Element substrate 223 Reflective members 224, 324, 424 Sealing resin 140, 240, 340 Reflective sheets 150, 250, 350 Optical film 260, 360 Frame 270, 370 Wiring substrate 320, 420, 520 LED array module 322, 422 Module substrate 430, 530 Wiring substrate 440 Holding member 450, 550 Reflective sheet 451, 551 Specular reflection sheet 460, 560 Prism sheet 461b, 461t, 561b, 561t Specular reflection layer 561 Specular reflection Layers 470, 570 Diffusion sheet 480, 580 Frame 590 Slit
670 Specular reflection plate
Pex, Pexb, Pext Projection

Claims (4)

A light emitting element array module in which a plurality of light emitting elements are arranged on an array module substrate and the light emitting elements are sealed with a transparent material to form a light emitting portion;
A wiring board on which a plurality of the light emitting element array modules are arranged;
A pressing member provided in the side surface direction of the light emitting element array module on the wiring board in the vicinity of the light emitting portion of the light emitting element array module;
The light-emitting element array module has a light incident surface on which a light incident surface is incident on a side surface, and the light introduced from the light incident surface is emitted from one of the two main surfaces facing each other. A light guide plate for illumination;
A reflective sheet that faces the opposite exit surface facing the exit surface of the light guide plate and reflects light leaking from the opposite exit surface in the exit surface direction;
Comprising at least two reflecting surfaces provided so as to surround a space between the light emitting portion of the light emitting element array module and the incident surface of the light guide plate;
The width in the direction orthogonal to the arrangement direction of the light emitting portions of the light emitting element array module is configured to be smaller than the width of the incident surface of the light guide plate, and the light emitting portions of the light emitting element array module and the light guide plate are incident on the light emitting portion array module. A reflection surface provided between the light-emitting element array module and the light guide plate, and the reflection sheet is configured such that one end of the reflection sheet is closer to the light-emitting element than the incident surface of the light guide plate. An edge input type backlight, wherein the backlight is formed so as to protrude toward the array module, and the protruding portion is disposed between the light emitting portion of the light emitting element array module and the pressing member . The edge input according to claim 1, wherein the reflective sheet has diffuse reflectivity, and the one reflective surface is formed by forming a specular reflective layer on the diffuse reflective surface of the reflective sheet. Type backlight. On the exit surface side of the light guide plate, a prism sheet for controlling the directivity of the emitted light are arranged, the prism sheet, the protruding to the light emitting element array module side of the incident surface of one of its sides before Kishirube light plate And the projecting portion is disposed between the light emitting portion of the light emitting element array module and the pressing member, and one reflecting surface is formed on the projecting portion. , edge input type backlight according to claim 1. 4. The edge input type backlight according to claim 3 , wherein the one reflection surface is formed by forming a specular reflection layer on the protruding portion on the prism sheet. 5.

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