JP2006171253A - Light guide plate of backlight assembly - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light guide plate of a backlight assembly for a liquid crystal display, wherein the "eyeball phenomenon", by which a section facing a light-emitting diode in a light emission surface light-emits brightly, as compared with the other sections is prevented. <P>SOLUTION: In the light guide plate 3 or 17, a light-emitting surface 11 of the front surface thereof emits light by the light made incident from its end surface side by using a light source disposed at light incident end surface 3a or 17a of the light guide plate 3 or 17. A plurality of grooves 16, extended from a light-incident side end part toward the light-emitting surface 11, are formed within at least one masked range of the front or the rear of a light-incident end edge 3X or 17X which is provided at the light-incident end part of the light guide plate 3 or 17 and at least one part of which is masked at assembling. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a light guide plate of a backlight assembly incorporated in a backlight assembly of a liquid crystal display.

  Conventionally, as a backlight assembly of a liquid crystal display, a structure including a light guide plate, a reflection sheet, and a light emitting diode (LED) is known (see, for example, Patent Document 1). In the backlight assembly (backlight panel device), an LED is attached to the lower end surface of the light guide plate. An LED lighting circuit pattern and a light-shielding pattern are simultaneously formed on the surface of the reflection sheet by silk printing or the like with a conductive ink such as silver / carbon ink.

  On the surface of the light guide plate, a light distribution pattern which is an irregular reflection surface such as a minute dot is formed by screen printing or the like. The light distribution pattern is formed on the entire surface of the light guide plate using translucent ink so that a halftone dot pattern with an area ratio of 20 to 60% changes steplessly from the lower end side to the upper end side of the light guide plate. It has been printed over.

  In the light guide plate, when light enters from the lower end surface of the light guide plate into the light guide plate, the entered light is irregularly reflected by the light distribution pattern, and the light distribution pattern portion is substantially uniform when viewed from the surface side of the light guide plate. It has a structure that emits light at a brightness of.

  The light shielding pattern is formed entirely on the left and right at a height position directly below the LED lighting circuit pattern position. The light-shielding pattern prevents light from the LED from leaking to the outside through the reflection sheet, and prevents light-emitting unevenness in which the portion where the light-emitting diode is disposed becomes brighter than other portions.

  On the other hand, as shown in FIG. 12, a light guide plate is also known in which a light-emitting side end portion is provided with a concave-convex light-emitting diode mounting portion having a mountain shape in plan view in correspondence with the light-emitting diode position. “Eyeball phenomenon” in which light emitted from the light emitting diode is diffused and introduced into the introduction plate by the uneven mounting portion, and the part facing the light emitting diode on the light emitting surface emits light brighter than other parts. It has a structure to prevent. In addition, the patent document and nonpatent literature regarding this light-guide plate are not known.

  In any of the above prior arts, light emitted from the LED enters the light guide plate from the portion of the light incident side end face of the light guide plate facing the LED, and the light emitting surface of the light guide plate emits light by entering the light guide plate. To do. For this reason, in the case of the structure that prevents the “eyeball phenomenon” due to the light shielding pattern, the light entering the light guide plate is irregularly reflected by the light distribution pattern, but the incident light unevenness of the light incident side end surface of the light guide plate is unavoidable, There is a drawback that a “eyeball phenomenon” occurs in which the portion facing the LED emits light brighter than other portions.

  The light shielding pattern only prevents the light from the LED from leaking outside through the reflective sheet. For this reason, it is possible to prevent light emission unevenness that occurs when light from the LED leaks to the outside through the reflection sheet, but the “eye phenomenon” due to uneven light incident intensity from the lower end surface of the light guide plate. There is no effect on. Moreover, the thing provided with the uneven | corrugated attachment part has the problem that the diffusion of the light by an attachment part is insufficient and it is difficult to avoid the said "eyeball phenomenon".

  In order to solve the above problems, the light guide plate of the backlight assembly of the present invention includes a light guide plate 3 and 17 where the light emitting surface 11 emits light by light incident from the end surface side, and light incident on the light guide plates 3 and 17. And a light source disposed on the side end faces 3a, 17a, and a light incident side edge 3x, 17x at least partially masked at the time of assembly at the light incident side end of the light guide plate 3, 17 In the backlight assembly, a plurality of grooves extending in the direction from the light incident side end toward the light emitting surface 11 within the masked range of at least one of the front and back surfaces of the light incident side edges 3x and 17x of the light guide plates 3 and 17. The first feature is that 16 is formed.

  Secondly, the groove 16 is formed corresponding to the light source position.

  Thirdly, the depth of the groove 16 gradually decreases as it approaches the light emitting surface 11 and becomes 0 at the groove end.

  Fourth, the cross-sectional shape of the groove 16 is characterized in that the groove width gradually decreases in the depth direction and becomes 0 at the deepest position.

  Fifth, the cross-sectional shape of the groove 16 is V-shaped, arc-shaped, or elliptical arc-shaped.

  Sixth, the light source is characterized by comprising a light emitting diode 9 attached so that the light emitting surface faces the end surfaces 3a and 17a of the light guide plates 3 and 17.

  According to the structure of the present invention configured as described above, a part of the light immediately after entering the light incident side end of the light guide plate from a light source such as a light emitting diode is irregularly reflected by the groove and is reflected in the light guide plate. The light diffuses, and light enters the light incident side end of the light guide plate substantially uniformly. As a result, the “eyeball phenomenon” in which the portion facing the light source on the light emitting surface becomes brighter than the other portions can be prevented, and the light emission unevenness on the light emitting surface can be prevented.

  Note that light from the light source enters from a portion facing the light source on the light incident side end face of the light guide plate. For this reason, by forming a groove at least in a portion corresponding to the light source position and irregularly reflecting the light, the “eyeball phenomenon” can be prevented, and the “eyeball phenomenon” can be prevented with a small number of grooves. .

  At this time, by setting the depth of the groove to be gradually shallower as it approaches the light emitting surface and to be 0 at the groove end, light is effectively diffused over the entire length of the groove, and light is concentrated at the groove end. Occurrence of the eyeball phenomenon due to is prevented.

  In addition, by making the cross-sectional shape of the groove gradually V-shaped, arc-shaped or elliptical arc in which the groove width gradually decreases in the depth direction and becomes 0 at the deepest position, light is effectively emitted over the entire circumferential surface of the groove. The above-described eyeball phenomenon due to the concentration of light at the bottom of the groove is prevented. By making the cross-sectional shape of the groove V-shaped, arc-shaped or elliptical arc-shaped, the groove width gradually decreases in the depth direction, and a groove having a cross-sectional shape that becomes 0 at the deepest position is easily formed. be able to.

  FIGS. 1, 2A and 2B are model diagrams showing the structure of a backlight assembly used in a liquid crystal display or the like. The backlight assembly 1 has a structure in which a reflection sheet 2, a light guide plate 3, a diffusion sheet (diffuser) 4, and lens sheets 5 and 6 are sequentially laminated in a frame body 7 from the back side to the front side to form a unit. It has become.

  A light emitting diode 9 serving as a light source is attached to the light incident side end face 3 a of the light guide plate 3. The light emitting diode 9 is mounted on a film substrate or the like and is placed on the base portion 8 of the frame body 7. The light emitted from the light emitting diode 9 enters the light guide plate 3 from the light incident side end surface 3a of the light guide plate 3, and the light emitting surface 11 on the front side of the light guide plate 3 emits light by this light.

  The backlight assembly 1 has a structure in which light emitted from the light emitting surface 11 is diffused by the diffuser 4 and the front lens sheet 6 emits light. The reflection sheet 2 reflects light leaking to the back side of the light guide plate 3 (reflection surface 11) to the front side.

  FIG. 3 is an enlarged perspective view of the light guide plate 3 to which the light emitting diode 9 is attached. The light guide plate 3 is formed of a material having high light transmittance such as a transparent acrylic resin. The light emitting diode 9 has an end surface on the light guide plate 3 side as a light emitting surface. An area separated from the light emitting diode side end on the surface of the light guide plate 3 by a predetermined distance is a light emitting surface 11.

  A plurality of vertical grooves 12 are formed in the light emitting surface 11 in the horizontal direction. The light emitting surface 11 is a chevron uneven surface by the groove 12. A plurality of lateral grooves 13 are formed in the vertical direction at the back side of the light emitting surface 11 on the back surface of the light guide plate 3. The back surface of the light emitting surface 11 is an uneven surface rotated 90 degrees with respect to the uneven surface of the light emitting surface 11 by the groove 13.

  The light from the light emitting diode 9 that has entered the light guide plate 3 from the light incident side end surface 3a of the light guide plate 3 is irregularly reflected toward the surface side by the uneven surface on the back surface of the light emitting surface 11, and further the light emitting surface 11 (front surface side). It also reflects irregularly. Thereby, the light emitting surface 11 emits light almost uniformly toward the surface side by the light of the light emitting diode 9.

  As shown in FIGS. 2A and 2B, a light shielding film 14 is provided on the surface side of the backlight assembly 1. The light shielding film 14 has a light shielding portion 14 a at a portion facing the base portion 8. The other part of the light shielding film 14 is a transparent part 14b that can transmit light.

  The light incident side edge 3X, which is outside the light emitting area on the light incident side of the light emitting diode 9 and the light guide plate 3, is located on the back side of the light shielding portion 14a. The entire light incident side edge 3 </ b> X is masked by the light shielding portion 14 a, and the light from the light emitting diode 9 does not leak to the front side of the light shielding film 14.

  On the front side of the light incident side edge 3X in the light guide plate 3, a plurality of grooves 16 are formed over substantially the entire width. The groove 16 extends from the light incident side end of the light guide plate 3 toward the light emitting surface 11. The groove 16 has a V-shaped cross section when viewed from the end face side as shown in FIG. 4A, and the depth gradually increases as the light emitting area 11 is approached as shown in FIG. 4B. The shape becomes shallow and the depth becomes 0 at the groove end.

  Since the groove 16 is formed on the light incident side edge 3X of the light guide plate 3, when the backlight assembly 1 is assembled, it is masked on the surface side of the backlight assembly 1 by the light shielding portion 14a of the light shielding film 14.

  A part of the light emitted from the light emitting diode 9 is irregularly reflected by the groove 16 on the surface side (light emitting area 11 side) of the light guide plate 3 immediately after entering the light guide plate 3 from the light incident side end portion 3a. The light diffuses in the light guide plate 3 and travels so that light enters the light incident side end surface 3a substantially uniformly. Thereby, the “eyeball phenomenon” in which the portion of the light emitting surface 11 facing the light emitting diode 9 becomes brighter than the other portions is prevented, and uneven light emission on the light emitting surface 11 is prevented.

  At this time, the depth of the groove 16 gradually decreases as it approaches the light emitting area 11, and the depth becomes 0 at the groove end. Therefore, the light that has traveled straight into the groove travels straight and concentrates at the groove end. The light is effectively diffused over the entire length of the groove 16 without causing the inconvenience of emitting light brightly. This prevents the eyeball phenomenon from occurring due to light emission at the end of the groove 16.

  Further, since the groove 16 has a V-shaped cross section and the groove width is 0 at the deepest position, the light is diffusely reflected obliquely upward with respect to the entire circumferential surface of the groove 16 to effectively diffuse the light. This prevents inconvenience that light concentrates on the bottom of the groove 16 and emits bright light, and the above-mentioned eyeball phenomenon due to light emission at the bottom of the groove 16 is prevented.

  The light guide plate 3 emits light toward the surface at the portion of the groove 16, but the groove 16 is masked on the surface side of the backlight assembly 1 by the light shielding portion 14 a of the light shielding film 14. After the assembly 1 is assembled, light emission toward the surface of the groove 16 is not a problem, and light emission unevenness of the light emitting surface 11 is not caused.

  As shown in FIGS. 5A and 5B, the grooves 16 may be formed not only on the front surface side of the light incident side end surface 3a but also on the back surface side opposite to each other. In this case, the occurrence of irregular reflection of the light emitted from the light emitting diode 9 in the groove 16 is increased, the effect of preventing the eyeball phenomenon is improved, and the light emission on the light emitting surface 11 can be made more uniform.

  Moreover, the groove | channel 16 can also be provided only in the back surface side of the light-incidence side end surface 3a. However, in this case, since the light emitted from the light emitting diode 9 is less diffused and diffusely reflected on the surface side of the light guide plate 3, compared to the case where the groove 16 is provided only on the surface side of the light incident side end surface 3a, The effect of preventing the eyeball phenomenon is reduced.

  The groove 16 can be provided only at a position corresponding to at least the light emitting surface of the light emitting diode 9. In this case, the “eyeball phenomenon” can be prevented with a small number of grooves 16 by diffusely reflecting light only at a position corresponding to the light emitting surface of the light emitting diode 9.

  As shown in FIGS. 6A and 6B, the groove 16 has an elliptical arc cross section viewed from the end face side of the groove 16, and the depth gradually decreases as the light emitting area 11 is approached. The depth may be 0 in FIG. In this case, the same effect as that of the groove having the V-shaped cross section can be obtained.

  In addition, the cross-sectional shape seen from the end surface side of the groove | channel 16 can also be made into the circular arc shape of a perfect circle. Although not shown, a groove 16 may be formed on the back side of the light incident side edge 3X of the light guide plate 3 so as to be opposite to the surface 16 of the light incident side edge 3X. Further, as in the case of the groove having the V-shaped cross section, the groove 16 having an elliptical arc shape cross section or an arc shape cross section is formed only on the back surface side of the light incident side edge 3X of the light guide plate 3, or at least a light emitting diode It can also be provided only at a position corresponding to the light emitting surface 9. The effects in this case and the disadvantages associated therewith are the same as described above.

  As shown in FIG. 7, the light incident side end surface 17a is thicker than the flat light emitting surface 11 and the light incident side edge 17X has a trapezoidal cross section. There is a light guide plate 17. This type of light guide plate 17 makes it possible to make the backlight assembly 1 as thin as possible.

  Even when the light guide plate is of the above type, a plurality of grooves 16 having a V-shaped cross section are formed over substantially the entire width of the light incident side edge 17X of the light guide plate 17 as shown in FIG. By doing so, the “eyeball phenomenon” on the light emitting surface 11 can be suppressed as described above.

  Since the light incident side edge 17X portion of the light guide plate 17 has a trapezoidal cross section as shown in FIG. 8B, the groove 16 is provided in parallel to the light emitting surface portion. As the depth of 16 approaches the light emitting surface 11, it gradually becomes shallower and the depth becomes 0 at the groove end. For this reason, formation of the groove | channel 16 is easy.

  Since the formation of the groove 16 is easy, as shown in FIGS. 9 (a) and 9 (b), the groove 16 is also formed on the light incident side edge 17 </ b> X on the back surface side of the light incident side edge 17 </ b> X. The groove 16 formed on the surface side of the edge 17X can be easily formed opposite to the front and back, and the effect of preventing the eyeball phenomenon can be improved as described above.

  As shown in FIG. 10A, the cross-sectional shape viewed from the end face side of the groove 16 may be an elliptical arc shape. As shown in FIG. 10B, the groove 16 is provided in parallel to the light emitting surface portion, and the depth of the groove 16 gradually decreases as the light emitting surface 11 is approached. The depth is zero.

  In this case, the same effect as that of the groove having the V-shaped cross section can be obtained. In addition, the cross-sectional shape seen from the end surface side of the groove | channel 16 can also be made into the circular arc shape of a perfect circle. Even if the cross-sectional shape viewed from the end surface side of the groove 16 is any of the above cases, the groove 16 is on the back surface side of the light incident side edge 17X in the light guide plate 3 and on the surface side of the light incident side edge 17X. It can be easily formed opposite to the groove 16 formed on the front and back, and the effect of preventing the eyeball phenomenon can be improved.

  Also in the light guide plate 17, the groove 16 is formed only on the back surface side of the light incident side edge 17 </ b> X of the light guide plate 17, or the position corresponding to at least the light emitting surface of the light emitting diode 9. It can also be provided only in The effects in this case and the disadvantages associated therewith are the same as described above.

  FIG. 11 is a plan view of the light guide plate A having the dimensions of width × length × thickness = 30.5 × 44 × 0.65 (mm) to which three light emitting diodes D are attached. The light guide plate A has a light emitting surface B of 29.5 × 39.5 (mm) in plan view, and the length from the light incident side end of the light guide plate A to the start end of the light emitting surface B is 2.9 mm. On the surface side of the light incident side edge C of the light guide plate A, a groove E is formed over the entire width.

  On the measurement line L offset by 3 mm from the starting end of the light emitting surface B, luminance measurement points are set every 4.2 mm from the center line of the light emitting surface B of the light guide plate A to the left and right. The luminance was measured as measurement points 1 to 7 in order.

  A light guide plate A ′ having the same shape as the light guide plate A except that a mounting portion F of an uneven light emitting diode D ′ is provided instead of the groove E shown in FIG. Therefore, the luminance was measured in the same manner as described above. In FIG. 12, B ′ is the light emitting surface, C ′ is the light incident side edge of the light guide plate A ′, and has the same shape as the light emitting surface B and the light incident side edge C of the light guide plate A.

  FIG. 13 is a graph of measurement results. The conventional light guide plate A ′ (dotted line) is formed with a groove E while the luminance of the measurement points 2, 4 and 6 facing the light-emitting diode D ′ is extremely high compared to the other measurement points. In the light guide plate A (solid line), the difference in luminance between the measurement points 2, 4, 6 and the other measurement points substantially facing the light-emitting diode D is small, and it can be said that the “eye phenomenon” is almost eliminated.

It is a sectional side view of a backlight assembly model. (A) is the front view seen from the light emission surface side of a backlight assembly, (b) is the front view which looked at the light-guide plate integrated in the backlight assembly from the light emission surface side. It is an expansion perspective view of the light-guide plate in the state in which the light emitting diode was attached. (A) is an expanded sectional view of a groove when the light guide plate of FIG. 3 is viewed from the end surface side, and (b) is an enlarged side sectional view of a groove portion in the light guide plate of FIG. (A) is an enlarged sectional view of a groove when the light guide plate having grooves formed on both front and back surfaces is viewed from the end surface side, and (b) is an enlarged side of the groove portion in the light guide plate having grooves formed on both front and back surfaces. It is sectional drawing. (A) is an expanded sectional view of the groove | channel of the other shape when seeing a light-guide plate from the end surface side, (b) is an expanded side sectional view of the groove part of the other shape in a light-guide plate. It is an expansion perspective view of the light guide plate of the other shape in the state where the light emitting diode was attached. (A) is an expanded sectional view of the groove when the light guide plate of FIG. 7 is viewed from the end surface side, and (b) is an enlarged side sectional view of the groove portion in the light guide plate of FIG. (A) is an enlarged sectional view of a groove when the light guide plate having grooves formed on both front and back surfaces is viewed from the end surface side, and (b) is an enlarged side of the groove portion in the light guide plate having grooves formed on both front and back surfaces. It is sectional drawing. (A) is an expanded sectional view of the groove | channel of the other shape when seeing a light-guide plate from the end surface side, (b) is an expanded side sectional view of the groove part of the other shape in a light-guide plate. It is a front view of the light-guide plate used for the measurement of a brightness | luminance. It is a front view of the conventional light-guide plate provided with the attachment part of the light emitting diode used for the measurement of a brightness | luminance. It is a graph which shows the measurement result of a brightness | luminance.

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 Light guide plate 3a Light incident side end surface 3x Light incident side edge 9 Light emitting diode 11 Light emitting surface 16 Groove 17 Light guide plate 17a Light incident side end surface 17x Light incident side edge

Claims (6)

  The light guide plates (3) and (17) in which the light emitting surface (11) emits light by the light incident from the end surface side, and the light incident side end surfaces (3a) and (17a) of the light guide plates (3) and (17). , And a light incident side edge (3x) that is outside the light emitting area that is at least partially masked during assembly at the light incident side end of the light guide plate (3), (17). In the backlight assembly of the liquid crystal display provided with (17x), within the masked range of at least one of the front and back surfaces of the light incident side edges (3x) and (17x) of the light guide plates (3) and (17) The light guide plate of the backlight assembly in which a plurality of grooves (16) extending in the direction of the light emitting surface (11) from the light incident side end are formed.   The light guide plate of the backlight assembly according to claim 1, wherein the groove (16) is formed so as to correspond to a light source position.   The light guide plate of a backlight assembly according to claim 1 or 2, wherein the depth of the groove (16) gradually becomes shallower as it approaches the light emitting surface (11) and becomes 0 at the end of the groove.   The light guide plate of a backlight assembly according to claim 3, wherein the cross-sectional shape of the groove (16) is such that the groove width gradually decreases in the depth direction and becomes 0 at the deepest position.   The light guide plate of the backlight assembly according to claim 4, wherein the cross-sectional shape of the groove (16) is V-shaped, arc-shaped, or elliptical arc-shaped.   The light source comprises a light emitting diode (9) mounted such that the light emitting surface faces the end surfaces (3a), (17a) of the light guide plates (3), (17). Backlight assembly light guide plate.

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