JP2019021519A - Light guide plate and injection molding method of light guide plate - Google Patents

Abstract

To provide a light guide plate in which generation of luminance unevenness and color unevenness are reduced.SOLUTION: A light guide plate (1) has a non-through hole (11) opening on a surface (5) of a section (10) between an incident part (7) and a recess (8) and extending toward a rear surface (6), and irregularity (12) is formed on an inner surface close to the surface (5) of the non-through hole (11). In resin mold of the light guide plate, molten resin (28) is injected and filled in a cavity (27) formed by clamping a first mold (21)in which a stamper (24) formed into an irregular shape (23) is arranged and a second mold (22) which has a recess (25) for forming a molded article and a slidable pin (26), and before start of pressure holding after filling the resin (28), the pin (26) is inserted in the cavity (27) to a position where a tip does not come into contact with the stamper (24), and the shape of the molded article is made in the pressure holding step.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a surface-emitting light guide plate that uniformly emits light on a display surface and a method for manufacturing the same.

  Patent Document 1 describes a light guide plate shown in FIG.

  In this light guide plate 51, the light from the point light source 52 enters from the incident surface 51 a, and the light introduced into the light guide plate 51 is reflected by the inclined surface of the V-groove 53 formed on the back surface and is reflected on the surface of the light guide plate 51. The light is emitted from the display area 51b, and the display area 51b emits light. A plurality of through holes 54 are formed in the light guide plate 51 in the section between the incident surface 51a and the V-groove 53 along the incident surface 51a in order to make the display region 51b emit light uniformly. In FIG. 12, a row of through holes 54 are formed along the incident surface 51a. Also, there is a case in which a plurality of rows of through holes 54 are formed as shown in FIG.

  Patent Document 2 describes a light guide plate shown in FIGS. 14 and 15.

  The light guide plate 61 has a through hole 62 extending from the back surface to the front surface along a concave light incident portion 63. Light incident on the light guide plate 61 from the point light source 64 is diffused through the through-hole 62 and is emitted from the display area 61 b on the surface of the light guide plate 61. In some cases, instead of the through hole 62, a non-through hole 65 opened on the back surface is formed as shown in FIG.

  In the light guide plate, a fine uneven shape is provided on the incident surface. In order to obtain an injection-molded product having a fine uneven shape, it is known that a stamper provided with a fine uneven shape on a metal plate is molded into a mold and molded as shown in Patent Document 3. ing.

JP 2003-100132 A JP 2000-30520 A JP-A-8-6017

  However, when the light guide plates 51 and 61 having the through holes 54 and 62 and the non-through holes 65 are formed by the resin injection molding method in order to uniformly emit light from the light source, the following problems occur. .

  That is, in order to flow and fill the molten resin into the cavity portion provided in the mold through the sprue gate of the mold, the through holes 54 and 62 in the molded product (light guide plate) and non- Since a pin fixed by a mold is disposed in the through hole 65 portion, the pin hinders resin flow, and a weld that is a flow pattern is generated, and the weld forms a light guide plate with uneven light emission. End up.

  In addition, since the pins prevent the resin from being filled, there arises a problem that the resin cannot be filled to the flow end of the light guide plate. Furthermore, in the configuration in which the through holes 54 and 62 and the non-through holes 65 are arranged in a plurality of rows, a great problem arises in the generation and filling of welds.

  Even if the non-through hole 65 is used, the original purpose cannot be achieved if the light travels straight through the non-through hole. As a result, the pins constituting the non-through hole 65 have a depth sufficient to prevent the resin from flowing. It becomes the fixed pin. In particular, when there is a light incident part on the entire circumference or almost the entire circumference of the surface light-emitting light guide plate, or due to the shape restriction of the light guide plate, the gate that is the entrance for filling the mold resin is only in the light incident part. In the case where the setting cannot be made, the resin must flow through the pins, so the problem of weld due to flow always occurs. In some cases, a problem that the resin cannot be completely filled up to the flow end of the light guide plate occurs.

  In addition, the number of times of light refraction inside the light guide plate is increased by the through holes 54 and 62 and the non-through holes 65, so that light is not attenuated or refracted at the refracted portion, and light emitted from the emission surface is guided. The amount of light that reaches the opposite side of the light plate from the light source is reduced, resulting in a problem that the light emission efficiency is reduced or uneven light emission occurs.

  In the case of a mold configuration incorporating a stamper, if a through hole or a non-through hole is to be provided in the light incident part for the purpose of uniformly emitting light from the light source, the following two methods are used. Can be considered.

  The first method is to incorporate a pin in the fixed mold, open a through hole in the stamper, and set the stamper in the mold through the pin. The stamper is manufactured by electroforming, Since the material is Ni or Ni alloy, the linear expansion coefficient is different from that of the metal constituting the mold, so that the position of the fixing pin on the stamper mold side is displaced, and the stamper is deformed or damaged. .

  The second method is to insert a pin in the movable mold opposite to the fixed mold on the side where the mold stamper is installed, press the pin directly against the stamper surface, and penetrate the light guide plate. There are methods for forming holes and non-through holes. In this case, since the material of the stamper is Ni or Ni alloy, there is a problem that the hardness is low and the structure in which the pin is directly pressed against the stamper is damaged and deformed. There is a method of incorporating a pin from the opposite side (movable side) to the side where the stamper is incorporated (movable side) and making it a non-through hole, but in this case, the problem associated with the stamper does not occur, but as described above, melting A molding problem such as poor resin flow occurs.

  An object of this invention is to provide the light-guide plate which can solve the poor flow of the molten resin at the time of shaping | molding, and can implement | achieve uniform and favorable surface emission, and its manufacturing method.

  In the light guide plate of the present invention, the light incident inside from the light incident portion between the back surface and the front surface is reflected by the reflecting surface of the concave portion formed in the back surface so as to be depressed toward the front surface, and the reflected light is reflected. In the light guide plate that exits from the front surface, a non-through hole having a depth that opens at the front surface in a section between the light incident portion and the recess and extends toward the back surface and does not penetrate the back surface is provided. Unevenness is formed on the inner surface close to the surface of the through hole.

  The light guide plate injection molding method of the present invention is a second mold having a first mold having a stamper having a finely concavo-convex shape on its surface, a recess for forming a molded product, and a pin slidable into the recess. The mold is clamped, the molten resin is injected and filled into the cavity formed by clamping the mold, and the pin is brought to a position where the tip does not contact the stamper after filling the resin and before starting the pressure holding. Is inserted into the cavity, and the shape of the molded product is formed in a pressure-holding step.

  According to the structure of this light guide plate, a non-through hole having a depth that opens at the surface of the section between the light entrance portion and the recess and extends toward the back surface and does not penetrate the back surface is provided on the inner surface near the surface of the non-through hole. Since the projections and depressions are formed, it is possible to realize uniform and excellent surface emission on the emission surface.

  Further, according to the structure of the injection molding method of the light guide plate, when injecting and filling the molten resin into the cavity formed by clamping, the pin for forming the non-through hole does not protrude into the cavity. Therefore, it is possible to eliminate filling defects that hinder the weld during injection flow and the transfer of a minute uneven shape which is a continuous or discontinuous prism shape. The pin is inserted into the cavity until the tip does not touch the stamper after filling the resin until the start of pressure holding, and the shape of the molded product is created in the pressure holding process, so the pin for forming the non-through hole breaks the stamper Therefore, a good light guide plate can be manufactured over a long period of time.

The front view which looked at the light-guide plate of Embodiment 1 of this invention from the back surface side facing the surface used as an output surface The front view which looked at the light-guide plate of the form 1 from the surface side used as an output surface (A) A-AA sectional view of the vicinity of the light entrance portion of the light guide plate of the same embodiment, (b) a plan view of the light guide plate viewed from the surface side, and (c) B-BB of the vicinity of the light entrance portion. Enlarged sectional view Sectional drawing of the injection mold used for resin molding of the light guide plate of the embodiment The perspective view of the recessed part of the 2nd metal mold | die of the embodiment Sectional drawing of the mold-closed state of the resin molding of the same embodiment Sectional view at the start of filling in resin molding of the same embodiment Sectional drawing immediately after completion of resin molding filling of the same embodiment Sectional drawing of the mold open state of the embodiment The front view which looked at the light-guide plate of Embodiment 2 of this invention from the back surface side The enlarged plan view which looked at the light-guide plate of the embodiment from the surface side The perspective view of the light-guide plate described in patent document 1 The perspective view of another light-guide plate described in patent document 1 The perspective view of the light-guide plate described in patent document 2 Enlarged view of the main part of FIG. Sectional drawing of another light-guide plate described in patent document 2

  Hereinafter, each embodiment of the present invention will be described with reference to FIGS.

(Embodiment 1)
1 and 2 show a display device 2 using the light guide plate 1 of the first embodiment.

  The display device 2 includes a plate-like rectangular light guide plate 1 formed by resin-molding a translucent resin material, and light source substrates 3a, 3b, 3c, and 3d as light sources. Light emitting diodes (hereinafter referred to as LEDs) 4 are mounted on the light source substrates 3a to 3d at intervals. Light from the light source substrates 3a to 3d is incident between the front surface 5 of the light guide plate 1 and the back surface 6 of the light guide plate 1 shown in FIG. Yes. On the back surface 6 of the light guide plate 1, as shown in FIG. 3A, a minute continuous or non-continuous prism formed in a recess toward the front surface 5 or a concave portion 8 composed of a minute dot shape is formed. ing. 1 and 2, the illustration of the recess 8 is omitted. The recess 8 is formed inside the display area 9 indicated by a virtual line.

  The light that enters the light guide plate 1 is reflected by the recess 8 formed on the back surface 6 and is emitted from the front surface 5 to the outside of the light guide plate 1. On the surface 5 of the light guide plate 1, a section 10 between the light incident portion 7 and the display region 9 has a non-through hole 11 extending toward the back surface 6 and having a depth that does not penetrate the back surface 6. A plurality of portions are formed at predetermined intervals along the length direction of the portion 7.

  Note that the non-through hole 65 shown in FIG. 16 showing the conventional example opens on the back surface opposite to the emission surface, whereas the non-through hole 11 of this embodiment is the emission surface. The difference is that the surface 5 is open.

  Furthermore, the back end surface, which is the inner surface close to the back surface 6 of the non-through hole 11 of this embodiment, is parallel to the light incident from the nearest light incident portion 7 as shown in FIGS. 2 and 3B and 3C. A prism-shaped groove 12 having a triangular cross section is formed.

  The light guide plate 1 can be resin-molded by an injection mold 20 shown in FIG.

  The injection mold 20 includes a first mold 21 on the fixed side and a second mold 22 on the movable side. The first mold 21 incorporates a stamper 24 provided with minute irregularities 23 on the surface. The unevenness 23 of the stamper 24 is for forming the recess 8 in the back surface 6 of the light guide plate 1.

  The cavity recess 25 constituting the plate thickness of the light guide plate 1 is formed only in the second mold 22 of the first mold 21 and the second mold 22. Further, the second mold 22 incorporates a plurality of pins 26, 26,... That are driven in a protruding state in which the tip protrudes into the cavity recess 25 and in a retracted state in which the second recess 22 retracts from the cavity recess 25. . The plurality of pins 26, 26,... Are for forming a plurality of non-through holes 11 in the light guide plate 1. On the end face of the tip of the pins 26, 26,..., Irregularities (not shown) for forming the grooves 12 are formed on the back end face of the non-through hole 11 of the light guide plate 1. FIG. 5 shows the cavity recess 25 with a plurality of pins 26, 26,.

  6 to 9 show a resin molding process.

  FIG. 6 shows a state in which a cavity 27 surrounded by a stamper 24 and a cavity recess 25 is pressed after the second mold 22 is pressed against the first mold 21 by applying pressure by a mold clamping mechanism (not shown). The state before the molten resin is injected is shown. The tips of the projecting pin pins 26, 26,... Do not contact the stamper 24.

  In the process of FIG. 7 in which the molten resin 28 flows from the gate 31 to the cavity 27 through the sprue 29 and the runner 30 after the first mold 21 and the second mold 22 are clamped, the pins 26, 26,. Is driven in a retracted state where it does not protrude into the cavity recess 25. Since the pins 26, 26,... Are in the retracted state, the tip 28a of the molten resin flows without being blocked by the pins 26, 26,. Filled in.

  After injection filling, the pins 26, 26,... Are inserted as shown in FIG. 8 during the period from the start of the pressure holding process where the pressure is applied to the fluid resin and the pins 26, 26,. The position that does not contact the stamper 24 is raised as the upper limit. The operation means of the pins 26, 26,... Is not described, but can be driven by an air cylinder, an electromagnetic solenoid or the like.

  FIG. 9 shows a mold open state in which the cooling of the first mold 21 and the second mold 22 is completed through the pressure holding process.

  According to this configuration, since the cavity 27 does not have a convex shape that hinders the flow when the resin is filled, a uniform light guide plate 1 without welds can be obtained. In the light guide plate 1 obtained by the above configuration, a light source The light from the LEDs 4 on the substrates 3a to 3d can be refracted or totally reflected at the interface between the shape of the non-through hole 11 and the space inside.

  Moreover, since the tips of the pins 26, 26,... Do not come into contact with the stamper 24 by using the non-through hole 11, the material is Ni or Ni alloy and the stamper 24 having low strength is damaged. In addition, the life of the stamper 24 can be extended.

  Since the non-through hole 11 is formed in a portion entering the inside from the light incident portion 7 of the light guide plate 1, even when the light incident portion 7 exists on the entire periphery as shown in FIGS. 1 and 2, the gate portion Other than the above, the shape is as it is after molding, and the gate surface may be flat because the end surface may be flat.

  Furthermore, even if the light guide plate 1 has an end surface without the light incident portion 7, if the end surface requires a complicated shape due to design, assembly, or the like, a gate that is a resin inlet is set from that portion. For example, the gate must be newly removed after molding, and at the same time, the complicated shape must be cut one by one. According to this embodiment, it is possible to set the gate 31 that is an inflow port of the resin even on the light incident surface, and it is possible to set the gate 31 at a position where the post-processing is least or an optimum position for filling. Become.

  Furthermore, as shown in FIG. 3C and the like, the amount of light transmitted through the non-through hole 11 cannot be reduced by adding a prism-shaped groove 12 to the tip of the non-through hole 11. Specifically, in the case of a through hole, light that travels straight from the light source is refracted or totally reflected at the interface between the shape of the through hole and the space inside the through hole. There is no light traveling to the end side of the light guide plate. By setting the non-through hole 11, the amount of light that passes through the top surface of the non-through hole 11 and reaches the end side of the light guide plate can be ensured to some extent. As a result, light leaks from the light exit surface, and the light quantity of the light exiting from the light exit surface decreases as the number of refractions increases. Since the groove 12 is formed in the back end surface of the non-through hole 11 of this embodiment, light that refracts in the direction in which light directly exits from the exit surface disappears on the surface, so that light enters from the light source substrates 3a to 3d. Therefore, the light that has passed through the light source from the top surface of the non-through hole 11 can be eliminated without going straight through to the opposite side of the light source, and a light guide plate having a uniform light emitting surface can be realized.

  In the present embodiment, the prism-shaped groove 12 having a triangular cross section is provided on the back end face of the non-through hole 11, but the cross section may be a fine irregularity such as a funnel shape or a square shape.

  The light guide plate 1 can realize uniform light emission in a picture switching display device or the like in which the light incident direction needs to be incident from all end faces of the light guide plate. In addition to a specific example of a light guide plate of a display device that displays a picture, it can also be used as a light emitting device such as a backlight of various display panels.

  In addition, because the light connected to the light incident surface or the fine shape directly on the light incident surface does not cause uniform light emission, there is a light incident portion at the end of the entire circumference or almost the entire circumference of the light guide plate. Even if it exists, or if the gate that is the entrance of the flow path for filling the resin from other than the light entrance part cannot be set due to the shape limitation of the light guide plate, the entire surface that emits light uniformly can be set by freely setting the gate A stamper type light guide plate which is a light emitting device or a partial light emitting device can be manufactured by an injection molding method.

(Embodiment 2)
10 and 11 show a second embodiment of the present invention.

  In the first embodiment, a plurality of non-through holes 11 arranged in a line along the light incident portion 7 are formed in the light guide plate 1. However, in the second embodiment, a plurality of rows are formed along the light incident portion 7. The point which forms the some non-through-hole 11 located in a line in the light-guide plate 1 differs from Embodiment 1. FIG. The rest is the same as in the first embodiment.

  As shown in FIG. 11, the light source width W <b> 1 of light traveling straight from the LEDs 4 of the light source substrates 3 a to 3 d is larger than the width W <b> 2 of the non-through hole 11. Therefore, in the second embodiment, a plurality of non-through holes 11 arranged in a plurality of rows along the light incident portion 7 are formed in the light guide plate 1. In the case where the width W2 of the non-through hole 11 is smaller than the light source width W1 of the LED 4, a part of the light incident from the LED 4 does not enter the light guide plate 1 simply by forming a plurality of non-through holes 11 arranged in a row in the light guide plate 1. Although diffused by the non-through hole 11 close to the light surface, light that passes straight through the non-through hole 11 is generated. In order to prevent this, the width W2 of the non-through hole 11 may be set larger than the light source width W1, but the non-through hole 11 becomes larger by that amount, and as a result, there is no gap adjacent to the non-through hole 11, The shape of the light guide plate 1 cannot be maintained.

  Therefore, as shown in FIG. 10 and FIG. 11, diffusion is performed by the non-through holes 11 of the first group 41 separately from the first group 41 of the plurality of non-through holes 11 arranged in a line along the light incident surface. A second group 42 composed of a plurality of non-through holes 11 arranged in a line along the light incident portion 7 is provided between the first group 41 and the display area 9 so as to receive and diffuse light that has traveled straight. By providing the diffusion plate 1, all or most of the light incident on the light guide plate 1 can be diffused by being refracted or totally reflected by the non-through holes 11 of the first and second groups 41 and 42. .

  As described above, by disposing a plurality of rows of non-through holes 11 in the light guide plate 1, the display region 9 of the light guide plate 1 can be caused to emit light uniformly.

  In the case of the light guide plate 1 according to the second embodiment, the second embodiment also uses the injection mold 13 provided with two rows of pins 26, 26,. Resin molding can be performed by performing the same process as in the case of 1.

  In the second embodiment, the case of the non-through holes 11 arranged in two rows of the first and second groups 41 and 42 has been described, but the non-through holes 11 are arranged in a plurality of rows of three or more rows. You can also

  In each of the above-described embodiments, the cross-sectional shape of the non-through hole 11 is circular, but may be an ellipse or a polygon.

  The light guide plate of the present invention has uniform light emission in a pattern switching display device or the like in which a light incident direction needs to be incident from all end faces of the surface light emitting light guide plate, and is a light emitting device such as a backlight. The present invention can also be applied to make the light source of the light emitting diode uniform by using only the light guide plate.

DESCRIPTION OF SYMBOLS 1 Light guide plate 2 Display apparatus 3a, 3b, 3c, 3d Light source board 4 Light emitting diode 5 The surface of the light guide plate 1 6 The back surface of the light guide plate 1 7 Light incident part 8 Recessed part 9 Display area 10 Between the light incident part 7 and the display area 9 Section 11 Non-through hole 12 Groove 20 Injection mold 21 First mold 22 Second mold 23 Concavity and convexity 24 Stamper 25 Cavity recess 26, 26,... Pin 27 Cavity 28 Molten resin 28a Tip of molten resin 29 Spru 30 Runner 31 Gates 41 and 42 First and second groups W1 Light source width W2 Width of the non-through hole 11

Claims (5)

In a light guide plate in which light incident inside from a light incident portion between a back surface and a front surface is reflected by a concave surface formed to be depressed toward the front surface on the back surface, and the reflected light is emitted from the front surface ,
A non-through hole with a depth that opens at the front surface of the section between the light incident portion and the recess and extends toward the back surface and does not penetrate the back surface;
Formed irregularities on the inner surface near the surface of the non-through hole,
Light guide plate. The shape of the unevenness provided in the non-through hole is a prism shape extending in parallel with the light incident from the nearest light incident part,
The light guide plate according to claim 1. The cross-sectional shape of the non-through hole is any one of a circle, an ellipse, and a polygon,
The light guide plate according to claim 1 or 2. Clamping a first mold having a stamper with fine irregularities formed on the surface, and a second mold having a recess that forms a molded product and a pin that can slide into the recess,
Injecting and filling molten resin into the cavity formed by clamping the mold,
Inserting the pin into the cavity until the position where the tip does not contact the stamper after filling the resin until the start of pressure holding, and forming the shape of the molded article in the pressure holding step,
An injection molding method for a light guide plate. The pin has a concavo-convex shape at the tip,
The light guide plate injection molding method according to claim 4.

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