JP5353602B2 - Manufacturing method of light source unit - Google Patents

Description

The present invention relates to a method for manufacturing a light source unit in which a light emitting element is mounted on a circuit board.

  As a display device represented by a liquid crystal display device, a type having a built-in light source is widely used in order to obtain brightness necessary for image display. For example, in a display device such as a color notebook PC using a TFT type liquid crystal panel or STN type (super TN type) liquid crystal panel, a light source is arranged on the back side (back side) of the liquid crystal panel, and light emitted from this light source is transmitted. A backlight system that is incident on a liquid crystal panel is often used.

  By the way, in this type of display device, the power consumed by the light source used in the backlight system accounts for most of the power consumed by the entire device. Therefore, the improvement of the light source efficiency is a problem in the present work in which reduction of the total power is strongly demanded.

  Conventionally, as a measure for improving the light source efficiency, a light emitting diode (LED) or the like is used as a light source to increase the power-luminescence conversion efficiency, or the so-called local dimming method is applied, and the necessary amount according to the surrounding brightness. Only light emission (dimming) is used to increase the transmission and utilization efficiency of light emitted from the light source.

  In addition, as a means for increasing the light transmission and utilization efficiency, an optical sheet having a brightness enhancement film such as BEF (registered trademark of 3M USA: Brightness Enhancement Film) is disposed between the light source or the light guide plate and the liquid crystal panel. It is widely known and used in practice.

  This brightness enhancement film is an optical film in which prisms having a triangular cross section are arranged in one direction on one surface portion (that is, a repetitive array structure of prisms arranged in one direction). It has the function of enabling the recycling of light by direction change (reversion) and retroreflection (see, for example, Patent Documents 1 to 3). For this reason, it becomes possible to obtain desired front luminance while reducing power consumption by adopting the above-described luminance enhancement film represented by BEF for the display device. Actually, since it is necessary to control the luminance of the display light in the horizontal and vertical directions of the display device, the two optical sheets provided with the luminance enhancement film so that the arrangement directions of the prism groups intersect each other. Are often used in a superimposed manner.

  In addition, a lens sheet using a microlens sheet as a lens sheet having a simple sheet structure has been proposed (for example, see Patent Document 4).

  Further, even in a large display device, in addition to a conventional direct type CCFL (cold cathode tube) backlight unit and a direct type LED type backlight unit, a light guide plate type backlight unit (for example, Patent Documents 1 and 2). Is being put to practical use.

Japanese Patent Publication No. 01-37801 Japanese Patent Laid-Open No. 06-102506 Japanese National Patent Publication No. 10-506500 JP 2006-301582 A

  As described above, increasing the light utilization efficiency of the display device can lead to energy saving and improvement of the brightness of the display.

  However, as a conventional light source unit, for example, when a light emitting element or the like is used as a light source, as shown in FIG. 3, the light source unit has a prism shape with a predetermined distance above the light emitting element 22 mounted on the circuit board 21. It is assumed that the optical sheet 23 is arranged. In such a configuration, a reflection loss due to the reflected light 24 from the light incident surface of the optical sheet 23 becomes a problem.

  Therefore, when using a light emitting element or the like, it is an important point to reduce the reflection loss at the incident surface of the optical sheet 23.

  Usually, the light loss between the light emitting element 22 and the optical sheet 23, which is a light source, is filled with a filler to form an optical joint surface, thereby reducing the reflection loss at the light incident surface. Not taken. In addition, the filler used here requires transparency and durability, and also requires a bonding step, leading to a problem of cost increase.

  In addition, when a prism sheet having a specific surface shape is used as the optical sheet 23, it is difficult to form the optical bonding surface because it cannot contact the back side, and as a result, the yield is improved. It becomes difficult.

  By the way, if the resin is injected into a mold closed by injection or the like, a circuit board on which a light emitting element is mounted is set in a mold engraved with a lens, and then the molten optical resin is injected and cooled and cured. Thus, the same effect can be obtained without a filler.

  However, the injection method is limited in size, and there are tact and mold costs, which are the work methods that move to the next after each process in a fixed flow work, and it is restricted from the viewpoint of productivity. Is big.

  In general injection, since the mold is heated during operation, it is necessary to consider thermal damage to the circuit board set in the mold, which is desirable from the standpoint of circuit board protection and workability. It is not a thing.

The present invention has been made in view of the above circumstances, and provides a method for manufacturing a highly efficient light source unit with excellent productivity by integrating light source components and an optical sheet without impairing productivity. With the goal.

In order to solve the above-described problems, the present invention provides a transport system composed of a plurality of rollers, a T die installed immediately above a desired position of a transport line by the transport system, and a predetermined position from directly below the T die. An embossing roll having a cooling mechanism that is arranged shifted to the downstream side of the distance and has an embossing of a predetermined optical shape on the surface, and on a circuit board including a light emitting element conveyed by the conveying system Then, a sheet-like molten optical resin is extruded from the T-die, and a predetermined optical shape embossing applied to the surface of the embossing roll before the molten optical resin is cured is applied to the optical resin surface. when transferring, the cooling and the optical resin by cooling mechanism, said rotating by a cooling roll to face to the embossing roll is installed in the transport line lower side provided with the embossing roll By performing transfer processing in the embossed said optical resin surface of the predetermined optical shape while subjected to a cooling of the substrate, and the gap is removed at the boundary between the optical resin and the circuit board including a light emitting element, It is a manufacturing method of the light source unit which performs simultaneously transfer of the optical shape to the optical resin surface.

  According to the present invention, it is possible to integrate a light source component and an optical sheet without impairing productivity, and to provide a highly efficient light source unit, display device, and light source unit manufacturing method excellent in productivity. Can do.

The block diagram which shows one Embodiment of the light source unit which concerns on this invention. The figure explaining the manufacturing method of the light source unit which concerns on this invention . The figure for demonstrating the conventional light source unit.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a block diagram showing an embodiment of a light source unit according to the present invention.

  The light source unit includes a circuit board 1 having a wiring pattern 1b formed on a board 1a, a light emitting element 2 disposed on the circuit board 1 and having terminal portions 2a at both ends, and light emission at a predetermined position on the circuit board 1. A laminated structure is formed by a solder weld portion 3 to which the element 2 is attached and an optical resin layer 4 filled so as to cover the periphery of the light emitting element 2, and serves as an emission side surface of the light beam 5 from the light emitting element 2. An optical shape portion 6 is formed on the outer surface of the optical resin layer 4.

  The substrate 1a may be a material that has been widely used conventionally, for example, a material such as glass epoxy or paper bakelite, and the number of layers may be a single layer to a double-sided plate, a four-layer plate, or a highly laminated substrate of six layers or more. It can be used without any particular restrictions.

  The wiring pattern 1b on the substrate 1a is formed with an arbitrary pattern according to the electrode shape of the light emitting element 2, or according to the number of light emitting elements and the arrangement of the light emitting elements.

  As the light emitting element 2, for example, a light emitting diode (LED) is used. In the light emitting diode, when a forward voltage is applied to the PN junction of the semiconductor diode, holes from the P region and electrons from the N region move toward the PN junction region and current flows. At this time, in the vicinity of the PN junction, a phenomenon called recombination occurs in which electrons and holes are bonded to each other and disappear. The difference between the combined energy after this recombination and the energy of electrons and holes becomes a light beam 5 and is emitted in the direction of the optical shape portion 6.

  The optical resin layer 4 corresponds to the optical sheet described above, and an optical coupling that does not sandwich a void layer (air layer) or the like at the interface between the light emitting element 2 and the optical resin layer 4 is obtained, and In order to obtain sufficient mechanical bonding strength, parts other than the light emitting element 2 are taken into consideration and integrated by fitting, adhesion, adhesion, or the like. A specific method for manufacturing the optical resin layer 4 will be described later.

  The optical resin layer 4 is an interface between the light emitting element 2 and the light emitting part 2 of the light emitting part 2 on the element surface by filling the periphery of the light emitting part with the optical resin and integrating with the light emitting element 2. In addition, it is possible to prevent reflection that occurs at the time of entering the optical film composed of the optical resin layer 4 and the optical shape portion 6.

  When the optical resin is actually filled around the light emitting portion of the light emitting element 2, the circuit board 1 on which the light emitting element 2 such as a light emitting diode is mounted in advance is prepared, and the optical resin is filled around the light emitting portion of the light emitting element 2. Thus, the optical resin layer 4 is formed, and the optical shape portion 6 is provided on the surface of the optical resin layer 4.

  The optical resin that forms the optical resin layer 4 is, for example, polycarbonate resin, acrylic resin, fluorine acrylic resin, silicone acrylic resin, epoxy acrylate resin, polystyrene resin, cycloolefin polymer, methylstyrene resin, fluorene resin, pyripropylene. From the viewpoint of productivity, it is preferable to use a transparent resin made of a thermoplastic resin.

  In addition, when the heat resistance and stability of a product are required, it is desirable to use a thermosetting resin.

  In addition, if the refractive index is set to be the same, such as using the same material for the optical resin and the sealing agent for the light emitting element 2, reflection at the interface will not occur, which is preferable from the viewpoint of light utilization efficiency. Even if the refractive indexes are not the same, the reflection at the interface can be reduced by bringing both refractive indexes close to each other, which is desirable from the viewpoint of light utilization efficiency.

  The optical shape portion 6 is formed on the outer surface of the optical resin layer 4. That is, by forming the optical shape portion 6 directly on the light emitting surface side of the optical resin layer 4, the light distribution pattern of the emitted light can be adjusted, and optical characteristics according to the purpose can be given.

  Specifically, the prism shape is common, but depending on the pattern of the plate, such as a stripe shape such as a cylindrical lens shape, a structure in which lenses such as a microlens array are two-dimensionally arranged, and a combination thereof. Depending on the purpose of use, various shapes can be given.

  Further, by containing or dispersing a pigment or dye such as a diffusing agent in the optical resin layer 4, it is possible to further adjust the light distribution pattern. As the diffusing agent, for example, a filler (transparent particles) made of an inorganic oxide or a resin is preferably used. Examples of the transparent particles made of an inorganic oxide include silica and alumina. Moreover, a white pigment and air bubbles can also be used as a diffusing agent.

Next, a method for manufacturing a light source unit according to the present invention will be described with reference to the drawings.
The optical unit can be manufactured by, for example, an extrusion molding method. FIG. 2 is a diagram illustrating a method of manufacturing the light source unit of the present embodiment by an extrusion molding method.

  First, the light source unit substrate 7 in which the light emitting element 2 is mounted on the circuit board 1 in advance is transported so as to pass directly under the extruder T die 12 by the transport system 11 including a plurality of transport rollers. A cooling roller 13 is disposed on the lower side and a roll mold plate 14 is disposed on the upper side so as to sandwich the conveyance line of the conveyance system 11 separately from the conveyance system 11 immediately below the extruder T die 12.

  The light source unit substrate 7 enters between the cooling roller 13 and the roll mold plate 14 by conveyance by the conveyance system 11, but immediately before the entry, the molten optical resin is extruded and flowed down from the extruder T die 12. Optical resin is applied to the upper surface of the circuit board 2 including the light emitting element 2. At this time, light is emitted by a desired optical shape (emboss) engraved on the surface of the roll mold plate 14 while applying sufficient pressure to the optical resin melted by the roll mold plate 14 disposed on the transport line. By pressing the optical resin on the circuit board 2 on which the element 2 is mounted, the optical shape portion 6 is formed on the outer surface of the optical resin.

  That is, a roll mold that becomes an embossing roll carved into a desired optical shape after the optical resin is extruded into a flat plate shape by an extrusion method using a T-die 12 and sheeted on the circuit board 1 before the optical resin is cured. The optically shaped portion 6 is formed on the surface of the optical resin layer 4 by being sandwiched between the plates 14.

  At this time, the optical shape portion 6 is formed on the optical resin layer 4, and at the same time, the degree of adhesion between the circuit board 1 and the optical resin layer 4 is increased, and further, the optical coupling between the light emitting element 2 and the optical resin layer 4 is enhanced. Is.

  Furthermore, the roll mold plate 14 is used by setting the temperature and speed suitable for shaping the optical shape by providing the function of cooling the optical resin.

  Further, if necessary, a cooling roll (not shown) may be arranged in association with the surface corresponding to the back surface side of the optical resin layer 4 to facilitate the shaping of the optical shape. Since this cooling roll corresponds to the uneven shape on the surface of the circuit board, it can be used for various types of rubber rolls.

  Further, a cooling roller 13 is disposed so as to face the roll mold plate 14 across the conveyance line. The cooling roller 13 forms the optical resin layer 4 and simultaneously forms the back side of the circuit board 1. By cooling, it is possible to protect the light emitting element 2 mounted in advance on the substrate 1 a and circuit components such as a semiconductor that drives the light emitting element 2 from the temperature when the optical resin layer 4 is formed.

  In particular, when a resin that melts at a high temperature, such as a polycarbonate resin, is used as the optical resin, the circuit board 1 is also temporarily heated to a high temperature. Therefore, it is desirable to cool from the viewpoint of circuit protection.

  By the way, in the light source unit in which the optical resin layer 4 is applied on the circuit board 1 on which the light emitting element 2 is mounted as described above, it is necessary to remove the protruding portion of the melted optical resin and to adjust the shape to a desired shape. Therefore, a cutting mechanism 15 that operates in synchronization with the transport speed of the transport system 11 is disposed and cut into a desired shape.

  Note that a Thomson cutter, a laser cutter, or the like may be provided in order to accurately cut the cross-sectional shape.

  Further, if the productivity is satisfactory, off-line end surface processing may be performed. In short, an appropriate cutting means can be selected according to the production quantity and tact.

  Therefore, according to the embodiment as described above, the light beam 5 emitted from the light emitting element 2 is taken into the optical resin layer 4 without touching the interface with the air, compared with the method using the conventional optical sheet, Since it reaches the optical shape part 6 shaped in the resin layer 4, there is no reflection loss at the interface, the light beam 5 emitted from the light emitting element 2 can be efficiently extracted, and a bright light source can be obtained with the same power. it can.

  Further, an optical resin is extruded into a flat plate shape by an extrusion method using a T-die 12 and pressed with a roll die plate 14 engraved with an optical shape before the resin is cured, whereby an optical shape portion is formed on the surface of the optical resin layer 4. Therefore, the light usage efficiency can be improved by shaping the optical shape according to the desired optical characteristics such as the backlight for liquid crystal displays and digital signage (digital electronic outdoor advertising). Can be improved.

  In addition, the optical properties can be adjusted by containing or dispersing pigments or dyes in the optical resin for adjusting the optical properties.

  Furthermore, since the circuit board 1 on which the light emitting element 2 is mounted and the optical resin layer 4 corresponding to the optical sheet can be integrated, the number of constituent members can be reduced compared to a method in which the optical sheet is bonded with an adhesive, and the like. Since it is a simple process that can be collectively manufactured in a process corresponding to sheet forming, it can be produced at low cost.

  Furthermore, the series of manufacturing processes is not only simpler than the injection method described above, but also does not require a large closed mold, and intermittent roll forming is possible, resulting in high production capacity per hour. It can be said that this method is suitable for mass production.

  Further, the circuit board 1 is heated until the resin comes into contact with it and is cooled, and the heating amount can be suppressed to the minimum necessary as compared with the injection method.

  In addition, since the optical resin layer 4 is directly formed on the circuit board 1 on which the light emitting element 2 is mounted, an adhesive material serving as an adhesive layer can be omitted, and it has excellent characteristics in terms of environmental resistance such as temperature and humidity.

(Other embodiments)
(1) In the above embodiment, the light source unit has been described. However, since the optical resin layer 4 is formed directly on the circuit board 1 on which the light emitting element 2 is mounted as described above, no adhesive material is required. Environmental resistance such as temperature and humidity can be improved. Therefore, when the light source unit for a liquid crystal display is incorporated and used, it will have excellent environmental resistance, and it will maintain durability and stability over a long period of time even when the temperature inside the TV case rises. Can do.

(2) Although a light emitting diode (LED) is generally used as the light emitting element 2, a laser diode (LD), an organic EL (OLED), or the like may be used, and is not particularly limited.

  In addition, the present invention is not limited to the above-described embodiments and examples, and various modifications can be made without departing from the scope of the invention.

(3) Furthermore, the light source unit according to the present invention can be used for all liquid crystal display devices, and can be used as a surface emitting light source whose light emission angle is adjusted in advance. It can also be used for backlights for signboards and signs.

  DESCRIPTION OF SYMBOLS 1 ... Circuit board, 1a ... Board | substrate, 1b ... Wiring pattern, 2 ... Light emitting element, 4 ... Optical resin layer, 5 ... Light beam, 6 ... Optical shape part, 7 ... Light source unit board | substrate, 11 ... Conveyance system, 12 ... Extruder T die, 13 ... cooling roller, 14 ... roll mold plate, 15 ... cutting machine.

Claims (1)

A conveying system composed of a plurality of rollers, a T die installed immediately above a desired position of a conveying line by this conveying system, and a predetermined distance on the downstream side from a position below the T die and arranged downstream. And an embossing roll with a cooling mechanism that is embossed with an optical shape of
A sheet-like molten optical resin is extruded from the T-die onto a circuit board including a light emitting element conveyed by the conveying system, and the embossing roll is cured before the molten optical resin is cured. When the embossing having a predetermined optical shape applied to the surface of the sheet is transferred to the surface of the optical resin, the cooling of the optical resin by the cooling mechanism provided in the embossing roll, and the lower side of the transport line facing the embossing roll The circuit board including the light emitting element and the optical resin are formed by transferring the emboss of the predetermined optical shape to the surface of the optical resin in a state where the circuit board is cooled by a cooling roll installed on the optical resin. The method of manufacturing a light source unit is characterized in that the removal of the gap at the boundary between the optical shape and the transfer of the optical shape onto the surface of the optical resin is simultaneously performed.

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