TW201423178A - Light guide plate, planar light source apparatus, transmissive image display apparatus, and light guide plate manufacturing method - Google Patents

Abstract

According to one embodiment of the present invention, a light guide plate outputs light, as planar light, from a light output surface intersecting a light input surface, said light having been inputted from the light input surface. The light guide plate is provided with a light guide plate base material section, which has the light input surface and the light output surface, and which is formed of a transparent and flexible material.

Description

Light guide plate, surface light source device, transmissive image display device, and method of manufacturing light guide plate

The present invention relates to a light guide plate, a surface light source device, a transmissive image display device, and a method of manufacturing a light guide plate.

In the transmissive image display unit such as a liquid crystal panel, the transmissive image display unit itself does not emit light, and an image is displayed by illumination by a separately provided surface light source device. An example of the surface light source device is a side light type surface light source device including a light guide plate and a light source unit disposed on the side. A transmissive image display device including the transmissive image display unit and the surface light source device is widely known.

In recent years, it has been demanded to be applied to a flexible display device such as an electronic paper. For example, a self-luminous type display device using organic EL (Organic Electro-Luminescence) is known (refer to Patent Document 1).

Prior technical literature Patent literature

Patent Document 1: Japanese Patent Laid-Open No. 2004-11879

A flexible device is known as a self-luminous display device using an organic EL. Recently, a non-light-emitting display device using a transmissive image display unit such as a liquid crystal panel is required to be flexible. In order to make the non-light-emitting display device a flexible device, the light guide plate must also be flexible.

Accordingly, an object of the present invention is to provide a flexible light guide plate, a surface light source device including the same, a transmissive image display device, and a method of manufacturing the same.

A light guide plate according to an aspect of the present invention is a light guide plate that emits light incident from an incident surface from an exit surface intersecting the incident surface as a planar light. The light guide plate includes a light guide plate base portion having an incident surface and an exit surface, and includes a transparent and flexible material.

The light guide plate base portion contains a transparent and soft material, so that the light guide plate has flexibility.

In one embodiment, the light guide plate may further include a plurality of light scattering portions disposed on the back surface of the substrate portion of the light guide plate opposite to the exit surface, and scattering at least a portion of the light incident from the incident surface To the exit side.

In one embodiment, the material of the light guide plate base material portion may be a material containing a total light transmittance of the base material for measurement of the material of 80% or more. In this case, the base portion for measurement is a rectangular parallelepiped having a length in the longitudinal direction of 250 mm in plan view. Further, the amount of light that is incident from the first side surface orthogonal to the longitudinal direction and that is emitted from the second side surface opposite to the first side surface is Q _out , and the amount of light incident on the first side surface is set. For Q _in , the total light transmittance is defined by Q _out /Q _in .

In one embodiment, the light guide plate may have a flexibility in which the innermost radius is 2.5 cm or less when it is wound into a roll shape.

In one embodiment, the thickness of the light guide plate base material portion may be 0.7 mm or less.

In one embodiment, the light guide plate further includes a plurality of light scattering portions, which are disposed on the back surface of the light guide plate base portion opposite to the exit surface, and scatter at least a portion of the light incident from the incident surface to the exit On the surface side, the light scattering portion may be a light scattering point having a substantially circular shape in plan view. In this case, when the thickness of the base material portion of the light guide plate is D and the diameter of the light scattering portion is F, the F/D may be 0.33 or less.

Another aspect of the present invention provides a surface light source device comprising: one aspect of the present invention described above a light guide plate; and a light source that supplies light to an incident surface of the light guide plate.

A transmissive image display device according to still another aspect of the present invention includes: the light guide plate according to an aspect of the present invention; a light source that supplies light to an incident surface of the light guide plate; and a transmissive image display portion that receives the light from The surface of the light guide plate displays light.

Another aspect of the present invention for manufacturing a light guide plate is a method of manufacturing a light guide plate which is transparent and flexible, and which emits a planar light from an exit surface intersecting the incident surface. The method for producing a light guide plate includes the steps of: continuously extruding a transparent and soft thermoplastic resin in a molten state to produce a resin sheet; and winding the resin sheet into a roll shape to be carried; on the main surface of the resin sheet And printing a plurality of light scattering portions for scattering at least a portion of the light incident from the incident surface to the exit surface side; and obtaining a guide by cutting the resin sheet printed with the plurality of light scattering portions to a specific size Light board.

The resin sheet is formed by continuously extruding a thermoplastic resin in a molten state, and thus is long in the extrusion direction. Since the long resin sheet is wound into a roll and conveyed, for example, in the case of transporting the resin sheet in the manufacturing process, the conveyance operation is easy.

According to the present invention, a flexible light guide plate, a surface light source device including the light guide plate, a transmissive image display device, and a method of manufacturing the light guide plate can be provided.

1‧‧‧Transmissive image display device

2‧‧‧Light source department

2A‧‧‧ point light source

3‧‧‧Transmission type image display unit

4‧‧‧ surface light source device

10‧‧‧Light guide plate

11‧‧‧Light guide plate base

11a‧‧‧Incoming surface

11b‧‧‧Outlet

11c‧‧‧back

11d‧‧‧ side

12‧‧‧Light Scattering Department

20‧‧‧ samples (measurement base)

20a‧‧‧Incoming surface

20b‧‧‧ side

30‧‧‧Light source department

31‧‧‧Detection Department

40‧‧‧Manufacture of equipment

41‧‧‧Extrusion machine

41a‧‧‧Resin input

42‧‧‧die

43A‧‧‧1st squeeze roller

43B‧‧‧2nd squeeze roller

43C‧‧‧3rd squeeze roller

44‧‧‧Cutting machine

45‧‧‧Printing Department

50‧‧‧roll

D‧‧‧thickness

F‧‧‧diameter

R‧‧‧ Radius

Q _in ‧‧‧Injection

Q _out ‧‧‧Amount of shots

S‧‧‧Resin sheet

S10~S13‧‧‧ steps

Fig. 1 is a schematic view showing a light guide plate of an embodiment.

Figure 2 is a diagram for explaining the total light transmittance.

Fig. 3 is a schematic view showing a state in which the light guide plate shown in Fig. 1 is wound around a roller.

Fig. 4 is a view showing a schematic configuration of an example of a device for manufacturing the light guide plate shown in Fig. 1.

Fig. 5 is a flow chart showing a method of manufacturing a light guide plate.

Fig. 6 is a schematic view showing a schematic configuration of a transmissive image display device to which a light guide plate is applied.

Fig. 7 is a view showing a modification of the method of manufacturing the light guide plate.

Fig. 8 is a view showing a modification of the winding method of the light guide plate.

Fig. 9 is a schematic view showing a state in which a modification of the light guide plate shown in Fig. 1 is wound around a roller.

Fig. 10 is a view showing still another modification of the winding method of the light guide plate.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the description of the drawings, the same components are denoted by the same reference numerals, and the description thereof will not be repeated. The size ratio of the schema is not necessarily consistent with the description. In the description, the terms indicating "upper" and "lower" are based on the convenience of the state shown in the drawing.

Fig. 1 is a schematic view showing a light guide plate of an embodiment. The light guide plate 10 includes a plate-shaped light guide plate base portion 11. The light guide plate base portion 11 has an incident surface 11a for light incident, an exit surface 11b for emitting light, and a rear surface 11c which is located on the opposite side of the exit surface 11b. The incident surface 11a is a side surface that intersects the exit surface 11b and the back surface 11c (in FIG. 1, orthogonal to the exit surface 11b and the back surface 11c). The incident surface 11a functions as an incident surface of the light guide plate 10. The exit surface 11b functions as an exit surface of the light guide plate 10. Examples of the planar shape of the light guide plate base portion 11 (the shape viewed from the thickness direction) include a rectangle and a square. The light guide plate base portion 11 guides light incident from the incident surface 11a toward the side opposite to the incident surface 11a. Hereinafter, the direction from the incident surface 11a toward the side surface 11d is also referred to as a light guiding direction.

A plurality of light scattering portions 12 are provided on the back surface 11c. The light scattering portion 12 scatters light incident from the incident surface 11a. Thereby, at least a part of the light incident from the incident surface 11a and scattered by the light scattering portion 12 is transmitted toward the exit surface 11b side. That is, at least a part of the light incident from the incident surface 11a is reflected by the light scattering portion 12 to the exit surface 11b side. The arrangement state of the plurality of light scattering portions 12 and the shape of each of the light scattering portions 12 may be set such that the light emitted from the exit surface 11b has a desired characteristic. For example, the arrangement state of the plurality of light-scattering sections 12 and the shape of each of the light-scattering sections 12 may be set such that light of uniform brightness is emitted from the exit surface 11b. Light dispersion Examples of the projecting portion 12 may include lenticular, quadrangular pyramidal, and plate-shaped light scattering dots. The light scattering portion 12 may be convex or concave. The light scattering portion 12 may be a convex portion or a concave portion that extends in the direction perpendicular to the light guiding direction on the back surface 11c. In this case, a plurality of light scattering sections 12 are arranged side by side in the light guiding direction. The light scattering portion 12 may also contain diffusing particles.

The light scattering portion 12 can be formed, for example, by a printing method. Examples of the printing method for forming the light scattering portion 12 may include screen printing, inkjet printing, and screen printing. Further, as shown in FIG. 9, the light-scattering portion 12 may be formed in a concave shape by a method of irradiating laser light, or may be formed in a concave shape or a convex shape by pressing a stamper having fine irregularities.

In the method of inkjet printing, a smaller light scattering portion 12 can be formed. When the light scattering portion 12 is small, even if the thickness of the light guide plate 10 is thin, it is difficult to see the light scattering portion 12 from the side of the emission surface 11b. Before the inkjet printing is performed, the liquid-repellent treatment may be performed on the back surface 11c of the light guide plate base portion 11 as a pretreatment. Examples of the material of the light scattering portion 12 may include white ink, ultraviolet curable resin, or the like.

Examples of the liquid-repellent treatment include a treatment using a surface modifier as a liquid repellent, a treatment using various energy rays, a treatment using chemical adsorption, and a treatment using graft polymerization on the surface of the material.

The treatment with the surface modifier is performed on the back surface 11c to form a liquid-repellent layer to which a small amount of the surface modifier is added. Examples of the surface modifier of the liquid repellent agent include an ethylene-based polymer having a perfluoroalkyl group (Rf group) in the side chain, and an anthracene containing an Rf group. The liquid-repellent layer can be formed by immersing the surface modifier in waste paper or the like on the back surface 11c, or spraying the surface modifier on the back surface 11c by spray coating or inkjet printing.

The treatment using various energy lines causes the back surface 11c to have liquid repellency by the energy line. Examples of the energy line may include a plasma, an electron beam, an ion beam, and the like. In the case of using the liquid treatment in the case of using plasma treatment, it may include: by means of plasma. After etching to roughen the back surface 11c, a liquid-repellent monomolecular film is formed on the roughened surface; The back surface 11c is fluorinated by a fluorine-based gas plasma; a film containing a liquid-repellent compound is formed on the back surface 11c by plasma CVD (Chemical Vapor Deposition); and the back surface 11c is formed by plasma polymerization. A liquid-repellent film or the like is formed thereon.

In the example of the surface roughening treatment, the back surface 11c may be provided with a concavo-convex shape by hot pressing, etching by a chemical, blasting treatment, or the like.

In the chemical adsorption treatment, it is preferred to modify the end of the adsorption molecule with fluorine. Particularly, as the terminal substituent, a CF3 group is preferred from the viewpoint of liquid repellency.

In the example of such a treatment, the fluorination of the back surface 11c by the fluorine-based gas plasma is preferable in that it can be easily and uniformly surface-treated.

In the case of performing inkjet printing, the back surface 11c of the light guide plate base portion 11 may be subjected to a hydrophilization treatment as a pretreatment thereof. Examples of the hydrophilization treatment include ultraviolet irradiation, contact with an alcohol, and plasma treatment. Ultraviolet irradiation can be performed using a low pressure mercury lamp, a metal halide lamp, or the like. Ultraviolet irradiation can be carried out in an air environment or in an ozone environment. The contact of the surface of the acrylic resin sheet with the alcohol can be carried out, for example, by rubbing the surface of the acrylic resin sheet with a fibrous substrate such as a waste cloth impregnated with alcohol. As the alcohol, for example, isopropyl alcohol (IPA) is used. An example of plasma treatment is corona treatment.

Hereinafter, the configuration of the light guide plate 10 will be described in detail. The light guide plate 10 is a flexible light guide plate 10. Specifically, the light guide plate base portion 11 is transparent and flexible. The light guide plate base portion 11 contains a transparent and soft material. More specifically, the light guide plate base portion 11 may contain a so-called elastomer. Examples of the material of the light guide plate base portion 11 include an acrylic resin, a styrene resin, a polymethyl methacrylate (PMMA) resin, a polystyrene (PS) resin, and MS (methyl methacrylate-styrene copolymer). Resin, polycarbonate resin, AS (acrylonitrile-styrene copolymer) resin, cycloolefin resin, polyethylene resin, polyacrylic resin, and polyethylene terephthalate resin. Preferably, the material of the light guide plate base portion 11 may be a block copolymer of methyl methacrylate and butyl acrylate. In one embodiment, the guide The light-plate base portion 11 may be a sheet-like molded product obtained by laminating a polycarbonate resin layer on one surface or both surfaces of an acrylic resin layer. The light guide plate base portion 11 may contain additives such as a light diffusing agent, an ultraviolet absorber, an antistatic agent, an antioxidant, a processing stabilizer, a flame retardant, and a lubricant, without departing from the scope of the invention.

The light guide plate 10 may be transparent to guide the light to the extent that the light guide plate 10 can be used. In one embodiment, a specific sample (base material for measurement) 20 is produced from the same material as the material (substrate) constituting the light guide plate base portion 11, and the total light transmittance Tt of the sample 20 is 80% or more. Preferably, it is preferably 85% or more.

A method of measuring the total light transmittance Tt will be described with reference to Fig. 2 . Figure 2 is an explanatory diagram for explaining the total light transmittance. First, a sample 20 having a length of 250 mm, a width of 40 mm, and a thickness of 2 mm was prepared by using the same material as the light guide plate base portion 11. With respect to the sample 20, the light source unit 30 measures the light incident on one side surface (first side surface) 20a from the light source unit 30, and the other side surface (opposite side of the side surface 20a) facing the side surface 20a ( The second side) 20b emits light. The detecting unit 31 is, for example, a long light path measuring device (U-4100) manufactured by Hitachi High-Tech Co., Ltd., a joint-stock company. When the amount of light incident on the side surface 20a which is the incident surface is Q _in and the amount of light outputted from the side surface 20b is Q _out , the total light transmittance Tt is expressed by the following formula (2) .

Tt=Q _out /Q _in ...(2)

As shown in FIG. 1, when the thickness of the light guide plate base portion 11 is D, in one embodiment, the thickness D is preferably 0.1 mm to 0.7 mm, more preferably 0.2 mm to 0.4 mm. .

In one embodiment, the light guide plate 10 has a softness at the innermost side when the light guide plate 10 is wound into a roll shape, preferably 2.5 cm or less, more preferably 1.5 cm or less. The details will be described with reference to FIGS. 3 and 9. 3 and FIG. 9 are schematic cross-sectional views showing a state in which the cross section perpendicular to the center line of the roll is cut in a state where the light guide plate is wound around the roll. The light guide plate 10 has a degree of flexibility in that the light guide plate 10 is wound around a roller 50 having a radius R. In this case, the light guide plate 10 may be closely wound around a roll 50 preferably having a radius R of 2.5 cm or less, more preferably a radius R of 1.5 cm or less. The above-described softness of the light guide plate 10 can be achieved as long as the light guide plate base portion 11 has the same flexibility.

As shown in FIG. 1, the light scattering portion 12 has a plan view shape (a shape viewed from the thickness direction of the light guide plate base portion 11) of the light scattering point in a case of a lenticular or dome-shaped light scattering point. shape. In the case where the diameter of the light-scattering portion 12 having a substantially circular planar shape is F, the F/D is preferably 0.33 or less, and more preferably 0.13 or less.

The light guide plate 10 having the above configuration can be manufactured by using the manufacturing apparatus shown in FIG. Fig. 4 is a view showing a schematic configuration of an example of a device for manufacturing the light guide plate shown in Fig. 1. The light guide plate 10 is manufactured by extrusion molding using the manufacturing apparatus 40 shown in FIG.

The manufacturing apparatus 40 mainly includes an extruder 41 that extrudes a raw material resin of the light guide plate base portion 11 in a heated and molten state, and a die 42 that continuously feeds the raw material resin from the extruder 41 in a sheet state. The long resin sheet S is extruded and formed, and the first pressing roll 43A, the second pressing roll 43B, and the third pressing roll 43C are disposed on the downstream side of the die 42 in order from each other. An example of the die 42 is a T-die.

Fig. 5 is a flow chart showing a method of manufacturing a light guide plate. As shown in FIG. 5, the manufacturing method of the light guide plate 10 includes the resin sheet manufacturing step S10, the transporting step S11, the printing step S12, and the cutting step S13. Each step will be described.

(Resin Sheet Manufacturing Step S10)

The resin sheet S is manufactured by the manufacturing apparatus 40. Specifically, the raw material resin is introduced into the resin inlet port 41a of the extruder 41. The extruder 41 melts and kneads the input raw material resin. Thereafter, the extruder 41 supplies the raw material resin after melt-kneading to the die 42, and continuously extrudes from the die 42 in a sheet form to form a resin sheet S.

The resin sheet S discharged from the die 42 passes between the first pressing roller 43A and the second pressing roller 43B. At this time, the resin sheet S is in the thickness direction by the first pressing roller 43A and the second pressing roller 43B. Clamped up and squeezed by it. The resin sheet S having passed between the first pressing roll 43A and the second pressing roll 43B is then pressed between the second pressing roll 43B and the third pressing roll 43C.

The resin sheet S that has passed through the third pressing roll 43C has flexibility. Therefore, as shown in FIG. 4, the resin sheet S which has passed through the third squeeze roll 43C is wound into a roll shape.

(Transfer step S11)

After the resin sheet S of a certain fixed length is wound into a roll shape, the resin sheet S is cut. The cutting of the resin sheet S can be carried out using a cutter 44 disposed on the downstream side of the third pressing roll 43C. Thereafter, the roll-shaped resin sheet S is transferred to a place where the printing step is performed. The resin sheet S wound in a roll shape is referred to as a resin sheet roll.

(Printing step S12)

While the resin sheet S is pulled out from the resin sheet roll, a plurality of light scattering portions 12 are printed on the main surface of the resin sheet S. An example of the printing method is the above method (for example, inkjet printing or the like).

(cutting step S13)

The resin sheet S on which the main surface has been printed is cut to a specific size, whereby the light guide plate 10 is obtained. The cutting of the resin sheet S can be performed by using a cutter similar to the cutter 44.

In the light guide plate 10 having the above configuration, light incident from the incident surface 11a of the light guide plate base portion 11 is transmitted through the light guide plate 10, specifically, in the light guide plate base portion 11, while being totally reflected. During the transmission of the light, if the light is scattered by the light scattering portion 12, the light scattered on the light scattering portion 12 and transmitted to the side of the exit surface 11b is emitted from the exit surface 11b. The light incident from the incident surface 11a is transmitted through the light guide plate 10, and a part thereof is emitted from the exit surface 11b, whereby the planar light is emitted from the exit surface 11b.

Since the light guide plate 10 has flexibility, the light guide plate 10 can be wound around the roller 50 as schematically shown in FIGS. 3 and 9. As a result, for example, even a liquid crystal display of 32 inches or more The light guide plate 10 used in a large-sized transmissive image display device such as a device is also easily transported. In particular, when the light guide plate 10 has flexibility as exemplified, the state in which the light guide plate 10 is wound into a roll shape becomes smaller and is easily conveyed. Moreover, in the manufacturing method exemplified, the light guide plate base portion 11 can be wound into a roll shape and conveyed to the subsequent step, so that it is easy to transport the light guide plate.

As shown in Fig. 1, when a plurality of light-scattering portions 12 are formed on the back surface 11c of the light-guide plate base portion 11, by a printing method or the like, a concave-convex shape or the like is applied to the back surface 11c itself for scattering. In the case of the processing, the stress concentration at the position of the light-scattering portion 12 when the light guide plate 10 is bent can be alleviated as compared with the case where the light-scattering portion is embedded in the light-guide plate base portion 11. As a result, the durability of the light guide plate 10 can be improved.

Further, since the light guide plate 10 has flexibility, the transmissive image display device including the light guide plate 10 can be formed as a flexible transmissive image display device.

Fig. 6 is a schematic view showing a schematic configuration of a transmissive image display device to which the light guide plate 10 is applied. In Fig. 6, the cross-sectional configuration of the transmissive image display device 1 is shown. The transmissive image display device 1 can be preferably used as a mobile phone, a display device of various electronic devices, a television device, and the like.

The transmissive image display device 1 includes a light guide plate 10, a light source unit 2 disposed on the side of the light guide plate 10, and a transmissive image display unit 3 disposed on the front side of the light guide plate 10 (in FIG. 1). Upper side). At least one optical film can be disposed between the light guide plate 10 and the transmissive image display unit 3. Examples of the optical film are a diffusion film, a ruthenium film, and a brightness enhancement film. The optical film is flexible.

The light source unit 2 includes a plurality of point light sources 2A arranged in a line shape. An example of the point light source 2A is a light emitting diode. The light source unit 2 is not limited to a point light source, and may be a linear light source such as a fluorescent lamp (cold cathode ray lamp). The light source unit 2 may include a reflector that reflects light on the opposite side of the light guide plate 10 in order to efficiently enter the light guide plate 10 side.

The light guide plate 10 and the light source unit 2 shown in FIG. 6 constitute a supply surface to the transmissive image display unit 3. The light source device 4 of the light. When an optical film is provided between the transmissive image display unit 3 and the light guide plate 10, the optical film can also be regarded as a constituent element of the surface light source device 4.

The transmissive image display unit 3 illuminates the surface light emitted from the light guide plate 10 to display an image. An example of the transmissive image display unit 3 is a liquid crystal display panel which is a polarizing plate bonding body in which linear polarizing plates are disposed on both surfaces of a liquid crystal cell. The transmissive image display unit 3 has flexibility. The flexible transmissive image display unit 3 can be realized by replacing the glass substrate used in the conventional liquid crystal display panel or the like with a soft plastic.

In the transmissive image display device 1 of the above configuration, the frame that holds the transmissive image display unit 3, the light guide plate 10, the light source unit 2, and the like is flexible and can be bent. The flexible frame can be realized by including a resin having flexibility or the like. In general, the housing that holds the transmissive image display unit 3, the light guide plate 10, the light source unit 2, and the like includes a front side frame that holds the transmissive image display unit 3, and a rear side frame that holds the light guide plate 10 and the light source. Department 2. The front side frame is fixed to the back side frame.

The embodiment of the present invention has been described above, but the present invention is not limited to the embodiment described above, and various modifications can be made without departing from the spirit and scope of the invention.

For example, the printing step S12 may be performed before the transporting step S11. In this case, as shown in FIG. 7, the light scattering portion is printed on the main surface of the resin sheet S by the printing portion 45 before the continuous resin sheet that has passed through the third pressing roller 43C is wound into a roll shape. 12. In Fig. 7, the display of the light scattering portion 12 is omitted. The printing unit 45 is a device that executes the above-described printing method. For example, in the case of inkjet printing, the printing unit 45 includes an inkjet head.

Alternatively, the flexible light guide plate 10 can be manufactured by using a flexible material for the material of the light guide plate 10 without using the transport step S11 of winding the resin sheet S into a roll. In this case, for example, after the printing process is performed on the resin sheet S that has passed through the third pressing roll 43C, the cutting step S13 of cutting the resin sheet S may be performed. Alternatively, after the resin sheet S is subjected to the cutting step S13 to obtain the light guide plate base portion 11, the printing step S12 may be performed on the light guide plate base portion 11.

3 and FIG. 9 show an example of a winding method in the case where the light guide plate 10 is wound into a roll shape, but the winding method of the light guide plate 10 is not limited to the form shown in FIGS. 3 and 9. For example, as shown in FIGS. 8 and 10, the light guide plate 10 may be wound so that the light scattering portion 12 is located inside. In other words, when the light guide plate 10 is wound into a roll shape, either one of the exit surface 11b and the back surface 11c of the light guide plate base portion 11 may be directed inward. This is also the case when the resin sheet S on which the light-scattering portion 12 is printed is wound as shown in FIG.

In FIGS. 3, 8, 9, and 10, in order to clearly show the configuration of the light guide plate 10, the light guide plate base portion 11 and the light scattering portion 12, in particular, the light scattering portion 12 are emphasized and largely shown. However, the light scattering portion 12 has a thickness of usually 100 μm or less, and is usually 50 μm or less. In other words, when the flexibility of the light guide plate 10 is defined by the innermost radius of the state in which the light guide plate 10 is wound into a roll, the thickness of the light scattering portion 12 is as small as negligible. Therefore, even if the light guide plate 10 is wound around the core roller 50 so that the light scattering portion 12 is inside, the radius of the roller 50 can be regarded as being wound into the same as in the case of FIGS. 3 and 9. The radius of the innermost side of the rolled light guide plate 10. Alternatively, when the light guide plate 10 is wound into a roll shape so that the light scattering portion 12 is inside, the radius may be determined based on the back surface 11c of the light guide plate base portion 11. 3, 8, 9, and 10 show a state in which the light guide plate 10 is wound around the core roller 50, and the light guide plate 10 may be wound so that the light scattering portion 12 may be inside. The same is true when the roll 50 as the core is not used.

A plurality of convex portions may be formed on the exit surface 11b. Each convex portion extends in the light guiding direction of the light incident from the incident surface 11a, that is, in the direction from the incident surface 11a toward the side surface 11d. Examples of the shape of the cross section of the convex portion orthogonal to the extending direction of the convex portion include a lens shape such as a lenticular lens and a meandering shape. The plurality of convex portions are arranged side by side in a direction orthogonal to the light guiding direction. Such a convex portion can be formed, for example, by forming a plurality of convex portions on the first pressing roller 43A, the second pressing roller 43B, and the third pressing roller 43C. A stamp is formed, and a convex portion is formed by the transfer mold. The exit surface 11b includes a plurality of convex portions, This improves the straightness of the light incident on the light guide plate 10. As a result, when the light guide plate 10 is used for the transmissive image display device 1, local dimming control can be performed.

Further, although one side surface is exemplified as the incident surface 11a of the light guide plate base portion 11, the light may be incident on the light guide plate base portion 11 from the side surface other than the incident surface 11a as exemplified. For example, the side surface 11d can also function as an incident surface. Further, either or both of the other two side surfaces of the light guide plate base portion 11 that intersect (for example, orthogonal to) the incident surfaces 11a and 11d may function as an incident surface.

10‧‧‧Light guide plate

11‧‧‧Light guide plate base

11a‧‧‧Incoming surface

11b‧‧‧Outlet

11c‧‧‧back

11d‧‧‧ side

12‧‧‧Light Scattering Department

D‧‧‧thickness

F‧‧‧diameter

Claims (9)

A light guide plate that emits light incident from an incident surface as a planar light from an exit surface intersecting the incident surface, and includes a light guide plate base portion having the incident surface and the exit surface, and Contains a transparent and flexible material. The light guide plate of claim 1, further comprising a plurality of light scattering portions disposed on a back surface of the light guide plate base portion opposite to the exit surface and allowing light incident from the incident surface At least a portion is scattered to the side of the exit surface. The light guide plate according to claim 1 or 2, wherein the material of the light guide plate base material portion comprises a material having a total light transmittance of 80% or more of the base material for measurement of the material, and the substrate portion for measurement is a plan view a rectangular parallelepiped having a length of 250 mm in the longitudinal direction of the shape, and the amount of light that is incident from the first side surface orthogonal to the longitudinal direction and emitted from the second side surface opposite to the first side surface is Q _out . When the amount of light incident on the first side surface is Q _in , the total light transmittance is defined as Q _out /Q _in . The light guide plate according to any one of claims 1 to 3, which has a flexibility in which the innermost radius is 2.5 cm or less when wound into a roll shape. The light guide plate according to any one of claims 1 to 4, wherein the thickness of the substrate portion of the light guide plate is 0.7 mm or less. The light guide plate according to any one of claims 1 to 5, further comprising a plurality of light scattering portions, which are disposed on a back surface of the light guide plate base portion opposite to the exit surface, and At least a part of the light incident on the incident surface is scattered to the side of the emission surface, and the light scattering portion is a light scattering point having a substantially circular shape in plan view. When the thickness of the light guide plate base material portion is D and the diameter of the light scattering portion is F, the F/D is 0.33 or less. A surface light source device comprising: the light guide plate according to any one of claims 1 to 6; and a light source that supplies light to the incident surface of the light guide plate. A transmissive image display device comprising: the light guide plate according to any one of claims 1 to 6; a light source that supplies light to the incident surface of the light guide plate; and a transmissive image display portion that receives the light from The planar light of the light guide plate displays an image. A method for manufacturing a light guide plate, which is a light guide plate which is transparent and has flexibility and emits a planar light from an exit surface intersecting with an incident surface, and includes the steps of: continuously extruding transparent and soft in a molten state; Producing a resin sheet by using a thermoplastic resin; and conveying the resin sheet in a roll shape; and printing on the main surface of the resin sheet to scatter at least a part of light incident from the incident surface to the exit surface a plurality of light scattering portions on the side; and a light guide plate obtained by cutting a resin sheet on which the plurality of light scattering portions are printed to a specific size.