JP5310216B2 - Method for manufacturing light guide plate - Google Patents

Description

  The present invention relates to a method for manufacturing a light guide plate and a light guide plate.

  A light guide plate made of a thermoplastic resin is installed inside a signboard or the like, and is used for the purpose of changing light from a so-called edge light type light source into uniform surface light emission. In recent years, the use of light guide plates not only for signboards but also for lighting applications has been expanded.

  A signboard or lighting may require a curved shape in order to provide design. In this case, it is required to process the light guide plate into a curved shape in accordance with the shape of the signboard or illumination.

  As a method of forming a curved light guide plate with a thermoplastic resin, a method of obtaining a predetermined shape after cooling the thermoplastic resin sheet to a temperature higher than the softening temperature by using a heat oven or the like, and following a mold with a predetermined shape Is known (see, for example, Patent Documents 1 and 2 below).

In Patent Document 1 below, a light guide plate in which a thermoplastic resin such as an acrylic resin is formed into a sheet shape can be bent while being heated to a temperature higher than the plastic deformation temperature of the thermoplastic resin, specifically about 90 ° C. Have been described.
In the following Patent Document 2, a light guide plate in which a thermoplastic resin such as an acrylic resin is molded into a sheet shape is bent while being heated to a temperature in the range of a deflection temperature under load of the thermoplastic resin of −20 to 0 ° C. Is described.

JP 2004-252292 A JP 2007-268724 A

  When bending a light guide plate made of a thermoplastic resin in a heated state, the brightness uniformity of the light guide plate after bending is not practically problematic and suppresses a decrease in the brightness of the light guide plate before and after bending. Is required. In addition, even when the light guide plate is used for a long period of time, good mechanical properties are also required, such as the generation of cracks due to impact can be suppressed while maintaining the initial shape of the bent shape.

  The present invention has been made in view of the above problems, and a method for manufacturing a light guide plate capable of realizing a balance between high luminance and uniformity after bending and good mechanical properties, and such a light guide plate. Is to provide.

  The method for producing a light guide plate of the present invention comprises a substrate formed of a thermoplastic resin and having a dot pattern or groove arranged on at least one surface, and a heating deflection temperature of the thermoplastic resin + 10-40 ° C. It is characterized by bending in a heated state.

  In the light guide plate manufacturing method of the present invention, as a more specific embodiment, the thermoplastic resin may be an acrylic resin, and the heating temperature may be 110 ° C. or higher and 140 ° C. or lower.

  Moreover, in the manufacturing method of the light-guide plate of this invention, the heating time of the said base material by the said heating temperature may be 15 minutes or more and 40 minutes or less as a more concrete embodiment.

  Moreover, in the manufacturing method of the light-guide plate of this invention, the thickness of the said base material may be 2 mm or more and 10 mm or less as a more concrete embodiment.

Moreover, in the manufacturing method of the light guide plate of the present invention, as a more specific embodiment, the dot pattern or the groove is formed on one surface of the base material,
The other surface of the substrate may be heated to the heating temperature, and the substrate may be bent in a state where the temperature of the one surface is less than the heating temperature.

  In the light guide plate manufacturing method of the present invention, as a more specific embodiment, the bending may be performed by forming the substrate into a three-dimensional curved surface by a free blow method or a free vacuum method. .

  The light guide plate of the present invention is obtained by the above light guide plate manufacturing method.

  The light guide plate of the present invention is made of a thermoplastic resin plate material bent into a three-dimensional curved surface, and has dot patterns or grooves arranged on at least one surface of the plate material.

  According to the present invention, the brightness of the light guide plate before and after bending and the uniformity of the light guide plate can be suppressed to such a level that there is no practical problem. There is provided a light guide plate capable of suppressing the above.

(A) is a disassembled perspective view of the shaping | molding apparatus and base material used for this method, (b) is BB sectional drawing of (a). (A) is a perspective view which shows a mode that a base material is bent into a spherical shape by the free blow method, (b) is a perspective view which shows the light-guide plate obtained by this method. It is a perspective view of the illuminating device formed by attaching a light source to the periphery of the light-guide plate obtained by this method.

Hereinafter, an embodiment of a method for manufacturing a light guide plate according to the present invention (hereinafter may be referred to as the present method) will be described.
First, an outline of this method will be described.

  In this method, a substrate made of a thermoplastic resin and formed by arranging dot patterns or grooves on at least one surface is bent in a state where the substrate is heated to a heating temperature of the thermoplastic resin under a load deflection temperature of 10 to 40 ° C. It is characterized by doing.

Here, the temperature of the base material made of a thermoplastic resin refers to the temperature at any location on the surface or inside of the base material.
The deflection temperature under load is also called a heat distortion temperature, and can be measured according to ASTM D648 or JIS 7191.

  The thermoplastic resin used in this method is not particularly limited, but preferably has transparency, acrylic resin (methacrylic resin), polycarbonate resin, polyvinyl chloride resin, amorphous polyester resin, amorphous olefin type. Resins, polystyrene resins, AS resins (acrylonitrile, styrene copolymer compounds) can be exemplified. Among these, by using acrylic resin in particular, it is possible to obtain a light guide plate having a high average luminance and a low luminance distribution.

The acrylic resin preferably contains 50% by mass or more of methyl methacrylate from the viewpoint of transparency.
In addition, the acrylic thermoplastic resin used in the present method may contain an alkyl (meth) acrylate monomer other than methyl methacrylate or an aromatic vinyl compound as a copolymerization component. Furthermore, the thermoplastic resin may contain additives such as impact strength improvers and flame retardants.

  As long as the optical performance of the light guide plate is not impaired, the thermoplastic resin may be blended with an inorganic or organic transparent filler to impart mechanical strength or flame retardancy.

A base material made of a thermoplastic resin has dot patterns or grooves arranged in advance on at least one surface. That is, the base material used in the present method is a light guide plate formed into a flat plate or sheet.
A dot pattern or a groove (hereinafter sometimes referred to as a light guide pattern) is a concavo-convex portion for changing light from a so-called edge light type light source into uniform surface light emission. The light guide pattern may be formed only on one main surface of the base material, or may be formed on both main surfaces.

The light guide pattern can be formed on the surface of the substrate by hot pressing a thermoplastic resin.
Such hot pressing is preferably performed at a temperature higher than + 60 ° C. than the deflection temperature under load and the glass transition temperature of the thermoplastic resin, and the substrate is preferably formed into a flat plate shape. Thereby, the formation position and shape of the light guide pattern can be realized with high accuracy as desired.

The base material used in this method has a light guide pattern formed by uneven processing of the base material itself. That is, the light guide pattern is formed of the same material as the base material.
Here, some light guide plates are provided with light guide performance by kneading a diffusing agent or diffusing beads (such as diffusing agent) into a thermoplastic resin, or those that form a light guide pattern by a printing method. To do. However, in the case of this kind of light guide plate, there is a possibility that the light guide performance is lowered by bending. When a light guide plate that is uniformly kneaded with a diffusing agent is bent, the dispersion density of the diffusing agent is increased inside the bending process, and conversely, the dispersion density is decreased outside the bending process. This is because unevenness occurs. Moreover, when the light guide plate on which the light guide pattern is printed is bent, the printed pattern may be peeled off.
On the other hand, when the light guide pattern is formed by the uneven processing of the base material as in this method, the collapse of the light guide pattern before and after the bending process is suppressed, and the uniform luminance distribution in the light guide plate after the bending process Can be obtained.

Furthermore, the light guide pattern is particularly preferably a dot pattern, particularly a halftone dot pattern in which cylindrical or hemispherical convex portions are two-dimensionally distributed on the surface of the substrate.
In the case of a groove pattern in which grooves such as V-grooves are formed in a stripe shape or a lattice shape, there is a possibility that the groove angle varies due to the bending process of the substrate and the light guide characteristics vary. On the other hand, in the case of a dot pattern in which convex portions are dispersedly arranged, even if the entire substrate is curved by bending, the convex portions follow the base material while maintaining the protruding direction with respect to the base material and the shape of the convex portions themselves. This is because there is little variation in the light guide characteristics.

  The thickness of the substrate is preferably 2 mm or more and 10 mm or less. By using a base material having a thickness in the above range, light from the light source (hereinafter sometimes referred to as light source light) can be efficiently guided to the light guide plate, while shortening heating time, improving productivity, and reducing weight. It can be balanced.

  The base material is bent while being heated to a heating temperature of 10 to 40 ° C. under the load deflection temperature of the thermoplastic resin. More specifically, when the thermoplastic resin is mainly composed of an acrylic resin, the heating temperature is preferably 110 ° C. or higher and 140 ° C. or lower. More specifically, bending is preferably performed at 110 ° C. or higher and 130 ° C. or lower.

Moreover, the heating temperature of a base material shall be below melting | fusing point of a thermoplastic resin.
By setting the temperature of the base material during heating to a deflection temperature under load of + 40 ° C. or lower and a melting point or lower, the shape of the light guide pattern provided on the surface of the base material is not destroyed, and the light source light is emitted before and after bending. It can suppress that a reflection angle fluctuates. Thereby, the brightness fall in a light-guide plate and the nonuniformity of brightness distribution can be prevented.
Furthermore, the base material at the time of heating can be processed into a desired shape in accordance with the mold shape at the time of bending by setting the temperature of the base material to a deflection temperature under load + 10 ° C. or higher. In other words, the mold reproducibility of the substrate can be maintained. Thereby, since the internal strain of the bent base material is suppressed, the mechanical properties of the molded light guide plate are improved, and specifically, deformation during long-term use and cracking during impact application are prevented.

  The heating means in this method is not particularly limited, and an apparatus based on any heating principle of convection, conduction, and radiation may be used. For example, a radiant heating device that irradiates the substrate surface with infrared rays or microwaves, a convection heating hot air circulation oven that contacts hot air with the substrate surface, a conduction heating hot plate heating oven that contacts the hot plate with the substrate Etc. can be illustrated.

  When heating a base material, you may set the preset temperature of a heating means 10-20 degreeC higher than the desired heating temperature in a base material. This is because, in the case of a convection heating type or conduction heating type heating means, the temperature of the base material, which is an object to be heated, is generally about 10 to 20 ° C. lower than the set temperature of the heating means.

  In heating the substrate to the above heating temperature, the entire substrate may be heated to a uniform temperature, or the light guide pattern forming surface, the non-forming surface and the substrate interior of the substrate may be heated to different temperatures. You may heat.

When the surface and the inside of the substrate are heated to a uniform temperature, residual internal strain during bending is reduced, and good mechanical properties can be obtained for the molded light guide plate.
On the other hand, when a base material in which a light guide pattern is formed only on one main surface (hereinafter sometimes referred to as a base material of a single-sided light guide pattern) is used in the present method, You may make a temperature difference. Specifically, bending may be performed while maintaining the temperature of the light guide pattern forming surface at a lower temperature than the non-formed surface or the inside of the base material.

  That is, in bending the base material of the single-sided light guide pattern, the non-formation surface of the light guide pattern (hereinafter sometimes referred to as a flat surface) is heated to the above heating temperature, and the light guide pattern formation surface (hereinafter, The substrate may be bent in a state where the temperature of the pattern surface is sometimes lower than the heating temperature. Thereby, it can prevent suitably that a light guide pattern loses | disappears or deform | transforms by heat-melting.

  In this case, as the heating means, an apparatus that heats the flat surface by convection, conduction, or radiation can be used. Specifically, the flat surface may be irradiated with microwaves or infrared rays by a radiant heating device, hot air may be blown onto the flat surface, or a hot plate may be brought into contact with the flat surface.

At this time, the temperature of the pattern surface may be controlled to a predetermined temperature lower than the heating temperature by using a method such as air cooling (convection) or heat sink joining (conduction).
The control temperature of the pattern surface is lower than the heating temperature of the flat surface, and it is preferable that the deflection temperature under load +0 to + 20 ° C. By setting the pattern surface to be equal to or higher than the deflection temperature under load, good mechanical properties can be obtained for the molded light guide plate without impairing the bending workability of the base material.

  By such temperature control, it is possible to suitably suppress the light guide pattern formed on the pattern surface from disappearing or deforming due to heat melting.

In this method, the heating time of the substrate at the above heating temperature is preferably 15 minutes or more and 40 minutes or less. By setting it as said time range, the difference of the temperature of the heating surface and internal temperature in a base material can be suppressed, and the brightness fall of a light-guide plate and brightness nonuniformity before and behind a bending process can be reduced.
Moreover, it is preferable to adjust the heating time of a base material with the board thickness of a base material. For example, when the thickness is 2 mm, the heating time is 15 to 25 minutes, and when the thickness is 8 mm, the heating time is 20 to 40 minutes.

  In this method, the specific method of bending is not particularly limited. For example, the heated substrate may be pressed by a mold having a curved concave surface (female mold) and a convex surface (male mold). Or you may roll the base material set with respect to the concave surface with the roller.

Alternatively, the bending process may be performed by forming the base material into a three-dimensional curved surface by a free blow method or a free vacuum method.
According to the free blow method or the free vacuum method, the protrusion formed on the bent portion of the base material is not crushed by the mold. For this reason, the light source light can be reflected at the expected reflection angle at the projection located on the three-dimensional curved surface of the molded light guide plate.

  Here, a three-dimensional curved surface is a figure that is defined by two independent parameters in a three-dimensional space and cannot be established by plane deformation. Examples of the three-dimensional curved surface include a spherical surface (including a partial spherical surface such as a hemispherical surface), and a bowl-shaped or flange-shaped curved surface.

Hereinafter, this method will be described more specifically with reference to the drawings.
FIG. 1A is an exploded perspective view of a molding apparatus 10 for bending a base material by a free blow method or a free vacuum method, and a base material 20 that is molded into a three-dimensional curved surface by the molding device 10.
FIG. 1B is a cross-sectional view taken along the line BB of FIG. 1A. Only the central portion is shown, and both ends are omitted.

As shown in FIG. 2B, the substrate 20 having a single-sided light guide pattern is used in this method. The lower surface of the substrate 20 is a pattern surface 21 in which a large number of hemispherical protrusions 22 are arranged in the surface, and the upper surface is a flat surface 23.
The protrusion 22 has a diameter that increases according to the distance from the four sides of the substrate 20, and the protrusion 22 having the maximum diameter is formed at the center of the pattern surface 21.
Thereby, in the light guide plate 40 after bending (see FIG. 2B), the light source light incident in the in-plane direction can be reflected in the perpendicular direction with uniform luminance.

The molding apparatus 10 is formed by combining a pressure-increasing / decreasing unit 11 and a holding frame 12. The pressurizing / depressurizing unit 11 has a box shape, the upper surface (mounting surface 13) is formed flat, and the cavity 14 is formed inside. An opening 15 is formed in the mounting surface 13, and the opening 15 communicates with the cavity portion 14.
An air supply / exhaust pipe 16 is provided in communication with the cavity 14. A pump (not shown) is connected to the supply / exhaust pipe 16 so that the internal pressure of the cavity 14 can be increased to a pressure higher than atmospheric pressure or reduced to a pressure lower than atmospheric pressure.
The shape of the opening 15 is not particularly limited, but FIG. 1A illustrates a circular case.

  Similar to the opening 15, a circular through hole 17 is formed through the holding frame 12. The diameter of the opening 15 and the diameter of the through hole 17 may be the same or different from each other. When the diameters of the opening 15 and the through-hole 17 are different from each other, the opening 15 or the through-hole 17 corresponding to the bulging side of the substrate 20 may be made larger in diameter. That is, as will be described later with reference to FIG. 2A, when the base material 20 is bent by a free blow method in which the cavity portion 14 is pressurized and the base material 20 is expanded outside the cavity portion 14, The through hole 17 corresponding to the bulging side of the material 20 may be larger in diameter than the opening 15. Further, in the case of the free vacuum method in which the cavity portion 14 is decompressed and the base material 20 is bulged toward the inside of the cavity portion 14 by atmospheric pressure, the opening 15 and the through-hole 17 have the same diameter or bulge. The opening 15 of the pressurizing / depressurizing unit 11 corresponding to the side is preferably larger in diameter than the through hole 17 of the holding frame 12.

  Here, the peripheral edge of the through hole 17 or the opening 15 that is located on the bulging side of the base material 20 forms a bulging contour line of the light guide plate 40 formed by the free blow method or the free vacuum method. . The pressed air side that presses the base material 20 with high-pressure air or atmospheric pressure is the immersive side of the base material 20. For this reason, the opening 15 and the through-hole 17 have the same diameter, or the bulging side has a larger diameter, so that the pressing force by high-pressure air or atmospheric pressure is suitable for the bulging portion of the base material 20. Can be applied.

In the molding apparatus 10 illustrated in FIG. 1A, both the mounting surface 13 and the holding frame 12 of the pressure increasing / decreasing unit 11 are rectangular.
A fixing tool 18 is provided around the through hole 17 in the holding frame 12.
On the other hand, the mounting surface 13 of the pressurizing / depressurizing portion 11 is provided with an engaging portion 19 that engages with the fixture 18 in a state where the opening 15 and the through hole 17 are aligned.

The holding frame 12 and the mounting surface 13 are both formed flat and sandwich the base material 20 to be bent by this method.
The fixing tools 18 are provided at the four corners of the holding frame 12, respectively. The interval between the fixtures 18 is longer than the side length of the base material 20, and the fixture 18 and the engagement portion 19 are in the state where the base material 20 is sandwiched between the holding frame 12 and the mounting surface 13. Engage with each other without interfering with 20.

Fig.2 (a) is a perspective view which shows a mode that the base material 20 is bent into spherical shape by the free blow method.
The base material 20 heated to a predetermined heating temperature selected from the deflection temperature under load +10 to 40 ° C. has a three-dimensional region exposed from the through hole 17 due to the pressing force of the high-pressure air F supplied from the air supply / exhaust pipe 16. Swells into a curved surface.

Here, the timing of heating the base material 20 may be before the base material 20 is set on the mounting surface 13 of the molding apparatus 10 or after the base material 20 is set on the mounting surface 13 of the molding apparatus 10. .
In other words, the base material 20 that has been heated to a predetermined heating temperature in advance by the heating device may be transferred to the molding device 10 manually or by a conveying device and set on the mounting surface 13. Alternatively, the base material 20 may be heated by a heating device in a state in which the normal temperature base material 20 is set on the mounting surface 13 of the molding apparatus 10.
In the former case, it is not necessary for the molding apparatus 10 to include heating means, and the molding apparatus 10 can be simplified. On the other hand, in the latter case, heat is not removed while the heated base material 20 is set on the mounting surface 13, and the base material 20 can be bent while being temperature-controlled uniformly and with high accuracy. .

  In this method, the base material 20 may be heated at any timing. In the case of the base material 20 having a plate thickness of 3 to 10 mm as in the present embodiment, the base material 20 has excellent shape stability and heat capacity compared to the case of a sheet-like base material of about 1 mm or less. Therefore, the substrate 20 may be heated in advance with a heating device and then set in the molding device 10. In this case, when the base material 20 is bent, the heating temperature of the base material 20 by the heating device is the load deflection temperature + 10-40 ° C. so that the temperature becomes a predetermined temperature of the load deflection temperature + 10-40 ° C. It is good also as the said predetermined temperature + 10-20 degreeC. As an example, the heating set temperature of the base material 20 by the heating device is set to a temperature range of the deflection temperature under load + 30 to 40 ° C., and the surface temperature of the base material 20 at the time of bending is set to a temperature range of the deflection temperature under load + 10 to 20 ° C. can do.

  The heated base material 20 is set on the mounting surface 13 of the molding apparatus 10 as shown in FIG. And the base material 20 is pinched | interposed with the holding frame 12, the fixing tool 18 and the engaging part 19 (refer Fig.1 (a)) are engaged, and the base material 20 is firmly clamped by the shaping | molding apparatus 10. FIG.

  In addition, when heating the base material 20 in the state which set the base material 20 to the mounting surface 13 of the shaping | molding apparatus 10, the infrared oven (irradiating infrared rays to the flat surface 23 exposed from the through-hole 17 as a heating means ( (Not shown) may be used. In addition to the use of an infrared oven, a heating wire is embedded in the holding frame 12 and the mounting surface 13 of the molding apparatus 10, and the peripheral edge sandwiched between the holding frame 12 and the mounting surface 13 in the base material 20. The region may be conductively heated.

  By blowing high-pressure air F from the air supply / exhaust pipe 16 into the cavity 14 (see FIG. 1A) in a state where the flat surface 23 of the base material 20 is heated for a predetermined heating temperature and for a predetermined time. The base material 20 bulges and deforms with the opening shape of the through hole 17 as the contour line. The through-hole 17 of this embodiment is circular, and the base material 20 bulges into a spherical shape.

  FIG. 2B is a perspective view showing the light guide plate 40 (hereinafter referred to as the light guide plate 40 of the present embodiment) obtained by this method.

  The light guide plate 40 of the present embodiment is made of a thermoplastic resin plate bent into a three-dimensional curved surface, and a light guide pattern is arranged on at least one surface of the plate.

The light guide plate 40 of the present embodiment includes a bulging portion 41 that is bent into a spherical shape, and a bowl-shaped flat portion 42 that is continuously formed around the bulging portion 41. A boundary line 43 between the bulging portion 41 and the flat portion 42 is circular.
The inner surface of the bulging portion 41 and the lower surface of the flat portion 42 are pattern surfaces 21 formed by arranging light guide patterns, and the protrusions 22 (see FIG. 1B) are formed in a dispersed manner. .

FIG. 3 is a perspective view of an illumination device 50 in which the light source 30 is mounted on the periphery of the light guide plate 40 of the present embodiment.
In the light guide plate 40 of the present embodiment, the flat portion 42 has a rectangular shape, and the light sources 30 are mounted on the four sides thereof. An example of the light source 30 is a linear light source in which a plurality of LEDs (Light Emitting Diodes) are linearly arranged.
In the figure, for the sake of explanation, one of the four light sources 30 (light source 31) is shown separated from the flat portion.

On the pattern surface 21 of the light guide plate 40, a reflection sheet (not shown) for specularly reflecting the light source light is attached.
Further, on the flat surface (pattern non-formation surface) 23 of the light guide plate 40, a diffusion plate that uniformly diffuses the light source light reflected from the protrusions 22 (see FIG. 1B) and emitted from the flat surface 23 (Not shown) is applied.

The irradiation direction of the light source light from the light source 30 in the illumination device 50 is the in-plane direction of the flat portion 42. That is, the light source light is incident on the light guide plate 40 from the light source 30 in the in-plane direction of the flat portion 42.
Accordingly, the light source light incident in the in-plane direction of the flat portion 42 is specularly reflected on the pattern surface 21 or the flat surface 23 except when reflected by the protrusion 22 (see FIG. 1B). Stay inside.
Here, in the light guide plate 40 of the present embodiment, the flat portion 42 and the bulging portion 41 are smoothly continuous at the boundary line 43. For this reason, the light source light traveling inside the flat portion 42 is introduced into the bulging portion 41 without being irregularly reflected at the boundary line 43.
The light source light introduced into the bulging portion 41 is also mirror-reflected by the pattern surface 21 or the flat surface 23 on the front and back surfaces of the bulging portion 41 except in the case where it is reflected by the protrusion 22, and the inside of the light guide plate 40 is directed in the in-plane direction. Proceed to.
When the light source light is reflected by the protrusions 22 formed on the flat part 42 or the bulging part 41 of the light guide plate 40, the light source light is specularly reflected from the protrusion 22 toward the flat surface 23 or by the reflection sheet. Progress in the thickness direction. The light source light traveling in the thickness direction of the light guide plate 40 passes through the flat surface 23 and leaks to the outside of the light guide plate 40, causing the light guide plate 40 to emit light uniformly.
At this time, as described above, in the light guide plate 40 according to the present embodiment, the diameter of the protrusion 22 at the center of the plane is maximized, so that the light guide plate 40 has a flat portion 42 and a bulging portion 41 with uniform brightness. Emits light.

  The light guide plate 40 shown in FIG. 3 has a rectangular shape in plan view and includes flat portions 42 at the four corners around the bulging portion 41, but the present invention is not limited to this. For example, the flat portion 42 may be cut away leaving only the bulging portion 41 to form a light guide plate 40 having a circular shape in plan view. Further, the flat portion 42 may be formed in a belt shape having a predetermined width, and may be formed in an annular shape around the bulge portion 41. When the light source 30 is attached to the light guide plate 40 that is circular in plan view, the light source 30 may be curved and provided around the end surface of the light guide plate 40.

In the illumination device 50 of the present embodiment, the protrusion 22 and the reflection sheet are formed inside the bulged portion 41 formed in a convex shape, and light source light can be emitted radially.
On the other hand, by forming the bulging portion 41 in a concave shape, the light source light can be focused and emitted.

  Like the light guide plate 40 of the present embodiment, a light guide pattern is formed on at least one surface of a thermoplastic resin plate material, and this is bent into a three-dimensional curved surface, whereby various three-dimensional illumination devices can be obtained. Can be obtained. Therefore, instead of the spherical bulging portion 41 as illustrated above, the bulging portion 41 shaped like a character, a symbol, or a figure is configured with a three-dimensional curved surface, thereby having high designability and visibility. A lighting device can be created. The bulging portion 41 having an arbitrary shape can be realized by changing the shape of the through hole 17, changing the relative position between the opening 15 and the through hole 17, and adjusting the flow rate of the high-pressure air F. That is, the shape of the boundary line 43 of the bulging portion 41 can be changed by changing the shape of the through hole 17. The rising angle of the bulging portion 41 can be adjusted by changing the diameter and offset position of the opening 15 with respect to the through-hole 17 and the profile of the supply amount of the high-pressure air F.

  Hereinafter, although this method is demonstrated in detail based on an Example and a comparative example, this method is not limited to this. Moreover, it measured about the average brightness | luminance and brightness nonuniformity of the base material before and behind a bending process. The results are shown in Table 1 below.

Example 1
<Luminance measurement>
A light guide plate made of methacrylic resin with a length of 910 mm x width of 200 mm x thickness of 8 mm, and a cylindrical dot pattern dispersed on the back surface of methacrylic resin (Trademark)).
Specifically, a diffusion plate (Sumitex (registered trademark) 032 2 mm thick manufactured by Sumitomo Chemical Co., Ltd.) is installed on the surface of the light guide plate formed flat, and a reflective film (Inaba Electric Co. White film) was installed. Moreover, the short side which opposes each other among light guide plates was made into the light entrance, respectively, and the end surface was opened, and said reflection film was installed in the end surface of two sides (long side) other than a short side.
Then, using two types of linear light sources, LED (three one manufactured by Inaba Electric Co., Ltd.) as a light source, light was incident inward in the long side direction from the end surfaces of the opposing short sides.
In this state, using a luminance meter (BM-9 manufactured by Topcon Corporation), the luminance of the surface of the diffusion plate was measured at a pitch of 50 mm in the length direction with respect to the center portion (width center) in the long side direction. Asked. Further, the difference between the maximum value and the minimum value of the measured values was acquired as luminance unevenness.

<Bending process>
Next, the substrate was heated in a hot air circulation oven at 130 ° C. for 34 minutes. The sheet surface temperature was stable at 120 ° C. The deflection temperature under load of the methacrylic resin used in this example was 100 ° C., and the heating temperature was the temperature of deflection under load of methacrylic resin + 20 ° C.
The heated substrate was bent along a female die having a radius of curvature (hereinafter, R) of 500 mm so that the length direction was R500 mm.
The diffuser plate was installed on the surface of the bent product thus obtained, and the reflective film was installed on the end surfaces of the two sides other than the back surface and the end surfaces of the short sides facing each other (light entrance). Then, light was incident from the light entrance using the LED as a light source. In this state, using the luminance meter, the luminance of the surface of the diffused plate after bending was measured at a 50 mm pitch in the length direction at the center portion (width center) in the long side direction to obtain the average luminance. . Further, the difference between the maximum value and the minimum value of the measured values was acquired as luminance unevenness. And the ratio of the brightness nonuniformity with respect to average brightness | luminance in the light-guide plate after a bending process was computed. Here, when the luminance unevenness is 50% or less with respect to the average luminance of the light guide plate, it can be generally evaluated that the luminance unevenness is not problematic in practical use.

As a result, the average brightness of the surface of the diffusion plate before bending was 325 cd / m ² , whereas the average brightness after processing was 230 cd / m ² . Therefore, the decrease in average luminance was 29%, which was within 30%.
Luminance unevenness is the difference between the measured maximum and minimum values of luminance before processing whereas was 102cd / m ^2, after processing was 48 cd / m ^2. Therefore, luminance unevenness to bending the average luminance after processing ^{(230cd / m 2) (48cd} / m 2) is 21%, 50% or less.

(Example 2)
The substrate having a length of 820 mm, a width of 300 mm, and a thickness of 8 mm was heated in a hot air circulation oven at 140 ° C. for 34 minutes. The surface temperature of the substrate was stabilized at 130 ° C., which is the deflection temperature under load of methacrylic resin + 30 ° C.
The base material in a heated state was bent along the inner surface of the cylinder so that the light guide pattern was on the inside, and bent in the length direction into a cylindrical shape with a diameter of 260 mm. The diffusion plate was installed on the outer surface of the cylindrical product thus obtained. Moreover, the short side which mutually opposes among the base materials was made into the light entrance, and the said reflective film was installed in the end surface of two sides (long sides) other than the back surface of a base material, and a light entrance. Then, light was incident from the light entrance using the LED as a light source. In this state, the luminance of the surface of the diffusion plate before and after bending was measured at a 50 mm pitch in the length direction at the center portion (width center) in the long side direction using the luminance meter.

As a result, the average luminance on the surface of the diffusion plate before processing was 305 cd / m ² , whereas the average luminance after processing was 260 cd / m ² . Therefore, the decrease in average luminance was 15%.
The luminance unevenness, before processing whereas was 60 cd / ^{m 2,} after processing was 104cd / ^{m 2.} Therefore, luminance unevenness to bending the average luminance after processing ^{(260cd / m 2) (104cd} / m 2) is 40%, 50% or less.

(Comparative Example 1)
The average luminance and luminance unevenness on the surface of the diffusion plate were measured in the same manner as in Example 1 except that the temperature setting of the hot air circulation oven was set to 160 ° C. The surface temperature of the heated substrate was stabilized at 150 ° C., which is the deflection temperature under load of methacrylic resin + 50 ° C.
As a result, the average luminance of the surface of the diffusion plate before processing was 308 cd / m ² , whereas the average luminance after processing was 136 cd / m ² . Therefore, the decrease in average luminance was 56%, exceeding 30%.
The luminance unevenness, before processing whereas was 122cd / ^{m 2,} after processing was 76cd / ^{m 2.} Therefore, luminance unevenness to bending the average luminance after processing ^{(136cd / m 2) (76cd} / m 2) is 56%, more than 50%.

(Comparative Example 2)
A flat plate-like methacrylic resin base material without a cylindrical dot pattern was used as the light guide plate, and the temperature of the hot air circulation oven was set to 140 ° C. Average luminance and luminance unevenness were measured. The base material (light guide plate) was provided with light guide performance by kneading polystyrene polymer fine particles as a diffusing agent. The surface temperature of the heated substrate was stabilized at 130 ° C., which is the deflection temperature under load of methacrylic resin + 30 ° C.
As a result, the average luminance of the surface of the diffusion plate before processing was 254 cd / m ² , whereas the average luminance after processing was 148 cd / m ² . Therefore, the decrease in average luminance was 42%, exceeding 30%.
The luminance unevenness, before processing whereas was 142cd / ^{m 2,} after processing was 146cd / ^{m 2.} Therefore, luminance unevenness to bending the average luminance after processing ^{(148cd / m 2) (146cd} / m 2) is 99%, more than 50%.

(Comparative Example 3)
The base material used in Example 1 was heated in a hot air circulation oven at 110 ° C. for 34 minutes. The surface temperature of the heated substrate was stable at 100 ° C., which is the deflection temperature under load of methacrylic resin + 0 ° C.
The base material in a heated state was bent along an R500 mm female mold so that the length direction was R500 mm.
As a result, the curvature radius of the obtained processed product was 560 mm, which was 12% larger than that of the female mold. That is, the processed product of this comparative example cannot obtain the reproducibility of the mold. Therefore, evaluation after luminance measurement and bending was not performed.

As shown in Table 1, the light guide plates of Examples 1 and 2 in which the surface temperature of the base material made of a thermoplastic resin was bent at a deflection temperature under load of + 20 ° C. and + 30 ° C. were uneven brightness after processing. It was found that the average luminance was reduced to 50% or less and the average luminance reduction rate before and after the processing was reduced to 30% or less.
On the other hand, in the light guide plate of Comparative Example 1 in which the surface temperature of the substrate is a deflection temperature under load + 50 ° C. and Comparative Example 2 having no dot pattern or groove, uneven luminance after processing is 50% of the average luminance. In addition, the average brightness before and after processing decreased by over 30%.
In addition, the light guide plate of Comparative Example 3 in which the surface temperature of the base material is a deflection temperature of load + 0 ° C. has a curvature radius of 12% larger than the curvature radius of the mold, and appropriately performs bending. I found it impossible.

The above embodiments and examples include the following technical ideas.
(1) A light guide plate characterized by bending the surface temperature of a thermoplastic resin sheet having a dot pattern or groove provided on at least one surface thereof to 110 ° C. or higher and 140 ° C. or lower by a thermal oven. Manufacturing method of
(2) The method for producing a light guide plate according to (1), wherein the heating time is 15 minutes or more and 40 minutes or less;
(3) The method for manufacturing a light guide plate according to (1) or (2) above, wherein the thermoplastic resin sheet includes an acrylic resin;
(4) The method for producing a light guide plate according to any one of (1) to (3), wherein the thermoplastic resin sheet has a thickness of 3 mm or more and 10 mm or less;
(5) A light guide plate obtained by the method for manufacturing a light guide plate according to any one of (1) to (4).
Hereinafter, examples of the reference form will be added.
1. Bending a substrate made of a thermoplastic resin and having a dot pattern or groove formed on at least one surface thereof while being heated to a heating deflection temperature of the thermoplastic resin of +10 to 40 ° C. A manufacturing method of a light guide plate characterized by the above.
2. The thermoplastic resin is an acrylic resin, and the heating temperature is 110 ° C. or higher and 140 ° C. or lower. The manufacturing method of the light-guide plate of description.
3. The heating time of the substrate at the heating temperature is 15 minutes or more and 40 minutes or less. Or 2. The manufacturing method of the light-guide plate of description.
4). 1. The thickness of the base material is 2 mm or more and 10 mm or less. To 3. The manufacturing method of the light-guide plate in any one of.
5. While the dot pattern or the groove is formed on one surface of the substrate,
1. The other surface of the substrate is heated to the heating temperature, and the substrate is bent in a state where the temperature of the one surface is lower than the heating temperature. To 4. The manufacturing method of the light-guide plate in any one of.
6). The bending is performed by forming the substrate into a three-dimensional curved surface by a free blow method or a free vacuum method. To 5. The manufacturing method of the light-guide plate in any one of.
7.1. To 6. A light guide plate obtained by the method for producing a light guide plate according to any one of the above.
8). A light guide plate comprising a plate of thermoplastic resin bent into a three-dimensional curved surface, and having dot patterns or grooves arranged on at least one surface of the plate.

DESCRIPTION OF SYMBOLS 10 Molding device 11 Pressure-reducing part 12 Holding frame 13 Placement surface 14 Cavity part 15 Opening 16 Supply / exhaust pipe 17 Through-hole 18 Fixing tool 19 Engagement part 20 Base material 21 Pattern surface 22 Projection 23 Flat surface 30, 31 Light source 40 Guide Light plate 41 Swelling part 42 Flat part 43 Boundary line 50 Illumination device F High pressure air

Claims (8)

The surface of the base material of a thermoplastic resin ing by hot press, so that the cylindrical or hemispherical screen pattern convex portions are two-dimensionally distributed are formed on at least one surface of said substrate A step of processing the surface of the substrate;
A step of bending in a state where the dot pattern is the base material formed by arranging and heated to the heating temperature of the heat deflection temperature + 10 to 40 ° C. for the thermoplastic resin,
The manufacturing method of the light-guide plate containing this .   The method for producing a light guide plate according to claim 1, wherein the thermoplastic resin is an acrylic resin, and the heating temperature is 110 ° C. or higher and 140 ° C. or lower.   The method for manufacturing a light guide plate according to claim 1 or 2, wherein the heating time of the base material by the heating temperature is 15 minutes or more and 40 minutes or less.   The thickness of the said base material is 2 mm or more and 10 mm or less, The manufacturing method of the light-guide plate in any one of Claim 1 to 3 characterized by the above-mentioned. While the halftone dot pattern is formed on one surface of the substrate,
The other surface of the base material is heated to the heating temperature, and the base material is bent in a state where the temperature of the one surface is lower than the heating temperature. The manufacturing method of the light-guide plate of description.   6. The method of manufacturing a light guide plate according to claim 1, wherein the bending process is performed by forming the base material into a three-dimensional curved surface by a free blow method or a free vacuum method.   In the step of hot-pressing the surface of the base material, the surface of the base material is hot-pressed at a temperature that is 60 ° C or higher than the deflection temperature under load and the glass transition temperature of the thermoplastic resin. The manufacturing method of the light-guide plate in any one.   The said light-guide plate manufacturing method in any one of Claim 1 to 7 in which the said process which heat-presses the surface of the said base material is shape | molded in the flat plate shape.

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