JP2007214098A - Light guide plate made of transparent resin and surface light source device, as well as manufacturing method of light guide plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a very thin light guide plate of which the thickness is below 0.7 mm. <P>SOLUTION: The light guide plate is composed of a transparent thermoplastic resin, and provided with a first face, a second face opposed to the first face, a first side face, a second side face, a third side face opposed to the first side face, and a fourth side face opposed to the second side face. On the front surface of the first face, convex parts and/or recessed parts are provided. The length in the longitudinal direction of the light guide plate which is the length between the first side face and the third side face is 40 mm or more and 70 mm or less. The thickness of a region occupying at least 80% of the light guide plate is 0.1 mm or more, and 0.55 mm or less. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention is used for a liquid crystal display device used in a personal computer, a mobile phone, a PDA (personal digital assistant), a car navigation device, a game machine, etc., or in other applications. The present invention relates to a transparent thermoplastic resin light guide plate, a planar light source device incorporating the light guide plate, and a method of manufacturing the light guide plate.

  Liquid crystal display devices used in personal computers, mobile phones, PDAs, car navigation devices, game consoles, etc., meet the demands for thin, lightweight, power saving, high brightness and high definition of liquid crystal display devices. Therefore, a planar light source device is incorporated. The light guide plate has a first surface and a flat second surface facing the first surface, and is generally made of a transparent material.

  A light guide plate 40 whose schematic cross-sectional view is shown in FIG. 1A includes a first surface 41, a second surface 43 facing the first surface 41, a first side surface 44, a second side surface 45, and a first side surface. And a fourth side surface 47 opposite to the second side surface 45. An uneven portion 42 is provided on the surface portion of the first surface 41.

  In the backlight type planar light source device in the liquid crystal display device, the second surface 43 of the light guide plate 40 faces the liquid crystal display device 60 as shown in a schematic cross-sectional view in FIG. Are arranged to be. The light emitted from the light source 50 and incident from the first side surface 44 of the light guide plate 40 is reflected by the first surface 41 and emitted from the second surface 43, and light transmitted through the first surface 41. It is divided into. The light transmitted through the first surface 41 is reflected by the reflecting member 51 disposed at a position facing the first surface 41, enters the light guide plate 40 again, and is emitted from the second surface 43. The light emitted from the second surface 43 is guided to the liquid crystal display device 60 disposed to face the second surface 43. Between the liquid crystal display device 60 and the second surface 43 of the light guide plate 40, a prism sheet 55 and a diffusion sheet 52 are usually placed in an overlapping manner to diffuse light uniformly.

  Further, in the front light type planar light source device in the liquid crystal display device, the second surface 43 of the light guide plate 40 faces the liquid crystal display device 60 as shown in a conceptual diagram in FIG. Has been placed. Then, the light emitted from the light source 50 and incident from the first side surface 44 of the light guide plate 40 is reflected by the first surface 41 and emitted from the second surface 43. And the liquid crystal display device 60 arrange | positioned in the position facing the 2nd surface 43 is allowed to pass, it is reflected by the reflection member 54, and the liquid crystal display device 60 is allowed to pass through again. The light further passes through an antireflection layer (not shown) formed on the retardation film 53 and the second surface 43 of the light guide plate 40 and is emitted from the first surface 41 of the light guide plate 40 to be recognized as an image. Is done. The front light type planar light source device is brighter than the backlight type planar light source device, and has a merit that power consumption can be reduced because it is a method that can be brightened only by outside light in the daytime.

  By the way, the prism sheet 55 is expensive, and when using a plurality of sheets, there is a problem that the number of assembling steps increases. Therefore, such a problem is solved by forming the prism-shaped uneven portion 42 on the first surface 41 of the light guide plate 40 (see, for example, Japanese Patent Laid-Open No. 10-55712). Here, in order to achieve low power consumption and high luminance, it is necessary to increase the density of the prism-shaped uneven portions 42 as much as possible to improve luminance efficiency. In addition, it has been studied to provide a blast texture having a light diffusing effect on the second surface 43 to eliminate the diffusion sheet.

  Conventionally, such a light guide plate is manufactured based on an injection molding method. That is, a light guide plate is formed by injecting a transparent molten thermoplastic resin into a cavity through a molten resin injection portion using a mold assembly including a molten resin injection portion (gate portion) and a cavity. . A material such as PMMA has been used as the transparent thermoplastic resin. However, heat generated in devices such as mobile phones and PDAs tends to increase and is being replaced with polycarbonate resin having high heat resistance.

  In addition, the thickness of a liquid crystal display device used in a mobile phone or the like is currently about 3 mm, and the thickness of the light guide plate is the thinnest, about 0.7 mm. In order to meet the strong demand for further reducing the thickness of the liquid crystal display device, the thickness of the light guide plate is required to be less than 0.7 mm.

JP 10-138275 A JP 10-052839 A JP 10-055712 A JP 11-058406 A JP-A-2004-050819 JP 2003-014938 A

  Japanese Patent Laid-Open No. 10-138275 discloses a light guide plate having a thickness of 0.1 mm to 10 mm and an injection molding method thereof. Japanese Patent Application Laid-Open No. 10-052839 and Japanese Patent Application Laid-Open No. 10-055712 disclose a light guide plate having a thin portion of 0.1 mm to 1 mm and a difference between the thick portion and the thin portion of 0.5 mm or more and an injection molding method thereof. Has been. Furthermore, JP-A-11-058406 discloses a thin plate-shaped molded product having a thickness of 0.1 mm to 7 mm and an injection molding method thereof. Japanese Patent Application Laid-Open No. 2004-050819 discloses a molded body of 0.1 mm to 30 mm and a molding method thereof. In addition, when a light guide plate having prism-shaped irregularities on the surface is molded based on an injection molding method using polycarbonate resin having poor fluidity, a prism is formed on the surface portion of the light guide plate located far from the gate portion. For example, Japanese Patent Application Laid-Open No. 2003-14938 discloses a means for solving the problem that an uneven portion having a shape cannot be formed.

  However, in the examples disclosed in these patent publications, the thickness of the light guide plate and the molded product is 0.7 mm or more. Further, the light guide plate and the molded product have a size of 100 mm or more. Light guide plates and molded articles having such thickness and size can be molded by the methods disclosed in these patent publications. However, when the manufacture based on the injection molding method of the light guide plate having a thickness of less than 0.7 mm is attempted based on the technology disclosed in these patent publications, the flow end (the farthest from the molten resin injection portion (gate portion)) The portion of the cavity corresponding to (2)) cannot be completely filled with the molten thermoplastic resin, and the desired light guide plate cannot actually be manufactured.

  Accordingly, an object of the present invention is to provide a very thin light guide plate having a thickness of less than 0.7 mm, a planar light source device incorporating the light guide plate, and a method for manufacturing the light guide plate. .

The light guide plate of the present invention for achieving the above object is made of a transparent thermoplastic resin, and includes a first surface, a second surface facing the first surface, a first side surface, a second side surface, and the first side surface. A light guide plate having a third side surface facing the second side surface and a fourth side surface facing the second side surface,
The surface portion of the first surface is provided with a convex portion and / or a concave portion (that is, the convex portion is provided, or the concave portion is provided, or the convex portion and the concave portion are provided. )
The length in the longitudinal direction of the light guide plate, which is the length between the first side surface and the third side surface, is 40 mm or more and 130 mm or less, preferably 45 mm or more and 120 mm or less,
The thickness of the region occupying at least 80% of the light guide plate is 0.1 mm or more and 0.55 mm or less, preferably 0.15 mm or more and 0.50 mm or less,
The flatness is 200 μm or less.

Moreover, the planar light source device of the present invention for achieving the above object is
A light guide plate and a light source,
The light guide plate is
Made of transparent thermoplastic resin,
A first surface, a second surface facing the first surface, a first side surface, a second side surface, a third side surface facing the first side surface, and a fourth side surface facing the second side surface;
The surface portion of the first surface is provided with a convex portion and / or a concave portion (that is, the convex portion is provided, or the concave portion is provided, or the convex portion and the concave portion are provided. )
The length in the longitudinal direction of the light guide plate, which is the length between the first side surface and the third side surface, is 40 mm or more and 130 mm or less, preferably 45 mm or more and 120 mm or less,
The thickness of the region occupying at least 80% of the light guide plate is 0.1 mm or more and 0.55 mm or less, preferably 0.15 mm or more and 0.50 mm or less,
The flatness is 200 μm or less,
Light is incident from the first side surface of the light guide plate, and light is emitted from the first surface and / or the second surface.

  In the planar light source device, the light source is disposed on, for example, a first side surface (light incident surface) that is an end portion of the light guide plate. Then, the light emitted from the light source and incident on the light guide plate from the first side surface is scattered by the convex portion or the concave portion formed on the first surface of the light guide plate, and is emitted from the first surface and / or the second surface. .

Furthermore, the manufacturing method of the light guide plate of the present invention for achieving the above object is as follows.
Made of transparent thermoplastic resin, first surface, second surface facing the first surface, first side surface, second side surface, third side surface facing the first side surface, and facing the second side surface The fourth side
The surface portion of the first surface is provided with a convex portion and / or a concave portion,
The length in the longitudinal direction of the light guide plate, which is the length between the first side surface and the third side surface, is 40 mm or more and 130 mm or less,
The thickness of the region occupying at least 80% of the light guide plate is 0.1 mm or more and 0.55 mm or less,
A method of manufacturing a light guide plate having a flatness of 200 μm or less,
A molten resin injection portion for injecting a molten thermoplastic resin into the cavity from a cavity and a portion (cavity surface) corresponding to any side surface of the light guide plate, and a first mold portion and a second mold Using a mold assembly composed of a mold part,
(A) After the first mold part and the second mold part are clamped with a clamping force F ₀ to form a cavity,
(B) Injecting a transparent molten thermoplastic resin from the molten resin injection portion into the cavity,
(C) t seconds after the completion of the injection process of the molten thermoplastic resin into the cavity or after the completion of the injection process of the molten thermoplastic resin into the cavity and the subsequent pressure holding process (However, 0 seconds ≦ t ≦ 8.0 seconds), the mold clamping force is 0.5F ₀ or less,
(D) After the thermoplastic resin in the cavity is cooled and solidified, the first mold part and the second mold part are opened, and the light guide plate is taken out.
It consists of each process.

In the method for manufacturing the light guide plate of the present invention, simultaneously with the completion of the injection process of the molten thermoplastic resin into the cavity (that is, t = 0) or until 8.0 seconds have elapsed (that is, 0). <T ≦ 8.0 seconds), or simultaneously with the completion of the injection process of the molten thermoplastic resin into the cavity and the subsequent pressure holding process (the pressure holding time is t ′ seconds) (that is, t = 0) ), Or until 8.0 seconds elapse (that is, 0 <t ≦ 8.0 seconds), the mold clamping force F ₁ is set to 0.5 F ₀ or less, but preferably 0.5 seconds ≦ t ≦ 6 seconds, more preferably 1 second ≦ t ≦ 4 seconds, and more realistically, the time t may be set by observing the deformation state of the molded light guide plate. If the value of t exceeds 8 seconds, shrinkage due to cooling of the thermoplastic resin in the cavity is usually completed, and distortion remains in the thermoplastic resin, so that the light guide plate is twisted or swollen. May occur or the flatness may decrease. Further, 0 ≦ F ₁ / F ₀ ≦ 0.5, more preferably 0 ≦ F ₁ / F ₀ ≦ 0.4, and still more preferably 0 ≦ F ₁ / F ₀ ≦ 0.3. More realistically, the values of F ₀ and F ₁ may be set by observing the deformation state of the molded light guide plate. If the mold clamping force F ₁ is not less than 0.5 F ₀ , the distortion generated inside the thermoplastic resin in the cavity is difficult to be released, and the light guide plate is twisted or swollen, or the flatness is lowered. There is a fear.

The value of the clamping force F _0, when a maximum cross-sectional area of the light guide plate obtained by cutting the light guide plate in the direction in which the clamping force F ₀ exerted by a virtual plane perpendicular to the S _MAX (cm ^2),
F ₀ ≧ 9.8 × 10 ³ × S _MAX (N) (= S _MAX × 10 ³ kgf)
It is desirable to satisfy The upper limit value of the mold clamping force F ₀ depends on the injection molding apparatus to be used, and examples thereof include 2.9 × 10 ⁴ × S _MAX (N) (= S _MAX × 3 × 10 ³ kgf). . If the value of the mold clamping force F ₀ is too small, there is a risk that burrs will occur on the light guide plate. If it is too large, it will not be possible to prompt the exhaust of the gas from the parting line or the resin. Since the fluidity of the molten thermoplastic resin in the cavity becomes slightly inferior and distortion may remain in the light guide plate, the value of the mold clamping force F ₀ needs to be adjusted appropriately.

Usually, a mold assembly composed of a fixed mold part and a movable mold part, in which a thermoplastic resin measured, plasticized and melted in an injection cylinder provided in an injection molding apparatus is injected from the injection cylinder. Is introduced (injected) into the cavity through a sprue and a molten resin injection part (gate part) provided in the container, and the pressure is maintained. In the pressure-holding process, by switching to an arbitrarily adjustable pressure (secondary injection pressure) different from the injection pressure, the molten thermoplastic resin is prevented from backflow, and the thermoplastic resin in the cavity is cooled and solidified. The melted thermoplastic resin is replenished into the cavity to prevent mold shrinkage. Since the holding pressure is not required after the molten resin injection part (gate part) is solidified, the pressure holding process time (pressure holding time) is usually the time until the molten resin injection part (gate part) solidifies. t 'is determined. In the light guide plate manufacturing method of the present invention, an extremely thin light guide plate having a thickness of 0.1 mm to 0.55 mm is injection-molded, so that the pressure holding time t ′ may be set to 0 seconds in some cases. Although not limited, for example, the pressure holding time (pressure holding time) t ′ for applying a pressure of 1 × 10 ⁸ Pa or less as the pressure holding pressure is 2 seconds or less (t ′ ≦ 2), preferably 0.1 seconds ≦ t ′ ≦ 1 second is desirable. If the pressure (holding pressure) in the pressure holding process is too high or the pressure holding time is too long, the light guide plate will be deformed. After t seconds have elapsed from the completion of the injection process of the molten thermoplastic resin into the cavity, the mold clamping force is set to 0.5 F ₀ or less, but t seconds from the completion of the injection process of the molten thermoplastic resin into the cavity. Until the time elapses, the clamping force is maintained at F ₀ and no pressure is maintained (that is, no pressure is applied from the injection cylinder to the thermoplastic resin in the cavity). Alternatively, after the elapse of t seconds from the completion of the injection process of the molten thermoplastic resin into the cavity and the subsequent pressure holding process, the mold clamping force is set to 0.5 F ₀ or less. The mold clamping force is kept at F ₀ until t seconds elapse from the completion of the resin pressure holding process. Since the pressure holding process is completed, no pressure is applied from the injection cylinder to the thermoplastic resin in the cavity.

  In the light guide plate manufacturing method of the present invention, if necessary, air is blown through the cavity before mold opening to release the light guide plate from the cavity surface to reduce mold release resistance, or during mold opening or before ejection. By using the blow together, it becomes possible to suppress the deformation of the light guide plate with improved transferability when released, and the flatness can be improved more effectively.

  In the light guide plate, planar light source device or light guide plate manufacturing method of the present invention (hereinafter, these may be collectively referred to simply as “the present invention”), the flatness of the light guide plate is 200 μm or less, preferably 150 μm. Hereinafter, it is more preferable that the thickness is 100 μm or less.

The flatness can be measured based on JIS B 7513-1992. However, since the light guide plate is thin, it may be bent by the contact pressure of the probe and an accurate value may not be obtained. Therefore, it is possible to perform measurement using a low pressure probe or a non-contact color laser probe with a low contact pressure. desirable. In particular,
(1) As a whole, a light guide plate having a thin plate shape with a substantially constant thickness,
(2) A light guide plate in which a portion in the vicinity of the first side surface which is a light incident surface is thick, and the thickness of the other portion is substantially constant,
(3) A wedge-shaped guide whose thickness decreases from the first side surface that is the light incident surface toward the third side surface that is the surface facing the light incident surface (for example, the side surface located in the vicinity of the molten resin injection portion). Light plate,
In general, there are three types, but the surface corrected by measuring at least three locations of the light guide plate placed on the surface plate is used as a reference surface, and at least 21 locations on the sample surface are measured to obtain flatness. At that time, in the case of a light guide plate having a certain thickness, the four corners and the vicinity of the center must be measured. In the light guide plate in which the portion near the first side surface that is the light incident surface is thick, it is desirable to avoid measurement at this thick portion. In addition, when the light guide plate is thick only on the first side, it is desirable to avoid measurement at that portion. In addition, let a sample surface be the 1st surface in which the convex part and / or the recessed part are provided.

In the light guide plate or the planar light source device of the present invention, any one of the cavity and the light guide plate (the first side, the second side, the third side, or the fourth side, preferably the first side ) Using a mold assembly with a molten resin injection part for injecting molten thermoplastic resin into the cavity from the cavity surface corresponding to the light guide plate, the transparent molten thermoplastic resin through the molten resin injection part Therefore, it is preferable to form by being injected into the cavity. In this case, or in the method of manufacturing the light guide plate of the present invention, for example, the length in the longitudinal direction of the light guide plate, which is the length between the first side surface and the third side surface, is 52 mm. Using a thermoplastic resin with a Q value of 0.60 on a light guide plate with a thickness of 0.3 mm, the molten thermoplastic resin was passed through the molten resin injection part under injection conditions at a resin temperature of 330 ° C. The resin injection speed when molding by injection into the cavity is 1.2 m · sec ⁻¹ or more, preferably 1.5 m · sec ⁻¹ or more, more preferably 2.0 m · sec ⁻¹ or more. Is desirable. In general, in a normal injection molding method, a resin injection speed when a molten thermoplastic resin is injected into a cavity through a molten resin injection portion is 0.1 m · sec ^{−1 to} 0.3 m · sec ^{− About 1} In the preferred embodiment of the present invention, the resin injection speed is 20 times or more faster than the conventional injection molding method. In this way, by injecting a transparent molten thermoplastic resin into the cavity through the molten resin injection part at a high resin injection speed that is not comparable to the conventional technology, it is melted into the thin cavity. The thermoplastic resin can be reliably and completely filled. By setting the resin temperature to 360 ° C. or more, molding based on the conventional injection molding method of about 0.1 m · sec ^{−1 to} 0.3 m · sec ⁻¹ becomes possible, but depending on molding conditions, There is a risk that the thermoplastic resin will turn yellow due to thermal decomposition, leading to a reduction in luminance and quality of the light guide plate.

  Further, in the present invention including the above-described embodiment, a nesting body made of zirconia ceramics or conductive zirconia ceramics, and a cavity for forming convex portions and / or concave portions on the first surface of the light guide plate It is preferable that a nesting made of a metal layer provided on the surface of the nesting body facing the rim and provided with a concave portion and / or a convex portion is disposed inside the mold assembly.

  By constituting the nesting body from a material having a low thermal conductivity such as zirconia ceramics or conductive zirconia ceramics, it is possible to prevent rapid cooling of the molten thermoplastic resin in the cavity, resulting in improved fluidity of the molten thermoplastic resin, It is possible to avoid the formation of a solidified layer on the molten thermoplastic resin in contact with the layer, and even though the cavity thickness is very thin, the inside of the cavity is surely and completely made of molten thermoplastic resin. Can be filled. In addition, the concave portions and / or convex portions provided in the metal layer can be reliably and accurately transferred to the light guide plate with high accuracy.

  In the present invention including the above preferred embodiment, the light is incident from the first side surface of the light guide plate and is not limited, but the molten thermoplastic resin is introduced into the cavity from the cavity surface corresponding to the third side surface of the light guide plate. It is preferable to have a configuration for injection.

In the present invention including the above preferred embodiments, the Q value of the thermoplastic resin is preferably 0.5 cm ³ · sec ⁻¹ or more, preferably 0.6 cm ³ · sec ⁻¹ or more. Here, the Q value of the thermoplastic resin was determined by applying a load of 1.57 × 10 ⁷ Pa (160 kgf / cm ² ) to the molten thermoplastic resin heated to 280 ° C. using a Koka type flow tester (manufactured by Shimadzu Corporation). ), The amount of molten thermoplastic resin that flows out from a nozzle having a diameter of 1 mm and a length of 10 mm (unit: cm ³ · sec ⁻¹ ). It can be said that the higher the Q value, the better the fluidity of the molten thermoplastic resin. If the Q value is too high, the toughness of the thermoplastic resin is lost, and the light guide plate tends to break. Therefore, an upper limit value of the actual Q value is 1.5 cm ³ · sec ^−1. it can. Incidentally, for example, in the conventional aromatic polycarbonate resin, the maximum value of Q value, at most, only 0.36~0.40cm ³ · sec ^-1, at 0.5 cm ³ · sec ^-1 or more The above-mentioned Q value is a very high value that has never existed before.

  In the present invention including various preferred embodiments described above, as the thermoplastic resin, aromatic polycarbonate resin, polymethyl methacrylate resin, “ZEONOR” manufactured by Nippon Zeon Co., Ltd., which is a norbornene-based polymer resin, and the like. Examples thereof include a transparent thermoplastic resin such as a cycloolefin resin, a transparent polyimide resin, an alicyclic acrylic resin, and a styrene resin such as polystyrene, preferably an aromatic polycarbonate resin.

  Polycarbonates suitable for use in the present invention can be produced based on known methods such as interfacial polymerization, pyridine, transesterification, and ring-opening polymerization of cyclic carbonate compounds. Can be mentioned. Specifically, an aromatic dihydroxy compound or a small amount thereof and a small amount of a polyhydroxy compound, carbonyl chloride generally known as phosgene, or a carbonic acid diester represented by dimethyl carbonate or diphenyl carbonate, carbon monoxide or carbon dioxide It is a polymer or copolymer of a linear or branched thermoplastic aromatic polycarbonate obtained by reacting the carbonyl compound mentioned above.

  As an aromatic dihydroxy compound as a raw material, for example, 2,2-bis (4-hydroxyphenyl) propane [= bisphenol A], 2,2-bis (4-hydroxy-3,5-dimethylphenyl) propane, 2,2 -Bis (4-hydroxy-3,5-diethylphenyl) propane, 2,2-bis (4-hydroxy- (3,5-diphenyl) phenyl) propane, 2,2-bis (4-hydroxy-3,5) -Dibromophenyl) propane, 2,2-bis (4-hydroxyphenyl) pentane, 2,4'-dihydroxy-diphenylmethane, bis- (4-hydroxyphenyl) methane, bis- (4-hydroxy-5-nitrophenyl) Methane, 1,1-bis (4-hydroxyphenyl) ethane, 3,3-bis (4-hydroxyphenyl) pentane, 1, -Bis (4-hydroxyphenyl) cyclohexane, bis (4-hydroxyphenyl) sulfone, 2,4'-dihydroxydiphenylsulfone, bis (4-hydroxyphenyl) sulfide, 4,4'-dihydroxydiphenyl ether, 4,4'- Examples include dihydroxy-3,3′-dichlorodiphenyl ether, 4,4′-dihydroxy-2,5-diethoxydiphenyl ether, and the like, preferably bis (4-hydroxyphenyl) alkanes, particularly preferably. 2,2-bis (4-hydroxyphenyl) propane [referred to as bisphenol A]. These aromatic dihydroxy compounds can be used alone or in admixture of two or more.

  To obtain branched polycarbonate, phloroglucin, 4,6-dimethyl-2,4,6-tris (4-hydroxyphenyl) heptene-2, 4,6-dimethyl-2,4,6-tris (4-hydroxy Phenyl) heptane, 2,6-dimethyl-2,4,6-tris (4-hydroxyphenyl) heptene-3, 1,3,5-tris (4-hydroxyphenyl) benzene, 1,1,1-tris ( Polyhydroxy compounds represented by 4-hydroxyphenyl) ethane or the like, or 3,3 bis (4-hydroxyaryl) oxindole (= isatin bisphenol), 5-chlorisatin bisphenol, 5,7-dichloroisatin bisphenol , 5-bromoisatin bisphenol and the like are used as a part of the above-mentioned aromatic dihydroxy compounds. Well, usage, 0.01 to 10 mol%, preferably from 0.1 to 2 mol%.

  In the reaction by the interfacial polymerization method, in the presence of an organic solvent inert to the reaction, an alkaline aqueous solution, the pH is usually kept at 10 or more, an aromatic dihydroxy compound and an appropriate molecular weight modifier (end stopper), as required Polycarbonate by performing interfacial polymerization by adding a polymerization catalyst such as tertiary amine or quaternary ammonium salt after reacting with phosgene, using an antioxidant for antioxidant of the aromatic dihydroxy compound accordingly Can be obtained. The addition of the molecular weight regulator is not particularly limited as long as it is from the time of phosgenation to the start of the polymerization reaction. The reaction temperature is 0 to 35 ° C., and the reaction time is several minutes to several hours.

  Here, examples of the organic solvent inert to the reaction include chlorinated hydrocarbons such as dichloromethane, 1,2-dichloroethane, chloroform, monochlorobenzene and dichlorobenzene, and aromatic hydrocarbons such as benzene, toluene and xylene. be able to. Examples of the molecular weight regulator or the terminal terminator include compounds having a monovalent phenolic hydroxyl group. Specifically, m-methylphenol, p-methylphenol, m-propylphenol, p-propylphenol, p -Tert-butylphenol, p-long chain alkyl-substituted phenol and the like can be mentioned. The usage-amount of a molecular weight modifier is 50-0.5 mol with respect to 100 mol of aromatic dihydroxy compounds, Preferably, it is 30-1 mol. As a polymerization catalyst, tertiary amines such as trimethylamine, triethylamine, tributylamine, tripropylamine, trihexylamine, pyridine; quaternary ammonium salts such as trimethylbenzylammonium chloride, tetramethylammonium chloride, triethylbenzylammonium chloride, etc. Can be mentioned.

  The reaction by the transesterification method is a transesterification reaction between a carbonic acid diester and an aromatic dihydroxy compound. Usually, the molecular weight of the desired polycarbonate and the amount of terminal hydroxyl groups are determined by adjusting the mixing ratio of the carbonic acid diester and the aromatic dihydroxy compound or adjusting the degree of vacuum during the reaction. As a more aggressive method, an adjustment method in which a terminal terminator is added separately during the reaction is also well known. Examples of the terminal terminator at this time include monohydric phenols, monovalent carboxylic acids, and carbonic acid diesters. The amount of terminal hydroxyl groups has a great influence on the thermal stability, hydrolysis stability, color tone and the like of the polycarbonate, and is preferably 1000 ppm or less, particularly preferably 700 ppm or less, in order to impart practical physical properties. In addition, in the polycarbonate produced by the transesterification method, if the amount of terminal hydroxyl groups is too small, the molecular weight does not increase and the color tone deteriorates, so 100 ppm or more is preferable. Therefore, it is common to use an equimolar amount or more of carbonic acid diester with respect to 1 mol of the aromatic dihydroxy compound, and it is preferably used in an amount of 1.01-1.30 mol.

When producing a polycarbonate by the transesterification method, a transesterification catalyst is usually used. The transesterification catalyst is not particularly limited, but alkali metal compounds and / or alkaline earth metal compounds are mainly used, and supplementary basic boron compounds, basic phosphorus compounds, basic ammonium compounds, or amine-based catalysts It is also possible to use a basic compound such as a compound in combination. In the transesterification reaction using such raw materials, the reaction is carried out at a temperature of 100 to 320 ° C., and finally, a secondary reaction such as aromatic hydroxy compound is performed under a reduced pressure of 2.7 × 10 ² Pa ( ² mmHg) or less. The method of performing a melt polycondensation reaction, removing a product is mentioned. The melt polycondensation can be carried out batchwise or continuously. However, in the case of a polycarbonate suitable for use in the present invention, it is preferably carried out continuously from the viewpoint of stability and the like. In the transesterification method, it is preferable to use a compound that neutralizes the catalyst, for example, a sulfur-containing acidic compound, or a derivative formed therefrom, as the catalyst deactivator in the polycarbonate, and the amount thereof is determined according to the alkali of the catalyst. It is added in a range of 0.5 to 10 equivalents, preferably 1 to 5 equivalents relative to the metal, and is usually added in a range of 1 to 100 ppm, preferably 1 to 20 ppm based on the polycarbonate.

In the present invention including various preferred embodiments described above, the thermoplastic resin has a viscosity average molecular weight (Mv) of 1.0 × 10 ^{4 to} 1.5 × 10 ⁴ , preferably 1.1 × 10 ^{4 to} 1. Desirably, 4 × 10 ⁴ aromatic polycarbonate resin. In addition, when the viscosity average molecular weight of the aromatic polycarbonate resin is less than 1.0 × 10 ⁴ , the mechanical strength of the light guide plate is lowered and the required performance of the light guide plate may not be satisfied. On the other hand, when the viscosity average molecular weight of the aromatic polycarbonate resin exceeds 1.5 × 10 ⁴ , the fluidity of the molten aromatic polycarbonate resin is inferior, a problem occurs in moldability, and it is difficult to obtain a desired light guide plate. Become.

  The viscosity average molecular weight (Mv) was calculated by the following equation using the intrinsic viscosity [η] obtained from the solution viscosity measured at 25 ° C. with an Ubbelohde viscometer using methylene chloride as a solvent.

η = 1.23 × 10 ⁻⁴ × Mv ^0.83

  In the present invention including the various preferred embodiments described above, the light guide plate in the xy chromaticity diagram in the CIE 1931 XYZ color system, which is an international display method formulated in 1931 by CIE (Commission Internationale de l'Eclairage) The value (x, y) of x ≦ 0.375 and y ≦ 0.335, preferably satisfy x ≦ 0.370 and y ≦ 0.330. If the value of (x, y) of the light guide plate deviates from this range, the color of the light guide plate becomes yellow and the appearance is not so good. Note that the value of (x, y) of the light guide plate in the xy chromaticity diagram is measured using a luminance LED SR3, BM7 or BM5A manufactured by Topcon Corporation using a white LED as a light source. It is an average value of the measurement results at three locations (measurement range: diameter 10 mm) of the farthest light guide plate portion.

  More specifically, the value of (x, y) in an xy chromaticity diagram including luminance measurement (also called a CIE system or CIE chromaticity diagram) can be determined based on the following method. That is, for example, in a dark room, a light guide plate is placed on a unit that can guide light from the light incident surface of the light guide plate to the light guide plate, and light emitted from the lamp is guided from the light incident surface of the light guide plate to the light guide plate. . And the brightness | luminance of the light inject | emitted from the light guide plate is measured with the luminance meter arrange | positioned about 35 cm above the light guide plate. By changing the distance from the light guide plate to the luminance meter, the size of the measurement range can be changed. In addition, it is desirable to measure the luminance of the light guide plate, etc., by dividing the light guide plate as evenly as possible by the number of measurement points and at the center of the divided area.

  In the present invention including the various preferred embodiments described above, the light guide plate as a whole has a thin plate shape with a substantially constant thickness, and light is incident from the first side surface (light incident surface) of the light guide plate, The light can be emitted from the first surface and / or the second surface, or the whole has a wedge-shaped truncated quadrangular pyramid shape, and two opposing side surfaces of the truncated quadrangular pyramid are guided. Corresponds to the first and second surfaces of the light plate, the bottom of the truncated quadrangular pyramid corresponds to the first side of the light guide plate, the top surface of the truncated quadrangular pyramid corresponds to the third side of the light guide plate, The remaining two opposite side surfaces of the quadrangular pyramid correspond to the second side surface and the fourth side surface of the light guide plate, and light enters from the first side surface (light incident surface) of the light guide plate, and the first surface and / or the second side surface. The light can be emitted from the surface. Alternatively, the light guide plate has a thin plate shape in which 80% or more of the whole has a substantially constant thickness, and the remaining portion gradually increases in thickness, and that portion terminates at the first side surface (light incident surface). It can also be set as the structure. In the light guide plate having a thin plate shape, the thickness of the light guide plate is expressed as “substantially constant” as a whole. This is because the thickness of the light guide plate may vary due to the variation, but the thickness variation of the light guide plate is included.

  In the present invention, the “transparent thermoplastic resin” means a thermoplastic resin having a parallel light transmittance of 85% or more measured based on Section 5.5.2 (Measurement method A) of JIS K 7105-1981. Point to. In the measurement, the thickness of the resin test piece is set to 3.0 mm.

  The thickness of the light guide plate is measured using a micrometer, and the average thickness is obtained by measuring at least nine locations of the light guide plate. In addition, it is desirable to obtain the thickness difference. Here, when obtaining the thickness difference, in particular, the portion of the light guide plate corresponding to the portion of the cavity located in the vicinity of the molten resin injection portion (for example, the portion of the light guide plate in the vicinity of the third side surface) and the flow end Since the difference in thickness between the light guide plate portion corresponding to the corresponding cavity portion (for example, the light guide plate portion in the vicinity of the first side surface that is the light incident surface) tends to be the largest, It is desirable to obtain the thickness difference by measuring the thickness of these portions. In the light guide plate having a certain thickness, it is desirable that the thickness difference is 80 μm or less. If it exceeds 80 μm, the actual luminance value may be smaller than the luminance value based on the optical design of the light guide plate. For example, it becomes difficult to incorporate the light guide plate into a thin liquid crystal display device unit. If it is incorporated in, the pressure is applied to the liquid crystal display device body, and there is a risk that the liquid crystal display device body may be damaged.

  In the light guide plate, a convex portion or a concave portion may not be formed on the peripheral portion of the first surface, or the size or surface roughness of the convex portion or the concave portion, which will be described later, is not provided on the peripheral portion of the first surface. It does not have to satisfy the regulations. That is, the first surface portion that does not substantially contribute to light scattering or the like may not have a convex portion or a concave portion, or the size of the convex portion or the concave portion and the surface roughness are satisfied. You don't have to.

  When the light guide plate of the present invention is used in a liquid crystal display device, it can be incorporated into an edge type backlight type surface light source device or an edge type front light type surface light source device. That is, these planar light source devices correspond to the planar light source device of the present invention.

  In the edge type backlight type planar light source device, a light source composed of, for example, a fluorescent lamp or a light emitting diode (LED) is disposed in the vicinity of the first side surface of the light guide plate. And the reflection member is arrange | positioned facing the 1st surface of a light-guide plate. Further, a liquid crystal display device is disposed to face the second surface of the light guide plate. The light emitted from the light source is incident on the light guide plate from the first side surface of the light guide plate, collides with the convex portion or the concave portion of the first surface, is scattered, is emitted from the first surface, and is reflected by the reflecting member, The light enters the first surface again, is emitted from the second surface, and irradiates the liquid crystal display device. For example, a diffusion sheet may be disposed between the liquid crystal display device and the second surface of the light guide plate.

  Even in the edge type front light type planar light source device, for example, a light source composed of a fluorescent lamp or a light emitting diode is disposed in the vicinity of the first side surface of the light guide plate. And the liquid crystal display device is arrange | positioned facing the 2nd surface of a light-guide plate. The light emitted from the light source is incident on the light guide plate from the first side surface of the light guide plate, collides with the convex portion or the concave portion of the first surface, is scattered, is emitted from the second surface, and is used as a retardation film or a polarizing film. Pass through the liquid crystal display device. And the light inject | emitted from the liquid crystal display device is reflected by the reflective member arrange | positioned on the outer side of a liquid crystal display device, passes a liquid crystal display device again, passes a phase difference film or a polarizing film, Furthermore, a light guide plate Through the first surface of the light guide plate. This light is recognized as an image or the like displayed on the liquid crystal display device. Usually, an antireflection layer is formed on the second surface of the light guide plate.

  In the planar light source device of the present invention, the light emitted from the light source may be guided directly to the light guide plate or indirectly to the light guide plate. In the latter case, for example, an optical fiber may be used. The light source can be an artificial light source such as a fluorescent lamp, an incandescent lamp, a light-emitting diode, or a fluorescent tube, depending on the configuration, structure, usage, etc. of the planar light source device, or natural light such as sunlight. You can also

  The height, depth, pitch, and shape of the convex portion or concave portion provided on the first surface of the light guide plate may be constant or may be changed as the distance from the light source increases. In the latter case, for example, the pitch of the convex portion or the concave portion may be made finer as the distance from the light source increases. In addition, the pitch of a convex part or the pitch of a recessed part means the pitch of the convex part along the light-incidence direction to a light-guide plate, or the pitch of a recessed part.

In the present invention, the convex portion provided on the first surface has a height of 5 × 10 ⁻⁷ m to 6 × 10 ⁻⁵ m, preferably 1 × 10 ⁻⁶ m to 5 × 10 ⁻⁵ m. It is preferably 2 × 10 ⁻⁶ m to 4 × 10 ⁻⁵ m, and the pitch is 5 × 10 ⁻⁷ m to 4 × 10 ⁻⁴ m, preferably 5 × 10 ⁻⁶ m to 3.5 × 10 ^−. It is desirable that the ^{distance be 4} m, more preferably 3 × 10 ⁻⁵ m to 3.0 × 10 ⁻⁴ m. Alternatively, the recess provided in the first surface has a depth of 5 × 10 ⁻⁷ m to 6 × 10 ⁻⁵ m, preferably 1 × 10 ⁻⁶ m to 5 × 10 ⁻⁵ m, more preferably 2 × 10 ⁻⁶ m to 4 × 10 ⁻⁵ m, and the pitch is 5 × 10 ⁻⁷ m to 4 × 10 ⁻⁴ m, preferably 5 × 10 ⁻⁶ m to 3.5 × 10 ⁻⁴ m. More preferably, the thickness is 3 × 10 ⁻⁵ m to 3.0 × 10 ⁻⁴ m. Alternatively, 70% or more, preferably 80% or more of the total number of convex portions and / or concave portions provided on the first surface has a surface roughness of 0.3 μm or less, preferably 0.15 μm or less, more preferably 0. It is desirable to satisfy 0.08 μm or less. In addition, the surface roughness of the flat part of the 1st surface of the light-guide plate located between a convex part, or the surface of the flat part of the 1st surface of a light-guide plate located between a recessed part and a recessed part The roughness is not particularly specified. That is, the surface roughness R _Z of the flat portion of the first surface of the light guide plate may be 0.3 μm or less, a value exceeding 0.3 μm, or fine unevenness may be provided. Alternatively, in the light guide plate, the flat portion may not exist in the portion of the first surface of the light guide plate located between the convex portion and the convex portion, or between the concave portion and the concave portion. That is, it can also be set as the structure by which the uneven | corrugated | grooved part was provided in the 1st surface of the light-guide plate.

  The convex portion and / or the concave portion provided on the first surface of the light guide plate has a continuous linear convex shape and / or concave shape extending along a direction forming a predetermined angle with the light incident direction to the light guide plate. It can be configured. Here, as a continuous linear convex shape and / or concave cross-sectional shape when the light guide plate is cut in a virtual plane perpendicular to the first surface in the light incident direction to the light guide plate, a triangle; a square, Various smooth curves such as an arbitrary quadrangle including a rectangle and a trapezoid; an arbitrary polygon; a part of a circle, a part of an ellipse, a part of a parabola, and a part of a hyperbola can be exemplified. The direction that forms a predetermined angle with the light incident direction on the light guide plate means a direction of 60 degrees to 120 degrees when the light incident direction on the light guide plate is 0 degrees. In the following description, the “direction of forming a predetermined angle with the light incident direction on the light guide plate” is also used in the same meaning.

  Or each convex part and / or each recessed part provided in the 1st surface are the discontinuous convex shape arranged on the virtual straight line along the direction which makes a predetermined angle with the light incident direction to a light-guide plate. And it can also be set as the structure which has a concave shape. Here, as a discontinuous convex shape and / or concave shape, a polygonal column including a pyramid, a cone, a cylinder, a triangular column and a quadrangular column; a part of a sphere, a part of a spheroid, a part of a rotating parabola Various smooth curved surfaces such as a part of a rotating hyperbola can be exemplified.

The surface roughness when the discontinuous convex shape or concave shape is a curved surface is preferably defined by the surface roughness R _t , and the surface roughness when the discontinuous convex shape or concave shape is otherwise, or The surface roughness in the case of a continuous convex shape or concave shape is preferably defined by the surface roughness R _Z. The surface roughness R _Z and the surface roughness R _t are based on the provisions of JIS B 0601-2001.

  The second surface of the light guide plate is preferably a substantially flat surface, but the second surface is not limited to such a shape, and may be a mirror surface, for example, a fine uneven surface. .

In addition, in order to shape | mold the 2nd surface of a light-guide plate, it can be set as the structure further provided with the 2nd insert arrange | positioned inside the mold assembly. In this case, when the light guide plate is used in the backlight type planar light source device, the surface of the second nesting facing the cavity may be a mirror surface or a blast surface. On the other hand, when the light guide plate is used in a front light type planar light source device, the surface of the second nesting facing the cavity needs to be a mirror surface. Here, when the surface of the second nesting facing the cavity is a mirror surface, the surface roughness R _Z of the surface of the second nesting facing the cavity is 0.01 μm to 0.1 μm, preferably 0.01 μm. It is desirable that the thickness is 0.08 μm, more preferably 0.01 μm to 0.05 μm. The second nesting can be composed of zirconia ceramics, or can be composed of zirconia ceramics or conductive zirconia ceramics and a metal layer. In the former case, the surface roughness R _Z of the zirconia ceramics only needs to satisfy the above value, and in the latter case, the surface roughness R _Z of the metal layer surface only needs to satisfy the above value. In addition, the 2nd nesting of these structures may be called the ceramic 2nd nesting for convenience. In some cases, the second nesting may be made of metal. Furthermore, the nesting and the second nesting made of ceramics may be collectively referred to as “nesting or the like”.

  Hereinafter, nesting and the like will be described.

The zirconia ceramics or conductive zirconia ceramics constituting the nesting body such as the nesting are preferably made of partially stabilized zirconia ceramics. When the nesting body such as a nesting body is composed of partially stabilized zirconia ceramics, the partial stabilizer in the partially stabilized zirconia ceramics is calcia (calcium oxide, CaO), yttria (yttrium oxide, Y ₂ O ₃ ), magnesia (oxidized). It is preferably made of at least one material selected from the group consisting of magnesium (MgO), silica (silicon oxide, SiO ₂ ) and ceria (cerium oxide, CeO ₂ ). The proportion of the partial stabilizer contained in the zirconia ceramic or the conductive zirconia ceramic is 3 to 15 mol%, preferably 6 to 10 mol%, preferably yttria when the partial stabilizer is calcia. 1 mol% to 8 mol%, preferably 2 mol% to 5 mol%, magnesia 4 mol% to 15 mol%, preferably 8 mol% to 10 mol%, ceria 3 mol% to 18 mol% It is desirable that the amount be 6 mol%, preferably 6 mol% to 12 mol%.

  In nesting or the like, the thickness of the nesting body is desirably 0.1 mm to 10 mm, preferably 0.5 mm to 10 mm, more preferably 1 mm to 7 mm, and still more preferably 2 mm to 5 mm. When the thickness of the nesting body is less than 0.1 mm, the heat insulating effect due to nesting or the like is reduced, and the molten thermoplastic resin injected into the cavity may be rapidly cooled, so that it is difficult to form a convex portion or a concave portion on the light guide plate. There is. Further, when fixing the insert or the like to the metal or alloy mold assembly, the insert or the like may be adhered to the inside of the mold assembly using, for example, a thermosetting adhesive. If the thickness of the adhesive is less than 0.1 mm, uneven stress will remain in the insert if the film thickness of the adhesive is non-uniform, resulting in the phenomenon that the surface of the light guide plate swells, or the molten thermoplastic injected into the cavity The insert may be damaged by the pressure of the resin. On the other hand, when the thickness of the nesting body exceeds 10 mm, the heat insulating effect due to nesting or the like becomes too great, and the light guide plate may be deformed after the light guide plate is taken out unless the cooling time of the resin in the cavity is extended. Therefore, problems such as extending the molding cycle may occur.

The surface roughness R _Z of the surface of the nesting body facing the cavity is preferably 0.1 μm to 10 μm, preferably 0.1 μm to 8 μm, more preferably 0.1 μm to 5 μm. By setting the surface roughness R _Z of the surface of the nesting body facing the cavity to 0.1 μm or more, an anchor effect can be obtained when a metal layer is formed on the surface by electroless plating. It is possible to form a metal layer by electroless plating. On the other hand, when the surface roughness R _Z of the surface of the nesting body facing the cavity exceeds 10 μm, the surface of the metal layer becomes rough, and the time required for surface polishing of the metal layer increases or the pin of the metal layer Holes are likely to occur. The surface of the nested body facing the cavity can be roughened by blasting or etching.

The thermal conductivity of zirconia ceramics, conductive zirconia ceramics or partially stabilized zirconia ceramics constituting the nesting body is 8.5 J / (m · s · K) or less [8.5 W / (m · K) or less, or 2 × 10 ⁻² cal / (cm · s · K) or less], specifically, about 3.5 to 6 J / (m · s · K). When the nesting body is made of an inorganic material having a thermal conductivity exceeding 8.5 J / (m · s · K), the molten thermoplastic resin in the cavity is rapidly cooled by nesting or the like, depending on the molding conditions. For this reason, there may be a case where only an appearance comparable to that of a light guide plate formed using a mold assembly made of ordinary carbon steel or the like not provided with a nesting or the like may be obtained.

  A part of the cavity provided in the mold assembly is configured by nesting or the like. Here, configuring a part of the cavity means configuring a part of the cavity surface that defines the outer shape of the light guide plate. means. More specifically, the cavity includes, for example, a surface (cavity surface of the mold part) constituting the cavity formed in the first mold part or the second mold part constituting the mold assembly, Depending on the case, it is comprised from the surface (cavity surface of a nest | insert) which comprises a part of cavity formed in the nest | insert. The same applies to the following description. In addition, the metal layer provided with the recessed part and / or convex part also comprises a cavity surface. A metal layer having a concave portion or a convex portion is disposed on the entire cavity surface such as a nest or a desired portion. In the latter case, the cavity surface of the insert other than the desired part may be composed of a flat metal layer.

  In the nesting or the like, the metal layer only needs to be disposed at least on the cavity surface of the nesting, and may be provided on the entire surface of the nesting body.

The required surface roughness of the concave and / or convex surface provided in the metal layer is a mirror-like prism-like shape and a dot-like shape obtained by etching or machining. Although it differs from the case, it is desirable that it is 0.5 μm or less. In addition, 80% or more, preferably 90% or more of the total number of recesses provided in the metal layer has a surface roughness of 0.5 μm or less in the case of a dot shape, and a surface roughness of 0.1 μm or less in the case of mirror finishing. Preferably, it is 0.05 μm, more preferably 0.01 μm or less. Surface roughness discontinuous convex shape in the case of curved surfaces, it is preferable to define in the surface roughness R _t, the surface roughness discontinuous convex shape in the case of other, or, in the case of continuous convex The surface roughness is preferably defined by the surface roughness R _Z.

Here, in nesting or the like, the metal layer is made of at least one material selected from the group consisting of Cr, Cr compound, Cu, Cu compound, Ni and Ni compound, and the depth of the recess provided in the metal layer. Where d is the thickness t (unit: m) of the metal layer is (d + 5) × 10 ⁻⁶ m ≦ t ≦ 5 × 10 ⁻⁴ m, preferably (d + 10) × 10 ⁻⁶ m ≦ t It is desirable to satisfy ≦ 1 × 10 ⁻⁴ m. Alternatively, when the height of the protrusion provided on the metal layer is h, the thickness t (unit: m) of the metal layer is (h + 5) × 10 ⁻⁶ m ≦ t ≦ 5 × 10 ⁻⁴ m. Preferably, (h + 10) × 10 ⁻⁶ m ≦ t ≦ 1 × 10 ⁻⁴ m is satisfied. Accordingly, the concave portion or the convex portion can be formed on the metal layer by various methods, and the metal layer can be easily processed with a general cutting machine. In addition, even when the molten thermoplastic resin injected into the cavity comes into contact with the metal layer, the molten thermoplastic resin can be prevented from being rapidly cooled. Furthermore, the fine adjustment of the nesting with respect to the mold part (in some cases, the nesting mounting part or the nesting core) can be easily performed. In addition, high scratch resistance and surface hardness can be obtained. Here, the thickness t of the metal layer refers to the surface of the nesting body (when an active metal film to be described later is formed) , The distance to the interface between the active metal film and the metal layer.

  In nesting or the like, the metal layer may be composed of one layer or a plurality of layers. Specific examples of the Cr compound include a nickel-chromium alloy. Specific examples of the Cu compound include a copper-zinc alloy, a copper-cadmium alloy, and a copper-tin alloy. Further, as the Ni compound, specifically, nickel-phosphorus alloy (Ni-P alloy), nickel-iron alloy, nickel-cobalt alloy, nickel-tin alloy, nickel-iron-phosphorus alloy (Ni-Fe- P-based alloy) and nickel-cobalt-phosphorous alloy (Ni-Co-P-based alloy). When high scratch resistance is required for the metal layer, for example, the metal layer is preferably composed of chromium (Cr). On the other hand, the metal layer is not required to have scratch resistance as much as the left, but when the thickness is required, for example, the metal layer is preferably made of copper (Cu). Furthermore, when the metal layer is required to have a certain degree of scratch resistance and also requires a thickness, for example, the metal layer is preferably composed of nickel (Ni). Furthermore, when the metal layer is required to have a thickness and surface hardness is required, the metal layer is composed of two layers, for example, the lower layer is composed of copper (Cu) or nickel (Ni). It is preferable to adjust the thickness to a desired thickness, while the upper layer is made of thin chromium (Cr).

  Formation of the concave portion or the convex portion in the metal layer such as nesting can be performed by a physical method or a chemical method. By machining using a diamond tool, a concave portion or a convex portion can be formed in the metal layer. In addition, when a concave or convex portion is formed by a chemical method, a resist layer is applied to the surface of the metal layer, and for example, a pattern is formed on the resist layer by irradiating the resist layer with ultraviolet rays through a desired mask. By forming or forming a resist layer by a printing method, and then etching the metal layer using the resist layer as an etching mask, a concave portion or a convex portion can be formed in the metal layer. If desired, the resist layer may be formed and etched a plurality of times to form a concave portion or a convex portion.

  In nesting, etc., as a method of arranging a metal layer on the surface of the nesting body, specifically, for example, as a method of forming a metal layer on the surface of the nesting body, electroplating, electroless plating, electroless plating and electro A combination of plating methods can be mentioned. When applying the electroplating method, it is not essential to form an active metal film, which will be described later, but after roughening the surface of the nested body facing the cavity, electroless plating is performed, and then electroplating is performed. Need to do.

In nesting and the like, zirconia ceramics constituting the nesting body refers to those having no conductivity, that is, those having a volume resistivity exceeding 1 × 10 ⁹ Ω · cm. In such a nesting or the like, the nesting body can be made of zirconia ceramics, and an active metal film can be formed between the nesting body and the metal layer. Such a configuration is referred to as a first configuration such as nesting for convenience.

In the first configuration such as nesting, the active metal film includes a metal selected from the group consisting of Ti, Zr and Be (active metal) and a metal selected from the group consisting of Ni, Cu, Ag and Fe. The active metal film is made of a eutectic composition and has a thickness of 1 × 10 ⁻⁶ m to 5 × 10 ⁻⁵ m, preferably 3 × 10 ⁻⁶ m to 4 × 10 ⁻⁵ m. More specifically, as the eutectic composition, for example, Ti—Ni, Ti—Cu, Ti—Cu—Ag, Ti—Ni—Ag, Zr—Ni, Zr—Fe, Be—Cu, Be—Ni are used. Can be mentioned. By setting the thickness of the active metal film to 1 × 10 ⁻⁶ m to 5 × 10 ⁻⁵ m, it is possible to obtain an active metal film having high conductivity, that is, for non-conductive zirconia ceramics. Conductivity can be imparted, and the metal layer can be formed, for example, by electroplating.

  As a method for forming the active metal film, an active metal solder method can be exemplified. By employing the active metal solder method, the active metal film can obtain high adhesion to the surface of the nested body. Moreover, a metal layer comes to have high adhesive force with respect to a nesting body. Here, the active metal solder method means that a paste made of a metal material constituting the active metal film is applied to the surface of the nesting body by, for example, a screen printing method, and is about 800 ° C. to 1000 ° C. in vacuum or in an inert gas. A method of baking at a high temperature of ° C.

Alternatively, in a nesting or the like, the nesting body can be made of a conductive zirconia ceramic having a volume resistivity of 1 × 10 ⁹ Ω · cm or less, preferably 1 × 10 ⁴ Ω · cm or less. Such a configuration is referred to as a second configuration such as nesting for convenience. When the volume specific resistance value of the conductive zirconia ceramic exceeds 1 × 10 ⁹ Ω · cm, the zirconia ceramic becomes an insulator, so that it is difficult to directly form a metal layer on the surface of the nested body. The lower limit of the volume resistivity value of the conductive zirconia ceramics is preferably 1 × 10 ⁻⁴ Ω · cm.

In the second configuration such as nesting, in order to make the zirconia ceramics conductive, a conductivity imparting agent may be added to the zirconia ceramics. Examples of the conductivity imparting agent include at least one of Fe ₂ O ₃ , NiO, Co ₃ O ₄ , Cr ₂ O ₃ , TiO ₂ , and TiN. Alternatively, as the conductivity imparting agent, TiC, It is also possible to list at least one of carbides such as WC and TaC. The content of the conductivity imparting agent in the conductive zirconia ceramics is desirably 10% by weight or more. If it is less than 10% by weight, it may be difficult to make the volume resistivity value 1 × 10 ⁹ Ω · cm or less. On the other hand, if a large amount of the conductivity imparting agent is added, the volume resistivity value of the zirconia ceramics decreases, but the strength of the nested body that is the obtained sintered body is impaired. Therefore, it is desirable to make it 40% by weight or less.

In the second configuration such as nesting, the conductive zirconia ceramics may contain a sintering temperature inhibitor in a range of 3 wt% or less. When using Fe ₂ O ₃ , NiO, Co ₃ O ₄ , Cr ₂ O ₃ , TiO ₂ , or TiN as the conductivity imparting agent, oxidation of Ca, K, Na, Mg, Zn, Sc, etc. as the sintering temperature inhibitor When a carbide such as TiC, WC, or TaC is used as the conductivity-imparting agent, examples of the sintering temperature inhibitor include Al ₂ O ₃ and TiO ₂ . If these sintering temperature inhibitors are contained in the range of 3% by weight or less, the firing temperature can be lowered to suppress grain growth of the zirconia and the conductivity-imparting agent. Mechanical properties can be enhanced.

  In the first configuration such as nesting, if the active metal solder method is adopted for forming the active metal film, the active metal film can obtain high adhesion to the surface of the nesting body, The metal layer can obtain high adhesion. Furthermore, if an active metal film is provided in the first configuration such as nesting, the surface of the nesting body has conductivity, and the metal layer can be formed by, for example, electroplating. Alternatively, by defining the surface roughness of the surface of the nesting body facing the cavity, a metal layer can be formed on the nesting body based on the electroless plating method, and the metal layer is laid on the nesting body. The layer can obtain high adhesion. On the other hand, in the second configuration such as nesting, the metal layer can be directly formed on the surface of the nesting body by forming the nesting body from conductive zirconia ceramics. In addition, since the metal layer is provided on the outermost surface of the nest and the like, it becomes possible to easily form a convex portion or a concave portion on the metal layer on the surface of the nest body facing the cavity by various processing methods. High scratch resistance and surface hardness can be obtained. Moreover, if the fine crack which generate | occur | produced in the outer peripheral part of the nesting body at the time of processing of a nesting body is coat | covered with a metal layer, since the crack will not contact a molten thermoplastic resin, a nesting etc. are hard to be damaged.

  In order to prevent the fine cracks generated at the edge of the nesting body from coming into contact with the molten thermoplastic resin and damaging the nesting, etc. It is preferable not to concentrate. Alternatively, in some cases, it is preferable to provide a curvature surface with a radius of 0.3 mm or less or a C-plane cut to avoid stress concentration on the edge portion of the nested body.

  As a method of arranging a metal layer on the surface of the nesting body in nesting or the like, a method of placing a detachable metal layer (metal film) on the nesting body made of zirconia ceramics can be cited as an alternative. it can. Examples of a method for producing a detachable metal layer (metal film) include a method in which a mother mold having a concavo-convex portion using a photoresist on a glass surface is used and an electroforming method is used. When the metal layer (metal film) is detachably placed on the nesting body, the metal layer (metal film) is prevented from moving due to the flow of the molten thermoplastic resin injected into the cavity during molding. (Metal film) is preferably fixed to the nesting body by vacuum suction at the periphery of the nesting body, or is preferably pressed with another metal block together with the outer peripheral part of the nesting body. Instead, a metal layer (metal film) may be simply placed on the nested body.

  In some cases, the nesting body may be made of metal, and a zirconia ceramic layer may be formed on the nesting body made of metal. As a method for forming the zirconia ceramic layer, a thermal spraying method can also be exemplified. That is, it is a method of spraying the powder composed of the above-described zirconia composition at a high temperature against a metal nesting body using a spray gun, and there is arc spraying, plasma spraying, etc., but when spraying the zirconia composition, Since the melting point is high, a plasma spraying method capable of generating a high temperature is effective. The thickness of the zirconia ceramic layer is preferably 0.5 mm to 2 mm. If it is too thick, the zirconia ceramic layer may be broken by strain. In order to improve the adhesion between the metal nesting body and the zirconia ceramic layer, it is preferable to spray the zirconia composition after spraying a metal such as Ni-Cr. When arranging a metal layer on the surface of the obtained zirconia ceramic layer, the method mentioned above can be mentioned.

The light guide plate of the present invention or the light source plate constituting the planar light source device of the present invention is preferably manufactured (molded) by the method of manufacturing the light guide plate. However, depending on the specifications of the light guide plate, a thermoplastic resin may be used. An injection molding method generally used for molding can also be adopted. That is, the first mold part and the second mold part constituting the mold assembly are clamped, the molten thermoplastic resin is injected from the molten resin injection part into the cavity, and the transparent resin in the cavity is then injected. Can be cooled and solidified, and then the first mold part and the second mold part are opened, and the light guide plate is taken out from the mold assembly. Alternatively, the mold assembly is structured so that the volume of the cavity can be made variable, and the first mold part is set so that the volume (V _C ) of the cavity is larger than the volume (V _M ) of the light guide plate to be molded. And the second mold part are clamped, and a molten thermoplastic resin is injected into the cavity (volume: V _C ), before and simultaneously with the start of injection of the molten thermoplastic resin, during injection, or during injection After the completion, a method of reducing the volume of the cavity to the volume of the light guide plate to be molded (volume: V _M ) (injection compression molding method) may be used. The time when the volume of the cavity becomes the volume (V _M ) of the light guide plate to be molded can be during the injection of the molten thermoplastic resin or after the injection is completed (including the completion of the injection). As a structure of such a mold assembly, a structure in which an imprint structure is formed by the first mold part and the second mold part, or a movable core in the cavity that can change the volume of the cavity The structure which the type | mold assembly is further equipped can be mentioned. The movement of the core can be controlled by, for example, a hydraulic cylinder.

  Examples of the molten resin injection part include a side gate structure, a tab gate structure, and a film gate structure. The molten resin injection part only needs to open to the cavity in the cavity surface corresponding to any side surface of the light guide plate, and is opposed to the first side surface that is the light incident surface or the first side surface that is the light incident surface. The cavity surface corresponding to the third side surface may be opened to the cavity, and in some cases, the cavity surface may be opened to the cavity surface corresponding to the second side surface or the fourth side surface.

  In the light guide plate or the planar light source device of the present invention, the convex portion and / or the concave portion is provided on the surface portion of the first surface of the light guide plate, and the length between the first side surface and the third side surface. The length of the light guide plate in the longitudinal direction is 40 mm or more and 130 mm or less, and the thickness of the region occupying at least 80% of the light guide plate is 0.1 mm or more and 0.55 mm or less. Even when the thickness of the liquid crystal display device is further reduced, the light guide plate can be reliably incorporated into the liquid crystal display device. In addition, by defining the flatness of the light guide plate to be 200 μm or less, it is possible to surely avoid the occurrence of problems such as the appearance of the light guide plate being greatly swelled or the average luminance value and luminance uniformity value of the light guide plate being reduced. be able to.

In the light guide plate manufacturing method of the present invention, after t seconds have elapsed from the completion of the injection process of the molten thermoplastic resin into the cavity, or after the injection process of the molten thermoplastic resin into the cavity and the subsequent steps. After t seconds have elapsed from completion of the pressure-holding process (however, 0 seconds ≤ t ≤ 8.0 seconds), the mold clamping force is set to 0.5 F ₀ or less to occur when the thermoplastic resin in the cavity is cooled. Distortion, or distortion caused by shrinkage can be reduced, so that distortion inside the light guide plate is reduced, and the light guide plate is not twisted or swollen, and a light guide plate having high flatness can be formed. it can. In addition, the manufacturing method of the light-guide plate of this invention can be achieved by modifying the software which controls the action | operation of an injection molding apparatus.

  Hereinafter, the present invention will be described based on examples with reference to the drawings.

  Example 1 relates to a light guide plate and a planar light source device of the present invention. A schematic cross-sectional view of the light guide plate 40 and the planar light source device of Example 1 is shown in FIG. Moreover, the typical perspective view of the light-guide plate 40 of Example 1 is shown to (B) of FIG.

  The nominally 2.3 inch light guide plate 40 of the first embodiment is made of a transparent thermoplastic resin, and has a first surface 41, a second surface 43 facing the first surface 41, a first side surface 44, and a second side surface 45. , A third side face 46 facing the first side face 44, and a fourth side face 47 facing the second side face 45. An uneven portion 42 is provided on the surface portion of the first surface 41. The light guide plate 40 as a whole has a thin plate shape with a substantially constant thickness, and light is incident from the first side surface 44 of the light guide plate 40 and light is emitted from the first surface 41 and the second surface 43.

  In Example 1, the surface portion of the first surface 41 is provided with uneven portions 42 having a height of 10 μm and a pitch of 50 μm. The concavo-convex portion 42 provided on the surface portion of the first surface 41 is a direction (specifically, a direction that makes a predetermined angle with the light incident direction to the light guide plate 40 (may be indicated by a white arrow in the drawing). , A substantially straight concavo-convex shape extending along a substantially perpendicular direction). That is, the cross-sectional shape of the concavo-convex part 42 when the light guide plate 40 is cut in a virtual plane perpendicular to the first surface 41 in the light incident direction to the light guide plate 40 is a sawtooth shape (cross-sectional shape: triangle). In other words, in the light guide plate 40 of Example 1, there is no flat portion in the portion of the first surface 41 of the light guide plate 40 located between the uneven portion 42 and the uneven portion 42.

  In the backlight type planar light source device in the liquid crystal display device, the second surface 43 of the light guide plate 40 is connected to the liquid crystal display device 60 in the same manner as shown in the schematic sectional view of FIG. It arrange | positions so that it may oppose. The light emitted from the light source 50 and incident from the first side surface 44 of the light guide plate 40 is reflected by the first surface 41 and emitted from the second surface 43, and light transmitted through the first surface 41. It is divided into. The light transmitted through the first surface 41 is reflected by the reflecting member 51 disposed at a position facing the first surface 41, enters the light guide plate 40 again, and is emitted from the second surface 43. The light emitted from the second surface 43 is guided to the liquid crystal display device 60 disposed to face the second surface 43. One diffusion sheet 52 and one prism sheet 55 are arranged between the liquid crystal display device 60 and the second surface 43 of the light guide plate 40 to uniformly diffuse light. A convex portion (not shown) having a continuous convex shape provided on the surface of the prism sheet 55 extends along a direction substantially parallel to the light incident direction to the light guide plate 40.

  Further, in the front light type planar light source device in the liquid crystal display device, the second surface 43 of the light guide plate 40 faces the liquid crystal display device 60 in the same manner as shown in the conceptual diagram in FIG. Is arranged. Then, the light emitted from the light source 50 and incident from the first side surface 44 of the light guide plate 40 is reflected by the first surface 41 and emitted from the second surface 43. And the liquid crystal display device 60 arrange | positioned in the position facing the 2nd surface 43 is allowed to pass, it is reflected by the reflection member 54, and the liquid crystal display device 60 is allowed to pass through again. The light further passes through an antireflection layer (not shown) formed on the retardation film 53 and the second surface 43 of the light guide plate 40 and is emitted from the first surface 41 of the light guide plate 40 to be recognized as an image. Is done.

  In the first embodiment or the second to fifth embodiments described later, the cavity 18 and the third side surface 46 of the light guide plate 40 are formed as shown schematically in FIGS. A light guide plate is manufactured by using a mold assembly including a molten resin injection portion 19 (having a side gate structure) for injecting a molten thermoplastic resin into a cavity from a corresponding cavity surface. More specifically, the mold assembly includes a first mold part 10 (movable mold part) and a second mold part (fixed mold part) 13, and the first mold part. The cavity 18 is formed by clamping the 10 and the second mold part 13. 2B is a schematic end view along the flow direction of the molten thermoplastic resin injected into the cavity 18, and in FIG. 2B, the left-hand side of the cavity 18 is the light guide plate. 40 corresponds to a portion forming the third side surface 46, and the right-hand side of the cavity 18 corresponds to a portion forming the first side surface 44 of the light guide plate 40. On the other hand, FIG. 2A is a schematic end view along a direction perpendicular to the flow direction of the molten thermoplastic resin injected into the cavity 18, and in FIG. The left hand side corresponds to a portion that forms the fourth side surface 47 of the light guide plate 40, and the right hand side of the cavity 18 corresponds to a portion that forms the second side surface 45 of the light guide plate 40.

As shown in the conceptual diagram of FIG. 12, the injection molding apparatus includes an injection cylinder 200 having a screw 201 for supplying a molten thermoplastic resin, a fixed platen 210, a movable platen 211, a tie bar 212, and a mold clamping hydraulic cylinder. 213 and a hydraulic piston 214. The movable platen 211 can be translated on the tie bar 212 by the operation of the hydraulic piston 214 in the mold clamping hydraulic cylinder 213. The second mold part (fixed mold part) 13 is attached to the fixed platen 210, and the first mold part (movable mold part) 10 is attached to the movable platen 211. The first mold part (movable mold part) 10 is engaged with the second mold part (fixed mold part) 13 by the movement of the movable platen 211 in the direction of the arrow “A” in FIG. The mold part (fixed mold part) 13 and the first mold part (movable mold part) 10 are clamped with a clamping force F ₀ to form the cavity 18. The mold clamping force F ₀ is controlled by the mold clamping hydraulic cylinder 213. Further, for example, in the method of manufacturing the light guide plate of the present invention, the clamping force is reduced from F ₀ to F ₁ based on the control of the clamping cylinder 213, and further, in the direction of arrow “B” in FIG. The first mold part (movable mold part) 10 is engaged with the second mold part (fixed mold part) 13 by the movement of the first mold part (movable mold part) 10 to The first mold part (movable mold part) 10 and the second mold part (fixed mold part) 13 are opened.

  In the mold assembly according to the first embodiment, the nesting body 21 made of zirconia ceramics and the surface of the nesting body 21 facing the cavity 18 to form the uneven portion 42 on the first surface 41 of the light guide plate 40. A nest 20 made of a metal layer 22 is provided in the mold assembly. A schematic perspective view of the insert 20 is shown in FIG. Furthermore, a second insert 30 having the same structure as that of the insert 20 is disposed inside the mold assembly. Specifically, the second nesting 30 is used to form the nesting body 31 made of zirconia ceramics and the second surface 43 of the light guide plate 40 in order to form the second surface 43 of the light guide plate 40. The metal layer 32 is formed on the surface of the nesting body 31 facing the cavity 18 (provided that no convex and concave portions are provided). The insert 20 and the second insert 30 constitute a part of the cavity 18 provided in the mold assembly. The insert 20 is attached to the insert attachment member 11, and the insert attachment member 11 is fixed to the first mold part 10 by a bolt 16. On the other hand, the second nesting 30 is attached to the second nesting attachment member 14, and the second nesting attachment member 14 is fixed to the second mold part 13 by a bolt 17.

  As a specific method of attaching the insert 20 to the insert mounting member 11, the groove portion 23 is formed on two opposing side surfaces of the insert 20, and the groove portion is also formed on the portion of the insert mounting member 11 facing the groove portion 23. A method of disposing a locking member 12 made of a soft material such as copper, brass, or rubber in these grooves can be mentioned. The specific method of attaching the second insert 30 to the second insert attachment member 14 also includes forming a groove on two opposing side surfaces of the second insert 30, and a second insert attachment member facing the groove. It is possible to form a groove portion in the portion 14 and to dispose the locking member 15 made of a soft material such as copper, brass, or rubber in the groove portion. By adopting such an attachment method, it is possible to reliably prevent the edge portions of the insert 20 and the second insert 30 from being damaged.

The insert 20 is used to mold the first surface 41 of the light guide plate 40, and is partially stabilized zirconia ceramics (partially stabilized zirconium oxide, ZrO) containing yttria (Y ₂ O ₃ ) as a partial stabilizer. ₂ ) and a metal layer 22 formed on the surface of the nesting body 21 facing the cavity 18 in order to form the concavo-convex portion 42 of the light guide plate 40. The proportion of the partial stabilizer contained in the partially stabilized zirconia ceramics having the composition of ZrO ₂ —Y ₂ O ₃ was 3 mol%. The thermal conductivity of partially stabilized zirconia ceramics is about 3.8 J / (m · s · K). The depth d of the serrated (prism) -shaped concavo-convex portion provided on the metal layer 22 is 10 μm, the pitch P is 50 μm, and has a saw-tooth shape (cross-sectional shape: triangle). The concavo-convex portion provided on the metal layer 22 has a continuous linear concavo-convex shape extending along a direction (specifically, a substantially perpendicular direction) forming a predetermined angle with the light incident direction to the light guide plate. Furthermore, it has a shape complementary to the concavo-convex portion 42 formed on the first surface 41 of the light guide plate 40. The portion where the uneven portion is formed corresponds to the cavity surface 20 </ b> A of the insert 20. The surface roughness R _Z of the surface of the uneven portion provided on the metal layer 22 (more specifically, the surface of the entire uneven portion) is 0.2 μm or less (specifically, R _Z = 0.01 μm on average) ).

The metal layer 22 is composed of two layers of a Ni layer having a thickness of 5 μm formed by an electroplating method and a Ni compound layer having a thickness of 100 μm formed thereon (a Ni-P layer formed by electroless plating). Become. That is, the thickness t of the metal layer 22 is 105 μm. In the drawing, the metal layer 22 is represented by one layer. The surface roughness R _Z of the surface of the nesting body 21 facing the cavity 18 is 0.5 μm. Further, an active metal film (not shown) made of a Ti—Cu—Ag eutectic composition having a thickness of 10 μm is formed between the nesting body 21 and the metal layer 22. This active metal film is formed by an active metal solder method.

Specifically, the nesting body 21 was produced by press-molding a mixture of zirconia (ZrO ₂ ) powder and Y ₂ O ₃ powder and then firing. Thereafter, the surface of the nesting body 21 facing the cavity 18 was polished and finished with a diamond grindstone, and the surface roughness R _Z of the surface was set to 0.5 μm. Next, an active metal film was formed on the entire surface of the nesting body 21 based on the active metal solder method. Specifically, an active metal film was formed by applying a paste made of a Ti—Cu—Ag eutectic composition to the entire surface of the nesting body 21 and baking it at a high temperature of about 800 ° C. in a vacuum. Thereafter, a nickel layer was formed on the active metal film by electroplating, and a Ni-P layer was further formed thereon by electroless plating. Thereafter, the Ni—P layer was subjected to machining using a diamond tool in which sawtooth (prism) -shaped irregularities were formed, and irregularities were formed in the metal layer 22.

The second nesting 30 can also be manufactured by the same method as the nesting 20 except that the uneven portion is not formed on the metal layer 32. The surface roughness R _Z of the metal layer 32 is 0.01 μm.

  On the other hand, the first mold part (movable mold part) 10 and the second mold part (fixed mold part) 13 were produced from carbon steel S55C, and were subjected to cutting work to provide a nested mounting part. Then, the nesting 20 and the second nesting 30 were attached to the nesting attachment portion based on the method described above.

  The first mold part (movable mold part) 10 and the second mold part (fixed mold part) 13 thus fabricated were assembled to obtain a mold assembly of Example 1. After the completed mold assembly is attached to the molding apparatus, the mold assembly is heated to 130 ° C. using a mold temperature controller and then rapidly cooled to 40 ° C. No damage such as cracking occurred in 30. Further, the metal layers 22 and 32 were not damaged.

A TR100EH2 injection molding machine manufactured by Zodick Plastics Co., Ltd. was used as a molding apparatus. Moreover, injection molding was performed using an aromatic polycarbonate resin having a viscosity average molecular weight and a Q value shown in Table 1 as a transparent resin. Table 1 shows molding conditions such as resin temperature, mold temperature, and resin injection speed. Then, the first mold part 10 and the second mold part 13 are clamped to obtain the state shown in FIGS. 2A and 2B, and then measured and melted in the injection cylinder 200. The transparent molten thermoplastic resin was injected into the cavity 18 through the molten resin injection portion 19 (having a side gate structure). After a predetermined amount (amount that completely fills the cavity 18) of molten polycarbonate resin is injected into the cavity 18 through the molten resin injection portion 19, the polycarbonate resin in the cavity 18 is cooled and solidified, and after 30 seconds, the mold The mold of the assembly was opened, and the light guide plate 40 was taken out from the mold assembly. In Examples 1 to 4 or Comparative Examples 1 to 3, the light guide plate was manufactured based on a conventional injection molding method. That is, the mold clamping force was kept at the value F ₀ from the time of mold clamping of the first mold part 10 and the second mold part 13 to the mold opening. here,
F ₀ = 4.9 × 10 ⁵ (N)
(= 50 tons / f)
It was. The holding pressure and holding time were as follows.
Holding pressure = 70 × 10 ⁶ Pa
Holding time = 1.5 seconds

The length L _L in the longitudinal direction of the light guide plate 40, which is the length between the first side surface 44 and the third side surface 46 of the obtained light guide plate 40, the length L _S in the direction perpendicular to the longitudinal direction, and the average thickness Table 1 shows the thickness difference, flatness, (x, y) value, and luminance average value.

  In addition, the luminance measurement measured the luminance in nine places in the measurement range of diameter 10mm using Topcon BM5A. The measurement range with a diameter of 10 mm was set to nine locations, three at the portion of the light guide plate 40 corresponding to the vicinity of the molten resin injection portion, three at the central portion of the light guide plate, and three near the end of the light guide plate.

Furthermore, the surface roughness of the surface of the concavo-convex portion 42 provided on the surface portion of the first surface 41 (more specifically, the surface of the entire concavo-convex portion) is measured using a surface roughness / shape measuring instrument Foam Talysurf. When the thickness R _Z was measured, all of the uneven portions 42 (more specifically, the entire surface of the uneven portions) were R _Z 0.3 μm or less. Specifically, the first surface 41 located in the vicinity of the third side surface 45 has an R _Z of about 0.01 μm in the concavo-convex portion 42 provided on the surface portion of the first surface 41 located in the vicinity of the first side surface 44. R _Z of the concavo-convex portion 42 provided on the surface portion of the film was about 0.02 μm.

Aromatic polycarbonate resin having predetermined physical properties (viscosity average molecular weight and Q value) although the thickness of the cavity is as thin as 0.27 mm and the length L _L in the longitudinal direction of the light guide plate 40 is as long as 52 mm. And the mold 18 is molded under predetermined molding conditions (resin temperature, mold temperature, resin injection speed), so that the cavity 18 is completely filled with the thermoplastic resin, and the light guide plate 40 having a desired shape is molded. I was able to. Further, the average thickness, thickness difference, flatness, (x, y) value, and luminance average of the light guide plate were also within the desired ranges.

The second embodiment is a modification of the first embodiment. In Example 2, the same mold assembly, insert, etc. (with different dimensions) as in Example 1 were used. The difference between Example 2 and Example 1 is that
(1) A point in which an aromatic polycarbonate resin having a viscosity average molecular weight lower than that of the aromatic polycarbonate resin of Example 1 and a high Q value is used. (2) The resin temperature is increased by 10 ° C. to 340 ° C. (3) Resin injection speed is reduced by 300 mm · sec ⁻¹ to 1200 mm · sec ⁻¹ , and injection rate is different (4) The nominal dimension of the light guide plate 40 is 2.6 inches There are 4 points.

The length L _L in the longitudinal direction of the obtained light guide plate 40, the length L _S in the direction perpendicular to the longitudinal direction, the average thickness, the thickness difference, the flatness, the (x, y) value, the luminance average value, Table 1 shows.

In Example 2, although the thickness of the cavity is very thin as 0.27 mm and the length L _L in the longitudinal direction of the light guide plate 40 is as long as 58 mm, the predetermined physical properties (viscosity average molecular weight and Since the aromatic polycarbonate resin having a Q value) is used and molded under predetermined molding conditions (resin temperature, mold temperature, resin injection speed), the cavity 18 is completely filled with the thermoplastic resin, and the desired The light guide plate 40 having a shape could be formed. Further, the average thickness, thickness difference, flatness, (x, y) value, and luminance average of the light guide plate were also within the desired ranges.

The third embodiment is also a modification of the first embodiment. In Example 3, a mold assembly, a nesting, and the like (having different dimensions) having the same structure as in Example 1 were used. The difference between Example 3 and Example 1 is that
(1) A point in which an aromatic polycarbonate resin having a viscosity average molecular weight lower than that of the aromatic polycarbonate resin of Example 1 and a high Q value is used. (2) The resin temperature is increased by 10 ° C. to 340 ° C. (3) The point at which the resin injection speed is reduced by 1200 mm · sec ⁻¹ to 300 mm · sec ⁻¹ and the injection rate is different. (4) The nominal dimension of the light guide plate 40 is set to 3.0 inches. (5) The thickness of the cavity 18 is at five points of 0.37 mm.

The length L _L in the longitudinal direction of the obtained light guide plate 40, the length L _S in the direction perpendicular to the longitudinal direction, the average thickness, the thickness difference, the flatness, the (x, y) value, the luminance average value, Table 1 shows.

In Example 3, although the thickness of the cavity is very thin as 0.37 mm and the length L _L in the longitudinal direction of the light guide plate 40 is 64 mm, the predetermined physical properties (viscosity average molecular weight) And the Q value), the cavity 18 is completely filled with the thermoplastic resin and is desired because it is molded under predetermined molding conditions (resin temperature, mold temperature, resin injection speed). The light guide plate 40 having the following shape could be formed. Further, the average thickness, thickness difference, flatness, (x, y) value, and luminance average of the light guide plate were also within the desired ranges.

The fourth embodiment is also a modification of the first embodiment. In Example 4, a mold assembly and a molding apparatus having the same structure as Example 1 were used. The difference between Example 4 and Example 1 is that
(1) The point where the insert and the second insert are made of steel (2) The point where the resin temperature is increased by 20 ° C and 350 ° C (3) The resin injection speed is decreased by 800 mm · sec- ¹ There are four points, that is, 700 mm · second ⁻¹ and a difference in the emission rate. (4) The nominal dimension of the light guide plate 40 is 2.0 inches.

The length L _L in the longitudinal direction of the obtained light guide plate 40, the length L _S in the direction perpendicular to the longitudinal direction, the average thickness, the thickness difference, the flatness, the (x, y) value, the luminance average value, Table 1 shows.

  In Example 4, although the thickness of the cavity was as thin as 0.27 mm and the nesting and the second nesting were made of steel, predetermined physical properties (viscosity average molecular weight) And the Q value), the cavity 18 is completely filled with the thermoplastic resin and is desired because it is molded under predetermined molding conditions (resin temperature, mold temperature, resin injection speed). The light guide plate 40 having the following shape could be formed. Further, the average thickness, thickness difference, flatness, (x, y) value, and luminance average of the light guide plate were also within the desired ranges.

  For comparison, Comparative Examples 1 to 3 shown in Table 2 were performed.

Here, in Comparative Example 1, a mold assembly and a molding apparatus having the same structure as Example 1 were used. The difference between Comparative Example 1 and Example 1 is that
(1) Points where the nest and the second nest are made of steel (2) Points where the viscosity average molecular weight is higher than that of the aromatic polycarbonate resin of Example 1 and a low Q value is used (3) Resin The temperature is raised by 20 ° C. and is at 3 points of 350 ° C.

In Comparative Example 2, a mold assembly and a molding apparatus having the same structure as in Example 1 were used. The difference between Comparative Example 2 and Example 1 is that
(1) Points where the nest and the second nest are made of steel (2) Points where the viscosity average molecular weight is higher than that of the aromatic polycarbonate resin of Example 1 and a low Q value is used (3) Resin (4) Resin injection speed is reduced by 300 mm · sec ⁻¹ to 1200 mm · sec ⁻¹ , and injection rate is different. In the point.

Furthermore, also in Comparative Example 3, a mold assembly and a molding apparatus having the same structure as Example 1 were used. The difference between Comparative Example 3 and Example 1 is that
(1) The use of an aromatic polycarbonate resin having a viscosity average molecular weight higher than that of the aromatic polycarbonate resin of Example 1 and a low Q value (2) The resin temperature was raised by 20 ° C. to 350 ° C. (3) The resin injection speed is reduced to 800 mm · second ⁻¹ to 700 mm · second ⁻¹ , and the injection rate is different.

The length L _L of the light guide plate obtained in Comparative Examples 1 to 3 in the longitudinal direction, the length L _S in the direction perpendicular to the longitudinal direction, the average thickness, the thickness difference, the flatness, (x, y) Table 2 shows values and luminance average values.

  In Comparative Example 1, the Q value of the thermoplastic resin is low (that is, the viscosity of the molten thermoplastic resin is high), and in the combination of the steel insert and the second insert, the cavity is made of the molten thermoplastic resin. Could not be filled.

  On the other hand, in Comparative Example 2, although the Q value of the thermoplastic resin is low (that is, the viscosity of the molten thermoplastic resin is high), the resin temperature is set to 370 ° C. Could be filled with. However, the flatness value of the obtained light guide plate was poor, and the luminance average value was also low.

  Further, in Comparative Example 3, although the thermoplastic resin has a low Q value (that is, the viscosity of the molten thermoplastic resin is high), the nesting and the second nesting are partially stabilized zirconia as in Example 1. Since it was made from ceramics, the cavity could be filled with molten thermoplastic resin even when the resin temperature was 350 ° C. However, the flatness value of the obtained light guide plate was poor.

Example 5 relates to a method of manufacturing the light guide plate of the present invention. In Example 5, the same injection molding machine as in Example 1 was used. Further, injection molding was performed using an aromatic polycarbonate resin having a viscosity average molecular weight and a Q value shown in Table 3 as a transparent resin. Also, the molding conditions such as the resin temperature, mold temperature, resin injection speed, mold clamping force F ₀ , mold clamping force F ₁ , and time t in Example 5 are as shown in Table 3. Furthermore, the length L _L in the longitudinal direction of the light guide plate 40, which is the length between the first side surface 44 and the third side surface 46 of the obtained light guide plate 40, and the length L _S in the direction perpendicular to the longitudinal direction. Table 3 shows the average thickness, thickness difference, flatness, (x, y) value, and luminance average value.

In the fifth embodiment, the second mold part (fixed mold part) 13 and the first mold part (movable mold part) 10 are clamped with a mold clamping force F ₀ . 2 (A) and (B), the molten thermoplastic resin that has been weighed, plasticized, and melted in the injection cylinder 200 is used as a sprue 215 and a molten resin injection portion 19 (having a side gate structure). ) To the cavity 18. A predetermined amount (amount that completely fills the cavity 18) of the molten thermoplastic resin is injected into the cavity 18 through the molten resin injection portion 19, and t seconds from the completion of the injection process of the molten thermoplastic resin into the cavity 18 Or after a lapse of t seconds from the completion of the injection process of the molten thermoplastic resin into the cavity 18 and the subsequent pressure holding process, the mold clamping force is set to 0.5 F ₀ or less, After the thermoplastic resin was cooled and solidified, the second mold part (fixed mold part) 13 and the first mold part (movable mold part) 10 were opened, and the light guide plate was taken out.

  From Table 3, it can be seen that by adopting the light guide plate manufacturing method of Example 5, a more excellent value can be obtained as the flatness value of the light guide plate.

  As mentioned above, although this invention was demonstrated based on the preferable Example, this invention is not limited to these. The structure of the mold assembly, the transparent thermoplastic resin used, the injection molding conditions, the structure of the nesting and the second nesting, the structure, the structure of the light guide plate, and the structure are examples and can be appropriately changed. .

  The results of various tests using aromatic polycarbonate resin are shown in FIG. In FIG. 11, the “thickness” value (unit: mm) on the horizontal axis means the thickness of the light guide plate, and the “flow length” value (unit: mm) on the vertical axis indicates the first side surface and the first side. It means the length in the longitudinal direction of the light guide plate, which is the length between the three side surfaces. In addition, "high speed molding machine (heat insulation)", "high speed molding machine (steel)", "general molding machine (heat insulation)", "general molding machine (steel)", "high temperature molding", "general temperature molding" The meanings of “material” and “general material” are as described below.

"High-speed molding machine (heat insulation)"
... Using the same insert as described in Example 1 and molding with a resin injection speed of 2000 mm · sec- ¹ .
"High-speed molding machine (steel)"
... Using inserts made from steel and molding with a resin injection speed of 2000 mm · sec- ¹ .
"General molding machine (heat insulation)"
... Using the same insert as described in Example 1, and molding with a resin injection speed of 100 mm · sec- ¹ .
"General molding machine (steel)"
... Using inserts made from steel and molding with a resin injection speed of 100mm · sec- ¹ .
"High temperature molding"
... Molding at resin temperature 350 ° C and mold temperature 120 ° C.
"General temperature forming"
... Molding at resin temperature 290 ° C and mold temperature 80 ° C.
"material"
... Aromatic polycarbonate resin having a viscosity average molecular weight of 1.2 × 10 ⁴ and a Q value of 1.20.
"General Materials"
... Aromatic polycarbonate resin having a viscosity average molecular weight of 1.6 × 10 ⁴ and a Q value of 0.36.

  From FIG. 11, it is possible to form a light guide plate having a longer length in the longitudinal direction by using a nesting made of zirconia ceramics, and in the longitudinal direction by using a thermoplastic resin having a high Q value. It can be seen that a light guide plate having a longer length can be formed, and a light guide plate having a longer length in the longitudinal direction can be formed even by high temperature molding.

  Alternatively, the insert 20 can be made by the method described below. The second nesting 30 can also be produced by a similar method.

First, the insert body 21 is obtained by press-molding partially stabilized zirconia and then firing it. Thereafter, a blasting process using alumina particles is performed on the surface of the nesting body 21 facing the cavity 18 to set the surface roughness R _Z of the surface to 2 μm. Next, a 2 μm thick Ni—P layer is formed on the surface of the nesting body 21 by electroless plating, and then a 5 μm thick Ni layer is formed thereon by electroplating. A Ni—P layer having a thickness of 100 μm is formed thereon by electroless plating. Thereafter, the Ni—P layer is subjected to machining using a diamond tool in which sawtooth (prism) -shaped uneven portions are formed, and the uneven portions are formed in the metal layer 22.

Alternatively, the nesting body 21 can be composed of partially stabilized conductive zirconia ceramics. A metal layer 22 is formed on the surface of the nesting body 21 facing the cavity. That is, the nesting body 21 is specifically made of partially stabilized zirconia (ZrO ₂ —Y ₂ O ₃ ) ceramics and contains 8% by weight of Fe ₂ O ₃ as a conductivity imparting agent. Further, the proportion of Y ₂ O ₃ which is a partial stabilizer contained in the partially stabilized zirconia ceramic is 3 mol%. Such a conductive zirconia ceramic has a thermal conductivity of about 3.8 J / (m · s · K) and a volume resistivity of 1 × 10 ⁸ Ω · cm. The metal layer 22 is made of chromium (Cr). A metal layer 22 is formed on the entire surface of the nesting body 21 by electroplating.

  4 (A) to (E), FIG. 5 (A) to (B), FIG. 6 (A) to (B), FIG. 7 (A) to (D), and FIG. 8 (A). Various modifications of the light guide plate are shown in FIGS.

  The light guide plate 40A to light guide plate 40E and the light guide plate 140A to light guide plate 140D shown in schematic sectional views in FIGS. 4A to 4E and 7A to 7D are wedge-shaped as a whole. It has a truncated quadrangular pyramid shape, and two opposing side faces of the truncated quadrangular pyramid correspond to the first surface 41, 141 and the second surface 43, 143 of the light guide plate, and the bottom surface of the truncated quadrangular pyramid is guided. Corresponds to the first side surface 44, 144 (thick end) of the light plate, the top surface of the truncated quadrangular pyramid corresponds to the third side surface 46, 146 of the light guide plate, and the remaining two opposing sides of the truncated quadrangular pyramid The side surfaces to correspond correspond to the second side surfaces 45 and 145 and the fourth side surfaces 47 and 147 of the light guide plate. Then, light enters from the first side surfaces 44 and 144 of the light guide plate, and light exits from the first surfaces 41 and 141 and / or the second surfaces 43 and 143. The thickness of the first side surfaces (light incident surfaces) 44 and 144 corresponding to the bottom surface of the truncated quadrangular pyramid is, for example, 0.5 mm, and the thickness of the third side surfaces 46 and 146 corresponding to the top surface of the truncated quadrangular pyramid. For example, 0.2 mm. The width of the light guide plate is set to 42 mm, for example, and the length is set to 58 mm, for example. Here, the width of the light guide plate means the length of the light guide plate in the direction perpendicular to the paper surface of FIGS. 4 and 7, and the length of the light guide plate is the guide in the left-right direction parallel to the paper surface of FIGS. It means the length of the light plate.

  In the light guide plate 40A shown in the schematic cross-sectional view of FIG. 4A, the uneven portion 42A provided on the surface portion of the first surface 41 forms a predetermined angle with the light incident direction to the light guide plate 40A. The light guide plate has a continuous linear concavo-convex shape extending along a direction (specifically, a substantially right angle direction), and is a light incident direction to the light guide plate 40A and a virtual plane perpendicular to the first surface 41 The cross-sectional shape of the continuous uneven shape when cutting 40A is a sawtooth shape (cross-sectional shape: triangle). Note that the reference numerals in the figure that are the same as those shown in FIG. 1A mean the same components.

  4B shows a schematic cross-sectional view, and in the light guide plate 40B shown in FIG. 5A a schematic perspective view, the convex portion 42B provided on the surface portion of the first surface 41 is The light incident direction to the light guide plate 40B has a continuous linear convex shape extending along a direction (specifically, substantially perpendicular direction) forming a predetermined angle with the light incident direction to the light guide plate 40B. However, the continuous convex cross-sectional shape when the light guide plate 40B is cut in a virtual plane perpendicular to the first surface 41 is a trapezoid.

  4C shows a schematic cross-sectional view, and in the light guide plate 40C shown in FIG. 5B a schematic perspective view, a convex portion provided on the surface portion of the first surface 41 42C has a discontinuous convex shape arranged on a virtual straight line along a direction (specifically, a substantially perpendicular direction) forming a predetermined angle with the light incident direction to the light guide plate 40C. The continuous convex shape is a pyramid or pyramid.

  Further, in FIG. 4D, a schematic cross-sectional view is shown, and in the light guide plate 40D whose schematic perspective view is shown in FIG. 6A, a convex portion provided on the surface portion of the first surface. 42D has a discontinuous convex shape arranged on an imaginary straight line along a direction (specifically, a substantially perpendicular direction) forming a predetermined angle with the light incident direction to the light guide plate. The convex shape of is substantially a hemisphere.

  4E shows a schematic cross-sectional view, and in the light guide plate 40E shown in FIG. 6B a schematic perspective view, a convex portion 42E provided on the surface portion of the first surface. Has a discontinuous convex shape arranged on an imaginary straight line along a direction (specifically, a substantially perpendicular direction) forming a predetermined angle with the light incident direction to the light guide plate. The convex shape is a cylinder.

  7A shows a schematic cross-sectional view, and in the light guide plate 140A shown in FIG. 8A with a schematic perspective view, the concave portion 142A provided on the surface portion of the first surface 41 is Light incident on the light guide plate 140A having a continuous linear concave shape arranged along a direction (specifically, a substantially perpendicular direction) forming a predetermined angle with the light incident direction on the light guide plate 140A The continuous concave shape when the light guide plate 140A is cut in a virtual plane perpendicular to the first surface 141 in the direction is a trapezoid.

  7B shows a schematic cross-sectional view, and in the light guide plate 140B shown in FIG. 8B a schematic perspective view, a concave portion 142B provided on the surface portion of the first surface 41. Has a continuous linear concave shape arranged along a direction (specifically, a substantially perpendicular direction) forming a predetermined angle with the light incident direction to the light guide plate 140B. The continuous concave shape when the light guide plate 140A is cut in a virtual plane perpendicular to the first surface 141 in the light incident direction is a triangle.

  Furthermore, in the light guide plate 140C shown in a schematic cross-sectional view in FIG. 7C, the concave portion 142C provided on the surface portion of the first surface 141 has a predetermined angle with the light incident direction to the light guide plate 140C. , And a discontinuous concave shape arranged on a virtual straight line along a direction (specifically, a substantially perpendicular direction), and the discontinuous concave shape is a substantially hemisphere.

  Further, in the light guide plate 140D shown in the schematic cross-sectional view of FIG. 7D, the concave portion 142D provided in the surface portion of the first surface 141 has a predetermined angle with the light incident direction to the light guide plate 140D. It has a discontinuous concave shape arranged on an imaginary straight line along a formed direction (specifically, a substantially perpendicular direction), and the discontinuous concave shape is a cylinder.

The fixing method described in the first embodiment as a fixing method of the nesting 20 and the second nesting 30 to the first mold part 10 (movable mold part) and the second mold part (fixed mold part) 13. In addition, for example, a method described below can be cited. 9A shows a state in which the mold assembly is clamped, and FIG. 10A shows a state in which the mold assembly is opened. ) And FIG. 10 (A), a mold assembly showing a schematic cross-sectional view,
(A) A transparent resin light guide plate that includes a first mold part (movable mold part) 110 and a second mold part (fixed mold part) 113, and in which a cavity 118 is formed when the mold is clamped. A mold assembly for molding,
(B) a side gate type molten resin injection portion (not shown) for introducing a molten transparent resin into the cavity 118;
(C) a nest 120 disposed in the first mold part 110 and constituting a part of the cavity 118;
(D) a second nest 130 disposed in the second mold part 113 and constituting a part of the cavity 118;
It has.

  The mold assembly is further provided with a covering plate 111 that is attached to the first mold part 110 by a bolt 116 and forms a part of the cavity 118 and covers the end face of the insert 120. The covering plate 111 covers the end surface of the entire circumference of the insert 120. Furthermore, a second covering plate 114 which is attached to the second mold part 113 by a bolt 117 and constitutes a part of the cavity 118 and covers the end face of the second insert 130 is further provided. The second covering plate 114 covers the end surface of the entire circumference of the second insert 130. The covering plate 111 and the second covering plate 114 are provided with a molten resin injection portion (not shown).

FIG. 10B is a schematic enlarged cross-sectional view, and FIG. 9B is a schematic enlarged partial cross-sectional view showing a nesting 120 (thickness 3.0 mm) of the light guide plate. Nested body 121 made of partially stabilized zirconia ceramics (partially stabilized zirconium oxide, ZrO ₂ ) used to mold the first surface and containing yttria (Y ₂ O ₃ ) as a partial stabilizer; In order to form the first surface of the light guide plate, it is composed of a metal layer 122 provided on the surface of the nesting body 121 facing the cavity 118 and provided with an uneven portion 123 having a sawtooth (prism) shape. A schematic sectional view of the nesting body 121 is shown in FIG. The concavo-convex portion 123 provided in the metal layer 122 has a continuous concave shape extending along a direction (specifically, a substantially perpendicular direction) that forms a predetermined angle with the light incident direction to the light guide plate. Has a shape complementary to the concavo-convex portion formed on the first surface 41 of the light guide plate 40. The portion where the uneven portion 123 is formed corresponds to the cavity surface 120 </ b> A of the insert 120.

The metal layer 122 is composed of two layers, a Ni layer having a thickness of 5 μm formed by electroplating and a Ni compound layer (Ni-P layer formed by electroless plating) having a thickness of 100 μm formed thereon. . That is, the thickness t of the metal layer 122 is 105 μm. In the drawing, the metal layer 122 is represented by one layer. The surface roughness R _Z of the surface of the nested body 121 facing the cavity 118 is 0.5 μm. Further, an active metal film 124 made of a Ti—Cu—Ag eutectic composition having a thickness of 10 μm is formed between the nested body 121 and the metal layer 122. The active metal film 124 is formed by an active metal solder method.

  On the surface of the portion of the nesting body 121 that faces the coating plate 111 in a state where the first mold part 110 and the second mold part 113 are clamped, a metal layer 122B (FIG. B)) is formed. The metal layer 122B is formed at the same time as the metal layer 122, and an active metal film 124 is formed under the metal layer 122B.

Specifically, the nesting body 121 was produced by press-molding a mixture of zirconia (ZrO ₂ ) powder and Y ₂ O ₃ powder and then firing (see the schematic cross-sectional view of FIG. 9C). ). Thereafter, polishing and finishing using a diamond grindstone is performed on the surface of the nesting body 121 facing the cavity 118 (referred to as the surface 121A) and the surface of the nesting body 121 facing the coating plate 111 (referred to as the surface 121B). The surface roughness R _Z of the surfaces 121A and 121B was 0.5 μm. Next, an active metal film 124 was formed on the surfaces 121A and 121B of the nesting body 121 based on the active metal solder method. Specifically, the active metal film 124 is formed by applying a paste made of a Ti—Cu—Ag eutectic composition to the surfaces 121A and 121B of the nesting body 121 and baking it at a high temperature of about 800 ° C. in a vacuum. Formed. Thereafter, the portion of the nested body 121 other than the portion where the active metal film 124 is formed is masked, a nickel layer is formed by electroplating, and a Ni-P layer is further formed thereon by electroless plating. Formed. Thereafter, the Ni—P layer was subjected to machining using a diamond tool in which sawtooth (prism) shaped irregularities were formed, and irregularities 123 were formed in the metal layer 122.

Except for the point that the surface (cavity surface) is flat, the second nest 130 has substantially the same configuration and structure as the nest 120. The surface roughness R _Z of the metal layer 132 is 0.01 μm.

  The 1st metal mold part (movable metal mold part) 110 was produced from carbon steel S55C, the cutting process was performed, and the nest | attachment mounting part was provided. The metal layer 122B formed on the surface 121B was cut using a plane cutting machine for metal processing. Then, the insert 120 was attached to the insert mounting portion, the end surface of the insert 120 was covered with the covering plate 111, and the covering plate 111 was fixed to the first mold part 110 with the bolt 116.

  Moreover, the 2nd metal mold | die part (fixed metal mold | die part) 113 was produced from carbon steel S55C, the cutting process was performed, and the insertion mounting part was provided. Then, the second insert 130 is attached to the insert mounting portion, the end surface of the second insert 130 is covered with the second covering plate 114, and the second covering plate 114 is covered with the second mold portion 113 with the bolt 117. Fixed to.

  By using the mold assembly thus obtained, the light guide plate can be injection-molded by the same method as described in the first to fifth embodiments.

1A is a schematic cross-sectional view of a light guide plate and a planar light source device. FIGS. 1B and 1C are conceptual diagrams of a conventional backlight type planar light source device. FIG. 3 is a conceptual diagram of a front light type planar light source device. FIG. 2A is a schematic end view of the mold assembly along a direction perpendicular to the flow direction of the molten thermoplastic resin injected into the cavity, and FIG. It is a typical end view of the mold assembly along the flow direction of the molten thermoplastic resin injected into the inside. 3A is a schematic perspective view of the nesting, and FIG. 3B is a schematic perspective view of the light guide plate in the first embodiment. 4A to 4E are schematic cross-sectional views of modifications of the light guide plate. 5A and 5B are schematic perspective views of modifications of the light guide plate shown in FIGS. 4B and 4C, respectively. 6A and 6B are schematic perspective views of modifications of the light guide plate shown in FIGS. 4D and 4E, respectively. FIGS. 7A to 7D are schematic cross-sectional views of other modified examples of the light guide plate. FIGS. 8A and 8B are schematic perspective views of modifications of the light guide plate shown in FIGS. 7A and 7B, respectively. Each of (A), (B), and (C) of FIG. 9 is a schematic cross-sectional view showing a clamped state of a modified example of the mold assembly, and a schematic partial cross-sectional view of the modified example of the insert. FIG. 5 is a schematic cross-sectional view of a modified example of the nesting body. Each of (A) and (B) of FIG. 10 is a schematic cross-sectional view showing a mold opened state of the modified example of the mold assembly shown in FIG. 9 and a schematic enlarged view of the modified example of the insert. FIG. FIG. 11 is a graph showing the relationship between the thickness of the obtained light guide plate and the length of the light guide plate in the longitudinal direction by performing various tests using the same aromatic polycarbonate resin as in Example 3. FIG. 12 is a conceptual diagram of an injection molding apparatus suitable for carrying out the first to fifth embodiments.

Explanation of symbols

10, 110 ... first mold part (movable mold part), 11 ... nest mounting member, 12, 15 ... locking member, 13, 113 ... second mold part ( Fixed mold part), 14 ... second insert mounting member, 16, 17, 116, 117 ... bolt, 18, 118 ... cavity, 19 ... molten resin injection part, 111 ... Cover plate 114 ... Second cover plate 20, 120 ... Nest, 20A, 120A ... Cavity surface of the nest, 21, 121 ... Nest body, 22, 122 ... Metal layer, 23, 123 ... groove, 30, 130 ... second nesting, 40, 40A, 40B, 40C, 40D, 40E, 140A, 140B, 140C, 140D ... light guide plate, 41, 141 ... First surface, 42, 42A, 42B, 42 , 42D, 42E, 142A, 142B, 142C, 142D... Concavo-convex part, convex part or concave part, 43, 143 ... second surface, 44, 144 ... first side surface, 45, 145 ... first 2 side surfaces, 46, 146 ... 3rd side surface, 47, 147 ... 4th side surface, 50 ... light source, 51 ... reflection member, 52 ... diffusion sheet, 53 ... retardation film , 54... Reflective member, 55... Prism sheet, 60... Liquid crystal display device, 200... Injection cylinder, 201 ... screw, 210 .. fixed platen, 211. ... Tie bar, 213 ... Hydraulic cylinder for clamping, 214 ... Hydraulic piston

Claims (11)

Made of transparent thermoplastic resin, first surface, second surface facing the first surface, first side surface, second side surface, third side surface facing the first side surface, and facing the second side surface A light guide plate having a fourth side surface,
The surface portion of the first surface is provided with a convex portion and / or a concave portion,
The length in the longitudinal direction of the light guide plate, which is the length between the first side surface and the third side surface, is 40 mm or more and 130 mm or less,
The thickness of the region occupying at least 80% of the light guide plate is 0.1 mm or more and 0.55 mm or less,
A light guide plate having a flatness of 200 μm or less. Using a mold having a molten resin injection portion for injecting a molten thermoplastic resin into the cavity from the cavity and the cavity surface corresponding to any side surface of the light guide plate,
The light guide plate according to claim 1, wherein the light guide plate is formed by injecting a transparent molten thermoplastic resin into a cavity through a molten resin injection portion.   A nesting body made of zirconia ceramics or conductive zirconia ceramics, and in order to form a convex part and / or a concave part on the first surface of the light guide plate, are arranged on the surface of the nesting body facing the cavity, 3. The light guide plate according to claim 2, wherein a nesting made of a metal layer provided with a convex portion is disposed inside the mold. Light is incident from the first side surface of the light guide plate,
The light guide plate according to claim 2 or 3, wherein molten thermoplastic resin is injected into the cavity from a cavity surface corresponding to the third side surface of the light guide plate. 5. The light guide plate according to claim 1, wherein the thermoplastic resin has a Q value of 0.5 cm ³ · sec ⁻¹ or more. The thermoplastic resin according to any one of claims 1 to 5, wherein the thermoplastic resin is an aromatic polycarbonate resin having a viscosity average molecular weight of 1.0 x 10 ^{4 to} 1.5 x 10 ^4. Light board.   The value of (x, y) in the xy chromaticity diagram of the light guide plate in the CIE 1931 XYZ color system satisfies x ≦ 0.375 and y ≦ 0.335. The light guide plate according to any one of claims 6 to 6. The light guide plate as a whole has a thin plate shape with a substantially constant thickness,
8. The light guide plate according to claim 1, wherein light is incident from the first side surface of the light guide plate and light is emitted from the first surface and / or the second surface. 9. Overall, it has a wedge-shaped truncated quadrangular pyramid shape,
Two opposing side faces of the truncated quadrangular pyramid correspond to the first and second faces of the light guide plate, the bottom face of the truncated quadrangular pyramid corresponds to the first side face of the light guiding plate, and the top face of the truncated quadrangular pyramid is Corresponds to the third side surface of the light guide plate, the remaining two opposing side surfaces of the truncated quadrangular pyramid correspond to the second side surface and the fourth side surface of the light guide plate,
8. The light guide plate according to claim 1, wherein light is incident from the first side surface of the light guide plate and light is emitted from the first surface and / or the second surface. 9. A planar light source device comprising a light guide plate and a light source,
The light guide plate is
Made of transparent thermoplastic resin,
A first surface, a second surface facing the first surface, a first side surface, a second side surface, a third side surface facing the first side surface, and a fourth side surface facing the second side surface;
The surface portion of the first surface is provided with a convex portion and / or a concave portion,
The length in the longitudinal direction of the light guide plate, which is the length between the first side surface and the third side surface, is 40 mm or more and 130 mm or less,
The thickness of the region occupying at least 80% of the light guide plate is 0.1 mm or more and 0.55 mm or less,
The flatness is 200 μm or less,
A planar light source device, wherein light is incident from a first side surface of a light guide plate and light is emitted from a first surface and / or a second surface. Made of transparent thermoplastic resin, first surface, second surface facing the first surface, first side surface, second side surface, third side surface facing the first side surface, and facing the second side surface The fourth side
The surface portion of the first surface is provided with a convex portion and / or a concave portion,
The length in the longitudinal direction of the light guide plate, which is the length between the first side surface and the third side surface, is 40 mm or more and 130 mm or less,
The thickness of the region occupying at least 80% of the light guide plate is 0.1 mm or more and 0.55 mm or less,
A method of manufacturing a light guide plate having a flatness of 200 μm or less,
A cavity and a molten resin injection part for injecting a molten thermoplastic resin into the cavity from a part corresponding to any side surface of the light guide plate are provided. From the first mold part and the second mold part, Using the configured mold assembly,
(A) After the first mold part and the second mold part are clamped with a clamping force F ₀ to form a cavity,
(B) Injecting a transparent molten thermoplastic resin from the molten resin injection portion into the cavity,
(C) t seconds after the completion of the injection process of the molten thermoplastic resin into the cavity or after the completion of the injection process of the molten thermoplastic resin into the cavity and the subsequent pressure holding process (However, 0 seconds ≦ t ≦ 8.0 seconds), the mold clamping force is 0.5F ₀ or less,
(D) After the thermoplastic resin in the cavity is cooled and solidified, the first mold part and the second mold part are opened, and the light guide plate is taken out.
A method of manufacturing a light guide plate comprising the steps.

Images