JP2012113097A - Light-diffusing plate, surface light source device, liquid crystal display device and method for manufacturing surface pattern transfer resin sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light-diffusing plate capable of suppressing illumination unevenness regardless of viewing angles while maintaining good light-transmitting property, and to provide a surface light source device and a liquid crystal display device having the plate.SOLUTION: A light-diffusing plate 9 comprises a light-transmitting resin having a back face 18 where a fine concavo-convex pattern 19 is formed and a front face 15 where a plurality of linear projection lines 16 having a semi-circular cross section are formed parallel to one another. The plate has an internal haze of 0 to 60% and external haze of 71 to 99% based on the fine concavo-convex pattern 19.

Description

  The present invention relates to a light diffusing plate, a surface light source device provided with the light diffusing plate, a liquid crystal display device, and a surface shape transfer resin sheet capable of producing a light diffusing plate.

Conventionally, as an irradiation method of a liquid crystal display device, for example, a “direct type” in which a plurality of cold cathode tubes are irradiated from directly under a liquid crystal panel is known.
In the direct type liquid crystal display device, since the cold cathode tube as a light source is arranged directly under the liquid crystal panel, an image of the light source (lamp unevenness) may be seen through the screen. Therefore, in order to eliminate lamp unevenness, a light diffusion plate is installed between the liquid crystal panel and the light source.

  As such a light diffusion plate, for example, a diffusion plate manufactured by extruding a mixed resin of acrylic resin and silicone fine particles and having a haze of 92% has been proposed (for example, see Patent Document 1).

JP 2007-102066 A

However, the unevenness of the lamp unevenness changes with a change in the viewing angle (viewing position) of the liquid crystal display device. Therefore, even if the lamp unevenness is not visible when the liquid crystal display device is viewed from the front, the lamp unevenness may be visible when the liquid crystal display device is viewed obliquely.
Therefore, it is conceivable to eliminate lamp unevenness by increasing the thickness of the light diffusion plate regardless of the angle at which the liquid crystal display device is viewed. However, if the light diffusing plate is thick, the light transmissive property of the light diffusing plate may be reduced.

An object of the present invention is to provide a light diffusing plate, a surface light source device, and a liquid crystal display device in which illumination unevenness (lamp unevenness) is suppressed regardless of the viewing angle while maintaining good translucency.
Another object of the present invention is to produce a surface shape transfer resin sheet capable of producing a light diffusing plate in which illumination unevenness (lamp unevenness) is suppressed regardless of the viewing angle while maintaining good translucency. Is to provide a method.

In order to achieve the above object, the light diffusing plate of the present invention is opposite to the first surface on which fine irregularities are formed and the first surface on which a plurality of linear protrusions are formed in parallel to each other. A light diffusing plate made of a translucent resin having a second surface on the side, wherein the light diffusing plate has an internal haze of 0 to 60% and an external haze of 71 to 99% based on the fine irregularities. It is characterized by that.
The light diffusing plate of the present invention includes a light control plate that emits light incident from the first surface from the second surface, and the ridge is cut along a width direction orthogonal to the longitudinal direction. In the orthogonal cross section appearing in Fig. 2, the axis passing through both ends of the bottom of the ridge is the X axis, the axis passing through the middle of both ends is the Z axis, and the length between the both ends is W when is _a, the shape of the orthogonal section of the ridges, in a condition satisfying _{-0.475 × W a ≦ x ≦ 0.475} × W a, a function satisfying the following formula (1) Z (x) It is preferred that

However, in the above formula (1), Z ₀ (x) satisfies the following formula (2).

(In the formula (2), C ₂ = 0.762469824257553, C ₄ = 0.298075662622927, C ₆ = −0.5596293831533661, C ₈ = 0.8964682802533265, C ₁₀ = −0.656716416621371515, C ₁₂ = −0. _{615726418495985, C 14 = 1.245151353938560, C} 16 = -0.520559083769482)
Further, the surface light source device of the present invention is disposed in the lamp box so as to be opposed to the resin lamp box formed in a box shape whose front side is open and the open surface of the lamp box. The plurality of light sources arranged and the light that closes the open surface by being in contact with an edge frame portion of the lamp box that is arranged so that the first surface faces the light source and forms an outline of the open surface And a diffusion plate.

The liquid crystal display device according to the present invention includes the surface light source device and a liquid crystal panel disposed on the front side of the surface light source device.
Furthermore, in the method for producing a surface shape transfer resin sheet of the present invention, the first surface and the second surface opposite to the first surface are formed by continuously extruding the translucent resin from the die in a heated and melted state. A sheet manufacturing process for manufacturing the continuous resin sheet, a first pressing process for sandwiching the continuous resin sheet between the first roll and the second roll, and the continuous resin sheet being conveyed while being in close contact with the second roll. A second pressing step of sandwiching the conveyed continuous resin sheet between the second roll and the third roll, and an arithmetic average roughness Ra = 20 μm on the peripheral surface of the second roll. A mat transfer mold having fine irregularities of 30 μm and 10-point average roughness Rz = 100 μm to 150 μm is formed, and in the first pressing step, the mat transfer mold is the first surface of the continuous resin sheet. An intaglio transfer mold having a plurality of concave strips that are transferred and linearly extend along the circumferential direction of the third roll is formed on the circumferential surface of the third roll. In the pressing step, the intaglio transfer mold is transferred to the second surface of the continuous resin sheet.

The light diffusing plate of the present invention has an internal haze of 0 to 60% and an external haze based on fine irregularities of 71 to 99%. Therefore, the lamp unevenness is maintained regardless of the viewing angle while maintaining good translucency. Can be suppressed.
Further, in the surface light source device of the present invention, since the open surface of the lamp box is closed with the light diffusion plate of the present invention, lamp unevenness is suppressed. Therefore, high quality light can be obtained.

In the liquid crystal display device of the present invention, since the open surface of the lamp box is closed with the light diffusion plate of the present invention, lamp unevenness does not occur. Therefore, high quality light can be obtained.
Furthermore, the method for producing a surface shape transfer resin sheet of the present invention can quickly transfer the surface shape of a transfer mold with high accuracy. Therefore, the target surface shape transfer resin sheet can be produced with good productivity while suppressing the surface state defect. As a result, the production efficiency of the light diffusing plate can be improved.

1 is a schematic side view of a liquid crystal display device according to an embodiment of the present invention. It is a typical perspective view of the liquid crystal display device shown in FIG. It is a typical perspective view of the light diffusing plate concerning one embodiment of the present invention. FIG. 4 is an enlarged cross-sectional view of a main part of the light diffusing plate of FIG. 3, showing a cross section taken along the line IV-IV of FIG. It is a principal part expanded sectional view of the lamp box which shows the attachment state of a light diffusing plate. It is a schematic block diagram of the manufacturing apparatus used for the manufacturing method of the laminated resin sheet which concerns on one Embodiment of this invention. It is a typical sectional view of the mat transfer type which an intermediate roll has. It is a typical sectional view of the intaglio transfer type which a lower roll has.

<Overall configuration of liquid crystal display device>
FIG. 1 is a schematic side view of a liquid crystal display device according to an embodiment of the present invention. FIG. 2 is a schematic perspective view of the liquid crystal display device shown in FIG.
The liquid crystal display device 1 (liquid crystal television) is a so-called direct liquid crystal display device, and includes a backlight system 2 as a surface light source device and a liquid crystal panel 3 disposed in front of the backlight system 2. In FIG. 1 and FIG. 2, the liquid crystal display device 1 is shown in a posture with its front side facing the upper side of the drawing for the sake of convenience. Further, the scales of the constituent members such as the liquid crystal display device 1, the backlight system 2, and the liquid crystal panel 3 shown in the following drawings are set for convenience of explanation, and the scales of all the constituent members are the same. Not that.

The backlight system 2 has a rectangular plate-shaped rear wall 4 and a rectangular frame-shaped side wall 5 integrally standing upright from the periphery of the rear wall 4, and is made of a thin box-shaped resin whose front side is open. The lamp box 6 includes a plurality of linear light sources 7 provided in the lamp box 6, and a light diffusing plate 9 that closes an open surface 8 (front surface) of the lamp box 6.
That is, the box-shaped lamp box 6 has an open surface 8 whose outline is formed by a rectangular frame-like side wall 5, and a linear light source 7 is provided in a space surrounded by the side wall 5 and the rear wall 4. On the inner surface of the rear wall 4 of the lamp box 6, for example, a reflecting plate (not shown) for reflecting light incident from the linear light source 7 to the rear wall 4 side toward the open surface 8 side of the box is attached to the whole. It has been.

The linear light source 7 is, for example, a cylindrical lamp having a diameter of 2 mm to 4 mm. The plurality of linear light sources 7 are arranged in parallel with each other at an equal interval in a state of being spaced apart from the back surface 18 of the light diffusing plate 9.
The distance L between the centers of the adjacent linear light sources 7 is preferably 10 mm or more from the viewpoint of power saving. Moreover, it is preferable that the distance D of the back surface 18 (for example, center part in the back surface 18) of the light diffusing plate 9 and the center of the linear light source 7 is 50 mm or less from a viewpoint of thickness reduction. Further, the ratio of the distance L to the distance D (L / D) is preferably 1.0 to 6.0. In particular, the distance L is preferably 10 mm to 100 mm, and the distance D is preferably 3 mm to 50 mm. Moreover, the distance F between the center of the linear light source 7 and the rear wall 4 inner surface (reflection plate) of the lamp box 6 is, for example, 2.0 mm to 10.0 mm. The number of the linear light sources 7 is inevitably determined by the size of the lamp box 6 (screen size of the liquid crystal display device 1) and the interval L. For example, in the 32 type liquid crystal display device 1, it is 6 to 10 pieces. Preferably there is. In FIGS. 1 and 2, only five linear light sources 7 are shown for ease of illustration.

Moreover, as the linear light source 7, well-known cylindrical lamps, such as a fluorescent tube (cold cathode tube), a halogen lamp, a tungsten lamp, can be used, for example. Further, as the light source of the backlight system 2, a point light source such as a light emitting diode (LED) can be used instead of the linear light source 7.
The liquid crystal panel 3 includes a liquid crystal cell 10 and a pair of polarizing plates 11 and 12 that sandwich the liquid crystal cell 10 from both sides in the thickness direction. Such a liquid crystal panel 3 is disposed on the front surface of the backlight system 2 so that the polarizing plate 11 on the back side and the light diffusion plate 9 face each other.

As the liquid crystal cell 10, for example, a known liquid crystal cell such as a TFT liquid crystal cell or an STN liquid crystal cell can be used.
<Configuration of light diffusion plate>
FIG. 3 is a schematic perspective view of a light diffusion plate according to an embodiment of the present invention. 4 is an enlarged cross-sectional view of a main part of the light diffusing plate of FIG. 3, and shows a cross section taken along the line IV-IV of FIG. FIG. 5 is an enlarged cross-sectional view of a main part of the lamp box showing a mounted state of the light diffusion plate.

As shown in FIG. 3, the light diffusion plate 9 is formed in a square plate shape that is substantially the same as the frame shape of the side wall 5 of the lamp box 6.
The light diffusion plate 9 is a light-transmitting laminated light diffusion plate (in this embodiment, a two-layer light diffusion plate) in which two resin layers are laminated in the thickness direction. And a sub-layer 14 laminated on the back side of the material layer 13.

On the surface of the base material layer 13 (the front surface 15 of the light diffusing plate 9), a plurality of semicircular ridges 16 linearly extending between a pair of opposed peripheral edges of the light diffusing plate 9 are formed in a streak shape. That is, on the front surface 15 (first surface) of the light diffusing plate 9, semicircular ridges 16 and concave ridges 17 between adjacent semicircular ridges 16 are alternately formed in parallel.
Semicircular projections 16, orthogonal cross-section has a contour of substantially semicircular shape (a cylindrical lens shape) appearing when cut along the width direction W _D perpendicular to the longitudinal direction L _D. An example of the contour shape of the semicircular ridge 16 will be specifically described with reference to FIG.

The cross-sectional shape of the semicircular ridge 16 is, for example, an axis passing through both ends of the bottom of the semicircular ridge 16 (a semicircular chord forming the outline of the semicircular ridge 16) as the X axis, , The axis perpendicular to the X axis (perpendicular from the top of the semicircular arc to the X axis) is the Z axis, and the length between both ends of the bottom of the semicircular ridge 16 is W _a- This is expressed by a function Z (x) that satisfies the following formula (1) under the condition of 0.475 × W _a ≦ x ≦ 0.475 × W _a .

However, in the above formula (1), Z ₀ (x) satisfies the following formula (2).

(In the formula (2), C ₂ = 0.762469824257553, C ₄ = 0.298075662622927, C ₆ = −0.5596293831533661, C ₈ = 0.8964682802533265, C ₁₀ = −0.656716416621371515, C ₁₂ = −0. _{615726418495985, C 14 = 1.245151353938560, C} 16 = -0.520559083769482)
In the formula (2), the width W _a of the semicircular ridge 16 is, for example, 40 μm or more, and preferably 80 μm or more. If the width W _a is 40μm or more, it is possible to easily form a semi-circular ridges 16. As the width _{W a,} for example, 800 [mu] m or less, preferably not more than 450 [mu] m. If the width W _a is less than 800 [mu] m, the pattern caused by the semi-circular projections 16 can be made inconspicuous enough not visible to the naked eye. Specifically, the width _{W a, 410μm, 400μm, 325μm} , 280μm and 100μm can be exemplified. However, the value of the width W _a is not limited to this.

Note that the cross-sectional shape of the semicircular ridge 16 is represented by a function Z (x) that satisfies the above formula (1) under the condition that −0.475 × W _a ≦ x ≦ 0.475 × W _a. That's fine. This is because the molding error tends to be relatively large in the vicinity of the hem of the semicircular ridge 16 (near both ends), but the influence of the shape in the vicinity of the hem on the light diffusibility is small.
A large number of semicircular ridges 16 are arranged at an equal interval E ₁ (for example, ₁ μm to 15 μm) in parallel with each other. The distance (pitch P ₁ ) between the centers (Z-axis in FIG. 4) of the adjacent semicircular ridges 16 is, for example, 40 μm to 800 μm. The ratio of the height H to the pitch _{P 1} of the semi-circular protrusions 16 (H / _{P 1)} is, for example, 0.2 to 0.8.

On the other hand, many fine irregularities 19 are formed on the surface of the sub-layer 14 (the back surface 18 of the light diffusion plate 9). The fine irregularities 19 are distributed almost uniformly over the entire back surface 18, and the back surface 18 (second surface) of the light diffusing plate 9 is a mat surface on which the fine irregularities 19 are entirely formed.
The shape of the fine unevenness 19 can be represented by, for example, the surface roughness. As an example, arithmetic mean roughness Ra of the fine unevenness | corrugation 19 is a value measured based on ISO 4287-1997, for example, is 8 micrometers-25 micrometers, Preferably, it is 10 micrometers-20 micrometers.

Moreover, the ten-point average roughness Rz of the fine unevenness | corrugation 19 is a value measured based on ISO 4287-1997, for example, is 40 micrometers-110 micrometers, Preferably, it is 50 micrometers-100 micrometers.
Further, as shown in FIG. 5, the thickness t ₁ of the base material layer 13 is thicker than the thickness t ₂ of the sublayer 14, for example, 0.05 mm to 9 mm, preferably 0.9 mm to 3 mm. The thickness _{t 2} of the sublayer 14 is, for example, 0.03Mm～1mm, preferably from 0.05 mm to 0.1 mm. The total thickness T of the light diffuser plate 9 plus the thickness _{t 2} of the thickness _{t 1} and the sublayer 14 of the base layer 13 is, for example, 0.1 mm to 10 mm, preferably 1. It is 0 mm to 4.0 mm.

The raw material for the light diffusion plate 9 is not particularly limited, and for example, a known translucent resin can be used.
Examples of the translucent resin include resins having a refractive index of 1.49 to 1.62. Specifically, acrylic resin, styrene resin, polycarbonate, polyethylene, polypropylene, cyclic polyolefin, cyclic olefin copolymer, polyethylene terephthalate, MS resin (methyl methacrylate-styrene copolymer resin), ABS resin (acrylonitrile- Butadiene-styrene copolymer resin) and AS resin (acrylonitrile-styrene copolymer resin).

The said translucent resin can be used individually or in combination with 2 or more types. Moreover, among these, Preferably, a styrene resin is mentioned, More preferably, single use of a styrene resin is mentioned.
Moreover, the raw material resin A used as the raw material of the base material layer 13 and the raw material resin B used as the raw material of the sublayer 14 may be the same or different. The combination of the raw material resin A and the raw material resin B is preferably a combination of the same kind of translucent resin, and more preferably a combination in which both the raw material resins A and B contain a styrene resin. Particularly preferably, a combination in which the styrenic resin is used alone for both of the raw material resins A and B is mentioned.

Moreover, the light diffusing plate 9 can contain a light diffusing agent (light diffusing particles) if necessary.
The light diffusing agent is not particularly limited as long as it has a refractive index different from that of the translucent resin constituting the light diffusing plate 9 and can diffuse transmitted light. For example, as an inorganic light diffusing agent, calcium carbonate, Examples thereof include barium sulfate, titanium oxide, aluminum hydroxide, silica, glass, talc, mica, white carbon, magnesium oxide, and zinc oxide. These may be subjected to a surface treatment with a fatty acid or the like.

Examples of the organic light diffusing agent include styrene polymer particles, acrylic polymer particles, and siloxane polymer particles. Preferably, the weight average molecular weight is 500,000 to 5,000,000. Examples include coalescent particles and crosslinked polymer particles having a gel fraction of 10% by mass or more when dissolved in acetone.
The light diffusing agents can be used alone or in combination of two or more.

  When the light diffusing plate 9 contains a light diffusing agent, the blending ratio of the light diffusing agent is 0.0005 to 0.002 parts by mass, preferably 0.0007 to 0 parts per 100 parts by mass of the translucent resin. 0.001 part by mass. Moreover, a light-diffusion agent can be used as a masterbatch with the said translucent resin. Further, the absolute value of the difference between the refractive index of the translucent resin and the refractive index of the light diffusing agent is usually 0.01 to 0.20, preferably 0.02 to 0.02 from the viewpoint of light diffusibility. 0.15.

In the present embodiment, it is particularly preferable to use a light-transmitting resin that does not contain a light diffusing agent as the raw material of the light diffusing plate 9.
In addition, various additives such as ultraviolet absorbers, heat stabilizers, antioxidants, weathering agents, light stabilizers, optical brighteners, processing stabilizers, and the like may be added to the light diffusion plate 9 as necessary. You can also.
When adding an ultraviolet absorber, it is preferable to add 0.1-3 mass parts of ultraviolet absorbers with respect to 100 mass parts of translucent resin. If it is the above-mentioned range, the bleeding to the surface of an ultraviolet absorber can be suppressed and the external appearance of the light diffusing plate 9 can be maintained favorable.

Moreover, when adding a heat stabilizer further, it is preferable to add 0.01-1 mass part of heat stabilizers with respect to 100 mass parts of translucent resin.
As shown in FIG. 5, the light diffusion plate 9 diffuses light with respect to the side wall 5 of the lamp box 6 at a position where the semicircular ridges 16 are parallel to the linear light source 7 in the lamp box 6. The back surface 18 of the plate 9 is brought into contact with the lamp box 6 and fixed to the lamp box 6. Thereby, the open surface 8 of the lamp box 6 is blocked by the light diffusion plate 9.
<Method for producing light diffusion plate (laminated resin sheet)>
The light diffusion plate 9 described above can be produced by cutting a laminated resin sheet produced by the following method.

FIG. 6 is a schematic configuration diagram of a manufacturing apparatus used in the method for manufacturing a laminated resin sheet according to one embodiment of the present invention. FIG. 7 is a schematic cross-sectional view of a mat transfer mold included in the intermediate roll. FIG. 8 is a schematic cross-sectional view of an intaglio transfer mold that the lower roll has.
The sheet manufacturing apparatus 21 includes a main extruder 22 for heating and melting the raw material resin A of the base material layer 13, an auxiliary extruder 23 for heating and melting the raw material resin B of the sublayer 14, and the extruders 22 and 23. The feed block 24 to which the resin melted in step 1 is supplied, the die 25 for extruding the resin in the feed block 24 into a sheet shape, and three pressing rolls for forming the laminated resin sheet 33 extruded from the die 25 26-28.

As the main extruder 22 and the auxiliary extruder 23, for example, a known extruder such as a single screw (single screw) extruder or a twin screw extruder can be used. The main extruder 22 and the auxiliary extruder 23 are attached with hoppers 29 and 30 for charging resin into the cylinders.
The feed block 24 is not particularly limited as long as it is a type that can supply two or more kinds of resins to the die 25 and can be co-extruded in a laminated state. For example, a two-type two-layer distribution type, a two-type three-layer distribution type, etc. A known feed block can be used. In this embodiment, since the two-layer light diffusing plate 9 is produced, a two-kind two-layer distribution type is used.

The die 25 is not particularly limited as long as it is a co-extrusion die, and for example, a known die such as a multi-manifold die can be used. The width of the lip of the die 25 is selected according to the width of the target laminated resin sheet 33 and is, for example, 200 mm to 3000 mm.
The three pressing rolls 26 to 28 constitute a mechanism for forming irregularities on the surface 40 of the laminated resin sheet 33 by a transfer mold while molding the laminated resin sheet 33 by pressing.

  In addition, the surface 40 of the laminated resin sheet 33 is a surface that forms the front surface 15 (the surface of the base material layer 13) of the light diffusing plate 9, and is finally a second surface on which the semicircular ridges 16 are formed. It is a shape transfer surface. On the other hand, the back surface 39 of the laminated resin sheet 33 is a surface on which the back surface 18 (the surface of the sublayer 14) of the light diffusing plate 9 is formed, and the mat surface as the first surface on which fine irregularities 19 are finally formed. It is.

Each of the three pressing rolls 26 to 28 is composed of a cylindrical metal roll (for example, made of chromium, copper, nickel, stainless steel, or a resin surface material), and the temperature of the peripheral surface (surface It is a cooling roll having a function of adjusting (temperature).
The three pressing rolls 26 to 28 have an axis parallel to each other as an upper roll 26 as a first roll, an intermediate roll 27 as a second roll, and a lower roll 28 as a third roll in order from top to bottom. It is arranged in the vertical direction so that A minute gap is formed between adjacent rolls for allowing the resin to pass therethrough with a predetermined thickness.

Moreover, the diameter of each roll is 100 mm-500 mm, for example. Moreover, when a metal roll is used as the pressing rolls 26 to 28, the surface thereof may be subjected to plating treatment such as chrome plating, copper plating, nickel plating, Ni-P plating, or the like.
The peripheral surface 31 of the upper roll 26 is formed into a smooth surface by, for example, mirror finishing.

On the peripheral surface 32 of the intermediate roll 27, a mat transfer mold 34 for forming fine irregularities 19 on the laminated resin sheet 33 is provided.
As shown in FIG. 7, the mat transfer mold 34 has fine irregularities 35 opposite to the minute irregularities 19 on the back surface 18 on the sublayer 14 side of the light diffusion plate 9 on the peripheral surface 32 of the intermediate roll 27. It is formed so as to be distributed in large numbers. That is, the surface of the mat transfer mold 34 is a mat surface in which fine irregularities 35 are distributed almost uniformly over the entire surface, and its arithmetic average roughness Ra is, for example, 20 μm to 30 μm. The ten-point average roughness Rz is, for example, 100 μm to 150 μm.

An intaglio transfer mold 37 for forming the semicircular ridges 16 on the laminated resin sheet 33 is provided on the peripheral surface 36 of the lower roll 28.
As shown in FIG. 8, the intaglio transfer mold 37 has a plurality of semicircular concave stripes 38 opposite to the cylindrical lens-shaped semicircular convex stripes 16 formed in a streak shape along the circumferential direction of the lower roll 28. ing. That is, the semicircular groove 38 has a substantially semicircular arc shaped cut surface perpendicular to the longitudinal direction (circumferential direction), and the depth D _ep is the height H of the semicircular protrusion 16. It is slightly larger than (for example, 3 μm to 450 μm). Moreover, the distance (pitch P ₂ ) between the centers of adjacent semicircular concave stripes 38 is appropriately determined according to the shape of the semicircular convex stripes 16. The difference between the height H of the semicircular ridge 16 and the depth D _ep of the semicircular ridge 38 is the transfer when the intaglio transfer mold 37 is transferred to the laminated resin sheet 33 to form the semicircular ridge 16. This is due to the rate (%).

The mat transfer mold 34 may be provided on the lower roll 28, and the intaglio transfer mold 37 may be provided on the intermediate roll 27.
As a raw material for the mat transfer mold 34 and the intaglio transfer mold 37, for example, an organic material can be used.
The organic material only needs to have heat resistance capable of maintaining the shape of the transfer mold even when repeatedly pressed against the laminated resin sheet 33 immediately after being extruded from the die 25 in the heat-melted state. For example, thermosetting Examples thereof include resins such as resins and thermoplastic resins.

Examples of the thermosetting resin include phenol resin, epoxy resin, melamine resin, urea resin, polyimide resin (PI resin), unsaturated polyester resin, alkyd resin, and the like.
Examples of the thermoplastic resin include styrene resin, acrylic resin, polyethylene resin, polypropylene resin, cyclic olefin polymer resin, allylonitrile-butadiene-styrene resin (ABS resin), polyethylene terephthalate resin (PET resin), and polycarbonate. Examples thereof include a resin (PC resin), a polyethersulfone resin (PES resin), and a thermoplastic polyimide resin (PI resin).

Among these, Preferably, the Vicat softening point (JIS K7206-1999 A50) is 40 degreeC or more higher than the Vicat softening point of the laminated resin sheet 33 extruded from the die | dye 25, and the crosslinked thermoplastic resin is mentioned. It is done.
As a specific example of the organic material, an organic material film on which the above-described opposite transfer mold is formed can be used as the mat transfer mold 34 and the intaglio transfer mold 37.

The thickness of the organic material film (the mat transfer mold 34 and the intaglio transfer mold 37) is, for example, 0.05 mm to 5 mm. When the thickness is in the above-described range, the transfer can be favorably performed on the laminated resin sheet 33.
Next, a method for manufacturing the laminated resin sheet 33 using the above-described manufacturing apparatus will be described.
(1) Sheet Manufacturing Process First, the raw material resin A of the base material layer 13 is put into the hopper 29 of the main extruder 22, melted and kneaded, and then supplied to the feed block 24. On the other hand, the raw material resin B of the sublayer 14 is put into the hopper 30 of the auxiliary extruder 23, melted and kneaded, and then supplied to the feed block 24. The cylinder temperatures of the main extruder 22 and the auxiliary extruder 23 are set to 190 ° C. to 250 ° C., for example.

Next, the resin in the feed block 24 is coextruded from the die 25 (die temperature is, for example, 220 ° C. to 280 ° C.), so that the two-layered laminated resin sheet 33 including the base material layer 13 and the sublayer 14 is formed. As a continuous extrusion.
(2) Pressing Step The laminated resin sheet 33 extruded from the die 25 is molded by being pressed and cooled by pressing rolls 26 to 28 as shown in FIG.

Specifically, the resin coextruded from the die 25 is first fed between the upper roll 26 and the intermediate roll 27 (gap) (at this time, a melt bank is formed as necessary). The upper roll 26 and the intermediate roll 27 are sandwiched and pressed (first pressing step).
Then, it is conveyed in close contact with the peripheral surface 32 of the intermediate roll 27 (conveying process) and cooled at that time. The surface temperature of the upper roll 26 and the intermediate roll 27 is preferably lower than the extrusion temperature of the laminated resin sheet 33, and is, for example, 50 ° C to 120 ° C. When pressed by the upper roll 26 and the intermediate roll 27, the mat transfer mold 34 of the intermediate roll 27 is transferred onto the back surface 39 of the laminated resin sheet 33 (the back surface 18 of the light diffusion plate 9). Many irregularities 19 are formed.

  Thereafter, the intermediate roll 27 and the lower roll 28 are sandwiched and pressed (second pressing step). The surface temperature of the lower roll 28 is, for example, 50 ° C to 120 ° C. Then, when pressed by the intermediate roll 27 and the lower roll 28, the intaglio transfer mold 37 is transferred to the surface 40 of the laminated resin sheet 33 (the front surface 15 of the light diffusion plate 9) so that the sheet flows in the flow direction. A large number of parallel strip-like semicircular ridges 16 are formed.

The laminated resin sheet 33 as a surface shape transfer resin sheet is manufactured through the above steps. Thereafter, the light diffusing plate 9 can be obtained by further cooling the laminated resin sheet 33 and then cutting the laminated resin sheet 33 in an appropriate size.
<Physical properties of light diffusion plate>
The light diffusion plate 9 obtained as described above has, for example, a total light transmittance of 75 to 93%, preferably 77 to 86%, measured in accordance with JIS K7361-1 (1997). It is.

Moreover, the haze (Haze) measured based on JISK7361-1 (1997) is 90 to 99%, Preferably it is 97 to 99%.
The light diffusing plate 9 has an internal haze (0 to 60%, preferably 0 to 10%).
The internal haze is the degree of cloudiness caused by scattering generated by the internal scattering particles contained in the light diffusing plate 9.

For example, the internal haze is obtained by attaching a correction member having the same refractive index as that of each of the raw material resins A and B constituting both the front surface 15 and the back surface 18 of the light diffusing plate 9, The measurement can be performed in accordance with JIS K7136 after erasing the influence (cloudiness degree) caused by scattering caused by the shape of the fine unevenness 19.
Further, the light diffusing plate 9 has an external haze (Haze) based on the fine irregularities 19 of the sublayer 14 measured in accordance with JIS K7136 is 71 to 99%, preferably 80 to 95%. .

The external haze is the degree of cloudiness caused by scattering caused by the surface shape such as the height of the fine irregularities 19 of the sublayer 14.
The external haze is, for example, scattering caused by the shape of the semicircular ridge 16 by attaching a correction member having the same refractive index as that of the raw material resin A constituting the base material layer 13 to the front surface 15 of the light diffusion plate 9. After erasing the influence (cloudiness degree) due to, it can be measured according to JIS K7136.

As described above, the light diffusing plate 9 has an internal haze of 0 to 60%, and an external haze based on the fine irregularities 19 of the sublayer 14 is 71 to 99%, so that it maintains a good translucency. However, lamp unevenness can be suppressed regardless of the angle (viewing angle) at which the frontmost polarizing plate 12 is viewed.
In the backlight system 2 and the liquid crystal display device 1 provided with the light diffusing plate 9, since the open surface 8 of the lamp box 6 is closed with the light diffusing plate 9, lamp unevenness is suppressed. Therefore, high quality light can be obtained.

Furthermore, according to the method for manufacturing the laminated resin sheet 33, the surface shapes of the mat transfer mold 34 and the intaglio transfer mold 37 can be transferred quickly and accurately. Therefore, the target laminated resin sheet 33 can be manufactured with high productivity while suppressing surface defects. As a result, the production efficiency of the light diffusing plate 9 can be improved.
As mentioned above, although one Embodiment of this invention was described, this invention can also be implemented in another embodiment.

For example, the resin plate as the light diffusing plate is not limited to the two-layer resin plate such as the light diffusing plate 9, and may be, for example, a single-layer resin plate or a resin plate composed of three or more layers. Good.
Further, for example, in the above-described embodiment, the multiple semicircular ridges 16 are formed in a cylindrical lens shape extending along one direction parallel to the front surface 15 of the light diffusing plate 9 (one-dimensional type) (FIG. 2 reference) may be formed in a cylindrical lens shape extending along two different directions parallel to the front surface 15 of the light diffusion plate 9 (for example, two directions orthogonal to each other) (that is, in a two-dimensional type). May be).

In addition, the cylindrical lens-shaped semicircular ridges 16 may be arranged, for example, in a state where a large number of non-continuous semicircular ridges are separated from each other in the longitudinal direction.
In the above-described embodiment, the contour shape of the cut surface of the semicircular ridge 16 has been described as being a semicircular arc shape, but is not limited to a semicircular arc shape. The shape may correspond to any one of the members cut by a plane not included. Moreover, a semi-elliptical arc shape, a flat curve line shape, etc. may be sufficient. That is, the term “semicircular ridge” is used to include a ridge having a cross section having such a shape.

Further, for example, if the roll is irrelevant in terms of transfer technology for assisting the conveyance or adhesion between the laminated resin sheet 33 and the pressing rolls 26 to 28, the laminated resin sheet 33 and each transfer mold (the mat transfer mold 34 and the intaglio transfer mold 37). ) (A touch roll) may be provided.
The light diffusing plate 9 is preferably used as a light diffusing plate for a backlight, but is not particularly limited to such applications.

  Moreover, although the said backlight system 2 is used suitably as a surface light source device for liquid crystal display devices, it is not limited to such a use in particular.

Next, although this invention is demonstrated based on an Example and a comparative example, this invention is not limited by the following Example.
<Raw material for laminated resin sheet>
The following materials (1) to (6) were prepared as raw materials for the laminated resin sheet.
(1) Translucent resin A
Styrene resin (Toyo Styrene "HRM40" refractive index 1.59)
(2) Translucent resin B
MS resin (manufactured by Nippon Steel Chemical Co., Ltd. “MS200NT (styrene / methyl methacrylate = 80 parts by mass / 20 parts by mass)”, refractive index 1.57)
(3) Light diffusing agent A
PMMA crosslinked particles (refractive index 1.49 weight average particle diameter 35 μm)
(4) Light diffusing agent B
Acrylic crosslinked particles (refractive index 1.49 weight average particle diameter 0.8 μm)
(5) Light diffusing agent master batch A (pellet)
After dry blending 92 parts by mass of translucent resin B and 8 parts by mass of light diffusing agent A, the blended product was put into a hopper of an extruder having a screw diameter of 30 mm and melt-mixed in a cylinder. And it prepared by extruding in the shape of a strand (string) in the state which melt-mixed the blend, and pelletizing.
(6) Light diffusing agent masterbatch B
After 99.6 parts by mass of translucent resin A and 0.4 parts by mass of light diffusing agent B were dry blended, the blended product was put into a hopper of an extruder having a screw diameter of 30 mm and melt-mixed in a cylinder. . And it prepared by extruding in the shape of a strand (string) in the state which melt-mixed the blend, and pelletizing.
<Configuration of production apparatus for laminated resin sheet>
An apparatus having the same configuration as the sheet manufacturing apparatus 21 shown in FIG. 6 was used. In addition, the following rolls (1) to (3) were prepared as polishing rolls attached to the apparatus.
(1) Polishing roll A
A metal roll (diameter: 450 mm) having an intaglio transfer mold on its peripheral surface. That is, on the peripheral surface of the polishing roll A, a plurality of concave strips having a semicircular cross section that circulates in the circumferential direction are formed in parallel to each other in a line shape. Incidentally, the pitch _{P 2} of the adjacent concave and 350 .mu.m, was 183μm depth _{D ep} concave stripes.
(2) Polishing roll B
A metal roll (diameter: 450 mm) provided with a mat transfer mold on the peripheral surface. That is, the peripheral surface of the polishing roll B is a mat surface on which many fine irregularities are formed. The arithmetic average roughness Ra of the fine irregularities was 23.7 μm, and the ten-point average roughness Rz was 119.6 μm.
(3) Polishing roll C
A metal roll (diameter: 450 mm) whose peripheral surface is mirror-finished.
(4) Polishing roll D
A metal roll (diameter: 450 mm) having an intaglio transfer mold on its peripheral surface. That is, on the peripheral surface of the polishing roll D, a plurality of concave strips having a semicircular cross section that circulates in the circumferential direction are formed in parallel to each other in a line shape. Incidentally, the pitch _{P 2} of the adjacent concave and 280 .mu.m, was 123μm depth _{D ep} concave stripes.
(5) Polishing roll E
A metal roll (diameter: 450 mm) provided with a mat transfer mold on the peripheral surface. That is, the peripheral surface of the polishing roll E is a mat surface on which a number of fine irregularities are formed. The arithmetic average roughness Ra of the fine irregularities was 6.9 μm, and the ten-point average roughness Rz was 46.6 μm.
<Examples 1-8 and Comparative Examples 1-9>
In each example and each comparative example, rolls corresponding to the following Table 1 and Table 2 were mounted as the upper roll, the intermediate roll, and the lower roll of the sheet manufacturing apparatus.

Next, the raw material resin A shown in Table 1 and Table 2 below was melt-kneaded by a main extruder having a temperature in the cylinder of 190 ° C. to 250 ° C., and then supplied to the two-layer distribution type feed block. Further, the raw material resin B shown in Table 1 below was melt-kneaded with an auxiliary extruder having a temperature in the cylinder of 190 ° C. to 250 ° C., and then supplied to the two-layer distribution type feed block.
Next, the resin supplied from the main extruder to the feed block becomes a base material layer (raw material resin A layer), and the resin supplied from the auxiliary extruder to the feed block becomes a sublayer (raw material resin B layer). The resin in the feed block was coextruded with a multi-manifold die (width: 1500 mm) at an extrusion resin temperature of 250 ° C. Then, the laminated resin sheet of 2 layers of width 1300mm and total thickness 1.2mm (base material layer 1.15mm, sublayer 0.05mm) was produced by pressing and cooling with an upper, middle, and lower roll.
<Evaluation>
(1) Production of light diffusing plate (laminated resin plate) A light diffusing plate was produced by cutting each laminated resin sheet produced in the above examples and comparative examples with an appropriate length. About the produced light diffusing plate, the physical-property measurement and evaluation of the following (2)-(5) were implemented.
(2) Transfer rate The cross-sectional shape of the semicircular ridge formed on the surface of the base material layer (raw material resin A layer) of each light diffusing plate was measured using an ultra-deep shape measuring microscope (“VK-8500” manufactured by KEYENCE). And the height H of the semicircular ridge was measured. And by calculating | requiring the ratio of the height H of a semicircle protruding item _{| line with} respect to the depth Dep of the recessed item formed in the surrounding surface of an intermediate | middle roll, the transcription | transfer rate of a semicircle protruding item _{| line} (= H / _Dep * 100 ( %)). The calculation results are shown in Table 1 and Table 2 below.
(3) Sublayer surface roughness (a) Arithmetic average roughness Ra
The arithmetic average roughness Ra of the surface of the sublayer of each light diffusion plate was measured according to ISO 4287-1997. Specifically, the arithmetic average roughness Ra of the mat surface of the light diffusing plate was measured using a surface roughness meter (“SJ-201P” manufactured by Mitutoyo). The measurement conditions of the surface roughness meter were set to cut-off value: 0.8 × 1, measurement range: auto. The measurement results are shown in Tables 1 and 2 below.
(I) Ten-point average roughness Rz
The ten-point average roughness Rz of the surface of the sublayer of each light diffusion plate was measured according to ISO 4287-1997. Specifically, the ten-point average roughness Rz of the mat surface of the light diffusion plate was measured using a surface roughness meter (“SJ-201P” manufactured by Mitutoyo). The measurement conditions of the surface roughness meter were set to cut-off value: 0.8 × 1, measurement range: auto. The measurement results are shown in Tables 1 and 2 below.
(4) Total light transmittance Tt and haze
(A) Whole board (no correction)
The total light transmittance Tt and haze of each light diffusing plate is measured using a transmittance meter (“HM-150” manufactured by Murakami Color Research Laboratory), and Tt conforms to JIS K7361-1 (1997). The haze was measured according to JIS K7136. The measurement results are shown in Tables 1 and 2 below. At the time of measurement, the measurement was performed with the base layer side on which the semicircular ridges of the resin plate were formed facing the integrating sphere and the pitch interval direction toward the left and right sides.
(A) Correction by liquid immersion 1 After applying a refractive liquid having the same refractive index as the raw material resin A constituting the base material layer to the surface of the base material layer of each light diffusion plate, a correction film made of the raw material resin A The effect due to scattering generated by the shape of the semicircular ridge was eliminated. On the other hand, after applying a refraction liquid having the same refractive index as that of the raw material resin B constituting the sublayer to the surface of the sublayer of each light diffusion plate, a correction film made of the raw material resin B is pasted to make fine The influence caused by the scattering caused by the uneven shape was eliminated.

And the total light transmittance Tt and the haze (Haze) of the light diffusing plate in a state where the correction film was stuck on both surfaces were measured by the same apparatus and conditions as in (a) above. The measurement results are shown in Tables 1 and 2 below. The measured haze shows the internal haze caused only by the substance contained in the resin plate because the influence caused by the scattering caused by the shapes of the semicircular ridges and the fine irregularities is eliminated. .
(C) Correction by liquid immersion 2 After applying a refractive liquid having the same refractive index as the raw material resin A constituting the base material layer to the surface of the base material layer of each light diffusion plate, a correction film made of the raw material resin A The effect due to scattering generated by the shape of the semicircular ridge was eliminated.

And the total light transmittance Tt and the haze (Haze) of the light diffusing plate in a state where the correction film was attached to the surface of the base material layer were measured by the same apparatus and conditions as in (a) above. The measurement results are shown in Tables 1 and 2 below. The measured haze shows the external haze caused by the shape of fine irregularities on the sub-layer side of the resin plate, since the influence caused by the scattering generated by the shape of the semicircular ridge is eliminated.
(5) Lamp unevenness (A) Examples 1-4 and Comparative Examples 1-6
A lamp box (screen size 32 type 4: 3 normal) having an open front side was prepared, and eight cold cathode tubes (diameter: 4.0 mm) were arranged in parallel in the lamp box. The arrangement conditions of the cold cathode tubes were such that the distance L between the centers of adjacent tubes was 45.0 mm, and the distance F between the center of the tube and the reflector (the bottom surface of the lamp box) was 5.5 mm.

Next, with the cold cathode tube in the lamp box turned on, the light diffusion plate is fixed to the front frame of the lamp box so that the cold cathode tube and the back surface (sublayer surface) of the light diffusion plate face each other. As a result, the open surface of the lamp box was blocked. In the state where the light diffusion plate was set, the distance D between the back surface of the light diffusion plate and the center of the cold cathode tube was 18.4 mm.
After fixing the light diffusing plate, it was visually evaluated whether or not an image of the tube (lamp unevenness) could be seen through the light diffusing plate without the liquid crystal panel. The evaluation results are shown in Table 1 and Table 2 below.

In Table 1, “◯” indicates that the tube image was not seen at all regardless of the viewing angle of the screen, and “△” indicates that the tube image was visible depending on the viewing angle. , “×” indicates that the image of the tube can be seen no matter where the screen is viewed.
(A) Examples 5 to 8 and Comparative Examples 7 to 9
Evaluation was performed under the same conditions as in (a) above, except that the distance D between the back surface of the light diffusion plate and the center of the cold cathode tube was 15.1 mm in the state where the light diffusion plate was set. The evaluation results are shown in Table 1 and Table 2 below.

DESCRIPTION OF SYMBOLS 1 Liquid crystal display device 2 Backlight system 3 Liquid crystal panel 5 Side wall 6 Lamp box 7 Linear light source 8 Open surface 9 Light diffusing plate 15 Front surface (of light diffusing plate) 16 Semicircular protrusion 18 (Back surface of light diffusing plate) 19 Fine 25 Concavities and convexities 25 Die 26 Upper roll 27 Intermediate roll 28 Lower roll 32 (Intermediate roll) peripheral surface 33 Laminated resin sheet 34 Matt transfer mold 35 Fine unevenness 36 (Lower roll) peripheral surface 37 Intaglio transfer mold 38 Semicircular groove 39 Back surface (of laminated resin sheet) 40 Front surface (of laminated resin sheet)

Claims (5)

Light diffusion made of a translucent resin having a first surface on which fine irregularities are formed and a second surface opposite to the first surface, on which a plurality of linear protrusions are formed in parallel to each other A board,
The light diffusing plate has 0 to 60% internal haze and 71 to 99% external haze based on the fine irregularities. The light diffusing plate includes a light control plate that emits light incident from the first surface from the second surface;
In an orthogonal cross section that appears when the ridge is cut along a width direction orthogonal to the longitudinal direction, an axis passing through both ends of the bottom of the ridge is defined as an X axis, passing through the middle of the both ends, and the X When the axis perpendicular to the axis is the Z-axis and the length between both ends is W _a ,
The shape of the orthogonal cross section of the ridge is expressed by a function Z (x) that satisfies the following formula (1) under the condition that −0.475 × W _a ≦ x ≦ 0.475 × W _a. The light diffusing plate according to claim 1, wherein the light diffusing plate is characterized.

However, in the above formula (1), Z ₀ (x) satisfies the following formula (2).

(In the formula (2), C ₂ = 0.762469824257553, C ₄ = 0.298075662622927, C ₆ = −0.5596293831533661, C ₈ = 0.8964682802533265, C ₁₀ = −0.656716416621371515, C ₁₂ = −0. _{615726418495985, C 14 = 1.245151353938560, C} 16 = -0.520559083769482) A resin lamp box formed in a box shape with the front side open;
A plurality of light sources arranged spaced apart from each other in the lamp box so as to face the open surface of the lamp box;
The light according to claim 1, wherein the first surface is disposed so as to face the light source, and closes the open surface by abutting against an edge frame portion of the lamp box that forms an outline of the open surface. A surface light source device comprising a diffusion plate. A surface light source device according to claim 3,
A liquid crystal display device comprising: a liquid crystal panel disposed on the front side of the surface light source device. A sheet manufacturing process for manufacturing a continuous resin sheet having a first surface and a second surface opposite to the first surface by continuously extruding the translucent resin from the die in a heated and melted state;
A first pressing step of sandwiching the continuous resin sheet between a first roll and a second roll;
A transporting step of transporting the continuous resin sheet while being in close contact with the second roll;
Including a second pressing step of sandwiching the conveyed continuous resin sheet between the second roll and the third roll,
On the peripheral surface of the second roll, a mat transfer mold having fine irregularities of arithmetic average roughness Ra = 20 μm to 30 μm and ten-point average roughness Rz = 100 μm to 150 μm is formed,
In the first pressing step, the mat transfer mold is transferred to the first surface of the continuous resin sheet,
An intaglio transfer mold having a plurality of indentations parallel to each other and extending linearly along the circumferential direction of the third roll is formed on the circumferential surface of the third roll,
In the second pressing step, the intaglio transfer mold is transferred onto the second surface of the continuous resin sheet.

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