JP3022460B2 - Surface light source element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a surface light source element using a resin sheet as a light guide.

[0002]

2. Description of the Related Art As a light diffusing resin sheet, a transparent resin sheet whose surface is made uneven using a mold, and a light diffusing agent or a light scattering agent coated on the back surface of the transparent resin sheet are known. I have. As a design sheet, there is known a sheet obtained by applying light and shade printing, shadow printing, and the like to the surface of a transparent resin sheet, and a sheet having an uneven shape formed inside the sheet.

Japanese Patent Publication No. 7-36742 discloses a glittering decorative sheet in which a transparent resin layer, a transparent embossed resin layer, and a light reflecting layer are sequentially laminated. However,
This sheet has a light reflection layer laminated on the uneven portion of the transparent embossed resin layer, and is not suitable for a light guide used by irradiating light from the back or side surface of the sheet.

Japanese Patent Laid-Open Publication No. Hei 3-256735 discloses that a V-shaped groove is formed on one surface of a polyvinyl chloride sheet, and the other surface is smooth on the surface of the sheet on which the V-shaped groove is formed. A composite sheet to which a polyvinyl chloride sheet is adhered,
A cut glass sheet in which a sealed air layer is formed in the V-shaped groove is disclosed. However, since the difference in the refractive index between the resin layer and the air layer is too large for the sheet having the structure in which the air layer is present inside, the light diffusion property is too large,
Not suitable for use as a light guide.

On the other hand, as a back light source device used for a liquid crystal display device, a signboard, a traffic guide plate, and the like, there is an edge light type in which a linear light source is disposed on an end face of a plate-shaped light guide. Such an edge light type back light source device
Usually, a plate-shaped transparent material such as an acrylic resin plate is used as the light guide,
This is a device in which light from a light source disposed at one end of the light guide is made incident on the light guide, and light is emitted from the surface (light emission surface) of the light guide in a planar manner. The light guide used here usually has
A light scattering part and / or a light diffusion part is formed on the front surface or the back surface. In such a surface light source element, it is necessary to ensure the uniformity of the luminance of the emitted light without being affected by the distance from the light source. This performance is particularly important for large surface light source elements.

Japanese Unexamined Patent Publication No. 5-127159 discloses a surface light source element in which a light diffusing substance such as titanium white is printed in the form of dots on the surface of a light guide and a prism sheet is mounted on a light emitting surface. Has been disclosed. Such a surface light source element can obtain uniform brightness by changing the dot coverage according to the distance from the light source. However, on the other hand, the dot pattern must be concealed by a sheet having a light diffusing property, which results in a decrease in luminance and a complicated configuration of the surface light source element.

Japanese Patent Application Laid-Open No. 2-84618 discloses a surface light source in which at least one of a surface (light emitting surface) of a light guide and a back surface thereof has a matte surface, and a prism sheet is mounted on the light emitting surface. An element is disclosed. With such a surface light source element, very high luminance can be obtained, but it is not satisfactory in the uniformity of luminance of emitted light.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a surface light source element using a resin sheet as a light guide.

[0009]

The above object of the present invention is achieved by the present invention having the following constitution. 1. It has a laminated structure in which a transparent resin layer C is sandwiched between a transparent resin layer A and a transparent resin layer B, the outer surface is a smooth resin sheet, and the adjacent resin layers have different refractive indices of resin. When the thickness direction of the sheet is y and the width direction is x, x
In a cross section indicated by the y-plane, at least one of a boundary surface between the resin layer A and the resin layer C and a boundary surface between the resin layer B and the resin layer C has a concave-convex resin sheet, and the light guide (51) A reflector (52) is provided on the back surface of the light guide, a light source (53) is provided on at least one end surface (yz surface) in the x direction of the light guide, and light is emitted from the surface of the light guide. A surface light source element having a light-diverting sheet (54) having a function of changing light in a direction normal to the light guide, provided on the surface of the light guide.

[0010] 2. A resin sheet having a laminated structure of a transparent resin layer A and a transparent resin layer B, and having a smooth outer surface,
In the cross section indicated by the xy plane when the refractive index of the resin of the adjacent resin layers is different and the thickness direction of the sheet is y and the width direction is x, the boundary surface between the resin layer A and the resin layer B is uneven. A light guide (51) is a resin sheet having a shape, a reflector (52) is provided on the back surface of the light guide, and a light source (53) is provided on at least one end face (yz plane) in the x direction of the light guide. A surface light source element comprising: a light diverting sheet (54) having a function of changing the light emitted from the surface of the light guide in a direction normal to the light guide.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a resin sheet manufacturing apparatus, a manufacturing method, a resin sheet, and a surface light source element of the present invention which can be used for the surface light source element of the present invention will be sequentially described. In an apparatus useful for manufacturing a resin sheet used for the surface light source element of the present invention, the X direction coincides with the width direction of the resin sheet, the Y direction coincides with the thickness direction of the resin sheet, and the Z direction coincides with the traveling direction of the resin sheet. . The Z direction can be taken in the vertical direction as shown in FIG. 4 or in the horizontal direction as shown in FIG.

This apparatus has a great feature in the shape and arrangement of the two flow paths 41 and / or 42 for flowing the resin a for the resin layer A and the resin b for the resin layer B in the composite flow forming section 22. (FIG. 4). That is, the shapes of the flow paths 41 and / or 42 in the XZ cross section include a portion Rn and / or Ln having a large height in the Z direction and a portion Rm and / or a portion having a small height (may be zero) in the Z direction. Alternatively, Lm is alternately arranged (FIG. 6).

FIG. 1 shows a resin a for forming a resin layer A.
And an apparatus in the case where the resin b for forming the resin layer B is the same resin. This resin is converted into resin a (b)
And The resin a (b) is melt-extruded into the shaping head by the first extruder 1, reaches the first metering pump 3 through the first channel 11, and the resin c for forming the resin layer C is the first resin. 2
It is melt-extruded into the same shaping head by the extruder 2 and reaches the second metering pump 4 through the second channel 12. Resin a (b)
Are distributed to two flow paths 13 and 16 on the left and right sides by a distribution nozzle provided in the die pack 5, and form resin flows of the resin a and the resin b, respectively (FIG. 3). The resin c is guided to the flow channel 31 by the distribution nozzle via the flow channel 14 provided in the die pack 5 (FIG. 4).

When the resin a and the resin b are different resins, one of the resins is supplied by a third extruder (not shown). The resin c is discharged from the slit-shaped flow path 31 into the composite flow forming section 22, and forms a sheet-shaped flow having a predetermined thickness (FIG. 4). On the other hand, resin a and resin b
Forms a composite resin flow by sandwiching the resin c discharged to the composite flow forming section 22 from both sides, and the composite resin is extruded from the composite outlet 23. After the composite resin is taken up by the cooling roll group 10 and shaped into a sheet,
The sheet is cut into a predetermined length by the sheet cutter 15 (FIGS. 1 and 2). In the case of shaping the film into a thin film, the film is wound on a winder via a cooling roll.

In the composite flow forming section 22, the resin c is affected by the resin a and the resin b due to the relative positional relationship between the flow paths 41 and 42 and the cross-sectional shape in the XY cross section is desired. It is transformed into the shape of Hereinafter, a method for manufacturing a resin sheet that can be used in the present invention will be described with reference to the drawings.

1 to 4 are views schematically showing an example of a manufacturing apparatus according to a first embodiment of a resin sheet useful for a surface light source element of the present invention, and FIGS. 1 and 2 are schematic views of the whole apparatus. FIGS. 3 and 4 are a plan sectional view and a longitudinal sectional view showing an example of the internal structure of the device. FIG.
It is a perspective view from the II line direction.

FIGS. 6 and 7 show resin flow paths in a manufacturing apparatus which is a typical embodiment of the above apparatus.
FIG. 7 is a sectional view taken along line III-III shown in FIG. 4, and FIG. 7 is a sectional view taken along line IV-IV shown in FIG. In this device, the flow channel 31 has an outlet with a constant interval from one end of the composite flow forming portion 22 in the X direction to the other end.

The portions Ln and Lm of the channel 41 and the portion R of the channel 42
n and Rm are arranged symmetrically with respect to the XZ plane including the flow path 31. The lengths of the portions Ln and Rn in the X direction are equal,
The lengths of the portions Lm and Rm are also equal. The heights of ΔLn and ΔRn in the Z direction are equal, and the heights of ΔLm and ΔRm are also equal.
The widths and heights of these portions Ln, Lm and portions Rn, Rm can be changed as appropriate in each device or even in the same device. The flow rate and flow rate of the resin a and the resin b are determined by the width and height of these flow paths.

FIG. 8 shows a cross-sectional shape of the resin layer at a position downstream of the composite resin flow path with respect to FIG. Channel 31
The resin c that has flowed out of the plate is deformed by the flow action of the resin a and the resin b indicated by the arrows in FIG. 6, and the sectional shape of the resin layer C is a lens-shaped block as shown in FIGS. 8 and 15a. Have a continuous structure. In FIG. 8, in order to facilitate understanding of the relationship between the shapes of the flow channels 41 and 42 and the cross-sectional shape of the finally manufactured resin sheet,
Flow paths 41 and 42 upstream of the position in this figure are written for convenience.

FIGS. 9 and 10 are diagrams schematically showing another example of the device according to the first embodiment. FIG.
It is arrow sectional drawing of the I-III line. In the apparatus of FIG.
The portion Ln of the channel 41 and the channel
Rm is arranged symmetrically, and Lm of the passage 41 and Rn of the passage 42 are arranged symmetrically. The cross-sectional shapes of the flow paths 41 and 42 are the same as in FIG. FIG. 10 is a composite diagram displayed in the same manner as in FIG.

When this apparatus is used, a resin sheet as shown in FIG. 10 or FIG. 15d is manufactured. FIG. 11 is a schematic plan sectional view showing another example of the internal structure of the apparatus for manufacturing a resin sheet useful for the surface light source element of the present invention. The difference from the device according to the first embodiment (FIG. 3) is that there is no flow path for resin c, and the other points are basically the same as those of the device according to the first embodiment. is there.

That is, this device has the same composite resin channel 21 and channels 41 and 42 as the device according to the first embodiment. Various arrangements, sizes and shapes of the portions Ln and Lm of the flow channel 41 and the portions Rn and Rm of the flow channel 42 can be adopted as in the case of the device according to the first embodiment. In the apparatus of FIG. 12, with respect to the XZ plane passing through the center of the composite flow forming section 22,
The portion Ln of the channel 41 and the Rm of the channel 42 are symmetrical, and the Lm of the channel 41
And Rn of the flow path 42 are symmetrically arranged. The cross-sectional shapes of the flow paths 41 and 42 are the same as in FIG. With this device,
As shown in FIG. 13, a resin sheet having a polygonal line shape in the xy cross section of the boundary surface between both resin layers is manufactured. FIG. 13 is a composite diagram displayed in the same manner as in FIG.

In the present invention, a wide range of thermoplastic resins can be used as the resin. The resins a, b, and c for the resin layers A, B, and C are not particularly limited as long as they have transparency. For example, various acrylic resins represented by polyethylene terephthalate, polyvinyl chloride, polystyrene, polycarbonate, polymethyl methacrylate, amorphous polyolefin, polyamide, polymethylpentene, copolymer resins or blend resins thereof, acrylonitrile / styrene Copolymer, methyl methacrylate / styrene copolymer, and the like. When transparency, weather resistance and the like are particularly required, an acrylic resin is preferable, and polymethyl methacrylate is particularly preferable.

The combination of each resin a, resin b, and resin c is appropriately selected according to the purpose. When imparting light diffusion, it is necessary to consider the difference in refractive index. Since the adhesion between the resins affects the productivity of the sheet, it is necessary to consider the adhesion between the resins. It is also important to use a combination of resins having a small difference in the melting temperature of each resin to be laminated.

In order to prevent sheet warpage, A, C, B
It is preferable that the physical properties of the resins a and b of the layer A and the layer B are the same or similar.
And the resin b are preferably the same or the same resin. In addition, when a resin sheet is given a design or a sense of depth, or when it is given an optical property, it can be colored by mixing an organic or inorganic dye or pigment in each resin layer. A diffusing agent or the like can be mixed.

FIGS. 14A to 14I, FIGS. 15A to 15K, and FIGS. 15A to 15K show the concavo-convex shape of the interface between the resin layers formed on the xy section of the sheet.
16a to h, linear shapes such as a polygonal line shape, a saw blade shape, a semicircle shape, a semielliptical shape, a wavy shape, an nth parabolic shape,
It is possible to take a curved shape such as a parabola of order / n. When imparting light diffusing property to the resin sheet, in the xy cross section of the sheet, the light is appropriately selected by appropriately selecting the angle α or h / p between the boundary surface having the uneven shape shown in FIGS. 15A and 16B and the sheet surface. Diffusivity can be adjusted. In addition, the repetition pitch p of the concavo-convex unit, the resin layer C or the resin layer B
(That is, the values of v and t in the figure), the thickness of the entire sheet, and the like are appropriately determined according to the purpose of providing the function. In addition, the value of the repetition pitch p or h / p in the unevenness unit can be appropriately changed even in one sheet. However, from the viewpoint of achieving uniform light diffusion, it is preferable that the pitch p be the same in one sheet.

Next, the surface light source device of the present invention will be described. Since the resin sheet as described above has excellent light diffusing properties, it can be used as a light guide of a surface light source element. For the surface light source element, the same directions as the x, y, and z directions of the resin sheet constituting the surface light source are defined as the x, y, and z directions, respectively. For the light guide (resin sheet), for convenience of explanation, the reflection material 52 is used.
The side on which is pasted is referred to as the back surface (or lower surface), and the side on which the light diverting sheet 54 such as a prism is laminated is referred to as the front surface (or upper surface) (FIG. 17). Therefore, these vertical relations do not always coincide with the vertical relation when the surface light source element is actually used.

In the surface light source device of the present invention, the light source 53 is provided on the light guide and at least one end surface (yz surface) in the x direction. In FIG. 17, it is installed on only one end face.
A reflecting material is appropriately applied to the other two or three end surfaces where the light source is not installed. When the light guide is composed of two or more resin layers having different refractive indexes, and the interface between the resin layers has an uneven shape, light is reflected or refracted at the interface and the surface of the light guide according to Snell's law. While propagating through the light guide. Of the light reaching the front or back surface of the light guide, light exceeding the critical angle is emitted out of the light guide.

The inventors of the present invention have found that in the surface light source element, the relationship between the light output intensity (I) at a certain point and the output light intensity (I ₀ ) at the end of the light incident surface is determined by the output rate (ψ), It was experimentally found that the distance (L ') from the light incident surface and the thickness (t) of the light guide were expressed by the following equation (1). I = I ₀ (1−ψ / 100) ^{L ′ / t} (1) If the length (L) and the thickness (t) of the light guide are determined from the equation (1), the emission rate (ψ) It can be seen that the uniformity of the luminance in the light emitting surface is determined by the above.

The emission rate (ψ) of the light guide is determined by measuring the luminance at the center of the light guide in the z-direction at intervals of 20 mm from the light incident surface and determining the ratio of the distance from the light incident surface to the thickness. (L '
/ T) is plotted on the abscissa and the logarithm of the luminance is plotted on the ordinate, and its slope (K) is obtained by the following equation (2). ψ = (1−10 ^K ) × 100 (2) In the present invention, the surface light source element is obtained by using the degree of variation (R%) represented by the following equation (3) as a measure of the uniformity of the luminance distribution. Were evaluated for the uniformity of the luminance distribution. The degree of variation (R%) is about 15% from the light-incident end face toward the x-direction at the approximate center of the light guide in the z-direction.
at points separated by mm and every 20 mm thereafter
The luminance is measured at intervals of 20 mm within the range up to the opposite end, and the maximum value of the measured luminance (I _max ), the minimum value of the measured luminance (I _min ), and the average value of the measured luminance (I _av ) are obtained. (3).

[0031] _{R% = {(I max -I} min) / I av} × 100 ... (3) As a result, the output rate ([psi) and the variation degree (R%), the light guide length (L ) And the thickness (t) are found to have a specific relationship. As the emission rate (ψ) increases, the degree of variation (R%) increases accordingly, and the emission rate (ψ) is constant. Then, the ratio (L) of the length (L) and the thickness (t) of the light guide is
/ T) increases, the degree of variation (R%) also increases. That is, in a light guide of a certain size,
The uniformity (variability) of the luminance distribution in the light exit surface of the light guide depends on the exit rate (ψ) from the light guide, and the luminance distribution is controlled by controlling the exit rate (ψ). It can be seen that the uniformity can be achieved.

On the other hand, the surface light source element needs to efficiently emit the light incident from the incident end face from the light emitting face. Therefore, the light emission rate (ψ) of the light guide must be a certain value or more. If the emission rate is too low, the amount of light that reciprocates in the light guide without being emitted from the emission surface increases. That is, the emission rate (ψ) of the light guide is set to an optimal value that is appropriate for the size of the light guide in consideration of both the uniformity of the brightness distribution in each region of the light emission surface and the increase in brightness. is necessary.

As a resin sheet suitable for such a light guide, a difference in refractive index between resins of adjacent resin layers is 0.03 to 0.03.
It is preferably 0.3, more preferably 0.05 to 0.25, and particularly preferably 0.05 to 0.20. If the refractive index difference is too small, the change in the light traveling direction at the resin interface will be too small, and the emission rate (ψ) of the light guide will be too small. Conversely, if the difference in the refractive index is too large, the change in the traveling direction of light at the resin interface is too large, and the emission rate (ψ) of the light guide is too large.

Preferred combinations of resins include combinations of polycarbonate, polyethylene terephthalate, polystyrene, polyethylene, or the like with polymethyl methacrylate. When the resin sheet of the present invention is used as a light guide for a surface light source element, the emission rate of the light guide is the same as the pitch p and the ratio h / p in FIGS. 15A to 15K and FIGS.
Affected by

The difference in the refractive index between the adjacent resin layers is 0.03 to
When the pitch p and the height h of the uneven shape of the boundary surface of the resin layer in the xy cross section are both constant, h /
The value of p is preferably about 0.05 to 0.5. It is desirable that the pitch of the uneven shape is about 600 μm or less.
Those larger than this are not suitable for applications where appearance is important, such as signboards, traffic guide boards, and liquid crystal display devices, because the uneven structure is visible to the naked eye. When it is used for a surface light source element for a liquid crystal display device, it is preferable that the thickness is about 200 μm or less. Although the lower limit value of the pitch of the uneven shape is not particularly limited, it is preferably about 50 μm or more in consideration of ease of manufacturing.

When the resin sheet of the present invention is used as a light guide in an edge light type surface light source element as shown in FIG. 17, the light emitted from the light guide surface exhibits its maximum light intensity. The direction is inclined at least 50 degrees in the x direction with respect to the normal to the surface (xz plane). Therefore, it is necessary to change the direction of the emitted light to the normal direction where the observer is located.
Therefore, in the surface light source element of the present invention, the light diverting sheet 54 is placed on the light guide.

Examples of the light diverting sheet include a diffusion sheet and a lens sheet in which a large number of columnar lens units are arranged on at least one surface so that the longitudinal directions of the columns are parallel. The shape of the lens constituting the lens sheet can be various types depending on the purpose, for example,
Examples include a prism shape, a lenticular lens shape, and a corrugated shape. The pitch of the lens unit of the lens sheet is
It is preferably about 30 to 500 μm. In addition, the lens sheet can be placed so that the lens surface is on the light guide side or on the opposite side in consideration of the distribution of light emitted from the light guide.

When a prism sheet is used as the lens sheet, the prism apex angle is appropriately selected according to the distribution of light emitted from the light guide, but is generally 50-1.
It is preferable to set the range to 20 degrees. In the surface light source element of the present invention, a plurality of light diverting sheets can be used by being superposed as necessary. For example, when using two lens sheets, the two lens sheets
They can be stacked so that the longitudinal directions of the columns of the columnar lens units are parallel to each other, or can be stacked at an angle. The lens sheets can be mounted so that each lens surface is in either the upper or lower direction, or the lens surfaces of both lens sheets can be mounted in opposite directions. .

A preferred example of using a plurality of lens sheets as the light diverting sheet will be described below. A prism sheet is used as a lens sheet. The first prism sheet has a prism surface facing the light guide (that is, downward), and the longitudinal direction of the columnar prism unit is z of the surface light source element.
It is placed on the surface of the light guide so as to be parallel to the axial direction. The second prism sheet is placed on the first prism sheet with the prism surface opposite to the light guide (that is, facing upward), and the longitudinal direction of the columnar unit of the prism is the surface light source element. To be parallel to the x-axis direction. At this time, the first prism sheet having a vertex angle of 50 to 70 degrees is used, and the second prism sheet has a vertex angle of 80 degrees.
It is desirable to use one having a temperature of 100 degrees.

When only one lens sheet is used as the light diverting sheet, a prism sheet having an apex angle of 50 to 70 degrees is used, and the prism surface is on the light guide side, and the longitudinal direction of the columnar unit of the lens is used. Is preferably placed so as to be parallel to the z-axis of the surface light source element.

[0041]

The present invention will be described below in detail with reference to examples. The evaluation method of the surface light source element is as follows. 1. Measurement of luminance value in normal direction (1) Small surface light source element As shown in FIG. Excluding the first 5 mm in the x direction from the light incident surface, the light incident surface is divided into squares of 20 mm square, which are defined as regions i, ii, iii,... N.

A cold cathode fluorescent lamp 53 (KC130T4E 4 mmφ × 130 mm, manufactured by Matsushita Electric Co., Ltd.) installed on one end surface (yz surface) in the x direction of the light guide is connected to a DC power supply via an inverter (CXA-M10L manufactured by TDK). Connect and apply DC12V to light up. The surface light source element is placed on the measuring table. Next, a luminance meter 56 (Minolta nt) is passed through the center of the measurement area i in the normal direction of the xz plane.
-1)). Further, the luminance meter is fixed at a distance from the surface light source element so that the measurement circle of the luminance meter is 8 to 9 mmφ. In this state, the normal luminance of the measurement area i is measured, and this value is defined as Gi.

The surface light source element is moved by 20 mm in the x direction, and the normal luminance value of the area ii is measured in the same manner, and this value is defined as Gii. By repeating this operation, the normal luminance value is measured for all the regions. (2) Large surface light source device The measurement is performed in the same manner as in the above (1) small surface light source device, except that a 30 W fluorescent lamp is used as the light source. 2. Emission Rate Using the values of Gi to Gn measured in the above 1, the horizontal axis represents the ratio (L '/ t) between the distance between the center of each measurement area and the light incident end of the light guide and the light guide thickness. The vertical axis is the logarithm of the normal luminance (log
Gi ... log Gn) are plotted. After obtaining the slope (K) of the straight line obtained by the plot, the emission rate (ψ) is obtained by the above equation (2). 3. Variation (R%) Among the Gi to Gn measured in the above 1, the maximum value is I
Assuming that max is the minimum value, Imin is the minimum value, and Iav is the average value, R% is calculated from the above equation (3).

REFERENCE EXAMPLE 1 Polymethyl methacrylate (Acrypet MD, manufactured by Mitsubishi Rayon Co., Ltd.) as resin a and resin b, and polycarbonate (Iupilon H, manufactured by Mitsubishi Gas Chemical Co., Ltd.) as resin c.
-3000). The apparatus shown in FIGS. 1 to 5 was used.
As the die 8 for the resin c, a die having a slit gap of 1.7 mm at the outlet of the flow path 31 was used, and as the die 9, the composite flow forming portion having the structure shown in FIGS. 6 and 7 was used. The groove portions ΔRn and ΔLn were 1 mm, the pitch P of the groove portions was 5 mm, and the width of the portions Ln and Rn was 2.5 mm (P / 2).

The shaping temperature was 260 ° C. The polymethyl methacrylate is melted in the first extruder 1, passed through the extrusion channel 13 and supplied to the die 9.
Flowed into. At the same time, the polycarbonate was melted in the second extruder 2 and supplied to the die 8 through the extrusion flow path 14 and flowed into the composite flow forming section 22 from the flow paths 41 and 42.
The width (X direction) of the composite resin channel 21 is 50 cm and the thickness (Y direction)
Was set to 5 mm. In the composite flow forming section, the two resins were combined to form a composite resin flow, which was extruded from the composite outlet 23 to produce a composite sheet having a thickness of 5 mm and a width of 50 cm.

The sheet obtained had a smooth outer surface, no warp, a cross section having the shape shown in FIG. 15a, a pitch of the irregularities of 5 mm, and h / p of 0.25. This sheet had good external appearance and light transmittance, was free from uneven light diffusion, and was suitable for applications such as a diffusion plate. Reference Example 2 The thickness (Y direction) of the composite resin channel 21 is 3 mm, and the width (X direction).
Is 60 cm, the slit gap at the outlet of the flow channel 31 is 2.6 mm, the pitch P of the groove is 0.3 mm, and the width of the portions Ln and Rn is 0.15 mm.
A sheet having a thickness of 3 mm and a width of 60 cm was continuously formed in the same manner as in Reference Example 1 except that (P / 2) was used.

The resulting sheet had a smooth outer surface, no warp, and a cross section having the shape shown in FIG. 15e. The pitch p of the irregularities was 0.3 mm, and h / p was 0.15. . This sheet was good in both appearance and light transmittance, and had no unevenness in light diffusion, and was suitable for applications such as a diffusion plate and a light guide. Reference Example 3 As a structure of the flow paths 41 and 42, as shown in FIG.
A resin sheet having a thickness of 3 mm and a width of 60 cm was continuously formed in the same manner as in Reference Example 2 except that a resin sheet having a structure in which the position was relatively shifted by P / 2 was used.

The obtained sheet had a smooth outer surface, no warp, and a cross section having a shape in which the pitch of the upper and lower convex portions was relatively shifted by p / 2, as shown in FIG. 15h. Reference Example 4 The thickness (Y direction) of the composite resin flow path is 3 mm, the thickness (Y direction) of the flow path 31 is 2.8 mm, and the pitch P of the grooves of the flow paths 41 and 42 is set.
Was set to 0.15 mm and the width of the portions Ln and Rn was set to 0.075 mm (P / 2), and a sheet having a thickness of 3 mm and a width of 60 cm was continuously formed in the same manner as in Reference Example 2.

The resulting sheet had a smooth outer surface, no warpage, and a cross section having the shape shown in FIG. 15e. Reference Example 5 The thickness (Y direction) of the composite resin flow path is 10 mm, the thickness (Y direction) of the flow path 31 is 9.6 mm, and the pitch P of the grooves of the flow paths 41 and 42 is P.
Was set to 0.5 mm and the width of the portions Ln and Rn was set to 0.25 mm (P / 2), and a sheet having a thickness of 10 mm and a width of 60 cm was continuously formed in the same manner as in Reference Example 2.

The resulting sheet had a smooth outer surface, no warpage, and a cross section having the shape shown in FIG. 15e. Reference Example 6 The same polymethyl methacrylate as in Reference Example 1 was used as resin a, and the same polycarbonate as in Reference Example 1 was used as resin b. The apparatus shown in FIGS. 1, 2, 11, 12, and 13 was used. The groove portions ΔRn and ΔLn were 1 mm, the pitch P of the groove portions was 5 mm, and the width of the portions Ln and Rn was 2.5 mm (P / 2).

The shaping temperature was 260 ° C. The polymethyl methacrylate is melted in the first extruder 1, passed through the extrusion channel 13 and supplied to the die 9.
Flowed into. At the same time, the polycarbonate was melted in the second extruder 2, supplied to the die 9 through the extrusion channel 14, and allowed to flow into the composite flow forming section 22 from the channel 42. In the composite flow forming section, the two resins were combined to form a composite resin flow, which was extruded from the composite outlet 23 to produce a composite sheet having a thickness of 5 mm and a width of 50 cm.

The obtained sheet had a smooth outer surface, no warp, a cross section having the shape shown in FIG. 16b, an apex angle β of about 90 degrees, and a pitch of unevenness of 5 mm. This sheet had good external appearance and light transmittance, was free from uneven light diffusion, and was suitable for applications such as a diffusion plate. Reference Example 7 The thickness (Y direction) of the composite resin flow path was 3 mm, and the flow paths 41 and 42 were used.
The groove pitch P is 0.3 mm and the width of the parts Ln and Rn is 0.1
3 mm in the same manner as in Reference Example 6 except that mm (P / 3) was used.
Sheets having a thickness of 50 cm and a width were continuously formed.

The resulting sheet had a smooth outer surface, no warp, and a cross section having the shape shown in FIG. 16h. Example 1 This is an example of a small surface light source element. The resin sheet obtained in Reference Example 2 was 100 mm long in the z direction and 300 mm long in the x direction.
Into a light guide (small surface light source element) for measuring the emission ratio. A silver-deposited PET (polyethylene terephthalate) film is adhered to the two xy end faces in the length direction of the light guide with an adhesive, and a silver-deposited PET film is taped to the back of the light guide to form a reflection surface. did. Further, a cold-cathode tube is installed beside the other yz end face of the light guide so that the long side of the tube is in the z-direction, and the cold-cathode tube and the light guide are silver-evaporated PE.
Covered with T film.

On the other hand, a large number of columnar prism units having an apex angle of 63 degrees and a pitch of 50 μm are formed on a PET film with an acrylic UV curable resin having a refractive index of 1.53 so that their longitudinal directions are parallel to each other. Was manufactured. This was placed on the surface of the light guide with the prism surface facing down and the longitudinal direction of the prism unit was in the z direction.
The emission efficiency of the small surface light source device manufactured as described above was evaluated, and the results shown in Table 1 were obtained.

In the same manner as described above, the resin sheet obtained in Reference Example 2 was cut into a length of 100 mm in the z direction and a length of 105 mm in the x direction to obtain a light guide. A silver-evaporated PET film was adhered to the two xy end faces and one yz end face of the light guide with an adhesive, and a cold cathode tube was placed beside the other yz end face of the light guide. Other conditions were the same as above to produce a small surface light source element for evaluating the degree of variation, and the results in Table 1 were obtained.

Examples 2 to 4 Using the resin sheets obtained in Reference Examples 3, 4 and 7, a small surface light source element was manufactured in the same manner as in Example 1, and the performance was evaluated. The results in Table 1 were obtained. Comparative Example 1 Two acrylic resin plates of 1.5 mm × 100 mm (z direction) × 300 mm (x direction) were prepared. One side (front side) of one resin plate
Then, a columnar prism having a pitch of 0.1 mm and h / p = 0.25 was formed in parallel with the z direction by thermal transfer using a mold. Another acrylic resin plate was superposed and bonded on the prism-formed surface of the plate with the prism-formed surface facing upward to produce a light guide having a hollow concavo-convex portion (FIG. 19). Using this light guide, in the same manner as in Example 1, a small surface light source element for emission rate evaluation was manufactured.
The performance was evaluated, and the results in Table 1 were obtained.

Next, 1.5 mm × 100 mm (z direction) × 105 mm
Two (x-direction) acrylic resin plates were prepared, and in the same manner as above, a small surface light source element for evaluating the degree of variation was manufactured.
The performance was evaluated, and the results in Table 1 were obtained. Each of the obtained surface light source elements had a high emission rate and a high degree of variation. COMPARATIVE EXAMPLE 2 One of a 3 mm × 100 mm (Z direction) × 300 mm (X direction) transparent acrylic plate was used by using a mold in which a rough surface was formed by performing a blast treatment using glass beads on a mirror-finished stainless steel plate. The rough surface was transferred to the surface by thermal transfer to obtain a light guide. Also, 3mm x 100mm (Z direction) x 1
The rough surface was transferred by thermal transfer to one surface of a 05 mm (X direction) transparent acrylic plate to obtain a light guide. Using these light guides, a small surface light source element was manufactured in the same manner as in Example 4, and its performance was evaluated. The results shown in Table 1 were obtained.

Each of the obtained surface light source elements had a high emission rate and a high degree of variation. Comparative Example 3 Using a white paint containing titanium oxide particles on the back surface of an acrylic resin plate of 3 mm × 100 mm (z direction) × 105 mm (x direction),
A speckle pattern was formed by screen printing. At this time, the density of the spots was reduced near the light incident side end surface, and increased as the distance from the light incident surface in the x direction increased. Using this as a light guide, a small surface light source element was manufactured in the same manner as in Example 4, and its performance was evaluated. The results in Table 1 were obtained.

In the obtained surface light source element, a spot pattern was observed through the prism although the degree of variation was small. Embodiment 5 This is an embodiment of a large surface light source element. The resin sheet obtained in Reference Example 5 was cut, and 10 mm × 600 mm (z direction) ×
Two light guides of 1000 mm (x direction) were obtained.

Using these light guides, in the same manner as in Example 1, a large surface light source element for evaluating the emission ratio and for evaluating the degree of variation was manufactured, and its performance was evaluated. The results shown in Table 1 were obtained. Comparative Example 4 The large surface light source elements shown in Table 1 were manufactured in the same manner as in Comparative Example 1, and the performance was evaluated. The results shown in Table 1 were obtained.

[0061]

[Table 1]

[0062]

According to the present invention, a surface light source element can be obtained by using a resin sheet as a light guide.

[Brief description of the drawings]

FIG. 1 is a schematic plan view of an example of an apparatus useful for manufacturing a resin sheet used for a surface light source element of the present invention.

FIG. 2 is a schematic side view of the apparatus of FIG.

FIG. 3 is a schematic plan sectional view schematically showing an example of the internal structure of the apparatus shown in FIG.

FIG. 4 is a sectional view taken along the line II in FIG. 3;

FIG. 5 is a perspective view taken along the line II-II in FIG. 4;

FIG. 6 is a schematic sectional view for explaining an example of a resin flow path in the apparatus of FIG.

FIG. 7 is a sectional view taken along line IV-IV in FIG. 6;

FIG. 8 is a schematic diagram showing a cross-sectional shape of a resin layer formed in the composite resin flow channel shown in FIG.

FIG. 9 is a schematic cross-sectional view for explaining another example of the resin flow path in the apparatus of FIG.

10 is a schematic diagram illustrating a cross-sectional shape of a resin layer formed in the composite resin flow channel in FIG.

FIG. 11 is a schematic plan sectional view showing another example of the internal structure of an apparatus useful for manufacturing a resin sheet used for the surface light source element of the present invention.

FIG. 12 is a schematic cross-sectional view illustrating an example of a resin flow path in the apparatus of FIG.

13 is a schematic diagram showing a cross-sectional shape of a resin layer formed in the composite resin flow channel in FIG.

14a to 14i are cross-sectional views each showing an example of the structure of a resin sheet obtained by the device of the present invention.

15a to 15k are cross-sectional views each showing another example of the structure of the resin sheet obtained by the apparatus of the present invention.

16a to 16h are cross-sectional views each showing another example of the structure of the resin sheet obtained by the apparatus of the present invention.

FIG. 17 is a schematic view illustrating an example of the surface light source element of the present invention.

FIG. 18 is a schematic diagram for explaining a method for evaluating a surface light source element in an example.

FIG. 19 is a cross-sectional view illustrating a structure of a resin sheet obtained in a comparative example in which an air layer exists inside.

[Explanation of symbols]

 21 ... Resin flow path 22 ... Composite flow forming part 23 ... Composite flow outlet 31 ... Slit-shaped flow path 41, 42 ... Resin flow path for resin layer 51 ... Light guide 52 ... Reflective agent 53 ... Light source 54 ... Light deflection sheet

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Kazuki Chiba 3816 Noto, Tama-ku, Kawasaki City, Kanagawa Prefecture, Mitsubishi Rayon Co., Ltd. Tokyo Technical Information Center (58) Field surveyed (Int. Cl. ⁷ , DB name) ) B32B 1/00-35/00 G02B 6/00-6/00 351

Claims (4)

(57) [Claims] 1. A resin sheet having a laminated structure in which a transparent resin layer C is sandwiched between a transparent resin layer A and a transparent resin layer B, wherein the outer surface is a smooth resin sheet, When the refractive index is different and the thickness direction of the sheet is y and the width direction is x, the boundary surface between the resin layers A and C and the resin layers B and C A light guide (51) is a resin sheet in which at least one of the boundary surfaces of the light guide has an uneven shape, and a reflecting material (52) is provided on the back surface of the light guide. A light source (53) is installed on the surface of the light guide, and a light diverting sheet (54) having the function of changing the light emitted from the surface of the light guide in the normal direction of the light guide is placed on the surface of the light guide. The installed surface light source element. 2. The liquid crystal surface light source device according to claim 1, wherein the unevenness of the boundary surface of the resin layer in the xy cross section of the resin sheet is an unevenness having a pitch p of 50 to 200 μm. 3. A resin sheet having a laminated structure of a transparent resin layer A and a transparent resin layer B, having a smooth outer surface, wherein the adjacent resin layers have different refractive indices of resin, and have a thickness of the sheet. In a cross section represented by an xy plane when the direction is y and the width direction is x, a resin sheet having a concavo-convex shape at a boundary surface between the resin layer A and the resin layer B is defined as a light guide (51). A reflector (52) is installed on the back surface of the light body, a light source (53) is installed on at least one end face (yz plane) in the x direction of the light guide, and light emitted from the surface of the light guide is guided. A surface light source element in which a light diverting sheet (54) having a function of changing the direction of the light body in the normal direction is provided on the surface of the light guide. 4. The surface light source element for a liquid crystal according to claim 3, wherein the uneven shape of the boundary surface of the resin layer in the xy cross section of the resin sheet is an uneven shape having a pitch p of 50 to 200 μm.