JP2012037484A - Shape evaluation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a shape evaluation method that easily evaluates a rugged shape formed on a light control plate.SOLUTION: The present invention relates to a shape evaluation method of evaluating a rugged shape 13 of a sample light control plate 1 having a first surface 11 on which the rugged shape 13 is formed and a second surface 12 which is positioned on the opposite side from the first surface 11, the rugged shape 13 extending in a first direction. The shape evaluation method includes an acquisition process of acquiring an index representing the rugged shape 13 for the sample light control plate 1 by measuring at least one of first total light transmittance Tt1 when light is made incident from the first surface 11 and second total light transmittance Tt2 when light is made incident from the second surface 12, the index being defined using at least one of the first total light transmittance Tt1 and second total light transmittance Tt2; and an evaluation process of evaluating the rugged shape 13 of the sample light control plate 1 from the index acquired in the acquisition process based upon the correlation between an index and a rugged shape previously acquired for a reference light control plate whose rugged shape is already known.

Description

  The present invention relates to a shape evaluation method, and more particularly, to a method for evaluating an uneven shape formed on the surface of a light control plate.

  As an optical component for uniformly emitting incident light, there is a light control plate such as a light diffusion plate. In recent years, a light control plate is known in which fine irregularities are formed on the surface to make the emitted light uniform. In such a light control plate, the emission performance varies depending on the shape of the unevenness. For this reason, it is inspected whether the formed uneven shape is a desired uneven shape.

  As a method for evaluating the concavo-convex shape for the inspection of the concavo-convex shape, Patent Document 1 (Japanese Patent Laid-Open No. 2007-270132) describes a method for evaluating the concavo-convex shape formed on the optical sheet using a horizontal force microscope. Has been. Further, in Patent Document 2 (Japanese Patent Laid-Open No. 10-119096), a two-dimensional planar image and a three-dimensional stereoscopic image of a mold and a molded product are respectively acquired by a laser microscope, and a concave portion on the mold side is obtained from these images. The method of calculating the volume of this and the volume of the convex part of a molded product, and evaluating uneven | corrugated shape is described.

JP 2007-270132 A JP 10-1119096 A

  However, in the methods disclosed in Patent Document 1 and Patent Document 2, in order to observe the uneven shape formed on the light control plate with a microscope, a test cross-section piece of the light control plate to be evaluated for the uneven shape is used. It is necessary to prepare. Further, since the light control plate is often a transparent member, it is necessary to devise such as coloring in order to clearly grasp the shape with a microscope.

  An object of this invention is to provide the shape evaluation method which can evaluate easily the uneven | corrugated shape formed in the light-control board.

The shape evaluation method according to the present invention has a first surface on which a concavo-convex shape is formed and a second surface located on the opposite side of the first surface, and a concave portion or A shape evaluation method for evaluating the concavo-convex shape of the sample light control plate in which the convex portion extends in the first direction, and includes the following acquisition step and evaluation step.
Acquisition step: an index defined using at least one of the first total light transmittance when light is incident from the first surface and the second total light transmittance when light is incident from the second surface A step of acquiring at least one of the first and second total light transmittances with respect to the sample light control plate and obtaining the index by using as an index representing the uneven shape.
Evaluation step: A step of evaluating the concavo-convex shape of the sample light control plate from the index acquired in the acquisition step based on the correlation between the index and the concavo-convex shape acquired in advance with respect to the reference light control plate having a known concavo-convex shape.

  In this shape evaluation method, the above-mentioned index is obtained by measuring at least one of the first and second total light transmittances, instead of evaluating the concavo-convex shape by observing with a microscope or the like. The uneven shape is evaluated. Thereby, in order to evaluate the uneven shape of the light control plate, it is not necessary to prepare a test cross-section piece for observation with a microscope or the like. Further, the first and second total light transmittances that define the index can be easily measured using, for example, a transmittance meter. As a result, it is possible to easily evaluate the uneven shape formed on the light control plate.

  In the shape evaluation method according to the present invention, the light incident on the first surface in the measurement of the first total light transmittance is light that has passed through a slit extending in a direction orthogonal to the first direction. The light incident on the second surface in the measurement of the second total light transmittance can be light that has passed through a slit extending in a direction that coincides with the first direction.

  In this shape evaluation method, in the first total light transmittance, the influence of the constituent material of the light control plate is large, and the influence of the uneven shape tends to be small. In the second total light transmittance, the light control plate There is a tendency that it is easily influenced by both of the constituent materials and the like and the uneven shape. Here, the index is defined using at least one of the first and second total light transmittances. Thus, for example, the index can be appropriately defined according to the constituent material of the light control plate, and the uneven shape of the light control plate can be more accurately evaluated.

  The index may be a difference between the first total light transmittance and the second total light transmittance, or may be the second total light transmittance.

  When the index is the difference between the first total light transmittance and the second total light transmittance, the degree affected by the concavo-convex shape can be extracted, so the light control plate can be extracted more accurately. The uneven shape can be evaluated. Further, when the index is the second total light transmittance, the uneven shape of the light control plate can be more easily evaluated.

  According to the present invention, it is possible to easily evaluate the uneven shape formed on the light control plate.

It is a perspective view of the light diffusing plate measured by the shape evaluation method concerning this embodiment. It is the enlarged view which expanded the schematic block diagram and B part of the manufacturing apparatus which manufactures a resin sheet, and showed the layer structure of the resin sheet typically. It is a principal part expanded sectional view of the shape roll with which it mounts | wears as a lower roll. It is a flowchart which shows the shape evaluation method which concerns on this embodiment. It is a schematic diagram for demonstrating the acquisition method of a total light transmittance. It is a schematic diagram for demonstrating the acquisition method of a 1st total light transmittance. It is a schematic diagram for demonstrating the acquisition method of the 2nd total light transmittance. It is a principal part expanded sectional view of the shape roll with which the lower roll which concerns on a present Example is mounted | worn. It is the graph which showed the height of the convex part acquired by the shape evaluation method which concerns on a present Example, and the height of the convex part acquired by the cross-section observation method.

  Hereinafter, embodiments of a shape evaluation method according to the present invention will be described with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. Further, the dimensional ratios in the drawings do not necessarily match those described.

(Light diffusion plate)
First, the light diffusing plate 1 on which the concavo-convex shape evaluated by the shape evaluation method according to the present embodiment is described with reference to FIG. As shown in FIG. 1, the light diffusing plate 1 has a first surface 11 and a second surface 12. The second surface 12 is a surface located on the opposite side to the first surface 11. Light incident from the first surface 11 can be emitted from the second surface 12.

  A convex portion 13 is formed on the first surface 11. The convex portion 13 extends in the first direction X11 and is formed in parallel in a second direction X12 orthogonal to the first direction X11. Accordingly, the first surface 11 has a concavo-convex shape formed by the plurality of convex portions 13. The convex part 13 is formed in a semicircular arc shape in cross section perpendicular to the first direction X11, and its height H is, for example, 5 μm to 500 μm. In addition, the cross-sectional shape of the convex part 13 is not only a semicircular arc shape as shown in FIG. 1, but also a shape corresponding to any one member of, for example, a cylindrical body cut by a plane not including its axis ( (Cylindrical lens shape). Further, the cross-sectional shape of the convex portion 13 may be a semi-elliptical arc shape, a flat curved line shape, or the like. The second surface 12 is usually a flat surface, and may be a smooth surface that does not have light diffusibility. However, the second surface 12 may be a surface having light diffusibility over the entire surface. Such a light diffusing plate is suitably used in a transmissive image display device such as a liquid crystal television, for example. Specifically, the light diffusing plate is disposed on a plurality of light sources, and uniformizes incident light from the light sources to achieve a luminance uniformity degree. Used to generate high planar light.

[Production method of light diffusion plate]
Next, a method for manufacturing the light diffusing plate 1 will be described with reference to FIGS. FIG. 2A is a schematic configuration diagram of a manufacturing apparatus for manufacturing a resin sheet to be a light diffusing plate. FIG. 2B is an enlarged view schematically showing the layer structure of the resin sheet by enlarging the B portion. FIG. 3 is an enlarged cross-sectional view of a main part of a shape roll mounted as a lower roll.

  The light diffusing plate 1 is manufactured by a resin sheet manufacturing apparatus 3 as shown in FIG. The resin sheet manufacturing apparatus 3 includes a first extruder 31 for heating and melting the translucent resin of the base layer (intermediate layer) 16 (see FIG. 2B), and a surface layer 15 (see FIG. 2B). The second extruder 32 for heating and melting the translucent resin, the feed block 33 to which the resin melted by the first and second extruders 31 and 32 is supplied, and the resin in the feed block 33 are in a sheet state A die 34 for extruding, and three pressing rolls 35 to 37 for molding the sheet-like resin extruded from the die 34.

  As the 1st and 2nd extruders 31 and 32, well-known extrusion molding machines, such as a single screw extruder and a twin screw extruder, can be used, for example. The first and second extruders 31 and 32 are provided with hoppers 38 and 39 for introducing resin into the cylinders of the extruder.

  The feed block 33 is not particularly limited as long as it is a type that can supply two or more kinds of resins to the die 34 and can be co-extruded in a laminated state. For example, a known feed block such as a two-type two-layer distribution type is used. Can do.

  The die 34 is not particularly limited as long as it is a co-extrusion die, and a known die such as a multi-manifold die can be used.

  The three pressing rolls 35 to 37 are each made of a cylindrical metal roll (for example, made of stainless steel, steel, etc.), and are continuously arranged in the vertical direction with all the rotation axes in parallel. In this specification, the three pressing rolls 35-37 shown to FIG. 2 (A) are called the upper roll 35, the intermediate | middle roll 36, and the lower roll 37 in an order from the top. In addition, the three press rolls 35-37 may be arrange | positioned continuously in the horizontal direction. A minute gap is formed between adjacent pressing rolls to allow the resin to pass through at a predetermined thickness. Moreover, the diameter of each press roll 35-37 is 100 mm-500 mm, for example.

  The peripheral surface of the upper roll 35 and the peripheral surface of the intermediate roll 36 are smoothed by, for example, mirror finishing. As shown in FIG. 3, a plurality of concave grooves 52 opposite to the semicircular arc-shaped convex portion 13 are formed in a streak pattern along the circumferential direction of the lower roll 37 on the peripheral surface of the lower roll 37. Yes. That is, the groove 52 has a substantially semicircular arc shaped cut surface perpendicular to the longitudinal direction (circumferential direction). The depth D of the concave groove 52 may be formed slightly larger than the height H of the convex portion 13.

  Next, the manufacturing method of the light diffusing plate 1 using the said manufacturing apparatus is demonstrated, referring FIG. 2 (A), FIG. 2 (B), and FIG. First, the translucent resin that becomes the base layer 16 is put into the hopper 38 of the first extruder 31, melted and kneaded, and then supplied to the feed block 33. On the other hand, a translucent resin that becomes the surface layer 15 is put into the hopper 39 of the second extruder 32, melted and kneaded, and then supplied to the feed block 33.

  Next, the resin in the feed block 33 is coextruded from the die 34. Thereby, the three-layer resin sheet 2 (refer FIG. 2 (B)) formed from the base layer 16 and the surface layer 15 which pinches | interposes the said base layer 16 is extruded continuously.

  Next, the resin sheet 2 as a continuous resin sheet extruded from the die 34 is sandwiched and pressed between the upper roll 35 and the intermediate roll 36 as shown in FIG. It is transported in close contact with the peripheral surface and cooled at that time.

  Thereafter, the resin sheet 2 is sandwiched and pressed between the intermediate roll 36 and the lower roll 37. Then, when the intermediate roll 36 and the lower roll 37 are pressed, the concave groove 52 formed on the peripheral surface of the lower roll 37 is transferred to one surface 2 a of the resin sheet 2. As a result, the resin sheet 2 is formed with a plurality of streak-like convex portions 13 parallel to the sheet flow direction.

  The resin sheet 2 is manufactured through the above steps, and then, after the resin sheet 2 is further cooled, the light diffusion plate 1 is obtained by cutting the resin sheet 2 in an appropriate size. The light diffusing plate 1 manufactured in this way has a three-layer structure. In FIG. 1, these layers are schematically shown without being explicitly shown.

  The light diffusion plate 1 is made of a translucent material. The refractive index of the translucent material is usually 1.46 to 1.62. Examples of the light-transmitting material include a light-transmitting resin material and a light-transmitting glass material. Examples of the light-transmitting resin material include PMMA (polymethyl methacrylate resin) (refractive index 1.49), cycloolefin resin ( Refractive index 1.51-1.55), polycarbonate resin (refractive index: 1.59), MS resin (methyl methacrylate-styrene copolymer resin) (refractive index: 1.56-1.59), polystyrene resin (Refractive index: 1.59), AS resin (acrylonitrile-styrene copolymer resin) (refractive index: 1.56-1.59), etc. are exemplified, preferably in terms of cost and low moisture absorption. Polystyrene resin.

[Evaluation method of height of convex part]
Next, a method for evaluating the shape of the convex portion 13 formed on the light diffusing plate 1 (shape evaluation method) will be described with reference to FIGS. In this embodiment, paying attention to the height H of the convex part 13 as an uneven | corrugated shape, this uneven | corrugated shape is evaluated by calculating | requiring the said height H. FIG. FIG. 4 is a flowchart illustrating the shape evaluation method according to the embodiment.

  The shape evaluation method of the light diffusing plate of the present embodiment is different from the conventional shape evaluation method in which the shape of the concavo-convex is evaluated by observing the cross section of the light diffusing plate 1 with a microscope. It is characterized in that the uneven shape is evaluated by measuring the first and second total light transmittances Tt1 and Tt2 of the sample light diffusion plate (sample light control plate).

  In the method for evaluating the shape of the light diffusing plate of the present embodiment, as shown in FIG. 4, first, based on a plurality of reference light diffusing plates (reference light control plates), the first total light transmittance Tt1 and the second A correlation between the index defined by the difference from the total light transmittance Tt2 and the height of the convex portion in the reference light diffusion plate is obtained (S1: preparation step). The reference light diffusion plate is a light diffusion plate having a known uneven shape.

  Here, the first and second total light transmittances Tt1 and Tt2 that define the index will be described with reference to FIGS. For convenience of explanation, the sample light diffusion plate and the reference light diffusion plate are also shown as the light diffusion plate 1.

  The total light transmittances as the first and second total light transmittances Tt1 and Tt2 are measured in accordance with JIS K7361-1 (1997). That is, as schematically shown in FIG. 5, a slit 62 is provided between the light source 61 and the light diffusing plate 1, and the light diffusing plate 1 is irradiated with the light output from the light source 61 and passing through the slit 62. Measured based on the transmitted light received at 63. However, the first and second total light transmittances Tt1 and Tt2 are different from each other in the arrangement relationship between the slit 62 and the light diffusion plate 1 as described below.

  As shown in FIG. 6, the first total light transmittance Tt1 is such that the long side direction X22 of the open portion of the slit 62 and the extending direction X11 of the convex portion 13 are orthogonal to each other, and the convex portion 13 is formed. Further, the value measured by arranging the light diffusing plate 1 with the first surface 11 facing the light source 61.

  As shown in FIG. 7, the second total light transmittance Tt2 is such that the long side direction X21 of the open portion of the slit 62 and the extending direction X11 of the convex portion 13 coincide with each other, and the convex portion 13 is formed. This is a value measured by arranging the light diffusing plate 1 with the second surface 12 not facing the light source 61.

  The correlation in the preparation step S1 is, for example, an index defined by the difference between the first total light transmittance Tt1 and the second total light transmittance Tt2 of the plurality of reference light diffusion plates and the convexity of the reference light diffusion plate. Based on the height of the part, it can be obtained using the least square method. What is necessary is just to acquire the height of the convex part of a reference | standard light diffusing plate by the cross-sectional observation method using a microscope etc., for example.

  Returning to FIG. 4, next, the first and second total light transmittances Tt1 and Tt2 of the sample light diffusion plate are measured to acquire the index (S2: acquisition step). The sample light diffusing plate is a light diffusing plate to be evaluated for unevenness. The first and second total light transmittances Tt1 and Tt2 of the light diffusion plate 1 (hereinafter referred to as the sample light diffusion plate 1) as the sample light diffusion plate are as described in JIS K7361-1 (1997). In conformity, it is measured using a transmission meter. The details of the first and second total light transmittances Tt1 and Tt2 are as described above.

  Next, by calculating the height H of the convex portion 13 of the sample light diffusing plate 1 from the index acquired in the acquiring step S2 based on the correlation acquired in advance based on the reference light diffusing plate in the preparation step S1, the unevenness is obtained. The shape is evaluated (S3: evaluation step). Specifically, the above-mentioned index acquired from the measured values of the first and second total light transmittances Tt1 and Tt2 in the acquisition step S2 is substituted into the relational expression acquired in advance in the preparation step S1 as a correlation. The concavo-convex shape is evaluated by obtaining the height H of the convex portion 13 of the light diffusing plate 1.

  As described above, according to the shape evaluation method of the present embodiment, the first and second shapes are not evaluated by obtaining the height H of the convex portion 13 by observing with a microscope or the like, but evaluating the concave and convex shape. By measuring the total light transmittances Tt1 and Tt2, the height H of the convex portion 13 is obtained to evaluate the concave-convex shape. Thereby, in order to evaluate the uneven shape of the sample light diffusing plate 1, it is not necessary to prepare a test cross-section piece for observation with a microscope or the like. Further, the first and second total light transmittances Tt1 and Tt2 for obtaining the index can be easily measured using a transmittance meter or the like. As a result, the uneven shape formed on the sample light diffusion plate 1 can be easily evaluated.

  In addition, according to the shape evaluation method of the present embodiment, the index is defined using the difference between the first total light transmittance Tt1 and the second total light transmittance Tt2, and thus the height of the uneven shape. That is, the height H of the convex portion 13 constituting the concavo-convex shape can be more accurately evaluated. This will be described below.

That is, as a result of examining the measurement method of the total light transmittance of the light diffusing plate formed with the convex portion, the present inventors,
(1) In the first total light transmittance Tt1 acquired by the arrangement relationship as shown in FIG. 6, other factors than the influence of the height of the convex portion of the light diffusing plate, for example, the light diffusing plate are added. The influence of the concentration of the diffusing agent tends to be greater,
(2) The second total light transmittance Tt2 obtained by the arrangement relationship as shown in FIG. 7 is affected by the concentration of the diffusing agent added to the light diffusing plate, but the height of the convex portion of the light diffusing plate. Tend to be more influential,
I found.

  Therefore, in the present embodiment, by using the above trends (1) and (2), for example, other factors such as the concentration of the diffusing agent added to the light diffusing plate 1 and the convex portions formed on the light diffusing plate. The factor of height is separated. That is, by using an index defined by the difference between the first total light transmittance Tt1 and the second total light transmittance Tt2, the degree affected by the height H of the convex portion 13 is clearly extracted. Therefore, the height H of the convex portion 13 of the light diffusing plate 1, that is, the concave / convex shape can be evaluated more accurately.

〔Example〕
Hereinafter, examples of the shape evaluation method according to the present embodiment will be described mainly with reference to FIGS. 8 and 9. FIG. 8A and FIG. 8B are enlarged cross-sectional views of main parts of a shape roll mounted as a lower roll according to the present embodiment. FIG. 9 is a chart showing the height of the convex portion obtained by the shape evaluation method according to the present embodiment and the height of the convex portion obtained by the cross-sectional observation method.

<Raw material of resin sheet>
In this example, the following two types of translucent resins A and B were prepared as raw materials for the resin sheet.
(1) Translucent resin A
Styrene resin (Toyo Styrene "HRM40", refractive index 1.59)
(2) Translucent resin B
MS resin (“MS200NT” manufactured by Nippon Steel Chemical Co., Ltd., refractive index 1.57, styrene / methyl methacrylate = 80 parts by mass / 20 parts by mass)

<Configuration of resin sheet manufacturing apparatus>
In this example, an apparatus having the same configuration as the resin sheet manufacturing apparatus 3 as shown in FIG. 2 was used. At that time, two types of shape rolls 51A and 51B to be mounted as the lower roll 37 were prepared.
(1) Shape roll 51A
On the peripheral surface of the shape roll 51A, as shown in FIG. 8A, a plurality of concave grooves 52A having a semicircular cross section that circulates in the circumferential direction are formed in a streak shape in parallel with each other. Pitch _{P A} of adjacent groove 52A is 300 [mu] m, the depth _{D A} of the groove 52A is 210 .mu.m.
(2) Shape roll 51B
On the peripheral surface of the shape roll 51B, as shown in FIG. 8B, a plurality of concave grooves 52B having a semicircular cross section that circulates in the circumferential direction are formed in a streak shape in parallel with each other. Pitch _{P B} of adjacent grooves 52B is 250 [mu] m, the depth _{D B} of the groove 52B is 110 [mu] m.

<Manufacture of resin sheet>
A shape roll 51 </ b> A was mounted as the lower roll 37 in the resin sheet manufacturing apparatus 3. Next, the translucent resin A was melt-kneaded by the first extruder 31 having a temperature in the cylinder of 190 to 250 ° C. and then supplied to the feed block 33. The translucent resin B was melt-kneaded by a second extruder having a temperature in the cylinder of 190 to 250 ° C., and then supplied to the feed block 33.

  Next, the resin supplied from the first extruder 31 to the feed block 33 becomes the base layer 16 and the resin supplied from the second extruder 32 to the feed block 33 becomes the surface layer 15. The resin was coextruded with the die 34 at an extrusion resin temperature of 250 ° C. The coextruded resin sheet 2 was pressed and cooled by the upper roll 35, the intermediate roll 36, and the shape roll 51A. Thus, the resin sheet 2 comprised from three layers (intermediate layer 1.9 mm, surface layer 0.05 mm x 2) with a thickness of 2.0 mm was manufactured. Thereafter, the resin sheet 2 was further cooled and cut to an appropriate size to produce a light diffusion plate.

  In the production process of the resin sheet, when the resin coextruded from the die 34 is sandwiched and pressed between the shape roll 51A and the intermediate roll 36, one surface 2a of the resin sheet 2 is a peripheral surface of the shape roll 51A. The concave grooves 52A formed in the above are transferred, and the fine convex portions 13 are formed. At this time, the light diffusing plates 101 to 103 each having the transfer rate adjusted were prepared by changing the surface temperature of the shape roll 51A.

  Next, the shape roll 51B was mounted as the lower roll 37 in the resin sheet manufacturing apparatus 3, and the light diffusion plates 104 to 107 were produced by the same method as described above.

<Measurement of total light transmittance>
The first and second total light transmittances Tt1 and Tt2 for each of the light diffusing plates 101 to 107 manufactured by the above-described method are measured using a transmittance meter (“HM-150” manufactured by Murakami Color Research Laboratory). And measured according to JIS K7361-1 (1997). At the time of measurement, the distance from the slit 62 shown in FIG. 5 to the light source 61 side surface of the light diffusing plates 101 to 107 to be measured is 13.1 mm, and the integration in the light diffusing plates 101 to 107 to be measured is performed. The distance from the surface on the sphere 63 side to the integrating sphere 63 was 1.0 mm. An integrating sphere 63 having a diameter of 150 mm and an inlet opening of 20 mmΦ was used, and BaSo ₄ was applied to the inner surface thereof. As the light source 61, a halogen lamp with a dichroic mirror (12V50W) was employed, and the light flux thereof was 14 mmΦ.

  As shown in FIG. 6, the long side direction X22 of the open part of the slit 62 and the extending direction X11 of the convex part 13 are orthogonal to each other, and the first surface 11 on which the convex part 13 is formed is a light source. The first total light transmittance Tt1 was measured by arranging light diffusion plates 101 to 107 as sample light diffusion plates toward 61. Further, as shown in FIG. 7, the long side direction X21 of the open portion of the slit 62 and the extending direction X11 of the convex portion 13 are made to coincide with each other, and the second surface 12 on which the convex portion 13 is not formed is formed. The second total light transmittance Tt2 was measured by disposing the light diffusion plates 101 to 107 as sample light diffusion plates toward the light source 61. The measured first and second total light transmittances Tt1 and Tt2 of the light diffusion plates 101 to 107 are as shown in FIG.

<Evaluation of the shape of the light diffusion plate>
The first and second total light transmittances Tt1 and Tt2 measured by the method described above were substituted into the following formula (1) obtained in advance to obtain the height H of the convex portion 13. The following equation (1) was obtained using the least square method based on the difference between Tt1 and Tt2 and the measured value of the height H of the convex portion 13 based on a plurality of reference light diffusion plates. In the following formula (1), the relational expression was defined so that the average of the transmittance measurement values at each transfer rate was within 5 μm as compared with the average of the cross-section measurement values.

H = {K1 × (Tt2−Tt1 + 80) ² + {K2 × (Tt2−Tt1 + 80)} + K3 (1)
K1: 0.068
K2: -13.8
K3: 687
Tt1: 75% ≦ Tt1 ≦ 90%
As a result, the obtained height H of the convex portions 13 of the light diffusion plates 101 to 107 is as shown in FIG. Then, based on the obtained height H of the convex portions 13, the uneven shapes of the light diffusion plates 101 to 107 as the sample light diffusion plate 1 are evaluated.

  The constant K1 in the above formula (1) can be set in the range of 0.068 ± 0.0005. The constant K2 can be set in the range of −13.8 ± 0.08. The constant K3 can be set in a range of 687 ± 0.5. Moreover, although the said Formula (1) gave and demonstrated the example calculated | required using the least squares method, it is not limited to this.

<Verification of evaluation>
In order to examine the consistency between the height H of the protrusion 13 thus obtained and the shape height h by the cross-sectional observation method, the light diffusion plates 101 to 107 are convex by the cross-section observation method using a microscope. Thirteen pitches p and heights h were measured. The pitch p and height h of the light diffusion plates 101 to 107 measured by this cross-sectional observation method are as shown in FIG.

  For example, for the light diffusing plate 101 having a measured value of the shape pitch p by the cross-sectional observation method of 300 μm and a measured value of the shape height h of 190.7 mm, the first total light transmittance Tt1 is 81.6%, The light transmittance Tt1 was 48.1%. Then, when the first and second total light transmittances Tt1 and Tt2 were substituted into the relational expression (1) to obtain the height H of the convex portion 13, the value was 180.5. The other light diffusion plates 102 to 107 are as shown in the chart of FIG. 9, and a description thereof is omitted here. As shown in FIG. 9, for the light diffusing plates 101 to 107, the height H of the convex portion 13 obtained by the shape evaluation method of the present embodiment is substantially the same as the height h of the convex portion 13 measured by the cross-sectional observation method. I was able to confirm. Thereby, it was confirmed that there is consistency between the height H obtained by the shape evaluation method of the present embodiment and the height h measured by the cross-sectional observation method, and the uneven shape can be appropriately evaluated.

  As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said embodiment, A various change is possible in the range which does not deviate from the meaning of invention.

  In the said embodiment, although the example which uses the difference of 1st total light transmittance Tt1 and 2nd total light transmittance Tt2 as a parameter | index was demonstrated, it is not limited to this. The index may be defined using at least one of the first and second total light transmittances Tt1 and Tt2, and the index is defined using one of the first and second total light transmittances Tt1 and Tt2. In this case, the height H of the convex portion 13 of the light diffusing plate 1 can be obtained more simply and the uneven shape can be evaluated. In addition, from the viewpoint of measuring more accurately, when using an index defined using one of the first and second total light transmittances Tt1 and Tt2, the concentration of the diffusing agent added to the light diffusing plate 1 is It is known that the concentration is low (depending on the refractive index of the diffusing agent, for example, 3% or less, more preferably 1% or less). This is because the influence of the uneven shape is easily reflected by the total light transmittance. Furthermore, when one of the first and second total light transmittances Tt1 and Tt2 is used as an index, it is more preferable to use the second total light transmittance Tt2 as an index. This is because, in the second measurement of the total light transmittance, since the uneven shape is arranged on the emission side, the influence of the uneven shape is easily reflected in the total light transmittance.

  In the said embodiment, although the 1st total light transmittance demonstrated and demonstrated the example acquired by the arrangement | positioning relationship as shown in FIG. 6, it is not limited to this. For example, the first total light transmittance may be measured by arranging the light diffusing plate 1 shown in FIG. 6 so that the extending direction X11 of the convex portion 13 coincides with the long side direction X22 of the slit 62. . The same applies to the second total light transmittance, and the light diffusing plate 1 shown in FIG. 7 is arranged so that the extending direction X11 of the convex portion 13 is orthogonal to the long side direction X21 of the slit 62, The second total light transmittance may be measured. In this case, the index may be appropriately defined according to the characteristics of the constituent material of the light diffusing plate 1 and the correlation between the index and the height of the convex portion may be obtained in advance. Then, even when such measurement results of the first and second total light transmittances are used, the height H of the convex portion 13 can be obtained as in the above embodiment.

  Moreover, in the said Example, although it gave and demonstrated to the example which uses a styrene resin and MS resin together as a raw material of a resin sheet, it is not limited to this, A well-known translucent resin is used. Can be used. Examples of the translucent resin include acrylic resin, polycarbonate, polyethylene, polypropylene, cyclic polyolefin, cyclic olefin copolymer, polyethylene terephthalate, ABS resin (acrylonitrile-butadiene-styrene copolymer resin), AS resin (acrylonitrile-styrene). Copolymer resin). Moreover, the said translucent resin can be used individually or in combination with 2 or more types.

  Moreover, in the said embodiment, as shown in FIG.2 (B), although the light diffusing plate 1 gave and demonstrated the example comprised by 3 layers, it is not limited to this, 1 layer, 2 layers, Alternatively, it may be a light diffusing plate composed of four or more layers.

  In the above-described embodiment, the light diffusing plate 1 having a concavo-convex shape formed by a plurality of convex portions 13 has been described as an example. However, the concavo-convex shape may be formed by forming a plurality of concave portions. .

  In the above embodiment, the light control plate is described as the light diffusing plate 1. However, the present invention is not limited to this, and the light output from the plurality of light sources is parallel to the plane on which the plurality of light sources are arranged. Any optical component that adjusts the uniformity of luminance in a plane may be used. For example, the light control plate may be a brightness adjusting plate having the above-described uneven shape on the light incident side of a plate made of a transparent material that does not contain a light diffusing agent.

  Moreover, in the said embodiment, in order to evaluate uneven | corrugated shape, the example which calculates | requires the height H of the convex part 13 was given and demonstrated. That is, for example, the pitch or the like is transferred almost in accordance with the mold. However, the present invention is not limited to this. For example, the concavo-convex shape can be evaluated by obtaining an aspect ratio or the like of the convex portions arranged in parallel to form the concavo-convex shape. In this case, a correlation may be acquired with respect to the aspect ratio.

  DESCRIPTION OF SYMBOLS 1 ... Light diffusing plate (light control board), 2 ... Resin sheet, 3 ... Resin sheet manufacturing apparatus, 11 ... 1st surface, 12 ... 2nd surface, 13 ... Convex part, 15 ... Surface layer, 16 ... Base layer, 31 ... 1st extruder, 32 ... 2nd extruder, 33 ... Feed block, 34 ... Die, 35 ... Upper roll, 36 ... Intermediate roll, 37 ... Lower roll, 38, 39 ... Hopper, 51A, 51B ... Shape roll 52, 52A, 52B ... concave groove, 61 ... light source, 62 ... slit, 63 ... integrating sphere, 101-107 ... light diffusion plate (light control plate).

Claims (4)

It has a first surface on which the concavo-convex shape is formed and a second surface located on the opposite side of the first surface, and the concave portion or the convex portion constituting the concavo-convex shape is in the first direction. A shape evaluation method for evaluating the concavo-convex shape of an extended sample light control plate, the shape evaluation method comprising the following acquisition step and evaluation step.
Acquisition step: defined by using at least one of the first total light transmittance when light is incident from the first surface and the second total light transmittance when light is incident from the second surface. And measuring the at least one of the first and second total light transmittances with respect to the sample light control plate to obtain the index.
Evaluation step: Based on the correlation between the index acquired in advance with respect to a reference light control plate having a known concavo-convex shape and the concavo-convex shape, from the index acquired in the acquisition step, the concavo-convex shape of the sample light control plate The process of evaluating. The light incident on the first surface during the measurement of the first total light transmittance is light that has passed through a slit extending in a direction orthogonal to the first direction;
The light incident on the second surface at the time of measuring the second total light transmittance is light that has passed through a slit extending in a direction that coincides with the first direction.
The shape evaluation method according to claim 1. The indicator is a difference between the first total light transmittance and the second total light transmittance.
The shape evaluation method according to claim 2. The indicator is the second total light transmittance.
The shape evaluation method according to claim 2.

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