JP2012052900A - Evaluation device for reflection bases and evaluation method for reflection bases - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an evaluation device for reflection bases that is capable of evaluating reflection bases even in-line during a manufacturing process thereof and reliably assessing by a simple method properties of the base surface that would invite luminance unevenness, and a reflection base.SOLUTION: Surface profile information on a reflection base 7 is acquired with a laser displacement meter 3; next, the acquired uneven profile information is subjected to Fourier transform to obtain any relationship between frequency and intensity regarding the uneven profile of the reflection base; then, a calculated relationship between frequency and intensity is compared with preset reference data; and, if the intensity surpasses 0.6 within a prescribed frequency range, the base is judged to be rejectable or, if no datum obtained surpasses 0.6 in the pertinent region of judgment, it is judged to be acceptable.

Description

  The present invention relates to a reflection substrate evaluation apparatus and a reflection substrate evaluation that can evaluate the substrate surface properties that cause uneven brightness, particularly in a reflection substrate used in a backlight unit such as a liquid crystal television. It is about the method.

  A backlight unit used for a display of a liquid crystal television or the like uses a reflective substrate such as a sheet shape, a film shape, or a plate shape that reflects light to the light guide plate. In this case, the reflective base material is placed behind the light guide plate, and light is emitted uniformly to the entire surface of the light guide plate (that is, the entire display surface) by, for example, irradiating light from the side of the light guide plate by the edge light method. Is done.

  On the other hand, if there is a problem in the member used (for example, the reflective base material), uneven brightness may occur in the display. The luminance unevenness is a portion in which a portion having a high luminance or a low luminance is generated even when the luminance is supposed to be visually recognized on the entire display surface. When such luminance unevenness occurs, an accurate image cannot be reproduced, and the viewer of the display is uncomfortable.

  For such display brightness unevenness, the brightness distribution information of the display screen of the display is acquired, and the background brightness with respect to the brightness change amount obtained from the difference between the brightness distribution information and the background brightness of the brightness distribution information is calculated. A contrast image representing a ratio is generated, and a contrast sensitivity function according to human visual characteristics is set in a two-dimensional Fourier spectrum obtained by two-dimensional Fourier transform of the contrast image according to at least one of the background luminance and the display screen size. Multiplication is performed, and the result is subjected to inverse two-dimensional Fourier transform to generate a two-dimensional image for evaluation in which the intensity of the luminance unevenness component is included in the luminance information, and the luminance unevenness is quantitatively evaluated based on the luminance information of the two-dimensional image for evaluation. There is a display evaluation method (Patent Document 1).

JP 2009-180583 A

  However, the method of Patent Document 1 quantitatively evaluates the luminance unevenness after the reflective base material is manufactured and then assembled as a backlight unit. Therefore, in the case where there is an abnormality in the reflective base material, it is possible to evaluate the luminance unevenness caused by this only after the reflective base material is assembled as a backlight unit.

  On the other hand, if wrinkles or the like are formed on the surface of the reflective substrate, unevenness in brightness may occur due to the uneven shape of the surface such as “wrinkles”. That is, when a backlight unit is assembled using a reflective base material having a certain degree of unevenness on the surface, uneven brightness may be confirmed.

  For example, FIG. 8 is a diagram showing a conventional reflective base material 30 and a display 33 using the same. As shown to Fig.8 (a), as for the reflective base material 30, the unevenness | corrugation 31 which arises in a manufacturing process may be formed in the surface. In particular, in the foam base material, since there is a heating process, wrinkle-like irregularities 31 may be formed on the surface of the reflective base material 30. Such irregularities 31 are often formed along the longitudinal direction in the manufacturing process of the reflective substrate 30, for example.

  If the unevenness 31 is larger than a certain size, it causes luminance unevenness. For example, when a backlight unit is configured using such a reflective base material 30 and light is applied to the backlight unit and confirmed from the front surface of the display, luminance unevenness 35 occurs in a range corresponding to the form of the irregularities 31. There is. Therefore, before assembling as a backlight unit, by measuring the surface unevenness amount of the reflective base material and evaluating the reflective base material, the reflective base material having a large unevenness of a predetermined value or more is discarded. Generation of unevenness can be prevented.

  However, as described above, when the pass / fail judgment of the reflective base material is performed only by the unevenness amount, the reflective base material that does not actually cause luminance unevenness may be determined to be rejected depending on the period of the wave. is there. In other words, the pass / fail judgment based on only the surface irregularity amount may result in excessive quality. Therefore, a more reliable evaluation method is desired.

  The present invention has been made in view of such a problem, and can be evaluated even in-line in the manufacturing process of a reflective substrate, and evaluates the surface property of the substrate that causes the occurrence of luminance unevenness with a simple method. It is an object of the present invention to provide a reflective base material evaluation apparatus and a reflective base material that can be used.

  In order to achieve the above-described object, the present invention is an apparatus for evaluating a reflective substrate, and detects the amount of unevenness by detecting a surface uneven shape of the reflective substrate by moving a displacement sensor relative to the surface of the reflective substrate. Means, frequency calculation means for obtaining a relationship between frequency and intensity by Fourier transforming the unevenness information detected by the unevenness amount detection means, and wave information obtained by the frequency calculation means using a preset reference Reflection characterized by comprising: pass / fail judgment means for rejecting those having intensity exceeding the reference data in the wave information, and accepting those having no intensity exceeding the reference data in the wave information. It is a base-material evaluation apparatus.

  The reflective base material is a foam base material for a backlight unit, and the unevenness detecting means is capable of reciprocating the displacement sensor with respect to the width direction of the reflective base material. In the wave information, it is desirable to compare the reference data with respect to the predetermined range of frequencies or the intensity of the predetermined range of wavelengths calculated from the frequency.

  According to the first invention, the surface information of the reflective base material obtained by the displacement sensor is acquired, and this is subjected to Fourier transform, so that the wave information (relationship between frequency and intensity) with respect to the uneven surface shape of the reflective base material. Can be obtained. In addition, by comparing this wave information with reference data and determining that the data exceeding this reference is rejected, it is possible to perform pass / fail determination based not only on the maximum unevenness but also on more detailed unevenness information. .

  More specifically, it is possible to make a pass / fail judgment based on whether or not the intensity in the predetermined range of the frequency (or wavelength obtained therefrom) is larger than the reference data from the obtained wave information. For this reason, it is possible to carry out evaluation by extracting only the uneven shape that particularly adversely affects luminance unevenness. Therefore, it is possible to more reliably detect the uneven shape that causes the luminance unevenness and perform a qualified pass / fail determination.

  The second invention is a method for evaluating a reflective substrate, wherein a displacement sensor is moved relative to the surface of the reflective substrate to detect surface unevenness information of the reflective substrate (a) and detected. A step (b) for acquiring wave information which is a relationship between frequency and intensity by Fourier transforming the uneven information, and a step (c) for comparing the intensity in the wave information with preset reference data. A method for evaluating a reflective base material comprising: determining, in the wave information, that having an intensity exceeding the reference data is rejected, and determining that a wave having no intensity exceeding the reference data is acceptable.

The step (c)
When the number of measurement points is N, if the intensity for the frequency corresponding to the wavelength of 128 mm or less exceeds 0.6 N / 128, it may be rejected, and if it is 0.6 N / 128 or less, it may be determined to be acceptable. .

  After the step (a), the method further includes a step (d) of calculating a maximum unevenness amount from the unevenness information obtained in the step (a), and evaluation is performed if the maximum unevenness amount is not more than a specified value. The process (b) and subsequent steps can be performed only when the maximum unevenness amount is not less than a specified value.

  In this case, if the maximum unevenness obtained in the step (d) is 50 μm or less, the result is acceptable, and only when the amount exceeds 50 μm, the steps (b) and after may be performed.

  According to the second invention, since the wave information can be obtained from the unevenness information on the surface of the reflective substrate, the surface shape that causes the luminance unevenness can be detected more reliably as described above.

  As reference data for the pass / fail judgment, the intensity in the wavelength range of 128 mm or less (corresponding frequency) is set to 0.6 N / 128 or less when the number of measurement points is N, thereby causing luminance unevenness. Can be reliably detected. That is, when the intensity in the above-described range exceeds 0.6 N / 128, the probability of occurrence of luminance unevenness increases, so that a reflective substrate exceeding this is determined as a failure determination.

  In addition, before obtaining wave information, the maximum unevenness amount is calculated from the unevenness information, and if this value is equal to or less than a predetermined reference value, it will be accepted, and only for those that fail this will be subjected to the method of the present invention. By applying, the reflective substrate can be more reliably evaluated. That is, a smooth reflective substrate with almost no unevenness will not cause luminance unevenness, but if the unevenness exceeds a predetermined value, the wave information will be analyzed in more detail to obtain only the unevenness. Then, although it is rejected, a reflective base material that does not cause luminance unevenness can be remedied.

  According to the present invention, an evaluation apparatus for a reflective base material that can be evaluated in-line in the production process of the reflective base material, and can reliably evaluate the base material surface properties that cause the occurrence of luminance unevenness by a simple method. And a reflective substrate can be provided.

The block diagram of the reflective base-material evaluation apparatus 1. FIG. The hardware block diagram of the analyzer 5. FIG. The flowchart which shows the flow of the reflective base material evaluation apparatus 1. FIG. The figure which shows the measurement part of the laser displacement meter 3 with respect to the reflective base material 7. FIG. The figure which shows operation | movement of the laser displacement meter with respect to the reflective base material 7. FIG. The figure which shows uneven | corrugated information. The figure which shows wave information. The figure which shows generation | occurrence | production of the brightness | luminance nonuniformity with the conventional reflective base material.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram showing a reflective substrate evaluation apparatus 1 according to the present invention. The reflective base material evaluation apparatus 1 is mainly composed of a laser displacement meter 3 which is an unevenness detecting means, an analysis apparatus 5 and the like.

  The reflective substrate 7 is a resin substrate such as a foam, and is formed in a sheet shape, a film shape, a plate shape, or the like. More specifically, it can be suitably used for a thermoplastic resin sheet having fine bubbles or pores having an average cell diameter of 50 nm or more and 50 μm or less inside. As such a sheet, for example, an extruded sheet of polyethylene terephthalate is impregnated with carbon dioxide gas under high pressure and then heated and foamed, and a foamed plastic light reflecting sheet having an internal cell diameter of 50 μm or less is used. There are (for example, MCPET (registered trademark) manufactured by Furukawa Electric Co., Ltd.). Further, another preferred example of the reflective substrate 7 is a thermoplastic resin film containing a filler, in which a plurality of films in which a large number of voids are formed with the filler as a nucleus, or the film is made of polyethylene terephthalate. What was bonded to resin sheets, such as these, is mentioned. The thermoplastic resin containing the filler is a porous stretched film in which a void is formed by forming a film, an unstretched film containing the filler, and stretching the unstretched stretched film. Is preferred. It should be noted that additives such as antioxidants, ultraviolet inhibitors, lubricants, pigments, reinforcing agents and the like can be appropriately added to the resins used for the sheets and films. Moreover, you may shape | mold the coating layer containing these additives on a sheet | seat and a film. In addition, although the example shown in FIG. 1 shows an example in which the reflective substrate evaluation apparatus 1 is installed in a production line for performing foaming treatment or the like on the long reflective substrate 7 wound in a roll shape, Evaluation may be performed by arranging the reflective base material evaluation device 1 separately from the manufacturing process of the reflective base material 7.

  The laser displacement meter 3 is arranged at a predetermined distance from the surface of the reflective base material 7 and maintains a constant distance with respect to the surface of the reflective base material 7 while being perpendicular to the traveling direction of the reflective base material 7 (that is, the reflection base). It can move in the width direction of the base material 7. Therefore, the laser displacement meter 3 can detect irregularities on the surface of the target reflective substrate 7 (the amount of irregularities in the surface direction of the entire reflective substrate including all “wrinkles” and thickness changes). In addition, if the uneven | corrugated information of the reflective base material 7 is detectable, it may not be the laser displacement meter 3, and you may use another detection means.

  The analysis device 5 can acquire information from the laser displacement meter 3, perform various analyzes and pass / fail determinations, and can control the operation of the laser displacement meter 3. A general computer can be used as the analysis apparatus.

  FIG. 2 is a hardware configuration diagram of a computer that implements the analysis device 5. In the analysis device 5, a control unit 9, a storage unit 11, a media input / output unit 13, a communication control unit 15, an input unit 17, a display unit 19, a peripheral device I / F unit 21, and the like are connected via a bus 23. .

  The control unit 9 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. The CPU calls and executes a program stored in the storage unit 11, ROM, recording medium, etc. to the work memory area on the RAM, drives and controls each device connected via the bus 23, and controls the laser displacement meter 3. The operation can be controlled.

  The ROM is a non-volatile memory and permanently holds a computer boot program, a program such as BIOS, data, and the like. The RAM is a volatile memory, and temporarily holds a program, data, and the like loaded from the storage unit 11, ROM, recording medium, and the like, and includes a work area used by the control unit 9 for performing various processes.

  The storage unit 11 is an HDD (hard disk drive), and stores a program executed by the control unit 9, data necessary for program execution, an OS (operating system), and the like. As for the program, a control program corresponding to an OS (operating system) and an application program corresponding to processing described later are stored. Each of these program codes is read by the control unit 9 as necessary, transferred to the RAM, read by the CPU, and executed as various means.

  The media input / output unit 13 performs data input / output, for example, floppy (registered trademark) disk drive, CD drive (-ROM, -R, RW, etc.), DVD drive (-ROM, -R, -RW, etc.). And media input / output devices such as MO drives.

  The communication control unit 15 includes a communication control device, a communication port, and the like, and is a communication interface that mediates communication between a computer and a network, and performs communication control with the laser displacement meter 3 and the like.

  The input unit 17 inputs data and includes, for example, a keyboard, a pointing device such as a mouse, and an input device such as a numeric keypad. An operation instruction, an operation instruction, data input, and the like can be performed on the computer via the input unit 17.

  The display unit 19 includes a display device such as a CRT monitor and a liquid crystal panel, and a logic circuit (such as a video adapter) for realizing a video function of the computer in cooperation with the display device.

  The peripheral device I / F (interface) unit 21 is a port for connecting a peripheral device to the computer, and the computer transmits and receives data to and from the peripheral device via the peripheral device I / F unit 21. The peripheral device I / F unit 21 is configured by USB, IEEE1394, RS-232C, or the like, and usually includes a plurality of peripheral devices I / F. The connection form with the peripheral device may be wired or wireless. The bus 23 is a path that mediates transmission / reception of control signals and data signals between the devices. Note that the analysis device 5 does not require all the above configurations as long as it can perform the functions described below.

  Next, a method for evaluating the reflective base material 7 using the reflective base material evaluation apparatus 1 will be described. FIG. 3 is a flowchart illustrating the flow of the reflective base material evaluation apparatus 1.

  First, as shown in FIG. 4, the laser displacement meter 3 is moved or reciprocated with respect to the width direction of the reflective base material 7 to detect the surface unevenness amount of the reflective base material 7 (step 101). Note that the surface unevenness amount includes not only a change in the thickness of the reflective substrate 7 but also wrinkles and deformations that occur in the reflective substrate itself. The reason for inspecting not the manufacturing direction of the reflective base material 7 but the width direction is that the surface irregularities (wrinkles, etc.) of the reflective base material 7 are greatly generated in the width direction in relation to the manufacturing process. is there.

  Specifically, the laser displacement meter 3 moves the surface of the reflective substrate 7 while the laser displacement meter 3 is driven by the controller 9 described above to drive the laser displacement meter 3 with a drive unit (not shown). Obtain shape information (concave / convex information). The moving speed of the laser displacement meter 3 is set according to the manufacturing speed or the like of the reflective base material 7. For example, by inputting a condition (manufacturing speed) through the input unit 17, a detection condition corresponding to this is stored in the storage unit 11. What is necessary is just to read more and control by the control part 9. The means for detecting the surface unevenness amount of the reflective substrate 7 by the control unit 9 and the laser displacement meter 3 described above is referred to as surface unevenness amount detecting means.

  Next, the maximum unevenness amount is calculated from the obtained unevenness information, and it is determined whether or not this exceeds a prescribed value of 50 μm (step 102). The specified value is set as appropriate according to the quality required for the product. FIG. 5 is a conceptual diagram showing the obtained uneven information. The maximum value and the minimum value are obtained from the unevenness information obtained in the inspection range (for example, the moving range in the width direction of the reflective base material 7), and this difference is set as the maximum unevenness amount.

  Specifically, the control unit 9 calculates the maximum unevenness amount from the maximum value and the minimum value of the unevenness information, reads a preset reference value from the storage unit 11 and compares them, and the maximum unevenness amount is determined. It is determined whether or not the reference value is exceeded. As the reference value of the maximum unevenness amount, the maximum unevenness amount and the luminance unevenness tendency for each target product may be investigated in advance, and the maximum value of the maximum unevenness amount that does not cause the unevenness of brightness may be set as the reference value.

  If the calculated maximum unevenness amount is equal to or less than a reference value (for example, 50 μm), a pass determination is performed (step 107). In the conventional determination based only on the unevenness amount, the determination ends, and the reflective base material 7 exceeding the reference value is discarded.

  In the present invention, the unevenness information is Fourier-transformed for the case where the maximum unevenness amount exceeds the reference value in step 102, and the relationship between the frequency and the intensity is obtained for the surface unevenness shape of the reflective substrate (step 103). Note that the above step 102 may be omitted, and the evaluation after step 103 may be performed on all the specimens.

  Here, the frequency depends not only on the uneven shape of the reflective substrate 7 but also on the moving speed of the laser displacement meter 3 relative to the reflective substrate 7 (measurement speed of the uneven shape). For this reason, the moving speed of the laser displacement meter 3 is set in advance. The moving speed of the laser displacement meter 3 is, for example, about 200 mm / s or less.

  Specifically, the unevenness information obtained in the control unit is Fourier-transformed by the frequency calculation means to obtain the relationship between the frequency and the intensity. The obtained frequency may be converted into a wavelength in consideration of the measurement conditions of the laser displacement meter 3 and the like. In the following example, an example in which a frequency is handled is shown, but naturally the evaluation may be performed by converting into a wavelength.

  As shown in FIG. 6 (a), when the laser displacement meter is reciprocated in the width direction of the reflective base material 7 while the reflective base material 7 moves in the traveling direction (the direction of arrow B in the figure), the laser displacement meter The measurement part (measurement direction) by does not coincide with the width direction of the reflective base material 7 and is measured obliquely according to the moving speed of the reflective base material 7 (C direction in the figure). On the other hand, as shown in FIG.6 (b), when it measures similarly in the state which fixed the reflective base material 7a, a measurement part will correspond to the width direction of the reflective base material 7a (D direction in a figure).

  However, in the present invention, as described above, when the laser displacement meter 3 is moved in the width direction while the reflecting base material 7 is moving, the unevenness information obtained by actually measuring obliquely is also reflected on the reflecting substrate. It is defined as unevenness information in the width direction of the material 7. That is, the detected unevenness information is not necessarily information in a direction strictly perpendicular to the width direction of the reflective base material 7, and unevenness information measured slightly obliquely from the width direction of the reflective base material 7 is also reflected It is assumed that the uneven information in the width direction of the substrate 7 is handled.

  Next, the relationship (wave information) between the frequency (wavelength) and intensity calculated by the frequency calculating means is compared with preset reference data (step 104). That is, the maximum intensity in the frequency (wavelength) region within a predetermined range is compared with a numerical value in the reference data. The reference data depends on the number of measurement points of unevenness in the width direction, but when the number of measurement points is 128, as the reference data, for example, the intensity of a predetermined range of frequencies (wavelengths) is 0.6 or less. I will do it. Each time the number of measurement points increases to 128, 256, 512,..., The numerical value of the reference data (the intensity of a predetermined range of frequencies (wavelengths)) is set to 0.6, 1.2, 2.4. (For example, if the number of measurement points is N, reference data = 0.6 N / 128). The reference data may be obtained in advance by examining the tendency of occurrence of intensity and luminance unevenness corresponding to the measurement conditions for each target product, and obtaining the intensity at which luminance unevenness does not occur at a predetermined frequency. In the following example, a case where the number of measurement points is 128 and the reference data is 0.6 is described. Next, it is determined whether or not there is data exceeding 0.6 as the intensity of the area (step 105). If the intensity exceeds 0.6, a failure determination is made, and if there is no data exceeding 0.6 in the determination area, a determination is made (step 106, step 107).

  Specifically, reference data (frequency region for determination (frequency range for determination) is read from the storage unit 11 or the like with respect to the wave information (relationship between frequency and intensity) Fourier-transformed by the control unit 9 by the pass / fail determination means. The reference intensity in the wavelength region) is defined in advance by the above-described method, and it is determined whether there is data exceeding the reference data in the frequency region (wavelength region).

  Further, by the pass / fail determination means, the control unit 9 determines that the data exceeds the reference data based on the above determination, and determines that the data is unacceptable.

  FIG. 7 is a conceptual diagram showing a comparison between wave information for determining pass / fail and reference data. As described above, the wave information obtained by the frequency calculation means is indicated by the relationship between the wavelength (or frequency) and the intensity. The pass / fail determination means determines whether or not there is data exceeding a reference value (F in the figure) in the evaluation range 25 that is a wavelength range (frequency range) for evaluation. That is, in the evaluation range 25, if there is data exceeding the reference value, the data is rejected. That is, it is not necessary to make a determination on the strength except for the evaluation range 25. The evaluation range 25 may be determined by investigating each wavelength (frequency), intensity, and luminance unevenness in advance, and setting a wavelength (frequency) range in which luminance unevenness does not occur. For example, if a predetermined wavelength is set as the evaluation range, the uneven shape having a longer wavelength than that has a small effect on luminance unevenness, and therefore can be excluded from the evaluation range. The evaluation range may be, for example, a wavelength of 128 mm or less.

  The obtained determination data may be displayed on the display unit 19 or the like, and can be stored in the storage unit 11 as evaluation data. It is also possible to give feedback to the manufacturing process via a network or the like and instruct to discard the rejected product in a subsequent process. Thus, the evaluation of the reflective base material 7 is completed. The evaluation may be repeated at predetermined intervals or may be performed continuously.

  Note that, as described above, the reference data is prepared by preparing samples of reflective substrates having irregularities with various periods and sizes, incorporating a backlight unit, and visually checking for occurrence of uneven brightness. The intensity according to the frequency (wavelength) to be generated and the number of measurement points is specified and determined in advance.

  In the above-described embodiment, the specific wavelength that causes the maximum unevenness amount and the luminance unevenness is determined from the information obtained by one laser displacement meter 3, but the maximum unevenness is separately provided on the upstream side of the laser displacement meter 3. A maximum unevenness measuring device for use in determining the amount may be separately provided.

  According to the present invention, it is possible to reliably evaluate the pass / fail of the surface irregularities of the reflective base material 7 that causes luminance unevenness. In particular, evaluation of only the maximum unevenness amount results in excessive quality, but by determining the intensity of the uneven component in the frequency (wavelength) region that tends to adversely affect luminance unevenness, for example, unevenness that does not affect luminance unevenness. The shape can be treated as acceptable.

  Next, an evaluation example using the evaluation method according to the present invention will be described. The reflective base material which is the subject was manufactured as follows.

  First, 2 parts by weight of a polyester elastomer (manufactured by Mitsubishi Chemical Corporation, Primalloy (registered trademark) B1942N) is added to 100 parts by weight of polyethylene terephthalate (manufactured by Nippon Unipet Co., Ltd., RT-553C) and kneaded. It was formed into a sheet of 48 mm thickness × 540 mm width × 355 m length. This resin sheet and an olefin-based non-woven fabric separator were overlapped and rolled into a roll shape so that there was no portion where the surfaces of the resin sheets contacted each other.

  Thereafter, the roll was put in a pressure vessel, pressurized to 5.2 MPa with carbon dioxide, and carbon dioxide was permeated into the resin sheet. The carbon dioxide gas permeation time into the resin sheet was 35 hours. Next, the roll was taken out from the pressure vessel, and only the resin sheet was continuously supplied to a hot air circulation type foaming furnace set at 220 ° C. while removing the separator, and foamed. The obtained foam was uniformly foamed, the average cell diameter was 0.9 μm and the thickness of the foam was 0.7 mm, and the total reflectance of the foam sheet was 99.9%. Met.

  A plurality of samples cut to a width of 520 mm are taken out from the obtained reflective substrate, and a laser displacement meter is placed at a predetermined height in the width direction (direction perpendicular to the longitudinal direction in the manufacturing process) at a speed of 50 mm / s, It was moved at a pitch of about 4 mm to detect the surface unevenness of the reflective substrate at 128 measurement points, and each was evaluated by the method described above.

  Furthermore, the backlight unit was temporarily assembled with respect to the reflective base material after evaluation, and the luminance on the surface of the display was evaluated. As a configuration of the backlight unit, a light guide plate, a first diffusion film, a prism sheet, and a second diffusion film were assembled in this order on a reflective substrate. An LED (Light Emitting Diode) light source is provided on the side of the light guide plate as an edge light system. The prism sheet is a material PET having a thickness of 0.30 mm, the first diffusion film is a material PET having a thickness of 0.31 mm, the second diffusion film is a material PET having a thickness of 0.38 mm, and the light guide plate is 4. An acrylic material having a thickness of 0 mm was used.

  A two-dimensional color luminance meter (CA2000 manufactured by Konica Minolta Sensing Co., Ltd.) was installed on the surface side of the light guide plate in a direction perpendicular to the light guide plate, and the luminance of the entire surface of the light guide plate was measured. Color tone image processing was performed on the obtained luminance, and the occurrence of luminance unevenness was evaluated visually based on the image. For example, it was visually evaluated whether there was a change in luminance discontinuous with the surroundings or a partial change in luminance. The results are shown in Table 1.

  “Maximum unevenness of 50 μm or less” in Table 1 was determined by investigating the maximum unevenness of each specimen, and “×” was determined to exceed 50 μm. In the above example, only those with the maximum unevenness exceeding 50 μm were targeted. As described above, when the maximum unevenness amount was 50 μm or less, no luminance unevenness occurred. Further, “maximum intensity / maximum intensity wavelength” indicates the maximum intensity of the Fourier-transformed wave based on the wave information of the concavo-convex shape obtained by the above-described method and the wavelength that is the maximum intensity (wavelength Was obtained from the frequency and measurement conditions). In addition, in the evaluation method of the present invention, “main evaluation” is “x” if the reference data is 0.6, and an intensity exceeding 0.6 is recognized in the region where the wavelength is 128 mm or less. When it was 6 or less, it was set as “◯”. In addition, “brightness unevenness” was actually assembled temporarily with a backlight unit, and the brightness on the surface of the display was evaluated. The thing was made into "(circle)".

  As shown in Table 1, even when the maximum unevenness amount exceeds 50 μm, there is an example in which luminance unevenness does not occur depending on the unevenness property. For example, no. 2, no. In No. 3, the intensity was 0.6 or less, and luminance unevenness did not occur. No. No. 6 had an intensity exceeding 0.6, but no luminance unevenness occurred because the wavelength exceeded 128 mm. In other words, luminance unevenness does not occur with unevenness of a wavelength component of a certain degree or more.

  On the other hand, no. 1, no. 4, no. No. 5 has a luminance non-uniformity because the intensity in the wavelength range of 128 mm or less exceeds 0.6.

  As mentioned above, although embodiment of this invention was described referring an accompanying drawing, the technical scope of this invention is not influenced by embodiment mentioned above. It is obvious for those skilled in the art that various modifications or modifications can be conceived within the scope of the technical idea described in the claims, and these are naturally within the technical scope of the present invention. It is understood that it belongs.

DESCRIPTION OF SYMBOLS 1 ......... Reflective substrate evaluation apparatus 3 ......... Laser displacement meter 5 ......... Analyzer 7 ......... Reflective substrate 30 ......... Reflective substrate 31 ......... Unevenness 33 ......... Display 35 ......... Uneven brightness

Claims (6)

An evaluation apparatus for a reflective substrate,
An unevenness detecting means for detecting a surface unevenness shape of the reflective substrate by moving a displacement sensor relative to the surface of the reflective substrate;
Frequency calculation means for Fourier-transforming the unevenness information detected by the unevenness amount detection means to obtain the relationship between frequency and intensity,
The wave information obtained by the frequency calculation means is compared with preset reference data, the wave information having a strength exceeding the reference data is rejected, and the wave information having no strength exceeding the reference data Pass / fail judgment means to pass,
The evaluation apparatus of the reflective base material characterized by comprising. The reflective substrate is a foam substrate for a backlight unit,
The unevenness detecting means is capable of reciprocating the displacement sensor with respect to the width direction of the reflective substrate,
2. The reflection base material according to claim 1, wherein the pass / fail judgment is performed by comparing a reference range with respect to a predetermined range of frequencies or a predetermined range of wavelengths calculated from the frequency in the wave information. Evaluation device. A method for evaluating a reflective substrate,
(A) detecting a surface unevenness information of the reflective substrate by moving a displacement sensor relative to the surface of the reflective substrate;
(B) obtaining wave information that is a relationship between frequency and intensity by Fourier-transforming the detected unevenness information;
A step (c) of comparing the intensity in the wave information with preset reference data;
Comprising
A method for evaluating a reflective base material, wherein in the wave information, one having an intensity exceeding the reference data is rejected, and one not having an intensity exceeding the reference data is determined to be acceptable. The step (c)
When the number of measurement points is N, when the intensity for the frequency corresponding to the wavelength of 128 mm or less exceeds 0.6 N / 128, it is rejected, and when it is 0.6 N / 128 or less, it is judged as acceptable. The method for evaluating a reflective substrate according to claim 3. After the step (a), the method further comprises a step (d) of calculating a maximum unevenness amount from the unevenness information obtained by the step (a).
5. The evaluation is terminated if the maximum unevenness is not more than a specified value, and the step (b) and subsequent steps are performed only when the maximum unevenness is not less than a specified value. Evaluation method of reflective substrate.   The reflective substrate according to claim 5, wherein the step (b) and subsequent steps are performed only when the maximum unevenness obtained in the step (d) is 50 μm or less, and only when it exceeds 50 μm. Evaluation methods.

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