JP2016110118A - Invisible ray reflective sheet, optical sheet, and display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an invisible ray reflective sheet having improved reflection characteristics.SOLUTION: An invisible ray reflective sheet of the present invention includes a base material having a concavo-convex surface formed on a reference surface thereof, and a reflective layer, for reflecting invisible light rays, formed along the concavo-convex surface. When a "tilt angle" is defined as an angle at which a tangent of the concavo-convex surface is tilted relative to the reference surface, a distribution proportion of 25-degrees tilt angle is no less than 1.0 [%/deg], and a proportion of area of regions with tilt angles of 40 degrees or greater projected on the reference surface to total area of the reference surface is no more than 20%, which provides improved reflection characteristics.SELECTED DRAWING: Figure 5

Description

  The present disclosure relates to a non-visible light reflecting sheet, an optical sheet, and a display device.

  A technique is known in which coordinates on a display device are detected by an input pen or the like, and the display device displays information such as characters based on coordinate information detected by the input pen. In realizing this technology, the display device includes a reflective layer that reflects invisible light emitted from the input pen (for example, disclosed in Patent Document 1).

JP 2008-209598 A

  It is desirable that the input operation to the display device with the input pen can be performed comfortably. As a method for realizing this, there is a method in which a reflective layer having better reflection characteristics with respect to invisible light is provided in the display device, and the detection accuracy of the invisible light by the input pen is increased.

  The present disclosure has been made in view of the above problems, and an object thereof is to provide a non-visible light reflecting sheet, an optical sheet, and a display device having better reflection characteristics with respect to non-visible light.

  The present disclosure includes a base material having a concavo-convex surface on a reference surface and a reflective layer that reflects invisible light formed along the concavo-convex surface, and an angle at which a tangent to the concavo-convex surface is inclined with respect to the reference surface Is a tilt angle, the distribution rate when the tilt angle is 25 deg is 1.0% / deg or more, and the total of the reference planes of the projected area onto the reference plane of the region where the tilt angle is 40 deg or more It is a non-visible light reflecting sheet having a ratio in area of 20% or less.

  According to the present disclosure, it is possible to provide a non-visible light reflection sheet, an optical sheet, and a display device that have better reflection characteristics with respect to non-visible light.

1 is a schematic diagram of an information display system according to an embodiment. In the information display system by embodiment, it is a schematic diagram which shows the structure of the electronic pen 100 and the display apparatus 200. FIG. 12 is an explanatory diagram illustrating an example of a position information pattern arranged on a display unit 240 of the display device 200. FIG. It is explanatory drawing which shows the dot arrange | positioned shifted to the right side from the reference | standard for calculating | requiring a position coordinate from a position information pattern. It is explanatory drawing which shows the dot arrange | positioned shifted upwards from the reference | standard for calculating | requiring a position coordinate from a positional information pattern. It is explanatory drawing which shows the dot arrange | positioned shifted to the left from the reference | standard for calculating | requiring a position coordinate from a position information pattern. It is explanatory drawing which shows the dot arrange | positioned shifted from the reference | standard for calculating | requiring a position coordinate from a positional information pattern below. In the display apparatus 200, it is a schematic block diagram which shows the structure of the optical sheet 300 which has arrange | positioned the positional information pattern. It is a figure for demonstrating the conditions for reflecting infrared light from the electronic pen 100 to an incident direction. It is a figure which shows the relationship between the incident angle of light (attitude angle of the electronic pen 100) (phi), and inclination-angle (theta) required in order to generate a return reflection with respect to the incident angle (phi). It is a figure which shows the abundance ratio of the surface in the vicinity of a certain specific inclination angle in the uneven surface on the uneven base material 322. It is a figure which shows the distribution rate of the surface in the vicinity of a certain specific inclination angle in the uneven surface on the uneven base material 322. FIG. It is a figure which shows the abundance ratio of the surface in the vicinity of a certain specific inclination angle in the uneven surface on the uneven base material 322. It is a figure which shows the distribution rate of the surface in the vicinity of a certain specific inclination angle in the uneven surface on the uneven base material 322. FIG. It is a figure which shows the surface photograph in Example 1. FIG. It is a figure which shows the surface photograph in Example 2. FIG. 6 is a view showing a surface photograph in Example 3. FIG. It is a figure which shows the surface photograph in the comparative example 1. FIG. It is a figure which shows the surface photograph in the comparative example 2. It is a figure which shows distribution rate f ((theta)) with respect to inclination-angle (theta) in an Example and a comparative example. It is a figure which shows the structure of the test sheet | seat 400 and the diffuse reflection measuring apparatus 430. It is a figure which shows the diffuse reflectance with respect to each measurement angle in wavelength 950nm in an Example and a comparative example. It is a figure which shows the reflectance with respect to the wavelength in an Example and a comparative example.

  Hereinafter, embodiments will be described in detail with reference to the drawings as appropriate. However, more detailed description than necessary may be omitted. For example, detailed descriptions of already well-known matters and repeated descriptions for substantially the same configuration may be omitted. This is to avoid the following description from becoming unnecessarily redundant and to facilitate understanding by those skilled in the art.

  The inventor provides the accompanying drawings and the following description in order for those skilled in the art to fully understand the present disclosure, and is not intended to limit the subject matter described in the claims. Absent.

  Hereinafter, a case where a liquid crystal display device is used will be described as an example of the display device 200 according to the information display system according to the embodiment of the present disclosure. However, the present disclosure is not limited to the liquid crystal display device, and other display devices such as an EL (Electro Luminescence) display device may be used.

  FIG. 1 is a schematic diagram of an information display system according to an embodiment. As shown in FIG. 1, the information display system includes an electronic pen 100 and a display device 200. The user uses the electronic pen 100 in proximity to the display unit 240 of the display device 200. At this time, the electronic pen 100 optically reads the position information pattern formed on the display unit 240 of the display device 200. The electronic pen 100 transmits the read position information pattern to the display device 200, thereby notifying the display device 200 of the close position. Based on the position information pattern notified by the electronic pen 100, the display device 200 causes the display unit 240 to display characters or graphics handwritten by the user. Accordingly, the user can enter characters on the display unit 240 of the display device 200 so that the characters are handwritten on the paper with an ink pen.

  FIG. 2 is a schematic diagram illustrating the configuration of the electronic pen 100 and the display device 200 in the information display system according to the embodiment.

  As illustrated in FIG. 2, the electronic pen 100 includes a processing circuit 110, a transmission unit 120, a pen tip 130, a pressure sensor 131, a switch 140, an LED (Light Emitting Diode) 150, condenser lenses 151 and 160, and an IR (Infra Red). ) A filter 161 and an image reading unit 162 are provided. On the other hand, the display device 200 includes a receiving unit 210, a processing circuit 220, a panel driving circuit 230, and a display unit 240.

  The pen tip 130 is disposed at the tip of the electronic pen 100. When the pen tip 130 contacts the display unit 240 of the display device 200, the pressure sensor 131 disposed inside the electronic pen 100 detects the writing pressure of the pen tip 130. Then, the pressure sensor 131 notifies the processing circuit 110 of a signal indicating that the writing pressure has been detected. In response to the transmission of this signal, the processing circuit 110 starts the irradiation of the illumination light 152 having spectral characteristics in the infrared region by the LED 150 and the reading output of the image reading unit 162. However, the present disclosure is not limited to a configuration in which the operation of the LED 150 and the image reading unit 162 is started when the pressure sensor 131 senses writing pressure. For example, even when the electronic pen 100 is separated from the display unit 240 in response to the user pressing the switch 140 for inputting a reading command, the operation of the LED 150 and the image reading unit 162 is performed. May start.

  The illumination light 152 emitted from the LED 150 of the electronic pen 100 is collected by the condenser lens 151 and then irradiated to the proximity position of the display unit 240 of the display device 200. The illumination light 152 is reflected by the display unit 240 of the display device 200 and becomes reflected light 163. The reflected light 163 is collected by the condenser lens 160, passes through the IR filter 161 that blocks visible light and transmits infrared light, and then enters the image reading unit 162. The image reading unit 162 includes an image sensor (CCD or the like) that receives infrared light and generates an image.

  The reflected light 163 reflected by the display unit 240 of the display device 200 includes information regarding the position information pattern corresponding to the position where the electronic pen 100 is brought close to the display device 240. The image reading unit 162 captures the reflected light 163 including information on the position information pattern and generates an image. The image generated by the image reading unit 162 is sent to the processing circuit 110. The processing circuit 110 recognizes a dot-shaped image included in the position information pattern from the acquired image, processes the recognized image data, and detects the coordinates of the position designated by the electronic pen 100. The processing circuit 110 sends the detected coordinate data to the transmission unit 120. The transmission unit 120 transmits coordinate data to the reception unit 210 of the display device 200 by wireless communication.

  The display device 200 controls the panel driving circuit 230 by processing the coordinate data received by the receiving unit 210 with the processing circuit 220. As a result, characters, graphics, and the like are displayed on the display unit 240 based on the coordinate position recognized by the electronic pen 100.

  In the above series of operations, coordinate detection is performed following the moving electronic pen 100. Therefore, the image reading unit 162 opens the shutter intermittently. The shorter the opening time, the smaller the image blur during the exposure time, and the faster the electronic pen 100 can be moved. The exposure time is automatically adjusted to the minimum time for obtaining the necessary image brightness. The brightness of the image per unit exposure time is determined by the illumination capability of the LED 150 and the reflection performance of the optical sheet 300 described later in detail. That is, the higher the illumination ability of the LED 150 and the reflection ability of the optical sheet 300, the shorter the exposure time, and the faster the electronic pen 100 can be moved. Further, the LED 150 only needs to emit light during the exposure time. When the LED 150 having a certain illumination capability is used, the higher the reflection capability of the optical sheet 300, the lower the power consumption.

  As shown in FIG. 2, since the LED 150 and the image reading unit 162 are close to each other inside the electronic pen 100, the incident angle of the illumination light 152 to the optical sheet 300 and the effective reflected light that contributes to image reading. It is necessary to make the reflection angle of 163 substantially equal. Therefore, the reflectivity of the optical sheet 300 is not sufficient for general reflectivity, and the ability to reflect light in the vicinity of that direction is required according to the incident direction of light. Details of the configuration of the optical sheet 300 will be described later.

  Next, a position information pattern optically read by the electronic pen 100 will be described with reference to FIGS. FIG. 3 is an explanatory diagram illustrating an example of a position information pattern arranged on the display unit 240 of the display device 200. FIG. 4 is an explanatory diagram illustrating an example of a method for obtaining position coordinates from a position information pattern.

  As shown in FIG. 3, a position information pattern in which a plurality of dots 311 are formed in a specific arrangement pattern is arranged in the display area of the display unit 240 of the display device 200. On the display area of the display unit 240, a unit area of m dots × n dots is defined. In the present embodiment, for example, a pixel area of 6 dots × 6 dots is set as a unit area. At this time, the electronic pen 100 reads the dot-shaped arrangement formed as the position information pattern in the unit area on the display unit 240 that is close to the electronic pen 100, and indicates the position in which the electronic pen 100 is in close proximity. Recognize coordinates.

  As shown in FIG. 3 and FIGS. 4A to 4D, the dots 311 of the position information pattern are arranged with reference to the intersection formed by the grid-like reference line X and the reference line Y. Specifically, the dot 311a, the dot 311b, the dot 311c, and the dot 311d are arranged so as to shift to any one of the right side, the upper side, the left side, and the lower side with respect to the reference intersection point, and an array pattern by a plurality of dots 311 Is forming. For example, codes indicating the position coordinates of “1”, “2”, “3”, and “4” are assigned to the arrangement of the dots 311a, 311b, the dot 311c, and the dot 311d. When the unit area is 6 dots × 6 dots, 36 dots 311 are arranged in any one of the four types of shift positions shown in FIGS. 4A to 4D in the unit area. Corresponding to the number of combinations of shift positions of the 36 dots 311, the coordinate position of the unit area is defined. Thereby, according to the specific position in the display part 240, the position information pattern showing the coordinate position of the specific position can be formed. The electronic pen 100 can determine the position coordinates of the unit region by reading the dots 311 formed in the position information pattern in the unit region.

  The dots 311 forming the position information pattern transmit visible light while absorbing infrared light (invisible light), or transmit visible light while reflecting infrared light (invisible light). Formed from material. Thereby, the influence with respect to the visibility of the display image by the light of the visible light area | region displayed on the display part 240 of the display apparatus 200 can be decreased.

  The dots 311 may be formed of a material having light scattering and diffraction grating characteristics so that the direction of incident light is changed by irradiation with infrared light. In this case, since the dots 311 have light scattering properties and diffractive properties, the incident light is reflected (scattered, diffused, diffracted, phase-changed, bent) by the dots 311 and then the display device 200 again. Is output outside of. With this reflected light, the electronic pen 100 can detect the positional information pattern formed by the dots 311.

  Next, an example of a configuration related to the reflection of infrared light of the display device 200 will be described with reference to FIG. FIG. 5 is a schematic configuration diagram showing the configuration of the optical sheet 300 in which the position information pattern is arranged in the display device 200. However, in FIG. 5, the electronic pen 100 is simplified by describing only typical optical elements among the components shown in FIG.

  As shown in FIG. 5, the display device 200 is configured by laminating an optical sheet 300, a transparent adhesive layer 330, and a liquid crystal panel 340.

  The optical sheet 300 is configured by laminating a dot pattern sheet 310, a transparent adhesive layer 313, and an infrared reflection sheet 320.

  The dot pattern sheet 310 is provided with a positional information pattern formed by a plurality of dots 311 on a PET film 312 as a base material.

  The PET film 312 protects the surface of the display unit 240 of the display device 200. The PET film 312 functions as a base material for laminating layers such as the dots 311. A plurality of dots 311 are laminated on the back surface of PET film 312 (the lower surface in FIG. 5). The dots 311 protrude from the back surface of the PET film 312 by the thickness of the dots 311. A position information pattern is formed by a set of a plurality of dots 311 in the unit area.

  As shown in FIG. 6, the infrared reflective sheet 320 includes an uneven base 322 having an uneven surface 324 on a reference surface, and an infrared reflective layer 321 formed along the uneven surface 324 of the uneven base 322. It is configured. The concavo-convex base material 322 has a concavo-convex surface 324 having a fine concavo-convex shape in which an inclination at a predetermined angle with respect to the reference surface 323 is defined in order to improve infrared reflection performance. Specifically, when the concavo-convex base material 322 and the infrared reflective sheet 320 have an absolute angle (<90 deg) at which the tangent of each concavo-convex shape of the concavo-convex surface 324 is inclined with respect to the reference surface 323 as an absolute inclination angle θ, The distribution rate f (θ = 25 deg) when the absolute inclination angle θ of the concavo-convex surface 324 is 25 deg is 1.0 [% / deg] or more, and the concavo-convex surface 324 has an effective total area of the infrared reflective sheet 320. The ratio of the projected area occupied by the region having the absolute inclination angle θ of 40 degrees or more is set to 20% or less. Here, the distribution rate f (θ) is expressed by the following formula (1).

f (θ) = (ds / Sa) / dθ (1)
Sa represents the effective total area of the infrared reflective sheet 320. The effective total area is the total projected area of a region (effective surface) where the uneven shape of the uneven surface 324 is formed substantially uniformly. dθ represents a minute angle in the vicinity of the absolute inclination angle θ. ds indicates a projected area occupied by a region where the absolute inclination angle of the uneven surface 324 is in the range of θ to θ + dθ within the effective plane. The projected area is not the area of the curved surface along the concavo-convex shape of the concavo-convex surface 324 but the area of the plane projected on the flat surface (reference surface) obtained by averaging the concavo-convex surface 324.

  By forming the uneven surface 324 of the uneven substrate 322 in this manner, the infrared reflective sheet 320 has better reflection characteristics with respect to infrared light, and the color shifts from the infrared region to the visible region. Can be avoided. Therefore, the reading accuracy of the position information pattern by the electronic pen 100 can be ensured, and the image quality when the image is displayed with visible light can be ensured. The measurement results for explaining this effect will be described in detail later as Examples 1 to 3 and Comparative Examples 1 and 2.

  The infrared reflection layer 321 is a layer that reflects infrared light while transmitting visible light. When viewed microscopically, the infrared reflection layer 321 mirrors infrared rays. On the other hand, when viewed macroscopically, the infrared reflection sheet 320 functions as an infrared diffuse reflection member that diffuses and reflects infrared rays because the infrared reflection layer 321 is formed along the uneven surface 324.

  The transparent adhesive layer 313 is a layer for adhering the dot pattern sheet 310 and the infrared reflective sheet 320. The transparent adhesive layer 313 has a refractive index substantially equal to the refractive index of the material of the PET film 312 and the uneven substrate 322. The surface of the dot pattern sheet 310 on the infrared reflection sheet 320 side has an uneven shape due to the dots 311. The surface of the infrared reflection sheet 320 on the dot pattern sheet 310 side also has an uneven shape due to the uneven surface 324. Therefore, when adhering the dot pattern sheet 310 and the infrared reflective sheet 320, the transparent adhesive layer 313 fills the gap by flattening each other's concave-convex shape and optically couples them.

  The transparent adhesive layer 330 is a layer for bonding the infrared reflective sheet 320 and the liquid crystal panel 340. Similar to the transparent adhesive layer 313, the transparent adhesive layer 330 has a refractive index substantially equal to the refractive index of the material of the PET film 312 and the concavo-convex base material 322.

  The liquid crystal panel 340 is a device that displays an image based on visible light irradiation from a backlight device (not shown) by controlling the orientation of liquid crystal molecules.

  As shown in FIG. 5, since the LED 150 and the image reading unit 162 provided in the electronic pen 100 are provided close to each other, the incident angle of the illumination light 152 that illuminates the effective portion and the image reading unit 162 are effectively used. The reflection angles of the reflected light 163 to be input are substantially equal to each other and change according to the posture angle of the electronic pen 100. That is, by reflecting the light in various directions with respect to illumination light having various incident angles, the position information pattern can be optically read even when used in various pen postures.

  Here, the conditions of the optical sheet 300 for reflecting the reflected light in the direction in which the illumination light 152 is incident from the electronic pen 100 will be described with reference to FIG. In FIG. 6, the transparent adhesive layer 313, the infrared reflective layer 321, and the uneven base material 322 are shown in the configuration of the display device 200.

  The uneven surface 324 formed by the uneven substrate 322 is covered and flattened by the transparent adhesive layer 313. The refractive index of the transparent adhesive layer 313 is n (for example, n = 1.5), the incident angle of light (≈the attitude angle of the electronic pen 100) is φ, and the refractive angle in the transparent adhesive layer 313 is θ (reference plane 323). The angle coincides with the absolute inclination angle at which the tangent line of the uneven surface 324 is inclined). At this time, the refraction angle θ in the transparent adhesive layer 313 is obtained by the following formula (2) according to Snell's law.

θ = sin ⁻¹ {sin (φ) / n} (2)
When the uneven surface 324 having an inclination angle corresponding to the refraction angle θ calculated by Expression 2 is present on the uneven substrate 322 when the posture angle φ of the electronic pen 100 is changed, the illumination light 152 is emitted from the electronic pen 100. Reflected light that returns and reflects in the incident direction is generated.

  FIG. 7 shows a case where the incident angle of light (attitude angle of the electronic pen 100) φ and the return reflection with respect to the incident angle φ when the refractive index n of the transparent adhesive layer 313 is 1.5. The result of having calculated the relationship with required inclination | tilt angle (theta) is shown.

  For example, when the posture angle of the electronic pen 100 is 40 deg, an uneven surface 324 having an inclination angle in the vicinity of an angle of 25 deg is required on the uneven substrate 322 in order to enable reading of the position information pattern. The higher the probability that the concave / convex surface 324 having an inclination angle in the vicinity of the angle 25 deg on the concave / convex base material 322 is higher, the brighter infrared reflected light can be expected from the electronic pen 100.

  Assuming that the maximum posture angle of the electronic pen 100 is about 75 deg slightly inclined from the vertical (90 deg), as shown in FIG. 7, the angle of the inclined surface of the concavo-convex surface 324 on the concavo-convex base material 322 is It can be seen that the distribution is preferably between 0 deg and 40 deg. As shown in FIG. 7, the presence of the concave / convex surface 324 having an inclination angle larger than 40 deg causes total reflection at the time of emission on the flattened surface, which in turn reduces the reflection efficiency.

  8A to 8D are diagrams showing the abundance ratio and distribution ratio of a surface in the vicinity of a specific inclination angle on the uneven surface 324 on the uneven substrate 322. FIG. As a method for quantifying the inclination angle distribution of the uneven surface 324, means for displaying as a histogram from measurement data such as a three-dimensional measuring instrument or a laser microscope is known.

  8A and 8C are histograms created from the same virtual population, the horizontal axis is the range of the inclination angle (absolute inclination angle θ) of the uneven surface 324, and the vertical axis is the inclination angle indicated by each horizontal axis. The abundance ratio on the concavo-convex base material 322 of the nearby surface is shown. Note that FIG. 8A is disassembled and displayed in the range of the inclination angle of 5 deg, whereas FIG. 8C is disassembled and displayed in the range of 10 deg. Since both FIGS. 8A and 8C are created from the same population, their profiles are similar, but the vertical axis differs by about twice.

  On the other hand, FIGS. 8B and 8D are graphs of the distribution ratios created from FIGS. 8A and 8C, respectively. 8A and 8C, the abscissa represents the median value of each region decomposed with respect to the inclination angle indicated by the horizontal axis, and the abundance ratio [%] of the surface of the inclination angle range indicated by each region on the concavo-convex substrate 322 is expressed as The value divided by the range of [deg] is the distribution rate [% / deg] and is displayed on the vertical axis.

  By displaying in this way, it is possible to perform quantification independent of how the angle range is resolved.

  Although details are omitted, when the uneven surface 324 is formed of a transparent material like the uneven substrate 322, a parallel light beam is incident on the uneven surface 324, and the luminous intensity distribution of the transmitted light is measured. The inclination angle distribution of the concavo-convex surface 324 may be calculated by solving a differential equation in which a differential expression that is a definition expression of luminous intensity and a differential expression that is a definition expression of the inclination angle distribution are combined.

  Hereinafter, examples and comparative examples according to the present disclosure will be described with reference to the drawings.

  9A to 9E are diagrams showing surface photographs in Examples and Comparative Examples. FIG. 10 is a diagram illustrating a distribution rate with respect to the inclination angle θ in the example and the comparative example (distribution rate obtained by performing the quantification described with reference to FIG. 8). FIG. 11 is a diagram illustrating the configuration of the test sheet 400 and the configuration of the diffuse reflection measurement apparatus 430. FIG. 12 is a diagram showing the diffuse reflectance for each measurement angle at a wavelength of 950 nm in the example and the comparative example. FIG. 13 is a diagram showing spectral reflectances in Examples and Comparative Examples. In Examples 1 to 3 and Comparative Examples 1 and 2, the characteristics of the inclined surface distribution of the concavo-convex base material 322, the image quality (brightness, contrast) of the display device 200, and the reading performance of the position information pattern by the electronic pen 100 Table 1 shows a summary of the evaluation results.

  The measurement results according to Examples 1 to 3 and Comparative Examples 1 and 2 will be described. Reference numerals a to e are attached to the end of the configurations according to Examples 1 to 3 and Comparative Examples 1 and 2, respectively, for identification. However, in Examples 1 to 3 and Comparative Examples 1 and 2, when the configuration is the same, no reference is given.

Example 1
The electronic pen 100 was configured using an infrared light emitting LED having a peak wavelength of 950 nm as the LED 150.

  As shown in FIG. 11, a test sheet 400a according to Example 1 was formed. The test sheet 400a eliminates the influence of the infrared absorption dots 311 provided on the dot pattern sheet 310, and purely evaluates the characteristics of the infrared reflection sheet 320a, so that the infrared reflection sheet 320a (infrared reflection layer 321) is used. , The concavo-convex base material 322a) and the PET film 312 on which the dots 311 are not formed are joined by the transparent adhesive layer 313. Further, a black sheet 410 is used instead of the liquid crystal panel 340.

  The uneven substrate 322a according to Example 1 has the surface shape shown in the surface photograph of FIG. 9A, and in the graph of FIG. 10, the absolute inclination angle distribution (with respect to the inclination angle θ) of the uneven shape shown by the solid line (Example 1). Distribution rate f (θ)). More specifically, as shown in Table 1, the uneven substrate 322a has a distribution rate f (25 deg) of 1.4 [% / deg] with an absolute inclination angle of 25 deg on the uneven surface 324a. Further, in the uneven substrate 322a, the ratio of the projected area occupied by the region where the absolute inclination angle of the uneven surface 324a is 40 degrees or more in the effective total area of the infrared reflective sheet 320a is 1.0%.

  On the uneven surface 324a of the uneven substrate 322a, several layers of optical materials having different refractive indexes were alternately laminated by a sputtering method to provide an infrared reflection layer 321 to obtain an infrared reflection sheet 320a.

  Next, measurement of the diffuse reflection characteristics of the test sheet 400a created as described above will be described. The diffuse reflection characteristic is measured by using a diffuse reflection measurement device 430 as shown in FIG. 11 and capturing only the component that is irradiated with light from a specific angle and returned in the incident direction. The diffuse reflection measurement device 430 includes a light source, a spectroscope, and a probe 432 (not shown). The light source emits light including light from the visible region to the infrared region. Light emitted from the light source is incident on the test sheet 400 a via the probe 432. The probe 432 includes seven optical fibers, one at the center is connected to the spectroscope, and six at the periphery are connected to the light source. The probe 432 is inclined by a measurement angle φ (corresponding to the absolute inclination angle φ of the electronic pen 100) from the normal direction of the surface of the test sheet 400a, and irradiates the test sheet 400a with light. The test sheet 400 a reflects part of the light emitted from the probe 432 toward the probe 432. This reflected light is guided to the spectroscope via the probe 432. Thus, the spectroscope performs spectroscopic measurement.

  As a reference for spectroscopic measurement, a standard reflector 420 having a complete diffusion surface laminated on the surface as shown in FIG. 11 is used. Then, the diffuse reflectance of the test sheet 400a is calculated by taking a ratio between the measurement result obtained by the diffuse reflection measurement device 430 and the measurement result obtained by the standard reflection plate 420.

  The diffuse reflectance for each measurement angle at a wavelength of 950 nm is shown by the solid line (Example 1) in the graph of FIG. By evaluating the wavelength 950 nm, which is the emission peak wavelength of the LED 150 of the electronic pen 100, it can be used as an index of the reading performance of the electronic pen 100. As shown in FIG. 12, it can be seen that the test sheet 400a maintains a diffuse reflectance of about 10% with respect to light irradiation of 950 nm even when tilted to a measurement angle of 50 deg.

  Subsequently, the spectral reflectance of the test sheet 400a was measured using a general spectrophotometer. A light is incident at a measurement angle of 8 degrees from the PET film 312 side of the test sheet 400a, and the spectrum is acquired by capturing the reflected light with an integrating sphere. Under the same conditions as those for the test sheet 400a, a standard reflector as a reference The diffuse reflectance was calculated from the ratio of 420 to the standard spectrum measured.

  The measurement result of the spectral reflectance in Example 1 is shown by the solid line (Example 1) in the graph of FIG. As shown by the solid line in the graph of FIG. 13, the LED 150 exhibits a high reflectance of 70% or more near the peak wavelength of 950 nm, and about 10% in the visible light region having a wavelength of 430 nm to 700 nm, the Fresnel reflection at the air interface. The reflectivity was low enough to meet

  Subsequently, the dot pattern sheet 310 was laminated on the infrared reflective sheet 320a used for the test sheet 400a of Example 1, thereby forming an optical sheet 300a. The dot pattern sheet 310 includes dots 311 which are infrared absorption layers having a transmittance at 950 nm of 5% (absorption rate 95%) and an effective visible light transmittance of 80%. Further, the surface of the dot pattern sheet 310 on which the concavo-convex shape is formed by the dots 311 and the surface on which the concavo-convex shape of the concavo-convex base material 322a of the infrared reflection sheet 320a are laminated with the infrared reflection layer 321a are bonded together with an acrylic transparent adhesive. The optical sheet 300a was formed by bonding with the layer 313. Furthermore, the optical sheet 300a was bonded to the liquid crystal panel 340 to configure the display device 200a.

  When a reading test of the position information pattern was performed on the display device 200a with the electronic pen 100, the exposure time was short when the posture of the electronic pen 100 was vertical (0 deg) near the display unit 240 of the display device 200a. It was possible to obtain a clear image and to follow an extremely fast pen speed. As a result, power consumption could be reduced.

  The diffuse reflectance decreases as the inclination angle from the vertical direction of the display unit 240 of the display device 200a of the electronic pen 100 increases. Therefore, it is necessary to increase the exposure time of the image reading unit 162, but it is possible to obtain a good image up to an inclination angle of 50 deg, and the position information pattern detection operation is good.

  Further, when an image was displayed on the liquid crystal panel 340 with visible light, the display quality was good with almost no decrease in the brightness of the image light from the state in which the optical sheet 300a was not laminated and contrast deterioration due to an increase in external light reflection.

(Example 2)
Similar to Example 1, a test sheet 400b, an optical sheet 300b, and a display device 200b according to Example 2 were formed, and various characteristics were measured.

  Differences from the first embodiment will be described. The uneven base material 322b according to Example 2 has the surface shape indicated by the surface photograph of FIG. 9B, and the absolute inclination angle distribution (inclination angle) of the uneven shape indicated by the broken line (Example 2) in which the graph interval of FIG. 10 is short. A diffusion sheet having a distribution ratio f (θ) with respect to θ is used. More specifically, as shown in Table 1, the uneven substrate 322b has a distribution rate f (25 deg) of 2.7 [% / deg] with an absolute inclination angle θ of 25 deg on the uneven surface 324b. Furthermore, in the uneven base 322b, the ratio of the projected area occupied by the region where the absolute inclination angle of the uneven surface 324b is 40 degrees or more in the effective total area of the infrared reflective sheet 320b is 16.4%.

  As shown by the short dashed line (Example 2) in the graph of FIG. 12, the test sheet 400b maintains a diffuse reflectance of about 20% even when tilted to a measurement angle of 50 deg.

  The measurement result of the reflectance with respect to the irradiation wavelength in Example 2 is shown by a broken line (Example 2) having a short interval in the graph of FIG. As shown by the dotted line in the graph of FIG. 13, the reflection peak wavelength is slightly shifted to the short wavelength side as compared with Example 1 indicated by the solid line, and the reflectance in the vicinity of 950 nm is slightly reduced, but is close to 60%. showed that. Further, in the visible range, a slight increase in reflectance was observed in the long wavelength range, but the increase from Fresnel reflection was slight.

  When the display device 200b was subjected to a position information pattern reading test with the electronic pen 100, the position of the position information pattern was determined so that the posture of the electronic pen 100 was in a range of vertical (0 deg) to 50 deg with respect to the display unit 240 of the display device 200b. Detection was good.

  In addition, when an image is displayed on the liquid crystal panel 340 with visible light, a decrease in luminance of the image light from the state where the optical sheet 300b is not stacked is hardly recognized.

  However, a slightly reddish reflection occurred in a bright environment, and contrast degradation due to increased external light reflection was slightly observed in dark scenes.

(Example 3)
Similar to Example 1, a test sheet 400c, an optical sheet 300c, and a display device 200c according to Example 3 were formed, and various characteristics were measured.

  Differences from the first embodiment will be described. The uneven substrate 322c according to Example 3 has the surface shape shown in the surface photograph of FIG. 9C, and the absolute inclination angle distribution (inclination angle) of the uneven shape indicated by the broken line (Example 3) in which the interval of the graph of FIG. 10 is short. A lens array sheet having a distribution ratio f (θ) with respect to θ is used. More specifically, as shown in Table 1, the uneven substrate 322c has a distribution rate f (25 deg) of 5.3 [% / deg] when the absolute inclination angle θ on the uneven surface 324c is 25 deg. Further, in the uneven substrate 322c, the ratio of the projected area occupied by the region where the absolute inclination angle of the uneven surface 324c is 40 degrees or more in the effective total area of the infrared reflective sheet 320c is 0.7%.

  As shown by the short dashed line (Example 3) in the graph of FIG. 12, the diffuse reflectance of the test sheet 400c is maintained at about 50% over a wide range from 20 degrees to 50 degrees regardless of the measurement angle.

  The measurement result of the reflectance with respect to the irradiation wavelength in Example 3 is shown by a broken line (Example 3) having a short interval in the graph of FIG. As shown by the short dashed line in the graph of FIG. 13, the reflection peak wavelength is slightly shifted to the short wavelength side and the reflectance in the vicinity of 950 nm is slightly lowered as compared with Example 1 indicated by the solid line. The value was close to%. Further, in the visible range, a slight increase in reflectance was observed in the long wavelength range, but the increase from Fresnel reflection was slight.

  When the display device 200c was subjected to a position information pattern reading test with the electronic pen 100, the position of the position information pattern was determined so that the posture of the electronic pen 100 was in the range of vertical (0 deg) to 50 deg with respect to the display unit 240 of the display device 200c. Detection was good.

  In addition, when an image is displayed on the liquid crystal panel 340 with visible light, a decrease in luminance of the image light from the state where the optical sheet 300c is not stacked is hardly recognized.

  However, a slightly reddish reflection occurred in a bright environment, and slight deterioration in contrast due to increased external light reflection was observed in dark scenes.

(Comparative Example 1)
As in Examples 1 to 3, a test sheet 400d, an optical sheet 300d, and a display device 200d according to Comparative Example 1 were formed.

  Differences from the first to third embodiments will be described. The uneven base material 322d according to Comparative Example 1 has the surface shape indicated by the surface photograph of FIG. 9D, and the absolute inclination angle distribution (distribution with respect to the inclination angle θ) indicated by the long dashed line (Comparative Example 1) in the graph of FIG. Rate f (θ)). More specifically, as shown in Table 1, the uneven base material 322d has a distribution rate f (25 deg) of 0.3 [% / deg] when the absolute inclination angle θ on the uneven surface 324d is 25 deg. Further, in the concavo-convex substrate 322d, the ratio of the projected area occupied by the region where the absolute inclination angle of the concavo-convex surface 324d is 40 degrees or more in the effective total area of the infrared reflective sheet 320d is 0.3%.

  As shown by the long dashed line in the graph of FIG. 10 (Comparative Example 1), the inclined surface distribution of the concavo-convex surface 324d of the concavo-convex substrate 322c has a peak in the vicinity of 5 deg. There were few.

  As shown by the long dashed line in the graph of FIG. 12 (Comparative Example 1), the diffuse reflectance of the test sheet 400d rapidly decreases as the measurement angle increases, and is 10% at 30 degrees and 5% or less at 40 degrees or more. there were.

  Moreover, the measurement result of the reflectance with respect to the irradiation wavelength in Comparative Example 1 is shown by a broken line (Comparative Example 1) having a long interval in the graph of FIG. As shown by the long dashed line in the graph of FIG. 13, the LED 150 exhibits a high reflectance of 70% or more near the peak wavelength of 950 nm, and in the visible light region of 430 nm to 700 nm, about 10% at the air interface. The reflectivity is low enough to match the Fresnel reflection.

  When a reading test of the position information pattern was performed on the display device 200d with the electronic pen 100, the position information pattern was detected very well when the posture of the electronic pen 100 was near (0 deg) perpendicular to the display surface of the display device 200d. Although it was possible, the brightness and contrast of the infrared image that could be acquired with a pen posture exceeding 30 degrees were insufficient, and coordinates could not be detected when the posture of the electronic pen 100 was tilted to 40 degrees or more.

  This is because the concavo-convex surface 324d of the infrared reflection sheet 320d lacks the component ratio (distribution rate) in the vicinity of the inclination angle of 25 deg necessary for generating back reflection when the posture of the electronic pen 100 is 40 deg. It is thought to be because.

  In addition, when an image was displayed on the liquid crystal panel 340 with visible light, the luminance and contrast of the image light from the state where the optical sheet 300d was not laminated were hardly observed, and the display quality was good.

(Comparative Example 2)
Similar to Examples 1 to 3 and Comparative Example 1, a test sheet 400e, an optical sheet 300e, and a display device 200e according to Comparative Example 2 were formed, and various characteristics were measured.

  Differences from Examples 1 to 3 and Comparative Example 1 will be described. The uneven base material 322e according to Comparative Example 2 has the surface shape indicated by the surface photograph of FIG. 9E, and the absolute inclination angle distribution (with respect to the inclination angle θ) of the uneven shape indicated by the one-dot chain line (Comparative Example 2) of the graph of FIG. A lens array sheet having a distribution rate f (θ)) is used. More specifically, as shown in Table 1, the uneven substrate 322e has a distribution rate f (25 deg) of 1.9 [% / deg] with an absolute inclination angle θ of 25 deg on the uneven surface 324e. Further, in the concavo-convex base material 322e, the ratio of the projected area occupied by the region where the absolute inclination angle of the concavo-convex surface 324e is 40 degrees or more in the effective total area of the infrared reflective sheet 320e is 35.0%. In addition, as shown by the dashed-dotted line (comparative example 2) of the graph of FIG. 10, the inclined surface distribution of the uneven surface 324e of the uneven base material 322e is substantially in agreement with the calculation result of a hemisphere.

  The measurement result of the reflectance with respect to the irradiation wavelength in Comparative Example 2 is shown by a one-dot chain line (Comparative Example 2) in the graph of FIG. As shown by the alternate long and short dash line in the graph of FIG. 13, the wavelength selectivity was hardly shown, and the reflectance was higher in the visible range than in Examples 1 to 3 and Comparative Example 1. This is because the uneven surface 324e of the infrared reflection sheet 320e contains a large amount of tilt components of 40 deg or more that do not contribute to the return reflection to the electronic pen 100. As a result, the shift of the selected wavelength characteristics due to the oblique incidence, the emission of the reflected light This is thought to be due to total reflection on the surface. When the infrared reflection sheet 320e having such optical characteristics is provided on the display surface of the display device 200, the brightness of the image by visible light is greatly impaired, and contrast deterioration with respect to external light is remarkably deteriorated, so that the display quality of the image is greatly impaired. . Therefore, in Comparative Example 2, no further evaluation such as a position information pattern reading test with the electronic pen 100 was performed.

  As described above, as shown in Table 1, the distribution of the inclined surface of the concavo-convex base material 322 is concentrated to 10 deg or less, and the distribution rate of 25 deg is as small as 0.3 [% / deg]. The video quality of 200 can ensure a certain standard or more. However, the angle of the pen posture at which the electronic pen 100 can accurately read the position information pattern is limited, and the reading of the position information pattern becomes insufficient particularly at 40 deg, which is a pen posture angle that is frequently used.

  On the other hand, in Comparative Example 2 in which the component having a substantially hemispherical shape and the angle of the inclined surface of the concavo-convex base material 322 is as large as 35% is as large as 35%, it becomes difficult to achieve the target wavelength selection characteristics, and the video quality of the display device 200 It is difficult to ensure a certain level above a certain level.

  From the above, the infrared reflection sheet 320 (uneven base material 322) has an absolute angle (<90 deg) at which the tangent of each uneven surface of the uneven surface 324 is inclined with respect to the reference surface 323 as an absolute inclination angle θ. The distribution ratio f (θ = 25 deg) when the absolute inclination angle θ of the concavo-convex surface 324 is 25 deg is 1.0 [% / deg] or more, and the concavo-convex surface 324 is in the effective total area of the infrared reflective layer 321. The ratio of the projected area onto the reference plane 323 occupied by the region having the absolute inclination angle θ of 40 degrees or more is 20% or less. By forming the concave / convex surface 324 of the concave / convex base material 322 in this manner, it has better reflection characteristics with respect to infrared light and avoids a shift in color from the infrared region to the visible region. be able to. Therefore, the reading accuracy of the position information pattern by the electronic pen 100 can be ensured, and the image quality when the image is displayed with visible light can be ensured.

(Other embodiments)
As described above, the embodiments have been described as examples of the technology in the present disclosure. However, the technology in the present disclosure is not limited to this, and can also be applied to an embodiment in which changes, substitutions, additions, omissions, and the like are appropriately performed. Moreover, it is also possible to combine each component demonstrated by the said embodiment, and it can also be set as a new embodiment. Therefore, other embodiments will be exemplified below.

  In the above embodiment, infrared light is used for the LED 150 of the electronic pen 100, the absorption wavelength of the dots 311 of the dot pattern sheet 310 is infrared, and the infrared reflection sheet 320 is used. However, the present disclosure is not limited to this. . For example, an ultraviolet light emission may be used for the LED 150, the absorption wavelength of the dot pattern sheet 310 may be ultraviolet light, and an uneven reflection sheet that reflects ultraviolet light may be used. In short, any system may be used as long as the electronic pen 100 optically reads the position information pattern formed on the display unit 240 using invisible light.

  In the present embodiment, the refractive index n of the transparent adhesive layer 313, the PET film 312 and the concavo-convex base material 322 constituting the optical sheet 300 is 1.5, but the refractive index n is 1.45 to 1.65. The case was tested with similar results.

  As described above, the embodiments have been described as examples of the technology in the present disclosure. For this purpose, the accompanying drawings and detailed description are provided.

  Accordingly, among the components described in the attached drawings and detailed description, not only the components essential for solving the problem, but also the components not essential for solving the problem in order to exemplify the above technique. May also be included. Therefore, it should not be immediately recognized that these non-essential components are essential as those non-essential components are described in the accompanying drawings and detailed description.

  Moreover, since the above-mentioned embodiment is for demonstrating the technique in this indication, a various change, substitution, addition, abbreviation, etc. can be performed in a claim or its equivalent range.

  As described above, the present disclosure is an invention useful for comfortably performing an input operation on a display device using an input pen.

DESCRIPTION OF SYMBOLS 100 Electronic pen 110 Processing circuit 120 Transmitter 130 Pen tip 131 Pressure sensor 140 Switch 150 LED
151 Condensing lens 152 Illuminating light 160 Condensing lens 161 IR filter 162 Image reading unit 163 Reflected light 200, 200a, 200b, 200c, 200d, 200e Display device 210 Receiving unit 220 Processing circuit 230 Panel driving circuit 240 Display unit 300, 300a , 300b, 300c, 300d, 300e Optical sheet 310 Dot pattern sheet 311, 311a, 311b, 311c, 311d, 311e Dot 312 PET film 313 Transparent adhesive layer 320, 320a, 320b, 320c, 320d, 320e Infrared reflective sheet 321 321a Infrared reflective layer 322, 322a, 322b, 322c, 322d, 322e Uneven substrate 323 Reference surface 324, 324a, 324b, 324c, 324d, 324e Uneven surface 3 0 transparent adhesive layer 340 liquid crystal panel 400,400a, 400b, 400c, 400d, 400e test sheet 410 black sheet 420 standard reflecting plate 430 diffuse reflectance measuring apparatus 432 probe

Claims (5)

A substrate having an uneven surface on a reference surface;
A reflective layer that reflects non-visible light formed along the uneven surface,
When the angle at which the tangent of the concavo-convex surface is inclined with respect to the reference surface is defined as an inclination angle, the distribution rate when the inclination angle is 25 deg is 1.0% / deg or more, and the inclination angle A non-visible light reflecting sheet in which the ratio of the projected area of the region of 40 deg or more to the reference surface in the total area of the reference surface is 20% or less. The non-visible light reflecting sheet according to claim 1, wherein the distribution ratio is obtained by Formula 1.
(Formula 1)
f (θ) = (ds / Sa) / dθ
here,
f (θ): Distribution rate θ: Angle of inclination of the unevenness [deg]
dθ: Minute angle near θ [deg]
ds: Projected area on the reference plane in a region where the inclination angle of the concavo-convex surface is in the range of θ to θ + dθ Sa: The effective total area of the reflective layer. A non-visible light reflecting sheet;
A pattern sheet laminated on the non-visible light reflecting sheet and provided with a pattern showing position information by absorbing or reflecting non-visible light, and an optical sheet comprising:
The invisible light reflecting sheet is
A base material having an uneven surface on a reference surface, and a reflective layer that reflects invisible light formed along the uneven surface,
When the angle at which the tangent of the concavo-convex surface is inclined with respect to the reference surface is defined as an inclination angle, the distribution rate when the inclination angle is 25 deg is 1.0% / deg or more, and the inclination angle An optical sheet in which the ratio of the projected area of the region of 40 deg or more to the reference surface to the total area of the reference surface is 20% or less.   The optical sheet according to claim 3, wherein the refractive index is 1.45 to 1.65. A display panel having a display area for displaying an image;
An optical sheet disposed on the display area, and a display device comprising:
The optical sheet includes a non-visible light reflecting sheet, and a pattern sheet laminated on the non-visible light reflecting sheet and provided with a pattern indicating position information by absorbing or reflecting non-visible light,
The invisible light reflecting sheet includes a base material having an uneven surface on a reference surface, and a reflective layer that reflects the invisible light formed along the uneven surface,
When the angle at which the tangent of the concavo-convex surface is inclined with respect to the reference surface is defined as an inclination angle, the distribution rate when the inclination angle is 25 deg is 1.0% / deg or more, and the inclination angle A display device in which a ratio of a projected area of the region of 40 deg or more to the reference surface to a total area of the reference surface is 20% or less.