JP2005055736A - Optical sheet and liquid crystal display and display apparatus equipped with the optical sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical sheet having specified light shielding performance at a visual angle in one side and preventing significant decrease in the luminance at a visual angle in the other side. <P>SOLUTION: The optical sheet 17 has a plurality of peaks 17c having a sawtooth cross section on one surface of a sheet having light transmitting property, with each peak 17c comprising slopes with an asymmetric cross section and different slope lengths from each other and having a light shielding layer 31 or a layer having wavelength-dependent transmittance in the shorter slope 17c-1 side. A liquid crystal display 10 is provided which has the optical sheet 17 disposed between a backlight 11 and a liquid crystal panel 12. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical sheet, a liquid crystal display device including the optical sheet, and a display device, and more specifically, an optical sheet that can change light transmittance according to a viewing angle, and a viewing angle provided with the optical sheet. The present invention relates to a liquid crystal display device and a display device in which image visibility changes.

  2. Description of the Related Art Conventionally, in an in-vehicle liquid crystal display device used for an automobile car navigation device, an automobile TV, and the like, when an image displayed on a liquid crystal panel is reflected on a windshield, an image displayed on a night drive or a tunnel drive is displayed. A virtual image enters the field of view and deteriorates the forward visibility. In the worst case, an intersection accident or rear-end collision may occur due to neglect of the signal due to carelessness in the forward direction. Accordingly, automobile manufacturers have adopted a liquid crystal display device having a characteristic that allows an image to be seen only within a specific viewing angle range to prevent the image from being reflected on the windshield.

  Similarly, the liquid crystal display screen of an ATM (automatic cash dispenser) of a financial institution cannot be viewed beyond a predetermined angle so that important personal financial information cannot be seen by a person waiting for the turn. Furthermore, it has a characteristic that the image cannot be visually recognized from a predetermined viewing angle range.

  As a liquid crystal display device capable of limiting the viewing angle range as described above, the one shown in FIG. 16 is disclosed in Japanese Patent Laid-Open No. 2002-124112.

In this liquid crystal display device 1, a liquid crystal panel 2 and a backlight 3 are arranged to face each other, and the backlight 3 includes a linear light source 4, a reflection sheet 5, a light guide 6, a prism sheet 7, and a light shielding louver film 8. I have. As shown in FIG. 17, in the light-shielding louver film 8, a louver film 8c is bound between a front surface base material 8a and a back surface base material 8b, and the louver film 8c is arranged vertically (louver angle 0 °). The louver shading plate 8c-1 and the transparent layer 8c-2 thus arranged are arranged at an equal pitch to limit the outgoing angle of transmitted light within the θ range.
As shown in FIG. 18, the light transmitted through the light shielding louver film 8 exhibits a characteristic transmission profile in the direction perpendicular to the longitudinal direction of the light shielding plate 8c-1. That is, the transmittance becomes maximum at an incident angle of 0 °, and the transmittance decreases linearly as the absolute value of the incident angle increases.
In the liquid crystal display device 1 in which the light shielding louver film 8 is interposed between the backlight 3 and the liquid crystal panel 2, the backlight 3 itself under the light shielding louver film 8 has a light distribution as shown in FIG. When the light distribution characteristic is multiplied by the transmission profile of the light shielding louver film 8, the liquid crystal display device 1 as a whole exhibits the light distribution characteristic shown in FIG. That is, the liquid crystal display device 1 provided with the transmissive louver film 8 can visually recognize an image from a predetermined viewing angle range (about ± 30 °), but cannot view an image from other angles. it can. In addition, the vertical axis | shaft of FIG. 19 represents the relative brightness | luminance which makes the brightness | luminance of the backlight 3 in the viewing angle 0 degree 100%.
JP 2002-124112 A

  However, with the diversification of lifestyles, various contents such as movies, music, news, variety, etc., are being slowly reclined on DVDs and TVs using the liquid crystal display device 1 in a car, and are gradually being appreciated. Yes. When the liquid crystal display device 1 using the conventional light-shielding louver film 8 is viewed during reclining, the light-shielding louver film is viewed from a considerably lower angle with respect to the normal direction of the display surface of the liquid crystal display device 1. There is a problem that the dimming effect by 8 is large and the luminance is greatly lowered, the screen is very dark and the visibility is deteriorated.

  Further, even when the liquid crystal display device 1 is installed at an angle at which an image can be visually recognized, a periodic black streak pattern (moire) is observed due to variations in pitch of the louver light shielding plate 8c-1 of the light shielding louver film 8. There is.

  The present invention has been made in view of the above problems, and has a predetermined light-shielding performance at one side angle, but does not cause a significant decrease in luminance at the other side angle and also produces a black stripe pattern. It is an object of the present invention to provide a display device and an optical sheet used therefor.

  In order to solve the above-mentioned problems, the present invention firstly has a large number of ridges arranged in a sawtooth cross-section on one side of a light-transmitting sheet, and shields light on a slope on one side of the ridge. An optical sheet characterized by providing a layer is provided.

  With the above configuration, since the light shielding layer is provided on the slope on one side of each mountain portion arranged side by side on the sheet side, the transmitted light is refracted and totally reflected only on the slope on the other side without the light shielding layer. In addition, light that has a surface reflecting function and is incident on one side of the inclined surface having the light shielding layer is absorbed. Therefore, the outgoing light that has passed through the optical sheet can form an outgoing profile that is deflected as a whole, with the direction that passes through the slope side without the light-shielding layer at the peak as the main direction.

  Each of the peak portions is asymmetric in cross section and has a different slope length, and the light shielding layer is provided on the short slope side.

  By making the cross-sectional shape of the mountain portion asymmetric, the projected area of the short slope on the sheet surface becomes smaller than the projected area of the long slope on the sheet surface. By providing a light-shielding layer on the short slope side where the projected area is small, the amount of light that is incident mainly in the direction perpendicular to the sheet surface is more transmitted through the long slope than the amount absorbed by the short slope. Therefore, it is possible to suppress a decrease in luminance of the emitted light that has passed through the optical sheet.

  In addition, as a specific example of the light shielding layer, it is preferable to use carbon black, a metal-based paint, a black dye, or a black pigment, but the material is not limited to this as long as the material has a light shielding property.

  Secondly, according to the present invention, a large number of peaks are provided side by side in a sawtooth shape on one side of a light-transmitting sheet, and the visible light transmittance depends on the wavelength on the slope on one side of the peaks. An optical sheet characterized in that a light transmittance wavelength-dependent layer is provided.

  With the above configuration, since the light transmittance wavelength-dependent layer is provided on the slope on one side of each peak portion arranged side by side on the one surface side of the sheet, all wavelengths are on the other slope without the light transmittance wavelength-dependent layer. The light incident on the slope on one side of the wavelength-dependent layer of light transmittance mainly transmits light having a specific range of wavelengths and has other functions. Wavelength light is mainly absorbed. That is, the light transmittance wavelength-dependent layer increases the transmittance of light of a specific range of wavelengths, while decreasing (or zero) the transmittance of light of wavelengths outside the range. Therefore, the outgoing light transmitted through the optical sheet forms a polarized outgoing profile as a whole, with the direction transmitting through the slope side without the light transmittance wavelength-dependent layer at the peak as a whole, and the light transmittance wavelength-dependent layer It is possible to emit only light of a specific range of wavelengths (light of a certain color) from a certain slope. That is, the short slope provided with the light transmittance wavelength-dependent layer serves as a kind of optical bandpass filter.

  Each of the peaks has an asymmetric cross section and a different slope length, and the light transmittance wavelength-dependent layer is provided on the short slope side.

  As in the case of the light-shielding layer, the cross-sectional shape of the peak is asymmetrical, and a light transmittance wavelength-dependent layer is provided on the short slope surface with a small projected area on the sheet surface. Since the amount of light incident on the light is transmitted through the long slope is larger than the amount absorbed by the short slope, it is possible to suppress a decrease in luminance of the emitted light that has passed through the optical sheet. Note that light having a wavelength in a specific range is transmitted even on a short slope with a light transmittance wavelength-dependent layer, which can contribute to suppression of a decrease in luminance.

  The light transmittance wavelength-dependent layer has a transmittance of 25% or less for visible light having a wavelength of 500 nm or more.

  With the above configuration, the transmittance of light of green, yellow, orange, and red in the visible light spectrum is small, and the color shown by the human visual sensitivity curve (FIG. 6) does not emit a color that gives a strong sense of brightness. Light transmittance This is suitable when it is not desirable for humans to recognize light transmitted through the wavelength-dependent layer.

  The light transmittance wavelength-dependent layer preferably has a visible light transmittance of a wavelength smaller than 500 nm larger than a visible light transmittance of a wavelength of 500 nm or more.

  Generally, a phenomenon is known in which chromaticity shifts to yellow when transmitted white light is viewed from an oblique side (large viewing angle), that is, a phenomenon in which chromaticity transitions to the opposite side of the blue region in chromaticity coordinates (FIG. 10). Yes. Therefore, with the above configuration, light that is transmitted mainly through the light transmittance wavelength-dependent layer and is emitted in an oblique direction increases the transmittance of blue light having a wavelength of less than 500 nm. The chromaticity shift is reduced by the offset effect of yellow and blue in FIG. 10), and white can be maintained as much as possible even when viewed obliquely.

  Specific examples of the light transmittance wavelength-dependent layer include azo lake paints, azo paints, phthalocyanine paints, indico paints, perinone paints, phthalone paints, dioxane paints, quinacridkin paints, and isoindolinone paints. Alternatively, it is preferable to use a metal-based paint, but the material is not limited to this as long as the visible light transmittance depends on the wavelength.

The optical sheet is provided by laminating a ridge-forming film provided with the ridges on one surface side of a flat sheet-like base film,
The base film is made of polyethylene terephthalate, polycarbonate, cycloolefin or polyolefin,
The peak forming film is preferably made of a UV curable acrylic resin, an acrylic resin, a methacrylic resin, or a urethane resin.

  If it is set as the said structure, a highly transparent base film part is provided as a base material of an optical sheet, adhesiveness with a peak formation film is also favorable, and an optical sheet with high reliability can be produced. In addition, since it has a two-layer structure, the heat resistance level can be easily changed by changing the thickness of the base film, and thermal deformation can be easily suppressed by overlapping the base films. . Furthermore, by using the above-mentioned materials for the base film and the ridge forming film, it is inexpensive, high transparency and high reliability can be obtained, and workability is also improved.

  Thirdly, the present invention provides a liquid crystal display device characterized in that the optical sheet is interposed between a backlight and a liquid crystal panel.

In the liquid crystal display device having the above-described configuration, an image cannot be viewed (or difficult to view) from one viewing angle, while an image can be reliably viewed from the other viewing angle. For example, when this LCD device is set on a dashboard in an automobile with the normal direction of the slope with the light shielding layer of the optical sheet facing the upper windshield, the image is reflected on the windshield. Can be prevented. Further, since the viewpoint at the seat position at the time of reclining is the normal direction of the slope without the light shielding layer, it is possible to view the image while maintaining display quality with sufficient luminance. (The same principle applies when a light transmittance wavelength-dependent layer is used instead of the light shielding layer)
The optical sheet is preferably offset so that the extending direction of the peaks is not parallel to the pixel arrangement direction of the liquid crystal panel.

  When the liquid crystal display screen is viewed obliquely due to the influence of the light-shielding layer or light transmittance wavelength-dependent layer of the optical sheet, moire fringes that are black and white stripes may be observed. However, according to the above configuration, since the pixel arrangement direction of the liquid crystal panel and the extending direction of the peak portion of the optical sheet are offset without being parallel, the period of light and dark is so difficult to be recognized by the resolution of the human eye. It can be shortened and the occurrence of moire can be prevented.

  The pitch of each peak portion of the optical sheet is set to be equal to or less than the pixel pitch of the liquid crystal panel.

  That is, if the pitch between the peaks arranged in parallel with the optical sheet is larger than the pixel pitch of the liquid crystal panel, there is a possibility that a portion where the light shielding layer or the light transmittance wavelength-dependent layer covers the pixel occurs. As described above, by setting the pixel pitch or less, all the pixels can be reliably displayed.

  Fourthly, the present invention provides a display device characterized in that the optical sheet is disposed on the front side of the image display unit.

  With the above configuration, external light such as sunlight can be absorbed by the light-shielding layer or the light transmittance wavelength-dependent layer to prevent reflection, and the screen can be easily viewed. In particular, it is effective when employed in a display device used outdoors such as a mobile phone, a PDA, or a digital camera. The display device is not particularly limited, and can be applied to any display device such as an organic EL display, an inorganic EL display, a plasma display (PDP), a cathode ray tube, and a liquid crystal display device.

  As is clear from the above description, according to the optical sheet of the first invention, light is absorbed by the slope with the light shielding layer at the mountain portion, while the light is transmitted on the slope side without the light shielding layer. The emitted light profile can be formed. Further, by providing the light shielding layer on the short slope side having a small projected area with an asymmetrical peak, it is possible to suppress a decrease in the luminance of the emitted light transmitted through the optical sheet.

  According to the optical sheet of the second aspect of the present invention, a light exiting wavelength-dependent layer can be formed as a whole with a light-transmitting wavelength-dependent layer being formed as a whole with a direction transmitting through a slope without a light-transmitting wavelength-dependent layer as a main direction. The slope serves as an optical bandpass filter. Specifically, by setting the transmittance of visible light having a wavelength of 500 nm or more to 25% or less, it is possible to prevent a human being from emitting a color that is easily perceived as bright. Furthermore, the chromaticity shift at a large viewing angle can be reduced by setting the transmittance of blue visible light having a wavelength smaller than 500 nm to be larger than the transmittance of visible light having a wavelength of 500 nm or more.

  According to the liquid crystal display device of the third aspect of the invention, an image cannot be viewed (or difficult to view) from one viewing angle, while an image can be reliably viewed from the other viewing angle. This is suitable for preventing reflection of images on the windshield when set on the dash panel, and for preventing snooping at financial institution ATMs. Further, by offsetting the pixel arrangement direction of the liquid crystal panel and the extending direction of the peak portion of the optical sheet, it is possible to prevent the occurrence of moire fringes when the display screen is viewed obliquely.

  According to the display device of the fourth invention, by arranging the optical sheet on the front side of the image display unit, external light such as sunlight is absorbed by the light shielding layer or the light transmittance wavelength dependent layer to prevent reflection. And the visibility of the screen can be improved.

  A first embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic sectional view of a liquid crystal display device 10, which is sandwiched between a backlight 11 and a liquid crystal panel 12 by a metal bezel 27 with an optical sheet 17 interposed between a prism sheet 16 and an optical sheet 17.

  The backlight 11 is disposed on the reflection sheet 15, a chassis 21 made of a resin molded product having a frame portion at the periphery of the bottom of the rectangular shape, a reflection sheet 15 laid on the bottom of the chassis 21 and made of foamed PET. A rectangular light guide plate 14 made of an acrylic resin molded product and a pair of linear light sources (cold cathode lamps) 13 disposed opposite to both sides of the light guide plate 14. The light guide plate 14 scatters the outgoing light by using the outgoing surface 14a as a non-glossy surface by sandblasting or the like.

  The liquid crystal panel 12 encloses a liquid crystal 18 between transparent substrates 19 and 20 arranged opposite to each other to form a large number of pixels arranged in a matrix, and incident light and outgoing light are further formed on both sides thereof. Polarizing plates 29 and 30 are provided for aligning the directions of the polarization planes.

  The backlight 11, the prism sheet 16, and the optical sheet 17 are held by a housing 23. In addition, a circuit board 25 is connected to the driver 26 for driving the liquid crystal panel via a flexible printed board in order to control the alignment state of the liquid crystal 18.

  In the prism sheet 16, a plurality of prisms 16 a having an isosceles triangle cross section are periodically arranged on the exit surface side, and the polarized light exiting the light guide plate 14 is refracted and condensed in the normal direction. .

  As shown in FIGS. 2 and 3, the optical sheet 17 has a UV curable acrylic resin, an acrylic resin, a methacrylic resin, or a plastic film on the upper surface side of a flat sheet-like base film portion 17b made of polyethylene terephthalate, polycarbonate, cycloolefin, or polyolefin. The crest forming portion 17a having a multi-step surface having a sawtooth cross section made of urethane resin is provided by being laminated. The ridge forming portion 17a is asymmetrical in cross section and includes a short inclined surface 17c-1 and a long inclined surface 17c-2, and is provided with a large number of ridge portions 17c extending in the Y direction in the X direction, and carbon black on the short inclined surface 17c-1 side. The light-shielding layer 31 is formed by applying a light-shielding material made of a metallic paint black dye or black pigment. In addition, it cannot be overemphasized that a light shielding film etc. may be used for a light shielding layer instead of the said light-shielding material.

  The oblique angle α of the long slope 17c-2 of the mountain portion 17c is 20 ° to 30 °, and the oblique angle β of the short slope 17c-1 is 2 ° to 6 °.

  Further, the pitch P between the adjacent peaks 17c is preferably equal to or less than the pixel pitch of the liquid crystal panel 12. In this embodiment, the pitch P is set to 100 to 140 μm in consideration of a mold or the like, but is not limited thereto. .

  The height h of the entire optical sheet 17 is 150 to 250 μm, and the height h2 of the base film portion 17 b is 75 to 150 μm. The height h1 of the peak forming portion 17a is 30 to 90 μm. Specifically, when the pitch P of the peak portion 17c is 100 μm, h1 is 36.4 to 57.7 μm, and the pitch P is 120 μm. When h1 = 43.7 to 69.3 μm and the pitch P = 140 μm, h1 = 51.0 to 80.8 μm.

  Next, the operation of the optical sheet 17 in the liquid crystal display device 10 will be described.

  The light emitted from the linear light source 1 is reflected directly or indirectly by the reflection sheet 15 and is incident on the light guide plate 14, and the light emitted from the exit surface 14 a of the light guide plate 14 is away from the linear light source 13. It is biased to. The polarized outgoing light is incident on the upward prism sheet 16 and is refracted into the outgoing profile collected in the normal direction by the prism 16a, and the outgoing light enters the optical sheet 17.

  Most of the main light incident on the optical sheet 17 strikes the long slope 17c-2 and is refracted to be emitted to the liquid crystal panel 12 side. At this time, a light beam that has reached the long inclined surface 17c-2 but has an internal reflection critical angle is internally reflected by this surface. On the other hand, inferior light reaches the short slope 17c-1 side, but this inferior light is absorbed by the light shielding layer 31 applied on the short slope 17c-1 and does not emit light to the liquid crystal panel 12 side. Therefore, according to the optical sheet 17, while shielding light in the normal direction of the short slope 17c-1, it is possible to maintain the light transmittance in the normal direction of the long slope 17c-2 so as not to be significantly reduced. Become. When light having such an emission profile is transmitted through the liquid crystal panel 12, the image is viewed when viewed from one viewing angle (upper left in FIG. 1) with respect to the normal direction of the display surface of the liquid crystal display device 10. The image cannot be visually recognized, and the image can be viewed well when viewed from the viewing angle on the other side (upper right in FIG. 1).

  As an application example of the liquid crystal display device 10, FIG. 4 shows a case where the liquid crystal display device 10 of the present invention is set on a dashboard in an automobile.

  With the normal direction (that is, the light shielding direction) of the short slope 17c-1 of the optical sheet 17 facing the upper windshield G, the normal direction of the display surface is directed toward the viewpoint of the normal sheet S1 position. A display device 10 is arranged.

  By so doing, no light is emitted to the windshield G side, so that the image can be prevented from being reflected on the windshield G. In addition, the viewpoint at the position of the sheet S2 at the time of reclining is the normal direction of the long slope 17c-2 of the optical sheet 17, and sufficient light transmittance is maintained, so that an image can be viewed without feeling uncomfortable with the display quality. It becomes possible to do.

  The application example of the liquid crystal display device 10 is suitable not only for use as a display device for car navigation or TV for automobiles but also for other uses such as an ATM display screen used in financial institutions. Further, the optical sheet 17 may be disposed on the display surface side of the liquid crystal panel 12.

  A specific example of the first embodiment will be described. The optical sheet 17 of Example 1 uses PET (polyethylene terephthalate) for the base film portion 17b, and acrylic resin for the peak forming portion 17a. The oblique surface α of the long inclined surface 17c-2 is 25 °, and the short inclined surface 17c- 1 is 4 °, the pitch P of the peaks 17c is 100 μm, the height h of the entire optical sheet 17 is 200 μm, the height h1 of the peaks 17a is 100 μm, and the height h2 of the base film portion 17b is 100 μm. Further, the light shielding layer 31 is formed by applying carbon black to the short slope 17c-1.

  FIG. 5 shows the light distribution characteristics of the liquid crystal display device 10 using the optical sheet 17 having the above configuration. In the graph, the normal direction of the liquid crystal display surface is a viewing angle of 0 °, the positive direction of the viewing angle is the normal direction side of the long slope 17c-2, and the negative direction of the viewing angle is the normal direction side of the short slope 17c-1. It is said. That is, the viewing angle in FIG. 5 is an inclination angle in the X direction in FIG.

  According to the present invention, the luminance is extremely low when approaching −30 ° on the minus side of the viewing angle, and the luminance tends to become zero at −40 °, while the peak value of 50 is even at about 30 ° on the plus side of the viewing angle. % Of sufficient brightness is secured. Moreover, when the light distribution characteristic of the liquid crystal display device 1 using the conventional light-shielding louver film 8 is displayed in the graph, it can be seen that the front luminance of the present invention is higher than the conventional one.

  That is, according to the present invention, the absolute luminance in the front direction and the positive viewing angle direction can be greatly improved while meeting the need to suppress the luminance in the negative viewing angle direction. Proven. This is because the light emitted from the prism sheet 16 is not emitted most strongly in the front direction but is shifted in the inclined direction, and the conventional light-shielding louver film 8 could not correct the deflection tendency. This is because by using the optical sheet 17 of the present invention, correction is made so that a luminance peak generally comes in the front direction.

  Next, a second embodiment will be described. The difference from the first embodiment is that a light transmittance wavelength-dependent layer is provided instead of the light shielding layer 31 on the short slope 17c-1 of the optical sheet 17. Other configurations are the same as those of the first embodiment.

  The light transmittance wavelength-dependent material forming the light transmittance wavelength-dependent layer is an azo lake paint, azo paint, phthalocyanine paint, indico paint, perinone paint, phthalone paint, dioxane paint, quinacridkin paint The transmittance of visible light having a wavelength of 500 nm or more is 25% or less, while the transmittance of visible light having a wavelength of less than 500 nm is that of visible light having a wavelength of 500 nm or more. A value larger than the transmittance is shown. That is, while allowing mainly visible light of blue / purple to be transmitted, the transmittance of visible light of other wavelengths is suppressed.

  As shown in FIG. 6, a human has a specific visibility curve according to the wavelength of visible light, and does not feel the same brightness in the entire visible light. Visibility is strong in the green / yellow region, but the visibility is greatly reduced in the blue / purple region. In addition, it has been found that the orange / red region has a much lower visibility, but it is stronger than the blue / purple region.

  That is, it can be said that humans feel brightness mainly by stimulation by light in the green / yellow region, and the necessity of completely shielding the short slope 17c-1 region as in the first embodiment is somewhat relaxed. Is done. From this, it is possible to transmit blue / purple visible light with low visibility, while absorbing visible light of other colors, so that the human visibility as seen from the normal direction side of the short slope 17c-1 Can be suppressed.

  According to the human relative visibility curve, since the relative visibility is also low in the red region, the light transmittance wavelength-dependent layer may transmit the red region instead of transmitting the blue / purple region. In that case, the transmittance of visible light having a wavelength of 650 nm or less is preferably 25% or less, and the transmittance of visible light having a wavelength of more than 650 nm is preferably larger than the transmittance of visible light having a wavelength of 650 nm or less.

  A specific example of the second embodiment will be described. Example 2 is the same as Example 1 except that a light transmittance wavelength-dependent layer is provided instead of the light shielding layer 31 on the short slope 17c-1. The light transmittance wavelength-dependent material forming the light transmittance wavelength-dependent layer uses a kyanite blue pigment (azurite). Note that a lapis lazuli blue pigment can be expected to have the same effect. Further, a mixed color pigment obtained by adding a black pigment to these blue pigments may be used.

  FIG. 7 shows the relationship between the wavelength of light transmitted through the short slope 17c-1 coated with the light transmittance wavelength-dependent material and the transmittance. It can be seen that visible light in the green, yellow, orange, and red regions having a wavelength of 500 nm or more has a transmittance of about 10% and is sufficiently absorbed. On the other hand, the visible light in the blue / violet region with a wavelength smaller than 500 nm has an increased transmittance, but it is not sufficiently transmitted but absorbs to some extent. That is, the light transmittance wavelength-dependent layer serves as a kind of optical bandpass filter.

  FIG. 8 shows a spectrum of light emitted from the liquid crystal display device. The conventional curve in the figure represents the emission spectrum in front of the liquid crystal display device 1 shown in FIG. The curve of the present invention in the figure is obtained by multiplying the conventional curve by the transmittance curve of FIG. 7 on the assumption that all incident light has passed through the short slope 17c-1 coated with the light transmittance wavelength-dependent material. Represents what you did. According to this, almost no visible light having a wavelength of 500 nm or more is emitted, and blue / purple light having a very small color stimulus value as seen from the relative visibility curve in FIG. 6 is transmitted. Visible light transmitted through the layers is difficult for humans to perceive as brightness.

FIG. 9 shows a change in chromaticity at the viewing angle in the extending direction of the peak portion 17c of the first and second embodiments. (That is, the viewing angle in FIG. 9 is the angle of inclination in the Y direction in FIG. 3).
In Example 1, when viewed through the liquid crystal panel 12, the chromaticity x and the chromaticity y greatly increase as the absolute value of the viewing angle increases. Considering this with reference to the chromaticity coordinates shown in FIG. 10, in a front view with a viewing angle of 0 °, white light with chromaticity x = about 0.313 and chromaticity y = about 0.329 is obtained. It can be said that as the absolute value increases, a chromaticity shift occurs in the yellow region in the upper right direction in FIG. This is a phenomenon commonly seen in typical liquid crystal display devices.

  However, in Example 2, as shown in FIG. 9, it can be seen that the increase in chromaticity x and chromaticity y when the absolute value of the viewing angle increases is reduced. That is, it can be said that the white color can be maintained relatively even at a position where the absolute value of the viewing angle is large and the amount of chromaticity shift to the yellow region is reduced in the chromaticity coordinates of FIG.

  This reduction in chromaticity shift is mainly caused by blue light that is refracted, diffused, and scattered and reflected from the short slope 17c-1 provided with the light transmittance wavelength-dependent layer, particularly in a region where the absolute value of the viewing angle is large. As a result, the chromaticity shift in the lower left direction is caused in the chromaticity coordinates of FIG. 10, and the effect of canceling out the chromaticity shift to the yellow region in the upper right direction is obtained.

  11 to 13 show a third embodiment. The difference from the first embodiment is that the extending direction of the crest 37c of the optical sheet 37 is inclined.

  As shown in FIGS. 11 and 13, the optical sheet 37 has a UV curable acrylic resin, an acrylic resin, a methacrylic resin, or a plastic film on the upper surface side of a flat sheet-like base film portion 37b made of polyethylene terephthalate, polycarbonate, cycloolefin, or polyolefin. A ridge forming portion 37a having a multi-step surface having a sawtooth cross section made of urethane resin is provided in a stacked manner. The crest forming portion 37a is asymmetric in cross section and includes a large number of crest portions 37c made up of a short inclined surface 37c-1 and a long inclined surface 37c-2, and the extending direction of the crest portion 37 is inclined by an angle θ. Further, a light-shielding layer is provided by applying a light-shielding material made of carbon black, metal paint, black dye or black pigment to the short slope 37c-1. Since other configurations are the same as those of the optical sheet 17 of the first embodiment, description thereof is omitted.

  By interposing the optical sheet 37 between the backlight 11 and the liquid crystal panel 12, as shown in FIG. 12, the arrangement direction of the pixels 40 of the liquid crystal panel 12 and the extending direction of the crests 37c are non-parallel. They are arranged so as to intersect by an angle θ. This intersection angle θ will be referred to as an offset angle. By intentionally shifting the extending direction of the peak portion 37c of the optical sheet 37 with respect to the arrangement direction of the pixels 40 as described above, it is possible to prevent the occurrence of moire fringes on the display surface. Needless to say, instead of the light shielding layer 31, a light transmittance wavelength-dependent layer may be provided on the short slope 37c-1 as in the second embodiment.

  Next, the correlation between the offset angle θ of the crest 37c of the optical sheet 37 and the arrangement pitch P of the crest 37c is examined.

  If the offset angle θ is large, the occurrence of moire can be prevented, but if the direction of the short inclined surface 37c-1 itself of the optical sheet 37 changes so much, the light shielding direction will be deviated from the direction in which the viewing angle is to be limited. The angle θ is preferably as small as possible. Therefore, suitable values of the offset angle θ and the pitch P will be examined below using specific examples.

  First, as shown in Table 1, a liquid crystal panel 12 having a 7-type VGA (640 × RGB × 480) and a pixel 40 having a length L = 190.5 μm and a width W = 63.5 μm is used. The minimum offset angle θ at which moire fringes are eliminated was examined for each optical sheet 37 with different pitches P of the crests 37c. In the table, “height H” and “length A” indicate the dimension used for calculating the offset angle θ as shown in FIG.

次いで、７型ＥＧＡ（４００×ＲＧＢ×２３４）で、画素４０のサイズが長さＬ＝３５５μｍ、幅Ｗ＝１３０μｍとする液晶パネル１２を用いた場合について、 表２に示すように、山部３７ｃのピッチＰを異ならせた夫々の光学シート３７で、モアレ縞が解消される最小のオフセット角θを調べた。

Next, in the case of using the liquid crystal panel 12 with a 7-inch EGA (400 × RGB × 234) and the size of the pixel 40 having a length L = 355 μm and a width W = 130 μm, as shown in Table 2, a peak portion 37c The minimum offset angle θ at which moire fringes are eliminated was examined for each of the optical sheets 37 having different pitches P.

表１と表２の結果を図１４にプロットして示す。図１４によれば、７型ＶＧＡパネル仕様では、山部３７のピッチＰが１３０μｍ近傍あるいは６０μｍ以下とすれば、オフセット角θが約６°あるいは約９°の小さい値でもモアレ縞が解消できることが分かる。一方、７型ＥＧＡパネル仕様では、概ね１１０μｍ以下のピッチＰとすれば、オフセット角が約６°〜９°の小さい値でもモアレ縞が解消できることが分かる。ここで、７型ＶＧＡと７型ＥＧＡの双方のモアレ縞を小さいオフセット角θで解消できる光学シート３７を提供する場合には、山部３７ｃのピッチＰを１２０μｍ近傍あるいは６０μｍ以下とすればよいことが分かる。

The results of Table 1 and Table 2 are plotted in FIG. According to FIG. 14, in the 7-inch VGA panel specification, when the pitch P of the crests 37 is about 130 μm or 60 μm or less, moire fringes can be eliminated even with a small offset angle θ of about 6 ° or about 9 °. I understand. On the other hand, in the 7-inch EGA panel specification, it can be seen that if the pitch P is approximately 110 μm or less, moire fringes can be eliminated even with a small offset angle of about 6 ° to 9 °. Here, when providing the optical sheet 37 capable of eliminating the moiré fringes of both the 7-type VGA and the 7-type EGA with a small offset angle θ, the pitch P of the crests 37c may be set to be close to 120 μm or 60 μm or less. I understand.

  In view of the above matters, in the case of the above-mentioned 7-type VGA liquid crystal panel, it is preferable that the pitch P of the crests 37c of the optical sheet 37 is about 120 to 140 μm or 60 μm or less and the offset angle θ is about 10 °. It is. In the case of the 7-type EGA liquid crystal panel, it is preferable that the pitch P of the crests 37c of the optical sheet 37 is about 100 to 120 μm or 70 μm or less, and the offset angle θ is about 10 °.

  FIG. 15 shows a fourth embodiment. The application example of the optical sheets 17 and 37 of 1st Embodiment, 2nd Embodiment, and 3rd Embodiment is shown.

  Conventionally, any display device such as an organic EL display, inorganic EL display, plasma display (PDP), cathode ray tube, liquid crystal display, etc., reflects external light such as sunlight on the display surface and enters the eyes, so that an image can be visually recognized. Sometimes it was difficult. Therefore, as shown in FIG. 15, by arranging the optical sheet 17 of the present invention on the front side of the display surface 50 a of the display device 50, external light such as sunlight is absorbed by the light shielding layer 31 to prevent reflection. It is possible to make it easier to visually recognize the screen. In particular, it is effective when employed in a display device used outdoors such as a mobile phone, a PDA, or a digital camera.

It is a schematic sectional drawing of the liquid crystal display device of 1st Embodiment of this invention. It is principal part sectional drawing of the optical sheet of 1st Embodiment of this invention. It is a schematic perspective view of the optical sheet of 1st Embodiment of this invention. It is drawing which shows the use condition at the time of vehicle mounting of the liquid crystal display device of 1st Embodiment of this invention. 1 is a diagram illustrating light distribution characteristics of a liquid crystal display device according to a first embodiment of the present invention. It is a figure which shows the human specific visual sensitivity curve and the spectral distribution of visible light. It is drawing which shows the transmittance | permeability of the short slope area | region of the optical sheet of 2nd Embodiment of this invention. It is drawing which shows the spectrum of the light radiate | emitted from the liquid crystal display device of 2nd Embodiment of this invention. It is drawing which shows the chromaticity change of the liquid crystal display device of 2nd Embodiment of this invention. It is drawing which shows chromaticity coordinates. It is a schematic perspective view which shows the liquid crystal display device of 3rd Embodiment of this invention. It is drawing which shows the relationship between the pixel of the liquid crystal display device of 3rd Embodiment of this invention, and an optical sheet. It is principal part sectional drawing of the optical sheet of 3rd Embodiment of this invention. It is drawing which shows the relationship between the pitch of the peak part of the optical sheet of 3rd Embodiment of this invention, and an offset angle. It is drawing which shows the display apparatus of 4th Embodiment of this invention. It is a schematic sectional drawing of the liquid crystal display device of a prior art example. It is an expanded sectional view of the light-shielding louver film of a prior art example. It is drawing which shows the transmittance | permeability of the light-shielding type louver film of a prior art example. It is drawing which shows the light distribution characteristic of the liquid crystal display device of a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Liquid crystal display device 11 Backlight 12 Liquid crystal panel 13 Linear light source 14 Light guide plate 15 Reflective sheet 16 Prism sheet 17, 37 Optical sheet 17a Mountain part shaping | molding part 17b Base film part 17c Mountain part 17c-1 Short slope 17c-2 Long slope DESCRIPTION OF SYMBOLS 18 Liquid crystal 19, 20 Transparent substrate 21 Chassis 23 Case 24 Flexible printed circuit board 25 Circuit board 26 Driver 27 Bezel 29, 30 Polarizing plate 31 Light shielding layer 50 Display device 50 Display surface

Claims (13)

  An optical sheet characterized in that a large number of crests are provided side by side in a sawtooth shape on the one surface side of a light-transmitting sheet, and a light shielding layer is provided on one side of the crest.   2. The optical sheet according to claim 1, wherein each of the peak portions is asymmetric in cross section and has a different slope length, and the light shielding layer is provided on the short slope side.   The optical sheet according to claim 1, wherein the light shielding layer is made of carbon black, a metal-based paint, a black dye, or a black pigment.   A light transmittance wavelength in which a large number of crests are arranged side by side in a sawtooth shape on one side of a sheet having light transmissivity, and the visible light transmittance depends on the wavelength on one side of the crest. An optical sheet comprising a dependency layer.   5. The optical sheet according to claim 4, wherein each of the peak portions has an asymmetric cross section and a different slope length, and the light transmittance wavelength-dependent layer is provided on the short slope side.   The optical sheet according to claim 4 or 5, wherein the light transmittance wavelength-dependent layer has a transmittance of visible light having a wavelength of 500 nm or more of 25% or less.   The said light transmittance wavelength dependent layer makes the transmittance | permeability of visible light whose wavelength is smaller than 500 nm larger than the transmittance | permeability of visible light whose wavelength is 500 nm or more. Optical sheet.   The light transmittance wavelength-dependent layer is composed of an azo lake paint, azo paint, phthalocyanine paint, indico paint, perinone paint, phthalone paint, dioxane paint, quinacridkin paint, isoindolinone paint or metal paint. The optical sheet according to claim 4, comprising: The optical sheet is provided by laminating a ridge-forming film provided with the ridges on one surface side of a flat sheet-like base film,
The base film is made of polyethylene terephthalate, polycarbonate, cycloolefin or polyolefin,
The optical sheet according to any one of claims 1 to 8, wherein the peak forming film is made of a UV curable acrylic resin, an acrylic resin, a methacrylic resin, or a urethane resin.   10. A liquid crystal display device comprising the optical sheet according to claim 1 interposed between a backlight and a liquid crystal panel.   The liquid crystal display device according to claim 10, wherein the optical sheet is offset so that an extending direction of the peak portion is not parallel to a pixel arrangement direction of the liquid crystal panel.   The liquid crystal display device according to claim 10 or 11, wherein a pitch of each peak portion of the optical sheet is equal to or less than a pixel pitch of the liquid crystal panel. A display device comprising the optical sheet according to any one of claims 1 to 9 disposed on a front side of an image display unit.

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