JP2008145883A - Light diffusion sheet for liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light diffusion sheet for a liquid crystal display device which has both a light diffusion function and a near-infrared light absorption function and which can suppress emission of near-infrared light from the liquid crystal display device and a deterioration in performances such as luminance of the liquid crystal display device. <P>SOLUTION: The light diffusion sheet for the liquid crystal display device is equipped with a transparent base material layer and a light diffusion layer layered on a surface side of the base material layer and contains a near-infrared light absorbent and has a near-infrared light transmittance of 50% or less. Preferably a sticking prevention layer comprising beads dispersed in a binder is provided on a rear surface side of the base material layer. Preferably the near-infrared light absorbent is contained in the base material layer, the light diffusion layer and/or the sticking prevention layer. A near-infrared light absorption layer containing the near-infrared light absorbent can be provided. Preferably visible light transmittance is 50% or more and all light transmittance is 50% or more. Preferably a retardation value of the base material layer is 50 nm or less. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a light diffusion sheet for a liquid crystal display device having a near infrared absorption function as well as a light diffusion function for diffusing transmitted light.

  Liquid crystal display devices (LCDs) are widely used as flat panel displays taking advantage of their thin, lightweight, and low power consumption features, and their uses are for information displays such as mobile phones, personal digital assistants (PDAs), personal computers, and televisions. It is expanding year by year as a device. In recent years, characteristics required for liquid crystal display devices vary depending on the application, and examples include bright (higher brightness), easier viewing (wider viewing angle), energy saving, thinner and lighter, and the like.

  As shown in FIG. 6, the conventional general liquid crystal display device has a structure in which a liquid crystal display element 51, various optical sheets 52, and a backlight 53 are superposed in this order from the front surface side to the back surface side. The liquid crystal display element 51 has a structure in which a liquid crystal cell 56 is sandwiched between a pair of polarizing plates 54 and 55, and various display modes such as TN and IPS have been proposed. The backlight 53 illuminates the liquid crystal display element 51 from the back side, and forms such as an edge light type (side light type) and a direct type are widespread. The various optical sheets 52 are superimposed between the liquid crystal display element 51 and the backlight 53, and in order to make the light emitted from the surface of the backlight 53 enter the entire surface of the liquid crystal display element 51 efficiently and uniformly, the normal direction A light diffusion sheet, a prism sheet, and the like having optical functions such as refraction to the side and diffusion are provided.

  Since the polarizing plates 54 and 55 of the liquid crystal display element 51 absorb 50% of light in principle due to the absorption dichroism, this is one of the major reasons for reducing the light use efficiency of the liquid crystal display device. In order to improve the decrease in the light utilization efficiency of the polarizing plates 54 and 55, a technique of superimposing a reflective polarizing plate (polarization separator) on the back side of the back side polarizing plate 55 in the liquid crystal display device, or the back side polarizing plate 55 A technique using a reflective polarizing plate instead of the above has been developed. In this reflection polarizing plate, the transmission axis component of the back surface side polarizing plate 55 is transmitted as it is, and the other polarization components are returned to the lower side to reuse the light beam.

The optical sheet 52 is specifically a light diffusion sheet, a prism sheet or the like, and is generally a transparent base layer made of synthetic resin, and a light diffusion layer or prism laminated on the surface of the base layer. And an optical layer such as a row layer (see, for example, JP 2000-89007 A and JP 2004-4970 A). These conventional optical sheets 52 are configured to perform optical functions such as refraction and diffusion in the normal direction by an optical layer having a predetermined structure, and are intended to control visible light.
JP 2000-89007 A JP 2004-4970 A

  Until now, it was thought that there was no near-infrared emission from the liquid crystal display device, so the above conventional liquid crystal display device was designed with the intention of improving brightness, wide viewing angle, energy saving, thinning and weight reduction, etc. It does not have a function to prevent the emission of near infrared rays.

  However, the present inventor has found that near-infrared rays are emitted from the above-described conventional liquid crystal display device due to a cold cathode tube used as a light source of the backlight 53 or the like. As described above, near infrared rays emitted from the liquid crystal display device may cause a malfunction in a remote control system of home appliances such as televisions, air conditioners, and videos that use near infrared rays. There is also a risk of adverse effects on the human body. In particular, today, an increase in the screen of a liquid crystal display device is promoted and the output of the backlight 53 tends to increase, so that the influence of the above-described near infrared emission is expected to increase.

  The present invention has been made in view of these disadvantages, and has a near-infrared absorption function in addition to a light diffusion function, and can suppress a decrease in performance such as near-infrared emission and luminance of a liquid crystal display device. The object is to provide a light diffusion sheet for a liquid crystal display device.

The invention made to solve the above problems is
A light diffusion sheet for a liquid crystal display device comprising a transparent substrate layer and a light diffusion layer laminated on the surface side of the substrate layer,
Contains a near infrared absorber,
A light diffusing sheet for a liquid crystal display device having a near infrared transmittance of 50% or less.

  The light diffusion sheet for a liquid crystal display device contains a near-infrared absorber and has a near-infrared absorptivity adjusted to 50% or less, so that it effectively absorbs near-infrared light emitted from the backlight of the liquid crystal display device. In addition, it is possible to suppress the emission of near infrared rays to the outside. Therefore, the light diffusion sheet for a liquid crystal display device can prevent adverse effects on the human body due to near infrared rays emitted from the liquid crystal display device and malfunctions of various home appliance remote control devices.

  A sticking prevention layer in which beads are dispersed in a binder may be provided on the back side of the base material layer. Thus, by providing a sticking prevention layer on the back surface side of the base material layer, for example, in a liquid crystal display device, sticking with a light guide plate, a prism sheet, or the like disposed on the back surface side of the light diffusion sheet is prevented.

  It is good to contain a near-infrared absorber in the said base material layer, a light-diffusion layer, and / or a sticking prevention layer. By kneading the near-infrared absorber in the basic constituent layer of the light diffusing sheet in this way, the near-infrared absorbing function is expressed without increasing the number of layers, contributing to the thinning of the light diffusing sheet and the prevention of luminance reduction. .

  On the other hand, you may provide the near-infrared absorption layer containing the said near-infrared absorber. By separately providing the near-infrared absorbing layer in this manner, optical design such as light diffusibility of the light diffusing sheet becomes easy, and control of the near-infrared absorbing function becomes easy and reliable.

  In the light diffusion sheet for liquid crystal display devices, the visible light transmittance is preferably 50% or more, and the total light transmittance is preferably 50% or more. In this way, by suppressing the visible light transmittance and the total light transmittance within the above ranges, it is possible to suppress a decrease in luminance of the liquid crystal display device due to the light diffusion sheet for the liquid crystal display device having a near infrared absorption function. Can do.

  The retardation value of the substrate layer is preferably 50 nm or less. In a liquid crystal display device, in order to improve the utilization efficiency of light rays, the polarization direction of incident light rays (the maximum plane direction of the polarization component of light rays) in the transmission direction of the back side polarizing plate (or the reflective polarizing plate on the back side) of the liquid crystal display element ) Are designed to match the polarization characteristics of the backlight and various optical sheets. Therefore, by reducing the retardation value of the base material layer in this way, the action of converting the polarization direction of the transmitted light by the light diffusion sheet for the liquid crystal display device is suppressed, and the optimum polarization in the transmission axis direction of the polarizing plate or the like The influence of the light diffusion sheet for liquid crystal display device on the control and controllability can be suppressed.

  Polyethylene terephthalate or polycarbonate may be used as the matrix resin constituting the base material layer. Since such polyethylene terephthalate is inexpensive and excellent in various functions such as strength and heat resistance, the base layer is formed using polyethylene terephthalate as the main polymer, thereby reducing the cost, strength, and heat resistance of the light diffusion sheet for liquid crystal display devices. And thermal dimensional stability are promoted. In addition, since the retardation value of polycarbonate is easy to control, the retardation value of the light diffusion sheet for liquid crystal display devices can be easily and reliably within the above-mentioned small range by forming the base material layer with polycarbonate as the main polymer. Can be adjusted.

  The average thickness of the base material layer is preferably 25 μm or more and 1000 μm or less. As described above, the adverse effect of near infrared rays emitted from the liquid crystal display device is considered to be as great as that of a large screen liquid crystal display device. Thus, by setting the average thickness of the base material layer in the above range, the liquid crystal display Properties such as the strength and anti-bending property of the light diffusing sheet for the device are improved, and the liquid crystal display device can be enlarged.

  The surface roughness (Ra) in the light diffusion layer is preferably 0.1 μm or more and 0.5 μm or less, and the surface roughness (Ry) is preferably 1 μm or more and 20 μm or less. In this way, by setting the surface roughness (Ra) and the surface roughness (Ry) of the light diffusion layer in the above ranges, the liquid crystal display device can suppress the decrease in the total light transmittance of the light diffusion sheet for the liquid crystal display device. Can prevent glare on the screen.

  The light diffusing layer includes (a) a light diffusing agent and its binder (bead coating layer, etc.), and (b) a fine concavo-convex shape (mat layer, microlens array layer, prism sheet). Prism row layer, etc.). Since such optical sheets such as bead coated sheets, mat sheets, microlens sheets, and prism sheets are usually used in liquid crystal display devices, the light for the liquid crystal display device is generally used as an optical sheet like the means. By using the diffusion sheet, it is possible to prevent near infrared rays from being emitted without causing an increase in the number of optical sheets of the liquid crystal display device, and to prevent malfunction of the home appliance remote control device.

  In the present invention, “near-infrared transmittance” means the transmittance of light having a wavelength of 900 nm to 1100 nm, and “visible light transmittance” means the transmittance of light having a wavelength of 400 nm to 700 nm. To do. “Surface roughness (Ra)” means arithmetic average roughness, and “surface roughness (Ry)” means maximum roughness.

  As described above, the light diffusion sheet for a liquid crystal display device of the present invention has a near-infrared absorption function in addition to a light diffusion function, and an error of home appliance remote control equipment due to the emission of near-infrared light from the liquid crystal display device. It is possible to prevent adverse effects such as operation and to suppress a decrease in performance such as luminance of the liquid crystal display device.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate. FIG. 1 is a schematic cross-sectional view showing a light diffusing sheet for a liquid crystal display device according to an embodiment of the present invention, and FIG. 2 is a light diffusing material for a liquid crystal display device according to a different form from the light diffusing sheet for a liquid crystal display device shown in FIG. 3 is a schematic cross-sectional view showing a sheet, FIG. 3 is a schematic cross-sectional view showing a light diffusion sheet for a liquid crystal display device according to a different form from the light diffusion sheet for a liquid crystal display device of FIGS. 1 and 2, and FIG. FIG. 5 is a schematic cross-sectional view showing a light diffusing sheet for a liquid crystal display device according to a different form from the light diffusing sheet for a liquid crystal display device shown in FIGS. 2 and 3, and FIG. 5 is a liquid crystal display shown in FIG. 1, FIG. 2, FIG. It is a typical sectional view showing the light diffusion sheet for liquid crystal displays concerning the form different from the light diffusion sheet for devices.

  1 includes a base material layer 2, a light diffusion layer 3 laminated on the surface of the base material layer 2, and a near infrared absorbing layer 4 laminated on the back surface of the base material layer 2. And.

  Since the base material layer 2 needs to transmit light, it is made of a synthetic resin that is transparent, particularly colorless and transparent. The synthetic resin used for the base material layer 2 is not particularly limited, and examples thereof include polyethylene terephthalate, polyethylene naphthalate, acrylic resin, polycarbonate, polystyrene, polyolefin, cellulose acetate, and weather resistant vinyl chloride. . Among them, polyethylene terephthalate which is excellent in transparency, strength, heat resistance, thermal dimensional stability and anti-bending property is preferable, and polycarbonate which is excellent in retardation value controllability is preferable.

  Although it does not specifically limit as average thickness of the base material layer 2, 25 micrometers or more and 1000 micrometers or less, Especially 150 micrometers or more and 800 micrometers or less, Furthermore, 188 micrometers or more and 500 micrometers or less are preferable. When the average thickness of the base material layer 2 is less than the above range, the light diffusion sheet for liquid crystal display device has poor properties such as strength and anti-bending property, and cannot cope with an increase in screen size of the liquid crystal display device. There is a fear. On the other hand, when the thickness of the base material layer 2 exceeds the above range, the luminance of the liquid crystal display device may be lowered, and it is against the demand for thinning the liquid crystal display device.

  The light diffusion layer 3 has a minute and random uneven shape on the surface. A function of diffusing transmitted light is achieved by the fine unevenness on the surface of the light diffusion layer 3. The light diffusion layer 3 may be integral with or separate from the base material layer 2. The light diffusing layer 3 is formed of the same synthetic resin as that of the base material layer 2, and is an active energy ray curable resin such as an ultraviolet curable resin and an electron beam curable resin excellent in moldability of an uneven shape, transparency. Polyethylene terephthalate having excellent strength and polycarbonate having excellent controllability of retardation value are particularly preferred. Moreover, it is also preferable to use a polyethylene terephthalate film, a polyethylene naphthalate film or a polycarbonate film as the base material layer 2 and to form the light diffusion layer 3 with an ultraviolet curable resin or the like thereon.

  The surface roughness (Ra) of the light diffusion layer 3 is preferably 0.1 μm or more and 0.5 μm or less, and particularly preferably 0.2 μm or more and 0.4 μm or less. Further, the surface roughness (Ry) of the light diffusion layer 3 is preferably 1 μm or more and 20 μm or less, and particularly preferably 5 μm or more and 15 μm or less. Thus, by setting the surface roughness (Ra) and the surface roughness (Ry) of the light diffusion layer 3 in the above ranges, the liquid crystal while suppressing a decrease in the total light transmittance of the light diffusion sheet 1 for the liquid crystal display device. It is possible to effectively prevent glare on the screen of the display device.

  The lower limit of the refractive index of the material constituting the light diffusion layer 3 is preferably 1.3 and particularly preferably 1.45. On the other hand, the upper limit of the refractive index of this material is preferably 1.8, and particularly preferably 1.6. Among these ranges, the refractive index of the material constituting the light diffusion layer 3 is most preferably 1.5. Thus, by making the refractive index of the material constituting the light diffusing layer 3 in the above range, the lens-like refracting action on the surface irregularity shape is effectively achieved, and the diffusing function of the light diffusing sheet 1 for the liquid crystal display device. Is increased.

  In addition to the above synthetic resin, for example, a filler, a plasticizer, a stabilizer, a deterioration inhibitor, a dispersant, and the like may be blended in the base material layer 2 and the light diffusion layer 3.

  The near-infrared absorbing layer 4 has a synthetic resin that is a matrix (binder) and a near-infrared absorber mixed in the synthetic resin. The synthetic resin used for the near-infrared absorbing layer 4 is not particularly limited as long as it is transparent, particularly colorless and transparent so as to transmit light. Specifically, the above-mentioned active energy ray-curable resin, Examples thereof include polycarbonate resins, poly (meth) acrylate resins, cyclic olefin resins, polyester resins, polystyrene, polyvinyl chloride, and polyvinyl acetate. Of these, active energy ray-curable resins having good moldability, acrylic resins having high transparency, and polycarbonate resins having good retardation value controllability are preferable.

  As a near-infrared absorber, what has a high transmittance | permeability with respect to visible light and absorbs a lot of near-infrared light is preferable, and specifically, (a) an imonium compound, a diimonium compound, an aluminum salt compound, Organic near-infrared absorbers such as nitroso compounds and their metal complex salts, cyanine compounds, squarylium compounds, thiol nickel complex compounds, phthalocyanine compounds, triallylmethane compounds, naphthoquinone compounds, anthraquinone compounds, amino compounds, (B) Tin oxide doped with carbon black, antimony oxide or indium oxide, inorganic near infrared absorbers such as oxides, carbides or borides of metals belonging to Group 4, 5 or 6 of the periodic table, and these These compounds can be used in appropriate combination. Among them, an imonium compound, a diimonium compound, or an aluminum salt compound that is excellent in near-infrared absorptivity, visible light transmittance, heat resistance, light resistance and the like is particularly preferable.

  When the near-infrared absorbing layer 4 is formed into a film (sheet), the amount of the near-infrared absorbing agent is 0.01 parts by mass or more and 8 parts by mass or less with respect to 100 parts by mass (solid content conversion) of the matrix synthetic resin. Preferably, 0.03 to 1 part by mass is particularly preferable. On the other hand, the blending amount of the near-infrared absorber when coating the near-infrared absorbing layer 4 is preferably 1 part by mass or more and 40 parts by mass or less with respect to 100 parts by mass (converted to solid content) of the matrix synthetic resin. 2 parts by mass or more and 15 parts by mass or less is particularly preferable. If the blending amount of the near-infrared absorber is smaller than the above range, a sufficient near-infrared absorbing function may not be obtained. Conversely, if the blending amount of the near-infrared absorbing agent exceeds the above range, the visible light transmittance decreases. There is a fear.

  The average thickness of the near-infrared absorbing layer 4 is appropriately determined so that the visible light transmittance and the near-infrared absorbing property are suitably balanced from the relationship with the blending amount of the near-infrared absorber. Specifically, the average thickness of the near-infrared absorbing layer 4 when forming a film (sheet) is preferably 10 μm or more and 500 μm or less, and particularly preferably 50 μm or more and 100 μm or less. On the other hand, the average thickness of the near-infrared absorbing layer 4 when coating is formed is preferably 1 μm or more and 50 μm or less, and particularly preferably 3 μm or more and 20 μm or less.

  The near-infrared absorbing layer 4 includes, in addition to the synthetic resin and the near-infrared absorber, for example, an antioxidant, a halogen agent, a phosphoric acid-based flame retardant, a heat-resistant anti-aging agent, an ultraviolet absorber, a lubricant, an antistatic agent. An agent or the like can be blended.

The method for producing the light diffusion sheet 1 for a liquid crystal display device is not particularly limited as long as the above structure can be formed, and various methods are employed. As a formation method of the base material layer 2 and the light diffusion layer 3, after forming the base material layer 2, a method of forming the light diffusion layer 3 separately, a method of integrally forming the base material layer 2 and the light diffusion layer 3, and Is possible, specifically,
(A) A method of laminating a synthetic resin on a sheet mold having an inverted shape of the surface of the light diffusion layer 3 and peeling off the sheet mold;
(B) an injection molding method in which a molten resin is injected into a mold having an inverted shape of the surface of the light diffusion layer 3;
(C) A method of transferring the shape by re-heating the sheeted resin and pressing between the same mold and metal plate as described above,
(D) An extruded sheet molding method in which a molten resin is passed through a nip between a roll mold having a reverse shape of the surface of the light diffusion layer 3 on the peripheral surface and another roll, and the shape is transferred.
(E) An ultraviolet curable resin is applied to the base material layer 2, and the shape is transferred to an uncured ultraviolet curable resin by pressing against a sheet mold, a mold or a roll mold having the same inverted shape as described above. To cure the UV curable resin by applying
(F) An uncured ultraviolet curable resin is filled and applied to a mold or roll mold having the same inverted shape as above, pressed by the substrate layer 2, leveled, and irradiated with ultraviolet rays to cure the ultraviolet curable resin. How to
(G) There is a method of using an electron beam curable resin instead of an ultraviolet curable resin.

Next, as a method for forming the near-infrared absorbing layer 4, specifically,
(A) A coating solution prepared by dissolving or dispersing the above-described synthetic resin and near-infrared absorber in an organic solvent is prepared, and this coating solution is dipped on the back surface of the base material layer 2, a flow coating method, a spray method, Bar coating method, gravure coating method, roll coating method, blade coating method and coating method such as air knife coating method, a method of curing,
(B) A mixture of the above-described synthetic resin and near-infrared absorber is formed into a film or sheet using a method such as photocuring, injection molding, T-die molding, calendar molding, compression molding, or casting, and a base material layer A method of adhering to the back surface of 2,
(C) There is a method of directly laminating a mixture of the above-mentioned synthetic resin and near infrared absorber on the back surface of the base material layer 2 by dry lamination using a T die or the like.

  Since the light diffusing sheet 1 for a liquid crystal display device includes the near-infrared absorbing layer 4 containing a near-infrared absorber, it effectively absorbs near-infrared rays emitted from the backlight of the liquid crystal display device, Release of infrared rays to the outside can be suppressed. Therefore, the light diffusing sheet 1 for a liquid crystal display device can prevent a malfunction of a remote control system of home appliances caused by near infrared rays emitted from the liquid crystal display device and adverse effects on the human body.

  The near-infrared transmittance of the light diffusion sheet 1 for a liquid crystal display device is 50% or less, preferably 30% or less, and particularly preferably 10% or less. By setting the near-infrared transmittance in the above range, it is possible to effectively prevent inconveniences such as malfunction of a remote control system of home appliances caused by near-infrared rays emitted from the liquid crystal display device and adverse effects on the human body. .

  In the light diffusion sheet 1 for the liquid crystal display device, the visible light transmittance is preferably 50% or more, and the total light transmittance is preferably 50% or more. In this way, by setting the visible light transmittance and the total light transmittance to the above ranges, a decrease in luminance of the liquid crystal display device due to the light diffusion sheet 1 for liquid crystal display device having a near infrared absorption function is suppressed. be able to.

  The retardation value of the base material layer 2 is preferably 50 nm or less. Thus, by making the retardation value of the base material layer 2 relatively small, the action of converting the polarization direction with respect to the transmitted light of the light diffusion sheet 1 for the liquid crystal display device is suppressed, and the transmission axis of a polarizing plate or the like in the liquid crystal display device. The influence which the said light-diffusion sheet | seat 1 for liquid crystal display devices has with respect to the optimization and controllability of the polarization | polarized-light to a direction can be suppressed. For this reason, in the liquid crystal display device, the light diffusion sheet 1 for the liquid crystal display device is brought close to the back surface of the liquid crystal display element without adversely affecting the optical action as described above, particularly the back surface side (back surface) of the back surface side polarizing plate. Between the side polarizing plate and the reflective polarizing plate). As a result, the use efficiency of the light beam is suppressed, and the brightness reduction of the liquid crystal display device due to the near infrared absorption function is remarkably suppressed. be able to.

  The light diffusion sheet 11 for a liquid crystal display device in FIG. 2 includes a base material layer 12 and a light diffusion layer 3 laminated on the surface of the base material layer 12. The light diffusion layer 3 is formed separately from the base material layer 12, and the content thereof is the same as that of the light diffusion sheet 1 for a liquid crystal display device shown in FIG.

  As for the base material layer 12, the near-infrared absorber is kneaded in the synthetic resin. The average thickness of the base material layer 12, the synthetic resin used, the retardation value, and the like are the same as those of the base material layer 2 of the light diffusion sheet 1 for a liquid crystal display device. Moreover, the specific content, blending amount, and the like of the near-infrared absorber in the base material layer 12 are the same as those of the near-infrared absorbing layer 4 of the light diffusion sheet 1 for liquid crystal display device. Further, the near-infrared transmittance, visible light transmittance and total light transmittance of the light diffusion sheet 11 for liquid crystal display device are the same as those of the light diffusion sheet 1 for liquid crystal display device.

  The light diffusing sheet 11 for liquid crystal display device effectively absorbs near infrared rays emitted from the backlight of the liquid crystal display device in the same manner as the light diffusing sheet 1 for liquid crystal display devices, and emits near infrared rays to the outside. Can be suppressed. Moreover, since the near-infrared absorption layer can be abbreviate | omitted, the said light-diffusion sheet 11 for liquid crystal display devices can promote the brightness | luminance and thickness reduction of a liquid crystal display device.

  The light diffusion sheet 21 for a liquid crystal display device in FIG. 3 includes a base material layer 22 and a light diffusion layer 23 laminated on the surface of the base material layer 22. The base material layer 22 and the light diffusion layer 23 are integrally formed.

  In the base material layer 22 and the light diffusion layer 23, a near-infrared absorber is kneaded in a synthetic resin. The average thickness of the base material layer 12, the synthetic resin used, the retardation value, and the like are the same as those of the base material layer 2 of the light diffusion sheet 1 for a liquid crystal display device. The shape, surface roughness, and the like of the light diffusion layer 23 are the same as those of the light diffusion sheet 1 for a liquid crystal display device. In addition, the specific content, blending amount, and the like of the near-infrared absorber in the base material layer 12 and the light diffusion layer 23 are the same as those in the near-infrared absorption layer 4 of the light diffusion sheet 1 for liquid crystal display device. Further, the near-infrared transmittance, visible light transmittance and total light transmittance of the light diffusion sheet 21 for liquid crystal display device are the same as those of the light diffusion sheet 1 for liquid crystal display device.

  The light diffusing sheet for liquid crystal display device 21 effectively absorbs near infrared rays emitted from the backlight of the liquid crystal display device in the same manner as the light diffusing sheet for liquid crystal display devices 1 and emits near infrared rays to the outside. Can be suppressed. Moreover, since the near-infrared absorption layer can be abbreviate | omitted, the said light-diffusion sheet 21 for liquid crystal display devices can accelerate | stimulate the brightness | luminance and thickness reduction of a liquid crystal display device. Furthermore, since the base material layer 22 and the light diffusion layer 23 are integrally formed, the light diffusion sheet 21 for a liquid crystal display device has high manufacturability and can promote low cost.

  The light diffusion sheet 31 for a liquid crystal display device in FIG. 4 includes a base material layer 2, a light diffusion layer 32 laminated on the surface of the base material layer 2, and a near infrared absorption layer 4 laminated on the back surface of the base material layer 2. And. The base material layer 2 and the near-infrared absorbing layer 4 of the light diffusion sheet 31 for liquid crystal display device are the same as the light diffusion sheet 1 for liquid crystal display device of FIG.

  The light diffusing layer 32 includes a light diffusing agent 33 laid substantially uniformly and densely on the surface of the base material layer 2 and a binder 34 for fixing the light diffusing agent 33. The light diffusing agent 33 is covered with a binder 34. Thus, the light diffusing agent 33 contained in the light diffusing layer 32 can uniformly diffuse the light beam that passes through the light diffusing layer 32 from the back side to the front side. The light diffusing agent 33 forms fine convex portions on the surface of the light diffusion layer 32 substantially uniformly and substantially densely. Thus, the light can be better diffused by the lens-like refracting action of fine irregularities formed on the surface of the light diffusion sheet 31 for liquid crystal display devices. Although the average thickness of the light-diffusion layer 32 is not specifically limited, For example, it is about 1 micrometer or more and 30 micrometers or less.

  The light diffusing agent 33 is a particle having a property of diffusing light, and is roughly classified into an inorganic filler and an organic filler. Specifically, silica, aluminum hydroxide, aluminum oxide, zinc oxide, barium sulfide, magnesium silicate, or a mixture thereof can be used as the inorganic filler. Specific examples of the organic filler include acrylic resin, acrylonitrile resin, polyurethane, polyvinyl chloride, polystyrene, polyacrylonitrile, polyamide, and the like. Among these, highly transparent acrylic resins are preferable, and polymethyl methacrylate (PMMA) is particularly preferable.

  The shape of the light diffusing agent 33 is not particularly limited, and examples thereof include a spherical shape, a cubic shape, a needle shape, a rod shape, a spindle shape, a plate shape, a scale shape, and a fiber shape, and among them, a spherical shape having excellent light diffusibility. The beads are preferred.

  The lower limit of the average particle diameter of the light diffusing agent 33 is preferably 1 μm, particularly 2 μm, and more preferably 5 μm, and the upper limit of the average particle diameter of the light diffusing agent 33 is preferably 50 μm, particularly 20 μm, and more preferably 15 μm. This is because if the average particle diameter of the light diffusing agent 33 is less than the above range, the unevenness of the surface of the light diffusing layer 32 formed by the light diffusing agent 33 becomes small and does not satisfy the light diffusibility required for the light diffusing sheet. On the contrary, if the average particle diameter of the light diffusing agent 33 exceeds the above range, the thickness of the light diffusing sheet 31 for the liquid crystal display device increases, and uniform diffusion becomes difficult. .

  The lower limit of the amount of the light diffusing agent 33 (the amount in terms of solid content relative to 100 parts of the base polymer in the polymer composition that is the forming material of the binder 34) is preferably 10 parts, particularly 20 parts, and more preferably 50 parts, The upper limit of this amount is preferably 500 parts, particularly 300 parts, and more preferably 200 parts. This is because if the blending amount of the light diffusing agent 33 is less than the above range, the light diffusing property becomes insufficient. On the other hand, if the blending amount of the light diffusing agent 33 exceeds the above range, the light diffusing agent 33 is fixed. It is because the effect to do falls. In the case of a so-called upward light diffusion sheet disposed on the surface side of the prism sheet, high light diffusibility is not required, so the amount of the light diffusing agent 33 is 10 parts or more and 40 parts or less, particularly 10 parts. The amount is preferably 30 parts or less.

  The binder 34 is formed by crosslinking and curing a polymer composition containing a base polymer. The light diffusing agent 33 is arranged and fixed on the entire surface of the base material layer 2 by the binder 34 at substantially equal density. In addition, the polymer composition for forming the binder 34 includes, for example, a fine inorganic filler, a curing agent, a plasticizer, a dispersant, various leveling agents, an ultraviolet absorber, an antioxidant, a viscosity modifier, A lubricant, a light stabilizer and the like may be appropriately blended.

  The base polymer is not particularly limited, and examples thereof include acrylic resins, polyurethanes, polyesters, fluorine resins, silicone resins, polyamideimides, epoxy resins, ultraviolet curable resins, and the like. Can be used singly or in combination of two or more. In particular, the base polymer is preferably a polyol that has high processability and can easily form the light diffusion layer 32 by means such as coating. In addition, the base polymer used for the binder 34 is preferably transparent from the viewpoint of increasing light transmittance, and is particularly preferably colorless and transparent.

  The polyol used as the base polymer of the polymer composition is obtained by polymerizing a polyester polyol and a monomer component containing the hydroxyl group-containing unsaturated monomer, and a (meth) acryl unit or the like. An acrylic polyol having is preferable. The binder 34 having such a polyester polyol or acrylic polyol as a base polymer has high weather resistance, and can suppress yellowing of the light diffusion layer 32 and the like. In addition, any one of this polyester polyol and acrylic polyol may be used, and both may be used.

  The number of hydroxyl groups in the polyester polyol and acrylic polyol is not particularly limited as long as it is 2 or more per molecule, but if the hydroxyl value in the solid content is 10 or less, the number of crosslinking points decreases, and the solvent resistance , Film properties such as water resistance, heat resistance and surface hardness tend to decrease.

  The polymer composition may contain a fine inorganic filler. By containing the fine inorganic filler in the binder 34, the heat resistance of the light diffusion layer 32 and the light diffusion sheet 31 for liquid crystal display devices is improved. The inorganic material constituting the fine inorganic filler is not particularly limited, and an inorganic oxide is preferable. This inorganic oxide is defined as various oxygen-containing metal compounds in which a metal element mainly forms a three-dimensional network through bonds with oxygen atoms. In addition, as the metal element constituting the inorganic oxide, for example, an element selected from Groups 2 to 6 of the Periodic Table of Elements is preferable, and an element selected from Groups 3 to 5 of the Periodic Table of Elements is more preferable. In particular, an element selected from Si, Al, Ti, and Zr is preferable, and colloidal silica in which the metal element is Si is most preferable as a fine inorganic filler in terms of heat resistance improvement effect and uniform dispersibility. The shape of the fine inorganic filler may be any particle shape such as a spherical shape, a needle shape, a plate shape, a scale shape, and a crushed shape, and is not particularly limited.

  The lower limit of the average particle size of the fine inorganic filler is preferably 5 nm, and particularly preferably 10 nm. On the other hand, the upper limit of the average particle size of the fine inorganic filler is preferably 50 nm, particularly preferably 25 nm. This is because if the average particle size of the fine inorganic filler is less than the above range, the surface energy of the fine inorganic filler becomes high and aggregation or the like is likely to occur. Conversely, if the average particle size exceeds the above range, This is because it becomes cloudy under the influence of a short wavelength, and the transparency of the light diffusion sheet 31 for liquid crystal display devices cannot be maintained completely.

  The lower limit of the amount of the fine inorganic filler based on 100 parts of the base polymer (the amount of only the inorganic component) is preferably 5 parts, particularly preferably 50 parts in terms of solid content. On the other hand, the upper limit of the amount of the fine inorganic filler is preferably 500 parts, more preferably 200 parts, and particularly preferably 100 parts. This is because if the blending amount of the fine inorganic filler is less than the above range, the heat resistance of the light diffusion sheet 31 for liquid crystal display devices may not be sufficiently exhibited. If the above range is exceeded, blending into the polymer composition becomes difficult, and the light transmittance of the light diffusion layer 32 may be reduced.

  As the fine inorganic filler, a material having an organic polymer fixed on its surface may be used. Thus, by using the organic polymer-fixed fine inorganic filler, the dispersibility in the binder 34 and the affinity with the binder 34 can be improved. The organic polymer is not particularly limited with respect to its molecular weight, shape, composition, presence or absence of a functional group, and any organic polymer can be used. Moreover, about the shape of an organic polymer, the thing of arbitrary shapes, such as a linear form, a branched form, and a crosslinked structure, can be used.

  The fine inorganic filler may contain an organic polymer in the fine particles. As a result, moderate softness and toughness can be imparted to the inorganic material that is the core of the fine inorganic filler.

  The base polymer is preferably a polyol having a cycloalkyl group. In this way, by introducing a cycloalkyl group into the base polymer (polyol) constituting the binder 34, the hydrophobicity of the binder 34 such as water repellency and water resistance becomes high, and the said polymer under high temperature and high humidity conditions. The bending resistance, dimensional stability, etc. of the light diffusion sheet 31 for liquid crystal display devices are improved. Further, the basic properties of the coating film such as the hardness, weather resistance, feeling of holding, and solvent resistance of the light diffusion layer 32 are improved. Furthermore, the affinity with the fine inorganic filler having the organic polymer fixed on the surface and the uniform dispersibility of the fine inorganic filler are further improved.

  The cycloalkyl group is not particularly limited, and examples thereof include a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclononyl group, a cyclodecyl group, a cycloundecyl group, a cyclododecyl group, a cyclotridecyl group, Examples thereof include a cyclotetradecyl group, a cyclopentadecyl group, a cyclohexadecyl group, a cycloheptadecyl group, and a cyclooctadecyl group.

  The polyol having a cycloalkyl group can be obtained by copolymerizing a polymerizable unsaturated monomer having a cycloalkyl group. The polymerizable unsaturated monomer having a cycloalkyl group is a polymerizable unsaturated monomer having at least one cycloalkyl group in the molecule. The polymerizable unsaturated monomer is not particularly limited, and examples thereof include cyclohexyl (meth) acrylate, methylcyclohexyl (meth) acrylate, tert-butylcyclohexyl (meth) acrylate, and cyclododecyl (meth) acrylate.

  Moreover, it is good to contain isocyanate as a hardening | curing agent in a polymer composition. Thus, by containing an isocyanate hardening | curing agent in a polymer composition, it becomes a much stronger crosslinked structure and the film physical property of the light-diffusion layer 32 further improves. As this isocyanate, the same substance as the polyfunctional isocyanate compound is used. Of these, aliphatic isocyanates that prevent yellowing of the coating are preferred.

  Furthermore, an antistatic agent may be kneaded in the polymer composition. By forming the binder 34 from the polymer composition in which the antistatic agent is kneaded in this way, an antistatic effect is exhibited in the light diffusing sheet 31 for the liquid crystal display device, and dust is sucked or stacked with a prism sheet or the like. It is possible to prevent inconveniences caused by electrostatic charging such as difficulty in alignment. Further, when the surface is coated with an antistatic agent, the surface becomes sticky or contaminated, but such an adverse effect is reduced by kneading into the polymer composition. The antistatic agent is not particularly limited. For example, anionic antistatic agents such as alkyl sulfates and alkyl phosphates, cationic antistatic agents such as quaternary ammonium salts and imidazoline compounds, polyethylene glycol type Nonionic antistatic agents such as polyoxyethylene sorbitan monostearic acid ester and ethanolamides, and high molecular antistatic agents such as polyacrylic acid are used. Among these, a cationic antistatic agent having a relatively large antistatic effect is preferable, and an antistatic effect is exhibited by addition of a small amount.

  Moreover, it is good to contain a ultraviolet absorber in the said polymer composition. By forming the binder 34 from the polymer composition containing the ultraviolet absorber in this manner, the light diffusing sheet 31 for the liquid crystal display device is given an ultraviolet cut function, and a small amount of ultraviolet rays emitted from the lamp of the backlight unit are generated. It can cut and prevent destruction of the liquid crystal layer by ultraviolet rays.

  The ultraviolet absorber is not particularly limited as long as it is a compound that absorbs ultraviolet rays and can be efficiently converted into heat energy, and is stable to light, and a known one can be used. . Among them, salicylic acid-based UV absorbers, benzophenone-based UV absorbers, benzotriazole-based UV absorbers, and cyano have a high UV-absorbing function, good compatibility with the above-mentioned base polymer, and exist stably in the base polymer. An acrylate ultraviolet absorber is preferable, and one or more selected from these groups may be used. As the ultraviolet absorber, a polymer having an ultraviolet absorbing group in the molecular chain (for example, “Udable UV” series of Nippon Shokubai Co., Ltd.) is also preferably used. By using a polymer having an ultraviolet absorbing group in such a molecular chain, the binder 34 is highly compatible with the main polymer, and deterioration of the ultraviolet absorbing function due to bleeding out of the ultraviolet absorbent can be prevented. It is also possible to use a polymer having an ultraviolet absorbing group in the molecular chain as the base polymer of the binder 34. Further, it is possible to use the polymer to which the ultraviolet absorbing group is bonded as the base polymer of the binder 34, and further to contain an ultraviolet absorber in the base polymer, so that the ultraviolet absorbing function can be further improved.

  The lower limit of the content of the ultraviolet absorber with respect to the base polymer of the binder 34 is preferably 0.1% by mass, particularly 1% by mass, and more preferably 3% by mass, and the upper limit of the content of the ultraviolet absorber is 10% by mass. In particular, 8% by mass, and further 5% by mass are preferable. This is because if the mass ratio of the ultraviolet absorbent to the base polymer is smaller than the lower limit, the ultraviolet absorbing function of the light diffusion sheet 31 for liquid crystal display devices cannot be effectively achieved. This is because if the mass ratio of the absorbent exceeds the above upper limit, the base polymer is adversely affected, and the strength and durability of the binder 34 are reduced.

  It is also possible to use an ultraviolet stabilizer (including a base polymer in which an ultraviolet stabilizing group is bonded to a molecular chain) instead of the ultraviolet absorbent or together with the ultraviolet absorbent. By this ultraviolet stabilizer, radicals generated by ultraviolet rays, active oxygen and the like are inactivated, and ultraviolet stability, weather resistance and the like can be improved. As this ultraviolet stabilizer, a hindered amine ultraviolet stabilizer having high stability against ultraviolet rays is preferably used. In addition, the combined use of an ultraviolet absorber and an ultraviolet stabilizer significantly improves deterioration prevention and weather resistance due to ultraviolet rays.

  Next, a manufacturing method of the light diffusion sheet 31 for the liquid crystal display device will be described. The manufacturing method of the light diffusing sheet 31 for a liquid crystal display device includes (a) a step of manufacturing a light diffusing layer coating liquid by mixing a light diffusing agent 33 with a polymer composition constituting the binder 34, and (b) ) A step of laminating the light diffusion layer 32 by coating the surface of the base material layer 2 with the coating solution for the light diffusion layer, and (c) a step of laminating the near infrared absorption layer 4. The means for laminating the near-infrared absorbing layer 4 is the same as that of the light diffusion sheet 1 for a liquid crystal display device.

  The light diffusion sheet 31 for a liquid crystal display device has high light diffusion due to reflection and refraction at the interface of the light diffusing agent 33 contained in the light diffusion layer 32 and refraction at fine irregularities formed on the surface of the light diffusion layer 32. And has a refraction function (condensation diffusion function) toward the normal direction due to the light diffusion function. Moreover, the light diffusion sheet 31 for liquid crystal display devices is a near-infrared ray emitted from the backlight of the liquid crystal display device by the near-infrared absorbing layer 4 containing a near-infrared absorbing agent, like the light diffusion sheet 1 for liquid crystal display devices. Can be effectively absorbed, and the malfunction of the remote control system of home appliances and the adverse effect on the human body caused by the near infrared rays emitted from the liquid crystal display device can be prevented. Further, the light diffusing sheet 31 for the liquid crystal display device is replaced with a general light diffusing sheet normally used in a liquid crystal display device, without causing an increase in the number of optical sheets of the liquid crystal display device, Near-infrared emission is prevented, and as a result, a decrease in luminance of the liquid crystal display device due to the development of the near-infrared absorbing function can be suppressed.

  The light diffusion sheet 41 for a liquid crystal display device in FIG. 5 includes a base material layer 2, a light diffusion layer 32 laminated on the front side of the base material layer 2, and a near infrared absorption layer 4 laminated on the back surface of the base material layer 2. And an anti-sticking layer 42 laminated on the back surface of the near-infrared absorbing layer 4. The base material layer 2 and the near-infrared absorbing layer 4 in the light diffusion sheet 41 for the liquid crystal display device are the same as the light diffusion sheet 1 for the liquid crystal display device, and the light diffusion layer 32 is the same as the light diffusion sheet 31 for the liquid crystal display device. It is the same.

  The anti-sticking layer 42 includes a binder 44 and beads 43 dispersed in the binder 44. The binder 44 is also formed by crosslinking and curing a polymer composition similar to the binder 34 of the light diffusion layer 32. Further, as the material of the beads 43, the same material as the light diffusing agent 33 of the light diffusing layer 32 is used. The thickness of the anti-sticking layer 42 (the thickness of the binder 44 portion where the beads 43 are not present) is not particularly limited, but is, for example, about 1 μm to 10 μm.

  The blending amount of the beads 43 is relatively small, the beads 43 are separated from each other and dispersed in the binder 44, and many of the beads 43 have a very small lower end protruding from the binder 44. Therefore, when the light diffusing sheet 41 for liquid crystal display device is laminated with the light guide plate, the lower end of the protruding beads 43 abuts on the surface of the light guide plate or the like, and the entire back surface of the light diffusing sheet 41 for liquid crystal display device is the light guide plate or the like. There is no contact. Thereby, sticking between the light diffusion sheet 41 for the liquid crystal display device and the light guide plate or the like is prevented, and uneven brightness of the screen of the liquid crystal display device is suppressed.

  Next, a method for manufacturing the light diffusion sheet 41 for a liquid crystal display device will be described. The manufacturing method of the light diffusing sheet 41 for the liquid crystal display device includes: (a) a step of manufacturing a light diffusing layer coating liquid by mixing the light diffusing agent 33 with the polymer composition constituting the binder 34; ) A step of laminating the light diffusing layer 32 by applying this coating solution for the light diffusing layer on the surface of the base material layer 2; and (c) laminating the near infrared absorbing layer 4 on the back surface of the base material layer 2. A step, (d) a step of producing a coating solution for the anti-sticking layer by mixing the beads 43 with the polymer composition constituting the binder 44, and (e) a near-infrared absorption of the coating solution for the anti-sticking layer. A step of laminating the anti-sticking layer 42 by coating on the back surface of the layer 4. The means for laminating the near-infrared absorbing layer 4 is the same as that of the light diffusion sheet 1 for a liquid crystal display device.

  The light diffusion sheet 41 for a liquid crystal display device has a high light diffusion function (condensation diffusion function) due to the light diffusion layer 32 in the same manner as the light diffusion sheet 31 for a liquid crystal display device. The light diffusion sheet 41 for a liquid crystal display device is a near infrared ray emitted from the backlight of the liquid crystal display device by the near infrared absorption layer 4 containing a near infrared absorber, as in the light diffusion sheet 1 for a liquid crystal display device. Can be effectively absorbed, and the malfunction of the remote control system of home appliances and the adverse effect on the human body caused by the near infrared rays emitted from the liquid crystal display device can be prevented. Further, the light diffusion sheet 41 for the liquid crystal display device is prevented from sticking to the light guide plate or the like by the anti-sticking layer 42 laminated on the back surface side, and the luminance unevenness of the screen of the liquid crystal display device is suppressed.

  The light diffusion sheet for a liquid crystal display device of the present invention is not limited to the above embodiment. For example, other layers such as an ultraviolet absorber layer, an antistatic agent layer, a top coat layer, and an anchor coat layer may be laminated.

  In the light diffusion sheet 1 for a liquid crystal display device or the light diffusion sheet 11 for a liquid crystal display device, the light diffusion layer 3 may also contain a near infrared absorber. Further, in the light diffusing sheet 1 for liquid crystal display device or the light diffusing sheet 11 for liquid crystal display device, a microlens array comprising a plurality of microlenses is provided on the surface in place of the light diffusing layer 3 having minute and random irregular shapes on the surface. And a light diffusion layer having a plurality of triangular prisms on the surface.

  In the light diffusion sheet 31 for liquid crystal display device or the light diffusion sheet 41 for liquid crystal display device, the near-infrared absorbing layer 4 is omitted, and the base material layer 12 of the light diffusion sheet 11 for liquid crystal display device is used instead of the base material layer 2. be able to. Further, in the light diffusion sheet 31 for liquid crystal display device or the light diffusion sheet 41 for liquid crystal display device, the near infrared absorption layer 4 is omitted, the binder 34 of the light diffusion layer 32, the light diffusion agent 33 of the light diffusion layer 32, and the anti-sticking layer. A near-infrared absorbing agent may be contained in the binder 44 of 42 and / or the beads 43 of the anti-sticking layer 42. This means also provides a near infrared absorption function.

  As described above, the light diffusion sheet of the present invention is useful as a component of a liquid crystal display device, and is particularly suitable for use in a transmissive liquid crystal display device.

1 is a schematic cross-sectional view showing a light diffusion sheet for a liquid crystal display device according to an embodiment of the present invention. Typical sectional drawing which shows the light-diffusion sheet for liquid crystal display devices which concerns on the form different from the light-diffusion sheet for liquid crystal display devices of FIG. Typical sectional drawing which shows the light-diffusion sheet for liquid crystal display devices which concerns on the form different from the light-diffusion sheet for liquid crystal display devices of FIG.1 and FIG.2. Typical sectional drawing which shows the light-diffusion sheet for liquid crystal display devices which concerns on the form different from the light-diffusion sheet for liquid crystal display devices of FIG.1, FIG2 and FIG.3 FIG. 1, FIG. 2, FIG. 3 and FIG. 4 are schematic cross-sectional views showing a light diffusion sheet for liquid crystal display devices according to a different form from the light diffusion sheet for liquid crystal display devices of FIG. Schematic sectional view showing a general liquid crystal display device

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light diffusion sheet for liquid crystal display devices 2 Base material layer 3 Light diffusion layer 4 Near-infrared absorption layer 11 Light diffusion sheet for liquid crystal display devices 12 Base material layer 21 Light diffusion sheet for liquid crystal display devices 22 Base material layer 23 Light diffusion layer 31 Light diffusion sheet for liquid crystal display device 32 Light diffusion layer 33 Light diffusing agent 34 Binder 41 Light diffusion sheet for liquid crystal display device 42 Anti-sticking layer 43 Beads 44 Binder

Claims (11)

A light diffusion sheet for a liquid crystal display device comprising a transparent substrate layer and a light diffusion layer laminated on the surface side of the substrate layer,
Contains a near infrared absorber,
A light diffusing sheet for a liquid crystal display device having a near infrared transmittance of 50% or less.   The light-diffusion sheet for liquid crystal display devices of Claim 1 provided with the sticking prevention layer in which a bead disperse | distributes in a binder on the back surface side of the said base material layer.   The light-diffusion sheet for liquid crystal display devices of Claim 1 or Claim 2 which contains a near-infrared absorber in the said base material layer, a light-diffusion layer, and / or a sticking prevention layer.   The light-diffusion sheet for liquid crystal display devices of Claim 1 or Claim 2 provided with the near-infrared absorption layer containing the said near-infrared absorber.   The light diffusion sheet for a liquid crystal display device according to any one of claims 1 to 4, wherein the visible light transmittance is 50% or more and the total light transmittance is 50% or more.   The light diffusion sheet for a liquid crystal display device according to claim 1, wherein the retardation value of the base material layer is 50 nm or less.   The light diffusing sheet for a liquid crystal display device according to any one of claims 1 to 6, wherein polyethylene terephthalate or polycarbonate is used as a matrix resin constituting the base material layer.   The light diffusion sheet for a liquid crystal display device according to any one of claims 1 to 7, wherein an average thickness of the base material layer is 25 µm or more and 1000 µm or less.   9. The surface roughness (Ra) in the light diffusion layer is 0.1 μm or more and 0.5 μm or less, and the surface roughness (Ry) is 1 μm or more and 20 μm or less. 9. Light diffusion sheet for liquid crystal display devices.   The light diffusion sheet for a liquid crystal display device according to any one of claims 1 to 9, wherein the light diffusion layer has a light diffusion agent and a binder thereof. The light diffusion sheet for a liquid crystal display device according to any one of claims 1 to 9, wherein the light diffusion layer has a minute uneven shape on a surface thereof.

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