JP2019036379A - Light guide plate - Google Patents

Abstract

To provide a light guide plate with reduced variations in chromaticity of light extracted from a light extraction surface of a glass plate.SOLUTION: A light guide plate has a glass plate having an end surface receiving light incoming from a light source, a first main surface for extracting the light having come into the end surface, and a second main surface facing the first main surface, with the second main surface having a plurality of light scattering parts having hollow particles. The glass plate comprises a glass that contains, in terms of mass percent on an oxide basis, FeOof 1 mass ppm-50 mass ppm, NiO of 0.01 mass ppm-2.0 mass ppm, CrOof 0.01 mass ppm-2.0 mass ppm, MnOof 0.01 mass ppm-50 mass ppm, TiOof 0.01 mass ppm-1000 mass ppm and has an iron redox of 25% or less .SELECTED DRAWING: Figure 1

Description

  The present invention relates to a light guide plate used in a liquid crystal display device.

  Since the liquid crystal display device is used as a television, a personal computer, or various monitors, high brightness and high color reproducibility are required. The liquid crystal display device includes a liquid crystal panel, a light guide plate facing the liquid crystal panel, and a light source that irradiates the liquid crystal panel with light through the light guide plate (see, for example, Patent Document 1). The light guide plate has a resin plate as a base material and a light scattering portion formed on the resin plate. The light guide plate is required to be highly transmissive and to extract light of an achromatic color and a uniform color in the plane as much as possible. This demand is further increased as the liquid crystal display device becomes thinner and larger.

  The resin plate has an end face on which light is incident from a light source, a light extraction surface from which light incident on the end face is extracted, and a light scattering surface facing the light extraction surface. A plurality of light scattering portions are arranged on the light scattering surface. Each light scattering portion includes a plurality of light scattering particles and a binder that binds the plurality of light scattering particles. The light scattering particles and the binder have different refractive indexes.

  Light from the light source enters the inside of the resin plate from the end surface of the resin plate, repeats total reflection, spreads throughout the inside of the resin plate, and is scattered by the light scattering surface of the resin plate from the light extraction surface of the resin plate. Get out and illuminate the LCD panel.

Japanese Patent No. 5302935

  In recent years, a glass plate has been studied as a base material for a light guide plate from the viewpoints of rigidity, heat resistance and water resistance.

  Unlike light propagating in resin, light propagating in glass is absorbed in glass. What is absorbed is a predetermined wavelength component of the incident light. On the other hand, at least a part of the wavelength component that is not absorbed in the glass is scattered by the light scattering portion. Of the light that is scattered and propagates in the glass, the wavelength component is absorbed in the glass, while the non-absorbed wavelength component is again incident on the light scattering portion and scattered to repeat from the light extraction surface. Exit. As a result, there has been a problem that the chromaticity of light extracted from the light extraction surface varies greatly depending on the distance from the light source, and color unevenness occurs.

  The present invention has been made in view of the above problems, and a main object of the present invention is to provide a light guide plate in which unevenness in color of light extracted from the light extraction surface of the glass plate is reduced to an invisible level.

In order to solve the above problems, according to one aspect of the present invention,
A glass plate having an end face into which light is incident from a light source, a first main surface for taking out light incident on the end face, and a second main surface facing the first main surface;
A light guide plate comprising a plurality of light scattering parts containing hollow particles on the second main surface,
The glass plate is represented by mass percentage based on oxides, _Fe 2 _{O 3} 1 wt ppm~50 mass ppm, NiO 0.01 mass ppm~2.0 mass ppm, _Cr 2 _{O 3} 0.01 wt It is characterized by comprising a glass containing ppm to 2.0 mass ppm, MnO ₂ 0.01 mass ppm to 50 mass ppm, TiO ₂ 0.01 mass ppm to 1000 mass ppm, and iron redox being 25% or less. A light guide plate is provided.

  According to one embodiment of the present invention, a light guide plate is provided in which variation in chromaticity of light extracted from a light extraction surface of a glass plate is reduced.

It is a figure which shows the liquid crystal display device containing the light-guide plate by one Embodiment. It is a figure which shows the measuring point of the chromaticity of the glass light-guide plate by Example 1. FIG. It is a figure which shows another measuring point of the chromaticity of the glass light-guide plate by Example 1. FIG.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In the drawings, the same or corresponding components are denoted by the same or corresponding reference numerals, and description thereof is omitted. In this specification, “to” representing a numerical range means a range including numerical values before and after the numerical range.

  FIG. 1 is a diagram illustrating a liquid crystal display device including a light guide plate according to an embodiment. The liquid crystal display device includes a liquid crystal panel 10, a light guide plate 20 facing the liquid crystal panel 10, and a light source 50 that emits light to the liquid crystal panel 10 through the light guide plate 20.

  The liquid crystal panel 10 includes, for example, an array substrate, a color filter substrate, and a liquid crystal layer. The array substrate includes a substrate and an active element (for example, TFT) formed on the substrate. The color filter substrate includes a substrate and a color filter formed on the substrate. The liquid crystal layer is formed between the array substrate and the color filter substrate.

  The light guide plate 20 includes a glass plate 30 as a base material and a light scattering portion 40.

  The glass plate 30 may be a flat plate. The plate thickness of the glass plate 30 is preferably 10 mm or less, more preferably 4 mm or less. Even more preferably, it is 3 mm or less. If the plate thickness is 10 mm or less, the weight and thickness of the liquid crystal display device can be in an appropriate range. Further, the thickness of the glass plate 30 is preferably 0.3 mm or more, more preferably 0.7 mm or more. Still more preferably, 1.0 mm or more is good. If the plate thickness is 0.3 mm or more, it has appropriate rigidity and can ensure the self-supporting property of a single glass. Further, if the plate thickness is 0.3 mm or more, the glass plate thickness is equal to or greater than the width of the light source, so that light can be efficiently incident on the glass plate 30. The plate thickness of the glass plate 30 is substantially uniform.

  The glass plate 30 has the 1st end surface 31 in which the light source 50 is arrange | positioned. The first end surface 31 is also referred to as a light incident surface 31. The light incident surface 31 is a surface on which light from the light source 50 is incident.

  The glass plate 30 has a second end face 32 that faces the first end face 31. The second end face 32 is also referred to as a light incident face 32. A light reflection layer may be formed on the light incident surface 32. The light reflecting layer reflects light propagating through the glass plate 30 toward the inside of the glass plate 30. The brightness of the glass plate 30 can be improved.

  The glass plate 30 has a first main surface 35 that faces the liquid crystal panel 10. The first main surface 35 is also referred to as a light extraction surface 35. The light extraction surface 35 is a surface for extracting light propagating inside the glass plate 30.

  The glass plate 30 has a second main surface 36 that faces the first main surface 35. This second main surface 36 is also called a light scattering surface 36. The light scattering surface 36 is a surface on which the light scattering portion 40 is formed.

  The light scattering unit 40 is disposed on the light scattering surface 36 and scatters at least part of the light propagating through the glass plate 30. The light scattering portion 40 is formed in a dot shape, for example, and is disposed so as to become denser as it goes farther from the first end surface 31 toward the second end surface 32.

  Details of the glass plate 30 and the light scattering portion 40 will be described later.

  When the direction from the light incident surface 31 to the light incident surface 32 of the glass plate 30 is vertical, such a configuration is effective in terms of suppressing color unevenness of the light guide plate when the vertical dimension is 482 mm or more. is there. The longitudinal dimension that effectively enables color unevenness suppression of the light guide plate of the present invention is 500 mm or more, particularly 550 mm or more.

  The light source 50 irradiates the light incident surface 31 of the glass plate 30 with light. Light from the light source 50 enters the inside from the light incident surface 31 of the glass plate 30, repeats total reflection, spreads over the entire interior, and is scattered by the light scattering surface 36 to exit from the light extraction surface 35, so that the liquid crystal panel Illuminate 10 uniformly from behind.

  As the light source 50, for example, a white LED is used. The white LED may be composed of, for example, a blue LED and a phosphor that receives and emits light from the blue LED. Examples of the phosphor include YAG, oxide, aluminate, nitride, oxynitride, sulfide, oxysulfide, rare earth oxysulfide, halophosphate, and chloride.

  For example, the white LED may be composed of a blue LED and a yellow phosphor. Moreover, white LED may be comprised by blue LED, green fluorescent substance, and red fluorescent substance. Since the light from the latter white LED is a mixture of the three primary colors of light, it is more excellent in color rendering.

  Note that a scattering film, a brightness enhancement film, a reflective polarizing film, a 3D film, a polarizing plate, and the like may be disposed between the light guide plate 20 and the liquid crystal panel 10. A reflective film or the like may be disposed behind the light guide plate 20. The light source 50, the light guide plate 20, and various optical films are collectively referred to as a backlight unit.

(Light scattering part)
The light scattering unit 40 includes a plurality of hollow particles 41. In applying the hollow particles to the glass plate, a known method can be applied. For example, a method in which a mixed solution of the hollow particles 41 and the binder 42 is applied to glass and then cured by ultraviolet irradiation can be applied.

  When the light scattering portion is formed of general solid fine particles, the light emitted near the incident light facing surface 32 becomes yellowish, and the color unevenness is remarkable. In light scattering by solid particles, the shorter the wavelength, the stronger the scattering intensity, and there is a tendency to scatter mainly forward. It is considered that the light emitted to the incident light facing surface 32 side becomes red after scattering, and becomes yellow on the incident light facing surface 32 side due to the color mixture with the light that has become green after being absorbed by the glass.

  When the light scattering portion is formed of hollow particles, color unevenness is suppressed as compared with the case of using solid particles, but if the absorbance of the glass is not designed appropriately, the light is emitted near the incident light face 32. The light will turn blue. This is because in light scattering by hollow particles, the longer the wavelength, the stronger the scattering intensity and the stronger the backward scattering.

  The hollow particles 41 have, for example, an outer shell and voids formed inside the outer shell. The outer shell is formed of a polymer, for example. The outer diameter of the hollow particles 41 is, for example, 0.4 μm to 5 μm, preferably 0.4 μm to 4 μm, more preferably 0.4 μm to 3 μm, and further preferably 0.5 μm to 2 μm. Hereinafter, the manufacturing method of the hollow particle 41 is demonstrated.

  A specific monomer (first polymerizable monomer) (α) is emulsion-polymerized in an aqueous medium to prepare a dispersion of the first polymer particles (i), and then the surface layer of the first polymer particles (i) is specified Preparing a dispersion of core-shell polymer particles (ii) coated with a shell layer comprising a second polymer derived from the second polymerizable monomer (β) and an unreacted second polymerizable monomer (β); The pH of the dispersion of the core-shell polymer particles (ii) is adjusted to 7 or more (25 ° C. converted value) with a volatile base, and the core-shell polymer particles (ii) are neutralized and swollen to form crosslinked hollow polymer particles An aqueous dispersion (iii) is prepared. The crosslinked hollow polymer particle aqueous dispersion (iii) is dried to obtain hollow particles made of a substance containing a polymer and air.

  The first polymerizable monomer (α) is an unsaturated carboxylic acid (α-1) (hereinafter sometimes referred to as “monomer (α-1)”) and a radical polymerizable monomer (α-2) (hereinafter referred to as “monomer (α-1)”). It may be referred to as “monomer (α-2)”.

  Examples of the monomer (α-1) include mono- or dicarboxylic acids such as (meth) acrylic acid, crotonic acid, maleic acid, fumaric acid, and itaconic acid, and acid anhydrides of the dicarboxylic acid.

  Examples of the monomer (α-2) include unsaturated carboxylic acid esters such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate, Examples thereof include aromatic monomers such as styrene and α-methylstyrene, (meth) acrylonitrile, vinyl acetate, N, N-dimethyl (meth) acrylamide and the like.

  A core-shell polymer in which the surface layer of the first polymer particles (i) is coated with a shell layer containing a second polymer derived from a specific second polymerizable monomer (β) and an unreacted second polymerizable monomer (β) About the method of preparing the dispersion of particle | grains (ii), it is possible to carry out as follows.

  The second polymerizable monomer (β) is a crosslinkable radically polymerizable monomer (β-1) (hereinafter sometimes referred to as “monomer (β-1)”) 10 mass% to 80 mass%, unsaturated carboxylic acid. Acid (β-2) (hereinafter sometimes referred to as “monomer (β-2)”) 0% by mass to 20% by mass and other radical polymerizable monomers copolymerizable with monomer (β-1) ( β-3) (hereinafter sometimes referred to as “monomer (β-3)”) 0% by mass to 90% by mass.

  After preparing the first polymer particles (i), 100 parts by mass of the second polymerizable monomer (β) is emulsified in an aqueous solvent in the presence of 5 parts by mass to 1000 parts by mass of the first polymer particles (i). A core-shell shape in which a shell layer containing a second polymer derived from the second polymerizable monomer (β) and an unreacted second polymerizable monomer (β) is coated on the surface layer of the first polymer particles (i) by polymerization. A dispersion of polymer particles (ii) is prepared.

  As the monomer (β-1), divinylbenzene, trivinylbenzene, dicyclopentadiene, butadiene, isoprene, allyl glycidyl ether, glycidyl (meth) acrylate, ethylene glycol dimethacrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol Crosslinkable radically polymerizable monomers such as tri (meth) acrylate and dipentaerythritol hexa (meth) acrylate can be used.

  As the monomer (β-2), the same unsaturated carboxylic acid as the example of the monomer (α-1) described above can be used, and (meth) acrylic acid is particularly preferable from the viewpoint of particle stability. Itaconic acid and the like are preferable.

  Examples of the monomer (β-3) include monoethylenic aromatic compounds such as styrene and α-methylstyrene, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, Non-crosslinkable radically polymerizable monomers such as unsaturated carboxylic acid esters such as 2-ethylhexyl (meth) acrylate, (meth) acrylonitrile, vinyl acetate and N, N-dimethyl (meth) acrylamide can be used. Among these, monoethylenic aromatic compounds such as styrene are preferable.

  In addition, without isolating the hollow particles, a binder component for forming the binder 42 by obtaining a hollow particle-containing liquid composition by solvent replacement with the crosslinked hollow polymer particle aqueous dispersion (iii), and other desired It is also possible to add a component to be used for forming a dot pattern containing hollow particles.

  Moreover, as for the details of the method for producing the hollow particles, it is desirable to follow the method described in International Publication No. 2005/071014.

  As the binder 42, a resin having high transparency to visible light is used. Such a resin is preferably at least one selected from the group consisting of a thermosetting resin, a thermoplastic resin, and a photocurable resin.

  As the thermosetting resin used for the binder 42, known resins can be used, and epoxy resins, melamine resins, and phenol resins are preferable. These may be used alone or in combination of two or more.

  As the thermoplastic resin used for the binder 42, known resins can be used. Preferably, olefinic resins such as polyethylene and polypropylene, fluororesins such as acrylic resins, ABS resins, MS resins, styrene resins, and polyvinylidene fluoride are used. An olefin resin, and more preferably a fluoroolefin resin such as an acrylic resin, an MS resin, a styrene resin, or polyvinylidene fluoride. These may be used alone or in combination of two or more.

  Examples of the photocurable resin used for the binder 42 include a high molecular weight photocurable resin. As the high molecular weight photocurable resin, any known one can be used without particular limitation as long as a photopolymerizable group is introduced into the polymer skeleton. Examples of such a polymer skeleton include a polyethylene skeleton, a polyurethane skeleton, a polyester skeleton, a polyamide skeleton, a polyimide skeleton, a polyoxyalkylene skeleton, and a polyphenylene skeleton, and a polyethylene skeleton and a polyurethane skeleton are preferable. Examples of the photopolymerizable group include (meth) acryloyl group, alkenyl group, cinnamoyl group, cinnamylideneacetyl group, benzalacetophenone group, styrylpyridine group, α-phenylmaleimide, phenylazide group, sulfonylazide group, carbonyl Azide group, diazo group, o-quinonediazide group, furylacryloyl group, coumarin group, pyrone group, anthracene group, benzophenone group, benzoin group, stilbene group, dithiocarbamate group, xanthate group, 1,2,3-thiadiazole group, cyclo A propene group azadioxabicyclo group and the like can be mentioned, and preferred photopolymerizable groups are a (meth) acryloyl group and a cinnamoyl group, and a (meth) acryloyl group is particularly preferred. These may be used alone or in combination of two or more.

  The ratio between the resin as the binder and the hollow particles can be adjusted as appropriate according to the method of coating the glass, the viscosity, and the like.

(Glass plate)
As the glass of the glass plate 30, for example, the following highly transmissive glass is used. The following highly transmissive glass has a low absorbance in the entire wavelength range of visible light (380 to 780 nm) as compared with general glass, and the wavelength dependency of the absorbance is appropriately designed. Therefore, when the following highly transmissive glass is used as the light guide plate, the luminance of light emitted from the main surface is high, and the in-plane chromaticity difference is kept small.

  Here, the wavelength dependence of absorbance refers to the difference in light absorbance for each wavelength band of visible light. When hollow particles are used for the light scattering portion and high transmittance glass whose wavelength dependency of absorbance is not properly designed is used as the light guide plate, the light emitted in the vicinity of the incident light face 32 becomes closer to blue. End up.

  However, the high-transmission glass in the present invention is designed so that the wavelength dependence of absorbance is appropriately designed, and blue light is absorbed by the glass as it is guided, so the chromaticity of the emitted light is uniform throughout the surface. It is. Specifically, the high transmittance glass in the present invention is designed such that the blue absorbance is slightly larger than the red absorbance. However, the blue absorbance is not too high, and color unevenness due to glass absorption does not appear remarkably.

The main factor of light absorption of the glass plate is iron ions contained as impurities. Iron is unavoidably contained as a raw material for industrially produced glass, and it is inevitable that iron is mixed into the glass. Iron ions take the form of divalent (Fe ²⁺ ) and trivalent (Fe ³⁺ ) in the glass, but what is particularly problematic is Fe ²⁺ having a wide absorption at wavelengths of 490 to 780 nm. Fe ³⁺ has an absorption band at a wavelength of 380 to 490 nm, but its influence is small because the extinction coefficient per unit concentration is one digit smaller than that of Fe ²⁺ . The iron content in the glass plate 30 and the ratio of divalent (Fe ²⁺ ) and trivalent (Fe ³⁺ ) must be appropriately adjusted so that the in-plane chromaticity difference can be kept small.

  In particular, when considering the use of a glass plate as a light guide for an edge light type planar light emitting device such as a liquid crystal television, from the viewpoint of reducing the chromaticity difference in the screen of the liquid crystal television, a wavelength of 380 to 380 is used. It is important to consider the scattering characteristics at the light scattering portion in the internal transmittance spectrum of the glass plate in the entire wavelength region of 780 nm. For example, in the light guide of a liquid crystal television, the color can be accurately reproduced near the light source because the light propagation distance is short, but as the distance from the light source increases, the influence of the wavelength dependence of scattering at the scattering portion increases. The color shifts. In particular, the chromaticity difference is likely to occur as the liquid crystal television has a larger screen.

Highly transmissive glass is expressed in terms of oxide based mass percentage, Fe ₂ O ₃ is 1 mass ppm to 50 mass ppm, NiO is 0.01 mass ppm to 2.0 mass ppm, and Cr ₂ O ₃ is 0.01 mass. It contains ppm to 2.0 mass ppm, 0.01 mass ppm to 50 mass ppm of MnO ₂ , 0.01 mass ppm to 1000 mass ppm of TiO ₂ , and iron redox is 25% or less.

  Representative examples of the highly transmissive glass include the following three types: (1) glass A, (2) glass B, and (3) glass C. In the following description of glasses A to C, the glass composition and refractive index are average values, “%” means mass%, and “ppm” means mass ppm.

Glass A is an oxide-based mass percentage display, with SiO ₂ 60-60%, Al ₂ O ₃ 0-7%, MgO 0-10%, CaO 0-20%, and SrO 0-15. %, BaO 0-15%, Na ₂ O 3-20%, K ₂ O 0-10%, Fe ₂ O _{3 1} ppm-50 ppm, NiO 0.01 ppm-2.0 ppm, Cr ₂ O ₃ to 0.01 ppm to 2.0 ppm, MnO ₂ to 0.01 mass ppm to 50 mass ppm, and TiO ₂ to 0.01 mass ppm to 1000 mass ppm. The iron redox of glass A is 25% or less. The refractive index at room temperature of the glass A helium d-line (wavelength 587.6 nm) is 1.45 to 1.60. Specific examples include Examples 1 to 4 and Example 15 in Table 1.

Glass B is expressed in terms of mass percentage based on oxide, and SiO ₂ is 45 to 80%, Al ₂ O ₃ is more than 7% and 30% or less, B ₂ O _{3 is 0} to 15%, MgO is 0 to 15%, CaO 0-6% of SrO 0-5%, containing 0-5% of BaO, a Na ₂ O 7 to 20% 0% of _{K 2} O, the ZrO ₂ 0% Fe ₂ the O ₃ 1ppm~50ppm, 0.01ppm~2.0ppm the NiO, 0.01ppm~2.0ppm the _Cr 2 _{O 3,} MnO ₂ and 0.01 mass ppm~50 mass ppm, the TiO ₂ 0.01 Contains ppm to 1000 ppm by mass. The iron redox of glass B is 25% or less. The refractive index at room temperature of the helium d-line (wavelength 587.6 nm) of glass B is, for example, 1.45 to 1.60. Glass B is easy to ion exchange and easy to chemically strengthen. Specific examples include Examples 5 to 11 in Table 1.

Glass C is an oxide-based mass percentage display, and SiO ₂ is 45 to 70%, Al ₂ O ₃ is 10 to 30%, B ₂ O _{3 is 0} to 15%, MgO, CaO, SrO and BaO are total. 5 to 30%, Li ₂ O, Na ₂ O and K ₂ O in total of 0% or more and less than 3%, Fe ₂ O ₃ 1-50 ppm, NiO 0.01 ppm-2.0 ppm, Cr ₂ It contains 0.01 ppm to 2.0 ppm of O ₃ , 0.01 mass ppm to 50 mass ppm of MnO _2, and 0.01 mass ppm to 1000 mass ppm of TiO ₂ . The iron redox of glass C is 25% or less. The refractive index at room temperature of the helium d-line (wavelength 587.6 nm) of glass C is, for example, 1.45 to 1.60. Specific examples include Examples 12 to 14 in Table 1.

The composition range of each component of glass A, B, and C is demonstrated below.
SiO ₂ is a main component of glass.
In order to maintain the weather resistance and devitrification properties of the glass, the content of SiO ₂ is preferably 60% or more, more preferably 63% or more in the glass A in terms of oxide-based mass percentage, and the glass B Is preferably 45% or more, more preferably 50% or more. In the glass C, it is preferably 45% or more, more preferably 50% or more.
On the other hand, the content of SiO ₂ is easy to dissolve and the foam quality is good, and the content of divalent iron (Fe ²⁺ ) in the glass is kept low, and the optical properties are good. Therefore, in glass A, it is preferably 80% or less, more preferably 75% or less, in glass B, preferably 80% or less, more preferably 70% or less, and in glass C, preferably 70% or less, more preferably 65% or less.

Al ₂ O ₃ is an essential component for improving the weather resistance of the glass B and C. In the glass A, the content of Al ₂ O ₃ is preferably 0% or more, more preferably 2% or more. In the glass B, the content is preferably more than 7%, more preferably 10% or more. In C, it is preferably 10% or more, more preferably 13% or more.
However, in order to keep the content of divalent iron (Fe ²⁺ ) low, make the optical properties good, and make the foam quality good, the content of Al ₂ O ₃ is preferably in the glass A. 7% or less, more preferably 5% or less, in glass B, preferably 30% or less, more preferably 23% or less, and in glass C, preferably 30% or less, more preferably 20% or less. It is.

B ₂ O ₃ is a component that promotes melting of the glass raw material and improves mechanical properties and weather resistance, but it does not cause inconveniences such as generation of striae due to volatilization and furnace wall erosion. The content of B ₂ O ₃ is preferably 5% or less, more preferably 3% or less in the glass A, and preferably 15% or less, more preferably 12% or less in the glasses B and C. It is.

Alkali metal oxides such as Li ₂ O, Na ₂ O, and K ₂ O are useful components for accelerating melting of glass raw materials and adjusting thermal expansion, viscosity, and the like.
Therefore, in the glass A, the content of Na ₂ O is preferably 3% or more, more preferably 8% or more. In the glass B, the content of Na ₂ O is preferably 7% or more, more preferably 10% or more. However, the content of Na ₂ O is preferably 20% or less in the glasses A and B in order to maintain the clarity during melting and maintain the foam quality of the produced glass, and 15% or less. More preferably, in glass C, it is preferably less than 3%, more preferably 1% or less.
Further, the content of K ₂ O is preferably 10% or less, more preferably 7% or less in the glasses A and B, and preferably 2% or less, more preferably 1% in the glass C. It is as follows.
Further, Li ₂ O is an optional component, but in order to facilitate vitrification, to keep the iron content contained as an impurity derived from the raw material low, and to keep the batch cost low, in glasses A, B and C, Li ₂ O can be contained at 2% or less.
In addition, the total content of these alkali metal oxides (Li ₂ O + Na ₂ O + K ₂ O) maintains the clarification at the time of melting, and in order to maintain the foam quality of the glass produced, in the glasses A and B, Preferably, it is 5% to 20%, more preferably 8% to 15%. In the glass C, it is preferably 0% to less than 3%, more preferably 0% to 1%.

Alkaline earth metal oxides such as MgO, CaO, SrO, and BaO are useful components for accelerating melting of glass raw materials and adjusting thermal expansion, viscosity, and the like.
MgO has the effect of lowering the viscosity during glass melting and promoting the melting. Moreover, since there exists an effect | action which reduces specific gravity and makes a glass plate hard to wrinkle, it can be contained in glass A, B, and C. Further, in order to reduce the thermal expansion coefficient of the glass and to improve the devitrification properties, the content of MgO is preferably 10% or less, more preferably 8% or less in the glass A, In the glass B, it is preferably 15% or less, more preferably 12% or less, and in the glass C, it is preferably 10% or less, more preferably 5% or less.

  CaO is a component that promotes melting of the glass raw material and adjusts viscosity, thermal expansion, and the like, and therefore can be contained in the glasses A, B, and C. In order to obtain the above action, in the glass A, the content of CaO is preferably 3% or more, more preferably 5% or more. In order to improve devitrification, the glass A is preferably 20% or less, more preferably 10% or less, and the glass B is preferably 6% or less, more preferably 4%. It is as follows.

  SrO has the effect of increasing the thermal expansion coefficient and lowering the high temperature viscosity of the glass. In order to obtain such an effect, SrO can be contained in the glasses A, B and C. However, in order to keep the thermal expansion coefficient of the glass low, it is preferably 15% or less in the glass A and C, more preferably 10% or less, and in the glass B, 5% or less. Preferably, it is more preferably 3% or less.

  BaO, like SrO, has the effect of increasing the thermal expansion coefficient and lowering the high temperature viscosity of the glass. In order to acquire said effect, BaO can be contained in glass A, B, and C. FIG. However, in order to keep the thermal expansion coefficient of the glass low, it is preferably 15% or less in the glass A and C, more preferably 10% or less, and in the glass B, 5% or less. Preferably, it is more preferably 3% or less.

  Further, the total content of these alkaline earth metal oxides (MgO + CaO + SrO + BaO) is preferably 10% in the glass A in order to keep the coefficient of thermal expansion low, good devitrification properties and maintain strength. -30%, more preferably 13% -27%, in glass B, preferably 1% -15%, more preferably 3% -10%, in glass C, preferably 5-30% %, More preferably 10% to 20%.

Glasses A, B, and C may contain 10% or less, preferably 5% or less, of ZrO ₂ as an optional component in order to improve the heat resistance and surface hardness of the glass. If ZrO ₂ is 10% or less, it is preferable because the glass is hardly devitrified.

Glasses A, B, and C contain 1 ppm to 50 ppm of Fe ₂ O ₃ from the viewpoint of improving the meltability of the glass. Here, the amount of _Fe 2 _{O 3} refers to the total iron oxide amount in terms of _Fe 2 _{O 3.} The total iron oxide content is preferably 1 ppm to 50 mass ppm, more preferably 1 ppm to 20 mass ppm. If the total iron oxide content is 1 ppm or more, the infrared absorption of the glass becomes appropriate, so that the meltability can be improved, and the cost of refining the raw material does not increase. Moreover, if the total iron oxide amount is 50 ppm or less, the coloring of the glass is suppressed, and an appropriate visible light transmittance can be secured.

In glasses A, B and C, the proportion of divalent iron in the total iron is represented by iron redox. Iron redox, the mass of the bivalent iron terms of Fe ₂ O _3, shows the rate at percentage relative to the mass of total iron as calculated as Fe ₂ O _3. Total iron is the sum of divalent iron and trivalent iron. The ratio of divalent iron to trivalent iron is obtained by a Mossbauer absorption spectrum measured at 25 ° C. The smaller the iron redox, the smaller the proportion of divalent iron in the total iron. Since divalent iron has a larger absorption coefficient than trivalent iron, it is preferable that the iron redox is small. In glasses A, B and C, the iron redox is 25% or less. More preferably, it is 20% or less, and more preferably 15% or less. Iron redox is preferably 3% or more in consideration of productivity and cost.

The glass A, B and C may contain SO ₃ as a fining agent. In this case, the SO ₃ content is preferably more than 0% and 0.5% or less in terms of mass percentage. 0.4% or less is more preferable, 0.3% or less is more preferable, and 0.25% or less is further preferable.

The glass A, B and C may contain one or more of _Sb 2 _O 3, SnO ₂ and _As 2 _{O 3} as an oxidizing agent and a clarifying agent. In this case, the content of Sb ₂ O ₃ , SnO ₂ or As ₂ O ₃ is preferably 0 to 0.5% in terms of mass percentage. 0.2% or less is more preferable, 0.1% or less is more preferable, and it is further more preferable not to contain substantially.
However, since Sb ₂ O ₃ , SnO ₂ and As ₂ O ₃ act as an oxidizing agent for glass, they may be added within the above range depending on the purpose of adjusting the amount of Fe ^{2+ in} the glass. However, As ₂ O ₃ is not positively contained from the environmental viewpoint.

  Glasses A, B, and C contain NiO. The content of NiO is 0.01 ppm or more and 2.0 ppm or less with respect to the total amount of the glass composition described above in order to suppress color unevenness in the plane of the light guide plate. In particular, since NiO has strong absorption in the vicinity of a wavelength of 450 nm, the content of NiO is preferably 0.01 ppm or more and 1.0 ppm or less from the viewpoint of suppressing color unevenness due to absorption of the glass plate. More preferably, the content is not less than 0.01 ppm and not more than 0.4 ppm.

Glasses A, B and C contain Cr ₂ O ₃ . The content of cr ₂ O ₃ is the total amount of the glass composition described above with respect to, at least 0.01 ppm 2.0 ppm or less. However, since Cr ₂ O ₃ has strong absorption near wavelengths of 450 nm and 650 nm, the content of Cr ₂ O ₃ is 0.01 ppm or more from the viewpoint of suppressing color unevenness due to absorption of the glass plate. It is preferably 0 ppm or less, and more preferably 0.01 ppm or more and 0.4 ppm or less.

Glasses A, B and C contain MnO ₂ . The content of MnO ₂ is 0.01 ppm to 50 ppm with respect to the total amount of the glass composition described above. In particular, from the viewpoint of not reducing the internal transmittance of the glass plate at a wavelength of 400 to 700 nm, the content of MnO ₂ is preferably 0.01 ppm or more and 10 ppm or less, more preferably 0.01 ppm or more and 5 ppm or less. preferable.

Glass A, B and C contains TiO _2. The content of TiO ₂ is 0.01 ppm or more and 1000 ppm or less with respect to the total amount of the glass composition described above. In particular, from the viewpoint of not reducing the internal transmittance of the glass plate at a wavelength of 400 to 700 nm, the content of TiO ₂ is preferably 0.01 ppm to 500 ppm, more preferably 0.01 ppm to 100 ppm. preferable.

Glass A, B and C may include CeO _2. CeO ₂ has an effect of lowering iron redox, and the absorbance of the glass at a wavelength of 400 to 700 nm can be reduced. The CeO ₂ content is preferably 1000 ppm or less with respect to the total amount of the glass composition described above. A CeO ₂ content of 1000 ppm or less is preferred because it does not absorb visible light too much and the iron redox can be maintained at 3% or more. The CeO ₂ content is more preferably 500 ppm or less, further preferably 400 ppm or less, particularly preferably 300 ppm or less, and most preferably 200 ppm or less.

Glasses A, B and C may contain at least one component selected from the group consisting of CoO, V ₂ O ₅ and CuO. When these components are contained, they also function as components that absorb visible light, and therefore the content of the components is preferably 10 ppm or less with respect to the total amount of the glass composition described above. In particular, it is preferable that these components are not substantially contained so as not to reduce the internal transmittance of the glass plate at a wavelength of 400 to 700 nm.

ところで、光源５０からの入射光は、ガラス板３０中で吸収されながら個々の光散乱部４０において散乱されてガラス板３０中を伝搬する。

By the way, incident light from the light source 50 is scattered in the individual light scattering portions 40 while being absorbed in the glass plate 30 and propagates in the glass plate 30.

  According to the present embodiment, the wavelength dependency of the scattering efficiency is reduced by the wavelength dependency of the absorbance by using a predetermined highly transmissive glass as the glass of the glass plate 30. Thereby, the fluctuation | variation of chromaticity according to the distance from the light source 50 can be suppressed. This effect is remarkable when the glass plate 30 has a substantially rectangular shape in plan view and has a length of 482 mm or more in a direction from the end surface where light enters to the end surface facing the end surface.

[Example 1]
In Example 1, a glass light guide plate was produced by printing a diffusion ink in a dot pattern on one main surface of a glass plate and curing it by ultraviolet irradiation. As the glass of the glass plate, the glass of Example 15 shown in Table 1 was used. The glass plate was substantially rectangular in plan view and had a diagonal length of 1396 mm (55 inches). The dimensions of the glass plate were 1214 mm wide, 689 mm long, and 2.1 mm thick. Of the four end surfaces of the glass plate, the light incident surface was mirror-finished and the remaining three surfaces were roughed. As the diffusion ink, an ink containing ultraviolet curable hollow particles (manufactured by JSR, product number: SX8034) was used.

  The produced glass light guide plate was replaced with the acrylic light guide plate of the backlight unit taken out from a ready-made liquid crystal display (SONY Co., Ltd., KD-55X8500B). Then, the light source of the backlight unit was turned on in the dark room, and the chromaticity variation of the light extracted from the light extraction surface of the glass light guide plate was measured.

  FIG. 2 is a diagram illustrating measurement points of chromaticity of the glass light guide plate according to the first embodiment. In FIG. 2, H is the horizontal dimension (1214 mm) of the glass plate 30, and V is the vertical dimension (689 mm) of the glass plate 30. The nine measurement points P1-1, P1-2, P1-3, P2-1, P2-2, P2-3, P3-1, P3-2, and P3-3 shown in FIG. Chromaticity coordinates x and y were measured. For the measurement, a two-dimensional color luminance meter CA-2000 manufactured by Konica Minolta Co., Ltd. was used.

[Example 2]
In Example 2, a glass light guide plate was produced in the same manner as in Example 1 except that a reflective tape was attached to the end surface facing the light incident surface among the four end surfaces of the glass plate, and variations in chromaticity were measured. As the reflective tape, a light-shielding polyester film adhesive tape (manufactured by Teraoka Seisakusho, product number: 6371 0.06 black and white HF) was used.

[Comparative Example 1]
In Comparative Example 1, a glass light guide plate was prepared and the chromaticity variation was measured in the same manner as in Example 1 except that a highly reflective white ink (product number: GLS-HF CLEAR) was used as the diffusion ink. did. This highly reflective white ink contained solid silica particles and a binder.

[Comparative Example 2]
In Comparative Example 2, a glass light guide plate was prepared and the chromaticity variation was measured in the same manner as in Comparative Example 1, except that a reflective tape was attached to the end surface facing the light incident surface among the four end surfaces of the glass plate. Note that the same reflective tape as in Example 2 was used.

[Evaluation results]
The evaluation results are shown in Tables 2 and 3.

  In Table 2, Δx is the chromaticity coordinate at nine measurement points P1-1, P1-2, P1-3, P2-1, P2-2, P2-3, P3-1, P3-2, and P3-3. The magnitude of the difference between the maximum value and the minimum value of x, Δy is nine measurement points P1-1, P1-2, P1-3, P2-1, P2-2, P2-3, P3-1, P3- 2 represents the magnitude of the difference between the maximum value and the minimum value of the chromaticity coordinates y in P3-3.

表２から明らかなように、実施例１および２では、ガラス板のガラスとして所定の高透過ガラスを用い、且つ、光散乱部として中空粒子を含むものを用いたので、色度のばらつきはいずれもΔｙ≦０．０３０と小さかった。一方、比較例１および２では、光散乱部として中実のシリカ粒子を含むものを用いたので、色度のばらつきがΔｙ≦０．０３０を満たさなかった。

As is clear from Table 2, in Examples 1 and 2, since a predetermined high-transmittance glass was used as the glass of the glass plate and a hollow particle was used as the light scattering portion, the chromaticity variation was Was also as small as Δy ≦ 0.030. On the other hand, in Comparative Examples 1 and 2, since a light scattering part containing solid silica particles was used, the chromaticity variation did not satisfy Δy ≦ 0.030.

表３は、測定点を縦方向に等間隔の９点、横方向に３点の計２７点として（図３参照）、色度座標ｙを取得し、入光面に最も近い位置Ｐ１１ではｙの最小値、それ以外の位置Ｐ１２〜Ｐ１９ではｙの最大値を示したものである。表３において、Δｙは、入光面に最も近い位置Ｐ１１におけるｙの最小値と、それ以外の各位置Ｐ１２〜Ｐ１９におけるｙの最大値との差の大きさをあらわす。そして上記した色度ばらつきとして好適な範囲、Δｙ≦０．０３０を基準として、これを満たす縦寸法を求めた。

Table 3 shows that the measurement points are 9 points equally spaced in the vertical direction and 3 points in the horizontal direction (see FIG. 3), and the chromaticity coordinates y are obtained, and at the position P11 closest to the light incident surface, y In other positions P12 to P19, the maximum value of y is shown. In Table 3, Δy represents the magnitude of the difference between the minimum value of y at the position P11 closest to the light incident surface and the maximum value of y at the other positions P12 to P19. Then, a vertical dimension satisfying the above-described range suitable for chromaticity variation, Δy ≦ 0.030, was obtained.

  As described above, the glass plate of the embodiment of the present invention is 55 inches in size. Comparative Examples 1 and 2 satisfy the standard if the vertical dimension is 482 mm or less, whereas Δy ≦ 0.030 is not satisfied when the vertical dimension exceeds 482 mm, whereas Examples 1 and 2 satisfy the standard at all measurement points. That is, it is shown that a glass plate having a longitudinal dimension of 482 mm can satisfy Δy ≦ 0.030 if the highly transmissive glass in the present invention is used.

[Test example]
An example in which the chromaticity of light emitted from the first main surface 35 of the glass plate 30 is analyzed by simulation will be described. For this simulation analysis, ray tracing software (Light Tools: manufactured by Cybernet System) was used.

  In this analysis, the size of the glass plate 30 is assumed to be 690 mm × 100 mm, and the plate thickness is assumed to be 2.1 mm. A plurality of LED light sources are arranged so as to face the side of 100 mm, and light is guided in the direction of the long side (side of 690 mm). In addition, a reflective sheet was disposed so as to face the second main surface 36 of the glass plate 30. A plurality of light scattering portions 40 are provided on the second main surface 36 so that light is emitted from the first main surface 35 with uniform luminance. By emitting a total of 10 million rays from the LED light source and tracking them, the distribution of chromaticity of the light emitted from the first main surface 35 was analyzed.

  The light scattering portion 40 contained 20 volume% solid particles or 20 volume% hollow particles. As solid particles, silica particles were assumed, the refractive index was 1.46, and the diameter was 2000 nm. As hollow particles, polymer particles having a core-shell structure were assumed, and the refractive index of the hollow portion was 1.00 and the diameter was 300 nm. In modeling hollow particles, since the shell portion has a refractive index approximately equal to that of the surrounding binder, there is no problem even if only the hollow portion is modeled. The refractive indexes of the glass plate 30 and the binder 42 were 1.52.

When the glass plate 30 is a high transmission glass that does not contain any of Fe ₂ O ₃ , NiO, Cr ₂ O ₃ , MnO ₂ , and TiO _2, and solid particles are used for the light scattering portion 40, the first main The difference between the maximum value and the minimum value of the chromaticity coordinate y of the light emitted from the surface is 0.0093, and the chromaticity coordinate y increases as the distance from the light incident surface 31 increases.

When glass plate 30 is made of a highly transmissive glass that does not contain any of Fe ₂ O ₃ , NiO, Cr ₂ O ₃ , MnO ₂ , and TiO ₂ and hollow particles are used for light scattering portion 40, the first main surface The difference between the maximum value and the minimum value of the chromaticity coordinate y of the light emitted from the light source is 0.0057, and the chromaticity coordinate y decreases as the distance from the light incident surface 31 increases.

As the glass plate 30, _Fe 2 _{O 3} 19 ppm by weight, NiO 0.19 mass ppm, _Cr 2 _{O 3} 0.22 wt ppm, MnO ₂ 0.10 mass ppm, a TiO ₂ 0.10 wt ppm When a high-transmission glass containing 18.4% of iron redox is set and hollow particles are used for the light scattering portion 40, the maximum and minimum chromaticity coordinates y of light emitted from the first main surface The difference from the value was 0.0007, and the chromaticity coordinate y was almost uniform over the surface.

As the glass plate 30, Fe ₂ O ₃ is 24 mass ppm, NiO is 0.19 mass ppm, Cr ₂ O ₃ is 0.22 mass ppm, MnO ₂ is 0.10 mass ppm, TiO ₂ is 0.10 mass ppm. When the high-transmission glass containing 14.6% of iron redox is set and hollow particles are used for the light scattering portion 40, the maximum and minimum chromaticity coordinates y of the light emitted from the first main surface The difference from the value was 0.0006, and the chromaticity coordinate y was almost uniform over the surface.

  From the above results, when solid particles are used for the light scattering part and high transmission glass that is not suitable for glass is used, the outgoing light shifts to yellow as it moves away from the light incident surface due to the wavelength dependence of scattering. I understand that. Further, the color unevenness in the surface is large and is not preferable.

  It can be seen that when hollow particles are used for the light scattering portion and high transmission glass that is not suitable for glass is used, the emitted light shifts to blue as it leaves the light incident surface due to the wavelength dependence of scattering. Further, the color unevenness in the surface is large and is not preferable.

  When hollow particles are used for the light scattering part and the high transmission glass of the present invention is used for the glass, the color change of the emitted light due to the wavelength dependence of the scattering is canceled by the absorption characteristics of the glass, There is almost no color unevenness and is preferable.

  As mentioned above, although embodiment of the light-guide plate etc. were described, this invention is not limited to the said embodiment etc., Various deformation | transformation and improvement are possible within the range of the summary of this invention described in the claim. is there.

  For example, the liquid crystal display device of the above embodiment is a transmissive type, but may be a reflective type, and the light guide plate 20 may be disposed in front of the liquid crystal panel 10 (user side). Light from the light source 50 enters inside from the end face of the light guide plate 20, exits from the main surface (rear face) of the light guide plate 20 facing the liquid crystal panel 10, and uniformly illuminates the liquid crystal panel 10 from the front.

  Moreover, although the light source of the said embodiment is white LED, a fluorescent tube may be sufficient. Moreover, the kind of white LED is not specifically limited, For example, you may make fluorescent substance light-emit using ultraviolet LED with a wavelength shorter than blue LED instead of blue LED. Further, instead of the phosphor-type white LED, a three-color LED-type white LED may be used.

DESCRIPTION OF SYMBOLS 10 Liquid crystal panel 20 Light guide plate 30 Glass plate 31 1st end surface (light-incidence surface)
32 2nd end surface 35 1st main surface (light extraction surface)
36 Second main surface (light scattering surface)
40 Light scattering part 41 Hollow particle 42 Binder 50 Light source

Claims (3)

A glass plate having an end face into which light is incident from a light source, a first main surface for taking out light incident on the end face, and a second main surface facing the first main surface;
A light guide plate comprising a plurality of light scattering parts containing hollow particles on the second main surface,
The glass plate is represented by mass percentage based on oxides, _Fe 2 _{O 3} 1 wt ppm~50 mass ppm, NiO 0.01 mass ppm~2.0 mass ppm, _Cr 2 _{O 3} 0.01 wt It is characterized by comprising a glass containing ppm to 2.0 mass ppm, MnO ₂ 0.01 mass ppm to 50 mass ppm, TiO ₂ 0.01 mass ppm to 1000 mass ppm, and iron redox being 25% or less. A light guide plate.   2. The light guide plate according to claim 1, wherein the glass plate is substantially rectangular in a plan view and has a length of 482 mm or more in a direction from an end surface on which light is incident toward an end surface facing the end surface.   The light guide plate according to claim 1, wherein the glass plate has a thickness of 0.3 to 10 mm.

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