| Clad glass composition and mother glass rod for gradient-index rod lens formed using the same, gradient-index rod lens and method of manufacturing the same, rod lens array, and image processor -> Monitor Keywords |
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  Clad glass composition and mother glass rod for gradient-index rod lens formed using the same, gradient-index rod lens and method of manufacturing the same, rod lens array, and image processorUSPTO Application #: 20060019815Title: Clad glass composition and mother glass rod for gradient-index rod lens formed using the same, gradient-index rod lens and method of manufacturing the same, rod lens array, and image processor Abstract: The present invention provides a clad glass composition that is excellent in devitrification resistance and that prevents the whole mother glass rod from devitrifying by preventing a core glass composition from devitrifying in forming a mother glass rod using a concentric crucible drawing method. The clad glass composition forms a clad of a mother glass rod for a gradient-index rod lens having a core/clad structure. The clad glass composition includes the following components, indicated by mol %: 45 to 65% SiO2; 0.5 to 10% TiO2; 0 to 15% B2O3; 0 to 7% Al2O3; 0.1 to 10% Bi2O3; 0 to 5% Li2O; 5 to 30% Na2O; 0 to 10% K2O; 0 to 15% MgO; 0 to 10% CaO; 0 to 10% SrO; 0.5 to 10% BaO; 0 to 10% Cs2O; 0 to 10% ZnO; 0 to 7% Y2O3; 0 to 7% Nb2O5; 0 to 7% In2O3; 0 to 7% La2O3; 0 to 10% Ta2O5; 0 to 7% ZrO2; and 0 to 1% Sb2O3, where the total of Li2O+Na2O+K2O is in the range of 5 to 35 mol %, the total of MgO+CaO+SrO+BaO is in the range of 2 to 20 mol %, the total of Li2O+Na2O+K2O+MgO+CaO+SrO+BaO is in the range of 7 to 50 mol %, and the total of Cs2O+ZnO+Y2O3+Nb2O5+In2O3+La2O3+ZrO2+Ta2O5 is in the range of 0 to 15 mol %. In the clad glass composition, at least two molar ratios selected from the group consisting of MgO/(MgO+CaO+SrO+BaO); CaO/(MgO+CaO+SrO+BaO); SrO/(MgO+CaO+SrO+BaO); and BaO/(MgO+CaO+SrO+BaO) are at least 0.1. The clad glass composition is substantially free from lead and has a refractive index in the range of 1.56 to 1.68. (end of abstract) Agent: Hamre, Schumann, Mueller & Larson, P.C. - Minneapolis, MN, US Inventors: Teruhide Inoue, Kunihiro Nomiyama, Koichi Sakaguchi USPTO Applicaton #: 20060019815 - Class: 501072000 (USPTO) Related Patent Categories: Compositions: Ceramic, Ceramic Compositions, Glass Compositions, Compositions Containing Glass Other Than Those Wherein Glass Is A Bonding Agent, Or Glass Batch Forming Compositions, Silica Containing, 40 Percent - 90 Percent By Weight Silica, And Divalent Metal Oxide (e.g., Oxides Of Zinc, Cadmium, Beryllium, Alkaline Earth Metal, Magnesium, Etc.) The Patent Description & Claims data below is from USPTO Patent Application 20060019815. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates generally to a glass composition (a clad glass composition) that forms a clad of a mother glass rod for gradient-index rod lens having a core/clad structure, and a mother glass rod for a gradient-index rod lens formed using the same. The present invention also relates to a gradient-index rod lens formed of the mother glass rod and a method of manufacturing the same as well as a rod lens array and an image processor that include the rod lens. [0003] 2. Related Background Art [0004] A gradient-index rod lens (hereinafter also referred to simply as a "rod lens") is a rod-shaped optical element having a refractive index distribution from its center to its periphery in the section thereof. The rod lens can exhibit lens functions such as, for instance, an imaging function even when both the end faces thereof are flat, and has many features including one that facilitates the production of lenses with minute diameters, for instance. Using such features, a rod lens array in which the rod lenses described above are arrayed is employed for a wide range of uses as an imaging lens in an optical system of an image processor (for example, an image-forming apparatus such as an LED array printer, a liquid crystal shutter printer, etc, or an image scanner such as a facsimile, a scanner, etc.). [0005] The gradient-index rod lens usually is formed by providing a mother glass rod for a gradient-index rod lens (hereinafter also referred to simply as a "mother glass rod") with a refractive index distribution. The mother glass rod is manufactured by a direct drawing method (a continuous drawing method) that has been used widely due to its excellent productivity. In the direct drawing method, as shown in FIG. 10, molten glass 101 that has been subjected to a degassing process (a fining process) as required is put into a crucible 103 that is kept warm with a heater 102. The molten glass 101 flows out of the lower end of a nozzle 104 located in a lower end portion of the crucible 103 while being cooled gradually inside the nozzle 104. Thereby a mother glass rod (a fiber) 105 with a diameter of about 0.1 mm to 4 mm can be formed continuously through hot drawing. In this method, the drawing speed (a formation speed) at which the mother glass rod 105 is drawn can be several tens of meters per minute while the crucible 103 can be charged with the molten glass continuously. Thus the productivity in manufacturing the mother glass rod can be increased. [0006] The direct drawing method, however, has a disadvantage that the molten glass 101 tends to devitrify when being cooled gradually inside the nozzle 104. Particularly, molten glass that is free from lead (whose typical composition is PbO) tends to devitrify when being drawn by the direct drawing method using a crucible. [0007] In order to prevent such devitrification from occurring during the drawing, for instance, JP8(1996)-13691A discloses a method in which additives such as BPO.sub.4, Al.sub.2(PO.sub.3).sub.3, etc. are added to molten glass. [0008] Furthermore, JP5(1993)-72337A discloses a method of forming a mother glass rod 118 having a structure (a core/clad structure) composed of a core 116 and a clad 117 covering the core 116 by the direct drawing method (a concentric crucible drawing method) using a concentric crucible 115 including an inner crucible 113 and an outer crucible 114 (see FIG. 11). The inner crucible 113 and the outer crucible 114 are charged with a core glass composition 111 that forms the core 116 and a clad glass composition 112 that forms a clad 117, respectively, with the core glass composition 111 and the clad glass composition 112 being in a molten state. The respective glass compositions are allowed to flow out from a nozzle 119 located in the lower end portion of the concentric crucible 115 to form the mother glass rod 118. The mother glass rod 118 thus formed can be drawn out continuously with rollers 120. In this case, when a glass composition that tends not to cause devitrification is employed as the clad glass composition 112, the core glass composition 111 can be prevented from coming into contact with the nozzle 119 even in the temperature region where devitrification tends to occur in the case of using the direct drawing method. Accordingly, the core glass composition 111 can be prevented from devitrifying and thus the whole mother glass rod 108 can be prevented from devitrifying during the drawing. [0009] JP2004-151682A discloses an example of the clad glass composition that tends not to cause devitrification, specifically: [0010] a clad glass composition of a mother glass rod for a gradient-index rod lens that is substantially free from PbO (unless containing both TiO.sub.2 and La.sub.2O.sub.3), [0011] wherein the clad glass composition is substantially free from PbO and substantially includes the following components, indicated by mol %: [0012] 45 to 65% SiO.sub.2; [0013] 3 to 30% Na.sub.2O; [0014] 0 to 10% K.sub.2O; [0015] 0 to 15% MgO; [0016] 0 to 20% BaO; [0017] 0 to 15% B.sub.2O.sub.3, [0018] 0 to 10% ZnO; [0019] 0 to 10% TiO.sub.2; [0020] 0 to 7% Y.sub.2O.sub.3; [0021] 0 to 7% ZrO.sub.2; [0022] 0 to 7% Nb.sub.2O.sub.5; [0023] 0 to 7% In.sub.2O.sub.3; [0024] 0 to 7% La.sub.2O.sub.3; and [0025] 0 to 10% Ta.sub.2O.sub.5, [0026] where the total of Na.sub.2O+K.sub.2O is in the range of 3 to 35 mol %, [0027] the total of MgO+BaO is in the range of 0 to 25 mol %, and [0028] the total of B.sub.2O.sub.3+ZnO+TiO.sub.2+Y.sub.- 2O.sub.3+ZrO.sub.2+Nb.sub.2O.sub.5+In.sub.2O.sub.3+La.sub.2O.sub.3+Ta.sub.- 2O.sub.5 is in the range of 0 to 20 mol %. SUMMARY OF THE INVENTION [0029] The present invention is intended to provide a clad glass composition that is different in composition from such a conventional clad glass composition but is excellent in devitrification resistance and prevents a core glass composition from devitrifying to make it possible to prevent a mother glass rod as a whole from devitrifying in forming the mother glass rod using the concentric crucible drawing method. [0030] The present invention also is intended to provide a mother glass rod, a rod lens, a rod lens array, and an image processor that are formed using the above-mentioned clad glass composition of the present invention, as well as a method of manufacturing the above-mentioned rod lens. [0031] The clad glass composition of the present invention forms a clad of a mother glass rod for a gradient-index rod lens having a core/clad structure, [0032] wherein the clad glass composition includes the following components, indicated by mol %: [0033] 45 to 65% SiO.sub.2; [0034] 0.5 to 10% TiO.sub.2; [0035] 0 to 15% B.sub.2O.sub.3; [0036] 0 to 7% Al.sub.2O.sub.3; [0037] 0.1 to 10% Bi.sub.2O.sub.3; [0038] 0 to 5% Li.sub.2O; [0039] 5 to 30% Na.sub.2O; [0040] 0 to 10% K.sub.2O; [0041] 0 to 15% MgO; [0042] 0 to 10% CaO; [0043] 0 to 10% SrO; [0044] 0.5 to 10% BaO; [0045] 0 to 10% Cs.sub.2O; [0046] 0 to 10% ZnO; [0047] 0 to 7% Y.sub.2O.sub.3; [0048] 0 to 7% Nb.sub.2O.sub.5; [0049] 0 to 7% In.sub.2O.sub.3; [0050] 0 to 7% La.sub.2O.sub.3; [0051] 0 to 10% Ta.sub.2O.sub.5; [0052] 0 to 7% ZrO.sub.2; and [0053] 0 to 1% Sb.sub.2O.sub.3, [0054] where the total of Li.sub.2O+Na.sub.2O+K.sub.2O is in the range of 5 to 35 mol %, [0055] the total of MgO+CaO+SrO+BaO is in the range of 2 to 20 mol %, [0056] the total of Li.sub.2O+Na.sub.2O+K.sub.2O+MgO+CaO+SrO+BaO is in the range of 7 to 50 mol %, and [0057] the total of CS.sub.2O+ZnO+Y.sub.2O.sub.3+Nb.sub.2O.su- b.5+In.sub.2O.sub.3+La.sub.2O.sub.3+ZrO.sub.2+Ta.sub.2O.sub.5 is in the range of 0 to 15 mol %, [0058] at least two molar ratios selected from the group consisting of: [0059] MgO/(MgO+CaO+SrO+BaO); [0060] CaO/(MgO+CaO+SrO+BaO); [0061] SrO/(MgO+CaO+SrO+BaO); and [0062] BaO/(MgO+CaO+SrO+BaO) [0063] are at least 0.1, and [0064] the clad glass composition is substantially free from lead and has a refractive index in the range of 1.56 to 1.68. [0065] The mother glass rod for a gradient index rod lens of the present invention has a core/clad structure, [0066] wherein a clad glass composition that forms a clad is the above-mentioned clad glass composition of the present invention, and [0067] a core glass composition that forms a core has a different composition from the clad glass composition. [0068] The mother glass rod for a gradient-index rod lens of the present invention has a core/clad structure, [0069] wherein a clad glass composition that forms a clad is the above-mentioned clad glass composition of the present invention, [0070] a core glass composition that forms a core includes the following components, indicated by mol %: [0071] 40 to 65% SiO.sub.2; [0072] 1 to 10% TiO.sub.2; [0073] 0 to 20% B.sub.2O.sub.3; [0074] 0 to 10% Al.sub.2O.sub.3; [0075] 5 to 12% Li.sub.2O; [0076] 5 to 15% Na.sub.2O; [0077] 0 to 16% MgO; [0078] 0 to 15% CaO; [0079] 0.1 to 12% SrO; [0080] 0.1 to 12% BaO; [0081] 0 to 3% Cs.sub.2O; [0082] 0 to 8% ZnO; [0083] 0 to 5% Y.sub.2O.sub.3; [0084] 0 to 5% Nb.sub.2O.sub.5; [0085] 0 to 5% In.sub.2O.sub.3; [0086] 0 to 5% La.sub.2O.sub.3; [0087] 0 to 5% Ta.sub.2O.sub.5; [0088] 0 to 1% SnO.sub.2; [0089] 0 to 1% Sb.sub.2O.sub.3; and [0090] 0 to 1% As.sub.2O.sub.3, [0091] where the total of SiO.sub.2+TiO.sub.2+B.sub.2O.- sub.3+Al.sub.2O.sub.3 is in the range of 50 to 70 mol %, [0092] the total of Li.sub.2O+Na.sub.2O is in the range of 10 to 27 mol %, [0093] the molar ratio of Li.sub.2O/Na.sub.2O is in the range of 0.7 to 2, and [0094] the total of MgO+CaO+SrO+BaO is in the range of 5 to 36 mol %, [0095] at least two values selected from the contents by percentage of CaO, SrO, and BaO are in the range of 0.1 to 15 mol %, [0096] at least two molar ratios selected from the group consisting of: [0097] MgO (MgO+CaO+SrO+BaO); [0098] CaO/(MgO+CaO+SrO+BaO); [0099] SrO/(MgO+CaO+SrO+BaO); and [0100] BaO/(MgO+CaO+SrO+BaO) [0101] are at least 0.1, and [0102] the core glass composition is substantially free from lead. [0103] The gradient-index rod lens of the present invention is a rod lens obtained by providing the above-mentioned mother glass rod for a gradient-index rod lens of the present invention with a refractive index distribution by an ion exchange method. [0104] The rod lens array of the present invention includes at least two gradient-index rod lenses according to the present invention, wherein the rod lenses are arrayed and formed into one body, with their optical axes being substantially in parallel with each other. [0105] The image processor of the present invention includes the above-mentioned rod lens array of the present invention, wherein the rod lens array serves as an imaging optical system. [0106] The method of manufacturing a gradient-index rod lens of the present invention includes: charging a crucible (an outer crucible) located on the outer side of a concentric crucible with a melt of a clad glass composition (a clad glass composition that is in a molten state, i.e. a molten clad glass composition) having a composition (A); charging a crucible (an inner crucible) located on the inner side of the concentric crucible with a melt of a core glass composition (a core glass composition that is in a molten state, i.e. a molten core glass composition) having a composition (B); forming a mother glass rod for a gradient-index rod lens having a core/clad structure by a concentric crucible drawing method; and providing the mother glass rod with a refractive index distribution by an ion exchange method in which the mother glass rod formed above is immersed in molten salt containing sodium, [0107] wherein the clad glass composition having the composition (A) includes the following components, indicated by mol %: [0108] 45 to 65% SiO.sub.2; [0109] 0.5 to 10% TiO.sub.2; [0110] 0 to 15% B.sub.2O.sub.3; [0111] 0 to 7% Al.sub.2O.sub.3; [0112] 0.1 to 10% Bi.sub.2O.sub.3; [0113] 0 to 5% Li.sub.2O; [0114] 5 to 30% Na.sub.2O; [0115] 0 to 10% K.sub.2O; [0116] 0 to 15% MgO; [0117] 0 to 10% CaO; [0118] 0 to 10% SrO; [0119] 0.5 to 10% BaO; [0120] 0 to 10% Cs.sub.2O; [0121] 0 to 10% ZnO; [0122] 0 to 7% Y.sub.2O.sub.3; [0123] 0 to 7% Nb.sub.2O.sub.5; [0124] 0 to 7% In.sub.2O.sub.3; [0125] 0 to 7% La.sub.2O.sub.3; [0126] 0 to 10% Ta.sub.2O.sub.5; [0127] 0 to 7% ZrO.sub.2; and [0128] 0 to 1% Sb.sub.2O.sub.3, [0129] where the total of Li.sub.2O+Na.sub.2O+K.sub.2O is in the range of 5 to 35 mol %, [0130] the total of MgO+CaO+SrO+BaO is in the range of 2 to 20 mol %, [0131] the total of Li.sub.2O+Na.sub.2O+K.sub.2O+MgO+CaO+SrO+BaO is in the range of 7 to 50 mol %, and [0132] the total of Cs.sub.2O+ZnO+Y.sub.2O.sub.3+N- b.sub.2O.sub.5+In.sub.2O.sub.3+La.sub.2O.sub.3+ZrO.sub.2+Ta.sub.2O.sub.5 is in the range of 0 to 15 mol %, [0133] at least two molar ratios selected from the group consisting of: [0134] MgO/(MgO+CaO+SrO+BaO); [0135] CaO/(MgO+CaO+SrO+BaO); [0136] SrO/(MgO+CaO+SrO+BaO); and [0137] BaO/(MgO+CaO+SrO+BaO) [0138] are at least 0.1, and [0139] the clad glass composition is substantially free from lead and has a refractive index in the range of 1.56 to 1.68, and [0140] wherein the core glass composition having the composition (B) includes the following components, indicated by mol %: [0141] 40 to 65% SiO.sub.2; [0142] 1 to 10% TiO.sub.2; [0143] 0 to 20% B.sub.2O.sub.3; [0144] 0 to 10% Al.sub.2O.sub.3; [0145] 5 to 12% Li.sub.2O; [0146] 5 to 15% Na.sub.2O; [0147] 0 to 16% MgO; [0148] 0 to 15% CaO; [0149] 0.1 to 12% SrO; [0150] 0.1 to 12% BaO; [0151] 0 to 3% Cs.sub.2O; [0152] 0 to 8% ZnO; [0153] 0 to 5% Y.sub.2O.sub.3; [0154] 0 to 5% Nb.sub.2O.sub.5; [0155] 0 to 5% In.sub.2O.sub.3; [0156] 0 to 5% La.sub.2O.sub.3; [0157] 0 to 5% Ta.sub.2O.sub.5; [0158] 0 to 1% SnO.sub.2; [0159] 0 to 1% Sb.sub.2O.sub.3; and [0160] 0 to 1% As.sub.2O.sub.3, [0161] where the total of SiO.sub.2+TiO.sub.2+B.sub.2O.sub.3+Al.sub.2O.sub.3 is in the range of 50 to 70 mol %, [0162] the total of Li.sub.2O+Na.sub.2O is in the range of 10 to 27 mol %, [0163] the molar ratio of Li.sub.2O/Na.sub.2O is in the range of 0.7 to 2, and [0164] the total of MgO+CaO+SrO+BaO is in the range of 5 to 36 mol %, [0165] at least two values selected from the contents by percentage of CaO, SrO, and BaO are in the range of 0.1 to 15 mol %, [0166] at least two molar ratios selected from the group consisting of: [0167] MgO/(MgO+CaO+SrO+BaO); [0168] CaO/(MgO+CaO+SrO+BaO); [0169] SrO/(MgO+CaO+SrO+BaO); and [0170] BaO/(MgO+CaO+SrO+BaO) [0171] are at least 0.1, and [0172] the core glass composition is substantially free from lead. BRIEF DESCRIPTION OF THE DRAWINGS [0173] FIG. 1A is a schematic view showing an example of the mother glass rod according to the present invention while FIG. 1B is a cross-sectional view showing a section of the mother glass rod shown in FIG. 1A cut at a plane perpendicular to the direction of the optical axis thereof. [0174] FIG. 2 is a diagram that schematically shows an example of the refractive index profile of the mother glass rod according to the present invention. [0175] FIG. 3 is a partial cross-sectional view to be used for explaining an example of the concentric crucible drawing method for forming the mother glass rod of the present invention. Continue reading... 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