Vehicle front glass

Abstract

The present invention aims to provide a vehicular windshield having a laminated glass structure in which an interlayer film for laminated glass is interposed between at least a pair of glass plates, which contains few air bubbles remaining between the glass plates and the interlayer film for laminated glass to have an excellent appearance and is less likely to cause ghosting when external rays of light are seen through the vehicular windshield.

Claims

1. A vehicular windshield comprising at least a pair of glass plates and an interlayer film for laminated glass interposed between the pair of glass plates, the interlayer film for laminated glass including a laminate of a sound insulation layer interposed between two protective layers, the sound insulation layer containing 45 to 80 parts by mass of a plasticizer based on 100 parts by mass of polyvinyl acetal, the protective layers each containing 20 to 45 parts by mass of a plasticizer based on 100 parts by mass of polyvinyl acetal, both of the protective layers having recesses and projections on a surface, the recesses having a groove shape with a continuous bottom and being regularly arranged adjacently in parallel with one another, the groove shape with a continuous bottom of the recesses on the surface of both of the protective layers being arranged in a direction that forms an angle of 30 or less relative to a perpendicular direction of the vehicular windshield, and the groove shape with a continuous bottom of the recesses on the surface of both of the protective layers being arranged in a direction that forms an intersection angle of 20 or less with respect to each other.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a schematic view illustrating an example of an interlayer film for laminated glass in which recesses having a groove shape with a continuous bottom are arranged at equal intervals and adjacently in parallel with one another on a surface.

(2) FIG. 2 is a schematic view illustrating an example of an interlayer film for laminated glass in which recesses having a groove shape with a continuous bottom are arranged at equal intervals and adjacently in parallel with one another on a surface.

(3) FIG. 3 is a schematic view illustrating an example of an interlayer film for laminated glass in which recesses having a groove shape with a continuous bottom are arranged at unequal intervals and adjacently in parallel with one another on a surface.

(4) FIG. 4 is a schematic view for explaining the angle formed between the perpendicular direction of the vehicular windshield and the direction of the recesses in the shape of engraved lines on the surface of the interlayer film for laminated glass.

DESCRIPTION OF EMBODIMENTS

(5) Embodiments of the present invention are more specifically described in the following with reference to, but not limited to, examples.

EXAMPLE 1

(6) (1) Preparation of Resin Composition for Sound Insulation Layer

(7) Polyvinyl butyral (acetyl group content of 12 mol %, butyral group content of 66 mol %, hydroxy group content of 22 mol %) was prepared by acetalization of polyvinyl alcohol having an average degree of polymerization of 2400 with n-butyraldehyde. An amount of 100 parts by mass of the obtained polyvinyl butyral was blended with 60 parts by mass of triethylene glycol-di-2-ethylhexanoate (3GO) as a plasticizer and sufficiently kneaded with a mixing roll to give a resin composition for a sound insulation layer.

(8) (2) Preparation of Resin Composition for Protective Layer

(9) Polyvinyl butyral (acetyl group content of 1 mol %, butyral group content of 69 mol %, hydroxy group content of 30 mol %) was prepared by acetalization of polyvinyl alcohol having an average degree of polymerization of 1700 with n-butyraldehyde. An amount of 100 parts by mass of the obtained polyvinyl butyral was blended with 40 parts by mass of triethylene glycol-di-2-ethylhexanoate (3GO) as a plasticizer and sufficiently kneaded with a mixing roll to give a resin composition for a protective layer.

(10) (3) Production of Interlayer Film for Laminated Glass

(11) The obtained resin composition for a sound insulation layer and the resin composition for a protective layer were co-extruded from a co-extruder to produce an interlayer film (sound-insulating interlayer film) for laminated glass having a triple layer structure in which an layer A (protective layer) formed of the resin composition for a protective layer with a thickness of 350 m, a layer B (sound insulation layer) formed of the resin composition for a sound insulation layer with a thickness of 100 m, and a layer C (protective layer) formed of the resin composition for a protective layer with a thickness of 350 m are laminated in said order.

(12) (4) Impartment of Projections and Recesses

(13) In the first step, a pattern of projections and recesses was randomly transferred to both surfaces of the interlayer film for laminated glass by the following process. First, random projections and recesses were formed on iron roll surfaces with an abrasive material, and the iron rolls were subjected to vertical grinding. Finer projections and recesses were further formed on planar portions after the grinding with a finer abrasive material. In this manner, a pair of rolls in the same shape having a coarse main embossed pattern and a fine sub-embossed pattern were obtained. The pair of rolls were used as a device for transferring a pattern of projections and recesses to transfer a random pattern of projections and recesses to both faces of the obtained interlayer film for laminated glass. The transferring conditions employed here were a temperature of the interlayer film for laminated glass of 80 C., a temperature of the rolls of 145 C., a linear velocity of 10 m/min, and a linear pressure of 10 to 200 kN/m. The shaped interlayer film for laminated glass had a surface roughness measured based on the ten-point average roughness Rz in accordance with JIS B 0601 (1994) of 20 m. The surface roughness was determined by processing data of a digital signal measured with a surface roughness measuring device (produced by Kosaka Laboratory Ltd., SE1700). The measurement direction was perpendicular to the engraved lines. Measurement was performed under the conditions of a cut-off value of 2.5 mm, a standard length of 2.5 mm, an evaluation length of 12.5 mm, a tip radius of a probe of 2 m, a tip angle of 60, and a measurement speed of 0.5 mm/s.

(14) In the second step, projections and recesses having a groove shape with a continuous bottom (shape of an engraved line) were imparted to a surface of the interlayer film for laminated glass by the following process.

(15) A pair of rolls including a metal roll having a surface milled with a triangular oblique line-type mill (produced by YURIROLL Co., Ltd.) and a rubber roll having a JIS hardness of 45 to 75 was used as a device for transferring a pattern of projections and recesses. The obtained interlayer film for laminated glass to which the random pattern of projections and recesses was transferred in the first step was passed through the device for transferring a pattern of projections and recesses, whereby projections and recesses in which recesses having a groove shape with a continuous bottom (shape of an engraved line) were arranged in parallel with one another at equal intervals were imparted to the surface of the layer A of the interlayer film for laminated glass. The transferring was performed under the conditions of a temperature of the interlayer film for laminated glass of ambient temperature, a roll temperature of 130 C., a linear velocity of 10 m/min, a film width of 1.5 m, and a pressure of 500 kPa.

(16) Subsequently, the similar treatment was performed to impart recesses having a groove shape with a continuous bottom (shape of an engraved line) to the surface of the layer C of the interlayer film for laminated glass, except that the shape of the projections and recesses on a metal roll used was different.

(17) The surfaces (observation range of 20 mm20 mm) of the layer A and the layer C of the obtained interlayer film for the laminated glass were observed with an optical microscope (produced by SONIC, BS-8000III) to measure the interval between adjacent recesses. The average value of the shortest distance between the deepest bottoms of adjacent recesses was taken as the interval between recesses. The interval between the recesses on the layer A was 750 m. The interval between the recesses on the layer C was 500 m. The average value and the maximum value of the shortest distances were the same on each layer.

(18) The groove depth (Rzg) of the recesses on the surfaces of the layer A and the layer C of the obtained interlayer film for laminated glass was the average value of the groove depths for the standard length measured at five points. The groove depths were calculated based on the average line (a line that is set such that the sum of the squares of the deviations from that line to the roughness curve be minimized) of a roughness curve, as specified in JIS B-0601 (1994) Surface roughness-Definition and designation with the standard length set to 2.5 mm. The average of the groove depths of the number of the measured grooves was taken as the groove depth for the standard length. The number of grooves of the layer A was 4 and the number of grooves of the layer C was 5. The groove depth (Rzg) of the recesses on each of the surfaces of the layer A and the layer C was determined by processing data of a digital signal measured with a surface roughness measuring device (produced by Kosaka Laboratory Ltd., SE1700). The measurement direction was perpendicular to the engraved line. Measurement was performed under the conditions of a tip radius of a probe of 2 m, a tip angle of 60, and a measurement speed of 0.5 mm/s. The groove depth (Rzg) of the recesses on the surface of the layer A was 22 m. The groove depth (Rzg) of the recesses on the surface of the layer C was 18 m.

(19) (5) Preparation of Vehicular Windshield

(20) A vehicular windshield was produced by preliminarily pressure-bonding the obtained interlayer film for laminated glass having projections and recesses on the surface by vacuum deaeration, followed by full pressure-bonding thereof, as described below.

(21) (Direction Adjustment of Interlayer Film for Laminated Glass)

(22) The interlayer film was interposed between two clear glass plates for vehicular windshield (in the shape as illustrated in FIG. 4, 2.5 mm in thickness). The portions of the film protruding from the plates were cut off. A laminated glass component was thus prepared.

(23) At this time, the interlayer film for laminated glass was arranged in such a manner that the direction of the recesses in the shape of engraved lines on the surface of the layer A forms an angle of 0 relative to the perpendicular direction of the vehicular windshield and the direction of the recesses in the shape of engraved lines on the surface of the layer C forms an angle of 10 relative to the perpendicular direction of the vehicular windshield.

(24) (Vacuum Deaeration Method)

(25) The obtained laminated glass component was placed into a rubber bag, which was connected to a vacuum suction device. The rubber bag was held under a reduced pressure of 60 kPa (absolute pressure of 16 kPa) for 10 minutes with heating so that the temperature (preliminary pressure-bonding temperature) of the laminated glass component reached 70 C. Thereafter, the pressure was returned to atmospheric pressure, whereby the preliminary pressure-bonding was completed. The preliminary pressure-bonding was performed under three different conditions of the deaeration starting temperature of 40 C., 50 C., and 60 C.

(26) (Full Pressure-bonding)

(27) The laminated glass component preliminarily pressure-bonded by the above method was placed in an autoclave and held under the conditions of a temperature of 140 C. and a pressure of 1300 kPa for 10 minutes. Thereafter, the temperature was lowered to 50 C. and the pressure was returned to atmospheric pressure, whereby the full pressure-bonding was completed. In this manner, a vehicular windshield was produced.

EXAMPLES 2 to 11

(28) Interlayer films for laminated glass were produced in the same manner as in Example 1, except that the kind of the triangular oblique line-type mill used in impartment of projections and recesses was changed and that the interval and the groove depth (Rzg) of the recesses on the surface of the layer A and the layer C were changed as shown in Table 1.

(29) Vehicular windshields were produced in the same manner as in Example 1, except that the interlayer film for laminated glass was arranged in production of the vehicular windshield in such a manner that the direction of the recesses in the shape of engraved lines formed an angle as shown in Table 1 relative to the perpendicular direction of the vehicular windshield.

EXAMPLES 12 to 15

(30) Interlayer films for laminated glass were produced in the same manner as in Example 1, except that the acetyl group content, the butyral group content, and the hydroxy group content of the polyvinyl butyral used for the protective layer and the sound insulation layer and the plasticizer content were changed as shown in Table 1 and that the kind of the triangular oblique line-type mill used in impartment of projections and recesses was changed, and that the interval and the groove depth (Rzg) of the recesses on the surface of the layer A and the layer C were changed as shown in Table 1. The polyvinyl butyral used for the protective layer and the sound insulation layer was obtained by acetalization of polyvinyl alcohol having an average degree of polymerization of 1700 with n-butyraldehyde.

(31) Vehicular windshields were produced in the same manner as in Example 1, except that the direction of the recesses in the shape of engraved lines on the surface of the obtained interlayer film for laminated glass was set to form an angle as shown in Table 1 relative to the perpendicular direction of the vehicular windshield.

COMPARATIVE EXAMPLES 1 to 4

(32) Interlayer films for laminated glass were produced in the same manner as in Example 1, except that the kind of the triangular oblique line-type mill used in impartment of projections and recesses was changed and that the interval and the groove depth (Rzg) of the recesses on the surface of the layer A and the layer C were changed as shown in Table 2.

(33) Vehicular windshields were produced in the same manner as in Example 1, except that the direction of the recesses in the shape of engraved lines on the surface of the obtained interlayer film for laminated glass was set to form an angle as shown in Table 2 relative to the perpendicular direction of the vehicular windshield.

(34) (Evaluation)

(35) The vehicular windshields obtained in the examples and comparative examples were evaluated as follows.

(36) Tables 1 and 2 show the results. In the tables, the Bu degree means the butyral group content, the OH degree means the hydroxy group content, the Ac degree means the acetyl group content, and Plasticizer (parts) means the plasticizer content based on 100 parts by mass of polyvinyl butyral.

(37) (1) Evaluation on Appearance

(38) The obtained vehicular windshield was heated in an oven at 140 C. for two hours. Thereafter, the vehicular windshield was taken out of the oven and allowed to stand to cool for three hours. The appearance of the cooled vehicular windshield was visually observed. Twenty vehicular windshields were tested, and the number of vehicular windshields in which foam (air bubbles) was generated between the glass plate and the interlayer film for laminated glass was determined. When the number of the vehicular windshields with bubbles was 5 or less under all conditions, it was evaluated O (good). When the number of the vehicular windshields with bubbles was 6 or more under all conditions, it was evaluated as (poor).

(39) (2) Evaluation on Ghosting

(40) The light source was a 10 W silica bulb (produced by Kyokko Electric Co., Ltd., PS55 E 26 110V-10 W, total flux of 70 lm) to simulate a light source having a general intensity which can be incident on windowpanes of automobiles, aircraft, buildings or the like. Evaluation on ghosting on the obtained vehicular windshield was performed by a method in conformity with JIS R 3212 (2008). An image with a separation of more than 6.5 minutes of arc was regarded to be a ghost image. An image with a separation of 6.5 minutes of arc or less was regarded to be a single image. When a single image with a separation of 3.5 minutes of arc or less was observed, it was evaluated as OO (excellent). When a single image with a separation of more than 3.5 minutes of arc but not more than 6.5 minutes of arc was observed, it was evaluated as O (good). When a ghost image was observed, it was evaluated as (poor).

(41) The mounting angle to the actual vehicle was set to 20.

(42) TABLE-US-00001 TABLE 1 Exam- Exam- Exam- Exam- Exam- ple 1 ple 2 ple 3 ple 4 ple 5 Formulation Composition of Bu degree (mol %) 69 69 69 69 69 protective layer OH degree (mol %) 30 30 30 30 30 Ac degree (mol %) 1 1 1 1 1 Pasticizer (parts) 40 40 40 40 40 (phr) Composition of Bu degree (mol %) 66 66 66 66 66 sound insulation OH degree (mol %) 22 22 22 22 22 layer Ac degree (mol %) 12 12 12 12 12 Plasticizer (parts) 60 60 60 60 60 (phr) Projections Interval of recesses (m) 750 750 750 750 750 and recesses Groove depth (Rzg) of recesses (m) 30 24 22 20 40 on surface of Angle of direction of recesses in the 0 20 0 5 0 layer A shape of engraved lines () Projections Interval of recesses (m) 500 500 500 500 500 and recesses Groove depth (Rzg) of recesses (m) 24 19 19 17 37 on surface of Angle of direction of recesses in the 10 30 30 15 10 layer C shape of engraved lines () Evaluation on Deaeration starting temperature/ C. 40 50 60 40 50 60 40 50 60 40 50 60 40 50 60 deaeration Preliminary pressure-bonding completion 70 70 70 70 70 70 70 70 70 70 70 70 70 70 70 properties temperature/ C. Baking test 0 0 1 0 1 1 0 0 1 0 1 1 0 0 0 (Number of vehicular windshields with bubbles/20 vehicular windshields) Evaluation on ghosting Exam- Exam- Exam- Exam- Exam- ple 6 ple 7 ple 8 ple 9 ple 10 Formulation Composition of Bu degree (mol %) 69 69 69 69 69 protective layer OH degree (mol %) 30 30 30 30 30 Ac degree (mol %) 1 1 1 1 1 Pasticizer (parts) 40 40 40 40 40 (phr) Composition of Bu degree (mol %) 66 66 66 66 66 sound insulation OH degree (mol %) 22 22 22 22 22 layer Ac degree (mol %) 12 12 12 12 12 Plasticizer (parts) 60 60 60 60 60 (phr) Projections Interval of recesses (m) 750 400 400 300 300 and recesses Groove depth (Rzg) of recesses (m) 12 16 18 18 23 on surface of Angle of direction of recesses in the 0 0 20 5 10 layer A shape of engraved lines () Projections Interval of recesses (m) 500 400 400 400 400 and recesses Groove depth (Rzg) of recesses (m) 10 21 15 23 15 on surface of Angle of direction of recesses in the 10 10 20 10 20 layer C shape of engraved lines () Evaluation on Deaeration starting temperature/ C. 40 50 60 40 50 60 40 50 60 40 50 60 40 50 60 deaeration Preliminary pressure-bonding completion 70 70 70 70 70 70 70 70 70 70 70 70 70 70 70 properties temperature/ C. Baking test 0 1 2 0 0 1 1 1 1 0 1 1 0 1 1 (Number of vehicular windshields with bubbles/20 vehicular windshields) Evaluation on ghosting

(43) TABLE-US-00002 TABLE 2 Exam- Exam- Exam- Exam- Exam- ple 11 ple 12 ple 13 ple 14 ple 15 Formulation Composition of Bu degree (mol %) 69 69 68.5 69 69.9 protective layer OH degree (mol %) 30 30 31 30.5 29 Ac degree (mol %) 1 1 0.5 0.5 1.1 Plasticizer (parts) 40 36 36 37.5 39 (phr) Composition of Bu degree (mol %) 66 65.5 67 71 78 sound insulation OH degree (mol %) 22 24.5 25 23 20.5 layer Ac degree (mol %) 12 10 8 6 1.5 Plasticizer (parts) 60 75 75 76 77 (phr) Projections Interval of recesses (m) 190 750 750 750 750 and recesses Groove depth (Rzg) of recesses (m) 15 30 12 12 12 on surface Angle of direction of recesses in the 20 0 0 0 0 of layer A shape of engraved lines () Projections Interval of recesses (m) 195 500 500 500 500 and recesses Groove depth (Rzg) of recesses (m) 15 24 10 10 10 on surface Angle of direction of recesses in the 10 10 10 10 10 of layer C shape of engraved lines () Evaluation on Deaeration starting temperature/ C. 40 50 60 40 50 60 40 50 60 40 50 60 40 50 60 deaeration Preliminary pressure-bonding completion 70 70 70 70 70 70 70 70 70 70 70 70 70 70 70 properties temperature/ C. Baking test 0 0 0 0 0 1 0 0 1 0 0 1 0 0 1 (Number of vehicular windshields with bubbles/20 vehiclar windshields) Evaluation on ghosting Compar- Compar- Compar- Compar- ative ative ative ative Exam- Exam- Exam- Exam- ple 1 ple 2 ple 3 ple 4 Formulation Composition of Bu degree (mol %) 69 69 69 69 protective layer OH degree (mol %) 30 30 30 30 Ac degree (mol %) 1 1 1 1 Plasticizer (parts) 40 40 40 40 (phr) Composition of Bu degree (mol %) 66 66 66 66 sound insulation OH degree (mol %) 22 22 22 22 layer Ac degree (mol %) 12 12 12 12 Plasticizer (parts) 60 60 60 60 (phr) Projections Interval of recesses (m) 750 750 750 750 and recesses Groove depth (Rzg) of recesses (m) 28 22 9 9 on surface Angle of direction of recesses in the 30 80 0 0 of layer A shape of engraved lines () Projections Interval of recesses (m) 500 500 500 500 and recesses Groove depth (Rzg) of recesses (m) 25 17 7 7 on surface Angle of direction of recesses in the 40 90 10 10 of layer C shape of engraved lines () Evaluation on Deaeration starting temperature/ C. 40 50 60 40 50 60 40 50 60 40 50 60 deaeration Preliminary pressure-bonding completion 70 70 70 70 70 70 70 70 70 70 70 70 properties temperature/ C. Baking test 0 0 1 0 0 1 6 7 9 6 7 9 (Number of vehicular windshields with bubbles/20 vehiclar windshields ) x x Evaluation on ghosting x x

INDUSTRIAL APPLICABILITY

(44) The present invention can provide a vehicular windshield having a laminated glass structure in which an interlayer film for laminated glass is interposed between at least a pair of glass plates, which contains few air bubbles remaining between the glass plates and the interlayer film for laminated glass to have an excellent appearance and is less likely to cause ghosting when external rays of light are seen through the vehicular windshield.

REFERENCE SIGNS LIST

(45) 1. Arbitrarily selected recess

(46) 2. Recess adjacent to the arbitrarily selected recess

(47) 3. Recess adjacent to the arbitrarily selected recess

(48) A. Interval between recess 1 and recess 2

(49) B. Interval between recess 1 and recess 3

(50) 11. Vehicular windshield

(51) 21. Perpendicular direction of vehicular windshield

(52) 31. Recess having a groove shape with a continuous bottom (shape of engraved line) on surface of interlayer film for laminated glass

(53) C. Angle between perpendicular direction of vehicular windshield and direction of recess in the shape of engraved line

(54) D. Mounting angle of vehicular windshield