Patent Publication Number: US-11642872-B2

Title: Intermediate film for laminated glass, roll body, and laminated glass

Description:
TECHNICAL FIELD 
     The present invention relates to an interlayer film for laminated glass which is used for obtaining laminated glass. Moreover, the present invention relates to a roll body and laminated glass both of which are prepared with the interlayer film for laminated glass. 
     BACKGROUND 
     Since laminated glass generally generates only a small amount of scattering glass fragments even when subjected to external impact and broken, laminated glass is excellent in safety. As such, the laminated glass is widely used for automobiles, railway vehicles, aircraft, ships, buildings and the like. The laminated glass is produced by sandwiching an interlayer film for laminated glass between a pair of glass plates. 
     Moreover, as the laminated glass used for automobiles, a head-up display (HUD) has been known. In the HUD, on the windshield of an automobile, measured information such as the speed which is traveling data of the automobile and the like can be displayed. 
     In the HUD, there is a problem that the measured information displayed on the windshield is doubly observed. 
     In order to suppress double images, a wedge-shaped interlayer film has been used. The following Patent Document 1 discloses a sheet of laminated glass in which a wedge-shaped interlayer film having a prescribed wedge angle is sandwiched between a pair of glass plates. In such a sheet of laminated glass, by the adjustment of the wedge angle of the interlayer film, a display of measured information reflected by one glass plate and a display of measured information reflected by the other glass plate can be focused into one point to make an image in the visual field of a driver. For that reason, the display of measured information is hard to be observed doubly and the visibility of a driver is hardly hindered. 
     RELATED ART DOCUMENT 
     Patent Document 
     
         
         Patent Document 1: JP H4-502525 T 
       
    
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     In conventional interlayer films, it is difficult to sufficiently suppress double images. Investigation carried out by the present inventors led to the finding that only controlling a wedge angle from one end to the other end cannot sufficiently suppress double images. It was found that there is variation in double images in laminated glass particularly in the direction perpendicular to the direction connecting one end and the other end of the interlayer film, and double images cannot be sufficiently suppressed. 
     It is an object of the present invention to provide an interlayer film for laminated glass capable of reducing the variation in double images in laminated glass in the direction perpendicular to the direction connecting one end and the other end of the interlayer film, and effectively suppressing double images. It is also an object of the present invention to provide a roll body and laminated glass prepared with the aforementioned interlayer film for laminated glass. 
     Means for Solving the Problems 
     According to a broad aspect of the present invention, there is provided an interlayer film for laminated glass (in this description, “interlayer film for laminated glass” is sometimes abbreviated as “interlayer film”) for use in laminated glass, the interlayer film for laminated glass having one end and the other end being at the opposite side of the one end, the other end having a thickness of larger than a thickness of the one end, the interlayer film for laminated glass as a whole having a wedge angle of 0.1 mrad or more, the interlayer film for laminated glass having a thickness varying region in a region extending in the direction perpendicular to the direction connecting the one end and the other end of the interlayer film, the thickness varying region having a standard deviation of 11 partial wedge angles measured by the following measuring method of 0.040 mrad or less. 
     Method for measuring 11 partial wedge angles: 11 points are selected at 10 cm intervals in the direction perpendicular to the direction connecting the one end and the other end of the interlayer film. At each of the 11 points, a partial wedge angle is measured in the region extending from the position of 6 cm on the one end side from the center between the one end and the other end of the interlayer film, to the position of 14 cm on the one end side from the center between the one end and the other end of the interlayer film. By conducting measurement at all the 11 points, measurement values of 11 partial wedge angles are obtained. 
     In a specific aspect of the interlayer film according to the present invention, a mean of the 11 partial wedge angles in the thickness varying region is 0.1 mrad or more and 0.9 mrad or less. 
     It is preferred that the interlayer film contain a thermoplastic resin. It is preferred that the interlayer film contain a plasticizer. 
     In a specific aspect of the interlayer film according to the present invention, the interlayer film includes a layer containing a thermoplastic resin, and a plasticizer in a content of 25 parts by weight or more and 45 parts by weight or less, relative to 100 parts by weight of the thermoplastic resin. 
     In a specific aspect of the interlayer film according to the present invention, the interlayer film includes a first layer, and a second layer arranged on a first surface side of the first layer. 
     In a specific aspect of the interlayer film according to the present invention, the first layer contains a polyvinyl acetal resin, the second layer contains a polyvinyl acetal resin, and the content of the hydroxyl group of the polyvinyl acetal resin in the first layer is lower than the content of the hydroxyl group of the polyvinyl acetal resin in the second layer. 
     In a specific aspect of the interlayer film according to the present invention, the first layer contains a polyvinyl acetal resin, the second layer contains a polyvinyl acetal resin, the first layer contains a plasticizer, the second layer contains a plasticizer, and the content of the plasticizer in the first layer relative to 100 parts by weight of the polyvinyl acetal resin in the first layer is larger than the content of the plasticizer in the second layer relative to 100 parts by weight of the polyvinyl acetal resin in the second layer. 
     According to a broad aspect of the present invention, there is provided a roll body including a winding core and the above-described interlayer film for laminated glass, the interlayer film for laminated glass being wound around an outer periphery of the winding core. 
     According to a broad aspect of the present invention, there is provided a laminated glass including a first lamination glass member, a second lamination glass member, and an interlayer film part arranged between the first lamination glass member and the second lamination glass member, the interlayer film part being formed of the interlayer film for laminated glass described above. 
     Effect of the the Invention 
     The interlayer film for laminated glass according to the present invention is an interlayer film for laminated glass used in laminated glass. The interlayer film for laminated glass according to the present invention has one end and the other end being at the opposite side of the one end. In the interlayer film for laminated glass according to the present invention, the thickness of the other end is larger than the thickness of the one end, and the wedge angle of the interlayer film for laminated glass as a whole is 0.1 mrad or more. The interlayer film for laminated glass according to the present invention has a thickness varying region having a standard deviation of 11 partial wedge angles of 0.040 mrad or less in a region extending in the direction perpendicular to the direction connecting the one end and the other end of the interlayer film. Since the interlayer film for laminated glass according to the present invention is provided with the aforementioned configuration, it is possible to reduce the variation in double images in laminated glass prepared with the interlayer film for laminated glass according to the present invention in the direction perpendicular to the direction connecting one end and the other end of the interlayer film for laminated glass according to the present invention, and it is possible to effectively suppress double images. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIGS.  1 ( a ) and ( b )  are a sectional view and a front view, respectively, schematically showing an interlayer film for laminated glass, in accordance with a first embodiment of the present invention. 
         FIGS.  2 ( a ) and ( b )  are a sectional view and a front view, respectively, schematically showing an interlayer film for laminated glass, in accordance with a second embodiment of the present invention. 
         FIG.  3    is a sectional view schematically showing an interlayer film for laminated glass in accordance with a third embodiment of the present invention. 
         FIG.  4    is a sectional view schematically showing an interlayer film for laminated glass in accordance with a fourth embodiment of the present invention. 
         FIG.  5    is a sectional view schematically showing an interlayer film for laminated glass in accordance with a fifth embodiment of the present invention. 
         FIG.  6    is a sectional view schematically showing an interlayer film for laminated glass in accordance with a sixth embodiment of the present invention. 
         FIG.  7    is a sectional view showing an example of laminated glass prepared with the interlayer film for laminated glass shown in  FIG.  1   . 
         FIG.  8    is a perspective view schematically showing a roll body prepared by winding the interlayer film for laminated glass shown in  FIG.  1   . 
         FIG.  9    is a view for illustrating selection points for measuring 11 partial wedge angles of the interlayer film for laminated glass shown in  FIGS.  1 ,  8   . 
         FIG.  10    is a figure for explaining a preliminary pressing method used in evaluation of double images in Examples. 
     
    
    
     MODE(S) FOR CARRYING OUT THE INVENTION 
     Hereinafter, the details of the present invention will be described. 
     The interlayer film for laminated glass (in the present specification, sometimes abbreviated as “interlayer film”) according to the present invention is used for laminated glass. 
     The interlayer film according to the present invention has a one-layer structure or a two or more-layer structure. The interlayer film according to the present invention may have a one-layer structure and may have a two or more-layer structure. The interlayer film according to the present invention may have a two-layer structure, may have a two or more-layer structure, may have a three-layer structure and may have a three or more-layer structure. The interlayer film according to the present invention may be a single-layered interlayer film and may be a multi-layered interlayer film. 
     The interlayer film according to the present invention has one end and the other end being at the opposite side of the one end. The one end and the other end are end portions of both sides facing each other in the interlayer film. In the interlayer film according to the present invention, the thickness of the other end is larger than the thickness of the one end. 
     The interlayer film according to the present invention as a whole has a wedge angle of 0.1 mrad or more. 
     The interlayer film according to the present invention has a thickness varying region having a standard deviation of 11 partial wedge angles measured by the following measuring method of 0.040 mrad or less in a region extending in the direction perpendicular to the direction connecting the one end and the other end of the interlayer film. 
     Method for measuring 11 partial wedge angles: 11 points are selected at 10 cm intervals in the direction perpendicular to the direction connecting the one end and the other end of the interlayer film. At each of the 11 points, a partial wedge angle is measured in the region extending from the position of 6 cm on the one end side from the center between the one end and the other end of the interlayer film, to the position of 14 cm on the one end side from the center between the one end and the other end of the interlayer film. By conducting measurement at all the 11 points, measurement values of 11 partial wedge angles are obtained. 
     Since the present invention is provided with the aforementioned configuration, it is possible to reduce the variation in double images in laminated glass prepared with the interlayer film according to the present invention in the direction perpendicular to the direction connecting one end and the other end of the interlayer film according to the present invention, and it is possible to effectively suppress double images. For example, by locating the thickness varying region in a region for display that corresponds to a display region of a head-up display, it is possible to display information relatively excellently while effectively suppressing double images. 
     It suffices that the interlayer film according to the present invention partially have a thickness varying region in which a standard deviation of 11 partial wedge angles satisfies the above-described upper limit. The position of the thickness varying region existing in the interlayer film according to the present invention is not particularly limited in the direction perpendicular to the direction connecting the one end and the other end of the interlayer film. It is preferred that the center in the direction perpendicular to the direction connecting the one end and the other end of the interlayer film exist in the thickness varying region. It is preferred that the region of 100 cm extending in the direction perpendicular to the direction connecting the one end and the other end of the interlayer film centered at the center in the direction perpendicular to the direction connecting the one end and the other end of the interlayer film correspond to the thickness varying region. 
     Next, a method for measuring 11 partial wedge angles is described more specifically. 
     Method for Selecting 11 Points for Measuring Partial Wedge Angles: 
     First, 11 points (selection points, called selection points differentially from later-described measurement points) are selected at 10 cm intervals in the direction perpendicular to the direction connecting the one end and the other end of the interlayer film. That is, in a region of 100 cm extending in the direction perpendicular to the direction connecting the one end and the other end of the interlayer film, 11 points (selection points) are selected at 10 cm intervals. Among the 11 points (selection points), the point (selection point) situated closest to the one side in the direction perpendicular to the direction connecting the one end and the other end of the interlayer film is referred to as a first selection point. A second selection point is the point distanced from the first selection point by 10 cm on the other side in the direction perpendicular to the direction connecting the one end and the other end of the interlayer film. An n-th selection point (n is an integer of 2 to 11) is the point distanced from the first selection point by 10× (n−1) cm on the other side in the direction perpendicular to the direction connecting the one end and the other end of the interlayer film. An n-th selection point (n is an integer of 2 to 11) is the point distanced from the n−1-th selection point by 10 cm on the other side in the direction perpendicular to the direction connecting the one end and the other end of the interlayer film. The distance between the first selection point and the eleventh selection point is 100 cm. 
     Method for Measuring Partial Wedge Angles at 11 Points (Selection Points): 
     At each of the first to n-th 11 selection points (n is an integer of 2 to 11), a partial wedge angle is measured in the region extending from the position of 6 cm on the one end side from the center between the one end and the other end of the interlayer film, to the position of 14 cm on the one end side from the center between the one end and the other end of the interlayer film. A partial wedge angle is measured in a region of 8 cm in the direction connecting the one end and the other end of the interlayer film centered at the position of 10 cm on the one end side from the center between the one end and the other end of the interlayer film. A position of 6 cm on the one end from the center between the one end and the other end of the interlayer film is defined as a first measurement point (called a measurement point differentially from the selection point). A second measurement point is a point distanced from the first measurement point (position of 6 cm on the one end side from the center between the one end and the other end of the interlayer film) by 2 mm on the one end side. An m-th measurement point (m is an integer of 2 to 41) is the point distanced from the first measurement point (position of 6 cm on the one end side from the center between the one end and the other end of the interlayer film) by 2×(m−1) mm on the one end side. An m-th measurement point (m is an integer of 2 to 41) is the point distanced from the m−1-th measurement point by 2 mm on the one end side. The distance between the first measurement point and the 41st measurement point is 8 cm. 
     At each of the 11 selection points, thickness is measured at the first to the m-th measurement points (m is an integer of 2 to 41). A primary line is obtained by the least squares method by plotting the distance (unit: mm) from the position of 6 cm on the one end side from the center between the one end and the other end of the interlayer film (the position where x=0 mm) to the measurement point toward the one end on the x-axis, and the thickness of the interlayer film (unit: μm) on the y-axis. The interior angle formed by the obtained primary line and the line of y=0 is regarded as a partial wedge angle at one of the selection points. 
     By conducting measurement at all the 11 selection points, measurement values of 11 partial wedge angles are obtained. 
     As a measuring device for use for measurement of a partial wedge angle at each measurement point of the interlayer film, a contact type thickness measuring instrument “TOF-4R” (available from Yamabun Electronics Co., Ltd.) or the like can be recited. 
     From the viewpoint of further reducing the variation in double images in laminated glass in the direction perpendicular to the direction connecting one end and the other end of the interlayer film, and suppressing double images more effectively, a standard deviation of 11 partial wedge angles in the thickness varying region is preferably 0.035 mrad or less, more preferably 0.025 mrad or less, further preferably 0.015 mrad or less, especially preferably 0.010 mrad. 
     From the viewpoint of further reducing the variation in double images in laminated glass in the direction perpendicular to the direction connecting one end and the other end of the interlayer film, and suppressing double images more effectively, the mean of the 11 partial wedge angles of the thickness varying region is preferably 0.1 mrad or more, more preferably 0.2 mrad or more. When the mean of partial wedge angles is the above lower limit or more, it is possible to obtain laminated glass suited for cars such as a truck or a bus in which the attachment angle of the windshield is large. 
     From the viewpoint of further reducing the variation in double images in laminated glass in the direction perpendicular to the direction connecting one end and the other end of the interlayer film, and suppressing double images more effectively, the mean of the 11 partial wedge angles of the thickness varying region is preferably 0.9 mrad or less, more preferably 0.8 mrad or less. When the mean of partial wedge angles is the above upper limit or less, it is possible to obtain laminated glass suited for cars such as a sports car in which the attachment angle of the windshield is small. 
     As a method for controlling the standard deviation of the 11 partial wedge angles, and the mean of the 11 partial wedge angles, the following methods can be recited. A method of improving the homogeneity of the ingredients contained in the composition. A method of suppressing the variation in speed of conveying the composition to the die by controlling the pressure in preparation of the interlayer film by melt extrusion. A method of uniformizing the take-up speed of the melt-extruded interlayer film in preparation of the interlayer film by melt extrusion. 
     The interlayer film according to the present invention has, for example, a region for display corresponding to a display region of a head-up display. The region for display is a region capable of favorably displaying information. 
     From the viewpoint of suppressing the double images more effectively, it is preferred that the thickness increases from the one end toward the other end in a region of 80% or more (more preferably 85% or more, further preferably 90% or more, particularly preferably 95% or more) of the region between a position of 6 cm toward the other end from the one end and a position of 63.8 cm toward the other end from the one end. From the viewpoint of suppressing the double images more effectively, it is preferred that the thickness increases from the one end toward the other end in a region of 80% or more (more preferably 85% or more, further preferably 90% or more, particularly preferably 95% or more) of the region between a position of 8 cm toward the other end from the one end and a position of 61.8 cm toward the other end from the one end. From the viewpoint of suppressing the double images more effectively, it is preferred that the thickness increases from the one end toward the other end in a region of 80% or more (more preferably 85% or more, further preferably 90% or more, particularly preferably 95% or more) of the region between a position of 9 cm toward the other end from the one end and a position of 60.8 cm toward the other end from the one end. From the viewpoint of suppressing the double images more effectively, it is preferred that the thickness increases from the one end toward the other end in a region of 80% or more (more preferably 85% or more, further preferably 90% or more, particularly preferably 95% or more) of the region between a position of 9.5 cm toward the other end from the one end and a position of 60.3 cm toward the other end from the one end. It is more preferred that the thickness increases from the one end toward the other end in a region of 80% or more (more preferably 85% or more, further preferably 90% or more, particularly preferably 95% or more) of the region between a position of 10 cm toward the other end from the one end and a position of 59.8 cm toward the other end from the one end. 
     The interlayer film according to the present invention is suitably used for laminated glass serving as a head-up display (HUD). It is preferred that the interlayer film according to the present invention be an interlayer film for HUD. 
     It is preferred that the interlayer film according to the present invention have a region for display corresponding to a display region of HUD. From the viewpoint of suppressing the double images more effectively, it is preferred that the interlayer film according to the present invention have the region for display in a region extending from a position of 6 cm from the one end toward the other end to a position of 63.8 cm from the one end toward the other end. From the viewpoint of suppressing the double images more effectively, it is preferred that the interlayer film according to the present invention have the region for display in a region extending from a position of 8 cm from the one end toward the other end to a position of 61.8 cm from the one end toward the other end. From the viewpoint of suppressing the double images more effectively, it is preferred that the interlayer film according to the present invention have the region for display in a region extending from a position of 9 cm from the one end toward the other end to a position of 60.8 cm from the one end toward the other end. From the viewpoint of suppressing the double images more effectively, it is preferred that the interlayer film according to the present invention have the region for display in a region extending from a position of 9.5 cm from the one end toward the other end to a position of 60.3 cm from the one end toward the other end. It is more preferred that the interlayer film according to the present invention have the region for display in a region extending from a position of 10 cm from the one end toward the other end to a position of 59.8 cm from the one end toward the other end. 
     From the viewpoint of suppressing the double images effectively, it is preferred that the interlayer film have a portion with a sectional shape in the thickness direction of a wedge-like shape in the region between a position of 6 cm toward the other end from the one end and a position of 63.8 cm toward the other end from the one end. From the viewpoint of suppressing the double images effectively, it is preferred that the interlayer film have a portion with a sectional shape in the thickness direction of a wedge-like shape in the region between a position of 8 cm toward the other end from the one end and a position of 61.8 cm toward the other end from the one end. From the viewpoint of suppressing the double images effectively, it is preferred that the interlayer film have a portion with a sectional shape in the thickness direction of a wedge-like shape in the region between a position of 9 cm toward the other end from the one end and a position of 60.8 cm toward the other end from the one end. From the viewpoint of suppressing the double images effectively, it is preferred that the interlayer film have a portion with a sectional shape in the thickness direction of a wedge-like shape in the region between a position of 9.5 cm toward the other end from the one end and a position of 60.3 cm toward the other end from the one end. It is more preferred that the interlayer film have a portion with a sectional shape in the thickness direction of a wedge-like shape in the thickness direction in the region between a position of 10 cm toward the other end from the one end and a position of 59.8 cm toward the other end from the one end. The portion with a sectional shape in the thickness direction of a wedge-like shape may exist in a part or the whole of the region to the aforementioned position (for example, 63.8 mm) from the one end toward the other end. 
     The interlayer film according to the present invention may have a shading region. The shading region may be separate from the region for display. The shading region is provided so as to prevent a driver from feeling glare while driving, for example, by sunlight or outdoor lighting. The shading region can be provided so as to impart the heat blocking property. It is preferred that the shading region be located in an edge portion of the interlayer film. It is preferred that the shading region be belt-shaped. 
     In the shading region, a coloring agent or a filler may be used so as to change the color and the visible light transmittance. The coloring agent or the filler may be contained in a partial region in the thickness direction of the interlayer film or may be contained in the entire region in the thickness direction of the interlayer film. 
     From the viewpoint of providing better display, and further broadening the field of view, the visible light transmittance of the region for display is preferably 80% or more, more preferably 88% or more, further preferably 90% or more. It is preferred that the visible light transmittance of the region for display be higher than the visible light transmittance of the shading region. The visible light transmittance of the region for display may be lower than the visible light transmittance of the shading region. The visible light transmittance of the region for display is higher than the visible light transmittance of the shading region preferably by 50% or more, more preferably by 60% or more. 
     When the visible light transmittance varies in the interlayer film of each of the region for display and the shading region, the visible light transmittance is measured at the center position of the region for display and at the center position of the shading region. 
     The visible light transmittance at a wavelength ranging from 380 to 780 nm of the obtained laminated glass can be measured by using a spectrophotometer (“U-4100” available from Hitachi High-Tech Science Corporation) in conformity with JIS R3211 (1998). As the glass plate, it is preferred to use clear glass having a thickness of 2 mm. 
     It is preferred that the region for display have a length direction and a width direction. For excellent versatility of the interlayer film, it is preferred that the width direction of the region for display be the direction connecting the one end and the other end. It is preferred that the region for display be belt-shaped. 
     It is preferred that the interlayer film has an MD direction and a TD direction. For example, the interlayer film is obtained by melt extrusion molding. The MD direction is a flow direction of an interlayer film at the time of producing the interlayer film. The TD direction is a direction orthogonal to the flow direction of an interlayer film at the time of producing the interlayer film and a direction orthogonal to the thickness direction of the interlayer film. It is preferred that the one end and the other end be located on either side of the TD direction. 
     From the viewpoint of better display, it is preferred that the interlayer film have a portion with a sectional shape of wedge-like shape in the thickness direction. It is preferred that the sectional shape in the thickness direction of the region for display be a wedge-like shape. 
     Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. 
       FIGS.  1 ( a ) and ( b )  are a sectional view and a front view, respectively, schematically showing an interlayer film for laminated glass in accordance with a first embodiment of the present invention.  FIG.  1 ( a )  is a sectional view along the line I-I in  FIG.  1 ( b ) . The size and dimension of the interlayer film in  FIG.  1    and later described drawings are appropriately changed from the actual size and shape for convenience of illustration. 
     In  FIG.  1 ( a ) , a section in the thickness direction of an interlayer film  11  is shown. In this connection, in  FIG.  1 ( a )  and later described drawings, for convenience of illustration, the thicknesses of an interlayer film and respective layers constituting the interlayer film and the wedge angle (θ) are shown so as to be different from actual thicknesses thereof and an actual wedge angle. 
     The interlayer film  11  is provided with a first layer (intermediate layer), a second layer  2  (surface layer), and a third layer  3  (surface layer). The second layer  2  is arranged on a first surface side of the first layer  1  to be layered thereon. The third layer  3  is arranged on a second surface side opposite to the first surface of the first layer  1  to be layered thereon. The first layer  1  is arranged between the second layer  2  and the third layer  3  to be sandwiched therebetween. The interlayer film  11  is used for obtaining laminated glass. The interlayer film  11  is an interlayer film for laminated glass. The interlayer film  11  is a multilayer interlayer film. 
     The interlayer film  11  has one end  11   a  and the other end  11   b  at the opposite side of the one end  11   a . The one end  11   a  and the other end  11   b  are end parts of both sides facing each other. The sectional shape in the thickness direction of each of the second layer  2  and the third layer is a wedge-like shape. The sectional shape in the thickness direction of the first layer  1  is a rectangular shape. The thicknesses of the second layer  2  and the third layer  3  are larger in the other end  11   b  side than in the one end  11   a  side. Accordingly, the thickness of the other end  11   b  of the interlayer film  11  is larger than the thickness of the one end  11   a  thereof. Accordingly, the interlayer film  11  has a region being thin in thickness and a region being thick in thickness. 
     The interlayer film  11  has a region where the thickness increases from the one end  11   a  side to the other end  11   b  side. In the interlayer film  11 , the increment of the thickness is constant from the one end  11   a  side to the other end  11   b  side in the region where the thickness increases. 
     The interlayer film  11  has a region for display R 1  corresponding to a display region of a head-up display. The interlayer film  11  has a surrounding region R 2  neighboring the region for display R 1 . 
     The interlayer film  11  has a shading region R 3  that is separate from the region for display R 1 . The shading region R 3  is located in an edge portion of the interlayer film  11 . 
     The interlayer film has a shape as shown in  FIG.  1 ( a ) , and may have a one-layer structure, a two-layer structure or four or more-layer structure. 
       FIG.  8    is a perspective view schematically showing a roll body prepared by winding the interlayer film for laminated glass shown in  FIG.  1   . 
     An interlayer film  11  may be wound to be formed into a roll body  51  of the interlayer film  11 . 
     The roll body  51  shown in  FIG.  8    includes a winding core  61  and the interlayer film  11 . The interlayer film  11  is wound around an outer periphery of the winding core  61 . 
       FIG.  9    is a view for illustrating selection points for measuring 11 partial wedge angles of the interlayer film for laminated glass shown in  FIGS.  1 ,  8   . In  FIG.  9   , selection points N for measuring 11 partial wedge angles are indicated. At the 11 selection points N, measurement is conducted at 41 measurement points at intervals of 2 mm in the vertical direction per one bold line of the 11 selection points N. 
       FIGS.  2 ( a ) and ( b )  are a sectional view and a front view, respectively, schematically showing an interlayer film for laminated glass in accordance with a second embodiment of the present invention.  FIG.  2 ( a )  is a sectional view along the line I-I in  FIG.  2 ( b ) . In  FIG.  2 ( a ) , a section in the thickness direction of an interlayer film  11 A is shown. 
     The interlayer film  11 A shown in  FIG.  2    is provided with a first layer  1 A. The interlayer film  11 A has a one-layer structure composed only of the first layer  1 A and is a single-layered interlayer film. The interlayer film  11 A is singly constituted by the first layer  1 A. The interlayer film  11 A is used for obtaining laminated glass. The interlayer film  11 A is an interlayer film for laminated glass. 
     The interlayer film  11 A has one end  11   a  and the other end lib at the opposite side of the one end  11   a . The one end  11   a  and the other end  11   b  are end parts of both sides facing each other. The thickness of the other end  11   b  of the interlayer film  11 A is larger than the thickness of the one end  11   a  thereof. Accordingly, the first layer  1 A and the interlayer film  11 A have a region being thin in thickness and a region being thick in thickness. 
     The interlayer film  11 A has a region where the thickness increases from the one end  11   a  side to the other end  11   b  side. In the interlayer film  11 A, the increment of the thickness is constant from the one end  11   a  side to the other end  11   b  side in the region where the thickness increases. 
     The interlayer film  11 A and the first layer  1 A have portions  11 Aa,  1 Aa having a rectangular sectional shape in the thickness direction, and portions  11 Ab,  1 Ab having a wedge-like sectional shape in the thickness direction. 
     The interlayer film  11 A has a region for display R 1  corresponding to a display region of a head-up display. The interlayer film  11 A has a surrounding region R 2  neighboring the region for display R 1 . 
     The interlayer film  11 A has a shading region R 3  that is separate from the region for display R 1 . The shading region R 3  is located in an edge portion of the interlayer film  11 A. 
     The interlayer film has a shape as shown in  FIG.  2 ( a )  and may have a two or more layer structure. 
       FIG.  3    is a sectional view schematically showing an interlayer film for laminated glass in accordance with a third embodiment of the present invention. In  FIG.  3   , a section in the thickness direction of an interlayer film  11 B is shown. 
     The interlayer film  11 B shown in  FIG.  3    is provided with a first layer  1 B (intermediate layer), a second layer  2 B (surface layer), and a third layer  3 B (surface layer). The interlayer film  11  and the interlayer film  11 B are different from each other in the increment of the thickness in the region where the thickness increases. 
     The interlayer film  11 B has a region where the thickness increases from the one end  11   a  side to the other end  11   b  side. The interlayer film  11 B has a part where the increment of the thickness increases from the one end  11   a  side to the other end  11   b  side in the region where the thickness increases. The interlayer film  11 B has a region with a sectional shape in the thickness direction of a wedge-like shape. The interlayer film  11 B has a part where the wedge angle increases from the one end side to the other end side in the region with a sectional shape in the thickness direction of a wedge-like shape. 
       FIG.  4    is a sectional view and a front view schematically showing an interlayer film for laminated glass in accordance with a fourth embodiment of the present invention. In  FIG.  4   , a section in the thickness direction of an interlayer film  11 C is shown. 
     The interlayer film  11 C shown in  FIG.  4    includes a first layer  1 C. The interlayer film  11 C has a one-layer structure composed only of the first layer  10  and is a single-layered interlayer film. The interlayer film  11 A and the interlayer film  11 C are different from each other in the increment of the thickness in the region where the thickness increases. 
     The interlayer film  11 C has a region where the thickness increases from the one end  11   a  side to the other end  11   b  side. The interlayer film  11 C has a part where the increment of the thickness increases from the one end  11   a  side to the other end  11   b  side in the region where the thickness increases. The interlayer film  11 C has a region with a sectional shape in the thickness direction of a wedge-like shape. The interlayer film  11 C has a part where the wedge angle increases from the one end side to the other end side in the region with a sectional shape in the thickness direction of a wedge-like shape. 
     The interlayer film  11 C and the first layer  1 C have portions  11 Ca,  1 Ca having a rectangular sectional shape in the thickness direction, and portions  11 Cb,  1 Cb having a wedge-like sectional shape in the thickness direction. 
       FIG.  5    is a sectional view schematically showing an interlayer film for laminated glass in accordance with a fifth embodiment of the present invention. In  FIG.  5   , a section in the thickness direction of an interlayer film  11 D is shown. 
     The interlayer film  11 D shown in  FIG.  5    includes a first layer  1 D (intermediate layer), a second layer  2 D (surface layer), and a third layer  3 D (surface layer). The interlayer film  11  and the interlayer film  11 D are different from each other in the increment of the thickness in the region where the thickness increases. 
     The interlayer film  11 D has a region where the thickness increases from the one end  11   a  side to the other end  11   b  side. The interlayer film  11 D has a part where the increment of the thickness decreases from the one end  11   a  side to the other end  11   b  side in the region where the thickness increases. The interlayer film  11 D has a region with a sectional shape in the thickness direction of a wedge-like shape. The interlayer film  11 D has a part where the wedge angle decreases from the one end side to the other end side in the region with a sectional shape in the thickness direction of a wedge-like shape 
       FIG.  6    is a sectional view schematically showing an interlayer film for laminated glass in accordance with a sixth embodiment of the present invention. In  FIG.  6   , a section in the thickness direction of an interlayer film  11 E is shown. 
     The interlayer film  11 E shown in  FIG.  6    includes a first layer  1 E. The interlayer film  11 E has a one-layer structure composed only of the first layer  1 E and is a single-layered interlayer film. The interlayer film  11 A and the interlayer film  11 E are different from each other in the increment of the thickness in the region where the thickness increases. 
     The interlayer film  11 E has a region where the thickness increases from the one end  11   a  side to the other end  11   b  side. The interlayer film  11 E has a part where the increment of the thickness decreases increases from the one end  11   a  side to the other end  11   b  side in the region where the thickness increases decreases. The interlayer film  11 E has a region with a sectional shape in the thickness direction of a wedge-like shape. The interlayer film  11 E has a part where the wedge angle decreases from the one end side to the other end side in the region with a sectional shape in the thickness direction of a wedge-like shape. 
     The interlayer film  11 E and the first layer  1 E have portions  11 Ea,  1 Ea having a rectangular sectional shape in the thickness direction, and portions  11 Eb,  1 Eb having a wedge-like sectional shape in the thickness direction. 
     It is preferred that the interlayer film have a portion with a sectional shape in the thickness direction of a wedge-like shape. It is preferred that the interlayer film have a portion where the thickness gradually increases from one end toward the other end. It is preferred that the sectional shape in the thickness direction of the interlayer film be a wedge-like shape. Examples of the sectional shape in the thickness direction of the interlayer film include a trapezoidal shape, a triangular shape, a pentagonal shape, and the like. 
     In the above-described interlayer film, the thickness may not increase evenly from the one end toward the other end of the interlayer film. The above-described interlayer film may have a projecting portion on the surface, or a recess portion on the surface. 
     From the viewpoint of further suppressing double images, it is preferred that the interlayer film have a part where the increment of the thickness increases from the one end side to the other end side in the region where the thickness increases. From the viewpoint of further suppressing double images, it is preferred that the interlayer film have a part where the wedge angle increases from the one end side to the other end side in the region where the sectional shape in the thickness direction is a wedge-like shape. 
     In order to suppress double images, the wedge angle (θ) of the interlayer film can be appropriately set according to the fitting angle of laminated glass. The wedge angle (θ) is a wedge angle in the entire interlayer film. From the viewpoint of further suppressing double images, the wedge angle (θ) of the interlayer film is 0.1 mrad (0.00575 degrees) or more, more preferably 0.2 mrad (0.0115 degrees) or more. From the viewpoint of further suppressing double images, the wedge angle (θ) of the interlayer film is preferably 2 mrad (0.1146 degrees) or less, and more preferably 0.7 mrad (0.0401 degrees) or less. The wedge angle (θ) of the interlayer film is an interior angle formed at the intersection point between a straight line connecting surface parts on the one side of the interlayer film (first surface part) of the maximum thickness part and the minimum thickness part in the interlayer film, and a straight line connecting surface parts of the other side of the interlayer film (second surface part) of the maximum thickness part and the minimum thickness part in the interlayer film. 
     When there are a plurality of maximum thicknesses parts, there are a plurality of minimum thicknesses parts, or the minimum thickness part is located in a certain region, the maximum thickness part and the minimum thickness part for determining the wedge angle θ are selected so that the wedge angle θ to be determined is the maximum. 
     The thickness of the interlayer film is not particularly limited. The thickness of the interlayer film refers to the total thickness of the respective layers constituting the interlayer film. Thus, in the case of a multi-layered interlayer film  11 , the thickness of the interlayer film refers to the total thickness of the first layer  1 , the second layer  2 , and the third layer  3 . 
     The maximum thickness of the interlayer film is preferably 0.1 mm or more, more preferably 0.25 mm or more, further preferably 0.5 mm or more, especially preferably 0.8 mm or more and is preferably 3 mm or less, more preferably 2 mm or less, further preferably 1.5 mm or less. 
     A distance between the one end and the other end is defined as X. It is preferred that the interlayer film have a minimum thickness in the region at a distance of 0X to 0.2X inwardly from the one end, and a maximum thickness in the region at a distance of 0X to 0.2X inwardly from the other end. It is more preferred that the interlayer film have a minimum thickness in the region at a distance of 0X to 0.1X inwardly from the one end, and a maximum thickness in the region at a distance of 0X to 0.1X inwardly from the other end. It is preferred that the interlayer film have a minimum thickness at the one end and the interlayer film have a maximum thickness at the other end. 
     The interlayer films  11 ,  11 A,  11 B,  11 C,  118 ,  11 E have a maximum thickness in the other end  11   b  and a minimum thickness in the one end  11   a.    
     The interlayer film may have a uniform-thickness part. The uniform-thickness part means that the variation in thickness does not exceed 10 μm per a distance range of 10 cm in the direction connecting the one end and the other end of the interlayer film. Therefore, the uniform-thickness part refers to the part where the variation in thickness does not exceed 10 μm per a distance range of 10 cm in the direction connecting the one end and the other end of the interlayer film. To be more specific, the uniform-thickness part refers to the part where the thickness does not vary at all in the direction connecting the one end and the other end of the interlayer film, or the thickness varies by 10 μm or less per a distance range of 10 cm in the direction connecting the one end and the other end of the interlayer film. 
     From the viewpoint of the practical aspect and the viewpoint of sufficiently enhancing the adhesive force and the penetration resistance, the maximum thickness of a surface layer is preferably 0.001 mm or more, more preferably 0.2 mm or more, further preferably 0.3 mm or more, and is preferably 1 mm or less, and more preferably 0.8 mm or less. 
     From the viewpoint of the practical aspect and the viewpoint of sufficiently enhancing the penetration resistance, the maximum thickness of a layer (intermediate layer) arranged between two surface layers is preferably 0.001 mm or more, more preferably 0.1 mm or more, and further preferably 0.2 mm or more and is preferably 0.8 mm or less, more preferably 0.6 mm or less, and further preferably 0.3 mm or less. 
     The distance X between one end and the other end of the interlayer film is preferably 3 m or less, more preferably 2 m or less, especially preferably 1.5 m or less, and is preferably 0.5 m or more, more preferably 0.8 m or more, especially preferably 1 m or more. 
     As a measuring device for use for measurement of a partial wedge angle of the interlayer film, a wedge angle θ of the interlayer film, and a thickness of the interlayer film, a contact type thickness measuring instrument “TOF-4R” (available from Yamabun Electronics Co., Ltd.) or the like can be recited. 
     Measurement of the thickness is conducted so that the distance is the shortest from the one end toward the other end by using the above-described measuring device at a film conveyance speed of 2.15 to 2.25 mm/minutes. 
     As a measuring device for use for measurement of a partial wedge angle of the interlayer film, a wedge angle θ of the interlayer film, and a thickness of the interlayer film after the interlayer film is made into laminated glass, a non-contact type multilayer film thickness measuring instrument “OPTIGAUGE” (available from Lumetrics, Inc.) or the like can be recited. The thickness of the interlayer film can be measured while the interlayer film is in the laminated glass. 
     Hereinafter, the details of materials constituting the respective layers of a multi-layered interlayer film and the single-layered interlayer film will be described. 
     (Resin) 
     It is preferred that the interlayer film contain a resin. One kind of the resin may be used alone, and two or more kinds thereof may be used in combination. 
     Examples of the resin include thermosetting resins and thermoplastic resins. 
     It is preferred that the interlayer film contain a resin (hereinafter, sometimes described as a resin (0)). It is preferred that the interlayer film contain a thermoplastic resin (hereinafter, sometimes described as a thermoplastic resin (0)). It is preferred that the interlayer film contain a polyvinyl acetal resin (hereinafter, sometimes described as a polyvinyl acetal resin (0)) as the thermoplastic resin (0). It is preferred that the first layer contain a resin (hereinafter, sometimes described as a resin (1)). It is preferred that the first layer contain a thermoplastic resin (hereinafter, sometimes described as a thermoplastic resin (1)). It is preferred that the first layer contain a polyvinyl acetal resin (hereinafter, sometimes described as a polyvinyl acetal resin (1)) as the thermoplastic resin (1). It is preferred that the second layer contain a resin (hereinafter, sometimes described as a resin (2)). It is preferred that the second layer contain a thermoplastic resin (hereinafter, sometimes described as a thermoplastic resin (2)). It is preferred that the second layer contain a polyvinyl acetal resin (hereinafter, sometimes described as a polyvinyl acetal resin (2)) as the thermoplastic resin (2). It is preferred that the third layer contain a resin (hereinafter, sometimes described as a resin (3)). It is preferred that the third layer contain a thermoplastic resin (hereinafter, sometimes described as a thermoplastic resin (3)). It is preferred that the third layer contain a polyvinyl acetal resin (hereinafter, sometimes described as a polyvinyl acetal resin (3)) as the thermoplastic resin (3). The resin (1), the resin (2), and the resin (3) may be the same as or different from one another. For still higher sound insulating properties, it is preferred that the resin (1) be different from the resin (2) and the resin (3). The thermoplastic resin (1), the thermoplastic resin (2), and the thermoplastic resin (3) may be the same or different from one another. For still higher sound insulating properties, it is preferred that the thermoplastic resin (1) be different from the thermoplastic resin (2) and the thermoplastic resin (3). Each of the polyvinyl acetal resin (1), the polyvinyl acetal resin (2) and the polyvinyl acetal resin (3) may be the same or different from one another. For still higher sound insulating properties, it is preferred that the polyvinyl acetal resin (1) be different from the polyvinyl acetal resin (2) and the polyvinyl acetal resin (3). One kind of each of the thermoplastic resin (0), the thermoplastic resin (1), the thermoplastic resin (2), and the thermoplastic resin (3) may be used alone and two or more kinds thereof may be used in combination. One kind of each of the polyvinyl acetal resin (0), the polyvinyl acetal resin (1), the polyvinyl acetal resin (2), and the polyvinyl acetal resin (3) may be used alone and two or more kinds thereof may be used in combination. 
     Examples of the thermoplastic resin include a polyvinyl acetal resin, a polyester resin, an ethylene-vinyl acetate copolymer resin, an ethylene-acrylic acid copolymer resin, a polyurethane resin, a polyvinyl alcohol resin, and the like. Thermoplastic resins other than these may be used. The polyoxymethylene (or polyacetal) resin is included in the polyvinyl acetal resin. 
     It is preferred that the resin be a thermoplastic resin. The thermoplastic resin is more preferably a polyvinyl acetal resin or a polyester resin, and is further preferably a polyvinyl acetal resin. By using a polyvinyl acetal resin and a plasticizer together, the adhesive force of the interlayer film according to the present invention to a lamination glass member or another interlayer film is further enhanced. It is preferred that the polyvinyl acetal resin be a polyvinyl butyral resin. 
     For example, the polyvinyl acetal resin can be produced by acetalizing polyvinyl alcohol (PVA) with an aldehyde. It is preferred that the polyvinyl acetal resin be an acetalized product of polyvinyl alcohol. For example, the polyvinyl alcohol can be obtained by saponifying polyvinyl acetate. The saponification degree of the polyvinyl alcohol generally lies within the range of 70 to 99.9% by mole. 
     The average polymerization degree of the polyvinyl alcohol (PVA) is preferably 200 or more, more preferably 500 or more, even more preferably 1500 or more, further preferably 1600 or more, especially preferably 2600 or more, most preferably 2700 or more and is preferably 5000 or less, more preferably 4000 or less, further preferably 3500 or less. When the average polymerization degree is the above lower limit or more, the penetration resistance of laminated glass is further enhanced. When the average polymerization degree is the above upper limit or less, formation of an interlayer film is facilitated. 
     The average polymerization degree of the polyvinyl alcohol is determined by a method in accordance with JIS K6726 “Testing methods for polyvinyl alcohol”. 
     The number of carbon atoms of the acetal group contained in the polyvinyl acetal resin is not particularly limited. The aldehyde used at the time of producing the polyvinyl acetal resin is not particularly limited. It is preferred that the number of carbon atoms of the acetal group in the polyvinyl acetal resin fall within the range of 3 to 5 and it is more preferred that the number of carbon atoms of the acetal group be 3 or 4. When the number of carbon atoms of the acetal group in the polyvinyl acetal resin is 3 or more, the glass transition temperature of the interlayer film is sufficiently lowered. The number of carbon atoms of the acetal group in the polyvinyl acetal resin may be 4 or 5. 
     The aldehyde is not particularly limited. In general, an aldehyde with 1 to 10 carbon atoms is preferably used. Examples of the aldehyde with 1 to 10 carbon atoms include formaldehyde, acetaldehyde, propionaldehyde, n-butyraldehyde, isobutyraldehyde, n-valeraldehyde, 2-ethylbutyraldehyde, n-hexylaldehyde, n-octylaldehyde, n-nonylaldehyde, n-decylaldehyde, benzaldehyde, and the like. Propionaldehyde, n-butyraldehyde, isobutyraldehyde, n-hexylaldehyde, or n-valeraldehyde is preferred, propionaldehyde, n-butyraldehyde, or isobutyraldehyde is more preferred, and n-butyraldehyde is further preferred. One kind of the aldehyde may be used alone, and two or more kinds thereof may be used in combination. 
     The content of the hydroxyl group (the amount of hydroxyl groups) of the polyvinyl acetal resin (0) is preferably 15% by mole or more and more preferably 18% by mole or more and is preferably 40% by mole or less and more preferably 35% by mole or less. When the content of the hydroxyl group is the above lower limit or more, the adhesive force of the interlayer film is further enhanced. Moreover, when the content of the hydroxyl group is the above upper limit or less, the flexibility of the interlayer film is enhanced and the handling of the interlayer film is facilitated. 
     The content of the hydroxyl group (hydroxyl group amount) of the polyvinyl acetal resin (1) is preferably 17% by mole or more, more preferably 20% by mole or more, and further preferably 22% by mole or more. The content of the hydroxyl group (the amount of hydroxyl groups) of the polyvinyl acetal resin (1) is preferably 30% by mole or less, more preferably 28% by mole or less, still more preferably 27% by mole or less, further preferably 25% by mole or less, especially preferably less than 25% by mole, especially preferably 24% by mole or less. When the content of the hydroxyl group is the above lower limit or more, the mechanical strength of the interlayer film is further enhanced. In particular, when the content of the hydroxyl group of the polyvinyl acetal resin (1) is 20% by mole or more, the resin is high in reaction efficiency and is excellent in productivity, when being 28% by mole or less, the sound insulating properties of laminated glass are further enhanced, and when being 28% by mole or less, the sound insulating properties are further enhanced. Moreover, when the content of the hydroxyl group is the above upper limit or less, the flexibility of the interlayer film is enhanced and the handling of the interlayer film is facilitated. 
     Each of the contents of the hydroxyl group of the polyvinyl acetal resin (2) and the polyvinyl acetal resin (3) is preferably 25% by mole or more, more preferably 28% by mole or more, more preferably 30% by mole or more, still more preferably more than 31% by mole, further preferably 31.5% by mole or more, further preferably 32% by mole or more, and especially preferably 33% by mole or more. Each of the contents of the hydroxyl group of the polyvinyl acetal resin (2) and the polyvinyl acetal resin (3) is preferably 38% by mole or less, more preferably 37% by mole or less, further preferably 36.5% by mole or less, especially preferably 36% by mole or less. When the content of the hydroxyl group is the above lower limit or more, the adhesive force of the interlayer film is further enhanced. Moreover, when the content of the hydroxyl group is the above upper limit or less, the flexibility of the interlayer film is enhanced and the handling of the interlayer film is facilitated. 
     From the viewpoint of further enhancing the sound insulating properties, it is preferred that the content of the hydroxyl group of the polyvinyl acetal resin (1) be lower than the content of the hydroxyl group of the polyvinyl acetal resin (2). From the viewpoint of further enhancing the sound insulating properties, it is preferred that the content of the hydroxyl group of the polyvinyl acetal resin (1) be lower than the content of the hydroxyl group of the polyvinyl acetal resin (3). From the viewpoint of still further enhancing the sound insulating properties, the absolute value of a difference between the content of the hydroxyl group of the polyvinyl acetal resin (1) and the content of the hydroxyl group of the polyvinyl acetal resin (2) is preferably 1% by mole or more, more preferably 5% by mole or more, further preferably 9% by mole or more, especially preferably 10% by mole or more, most preferably 12% by mole or more. From the viewpoint of still further enhancing the sound insulating properties, the absolute value of a difference between the content of the hydroxyl group of the polyvinyl acetal resin (1) and the content of the hydroxyl group of the polyvinyl acetal resin (3) is preferably 1% by mole or more, more preferably 5% by mole or more, further preferably 9% by mole or more, especially preferably 10% by mole or more, most preferably 12% by mole or more. An absolute value of difference between the content of the hydroxyl group of the polyvinyl acetal resin (1) and the content of the hydroxyl group of the polyvinyl acetal resin (2) is preferably 20% by mole or less. An absolute value of difference between the content of the hydroxyl group of the polyvinyl acetal resin (1) and the content of the hydroxyl group of the polyvinyl acetal resin (3) is preferably 20% by mole or less. 
     The content of the hydroxyl group of the polyvinyl acetal resin is a mole fraction, represented in percentage, obtained by dividing the amount of ethylene groups to which the hydroxyl group is bonded by the total amount of ethylene groups in the main chain. For example, the amount of ethylene groups to which the hydroxyl group is bonded can be determined in accordance with JIS K6728 “Testing methods for polyvinyl butyral”. 
     The acetylation degree (the amount of acetyl groups) of the polyvinyl acetal resin (0) is preferably 0.1% by mole or more, more preferably 0.3% by mole or more, further preferably 0.5% by mole or more and is preferably 30% by mole or less, more preferably 25% by mole or less, and further preferably 20% by mole or less. When the acetylation degree is the above lower limit or more, the compatibility between the polyvinyl acetal resin and a plasticizer is enhanced. When the acetylation degree is the above upper limit or less, with regard to the interlayer film and laminated glass, the moisture resistance thereof is enhanced. 
     The acetylation degree (the amount of acetyl groups) of the polyvinyl acetal resin (1) is preferably 0.01% by mole or more, more preferably 0.1% by mole or more, even more preferably 7% by mole or more, further preferably 9% by mole or more and is preferably 30% by mole or less, more preferably 25% by mole or less, further preferably 24% by mole or less, especially preferably 20% by mole or less. When the acetylation degree is the above lower limit or more, the compatibility between the polyvinyl acetal resin and a plasticizer is enhanced. When the acetylation degree is the above upper limit or less, with regard to the interlayer film and laminated glass, the moisture resistance thereof is enhanced. In particular, when the acetylation degree of the polyvinyl acetal resin (1) is 0.1% by mole or more and is 25% by mole or less, the resulting laminated glass is excellent in penetration resistance. 
     The acetylation degree of each of the polyvinyl acetal resin (2) and the polyvinyl acetal resin (3) is preferably 0.01% by mole or more and more preferably 0.5% by mole or more and is preferably 10% by mole or less and more preferably 2% by mole or less. When the acetylation degree is the above lower limit or more, the compatibility between the polyvinyl acetal resin and a plasticizer is enhanced. When the acetylation degree is the above upper limit or less, with regard to the interlayer film and laminated glass, the moisture resistance thereof is enhanced. 
     The acetylation degree is a mole fraction, represented in percentage, obtained by dividing the amount of ethylene groups to which the acetyl group is bonded by the total amount of ethylene groups in the main chain. For example, the amount of ethylene groups to which the acetyl group is bonded can be determined in accordance with JIS K6728 “Testing methods for polyvinyl butyral”. 
     The acetalization degree of the polyvinyl acetal resin (0) (the butyralization degree in the case of a polyvinyl butyral resin) is preferably 60% by mole or more and more preferably 63% by mole or more and is preferably 85% by mole or less, more preferably 75% by mole or less, further preferably 70% by mole or less. When the acetalization degree is the above lower limit or more, the compatibility between the polyvinyl acetal resin and a plasticizer is enhanced. When the acetalization degree is the above upper limit or less, the reaction time required for producing the polyvinyl acetal resin is shortened. 
     The acetalization degree of the polyvinyl acetal resin (1) (the butyralization degree in the case of a polyvinyl butyral resin) is preferably 47% by mole or more and more preferably 60% by mole or more and is preferably 85% by mole or less, more preferably 80% by mole or less, further preferably 75% by mole or less. When the acetalization degree is the above lower limit or more, the compatibility between the polyvinyl acetal resin and a plasticizer is enhanced. When the acetalization degree is the above upper limit or less, the reaction time required for producing the polyvinyl acetal resin is shortened. 
     The acetalization degree of each of the polyvinyl acetal resin (2) and the polyvinyl acetal resin (3) (the butyralization degree in the case of a polyvinyl butyral resin) is preferably 55% by mole or more and more preferably 60% by mole or more and is preferably 75% by mole or less and more preferably 71% by mole or less. When the acetalization degree is the above lower limit or more, the compatibility between the polyvinyl acetal resin and a plasticizer is enhanced. When the acetalization degree is the above upper limit or less, the reaction time required for producing the polyvinyl acetal resin is shortened. 
     The acetalization degree is determined in the following manner. From the total amount of the ethylene group in the main chain, the amount of the ethylene group to which the hydroxyl group is bonded and the amount of the ethylene group to which the acetyl group is bonded are subtracted. The obtained value is divided by the total amount of the ethylene group in the main chain to obtain a mole fraction. The mole fraction represented in percentage is the acetalization degree. 
     In this connection, it is preferred that the content of the hydroxyl group (the amount of hydroxyl groups), the acetalization degree (the butyralization degree) and the acetylation degree be calculated from the results determined by a method in accordance with JIS K6728 “Testing methods for polyvinyl butyral”. In this context, a method in accordance with ASTM D1396-92 may be used. When the polyvinyl acetal resin is a polyvinyl butyral resin, the content of the hydroxyl group (the amount of hydroxyl groups), the acetalization degree (the butyralization degree) and the acetylation degree can be calculated from the results measured by a method in accordance with JIS K6728 “Testing methods for polyvinyl butyral”. 
     (Plasticizer) 
     From the viewpoint of further enhancing the adhesive force of an interlayer film, it is preferred that the interlayer film according to the present invention contain a plasticizer (hereinafter, sometimes described as a plasticizer (0)). It is preferred that the first layer contain a plasticizer (hereinafter, sometimes described as a plasticizer (1)). It is preferred that the second layer contain a plasticizer (hereinafter, sometimes described as a plasticizer (2)). It is preferred that the third layer contain a plasticizer (hereinafter, sometimes described as a plasticizer (3)). When the thermoplastic resin contained in the interlayer film is a polyvinyl acetal resin, it is especially preferred that the interlayer film (the respective layers) contain a plasticizer. It is preferred that a layer containing a polyvinyl acetal resin contain a plasticizer. 
     The plasticizer is not particularly limited. As the plasticizer, a conventionally known plasticizer can be used. One kind of the plasticizer may be used alone, and two or more kinds thereof may be used in combination. 
     Examples of the plasticizer include organic ester plasticizers such as a monobasic organic acid ester and a polybasic organic acid ester, organic phosphate plasticizers such as an organic phosphate plasticizer and an organic phosphite plasticizer, and the like. Organic ester plasticizers are preferred. It is preferred that the plasticizer be a liquid plasticizer. 
     Examples of the monobasic organic acid ester include a glycol ester obtained by the reaction of a glycol with a monobasic organic acid, and the like. Examples of the glycol include triethylene glycol, tetraethylene glycol, tripropylene glycol, and the like. Examples of the monobasic organic acid include butyric acid, isobutyric acid, caproic acid, 2-ethylbutyric acid, heptanoic acid, n-octylic acid, 2-ethylhexanoic acid, n-nonylic acid, decylic acid, benzoic acid and the like. 
     Examples of the polybasic organic acid ester include an ester compound of a polybasic organic acid and an alcohol having a linear or branched structure of 4 to 8 carbon atoms. Examples of the polybasic organic acid include adipic acid, sebacic acid, azelaic acid, and the like. 
     Examples of the organic ester plasticizer include triethylene glycol di-2-ethylpropanoate, triethylene glycol di-2-ethylbutyrate, triethylene glycol di-2-ethylhexanoate, triethylene glycol dicaprylate, triethylene glycol di-n-octanoate, triethylene glycol di-n-heptanoate, tetraethylene glycol di-n-heptanoate, dibutyl sebacate, dioctyl azelate, dibutyl carbitol adipate, ethylene glycol di-2-ethylbutyrate, 1,3-propylene glycol di-2-ethylbutyrate® 1,4-butylene glycol di-2-ethylbutyrate, diethylene glycol di-2-ethylbutyrate, diethylene glycol di-2-ethylhexanoate, dipropylene glycol di-2-ethylbutyrate, triethylene glycol di-2-ethylpentanoate, tetraethylene glycol di-2-ethylbutyrate, diethylene glycol dicaprylate, diethylene glycol dibenzoate, dipropylene glycol dibenzoate, dihexyl adipate, dioctyl adipate, hexyl cyclohexyl adipate, a mixture of heptyl adipate and nonyl adipate, diisononyl adipate, diisodecyl adipate, heptyl nonyl adipate, dibutyl sebacate, oil-modified sebacic alkyds, a mixture of a phosphoric acid ester and an adipic acid ester, and the like. Organic ester plasticizers other than these may be used. Other adipic acid esters other than the above-described adipic acid esters may be used. 
     Examples of the organic phosphate plasticizer include tributoxyethyl phosphate, isodecyl phenyl phosphate, triisopropyl phosphate, and the like. 
     It is preferred that the plasticizer be a diester plasticizer represented by the following formula (1). 
     
       
         
         
             
             
         
       
     
     In the foregoing formula (1), R1 and R2 each represent an organic group with 5 to 10 carbon atoms, R3 represents an ethylene group, an isopropylene group, or an n-propylene group, and p represents an integer of 3 to 10. It is preferred that R1 and R2 in the foregoing formula (1) each be an organic group with 6 to 10 carbon atoms. 
     It is preferred that the plasticizer include triethylene glycol di-2-ethylhexanoate (3GO), triethylene glycol di-2-ethylbutyrate (3GH) or triethylene glycol di-2-ethylpropanoate. It is more preferred that the plasticizer include triethylene glycol di-2-ethylhexanoate (3GO) or triethylene glycol di-2-ethylbutyrate (3GH), and it is further preferred that the plasticizer include triethylene glycol di-2-ethylhexanoate. 
     From the viewpoint of suppressing the change in partial wedge angle more effectively at the time of preparation of laminated glass, and suppressing double images in laminated glass more effectively, it is preferred that the interlayer film according to the present invention include a layer containing a thermoplastic resin, and a plasticizer in a content of 25 parts by weight or more and 45 parts by weight or less, relative to 100 parts by weight of the thermoplastic resin. In this case, the content of the plasticizer in the layer containing the thermoplastic resin and the plasticizer is more preferably 35 parts by weight or less, further preferably 32 parts by weight or less, and especially preferably 30 parts by weight or less. 
     In the interlayer film, a content of the plasticizer (0) relative to 100 parts by weight of the resin (0) (when the resin (0) is thermoplastic resin (0), 100 parts by weight of the thermoplastic resin (0); when the resin (0) is polyvinyl acetal resin (0), 100 parts by weight of the polyvinyl acetal resin (0)) is referred to as content (0). The content (0) is preferably 25 parts by weight or more, more preferably 30 parts by weight or more, and is preferably 100 parts by weight or less, more preferably 60 parts by weight or less, further preferably 50 parts by weight or less. When the content of the plasticizer (0) is the above lower limit or more, the penetration resistance of laminated glass is further enhanced. When the content of the plasticizer (0) is the above upper limit or less, the transparency of the interlayer film is further enhanced. Further, when the content of the plasticizer (0) is the aforementioned lower limit or more and the aforementioned upper limit or less, it is possible to suppress the change in partial wedge angle more effectively at the time of preparation of laminated glass, and suppress double images in laminated glass more effectively. 
     In the first layer, a content of the plasticizer (1) relative to 100 parts by weight of the resin (1) (when the resin (1) is thermoplastic resin (1), 100 parts by weight of the thermoplastic resin (1); when the resin (1) is polyvinyl acetal resin (1), 100 parts by weight of the polyvinyl acetal resin (1)) is referred to as content (1). The content (1) is preferably 50 parts by weight or more, more preferably 55 parts by weight or more, further preferably 60 parts by weight or more, and is preferably 100 parts by weight or less, more preferably 90 parts by weight or less, further preferably 85 parts by weight or less, especially preferably 80 parts by weight or less. When the content (1) is the above lower limit or more, the flexibility of the interlayer film is enhanced and the handling of the interlayer film is facilitated. When the content (1) is the above upper limit or less, the penetration resistance of laminated glass is further enhanced. 
     In the second layer, a content of the plasticizer (2) relative to 100 parts by weight of the resin (2) (when the resin (2) is thermoplastic resin (2), 100 parts by weight of the thermoplastic resin (2) when the resin (2) is polyvinyl acetal resin (2), 100 parts by weight of the polyvinyl acetal resin (2)) is referred to as content (2). In the third layer, a content of the plasticizer (3) relative to 100 parts by weight of the resin (3) (when the resin (3) is thermoplastic resin (3), 100 parts by weight of the thermoplastic resin (3); when the resin (3) is polyvinyl acetal resin (3), 100 parts by weight of the polyvinyl acetal resin (3)) is referred to as content (3). Each of the content (2) and the content (3) is preferably 10 parts by weight or more, more preferably 15 parts by weight or more, further preferably 20 parts by weight or more, especially preferably 24 parts by weight or more, and most preferably 25 parts by weight or more. Each of the content (2) and the content (3) is preferably 45 parts by weight or less, more preferably 40 parts by weight or less, further preferably 35 parts by weight or less, especially preferably 32 parts by weight or less, and most preferably 30 parts by weight or less. When the content (2) and the content (3) are the above lower limit or more, the flexibility of the interlayer film is enhanced and the handling of the interlayer film is facilitated. When the content (2) and the content (3) are the above upper limit or less, the penetration resistance of laminated glass is further enhanced. 
     For the purpose of enhancing the sound insulating properties of laminated glass, it is preferred that the content (1) be larger than the content (2) and it is preferred that the content (1) be larger than the content (3). 
     From the viewpoint of further enhancing the sound insulating property of laminated glass, each of the absolute value of difference between the content (2) and the content (1) and the absolute value of difference between the content (3) and the content (1) is preferably 10 parts by weight or more, more preferably 15 parts by weight or more, and further preferably 20 parts by weight or more. Each of the absolute value of difference between the content (2) and the content (1) and the absolute value of difference between the content (3) and the content (1) is preferably 80 parts by weight or less, more preferably 75 parts by weight or less, further preferably 70 parts by weight or less. 
     (Heat Shielding Substance) 
     It is preferred that the interlayer film contain a heat shielding substance (heat shielding compound). It is preferred that the first layer contain a heat shielding substance. It is preferred that the second layer contain a heat shielding substance. It is preferred that the third layer contain a heat shielding substance. One kind of the heat shielding substance may be used alone, and two or more kinds thereof may be used in combination. 
     It is preferred that the heat shielding substance contain at least one kind of Ingredient X among a phthalocyanine compound, a naphthalocyanine compound, and an anthracyanine compound or contain heat shielding particles. In this case, the heat shielding compound may be constituted of both of the Ingredient X and the heat shielding particles. 
     Ingredient X: 
     It is preferred that the interlayer film include at least one kind of Ingredient X among a phthalocyanine compound, a naphthalocyanine compound, and an anthracyanine compound. It is preferred that the first layer contain the Ingredient X. It is preferred that the second layer contain the Ingredient X. It is preferred that the third layer contain the Ingredient X. The Ingredient X is a heat shielding substance. One kind of the Ingredient X may be used alone, and two or more kinds thereof may be used in combination. 
     The Ingredient X is not particularly limited. As the Ingredient X, conventionally known phthalocyanine compound, naphthalocyanine compound and anthracyanine compound can be used. 
     Examples of the Ingredient X include phthalocyanine, a derivative of phthalocyanine, naphthalocyanine, a derivative of naphthalocyanine, anthracyanine, and a derivative of anthracyanine, and the like. It is preferred that each of the phthalocyanine compound and the derivative of phthalocyanine have a phthalocyanine skeleton. It is preferred that each of the naphthalocyanine compound and the derivative of naphthalocyanine have a naphthalocyanine skeleton. It is preferred that each of the anthracyanine compound and the derivative of anthracyanine have an anthracyanine skeleton. 
     With regard to the interlayer film and laminated glass, from the viewpoint of further enhancing the heat shielding properties thereof, it is preferred that the Ingredient X be at least one kind selected from the group consisting of phthalocyanine, a derivative of phthalocyanine, naphthalocyanine and a derivative of naphthalocyanine, and it is more preferred that the Ingredient X be at least one kind among phthalocyanine and a derivative of phthalocyanine. 
     From the viewpoints of effectively enhancing the heat shielding properties and maintaining the visible light transmittance at a higher level over a long period of time, it is preferred that the Ingredient X contain vanadium atoms or copper atoms. It is preferred that the Ingredient X contain vanadium atoms and it is also preferred that the Ingredient X contain copper atoms. It is more preferred that the Ingredient X be at least one kind among phthalocyanine containing vanadium atoms or copper atoms and a derivative of phthalocyanine containing vanadium atoms or copper atoms. With regard to the interlayer film and laminated glass, from the viewpoint of still further enhancing the heat shielding properties thereof, it is preferred that the Ingredient X have a structural unit in which an oxygen atom is bonded to a vanadium atom. 
     In 100% by weight of the interlayer film or in 100% by weight of a layer containing the Ingredient X (a first layer, a second layer, or a third layer), the content of the Ingredient X is preferably 0.001% by weight or more, more preferably 0.005% by weight or more, further preferably 0.01% by weight or more, especially preferably 0.02% by weight or more. In 100% by weight of the interlayer film or in 100% by weight of a layer containing the Ingredient X (a first layer, a second layer, or a third layer), the content of the Ingredient X is preferably 0.2% by weight or less, more preferably 0.1% by weight or less, further preferably 0.05% by weight or less, especially preferably 0.04% by weight or less. When the content of the Ingredient X is the above lower limit or more and the above upper limit or less, the heat shielding properties are sufficiently enhanced and the visible light transmittance is sufficiently enhanced. For example, it is possible to make the visible light transmittance 70% or more. 
     Heat Shielding Particles: 
     It is preferred that the interlayer film contain heat shielding particles. It is preferred that the first layer contain the heat shielding particles. It is preferred that the second layer contain the heat shielding particles. It is preferred that the third layer contain the heat shielding particles. The heat shielding particle is of a heat shielding substance. By the use of heat shielding particles, infrared rays (heat rays) can be effectively cut off. One kind of the heat shielding particles may be used alone, and two or more kinds thereof may be used in combination. 
     From the viewpoint of further enhancing the heat shielding properties of laminated glass, it is more preferred that the heat shielding particles be metal oxide particles. It is preferred that the heat shielding particle be a particle (a metal oxide particle) formed from an oxide of a metal. 
     The energy amount of an infrared ray with a wavelength of 780 nm or longer which is longer than that of visible light is small as compared with an ultraviolet ray. However, the thermal action of infrared rays is large, and when infrared rays are absorbed into a substance, heat is released from the substance. Accordingly, infrared rays are generally called heat rays. By the use of the heat shielding particles, infrared rays (heat rays) can be effectively cut off. In this connection, the heat shielding particle means a particle capable of absorbing infrared rays. 
     Specific examples of the heat shielding particles include metal oxide particles such as aluminum-doped tin oxide particles, indium-doped tin oxide particles, antimony-doped tin oxide particles (ATO particles), gallium-doped zinc oxide particles (GZO particles), indium-doped zinc oxide particles (IZO particles), aluminum-doped zinc oxide particles (AZO particles), niobium-doped titanium oxide particles, sodium-doped tungsten oxide particles, cesium-doped tungsten oxide particles, thallium-doped tungsten oxide particles, rubidium-doped tungsten oxide particles, tin-doped indium oxide particles (ITO particles), tin-doped zinc oxide particles and silicon-doped zinc oxide particles, lanthanum hexaboride (LaB 6 ) particles, and the like. Heat shielding particles other than these may be used. Since the heat ray shielding function is high, preferred are metal oxide particles, more preferred are ATO particles, GZO particles, IZO particles, ITO particles or tungsten oxide particles, and especially preferred are ITO particles or tungsten oxide particles. In particular, since the heat ray shielding function is high and the particles are readily available, preferred are tin-doped indium oxide particles (ITO particles), and also preferred are tungsten oxide particles. 
     With regard to the interlayer film and laminated glass, from the viewpoint of further enhancing the heat shielding properties thereof, it is preferred that the tungsten oxide particles be metal-doped tungsten oxide particles. Examples of the “tungsten oxide particles” include metal-doped tungsten oxide particles. Specifically, examples of the metal-doped tungsten oxide particles include sodium-doped tungsten oxide particles, cesium-doped tungsten oxide particles, thallium-doped tungsten oxide particles, rubidium-doped tungsten oxide particles, and the like. 
     With regard to the interlayer film and laminated glass, from the viewpoint of further enhancing the heat shielding properties thereof, cesium-doped tungsten oxide particles are especially preferred. With regard to the interlayer film and laminated glass, from the viewpoint of still further enhancing the heat shielding properties thereof, it is preferred that the cesium-doped tungsten oxide particles be tungsten oxide particles represented by the formula: Cs 0.33 WO 3 . 
     The average particle diameter of the heat shielding particles is preferably 0.01 μm or more, more preferably 0.02 μm or more, and is preferably 0.1 μm or less and more preferably 0.05 μm or less. When the average particle diameter is the above lower limit or more, the heat ray shielding properties are sufficiently enhanced. When the average particle diameter is the above upper limit or less, the dispersibility of heat shielding particles is enhanced. 
     The “average particle diameter” refers to the volume average particle diameter. The average particle diameter can be measured using a particle size distribution measuring apparatus (“UPA-EX150” available from NIKKISO CO., LTD.), or the like. 
     In 100% by weight of the interlayer film or in 100% by weight of a layer containing the heat shielding particles (a first layer, a second layer, or a third layer), each content of the heat shielding particles (in particular, the content of tungsten oxide particles) is preferably 0.01% by weight or more, more preferably 0.1% by weight or more, further preferably 1% by weight or more, especially preferably 1.5% by weight or more. In 100% by weight of the interlayer film or in 100% by weight of a layer containing the heat shielding particles (a first layer, a second layer, or a third layer), each content of the heat shielding particles (in particular, the content of tungsten oxide particles) is preferably 6% by weight or less, more preferably 5.5% by weight or less, further preferably 4% by weight or less, especially preferably 3.5% by weight or less, most preferably 3% by weight or less. When the content of the heat shielding particles is the above lower limit or more and the above upper limit or less, the heat shielding properties are sufficiently enhanced and the visible light transmittance is sufficiently enhanced. 
     (Metal Salt) 
     It is preferred that the interlayer film contain at least one kind of metal salt (hereinafter, sometimes described as Metal salt M) among an alkali metal salt, an alkaline earth metal salt, and a magnesium salt. It is preferred that the first layer contain the Metal salt M. It is preferred that the second layer contain the Metal salt M. It is preferred that the third layer contain the Metal salt M. By the use of the Metal salt M, controlling the adhesivity between the interlayer film and a lamination glass member such as a glass plate or the adhesivity between respective layers in the interlayer film is facilitated. One kind of the Metal salt M may be used alone, and two or more kinds thereof may be used in combination. 
     It is preferred that the Metal salt M contain at least one kind of metal selected from the group consisting of Li, Na, K, Rb, Cs, Mg, Ca, Sr and Ba. It is preferred that the metal salt included in the interlayer film contain at least one kind of metal among K and Mg. 
     Moreover, it is more preferred that the Metal salt M be an alkali metal salt of an organic acid with 2 to 16 carbon atoms, an alkaline earth metal salt of an organic acid with 2 to 16 carbon atoms, and a magnesium salt of an organic acid with 2 to 16 carbon atoms, and it is further preferred that the Metal salt M be a magnesium carboxylate with 2 to 16 carbon atoms or a potassium carboxylate with 2 to 16 carbon atoms. 
     Examples of the magnesium carboxylate with 2 to 16 carbon atoms and the potassium carboxylate with 2 to 16 carbon atoms include magnesium acetate, potassium acetate, magnesium propionate, potassium propionate, magnesium 2-ethylbutyrate, potassium 2-ethylbutanoate, magnesium 2-ethylhexanoate, potassium 2-ethylhexanoate, and the like. 
     The total of the contents of Mg and K in an interlayer film containing the Metal salt M or a layer containing the Metal salt M (a first layer, a second layer, or a third layer) is preferably 5 ppm or more, more preferably 10 ppm or more, and further preferably 20 ppm or more and is preferably 300 ppm or less, more preferably 250 ppm or less, and further preferably 200 ppm or less. When the total of the contents of Mg and K is the above lower limit or more and the above upper limit or less, the adhesivity between the interlayer film and a glass plate or the adhesivity between respective layers in the interlayer film can be further well controlled. 
     (Ultraviolet Ray Screening Agent) 
     It is preferred that the interlayer film contain an ultraviolet ray screening agent. It is preferred that the first layer contain an ultraviolet ray screening agent. It is preferred that the second layer contain an ultraviolet ray screening agent. It is preferred that the third layer contain an ultraviolet ray screening agent. By the use of an ultraviolet ray screening agent, even when the interlayer film and the laminated glass are used for a long period of time, the visible light transmittance becomes further hard to be lowered. One kind of the ultraviolet ray screening agent may be used alone, and two or more kinds thereof may be used in combination. 
     Examples of the ultraviolet ray screening agent include an ultraviolet ray absorber. It is preferred that the ultraviolet ray screening agent be an ultraviolet ray absorber. 
     Examples of the ultraviolet ray screening agent include an ultraviolet ray screening agent containing a metal atom, an ultraviolet ray screening agent containing a metal oxide, an ultraviolet ray screening agent having a benzotriazole structure (a benzotriazole compound), an ultraviolet ray screening agent having a benzophenone structure (a benzophenone compound), an ultraviolet ray screening agent having a triazine structure (a triazine compound), an ultraviolet ray screening agent having a malonic acid ester structure (a malonic acid ester compound), an ultraviolet ray screening agent having an oxanilide structure (an oxanilide compound), an ultraviolet ray screening agent having a benzoate structure (a benzoate compound), and the like. 
     Examples of the ultraviolet ray screening agent containing a metal atom include platinum particles, particles in which the surface of platinum particles is coated with silica, palladium particles, particles in which the surface of palladium particles is coated with silica, and the like. It is preferred that the ultraviolet ray screening agent not be heat shielding particles. 
     The ultraviolet ray screening agent is preferably an ultraviolet ray screening agent having a benzotriazole structure, an ultraviolet ray screening agent having a benzophenone structure, an ultraviolet ray screening agent having a triazine structure, or an ultraviolet ray screening agent having a benzoate structure. The ultraviolet ray screening agent is more preferably an ultraviolet ray screening agent having a benzotriazole structure or an ultraviolet ray screening agent having a benzophenone structure, and is further preferably an ultraviolet ray screening agent having a benzotriazole structure. 
     Examples of the ultraviolet ray screening agent containing a metal oxide include zinc oxide, titanium oxide, cerium oxide, and the like. Furthermore, with regard to the ultraviolet ray screening agent containing a metal oxide, the surface thereof may be coated with any material. Examples of the coating material for the surface of the ultraviolet ray screening agent containing a metal oxide include an insulating metal oxide, a hydrolyzable organosilicon compound, a silicone compound, and the like. 
     Examples of the insulating metal oxide include silica, alumina, zirconia, and the like. For example, the insulating metal oxide has a band-gap energy of 5.0 eV or more. 
     Examples of the ultraviolet ray screening agent having a benzotriazole structure include 2-(2′-hydroxy-5′-methylphenyl)benzotriazole (“Tinuvin P” available from BASF Japan Ltd.), 2-(2′-hydroxy-3′,5′-di-t-butylphenyl)benzotriazole (“Tinuvin 320” available from BASF Japan Ltd.), 2-(2′-hydroxy-3′-t-butyl-5-methylphenyl)-5-chlorobenzotriazole (“Tinuvin 326” available from BASF Japan Ltd.), 2-(2′-hydroxy-3′,5′-di-amylphenyl)benzotriazole (“Tinuvin 328” available from BASF Japan Ltd.), and the like. It is preferred that the ultraviolet ray screening agent be an ultraviolet ray screening agent having a benzotriazole structure containing a halogen atom, and it is more preferred that the ultraviolet ray screening agent be an ultraviolet ray screening agent having a benzotriazole structure containing a chlorine atom, because those are excellent in ultraviolet ray screening performance. 
     Examples of the ultraviolet ray screening agent having a benzophenone structure include octabenzone (“Chimassorb 81” available from BASF Japan Ltd.), and the like. 
     Examples of the ultraviolet ray screening agent having a triazine structure include “LA-F70” available from ADEKA CORPORATION, 2-(4,6-diphenyl-1,3,5-triazine-2-yl)-5-[(hexyl)oxy]-phenol (“Tinuvin 1577FF” available from BASF Japan Ltd.), and the like. 
     Examples of the ultraviolet ray screening agent having a malonic acid ester structure include dimethyl 2-(p-methoxybenzylidene)malonate, tetraethyl-2,2-(1,4-phenylenedimethylidene)bismalonate, 2-(p-methoxybenzylidene)-bis(1,2,2,6,6-pentamethyl-4-piperidinyl)malonate, and the like. 
     Examples of a commercial product of the ultraviolet ray screening agent having a malonic acid ester structure include Hostavin B-CAP, Hostavin PR-25 and Hostavin PR-31 (any of these is available from Clariant Japan K.K.). 
     Examples of the ultraviolet ray screening agent having an oxanilide structure include a kind of oxalic acid diamide having a substituted aryl group and the like on the nitrogen atom such as N-(2-ethylphenyl)-N′-(2-ethoxy-5-t-butylphenyl)oxalic acid diamide, N-(2-ethylphenyl)-N′-(2-ethoxy-phenyl)oxalic acid diamide and 2-ethyl-2′-ethoxy-oxanilide (“Sanduvor VSU” available from Clariant Japan K.K.). 
     Examples of the ultraviolet ray screening agent having a benzoate structure include 2,4-di-tert-butylphenyl-3,5-di-tert-butyl-4-hydroxybenzoate (“Tinuvin 120” available from BASF Japan Ltd.), and the like. 
     In 100% by weight of the interlayer film or in 100% by weight of a layer containing the ultraviolet ray screening agent (a first layer, a second layer, or a third layer), the content of the ultraviolet ray screening agent and the content of the benzotriazole compound are preferably 0.1% by weight or more, more preferably 0.2% by weight or more, further preferably 0.3% by weight or more, especially preferably 0.5% by weight or more. In 100% by weight of the interlayer film or in 100% by weight of a layer containing the ultraviolet ray screening agent (a first layer, a second layer, or a third layer), the content of the ultraviolet ray screening agent and the content of the benzotriazole compound are preferably 2.5% by weight or less, more preferably 2% by weight or less, further preferably 1% by weight or less, especially preferably 0.8% by weight or less. When the content of the ultraviolet ray screening agent is the above-described lower limit or more and the above-described upper limit or less, deterioration in visible light transmittance after a lapse of a period can be further suppressed. In particular, by setting the content of the ultraviolet ray screening agent to be 0.2% by weight or more in 100% by weight of a layer containing the ultraviolet ray screening agent, with regard to the interlayer film and laminated glass, the lowering in visible light transmittance thereof after the lapse of a certain period of time can be significantly suppressed. 
     (Oxidation Inhibitor) 
     It is preferred that the interlayer film contain an oxidation inhibitor. It is preferred that the first layer contain an oxidation inhibitor. It is preferred that the second layer contain an oxidation inhibitor. It is preferred that the third layer contain an oxidation inhibitor. One kind of the oxidation inhibitor may be used alone, and two or more kinds thereof may be used in combination. 
     Examples of the oxidation inhibitor include a phenol-based oxidation inhibitor, a sulfur-based oxidation inhibitor, a phosphorus-based oxidation inhibitor, and the like. The phenol-based oxidation inhibitor is an oxidation inhibitor having a phenol skeleton. The sulfur-based oxidation inhibitor is an oxidation inhibitor containing a sulfur atom. The phosphorus-based oxidation inhibitor is an oxidation inhibitor containing a phosphorus atom. 
     It is preferred that the oxidation inhibitor be a phenol-based oxidation inhibitor or a phosphorus-based oxidation inhibitor. 
     Examples of the phenol-based oxidation inhibitor include 2,6-di-t-butyl-p-cresol (BHT), butyl hydroxyanisole (BHA), 2,6-di-t-butyl-4-ethylphenol, stearyl β-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 2,2′-methylenebis-(4-methyl-6-butylphenol), 2,2′-methylenebis-(4-ethyl-6-t-butylphenol), 4,4′-butylidene-bis-(3-methyl-6-t-butylphenol), 1,1,3-tris-(2-methyl-hydroxy-5-t-butylphenyl)butane, tetrakis[methylene-3-(3′,5′-butyl-4-hydroxyphenyl)propionate]methane, 1,3,3-tris-(2-methyl-4-hydroxy-5-t-butylphenol)butane, 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, bis(3,3′-t-butylphenol)butyric acid glycol ester, bis(3-t-butyl-4-hydroxy-5-methylbenzenepropanoic acid)ethylenebis(oxyethylene), and the like. One kind or two or more kinds among these oxidation inhibitors are preferably used. 
     Examples of the phosphorus-based oxidation inhibitor include tridecyl phosphite, tris(tridecyl) phosphite, triphenyl phosphite, trinonylphenyl phosphite, bis(tridecyl)pentaerithritol diphosphite, bis(decyl)pentaerithritol diphosphite, tris(2,4-di-t-butylphenyl) phosphite, bis(2,4-di-t-butyl-6-methylphenyl)ethyl ester phosphorous acid, 2,2′-methylenebis(4,6-di-t-butyl-1-phenyloxy)(2-ethylhexyloxy)phosphorus, and the like. One kind or two or more kinds among these oxidation inhibitors are preferably used. 
     Examples of a commercial product of the oxidation inhibitor include “IRGANOX 245” available from BASF Japan Ltd., “IRGAFOS 168” available from BASF Japan Ltd., “IRGAFOS 38” available from BASF Japan Ltd., “Sumilizer BHT” available from Sumitomo Chemical Co., Ltd., “H-BHT” available from Sakai Chemical Industry Co., Ltd., “IRGANOX 1010” available from BASF Japan Ltd., and the like. 
     With regard to the interlayer film and laminated glass, in order to maintain high visible light transmittance thereof over a long period of time, it is preferred that the content of the oxidation inhibitor be 0.1% by weight or more in 100% by weight of the interlayer film or in 100% by weight of the layer containing the oxidation inhibitor (a first layer, a second layer or a third layer). Moreover, since an effect commensurate with the addition of an oxidation inhibitor is not attained, it is preferred that the content of the oxidation inhibitor be 2% by weight or less in 100% by weight of the interlayer film or in 100% by weight of the layer containing the oxidation inhibitor. 
     (Other Ingredients) 
     Each of the interlayer film, the first layer, the second layer, and the third layer may contain additives such as a coupling agent, a dispersing agent, a surfactant, a flame retardant, an antistatic agent, a pigment, a dye, an adhesivity adjusting agent other than metal salt, a moisture-resistance agent, a fluorescent brightening agent, and an infrared ray absorber, as necessary. One kind of these additives may be used alone, and two or more kinds thereof may be used in combination. 
     (Laminated Glass) 
       FIG.  7    is a sectional view showing an example of laminated glass prepared with the interlayer film for laminated glass shown in  FIG.  1   . 
     A laminated glass  21  shown in  FIG.  7    is provided with an interlayer film part  11 X, a first lamination glass member  22 , and a second lamination glass member  23 . The interlayer film part  11 X is arranged between the first lamination glass member  22  and the second lamination glass member  23  to be sandwiched therebetween. The first lamination glass member  22  is arranged on a first surface of the interlayer film part  11 X. The second lamination glass member  23  is arranged on a second surface opposite to the first surface of the interlayer film part  11 X. The interlayer film part  11 X is formed of the interlayer film  11  shown in  FIG.  1   . The interlayer film part  11 X includes a first layer  1 X derived from the first layer  1 , a second layer  2 X derived from the second layer, and a third layer  3 X derived from the third layer. The first layer  1 X is formed of the first layer  1 . The second layer  2 X is formed of the second layer  2 . The third layer  3 X is formed of the third layer  3 . 
     Examples of the lamination glass member include a glass plate, a PET (polyethylene terephthalate) film, and the like. As the laminated glass, laminated glass in which an interlayer film is sandwiched between a glass plate and a PET film or the like, as well as laminated glass in which an interlayer film is sandwiched between two glass plates, is included. The laminated glass is a laminate provided with a glass plate, and it is preferred that at least one glass plate be used. It is preferred that each of the first lamination glass member and the second lamination glass member be a glass plate or a PET (polyethylene terephthalate) film and the interlayer film include at least one glass plate as the first lamination glass member or the second lamination glass member. It is especially preferred that both of the first lamination glass member and the second lamination glass member be glass plates. 
     Examples of the glass plate include a sheet of inorganic glass and a sheet of organic glass. Examples of the inorganic glass include float plate glass, heat ray-absorbing plate glass, heat ray-reflecting plate glass, polished plate glass, figured glass, wired plate glass, green glass, and the like. The organic glass is synthetic resin glass substituted for inorganic glass. Examples of the organic glass include a polycarbonate plate, a poly(meth)acrylic resin plate, and the like. Examples of the poly(meth)acrylic resin plate include a polymethyl (meth)acrylate plate, and the like. 
     Although respective thicknesses of the first lamination glass member and the second lamination glass member are not particularly limited, the thickness is preferably 1 mm or more and is preferably 5 mm or less. When the lamination glass member is a glass plate, the thickness of the glass plate is preferably 1 mm or more and is preferably 5 mm or less. When the lamination glass member is a PET film, the thickness of the PET film is preferably 0.03 mm or more and is preferably 0.5 mm or less. 
     The method for producing the laminated glass is not particularly limited. First, the interlayer film is sandwiched between the first lamination glass member and the second lamination glass member to obtain a laminate. Then, for example, by passing the obtained laminate through pressure rolls or subjecting the obtained laminate to decompression suction in a rubber bag, the air remaining between the first lamination glass member and the interlayer film, and between the second lamination glass member and the interlayer film is removed. Then, the laminate is preliminarily bonded together at about 70 to 110° C. to obtain a preliminarily press-bonded laminate. Next, by putting the preliminarily press-bonded laminate into an autoclave or by pressing the laminate, the laminate is press-bonded at about 120 to 150° C. and under a pressure of 1 to 1.5 MPa. In this way, laminated glass can be obtained. 
     The laminated glass can be used for automobiles, railway vehicles, aircraft, ships, buildings, and the like. It is preferred that the laminated glass be laminated glass for building or for vehicles and it is more preferred that the laminated glass be laminated glass for vehicles. The laminated glass can also be used for applications other than these applications. The laminated glass can be used for a windshield, side glass, rear glass, or roof glass of an automobile, and the like. Since the laminated glass is high in heat shielding properties and is high in visible light transmittance, the laminated glass is suitably used for automobiles. 
     The laminated glass is a kind of laminated glass serving as a head-up display (HUD). In the laminated glass, measured information such as the speed which is sent from a control unit and the like can be projected onto the windshield from a display unit of the instrumental panel. As such, without making a driver of an automobile move his or her visual field downward, a front visual field and measured information can be visually recognized simultaneously. 
     Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples. The present invention is not limited only to these examples. 
     In polyvinyl acetal resins used, n-butyraldehyde which has 4 carbon atoms is used for the acetalization. With regard to the polyvinyl acetal resin, the acetalization degree (the butyralization degree), the acetylation degree and the content of the hydroxyl group were measured by a method in accordance with JIS K6728 “Testing methods for polyvinyl butyral”. In this connection, even in the cases of being measured according to ASTM D1396-92, numerical values similar to those obtained by a method in accordance with JIS K6728 “Testing methods for polyvinyl butyral” were exhibited. 
     Example 1 
     Preparation of Composition for Forming First Layer: 
     The following ingredients were mixed, and kneaded sufficiently with a mixing roll to obtain a composition for forming a first layer. Other ingredients were added to the polyvinyl acetal resin. 
     Polyvinyl acetal resin (content of hydroxyl group: 22% by mole, acetylation degree: 13% by mole, acetalization degree: 65% by mole): 100 parts by weight 
     Triethylene glycol di-2-ethylhexanoate (3GO): 60 parts by weight 
     Tinuvin 326 (2-(2′-hydroxy-3′-t-butyl-5-methylphenyl)-5-chlorobenzotriazole, “Tinuvin 326” available from BASF Japan Ltd.): 0.2 parts by weight 
     BHT (2,6-di-t-butyl-p-cresol): 0.2 parts by weight 
     Preparation of Composition for Forming Second Layer and Third Layer: 
     The following ingredients were mixed, and kneaded sufficiently with a mixing roll to obtain a composition for forming a second layer and a third layer. Other ingredients were added to the polyvinyl acetal resin. 
     Polyvinyl acetal resin (content of hydroxyl group: 30.5% by mole, acetylation degree: 1% by mole, acetalization degree: 68.5% by mole): 100 parts by weight 
     Triethylene glycol di-2-ethylhexanoate (3GO): 38 parts by weight 
     Tinuvin 326 (2-(2′-hydroxy-3′-t-butyl-5-methylphenyl)-5-chlorobenzotriazole, “Tinuvin 326” available from BASF Japan Ltd.): 0.2 parts by weight 
     BHT (2,6-di-t-butyl-p-cresol): 0.2 parts by weight 
     Preparation of Interlayer Film: 
     The composition for forming the first layer, and the composition for forming the second layer and the third layer were coextruded by using a co-extruder. At this time, the speed of conveying the composition to the die and the take-up speed of the melt-extruded interlayer film were controlled by controlling the pressure. A wedge-like interlayer film having a multilayer structure of the second layer/the first layer/the third layer was prepared. Under the condition of the winding tension of 300 N, 125 m of the interlayer film for laminated glass was wound around a winding core (material: talc-containing polypropylene) (15 cm in outer diameter, 120 cm in height) available from KOGA POLYMER CO., LTD. so that the extruding direction of the two resin films and the outer circumferential direction of the winding core coincide with each other, to obtain a roll body. The interlayer film in each of Example 1, later-described Examples 2 to 8 and Comparative Example 1 has a minimum thickness at one end and has a maximum thickness at the other end. In the interlayer film obtained in Example 8, the thickness does not increase evenly from the one end toward the other end, and the interlayer film obtained in Example 8 has a projecting portion at the position of 0.25X from the one end. 
     Examples 2 to 8 and Comparative Example 1 
     An interlayer film and a roll body were obtained in the same manner as in Example 1 except that the minimum thickness, the maximum thickness, the distance from one end to the other end, the standard deviation of 11 partial wedge angles, and the mean of 11 partial wedge angles in the interlayer film were set as shown in Table 1. In Examples 2 to 8 and Comparative Example 1, the same kinds of the ultraviolet ray screening agent and the oxidation inhibitor as those in Example 1 were mixed in the same mixing amount as that in Example 1 (0.2 parts by weight relative to 100 parts by weight of the polyvinyl acetal resin). In Examples 1 to 4 and Comparative Example 1, the speed of conveying the composition to the die and the take-up speed of the melt-extruded interlayer film were respectively changed within the range of 500 kg/h to 1100 kg/h, and the range of 5 m/min to 20 m/min by controlling the pressure. 
     Example 9 
     Preparation of Composition for Forming Single-Layered Interlayer Film: 
     The following ingredients were mixed, and kneaded sufficiently with a mixing roll to obtain a composition for forming a single-layered interlayer film. Other ingredients were added to the polyvinyl acetal resin. 
     Polyvinyl acetal resin (content of hydroxyl group: 30.5% by mole, acetylation degree: 1% by mole, acetalization degree: 68.5% by mole): 100 parts by weight 
     Triethylene glycol di-2-ethylhexanoate (3GO): 39 parts by weight Tinuvin 326 (2-(2′-hydroxy-3′-t-butyl-5-methylphenyl)-5-chlorobenzotriazole, “Tinuvin 326” available from BASF Japan Ltd.): 0.2 parts by weight 
     BHT (2,6-di-t-butyl-p-cresol): 0.2 parts by weight 
     The composition for forming a single-layered interlayer film was extruded by using an extruder. At this time, the speed of conveying the composition to the die and the take-up speed of the melt-extruded interlayer film were controlled by controlling the pressure. A wedge-like interlayer film having a one-layer structure was prepared. Under the condition of the winding tension of 300 N, 125 m of the interlayer film for laminated glass was wound around a winding core (material: talc-containing polypropylene) (15 cm in outer diameter, 120 cm in height) available from KOGA POLYMER CO., LTD. so that the extruding direction of the two resin films and the outer circumferential direction of the winding core coincide with each other, to obtain a roll body. The interlayer film obtained in each of Example and the later-described Comparative Example 2 has a minimum thickness at one end and has a maximum thickness at the other end. 
     Comparative Example 2 
     An interlayer film and a roll body were obtained in the same manner as in Example 9 except that the minimum thickness, the maximum thickness, the distance from one end to the other end, the standard deviation of 11 partial wedge angles, and the mean of 11 partial wedge angles in the interlayer film were set as shown in Table 2. In Comparative Example 2, the same kinds of the ultraviolet ray screening agent and the oxidation inhibitor as those in Example 9 were mixed in the same mixing amount as that in Example 9 (0.2 parts by weight relative to 100 parts by weight of the polyvinyl acetal resin). 
     (Evaluation) 
     (1) Measurement of 11 Partial Wedge Angles 
     An interlayer film (1000 mm in length from one end to the other end×1500 mm in length of the machine direction) was prepared. Eleven selection points were selected so that the center position of the machine direction of the interlayer film was the fifth selection point in the machine direction of the interlayer film. 
     By the measuring method as described above, 11 partial wedge angles were measured. At each of the above-described first to n-th 11 selection points (n is an integer of 2 to 11), a partial wedge angle was measured in the region extending from the position of 6 cm on the one end side from the center between the one end and the other end of the interlayer film, to the position of 14 cm on the one end side from the center between the one end and the other end of the interlayer film. At each one point of the selection points, thickness was measured at 41 measurement points of the first to the m-th measurement points (m is an integer of 2 to 41). In the method as described above, measurements of 11 partial wedge angles at each of 11 selection points were obtained. A standard deviation of 11 partial wedge angles and a mean of 11 partial wedge angles were calculated. 
     Partial wedge angle was measured with “TOF-4R” available from Yamabun Electronics Co., Ltd. in the method as described above. 
     (2) Double Images 
     A pair of glass plates (clear glass, the size of 1500 mm×1000 mm, 2 mm in thickness) was prepared. 
     An interlayer film (1000 mm in length from one end to the other end×1500 mm in length of the machine direction) with a size corresponding to the size of the glass plate was sandwiched between the pair of glass plates to obtain a laminate. As shown in  FIG.  10   , the obtained laminate was fitted into a frame of an EPDM-made rubber tube (frame member). The rubber tube had a width of 15 mm. Next, the laminate fitted into a frame of an EPDM-made rubber tube was preliminarily press-bonded by a vacuum bag method. The preliminarily press-bonded laminate was subjected to press-bonding at 150° C. and a pressure of 1.2 MPa with the use of an autoclave to obtain a sheet of laminated glass. 
     The obtained sheet of laminated glass was installed at a position of the windshield so that the machine direction was transverse. The information to be displayed, which is emitted from a display unit installed below the sheet of laminated glass, was reflected in the sheet of laminated glass. The display position was the following three points: 1) the center of the machine direction of the interlayer film, 2) the position distanced leftward from the center by 45 cm, and 3) the position distanced rightward from the center by 45 cm, at the position of 10 cm on the one end side from the center connecting the one end and the other end. Presence or absence of a double image was visually checked at each of the three positions. The double images were judged according to the following criteria. 
     [Criteria for Judgment on Double Images] 
     
         
         
           
             o: Double images are not confirmed at all of three points 
             x: Double images are confirmed at any of three points 
           
         
       
    
     The details and the results are shown in the following Table 1 and Table 2. 
     
       
         
           
               
               
               
               
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
             
            
               
                   
                   
                   
                   
                   
                   
                   
                 Comparative 
               
               
                   
                   
                   
                 Example 1 
                 Example 2 
                 Example 3 
                 Example 4 
                 Example 1 
               
               
                   
               
               
                 Configuration 
                 Thickness of one 
                 μm 
                 829 
                 839 
                 786 
                 819 
                 837 
               
               
                 of interlayer 
                 end 
               
               
                 film 
                 Thickness of the 
                 μm 
                 1318 
                 1304 
                 1189 
                 1159 
                 1311 
               
               
                   
                 other end 
               
               
                   
                 Distance from one 
                 mm 
                 1142 
                 1142 
                 1092 
                 1088 
                 1065 
               
               
                   
                 end to the other 
               
               
                   
                 end 
               
               
                 Evaluation 
                 Standard deviation 
                 mrad 
                 0.038 
                 0.025 
                 0.036 
                 0.037 
                 0.041 
               
               
                   
                 of 11 partial wedge 
               
               
                   
                 angles 
               
               
                   
                 Mean of 11 partial 
                 mrad 
                 0.554 
                 0.503 
                 0.354 
                 0.339 
                 0.463 
               
               
                   
                 wedge angles 
               
               
                   
                 Double images 
                   
                 ∘ 
                 ∘ 
                 ∘ 
                 ∘ 
                 x 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                   
                   
                 Example 5 
                 Example 6 
                 Example 7 
                 Example 8 
               
               
                   
               
               
                 Configuration 
                 Thickness of one 
                 μm 
                 810 
                 789 
                 795 
                 770 
               
               
                 of interlayer 
                 end 
               
               
                 film 
                 Thickness of the 
                 μm 
                 1112 
                 1151 
                 1270 
                 1310 
               
               
                   
                 other end 
               
               
                   
                 Distance from one 
                 mm 
                 1007 
                 1124 
                 1057 
                 972 
               
               
                   
                 end to the other 
               
               
                   
                 end 
               
               
                 Evaluation 
                 Standard deviation 
                 mrad 
                 0.014 
                 0.007 
                 0.004 
                 0.010 
               
               
                   
                 of 11 partial wedge 
               
               
                   
                 angles 
               
               
                   
                 Mean of 11 partial 
                 mrad 
                 0.51 
                 0.331 
                 0.454 
                 0.476 
               
               
                   
                 wedge angles 
               
               
                   
                 Double images 
                   
                 ∘ 
                 ∘ 
                 ∘ 
                 ∘ 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                   
                 Comparative 
               
               
                   
                 Example 9 
                 Example 2 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 Configuration 
                 Thickness of one end 
                 μm 
                 777 
                 813 
               
               
                 of interlayer 
                 Thickness of the other 
                 μm 
                 1184 
                 1435 
               
               
                 film 
                 end 
               
               
                   
                 Distance from one end 
                 mm 
                 1050 
                 1012 
               
               
                   
                 to the other end 
               
               
                 Evaluation 
                 Standard deviation of 
                 mrad 
                 0.020 
                 0.045 
               
               
                   
                 11 partial wedge 
               
               
                   
                 angles 
               
               
                   
                 Mean of 11 partial 
                 mrad 
                 0.417 
                 0.610 
               
               
                   
                 wedge angles 
               
               
                   
                 Double images 
                   
                 ∘ 
                 x 
               
               
                   
               
            
           
         
       
     
     In this connection, sheets of laminated glass prepared with interlayer films obtained in Examples 1 to 8 respectively were evaluated for the sound insulating properties with sound transmission losses, and as a result, it was confirmed that the sheets were excellent in sound insulating properties. 
     EXPLANATION OF SYMBOLS 
     
         
         
           
               1 ,  1 A,  1 B,  1 C,  1 D,  1 E,  1 X: First layer 
               1 Aa,  1 Ca,  1 Ea: Portion having sectional shape in thickness direction of rectangular shape 
               1 Ab,  1 Cb,  1 Eb: Portion having sectional shape in thickness direction of wedge-like shape 
               2 ,  2 B,  2 D,  2 X: Second layer 
               3 ,  3 B,  3 D,  3 X: Third layer 
               11 ,  11 A,  11 B,  11 C,  11 D,  11 E: Interlayer film 
               11 X: Interlayer film part 
               11   a : One end 
               11   b : Other end 
               11 Aa,  11 Ca,  11 Ea: Portion having sectional shape in thickness direction of rectangular shape 
               11 Ab,  11 Cb,  11 Eb: Portion having sectional shape in thickness direction of wedge-like shape 
               21 : Laminated glass 
               22 : First lamination glass member 
               23 : Second lamination glass member 
             R 1 : Region for display 
             R 2 : Surrounding region 
             R 3 : Shading region 
               51 : Roll body 
               61 : Winding core