Colored interlayer for laminated glass with improved optical properties

Abstract

The present invention relates to an intermediate layer film for laminated glass comprising four or more layers, including a colored layer having improved optical properties, particularly for vehicle windows.

Description

Technical Field

[0001] The present invention relates to an interlayer film for laminated glass including four or more layers including a colored layer having improved optical properties, particularly for vehicle side windows.

Background Art

[0002] A glass laminate including two glass sheets joined to each other with an interlayer film containing a thermoplastic resin is widely known, for example, for vehicle windows.

[0003] So-called sound-insulating glass is used to improve the comfort for passengers inside a vehicle. This generally includes a three-layer sound-insulating interlayer film including a softer sound-insulating layer and two protective layers disposed on both sides of the sound-insulating layer. The sound-insulating layer usually contains a polyvinyl acetal resin having high compatibility with a plasticizer used, and thus becomes softer, and therefore provides good sound-insulating properties. The protective layer prevents the bleeding of a large amount of plasticizer in the sound-insulating layer and provides stability and ease of use.

[0004] It is also known to use tinted windows for rear side windows, sunroofs and rear windows in passenger cars to provide privacy and protection against sunlight for rear seat passengers.

[0005] Such tinted windows that provide sound-insulating properties at the same time are used particularly for luxury cars. However, it has been previously reported that when a colored layer is overlaid together with a sound-insulating three-layer film, a pattern of bright streaks and dark streaks may be seen, which may result in undesirable optical properties in the final glass laminate. However, such appearance defects are not acceptable in the luxury car market.

[0006] The appearance of such patterns, also known as color unevenness, is usually explained by the fact that the surface of the interlayer film for laminated glass is generally embossed to form recesses in order to allow for good degassing properties during the lamination process.

[0007] In the general manufacturing of laminated glass, the laminate, which includes at least one interlayer film for laminated glass sandwiched between two glass plates, is passed through a nip roll to remove air, or placed in a rubber bag under vacuum, and residual air is removed between the glass plates and the interlayer film while pressurizing the bond.

[0008] Next, during the lamination stage, when the surface of the interlayer is pressed against the glass sheet at high temperature and pressure, any depressions on the surface of the interlayer film are removed. However, when the surface of the interlayer is pressed against another interlayer, these depressions may create patterns within the colored layer and / or the relatively soft sound-insulating layer, and such patterns are not completely removed during the lamination stage, causing color unevenness. Several approaches have been taken to mitigate color unevenness, including increasing the distance between the depressions and the colored layer. However, the inventors have found that a specific design of the roughness pattern of the colored layer itself plays a crucial role in preventing color unevenness.

[0009] Generally, colored interlayers with sound-insulating properties are produced by adding a coloring agent to the main body of the sound-insulating three-layer structure itself. However, such products are difficult to recycle because colored three-layer structures can only be used for other colored laminates, and such applications are very limited. [Overview of the project] [Problems that the invention aims to solve]

[0010] On the other hand, in the glass industry, it is becoming increasingly important to provide sustainable products by recycling the interlayers used in laminated glass. One advantage of the present invention is that the color is provided in an additional colored layer, which can be separated from the sound-insulating portion of the interlayer body by slicing the colored layer from the interlayer body according to a process disclosed, for example, in European Patent Application Publication No. 3808558 (EP 3808558 A1). Thus, only a portion of the interlayer needs to be recycled for colored applications, while the interlayer body can be recycled for all standard colorless applications. [Means for solving the problem]

[0011] Accordingly, the present invention relates to an intermediate layer film for laminated glass comprising four or more layers, each containing polyvinyl acetal and a plasticizer, wherein the four or more layers are in the following order: • A colored layer comprising polyvinyl acetal, a plasticizer, and at least one colorant. • A first protective layer containing polyvinyl acetal and a plasticizer, • A sound insulation layer containing polyvinyl acetal and a plasticizer, and • A second protective layer containing polyvinyl acetal and plasticizer. The present invention relates to an intermediate layer film in which layers are superimposed on each other, and the colored layer has a roughness on at least one side of its surface such that the 10-point average roughness Rz measured in accordance with DIN EN ISO 4287 is 5 to 30 μm and the average width Rsm measured in accordance with DIN EN ISO 4287 is 10 to 1000 μm.

[0012] The feature “in the following order” is intended to indicate that the four layers essential to the present invention exist in the order required by the claims. However, additional layers may exist above, below, or between those four layers.

[0013] Preferably, the colored layer has a roughness on both surfaces such that the 10-point average roughness Rz measured in accordance with DIN EN ISO 4287 is 5 to 30 μm and the average width Rsm measured in accordance with DIN EN ISO 4287 is 10 to 1000 μm.

[0014] Preferably, Rz is 10 to 20 μm, more preferably 12.5 to 17.5 μm.

[0015] Preferably, Rsm is 700-900 μm or 500-800 μm, and more preferably 850-950 μm.

[0016] In other embodiments, the first protective layer may have an embossed pattern, where the values ​​for Rz and / or Rsm are within the same range as those shown for the colored layer.

[0017] When polyvinyl acetal film is recycled, for example, from trimmings obtained during the manufacture of glass laminates, the recycled polyvinyl acetal material may have higher haze values ​​or yellowing issues due to repeated extrusion processes carried out under high temperature and pressure, which can lead to partial degradation of the polyvinyl acetal. However, when such recycled material is used for colored glass laminates, the problems associated with increased haze and yellowing are mitigated because the color of the colored layer masks these slight optical defects.

[0018] Accordingly, in other embodiments of the present invention, the polyvinyl acetal in the colored layer comprises at least 75% by mass, preferably at least 90% by mass, and most preferably at least 95% by mass of recycled polyvinyl acetal. Most preferably, all of the polyvinyl acetal in the colored layer is derived from recycled material.

[0019] Preferably, the polyvinyl acetal in each of the four or more layers contains at least 75% by mass, more preferably at least 90% by mass, and most preferably at least 95% by mass of recycled polyvinyl acetal. In particular, all of the polyvinyl acetal in each of the four or more layers is derived from recycled material.

[0020] Preferably, the colored layer covers the entire surface area of ​​the intermediate film. In other words, the entire intermediate layer appears colored, preferably with a predetermined shade of gray.

[0021] The individual films used in this invention may be used in almost any thickness, as long as they do not adversely affect the sound insulation properties and provide a sufficiently colored appearance for the colored layer. For example, all individual films may have the same thickness, but combinations of individual films of various thicknesses are also possible.

[0022] Preferably, the thickness of the colored layer is 150 to 500 μm, more preferably 250 to 350 μm.

[0023] Preferably, the total thickness of the first protective layer, the second protective layer, and the sound insulation layer combined is 450 to 750 μm, more preferably 550 to 650 μm.

[0024] The individual films according to the present invention contain a plasticizer-containing polyvinyl acetal obtained by acetalizing fully or partially saponified polyvinyl alcohol with an aldehyde. The sound-insulating layer preferably contains polyvinyl acetal having a proportion of polyvinyl alcohol groups of 17 to 22% by mass, preferably 18 to 21% by mass, and more preferably 19.5 to 20.5% by mass. Preferably, the protective layer and the colored layer each contain polyvinyl acetal having a proportion of polyvinyl alcohol groups of less than 14% by mass, preferably 11 to 13.5% by mass, and more preferably less than 11.5 to 13% by mass.

[0025] The polyvinyl alcohol content and polyvinyl acetate content of the polyvinyl acetal are specified in accordance with ASTM D 1396-92.

[0026] The compatibility between the plasticizer and the polyvinyl alcohol partially acetalized generally decreases with the decrease in the polarity of the plasticizer. Therefore, plasticizers with higher polarity have higher compatibility with polyvinyl acetal than those with lower polarity. Alternatively, the compatibility of plasticizers with lower polarity increases with the increase in the degree of acetalization, that is, with the decrease in the number of hydroxy groups and thus the decrease in the polarity of the polyvinyl acetal.

[0027] Individual films may contain the same or different plasticizers. The use of the same plasticizer is preferred, and the composition of the plasticizer formulation within an individual film may change somewhat as a result of migration.

[0028] Individual films can include at least one plasticizer or plasticizer formulation of the following plasticizers known for PVB films: esters of polyvalent aliphatic or aromatic acids, such as dialkyl adipates, such as dihexyl adipate, dioctyl adipate, hexyl cyclohexyl adipate, a mixture of heptyl adipate and nonyl adipate, diisononyl adipate, heptyl nonyl adipate, and esters of adipic acid with alicyclic or ether bond-containing ester alcohols; dialkyl sebacates, such as dibutyl sebacate, and esters of sebacic acid with alicyclic or ether bond-containing ester alcohols; esters of phthalic acid, such as butyl benzyl phthalate or bis-2-butoxyethyl phthalate; esters of cyclohexanedicarboxylic acid, such as diisononyl 1,2-cyclohexanedicarboxylate; Esters or ethers of polyvalent aliphatic or aromatic alcohols or oligoether glycols having one or more unbranched or branched aliphatic or aromatic substituents, such as diglycols, triglycols or tetraglycols, and linear or branched aliphatic or alicyclic carboxylic acids; diethylene glycol bis(2-ethylhexanoate), triethylene glycol bis(2-ethylhexanoate), triethylene glycol bis(2-ethylbutanoate), tetraethylene glycol bis-n-heptanoate, triethylene glycol bis-n-heptanoate, triethylene glycol bis-n-hexanoate, tetraethylene glycol dimethyl ether, and / or dipropylene glycol benzoate can be given as examples for the latter group; Phosphates with aliphatic or aromatic ester alcohols, e.g., tris(2-ethylhexyl) phosphate (TOF), triethyl phosphate, diphenyl-2-ethylhexyl phosphate, and / or tricresyl phosphate; Esters of citric acid, succinic acid, and / or fumaric acid.

[0029] Particularly preferably, one or more of the following plasticizers are used: Di(2-ethylhexyl) sebacate (DOS), di(2-ethylhexyl) adipate (DOA), dihexyl adipate (DHA), dibutyl sebacate (DBS), triethylene glycol bis-n-heptanoate (3G7), tetraethylene glycol bis-n-heptanoate (4G7), triethylene glycol bis(2-ethylhexanoate) (3GO or 3G8), tetraethylene glycol bis(n-2-ethylhexanoate) (4GO or 4G8), di(2-butoxyethyl) adipate (DBEA), di(2-butoxyethoxyethyl)adipate (DBEEA), di(2-butoxyethyl)sebacate (DBES), di(2-ethylhexyl)phthalate (DOP), di-isononylphthalate (DINP), triethylene glycol bis-isononanoate, triethylene glycol bis(2-propylhexanoate), 1,2-cyclohexanedicarboxylic acid diisononyl ester (DINCH), tris(2-ethylhexyl)phosphate (TOF), and dipropylene glycol benzoate.

[0030] Furthermore, individual films according to the present invention may contain further additives known to those skilled in the art, such as residual water, UV absorbers, antioxidants, adhesion modifiers, fluorescent whitening agents, stabilizers, colorants, processing aids, organic or inorganic nanoparticles, fumed silica, and / or surfactants.

[0031] Films based on plasticizer-containing polyvinyl acetal preferably contain polyvinyl butyral (PVB), which is obtained by acetalizing polyvinyl alcohol together with butyraldehyde.

[0032] The polyvinyl acetal in the sound insulation layer preferably contains 5 to 8 mol% of polyvinyl acetate groups, while the protective layer and colored layer particularly preferably contain polyvinyl acetal with a polyvinyl acetate group ratio of 0.1 to 11 mol%, preferably 0.1 to 4 mol%, and more preferably 0.1 to 2 mol%.

[0033] Preferably, the colorants are at least one dye and / or pigment. They may be any suitable coloring material, either inorganic or organic, and must not dissolve in the polymer matrix and therefore withstand migration from the colored layer to other layers.

[0034] Preferably, carbon black, iron oxide, titanium dioxide, or spinel pigments are used as pigments. The pigments can be dispersed in the same polyvinyl acetal and / or plasticizer used to produce the colored layer before extrusion into the masterbatch. Preferably, the colorant is added to the colored layer during extrusion in an amount that provides a predetermined shade of gray in the final laminate.

[0035] In another embodiment, the present invention relates to a laminate comprising an intermediate layer according to the present invention sandwiched between two glass sheets, for example, two glass sheets each having a thickness of 1.0 to 2.5 mm, preferably 1.5 to 2.0 mm.

[0036] In yet another embodiment, the present invention relates to the use of such laminates as side windows, sunroofs and / or rear windows for vehicles, particularly as rear side windows.

[0037] Preferably, the colored film is manufactured separately from the other layers by extrusion, while the sound insulation layer is extruded together with the two protective layers. These layers are then stacked and bonded between the two glass sheets.

[0038] Methods well known to those skilled in the art can be used to bond the layered bodies together, and pre-laminates may or may not be manufactured in advance.

[0039] The so-called "autoclave process" is carried out for about two hours at an elevated pressure of approximately 10-15 bar and a temperature of 100-150°C. For example, the vacuum bag or vacuum ring method described in European Patent No. 1235683 (EP 1 235 683 B1) operates at approximately 200 mbar and 130-145°C.

[0040] Vacuum bonding apparatus may be used. These consist of a heating and evacuating chamber where laminated glass can be bonded within 30 to 60 minutes. A reduced pressure of 0.01 to 300 mbar and a temperature of 100 to 200°C, particularly 130 to 160°C, have proven to be practically useful.

[0041] Accordingly, the present invention relates to a method for manufacturing an intermediate layer according to the present invention, comprising the following steps: • A step of providing at least a portion of polyvinyl acetal for a colored layer by shredding a pre-extruded polyvinyl acetal film. • A step in which shredded polyvinyl acetal from a preceding stage is extruded together with a coloring agent to form a colored layer. The step of providing a layered body comprising a colored layer, a first protective layer, a sound-insulating layer, and a second protective layer in that order, and • The step of bonding the resulting intermediate layer between two glass sheets. The same also relates to the aforementioned method, including the method described above. [Brief explanation of the drawing]

[0042] [Figure 1] This figure shows a photographic image of a laminate manufactured according to the laminate fabrication procedure 1. [Figure 2] This figure shows a photographic image of a laminate manufactured according to the laminate fabrication procedure 1. [Figure 3] This figure shows a photographic image of a laminate manufactured according to the laminate fabrication procedure 1. [Examples]

[0043] method Measurement of L*a*b and TL The color space values ​​L*a*b of the intermediate layer were measured using a HunterLab ColorQuest XE spectrophotometer (commercially available from Hunter Associates Laboratory, Inc.) in accordance with ASTM E 313 (illuminant C, observation angle 2°).

[0044] Measurement of Rz and Rsm The surface properties Rz and Rsm of the film were measured in accordance with DIN EN ISO 4287.

[0045] Photograph of a laminate In a darkroom, a 30cm x 30cm laminate was placed horizontally on a light table with a 65cm x 45cm illumination area. An opaque black frame was placed around the laminate to prevent light that did not pass through the laminate from entering the camera lens. The LED lamp type used was 2-CB-D65, with D65 standard light at a color temperature of 6500K and a brightness of 5000lx.

[0046] The camera was fixed to a shelf on the stacked structure, with the lens 50 cm away from the stack. For the photographs, an aperture of f / 5.6 and exposure times of 1 / 160 sec to 1 / 40 sec were used, as shown below.

[0047] The photograph has a size of 6000px x 4000px, corresponding to the area of ​​approximately 69cm x 46cm surrounding the laminate. To better show the observed optical impression, an area of ​​approximately 434px x 434px, corresponding to 5cm x 5cm, was cropped from the photograph at the center of the top of the laminate. This area was edited using a standard image editing program (Microsoft PowerPoint) to increase its brightness and contrast as shown below.

[0048] Film production Fabrication of a transparent monolayer A commercially available Trosifol® Clear 0.76mm was used.

[0049] Fabrication of a transparent three-layered structure I used commercially available Trosifol® SC Multilayer 0.50mm.

[0050] Preparation of colored monolayers Colored monolayers were manufactured by film extrusion using a single-screw extruder. Recycled PVB trimmings were extruded together with a colored PVB masterbatch as raw materials. Both materials were ground into flakes of approximately 5 mm in a water-cooled mill, then transferred to a water-cooled mixing tank, and from the tank to the extruder funnel. The film was extruded through a flat slit die and cooled in a water bath. The film thickness was adjusted to a target of 380 μm by controlling the roller speed. The surface roughness of the film was controlled by controlling the die slit size and die lip temperature.

[0051] Fabrication of laminates Step 1 A standard test laminate measuring 30 cm x 30 cm was prepared using conventional clear glass (Planiclear® 2.1 mm) washed with deionized water at <5 μS in a flat glass washing machine, along with films A and B, in the following stacking order: bottom glass - film A - film B - top glass. Film A was used either as is, with its original surface roughness, or after its surface roughness was modified as described in step 2.

[0052] The sandwiches were pre-bonded in industry-standard vacuum bags in two consecutive stages: (1) at room temperature and 0.1 bar for 20 minutes, and (2) at 90°C and 0.1 bar for 20 minutes. From these pre-bonded layers, the final laminates were produced in industry-standard autoclaves at a maximum temperature of 140°C and a maximum bar of 12 bar.

[0053] Step 2 To modify the surface roughness of film A, including parameters Rz and Rsm, a 30cm x 30cm laminate was manufactured using conventional transparent glass (Planiclear® 2.1mm) washed with deionized water at <5μS in a flat glass washing machine, together with a commercially available PET (polyethylene terephthalate) film having a thickness of approximately 0.18mm and low adhesion to both PVB and glass, in the following stacking order: bottom glass - PET - film A - PET - top glass.

[0054] The sandwiches were pre-bonded in industry-standard vacuum bags in two consecutive stages: (1) at room temperature and 0.1 bar for 20 minutes, and (2) at 90°C and 0.1 bar for 20 minutes. From these pre-bonded layers, the final laminates were produced in industry-standard autoclaves at a maximum temperature of 140°C and a maximum bar of 12 bar.

[0055] Film A with modified surface roughness was obtained by removing both glass layers and both PET layers from the sandwich after final lamination. Next, a normal test laminate was fabricated using film A with modified surface roughness as described in step 1.

[0056] Table 1 shows the films used, along with their roughness parameters Rz and Rsm and color space parameters. Film #2 was manufactured from film #1 according to laminate fabrication procedure 2. The Rsm value for film #2 is not shown because this low Rz value is meaningless with the measurement method used. Films #1, #3, and #4 were manufactured as described in the film fabrication section.

[0057] Interpretation of the photograph Example 1 To demonstrate the effect of Rz and Rsm of colored films on the visibility of color unevenness, laminates were fabricated according to Lamination Preparation Procedure 1. The films used are shown in Table 1 along with their roughness parameters Rz and Rsm and color space parameters. Films #1, #2, #3, #4, and #5 were fabricated as described in Film Preparation.

[0058] Table 1. Films used for bonding and subsequent optical evaluation using photographic images. [Table 1]

[0059] Figure 1 shows photographic images of laminates manufactured according to laminate fabrication procedure 1, with film A=film #1 and film B=film #5 (Figure 1a), film A=film #2 and film B=film #5 (Figure 1b), film A=film #3 and film B=film #5 (Figure 1c), and film A=film #4 and film B=film #5 (Figure 1d). The photographs were taken with an exposure time of 1 / 80 second. The images show a 5cm × 5cm area as indicated in the photograph of the laminate, with the brightness changed by +10% and the contrast changed by +80%. Figure 1a (film #1 with high Rz and high Rsm) shows a distinct wavy pattern of repeating light and dark streaks.

[0060] Figures 1b and 1c (films #2 and #3 with high Rz and low Rsm) show a coarse pattern of bright and dark spots, but no repeating pattern is observed, in contrast to Figure 1a, which is due to the low Rsm. Figure 1d (film #4 with low Rz and low Rsm) shows a smooth pattern with no distinct bright and dark spots or repeating pattern, which is due to the low Rz and low Rsm, respectively.

[0061] Example 2 To further demonstrate the effect of Rz in colored films on the visibility of color unevenness, laminates were fabricated according to Lamination Procedure 1. The films used are shown in Table 2 along with their roughness parameters Rz and Rsm and color space parameters. Film #7 was fabricated from film #6 according to Lamination Procedure 2. The Rsm value for film #7 is not shown because, given the low Rz value, it is meaningless with the measurement method used. Films #6, #8, and #9 were fabricated as described in Film Fabrication.

[0062] Table 2. Films used for bonding and subsequent optical evaluation using photographic images. [Table 2]

[0063] Figure 2 shows photographic images of laminates manufactured according to Laminate Fabrication Procedure 1, with film A = film #6 and film B = film #8 (left image), and film A = film #7 and film B = film #8 (right image). The photographs were taken with an exposure time of 1 / 80 second. The images show a 5cm x 5cm area as indicated within the photograph of the laminate. In the left image, the brightness has been changed by +10% and the contrast by +90%, while in the right image, the brightness has been changed by +14% and the contrast by +90%.

[0064] Figure 3 shows photographic images of laminates manufactured according to Laminate Fabrication Procedure 1, with film A = film #6 and film B = film #9 (left image), and film A = film #7 and film B = film #9 (right image). The images show a 5cm x 5cm area as indicated within the photograph of the laminate, and the brightness of both images has been changed by +14% and the contrast by +90%.

[0065] Both Figures 2 and 3 show a distinct wavy pattern of repeating light and dark streaks in the laminate using film #6 (left image, higher Rz), and this pattern is absent in the laminate using film #7 (right image, lower Rz).

Claims

1. An intermediate layer film for laminated glass comprising four or more layers, each containing polyvinyl acetal and a plasticizer, wherein the four or more layers are in the following order: - A colored layer comprising polyvinyl acetal, a plasticizer, and at least one coloring agent. - A first protective layer containing polyvinyl acetal and a plasticizer, - A sound insulation layer containing polyvinyl acetal and a plasticizer, and - A second protective layer containing polyvinyl acetal and a plasticizer. The intermediate layer film is superimposed on each other, and the colored layer has a roughness on at least one side of its surface such that the 10-point average roughness Rz measured in accordance with DIN EN ISO 4287 is 5 to 30 μm and the average width Rsm measured in accordance with DIN EN ISO 4287 is 10 to 1000 μm.

2. The intermediate layer film according to claim 1, wherein the colored layer has a roughness on both of its surfaces such that the 10-point average roughness Rz measured in accordance with DIN EN ISO 4287 is 5 to 30 μm and the average width Rsm measured in accordance with DIN EN ISO 4287 is 10 to 1000 μm.

3. An intermediate layer film according to claim 1 or 2, wherein Rz is 10 to 20 μm.

4. An intermediate layer film according to any one of claims 1 to 3, wherein the Rsm is 700 to 900 μm.

5. The intermediate layer film according to any one of claims 1 to 4, wherein the polyvinyl acetal in the colored layer comprises at least 75% by mass of recycled polyvinyl acetal.

6. The intermediate layer film according to any one of claims 1 to 5, wherein the polyvinyl acetal in each of the four or more layers comprises at least 75% by mass of recycled polyvinyl acetal.

7. The intermediate film according to any one of claims 1 to 6, wherein the colored layer covers the entire surface area of ​​the intermediate film.

8. The intermediate layer film according to any one of claims 1 to 7, wherein the thickness of the colored layer is 150 to 500 μm.

9. The intermediate layer film according to any one of claims 1 to 8, wherein the total thickness of the first protective layer, the second protective layer, and the sound insulation layer combined is 450 to 750 μm.

10. The intermediate layer film according to any one of claims 1 to 9, wherein the coloring agent is at least one dye and / or pigment.

11. The intermediate layer film according to any one of claims 1 to 10, wherein the coloring agent is added to the colored layer during extrusion in an amount that provides a predetermined gray hue in the final laminate.

12. The intermediate layer film according to any one of claims 1 to 11, wherein the polyvinyl acetal is polyvinyl butyral.

13. A laminate comprising an intermediate layer according to any one of claims 1 to 12, sandwiched between two glass sheets.

14. Use of the laminate according to claim 13 as a side window, sunroof and / or rear window for a vehicle.

15. A method for manufacturing an intermediate layer according to claim 12, comprising the following steps: - A step of providing at least a portion of polyvinyl acetal for a colored layer by shredding a pre-extruded polyvinyl acetal film. - A step in which shredded polyvinyl acetal from a preceding stage is extruded together with a polyvinyl acetal masterbatch containing a coloring agent to form a colored layer. - A step of providing a layered body comprising a colored layer, a first protective layer, a sound-insulating layer, and a second protective layer in that order, and - The step of bonding the intermediate layer formed in this way between two glass sheets. The method, including the method described above.

Images