Intermediate film structure for sandwich panel, sandwich panel structure, and projection system for automobile skylight glass

Abstract

Provided are an intermediate film structure for a sandwich panel, a sandwich panel structure, and a projection system for an automobile skylight glass, whereby sufficient image clarity can be obtained in a light scattering mode and sufficient transparent visibility can be obtained in a light transmission mode. An intermediate film structure (1) for a sandwich panel, which is used by being sandwiched between two transparent panels (30, 31), and which is provided with a first thermoplastic sheet (10) disposed on the outdoor side (A), a second thermoplastic sheet (11) disposed on the indoor side (B), and a polymer scattering liquid crystal film (20) provided between the first thermoplastic sheet (10) and the second thermoplastic sheet (11), the brightness L * of the first thermoplastic sheet (10) and the second thermoplastic sheet (11) is 90 or less, the visible light transmittance of the first thermoplastic sheet (10) is less than the visible light transmittance of the second thermoplastic sheet (11), and the visible light transmittance of the second thermoplastic sheet (11) is 10% or more.

Description

Technical Field

[0001] The present invention relates to an interlayer film structure for laminated panels used between two transparent panels, a laminated panel structure including the interlayer film structure for laminated panels, and a projection system for automotive sunroof glass. Background Art

[0002] In vehicles such as automobiles, a full glass roof design in which the top is covered with glass up to the top or a seamless design in which the joint portion between the glass and the vehicle body is removed has attracted attention, and in particular, the top design has been focused on. In the full glass roof design structure in which the glass area of the top portion becomes large, it is impossible to secure a space for installing a mechanical shielding device such as a window switch unit, and it is difficult to introduce it in practical use.

[0003] Therefore, in a large-area roof structure, a large amount of sunlight and heat rays may flow in from above the head. Therefore, research has been conducted on introducing a dark-colored laminated panel structure or the like to block external light. However, when using a dark-colored laminated panel structure, it is difficult to obtain the advantage of a skylight glass (roof glass) that an open feeling can be obtained, and it is impossible to fully meet the needs of users.

[0004] Therefore, in skylight glass, as an alternative means to a mechanical shielding device, research has also been conducted on applying a light control film such as a polymer dispersed liquid crystal (PDLC) film. Generally, when no voltage is applied to the PDLC film, the liquid crystal is irregularly oriented and exhibits a light scattering mode that causes strong light scattering. When a voltage is applied, the liquid crystal is aligned and exhibits a light transmission mode with high light transmittance, and functions as an alternative to a sunshade. When using a PDLC film as skylight glass, there is a problem of poor aesthetics due to a yellowish appearance in the light scattering mode. Therefore, in order to suppress the yellowish appearance of skylight glass, it has been proposed to include a blue layer in the PDLC film (for example, refer to Patent Document 1).

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: German Utility Model Publication No. 202021104310 Summary of the Invention

[0008] Problems to be Solved by the Invention

[0009] When using a PDLC film for skylight glass, if the PDLC film is set to the light scattering mode, the haze value becomes high and the light transmittance becomes low. Therefore, the inventors have studied using a skylight glass equipped with a PDLC film as a screen. Specifically, research has been conducted on irradiating light from a projector or the like onto a skylight glass set to the light scattering mode to display characters, symbols, graphics, images, etc., thereby performing a vehicle space show in a vehicle such as an automobile.

[0010] However, there is a problem that sufficient image clarity cannot be obtained in the light scattering mode for a skylight glass assembled with a PDLC film. For example, even when using the skylight glass described in Patent Document 1, sufficient image clarity cannot be improved.

[0011] Therefore, the present invention has been made in view of the above problems, and its object is to provide an interlayer film structure for a sandwich panel, a sandwich panel structure, and a projection system for an automotive skylight glass that can obtain sufficient image clarity in the light scattering mode and sufficient transparent visibility in the light transmission mode.

[0012] Means for Solving the Problems

[0013] As a result of intensive studies by the present inventors, it has been found that by forming an interlayer film structure for a sandwich panel used between two transparent panels, which includes a specific first thermoplastic sheet disposed on the outdoor side, a specific second thermoplastic sheet disposed on the indoor side, and a polymer-dispersed liquid crystal film disposed between the first thermoplastic sheet and the second thermoplastic sheet, the above problems can be solved, and thus the following present invention has been completed.

[0014] [1] An interlayer film structure for a sandwich panel, which is an interlayer film structure for a sandwich panel used between two transparent panels, and includes: a first thermoplastic sheet disposed on the outdoor side, a second thermoplastic sheet disposed on the indoor side, and a polymer-dispersed liquid crystal film disposed between the first thermoplastic sheet and the second thermoplastic sheet, wherein the luminance L* of the first thermoplastic sheet and the second thermoplastic sheet is 90 or less, the visible light transmittance of the first thermoplastic sheet is less than the visible light transmittance of the second thermoplastic sheet, and the visible light transmittance of the second thermoplastic sheet is 10% or more.

[0015] [2] The interlayer film structure for a sandwich panel according to [1], wherein the visible light transmittance of the first thermoplastic sheet is 50% or less.

[0016] [3] The interlayer film structure for a sandwich panel according to [1] or [2], wherein the visible light transmittance measured with the polymer-dispersed liquid crystal film in the light transmission mode is 20% or less.

[0017] [4] The interlayer film structure for a sandwich panel according to any one of [1] to [3], which is used for an automobile.

[0018] [5] A sandwich panel structure, which includes the interlayer film structure for a sandwich panel according to any one of [1] to [4] and two transparent panels, and the interlayer film structure for a sandwich panel is disposed between the two transparent panels.

[0019] [6]The laminated panel structure according to [5] is for a skylight glass.

[0020] [7]A projection system for an automotive skylight glass includes: the laminated panel structure according to [6] for the skylight glass; and a light source for projecting an image onto the aforementioned laminated panel structure.

[0021] Effects of the Invention

[0022] According to the present invention, there can be provided an interlayer film structure for a laminated panel, a laminated panel structure, and a projection system for an automotive skylight glass that can achieve sufficient image clarity in a light scattering mode and sufficient transparent visibility in a light transmission mode. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic cross-sectional view showing the interlayer film structure for a laminated panel according to an embodiment of the present invention.

[0024] Figure 2 It is a schematic view showing the use of the interlayer film structure for a laminated panel according to an embodiment of the present invention.

[0025] Figure 3 It is a schematic cross-sectional view showing the projection system for an automotive skylight glass of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0026] Hereinafter, the present invention will be described with reference to embodiments.

[0027] <Interlayer Film Structure for a Laminated Panel>

[0028] As Figure 1 shown, the interlayer film structure 1 for a laminated panel (hereinafter also referred to as "interlayer film structure") according to an embodiment of the present invention is used by being sandwiched between two transparent panels 30 and 31. The interlayer film structure 1 includes a first thermoplastic sheet 10 disposed on the transparent panel 30 side, a second thermoplastic sheet 11 disposed on the transparent panel 31 side, and a polymer-dispersed liquid crystal film (hereinafter also referred to as PDLC film) 20 provided between the first thermoplastic sheet 10 and the second thermoplastic sheet 11.

[0029] It should be noted that in the laminated panel, the transparent panel 30 is disposed on the outdoor side A, and the transparent panel 31 is disposed on the indoor side. Therefore, the first thermoplastic sheet 10 is disposed on the outdoor side A, and the second thermoplastic sheet 11 is disposed on the indoor side B. For example, in the case of being used for vehicle applications such as automobiles, the first thermoplastic sheet 10 is disposed on the outside of the vehicle, and the second thermoplastic sheet 11 is disposed on the inside of the vehicle.

[0030] [L*a*b* of the Thermoplastic Sheet]

[0031] The luminance L* of both the first thermoplastic sheet 10 and the second thermoplastic sheet 11 is 90 or less. If the luminance L* of at least either the first thermoplastic sheet 10 or the second thermoplastic sheet 11 is greater than 90, sufficient image clarity cannot be obtained when the intermediate film structure 1 is used as a screen. From the viewpoint of obtaining sufficient image clarity, the luminance L* of the first thermoplastic sheet 10 and the second thermoplastic sheet 11 is preferably 85 or less, more preferably 80 or less, and further preferably 75 or less. In addition, from the viewpoint of improving the transparent visibility of the intermediate film structure 1, the luminance L* of the first thermoplastic sheet 10 and the second thermoplastic sheet 11 is preferably 20 or more, more preferably 30 or more, and further preferably 50 or more.

[0032] The luminance L* of the first thermoplastic sheet 10 and the second thermoplastic sheet 11 may be the same or different from each other. In the case of being different, the luminance of either one may be high, but preferably the luminance L* of the first thermoplastic sheet 10 is lower than the luminance L* of the second thermoplastic sheet 11. The difference in the luminance L* between the first thermoplastic sheet 10 and the second thermoplastic sheet 11 at this time is not particularly limited, and from the viewpoint of image clarity, it is preferably 4 or more, and more preferably 8 or more.

[0033] It should be noted that the luminance L* of the first thermoplastic sheet 10 and the second thermoplastic sheet 11 in this specification is obtained by measuring a sandwich panel structure produced by bonding the first thermoplastic sheet 10 and the second thermoplastic sheet 11 in a manner of being respectively sandwiched between two transparent glass plates. In addition, the luminance L* in this specification is defined using the CIE1976L*a*b* color system.

[0034] The specific measurement method of the luminance L* in this specification is as shown in the following examples.

[0035] The chromaticity a* of both the first thermoplastic sheet 10 and the second thermoplastic sheet 11 defined using the CIE1976L*a*b* color system is preferably -20 or more and 20 or less, more preferably -15 or more and 15 or less, and further preferably -10 or more and 10 or less.

[0036] The chromaticity b* of both the first thermoplastic sheet 10 and the second thermoplastic sheet 11 defined using the CIE1976L*a*b* color system is preferably -20 or more and 20 or less, more preferably -15 or more and 15 or less, and further preferably -10 or more and 10 or less.

[0037] By making the chromaticity a* and chromaticity b* of the first thermoplastic sheet 10 and the second thermoplastic sheet 11 within the above ranges, the appearance can be made good, and the color reproducibility when functioning as a screen can be made good.

[0038] It should be noted that the chromaticity a* and chromaticity b* of the first thermoplastic sheet 10 and the second thermoplastic sheet 11 in this specification are obtained by measuring the sandwich panel structure body produced by bonding the first thermoplastic sheet 10 and the second thermoplastic sheet 11 in a manner of being respectively clamped by two transparent glass plates.

[0039] [Visible light transmittance of thermoplastic sheet]

[0040] The visible light transmittance of the first thermoplastic sheet 10 is less than that of the second thermoplastic sheet 11. If the visible light transmittance of the first thermoplastic sheet 10 is greater than that of the second thermoplastic sheet, sufficient image clarity cannot be obtained when the intermediate film structure body 1 functions as a screen.

[0041] It should be noted that the visible light transmittance of the first thermoplastic sheet 10 and the second thermoplastic sheet 11 in this specification is obtained by measuring the sandwich panel structure body produced by bonding the first thermoplastic sheet 10 and the second thermoplastic sheet 11 in a manner of being respectively clamped by two transparent glass plates. In addition, the measurement method of the visible light transmittance in this specification is as shown in the following examples.

[0042] The visible light transmittance (Tv2) of the second thermoplastic sheet 11 is 10% or more. If the visible light transmittance (Tv2) of the second thermoplastic sheet 11 is less than 10%, sufficient transparent visibility cannot be obtained when the intermediate film structure body 1 functions in a light transmission mode. From the viewpoint of obtaining sufficient transparent visibility, the visible light transmittance (Tv2) of the second thermoplastic sheet 11 is preferably 40% or more, more preferably 60% or more, and further preferably 70% or more. In addition, from the viewpoint of obtaining sufficient image clarity, the visible light transmittance (Tv2) of the second thermoplastic sheet 11 is preferably 95% or less, more preferably 90% or less, and further preferably 86% or less.

[0043] From the viewpoint of obtaining sufficient image clarity, the visible light transmittance (Tv1) of the first thermoplastic sheet 10 is preferably 50% or less, more preferably 45% or less, and further preferably 40% or less. In addition, from the viewpoint of obtaining sufficient transparent visibility, the visible light transmittance (Tv1) of the first thermoplastic sheet 10 is preferably 4% or more, more preferably 6% or more, and further preferably 20% or more.

[0044] The difference (Tv2 - Tv1) between the visible light transmittance (Tv2) of the second thermoplastic sheet 11 and the visible light transmittance (Tv1) of the first thermoplastic sheet 10 is preferably 4% or more, more preferably 15% or more, and further preferably 30% or more. By making the difference (Tv2 - Tv1) be above the above lower limit value, sufficient image clarity can be obtained when the intermediate film structure body 1 functions as a screen.

[0045] It should be noted that the visible light transmittance of the transparent glass plate used in the measurement of L*a*b* and visible light transmittance is 90.5% when measured in accordance with JIS R 3106:1998 at a thickness of 2.5 mm. In addition, for this transparent glass plate, using the CIE standard light source D65 and the 10° field of view color matching functions specified in JIS Z 8781-1 (2012), JIS Z 8781-2 (2012), and JIS Z 8781-4 (2013), a* = -0.6, b* = 0.2, and the haze is 0.2% or less. The above transparent glass plate is also referred to as a reference transparent glass.

[0046] [Thermoplastic sheet]

[0047] As described above, the intermediate film structure 1 for the panel includes a first thermoplastic sheet 10 and a second thermoplastic sheet 11.

[0048] The first thermoplastic sheet 10 and the second thermoplastic sheet 11 are layers containing a thermoplastic resin. By making the first thermoplastic sheet 10 and the second thermoplastic sheet 11 contain a thermoplastic resin, it is easy to exhibit the function as an adhesive layer, and the adhesiveness to the PDLC film 20 and the transparent panels 30, 31 becomes good.

[0049] The thermoplastic resin is not particularly limited, and examples thereof include polyvinyl acetal resin, ethylene-vinyl acetate copolymer resin, ionomer resin, polyurethane resin, thermoplastic elastomer, acrylic resin, acrylic-vinyl acetate copolymer resin, polyvinyl alcohol resin, polyolefin resin, polyvinyl acetate resin, and polystyrene resin. By using these resins, it is easy to ensure the adhesiveness to the PDLC film 20 and the transparent panels 30, 31.

[0050] In the first thermoplastic sheet 10 and the second thermoplastic sheet 11, the thermoplastic resin may be used alone as 1 type, or 2 or more types may be used in combination.

[0051] In addition, among the above, it is preferably at least 1 type selected from polyvinyl acetal resin and ethylene-vinyl acetate copolymer resin. In particular, when used in combination with a plasticizer, from the viewpoint of exhibiting excellent adhesiveness to the transparent panels 30, 31 formed of glass or the like, polyvinyl acetal resin is more preferred.

[0052] The resin constituting the first thermoplastic sheet 10 and the second thermoplastic sheet 11 may be appropriately selected from the resins listed above. In addition, the resins constituting each thermoplastic sheet may be different resins, and it is preferable that they are the same as each other. Therefore, the resins constituting the first thermoplastic sheet 10 and the second thermoplastic sheet 11 are preferably both polyvinyl acetal resin or ethylene-vinyl acetate copolymer resin, and more preferably both polyvinyl acetal resin.

[0053] (Polyvinyl acetal resin)

[0054] The polyvinyl acetal resin is not particularly limited as long as it is a polyvinyl acetal resin obtained by acetalizing polyvinyl alcohol (PVA) with an aldehyde.

[0055] The above-mentioned aldehyde is not particularly limited, and an aldehyde having 1 to 10 carbon atoms is usually suitable for use. The aldehyde having 1 to 10 carbon atoms is not particularly limited, and examples thereof include n-butanal, isobutanal, n-pentanal, 2-ethylbutanal, n-hexanal, n-octanal, n-nonanal, n-decanal, formaldehyde, acetaldehyde, benzaldehyde, etc. These aldehydes can be used alone or in combination of two or more.

[0056] Among the above, n-butanal, n-hexanal, and n-pentanal are preferred, and n-butanal is more preferred. Therefore, the polyvinyl acetal resin is preferably polyvinyl butyral resin.

[0057] Polyvinyl alcohol (PVA) is obtained by saponifying a polyvinyl ester such as polyvinyl acetate, for example. The saponification degree of polyvinyl alcohol is usually 70 to 99.9 mol%. The polyvinyl acetal resin can be used alone or in combination of two or more.

[0058] The average degree of polymerization of PVA is preferably 200 or more, more preferably 500 or more, further preferably 1,000 or more, and still more preferably 1,500 or more. If the average degree of polymerization is set to the above lower limit or more, the penetration resistance of the sandwich panel structure becomes high. In addition, the average degree of polymerization of PVA is preferably 5,000 or less, more preferably 4,000 or less, further preferably 3,500 or less, and still more preferably 2,500 or less.

[0059] It should be noted that the average degree of polymerization of polyvinyl alcohol is determined by the method based on JIS K 6726 "Test Method for Polyvinyl Alcohol".

[0060] The amount of hydroxyl groups in the polyvinyl acetal resin is preferably 15 mol% or more, and preferably 38 mol% or less. By setting the amount of hydroxyl groups to 15 mol% or more, the adhesiveness is likely to be good, and the penetration resistance of the sandwich panel structure and the like are likely to be good. In addition, by setting the amount of hydroxyl groups to 38 mol% or less, the sandwich panel structure is prevented from becoming too hard. From the viewpoint of adhesiveness to a glass plate and the like, the amount of hydroxyl groups is more preferably 20 mol% or more, and further preferably 25 mol% or more. In addition, the amount of hydroxyl groups is more preferably 35% or less, and further preferably 33 mol% or less.

[0061] In the case of using polyvinyl butyral resin as the polyvinyl acetal resin, from the same viewpoint, the amount of hydroxyl groups is also 15 mol% or more, preferably 38 mol% or less, more preferably 20 mol% or more, further preferably 25 mol% or more, more preferably 35 mol% or less, and further preferably 33 mol% or less.

[0062] The amount of hydroxyl groups in the polyvinyl acetal resin is the value obtained by dividing the amount of vinyl groups bonded with hydroxyl groups by the total amount of vinyl groups in the main chain and expressing it as a mole fraction in percentage. The amount of vinyl groups bonded with hydroxyl groups can be measured according to, for example, JIS K 6728 "Test Methods for Polyvinyl Butyral".

[0063] The degree of acetalization of the above polyvinyl acetal resin is preferably 47 mol% or more and preferably 85 mol% or less. The degree of acetalization is more preferably 55 mol% or more, further preferably 60 mol% or more, and also more preferably 80 mol% or less, further preferably 75 mol% or less.

[0064] It should be noted that when the acetal group is a butyral group and the polyvinyl acetal resin (A) is a polyvinyl butyral resin, the degree of acetalization refers to the degree of butyralization.

[0065] The above degree of acetalization is the value obtained by expressing the following mole fraction as a percentage, and the mole fraction is obtained by dividing the value obtained by subtracting the amount of vinyl groups bonded with hydroxyl groups and the amount of vinyl groups bonded with acetyl groups from the total amount of vinyl groups in the main chain by the total amount of vinyl groups in the main chain. The degree of acetalization (degree of butyralization) can be calculated based on, for example, the results measured by the method based on JIS K6728 "Test Methods for Polyvinyl Butyral".

[0066] The degree of acetylation of the polyvinyl acetal resin is preferably 30 mol% or less, more preferably 20 mol% or less, further preferably 10 mol% or less, and even more preferably 2 mol% or less. If the degree of acetylation is below the above upper limit, the moisture resistance of the interlayer film structure for the sandwich panel and the sandwich panel structure becomes higher. In addition, the degree of acetylation is not particularly limited, preferably 0.01 mol% or more, and more preferably 0.1 mol% or more.

[0067] The above degree of acetylation is the value obtained by expressing the following mole fraction as a percentage, and the mole fraction is the mole fraction obtained by dividing the amount of vinyl groups bonded with acetyl groups by the total amount of vinyl groups in the main chain. The amount of vinyl groups bonded with acetyl groups can be measured according to, for example, JIS K 6728 "Test Methods for Polyvinyl Butyral".

[0068] (Ethylene-vinyl acetate copolymer resin)

[0069] As the ethylene-vinyl acetate copolymer resin, it can be a non-crosslinked ethylene-vinyl acetate copolymer resin. Additionally, it can be a high-temperature crosslinked ethylene-vinyl acetate copolymer resin. Further, as the ethylene-vinyl acetate copolymer resin, an ethylene-vinyl acetate modified resin such as a saponified ethylene-vinyl acetate copolymer or a hydrolyzate of ethylene-vinyl acetate can also be used.

[0070] The vinyl acetate content of the ethylene-vinyl acetate copolymer resin measured according to JIS K 6730 "Test Methods for Ethylene-Vinyl Acetate Resins" or JIS K 6924-2:1997 is preferably 10 to 50% by mass, more preferably 20 to 40% by mass. By setting the vinyl acetate content above their lower limit values, the adhesiveness to glass becomes high. Additionally, the penetration resistance of the sandwich panel structure easily becomes good. Further, by setting the vinyl acetate content below their upper limit values, the breaking strength of the intermediate film structure 1 becomes high and the impact resistance of the sandwich panel structure becomes good.

[0071] (Plasticizer)

[0072] Both the first thermoplastic sheet 10 and the second thermoplastic sheet 11 preferably further contain a plasticizer. The first thermoplastic sheet 10 and the second thermoplastic sheet 11 become soft by containing a plasticizer. As a result, the intermediate film structure 1 also becomes soft. Additionally, when the intermediate film structure 1 is used for a sandwich panel structure, the softness of the sandwich panel structure is improved and the penetration resistance is also improved. Furthermore, high adhesiveness to the PDLC film 20 and the transparent panels 30, 31 can also be exhibited.

[0073] When using a polyvinyl acetal resin as the thermoplastic resin, it is particularly effective to make each thermoplastic sheet contain a plasticizer. Therefore, the first thermoplastic sheet 10 more preferably contains a polyvinyl acetal resin and a plasticizer. Additionally, the second thermoplastic sheet 11 also more preferably contains a polyvinyl acetal resin and a plasticizer.

[0074] Examples of the plasticizer include organic ester plasticizers such as monobasic organic acid esters and polybasic organic acid esters, and phosphorus-based plasticizers such as organic phosphate plasticizers and organic phosphite plasticizers. Among them, organic ester plasticizers are preferred.

[0075] Examples of the organic ester plasticizer include, for example, triethylene glycol bis(2-ethylbutyrate), triethylene glycol bis(2-ethylhexanoate), triethylene glycol dioctanoate, triethylene glycol bis(n-octanoate), triethylene glycol bis(n-heptanoate), tetraethylene glycol bis(n-heptanoate), tetraethylene glycol bis(2-ethylhexanoate), dibutyl sebacate, dioctyl azelate, dibutyl carbitol adipate, ethylene glycol bis(2-ethylbutyrate), 1,3-propanediol bis(2-ethylbutyrate), 1,4-butanediol bis(2-ethylbutyrate), 1,2-butanediol bis(2-ethylbutyrate), diethylene glycol bis(2-ethylbutyrate), diethylene glycol bis(2-ethylhexanoate), dipropylene glycol bis(2-ethylbutyrate), triethylene glycol bis(2-ethylvalerate), tetraethylene glycol bis(2-ethylbutyrate), diethylene glycol dioctanoate, triethylene glycol bis(n-heptanoate), tetraethylene glycol bis(n-heptanoate), triethylene glycol bis(2-ethylbutyrate), dihexyl adipate, dioctyl adipate, hexylcyclohexyl adipate, diisononyl adipate, heptylnonyl adipate, dibutyl sebacate, oil-modified sebacic alkyd, a mixture of a phosphate ester and an adipate ester, a mixed adipate ester, etc. As the mixed adipate ester, an adipate ester produced from two or more kinds of alcohols selected from alkyl alcohols having 4 to 9 carbon atoms and cyclic alcohols having 4 to 9 carbon atoms can be mentioned.

[0076] Among the above plasticizers, triethylene glycol bis(2-ethylhexanoate) (3GO) is particularly preferably used.

[0077] The content of the plasticizer in each of the first thermoplastic sheet 10 and the second thermoplastic sheet 11 is not particularly limited, and is preferably 10 parts by mass or more and 100 parts by mass or less with respect to 100 parts by mass of the thermoplastic resin. If the content of the plasticizer is 10 parts by mass or more, the intermediate film structure 1 becomes moderately soft. Therefore, when the intermediate film structure 1 is used for the sandwich panel structure, the penetration resistance and the like of the sandwich panel structure become good. In addition, if the content of the plasticizer is 100 parts by mass or less, separation of the plasticizer from the thermoplastic sheet can be prevented. The content of the plasticizer is more preferably 20 parts by mass or more, further preferably 30 parts by mass or more, further preferably 35 parts by mass or more, and in addition, more preferably 70 parts by mass or less, further preferably 63 parts by mass or less. The contents of the plasticizer in the first thermoplastic sheet 10 and the second thermoplastic sheet 11 may be the same as or different from each other.

[0078] The first thermoplastic sheet 10 and the second thermoplastic sheet 11 are mainly composed of a resin or a resin and a plasticizer, respectively. In the first thermoplastic sheet 10 and the second thermoplastic sheet 11, the total amount of the thermoplastic resin and the plasticizer is usually 70% by mass or more, preferably 80% by mass or more and less than 100% by mass, and further preferably 90% by mass or more and less than 100% by mass based on the total amount of each thermoplastic sheet.

[0079] (Colorant)

[0080] Both the first thermoplastic sheet 10 and the second thermoplastic sheet 11 preferably contain a colorant. By containing a colorant, the first thermoplastic sheet 10 and the second thermoplastic sheet 11 can appropriately adjust the lightness L*, chromaticity a*, and chromaticity b*, and sufficient image clarity can be obtained in the light scattering mode.

[0081] The colorant only needs to be uniformly dispersed in the first thermoplastic sheet 10 and the second thermoplastic sheet 11.

[0082] The colorant used is not particularly limited, and pigments conventionally compounded into thermoplastic sheets can be used, such as pigments of blue, yellow, red, green, purple, white, black, etc. Pigments or dyes can be used as the pigments. By using a colorant, the first thermoplastic sheet 10 and the second thermoplastic sheet 11 can color the sandwich panel into a desired color, and the designability of the sandwich panel can be improved.

[0083] Examples of the pigments used in the first thermoplastic sheet 10 and the second thermoplastic sheet 11 include carbon black, copper phthalocyanine pigments such as pigment blue, phthalocyanine pigments such as cobalt phthalocyanine pigment, anthraquinone pigments, perylene pigments, diketopyrrolopyrrole pigments, quinacridone pigments, pyrenone pigments, thioindigo pigments, isoindoline pigments, isoindolinone pigments, quinophthalone pigments, vat pigments, dioxazine pigments, pyrrocoline pigments, fluoranthrene pigments, azo pigments, titanium oxide pigments, calcium carbonate pigments, metal oxide pigments, Ni complex pigments, other metal complex pigments, etc.

[0084] In addition, examples of the dyes include azo dyes, cyanine dyes, triphenylmethane dyes, phthalocyanine dyes, anthraquinone dyes, naphthoquinone dyes, quinoneimine dyes, methylene dyes, azomethine dyes, squarylium dyes, acridine dyes, styryl dyes, coumarin dyes, quinoline dyes, nitro dyes, etc. The dyes can be disperse dyes.

[0085] The pigments and dyes constituting the above colorant can be directly compounded into the resin, or can be compounded into the resin on the basis of being made into forms such as ink or toner.

[0086] As the colorant, it is preferably to contain a black colorant such as carbon black. By using a black colorant, it is easy to reduce the lightness with a small amount of colorant. In addition, it is easy to prevent the absolute values of a* and b* from becoming too high, and it is easy to improve the color reproducibility of the image when used as a screen. It is preferred that either the first thermoplastic sheet 10 or the second thermoplastic sheet 11 contains a black colorant, and it is more preferred that both contain a black colorant.

[0087] The content of the plasticizer in each of the first thermoplastic sheet 10 and the second thermoplastic sheet 11 is not particularly limited, as long as it is appropriately adjusted so that the visible light transmittance, L*, a*, and b* values of each thermoplastic sheet fall within the above-mentioned desired ranges.

[0088] In the first thermoplastic sheet 10 and the second thermoplastic sheet 11 of the present invention, in addition to the colorant, various additives such as a heat insulating agent, an ultraviolet absorber, an antioxidant, a light stabilizer, an ultraviolet absorber, and an antioxidant may be appropriately contained.

[0089] The thickness of the first thermoplastic sheet 10 is not particularly limited. For example, it is 0.05 mm or more, preferably 0.1 mm or more, and more preferably 0.2 mm or more. Additionally, the thickness of the first thermoplastic sheet 10 is not particularly limited. For example, it is 1 mm or less, preferably 0.8 mm or less, and more preferably 0.5 mm or less. By making the thickness of the first thermoplastic sheet 10 equal to or greater than the above lower limit value, sufficient image clarity can be obtained in the light scattering mode. Additionally, by making the thickness of the first thermoplastic sheet 10 equal to or less than the above upper limit value, sufficient transparent visibility can be obtained in the light transmission mode without increasing the thickness of the intermediate film structure 1 to an unnecessary extent.

[0090] The thickness of the second thermoplastic sheet 11 is not particularly limited. For example, it is 0.05 mm or more, preferably 0.1 mm or more, and more preferably 0.2 mm or more. Additionally, the thickness of the second thermoplastic sheet 11 is not particularly limited. For example, it is 1 mm or less, preferably 0.8 mm or less, and more preferably 0.5 mm or less. By making the thickness of the second thermoplastic sheet 11 equal to or greater than the above lower limit value, sufficient image clarity can be obtained in the light scattering mode. Additionally, by making the thickness of the second thermoplastic sheet 11 equal to or less than the above upper limit value, sufficient transparent visibility can be obtained in the light transmission mode without increasing the thickness of the intermediate film structure 1 to an unnecessary extent.

[0091] It should be noted that the thicknesses of the first thermoplastic sheet 10 and the second thermoplastic sheet 11 are preferably thin. In particular, by reducing the thickness of the first thermoplastic sheet 10, the image clarity is improved, which is preferred.

[0092] Commercially available products may be used for the first thermoplastic sheet 10 and the second thermoplastic sheet 11. For example, products of the "S-LEC Film" series manufactured by Sekisui Chemical Co., Ltd. may be used.

[0093] [PDLC film]

[0094] The PDLC film 20 is a light modulating body capable of switching between a light transmission mode and a light scattering mode. The PDLC film 20 has a high visible light transmittance in the light transmission mode. In addition, the visible light transmittance of the PDLC film 20 in the light scattering mode is lower than that in the light transmission mode. In addition, the haze value is also higher compared to the light transmission mode. The switching between the light transmission mode and the light scattering mode of the PDLC film 20 is performed by whether a voltage is applied.

[0095] In the present invention, by using the PDLC film, it is easy to increase the visible light transmittance in the light transmission mode. On the other hand, high light scattering can be obtained in the light scattering mode, it is easy to increase the haze value in the light scattering mode, and when used as a screen, it is easy to make the image clarity good.

[0096] The PDLC film 20 includes, for example, two substrate films and a light modulating layer disposed between the two substrate films. As the substrate film, polyester resins such as polyethylene terephthalate and polyethylene naphthalate; cellulose derivatives such as acrylic resins and triacetyl cellulose (TAC); resin films using resin components such as polyethersulfone (PES) resin and polyimide resin can be cited. Among these, from the viewpoint of processability and the like, a polyester resin film is preferred, and among them, a polyethylene terephthalate film is more preferred.

[0097] In addition, an electrode layer can be provided on the surfaces of the two substrate films on the side of the light modulating layer. As the electrode layer, as long as it is a known transparent electrode material in the art, it can be used without particular limitation, and examples include indium tin oxide (ITO) conductive films, tin oxide conductive films, zinc oxide conductive films, polymer conductive films, and the like. Among these, an ITO conductive film is preferred. The electrode layer is connected to a lead-out electrode, and a voltage can be applied between the electrode layers by means of the lead-out electrode.

[0098] The light modulating layer in the PDLC film 20 is, for example, a liquid crystal layer, and the liquid crystal layer of the PDLC film 20 is composed of polymer dispersed liquid crystal (PDLC). Examples of the polymer dispersed liquid crystal include a liquid crystal called network type liquid crystal in which a polymer forms a network structure in the liquid crystal layer.

[0099] Examples of the liquid crystal layer include a layer formed by using spacers and the like to form a space for filling liquid crystal inside, filling the liquid crystal into the space and sealing it, but spacers may not be provided. In addition, as the liquid crystal, it can be in any form, it can be TN type or STN type. In addition, an alignment film can be appropriately provided between the light modulating layer and the electrode layer. By providing the alignment film, the PDLC film 20 can also be made into the reverse type described later.

[0100] The PDLC film 20 changes the orientation state of the liquid crystal layer by applying a voltage between the electrode layers, thereby switching between light transmission and light scattering. The PDLC film 20 can be either a conventional type or a reverse type. The conventional type is the type that exhibits a light transmission mode when a voltage is applied (voltage ON) and a light scattering mode when no voltage is applied (voltage OFF). In addition, the reverse type is the type that exhibits a light transmission mode when no voltage is applied and a light scattering mode when a voltage is applied.

[0101] As described above, the PDLC film 20 has a high visible light transmittance and a small haze value in the light transmission mode. The specific visible light transmittance of the PDLC film 20 in the light transmission mode is, for example, 60% or more, preferably 70% or more, and more preferably 75% or more. By having the above visible light transmittance, the light transmittance of the sandwich panel structure can be sufficiently improved in the light transmission mode. For example, if it is used for the skylight glass of an automobile, a sufficient sense of openness can be obtained.

[0102] In addition, the haze value of the PDLC film 20 in the light transmission mode is, for example, 30% or less, preferably 20% or less, and further preferably 10% or less.

[0103] It should be noted that the visible light transmittance of the PDLC film 20 in the light transmission mode only needs to be 100% or less, and is 99% or less in practical use. In addition, the haze value only needs to be 0% or more, and is, for example, 1% or more in practical use.

[0104] On the other hand, in the light scattering mode, the haze value of the PDLC film 20 is, for example, 70% or more, preferably 80% or more, and more preferably 90% or more. When the haze value becomes high in this way in the light scattering mode, the light shielding property becomes high, and the inflow of heat rays can be appropriately prevented in the light scattering mode. In addition, when used as a screen, sufficient image clarity can be obtained.

[0105] In addition, in the light scattering mode, the visible light transmittance of the PDLC film 20 is also lower than that in the light transmission mode, for example, 40% or less, preferably 20% or less, and more preferably 10% or less. As described above, if the light transmittance in the light scattering mode becomes low, the inflow of heat rays can be appropriately prevented in the light scattering mode. In addition, when used as a screen, sufficient image clarity can be obtained.

[0106] It should be noted that the haze value of the PDLC film 20 in the light scattering mode only needs to be 100% or less, and is about 99% or less in practical use. In addition, the visible light transmittance only needs to be 0% or more, and is, for example, about 1% or more in practical use.

[0107] It should be noted that the PDLC film 20 exhibits either a light scattering mode or a light transmission mode in the state where no voltage is applied, as long as it falls within the above-mentioned haze value and visible light transmittance range in this mode. In addition, the PDLC film 20 exhibits the other of the light scattering mode and the light transmission mode in the state where a voltage is applied, as long as it becomes the above-mentioned haze value and visible light transmittance in this mode. The applied voltage value is not limited, as long as it becomes the above-mentioned haze value and visible light transmittance at any voltage value.

[0108] It should be noted that the visible light transmittance of the PDLC film 20 can be measured using a spectrophotometer in accordance with JIS R 3106:2019. In addition, the haze value can be measured using a haze meter (e.g., "TC-HIIIDPK" manufactured by Tokyo Denshoku Co., Ltd.) in accordance with JIS K 6714.

[0109] The thickness of the PDLC film 20 is not particularly limited. For example, it is 0.05 mm or more and 2 mm or less, preferably 0.1 mm or more and 1 mm or less, and more preferably 0.2 mm or more and 0.8 mm or less.

[0110] Commercially available products can be used for the PDLC film 20. Specifically, conventional types of the "LC MAGIC" series manufactured by Toppan Printing Co., Ltd. can be cited [light transmission mode: haze value 5%, parallel line transmittance 82%; light scattering mode: haze value 98%, parallel line transmittance 1% (catalog value)], reverse types [light transmission mode: haze value 10%, parallel line transmittance 80%; light scattering mode: haze value 92%, parallel line transmittance 7% (catalog value)]. Furthermore, window types of "UMU" manufactured by Nippon Sheet Glass UMU Products Co., Ltd. can be cited [light transmission mode: haze value 6%, parallel line transmittance 74%; light scattering mode: haze value 86%, parallel line transmittance 5% (catalog value)], etc. In addition, "LC-W" of Gauzy Co., Ltd. can be cited.

[0111] [Switch]

[0112] The intermediate film structure 1 may include a switching member (not shown). The switching member is a member for controlling the PDLC film 20. The switching member can control whether to apply a voltage between the electrode layers of the PDLC film 20 through a switch input. Thus, the switching member can switch between the light transmission mode and the light scattering mode of the PDLC film 20.

[0113] It should be noted that the switching member can be disposed outside the intermediate film structure 1, and is preferably constituted by a contact sensor disposed inside the intermediate film structure 1. Therefore, the PDLC film 20 is preferably controlled by the contact sensor.

[0114] [Adhesive layer]

[0115] Regarding the intermediate film structure 1, for example, an adhesive layer (not shown) is provided in at least one of the spaces between the first thermoplastic sheet 10 and the PLDC film 20 and between the second thermoplastic sheet 11 and the PLDC film 20. The PLDC film 20 can be adhered to at least one of the first thermoplastic sheet 10 and the second thermoplastic sheet 11 by means of the adhesive layer. Among them, it is preferable not to provide an adhesive layer between them, but the PLDC film 20 is directly adhered to the first thermoplastic sheet 10. Similarly, the PLDC film 20 is preferably directly adhered to the second thermoplastic sheet 11.

[0116] In addition, regarding the intermediate film structure 1, for example, an adhesive layer is provided on the outer side of at least one of the first thermoplastic sheet 10 and the second thermoplastic sheet 11. At least one of the first thermoplastic sheet 10 and the second thermoplastic sheet 11 can be adhered to the transparent panels 30, 31 by means of the adhesive layer. Among them, it is preferable not to provide an adhesive layer on the outer side of the first thermoplastic sheet 10, but the first thermoplastic sheet 10 is directly adhered to the transparent panel 30. Similarly, it is preferable not to provide an adhesive layer on the outer side of the second thermoplastic sheet 11, but the second thermoplastic sheet 11 is directly adhered to the transparent panel 31.

[0117] The adhesive layer is not particularly limited as long as it is composed of a known material. For example, it can be composed of the above-mentioned thermoplastic resin.

[0118] In the present invention, in the manufacture of the intermediate film structure, first, a PLDC film and resin films for forming the first thermoplastic sheet and the second thermoplastic sheet are prepared.

[0119] And the PLDC film and the resin films can be appropriately overlapped. For example, as Figure 1 shown, when there is 1 PLDC film, two resin films can be prepared and overlapped in the order of resin film / PLDC film / resin film. In addition, when there are two PLDC films, three resin films can be prepared and overlapped in the order of resin film / PLDC film / resin film / PLDC film / resin film. When there are three or more PLDC films, the resin film / PLDC film can be overlapped alternately in the same way.

[0120] In addition, in cases where an adhesive layer is provided between the PLDC film and the first thermoplastic sheet, the second thermoplastic sheet, etc., or on the surface of the intermediate film structure, resin films for forming the adhesive layer can be appropriately overlapped.

[0121] As described above, the laminate obtained by overlapping the PLDC film and the resin films can be used to manufacture the intermediate film structure by, for example, applying pressure along the thickness direction or thermocompression bonding under negative pressure.

[0122] [Optical properties of the intermediate film structure for the laminated panel]

[0123] (Visible light transmittance when the PDLC film is in the light scattering mode)

[0124] Regarding the intermediate film structure 1 of the present invention, in the laminated panel structure produced by using the intermediate film structure 1 under specified conditions, the visible light transmittance measured with the PDLC film 20 in the light scattering mode is preferably 2% or less. Additionally, the visible light transmittance is more preferably 0.1% or more and 1% or less, and even more preferably 0.2% or more and 1% or less.

[0125] As described above, if the visible light transmittance can be adjusted to 2% or less, in the intermediate film structure 1, visible light is sufficiently blocked. For example, when used for automotive window glass, especially for sunroof glass, it can prevent the interior of the vehicle from being irradiated by sunlight. Additionally, if it is 0.1% or more, a specified amount of visible light is transmitted. Therefore, it can prevent being completely blocked by the intermediate film structure 1 and can also obtain a certain sense of openness.

[0126] It should be noted that the laminated panel structure produced under specified conditions refers to the laminated panel structure obtained by bonding two reference transparent glasses with a thickness of 2.5 mm with the intermediate film structure 1.

[0127] (Visible light transmittance when the PDLC film is in the light transmission mode)

[0128] Regarding the intermediate film structure 1 of the present invention, in the laminated panel structure produced by using the intermediate film structure 1 under specified conditions, from the perspective of being able to observe the outside through the laminated panel structure, the visible light transmittance measured with the PDLC film 20 in the light transmission mode is, for example, 3% or more, preferably 10% or more. Additionally, the visible light transmittance measured with the PDLC film 20 in the light transmission mode is more preferably 15% or more, further preferably 20% or more. Additionally, the visible light transmittance is preferably 60% or less, more preferably 50% or less, and further preferably 40% or less.

[0129] When the PDLC film 20 is in the light transmission mode, if the visible light transmittance is 10% or more, it is possible to easily observe the outside through the laminated panel structure. Additionally, various external lights can enter the interior through the laminated panel structure. Therefore, even in poor weather or at night, a specified amount or more of external light can enter, and a sense of openness can be obtained even in such an environment.

[0130] [Laminated panel structure]

[0131] As Figure 1As shown above, the sandwich panel structure 100 of the present invention includes the above-mentioned intermediate film structure 1 and two transparent panels 30 and 31, and the intermediate film structure 1 is disposed between the two transparent panels 30 and 31. In the sandwich panel structure 100, the two transparent panels 30 and 31 are bonded by the above-mentioned intermediate film structure 1.

[0132] Examples of the transparent panels 30 and 31 include glass plates. The glass plate can be either inorganic glass or organic glass, and inorganic glass is preferred. There is no particular limitation on the inorganic glass, and examples include transparent glass, transparent float glass, float plate glass, tempered glass, colored glass, polished plate glass, embossed glass, wired glass, wired laminated glass, ultraviolet absorption plate glass, infrared reflection plate glass, infrared absorption plate glass, green glass, etc.

[0133] In addition, as the organic glass, glass commonly referred to as acrylic glass can be used. There is no particular limitation, and examples include organic glass composed of polycarbonate plates, polymethyl methacrylate plates, polyester plates, etc.

[0134] The two transparent panels 30 and 31 can be made of the same material or different materials. For example, one can be inorganic glass and the other can be organic glass. Preferably, both of the two transparent panels 30 and 31 are inorganic glass or organic glass, and more preferably both are inorganic glass.

[0135] There is no particular limitation on the thickness of each of the above-mentioned transparent panels 30 and 31. It is preferably 0.5 mm or more and 3.2 mm or less, more preferably 0.7 mm or more and 2.7 mm or less, and further preferably 1.0 mm or more and 2.6 mm or less. By setting it within the above range, a predetermined mechanical strength can be imparted to the sandwich panel structure 100 and the overall thickness of the sandwich panel structure can be made below a predetermined value.

[0136] The thickness of the sandwich panel structure 100 of the present invention is preferably 7 mm or less. By making the thickness 7 mm or less, it can be suitably used for automotive window glass, and can be particularly suitably used for automotive skylight glass. In addition, there is no particular limitation on the lower limit value of the thickness of the sandwich panel structure. For example, it is 4 mm or more, preferably 5 mm or more.

[0137] (Manufacturing method of sandwich panel structure)

[0138] There is no particular limitation on the manufacturing method of the sandwich panel structure. It can be obtained, for example, by disposing an intermediate film structure between two transparent panels and performing hot pressing using an autoclave or the like.

[0139] In addition, in the present invention, the sandwich panel structure can be manufactured while forming the intermediate film structure. Specifically, the PDLC film can be appropriately overlapped with the resin films of the first thermoplastic sheet and the second thermoplastic sheet, and while the obtained laminate is disposed between two transparent panels, hot pressing is performed using an autoclave or the like, whereby the sandwich panel structure is obtained while forming the intermediate film structure.

[0140] [Use]

[0141] The intermediate film structure 1 and the sandwich panel structure 100 of the present invention can be used for window glasses of various vehicles such as automobiles, airplanes, ships, buildings, etc., and are preferably used for vehicle applications.

[0142] In an automobile, sometimes heat rays flow into the vehicle from the outside through the window glass, resulting in the interior of the vehicle becoming hot. Similarly, in a building, sometimes heat rays flow into the building through the window glass, resulting in the interior of the building becoming hot. However, the intermediate film structure of the present invention blocks light by appropriately combining the modes of the PDLC film, thereby being able to appropriately prevent heat rays from flowing into the vehicle or the interior of the building.

[0143] In addition, the intermediate film structure 1 and the sandwich panel structure 100 of the present invention are particularly preferably used for automobile applications. In the case of being used for automobile applications, they can be used for any window glass such as side glass, rear glass, sunroof glass, etc. As Figure 2 shown, the intermediate film structure 1 and the sandwich panel structure 100 are preferably used as sunroof glass on the top (roof) 111 of the automobile 110. The intermediate film structure 1 and the sandwich panel structure 100 of the present invention are more likely to obtain a sense of openness by being used for sunroof glass.

[0144] It should be noted that the sunroof glass only needs to be disposed at least partially on the top. For example, the glass disposed over the top and the rear is also regarded as the sunroof glass. It should be noted that the top of the automobile is the part constituting the top surface of the vehicle body, and the sunroof glass is usually disposed along the horizontal direction or slightly inclined (e.g., within 20°) with respect to the horizontal direction. The inclination refers to the slope with respect to the horizontal direction when the ends of the glass disposed at the top position are connected by a straight line.

[0145] In addition, the sunroof glass has, for example, 0.5 mm 2 or more, preferably has 1 m 2 or more, and more preferably has 1.5 m 2 or more of an area.

[0146] The intermediate film structure 1 and the sandwich panel structure 100 of the present invention can be used by appropriately switching the light transmission mode and the light scattering mode of the PDLC film 20 and appropriately adjusting the visible light transmittance.

[0147] For example, in a case where light from the outside is to be blocked or where the top surface or the like is to be used as a screen, the PDLC film 20 can be set to the light scattering mode. When the light scattering mode is selected, it is difficult to observe the outside through the sandwich panel structure 100, but the function as a screen is improved.

[0148] On the other hand, in a case where it is desired to observe the outside through the sandwich panel structure 100 or where an open feeling is to be obtained, the PDLC film 20 can be set to the light transmission mode.

[0149] <Automobile sunroof glass projection system>

[0150] As Figure 3 shown, the automobile sunroof glass projection system of the present invention includes the above-described sandwich panel structure 100 and a light source 120 that projects an image onto the sandwich panel structure 100.

[0151] The light source 120 is provided inside the vehicle (indoor side B). The light source 120 is not particularly limited and can be provided inside the instrument panel or on the upper part of the instrument panel. In addition, the light source 120 can be provided, for example, on the rear side of the rear seat, on the top, or between the front seat and the rear seat. The light source 120 can use, for example, a projector capable of projecting various images, and can be a full-color (RGB) projector or a projector that emits monochromatic light such as an LED projector. In addition, it can also be an ultra-short throw (UST: Ultra-Short-Throw) projector or the like. In addition, an image display system using a digital mirror device known as a so-called DLP (registered trademark) projector can also be used.

[0152] In addition, in the case of displaying fixed images, fixed information, etc. without changing the displayed image, it is not necessary to use a projector, and a light source 120 that irradiates the sandwich panel structure with specified light corresponding to the image can be used.

[0153] Regarding the above projection system, an example of applying the sandwich panel structure 100 to an automobile sunroof glass has been described, but it is not necessary to apply it to an automobile sunroof glass, and it can be applied to other automobile glasses, such as side glasses and rear glasses. In addition, it can be used not only for automobile applications but also for vehicle applications other than automobiles and building applications.

[0154] Examples

[0155] The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples at all.

[0156] <Measurement method>

[0157] As described in the specification, the luminance (L*), chromaticity (a*b*), and visible light transmittance of the first thermoplastic sheet and the aforementioned second thermoplastic sheet are measured in the form of a laminated glass for measurement by the following method. It should be noted that the conditions for manufacturing the laminated glass for measurement are set to be the same as those for manufacturing the following laminated panel structure.

[0158] In addition, the visible light transmittance of the laminated panel structure is measured by the following method.

[0159] [L*a*b* Measurement]

[0160] Regarding the laminated glass, in accordance with JIS R 3212:2015, a spectrophotometer ("U-4100" manufactured by Hitachi High-Tech Science Corporation) is used to measure the spectral transmittance. During the measurement, the integrating sphere is arranged to receive only the parallel light transmitted through the laminated glass. The laminated glass is placed at a position 13 cm away from the integrating sphere in a manner that it is on the optical path between the light source and the integrating sphere and parallel to the normal of the optical axis to measure the spectral transmittance. In addition, regarding the measurement conditions, the scanning speed is set to 300 nm / min, the slit width is set to 8 nm, and for other measurement conditions, the CIE standard light source D65 and the 10° field-of-view color matching function specified in JIS Z 8781-1:2012, JIS Z 8781-2:2012, and JIS Z 8781-4:2013 are used to measure L*, a*, and b*.

[0161] [Visible Light Transmittance (Tv)]

[0162] The measurement is carried out in accordance with JIS R 3106:2019 using a spectrophotometer (manufactured by Hitachi High-Tech Science Corporation, product name "U-4100").

[0163] [Evaluation Method]

[0164] [Image Clarity]

[0165] For the laminated panel structures obtained in the examples and comparative examples, the image clarity of the light scattering pattern of the PDLC film is evaluated. Specifically, on a sunny day, the laminated panel structures obtained in the examples and comparative examples are set on the top of a hypothetical car placed outdoors. And, with the PDLC film of the laminated panel structure in the OFF (light scattering mode) state, an image is projected onto the laminated panel structure from the inside of the car using a high-brightness projector (manufactured by OPTOMA Corporation, product name "ML1050ST+"), and the image clarity when observing the image from the inside of the car is evaluated visually according to the following judgment criteria.

[0166] A: The projected image is clearly visible.

[0167] B: The projected image is blurred, but it can be observed.

[0168] C: The projected image is blurred and cannot be observed.

[0169] [Transmission visibility]

[0170] For the sandwich panel structures obtained in the examples and comparative examples, the transmission visibility of the light transmission mode of the PDLC film was evaluated. Specifically, on a sunny day, the sandwich panel structures obtained in the examples and comparative examples were set on the top of a hypothetical car placed outdoors. And, with the PDLC film of the sandwich panel structure in the ON (light transmission mode) state, the scenery outdoors was observed from the indoor side through the sandwich panel structure, and the evaluation was carried out according to the following judgment criteria.

[0171] A: The scenery outdoors is clearly visible.

[0172] B: The scenery outdoors is slightly dim, but it can be seen clearly.

[0173] C: The scenery outdoors cannot be observed or even if it is observed, it cannot be seen clearly.

[0174] [Example 1]

[0175] First, the following materials were prepared.

[0176] · First thermoplastic sheet: PVB film (manufactured by Sekisui Chemical Co., Ltd., product name “S-LEC Film #7008” (gray), thickness 0.76 mm

[0177] · Second thermoplastic sheet: PVB film (manufactured by Sekisui Chemical Co., Ltd., product name “S-LEC Film #7013” (gray), thickness 0.76 mm

[0178] · PDLC film: Polymer dispersed liquid crystal film (manufactured by Gauzy Co., Ltd., product name “PDLC-A”), showing a light scattering mode under voltage OFF and a light transmission mode under voltage ON (70 V), thickness 0.38 mm

[0179] · Transparent panel: The reference transparent glass described in the specification, thickness 2.5 mm

[0180] The first thermoplastic sheet, the PDLC film, and the second thermoplastic sheet were sequentially overlapped and hot-pressed at 70 °C and -780 mbar (gauge pressure), thereby integrating them to obtain an intermediate film structure for a sandwich panel. Then, the obtained intermediate film structure for a sandwich panel and another transparent panel were overlapped on the transparent panel, and using an autoclave, they were integrated under the conditions of 90 °C and 3 bar (gauge pressure) to obtain a sandwich panel structure. As Figure 1As shown, the sandwich panel structure has a laminated structure of a transparent panel / a first thermoplastic sheet / a PDLC film / a second thermoplastic sheet / a transparent panel.

[0181] [Example 2]

[0182] Except for changing the first thermoplastic sheet and the second thermoplastic sheet as shown below, the same materials as in Example 1 are used.

[0183] · First thermoplastic sheet: PVB film (manufactured by Sekisui Chemical Co., Ltd., product name “S-LEC Film#9048” (bronze), thickness 0.38 mm

[0184] · Second thermoplastic sheet: PVB film (manufactured by Sekisui Chemical Co., Ltd., product name “S-LEC Film#7082” (gray), thickness 0.76 mm

[0185] [Example 3]

[0186] Except for changing the first thermoplastic sheet and the second thermoplastic sheet as shown below, the same materials as in Example 1 are used.

[0187] · First thermoplastic sheet: PVB film (manufactured by Sekisui Chemical Co., Ltd., product name “S-LEC Film#7030” (gray), thickness 0.38 mm

[0188] · Second thermoplastic sheet: PVB film (manufactured by Sekisui Chemical Co., Ltd., product name “S-LEC Film#7082” (gray), thickness 0.76 mm

[0189] [Example 4]

[0190] Except for changing the first thermoplastic sheet and the second thermoplastic sheet as shown below, the same materials as in Example 1 are used.

[0191] · First thermoplastic sheet: PVB film (manufactured by Sekisui Chemical Co., Ltd., product name “S-LEC Film#5035” (green), thickness 0.38 mm

[0192] · Second thermoplastic sheet: PVB film (manufactured by Sekisui Chemical Co., Ltd., product name “S-LEC Film#7082” (gray), thickness 0.76 mm

[0193] [Comparative Example 1]

[0194] Except for changing the first thermoplastic sheet and the second thermoplastic sheet as shown below, the same materials as in Example 1 are used.

[0195] · First thermoplastic sheet: PVB film (manufactured by Sekisui Chemical Co., Ltd., product name "38CLR", thickness 0.76 mm

[0196] · Second thermoplastic sheet: PVB film (manufactured by Sekisui Chemical Co., Ltd., product name "S-LEC Film#7018" (gray), thickness 0.76 mm

[0197] [Comparative Example 2]

[0198] Except for changing the first thermoplastic sheet and the second thermoplastic sheet as shown below, the same materials as in Example 1 were used.

[0199] · First thermoplastic sheet: PVB film (manufactured by Sekisui Chemical Co., Ltd., product name "S-LEC Film#7002" (gray), thickness 0.76 mm

[0200] · Second thermoplastic sheet: PVB film (manufactured by Sekisui Chemical Co., Ltd., product name "S-LEC Film#7008" (gray), thickness 0.76 mm

[0201] [Comparative Example 3]

[0202] Except for changing the first thermoplastic sheet and the second thermoplastic sheet as shown below, the same materials as in Example 1 were used.

[0203] · First thermoplastic sheet: PVB film (manufactured by Sekisui Chemical Co., Ltd., product name "S-LEC Film#8174" (gray), thickness 0.76 mm

[0204] · Second thermoplastic sheet: PVB film (manufactured by Sekisui Chemical Co., Ltd., product name "S-LEC Film#6001" (blue), thickness 0.76 mm

[0205] For the sandwich panel structures obtained in the examples and comparative examples, the visible light transmittance of the light transmission mode of the PDLC film was measured. The results are shown in Table 1.

[0206] [Table 1]

[0207]

[0208] As shown in Table 1, the luminance L* of the first thermoplastic sheet and the second thermoplastic sheet in the sandwich panel structures of Examples 1 to 4 was 90 or less, satisfying the condition that the visible light transmittance of the first thermoplastic sheet is less than that of the second thermoplastic sheet. Therefore, good image clarity can be obtained. In addition, the visible light transmittance of the second thermoplastic sheet in the sandwich panel structures of Examples 1 to 4 was 10% or more. Therefore, good transparent visibility can be obtained.

[0209] On the other hand, the sandwich panel structure of Comparative Example 1 does not satisfy the condition that the visible light transmittance of the first thermoplastic sheet is less than that of the second thermoplastic sheet. Therefore, sufficient image clarity cannot be obtained. In the sandwich panel structure of Comparative Example 2, the visible light transmittance of the second thermoplastic sheet is not 10% or more. Therefore, sufficient transparent visibility cannot be obtained. The sandwich panel structure of Comparative Example 3 does not satisfy the condition that the luminance L* of both the first thermoplastic sheet and the second thermoplastic sheet is 90 or less, so sufficient image clarity cannot be obtained.

[0210] Description of Reference Numerals

[0211] 1 Interlayer film structure for sandwich panel (interlayer film structure)

[0212] 10 First thermoplastic sheet

[0213] 11 Second thermoplastic sheet

[0214] 20 Polymer-dispersed liquid crystal film (PDLC film)

[0215] 30, 31 Transparent panel

[0216] 100 Sandwich panel structure

[0217] 110 Automobile

[0218] 111 Top

[0219] 120 Light source

Claims

1. An intermediate film structure for a laminated panel, which is an intermediate film structure for a laminated panel used by being sandwiched between two transparent panels, and includes: A first thermoplastic sheet disposed on the outdoor side, a second thermoplastic sheet disposed on the indoor side, and a polymer-dispersed liquid crystal film provided between the first thermoplastic sheet and the second thermoplastic sheet, The luminance L* of the first thermoplastic sheet and the second thermoplastic sheet is 90 or less, The visible light transmittance of the first thermoplastic sheet is less than the visible light transmittance of the second thermoplastic sheet, The visible light transmittance of the second thermoplastic sheet is 10% or more.

2. The intermediate film structure for a sandwich panel according to claim 1, wherein, The visible light transmittance of the first thermoplastic sheet is 50% or less.

3. The intermediate film structure for a sandwich panel according to claim 1, wherein, The visible light transmittance measured with the polymer-dispersed liquid crystal film in the light transmission mode is 20% or less.

4. The intermediate film structure for a laminated panel according to claim 1, which is used for an automobile.

5. A laminated panel structure, which includes the intermediate film structure for a laminated panel according to any one of claims 1 to 4 and two transparent panels, The intermediate film structure for a laminated panel is disposed by being sandwiched between the two transparent panels.

6. The laminated panel structure according to claim 5, which is used for a skylight glass.

7. A projection system for an automobile skylight glass, which includes: The laminated panel structure according to claim 6 for a skylight glass; and A light source that projects an image onto the laminated panel structure.

Images